Boiler system with tail flue communicating with the flue gas outlet of the combustion device

Abstract

The present application relates to a kind of tail flue and the flue gas outlet of combustion device are communicated boiler system and a kind of operation method of boiler system, the boiler system includes: boiler, is provided with heating surface, the heating surface includes the low-temperature superheater and / or low-temperature reheater being arranged in the tail flue of boiler;And combustion device, the combustion device is provided with combustion space independent of boiler furnace, the flue gas outlet of combustion space is communicated with tail flue, and the position communicated with tail flue is in the flow direction of boiler flue gas upstream low-temperature superheater and / or low-temperature reheater.The present application also relates to a kind of boiler-turbine equipment.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of energy technology, and in particular to a boiler system in which the tail flue is connected to the flue gas outlet of the combustion device, a method for operating the boiler system, and a boiler-turbine equipment. Background Technology

[0002] With the development of renewable energy, the demand for peak shaving in the power system will increase significantly, which will cause thermal power generation to undertake more peak shaving tasks, impacting the stability and economy of coal-fired power plants operating under ultra-low loads.

[0003] When the operating load is far below the design conditions, the heat generated by fuel combustion in the furnace is insufficient, resulting in a significant reduction in the heat absorption of superheated and reheated steam. Steam parameters deviate severely from the design conditions, leading to a substantial decrease in power generation efficiency and a significant increase in coal consumption, thus raising the cost of peak-shaving operation. Simultaneously, to ensure environmental compliance, the SCR inlet flue gas temperature must be maintained within a certain range. Therefore, power plants often use flue gas bypasses to skip the low-temperature reheater or economizer, further exacerbating the insufficient steam parameters. By sacrificing efficiency to ensure environmentally friendly operation, power generation costs are further increased.

[0004] In addition, another existing technology is to improve the radiative heat transfer level of the superheater and reheater and improve steam parameters by moving the upper burner above the boiler furnace or adding a layer of burners above it. However, this method results in insufficient combustion space, reduced boiler combustion efficiency, and limited effectiveness. Summary of the Invention

[0005] To address at least one aspect of the aforementioned technical problems, this invention is proposed.

[0006] According to one aspect of an embodiment of the present invention, a boiler system in which the tail flue is connected to the flue gas outlet of a combustion device is provided, comprising:

[0007] A boiler, provided with a heating surface, said heating surface including a low-temperature superheater and / or a low-temperature reheater disposed in the tail flue of the boiler; and

[0008] The combustion device has a combustion space independent of the boiler furnace.

[0009] The flue gas outlet of the combustion space is connected to the tail flue, and the location of the connection with the tail flue is upstream of the low-temperature superheater and / or low-temperature reheater in the direction of flue gas flow in the boiler.

[0010] This invention also proposes a method for operating a boiler system, including the following steps:

[0011] A combustion device is provided, wherein the combustion device is provided with a combustion space independent of the boiler furnace, the flue gas outlet of the combustion space is connected to the tail flue, and the position of the connection with the tail flue is upstream of the low temperature superheater and / or low temperature reheater in the direction of flue gas flow in the boiler.

[0012] When the boiler load is lower than the predetermined value, the combustion device is operated to increase the temperature of the flue gas entering the low-temperature superheater and / or low-temperature reheater.

[0013] The present invention also relates to a boiler-turbine device, including the above-mentioned boiler system; a steam turbine and a generator. Attached Figure Description

[0014] The following description and accompanying drawings will better aid in understanding these and other features and advantages of the various embodiments disclosed herein, wherein the same reference numerals in the drawings always denote the same parts, wherein:

[0015] Figure 1 This is a schematic diagram of a power plant equipment according to an exemplary embodiment of the present invention, which also shows a boiler system in which the tail flue is connected to the flue gas outlet of the combustion device according to an exemplary embodiment of the present invention. Detailed Implementation

[0016] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof. These are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0017] In this invention, the reference numerals are as follows:

[0018] 11: Boiler;

[0019] 12: High-temperature superheater or high-temperature reheater;

[0020] 13: Low-temperature superheater;

[0021] 14: Economizer;

[0022] 15: Low-temperature reheater;

[0023] 21: Combustion device.

