A method for producing high-purity benzene from crude benzene
By using a composite extractant of N-methylpyrrolidone and diethanolamine and a secondary distillation process, the environmental pollution and high energy consumption problems in crude benzene refining were solved, and the production of high-purity benzene and the efficient recovery of thiophene were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-31
- Publication Date
- 2026-04-03
AI Technical Summary
Existing crude benzene refining technologies suffer from environmental pollution, high energy consumption, large equipment investment, and low purity and yield of benzene, toluene, and xylene, making it difficult to meet the production demand for high-purity benzene.
Using a composite solvent of N-methylpyrrolidone and diethanolamine as extractants, combined with a secondary distillation process, and through a multi-stage extractive distillation column and heat recovery device, benzene is separated and purified to produce high-purity benzene for use.
It has achieved the production of high-purity (99.99%) benzene, reduced energy consumption and production costs, recovered thiophene products, reduced environmental pollution, and met the national standard for superior products.
Smart Images
Figure CN117430477B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical technology and relates to a method for producing high-purity benzene from crude benzene. Background Technology
[0002] Benzene is a crucial raw material in the petrochemical industry, used in the synthesis of rubber, resins, fibers, pharmaceuticals, pesticides, explosives, and dyes, among other important chemical products. Currently, there are three main refining technologies for crude benzene from coking plants: acid washing, hydrorefining, and extractive distillation. Acid washing is a simple and mature process with low equipment investment, operating at ambient temperature and pressure. Because acid washing destroys most of the sulfides, the three benzene compounds (benzene, xylene, and benzoylene) can be separated by ordinary distillation. However, the purity and yield of these compounds are very low. Furthermore, the acid tar and waste residue generated during acid washing are difficult to treat, posing serious environmental pollution problems. Another key issue is the incomplete removal of sulfides, limiting the use of acid-washed benzene in certain fields. Catalytic hydrogenation yields high-quality benzene, which can replace petroleum benzene in some areas. However, regardless of whether hydrogenation is done at high or low temperatures, the reaction conditions are harsh, requiring large equipment investments and high energy consumption. The sulfides are converted to H2S, which cannot be further utilized effectively. To reduce environmental pollution, simplify the process, improve the yield of benzene, toluene, and xylene, and recover the more important thiophene product, China has developed crude benzene refining technology based on extractive distillation in recent years. However, the purity of the obtained product still needs to be further improved. Summary of the Invention
[0003] This invention proposes a method for producing high-purity benzene from crude benzene. The entire process generates no waste, has low energy consumption, and yields a high-purity product.
[0004] The technical solution of this invention is implemented as follows:
[0005] A method for producing high-purity benzene from crude benzene includes the following steps:
[0006] After removing heavy impurities by distillation, crude benzene is further refined using an extractant to produce pure benzene; the extractant is N-methylpyrrolidone and diethanolamine in a mass ratio of 1.2-1.7:1.
[0007] Specifically, it includes the following steps:
[0008] A. Crude benzene separation unit:
[0009] Crude benzene is preheated by a preheater and then enters the two-benzene tower. The bottom product, heavy benzene, is collected from the bottom of the tower and pumped into the heavy benzene tank. The top product is collected and enters the primary distillation tower.
[0010] The top product from the primary distillation column enters the primary fraction storage tank, while the bottom product enters the crude benzene column.
[0011] The top product from the crude benzene tower enters the benzene refining unit, while the bottom product enters the crude toluene tower.
[0012] B. Pure Benzene Refining Unit:
[0013] The crude benzene drawn from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 removal tower. The material drawn from the top of the tower enters the benzene non-aromatic storage tank, and the material from the bottom of the tower enters the benzene non-aromatic removal tower.
[0014] The top product from the benzene dearomatic distillation column enters either the benzene non-aromatic tank or the crude benzene storage tank, while the bottom product enters the benzene extraction distillation column.
[0015] The top product from the benzene extractive distillation column enters the pure benzene tank, while the bottom product enters the benzene extractant regeneration column. The extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 4-8:1, and the extractant is N-methylpyrrolidone and diethanolamine in a mass ratio of 1.2-1.7:1.
[0016] The material collected from the top of the benzene extractant regeneration tower enters the benzene secondary extractive distillation tower, while the material from the bottom of the tower re-enters the benzene extractive distillation tower from the top.
