Dry quenching automatic nitrogen charging system and control method

Abstract

The invention belongs to the technical field of coking production safety control, and relates to a dry quenching automatic nitrogen charging system and a control method, which effectively solve the problems of combustible gas concentration control lag and dependence on manpower in the traditional dry quenching production by integrating gas detection, automatic control and grading regulation technologies. The system can realize advanced intervention before the concentration exceeds the standard and stage treatment after the concentration exceeds the standard, meanwhile, stable nitrogen supply is guaranteed, and the safety and economical efficiency of dry quenching production are remarkably improved. In the future, a control algorithm can be further optimized, the concentration prediction precision is improved by combining an artificial intelligence technology, and more intelligent dynamic adjustment is realized.

Description

Technical Field

[0001] This invention belongs to the field of safety control technology in coking production, specifically relating to an emergency nitrogen charging system and its automatic control method based on dynamic graded regulation of combustible gas concentration in a dry quenching coke circulation system. It is applicable to gas explosion protection in dry quenching coke devices in industries such as coking and steel, particularly for proactive intervention and graded response to abnormal fluctuations in H2, CO, and O2 concentrations in the circulating gas. Background Technology

[0002] Dry quenching (CDQ) is a coke quenching method that uses inert gas to cool red-hot coke. In the process, red-hot coke at 1000℃ is loaded from the top of the quenching furnace. Low-temperature inert circulating gas at 130℃ is blown into the red-hot coke layer of the cooling section by a circulating fan, absorbing the sensible heat of the coke. The cooled coke (below 200℃) is discharged from the bottom of the furnace. High-temperature inert gas from the annular flue of the furnace flows through the boiler for heat exchange, generating steam. The cooled inert gas is then blown back into the furnace by the circulating fan, circulating within a closed system. The explosion risk of combustible components (mainly carbon monoxide and hydrogen) in the circulating gas is a core aspect of safety management during production. Essentially, it involves a violent chemical reaction triggered when combustible gas mixes with oxygen at a certain concentration and encounters an ignition source. To control the concentration of combustible components in the circulating gas, one approach is to introduce a suitable amount of air to burn off the combustible gas, and another is to introduce a suitable amount of nitrogen to dilute the concentration of the combustible gas components.

[0003] 1. Gas Risk Mechanism in Dry Quenching Coke Oven Process: The circulating gas system of dry quenching coke oven has inherent safety hazards: Accumulation of combustible gases: When the circulating gas flows through the 900-960℃ red coke layer, the following reactions occur: C + O2 = CO2; CO2 + C = 2CO; C + 2H2 = CH4. With the increase of the number of cycles, the CO concentration in the system accumulates, and H2 is released from the volatile matter of coke. Under typical operating conditions, the concentration of combustible gases can reach the following table.

[0004]

[0005] Oxygen infiltration: Air leakage in the negative pressure section (-500 to -1000 Pa) may cause deflagration when O2 > 1%.

[0006] 2. Analysis of existing technical defects: (1) Lagging control methods: Post-intervention type: Currently, the “excess-nitrogen filling” mode is adopted. It takes about 5 minutes on average from the concentration exceeding the standard to the nitrogen injection, which cannot suppress the risk of the concentration rising period.

[0007] High dependence on manual operation: The valve opening needs to be manually adjusted by on-site personnel, and the response delay is >3 minutes.

[0008] (2) Insufficient equipment reliability: detector failure: coke powder (particle size ≤10μm) adheres to the sensor probe, affecting the detection accuracy.

[0009] Nitrogen supply fluctuation: The single-channel nitrogen pressure fluctuation range is ±0.2MPa, resulting in a nitrogen charging flow deviation of >15%.

[0010] (3) Poor economic efficiency: Traditional fixed flow nitrogen filling (3000m) 3 The waste of nitrogen (based on four 150t / h dry quenching units) is calculated as follows: Annual waste = 4 × 3000 × 24 × 365 × 0.3 (ineffective nitrogen charging ratio) = 3,153,600 m³ 3 The cost is approximately 378,400 yuan per year.

[0011] The technical problem to be solved by the present invention is to provide an emergency nitrogen charging system and control method for dry quenching coke ovens, which realizes the early charging of nitrogen during the rising period of combustible gas concentration to prevent the combustible gas concentration from exceeding the standard, and automatically adjusts the nitrogen charging of dry quenching coke ovens according to different levels after exceeding the standard, integrating the solution of "advance prediction, graded control and equipment protection". Summary of the Invention

[0012] The purpose of this invention is to address the above-mentioned problems by providing an automatic nitrogen charging system and control method for dry quenching coke.

