A purification apparatus and method for 1,2-dichloropropane byproduct from a chloropropene plant.

Abstract

The application discloses a 3-chloropropylene device by-product 1,2-dichloropropane refining device and method, in particular, the 3-chloropropylene device by-product 1,2-dichloropropane purity reaches >=99.9% by using the extraction rectification technology, residual dichloropropylene is <100ppm, the economic value of the product is improved, the extraction rectification technology plays the role of energy saving and consumption reduction, and has wide industrialization application prospect.

Description

Technical Field

[0001] This invention belongs to the field of chemical by-product purification technology, specifically relating to a purification apparatus and method for 1,2-dichloropropane by-product from a 3-chloropropene plant. In particular, extractive distillation technology is used to achieve a purity of ≥99.9% for the 1,2-dichloropropane by-product from the 3-chloropropene plant, with residual dichloropropene <100ppm. Background Technology

[0002] 1,2-Dichloropropane is an excellent organic solvent and chemical intermediate. It can be used to formulate paints, inks, thinners, and PVC adhesives. It can replace xylene and other benzene compounds in the production of benzene-free banana oil, thinner, and polyurethane thinners. It is also a major raw material for pesticide emulsifiers, lubricants, flame retardants, plasticizers, oilfield demulsifiers, detergents, and nonionic surfactants. Dichloropropane is also an important raw material for cosmetics and pharmaceuticals. Industrially, it can also be used as a raw material for the production of tetrachloropropene. However, when using 1,2-dichloropropane as a raw material for the production of tetrachloropropene, the dichloropropene content must be below 100 ppm.

[0003] The high-temperature 3-chloropropene process produces a large amount of DD mixture (a mixture of dichloropropane and dichloropropene) as a byproduct. Its main components are 1,2-dichloropropane, cis-1,3-dichloropropene, trans-1,3-dichloropropene, 2,3-dichloropropene, and 3,3-dichloropropene. After separating 1,3-dichloropropene from the DD mixture, it becomes crude 1,2-dichloropropane, whose main components are 1,2-dichloropropane (75-85%, wt%), 1-chloropropane (1-3%), 1-chloropropene (2-4%), 2-chloropropene (1-3%), 1,5-hexadiene (2-4%), cis-1,3-dichloropropene (4-6%), 2,3-dichloropropene (2-8%), and 3,3-dichloropropene (4-6%). As a raw material for the production of tetrachloropropene, the dichloropropene content of 1,2-dichloropropane must be below 100 ppm. Practice has shown that 3,3-dichloropropene, 2,3-dichloropropene and 1,2-dichloropropane have very low relative volatility, making them difficult to separate by ordinary distillation and requiring high energy consumption.

[0004] Therefore, there is a need to develop a more economical, energy-efficient, and environmentally friendly process for separating 1,2-dichloropropane. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention utilizes extractive distillation technology to design an economical, environmentally friendly, and more energy-efficient device and method that can achieve efficient separation of 1,2-dichloropropane, obtaining a high-purity product with a dichloropropene content of <100ppm and 1,2-dichloropropane ≥99.9%, saving energy consumption and improving the application value of the product.

[0006] One of the objectives of this invention is to provide a purification apparatus for 1,2-dichloropropane byproduct of a 3-chloropropene plant.

[0007] The second objective of this invention is to provide a purification method for 1,2-dichloropropane, a byproduct of a 3-chloropropene plant.

[0008] According to one aspect of the present invention, a purification apparatus for 1,2-dichloropropane byproduct of a 3-chloropropene plant is provided, comprising a light-light-removal column, an extractive distillation column, and an extractant recovery column.

[0009] The light component removal tower is provided with a discharge port at the top for removing light components, a feed port in the middle of the tower body for receiving raw materials, and a liquid outlet at the bottom of the tower for discharging liquid substances.