[0017] The top product from the benzene secondary extractive distillation column is returned to the CS2 removal column, while the bottom product enters the benzene secondary extractant regeneration column.
[0018] The material collected from the top of the benzene secondary extractant regeneration tower enters the thiophene refining tower, while the material from the bottom of the tower re-enters the benzene secondary extractive distillation tower from the top.
[0019] In a preferred embodiment of the present invention, the pressure at the top of the two benzene tower is -50-60 kPa and the temperature at the top of the tower is 65-70°C; the preheating temperature of the preheater is 70-95°C.
[0020] As a preferred embodiment of the present invention, the pressure at the top of the primary distillation column is 1.5-2.5 kPa and the temperature at the top of the column is 50-60°C.
[0021] In a preferred embodiment of the present invention, the pressure at the top of the crude benzene tower is -55-65 kPa and the temperature at the top of the tower is 50-60°C.
[0022] As a preferred embodiment of the present invention, the pressure at the top of the CS2 removal tower is -55 to 65 kPa, and the temperature at the top of the tower is 50 to 55°C.
[0023] In a preferred embodiment of the present invention, the pressure at the top of the benzene-de-aromatic tower is 0 kPa and the temperature at the top of the tower is 75-80°C.
[0024] As a preferred embodiment of the present invention, the pressure at the top of the benzene extraction distillation column is -45-55 kPa and the temperature at the top of the column is 55-60℃.
[0025] As a preferred embodiment of the present invention, the pressure at the top of the benzene extractant regeneration tower is -45-55 kPa and the temperature at the top of the tower is 60-70℃.
[0026] As a preferred embodiment of the present invention, the top pressure of the benzene secondary extractive distillation column is -45-55 kPa and the top temperature is 55-60°C; the top pressure of the benzene secondary extractant regeneration column is -45-55 kPa and the top temperature is 78-85°C.
[0027] The working principle and beneficial effects of this invention are as follows:
[0028] 1. This invention combines a composite extraction solvent with a secondary distillation extraction process to obtain a benzene product with a purity of 99.99%. Its color number, bromine value, crystallization point, sulfur and nitrogen impurity content, and other indicators all meet the national standard GB / T 2283-2008 superior grade standard, which can replace petroleum benzene. At the same time, thiophene is efficiently recovered with a purity greater than 99.7% and a recovery rate greater than 97%.
[0029] 2. Compared with existing extraction distillation processes, the composite extraction solvent of this invention has high selectivity, increases the relative volatility between components, reduces the amount of extractant used, and lowers the energy consumption and production cost of the process, resulting in significant energy-saving effects. Attached Figure Description
[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0031] Figure 1 This is a schematic diagram of the crude benzene separation unit of the present invention;
[0032] Figure 2 This is a schematic diagram of the crude benzene refining unit process of the present invention. Detailed Implementation
[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0034] like Figure 1 The diagram shown is a schematic flow chart of the crude benzene separation unit of the present invention; the crude benzene separation is to separate crude benzene into heavy benzene, initial fraction, sulfur-containing benzene, sulfur-containing toluene, and a mixture of xylene containing styrene.
[0035] Specifically, crude benzene is preheated by a preheater and then enters the two-benzene tower. Heavy benzene, a byproduct, is collected from the bottom of the tower and pumped into a heavy benzene tank. The vapor at the top of the tower is condensed by a condenser, with part of it being refluxed and the rest being collected from the top of the tower and entering the primary distillation tower, with a reflux ratio of 0.5-1. The preheating temperature of the preheater is 70-95℃. The crude benzene is coking crude benzene feedstock.
[0036] After the vapor at the top of the primary distillation column is condensed by the condenser, part of it is refluxed and part is collected and sent to the primary distillate storage tank. The reflux ratio is 2-4. The bottom material of the column enters the crude benzene column.
[0037] The vapor from the top of the crude benzene tower is condensed by a condenser, with part of it being refluxed and part being collected and sent to the benzene refining unit. The reflux ratio is 0.8-1.5. The bottom material of the tower enters the crude toluene tower.
[0038] After the vapor from the top of the crude toluene tower is condensed by the condenser, part of it is refluxed and part is collected and sent to the toluene refining unit. The reflux ratio is 1-3. The bottom material of the tower enters the crude xylene tower (the crude xylene tower is drawn in by vacuum).
