System for heating primary air and secondary air through large slag waste heat of coal-fired power plant boiler

Abstract

The utility model provides a system for heating primary air and secondary air by large slag waste heat of a coal-fired power plant boiler, which comprises a tubular heat exchanger which is arranged at a dry bottom hopper below a boiler hearth in the left-right direction of the bottom of the dry bottom hopper. A cooling water outlet of the tubular heat exchanger is divided into two paths, one path is connected with a primary air heater arranged at an inlet of the primary fan, and the other path is connected with a secondary air heater arranged at a secondary air inlet; heat carried by large slag discharged by a boiler is used for heating inlet air temperature of the primary fan and the secondary fan, steam extraction of a steam turbine is reduced, more steam enters the steam turbine to do work, and the load capacity of a unit is effectively improved.

Description

Technical Field

[0001] The utility model belongs to the field of coal burning, and in particular relates to a system for heating primary and secondary air by using waste heat from large slag of a coal-fired power station boiler. Background Art

[0002] The slag generated by the combustion of pulverized coal in coal-fired power plant boilers falls from the furnace to the slag picker and is taken away after cooling. Before entering the slag picker, its temperature is 600-800℃. After entering the slag picker, it will be cooled to 60-80℃ by air or water and then taken away by the slag picker chain. Therefore, the heat carried by the slag is not used and discharged. This part of heat is included in the physical heat loss of the slag in the process of boiler efficiency calculation. Therefore, making good use of this part of heat can improve the boiler efficiency and improve the economy of the whole plant.

[0003] At the same time, the power plant also needs to increase the temperature of the primary and secondary air entering the air preheater to prevent blockage of the air preheater and make the primary and secondary air temperatures reach higher values. The current conventional design is to install primary and secondary air heaters on the pipes entering the air preheater from the primary and secondary fan outlets. This part of the steam source comes from the steam extraction of the steam turbine, which occupies the steam entering the steam turbine, resulting in a decrease in the unit's load capacity. Summary of the invention

[0004] The utility model aims to provide a system for heating primary and secondary air by using waste heat from large slag in a coal-fired power station boiler, which solves the defect of waste of resources in the existing primary and secondary air heating.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0006] The utility model provides a system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler, comprising a tubular heat exchanger, which is arranged at a cold ash hopper below the furnace of the boiler and arranged in the left and right directions along the bottom of the cold ash hopper;

[0007] The cooling water outlet of the tubular heat exchanger is divided into two paths, one of which is connected to a primary air heater disposed at the primary air fan inlet, and the other is connected to a secondary air heater disposed at the secondary air inlet.

[0008] Preferably, the cooling water outlet of the tubular heat exchanger is connected to the primary air heater and the secondary air heater respectively through a water supply main pipe.

[0009] Preferably, the water outlet in the water supply main pipe is connected to the primary air heater and the secondary air heater through the primary air heater water inlet pipe and the secondary air heater water inlet pipe respectively.

[0010] Preferably, the cooling water inlet of the tubular heat exchanger is connected to the water injection pipeline through a return water main pipe.

[0011] Preferably, a variable frequency water pump is provided on the water return main pipe.

[0012] Preferably, an electric water injection door is provided on the water injection pipeline.

[0013] Preferably, a water discharge pipe is also provided on the water return main pipe.

[0014] Preferably, a water discharge pipe electric door is provided on the water discharge pipe.

[0015] Preferably, the tubular heat exchanger comprises an inlet header, heat exchange tubes and an outlet header, wherein:

[0016] The heat exchange tubes are provided in plurality, and the plurality of heat exchange tubes are evenly distributed on the inlet header and communicated with the inlet header; the free ends of the heat exchange tubes are communicated with the outlet header;

[0017] The inlet header is provided with a return water main pipe, and the outlet header is connected with a water supply main pipe.

[0018] Compared with the prior art, the beneficial effects of the utility model are:

[0019] The utility model provides a system for heating primary and secondary air with waste heat from large slag in a coal-fired power station boiler. The system utilizes the heat carried by the large slag discharged from the boiler to heat the inlet air temperature of the primary and secondary fans, thereby reducing the steam extraction of the steam turbine and allowing more steam to enter the steam turbine to do work, thereby effectively improving the load capacity of the unit. In addition, the primary air heat exchanger and the secondary air heat exchanger are arranged at the inlet of the primary fan and the secondary fan. Therefore, when the primary air heat exchanger and the secondary air heat exchanger leak, there is no need to stop the fan for processing; at the same time, the heat carried by the large slag in the boiler is utilized, and the economy of the entire plant is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a system schematic diagram of the utility model;

