Simulation of Combined Cycles With Black Liquor Gasification

Abstract

Black liquor, a residual of the chemical pulp industry, is a biofuel with great potential for increasing power generation. This may be accomplished by replacing the conventional recovery process using a Tomlinson recovery boiler with black liquor gasification. In addition, there are other considerable advantages. The gasification of black liquor gives new degrees of freedom since the combustible gas may be used in a multitude of ways. For a full scale plant, a combined cycle may be an efficient way to produce process heat and power. Comparison is made with conventional CHP using a Tomlinson boiler and a steam cycle. It is shown that the generated power could be up to twice that of the conventional plant with an electrical efficiency of 30% and a total efficiency of 77% (HHV). However, the characteristics of a combined cycle in this kind of process integrated application will be quite different than those of a stand-alone powerplant. This is clearly shown when competed with conventional natural gas fired combined cycles. This paper includes thorough analysis of some of the most important parameters of the combined cycle. It is shown that the gas turbine characteristics are the critical factors for providing a high electric efficiency. The effects of supplementary firing we also investigated. Hereby, an optimum for the steam cycle data is established.