Harmless emission device for volatile organic gas in dimethyl oxalate storage tank

Abstract

The utility model belongs to the technical field of oxalate storage, and particularly relates to a harmless discharging device for volatile organic gas in a dimethyl oxalate storage tank, which comprises a storage tank and a liquid seal tank, the top end of the storage tank is connected with a discharging pipe, and a pressure transmitter for detecting air pressure in the tank is fixedly mounted on the storage tank. A regulating valve I in signal connection with the pressure transmitter is mounted on the discharge pipe, one end, far away from the storage tank, of the discharge pipe extends into the liquid seal tank and is positioned below the liquid level in the liquid seal tank, methanol is contained in the liquid seal tank, and the top end of the liquid seal tank is connected with a tail gas pipe. According to the utility model, organic matter gas in the storage tank is discharged into the liquid seal tank and is washed and dissolved by methanol, so that organic matters are prevented from being discharged into the atmosphere, zero emission of harmful substances is realized, and the device is environment-friendly.

Description

Technical Field

[0001] The utility model belongs to the technical field of oxalate storage, and particularly relates to a harmless emission device for volatile organic gases in a dimethyl oxalate storage tank. Background Art

[0002] In the oxalate hydrogenation method in the coal-to-ethylene glycol technology, coal is used as a raw material to produce syngas, and then through a catalytic reaction, dimethyl oxalate is generated, and finally ethylene glycol is produced by hydrogenation. In the process of preparing dimethyl oxalate, CO couples with methyl nitrite to generate dimethyl oxalate and NO. After separation from dimethyl oxalate, NO enters a regeneration reactor to react with methanol and oxygen to generate methyl nitrite, and then methyl nitrite returns to the CO coupling reaction tower as a raw material to synthesize dimethyl oxalate. In the above process, the by-products of the CO coupling reaction with methyl nitrite are dimethyl carbonate and methyl formate, and the hydrolysis products of dimethyl carbonate and methyl formate are methanol. Therefore, in actual production, the dimethyl oxalate product contains organic substances such as dimethyl carbonate, methyl formate and methanol. Since the melting point of dimethyl oxalate is 54°C, in order to avoid crystallization blockage in the dimethyl oxalate conveying pipeline, a temperature above 70°C is generally used for the conveyance of dimethyl oxalate. The dimethyl oxalate product is conveyed to a storage tank for temporary storage. The temperature in the storage tank is relatively high, while the boiling point of methanol is 65°C and the boiling point of dimethyl carbonate is 90°C, which are easily volatilized into gas in the storage tank, resulting in an increase in the internal pressure of the storage tank. To ensure the safety of the storage tank, it is necessary to discharge the gaseous substances in the storage tank under high pressure. The existing dimethyl oxalate storage tanks generally adopt high-point discharge. Under the condition that the temperature is greater than 70°C, organic substances will be discharged into the atmosphere, which is not conducive to the environment. Content of the Utility Model

[0003] The utility model aims to provide a harmless emission device for volatile organic gases in a dimethyl oxalate storage tank to solve the problem of discharging organic substances from the dimethyl oxalate storage tank.

[0004] To achieve the above purpose, the solution of the utility model is: a harmless emission device for volatile organic gases in a dimethyl oxalate storage tank, including a storage tank, and further including a liquid seal tank. The top of the storage tank is connected with a discharge pipe. A pressure transmitter for detecting the air pressure in the tank is fixedly installed on the storage tank. A regulating valve I signal-connected to the pressure transmitter is installed on the discharge pipe. The end of the discharge pipe far from the storage tank extends into the liquid seal tank and is below the liquid level in the liquid seal tank. The liquid seal tank is filled with methanol, and the top of the liquid seal tank is connected with a tail gas pipe.

[0005] The working principle and beneficial effects of this solution are as follows: In this solution, a pressure transmitter is used to detect the air pressure in the storage tank. When the air pressure exceeds the standard, the regulating valve I on the discharge pipe automatically opens, and the organic gas (bleed gas) in the storage tank is discharged into the liquid seal tank through the discharge pipe, where it is washed and dissolved by the methanol in the liquid seal tank. The methanol, dimethyl carbonate, and dimethyl oxalate in the gas are dissolved, and the remaining tail gas (mainly composed of nitrogen and trace methanol) is sent to the incinerator for incineration through the tail gas pipe, thus avoiding the emission of organic substances into the atmosphere, achieving zero emission of harmful substances, and being environmentally friendly. Moreover, when the air pressure in the storage tank drops to the safe value, the regulating valve I automatically closes.

[0006] Optionally, one end of the discharge pipe located in the liquid seal tank is provided with a coiled pipe, and a number of air holes are arranged along the circumferential direction of the liquid seal tank on the coiled pipe.

