SCR denitration reactor ash removal system control method and ash removal system

Abstract

A control method for an ash removal system of an SCR (Selective Catalytic Reduction) denitration reactor relates to the technical field of SCR denitration, the diameter and spacing of spray holes of a rake-type ash remover and the distance from the rake-type ash remover to a catalyst are set, and the spray holes are alternately controlled by an ash removal compressed air system and an anti-blocking compressed air system, so that the energy consumption of the system is reduced; the deashing compressed air system adjusts the output air volume in real time according to the pressure difference between the two ends of the catalyst, so that the output power of the deashing fan is reduced, energy consumption is further reduced, meanwhile, through the arrangement of the anti-blocking compressed air system, when the deashing compressed air system stops working, dust particles, air molecules and the like are separated, and the deashing effect is improved. And dust particles are destroyed and prevented from being combined on the surface of the catalyst, so that the catalyst is in a suspended fluidized state and is taken away by flue gas or self gravity. The invention further provides an ash removal system of the SCR denitration reactor.

Description

Technical Field

[0001] The present invention relates to the technical field of SCR denitration, and in particular to a control method for a cleaning system of an SCR denitration reactor and a cleaning system applying the control method for a cleaning system of an SCR denitration reactor. Background Art

[0002] The SCR denitrification technology for cement kiln flue gas currently mostly uses a high-temperature and high-dust process, that is, the exhaust gas from the cement kiln directly enters the SCR denitrification system from the outlet of the preheater, and the NO in the flue gas x It is mixed with ammonia injected by the supplementary ammonia injection system, and undergoes reduction reaction through the catalyst to complete the predetermined denitration process. The flue gas after denitration continues to enter the subsequent production process. The flue gas temperature here is 280-350℃, which is suitable for the reaction temperature of most catalysts, and is therefore widely used.

[0003] Since the dust concentration in the flue gas at the cement kiln outlet is very high, there is a risk of clogging the catalyst and accelerating the wear of the catalyst, so a safe and reliable cleaning system is required. The rake + acoustic wave collaborative cleaning technology commonly used in the current cleaning system in the market adopts a cleaning method with small flow and high pressure. Although it can solve the problem of catalyst dust accumulation to a certain extent, there are still blind spots for cleaning, and the energy consumption is high, which restricts the operation continuity of the cement kiln denitrification system. Summary of the invention

[0004] In view of the problems and shortcomings in the prior art, the first object of the present invention is to provide a SCR denitration reactor cleaning system control method, which adopts a large flow and low pressure cleaning method to effectively solve the problems of the existing small flow and high pressure cleaning method, such as the dead corner of cleaning and high energy consumption. The second object of the present invention is to provide a cleaning system using the above-mentioned SCR denitration reactor cleaning system control method.

[0005] The technical solution of the present invention is as follows:

[0006] A control method for a cleaning system of an SCR denitration reactor, the cleaning system comprising a rake-type cleaner arranged above each layer of catalyst, a pressure differential sensor being arranged thereon, the nozzle hole diameter of the rake-type cleaner being 1.5-2.5 mm, the nozzle outlet pressure being 0.08-0.12 MPa, the nozzle being 25-35 mm away from the catalyst surface, the rake-type cleaner being alternately controlled by a cleaning compressed air system and an anti-blocking compressed air system; the cleaning compressed air system comprising a cleaning fan connected to the rake-type cleaner through a first conveying pipe, and a first control valve being arranged on the first conveying pipe; the anti-blocking compressed air system comprising an anti-blocking fan and a second conveying pipe, wherein one end of the second conveying pipe is connected to the anti-blocking fan, and the other end is connected to a pipe section downstream of the first control valve of the first conveying pipe, and a second control valve is arranged thereon;

[0007] The control method comprises the following steps:

[0008] S1, start the system and automatically enter the dust cleaning mode;

[0009] S2, open the first control valve and close the second control valve;

[0010] S3, start the dust cleaning fan;

[0011] S4, determining whether the pressure difference across the catalyst is greater than a first specified value;

