CN219150085U - Polylactic acid production system - Google Patents
Polylactic acid production system Download PDFInfo
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- CN219150085U CN219150085U CN202223435197.0U CN202223435197U CN219150085U CN 219150085 U CN219150085 U CN 219150085U CN 202223435197 U CN202223435197 U CN 202223435197U CN 219150085 U CN219150085 U CN 219150085U
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Abstract
The utility model belongs to the technical field of chemical production equipment, and particularly relates to a polylactic acid production system, which comprises a dehydration Ji Juda, a cracking cyclization reactor, a polymerization tower and an end-capped devolatilizer which are sequentially communicated, wherein a falling film crystallizer and/or a static crystallizer is arranged on a communication pipeline between the cracking cyclization reactor and the polymerization tower.
Description
Technical Field
The utility model belongs to the technical field of chemical production equipment, and particularly relates to a polylactic acid production system.
Background
Polylactic acid is a pale yellow or transparent polymer material, and has a glass transition temperature of 50-60 ℃, a melting point of 170-180 ℃, and is soluble in dichloroethane, acetonitrile, chloroform, dichloromethane and the like, and insoluble in water, ethanol, methanol and the like. Polylactic acid has good biodegradability, can be degraded into lactic acid in vivo, and can be widely applied to the fields of biomedicine, fiber, plastic, film and the like.
At present, the polylactic acid is generally prepared by the following two modes: (1) a direct condensation method of lactic acid, also called as a one-step method; (2) Lactic acid is dehydrated to generate an oligomer, lactide is generated by depolymerizing the oligomer, and then ring-opening polymerization is carried out under the action of a catalyst to obtain polylactic acid (also called a two-step method). The direct condensation method of lactic acid has simple process, but the direct condensation method of lactic acid can generate an equilibrium state in a system to a certain extent, and high molecular weight polylactic acid is difficult to obtain. Therefore, a two-step method is commonly used to prepare the high molecular weight polylactic acid. In the two-step process, the synthesis and purification of lactide are critical, wherein the purification of lactide is the most critical in the whole two-step process, and only lactide with high purity can be used for synthesizing polylactic acid with high molecular weight. Obviously, the two-step method involves a purification step of lactide, and has complex technical process and high cost.
In view of the above, there is a need for a polylactic acid production system capable of achieving efficient synthesis and purification of lactide to simplify the production process of high molecular weight polylactic acid and reduce the cost.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present utility model is to provide a polylactic acid production system for simplifying the production process of high molecular weight polylactic acid and reducing the cost.
The utility model provides a polylactic acid production system which comprises a dehydration Ji Juda, a cracking cyclization reactor, a polymerization tower and a terminal devolatilizer which are sequentially communicated, wherein a falling film crystallizer and/or a static crystallizer are arranged on a communication pipeline between the cracking cyclization reactor and the polymerization tower.
The principle of the polylactic acid production system of the utility model is as follows: the falling film crystallizer and/or the static crystallizer are/is arranged on the communication pipeline between the cracking cyclization reactor and the polymerization tower, so that the purity of the lactide can be improved, the production process of the high molecular weight polylactic acid is simplified, and the cost is reduced.
Alternatively, the cleavage cyclization reactor is a plug flow reactor.
In the utility model, the pyrolysis cyclization reactor is arranged to be a plug flow reactor, so that the oligomer and the catalyst generated by lactic acid depolymerization can be continuously mixed, efficiently transferred and distributed and dispersed in the plug flow reactor, and the mass transfer efficiency and the heat transfer efficiency are effectively improved; the oligomer and the catalyst flow in a plug flow reactor in a plug flow manner, so that the residence time of the oligomer and the catalyst in the plug flow reactor is kept consistent, the whole reaction process is more stable, and the high yield and the high conversion rate of the cracking cyclization reaction are realized.
Optionally, the polylactic acid production system further comprises a rectifying device, wherein the rectifying device is positioned on a communication pipeline between the cracking cyclization reactor and the falling film crystallizer or the static crystallizer.
According to the utility model, the rectification device is additionally arranged on the communication pipeline between the cracking cyclization reactor and the falling film crystallizer or the static crystallizer, so that the lactide obtained through the cracking cyclization reaction can be separated and purified in advance, and the energy consumption in the subsequent crystallization process is reduced.
