What are the principles and advantages and disadvantages of using the burner flue gas recirculation method to regulate the reheat steam temperature?
What are the principles and advantages and disadvantages of using the burner flue gas recirculation method to regulate the reheat steam temperature?
The burner flue gas recirculation method is to pressurize a portion of the flue gas with a temperature of 250-350 ℃ after the economizer, and then send it into the furnace through the recirculation fan, changing the heat absorption ratio between the radiation heating surface and the convection heating surface to achieve the purpose of regulating the reheat steam temperature. The characteristics of flue gas recirculation regulation are related to the amount of recycled flue gas, the location of flue gas extraction, and the location of the flue gas being sent into the furnace. The larger the amount of circulating flue gas, the higher the temperature of the extracted flue gas, and the lower the position where it is sent into the furnace, the greater the amplitude of reheat steam temperature regulation.
When the recirculating flue gas from the burner is fed into the lower part of the furnace, as the amount of recirculating flue gas increases, the radiation heat absorption of the furnace decreases due to the decrease in furnace temperature, while the outlet flue gas temperature of the furnace does not decrease significantly. The reheater is usually arranged in the convection flue. Due to the small change in heat transfer temperature difference of the reheater, the increase in flue gas volume leads to an increase in smoke velocity. The increase in heat transfer coefficient of the reheater leads to an increase in heat absorption, resulting in an increase in reheat steam temperature.
Usually, for every 1% increase in the recirculation flue gas volume of the burner, the reheat steam temperature can increase by about 2 ℃. If the smoke recirculation rate is 20%~25%, the range of reheat temperature adjustment can reach 40%? 50 ℃. The influence of flue gas recirculation on the thermal characteristics of boilers. Due to the fact that flue gas recirculation is put into operation at low load and low reheat steam temperature, and stopped at rated load, there is no need to use other temperature reduction methods in the design. It is necessary to have a certain margin of heat transfer area in the reheater, so the metal consumption of the reheater is low and the investment can be reduced.
The adjustment inertia of the burner flue gas recirculation is not large, and the reheat steam temperature adjustment is relatively sensitive.