Dimethyl phosphite production tail gas negative pressure treatment device

Abstract

The utility model discloses a negative-pressure treatment device for tail gas generated in dimethyl phosphite production. The negative-pressure treatment device comprises a vacuum part, a condensation part and an absorption treatment part, the vacuum part comprises a buffer tank A, a Roots vacuum pump unit and a buffer tank B, the buffer tank A is provided with a tail gas inlet A, a tail gas outlet A and a methanol collecting tank A, the tail gas outlet A is connected with the Roots vacuum pump unit through a gas inlet pipeline, the Roots vacuum pump unit is connected with the buffer tank B through a gas outlet pipeline, and the top of the buffer tank B is provided with a tail gas outlet B; a methanol collecting tank B is arranged at the bottom of the buffer tank B; the condensing part comprises a condenser and a methanol collecting tank C, the tail gas outlet B is connected with the condenser, and the lower end of the condenser is connected with the methanol collecting tank C; the absorption treatment part comprises a multi-stage water absorption tower and an alkali absorption tower, the condenser is connected with the multi-stage water absorption tower, the multi-stage water absorption tower is connected with the alkali absorption tower, and a tail gas output pipeline is arranged at the top of the alkali absorption tower; the device disclosed by the utility model has the advantages of low production cost, high recycling rate and good chloromethane product quality.

Description

Technical Field

[0001] This utility model belongs to the technical field of dimethyl phosphite production equipment, specifically relating to a negative pressure treatment device for tail gas in dimethyl phosphite production. Background Technology

[0002] Dimethyl phosphite is an important product in fine chemicals. It is an intermediate in the production of pesticides such as glyphosate, trichlorfon, isoprothiolane, and dimethoate. It is also a raw material for organophosphorus corrosion inhibitors, dye additives, plastic additives, and flame retardants. It can be used to synthesize water treatment agents and as a methylating agent in the synthesis of quaternary ammonium salt bactericides, antistatic agents, and softeners.

[0003] With the rise of the domestic herbicide industry, the production of glyphosate has been increasing, leading to a growing demand for dimethyl phosphite, a raw material for glyphosate production, and increasingly stringent quality requirements. Currently, the most common industrial synthesis method for dimethyl phosphite in China uses methanol and phosphorus trichloride as raw materials under specific conditions; this method is relatively simple and easy to operate. The production and distillation of dimethyl phosphite are carried out under negative pressure. During this process, a large amount of byproduct gas chloromethane is generated, which, along with the raw material methanol, forms the production tail gas, the main component of which is chloromethane. Typically, the dimethyl phosphite production tail gas is neutralized and dried with concentrated sulfuric acid under negative pressure to purify the chloromethane to a qualified level before being used as a raw material in other production processes, such as the synthesis of new energy materials. However, existing negative pressure systems typically employ multiple W-type reciprocating vacuum pumps connected in parallel. These systems generally suffer from low efficiency, excessive power consumption, and high energy consumption during operation. The exhaust gas temperature is too high, requiring significant power for compression during chloromethane recovery, resulting in high noise levels, a poor working environment, and frequent maintenance. Furthermore, methanol in the exhaust gas is difficult to collect, and hydrogen chloride absorption is incomplete, significantly impacting the subsequent drying of chloromethane with concentrated sulfuric acid and the quality of the chloromethane product. This not only leads to methanol cost losses but also, due to excessively high methanol content, directly increases the consumption of concentrated sulfuric acid, making it difficult to guarantee the purity of the chloromethane. Therefore, to address the problems of high power consumption, high noise, frequent maintenance, and incomplete exhaust gas treatment with numerous impurities in negative pressure systems, it is urgent to improve the existing negative pressure treatment device for dimethyl phosphite production exhaust gas, thereby achieving energy saving, consumption reduction, and improved chloromethane product quality. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a negative pressure treatment device for the tail gas of dimethyl phosphite production with low production cost, high recycling rate, and good quality of chloromethane products.