Optionally, the rectification apparatus comprises a light ends removal column and/or a heavy ends removal column.
Optionally, an air outlet is arranged at the upper part of the end-capped devolatilizer, and the air outlet is communicated with the light component removing tower and/or the heavy component removing tower.
In the utility model, the gas outlet of the end-capped devolatilizer is communicated with the light component removing tower and/or the heavy component removing tower, so that lactide discharged by the end-capped devolatilizer can be returned to the light component removing tower and/or the heavy component removing tower, and the yield is further improved.
Optionally, the falling film crystallizer and/or the static crystallizer are provided with a waste liquid outlet which is communicated with the light component removal tower and/or the heavy component removal tower.
In the utility model, the waste liquid outlet of the falling film crystallizer and/or the static crystallizer is communicated with the light component removing tower and/or the heavy component removing tower, so that lactide in the waste liquid obtained by separation and purification of the falling film crystallizer and/or the static crystallizer can be sent into the light component removing tower and/or the heavy component removing tower, and the yield is further improved.
Alternatively, the static crystallizer is a plate-type static crystallizer.
Optionally, the polylactic acid production system further comprises a prepolymerization reactor located on a communication pipe between the polymerization tower and the falling film crystallizer or the static crystallizer.
In the utility model, by additionally arranging the prepolymerization reactor on the communication pipeline between the polymerization tower and the falling film crystallizer or the static crystallizer, the lactide and the catalyst can be subjected to preliminary polymerization reaction in the prepolymerization reactor, and the lactide which does not participate in the polymerization reaction after the polymerization reaction enters the polymerization tower to continue the reaction, thereby improving the yield.
Alternatively, the prepolymerization reactor employs a microreactor.
According to the utility model, the pre-polymerization reactor is arranged to be a micro-reactor, so that the lactide and the catalyst in the micro-reactor can carry out sufficient mass transfer and heat transfer, the lactide can be thoroughly reacted, and the content of the lactide in the reaction liquid is greatly reduced.
Optionally, the polylactic acid production system further comprises a cold coal storage container, a heat medium storage container and a heat pump system, wherein the heat pump system is communicated with the cold coal storage container and the heat medium storage container, the cold coal storage container and the heat medium storage container are both communicated with the falling film crystallizer and/or the static crystallizer, and the heat medium storage container is also communicated with the end-capped devolatilizer.
According to the utility model, the cold coal storage container, the heat medium storage container and the heat pump system are additionally arranged, the heat pump system is communicated with the cold coal storage container and the heat medium storage container, the cold coal storage container and the heat medium storage container are both communicated with the falling film crystallizer and/or the static crystallizer, and the heat medium storage container is also communicated with the end-capped devolatilizer, so that the crystallization temperature, the crystallization time, the devolatilization temperature and the devolatilization time can be precisely controlled, the purity of lactide and polylactic acid can be further improved, and the energy consumption is reduced.
Drawings
Fig. 1 is a schematic structural view of a polylactic acid production system according to example 1;
fig. 2 is a schematic structural view of the polylactic acid production system according to example 2;
FIG. 3 is a schematic view showing the structure of the polylactic acid production system according to example 3;
fig. 4 is a schematic structural view of the polylactic acid production system according to example 4;
fig. 5 is a schematic structural view of the polylactic acid production system according to embodiment 5;
FIG. 6 is a schematic view showing the structure of the polylactic acid production system according to example 6;
fig. 7 is a schematic structural view of the polylactic acid production system according to embodiment 7;
fig. 8 is a schematic structural view of the polylactic acid production system according to example 8.
Reference numerals
1-dehydration Ji Juda;
a 2-cleavage cyclization reactor;
3-a light component removing tower;
4-a heavy-duty removal tower;
5-falling film crystallizer;
6-a static crystallizer;
7-a polymerization column;
8-end capped devolatilizer;
9-a prepolymerization reactor;
10-a hot coal storage vessel;
11-a cold coal storage container;
12-heat pump system.
Detailed Description
Other advantages and effects of the present utility model will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present utility model with reference to specific examples. The utility model may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present utility model.
