CN111828950A - A flue gas waste heat utilization system - Google Patents

Abstract

The invention discloses a flue gas waste heat utilization system, which belongs to the field of energy saving and emission reduction of thermal power units. A flue gas cooler of the flue gas waste heat utilization system is provided with a condensed water inlet a1 and a condensed water outlet a2 that are connected; a condensed water inlet pipe The water inlet end of the circuit is connected with the low pressure heater pipeline, the water outlet end of the condensate water inlet pipe is connected with the condensate water inlet a1, the water inlet end of the condensate water return line is connected with the condensate water outlet a2, and the condensate water return line is connected with the condensate water outlet a2. The water outlet is connected with the low-pressure heater pipeline; the air heater is provided with a connected condensate inlet b1 and a condensate outlet b2, and a connected cold air inlet and a hot air outlet. The condensate inlet b1 is communicated with the condensate outlet a2, and the condensate The outlet b2 is communicated with the condensed water return pipeline; the cold air inlet is communicated with the blower, and the hot air outlet is communicated with the air preheater. The flue gas waste heat utilization system realizes the cascade utilization of the boiler flue gas waste heat, improves the thermal efficiency of the boiler, and at the same time can prevent the hot air at the hot air outlet of the heater from overheating.

Description

A flue gas waste heat utilization system

technical field

The invention relates to the technical field of energy saving and emission reduction of thermal power units, in particular to a system for utilizing waste heat of flue gas.

Background technique

In my country's thermal power plants, 70% to 80% of the overall heat loss of the boiler is exhaust heat loss. When the exhaust gas temperature rises by 10℃～15℃, the boiler efficiency will decrease by 1%, and the annual average standard coal consumption will increase by 3～4g/(kW·h). With the increasingly strict energy conservation and emission reduction policies and rising energy prices, the importance of rational utilization of boiler flue gas waste heat is increasing.

The most common method of traditional flue gas waste heat utilization is to arrange a low-temperature economizer in the tail flue after the air preheater, and use the flue gas waste heat to heat the condensed water in the regenerative system to reduce the extraction steam of the regenerative system. The saved extraction steam enters the subsequent steam turbine to continue to expand and do work, and the total output of the steam turbine increases, thereby improving the economy of the entire unit.

The above-mentioned flue gas waste heat utilization schemes mainly have the following disadvantages:

(1) The waste heat of flue gas absorbed by the primary waste heat utilization system is directly used to heat the flue gas at the entrance of the chimney, resulting in energy waste.

(2) In summer working conditions, the exhaust gas temperature of the boiler is high, and the heat recovered by the secondary flue gas waste heat recovery system increases, which is likely to cause the hot air at the heater outlet to overheat.

(3) The waste heat of flue gas recovered by the low-temperature economizer only heats the condensed water, and the waste heat of flue gas has not been utilized in cascade, and the utilization rate of waste heat is low.

Therefore, there is an urgent need to propose a flue gas waste heat utilization system to solve the above technical problems existing in the prior art.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a flue gas waste heat utilization system, which can realize the cascade utilization of flue gas waste heat, has high energy utilization rate, and can avoid overheating of hot air at the outlet of the heater.

For achieving the above object, the technical scheme adopted in the present invention is:

A flue gas waste heat utilization system, comprising a blower, an air preheater, a low-pressure heater group, a condensate water inlet pipeline, a condensate water return pipeline, a flue gas cooler, an air heater and a flue gas treatment device;

The low-pressure heater group includes a plurality of low-pressure heaters, and the plurality of low-pressure heaters are connected in sequence through the low-pressure heater pipeline; the water inlet end of the low-pressure heater pipeline is connected to the condensed water source, and the low-pressure heater The outlet end of the deaerator pipeline is connected to the deaerator;

The flue gas cooler is provided with a condensed water inlet a1 and a condensed water outlet a2 that communicate with each other, and a flue gas inlet and a flue gas outlet that communicate with each other; the water inlet end of the condensed water inlet pipeline is connected to the low pressure heating The water outlet end of the condensate water inlet pipe is communicated with the condensate water inlet a1, the water inlet end of the condensate water return pipe is communicated with the condensate water outlet a2, and the condensate water return pipe The water outlet end of the road is communicated with the low-pressure heater pipeline; the flue gas inlet is communicated with the air preheater, and the flue gas outlet is communicated with the flue gas treatment device;

