Thermal coupling heat exchange equipment for continuous distillation and continuous distillation method of polyolefin catalyst mother liquor

Abstract

The invention relates to the field of polyolefin catalyst mother liquor treatment, and discloses thermal coupling heat exchange equipment for continuous distillation and a continuous distillation method of polyolefin catalyst mother liquor. The thermal coupling heat exchange equipment for continuous distillation comprises an evaporation unit and a heat exchange unit, wherein the evaporation unit is used for continuously distilling materials; the top of the heat exchange unit is connected with the top of the evaporation unit, and the heat exchange unit comprises an upper feed preheating section and a lower cooling section, the upper feed preheating section is used for enabling top fractions from the top of the evaporation unit to exchange heat with fed materials, and the lower cooling section is used for cooling the top fractions subjected to heat exchange with the fed materials; and the feeding unit is partially arranged in the upper feeding preheating section and is used for feeding the material preheated by the upper preheating section into the evaporation unit for evaporation. By using the thermal coupling heat exchange equipment and method for continuous distillation, the temperature control of the fed material is more stable, and the operation stability of an evaporation device can be improved.

Description

Technical Field

[0001] The invention relates to the field of polyolefin catalyst mother liquor treatment, and in particular to a thermal coupling heat exchange device for continuous distillation and a continuous distillation method for polyolefin catalyst mother liquor. Background Art

[0002] Distillation is often used in chemical production to achieve rapid separation of materials with large boiling point differences. Some of the distillation processes are continuous distillation processes with continuous feeding and continuous extraction. In recent years, molecular distillation and thin film evaporation processes with short residence time and low evaporation temperature, which are suitable for efficient, high-speed and low-temperature separation of heat-sensitive materials, have been widely used. The evaporator used in this type of evaporation process has a small heat transfer area. Therefore, in order to ensure continuity, stability and full separation, high requirements are placed on the temperature of the material entering the evaporator. Generally, the feed temperature needs to be stable and close to the boiling point of the low-boiling component. In the common process design of this type of equipment, it is necessary to design a preheater with temperature adjustment function for the feed logistics to facilitate feed temperature adjustment. The temperature regulation control function of this type of preheater generally achieves temperature control by adjusting the amount of heat medium introduced according to the preheater outlet temperature. However, the regulation process often causes the preheater material outlet temperature to fluctuate due to the lag in adjustment feedback. This fluctuation will be amplified, especially when the feed flow rate changes or the temperature of the material entering the preheater changes. However, since this type of evaporator has a high evaporation efficiency and is highly sensitive to temperature, the control fluctuation of the feed preheater often has a significant impact on the separation efficiency of the evaporator. Summary of the invention

[0003] The purpose of the present invention is to overcome the problem in the prior art that the temperature control of the feed material is prone to fluctuation and instability, and to provide a thermally coupled heat exchange device for continuous distillation and a continuous distillation method for a polyolefin catalyst mother liquor. By using the thermally coupled heat exchange device for continuous distillation of the present invention, the temperature control of the feed material is more stable, and the operating stability of the evaporation device can be improved.

[0004] In order to achieve the above object, the present invention provides a thermal coupling heat exchange device for continuous distillation in a first aspect, characterized in that the device comprises:

[0005] An evaporation unit, which is used to continuously distill the material;

[0006] a heat exchange unit, the top of which is connected to the top of the evaporation unit, and comprises an upper feed preheating section for exchanging heat between the top fraction from the top of the evaporation unit and the feed, and a lower cooling section for cooling the top fraction after heat exchange with the feed; and

[0007] The feeding unit is partially arranged in the upper feeding preheating section and is used to feed the material preheated by the upper preheating section into the evaporation unit for evaporation.

[0008] Preferably, the evaporation unit is a thin film evaporation device.

[0009] Preferably, the upper feed preheating section and the lower cooling section are an integrated structure.

[0010] Preferably, the structure of the upper feed preheating section is a coil type, a folded plate type, a tube shell type or a combination thereof.

[0011] Preferably, the structure of the lower cooling section is shell and tube type and / or coil type.

[0012] Preferably, the bottom of the heat exchange unit has a liquid discharge port.

