A generalized heat recovery system for boiler and heat recovery method

Abstract

The present invention discloses a generalized heat recovery system for a machine and a boiler and a heat recovery method. The system comprises a pre-economizer module, an air preheater bypass module, a cold air heating module, an air temperature control module and a pulverized coal heating module. The pre-economizer module and the air preheater bypass module are arranged downstream of an original economizer of the boiler along the flow of flue gas. The inlet of the air preheater bypass module is arranged between the pre-economizer module and the air preheater and is connected to the flue. The outlet of the air preheater bypass module is connected to the flue behind the air preheater. The air temperature control module is arranged at the hot primary air outlet on the air side of the air preheater; the cold air heating module is arranged on the path before the cold primary air enters the air preheater. The system of the present invention is adopted to improve the heat recovery amount and the heat recovery efficiency of the machine and the boiler as much as possible, which is reflected in not increasing the exhaust volume of the steam turbine as much as possible on the steam turbine side, and in the boiler side, the exhaust gas of the boiler air preheater is used as the heat source for heat recovery, and the heat recovery utilization quality is improved as much as possible through system optimization.

Description

Technical Field

[0001] The present invention belongs to the field of heat recovery of a machine and boiler, and in particular relates to a generalized heat recovery system of a machine and boiler and a heat recovery method. Background Art

[0002] Conventional heat recovery systems are mainly heat recovery on the steam turbine side, and the heat recovery object is high-pressure feed water. The heat recovery of feed water reduces the exhaust loss of the steam turbine, and reduces the heat consumption level of the steam turbine. However, for power plants, the lowest heat consumption value of the steam turbine does not mean the highest overall efficiency of the unit. For example, the increase in feed water temperature will affect the boiler outlet temperature to a certain extent, thereby affecting the boiler efficiency. In essence, the highest efficiency of a power plant should be the operating condition with the lowest actual coal consumption. In order to further reduce the actual coal consumption of the power plant, this generalized heat recovery scheme is proposed. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a generalized heat recovery system and heat recovery method for turbines and boilers, which fully recovers system heat from the turbine side and the boiler side, thereby improving the overall efficiency of the turbines and boilers and reducing coal consumption.

[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a generalized heat recovery system for a boiler, including a pre-economizer module, an air preheater bypass module, a cold air heating module and an air temperature control module. The pre-economizer module and the air preheater bypass module are arranged downstream of the original economizer of the boiler along the flow direction of the flue gas. The air preheater bypass module is arranged in parallel with the air preheater. The air preheater bypass module is arranged downstream of the pre-economizer module. The outlet of the air preheater bypass module is connected to the flue behind the air preheater. The air temperature control module is arranged at the hot primary air outlet on the air side of the air preheater; the cold air heating module is arranged on the path before the cold primary air enters the air preheater, and the cold air heating module is used to obtain the heat of the flue gas, steam turbine extraction or condensed water to heat the cold air.

[0005] The water inlet of the pre-economizer module is connected to the high-pressure water supply pipeline, and the water outlet of the pre-economizer module is connected to the water inlet of the economizer; circulating water heat exchange is adopted in the air preheater bypass module.

[0006] The cold air heating module includes at least one of a steam high-temperature heater, a drain cooling heater, a heat medium water air preheater and a cold end heat exchanger, wherein the cold end heat exchanger is arranged at the air inlet of the cold air, and the cold end heat exchanger is connected to the circulating water pipeline of the cooling tower; the steam high-temperature heater is connected to the five-extraction or six-extraction pipeline of the steam turbine unit, and the drain cooling heater is connected to the drain pipeline of the steam turbine unit;

[0007] When a steam high-temperature warm air heater and a drain cooling air heater are arranged at the same time, the drain cooling air heater is connected to the steam high-temperature warm air heater;

[0008] When a steam high-temperature warm air heater, a drain cooling air heater and a heat medium water air preheater are arranged at the same time, the heat medium water air preheater includes an air side heat exchanger and a flue gas side heat exchanger which are interconnected, and the steam high-temperature warm air heater and the drain cooling air heater are arranged on the air side. Along the air flow direction, the air side heat exchanger is arranged in the downstream direction of the drain cooling air heater, and the steam high-temperature warm air heater is arranged in the downstream direction of the air side heat exchanger.

