In-plant vocational training report 9 th May – 9 th July2013 NIRAJ KUMAR BAIRAGI IIT KANPURPREFACE Industrial training plays a vital role in the progress of future engineers. Not only does it provide insights about the industry concerned, it also bridges the gap between theory and practical knowledge. We were fortunate that we were provided with an opportunity of undergoing Industrial training at DCM Shriram Consolidated Ltd (DSCL), Kota, one of the leading fertilizer companies in India. The experience gained during this short period was fascinating to say the least. It was a tremendous feeling to observe the operation of different equipments and processes. It was overwhelming for us to notice how such a big plant is being monitored and operated with proper co-ordination to obtain desired results. This project is aimed at developing the process design of the ammonia preheater used in the Urea Plant. Presently four shell and tube heat exchangers are being used for this purpose and we were asked to design a single shell and tube heat exchanger which can be used in place of the four heat exchangers. Kern’s Method was used for the design purpose. During our training we realized that in order to be a successful process engineer one needs to possess a sound theoretical base along with the acumen for effective practical application of the theory. Thus, we hope that this industrial training serves as a stepping-stone for us and helps to be successful in future. 2 CERTIFICATE This is to certify that NIRAJ KUMAR BAIRAGI, student of INDIAN INSTITUTE OF TECHNOLOGY, KANPUR has done his Summer Training at Urea Plant and Project Report entitled “Summer Training Report” is a record of candidate’s own work carried out by him under my supervision and guidance during the period 9 May to 9 th th June, 2013 at Shriram fertilizers and Chemicals, Kota. Mr. Hari Om Mishra Head of Department (Urea Plant) 3 . Kota over a period of 6 weeks and for making it happen and providing us with necessary inputs as and when needed. I express my gratitude to my institute. Manager. K. Last but not the least. It is my profound privilege to express my sincere gratitude and heartfelt indebtness to my advisor Mr. BRIJESH KUMAR PAL IIT ROORKEE . HR Manager for granting us permission to undergo training at DSCL. He also made the visit to the urea plant worth by explaining functions of every equipment in detail. I would like to express my gratitude towards the technical and support staff at DSCL. who inculcated in me the inspiration and enthusiasm to undertake this training that will always remain with me.ACKNOWLEDGEMENT We would like to express our deep sense of gratitude to Mrs. J. He was kind enough to guide me throughout the project and cleared all my doubts related to the project. The teaching staff has been the path providers and the non-teaching staff the supporters. They were very helpful and always encouraged us to get an insight in to the work. Fertilizer R&D and Mr. who has helped me in my project for developing the process design of Ammonia preheater. M. HOD Urea Plant. I feel immense pleasure in expressing my thanks towards Mr. Tandon. Choudhary. Dinesh Prasad Bhatt. Indian Institute of Technology Roorkee for giving me an opportunity to grow and develop my thoughts for my future life. The topic of training was selected based upon the latest developments and applications of the technology in the industry. The help and support of my friends and colleagues during the tenure of the training was enormous and is acknowledged from the core of my heart. who has helped me in better understanding of the manufacturing process of urea theoretically and practically. Neha Agrawal. Hari Om Mishra. I would also like to express my gratitude towards my mentor Mr.S. 4 . ..................................... 27 30 30 PROJECT................................................................................................................. PROCESS DESIGN OF AMMONIA PREHEATER..................................................................................... 8 14 23 24 26 PROCESS DESCRIPTION................................................................................................ MAJOR ENGINEERING PROBLEMS..... 6 UREA PLANT AT SFC (DSCL KOTA)............................................. CRITICAL PARAMETERS OF PRODUCT QUALITY........................................................................................................................................................................................................................................................................................................................................................................................................... POLLUTION CONTROL AND INDUSTRIAL SAFETY TYPES OF POLLUTION IN FERTILIZER INDUSTRIES................................TABLE OF CONTENTS INTRODUCTION............. ........................................................................................... NEEM COATED UREA.................................................................... 5 . DSCL comprises the following list of processing plants in it : Urea Plant Ammonia Plant PVC Plant Cement Plant Thermal Power Plant Carbide Plant Fenesta 1. India.Alkali capacity is 765 TPD. i. SFC provides a great opportunity for training to more than 200 students every year. The Company has two manufacturing facilities located at Kota (Rajasthan) and Bharuch (Gujarat) with full coal based captive power. K.K. Compressed Hydrogen and Sodium Hypochlorite.Vinyl business: Chlor. ii. Stable Bleaching powder. which PVC compounds of the Company is the largest manufacturer the organized sector is backed by an innovative Polymer Application Developmentin Centre (iPAC) at Gurgaon. Kota by DSCL.Alkali: This comprises of Caustic Soda(Lye and flakes). SFC is managed by Mr. Kaul and his very capable team. 6 . located at Kota.INTRODUCTION DSCL: AN OVERVIEW DCM SHRIRAM CONSOLIDATED LIMITED KOTA – Shriram Fertilizers & Chemicals(SFC) is a large and great facility established in the Shriram Nagar. covering manufacture of PVC resins. Chloro. Chlorine and associate chemicals including Hydrochloric acid. Plastics Business : This is highly integrated. ~ 143 MW of Generating capacity is used to supply power to the above said businesses orPower sell power in the market depending upon the economic effectiveness. chlorine and coal based power. By having Training Centre in its facility. Calcium Carbide and PVC Compounds PVC Resin is fully integrated with captive production of acetylene. The Company’s total Chlor. iii.4 Million tonne capacity is based on waste generated from the Calcium carbide production process. 