A continuous evaporative rectification apparatus

Abstract

A continuous evaporation rectification device, comprising a wiped evaporator, a first evaporation kettle, a second evaporation kettle and a rectification separation tower, the bottom of the wiped evaporator is connected with the first evaporation kettle, the first evaporation kettle is further connected with the second evaporation kettle, the connecting pipeline comprises a reactant material transmission pipe and an evaporation gas reflux pipe, the direction of the reactant material transmission is opposite to the direction of the evaporation gas reflux, that is, the reactant material is discharged after being further evaporated in the first and second evaporation kettles in turn after being discharged from the bottom of the wiped evaporator, the evaporation gas generated by the second evaporation kettle is refluxed to the first evaporation kettle, mixed with the evaporation gas generated by the first evaporation kettle and then refluxed to the wiped evaporator, mixed with the evaporation gas generated by the wiped evaporator after countercurrent mass transfer and heat transfer with the feed liquid in the wiped evaporator and then enters the rectification separation tower from the wiped evaporation gas outlet; the upper part of the wiped evaporator is connected with the lower part of the rectification separation tower, the connecting pipeline comprises an evaporation gas transmission pipe and a reflux liquid transmission pipe.

Description

Technical Field

[0001] This invention relates to a continuous evaporation distillation apparatus. Background Technology

[0002] In some reaction systems, there are problems such as high viscosity of reaction products and difficulty in evaporating and separating the target substance, by-products, and solvent.

[0003] For example, in the following reaction using dimethyl malonate, sodium methoxide, and 6-ethylthio-3-hepten-2-one as raw materials, the generated methanol needs to be removed before subsequent reactions to avoid undesirable side effects. However, in the initial stage of dealcoholization, the reaction product has high viscosity, poor flowability, and is difficult to handle.

[0004]

[0005] SEt represents ethylthio group. Summary of the Invention

[0006] This application provides:

[0007] (1) A continuous evaporation distillation apparatus, comprising: a scraped evaporator, a primary evaporator, a secondary evaporator, and a distillation separation column.

[0008] The bottom of the scraped evaporator is connected to the first-stage evaporator, which is then connected to the second-stage evaporator. The connecting pipes include a reactant transfer pipe and an evaporation gas return pipe. The reactant transfer direction is opposite to the evaporation gas return direction. That is, after the reactant comes out from the bottom of the scraped evaporator, it is further evaporated in the first-stage and second-stage evaporators before being discharged. The evaporation gas generated in the second-stage evaporator is returned to the first-stage evaporator and mixed with the evaporation gas generated in the first-stage evaporator before returning to the scraped evaporator. In the scraped evaporator, it undergoes countercurrent mass transfer and heat transfer with the feed liquid and then mixes with the evaporation gas generated in the scraped evaporator before entering the distillation separation tower from the scraped evaporation gas outlet.

[0009] The upper part of the scraped evaporator is connected to the lower part of the distillation separation column, and the connecting pipeline includes an evaporation gas transmission pipe and a reflux liquid transmission pipe.

[0010] (2) The continuous evaporation distillation equipment described in (1) above, wherein the upper part of the distillation separation tower is equipped with an internal cooling condenser.

[0011] (3) The continuous evaporation distillation equipment described in (1) or (2) above, wherein the internal cooling condenser is a U-shaped condenser.

[0012] (4) The continuous evaporation distillation equipment described in any one of (1) to (3) above, wherein the distillation separation tower is provided with a reflux ratio controller.

[0013] (5) The continuous evaporation distillation equipment described in any one of (1) to (4) above, wherein the scraped evaporator, the primary evaporator and the secondary evaporator are respectively provided with jackets on the outside.

[0014] (6) In any one of (1) to (5) above, the continuous evaporation distillation equipment, the scraped evaporator, the primary evaporator and the secondary evaporator all use steam as a heat source.

[0015] (7) In any one of (1) to (6) above, the material outlet diameter at the bottom of the scraped evaporator is 300 to 600 mm.

[0016] (8) The continuous evaporative distillation apparatus described in any one of (1) to (7) above, used for separating the reaction products of the following reaction,

[0017]

[0018] SEt represents ethylthio group.

[0019] (9) The continuous evaporation distillation apparatus described in (8) above, wherein the solvent of the reaction is xylene, trimethylbenzene, ethylbenzene, diethylbenzene or triethylbenzene, or a mixture of two or more of them.

[0020] The continuous evaporative distillation apparatus of this application is particularly suitable for reactions in which the viscosity of the post-reaction material is high and the evaporation and separation of the product and solvent is difficult, such as the reaction described above using dimethyl malonate, sodium methoxide, and 6-ethylthio-3-hepten-2-one as raw materials. The continuous evaporative distillation apparatus of this application can efficiently separate the reaction products of such reactions. Attached Figure Description

[0021] Appendix Figure 1 This is a schematic diagram of a preferred embodiment of the continuous evaporation distillation equipment of the present invention.

