A biomass boiler heating unit cold slag waste heat recovery and utilization device

Abstract

The present application relates to a kind of biomass boiler heating unit cold slag waste heat recovery device, including desalted water pump, the water outlet of desalted water pump is communicated with the water inlet of cold slag by first pipeline, first pipeline is provided with orifice plate, the water outlet of cold slag is communicated with the water inlet of drain tank by second pipeline, the water outlet of drain tank is communicated with the water inlet of deaerator by third pipeline, third pipeline is provided with drain pump, the water outlet of deaerator is communicated with the water inlet of boiler by fourth pipeline, the gas outlet of boiler is communicated with the gas inlet of steam turbine by fifth pipeline.The desalted water is stored in drain tank and buffered, which avoids the adverse effects on the heat recovery system caused by the large water temperature fluctuation of the water outlet of cold slag, compared with conventional condensate waste heat recovery device, the deaerator of the present application uses steam extraction with higher thermal efficiency and better thermal economy, the orifice plate reduces the pressure of desalted water, which reduces the requirements of water pressure on the heat exchange tube of cold slag and desalted water conveying pipeline.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biomass boilers, and particularly relates to a device for recovering and utilizing waste heat of a slag cooler of a biomass boiler heating unit. BACKGROUND

[0002] The slag discharge temperature of a biomass circulating fluidized bed boiler is very high (often reaching 850-1000 DEG C), and because of the large amount of impurities such as mud in the biomass fuel, the biomass boiler has a large amount of slag discharge, and recovering the heat of the slag cooler of the biomass boiler can significantly improve the power generation efficiency of the biomass power generation unit, and is of great significance to saving the fuel cost of the power plant and energy saving and efficiency improvement.

[0003] In a steam thermodynamic cycle, a part of steam is usually extracted from several intermediate stages of a steam turbine and sent to a feedwater heater for heating of boiler feedwater, and the steam extraction of each stage is sent to a high-pressure heater, a deaerator and a low-pressure heater, and the extraction efficiency of each stage decreases in turn.

[0004] At present, the heat recovery of the slag cooler usually adopts a condensate water recovery slag cooler heat recovery scheme, that is, the low-temperature condensate water condensed in a condenser is sent to a shaft seal heater by a condensate water pump, then is introduced from the outlet of the shaft seal heater before the low-temperature condensate water enters a low-pressure heater, is sent to the slag cooler to recover the heat of the slag cooler, and then is returned to the inlet of the low-pressure heater or directly enters the deaerator, and then is sent to the boiler by a feedwater pump for generating steam, and the cycle is used. However, the conventional scheme has the following disadvantages: 1) the slag amount of the biomass boiler is unstable, so the slag amount of the slag cooler often fluctuates and changes greatly, and thus the condensate water temperature at the outlet of the slag cooler fluctuates greatly, which has a great influence on the heat recovery system; 2) in the low-pressure heater condensate water system for recovering and utilizing the waste heat of the slag cooler, the low-pressure heater extracts low-pressure steam in the rear stage of the low-pressure cylinder of the steam turbine, and the extraction efficiency of the low-pressure steam is low, so the efficiency of the waste heat recovery and utilization is also low; 3) and the low-pressure heater condensate water needs to be pressurized by a condensate water pump for transportation, the pressure of the condensate water is relatively high, and the water quality requirement is also high, so the requirements of the heat exchange pipe of the slag cooler and the condensate water conveying pipeline are also high, and the slag cooler has the risk of leakage which endangers the condensate water and the entire low-pressure heat recovery system. SUMMARY

[0005] The main purpose of the present application is to provide a device for recovering and utilizing waste heat of a slag cooler of a biomass boiler heating unit, which can effectively solve the problems in the background art.

[0006] To achieve the above purpose, the present application is implemented by the following technical scheme:

[0007] The application discloses a biomass boiler heating unit cold slag cooler waste heat recycling device, which comprises a desalted water pump, a cold slag cooler, a drain tank, a deaerator, a boiler and a steam turbine.

[0008] Preferably, the third pipeline is divided into two parallel branch pipelines, and a drain pump is arranged on each of the two branch pipelines.

[0009] Preferably, the application further comprises an industrial water mother pipe and a mechanical ventilation tower, wherein the outlet of the industrial water mother pipe is connected with the inlet of the cold slag cooler through a sixth pipeline, and the outlet of the cold slag cooler is connected with the inlet of the mechanical ventilation tower through a seventh pipeline.

[0010] Preferably, the application further comprises a drainage ditch, wherein the inlet of the drainage ditch is connected with the outlet of the cold slag cooler through an eighth pipeline.

