REPORTDate Version No 20 January 2011 1 Energy consumption in the pulp and paper industry - Model mills 2010 Integrated fine paper mill ÅF-ENGINEERING AB Market Area Forest Industry ÅForsk Reference: 09-163 ÅF-Engineering AB Frösundaleden 2, SE-169 99 Stockholm, Sweden. Phone +46 10 505 00 00. Fax +46 10 505 00 10. www.afconsult.com VAT No SE556224801201. Registered office Stockholm. http://km.afconsult.com/projects/10090/documents/reports/fine paper/fine paper final.docx Contents Page 1 2 2.1 2.2 2.3 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.7.1 3.8 3.9 3.9.1 3.9.2 3.9.3 3.10 3.11 3.12 3.13 3.13.1 3.13.2 3.13.3 3.13.4 3.13.5 3.13.6 3.13.7 3.13.8 3.13.9 3.13.10 3.13.11 3.14 3.15 3.16 3.17 3.18 3.19 4 INTRODUCTION MODEL MILL - OVERVIEW General Design Criteria Mill production and capacity Energy systems and balances MODEL MILL – PROCESS DESCRIPTION Wood Supply Woodyard Digester Brownstock deknotting and screening Oxygen delignification Pulp washing Bleaching System closure and degree of bleach plant filtrate recovery Chlorine dioxide generation Evaporation Handling of condensates Handling of non-condensable gases Tall oil recovery Recovery boiler Causticizing Lime kiln Paper Mill Capacity Stock preparation Bleached kraft supply Broke system Mixing/machine chest Filler supply Short circulation Paper machine Fresh water system White water system and buffer volumes Energy aspects of the paper machine Power boiler Steam turbines and steam distribution Cooling and recovery of low-temperature heat Effluent treatment Spill handling system Water supply and treatment MODEL MILL - ENERGY BALANCE 5 6 6 6 9 13 13 13 13 15 15 15 16 17 18 19 20 20 21 21 23 24 25 25 27 27 27 27 27 28 28 30 30 30 32 33 33 34 35 36 38 5 5.1 5.1.1 5.1.2 5.1.3 5.1.4 5.1.5 5.1.6 5.1.7 5.1.8 5.1.9 5.1.10 5.2 6 COMPARISON OF MODEL MILL AND TYPICAL MILL41 Type mill –process description 43 Digester 43 Oxygen stage 44 Pulp washing 44 Bleaching 44 Paper machine 45 Evaporation 46 Recovery boiler 46 Lime kiln 47 Power boiler 47 Steam turbines and steam distribution 47 Energy balance comparison – Model mill vs type mill 48 REFERENCES 53 Appendices Appendix 1 Model mill .Mass balance block diagrams Appendix 2 Model mill .Energy balances Appendix 3 Model mill – Secondary heat balance . . and indicated that the main development in the existing Nordic pulp and paper mills between 2000 and 2007 has been an increase in cogenerated power. This survey was updated in 2007. The FRAM project also included type mills which represented typical. and an increase in biofuel usage. The main emphasis in this study is on the technical changes which have affected energy consumption and production. To help highlight potential energy improvements in existing mills. with the pulp mill producing softwood and hardwood pulp in campaigns Kraftliner mill Magazine paper mill. existing Nordic mills. bleached super calendered (SC) TMP There was no eucalyptus kraft pulp mill in the FRAM project. In the FRAM project the energy consumption of the type mills considered data from a survey of energy consumption and production in the Swedish pulp and paper industry which was conducted in 2000. and two hardwood mills (birch and eucalyptus) Integrated fine paper mill. the type mill is included here for comparison to the model mill. Four different types of pulp and paper mills are considered: Bleached market kraft pulp mills – one softwood mill (pine). but such a mill has been included in this study. Each of the reference mills from the FRAM project has been reviewed by ÅF. and in some cases data from the major mill equipment suppliers. Material and energy balances have been calculated for the 2010 model mill using spreadsheet models developed by ÅF.Integrated fine paper mill 20 January 2011 Page 5 1 Introduction The purpose of this ÅForsk financed study is to update the hypothetical reference mills developed in the 2005 FRAM project to reflect the technical changes that have occurred in recent years. The type mills in this study are identical to the type mills from the FRAM project. Modifications made in this study are based on ÅF/Innventia experience with existing mills. The kraft pulp mills have also been reviewed by Innventia. In general the key process data used in the balances in this study are conservative and should not exclude any of the major pulp mill equipment suppliers. and consequently the required capacity of the chemical recovery line .1 General Design Criteria The integrated fine paper mill produces softwood and hardwood pulp in campaigns in the pulp mill. on the level of newer modern mills cost-effective solutions Different suppliers offer different process equipment. The needed capacities of the various departments in the pulp mill are different when producing softwood and hardwood pulp.overview 2. This means that the black liquor dry solids per ton of pulp is higher for softwood than for hardwood. 2. The design of the mill considers: high. consistent paper quality which is competitived on the international market the product is elemental chlorine free (ECF) low specific consumptions of wood. The model mill is not based on equipment from any one supplier. and minimal usage of fossil fuels low environmental emissions. chemicals and water high energy efficiency maximized production of bio-energy.2 Mill production and capacity The pulp mill produces bleached softwood and hardwood pulp in compaigns. The pulp mill is similar to the bleached kraft market pulp mills in this study except for the dryer and paper machine parts.Integrated fine paper mill 20 January 2011 Page 6 2 Model mill . The main difference between hardwood and softwood is that hardwood has a higher yield. The mill design is based on best available and commercially proven technology in the Nordic countries. dry solids-. Block diagrams which summarize the mass balances for both softwood and hardwood operation are included in Appendix 1. The balances cover mainly wood/fibre-. The total production is 3130 t/d at pulp mill MCR. . 56% bleached hardwood pulp and 25% filler. At these production rates the load on the recovery boiler is approximately constant. The pulp mill has a maximum continuous rate (MCR) of 2000 ADt/d for softwood and 2500 ADt/d for hardwood. Mass balances have been prepared for the pulp mill at mill MCR conditions to determine the capacity requirements for the main mill areas. Table 2-1 summarizes the key operating and dimensioning data and for the pulp mill. The paper machine furnish consists of 19% bleached softwood pulp. causticizing and lime. Table 2-2 summarizes the key operating data for the paper machines.Integrated fine paper mill 20 January 2011 Page 7 is greater for a softwood mill compared to a hardwood mill with the same pulp produciton capacity. evaporation-. The fine paper mill has two paper machines with the same design and production. The paper is surface sized with starch to improve strength properties of the paper. virgin solids Net useful heat from liquor Causticizing and Lime Kiln Causticizing efficiency Total white liquor production Lime kiln load Active CaO in lime Lime kiln fuel ADt/24 h Softwood 2 000 Birch 2 500 t/24 h t/24 h 4 072 420 Cont 30 47.spill ditto dry solids content Strong black liquor. ash Total evaporation. Summary of pulp mill key operating data.8 3 668 10.5 35 % NaOH.0 20.0 35 4 610 642 Cont 17 51.5 2.% mole-% kg/ADt kg/ADt 12 25 20 12 18 14 m /ADt unbl.Integrated fine paper mill 20 January 2011 Page 8 Table 2-1. dry solids content incl.7 80 840 MJ/kg t/24 h MJ/kg DS MW 14.0 18.0 80 771 981 15. Pulp production Wood yard Wood to digester Bark and wood waste Digester Plant Kappa number Unscreened deknotted digester yield Alkali charge on wood as effective alkali Sulphidity (white liquor) Oxygen Stage Kappa number after oxygen stage Alkali charge as NaOH Oxygen charge Washing Department Dilution factor in the last stage Evaporation Plant Weak black liquor to evaporation.3 413 13.5 t/h % % t/h 913 16. excl.0 426 mole-% 3 m /24 h t/24 h % 82 82 7 831 7 541 534 554 90 90 Bark / wood waste . 3 2.0 3 477 10. including spill Recovery Boiler Estimated higher heating value of virgin DS Strong liquor virgin solids to mixing tank Net useful heat from liquor. Summary of paper mill key operating data. The lime kiln is fired with bark powder. During hardwood campaigns the steam from the recovery boiler is not sufficient for the mill’s requirement. or gasified bark. . Speed at pope Width on pope Grammage Production on pope (100% eff. and additional power is purchased.) Paper dryness PM furnish composition -Hard wood -Soft wood -Filler -Surface size of paper (starch) Paper mill efficiency Operating days per year Paper production net (PM1 + PM2). When all available falling bark is burned in the power boiler there is an excess of steam which is utilized in a condensing turbine to produce in power. and additional steam from the power boiler is required.3 Energy systems and balances The fine paper model mill is very energy efficient and the black liquor alone produces enough steam to satisfy the process steam consumption of the mill during softwood campaigns. Kraft mill MCR Paper production net (PM1 + PM2) Bleached hardwood consumption Bleached softwood consumption Filler consumption Starch consumption m/min M 2 g/m t/h % 1 690 9 80 (75-160) 73. In both softwood and hardwood campaigns the power produced is still not sufficient to meet the mill’s demand. and the remaining bark from the woodyard and chip screening is burned in the power boiler.1 93 % % % % % Days t/day t/a ADt/a ADt/a t100/a t100/a 56 19 25 3 82 355 3 100 1 022 000 573 000 191 000 235 000 27 600 2.Integrated fine paper mill 20 January 2011 Page 9 Table 2-2. based on mill experience Paper machine power consumption has been reduced from 600 kWh/t to 550 kWh/t. . more chlorine dioxide and less hydrogen peroxide allow a lower bleaching temperature Dryness the papermachine press section to the dryer has been increased from 50% in the FRAM project to about 52%. 505oC (increased from 80 bar(g) and 490oC in the FRAM project) Feed water preheating to 175oC to increase HP steam generation (increased from 146oC in the FRAM project) Recovery boiler flue gas cooler to reduce LP steam consumed in air preheating Top preheating of all recovery boiler combustion air to 205oC (85% of combustion air heated to 165oC in the FRAM project) Latest technology for pulp digesting which has a lower cooking temperature than other systems 7 effect evaporation plant (6 effect evaporation plant in the FRAM project) Digester steam consumption has increased increased slightly with the new liquor extraction Steam consumption in the bleach plant is reduced.machine Pressurized condensate system High temperature of hot water.Integrated fine paper mill 20 January 2011 Page 10 Some key items which have been changed in the model mill compared to the reference mill in the FRAM study include: HP steam data 100 bar(g). based on mill experience A net reduction in mill steam demand compared to the FRAM study makes a condensing turbine a feasible option. and maximum use of hot water instead of steam in the bleach plant. and paper machine Bark press for bark to the power boiler Table 2-4 compares the overall steam and power balances for the 2010 model mill and the FRAM reference mill.90oC. 85 . Additional factors (which were also relevant in the FRAM project) which make the model mill energy efficient include: Recovery boiler sootblowing steam is extracted at 25 bar(g) from the turbine instead of using HP steam Low pressure steam used in the paper . 