[0013] The objective of this invention is achieved as follows: an automatic nitrogen charging system for dry quenching coke ovens, including a dry quenching coke oven, a gas circulation detection device, a nitrogen supply device, and a dry quenching coke oven dispersion control system; the gas circulation detection device includes: an air regulating valve installed on the inlet pipe of the dry quenching coke oven, a circulating gas collecting pipe installed on the outlet pipe of the dry quenching coke oven circulating fan, a gas analyzer installed after the secondary dust removal device, and a gas temperature sensor installed after the primary dust removal device; the nitrogen supply device includes: a nitrogen buffer tank installed between the main nitrogen pipeline and the dry quenching oven, a nitrogen pressure sensor installed on the outlet pressure gauge of the nitrogen buffer tank, a main nitrogen valve installed on the nitrogen pipeline, and a backup nitrogen regulating valve installed before entering the nitrogen buffer tank, the backup nitrogen regulating valve being the same as the main valve and located on the nitrogen bypass pipe, activated when the nitrogen supply from the pipeline is insufficient, and an emergency nitrogen regulating valve installed at the bottom of the dry quenching oven.

[0014] A control method for an automatic nitrogen charging system for dry quenching coke, characterized by the following steps: Step 1: Concentration exceedance judgment: The DCS collects data from the gas analyzer and judges whether the following indicators exceed the standard: For H2 concentration, if H2 concentration > 2%, it is judged as exceeding the standard, proceed to Step 2; For CO concentration, if CO concentration > 6%, it is judged as exceeding the standard, proceed to Step 2; For O2 concentration, if O2 concentration > 0.75%, it is judged as exceeding the standard, proceed to Step 3; If O2 concentration ≤ 0.75%, it is judged as not exceeding the standard, proceed to Step 5; Step 2: Air conditioning valve control: When the H2 or CO concentration exceeds the standard, the DCS controls the air conditioning valve according to the gas temperature. Temperature sensor data T controls the opening of the air regulating valve: If T > 600℃, the air regulating valve opens to its maximum, introducing combustible gas to the air combustion section to reduce the concentration; if T ≤ 600℃, the air regulating valve closes. Step 3: Emergency nitrogen charging graded control: Based on the exceedance levels of H2, CO, and O2, the DCS initiates the corresponding level of nitrogen charging: Level 1 exceedance: If H2 concentration > 6%, CO concentration > 8%, or O2 concentration > 1%, the emergency nitrogen regulating valve opens to its maximum for rapid nitrogen charging; Level 2 exceedance: If H2 concentration ≤ 6%, CO concentration ≤ 8%, and O2 concentration ≤ 1%, the emergency nitrogen regulating valve opens to 70±5% for stable nitrogen charging. All proceed to step eight to ensure nitrogen supply; Step four: Emergency investigation activation: In case of excessive O2 concentration, the DCS starts a timer: if the O2 concentration is <1%, the timer is reset to zero; if the timer continues for 5 ± 0.5 minutes and the O2 concentration is ≥1%, the system alarms and initiates an emergency investigation to check for leaks in the negative pressure section; Step five: Concentration change rate judgment: When the gas concentration is not excessive, the DCS analyzes the concentration change rate: H2 growth rate, if the H2 growth rate is >0.5% / min, proceed to step six; CO growth rate, if the CO growth rate is >1% / min, proceed to step six; O2 growth rate, if the O2 growth rate is ≤1% / min, proceed to step six. % / min, proceed to step seven; Step six: Pre-charge nitrogen control: When the concentration increases rapidly, the emergency nitrogen regulating valve is opened to 40±5% to pre-charge nitrogen and prevent the concentration from exceeding the standard; Step seven: Valve closure: If the concentration change is stable, close the emergency nitrogen regulating valve and stop charging nitrogen; Step eight: Nitrogen supply regulation: The DCS regulates the gas source according to the nitrogen buffer tank pressure P: P>0.7MPa, the pipeline nitrogen regulating valve is opened to 60±5%; 0.5MPa≤P≤0.7MPa, the pipeline nitrogen regulating valve is opened to the maximum; P<0.5MPa, both the pipeline nitrogen regulating valve and the standby nitrogen regulating valve are opened to the maximum to ensure sufficient nitrogen.

[0015] The beneficial effects of this invention are: 1. Automated control: The DCS realizes the full automation of data acquisition and valve adjustment, which greatly reduces manual intervention and significantly improves the system's response speed.

