A system for optimizing phosgene circulation in the production process of 1,5-pentamethylene diisocyanate

Abstract

The utility model relates to a system of optimizing 1, 5 - pentane diisocyanate production process in phosgene circulation, its characterized in that: tail gas main pipe connects first heat exchanger import, and first heat exchanger export inserts phosgene absorption purification tower, and the liquid phase export of phosgene absorption purification tower bottom connects photochemical liquid discharge pipe, and photochemical liquid discharge pipe passes through first magnetic drive pump and inserts second heat exchanger bottom inlet, and second heat exchanger top export returns and inserts phosgene absorption purification tower, photochemical liquid discharge pipe still connects liquid collecting pipe, and liquid collecting pipe inserts fourth heat exchanger inlet, and fourth heat exchanger export inserts phosgene storage jar. The system not only can effectively reduce the phosgene flash evaporation in the phosgene tank caused by pressure relief before the gaseous phosgene enters the phosgene tank, improve the safety of system, and through increasing phosgene purification tower, reduce the hydrogen chloride content in the recycled phosgene, improve the yield of reaction. Simple operation process is suitable for large industrial production.

Description

Technical Field

[0001] This utility model belongs to the field of chemical technology equipment, specifically relating to a system for optimizing the phosgene cycle of 1,5-pentanediisocyanate. Background Technology

[0002] 1,5-Pentanediisocyanate (PDI), also known as pentamethylene diisocyanate, is a novel aliphatic diisocyanate. Due to its unique pentamethylene chain structure, polyurethane materials synthesized from it exhibit excellent resistance to yellowing, hydrolytic stability, and good optical properties. In recent years, with the increasing demand for high-performance and specialty polyurethanes, the research and application of PDI have received widespread attention. PDI is typically synthesized from bio-based 1,5-pentanediamine (PDA) via phosgenation and is sold as PDI biuret or trimer, used in the synthesis of yellowing-resistant polyurethane coatings, adhesives, inks, and artificial leather, possessing extremely broad market and application prospects.

[0003] Currently, industrial-scale PDI production still primarily relies on the phosgene process. Research focuses on three key areas: first, process safety: improving phosgene leak monitoring and emergency response systems; second, catalyst optimization: enhancing the selectivity of the phosgenation reaction and reducing byproduct formation; and third, tail gas treatment: developing efficient phosgene decomposition and recovery technologies to achieve environmentally friendly emissions. This invention focuses on tail gas treatment, optimizing and modifying the phosgene circulation system to increase system safety and improve reaction yield. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is: a system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate, comprising a phosgene absorption and purification tower, characterized in that: the tail gas main pipe is connected to the inlet of the first heat exchanger, the outlet of the first heat exchanger is connected to the phosgene absorption and purification tower, the liquid phase outlet at the bottom of the phosgene absorption and purification tower is connected to the photochemical liquid discharge pipe, the photochemical liquid discharge pipe is connected to the bottom inlet of the second heat exchanger through a first magnetic pump, and the top outlet of the second heat exchanger returns to the phosgene absorption and purification tower; a liquid sampling pipe is also connected to the photochemical liquid discharge pipe, the liquid sampling pipe is connected to the inlet of the fourth heat exchanger, and the outlet of the fourth heat exchanger is connected to the phosgene storage tank; The gas phase outlet at the top of the phosgene absorption and purification tower is connected to the third heat exchanger through the first gas phase pipe. The gas phase outlet at the top of the third heat exchanger is connected to the gas-liquid separator through the second gas phase pipe. The third gas phase pipe at the top of the gas-liquid separator is connected to the tail gas absorption device.

[0006] Furthermore, the condensate outlet at the bottom of the third heat exchanger is connected to the first reflux pipe, which returns to the phosgene absorption and purification tower.

[0007] Furthermore, the liquid phase outlet at the bottom of the gas-liquid separator is connected to a second reflux pipe, which is then connected to a phosgene absorption and purification tower.

[0008] Furthermore, the bottom outlet of the phosgene storage tank is connected to a delivery pipe, which is connected to the reaction system via a second magnetic pump.

[0009] Furthermore, control valves are installed on the exhaust gas main pipe, liquid collection pipe, delivery pipe, and third gas phase pipe.

[0010] Furthermore, the exhaust gas from the exhaust manifold is a positive-pressure phosgene-containing gas generated during the cold and hot photochemical reactions, continuous injection reactions, and phosgene synthesis reactions.