30 0.51 4.39 19.74 9.48 2.74 1.31 15.46 0.88 0.64 0.Integrated fine paper mill 20 January 2011 Page 11 Table 2-3.83 13.78 1.23 19.27 13. Summary of steam and power balances – FRAM reference.77 10.70 16.74 11.90 3.35 16.31 kWh/t paper 769 142 911 kWh/ADt pulp kWh/t paper kWh/ADt pulp 1139 236 1375 728 151 879 1203 222 1425 1375 879 1425 911 .26 12.38 0. STEAM BALANCE Generation Recovery boiler Power boiler Secondary heat Total steam generation Consumption Process steam Back pressure turbine Condensing turbine Total steam consumption POWER BALANCE Generation Back pressure power Condensing power Purchased power Total power generation Consumption Total power consumption Softwood GJ/ADt pulp GJ/t paper 17.60 13.77 11.20 2.97 1.57 12.60 Hardwood GJ/ADt pulp GJ/t paper 14. 35 19.43 0.Integrated fine paper mill 20 January 2011 Page 12 Table 2-4.Model mills 2010.72 1. STEAM BALANCE Generation Recovery boiler Power boiler Secondary heat Total steam generation Consumption Process steam Back pressure turbine Condensing turbine Total steam consumption POWER BALANCE Generation Back pressure power Condensing power Purchased power Total power generation Consumption Total power consumption Softwood GJ/ADt pulp GJ/t paper 17.98 kWh/t paper 797 155 0 951 kWh/ADt pulp kWh/t paper kWh/ADt pulp 1152 174 128 1455 736 111 82 930 998 194 0 1191 1455 930 1191 951 .97 1.39 0.22 12.58 13.61 4.50 9.70 2.59 Hardwood GJ/ADt pulp GJ/t paper 14.69 8.36 17.75 1.75 1.29 13.78 19.98 0.80 3.69 11.42 2.50 11.98 17.53 0.71 2.30 1.98 13. Summary of steam and power balances.82 1.14 12.59 11.94 0. The birch is mainly Betula spp. Chips are presteamed and impregnated with white . over-sized chips are taken to a re-chipper and then back to chip screening. and both alternatives have pros and cons. in general the batch processes.3 Digester Either continuous or batch digesting can be used. logs are cut to chips. with bark. The relation between roundwood with bark and sawmill chips is 70% roundwood and 30% sawmill chips. is one example of a modern cooking system.Integrated fine paper mill 20 January 2011 Page 13 3 Model mill – process description 3. Fines are stored and burned in the power boiler. After debarking the logs are transported to a metal detector and a water stone trap. mainly aspen. 3. The Metso Compact Cooking concept. as marketed today have higher steam consumption than the continuous processes.2 Woodyard The debarking is performed in dry debarking drums which are designed for a barking efficiency of 95%. The de-icing water is heated by the means of heat exchanging with surplus hot water. Thus the continuous cooking process has been selected for this study. the rest is burned in the power boiler. Consistent chip thickness is important for uniform cooking and a low pins fraction is important for the runnability of the digester. The chips are therefore screened to get an optimal chip size. There is a closed re-circulation of sprinkling and deicing water. A portion of the bark is utilized as fuel for the lime kiln. 3. The supply is 100% as roundwood. Accepted chips are transported to a chip silo. The effluent is collected together with the press water from the bark presses in a sedimentation basin for re-circulation. The sludge from the sedimentation basin is burned in the power boiler. Continuous digesters are the dominant technology for both existing and new mills. see Figure 3-1. Over-thick.1 Wood Supply The softwood raw material consists of 50% pine (Pinus sylvestris) and 50% spruce (Picea abies). Also. In the chipper. with about 10% other hardwoods. white liquor Extracted turpentine SW 30 47 140 20. Digester key figures. and 138oC for hardwood. digester blowline Deknotted digester yield White liquor AA concentration Alkali charge on wood as effective alkali Sulphidity.% % kg/ADtdig In order to improve yield and fibre strength the kappa number after cooking could be increased by some units.0 35 2 HW 17 51 140 18. the transfer circulation between the impregnation vessel and the digester. Example continuous cooking system (Metso Compact Cooking). Kappa number. Figure 3-1. and the cooking is performed at a relatively high alkalinity with co-current liquor flow at relatively low temperature.5 35 0 % NaOH. Andritz DownFlow LoSolids cooking system without or with pressurized impregnation vessel is another example of a modern cooking system. Table 3-1. Black liquor is extracted for evaporation via a single stage flash tank from the impregnation vessel. g/l NaOH.Integrated fine paper mill 20 January 2011 Page 14 liquor and black liquor at atmospheric conditions in a vessel. . This should however be balanced with the delignification in the oxygen stage. The cooking temperature is about 143oC for softwood. Integrated fine paper mill 20 January 2011 Page 15 3. Oxygen delignification key figures. Oxidized white liquor is the primary alkali source.6 Pulp washing The brown stock wash consists of: Two stages of pre-oxygen washing for hardwood and three stages for softwood. 3. These wash presses may both be placed after the oxygen bleached . Post oxygen washing with one 2-stage DD washer before the oxygen bleached storage tower.5 Oxygen delignification Oxygen delignification is done in two stages without intermediate washing to a kappa number of 12 for softwood and 10 for hardwood. Either wash presses or drum displacement (DD) filters can be used.6 1. plastic.3 25 20 95/98 HW 12 1. The knots are recooked. as NaOH Oxygen charge Temperature SW 12 3. One of them is very high cleanliness. Screen rejects from the last screening stage end up as effluent treatment sludge which is burned in the power boiler. After deknotting the pulp is screened at 3-4% consistency by barrier (slotted) screens in three or four stages. i.e. a low content of shives and coloured spots originating from the pulpwood (resin and bark) as well as foreign materials such as sand. Alternatively two wash presses could be used.4 Brownstock deknotting and screening There are several important quality parameters for pulp. Table 3-2. Kappa number after oxygen stage Dissolved DS (yield losses) MgSO4 charge Alkali charge oxidised WL. Pressurized deknotting separates knots from the pulp.8 2.0 18 14 95/101 % kg/ADt O2 kg/ADt O2 ºC 3. To optimise the delignification in the initial and final phases the reaction time is approximately 10 minutes in the 1st stage and approximately 60 minutes in the 2nd stage. rubber and rust. Hexenuronic acids are effectively removed in Dhot-stages. excluding the bleach plant filtrate recirculated to brown stock washing. . and the sequence is Dhot(EPO)DP. not attained on softwood pulps as they contain considerably less hexenuronic acids than hardwood pulps. These benefits are. however. one of the presses could be before the tower and one after (pre bleach press).Integrated fine paper mill 20 January 2011 Page 16 storage tower or. For hardwood pulp the first stage is operated as a Dhot-stage. For softwood pulp the first stage is operated as a “conventional” D-stage. The bleach plant is designed with four bleaching stages. One example of a typical brownstock washing system (Metso).7 Bleaching Both the softwood and birch pulps are bleached to a final brightness of 90% ISO. The main reasons for selecting a hot first D stage for hardwood pulp are that a lower charge of ClO2 is required to attain the required pulp brightness and less brightness reversion of the fully bleached pulp. Figure 3-2. Figure 3-2 shows one alternative for brownstock washing. Wash presses are used for all washing in the bleach plant.5 m3/ADt. The carryover of COD from the oxygen delignification to the bleach plant is calculated to be approx 5 kg COD/ADt. 3. and the sequence is D(EPO)DP. The brownstock washing dilution factor is 2. 5% and a total yield of about 49%.5-4 ~10 7 3 5 6 1 12 1 6 6 0. Kappa number of pulp to bleaching: 12. which corresponds to a total yield of about 44%.5-11 3.5 1.Integrated fine paper mill 20 January 2011 Page 17 The last bleaching stage could be a D-stage instead of a P-stage. 3. hydrogen peroxide and sodium hydroxide.5-4 P 75-80 150 ~10 (a) After P-stage 9 6 5 6 1 13 1 6 4 0. ClO2 as ClO2 and not as active Cl. and Table 3-4. Kappa number of pulp to bleaching: 10. . Table 3-3. For hardwood the bleaching sequence results in a yield of about 97.5 (a) For softwood the bleaching sequence results in a yield of 98%. Expected chemical charges for the birch kraft pulp with the sequence Dhot(EPO)DP to 90%ISO brightness ( kg/ADt). where the risk for scaling is the lowest. This is partly an economic decision which depends on the prices of chlorine dioxide. The expected bleach plant chemical charges and conditions are summarized in Table 3-3. for example mixing should be performed within critical temperature and pH limits. high bleaching chemical consumption. ClO2 as ClO2 and not as active Cl. Expected chemical charges for the SW kraft pulp with the sequence D(EPO)DP to 90%ISO brightness ( kg/ADt).5-11 D 75-80 150 3.5 1.5 (EPO) 80-85 75 10. Stage Temp (C) Time (min) pH ClO2 O2 H2O2 NaOH H2SO4 SO2 or NaHSO3 as SO2 D 70 60 ~2. Stage Temp (C) Time (min) pH ClO2 O2 H2O2 NaOH H2SO4 SO2 or NaHSO3 as SO2 Dhot 85-90 120 (EPO) 85-90 60 D 75-80 150 P 75-80 150 (a) After P-stage ~3 10. Bleach plant liquors must be handled in an optimal manner.7.1 System closure and degree of bleach plant filtrate recovery A high degree of system closure can create problems with scale formation within the bleach and evaporation plants.5 (a) Table 3-4. corrosion and plugging problems in the recovery boiler and problems controlling the Na/S balance of the mill. A final P-stage in place of a final Dstage may also decrease brightness reversion of the pulp. 8 Chlorine dioxide generation The selection of the chlorine dioxide process (R8 or R10) is mainly based on the millwide sodium/sulphur balance.Integrated fine paper mill 20 January 2011 Page 18 Based on experience a relatively conservative approach regarding system closure has been adopted to ensure sustained trouble free operation with good economics. Figure 3-2 shows the approximate liquor flows in the bleach plant. The bleach plant is designed to release 10-15 t/ADt of effluent.1 t/ADt 4. (R8 and R10 are the trade names from Erco. The filtrate from this wash press is then used as wash liquor on the 2nd D stage wash press. The filtrate from the (EPO) wash press is then transferred as wash liquor to the 2nd wash press after the oxygen stage. This range includes an allowance for up to 5 t/ADt of fresh water. Eka (Akzo Nobel) has similar processes called SVP. The dilution factor is about 2 t/ADt. 6 t/ADt of effluent is discharged from the paper machines.1 t/ADt Chemicals Hot water xx t/ADt ~2 t/ADt HD O2 D EPO D P To 1st O2 washer 4. Fresh water is used as wash liquor on the (EPO) stage wash press and condensate is used as wash liquor on the 1st D-stage press.) . 