CN111514602A - Method and device for removing dichloromethane in high-boiling-point thermosensitive material - Google Patents
Method and device for removing dichloromethane in high-boiling-point thermosensitive material Download PDFInfo
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- CN111514602A CN111514602A CN202010239930.8A CN202010239930A CN111514602A CN 111514602 A CN111514602 A CN 111514602A CN 202010239930 A CN202010239930 A CN 202010239930A CN 111514602 A CN111514602 A CN 111514602A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D3/14—Fractional distillation or use of a fractionation or rectification column
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
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Abstract
The invention belongs to the field of high-vacuum refining of high-boiling-point heat-sensitive materials, and discloses a method and a device for removing dichloromethane in high-boiling-point heat-sensitive materials. By applying the method, the dichloromethane-containing high-boiling-point heat-sensitive material enters a tower kettle tank through a feed pump, enters a falling film reboiler through a circulating pump, a gas-liquid mixture enters the tower kettle tank, a gas phase discharged from the tower kettle tank enters a rectifying tower, the gas phase at the top of the tower is condensed through a primary condenser, a condensate is collected and then passes through a reflux distributor, and a part of the condensate is extracted and a part of the condensate is refluxed. With the reduction of the content of the dichloromethane in the tower bottom and the lower and lower system pressure, the gas phase at the tower top can not be condensed, and the residual dichloromethane in the kettle liquid is removed by cooling the kettle liquid as reflux. By adopting the technical scheme, the temperature of the tower kettle can be effectively controlled, the decomposition or polymerization of kettle liquid is avoided, the device can adopt semi-continuous operation, has large operation elasticity, and is suitable for refining high-boiling-point thermosensitive materials containing light components.
Description
Technical Field
The invention belongs to the field of high-vacuum refining of high-boiling-point thermosensitive materials, and particularly relates to a method and a device for removing dichloromethane from high-boiling-point thermosensitive materials.
Background
Methylene chloride is used as a nonflammable solvent, can be used as a solvent, an extractant and the like of various organic polymers, such as perfume, and is removed after various treatments, and the methylene chloride is a high-boiling-point heat-sensitive material. Rectification is the most basic method for realizing separation, and in the conventional rectification process, a pressure reduction method is often adopted, so that the temperature required in the rectification process can be effectively reduced, and the decomposition or polymerization of some substances due to heating can be avoided. However, for materials with high boiling point and heat sensitivity, a common vacuum distillation method is not suitable for being used, because in the vacuum distillation process, the temperature of the tower kettle is controlled to be the highest and cannot exceed a certain value, the dichloromethane content in the tower kettle is higher at the beginning, the vacuum degree of the system is not required to be too high, when the dichloromethane content in the tower kettle is less, the vacuum degree of the system is required to be very high, some material systems are required to be close to vacuum, and at the moment, the gas phase at the tower top cannot be condensed, namely, no reflux exists.
In the process of reduced pressure distillation, the temperature of the tower kettle meets the requirement, normal reflux of the tower top is ensured, when the pressure of the tower top is-1 KPaA, the temperature of the tower top is-45 ℃, ultra-low temperature refrigeration equipment is needed, the equipment investment is large, and the operation cost is high.
By utilizing the principle of absorption and evaporation, when the gas phase led out from the top of the tower in the pressure reduction process cannot be condensed, an absorbent can be added from the top of the tower to be used as reflux, new substances outside the system are not added in the rectification process, the temperature of the tower bottom liquid is reduced to a certain temperature through a cooler and the tower bottom liquid is injected into the top of the tower as reflux, the temperature of the tower bottom liquid is high and is higher than that of the pressure liquid at the top of the tower, if the temperature is not reduced, more materials are subjected to flash evaporation loss when entering the top of the tower, and if the temperature is too low.
Disclosure of Invention
The invention aims to provide a method and a device for removing dichloromethane in high-boiling-point thermosensitive materials, which adopt an absorption evaporation method to solve the problem that a small amount of dichloromethane in the high-boiling-point thermosensitive materials is difficult to remove in the prior art, and the method has a short process flow, is suitable for materials with the characteristics of high-boiling-point thermosensitive properties and the like, and has high operation flexibility.
