System and method for heating primary air, fed water and circulating water through bypass flue gas

Abstract

The invention discloses a system and method for heating primary air, fed water and circulating water through bypass flue gas. A hot flue gas outlet of a coal-fired boiler of the system is divided intoa hot flue gas main path and a hot flue gas bypass; the hot flue gas main path communicates with flue gas bins of a three-portion bin preheater, and the flue gas bins communicate with a cold flue gasmain path; the hot flue gas bypass is provided with a baffle door and communicates with a fed water heat exchanger, a high-temperature primary air heat exchanger, a steam air heater circulating waterheat exchanger and a low-temperature primary air heat exchanger in sequence; the low-temperature primary air heat exchanger communicates with a cold flue gas bypass; wherein the fed water heat exchanger heats the fed water, the low-temperature primary air heat exchanger and the high-temperature primary air heat exchanger heat cold primary air, and a water pipe and the steam air heater circulatingwater heat exchanger heat the circulating water. According to the method, the fed water, the primary air and the circulating water are heated at the same time through waste heat of bypass flue gas. Through the system and method, utilization of the waste heat of the flue gas is substantially improved, and environment protecting, energy saving and cost reducing are more facilitated.

Description

technical field [0001] The invention relates to a system and method, in particular to a system and method for heating primary air, feed water and circulating water by using bypass flue gas. Background technique [0002] The air preheater is one of the important components of the pulverized coal boiler system, which plays a role in reducing the exhaust gas temperature, increasing the temperature of the combustion air, making the fuel easy to ignite, stable combustion and improving combustion efficiency. The air preheater mainly includes three compartments, shell and tube two forms. At present, more than 90% of coal-fired boilers in power stations use three-compartment air preheaters, and the three compartments circulate hot flue gas, primary air and secondary air respectively. In the current pulverized coal boiler system, the high-temperature flue gas generated by the coal-fired boiler is mainly sent to the three-compartment air preheater to heat the air for combustion (that...

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Problems solved by technology

In the current pulverized coal boiler system, the high-temperature flue gas generated by the coal-fired boiler is mainly sent to the three-compartment air preheater to heat the air for combustion (that is, the secondary air). The heat of the flue gas is sufficient, which leads to a waste of energy; at the same time, the waste heat of the flue gas in the bypass has not been fully utilized in cascades, which not only causes a waste of energy, but also is not conducive to environmental protection and energy saving. The system and method for heating the primary air, feed water and heater circulating water at the same time will consume a lot of energy to heat the primary air, feed water and heater circulating water, which will increase the operating cost to a certain extent

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