International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 5 - Mar 2014 Single Stage Brine Filtration System in Chlor-Alkali Industries Unnikrishnan H 1 , Rakesh A2 1 M Tech Student , 2Assistant Professor Production and Industrial Engineering, SCMS School of Engineering & Technology, Kerala, India Abstract— The Conventional Brine Filtration in Chlor-Alkali industries is done using clarifier and precoat systems which is time consuming and requires huge amount of electricity .It also generates large amount of sludge causing environmental pollution .The maintenance cost is also high these problems are overcome by single stage brine filtration system. This report compares the present and conventional filtration systems and its benefits. The use of new system like PTFE membrane for brine filtration is also included. This report is based on the study conducted on one of the Chlor - Alkali plant in Kerala. Keywords— Clarifier, PTFE membrane, Saturator. I. INTRODUCTION The main raw material of chlor-alkali plant is the salt. The salt is purified only after making it into brine after which it is filtered using the clarifier and other secondary filters. The purified brine is fed towards electrolyser where it is converted into different by products like chlorine, hydrogen and caustic soda. The caustic soda which is one the main product in the chlor-alkali industry used in the manufacture of soaps and detergents, the quality of the caustic soda depends on the quality of brine used. The traditional filtration of brine is done through two stages. The first stage is the primary filtration stage in which the majority of impurities are removed in the form of sludge and the second stage helps in ultra-high purification and ionization of brine before being fed to the electrolyser. maintenance and service of the clarifier. The disposal of the sludge within the limited space is also a main concern. The process of single stage filtration tackles most of problems in primary filtration and maintaining the quality of the brine .Maintenance cost was reduced to much extend and the sludge disposal cost was reduced up to 55%.The process flow diagram is shown in fig 1. II. METHODOLOGY A study was conducted one of the chlor-alkali industry during which it was found that most of the problems occurred in primary stage of brine filtration and the company has incurred more expenditure on the maintenance of the current system. A cause and effect diagram could reveal reasons behind. Fig 2 shows the cause and effect diagram. Fig 2 Cause and Effect Diagram A. The main problems associated with the present brine filtration where the following: Fig 1 Process Flow Diagram During the study majority of the problems encountered was on the first stage which includes frequent maintenance of clarifier, large energy consumption and sludge disposal problems. Companies spend large amount of money on ISSN: 2231-5381 Frequent maintenance of machines Large energy consumption Sludge disposal cost Safety problems http://www.ijettjournal.org Page 246 International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 5 - Mar 2014 The equipment’s were undergoing frequent maintenance which increased the overall maintenance cost. The main equipment’s undergoing the brine filtration was clarifier, precoat system and anthracite filters. Most of the brine was filtered by the clarifier. Wearing of the rubber lining inside the clarifier was a common problem. Since the clarifier is the only filter removing more than 70 % sludge in the brine therefore it is considered as the primary source of filtration. The energy consumption was high due the use of turbines running continuously there were other pumps and motors for maintaining the flow in the line. The sludge generated from the clarifier was nearly 1.5 TPD (tonnes per day) effective disposal mechanism was one of the main issue resulting in environmental pollution due to which the company has to spend more expenditure for the sludge handling and disposal. Adequate safety measure has to be taken by the workers while repairing the Clarifier when it is at full capacity. The fig 3 shows the yearly maintenance done on the primary brine filtration systems. Fig 3 Number of Maintenance done on Brine Filtration Plant B. Economic Life of the Clarifier The clarifier has an economic life of 12 years after which the total cost of the equipment start rising as shown in Fig 4. . Fig 4 Economic Life of Clarifier ISSN: 2231-5381 Fig 5 Process Flow Diagram for Brine Filtration (Traditional Systems) III. SUGGESTION OF NEW SYSTEM Expert discussion was undergone to resolve the present issue after which we reached at a conclusion of replacing the present stem with light weight PTFE (polytetrafluoroethylene) membrane. The PTFE membrane has many advantages compared to the present system. It can filter up to submicron level. The PTFE membrane is applied at many of the recent technologies where filtration is an essential part. The conventional filtration is done through multiple steps before reaching to the electrolyser but the PTFE membrane does not require clarifier and precoat systems which reduces much of the operation and maintenance cost. A bundle of tube inserted with PTFE membrane will be placed inside a dome like structure will be used for the brine filtration. The brine enters the bottom part of the vessel and passes through the tube during which much of the suspended solids gets absorbed and crystal clear brine will reach at the top surface. The solid sludge is removed by back wash process. It is also seen that economic life of the PTFE membrane is high compared to the traditional systems. A. Analysis of suggested system The analysis of suggested system includes its cost and economic life which will be compared to the present systems. The single stage filtration removes much of the problems present in the conventional filtration the main advantage is the energy consumption is less and also the sludge generate from the suggested system is very less compared to the present system since the sludge quantity is directly proportional to the cost of handling and disposal they also tend get reduced. Skilled operators were required for operation of the clarifier and precoat systems as they have to undergo periodic maintenance inside the clarifier which was mainly an accident prone area. The operators were subjected to serious health issues due to the direct exposure of brine. Since the suggested is a closed container there will be no direct exposure of the operator which will reduce much of the health related issues. B. Cost Analysis of the suggested system The cost analyses include cost of purchase of the new system replacement of present system its scrap value and demolishing cost etc. payback period has been estimated as shown in Table 1. http://www.ijettjournal.org Page 247 International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 5 - Mar 2014 Table 1 Cost Analysis of the Suggested System IV. MODIFICATION PRESENT LAYOUT WITH SUGGESTED SYSTEM Fig 6 Process Layout with Suggested System The modification of the present system with suggested as shown in Fig 6 removes Clarifier, Precoat systems and anthracite filters etc. The payback period is estimated to about 5.8 years. C. Economic analysis of the suggested system Table 2 Economic Life of the Suggested System V. CONCLUSIONS The replacement of conventional brine filter with one step brine filtration process which will reduce the operation and maintenance cost, sludge disposal cost and safety problems. It is understood that 55% of the maintenance and the operation cost can be saved per year. The sludge disposal cost has been reduced to 45 % and the annual sludge generate is reduced to 0.25 TPD. The proposed system has an economic life of 25 years compared to the present system of 12 years. The average total cost of the conventional system can be saved when it is replaced by proposed system .The payback period for the proposed system is 5.8 years REFERENCES [i] [ii] [iii] [iv] [v] [vi] [vii] Thomas F. O'Brien, Tilak V. Bommaraju, Fumio Hine, Handbook of Chlor-Alkali Technology: Volume I, Springer, 2013. Rome-Ming Wu, Tsung-Hao Lee and Wen-Jie Yang, A Study of Water Treatment Clarifier, Tamsui, Taiwan 251, R.O.C. , Methods for the Determination of Inorganic Substances in Environmental Samples (EPA/600/R-93/100), National Technical Information Service (NTIS),,Cincinnati, OH, 1993. E.G. Beaudry, J.R. Herron, S.W. Peterson, Direct Osmosis Concentration of Waste, Water: Final Report, Osmotek Inc., Corvallis, OR, 1999. M. Flynn, J. Fisher, B. Borchers, An Evaluation of Potential Mars Transit Vehicle Water Treatment Systems, NASA Ames Research Center,Moffett Field, CA, 1998. D. FILMTEC, Reverse Osmosis System Analysis (ROSA), 2007 Electrodialysis and Electrodialysis Reversal (M38), 2nd, American 2nd, AmericanWaterWorks Association, Denver, CO, 1995. The economic life of the suggested system is estimated to be about 25 years . ISSN: 2231-5381 http://www.ijettjournal.org Page 248