The method and the device for removing the dichloromethane in the high-boiling-point heat-sensitive material comprise the following steps:
s1, feeding a material containing dichloromethane to a tower kettle tank through a feeding pump, starting a tower kettle circulating pump, circulating the material between the tower kettle tank and a falling film reboiler, and starting a vacuum system to adjust the pressure in the system at any time, wherein the specific pressure value is related to the content of dichloromethane in the material, namely the tower kettle is ensured not to be over-temperature in the rectification process;
s2, heating the falling film reboiler by using saturated steam or other heat sources, enabling a gas-liquid mixture from the bottom to enter a tower kettle tank, enabling a gas phase to enter a rectifying tower, enabling the gas phase at the top of the tower to pass through a first-stage condenser condensate to be cooled, enabling the condensate to automatically flow through a collector to be collected and extracted, enabling a part of the top of the rectifying tower to flow back through a reflux distributor, extracting a part of the top of the rectifying tower to a receiving tank, and extracting qualified dichloromethane to a dichloromethane tank;
s3, when the content of dichloromethane in the tower bottom liquid is low, the operation pressure is reduced to control the tower bottom temperature, at the moment, the gas phase at the tower top cannot be condensed, namely, no reflux exists, the tower bottom liquid is cooled by a circulating pump through a tower bottom liquid cooler and then is used as reflux to be injected into the top of a rectifying tower, and unqualified dichloromethane is extracted to a transition fraction tank;
and S4, sampling and analyzing the tower bottom liquid, and pumping the qualified tower bottom liquid out of the system through a circulating pump.
The invention aims to provide a method capable of removing dichloromethane in high-boiling-point heat-sensitive materials and a device for the method.
Further, the outlet of the vacuum system is directly connected with a condenser of a vacuum pump, and the condensed feed liquid returns to the raw material tank area.
Preferably, based on the principle of absorption evaporation, when the content of dichloromethane in the tower bottom liquid is low, the system pressure is low, a gas phase led out from the top of the rectifying tower cannot be condensed, no new substance is led in the rectifying process, the temperature of the tower bottom liquid is reduced to 40-80 ℃ through a cooler, and the liquid is fed into the top of the tower as reflux.
Further, the device can adopt a semi-continuous operation mode or an intermittent operation mode, wherein the semi-continuous operation mode comprises the steps of continuously feeding, continuously extracting dichloromethane from the top of the tower, stopping feeding when the liquid level of the tower kettle tank reaches about 80%, and continuously extracting from the top of the tower until the liquid in the tower kettle is qualified; the batch operation mode is batch processing; the semi-continuous operation mode is suitable for materials with high dichloromethane content, and the batch operation mode is suitable for materials with low dichloromethane content.
Furthermore, the rectifying tower reboiler adopts a falling film reboiler, the tube pass operating pressure of the falling film reboiler is 100-2 KPaA, and the material gasification rate of the tube pass is 0.5-0.01.
Further, the operating pressure of the rectifying tower is 100-0.5 KPaA, and the packing of the rectifying tower is efficient regular packing.
Preferably, the temperature of the material discharged from the tower bottom liquid condenser is 40-80 ℃, and the mass ratio of the material to the gas phase at the top of the tower is 0.5-2.
Preferably, the qualified material is extracted from the tower kettle tank under the condition that the device is not stopped, and the extraction is stopped when the liquid level of the tower kettle tank is lower than 10 percent, and then the device is stopped.
Compared with the prior art, the invention has the beneficial effects that:
the method and the device for removing the dichloromethane in the high-boiling-point thermosensitive material can remove the dichloromethane in the high-boiling-point thermosensitive material, the mass fraction of the recycled dichloromethane is more than 99.9%, and the mass fraction of the dichloromethane content in the material is less than 1%.