[0013] According to a second aspect of the present invention, a method for continuous distillation of a polyolefin catalyst mother liquor is provided, wherein the method adopts the thermally coupled heat exchange device for continuous distillation described in the first aspect of the present invention to perform continuous distillation, and comprises the following steps: continuously feeding the polyolefin catalyst mother liquor into the evaporation unit through the feeding unit for continuous distillation, and sending the obtained top fraction into the heat exchange unit, so that the top fraction undergoes a first heat exchange with the raw material in the feeding unit in the upper preheating section, and the top fraction after the heat exchange undergoes a second heat exchange with the lower cooling section to obtain a liquid phase.

[0014] Preferably, the evaporation unit is a thin film evaporation device.

[0015] Preferably, the feed temperature of the raw material is 0-60°C.

[0016] Preferably, the distillation temperature is 80-150°C, and the distillation pressure is -95-100Kpa.

[0017] Preferably, the temperature of the secondary steam of the top fraction is 80-120°C.

[0018] Preferably, the first heat exchange causes the temperature of the raw material to be 60-100°C.

[0019] Preferably, the second heat exchange is performed so that the temperature of the material after the heat exchange is 20-80°C.

[0020] Preferably, the polyolefin catalyst mother solution contains 20-45 volume % of titanium tetrachloride, 45-65 volume % of toluene and 5-12 volume % of high boiling substances containing esters.

[0021] Through the above technical solution, by using the thermal coupling heat exchange equipment for continuous distillation of the present invention, the temperature control of the feed material is more stable, which can improve the operating stability of the evaporation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the thermally coupled heat exchange device for continuous distillation of the present invention.

[0023] Description of Reference Numerals

[0024] 1Evaporation unit 2Heat exchange unit

[0025] 21 Upper feed preheating section 22 Lower cooling section

[0026] 3 Feeding unit DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] According to a first aspect of the present invention, there is provided a thermally coupled heat exchange device for continuous distillation, characterized in that the device comprises:

[0029] An evaporation unit 1, which is used to continuously distill the material;

[0030] a heat exchange unit 2, the top of which is connected to the top of the evaporation unit, comprising an upper feed preheating section 21 for exchanging heat between the top fraction from the top of the evaporation unit 1 and the feed, and a lower cooling section 22 for cooling the top fraction after heat exchange with the feed; and

[0031] The feeding unit 3 is partially disposed in the upper feeding preheating section 21 and is used to feed the material preheated by the upper preheating section 21 into the evaporation unit 1 for evaporation.

[0032] According to the present invention, the evaporation unit 1 may be any device used for continuous evaporation in the art, such as a thin film evaporation device, a kettle distillation device with continuous distillation capability, a distillation tower, etc. Among them, a thin film evaporation device is preferred due to the thermal sensitivity of some materials.

[0033] According to the thermally coupled heat exchange equipment for continuous distillation of the present invention, the upper feed preheating section 21 and the lower cooling section 22 can be a split structure or an integrated structure. Preferably, the upper feed preheating section 21 and the lower cooling section 22 are an integrated structure.

[0034] According to the thermally coupled heat exchange equipment for continuous distillation of the present invention, the structure of the upper feed preheating section 21 is coil type, folded plate type, shell and tube type or a combination thereof; preferably coil type, folded plate type or shell and tube type.

[0035] When the structure of the upper feed preheating section 21 is a coil type, its specific structure is that the coil can be spirally wound around the center line of the shell side, and the tube side material and the shell side secondary steam are heat exchanged in a countercurrent manner.

[0036] When the structure of the upper feed preheating section 21 is a folding plate type, its specific structure is a double-layer rolled plate structure or a folding plate structure, in which the secondary steam is condensed through one layer of the folding plate and collected to enter the second heat exchange section, and the preheated material is heated through another layer of the folding plate and then enters the evaporator.

[0037] When the structure of the upper feed preheating section 21 is a shell and tube type, its specific structure is a tube-in-tube structure, which can be a single-pass tube-in-tube structure or a multi-pass tube-in-tube structure, wherein the secondary steam is cooled in the shell and collected.

[0038] The structure of the upper feed preheating section 21 can be designed according to factors such as the characteristics of the cold and hot fluids and the amount of material.

