O-xylene feeding device in phthalic anhydride production process

Abstract

The utility model belongs to the technical field of phthalic anhydride production devices, and particularly relates to an o-xylene feeding device in a phthalic anhydride production process. The o-xylene feeding device in the phthalic anhydride production process comprises an o-xylene storage tank, the o-xylene storage tank is connected with an o-xylene filter set through a delivery pump, a liquid phase three-way valve is arranged behind the o-xylene filter set, the liquid phase three-way valve is provided with a pipeline connected with an o-xylene preheater, the o-xylene preheater is connected with a vaporizer, and the vaporizer is connected with the o-xylene storage tank. Two branches are arranged behind the top of the vaporizer through a gas-phase three-way valve, one branch is a gas-adjacent xylene conveying pipeline, and the other branch is connected with the heat exchanger. According to the o-xylene feeding device in the phthalic anhydride production process, stable feeding of o-xylene is guaranteed, meanwhile, due to the fact that the heat exchange device and the recovery device are arranged, recovery of o-xylene is achieved when a system is shut down or overhauled, waste of raw materials is reduced, environmental pollution is reduced due to the closed recovery device, and the safety coefficient of a production system is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of phthalic anhydride production devices, and in particular relates to an o-xylene feeding device in the phthalic anhydride production process. Background Art

[0002] Phthalic anhydride (ortho-phthalic anhydride) is an important organic chemical raw material, and its industrial chain covers the fields of synthetic materials, fine chemicals and end-consumer products. In the polymer materials industry, phthalic anhydride is used to generate o-xylene dicarboxylic acid ester plasticizers through esterification reaction, which are widely used in the processing of polyvinyl chloride (PVC) products; at the same time, as the core monomer of unsaturated polyester resin, it supports the production of composite materials such as fiberglass and artificial marble; in the coatings industry, alkyd resins synthesized from phthalic anhydride give paints excellent film-forming properties and weather resistance.

[0003] At present, the mainstream production process of phthalic anhydride is based on the o-xylene oxidation method (o-method). After o-xylene is vaporized, it is mixed with preheated air to generate crude phthalic anhydride under the action of a catalyst. The condensed crude phthalic anhydride is pumped to the refining section for treatment, where phthalic anhydride is purified to produce high-purity phthalic anhydride.

[0004] CN211799785U discloses a phthalic anhydride safety production system, which eliminates the ignition source by adding an electromagnetic separator to the o-xylene feed section, and uses magnetic force to adsorb metal particle impurities such as rust entrained in the air to prevent them from entering the reactor and becoming a high-temperature ignition source. At the same time, a thermometer, a filter, a one-way valve and a pressure / flow meter are added to achieve precise control of the temperature and flow of the mixed gas, further improving safety. However, this process mainly focuses on the removal of impurities in the air and impurities after mixing, and does not remove impurities from o-xylene in the early stage of vaporization, which can easily cause unstable operation of the o-xylene feed section equipment and increase the loss of o-xylene, causing greater safety hazards to subsequent production. Utility Model Content

[0005] The purpose of the utility model is to provide an o-xylene feeding device in the production process of phthalic anhydride, which ensures the stable feeding of o-xylene and realizes the recovery of o-xylene when the system is shut down or repaired by arranging a heat exchange device and a recovery device, thereby reducing the waste of raw material resources. The closed recovery device reduces environmental pollution and improves the safety factor of the production system.

[0006] The o-xylene feeding device in the phthalic anhydride production process of the utility model comprises an o-xylene storage tank, which is connected to an o-xylene filter group through a delivery pump, a liquid phase three-way valve is arranged behind the o-xylene filter group, two branches are arranged behind the liquid phase three-way valve, one is connected to an o-xylene preheater, and the other is connected to an o-xylene buffer recovery tank; the o-xylene preheater is connected to a vaporizer; two branches are arranged on the top of the vaporizer after passing through a gas phase three-way valve, one is a gas o-xylene delivery pipeline, and the other is connected to a heat exchanger, and a pipeline connected to the o-xylene buffer recovery tank is arranged at the bottom of the heat exchanger.

[0007] Preferably, a differential pressure sensor is provided at the o-xylene filter group, and the o-xylene filter group consists of two parallel filters; further, the two filters can be selected to work simultaneously or one can be on and the other can be on standby according to actual production conditions.

[0008] Preferably, the front end of the o-xylene filter group is connected to the back-blowing air outlet pipeline, and the rear end of the o-xylene filter group is connected to the back-blowing air inlet pipeline; further, control valves are provided on the pipelines to prevent backflow.

[0009] Preferably, the bottom of the o-xylene buffer recovery tank is connected to the o-xylene storage tank via a reflux pump, and a liquid level meter is provided on the o-xylene buffer recovery tank.

[0010] Preferably, the o-xylene preheater is provided with a pipeline connected to the o-xylene buffer recovery tank, and further, a control valve is provided on the pipeline.

[0011] Preferably, a pipeline connected to the o-xylene buffer recovery tank is provided at the bottom of the vaporizer.

