A multi-product cogeneration system using combined coal gasification and combustion

A new system has been developed for clean and highly efficient utilization of coal. The coal is first gasified and the fuel gas is then used for industrial purposes in town gas or as a fuel for gas turbines. The char residue from the gasifier is burned in a circulating fluidized-bed combustor to generate steam for power generation, process heating, refrigeration, air conditioning, etc. The ash is used to produce construction materials. Metals such as vanadium and uranium can be extracted if the metal contents of coal are sufficiently high. An important system component is the combined gasifier-combustor. Experiments show that the system can produce gas and steam simultaneously. The gas heating value is 10-14 MJ/Nm3 and the fuel conversion is over 90%. The system has low emissions and low cost. A demonstration system has been constructed at the Yangzhong Thermal Power Plant in Jiangshu Province of China. It produces 3,500 Nm3/h of dry gas and 75 mt/h steam. The CFB boiler has been in commercial operation since April 1995. It has high efficiency, good fuel adaptability, and a high load turndown ratio.