[0010] The extractive distillation column is located downstream of the light-light product removal column. The top of the extractive distillation column is provided with a discharge port for discharging the final purified 1,2-dichloropropane. The upper part of the column is provided with an extractant inlet for injecting extractant into the extractive distillation column. The middle part of the column is provided with a feed inlet, which is connected to the liquid outlet of the light-light product removal column through a pipeline for receiving material from the light-light product removal column. The bottom of the column is provided with a liquid outlet for discharging liquid substances.

[0011] The extractant recovery tower is located downstream of the extractive distillation tower. The top of the extractant recovery tower has a discharge port for discharging the heavy components extracted by distillation. The middle of the tower has a feed port connected to the liquid outlet of the extractive distillation tower via a pipeline for receiving material from the extractive distillation tower. The bottom of the tower has a liquid outlet for discharging the separated extractant. This liquid outlet is connected to the extractant feed port of the extractive distillation tower via a pipeline for transporting the separated and recovered extractant back into the extractive distillation tower.

[0012] Preferably, the light-weight removal tower is a packed tower, and the tower is equipped with packing support, liquid distributor, redistributor and demister.

[0013] Preferably, the extractive distillation column is a packed column, and the column is equipped with packing support, liquid distributor, redistributor and demister.

[0014] Preferably, the extractant recovery tower is a packed tower, and the tower is equipped with packing support, liquid distributor, redistributor and demister.

[0015] Preferably, a condenser is further provided at the discharge port at the top of the light component removal tower. The light components discharged through the discharge port are condensed by the condenser, and part of them are returned to the light component removal tower to maintain the material balance in the tower, while the rest are discharged out of the system.

[0016] Preferably, a reboiler is further provided at the liquid outlet at the bottom of the light-weight removal tower. The liquid substance discharged through the liquid outlet is further vaporized by the reboiler and part of it is returned to the light-weight removal tower to maintain the material balance in the tower. The rest is transported to the extractive distillation tower through a pipeline.

[0017] Preferably, a vaporizer is further installed on the pipeline connecting the liquid outlet at the bottom of the light-removal column and the extractive distillation column to further vaporize the liquid substance to achieve the temperature and state required by the extractive distillation column.

[0018] Preferably, the outlet at the top of the extractive distillation column is further equipped with a condenser. The final product, purified 1,2-dichloropropane, discharged through the outlet is partially refluxed back to the extractive distillation column after being condensed by the condenser to maintain the material balance within the extractive distillation column, while the remainder is discharged through a pipeline.

[0019] Preferably, a reboiler is further provided at the liquid outlet at the bottom of the extractive distillation column. The liquid substance discharged through the liquid outlet is further vaporized by the reboiler and part of it is returned to the extractive distillation column to maintain the material balance in the column. The remainder is transported to the extractant recovery column through a pipeline.

[0020] Preferably, a condenser is further provided at the outlet of the extractant recovery tower. The heavy components discharged from the extractive distillation through the outlet are condensed by the condenser and partially returned to the extractant recovery tower to maintain the material balance in the extractant recovery tower. The remainder is discharged through a pipeline.

[0021] Preferably, a reboiler is further provided at the liquid outlet at the bottom of the extractant recovery tower. The liquid substance discharged through the liquid outlet is further vaporized by the reboiler and part of it is returned to the extractant recovery tower to maintain the material balance in the tower. The rest is transported to the extractive distillation tower through a pipeline.

[0022] According to another aspect of the present invention, a method for purifying 1,2-dichloropropane, a byproduct of a 3-chloropropene plant, is provided, the method comprising:

[0023] 1) The crude 1,2-dichloropropane byproduct of the 3-chloropropene unit is fed into the light component removal tower. Water, 1-chloropropane, 1-chloropropene, 2-chloropropene and 1,5-hexadiene and other light components are removed from the top of the tower. The bottom material of the light component removal tower is transported through pipeline to the extractive distillation tower.