[0005] The purpose of this utility model is achieved as follows: a negative pressure treatment device for tail gas from dimethyl phosphite production, comprising a vacuum section, a condensation section, and an absorption treatment section;

[0006] The vacuum section includes a buffer tank A, a Roots vacuum pump unit, and a buffer tank B. Buffer tank A has a tail gas inlet A on one side, a tail gas outlet A on the top, and a methanol collection tank A at the bottom. The tail gas outlet A is connected to the Roots vacuum pump unit via an inlet pipe. The Roots vacuum pump unit is connected to one side of buffer tank B via an outlet pipe. Buffer tank B has a tail gas outlet B on the top and a methanol collection tank B at the bottom.

[0007] The condensation section includes a condenser and a methanol collection tank C. The exhaust gas outlet B is connected to the condenser, and the lower end of the condenser is connected to the methanol collection tank C.

[0008] The absorption treatment unit includes a multi-stage water absorption tower and an alkali absorption tower. The condenser is connected to the multi-stage water absorption tower, and the multi-stage water absorption tower is connected to the alkali absorption tower. The top of the alkali absorption tower is provided with a tail gas output pipe.

[0009] Preferably, the Roots vacuum pump unit includes multiple Roots vacuum pumps connected in series, each of which is equipped with a cooler located below the Roots vacuum pump. The cooler has a methanol discharge port connected to a small collection tank.

[0010] Preferably, a vacuum pressure gauge A and a gas composition analyzer A are installed on the air inlet pipe, and a vacuum pressure gauge B is installed on the air outlet pipe.

[0011] Preferably, methanol collection tank A, methanol collection tank B and methanol collection tank C are all equipped with top-mounted magnetic level gauges.

[0012] Preferably, the condenser is a tubular condenser, the main body of which is a graphite condenser, and the condensing medium is chilled brine.

[0013] Preferably, the multi-stage water absorption tower includes multiple water absorption towers connected in series. Each water absorption tower includes a bottom and a tower body. A magnetic level gauge is installed in the bottom of the bottom. A circulation port is provided at the bottom of the bottom. An air outlet is provided at the top of the tower body. A demister is installed on the upper part of the tower body. A reflux port is provided below the demister. Packing material is installed in the middle of the tower body. A grid plate is provided below the packing material. An air inlet is provided at the bottom of the tower body. A circulation pipe is provided between the circulation port and the reflux port. A circulation pump, an online liquid flow meter, an online COD monitor, a pH meter, and control valves are installed on the circulation pipe. The alkali absorption tower has the same configuration as the water absorption tower.

[0014] Preferably, the filler is a titanium alloy or plastic.

[0015] Preferably, a gas composition analyzer B and a moisture detector are installed on the exhaust gas output pipe.

[0016] Due to the adoption of the above technical solutions, the beneficial effects of this utility model are as follows: This utility model uses a Roots vacuum pump unit to replace the original multiple W-type reciprocating vacuum pumps, which reduces power and energy consumption, and also reduces noise pollution, maintenance difficulty, and maintenance frequency, effectively saving production costs; This utility model uses buffer tank A, methanol collection pipe A, buffer tank B, methanol collection tank B, condenser and methanol collection tank C, as well as multi-stage water absorption tower and alkali absorption tower to sequentially remove methanol and hydrogen chloride. It can condense and collect the methanol component in the tail gas multiple times, which is convenient for recycling. While removing impurities, it also reduces the cost of subsequent concentrated sulfuric acid drying gas. It can also remove impurities such as hydrogen chloride and further absorb the uncondensed methanol, which greatly improves the quality of tail gas purification treatment; In summary, this utility model has the advantages of low production cost, high recycling rate, and good quality chloromethane product. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0018] Figure 2 This is a schematic diagram of the structure of the multi-stage water absorption tower of this utility model.

