System and method for controlling operation of denitrated urea ammonia preparation hydrolyzer

Abstract

The invention discloses a denitration urea ammonia preparation hydrolyzer operation control system and a control method. The system comprises a hydrolysis reactor I, a hydrolysis reactor II, a denitration generator set I and a denitration generator set II, wherein the hydrolysis reactor I and the hydrolysis reactor II are arranged in parallel, and the denitration generator set I and the denitration generator set II correspond to each other. Wherein an ammonia outlet of the hydrolysis reactor I is connected with a denitration generator set I through an ammonia supply main pipeline I provided with an outlet valve I, and an ammonia outlet of the hydrolysis reactor II is in butt joint with a denitration generator set II through an ammonia supply main pipeline II provided with an outlet valve II; and a communication pipe for bidirectional fluid communication is arranged between the two ammonia supply main pipelines, and the pipeline is provided with an intelligent isolating valve, so that the opening and closing states of a medium conveying passage can be accurately regulated and controlled. The system intelligently selects a single-machine operation mode or a double-machine operation mode through a load response mechanism based on real-time load parameters of the denitration generator set, and realizes flexible switching of point-to-point independent ammonia supply or cross-system combined ammonia supply between the hydrolysis reactor and the generator set by means of valve cooperative control.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas denitrification engineering, and particularly relates to an SCR denitrification system operation control device and control method based on urea hydrolysis to produce ammonia, which is applicable to the nitrogen oxide reduction system of coal-fired power plants and industrial boilers. Background Art

[0002] The SCR denitrification technology mainly uses liquid ammonia, ammonia water or urea as a reducing agent to produce ammonia, and carries out a denitrification reduction reaction under the action of a catalyst. Among them, using liquid ammonia evaporation to prepare ammonia has the cheapest investment, the lowest transportation and use costs, but the liquid ammonia system has major safety hazards and safety accidents occur frequently; the investment, operation and transportation costs of the ammonia water system are all very high, which is safer than liquid ammonia, but there are still certain safety hazards; the investment and operation costs of the urea system are relatively high compared with the liquid ammonia system, but the transportation costs are comparable, and the urea system basically has no safety hazards and is the safest ammonia preparation technology.

[0003] The urea solution is heated and pressurized by a hydrolyzer and decomposed into ammonia and carbon dioxide. The existing urea hydrolysis to ammonia systems mostly adopt a fixed configuration operation mode, which has the following defects:

[0004] 1. When the load fluctuates, the ammonia supply regulation response lags, affecting the denitrification efficiency;

[0005] 2. The redundant configuration of equipment leads to too high energy consumption;

[0006] 3. The operation mode switching requires manual intervention, which has operation risks;

[0007] 4. The standby equipment cannot maintain a hot standby state, and the restart takes time and energy;

[0008] In view of the above problems, a solution is proposed below. Summary of the Invention

[0009] In view of the technical limitations of the existing urea hydrolysis to ammonia systems, the present invention proposes an operation control system with dynamic load response ability and intelligent switching function, and realizes the seamless switching and energy efficiency optimization of the ammonia supply system by constructing a cooperative operation mechanism of dual hydrolysis reactors.

[0010] The above technical objectives of the present invention are achieved through the following technical solutions:

[0011] A running control system for a denitrification urea ammonia hydrolysis device, comprising a first hydrolysis reactor, a first denitrification generator set, a second hydrolysis reactor and a second denitrification generator set; the ammonia outlets of the first hydrolysis reactor and the second hydrolysis reactor are respectively communicated with the first denitrification generator set and the second denitrification generator set through a first ammonia supply pipeline and a second ammonia supply pipeline; a flexible switching module is connected between the first ammonia supply pipeline and the second ammonia supply pipeline to form a two-way fluid communication loop, and the flexible switching module includes a connecting pipe erected between the two pipelines, and an isolation regulating valve for dynamically adjusting and controlling the pipeline connection state is arranged on the connecting pipe; load response control modules and hot standby maintaining devices are arranged on both the first hydrolysis reactor and the second hydrolysis reactor.

[0012] Further, pressure relief branches are integrated on both the first ammonia supply pipeline and the second ammonia supply pipeline, pressure relief control valves are installed on the pressure relief branches, and steam purging devices are connected.

[0013] Further, both the first hydrolysis reactor and the second hydrolysis reactor are communicated with a urea tank through a urea solution supply pipeline; a urea solution inlet valve is arranged at the terminal of the urea solution supply pipeline, and a urea solution circulation loop is arranged in parallel on the urea solution supply pipeline.