[0024] 2) The extractant is fed from the extractant inlet in the upper section of the extractive distillation column. The extractive distillation column is operated under reduced pressure. The top product is 1,2-dichloropropane, and the bottom products 3,3-dichloropropene, cis-1,3-dichloropropene, and 2,3-dichloropropene, together with the extractant, enter the extractant recovery column.

[0025] 3) The extractant recovery tower is operated under reduced pressure. The top product of the tower is a mixture of 3,3-dichloropropene, cis-1,3-dichloropropene and 2,3-dichloropropene, and the bottom product of the tower is the extractant, which is recycled to the extractive distillation tower.

[0026] Preferably, by weight percentage, the crude 1,2-dichloropropane contains 75-85% 1,2-dichloropropane, 1-3% 1-chloropropane, 2-4% trans-1-chloropropene, 1-3% 2-chloropropene, 2-4% 1,5-hexadiene, 4-6% cis-1,3-dichloropropene, 2-8% 2,3-dichloropropene, 4-6% 1,1-dichloropropene, and 4-6% 3,3-dichloropropene, etc.

[0027] Preferably, the theoretical plate number of the light-light removal tower T101 in step 1) is 50-80, the tower top pressure is 95-105 kPaA, and the operating reflux ratio is 3-8.

[0028] Preferably, a condenser is installed at the top of the light-weight removal tower in step 1), and its condensation temperature is 30-40°C.

[0029] Preferably, a vaporizer is installed on the pipeline connecting the light-weight removal tower and the extractive distillation tower, with a vaporization pressure of 125-135 kPaA and a vaporization temperature of 30-40°C.

[0030] Preferably, the extractive distillation column has 50-70 theoretical plates, operates under reduced pressure, has a top pressure of 10-30 kPaA, a top condensation temperature of 40-60°C, an operating reflux ratio of 0.3-1, and a mass ratio of extractant to feed of 3-10.

[0031] Preferably, the extractant recovery tower has a theoretical plate number of 45–75, a top temperature of 25–40°C, a top pressure of 5–20 kPaA, and an operating reflux ratio of 15–30.

[0032] Preferably, the feed inlet of the light component removal column is located at theoretical plates 30-50. The feed inlet of the extractive distillation column is located at theoretical plates 40-60, and the extractant inlet is located at theoretical plates 5-10. The feed inlet of the extractant recovery column is located at theoretical plates 38-62.

[0033] Preferably, the light component removal tower is a packed tower, and the packing material is small metal Baur ring packing, metal corrugated packing, or metal wire mesh corrugated packing, preferably metal wire mesh corrugated packing. The extractive distillation tower is a packed tower, and the packing material is metal corrugated packing, metal wire mesh corrugated packing, or metal perforated plate corrugated packing, preferably metal perforated plate corrugated packing. The extractant recovery tower is a packed tower, and the packing material is metal corrugated packing or metal wire mesh corrugated packing, preferably metal wire mesh corrugated packing.

[0034] Preferably, the extractant is one or more of N,N-dimethylformamide, N-methylpyrrolidone, ethylene glycol, n-octanol, phenol, N-formylmorpholine, and sulfolane.

[0035] Beneficial effects

[0036] The apparatus according to the present invention utilizes a combination of a light-light-removal tower, an extractive distillation tower, and an extractant recovery tower, and accurately designs operating parameters, especially the selection and dosage of the extractant, to ensure that the purity of 1,2-dichloropropane by-product from the 3-chloropropene unit is ≥99.9% and the residual dichloropropene is <100ppm, thereby improving the economic value of the product. The extractive distillation technology plays a role in energy saving and consumption reduction, and has broad prospects for industrial application. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the refining apparatus according to the present invention.

[0039] T101 is the light component removal tower, T102 is the extractive distillation tower, and T103 is the extractant recovery tower; E101, E103, and E105 are the top condensers of each tower, E102, E104, and E106 are the bottom reboilers of each tower, E201 is the vaporizer, and S1, S2, S3, S4, S5, and S6 are the material numbers. Detailed Implementation

[0040] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0041] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0042] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0043] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0044] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0045] To clarify the invention, parts irrelevant to the description have been omitted from the drawings, and throughout the specification, the same or similar parts are indicated by the same reference numerals.

