Light Metals 2007 Edited by Morten Sørlie TMS (The Minerals, Metals & Materials Society), 2007Light Metals Edited by TMS (The Minerals, Metals & Materials Society), 2007 MANUFACTURE OF DETERGENT GRADE ZEOLITE-A FROM SODIUM ALUMINATE LIQUOR OF ALUMINA REFINERY, DAMANJODI : NALCO’S EXPERIENCE & SUCCESS STORY C.R.Mishra & B.S.Pani Research & Development Department, National Aluminium Company Limited (A Government of India Enterprise) Nalco Bhawan, P-1, Nayapalli, Bhubaneswar – 751013, Orissa, India Keywords: Sodium Aluminate Liquor, Sodium Silicate Solution, Gel Formation, Spray Drying, STPP Abstract A Cost-effective Technology has been developed for Manufacture of Detergent Grade Zeolite-A from the Sodium Aluminate Liquor of NALCO’s Alumina Refinery, Damanjodi. The Technology was developed jointly by NALCO and Central Salt and Marine Chemicals Research Institute (CSMCRI), Bhavnagar, India through extensive Laboratory work as well as Pilot Plant trials. Based on the Technology so developed, NALCO have set up a commercial plant to produce Detergent Grade Zeolite-A .The Plant has been positioned directly in the liquor loop of its 1.575 mln.tpy Alumina Refinery. The NALCO-CSMCRI technology is based on their internationally patented process. The uniqueness of the process is its adaptability to integrate into the operational loop of a Bayer Process based technology without disturbing the alumina production cycle. Use of in-process aluminate liquor as the main feed stock material results in excess 20% reduction in cash cost of production as compared to the conventional route of Sodium Hydroxide and Alumina to produce aluminate liquor. The Detergent Grade Zeolite-A Plant was commissioned in 2001 and is in steady commercial operations since then. Zeolite-A produced at NALCO matches well with that of the international standards and has been well accepted by detergent manufacturers for producing a wide range of domestic and industrial grade detergents. NALCO and CSMCRI are now in a position to offer technology and project consultancy globally for setting up of Zeolite-A Plants in Bayer Process based primary alumina producing industries. compounds or for the selective adsorption of gases. These unique properties are utilized in diverse industrial process such as the purification of water as well as other liquids and gases, chemical separations, catalysis and the decontamination of radioactive wastes. Detergent Mineral Detergent builders have experienced major changes over the past twenty-thirty years. With more and more nations banning Sodium Tri-Poly Phosphate (STPP) based detergents alternative eco-friendly builder material i.e. synthetic Zeolite (Zeolite-A) used as builder material has come to the centre stage. Besides, the changes in use of Zeolite-A builder material, the trend towards liquid and compact detergents led to a sharp reduction in the use of Sodium Sulphate as a filler agent. The Zeolite used in detergents is termed as Zeolite-A. The composition of Zeolite-A is therefore 1 mole of Soda and Alumina with 2 moles of Silica and 4.5 moles of water, which is equivalent to 22% water at complete equilibrium. Zeolite-A In recent years, there is wide acceptance and interest in the worldwide detergent industry in the eco-friendly builder material: Zeolite-A. The principle cause for the same being the need to reduce or eliminate the eutrophication (a process of diminishing the percentage of dissolved oxygen in water bodies and thereby affecting marine life) caused through the discharge of phosphates in the laundry effluents. This civic need has resulted in rapid growth in demand of Zeolite-A as phosphate substitute material in detergents and industrial cleaning agents. In detergent powders, builders also required to carry absorbed liquid components of the formulations (e.g. surfactants) in order to produce a dry free-flowing material. Historically, STPP was the universally preferred builder. This material, which contains essential plant nutrients, was originally considered to be safe and environmentally acceptable. However, it emerged during the early seventies that excessive amounts of phosphates in surface water contribute to eutrophication. Since detergent phosphates accounted for substantial proportion (about one third) of the phosphate burden on the aquatic environment, detergent manufacturers voluntarily developed alternatives to maintain their high environment standards. Synthetic Detergent Grade Zeolites (Sodium Alumino Silicates), which are similar to natural minerals, were found to be highly effective builders. Given their function, effectiveness and their safe ecological properties, synthetic Zeolites have been widely Introduction Zeolites are aluminosilicate minerals that contain alkali and alkaline –earth metals such as sodium, potassium and calcium and water molecules within their structural framework. Na2O . Al2O3 . 