It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present utility model by way of illustration, and only the components related to the present utility model are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex. The structures, proportions, sizes, etc. shown in the drawings attached hereto are for illustration purposes only and are not intended to limit the scope of the utility model, which is defined by the claims, but rather by the claims. Also, the terms "upper", "top", "bottom" and the like are used herein for descriptive purposes only and not for purposes of limitation, and are intended to limit the scope of the utility model as defined by the claims.
The utility model provides a polylactic acid production system, which comprises a dehydration Ji Juda, a cracking cyclization reactor, a polymerization tower and a terminal devolatilizer which are sequentially communicated, wherein a communication pipeline between the cracking cyclization reactor and the polymerization tower is provided with a falling film crystallizer and/or a static crystallizer;
the cracking cyclization reactor adopts a plug flow reactor;
a light component removing tower and/or a heavy component removing tower are arranged on a communication pipeline between the cracking cyclization reactor and the falling film crystallizer or the static crystallizer;
the upper part of the end-capped devolatilizer is provided with an air outlet which is communicated with the light component removing tower and/or the heavy component removing tower;
the static crystallizer adopts a plate-type static crystallizer, and the falling film crystallizer and/or the static crystallizer are/is provided with a waste liquid outlet which is communicated with the light component removing tower and/or the heavy component removing tower.
In another embodiment of the present utility model, the polylactic acid production system further comprises a prepolymerization reactor, wherein the prepolymerization reactor is positioned on a communication pipeline between the polymerization tower and the falling film crystallizer or the static crystallizer, and the prepolymerization reactor adopts a micro-reactor.
In another embodiment of the utility model, the polylactic acid production system further comprises a cold and hot coal storage container and a heat pump system which are communicated, wherein the cold coal storage container and the heat medium storage container are both communicated with the falling film crystallizer and/or the static crystallizer, and the heat medium storage container is also communicated with the end-capped devolatilizer.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The present utility model will be described in detail with reference to specific exemplary examples. It is also to be understood that the following examples are given solely for the purpose of illustration and are not to be construed as limitations upon the scope of the utility model, as many insubstantial modifications and variations are within the scope of the utility model as would be apparent to those skilled in the art in light of the foregoing disclosure. The specific process parameters and the like described below are also merely examples of suitable ranges, i.e., one skilled in the art can make a suitable selection from the description herein and are not intended to be limited to the specific values described below. The term "wt%" as used herein refers to the mass content unless otherwise specified.
Example 1
Referring to fig. 1, fig. 1 is a schematic structural diagram of a polylactic acid production system according to the present embodiment, which is used for producing polylactic acid.
As shown in fig. 1, the polylactic acid production system of the present embodiment comprises a dehydration oligomerization tower 1, a cleavage cyclization reactor 2, a light component removal tower 3, a heavy component removal tower 4, a polymerization tower 7 and a terminal devolatilizer 8 which are sequentially communicated, wherein a falling film crystallizer 5 and a static crystallizer 6 are arranged on a communicating pipeline between the heavy component removal tower 4 and the polymerization tower 7.
With continued reference to fig. 1, the dehydration oligomerization tower 1 is used as a reaction vessel for dehydration oligomerization of lactic acid to form an oligomer, and the lactic acid is dehydrated and oligomerized to form an oligomer under the catalysis of a first catalyst (at least one of tin, stannous chloride and stannous octoate) in the dehydration oligomerization tower 1. The dehydration oligomerization tower 1 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown), a discharge outlet (not shown) and an air outlet (not shown). The discharge port is positioned at the bottom of the dehydration oligomerization tower 1, and the air outlet is positioned at the top of the dehydration oligomerization tower 1. The dehydration oligomerization tower 1 can adopt a packing rectifying tower and a falling film reboiler, which are the prior art and are not described in detail herein.
With continued reference to fig. 1, the cleavage cyclization reactor 2 serves as a reaction vessel for the cleavage cyclization of oligomers to lactide under the catalysis of a second catalyst (e.g., zinc lactate). The cracking cyclization reactor 2 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown) and a discharge outlet (not shown), the feed inlet of the cracking cyclization reactor 2 is communicated with the discharge outlet of the dehydration oligomerization tower 1, and a switching valve (not shown) and a centrifugal pump (not shown) are arranged on a communication pipeline between the cracking cyclization reactor 2 and the dehydration oligomerization tower 1. The cleavage cyclization reactor 2 employs a plug flow reactor (a plug flow reactor having a specific structure shown in CN 214553429U). The plug flow reactor is prior art and will not be described in detail here.
