CN202109463U - A combined flue gas waste heat comprehensive utilization system - Google Patents

Abstract

A combined flue gas waste heat comprehensive utilization system, by arranging the first-stage flue gas cooler and the second-stage flue gas cooler before and after the dust collector, a cascade utilization of exhaust waste heat is formed, and the high-temperature section of the flue gas is heated with a high fire quotient The condensed water and the low-temperature section of flue gas heat the cold air with low fire quotient; the cooler of the low-temperature section of flue gas and the cooler of the high-temperature section of flue gas operate in series, which improves the temperature level of the inlet water temperature and closed circulating water of the second-stage flue gas cooler , which reduces the risk of low-temperature corrosion of the flue gas cooler and the freezing of closed circulating water.

Description

A combined flue gas waste heat comprehensive utilization system

technical field

The utility model relates to the technical field of comprehensive utilization of flue gas waste heat, in particular to a combined system for comprehensive utilization of flue gas waste heat.

Background technique

The large consumption of fossil fuels and the excessive growth of consumption have made people feel the end of their reserves in the foreseeable future; coal-fired power generation units using fossil fuels account for more than 70%, so how to reduce the energy consumption of coal-fired power plant boilers in my country? Consumption has become the focus of today's work. In recent years, due to the sharp rise in international energy prices, the price of coal used in domestic power generation has also risen very high, power generation companies have suffered serious losses, and the significance of energy conservation and consumption reduction has become increasingly prominent. Therefore, in close connection with the needs of my country's coal-fired power plant boilers for energy saving and consumption reduction, and aiming at the problem that the exhaust gas temperature of power plant boilers is generally 10-50 °C higher than the design value, it is of great significance to study the methods and key technologies for comprehensive utilization of flue gas waste heat. Application value and prospect. According to experience, when the exhaust gas temperature rises by 10°C, the boiler efficiency will decrease by 0.5%, and the coal consumption of standard power supply will increase by 2g/kWh. The economic prospect of flue gas waste heat utilization is very considerable. A considerable number of power plant boilers use bag filters. Too high exhaust gas temperature is not conducive to the life and operation safety of bag filters, and it is urgent to reduce the exhaust gas temperature. When the rotary air preheater is in operation in winter, the current jump of the air preheater and low-temperature corrosion often occur because the heater cannot be put into operation, so it is urgent to put the heater into operation economically and safely. Therefore, it is of great significance to study a comprehensive utilization system of flue gas waste heat combined with heater and low-temperature economizer to improve the safety and reliability of boiler operation.

my country's power plant boilers use low-temperature economizers to use flue gas waste heat and apply heaters to solve low-temperature corrosion and ash blocking of boiler air preheaters. However, it has the following disadvantages:

1) Using auxiliary steam as the heat source of the air heater will reduce the thermal economy in most cases, especially when the parameters of the air heater are not selected properly, it will be greatly reduced. The reason is that after the temperature rise of the air heater exceeds the critical temperature rise, the heat loss caused by the increase in the exhaust gas temperature will be greater than the return heat gain of the air heater.

2) The flue gas cooler in the low-temperature economizer system is placed in the tail flue behind the air preheater. Due to the limited space, the reduction in exhaust gas temperature is limited; the flue gas cooler, that is, the feed water heater, is placed directly in the flue. The working conditions of the flue are harsh, and there are risks of low-temperature corrosion and wear. Once the flue gas cooler leaks, it will seriously affect the safety of the boiler water system.

In the utility model patent of "a water-medium boiler exhaust heat recovery and utilization device" with application number 201020020529.7, the device has two closed cycles, one of which is composed of a flue gas cooler and a flue gas cooler inlet and outlet. The second is composed of flue gas cooler, flue gas cooler inlet and outlet header, circulating water pump, gate valve, waste heat utilization pilot valve and air heater. In summer, the first closed cycle runs. The closed cycle cooling water is released in the feed water heater by the heat absorbed in the flue gas cooler. The cooling medium in the feed water heater is the low pressure feed water from the low pressure heater. The low-pressure feed water that has absorbed heat in the feed water heater enters the deaerator; in winter, the second closed cycle runs, and the closed cycle water releases the heat absorbed in the flue gas cooler in the air heater to improve The purpose of controlling the cold air temperature of the boiler and preventing low-temperature corrosion of the air preheater. The switching of the two cycles is realized by the switch of the gate valve and the waste heat utilization pilot valve, which has the following disadvantages:

1) The system adopts a surface heat exchanger, which increases the safety of the boiler water system operation, but reduces the thermal economy of the system.