2 SiO2 . 4.5 H2O They are relatively porous, enclosing inter-connected cavities in which the metal cations and water molecules reside. Because of the presence of water, the Zeolites swell and boil upon heating, and they were named by the Swedish mineralogist A.F.Cronstedt, in 1756, in allusion to this property (i.e., from the Greek Zein, “to boil” and lithos, “stone”). The cations and the water molecules have considerable freedom of movement within the framework of aluminium, oxygen and silicon atoms; this gives the Zeolites the cation exchange and reversible dehydration properties. The porous frame-work of the Zeolites enables them to act as molecular sieves, i.e., they are used to separate molecular mixtures on the basis of the size and shape of molecular 119 both the feed stock materials were tried for production of Zeolite-A. National Aluminium Company (NALCO ) & India’s Interest NALCO’s Corporate R&D. thereby decreasing deposits on textiles and on washing machine parts. caused by redeposit of solid during repeated wash cycles. Zeolite-A crystals do not remain on fabrics and are easily removed on rinsing. Zeolite-based compacts and super-concentrates offer important environmental advantages and cost competitiveness. Zeolite-A can minimize this effect by removing (by adsorption) dissolved matter. gives excellent results in achieving superior and economical wash. there is continuous research in development of more efficient builder and filler materials. Bhavnagar. 120 . It coagulates the colloidal dirt and pigments causing easy removal. The water softening action of Zeolite-A reduces precipitate formation. It can also be included in a wide variety of domestic and heavyduty laundry liquids (super-concentrates). use of Zeolite-A in place of STPP adapts well into existing production facilities of detergent manufacturing. as a part of its continued endeavours towards development of new products & processes for production of different value added items. a Research Laboratory of Government of India’s Council of Scientific & Industrial Research and jointly developed a novel process know-how for manufacture of Detergent Grade Zeolite-A at a commercial scale using separately Alumina Tri-Hydrate (ATH) and Sodium Aluminate Liquor as the main feed stock materials. Furthermore. Repeated laboratory and pilot scale experiments were conducted which established identical product quality of Zeolite-A matching with international specifications. the ion exchange is strongly enhanced with increase in temperature. the stiff competition it faces from more expensive enzymes. is the preferred builder for detergents designed for brightly coloured clothing. Damanjodi in the district of Koraput. Zeolite-A enhances detergent performance due to electrostatic effect and supports soil/dirt removal. Zeolite-A being not only efficient but also cost effective has well withstood. The presence of Zeolite-A does not interfere with the biodegradation of Linear Alkyl Benzene Sulphonates (LABS). The main function of Zeolite-A is to soften the wash water by reducing calcium and magnesium concentration. It also be noted that due to the increasingly stringent environmental protection law to protect natural and man made water bodies. Zeolite-A has contributed to the development of compact detergent powders through its high absorptive capacity for surfactants. Due to cubical shape with rounded corners and edges. preventing greying thereby. Zeolite-A is a stable detergent builder material under all washing conditions. Zeolite-A increases efficiency of bleaching agents by the removal of metal ions in the wash and supports the foam-suppressing action of soaps. The unwanted water-soluble dirt molecules do not finish up on the other articles but are absorbed on Zeolite