Specifically, in this embodiment, by setting the cleavage cyclization reactor 2 to be a plug flow reactor, the oligomer produced by depolymerizing lactic acid and the second catalyst can be continuously mixed, efficiently transferred and distributed and dispersed in the plug flow reactor, so that the mass transfer efficiency and the heat transfer efficiency are effectively improved; the oligomer and the second catalyst flow in a plug flow reactor in a plug flow manner, so that the residence time of the oligomer and the second catalyst in the plug flow reactor is kept consistent, the whole reaction process is more stable, and the high yield and the high conversion rate of the cracking cyclization reaction are realized.
With continued reference to fig. 1, the light component removal column 3 is used for preliminary separation and purification of the crude lactide material obtained by the cleavage cyclization reaction to remove light components (substances with boiling points lower than that of lactide, such as free acids, etc.) from the crude lactide material. The light component removing tower 3 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown), a discharge outlet (not shown) and an exhaust outlet (not shown). The feed inlet of the light component removal tower 3 is communicated with the discharge outlet of the cracking cyclization reactor 2, and a communication pipeline between the light component removal tower 3 and the cracking cyclization reactor 2 is provided with a switch valve (not shown) and a centrifugal pump (not shown). The light component removing tower 3 can be a light component removing tower, which is in the prior art and is not described in detail herein.
With continued reference to fig. 1, the de-heavies column 4 is used to further separate and purify the crude lactide material obtained by the cleavage cyclization reaction to remove heavy components (materials with boiling points higher than that of lactide, such as oligomers, etc.) from the crude lactide material. The weight removing tower 4 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown) and a discharge outlet (not shown). The feed inlet of the heavy-removal tower 4 is communicated with the discharge outlet of the light-removal tower 3, and a switching valve (not shown) and a centrifugal pump (not shown) are arranged on a communicating pipeline between the heavy-removal tower 4 and the light-removal tower 3. The heavy component removing tower 4 can be a heavy component removing tower, which is in the prior art and is not described in detail herein.
Specifically, in this embodiment, by adding the light component removal tower 3 and the heavy component removal tower 4 to the communication pipeline between the pyrolysis cyclization reactor 2 and the falling film crystallizer 5, the lactide obtained through the pyrolysis cyclization reaction can be separated and purified in advance, and further, the energy consumption in the subsequent crystallization process can be further reduced.
With continued reference to fig. 1, the falling film crystallizer 5 is used for further separation and purification of the lactide material previously separated and purified by the light component removal tower 3 and heavy component removal tower 4. The falling film crystallizer 5 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown), a discharge outlet (not shown), a waste liquid outlet (not shown), a cold and hot coal inlet (not shown), a cold and hot coal outlet (not shown) and a crystallization mother liquor outlet (not shown). The feed inlet of the falling film crystallizer 5 is communicated with the discharge outlet of the de-weight tower 4, and a switch valve (not shown) and a centrifugal pump (not shown) are arranged on a communicating pipeline between the falling film crystallizer 5 and the de-weight tower 4. The waste liquid outlet of the falling film crystallizer 5 is communicated with the feed inlet of the light component removing tower 3 and/or the heavy component removing tower 4, and a communication pipeline between the waste liquid outlet of the falling film crystallizer 5 and the feed inlet of the light component removing tower 3 and/or the heavy component removing tower 4 is provided with a switch valve (not shown) and a centrifugal pump (not shown). The falling film crystallizer 5 may be a falling film crystallizer (such as CN 211025203U) capable of countercurrent heat transfer, which is the prior art and is not described herein.