[0012] S4a, if it is determined that the pressure difference between the two ends of the catalyst is greater than the first specified value, then enter the high-pressure cleaning mode and adjust the output air volume of the cleaning fan;

[0013] or:

[0014] S4b, if it is determined that the pressure difference across the catalyst is not greater than the first specified value, then enter the low-pressure cleaning mode, reduce the output air volume of the cleaning fan, and determine whether the pressure difference across the catalyst is less than the second specified value;

[0015] If it is determined that the pressure difference across the catalyst is less than the second specified value, the anti-blocking mode is entered and step S5 is executed;

[0016] If it is determined that the pressure difference across the catalyst is not less than the second specified value, step S4b is executed;

[0017] S5, close the first control valve and open the second control valve;

[0018] S6, stop the dust cleaning fan and start the anti-blocking fan.

[0019] According to a specific embodiment, a controller is used to obtain a signal from a pressure difference sensor to determine the pressure difference at both ends of the catalyst, and to control the switch state of the first control valve and the second control valve. The dust cleaning fan adopts an oil-free screw blower, and the anti-blocking fan adopts a centrifugal fan. The controller adopts a PLC controller, and the controller controls the start or stop state of the dust cleaning fan and the anti-blocking fan according to the switch state of the first control valve and the second control valve.

[0020] The first conveying pipe and the second conveying pipe are both provided with pressure sensors for measuring the wind pressure of the first conveying pipe and the second conveying pipe so as to feedback the output air volume of the dust cleaning fan and the anti-blocking fan through the controller. The pressure sensors are respectively located upstream of the first control valve or the second control valve.

[0021] In order to prevent smoke in the SCR reactor from backflowing into the second delivery pipe, a check valve is also provided on the second delivery pipe, located on the pipe section downstream of the second control valve and close to the connection between the second delivery pipe and the first delivery pipe.

[0022] According to a specific embodiment, the end of the first delivery pipe is connected to the rake-type dust collectors of each layer through a plurality of first delivery branches connected in parallel, the end of the second delivery pipe is connected to a plurality of second delivery branches in parallel, the other end of the second delivery branch is connected to the first delivery branch and is located downstream of the first control valve. The check valve is arranged on the second delivery branch and close to the connection with the first delivery branch.

[0023] In order to increase the air volume of the rake dust cleaner, the spray hole density is increased, that is, the spray hole spacing of the rake dust cleaner is 11-12mm. A plurality of rake dust cleaners are arranged in parallel above each layer of catalyst, and are respectively connected to the dust cleaning fan through the first conveying pipe.

[0024] A ash cleaning system for an SCR denitration reactor, the ash cleaning system comprising a rake-type ash cleaner arranged above each layer of catalyst, characterized in that the diameter of the spray hole of the rake-type ash cleaner is 1.5-2.5 mm, the nozzle outlet pressure is 0.08-0.12 MPa, the distance between the nozzle and the catalyst surface is 25-35 mm, and the rake-type ash cleaner is alternately controlled by a ash cleaning compressed air system and an anti-blocking compressed air system;

[0025] The dust cleaning compressed air system includes a dust cleaning fan connected to the rake dust cleaner through a first conveying pipe, and a first control valve is provided on the first conveying pipe;

[0026] The anti-blocking compressed air system includes an anti-blocking fan and a second delivery pipe, wherein one end of the second delivery pipe is connected to the anti-blocking fan, and the other end is connected to the pipe section behind the first control valve of the first delivery pipe, and a second control valve is arranged on the second delivery pipe.

[0027] Optionally, an ultrasonic cleaner can be arranged above the catalyst to clean the catalyst in combination with a rake cleaner, and the rake cleaners on each layer of catalyst are activated separately according to the pressure difference.

[0028] The present invention realizes a cleaning method with large flow and small pressure by setting the diameter and spacing of the spray holes of the rake-type dust cleaner and the distance between the spray holes and the catalyst, and by using an oil-free screw blower to transport airflow to the rake-type dust cleaner through a first conveying pipeline, so as to reduce the wear of the catalyst by the large blowing airflow pressure and increase the service life of the catalyst.