particles. Zeolite-A can reduce this effect by adsorption of dissolved dyes. Toxicologically it is safe. the Cost economics of using Sodium Aluminate Liquor was comparatively attractive from various techno-commercial considerations. thus. Zeolite-A particles tend to form aggregate with other sewage constituents and are largely eliminated in the presedimentation of sewage treatment. During the course of its said R&D effort. Zeolite-A releases fewer sodium ions. which is enhanced by a high concentration of sodium ions in the wash water. and. The exchange of sodium for calcium ions is partly dependent on temperature and alkalinity. Average particle size 4 micron and maximum size not exceeding 20 micron of Zeolite-A has made it suitable to pass thought the mesh size of clothes. Though. till date. with suitable co-builder. The R&D and Pilot Plant Studies were entirely funded by NALCO that ultimately succeeded in developing a unique Zeolite-A industrial production technology in the year 1996. Alkaline reaction which is preferable for washing (with pH less that 12). ensuring maximum builder efficiency during the complete wash process. More importantly. Applications and Consumer Acceptance Unique combination of functional properties has led to Zeolite-A being widely accepted by detergent manufacturers worldwide. whereas for magnesium. Zeolite-A acts in competition with the fabrics during the deposition of sparingly soluble compounds and reduces incrustation of the laundry. hence.accepted as environmentally compatible builders and there has been a continuous worldwide shift from phosphate to Zeolite usage based detergents. thereby decreasing deposits on textiles and on washing machine parts. Orissa. Functional Properties and Advantages of Zeolite-A Higher sequestering (removing soil or dirt particles from fabrics) power for calcium ions even at higher temperature. Gujarat. India. India using Alumina Tri-Hydrate (ATH) or Sodium Aluminate Liquor of Bayer Process Stream as the main feed stock material. Zeolite-A. was working for development of a technology for setting up of a Detergent Grade Zeolite-A production plant since 1986-87 at its Alumina Refinery Unit. How Zeolite-A works The main function of Zeolite-A is to soften the wash water by reducing calcium and magnesium concentrations in the wash feed water. Zeolite-A is formulated in detergents to the extent of 2530%. Compared with water soluble builders. A general problem in washing is the graying or yellowing of laundry. NALCO collaborated with Central Salt & Marine Chemical Research Institute. Another problem is dye transfer to noncoloured textiles. Repeated cross checking of the product quality in the third party laboratories was taken up by NALCO which established conclusively that the product quality is repeatable and at par with the international standards. The water softening action of Zeolite-A reduces precipitate formation. Zeolite-A and Alumina production in the same factory increased profitability of the factory significantly and utilization of equipment became maximum. Zeolite has no hazardous or harmful impact on microorganisms. It was found that ZeoliteA is essentially non-toxic via oral. ocular and respiratory routes of exposure and it comes under safe category for consumers and plant workers. NALCO took an investment decision for setting up of a 10. NALCO had the following specific advantages for entry into the production of Zeolite-A due to the following inbuilt strength available with the company. NALCO had sound raw material base i. Russia and in EPO countries viz. The technology so developed jointly by NALCO & CSMCRI. The use of Zeolite-A in detergents poses no risk to man or the environment. the demand of detergent grade Zeolite in India will rise substantially. Detergent grade Zeolites generally enter the environment via the sewerage system. It is safe from both human and environmental standpoint. (i) Special investment advantages were available in Zeolite-A plant which was set up directly in the loop of Alumina Refinery thereby it was economical and production cost was reduced by at least 20% compared to any remotely located Zeolite Plant. Germany & France. (vii) (viii) Since no fresh capacities for Zeolite manufacturing are in the pipeline in the country. Patent Application has also been filed in India and awaiting