With continued reference to fig. 1, the static crystallizer 6 is used for purifying the crystallization mother liquor obtained by the purification of the falling film crystallizer 5 to recover lactide in the crystallization mother liquor. The static crystallizer 6 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown), a discharge outlet (not shown), a waste liquid outlet (not shown), a cold and hot coal inlet (not shown) and a cold and hot coal outlet (not shown). The feed inlet of the static crystallizer 6 is communicated with the crystallization mother liquor outlet of the falling film crystallizer 5, and a switch valve (not shown) and a centrifugal pump (not shown) are arranged on a communicating pipeline between the static crystallizer 6 and the falling film crystallizer 5. The waste liquid outlet of the static crystallizer 6 is communicated with the feed inlet of the light component removal tower 3 and/or heavy component removal tower 4, and a switch valve (not shown) and a centrifugal pump (not shown) are arranged on a communicating pipeline between the waste liquid outlet of the static crystallizer 6 and the feed inlet of the light component removal tower 3 and/or heavy component removal tower 4. The static crystallizer 6 may be a plate-type static crystallizer (e.g., a plate heat exchanger crystallizer operated intermittently). The plate-type static crystallizer is the prior art and is not described in detail here.
Specifically, by connecting the waste liquid outlets of the falling film crystallizer 5 and the static crystallizer 6 to the feed inlets of the light component removal column 3 and/or heavy component removal column 4, lactide in the waste liquid separated and purified by the falling film crystallizer 5 and the static crystallizer 6 can be sent to the light component removal column 3 and/or heavy component removal column 4, thereby further improving the yield.
The principle of the polylactic acid production system of this embodiment is: by providing the falling film crystallizer 5 and/or the static crystallizer 6 on the communication pipe between the de-weight column 4 and the polymerization column 7, the purity of lactide can be improved, thereby simplifying the production process of high molecular weight polylactic acid and reducing the cost.
With continued reference to fig. 1, a polymerization column 7 is used as a reaction vessel for the polymerization of high purity lactide, and in the polymerization column 7, high purity lactide is polymerized in the presence of an initiator (e.g., pentaerythritol) and a third catalyst (e.g., zrO 2 -CeO 2 Solid superacid catalyst) to produce high molecular weight polylactic acid. The polymerization column 7 is provided with a temperature adjusting assembly (not shown), a pressure adjusting assembly (not shown), a feed inlet (not shown) and a discharge outlet (not shown). The feed inlet of the polymerization tower 7 is communicated with the discharge outlet of the falling film crystallizer 5 and the discharge outlet of the static crystallizer 6, and a communicating pipeline between the polymerization tower 7 and the static crystallizer 6 and a communicating pipeline between the polymerization tower 7 and the falling film crystallizer 5 are respectively provided with a switch valve (not shown) and a centrifugal pump (not shown). The polymerization column 7 may employ a DSR type reactor. The DSR-type reactor is prior art and is not described in detail herein.
With continued reference to fig. 1, the end-capping devolatilizer 8 is used as a reaction vessel for end-capping the crude lactic acid obtained by polymerization, and recovering lactide from the crude lactic acid. In the capping devolatilizer 8, the lactic acid undergoes a capping reaction under the action of a capping agent (at least one of phosphorus compounds, antioxidants, acrylic acid derivatives, and organic peroxides). The end-capped devolatilizer 8 is provided with a temperature adjusting component (not shown), a pressure adjusting component (not shown), a feed inlet (not shown), a discharge outlet (not shown) and an air outlet (not shown), and the air outlet is positioned on the upper portion of the end-capped devolatilizer 8. The feed inlet of the end-capped devolatilizer 8 is communicated with the discharge outlet of the polymerization tower 7, the gas outlet of the end-capped devolatilizer 8 is communicated with the feed inlet of the light-weight removal tower 3 and/or the heavy-weight removal tower 4, and a communicating pipeline between the end-capped devolatilizer 8 and the polymerization tower 7 and a communicating pipeline between the end-capped devolatilizer 8 and the light-weight removal tower 3 and/or the heavy-weight removal tower 4 are provided with a switch valve (not shown) and a centrifugal pump (not shown). The end cap devolatilizer 8 may be a DSXL end cap devolatilizer. The DSXL type end-capped devolatilizer is prior art and is not described in detail herein.
Specifically, the gas outlet of the end-capped devolatilizer 8 is connected to the feed inlet of the light component removal column 3 and/or heavy component removal column 4, so that lactide removed from lactic acid can be sent to the light component removal column 3 and/or heavy component removal column 4 for recycling, thereby improving the yield.