[0029] The rake-type ash cleaner is alternately controlled by the ash cleaning compressed air system and the anti-blocking compressed air system to reduce the energy consumption of the system. At the same time, through the setting of the anti-blocking compressed air system, when the ash cleaning compressed air system stops working, the ash particles and air molecules are separated, destroying and preventing the ash particles from combining on the catalyst surface, making them in a suspended fluidized state so that they can be taken away by the flue gas or its own gravity, reducing the blockage of the catalyst.

[0030] In addition, the cleaning compressed air system adjusts the output air volume in real time according to the pressure difference at both ends of the catalyst, thereby reducing the output power of the cleaning fan and further reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A connection diagram for implementation;

[0032] Figure 2 is a flow chart of the control method;

[0033] 100. SCR reactor; 1. Soot cleaning fan; 2. First control valve; 3. Rake-type soot cleaner; 4. Anti-blocking fan; 5. Second control valve; 6. Sonic soot cleaner; 10. First conveying pipe; 20. Second conveying pipe. DETAILED DESCRIPTION

[0034] The technical means adopted to achieve the predetermined inventive objectives of the present invention will be further described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0035] See also Figure 1 and Figure 2 As shown, Figure 1 It is a connection schematic diagram of the SCR denitration reactor cleaning system of the present invention; Figure 2 The present invention is a flow chart of the SCR denitration reactor cleaning system control method.

[0036] A control method for a cleaning system of an SCR denitration reactor, the cleaning system comprising a rake cleaner 3 arranged above each layer of catalyst, a pressure difference sensor being provided on the rake cleaner 3, a nozzle hole diameter of the rake cleaner 3 being 1.5-2.5 mm, preferably 2 mm, a nozzle outlet pressure of 0.08-0.12 MPa, a nozzle distance of 25-35 mm from the catalyst surface, preferably 30 mm, the rake cleaner 3 being alternately controlled by a cleaning compressed air system and an anti-blocking compressed air system; the cleaning compressed air system comprising a cleaning fan 1, connected to the rake cleaner 3 through a first conveying pipe 10, and a first control valve 2 being provided on the first conveying pipe 10; the anti-blocking compressed air system comprising an anti-blocking fan 4 and a second conveying pipe 20, wherein one end of the second conveying pipe 20 is connected to the anti-blocking fan 4, and the other end is connected to a pipe section downstream of the first control valve 2 of the first conveying pipe 10, and a second control valve 5 is provided on the second conveying pipe 20.

[0037] The design idea of ​​the control method is: the rake-type dust cleaner 3 is alternately controlled by a dust cleaning compressed air system and an anti-blocking compressed air system. When there is a certain amount of smoke, the dust cleaning compressed air system is enabled for cleaning. When the smoke concentration drops to a certain standard, the dust cleaning compressed air system is stopped, and the anti-blocking compressed air system is enabled to stop the cleaning work. At the same time, a small amount of air flow is maintained to enter, destroying and preventing ash particles from combining on the catalyst surface, making it in a suspended state, and preventing smoke particles from blocking and entering the rake-type dust cleaner 3.

[0038] The cleaning compressed air system adjusts the output power of the soot blower through the pressure difference at both ends of the catalyst, thereby controlling its output air volume, i.e., the air volume and pressure of the spray hole of the rake-type soot cleaner 3, i.e., when the smoke concentration in the SCR reactor 100 is high, the air volume is increased, and when the smoke concentration is low, the air volume is decreased, thereby reducing the power consumption of the cleaning fan 1. At the same time, in the first working condition, if Figure 2 As shown, the smoke concentration in the SCR reactor 100 is relatively high, and the high-efficiency cleaning mode, i.e., the high-pressure cleaning mode, is selected. The corresponding processing steps are: S1, start the system and automatically enter the cleaning mode; S2, open the first control valve 2, and close the second control valve 5; S3, start the cleaning fan 1; S4a, determine that the pressure difference at both ends of the catalyst is greater than the first specified value, enter the high-pressure cleaning mode, and adjust the output air volume of the cleaning fan 1. The catalyst is cleaned at high pressure, and the pressure difference measurement and high-pressure cleaning work at both ends of the catalyst are cyclically performed until the pressure difference at both ends of the catalyst is not greater than the first specified value. Among them, the first specified value is usually any value between 105-115Pa.