[0039] The crude xylene from the top of the column enters the xylene refining unit, and the crude xylene from the bottom enters the heavy benzene tank. (The light component is collected first from the top of the column, then the early transition component, then the crude xylene, and finally the late transition component. The light component is returned to the crude benzene tank, the transition component is returned to the feed tank, the crude xylene enters the corresponding storage tank, and the residue is pumped into the heavy benzene storage tank.)
[0040] like Figure 2 This is a schematic diagram of the crude benzene refining unit process of the present invention, namely a schematic diagram of the benzene extraction and distillation process; it removes alkanes, alkenes, cycloalkanes and thiophenes from benzene to produce qualified pure benzene and thiophene products.
[0041] Specifically, the crude benzene collected from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 removal tower. The top of the tower enters the benzene non-aromatic storage tank (it can also be returned to the crude benzene tank when the benzene content is high), and the bottom material enters the benzene non-aromatic removal tower with a reflux ratio of 0.5-2.
[0042] The top product from the benzene dearomatic distillation column is fed into the benzene non-aromatic tank or the crude benzene storage tank, while the bottom product is fed into the benzene extraction distillation column with a reflux ratio of 0.5-2.
[0043] After condensation, the top vapor phase of the benzene extractive distillation column is collected as pure benzene with a purity of 99.99% and a thiophene content of less than 1 ppm, and enters the pure benzene tank. The bottom material enters the benzene extractant regeneration column with a reflux ratio of 0.5-2. The benzene extractive distillation column is equipped with a heat recovery device to fully utilize the heat of the extractant and reduce the amount of primary heat used. The extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 4-8:1, and the extractant is N-methylpyrrolidone and diethanolamine with a mass ratio of 1.2-1.7:1.
[0044] The top of the benzene extractant regeneration column is fed into the benzene secondary extractive distillation column with a reflux ratio of 0.5-2. The bottom material (after passing through the two intermediate reboilers of the benzene extractive distillation column, the reboiler of the crude benzene column, the reboiler of the primary distillation column, the crude benzene preheater, and the reboiler of the CS2 removal column) enters the extractant cooler and is cooled to the appropriate temperature (32-37℃ / 0.2 MPa) before re-entering the benzene extractive distillation column from the top. The regenerated extractant is recycled after heat recovery.
[0045] The top product from the benzene secondary extractive distillation column is returned to the CS2 removal column, while the bottom product enters the benzene secondary extractant regeneration column with a reflux ratio of 0.5-2. The secondary extractive distillation column is also equipped with a heat recovery device.
[0046] The top of the benzene secondary extractant regeneration tower is fed into the thiophene refining tower with a reflux ratio of 0.5-2. The bottom material is fed back into the benzene secondary extractive distillation tower from the top. The bottom extractant is recycled after heat recovery.
[0047] Thiophene with a purity of 99.7% or higher is collected from the top of the thiophene refining column and enters the product tank. (When the initial benzene content is high, it directly enters the feed tank of the benzene secondary extractive distillation column. Later, the transition components enter the thiophene feed tank, and the thiophene product with a purity of 99.5% or higher enters the thiophene receiving tank. After the thiophene product is collected, the top of the column is collected into the toluene receiving tank, and finally, the material in the toluene receiving tank is returned to the crude benzene tank by a pump.)
[0048] Example 1
[0049] A method for producing high-purity benzene from crude benzene includes the following steps:
[0050] A. Crude benzene separation unit:
[0051] Crude benzene is preheated by a preheater and then enters a two-benzene tower (top pressure -55 kPa, top temperature 68°C). Heavy benzene, a byproduct, is collected from the bottom of the tower and pumped into a heavy benzene tank. The top vapor is condensed by a condenser and partially refluxed, while the top portion is collected and enters the primary distillation tower with a reflux ratio of 0.5-1. The preheater temperature is 80°C.
[0052] The vapor at the top of the primary distillation column (top pressure 2 kPa, top temperature 55℃) is condensed by the condenser, and part of it is refluxed and part of it is collected and enters the primary fraction storage tank. The reflux ratio is 3:1. The bottom material enters the crude benzene column.
[0053] The vapor at the top of the crude benzene tower (top pressure -60 kPa, top temperature 54℃) is condensed by a condenser, with part of it being refluxed and part being collected and sent to the benzene refining unit, with a reflux ratio of 1.2:1. The bottom material enters the crude toluene tower.
