Tail gas treatment system for PBAT production line

Abstract

The utility model discloses a tail gas treatment system for a PBAT production line. An outlet of an esterification gas phase pipe is connected with a tail gas pipeline through an esterification liquid ring vacuum pump set; an outlet of the esterification wastewater pipe is connected with an inlet of the THF recovery rectifying tower, and a top exhaust port of the THF recovery rectifying tower is connected with a tail gas pipeline through a tower top condenser; an outlet of the polycondensation gas phase pipe is connected with a suction port of the steam-jet pump through the scraper spraying condenser, and an exhaust port of the steam-jet pump is connected with a tail gas pipeline through the mechanical vacuum pump set; an outlet of the tail gas pipeline is respectively connected with an inlet of the gas-liquid separation tank and a main inlet of the Venturi tube, and a bottom outlet of the gas-liquid separation tank is connected with the BDO receiving tube through a liquid seal bend; a wire mesh demister is arranged on the upper portion of an inner cavity of the gas-liquid separation tank, a top outlet of the gas-liquid separation tank is connected with a suction inlet of the Venturi tube, and an outlet of the Venturi tube is connected with the natural gas heat conduction oil furnace. According to the system, media and waste heat in tail gas can be recycled, the production cost is reduced, and meanwhile environmental benefits are improved.

Description

Technical Field

[0001] The utility model relates to a tail gas treatment system for a PBAT production line, belonging to the technical field of DOTP production devices. Background Art

[0002] Polybutylene terephthalate adipate (PBAT) is a biodegradable material. Its waste products can be quickly degraded in soil or water. The degradation products are non-toxic and widely used. It can be used to make disposable shopping bags, agricultural films, biomedical polymer materials, packaging bottles, etc. It can effectively solve white pollution and is increasingly used.

[0003] PBAT production is divided into esterification and polycondensation stages, both of which are high-temperature environments. The raw material 1,4-butanediol (BDO) is prone to side reactions at high temperatures to produce tetrahydrofuran. Part of it is condensed, distilled and purified as a by-product and sold, and part of it enters the exhaust system. The tetrahydrofuran content in the exhaust gas is generally 1500~3000mg / m³, which is much higher than the 50mg / m³ specified in the "Synthetic Resin Industry Pollutant Emission Standard" (GB 31572-2015).

[0004] The Chinese utility model patent with the announcement number CN 220531197U discloses a tail gas treatment device for PBAT and PBS polycondensation, including a base, an air intake box is arranged above the base, a filter cartridge is connected to the air intake box, a tail gas treatment box is connected to one side of the filter cartridge, a filter screen is arranged in the inner cavity of the filter cartridge, the filter cartridge is connected to the tail gas treatment box pipeline, a water tank is arranged on the tail gas treatment box, a nozzle is connected to the water tank, the nozzle is fixedly connected to the upper end of the inner cavity of the tail gas treatment box, and a water outlet valve is connected to the tail gas treatment box. When the utility model is used, it is convenient to use the activated carbon filter and the atomizing head for tail gas treatment, thereby reducing the impact of the gas on the environment, but the following problems still exist:

[0005] 1. The tail gas contains a large amount of organic matter, and the considerable calorific value is not fully utilized;

[0006] 2. Use activated carbon adsorption and filtration. The adsorption saturated activated carbon is hazardous waste, which will cause new environmental problems. It needs to be entrusted to a qualified unit for treatment, which will increase the cost of the enterprise and the risk of violation.

[0007] 3. The tail gas contains water, which affects the adsorption effect of activated carbon;

[0008] 4. Manual regular analysis and regular replacement of activated carbon are required, which generates hazardous solid waste and has high treatment costs;

[0009] 5. When the activated carbon is saturated and replaced, the tail gas is discharged into the air, causing environmental pollution;

[0010] 6. Tetrahydrofuran has a strong odor and low toxicity. Manual handling will affect the physical and mental health of workers. Utility Model Content

[0011] The purpose of the utility model is to overcome the problems existing in the prior art and provide a PBAT production line tail gas treatment system that can recover the medium and waste heat in the tail gas, reduce natural gas consumption and tail gas emissions, avoid the generation of hazardous solid waste, reduce production costs, and improve environmental benefits.

