Method and device for utilizing secondary steam in caprolactam refining process
In the caprolactam refining process, using hydrogenated material cassium water instead of hot water to condense caprolactam secondary steam, the problems of waste of heat and large amount of circulating water in the prior art are solved, and efficient use of heat and resource conservation are achieved.
Patent Information
- Application Number
- CN202510107731.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2025-05-06
AI Technical Summary
In the existing caprolactam refining process, the heat of the secondary steam is mainly cooled by circulating water, resulting in waste of heat and an increase in circulating water usage.
The hydrogenated material is used to replace hot water to cool the secondary steam of caprolactam, and the heat is directly used to heat the hexa water to reduce the amount of circulating water and avoid the heat loss of hot water heat exchange.
Through this method, caprolactam steam consumption and circulating water consumption are reduced, heat loss of hot water heat exchange is avoided, and heat utilization efficiency is improved.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of caprolactam production, and in particular to a method and device for utilizing secondary steam in a caprolactam refining process. Background Art
[0002] The caprolactam industry has developed rapidly, and the current single-line production capacity has reached 300,000 tons. When the distillation process produces finished caprolactam, multiple distillation towers are generally operated in parallel and then in series. Caprolactam is an important chemical raw material in the field of synthetic fibers and engineering plastics. When used as a polymerization raw material for nylon 6, its quality requirements are very strict. At present, the refining of amide oil for preparing caprolactam by cyclohexanone oxime liquid-phase Beckmann rearrangement mainly undergoes benzene extraction, water back extraction, ion exchange, hydrogenation, evaporation and distillation-related process operations. The heat of condensation of caprolactam secondary steam is much greater than the heat required for hydrogenation preheating. During the refining process, crude caprolactam is flash evaporated under high vacuum, and the caprolactam steam is condensed into liquid caprolactam by hot water. The heat brought by the phase change is used as the heat source of the hot water system. During the design, part of the hot water is used for preheating of hexane water in the hydrogenation process, a small part of the hot water heat is used for heating the device pipeline, and most of the excess heat is cooled by circulating water, resulting in heat waste. Summary of the invention
[0003] In view of the above problems existing in the prior art, the present application provides a method for utilizing secondary steam in the caprolactam refining process. The method provided in the present application utilizes hydrogenated material hexyl water instead of hot water to cool the caprolactam secondary steam, and the heat is directly used for heating hexyl water, which not only reduces the amount of circulating water, but also avoids heat loss in hot water heat exchange and the problem that water can only be heated to 100°C.
[0004] Specifically, the present application provides a method for utilizing secondary steam in a caprolactam refining process, which comprises: introducing hydrogenated hexyl water into a distillation process, so that the hydrogenated hexyl water and the caprolactam secondary steam are heat exchanged.
[0005] In some embodiments, the method for utilizing secondary steam in the caprolactam refining process provided in the present application comprises the following steps:
[0006] S1: introducing hexyl water feed into an ion exchange process for ion exchange treatment to obtain ion exchange treated hexyl water;
[0007] S2: introducing the deionized hexyl water into a hydrogenation step for hydrogenation to obtain hydrogenated hexyl water;
[0008] S3: introducing the hydrogenated hexyl water into the distillation process, so that the hydrogenated hexyl water and the caprolactam secondary steam are heat exchanged to obtain the heat exchanged hexyl water;
[0009] S4: introducing the hexyl water after heat exchange into evaporation, pre-distillation and distillation process.
[0010] In some embodiments, the method further comprises:
[0011] S5: The caprolactam secondary steam exchanges heat with hot water, and the hot water after the heat exchange is used to heat the caprolactam water for ion exchange treatment.
[0012] In some embodiments, in the hydrogenation process, a first shut-off valve is provided on the outlet water pipeline of the hydrogenation treatment.
[0013] In some embodiments, during the distillation process, a second shut-off valve is provided on the hot water pipe at the top of the distillation tower.
