Essar Steel: Ceramic filters for emission reductions
Iron ore slurry (a suspension of insoluble particles, usually in water) received in Essar’s Visakhapatnam iron ore pelletisation plant undergoes filtration prior to being sent for further processing. Green pellets are made and heat hardened to achieve the required physical and metallurgical properties. The filtration process installed during the plant’s construction in 1992 used seven vacuum disc filter modules and was highly energy-intensive.
During a 2004 filtration unit expansion, Essar had the opportunity to change to a less energy-intensive filter technology. Of the various technologies considered, the company chose ceramic filters.
This technology is still relatively new and had not been used in India. However, Essar decided to adopt it for its potential to reduce energy use and greenhouse gas emissions from captive power plans and plants connected to the regional electricity grid.
Eight high flow CC-45 and two CC-60 Ceramec® capillary filters were installed. These were provided by Larox OYJ of Lappeenranta, Finland, a filtration solution provider in solid and liquid separations.
The filters use a micro-porous ceramic material that behaves like a large network of narrow capillaries. When pressure is applied over the wetted surface, pores push the water out whilst the capillary force within the material keeps the water in. When these two forces equalise there is no airflow and a vacuum is created within the ceramic. As the filter discs rotate through the slurry in the slurry basin, the vacuum sucks impurities onto the filter plates to form a filter cake.
The filter cake is dewatered using a vacuum filtrate system. Then the dewatered dry cake is removed with ceramic scrapers and filter plates are cleaned with brief back-flushing, using filtrate water recycled after cake discharge. Final regeneration of the filter plates takes place using an ultrasonic and chemical cleaning system.
With a specific energy consumption of 0.35kwh/tonne of filter cake production, compared to 5.68 kwh/tonne of filter cake production for conventional vacuum disc filters, the new system saves 18,130 MWh/year.
The project is in line with India’s sustainable development policies. It contributes to the regional and global environment by increasing job opportunities for the local community, reducing pollution and GHG emissions, and conserving the region’s natural resources.
Last updated: June 2010