[0046] Furthermore, for ease of explanation, the dimensions and thicknesses of each component shown in the accompanying drawings are arbitrarily illustrated; therefore, the invention is not necessarily limited to those shown in the drawings.

[0047] Throughout the specification, when it is said that an element is "connected" to another element, it includes not only "direct connection" but also "indirect connection" between other components. Furthermore, when it is said that an element "comprises" a part, it means that the element may further include other parts rather than exclude them, unless otherwise explicitly stated.

[0048] The terms “first,” “second,” etc., used in this article are used to explain various constituent elements, and they are only used for the purpose of distinguishing one constituent element from another.

[0049] Furthermore, the terminology used herein is for the purpose of explaining exemplary embodiments only and is not intended to limit the invention. Singular expressions also include their plural expressions unless otherwise expressly indicated in the context. Terms such as “comprising,” “equipped with,” or “having” as used herein are used to specify the presence of a practical characteristic, number, step, constituent element, or combination thereof, and should be understood to not exclude the possibility of the addition or presence of one or more other characteristics, numbers, steps, constituent elements, or combinations thereof.

[0050] Furthermore, if a layer or element is referred to as being formed "above" or "on top of" a "layer" or "element", it means that each layer or element is formed directly on that layer or element, or that other layers or elements may be formed between layers, bodies, or substrates.

[0051] The following is in conjunction with the appendix Figure 1 This invention provides a detailed description of a purification apparatus for 1,2-dichloropropane byproduct from a 3-chloropropene plant and its process method.

[0052] like Figure 1 As shown, the purification unit for 1,2-dichloropropane byproduct of a 3-chloropropene plant according to the present invention includes a light-removal tower T101, an extractive distillation tower T102, and an extractant recovery tower T103.

[0053] The light component removal tower T101 is provided with a discharge port at the top for removing light components, a feed port in the middle of the tower for receiving raw materials, and a liquid outlet at the bottom for discharging liquid substances. Preferably, the light component removal tower T101 is a packed tower, and is equipped with packing supports, a liquid distributor, a redistributor, and a demister, etc.

[0054] Preferably, a condenser E101 is further provided at the discharge port at the top of the light component removal tower T101. The light component discharged through the discharge port is condensed by the condenser E101 and part of it is returned to the light component removal tower T101 to maintain the material balance in the tower, while the rest is discharged out of the system.

[0055] Preferably, a reboiler E102 is further provided at the liquid outlet at the bottom of the light-light-removal tower T101. The liquid substance discharged through the liquid outlet is further vaporized by the reboiler E102 and part of it is returned to the light-light-removal tower T101 to maintain the material balance in the tower. The rest is transported to the extractive distillation tower T102 through pipeline.

[0056] The light-weight removal tower T101 is filled with packing material, which is selected from small metal Baur ring packing, metal corrugated packing, and metal wire mesh corrugated packing, preferably metal wire mesh corrugated packing.

[0057] The extractive distillation column T102 is located downstream of the light-light product removal column T101. The extractive distillation column T102 has a discharge port at the top for discharging the purified 1,2-dichloropropane as the final product. The upper part of the column has an extractant inlet for injecting extractant into the extractive distillation column T102. The middle part of the column has an inlet connected to the liquid outlet of the light-light product removal column T101 via a pipeline for receiving material from the light-light product removal column T101. The bottom of the column has a liquid outlet for discharging liquid substances.

[0058] Preferably, the outlet at the top of the extractive distillation column T102 is further equipped with a condenser E103. The final product purified 1,2-dichloropropane discharged through the outlet is partially refluxed back to the extractive distillation column T102 after being condensed by the condenser E103 to maintain the material balance in the extractive distillation column T102, and the remainder is discharged through a pipeline.

