Incinerator flue gas and air mixed air distribution system and control method thereof

Abstract

The invention discloses an incinerator flue gas and air mixing air distribution system and a control method thereof.The incinerator flue gas and air mixing air distribution system comprises an air main pipe, an air fan is arranged at one end of the air main pipe, and the side wall of the air main pipe communicates with one end of an air conveying pipeline; the other end of the air conveying pipeline is communicated with the flue gas and air mixing expansion section pipeline through a mixed gas combining pipeline, a through hole is formed in the side wall of the air conveying pipeline, a flue gas conveying pipeline is arranged in the through hole, a flue gas adjusting valve is arranged on the flue gas conveying pipeline, and an oxygen meter is arranged in the mixed gas combining pipeline. By adopting the control system, the oxygen concentration of an original boiler outlet is reduced by 2-3%; primary air energy consumption is saved, NOx is reduced by 30%-50%, and part of garbage incinerators are directly reduced to 200 mg / Nm < 3 > or below; therefore, the boiler load is more stable, the air distribution is uniform, the partial combustion phenomenon is effectively changed, and the evaporation capacity is improved by 2-5%.

Description

Technical Field

[0001] The invention belongs to the technical field of low-nitrogen combustion, and in particular relates to an incinerator flue gas and air mixing and distribution system and a control method thereof. Background Art

[0002] At present, the requirements for boiler flue gas emission indicators for incineration projects in various regions are becoming more and more stringent, especially for NO x The emission concentration control of NO x The photochemical smog formed threatens human life and health and has attracted much attention. x Controlled at 100mg / Nm 3 In the following, the SCR process must be used, but the investment and operation costs of this process are high and the process is complicated. Therefore, from the perspective of saving investment and operating costs, source reduction is the most important way to control NO x The best solution for emission concentration. Source reduction is mainly achieved by changing the combustion conditions through air distribution, thereby reducing NO x The amount of generated is reduced.

[0003] The patent with publication number CN117231987A discloses a deep low-nitrogen combustion air distribution system suitable for waste incinerators, including a flue gas recirculation system and a graded air system. The graded air system includes a graded air fan and a graded air nozzle. The design of the graded air system increases the flue gas mixing intensity above the material layer and below the secondary air. A flue gas heater is set at the outlet of the recirculation fan, and a mixer is set to mix with the primary air. During the actual on-site transformation process, the space is compact, the mixer is set small, and it is difficult to mix evenly, resulting in large fluctuations in the combustion conditions and difficulty in stable operation.

[0004] However, the existing flue gas and air (primary air, secondary air) entering the incinerator have different compositions, pressures and flows. The two parts are relatively independent during the transportation process, which is prone to cross-flow or vortex, affecting the actual operation. In addition, the cost of setting up a separate mixing system is high, the space is large, and the process is complicated, so many project modifications cannot be implemented; the existing flue gas and air are mixed at the inlet of the (primary air, secondary air) fan, which has high requirements on the fan performance parameters, and the phenomenon of difficult adjustment of working conditions occurs frequently, and even aggravates the corrosion of the fan.

[0005] In order to solve the above problems, the present invention proposes an incinerator flue gas and air mixing air distribution system and a control method thereof. Summary of the invention

[0006] Technical problems to be solved: In view of the above technical problems, the present invention provides an incinerator flue gas and air mixing air distribution system and a control method thereof, which can effectively solve the shortcomings of uneven mixing of flue gas and air in the above air distribution system, high cost, large space and complex process of setting up a separate mixing system, placing the flue gas and air mixing at the fan inlet, high requirements on the fan performance parameters, and frequent difficulties in adjusting the working conditions.

[0007] Technical solution: In the first aspect, the present invention provides an incinerator flue gas and air mixing and distribution system, including an air main pipe, one end of the air main pipe is provided with an air fan, the side wall of the air main pipe is connected with one end of an air delivery pipe, the other end of the air delivery pipe is connected with a flue gas and air mixing expansion section pipe through a mixing and gas pipe, a through hole is opened on the side wall of the air delivery pipe, a flue gas delivery pipe is arranged in the through hole, a flue gas delivery pipe is provided on the flue gas delivery pipe, a flue gas regulating valve is provided on the flue gas delivery pipe, and an oxygen meter is provided in the mixing and gas pipe.

[0008] Preferably, the angle between the smoke conveying duct and the horizontal section of the air conveying duct is a, and the value of a is 16° to 75°.

