Propylene glycol methyl ether reaction dealcoholization equipment and process method for improving energy recycling efficiency

Abstract

The application discloses propylene glycol methyl ether reaction dealcoholization equipment and process method for improving energy recycling efficiency, and relates to the technical field of fine chemicals production. The propylene glycol methyl ether reaction dealcoholization equipment comprises a reactor, a pressure stabilizing tank, a flash tank, a reaction liquid tank, a reaction liquid pump, a reaction liquid tail cooler, a methanol tower reboiler, a methanol tower, a methanol tower condenser and a methanol tower tail cooler; the reactor is connected with the flash tank, and the flash tank is connected with the reaction liquid tank and the methanol tower. The production process method comprises the following steps: after etherification reaction of methanol and propylene oxide, the methanol enters the flash tank; the vaporized part of the methanol directly enters the methanol tower under the traction of micro negative pressure; and the remaining liquid phase in the flash tank enters the reaction liquid tank and then enters the methanol tower. The application has the advantages that the energy-saving mode is adopted to extract the methanol in the ether reaction liquid, a part of the methanol in the ether reaction liquid is directly in the gas phase and enters the methanol tower by using the heat of the etherification reaction and a certain negative pressure, the production process is more efficient, the production energy consumption is reduced, and energy is saved.

Description

Technical Field

[0001] This invention relates to the field of fine chemical production technology, specifically to equipment and process for the deethanolination of propylene glycol methyl ether to improve energy recovery and utilization efficiency. Background Technology

[0002] With the rapid development of the chemical industry, while creating wealth for humanity, it also has a significant impact on energy consumption and safety. The government has consistently encouraged the adoption of new energy sources or energy-saving processes to replace high-energy-consuming processes, and the use of safer processes to replace hazardous processes. Propylene glycol methyl ether is mainly used as a solvent, dispersant, and diluent. It is also used as a fuel antifreeze, extractant, and intermediate for the herbicide metolachlor. As a solvent, dispersant, or diluent, it is used in the coatings, inks, printing and dyeing, pesticides, cellulose, and acrylate industries. It can also be used as a fuel antifreeze, cleaning agent, extractant, and non-ferrous metal beneficiation agent. Furthermore, it is used as a raw material for organic synthesis, primarily as an excellent solvent for nitrocellulose, alkyd resins, and maleic anhydride-modified phenolic resins. It is also used as an antifreeze for jet fuels and as an additive in brake fluids.

[0003] The production process of propylene glycol methyl ether involves the reaction of methanol and propylene oxide. Because propylene oxide is relatively hazardous, methanol is used in excess during the reaction to ensure complete reaction of propylene oxide. Furthermore, since propylene glycol methyl ether has a boiling point of 120°C, the finished product is gradually separated by distillation, which consumes a large amount of steam. Therefore, the production process should pay more attention to energy recycling. However, our traditional production process consumes a lot of energy, so it is necessary to develop a process that improves the energy recovery and utilization efficiency of propylene glycol methyl ether.