[0059] Preferably, a reboiler E104 is further provided at the liquid outlet at the bottom of the extractive distillation column T102. The liquid substance discharged through the liquid outlet is further vaporized by the reboiler E104, and part of it is returned to the extractive distillation column T102 to maintain the material balance in the column. The rest is transported to the extractant recovery column T103 through pipeline.

[0060] Preferably, the extractive distillation column T102 is filled with packing material, and the column is equipped with packing support, liquid distributor, redistributor and demister.

[0061] The extractant recovery tower T103 is located downstream of the extractive distillation tower T102. The top of the extractant recovery tower T103 has a discharge port for discharging the heavy components extracted and distilled. The middle of the tower has a feed port, which is connected to the liquid outlet of the extractive distillation tower T102 via a pipeline to receive material from the extractive distillation tower T102. The bottom of the tower has a liquid outlet for discharging the separated extractant. This liquid outlet is connected to the extractant feed port of the extractive distillation tower T102 via a pipeline to transport the separated and recovered extractant back into the extractive distillation tower T102.

[0062] Preferably, a condenser E105 is further provided at the outlet of the extractant recovery tower T103. The heavy components discharged from the extractant distillation through the outlet are condensed by the condenser E105 and partially flowed back to the extractant recovery tower T103 to maintain the material balance in the extractant recovery tower T103. The remainder is discharged through a pipeline.

[0063] Preferably, a reboiler E106 is further provided at the liquid outlet at the bottom of the extractant recovery tower T103. The liquid substance discharged through the liquid outlet is further cooled by the reboiler E106 and part of it is returned to the extractant recovery tower T103 to maintain the material balance in the tower. The rest is transported to the extractive distillation tower T102 through pipeline.

[0064] Preferably, the extractant recovery tower T103 is filled with packing material, and the tower is equipped with packing support, liquid distributor, redistributor and demister.

[0065] The process steps for refining 1,2-dichloropropane, a byproduct of the 3-chloropropene unit, using the refining apparatus according to the present invention are as follows: The crude 1,2-dichloropropane byproduct from the 3-chloropropene unit is first fed into a light-light-removal distillation column T101. The light-light-removal distillation column T101 has 50-80 theoretical plates, and the feed position is located at theoretical plates 30-50. The condenser at the top of the column has a condensation temperature of 30-40°C and a pressure of 95-105 kPaA; the operating reflux ratio is 3-8. After the vapor phase at the top of the light-light-removal distillation column T101 is condensed by condenser E101, a portion is refluxed back into the light-light-removal distillation column T101. The other portion (S1), consisting of water, 1-chloropropane, trans-1-chloropropene, 2-chloropropene, and a small amount of azeotropic 1,2-dichloropropane, is discharged from the system. The bottom product (S2) is transported to the extractive distillation column T102 via pipeline. In a preferred embodiment, the bottom product contains 83 wt% DCP (1,2-dichloropropane). In a preferred embodiment, a vaporizer E201 is further provided on the pipeline connecting the liquid outlet at the bottom of the light removal column T101 to the extractive distillation column T102 for further vaporizing the liquid substance to achieve the temperature and state required by the extractive distillation column T102.

[0066] Extractive distillation column T102 receives the material and extractant from the light-weight distillation column T101 for extraction. The extractive distillation column T102 has 50-70 theoretical plates, with the feed inlet located on theoretical plates 40-60 and the extractant inlet located on theoretical plates 5-10. Distillation is performed under reduced pressure, with a top pressure of 10-30 kPaA and a top condensation temperature of 40-60°C. The operating reflux ratio is 0.3-1, and the extractant-to-feed mass ratio is 3-10. The vapor phase at the top of extractive distillation column T102 is condensed by condenser E103, with a portion refluxed and the remainder cooled and discharged. The effluent is ≥99.9% 1,2-dichloropropane (S3). The bottom material of the column is 3,3-dichloropropene, cis-1,3-dichloropropene and 2,3-dichloropropene with extractant. Part of it is returned to the extractive distillation column T102 to maintain the reaction balance in the column, and the rest (S4) is vaporized by the vaporizer E201 and then enters the extractant recovery column T103.

