Tail gas treatment device in phthalic anhydride production

Abstract

The utility model belongs to the technical field of chemical equipment, and discloses a tail gas treatment device in phthalic anhydride production, which comprises a reactor, a gas cooler, a switching cooler, an incinerator and a washing tower which are sequentially communicated through pipelines and valves, an electrostatic tower is arranged at the top of the washing tower, a plurality of groups of electrostatic adsorption electrode components and high-voltage discharge electrode combinations are arranged in the electrostatic tower, a tail gas outlet is formed in the top of the electrostatic tower, and the bottom of the electrostatic tower is communicated to an inner cavity of the washing tower; the spraying device comprises a spraying liquid input pipe and a square latticed spraying pipe communicated with the spraying liquid input pipe, the spraying pipe is formed by crossing and communicating five transverse pipes and five longitudinal pipes which are arranged in parallel, and spiral nozzles spraying downwards are arranged at the joints of the transverse pipes and the longitudinal pipes. According to the tail gas treatment device, harmful gas and impurities in tail gas are thoroughly treated, the treatment effect is good, and the environmental safety is effectively guaranteed.

Description

Technical Field

[0001] The utility model relates to the technical field of chemical equipment, in particular to a tail gas treatment device in phthalic anhydride production. Background Art

[0002] At present, the process of preparing phthalic anhydride by the naphthalene method mainly involves fully and evenly mixing industrial naphthalene with air in a certain proportion and then sending it into a reactor to undergo an oxidation reaction to obtain phthalic anhydride and byproducts naphthoquinone and maleic anhydride, and then entering a gas cooler in the form of gas for heat exchange, and finally condensing through a switching condenser to obtain solid crude phthalic anhydride, which is then distilled to obtain qualified phthalic anhydride products. The tail gas treatment method is that the tail gas from the switching condenser is first incinerated in a thermal storage incinerator, and then enters a tail gas scrubber for spray washing, and is discharged into the atmosphere after washing. However, due to the characteristics of large air volume and high tail gas concentration in the production of phthalic anhydride, the incinerator contains a large amount of unconverted raw materials and organic substances such as carbon monoxide during the incineration process. The spray nozzles in the scrubber are arranged in five horizontal rows, with 7 nozzles in the middle three rows and 3 nozzles in each of the two rows on both sides, for a total of 27 nozzles. However, the spraying effect of this arrangement is poor, and the tail gas after washing still contains some benzene and hydrocarbon organic substances, which will seriously affect environmental safety when released into the air. Summary of the invention

[0003] The technical problem to be solved by the utility model is to provide a tail gas treatment device in the production of phthalic anhydride, which overcomes the defects of the prior art, makes the harmful gases and impurities in the tail gas be treated thoroughly, has good treatment effect, and effectively ensures environmental safety.

[0004] In order to solve the above technical problems, the technical solution of the utility model is:

[0005] A tail gas treatment device in phthalic anhydride production comprises a reactor, a gas cooler, a switching cooler, an incinerator and a washing tower which are connected in sequence through pipelines and valves; an electrostatic tower is arranged on the top of the washing tower, and a combination of several groups of electrostatic adsorption pole components and high-voltage discharge poles are arranged in the electrostatic tower; a tail gas outlet is arranged on the top of the electrostatic tower, and the bottom is connected to the inner cavity of the washing tower; a spray device is arranged on the upper part of the inner cavity of the washing tower, and the spray device comprises a spray liquid input pipe and a square grid-shaped spray pipe connected to the spray liquid input pipe, and the spray pipe is composed of five parallel horizontal pipes and five vertical pipes which are cross-connected, and spiral nozzles for downward spraying are arranged at the connection between all horizontal pipes and vertical pipes.

[0006] Preferably, the gas cooler is a two-stage cooler, in which saturated 6.0 MPa high-pressure steam is generated in the first stage, and in the second stage, water is heated for the boiler that generates the steam.

[0007] Preferably, there are five switching coolers. The switching coolers are loaded and unloaded in a set periodic sequence, so that phthalic anhydride is separated from the reaction product gas to obtain solid crude phthalic anhydride, and the crude phthalic anhydride is further distilled to obtain qualified phthalic anhydride products; the tail gas from the switching cooler is first incinerated in a heat storage incinerator, and then enters the tail gas washing tower for spray washing.

[0008] Preferably, a washing liquid circulation pool is provided at the bottom of the washing tower, and a washing liquid circulation system is provided between the washing tower and the washing liquid circulation pool.

[0009] Furthermore, the washing liquid circulation system includes a circulation pump and a spray liquid input pipe.

[0010] Preferably, the spiral nozzle is a DN8 spiral nozzle.

