CN111574375A - Separation method and separation equipment for methyl acrylate crude product gas - Google Patents
Separation method and separation equipment for methyl acrylate crude product gas Download PDFInfo
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- CN111574375A CN111574375A CN202010573201.6A CN202010573201A CN111574375A CN 111574375 A CN111574375 A CN 111574375A CN 202010573201 A CN202010573201 A CN 202010573201A CN 111574375 A CN111574375 A CN 111574375A
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- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 title claims abstract description 272
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- 238000010533 azeotropic distillation Methods 0.000 claims abstract description 135
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 129
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- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
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- BHIWKHZACMWKOJ-UHFFFAOYSA-N methyl isobutyrate Chemical compound COC(=O)C(C)C BHIWKHZACMWKOJ-UHFFFAOYSA-N 0.000 description 2
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
- C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
- C07C67/58—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
Abstract
The invention provides a separation method and equipment of crude methyl acrylate product gas, wherein the method comprises the following steps: carrying out light component removal treatment on crude methyl acrylate product gas; carrying out azeotropic distillation treatment on the methyl acrylate crude product gas after light component removal to remove formaldehyde and heavy ester components; the compressed vapor at the top of the tower subjected to azeotropic rectification is used as a heat source of a reboiler for light component removal treatment; extracting and rectifying the formaldehyde solution obtained by azeotropic distillation by using water to remove a methanol component; extracting the formaldehyde solution after the extraction and rectification treatment, extracting the formaldehyde solution by using a first extracting agent to remove heavy ester components in the formaldehyde solution, and extracting an oil phase by using a second extracting agent to remove formaldehyde; carrying out heavy component removal treatment on the oil phase obtained by the extraction treatment, and recovering light ester and water respectively as an extracting agent for the extraction treatment; and (4) carrying out steam stripping treatment on the water phase obtained by the extraction treatment. The invention can obviously reduce the energy consumption of the device and reduce the cost.
Description
Technical Field
The invention relates to the technical field of ester-aldol system separation, in particular to a separation method and separation equipment for crude product gas of coal-based methyl acetate and methyl acrylate prepared from formaldehyde.
Background
In both the polyvinyl alcohol and terephthalic acid production processes, a large amount of methyl acetate is produced as a by-product. The alcoholysis waste liquid of 1.6 tons of methyl acetate is produced as a byproduct in every 1 ton of polyvinyl alcohol production, and the main components of the alcoholysis waste liquid are more than 75% of methyl acetate and less than 25% of methanol. Because methyl acetate and methanol can form an azeotrope, methyl acetate is often required to be purified by a separation method with high energy consumption, long flow and high cost, but as methyl acetate and methanol in China enter a serious surplus period, the economic benefit of separating methyl acetate and methanol from alcoholysis waste liquid is not obvious, so that good economic benefit and social benefit can be achieved if a byproduct, namely methyl acetate, is directly converted into a product with high added value without purification.
Methyl acrylate is an important synthetic intermediate and a monomer for synthesizing high molecular polymers, and is widely applied to the industries of chemical fibers, textiles, rubber, medicines, resins, papermaking, adhesives, coatings, leather and the like. At present, methyl acrylate is mainly prepared by adopting a propylene oxidation method suitable for large-scale production, a propylene route method seriously depends on petroleum refining products, in recent years, the petroleum import quantity in China is continuously increased, the external dependence is increased year by year, and the international crude oil market is complex and sensitive.
In addition, with the vigorous development of the coal chemical industry, the formaldehyde in the domestic mature coal-based route has excess capacity, so that the development of the route for synthesizing methyl acrylate from coal-based methyl acetate and formaldehyde has important significance.
In recent years, research works of synthesizing Methyl Acrylate (MA) by taking methyl acetate and formaldehyde as raw materials and then preparing Methyl Propionate (MP) by hydrogenating methyl acrylate so as to prepare Methyl Methacrylate (MMA) with high added value are carried out by many scientific research units at home and abroad. The synthesis of MA by using methyl acetate and formaldehyde as raw materials and methanol as a solvent is the most critical step in the MMA technical route, and can be called as the bottleneck of preparing MMA from coal-based methyl acetate and formaldehyde. The crude methyl acrylate product gas contains a small amount of impurities such as methacrolein, methyl propionate, methyl methacrylate, acetic acid, heavy esters and the like besides water produced in the main reaction, methanol used as a solvent for the reaction, and unreacted methyl acetate and formaldehyde. And the boiling point of MA is close to that of the impurities, or because MA and the impurities form a plurality of groups of azeotropic systems, the traditional separation method is difficult to recover high-purity MA from MA crude product gas, in addition, high-concentration MA is easy to polymerize, and the separation and purification difficulty of MA crude product gas is increased due to the characteristic that unreacted formaldehyde is easy to polymerize at low temperature. Therefore, a method for separating crude methyl acrylate product gas with low energy consumption, low investment and high recovery rate of each component is needed.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a method and equipment for separating crude product gas of methyl acrylate (MA for short), which have the characteristic of low energy consumption.
In one aspect, an embodiment of the present invention provides a method for separating a crude methyl acrylate product gas, including:
carrying out light component removal treatment on crude methyl acrylate product gas, and recovering light components as raw materials;
carrying out azeotropic rectification treatment on the methyl acrylate crude product gas after light component removal to remove formaldehyde and heavy ester components; wherein, the gas phase at the top of the azeotropic distillation tower is compressed and heated to be used as a reboiler heat source for light component removal treatment;
carrying out extractive distillation treatment on the formaldehyde solution obtained by azeotropic distillation treatment by using water so as to remove a methanol component in the formaldehyde solution;
extracting the formaldehyde solution subjected to extractive distillation and methanol removal, wherein a first extracting agent is used for extracting the formaldehyde solution to remove heavy ester components in the formaldehyde solution, and a second extracting agent is used for extracting an oil phase to remove formaldehyde;
carrying out weight removal treatment on the oil phase obtained by the extraction treatment, and recovering light ester and water to be respectively used as the first extracting agent and the second extracting agent of the extraction treatment; wherein, the intermediate reboiler for the weight removal treatment adopts the tower top gas phase of the weight removal treatment as a heat source after being compressed and heated;
and (4) carrying out steam stripping treatment on the water phase obtained by the extraction treatment so as to recover the light ester component and obtain the dilute formaldehyde aqueous solution at the bottom of the tower.
In some embodiments, the methyl acrylate raw product gas is subjected to a de-lightening process comprising:
cooling the methyl acrylate crude product gas to a preset temperature, and enabling the methyl acrylate crude product gas to enter a lightness-removing tower in a gas phase state for lightness-removing treatment;
cooling the gas phase at the top of the light component removal tower to a preset temperature by an air cooler, allowing the gas phase to enter a light component removal tower reflux tank, allowing the condensate in the light component removal tower reflux tank to return to the light component removal tower as reflux, cooling the gas phase component at the top of the light component removal tower to the preset temperature by water, allowing the condensate in the light component removal tower top tank to return to a methyl acrylate reaction unit as a recovered light component;
and (4) performing azeotropic distillation treatment on the light component removal tower bottom liquid after pressure increase by a pump.
In some embodiments, the methyl acrylate raw product gas after light component removal is subjected to azeotropic distillation treatment, which comprises:
after the crude product gas of methyl acrylate is subjected to lightness removing treatment, the crude product gas is sent to an azeotropic rectifying tower for azeotropic rectification after pressure increase;
after the gas phase at the top of the tower after the azeotropic distillation treatment is subjected to heat exchange by the light component removal tower reboiler, the gas phase is cooled to a preset temperature by water and enters a reflux tank of the azeotropic distillation tower, a part of condensate in the reflux tank of the azeotropic distillation tower is used as reflux to return to the azeotropic distillation tower, and the other part of condensate is sent to a downstream methyl acrylate hydrogenation unit;
an azeotropic distillation tower reboiler of the azeotropic distillation tower can adopt low-pressure steam as a heat source;
and the tower bottom liquid of the azeotropic distillation tower is subjected to extraction and distillation treatment after being subjected to pressure increase by a pump.
In some embodiments, the formaldehyde solution obtained by the azeotropic distillation treatment is subjected to extractive distillation treatment by using water, and the extractive distillation treatment comprises the following steps:
carrying out pressure raising on the formaldehyde solution obtained by azeotropic distillation treatment, and then sending the formaldehyde solution to an extraction and distillation tower for extraction and distillation treatment;
cooling the gas phase at the top of the extractive distillation tower to a preset temperature by adopting an air cooler, wherein one part of the obtained condensate is used as reflux, and the other part of the obtained condensate is used as a methanol solvent and returns to the methyl acrylate reaction unit;
a reboiler of the extractive distillation column can adopt low-pressure steam as a heat source;
and cooling the formaldehyde-rich solution at the bottom of the extraction and rectification tower by circulating water, and performing extraction treatment after the formaldehyde-rich solution is subjected to pressure increase by a pump.
In some embodiments, the oil phase from the extraction process is subjected to a de-weighting process comprising:
feeding the heavy ester oil-rich phase obtained from the extraction treatment into a de-weighting tower to remove heavy components in the oil phase and recovering an extracting agent;
compressing and heating the top gas phase of the de-heavy tower to serve as a heat source of a boiler in the de-heavy tower of the de-heavy tower, cooling the top gas phase of the de-heavy tower subjected to heat exchange by the boiler in the de-heavy tower to a preset temperature by water, entering a reflux tank of the de-heavy tower for oil-water stratification, returning one part of the oil phase subjected to pressure boosting to the de-heavy tower as reflux, returning the other part of the oil phase subjected to pressure boosting to the bottom of the extraction tower as a first extractant, and returning the water phase subjected to pressure boosting to the top of the extraction tower as a second extractant;
a reboiler of the heavy component removal tower can adopt low-pressure steam as a heat source;
and (4) recovering heavy components in the tower kettle of the de-heavy tower.