[0011] Preferably, the application further comprises a blowdown cooling pool, wherein the inlet of the blowdown cooling pool is connected with the outlet of the drain tank through a ninth pipeline.

[0012] Preferably, the cold slag cooler is a drum-type cold slag cooler.

[0013] Preferably, the number of the cold slag coolers is four, which comprises two single-cylinder cold slag coolers and two multi-pipe drum-type cold slag coolers.

[0014] Preferably, a first check valve is arranged on the first pipeline.

[0015] Preferably, a second check valve is arranged on the sixth pipeline.

[0016] The application provides a biomass boiler heating unit cold slag cooler waste heat recycling device, which has the following beneficial effects.

[0017] 1. The desalted water is stored and buffered in the drain tank, so that the unstable slag amount generated by the biomass boiler, the sharp fluctuation and change of the slag amount of the cold slag cooler and the large water temperature fluctuation of the outlet of the cold slag cooler can be avoided, and the adverse influence of the water temperature fluctuation on the heat recovery system can be avoided.

[0018] 2、Compared with the conventional condensate water waste heat recovery device, the application does not need the low-pressure steam to heat the condensate water by the low-pressure heater, the heat efficiency of the steam extraction used by the deaerator is higher, the new power generation of the steam turbine is larger according to the equivalent enthalpy drop principle, the thermal economy is better, and the energy saving and consumption reducing effect is better.

[0019] 3、The throttling orifice plate on the first pipeline depressurizes the desalted water, reduces the requirement of water pressure on the heat exchange pipe of the slag cooler and the desalted water conveying pipeline, thereby reducing the manufacturing cost of the heat exchange pipe of the slag cooler and the desalted water conveying pipeline, and reducing the risk that the leakage of the slag cooler affects the regenerative system of the steam turbine. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a working flow structure schematic diagram of the application.

[0021] In the figure: 1, desalted water pump; 2, slag cooler; 3, drain tank; 4, deaerator; 5, boiler; 6, steam turbine; 7, drain pump; 8, industrial water mother pipe; 9, mechanical draft tower; 10, drainage ditch; 11, blowdown cooling pool; 12, first check valve; 13, second check valve; 101, first pipeline; 102, second pipeline; 103, third pipeline; 104, fourth pipeline; 105, fifth pipeline; 106, sixth pipeline; 107, seventh pipeline; 108, eighth pipeline; 109, ninth pipeline; DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the application more clear, the technical scheme in the application will be described clearly and completely below in combination with the drawings of the application.

[0023] The technical scheme in the application will be described clearly and completely below in combination with the embodiments, obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the application.

[0024] In the description of the application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Examples, such as Figure 1 As shown, a waste heat recovery device for a biomass boiler heating unit includes a demineralized water pump 1, a slag cooler 2, a condensate tank 3, a deaerator 4, a boiler 5, and a steam turbine 6. The outlet of the demineralized water pump 1 is connected to the inlet of the slag cooler 2 via a first pipeline 101, and a throttling orifice plate is provided on the first pipeline 101. The outlet of the slag cooler 2 is connected to the inlet of the condensate tank 3 via a second pipeline 102. The outlet of the condensate tank 3 is connected to the inlet of the deaerator 4 via a third pipeline 103, and a condensate pump 7 is provided on the third pipeline 103. The outlet of the deaerator 4 is connected to the inlet of the boiler 5 via a fourth pipeline 104. The outlet of the boiler 5 is connected to the inlet of the steam turbine 6 via a fifth pipeline 105.

[0027] Working principle:

[0028] When the biomass boiler heating unit extracts steam for external heating, an equal amount of normal temperature desalted water needs to be supplemented, which is usually directly supplemented to the condenser or deaerator 4. The application uses normal temperature desalted water as a cooling medium to recover the waste heat of high-temperature slag discharged from the slag cooler 2. When working, the normal temperature desalted water enters the slag cooler 2 from the first pipeline 101 through the desalted water pump 1 and exchanges heat with the high-temperature slag. The throttling orifice plate on the first pipeline 101 depressurizes the desalted water, reduces the water pressure requirement on the heat exchange pipe of the slag cooler 2 and the desalted water conveying pipeline, thereby reducing the manufacturing cost of the heat exchange pipe of the slag cooler 2 and the desalted water conveying pipeline, and reducing the risk of the slag cooler 2 leakage affecting the regenerative system of the steam turbine 6. The desalted water after heat exchange is heated to about 70℃, enters the drain tank 3 from the second pipeline 102, and is stored and buffered in the drain tank 3 to avoid the unstable slag amount generated by the biomass boiler 5, the drastic fluctuation and change of the slag amount of the slag cooler 2, and the large water temperature fluctuation of the slag cooler 2 outlet, which causes adverse effects on the regenerative system. After the storage and buffering of the drain tank 3, the desalted water enters the deaerator 4 from the third pipeline 103 through the drain pump 7 for further heating. The desalted water after further heating enters the boiler 5 from the fourth pipeline 104 to be heated into steam. The steam enters the steam turbine 6 from the fifth pipeline 105 to make the steam turbine 6 work. The steam turbine 6 is connected to a generator to generate electricity. Compared with the conventional condensate waste heat recovery device, the application does not need a low-pressure heater to heat the condensate water with low-pressure steam. The deaerator 4 uses the extracted steam with higher heat efficiency. According to the equivalent enthalpy drop principle, the steam turbine 6 generates more power, has better thermal economy, and has better energy saving and consumption reduction effect.

