A yellow phosphorus phosphoric acid tail gas treatment device and treatment process

Abstract

The present application belongs to the technical field of acid mist treatment, and the present application discloses a yellow phosphorus phosphoric acid tail gas treatment device and treatment process. The above-mentioned yellow phosphorus phosphoric acid tail gas treatment device includes a spray tower, a defoaming tower, a water washing tower and a demisting tower connected in sequence, and also includes an alkali solution collection pool; the above-mentioned yellow phosphorus phosphoric acid tail gas treatment process includes a spray tower atomization spraying primary acid removal, a wire mesh defoamer secondary acid removal, a water washing tower tertiary acid removal and a demisting tower four times acid removal, a total of four-stage acid mist removal process. The yellow phosphorus phosphoric acid tail gas treatment device and treatment process of the present application can greatly improve the recovery rate of phosphoric acid in phosphoric acid tail gas, while reducing the concentration of phosphoric acid mist in the tail gas during discharge, and is environmentally friendly, simple in structure, and has a long operation cycle.

Description

Technical Field

[0001] The present application relates to the technical field of acid mist treatment, and in particular to a device and process for treating tail gas from yellow phosphorus phosphoric acid production. Background Art

[0002] The thermal phosphoric acid production process is mainly divided into three relatively independent processes: smelting (extracting yellow phosphorus from phosphate rock), yellow phosphorus combustion, and phosphorus pentoxide hydration. The step of yellow phosphorus combustion is as follows: solid yellow phosphorus is heated and melted into liquid yellow phosphorus by water vapor (provided by a special coal-fired boiler) in a phosphorus melting tank, and the liquid yellow phosphorus is sprayed into a combustion tower for atomization and combustion by a phosphorus spray gun under the action of compressed air. The combustion tail gas is sent to a hydration tower for circulation and heat exchange, and the product is obtained after arsenic removal, filtration and other operations after meeting the requirements. The tail gas output by the hydration tower contains a large amount of water vapor and phosphorus-containing waste, which will pollute the environment if discharged directly. In the prior art, a fiber dust collector and a cyclone separator connected in sequence are used to treat the tail gas, which has the following problems: (1) The tail gas contains a large amount of acid droplets. Directly passing the tail gas into the fiber dust collector will corrode the fibers in the fiber dust collector. The fiber filter belt inside the fiber dust collector needs to be replaced on time, and the maintenance cost is too high; (2) The treatment effect is not good, and the P content in the exhaust gas is greater than 0.05%. Summary of the invention

[0003] In order to solve at least one of the above technical problems and develop a phosphoric acid tail gas treatment process that improves the phosphoric acid mist treatment effect and reduces maintenance costs, the present application provides a yellow phosphorus phosphoric acid tail gas treatment device and a treatment process.

[0004] On the one hand, the present application provides a yellow phosphorus phosphoric acid tail gas treatment device, comprising a spray tower, a defoaming tower, a water washing tower and a demisting tower connected in sequence, and also comprising an alkali liquid collection tank; an air inlet pipe is provided on the top of the spray tower, an atomizing spray gun is provided in the spray tower, the atomizing spray gun is connected to the outlet end of a hydraulic pump 1 through a pipeline, and the inlet end of the hydraulic pump 1 is connected to the alkali liquid collection tank;

[0005] The defoaming tower is provided with a wire mesh defoamer; the water washing tower is provided with a packing layer, a spray device and a fiber defoamer from bottom to top, the spray device is connected to the outlet end of the second hydraulic pump through a pipeline, and the inlet end of the second hydraulic pump is connected to the alkali liquid collection tank; the top of the defoaming tower is provided with an exhaust pipe, and the defoaming tower is provided with an electrostatic defoamer; the alkali liquid collection tank is located at the bottom of the spray tower, the defoaming tower and the water washing tower, and the bottoms of the spray tower, the defoaming tower and the water washing tower are connected to the alkali liquid collection tank.

