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.
Highlights
By the end of 2019, the proportion of coal-fired installed capacity will still account for 55% of the power structure [1]
The reheat steam temperature of the double reheat million kilowatt boiler is regulated at the flue gas side by means of flue gas recirculation (FGR) and flue gas damper
FGR is to extract a part of the flue gas with low temperature from the tail of the boiler and input it into the furnace of the boiler through the recirculation fan, so as to reduce the temperature of the furnace
Summary
By the end of 2019, the proportion of coal-fired installed capacity will still account for 55% of the power structure [1]. The double reheat technology has become one of the most effective ways to improve the efficiency of coal-fired power plants [4]. By increasing the pressure of superheated steam and the temperature of reheated steam, the double reheat technology increases the cycle efficiency and the thermal efficiency of the unit. It reduces the coal consumption of the unit, improves the thermal economy, and reduces the emission of pollutants. It can improve the operating conditions of the last stage blade and make the unit safer. The steam temperature regulation of the reheat unit is the key to the safe and efficient operation of the unit
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