Starting method of NO gas production device in coal ethylene glycol

Abstract

The invention belongs to the technical field of NO gas preparation in the production process of coal ethylene glycol devices, and discloses a start-up method of an NO gas production device in coal ethylene glycol, which comprises the following steps: step 1): preparing materials; according to the driving method disclosed by the invention, key process indexes such as nitric acid dropping speed, pressure, temperature and NO gas flow are strictly controlled in the whole driving process, so that severe reaction and overpressure safety accidents are prevented, and the gas quantity required by a downstream dimethyl oxalate synthesis unit is stably supplied.

Description

Technical Field

[0001] This invention belongs to the field of NO gas preparation technology in the production process of coal-to-ethylene glycol plants, and relates to a start-up method for a NO gas production plant in coal-to-ethylene glycol. Background Technology

[0002] Coal-to-ethylene glycol production uses coal gas (CO, H2) as raw material, synthesizing dimethyl oxalate (DMO) via carbonylation with carbon monoxide, and then hydrogenating DMO to produce ethylene glycol. The synthesis of DMO involves two processes: the synthesis of DMO and the regeneration of methyl nitrite (MN). In the methyl nitrite regeneration reaction, for every unit of NO consumed, one unit of methyl nitrite is generated. This generated methyl nitrite is then consumed in the DMO synthesis reaction, producing an equimolar amount of NO. Nitrogen is balanced throughout the entire DMO synthesis process, so NO is not explicitly shown in the overall reaction equation. However, in actual production, side reactions and small amounts carried over in the exhaust system lead to nitrogen loss. Therefore, during start-up and normal operation, a certain amount of NO is typically added to the synthesis system to maintain nitrogen balance and ensure the smooth progress of the DMO synthesis reaction.

[0003] Currently, the common method for NO gas production is acid hydrolysis: NaNO2 solid is mixed with metered demineralized water in a sodium nitrite stirred tank to form a NaNO2 solution, which then enters the sodium nitrite reactor. In the reactor, NaNO2 reacts with HNO3 solution from a nitric acid metering tank, converting into a reaction gas mainly composed of NO and a NaNO3 solution. The gas phase after the reaction goes to the dimethyl oxalate synthesis unit, while the liquid phase is discharged into the reaction liquid discharge tank. When starting up a coal-to-ethylene glycol plant, the start-up time of the NO gas production unit needs to be determined according to the requirements of the dimethyl oxalate synthesis unit, and strict control of the temperature and pressure of each piece of equipment is required, especially the nitric acid dripping rate. Excessive dripping speed leads to a violent reaction and a risk of overpressure. Current NO gas production unit start-up methods are prone to unstable gas production, unstable pressure, and overpressure, and cannot adequately meet the requirements of the dimethyl oxalate synthesis unit. Summary of the Invention

[0004] This invention addresses the technical problems of unstable gas flow, unstable pressure, and easy overpressure in the start-up methods of NO gas production units. It provides a start-up method for a NO gas production unit in coal-to-ethylene glycol production, wherein the nitric acid dropping rate is controlled at 0.25 m / s during the initial reaction stage. 3 / h, the maximum flow rate of nitric acid does not exceed 0.9 m 3 With a reactor temperature below 36℃ and a reactor pressure below 0.185MPa, the gas supply to the downstream dimethyl oxalate synthesis unit is stable.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for starting up a NO gas production unit in coal-to-ethylene glycol production, comprising the following steps: Step 1): Prepare the ingredients; Step 2): Pre-start preparation: After the interlock debugging and system nitrogen purging are completed, open the valve on the inlet pipeline from the nitric acid storage tank to the nitric acid drip pump, and add circulating water to the reactor according to the reaction temperature; pump the 34% sodium nitrite solution prepared in dissolving tank B into the reactor through the dissolving tank B discharge pump, ensuring that there is one batch of material in both the reactor and dissolving tank B, and start the stirring motor when the reactor liquid level reaches 10%; Step 3): Driving: a. Upon receiving the NO replenishment instruction, open the NO gas outlet valve of the reactor and the NO gas external supply self-regulating valve of the NO gas buffer tank, and confirm that the pipeline from the NO gas to the dimethyl oxalate synthesis unit is unobstructed. b. Instruct on-site personnel to open the valves before and after the nitric acid dripping regulating valve, start the nitric acid dripping pump, and then, in a controlled manner, open the emergency shut-off valve on the nitric acid dripping pipeline corresponding to the reactor. Slowly open the nitric acid dripping regulating valve by increasing the valve position by 0.1% every 10 seconds to control the nitric acid dripping flow rate at 0.25 m / s. 3 / h; c. Monitor the pressure and temperature changes of the reactor. When the reactor pressure is equal to the pressure of the dimethyl oxalate synthesis unit, the NO flow meter at the outlet of the NO gas buffer tank will start displaying the flow rate; when the NO flow meter displays 60 Nm... 3 When the nitric acid dripping regulating valve is opened at / h, the opening should not be increased, and the system should be kept running stably for 10 min. d. Gradually increase the opening of the nitric acid dripping regulating valve according to the NO requirement of the dimethyl oxalate synthesis unit, controlling the NO flow rate to be less than 200 Nm³. 3 / h, reactor pressure less than 0.185 MPa, reactor temperature less than 36 ℃, and maximum nitric acid dripping rate controlled not to exceed 0.9 m³ / h; e. Monitor the changes in the NO flow meter. When the NO outlet flow meter starts to drop sharply or shows zero, and the pressure of the reactor starts to drop slowly until it is equal to the pressure of the dimethyl oxalate synthesis unit, it indicates that the reaction endpoint has been reached. The central control unit closes the nitric acid dripping regulating valve and the emergency shut-off valve on the nitric acid dripping pipeline corresponding to the reactor, shuts off the nitric acid dripping pump, and notifies on-site personnel to close the valves before and after the nitric acid dripping regulating valve. f. After the reaction is complete, continue stirring for 10 minutes, start the alkali solution dripping pump to add alkali solution to the reaction vessel, and stop the alkali solution dripping pump when the pH reaches 7. Close the alkali solution dripping shut-off valve and the manual valves before and after the regulating valve.

