CN102230615B - Combined type flue gas residual heat comprehensive utilization system - Google Patents

Abstract

The invention discloses a combined type flue gas residual heat comprehensive utilization system. A first-stage flue gas cooler and a second-stage flue gas cooler are arranged in front of and behind a dust collector respectively to realize stepped utilization of residual heat of exhaust smoke; condensed water with high entropy is heated at a flue gas high-temperature section; cold air with low entropy is heated in a flue gas low-temperature section; and a flue gas low-temperature section cooler and a flue gas high-temperature section cooler run in series. By adopting the comprehensive utilization system, the inlet water temperature level and the closed circulation water temperature level of the second-stage flue gas cooler are raised, and the risks of low-temperature corrosion and closed circulating water freezing in the flue gas cooler are decreased.

Description

A combined flue gas waste heat comprehensive utilization system

technical field

The invention 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 reach The purpose of increasing the temperature of the cold air of the boiler and preventing the 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 the present invention 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 problems caused by the exhaust gas temperature. High impact on the safety of the bag filter operation, and solve the problems of using auxiliary steam to heat the heater, the low utilization hours of the surface heat exchanger, poor thermal economy and even low-temperature corrosion of the air preheater , In addition, it also has the advantage of being adjustable.

In order to achieve the above object, the technical scheme adopted in the present invention 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 present invention.

Detailed ways

The present invention will be described in more detail below in conjunction with the accompanying drawings.

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 present invention is as follows: under the working condition of low air temperature, low-pressure feed water is introduced from the water inlet of the third low-pressure heater 5, condensed water is introduced from the water supply port of the water supply tank 8 to replenish water, and cold water is introduced from the air inlet of the air heater 7. Air, the flue gas is introduced from the flue gas inlet of the air preheater 1, the steam is extracted from the steam inlet of the deaerator 2, the steam is extracted from the front steam port of the first low-pressure heater 3, and the front steam port of the second low-heater 4 Steam extraction and the front steam inlet of the third low-pressure heater 5 extract steam, 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 12 The switch gate valve 13 set between the pipelines and close 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 cooler 6. 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 then sent to the dust collector 9 for dust removal into the second-stage flue gas cooler 10, and the 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 dust and outputs the flue gas, while the second-stage flue gas The condensed water replenishment in the air 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, and then The condensed water replenishment after the heating 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 set between the pipeline between the pipeline and the pipeline of the second closed cooling pump 12 closes the water outlet of the second-stage flue gas cooler 10 and the water inlet of the first-stage flue gas cooler 6. gate.

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. A combined flue gas waste heat comprehensive utilization system, comprising an air preheater (1) with an air outlet and a flue gas inlet, characterized in that: the air inlet of the air preheater (1) is located at the same location as the air preheater The air outlet of the air heater (7) arranged in the air duct after the air preheater (1) is connected through a pipe, and the flue gas outlet of the air preheater (1) is connected with the first-stage flue gas outlet arranged in the tail flue. The flue gas inlet of the gas cooler (6), the flue gas outlet of the first-stage flue gas cooler (6) are the same as the dust inlet of the dust collector (9) and the dust outlet of the dust collector (9) is the same as the flue gas The flue gas inlets of the second-stage flue gas cooler (10), which are exported and arranged in the tail flue, 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 heater ( 7) The water inlet and the water outlet are connected through a pipeline with a switching gate valve (13), and the pipeline between the water outlet of the second-stage flue gas cooler (10) and the water inlet of the heater (7) is connected through a belt The pipeline with switching gate valve (13) communicates with the water inlet and water outlet of the water replenishment tank (8) with the water replenishment port, and the water inlet of the second-stage flue gas cooler (10) and the outlet of the heater (7) The pipeline between the water outlets 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 (13) through a pipeline with a switching gate valve (13). 6) is connected to the water inlet, and the water outlet of the first-stage flue gas cooler (6) is connected to the water inlet of the deaerator (2) with a suction port and a water outlet, and the deaerator (2) The water inlet 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 water inlet of the second low addition (4) is communicated with the water outlet of the third low addition (5) with the forward steam port by pipeline, the steam outlet of the first low addition (3) and the second low addition ( The steam inlet of 4) is connected through the pipeline, the steam outlet of the second low-level heater (4) is connected with the steam inlet of the third low-level heater (5) through the pipeline, and the water outlet of the first low-level heater (3) is the same as The pipeline between the water inlet of the second low plus (4) and the steam outlet of the second low plus (4) and the steam inlet of the third low plus (5) passes through with a switching gate valve (13) and is provided with the first The pipeline of the second closed cooling pump (12) is connected with the water inlet of the second-stage flue gas cooler (10), and the water outlet of the second-stage flue gas cooler (10) is connected with the first-stage flue gas cooler (6). The pipeline between the water inlets is communicated with the pipeline provided with the second closed cooling pump (12) through a switching gate valve (13). 2. The combined flue gas waste heat comprehensive utilization system according to claim 1, characterized in that: the wall temperature of the heated surface of the first-stage flue gas cooler (6) and the second-stage flue gas cooler (10) is higher than that of the acid The dew point temperature is 15°C, and corrosion-resistant steel is used in the low temperature section. the

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