Analysis of Gas Recirculation Influencing Factors of a Double Reheat 1000 MW Unit with the Reheat Steam Temperature under Control

Abstract

In this paper, the simulation software EBSILON is used to simulate the reheat units, and the reheat temperature control mode is deeply explored. In the benchmark system, the influence of different load intermediate point temperature on the flue gas recirculation (FGR) is analyzed. Then, the effects of load, coal quality, excess air factor, and feed water temperature on FGR are studied under the premise of intermediate point temperature as design value, and the cause for FGR change is analyzed by comparing the cutoff bypass flue (CBF) system. The results show that under any load, the FGR decreases with the increase of the intermediate point temperature, while under low load, the change of the intermediate point temperature has a greater impact on the FGR rate. When the intermediate point temperature remains constant, the FGR plunge has an increase of load at low load and is almost unchanged at high load; the FGR rate of coal with low calorific value and high moisture content is low and the coal with low volatile and high ash content has great influence on reheat steam temperature; and the excess air factor and feed water temperature are inversely proportional to the flue gas recirculation rate. In the CBF system, the change trend is similar to the reference system, but under the same working condition, the FGR rate is higher than the latter.