[0039] According to the thermally coupled heat exchange equipment for continuous distillation of the present invention, the structure of the lower cooling section 22 is a shell and tube heat exchanger (wherein the shell side medium is the refrigerant, and the tube side medium is the secondary steam passing through the upper first heat exchange section) and / or a coil heat exchanger (wherein the tube side can be the refrigerant, and the shell side is the secondary steam and condensate).

[0040] According to the thermally coupled heat exchange device for continuous distillation of the present invention, preferably, the bottom of the heat exchange unit 2 has a liquid discharge port.

[0041] According to a second aspect of the present invention, a method for continuous distillation of a polyolefin catalyst mother liquor is provided, wherein the method adopts the thermally coupled heat exchange device for continuous distillation described in the first aspect of the present invention to perform continuous distillation, and comprises the following steps: continuously feeding the polyolefin catalyst mother liquor into the evaporation unit 1 through the feeding unit 3 for continuous distillation, and sending the obtained top fraction into the heat exchange unit 2, so that the top fraction undergoes a first heat exchange with the raw material in the feeding unit 3 in the upper preheating section 21, and the top fraction after heat exchange undergoes a second heat exchange with the lower cooling section 22 to obtain a liquid phase.

[0042] According to the method of the present invention, preferably, the evaporation unit 1 is a thin film evaporation device.

[0043] According to the method of the present invention, preferably, the feed temperature of the raw material is 0-60°C, preferably 10-50°C, more preferably 15-30°C. For example, it can be: 10°C, 15°C, 20°C, 23°C, 30°C, etc.

[0044] According to the method of the present invention, preferably, the distillation temperature is 80-150°C, and the vacuum degree is -95-100Kpa; more preferably, the distillation temperature is 80-110°C, and the vacuum degree is -60-90Kpa.

[0045] According to the method of the present invention, the temperature of the secondary steam of the top fraction is 80-120°C, preferably 80-90°C.

[0046] According to the method of the present invention, preferably, the first heat exchange makes the temperature of the raw material 60-100°C, more preferably, the first heat exchange makes the temperature of the raw material 60-70°C.

[0047] According to the method of the present invention, preferably, the second heat exchange makes the temperature of the material after heat exchange be 20-50°C, and more preferably, the second heat exchange makes the temperature of the material after heat exchange be 20-30°C.

[0048] According to the method of the present invention, the polyolefin catalyst mother liquor refers to a solvent mixture produced after the solid-liquid separation of the catalyst, auxiliary agent, solvent, etc. after the synthesis of the polyolefin catalyst.

[0049] According to the method of the present invention, the polyolefin catalyst mother solution may contain 20-45 volume % of titanium tetrachloride, 45-65 volume % of toluene and 5-12 volume % of high boiling substances containing esters.

[0050] The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

[0051] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0052] The content of titanium tetrachloride in the mother liquor of the polyolefin catalyst used in the following examples is 42.6% (volume), the content of toluene is 48.5% (volume), and the content of high-boiling substances containing lipids in the heavy component is 10% (volume).

[0053] Example 1

[0054] This embodiment adopts Figure 1The device shown in the figure comprises: an evaporation unit 1 (specifically a thin film evaporator, purchased from Wuxi Lima Chemical Machinery Co., Ltd., model GXZ-6B), a heat exchange unit 2, the top of which is connected to the top of the evaporation unit 1, comprising an upper feed preheating section 21 for exchanging heat between the top fraction from the top of the evaporation unit 1 and the feed, and a lower cooling section 22 for cooling the top fraction after heat exchange with the feed; and a feed unit 3, part of which is arranged in the upper feed preheating section 21, for feeding the material preheated by the upper feed preheating section 21 into the evaporation unit 1 for evaporation.

[0055] Among them, the specific structure of the upper feed preheating section 21 is a coil; the specific structure of the lower cooling section 22 is a shell and tube single-pass tube condenser, using water with a temperature of 24°C as the cooling medium; the specific structure of the feed unit is a closed pipeline transportation structure with a flow regulation function.