[0006] In the above technical solution, the specific steps of step 1) ingredient preparation are as follows: 1.1) Discharging sodium nitrite solution: a. After the purchased sodium nitrite solution tanker arrives at the designated location and the sample analysis is qualified, connect the unloading pipeline; b. Close the valve between the bottom outlet of dissolving vessel A and the discharge pump of dissolving vessel A, open the unloading pipeline valve, open the inlet valve of the discharge pump of dissolving vessel A and the tank truck unloading valve, and open the exhaust valve of the discharge pump of dissolving vessel A. c. After venting is completed, open the valve between the discharge pump of dissolving vessel A and the top inlet of dissolving vessel A, close the valve between the discharge pump of dissolving vessel A and the top inlet of dissolving vessel B, start the discharge pump of dissolving vessel A, and open the outlet valve of the discharge pump of dissolving vessel A to unload the vehicle; d. When the liquid level in dissolving tank A reaches 18% to 19%, close the outlet valve of the discharging pump of dissolving tank A, stop the pump, close the unloading pipeline valve, open the valve between the bottom outlet of dissolving tank A and the discharging pump of dissolving tank A, close the valve between the discharging pump of dissolving tank A and the top inlet of dissolving tank A, open the valve between the discharging pump of dissolving tank A and the top inlet of dissolving tank B, start the discharging pump of dissolving tank A, open the outlet valve of the discharging pump of dissolving tank A, and after all the sodium nitrite solution in dissolving tank A is sent to dissolving tank B, start the stirring motor of dissolving tank B for standby. Alternatively, 1.2) Solid sodium nitrite feeding and batching: a. 4.8 m 3 Add demineralized water to the demineralized water metering tank until water flows out of the overflow port, then put the demineralized water into the dissolving kettle A; b. After the demineralized water is fed, start the stirring motor of dissolving tank A and add 2.5 tons of sodium nitrite to dissolving tank A to dissolve it completely; c. Start the discharge pump of dissolving vessel A to pump the sodium nitrite solution to dissolving vessel B for later use. Stop stirring before starting the pump.

[0007] The above technical solution further includes the following starting method: Step 4): Discharging material, the specific steps of which are as follows: a. Stop the agitator in the reactor, close the NO gas recovery valve of the reaction liquid discharge tank, and open the discharge valve of the reactor. The reactor will slowly discharge the reaction liquid into the discharge tank, maintaining the reactor pressure at no less than 0.05 MPa during discharge. When the reactor pressure drops below 0.05 MPa, close the discharge valve, open the nitrogen purging valve to purge with nitrogen, and control the reactor pressure to no more than 0.1 MPa. Then open the discharge valve again to discharge the reaction liquid. Discharge ends when there is no liquid level in the reactor, the liquid level in the discharge tank stops rising, and the pressures of the reactor and the discharge tank are the same. Close the discharge valve. It is strictly forbidden for the reactor pressure to be negative during the discharge process. b. Open the NO gas recovery valve from the reaction liquid discharge tank to the nitrogen oxide recovery system to recover the NO gas in the reaction liquid discharge tank; c. Turn on the reaction liquid discharge pump to send the reaction liquid to the sodium nitrate solution evaporation, concentration, drying, and packaging system to recover the by-product sodium nitrate.