[0012] In order to solve the above technical problems, the PBAT production line tail gas treatment system of the utility model includes an esterification gas phase pipe, an esterification wastewater pipe and a condensation gas phase pipe, the outlet of the esterification gas phase pipe is connected to the suction port of the esterification liquid ring vacuum pump group, and the exhaust port of the esterification liquid ring vacuum pump group is connected to the tail gas pipeline;

[0013] The outlet of the esterification wastewater pipe is connected to the inlet of the THF recovery distillation tower, the top exhaust port of the THF recovery distillation tower is connected to the air inlet of the THF recovery tower top condenser, and the exhaust port of the THF recovery tower top condenser is connected to the tail gas pipeline;

[0014] The outlet of the polycondensation gas phase pipe is connected to the air inlet of the scraper spray condenser, the top exhaust port of the scraper spray condenser is connected to the suction port of the BDO steam jet pump, the exhaust port of the BDO steam jet pump is connected to the suction port of the mechanical vacuum pump group, and the exhaust port of the mechanical vacuum pump group is connected to the tail gas pipeline;

[0015] The outlet of the tail gas pipeline is respectively connected to the inlet of the gas-liquid separation tank and the main inlet of the venturi tube, and the bottom outlet of the gas-liquid separation tank is connected to the BDO receiving pipe through a liquid seal bend; a wire mesh demister is provided on the upper part of the inner cavity of the gas-liquid separation tank, the top outlet of the gas-liquid separation tank is connected to the suction inlet of the venturi tube, and the outlet of the venturi tube is connected to the natural gas thermal oil furnace.

[0016] Furthermore, the bottom drain port of the scraper spray condenser is connected to the inlet of the polycondensation hot well, and the top exhaust port of the polycondensation hot well is connected to the tail gas pipeline.

[0017] Furthermore, the bottom drainage port of the polycondensation hot well is connected to the inlet of a spray circulation pump, the outlet of the spray circulation pump is connected to the hot side inlet of a spray cooler, and the hot side outlet of the spray cooler is connected to the top spray port of the scraper spray condenser.

[0018] Furthermore, the vacuum spray liquid outlet of the BDO steam jet pump is connected to the inlet of the vacuum liquid seal tank, and the top exhaust port of the vacuum liquid seal tank is connected to the tail gas pipeline.

[0019] Furthermore, the bottom drain port of the vacuum liquid seal tank is connected to the inlet of a vacuum liquid circulation pump, the outlet of the vacuum liquid circulation pump is connected to the hot side inlet of a vacuum liquid cooler, and the hot side outlet of the vacuum liquid cooler is connected to the spray port of the BDO steam jet pump.

[0020] Furthermore, a tail gas regulating valve is provided on the main inlet pipeline of the venturi tube, and the opening of the tail gas regulating valve is controlled by the top pressure of the gas-liquid separation tank.

[0021] Furthermore, a BDO discharge regulating valve is installed in the BDO receiving pipe, and the opening of the BDO discharge regulating valve is controlled by the lower liquid level of the gas-liquid separation tank.

[0022] Compared with the prior art, the utility model has achieved the following beneficial effects: 1. The production of PBAT device requires heat transfer oil to provide reaction heat. The heat of heat transfer oil comes from the natural gas heat medium furnace. The tail gas contains a large amount of tetrahydrofuran, which has considerable calorific value. This system sends the tail gas into the heat medium furnace for incineration, which is fully burned into water and carbon dioxide, meets the emission standards, and can reduce the consumption of natural gas at the same time;

[0023] 2. To prevent moisture from entering the heat medium furnace and affecting the combustion effect of the heat medium furnace, the tail gas first enters the gas-liquid separation tank to remove moisture from the tail gas;

[0024] 3. Set up a Venturi tube to use the suction effect to ensure that the exhaust gas has sufficient pressure head to enter the heat medium furnace;

[0025] 4. Set up automatic liquid level control for automatic liquid discharge, without manual processing throughout the process;

[0026] 5. The commissioning of this system has good tail gas treatment effect, full utilization of calorific value, reduced production costs, high degree of automation, and ensured the stable production of the full-continuous PBAT production device;

[0027] 6. Avoid the generation of hazardous solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. The accompanying drawings are only provided for reference and explanation and are not intended to limit the present invention.