[0067] The extractant recovery tower T103 is a packed tower, with packing materials including corrugated metal packing, wire mesh corrugated metal packing, and perforated metal packing, preferably perforated metal packing. The theoretical plate number is 45–75, and the feed position is located at the 38th–62nd theoretical plate. The tower top temperature is 25–40℃, and the pressure is 5–20 kPaA; the operating reflux ratio is 15–30. The extractant is fed from the upper half of the tower. After the top material is condensed by condenser E105, a portion is refluxed, and the other output (S5) consists of 3,3-dichloropropene, cis-1,3-dichloropropene, and 2,3-dichloropropene. The bottom output is the extractant, a portion of which is returned to the extractant recovery tower T103, and the remainder (S6) is returned to the extractive distillation tower T102 for recycling.

[0068] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0069] Example 1

[0070] like Figure 1 As shown, the process steps for producing 1,2-dichloropropane as a byproduct of an extractive distillation unit for refining 3-chloropropene are as follows:

[0071] The 3-chloropropene unit produces 1255 kg / h of crude 1,2-dichloropropane as a byproduct. Its composition is 1,2-dichloropropane (80%, wt%), 1-chloropropane (1%), 1-chloropropene (2%), 2-chloropropene (1.5%), 1,5-hexadiene (2.1%), cis-1,3-dichloropropene (5%), 2,3-dichloropropene (3%), 3,3-dichloropropene (5%), and water (0.4%). This product enters the light-light distillation column T101. Column T101 is packed with corrugated metal wire mesh packing with 60 theoretical plates. The feed is located at the 40th theoretical plate. The top condenser operates at a condensation temperature of 36°C and a pressure of 100 kPaA. The operating reflux ratio is 5:1.

[0072] The vapor phase from the top of the light component removal distillation column T101 is condensed in condenser E101, with a portion being refluxed and the remainder discharged. This process removes light components such as water, 1-chloropropane, 1-chloropropene, 2-chloropropene, and 1,5-hexadiene. The 1,2-dichloropropane loss at the top of the column is 20 kg / h. The bottom product is transported to the extractive distillation column T102 via vaporizer E201, which has a heat load of 92 kW.

[0073] The extractive distillation column T102 is packed with perforated metal corrugated packing, with 60 theoretical plates. The feed is located on the 50th theoretical plate, and the extractant is ethylene glycol at a mass ratio of 6.8 (extractant to feed), located on the 8th theoretical plate. Vacuum distillation is performed at a top pressure of 20 kPaA and a top condensation temperature of 48°C; the operating reflux ratio is 0.2. In T102, the vapor phase at the top is condensed in a condenser, with a portion refluxed and a portion discharged. The top discharge is 1,2-dichloropropane with a purity of 99.99%. The bottom product is a mixture of 3,3-dichloropropene, cis-1,3-dichloropropene, 2,3-dichloropropene, ethylene glycol, and a small amount of 1,2-dichloropropane, which is piped into the extractant recovery column T103.

[0074] The extractant recovery tower T103 is packed with corrugated metal perforated plate packing, with a theoretical plate count of 60. The feed position is located at the 45th theoretical plate. The top temperature is 30°C, the pressure is 10 kPaA, and the operating reflux ratio is 20. After the top material is condensed in the condenser, part of it is refluxed and part is discharged. The discharge is a mixture of 3,3-dichloropropene, cis-1,3-dichloropropene, 2,3-dichloropropene, and a small amount of 1,2-dichloropropane. The bottom discharge is ethylene glycol with a purity of 99.99%, which is returned to the extractive distillation tower T102 for recycling. The lost ethylene glycol is replenished with fresh ethylene glycol.