[0016] 2. Preventive mechanism: It can monitor the rate of concentration change in real time and purge with nitrogen in advance when the concentration of combustible gas is rising rapidly but not exceeding the standard, effectively avoiding the occurrence of concentration exceeding the standard.

[0017] 3. Graded adjustment strategy: The amount of nitrogen charged is controlled differently according to the level of combustible gas exceeding the standard, which not only ensures production safety, but also saves nitrogen resources.

[0018] 4. Precision detection design: The gas density-based detection instrument, combined with a dust removal device, improves detection accuracy and extends the service life of the equipment.

[0019] 5. Stable gas supply guarantee: Through dual gas sources (oxygen production station + backup liquid nitrogen) and dynamic pressure regulation, the nitrogen supply is guaranteed to be uninterrupted in emergency situations. Attached Figure Description

[0020] The present invention will now be further described with reference to the accompanying drawings.

[0021] Figure 1 This is a flowchart of the hierarchical control process of the present invention.

[0022] Figure 2 This is the system control flowchart of the present invention. Detailed Implementation

[0023] Key technical features of this invention: Early warning nitrogen purging: Nitrogen purging is initiated before the concentration change rate (H2 > 0.5% / min, CO > 1% / min) exceeds the limit. Risk grading control: Level 1 high risk (H2 > 6% / CO > 8% / O2 > 1%) → < full flow nitrogen purging; Level 2 medium risk < → < 70% flow nitrogen purging. Safety interlock design: The air valve is forcibly shut off when the temperature is ≤ 600℃ to eliminate the risk of explosion. Dual gas source guarantee: The oxygen generator / liquid nitrogen source is dynamically switched based on pressure thresholds. Optimized detection: Detectors are arranged in layers according to gas density (H2 < CO < O2) to improve accuracy.

[0024] (I) System Composition: 1. Dry Quenching Coke Oven: As the core equipment, its main function is to use circulating gas to cool the red coke, and at the same time raise the temperature of the circulating gas to provide high-temperature gas for subsequent waste heat recovery.

[0025] 2. Gas circulation detection device: (1) Air regulating valve: installed on the air inlet pipe of dry quenching coke oven, used to control the amount of air introduced, thereby regulating the composition of circulating gas.

[0026] (2) Circulating gas collection pipe: It is responsible for collecting the circulating gas discharged from the dry quenching coke oven and transporting it to the inlet of the waste heat boiler. A primary dust removal device is installed at its inlet to filter out most of the dust in the circulating gas, so as to avoid impurities affecting the detection accuracy and equipment life.

[0027] (3) Gas analyzer: Installed after the secondary dust removal device, according to the gas density difference (H2<CO<O2), H2 content detector, CO content detector and O2 content detector are installed from bottom to top to ensure the accuracy of each gas component detection.

[0028] (4) Gas temperature sensor: Also installed after the primary dust removal device, it is used to monitor the temperature of the circulating gas in real time and provide a basis for the control of the air regulating valve.

[0029] 3. Nitrogen supply device: (1) Nitrogen buffer tank: used to store nitrogen and stabilize pipeline pressure. A nitrogen pressure sensor is installed on the tank to monitor the pressure inside the tank in real time.

[0030] (2) Main nitrogen valve in the pipeline: controls the flow rate of nitrogen supplied from the oxygen production station to the nitrogen buffer tank, and is the main regulating component for conventional nitrogen supply. Standby nitrogen regulating valve: activates when the nitrogen supply in the pipeline is insufficient, controls the supply of standby liquid nitrogen to the nitrogen buffer tank, and ensures emergency gas supply.

[0031] (3) Emergency nitrogen regulating valve: It regulates the flow rate of nitrogen from the nitrogen buffer tank to the dry quenching coke oven and is a key component for emergency nitrogen charging.

[0032] 4. Dry Quenching Control Station DCS (Distributed Control System for Dry Quenching): As the core of the system, it has the following functions: acquiring real-time data from the gas analyzer, gas temperature sensor, and nitrogen pressure sensor; controlling the opening of air regulating valves, emergency nitrogen regulating valves, pipeline nitrogen regulating valves, and standby nitrogen regulating valves according to preset logic; and realizing automated monitoring, alarm, and control of the system. The dry quenching control station DCS is located in the central control room and is electrically connected to all valves.

[0033] (II) System Working Principle: The system acquires real-time data on the composition (H2, CO, O2 concentrations), temperature, and nitrogen buffer tank pressure of the circulating gas through a gas circulation detection device, and transmits this data to the DCS for analysis and processing. When the DCS detects that the concentration of combustible gas exceeds the standard or rises rapidly, it automatically adjusts the opening of each valve and charges the dry quenching coke oven with nitrogen through the nitrogen supply device to dilute the concentration of combustible gas. At the same time, the DCS adjusts the gas supply according to the pressure of the nitrogen buffer tank to ensure a continuous and stable nitrogen charging process.

