Calculation method research of power supply coal consumption of coal-fired cogeneration unit

Abstract

An improved method is proposed in this paper to better calculate the power supply coal consumption of coal-fired cogeneration unit, which eliminates the problem that the power supply coal consumption is strongly affected by the extraction steam parameters and flow using the original calculation method. Through in-depth analysis of the cogeneration unit steam power cycle, a transform calculation method of power supply coal consumption and heating supply coal consumption for cogeneration unit is established. Using this transform method to calculate power supply coal consumption of cogeneration unit is equivalent to dividing the heating unit into two parts, i.e., pure condensing power generation and back pressure cogeneration. The power supply coal consumption of pure condensing power generation part could be calculated by deducting the amount of electricity and of heating absorption of back pressure cogeneration part from the cogeneration unit. It can be used as the deductible transform power supply coal consumption of cogeneration unit. For example, the values of power supply coal consumption and heating supply coal consumption of two 350 MW supercritical cogeneration units are calculated in this paper. Affected by the efficiency of the turbine, the transform power supply coal consumption of unit 1 increases with the heating increase, while the transform power supply coal consumption of unit 2 decreases slightly with the heating increase. The transform heating coal consumption of two units is less than the result calculated from original calculation method. The results with the improved method can better reflect the energy efficiency of the unit equipment and plant management level.