The invention has simple and short process, is suitable for the materials with wide content range of dichloromethane and heat sensitivity, is convenient to operate and easy to control, and has good economic benefit.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram showing the structure of a method and an apparatus for removing methylene chloride from a high-boiling-point heat-sensitive material according to an embodiment of the present invention;
description of reference numerals:
1-tower kettle tank, 2-falling film reboiler, 3-rectifying tower, 4-first-stage condenser, 5-second-stage condenser, 6-kettle liquid cooler, 7-dichloromethane tank, 8-transition fraction tank and 9-circulating pump
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs.
The following detailed description of specific embodiments of the present invention will be described in further detail with reference to the accompanying drawings, which are provided for illustration of the present invention and are not intended to limit the scope of the present invention.
A method and a device for removing dichloromethane in high-boiling-point heat-sensitive materials comprise the following steps:
and (2) conveying the high-boiling-point heat-sensitive material containing dichloromethane with the mass fraction of 0.05-0.95 to a tower kettle tank through a feeding pump, allowing the material to enter a falling film reboiler through a circulating pump, allowing the material to enter a heat exchange tube through a distributor for film distribution and evaporation, allowing an evaporated gas-liquid mixture to flow out of the bottom of the falling film reboiler, allowing the gas-liquid mixture to automatically flow into a gas tower kettle tank, completing gas-liquid separation at the bottom of the gas tower kettle tank, and allowing a gas phase to enter.
When the content of dichloromethane in the tower kettle tank material is high, the gas phase coming out of the top of the rectifying tower is mainly dichloromethane, and after condensation, one part of the gas phase is extracted into the dichloromethane tank, and the other part of the gas phase is taken as reflux, wherein the reflux ratio is 0.5-3.
As the content of dichloromethane in the tower tank material decreases, the pressure inside the system needs to be reduced to control the temperature of the tower tank to be maintained below the preset temperature, and the temperature at the top of the tower also decreases, so that the reflux is gradually increased.
When the pressure of the system is reduced until the gas phase at the top of the tower can not be condensed, the material in the tower kettle tank is cooled by a cooler through a circulating pump and is sent to the top of the tower as reflux, the temperature is controlled to be 40-80 ℃, the mass ratio of the material to the gas phase at the top of the tower is 0.5-2, and unqualified dichloromethane is extracted from the top of the tower and is sent to a transition fraction tank.
And (3) the material in the tower kettle tank is qualified through sampling analysis, the mass fraction of dichloromethane in the material is lower than 1%, the material is sent out of a boundary region, when the liquid level in the tower kettle tank is as low as 10%, extraction is stopped, heating of a heat source of a falling film reboiler is stopped, and circulation is stopped when the temperature is reduced to a preset value.
In the process of removing dichloromethane from high-boiling-point heat-sensitive materials, the temperature in a tower kettle is controlled, the pressure reduction operation is adopted, the operation pressure is 100-0.5 KPaA, and the operation temperature at the top of the tower is-45-40 ℃. In addition, a feeding pipe, a primary distributor, a secondary distributor and a distribution head are arranged in an upper pipe box of the falling film reboiler, so that the decomposition or polymerization of materials in the evaporation process is avoided.
The rectification column is filled with high-efficiency structured packing, and the structured packing can be plate corrugated packing, wire mesh packing and the like. In addition, if the viscosity of the treated material is too high, a packed tower is not suitable, a plate writing tower can be used, and trays such as sieve tray can be used.
The material is transferred from the column bottom tank to the falling film reboiler and from the column bottom tank to the top of the rectifying column, and the circulating pump may be selected according to the required transfer flow rate and lift, and is not particularly limited. In addition, when the pressure inside the system is reduced, the installation height of the circulating pump only needs to have the capacity of preventing the circulating pump from generating cavitation.
It should be noted that the first-stage condenser and the rectifying tower are directly connected by a flange, the top of the tower is provided with a liquid phase collector, and a certain distance is required between a top extraction port and a reflux port of the tower. In addition, the primary condenser and the secondary condenser are arranged as close as possible in terms of spatial arrangement. In addition, the first-stage condenser to the receiving tank and the second-stage condenser to the receiving tank are all performed by gravity flow, and the relative positions need to be considered in the spatial arrangement.
