Heat recovery device of rotary air preheater

Abstract

A heat recovery device of a rotary air preheater comprises the rotary air preheater, the rotary air preheater is rotationally arranged in an air main pipe and a smoke main pipe, an ash spraying pipe is arranged in the smoke main pipe, an outlet of the ash spraying pipe faces the rotary air preheater, the ash spraying pipe is connected with an ash source through an ash leading-in pipeline, and the ash leading-in pipeline is connected with the smoke source. And an ash pump is arranged on the ash leading-in pipeline. The ash spraying outlet directly acts on one side of the smoke main pipe of the rotary air preheater, the effects of heating and washing away pollutants such as ammonium bisulfate remaining on the air preheater can be achieved, and therefore the effects of saving energy, reducing heat exchange loss and removing the pollutants can be achieved.

Description

Technical Field

[0001] The present application relates to a heat recovery device for a rotary air preheater. Background Art

[0002] A rotary air preheater is a device specifically used to improve the heat exchange efficiency of a boiler and reduce energy consumption. By slowly rotating, flue gas enters its flue gas side and is then discharged. In this process, the heat in the flue gas is absorbed by the fins. As the air preheater continues to rotate, the fins turn to the air side and transfer the absorbed heat to the air about to enter the boiler. The heat receiving surface of the air preheater is installed in a rotatable cylindrical rotor, and the rotor is also divided into several fan-shaped compartments, and each compartment is filled with heat transfer devices made of metal sheets. The top and bottom of the circular shell are divided into three main parts: a flue gas flow area, a sealing area, and an air flow area. During use, the corrugated plates at the cold end of the rotary air preheater are prone to ash accumulation and blockage. Currently, the general method is to use externally introduced air for blowing, but the cleaning effect is not good. On the other hand, a large amount of heat is contained in the ash discharged from the boiler, but very little of it is currently utilized, resulting in a certain waste of high-quality energy in the boiler. Summary of the Invention

[0003] To solve the above problems, the present application proposes a heat recovery device for a rotary air preheater, including a rotary air preheater rotatably arranged in an air main pipe and a flue gas main pipe. A ash ejection pipe is arranged in the flue gas main pipe, and the outlet of the ash ejection pipe faces the rotary air preheater. The ash ejection pipe is connected to an ash source through an ash introduction pipeline, and an ash pump is arranged on the ash introduction pipeline. The present application utilizes the direct action of the ash ejection outlet on one side of the flue gas main pipe of the rotary air preheater, which can play a role in heating and flushing pollutants such as ammonium bisulfate remaining on the air preheater, thereby achieving the effects of saving energy, reducing heat transfer losses, and removing pollutants.

[0004] Preferably, the ash ejection pipe is arranged at one end of the rotary air preheater that has just rotated into the flue gas main pipe;

[0005] A stop valve is arranged on the ash introduction pipeline. The ash ejection pipe includes a vertical introduction pipeline arranged along the axial direction of the flue gas main pipe. A tail cavity is arranged at the end of the vertical introduction pipeline, and several bottom transverse pipelines are arranged on the tail cavity; several middle transverse pipelines are arranged on the vertical introduction pipeline.

[0006] Preferably, the middle transverse pipelines are arranged in a spiral direction;

[0007] The flow diameter of the middle transverse pipelines is smaller than that of the bottom transverse pipelines;

[0008] The length of the middle transverse pipelines is shorter than that of the bottom transverse pipelines.

[0009] Preferably, the diameter of the middle horizontal pipe is 1 / 3 - 1 / 2 of the bottom horizontal pipe;

[0010] The length of the middle horizontal pipe is 1 / 6 - 1 / 4 of the bottom horizontal pipe.

[0011] Preferably, the number of the middle horizontal pipes is not less than two and they are evenly distributed in the projection direction according to 360°; the number of the bottom horizontal pipes is not less than two and they are evenly distributed according to 360°. The present application adopts the compound mode of the vertical inlet pipe and the bottom horizontal pipe, so that the ash energy of the present application can be evenly introduced into the space where it is located, avoiding accumulation, having a better heat exchange effect, and also having a better scouring effect, thereby improving the heat exchange efficiency of the present application.

[0012] Preferably, the ash inlet pipe includes a main powder pipe, and the main powder pipe is connected to the ash source through a plurality of powder pipe branches.

[0013] Preferably, the ash source includes an economizer ash hopper and a denitration ash hopper; the economizer ash hopper and the denitration ash hopper are respectively connected to the main powder pipe through powder pipe branches, a first ash source valve is arranged on the economizer ash hopper, and a second ash source valve is arranged on the denitration ash hopper.