[0008] The above technical solution also includes the following driving method: Step 5): Abnormal handling, the specific steps of which are as follows: a. When the overpressure interlock of the reactor opens the emergency vent valve or safety valve of the reactor, NO gas is discharged to the NO gas collection tank. The NO gas collection tank collects the toxic gas and then recovers it to the nitrogen oxide recovery system for recycling. b. The nitric acid dripping rate and reactor temperature should be strictly controlled during the reaction process. Nitric acid dripping must be stopped if the water supply to the reactor is interrupted, the power is cut off, the stirrer malfunctions, or the temperature or pressure exceeds the limit. c. If any abnormal pressure or temperature occurs during the reaction, the addition of nitric acid must be stopped immediately and the cause investigated. d. If the reaction is not obvious or does not occur after adding nitric acid to the reactor, the emergency shut-off valve and the nitric acid adding regulating valve on the nitric acid adding pipeline should be closed. Check if there is a problem with the ingredients, check if the purity of the raw materials sodium nitrite and nitric acid is up to standard, and check if the nitric acid pipeline is blocked. e. If the agitator in the reactor stops and there is unreacted material, first turn on the alkali drip pump to add alkali solution to the reactor, then jog the agitator. If the pressure fluctuation in the reactor is not significant, then start the agitator again. If the pressure rises significantly, jog the agitator several times, and then start the agitator again. f. During the process of discharging the reaction liquid from the reactor to the discharge tank, attention should be paid to the pressure changes inside the discharge tank. If any abnormality occurs, the reactor discharge valve should be closed immediately.

[0009] In the above technical solution, the concentration of nitric acid in the nitric acid storage tank is not less than 65%.

[0010] In the above technical solution, the NaOH concentration in the alkaline storage tank is not less than 32%.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses a 34% sodium nitrite solution and 65% nitric acid as raw materials to generate NO gas, which is then sent to the downstream dimethyl oxalate synthesis unit to replenish the NO generated during the initial start-up and subsequent NO loss during operation. Throughout the start-up process, key process parameters such as nitric acid dropping rate, pressure, temperature, and NO gas flow rate are strictly controlled. In the initial stage of the reaction, the nitric acid dropping rate is controlled at 0.25 m / s. 3 / h, the maximum flow rate of nitric acid does not exceed 0.9 m 3The reactor temperature is below 36℃ and the reactor pressure is less than 0.185MPa per hour to prevent violent reactions and overpressure accidents, and to ensure a stable supply of gas required by the downstream dimethyl oxalate synthesis unit. Attached Figure Description

[0012] Figure 1 This is a process flow diagram of NO gas production in the coal-to-ethylene glycol unit of the present invention.

[0013] The following labels in the attached diagram are: 1 - Demineralized water metering tank; 2 - Dissolving vessel A; 3 - Dissolving vessel B; 4 - Nitric acid storage tank; 5 - Alkali storage tank; 6 - Reactor A; 7 - Reactor B; 8 - NO gas buffer tank; 9 - Reaction liquid discharge tank; 10 - Discharge tank; 11 - Discharge pump for dissolving vessel A; 12 - Discharge pump for dissolving vessel B; 13 - Alkali unloading pump; 14 - Nitric acid unloading pump; 15 - Nitric acid dripping pump; 16 - Alkali dripping pump; 17 - Reaction liquid discharge pump. Detailed Implementation

[0014] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the test methods in the following embodiments are conventional methods.

