Urea pyrolyzing furnace metering distribution system with flow balance control function and control method

Abstract

The invention discloses a urea pyrolyzing furnace metering distribution system with flow balance control and a control method, and belongs to the technical field of flue gas denitration urea pyrolyzing furnaces. The system comprises a urea pyrolyzing furnace, the urea pyrolyzing furnace is connected with a group of adjustable and controllable spray gun modules, each adjustable and controllable spray gun module comprises a spray gun with a spray opening formed in the urea pyrolyzing furnace, and a first inlet of each spray gun communicates with a urea solution conveying channel; and a branch pneumatic switch valve, a spray gun branch pneumatic control valve and a spray gun branch urea solution flow meter are arranged on the spray branch pipe. Based on the structural design of the multi-branch spray gun module, corresponding balance control logic and a spray gun flow PID control program are matched, so that the automatic switching of the quantity of spray guns and the balance control of the spray flow of the metering distribution system along with the load change of the boiler can be realized; the problem that when the boiler is in low load, multiple spray guns operate at the same time, the spraying flow is low, and consequently atomization is uneven is solved, the efficiency of the urea pyrolyzing furnace is improved, and the probability that non-pyrolyzed urea forms crystals at the tail of the pyrolyzing furnace and an outlet pipeline is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas denitration urea pyrolysis furnaces, and in particular relates to a flow balance controlled urea pyrolysis furnace metering and distribution system and a control method. Background Art

[0002] Urea pyrolysis ammonia production technology is widely used in domestic SCR denitrification systems due to its mature technology and high efficiency. The system process flow is: solid urea is prepared into a urea solution with a mass fraction concentration of 45-55%, and is transported to the metering and distribution system through a urea solution circulation pump. The metering and distribution system distributes the spray gun flow according to the control logic instructions and then sprays the urea solution evenly into the pyrolysis furnace, decomposing it into NH3, H2O and CO2 at high temperature. This decomposition process is mixed with high-temperature dilution air to generate ammonia with a concentration of less than 5%, which is then sprayed into the SCR flue gas denitrification reactor to complete the denitrification reaction. In the traditional urea pyrolysis furnace metering and distribution system, each distribution circuit adopts a control method of synchronously adjusting the flow rate of urea solution. When the boiler load is reduced, the spray gun is not shut down, the number of running spray guns is reduced, and the flow rate of a single spray gun is increased. As a result, the flow rate of a single spray gun is too low, resulting in poor spray gun atomization effect, part of the urea is not completely pyrolyzed, and the efficiency of the urea pyrolysis furnace is reduced. At the same time, the unpyrolyzed urea forms crystals at the tail of the pyrolysis furnace and the outlet pipe, affecting the normal operation of the system. Due to incomplete pyrolysis and crystal blockage, it may be necessary to increase the frequency of maintenance and cleaning, which not only increases the investment of manpower and material resources, but also may affect the normal operation time and efficiency of the equipment, thereby increasing the operating cost. Summary of the invention

[0003] The object of the present invention is to provide a urea pyrolysis furnace metering and distribution system and a control method with flow balance control, so as to solve the problem of uneven urea atomization distribution caused by the reduction of urea solution flow rate of the spray gun of the urea pyrolysis furnace system after the boiler load is reduced.

[0004] The present invention provides the following technical solution: a flow balance controlled urea pyrolysis furnace metering and dispensing system, comprising a urea pyrolysis furnace, the urea pyrolysis furnace being connected with a group of adjustable spray gun modules used in conjunction with each other for controlling the feeding of urea solution into the urea pyrolysis furnace, the adjustable spray gun module comprising a spray gun with a spray port arranged inside the urea pyrolysis furnace, a first inlet of the spray gun being connected with a urea solution delivery channel through a spray branch pipe, the spray branch pipe being provided with a branch pneumatic switch valve, a spray gun line pneumatic regulating valve and a spray gun line urea solution flow meter.