[0021] Figure 2 It is a schematic diagram of the structure of the tubular heat exchanger of the utility model;

[0022] In the figure: 1-furnace; 2-tubular heat exchanger; 3-frequency conversion water pump; 4-return main pipe; 5-water supply main pipe; 6-primary air heater water inlet pipe; 7-secondary air heater water inlet pipe; 8-primary air heater; 9-secondary air heater; 10-primary air heater water outlet pipe; 11-secondary air heater water outlet pipe; 12-cold primary air; 13-hot primary air; 14-cold secondary air; 15-hot secondary air; 16-water injection pipe; 17-water injection pipe electric door; 18-drain pipe; 19-drain pipe electric door; 20-primary heater emptying electric door; 21-secondary air heater emptying electric door; 22-inlet header; 23-heat exchange tube; 24-outlet header; 25-primary fan; 26-secondary fan. DETAILED DESCRIPTION

[0023] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0024] Example 1

[0025] like Figure 1 and Figure 2 As shown, the present embodiment provides a system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler, comprising a tubular heat exchanger 2, a variable frequency water pump 3, a return water main pipe 4, a water supply main pipe 5, a primary air heat exchanger inlet pipe 6, a secondary air heat exchanger inlet pipe 7, a primary air heat exchanger 8, a secondary air heat exchanger 9, a primary air heat exchanger outlet pipe 10, a secondary air heat exchanger outlet pipe 11, cold primary air 12, hot primary air 13, cold secondary air 14, hot secondary air 15, a water injection pipe 16, a water injection pipe electric door 17, a water discharge pipe 18, a water discharge pipe electric door 19, a primary air heater emptying electric door 20, a secondary air heater emptying electric door 21, a primary fan 25 and a secondary fan 26, wherein:

[0026] A tubular heat exchanger 2 is arranged at the cold ash hopper below the furnace 1, and the tubular heat exchanger 2 is arranged along the left and right direction of the bottom of the cold ash hopper.

[0027] The water inlet of the tubular heat exchanger is connected to the water return main pipe 4 , and the water outlet of the tubular heat exchanger is connected to the water supply main pipe 5 .

[0028] The return water main pipe 4 is provided with a variable frequency water pump 3 .

[0029] A portion of the water in the water supply main pipe 5 enters the primary air heat exchanger 8 arranged at the entrance of the primary fan 25 through the primary air heat exchanger water inlet pipe 6 to exchange heat with the cold primary air 12, so that the cold primary air 12 is heated into hot primary air 13 and enters the primary fan 25;

[0030] Another part of the water in the water supply main pipe 5 enters the secondary air heat exchanger 9 arranged at the inlet of the secondary fan 26 through the secondary air heat exchanger water inlet pipe 7 to exchange heat with the cold secondary air 14, so that the cold secondary air 14 is heated into hot secondary air 15 and enters the secondary fan 26.

[0031] In this embodiment, the primary air heat exchanger and the secondary air heat exchanger are arranged on the inlet flues of the primary and secondary fans, which has the following advantages:

[0032] (1) When designing many power plants, there is insufficient space in the connecting ducts from the outlet of the primary and secondary fans to the inlet of the air preheater, and there is not enough space to install a heat exchanger;

[0033] (2) The inlet of the primary fan and the secondary fan is at a slight negative pressure, and the outlet pipes of the primary fan and the secondary fan are at a positive pressure of 4kPa to 12kPa. When a leakage occurs in the primary air heat exchanger and the secondary air heat exchanger, if they are arranged at the outlet of the primary fan and the secondary fan, the pressure here is too high and the primary fan and the secondary fan need to be stopped for fault handling. However, if the primary air heat exchanger and the secondary air heat exchanger are arranged at the inlet of the primary fan and the secondary fan, there is no need to stop the fan for handling.

[0034] The water return main pipe is also provided with a water injection pipe 16 and a water discharge pipe 18 , wherein the water injection pipe 16 is provided with a water injection electric door 17 ; and the water discharge pipe 18 is provided with a water discharge pipe electric door 19 .

[0035] A primary air heat exchanger vent door 20 is arranged at the high point of the primary air heat exchanger, and a secondary air heat exchanger vent door 21 is arranged at the high point of the secondary air heat exchanger. The vent door 21 is provided because when the empty pipe is filled with water, there is air in the pipe, and the water cannot completely fill the pipe, affecting the heat exchange efficiency. Therefore, it is necessary to set a vent point at the high point of the pipe to discharge the air in the pipe.