2) The flue gas cooler operates in two working conditions of heating boiler feed water and cold air. When heating cold air, the surface heat exchanger is not put into use, and the utilization hours are low.

3) Simultaneous operation of boiler feed water and cold air cannot be realized, and the adjustability is poor.

Contents of the invention

In order to overcome the deficiencies in the prior art above, the purpose of this utility model is to provide a combined flue gas waste heat comprehensive utilization system, which solves the economic problems of high exhaust gas temperature and large exhaust gas loss in power plants, and also solves the The high smoke temperature affects the safety of the bag filter operation, and solves the problem that the auxiliary steam heating heater cannot be turned on, the surface heat exchanger is not put into use, the utilization hours are low, the thermal economy is poor, and even the air preheater is caused by low temperature corrosion It also has the advantage of being adjustable.

In order to achieve the above object, the technical solution adopted in the utility model is:

A combined flue gas waste heat comprehensive utilization system includes an air preheater 1 with an air outlet and a flue gas inlet. The air inlet of the air preheater 1 is located behind the air preheater 1 and arranged in the air duct. The air outlet of the blower 7 is connected through a pipeline, and the flue gas outlet of the air preheater 1 is connected with the flue gas inlet of the first-stage flue gas cooler 6 and the first-stage flue gas cooler arranged in the tail flue. The flue gas outlet of 6 is connected with the dust inlet of the dust collector 9 and the dust outlet of the dust collector 9 is connected with the flue gas inlet of the second-stage flue gas cooler 10 which has a flue gas outlet and is arranged in the tail flue through pipes respectively The water outlet and water inlet of the second-stage flue gas cooler 10 are respectively connected with the water inlet and water outlet of the heater 7 through a pipeline with a switching gate valve 13, and the water outlet of the second-stage flue gas cooler 10 The pipeline between the water inlet of the heater 7 is connected with the water inlet and the water outlet of the water supply tank 8 with the water supply port through a pipeline with a switching gate valve 13, and the water inlet of the second-stage flue gas cooler 10 and the The pipeline between the water outlets of the heater 7 is also provided with a first closed cold pump 11, and the water outlet of the second-stage flue gas cooler 10 is also connected to the first-stage flue gas cooler 6 through a pipeline with a switching gate valve 13. The water inlet of the first-stage flue gas cooler 6 is connected with the water inlet of the deaerator 2 with the suction port and the water outlet, and the water inlet of the deaerator 2 is also connected with the water inlet with the forward steam The water outlet of the first low plus 3 of the mouth is connected, the water inlet of the first low plus 3 is connected with the water outlet of the second low plus 4 with the forward steam port and the water inlet of the second low plus 4 is the same with the forward steam The water outlet of the third low plus 5 of the port is connected through a pipeline, the steam outlet of the first low plus 3 is connected with the steam inlet of the second low plus 4 through a pipeline, and the steam outlet of the second low plus 4 is connected with the first low plus 4 The steam inlet of the third low plus 5 is connected through pipelines, the water outlet of the first low plus 3 is connected with the water inlet of the second low plus 4, the steam outlet of the second low plus 4 and the steam inlet of the third low plus 5 The pipeline between them communicates with the water inlet of the second-stage flue gas cooler 10 through a pipe with a switching gate valve 13 and a second closed cold pump 12, and the water outlet of the second-stage flue gas cooler 10 is connected to the first The pipes between the water inlets of the first-stage flue gas coolers 6 communicate with the pipes provided with the second closed cold pump 12 through the switching gate valve 13 .