[0004] The main process of deethanolating propylene glycol methyl ether reaction solution involves the reaction solution being distilled and separated in a methanol tower after the etherification reaction. The main production process flow of the deethanolating propylene glycol methyl ether reaction solution in the existing technology is shown in the attached figure. Figure 1 As shown, the raw materials methanol and propylene oxide first react in reactor 1, and then, under the protection of pressure stabilizing tank 2, are cooled by reaction liquid cooler 3 before entering reaction liquid tank 4. The tail gas from reaction liquid tank 4 is connected to reaction liquid tail cooler 6. The etherification reaction mixture (methanol, propylene glycol methyl ether, 2-methoxy-1-propanol) enters methanol tower 8 through reaction liquid pump 5 for de-alcoholization. Methanol tower 8 is heated by methanol tower reboiler 7 to completely separate methanol from the mixture. After being cooled by methanol tower condenser 9, it enters methanol tower condensate intermediate tank. The tail gas enters methanol tower tail cooler 10 for cooling. The mixture (propylene glycol methyl ether, 2-methoxy-1-propanol) in the tower bottom enters the next rectification process to extract propylene glycol methyl ether product. The temperature after the etherification reaction is about 115℃, which needs to be cooled before entering the reaction liquid tank, and then pumped into methanol tower by reaction liquid pump. Then, methanol tower reboiler is heated and then distilled, which causes a lot of energy loss. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide equipment and process for the de-alcoholization reaction of propylene glycol methyl ether to improve energy recovery and utilization efficiency. It can solve the problems of high energy consumption and serious energy loss in the de-alcoholization reaction of propylene glycol methyl ether in the prior art, making the propylene glycol methyl ether production process more efficient, while reducing energy consumption in production, and achieving the purpose of energy saving and consumption reduction.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: a propylene glycol methyl ether reaction deethanolination device for improving energy recovery and utilization efficiency includes a reactor, a pressure stabilizing tank, a flash tank, a reaction liquid tank, a reaction liquid pump, a reaction liquid tail cooler, a methanol tower reboiler, a methanol tower, a methanol tower condenser, and a methanol tower tail cooler. The reactor's reaction liquid outlet is connected to the flash tank's feed inlet via pipe A, and a pressure stabilizing tank is connected to pipe A. The flash tank's discharge outlet is connected to the reaction liquid tank's inlet via pipe B, and the flash tank's discharge outlet is connected to the methanol tower's upper section inlet via pipe K. The outlet of the reaction liquid tank is connected to the inlet of the reaction liquid pump via pipe D, and the vent at the top of the reaction liquid tank is connected to the inlet of the reaction liquid tail cooler via pipe C. The outlet of the reaction liquid pump is connected to the inlet of the methanol tower via pipe E; The methanol tower gas phase inlet is connected to the upper gas phase port of the methanol tower reboiler via pipe F; the methanol tower liquid phase outlet is connected to the lower liquid phase port of the methanol tower reboiler via pipe G. The vapor outlet at the top of the methanol tower is connected to the inlet of the methanol tower condenser via pipe H. The outlet of the methanol tower condenser discharges cooled methanol into the methanol reflux tank. The outlet of the methanol tower condenser is connected to the tail cooler of the methanol tower via pipe I, which sends the vapor to the tail cooler for cooling. The outlet of the tail cooler of the methanol tower is connected to the vacuum system via pipe J.

[0007] Furthermore, a methanol tower feed flow meter is installed on the pipeline E.

[0008] Furthermore, a sampling point is provided at the outlet of the reaction liquid pump.

[0009] A process method for producing propylene glycol methyl ether using a propylene glycol dehydrogenation reaction device that improves energy recovery and utilization efficiency is characterized by the following steps: S1, methanol and propylene oxide undergo an etherification reaction in a reactor. After the reaction is completed, the mixture is stably introduced into a flash tank under the protection of a pressure stabilizing tank. S2. After the etherification reaction is completed and discharged from the reaction system into the flash tank, part of the vaporized methanol enters the methanol tower directly from the gas phase pipeline K under slight negative pressure. S3. The remaining methanol, propylene glycol methyl ether, and 2-methoxy-1-propanol liquid phase in the flash tank enter the reaction tank and are then continuously pumped into the methanol tower by the reaction pump. The continuous operation involves sampling and analysis at sampling points to determine the methanol content in the reaction liquid, and the methanol tower feed rate is observed through the methanol tower feed flow meter. S4. The methanol tower is heated by the methanol tower reboiler to separate methanol from propylene glycol methyl ether and 2-methoxy-1-propanol. The bottom temperature of the methanol tower is controlled at 115~125℃ and the top temperature of the tower is controlled at 55~60℃. S5. Methanol gas phase is discharged from the methanol tower, cooled by the methanol tower condenser and methanol tower tail cooler, and then collected in the reflux tank for continued recycling. The outlet pipeline of the methanol tower tail cooler is connected to the vacuum system.

[0010] Furthermore, in step S2, the negative pressure is -35 kPa.

[0011] Furthermore, the pressure of the methanol tower is maintained at -35 kPa.