[0036] The operation mode of this embodiment is as follows:

[0037] Before igniting the boiler, close the water discharge electric door 19, open the primary air heat exchanger vent door 20, the secondary air heat exchanger vent door 21 and the water injection electric door 17;

[0038] After the entire system is filled with water through the water injection pipe 16, the primary air heat exchanger vent door 20, the secondary air heat exchanger vent door 21 and the water injection electric door 16 are closed, and the variable frequency water pump 3 is started to establish a water circulation system.

[0039] After the boiler is ignited, the large slag of the boiler falls through the gap between the heat exchange tubes of the tubular heat exchanger 2 and enters the slag remover. The high-temperature large slag exchanges heat with cooling water to form high-temperature hot water, which passes through the water supply main pipe 5, the primary air heat exchanger inlet pipe 6 and the secondary air heat exchanger inlet pipe 7 to enter the primary air heat exchanger 8 and the secondary air heat exchanger 9. After heat exchange, it becomes low-temperature water and enters the return water main pipe through the primary air heat exchanger outlet pipe 10 and the secondary air heat exchanger outlet pipe 11. After being pressurized by the variable frequency water pump 3, it enters the tubular heat exchanger again and is heated by the high-temperature large slag. It passes through the water supply main pipe 5, the primary air heat exchanger inlet pipe 6 and the secondary air heat exchanger inlet pipe 7 to heat the primary air and secondary air, forming a cycle. The cold primary air 12 is heated into hot primary air 13 through the primary air heat exchanger 8 to enter the primary fan 25, and the cold secondary air 14 is heated into hot secondary air 15 through the secondary air heat exchanger 9 to enter the secondary fan 26.

[0040] After the boiler is shut down or the primary air heat exchanger and the secondary air heat exchanger are shut down for various reasons, open the primary air heat exchanger vent door 20, the secondary air heat exchanger vent door 21, and the drain pipe electric door 19 to drain the water in the system.

[0041] Example 2

[0042] On the basis of Example 1, this embodiment provides a system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler, wherein the tubular heat exchanger 2 includes an inlet header 22, heat exchange tubes 23 and an outlet header 24, wherein:

[0043] A plurality of heat exchange tubes 23 are provided, and the plurality of heat exchange tubes are evenly distributed on the inlet header 22 and communicated with the inlet header 22 ; the free ends of the heat exchange tubes are communicated with the outlet header 24 .

[0044] The inlet header 22 is connected to the water return main pipe 4 , and the outlet header 24 is connected to the water supply main pipe 5 .

[0045] In this embodiment, a heat exchange tube 23 is arranged every 30 cm between the inlet header 22 and the outlet header 24 .

[0046] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A system for heating primary and secondary air with waste heat from large slag in coal-fired power station boilers, characterized in that: It includes a tubular heat exchanger, which is arranged at the cold ash hopper below the boiler furnace and arranged along the left and right directions of the bottom of the cold ash hopper; The cooling water outlet of the tubular heat exchanger is divided into two paths, one of which is connected to a primary air heater disposed at the primary air fan inlet, and the other is connected to a secondary air heater disposed at the secondary air inlet.

2. A system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 1, characterized in that: The cooling water outlet of the tubular heat exchanger is respectively connected to the primary air heater and the secondary air heater through the water supply main pipe.

3. A system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 2, characterized in that: The water outlet in the water supply main pipe is connected to the primary air heater and the secondary air heater through the primary air heater water inlet pipe and the secondary air heater water inlet pipe respectively.

4. The system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 1 is characterized in that: The cooling water inlet of the tubular heat exchanger is connected to the water injection pipeline through the return water main pipe.

5. A system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 4, characterized in that: The return water main pipe is provided with a variable frequency water pump.

6. A system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 4, characterized in that: The water injection pipeline is provided with a water injection electric door.

7. A system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 4, characterized in that: The return water main pipe is also provided with a water discharge pipe.

8. A system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 7, characterized in that: The drain pipe is provided with a drain pipe electric door.

9. The system for heating primary and secondary air with waste heat from large slag of a coal-fired power station boiler according to claim 1 is characterized in that: The tubular heat exchanger comprises an inlet header, heat exchange tubes and an outlet header, wherein: The heat exchange tubes are provided in plurality, and the plurality of heat exchange tubes are evenly distributed on the inlet header and communicated with the inlet header; the free ends of the heat exchange tubes are communicated with the outlet header; The inlet header is provided with a return water main pipe, and the outlet header is connected with a water supply main pipe.

Images