grant of the same. Zeolites improve sludge settleability and can be removed by sedimentation. of India. Bhavnagar was licensed to NALCO through National Research Development Corporation (NRDC). Patenting of Know-how The Process Know-How has been patented jointly in the names of NALCO & NRDC. the estimated Zeolite content as a builder material in Zeolite based detergent being 25% and with an annual shift of 5% of total detergent production towards Zeolite based manufacturing. Sodium Aluminate Liquor available for putting up such a diversification unit. Zeolite-A is completely safe from environmental point of view. at the very laboratory and pilot plant test stages for process and product optimization. Bureau of Indian Standards (BIS) has introduced and “Eco-Mark” scheme for detergents. Health and safety aspects of detergent grade Zeolite have been studied extensively. Synthetic Zeolites do not cause any respiratory problems either.000 tpy) commercial plant. Australia. NALCO being one of the lowest cost producer of Alumina in the world. time was ripe for NALCO to take an appropriate investment decision in the project. Further. It is also safe for the plant workers. the novelty of the process and its capability to be scaled up to a commercial size plant. Lowest production costs and high profit of synthetic Zeolite produced in the loop of Alumina production warranted NALCO to opt for entering into such a model diversification project. New Delhi through Patent Cooperation Treaty (PCT) Route and Patent has been granted in China. water flora or fauna and does not derange biological flows or waste waters. Infrastructure and auxillary plants were readily available and NALCO wanted to exploit it to the best possible applicational frontiers. New Delhi. Detergent grade synthetic Zeolite (Zeolite-A) replaces STPP as the builder materials in detergents. Zeolite-A is safe for the environment at concentrations resulting from its use in laundry detergents. Further scaling up is 121 . It is safe from dermal. at an investment of 250 million US$.Keeping in view. contributing to the removal of poisonous substances from surface water. the leading engineering consultancy firm of India. Comprehensive studies have shown that any settling out of detergent grade Zeolite in sewers is not a problem. technology warehousing and marketing arm of the Govt. The detergents qualifying for getting this “Eco-Mark” should not have any “Phosphate Builders”. Production of Synthetic Zeolite in the loop of Alumina Refinery is a completely closed cycle without any harmful effect on the environment. Aluminium producer of India. Environmental & Safety Aspects of the Project (i) (ii) (iii) (iv) (v) (vi) (vii) (viii) (ix) (x) (xi) (xii) (xiii) Production of Zeolite-A belongs to distinctly “Clean Technologies” and hence “Eco-friendly”. Zeolite does not act as fertilizer. ocular and respiratory routes of exposures. 25-30% of total detergent market in India is expected to shift towards Zeolite based detergents in coming 5-6 years. (ii) (iii) (iv) (v) (vi) (xiv) NALCO’s Zeolite-A NALCO’s Detergent Grade Zeolite (Zeolite-A) Plant is based on indigenously developed technologies and is scaled up to appropriate commercial size plant. During sewage treatment. The usage of STPP in detergent production is legislatively banned or heavily restricted in most of developed countries as well as in several developing countries. Zeolites in wastewater behave physically like other inorganic particulate matter.000 TPA Detergent Grade ZeoliteA plant in the loop of its Alumina Refinery. designing and scaling up to a modest size (10. NALCO wanted to tap a major share of this demand at a right time and utilizing the right technological opportunities. dermal. Based on the successful outcome of laboratory & pilot scale experimentations. Favourable market situations both domestic and international were one of the major guiding factors for entry into such novel areas of diversifications. NALCO’s Best Advantage Being the largest Alumina. took best advantages of the situation and opted for selecting Sodium Aluminate Liquor as the principal feedstock material for production of Zeolite-A instead of with Alumina Tri-Hydrate (ATH) for the same. NALCO engaged Engineers India Limited (EIL). Zeolite has great capability of Ion Exchange and linkage of several