[0029] Figure 1 This is a flow chart of the tail gas treatment system of the PBAT production line of the utility model;

[0030] In the figure: 1. THF recovery distillation tower; 2. THF recovery tower top condenser; 3. Esterification liquid ring vacuum pump group; 4. Scraper spray condenser; 5. Polycondensation hot well; 6. Spray circulation pump; 7. Spray cooler; 8. BDO steam jet pump; 9. Vacuum liquid seal tank; 10. Vacuum liquid circulation pump; 11. Vacuum liquid cooler; 12. Mechanical vacuum pump group; 13. Gas-liquid separation tank; 13a. Wire mesh demister; 14. Venturi tube; 15. Natural gas thermal oil boiler; 16. Sewage treatment station;

[0031] G1. Esterification gas phase pipe; G2. Esterification wastewater pipe; G3. Polycondensation gas phase pipe; G4. BDO receiving pipe;

[0032] V1. Exhaust regulating valve; V2. BDO emission regulating valve. DETAILED DESCRIPTION

[0033] In the following description of the utility model, the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the utility model and simplifying the description, and do not mean that the device must have a specific direction.

[0034] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below with reference to specific illustrations.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0036] like Figure 1 As shown, the PBAT production line tail gas treatment system of the utility model includes a THF recovery distillation tower 1, a THF recovery tower top condenser 2, an esterification liquid ring vacuum pump group 3, a scraper spray condenser 4, a polycondensation hot well 5, a spray circulation pump 6, a spray cooler 7, a BDO steam jet pump 8, a vacuum liquid seal tank 9, a vacuum liquid circulation pump 10, a vacuum liquid cooler 11, a mechanical vacuum pump group 12, a gas-liquid separation tank 13, a venturi tube 14 and a natural gas thermal oil furnace 15.

[0037] The PBAT continuous production device adopts esterification and continuous polymerization technology, including two stages of esterification reaction and polycondensation reaction. The raw materials of terephthalic acid (PTA), adipic acid (AA), and 1,4-butanediol (BDO) react at a certain temperature and pressure to produce esters and water. At the same time, BDO is cyclized at high temperature to produce tetrahydrofuran (THF) and water.

[0038] The outlet of the esterification gas phase pipe G1 is connected to the suction port of the esterification liquid ring vacuum pump group 3, and the exhaust port of the esterification liquid ring vacuum pump group 3 is connected to the tail gas pipeline; the esterification gas phase separated by the esterification separation tower enters the esterification liquid ring vacuum pump group 3 through the esterification gas phase pipe G1, which contains THF and water, a part of which is cooled and captured by the low-temperature water in the esterification liquid ring vacuum pump group 3, and the non-condensable gas enters the tail gas pipeline through the gas phase port.

[0039] The main components of the esterification wastewater generated in the esterification stage are THF and water. The outlet of the esterification wastewater pipe G2 is connected to the inlet of the THF recovery distillation tower 1, the top exhaust port of the THF recovery distillation tower 1 is connected to the air inlet of the THF recovery tower top condenser 2, and the exhaust port of the THF recovery tower top condenser 2 is connected to the tail gas pipeline; the esterification wastewater enters the THF recovery distillation tower 1 through the esterification wastewater pipe G2 for distillation and purification, the gas phase rises and enters the THF recovery tower top condenser 2 for condensation, and the non-condensable gas enters the tail gas pipeline.

[0040] The outlet of the polycondensation gas phase pipe G3 is connected to the air inlet of the scraper spray condenser 4, the top exhaust port of the scraper spray condenser 4 is connected to the suction port of the BDO steam jet pump 8, the exhaust port of the BDO steam jet pump 8 is connected to the suction port of the mechanical vacuum pump group 12, and the exhaust port of the mechanical vacuum pump group 12 is connected to the tail gas pipeline. The bottom drain port of the scraper spray condenser 4 is connected to the inlet of the polycondensation hot well 5, and the top exhaust port of the polycondensation hot well 5 is connected to the tail gas pipeline.