[0015] Example 1 like Figure 1The diagram shows the process flow of the NO gas production unit in a coal-to-ethylene glycol plant. The unit includes a demineralized water metering tank 1, two dissolving tanks: dissolving tank A 2 and dissolving tank B 3, a nitric acid storage tank 4, an alkali storage tank 5, two reaction tanks: reaction tank A 6 and reaction tank B 7, an NO gas buffer tank 8, a reaction liquid discharge tank 9, a discharge tank 10, a discharging pump for dissolving tank A 11, a discharging pump for dissolving tank B 12, an alkali unloading pump 13, a nitric acid unloading pump 14, a nitric acid dripping pump 15, an alkali dripping pump 16, and a reaction liquid discharge pump 17. Specifically: Alkali unloading pump 13 is connected to the alkali tanker via an unloading pipeline; nitric acid unloading pump 14 is connected to the nitric acid tanker via an unloading pipeline; nitric acid dripping pump 15 is connected to reactor A6 and reactor B7 via pipelines and valves; alkali dripping pump 16 is connected to reactor A6 and reactor B7 via pipelines and valves; the inlet of demineralized water metering tank 1 is connected to demineralized water from outside the boundary, and the outlet is connected to dissolving reactor A2; the bottom of dissolving reactor A2 is connected to the sodium nitrite solution tanker and the inlet pipeline of dissolving reactor A discharge pump 11 via a pipeline; the outlet pipeline of dissolving reactor A discharge pump 11 is connected to the top inlet of dissolving reactor A2 and the top inlet of dissolving reactor B3 respectively; the bottom outlet of dissolving reactor B3 is connected to the inlet pipeline of dissolving reactor B discharge pump 12; the outlet pipeline of dissolving reactor B discharge pump 12 is connected to reactor A6 and reactor B7; reactor A6 and reactor B7 are connected to each other. The top gas outlet of reactor 7 is connected to NO gas buffer tank 8, discharge tank 10, and venting pipeline. The top gas outlet of reaction liquid discharge tank 9 is also connected to discharge tank 10. The bottom liquid outlets of reactor A 6 and reactor B 7 are connected to reaction liquid discharge tank 9. The bottom liquid outlet of NO gas buffer tank 8 is connected to the top of reactor A 6 and reactor B 7. In addition, dissolving tank A 2 and dissolving tank B 3 are connected to the circulating water system. The top gas outlet of NO gas buffer tank 8 is connected to the downstream dimethyl oxalate synthesis unit through pipeline. Both reaction liquid discharge tank 9 and NO gas collection tank 10 are connected to the nitrogen oxide recovery system through pipeline. The reaction liquid discharge pump 17 is connected to the sodium nitrate solution evaporation, concentration, drying, and packaging system through pipeline. The demineralized water metering tank 1, two dissolving kettles, two reaction kettles, nitric acid storage tank 4, alkali storage tank 5, NO gas buffer tank 8, reaction liquid discharge tank 9, and discharge tank 10 are all equipped with liquid level sensors. The two reaction kettles and discharge tank 10 are also equipped with temperature sensors and pressure sensors. These sensors are all commonly used instruments in the chemical industry.

[0016] In this embodiment, the nitric acid concentration in nitric acid storage tank 4 is no less than 65%, the NaOH concentration in alkali storage tank 5 is no less than 32%, and the concentration of the purchased sodium nitrite solution is 34%. The volumes of dissolving vessels A2 and B3 are 17.1 m³. 3 The temperature is controlled at 20~35 ℃, the pressure is at atmospheric pressure, and the liquid level is controlled within the range of 20~60%; the volume of reactor A6 and reactor B7 is 17.1 m³. 3The temperature is controlled between 10 and 40 ℃, the pressure between 0.06 and 0.185 MPa, and the liquid level between 30 and 55%. Two reactors are equipped with rupture discs. If the emergency vent valve and safety valve cannot release pressure in time, the rupture discs will rupture to release pressure and prevent overpressure and explosion. The NO gas flow meter has a flow rate of 0–290 Nm³ / h, a high alarm value of 300 Nm³ / h, and a very high alarm value of 400 Nm³ / h.

[0017] The chemical reaction in the NO gas production unit takes place within a reactor. The reaction materials must be prepared according to strict proportions. Controlling the nitric acid dropping rate is crucial for the entire reaction; excessively rapid dropping leads to a violent reaction and a risk of overpressure. Pressure, temperature, and NO gas flow rate are also key process parameters. Higher temperatures increase the reaction rate, while lower temperatures relatively decrease it. The pressure throughout the reaction is determined by the nitric acid dropping rate and the pressure in the downstream dimethyl oxalate synthesis unit. The gaseous product NO is a colorless gas. During production, NO gas leakage must be strictly prevented. Leakage will release a brown, oxidizing fume upon contact with air. It is easily oxidized in air to nitrogen dioxide, which is highly corrosive and toxic.

[0018] Main reaction: 3NaNO2 + 2HNO3 = 3NaNO3 + H2O + 2NO↑; Side reaction: HNO3 + NaOH = NaNO3 + H2O.

[0019] Taking reactor A6 as the primary reactor and reactor B7 as the backup reactor as an example, the start-up method of the above-mentioned NO gas production unit in coal-to-ethylene glycol includes the following steps: Step 1): Ingredients: 1.1) Discharging sodium nitrite solution: a. After the purchased sodium nitrite solution tanker arrives at the designated location and the sample analysis is qualified, the unloading pipeline is connected.