3. Hot/cold water Clean condensate Hot water ~5 t/ADt 4. Hot water is used as wash liquor on the wash press after the P-stage. The extra intake of fresh water also makes it possible to bleed out metals and Cl--ions. The approximate liquor flows (t/ADt) of the ECF bleach plant. This extra intake of fresh water can be used for dilution at any position in the bleach plant where there is a risk for precipitation. Additionally.5 t/ADt To treatment ~10t/ADt To treatment ~5 t/ADt Figure 3-3. The body operating with the strongest liquor in the first effect is heated by intermediate pressure steam from a steam ejector driven by MP steam and compressing LP steam. a strong black liquor storage tank is placed after the second effect. Ash mixing is done before the first effect. spills and condensates. Since there is no soap splitting and an excess of sulphur in the hardwood mill the R10 process is selected to minimize the amount of excess sulphur (which is purged as recovery boiler precipitator ash). Washing of the first effect is done one body at a time using weak black liquor. The (Na3H(SO4)2) by product.Integrated fine paper mill 20 January 2011 Page 19 In both the R8 and R10 processes purchased sodium chlorate reacts with sulphuric acid.9 Evaporation The evaporation plant is a conventional 7-effect system utilising LP and MP steam (Figure 3-4). All evaporator bodies are of the falling-film type. The first effect is divided into three bodies connected in series on the liquor side. It is designed to produce 80% dry solids liquor (including recovery boiler ash). Firing liquor at 80% DS is produced in the first effect. and to facilitate ash mixing. The firing liquor storage tank is pressurized due to the high dry solids content. Sludge from the biological treatment is mixed into the black liquor in an intermediate storage tank. and the seven effects are designed to operate in counter-current fashion. intermediate and strong black liquors well as for soap. In the softwood mill the R8 process is selected. and the H2SO4 is returned to the ClO2 generation process. i. The R10 process however has an additional step where Na3H(SO4)2 is split into Na2SO4 and H2SO4.e. To avoid upsets in firing liquor concentration when washing. to produce chlorine dioxide and the by-product Na3H(SO4)2. . Tanks are installed for weak. with live steam being fed to the first effect and weak liquor to the seventh effect. with methanol as the reducing agent. is used to partially replace sulphuric acid used for soap splitting. The other two bodies in the first effect are heated by LP steam only. 3. In mills which have a large excess of sulphur. Both strong gases and weak gases are burned in the recovery boiler.9.2 Handling of non-condensable gases Non-condensable gases (NCGs) are collected throughout the mill. A methanol rectification column with turpentine decanter and foul methanol liquid storage is also included. The stripping column is integrated within the evaporation plant to reduce the live steam consumption (Figure 3-4). . The surface condenser is designed for a warm water temperature of 50°C and to give condensate separation in principle as for the evaporators. Approximately 3. Evaporation condensates are divided depending on contamination degree and distributed to different consumers within the mill. 80oC) is used as wash liquor in the bleach plant.1 Handling of condensates A stripping system for foul condensates from the digester and evaporation systems is included.Integrated fine paper mill 20 January 2011 Page 20 3. an alternative is to incinerate the gases in a dedicated boiler. The methanol is incinerated in the recovery boiler. Approximately 4. 65oC) is used in the causticizing plant. and is discharged as effluent. Figure 3-4. The remaining condensate is also clean condensate.9. Evaporation plant including condensate stripper.5 m3/ADt intermediate condensate (approximately 1000 mg/l COD.5 m3/ADt of the cleanest condensate (approximately 200 mg/l COD. 3. These boilers were in general designed for 60 bar steam pressure and corresponding temperatures. the tall oil production is assumed to be 35 kg/ADt for softwood. With increasing electricity prices three new recovery boilers in Sweden have been designed for higher steam pressure and temperature. which means a sharp increase in investment and maintenance costs. At higher steam temperatures more expensive metallurgy is required for the superheater. has had higher electricity prices. where it is upgraded to crude tall oil. Some mills use carbon dioxide to pre-treat the soap. Finland. In this study the recovery boiler is designed to produce high pressure steam at 100 bar(g) and 505C. There is no soap from hardwood.Integrated fine paper mill 20 January 2011 Page 21 3. The water phase is separated from the soap oil.9. In Sweden the majority of existing recovery boilers were designed when electricity prices were low. The product after this pretreatment is a mixture of soap and tall oil (soap oil). The most common type of tall oil plant uses sulphuric acid for soap splitting. The soap is then pumped to the tall oil plant. and the majority of recovery boilers operate at 80-90 bar. Pre-treatment with carbon dioxide however reduces the sulphuric acid requirement by about 40%. and then the soap oil is treated with sulphuric acid as in a traditional tall oil plant. Mills that use an R8 process for chlorine dioxide generation can use the sodium sesquisulphate (Na3H(SO4)2) by-product to partly replace H2SO4 that would otherwise have been used for soap splitting. and a water phase containing sodium bicarbonate. . Higher steam pressure and temperature cannot be economically justified with low electricity prices.10 Recovery boiler The optimum recovery boiler steam pressure and temperature is not the same in different regions. and sulphur is thus added to the recovery cycle. With 50% pine and 50% spruce. The amount of soap depends on the wood used for pulping. 3. for example. In contrast. Newer boilers are often designed for greater than 100 bar pressure to maximize power generation.3 Tall oil recovery Soap that separates in the weak and intermediate black liquor tanks is decanted to a soap decanter and then led to a separate storage tank. Sootblowing steam 25 bar (g) FW heater HP steam 100 bar(g).l. 505 °C Boiler feed water FW heater Electrostatic Precipitator Flue gas cooler Flue gas Top preheated Combustion air Black liquor 80 %DS (incl. plant) .Integrated fine paper mill 20 January 2011 Page 22 Some of the key factors in the recovery boiler design which are related to maximizing power generation include: Feedwater preheating which increases steam generation and consequently the power generation. dust and biosludge) Weak wash Green liquor Smelt Dissolver Dust purge NCGs Dust recycle (mixed with b. Sootblowing steam is extracted from the turbine instead of using high pressure steam from the recovery boiler. The LP steam can instead be sent to a condensing turbine to produce power. Also reduces the negative impact of increased flue gas temperature due to feedwater preheating. Top preheating heating of all combustion air to about 205oC to increase power generation. One drawback of feedwater preheating is increased flue gas temperature after the economiser which increases the flue gas loss and increases the cost of the precipitator. in evap. Flue gas cooling after the precipitator – the heat uptake in the cooler will typically replace LP steam for combustion air preheating. Most of the dust is recycled and mixed with the black liquor in the evaporation plant. Dust that is not captured in the economizer section is removed in the electrostatic precipitator (ESP). The causticized liquor is filtered in a pressure disc filter. with the additional benefit of reducing potassium and chloride concentrations in the liquor cycle. which leads to low sulphur emissions from the bed. Alternatively the causticized liquor could be filtered using tube filters followed by another set of tube filters for the weak wash. Recovery boiler and smelt dissolver. A fraction of the dust is purged. Slaking and causticizing is performed in a single line with causticizing vessels in series.9. so the limits for chloride and potassium can be met by purging a small amount of precipitator dust (which is anyways necessary to maintain the sulphur and sodium balance). Green liquor from the storage tank is cooled in a flash-type green liquor cooler before the lime slaker-classifier. as described in section 3. The main advantage of a disc filters over other types of white liquor filters is the low liquor content of the discharged lime mud which eliminates the need for a separate lime mud washing stage.0% for potassium. Softwood and birch have relatively low levels of chloride and potassium. At the design pressure and temperatures for this boiler the maximum chloride concentration in the liquor is about 0. The dregs are washed and dewatered in a filter press before being discharged. Exceeding these concentrations increases the risk for recovery boiler corrosion and plugging problems.11 Causticizing The mill is equipped with conventional causticizing with both green liquor and white liquor filtration. The high liquor concentration contributes to a high bed temperature.Integrated fine paper mill 20 January 2011 Page 23 Figure 3-5. The green liquor is filtered in two parallel green liquor filter units. . mainly to control sulphur and sodium. With increased recovery boiler temperature and pressure the tolerance for potassium and chloride in the black liquor is reduced. Combustion air is distributed on multiple levels to facilitate complete combustion and minimize NOx formation. Dregs and grits are combined and sent to landfill. Condensate from the evaporation plant is used for dregs washing. 3.3 wt% and about 2. 3.Integrated fine paper mill 20 January 2011 Page 24 Green liquor Green liquor dregs Causticizer Lime kiln Condensate Slaker Lime mud removal Lime mud filter Disk filter Weak wash to smelt dissolver tank White liquor filter Clarified white liquor Figure 3-6. and since the late 1980’s a large number of existing kilns have been equipped with an external dryer to increase kiln capacity. . Condensate from the evaporation plant is used for lime mud dilution and hot water for the lime mud filter wash showers. Lime mud from the lime mud vessel is pumped to the agitated lime mud storage tank. Spills are reclaimed from two spill sumps and pumped to the weak wash storage tank. This arrangement allows a shorter kiln compared to a conventional kiln where the lime mud is dried inside the kiln. The external lime mud dryer consists of a vertical flue gas duct where the lime mud is dried and preheated by the hot flue gases.12 Lime kiln The lime kiln is equipped with an external lime mud dryer and modern product coolers. Modern types of product coolers demand less space and have lower radiation heat losses than conventional planetary coolers. White liquor preparation (white liquor disc filter option). External lime mud dryers are incorporated in the majority of new kilns today. The lime mud is washed and dewatered on a lime mud disc or drum filter. The dry mud is separated from the flue gases in a cyclone and then introduced to the kiln. the the paper mill has two identical paper machines. . a number of European mills use bark or wood residues as fuel for the lime kiln.Bleached softwood . Both PM1 and PM2 produce uncoated fine paper from softwood and hardwood. The biomass is either pulverized and fired directly.13. however. A detailed review of the biomass fuel is not in the scope of this project. or gasified and then fired in the kiln. primarily to control phosphate levels.13 Paper Mill 3. in terms of the overall mill energy balance they are similar. There are many differences between these two processes. The ID fan is installed downstream the precipitator. Each paper machine has an annual production of 511 000 t/a. The furnish composition is shown below. 