The air heater is provided with a condensed water inlet b1 and a condensed water outlet b2 that communicate with each other, and a cold air inlet and a hot air outlet that communicate with each other. The condensed water inlet b1 is communicated with the condensed water outlet a2, and the condensed water The outlet b2 is communicated with the condensate water return pipeline; the cold air inlet is communicated with the blower, and the hot air outlet is communicated with the air preheater.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

A condensate water inlet regulating valve, the condensate water inlet regulating valve is arranged in the condensate water inlet pipeline.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

A hot water recirculation circuit, the water inlet end of the hot water recirculation circuit is connected to the condensate water return pipeline, and the water outlet end of the hot water recirculation circuit is connected to the condensate water inlet pipeline.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

A recirculation regulating valve is arranged in the hot water recirculation circuit.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

The condensate water return regulating valve is arranged in the condensate water return pipeline.

As the preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas waste heat utilization system also includes:

The variable frequency booster pump is arranged in the condensate water inlet pipeline.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas cooler is a fin-and-tube heat exchanger arranged in a countercurrent flow.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the air heater is a spiral fin-and-tube heat exchanger arranged in a countercurrent flow.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the flue gas temperature at the flue gas outlet of the flue gas cooler is 90°C-100°C, and the flue gas resistance is 100Pa-800Pa.

As a preferred technical solution of the above-mentioned flue gas waste heat utilization system, the air temperature of the hot air outlet of the heater is 50°C-90°C, and the air resistance is 100Pa-800Pa.

Compared with the prior art, the beneficial effects of the present invention are:

The flue gas waste heat utilization system proposed by the present invention efficiently recovers and utilizes the flue gas waste heat by coordinating the waste heat, recuperation, and air heater systems. The thermal efficiency is improved, and the efficient utilization of energy is realized; at the same time, the flue gas waste heat utilization system heats the condensed water through the flue gas cooler, and the heated condensed water enters the air heater to heat the primary air or secondary air introduced by the blower, which can effectively prevent The hot air at the hot air outlet of the heater is overheated, which can also avoid the disadvantage that the air preheater occupies an excessively large area and is difficult to arrange when the conventional smoke recovery and exhaust system heats the hot air.

Description of drawings

FIG. 1 is a schematic diagram of a flue gas waste heat utilization system provided by a specific embodiment of the present invention.

In the picture:

1. Blower; 2. Air preheater; 3. Flue gas cooler; 4. Air heater; 5. Condensate inlet control valve; 6. Recirculation control valve; 7. Condensate return control valve; 8 , variable frequency booster water pump; 9, first low pressure heater; 10, second low pressure heater; 11, third low pressure heater; 12, fourth low pressure heater; 13, electrostatic precipitator; 14, induced draft fan; 15 , desulfurization tower; 16, economizer;

100, condensate water inlet pipeline; 101, first water inlet branch; 102, second water inlet branch; 200, condensate return pipeline; 300, low pressure heater pipeline; 400, hot water recirculation circuit.

Detailed ways

In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved more clearly, the technical solutions of the present invention are further described below with reference to the accompanying drawings and through specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the accompanying drawings only show some but not all of the parts related to the present invention.

In the description of the present invention, unless otherwise expressly specified and limited, the terms "connected", "connected" and "fixed" should be understood in a broad sense, for example, it may be a fixed connection, a detachable connection, or an integrated ; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include the first and second features in direct contact, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature is "below", "below" and "below" the second feature includes the first feature being directly below and diagonally below the second feature, or simply means that the first feature has a lower level than the second feature.

In the description of this embodiment, the terms "up", "down", "left", "right" and other azimuth or positional relationships are based on the azimuth or positional relationship shown in the drawings, which are only for convenience of description and simplification of operations, rather than indicating Or imply that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first" and "second" are only used for distinction in description, and have no special meaning.

