Product multi-stage rectification system for preparing cyclic carbonate by urea method

Abstract

The utility model relates to the technical field of carbonic ester production process equipment, and particularly discloses a product multi-stage rectification system for preparing cyclic carbonic ester by a urea method, aiming at the problem of poor separation and purification effect when a reaction product is rectified to process the carbonic ester in the process of preparing the carbonic ester from the industrial urea and propylene glycol in the prior art. Comprising a primary rectifying tower, the bottom of the primary rectifying tower is communicated with an auxiliary rectifying tower, and the side wall of the primary rectifying tower is communicated with a secondary rectifying tower through a conveying pipe; the material conveying pipe is provided with a main condenser, and the top of the auxiliary rectifying tower and the bottom of the secondary rectifying tower are both communicated with a product tank. According to the product multi-stage rectification system for preparing the cyclic carbonate by the urea method, the reaction product is treated by the multi-stage rectification tower, so that the purity of propylene carbonate can be improved, the product recovery rate can be improved, and the production of byproducts can be reduced.

Description

Technical Field

[0001] This utility model relates to the technical field of carbonate production process equipment, and more specifically, to a multi-stage distillation system for the preparation of cyclic carbonates using the urea method. Background Technology

[0002] In the industrial process of preparing propylene carbonate from urea and propylene glycol, distillation is often used to separate and purify the propylene carbonate produced by the reaction. Specifically, the reaction products of the above-mentioned raw materials mainly include propylene carbonate, but also include unreacted propylene glycol and impurities such as propylene glycol condensate byproducts. The purpose and function of distillation in treating these reaction products are mainly as follows:

[0003] (1) Effectively separate the products, by-products and unreacted raw materials in the reaction process to obtain high-purity propylene carbonate.

[0004] (2) In the reaction system, there are a large number of volatile or low-boiling-point by-products and other impurities. By utilizing the boiling point differences between different components to remove these impurities, the purity of the product can be improved. Furthermore, by removing excess raw materials and by-products, the forward reaction of the system can be promoted, thereby increasing the yield and reaction efficiency of propylene carbonate.

[0005] (3) Cost reduction and efficiency improvement: Distillation is an energy-efficient separation process. Using distillation to process reaction products can reduce energy consumption, thereby reducing the cost of the entire production process. At the same time, distillation can improve product purity and ensure that the quality of the product meets the preparation requirements, thus providing a guarantee for its subsequent reaction process.

[0006] However, in existing cyclic carbonate production processes, product distillation can only separate propylene carbonate from impurities such as byproducts or unreacted raw materials, but it is difficult to distinguish different components in the impurities, which leads to problems such as low utilization rate and poor product purification effect. Utility Model Content

[0007] The purpose of this invention is to solve the problem of poor separation and purification effect of propylene carbonate during the distillation process in the existing industrial production of propylene carbonate from urea and propylene glycol. This application provides a multi-stage distillation system for the preparation of cyclic carbonates using the urea method. By processing the reaction products through multi-stage distillation columns, the purity of propylene carbonate can be improved, the product recovery rate can be increased, and the production of by-products can be reduced.

[0008] This utility model is achieved through the following technical solution:

[0009] This invention provides a multi-stage distillation system for the preparation of cyclic carbonates using the urea process, comprising a primary distillation column, the bottom of which is connected to a secondary distillation column, and the sidewall of the primary distillation column being connected to a secondary distillation column via a feed pipe; the feed pipe is equipped with a main condenser, and the top of the secondary distillation column and the bottom of the secondary distillation column are both connected to a product tank.

[0010] Preferably, a return pipe is provided at the top of the primary distillation column, and the top of the secondary distillation column is connected to the return pipe.

[0011] Preferably, the top of the primary distillation column is connected to a primary circulation system, which includes a primary condenser, a primary condenser tank, and a primary pump connected in sequence. The primary condenser is connected to the top of the primary distillation column, one discharge end of the primary pump is connected to the side wall of the primary distillation column, and the other discharge end of the primary pump is connected to the head end of the return pipe.