544 spindles spinning unit at Tonk in Rajasthan. 6. research. production.P. located at Kota of 0. Bioseed (Hybrid Seeds): The Company’s Bioseed business is present across the value chain i. abd Cogen power capacity of 94. Urea: The Company has the dual feed naptha/ LNG based urea plant with a capacity of 3. Located at its integrated manufacturing facility at Kota. Agri. pesticides ets.Inputs: This business provides complete basket of agriinputs to farmers community by offering a range of fertilizers. extension activities and marketing with established significant presence in India. It is currently operating on 100% LNG. hybrid seeds.000 TCD in Central U. Other Businesses: Textiles: The Company has a smaal textile operation in the form of 14.2..e.nutrients. Hariyali Kisaan Bazaar: These are ‘Rural Business Centres” which are a one stop solution to the multiple needs of the rural communities. .P.5MW. Philippines and Vietnam. processing. It offers complete solutions starting from desgign . iv. Through its wide distribution network. ii.Business: i. 3. Fenesta: Fenesta building system manufactures UPVC windows(UnPlasticized PVC) and door systems under the brand “Fenesta”. China and Indonesia.79 lakh T. fabrications to installation at the customer’s site. The outlets provide full range of agri-inputs backed by customized agronomy services as well as other necessities and consumer goods. 5.A. Further Company has initiated its operations in Thailand. Sugar: The Company’s sugar business cpmprises of 4 facilities with a combined capacity of 33. Cement Business: The Cement business. Agri. micro. 4. 7 . With the availability of Reliance KG D6 gas. the plant has achieved utilization of 120% and can operate at the peak level of 1250-1300 MTPD.bottlenecking. Laboratory Urea Sale Department The “Stamicarbon Process” for the production of Urea using Ammonia and Carbondioxide as raw material is realized as total recycle process in total recycling of NH3(l) and CO2(g) and carbamate solutions. Kota) was commissioned in February 1969 with an installed capacity of 700 MTPD. plant has been operating on full gas since May’09. 8 .000 TPA of Urea at its integrated manufacturing complexes at Kota Rajasthan. The Company had entered into a long term gas supply agreement to procure Natural Gas from KG Basin. meeting its full requirement.C. In 2006-2007. DSCL’s Fertilizer Plant has an approved capacity of 379. now known as Chiyoda Corporation. The plant was expanded in August 1974 to 1000 MTPD by installing of balancing equipment and an additional 120 TPD ammonia synthesis loop in the ammonia plant by making minor modifications in the Urea Plant. The Company is the lowest cost producer of Urea in the Pre-92 Naphtha based group and markets its products under the “Shriram Urea” brand. The construction of the plant was done by Chiyoda Chemicals Engineering and construction Co. In a continuous endeavor towards energy conservation and de. the Fertilizer Plant was modified to be capable of having natural gas as its feed stocks besides naphtha. As a whole Urea Plant is totally dependent on the following plants: DM Plant Power Plant Plant Ammonia Other supporting services: Fertilizer Workshop Urea Bagging Plant P.L. The plant is based on Stamicarbon’s Total Recycle Process technology.UREA PLANT AT SFC (DSCL KOTA) Urea plant of SFC (DSCL. The Company has an extensive distribution network over the entire Northern and Central India. “Shriram Urea” is a trusted name and enjoys high brand equity amongst the farmers. USA and 1935. Studies are being made to coat urea with Zinc and Boron.UK. higher energy savings which boosted our earning and reduction in working capital which resulted in lower borrowings.014 MT of Uera was also converted to Neem Coated Urea. $$. In order to avail benefit of government policy on fortified fertilizer. 22014 MT of Urea was converted into Neem Coated Urea. The plants have been modified to use natural gas in 2006 and have been running fully on gas since May’09 with the availability if KG D6 gas. Further. Urea: An Overview Urea (identified 1773). The earning from the Fertilizer Business was up by 73% at Rs. efforts are made to produce additional quantities of urea over reassessed capacity to avail benefit of government policy. The Company also was able to produce 4000 tonnes over the base production inspite of undertaking a maintaining turnaround of 25 days the year.6 crores due to better efficiencies achieved by switch to gas from Naptha. Efforts are continuously being made towads further improving energy Efficiency and reduction/ Containment of fixed expenses. 1931.In addition to abive. 22.320 Crores.Germany .The use of Natural Gas (instead of naphtha) has major posi ves which include reduc on in Feedstock casts and consequently subsidy accruals by Rs. In line with government policy on the fortified fertilizers . Notification of revised NPS III schemes received and gain on account of additional production done in Fy 2009. the first organic compound prepared by inorganic synthesis (1828 Wohler) NH3 + HCNO → CO(NH2)2 Commercial production started in 1992. Urea has been considered as slow – release fertilizer since it must undergo two transportation Hydrolysis: CO(NH2)2 + H2O → 2NH3 + CO2 Nitrification: NH3 → Nitrite of Nitrate (Microbes. moist and warm soil) . 