[0054] The vapor at the top of the crude toluene tower (top pressure -80 kPa, top temperature 63.7℃) is condensed by the condenser, with part of it being refluxed and part being collected and sent to the toluene refining unit at a reflux ratio of 2:1. The bottom material enters the crude xylene tower (crude xylene tower is drawn in by vacuum).
[0055] The crude xylene column (top pressure -90 kPa, top temperature 75℃) is collected and enters the xylene refining unit, while the bottom product is collected and enters the heavy benzene tank. (The light component is collected first from the top of the column, then the pre-transition component, then the crude xylene, and finally the post-transition component. The light component is returned to the crude benzene tank, the transition component is returned to the feed tank, the crude xylene enters the corresponding storage tank, and the residue is pumped into the heavy benzene storage tank.)
[0056] B. Pure Benzene Refining Unit:
[0057] The crude benzene drawn from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 stripping tower (top pressure -60kPa, top temperature 52℃). The top material enters the benzene non-aromatic storage tank (it can also be returned to the crude benzene tank when the benzene content is high). The bottom material enters the benzene non-aromatic stripping tower with a reflux ratio of 1:1.
[0058] The top of the benzene dearomatic distillation column (top pressure 0 kPa, top temperature 78.5℃) is collected and sent to the benzene non-aromatic tank or the crude benzene storage tank, while the bottom material is sent to the benzene extractive distillation column with a reflux ratio of 2:1.
[0059] The vapor phase at the top of the benzene extractive distillation column (top pressure -50 kPa, top temperature 59.7℃) is condensed and collected into a pure benzene tank (the purity of benzene in the pure benzene tank is 99.99% and the thiophene content is 0.01 g / 100 ml, as determined by the method in national standard GB / T 2283-2008). The bottom material enters the benzene extractant regeneration column with a reflux ratio of 1.5:1. The benzene extractive distillation column is equipped with a heat recovery device to fully utilize the heat of the extractant and reduce the amount of heat used in the primary process. The extractant or regenerated extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 6:1. The extractant is N-methylpyrrolidone and diethanolamine in a mass ratio of 1.5:1.
[0060] The top of the benzene extractant regeneration column (top pressure -50 kPa, top temperature 65℃) is collected and enters the benzene secondary extractive distillation column with a reflux ratio of 2:1. The bottom material (collected from the bottom of the column, after passing through two intermediate reboilers of the benzene extractive distillation column, the reboiler of the crude benzene column, the reboiler of the primary distillation column, the crude benzene preheater, and the reboiler of the CS2 removal column, enters the extractant cooler and is cooled to the corresponding temperature (32~37℃ / 0.2 MPa)) and re-enters the benzene extractive distillation column from the top. The regenerated extractant is recycled after heat recovery.
[0061] The top of the benzene secondary extractive distillation column (top pressure -50 kPa, top temperature 59℃) is returned to the CS2 removal column, while the bottom material enters the benzene secondary extractant regeneration column at a reflux ratio of 2:1. The secondary extractive distillation column is also equipped with a heat recovery device. The extractant or regenerated secondary extractant enters from the top of the benzene extractive distillation column at a solvent ratio of 6:1. The extractant is N-methylpyrrolidone and diethanolamine in a mass ratio of 1.2:1.
[0062] The top of the benzene secondary extractant regeneration column (top pressure -50kPa, top temperature 80℃) is collected and enters the thiophene refining column with a reflux ratio of 2:1. The bottom material re-enters the benzene secondary extractive distillation column from the top, and the bottom extractant is recycled after heat recovery.
[0063] Thiophene with a purity of 99.7% or higher is collected from the top of the thiophene refining column (top pressure 0 kPa, top temperature 80–110°C) and enters the product tank. (Initially, when the benzene content is high, it directly enters the feed tank of the benzene secondary extractive distillation column; later, the transition components enter the thiophene feed tank; and the thiophene product with a purity of 99.5% or higher enters the thiophene receiving tank. After the thiophene product collection is completed, the top product is collected into the toluene receiving tank, and finally, the material in the toluene receiving tank is pumped back to the crude benzene tank).