3. A fraction of the lime mud is purged. Limestone is used for make-up.Integrated fine paper mill 20 January 2011 Page 25 Dust is removed from the flue gases by means of an electrostatic precipitator.Bleached hardwood 25% 75% 19% 56% The corresponding furnish requirements for each paper machine are: Bleached hardwood Bleached softwood Filler Starch 573 000 191 000 235 000 27 600 ADt/a ADt/a t100/a t100/a A block diagram for PM1 and PM2 is shown in Figure 3-7. and either can be used. however the main fuel for the lime kiln is bark or wood residue. To save on oil consumption.1 Capacity To match the capacity of the kraft pulp mill. PM furnish composition Filler Fibre . Process concept of the fine paper machines . soft wood pulp chest Bleached hard wood Bl. hard wood pulp chest Intermediate pulp Intermediate pulp chest Filler Refiner Soft wood dosing chest Refiner Hard wood dosing chest Mixing chest Screen Machine chest Filler Storage tower Broke dosing chest Filter Broke tower deaeration Screen and deaeration Wire silo Headbox Wire section Pulper Press White water tank Dryer Disc filter Sizer White water tower After dryer Pulper Pulper Pulper Pulper Calender Pulper Reel/Finishing Figure 3-7.Integrated fine paper mill 20 January 2011 Page 26 White water to bleaching plant Bleached soft wood Bl. 2 Stock preparation 3. The barrier screening system is installed between the mixing chest and the machine chest and in this position will screen both the virgin pulp supplied to the paper machine as well as the broke. In this mill hardwood and softwood are refined separately to optimise their properties. which is proportioned to the paper machine.5 Mixing/machine chest After the mixing chest there is a final consistency control and the thick stock is screened with slotted barrier screens.13.13. 3. Since there is not a perfect plug-flow through the pulp mill.13. the pulp is diluted and pumped via refiners to the hardwood and softwood dosing chests.4 Broke system Broke from all the pulpers on the machine is pumped via the couch pit to the broke storage tower (3500 m3). Broke. 3. there will be some intermediate pulp produced when changing from hardwood to softwood. pulp is diluted and proportioned to the mixing chest. pulp is diluted and pumped to their respective pulp chest.Integrated fine paper mill 20 January 2011 Page 27 3. the pulp is dewatered on a thickener and taken to the broke dosing chest at about 4% consistency.6 Filler supply Filler is dissolved and stored in a 1 000 m3 storage tower at 40% concentration. Filler is added to the short circulation of the paper machine. 3. There are three MC-storage towers of 10 000 m3 each for hardwood and three MC-storage towers of 7 500 m3 each for softwood. . This intermediate pulp is stored in a 3 500 m3 MC-tower. Intermediate pulp is pumped via the hardwood refiner to the hardwood dosing chest. From the dosing chests.13. From the pulp chests. From the MC-storage towers.3 Bleached kraft supply The pulp mill produces softwood and hardwood in campaigns of 30 h and 70 h respectively. From the broke tower. is pumped via a deflaker to the mixing chest and some of the pulp is re-circulated to the tower to increase the consistency in the tower.13. Since this correction is not made by the slice lip. de-aeration equipment. which means that dilution water is added via special control valves across the machine width in the headbox. the QCS-system. Filler is charged ahead of the head box pump. The paper machine is dimensioned for 1850 m/min. The dryer section consists of a pre-dryer section and an after dryer section. or alternatively only after the machine screen 3.13. The press concept is two straight shoe presses following each other giving a final dryness after the press section of approx. The short circulation then consists of the wire silo. fibre orientation is not influenced. The wire section is a modern twin wire section to give the best paper uniformity with regard to formation. 52%. The pre-dryer section is a combination of drying cylinders in an upper row and vacuum assisted rolls in a lower row integrated with an air handling system including web stabilising equipment for increased runnability and minimum energy consumption. Retention aids are added before the machine screen and after the machine screen. A high dryness content of the web leaving the press section as well as an equal-sidedness are other important factors the press section has to perform. .Integrated fine paper mill 20 January 2011 Page 28 3. The charge is controlled by the QCS-system to give a constant filler level in the paper independent of the amount of broke added.8 Paper machine The paper machine is based on a concept to allow for a high quality fine paper production at a high machine efficiency and high speed. The headbox is of dilution control type and the system includes two speed-controlled pumps. basis weight profile. ash profiles and sheet structure.7 Short circulation As a consequence of the barrier screening. Each valve setting is based on information from the measuring frame in the dry end. it is possible to reduce the power consumption by eliminating the hydrocyclone system in the short circulation. The press section is designed for optimum runnability of the machine by means of a closed web run from the wire section to the dryer section. de-aeration and a pressure screen. fan pump and machine screening in two stages. The paper machine headbox is of a cross profile dilution type.13. but through local changes in stock consistency. 6 m the nip load as well as the parent roll torque has to be controlled and this is the case with all modern reel system today.6 m a winder type giving a lower linear nip load between finished roll and supporting winder rolls is needed. but with a roll diameter of 1.Integrated fine paper mill 20 January 2011 Page 29 The sizer after the pre-dryer section adds surface size to both sides of the web by means of an application roll system to increase strength properties of the paper. Winding fine paper is not so critical as winding coated paper and for this reason a centre winder is not needed. This arrangement is for curl control of cutsize papers which need special consideration regarding flatness and runnability in copying machines etc. The sizer is followed by the after dryer section which is a combination of dryer cylinders and vacuum rolls in the first part followed by a conventional dryer section with drying cylinders both in top and bottom position. annual average m/min m/min m g/m2 t93/h % % % % % % days t93/day 1 850 1 690 9 80 (75-160) 73.1 93 56 19 25 3 82 355 1 439 . For finished rolls with a diameter of 1. Main data for papermachines Speed design Speed at pope Width on pope Grammage Production on pope (100% eff.) Paper dryness PM furnish composition -Hardwood -Softwood -Filler Surface size of paper (starch) Paper mill efficiency Operating days per year Paper production net.5-1.4-3.2-1.4 m a common two drum winder is sufficient. Main data for the papermachines are presented in Table 3-5. To build a high quality parent roll with a diameter of 3. The calender is of soft calender type in a tandem arrangement to give the optimum surface properties. This way of building a parent roll will give the best conditions when handling the roll in the winder. Table 3-5. The surplus clear filtrate is pumped to the bleach plant.0 GJ/t evaporated water is needed for drying. 3.13.13. Warm water is received from the kraft mill.and press sections and for dilution of different chemicals.10 White water system and buffer volumes The paper machine white water system consists mainly of a white water tank for paper machine excess water connected to a disc filter save-all. it is the used buffer volume that is important.13. Accidental discharges are avoided with a dimensioning of broke. About 3. which means that the white water storage towers in the system should have a volume corresponding to the total sum of all pulp storage towers. A white water tower which is always filled provides no buffer volume. A correct dimensioning and use of the storage buffer volumes also means minimal variations in the flow of waste water to the external treatment plant which should result in higher treatment efficiency and lower investment and operation costs for the external treatment plant. Used cooling waters and other uncontaminated process waters are collected separately and re-circulated via a cooling tower to the fresh water systems. The process related fresh water consumption is about 6 m3/t of paper. To be correct it is not the physical volumes that should be equal. Clear filtrate from the disc filter is used for showers in the wet end and is also stored in a white water storage tower (5 500 m3) to be used for consistency control and for broke dissolving.9 Fresh water system The warm water system is the main fresh water consumer in the paper mill. pulp and white water storage buffer volumes in balance. The efficiency of the paper machines (need for re-drying of broke) and the dryness of the paper .11 Energy aspects of the paper machine The main input of energy to the paper machines is steam for drying of the paper. Kraft mill MCR Paper production net t93/day t93/year 1 565 511 000 3. Warm water is mainly used for high pressure cleaning showers in the wire. 3.Integrated fine paper mill 20 January 2011 Page 30 Paper production net. 46 4. GJ/t paper GJ/t paper GJ/t paper kWh/t paper 3 m /t paper 52 93 0. A high temperature improves the dewatering on the wet end and minimises bacteriological and slime problems. the heat consumption for drying is 3. The desired level is somewhere in the range 5255oC. Steam is also used for heating purposes on the paper machine.0 . With a press dryness of 52%. screens.77 0.14 10 1.5 bar steam box heats the web to increase dryness and improve dryness profile. a final dryness of 93%.26 3.Integrated fine paper mill 20 January 2011 Page 31 after the press section are of great importance for the steam consumption. drives and refiners in the paper mill.0 3. In the press section a 3. The main part of this power consumption is in motors for pumps. 