[0005] Furthermore, the second inlet of the spray gun is connected to a compressed air channel for urea atomization, and the third inlet is connected to a compressed air channel for shutdown purging.

[0006] Furthermore, the branch pneumatic switch valve, the spray gun circuit pneumatic regulating valve and the spray gun circuit urea solution flow meter are arranged in sequence along the injection flow direction of the injection branch pipe.

[0007] Furthermore, a desalted water channel is connected to the pipeline between the branch pneumatic switch valve and the spray gun line pneumatic regulating valve.

[0008] Furthermore, at least one adjustable spray gun module is put into operation in the system.

[0009] Furthermore, the urea pyrolysis furnace is connected with a spare spray gun assembly, and the spare spray gun assembly has the same structure as the adjustable spray gun module.

[0010] Furthermore, the inlet of the urea pyrolysis furnace is connected to a hot air channel, and the outlet is connected to an ammonia spraying grid.

[0011] A control method for a urea pyrolysis furnace metering and distribution system with flow balance control, using three spray guns and one spare spray gun, comprises the following steps:

[0012] S1. The pyrolysis furnace system is put into automatic operation and enters low-load operation mode:

[0013] According to the denitrification inlet NO X The total amount of urea solution injection calculated value N required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. When the pyrolysis furnace enters the low-load operation mode, the two-spray gun operation mode is adopted, and the calculated value of the urea solution injection amount of a single spray gun is set to control the flow rate of the single spray gun within the flow range with the best atomization effect.

[0014] S2, the pyrolysis furnace is in low load operation mode and enters high load operation mode: according to the denitrification inlet NO X The total amount of urea solution injection calculated value N required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. When the pyrolysis furnace enters the high-load operation mode, the third spray gun module is also put into operation. At the same time, the urea solution injection amount setting value of a single spray gun is adjusted to control the flow rate of a single spray gun within the flow range with the best atomization effect.

[0015] S3, the pyrolysis furnace is in high load operation mode, enters low load operation mode: according to the denitrification inlet NO X The total urea injection amount N required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitrification efficiency. The N value is judged. When the pyrolysis furnace enters the low-load operation mode, the third spray gun module is shut down. At the same time, the set value of the urea solution injection amount of a single spray gun is adjusted to control the flow rate of a single spray gun within the flow range with the best atomization effect.

[0016] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The present invention arranges urea pneumatic regulating valves and branch urea solution flowmeters in each branch of the metering and distributing system of the urea pyrolysis furnace, and combines balanced control logic, a spray gun flow PID control program and other technical means to realize automatic switching of the number of spray guns and balanced control of the injection flow of the metering and distributing system following the change of boiler load, thereby improving the problem of uneven atomization caused by low injection flow when multiple spray guns are running simultaneously when the boiler is under low load, improving the efficiency of the urea pyrolysis furnace, and reducing the probability of unpyrolyzed urea forming crystals at the tail of the pyrolysis furnace and in the outlet pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the system of the present invention;

[0019] Figure 2 It is a schematic diagram of the flow balance control structure of the pyrolysis furnace spray gun of the present invention;

[0020] Figure 3 This is a schematic diagram of the spray gun flow PID control process used in the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments of the specification. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0023] See also Figure 1-3 A urea pyrolysis furnace metering and distribution system with flow balance control includes a urea pyrolysis furnace 1, a plurality of groups of adjustable spray gun modules and spare spray gun assemblies. In this embodiment, three groups of adjustable spray gun modules and one group of spare spray gun assemblies are used for illustration.

[0024] Specifically, the upper inlet of the urea pyrolysis furnace 1 is connected to a hot air channel, and the bottom outlet is connected to an ammonia spraying grid.

