Product separation system for preparing cyclic carbonate by urea method

Abstract

The utility model relates to the technical field of preparation of cyclic carbonate by a urea method, and aims to solve the problems of low separation rate and high energy consumption caused by direct separation and purification of products after reaction of urea and propylene glycol in the conventional rectifying tower. The utility model provides a product separation system for preparing cyclic carbonate by a urea method. The product separation system comprises a flash tower, a feeding pipe, a discharging pipe, a gas outlet pipe, a circulating pump and a vacuum pump group, the feeding pipe is communicated with a tower body of the flash tower; the discharge pipe is communicated with the tower bottom of the flash tower; the circulating pump is circularly communicated with the bottom of the flash tower; the gas outlet pipe is communicated with the top of the flash tower; the air outlet pipe is communicated with the vacuum pump set; the product separation system for preparing the cyclic carbonate by the urea method provided by the utility model not only has high separation efficiency, but also fully reduces the separation energy consumption, relieves the burden of subsequent rectification separation and purification, and improves the purity of the product.

Description

Technical Field

[0001] This invention relates to the field of urea method for preparing cyclic carbonates, and more specifically, to a product separation system for urea method for preparing cyclic carbonates. Background Technology

[0002] In the preparation of cyclic carbonates using the urea method, the reaction raw materials include urea, propylene glycol / ethylene glycol, and a solid catalyst. After the reaction of urea and propylene glycol is completed, the product needs to be separated and purified. In the existing technology, distillation columns are usually used directly for separation and purification, but the separation efficiency is low. For example, the patent with publication number CN112142599A discloses a low-energy-consumption, green carbonate product production method and system. Specifically, it uses multiple distillation columns for separation and purification as well as product recycling.

[0003] Based on the above description, there is an urgent need for a product separation system for the preparation of cyclic carbonates using the urea method that has high separation efficiency and low energy consumption. Utility Model Content

[0004] The purpose of this invention is to provide a product separation system for the preparation of cyclic carbonates using the urea method, aiming to solve the technical problems of low separation rate and high energy consumption in existing distillation columns that directly separate and purify the products after the reaction of urea and propylene glycol.

[0005] The embodiments of this utility model are achieved through the following technical solutions:

[0006] A product separation system for the preparation of cyclic carbonates using the urea process includes a flash tower, a feed pipe, a discharge pipe, a gas outlet pipe, a circulating pump, and a vacuum pump assembly. The feed pipe is connected to the body of the flash tower; the discharge pipe is connected to the bottom of the flash tower; the circulating pump is circulated to the bottom of the flash tower; the gas outlet pipe is connected to the top of the flash tower; and the gas outlet pipe is connected to the vacuum pump assembly.

[0007] Preferably, a vacuum buffer tank is connected between the outlet pipe and the vacuum pump assembly.

[0008] Preferably, a condensation system is connected between the outlet pipe and the vacuum buffer tank; the condensation system is connected to the flash tower.

[0009] Preferably, the condensation system includes a condenser, a condenser tank, and a reflux pump; one end of the condenser is connected to the outlet pipe; the other end of the condenser is connected to the condenser tank; the condenser tank is connected to the reflux pump; the reflux pump is connected to the flash tower; and the vacuum buffer tank is connected to the condenser tank.

[0010] Preferably, the reflux pump is connected to the top of the flash tower.

[0011] Preferably, a vapor phase cooler is provided between the condenser and the vacuum buffer tank.

[0012] Preferably, the reflux pump is connected to a drain pipe.

[0013] The technical solution of this utility model embodiment has at least the following advantages and beneficial effects:

[0014] The product separation system for the preparation of cyclic carbonates using the urea method provided by this utility model first introduces a flash distillation column before the product enters the distillation column. The pressure inside the flash distillation column is adjusted to absolute pressure. Since the temperature of the product coming out of the reactor is about 160-170℃, while the boiling point of propylene glycol at atmospheric pressure is 187℃, the propylene glycol will vaporize under absolute pressure, thus separating from the product ethylene carbonate (boiling point 242℃). This achieves preliminary separation of propylene glycol and the product before distillation, which not only has high separation efficiency but also significantly reduces separation energy consumption, alleviates the burden of subsequent distillation and purification, and improves product purity. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the system of this utility model.

[0017] Icons: 1-Flash tower, 2-Infeed pipe, 3-Outlet pipe, 4-Gas outlet pipe, 5-Circulating pump, 6-Vacuum pump set, 7-Vacuum buffer tank, 8-Condenser, 9-Condensation tank, 10-Reflux pump, 11-Vacuum phase cooler, 12-Drain pipe. Detailed Implementation

[0018] Example 1

[0019] Please see Figure 1 This utility model provides the following technical solution: a product separation system for the preparation of cyclic carbonates by the urea method, which is suitable for the separation of products before distillation.

[0020] Specifically, such as Figure 1As shown, a product separation system for the preparation of cyclic carbonates using the urea process includes a flash tower 1, a feed pipe 2, a discharge pipe 3, an exhaust pipe 4, a circulation pump 5, and a vacuum pump assembly 6. The feed pipe 2 is connected to the body of the flash tower 1; the discharge pipe 3 is connected to the bottom of the flash tower 1; the circulation pump 5 is circulated to the bottom of the flash tower 1; the exhaust pipe 4 is connected to the top of the flash tower 1; and the exhaust pipe 4 is connected to the vacuum pump assembly 6.