[0009] The air preheater bypass module includes a bypass flue, a bypass high-temperature heat exchanger and a bypass low-temperature heat exchanger. A bypass regulating damper is arranged in the bypass flue, a flue gas regulating damper is arranged on the flue gas side of the air preheater, and circulating water and flue gas are used for heat exchange in the bypass high-temperature heat exchanger and the bypass low-temperature heat exchanger; wherein, the bypass high-temperature heat exchanger is connected to the high-pressure feed water of the boiler system, and the bypass low-temperature heat exchanger heats the condensate of the steam turbine unit.

[0010] A powder delivery heating module is provided on the pipeline from the coal mill to the boiler fuel inlet.

[0011] The powder delivery heating module is connected to the air preheater bypass module or the steam turbine extraction pipeline through a pipeline, or the powder delivery heating module is connected to the air preheater bypass module and the steam turbine extraction pipeline.

[0012] The air temperature control module uses steam turbine extraction as the heat source, and the air temperature control module is connected to the steam turbine extraction pipeline and the high-pressure heater; or a high-temperature hot air preheater is arranged in parallel with the low-temperature superheater, low-temperature reheater or economizer heating surface as the heat source, and the air side outlet of the air preheater is connected to the high-temperature hot air preheater.

[0013] The pre-economizer module is provided with a water bypass, and the water bypass comprises a regulating valve, a shut-off valve and a connecting pipeline, and the water bypass is connected with the pre-economizer module and the economizer.

[0014] A generalized heat recovery method for a turbine and a boiler comprises the following steps: utilizing the heat of flue gas to heat high-pressure feed water to an upper limit temperature through a pre-economizer module and an air preheater bypass module; utilizing the heat of flue gas, steam turbine extraction and / or condensed water to heat cold air to an upper limit temperature of a cold air inlet allowed by an air preheater through a cold air heating module and an air temperature control module; partially or fully recovering the heat to the boiler for recovery through the pre-economizer module and the air preheater bypass module; and recovering the heat not recovered to the boiler through the pre-economizer module and the air preheater bypass module to the turbine.

[0015] The pulverized coal is heated to the upper limit temperature of the pulverized coal entering the furnace by using the steam extraction steam of the steam turbine or the heat of the flue gas; or the pulverized coal is heated to the upper limit temperature of the pulverized coal entering the furnace by using the steam extraction steam of the steam turbine and the heat of the flue gas.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] A pre-economizer module and an air preheater bypass module are arranged downstream of the original economizer of the boiler along the flow direction of the flue gas. The air preheater bypass module is arranged in parallel with the air preheater downstream of the pre-economizer module and is connected to the flue. The outlet of the air preheater bypass module is connected to the flue behind the air preheater. The air preheater bypass module first recovers part of the heat of the flue gas at the economizer outlet. The air temperature control module is arranged at the hot primary air outlet on the air side of the air preheater to reuse part of the heat of the flue gas. The cold air heating module is arranged on the path before the cold primary air enters the air preheater. It is used to obtain the heat of flue gas, steam turbine extraction or condensate to heat the cold air. After heating, the cold air will reduce the demand for heat from the air preheater flue gas, so the upstream flue gas can release more heat to heat the feed water or condensate; the flue gas at the economizer and air preheater outlets is graded and utilized, and the heat from the flue gas is recovered to heat different objects; the system of the present invention is used to increase the amount of heat recovered from the machine and boiler as much as possible, which is reflected on the steam turbine side as little as possible in not increasing the exhaust volume of the steam turbine, and on the boiler side as the exhaust gas from the boiler air preheater is used as the heat source for heat recovery, and through system optimization, the quality of heat recovery is improved as much as possible.