The wall temperature of the heated surface of the first-stage flue gas cooler 6 and the second-stage flue gas cooler 10 is 15°C higher than the acid dew point temperature, and corrosion-resistant steel is used in the low-temperature section.

By arranging the first-stage flue gas cooler 6 and the second-stage flue gas cooler 10 before and after the dust collector 9, a cascade utilization of exhaust waste heat is formed, the high-temperature section of the flue gas heats the condensate with high fire quotient, and the low-temperature section of the flue gas heats Cold air with low fire quotient; the cooler in the low-temperature section of flue gas and the cooler in the high-temperature section of flue gas operate in series, which increases the inlet water temperature and temperature level of the closed circulation water of the second-stage flue gas cooler 10, and reduces the flue gas cooling. The risk of low-temperature corrosion of the device and the freezing of closed circulating water.

Description of drawings

Accompanying drawing is the structural representation of working principle of the utility model.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is described in more detail.

As shown in the attached figure, the combined flue gas waste heat comprehensive utilization system includes an air preheater 1 with an air outlet and a flue gas inlet. The air inlet of the air preheater 1 is located behind the air preheater 1 and arranged in The air outlet of the air heater 7 with an air inlet in the air duct is connected through a pipe, and the flue gas outlet of the air preheater 1 is connected with the flue gas of the first-stage flue gas cooler 6 arranged in the tail flue. The inlet, the flue gas outlet of the first-stage flue gas cooler 6 and the dust inlet of the dust collector 9 and the dust outlet of the dust collector 9 are the same as the second-stage flue gas cooler with a flue gas outlet and arranged in the tail flue The flue gas inlets of 10 are respectively connected through pipelines, and the water outlet and water inlet of the second-stage flue gas cooler 10 are respectively connected with the water inlet and water outlet of the heater 7 through pipelines with switching gate valves 13. The pipeline between the water outlet of the first-stage flue gas cooler 10 and the water inlet of the air heater 7 is connected with the water inlet and the water outlet of the water supply tank 8 with the water supply port through a pipeline with a switching gate valve 13, and the second stage The pipeline between the water inlet of the flue gas cooler 10 and the water outlet of the air heater 7 is also provided with a first closed cold pump 11, and the water outlet of the second-stage flue gas cooler 10 passes through a pipeline with a switching gate valve 13 It is connected with the water inlet of the first-stage flue gas cooler 6, and the water outlet of the first-stage flue gas cooler 6 is connected with the water inlet of the deaerator 2 with steam inlet and water outlet, and the deaerator The water inlet of 2 is also connected with the water outlet of the first low plus 3 with the forward steam port, and the water inlet of the first low plus 3 is connected with the water outlet of the second low plus 4 with the forward steam port and the second low The water inlet of adding 4 is connected with the water outlet of the third low adding 5 with the forward steam port through the pipeline, and the steam outlet of the first low adding 3 is connected with the rear steam inlet of the second low adding 4 through the pipeline, and the second low adding 4 is connected through the pipeline. The steam outlet of the second low plus 4 and the rear steam inlet of the third low plus 5 are connected through pipelines, the water outlet of the first low plus 3 is connected with the water inlet of the second low plus 4 and the steam outlet of the second low plus 4 The pipe between the steam inlet of the third low-pressure heater 5 is connected to the water inlet of the second-stage flue gas cooler 10 through a pipe with a switching gate valve 13 and a second closed-cooling pump 12, and the second-stage flue gas The pipeline between the water outlet of the gas cooler 10 and the water inlet of the first-stage flue gas cooler 6 communicates with the pipeline provided with the second closed cooling pump 12 through a switching gate valve 13 . The wall temperature of the heated surface of the first-stage flue gas cooler 6 and the second-stage flue gas cooler 10 is 15°C higher than the acid dew point temperature, and corrosion-resistant steel is used in the low-temperature section.