In some embodiments, the aqueous phase from the extraction treatment is subjected to a stripping treatment comprising:
feeding the dilute formaldehyde solution obtained from the extraction treatment into a stripping tower to remove light ester components in the formaldehyde aqueous solution;
the gas phase at the top of the stripping tower is cooled to a preset temperature through circulating water, and the condensate is returned to the extraction tower after being pressurized;
a reboiler of a stripping tower of the stripping tower can adopt low-pressure steam as a heat source, and tower bottom liquid of the stripping tower is pumped to a dilute formaldehyde recovery system.
In some embodiments, the azeotropic distillation and the extractive distillation are performed by using a baffle distillation tower, a vertical baffle is arranged in the middle of the baffle distillation tower, the distillation tower is divided into an upper public distillation section, a lower public distillation section, and a distillation feed section and a side draw section which are arranged at two sides of the baffle, the crude methyl acrylate gas after the light component removal treatment and water used as an extracting agent enter from the distillation feed section, and the distillation feed section plays the role of a primary distillation tower to complete the separation of light components and heavy components; separating light components and intermediate components in the public rectification section, and compressing and heating the gas at the top of the tower to be used as a heat source of a reboiler of the light component removal tower; separating intermediate components and heavy components in the public stripping section, cooling the formaldehyde-rich solution in the tower kettle by water, and then sending the solution to the extraction treatment; the intermediate component methanol is obtained at the side line extraction section.
In a second aspect, an embodiment of the present invention provides a separation apparatus for a crude methyl acrylate product gas, including:
the light component removal tower system is used for carrying out light component removal treatment on crude methyl acrylate product gas, and light components are recovered as raw materials;
the rectifying tower system is connected with the light component removal tower system and is used for carrying out azeotropic rectification treatment and extractive rectification treatment on the crude methyl acrylate product gas after the light component removal treatment; wherein the azeotropic distillation treatment is carried out to remove formaldehyde and heavy ester components; the compressed vapor at the top of the tower subjected to azeotropic rectification is used as a heat source of a reboiler of the light component removal tower system; adopting water as an extracting agent to carry out extractive distillation treatment on the formaldehyde solution obtained by azeotropic distillation treatment so as to remove a methanol component in the formaldehyde solution;
the extraction tower is connected with the rectifying tower system and is used for extracting the formaldehyde solution obtained by the extraction and rectification treatment, wherein the formaldehyde solution is extracted by adopting a first extracting agent to remove heavy ester components in the formaldehyde solution, and the oil phase is subjected to formaldehyde removing treatment by adopting a second extracting agent;
a de-weighting tower system connected with the extraction tower and used for performing de-weighting treatment on the oil phase obtained by the extraction treatment and recovering light ester and water as the first extractant and the second extractant of the extraction treatment respectively; the middle reboiler heat source of the heavy component removal tower system adopts the tower top gas phase of the heavy component removal tower system as the heat source after compression and temperature rise;
and the stripping tower system is connected with the extraction tower and is used for carrying out stripping treatment on the water phase obtained by the extraction treatment so as to recover light ester components and obtain a dilute formaldehyde aqueous solution at the bottom of the tower.
In some embodiments, the light ends removal column system comprises:
the light component removal tower is used for carrying out light component removal treatment on crude methyl acrylate product gas which is cooled to a preset temperature and enters the light component removal tower in a gas phase state; pumping the tower bottom liquid of the light component removal tower, and then feeding the tower bottom liquid into the rectifying tower system for azeotropic rectification;
a light component removal tower reboiler which is connected with the light component removal tower and heats tower bottom liquid of the light component removal tower by taking tower top compressed steam subjected to azeotropic rectification as a heat source;
the light component removal tower top air cooler is connected with the top of the light component removal tower and is used for cooling the top gas phase of the light component removal tower to a preset temperature;
a light component removal tower reflux tank which is connected with the light component removal tower top air cooler and is used for accommodating the tower top gas phase of the light component removal tower cooled by the light component removal tower air cooler, and the condensate in the light component removal tower reflux tank is returned to the light component removal tower as reflux;
the top water cooler of the light component removal tower is connected with the reflux tank of the light component removal tower and is used for cooling the top gas-phase components of the reflux tank of the light component removal tower to a preset temperature;
and the top tank of the light component removal tower is connected with the water cooler at the top of the light component removal tower and is used for accommodating the top gas-phase components of the reflux tank of the light component removal tower after the water cooler at the top of the light component removal tower is cooled, and the condensate of the top tank of the light component removal tower is used as the recovered light components and is returned to the methyl acrylate reaction unit.
In some embodiments, the rectification column system comprises an azeotropic rectification column system for performing the azeotropic rectification process, the azeotropic rectification column system comprising:
the azeotropic distillation tower is connected with the light component removal tower system and is used for carrying out azeotropic distillation treatment on the methyl acrylate crude product gas after light component removal; the tower kettle of the azeotropic distillation tower is connected with the extraction distillation tower, so that tower kettle liquid of the azeotropic distillation tower is pumped and enters the extraction distillation tower for extraction distillation treatment;
the azeotropic distillation tower top gas compressor is connected with the tower top of the azeotropic distillation tower and is used for compressing and heating the tower top gas phase of the azeotropic distillation tower to be used as a reboiler heat source of the light component removal tower system;
the azeotropic distillation tower water cooler is connected with the light component removal tower reboiler and is used for cooling the tower top gas phase of the azeotropic distillation tower subjected to heat exchange by the reboiler of the light component removal tower system to a preset temperature;
the reflux tank of the azeotropic distillation tower is connected with the water cooler of the azeotropic distillation tower and is used for accommodating the overhead gas of the azeotropic distillation tower after the water cooler of the azeotropic distillation tower is cooled; one part of condensate in the reflux tank of the azeotropic distillation tower is returned to the azeotropic distillation tower as reflux, and the other part of condensate is sent to a downstream methyl acrylate hydrogenation unit;
and the azeotropic distillation tower reboiler is connected with the azeotropic distillation tower and used for providing heat energy for the azeotropic distillation tower, and the azeotropic distillation tower reboiler is connected with a low-pressure steam pipeline.
In some embodiments, the rectification column system comprises an extractive rectification column system, the extractive rectification column system uses water as an extractant to perform extractive rectification treatment on the formaldehyde solution obtained from the azeotropic rectification treatment, and the extractive rectification column system comprises:
the extraction and rectification tower is connected with the tower kettle of the azeotropic rectification tower and is used for carrying out extraction and rectification treatment on the formaldehyde solution obtained by the azeotropic rectification treatment;
the water cooler is connected with the kettle of the extraction and rectification tower, so that the formaldehyde-rich solution at the kettle of the extraction and rectification tower is cooled by circulating water, is subjected to pressure raising by a pump and then enters the extraction tower for extraction treatment;
the extraction and rectification tower condenser is connected with the top of the extraction and rectification tower and is used for cooling the top gas phase of the extraction and rectification tower to a preset temperature;
the reflux tank of the extraction and rectification tower is connected with the condenser of the extraction and rectification tower and is used for containing the overhead gas of the extraction and rectification tower after the condenser of the extraction and rectification tower is cooled, one part of condensate in the reflux tank of the extraction and rectification tower is returned to the extraction and rectification tower as reflux, and the other part of condensate is returned to the methyl acrylate reaction unit as a methanol solvent;
and the extraction and rectification tower reboiler is connected with the extraction and rectification tower and used for providing heat energy for the extraction and rectification tower, and the extraction and rectification tower reboiler is connected with a low-pressure steam pipeline.
In some embodiments, the de-heavies column system comprises:
the heavy component removing tower is connected with the extraction tower and is used for removing heavy components from the heavy ester-rich oil phase obtained by extraction treatment and recovering an extracting agent;
the top gas compressor of the de-heavy tower is connected with the de-heavy tower and is used for compressing and heating the top gas phase of the de-heavy tower;
the heavy component removal tower middle boiling device is connected with the heavy component removal tower top gas compressor, so that the tower top gas phase of the heavy component removal tower after being compressed and heated by the heavy component removal tower top gas compressor enters the heavy component removal tower middle boiling device as a heat source;
the heavy component removal tower top water cooler is connected with the heavy component removal tower middle boiler and is used for cooling the tower top gas phase of the heavy component removal tower subjected to heat exchange by the heavy component removal tower middle boiler to a preset temperature;
the heavy component removal tower reflux tank is connected with the heavy component removal tower top water cooler and is used for accommodating the tower top gas phase of the heavy component removal tower cooled by the heavy component removal tower top water cooler, the cooled tower top gas phase of the heavy component removal tower is subjected to oil-water stratification in the heavy component removal tower reflux tank, one part of the oil phase after being boosted is returned to the heavy component removal tower as reflux, the other part of the oil phase as a first extractant is returned to the bottom of the extraction tower, and the water phase after being boosted is returned to the top of the extraction tower as a second extractant;
and the heavy component removal tower reboiler is connected with the heavy component removal tower and used for providing heat energy for the heavy component removal tower, and a low-pressure steam pipeline is connected onto the heavy component removal tower reboiler.
In some embodiments, the stripper system comprises:
the stripping tower is connected with the extraction tower and is used for carrying out stripping treatment on the dilute formaldehyde solution obtained by the extraction treatment so as to remove light ester components in the formaldehyde solution; the tower kettle of the stripping tower is connected to a dilute formaldehyde recovery system through a pump;
the stripper condenser is connected with the top of the stripper and is used for cooling the gas phase at the top of the stripper to a preset temperature by water;
the stripper tower top tank is connected with the stripper tower condenser and used for accommodating the tower top gas phase of the stripper tower cooled by the stripper tower condenser, and the condensate in the stripper tower top tank is returned to the lower part of the extraction tower after being boosted;
and the stripping tower reboiler is connected with the stripping tower and used for providing heat energy for the stripping tower, and a low-pressure steam pipeline is connected to the stripping tower reboiler.
