Modern trend for Ash disposal in slurry form [Feb 2012]

February 10, 2012 6:27 am

During the last decade of 20th century, a very high demand for power had been forecast and the Government of India had initiated various plans to achieve the demand including addition of new major thermal power projects in India.  Major share of power from additional installed capacity of above thermal power plants was planned from coal based thermal power projects which produced huge amount of ash from low grade coal used for thermal power generation.
While utilisation of fly ash had been gathering momentum for cement manufacturing, road construction & other miscellaneous uses, however, major quantity of ash remained unused. The unused ash is disposed off in slurry form into an ash pond which is located at a distance of 1 km to 10 km or more depending upon land availability and the slurry was pumped using centrifugal pumps in concentration varying from 15 – 25 per cent which needs huge amount of water. For disposal of 100 TPH ash in lean slurry form in conventional method, water requirement would be about 300 to 400 M3 / hr while in HCSD system for disposal of same amount of ash, water requirement would be only 60 M3 /hr to 70 M3 /hr. In case of lean slurry system, the slurry generated is required to be pumped into ash pond leaving huge amount of free flowing water in ash ponds which is brought back to power plants through ash water recovery system and both these pumping consume huge amount of auxiliary power.
Ash handling system is a very important & critical auxiliary of any thermal power station and its reliable performance together with protection from ecological damages, posed a serious challenge for organisations engaged in the field of EPC. It therefore calls for evolving innovative ash handling methods for ash disposal which should not damage the environment near the plant and shall be eco-friendly too.
Ash handling plant configuration for various plants may differ from project to project depending upon various factors with one common factor being eco-friendly disposal of ash. In its pursuit to excel in providing innovative and cutting edge technologies in ash handling, the ash handling  division of Tecpro Systems Ltd (Erstwhile Tecpro AshTech Ltd / Mahindra AshTech Ltd) have introduced technology of high concentration slurry disposal, popularly known as HCSD system which uses much lesser quantity of water. The first such an HCSD system was introduced by us at Khaperkheda Thermal Power Station Unit # 3 & 4 (2 x 210 MW Units) of Maharashtra State Electricity Board and the plant was commissioned in the year 2000 and ever since it has become the trendsetter. Presently more than 15 power plants are already having HCSD Systems in operation and more than 20 power plants are having HCSD system contracts under execution. 
Major advantages of introducing HCSD system:• Lower cost of ownership for entire life of power plant• HCSD system requires only one fifth amount of water unlike lean slurry system• Less Auxiliary Power consumption since amount of fluid pumped is much less• No free water in HCSD system disposal area• Smaller Ash Pond is required which saves huge amount of project cost towards land and other social problems• No elaborate system for ash water recovery from ash pond• Does not require huge dyke construction• Problem of underground water contamination from Leachate containing harmful elements is avoided• No fugitive dust is generated• Slurry gets dried faster.