The production working process of the polylactic acid production system of this embodiment is as follows:
feeding liquid lactic acid (the purity is about 90wt%, the flow is 1000 kg/h) and a first catalyst (at least one of tin, stannous chloride and stannous octoate), wherein the dosage of the first catalyst is 0.15wt% of the mass of lactic acid contained in the liquid lactic acid) into a dehydration oligomerization tower 1 through a feed inlet, regulating the bottom temperature of the dehydration oligomerization tower 1 to 170-175 ℃, the top pressure to 2-3.5kPa, the top temperature to 89-91 ℃, dehydrating and oligomerization of the lactic acid to form an oligomer under the catalysis of the first catalyst, and discharging the obtained water through an air outlet at the upper part (cooling and then delivering the water to a wastewater treatment unit for treatment);
opening a switching valve and a centrifugal pump on a communication pipeline between the dehydration oligomerization tower 1 and the pyrolysis cyclization reactor 2, pumping the oligomer into the pyrolysis cyclization reactor 2, adding a second catalyst (zinc lactate, the dosage of which is 0.4wt% of the mass of the oligomer) into the pyrolysis cyclization reactor 2, adjusting the temperature of the pyrolysis cyclization reactor 2 to 230-235 ℃ and the pressure to 2-4kPa, and continuously mixing, efficiently transferring heat, distributing and dispersing the oligomer generated by depolymerization of the lactic acid and the second catalyst in the pyrolysis cyclization reactor 2, thereby effectively improving the mass transfer efficiency and the heat transfer efficiency; the oligomer and the second catalyst flow in a plug flow manner in the cracking cyclization reactor 2, so that the residence time of the oligomer and the second catalyst in the cracking cyclization reactor 2 is kept consistent, the whole reaction process is more stable, and the high yield and the high conversion rate of the cracking cyclization reaction are realized, so that a crude lactide material (the purity is about 98 wt%);
opening a switching valve and a centrifugal pump on a communication pipeline between the cracking cyclization reactor 2 and the light component removing tower 3, pumping the crude lactide material into the light component removing tower 3, adjusting the temperature of the light component removing tower 3 to be 140-150 ℃ and the pressure to be 8-10kPa, and separating light components (such as free acid and the like) in the crude lactide material;
opening a switching valve and a centrifugal pump on a communication pipeline between the light component removal tower 3 and the heavy component removal tower 4, pumping the crude lactide material into the heavy component removal tower 4, adjusting the temperature of the heavy component removal tower 4 to 160-170 ℃ and the pressure to 5-8kPa, and separating heavy components (such as oligomers and the like) in the crude lactide material;
opening a switching valve and a centrifugal pump on a communication pipeline between the falling film crystallizer 5 and the de-re-drying tower 4, pumping lactide materials separated and purified in advance through the de-light tower 3 and the de-re-drying tower 4 into the falling film crystallizer 5, cooling and crystallizing at a constant speed of 0.5 ℃/min through a refrigerant, then slowly heating up and sweating at a speed of 0.3 ℃/min through a heating medium to remove impurities so as to obtain a primary crystallization product, repeatedly crystallizing the primary crystallization product according to the conditions so as to obtain a secondary crystallization product, adjusting the temperature of the falling film crystallizer 5 to 40-140 ℃, further separating and purifying the lactide materials in the falling film crystallizer 5, opening the switching valve and the centrifugal pump on the communication pipeline between a waste liquid outlet of the falling film crystallizer 5 and a feed inlet of the de-light tower 3 and/or the de-re-drying tower 4, and delivering waste liquid separated and purified by the falling film crystallizer 5 into the de-light tower 3 and/or the de-re-drying tower 4 so as to recover lactide in the waste liquid, and improve the yield;
opening a switch valve and a centrifugal pump on a communication pipeline between the static crystallizer 6 and the falling film crystallizer 5, pumping the crystallization mother liquor obtained by separation and purification of the falling film crystallizer 5 into the static crystallizer 6, cooling and crystallizing at a constant speed of 0.2 ℃/min through a refrigerant, then slowly heating and sweating at a speed of 0.1 ℃/min through a heating medium to remove impurities to obtain a primary crystallization product, repeatedly crystallizing the primary crystallization product according to the conditions to obtain a secondary crystallization product, regulating the temperature of the static crystallizer 6 to 40-140 ℃, separating and purifying the crystallization mother liquor in the static crystallizer 6 to obtain high-purity lactide, opening the switch valve and the centrifugal pump on the communication pipeline between a waste liquor outlet of the static crystallizer 6 and a feed inlet of the light component removal tower 3 and/or the heavy component removal tower 4, and sending the waste liquor obtained by separation and purification of the static crystallizer 6 into the light component removal tower 3 and/or the heavy component removal tower 4 to recover lactide in the waste liquor, thereby improving the yield;