In some embodiments, the rectifying column system comprises a baffle rectifying column for performing azeotropic rectification treatment and extractive rectification treatment, a vertical baffle is arranged in the middle of the baffle rectifying column, the baffle divides the rectifying column into an upper public rectifying section, a lower public stripping section, a rectifying feed section and a side draw section which are positioned on two sides of the baffle, the crude methyl acrylate gas after light removal treatment and water as an extractant enter from the rectifying feed section, and the rectifying feed section is used as a primary fractionating column for performing primary fractionation to complete separation of light components and heavy components; the separation of light components and intermediate components is realized in the public rectification section, and the gas phase at the top of the clapboard rectification tower is compressed and heated and then enters a reboiler of the light component removal tower as a heat source; the separation of intermediate components and heavy components is realized in the common stripping section, and a tower kettle of the clapboard rectifying tower is connected with a kettle liquid water cooler of the extraction rectifying tower, so that the cooled formaldehyde-rich solution is extracted in the extraction tower; the side draw section is connected to a methyl acrylate reaction unit.
The separation method of methyl acrylate crude product gas provided by the embodiment of the invention can almost completely remove impurities such as methyl acetate, formaldehyde, water, methanol, methacrolein, methyl methacrylate, acetic acid, heavy ester and the like without losing MA, and trace MP enters a downstream MA hydrogenation MP preparation unit along with the MA product. In addition, the MA crude product gas (especially the MA crude product gas prepared by adopting coal-based methyl acetate and formaldehyde) separation method provided by the invention adopts a double-tower coupling heat pump formed by taking tower top compressed steam subjected to extractive distillation, double-solvent extraction and azeotropic distillation as a reboiler heat source for light component removal treatment, single-tower heat pump distillation formed by coupling tower top steam and an intermediate reboiler and an advanced partition plate distillation technology, so that the technical problem of high separation cost caused by low MA concentration in the MA crude product gas is solved.
Drawings
In the drawings, which are not necessarily drawn to scale, like reference numerals may describe similar components in different views. Like reference numerals having letter suffixes or different letter suffixes may represent different instances of similar components. The drawings illustrate various embodiments generally by way of example and not by way of limitation, and together with the description and claims serve to explain the disclosed embodiments. The same reference numbers will be used throughout the drawings to refer to the same or like parts, where appropriate. Such embodiments are illustrative, and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.
FIG. 1 is a flow chart of a process for the separation of a crude methyl acrylate product gas according to a first embodiment of the present invention;
FIG. 2 is a schematic view of a methyl acrylate raw product gas separation apparatus according to a first embodiment of the present invention;
FIG. 3 is a schematic view of a methyl acrylate raw product gas separation apparatus according to a second embodiment of the present invention;
figure 4 is a table of key stream results for a 4.6 million tons MA/year methyl acrylate raw product gas separation process provided by one embodiment of the present invention.
In the figure: 1-a light ends removal column system; 2-azeotropic distillation column system; 3-extractive distillation column system; 4-an extraction column; 5-a de-heaving column system; 6-a stripper system; 7-a baffle rectification column; 11-a light component removal tower; 12-a light ends removal column reboiler; 13-a light component removal tower top air cooler; 14-a light component removal tower reflux tank; 15-a water cooler at the top of the light component removal tower; 16-a light component removal tower top tank; 21-azeotropic distillation column; 22-azeotropic distillation column reboiler; 23-azeotropic distillation column overhead gas compressor; 24-azeotropic distillation column water cooler; 25-azeotropic distillation column reflux drum; 31-extractive distillation column; 32-extractive distillation column reboiler; 33-an extractive distillation column condenser; 34-reflux tank of extractive distillation column; 35-extracting rectifying tower bottom liquid water cooler; 51-a de-weighting tower; 52-a de-heavies column reboiler; 53-de-weighting overhead gas compressor; 54-a reboiler in the de-heavy column; 55-a water cooler at the top of the de-weighting tower; 56-heavy column reflux tank; 61-a stripper column; 62-stripper reboiler; 63-stripper condenser; 64-stripper overhead tank; 71-a common rectification section; 72-common stripping section; 73-a rectifying feed section; 74-side draw section; 75-a baffle rectifier compressor; 76-a water cooler on the top of the baffle rectification tower; 77-baffle rectification column reflux tank; 78-baffle rectifying column reboiler; 79-a water cooler for the bottom liquid of the clapboard rectifying tower.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings and the detailed description of embodiments of the invention, but is not intended to limit the invention.
The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element preceding the word covers the element listed after the word, and does not exclude the possibility that other elements are also covered. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
In the present invention, when it is described that a specific device is located between a first device and a second device, there may or may not be an intervening device between the specific device and the first device or the second device. When a particular device is described as being coupled to other devices, that particular device may be directly coupled to the other devices without intervening devices or may be directly coupled to the other devices with intervening devices.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs unless specifically defined otherwise. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
FIG. 1 is a flow chart of a method for separating crude product gas of methyl acrylate prepared from coal-based methyl acetate and formaldehyde according to an embodiment of the present invention; FIG. 2 is a schematic view of a methyl acrylate raw product gas separation apparatus according to a first embodiment of the present invention; FIG. 3 is a schematic view of a methyl acrylate raw product gas separation apparatus according to a second embodiment of the present invention. The devices shown in fig. 2 and 3 may implement the separation method of embodiments of the present invention. Referring to fig. 1 to 3, a method for separating a crude gas of methyl acrylate according to an embodiment of the present invention includes:
s1, carrying out light component removal treatment on crude methyl acrylate product gas, and recovering light components as raw materials;
s2, carrying out azeotropic rectification treatment on the methyl acrylate crude product gas after light component removal to remove formaldehyde and heavy ester components; wherein, the gas phase at the top of the azeotropic distillation tower is compressed and heated to be used as a reboiler heat source for light component removal treatment;
s3, performing extractive distillation treatment on the formaldehyde solution obtained by azeotropic distillation treatment by using water to remove a methanol component in the formaldehyde solution;
s4, carrying out extraction treatment on the formaldehyde solution subjected to extraction and rectification treatment and methanol removal, wherein a first extraction agent is adopted to extract the formaldehyde solution so as to remove organic components such as heavy ester, acetic acid and the like in the formaldehyde solution, and a second extraction agent is adopted to extract an oil phase so as to remove formaldehyde;
s5, carrying out heavy oil removal treatment on the oil phase obtained by the extraction treatment, and recovering light ester and water to be respectively used as the first extracting agent and the second extracting agent of the extraction treatment; wherein, the intermediate reboiler for the weight removal treatment adopts the tower top gas phase of the weight removal treatment as a heat source after being compressed and heated;
and S6, carrying out steam stripping treatment on the water phase obtained by the extraction treatment to recover the light ester component, thereby obtaining the dilute formaldehyde water solution at the bottom of the tower.
In the method for separating crude methyl acrylate product gas, which is particularly prepared from coal-based methyl acetate and formaldehyde, provided by the embodiment of the invention, the double-tower coupling heat pump formed by using the tower top compressed steam subjected to extractive distillation, double-solvent extraction and azeotropic distillation as the heat source of the reboiler subjected to light component removal treatment and the single-tower heat pump for rectifying the tower top steam coupled with the intermediate reboiler are adopted, so that the technical problem of high separation cost caused by low concentration of MA in the MA crude product gas is solved. The method for separating the crude product gas of methyl acrylate provided by the invention can almost completely remove impurities such as methyl acetate, formaldehyde, water, methanol, methacrolein, methyl methacrylate, acetic acid, heavy ester and the like without losing methyl acrylate, and trace MP enters a downstream MA hydrogenation MP preparation unit along with the MA product.
In some embodiments, in step S1, the high-temperature crude methyl acrylate gas from the MA reaction unit is cooled to a predetermined temperature, for example, 90 to 150 ℃, so that the crude product gas enters the lightness-removing column 11 in a gaseous state for lightness-removing treatment, thereby reducing the steam consumption of the reboiler 12 of the lightness-removing column connected to the column bottom and saving the energy consumption of the apparatus. The operating pressure range value of the light component removal tower 11 can be 0.05-0.40MPaG, the range is suitable for the separation process of light components in the crude product gas, and waste caused by overlarge pressure rise can be avoided.
In some embodiments, step S1 further includes: cooling the top gas phase of the light component removal tower 11 to a preset temperature, such as 50-90 ℃, by using a light component removal tower top air cooler 13, returning condensate generated by cooling the top gas phase of the light component removal tower 11 to the light component removal tower 11 as reflux, cooling the gas to the preset temperature, such as 30-60 ℃, by using a light component removal tower top water cooler 15, then entering a light component removal tower top tank 16, and returning the bottom condensate of the light component removal tower top tank 16 to the MA reaction unit as a raw material for recovering methyl acetate. Because the tower top adopts a two-stage condensation scheme, most of methyl acetate and methanol are condensed in the first stage, most of heat load is concentrated, and the final heat transfer temperature of the first stage condensation is higher, so that a more energy-saving air cooling scheme can be adopted, the consumption of circulating water of a condenser of the lightness-removing tower 11 is greatly reduced, and the energy consumption of the whole device can be reduced.