[0014] Preferably, the ash spraying operation is controlled in the following manner:

[0015] Obtain the flue gas temperature t1 below the rotary air preheater;

[0016] Obtain the acid dew point temperature t2 of the flue gas;

[0017] Calculate Δt = t2 - t1. If Δt is greater than the control threshold τ, then open the stop valve on the conduction pipe, and the ash sprayer starts the ash spraying operation.

[0018] Preferably, the acid dew point temperature is obtained in the following manner:

[0019] Obtain the SO2 concentration and NO x concentration in the flue gas;

[0020] Calculate the acid dew point temperature t2 according to the SO2 concentration and NO x concentration.

[0021] Preferably, it further includes obtaining the flue gas temperature t3 above the rotary air preheater;

[0022] When the stop valve is in the open state, the following periodic opening control is carried out:

[0023] Set the first opening time T1;

[0024] After the first opening time T1, if t2 ≥ a * t3, continue to open for the first opening time T1;

[0025] Repeat this process until t2 < a * t3, then perform the first closing time T2;

[0026] 0.6 ≥ a ≥ 0.5;

[0027] Then set the first closing time T2;

[0028] T2 = (t3 - t2) * T1 / (t2 - t1);

[0029] After the first closing time T2, if t2 ≤ b * t3, continue to extend the first closing time T2;

[0030] Repeat this process until t2 > b * t3, then perform the first closing time T3;

[0031] 0.8 ≥ b ≥ 0.7;

[0032] Then set the second opening time T3;

[0033] T3 = (t3 - t2) * T2 / (t2 - t1);

[0034] Make a judgment on whether to continue or change to closing according to the judgment condition of the first opening time T1, and cycle in the above order until a complete opening cycle is completed. The method of intermittent ash injection in this application can enable pollutants such as ammonium bisulfate to be recovered and treated in a timely manner, and through the intermittent injection method, ammonium bisulfate can be precipitated from the flue gas in a timely manner, and it also has a better heat exchange effect compared with continuous ash injection.

[0035] This application can bring the following beneficial effects:

[0036] 1. This application uses the ash spray outlet to directly act on one side of the main flue gas pipe of the rotary air preheater, which can play a role in heating and flushing pollutants such as ammonium bisulfate remaining on the air preheater, thereby saving energy, reducing heat exchange losses, and removing pollutants.

[0037] 2. This application adopts a combination of vertical inlet pipes and bottom horizontal pipes, so that the ash of this application can be evenly introduced into the space where it is located, avoiding accumulation, having a better heat exchange effect, and also having a better flushing effect, thereby improving the heat exchange efficiency of this application.

[0038] 3. The method of intermittent ash injection in this application can enable pollutants such as ammonium bisulfate to be recovered and treated in a timely manner, and through the intermittent injection method, ammonium bisulfate can be precipitated from the flue gas in a timely manner, and it also has a better heat exchange effect compared with continuous ash injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are provided to further understand the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0040] Figure 1 is a schematic structural diagram of the present application.

[0041] Figure 2 is a schematic structural diagram of the ash ejection pipe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] To clearly illustrate the technical features of the present solution, the present application will be described in detail below through specific embodiments and in conjunction with their accompanying drawings.

[0043] In terms of structural composition, as Figure 1-2 shown, a heat recovery device for a rotary air preheater includes a rotary air preheater 1, the rotary air preheater 1 is rotatably arranged in an air main pipe 2 and a flue gas main pipe 3, an ash ejection pipe 4 is arranged in the flue gas main pipe 3, the outlet of the ash ejection pipe 4 faces the rotary air preheater 1, the ash ejection pipe 4 is connected to an ash source through an ash introduction pipeline 5, and an ash pump 6 is arranged on the ash introduction pipeline 5.

[0044] The rotary air preheater 1 where the ash ejection pipe 4 is arranged just turns to one end of the flue gas main pipe 3; a stop valve 7 is arranged on the ash introduction pipeline 5, the ash ejection pipe 4 includes a vertical introduction pipeline 8 arranged along the axial direction of the flue gas main pipe, a tail cavity 9 is arranged at the end of the vertical introduction pipeline 8, and a plurality of bottom transverse pipelines 10 are arranged on the tail cavity 9; a plurality of middle transverse pipelines 11 are arranged on the vertical introduction pipeline 8.

[0045] The middle transverse pipelines 11 are arranged in a spiral direction; the flow diameter of the middle transverse pipelines 11 is smaller than that of the bottom transverse pipelines 10; the length of the middle transverse pipelines 11 is smaller than that of the bottom transverse pipelines 10. The diameter of the middle transverse pipelines 11 is 1 / 3 - 1 / 2 of that of the bottom transverse pipelines 10; the length of the middle transverse pipelines 11 is 1 / 6 - 1 / 4 of that of the bottom transverse pipelines 10. The number of the middle transverse pipelines 11 is not less than two and is evenly distributed in the projection direction along 360°; the number of the bottom transverse pipelines 10 is not less than two and is evenly distributed along 360°.