[0025] Specifically, the adjustable spray gun module includes a spray gun 5, which is arranged on the urea pyrolysis furnace 1, and its spray port is located in the internal cavity of the urea pyrolysis furnace 1. Its first inlet is connected to the urea solution delivery channel through the injection branch pipe 6, and the injection branch pipe 6 is provided with a branch pneumatic switch valve 2, a spray gun line pneumatic regulating valve 3 and a spray gun line urea solution flowmeter 4 in sequence along the delivery direction of the urea solution; and the injection branch pipe 6 is connected to the desalted water delivery channel through a pipeline between the branch pneumatic switch valve 2 and the spray gun line pneumatic regulating valve 3.

[0026] Specifically, the second and third inlets of the spray gun 5 are both connected to the compressed air delivery channel, which are used for urea atomization and shutdown purging of the spray gun 5 respectively.

[0027] In this embodiment, the waste heat boiler is operated at 100% BMCR load. X Concentration and denitration efficiency calculation: Taking the calculated value of 120kg / h as an example, the spray volume of 50% urea solution required by the pyrolysis furnace corresponding to the SCR reactor is 3 in use and 1 in reserve, and the rated flow rate of the spray gun is 50kg / h;

[0028] The working steps of the system in this embodiment are as follows:

[0029] S1. The pyrolysis furnace system meets the commissioning conditions and has been put into automatic operation state, entering the low-load operation mode: according to the denitrification inlet NO X The total amount of urea solution injection required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. If the total amount of urea solution injection is 40≤N≤80kg / h, the delay is 60S, and the pyrolysis furnace enters the low-load operation mode. The 2-gun operation mode is adopted. The urea solution injection amount of the single gun 5 is calculated as N / 2kg / h, so that the flow rate of the single gun 5 is controlled in the flow rate range with the best atomization effect; the gun operation sequence control steps are as follows: open the branch pneumatic switch valve 2 in the first gun module and the second gun module at the same time, open the branch regulating valve 3 in the two modules to 30% opening, and operate the flow PID control program of the two modules at the same time ( Figure 3 ), the urea solution injection amount of the spray gun 5 is set to SP=N / 2kg / h, and the urea solution injection amount of the spray gun 5 is controlled in real time according to the change of boiler load.

[0030] S2, the pyrolysis furnace is in low load operation mode and enters high load operation mode: according to the denitrification inlet NO XThe total amount of urea solution injection required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. If the total amount of urea solution injection N>80kg / h, the delay is 120S, the pyrolysis furnace enters the high-load operation mode, and the third spray gun module is also put into operation. At the same time, the urea solution injection amount setting value of the single spray gun 5 is adjusted to N / 3kg / h, so that the flow rate of the single spray gun 5 is controlled in the flow rate range with the best atomization effect; the sequential control steps are as follows: open the branch pneumatic switch valve 2 of the third spray gun module, open the branch regulating valve 3 in the third spray gun module to 30% opening, and put the flow PID control program of the third spray gun module into operation ( Figure 3 ), the urea solution injection amount setting values ​​of the three spray gun modules are all adjusted to SP=N / 3kg / h, and the urea solution injection amount of spray gun 5 is controlled in real time according to the change of boiler load.

[0031] S3, the pyrolysis furnace is in high load operation mode, enters low load operation mode: according to the denitrification inlet NO X The total urea injection amount N required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. If the urea injection amount is 40≤N≤80kg / h, the delay is 60S, the pyrolysis furnace enters the low-load operation mode, the third spray gun module is shut down, and the single spray gun urea solution injection amount setting value is adjusted to N / 2kg / h, so that the flow rate of the single spray gun 5 is controlled in the optimal flow rate range for atomization effect; the sequential control steps are as follows: close the branch pneumatic switch valve 2 in the third spray gun module, remove the spray gun flow PID control program ( Figure 3 ), open the branch regulating valve 3 in the third spray gun module to 0% opening, adjust the urea solution injection amount setting values ​​of the first and second spray gun modules to SP=N / 2kg / h, and control the urea solution injection amount of the spray gun 5 in real time according to the change of boiler load.