9 . it is very important ti achieve an even apread.India is the second largest producer and consumer of urea in the world. e. Therefore.dressed during the growing season. drilling must not occur on contact with or close to sed. In high rainfall area and on sandy soils (where nitrogen can be lost through leaching) andwhere good in. The demand and consumption of urea have been growing and the gap in demand / supply is being met by imports. due to the risk of germination damage. it has the lowest transportation costs per unit of nitrogen nutrient .season rainfall is expected . also very suitable for use in fertilizer solutions( in combination with ammonium nitrate:UAN). therefore. or during rain to minimize losses from volatilization(process wherein nitrogen is lost to the atmosphere as ammonia gas). Because of high nitrogen concentration in urea. in “foliar feed” fertilizers. In cultivating sugarcane. Low farm gate price (fixed by government) and high nitrogen content makes it a preferred choice of farmers. During summer . India is the second largest producer of Urea in the world and also the second largest consumer of Urea as well.. Urea is usually spread at rates between 40 and 300 kg/ha but rates vary. During 2009-10 the total urea production in the country was 21.7%). High Nitrogenous . which impairs plant growth. Urea has the highest nitrogen content of all solid nitrogenouds fertilizers in common use(46. granules are preferred over prills because of their narrower particles size distribution which is an advantage for mechanical application. Urea is not compatible with other fertilizers. urea can be side –or top. urea is highly soluble in water and is. In Grain and cotton crops. urea is side. The most common impurity of synthetic urea is biuret. urea is often spread just before . Smaller applications incur lower losses due to leaching. Urea dissolves in water for application as spray or through irrigation systems. Urea is the most widely used fertilizer in India and Constitutes about 72% of entire Fertilizer consumption.2 million MT and India had to import more than 5 million MT of urea to meet its demand. Urea is the most preferred fertilizer and constitutes about 72% of entire fertilizer consumption in the country. The application equipment must be correctly calibrated and properly used.dressed after planting and applied to each ratoon crop. More than 90% of world production of urea is destined for use as a nitrogenrelease fertilizer. For fertilizer use. urea is often applied at the time of the last cultivation before planting. Top-dressing is popular on pasture and forage crops.g. 10 .content as well as low farm gate price (which is fixed my government) makes it an attractive nutrient for the farmers vis-a-vis other nutrients. Used along the salts.guest complexes. ureaformaldhyde resin. As an additive ingredient in cigarettes. As an ingredient in some hair conditioners. designed to enhance flavor. As a raw material for the manufacturing of plastics specifically. The first reaction is spontaneous and complete . It does not promote metal corrosion to the extent that salt does. the secong is endothermic. while the second is -522 Kcal/ mol . Sometimes used as browning agent in factory. due to endothermic reaction it creates when mixed wuth water.produces pretzels.Urea’s commercial use includes: As a component of fertilizer and animal feed. provide the heat liberated thereby is discharged . producing precioitation. Main application grades of Urea are: Fertilizer Grade Cattle Feed Grade Technical Grade Chemistry of urea synthesis When CO2 and NH3 are brought together under the synthesis conditions of 200 atm the following reaction occur: 2NH3 (liquid) + CO2 (gas) → NH4COONH4 +38. The latter is waterproof and is used for marine plywood. As a flame. providing a relatively cheap source of fixed nitrogen to promote growth. inclusion compounds and adducts) was used in the past to separate paraffin.to. As an alternative rock salt in the de – icing of roadways and runways.formaldehyde). The ability of urea to form clathrates (also called host. It is also used as a reactant in some ready. facial cleansers. as a cloud seeding agent to expedite the condensation of water in clouds.use cold compresses for first-aid use. As a raw material for the manufacturing of various glues (ureaformaldehyde or urea-melamine.06 Kcal/mol NH4COONH4 → NH2CONH2 + H2O (Urea) The first reaction is strongly exothermic. bath oils and lotions.proofing agent. Active ingredients for diesel engine exhaust treatment AdBlue. 11 . slowly involving equilibrium reaction. 3 2 132.335 1 0 8 g /100ml (20˚C) 1 6 7 g /100ml (40˚C) 2 5 1 g /100ml (60˚C) 4 0 0 g /100ml (80˚C) 7 3 3 g /100ml (100˚C) pKBH+ =0. the equilibrium is about 46% conversion. 6 0. 3 2 Solubility in Water Basicity(pKb) Nitrogen % Content Specific heat @ 20˚C (Cal/g˚C) . PROPERTIES OF UREA Compound Molecular Formula Molar Mass(g/mol) Appearance Density(g/m3) Melting Point Specific Gravity Ur e a CH4N2O 60. the equilibrium reaction 2 shift to right by Le Chatelier’s principle.18 4 6.7˚C 1. When both the raw materials are presented in stoichiometric ratio.06 White solid without any odour 1. At higher N/C ration in the original synthesis moisture. due to which only par of the carbamate is converted into urea. Therefore there is very less change of cake formation now. In water (endothermic)(Cal/g˚C) Critical relative humidity 20˚C 30˚C 5 7. 12 .Heat of Sol.2% to 0. 8 8 1 % 7 3 % SPECIAL QUALITIES OF SHRIRAM UREA Dust Content: Dust content in Shriram Urea with new bucket has reduced to 0.4% with old bucket. 45% biuret.Brightness: Shriram urea is brighter as compared to few brands available in the market as there is not possibility of oil content in the process it is always milky white.67%. Moisture Content: Shriram Urea is produced with a process which results a least amount of moisture and biuret content.27% which is less than other brands average 0. Biuret: Shriram Urea Contains about 0. A study Conducted by analyzing different brands of Urea from retailer’s outlet shows that the moisture content in Shriram urea is 0. SFC urea Contains biuret less as compared to other brands. 13 . 14 . in a proportion so that O2 content in the supplied gas is kept between 0. Purity = 99. At the end of process description a section on recovery of some important compounds like ammonia and water is provided which consists of a figure which explains how exactly ammonia is recovered from the different section of the plant followed by a brief explanation of ‘Hydrolyser Stripper Unit’. Moisture = 1. 1. Urea is commercially manufactured using ‘ammonia’ and ‘carbon dioxide’ as raw materials coming from the Ammonia Plant.7 % and CO2 purity is at least 96 % by volume.0 – 98. Ammonia a. Utilities: Steam – Panel I/C regularly monitors the pressure . The plant includes the following sections: NH3 and CO2 Compression Synthesis Section 1 st nd Stage Recirculation 2 Stage Recirculation Crystallization. Carbon-dioxide a. temperature and flow of 14K & 4K steam supplied by Power & Ammonia Plant every hour at Control Room. Purity = 96.0 % by wt. (min) b. Drying and Remelting Prilling and Solid Handling Hydrolyser Stripper Unit Raw Materials: The basic raw materials used in production of urea are ammonia and carbondioxide which are supplied by the Ammonia Plant.4 – 0.5 % (Dry Basis) NOTE: Anti-corrosion air mixed with CO2. Oil = 10 ppm (max) c.PROCESS DESCRIPTION Urea plant at DSCL operated on the Stamicarbon Total recycle basis.0 % by wt. (max) 2. 