[0075] The apparatus and method of this invention can achieve the purification and extraction of 1,2-dichloropropane with a purity of 99.99%, which is extremely beneficial for subsequent utilization.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A refining method for 1,2-dichloropropane by-produced from a 3-chloropropene plant, the method comprising: 1) feeding the 3-chloropropene plant by-produced 1,2-dichloropropane crude into a light-removing column, removing water, 1-chloropropane, 1-chloropropene, 2-chloropropene and 1,5-hexadiene light components from the top of the column, and feeding the light-removing column bottom material into an extractive distillation column through a pipeline; 2) feeding an extractant into the extractive distillation column from an extractant feed port in the upper half of the column, operating the extractive distillation column under reduced pressure, and discharging 1,2-dichloropropane from the top of the column, and discharging 3,3-dichloropropene, cis-1,3-dichloropropene and 2,3-dichloropropene and the extractant from the bottom of the column into an extractant recovery column; 3) operating the extractant recovery column under reduced pressure, discharging a mixture of 3,3-dichloropropene, cis-1,3-dichloropropene and 2,3-dichloropropene from the top of the column, and discharging the extractant from the bottom of the column to be recycled to the extractive distillation column; the 1,2-dichloropropane crude contains 75-85% of 1,2-dichloropropane, 1-3% of 1-chloropropane, 2-4% of trans-1-chloropropene, 1-3% of 2-chloropropene, 2-4% of 1,5-hexadiene, 4-6% of cis-1,3-dichloropropene, 2-8% of 2,3-dichloropropene, 4-6% of 1,1-dichloropropene, and 4-6% of 3,3-dichloropropene, the percentages of the components being weight percentages, and the sum of the weight percentages of the components being 100%; the extractant is one or more of N,N-dimethylformamide, N-methylpyrrolidone, ethylene glycol, n-octanol, phenol, N-formylmorpholine and sulfolane.

2. The refining method according to claim 1, characterized by, the light-removing column T101 in step 1) has a theoretical plate number of 50-80, a top pressure of 95-105 kPaA, and an operating reflux ratio of 3-8.

3. The refining method according to claim 1, characterized by, A condenser is arranged at the top of the light-removing column in step 1), and has a condensing temperature of 30-40℃.

4. The refining method according to claim 1, characterized by, A vaporizer is arranged in a pipeline connecting the light-removing column and the extractive distillation column, and has a vaporizing pressure of 125-135 kPaA and a vaporizing temperature of 30-40℃.

5. The method of claim 1, wherein the refining is performed by a method comprising: The extractive distillation column has a theoretical plate number of 50-70, is operated under reduced pressure, has a top pressure of 10-30 kPaA, a top condensing temperature of 40-60℃, an operating reflux ratio of 0.3-1, and a mass ratio of extractant to feed of 3-10.

6. The method of claim 1, wherein The extractant recovery column has a theoretical plate number of 45-75, a top temperature of 25-40℃, a top pressure of 5-20 kPaA, and an operating reflux ratio of 15-30.

7. The method of claim 1, wherein the refining is performed by a method comprising: The light-removing column has a feed port at the 30th-50th theoretical plate, the extractive distillation column has a feed port for the raw material at the 40th-60th theoretical plate and a feed port for the extractant at the 5th-10th theoretical plate, and the extractant recovery column has a feed port at the 38th-62nd theoretical plate.

8. The method of claim 1, wherein the refining is performed by a method comprising: The light-removing column is a packed column, and the packing is small-sized metal Bourdon ring packing, metal corrugated packing or metal wire mesh corrugated packing; the extractive distillation column is a packed column, and the packing is metal corrugated packing, metal wire mesh corrugated packing or metal hole plate corrugated packing; and the extractant recovery column is a packed column, and the packing is metal corrugated packing or metal wire mesh corrugated packing.

9. The method of claim 8, wherein the refining is performed by a method comprising: The light-removing tower is a packed tower, and the packing is wire mesh ripple packing; the extractive rectification tower is a packed tower, and the packing is metal hole plate ripple packing; the extractant recovery tower is a packed tower, and the packing is wire mesh ripple packing.

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