[0021] In this embodiment, before the product enters the distillation column, it is introduced into the flash distillation column 3 to adjust the pressure inside the flash distillation column 3 to absolute pressure. Since the temperature of the product coming out of the reactor is about 170°C, and the boiling point of propylene glycol at atmospheric pressure is 187°C, the propylene glycol will vaporize under absolute pressure, thus separating from the product ethylene carbonate (boiling point 242°C). This achieves the separation of propylene glycol and product before distillation, which not only has high separation efficiency but also significantly reduces separation energy consumption, alleviates the burden of subsequent distillation and purification, and improves product purity. Specifically, the product is discharged from the reactor and then sent to the flash distillation column 3 for separation. The flash distillation column 3 is pre-vacuumed until it is in an absolute pressure state. After the product is sent into the flash distillation column 3, the propylene glycol vaporizes and is extracted from the outlet pipe 4 under the suction of the vacuum pump group 6. The product is repeatedly sent into the flash distillation column 3 for separation by the circulation pump 5 to improve the purity of the product. The separated product is discharged from the discharge pipe 3.

[0022] In this embodiment, the product sent from the reactor is atomized when it enters the flash tower to improve the vaporization rate and speed of propylene glycol. In addition, a valve is provided at one end of the feed pipe 2 near the flash tower 3. The valve is located near the flash tank to generate a sufficient negative pressure environment in the flash tank to promote flash evaporation of the material.

[0023] Specifically, such as Figure 1 As shown, a vacuum buffer tank 7 is connected between the air outlet pipe 4 and the vacuum pump assembly 6.

[0024] In this embodiment, the vacuum pump group 6 includes multiple vacuum pumps connected in parallel. Through multiple vacuum pumps and the vacuum buffer tank 7, the entire separation system, including the flash tower 3, can be fully evacuated. This ensures a continuous absolute pressure environment inside the flash tower 3 and efficiently extracts the separated vaporized propylene glycol, further improving the separation efficiency of propylene glycol.

[0025] Specifically, such as Figure 1As shown, a condensation system is connected between the outlet pipe 4 and the vacuum buffer tank 7; the condensation system is connected to the flash tower 1. The condensation system includes a condenser 8, a condenser tank 9, and a reflux pump 10; one end of the condenser 8 is connected to the outlet pipe 4; the other end of the condenser 8 is connected to the condenser tank 9; the condenser tank 9 is connected to the reflux pump 10; the reflux pump 10 is connected to the flash tower 1; and the vacuum buffer tank 7 is connected to the condenser tank 9.

[0026] In this embodiment, under the operation of the vacuum pump, the vaporized propylene glycol is extracted from the top of the flash tower 1, and then the product droplets entrained in the gas are condensed by the condenser 8. The product droplets are further condensed and merged by the condenser tank 9, and then recycled back to the flash tower 1 by the reflux pump 10, or discharged by the drain pipe 12 for the next distillation stage for rectification.

[0027] Specifically, such as Figure 1 As shown, the reflux pump 10 is connected to the top of the flash tower 1, thereby increasing the residence time of the material in the flash tower 1.

[0028] Specifically, such as Figure 1 As shown, a vapor phase cooler 11 is provided between the condenser 9 and the vacuum buffer tank 7.

[0029] In this embodiment, the vaporized propylene glycol can be cooled by the vapor phase cooler 11, which can minimize the escape of propylene glycol.

[0030] 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 product separation system for the preparation of cyclic carbonates using the urea method, characterized in that: It includes a flash tower (1), a feed pipe (2), a discharge pipe (3), an exhaust pipe (4), a circulation pump (5), and a vacuum pump group (6); the feed pipe (2) is connected to the tower body of the flash tower (1); the discharge pipe (3) is connected to the bottom of the flash tower (1); the circulation pump (5) is connected to the bottom of the flash tower (1); the exhaust pipe (4) is connected to the top of the flash tower (1); and the exhaust pipe (4) is connected to the vacuum pump group (6).

2. The product separation system for the preparation of cyclic carbonates by the urea method according to claim 1, characterized in that: A vacuum buffer tank (7) is connected between the air outlet pipe (4) and the vacuum pump assembly (6).

3. The product separation system for the preparation of cyclic carbonates by the urea method according to claim 2, characterized in that: A condensation system is connected between the gas outlet pipe (4) and the vacuum buffer tank (7); the condensation system is connected to the flash tower (1).

4. The product separation system for the preparation of cyclic carbonates by the urea method according to claim 3, characterized in that: The condensation system includes a condenser (8), a condenser tank (9), and a reflux pump (10); one end of the condenser (8) is connected to the outlet pipe (4); the other end of the condenser (8) is connected to the condenser tank (9); the condenser tank (9) is connected to the reflux pump (10); the reflux pump (10) is connected to the flash tower (1); and the vacuum buffer tank (7) is connected to the condenser tank (9).

5. The product separation system for the preparation of cyclic carbonates by the urea method according to claim 4, characterized in that: The reflux pump (10) is connected to the top of the flash tower (1).

6. The product separation system for the preparation of cyclic carbonates by the urea method according to claim 5, characterized in that: A vapor phase cooler (11) is provided between the condenser (9) and the vacuum buffer tank (7).

7. The product separation system for the preparation of cyclic carbonates by the urea method according to claim 4, characterized in that: The reflux pump (10) is connected to a drain pipe (12).

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