Thermally coupled heat exchange apparatus for continuous distillation and continuous distillation process of polyolefin catalyst mother liquor

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyolefin catalyst mother liquor treatment, in particular to a heat coupling heat exchange equipment for continuous distillation and a continuous distillation method of polyolefin catalyst mother liquor. BACKGROUND

[0002] In chemical production, distillation is often used to realize rapid separation of materials with large boiling point difference. Part of the distillation process is a continuous distillation process with continuous feeding and continuous collection. In recent years, molecular distillation and thin film evaporation processes, which are suitable for high-efficiency high-speed low-temperature separation of heat-sensitive materials due to their short residence time and low evaporation temperature, have been widely used. The evaporation equipment used in such evaporation processes has a small heat transfer area, so in order to ensure continuous and stable separation and achieve full separation, the temperature of the material entering the evaporation equipment needs to be relatively high. In the process design of such equipment, a preheater with temperature adjustment function is often designed for the feed stream to facilitate temperature adjustment. The temperature adjustment and control function of such preheaters is generally realized by adjusting the amount of heat medium entering according to the outlet temperature of the preheater, but the adjustment process often causes the outlet temperature of the preheater to fluctuate due to the lag of the adjustment feedback, especially when the feed flow rate changes or the temperature of the material entering the preheater changes, the fluctuation will be amplified. However, due to the high evaporation efficiency and strong temperature sensitivity of such evaporation equipment, the control fluctuation of the feed preheater often has a significant impact on the separation efficiency of the evaporation equipment. SUMMARY

[0003] The purpose of the present application is to overcome the problem of unstable control of the temperature of the feed material in the prior art, and to provide a heat coupling heat exchange equipment for continuous distillation and a continuous distillation method of polyolefin catalyst mother liquor. The heat coupling heat exchange equipment for continuous distillation of the present application has more stable control of the temperature of the feed material, which can improve the operation stability of the evaporation device.

[0004] To achieve the above purpose, the present application provides a heat coupling heat exchange equipment for continuous distillation, characterized in that the equipment comprises:

[0005] an evaporation unit for continuously distilling the material;

[0006] a heat exchange unit connected to the top of the evaporation unit, comprising an upper feed preheating section for heat exchange 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] a feeding unit, which is partially arranged in the upper feeding preheating section, for feeding the material preheated by the upper feeding preheating section into the evaporation unit for evaporation.

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

[0009] Preferably, the upper feeding preheating section and the lower cooling section are integrated.

[0010] Preferably, the upper feeding preheating section is in the form of a coil, a folded plate, a shell-and-tube or a combination thereof.

[0011] Preferably, the lower cooling section is in the form of a shell-and-tube and / or a coil.

[0012] Preferably, the bottom of the heat exchange unit is provided with a liquid discharge outlet.

[0013] According to the second aspect of the present application, there is provided a continuous distillation method of a polyolefin catalyst mother liquor, wherein the continuous distillation is performed by using the heat coupled heat exchange device for continuous distillation according to the first aspect of the present application, comprising the following steps: continuously feeding the polyolefin catalyst mother liquor into the evaporation unit through the feeding unit for continuous distillation, and feeding the obtained top fraction into the heat exchange unit, so that the top fraction is subjected to first heat exchange with the raw material in the feeding unit in the upper preheating section, and the heat exchanged top fraction is subjected to 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 feeding temperature of the raw material is 0-60℃.

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

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

[0018] Preferably, the first heat exchange makes the temperature of the raw material 60-100℃.

[0019] Preferably, the second heat exchange makes the temperature of the heat exchanged material 20-80℃.

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

[0021] By the technical scheme, the heat coupling heat exchange equipment for continuous distillation has stable feed material temperature control, and can improve the operation stability of the evaporation device. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the heat coupling heat exchange equipment for continuous distillation of the present application.

[0023] REFERENCE SIGNS

[0024] 1 evaporation unit 2 heat exchange unit

[0025] 21 upper feed preheating section 22 lower cooling section

[0026] 3 feed unit DETAILED DESCRIPTION

[0027] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the present application. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to also disclose all values individually. Combining the endpoints of the ranges with the individual points recited, new numeric ranges are created which are intended to be included in the disclosure.