3% surface size and 10% redrying. The high dryness of the pulp from the pulp mill means that only a small amount of thermal energy is transferred with the pulp from the pulp mill. The air to the blow boxes must also be heated with steam.77 GJ/t paper.82 0. the process water loses about 10 MW of heat to the surrounding air by evaporation. The total consumption of electric energy for the paper machine is about 550 kWh/t. Table 3-6.23 550 6.23 GJ/t paper.32 1. refining Water consumption % % t/t paper t/t paper t/t paper % t/t paper GJ/t evap. Paper machine energy consumption data Dryness to dryer Paper dryness Evaporated Evaporated sizing Sum evaporated Redrying etc Total evaporation Heat consumption Heat consumption drying Heat consumption miscellaneous Total heat consumption paper mill Power consumption incl. Most of this energy is going into the process flow as thermal energy and contributes to keeping the system temperature on a high level. On the wire section. To maintain the desired white water temperature. The total consumption of steam on the paper machine is about 4. heat is transferred from the heat recovery system of the drying section to the paper machine white water. Biosludge Falling Bark Electrostatic Precipitator Combustion air Figure 3-8. Bubbling fluidised bed power boiler .14 Power boiler The recovery boiler alone does not produce enough steam to meet the demand of the integrated fine paper mill.Integrated fine paper mill 20 January 2011 Page 32 3. plus sludge from the effluent treatment plant. and there is no need for an additional fossil fuel fired boiler dedicated for startups and shut downs. HP steam 100 bar(g). The power boiler is designed to provide steam for mill start-up and shut downs. The power boiler is designed with a bubbling fluidised bed (BFB). The power boiler is fuelled with wood residues from the woodyard and chip screening areas. A power boiler is therefore used to produce the additional steam. 505 °C Sootblowing steam 25 bar(g) Boiler feed water Flue gas Primary Sludge Sec. 0 25. Steam data.15 Steam turbines and steam distribution Steam is reduced through a backpressure steam turbine to 3. This pressure has been selected to facilitate maximum electric power production without requiring unnecessary large evaporator bodies or heat surfaces in the paper machines. the surface condenser of the evaporation plant. the system can be divided into two parts: one where heat is recovered for the production of warm and hot water. The cooling water system is integrated with the process water system. The design of the model mill is conventional.Integrated fine paper mill 20 January 2011 Page 33 3. The heat is used for hot water production and for boiler feedwater heating. Table 3-7. approximately one third of all the energy that is introduced with the fuel to the system will have to be cooled away by a cooling system. desuperheated °C 505 275 200 150 bar(g) 100. The secondary energy system comprises the recovery of heat that is generated from steam and electricity and that is finally withdrawn from the system by cooling. and the turpentine condenser. Intermediate pressure steam of 25 bar(g) is extracted for soot blowing and 9 bar(g) steam is extracted to the MP-steam system. another part where excess heat is cooled by the means of a cooling tower. the smelt dissolver vapour condenser. HP steam IP steam.16 Cooling and recovery of low-temperature heat In addition to normal heat losses of different kinds. MP steam and LP steam are de-superheated with boiler feedwater before distribution. .0 9.. except for the very low fresh water consumption. e. extracted for sootblowing MP steam.5 bar(g).5 3. HP steam not required in the process is utilised in a condensing steam turbine for further electric power generation. Cooling is carried out in cooling towers. In principle.g. See Appendix 3 for the secondary heat balance. Low-temperature heat is recovered from a number of sources in the kraft mill. Condensate from the evaporation plant is used in the pulp washing and in the lime mud wash. desuperheated LP steam.0 3. After the clarifier the suspended solids content is about 50 mg/l. After the primary clarifier the effluent is screened. Suspended solids out from the secondary clarifier are about 50 mg/l. Table 3-8. The activated sludge system is comprised of an aeration basin and secondary clarifier. and discharges are calculated as long term mean averages. Effluent treatment consists of pre-treatment. Inlet data to biological treatment. depending on the price). Softwood campaigns 60 000 1 220 73 000 50 3 000 ~37 ~7 3 000 Hardwood campaigns 70 000 1 200 84 000 50 3 500 ~37 ~7 3 500 Total effluent COD SS Temperature pH Primary sludge m /d mg/l kg/d mg/l kg/d °C kg DS/d 3 For biological treatment there is a bio-film reactor with suspended carriers followed by an activated sludge system. Effluent treatment is designed for hardwood campaigns. The estimated suspended solids content of the effluent from the mill pulp and paper mill is about 100 mg/l. primary treatment and biological treatment. before firing in the recovery boiler. In the pre-treatment there is a primary clarifier to remove fibre sludge. (cooling equipment and neutralisation). The biological sludge is dewatered to about 10% in a centrifuge and mixed with intermediate black liquor in the evaporation plant. . The primary sludge is dewatered in a centrifuge and incinerated in the power boiler (alternatively the primary sludge could be sold to a fluting mill or similar. and the pH is adjusted to about 7. COD reduction is estimated to be about 65-70% for softwood and about 70-75% for the hardwood mill.Integrated fine paper mill 20 January 2011 Page 34 3. The system is designed for low bio-sludge production and low nutrient discharges.17 Effluent treatment Pulp is produced in campaigns with softwood 25% of the time and hardwood 75% of the time. cooled to about 37oC with heat exchangers or cooling towers. Integrated fine paper mill 20 January 2011 Page 35 Nutrients Acid/Base (if necessary) (if necessary) Screen From Kraft Pulp mill Primary clarifier Cooling Biofilm reactor with suspended carriers Air Centrifuge Return sludge Polymer Biological sludge Centrifuge Aeration basin Secondary clarifier From Fine paper mill Primary sludge for fiber reuse Intermediate black liquor 80-90°C To recovery boiler Figure 3-10. as well as possible liquor contaminated condensates. The spill system includes: Adequate instrumentation to minimise the risk for overflow of tanks and equipment. and to detect accidental spills. Flow COD reduction COD out SS out m /d % kg/d mg/l kg/d kg/d 3 Softwood 60 000 65-70 < 25 550 50 3 000 ~ 7 100 Hardwood 70 000 70-75 < 25 200 50 3 500 ~9 700 Biological sludge 3. .18 Spill handling system Accidental spills caused by abnormal operation or equipment failures can be a significant contribution to the effluent emissions from the mill. The mill is designed with a comprehensive sewer system to collect accidental spills as close to the source as possible and directly recycle them to the proper process stage. The evaporation plant is designed with additional capacity to take care of black liquor spills in that area. Floor channels connected to pump sumps from which liquids can be pumped back to the process. and therefore it is important to minimise spills. Provisions to take care of process liquors when it is necessary to empty tanks or equipment for maintenance Retention dams around tanks and equipment. Outlet data from biological treatment. Effluent treatment plant Table 3-9. The water from the turbine oil cooler is dumped. The cooling is performed in a cooling tower. which means that part of the process water comes from the cooling water system. . The cooling water system is semi-open. As precipitation chemical some kind of Al-salt and polymer is used.Integrated fine paper mill 20 January 2011 Page 36 Emergency effluent treatment pond for major spills or upset conditions in the effluent treatment plant. Data. 3. raw water treatment. The amount of process water coming from the cooling system is controlled so that the cold water temperature is maintained at about 18oC. Well-educated and trained personnel who understand the importance of spill handling. chemically treated water. Clear water well. Table 3-10. Sand filtration. Chemical treatment in a dissolved air flotation (DAF).19 Water supply and treatment Water is basically used for two purposes in the mill: process water and cooling. Flow Raw water sludge m /d kg/d 3 70 000 – 80 000 ~2 700 The raw water intake should be arranged and designed to minimize the amount sand and other debris which enters the mill. including storage capacity for fire fighting. There are filters in the cooling water system to avoid impurities in the mill process water. There is a separate cooling water loop for the turbine. Other coolers in the mill are connected to the general mill process water system. Water from such coolers that could contaminate the water should also be dumped. The raw water quality is normally good in Nordic rivers. with the following treatment sequence: Water intake with coarse screening. Raw water sludge is discharged to the receiving water together with treated effluent. The mill water system has only one quality. Integrated fine paper mill 20 January 2011 Page 37 Al Polymer Air Screen Raw water intake Dissolved air flotation Sand filtration Clear water well Raw water sludge Figure 3-11. . Water treatment. the recovery boiler alone does not produce sufficient steam. and therefore the mill has a small bark boiler. a condensing turbine is included to maximize power generation. During hardwood campains however. fuel price. During softwood campaigns the recovery boiler alone produces sufficient steam for process steam consumption and cogeneration of power in the back-pressure turbine.energy balance The model integrated fine paper mill is very energy efficient. In this study it is assumed that only falling bark is available. Key factors which make the model mill energy efficient include: High HP steam data. and the resulting bark boiler and condensing turbine are relatively small. and electricity prices.Integrated fine paper mill 20 January 2011 Page 38 4 Model mill . Note that even with the condensing turbine the mill still needs to purchase electricity during both hardwood and softwood campaigns. Since the mill has a bark boiler and excess falling bark. In this case there is a slight excess of steam. In this case there is still an excess of bark which could be sold. more chlorine dioxide and less hydrogen peroxide allow a lower bleaching temperature Low pressure steam used in the paper machine . An alternative that must be evalulated in reality is purchasing bark to further increase power generation to meet the full demand of the mill and possibly produce power for sale. and all falling bark could be sold. Such an economic evaluation is very mill specific. 