[0041] The bottom drainage port of the polycondensation hot well 5 is connected to the inlet of the spray circulation pump 6, the outlet of the spray circulation pump 6 is connected to the hot side inlet of the spray cooler 7, and the hot side outlet of the spray cooler 7 is connected to the top spray port of the scraper spray condenser 4.

[0042] The polycondensation gas phase enters the scraper spray condenser 4 through the polycondensation gas phase pipe G3 and is sprayed and condensed. The spray coolant enters the polycondensation hot well 5 to filter and remove oligomers. The bottom drainage of the polycondensation hot well 5 is pumped out by the spray circulation pump 6, cooled by the spray cooler 7, and returned to the upper part of the scraper spray condenser 4 for circulation spraying to capture the BDO in the polycondensation gas phase. The non-condensable gas carried down by the spray coolant enters the tail gas pipeline through the gas phase port of the polycondensation hot well 5.

[0043] The vacuum spray liquid outlet of the BDO steam jet pump 8 is connected to the inlet of the vacuum liquid sealing tank 9, and the top exhaust port of the vacuum liquid sealing tank 9 is connected to the tail gas pipeline.

[0044] The bottom drain port of the vacuum liquid sealing tank 9 is connected to the inlet of the vacuum liquid circulation pump 10 , the outlet of the vacuum liquid circulation pump 10 is connected to the hot side inlet of the vacuum liquid cooler 11 , and the hot side outlet of the vacuum liquid cooler 11 is connected to the spray port of the BDO steam jet pump 8 .

[0045] The polycondensed gas phase that is not captured by the spraying enters the BDO steam jet pump 8 for further spray cooling, and enters the vacuum liquid sealing tank 9 after being condensed by the vacuum spraying liquid. The bottom discharge of the vacuum liquid sealing tank 9 is sent to the vacuum liquid cooler 11 by the vacuum liquid circulation pump 10 for cooling, and then returns to each stage of the BDO steam jet pump 8 for circulating spraying to capture the remaining BDO and water in the polycondensed gas phase.

[0046] The non-condensable gas carried down by the vacuum spray coolant enters the tail gas pipeline through the gas phase port of the vacuum liquid seal tank 9.

[0047] The condensation gas phase not captured by the spraying is pumped to the mechanical vacuum pump group 12 under the action of negative pressure, the non-condensable gas enters the tail gas pipeline through the gas phase port, and the separated liquid enters the sewage treatment station 16 for treatment.

[0048] The outlet of the tail gas pipeline is connected to the inlet of the gas-liquid separation tank 13 and the main inlet of the venturi tube 14 respectively. A wire mesh demister 13a is provided at the upper part of the inner cavity of the gas-liquid separation tank 13. The top outlet of the gas-liquid separation tank 13 is connected to the suction inlet of the venturi tube 14. The outlet of the venturi tube 14 is connected to the natural gas thermal oil furnace 15. The above tail gas pipelines can be merged into the tail gas main pipe, most of which enter the gas-liquid separation tank 13, and the moisture is removed by the wire mesh demister 13a at the top. A small part enters the venturi tube 14 as power gas. The main inlet pipeline of the venturi tube 14 is provided with a tail gas regulating valve V1. The opening of the tail gas regulating valve V1 is controlled by the top pressure of the gas-liquid separation tank 13, so that the amount of gas going to the venturi tube 14 is cascade controlled with the pressure of the gas-liquid separation tank 13. The rapid change of the passage of the venturi tube 14 causes a rapid change in the flow rate, forming a vacuum to suck the tail gas discharged from the top of the gas-liquid separation tank 13, and after merging, it goes to the natural gas thermal oil boiler 15 to be burned as fuel.

[0049] The bottom outlet of the gas-liquid separation tank 13 is connected to the BDO receiving pipe G4 through a liquid seal bend and a BDO discharge regulating valve V2, and the separated liquid enters the BDO receiving pipe G4 for collection and reuse. The opening of the BDO discharge regulating valve V2 is controlled by the lower liquid level of the gas-liquid separation tank 13. A certain liquid level is maintained in the gas-liquid separation tank 13 to prevent the incoming gas from short-circuiting and failing to remove water.