[0034] 1. Control methods: (1) Judgment of concentration exceeding the standard (S1): The DCS collects data from the gas analyzer and judges whether the following indicators exceed the standard: For H2 concentration (C1), if C1 > 2%, it is determined to be out of standard, and proceed to step S2; For CO concentration (C2), if C2 > 6%, it is determined to be exceeding the standard, and proceed to step S2; For O2 concentration (C3), if C3 > 0.75%, it is determined to exceed the standard, and proceed to step S3; if C3 ≤ 0.75%, it is determined to not exceed the standard, and proceed to step S5.

[0035] (2) Air regulating valve control (S2): When the H2 or CO concentration exceeds the standard, the DCS controls the opening of the air regulating valve according to the gas temperature sensor data (T): if T>600℃, the air regulating valve opens to the maximum, and air is introduced to burn some combustible gas to reduce the concentration; if T≤600℃, the air regulating valve closes to avoid the risk of explosion caused by air entering.

[0036] (3) Emergency nitrogen purging graded control (S3): Based on the exceedance levels of H2, CO, and O2, the DCS starts the corresponding level of nitrogen purging: Level 1 exceedance (high risk): If C1>6%, C2>8% or C3>1%, the emergency nitrogen regulating valve is opened to the maximum for rapid nitrogen purging; Level 2 exceedance (medium risk): If C1≤6%, C2≤8%, and C3≤1%, open the emergency nitrogen regulating valve to 70% and purge nitrogen smoothly. After completion, proceed to step S8 to ensure nitrogen supply.

[0037] (4) Emergency troubleshooting procedure initiated (S4): In case of excessive O2 concentration, DCS starts a timer: if C3 < 1%, the timer is reset to zero; if the timer continues for 5 minutes and C3 ≥ 1%, the system alarms and starts an emergency troubleshooting procedure to check whether there is a leak in the negative pressure section.

[0038] (5) Judgment of concentration change rate (S5): When the gas concentration does not exceed the standard, the DCS analyzes the concentration change rate: H2 growth rate (S1), if S1 > 0.5% / min, proceed to step S6; CO growth rate (S2), if S2 > 1% / min, proceed to step S6; O2 growth rate (S3), if S3 ≤ 1% / min, proceed to step S7.

[0039] (6) Pre-filling nitrogen control (S6): When the concentration increases rapidly, the emergency nitrogen regulating valve is opened to 40% to pre-fill nitrogen in order to prevent the concentration from exceeding the standard.

[0040] (7) Valve closed (S7): If the concentration change is stable, close the emergency nitrogen regulating valve and stop nitrogen charging.

[0041] (8) Nitrogen supply regulation (S8): The DCS regulates the gas source according to the pressure (P) of the nitrogen buffer tank: P > 0.7MPa, the pipeline nitrogen regulating valve is opened to 60%; 0.5MPa ≤ P ≤ 0.7MPa, the pipeline nitrogen regulating valve is opened to the maximum; P < 0.5MPa, both the pipeline nitrogen regulating valve and the standby nitrogen regulating valve are opened to the maximum to ensure sufficient nitrogen. Example 1

[0042] During a dry quenching coke production process, initially, the circulating gas concentrations were 1.5% H2, 5% CO, and 0.5%, with concentration changes within the normal range, and the emergency nitrogen regulating valve was closed. As production progressed, due to insufficient coke density, the H2 concentration increased at a rate of 0.6% / min. Upon detecting this change, the DCS (Distributed Control System) initiated step S6, automatically opening the emergency nitrogen regulating valve to 40% for pre-purging with nitrogen. After a period of nitrogen purging, the H2 concentration increase was contained and gradually stabilized, preventing the concentration from exceeding the standard. Example 2

[0043] In another production process, the CO concentration in the circulating gas suddenly rose to 7%, at which point the gas temperature was 550℃. The DCS determined that the CO concentration exceeded the standard while the temperature met the requirements, proceeding to step S2. Since the temperature T≤600℃, the air regulating valve remained closed. Simultaneously, the DCS determined that the CO concentration exceeded the standard and proceeded to step S3. Because the CO concentration C2>6% and C2≤8%, it was classified as a level 2 exceedance (medium hazard). The DCS opened the emergency nitrogen regulating valve to 70% for stable nitrogen purging, effectively reducing the CO concentration and ensuring production safety.

