Device and method for refining by-product 1, 2-dichloropropane of chloropropene device

Abstract

The invention discloses a device and a method for refining 1, 2-dichloropropane as a byproduct of a 3-chloropropene device, and particularly relates to a method for refining 1, 2-dichloropropane as a byproduct of the 3-chloropropene device by utilizing an extractive distillation technology, so that the purity of the 1, 2-dichloropropane as the byproduct of the 3-chloropropene device is greater than or equal to 99.9%, and the residue of dichloropropene is 1t; and the economic value of the product is improved, the extractive distillation technology has the effects of saving energy and reducing consumption, and the method has a wide industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of purification of chemical by-products, and specifically relates to a device and method for refining 1,2-dichloropropane produced as a by-product of a 3-chloropropylene device, and in particular, the extraction and distillation technology is used to make the purity of the 1,2-dichloropropane produced as a by-product of the 3-chloropropylene device reach ≥99.9%, and the residual dichloropropylene is less than 100 ppm. Background Art

[0002] 1,2-Dichloropropane is an excellent organic solvent and chemical intermediate. It can be used to prepare paints, inks, diluents and PVC adhesives. It can replace xylene and other benzenes to make benzene-free banana water, thinner, polyurethane diluents, etc. It is also the main raw material for pesticide emulsifiers, lubricants, flame retardants, plasticizers, oilfield demulsifiers, detergents, non-ionic surfactants, etc. At the same time, dichloropropane is also an important raw material for fine chemical products such as cosmetics and medicines. It can also be used as a raw material for the production of tetrachloropropene in industry. However, the use of 1,2-dichloropropane as a raw material for the production of tetrachloropropene requires that the dichloropropene content must be below 100ppm.

[0003] The high-temperature 3-chloropropene unit produces a large amount of DD mixture (mixture of dichloropropane and dichloropropene), the main components of which are 1,2-dichloropropane, cis-1,3-dichloropropene, trans-1,3-dichloropropene, 2,3-dichloropropene and 3,3-dichloropropene. After 1,3-dichloropropene is separated from the DD mixture, it becomes crude 1,2-dichloropropane, the main components of which are 1,2-dichloropropane (75-85%, wt%, the same below), 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%), 3,3-dichloropropene (4-6%), etc. 1,2-dichloropropane is used as a raw material for the production of tetrachloropropene, and the dichloropropene content must be below 100ppm. Practice has shown that the relative volatility of 3,3-dichloropropene, 2,3-dichloropropene and 1,2-dichloropropane is very small, and it is difficult and energy-intensive to separate them using ordinary distillation.

[0004] Therefore, it is necessary to develop a more economical, energy-saving and environmentally friendly process for separating 1,2-dichloropropane. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention designs an economical, environmentally friendly and more energy-saving device and method using extractive distillation technology, which can achieve efficient separation of 1,2-dichloropropane and obtain a high-purity product with a dichloropropylene content of <100ppm and 1,2-dichloropropane ≥99.9%, thereby saving energy consumption and improving the application value of the product.

[0006] One of the purposes of the present invention is to provide a purification device for 1,2-dichloropropane produced as a by-product of a 3-chloropropene device.

[0007] The second object of the present invention is to provide a method for refining 1,2-dichloropropane which is a by-product of a 3-chloropropylene unit.

[0008] According to one aspect of the present invention, the present invention provides a refining device for 1,2-dichloropropane produced as a by-product of a 3-chloropropylene unit, comprising a lightness removal tower, an extractive distillation tower and an extractant recovery tower.

[0009] The light-removal tower has 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.

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

[0011] The extractant recovery tower is located downstream of the extractive distillation tower. The extractant recovery tower is provided with a discharge port at the top for discharging the heavy components obtained by the extractive distillation. A feed port is provided in the middle of the tower body. The feed port is connected to the liquid outlet of the extractive distillation tower through a pipeline for receiving materials from the extractive distillation tower. A liquid outlet is provided at the bottom of the tower for discharging the separated extractant. The liquid outlet is connected to the extractant feed port of the extractive distillation tower through a pipeline for transporting the separated and recovered extractant back to the extractive distillation tower.