[0009] Furthermore, a Venturi baffle is provided on the side where the smoke delivery duct and the air delivery duct mix and ventilate, and the angle between the Venturi baffle and the horizontal section of the air delivery duct is b, b=a-15°, and the calculation formula of the Venturi baffle length is as follows:

[0010]

[0011] Where D is the diameter of the air duct; It is the baffle conversion coefficient, that is, the ratio of the length of the Venturi baffle projected onto the air delivery pipe to the diameter of the air delivery pipe, and its value is 0.3 to 0.5.

[0012] Preferably, the air fan (2) is a variable frequency fan.

[0013] Preferably, the air delivery pipeline (4) is provided with an air regulating valve (3), and an air flow meter is provided on the pipeline between the air regulating valve (3) and the air outlet of the air delivery pipeline (4).

[0014] Preferably, a smoke flow meter and a smoke oxygen meter are provided on the pipe between the smoke regulating valve (6) and the smoke outlet of the smoke conveying pipe (5).

[0015] In a second aspect, the present invention provides a control method for the air distribution system of the first aspect, comprising the following steps: mixing air and flue gas and then entering the furnace of the incinerator through the flue gas air mixing expansion section pipeline, adjusting the frequency of the air fan, the opening of the air regulating valve and the opening of the flue gas regulating valve, so that the oxygen concentration of the mixed gas entering the drying section is 7% to 10%, the oxygen concentration of the mixed gas entering the pyrolysis section is 10% to 15%, and the oxygen concentration of the mixed gas entering the combustion section is 15% to 20%, wherein the oxygen concentration C of the mixed gas 2 The calculation formula is as follows:

[0016]

[0017] In the formula, Q 1 is the value of the air flow meter; Q 2 is the value of the flue gas flow meter; C 1 is the oxygen concentration in the original flue gas.

[0018] Preferably, the specific control process is: when the oxygen concentration of the mixed gas C 2 When the incinerator is not equipped with enough air, the frequency of the air fan is increased to maintain the stable combustion condition. When the incinerator is fully equipped with air and preheated, the flue gas regulating valve is adjusted to reduce its opening to ensure the stable combustion condition. When the oxygen concentration of the mixed gas C 2 When the air volume is too high and the incinerator is insufficient, the combustion condition can be maintained stable by increasing the opening of the flue gas regulating valve; when the incinerator is sufficiently supplied with air and preheated, the air fan frequency can be reduced.

[0019] Beneficial effects: By adopting the control system of the present invention, the oxygen concentration at the original boiler outlet is reduced by 2-3%; the system of the present invention saves primary wind energy consumption, and NO x Reduce by 30-50%, some waste incinerators directly reduce to 200mg / Nm 3 As follows; during use, the control system of the present invention does not cause the phenomenon of unsmooth mixing of flue gas and air due to increase or decrease in flow rate, improves the gas blockage, and reduces the power consumption of the primary air fan; the application of the control system of the present invention makes the boiler load more stable, the air distribution is uniform, effectively changes the biased burning phenomenon, and increases the evaporation capacity by 2 to 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a flue gas and air mixing and air distribution system for an incinerator of the present invention;

[0021] Figure 2 It is a control schematic diagram of a flue gas and air mixing and air distribution system for an incinerator of the present invention;

[0022] Serial numbers in the figure: 1. Air main pipe, 2. Air fan, 3. Air regulating valve, 4. Air delivery pipeline, 5. Flue gas delivery pipeline, 6. Flue gas regulating valve, 7. Flue gas and air mixing expansion section pipeline, 8. Oxygen meter, 9. Venturi baffle, 10. Mixing and gas pipeline. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0024] Example 1

[0025] like Figure 1 As shown, a flue gas and air mixing and distribution system for an incinerator comprises an air main pipe 1, one end of the air main pipe 1 is provided with an air fan 2, the side wall of the air main pipe 1 is connected with one end of an air delivery pipe 4, the other end of the air delivery pipe 4 is connected with a flue gas and air mixing expansion section pipe 7 through a mixing and gas pipe 10, a through hole is opened on the side wall of the air delivery pipe 4, a flue gas delivery pipe 5 is arranged in the through hole, a flue gas regulating valve 6 is arranged on the flue gas delivery pipe 5, an oxygen meter 8 (zirconia oxygen meter) is arranged in the mixing and gas pipe 10, and the operating parameters can be adjusted in real time through the indication change of the zirconia oxygen meter, and the oxygen concentration can be adjusted in real time according to the drying, pyrolysis and combustion stages to ensure that the fuel in the incinerator is fully burned and there is no excess oxygen, thereby reducing the generation of nitrogen oxides.