[0018] Furthermore, a pulverized coal heating module is provided, and the pulverized coal is heated by using an air preheater bypass module and steam turbine extraction steam. The pulverized coal can be heated to its theoretical maximum temperature before entering the furnace, thereby improving the heat recovery efficiency of the boiler and steam turbine.

[0019] Furthermore, the cooling circulating water of various cooling towers such as intercooler towers and mechanical draft cooling towers is used as a heat source to heat the cold air, thereby increasing the temperature of the cold air entering the air preheater, which helps to reduce the exhaust steam of the steam turbine and reduce the heat absorbed by the flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the heat recovery system of Example 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the heat recovery system of Example 2 of the present invention.

[0022] Figure 3 This is a schematic diagram of the heat recovery system of Example 3 of the present invention.

[0023] Figure 4 This is a schematic diagram of the heat recovery system of Example 4 of the present invention.

[0024] Figure 5 This is a schematic diagram of the heat recovery system of Example 5 of the present invention.

[0025] In the attached figure, 1-pre-economizer module, 2-air preheater bypass module, 3-cold air heating module, 4-air temperature control module, 5-powder feeding heating module, 6-air preheater, 7-cooling circulating water system, 8-No. 3 high pressure heater, 9-deaerator, 10-economizer, 21-bypass flue, 22-bypass high temperature heat exchanger, 23-bypass low temperature heat exchanger, 31-steam high temperature warmer, 32-drain cooling warmer, 33-heat medium water air preheater, 331-air side heat exchanger, 332-flue gas side heat exchanger, 34-cold end heat exchanger, 41-air temperature control heat exchanger, 42-high temperature hot air preheater. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0027] The generalized heat recovery system of the machine and boiler takes the machine and boiler as the boundary condition. All heat in the power plant with a temperature higher than the ambient temperature can be used for heat recovery. Unlike the conventional flue gas waste heat utilization, the heat recovery object includes both waste heat such as exhaust gas and valuable heat such as steam turbine extraction, so it is generalized heat recovery; there are three boundary restriction conditions of the machine and boiler: first, the exhaust temperature limit of the boiler rotary air preheater, the inlet air temperature of the rotary air preheater can only be heated to the exhaust temperature minus about 20°C; second, the steam turbine feed water temperature limit, the minimum outlet flue gas temperature of the pre-economizer module 1 is the feed water temperature plus about 20°C; third, the coal quality condition limit, the maximum temperature of the pulverized coal pipeline is taken as the maximum allowable temperature of hot air powder delivery in the central storage pulverizing system; the present invention realizes the heat recovery system of the boiler and steam turbine by setting the pre-economizer module 1, the air preheater bypass module 2, the cold air heating module 3 and the air temperature control module 4, and further sets the powder delivery heating module 5, and through system optimization, the quality of heat recovery is improved as much as possible.

[0028] Embodiment 1,

[0029] refer to Figure 1 The present embodiment provides a generalized heat recovery system for a boiler, comprising a pre-economizer module 1, an air preheater bypass module 2, a cold air heating module 3 and an air temperature control module 4. The pre-economizer module 1, the air preheater bypass module 2 and the cold air heating module 3 are arranged along the flow direction of the flue gas. The inlet of the air preheater bypass module 2 is arranged between the pre-economizer module 1 and the air preheater 6 and is connected to the flue. The outlet of the air preheater bypass module 2 is connected to the flue behind the air preheater. The air temperature control module 4 is arranged at the outlet of the hot primary air. The water inlet of the pre-economizer module 1 is connected to the high-pressure water supply pipeline, and the water outlet of the pre-economizer module 1 is connected to the water inlet of the economizer.

[0030] The air preheater bypass module 2 includes a bypass flue 21, a bypass high-temperature heat exchanger 22 and a bypass low-temperature heat exchanger 23. A bypass regulating damper 23 is arranged in the bypass flue 21, and a flue gas regulating damper 51 is arranged on the flue gas side of the air preheater 6. Circulating water and flue gas are used for heat exchange in the bypass high-temperature heat exchanger 22 and the bypass low-temperature heat exchanger 23; wherein the bypass high-temperature heat exchanger 22 is connected to the high-pressure feed water of the boiler system, and the bypass low-temperature heat exchanger 23 heats the condensate of the steam turbine unit.