[0039] In the second working condition, the smoke concentration in the SCR reactor 100 is low, and the low power consumption mode, i.e., the low pressure cleaning mode, is selected. The corresponding processing steps are: S1, start the system and automatically enter the cleaning mode; S2, open the first control valve 2, and close the second control valve 5; S3, start the cleaning fan 1; S4b, determine that the pressure difference at both ends of the catalyst is not greater than the first specified value, enter the low pressure cleaning mode, reduce the output air volume of the cleaning fan 1, and perform the cleaning work; after working for a period of time, measure the pressure difference at both ends of the catalyst again, determine that the pressure difference at both ends of the catalyst is not less than the second specified value, and execute step S4b. That is, if the pressure difference at both ends of the catalyst is not less than the second specified value, low pressure cleaning will continue. Among them, the second specified value is usually any value between 85-95Pa.

[0040] In the third operating condition, after the dust cleaning system has been running for a period of time, the smoke concentration decreases and enters the anti-blocking mode. The anti-blocking fan 4 continuously outputs positive pressure airflow through the second conveying pipe 20 and the first conveying pipe 10 to the nozzle of the rake soot blower, thereby destroying and preventing the ash particles from combining on the catalyst surface, so that the smoke at both ends of the catalyst is always in a suspended fluidized state so that it can be carried away by the flue gas or its own gravity; at the same time, the smoke is prevented from flowing back through the nozzle of the rake soot cleaner 3 into the first conveying pipe 10 and the second conveying pipe 20, thereby blocking the first conveying pipe 10 and the second conveying pipe 20. The corresponding processing steps are: S1, start the system and automatically enter the cleaning mode; S2, open the first control valve 2, and close the second control valve 5; S3, start the cleaning fan 1; S4b, determine that the pressure difference at both ends of the catalyst is not greater than the first specified value, enter the low-pressure cleaning mode, lower the output air volume of the cleaning fan 1, and perform the cleaning work; after working for a period of time, measure the pressure difference at both ends of the catalyst again, determine that the pressure difference at both ends of the catalyst is less than the second specified value, and enter the anti-blocking mode; S5, close the first control valve 2, and open the second control valve 5; S6, stop the cleaning fan 1, and start the anti-blocking fan 4.

[0041] According to a specific embodiment, a controller is used to obtain a signal from a pressure difference sensor to determine the pressure difference at both ends of the catalyst, and to control the switch state of the first control valve 2 and the second control valve 5. The dust cleaning fan 1 adopts an oil-free screw blower, and its rated working pressure is 0.15MPa, the anti-blocking fan 4 adopts a centrifugal fan, and the controller adopts a PLC controller. The controller controls the start or stop state of the dust cleaning fan 1 and the anti-blocking fan 4 according to the switch state of the first control valve 2 and the second control valve 5.

[0042] The first conveying pipe 10 and the second conveying pipe 20 are both provided with pressure sensors for measuring the wind pressure of the first conveying pipe 10 and the second conveying pipe 20 so as to feed back the output air volume of the dust cleaning fan 1 and the anti-blocking fan 4 through the controller. The pressure sensors are respectively located upstream of the first control valve 2 or the second control valve 5.

[0043] In order to prevent the smoke in the SCR reactor 100 from backflowing into the second delivery pipe 20 , a check valve is further provided on the second delivery pipe 20 , which is located on the pipe section downstream of the second control valve 5 and close to the connection between the second delivery pipe 20 and the first delivery pipe 10 .

[0044] According to a specific embodiment, the end of the first delivery pipe 10 is connected to each layer of rake-type dust collectors 3 through a plurality of first delivery branches connected in parallel, and the end of the second delivery pipe 20 is connected to a plurality of second delivery branches in parallel, and the other end of the second delivery branch is connected to the first delivery branch and is located downstream of the first control valve 2. The check valve is arranged on the second delivery branch and close to the connection with the first delivery branch.