[0064] Comparative Example 1
[0065] A method for producing high-purity benzene from crude benzene includes the following steps:
[0066] A. Crude benzene separation unit:
[0067] Crude benzene is preheated by a preheater and then enters a two-benzene tower (top pressure -55 kPa, top temperature 68°C). Heavy benzene, a byproduct, is collected from the bottom of the tower and pumped into a heavy benzene tank. The top vapor is condensed by a condenser and partially refluxed, while the top portion is collected and enters the primary distillation tower with a reflux ratio of 0.5-1. The preheater temperature is 80°C.
[0068] The vapor at the top of the primary distillation column (top pressure 2 kPa, top temperature 55℃) is condensed by the condenser, and part of it is refluxed and part of it is collected and enters the primary fraction storage tank. The reflux ratio is 3:1. The bottom material enters the crude benzene column.
[0069] The vapor at the top of the crude benzene tower (top pressure -60 kPa, top temperature 54℃) is condensed by a condenser, with part of it being refluxed and part being collected and sent to the benzene refining unit, with a reflux ratio of 1.2:1. The bottom material enters the crude toluene tower.
[0070] The vapor at the top of the crude toluene tower (top pressure -80 kPa, top temperature 63.7℃) is condensed by the condenser, with part of it being refluxed and part being collected and sent to the toluene refining unit at a reflux ratio of 2:1. The bottom material enters the crude xylene tower (crude xylene tower is drawn in by vacuum).
[0071] The crude xylene column (top pressure -90 kPa, top temperature 75℃) is collected and enters the xylene refining unit, while the bottom product is collected and enters the heavy benzene tank. (The light component is collected first from the top of the column, then the pre-transition component, then the crude xylene, and finally the post-transition component. The light component is returned to the crude benzene tank, the transition component is returned to the feed tank, the crude xylene enters the corresponding storage tank, and the residue is pumped into the heavy benzene storage tank.)
[0072] B. Pure Benzene Refining Unit:
[0073] The crude benzene drawn from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 stripping tower (top pressure -60kPa, top temperature 52℃). The top material enters the benzene non-aromatic storage tank (it can also be returned to the crude benzene tank when the benzene content is high). The bottom material enters the benzene non-aromatic stripping tower with a reflux ratio of 1:1.
[0074] The top of the benzene dearomatic distillation column (top pressure 0 kPa, top temperature 78.5℃) is collected and sent to the benzene non-aromatic tank or the crude benzene storage tank, while the bottom material is sent to the benzene extractive distillation column with a reflux ratio of 2:1.
[0075] The vapor phase at the top of the benzene extractive distillation column (top pressure -50 kPa, top temperature 59.7℃) is condensed and collected into a pure benzene tank (the purity of benzene in the pure benzene tank is 99.68% and the thiophene content is 0.06 g / 100 ml, as determined by the method in national standard GB / T 2283-2008). The bottom material enters the benzene extractant regeneration column with a reflux ratio of 1.5:1. The benzene extractive distillation column is equipped with a heat recovery device to fully utilize the heat of the extractant and reduce the amount of heat used in the primary process. The extractant or regenerated extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 6:1. The extractant is N-methylpyrrolidone and diethanolamine in a mass ratio of 1.5:1.
[0076] The top of the benzene extractant regeneration column (top pressure -50 kPa, top temperature 65℃) is collected and enters the benzene de-aromatics column with a reflux ratio of 2:1. The bottom material (collected from the bottom of the column, after passing through two intermediate reboilers of the benzene extractive distillation column, the reboiler of the crude benzene column, the reboiler of the primary distillation column, the crude benzene preheater, and the reboiler of the CS2 removal column, enters the extractant cooler and is cooled to the corresponding temperature (32~37℃ / 0.2MPa)) and re-enters the benzene extractive distillation column from the top. The regenerated extractant is recycled after heat recovery.
[0077] Comparative Example 2
[0078] A method for producing high-purity benzene from crude benzene includes the following steps:
[0079] A. Crude benzene separation unit:
[0080] Crude benzene is preheated by a preheater and then enters a two-benzene tower (top pressure -55 kPa, top temperature 68°C). Heavy benzene, a byproduct, is collected from the bottom of the tower and pumped into a heavy benzene tank. The top vapor is condensed by a condenser and partially refluxed, while the top portion is collected and enters the primary distillation tower with a reflux ratio of 0.5-1. The preheater temperature is 80°C.