[0014] Further, the hot standby maintaining device includes a temperature reduction and pressure reduction integrated device, the hydrolysis reactor is communicated with the corresponding temperature reduction and pressure reduction integrated device through a steam transmission pipeline, and a steam inlet valve is arranged at the terminal of the steam transmission pipeline.

[0015] Further, a tracing device is connected to the connecting pipe.

[0016] Further, outlet valves are arranged at the ammonia outlet sections of both the first hydrolysis reactor and the second hydrolysis reactor.

[0017] Further, the load response control module adopts a load-ammonia supply coupling algorithm and a feedforward compensation mechanism before the switching process built in the DCS industrial control system.

[0018] A control method for a running control system of a denitrification urea ammonia hydrolysis device adopts dual-mode running control, and the dual-mode running control includes a single-machine running control mode and a dual-machine running control mode;

[0019] When the unit load ≤ a preset threshold value, the single-machine running control mode is adopted, one of the hydrolysis reactors is selected as the main running hydrolysis reactor, and the other is used as the standby hydrolysis reactor; the dynamic transfer of the ammonia supply load of the two units is realized through a regulating valve, and the standby hydrolysis reactor maintains the hot standby state; the specific steps are as follows:

[0020] S1: Check the tracing of the connecting pipe between the two groups of hydrolysis reactors;

[0021] S2: The NOX concentration at the outlet of the denitration reactors of the two sets of denitration generating units is controlled below the design value, and stable operation is maintained for no less than the preset time threshold.

[0022] S3: Open the isolation regulating valve between the two hydrolysis reactors.

[0023] S4: The two hydrolysis reactors operate in parallel. According to the actual working conditions, reduce the ammonia supply of the standby hydrolysis reactor, and at the same time increase the ammonia supply of the main operating hydrolyzer.

[0024] S5: Close the steam inlet valve, urea solution inlet valve and outlet valve of the standby hydrolysis reactor, and maintain it in a hot standby state. The ammonia steam generated by the reaction of the main operating hydrolyzer is used for the two denitration generating units.

[0025] When the unit load > the preset threshold, switch the single-unit operation control mode to the dual-unit operation control mode. The two hydrolyzers operate independently, and the NOx concentration is monitored in real time. Establish a mechanism for judging the preparatory conditions for mode switching. The specific steps are as follows:

[0026] S1: Open the steam inlet valve and urea solution inlet valve of the standby hydrolysis reactor, and raise the temperature and pressure of the hydrolyzer to the set value.

[0027] S2: The inlet and outlet NOX concentrations of the reactors of the two sets of denitration generating units are controlled below the design value, and stable operation is maintained for no less than the set time threshold.

[0028] S3: Open the outlet valve on the standby hydrolysis reactor.

[0029] S4: The two hydrolysis reactors operate in parallel. According to the actual working conditions, slowly reduce the ammonia supply of the main operating hydrolysis reactor, and at the same time increase the ammonia supply of the standby hydrolysis reactor.

[0030] S5: Close the isolation regulating valve between the two hydrolysis reactors, and the two sets of hydrolysis reactors respectively control the operation of the corresponding denitration generating units.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1) The system of the present invention is based on the design of a two-way fluid communication loop. With the help of the set valves, coordinated control realizes the flexible switching between "point-to-point" independent ammonia supply or "cross-system" combined ammonia supply between the hydrolysis reactor and the generating unit, and realizes the single-unit or dual-unit operation mode.

[0033] 2) In the present invention, according to the real-time load of the denitration generator set, the operation mode can be intelligently selected. When the load is low, only one hydrolysis reactor is required to supply ammonia to two units, reducing the operation of redundant equipment and lowering energy consumption; through the setting of the hot standby maintenance device, the standby reactor is kept in a hot standby state, avoiding the energy consumption of reheating and boosting pressure during cold start; through the load-ammonia supply coupling algorithm and the feedforward compensation mechanism, the ammonia supply amount is matched with the demand in real time, reducing the energy waste caused by excessive ammonia supply;

[0034] 3) In the present invention, when operating alone at low load, the number of starts and stops can be reduced, avoiding frequent equipment switching, and reducing mechanical wear and the accumulation of thermal stress; the ammonia supply pipeline is integrated with a pressure relief branch pipe and a steam purging device, which can prevent damage to the equipment caused by excessive pressure or pipeline blockage; and through valve regulation and pressure gradient control, the system parameters are maintained stable, reducing the risk of equipment overload;

[0035] 4) In the present invention, the standby reactor is kept in a hot standby state and can be quickly started, improving the emergency efficiency; the connection pipeline and the intelligent isolation valve support seamless flexible switching, ensuring the continuity of ammonia supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a system diagram of the embodiment;

[0037] Figure 2 It is a structural schematic diagram of hydrolysis reactor one of the embodiment;

[0038] Figure 3 It is a structural schematic diagram of hydrolysis reactor two of the embodiment.

