OCR Text |
Show WASTE GAS FIRING IN PROCESS HEATERS AND BOILERS EMMISSIONS The pollutants of primary concern from fired heaters and boilers are NQx, CO, particulates and unburned hydrocarbons. Because of the nature of the fuels discussed the potential for forming particulates is nil. Normally carbon formation is present when there are significant amounts of relatively heavy hydrocarbons which do not exist in the subject fuels. Since the concentration of hydrocarbons in the fuel is low, the potential for having high levels of unburned hydrocarbons in the flue products is low. Proper residence time required for incineration of CO also ensures destruction of the small amounts of hydrocarbon. NQx emissions, which are a prime concern, will also be low. NQx is generated by high combustion temperature and bound nitrogen in the fuel. Both field and development tests indicate that NQx levels for flex-gas firing are less than 0.05 lb/MM BTU fired. As indicated by Table I the flex-gas has one of the higher flame temperatures. Thus for most alternate fuels containing no nitrogen compounds, the NQx levels will be less than 0.05 lb/MM BTU fired. CONCLUSION High inert content alternate fuels, when proper consideration is given to the design of the combustion system, can provide attractive alternatives to the higher priced conventional fuels. The technology is available, in most cases, to provide a combustion system that will provide complete, stable combustion of the fuels. In addition because of the low combustion temperature, the formation of NOx is minimal if no nitrogen compounds are present in the fuel. In most cases the level can be expected to be lower than 0.05 lb/MM BTU fired. U.S. Department of the Interior, Bureau of Mines, Limits of Flammability of Gas and Vapors, Bulletin 503, 1952. 1.1.6 |