[0012] Preferably, the light-removal tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

[0013] Preferably, the extractive distillation tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

[0014] Preferably, the extractant recovery tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

[0015] Preferably, a condenser is further provided at the discharge port at the top of the light-removal tower, and the light components discharged through the discharge port are condensed by the condenser and partially refluxed to the light-removal tower to maintain the material balance in the tower, and the rest is discharged out of the system.

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

[0017] Preferably, a vaporizer is further arranged on the pipeline connecting the liquid outlet at the bottom of the light removal tower and the extractive distillation tower, for further vaporizing the liquid substance to reach the temperature and state required by the extractive distillation tower.

[0018] Preferably, a condenser is further provided at the discharge port arranged at the top of the extractive distillation tower, and the final product purified 1,2-dichloropropane discharged through the discharge port is partially refluxed to the extractive distillation tower after being condensed by the condenser to maintain the material balance in the extractive distillation tower, and the rest is discharged through a pipeline.

[0019] Preferably, a reboiler is further provided at the liquid outlet at the bottom of the extractive distillation tower, and the liquid substance discharged through the liquid outlet is further vaporized by the reboiler and partially refluxed to the extractive distillation tower to maintain the material balance in the tower, and the rest is transported to the extractant recovery tower through a pipeline.

[0020] Preferably, a condenser is further provided at the discharge port at the top of the extractant recovery tower, and the heavy components discharged from the extraction distillation through the discharge port are partially refluxed to the extractant recovery tower after condensation by the condenser to maintain the material balance in the extractant recovery tower, and the rest is discharged through a pipeline.

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

[0022] According to another aspect of the present invention, the present invention provides a method for refining 1,2-dichloropropane produced as a by-product of a 3-chloropropylene unit, the method comprising:

[0023] 1) The crude 1,2-dichloropropane by-product of the 3-chloropropene unit is transported to a light-removal tower, and light components such as water, 1-chloropropane, 1-chloropropene, 2-chloropropene and 1,5-hexadiene are removed from the top of the tower. The bottom material of the light-removal tower is transported to an extractive distillation tower through a pipeline.

[0024] 2) The extractant is fed from the extractant feed port of the upper half of the extractive distillation tower, the extractive distillation tower is operated under reduced pressure, the top discharge is 1,2-dichloropropane, and the bottom discharges 3,3-dichloropropylene, cis-1,3-dichloropropylene, 2,3-dichloropropylene and the extractant enter the extractant recovery tower.

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

[0026] Preferably, the crude 1,2-dichloropropane contains, by weight percentage, 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, 4-6% of 3,3-dichloropropene, etc.

[0027] Preferably, the lightness removal tower T101 in step 1) has a theoretical plate number of 50 to 80, a tower top pressure of 95 to 105 kPaA, and an operating reflux ratio of 3 to 8.

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

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

[0030] Preferably, the extractive distillation tower has a theoretical plate number of 50 to 70, vacuum distillation, a top pressure of 10 to 30 kPaA, a top condensation temperature of 40 to 60° C., an operating reflux ratio of 0.3 to 1, and a mass ratio of the extractant to the feed of 3 to 10.

[0031] Preferably, the number of theoretical plates of the extractant recovery tower is 45-75, the tower top temperature is 25-40° C., the tower top pressure is 5-20 kPaA; and the operating reflux ratio is 15-30.

[0032] Preferably, the feed inlet position of the lightness removal tower is at the 30th to 50th theoretical plate. The feed position of the raw material of the extractive distillation tower is at the 40th to 60th theoretical plate, the feed position of the extractant is at the 5th to 10th theoretical plate. The feed position of the extractant recovery tower is at the 38th to 62nd theoretical plate.