505oC Feed water preheating to 175oC to increase HP steam generation Recovery boiler flue gas cooler to reduce LP steam consumed in air preheating Top preheating of all recovery boiler combustion air to 205oC Recovery boiler sootblowing steam is extracted at 25 bar(g) from the turbine instead of using HP steam Latest technology for pulp digesting which has a lower cooking temperature than other systems 7 effect evaporation plant Steam consumption in the bleach plant is reduced. and depends on investment cost. 100 bar(g). marginal steam cost. and make use of the excess recovery boiler steam which otherwise would be wasted during softwood campaings. During both hardwood and softwood campaigns the back pressure power generation is not sufficient to meet the mill requirement. Overall energy balance – softwood campaigns .Integrated fine paper mill 20 January 2011 Page 39 Pressurized condensate system High temperature of hot water. and further details of the balances are included in Appendix 2.5 0. Model Fine paper SW campaign Pulp SW HW Market 2 000 ADt/d 2 000 ADt/d 0 ADt/d 0 ADt/d 35 MW 0.0 0.3 Sec heat 8.7 121.4 146 °C 1. tDS/d Sold bark. tDS/d 203 217 0 Figure 4-1.90oC.7 594. losses Steam to feedwater tank G 14.4 0.7 111.3 0.0 117.0 Condensate return 128 °C Bark to lime kiln. and paper machine Bark press for bark to the power boiler An overview of the energy system and balances for the model mill during softwood and hardwood campaigns are shown in Figure 4-1 and Figure 4-2.6 25.5 15.0 MW 75 °C 26.8 Recovery Boiler Soot blowing Air preheat Feedwater Preheating Steam flows t/h 505 °C 0.0 0.4 0.4 0.3 113 °C 96.5 10.2 2. and maximum use of hot water instead of steam in the bleach plant.0 0.9 3.0 2.5 0.0 0. white water system Evaporation Chemical preparation Causticising Paper machine Building heating Blow off Miscellaneous.0 Production Back-pressure Condensing Bought Sum 46.0 14.1 15 °C Mixed bed 420.1 45.0 121.5 MW G 62.0 11.7 46.0 bar(g) 96.0 bar(g) Powe r balance Consumption Process Sold Sum MW 121.4 9.7 35 °C Make-up 119.7 2. 85 .7 6.2 MW 0.8 35.5 bar(g) 34 °C 434.4 Air preheater bark boiler Digester Bleaching Oxygen stage Evaporation Chemical preparation Feedwater preheat Miscellaneous. losses Air preheater recovery boiler Air preheater power boiler Smelt shattering Digester Bleaching Pulp machine Pulp machine.4 3.0 MW 46.0 237.0 0.0 MW 412 MW 49.0 MP-steam 46.3 Bark Boiler 100 bar(g) 591. tDS/d Bark to bark boiller. 2 0.8 Air preheater bark boiler Digester Bleaching Oxygen stage Evaporation Chemical preparation Feedwater preheat Miscellaneous.2 MW G 66.4 52.0 0.0 4. tDS/d Bark to bark boiller.9 35 °C Make-up 144. losses Steam to feedwater tank G 20.0 bar(g) Powe r balance Consumption Process Sold Sum MW 124.1 21.7 3.4 MW 0.0 Production Back-pressure Condensing Bought Sum 64. losses Air preheater recovery boiler Air preheater power boiler Smelt shattering Digester Bleaching Pulp machine Pulp machine.0 0.0 0.Integrated fine paper mill 20 January 2011 Page 40 Model Fine paper HW campaign Pulp SW HW Market 2 500 ADt/d 0 ADt/d 2 500 ADt/d 0 ADt/d 70 MW 0.5 MW 75 °C 36.0 MW 97.1 112 °C 103.0 MP-steam 64. Overall energy balance – hardwood campaigns .0 37.0 124.9 3.9 644.1 4.5 Condensate return 129 °C Bark to lime kiln.1 124.1 16.4 Recovery Boiler 426 MW 505 °C Soot blowing Air preheat Feedwater Preheating Steam flows t/h 0.5 51.0 11.0 0.9 MW 64.9 3.4 0.0 25.2 0.0 15 °C Mixed bed 440.0 bar(g) 103.0 0.1 Sec heat 10.9 20. tDS/d Sold bark. tDS/d 211 432 0 Figure 4-2.0 127.0 237.5 9.9 0.5 bar(g) 32 °C 453.0 0.8 Bark Boiler 100 bar(g) 611.9 137.3 146 °C 3. white water system Evaporation Chemical preparation Causticising Paper machine Building heating Blow off Miscellaneous.8 1.1 0. is included here. The type mill has energy production and consumption similar to existing Swedish mills. . Table 5-1 and Table 5-2 summarize the key operating and dimensioning data for the type mill. from the FRAM project.Integrated fine paper mill 20 January 2011 Page 41 5 Comparison of model mill and typical mill To indicate potential energy savings. energy balances for a typical fine paper mill. compared to the model mill. Softwood Softwood Hardwood Hardwood Model Type Model Type 2 000 1 000 2 500 1 250 Pulp production Wood yard Wood to digester Bark and wood waste Digester Plant Kappa number Unscreened deknotted digester yield Alkali charge on wood as EA Sulphidity (white liquor) Oxygen Stage Kappa number after oxygen stage Alkali charge as NaOH Oxygen charge Washing Department Dilution factor in the last stage Evaporation Plant Weak black liquor to evaporation. including spill Recovery Boiler Estimated higher heating value of virgin DS Strong liquor virgin solids to mixing tank Net useful heat from liquor.0 80 771 441 16.0 20.3 200 mole-% 3 m /24 h t/24 h % 82 7 541 534 90 82 3 984 272 90 82 7 831 554 90 82 4 215 288 90 .1 20.5 t/h % % t/h 913 16.5 19.5 2. excl. 3 2. Type mill.Integrated fine paper mill 20 January 2011 Page 42 Table 5-1. dry solids content incl.7 80 840 475 16.5 195 13.0 3 477 10. Summary of key pulp mill data – Model mill vs.3 413 14.0 35 17 51.5 2.5 35 17 50.5 2.5 73 393 MJ/kg t/24 h MJ/kg DS MW 14. virgin solids Net useful heat from liquor Causticizing and Lime Kiln Causticizing efficiency Total white liquor production Lime kiln load Active CaO in lime ADt/24 h t/24 h t/24 h 4 072 420 2 065 193 4 610 642 2 328 298 % NaOH.0 35 kg/ADt kg/ADt 12 25 20 14 25 20 12 18 14 10 20 14 m /ADt unbl.9 73 359 981 15.0 1 778 9.spill ditto dry solids content Strong black liquor.0 426 13.0 35 27 46.8 3 668 10.0 18. ash Total evaporation.% mole-% 30 47.9 1 866 9. the alkali charge is increased.1. without chip bin presteaming. .8 80 (75-160) 37 93 % % % % 56 19 25 3 56 19 25 3 t/d t/a ADt/a ADt/a t100/a t100/a 3 100 1 022 000 573 000 191 000 235 000 27 600 1570 512 000 287 000 96 000 118 000 13 800 5.1 Type mill –process description Following is a brief description of the type mill. with emphasis on the factors which are different from the model mill. Kraft mill MCR Paper production net (PM1 + PM2) Bleached hardwood consumption Bleached softwood consumption Filler consumption Starch consumption m/min M 2 g/m t/h % 1 690 9 80 (75-160) 73 93 Type 980 7.Integrated fine paper mill 20 January 2011 Page 43 Table 5-2. 5. Model Speed at pope Width on pope Grammage Production on pope (100% eff. Summary of paper mill key operating data. To achieve maximum production in the digester. and which affect the mills’ energy balances.) Paper dryness PM furnish composition -Hard wood -Soft wood -Filler -Surface size of paper (starch) Paper production net (PM1 + PM2). The loading of the digester is also normally raised over the years and therefore the cooking temperature is higher than in new digesters. The type mill has a two flash digester and a cooking temperature of 165ºC for softwood and 162ºC for hardwood.1 Digester Many existing mills still use the old “conventional” two flash digester. WL (NaOH) ClO2 O2 H2SO4 NaOH H2O2 MgSO4 SO2 (OO) D0 (EOP) D1 D2 95 70 90 70 70 23 16 7 5 6 3 5 14 2 2 2 0.5 1 . Expected chemical charges for the HW kraft type mill with the sequence (OO)D(EOP)DD to 90% ISO brightness ( kg/ADt). The bleach plant is a little more open than in the model mill. ClO2 as ClO2 and not as active Cl. Expected chemical charges for the SW kraft type mill with the sequence (OO)D(EOP)DD) to 90% ISO brightness ( kg/ADt).1. The bleach plant has vacuum washers in all positions. 5.1. Washing before the stage is on a vacuum filter. Stage Temp (C) Ox. The type mill is assumed to have a retrofit oxygen stage with vacuum filter before oxygen stage and wash presses after. Stage Temp (C) Ox. which together with the higher wash water flows needed for filters results in about twice the effluent from the bleach plant compared to the model mill. ClO2 as ClO2 and not as active Cl. These require more washing liquid than wash presses and therefore increase the water consumption and the heat needed for heating the water.1.2 Oxygen stage The type mill has a single oxygen stage with limited kappa reduction from 27 to 16 on softwood. 5.4 Bleaching The ECF bleach sequence in the typical mill uses much more ClO2 and less H2O2 than in the model mill.5 1 Table 5-4. Hardwood is the same as in the reference mill. WL (NaOH) ClO2 O2 H2SO4 NaOH H2O2 MgSO4 SO2 (OO) D0 (EOP) D1 D2 95 70 90 70 70 30 21 8 7 7 3 4 17 2 2 2 1 0.3 Pulp washing Vacuum filters were once the standard equipment for pulp washing and many are still in use.Integrated fine paper mill 20 January 2011 Page 44 5. 17 to 10. Table 5-3. 2 ton/ADt H20 7. The liquor flows (m /ADt) of the type mill ECF bleach plant. giving higher energy consumption.4 ton/ADt 0.9 ton/ADt D2-filtrate 8.01 ton/ADt H 20 4. The water consumption is higher. about 46%.9 ton/ADt D0 OP D1 D2 To effluent treatment 4.4 ton/ADt 0. and production is usually not greater than 255 000 t/a. . about 1000 m/min. The forming section if of hybrid type.3 ton/ADt 0.8 ton/ADt 0. an initial fourdrinier forming followed by twin-wire forming.5 m3/ADt. i. The dryness after the press section is lower than in the reference mill. The press is a four-nip press section with a steam box before the fourth nip..8 ton/ADt Figure 5-1. about 700 kWh/t.1.Integrated fine paper mill 20 January 2011 Page 45 H20 8. Table 5-5 summarizes consumption data for the papermachine. The dilution factor is 2. The approach flow system is equipped with cleaners and is therefore more power consuming than the reference mill which has “guard screening” systems.5 Paper machine The type mill fine paper machines operate at lower speed.1 ton/ADt To D1-filter To effluent treatment 1.e. thereby giving a higher cost for heating The total consumption of electric energy is higher than the model mill. 3 5.4 ton/ADt To effluent treatment 8.3 ton/ADt 0.1 ton/ADt To effluent treatment 9. Many strippers today are therefore not fully integrated in the evaporation plant.6 Evaporation The capacity of existing evaporation plants can easily be increased in small steps by adding new evaporator bodies.0 3.50 3. Earlier most evaporation plants were built with five-effect economy. For the type mill it is assumed that the evaporation plant on average operates with 5.0 4.77 0. Also only the most contaminated condensate is stripped.1. After increasing the evaporation plant many existing mills therefore have a combination of five. A stripper for the evaporation plant is nowadays standard.and six-effect economy.26 3. but has not always been.51 0. The type mill has a conventional combustion air system where approximately 85% of the combustion air is heated to 165oC (compared to preheating of 100% of the combustion air to 205oC in the model mill). refining Water consumption % % t/t paper % t/t paper GJ/t evap.0 Type 46 93 1. 