[0020] b. Close the valve between the bottom outlet of dissolving vessel A2 and the discharge pump 11 of dissolving vessel A, open the unloading pipeline valve, open the inlet valve of discharge pump 11 of dissolving vessel A and the tank truck unloading valve, and open the exhaust valve of discharge pump 11 of dissolving vessel A.

[0021] c. After venting is completed, open the valve between the discharge pump 11 of dissolving vessel A and the top inlet of dissolving vessel A 2, close the valve between the discharge pump 11 of dissolving vessel A and the top inlet of dissolving vessel B 3, start the discharge pump 11 of dissolving vessel A, and open the outlet valve of the discharge pump 11 of dissolving vessel A to unload the vehicle.

[0022] d. When the liquid level in dissolving vessel A2 reaches 18%–19%, close the outlet valve of dissolving vessel A discharge pump 11, stop the pump, close the unloading pipeline valve, open the valve between the bottom outlet of dissolving vessel A2 and dissolving vessel A discharge pump 11, close the valve between dissolving vessel A discharge pump 11 and the top inlet of dissolving vessel A2, open the valve between dissolving vessel A discharge pump 11 and the top inlet of dissolving vessel B3, start dissolving vessel A discharge pump 11, open the outlet valve of dissolving vessel A discharge pump 11, and after all the sodium nitrite solution in dissolving vessel A2 is sent to dissolving vessel B3, start the stirring motor of dissolving vessel B3 for standby.

[0023] Alternatively, 1.2) Solid sodium nitrite feeding and batching: a. 4.8 m 3 Add demineralized water to the demineralized water metering tank 1 until water flows out of the overflow port, and then put the demineralized water into the dissolving kettle A2.

[0024] b. After the demineralized water is fed, start the stirring motor of dissolving tank A2 and add 2.5 tons of sodium nitrite (50 bags, 50 kg / bag) to dissolving tank A2 and dissolve it completely.

[0025] c. Start the discharge pump 11 of dissolving vessel A to pump the sodium nitrite solution to dissolving vessel B 3 for standby. Stop stirring before starting the pump.

[0026] Step 2): Pre-start preparation: After the interlock debugging and system nitrogen purging (oxygen content less than 0.5% is qualified), open the valve on the inlet pipeline from nitric acid storage tank 4 to nitric acid drip pump 15, and add circulating water to reactor A 6 and reactor B7 according to the reaction temperature; pump the 34% sodium nitrite solution prepared in dissolving tank B 3 into reactor A 6 and reactor B 7 through dissolving tank B discharge pump 12, ensuring that each of the two reactors and dissolving tank B 3 has one batch of material prepared. When the liquid level in reactor A 6 and reactor B 7 reaches 10%, start the stirring motor.

[0027] Step 3): Driving: a. Upon receiving the NO replenishment instruction, open the NO gas outlet valve of reactor A and the NO gas external supply self-regulating valve of NO gas buffer tank 8, and confirm that the pipeline from NO gas to the dimethyl oxalate synthesis unit is unobstructed.

[0028] b. Instruct on-site personnel to open the valves before and after the nitric acid dripping regulating valve, start the nitric acid dripping pump 15, and then open the emergency shut-off valve on the nitric acid dripping pipeline corresponding to reactor A6 from the central control unit. Slowly open the nitric acid dripping regulating valve by increasing the valve position by 0.1% every 10 seconds to control the nitric acid dripping flow rate at 0.25 m / s. 3 / h.

[0029] c. Monitor the pressure and temperature changes in reactor A6. When the pressure in reactor A6 is equal to the pressure in the dimethyl oxalate synthesis unit, the NO flow meter at the outlet of NO gas buffer tank 8 will begin to display the flow rate; when the NO flow meter displays 60 Nm... 3 When the nitric acid dripping regulating valve is opened at / h, the opening should not be increased, and the system should be kept running stably for 10 minutes.

[0030] d. Gradually increase the opening of the nitric acid dripping regulating valve according to the NO requirement of the dimethyl oxalate synthesis unit, controlling the NO flow rate to be less than 200 Nm³. 3 / h, the pressure in reactor A6 is less than 0.185 MPa, the temperature in reactor A6 is less than 36 ℃, and the maximum nitric acid dripping rate is controlled to not exceed 0.9 m³ / h.