[0031] The cold air heating module 3 includes a steam high-temperature warm air heater 31, a drain cooling air heater 32 and a heat medium water air preheater 33. The steam high-temperature warm air heater 31 and the drain cooling air heater 32 are arranged on the air side. The heat medium water air preheater 33 includes an air side heat exchanger 331 and a flue gas side heat exchanger 332 that are interconnected. The flue gas side heat exchanger 332 is used to absorb the flue gas heat at the outlet of the air preheater and transfer the heat to the air side heat exchanger 331 for heating the air on the air side. Optionally, along the air Flow direction, the air side heat exchanger 331 is arranged in the downstream direction of the drain cooling heater 32, the steam high temperature heater 31 is arranged in the downstream direction of the air side heat exchanger 331, the steam high temperature heater 31 is connected to the five-pump or six-pump of the steam turbine unit, the drain cooling heater 32 is connected to the steam high temperature heater 31, the five-pump or six-pump is cooled to drain after the air heated by the steam high temperature heater 31 and the drain cooling heater 32 is heat-exchanged, and the drain flows to the drain cooling heater 32 to exchange heat with the air from the fan;

[0032] The air temperature adjustment module 4 is used to heat the hot primary air, and the air temperature adjustment module 4 is arranged at the air side outlet of the air preheater.

[0033] As an optional embodiment, the air temperature control module 4 can use the three-extraction or four-extraction steam of the steam turbine unit to heat the cold primary air, and an air temperature control heat exchanger 41 is set at the outlet of the hot primary air. The working fluid inlet of the air temperature control heat exchanger 41 is connected to the three-extraction or four-extraction pipeline of the steam turbine unit, and the working fluid outlet of the air temperature control heat exchanger 41 is connected to the No. 3 high-pressure heater.

[0034] When the air temperature control module 4 adopts the third extraction or fourth extraction of the steam turbine as the heat source, the steam from the third extraction or fourth extraction of the steam turbine is still superheated steam after heating the hot primary air, and the superheated steam goes to the No. 3 high-pressure heater downstream; while using the third extraction or fourth extraction steam to heat the hot primary air, the No. 3 external steam cooler on the steam turbine side is cancelled.

[0035] The heat source of the air temperature control module 4 can also come from the high-temperature hot air preheater 42. The high-temperature hot air preheater 42 and the heating surfaces such as the low-temperature superheater, the low-temperature reheater or the economizer 10 are arranged in the same flue without a bypass.

[0036] Example 2

[0037] refer to Figure 2 Based on Example 1, in order to make more full use of heat, this embodiment sets a cold-end heat exchanger 34 at the air inlet on the air side. The cold-end heat exchanger 34 is connected to the circulating water pipeline of the cooling tower. The cold-end heat exchanger 34 exchanges heat with the circulating water and air of the cooling tower at the air inlet on the air side to preliminarily heat the air; the inlet of the cold-end heat exchanger 34 is connected to the cooling tower circulating water supply main pipe, and the outlet of the cold-end heat exchanger is connected to the cooling tower circulating water return main pipe, and the circulating water of various cooling towers such as intercooler towers and mechanical ventilation cooling towers is used as the heat source.

[0038] Example 3

[0039] refer to Figure 1 and Figure 3 Based on Example 1, this example provides a powder delivery heating module 5 on the pipeline from the coal mill to the boiler fuel inlet.

[0040] Of course, as an optional embodiment, the heat source of the powder delivery heating module 5 can come from the air preheater bypass module 2 or the steam turbine extraction, or can come from both the air preheater bypass module 2 and the steam turbine extraction. The powder delivery heating module 5 adopts a sleeve-type pressure-bearing powder delivery pipeline, the inside of the sleeve is an air-powder mixture, and there is steam or hot water between the pipes.