The working principle of the utility model is as follows: in the working condition of low temperature, the low-pressure feed water is introduced from the water inlet of the third low-pressure heater 5, the condensed water is introduced from the water supply port of the water supply tank 8, and the condensate water is supplied from the air inlet of the air heater 7. Cold air, flue gas is introduced from the flue gas inlet of the air preheater 1, steam is extracted from the steam inlet of the deaerator 2, steam is extracted from the front steam port of the first low-level heater 3, and the forward steam of the second low-level heater 4 Steam port extraction and the front steam port extraction of the third low-pressure heater 5, open the pipeline between the water outlet of the second-stage flue gas cooler 10 and the water inlet of the first-stage flue gas cooler 6 and the second closed cooling pump The switching gate valve 13 installed between the pipelines of 12 closes the inlet and outlet gate valves entering the second-stage flue gas cooler 10 and the second closed cold pump 12, and the flue gas preheated by the air preheater 1 is sent to the first-stage flue gas cooling 6, and the low-pressure feed water enters the first-stage flue gas cooler 6 through the third low-pressure feed 5 and the second low-pressure feed 4 under the action of steam extraction, and the preheated flue gas is cooled by the low-pressure feed water and sent to the dust collector 9 after dust removal sent to the second-stage flue gas cooler 10, and the condensed water replenishment is sent to the second-stage flue gas cooler 10 through the replenishment water tank 8, and the second-stage flue gas cooler 10 cools and removes dust and outputs the flue gas, while the second-stage The condensed water replenishment in the flue gas cooler 10 is cooled by the cold air through the heater 7, and returns to the replenishment water tank 8 to circulate water, and the cold air is sent to the air preheater 1 by the heater 7 to form hot air and then exported. The condensed water replenishment after heating thus returns to the first sub-cooler 3, at this moment, the second closed cooling pump 12 is stopped, and the water outlet of the second-stage flue gas cooler 10 and the water inlet of the first-stage flue gas cooler 6 are opened The switching gate valve 13 arranged between the pipeline between the pipeline and the pipeline of the second closed cold pump 12 is set on the pipeline between the water outlet of the second-stage flue gas cooler 10 and the water inlet of the first-stage flue gas cooler 6. gate valve.

Under the condition of high temperature, low-pressure feed water is introduced from the water inlet of the third low-pressure heater 5; The flue gas inlet of 1 introduces flue gas, extracts steam from the steam inlet of the deaerator 2, extracts steam from the front steam port of the first low-level heater 3, extracts steam from the front steam port of the second low-level tank 4, and extracts steam from the front steam port of the third low-level tank 5, extract steam from the front steam port, close the shut-off valve between the second stage flue gas cooler 10 and the heater 7, close the pipeline between the water inlet of the first stage flue gas cooler 6 and the second closed cooling pump The switching gate valve 13 installed between the pipelines of 12 closes the first closed cooling pump 11, and opens other switching gate valves and the second closed cooling pump 12, and the flue gas preheated by the air preheater 1 is sent to the first stage flue gas cooling 6, while the low-pressure feed water enters the second-stage flue gas cooler 10 under the action of steam extraction through the third low-pressure feed water 5 and the second low-pressure feed water heater 4, and the low-pressure feed water is sent to the first-stage flue gas cooler 6 after absorbing heat , and then sent to the deaerator 2. And stop using the condensed water replenishment.