[0033] Preferably, the lightness removal tower is a packed tower, and the packing is a small metal Bauer ring packing, a metal corrugated packing, a metal wire mesh corrugated packing, preferably a metal wire mesh corrugated packing. The extractive distillation tower is a packed tower, and the packing is a metal corrugated packing, a metal wire mesh corrugated packing, a metal perforated plate corrugated packing, preferably a metal perforated plate corrugated packing. The extractant recovery tower is a packed tower, and the packing is a metal corrugated packing, a metal wire mesh corrugated packing, preferably a 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 device according to the present invention utilizes a combination of a lightness removal tower, an extractive distillation tower and an extractant recovery tower, and accurately designs operating parameters, especially the selection and dosage of the extractant, so that the purity of the by-product 1,2-dichloropropane of the 3-chloropropene device 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 a wide prospect for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 It is a schematic diagram of the structure of the refining device according to the present invention.

[0039] Among them, T101 is a lightness removal tower, T102 is an extractive distillation tower, T103 is an extractant recovery tower; E101, E103, E105 are top condensers of each tower, E102, E104, E106 are bottom material reboilers of each tower, E201 is a vaporizer, and S1, S2, S3, S4, S5 and S6 are material numbers respectively. DETAILED DESCRIPTION

[0040] Hereinafter, the present invention will be described in detail. Before describing, it should be understood that the terms used in this specification and the appended claims should not be interpreted as being limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that the inventor is allowed to appropriately define the terms for the best interpretation. Therefore, the descriptions presented here are only preferred examples for illustrative purposes and are not intended to limit the scope of the present invention, so that it should be understood that other equivalents or improvements can be obtained therefrom without departing from the spirit and scope of the present invention.

[0041] In this document, the terms "include", "including", "have", "contain" or any other similar terms are open conjunctions, which are intended to cover non-exclusive inclusions. For example, a composition or product containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or product. In addition, unless otherwise explicitly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following situations satisfies the condition "A or B": 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), and A and B are both true (or exist). In addition, in this document, the interpretation of the terms "include", "including", "have", and "contain" should be considered to have been specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as "consisting of" and "consisting essentially of".

[0042] In this article, all features or conditions defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible secondary ranges and individual values ​​within the range, especially integer values. For example, the range description of "1 to 8" should be deemed to have specifically disclosed all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., especially secondary ranges defined by all integer values, and should be deemed to have specifically disclosed individual values ​​such as 1, 2, 3, 4, 5, 6, 7, 8, etc. within the range. Unless otherwise specified, the above interpretation method applies to all contents of the entire present invention, regardless of whether the range is broad or not.

[0043] If the 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 all ranges consisting of any upper limit or preferred value of the range and the lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, if a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0044] In this document, under the premise of achieving the purpose of the invention, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0045] In order to clarify the present invention, parts irrelevant to the description are omitted in the drawings, and the same or similar components are denoted by the same reference numerals throughout the specification.

[0046] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

[0047] Throughout the specification, when it is mentioned that a certain element is “connected” to another element, it includes not only “direct connection” but also “indirect connection” between other components. In addition, when it is mentioned that a certain element “includes” a certain component, it means that the element may further include other components rather than excluding other components, unless explicitly described to the contrary.

[0048] The terms “first”, “second” and the like used herein are used to explain various constituent elements, and they are used merely for the purpose of distinguishing one constituent element from another constituent element.

[0049] Furthermore, the terms used herein are only used to explain exemplary embodiments and are not intended to limit the present invention. Singular expressions also include plural expressions thereof, unless otherwise clearly indicated in the context. Terms such as "comprising", "equipped with" or "having" used herein are used to specify the existence of practical characteristics, numbers, steps, constituent elements or combinations thereof, and should be understood as not excluding the possibility of adding or existing one or more other characteristics, numbers, steps, constituent elements or combinations thereof.

[0050] Also, if a layer or an element is referred to as being formed “on” or “over” a “layer” or “element,” this means that each layer or element is formed directly on the layer or element, or other layers or elements may be formed between layers, bodies, or substrates.

[0051] The following is combined with Figure 1 , a device and a process method for refining 1,2-dichloropropane as a by-product of a 3-chloropropylene device are described in detail.

[0052] like Figure 1 As shown, the refining device for 1,2-dichloropropane produced as a by-product of a 3-chloropropylene unit according to the present invention includes a lightness removal tower T101, an extractive distillation tower T102 and an extractant recovery tower T103.