[0012] The advantages of this invention are: the basic process of the de-alcoholization step in the original propylene glycol methyl ether production process remains unchanged. Instead of the original reaction liquid being cooled by a cooler and then entering the reaction liquid tank, and then being pumped to the methanol tower by the reaction liquid pump, a portion of the methanol vapor phase is introduced into the methanol tower by a flash tank. The equipment does not require major modifications and the equipment improvement cost is low. Since the etherification reaction itself has a heat reaction end temperature of about 115℃, while the boiling point of methanol is 64.8℃, after the reaction ends, the methanol will be converted from liquid to gas after leaving the reaction system. By giving the methanol tower a certain negative pressure, the vaporized methanol can be guided directly into the tower, reducing the energy consumption for cooling and the power consumption of the reaction liquid pump, as well as reducing the load on the methanol tower and reducing the requirements of the methanol tower for steam. When production is relatively high, the methanol tower feed rate reaches 20m³. 3 For methanol towers, separation is difficult and the expected separation effect cannot be achieved. The methanol content in subsequent distillation processes is too high, and it is necessary to reduce the reaction feed load. This invention can reduce the methanol content in the feed, reduce the methanol tower feed rate, and the gaseous methanol is directly drawn into the tower by negative pressure to the condenser, which reduces the methanol tower load, enhances the separation effect, and significantly reduces the methanol content in the subsequent distillation tower. Due to the reduced feed rate to the methanol tower, the heating source for the reboiler can be replaced by the propylene glycol methyl ether vapor phase from the next distillation stage. The vapor phase temperature of propylene glycol methyl ether is approximately 135°C, while the boiling point of methanol is 64.8°C. The vapor phase temperature of propylene glycol methyl ether is 6m³. 3 The original steam consumption of the methanol tower was 5t / h. After the total amount of propylene glycol methyl ether gas phase was reduced, it met the heating requirements of the methanol tower, thus saving 5t / h of low-pressure steam consumption. Attached Figure Description

[0013] Figure 1 This is a simplified flow chart of the alcohol removal process of propylene glycol methyl ether reaction solution in the prior art; Figure 2 This is a simplified flow chart of the flash tank de-alcoholization process of the propylene glycol methyl ether reaction solution in this invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments will enable those skilled in the art to more fully understand this invention, but do not limit the invention to the scope of the described embodiments.

[0015] like Figure 2 As shown, the embodiment adopts the following technical solution: the propylene glycol methyl ether reaction de-alcoholization equipment for improving energy recovery and utilization efficiency includes a reactor 1, a pressure stabilizing tank 2, a flash tank 31, a reaction liquid tank 4, a reaction liquid pump 5, a reaction liquid tail cooler 6, a methanol tower reboiler 7, a methanol tower 8, a methanol tower condenser 9, and a methanol tower tail cooler 10.

[0016] The reaction liquid outlet of reactor 1 is connected to the feed inlet of flash tank 31 via pipe A. Pressure stabilizing tank 2 is connected to pipe A. The discharge outlet of flash tank 31 is connected to the inlet of reaction liquid tank 4 via pipe B. The discharge outlet of flash tank 31 is connected to the upper section inlet of methanol tower 8 via pipe K.

[0017] The outlet of the reaction tank 4 is connected to the inlet of the reaction pump 5 via pipe D, and the vent on the top of the reaction tank 4 is connected to the inlet of the reaction tail cooler 6 via pipe C.

[0018] The outlet of the reaction liquid pump 5 is connected to the inlet of the methanol tower 8 via pipe E. A methanol tower feed flow meter FT1 is installed on pipe E, and a sampling point X1 is set at the outlet of the reaction liquid pump.

[0019] The gas phase inlet of methanol tower 8 is connected to the upper gas phase port of methanol tower reboiler 7 via pipe F; the liquid phase outlet of methanol tower 8 is connected to the lower liquid phase port of methanol tower reboiler 7 via pipe G.

[0020] The gas phase outlet at the top of methanol tower 8 is connected to the inlet of methanol tower condenser 9 via pipe H. The outlet of methanol tower condenser 9 discharges cooled methanol into the methanol reflux tank. The outlet of methanol tower condenser 9 is connected to methanol tower tail cooler 10 via pipe I, which sends the gas phase to methanol tower tail cooler 10 for cooling. The outlet of methanol tower tail cooler 10 is connected to the vacuum system via pipe J.

[0021] A process method for producing propylene glycol methyl ether using a propylene glycol dehydrogenation reaction device that improves energy recovery and utilization efficiency is characterized by the following steps: S1, methanol and propylene oxide undergo an etherification reaction in reactor 1. After the reaction is completed, the mixture is stably introduced into flash tank 31 under the protection of pressure stabilizing tank 2.