[0014] In some embodiments, the first shut-off valve and the second shut-off valve are adjusted to directly introduce the hydrotreated hexyl water into the top of the distillation tower, so that the hydrotreated hexyl water exchanges heat with the caprolactam secondary steam, and the hot water is replaced to condense the caprolactam secondary steam.
[0015] In some embodiments, the temperature of the water feed is 40°C-50°C, for example, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or any thereof.
[0016] In some embodiments, the mass concentration of the hexane feed is 30%-35%, for example, 31%, 32%, 33% or 34%.
[0017] In some embodiments, the temperature of the hexyl water after heat exchange is 100°C-125°C, for example, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C, 120°C, 121°C, 122°C, 123°C, 124°C or any thereof. In some embodiments, the temperature of the hexyl water after heat exchange is 110°C-120°C.
[0018] In some embodiments, the deionized water is heated to 65°C-90°C, for example, 67°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 83°C, 85°C, 87°C or 89°C, preferably 75°C-80°C, and then introduced into the hydrotreatment process for hydrotreatment.
[0019] In some embodiments, the temperature of the hydroprocessing hexyl water is 65°C-90°C, for example, 67°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 83°C, 85°C, 87°C, 89°C or any thereof. In some embodiments, the temperature of the hydroprocessing hexyl water is 75°C-80°C.
[0020] In a second aspect, the present application provides a device for implementing the utilization method described in the first aspect, comprising:
[0021] An ion exchange device is used to perform ion exchange treatment on the hexyl water feed to obtain ion exchange treated hexyl water;
[0022] A hydrogenation device, used for hydrogenating the ion-treated hexyl water to obtain hydrogenated hexyl water;
[0023] A distillation device comprises a distillation tower, wherein the hydrogenated hexyl water and the caprolactam secondary steam are heat exchanged in a heat exchange system at the top of the distillation tower to obtain hexyl water and caprolactam products after heat exchange;
[0024] The evaporation device is used to process the water after heat exchange.
[0025] In some embodiments, in the hydrogenation device, a first shut-off valve is provided on the outlet water pipeline of the hydrogenation treatment.
[0026] In some embodiments, a second shut-off valve is provided on the hot water pipeline in the top heat exchange system of the distillation tower.
[0027] In some embodiments, the first shut-off valve and the second shut-off valve are adjusted to directly introduce the hydrotreated hexyl water into the top of the distillation tower, so that the hydrotreated hexyl water exchanges heat with the caprolactam secondary steam, and the hot water is replaced to condense the caprolactam secondary steam.
[0028] Compared with the prior art, the present invention has the following advantages:
[0029] The method provided in the present application utilizes hexyl water, a hydrogenated material, instead of hot water to cool the secondary steam of caprolactam, and the heat is directly used to heat the hexyl water, which not only reduces the amount of circulating water, but also avoids the problems of heat loss in hot water heat exchange and the problem that water can only be heated to 100°C. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 A flow chart showing secondary steam utilization according to some embodiments of the present application is shown.
[0031] Among them, 1-hexyl water feed, 2-hexyl water after desorption, 3-hexyl water after hydrogenation, 4-caprolactam secondary steam, 5-hexyl water after heat exchange, 6-caprolactam product, 7-hot water, 8-circulating water (cold). DETAILED DESCRIPTION
[0032] The embodiments of the present application will be described in detail below. The embodiments of the present application should not be interpreted as limiting the present application.
[0033] In addition, sometimes amounts, ratios and other numerical values are presented in a range format in this application. It should be understood that such a range format is for convenience and brevity, and should be flexibly understood to include not only the numerical values explicitly specified as range limits, but also all individual numerical values or sub-ranges included in the range, as if each numerical value and sub-range were explicitly specified.
[0034] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.
[0035] In the present application, "hexyl water" refers to an aqueous solution of caprolactam.
[0036] In the present application, there is no special restriction on the ion exchange process, which is mainly used to remove impurities (such as metal ions, chloride ions, etc.), and a suitable ion exchange resin can be selected according to needs.
