A superheating and reheating system suitable for a boiler of a combined heat and power unit

Abstract

The utility model discloses a kind of superheat reheating systems suitable for cogeneration unit boiler, including hearth, horizontal flue and tail vertical shaft flue, steam drum or water-steam separator, ceiling superheater, wall outlet converging header, low-temperature superheater, screen superheater and high-temperature superheater are sequentially connected;Tail vertical shaft flue is divided into front flue and rear flue by middle partition wall, horizontal flue is divided into upper horizontal flue and lower horizontal flue by transverse partition wall, and a section of longitudinal flue gas baffle wall is equipped in lower horizontal flue middle part;High-temperature reheater and low-temperature reheater connected are equipped in front flue from top to bottom, and the low-temperature superheater is located in rear flue, and flue gas adjusting baffle is equipped in front flue and rear flue;The outlet of high-temperature superheater is connected with high-pressure cylinder steam inlet;High-pressure cylinder steam outlet is sequentially connected with medium-pressure cylinder steam inlet by low-temperature reheater, high-temperature reheater;The utility model can improve the heating capacity of unit low load, so that reheater front heating steam extraction volume is not limited by the safety of boiler reheater heating surface.

Description

Technical Field

[0001] This utility model relates to a superheat reheat system for a boiler, and more particularly to a superheat reheat system suitable for boilers in combined heat and power units. Background Technology

[0002] To reduce carbon emissions, the national and local governments have mandated the shutdown of all small and medium-sized coal-fired boilers, with steam for industrial parks now supplied centrally by nearby power plants. To reduce coal consumption for power generation, generating units with heat load requirements must extract steam for heating (generally cold reheating). However, during low-load peak-shaving operation, the safety of the boiler reheater's heating surface and the low exhaust pressure of the turbine's high-pressure cylinder prevent the unit from meeting heating load and parameter requirements. Current technologies address the issue of insufficient heating parameters at low loads through methods such as central valve regulation and main steam desuperheating and pressure reduction. However, in existing boiler reheat systems, high-temperature reheaters are often located in horizontal flues (some boiler types use wall-mounted reheaters within the furnace). When the reheat steam flow rate decreases significantly under the corresponding combustion heat load, it is the main reason for overheating of the reheater's heating surface, preventing an increase in heating load. Due to safety concerns regarding the boiler reheater's heating surface, these technologies still struggle to meet heating load requirements during low-load operation. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned shortcomings of the existing technology by providing a superheated reheat system suitable for boilers in combined heat and power units. This system can improve the heating capacity of the unit under low load and enhance the safety of the reheat system.

[0004] To achieve the above objectives, this utility model provides a superheater / reheat system suitable for a combined heat and power (CHP) unit boiler, comprising a connected furnace, a horizontal flue and a tail vertical flue, a steam drum or steam-water separator, a roof superheater, a wall outlet manifold, a low-temperature superheater, a screen-type superheater, and a high-temperature superheater. The high-temperature superheater is located above the flame deflector at the inlet of the horizontal flue. The tail vertical flue is divided into an inner front flue and an outer rear flue by a central partition wall. The system is characterized in that: the upper end of the central partition wall is connected to a transverse partition wall located within the horizontal flue, and the horizontal flue... The bottom is connected to the furnace wall sidewall below the flame deflector. A longitudinal flue gas baffle wall connected to the transverse partition wall is provided in the middle of the lower horizontal flue below the transverse partition wall. A high-temperature reheater and a low-temperature reheater are connected from top to bottom in the front flue. The low-temperature superheater is located in the rear flue. Flue gas regulating baffles are provided in the front flue behind the low-temperature reheater and in the rear flue behind the low-temperature superheater. The outlet of the high-temperature superheater is connected to the steam inlet of the high-pressure cylinder through the main steam pipe. The exhaust port of the high-pressure cylinder is connected to the steam inlet of the intermediate-pressure cylinder in sequence through the low-temperature reheater and the high-temperature reheater.