[0022] S2. After the etherification reaction is completed and discharged from the reaction system into flash tank 31, part of the vaporized methanol enters methanol tower 8 directly from gas phase pipeline K under a slight negative pressure of -35 kPa.

[0023] S3, the remaining methanol in flash tank 31, as well as propylene glycol methyl ether and 2-methoxy-1-propanol liquid phase, enter reaction tank 4, and are then continuously pumped into methanol tower 8 by reaction pump 5. The continuous operation is carried out by sampling and analysis at sampling point X1 to determine the methanol content in the reaction liquid, and the methanol tower feed rate is observed by methanol tower feed flow meter FT1. The pressure of methanol tower 8 is maintained at -35 kPa.

[0024] S4, Methanol Tower 8 is heated by Methanol Tower Reboiler 7 to separate methanol from propylene glycol methyl ether and 2-methoxy-1-propanol. The bottom temperature of Methanol Tower 8 is controlled at 115~125℃ and the top temperature is controlled at 55~60℃.

[0025] S5. Methanol gas phase is discharged from methanol tower 8, cooled by methanol tower condenser 9 and methanol tower tail cooler 10, and then collected in the reflux tank for continued recycling. The outlet pipeline of methanol tower tail cooler 10 is connected to the vacuum system.

[0026] like Figure 1 As shown, the comparative example adopts the following technical solution: 1) After exiting reactor 1, the reaction liquid is cooled by reaction liquid cooler 3 and then enters reaction liquid tank 4; 2) The reaction liquid pump 5 continuously feeds the methanol tower 8; 3) Use low-pressure steam as a heating source to heat the methanol tower reboiler 7, control the temperature of the methanol tower 8 bottom to 130~140℃, and control the temperature of the tower top to 65~75℃. 4) Sampling analysis can reveal the material content at the control points.

[0027] Sampling analysis revealed the material content at the control points. Sampling analysis at point X1 showed that the methanol content in the reaction solution was approximately 53%, and the FT1 feed rate was 17.5 m³. 3 / h.

[0028] The equipment and processes used in the embodiments and comparative examples were all based on 14.5m. 3 / h of methanol and 4.5m 3 The reaction was carried out with propylene oxide at a concentration of / h, and the results were as follows: In the comparative example, sampling analysis at point X1 showed that the methanol content in the reaction solution was 60%, and the FT1 feed rate was 20m³. 3The low-pressure steam consumption is about 5t / h, which makes separation difficult for methanol tower 8 and fails to achieve the expected separation effect. The methanol content in the subsequent distillation process is too high, at 0.05%, so the reaction feed load needs to be reduced. In the embodiment, the flash evaporator 31 has a flow rate of 2.5m. 3 Methanol vapor was fed into the column at a rate of / h. Sampling and analysis at point X1 showed that the methanol content in the reaction liquid was 53%. The feed rate to methanol column 8FT1 was reduced to 17.5m³. 3 / h, avoiding the consumption of circulating water and reducing the power consumption of reaction liquid pump 5; due to the reduction in the feed rate of methanol tower 8, the heating source of methanol tower reboiler 7 can be replaced by the propylene glycol methyl ether vapor phase of the next rectification process. The vapor phase temperature of propylene glycol methyl ether is about 135℃, the boiling point of methanol is 64.8℃, and the vapor phase temperature of propylene glycol methyl ether is 6m 3 / h, the total feed volume of propylene glycol methyl ether vapor in methanol tower 8 is reduced by 2.5m³. 3 After / h, the heating requirements of methanol tower 8 are met, thereby saving 5t / h of low-pressure steam consumption; and the gaseous methanol entering the tower is directly drawn to the methanol tower condenser 9 by negative pressure, reducing the load on methanol tower 8, enhancing the separation effect, and the methanol content in the subsequent distillation tower is significantly reduced to 0.001%.