5. some are completely separate and some recover the steam partly in the evaporation plant.23 550 6.82 10 1. compared to the model mill where feedwater is preheated from 146oC to 175oC. The strong liquor from the evaporation plant has 72% dry solids content and only LP-steam is used for the evaporation.97 700 10 5. Paper machine consumption data – Model mill vs Type mill Dryness to dryer Paper dryness Evaporated Redrying etc Total evaporation Heat consumption Heat consumption drying Heat consumption miscellaneous Total heat consumption paper mill Power consumption incl.06 10 1. GJ/t paper GJ/t paper GJ/t paper kWh/t paper 3 m /t paper Model 52 93 0. The type mill has a separate stripper for 2 m3/ADt. The type mill has a feedwater temperature of 125oC.46 4.46 4. .Integrated fine paper mill 20 January 2011 Page 46 Table 5-5.5 effect economy.1.7 Recovery boiler The recovery boiler in the type mill does not have flue gas cooling as in the model mill. The type mill uses 60 bar and 450°C. Older digesters like the one chosen for the type mill. The MP-steam pressure is therefore increased from 9 to 10 bar(g) in the typical mill.10 Steam turbines and steam distribution The very clearly dominating data for the HP-steam in typical mills in Sweden today is 60 bar and 450ºC. 5. Due to the assumed high load on the recovery boiler the steam consumption for the soot blowing is increased from 1 to 1.1.Integrated fine paper mill 20 January 2011 Page 47 The soot blowing steam is extracted from the recovery boiler directly and not from the turbine. . Some mills operated at 40 bar and in Finland 80 bar is also common. The efficiency of the turbine is also lower than for modern turbines.5 GJ/ADt.8 Lime kiln The lime mud has a dryness of 70% and the lime kiln is fired with mineral oil. which are often overloaded. When the typical mill was originally built there was no steam surplus from liquor and falling bark. There is no bark press and the bark is fired at 40% dryness. Typical mill have increased production over the years with debottlenecking measures and the steam turbines have consequently become too small to take care of all the steam. and therefore no condensing turbine. The MP-steam pressure in the mill is normally set according to the demands from the digester.1. 5. PRVs.9 Power boiler With higher steam consumption in the type mill compared to the model mill. wood fuel must be purchased for the power boiler. The model mill has a modern digester with low cooking temperature. 5.1. The common feedwater temperature of 125ºC is used in the type mill compared to 146oC in the model mill. Part of the HP-steam must therefore be reduced directly to lower pressures by pressure reducing valves. need higher cooking temperatures. due both to wear and less original efficiency. Integrated fine paper mill 20 January 2011 Page 48 5.2 Energy balance comparison – Model mill vs type mill Steam and power balances, as well as bark balance for the model mill are compared to the type mill from the FRAM project in Table 5-6 to Table 5-11. Table 5-6. Steam balance, GJ/ADt pulp Consumption Recovery boiler soot blowing Recovery boiler blow down Power boiler Woodyard Digester Oxygen stage Bleaching Paper machine Evaporation Stripper Chemical preparation Causticising Hot water production Heating etc Miscellaneous, losses Total process consumption Surplus steam (blow off LP) Back-pressure turbine Condensing turbine Total consumption Production Recovery boiler Bark boiler Secondary heat Total production Softwood Model 1.02 0.05 0.02 0.00 1.55 0.08 0.22 6.62 3.49 0.00 0.10 0.00 0.00 0.00 0.45 13.61 0.00 4.30 1.78 19.69 Type 1.71 0.03 0.01 0.14 2.57 0.18 0.35 7.79 4.45 0.54 0.10 0.05 0.37 0.09 0.66 19.03 0.00 3.14 22.17 Hardwood Model Type 0.85 1.31 0.04 0.03 0.04 0.01 0.00 0.13 1.38 2.09 0.08 0.21 0.58 0.40 5.30 6.20 3.04 3.97 0.00 0.53 0.10 0.07 0.00 0.05 0.00 0.36 0.00 0.07 0.39 0.59 11.80 16.05 0.00 3.72 1.98 17.50 0.00 2.34 18.40 17.82 1.53 0.35 19.69 16.77 4.89 0.51 22.17 14.71 2.43 0.36 17.50 14.01 3.94 0.45 18.40 Integrated fine paper mill 20 January 2011 Page 49 Table 5-7. Steam balance, (GJ/t paper). Consumption Recovery boiler soot blowing Recovery boiler blow down Power boiler Woodyard Digester Oxygen stage Bleaching Paper machine Evaporation Stripper Chemical preparation Causticising Hot water production Heating etc Miscellaneous, losses Total process consumption Surplus steam (blow off LP) Back-pressure turbine Condensing turbine Total consumption Production Recovery boiler Bark boiler Secondary heat Total production Softwood Model Type Hardwood Model Type 0.65 0.03 0.01 0.00 0.99 0.05 0.14 4.23 2.23 0.00 0.06 0.00 0.00 0.00 0.29 8.70 0.00 2.75 1.14 12.59 1.09 0.02 0.01 0.09 1.64 0.11 0.22 4.96 2.83 0.34 0.06 0.03 0.24 0.06 0.42 12.12 0.00 2.00 0.00 14.12 0.68 0.03 0.03 0.00 1.10 0.06 0.46 4.23 2.43 0.00 0.08 0.00 0.00 0.00 0.31 9.42 0.00 2.97 1.58 13.98 1.04 0.02 0.01 0.10 1.66 0.17 0.32 4.94 3.16 0.42 0.06 0.04 0.29 0.06 0.47 12.78 0.00 1.86 0.00 14.65 11.39 0.98 0.22 12.59 10.68 3.11 0.32 14.12 11.75 1.94 0.29 13.98 11.15 3.14 0.36 14.65 Integrated fine paper mill 20 January 2011 Page 50 Table 5-8. Power balance, kWh/ADt pulp Power consumption Wood yard Digester Washing and screening Oxygen stage Bleaching Final screening Paper machine Evaporation Causticising, lime kiln incl. fuel gasifier Boiler house Cooling tower etc Raw water treatment and distribution Effluent treatment Chem preparation Miscellaneous, losses Sum Sold power Total Power production Back-pressure power Condensing power Bought power Sum Softwood Model Type 45 45 44 44 60 90 60 80 80 100 45 45 861 939 27 30 59 30 80 100 20 0 17 22 17 30 10 10 30 35 1455 1600 0 0 1455 1600 Hardwood Model Type 40 40 39 39 54 80 54 72 72 89 689 40 125 756 24 25 40 24 64 80 12 0 15 20 15 27 9 9 24 28 1191 1329 0 0 1191 1329 1152 174 128 1455 829 0 771 1600 998 194 0 1191 631 0 698 1329 000 0.063 0.210 0.376 Hardwood Model Type 0. lime kiln incl.257 0. Softwood Model 0.Integrated fine paper mill 20 January 2011 Page 51 Table 5-9.196 0.182 0.173 0.109 0 0.196 0. losses Sum Sold power Total Power production Back-pressure power Condensing power Bought power Sum Softwood Model Type Hardwood Model Type 29 28 38 38 51 29 550 17 38 51 13 11 11 6 19 930 0 930 29 28 57 51 64 29 598 19 19 64 0 14 19 6 22 1019 0 1019 32 31 43 43 58 550 100 19 32 51 10 12 12 7 19 951 0 951 32 31 64 57 71 32 602 20 19 64 0 16 21 7 22 1058 0 1058 736 111 82 930 528 0 491 1019 797 155 0 951 502 0 556 1058 Table 5-10. Bark balance.240 0 0.173 0. kWh/t paper Power consumption Wood yard Digester Washing and screening Oxygen stage Bleaching Final screening Pulp machine Evaporation Causticising.084 0.109 Type 0. fuel gasifier Boiler house Cooling tower etc Raw water treatment and distribution Effluent treatment Chem preparation Miscellaneous. DS t/ADt pulp.303 Bark from woodyard Bark to lime kiln Remaining bark Purchased bark Bark to bark boiler . Power balance.101 0.000 0.240 0. 000 0.138 0. Bark balance.134 0.067 0.125 0.070 0. DS t/t paper.241 .050 0.000 0.191 0.239 0.138 0.000 0.191 0.125 0. Softwood Model Type Bark from woodyard Bark to lime kiln Remaining bark Sold bark Bark to bark boiler Hardwood Model Type 0.065 0.Integrated fine paper mill 20 January 2011 Page 52 Table 5-11.205 0.116 0.070 0.000 0. R “Energiförbrukning I mass. 2003 Delin L. ”Magazine paper mill”. Stenberg E. Andersson R. Sivård Å. Backlund B. Berglin N. Sivård Å. Åberg M. Lundström A. 2004 Delin L. Lundström A.Integrated fine paper mill 20 January 2011 Page 53 6 References Delin L. Sivard Å. Andersson R. R “Energiförbrukning I mass.och pappersindustrin 2007”. Berglin N. 2004 Delin L. Eriksson T. Åberg M. Report FRAM 10. Report FRAM 11.och pappersindustrin 2000”. Sivård Å. ”Bleached market kraft pulp mill”. Lundström A. Samuelsson Å. Report FRAM 12. ”Integrated fine paper mill”. ”Kraftliner reference mill”. Eriksson T. Samuelsson Å. Berglin N. 2007 Wiberg. Åberg M. 2000 . Skogs Industrierna rapport. Backlund B. Skogs Industrierna rapport. 2004 Wiberg. Report FRAM 09. 0 0.0 4.0 % 12 25 kg/ADt 20 kg/ADt 2 kg/ADt 2. MCR Bleached Softwood 2000 ADt/d PROJECT Model mills 2010 DRAWING 20100426 v. TO PULP MACHINE 1800 BDt/d 0.0 8.5% 60 mg/kg DS 400 mg/kg DS 80 mg/kg DS 3. Bleaching Final screen Total yield (from dig feed) LOSSES % 0.0 % 1.0 0.0 Na K S OHHSS2O32SO42CO32AA TTA EA %SULPHIDITY ON AA g/L ACTUAL g/L as NaOH 93. as NaOH AA to digester. 2000 ADt/d WHITE LIQUOR 7 085 m3/d NCG BLACK LIQUOR 21 905 t/d 16.1 0.0 SULF8_1 model mills 2010.2 44.0 t/d NaOH O2 41 t/d MgSO4 5 t/d O2 ClO2 H2SO4 H2O2 SO2 LOSS AS WHITE LIQUOR 14 m3/d WHITE LIQUOR 443 m3/d NCG 4 072 BDt/d CHIP STORAGE & SCREENING Screen Losses 0.0 % 24.5 35% ClO 2 NaOH O2 H2O2 H2SO4 SO2 H2SO4 CH 3OH NaClO3 ÅF Engineering.0 115.8 21. as NaOH Knotted.0 MJ/kg DS 3 477 t/d DS 79 % EVAPORATION PLANT 771 t/h evap WHITE LIQUOR OXIDATION CHLORINE DIOXIDE PLANT BYPRODUCT SALT CAKE (Na2SO4) DE-BARKING & CHIPPING Losses 2. WEAK WASH RECOVERY BOILER METHANOL VIRGIN DS 14.2 98. MgSO4 to oxygen delig.8 22.0 12.0% PRESSURE SCREENS PREOXYGEN WASHING 1913 BDt/d 2126 ADt/d OXYGEN DELIGNIFICATION 1840 BDt/d 2045 ADt/d POSTOXYGEN WASHING 1840 BDt/d 2045 ADt/d D(EPO)DP BLEACH PLANT 1804 BDt/d 2004 ADt/d HD-STORAGE.20 2.0% 400 BDt/d TO BIOMASS BOILER 420 BDt/d MeOH H2SO4 NaClO3 PURCHASED LIMESTONE HANDLING ROUNDWOOD 3 268 BDt/d PURCHASED LIME HANDLING CAUSTIC HANDLING CAUSTIC HANDLING OXYGEN HANDLING MgSO4 HANDLING METHANOL HANDLING SULPHURIC ACID HANDLING SODIUM CHLORATE HANDLING HYDROGEN PEROXIDE HANDLING SO2 HANDLING WOOD SUPPLY Pine Spruce Roundwood with bark Bark on unbarked logs Saw mill chips Solid wood density Moisture Lignin in wood Cl in wood K in wood S in wood Extractives in wood 50% 50% 70 % 11 % 30 % 420 kg/m3 50. brownstock wash 30 20.80 11.Softwood bleached kraft pulp PRODUCTION DESIGN BASIS: OPERATING DAYS PER YEAR MILL EFFICIENCY AVERAGE DAILY PRODUCTION PULP MILL CAPACITY.1 20.1 % REJ.0 30. Forest Industry STOCKHOLM SWEDEN OVERALL MATERIAL BALANCE.4 3..5% 20 BDt/d 4 097 BDt/d CaCO3 SAW MILL CHIPS 1 229 BDt/d CaO 4 BDt/d Storage losses LIME KILN 90% CaO MUD REBURNT LIME 534 t/d CAUSTICIZING PLANT GREEN LIQ.9 13. 1. MCR ANNUAL PULP PRODUCTION 355 d/a 92% 1840 ADt/d 2000 ADt/d 653200 ADt/a KNOTS 19 BDt/d BROWN STOCK STORAGE DIGESTER PLANT 1933 BDt/d 2148 ADt/d BLOW TANK PRESSURE KNOTTERS 1914 BDt/d 2127 ADt/d 1.0 BDt/d ALKALI as NaOH 50.0 15.0 6.9 3.xlsm .2 WHITE LIQUOR SPECIFICATION BLEACH AND CHEMICAL PLANTS BLEACH PLANT kg/ADt t/d 6.1 96.2 % 47.3 15.8 49.0 8.8 1.0 44.0 4.5 1.0 160. NaOH O2 to oxygen delig.0% DIGESTER AND OXYGEN DELIGNIFICATION Kappa out of digester EA to digester.1 47.6 22.0 % 27.0 140.Appendix 1 Model mill .50 PULP YIELD AND LOSSES YIELD % Chip storage Chip screen Digester Knots Reject Oxygen delig.0 0. unscreened yield Kappa out if O2 stage Total alkali to O2 delig.0 CHLORIDE DIOXIDE PLANT t/ADt t/d 0.2 1. Dilution factor. NaOH O2 to oxygen delig.4 % 51.1 98.2 21.0 CHLORIDE DIOXIDE PLANT t/ADt t/d 0.5 0. as NaOH Knotted.2 48.50 PULP YIELD AND LOSSES YIELD % Chip storage Chip screen Digester Knots Reject Oxygen delig.8 WHITE LIQUOR SPECIFICATION BLEACH AND CHEMICAL PLANTS BLEACH PLANT kg/ADt t/d 6. Forest Industry STOCKHOLM SWEDEN OVERALL MATERIAL BALANCE.0 % 22.0 MJ/kg DS 3 668 t/d DS 79 % EVAPORATION PLANT 840 t/h evap WHITE LIQUOR OXIDATION CHLORINE DIOXIDE PLANT BYPRODUCT SALT CAKE (Na2SO4) CP DE-BARKING & CHIPPING Losses 2.0 6. Dilution factor.3 22.80 13.0 .5 1. as NaOH AA to digester.0 % 12 18 kg/ADt 14 kg/ADt 1 kg/ADt 2.0 10.9 17.5 10.0 4.6 51.1 20. MCR Hardwood 2500 ADt/d PROJECT Model mills 2010 DRAWING 20100426 v.5 35% ClO 2 NaOH O2 H2O2 H2SO4 SO2 H2SO4 CH 3OH NaClO3 ÅF Engineering..1 % REJ.0% 150 mg/kg DS 450 mg/kg DS 80 mg/kg DS 2.8 0.3 15.8 49. Bleaching Final screen Total yield (from dig feed) LOSSES % 0.0 160.0 55.2 0.0 Na K S OHHSS2O32SO42CO32AA TTA EA %SULPHIDITY ON AA g/L ACTUAL g/L as NaOH 92.0 t/d NaOH O2 36 t/d MgSO4 3 t/d O2 ClO2 H2SO4 H2O2 SO2 LOSS AS WHITE LIQUOR 17 m3/d WHITE LIQUOR 400 m3/d NCG 4 610 BDt/d CHIP STORAGE & SCREENING Screen Losses 0.5 0.Bleached hardwood pulp PRODUCTION DESIGN BASIS: OPERATING DAYS PER YEAR MILL EFFICIENCY AVERAGE DAILY PRODUCTION PULP MILL CAPACITY.0 140.2 BDt/d ALKALI as NaOH 45.4 97. MCR ANNUAL PULP PRODUCTION 355 d/a 92% 2300 ADt/d 2500 ADt/d 816500 ADt/a KNOTS 19 BDt/d BROWN STOCK STORAGE DIGESTER PLANT 2370 BDt/d 2633 ADt/d BLOW TANK PRESSURE KNOTTERS 2351 BDt/d 2612 ADt/d 0.2 1. MgSO4 to oxygen delig.0 37.0% 619 BDt/d TO BIOMASS BOILER 642 BDt/d MeOH H2SO4 NaClO3 PURCHASED LIMESTONE HANDLING ROUNDWOOD 5 261 BDt/d PURCHASED LIME HANDLING CAUSTIC HANDLING CAUSTIC HANDLING OXYGEN HANDLING MgSO4 HANDLING METHANOL HANDLING SULPHURIC ACID HANDLING SODIUM CHLORATE HANDLING HYDROGEN PEROXIDE HANDLING SO2 HANDLING WOOD SUPPLY Birch Other hardwoods Roundwood with bark Bark on unbarked logs Saw mill chips Solid wood density Moisture Lignin in wood Cl in wood K in wood S in wood Extractives in wood 90% 10% 100 % 11 % 0% 495 kg/m3 45.0 15.9 3.6 27.Appendix 1 Model mill .0 115.0 4.5% DIGESTER AND OXYGEN DELIGNIFICATION Kappa out of digester EA to digester. TO PULP MACHINE 2250 BDt/d 0.5% 23 BDt/d 4 642 BDt/d CaCO3 SAW MILL CHIPS 0 BDt/d CaO Ash 0 t/d 9 BDt/d Storage losses LIME KILN 90% CaO MUD REBURNT LIME 554 t/d CAUSTICIZING PLANT GREEN LIQ.7 % 1. 