[0046] The ash inlet pipe 5 includes a main powder pipe 12, and the main powder pipe 12 is connected to the ash source through a number of sub-powder pipes 13. A temporary storage bin can be set up to reduce fluctuations. The ash source includes an economizer ash hopper 14 and a denitration ash hopper 15; the economizer ash hopper 14 and the denitration ash hopper 15 are respectively connected to the main powder pipe 12 through sub-powder pipes 13. A first ash source valve 16 is provided on the economizer ash hopper 14, and a second ash source valve 17 is provided on the denitration ash hopper 15.

[0047] The ash spraying operation is controlled as follows:

[0048] Obtain the flue gas temperature t1 below the rotary air preheater 1;

[0049] Obtain the acid dew point temperature t2 of the flue gas;

[0050] Calculate Δt = t2 - t1. If Δt is greater than the control threshold τ, open the stop valve 7 on the conduction pipe, and the ash sprayer starts the ash spraying operation. The control threshold τ is generally controlled at 5°C.

[0051] The acid dew point temperature is obtained as follows:

[0052] Obtain the SO2 concentration and NO x concentration in the flue gas;

[0053] According to the SO2 concentration and NO x concentration, calculate the acid dew point temperature t2.

[0054] It also includes obtaining the flue gas temperature t3 above the rotary air preheater 1;

[0055] When the stop valve 7 is in the open state, the following periodic opening control is performed:

[0056] Set the first opening time T1; generally set it to 2 or 3 s first;

[0057] After the first opening time T1, if t2 ≥ a * t3, continue to open for the first opening time T1;

[0058] Repeat this way until t2 < a * t3 for the first closing time T2;

[0059] 0.6 ≥ a ≥ 0.5;

[0060] Then set the first closing time T2;

[0061] T2 = (t3 - t2) * T1 / (t2 - t1);

[0062] After the first closing time T2, if t2 ≤ b * t3, continue to extend the first closing time T2;

[0063] Repeat the above steps until t2 > b * t3, and then perform the first closing time T3;

[0064] 0.8 ≥ b ≥ 0.7;

[0065] Then set the second opening time T3;

[0066] T3 = (t3 - t2) * T2 / (t2 - t1);

[0067] Continue or change to the closing judgment according to the judgment condition of the first opening time T1, and perform the cycle in the above order until an opening cycle is completed.

[0068] To demonstrate the effectiveness of this application, the following comparison is made on the running project:

[0069] The control scheme of this application is controlled as follows:

[0070] Obtain the flue gas temperature t1 below the rotary air preheater 1;

[0071] Obtain the acid dew point temperature t2 of the flue gas;

[0072] Calculate Δt = t2 - t1. If Δt is greater than the control threshold τ, set to 5°C, then open the stop valve 7 on the conduction pipeline, and the ash sprayer starts to perform ash spraying operation.

[0073] The acid dew point temperature is obtained as follows:

[0074] Obtain the SO2 concentration and NO x concentration in the flue gas;

[0075] According to the SO2 concentration and NO x concentration, calculate the acid dew point temperature t2.

[0076] It also includes obtaining the flue gas temperature t3 above the rotary air preheater 1;

[0077] When the stop valve is in the open state, the following periodic opening control is performed:

[0078] Set the first opening time T1, set to 2s;

[0079] After the first opening time T1, if t2 ≥ a * t3, continue to open for the first opening time T1;

[0080] Repeat the above steps until t2 < a * t3, and then perform the first closing time T2;

[0081] a is set to 0.5;

[0082] Then set the first closing time T2;

[0083] T2 = (t3 - t2) * T1 / (t2 - t1);

[0084] After the first closing time T2, if t2 ≤ b * t3, continue to extend the first closing time T2;

[0085] Repeat this process until t2 > b * t3 to perform the first closing time T3;

[0086] b is set to 0.7;

[0087] Then set the second opening time T3;

[0088] T3 = (t3 - t2) * T2 / (t2 - t1). Continue or change to the judgment of closing according to the judgment condition of the first opening time T1, and perform the cycle in the above order until an opening cycle is completed.

[0089] After continuous operation for 3 h, measure that the change rate of the flue gas temperature at the inlet and outlet of the rotary air preheater satisfies: dt3 / dt1 > k;

[0090] Note: dt3: The change rate of the inlet temperature of the air preheater per minute; dt1: The change rate of the outlet temperature of the air preheater per minute. k: The air preheater coefficient.

