Energy consumption during transient operation of coal-fired generating units with cold end system back pressure regulation

Abstract

The dynamic characteristics of key parameters were investigated in this study, which reflected the operational flexibility and efficiency of thermal power units during load regulation. A refined model of the cold end of the unit was proposed. Simultaneously, an innovative exploration was conducted into the coordinated achievement of flexible load regulation and the promotion of energy-efficient operations. Two variables, the variable load rate and cooling water flow, were selected, and the continuous dynamic characteristics of unit energy consumption during load adjustment were determined. The ratio of total variable load coal consumption to load regulation and variable load time was defined as the average regulated coal consumption BZ, which was introduced to enhance the intuitive evaluation of flexibility and efficiency. It was shown that with the increase in variable load rate, there was a decrease observed in the total coal consumption during the variable load process. This trend was consistent with earlier publications. Concurrently, a reduction in cooling water flow had resulted in an increase in power generation coal consumption and a decrease in coal consumption for circulating cooling water pumps. The elevated rate of load variation was attributed to the increased flow of cooling water. A decrease of 14.9 % in back pressure was noted with the increase in the flow of the cooling water. As a result of this reduction in back pressure, the coal consumption rate for power generation was decreased by 1.334 g/kWh, reflecting a decrease of 0.43 %. Additionally, a reduction in total coal consumption of 0.16 t during variable load operation was witnessed, while a 1.97 % increase in the variable load rate was recorded. The optimal flexibility and coal-saving effect were achieved under the conditions of 30 MW/min and 60000 t/h, with ΔBZ = −50 g/(MW·s). Finally, the feasibility of the proposed scheme was verified through the case of a 350 MW unit.