[0012] Preferably, the top of the primary distillation column is connected to a secondary circulation system, which includes a secondary condenser, a secondary condenser tank, and a secondary pump connected in sequence. The secondary condenser is connected to the top of the secondary distillation column, one discharge end of the secondary pump is connected to the side wall of the secondary distillation column, and the other discharge end of the secondary pump is connected to the middle section of the return pipe.

[0013] Preferably, the tail end of the return pipe is connected to the feed port of the primary distillation column.

[0014] Preferably, the top of the secondary distillation column is connected to a secondary circulation system, which includes a secondary condenser, a secondary condenser tank, and a secondary pump connected in sequence. The secondary condenser is connected to the top of the secondary distillation column, one discharge end of the secondary pump is connected to the side wall of the secondary distillation column, and the other discharge end of the secondary pump is connected to the product tank.

[0015] Preferably, the bottom of the primary distillation column, the bottom of the secondary distillation column, and the bottom of the auxiliary distillation column are all provided with circulation pipes, and a reboiler is installed in the middle section of the circulation pipes.

[0016] Preferably, a discharge pipe is also provided at the bottom of the auxiliary distillation column.

[0017] The technical solution of this utility model has the following beneficial effects:

[0018] This invention relates to a multi-stage distillation system for the preparation of cyclic carbonates using the urea process. During the initial distillation, a large amount of propylene carbonate and low-boiling-point impurities are discharged from the top of the column. A second distillation is then performed, during which impurities are separated, and high-purity propylene carbonate is obtained through the second distillation. Furthermore, the liquid phase material after the initial distillation can be separated again through distillation. In other words, by processing the reaction products through a multi-stage distillation column, propylene carbonate and impurities with different boiling points can be separated and recovered separately, thereby improving the production efficiency of the preparation process and the comprehensive reuse rate of various materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the multi-stage distillation system for the preparation of cyclic carbonates using the urea method in this invention.

[0020] Figure reference numerals: 1-Primary distillation column, 11-Return feed pipe, 12-Primary condenser, 13-Primary condenser tank, 14-Primary pump, 2-Secondary distillation column, 21-Secondary condenser, 22-Secondary condenser tank, 23-Secondary pump, 24-Discharge pipe, 3-Secondary distillation column, 31-Secondary condenser, 32-Secondary condenser tank, 33-Secondary pump, 34-Circulation pipe, 35-Reboiler, 4-Feed transfer pipe, 41-Main condenser, 5-Product tank. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of instruments, equipment, reagents, or raw materials are not specified, they are all conventional products that can be purchased commercially. The following are specific embodiments in conjunction with the accompanying drawings.

[0022] like Figure 1 As shown, this embodiment provides a multi-stage distillation system for the preparation of cyclic carbonates using the urea method, including a primary distillation column 1, a secondary distillation column 2 connected to the bottom of the primary distillation column 1, and a secondary distillation column 3 connected to the side wall of the primary distillation column 1 via a feed pipe 4; the feed pipe 4 is equipped with a main condenser 41, and the top of the secondary distillation column 2 and the bottom of the secondary distillation column 3 are both connected to a product tank 5.

[0023] In this embodiment, a return pipe 11 is provided at the top of the primary distillation column 1, and the top of the secondary distillation column 3 is connected to the return pipe 11. The tail end of the return pipe 11 is connected to the feed port of the primary distillation column 1. Specifically, the return pipe 11 can first be sent to the raw material batching system and then to the primary distillation column 1. That is, the material discharged through the return pipe 11 can be recycled as raw material again.

[0024] In this embodiment, the top of the primary distillation column 1 is connected to a primary circulation system, which includes a primary condenser 12, a primary condenser tank 13, and a primary pump 14 connected in sequence. The primary condenser 12 is connected to the top of the primary distillation column 1, one discharge end of the primary pump 14 is connected to the side wall of the primary distillation column 1, and the other discharge end of the primary pump 14 is connected to the head end of the return pipe 11. The top of the primary distillation column 1 is connected to a secondary circulation system, which includes a secondary condenser 31, a secondary condenser tank 32, and a secondary pump 33 connected in sequence. The secondary condenser 31 is connected to the top of the secondary distillation column 3, one discharge end of the secondary pump 33 is connected to the side wall of the secondary distillation column 3, and the other discharge end of the secondary pump 33 is connected to the middle section of the return pipe 11.