[0006] By adopting the above technical scheme, the atomizing spray gun in the spray tower adopts a water vapor atomizing spray design, the water liquid atomizing particle size is small, which meets the phase change condensation conditions, and the water vapor atomizing particle size is 0.1-1um. The particulate matter in the phosphoric acid tail gas, phosphoric acid mist, etc., condense with the water vapor sprayed by the atomizing spray gun, grow in the spray tower and sink into the alkali liquid collection pool. The phosphoric acid mist in the phosphoric acid tail gas is a condensable particulate matter with good hydrophilicity. Since the phosphoric acid tail gas itself has a high water content, the present invention can form a higher supersaturation and supersaturated area in the spray tower and the defoaming tower connected to the spray tower by arranging the atomizing spray gun in the spray tower, and phase change condensation and growth occur in the supersaturated water vapor environment, which is easy to capture and remove the phosphoric acid mist using a wire mesh defoamer and a fiber defoamer in the subsequent use. When the phosphoric acid tail gas flows from the spray tower to the defoaming tower, the phosphoric acid tail gas can also transfer heat and mass on the liquid surface of the alkali liquid collection pool, which can cool the phosphoric acid tail gas and capture part of the phosphoric acid mist, thereby reducing the concentration and temperature of the phosphoric acid mist in the phosphoric acid tail gas as a whole. When the phosphoric acid tail gas flows from the spray tower to the defoaming tower, the overall temperature of the phosphoric acid tail gas can be reduced after passing through the liquid surface of the alkali liquid collection pool. The temperature reduction promotes the phase change, condensation and growth of the acid mist in the phosphoric acid tail gas in the supersaturated water vapor environment. The phosphoric acid tail gas enters the water scrubber, and the gas-liquid is fully mixed and heat and mass transfer is achieved in the packing layer of the water scrubber, which can reduce the concentration of the phosphoric acid mist in the phosphoric acid tail gas, and can also remove particulate matter, smoke and dust in the phosphoric acid tail gas by entering the liquid phase, while further cooling the phosphoric acid tail gas. During the entire process, the cooling of phosphoric acid tail gas and the capture of phosphoric acid mist are carried out alternately, so that the acid mist is captured layer by layer. Finally, under the action of the electrostatic precipitator, the acid mist content in the phosphoric acid tail gas can be maintained at an extremely low level. The acid mist captured in the electrostatic precipitator can also be collected at the bottom of the demister tower for subsequent recovery of phosphoric acid.

[0007] Preferably, the wire mesh demister has two layers of filler, and each layer is 200-350 mm high.

[0008] Preferably, the spraying density of the spraying device is 15-40m 3 / (m 2 h).

[0009] Preferably, the filler of the packing layer is a ceramic ring filler, and the filler height is 1500-2400mm.

[0010] Furthermore, the ceramic ring filler is a modified ceramic ring filler, and the preparation process of the modified ceramic ring filler includes: placing the ceramic ring in a mixed acid solution of 10-20wt% sulfuric acid and 8-15% hydrochloric acid for 5-8h, taking it out and cleaning it, adding it to a 20-30wt% polyvinyl alcohol aqueous solution and soaking it for 10-15h to obtain the modified ceramic ring filler, wherein the weight ratio of the ceramic ring to the mixed acid solution is 1:5-7, and the weight ratio of the ceramic ring to the polyvinyl alcohol aqueous solution is 1:10-13.

[0011] By adopting the above technical solution, an organic protective layer is formed on the surface of the modified ceramic ring filler, which enhances its acid and alkali resistance. At the same time, more particles appear on the surface of the ceramic ring, and the surface area is further increased, which is beneficial to the adsorption and capture of acid mist in phosphoric acid tail gas.

[0012] Preferably, the height of the spray tower is 8-12 m, the height of the defoaming tower is 7-10 m, and the interval between the spray tower and the defoaming tower is 4.5-8 m.

[0013] Preferably, the operating voltage of the electrostatic precipitator is 60-90KV, and the operating current is 200-500mA.

[0014] Preferably, a first fan is provided between the defoaming tower and the water washing tower, and a second fan is provided between the water washing tower and the demisting tower.

[0015] In a second aspect, the present application provides a treatment process applicable to the above-mentioned yellow phosphorus phosphoric acid tail gas treatment device, comprising the following steps:

[0016] S1. The phosphoric acid tail gas enters the spray tower from the air inlet pipe at the top of the spray tower. The atomizing spray gun atomizes the sprayed alkali solution. The atomized alkali solution reacts and settles with the acidic components in the phosphoric acid tail gas to perform a deacidification.

[0017] S2, the phosphoric acid tail gas after primary deacidification enters the defoamer tower, and the phosphoric acid tail gas passes through the wire mesh defoamer in the defoamer tower for secondary deacidification;

[0018] S3, the phosphoric acid tail gas after the secondary deacidification enters the water washing tower for the third deacidification, the spray device in the water washing tower sprays alkali solution, and the phosphoric acid tail gas and alkali solution are mixed with gas and liquid and heat and mass transfer is carried out in the packing layer; after the phosphoric acid tail gas passes through the packing layer and the spray device, the phosphoric acid tail gas passes through the fiber demister, and the acid mist in the phosphoric acid tail gas gathers and settles on the filaments in the fiber demister, flows through the packing layer, and then enters the alkali solution collection tank;

[0019] S4. After three times of deacidification, the phosphoric acid tail gas enters the demister and passes through the electrostatic demister for four times of deacidification. The phosphoric acid tail gas passing through the electrostatic demister is discharged into the atmosphere through the exhaust pipe at the top of the demister.