[0024] In power plant generator units equipped with boilers, the steam-water-heat distribution ratio under low and ultra-low load conditions is severely imbalanced and does not match actual demand. A large amount of heat is absorbed by the evaporation heating surface, while the superheated and reheated steam heating surface is insufficient. The core idea of ​​this invention is to supplement and optimize the heat distribution of the combustion and heating surface system by setting up an additional combustion device 21, or a combustion device 21 outside the boiler 11, to ensure steam parameters and unit efficiency. Simultaneously, the use of a flexibly adjustable combustion device makes the system more flexible.

[0025] The following are specific examples.

[0026] Figure 1 The illustrated embodiment relates to a coal-fired power plant operating system, the system comprising:

[0027] Boiler 11, the boiler includes a furnace and tail flue, burners, pulverizing and feeding system, and various heating surfaces arranged in the boiler furnace and tail flue (e.g., including high temperature superheater or high temperature reheater 12, low temperature superheater 13, economizer 14 and low temperature reheater 15). Although not shown, the tail flue may also be equipped with denitrification devices such as SCR reactors and air preheaters located downstream of the denitrification devices.

[0028] Steam turbines, generally speaking, include high-pressure cylinders, intermediate-pressure cylinders, and low-pressure cylinders. The gas discharged from the low-pressure cylinder enters the condenser.

[0029] Generator; and

[0030] Condensation unit and other auxiliary systems (not shown).

[0031] like Figure 1 As shown, the boiler system also includes a combustion device 21, a flue gas outlet of the combustion device, and a flue gas inlet connecting the reheater (low-temperature reheater) and / or superheater (low-temperature superheater) to supplement heat to the heating surfaces of the low-temperature superheater and / or low-temperature reheater (especially the low-temperature reheater), thereby improving steam parameters and increasing power generation efficiency.

[0032] Optionally, the space of the combustion device 21 can be much smaller than the boiler furnace, for example, one-fifth or less of the boiler furnace thermal power, and further, one-tenth or less of the boiler furnace thermal power.

[0033] In one embodiment of the present invention, the combustion device 21 may be another combustion device with a heating surface that is smaller in capacity and volume than the boiler.

[0034] In another embodiment of the present invention, when the combustion device 21 is a pulverized coal combustion device, the combustion device 21 includes a preheating burner. Optionally, the preheating burner can be a fluidized bed reactor. The preheating burner is used to partially combust the pulverized coal to release heat and heat itself to form a high-temperature gas-solid mixed fuel. The fluidized bed preheating burner has a strongly reducing atmosphere, in which the pulverized coal removes some nitrogen oxides, which is beneficial for controlling nitrogen oxides. At the same time, the combustion rate and burnout characteristics of the high-temperature gas-solid mixed fuel are better than those of pulverized coal, and it can be fully burned in a limited space.

[0035] When the combustion device 21 includes a preheating burner, and the outlet of the combustion device 21 is connected to the flue gas inlet of the low-temperature reheater 15, the combustion device 21 is also provided with a combustion passage to provide combustion space for the high-temperature gas-solid mixed fuel, forming high-temperature flue gas. In a further embodiment, the combustion passage can be configured with staged air distribution to control the combustion of nitrogen oxides, which helps reduce the pressure on the SCR denitrification unit. In an optional embodiment, the excess air coefficient at the combustion passage outlet is between 1.05 and 1.30.

