阅读说明：本技术 一种abs挤出机脱挥回收方法及回收系统 (Devolatilization recovery method and recovery system of ABS extruder ) 是由 王红艳 高飞 郑百清 王海娟 张秉建 李金宇 李名岩 李聪 武琳 卢家玉 于 2021-11-04 设计创作，主要内容包括：本发明公开了一种ABS挤出机脱挥回收系统,包括一级缓冲罐、二级缓冲罐、一级冷凝器、二级冷凝器；所述一级冷凝器和二级冷凝器下面分别设有一级缓冲罐、二级缓冲罐,所述一级缓冲罐下游布置有爪型真空泵,其中ABS挤出机设有三个脱挥口,所述ABS挤出机脱挥口的出口管线上设有两台氧气分析仪,所述两台氧气分析仪并联设置；所述ABS挤出机的第三脱挥口与二级冷凝器入口连通。本发明提供的一种ABS挤出机脱挥回收方法及回收系统,能够显著减少挤出机脱挥口有毒有害气体的排放量。系统中采用了爪型干式真空泵对系统进行抽真空,真空工艺流程无油,无水,对工艺介质没有污染,可实现工艺介质的清洁回收。(The invention discloses a devolatilization recovery system of an ABS extruder, which comprises a primary buffer tank, a secondary buffer tank, a primary condenser and a secondary condenser; a primary buffer tank and a secondary buffer tank are respectively arranged below the primary condenser and the secondary condenser, a claw-type vacuum pump is arranged at the downstream of the primary buffer tank, the ABS extruder is provided with three devolatilization ports, two oxygen analyzers are arranged on an outlet pipeline of the devolatilization ports of the ABS extruder, and the two oxygen analyzers are arranged in parallel; and a third devolatilization port of the ABS extruder is communicated with an inlet of the secondary condenser. The devolatilization recovery method and the devolatilization recovery system of the ABS extruder, provided by the invention, can obviously reduce the discharge amount of toxic and harmful gases at the devolatilization port of the extruder. A claw-type dry vacuum pump is adopted in the system to vacuumize the system, the vacuum process flow is oil-free and water-free, the process medium is not polluted, and the process medium can be cleanly recovered.)

1. The devolatilization recovery system of the ABS extruder is characterized by comprising a primary buffer tank (1), a secondary buffer tank (2), a primary condenser (4) and a secondary condenser (6); a primary buffer tank (1) and a secondary buffer tank (2) are respectively arranged below the primary condenser (4) and the secondary condenser (6), a claw-type vacuum pump (5) is arranged at the downstream of the primary buffer tank (1), wherein the ABS extruder is provided with three devolatilization ports, two oxygen analyzers (8) are arranged on an outlet pipeline of the devolatilization port of the ABS extruder (3), and the two oxygen analyzers (8) are arranged in parallel; and a third devolatilization port of the ABS extruder (3) is communicated with an inlet of the secondary condenser (6).

2. The devolatilization recovery system of the ABS extruder as claimed in claim 1, wherein pneumatic control valves are provided at the junctions of the third devolatilization pipeline of the ABS extruder (3) and the outlet pipelines of the first devolatilization port and the second devolatilization port, respectively, the pneumatic control valves are a control valve (17) for switching the volatile gas discharge path and a control valve (18) for switching the volatile gas discharge path.

3. The devolatilization recovery system of the ABS extruder as claimed in claim 1, wherein there are two parallel primary buffer tanks (1) and two parallel secondary buffer tanks (2).

4. The devolatilization recovery system of the ABS extruder as claimed in claim 1, wherein said primary buffer tank (1) and said secondary buffer tank (2) are respectively communicated with a recovery tank (7), and said recovery tank (7) is communicated with the reaction kettle.

5. The devolatilization and recovery system of the ABS extruder as claimed in claim 1, wherein an upper air outlet of the primary buffer tank (1) is communicated with the secondary condenser (6), and a claw vacuum pump (5) is arranged between the upper air outlet of the primary buffer tank (1) and the secondary condenser (6).

6. The devolatilization recovery system of an ABS extruder as claimed in claim 1, wherein said secondary buffer tank (2) is provided with a nitrogen purge device.

7. The devolatilization recovery system as claimed in claim 3 in which the two discharge lines of the secondary buffer tank (2) have outlet self-control valves interlocked with the pressure transducers of the secondary buffer tank.