[0050] The above description is only the preferred feasible embodiment of the utility model, which shows and describes the basic principle, main features and advantages of the utility model, but does not limit the scope of patent protection of the utility model. The technicians in this industry should understand that the utility model is not limited by the above embodiments. In addition to the above embodiments, the utility model can also have other implementation modes without departing from the spirit and scope of the utility model. The utility model will also have various changes and improvements. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the utility model. The scope of protection required by the utility model is defined by the attached claims and their equivalents. The technical features not described in the utility model can be achieved by or using existing technologies, which will not be repeated here.

Claims

1. A PBAT production line tail gas treatment system, comprising an esterification gas phase pipe, an esterification wastewater pipe and a condensation gas phase pipe, characterized in that: The outlet of the esterification gas phase pipe is connected to the suction port of the esterification liquid ring vacuum pump group, and the exhaust port of the esterification liquid ring vacuum pump group is connected to the tail gas pipeline; The outlet of the esterification wastewater pipe is connected to the inlet of the THF recovery distillation tower, the top exhaust port of the THF recovery distillation tower is connected to the air inlet of the THF recovery tower top condenser, and the exhaust port of the THF recovery tower top condenser is connected to the tail gas pipeline; The outlet of the polycondensation gas phase pipe is connected to the air inlet of the scraper spray condenser, the top exhaust port of the scraper spray condenser is connected to the suction port of the BDO steam jet pump, the exhaust port of the BDO steam jet pump is connected to the suction port of the mechanical vacuum pump group, and the exhaust port of the mechanical vacuum pump group is connected to the tail gas pipeline; The outlet of the tail gas pipeline is respectively connected to the inlet of the gas-liquid separation tank and the main inlet of the venturi tube, and the bottom outlet of the gas-liquid separation tank is connected to the BDO receiving pipe through a liquid seal bend; a wire mesh demister is provided on the upper part of the inner cavity of the gas-liquid separation tank, the top outlet of the gas-liquid separation tank is connected to the suction inlet of the venturi tube, and the outlet of the venturi tube is connected to the natural gas thermal oil furnace.

2. The PBAT production line tail gas treatment system according to claim 1, characterized in that: The bottom liquid discharge port of the scraper spray condenser is connected to the inlet of the polycondensation hot well, and the top exhaust port of the polycondensation hot well is connected to the tail gas pipeline.

3. The PBAT production line tail gas treatment system according to claim 2, characterized in that: The bottom drain port of the polycondensation hot well is connected to the inlet of the spray circulation pump, the outlet of the spray circulation pump is connected to the hot side inlet of the spray cooler, and the hot side outlet of the spray cooler is connected to the top spray port of the scraper spray condenser.

4. The PBAT production line tail gas treatment system according to claim 1, characterized in that: The vacuum spray liquid outlet of the BDO steam jet pump is connected to the inlet of the vacuum liquid seal tank, and the top exhaust port of the vacuum liquid seal tank is connected to the tail gas pipeline.

5. The PBAT production line tail gas treatment system according to claim 4, characterized in that: The bottom drain port of the vacuum liquid seal tank is connected to the inlet of the vacuum liquid circulation pump, the outlet of the vacuum liquid circulation pump is connected to the hot side inlet of the vacuum liquid cooler, and the hot side outlet of the vacuum liquid cooler is connected to the spray port of the BDO steam jet pump.

6. The PBAT production line tail gas treatment system according to any one of claims 1 to 5, characterized in that: An exhaust gas regulating valve is arranged on the main inlet pipeline of the venturi tube, and the opening degree of the exhaust gas regulating valve is controlled by the top pressure of the gas-liquid separation tank.

7. The PBAT production line tail gas treatment system according to any one of claims 1 to 5, characterized in that: A BDO discharge regulating valve is installed in the BDO receiving pipe, and the opening of the BDO discharge regulating valve is controlled by the lower liquid level of the gas-liquid separation tank.

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