[0037] In the present application, there is no special restriction on the hydrogenation process, which is mainly used to remove impurities such as unsaturated compounds, sulfides, nitrides, etc., so as to improve the purity of caprolactam. A suitable hydrogenation catalyst can be selected according to needs.
[0038] The present application provides a method for utilizing secondary steam in a caprolactam refining process, according to Figure 1 In the process shown, the hexyl water feed 1 is treated with ion exchange (ion exchange) to obtain hexyl water 2 after ion exchange. The hexyl water 2 after ion exchange enters the hydrogenation process for hydrogenation treatment to obtain hydrogenated hexyl water 3. The hydrogenated hexyl water 3 is directly introduced to the top of the distillation tower of the distillation process, and heat exchange is performed with the caprolactam secondary steam 4 to obtain hexyl water 5 after heat exchange and the caprolactam product 6. The hexyl water 5 after heat exchange enters the evaporation process, and performs pre-distillation and distillation post-treatment in sequence.
[0039] After the caprolactam secondary steam 4 exchanges heat with the hydrogenated hexyl water 3, the excess heat is used as a heat source for the hot water system, and is exchanged with the circulating water cooling 8 through a heat exchanger, and part of the hot water 7 before the heat exchange is supplied to the hydrogenated hexyl water 2 for heating.
[0040] Examples and Comparative Examples
[0041] Example 1
[0042] according to Figure 1 In the process shown, 40°C hexane water feed 1 is treated with ion exchange to obtain ion exchanged hexane water 2. The ion exchanged hexane water 2 enters the hydrogenation process for hydrogenation treatment to obtain hydrogenated hexane water 3.
[0043] The hexyl water pipeline of the hydrogenation treatment discharge and the hot water pipeline for condensing the secondary caprolactam steam at the top of the distillation tower are both provided with a shut-off valve. By adjusting the shut-off valve, the hexyl water 3 after hydrogenation is directly led to the hot water pipeline at the top of the distillation tower, replacing the hot water used to condense the caprolactam secondary steam 4, and heat-exchanging with the caprolactam secondary steam 4 to obtain the hexyl water 5 and the caprolactam product 6 after heat exchange. The temperature of the hexyl water 5 after heat exchange reaches 110-120°C, and then enters the evaporation process, and performs pre-distillation and distillation post-treatment in sequence.
[0044] After the caprolactam secondary steam 4 exchanges heat with the hydrogenated hexyl water 3, the excess heat is used as the heat source of the hot water system, and is exchanged with the circulating water cooling 8 through the heat exchanger. Part of the hot water 7 before the heat exchange is used to heat the dehydrogenated hexyl water 2, so that the temperature of the dehydrogenated hexyl water 2 reaches 75-80°C before entering the hydrogenation process.
[0045] Through the above process operation, the caprolactam steam consumption can be reduced by 0.24t / t hexane and the circulating water consumption can be reduced by 5t / t hexane.
[0046] Example 2
[0047] according to Figure 1 The process shown is different from that of Example 1 in that the temperature of the hexyl water 5 after heat exchange reaches 100-110° C. Through the above process operation, the caprolactam steam consumption can be reduced by 0.18 t / t hexyl and the circulating water consumption can be reduced by 3.75 t / t hexyl.
[0048] Example 3
[0049] according to Figure 1 The process shown is different from that of Example 1 in that the temperature of the hexyl water 5 after heat exchange reaches 120-130° C. Through the above process operation, the caprolactam steam consumption can be reduced by 0.3 t / t hexyl and the circulating water consumption can be reduced by 6.25 t / t hexyl.
[0050] Example 4
[0051] according to Figure 1 The process shown is different from that of Example 1 in that part of the hot water 7 after heat exchange is used to heat the hexyl water 2 after deionization, so that the temperature of the hexyl water 2 after deionization reaches 65-70°C before entering the hydrogenation process. Through the above process operation, the consumption of caprolactam steam can be reduced by 0.18t / t hexyl and the consumption of circulating water can be reduced by 3.75t / t hexyl.