[0007] In this solution, a number of air holes on the coiled pipe serve as the outlets of the gas. In this way, the gas can be divided into several small airflows, increasing the contact area between the gas and methanol, and thus ensuring that the organic substances are completely dissolved in methanol.

[0008] Optionally, the air holes are arranged obliquely downward.

[0009] In this solution, the gas has a relatively fast initial velocity when discharged through the air holes, and the oblique downward arrangement can slow down the upward floating speed of the gas in methanol, thereby prolonging the residence time of the gas in methanol.

[0010] Optionally, a methanol replenishing pipe is connected to the top end of the liquid seal tank, a methanol drain pipe is connected to the bottom end of the liquid seal tank, a liquid level transmitter for detecting the liquid level in the tank is fixedly installed on the liquid seal tank, a regulating valve III signal-connected to the liquid level transmitter is installed on the methanol replenishing pipe, and a regulating valve IV signal-connected to the liquid level transmitter is installed on the methanol drain pipe.

[0011] In this solution, the liquid level height in the liquid seal tank is detected by the liquid level transmitter. When the liquid level height is too high, the regulating valve IV automatically opens, and the methanol in the liquid seal tank is automatically discharged to the DMO withdrawal tank; when the liquid level height is too low, the regulating valve III automatically opens, and fresh methanol is replenished into the liquid seal tank, realizing the automatic control of the liquid level height in the liquid seal tank.

[0012] Optionally, the discharge pipe is connected to a nitrogen gas pipe, and the connection point of the nitrogen gas pipe and the discharge pipe is located between the storage tank and the regulating valve I. A regulating valve II signal-connected to the pressure transmitter is installed on the nitrogen gas pipe; a dimethyl oxalate drain pipe is connected to the bottom end of the storage tank, and a screw pump is installed on the dimethyl oxalate drain pipe.

[0013] In this solution, as the amount of dimethyl oxalate in the storage tank increases or decreases (the produced dimethyl oxalate is sent into the storage tank, and at the same time, the dimethyl oxalate in the storage tank is transported to the subsequent section through the dimethyl oxalate drain pipe for hydrogenation reaction), the air pressure in the storage tank fluctuates. When the air pressure in the storage tank is lower than the set pressure, the control valve II automatically opens, so as to supplement nitrogen into the storage tank through the nitrogen pipe and raise the air pressure in the storage tank to a safe value.

[0014] Optionally, a hot water jacket is sleeved outside the discharge pipe, and the hot water jacket is located at one end of the discharge pipe close to the storage tank.

[0015] In this solution, the discharge pipe is insulated by the hot water jacket, so that the gas in the pipe is kept at about 80 °C and the crystallization of dimethyl oxalate in the pipe is avoided.

[0016] Optionally, the length of the hot water jacket is more than 3m.

[0017] In this solution, the length of the hot water jacket is limited to more than 3m to ensure the heat exchange effect.

[0018] Optionally, a temperature transmitter for detecting the liquid temperature in the tank is fixedly installed on the liquid seal tank, and the temperature transmitter is signal-connected to the control valve III.

[0019] In this solution, the temperature of methanol in the liquid seal tank is detected by the temperature transmitter, so as to timely supplement fresh methanol (30 °C) and avoid too high temperature of methanol in the tank. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of a harmless emission device for volatile organic gases of a dimethyl oxalate storage tank in Embodiment 1 of the present utility model;

[0021] Figure 2 is a bottom view of the coiled pipe in Embodiment 1 of the present utility model;

[0022] Figure 3 is a schematic structural diagram of a harmless emission device for volatile organic gases of a dimethyl oxalate storage tank in Embodiment 2 of the present utility model. Detailed Description of the Embodiments

[0023] The following is further detailed through specific embodiments:

[0024] The marks in the attached drawings of the specification include: storage tank 1, liquid seal tank 2, discharge pipe 3, dimethyl oxalate inlet pipe 4, dimethyl oxalate drain pipe 5, pressure transmitter 6, control valve I 7, screw pump 8, nitrogen pipe 9, control valve II 10, hot water jacket 11, coiled pipe 12, air hole 121, tail gas pipe 13, methanol replenishing pipe 14, methanol drain pipe 15, liquid level transmitter 16, control valve III 17, control valve IV 18, temperature transmitter 19.

[0025] Example 1

[0026] This embodiment is basically as Figure 1 shown: A harmless emission device for volatile organic gases from a dimethyl oxalate storage tank, including a storage tank 1 and a liquid seal tank 2. A discharge pipe 3 is connected to the top of the storage tank 1, a dimethyl oxalate inlet pipe 4 is connected to the side end of the storage tank 1, and a dimethyl oxalate drain pipe 5 is connected to the bottom end of the storage tank 1. A pressure transmitter 6 for detecting the air pressure inside the tank is fixedly installed on the storage tank 1, and a control valve I 7 electrically connected to the pressure transmitter 6 is installed on the discharge pipe 3. The dimethyl oxalate inlet pipe 4 is used to transport newly synthesized dimethyl oxalate to the storage tank 1, and a check valve is installed on the dimethyl oxalate inlet pipe 4. A screw pump 8 is installed on the dimethyl oxalate drain pipe 5, and the dimethyl oxalate is pumped to the hydrogenation synthesis section (i.e., the subsequent section) by the screw pump 8.