[0036] like Figure 1 As shown, in a boiler unit with a dual-flue tail section, the low-temperature reheater 15 and the low-temperature superheater 13 are arranged in two separate flues. In this case, the high-temperature flue gas generated by the combustion device 21 is introduced into the flue where the low-temperature reheater is located. Simultaneously, the opening of the flue gas damper (not shown) is adjusted to distribute more flue gas flow generated by the boiler to the low-temperature superheater side flue, thereby ensuring that both the main and reheat steam achieve improved parameter quality. As can be understood, with a dual-flue tail section and the low-temperature reheater 15 and low-temperature superheater 13 arranged in two separate flues, the high-temperature flue gas generated by the combustion device 21 is introduced into the flue where the low-temperature superheater is located, and the opening of the flue gas damper (not shown) is adjusted to distribute more flue gas flow generated by the boiler to the low-temperature reheater side flue; or the high-temperature flue gas generated by the combustion device 21 is introduced into the flue where the low-temperature reheater is located, and the opening of the flue gas damper (not shown) is adjusted to distribute more flue gas flow generated by the boiler to the low-temperature superheater side flue, thereby ensuring that both the main and reheat steam achieve improved parameter quality.

[0037] For units with three tail flues, such as double reheat units, the tail flues respectively house a primary reheater, a secondary reheater, and a low-temperature superheater. Similarly, depending on the arrangement of the heating surfaces in the tail flues, the high-temperature flue gas generated by the combustion device 21 can be introduced upstream of the flues containing the reheaters and superheaters to increase heat exchange. Specifically, the boiler's tail flue is a three-flue system, with the low-temperature superheater, primary reheater, and secondary reheater respectively located within the three flues. The flue gas outlet of the combustion space is connected to the flue on the side containing the primary reheater, secondary reheater, or low-temperature reheater. The three flues are equipped with flue gas baffles (not shown) to divert flue gas from the boiler furnace to the other two flues, or the flue gas outlet of the combustion space is connected to the flue on the side containing the low-temperature superheater, primary reheater, and secondary reheater respectively.

[0038] In another embodiment, the high-temperature flue gas generated by the combustion device 21 can also be introduced into the turning chamber (the turning chamber is the transition part from the horizontal flue to the tail flue, or the turning chamber is part of the tail flue downstream of the horizontal flue), and the amount of flue gas entering different flues can be adjusted by the flue gas baffle (not shown).

[0039] exist Figure 1 In the illustrated embodiment, the flue gas outlet of the combustion device 21 connects to the low-temperature reheater 15 and the low-temperature superheater 13 in the tail flue, respectively. Combined with the adjustment of the flue gas damper (not shown), the requirements for superheated steam and reheated steam can be met with a relatively small adjustment range, thereby ensuring improved parameter quality for both main and reheated steam. Alternatively, valves can be installed on both flue gas paths. Specifically, the flue gas outlet of the combustion device 21, via a first valve (not shown), connects to the boiler 11 upstream of the low-temperature reheater 15 in the direction of boiler flue gas flow; the flue gas outlet of the combustion device 21, via a second valve (not shown), connects to the boiler 11 upstream of the low-temperature superheater 13 in the direction of boiler flue gas flow. Only one of the first or second valves can be installed, or both can be installed simultaneously.

[0040] exist Figure 1 In the illustrated embodiment, the flue gas outlet of the combustion device 21 is connected to the low-temperature reheater 15 and the low-temperature superheater 13 in the tail flue, respectively; however, the present invention is not limited thereto. The flue gas from the combustion device 21 may also be connected only upstream of the low-temperature superheater 13 or the low-temperature reheater 15, all of which are within the scope of protection of the present invention.

[0041] When boiler 11 enters low-load operation (e.g., load below 60% or even 50% of rated load) or ultra-low-load operation (e.g., load below 30% or even 20% of rated load), the heat generated by the additional combustion device 21 can be used to improve the parameters of superheated steam or reheat steam during low-load operation, thereby increasing the boiler's power generation efficiency under low load. Specifically, in the technical solution of this invention, by utilizing the flue gas generated by the combustion device 21, it is possible to ensure the parameters of superheated steam entering the high-pressure cylinder of the turbine, the parameters of reheat steam entering the intermediate-pressure cylinder of the turbine, and the parameters of steam entering the low-pressure cylinder from the intermediate-pressure cylinder when the boiler is under low load. This is beneficial to improving the power generation efficiency and stability of the boiler-turbine system under low-load operation, and such a configuration is also beneficial to peak shaving of coal-fired power generation systems.