[0081] The vapor at the top of the primary distillation column (top pressure 2 kPa, top temperature 55℃) is condensed by the condenser, and part of it is refluxed and part of it is collected and enters the primary fraction storage tank. The reflux ratio is 3:1. The bottom material enters the crude benzene column.
[0082] The vapor at the top of the crude benzene tower (top pressure -60 kPa, top temperature 54℃) is condensed by a condenser, with part of it being refluxed and part being collected and sent to the benzene refining unit, with a reflux ratio of 1.2:1. The bottom material enters the crude toluene tower.
[0083] The vapor at the top of the crude toluene tower (top pressure -80 kPa, top temperature 63.7℃) is condensed by the condenser, with part of it being refluxed and part being collected and sent to the toluene refining unit at a reflux ratio of 2:1. The bottom material enters the crude xylene tower (crude xylene tower is drawn in by vacuum).
[0084] The crude xylene column (top pressure -90 kPa, top temperature 75℃) is collected and enters the xylene refining unit, while the bottom product is collected and enters the heavy benzene tank. (The light component is collected first from the top of the column, then the pre-transition component, then the crude xylene, and finally the post-transition component. The light component is returned to the crude benzene tank, the transition component is returned to the feed tank, the crude xylene enters the corresponding storage tank, and the residue is pumped into the heavy benzene storage tank.)
[0085] B. Pure Benzene Refining Unit:
[0086] The crude benzene drawn from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 stripping tower (top pressure -60kPa, top temperature 52℃). The top material enters the benzene non-aromatic storage tank (it can also be returned to the crude benzene tank when the benzene content is high). The bottom material enters the benzene non-aromatic stripping tower with a reflux ratio of 1:1.
[0087] The top of the benzene dearomatic distillation column (top pressure 0 kPa, top temperature 78.5℃) is collected and sent to the benzene non-aromatic tank or the crude benzene storage tank, while the bottom material is sent to the benzene extractive distillation column with a reflux ratio of 2:1.
[0088] The vapor phase at the top of the benzene extractive distillation column (top pressure -50 kPa, top temperature 59.7℃) is condensed and collected into a pure benzene tank (the purity of benzene in the pure benzene tank is 99.73% and the thiophene content is 0.05 g / 100 ml, as determined by the method in national standard GB / T 2283-2008). The bottom material enters the benzene extractant regeneration column with a reflux ratio of 1.5:1. The benzene extractive distillation column is equipped with a heat recovery device to fully utilize the heat of the extractant and reduce the amount of heat used in the primary process. The extractant or regenerated extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 6:1, and the extractant is N-methylpyrrolidone.
[0089] The top of the benzene extractant regeneration column (top pressure -50 kPa, top temperature 65℃) is collected and enters the benzene secondary extractive distillation column with a reflux ratio of 2:1. The bottom material (collected from the bottom of the column, after passing through two intermediate reboilers of the benzene extractive distillation column, the reboiler of the crude benzene column, the reboiler of the primary distillation column, the crude benzene preheater, and the reboiler of the CS2 removal column, enters the extractant cooler and is cooled to the corresponding temperature (32~37℃ / 0.2 MPa)) and re-enters the benzene extractive distillation column from the top. The regenerated extractant is recycled after heat recovery.
[0090] The top of the benzene secondary extractive distillation column (top pressure -50 kPa, top temperature 59℃) is returned to the CS2 removal column, while the bottom material enters the benzene secondary extractant regeneration column with a reflux ratio of 2:1. The secondary extractive distillation column is also equipped with a heat recovery device. The extractant or regenerated secondary extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 6:1. The extractant is N-methylpyrrolidone.
[0091] The top of the benzene secondary extractant regeneration column (top pressure -50kPa, top temperature 80℃) is collected and enters the thiophene refining column with a reflux ratio of 2:1. The bottom material re-enters the benzene secondary extractive distillation column from the top, and the bottom extractant is recycled after heat recovery.
[0092] Thiophene with a purity of 99.7% or higher is collected from the top of the thiophene refining column (top pressure 0 kPa, top temperature 80–110°C) and enters the product tank. (Initially, when the benzene content is high, it directly enters the feed tank of the benzene secondary extractive distillation column; later, the transition components enter the thiophene feed tank; and the thiophene product with a purity of 99.5% or higher enters the thiophene receiving tank. After the thiophene product collection is completed, the top product is collected into the toluene receiving tank, and finally, the material in the toluene receiving tank is pumped back to the crude benzene tank).
