CN205606619U - Bypass type flue gas waste heat cascade utilization system of air preheater - Google Patents

Abstract

Air preheater bypass flue gas waste heat cascade utilization system, including the flue gas heat exchanger installed on the bypass flue between the air preheater inlet and the electrostatic precipitator inlet, and the flue gas heat exchanger installed at the flue gas heat exchanger inlet Circulation pump, a graded heater installed on the bypass pipe at the outlet of the feed water pump; the circulation pump boosts the pressure of part of the condensed water and then connects it to the flue gas heat exchanger to absorb the waste heat of the flue gas, and the heated condensed water is connected to the graded heater Part of the heat is released to the bypass feed water, and the condensed water after the heat release is led back to the heat recovery system through the inlet pipe of the deaerator, thereby realizing the purpose of heating the high-pressure feed water and low-pressure condensed water step by step with the waste heat of the flue gas, that is, the flue gas waste heat cascade use.

Description

Air preheater bypass type flue gas waste heat cascade utilization system

technical field

The utility model relates to the technical field of thermal power generation, in particular to an air preheater bypass type flue gas waste heat cascade utilization system.

Background technique

With the rising global energy prices and the deteriorating climate around the world, the country has more stringent requirements for energy conservation and consumption reduction. How to deeply tap the energy-saving potential of existing power plant units and reduce the production and operation costs of enterprises has become a common concern of every enterprise. important question.

The exhaust gas temperature of boilers in my country's active thermal power units is generally maintained at around 125-150 °C, which is higher than the design value. Generally, every 20°C increase in exhaust gas temperature will increase the heat loss of exhaust gas by 0.6% to 1.0%, which will have a negative impact on the economy of the unit. In recent years, boiler flue gas waste heat utilization devices have been widely used in the thermal power field, and a large number of units have carried out technical transformation projects of low-pressure economizers and similar systems. However, the existing retrofit projects generally use the waste heat absorbed by the flue gas to heat the condensate water and the heater system, and the energy level of the recovered energy is low, and the utilization effect is not high. If the energy level of the waste heat of the flue gas can be increased and used to heat high-energy working fluids such as feed water, the utilization efficiency of the waste heat will be significantly improved.

Contents of the invention

In order to overcome the problem of low utilization energy level in the above-mentioned prior art, the purpose of this utility model is to provide an air preheater bypass flue gas waste heat cascade utilization system, which utilizes the bypass flue in front of the air preheater Draw out a part of the flue gas and use its heat to heat part of the condensed water drawn out from the No. 2 low gas outlet. As the flow of flue gas entering the air preheater decreases, the temperature of the exhaust gas at the outlet of the air preheater decreases, and at the same time, the bypass flue gas After the flue gas in the duct is cooled by condensed water, the temperature of the flue gas also decreases. After the two streams of flue gas are mixed in the inlet flue of the electrostatic precipitator, the total exhaust gas temperature decreases, which is equivalent to absorbing the exhaust heat of the boiler, but The quality of the absorbed energy is significantly improved compared with the scheme of adding a flue gas heat exchanger directly at the outlet of the air preheater. Part of the waste heat of the flue gas with improved energy level is used to heat the high-pressure feed water diverted from the outlet of the feed water pump, and the other part of the heat is retained in the condensed water diverted before and finally led back to the heat recovery system through the inlet pipe of the deaerator. Through the above scheme The purpose of heating condensate water and feed water at the same time with the waste heat of the flue gas is realized, thereby improving the utilization energy level of the waste heat of the flue gas and achieving the effect of cascade utilization.

In order to realize above-mentioned utility model purpose, the technical scheme that the utility model takes is:

Air preheater bypass flue gas waste heat cascade utilization system, including flue gas heat exchanger 6 installed on the bypass flue between the inlet of air preheater 1 and the inlet of electrostatic precipitator 2, installed in the flue gas heat exchange The circulating pump 7 at the inlet of the device 6 is installed on the graded heater 8 at the outlet of the flue gas heat exchanger 6; the inlet of the circulating pump 7 is connected between the No. 2 low-pressure heater 10 and the No. 3 low-pressure heater 11 of the low-pressure heating system Between, the circulating water side outlet of the graded heater 8 is connected to the outlet of No. 4 low-pressure heater 12 of the low-pressure heating system, the feedwater side inlet of the graded heater 8 is connected to the outlet of the feedwater pump 14 of the high-grade heating system, and the graded heater 8 The outlet on the feed water side is connected to the outlet of No. 8 high-pressure heater 17 of the high-pressure heating system.

Part of the diverted condensed water is boosted by the circulating pump 7 and then connected to the flue gas heat exchanger 6 to absorb the waste heat of the flue gas. For waste heat, the condensed water at the outlet of the flue gas heat exchanger 6 continues to be connected to the multi-stage heat exchanger 8 to transfer part of its heat to the feed water, and the remaining heat in the condensed water is led back to the heat recovery system.

Compared with the prior art, the utility model has the following advantages:

After adopting the system of the utility model, the energy level of the same amount of flue gas waste heat can be improved, and the heat source has been rationally optimized. On this basis, the flue gas waste heat is used to heat the feed water and condensed water in sequence according to the energy level to realize smoke exhaust. The cascade utilization of waste heat improves energy utilization efficiency. The utility model adopts low-pressure condensed water as a heat acceptor and a carrier of high-energy waste heat at the same time, and finally releases it to the diverted feed water, avoiding the direct introduction of high-pressure feed water into the heat exchanger to absorb heat, reducing The investment in high-pressure pipelines is replaced by the installation of graded heaters on the outlet distribution pipelines of feed water pumps.