[0039] Figure 4 It is a logic control schematic diagram of the load response control module.

[0040] Reference numerals: 1, hydrolysis reactor one; 11, ammonia supply pipeline one; 2, hydrolysis reactor two; 21, ammonia supply pipeline two; 3, flexible switching module; 4, pressure relief pipe; 5, urea solution inlet pipe; 6, urea solution return pipe; 7, steam inlet pipe; 8, desuperheating and pressure reducing device; 9, steam purging device; 10, hot standby maintenance device; 12, tracing device; 13, isolation regulating valve; 14, denitration generator set one; 15, denitration generator set two; 16, load response control module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] The following is only the preferred embodiment of the present invention, and the protection scope is not limited to this embodiment. All technical solutions falling within the concept of the present invention shall fall within the protection scope of the present invention. The same components are denoted by the same reference numerals. It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the drawings, and the terms "bottom" and "top", "inner" and "outer" refer to the directions towards or away from the geometric center of a specific component, respectively.

[0042] As Figures 1 to 4 shown, a control system for the operation of a denitrification urea ammonia hydrolysis device includes a first hydrolysis reactor 1, a first denitrification power generation unit, a second hydrolysis reactor 2, and a second denitrification power generation unit. The structures of the two denitrification power generation units are the same. The denitrification power generation unit is a series of devices in the SCR process or the SCNR process except for the ammonia supply mechanism, such as boilers, SCR / SCNR reactors, etc. When the two denitrification power generation units are operating at high load, the two hydrolysis reactors provide energy one by one; when the two denitrification power generation units are operating at low load, one of the hydrolysis reactors is selected to provide energy.

[0043] The ammonia outlet of the first hydrolysis reactor 1 is connected to the first denitrification power generation unit through a first ammonia supply pipeline 11, and an outlet valve 1 is provided at the ammonia outlet of the first hydrolysis reactor 1; the ammonia outlet of the second hydrolysis reactor 2 is connected to the second denitrification power generation unit through a second ammonia supply pipeline 21, and an outlet valve 2 is provided at the ammonia outlet of the second hydrolysis reactor 2. The structures and operation modes of the two hydrolysis reactors are the same. Taking the first hydrolysis reactor 1 as an example, the ammonia generated in the first hydrolysis reactor 1 will be transported to the first denitrification power generation unit through the ammonia supply pipeline.

[0044] Both the first hydrolysis reactor 1 and the second hydrolysis reactor 2 are connected with a urea solution inlet pipe 5 and a steam inlet pipe 7. The urea solution inlet pipe 5 and the steam inlet pipe 7 are respectively used to transport raw materials into the corresponding hydrolysis reactors. A urea solution inlet valve is provided at the end of the urea solution inlet pipe 5, and a steam inlet valve is provided at the end of the steam inlet pipe 7. The two valves can regulate the feed amount of the raw materials.

[0045] A urea solution return pipe 6 is also connected to the urea solution inlet pipe 5. The urea aqueous solution is pumped out from the urea tank through the urea solution inlet pipe 5 and transported into the hydrolysis reactor. The liquid level of the reaction solution in the urea hydrolyzer is set, and by adjusting the opening of the urea solution supply regulating valve through PID, the supply amount can be controlled in real time, and the supply amount of the urea solution can be controlled through the setting of the valve on the urea solution inlet pipe 5.

[0046] A desuperheating and pressure reducing device 8 is also provided on the steam inlet pipe 7, which can cool down and reduce the pressure of the steam input from the outside into the hydrolysis reactor to meet the requirements.

[0047] A pressure relief pipe 4 is provided on both the ammonia supply pipeline 11 and the ammonia supply pipeline 21. A pressure relief valve is provided on the pressure relief pipe 4. When the air pressure in the first hydrolysis reactor 1 or the second hydrolysis reactor 2 is too high, pressure relief can be carried out through the pressure relief pipe 4 and the pressure relief valve to protect the safety of the first hydrolysis reactor 1 and the second hydrolysis reactor 2. To ensure safety, a steam purging device 9 is provided on the pressure relief pipe 4 for regular purging to keep the pressure relief pipe 4 unblocked.