[0053] The light-removal tower T101 has 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-removal tower T101 is a packed tower, and a packing support, a liquid distributor, a redistributor, a demister, etc. are arranged in the tower.

[0054] Preferably, a condenser E101 is further provided at the discharge port at the top of the light-removal tower T101, and the light components discharged through the discharge port are condensed by the condenser E101 and partially refluxed to the light-removal tower T101 to maintain the material balance in the tower, and 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-removal tower T101, and the liquid substance discharged through the liquid outlet is further vaporized by the reboiler E102 and partially refluxed to the light-removal tower T101 to maintain the material balance in the tower, and the rest is transported to the extractive distillation tower T102 through a pipeline.

[0056] The lightness removal tower T101 is filled with fillers, which are selected from small metal Bauer ring fillers, metal corrugated fillers, and metal wire mesh corrugated fillers, preferably metal wire mesh corrugated fillers.

[0057] The extractive distillation tower T102 is located downstream of the light-removing tower T101. The top of the extractive distillation tower T102 is provided with a discharge port for discharging the purified 1,2-dichloropropane of the final product. The upper part of the tower body is provided with an extractant feed port for injecting the extractant into the extractive distillation tower T102. The middle part of the tower body is provided with a feed port, which is connected to the liquid outlet of the light-removing tower T101 through a pipeline, and is used to receive the material from the light-removing tower T101. The bottom of the tower is provided with a liquid outlet for discharging liquid substances.

[0058] Preferably, a condenser E103 is further provided at the discharge port arranged at the top of the extractive distillation tower T102, and the final product purified 1,2-dichloropropane discharged through the discharge port is condensed by the condenser E103 and partially refluxed to the extractive distillation tower T102 to maintain the material balance in the extractive distillation tower T102, and the rest is discharged through a pipeline.

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

[0060] Preferably, the extractive distillation tower T102 is filled with packing, and a packing support, a liquid distributor, a redistributor and a demister are arranged in the tower.

[0061] The extractant recovery tower T103 is located downstream of the extractive distillation tower T102. The extractant recovery tower T103 is provided with a discharge port at the top for discharging the heavy components obtained by the extractive distillation. A feed port is provided in the middle of the tower body. The feed port is connected to the liquid outlet of the extractive distillation tower T102 through a pipeline for receiving the material from the extractive distillation tower T102. A liquid outlet is provided at the bottom of the tower for discharging the separated extractant. The liquid outlet is connected to the extractant feed port of the extractive distillation tower T102 through a pipeline for transporting the separated and recovered extractant back to the extractive distillation tower T102.

[0062] Preferably, a condenser E105 is further provided at the discharge port at the top of the extractant recovery tower T103, and the heavy components discharged from the extraction distillation through the discharge port are partially refluxed to the extractant recovery tower T103 after condensation by the condenser E105 to maintain the material balance in the extractant recovery tower T103, and the rest 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, and the liquid substance discharged through the liquid outlet is further cooled by the reboiler E106 and partially refluxed to the extractant recovery tower T103 to maintain the material balance in the tower, and the rest is transported to the extractive distillation tower T102 through a pipeline.

[0064] Preferably, the extractant recovery tower T103 is filled with packing, and a packing support, a liquid distributor, a redistributor and a demister are arranged in the tower.

[0065] The process steps of using the above-mentioned refining device according to the present invention to purify 1,2-dichloropropane produced as a byproduct of a 3-chloropropene device by extractive distillation are as follows: the crude 1,2-dichloropropane produced as a byproduct of the 3-chloropropene device first enters the light removal distillation tower T101, the theoretical plate number of the light removal distillation tower T101 is 50-80, and the feed position is located at the 30th to 50th theoretical plates. The condensation temperature of the top condenser is 30-40°C, the pressure is 95-105kPaA; the operating reflux ratio is 3-8. After the top gas phase of the light removal distillation tower T101 is condensed by the condenser E101, a part of the reflux re-enters the light removal distillation tower T101, and the other part of the material (S1) water, 1-chloropropane, trans-1-chloropropene, 2-chloropropene and a small amount of azeotropic 1,2-dichloropropane are discharged from the system together, and the bottom material (S2) is transported to the extractive distillation tower T102 through a pipeline. In a preferred embodiment, the bottom material 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 tower T101 and the extractive distillation tower T102, for further vaporizing the liquid material to reach the temperature and state required by the extractive distillation tower T102.

