Flue gas bypass system for increasing comprehensive temperature of cold end of rotary air pre-heater of boiler

Abstract

The utility model relates to the technical field of temperature treatment of rotary air pre-heaters, and particularly discloses a flue gas bypass system for increasing the comprehensive temperature of the cold end of a rotary air pre-heater of a boiler, which comprises a rotary air pre-heater and a flue gas air heater which are arranged in a flue gas air heater system, a hot smoke bypass pipeline is arranged at an inlet flue of the rotary air pre-heater; the lower end of the hot smoke bypass pipeline is connected to a primary air side smoke pipe box of the smoke air heater, and the hot smoke bypass pipeline is used for partially introducing high-temperature smoke fed into the rotary air pre-heater into the primary air side smoke pipe box and heating the primary air side smoke pipe box of the smoke air heater; the hot smoke bypass pipeline comprises a main pipeline, a plurality of branch pipelines are arranged at the lower end of the main pipeline side by side, and the branch pipelines are connected to a primary air side smoke pipe box of the air heater. The primary air side pipe box of the air heater is heated through the high-temperature flue gas, the cold end wall temperature of the primary air side of the rotary air preheater is increased, and the problem of ammonium bisulfate ash clogging of the rotary air preheater is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of rotary air preheater systems, in particular to a flue gas bypass system for raising the comprehensive temperature of a cold end of a rotary air preheater by a boiler. Background Art

[0002] With the changes in energy structure and fluctuations in the coal market in recent years, thermal power plants are facing increasingly severe resource challenges and environmental pressures. In actual operation, the quality of coal used by thermal power plants is often lower than the designed coal type, which is mainly reflected in the low average low calorific value of coal (only 15.5MJ / kg) and high sulfur content (the average sulfur content on the received basis is 3.55%). This coal quality characteristic has a great impact on the boiler operation efficiency and environmental emissions of thermal power plants, especially in thermal power plants using W-type flame boilers. Due to the particularity of its combustion characteristics, it leads to high NOx emission concentration and high ammonia escape rate. In addition, the use of high-sulfur, low-calorific value, and high-ash coal increases the content of compounds such as ammonium bisulfate in flue gas. These compounds are easy to form ammonium salt accumulation in the air preheater (air preheater), which in turn causes a series of problems such as air preheater blockage, high differential pressure on the smoke and wind side, high exhaust temperature, and poor heat exchange effect. This not only affects the combustion stability of the boiler, but also seriously reduces the operating economy of the thermal power unit.

[0003] To solve the above problems, at present, the rotary air preheater is also modified by coupling it with a three-dimensional finned tube flue gas heater. By increasing the comprehensive temperature of the cold end of the air preheater, the low-temperature corrosion and ammonium salt accumulation problems of the heat exchange components at the cold end of the air preheater are effectively alleviated. However, due to the special structure and working principle of the three-compartment rotary air preheater, when the rotor absorbs heat from the flue gas side and rotates to the primary air side, the metal wall temperature of the heat exchange component will be greatly reduced. Especially under low unit load, deep peak regulation and winter conditions, the risk of ammonium salt accumulation still exists.

[0004] Therefore, in view of the problem that the comprehensive temperature at the cold end of the rotary air preheater is low and easily causes ammonium salt accumulation, it is now necessary to provide a flue gas bypass system for the boiler to increase the comprehensive temperature of the cold end of the rotary air preheater. Utility Model Content