8. The devolatilization recovery method of the ABS extruder is characterized by comprising the following steps:

1) mixed gas of three devolatilization ports of the ABS extruder enters a primary condenser (4), the mixed gas is condensed by adopting an ethylene glycol aqueous solution with the freezing mass percentage of 50 percent at the temperature of minus 25 ℃, the condensed gas is conveyed into a primary buffer tank (1), uncondensed gas enters a claw type vacuum pump (5) through a gas outlet at the upper part of the primary buffer tank (1), passes through the claw type vacuum pump (5) and then enters a secondary condenser (6);

2) the liquid phase condensed by the secondary condenser (6) enters the secondary buffer tank (2), and the non-condensable gas is discharged through an air outlet at the upper part of the secondary buffer tank (2);

3) two oxygen analyzers (8) connected in parallel with an outlet pipeline of the devolatilization port of the ABS extruder are used for monitoring the oxygen content in the pipeline in real time, if air enters the pipeline, when the oxygen content analyzers reach a monitoring set value, a system controls a claw type vacuum pump (5) to stop, and simultaneously a control valve (18) of a second switching volatile gas exhaust path on a pipeline for communicating the third devolatilization port with an inlet of a secondary condenser (6) is opened;

4) the devolatilized gas of the ABS extruder flows to a secondary condenser (6) through a control valve for switching a discharge path of the volatilized gas, and is discharged outdoors after being condensed by the secondary condenser (6); and (3) opening a nitrogen purging valve of the secondary condenser (6) to perform nitrogen purging and replacement, and after the oxygen content in the system is qualified, closing a control valve (18) for switching the volatile gas discharge path by system control, and manually starting the claw type vacuum pump (5) again.

9. The devolatilization recovery method of ABS extruder as claimed in claim 8, wherein the inlet temperature of claw vacuum pump (5) is 170 ℃, the inlet pressure is 50Pa, and the inlet air amount is 1.5 kg/h.

Technical Field

The invention relates to the technical field of auxiliary devices of ABS extruders, in particular to a devolatilization recovery method and a devolatilization recovery system of an ABS extruder.

Background

The ABS extruder can generate partial volatile gas, the volatile gas is pumped out by a vacuum pump and condensed, the gas is evacuated, and the liquid phase is recovered; for example, in the prior art, most of the mixed gas of the volatile gas ethylbenzene, styrene, acrylonitrile and the like at the devolatilization outlet of the ABS extruder is condensed by a primary condenser and then falls into a buffer tank for recovery, and the non-condensable gas is directly led to a high point through a pipeline for safety emptying. Because only primary and normal pressure condensation is carried out, the recovery effect on acrylonitrile with relatively high volatility is poor. Acrylonitrile is not only flammable and explosive, but also belongs to toxic gas with serious harm.

Therefore, it is an urgent need to solve the problem of providing a method capable of increasing the recovery rate of the volatile gas of the ABS extruder, thereby reducing the emission of toxic and harmful gases.

Disclosure of Invention

In view of the above, the invention discloses and provides a devolatilization recovery method and a recovery system for an ABS extruder, so as to improve the recovery rate of volatile gas of the extruder;

the technical scheme provided by the invention is that the devolatilization recovery system of the ABS extruder comprises a primary buffer tank, a secondary buffer tank, a primary condenser and a secondary condenser; a primary buffer tank and a secondary buffer tank are respectively arranged below the primary condenser and the secondary condenser, a claw-type vacuum pump is arranged at the downstream of the primary buffer tank, the ABS extruder is provided with three devolatilization ports, two oxygen analyzers are arranged on an outlet pipeline of the devolatilization ports of the ABS extruder, and the two oxygen analyzers are arranged in parallel; and a third devolatilization port of the ABS extruder is communicated with an inlet of the secondary condenser.

Furthermore, a pneumatic control valve is arranged at the junction of a third devolatilization port pipeline of the ABS extruder and outlet pipelines of the first devolatilization port and the second devolatilization port, and the pneumatic control valve is a control valve for switching the volatile gas discharge path in a first mode and a control valve for switching the volatile gas discharge path in a second mode.

Furthermore, two primary buffer tanks are arranged in parallel, and two secondary buffer tanks are arranged in parallel.

Further, the first-stage buffer tank and the second-stage buffer tank are respectively communicated with a recovery tank, and the recovery tank is communicated with the reaction kettle.

Furthermore, an air outlet in the upper part of the primary buffer tank is communicated with the secondary condenser, and a claw type vacuum pump is arranged between the air outlet in the upper part of the primary buffer tank and the secondary condenser.