[0041] When the heat source of the powder feeding heating module 5 comes from the steam extraction of the steam turbine, the steam extraction of the steam turbine is drained back to the deaerator, and the steam extraction of the steam turbine adopts four extractions.

[0042] When the heat source of the powder feeding heating module 5 comes from the air preheater bypass module 2, the heating medium inlet and outlet are connected to the circulating water inlet and outlet of the air preheater bypass module 2. Specifically, the heating medium inlet and outlet of the powder feeding heating module 5 are connected to the circulating water inlet and outlet of the bypass low-temperature heat exchanger 23.

[0043] Example 4

[0044] refer to Figure 1 and Figure 4 Based on Example 1, the pre-economizer module 1 is arranged upstream of the original boiler economizer in the steam-water process, its inlet is high-pressure feed water from the steam turbine, and its outlet is connected to the original boiler economizer; in this embodiment, the pre-economizer module 1 is provided with a water bypass, and the water bypass includes a regulating valve, a shut-off valve and a connecting pipeline, and the water bypass connects the pre-economizer module 1 and the original boiler economizer.

[0045] The heat source of the air temperature control module 4 comes from the high-temperature hot air preheater 42. The high-temperature hot air preheater 42 and the heating surfaces such as the low-temperature superheater, the low-temperature reheater or the economizer 10 are arranged in the same flue without a bypass.

[0046] Example 5

[0047] Based on Examples 1, 2 and 3, there are three situations for the heat destination of the bypass heat exchanger of the air preheater bypass module 2: ① the heat goes only to the powder feeding heating module 5; ② the heat goes to the powder feeding heating module 5 and the high-pressure feed water on the steam turbine side; ③ the heat goes to the high-pressure feed water and condensate on the steam turbine side; the air preheater bypass module 2 includes a bypass flue 21, a bypass high-temperature heat exchanger 22 and a bypass low-temperature heat exchanger 23, a bypass regulating baffle 23 is arranged in the bypass flue 21, a flue gas regulating baffle 51 is arranged on the flue gas side of the air preheater 6, and circulating water and flue gas are used in the bypass high-temperature heat exchanger 22 and the bypass low-temperature heat exchanger 23 for heat exchange; wherein, the bypass high-temperature heat exchanger 22 is connected to the high-pressure feed water of the boiler system, and the bypass low-temperature heat exchanger 23 heats the condensate of the steam turbine unit.

[0048] The cold air heating module 3 includes any one, two or more of a heat medium water air preheater, a steam high temperature warm air heater, a drain cooling warm air heater and a cold end heat exchanger. The heat medium water air preheater includes an air side heat exchanger and a flue gas side heat exchanger. The flue gas side heat exchanger is arranged in the flue downstream of the air preheater. The flue gas side heat exchanger heats the water and then enters the air side heat exchanger. The hot water in the air side heat exchanger exchanges heat with the air and then enters the flue gas side heat exchanger. A steam high temperature warm air heater is arranged downstream of the air side. The heat medium of the steam high temperature warm air heater comes from five extractions or six extractions. The heat source of the flue gas side heat exchanger is the flue gas at the outlet of the air preheater. Figure 5 .

[0049] The steam high-temperature heater and the drain cooling heater are connected through a drain pipe. The heat source of the steam high-temperature heater is the extraction steam of the steam turbine unit, and the heat source of the drain cooling heater is the drain of the steam high-temperature heater. The steam high-temperature heater is arranged downstream of the heat medium water-air preheater, and the drain cooling heater is arranged upstream of the heat medium water-air preheater.

[0050] The present invention realizes partial or complete heat recovery to the boiler by arranging the pre-economizer module 1, the powder feeding heating module 5 and the air preheater bypass module 2, and recovers the rest to the steam turbine.

[0051] The air heat exchange heat is maximized through the cold end heat exchanger 34 of the cold air heating module 3, the heat medium water air preheater 33, the steam high temperature warm air heater 31 and the drain cooling warm air heater 32. Figure 5 .

