Superheater minimum stress unit start-up option of coal-fired power plant

Abstract

In the operation of coal-fired power plants, the provision of selecting the superheater minimum stress unit start-up option is presented in this paper. This stress minimization is necessary for tomorrow's business climate, of the electric-supply industry, with expanding deregulation and competition both domestic arid global. The start-up option recommended in the present paper is meant to influence the power plant automation in start-up and firing temperature controls. The stress temperatures characteristics for final superheater outlet temperatures are approximated and three selected unit start-up options are identified. The paper presents a practical mathematical formulation of the superheater heat transfer equilibrium. This is done for the unit start-up segment that is the low boiler continuous maximum rating (C.M.R.) range (0–20%). The mathematical formulation of the matrix equilibrium is modelled in the paper as a conductivity spring and a capacity spring opposed by heat fluxes. The heat flow equilibrium equation derived in the present paper is a nonlinear system in which the thermal properties vary with the superheater temperatures. A detailed solution is presented in the paper. Consequently, the paper presents two superheater axisymmetric finite element heat transfer and stress analysis models along with heat transfer and stress analysis results. The paper suggests that automation should include faster plant start-up according to the unit start-up option with the fastest firing rate, which yields minimum stress.