[0025] In this embodiment, the top of the secondary distillation column 2 is connected to a secondary circulation system, which includes a secondary condenser 21, a secondary condenser tank 22, and a secondary pump 23 connected in sequence. The secondary condenser 21 is connected to the top of the secondary distillation column 2, one discharge end of the secondary pump 23 is connected to the side wall of the secondary distillation column 2, and the other discharge end of the secondary pump 23 is connected to the product tank 5. A discharge pipe 24 is also provided at the bottom of the secondary distillation column 2.

[0026] In this embodiment, the bottom of the primary distillation column 1, the bottom of the secondary distillation column 3, and the bottom of the auxiliary distillation column 2 are all equipped with circulation pipes 34. The outlet end of the circulation pipe 34 is connected to the bottom of the distillation column, the inlet end of the circulation pipe 34 is connected to the side wall of the distillation column, and a reboiler 35 is installed in the middle section of the circulation pipe 34.

[0027] Using the multi-stage distillation system of this embodiment, propylene carbonate products with a purity exceeding 98% can be obtained after distillation operations in the secondary distillation column 3 and the auxiliary distillation column 2. The material discharged from the primary distillation column 1 and the secondary distillation column 3 through the return pipe 11 contains unreacted raw materials, which can be recovered and reused as raw materials. By processing the products in the reaction through multi-stage distillation columns, not only can the purity of propylene carbonate be improved, but also byproducts and other impurities can be separated and recovered for reuse.

[0028] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A multi-stage distillation system for the preparation of cyclic carbonates using the urea process, characterized in that, It includes a primary distillation column (1), the bottom of which is connected to a secondary distillation column (2), and the sidewall of the primary distillation column (1) is connected to a secondary distillation column (3) through a feed pipe (4). The feed pipe (4) is equipped with a main condenser (41), and the top of the secondary distillation column (2) and the bottom of the secondary distillation column (3) are both connected to the product tank (5).

2. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to claim 1, characterized in that, The primary distillation column (1) is provided with a return pipe (11) at the top, and the top of the secondary distillation column (3) is connected to the return pipe (11).

3. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to claim 2, characterized in that, The top of the primary distillation column (1) is connected to a primary circulation system, which includes a primary condenser (12), a primary condenser tank (13), and a primary pump (14) connected in sequence. The primary condenser (12) is connected to the top of the primary distillation column (1), one discharge end of the primary pump (14) is connected to the side wall of the primary distillation column (1), and the other discharge end of the primary pump (14) is connected to the head end of the return pipe (11).

4. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to claim 2, characterized in that, The top of the primary distillation column (1) is connected to a secondary circulation system, which includes a secondary condenser (31), a secondary condenser tank (32), and a secondary pump (33) connected in sequence. The secondary condenser (31) is connected to the top of the secondary distillation column (3), one discharge end of the secondary pump (33) is connected to the side wall of the secondary distillation column (3), and the other discharge end of the secondary pump (33) is connected to the middle section of the return pipe (11).

5. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to claim 2, characterized in that, The tail end of the return pipe (11) is connected to the feed port of the primary distillation column (1).

6. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to any one of claims 1 to 5, characterized in that, The top of the sub-distillation column (2) is connected to a sub-circulation system, which includes a sub-condenser (21), a sub-condenser tank (22), and a sub-pump (23) connected in sequence. The sub-condenser (21) is connected to the top of the sub-distillation column (2), one discharge end of the sub-pump (23) is connected to the side wall of the sub-distillation column (2), and the other discharge end of the sub-pump (23) is connected to the product tank (5).

7. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to claim 1, characterized in that, The bottom of the primary distillation column (1), the bottom of the secondary distillation column (3), and the bottom of the auxiliary distillation column (2) are all equipped with circulation pipes (34), and a reboiler (35) is installed in the middle section of the circulation pipes (34).

8. The multi-stage distillation system for the preparation of cyclic carbonates using the urea method according to claim 7, characterized in that, The bottom of the sub-distillation column (2) is also equipped with a discharge pipe (24).

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