[0022] Appendix Figure 2 This is a schematic diagram of a more preferred embodiment of the continuous evaporation distillation equipment of the present invention.

[0023] Explanation of reference numerals in the attached figures:

[0024] 1: Scraped evaporator;

[0025] 2: Primary evaporator;

[0026] 3: Secondary evaporator;

[0027] 4: Distillation and separation column;

[0028] 5: Packing material;

[0029] 6: Distributor;

[0030] 7. Drip tray;

[0031] 8. Internal cooling condenser;

[0032] 9. Reflux ratio controller. Detailed Implementation

[0033] The following is a detailed description of a preferred embodiment of the continuous evaporation distillation apparatus of this application. However, this application is not limited to this specific embodiment. Any modifications or changes that do not depart from the scope of this application shall fall within the scope of this application.

[0034] In this embodiment, the continuous evaporative distillation apparatus is used as an example to separate the reaction products obtained in the above-mentioned reaction using dimethyl malonate, sodium methoxide and 6-ethylthio-3-hepten-2-one as raw materials and xylene as solvent. However, it is not limited to this application. It can be used to separate the reaction products in any reaction with similar problems, namely, high viscosity of the material after the reaction and difficulty in the evaporation and separation of the product and the solvent.

[0035] The material after the above reaction is first introduced into the scraped evaporator 1, where most of the methanol in the reaction product is evaporated, thereby greatly reducing the viscosity of the reaction product, so that it can directly and smoothly enter the subsequent primary evaporator 2 and then the secondary evaporator 3. After further de-alcoholization in the two evaporators, the reaction liquid that has passed the de-alcoholization is taken out from the secondary evaporator 3.

[0036] After the reaction material is de-ethanolated in the above three-stage continuous evaporator for 1 hour, the methanol content decreases from about 30 wt% to below 0.3 wt%, or even below 0.1 wt%. A single-stage evaporator would require 5-6 hours to achieve the same level of methanol removal.

[0037] Therefore, the continuous evaporation equipment of this application significantly shortens the production time, thereby greatly increasing the production capacity and greatly reducing the production equipment. In the past, a batch reactor with an annual capacity of 4,000 tons often required ten five-sided reactors and supporting condensers, storage tanks, etc., which were huge equipment. However, this application only requires four core units: scraped evaporator 1, primary evaporator 2, secondary evaporator 3, and distillation separation tower 4 to achieve the same production capacity.

[0038] On the other hand, the evaporation gas generated from the secondary evaporator 3 returns to the primary evaporator 2 and enters the bottom of the scraped evaporator 1 together with the evaporation gas generated in the primary evaporator 2. After countercurrent mass transfer and heat transfer with the feed liquid in the scraped evaporator 1, it mixes with the evaporation gas generated in the scraped evaporator 1 and enters the distillation separation tower 4 from the scraped evaporation gas outlet.

[0039] Because the scraper evaporation gas outlet is close to the product feed inlet, the distance the evaporation gas travels is short, resulting in minimal loss. Furthermore, the methanol concentration is highest near the feed inlet, leading to a higher methanol content in the evaporation gas exiting the scraper evaporation gas outlet.

[0040] In the prior art, the structure of batch reactors operating independently in parallel with material transfer and evaporation gas transfer in the same direction is usually adopted. The structure of multiple reactors connected in series and material transfer and evaporation gas transfer in opposite directions as described in this application has not been reported.

[0041] The inventors of this application discovered that the compositions of the evaporating gases in the scraped evaporator 1, the primary evaporator 2, and the secondary evaporator 3 are different. If they are introduced directly into the distillation separation column 4 independently, the feed into the distillation separation column 4 will be uneven and unstable due to the different compositions of the evaporating gases. Therefore, it is necessary to constantly adjust its parameters, which is inconvenient to operate.

[0042] To solve the above problems, the inventors of this application designed the structure described above, in which the evaporated gases generated in different reactors are refluxed and mixed before being introduced into the distillation separation column 4. This can stabilize the composition of the evaporated gases entering the distillation separation column 4, thereby avoiding the inconvenience of constantly adjusting the parameters of the distillation separation column 4 as described above.

[0043] There are no particular limitations on the structure of the scraped evaporator 1, the primary evaporator 2, the secondary evaporator 3, and the distillation separation column 4; they can adopt known conventional structures.

[0044] In the above-mentioned scraped evaporator 1, primary evaporator 2 and secondary evaporator 3, steam is preferably used as the heat source for evaporation. Therefore, it is preferable to install jackets outside the scraped evaporator 1, primary evaporator 2 and secondary evaporator 3 respectively, so that the steam turns into condensate and flows out after circulating around the vessel once in the jacket.