Further, the secondary buffer tank is provided with a nitrogen purging device.

Furthermore, the outlet self-control valves on the discharge pipelines of the two secondary buffer tanks are interlocked with the pressure transmitters on the secondary buffer tanks.

On the other hand, the invention provides a devolatilization recovery method of an ABS extruder, which comprises the following steps:

1) the mixed gas of three devolatilization ports of the ABS extruder enters a primary condenser, the mixed gas is condensed by adopting a glycol aqueous solution with the freezing mass percentage of 50 percent at the temperature of minus 25 ℃, the condensed gas is conveyed into a primary buffer tank, the uncondensed gas enters a claw type vacuum pump through a gas outlet at the upper part of the primary buffer tank and enters a secondary condenser after passing through the claw type vacuum pump;

2) the liquid phase condensed by the secondary condenser enters a secondary buffer tank, and the non-condensable gas is discharged through an air outlet at the upper part of the secondary buffer tank;

3) monitoring the oxygen content in the pipeline in real time through two oxygen analyzers connected in parallel to an outlet pipeline of the devolatilization port of the ABS extruder, and if air enters the pipeline and the oxygen content analyzers reach a monitoring set value, stopping a system control claw type vacuum pump, and simultaneously opening a control valve of a second switching volatile gas discharge path on a pipeline for communicating a third devolatilization port with an inlet of a secondary condenser;

4) the devolatilized gas of the ABS extruder flows to a secondary condenser through a control valve for switching a devolatilized gas discharge path, and is discharged out of the room after being condensed by the secondary condenser; and (3) opening a nitrogen purging valve of the secondary condenser to perform nitrogen purging and replacement, and after the oxygen content in the system is qualified, closing a control valve for switching the volatile gas discharge path by the system control, and manually starting the claw type vacuum pump again.

Furthermore, the inlet temperature of the claw vacuum pump is 170 ℃, the inlet pressure is 50Pa, and the air input is 1.5 kg/h.

The invention provides a devolatilization recovery method and a devolatilization recovery system of an ABS extruder. Can obviously reduce the discharge of toxic and harmful gases at the devolatilization port of the extruder. The volatile gas recovered in the process method can be recycled as a raw material, so that the material loss is reduced, the pollution to the environment is reduced, and the effects of energy conservation and emission reduction are achieved. The system is vacuumized by adopting an LAHEE claw type dry vacuum pump, the vacuum process flow is oil-free and water-free, the process medium is not polluted, and the process medium can be cleanly recovered. Has higher vacuum stability and equipment safety, low energy consumption and high tail gas recovery cleanliness.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic structural view of a devolatilization recovery system of an ABS extruder according to an embodiment of the present disclosure.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of systems consistent with certain aspects of the invention, as detailed in the appended claims.

In the prior art, the vacuum system of the ABS extruder only has one vacuum pump, and if the oxygen content in the system exceeds the standard, equipment is shut down, so that the normal operation of the extruder is influenced. The embodiment relates to an ABS extruder devolatilization material of 1.5 kg/h; the feed composition is as follows:

feed composition

Serial number	Components	Content (wt%)
			1	Ethylbenzene production	67.7
2	Styrene (meth) acrylic acid ester	25.7
			3	Acrylonitrile	6.1
4	Small molecule polymers	0.5

A devolatilization recovery system of an ABS extruder comprises a primary buffer tank 1, a secondary buffer tank 2, a primary condenser 4 and a secondary condenser 6; a primary buffer tank 1 and a secondary buffer tank 2 are respectively arranged below the primary condenser 4 and the secondary condenser 6, a claw-type vacuum pump 5 is arranged at the downstream of the primary buffer tank 1, wherein the ABS extruder is provided with three devolatilization ports,

the three sight glass cover plates of the first devolatilization port, the second devolatilization port and the third devolatilization port of the extruder are locked by a lock catch, so that air cannot enter the system during vacuum pumping, and not less than 4 sight glass ports are formed. The guide shower is added after the manual valve of each devolatilization port, and micromolecule sticky substances in the vacuum pipeline can be discharged in a planned way. The specification of the pilot shower is DN20, each pilot shower is provided with a socket welding root valve, and the pipeline adopts316 stainless steel line.