[0011] The principle of this invention is as follows: A heat exchanger is used to condense the phosgene-containing gas phase entering the phosgene absorption and purification tower. The condensed photochemical liquid is then sent into the phosgene absorption and purification tower to prevent the phosgene-containing gas phase from entering the tower under pressure and in a saturated state. Depressurization before entering the tower prevents flash evaporation of phosgene in the phosgene tank. The heat exchanger is used to heat the photochemical liquid entering the phosgene absorption and purification tower. Taking advantage of the different boiling points of phosgene and hydrogen chloride, the non-condensable hydrogen chloride gas is discharged to the tail gas absorption device, increasing the phosgene concentration in the phosgene storage tank.

[0012] The beneficial effects of this invention are as follows: Utilizing a heat exchanger for condensation simplifies operation and effectively condenses the phosgene-containing gas phase entering the phosgene absorption and purification tower, preventing flash evaporation of pressurized supersaturated phosgene gas phase entering the tower; the phosgene absorption and purification system separates phosgene and hydrogen chloride, which have significantly different boiling points, improving the purity of recycled phosgene, reducing the generation of byproducts (hydrochloride, acyl chloride, and solid residue) during PDI synthesis, reducing equipment and pipeline blockage, and increasing reaction yield. The simple operation process makes it suitable for large-scale industrial production and demonstrates strong practicality and scalability within the industry. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the present invention.

[0014] In the diagram: 1-phosgene absorption and purification tower, 2-gas-liquid separator, 3-phosgene storage tank, L-tail gas main pipe, G-phosgene liquid discharge pipe, G1-liquid sampling pipe, G2-transfer pipe; C1-first gas phase pipe, C2-second gas phase pipe, C3-third gas phase pipe; R1-first reflux pipe, R2-second reflux pipe; H1-first heat exchanger, H2-second heat exchanger, H3-third heat exchanger, H4-fourth heat exchanger; B1-first magnetic pump, B2-second magnetic pump. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the embodiments. The embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0016] Example 1, see Figure 1 , A system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate includes a phosgene absorption and purification tower 1, characterized in that: the tail gas main pipe L is connected to the inlet of the first heat exchanger H1, the outlet of the first heat exchanger H1 is connected to the phosgene absorption and purification tower 1, the liquid phase outlet at the bottom of the phosgene absorption and purification tower 1 is connected to the phosgene liquid discharge pipe G, the phosgene liquid discharge pipe G is connected to the bottom inlet of the second heat exchanger H2 through the first magnetic pump B1, and the top outlet of the second heat exchanger H2 returns to the phosgene absorption and purification tower 1; the phosgene liquid discharge pipe G is also connected to the liquid sampling pipe G1, the liquid sampling pipe G1 is connected to the inlet of the fourth heat exchanger H4, and the outlet of the fourth heat exchanger H4 is connected to the phosgene storage tank 3; The gas phase outlet at the top of the phosgene absorption and purification tower 1 is connected to the third heat exchanger H3 through the first gas phase pipe C1. The gas phase outlet at the top of the third heat exchanger H3 is connected to the gas-liquid separator 2 through the second gas phase pipe C2. The third gas phase pipe C3 at the top of the gas-liquid separator 2 is connected to the tail gas absorption device.

[0017] The condensate outlet at the bottom of the third heat exchanger H3 is connected to the first reflux pipe R1, and the first reflux pipe R1 returns to the phosgene absorption and purification tower 1.

[0018] The liquid phase outlet at the bottom of the gas-liquid separator 2 is connected to the second reflux pipe R2, and the second reflux pipe R2 is connected to the phosgene absorption and purification tower 1.

[0019] The bottom outlet of the phosgene storage tank 3 is connected to the delivery pipe G2, and the delivery pipe G2 is connected to the reaction system through the second magnetic pump B2.

[0020] Control valves are installed on the exhaust gas main pipe L, liquid collection pipe G1, delivery pipe G2, and third gas phase pipe C3.

[0021] The exhaust gas from the exhaust manifold L is a positive-pressure phosgene-containing gas produced during cold and hot photochemical reactions, continuous injection reactions, and phosgene synthesis reactions.