[0093] Comparative Example 3
[0094] A method for producing high-purity benzene from crude benzene includes the following steps:
[0095] A. Crude benzene separation unit:
[0096] Crude benzene is preheated by a preheater and then enters a two-benzene tower (top pressure -55 kPa, top temperature 68°C). Heavy benzene, a byproduct, is collected from the bottom of the tower and pumped into a heavy benzene tank. The top vapor is condensed by a condenser and partially refluxed, while the top portion is collected and enters the primary distillation tower with a reflux ratio of 0.5-1. The preheater temperature is 80°C.
[0097] The vapor at the top of the primary distillation column (top pressure 2 kPa, top temperature 55℃) is condensed by the condenser, and part of it is refluxed and part of it is collected and enters the primary fraction storage tank. The reflux ratio is 3:1. The bottom material enters the crude benzene column.
[0098] The vapor at the top of the crude benzene tower (top pressure -60 kPa, top temperature 54℃) is condensed by a condenser, with part of it being refluxed and part being collected and sent to the benzene refining unit, with a reflux ratio of 1.2:1. The bottom material enters the crude toluene tower.
[0099] The vapor at the top of the crude toluene tower (top pressure -80 kPa, top temperature 63.7℃) is condensed by the condenser, with part of it being refluxed and part being collected and sent to the toluene refining unit at a reflux ratio of 2:1. The bottom material enters the crude xylene tower (crude xylene tower is drawn in by vacuum).
[0100] The crude xylene column (top pressure -90 kPa, top temperature 75℃) is collected and enters the xylene refining unit, while the bottom product is collected and enters the heavy benzene tank. (The light component is collected first from the top of the column, then the pre-transition component, then the crude xylene, and finally the post-transition component. The light component is returned to the crude benzene tank, the transition component is returned to the feed tank, the crude xylene enters the corresponding storage tank, and the residue is pumped into the heavy benzene storage tank.)
[0101] B. Pure Benzene Refining Unit:
[0102] The crude benzene drawn from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 stripping tower (top pressure -60kPa, top temperature 52℃). The top material enters the benzene non-aromatic storage tank (it can also be returned to the crude benzene tank when the benzene content is high). The bottom material enters the benzene non-aromatic stripping tower with a reflux ratio of 1:1.
[0103] The top of the benzene dearomatic distillation column (top pressure 0 kPa, top temperature 78.5℃) is collected and sent to the benzene non-aromatic tank or the crude benzene storage tank, while the bottom material is sent to the benzene extractive distillation column with a reflux ratio of 2:1.
[0104] The vapor phase at the top of the benzene extractive distillation column (top pressure -50 kPa, top temperature 59.7℃) is condensed and collected into a pure benzene tank (the purity of benzene in the pure benzene tank is 99.81% and the thiophene content is 0.04 g / 100 ml, as determined by the method in national standard GB / T 2283-2008). The bottom material enters the benzene extractant regeneration column with a reflux ratio of 1.5:1. The benzene extractive distillation column is equipped with a heat recovery device to fully utilize the heat of the extractant and reduce the amount of heat used in the primary process. The extractant or regenerated extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 6:1. The extractant is N-methylpyrrolidone and monoethanolamine in a mass ratio of 1.5:1.
[0105] The top of the benzene extractant regeneration column (top pressure -50 kPa, top temperature 65℃) is collected and enters the benzene secondary extractive distillation column with a reflux ratio of 2:1. The bottom material (collected from the bottom of the column, after passing through two intermediate reboilers of the benzene extractive distillation column, the reboiler of the crude benzene column, the reboiler of the primary distillation column, the crude benzene preheater, and the reboiler of the CS2 removal column, enters the extractant cooler and is cooled to the corresponding temperature (32~37℃ / 0.2 MPa)) and re-enters the benzene extractive distillation column from the top. The regenerated extractant is recycled after heat recovery.
[0106] The top of the benzene secondary extractive distillation column (top pressure -50 kPa, top temperature 59℃) is returned to the CS2 removal column, while the bottom material enters the benzene secondary extractant regeneration column at a reflux ratio of 2:1. The secondary extractive distillation column is also equipped with a heat recovery device. The extractant or regenerated secondary extractant enters from the top of the benzene extractive distillation column at a solvent ratio of 6:1. The extractant is N-methylpyrrolidone and monoethanolamine in a mass ratio of 1.2:1.