Description of drawings

Accompanying drawing is the structural representation of the utility model.

Among them, 1 is the air preheater, 2 is the electrostatic precipitator, 3 is the induced draft fan, 4 is the desulfurization tower, 5 is the chimney, 6 is the flue gas heat exchanger, 7 is the circulation pump, 8 is the graded heater, 9 is the No. 1 low-pressure heater, No. 2 low-pressure heater No. 10, No. 3 low-pressure heater No. 11, No. 4 low-pressure heater, No. 13 deaerator, No. 14 feed water pump, No. 6 high-pressure heater No. 15, No. 16 It is No. 7 high-pressure heater, and No. 17 is No. 8 high-pressure heater.

detailed description

Below in conjunction with accompanying drawing and specific embodiment, the utility model is described in further detail.

As shown in the drawings, the air preheater bypass flue gas waste heat cascade utilization system of the present utility model includes flue gas heat exchange installed on the bypass flue between the air preheater 1 inlet and the electrostatic precipitator 2 inlet device 6, a circulating pump 7 installed at the inlet of the flue gas heat exchanger 6, and a graded heater 8 installed at the outlet of the flue gas heat exchanger 6; the inlet of the circulating pump 7 is connected to No. 2 low-pressure heater of the low-pressure heating system Between No. 10 and No. 3 low-pressure heater 11, the circulating water side outlet of the graded heater 8 is connected to the outlet of No. 4 low-pressure heater 12 of the low-pressure heating system, and the feed water side inlet of the graded heater 8 is connected to the feed of the high-pressure heating system. The outlet of the water pump 14 and the outlet of the feed water side of the graded heater 8 are connected to the outlet of the No. 8 high-pressure heater 17 of the high-pressure heating system. The diverted part of the condensed water at the outlet of No. 2 low-pressure heater 10 is connected to the circulation pump 7 and then connected to the flue gas heat exchanger 6. In the flue gas heat exchanger 6, the inlet of the air preheater 1 and the inlet of the electrostatic precipitator 2 Part of the flue gas diverted on the bypass flue between the two transfers its heat to the condensed water, and the flue gas after heat release is led back to the original flue gas system by the entrance of the electrostatic precipitator 2 to complete the flue gas cycle. The condensed water continues to be connected to the graded heater 8. In the graded heater 8, the condensed water releases part of the heat to the part of the feed water diverted from the outlet of the feed water pump 14, and the feed water after absorbing heat is led back to the heat recovery system through the outlet of No. 8 high pressure heater 17 , to complete the water supply cycle, and the condensed water after heat release continues to be led back to the heat recovery system from the No. 4 low-pressure heater 12 outlet to complete the condensed water cycle.

As shown in the accompanying drawings, the method for cascaded utilization of flue gas waste heat in the system air preheater bypass type of the utility model is: the condensed water heated by the flue gas heat exchanger 6 is introduced into the graded heater 8 to release a part of the heat. The heat of high energy level and the remaining heat of lower energy level are retained in the condensed water and finally led back to the heating system by the inlet pipe of the deaerator 13 . Since the diverted condensed water does not absorb heat through the No. 3 low-pressure heater 11 and No. 4 low-pressure heater 12, the corresponding extraction steam flow rate decreases, and the exhausted extraction steam will enter the steam turbine to do work, so that the power of the unit is increased and the economy is improved. Thus, the effective utilization of low-level waste heat is realized; part of the feed water is diverted from the outlet pipe of the feed water pump 14 and sent to the graded heater 8 to exchange heat with the diverted condensate water. Return to heat system. Since the diverted feed water does not absorb heat through No. 6 high-pressure heater 15, No. 7 high-pressure heater 16, and No. 8 high-pressure heater 17, the corresponding extraction steam flow rate decreases, and the exhausted extraction steam will enter the steam turbine to do work, making the power of the unit Increase, economical improvement, thus realizing the effective utilization of high-energy level waste heat. Since the energy level of the waste heat of the flue gas is increased, and it is used to heat the high-pressure feed water and the low-pressure condensate water sequentially according to its energy level gradient, the cascade efficient utilization of the waste heat of the flue gas is realized.

Claims (1)

1. air preheater by-pass type fume afterheat gradient utilization system, it is characterised in that: include being arranged on air preheater (1) Flue gas heat-exchange unit (6) on bypass flue between entrance and electric cleaner (2) entrance, is arranged on flue gas heat-exchange unit (6) entrance Circulating pump (7), be arranged on the progressive solution device (8) that flue gas heat-exchange unit (6) exports；The entrance of described circulating pump (7) is connected to Between No. 2 low-pressure heaters (10) and No. 3 low-pressure heaters (11) of low adding system, the recirculated water of described progressive solution device (8) Side outlet connects the outlet of No. 4 low-pressure heaters (12) of low adding system, and the feedwater side entrance of progressive solution device (8) connects height and adds The outlet of the feed pump (14) of system, the feedwater side outlet of progressive solution device (8) connects No. 8 high-pressure heaters of high adding system (17) outlet.