[0005] The utility model aims to provide a flue gas bypass system for raising the comprehensive temperature of the cold end of a rotary air preheater by a boiler, heating the primary air side pipe box of the heater by high-temperature flue gas, raising the primary air temperature at the heater outlet, and further raising the cold end wall temperature on the primary air side of the rotary air preheater, thereby solving the problem of ammonium bisulfate ash blockage in the rotary air preheater.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] The utility model adds a bypass system to the inlet flue of the rotary air preheater, introduces a flue gas pipe box on the primary air side of the heater inlet, heats the pipe box on the primary air side of the heater by high-temperature flue gas, effectively increases the cold end wall temperature on the primary air side of the rotary air preheater, and reduces the risk of ammonium salt accumulation. Specifically, a flue gas bypass system for raising the comprehensive temperature of the cold end of a rotary air preheater by a boiler is provided, comprising a rotary air preheater and a flue gas heater arranged in a flue gas heater system; a hot smoke bypass pipe is provided at the inlet flue of the rotary air preheater; the lower end of the hot smoke bypass pipe is connected to the primary air side flue gas pipe box of the flue gas heater, and is used to introduce part of the high-temperature flue gas delivered to the rotary air preheater into the primary air side flue gas pipe box, so as to heat the primary air side flue gas pipe box of the flue gas heater; the hot smoke bypass pipe comprises a main pipe, the upper end of the main pipe is connected to the inlet flue of the rotary air preheater, and the lower end of the main pipe is provided with a plurality of branch pipes side by side, and the branch pipes are connected to the primary air side flue gas pipe box of the heater.

[0008] The principles and advantages of this solution are:

[0009] By adding a hot smoke bypass pipe to the inlet flue of the rotary air preheater, introducing the flue gas pipe box on the primary air side of the inlet of the flue gas heater, the high-temperature flue gas heats the primary air side pipe box of the flue gas heater, thereby increasing the primary air temperature at the outlet of the flue gas heater, thereby increasing the cold end wall temperature on the primary air side of the rotary air preheater, and solving the ammonium bisulfate ash blockage problem of the rotary air preheater. At this wind temperature, even if the unit burns high-sulfur coal, the rotary air preheater will not be blocked or corroded at low temperature, so the rotary air preheater can maintain good heat exchange capacity.

[0010] Since thermal power generation equipment is large in size and occupies a large area, in order to ensure smooth production processes and reduce operational complexity, the equipment in each process will be set up based on saving processes and reducing repeated operations, so that the arrangement between the equipment is compact and the adjustable space is small, so as to minimize the floor space and improve production efficiency. Therefore, there are great limitations on the transformation of equipment processes. However, this solution adds a hot smoke bypass pipeline in a limited space, without changing other production equipment, while reducing the transformation cost, making full use of the existing extremely small adjustable space, and introducing high-temperature flue gas into the flue gas pipe box on the primary air side of the flue gas heater inlet, heating the flue gas heater primary air side pipe box, and realizing the improvement of the comprehensive temperature of the cold end of the rotary air preheater, effectively solving the problems of blockage and low-temperature corrosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the flow structure of a flue gas bypass system for increasing the comprehensive temperature of the cold end of a rotary air preheater of a boiler according to the utility model;

[0012] Figure 2This is a schematic diagram of the installation position structure of a hot smoke bypass pipe of a flue gas bypass system for increasing the comprehensive temperature of the cold end of a rotary air preheater of a boiler according to the utility model;

[0013] Figure 3 It is a partial structural schematic diagram of a hot smoke bypass pipeline of a flue gas bypass system for increasing the comprehensive temperature of the cold end of a rotary air preheater of a boiler according to the utility model;

[0014] Figure 4 The utility model is a bottom view of a hot smoke bypass pipeline of a smoke bypass system for increasing the comprehensive temperature of the cold end of a rotary air preheater of a boiler. DETAILED DESCRIPTION

[0015] The following is further described in detail through specific implementation methods:

[0016] The reference numerals in the drawings of the specification include: a rotary air preheater 1, a flue gas heater 2, a hot smoke bypass duct 3, a primary air side flue gas pipe box 4, a main duct 5, and a branch duct 6.