[0028] According to the first aspect of the present application, a heat coupling heat exchange equipment for continuous distillation is provided, characterized in that the equipment comprises:

[0029] an evaporation unit 1 for continuous distillation of material;

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

[0031] a feed unit 3 partially arranged in the upper feed preheating section 21, for feeding the material preheated by the upper preheating section 21 into the evaporation unit 1 for evaporation.

[0032] According to the present application, the evaporation unit 1 can be various devices for continuous evaporation in the art, such as thin film evaporation device, kettle type distillation equipment with continuous distillation capacity, rectifying column, etc. Among them, the thin film evaporation device is preferred for consideration of the thermal sensitivity of part of the material.

[0033] The upper feed preheating section 21 and the lower cooling section 22 of the heat coupled heat exchange device for continuous distillation according to the present application can be of a split structure or of an integrated structure, and preferably, the upper feed preheating section 21 and the lower cooling section 22 are of an integrated structure.

[0034] The upper feed preheating section 21 of the heat coupled heat exchange device for continuous distillation according to the present application is of a coil type, a folded plate type, a shell-and-tube type, or a combination thereof, and preferably, is of a coil type, a folded plate type, or a shell-and-tube type.

[0035] When the upper feed preheating section 21 is of a coil type, the coil can be in a spiral form around the center line of the shell side, and the heat exchange between the tube side material and the shell side secondary steam is in a countercurrent manner.

[0036] When the upper feed preheating section 21 is of a folded plate type, the folded plate type can be of a double-layered plate structure or a folded plate structure, in which the secondary steam is condensed through one layer of the folded plate and collected into the second heat exchange section, and the preheated material is heated through another layer of the folded plate and then enters the evaporator.

[0037] When the upper feed preheating section 21 is of a shell-and-tube type, the shell-and-tube type can be of a single-pass tube or a multi-tube type, in which the secondary steam is cooled in the shell side and collected into the second heat exchange section.

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

[0039] The lower cooling section 22 of the heat coupled heat exchange device for continuous distillation according to the present application is of a shell-and-tube type heat exchanger (in which the shell side medium is a coolant, and the tube side medium is the secondary steam from the upper first heat exchange section) and / or a coil type heat exchanger (in which the tube side can be a coolant, and the shell side is the secondary steam and condensed liquid).

[0040] The heat coupled heat exchange device for continuous distillation according to the present application preferably has a liquid discharge outlet at the bottom of the heat exchange unit 2.

[0041] According to the second aspect of the present application, a continuous distillation method of a polyolefin catalyst mother liquor is provided, in which the heat coupled heat exchange device for continuous distillation according to the first aspect of the present application is used for continuous distillation, and the method comprises the following steps: continuously feeding the polyolefin catalyst mother liquor into the evaporation unit 1 through the feed unit 3 for continuous distillation, and feeding the obtained top fraction into the heat exchange unit 2, so that the top fraction is subjected to first heat exchange with the raw material in the feed unit 3 in the upper preheating section 21, and the heat-exchanged top fraction is subjected to second heat exchange with the lower cooling section 22 to obtain a liquid phase.

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

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

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

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

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

[0047] According to the method of the present application, preferably, the second heat exchange makes the temperature of the heat-exchanged material 20-50℃, more preferably, the second heat exchange makes the temperature of the heat-exchanged material 20-30℃.

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

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

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

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

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

[0053] Example 1

[0054] In this example, the polyolefin catalyst mother liquor used is prepared as follows: Figure 1The device shown is carried out, the device includes: evaporation unit 1 (specifically thin film evaporator, purchased from Wuxi Liming Chemical Machinery Co., Ltd. GXZ-6B type), heat exchange unit 2, the top of which is connected with the top of the evaporation unit 1, including an upper feed preheating section 21 for heat exchange 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 partially disposed 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] Wherein, the specific structure of the upper feed preheating section 21 is a coil; the specific structure of the lower cooling section 22 is a single tube pass shell and tube condenser, using water at a temperature of 24℃ as the cooling medium; the specific structure of the feed unit is a closed pipeline conveying structure with flow regulation function.