1.0 15.20 3. brownstock wash 17 18. WEAK WASH RECOVERY BOILER METHANOL VIRGIN DS 14.8 0. unscreened yield Kappa out if O2 stage Total alkali to O2 delig.8% PRESSURE SCREENS PREOXYGEN WASHING 2350 BDt/d 2611 ADt/d OXYGEN DELIGNIFICATION 2312 BDt/d 2569 ADt/d POSTOXYGEN WASHING 2312 BDt/d 2569 ADt/d D(EPO)DP BLEACH PLANT 2255 BDt/d 2505 ADt/d HD-STORAGE.5 % 22.7 6. 2500 ADt/d WHITE LIQUOR 7 414 m3/d NCG BLACK LIQUOR 23 545 t/d 15. 0 25. MCR of which softwood of which hardwood Market pulp Paper machine kJ/kg °C kJ/kg kJ/kg kJ/kg kJ/kg kJ/kg kJ/kg ADt/d 2000 2000 0 0 3130 63 315 315 622 3386 2944 2827 2748 0. preheated by sec heat Feedwater to boilers HP-steam MP2-steam. preheated by sec heat Turbine cond.5 EnerbalNew JTLDn6.97 100. desuperheated MP-steam.Appendix 2 Softwood ENERGY BALANCE ASSUMPTIONS Model Fine paper SW campaign Enthalpy etc Temp Pressure °C bar(g) 15 75 75 146 505 275 200 150 Make-up water before preheating Make-up water.xlsmSteamBal 1 .0 9.0 3.. desuperheated LP-steam./el efficiency turbine Produced pulp. desuperheated Mech. 0) (0.3 (0.0 53.7 0.Appendix 2 .0 0.0 0.0 0.0 2. losses Steam to feedwater tank Total LP-steam (62.9 0.0 18.9 46.7 2.1 1.1 23.4 113.0 14.0 1.0 0.4) (420.5 0.0 0.8 0.0 11.0 225.2 2.5) 0. losses Total MT-ånga LP-steam Air preheater recovery boiler Air preheater bark boiler Smelt shattering Woodyard Digesting Bleaching Evaporation Chemical preparation Causticising Paper machine Heating etc Blow off Miscellaneous.5 0.4 0.3 17.0 0.0 0.8 5.0 2.0 1.5 55.7 35.7 35.0 0.5 HP-steam Back-pressure turbine MP2-steam MP-steam LP-steam Condensing turbine condensing steam Direct reduction HP-MP Direct reduction HP-LP Soot blowing recovery boiler Blow down recovery boiler Soot blowing bark boiler Blow down bark boiler Total HP-steam MP2-steam Soot blowing recovery boiler Air preheater recovery boiler Feedwater interheater Soot blowing power boiler Total MP2-steam MP-steam Air preheater recovery boiler Air preheater bark boiler Feedwater preheater Digesting Bleaching Oxygen stage Evaporation Chemical preparation Paper machine Miscellaneous.7 0.6 18.9 9.0 2.0 36.0 234.0 71.0 8.7 0.7 6.0) (1.7 (11.0 3.0 1.0 117.5 0.0 35 46.0 0.1 142.8 0.3 45.0 0.0 0.Softwood STEAM CONSUMPTION Steam Flow t/h Condensate Temp Flow °C t/h Heat Effect MW 99.0) 0.5 66.0) (1.5 15.0 1.6) (10.0 0.6 0.4 0.6) 35.0 237.5 0.1 0.0 153.1 EnerbalNew JTLDn6.6 0.4) 41.0 0.0 3.3 0.0 111.1 45.0 0.0 0.4 416.0 (0.0 0.3 46.2 160 200 0.1 170 170 180 170 180 100 140 100 100 100 0.3 17.4 24.0 0.0) (20.0 0.0 3.0 0.6) (111.0 46.1 0.7 0.0 0.3 2.2 50.4) 0.0 0.0 29.7 (0.4 390.xlsmSteamBal 2 .8 0.0 148 148 140 100 100 105 100 100 100 0.2 1.7 0.0 0. 0 8.9 Effect MW 454.2 113.5 37.0 645.3 0.7 3.2 49.0 24.7 1.0 0.1 -1.4 MP-steam from boilers desuperheating water MP2-steam desuperheating water MP-steam drainage water LP-steam Secondary heat for preheating make-up water TOTAL STEAM PRODUCTION 0.Softwood SUMMARY STEAM CONSUMPTION HP-steam MP2-steam MP-steam LP-steam Make-up water TOTAL STEAM CONSUMPTION STEAM PRODUCTION Recovery boiler HP-steam soot blowing blow down feedwater preheat MP feedwater preheat MP2.xlsmSteamBal 3 .3 0.7 5.4 645.3 5.1 55.0 5.7 36.8 t/ADt 0.6 -10.8 71.6 1.10 Steam Flow t/h 50.0 6.8 3.0 14.8 2.0 66.0 0.5 -1.3 Heat Effect MW 142. LP-steam air preheating. MP2-steam Sum Extern överhettare Bark boiler HP-steam soot blowing blow down air preheating.3 1152 174 128 1455 96.5 0. LP-steam air preheating.7 121.0 3.1 167 53.3 117 390.1 455. lime kiln incl.6 412.9 POWER CONSUMPTION Wood yard Digester Washing and screening Oxygen stage Bleaching Final screening Paper machine Evaporation Causticising.0 0. MP-steam Sum t/ADt 7.1 416.0 121.4 0.3 Flow t/h 591.0 594.0 3. inter eco air preheating.4 0.0 0. losses Sum Sold power Total POWER PRODUCTION Back-presssure power Condensing power Bought power Sum kWh/ADt 45 44 60 60 80 45 861 27 59 80 20 17 17 10 30 1455 0 1455 MW 3.0 119.5 0.1 645. fuel gasifier Boiler house Cooling tower etc Raw water treatment and distribution Effluent treatment Chem preparation Miscellaneous.4 1.3 0.0 35.59 49.8 0.7 -4.0 6.0 Condensate Temp Flow °C t/h 46.5 10.Appendix 2 .0 455.8 0.7 1.3 EnerbalNew JTLDn6.7 2.0 -11.5 121. MP-steam air preheating.7 234.6 -20. preheated by sec heat Feedwater to boilers HP-steam MP2-steam.Hardwood ENERGY BALANCE ASSUMPTIONS Model Fine paper HW campaign Enthalpy etc Temp Pressure °C bar(g) 15 75 75 146 505 275 200 150 Make-up water before preheating Make-up water.5 EnerbalNew JTLDn6.0 3.Appendix 2 .97 100.xlsmSteamBal 1 .0 25./el efficiency turbine Produced pulp. desuperheated MP-steam. preheated by sec heat Turbine cond.0 9.. MCR of which softwood of which hardwood Market pulp Paper machine kJ/kg °C kJ/kg kJ/kg kJ/kg kJ/kg kJ/kg kJ/kg ADt/d 2500 0 2500 0 3130 63 315 315 622 3386 2944 2827 2748 0. desuperheated LP-steam. desuperheated Mech. 8 1.7 (0.6 0.0 11.5 2.6 0.8 436.6 19.9 0.0 19.3) 40.4 (0.0 3.4 1.0 3.1 73.5) (440.0 4.0 1.4 0.0 0.0 0.1 52.0 16.1 0.5 51.5 51.7 160 200 0. losses Steam to feedwater tank Total LP-steam (66.0 77.5 68.8 25.0 4.2 139.9 (0.0 0.6 170 170 180 170 180 100 140 100 100 100 0.4 37.0) (2.2 EnerbalNew JTLDn6.0 0.4 148 148 140 100 100 105 100 100 100 0. losses Total MT-ånga LP-steam Air preheater recovery boiler Air preheater bark boiler Smelt shattering Woodyard Digesting Bleaching Evaporation Chemical preparation Causticising Paper machine Heating etc Blow off Miscellaneous.0 69.1 0.8 18.9 0.0 0.0 3.0 0.0 127.0 0.1 0.8) 0.0) 0.0 8.1 0.4 37.1 21.Appendix 2 .5) (10.0 121.1 0.0) (137.0 3.4 10.xlsmSteamBal 2 .9 0.3 241.0) (2.8 18.3 30.3 57.0 0.5 0.0 153.0 4.8 2.3 64.0 0.2 24.Hardwood STEAM CONSUMPTION Steam Flow t/h Condensate Temp Flow °C t/h Heat Effect MW 107.9) 57.3 0.0 38.0) (21.0 0.0 237.9) 0.0 3.5 0.8 0.8 409.2 166.0 0.2 0.7 HP-steam Back-pressure turbine MP2-steam MP-steam LP-steam Condensing turbine condensing steam Direct reduction HP-MP Direct reduction HP-LP Soot blowing recovery boiler Blow down recovery boiler Soot blowing bark boiler Blow down bark boiler Total HP-steam MP2-steam Soot blowing recovery boiler Air preheater recovery boiler Feedwater interheater Soot blowing power boiler Total MP2-steam MP-steam Air preheater recovery boiler Air preheater bark boiler Feedwater preheater Digesting Bleaching Oxygen stage Evaporation Chemical preparation Paper machine Miscellaneous.7 3.0 0.0 0.3 2.0 0.0 0.0 64.5 (12.0 0.0 0.9 3.0 16.0 0.0 0.0 1.9 0.0 0.0 0.0 0.4 0.0 225.4 35 64.1 16.0) (0. 5 4.8 0.87 Steam Flow t/h 68.1 0.0 70.9 -2.1 0.5 425.0 714.7 117 409.4 t/ADt 0.7 2.2 506. inter eco air preheating.9 38.5 98.3 1. fuel gasifier Boiler house Cooling tower etc Raw water treatment and distribution Effluent treatment Chem preparation Miscellaneous.4 POWER CONSUMPTION Wood yard Digester Washing and screening Oxygen stage Bleaching Final screening Paper machine Evaporation Causticising.1 -4.4 714. MP-steam air preheating.6 1. losses Sum Sold power Total POWER PRODUCTION Back-presssure power Condensing power Bought power Sum kWh/ADt 40 39 54 54 72 40 689 24 40 64 12 15 15 9 24 1191 1 1191 MW 4.4 69.6 714.5 4.0 0.6 1. MP2-steam Sum Extern överhettare Bark boiler HP-steam soot blowing blow down air preheating.0 3.0 0.2 0.94 97.6 1.5 124.0 2.4 Effect MW 469.0 0.1 Condensate Temp Flow °C t/h 64.3 75.5 506.4 0.0 0.1 EnerbalNew JTLDn6.4 144. MP-steam Sum t/ADt 5.Hardwood SUMMARY STEAM CONSUMPTION HP-steam MP2-steam MP-steam LP-steam Make-up water TOTAL STEAM CONSUMPTION STEAM PRODUCTION Recovery boiler HP-steam soot blowing blow down feedwater preheat MP feedwater preheat MP2.6 241.2 4.8 0.5 0.6 5.0 124.1 124.6 0.6 7.1 998 194 0 1191 103.0 10.9 20.1 Flow t/h 611.6 -21.3 -10.0 614.3 MP-steam from boilers desuperheating water MP2-steam desuperheating water MP-steam drainage water LP-steam Secondary heat for preheating make-up water TOTAL STEAM PRODUCTION 0. LP-steam air preheating.Appendix 2 .1 5.0 0.0 -12.0 3.8 2.2 71.7 139.1 -2. lime kiln incl.2 167 57.2 73. LP-steam air preheating.xlsmSteamBal 3 .3 25.6 436.1 6.1 Heat Effect MW 166. 4 1.0 5.0 4.4 15.2 35 °C Printed 2010-07-08 .2 Water balance Warm and hotwater Model Fine paper SW campaign.26 GJ/ADt Turbine condenser 1.9 Bleaching 45.3 18 °C 55. SW °C 22.93 GJ/ADt 109.05 GJ/ADt Preheating condensate and make-up water 0.4 24.4 0.13 GJ/ADt Misc.Softwood 1 4.00 GJ/ADt Cooling liquor to hiheat wash 0.6 ClO2 Make-up Boilers 39.38 GJ/ADt Cooling HC-tower 0.3 22.8 90 °C 1.1 Cooling tower 25 °C 2.13 GJ/ADt 35 °C Effluent treatment Total t/ADt Water consumption Total effluent 24.0 3.1 Diss. cooling Terpentine condenser 0.0 1.5 0.0 0.5 Cooling bleach 1.0 Wood yard 1.3 29 °C 110. 4.3 3. Tank condenser 65 °C 0.4 Chemical preparation 0.6 7.17 GJ/ADt Bleach cooling 0.Appendix 3 .49 GJ/ADt 9.12 GJ/ADt 0.3 0.35 GJ/ADt 1.32 GJ/ADt Building heating 3.1 Paper machine 10.0 Causticising 15.3 Pulp wash 1.6 0.6 29 °C Liquor Evaporation 3.00 GJ/ADt Cooling liquor to evaporation 0.0 50 °C 4.0 1.3 8.9 filtrate 0.4 50 °C Cooling tower 1.0 0.6 0.0 0.6 4.46 GJ/ADt 3.19 GJ/ADt Cooling O2-filtrate 0.3 1.0 Misc.5 5. 0 0.1 18 °C 63.7 1.10 GJ/ADt Preheating condensate and make-up water 0.0 Misc.0 50 °C 3.0 0.2 Chemical preparation 0.98 GJ/ADt 35 °C Effluent treatment Total t/ADt Water consumption Total effluent 23.19 GJ/ADt Cooling O2-filtrate 0.20 GJ/ADt Turbine condenser 1. HW °C 20.Appendix 3.6 4.00 GJ/ADt Cooling liquor to evaporation 0.0 4.3 Bleaching 40.8 4.2 1.0 0.Hardwood 1 4.2 0.3 47 °C Cooling tower 0.0 1.1 20. 4.0 4.2 Cooling tower 25 °C 2.3 Pulp wash 1. Tank condenser 65 °C 0.2 2.2 Diss.0 2.5 1.3 Water balance Warm and hotwater Model Fine paper HW campaign.67 GJ/ADt 3.40 GJ/ADt Cooling HC-tower 0.51 GJ/ADt Building heating 3.3 35 °C Printed 2010-07-08 .0 3.26 GJ/ADt Misc.5 Paper machine 8.18 GJ/ADt Bleach cooling 0.5 ClO2 Make-up Boilers 34.4 23.2 0.8 89 °C 0.1 9.4 14. cooling Terpentine condenser 0.36 GJ/ADt 1.00 GJ/ADt Cooling liquor to hiheat wash 0.3 29 °C 125.5 29 °C Liquor Evaporation 3.04 GJ/ADt 8.23 GJ/ADt 0.0 Wood yard 1.80 GJ/ADt 124.6 Cooling bleach 3.8 7.3 0.9 0.7 filtrate 0.0 Causticising 25.