Under normal working conditions, low-pressure feed water is introduced from the water inlet of the third low-pressure heater 5, condensed water is introduced from the water replenishment port of the water tank 8 to replenish water, cold air is introduced from the air inlet of the air heater 7, and cold air is introduced from the air preheater 1. The flue gas inlet introduces the flue gas, extracts steam from the steam inlet of the deaerator 2, extracts steam from the front steam port of the first low-level heater 3, extracts steam from the front steam port of the second low-level heater 4, and extracts steam from the front steam port of the third low-level heater 5 Extract steam from the front steam port, close the switching gate valve 13 provided between the pipeline between the water outlet of the second-stage flue gas cooler 10 and the water inlet of the first-stage flue gas cooler 6 and the pipeline of the second closed cold pump 12 and Open other gate valves, the first closed cold pump 11 and the second closed cold pump 12, and the flue gas preheated by the air preheater 1 is sent to the first-stage flue gas cooler 6, while the low-pressure feed water is passed through the third low-pressure pump 5 and The second low-level heater 4 enters the first-stage flue gas cooler 6 under the action of steam extraction, and the preheated flue gas is cooled by low-pressure feed water and then sent to the dust collector 9 for dust removal and then sent to the second-stage flue gas cooler 10, while Condensed water replenishment is sent to the second-stage flue gas cooler 10 through the replenishing water tank 8, and the second-stage flue gas cooler 10 cools and removes the flue gas after dust removal, and the condensate water replenishment in the second-stage flue gas cooler 10 passes through the warm air The cooler 7 is cooled by cold air, and returns to the replenishing water tank 8 to circulate water, and the cold air is sent to the air preheater 1 by the heater 7 to form hot air, and then exported, and the heated condensed water replenishment returns to the first low-heater 3. Turn on the second closed cold pump 12 at this time, and close the pipeline between the water outlet of the second stage flue gas cooler 10 and the water inlet of the first stage flue gas cooler 6 and the pipe of the second closed cold pump 12 Switching gate valve 13 provided between.

Claims (2)

1. an assembled smoke gas residual heat integrative utilizes system; Comprise the air preheater (1) that has air outlet slit and smoke inlet; It is characterized in that: the air intake of air preheater (1) be located on air preheater (1) afterwards and the air outlet that is arranged in the steam air heater (7) in the air channel be connected through pipeline; The exhanst gas outlet of described air preheater (1) is connected through pipeline respectively with the smoke inlet that has exhanst gas outlet and be arranged in the second level gas cooler (10) in the back-end ductwork with the dust mouth of the dust inlet of the same deduster of exhanst gas outlet (9) of the smoke inlet, the first order gas cooler (6) that are arranged in the first order gas cooler (6) in the back-end ductwork and deduster (9); The water inlet of the same respectively steam air heater of the delivery port of second level gas cooler (10) and water inlet (7) and delivery port are connected through having the pipeline that switches gate valve (13); Pipeline between the water inlet of the delivery port of second level gas cooler (10) and steam air heater (7) is connected with the water inlet and the delivery port that have the water supply tank (8) of water supplement port through having the pipeline that switches gate valve (13); Pipeline between the delivery port of the water inlet of second level gas cooler (10) and steam air heater (7) also is provided with first closed cold pump (11); The delivery port of second level gas cooler (10) also is connected with the water inlet of first order gas cooler (6) through having the pipeline that switches gate valve (13); The delivery port of first order gas cooler (6) is connected with the water inlet that has the oxygen-eliminating device (2) of bleeding point and delivery port; And the water inlet of oxygen-eliminating device (2) also is connected with the first low delivery port that adds (3) of air intake before having; Second of the air intake low delivery port and the second low water inlet that adds (4) that adds (4) was connected through pipeline with the 3rd low delivery port that adds (5) that has preceding air intake before the first low water inlet that adds (3) had together; The first low venthole and the second low air intake that adds (4) that adds (3) is connected through pipeline; Second low venthole and the 3rd low air intake that adds (5) that adds (4) is connected through pipeline; The first low delivery port that adds (3) is connected with the water inlet of second level gas cooler (10) through having the pipeline that switches gate valve (13) and be provided with second closed cold pump (12) with the pipeline between the second low water inlet that adds (4) and the second low venthole that adds (4) and the 3rd low air intake that adds (5), and the pipeline between the water inlet of the delivery port of second level gas cooler (10) and first order gas cooler (6) is connected through switching gate valve (13) with the pipeline that is provided with second closed cold pump (12).

2. assembled smoke gas residual heat integrative according to claim 1 utilizes system, it is characterized in that: the heating surface wall temperature of first order gas cooler (6) and second level gas cooler (10) is higher than 15 ℃ of acid dew-point temperatures, adopts corrosion resisting steel in low-temperature zone simultaneously.

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