opening a communication pipe between the polymerization tower 7 and the static crystallizer 6 and between the polymerization tower 7 and the falling film crystallizer 5A switching valve and a centrifugal pump on a communication pipeline, the high-purity lactide is pumped into a polymerization tower 7, and an initiator pentaerythritol (the dosage of which is 5 weight percent of the mass of the high-purity lactide) and a third catalyst ZrO are added into the polymerization tower 7 2 -CeO 2 A solid superacid catalyst (the dosage is 0.15wt% of the mass of the high-purity lactide), the temperature of the polymerization tower 7 is regulated to be 180-220 ℃, the pressure is 2-6kPa, the high-purity lactide is added in an initiator pentaerythritol (the dosage is 5wt% of the mass of the high-purity lactide) and a third catalyst ZrO 2 -CeO 2 Polymerizing in the presence of solid super acid catalyst to obtain coarse lactic acid;
opening a switching valve and a centrifugal pump on a communication pipeline between the end-capping volatilizer 8 and the polymerization tower 7, pumping crude lactic acid into the end-capping volatilizer 8, wherein the lactic acid undergoes an end-capping reaction under the action of an end-capping agent (at least one of phosphorus compound, antioxidant, acrylic acid derivative and organic peroxide), wherein the dosage of the end-capping agent is 1.5wt% of the mass of the crude lactic acid, and lactide in the crude lactic acid is separated in the process; opening a switching valve and a centrifugal pump on a communication pipeline between the air outlet of the end-capped volatilizer 8 and the light component removing tower 3 and/or the heavy component removing tower 4, and sending the lactide into the light component removing tower 3 and/or the heavy component removing tower 4 to recover the lactide and improve the yield.
Example 2
As shown in fig. 2, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: the static crystallizer 6 is not included.
Example 3
As shown in fig. 3, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: the falling film crystallizer 5 is not included, and the discharge port of the de-weight tower 4 is communicated with the feed port of the static crystallizer 6.
Example 4
As shown in fig. 4, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: the light component removing tower 3 and the heavy component removing tower 4 are not included, and the discharge port of the cracking cyclization reactor 2 is communicated with the feed port of the falling film crystallizer 6.
Example 5
As shown in fig. 5, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: the light component removing tower 3 is not included, and the discharge port of the cracking cyclization reactor 2 is communicated with the feed port of the heavy component removing tower 6.
Example 6
As shown in fig. 6, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: the light component removing tower (4) is not included, and the discharge port of the light component removing tower (3) is communicated with the feed port of the falling film crystallizer (5).
Example 7
As shown in fig. 7, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: also comprises a prepolymerization reactor 9, wherein the prepolymerization reactor 9 is positioned on a communication pipeline between the polymerization tower 7 and the falling film crystallizer 5.
With continued reference to fig. 7, the prepolymerization reactor 9 is provided with a temperature adjusting assembly (not shown), a pressure adjusting assembly (not shown), a feed inlet (not shown) and a discharge outlet (not shown). The communication pipeline between the prepolymerization reactor 9 and the polymerization tower 7 and the communication pipeline between the prepolymerization reactor 9 and the falling film crystallizer 5 are respectively provided with a switch valve (not shown) and a centrifugal pump (not shown). The prepolymerization reactor 9 adopts a micro-reactor, which is the prior art and is not described in detail here.
Specifically, by adding the prepolymerization reactor 9 to the communication pipe between the polymerization tower 7 and the falling film crystallizer 5 and setting the prepolymerization reactor 9 to be a microreactor, the lactide and the second catalyst can be subjected to sufficient mass transfer and heat transfer, the lactide can be thoroughly reacted, and the yield can be improved.