[0029] The comparison of the above comparative examples and embodiments shows that: When using flash evaporator 31 to flash-distill a portion of the methanol before distillation in the column, the feed flow rate of the reaction liquid is reduced from 20 m³ / s. 3 / h becomes 17.5m 3 / h, the power of reaction liquid pump 5 is reduced; some methanol vapor is introduced into the tower from flash tank 31, avoiding the need for circulating water required for complete cooling of the reaction liquid and reducing the consumption of utilities; some methanol vapor is introduced into the tower from flash tank 31, reducing the methanol content in the reaction liquid from 60% to 53%, which facilitates purification in subsequent distillation operations; the reaction liquid feed flow rate is reduced from 20m³ / h. 3 / h becomes 17.5m 3 The reduction in the total amount of material per hour allows the propylene glycol methyl ether vapor phase to meet the heat requirements of the methanol distillation tower. Replacing low-pressure steam with propylene glycol methyl ether vapor phase saves approximately 5 t / h of low-pressure steam and also solves the cooling water requirement for propylene glycol methyl ether vapor phase cooling, greatly reducing energy consumption and achieving the effect of reuse.

[0030] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A propylene glycol methyl ether reaction de-alcoholization device for improving energy recovery and utilization efficiency, characterized in that: It includes a reactor, a pressure stabilizing tank, a flash tank, a reaction liquid tank, a reaction liquid pump, a reaction liquid tail cooler, a methanol tower reboiler, a methanol tower, a methanol tower condenser, and a methanol tower tail cooler; The reactor's reaction liquid outlet is connected to the flash tank's feed inlet via pipe A, and a pressure stabilizing tank is connected to pipe A. The flash tank's liquid phase outlet is connected to the reaction liquid tank inlet via pipe B, and the flash tank's gas phase outlet is connected to the methanol tower's upper section inlet via pipe K. The outlet of the reaction liquid tank is connected to the inlet of the reaction liquid pump via pipe D, and the vent at the top of the reaction liquid tank is connected to the inlet of the reaction liquid tail cooler via pipe C. The outlet of the reaction liquid pump is connected to the inlet of the methanol tower via pipeline E. A sampling point is set at the outlet of the reaction liquid pump, and a methanol tower feed flow meter is installed on pipeline E. The methanol tower gas phase inlet is connected to the upper gas phase port of the methanol tower reboiler via pipe F; the methanol tower liquid phase outlet is connected to the lower liquid phase port of the methanol tower reboiler via pipe G. The vapor outlet at the top of the methanol tower is connected to the inlet of the methanol tower condenser via pipe H. The outlet of the methanol tower condenser discharges cooled methanol into the methanol reflux tank. The outlet of the methanol tower condenser is connected to the tail cooler of the methanol tower via pipe I, which sends the vapor to the tail cooler for cooling. The outlet of the tail cooler of the methanol tower is connected to the vacuum system via pipe J.

2. A process method for producing propylene glycol methyl ether using the propylene glycol deethanolation equipment for improving energy recovery and utilization efficiency as described in claim 1, characterized in that: Includes the following steps: S1, methanol and propylene oxide undergo an etherification reaction in a reactor. After the reaction is completed, the mixture is stably introduced into a flash tank under the protection of a pressure stabilizing tank. S2. After the etherification reaction is completed and discharged from the reaction system into the flash tank, part of the vaporized methanol enters the methanol tower directly from the gas phase pipeline K under a slight negative pressure of -35 kPa. S3. The remaining methanol, propylene glycol methyl ether, and 2-methoxy-1-propanol liquid phase in the flash tank enter the reaction tank and are then continuously pumped into the methanol tower by the reaction pump. The continuous operation involves sampling and analysis at sampling points to determine the methanol content in the reaction liquid, and the methanol tower feed rate is observed through the methanol tower feed flow meter. S4. The methanol tower is heated by the methanol tower reboiler to separate methanol from propylene glycol methyl ether and 2-methoxy-1-propanol. The bottom temperature of the methanol tower is controlled at 115~125℃ and the top temperature of the tower is controlled at 55~60℃. S5. Methanol gas phase is discharged from the methanol tower, cooled by the methanol tower condenser and methanol tower tail cooler, and then collected from the methanol reflux tank for continued recycling. The outlet pipeline of the methanol tower tail cooler is connected to the vacuum system.

3. The process method for producing propylene glycol methyl ether using a propylene glycol deethanolation device that improves energy recovery and utilization efficiency, as described in claim 2, is characterized in that: The pressure of the methanol tower is maintained at -35 kPa.

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