In some embodiments, in step S1, the heat source of the reboiler 12 of the light component removal column is vapor compressed and heated at the top of the column for azeotropic distillation, so as to form a double-column coupled heat pump system, which can greatly save energy consumption; the residue in the light component removal tower 11 is pumped and then sent to an azeotropic distillation tower 21 for azeotropic distillation treatment.
In some embodiments, in step S2, the crude MA product gas after light component removal is subjected to azeotropic distillation to remove unreacted formaldehyde and heavy ester components in the product gas, the mixture of MA and methanol distilled from the top of the column is sent to a downstream MA hydrogenation unit, and the bottoms is pumped to the extractive distillation column 31 for extractive distillation. Because the mixture of MA and methanol is distilled from the top of the tower, the risk of high-concentration MA polymerization is avoided, and the methanol brought downstream along with MA does not influence the reaction of preparing MP by MA hydrogenation. This separation scheme avoids the use of energy intensive MA purification schemes due to the azeotrope formed by MA and methanol.
In some embodiments, in step S2, the overhead gas phase of the azeotropic distillation process is compressed and heated to serve as a heat source for the light component removal column reboiler 12, thereby forming a double column coupled heat pump distillation system. Therefore, the condition that the high-grade steam energy is used by the light component removal tower reboiler 12 is avoided, the circulating water consumption of the azeotropic distillation tower condenser is greatly reduced, and the energy-saving effect of the whole device is obvious only at the cost of consuming a small amount of compression work.
The azeotropic distillation column reboiler 22 may use low pressure steam as a heat source; the column bottom liquid of the azeotropic distillation column 21 is pumped to carry out extraction and distillation treatment.
In some examples, in step S3, the MA-removed formaldehyde solution is subjected to extractive distillation to remove methanol components from the formaldehyde solution. Wherein, water is used as an extracting agent to wash the methanol gas phase in the azeotropic distillation section so as to avoid the methanol fraction at the top of the tower from carrying formaldehyde components. The dosage (mass) of the extractant water is 0.3 to 10 times of the feeding amount (mass). The extractive distillation tower 31 can be operated at normal pressure, the steam at the top of the extractive distillation tower 31 can be cooled by an air cooler, one part of the cooled condensate is returned to the tower as reflux, and the other part of the cooled condensate is returned to the MA reaction unit as a recovered methanol solvent. The heat source of the reboiler 32 of the extractive distillation column can adopt low-pressure steam, and the bottom liquid of the extractive distillation column 31 is cooled to 30-50 ℃ by circulating water and then is pumped to remove pressure from the extraction column 4.
In some embodiments, in step S4, the formaldehyde-rich solution in the bottom of the extractive distillation column 31 is subjected to an extraction treatment with an ester (first extractant) to remove organic components such as heavy esters and acetic acid from the formaldehyde solution. The first extractant used is lighter methyl propionate, methyl acrylate, methyl isobutyrate, for example, methyl propionate can be selected as the first extractant. The dosage (mass) of the first extractant ester is 0.2 to 8 times of the feeding quantity (mass). The oil phase at the top of the tower is subjected to a formaldehyde removing treatment by using water (second extractant) so as to avoid the formaldehyde component from being brought into a downstream weight removing treatment (weight removing tower 51). The dosage (mass) of the second extractant water is 0.1 to 6 times of the feeding amount (mass). The light components from stripper 61 are returned to the lower portion of extractor 4 for re-separation to reduce the loss of the first extractant (ester). A small amount of water from de-heaving column 51 is returned to extraction column 4 as the second extractant. The extraction column 4 can be a rotating disc column, the operation temperature of the extraction column 4 can be 30-50 ℃, and the operation pressure can be 0.30-0.90 MPaG.
In some embodiments, in step S5, the oil phase from the top of the extraction column 4 is subjected to a de-weighting treatment by the de-weighting column 51, and the de-weighting column 51 has a recovery effect of the extractant. The de-heavy tower 51 can be operated at normal pressure, and for further energy saving, the de-heavy tower 51 is provided with a middle boiler, and the steam at the top of the de-heavy tower 51 is compressed and then used as the heat source of a middle boiler 54 of the de-heavy tower, so that the steam consumption of a reboiler 52 of the de-heavy tower is greatly reduced, and the circulating water consumption of a condenser of the de-heavy tower 51 is also reduced. The overhead gas of the de-weighting tower 51 after heat exchange by a boiler 54 in the de-weighting tower is cooled to a preset temperature, such as 30-50 ℃, and then enters a reflux tank 56 of the de-weighting tower, condensate is subjected to oil-water phase splitting operation in the reflux tank 56 of the de-weighting tower, one part of the oil phase after pressure increase is returned to the tower as reflux, the other part of the oil phase as a first extractant (ester) is returned to the bottom of the extraction tower 4, and the water phase after pressure increase is returned to the top of the extraction tower 4 as a second extractant (water). The heat source of the reboiler 52 of the heavy component removal tower can adopt low-pressure steam, and the heavy component at the tower bottom of the heavy component removal tower 51 can be further recycled and treated as a byproduct after the pressure is increased by a pump.
In some embodiments, in step S6, the dilute formaldehyde solution from the bottom of the extraction tower 4 is stripped by the stripping tower 61 to remove light ester components in the formaldehyde aqueous solution; the stripping column 61 may be operated at atmospheric pressure, and the overhead steam of the stripping column 61 is cooled to a predetermined temperature, for example, 30 to 50 ℃ by circulating water, and the condensate obtained by cooling is returned to the lower part of the extraction column 4 after being pressurized for ester recovery. The tower bottom liquid of the stripping tower 61 is pumped to a dilute formaldehyde recovery system.
As shown in fig. 2 to 3, the embodiment of the present invention also provides a separation apparatus for a crude methyl acrylate product gas, which can implement the separation method of the above embodiment, and the following embodiment of the separation apparatus can be used to understand the embodiment of the separation method, and the embodiment of the separation method can also be used to explain the embodiment of the separation apparatus.
Referring to fig. 2 and 3, an apparatus for separating a crude methyl acrylate product gas according to an embodiment of the present invention includes:
a light component removal tower system 1 for removing light components from the crude methyl acrylate product gas, and recovering light components as raw materials;
the rectifying tower system is connected with the light component removal tower system 1 and is used for carrying out azeotropic rectification treatment and extractive rectification treatment on the crude methyl acrylate product gas after the light component removal treatment; wherein, the azeotropic distillation treatment is carried out to remove heavy components such as formaldehyde, heavy ester and the like; the compressed vapor at the top of the tower subjected to azeotropic rectification is used as a heat source of a reboiler of the light component removal tower system 1; adopting water as an extracting agent to carry out extractive distillation treatment on the formaldehyde solution obtained by azeotropic distillation treatment so as to remove a methanol component in the formaldehyde solution;
the extraction tower 4 is connected with the rectifying tower system and is used for extracting the formaldehyde solution obtained by the extraction and rectification treatment, wherein the formaldehyde solution is extracted by adopting a first extracting agent to remove organic components such as heavy ester, acetic acid and the like in the formaldehyde solution, and the oil phase is subjected to formaldehyde removing treatment by adopting a second extracting agent;
the de-weighting tower system 5 is connected with the extraction tower 4 and is used for carrying out de-weighting treatment on the oil phase obtained by the extraction treatment and recovering light ester and water which are respectively used as a first extractant and a second extractant of the extraction treatment; the middle reboiler heat source of the heavy component removal tower system 5 adopts the tower top gas phase of the heavy component removal tower system 5 as the heat source after compression and temperature rise;
and the stripping tower system 6 is connected with the extraction tower 4 and is used for carrying out stripping treatment on the water phase obtained by the extraction treatment so as to recover light ester components and obtain the dilute formaldehyde aqueous solution at the bottom of the tower.
According to the separation equipment for the crude methyl acrylate product gas prepared from the coal-based methyl acetate and the formaldehyde, the double-tower coupling heat pump formed by using the extractive distillation, the double-solvent extraction tower 4 and the tower top compressed steam subjected to azeotropic distillation as the heat source of the reboiler of the light component removal tower system 1 and the heavy component removal tower system 5 formed by coupling the tower top steam and the intermediate reboiler are adopted, so that the technical problem that the separation cost is high due to the fact that the concentration of MA in the MA crude product gas is low is solved. The methyl acrylate crude product gas separation equipment provided by the invention can almost completely remove impurities such as methyl acetate, formaldehyde, water, methanol, methacrolein, methyl methacrylate, acetic acid, heavy ester and the like without losing methyl acrylate, and a trace amount of MP enters a downstream MA hydrogenation MP preparation unit along with a MA product.
In some embodiments, referring to fig. 1 and 2, the lightness-removing column system 1 comprises a lightness-removing column 11, a lightness-removing column reboiler 12, a lightness-removing column overhead air cooler 13, a lightness-removing column reflux drum 14, a lightness-removing column overhead water cooler 15, and a lightness-removing column overhead drum 16.
And the light component removal tower 11 is used for performing light component removal treatment on crude methyl acrylate product gas which is cooled to a preset temperature and enters the light component removal tower 11 in a gas phase state, and tower bottom liquid of the light component removal tower 11 is pumped and then enters a rectifying tower system for azeotropic rectification treatment. The preset temperature range can be, for example, 90-150 ℃, so that the product gas enters the lightness-removing column 11 in a gas phase state for lightness-removing treatment, the steam consumption of the reboiler 12 of the lightness-removing column is reduced, and the energy consumption of the device is saved. The operating pressure range value of the light component removal tower 11 can be 0.05-0.40MPaG, the range is suitable for the separation process of light components in the crude product gas, and waste caused by overlarge pressure rise can be avoided.