[0066] The extractive distillation tower T102 receives the material and the extractant from the light removal distillation tower T101 for extraction. The theoretical plate number of the extractive distillation tower T102 is 50 to 70, the feed position of the raw material is located at the 40th to 60th theoretical plates, and the feed position of the extractant is located at the 5th to 10th theoretical plates. The vacuum distillation is carried out, the top pressure is 10 to 30 kPaA, the top condensation temperature is 40 to 60°C; the operating reflux ratio is 0.3 to 1, and the mass ratio of the extractant to the feed is 3 to 10. After the top gas phase in the extractive distillation tower T102 is condensed by the condenser E103, a part of it is refluxed, and the other part is discharged after cooling. The output is ≥99.9% 1,2-dichloropropane (S3). The bottom materials are 3,3-dichloropropylene, cis-1,3-dichloropropylene, 2,3-dichloropropylene and extractant, part of which is returned to the extractive distillation tower T102 to maintain the reaction balance in the tower, and the rest (S4) is vaporized by the vaporizer E201 and then enters the extractant recovery tower T103.

[0067] The extractant recovery tower T103 is a packed tower, and the packing is metal corrugated packing, metal wire mesh corrugated packing, metal perforated plate corrugated packing, preferably metal perforated plate corrugated packing, the number of theoretical plates is 45-75, and the feeding position is located at the 38th to 62nd theoretical plates. The tower top temperature is 25-40°C, the pressure is 5-20kPaA; the operating reflux ratio is 15-30. The extractant is fed from the upper half of the tower body, and a part of the top material is refluxed after condensation by the condenser E105, and the other discharge (S5) is 3,3-dichloropropylene, cis-1,3-dichloropropylene and 2,3-dichloropropylene. The bottom discharge is the extractant, and part of the extractant returns to the extractant recovery tower T103, and the rest (S6) returns to the extractive distillation tower T102 for recycling.

[0068] The following examples are only listed as examples of embodiments of the present invention and do not constitute any limitation to the present invention. It can be understood by those skilled in the art that modifications within the scope of the essence and concept of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

[0069] Example 1

[0070] like Figure 1 As shown, the process steps of a 3-chloropropylene by-product 1,2-dichloropropane device using extractive distillation are as follows:

[0071] The 3-chloropropene unit produces 1,2-dichloropropane crude product of 1255 kg / h, which is composed of 1,2-dichloropropane (80%, wt%, the same below), 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%), and enters the light removal distillation tower T101. The packing of tower T101 is metal wire mesh corrugated packing with 60 theoretical plates, the feed position is the 40th theoretical plate, the condensation temperature of the top condenser is 36°C, and the pressure is 100 kPaA; the operating reflux ratio is 5:1.

[0072] The gas phase at the top of the light fractionation tower T101 is condensed by the condenser E101, part of which is refluxed and part of which is discharged, removing light components such as water, 1-chloropropane, 1-chloropropylene, 2-chloropropylene and 1,5-hexadiene. The loss of 1,2-dichloropropane at the top of the tower is 20Kg / h. The bottom material is transported to the extractive distillation tower T102 through the vaporizer E201. The heat load of E201 is 92KW.

[0073] The packing of extractive distillation tower T102 is corrugated metal perforated plate packing, with 60 theoretical plates, the raw material feed position is located at the 50th theoretical plate, the extractant is ethylene glycol, the mass ratio of the extractant to the feed is 6.8, and the feed position is located at the 8th theoretical plate. Vacuum distillation, tower top pressure 20kPaA, tower top condensation temperature 48℃; operating reflux ratio 0.2. After the top gas phase of T102 is condensed by the condenser, part of it is refluxed and part of it is discharged. The top discharge is 1,2-dichloropropane with a purity of 99.99%. The bottom material is a mixture of 3,3-dichloropropene, cis-1,3-dichloropropene and 2,3-dichloropropene, ethylene glycol and a small amount of 1,2-dichloropropane, which enters the extractant recovery tower T103 through a pipeline.