3 FLOW 3. Pressurized ammonia now heads up to Ammonia Pre-Heaters 23-501 A/B/C/D which are shell & tube heat exchangers. During the start up of the Plant. the whole of heater has to be supplied with middle pressure steam so as to evaporate the ammonia and to heat the vapor to about 150 in order to prevent cooling down of reactors preheated with 14 . Liquid ammonia at 23 atm gauge pressure & temperature of 40 maximum goes for filtration in Ammonia Filter Tank and then (with 10 ppm as maximum oil content left) to Ammonia Buffer Tank. Ammonia Reflux Pumps are then used to transfer the ammonia to the high-pressure Ammonia Feed Pumps(to prevent vapor lock in the pump. ammonia is transported to mixer 24-501.43 abs pressure & 40 temperature. After gain of sufficient heat to maintain desired reactor temperature (required ammonia temperature 85 ).38 PRESSURE (kg/cm2) 11.5 2. About 0.Cooling Water – The conformance of cooling water quality is monitored by Ammonia Plant on daily basis and records are kept. ammonia inlet temperature to the pump must be about 10 below the saturation temperature at the existing inlet pressure). For attaining this pressure.5 3.0 3.5% of O2 is introduced to CO2 before compression as its presence helps stainless steel to resist the corrosiveness of Carbamate.5 – 9. we need a finite amount of 2 temperature (190 ) and pressure (200 kg/cm ).0 – 9. Flow of the pressurized ammonia is regulated by the control valve FRC 504-1/2/3/4 provided in the discharge to suction bypass of each pump.0 – 8.5 – 3.0 5. following procedures are followed: • From a pressure of 1.8 – 14. CO 2 is sent for compression at Ammonia Plant end only – using 3 reciprocating 2 compressors to be compressed to about 200 kg/cm after the mixing of CO2 with anti-corrosion air (not being inert more than 4% by volume and 3 less than 15 mg/NM sulphur).5 – 4. Its temperature. pressure and flow are monitored by Urea Panel I/C hourly.5) (RX 1200) NH3 AND CO2 COMPRESSION: For synthesis reaction of Urea to happen.5 (MT/hr) (RX 8) (RX 2. Pressure of the discharged ammonia from Ammonia Feed Pumps is about 2 210 kg/cm . The supply characteristics of utilities for maintaining essential process control I/C are as follows:UTILITY 14K Steam 4K Steam Cooling Water TEMPERATURE ( ) 193-198 155 . and NH3 is pressurized at Urea Plant using ammonia feed pumps.160 20 . 15 . For shutdown purpose line from HP flush water pump 31-513 is installed in order to flush the inlet of the NH3.K steam. CO2 and Carbamate line of mixer24501 and the outlet line of reactors 24-502 B. mentioned figure is being called the ‘CO2 conversion per pass’. The system NH3-CO2-H2O shows at a certain pressure a certain temperature. In mixer. Total pressure inside the mixer is maintained by the use of let down valve PRC2 502 at 200 kg/cm which in turn results in the temperature of about 172-178 .SYNTHESIS: The feed components (pressurized NH 3 and compressed CO2) are pured in the orifice mixer 24-501 to mixed thoroughly which also have concentrated Carbamate (H2N-CO2-NH4) solution (43% NH3. The heat evolved during this reaction is being absorbed by the feed components themselves. Inside the reactor the conversion of about 64% of total CO2 feed into urea has been observed. some extra heat as sensible heat has been put in the ammonia feed so as to control the optimum temperature. These vapour escape from the top of first 2 2 . The overall heat of reaction inside the reactor is not sufficient enough to reach this required optimum temperature. the optimum temperature in the reactor remains at around 190 . Under design conditions NH3/CO2 ratio is 4 and H2O/CO2 ratio is equivalent to around 0. 31% CO2. An increase in NH3/CO2 ratio lowers while increases in H2O/CO2 ratio results in higher mixture temperature. The temperature of solution reduces due to evaporation of large amount of excess ammonia and part of the available Carbamate dissociating into ammonia and carbon dioxide. At constant pressure this temperature is supposed to change only with the change in the NH3/CO2 or H2O/CO2 ratio in the reactor feed. This part of the plant practically separates all the Carbamate. 21% H2O & 5% Urea(H2N-CO-NH2) – all by weight) coming from the recirculation section. This separation takes place in two stages. 13% CO2.64. the first stage operating at around 20 kg/cm and the second at 3 kg/cm . RECIRCULATION: Effluent from the two reactors consisting about 32% urea. the excess of ammonia and part of water from the remaining urea solution. First Stage: The reactor effluent is throttled through the letdown valve to about 20 atm g pressures. about 90% of the CO2 feed is spontaneously converted into Carbamate. Therefore. 18% H2O (by weight) and some of the unconverted Carbamate enters the first re-circulation section. 37% NH 3. The 16 .stage rectifying to MPCC (Middle Pressure Carbamate Condenser). The level in level tank is controlled by a control valve LRC-1501 or by regulating the speed of Carbamate pumps. The non-absorbed gases will rise through the condenser. The liquid from the first stage rectifying column is then fed to the first stage heaters and thus heated to about 160 . through submerged gas distributers. Rising vapours in the coulumn are cooled by this solution reducing the water vapour content in the gas stream considerably. The pressure in the cconditioned cooling water system is maintained by a head vessel on top of the prilling tower. This heat is removed by the conditioned cooling water flowing through the hairpin tubes of the condenser and circulated through water cooler by conditioned water pump. In the bottom of the MPCC a weaker Carbamate solution from washing column is introduced by means of intermediate Carbamate pump. The NH 3/CO2 in the gas is approximately 80. introduced into level tank. The heat input causes an additional vaporization of ammonia. The non-condensed NH3 and CO2 gases leave the top of level tank and are piped to the washing column. The solution temperature increases meanwhile to about 134 . into a Carbamate solution. During the formation of Carbamate from gaseous component ammonia and carbon dioxide and during the condensation of the entering water vapor heat is evolved in the condenser. 