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An Innovative application of Ultrafiltration membrane (UF) in chlor-alkali industry for brine treatment
Brine treatment in chloralkali industry comprises a series of unit operations, where the impurities such as Calcium, Magnesium, Iron are eliminated before it is fed to the electrolyers. Media and precoat filters form part of the conventional brine treatment system for the removal of suspended impurities such as calcium, magnesium, iron and barium suphate escaping through the brine coming from the clarifier. The polishing filter or the precoat filter removes the suspended impurities present in the brine before it is sent to the electrolyers.
Ultrafiltration technology is best explained as a membrane technology capable of rejecting particles of size of micro level. The ultrafiltration membrane for brine application has a pore size of 0.05 microns. The ultrafiltration system replaces pre-coat filters thus providing a most efficient system in terms of particle removal, power consumption and maintenance. In the process of brine treatment, the impurities in the salt such as calcium and magnesium are transformed to insoluble impurities. Majority of the precipitated impurities will settle at the clarifier and remaining escapes in the overflow. The suspended solids in the brine overflow is trapped in a series of filter to render the brine suitable for electrolysis.
MHT successfully implemented a Brine Treatment system, employing UF membrane system, for Chemfab Alkalis - Chlor-alkali plant. MHT used 150 KD membrane of pore size 0.05 microns and 16" dia membrane module, with a single membrane module area of 100 sq.m. The features of Ultrafiltration membrane system in brine systems are :
- It is a simple skid mounted merry-go-round system with all controls for operation and monitoring for continuous filtration.
- The operating cost is low compared to the conventional treatment plant.
- Eliminated handling of filter-aid and media. Thus reduction in solid waste.
- Reduced TOC content due to elimination of alpha-cellulose.
- Increase in the life of Ion exchange membranes due to reduced suspended solids in the brine.
- Increased life of Ion exchange resins due to lower suspended solids in the brine.
- Better efficiency of Ion exchange membranes due to enhanced quality of the brine.
- Unit PLC operated, no manpower required.
- Consistent secondary brine quality irrespective of feed brine quality to UF.
- Attractive payback < 3 yrs.
A typical UF Membrane plant in operation for clarification of hot brine in a chlor-alkali plant.
- Power savings < 0.2 kwH/cum
- Reduction in man-power
- Elimination of Anthracite filter
- Elimination of Alpha Cellulose System.
- Reduction in (make up) Ion Exchange resin.
- Savings in Consumption of chemicals - HCl, NaOH
- Reduction in maintenance of Alpha cellulose and Anthracite filter
UF Membrane Modules - supplied to U.S.A
Development of 400 mm dia membrane module
Advantages of 400 mm dia membrane module
- Proven technology
- Cost effective
- Proprietary design
- Lesser Foot Print
- Less Power consumption
- Low capital cost than any other system
- Very low maintenance cost
- Cost per unit production very less