[0042] Utilizing an additional combustion device 21 simultaneously helps to increase the tail gas temperature and the SCR inlet flue gas temperature, ensuring that the SCR operates within the denitrification reaction temperature window, thereby improving SCR denitrification efficiency and reducing ammonia slip. For example... Figure 1 As shown, in one embodiment of the invention, pulverized coal from the pulverizing system (which also supplies pulverized coal to the boiler 11) is introduced into the combustion device 21. This avoids the technical problem that the power plant needs to be equipped with a separate gas or oil system in order to ensure that the SCR operates within the denitrification reaction temperature window, thus increasing the operating cost.

[0043] exist Figure 1 In the illustrated embodiment, the combustion device 21 can be a preheating burner, i.e., a fluidized bed reactor, which can be used to partially combust pulverized coal to release heat and heat itself to form a high-temperature gas-solid mixed fuel, which then enters the subsequent combustion space for combustion and heat release. In one embodiment of the present invention, the combustion device 21 using the preheating burner structure can also directly use pulverized coal prepared by the power plant boiler pulverizing system. As mentioned above, this eliminates the need to introduce other fuels or other fuel preparation devices, thus avoiding increasing the complexity of the system.

[0044] Meanwhile, the combustion device 21, which adopts a preheating burner, can flexibly and freely adjust the load of the combustion device from 10% to 100%, thus matching the flexible and deep peak-shaving requirements of the power plant boiler 11.

[0045] The boiler system of the present invention is suitable for flexible peak-shaving retrofitting of power plants, especially subcritical and supercritical generator sets.

[0046] The above description also relates to a method of operating a boiler system, which involves operating the combustion device 21 to increase the temperature of the flue gas entering the low-temperature superheater and / or low-temperature reheater when the boiler load is below a predetermined value (e.g., when the boiler load is below 60% of the rated operating condition). This method can be used to maintain the parameters of the steam entering different cylinders of the turbine when the boiler is operating at low load.

[0047] Furthermore, in embodiments of the present invention, when the boiler 11 load is lower than a predetermined value under rated operating conditions, such as 30%, the combustion device can be operated or its thermal power adjusted to increase the temperature of the flue gas entering the low-temperature reheater. This is beneficial for controlling the parameters of the reheat steam, especially the low-pressure cylinder, of the turbine, thus achieving stable unit operation. Furthermore, when the combustion device consists of a preheating burner and a combustion chamber, the steam parameters can be controlled or adjusted by controlling the thermal power of the preheating burner and the heat release of the fuel in the combustion chamber.

[0048] The flue gas in the combustion device 21 is introduced into the tail flue. After absorbing heat from the heating surface, it is cooled to 450-950℃, and further to 500-750℃, for example 530℃, 550℃, 570℃, 590℃, 600℃, 620℃, 650℃, 670℃, 690℃, 700℃, and 720℃. Then it directly enters the vicinity of the inlet of the denitrification device. That is, high-temperature flue gas from the combustion space of the combustion device 21 is introduced upstream of the inlet of the denitrification device. This helps to keep the temperature of the flue gas entering the denitrification device within an appropriate range (i.e., within the denitrification reaction temperature window) to ensure the denitrification effect.

[0049] Based on the above, the present invention proposes the following technical solution:

[0050] 1. A boiler system in which the tail flue is connected to the flue gas outlet of the combustion device, comprising:

[0051] A boiler, provided with a heating surface, said heating surface including a low-temperature superheater and / or a low-temperature reheater disposed in the tail flue of the boiler; and

[0052] The combustion device has a combustion space independent of the boiler furnace.

[0053] The flue gas outlet of the combustion space is connected to the tail flue, and the location of the connection with the tail flue is upstream of the low-temperature superheater and / or low-temperature reheater in the direction of flue gas flow in the boiler.

[0054] 2. The boiler system according to 1, wherein:

[0055] The combustion space is equipped with a graded air distribution inlet, and the excess air coefficient at the outlet of the combustion space is between 1.05 and 1.3.