[0017] The embodiment is basically as shown in the attached Figure 1 As shown: A flue gas bypass system for a boiler to increase the comprehensive temperature of the cold end of a rotary air preheater. By adding a hot smoke bypass pipe 3 to the inlet flue of the rotary air preheater and introducing a flue gas pipe box 4 on the primary air side of the heater inlet, the cold end wall temperature of the primary air side of the rotary air preheater is increased to solve the ash blockage problem of the air preheater. It includes a rotary air preheater 1 and a flue gas heater 2 arranged in a flue gas heater system. In this embodiment, the rotary air preheater 1 includes a rotary air preheater A and a rotary air preheater B arranged side by side on both sides, and the flue gas heater 2 includes a flue gas heater A and a flue gas heater B respectively arranged below the rotary air preheater A and the rotary air preheater B. The flue gas heater A supplies air to the rotary air preheater A, and the flue gas heater B supplies air to the rotary air preheater B. The structures on both sides are consistent. For the convenience of description, in this embodiment, the rotary air preheater and the flue gas heater on the A side are taken as an example for explanation ( Figure 1 The hot smoke bypass duct on the middle B side is not drawn).

[0018] A hot smoke bypass pipe 3 is provided at the inlet flue of the rotary air preheater 1; the lower end of the hot smoke bypass pipe 3 is connected to the primary air side flue gas box 4 of the flue gas heater, and the high-temperature flue gas part fed into the rotary air preheater 1 is introduced into the primary air side flue gas box 4 through the provided hot smoke bypass pipe 3, thereby heating the primary air side flue gas box 4 of the flue gas heater, thereby increasing the primary air temperature at the heater outlet, and further increasing the comprehensive temperature of the cold end of the rotary air preheater.

[0019] In this embodiment, as shown in the attached Figure 2As shown, the hot smoke bypass pipeline 3 includes two main pipelines 5, which are the main pipeline of the left rotary air preheater A and the main pipeline of the right rotary air preheater B. The upper end of the left main pipeline is connected to the inlet flue of the left rotary air preheater A, and the upper end of the right main pipeline is connected to the inlet flue of the right rotary air preheater B. Taking the left main pipeline as an example, a plurality of branch pipelines 6 are arranged side by side at the lower end of the main pipeline 5, and the lower end of the branch pipeline 6 is connected to the primary air side flue gas pipe box 4 of the flue gas heater 2.

[0020] In this embodiment, the main pipeline 5 is a Z-shaped structure as a whole. The upper front end of the main pipeline 5 is connected to the inlet flue of the rotary air preheater 1. The middle part of the main pipeline 5 is vertically located on one side of the rotary air preheater to reduce the space occupied by the hot smoke bypass pipeline 3 and meet the layout requirements of the existing equipment. Figure 3 As shown, a plurality of branch pipes 6 are welded side by side at the lower end of the main pipe 5 , and the high-temperature flue gas entering the main pipe 5 is sent into the primary air side flue gas pipe box 4 through the branch pipes 6 .

[0021] In this embodiment, the diameter of the main pipe 5 is set to 820mm to ensure smooth flow of high-temperature flue gas and reduce the occupied area of ​​the hot smoke bypass pipe 3 so that it can be adapted to various systems and improve versatility. There are 8 branch pipes 6, which are evenly arranged at the lower end of the main pipe 5. Figure 4 As shown, the diameter of the branch pipe 6 is set to 219mm, and the spacing between adjacent branch pipes 6 is set to 500mm, so as to ensure that the high-temperature flue gas can be evenly introduced into the primary air side flue gas pipe box 4, improve the uniformity of heating, and ensure that the heat meets the heating requirements. Figure 4 The distance between the leftmost branch pipe and the end of the main pipe 5 is 200 mm to ensure that the high-temperature flue gas covers as much as possible and achieves comprehensive and uniform heating.

[0022] In this embodiment, a control valve is installed by bolts at the main pipeline 5 and the inlet flue of the rotary air preheater 1. The control valve is controlled by the main control system, and the opening of the control valve is adjusted according to the operating load of the heater. In this embodiment, the control valve can be a throttle valve or other device, which is not limited here.

[0023] The specific implementation process is as follows:

[0024] First, install the hot smoke bypass pipe to the inlet flue of the rotary air preheater, and connect the branch pipe to the primary air side flue gas box of the flue gas heater.