[0048] A flexible switching module 3 is provided between the ammonia supply pipeline 11 and the ammonia supply pipeline 21. The flexible switching module 3 includes a connecting pipe erected between the two ammonia supply pipelines. Both the ammonia supply pipeline 11 and the ammonia supply pipeline 21 are connected to the connecting pipe. An isolation valve is provided in the connecting pipe. When the isolation valve is opened, both hydrolysis reactors can supply ammonia to the other set of denitration generator sets; when the isolation valve is closed, both hydrolysis reactors can only supply ammonia to the denitration generator sets corresponding to them. To ensure safety, a tracing device 12 is connected to the connecting pipe to keep the connecting pipe unblocked.

[0049] Both hydrolysis reactors are provided with a load response control module and a hot standby maintenance device. The hot standby maintenance device includes a steam microcirculation loop and a pressure gradient maintaining unit. In this embodiment, the hot standby maintenance device includes a steam inlet pipe 7 and a desuperheating and pressure reducing device 8. The load response control module incorporates a load-ammonia supply coupling algorithm and a feedforward compensation mechanism during the switching process.

[0050] The working principle of the system in this embodiment is as follows:

[0051] The system includes two sets of structurally symmetric hydrolysis reaction units. Taking the first hydrolysis reactor 1 as an example: This reactor receives a urea solution with a concentration of 40% - 60% through the urea solution supply pipeline 5 and generates an NH3 / CO2 mixed gas through hydrolysis reaction. The steam delivery pipeline 7 provides saturated steam at 0.6 - 1.2 MPa, which is adjusted to 0.4 - 0.6 MPa and 130 - 160 °C by the desuperheating and pressure reducing integrated device 8 and then input into the reactor.

[0052] The dual-mode operation control logic is as follows:

[0053] Mode 1: The first hydrolysis reactor 1 is switched to the one-driving-two operation state (the principle of switching the second hydrolysis reactor 2 to the one-driving-two operation state is the same)

[0054] When the unit load ≤ the preset threshold, the system automatically selects the main operating hydrolyzer; the dynamic transfer of the ammonia supply load of the two units is realized through the regulating valve, and the standby hydrolyzer maintains the hot standby state (temperature 120 °C - 130 °C, pressure 0.3 MPa - 0.4 MPa):

[0055] S1: Check that the tracing of the connecting pipe between the two hydrolysis reactors is normal;

[0056] S2: The NOX concentration at the outlet of the denitration reactors of the two groups of denitration generating units is controlled below the design value, and stable operation is maintained for no less than 30 minutes;

[0057] S3: Open the isolation control valve 13 between the hydrolysis reactor 1 and the hydrolysis reactor 2;

[0058] S4: The hydrolysis reactor 1 and the hydrolysis reactor 2 operate in parallel. Slowly reduce the ammonia supply of the hydrolysis reactor 2 according to the actual working conditions, and at the same time increase the ammonia supply of the hydrolysis reactor 1; if the ammonia supply of the hydrolysis reactor 1 cannot meet the operation requirements of the denitration generating unit 2 during the switching process, the ammonia supply of the hydrolysis reactor 2 needs to be increased;

[0059] S5: Close the steam inlet valve, the urea solution inlet valve and the outlet valve 2 of the hydrolysis reactor 2, and maintain it in the hot standby state. The ammonia steam generated by the reaction of the hydrolysis reactor 1 is used for the two denitration generating units.

[0060] Mode 2: One - to - one operation

[0061] When the unit load > preset threshold, the two hydrolysis reactors operate independently; Monitor the NOx concentration in real - time (set value ≤ 50mg / Nm 3 ); Establish a mode - switching preparation condition judgment mechanism (stable operation ≥ 30min).

[0062] When the boiler load is about to increase:

[0063] S1: Open the steam inlet valve and the urea solution inlet valve of the hydrolysis reactor 2, and raise the temperature and pressure of the hydrolysis reactor to the set value;

[0064] S2: The inlet and outlet NOX concentrations of the reactors of the two groups of denitration generating units are controlled below the design value, and stable operation is maintained for no less than 30 minutes;

[0065] S3: Open the outlet valve 2 on the hydrolysis reactor 2;

[0066] S4: The hydrolysis reactor 1 and the hydrolysis reactor 2 operate in parallel. Slowly reduce the ammonia supply of the hydrolysis reactor 1 according to the actual working conditions, and at the same time increase the ammonia supply of the hydrolysis reactor 2; if the ammonia supply of the hydrolysis reactor 2 cannot meet the operation requirements of the denitration generating unit 2 during the switching process, the ammonia supply of the hydrolysis reactor 1 needs to be increased;

[0067] S5: Close the isolation valve between the hydrolysis reactor 1 and the hydrolysis reactor 2, and one - to - one operation is carried out between the two groups of hydrolysis reactors and the two groups of denitration generating units.