[0029] In the embodiment, the slag cooler 2 is a drum-type slag cooler 2, and the number of the slag coolers 2 is four, two of which are used normally and the other two are used as backup. Considering the uneven size of the discharged slag, two single-cylinder slag coolers 2 and two multi-pipe drum slag coolers 2 are used to discharge coarse slag and fine slag respectively. Each slag cooler 2 is designed to discharge a maximum of 2t / h of slag, and the design temperature of the slag entering the slag cooler 2 is 1000℃, and the design temperature of the slag discharged from the slag cooler 2 is 80℃.

[0030] The water temperature of the normal temperature desalted water is 20℃, and the pressure is about 0.5MPa after depressurization by the throttling orifice plate. The desalted water exchanges heat with the high-temperature slag in the slag cooler 2, and the water temperature of the desalted water rises to about 70℃. Compared with the 20℃ cold water directly supplemented to the deaerator 4, the amount of steam required by the deaerator 4 is reduced, so that the power generation of the steam turbine 6 is increased under the same fuel condition, the coal consumption of the steam turbine 6 for power generation is reduced, and the thermal economy of the biomass boiler heating unit is improved. The design flow of the desalted water is about 38.4t / h, which is equivalent to the heat load of the biomass boiler heating unit extracting steam for external heating. When the external heating capacity is greater than 38.4t / h, the additional desalted water can be supplemented to the condenser.

[0031] In the embodiment, the volume of the drain tank 3 is 20m 3, the third pipeline 103 is divided into two parallel branch pipelines, a drain pump 7 is arranged on each of the two branch pipelines, one drain pump 7 is used, and the other drain pump 7 is used as a backup, the single drain pump 7 can cope with the normal desalted water replenishment amount, the second drain pump 7 can be started according to the liquid level of the drain tank 3, so that the liquid level of the drain tank 3 is kept in a reasonable range, the rated flow of the drain pump 7 is 50 m 3 / h, and the head is 160 m. The flow of the single drain pump 7 considers the normal desalted water replenishment amount plus a part of the margin, and the flow of the single drain pump 7 is 50 t / h. The head of the drain pump 7 considers the pressure of the deaerator 4, the height difference between the deaerator 4 and the drain tank 3, and the along-the-way loss, and the head of the drain pump 7 is 160 m.

[0032] The first pipeline 101, the second pipeline 102, the third pipeline 103, the fourth pipeline 104, the fifth pipeline 105, the sixth pipeline 106, the seventh pipeline 107, the eighth pipeline 108, and the ninth pipeline 109 are all provided with gate valves, and the communication and closure of each pipeline are controlled through the gate valves.

[0033] As a further preferred scheme of the embodiment, an industrial water mother pipe 8 and a mechanical draft tower 9 are further included, a water outlet of the industrial water mother pipe 8 is communicated with a water inlet of the slag cooler 2 through the sixth pipeline 106, and a water outlet of the slag cooler 2 is communicated with a water inlet of the mechanical draft tower 9 through the seventh pipeline 107, when the biomass boiler heating unit is started at the initial stage, desalted water replenishment is not needed, or special situations occur, such as the desalted water replenishment amount is 0 or the heat of the slag cooler 2 is too small, industrial water from the industrial water mother pipe 8 and the sixth pipeline 106 enters the slag cooler 2 to exchange heat with high-temperature slag, and the industrial water after heat exchange enters the mechanical draft tower 9 to dissipate heat.

[0034] As a further preferred scheme of the embodiment, a first check valve 12 is arranged on the first pipeline 101, and the first check valve 12 prevents the backflow of desalted water, and a second check valve 13 is arranged on the sixth pipeline 106, and the second check valve 13 prevents the backflow of industrial water.