[0074] The packing of the extractant recovery tower T103 is a metal perforated plate corrugated packing, with 60 theoretical plates, and the feed position is located at the 45th theoretical plate. The tower top temperature is 30°C, the pressure is 10kPaA, and the operating reflux ratio is 20. After the tower top material is condensed by the condenser, part of it is refluxed and part of it is discharged. The discharge is a mixture of 3,3-dichloropropylene, cis-1,3-dichloropropylene and 2,3-dichloropropylene with 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, and the lost ethylene glycol is supplemented with fresh ethylene glycol.

[0075] By using the device and method of the present invention, 1,2-dichloropropane with a purity of 99.99% can be refined and extracted, which is extremely beneficial for subsequent utilization.

[0076] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A refining device for 1,2-dichloropropane produced as a byproduct of a 3-chloropropylene unit, comprising a lightness removal tower, an extractive distillation tower and an extractant recovery tower. The light-removal tower has 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. The extractive distillation tower is located downstream of the light-removal tower, the top of the extractive distillation tower is provided with a discharge port for discharging the purified 1,2-dichloropropane of the final product, the upper part of the tower body is provided with an extractant feed port for injecting the extractant into the extractive distillation tower, the middle part of the tower body is provided with a feed port, the feed port is connected to the liquid outlet of the light-removal tower through a pipeline, and is used to receive the material from the light-removal tower, and the bottom of the tower is provided with a liquid outlet for discharging liquid substances; The extractant recovery tower is located downstream of the extractive distillation tower. The extractant recovery tower is provided with a discharge port at the top for discharging the heavy components obtained by the extractive distillation. A feed port is provided in the middle of the tower body. The feed port is connected to the liquid outlet of the extractive distillation tower through a pipeline for receiving materials from the extractive distillation tower. A liquid outlet is provided at the bottom of the tower for discharging the separated extractant. The liquid outlet is connected to the extractant feed port of the extractive distillation tower through a pipeline for transporting the separated and recovered extractant back to the extractive distillation tower.

2. The refining device according to claim 1, characterized in that: The light-removal tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged; Preferably, the extractive distillation tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged; Preferably, the extractant recovery tower is a packed tower, in which a packing support, a liquid distributor, a redistributor and a demister are arranged.

3. The refining device according to claim 1, characterized in that: The discharge port at the top of the light-removal tower is further provided with a condenser, and the light components discharged through the discharge port are condensed by the condenser and partially refluxed to the light-removal tower to maintain the reaction balance of the materials in the tower, and the rest are led out of the system; Preferably, a reboiler is further provided at the liquid outlet at the bottom of the light-removal tower, and the liquid material discharged through the liquid outlet is further vaporized by the reboiler and then partially refluxed to the light-removal tower to maintain the reaction balance of the materials in the tower, and the rest is transported to the extractive distillation tower through a pipeline; Preferably, a vaporizer is further provided on the pipeline connecting the liquid outlet at the bottom of the light removal tower and the extractive distillation tower, for further vaporizing the liquid substance to reach the temperature and state required by the extractive distillation tower; Preferably, a condenser is further provided at the discharge port arranged at the top of the extractive distillation tower, and the purified 1,2-dichloropropane as the final product discharged through the discharge port is partially refluxed to the extractive distillation tower after being condensed by the condenser to maintain the material reaction balance in the extractive distillation tower, and the rest is discharged through a pipeline; Preferably, a reboiler is further provided at the liquid outlet at the bottom of the extractive distillation tower, and the liquid substance discharged through the liquid outlet is further vaporized by the reboiler and then partially refluxed to the extractive distillation tower to maintain the reaction balance of the materials in the tower, and the rest is transported to the extractant recovery tower through a pipeline; Preferably, a condenser is further provided at the discharge port at the top of the extractant recovery tower, and the heavy components discharged from the extraction and distillation through the discharge port are partially refluxed to the extractant recovery tower after being condensed by the condenser to maintain the material reaction balance in the extractant recovery tower, and the rest is discharged through a pipeline; Preferably, a reboiler is further provided at the liquid outlet at the bottom of the extractant recovery tower, and the liquid substance discharged through the liquid outlet is further vaporized by the reboiler and partially refluxed to the extractant recovery tower to maintain the reaction balance of the materials in the tower, and the rest is transported to the extractive distillation tower through a pipeline.