[0091] For comparison, compared with the above control method, instead of performing intermittent operation, only control whether Δt is 5 °C to perform continuous ash injection operation. After continuous operation for 3 h, measure the change rate of the flue gas temperature at the inlet and outlet of the rotary air preheater: dt3 / dt1 is about 0.8k.

[0092] Perform intermittent operation, but the intermittent value is set to 1 s. After continuous operation for 3 h, measure the change rate of the flue gas temperature at the inlet and outlet of the rotary air preheater: dt3 / dt1 is about 0.8k.

[0093] The above are only the embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A heat recovery device for a rotary air preheater, characterized in that: It includes a rotary air preheater which is rotatably arranged in the main air pipe and the main flue gas pipe. A ash ejection pipe is arranged in the main flue gas pipe, and the outlet of the ash ejection pipe faces the rotary air preheater. The ash ejection pipe is connected to an ash source through an ash introduction pipeline, and an ash pump is arranged on the ash introduction pipeline.

2. The heat recovery device of a rotary air preheater according to claim 1, wherein: The rotary air preheater where the ash ejection pipe is arranged just turns to one end of the main flue gas pipe; A stop valve is arranged on the ash introduction pipeline. The ash ejection pipe includes a vertical introduction pipeline arranged along the axial direction of the main flue gas pipe. A tail cavity is arranged at the end of the vertical introduction pipeline, and several bottom transverse pipelines are arranged on the tail cavity; several middle transverse pipelines are arranged on the vertical introduction pipeline.

3. The heat recovery device of a rotary air preheater according to claim 2, characterized in that: The middle transverse pipelines are arranged in a spiral direction; The flow diameter of the middle transverse pipelines is smaller than that of the bottom transverse pipelines; The length of the middle transverse pipelines is shorter than that of the bottom transverse pipelines.

4. The heat recovery device of a rotary air preheater according to claim 3, characterized in that: The diameter of the middle transverse pipelines is 1 / 3 - 1 / 2 of that of the bottom transverse pipelines; The length of the middle transverse pipelines is 1 / 6 - 1 / 4 of that of the bottom transverse pipelines.

5. The heat recovery device for a rotary air preheater according to claim 3, wherein: The number of the middle transverse pipelines is not less than two and is evenly distributed in the projection direction according to 360°; the number of the bottom transverse pipelines is not less than two and is evenly distributed according to 360°.

6. A heat recovery device for a rotary air preheater according to claim 1, characterized in that: The ash introduction pipeline includes a main powder pipe, and the main powder pipe is connected to the ash source through several powder pipe branches.

7. The heat recovery device of a rotary air preheater according to claim 1, characterized in that: The ash source includes a economizer ash hopper and a denitration ash hopper; the economizer ash hopper and the denitration ash hopper are respectively connected to the main powder pipe through powder pipe branches. A first ash source valve is arranged on the economizer ash hopper, and a second ash source valve is arranged on the denitration ash hopper.

8. The heat recovery device of a rotary air preheater according to claim 1, characterized in that: The ash spraying operation is controlled in the following way: Obtain the flue gas temperature t1 below the rotary air preheater; Obtain the acid dew point temperature t2 of the flue gas; Calculate Δt = t2 - t1. If Δt is greater than the control threshold τ, then open the stop valve on the conduction pipeline, and the ash sprayer starts to perform the ash spraying operation.

9. The heat recovery device of a rotary air preheater according to claim 8, wherein: The acid dew point temperature is obtained in the following way: Obtain the SO2 concentration and NO concentration in the flue gas x concentration; Based on the SO2 concentration and NO x concentration, calculate the acid dew point temperature t2.

10. The heat recovery device of a rotary air preheater according to claim 8, wherein: It further includes obtaining the flue gas temperature t3 above the rotary air preheater; When the stop valve is in the open state, the following periodic opening control is carried out: Set the first opening time T1; After the first opening time T1, if t2 ≥ a * t3, then continue to open for the first opening time T1; Repeat like this until t2 < a * t3 for the first closing time T2; 0.6≥a≥0.5； Then set the first closing time T2; T2 = (t3 - t2) * T1 / (t2 - t1); After the first closing time T2, if t2 ≤ b * t3, then continue to extend the first closing time T2; Repeat like this until t2 > b * t3 for the first closing time T3; 0.8≥b≥0.7； Then set the second opening time T3; T3 = (t3 - t2) * T2 / (t2 - t1); Continue the judgment according to the judgment condition of the first opening time T1 or change it to the judgment of closing, and perform the cycle in the above order until an opening cycle is completed.

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