4% CO2. the gas phase is separated from the liquid phase in first stage separator. and 5% urea. condensed water vapour and ammonia. The gas phase out of first stage separator is returned to the bottom of first stage rectifying column in which as mentioned before.In the bottom of washing column this gas is distributed through submersed through submersed gas distributor in the Carbamate . 40% CO2. In this condenser nearly all the water vapours will be absorbed and about 90% of the gaseous CO2 is converted into the Carbamate. The outgoing solution is transported to the secondary recirculation system containing 58% urea. Together with gaseous CO2. the water content of the gas stream is reduced. 10% NH3. The vapours leaving the first stage rectifying column are introduced into the bottom of the MPCC. 12% H2O. a concentrated Carbamate solution is produced having a temperature of about 100 the boiling of the solution at the existing pressure and approximate composition by weight of 43% NH 3. The temperature of conditioned cooling water is controlled by a three way valve in the bypass line of the water cooler. The solidification temperature of this is about 78 In the level tank the gas phase is separated from the liquid phase.temperature here drops to about 132 as heat required for the gas formation in here is being extracted as sensible heat from the incoming synthesis solution. 28% H 2O by weight. carbon dioxide and water from the solution. The concentrated Carbamate solution is recycled to the orifice mixer by centrifugal Carbamate pump or first stage Carbamate pumps. The remaining solution is distributed over the stainless steel IMTP (Intallox Metal Type Packing) rings of first stage rectifying column. leave at the top and are together with Carbamate solution. 17 .solution. This ammonia reflux. The heat required for this gas formation is extracted as sensible heat from the solution and causes a temperature drop to about 116 . Because of pressure drop. Second Stage: The solution leaving the bottom of the first stage re-circulation separator passes through level control valve LIC-502 which gives the pressure drop from 20 atm to 30 atm g. The ammonia gas from washing column is condensed in ammonia condensers A 1. In the bottom of washing column a weak Carbamate solution from stage nd Carbamate condenser is introduced by means of 2 stage Carbamate pump. A2 and B. This ammonia is absorbed in water at 20 atm g pressure by passing the gas stream through ammonia scrubber. The remaining . The concentrated Carbamate solution is recycled to MPCC by intermediate Carbamate pump. The pressure of the first stage recirculation is automatically control by the control valve PRC-503 in the off gas line from scrubber level tank through which the inert are vented to the atmosphere. The concentration can be adjusted by means of the amount of water fed to washing column via ammonia scrubber. so that a pure NH 3 gas. ammonia and CO2 will gasify during the expansion. The non-absorbed gases will rise through the column. The temperature is controlled by means of ammonia reflux. onto which ammonical water is fed from the scrubber. the quantity being dependent on the inlet cooling water temperature and the plant load. which is in the discharge of their pumps. with a temperature of about 50 leaves the washing column. Together with the gaseous CO2. The solidification temperature of this solution is about 70 . The non-condensed vapours from the ammonia condenser are fed to the scrubber. Normal cooling water is used. The pressure of 20 atm g is sufficient for optimum condensation purpose. The liquefied ammonia is flowing into ammonia buffer tank. The solution from the ammonia scrubber level tank is fed to the washing column and vapour with inert will escape to the atmosphere. a concentrated Carbamate solution is produced. Here ammonia is dissolved in the process water and heat is taken out by cooling water. Thus gaseous CO2 and water vapour are completely removed from the rising gases. a spray desk is fitted. During the formation of Carbamate from the gaseous components NH3 & CO2 and during the condensation of the entering water vapour heat is evolved in the bottom of the washing column. A control valve LRC-503 controls the level in the washing column. Nearly all of inert will escape in the first recirculation through PRC-503. These non-condensable inert will carry gaseous ammonia out of the system. condensed water vapour and NH 3. being vaporized absorbs the heat of reaction. In the top part of the column which is filled with raschig ring. which have small amount of ammonia vapour.In the washing column the remaining water vapour will be absorbed and about 95% of the gaseous CO2 is converted into the Carbamate. Rising vapour in column are cooled by this solution reducing the water vapour content in the gas stream considerably. The solution temperature increases meanwhile to about 125 . 18 .solution is distributed over the stainless steel rings of the second stage rectifying column. is mixed in MLT with the liquor effluent from the centrifuges. through which the inert are going to the vent stack. Due to this pressure drop a considerable amount of water vapour and some ammonia will escape from the solution. as described before the water content of the gas is reduced. Drying and Remelting: The solution from second stage re-circulation separator is throttle in valve LIC504 and enters flash drum. The pressure of the second stage re-circulation is controlled by FRC-505 in the off gas line from additional Carbamate level tank. Here the remaining gases condensed in a weak Carbamate solution. MLT is provided with a stirrer which is not in use. The gas phase from the separator is returned to the bottom of second stage rectifying column in which. which is operating under the vacuum. in order to dissolve the crystals strain from . the pressure in the flash drum is controlled in such a way that the outgoing liquid is at about 90 . 28. 