[0056] 3. The boiler system according to 1, wherein:

[0057] The boiler has a dual flue at the tail end, with the low-temperature superheater and the low-temperature reheater respectively located in the dual flue.

[0058] The flue gas outlet of the combustion space is connected to the flue on the side where the low-temperature superheater or low-temperature reheater is located, and the dual flue is provided with a flue gas baffle for diverting the flue gas from the boiler furnace to the other side flue, or the flue gas outlet of the combustion space is connected to the flue on the side where the low-temperature superheater and low-temperature reheater are located respectively.

[0059] 4. The boiler system according to 3, wherein:

[0060] The flue gas outlet of the combustion chamber leads to the flue gas duct where the low-temperature superheater is located; the flue gas damper is suitable for distributing more of the flue gas generated by the boiler to the flue gas duct on the low-temperature reheater side; or

[0061] The flue gas outlet of the combustion space is connected to the flue where the low-temperature reheater is located, and the flue gas damper is suitable for distributing more flue gas generated by the boiler to the flue on the low-temperature superheater side.

[0062] 5. The boiler system according to 1, wherein:

[0063] The boiler has a three-flue tail section, in which a low-temperature superheater, a primary reheater, and a secondary reheater are respectively installed.

[0064] The flue gas outlet of the combustion space is connected to the flue on the side where the primary reheater, secondary reheater, or low-temperature reheater is located, and the three flues are equipped with flue gas baffles for diverting the flue gas from the boiler furnace to the other two flues, or the flue gas outlet of the combustion space is connected to the flue on the side where the low-temperature superheater, primary reheater, and secondary reheater are located, respectively.

[0065] 6. The boiler system according to 1, wherein:

[0066] The boiler system has a denitrification device installed in the tail flue, downstream of the low-temperature reheater and / or low-temperature superheater in the direction of boiler flue gas flow.

[0067] 7. The boiler system according to any one of 1-6, wherein:

[0068] The combustion device also includes a preheating burner, the fuel outlet of which is connected to the combustion space.

[0069] 8. The system according to 7 further includes:

[0070] A pulverized coal supply device that supplies pulverized coal as fuel to a preheating burner and a boiler.

[0071] 9. The boiler system according to 8, wherein:

[0072] The preheating burner is a fluidized bed burner.

[0073] 10. The system according to 1, wherein:

[0074] The combustion device is a separate combustion device with a heating surface, which is smaller in capacity and volume than the boiler.

[0075] 11. The system according to 1, wherein:

[0076] The tail flue also includes a turning chamber located downstream of the horizontal flue of the boiler, and the flue gas outlet of the combustion space is connected to the turning chamber.

[0077] 12. The system according to 1, wherein:

[0078] The tail flue also includes a turning chamber located downstream of the horizontal flue of the boiler, and at least a portion of the combustion space is disposed within or as part of the tail flue.

[0079] 13. A method for operating a boiler system, comprising the following steps:

[0080] A combustion device is provided, wherein the combustion device is provided with a combustion space independent of the boiler furnace, the flue gas outlet of the combustion space is connected to the tail flue, and the position of the connection with the tail flue is upstream of the low temperature superheater and / or low temperature reheater in the direction of flue gas flow in the boiler.

[0081] When the boiler load is lower than the predetermined value, the combustion device is operated to increase the temperature of the flue gas entering the low-temperature superheater and / or low-temperature reheater.

[0082] 14. According to the method described in 13, wherein:

[0083] The boiler is equipped with a low-temperature reheater for heating the steam introduced into the intermediate-pressure cylinder of the steam turbine;

[0084] The flue gas outlet of the combustion space is connected to the tail flue of the boiler, and the connection point is upstream of the flue gas inlet of the low-temperature reheater.

[0085] When the boiler load is lower than the predetermined value, the combustion device is operated or the thermal power of the combustion device is adjusted to increase the temperature of the flue gas entering the low-temperature reheater.