[0011] Due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0012] The utility model adopts a square layout for the spraying device, and uses 25 spiral nozzles. The spiral nozzles can realize vortex spraying, have a large spraying area, and a uniform flow rate, and will not produce a diversion phenomenon, thereby ensuring the stability and uniformity of the spraying, and can also adjust the rotation direction and the rotation speed; therefore, it can replace the 27 nozzles originally used, saving the amount of nozzles, and through a reasonable design, it realizes spraying without dead angles, so that the organic matter and impurities in the exhaust gas are completely dissolved and washed; a small amount of organic matter and impurities that have not been washed rise with the flue gas into the electrostatic tower, and after being electrostatically adsorbed, they flow vertically down along the adsorption plate, and drip from the bottom of the plate into the washing tower, and the treated flue gas is discharged into the air from the exhaust duct at the top of the electrostatic tower.

[0013] Therefore, the utility model can thoroughly treat harmful gases and impurities in the tail gas, has good treatment effect, and effectively ensures environmental safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the equipment flow of an embodiment of the utility model;

[0015] Figure 2 This is a schematic diagram of a spray device in a washing tower according to an embodiment of the utility model:

[0016] In the figure, 1. reactor; 2. gas cooler; 3. switching cooler; 4. incinerator; 5. washing tower; 6. electrostatic tower; 7. spray device; 8. spiral nozzle. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 1 and Figure 2As shown, a tail gas treatment device in phthalic anhydride production includes a reactor 1, a gas cooler 2, a switching cooler 3, an incinerator 4 and a washing tower 5 which are connected in sequence through pipelines (not marked) and valves (not marked); an electrostatic tower 6 is provided on the top of the washing tower 5, and a combination of several groups of electrostatic adsorption pole components (not marked) and high-voltage discharge electrodes (not marked) are provided in the electrostatic tower 6. A tail gas outlet (not marked) is provided on the top of the electrostatic tower 6, and the bottom is connected to the inner cavity of the washing tower 5. A spray device 7 is provided on the upper part of the inner cavity of the washing tower 5. The spray device 7 includes a spray liquid input pipe (not marked) and a square grid-shaped spray pipe (not marked) connected to the spray liquid input pipe. The spray pipe is composed of five parallel horizontal pipes (not marked) and five vertical pipes (not marked) arranged in a cross-connected manner, and all the horizontal and vertical pipe connections are provided with spiral nozzles 8 for spraying downward.

[0019] During practical application, a mixture of naphthalene and air enters the reactor 1 from the top of the reactor 1, and reacts in the reaction tube to produce phthalic anhydride and by-products, and the reaction product gas comes out from the bottom of the reactor 1 and enters the gas cooler 2, which is mainly used for cooling the phthalic anhydride gas coming out of the reactor 1. The structure of the gas cooler 2 is a box-type heat exchanger, and the box shell passes the phthalic anhydride gas, and the internal tube bundle is divided into two sections to produce high-pressure steam; the phthalic anhydride gas enters the switching cooler 3 after cooling, and the switching cooler 3 is provided with five units, and loads and unloads according to the set cycle sequence, so that phthalic anhydride is separated from the reaction product gas to obtain solid crude phthalic anhydride, and the crude phthalic anhydride is distilled to obtain a qualified phthalic anhydride product; the tail gas coming out of the switching cooler 3 is first burned in an incinerator 4, and then enters a tail gas washing tower 5 for spraying and washing, and the tail gas after spraying also contains a small amount of organic gas and impurities, and these organic gases and impurities are further processed by an electrostatic tower 6, and the obtained tail gas is colorless, tasteless and free of impurities, and can be directly discharged into the atmosphere.

[0020] It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A tail gas treatment device in phthalic anhydride production, characterized in that: It comprises a reactor, a gas cooler, a switching cooler, an incinerator and a washing tower which are connected in sequence through pipelines and valves; an electrostatic tower is arranged on the top of the washing tower, and a combination of several groups of electrostatic adsorption pole components and high-voltage discharge poles are arranged in the electrostatic tower; an exhaust gas outlet is arranged on the top of the electrostatic tower, and the bottom is connected to the inner cavity of the washing tower; a spray device is arranged on the upper part of the inner cavity of the washing tower, and the spray device comprises a spray liquid input pipe and a square grid-shaped spray pipe connected to the spray liquid input pipe, and the spray pipe is composed of five parallel horizontal pipes and five vertical pipes which are cross-connected, and spiral nozzles for downward spraying are arranged at the connection between all horizontal pipes and vertical pipes.

2. The tail gas treatment device in the production of phthalic anhydride as claimed in claim 1, characterized in that: The gas cooler is a two-stage cooler.

3. The tail gas treatment device in the production of phthalic anhydride as claimed in claim 1, characterized in that: There are five switching coolers.

4. The tail gas treatment device in the production of phthalic anhydride as claimed in claim 1, characterized in that: A washing liquid circulation pool is arranged at the bottom of the washing tower, and a washing liquid circulation system is arranged between the washing tower and the washing liquid circulation pool.

5. The tail gas treatment device in the production of phthalic anhydride as claimed in claim 4, characterized in that: The washing liquid circulation system comprises a circulation pump and a spray liquid input pipe.

6. The tail gas treatment device in the production of phthalic anhydride as claimed in claim 1, characterized in that: The spiral nozzle is a DN8 spiral nozzle.

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