Feasibility and cost of converting oil- and coal-fired utility boilers to intermittent use of natural gas

Abstract

The continuous or intermittent use of natural gas in place of oil or coal in existing utility boilers would reduce emissions of sulfur and thereby the concentration of sulfate ions in precipitation. This report examines the technological feasibility and capital cost of retrofitting oil and coal fired utility boilers to burn intermittently natural gas and the parent fuel. Using extensive studies of the retrofitting of such boilers to burn synthetic gas of low to moderate heating value (LBG), it is found that natural gas closely simulates the combustion properties of LBG of medium heating value. Based upon this comparison, it is concluded that little or no modifications to the boiler are required to achieve the same boiler rating as when burning the original fuel, and that only a small efficiency penalty must be paid. Examination of the history of four eastern utility boiler conversions from oil to natural gas confirms these performance estimates, and shows that conversion costs for in-plant equipment are very small, less than 19 $(1985)/KW in all instances, while conversion times are less than one year (with little down time beyond that required for annual maintenance). Pipelining costs will vary with the local conditions.