[0027] A nitrogen gas pipe 9 is connected to the discharge pipe 3. The connection point of the nitrogen gas pipe 9 and the discharge pipe 3 is located between the storage tank 1 and the control valve I 7. A control valve II 10 electrically connected to the pressure transmitter 6 is installed on the nitrogen gas pipe 9. The control valve I 7 and the control valve II 10 are in a normally closed state. A hot water jacket 11 is sleeved outside the discharge pipe 3. The hot water jacket 11 is located at one end of the discharge pipe 3 close to the storage tank 1. The temperature of the heat exchange medium (water) in the hot water jacket 11 is 80°C, so as to keep the gas temperature in the pipe at about 80°C by using the hot water jacket 11 and prevent dimethyl oxalate from crystallizing in the discharge pipe 3.

[0028] The liquid seal tank 2 is filled with methanol. One end of the discharge pipe 3 far from the storage tank 1 extends into the liquid seal tank 2 and is located below the liquid level in the liquid seal tank 2. And, a coil pipe 12 is provided at one end of the discharge pipe 3 located in the liquid seal tank 2. Combined Figure 2 as shown, a plurality of air holes 121 are provided along the circumferential direction of the liquid seal tank 2 on the coil pipe 12. Specifically, the coil pipe 12 is close to the bottom of the liquid seal tank 2, and 5mm air holes 121 are opened at an angle of 45° obliquely downward every 50mm on the coil pipe 12. A tail gas pipe 13 and a methanol replenishing pipe 14 are connected to the top end of the liquid seal tank 2, a methanol drain pipe 15 is connected to the bottom end of the liquid seal tank 2. A liquid level transmitter 16 for detecting the liquid level inside the tank is fixedly installed on the liquid seal tank 2. A control valve III 17 electrically connected to the liquid level transmitter 16 is installed on the methanol replenishing pipe 14. A control valve IV 18 electrically connected to the liquid level transmitter 16 is installed on the methanol drain pipe 15. The control valve III 17 and the control valve IV 18 are in a normally closed state.

[0029] In actual use, the newly synthesized dimethyl oxalate is sent to storage tank 1 (the conveying temperature of dimethyl oxalate is 90 °C). The dimethyl oxalate in storage tank 1 will be sent to the hydrogenation synthesis section. Since the inflow and outflow of dimethyl oxalate are not balanced at all times, and methanol and dimethyl carbonate will evaporate at 90 °C, the air pressure in storage tank 1 fluctuates. The pressure transmitter 6 detects the air pressure in storage tank 1. When the air pressure in storage tank 1 is higher than the set pressure (0.4 MPa), the regulating valve I 7 automatically opens. The purge gas (organic gas in storage tank 1) enters the liquid seal tank 2 through the discharge pipe 3 and is divided into several small air streams through the air holes 121 on the coil 12 and discharged into methanol, and is washed and dissolved by methanol, so that the organic substances such as methanol, dimethyl carbonate, and dimethyl oxalate in the purge gas are dissolved in the liquid seal tank 2. The remaining tail gas (the main components are nitrogen and methanol) is discharged to the fractional incinerator through the tail gas pipe 13 for incineration, and zero emission of harmful substances can be achieved. Moreover, as the purge gas in storage tank 1 is discharged, the air pressure in storage tank 1 decreases. When the air pressure in storage tank 1 decreases to 0.4 MPa, the regulating valve I 7 automatically closes and stops exhausting. When the air pressure in storage tank 1 is lower than the set pressure (0.4 MPa), the regulating valve II 10 automatically opens, and nitrogen gas at 0.7 MPa is transported to storage tank 1 through the nitrogen gas pipe 9, so as to increase the air pressure in storage tank 1. When the air pressure in storage tank 1 rises to 0.4 MPa, the regulating valve II 10 automatically closes and stops nitrogen supplementation.