[0045] In addition, the discharge port diameter of the scraped evaporator 1 is usually around 100 mm, but in this application it is preferably designed to be 300-600 mm, so that materials with a certain viscosity can also be discharged smoothly.

[0046] In conventional designs, the distillation column and condenser are usually installed separately. This application allows for such a structure.

[0047] In a more preferred embodiment of this application, an integrated distillation-condensation design is adopted, in which the internal cooling condenser 8 is built into the distillation separation tower 4. This integrated structure has fewer flanges, better vacuum tightness, is easy to operate, saves connecting pipes, reduces vacuum pipe loss, and also reduces the size of the equipment.

[0048] Considering factors such as reducing gas pressure drop, a U-shaped condenser is preferred for the internal cooling condenser 8.

[0049] The mixed evaporated gas entering from the bottom of the distillation column 4 passes through the packing 5, and the methanol in it reaches the top of the column in gaseous form. After being cooled by the internal condenser 8, it becomes liquid and falls into the receiving pan 7. A portion of the liquid is collected as qualified methanol by the reflux ratio controller 9 located outside the distillation column 4, while the other portion is refluxed back into the distillation column 4. The reflux ratio controller 9 controls the ratio of collected methanol to refluxed methanol to achieve a good balance between the quality of the collected methanol and the quality of the reflux liquid.

[0050] In this embodiment, the methanol extracted from the distillation separation tower 4 has a purity of approximately 99.5%.

[0051] Preferably, a distributor 6 is provided above the packing 5 to disperse the methanol liquid returning to the distillation separation column 4 and increase its contact area with the packing 5.

[0052] The xylene vapor in the mixed evaporation gas entering from the bottom of the distillation separation column 4 meets the returning methanol liquid in the packing 5 and is cooled into liquid. The mixed liquid formed by the two is returned to the scraped evaporator 1 as reflux liquid to continue evaporation. At the same time, it can dilute the raw material liquid and improve the fluidity.

[0053] In this application, the reflux liquid containing an appropriate amount of methanol that flows back from the distillation separation column 4 returns only to the scraped evaporator 1, and does not flow back to the primary evaporator 2 and the secondary evaporator 3. This helps to ensure that the methanol content in the final de-alcoholized material coming out of the secondary evaporator 3 is qualified.

[0054] Industrial applicability

[0055] As described above, the continuous evaporation distillation equipment of this application is particularly suitable for reactions in which the viscosity of the post-reaction material is high and the evaporation separation of the product and solvent is difficult. It can efficiently and with high quality separate the reaction products and has great industrial practical value.

Claims

1. A continuous evaporation distillation apparatus, characterized in that, include: Scraped evaporator, primary evaporator, secondary evaporator, and distillation column. The bottom of the scraped evaporator is connected to the first-stage evaporator, which is then connected to the second-stage evaporator. The connecting pipes include a reactant transfer pipe and an evaporation gas return pipe. The reactant transfer direction is opposite to the evaporation gas return direction. That is, after the reactant comes out from the bottom of the scraped evaporator, it is further evaporated in the first-stage and second-stage evaporators before being discharged. The evaporation gas generated in the second-stage evaporator is returned to the first-stage evaporator and mixed with the evaporation gas generated in the first-stage evaporator before returning to the scraped evaporator. In the scraped evaporator, it undergoes countercurrent mass transfer and heat transfer with the feed liquid and then mixes with the evaporation gas generated in the scraped evaporator before entering the distillation separation tower from the scraped evaporation gas outlet. The upper part of the scraped evaporator is connected to the lower part of the distillation separation column, and the connecting pipeline includes an evaporation gas transmission pipe and a reflux liquid transmission pipe; The scraped evaporator, the primary evaporator, and the secondary evaporator are each equipped with an external jacket.

2. The continuous evaporation distillation apparatus according to claim 1, characterized in that, The upper part of the distillation separation tower is equipped with an internal cooling condenser.

3. The continuous evaporation distillation apparatus according to claim 2, characterized in that, The internal cooling condenser is a U-shaped condenser.

4. The continuous evaporation distillation apparatus according to any one of claims 1 to 3, characterized in that, The distillation separation column is equipped with a reflux ratio controller on the outside.

5. The continuous evaporation distillation apparatus according to any one of claims 1 to 3, characterized in that, The scraped evaporator, the primary evaporator, and the secondary evaporator all use steam as a heat source.

6. The continuous evaporation distillation apparatus according to any one of claims 1 to 3, characterized in that, The material outlet diameter at the bottom of the scraped evaporator is 300-600 mm.

7. The continuous evaporation distillation apparatus according to any one of claims 1 to 3, characterized in that, It is used to separate the reaction products of the following reactions. SEt represents ethylthio group.

8. The continuous evaporation distillation apparatus according to claim 7, characterized in that, The solvent for the reaction is xylene, trimethylbenzene, ethylbenzene, diethylbenzene or triethylbenzene, or a mixture of two or more of these.

Images