Air preheating and flue gas waste heat utilizing system and method

Abstract

The invention particularly aims to the technical field of boiler air preheating. A disclosed air preheating and flue gas waste heat utilizing system comprises a flue gas channel (17), an air channel (20), an air preheater (9), a condensed water flue heat exchanger (8) and a condensed water air channel heat exchanger (19), and further comprises a condensed water feeding main pipe (15) and a condensed water returning main pipe (12); the flue gas channel (17) and the air channel (20) are connected with the air preheater (9); the condensed water flue heat exchanger (8) is arranged on the flue gas channel (17) at the back of the air preheater (9) in a flue gas flowing direction; the condensed water air channel heat exchanger (19) is arranged on the air channel (20) at the front of the air preheater (9) in an air flowing direction. According to the air preheating and flue gas waste heat utilizing system, flue gas discharge and heat exchange can be automatically adjusted according to change of operation conditions; on the premise of ensuring the safety of a heated surface and the regular operation of the system, the maximization of the heat circulation efficiency and the system economical efficiency is ensured.

Description

technical field [0001] The invention belongs to the fields of heat recovery and utilization of boiler flue gas and production process exhaust gas, and is particularly aimed at the technical field of air preheating of boilers, and specifically relates to an air preheating and flue gas waste heat utilization system and method. Background technique [0002] Traditional air preheaters always have the coupling problems of equipment investment, heating surface safety, normal system operation and thermal efficiency. Increasing the investment in the heat exchange surface and transferring more heat of the flue gas to the air can improve the thermal efficiency of the system, but reducing the exhaust gas temperature is more likely to cause low-temperature corrosion of the heat exchange surface, causing serious ash blocking and reducing the heat transfer efficiency. On the contrary, if the exhaust gas temperature is increased, although the harm of low temperature corrosion and fouling c...

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Problems solved by technology

However, the low-temperature economizer scheme does not actually realize the cascade utilization of energy. The low-quality heat energy that can be returned to the boiler is used to squeeze out the steam turbine to extract steam, and to do a low-parameter Rankine cycle, which reduces the cycle thermal efficiency and economy of the system.

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