[0052] Example 5
[0053] according to Figure 1 The process shown is different from that of Example 1 in that part of the hot water 7 after heat exchange is used to heat the hexyl water 2 after deionization, so that the temperature of the hexyl water 2 after deionization reaches 85-90°C before entering the hydrogenation process. Through the above process operation, the consumption of caprolactam steam can be reduced by 0.3t / t hexyl and the consumption of circulating water can be reduced by 6.25t / t hexyl.
[0054] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.
Claims
1. A method for utilizing secondary steam in a caprolactam refining process, comprising introducing hydrogenated hexyl water into a distillation process, and exchanging heat between the hydrogenated hexyl water and the caprolactam secondary steam.
2. The utilization method according to claim 1, characterized in that: It includes the following steps: S1: introducing hexyl water feed into an ion exchange process for ion exchange treatment to obtain ion exchange treated hexyl water; S2: introducing the deionized hexyl water into a hydrogenation step for hydrogenation to obtain hydrogenated hexyl water; S3: introducing the hydrogenated hexyl water into the distillation process, so that the hydrogenated hexyl water and the caprolactam secondary steam are heat exchanged to obtain the heat exchanged hexyl water; S4: introducing the hexyl water after heat exchange into evaporation, pre-distillation and distillation process.
3. The utilization method according to claim 1 or 2, characterized in that: The method further comprises: S5: The caprolactam secondary steam exchanges heat with hot water, and the hot water after the heat exchange is used to heat the caprolactam water for ion exchange treatment.
4. The utilization method according to any one of claims 1 to 3, characterized in that: In the hydrogenation process, a first shut-off valve is provided on the water pipeline of the hydrogenation treatment. In the distillation step, a second shutoff valve is provided on the hot water pipe at the top of the distillation tower.
5. The utilization method according to claim 4, characterized in that: By adjusting the first shut-off valve and the second shut-off valve, the hydrotreated hexyl water is directly introduced into the top of the distillation tower, so that the hydrotreated hexyl water and the caprolactam secondary steam are heat exchanged, and the hot water is replaced to condense the caprolactam secondary steam.
6. The utilization method according to any one of claims 2 to 5, characterized in that: The temperature of the hexyl water feed is 40°C-50°C; the mass concentration of the hexyl water feed is 30%-35%wt.
7. The utilization method according to any one of claims 2 to 6, characterized in that: The temperature of the hexyl water after heat exchange is 100°C-125°C, preferably 110°C-120°C.
8. The utilization method according to any one of claims 2 to 7, characterized in that: The temperature for hydrogenating hexyl water is 65°C-90°C, preferably 75°C-80°C.
9. A device for implementing the utilization method according to any one of claims 1 to 8, comprising: An ion exchange device is used to perform ion exchange treatment on the hexyl water feed to obtain ion exchange treated hexyl water; A hydrogenation device, used for hydrogenating the ion-treated hexyl water to obtain hydrogenated hexyl water; A distillation device comprises a distillation tower, wherein the hydrogenated hexyl water and the caprolactam secondary steam are heat exchanged in a heat exchange system at the top of the distillation tower to obtain the hexyl water after heat exchange; The evaporation device is used to concentrate the water after heat exchange.
10. The device according to claim 9, characterized in that In the hydrogenation device, a first shut-off valve is provided on the water pipeline of the hydrogenation treatment outlet; In the tower top heat exchange system of the distillation tower, a second shut-off valve is provided on the hot water pipeline; Preferably, the first shut-off valve and the second shut-off valve are adjusted to directly introduce the hydrotreated hexyl water into the top of the distillation tower, so that the hydrotreated hexyl water exchanges heat with the caprolactam secondary steam, and the hot water is replaced to condense the caprolactam secondary steam.