Examples
The invention will be explained in further detail below with reference to an embodiment example and the accompanying drawings.
The composition of the high boiling point heat sensitive material containing dichloromethane and related parameters are as follows:
the mass fraction of methylene chloride contained was 92%, the throughput was 20 tons per day, and the feed temperature was 30 ℃.
The method and the device shown in the figure are adopted, and the specific parameters are as shown in the table:
by the method and the device, dichloromethane in the high-boiling-point thermosensitive material is removed, dichloromethane is recovered, and a semi-continuous operation mode is adopted, and the method comprises the following four stages:
continuously feeding a material containing 92 mass percent of dichloromethane to a tower kettle tank through a feed pump, starting a circulating pump when the liquid level reaches 60 percent, heating a falling film reboiler, wherein the saturated vapor pressure is 0.3MPa, the total reflux is about 1 hour, the pressure at the top of the tower is normal pressure, the temperature is 39.6 ℃, the temperature of the tower kettle tank is 59 ℃, dichloromethane is extracted from the top of the tower, and the reflux ratio is 0.5.
When the temperature of the tower kettle tank begins to rise to 70 ℃, the vacuum system is utilized to gradually reduce the pressure in the system, the temperature in the tower kettle tank is not higher than 75 ℃, the reflux is gradually increased to about 2, when the pressure in the system is 15Kpa, the capping temperature is-5 ℃, the temperature of the tower kettle is 74 ℃, the extraction is stopped, and the conventional cold source at the tower top is close to the condition that the condensation cannot be realized.
And (3) circularly pumping the tower kettle material to the tower top, cooling by a cooler at the temperature of 60 ℃, the flow rate of 91Kg/h, the temperature of the tower top of 47 ℃, the temperature of the tower kettle of 95 ℃, and switching a receiving tank extracted from the tower top to a transition fraction tank.
And (4) sampling and analyzing the tower kettle tank, if the tower kettle tank is qualified, starting to extract to the outside of a boundary area, stopping extracting when the liquid level of the tower kettle tank is reduced to 10%, stopping heating of a heat source of the falling film reboiler, stopping the circulating pump when the temperature is reduced to 40 ℃, and stopping the device.
By the method and the device for removing the dichloromethane, the content of the dichloromethane in the high-boiling-point thermosensitive material is less than 0.5 percent, and the purity (quality) of the recovered dichloromethane is more than 0.99.
It should be noted that the examples are provided only as illustrative embodiments of the present invention and are not to be construed as limiting; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art; modifications and variations of the present invention that are obvious to those skilled in the art are intended to fall within the scope of the appended claims.
Claims (9)
1. A method and a device for removing dichloromethane in high-boiling-point heat-sensitive materials are characterized by comprising the following steps:
s1, feeding the dichloromethane-containing high-boiling-point heat-sensitive material into a tower kettle tank (1) through a feeding pump, feeding the dichloromethane-containing high-boiling-point heat-sensitive material into a falling film reboiler (2) through a circulating pump (9), and starting a vacuum system to adjust the system pressure at any time;
s2, heating the falling film reboiler by using saturated steam or other heat sources, enabling a gas-liquid mixture from the bottom to enter a tower kettle tank, enabling a gas phase to enter a rectifying tower (3), enabling the gas phase at the top of the tower to pass through a first-stage condenser (4), cooling condensate, automatically flowing the condensate to a collector, collecting and extracting the condensate, enabling a part of the top of the rectifying tower to flow back through a reflux distributor, extracting a part of the top of the rectifying tower to a receiving tank, and extracting qualified dichloromethane to a dichloromethane tank (7);
s3, when the content of dichloromethane in the tower bottom liquid is low, the operation pressure is reduced to control the tower bottom temperature, at the moment, the gas phase at the tower top cannot be condensed, namely, no reflux exists, the tower bottom liquid is cooled by a circulating pump through a tower bottom liquid cooler (6) and then is used as reflux to be injected into the top of the rectifying tower, and unqualified dichloromethane is extracted to a transition fraction tank (8);
and S4, sampling and analyzing the tower bottom liquid, and pumping the qualified tower bottom liquid out of the system through a circulating pump.