[0005] This utility model divides the horizontal flue and the tail vertical flue into an interconnected upper horizontal flue and a rear flue, and a lower horizontal flue and a front flue. During operation, the flue gas in the furnace enters the upper horizontal flue and the rear flue, and the lower horizontal flue and the front flue, respectively, to exchange heat with the low-temperature superheater, the low-temperature reheater, and the high-temperature reheater. The steam from the steam-water separator is heated by the roof superheater, the wall outlet junction box, the low-temperature superheater, the screen-type superheater, and the high-temperature superheater, and then enters the high-pressure cylinder of the turbine to do work. The steam discharged from the high-pressure cylinder is then heated by the low-temperature reheater and the high-temperature reheater, and then enters the intermediate-pressure cylinder of the turbine to do work a second time.

[0006] This invention utilizes the vortex formed by flue gas as it passes through the flame deflector. Furthermore, the bottom of the horizontal flue below the flame deflector, in conjunction with the longitudinal flue gas baffle wall, forms a flue gas turning channel. During high boiler combustion loads, both the flue gas volume and temperature in the furnace are high. Due to the large inertia at the turn, most of the flue gas exchanges heat with the high-temperature superheater before entering the upper horizontal flue, preventing excessively high inlet flue gas temperatures. During low boiler combustion loads, both the flue gas volume and temperature in the furnace are low. The low upward inertia of the flue gas increases the amount of flue gas that enters the lower horizontal flue and exchanges heat with the two reheaters without exchanging heat with the high-temperature superheater. This is beneficial for increasing the flue gas temperature to meet the reheat steam temperature requirements. In addition, the amount of flue gas entering the front and rear flue can be adjusted by two flue gas regulating baffles, which can ensure that the steam parameters meet the requirements when the unit is operating at different loads, thereby improving the unit's peak shaving capacity and power generation economy. For heating units, since the reheater heating surface is arranged entirely in the front flue after the diversion flue, the heating surface does not bear the furnace radiation heat at all when the flue gas flows through the reheater, which can ensure the safety of the reheat system and make the extraction steam heat supply unrestricted, and can use all the reheat steam for heating at most.

[0007] As a further improvement of this utility model, the rear flue below the low-temperature superheater is connected to the air inlet of the blower through a duct, and the air outlet of the blower is connected to a three-way regulating valve through a pipeline. The two outlets of the three-way regulating valve are respectively connected to the lower part of the furnace and the front flue below the low-temperature reheater. By sending part of the flue gas back to the front flue below the low-temperature reheater and the lower part of the furnace through the blower, the safety of the reheat system can be further improved and the reheat steam temperature regulation capability can be increased, preventing low boiler combustion load and insufficient reheat steam temperature when a single steam turbine is running.

[0008] As a further improvement of this utility model, the bottom of the horizontal flue is inclined, and an ash leakage port is provided at its lower inner end; most of the ash is deposited at the inner end, and the ash leakage port can guide the ash back into the furnace for combustion.

[0009] In summary, this utility model can improve the heating capacity of heating units under low load, enhance the safety of reheat systems, and also improve the peak-shaving capacity and power generation economy of the units. Attached Figure Description

[0010] Figure 1 This is a front view of an embodiment of the present utility model.

[0011] Figure 2 This is a block diagram of the superheat and reheat system according to an embodiment of the present invention. Detailed Implementation

[0012] The present invention will be further described below with reference to the accompanying drawings.

