THE ENVIRONMENTAL BENEFIT OF COAL-GASIFICATION USING THE BGL GASIFIER

The British Gas coal gasification programme was concluded at the end of 1991, having achieved the objectives of demonstrating at a commercial scale the gasification of power station coals with the British Gas-Lurgi (BGL) gasifier to make a clean fuel gas for combined-cycle power generation and for making substitute natural gas (SNG). Three key elements of the programme were the purification of the crude gas from the gasifier, treatment of the water to an environmentally acceptable standard, and characterization of the leaching properties of the slag. Pilot plant work at the Westfield Development Centre demonstrated that the sulphur of the fuel gas could readily be reduced by >99% for combined-cycle applications and by the 99.95% required to avoid poisoning of the methanation catalyst for upgrading to SNG. Processes studied for water purification included incineration, catalytic wet air oxidation, and the biological route with reverse osmosis. There is a range of viable alternative process routes for water treatment enabling the water to be reused within the gasification complex or safely discharged into the environment. The slag is a highly inert material presenting no hazard to the environment.