[0019] In the diagram: 1. Exhaust gas inlet pipe; 2. Buffer tank A; 21. Exhaust gas inlet A; 22. Exhaust gas outlet A; 3. Inlet pipe; 4. Vacuum pressure gauge A; 5. Gas composition analyzer A; 6. Roots vacuum pump unit; 61. Roots vacuum pump; 62. Cooler; 63. Small collection tank; 7. Outlet pipe; 8. Vacuum pressure gauge B; 9. Buffer tank B; 91. Exhaust gas outlet B; 10. Methanol collection tank A; 11. Top-impact magnetic level gauge; 12. Methanol collection tank B; 13. Condenser; 14. Methanol collection tank C. 15. Multistage water absorption tower 151, water absorption tower 15101, tower bottom 15102, tower body 15103, air inlet 15104, grid plate 15105, packing 15106, demister 15107, air outlet 15108, reflux port 15109, circulation pipeline 15110, online COD monitor 15111, pH meter 15112, online liquid flow meter 15113, circulation pump 15114, control valve 15115, circulation port 15116, magnetic level gauge 16, alkali absorption tower 17, tail gas output pipeline 18, gas composition analyzer B 19, moisture monitor. Detailed Implementation

[0020] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 and Figure 2 As shown, this utility model provides a negative pressure treatment device for tail gas from dimethyl phosphite production, which is mainly used to solve the problems of high power consumption of vacuum pump in negative pressure system, high noise, frequent maintenance, incomplete tail gas treatment and many impurities in the existing technology of the device.

[0022] The device mainly consists of three parts: a vacuum section, a condensation section, and an absorption and treatment section.

[0023] The main equipment in the vacuum section is a vacuum unit, which provides negative pressure for the production of dimethyl phosphite in the workshop. The vacuum pump is preferably a Roots vacuum pump 61, which is quiet, energy-efficient, and stable in operation. The vacuum unit is a Roots vacuum pump unit 6, composed of multiple Roots vacuum pumps 61 connected in series, preferably 4-5. A vacuum pressure gauge A4 and a gas composition analyzer A5 are installed on the inlet pipe 3 of the Roots vacuum pump unit 6, and connected to a buffer tank A2. The air inlet of the buffer tank A2 is located on its side (i.e., the exhaust gas inlet A21), which is connected to the exhaust gas input pipe 1. The air outlet of the buffer tank A2 is located at its top (i.e., the exhaust gas outlet A22). A methanol discharge port is provided at the bottom of the buffer tank A2, and a control valve is installed. The material enters the methanol collection tank A10, which is equipped with a top-mounted magnetic level gauge 11. Each Roots vacuum pump 61 is equipped with a cooler 62, located below the Roots vacuum pump 61. The cooler 62 has cooling water inlet and outlet to cool the negative pressure exhaust gas flowing through it. A methanol discharge port is located below the cooler 62, and the material enters a small collection tank 63. The outlet of the Roots vacuum pump unit 6 is connected to a buffer tank B9 via an outlet pipe 7. The inlet of the buffer tank B9 is located on its side, and the outlet is located on its top (i.e., exhaust gas outlet B91). A vacuum pressure gauge B8 is installed on the outlet pipe 7. A methanol discharge port with a control valve is located at the bottom of the buffer tank B9, and the material enters a methanol collection tank B12. The methanol collection tank B12 is equipped with a top-mounted magnetic level gauge 11. The exhaust gas outlet 91 at the top of the buffer tank B9 is connected to a condenser.

[0024] The condensation section primarily condenses and collects methanol in the exhaust gas, removing methanol impurities and collecting it in methanol collection tank C14 for recycling. The condensation section mainly consists of condenser 13, whose gas inlet is connected to the exhaust gas outlet B91. Its main body is a graphite condenser, specifically a tubular condenser, which offers good condensation efficiency, thorough methanol condensation, and low methanol impurity levels in the exhaust gas. Condenser 13 has chilled brine inlet and outlet, and a methanol discharge port is located below condenser 13, allowing the material to enter methanol collection tank B14. Methanol collection tank B14 is also equipped with a top-mounted magnetic level gauge 11. The gas outlet of condenser 13 is connected to the absorption and treatment section via a pipeline.