Two oxygen analyzers 8 are arranged on an outlet pipeline of a devolatilization port of the ABS extruder 3, and the two oxygen analyzers 8 are arranged in parallel; the purpose is that the double insurance ensures the safe operation of the device; and a third devolatilization port of the ABS extruder 3 is communicated with an inlet of a secondary condenser 6. Two buffer tanks are respectively arranged below the first-stage condenser and the second-stage condenser and used for switching during discharging, the first-stage buffer tank 1 and the second-stage buffer tank 2 are respectively communicated with the recovery tank 7, and the recovery tank 7 is communicated with the reaction kettle. The liquid phase that this system discharged the buffer tank gets into the recovery tank, when the liquid level reachd appointed liquid level in the recovery tank, opens recovery tank outlet valve and sends the lime set to reation kettle. The top of the recovery tank 7 is provided with a safety valve;

as a further improvement of the technical scheme, the part 7 of the recovery tank is cooled and kept cold by adopting chilled water so as to reduce the liquid loss in the tank, and the recovery tank 7 is also provided with a DN25 nitrogen purging interface and is additionally provided with a root valve; the safety valve is arranged to realize overpressure relief in an accident state so as to protect the storage tank, and the relief pipeline is led to a high point outside the plant for emptying; the top of the recovery tank 7 is provided with a pressure transmitter, so that the alarm can be given when the pressure in the tank is high or low; the liquid level transmitter L is arranged, so that the high and low alarms of the liquid level in the tank can be realized. A combustible/toxic gas detection alarm is additionally arranged near the secondary buffer tank, so that the audible and visual alarm of a combustible/toxic gas leakage site and a control room can be realized. And important control parameter data such as oxygen content, the operating state of the claw vacuum pump, cooling water flow and the like are introduced to a master control room. The purpose is that the monitoring can be carried out at any time, and the adjustment is convenient in time.

The lower parts of the first-stage buffer tank 1 and the second-stage buffer tank 2 are provided with a freezing water coil pipe and kept cold so as to reduce the loss of liquid materials in the tanks. (coil pipe adopted304 stainless steel pipeline, about 24 meters, each storage tank companion cold coil inlet tube and wet return all add socket joint welding root valve.

The junction of the third devolatilization port pipeline of the ABS extruder 3 and the outlet pipelines of the first devolatilization port and the second devolatilization port is provided with a pneumatic control valve which is a control valve 17 for switching the volatile gas discharge path and a control valve 18 for switching the volatile gas discharge path respectively, so as to carry out effective nitrogen purging and switch the devolatilization gas discharge path of the extruder in an abnormal state.

The first-stage buffer tanks 1 are arranged in parallel, and the second-stage buffer tanks 2 are arranged in parallel. An air outlet in the upper part of the primary buffer tank 1 is communicated with the secondary condenser 6, and a claw type vacuum pump 5 is arranged between the air outlet in the upper part of the primary buffer tank 1 and the secondary condenser 6. The secondary buffer tank 2 is provided with a nitrogen purging device. And the outlet self-control valves on the discharge pipelines of the two secondary buffer tanks 2 are interlocked with the pressure transmitters on the secondary buffer tanks. The automatic opening of the discharge valve can be realized when the pressure in the tank is higher than 0.08MPa, and the automatic closing of the discharge valve can be realized when the pressure in the tank is lower than 0.05 MPa. The purpose is to reduce the loss of liquid material in the receiving tank.

After the tail gas of the extruder is treated by the system, the gas is discharged, the condensate returns to the front system, and no product is produced; the ABS extruder can generate partial volatile gas, the volatile gas is pumped out by a vacuum pump and condensed, the gas is evacuated, and the liquid phase is recovered. The system of the embodiment comprises two vacuum pumps, so that the stable operation of the ABS extruder can be ensured.

The embodiment also provides a devolatilization recovery method of the ABS extruder, which comprises the following steps:

1) the mixed gas of three devolatilization ports of the ABS extruder enters a primary condenser 4, the mixed gas is condensed by adopting an ethylene glycol aqueous solution with the freezing mass percentage of 50 percent at the temperature of minus 25 ℃, the condensed gas is conveyed into a primary buffer tank 1, the uncondensed gas enters a claw vacuum pump 5 through a gas outlet at the upper part of the primary buffer tank 1, and enters a secondary condenser 6 after passing through the claw vacuum pump 5;

2) the liquid phase condensed by the secondary condenser 6 enters the secondary buffer tank 2, and the non-condensable gas is discharged through an air outlet at the upper part of the secondary buffer tank 2;