And a light component removal tower reboiler 12 which is connected to the light component removal tower 11 and heats the tower bottom liquid of the light component removal tower 11 by using the tower top compressed vapor subjected to azeotropic distillation as a heat source. The heat source of a reboiler 12 of the light component removal tower is overhead steam subjected to azeotropic rectification after compression and temperature rise, and the two towers form a double-tower coupling heat pump system, so that the energy consumption of the whole device can be greatly saved; and pumping the residue in the light component removal tower 11, and then carrying out azeotropic distillation treatment.
A light component removal tower top air cooler 13 connected to the top of the light component removal tower 11 and configured to cool the top gas phase of the light component removal tower 11 to a predetermined temperature; for example 50-90 deg.c.
And the light component removal tower reflux tank 14 is connected with the light component removal tower top air cooler 13 and is used for accommodating the tower top gas phase of the light component removal tower 11 cooled by the light component removal tower top air cooler 13, and the condensate in the light component removal tower reflux tank 14 is returned to the light component removal tower 11 as reflux.
The top water cooler 15 of the light component removal tower is connected with the reflux tank 14 of the light component removal tower and is used for cooling the top gas-phase components of the reflux tank 14 of the light component removal tower to a preset temperature; for example 30-60 deg.c.
A light component removal tower top tank 16 which is connected with the light component removal tower top water cooler 15 and is used for accommodating the top gas phase component of the light component removal tower reflux tank 14 after the light component removal tower top water cooler 15 is cooled, and the condensate in the light component removal tower top tank 16 is used as the recovered light component and returns to the MA reaction unit; because the tower top adopts a two-stage condensation scheme, methyl acetate and methanol are mostly condensed in the first stage, most of heat load is concentrated, and the final heat transfer temperature of the first stage condensation is higher, a more energy-saving air cooling scheme can be adopted, so that the circulating water consumption of the condenser of the lightness-removing tower 11 is greatly reduced, and the energy consumption of the whole device can be reduced.
In some embodiments, referring to fig. 2, the rectification column system comprises an azeotropic rectification column system 2 for performing an azeotropic rectification process, the azeotropic rectification column system 2 comprising an azeotropic rectification column 21, an azeotropic rectification column reboiler 22, an azeotropic rectification column overhead gas compressor 23, an azeotropic rectification column water cooler 24, and an azeotropic rectification column reflux drum 25.
An azeotropic distillation column 21, which is connected with the lightness-removing column 11 of the lightness-removing column system 1 and is used for carrying out azeotropic distillation treatment on the lightness-removed crude methyl acrylate product gas; the tower bottom of the azeotropic distillation tower 21 is connected with the extraction distillation tower 31 of the subsequent extraction distillation tower system 3, so that the tower bottom liquid enters the extraction distillation tower 31 after being pumped and pressed by a pump for extraction distillation treatment;
and an azeotropic distillation column overhead gas compressor 23 connected to the top of the azeotropic distillation column 21, for compressing and heating the top gas phase of the azeotropic distillation column 21 to serve as a reboiler heat source for the light ends removal column 11 of the light ends removal column system 1. Thereby forming a double-tower coupled heat pump rectification system. Therefore, the condition that a high-grade steam energy source is used by the light component removal tower reboiler 12 is avoided, the circulating water consumption of a condenser (water cooler) of the azeotropic distillation tower 21 is greatly reduced, only a small amount of compression work is consumed, and the energy-saving effect of the whole device is obvious.
And the azeotropic distillation tower water cooler 24 is connected with the light component removal tower reboiler 12 and is used for cooling the tower top gas of the azeotropic distillation tower 21 subjected to heat exchange by the reboiler of the light component removal tower system 1 to a preset temperature.
The azeotropic distillation column reflux tank 25 is connected with the azeotropic distillation column water cooler 24 and is used for containing the overhead gas of the azeotropic distillation column 21 after the azeotropic distillation column water cooler 24 is cooled; a part of the condensate in the reflux drum 25 of the azeotropic distillation column is returned to the azeotropic distillation column 21 as reflux, and the other part is sent to the downstream MA hydrogenation unit.
And the azeotropic distillation tower reboiler 22 is connected with the azeotropic distillation tower 21 and is used for providing heat energy for the azeotropic distillation tower 21, and the azeotropic distillation tower reboiler 22 is connected with a low-pressure steam pipeline so as to adopt low-pressure steam as a heat source of the low-pressure steam.
In some embodiments, referring to fig. 2, the rectifying tower system includes an extractive rectifying tower system 3, the extractive rectifying tower system 3 uses water as an extractant to perform extractive rectification on the formaldehyde solution obtained by azeotropic rectification, and the extractive rectifying tower system 3 includes an extractive rectifying tower 31, an extractive rectifying tower reboiler 32, an extractive rectifying tower condenser 33, an extractive rectifying tower reflux tank 34, and an extractive rectifying tower still water cooler 35;
an extractive distillation column 31 connected to the column bottom of the azeotropic distillation column 21, for extractive distillation of the formaldehyde solution (column bottom of the azeotropic distillation column 21) obtained by the azeotropic distillation; the bottom of the extraction and rectification tower 31 is connected with the extraction tower 4, so that the formaldehyde-rich solution at the bottom of the extraction and rectification tower 31 is cooled by the water cooler 35 of the bottom liquid of the extraction and rectification tower, and then is pumped to enter the extraction tower 4 for extraction treatment;
the extraction and rectification tower condenser 33 is connected with the top of the extraction and rectification tower 31 and is used for cooling the top gas of the extraction and rectification tower 31 to a preset temperature; the extractive distillation column condenser 33 may employ an air cooler.
The extraction rectification tower reflux tank 34 is connected with the extraction rectification tower condenser 33 and is used for containing the overhead gas of the extraction rectification tower 31 after the extraction rectification tower condenser 33 is cooled, one part of condensate in the extraction rectification tower reflux tank 34 is returned to the extraction rectification tower 31 as reflux, and the other part of condensate is returned to the methyl acrylate reaction unit as a methanol solvent;
and the extraction and rectification tower reboiler 32 is connected with the extraction and rectification tower 31 and used for providing heat energy for the extraction and rectification tower 31, and the extraction and rectification tower reboiler 32 is connected with a low-pressure steam pipeline so as to adopt low-pressure steam as a heat source.
In some embodiments, referring to fig. 2 and 3, the de-heavies system 5 includes a de-heavies column 51, a de-heavies column reboiler 52, a de-heavies column overhead gas compressor 53, a de-heavies column mid-boiler 54, a de-heavies column overhead water cooler 55, and a de-heavies column reflux drum 56.
A de-weighting tower 51 connected to the extraction tower 4, for performing de-weighting treatment on the heavy ester-rich oil phase (the tower top oil phase of the extraction tower 4) obtained by the extraction treatment to remove heavy components in the oil phase and recover the extractant;
a de-heavy tower top gas compressor 53 connected with the de-heavy tower 51 and used for compressing and heating the tower top gas phase of the de-heavy tower 51;
and a de-heavy column middle boiling device 54 which is connected with the de-heavy column top gas compressor 53, so that the tower top gas phase of the de-heavy column 51 which is compressed and heated by the de-heavy column top gas compressor 53 enters the de-heavy column middle boiling device 54 as a heat source. The tower top steam of the de-heavy tower 51 is compressed and then used as a heat source of a boiler 54 in the de-heavy tower, so that the steam dosage of a reboiler 52 of the de-heavy tower is greatly reduced, and the circulating water dosage of a condenser of the de-heavy tower 51 is also reduced.
A de-heavy tower top water cooler 55 connected with the de-heavy tower middle boiling device 54 and used for cooling the tower top gas phase of the de-heavy tower 51 subjected to heat exchange by the de-heavy tower middle boiling device 54 to a preset temperature; for example 30-50 deg.c.
And the heavy component removal tower reflux tank 56 is connected with the heavy component removal tower top water cooler 55 and is used for accommodating the tower top gas phase of the heavy component removal tower 51 cooled by the tower top water cooler of the heavy component removal tower 51, the tower top gas of the cooled heavy component removal tower 51 is subjected to oil-water stratification in the heavy component removal tower reflux tank 56, one part of the oil phase after being boosted is returned to the heavy component removal tower 51 as reflux, the other part of the oil phase is returned to the bottom of the extraction tower 4 as a first extractant, and the water phase is returned to the top of the extraction tower 4 as a second extractant after being boosted.
A reboiler 52 of the heavy component removal column, which is connected to the heavy component removal column 51 and is used for providing heat energy for the heavy component removal column 51, and the reboiler 52 of the heavy component removal column is connected with a low pressure steam pipeline to use low pressure steam as a heat source;
the heavy component in the tower kettle of the de-heavy tower 51 is connected with a recovery processing system to recover the heavy component in the tower kettle.
In some embodiments, referring to fig. 2 and 3, stripper system 6 includes a stripper 61, a stripper reboiler 62, a stripper condenser 63, and a stripper overhead drum 64.
A stripping tower 61 connected to the extraction tower 4 for stripping the dilute formaldehyde solution (the tower bottom liquid of the extraction tower 4) obtained by the extraction treatment to remove the light ester component in the formaldehyde aqueous solution; the tower kettle of the stripping tower 61 is connected to a dilute formaldehyde recovery system through a pump;
a stripper condenser 63 connected to the top of the stripper 61 for water-cooling the top gas phase of the stripper 61 to a preset temperature. The stripper condenser 63 may employ a water cooler.
A stripper overhead tank 64 connected to the stripper condenser 63 for accommodating the overhead gas of the stripper 61 cooled by the stripper condenser 63, wherein the condensate in the stripper overhead tank 64 is returned to the extraction column 4 after being pressurized;
a stripping tower reboiler 62 connected to the stripping tower 61 for providing heat energy to the stripping tower 61, and a low pressure steam line connected to the stripping tower reboiler 62 for using the low pressure steam as a heat source thereof.