[0044] As can be seen from the above embodiments, the emergency nitrogen charging system and control method for dry quenching coke ovens of the present invention can effectively cope with various situations of changes in combustible gas concentration during dry quenching coke production, achieve precise control, and significantly improve the safety and stability of dry quenching coke production.

[0045] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. An automatic nitrogen charging system for dry quenching coke oven, comprising a dry quenching coke oven, characterized in that: It also includes a gas circulation detection device, a nitrogen supply device, and a dry quenching coke dispersion control system; The gas circulation detection device includes: an air regulating valve installed on the inlet pipe of the dry quenching coke oven; a circulating gas collecting pipe installed on the outlet pipe of the dry quenching coke circulating fan; a gas analyzer installed after the secondary dust removal device; and a gas temperature sensor installed after the primary dust removal device. The nitrogen supply device includes: a nitrogen buffer tank installed between the main nitrogen pipeline and the dry quenching furnace; a nitrogen pressure sensor installed on the outlet pressure gauge of the nitrogen buffer tank; a main nitrogen valve installed on the nitrogen pipeline; a backup nitrogen regulating valve installed before entering the nitrogen buffer tank; the backup nitrogen regulating valve, like the main valve, is located on the nitrogen bypass pipe and is activated when the nitrogen supply from the pipeline is insufficient; and an emergency nitrogen regulating valve installed at the bottom of the dry quenching furnace.

2. A control method for an automatic nitrogen charging system for dry quenching coke, characterized in that: Includes the following steps: Step 1: Concentration Exceedance Judgment: The DCS collects data from the gas analyzer and determines whether the following indicators exceed the limits: For H2 concentration, if H2 concentration > 2%, it is determined to exceed the limit, proceed to Step 2; For CO concentration, if CO concentration > 6%, it is determined to exceed the limit, proceed to Step 2; For O2 concentration, if O2 concentration > 0.75%, it is determined to exceed the limit, proceed to Step 3; If O2 concentration ≤ 0.75%, it is determined not to exceed the limit, proceed to Step 5; Step 2: Air Regulating Valve Control: When the H2 or CO concentration exceeds the standard, the DCS controls the opening of the air regulating valve based on the gas temperature sensor data T: if T > 600℃, the air regulating valve opens to its maximum, allowing air to be introduced to burn some combustible gas and reduce the concentration; if T ≤ 600℃, the air regulating valve closes. Step 3: Emergency Nitrogen Charging and Classified Control: Based on the exceedance levels of H2, CO, and O2, the DCS initiates nitrogen charging at the corresponding level: Level 1 exceedance: If H2 concentration > 6%, CO concentration > 8%, or O2 concentration > 1%, the emergency nitrogen regulating valve is opened to the maximum for rapid nitrogen charging; Level 2 exceedance: If H2 concentration ≤ 6%, CO concentration ≤ 8%, and O2 concentration ≤ 1%, the emergency nitrogen regulating valve is opened to 70±5% for stable nitrogen charging. After completion, proceed to Step 8 to ensure nitrogen supply; Step 4: Emergency Troubleshooting Activation: In case of excessive O2 concentration, the DCS starts a timer: if the O2 concentration is <1%, the timer is reset to zero; if the timer continues for 5±0.5 minutes and the O2 concentration is ≥1%, the system alarms and initiates an emergency troubleshooting process to check for leaks in the negative pressure section. Step 5: Determine the rate of concentration change: When the gas concentration does not exceed the standard, the DCS analyzes the rate of concentration change: H2 growth rate, if H2 growth rate > 0.5% / min, proceed to step 6; CO growth rate, if CO growth rate > 1% / min, proceed to step 6; O2 growth rate, if O2 growth rate ≤ 1% / min, proceed to step 7. Step Six: Pre-purging Nitrogen Control: When the concentration increases rapidly, the emergency nitrogen regulating valve is opened to 40±5% to pre-purify nitrogen and prevent the concentration from exceeding the standard; Step 7: Valve Closure: If the concentration change is stable, close the emergency nitrogen regulating valve and stop nitrogen charging; Step 8: Nitrogen Supply Adjustment: The DCS adjusts the gas supply according to the nitrogen buffer tank pressure P: P > 0.7 MPa, the pipeline nitrogen regulating valve is opened to 60 ± 5%; 0.5MPa≤P≤0.7MPa, the nitrogen regulating valve in the pipeline is opened to the maximum. When P < 0.5 MPa, both the pipeline nitrogen regulating valve and the standby nitrogen regulating valve are opened to their maximum to ensure sufficient nitrogen.

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