[0030] Furthermore, in the above process, when the purge gas initially enters the discharge pipe 3, it exchanges heat with the hot water jacket 11 to ensure that the temperature of the purge gas remains at about 80 °C, avoiding the crystallization of dimethyl oxalate in the purge gas in the pipe. In addition, the liquid level height in the liquid seal tank 2 is detected by the liquid level transmitter 16. When the liquid level height in the liquid seal tank 2 is higher than the set liquid level (75% of the internal height of the liquid seal tank 2), the regulating valve IV 18 automatically opens, and the methanol in the liquid seal tank 2 is discharged to the DMO withdrawal tank through the methanol drain pipe 15. The liquid level height in the liquid seal tank 2 gradually decreases. When the liquid level height drops to 55%, the regulating valve IV 18 automatically closes and stops methanol discharge. When the liquid level height in the liquid seal tank 2 is lower than the set liquid level (50% of the internal height of the liquid seal tank 2), the regulating valve III 17 automatically opens, and fresh methanol (30 °C) is supplemented into the liquid seal tank 2. The liquid level height in the liquid seal tank 2 gradually rises. When the liquid level height rises to 55%, the regulating valve III 17 automatically closes and stops methanol supplementation. In this way, the liquid level height in the liquid seal tank 2 can be ensured to be maintained within the set range. In addition, during operation, the worker regularly replaces the methanol in the liquid seal tank 2 according to the sampling and analysis effect of SC001.

[0031] Example 2

[0032] The difference between this example and Example 1 is that: as Figure 3As shown in the figure, in this embodiment, a temperature transmitter 19 for detecting the temperature of the liquid in the liquid seal tank 2 is fixedly installed on the liquid seal tank 2, and the temperature transmitter 19 is electrically connected to the control valve III 17.

[0033] In this embodiment, the temperature of methanol in the liquid seal tank 2 is detected by the temperature transmitter 19. When the temperature of methanol is higher than the preset temperature (45 °C), the control valve III 17 automatically opens to supplement fresh methanol (30 °C) into the liquid seal tank 2, thereby reducing the temperature of methanol in the tank. When the temperature of methanol in the tank drops to 35 °C, the control valve III 17 automatically closes to stop the methanol supplement. During the methanol supplement process, when the level transmitter 16 detects that the liquid level is too high, the control valve IV 18 automatically opens to discharge methanol to avoid too high a liquid level in the liquid seal tank 2.

[0034] The above are only embodiments of the present invention. Common knowledge such as specific structures and characteristics known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the present invention. The specific implementation manners and the like described in the specification can be used to explain the content of the claims.

Claims

1. An apparatus for harmless emission of volatile organic gases from a dimethyl oxalate storage tank, comprising a storage tank, characterized in that: It also includes a liquid-sealed tank. The top end of the storage tank is connected with a discharge pipe. A pressure transmitter for detecting the air pressure inside the tank is fixedly installed on the storage tank. A control valve I signal-connected to the pressure transmitter is installed on the discharge pipe. The end of the discharge pipe far from the storage tank extends into the liquid-sealed tank and is below the liquid level in the liquid-sealed tank. Methanol is contained in the liquid-sealed tank. The top end of the liquid-sealed tank is connected with a tail gas pipe.

2. The harmless emission device for volatile organic gases from the dimethyl oxalate storage tank according to claim 1, wherein: One end of the discharge pipe located in the liquid-sealed tank is provided with a coil pipe, and a plurality of air holes are arranged along the circumferential direction of the liquid-sealed tank on the coil pipe.

3. The harmless emission device for volatile organic gases from the dimethyl oxalate storage tank according to claim 2, wherein: The air holes are arranged obliquely downward.

4. The harmless emission device for volatile organic gases from the dimethyl oxalate storage tank according to claim 1, characterized in that: The top end of the liquid-sealed tank is connected with a methanol replenishing pipe, the bottom end of the liquid-sealed tank is connected with a methanol drainage pipe. A level transmitter for detecting the liquid level inside the tank is fixedly installed on the liquid-sealed tank. A control valve III signal-connected to the level transmitter is installed on the methanol replenishing pipe. A control valve IV signal-connected to the level transmitter is installed on the methanol drainage pipe.

5. The harmless emission device for volatile organic gases from the dimethyl oxalate storage tank according to claim 1, characterized in that: The discharge pipe is communicated with a nitrogen gas pipe, and the connection point of the nitrogen gas pipe and the discharge pipe is located between the storage tank and the control valve I. A control valve II signal-connected to the pressure transmitter is installed on the nitrogen gas pipe; The bottom end of the storage tank is connected with a dimethyl oxalate drainage pipe, and a screw pump is installed on the dimethyl oxalate drainage pipe.

6. The harmless emission device for volatile organic gases from the dimethyl oxalate storage tank according to claim 1, characterized in that: A hot water jacket is sleeved outside the discharge pipe, and the hot water jacket is located at the end of the discharge pipe close to the storage tank.

7. The device for harmless emission of volatile organic gases from the dimethyl oxalate storage tank according to claim 6, wherein: The length of the hot water jacket is more than 3m.

8. The harmless emission device for volatile organic gases from the dimethyl oxalate storage tank according to claim 4, wherein: A temperature transmitter for detecting the liquid temperature inside the tank is fixedly installed on the liquid-sealed tank, and the temperature transmitter is signal-connected to the control valve III.

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