In some embodiments, referring to fig. 3, the rectifying column system comprises a baffle rectifying column 7 for performing azeotropic rectification and extractive rectification, a vertical baffle is disposed in the middle of the baffle rectifying column 7, the baffle divides the rectifying column into an upper common rectifying section 71, a lower common stripping section 72, a rectifying feed section 73 and a side draw section 74 on both sides of the baffle, the crude methyl acrylate gas after light removal treatment and water as an extractant enter from the rectifying feed section 73, and the rectifying feed section 73 functions as a primary fractionating column to separate light components and heavy components; the separation of light components and intermediate components is realized in the common rectification section 71, and the gas at the top of the clapboard rectification tower 7 is compressed by a clapboard rectification tower compressor 75 and heated up to be used as a heat source of a light component removal tower reboiler 12 of the light component removal tower system 1; a partition rectifying tower water cooler 76 connected to the light component removal tower reboiler 12 for cooling the top gas of the partition rectifying tower subjected to heat exchange by the reboiler of the light component removal tower system 1 to a predetermined temperature; a partition rectifying tower reflux tank 77 connected with the partition rectifying tower water cooler 76, wherein one part of condensate in the partition rectifying tower reflux tank 77 is returned to the common rectifying section 71 as reflux, and the other part of condensate is sent to a downstream MA hydrogenation unit; the separation of the intermediate components and the heavy components is realized in the common stripping section 72, and the formaldehyde-rich solution at the bottom of the tower is sent to extraction treatment; an intermediate methanol fraction is obtained in the side offtake section 74. The splitter reboiler 78 is connected to a low pressure steam line to use low pressure steam as its heat source. The formaldehyde-rich solution in the bottom of the baffle plate rectifying tower 7 is cooled by a baffle plate rectifying tower bottom liquid water cooler 79 and then is sent to extraction treatment. . In this embodiment, the azeotropic distillation tower 21 and the extractive distillation tower 31 in the embodiment shown in fig. 2 are coupled to form a baffle distillation tower 7 in the embodiment shown in fig. 3; the clapboard rectifying tower is a special structure of a complete thermal coupling tower, and the ingenious use of the clapboard realizes the functions of two towers; compared with the traditional two-tower process, the process effectively avoids the remixing phenomenon in the two-tower process, is more effective in the thermodynamics of the tower, can also obviously reduce the load of a condenser and the load of a reboiler by the clapboard rectifying tower, and can save the equipment investment and the occupied area of the device.
The operation of the apparatus for separating crude methyl acrylate gas, which is prepared from coal-based methyl acetate and formaldehyde, according to the embodiment of the present invention is described in detail below with reference to a specific experimental procedure.
The crude methyl acrylate product gas containing 3.91 percent of nitrogen, 39.27 percent of methyl acetate, 6.91 percent of formaldehyde, 40.77 percent of methanol, 0.04 percent of methacrolein, 6.74 percent of methyl acrylate, 0.07 percent of methyl propionate, 0.08 percent of methyl methacrylate, 1.66 percent of water, 0.24 percent of acetic acid and 0.32 percent of heavy components is taken as an experimental object, the scale is 4.6 million tons/year of methyl acrylate, and the method is shown in figure 2 and comprises the following steps:
(1) removing light components from the product gas: the high-temperature methyl acrylate crude product gas from the MA reaction unit is subjected to heat exchange to 90-150 ℃, so that the product gas enters the light component removal tower 11 in a gas phase state, and the operating pressure of the light component removal tower 11 is 0.05-0.40 MPaG. The gas phase at the top of the light component removal tower 11 is cooled to 50-90 ℃ by a light component removal tower top air cooler 13, then enters a light component removal tower reflux tank 14, condensate is used as reflux to return to the light component removal tower 11, the gas is cooled to 30-60 ℃ by a light component removal tower top water cooler 15 and then enters a light component removal tower top tank 16, and the tank bottom condensate of the light component removal tower top tank 16 is used as a recovered methyl acetate raw material to return to the MA reaction unit. Because the tower top adopts a two-stage condensation scheme of air cooling and water cooling, the circulating water consumption of the condenser of the light component removal tower 11 is greatly reduced, and the energy consumption of the whole device is further reduced. The heat source of the light component removal tower reboiler 12 is steam compressed and heated at the top of the azeotropic distillation tower 21, and the two towers form a double-tower coupling heat pump system, so that the energy consumption of the whole device can be greatly saved; the tower bottom liquid of the light component removal tower 11 is pumped to the azeotropic distillation tower 21.
(2) And (3) rectifying product gas: and (2) carrying out azeotropic distillation treatment on the MA crude product gas subjected to light component removal in the step (1) through an azeotropic distillation tower 21 to remove unreacted formaldehyde, heavy ester and other heavy components in the product gas, wherein the azeotropic distillation tower 21 is operated at normal pressure to avoid formic acid generated by overhigh temperature of a pressurized operation tower kettle from corroding equipment. The gas phase at the top of the azeotropic distillation tower 21 is pressurized to 0.15-0.60MPaG by an azeotropic distillation tower top gas compressor 23, the temperature is correspondingly raised to 95-150 ℃, the heated tower top gas of the azeotropic distillation tower 21 is used as a heat source of a light component removal tower reboiler 12, so that a double-tower coupling heat pump distillation system is formed, the tower top gas of the azeotropic distillation tower 21 is cooled to 60-90 ℃ by an azeotropic distillation tower water cooler 24, condensate enters an azeotropic distillation tower reflux tank 25, one part of the condensate is used as reflux, and the other part of the condensate is used as a mixture of MA and methanol to a downstream MA hydrogenation unit. The heat source of the azeotropic distillation column reboiler 22 is low pressure steam. The tower bottoms are pumped to the extractive distillation tower 31. The light component removal tower 11 and the azeotropic distillation tower 21 form a double-tower coupling heat pump distillation system. Therefore, the condition that the high-grade steam energy is used by the light component removal tower reboiler 12 is avoided, the circulating water consumption of the condenser of the azeotropic distillation tower 21 is greatly reduced, only a small amount of compression work is consumed, and the energy-saving effect of the whole device is obvious.
(3) Concentrated aldehyde methanol removal: and (3) carrying out extraction and rectification treatment on the tower bottom concentrated formaldehyde solution of the azeotropic rectification tower 21 in the step (2), preferably operating the extraction and rectification tower 31 at normal pressure, distilling out a methanol component from the tower top, and washing the methanol gas phase in the rectification section by using an extractant (water) to prevent the methanol component from carrying formaldehyde in the tower top. The steam at the top of the tower is cooled to 50-80 ℃ through a condenser 33 of the extractive distillation tower, one part of the condensate is returned to the tower as reflux, and the other part of the condensate is returned to the MA reaction unit as recovered methanol. The condenser 33 of the extractive distillation tower is preferably an air cooler so as to reduce the consumption of circulating water of the device and save energy consumption. The heat source of the reboiler 32 of the extraction and rectification tower is low-pressure steam, the tower bottom liquid of the extraction and rectification tower 31 is cooled to 30-50 ℃ by circulating water through the water cooler 35 of the tower bottom liquid of the extraction and rectification tower, and then is pumped to pressure and sent to the extraction tower 4.
(4) Removing heavy ester from formaldehyde solution: and (3) extracting the formaldehyde-rich solution in the bottom of the extractive distillation tower 31 in the step (3) by using an ester (first extracting agent) through an extraction tower 4 so as to remove heavy esters and acetic acid components in the formaldehyde solution. The oil phase at the top of the extraction tower 4 is subjected to a formaldehyde removing treatment with water (second extractant) to prevent the formaldehyde component from being carried into the downstream de-heavy tower 51. The light ester component from the stripping column 61 is returned to the lower part of the extraction column 4 for re-separation to reduce the loss of the first extractant (ester). The light ester recovered from the de-heavies column 51 is returned to the bottom of the extraction column 4 as a first extractant, and a small amount of water from the de-heavies column reflux drum 56 is returned to the top of the extraction column 4 as a second extractant (water). The extraction column 4 may be in the form of a rotating tray column, and may be operated at a temperature of 30 to 50 ℃ and at a pressure of 0.30 to 0.90 MPaG.
(5) Removing weight and recovering an extracting agent: the ester oil-rich phase from the top of the extraction column 4 of step (4) is passed to a de-heaving column 51 to remove heavies from the oil phase. The operation pressure of the de-heavy tower 51 is 0.05-0.30MPaG, for further energy saving, the de-heavy tower 51 is provided with a de-heavy tower middle boiler 54, and the tower top gas of the de-heavy tower 51 is compressed by a de-heavy tower top gas compressor 53 and then is used as a heat source of the de-heavy tower middle boiler 54, so that the steam dosage of the de-heavy tower reboiler 52 is greatly reduced. The overhead gas of the de-weighting tower 51 after heat exchange by a boiler 54 in the de-weighting tower is cooled to 30-50 ℃ by a water cooler 55 at the top of the de-weighting tower, and then enters a reflux tank 56 of the de-weighting tower, the condensate is subjected to oil-water phase splitting operation in the reflux tank 56 of the de-weighting tower, one part of the oil phase after pressure increase is returned to the de-weighting tower 51 as reflux, the other part is returned to the bottom of the extraction tower 4 as a first extractant (ester), and the water phase after pressure increase is returned to the top of the extraction tower 4 as a second extractant (water). The heat source of the reboiler 52 of the de-heavy column is low-pressure steam, and the heavy components in the bottom of the de-heavy column 51 are used as by-products and can be further recycled after being pressurized by a pump.