[0013] like Figure 1 As shown, this embodiment describes a superheater-reheat system suitable for a cogeneration unit boiler, including a connected furnace 1, a horizontal flue 2, a tail vertical flue 3, a steam-water separator 4, a roof superheater 5, a wall outlet manifold 6, a low-temperature superheater 7, a screen-type superheater 8, and a high-temperature superheater 9. The screen-type superheater 8 is located in the upper part of the furnace, and the high-temperature superheater 9 is located above the flame deflector 10 at the inlet of the horizontal flue. The tail vertical flue 3 is divided into an inner front flue 12 and an outer rear flue 13 by a central partition wall 11. The upper end of the central partition wall 11 is connected to a transverse partition wall 14 located in the horizontal flue 2. The bottom of the horizontal flue 2 is integrally connected to the side wall of the furnace below the flame deflector 10. The transverse partition wall 14 divides the horizontal flue 2 into a lower horizontal flue 15 and an upper horizontal flue 16. The height of the high-temperature superheater 9 is from the lower horizontal flue... The horizontal flue 15 extends to above the ceiling at 1 / 4 of its inlet height. The bottom of the horizontal flue 2 is inclined, with an ash-leaking port 17 at its lower inner end. A longitudinal flue gas baffle 18 connected to the transverse partition wall 14 is located in the middle of the lower horizontal flue 15. A high-temperature reheater 19 and a low-temperature reheater 20 are connected from top to bottom within the front flue 12. The low-temperature superheater 7 is located within the rear flue 13. Flue gas regulating baffles 21 or 22 are provided in both the front flue 12 behind the low-temperature reheater 20 and the rear flue 13 behind the low-temperature superheater 7. The rear flue 13 below the low-temperature superheater 7 is connected to the air inlet of the fan 23 via a duct. The air outlet of the fan 23 is connected to a three-way regulating valve 24 via a pipe. The two outlets of the three-way regulating valve 24 are respectively connected to the lower part of the furnace 1 and the front flue 12 below the low-temperature reheater 22. Figure 2 As shown, the steam-water separator, roof superheater, wall-mounted outlet manifold, low-temperature superheater, screen-type superheater, and high-temperature superheater are connected in sequence. The outlet of the high-temperature superheater is connected to the steam inlet of the high-pressure cylinder through the main steam pipe. The exhaust port of the high-pressure cylinder is connected to the steam inlet of the intermediate-pressure cylinder in sequence through the low-temperature reheater and the high-temperature reheater.

[0014] The intermediate partition wall 11 and the transverse partition wall 14 can adopt a wall-encasing structure, and the longitudinal flue gas baffle wall 18 can adopt a water-cooled wall structure; during operation, the flue gas in the furnace first exchanges heat with the screen-type superheater 8 and the high-temperature superheater 9, and then enters the upper horizontal flue 16 and the rear flue 13 and the lower horizontal flue 15 and the front flue 12 respectively, and exchanges heat with the low-temperature superheater 7, the low-temperature reheater 20 and the high-temperature reheater 19; such as Figure 2 As shown, the steam from the steam-water separator is heated by the roof superheater, the wall outlet manifold, the low-temperature superheater, the screen superheater, and the high-temperature superheater before entering the high-pressure cylinder of the turbine to do work. The steam discharged from the high-pressure cylinder then enters the low-temperature reheater and the high-temperature reheater for heating before entering the intermediate-pressure cylinder of the turbine to do work a second time.