[0031] e. Monitor the changes in the NO flow meter. When the NO outlet flow meter starts to drop sharply or displays zero, and the pressure in reactor A6 starts to drop slowly until it is equal to the pressure in the dimethyl oxalate synthesis unit, it indicates that the reaction endpoint has been reached. The central control unit closes the nitric acid dripping regulating valve and the emergency shut-off valve on the nitric acid dripping pipeline corresponding to reactor A6, shuts off the nitric acid dripping pump 15 or performs reactor shut-off operation, and notifies on-site personnel to close the valves before and after the nitric acid dripping regulating valve.

[0032] f. After the reaction is complete, continue stirring for 10 minutes, start the alkali solution dripping pump 16 to start adding alkali solution to the reaction vessel A6, and stop the alkali solution dripping pump 16 when the pH is neutralized to 7. Close the alkali solution dripping shut-off valve and the manual valves before and after the regulating valve.

[0033] Step 4): Material discharge: a. Stop the agitator of reactor A6, close the NO gas recovery valve of the reaction liquid discharge tank 9, and open the discharge valve of reactor A6. Reactor A6 will slowly discharge into the reaction liquid discharge tank 9, maintaining the pressure of reactor A6 at no less than 0.05 MPa during discharge. When the pressure of reactor A6 is lower than 0.05 MPa, close the discharge valve, open the nitrogen purging valve of reactor A6 to perform nitrogen purging, and control the pressure of reactor A6 to no more than 0.1 MPa. Then open the discharge valve again to discharge. Discharge ends when there is no liquid level in reactor A6, the liquid level in the reaction liquid discharge tank 9 no longer rises, and the pressures of reactor A6 and the reaction liquid discharge tank 9 are the same. Close the discharge valve. During the discharge process, it is strictly forbidden for the pressure of reactor A6 to be negative to avoid damaging the rupture disc.

[0034] b. Open the NO gas recovery valve of the reaction liquid discharge tank 9 to the nitrogen oxide recovery system to recover the NO gas in the reaction liquid discharge tank 9.

[0035] c. Turn on the reaction liquid discharge pump 17 to send the reaction liquid to the sodium nitrate solution evaporation, concentration, drying and packaging system to recover the by-product sodium nitrate.

[0036] Step 5): Abnormal handling: a. When the overpressure interlock of reactor A6 opens the emergency vent valve or safety valve of reactor A6, NO gas is discharged to NO gas collection tank 10. NO gas collection tank 10 collects the toxic gas and recovers it to the nitrogen oxide recovery system for recycling.

[0037] b. The nitric acid dripping rate and the temperature of reactor A6 should be strictly controlled during the reaction process. Nitric acid dripping must be stopped if the water supply to reactor A6 is interrupted, the power is cut off, the stirrer malfunctions, or the temperature or pressure exceeds the limit.

[0038] c. If any abnormal pressure or temperature occurs during the reaction, the addition of nitric acid must be stopped immediately and the cause investigated. d. If the reaction is not obvious or does not occur after adding nitric acid to reactor A6 (under normal circumstances, gas is generated immediately after nitric acid enters reactor A6; if the reaction is not obvious or does not occur after adding nitric acid, do not blindly increase the amount of nitric acid added), the emergency shut-off valve and the nitric acid adding regulating valve on the nitric acid adding pipeline should be closed to investigate the cause, check whether there is a problem with the ingredients, check whether the purity of the raw materials sodium nitrite (solution / solid) and nitric acid is qualified, and check whether the nitric acid pipeline is blocked.

[0039] e. If the agitator in reactor A6 stops and there is unreacted material, do not start the agitator arbitrarily. First, turn on the alkali solution drip pump 16 to add alkali solution to reactor A6, then jog the agitator. If the pressure fluctuation inside the reactor is not significant, then start the agitator normally. If the pressure rises significantly, jog the agitator several times, and then start the agitator again.

[0040] f. During the discharge process from reactor A6 to the discharge tank 9, pay attention to the pressure changes inside the discharge tank 9 to prevent unreacted materials from entering the discharge tank and continuing to react, which could cause danger. If any abnormality occurs, the reactor discharge valve should be closed immediately.

[0041] When it is necessary to switch reactor B7, the steps are as follows: ① The central control unit must first close the emergency shut-off valve and the nitric acid dripping regulating valve on the nitric acid dripping pipeline after the reaction has just ended, and notify the on-site operators to close the valves before and after the nitric acid dripping regulating valve.

[0042] ② Open the NO gas outlet valve of the preparation reactor B7, and then open the valves before and after the nitric acid dropping regulating valve on the nitric acid dropping pipeline of the reactor.