[0035] As a further preferred scheme of the embodiment, a drain ditch 10 is further included, a water inlet of the drain ditch 10 is communicated with a water outlet of the slag cooler 2 through the eighth pipeline 108, when the steam extraction amount of the biomass boiler heating unit for external steam supply is stabilized at 30-40 t / h, the desalted water is opened in advance, at this time, the second pipeline 102, the sixth pipeline 106, and the seventh pipeline 107 are closed, the desalted water sequentially passes through the first pipeline 101, the slag cooler 2, and the eighth pipeline 108, and then is discharged to the drain ditch 10, and the desalted water flushes the heat exchange pipes of the slag cooler 2 and the impurities in the attached pipelines due to the use of industrial water, when the water hardness and the conductivity and other parameters meet the requirements of the boiler 5 for water supply, the second pipeline 102 is opened, and the desalted water replenishment enters the drain tank 3.

[0036] As a further preferred scheme of the embodiment, a blowdown cooling tank 11 is further included, a water inlet of the blowdown cooling tank 11 is communicated with a water outlet of the drain tank 3 through a ninth pipeline 109, the quality of the desalted water in the drain tank 3 can be detected on line by a water quality detection instrument, when the quality of the desalted water in the drain tank 3 is not up to the standard, the ninth pipeline 109 is communicated, the desalted water is discharged to the blowdown cooling tank 11, at this time, the missing desalted water is supplemented by the condenser.

[0037] Taking a 30 MW unit as an example, the thermal economic indexes of the unit to which the device is applied are shown in Table 1. After the waste heat of the slag cooler is recovered, the heat consumption rate of the unit is reduced, the consumption of biomass under the condition of the same power generation is reduced, the biomass fuel usage amount of about 1476 tons per year can be saved, the biomass fuel cost of 369,000 yuan per year is saved, and the energy saving and consumption reducing effect is remarkable.

[0038]

[0039] Table 1

[0040] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application is described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A biomass boiler heating unit cold slag waste heat recovery and utilization device, comprising a desalted water pump (1), a cold slag device (2), a drain tank (3), a deaerator (4), a boiler (5) and a steam turbine (6), characterized in that: The water outlet of the desalted water pump (1) is communicated with the water inlet of the slag cooler (2) through a first pipeline (101), the first pipeline (101) is provided with a throttle orifice plate, the water outlet of the slag cooler (2) is communicated with the water inlet of the drain tank (3) through a second pipeline (102), the water outlet of the drain tank (3) is communicated with the water inlet of the deaerator (4) through a third pipeline (103), the third pipeline (103) is provided with a drain pump (7), the water outlet of the deaerator (4) is communicated with the water inlet of the boiler (5) through a fourth pipeline (104), the gas outlet of the boiler (5) is communicated with the gas inlet of the steam turbine (6) through a fifth pipeline (105); Further comprising an industrial water mother pipe (8) and a mechanical draft tower (9), the water outlet of the industrial water mother pipe (8) is communicated with the water inlet of the slag cooler (2) through a sixth pipeline (106), the water outlet of the slag cooler (2) is communicated with the water inlet of the mechanical draft tower (9) through a seventh pipeline (107).

2. The biomass boiler heating unit cold slag cooler waste heat recovery and utilization device according to claim 1, characterized in that: The third pipeline (103) is divided into two parallel branch pipelines, and the two branch pipelines are both provided with a drain pump (7).

3. The biomass boiler heating unit cold slag waste heat recovery and utilization device according to claim 1, characterized in that: Further comprising a drainage ditch (10), the water inlet of the drainage ditch (10) is communicated with the water outlet of the slag cooler (2) through an eighth pipeline (108).

4. The biomass boiler heating unit cold slag waste heat recovery and utilization device according to claim 1, characterized in that: Further comprising a blowdown cooling pool (11), the water inlet of the blowdown cooling pool (11) is communicated with the water outlet of the drain tank (3) through a ninth pipeline (109).

5. The biomass boiler heating unit cold slag waste heat recovery and utilization device according to claim 1, characterized in that: The slag cooler (2) is a drum-type slag cooler.

6. The biomass boiler heating unit cold slag waste heat recovery and utilization device according to claim 5, characterized in that: The number of the slag coolers (2) is four, which are two single-cylinder type slag coolers and two multi-tube drum-type slag coolers.

7. The biomass boiler heating unit cold slag waste heat recovery and utilization device according to claim 1, characterized in that: The first pipeline (101) is provided with a first check valve (12).

8. The biomass boiler heating unit cold slag waste heat recovery and utilization device according to claim 1, characterized in that: The sixth pipeline (106) is provided with a second check valve (13).

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