[0052] The air temperature control module 4 ensures that the hot air temperature meets the drying output requirements of the coal mill.

[0053] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can make many modifications without departing from the spirit of the present invention and the scope of protection of the claims, all of which are protected by the claims of the present invention.

Claims

1. A generalized heat recovery system for a boiler, characterized in that: The invention comprises a pre-economizer module (1), an air preheater bypass module (2), a cold air heating module (3) and an air temperature control module (4). The pre-economizer module (1) and the air preheater bypass module (2) are arranged downstream of the original economizer of the boiler along the flow direction of the flue gas. The inlet of the air preheater bypass module (2) is arranged between the pre-economizer module (1) and the air preheater (6) and is connected to the flue. The outlet of the air preheater bypass module (2) is connected to the flue behind the air preheater. The block (4) is arranged at the hot primary air outlet on the air side of the air preheater (6); the cold air heating module (3) is arranged on the path before the cold primary air enters the air preheater (6), and the cold air heating module (3) is used to obtain heat from flue gas, steam turbine extraction or condensed water to heat the cold air; the water inlet of the pre-economizer module (1) is connected to the high-pressure water supply pipeline, and the water outlet of the pre-economizer module (1) is connected to the water inlet of the economizer (10); circulating water heat exchange is adopted in the air preheater bypass module (2); the coal mill A powder delivery heating module (5) is provided on the pipeline leading to the boiler fuel inlet; the powder delivery heating module (5) is connected to the air preheater bypass module (2) or the steam turbine extraction steam pipeline through a pipeline, or the powder delivery heating module (5) is connected to the air preheater bypass module (2) and the steam turbine extraction steam pipeline; the high-pressure feed water is heated to an upper limit temperature by utilizing the flue gas heat through the pre-economizer module (1) and the air preheater bypass module (2), and the flue gas, steam turbine extraction steam and / or The condensate heat heats the cold air to the upper limit temperature of the cold air inlet allowed by the air preheater, and part or all of the heat is recovered to the boiler through the pre-economizer module (1) and the air preheater bypass module (2). The heat not recovered to the boiler through the pre-economizer module (1) and the air preheater bypass module (2) is recovered to the steam turbine; the pulverized coal is heated to the upper limit temperature of the pulverized coal entering the furnace through the steam turbine extraction steam or flue gas; or the pulverized coal is heated to the upper limit temperature of the pulverized coal entering the furnace by using the steam turbine extraction steam and flue gas bypass heat.

2. The generalized heat recovery system for boilers according to claim 1 is characterized in that: The air preheater bypass module (2) comprises a bypass flue (21), a bypass high-temperature heat exchanger (22) and a bypass low-temperature heat exchanger, a bypass regulating damper is provided in the bypass flue (21), a flue gas regulating damper (51) is provided on the flue gas side of the air preheater (6), and circulating water and flue gas are used for heat exchange in the bypass high-temperature heat exchanger (22) and the bypass low-temperature heat exchanger; wherein the bypass high-temperature heat exchanger (22) is connected to the high-pressure feed water of the boiler system, and the bypass low-temperature heat exchanger heats the condensate of the steam turbine unit.

3. The generalized heat recovery system for boilers according to claim 1 is characterized in that: The air temperature control module (4) uses steam turbine extraction as a heat source, and the air temperature control module (4) is connected to the steam turbine extraction pipeline and the (3) high-pressure heater; or a high-temperature hot air preheater (42) is arranged in parallel with the heating surface of the low-temperature superheater, the low-temperature reheater or the economizer (10) as a heat source, and the air side outlet of the air preheater (6) is connected to the high-temperature hot air preheater (42).

4. The generalized heat recovery system for boilers according to claim 1 is characterized in that: The pre-economizer module (1) is provided with a water bypass, the water bypass comprising a regulating valve, a shut-off valve and a connecting pipeline, and the water bypass is connected between the pre-economizer module (1) and the economizer (10).

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