Thermal power plant medium-low temperature flue gas heat energy gradient utilization system and method

Abstract

The invention provides a thermal power plant medium-low temperature flue gas heat energy gradient utilization system and method. According to the thermal power plant medium-low temperature flue gas heat energy gradient utilization system, a Brayton cycle is arranged at thermal power plant boiler tail flues in a coupled mode, the thermal power plant boiler tail flues are separated flues, that is, two flues are adopted, one of the flues communicates with a flue gas inlet of an air pre-heater, and the other flue communicates with a flue gas inlet of a Brayton cycle heater; a working medium outlet of the Brayton cycle heater communicates with an inlet of a turbine; an outlet of the turbine communicates with a working medium inlet of a Brayton cycle cooler; a working medium outlet of the Brayton cycle cooler communicates with a working medium inlet of the Brayton cycle heater through an air compressor; a hot air outlet of the Brayton cycle cooler communicates with an air inlet of the air pre-heater; and an air outlet of the air pre-heater is connected with a boiler burner. The invention further discloses the flue gas heat energy gradient utilization method, the heat exchanging process of thermal power plant medium-low temperature flue gas can be optimized, the irreversible loss of the air pre-heater is reduced, accordingly, the efficiency of a whole thermal power plant is improved, the temperature of air entering the air pre-heater is increased at the same time, and safe operation of the air pre-heater is facilitated.

Description

technical field [0001] The invention relates to the technical field of thermal energy utilization in thermal power plants, in particular to a system and method for cascaded utilization of medium and low temperature flue gas thermal energy in thermal power plants. Background technique [0002] Thermal power generation is the main body of my country's electricity production. With the deepening of my country's energy conservation and emission reduction work, the utilization of exhaust heat has gradually attracted the attention of scholars. In the air preheater of a thermal power plant, since the heat released per unit temperature drop of boiler exhaust smoke is greater than the heat absorbed per unit temperature drop of boiler air supply, the heat exchange temperature difference at the flue gas outlet side (air inlet side) of the air preheater is large, reaching Above 100°C, resulting in a large irreversible loss of the air preheater. Contents of the invention [0003] In or...

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Problems solved by technology

In the air preheater of a thermal power plant, since the heat released per unit temperature drop of boiler exhaust smoke is greater than the heat absorbed per unit temperature drop of boiler air supply, the heat transfer temperature difference at the flue gas outlet side (air inlet side) of the air preheater is large, reaching Above 100°C, resulting in large irreversible losses of the air preheater

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