4. A method for refining 1,2-dichloropropane produced as a byproduct of a 3-chloropropylene unit, the method comprising: 1) The crude 1,2-dichloropropane by-product of the 3-chloropropene unit is transported to a light-removal tower, and light components such as water, 1-chloropropane, 1-chloropropene, 2-chloropropene and 1,5-hexadiene are removed from the top of the tower. The bottom material of the light-removal tower is transported to an extractive distillation tower through a pipeline; 2) the extractant is fed from the extractant feed port of the upper half of the extractive distillation tower, the extractive distillation tower is operated under reduced pressure, the top discharge is 1,2-dichloropropane, and the bottom discharges 3,3-dichloropropylene, cis-1,3-dichloropropylene, 2,3-dichloropropylene and the extractant enter the extractant recovery tower; 3) The extractant recovery tower is operated under reduced pressure, the top discharge is a mixture of 3,3-dichloropropylene, cis-1,3-dichloropropylene and 2,3-dichloropropylene, and the bottom discharge is the extractant to be recycled in the extractive distillation tower.

5. The refining method according to claim 4, characterized in that: Measured by weight percentage, the crude 1,2-dichloropropane 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.

6. The refining method according to claim 4, characterized in that: The light removal tower T101 in step 1) has a theoretical plate number of 50 to 80, a tower top pressure of 95 to 105 kPaA, and an operating reflux ratio of 3 to 8; Preferably, a condenser is provided at the top of the light removal tower in step 1), and the condensation temperature thereof is 30-40° C.; Preferably, a vaporizer is provided on the pipeline connecting the light removal tower and the extractive distillation tower, and the vaporization pressure is 125-135 kPaA and the vaporization temperature is 30-40°C; Preferably, the extractive distillation tower has a theoretical plate number of 50 to 70, vacuum distillation, a tower top pressure of 10 to 30 kPaA, a tower top condensation temperature of 40 to 60° C., an operating reflux ratio of 0.3 to 1, and a mass ratio of the extractant to the feed of 3 to 10; Preferably, the number of theoretical plates of the extractant recovery tower is 45 to 75, the tower top temperature is 25 to 40° C., the tower top pressure is 5 to 20 kPaA, and the operating reflux ratio is 15 to 30; Preferably, the feed inlet position of the lightness removal tower is the 30th to 50th theoretical plates; the raw material feed position of the extractive distillation tower is the 40th to 60th theoretical plates, the extractant feed position is the 5th to 10th theoretical plates; the feed position of the extractant recovery tower is the 38th to 62nd theoretical plates.

7. The purification method according to claim 4, characterized in that: The lightness removal tower is a packed tower, and the packing is a small metal Bauer ring packing, a metal corrugated packing, a metal wire mesh corrugated packing, preferably a metal wire mesh corrugated packing; the extraction distillation tower is a packed tower, and the packing is a metal corrugated packing, a metal wire mesh corrugated packing, a metal perforated plate corrugated packing, preferably a metal perforated plate corrugated packing; the extraction agent recovery tower is a packed tower, and the packing is a metal corrugated packing, a metal wire mesh corrugated packing, preferably a metal wire mesh corrugated packing.

8. The purification method according to claim 4, characterized in that: The extractant is one or more of N,N-dimethylformamide, N-methylpyrrolidone, ethylene glycol, n-octanol, phenol, N-formylmorpholine and sulfolane.

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