[0026] The angle between the horizontal section of the smoke delivery pipe 5 and the air delivery pipe 4 is a, and the value of a is 16° to 75°. A venturi baffle 9 is provided on the side where the smoke delivery pipe 5 and the air delivery pipe 4 mix and combine, and the angle between the venturi baffle 9 and the horizontal section of the air delivery pipe 4 is b, b=a-15°, and the calculation formula of the length of the venturi baffle 9 is as follows:

[0027]

[0028] Where D is the diameter of the air duct; is the Venturi baffle conversion coefficient, that is, the ratio of the length of the Venturi baffle projected onto the air delivery duct to the diameter of the air delivery duct, and is set at 0.3 to 0.5. The Venturi baffle 9 ensures that the flow rate and pressure in the air delivery duct 4 and the flue gas delivery duct 5 can be adjusted in real time according to the fluctuation of the combustion conditions of the incinerator, ensuring uniform mixing, uniform air distribution, and stable combustion.

[0029] The air fan 2 is a variable frequency fan.

[0030] The air delivery pipeline 4 is provided with an air regulating valve 3 , and an air flow meter is provided on the pipeline between the air regulating valve 3 and the air outlet of the air delivery pipeline 4 .

[0031] A flue gas flow meter and a flue gas oxygen meter are provided on the pipe between the flue gas regulating valve 6 and the smoke outlet of the flue gas conveying pipe 5 .

[0032] After the air and flue gas are mixed, they enter the incinerator furnace through the flue gas air mixing expansion section pipeline 7. By adjusting the frequency of the air fan 2, the opening of the air regulating valve 3 and the opening of the flue gas regulating valve 6, the oxygen concentration of the mixed gas entering the drying section is 7% to 10%, the oxygen concentration of the mixed gas entering the pyrolysis section is 10% to 15%, and the oxygen concentration of the mixed gas entering the combustion section is 15% to 20%. Among them, the oxygen concentration of the mixed gas C 2 The calculation formula is as follows:

[0033]

[0034] In the formula, Q 1 is the value of the air flow meter; Q 2 is the value of the flue gas flow meter; C 1 is the oxygen concentration in the original flue gas.

[0035] When the oxygen concentration of the mixed gas is C 2 When the incinerator is too low and the air volume is insufficient, the frequency of the air fan is increased to maintain a good combustion condition; when the incinerator is fully supplied with air and preheated, the flue gas regulating valve is adjusted to reduce its opening to ensure stable combustion conditions; when the oxygen concentration of the mixed gas C 2 When it is too high and the incinerator is not supplied with enough air, the combustion condition can be maintained stable by increasing the opening of the flue gas regulating valve; when the incinerator is fully supplied with air and preheated, the air fan frequency can be reduced.

[0036] Example 2

[0037] like Figure 2 As shown, the flue gas is introduced into the primary air in sections. Figure 1 The control system layout diagram shows that after the flue gas is mixed in, the physical and chemical reaction processes of different combustion sections can be controlled according to the oxygen concentration displayed by the zirconium oxide oxygen meter at the rear end. The first section is mainly drying, and the oxygen concentration is controlled within 10%. The second section is mainly pyrolysis. By adjusting the primary air and flue gas volume, the oxygen concentration is controlled at 10-15%. The third section is mainly combustion, and the oxygen concentration after mixing is controlled at 15%-18%. At the same time, high-temperature pyrolysis process also occurs in the first half of this section. The fourth section is the main combustion section, and the oxygen concentration is controlled at 17-20% to ensure full combustion of the organic components. Compared with the original air combustion, the oxygen concentration in the entire incinerator has dropped by 3.5%, greatly reducing NO x At the same time, the volatile matter produced by the pyrolysis in the second stage and the NO generated by the combustion in the third and fourth stages x Further reduction reaction occurs, and NO xReduce NO by 50% to achieve source reduction x .

[0038] Example 3

[0039] In a 750t / d waste incinerator in Tianjin, traditional air combustion is used, with six grate sections, of which the first and second sections are drying and preheating units, the third and fourth sections are combustion units, and the fifth and sixth sections are burnout units. x The initial concentration is 380 mg / Nm 3 The oxygen content at the boiler outlet fluctuates between 6 and 9%, and biased burning often occurs. The load fluctuates greatly, fluctuating between 55 and 70 t / h.

[0040] The first four sections were transformed by the control system of the present invention. After the transformation, the oxygen content of the first grate was controlled at 10%, the oxygen content of the second grate was controlled at 12%, the oxygen content of the third grate was controlled at 15%, and the oxygen content of the fourth grate was controlled at 18%. x The average value is about 200mg / Nm 3 , the oxygen content at the boiler outlet is 3.7-5%, the operation is continuous and stable, the boiler load is stable at 68-72t / h, and the reliability is further enhanced. x The emission reduction rate was about 47.3%, and the boiler load increased by an average of 2t / h, an increase of 2.8%.