2. The method and the device for removing the dichloromethane in the high-boiling-point heat-sensitive material according to claim 1 are characterized by comprising a falling film reboiler (2), a tower kettle tank (1), a rectifying tower (3), a primary condenser (4), a secondary condenser (5), a kettle liquid cooler (6), a dichloromethane tank (7), a transition fraction tank (8) and a circulating pump (9).
The tube pass outlet of the falling film reboiler (2) is connected with the gas-liquid mixing inlet of the tower kettle tank (1), the gas phase outlet of the tower kettle tank (1) is connected with the inlet of the rectifying tower (3), the bottom outlet of the rectifying tower (3) is connected with the liquid phase inlet of the tower kettle tank (1), the bottom outlet of the tower kettle tank (1) is connected with the inlet of the circulating pump (9), and the outlet of the circulating pump (9) is connected with the inlet of the falling film reboiler (2).
The tube side inlet of the first-stage condenser (4) is connected with the gas phase outlet of the rectifying tower (3) through a flange, the tube side outlet of the first-stage condenser (4) is connected with the shell side inlet of the second-stage condenser (5), and the shell side outlet of the second-stage condenser shell side (5) is connected with the inlets of the dichloromethane tank (7) and the transition fraction tank (8).
The outlet of the circulating pump (9) is connected with the shell pass inlet of the tower bottom liquid cooler (6), and the shell pass outlet of the tower bottom liquid cooler (6) is connected with the inlet of the rectifying tower (3).
3. The method and the device for removing the dichloromethane in the high-boiling-point heat-sensitive material as claimed in claim 1, wherein the operation mode can be batch operation or semi-continuous operation.
4. The method and the device for removing dichloromethane in high-boiling-point heat-sensitive materials as claimed in claim 1, wherein the operating pressure of the rectifying tower is 100-0.5 KPaA, and the packing is high-efficiency structured packing.
5. The method and apparatus for removing dichloromethane from high boiling point heat sensitive material as claimed in claim 1, wherein the distillation tower reboiler is a falling film reboiler, the tube side operating pressure is 100-2 KPaA, and the gasification rate of the tube side material is 0.5-0.01.
6. The method and apparatus for removing dichloromethane from a high boiling point heat sensitive material as claimed in claim 3, wherein the dichloromethane content in the feed material in the step S1 is 0.95-0.05.
7. The method and apparatus for removing dichloromethane from high boiling point heat sensitive material as claimed in claim 1, wherein the temperature of the material from the bottom condenser in step S3 is 40-80 ℃, and the mass ratio of the material to the gas phase at the top of the tower is 0.5-2.
8. The method and apparatus for removing dichloromethane from high boiling point heat sensitive material as claimed in claim 1, wherein the step of S4, the extraction of qualified material from the tower tank requires that the apparatus cannot be shut down.
9. The method and the device for removing the dichloromethane in the high-boiling-point heat-sensitive material as claimed in claim 2, wherein the primary condenser and the rectifying tower are directly connected by a flange.
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| CN202010239930.8A CN111514602B (en) | 2020-03-31 | 2020-03-31 | Method and device for removing dichloromethane in high-boiling-point thermosensitive material |
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| CN202010239930.8A CN111514602B (en) | 2020-03-31 | 2020-03-31 | Method and device for removing dichloromethane in high-boiling-point thermosensitive material |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112675667A (en) * | 2020-12-31 | 2021-04-20 | 江苏爱姆欧光电材料有限公司 | Recovery and absorption system and method for chloromethane in alkyl metal production process |
| CN114288699A (en) * | 2021-12-02 | 2022-04-08 | 徐州砥研医药科技有限公司 | Rectification device for preparing benzene-containing medical intermediate and working method thereof |
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