3) two oxygen analyzers 8 connected in parallel to an outlet pipeline of a devolatilization port of the ABS extruder are used for monitoring the oxygen content in the pipeline in real time, if air enters the pipeline, when the oxygen content analyzers reach a monitoring set value, a system controls a claw type vacuum pump 5 to stop, and simultaneously a control valve 18 of a second switching volatile gas exhaust path on a pipeline for communicating a third devolatilization port with an inlet of a secondary condenser 6 is opened;

4) the devolatilized gas of the ABS extruder flows to a secondary condenser 6 through a control valve for switching a discharge path of the volatilized gas, and is discharged out of the room after being condensed by the secondary condenser 6; and (3) opening a nitrogen purging valve of the secondary condenser (6) to perform nitrogen purging and replacement, and after the oxygen content in the system is qualified, closing a control valve (18) for switching the volatile gas discharge path under the control of the system, and manually starting the claw type vacuum pump (5) again.

Increase claw type vacuum pump 5 and carry out the evacuation to the system in 1 low reaches of one-level buffer tank, the vacuum pump export falls into second grade buffer tank 2 after entering 6 condensations of second grade condenser, and two buffer tanks are opened one and are equipped with, retrieve, and noncondensable gas leads to the high point through the pipeline and carries out the safety vent.

The embodiment sets a relatively perfect detection and automatic control system and a necessary signal interlocking protection system according to the scale of the process device, the process flow characteristics and the operation requirements. The specific system operation comprises the following steps:

nitrogen replacement before starting up: and manually opening a first nitrogen valve 9, a primary buffer tank inlet valve 10, a primary buffer tank outlet valve 11, a secondary buffer tank inlet valve 13, a secondary buffer tank outlet valve 14 and other automatic control valves, wherein nitrogen enters the primary buffer tank 1 from the primary condenser 4 and is discharged outdoors after passing through a claw type vacuum pump 5, a secondary condenser 6 and a secondary buffer tank 2.

After nitrogen replacement is carried out for 1 minute, a 1-take-off, 2-take-off and 3-take-off outlet hand valve, an air inlet main valve 16 and a control valve 18 of a second switching volatile gas discharge path are manually opened, a 3-take-off outlet first switching volatile gas discharge path control valve 17 is manually closed, and an inlet valve of a primary buffer tank is manually closed. And the nitrogen enters the extruder 3 from the degassing port 1 and the degassing port 2, and is discharged out of the room through a control valve 18 of a second switching volatile gas discharge path, the secondary condenser 6 and the 2-stage buffer tank 2 from the degassing port 3 in sequence.

After the nitrogen gas is replaced for 1 minute, the control valve 17 of the first switching volatile gas discharge path of the desorption 3 outlet is manually opened, the hand valve of the desorption 1 outlet and the desorption 2 outlet is closed, and the nitrogen gas is discharged from the desorption 3 port through the control valve 18 of the second switching volatile gas discharge path. After 1 minute of replacement with nitrogen gas, the control valve 18, the intake main valve 16, the valve 9 from the nitrogen main line, the primary buffer tank outlet valve 11, the secondary buffer tank inlet valve 13, and the secondary buffer tank outlet valve 14 from the second switching volatile gas discharge path were manually closed.

Starting up: the control valve 18 of the second switching volatile gas discharge path, the main air inlet valve 16, the primary buffer tank inlet valve 10, the primary buffer tank outlet valve 11, the first nitrogen supplementing valve 12, the secondary buffer tank inlet valve 13, the secondary buffer tank outlet valve 11 and the second nitrogen supplementing valve 15 are in a closed state, and the control valve 17 of the first switching volatile gas discharge path is in an open state.

In an automatic state, a system starting button is pressed, the main air inlet valve 16, the primary buffer tank inlet valve 10, the primary buffer tank outlet valve 11, the secondary buffer tank inlet valve 13 and the secondary buffer tank outlet valve 14 are automatically opened, and the system starts to operate normally.

Stopping the machine: normal shutdown conditions: and pressing a system stop button, closing the air inlet main valve 16, the primary buffer tank inlet valve 10, the primary buffer tank outlet valve 11, the secondary buffer tank inlet valve 13 and the secondary buffer tank outlet valve 14, stopping the operation of the claw type vacuum pump 5, automatically opening the first nitrogen supplementing valve 12 and the second nitrogen supplementing valve 15, and automatically closing the system after the system is filled with nitrogen to 0.05 MPa.