[0025] The absorption treatment unit primarily removes hydrogen chloride impurities from the tail gas. It employs a combination of a multi-stage water absorption tower 15 and an alkali absorption tower 16 to remove hydrogen chloride impurities and further absorb any uncondensed methanol. The multi-stage water absorption tower 15 consists of one or more water absorption towers 151 connected in series; the number of water absorption towers 151 is determined according to the application requirements. The water absorption tower 151 mainly includes a bottom 15101 and a tower body 15102. A magnetic level gauge 15116 is installed in the bottom 15101, and a circulation port 15115 is set at the bottom of the bottom 15101. A demister 15106 is installed above the tower body 15102, and a return port 15108 is set below the demister 15106. Packing material 15105 is installed in the middle. The packing material 15105 is made of titanium alloy or plastic, preferably plastic to save costs. Below the packing material 15105 is a grid plate 15104, and below the grid plate 15104 is an air inlet 15103, which is connected to the gas outlet of the condenser 13. A circulation pipe 15109 is installed between the circulation port 15115 and the return port 15108 via a circulation pump 15113. An online liquid flow meter 15112, an online COD detector 15110, a pH meter 15111, and a control valve 15114 are installed on the circulation pipe 15109 to facilitate analysis of water quality changes and control and timely replacement of the water absorption liquid. The alkali absorption tower 16 is a primary alkali absorption tower, with the same structure as the water absorption tower. The top of the alkali absorption tower 16 is a tail gas output pipe 17, on which a gas composition analyzer B18 and a moisture detector 19 are installed. By comparing the gas composition before and after treatment, the treatment effect can be clearly seen, and data support is provided for subsequent drying of chloromethane with concentrated sulfuric acid. The tail gas output pipe 17 is connected to external chloromethane drying and compression equipment.

[0026] The measuring equipment and instruments of this device all adopt digital display mode and have data remote transmission function to facilitate remote understanding and adjustment of the device's operation. To facilitate remote adjustment and control of the device's operation, a DCS control center can be equipped, and control valves can be installed at the required locations on the device, such as control valve 15114 on the circulation pipeline 15109 of the water absorption tower 151, including but not limited to the tail gas inlet A21, methanol discharge port, gas inlet of the Roots vacuum pump unit 6, gas inlet and gas outlet of the condenser 13, gas inlet of the multi-stage water absorption tower 15, gas inlet of the alkali absorption tower 16, etc.

[0027] After the above installation is completed, this utility model can be put into use. Turn on each Roots vacuum pump 61. Under negative pressure, the exhaust gas enters the buffer tank A2 from the exhaust gas inlet pipe 1 and exhaust gas inlet A21. The methanol produced by condensation in the buffer tank A2 is collected in the methanol collection tank A10 below it. The exhaust gas in the buffer tank A2 enters the Roots vacuum pump unit 6 through the exhaust gas outlet A22 and inlet pipe 3. The methanol produced by condensation in the cooler 62 below the Roots vacuum pump 61 is collected in the small collection tank 63 below it. The exhaust gas flowing through the Roots vacuum pump unit 6 enters the buffer tank B9 through the outlet pipe 7. The methanol produced by condensation in the buffer tank B9 is collected in the methanol collection tank B below it. 12. The tail gas in buffer tank B9 enters condenser 13 through tail gas outlet B91. The methanol produced by condensation in condenser 13 is collected in methanol collection tank C14 below it. The tail gas flowing through condenser 13 enters the gas inlet of multi-stage water absorption tower 15 through its gas outlet. The tail gas flowing through multi-stage water absorption tower 15 enters the gas inlet of alkali absorption tower 16 through its gas outlet. The tail gas flowing through alkali absorption tower 16 is sent to the subsequent chloromethane drying and compression equipment through tail gas output pipe 17.