[0012] Specifically, the o-xylene feeding device in the phthalic anhydride production process has a specific working process as follows: during the stable operation of the device, the raw material in the o-xylene storage tank is transported by a delivery pump, filtered by the o-xylene filter group, and then controlled by a liquid phase three-way valve to enter the o-xylene preheater for preheating. A pressure difference sensor is provided at the o-xylene filter group to monitor the use status of the o-xylene filter group. The preheated o-xylene enters the vaporizer. The vaporized o-xylene passes through the gas phase three-way valve at the top of the vaporizer and enters the next section through the o-xylene delivery pipeline, and participates in the reaction after mixing with air. Among them, the liquid phase three-way valve and the gas phase three-way valve are only set during use. A passage is set; when the pressure difference sensor senses a slight abnormal pressure difference at the o-xylene filter group, the delivery pump is stopped, the liquid phase three-way valve is closed, the back-blowing air inlet pipeline and the back-blowing air outlet pipeline connected to the o-xylene filter are opened, and the back-blowing air inlet pipeline delivers air into the o-xylene filter, and the filter element is purged with air to remove dirt and particulate matter attached to the surface. The purged air is delivered to the downstream section through the back-blowing air outlet pipeline, and the air after impurity removal can continue to be mixed with the o-xylene gas to react. After the purging is completed, the back-blowing air inlet pipeline and the back-blowing air outlet pipeline are closed, and the device works normally and continues to deliver o-xylene to participate in the reaction.

[0013] When the pressure difference sensor at the o-xylene filter group senses an abnormal pressure difference and the system is shut down for maintenance, the delivery pump stops working, and the liquid o-xylene in the o-xylene preheater and the vaporizer is transported to the o-xylene buffer recovery tank through the pipeline, and the uncondensed gas phase in the vaporizer enters the heat exchanger through the top gas phase three-way valve, and is transported to the o-xylene buffer recovery tank through the pipeline after condensation. The o-xylene buffer recovery tank is provided with a liquid level gauge. When the process liquid level is exceeded, the bottom valve opens, and the o-xylene is transported back to the o-xylene storage tank through the reflux pump; the purpose of the above process is to recover the o-xylene in the pipeline during the production process after the system is shut down, and the o-xylene in the o-xylene filter group can also be recovered to the o-xylene recovery tank when the o-xylene filter group is repaired to achieve closed recovery.

[0014] Compared with the prior art, the utility model has the following beneficial effects: the o-xylene feeding device in the phthalic anhydride production process of the utility model ensures stable and clean feeding of o-xylene by arranging a filter in the raw material section; by arranging a heat exchange device and a recovery device, the recovery of o-xylene when the system is shut down or overhauled is realized, thereby reducing the waste of raw materials; the closed recovery device reduces environmental pollution and improves the safety factor of the production system; finally, an air backflush pipeline is arranged to achieve continuous recycling of air while cleaning the filter group, thereby improving the utilization rate of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The utility model is a schematic diagram of the structure of an o-xylene recovery device in the phthalic anhydride production process.

[0016] In the figure: 1. o-xylene storage tank; 2. delivery pump; 3. o-xylene filter group; 4. o-xylene buffer recovery tank; 5. o-xylene preheater; 6. Reflux pump; 7. Liquid phase three-way valve; 8. Heat exchanger; 9. Vaporizer; 10. Gas phase three-way valve; 11. o-xylene delivery pipeline; 12. Liquid level meter; 13. Pressure difference sensor; 14. Back-blowing air inlet pipeline; 15. Back-blowing air outlet pipeline. DETAILED DESCRIPTION

[0017] The specific technical scheme of the utility model will be further described below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown, the o-xylene feeding device in the phthalic anhydride production process includes an o-xylene storage tank 1, an o-xylene preheater 5, and a vaporizer 9. The o-xylene storage tank 1 is connected to the o-xylene filter group 3 through a delivery pump 2, and the o-xylene filter group 3 is provided with a pipeline connected to the o-xylene preheater 5, and the o-xylene preheater 5 is connected to the vaporizer 9; the top of the vaporizer 9 is provided with two branches after passing through a gas phase three-way valve 10, one is a gas o-xylene delivery pipeline 11, and the other is connected to the heat exchanger 8, and the bottom of the heat exchanger 8 is provided with a pipeline connected to the o-xylene buffer recovery tank 4.

[0019] The o-xylene filter group 3 is provided with a differential pressure sensor 13, and the o-xylene filter group 3 is composed of two parallel filters.

[0020] The front end of the o-xylene filter group 3 is connected to the back-blowing air outlet pipeline 15 , and the rear end of the o-xylene filter group 3 is connected to the back-blowing air inlet pipeline 14 .

[0021] A liquid phase three-way valve 7 is arranged behind the o-xylene filter group 3 , and two branches are arranged at the liquid phase three-way valve 7 , one of which is connected to the o-xylene preheater 5 , and the other is connected to the o-xylene buffer recovery tank 4 .

[0022] The bottom of the o-xylene buffer recovery tank 4 is connected to the o-xylene storage tank 1 via a reflux pump 6 , and a liquid level meter 12 is provided on the o-xylene buffer recovery tank 4 .