[0068] In this embodiment, the load response control module consists of:

[0069] 1. Load - ammonia supply algorithm unit (multi - channel PID): Real - time monitor the load of the generator set, and automatically calculate and adjust the ammonia supply volume.

[0070] 2. Feed - forward compensation unit: Predict and eliminate system fluctuations (such as pressure changes) during mode switching.

[0071] 3. Valve controller: Precisely control pipeline valves (such as isolation valves, steam valves) to ensure synchronous switching.

[0072] 4. Sensor module: Monitor parameters such as pressure, temperature, and flow rate to ensure safe operation.

[0073] 5. Communication interface: Connect to the control system (DCS), receive instructions, and feedback data.

[0074] 6. Intelligent operation mode: Automatically switch between "one - to - one" or "one - to - two" ammonia supply modes according to the load level (such as 60% or 75% of the rated value) to ensure stable NOx concentration.

[0075] The system of this embodiment realizes the following functions through the load response control module:

[0076] 1. The hot standby maintenance device includes a steam micro - circulation loop (flow rate ≥ 200 kg / h) and a pressure gradient control system (ΔP ≤ 0.05 MPa);

[0077] 2. The load - ammonia supply coupling algorithm adopts a feed - forward compensation mechanism, and the response time ≤ 5 s;

[0078] 3. The DCS system integrates a device health status monitoring module to achieve preventive maintenance;

[0079] 4. Smooth switching: There is no disturbance during the switching process, the ammonia pressure fluctuation ≤ ± 5%, and the transfer rate ≤ 5% / min.

[0080] 5. Fast hot standby startup: The standby equipment maintains a temperature of 120 - 130 °C and a pressure of 0.3 - 0.4 MPa, and the emergency response speed is increased by 3 times.

[0081] The module realizes the efficient, stable, and safe automated operation of the denitration system through intelligent PID regulation, precise valve control, and real - time monitoring.

[0082] Example 1 (single - reactor dual - unit operation mode):

[0083] When the DCS monitors that the unit load ≤ 60% of the rated value, execute the following switching process:

[0084] S1: Execute the status detection of the tracing heating system of the connecting pipe between hydrolysis reactors;

[0085] S2: Ensure that the NOx concentration of the target unit is stable at 20 ± 5 mg / Nm3 for 30 min;

[0086] S3: Start the isolation valve and establish a dual ammonia supply channel;

[0087] S4: Implement dynamic transfer control of ammonia supply load, with a transfer rate ≤ 5% / min;

[0088] S5: Close the material channel of the standby unit and maintain the hot standby parameters: temperature 120°C - 130°C, pressure 0.3 MPa - 0.4 MPa.

[0089] Example 2 (independent operation mode of dual reactors):

[0090] When the unit load > 75% of the rated value:

[0091] S1: Start the gradient heating program of the standby unit, with a temperature rise rate ≤ 15°C / min;

[0092] S2: Establish a transition period of parallel operation of the dual systems ≥ 30 min;

[0093] S3: Use a fuzzy control algorithm for cross-regulation of ammonia supply;

[0094] S4: Control the ammonia pressure fluctuation ≤ ±5% during the final switch.

[0095] In the above specific embodiments, the technical problems solved, technical solutions and beneficial effects of the present invention are further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control system for the operation of a denitrification urea ammonia hydrolysis device, characterized in that: It includes hydrolysis reactor 1 (1), denitrification generating unit 1 (14), hydrolysis reactor 2 (2) and denitrification generating unit 2 (15); the ammonia outlets of hydrolysis reactor 1 (1) and hydrolysis reactor 2 (2) are respectively connected to denitrification generating unit 1 (14) and denitrification generating unit 2 (15) through ammonia supply pipelines 1 (11) and ammonia supply pipelines 2 (21); a flexible switching module (3) is connected between ammonia supply pipeline 1 (11) and ammonia supply pipeline 2 (21) to form a two-way fluid communication loop. The flexible switching module (3) includes a connecting pipe erected between the two pipelines, and an isolation regulating valve (13) for dynamically adjusting and controlling the pipeline connection state is provided on the connecting pipe; load response control modules and hot standby maintenance devices are provided on both hydrolysis reactor 1 (1) and hydrolysis reactor 2 (2).