[0022] Work process: (i) The positive-pressure phosgene-containing gas generated during the cold and hot photochemical reaction, continuous injection reaction, and phosgene synthesis reaction is continuously transported to the first heat exchanger H1 through the tail gas main L. By adjusting and controlling the flow rate of the cold medium (refrigerated chlorobenzene), the photochemical liquid condensed in the first heat exchanger H1 is transported to the phosgene absorption and purification tower 1; (ii) The photochemical liquid in the phosgene absorption and purification tower 1 enters the second heat exchanger H2 through the first magnetic pump B1. The second heat exchanger H2 is heated by 13 bar medium-pressure steam. The steam flow rate is controlled by the regulating valve. The photochemical liquid heated by the second heat exchanger H2 is transported to the phosgene absorption and purification tower 1 and circulated for heating until the temperature at the top of the phosgene absorption and purification tower 1 reaches 8-9℃. (III) The gas phase at the top of the phosgene absorption and purification tower 1 enters the third heat exchanger H3 through the first gas phase pipe C1. The condensate flows into the phosgene absorption and purification tower 1 through the first reflux pipe R1. The non-condensable gas in the third heat exchanger H3 enters the gas-liquid separator 2 through the second gas phase pipe C2. The gas-liquid separator 2 takes the photochemical liquid entrained in the gas and liquid and enters the phosgene absorption and purification tower 2 through the second reflux pipe R2. The non-condensable hydrogen chloride gas is transported to the tail gas absorption device for collection and alkaline destruction through the third gas phase pipe C3. (iv) When the hydrogen chloride gas in the phosgene absorption and purification tower 1 is completely separated, the photochemical liquid in the phosgene absorption and purification tower 1 is discharged through the photochemical liquid discharge pipe G and then through the first magnetic pump B1 and the delivery pipe G1 into the fourth heat exchanger H4 for condensation. The condensate of the fourth heat exchanger H4 is collected through the liquid phase outlet at the bottom of the fourth heat exchanger H4 and flows to the phosgene storage tank 3. The photochemical liquid purified in the phosgene storage tank 3 is transported to the reaction system through the second magnetic pump B2 and the delivery pipe G2 for recycling.

[0023] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to the above embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate, comprising a phosgene absorption and purification tower (1), characterized in that: The exhaust gas main pipe (L) is connected to the inlet of the first heat exchanger (H1), and the outlet of the first heat exchanger (H1) is connected to the phosgene absorption and purification tower (1). The liquid phase outlet at the bottom of the phosgene absorption and purification tower (1) is connected to the photochemical liquid discharge pipe (G). The photochemical liquid discharge pipe (G) is connected to the bottom inlet of the second heat exchanger (H2) through the first magnetic pump (B1). The top outlet of the second heat exchanger (H2) returns to the phosgene absorption and purification tower (1). The photochemical liquid discharge pipe (G) is also connected to the liquid collection pipe (G1). The liquid collection pipe (G1) is connected to the inlet of the fourth heat exchanger (H4), and the outlet of the fourth heat exchanger (H4) is connected to the phosgene storage tank (3). The gas phase outlet at the top of the phosgene absorption purification tower (1) is connected to the third heat exchanger (H3) through the first gas phase pipe (C1), the gas phase outlet at the top of the third heat exchanger (H3) is connected to the gas-liquid separator (2) through the second gas phase pipe (C2), and the third gas phase pipe (C3) at the top of the gas-liquid separator (2) is connected to the tail gas absorption device.

2. The system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate as described in claim 1, characterized in that: The condensate outlet at the bottom of the third heat exchanger (H3) is connected to the first reflux pipe (R1), and the first reflux pipe (R1) returns to the phosgene absorption and purification tower (1).

3. The system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate as described in claim 1, characterized in that: The liquid phase outlet at the bottom of the gas-liquid separator (2) is connected to the second reflux pipe (R2), and the second reflux pipe (R2) is connected to the phosgene absorption and purification tower (1).

4. The system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate as described in claim 1, characterized in that: The bottom outlet of the phosgene storage tank (3) is connected to the delivery pipe (G2), and the delivery pipe (G2) is connected to the reaction system through the second magnetic pump (B2).

5. The system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate as described in claim 1, characterized in that: Control valves are installed on the exhaust gas main pipe (L), liquid collection pipe (G1), delivery pipe (G2), and third gas phase pipe (C3).

6. The system for optimizing phosgene circulation in the production process of 1,5-pentanediisocyanate as described in claim 1, characterized in that: The exhaust gas from the exhaust manifold (L) is a positive-pressure phosgene-containing gas produced during the cold and hot photochemical reactions, continuous injection reactions, and phosgene synthesis reactions.

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