[0032] 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. A urea pyrolysis furnace metering and distribution system with flow balance control, characterized in that: The invention comprises a urea pyrolysis furnace (1), wherein a group of adjustable spray gun modules for use in conjunction with the urea pyrolysis furnace (1) and for controlling the feeding of urea solution into the urea pyrolysis furnace (1) are connected to the urea pyrolysis furnace (1), wherein the adjustable spray gun module comprises a spray gun (5) with a spray port arranged inside the urea pyrolysis furnace (1), wherein a first inlet of the spray gun (5) is connected to a urea solution delivery channel via a spray branch pipe (6), and wherein a branch pneumatic switch valve (2), a spray gun line pneumatic regulating valve (3) and a spray gun line urea solution flow meter (4) are arranged on the spray branch pipe (6).

2. A urea pyrolysis furnace metering and distribution system with flow balance control according to claim 1, characterized in that: The second inlet of the spray gun (5) is connected to a compressed air channel for urea atomization, and the third inlet is connected to a compressed air channel for shutdown purging.

3. The urea pyrolysis furnace metering and distribution system with flow balance control according to claim 2 is characterized in that: The branch pneumatic switch valve (2), the spray gun line pneumatic regulating valve (3) and the spray gun line urea solution flow meter (4) are arranged in sequence along the spray flow direction of the spray branch pipe (6).

4. The urea pyrolysis furnace metering and distribution system with flow balance control according to claim 3 is characterized in that: A desalted water channel is connected to the pipeline between the branch pneumatic switch valve (2) and the gun spray line pneumatic regulating valve (3).

5. The urea pyrolysis furnace metering and distribution system with flow balance control according to claim 4 is characterized in that: At least one adjustable spray gun module is put into operation in the system.

6. The urea pyrolysis furnace metering and distribution system with flow balance control according to claim 1 is characterized in that: The urea pyrolysis furnace (1) is connected to a spare spray gun assembly, and the spare spray gun assembly has the same structure as the adjustable spray gun module.

7. A urea pyrolysis furnace metering and distribution system with flow balance control according to any one of claims 1 to 6, characterized in that: The inlet of the urea pyrolysis furnace (1) is connected to a hot air channel, and the outlet is connected to an ammonia spraying grid.

8. The control method of a urea pyrolysis furnace metering and distribution system with flow balance control according to claim 7 is characterized in that: Using three spray guns (5) and one spare spray gun, the process includes the following steps: S1. The pyrolysis furnace system is put into automatic operation and enters low-load operation mode: According to the denitrification inlet NO X The total amount of urea solution injection calculated value N required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency, and the N value is judged. When the pyrolysis furnace enters a low-load operation mode, a two-spray gun operation mode is adopted, and the calculated value of the urea solution injection amount of a single spray gun (5) is set so that the flow rate of the single spray gun (5) is controlled within the flow rate range with the best atomization effect; S2, the pyrolysis furnace is in low load operation mode and enters high load operation mode: according to the denitrification inlet NO X The total amount of urea solution sprayed by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. When the pyrolysis furnace enters a high-load operation mode, the third spray gun module is also put into operation. At the same time, the urea solution spray amount setting value of the single spray gun (5) is adjusted so that the flow rate of the single spray gun (5) is controlled within the flow rate range with the best atomization effect. S3, the pyrolysis furnace is in high load operation mode, enters low load operation mode: according to the denitrification inlet NO X The total amount of urea solution injection calculated value N required by the pyrolysis furnace corresponding to the SCR reactor is calculated based on the concentration and denitration efficiency. The N value is judged. When the pyrolysis furnace enters the low-load operation mode, the third spray gun module is shut down, and the set value of the urea solution injection amount of the single spray gun is adjusted at the same time, so that the flow rate of the single spray gun (5) is controlled within the flow rate range with the best atomization effect.

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