(6) Dilute aldehyde stripping: and (4) feeding the dilute formaldehyde solution from the tower bottom of the extraction tower 4 in the step (4) into a stripping tower 61 to remove light ester components in the formaldehyde aqueous solution. The stripper 61 is operated at a pressure of 0.05 to 0.30 MPaG. The gas at the top of the stripping tower 61 is cooled to 30-50 ℃ by a stripping tower condenser 63, the condensate enters a stripping tower top tank 64, and the condensate is pumped and then returns to the lower part of the extraction tower 4 for ester recovery. The heat source of the stripping tower reboiler 62 is low-pressure steam, and the tower bottom liquid of the stripping tower 61 is pumped to a dilute formaldehyde recovery system.
Alternatively, referring to fig. 3, the azeotropic distillation column 21 in step S2 and the extractive distillation column 31 in step S3 may be coupled into one distillation column, i.e., the dividing wall distillation column 7, using a dividing wall. The baffle rectifying tower 7 is structurally characterized in that a vertical baffle is arranged in a rectifying tower, and the rectifying tower is divided into an upper common rectifying section 71 (equivalent to an azeotropic rectifying tower 21), a lower common stripping section 72 (equivalent to an extractive rectifying tower 31), and a rectifying feed section 73 and a side draw section 74 on two sides of the baffle. The rectification feed section 73 functions as a primary fractionator to complete the separation of light and heavy components; separation of light and intermediate components is achieved within the common rectification section 71 and liquid phase reflux is provided; separation of the intermediate and heavy components is effected in a common stripping section 72 and provides vapor phase reflux; high purity intermediate components are obtained in the side draw 74. The clapboard rectifying tower 7 is a special structure of a complete thermal coupling tower, and the ingenious use of the clapboard realizes the functions of two towers. The azeotropic distillation tower 21 and the extractive distillation tower 31 are coupled into one distillation tower, compared with the traditional two-tower process, the re-mixing phenomenon in the two-tower process is effectively avoided, the process is more effective in thermodynamics of the tower, the partition distillation tower 7 can also obviously reduce the load of a condenser and the load of a reboiler, and the equipment investment and the occupied area of the device can be saved. The baffle rectifying tower 7 can also solve the problem that the energy consumption of the extractive rectifying tower 31 is increased when the amount of methanol distilled from the top of the extractive rectifying tower 31 is large. The baffle rectification column 7 can reduce the energy consumption of the whole device.
The key stream experimental results of the first example are tabulated in fig. 4.
Moreover, although exemplary embodiments have been described herein, the scope thereof includes any and all embodiments based on the present invention with equivalent elements, modifications, omissions, combinations (e.g., of various embodiments across), adaptations or alterations. The elements of the claims are to be interpreted broadly based on the language employed in the claims and not limited to examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. It is intended, therefore, that the specification and examples be considered as exemplary only, with a true scope and spirit being indicated by the following claims and their full scope of equivalents.
The above description is intended to be illustrative and not restrictive. For example, the above-described examples (or one or more versions thereof) may be used in combination with each other. For example, other embodiments may be used by those of ordinary skill in the art upon reading the above description. In addition, in the above-described embodiments, various features may be grouped together to streamline the disclosure. This should not be interpreted as an intention that a disclosed feature not claimed is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that these embodiments may be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
The above embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and the scope of the present invention is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present invention, and such modifications and equivalents should also be considered as falling within the scope of the present invention.
Claims (14)
1. A process for the separation of crude methyl acrylate product gas comprising:
carrying out light component removal treatment on crude methyl acrylate product gas, and recovering light components as raw materials;
carrying out azeotropic rectification treatment on the methyl acrylate crude product gas after light component removal to remove formaldehyde and heavy ester components; wherein, the gas phase at the top of the azeotropic distillation tower is compressed and heated to be used as a reboiler heat source for light component removal treatment;
carrying out extractive distillation treatment on the formaldehyde solution obtained by azeotropic distillation treatment by using water so as to remove a methanol component in the formaldehyde solution;
extracting the formaldehyde solution subjected to extractive distillation and methanol removal, wherein a first extracting agent is used for extracting the formaldehyde solution to remove heavy ester components in the formaldehyde solution, and a second extracting agent is used for extracting an oil phase to remove formaldehyde;
carrying out weight removal treatment on the oil phase obtained by the extraction treatment, and recovering light ester and water to be respectively used as the first extracting agent and the second extracting agent of the extraction treatment; wherein, the intermediate reboiler for the weight removal treatment adopts the tower top gas phase of the weight removal treatment as a heat source after being compressed and heated;
and (4) carrying out steam stripping treatment on the water phase obtained by the extraction treatment so as to recover the light ester component and obtain the dilute formaldehyde aqueous solution at the bottom of the tower.
2. The process of claim 1, wherein the methyl acrylate raw product gas is subjected to a light removal treatment comprising:
cooling the methyl acrylate crude product gas to a preset temperature, and enabling the methyl acrylate crude product gas to enter a lightness-removing tower in a gas phase state for lightness-removing treatment;
cooling the gas phase at the top of the light component removal tower to a preset temperature by an air cooler, allowing the gas phase to enter a light component removal tower reflux tank, allowing the condensate in the light component removal tower reflux tank to return to the light component removal tower as reflux, cooling the gas phase component at the top of the light component removal tower to the preset temperature by water, allowing the condensate in the light component removal tower top tank to return to a methyl acrylate reaction unit as a recovered light component;
and (4) performing azeotropic distillation treatment on the light component removal tower bottom liquid after pressure increase by a pump.
3. The process of claim 1, wherein the azeotropic distillation treatment of the crude methyl acrylate product gas after light component removal comprises:
after the crude product gas of methyl acrylate is subjected to lightness removing treatment, the crude product gas is sent to an azeotropic rectifying tower for azeotropic rectification after pressure increase;
after the gas phase at the top of the tower after the azeotropic distillation treatment is subjected to heat exchange by the reboiler for the light component removal treatment, the gas phase is cooled to a preset temperature by water and then enters a reflux tank of the azeotropic distillation tower, one part of condensate in the reflux tank of the azeotropic distillation tower is used as reflux to return to the azeotropic distillation tower, and the other part of condensate is sent to a downstream methyl acrylate hydrogenation unit;
an azeotropic distillation tower reboiler of the azeotropic distillation tower can adopt low-pressure steam as a heat source;
and the tower bottom liquid of the azeotropic distillation tower is subjected to extraction and distillation treatment after being subjected to pressure increase by a pump.
4. The method according to claim 1, wherein the extractive distillation treatment of the formaldehyde solution obtained by the azeotropic distillation treatment with water comprises:
carrying out pressure raising on the formaldehyde solution obtained by azeotropic distillation treatment, and then sending the formaldehyde solution to an extraction and distillation tower for extraction and distillation treatment;
cooling the gas phase at the top of the extractive distillation tower to a preset temperature by adopting an air cooler, wherein one part of the obtained condensate is used as reflux, and the other part of the obtained condensate is used as a methanol solvent and returns to the methyl acrylate reaction unit;
a reboiler of an extraction rectifying tower of the extraction rectifying tower adopts low-pressure steam as a heat source;
and cooling the formaldehyde-rich solution at the bottom of the extraction and rectification tower by circulating water, and performing extraction treatment after the formaldehyde-rich solution is subjected to pressure increase by a pump.
5. The method of claim 1, wherein the de-weighting treatment of the oil phase from the extraction treatment comprises:
feeding the heavy ester oil-rich phase obtained from the extraction treatment into a de-weighting tower to remove heavy components in the oil phase and recovering an extracting agent;
compressing and heating the top gas phase of the de-heavy tower to serve as a heat source of a boiler in the de-heavy tower of the de-heavy tower, cooling the top gas phase of the de-heavy tower subjected to heat exchange by the boiler in the de-heavy tower to a preset temperature by water, and then layering the top gas phase in a reflux tank of the de-heavy tower, wherein one part of the pressurized oil phase is returned to the de-heavy tower as reflux, the other part of the pressurized oil phase is returned to the lower part of the extraction tower as a first extractant, and the pressurized water phase is returned to the upper part of the extraction tower as a second extractant;
a reboiler of the heavy component removal tower adopts low-pressure steam as a heat source;
and (4) recovering heavy components in the tower kettle of the de-heavy tower.
6. The process of claim 1, wherein the stripping treatment of the aqueous phase from the extraction treatment comprises:
feeding the dilute formaldehyde solution obtained from the extraction treatment into a stripping tower to remove light ester components in the formaldehyde aqueous solution;
the gas phase at the top of the stripping tower is cooled to a preset temperature through circulating water, and the condensate is returned to the extraction tower after being pressurized;
a reboiler of a stripping tower of the stripping tower adopts low-pressure steam as a heat source, and tower bottom liquid of the stripping tower is pumped to a dilute formaldehyde recovery system.
7. The method as claimed in claim 1, wherein a baffle distillation tower is adopted for the azeotropic distillation treatment and the extractive distillation treatment, a vertical baffle is arranged in the middle of the baffle distillation tower, the distillation tower is divided into an upper common distillation section, a lower common stripping section, a distillation feed section and a side draw section on two sides of the baffle distillation tower, the crude methyl acrylate product gas after the light component removal treatment and water as an extractant enter from the distillation feed section, and the distillation feed section plays the role of a primary distillation tower to complete the separation of light components and heavy components; separating light components from intermediate components in the public rectification section, and compressing and heating the overhead gas to be used as a heat source of a reboiler for light component removal treatment; separating intermediate components and heavy components in the public stripping section, cooling the formaldehyde-rich solution in the tower kettle by water, and then sending the solution to the extraction treatment; the intermediate component methanol is obtained at the side line extraction section.