[0041] Example 4

[0042] In a 300t / d waste incinerator in Shandong, traditional air combustion is used, with five sections of grates, of which the first and second sections are drying and preheating units, the third and fourth sections are combustion units, and the fifth section is the burnout unit. x The initial concentration is 320 mg / Nm 3 The oxygen content at the boiler outlet fluctuates between 7 and 10%, and partial burning often occurs. The load fluctuates greatly, with fluctuations of 17 to 22 t / h.

[0043] The first three sections were transformed by the control system of the present invention. After the transformation, the oxygen content of the first grate was controlled at 10%, the oxygen content of the second grate was controlled at 13%, the oxygen content of the third grate was controlled at 16%, and the fourth grate was introduced with 21% air, NO x The average value is about 176mg / Nm 3 The oxygen content at the boiler outlet is 3.7-4.5%, the operation is continuous and stable, the boiler load is 19-21t / h, the monthly average load increases by 1.1t / h, the boiler load increases by 5.5%, NO x The reduction rate is about 45%.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An incinerator flue gas and air mixing and distribution system, characterized in that: The invention comprises an air main pipe (1), one end of which is provided with an air blower (2), the side wall of the air main pipe (1) is connected with one end of an air delivery pipe (4), the other end of the air delivery pipe (4) is connected with a flue gas-air mixing expansion section pipe (7) through a mixing and gas duct (10), a through hole is provided on the side wall of the air delivery pipe (4), a flue gas delivery pipe (5) is provided in the through hole, a flue gas regulating valve (6) is provided on the flue gas delivery pipe (5), and an oxygen meter (8) is provided in the mixing and gas duct (10).

2. The incinerator flue gas and air mixing and distribution system according to claim 1, characterized in that: The angle between the horizontal section of the smoke conveying pipe (5) and the air conveying pipe (4) is a, and the value of a is 16° to 75°.

3. The incinerator flue gas and air mixing and distribution system according to claim 2, characterized in that: A venturi baffle (9) is provided on the side where the smoke delivery pipe (5) and the air delivery pipe (4) are mixed and discharged. The angle between the venturi baffle (9) and the horizontal section of the air delivery pipe (4) is b, where b=a-15°. The calculation formula for the length of the venturi baffle (9) is as follows: Where D is the diameter of the air duct; It is the baffle conversion coefficient, that is, the ratio of the length of the Venturi baffle projected onto the air delivery pipe to the diameter of the air delivery pipe, and its value is 0.3 to 0.

5.

4. The incinerator smoke and air mixing and distribution system according to claim 1, characterized in that: The air fan (2) is a variable frequency fan.

5. The incinerator smoke and air mixing and distribution system according to claim 1, characterized in that: The air delivery pipeline (4) is provided with an air regulating valve (3), and an air flow meter is provided on the pipeline between the air regulating valve (3) and the air outlet of the air delivery pipeline (4).

6. The incinerator smoke and air mixing and distribution system according to claim 1, characterized in that: A smoke flow meter and a smoke oxygen meter are provided on the pipe between the smoke regulating valve (6) and the smoke outlet of the smoke conveying pipe (5).

7. A method for controlling an air distribution system according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: mixing air and flue gas and then entering the incinerator furnace through the flue gas air mixing expansion section pipeline; adjusting the frequency of the air fan, the opening of the air regulating valve and the opening of the flue gas regulating valve so that the oxygen concentration of the mixed gas entering the drying section is 7% to 10%, the oxygen concentration of the mixed gas entering the pyrolysis section is 10% to 15%, and the oxygen concentration of the mixed gas entering the combustion section is 15% to 20%, wherein the calculation formula of the mixed gas oxygen concentration C2 is as follows: In the formula, Q1 is the value of the air flow meter; Q2 is the value of the flue gas flow meter; C1 is the oxygen concentration in the original flue gas.

8. The control method according to claim 7, characterized in that: The specific control process is: when the oxygen concentration C2 of the mixed gas is low and the air volume of the incinerator is insufficient, the air fan frequency is increased to maintain stable combustion conditions; when the incinerator is sufficiently supplied with air and preheated, the flue gas regulating valve is adjusted to reduce its opening to ensure stable combustion conditions; when the oxygen concentration C2 of the mixed gas is high and the air volume of the incinerator is insufficient, the flue gas regulating valve opening is increased to maintain stable combustion conditions; when the incinerator is sufficiently supplied with air and preheated, the air fan frequency can be reduced.

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