[0028] During this period, the negative pressure conditions in the control pipeline can be adjusted using vacuum pressure gauges A4 and B8; the tail gas treatment effect can be assessed by comparing the results before and after treatment using gas composition analyzers A5 and B18; methanol material in methanol collection tanks A10, B12, and C14 can be transferred out using the corresponding top-mounted magnetic level gauges 11, and methanol material in each small collection tank 63 can be transferred out periodically; the flow rate of the water absorption liquid in the circulation pipeline 15109 can be adjusted and controlled using online liquid flow meter 15112 and circulation pump 15113, and the water quality of the water absorption liquid can be monitored and replaced in a timely manner using online COD monitor 15110 and pH meter 15111, similar to the operation of the alkali absorption tower 16; and data support for the subsequent drying of chloromethane with concentrated sulfuric acid can also be provided using gas composition analyzer B18 and moisture detector 19.

[0029] In summary, this invention can effectively solve the problems of high power consumption, high noise, frequent maintenance, incomplete treatment of tail gas and many impurities in the existing negative pressure system for dimethyl phosphite production tail gas negative pressure treatment. It can effectively reduce production costs, improve methanol recovery and utilization rate, improve the quality of chloromethane products, and can be remotely controlled and adjusted to reduce the reaction time of abnormal problems. It can also reduce human resource input and expenditure, and is convenient, fast and effective.

[0030] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A negative pressure treatment device for tail gas from dimethyl phosphite production, characterized in that: It includes a vacuum section, a condensation section, and an absorption treatment section; The vacuum section includes a buffer tank A, a Roots vacuum pump unit, and a buffer tank B. Buffer tank A has a tail gas inlet A on one side, a tail gas outlet A on the top, and a methanol collection tank A at the bottom. The tail gas outlet A is connected to the Roots vacuum pump unit via an inlet pipe. The Roots vacuum pump unit is connected to one side of buffer tank B via an outlet pipe. Buffer tank B has a tail gas outlet B on the top and a methanol collection tank B at the bottom. The condensation section includes a condenser and a methanol collection tank C. The exhaust gas outlet B is connected to the condenser, and the lower end of the condenser is connected to the methanol collection tank C. The absorption treatment unit includes a multi-stage water absorption tower and an alkali absorption tower. The condenser is connected to the multi-stage water absorption tower, and the multi-stage water absorption tower is connected to the alkali absorption tower. The top of the alkali absorption tower is provided with a tail gas output pipe.

2. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 1, characterized in that: The Roots vacuum pump unit includes multiple Roots vacuum pumps connected in series. Each of the multiple Roots vacuum pumps is equipped with a cooler located below the Roots vacuum pump. The cooler has a methanol discharge port, which is connected to a small collection tank.

3. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 1, characterized in that: The intake pipe is equipped with a vacuum pressure gauge A and a gas composition analyzer A, and the outlet pipe is equipped with a vacuum pressure gauge B.

4. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 1, characterized in that: The methanol collection tanks A, B, and C are all equipped with top-mounted magnetic level gauges.

5. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 1, characterized in that: The condenser is a tubular condenser, the main body of which is a graphite condenser, and its condensing medium is chilled brine.

6. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 1, characterized in that: The multi-stage water absorption tower includes multiple water absorption towers connected in series. Each water absorption tower includes a bottom and a tower body. A magnetic level gauge is installed in the bottom of the bottom. A circulation port is provided at the bottom of the bottom. An air outlet is provided at the top of the tower body. A demister is installed on the upper part of the tower body. A reflux port is provided below the demister. Packing material is installed in the middle of the tower body. A grid plate is provided below the packing material. An air inlet is provided below the grid plate. A circulation pipe is provided between the circulation port and the reflux port. A circulation pump, an online liquid flow meter, an online COD monitor, a pH meter, and control valves are installed on the circulation pipe. The alkali absorption tower has the same setup as the water absorption tower.

7. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 6, characterized in that: The filler is made of titanium alloy or plastic.

8. The negative pressure treatment device for dimethyl phosphite production tail gas according to claim 1, characterized in that: A gas composition analyzer B and a moisture detector are installed on the exhaust gas output pipe.

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