As shown in FIG. 1 , this embodiment discloses a flue gas waste heat utilization system that coordinates waste heat, recuperation, and air heater systems, which can effectively reduce coal consumption of coal-fired generator sets and improve boiler efficiency to achieve efficient energy utilization. At the same time, the flue gas waste heat utilization system can effectively prevent the hot air at the hot air outlet of the heater 4 from overheating, and can also avoid the disadvantage that the air preheater 2 occupies an excessively large area and is difficult to arrange when the conventional smoke recovery and exhaust system heats the hot air. The flue gas waste heat utilization system mainly includes a blower 1, an air preheater 2, a low-pressure heater group, a condensate water inlet pipeline 100, a condensate water return pipeline 200, a flue gas cooler 3, an air heater 4 and a flue gas treatment. device.

Specifically, the low-pressure heater group includes a plurality of low-pressure heaters, and the plurality of low-pressure heaters are connected in sequence through the low-pressure heater pipeline 300; the water inlet end of the low-pressure heater pipeline 300 (shown as A in FIG. 1 ) is communicated From an external condensate water source (not shown in the figure), the outlet end of the low-pressure heater pipeline 300 (B shown in Figure 1 ) is connected to an external deaerator (not shown in the figure). Optionally, along the direction from the water inlet end to the water outlet end of the low pressure heater pipeline 300, the low pressure heater group includes four low pressure heaters, which are the first low pressure heater 9, the second low pressure heater 10, and the third low pressure heater. The heater 11 and the fourth low pressure heater 12, the inlet of the first low pressure heater 9 is communicated with the condensate water source, and the outlet of the fourth low pressure heater 12 is communicated with the deaerator. It can be understood that the number of low-pressure heaters included in the low-pressure heater group can be designed according to actual working conditions.

The flue gas cooler 3 is provided with a condensed water inlet a1 and a condensed water outlet a2 that communicate with each other, wherein the water inlet end of the condensed water inlet pipeline 100 is communicated with the low pressure heater pipeline 300, and the water outlet of the condensed water inlet pipeline 100 The end is connected to the condensate inlet a1, the inlet end of the condensate return pipeline 200 is connected to the condensate outlet a2, and the outlet end of the condensate return pipeline 200 is connected to the low pressure heater pipeline 300. Optionally, the water inlet end of the condensate water inlet pipeline 100 is provided with two water inlet branches, namely the first water inlet branch 101 and the second water inlet branch 102, wherein the first water inlet branch 101 is connected to the inlet of the first low-pressure heater 9, and the second water inlet branch 102 is connected to the outlet of the second low-pressure heater 10. Under this structure, two different temperatures of condensed water are mixed and then enter the condensed water inlet. The water pipeline 100 ensures that the water temperature of the mixed condensate meets the inlet water temperature requirement of the flue gas cooler 3 . It can be understood that the number of water inlet branches and the communication positions on the low-pressure heater pipeline 300 can be designed according to actual working conditions. The outlet end of the condensate water return pipeline 200 is communicated with the inlet of the fourth low pressure heater 12 .

Further, the flue gas cooler 3 is also provided with a flue gas inlet and a flue gas outlet that communicate with each other. The flue gas inlet is communicated with the air preheater 2, and the flue gas outlet is communicated with the flue gas treatment device. Under the above structure, the condensed water introduced by the condensed water inlet pipe 100 and the high-temperature flue gas discharged from the exhaust port of the air preheater 2 exchange heat in the flue gas cooler 3, and the condensed water absorbs the waste heat of the high-temperature flue gas After the water temperature rises, the temperature of the high-temperature flue gas decreases, and a part of the condensed water after the temperature rises is returned to the inlet of the fourth low-pressure heater 12 through the condensed water return pipe 200, thereby reducing the steam extraction volume of the low-pressure heater group and improving the steam turbine. of functional ability.

The air heater 4 is provided with a condensed water inlet b1 and a condensed water outlet b2 that communicate with each other, and a cold air inlet and a hot air outlet that communicate with each other. The condensate inlet b1 is connected to the condensate outlet a2 through a pipeline, and the condensate outlet b2 is connected to the condensate return pipeline 200 through a pipeline; Under this structure, another part of the condensed water heated up and the cold air introduced from the blower 1 conduct heat exchange in the air heater 4, and the cold air enters the air preheater 2 through the hot air outlet after absorbing heat, which improves the efficiency of entering the air preheater 2. The high-quality cold air temperature reduces the high-quality steam extraction volume of the original heater system of the power plant, thereby reducing the coal consumption of the unit for power generation. It should be noted that the blower 1 can introduce primary air or secondary air.