[0015] When this invention is used, the flue gas forms a vortex when passing through the flame deflector angle 10. The bottom of the horizontal flue duct 2 located below the flame deflector angle 10, in conjunction with the longitudinal flue gas baffle wall 18, forms a flue gas turning channel. This results in a flue gas temperature variation trend from the furnace outlet flue gas temperature to the reheater inlet flue gas temperature corresponding to the lower horizontal flue duct 15, which is consistent with the reheat steam temperature control trend. When the boiler is under high combustion load, the flue gas volume and temperature in the furnace are both high. Due to the large turning inertia, most of the flue gas exchanges heat with the high-temperature superheater 9 before entering the upper horizontal flue duct 16, preventing the inlet flue gas temperature of the lower horizontal flue duct 15 from being too high. When the boiler is under low combustion load, the flue gas volume and temperature in the furnace are both low. The low upward inertia of the flue gas causes it to enter the lower horizontal flue duct 16 without heat exchange with the high-temperature superheater 9. The increased flue gas volume for heat exchange with the two reheaters 19 and 20 is beneficial for raising the flue gas temperature to meet the reheat steam temperature requirements. In addition, the flue gas volume entering the front flue duct 12 and the rear flue duct 13 can be adjusted by the two flue gas regulating baffles 21 and 22, so that the reheat steam parameters can meet the requirements when the turbine is running at different loads. This can improve the unit's peak shaving capacity and power generation economy. For heating units, the flue gas regulating baffle 21 can be closed so that all the flue gas enters the rear flue duct 13. When the flue gas flows through the two reheaters, the heating surface can be completely free from furnace radiation heat due to the diversion channel, which can ensure the safety of the reheat system. It can meet the need to extract any amount of reheat steam before the inlet of the low-temperature reheater 20 for heating, and improve the unit's heating capacity at low loads.

[0016] The flue gas drawn from the rear flue 13 by the blower 23 can be sent back to the lower furnace and below the low-temperature reheater 20 respectively. The flue gas sent back to the low-temperature reheater 20 is mainly used to protect the reheater heating surface and prevent the flue gas regulating damper 21 below the low-temperature reheater 20 from not closing tightly when the turbine unit is shut down, so that the high-temperature flue gas in the furnace leaks into the front flue 12 and affects the safety of the reheater heating surface. The flue gas sent back to the lower part of the furnace increases the reheat steam temperature regulation capability, prevents insufficient reheat steam temperature when the boiler combustion load is low, and improves the economic efficiency of low-load power generation.

[0017] Ash can be drawn back into the furnace for combustion through the ash discharge port 17; for boilers with different parameters, the steam-water separator 4 can also be replaced by a steam drum, which can also meet the requirements.

[0018] The above embodiments have been used to illustrate the invention, but it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments.

Claims

1. A superheater-reheat system suitable for a combined heat and power (CHP) unit boiler, comprising a connected furnace, a horizontal flue and a tail vertical flue, a steam drum or steam-water separator, a roof superheater, a wall outlet manifold, a low-temperature superheater, a screen-type superheater and a high-temperature superheater, wherein the high-temperature superheater is located above the flame deflector at the inlet of the horizontal flue, and the tail vertical flue is divided into an inner front flue and an outer rear flue by a central partition wall; characterized in that: The upper part of the middle partition wall is connected to a transverse partition wall located in the horizontal flue. The bottom of the horizontal flue is connected to the side wall of the furnace below the flame deflector. A section of longitudinal flue gas baffle wall connected to the transverse partition wall is provided in the middle of the lower horizontal flue below the transverse partition wall. A high-temperature reheater and a low-temperature reheater are connected from top to bottom in the front flue. The low-temperature superheater is located in the rear flue. Flue gas regulating baffles are provided in the front flue behind the low-temperature reheater and in the rear flue behind the low-temperature superheater. The outlet of the high-temperature superheater is connected to the steam inlet of the high-pressure cylinder through the main steam pipe. The exhaust port of the high-pressure cylinder is connected to the steam inlet of the intermediate-pressure cylinder in sequence through the low-temperature reheater and the high-temperature reheater.

2. The superheated reheat system for a cogeneration unit boiler as described in claim 1, characterized in that: The rear flue below the low-temperature superheater is connected to the air inlet of the fan via a duct. The air outlet of the fan is connected to a three-way regulating valve via a pipeline. The two outlets of the three-way regulating valve are connected to the lower part of the furnace and the front flue below the low-temperature reheater, respectively.

3. A superheated reheat system suitable for boilers in cogeneration units as described in claim 1 or 2, characterized in that: The bottom of the horizontal flue is inclined, and the inner end at the lower position is provided with an ash leakage port.

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