[0107] The top of the benzene secondary extractant regeneration column (top pressure -50kPa, top temperature 80℃) is collected and enters the thiophene refining column with a reflux ratio of 2:1. The bottom material re-enters the benzene secondary extractive distillation column from the top, and the bottom extractant is recycled after heat recovery.
[0108] Thiophene with a purity of 99.7% or higher is collected from the top of the thiophene refining column (top pressure 0 kPa, top temperature 80–110°C) and enters the product tank. (Initially, when the benzene content is high, it directly enters the feed tank of the benzene secondary extractive distillation column; later, the transition components enter the thiophene feed tank; and the thiophene product with a purity of 99.5% or higher enters the thiophene receiving tank. After the thiophene product collection is completed, the top product is collected into the toluene receiving tank, and finally, the material in the toluene receiving tank is pumped back to the crude benzene tank).
[0109] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for producing high-purity benzene from crude benzene, characterized in that, Includes the following steps: A. Crude benzene separation unit: After being preheated by a preheater, the crude benzene feedstock from coking enters the two-benzene tower. The heavy benzene by-product is collected from the bottom of the tower and pumped into the heavy benzene tank, while the benzene collected from the top of the tower enters the primary distillation tower. The top product from the primary distillation column enters the primary fraction storage tank, while the bottom product enters the crude benzene column. The top product from the crude benzene tower enters the benzene refining unit, while the bottom product enters the crude toluene tower. B. Pure Benzene Refining Unit: The crude benzene drawn from the top of the crude benzene tower or the crude benzene storage tank enters the CS2 removal tower. The material drawn from the top of the tower enters the benzene non-aromatic storage tank, and the material from the bottom of the tower enters the benzene non-aromatic removal tower. The top product from the benzene dearomatic distillation column enters either the benzene non-aromatic tank or the crude benzene storage tank, while the bottom product enters the benzene extraction distillation column. The top product from the benzene extractive distillation column enters the pure benzene tank, while the bottom product enters the benzene extractant regeneration column. The extractant enters from the top of the benzene extractive distillation column with a solvent ratio of 4-8:1, and the extractant is N-methylpyrrolidone and diethanolamine in a mass ratio of 1.2-1.7:
1. The material collected from the top of the benzene extractant regeneration tower enters the benzene secondary extractive distillation tower, while the material from the bottom of the tower re-enters the benzene extractive distillation tower from the top. The top product from the benzene secondary extractive distillation column is returned to the CS2 removal column, while the bottom product enters the benzene secondary extractant regeneration column. The material collected from the top of the benzene secondary extractant regeneration tower enters the thiophene refining tower, while the material from the bottom of the tower re-enters the benzene secondary extractive distillation tower from the top.
2. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The pressure at the top of the two benzene tower is -50-60 kPa, and the temperature at the top of the tower is 65-70℃; the preheating temperature of the preheater is 70-95℃.
3. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The pressure at the top of the primary distillation column is 1.5-2.5 kPa, and the temperature at the top of the column is 50-60℃.
4. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The pressure at the top of the crude benzene tower is -55 to 65 kPa, and the temperature at the top of the tower is 50 to 60°C.
5. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The pressure at the top of the CS2 removal tower is -55 to 65 kPa, and the temperature at the top of the tower is 50 to 55℃.
6. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The pressure at the top of the benzene-to-nonaromatic tower is 0 kPa, and the temperature at the top of the tower is 75-80℃.
7. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The benzene extraction distillation column has a top pressure of -45 to 55 kPa and a top temperature of 55 to 60°C.
8. The method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The pressure at the top of the benzene extractant regeneration tower is -45 to 55 kPa, and the temperature at the top of the tower is 60 to 70°C.
9. A method for producing high-purity benzene from crude benzene according to claim 1, characterized in that, The benzene secondary extractive distillation column has a top pressure of -45-55 kPa and a top temperature of 55-60℃; the benzene secondary extractant regeneration column has a top pressure of -45-55 kPa and a top temperature of 78-85℃.
Citation Information
Patent Citations
Abstraction distillation system special for carbonization benezene or sulfureous containing benezene, and fine purification method
CN101270026A
DD106816A1