8. An apparatus for separating a crude methyl acrylate product gas, comprising:
the light component removal tower system is used for carrying out light component removal treatment on crude methyl acrylate product gas, and light components are recovered as raw materials;
the rectifying tower system is connected with the light component removal tower system and is used for carrying out azeotropic rectification treatment and extractive rectification treatment on the crude methyl acrylate product gas after the light component removal treatment; wherein the azeotropic distillation treatment is carried out to remove formaldehyde and heavy ester components; the compressed vapor at the top of the tower subjected to azeotropic rectification is used as a heat source of a reboiler of the light component removal tower system; adopting water as an extracting agent to carry out extractive distillation treatment on the formaldehyde solution obtained by azeotropic distillation treatment so as to remove a methanol component in the formaldehyde solution; the extraction tower is connected with the rectifying tower system and is used for extracting the formaldehyde solution obtained by the extraction and rectification treatment, wherein the formaldehyde solution is extracted by adopting a first extracting agent to remove heavy ester components in the formaldehyde solution, and the oil phase is subjected to formaldehyde removing treatment by adopting a second extracting agent;
a de-weighting tower system connected with the extraction tower and used for performing de-weighting treatment on the oil phase obtained by the extraction treatment and recovering light ester and water as the first extractant and the second extractant of the extraction treatment respectively; the middle reboiler heat source of the heavy component removal tower system adopts the tower top gas phase of the heavy component removal tower system as the heat source after compression and temperature rise;
and the stripping tower system is connected with the extraction tower and is used for carrying out stripping treatment on the water phase obtained by the extraction treatment so as to recover light ester components and obtain a dilute formaldehyde aqueous solution at the bottom of the tower.
9. The separation apparatus of claim 8, wherein the light ends removal column system comprises:
the light component removal tower is used for carrying out light component removal treatment on crude methyl acrylate product gas which is cooled to a preset temperature and enters the light component removal tower in a gas phase state; pumping the tower bottom liquid of the light component removal tower, and then feeding the tower bottom liquid into the rectifying tower system for azeotropic rectification;
a light component removal tower reboiler which is connected with the light component removal tower and heats tower bottom liquid of the light component removal tower by taking tower top compressed steam subjected to azeotropic rectification as a heat source;
the light component removal tower top air cooler is connected with the top of the light component removal tower and is used for cooling the top gas phase of the light component removal tower to a preset temperature;
a light component removal tower reflux tank which is connected with the light component removal tower top air cooler and is used for accommodating the tower top gas phase of the light component removal tower cooled by the light component removal tower air cooler, and the condensate in the light component removal tower reflux tank is returned to the light component removal tower as reflux;
the top water cooler of the light component removal tower is connected with the reflux tank of the light component removal tower and is used for cooling the top gas-phase components of the reflux tank of the light component removal tower to a preset temperature;
and the top tank of the light component removal tower is connected with the water cooler at the top of the light component removal tower and is used for accommodating the top gas-phase components of the reflux tank of the light component removal tower after the water cooler at the top of the light component removal tower is cooled, and the condensate of the top tank of the light component removal tower is used as the recovered light components and is returned to the methyl acrylate reaction unit.
10. The separation apparatus of claim 8, wherein the rectification column system comprises an azeotropic rectification column system for performing the azeotropic rectification process, the azeotropic rectification column system comprising:
the azeotropic distillation tower is connected with the light component removal tower system and is used for carrying out azeotropic distillation treatment on the methyl acrylate crude product gas after light component removal; the tower kettle of the azeotropic distillation tower is connected with the extraction distillation tower, so that tower kettle liquid of the azeotropic distillation tower is pumped and enters the extraction distillation tower for extraction distillation treatment;
the azeotropic distillation tower top gas compressor is connected with the tower top of the azeotropic distillation tower and is used for compressing and heating the tower top gas phase of the azeotropic distillation tower to be used as a reboiler heat source of the light component removal tower system;
the azeotropic distillation tower water cooler is connected with the light component removal tower reboiler and is used for cooling the tower top gas phase of the azeotropic distillation tower subjected to heat exchange by the reboiler of the light component removal tower system to a preset temperature;
the reflux tank of the azeotropic distillation tower is connected with the water cooler of the azeotropic distillation tower and is used for accommodating the overhead gas of the azeotropic distillation tower after the water cooler of the azeotropic distillation tower is cooled; one part of condensate in the reflux tank of the azeotropic distillation tower is returned to the azeotropic distillation tower as reflux, and the other part of condensate is sent to a downstream methyl acrylate hydrogenation unit;
and the azeotropic distillation tower reboiler is connected with the azeotropic distillation tower and used for providing heat energy for the azeotropic distillation tower, and the azeotropic distillation tower reboiler is connected with a low-pressure steam pipeline.
11. The separation apparatus according to claim 8, wherein the rectification column system comprises an extractive rectification column system, the extractive rectification column system adopts water as an extractant to carry out extractive rectification treatment on the formaldehyde solution obtained from the azeotropic rectification treatment, and the extractive rectification column system comprises:
the extraction and rectification tower is connected with the tower kettle of the azeotropic rectification tower and is used for carrying out extraction and rectification treatment on the formaldehyde solution obtained by the azeotropic rectification treatment;
the water cooler is connected with the kettle of the extraction and rectification tower, so that the formaldehyde-rich solution at the kettle of the extraction and rectification tower is cooled by circulating water, is subjected to pressure raising by a pump and then enters the extraction tower for extraction treatment;
the extraction and rectification tower condenser is connected with the top of the extraction and rectification tower and is used for cooling the top gas phase of the extraction and rectification tower to a preset temperature;
the reflux tank of the extraction and rectification tower is connected with the condenser of the extraction and rectification tower and is used for containing the overhead gas of the extraction and rectification tower after the condenser of the extraction and rectification tower is cooled, one part of condensate in the reflux tank of the extraction and rectification tower is returned to the extraction and rectification tower as reflux, and the other part of condensate is returned to the methyl acrylate reaction unit as a methanol solvent;
and the extraction and rectification tower reboiler is connected with the extraction and rectification tower and used for providing heat energy for the extraction and rectification tower, and the extraction and rectification tower reboiler is connected with a low-pressure steam pipeline.
12. The separation apparatus of claim 8, wherein the de-heaving column system comprises:
the heavy component removing tower is connected with the extraction tower and is used for removing heavy components from the heavy ester-rich oil phase obtained by extraction treatment and recovering an extracting agent;
the top gas compressor of the de-heavy tower is connected with the de-heavy tower and is used for compressing and heating the top gas phase of the de-heavy tower;
the heavy component removal tower middle boiling device is connected with the heavy component removal tower top gas compressor, so that the tower top gas phase of the heavy component removal tower after being compressed and heated by the heavy component removal tower top gas compressor enters the heavy component removal tower middle boiling device as a heat source;
the heavy component removal tower top water cooler is connected with the heavy component removal tower middle boiler and is used for cooling the tower top gas phase of the heavy component removal tower subjected to heat exchange by the heavy component removal tower middle boiler to a preset temperature;
the heavy component removal tower reflux tank is connected with the heavy component removal tower top water cooler and is used for accommodating the tower top gas phase of the heavy component removal tower cooled by the heavy component removal tower top water cooler, the cooled tower top gas phase of the heavy component removal tower is subjected to oil-water stratification in the heavy component removal tower reflux tank, one part of the oil phase after being boosted is returned to the heavy component removal tower as reflux, the other part of the oil phase is returned to the bottom of the extraction tower as a first extractant, and the water phase after being boosted is returned to the top of the extraction tower as a second extractant;
and the heavy component removal tower reboiler is connected with the heavy component removal tower and used for providing heat energy for the heavy component removal tower, and a low-pressure steam pipeline is connected onto the heavy component removal tower reboiler.
13. The separation apparatus of claim 8, wherein the stripper system comprises:
the stripping tower is connected with the extraction tower and is used for carrying out stripping treatment on the dilute formaldehyde solution obtained by the extraction treatment so as to remove light ester components in the formaldehyde solution; the tower kettle of the stripping tower is connected to a dilute formaldehyde recovery system through a pump;
the stripper condenser is connected with the top of the stripper and is used for cooling the gas phase at the top of the stripper to a preset temperature by water;
the stripper tower top tank is connected with the stripper tower condenser and used for accommodating the tower top gas phase of the stripper tower cooled by the stripper tower condenser, and the condensate in the stripper tower top tank is returned to the lower part of the extraction tower after being boosted;
and the stripping tower reboiler is connected with the stripping tower and used for providing heat energy for the stripping tower, and a low-pressure steam pipeline is connected to the stripping tower reboiler.
14. The separation device according to claim 8, wherein the rectification column system comprises a baffle rectification column for performing azeotropic rectification and extractive rectification, a vertical baffle is arranged in the middle of the baffle rectification column, the baffle divides the rectification column into an upper common rectification section, a lower common stripping section, a rectification feed section and a side draw section which are positioned on two sides of the baffle, the crude methyl acrylate gas after light component removal treatment and water as an extractant enter from the rectification feed section, and the rectification feed section is used as a primary fractionation column for performing primary fractionation to complete separation of light components and heavy components; the separation of light components and intermediate components is realized in the public rectification section, and the gas phase at the top of the clapboard rectification tower is compressed and heated and then enters a reboiler of the light component removal tower as a heat source; the separation of intermediate components and heavy components is realized in the common stripping section, and a tower kettle of the clapboard rectifying tower is connected with a kettle liquid water cooler of the extraction rectifying tower, so that the cooled formaldehyde-rich solution is extracted in the extraction tower; the side draw section is connected to a methyl acrylate reaction unit.
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| CN112374989A (en) * | 2020-11-25 | 2021-02-19 | 西南化工研究设计院有限公司 | Separation method of mixture containing formaldehyde and methanol |
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