[0045] In order to increase the air volume of the rake dust cleaner 3, the nozzle density is increased, that is, the nozzle spacing of the rake dust cleaner 3 is 11-12mm, preferably 11.2mm, and the nozzles are conical holes. A plurality of rake dust cleaners 3 are arranged in parallel above each layer of catalyst, and are connected to the dust cleaning fan 1 through the first conveying pipe 10 respectively.

[0046] The present invention also discloses a ash cleaning system for an SCR denitration reactor, the ash cleaning system comprises a rake-type ash cleaner 3 arranged above each layer of catalyst, the diameter of the spray hole of the rake-type ash cleaner 3 is 1.5-2.5 mm, preferably 2 mm, the nozzle outlet pressure is 0.08-0.12 MPa, the distance between the nozzle and the catalyst surface is 25-35 mm, preferably 30 mm, and the rake-type ash cleaner 3 is alternately controlled by a ash cleaning compressed air system and an anti-blocking compressed air system;

[0047] The cleaning compressed air system includes a cleaning fan 1, which is connected to a rake type cleaner 3 through a first conveying pipe 10, and a first control valve 2 is provided on the first conveying pipe 10. The cleaning fan is preferably an oil-free screw blower, and its rated working pressure is 0.15 MPa.

[0048] The anti-blocking compressed air system includes an anti-blocking fan 4 and a second delivery pipe 20, wherein one end of the second delivery pipe 20 is connected to the anti-blocking fan 4, and the other end is connected to the pipe section behind the first control valve 2 of the first delivery pipe 10, and a second control valve 5 is provided thereon.

[0049] Finally, it should be noted that the attached drawings of the embodiments are only used to illustrate the main working principles and cannot be understood as limiting the present invention. For example, although the low-pressure and low-distance rake-type cleaning implementation scheme of the present invention can be used to clean without the assistance of sound waves, the present invention does not require the cancellation of the ultrasonic cleaner. Therefore, an ultrasonic cleaner 6 is also illustrated above the catalyst. As an optional solution, the ultrasonic cleaner 6 assists the rake-type cleaner 3 in cleaning the catalyst. For another example, although it is not illustrated in the attached drawings, in a new technical improvement scheme, a countercurrent feedback pipeline controlled by a solenoid valve can be added between the flue gas outlet and the flue gas inlet of the catalyst. According to the pre-established influence curve of the cleaning pressure of the rake-type cleaner on the pressure difference at both ends of the catalyst, the solenoid valve opening is controlled in real time to offset and adjust the pressure difference at both ends of the catalyst, which can further improve the response accuracy.

[0050] The above is a preferred embodiment of the present invention, but the present invention is not limited to the above embodiments and examples. Various changes, equivalent substitutions, improvements, etc. made within the scope of knowledge of those skilled in the art without departing from the concept of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling a cleaning system of an SCR denitration reactor, wherein the cleaning system comprises a rake-type cleaner (3) arranged above each layer of catalyst, on which a pressure difference sensor is arranged, characterized in that: The diameter of the spray hole of the rake-type dust collector is 1.5-2.5 mm, the nozzle outlet pressure is 0.08-0.12 Mpa, the distance between the nozzle and the catalyst surface is 25-35 mm, and the rake-type dust collector is alternately controlled by a dust cleaning compressed air system and an anti-blocking compressed air system; The ash cleaning compressed air system comprises an ash cleaning fan (1), which is connected to a rake-type ash cleaner (3) via a first delivery pipe (10), and a first control valve (2) is provided on the first delivery pipe (10); the anti-blocking compressed air system comprises an anti-blocking fan (4) and a second delivery pipe (20), wherein one end of the second delivery pipe (20) is connected to the anti-blocking fan (4), and the other end is connected to a pipe section downstream of the first control valve (2) of the first delivery pipe, and a second control valve (5) is provided on the second delivery pipe; The control method comprises the following steps: S1, start the system and automatically enter the dust cleaning mode; S2, open the first control valve (2) and close the second control valve (5); S3, start the dust cleaning fan (1); S4, determining whether the pressure difference across the catalyst is greater than a first specified value; S4a, if it is determined that the pressure difference between the two ends of the catalyst is greater than the first specified value, then entering the high-pressure cleaning mode, and adjusting the output air volume of the cleaning fan (1); or: S4b, if it is determined that the pressure difference across the catalyst is not greater than the first specified value, then entering the low-pressure cleaning mode, lowering the output air volume of the cleaning fan (1), and determining whether the pressure difference across the catalyst is less than the second specified value; If it is determined that the pressure difference across the catalyst is less than the second specified value, the anti-blocking mode is entered and step S5 is executed; If it is determined that the pressure difference across the catalyst is not less than the second specified value, step S4b is executed; S5, close the first control valve (2) and open the second control valve (5); S6, stop the dust cleaning fan (1) and start the anti-blocking fan (4).