[0086] 15. A power plant equipment, comprising:

[0087] Boiler system according to any one of 1-12;

[0088] Steam turbine; and

[0089] dynamo.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for operating a boiler system, comprising the following steps: A combustion device is provided, wherein the combustion device is provided with a combustion space independent of the boiler furnace, the flue gas outlet of the combustion space is connected to the tail flue, and the position of the connection with the tail flue is upstream of the low temperature superheater and / or low temperature reheater in the direction of flue gas flow in the boiler. When the boiler load is lower than the predetermined value, the combustion device is operated to increase the temperature of the flue gas entering the low-temperature superheater and / or low-temperature reheater. The boiler is equipped with a low-temperature reheater for heating the steam introduced into the intermediate-pressure cylinder of the steam turbine; The flue gas outlet of the combustion space is connected to the tail flue of the boiler, and the connection point is upstream of the flue gas inlet of the low-temperature reheater. When the boiler load is lower than the predetermined value, the combustion device is operated or the thermal power of the combustion device is adjusted to increase the temperature of the flue gas entering the low-temperature reheater. The combustion space is equipped with a graded air distribution inlet, and the excess air coefficient at the outlet of the combustion space is between 1.05 and 1.

3. The boiler system has a denitrification device installed in the tail flue, downstream of the low-temperature reheater and / or low-temperature superheater in the direction of boiler flue gas flow. The combustion device further includes a preheating burner, the fuel outlet of which is connected to the combustion space; The preheating burner is a fluidized bed burner.

2. A boiler system according to the operating method of claim 1, comprising: A boiler is provided with a heating surface, the heating surface including a low-temperature superheater and / or a low-temperature reheater provided in the tail flue of the boiler. and The combustion device has a combustion space independent of the boiler furnace. The flue gas outlet of the combustion space is connected to the tail flue, and the location of the connection with the tail flue is upstream of the low-temperature superheater and / or low-temperature reheater in the direction of flue gas flow in the boiler.

3. The boiler system according to claim 2, wherein: The boiler has a dual flue at the tail end, with the low-temperature superheater and the low-temperature reheater respectively located in the dual flue. The flue gas outlet of the combustion space is connected to the flue on the side where the low-temperature superheater or low-temperature reheater is located, and the dual flue is provided with a flue gas baffle for diverting the flue gas from the boiler furnace to the other side flue, or the flue gas outlet of the combustion space is connected to the flue on the side where the low-temperature superheater and low-temperature reheater are located respectively.

4. The boiler system according to claim 3, wherein: The flue gas outlet of the combustion chamber leads to the flue gas duct where the low-temperature superheater is located; the flue gas damper is suitable for distributing more of the flue gas generated by the boiler to the flue gas duct on the low-temperature reheater side; or The flue gas outlet of the combustion space is connected to the flue where the low-temperature reheater is located, and the flue gas damper is suitable for distributing more flue gas generated by the boiler to the flue on the low-temperature superheater side.

5. The boiler system according to claim 2, wherein: The boiler has a three-flue tail section, in which a low-temperature superheater, a primary reheater, and a secondary reheater are respectively installed. The flue gas outlet of the combustion space is connected to the flue on the side where the primary reheater, secondary reheater, or low-temperature reheater is located, and the three flues are equipped with flue gas baffles for diverting the flue gas from the boiler furnace to the other two flues, or the flue gas outlet of the combustion space is connected to the flue on the side where the low-temperature superheater, primary reheater, and secondary reheater are located, respectively.

6. The boiler system according to claim 2, further comprising: A pulverized coal supply device that supplies pulverized coal as fuel to a preheating burner and a boiler.

7. The boiler system according to claim 2, wherein: The combustion device is a separate combustion device with a heating surface, which is smaller in capacity and volume than the boiler.

8. The boiler system according to claim 2, wherein: The tail flue also includes a turning chamber located downstream of the horizontal flue of the boiler, and the flue gas outlet of the combustion space is connected to the turning chamber.

9. The boiler system according to claim 2, wherein: The tail flue also includes a turning chamber located downstream of the horizontal flue of the boiler, and at least a portion of the combustion space is disposed within or as part of the tail flue.

10. A power plant equipment, comprising: Boiler system according to any one of claims 2-9; Steam turbine; and dynamo.

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