0. The gas phase is separated from the liquid phase in second stage re-circulation separator. which is also of submersed type. Urea solution pumps are installed to transport the urea solution via urea solution filter to the crystallization section. decreasing the solution temperature. The heat of reaction evolved during the condensation of water vapour. The gas phase is introduced in the bottom of the second stage additional Carbamate condenser.In the second stage re-circulation heater almost whole of CO2 and NH 3 still being present in the solution are removed by heating to about 150 . Crystallization. The solution over flows to the second stage additional Carbamate condenser level tank from where it is transported to second stage old carbamate condenser through second stage booster pump. The resulting concentration of urea in the solution being fed into urea buffer tank is about 70-75%. The solution and the non-condensed gases leave at the top of old Carbamate condenser and are separated in old level tanki 22-506. 0. ammonia absorption and Carbamate formation is absorbed in cooling water flowing through the tubes.4% biuret (by weight) flows to flash drum. The liquid phase is transported by means of second stage Carbamate pump to washing cooling column. The major proportions of the ammonia and CO2 in the vapours leaving second stage rectifying column are condensed in two (in series) second stage Carbamate condensers namely old and additional. The concentration of UBT and Mother Liquor Tank(MLT) solution are checked by measuring crystallization temperature point and comparing it with concentration vs crystallization point chart. A water connection is made to bottom of the additional Carbamate condenser in order to be able to adopt the concentration of the solution to the optimum condition. The incoming urea solution. The solution of about 70% urea.3% CO2. 1% NH 3. part of which is going to the centrifuges for rinsing. By means of air valve PRC-1501 in the vapour line to ejector to urea flash drum condenser.5% H2O. sieve bends and centrifuges. as per process requirement in the evaporator. 19 . This flow is controlled. From MLT the urea solution is pumped to the evaporator. The mother liquor separated from the slurry by means of sieve bends flows into MLT. This temperature is automatically controlled. Each by means of the sieve bends crystal slurry concentration is increased to about 45% by weight. From this tank the biuret concentration in the mother liquor relates to a maximum concentration that depending on the crystallization temperature to be sure on the urea is crystallizing. . The crystals still contain maximum 1. The heated air takes up the wet crystals and in transporting them through a pneumatic drying tube. in order to lower the final biuret content. The centrifuges are designed such that the crystals may be washed with a part of the frest urea feed. The washed urea crystals separated off in the centrifuges fall in to screw feeding system for the pneumatic drying system.the solution is concentrated under a pressure of 300-mm Hg abs.1 divider box which transfer it to the centrifuges. which regulate the fflow to the crystallizers. In crystallizers. In the down coming stream the super saturation will release on the circulating crystals until saturation of the liquid is obtained. which admits air before the ejectors. The crystallizers are provided with the level indicator controller. The liquor from the MLT is pumped to crystallizers in which a crystal suspension is in circulation. The biuret concentration in the system is about 8-9%. evaporation of the solvent take place under a pressure of 95 mm Hg abs and super saturation occurs in the surface region.5% of water and are dried in the pneumatic drying system to final moisture content of 0. The required absolute pressure in the condenser is maintained by the means of an evacuating system. Pressure is controlled through PRC-507 C/V. The vapours leaving the crystallisers and the evaporation section are condensed. In order not to exceed this maximum biuret concentration as much biuret in the form of mother liquor as corresponds with the fresh biret input must be continuously purged. The pressure is kept constant by pressure controllers. For pneumatic conveying of the crystals air is taken in via a filter and a blower for drying purposes this air is heated in a steam heater to a temperature of about 120 . The crystal suspension is extracted from the bottom and pumped by slurry pumps to sieve bends with a fixed capacity of 3 about 90 m /h. From the sieve bend the slurry is introduced into No. The concentrated solution of about 115 is mixed in the MLT with sieve bends solution from partial separation and the crystal strain from the centrifuges.3%. 3% is reached. 20 .the air takes up the moisture so that a final moisture content of the crystals of 0. the over size and the dust are dissolved in to the urea solution coming from UBT. The entire melting equipment is designed in such a way that the retention time is as short as possible in order to diminish biuret formation during remelting as much as possible. Out of this heater the solution flows via a filter to the rotating bucket. The heat of solidification is carried off by air sucked in through openings at bottom of the tower. The product separated in the cyclones goes to the melting equipment i. these two minimize the hold up in this vessel. the pneumatic tube is provided with steam jackets. During their fall the urea solidifies. In dust dissolving tank. By choosing a high circulating velocity in the remelter circuit. The product is transported via the product conveyor to the storage. out of which it over flows to a second heater. The melt is returned to the remelter. The separation of crystals from the air is carried out in cyclone. high heat transfer rates can be obtained and the dimensions of the heater can be as small as it is possible. The prill bucket distributes the urea melt in fine droplets over the tower diameter. The temperature is about 80 . The bucket is provided with a high level alarm in order to warn the operator when there is a danger of bucket over flow which might occur when the holes are getting clogged. The slurry is pumped from remelter to remelter heater where the suspended urea crystals are melted. on which a constant steam pressure is maintained. Conveyer loading chute transports the product into prill cooler where prills temperature is brought down and under size material is removed & discharged to dust dissolving tank. Therefore two buckets are provided. The product is fed in to remelter where it is suspended in to a circulating stream of molten urea. HYDROLYSER SECTION Feed to System: Desorption feed water from DWT is pumped through desorption feed pump to the LP absorber. The inlet and outlet of the remelter are tangential. provided with a stream cooil and a mixer. remelter.To add additional heat to the system. Prilling and Solid Handling: The concentrated urea melt from the remelter system is fed to urea melt distributor which is designed for net production of 1000 MTPD urea. The resulting solution flows to urea storage tank. The temperature in the remelter is kept around at 138 .e. The urea prill accumulating on the bottom of the tower are scrapped in to a slit by sccrapper. This heater is installed to melt the crystals still present in the remelter over flow. The temperature of desorption feed water varies between 40- . 