2. The dust cleaning system control method according to claim 1, characterized in that: A controller is used to obtain a signal from a pressure difference sensor to determine the pressure difference across the catalyst, and to control the switching states of the first control valve (2) and the second control valve (5).

3. The dust cleaning system control method according to claim 1, characterized in that: The dust cleaning fan (1) is an oil-free screw blower, the anti-blocking fan (4) is a centrifugal fan, and the controller is a PLC controller. The controller controls the start or stop state of the dust cleaning fan (1) and the anti-blocking fan (4) according to the switch state of the first control valve and the second control valve.

4. The dust cleaning system control method according to claim 1, characterized in that: The first conveying pipe (10) and the second conveying pipe (20) are both provided with pressure sensors for measuring the wind pressure of the first conveying pipe (10) and the second conveying pipe (20), thereby feeding back the output air volume of the dust cleaning fan (1) and the anti-blocking fan (4) through the controller.

5. The dust cleaning system control method according to claim 4, characterized in that: The pressure sensor is located upstream of the first control valve (2) or the second control valve (5), respectively.

6. The dust cleaning system control method according to claim 5, characterized in that: The second delivery pipe (20) is also provided with a check valve, which is located on the pipe section downstream of the second control valve (5) and close to the connection between the second delivery pipe (20) and the first delivery pipe (10).

7. The dust cleaning system control method according to claim 6, characterized in that: The end of the first conveying pipe (10) is connected to each layer of rake-type dust collectors (3) through a plurality of first conveying branch pipes connected in parallel, and the end of the second conveying pipe (20) is connected to a plurality of second conveying branch pipes in parallel, and the other end of the second conveying branch pipe is connected to the first conveying branch pipe and is located downstream of the first control valve (2).

8. The dust cleaning system control method according to claim 1, characterized in that: The spray hole spacing of the rake-type dust collector (3) is 11-12 mm.

9. The dust cleaning system control method according to claim 8, characterized in that: A plurality of rake-type dust cleaners (3) are arranged in parallel above each layer of catalyst and are respectively connected to the dust cleaning fan (1) via a first conveying pipe (10).

10. A SCR denitration reactor cleaning system, characterized in that: The cleaning system comprises a rake-type cleaner (3) arranged above each layer of catalyst, characterized in that the diameter of the nozzle of the rake-type cleaner (3) is 1.5-2.5 mm, the nozzle outlet pressure is 0.08-0.12 Mpa, the distance between the nozzle and the catalyst surface is 25-35 mm, and the rake-type cleaner (3) is alternately controlled by a cleaning compressed air system and an anti-blocking compressed air system; The ash cleaning compressed air system comprises an ash cleaning fan (1), which is connected to a rake-type ash cleaner (3) via a first conveying pipe (10), and a first control valve (2) is provided on the first conveying pipe (10); The anti-blocking compressed air system comprises an anti-blocking fan (4) and a second delivery pipe (20), wherein one end of the second delivery pipe (20) is connected to the anti-blocking fan (4), and the other end is connected to the pipe section behind the first control valve (2) of the first delivery pipe (10), and a second control valve (5) is provided on the second delivery pipe.

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