[0043] ③ After confirmation by the central control unit, the emergency shut-off valve on the nitric acid dripping pipeline to be put into use is opened, and then the nitric acid dripping regulating valve is slowly opened at a rate of 0.1% of the valve position every 10 seconds to control the nitric acid dripping flow rate to 0.25 m³ / h.

[0044] ④ Adjust the opening of the nitric acid dripping regulating valve according to the pressure of reactor B7 and the NO gas flow rate.

[0045] The embodiments described above are merely preferred embodiments of the present invention and are only used to explain the present invention. They are not intended to limit the scope of the present invention. For those skilled in the art, other implementation methods can be easily made by substitution or modification based on the technical content disclosed in this specification. Therefore, all changes and improvements made on the principle of the present invention should be included within the scope of the patent application of the present invention.

Claims

1. A method for starting up a NO gas production unit in coal-to-ethylene glycol, characterized in that, Includes the following steps: Step 1): Prepare the ingredients; Step 2): Preparations before starting: After the interlock debugging and system nitrogen replacement are completed, open the valve on the inlet pipeline from the nitric acid storage tank (4) to the nitric acid drip pump (15) and add circulating water to the reactor according to the reaction temperature; pump the 34% sodium nitrite solution prepared in the dissolving tank B (3) into the reactor through the dissolving tank B discharge pump (12) to ensure that there is a batch of material in both the reactor and the dissolving tank B (3); turn on the stirring motor when the reactor liquid level reaches 10%. Step 3): Driving: a. After receiving the NO replenishment instruction, open the NO gas outlet valve of the reactor and the NO gas external self-regulating valve of the NO gas buffer tank (8), and confirm that the pipeline from the NO gas to the dimethyl oxalate synthesis unit is unobstructed. b. Notify on-site personnel to open the valves before and after the nitric acid dripping regulating valve, start the nitric acid dripping pump (15), and then open the emergency shut-off valve on the nitric acid dripping pipeline corresponding to the reactor in the central control system. Slowly open the nitric acid dripping regulating valve by increasing the valve position by 0.1% every 10 seconds to control the nitric acid dripping flow rate to 0.25 m. 3 / h; c. Monitor the pressure and temperature changes of the reactor. When the pressure of the reactor is equal to that of the dimethyl oxalate synthesis unit, the NO flow meter at the outlet of the NO gas buffer tank (8) will start to display the flow rate; when the NO flow meter displays 60 Nm 3 When the nitric acid dripping regulating valve is opened at / h, the opening should not be increased, and the system should be kept running stably for 10 min. d. Gradually increase the opening of the nitric acid dripping regulating valve according to the NO requirement of the dimethyl oxalate synthesis unit, controlling the NO flow rate to be less than 200 Nm³. 3 / h, reactor pressure less than 0.185 MPa, reactor temperature less than 36 ℃, and maximum nitric acid dripping rate controlled not to exceed 0.9 m³ / h; e. Pay attention to the changes in the NO flow meter. When the NO outlet flow meter starts to drop sharply or shows zero, and the pressure of the reactor starts to drop slowly to the same level as the pressure of the dimethyl oxalate synthesis unit, it indicates that the reaction endpoint has been reached. The central control unit closes the nitric acid dripping regulating valve and the emergency shut-off valve on the nitric acid dripping pipeline corresponding to the reactor, shuts off the nitric acid dripping pump (15), and notifies the on-site personnel to close the valves before and after the nitric acid dripping regulating valve. f. After the reaction is completed, continue stirring for 10 min, start the alkaline solution dripping pump (16) to start adding alkaline solution to the reactor, stop the alkaline solution dripping pump (16) when the pH is neutralized to 7, and close the alkaline solution dripping shut-off valve and the manual valves before and after the regulating valve.