50 and flows between 30-35 m /h. 21 3 . 2 desorber is sent to No. Second Desorber: The outlet of hydrolyser column after hydrolyser heat exchangers is fed to No. 2 desorber here remaining ammonia and carbon dioxide are stripped by 4K steam vapors from No. Hydrolyser Stripper Column: This is the main part of system where urea is hydrolyzed into ammonia and carbon dioxide. First Desorber: Desorption water after absorbing NH3 and CO2 in LP absorber and exchanging heat in desorber heat exchanger is introduced in first desorber for stripping out ammonia and CO2 in it.5 kg/cm . 1 desorber where it is used as stripping agent for ammonia and CO2. Vapors from hydrolyser 2 are sent to first desorber pressure is maintained 18. Heat exchangers are operating as feed effluent exchangers. heat of reaction is given by 36K steam. Reflux Condenser: Vapors from desorber outlet at 112 are condensed here up to 54 . Stripped solution is taken to desorption heat exchanger where it is cooled. CO2 is fed at the bottom which helps in fixing NH 3.Desorption feed water from desorption feed pumps is sprayed at the top column where it absorbs NH3 vapor coming from reflux condenser level tank. the condensed vapor and liquid mixture are sent to reflux condenser level tank at 54 . 22 . 2. . Spraying Unit This unit consists of calibrated spray nozzle to spray neem oil water emulsion drawn from storage tank.NEEM COATED UREA The unit consists of three main parts: Concentrate Preparation Unit Emulsion Preparation Unit Spraying Unit Concentrate Preparation Unit In this unit 50 litres of neem oil and 2-5 litres of emulsifiers are added together and mixed thoroughly with the help of fan jet nozzles. Emulsion Preparation Unit The concentrate produced in concentrate preparation tank is transferred to emulsion preparation tank and 150 litres of warm water is added to it. The solution is stirred by circulating through specially designed ejector nozzles. Emulsion prepared in emulsion preparation tank is transferred to emulsion buffer tank. The neem oil and the emulsifier mixture prepared are taken into emulsion preparation tank via two ejector nozzles. on to the curtain of urea prills at conveyor no. mixing nozzles and acoustic nozzles. Oil emulsion at the rate of 120-150 litres/hr is sprayed for a prilling load of 40-50 Mt/h to get minimum of 300-500 PPM neem oil coated urea prills. 23 . . In case product contains oil. Vacuum in Flash drum Condenser.3% Prill size is to be monitored with bucket speed and confirmation with analysis by PCL. If it is high.8 mm will be more.5 % and air in the first stage should be about 12m /hr. At higher bucket speed. Prill size of less than 0.20%. check: Moisture content of crystals from centrifuges which should not exceed 1.30% by weight. following things has to be checked: Free ammonia in UBT. Prill size of less than 1. check urea solution.8 mm is to be maintained at less than 4%.0 mm is to be maintained at less than 4%. Free ammonia: It is to be maintained less than 0. At lower bucket speed. It is to be maintained with bucket speed. Adjust load on centrifuge and pusher strokes accordingly. which is to be maintained at less than 2 0. If colour is not OK.CRITICAL PARAMETERS OF PRODUCT QUALITY Colour: Product should be milky white in colour. following things were checked: O2% in CO2 should not be less than 0.3 mm is to be maintained at less than 0.5% Kg/cm absolute. Maintain the optimum bucket speed.760 Kg/m . prill size below 1mm will be more. 3 3 Moisture: It is to be maintained 0.If it is increases. Clean the bucket cone if desired prill size is not obtained. At higher speed bulk density will be more and vice –versa. Confirm from PCL analysis. Wash sieve bend for the proper filtration Bulk density: It is to be maintained between 700. Check and wash the sieve bends for proper filtration.02%. prill size above 2.5% by weight. Filter Cloth might have torn out. Sieve analysis: Prill size of more than 2. which should be less than 0. 24 . 65 and maximum limit is 1% as per SCF standard. If it is increases. 25 . following things has to be checked: Remelter heater temperature which should be between 137-139˚C. Increase rinsing flow to the particular centrifuge which contains high biuret. Biuret and rinsing flow to individual centrifuges. Ensure that indication is correct and instrument is calibrated.Biuret: It is to be maintained below 0. biuret is formed as H2N-CO2-NH4 ↔ H2N-CO-NH-CO-NH2 + NH3 .heat This is a slow and endothermic reaction and show that if one mole of ammonia is epelled out from two mole of urea. A biuret content of 1% is considered as a safe limit. as well as their vapours involved in the process. If for any reason the oxygen supply is cut-off.5% wt. Longer residence/ retention time at temperature. This means that the conditions are to be avoided particularly in places where there is sufficient time for biuret formation. . Biuret: A problem faced by every urea maker is the formation of biuret during the production process. Formation and Control: During the formation of urea. the unit should be shut down immediately. In the stamicarbon process corrosion is restricted to a negligible amount by utilizing its grade through current stainless steel and non-expensive patented oxygen is injected to maintain an oxidizing atmosphere. Biuret in fertilizer grade is considered harmful because of its damaging effects on several kinds of vegetation.MAJOR ENGINEERING PROBLEMS Corrosion: An important problem is the highly corrosive nature of the urea and the Carbamate solution. Its content in fertilizer grade urea has to keep as low as possible. The Biuret is favoured by following conditions: High urea concentration. Since the biuret is toxic/ harmful to plants/burns down green leaves. biuret is formed. High temperature. Low Ammonia concentration/ low vapour pressure. Permissible maximum biuret content in fertilizer grade urea is 1. 