[0023] The o-xylene preheater 5 is provided with a pipeline connected to the o-xylene buffer recovery tank 4 .

[0024] A pipeline connected to the o-xylene buffer recovery tank 4 is arranged at the bottom of the vaporizer 9 .

[0025] During the stable operation of the device, the raw material in the o-xylene storage tank 1 is transported by the delivery pump 2, filtered by the o-xylene filter group 3, and then controlled by the liquid phase three-way valve 7 to enter the o-xylene preheater 5 for preheating. A pressure difference sensor 13 is provided at the o-xylene filter group 3 to monitor the use status of the o-xylene filter group 3; the preheated o-xylene enters the vaporizer 9, and the vaporized o-xylene passes through the gas phase three-way valve 10 at the top of the vaporizer 9 and the o-xylene delivery pipeline 11 to enter the next section, and participates in the reaction after mixing with air; wherein, the liquid phase three-way valve 7 and the gas phase three-way valve 10 are only provided with one passage during use.

[0026] When the pressure difference sensor 13 at the o-xylene filter group 3 senses a slight abnormal pressure difference, the delivery pump 2 is stopped, the liquid phase three-way valve 7 is closed, and the back-blowing air inlet pipe 14 and the back-blowing air outlet pipe 15 connected to the o-xylene filter group 3 are opened. The back-blowing air inlet pipe 14 delivers air into the o-xylene filter group 3, and uses air to purge the filter element to remove dirt and particles attached to the surface; the purged air is sent to the downstream section through the back-blowing air outlet pipe 15, and the air can continue to mix with the o-xylene gas after impurities are removed for reaction; after the purge is completed, the back-blowing air inlet pipe 14 and the back-blowing air outlet pipe 15 are closed, and the device works normally and continues to deliver o-xylene to participate in the reaction.

[0027] When the pressure difference sensor 13 at the o-xylene filter group 3 senses an abnormal pressure difference and the system is shut down for maintenance, the delivery pump 2 stops working, and the liquid o-xylene in the o-xylene preheater 5 and the vaporizer 9 is transported to the o-xylene buffer recovery tank 4 through a pipeline; the uncondensed gas phase in the vaporizer 9 enters the heat exchanger 8 through the top gas phase three-way valve 10, and is transported to the o-xylene buffer recovery tank 4 through a pipeline after condensation. The o-xylene buffer recovery tank 4 is provided with a liquid level gauge 12. When the process liquid level is exceeded, the bottom valve is opened, and the o-xylene is transported back to the o-xylene storage tank 1 through the reflux pump 6; the purpose of the above process is to recover the o-xylene in the pipeline during the production process after the system is shut down, and the o-xylene in the o-xylene filter group 3 can also be recovered to the o-xylene buffer recovery tank 4 when the o-xylene filter group 3 is repaired to achieve closed recovery.

Claims

1. An o-xylene feeding device in a phthalic anhydride production process, characterized in that: The invention comprises an o-xylene storage tank (1), an o-xylene preheater (5), and a vaporizer (9). The o-xylene storage tank (1) is connected to an o-xylene filter group (3) via a delivery pump (2). The o-xylene filter group (3) is provided with a pipeline connected to the o-xylene preheater (5). The o-xylene preheater (5) is connected to the vaporizer (9). The top of the vaporizer (9) is provided with two branches after passing through a gas phase three-way valve (10), one of which is a gas o-xylene delivery pipeline (11) and the other is connected to a heat exchanger (8). The bottom of the heat exchanger (8) is provided with a pipeline connected to an o-xylene buffer recovery tank (4).

2. The o-xylene feeding device in the phthalic anhydride production process according to claim 1, characterized in that: A differential pressure sensor (13) is provided at the o-xylene filter group (3), and the o-xylene filter group (3) consists of two filters connected in parallel.

3. The o-xylene feeding device in the phthalic anhydride production process according to claim 1, characterized in that: The front end of the o-xylene filter group (3) is connected to the back-blowing air outlet pipeline (15), and the rear end of the o-xylene filter group (3) is connected to the back-blowing air inlet pipeline (14).

4. The o-xylene feeding device in the phthalic anhydride production process according to claim 1, characterized in that: A liquid phase three-way valve (7) is arranged behind the o-xylene filter group (3), and two branches are arranged at the liquid phase three-way valve (7), one of which is connected to the o-xylene preheater (5) and the other is connected to the o-xylene buffer recovery tank (4).

5. The o-xylene feeding device in the phthalic anhydride production process according to claim 1, characterized in that: The bottom of the o-xylene buffer recovery tank (4) is connected to the o-xylene storage tank (1) via a reflux pump (6), and a liquid level meter (12) is provided on the o-xylene buffer recovery tank (4).

6. The o-xylene feeding device in the phthalic anhydride production process according to claim 1, characterized in that: The o-xylene preheater (5) is provided with a pipeline connected to the o-xylene buffer recovery tank (4).

7. The o-xylene feeding device in the phthalic anhydride production process according to claim 1, characterized in that: A pipeline connected to the o-xylene buffer recovery tank (4) is provided at the bottom of the vaporizer (9).

Images