Example 8
As shown in fig. 8, the polylactic acid production system according to this embodiment differs from that according to example 1 in that: the device also comprises a hot coal storage container 10, a refrigerant storage container 11 and a heat pump system 12, wherein the end-capped devolatilizer 8 is provided with a heat medium inlet (not shown).
With continued reference to fig. 8, the heat pump system 12 communicates the hot coal storage vessel 10 with the refrigerant storage vessel 11. The heat pump system is a prior art and will not be described in detail here.
With continued reference to fig. 8, the cold coal storage container 11 and the heat medium storage container 10 are respectively used as storage containers for a refrigerant and a heat medium, the cold coal storage container 11 and the heat medium storage container 10 are both communicated with cold and hot coal inlets of the falling film crystallizer 5 and/or the static crystallizer 6, and the heat medium storage container 10 is also communicated with a heat medium inlet of the end-capped devolatilizer 8.
Specifically, in this embodiment, by adding the hot coal storage container 10, the refrigerant storage container 11 and the heat pump system 12, and connecting the hot coal storage container 10 and the refrigerant storage container 11 to the cold and hot coal inlets of the falling film crystallizer 5 and/or the static crystallizer 6, the hot coal storage container 10 is also connected to the hot medium inlet of the end-capped devolatilizer 8, so that the crystallization temperature, the crystallization time, the devolatilization temperature and the devolatilization time can be precisely controlled, and further the purity of lactide and the purity of polylactic acid can be improved, and the energy consumption can be reduced.
It should be understood that the order of the light component removal tower 3 and the heavy component removal tower 4 and the order between the falling film crystallizer 5 and the static crystallizer 6 can be adjusted by one skilled in the art based on the present embodiment. Namely, the discharge port of the cracking cyclization reactor 2 is communicated with the feed port of the de-weight tower 4, the discharge port of the de-weight tower 4 is communicated with the feed port of the de-light tower 3, the discharge port of the de-light tower 3 is communicated with the feed port of the static crystallizer 6, and the crystallization mother liquor outlet of the static crystallizer 6 is communicated with the feed port of the falling film crystallizer 5.
The above embodiments are merely illustrative of the principles of the present utility model and its effectiveness, and are not intended to limit the utility model. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the utility model. It is therefore intended that all equivalent modifications and changes made by those skilled in the art without departing from the spirit and technical spirit of the present utility model shall be covered by the appended claims.
Claims (10)
1. The polylactic acid production system is characterized by comprising a dehydration Ji Juda, a cracking cyclization reactor, a polymerization tower and an end-capped devolatilizer which are sequentially communicated, wherein a falling film crystallizer and/or a static crystallizer are arranged on a communication pipeline between the cracking cyclization reactor and the polymerization tower.
2. The polylactic acid production system according to claim 1, wherein the cleavage cyclization reactor is a plug flow reactor.
3. The polylactic acid production system according to claim 1, further comprising a rectifying device located on a communication pipe between the cleavage cyclization reactor and the falling film crystallizer or the static crystallizer.
4. A polylactic acid production system according to claim 3, wherein the rectifying means comprises a light component removal column and/or a heavy component removal column.
5. The polylactic acid production system according to claim 4, wherein an air outlet is provided at an upper portion of the end-capped devolatilizer, and the air outlet is communicated with the light component removal tower and/or heavy component removal tower.
6. The polylactic acid production system according to claim 4, wherein the falling film crystallizer and/or the static crystallizer is provided with a waste liquid outlet, which communicates with the light component removal column and/or the heavy component removal column.
7. The polylactic acid production system according to claim 1, wherein the static crystallizer is a plate-type static crystallizer.
8. The polylactic acid production system according to claim 1, further comprising a prepolymerization reactor located on a communication pipe between the polymerization tower and the falling film crystallizer or the static crystallizer.
9. The polylactic acid production system according to claim 8, wherein the pre-polymerization reactor employs a micro-reactor.
10. The polylactic acid production system of claim 1, further comprising a cold coal storage vessel, a heat medium storage vessel, and a heat pump system, wherein the heat pump system is in communication with the cold coal storage vessel and the heat medium storage vessel, wherein the cold coal storage vessel and the heat medium storage vessel are both in communication with the falling film crystallizer and/or the static crystallizer, and wherein the heat medium storage vessel is also in communication with the end-capped devolatilizer.
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