[0056] The specific steps are as follows:

[0057] The thin film evaporator is used for continuous distillation separation of the mother liquor of the polyolefin catalyst, under the conditions of a vacuum degree of -0.075Mpa and a feed amount of 600Kg / h for 24 hours of continuous distillation, wherein the distillation temperature is 98℃, the temperature of the top fraction secondary steam is 86℃, the heat exchange unit is used for feed preheating and secondary steam cooling, the design preheating area is 1㎡, the cooling section heat exchange area is 25㎡, and the circulating water is used as the coolant, the distillation system evaporator feed temperature can be continuously and stably maintained at 62-63℃, the fluctuation frequency is ≤1 / h, the temperature difference between the inlet and outlet of the cooling section circulating water is 5.7℃, and the temperature of the cooled liquid phase is 29.5℃.

[0058] Comparative Example 1

[0059] The same polyolefin catalyst mother liquor as in Example 1 is used, a preheater with a heat exchange area of 2㎡ is used as the feed preheating device, low pressure steam (≈0.2MPa) is used as the heating medium, the preheater outlet temperature is used as the control parameter, and the steam inlet amount is used as the adjusting variable for feed preheating operation, the device operating conditions are the same as in Example 1, and a vertical heat exchanger with a heat exchange area of 25㎡ is used as the secondary steam cooler for the evaporated material, the circulating water is used as the coolant, and the process control parameters are the same as in Example 1. As a result, the feed temperature can be continuously and stably maintained at 59-68℃, the fluctuation frequency is ≥10 / h, and the temperature difference between the inlet and outlet of the cooling section circulating water is 8.8℃.

[0060] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A continuous distillation process for a polyolefin catalyst mother liquor, characterized in that, The continuous distillation is carried out by using a heat-coupled heat exchange device for continuous distillation, which comprises: an evaporation unit (1) for continuously distilling materials; a heat exchange unit (2) connected to the top of the evaporation unit, comprising an upper feed preheating section (21) for heat exchanging the top fraction from the top of the evaporation unit (1) with feedstock and a lower cooling section (22) for cooling the top fraction after heat exchanging with feedstock; and a feed unit (3) partially 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, The continuous distillation method of the polyolefin catalyst mother liquor comprises the following steps: continuously feeding the polyolefin catalyst mother liquor into the evaporation unit (1) for continuous distillation through the feed unit (3), and feeding the obtained top fraction into the heat exchange unit (2) so that the top fraction is first heat exchanged with the raw material in the feed unit (3) in the upper feed preheating section (21), and the heat-exchanged top fraction is second heat exchanged with the lower cooling section (22) to obtain a liquid phase, so that the temperature control of the feed material of the temperature-sensitive evaporation unit is stable, and the operation stability of the evaporation unit is improved.

2. The method of claim 1, wherein, The evaporation unit (1) is a thin film evaporation device.

3. The method of claim 1, wherein, The upper feed preheating section (21) and the lower cooling section (22) are of an integrated structure.

4. The method of any of claims 1-3, wherein, The structure of the upper feed preheating section (21) is coil type, folded plate type, shell-and-tube type or a combination thereof.

5. The method of any of claims 1-3, wherein, The structure of the lower cooling section (22) is shell-and-tube type and / or coil type.

6. The method of any of claims 1-3, wherein, The bottom of the heat exchange unit (2) has a liquid discharge port.

7. The method of claim 1, wherein, The feed temperature of the raw material is 0-60℃.

8. The method of claim 2, wherein, The distillation temperature is 80-150℃, and the distillation pressure is -95~100Kpa.

9. The method of claim 1 or 7, wherein, The temperature of the top fraction secondary steam is 80-120℃.

10. The method of claim 1 or 7, wherein, The first heat exchange makes the temperature of the raw material 60-100℃.

11. The method of claim 1 or 7, wherein, The second heat exchange makes the temperature of the heat-exchanged material 20-80℃.

12. The method of claim 1 or 7, wherein, The polyolefin catalyst mother liquor contains 20-45% by volume of titanium tetrachloride, 45-65% by volume of toluene and 5-12% by volume of high-boiling substances containing esters.

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