In this embodiment, the flue gas cooler 3 is a fin-and-tube heat exchanger arranged in a countercurrent flow. The flue gas temperature at the flue gas outlet of the flue gas cooler 3 is designed to be 90°C-100°C, and the flue gas resistance is designed to be 100Pa-800Pa.

The air heater 4 is a spiral fin-and-tube heat exchanger arranged in a countercurrent flow. The air temperature at the hot air outlet of the heater 4 is designed to be 50°C-90°C, and the air resistance is designed to be 100Pa-800Pa.

Further, the flue gas waste heat utilization system further includes a variable frequency booster pump 8 arranged in the condensate water inlet pipeline 100 . The variable frequency booster pump 8 provides power for the entire condensate system. At the same time, when the unit load changes greatly, the variable frequency booster pump 8 is used to control the amount of condensed water by frequency conversion, so as to ensure that the outlet smoke temperature at the flue gas outlet of the flue gas cooler 3 is within the Within the design range, and ensure that the water temperature at the condensate outlet a2 of the flue gas cooler 3 meets the requirements of the heater 4 and the heat recovery system.

In order to prevent the low temperature corrosion of the flue gas cooler 3, it is required that the inlet water temperature at the condensate inlet a1 of the flue gas cooler 3 is not lower than the minimum required wall temperature, and the flue gas waste heat utilization system also includes a condensate water inlet regulating valve 5, The condensate water inlet regulating valve 5 is arranged in the condensate water inlet pipeline 100 . The automatic control of the inlet water temperature of the flue gas cooler 3 is realized by adjusting the opening of the condensate water inlet regulating valve 5 . Optionally, the inlet water temperature at the condensed water inlet a1 of the flue gas cooler 3 is designed to be 60° C.-80° C., which is beneficial to prevent low-temperature corrosion of the flue gas cooler 3 . Preferably, the condensate water inlet regulating valve 5 is arranged in the first water inlet branch 101 .

Further, in order to prevent the water temperature at the outlet of the second low pressure heater 10 from being too low when the unit is running at low load, the water temperature requirement at the inlet of the flue gas cooler 3 cannot be met only by adjusting the opening of the condensate water inlet regulating valve 5, The flue gas waste heat utilization system further includes a hot water recirculation circuit 400, the water inlet end of the hot water recirculation circuit 400 is connected to the condensate water return pipeline 200, and the water outlet end of the hot water recirculation circuit 400 is connected to the condensate water inlet pipeline 100 is preferably connected to the upstream of the variable frequency booster water pump 8 . The hot water recirculation circuit 400 is provided with a recirculation regulating valve 6. By adjusting the opening of the recirculation regulating valve 6, a part of the high temperature condensed water return water can be introduced into the condensed water inlet pipeline 100, and mixed with the low temperature condensed water into the smoke The gas cooler 3 increases the inlet water temperature of the flue gas cooler 3 and further avoids the occurrence of low temperature corrosion.

In order to prevent the exhaust gas temperature of the boiler from being too high in summer, causing the water temperature at the outlet of the flue gas cooler 3 to be too high, and indirectly causing the over-temperature warning of the air temperature at the outlet of the heater 4, the flue gas waste heat utilization system in this embodiment is used in the condensed water. A condensate return water regulating valve 7 is added to the return water pipeline 200 . The amount of high-temperature condensed water entering the heater 4 is adjusted by adjusting the opening of the condensate return water regulating valve 7 to ensure that the temperature of the hot air at the hot air outlet of the heater 4 does not exceed the temperature; at the same time, it can also prevent the unit from running at low load The temperature of the hot air of the heater 4 is too low to meet the operating requirements.

The flue gas treatment device in this embodiment is a desulfurization tower 15. An electrostatic precipitator 13 and an induced draft fan 14 are further provided between the flue gas outlet of the flue gas cooler 3 and the desulfurization tower 15. Optionally, the flue gas cooler 3 It can be arranged in the flue upstream of the electrostatic precipitator 13 or in the flue between the induced draft fan 14 and the desulfurization tower 15 . Further, an economizer 16 is also provided downstream of the smoke outlet of the air preheater 2 . It should be noted that the structures of the air preheater 2 , the economizer 16 , the electrostatic precipitator 13 and the desulfurization tower 15 in this embodiment are all conventional structures in the prior art, and the specific structures and working principles thereof are implemented in this embodiment. The example does not make specific statements.