26 . 1 ammonical nitrogen (max) II. Besides handling of slow material the fertilizer plant operates at high pressure and temperature. The ammonia plant is designed so as to shutdown automatically in case of any . IV.POLLUTION CONTROL AND INDUSTRIAL SAFETY TYPES OF POLLUTION IN FERTILIZER INDUSTRIES I.) and 69 mg/m (max. III. Safety Features Safety of workers and equipment in the plant is of prime importance in any industry extensive. EFFLUENT (PROCESS CONDENSATION FROM THE SYSTEM) PCBS = NH3 Content 5ppm (max) UREA content 5ppm (max) FREE AMMONIA FROM AMMONIA SCRUBBER PCBS = 332 Kg/h Exhaust gas (max) WASTE WATER PCBS = 100mg. environment consideration have been adopted right from the intial designing of plant besides of plant healthy operation practices. Safety measures are taken in the plant due to hazardous and toxic materials like naphtha and ammonia and also other highly inflammable and explosive gases like synthesis gas.) NH3 and Urea. the normal laid down by the control board standards. Pollution Control Fertilizer plant deal with hazardous and toxic materials which are extremely poisonous and can ever cause death. In the fertilizer plant. Hazardous chemicals and effluent stream are recycled as far as possible and the discharge leaving plant equals if not better. ATMOSPHERE POLLUTION BY UREA DUST FROM PRILLING TOWER Pollution Control board standard (PCBS) for urea dust content at out of dut 3 3 collector is 50 mg/m (max. H2 gas etc. As A result SFC has been awarded the state pollution control award. SFC has been aware of it and has taken actions which are beyond economic consideration. They do not leak into the atmosphere. 27 .emergency. chemical goes into specific drums and vessels. All hazardous material. Personal Protective Equipment’s(PPEs) used in Plant: Helmets. Normally we used ammonia PPEs for isolating the Ammonia leakages in the plant. Ammonia forms an One inflammable mixture in also air in the range of 16-25% concentration and it can lead to a cold burn also. We have Ammonia feed pumps. 28 . goggles. In addition to this firefighting arrangements in the form of fixed installations and a mobile fire brigade are available to fight and minimize the damage in case of fire. Their main functions are: Permit system observance Hot jot permit work General Vessel/confined space entry permit Work at high permit Excavation work permit General safety observation guarding monitoring Machine belt safety monitoring Conveyor control Hot job proof material/fitting Explosion Alarms No smoking First aid fire extinguisher Toxic hazard management Good Engineering practice monitoring The main hazard in urea plant is: Ammonia gas: of the raw materials in the plant is ammonia.Safety measures have to be full proof interlocks and trip devices have been provided to product the plant and machinery from damage in case of any disoperation due to any error by both the operating staff or malfunctioning of instruments. Ammonia canister Masks and onBA line BA set are gloves. This mixture can catch fire in presence of ignition source. ammonia canister mask and online sets. Self-contained breathing apparatus. SFC has a separate safety department which caters all the plants and is responsible for all safety measures. BA sets. However as ammonia is highly dispersible gas in air. In case of heavy ammonia leakage it can form an inflammable mixture. it gets diluted and can create only a rare chance of forming explosive mixture. hand aprons. Emergency response plans for each plant and a total complex have been etched and strict monitoring and adhesive is expected in each plant.available in the prominent locations. Training work force awareness in addition. 29 . It is necessary to use PPEs in case of Ammonia leakage for isolating the leak point. To control this much heat I have designed a vertical tower which containing tubes for cooling .7% Urea = 0.23 oC Tube = 25.8664 *103 Kcal/hr Now to find heat transfer area and heat transfer coefficient I used iterative method .3% Water = 94% Cooling water :Flow rate = 100om3/hr Inlet temp = 35 C DESIGN: As we now that absorption of ammonia is exothermic process which release much heat when we absorbed so if we design a normal absorption tower then we cann’t control this much heat and temperature will rise and if temp will rise then absorption of ammonia is cann. Absorbing agent :.8 (Kern Table 29) ( Kern Eq.2 mm (1 in) Iteration 1) Heat transfer area(A) = Q/U∆T = 200.PROJECT GIVEN: PROCESS DESIGN OF AMONIA SCRUBBING COLUMN Gases coming from ammonia condenser at 155.138 ft2 Flow rate(w) = 7275.79168 m2 No. So Amount of heat to be removed = 1322.45 LMTD for system = 13.3 ) Now So .25 lb/hr Mass Velocity (Gs) = 52681.058 lb/hr ft2 Reynolds No. (Res) = 3317. So basically it’s like a shell and tube heat exchanger.33 kgmol/hr Ammonia = 5% Carbon dioxide = 0. Allowable concentration of ammonia in exit gas mixture is 1.778 Shell dia = 25 in Shell side heat transfer coefficient :Area of shell(as) = 0.t be possible .13% of ammonia . Assume U = 500 Kcal / hr m2 oC (existing system’s) R= (T1-T2)/(t2-t1) = 0 S = (t2 –t1)/(T1-t1)= 0. of tubes = 252.12 m2 Tube area (at) = 0. 7.Liquid coming from Desorprion water tank Flow rate = 182.05% .25kgmol/hr containing 82. 40 Kcal / hr m2 oC So Finally Final Heat Transfer Area = 125.54 Kcal / hr m2 oC Ud = 124.377 D = 0.25 lb/hr Gt = 752944. 6.293 ft2 Flow rate (w) = 220462.8 Kcal / hr m2 oC Overall heat transfer coefficient :Uc = 363.04 Kcal / hr m2 oC Iteration 3) Uc = 193.594 at = 0.15(b) ) (Kern Table 10 ) (Kern Table 10) (Kern Figure 25) (Kern eq 6.9 Kcal / hr m2 oC Iteration 2) Uc = 197.5 hi = 799.5 in (Kern figure 28 ) ho = (Kern Eq.0722 Ret = 34699.5 ) (Kern 6.8 Kcal / hr m2 oC hio = 695.94 m2 Length of tube = 4m No of tube = 390 Shell Outer Diameter = 29 in Tube Diameter = 1 in Baffle spacing = 21.45 Kcal / hr m2 oC Ud = 173.8 lb/hr ft2 Velocity of fluid (V) = 3.38) (Kern 6.17 760.13) .JH = 30 and (c*µ/K)1/3 = 4.89 Kcal / hr m2 oC Tube side heat transfer coefficient :at’ = 0.43 Kcal / hr m2 oC Ud = 122. 31 .