2. The driving method according to claim 1, characterized in that, The specific steps for preparing the ingredients in step 1) are as follows: 1.1) Discharging sodium nitrite solution: a. After the purchased sodium nitrite solution tanker arrives at the designated location and the sample analysis is qualified, connect the unloading pipeline; b. Close the valve between the bottom outlet of dissolving kettle A (2) and the discharge pump (11) of dissolving kettle A, open the unloading pipeline valve, open the inlet valve of the discharge pump (11) of dissolving kettle A and the tank truck unloading valve, and open the exhaust valve of the discharge pump (11) of dissolving kettle A; c. After the venting is completed, open the valve between the discharge pump (11) of dissolving vessel A and the top inlet of dissolving vessel A (2), close the valve between the discharge pump (11) of dissolving vessel A and the top inlet of dissolving vessel B (3), start the discharge pump (11) of dissolving vessel A, and open the outlet valve of the discharge pump (11) of dissolving vessel A to unload the vehicle; d. When the liquid level in dissolving vessel A (2) reaches 18% to 19%, close the outlet valve of dissolving vessel A discharge pump (11), stop the pump, close the unloading pipeline valve, open the valve between the bottom outlet of dissolving vessel A (2) and the dissolving vessel A discharge pump (11), close the valve between the dissolving vessel A discharge pump (11) and the top inlet of dissolving vessel A (2), open the valve between the dissolving vessel A discharge pump (11) and the top inlet of dissolving vessel B (3), start dissolving vessel A discharge pump (11), open the outlet valve of dissolving vessel A discharge pump (11), send all the sodium nitrite solution in dissolving vessel A (2) to dissolving vessel B (3), and start the stirring motor of dissolving vessel B (3) for standby. Alternatively, 1.2) Solid sodium nitrite feeding and batching: a. 4.8 m 3 Add demineralized water to the demineralized water metering tank (1) until water flows out of the overflow port, and put the demineralized water into the dissolving kettle A (2); b. After the demineralized water is fed, start the stirring motor of dissolving tank A (2) and add 2.5 tons of sodium nitrite to dissolving tank A (2) to dissolve it completely; c. Start the discharge pump (11) of dissolving vessel A to pump the sodium nitrite solution to dissolving vessel B (3) for standby. Stop stirring before starting the pump.

3. The driving method according to claim 1, characterized in that, The starting method also includes: Step 4): Discharge, the specific steps of which are as follows: a. Stop the agitator of the reactor, close the NO gas recovery valve of the reaction liquid discharge tank (9), open the discharge valve of the reactor, and the reactor will slowly discharge the reaction liquid into the reaction liquid discharge tank (9). During the discharge, the pressure of the reactor should not be lower than 0.05 MPa. When the pressure of the reactor is lower than 0.05 MPa, close the discharge valve, open the nitrogen charging valve of the reactor to carry out nitrogen charging operation, control the pressure of the reactor not to be higher than 0.1 MPa, and then open the discharge valve to discharge the reaction liquid. When there is no liquid level in the reactor, the liquid level in the reaction liquid discharge tank (9) no longer rises, and the pressure of the reactor and the reaction liquid discharge tank (9) are the same, the discharge ends and the discharge valve is closed. During the discharge process, it is strictly forbidden for the pressure of the reactor to be negative. b. Open the NO gas recovery valve of the reaction liquid discharge tank (9) to the nitrogen oxide recovery system to recover the NO gas in the reaction liquid discharge tank (9); c. Turn on the reaction liquid discharge pump (17) to send the reaction liquid to the sodium nitrate solution evaporation, concentration, drying and packaging system to recover the by-product sodium nitrate.

4. The driving method according to claim 1, characterized in that, The driving method also includes: Step 5): Abnormal handling, the specific steps of which are as follows: a. When the overpressure interlock of the reactor opens the emergency vent valve or safety valve of the reactor, NO gas is discharged to the NO gas collection tank (10). The NO gas collection tank (10) collects the toxic gas and recovers it to the nitrogen oxide recovery system for recycling. b. The nitric acid dripping rate and reactor temperature should be strictly controlled during the reaction process. Nitric acid dripping must be stopped if the water supply to the reactor is interrupted, the power is cut off, the stirrer malfunctions, or the temperature or pressure exceeds the limit. c. If any abnormal pressure or temperature occurs during the reaction, the addition of nitric acid must be stopped immediately and the cause investigated. d. If the reaction is not obvious or does not occur after adding nitric acid to the reactor, the emergency shut-off valve and the nitric acid adding regulating valve on the nitric acid adding pipeline should be closed. Check if there is a problem with the ingredients, check if the purity of the raw materials sodium nitrite and nitric acid is up to standard, and check if the nitric acid pipeline is blocked. e. If the agitator in the reactor stops and there is unreacted material, first turn on the alkali drip pump to add alkali solution to the reactor, then jog the agitator. If the pressure fluctuation in the reactor is not significant, then start the agitator again. If the pressure rises significantly, jog the agitator several times, and then start the agitator again. f. During the process of discharging the reaction liquid from the reactor to the discharge tank (9), attention should be paid to the pressure change inside the discharge tank (9). If there is any abnormality, the reactor discharge valve should be closed immediately.

5. The driving method according to claim 1, characterized in that, The concentration of nitric acid in the nitric acid storage tank (4) is not less than 65%.

6. The driving method according to claim 1, characterized in that, The concentration of NaOH in the alkaline storage tank (5) shall not be less than 32%.

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