The flue gas waste heat utilization system provided in this embodiment heats the condensed water and the primary air/secondary air respectively by recovering the waste heat of the high-temperature flue gas discharged from the air preheater 2, thereby reducing the steam extraction volume and the warm air of the low-pressure heater group. The extraction steam volume of the device 4 can be reduced, thereby reducing the coal consumption of the unit; the flue gas waste heat utilization system has good adjustment performance and strong adaptability, and can meet the requirements even when the working conditions and ambient temperature change greatly, and has a simple structure and high reliability. It avoids the disadvantage that the air preheater 2 occupies an excessively large area and is difficult to arrange when the conventional smoke recovery and exhaust system heats hot air, and at the same time realizes the deep cascade utilization of the waste heat of the boiler flue gas and improves the efficiency of the boiler.

The above embodiments only illustrate the basic principles and characteristics of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention also has various changes and changes. These changes and changes are all falls within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A flue gas waste heat utilization system, characterized in that it comprises a blower (1), an air preheater (2), a low-pressure heater group, a condensate water inlet pipeline (100), and a condensate water return pipeline (200) , flue gas cooler (3), air heater (4) and flue gas treatment device; The low-pressure heater group includes a plurality of low-pressure heaters, and the plurality of low-pressure heaters are sequentially connected through a low-pressure heater pipeline (300); the water inlet end of the low-pressure heater pipeline (300) is connected to the condensed water a water source, the water outlet end of the low-pressure heater pipeline (300) is connected to the deaerator; The flue gas cooler (3) is provided with a condensed water inlet a1 and a condensed water outlet a2 that communicate with each other, and a flue gas inlet and a flue gas outlet that are communicated with each other; the water inlet of the condensed water inlet pipeline (100) The end is communicated with the low-pressure heater pipeline (300), the outlet end of the condensate water inlet pipeline (100) is communicated with the condensate inlet a1, and the inlet end of the condensate return pipeline (200) Connected with the condensed water outlet a2, the water outlet end of the condensed water return pipeline (200) is connected with the low-pressure heater pipeline (300); the flue gas inlet is connected with the air preheater (2) communication, the flue gas outlet is communicated with the flue gas treatment device; The air heater (4) is provided with a condensed water inlet b1 and a condensed water outlet b2 that communicate with each other, and a cold air inlet and a hot air outlet that communicate with each other. The condensed water inlet b1 is communicated with the condensed water outlet a2, so The condensed water outlet b2 is communicated with the condensed water return pipeline (200); the cold air inlet is communicated with the blower (1), and the hot air outlet is communicated with the air preheater (2). 2. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: A condensate water inlet regulating valve (5) is provided in the condensate water inlet pipeline (100). 3. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: A hot water recirculation circuit (400), the water inlet end of the hot water recirculation circuit (400) is connected to the condensed water return pipe (200), and the water outlet end of the hot water recirculation circuit (400) is communicated in the condensate water inlet pipeline (100). 4. The flue gas waste heat utilization system according to claim 3, wherein the flue gas waste heat utilization system further comprises: A recirculation regulating valve (6) is arranged in the hot water recirculation circuit (400). 5. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: A condensed water return regulating valve (7) is arranged in the condensed water return pipeline (200). 6. The flue gas waste heat utilization system according to claim 1, wherein the flue gas waste heat utilization system further comprises: The variable frequency booster pump (8) is arranged in the condensate water inlet pipeline (100). 7. The flue gas waste heat utilization system according to claim 1, wherein, The flue gas cooler (3) is a countercurrently arranged fin-and-tube heat exchanger. 8. The flue gas waste heat utilization system according to claim 1, wherein, The air heater (4) is a countercurrently arranged spiral fin-and-tube heat exchanger. 9. The flue gas waste heat utilization system according to claim 1, characterized in that, The flue gas temperature of the flue gas outlet of the flue gas cooler (3) is 90°C-100°C, and the flue gas resistance is 100Pa-800Pa. 10. The flue gas waste heat utilization system according to claim 1, wherein, The air temperature of the hot air outlet of the heater (4) is 50°C-90°C, and the air resistance is 100Pa-800Pa.

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