Fuel Utilization Monitoring Techniques for Large-Capacity Combined-Cycle Power Plants

Resumo

A technique for calculating the standardized indicators characterizing the thermal efficiency of combined-cycle power plants (CCPPs) using correlation equations linking the values of these indicators with different external conditions is proposed. The correlation equations were written using the results from measuring the outdoor air and cooling water temperatures; air barometric pressure and humidity; fuel (natural gas) flowrate, heating value, and density and load in steady-state operation modes of the CCPPs and their equipment. It is usually sufficient to have a sample with three groups each representing 15–20 operating modes: under winter conditions at an outdoor air temperature of –20 to –30°С, under summer conditions at an outdoor air temperature of above 20 to 30°С, and at an intermediate temperature of ±5 to ±7°С. In each group, it is sufficient to have two operating modes each with loads close to 0.5, 0.6, 0.7, 0.8, and 0.9 of the maximal value, and 5–10 operating modes with a close-to-nominal load. It is shown, taking a single-shaft 400 MW CCPP as an example, that the correlation equations adequately (with errors equal to approximately 1%) describe the results obtained experimentally in the normal operation modes. The developed technique opens the possibility to determine, in a more accurate and simple manner, the standardized heat rates and other technical-economic indicators of fuel utilization without using an excessive number of corrections able to distort the result. The technique can also be used for estimating the changes of CCPP indicators as a result of taking some or other measures in them.