heavy metals.e. above prepared sodium aluminate solution is added at the controlled rate to the sodium silicate solution previously transferred in the main reactor. When ageing is complete. previously taken into sodium silicate solution preparation tank. The dried product from product bin is then packed into standard polypropylene lined bags for marketing to the consumers. requisite quantity in volume is taken in a stirred solution tank. 1. using in-process Sodium Aluminate Liquor as the main feed stock. Ageing of Gel After completion of gel formation. Caustic Sodium Silicate Soda. 104 H2O) takes place in the reactor. is considered sufficient. After drying. gives a rare distinction to NALCO’s plant as being the only one of its kind. Zeolite-A Plant opens up new avenues for setting up a whole range of Alumino-Silicate products.2 Na2O.e. generated elsewhere in the Zeolite manufacturing process. Al2O3. After thorough mixing. it is then filtered in Polypropylene plate and frame filter. Process Description Preparation of Sodium Aluminate Solution Based on total Al2O3 and Na2O content in the sodium aluminate liquor drawn from Alumina Refinery. Al2O3 and Na2O contents of final dilute solution of sodium aluminate are determined and suitably corrected. fillers etc. Product quality specification of NALCO’s Zeolite-A is at par with international standards. This results in formation of final complex composition of detergent grade Zeolite-A.Sodium Silicate : less : more : less Only for crystallization Consumption of NaOH : more Raw material Silicate : less (based on one Water : more mole Al2O3) Heat Energy Requirement -for preparation of Sodium Aluminate solution -for aluminosilicate gel formation -for crystallization Unit operation -Dissolution of Alumina Trihydrate In caustic solution -Aluminosilicate gel formation at ~700C -Crystallization Hydrothermal Conditions for ~3h -Simple dilution of Bauxite leachate liquor -gel formation at ambient temp. NALCO Process : Items Raw materials Conventional Process NALCO Process Alumina Tri-Hydrate Bauxite Leachate Caustic Soda & Liquor.possible both through modular addition and module re-sizing routes. the product is stored in a product bin. Filtration of Product Slurry After cooling down the product slurry in heat exchanger. Preparation of Gel After preparation of above solutions. i. wet cake in the filter press is washed in two stages. Condensate per kg. The entire mass is then stirred to ensure homogenous mixing of all components. In this step. After washing aeration of wet washed cake using compressed air is done in the filter press itself to remove maximum water present in the cake and also to ease the cake removal operation from the filter-press. Drying of Wet Cake The wet cake obtained from the filter press is then dried in a spray drier to eliminate the requirement of pulveriser. reactor under constant agitation. After filtration. it is allowed to age for the optimized duration. catering to various other industrial applications like catalysts. The operation of the Zeolite-A Plant located adjacent to its Refinery Complex at Damanjodi is 100% environment friendly. known quantity of sodium silicate. immediately whole mass is heated in the same jacketed s. This reaction is carried out at room temperature and under constant agitation. calculated quantity of wash filtrate generated in Zeolite manufacturing process elsewhere and make up condensate is added to sodium aluminate liquor previously taken into stirred sodium aluminate solution preparation tank.8 SiO2. Firstly with filtrate of second washing stage. The temperature of the mass is raised to the previously optimized Comparison of Conventional Process Vs. The cake pH should come down to 10. The filtrate (which is mostly containing caustic soda) is stored in a proper storage tank and can be partly recycled in the process and remaining filtrate is returned to the Alumina Plant. and condensate. first part in the manufacture of detergent grade Zeolite-A process is preparation of gel. SiO2 and Na2O contents of the final solution are determined and suitably corrected before use for reaction. Use of Sodium Aluminate Liquor whose quality in terms of stringent chemical and physical liquor characteristics from Alumina Refinery requirement helps to produce high quality Zeolite-A in a cost-effective