[0025] Secondly, the control valve of the hot smoke bypass duct is operated and debugged. The control valve is set to the open state, and its initial opening is set to 50%. The overall operating load of the flue gas heater is observed, including the air temperature at the primary air outlet of the flue gas heater, the dry burning wall temperature of the primary air duct box, and the outlet smoke temperature on this side. The opening of the control valve is adjusted according to the operating load of the flue gas heater.

[0026] When the load is lower than 60%, the valve opening is controlled to be 100%, i.e. fully open; when the load is higher than 80%, the valve opening is controlled to be 30%; when the load is between 60% and 80%, the valve opening is controlled to be maintained at 50%.

[0027] After adding this bypass, the flue gas flow and velocity of the primary air duct box are supplemented to increase the temperature. Under the condition of 100% unit load, the bypass smoke volume is about 20000Nm 3 / h; Under the condition of 40% unit load, the bypass smoke volume is about 12000Nm 3 / h. Ensure the stability of the high-temperature flue gas introduced into the flue gas heater, and effectively increase the comprehensive temperature of the cold end of the rotary air preheater.

[0028] In this embodiment, by adding a hot smoke bypass pipe, the primary hot air temperature at the inlet of the rotary air preheater is increased from 80°C to 114°C, which significantly improves the comprehensive temperature of the cold end of the rotary air preheater. According to this calculation, at 90% load, when the inlet air temperature of the rotary air preheater reaches 114°C, the outlet smoke temperature of the rotary air preheater is 203.6°C, and the comprehensive temperature of the cold end of the rotary air preheater reaches 317.6°C, which can ensure that the rotary air preheater is not blocked by ammonium bisulfate. In this way, the risk of ammonium salt accumulation can be reduced, the differential pressure of the flue gas inlet and outlet of the rotary air preheater can be ensured to operate smoothly, and the reliability of the equipment can be improved.

[0029] The above is only an embodiment of the utility model, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the technical solution of the utility model, which should also be regarded as the protection scope of the utility model, and these will not affect the effect of the implementation of the utility model and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A flue gas bypass system for increasing the comprehensive temperature of the cold end of a rotary air preheater of a boiler, characterized in that: It comprises a rotary air preheater and a flue gas heater which are arranged in a flue gas heater system; a hot smoke bypass pipe is arranged at the inlet flue of the rotary air preheater; the lower end of the hot smoke bypass pipe is connected to the primary air side flue gas box of the flue gas heater, and is used for introducing part of the high-temperature flue gas sent into the rotary air preheater into the primary air side flue gas box to heat the primary air side flue gas box of the flue gas heater; the hot smoke bypass pipe comprises a main pipe, the upper end of the main pipe is connected to the inlet flue of the rotary air preheater, and the lower end of the main pipe is provided with a plurality of branch pipes in parallel, and the branch pipes are connected to the primary air side flue gas box of the heater.

2. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 1, characterized in that: The main pipeline is a Z-shaped structure and is vertically arranged on one side of the rotary air preheater; the branch pipelines are arranged side by side at the lower end of the main pipeline.

3. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 1, characterized in that: The diameter of the main pipeline is 820 mm.

4. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 1, characterized in that: The branch pipes are provided with 8 pieces and are evenly arranged at the lower end of the main pipe; the diameter of the branch pipes is 219 mm.

5. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 4, characterized in that: The spacing between adjacent branch pipes is set to 500 mm.

6. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 1, characterized in that: The distance between the branch pipe located at the outermost side of the main pipe and the end of the main pipe is 200 mm.

7. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 1, characterized in that: A control valve is provided at the main pipeline and the inlet flue of the rotary air preheater, and the opening of the control valve is adjusted according to the operating load of the flue gas heater.

8. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 1, characterized in that: The main pipeline includes two paths, which are respectively arranged at the inlet flues on the left and right sides of the rotary air preheater.

9. A flue gas bypass system for increasing the cold end comprehensive temperature of a rotary air preheater of a boiler according to claim 7, characterized in that: When the load is lower than 60%, the valve opening is controlled to 100%; when the load is higher than 80%, the valve opening is controlled to 30%; when the load is between 60% and 80%, the valve opening is controlled to 50%.

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