[0056] The specific steps are as follows:

[0057] The mother liquor of the polyolefin catalyst is continuously distilled and separated by a thin film evaporator. The continuous distillation is carried out for 24 hours under the conditions of -0.075Mpa vacuum and 600Kg / h feed rate. The distillation temperature is 98°C, the temperature of the secondary steam in the top fraction is 86°C, and a heat exchange unit is used for feed preheating and secondary steam cooling. The designed heat exchange area of ​​the preheating zone is 1㎡, the heat exchange area of ​​the cooling section is 25㎡, and circulating water is used as the refrigerant. The feed temperature of the evaporator of the distillation system can be continuously and stably maintained at 62-63℃, with a fluctuation frequency of ≤1 time / h. The temperature difference between the inlet and outlet of the circulating water in the cooling section is 5.7℃, and the temperature of the cooled liquid phase is 29.5℃.

[0058] Comparative Example 1

[0059] The same polyolefin catalyst mother liquid as in Example 1 was used, with a preheater with a heat exchange area of ​​2 m2 as the feed preheating equipment, low-pressure steam (≈0.2 MPa) as the heat medium, the preheater outlet temperature as the control parameter, and the steam input amount as the adjustment variable for feed preheating operation, and the equipment operating conditions were the same as in Example 1, while a vertical heat exchanger with a heat exchange area of ​​25 m2 was used as the evaporation material secondary steam cooler, circulating water was used as the refrigerant, and the process control parameters were the same as in Example 1. As a result, the feed temperature could be continuously and stably maintained at 59-68°C, the fluctuation frequency was ≥10 times / h, and the temperature difference between the inlet and outlet of the circulating water in the cooling section was 8.8°C.

[0060] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A thermally coupled heat exchange device for continuous distillation, characterized in that: The equipment includes: An evaporation unit (1) for continuously distilling a material; a heat exchange unit (2), the top of which is connected to the top of the evaporation unit, comprising an upper feed preheating section (21) for exchanging heat between the top fraction from the top of the evaporation unit (1) and the feed, and a lower cooling section (22) for cooling the top fraction after heat exchange with the feed; and A feeding unit (3) is partially disposed in the upper feeding preheating section (21) and is used to feed the material preheated by the upper feeding preheating section (21) into the evaporation unit (1) for evaporation.

2. The thermal coupling heat exchange device according to claim 1, wherein: The evaporation unit (1) is a thin film evaporation device.

3. The thermal coupling heat exchange device according to claim 1, wherein: The upper feed preheating section (21) and the lower cooling section (22) are an integrated structure.

4. The thermal coupling heat exchange device according to any one of claims 1 to 3, wherein: The structure of the upper feed preheating section (21) is a coil type, a folded plate type, a tube shell type or a combination thereof.

5. The thermal coupling heat exchange device according to any one of claims 1 to 3, wherein: The structure of the lower cooling section (22) is a shell and tube type and / or a coil type.

6. The thermal coupling heat exchange device according to any one of claims 1 to 3, wherein: The bottom of the heat exchange unit (2) is provided with a liquid discharge port.

7. A method for continuous distillation of polyolefin catalyst mother liquor, characterized in that: The continuous distillation is carried out by using the thermally coupled heat exchange device for continuous distillation as claimed in any one of claims 1 to 6. The method comprises the following steps: continuously feeding the polyolefin catalyst mother liquid into the evaporation unit (1) through the feeding unit (3) for continuous distillation, and sending the obtained top fraction into the heat exchange unit (2), so that the top fraction undergoes a first heat exchange with the raw material in the feeding unit (3) in the upper preheating section (21), and the top fraction after the heat exchange undergoes a second heat exchange with the lower cooling section (22) to obtain a liquid phase.

8. The method according to claim 7, wherein: The evaporation unit (1) is a thin film evaporation device.

9. The method according to claim 7, wherein: The feed temperature of the raw materials is 0-60°C.

10. The method according to claim 8, wherein: The distillation temperature is 80-150°C, and the distillation pressure is -95-100Kpa.

11. The method according to any one of claims 7 to 9, wherein: The temperature of the secondary steam of the top fraction is 80-120°C.

12. The method according to any one of claims 7 to 9, wherein: The first heat exchange makes the temperature of the raw material be 60-100°C.

13. The method according to any one of claims 7 to 9, wherein: The second heat exchange makes the temperature of the material after heat exchange be 20-80°C.

14. The method according to any one of claims 7 to 9, wherein: The polyolefin catalyst mother liquid contains 20-45 volume % of titanium tetrachloride, 45-65 volume % of toluene and 5-12 volume % of high boiling substances containing esters.

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