manner. temperature and after attaining the temperature.5 to 11. of dry Zeolite. and then with hot condensate. After thorough mixing. The complex gel formation (containing 3.s. (previously analyzed for Na2O and SiO2 content) is added to calculated volume of wash filtrate. -Crystallization at <1000C for <2h 122 . A condensate wash of 2:1. To adjust Na2O content in the final solution. Preparation of Sodium Silicate Solution Based on analysis and quantity of sodium aluminate solution to be reacted. Production of Zeolite-A directly in the loop of NALCO’s Alumina Refinery. the product slurry is transferred to the product slurry storage tank via a heat exchanger where the product slurry is cooled by using cooling water. 2 kg. Mixed solution is then stirred to ensure homogeneous mixing. Process Flow Sheet for Manufacture of Zeolite .A NALCO’s Zeolite-A Plant : An Overview of Reactors 123 . Seth and P. Bhubaneswar for kind permission for presentation of the paper in TMS–2007 Conference. P. th Specification of NALCO’s Zeolite-A PARAMETERS VALUE 1. August24-27.. Korea. M.R. p.Mishra.) 0. RP7.Comments -Higher raw matl.5 1. 90% Min. 160 85 ± 10 Not more than 4 micron 11 ± 0.5 6..Gandhi. gm/cc 6.Pradhan. Crystallinity (X-ray diffraction) (as compared with 4A BDH powder) 7. M.85 ± 0. 1(1). 1997. to need to use input material that make detergent effluents least polluting. 15 Edition. C. 1139-1143.0 ± 0.Seth. 15-20.Seth & P.19. Process Chemicals & Allied Products Ltd. C.Whiteness index Min. Kolkata.M. Sambalpur University.Gandhi. Amo Detergent Pvt. The New Encyclopaedia Britannica. Infinium Det-Chem Pvt.M.Natrajan.. 124 ..M. particle size. M. Ltd. M. Plant engineering. Kolkata and Jyothi Laboratories Limited..Oza.2 1.0 1.45 ± 0. Having successfully developed . References 1. Kolkata. p.R.1 Min. Sialca Industries. cost -low raw matl. Critical comments and suggestions received from Sri C. installed and operated the technology in-house and also successfully marketed the product to large numbers of indigenous buyers. Thus . Seoul. Bulk density. increasing consumerism is going to put greater pressure on environmental degradation with every passing year. 1996. NALCO during the course of investigation and setting up of the Zeolite-A Plant are also gratefully acknowledged. 11th International Zeolite Conference. pH (5% slurry) 4.Mishra. 1989. 5. Chemical Industry.R.R. 3. p. Kolkata. Eighth National Conference on Surfactants. R. Particle size analysis (a) % finer than 4.R.M. p. Zeolite-A Consumer Base NALCO is selling its Zeolite-A to leading Detergent Manufacturers viz. C.1. As the awareness for meeting the environmental requirement of protection of water bodies grows. Macropaedia.. Mumbai. Goa..Mishra & M.R. Waseda University. C..S. October 18-20..Natrajan. Ltd. Ahmedabad. 4. M/s Procter & Gamble. cost -Higher energy -low energy consumption consumption -More unit operations -less unit operations Acknowledgement Authors are grateful to the Management of National Aluminium Company Ltd.ZMPC’97 International Symposium on Zeolites and Mocroporous Crystals. 2.Somani.M. P. the demand for Zeolite-A is expected to increase manifold. Emulsions and Bio-Colloids. Mole composition (based on chemical analysis) 5. Japan 1997. Amochem. Technology. Calcium binding capacity mg CaO/gm of dry Zeolite 2. Vol. Total Project Management and Continued Technical Assistance (CTA) for any intending Zeolite-A producer world wide along with its collaborators CSMCRI (Process Designer) and EIL (Project Engineering).5 micron (Sedigraph) (b) Avg.Mishra.S. Chennai to the best of their satisfactions. the need for controlling degradation of water bodies and even decreasing sources of water for human and industrial consumption shrinks. NALCO is now ready to offer Process. Plans are afoot for export of Zeolite-A in International Market.Oza. R.168.R. August 12-17. Tokyo.0 (Max. 95% Na O Al O SiO HO 2 2 2 2 3 Conclusion Detergent Grade Zeolite (Zeolite-A) has a bright future ahead. India being a developing country. would also grow by the year. Indian J.Somani. Market take off stage has just reached in India and it will get a significant boost on introduction of legislative measures in the country as has already been done in most developing and developed countries of the world. Dona Chemical. d50 (Sedigraph) 3. Chairman –CumManaging Director.