Adjusting method combining steam air heater double-bypass wide load of flue gas waste heat recycling

Abstract

The invention discloses an adjusting method combining steam air heater double-bypass wide load of flue gas waste heat recycling. The method comprises the following steps that step 1, a flue gas coolercirculating water bypass, namely a flue gas cooler outlet smoke temperature is controlled within a set value; step 2, an auxiliary steam heater inlet flow, namely an air heater outlet air temperatureis controlled within a set temperature range; step 3, an air heater circulating water bypass, namely a flue gas cooler lowest wall temperature is controlled within a set temperature range; and step 4, an auxiliary steam heater outlet water temperature, namely a circulating water pump flow is controlled within a set temperature range. According to the method, on the basis of a full automatic control is realized when the wide load is changed, meanwhile, the problem that the flue gas cooler cannot be economically adjusted due to the fact that the water temperature of the inlet of the flue gas cooler is higher than the outlet air temperature of the air heater is solved; and the economical efficiency and the reliability of a whole waste heat recovery system are enhanced to the maximum extent.

Description

technical field [0001] The invention relates to a method for adjusting the waste heat recovery of flue gas combined with a warm air system, in particular to a method for adjusting the wide load of dual bypasses of a heater combined with waste heat recovery and utilization of flue gas. Background technique [0002] Due to large-scale energy-consuming projects such as thermal power, thermal power, metallurgy and petrochemical, the waste heat load of flue gas varies greatly according to the actual operation; the original flue gas entering the smoke cooler system and the wind parameters in the heater change greatly accordingly, and the Flue gas waste heat recovery-air heater combined system cannot operate under the design conditions. [0003] In the prior art, in order to adapt to the wide variation of flue gas waste heat, the flue gas waste heat recovery control controls the outlet flue gas temperature of the flue gas cooler at the set value by adjusting the amount of water ent...

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Problems solved by technology

[0003] In the prior art, in order to adapt to the wide variation of flue gas waste heat, the flue gas waste heat recovery control controls the outlet flue gas temperature of the flue gas cooler at the set value by adjusting the amount of water entering the flue gas cooler; When the temperature of the raw flue gas flowing is low, the heat released by the flue gas cooler is not enough to heat the air from the heater to the boiler inlet air temperature requirement, and the insufficient heat is supplemented by the auxiliary steam heater set as the heat medium water, and finally reaches the inlet air temperature. Temperature requirements; in conventional control, in order to ensure the normal use of the flue gas heat exchanger, the flue gas cooler controls the outlet flue gas temperature of the flue gas cooler by adjusting the inlet water into the flue gas cooler; it is controlled by the auxiliary steam heater Air temperature at the outlet of the air heater; under actual low-load conditions, the original flue gas temperature at the outlet of the flue gas cooler and the outlet air temperature at the outlet of the air heater are guaranteed; the heating surface of the heat exchanger is surplus under low load, and the flue gas is cooled The circulating water temperature at the outlet of the heater is higher than the design temperature, and the water volume is lower than the design water temperature. The outlet circulating water temperature of the air heater is lower than the design temperature due to excessive heat release, which will bring the following consequences: First, due to the If the temperature is higher than the design temperature, the total heat required by the auxiliary steam heater will remain unchanged because the temperature of the incoming water will increase, the design temperature and pressure of the auxiliary steam heater will decrease, and the design area of ​​the auxiliary steam heater will increase; secondly, after circulation , the outlet water temperature of the air heater is lower than the design setting value, resulting in the inlet water temperature of the flue gas cooler being lower than the design setting value, which brings the risk of low-temperature corrosion of the flue gas cooler and affects the normal operation life of the entire flue gas waste heat recovery; third, Due to the working characteristics of the frequency conversion circulating water pump, the water volume of the circulating water pump in normal operation is within a certain range. When the load is low, the circulating water volume required by the entire system is low, which may be lower than the minimum normal water volume of the frequency conversion circulating water pump.

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