The shutdown conditions of abnormal cooling water flow, temperature, claw vacuum pump current, temperature and the like are as follows: the claw type vacuum pump 5 stops running, the control valve 18 of the second switching volatile gas discharge path is automatically opened, the devolatilized gas of the extruder is discharged through a devolatilization outlet 3, meanwhile, the automatic control valve of the air inlet main valve 16, the primary buffer tank inlet valve 10, the primary buffer tank outlet valve 11, the secondary buffer tank inlet valve 13 and the secondary buffer tank outlet valve 14 is closed, the first nitrogen supplementing valve 12 and the second nitrogen supplementing valve 15 are automatically opened, and the system is automatically closed after nitrogen is filled to 0.05 MPa. After the trouble discharge, the claw vacuum pump 5 is started, and the control valve 18 for switching the volatile gas discharge path is closed.

When the oxygen content exceeds the standard or the oxygen analyzer fails, the system automatically stops the claw type vacuum pump 5, automatically closes the air inlet main valve 16, automatically closes the control valve 17 of the first switching volatile gas discharge path, automatically opens the control valve 18 of the second switching volatile gas discharge path, opens the first nitrogen valve 9 and the second nitrogen valve 91, at the moment, the first-stage buffer tank inlet valve 10, the first-stage buffer tank outlet valve 11, the second-stage buffer tank inlet valve 13 and the second-stage buffer tank outlet valve 14 are in an open state, and one path of nitrogen discharges the combustible gas outdoors through the first-stage condenser 4, the first-stage buffer tank 1, the claw type vacuum pump 5 and the second-stage buffer tank 2; and the other path of nitrogen is sent to an extruder, combustible gas in the system and devolatilized gas at the outlet of the extruder are swept to a secondary condenser 6 for condensation, the condensed liquid enters a 2-stage buffer tank 2, and the non-condensable gas is discharged out of the room through a discharge port of the buffer tank 2. When the oxygen content detected by the oxygen analyzer is qualified, the first nitrogen valve 9 and the second nitrogen valve 91 are automatically closed, the control valve 18 of the second switching volatile gas discharge path is automatically closed, and the control valve 17 of the first switching volatile gas discharge path is automatically opened.

Switching operation of two first-level buffer tanks and two second-level buffer tanks: when one of the primary buffer tanks is in a working state, the system is automatically switched to the working state of the other parallel primary buffer tank after the liquid level reaches a set value, the system is automatically closed after nitrogen is filled to 0.05MPa, and a discharge valve of the primary buffer tank is manually opened. The secondary buffer tank is the same as the case.

Under the normal operating condition, in order to reduce the gas volatilization in the primary buffer tank 1, when the pressure in the secondary buffer tank 2 reaches 0.08MPa, the secondary outlet valve 14 is automatically opened to discharge the gas outdoors, and when the pressure in the secondary buffer tank 2 is lower than 0.05MPa, the secondary outlet valve 14 is automatically closed.

The centralized pressure detection in the system selects a pressure transmitter, and the local pressure detection selects a spring tube pressure gauge or a diaphragm pressure gauge. The centralized liquid level detection adopts a double-flange, magnetic float or float liquid level transmitter, and the local liquid level detection adopts a glass plate liquid level meter or a quartz glass tube liquid level meter. A diffusion catalytic combustion type detector is selected.

In conclusion, the embodiment directly introduces the devolatilization outlet gas of the extruder to the inlet of the secondary condenser 6, so that the devolatilization discharge path of the extruder is switched when the system is in an abnormal state (such as the dew point of the system causes the oxygen content to exceed the standard), and effective nitrogen purging is performed. The outlet of the oxygen content analyzer is firstly condensed by a second-stage condenser 6 and then exhausted to the atmosphere. The secondary buffer tank 2 adds nitrogen purging and protection measures.

The system adopts the LAHEE claw type dry vacuum pump to vacuumize the system, adopts the spiral reverse claw principle and the composite sealing technology, has no oil and water in the vacuum process flow, does not pollute the process medium, and can realize the clean recovery of the process medium. Compared with the traditional water ring vacuum pump and the reciprocating vacuum pump, the water ring vacuum pump and the reciprocating vacuum pump have higher vacuum stability and equipment safety, and are low in energy consumption and high in tail gas recovery cleanliness. By the system and the method provided by the embodiment, the mass recovery rate of the volatile gas at the outlet of the extruder can be improved to 99.9% from 83.3% in the prior art.

Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.