2. The operation control system of the denitrification urea ammonia hydrolysis device according to claim 1, characterized in that, Pressure relief branches (4) are integrated on both ammonia supply pipeline 1 (11) and ammonia supply pipeline 2 (21). Pressure relief control valves are installed on the pressure relief branches (4), and a steam purging device (9) is connected.

3. The operation control system of the denitrification urea ammonia hydrolysis device according to claim 1, characterized in that, Both hydrolysis reactor 1 (1) and hydrolysis reactor 2 (2) are connected to the urea tank through urea solution supply pipelines (5); the terminal of the urea solution supply pipeline (5) is provided with a urea solution inlet valve, and a urea solution circulation loop (6) is arranged in parallel on the urea solution supply pipeline (5).

4. The operation control system of the denitrification urea ammonia hydrolysis device according to claim 1, characterized in that, The hot standby maintenance device includes a desuperheating and pressure reducing integrated device (8). The hydrolysis reactor is connected to the corresponding desuperheating and pressure reducing integrated device (8) through a steam transmission pipeline (7), and a steam inlet valve is provided at the terminal of the steam transmission pipeline (7).

5. The operation control system of a denitrification urea ammonia hydrolysis device according to claim 1, characterized in that, A tracing device (12) is connected to the connecting pipe (3).

6. The operation control system of a denitrification urea ammonia hydrolysis device according to claim 1, characterized in that Outlet valves are provided at the ammonia outlet sections of hydrolysis reactor 1 (1) and hydrolysis reactor 2 (2).

7. A denitrification urea ammonia hydrolysis device operation control system according to claim 1, characterized in that The load response control module adopts a load - ammonia supply coupling algorithm and a feedforward compensation mechanism for the switching process built into the DCS industrial control system.

8. The control method of an operation control system for a denitrification urea ammonia hydrolysis device according to any one of claims 1-7, characterized in that, Dual - mode operation control is adopted. The dual - mode operation control includes a single - unit operation control mode and a dual - unit operation control mode; When the unit load ≤ the preset threshold, the single - unit operation control mode is adopted. One of the hydrolysis reactors is selected as the main operating hydrolysis reactor, and the other is used as the standby hydrolysis reactor; the dynamic transfer of the ammonia supply load of the two units is realized through the regulating valve, and the standby hydrolysis reactor maintains the hot standby state; the specific steps are as follows: S1: Check the tracing of the connecting pipe between the two groups of hydrolysis reactors; S2: Control the NOX concentration at the outlet of the denitrification reactors of the two groups of denitrification generating units below the design value, and maintain stable operation for not less than the preset time threshold; S3: Open the isolation regulating valve (13) between the two hydrolysis reactors; S4: The two hydrolysis reactors operate in parallel. According to the actual working conditions, reduce the ammonia supply of the standby hydrolysis reactor, and at the same time increase the ammonia supply of the main operating hydrolysis reactor; S5: Close the steam inlet valve, urea solution inlet valve and outlet valve of the standby hydrolysis reactor, and maintain it in the hot standby state. The ammonia steam generated by the reaction of the main operating hydrolysis reactor is used for the two denitrification generating units. When the unit load > preset threshold value, switch the single-unit operation control mode to the dual-unit operation control mode. The two hydrolysis reactors operate independently, and the NOx concentration is monitored in real time. Establish a judgment mechanism for the preparatory conditions for mode switching. The specific steps are as follows: S1: Open the steam inlet valve and urea solution inlet valve of the standby hydrolysis reactor, and raise the temperature and pressure of the hydrolysis reactor to the set values. S2: Control the inlet and outlet NOX concentrations of the reactors of the two denitration generator sets below the design values, and maintain stable operation for no less than the set time threshold. S3: Open the outlet valve on the standby hydrolysis reactor. S4: The two hydrolysis reactors operate in parallel. Slowly reduce the ammonia supply of the main operating hydrolysis reactor according to the actual working conditions, and at the same time increase the ammonia supply of the standby hydrolysis reactor. S5: Close the isolation control valve (13) between the two hydrolysis reactors, and the two groups of hydrolysis reactors respectively control the operation of the corresponding denitration generator sets.

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