[0020] In summary, the present invention includes at least one of the following beneficial technical effects:

[0021] 1. The present invention adopts a multi-stage phosphoric acid mist absorption treatment process, and reduces the concentration of phosphoric acid mist in phosphoric acid tail gas through a four-stage acid discharge process, thereby greatly improving the recovery rate of phosphoric acid in phosphoric acid tail gas and reducing the concentration of phosphoric acid mist in tail gas during discharge.

[0022] 2. The phosphoric acid tail gas treatment equipment of the present invention has low maintenance cost and long equipment operation cycle, and the phosphoric acid in the alkali solution collection pool is also easy to collect, which is beneficial to reducing the overall cost of phosphoric acid tail gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural diagram of Example 1 of the present application.

[0024] Explanation of the reference numerals: 1. Inlet pipe; 2. Spray tower; 3. Defoaming tower; 4. Water washing tower; 5. Demisting tower; 6. Exhaust pipe; 7. Atomizing spray gun; 8. Hydraulic pump one; 9. Spray device; 10. Hydraulic pump two; 11. Fan one; 12. Fan two; 13. Alkali solution collecting tank; 14. Wire mesh demister; 15. Fiber demister; 16. Packing layer; 17. Electrostatic demister. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] Reference Figure 1 , Example 1 of the present application discloses a yellow phosphorus phosphoric acid tail gas treatment device, which includes a spray tower 2, a defoaming tower 3, a water washing tower 4 and a demisting tower 5 connected in sequence according to the treatment sequence of the phosphoric acid tail gas, and also includes an alkali solution collection pool 13;

[0028] Spray tower 2, the top of spray tower 2 is provided with air inlet pipe 1, air inlet pipe 1 connects the exhaust pipe of phosphoric acid tail gas and spray tower 2. The tower height of spray tower 2 in this embodiment is 10m, and the tower diameter is 3.5m. Atomizing spray gun 7 (manufacturer is Suzhou Siborun Fluid Technology Co., Ltd.) is provided at 8m in the tower height of spray tower 2, the nozzle of atomizing spray gun 7 is a fan-shaped nozzle, the nozzle output value is 250-280kg / h, the spray speed is 25-30m / s, atomizing spray gun 7 is arranged at the center of the tower height of 8m in the spray tower, and alkali solution is sprayed around. Atomizing spray gun 7 is connected to the outlet end of hydraulic pump 8 through a pipeline, and the inlet end of hydraulic pump 8 is connected to alkali solution collection pool 13, hydraulic pump 8 extracts alkali solution and sends it to atomizing spray gun 7, and the alkali solution will fall back into alkali solution collection pool 13 after atomizing spray gun 7 is sprayed, forming a circulation of alkali solution. The bottom of the spray tower 2 is an alkali liquid collection pool 13, and the spray tower 2 is connected to the defoaming tower 3 through the alkali liquid collection pool 13. After the phosphoric acid tail gas enters the spray tower 2, it sinks to the bottom of the spray tower 2 and then flows into the defoaming tower 3 under the suction of the fan 11. After the phosphoric acid tail gas enters the spray tower 2, part of the phosphoric acid mist in the tail gas condenses into droplets under the impact of the atomizing spray gun 7, thereby removing part of the phosphoric acid mist in the phosphoric acid tail gas.

[0029] Defoaming tower 3, the tower height of defoaming tower 3 in the present embodiment is 9m, and the tower diameter is 2.8m. Among them, the wire mesh defoamer 14 is located at the tower height of 6m, and there are two layers of porcelain fillers (the manufacturer is Ningbo Keyang Chemical Filling Co., Ltd.), and the thickness of each layer of porcelain fillers is 220mm. The bottom of defoaming tower 3 is an alkali liquid collection tank 13, and the defoaming tower is connected with the spray tower 2 through the alkali liquid collection tank 13. Although the defoaming tower 3 and the water scrubber 4 also share an alkali liquid collection tank 13, the two are not connected. The alkali liquid level position in the alkali liquid collection tank 13 is higher than the connecting part of the water scrubber 4 and the defoaming tower 3, so the phosphoric acid tail gas in the defoaming tower 3 cannot directly enter the water scrubber 4 from the bottom of the defoaming tower 3. The spacing between the defoaming tower 3 and the spray tower 2 is 6m. The top of the defoaming tower 3 is connected with a pipeline, which is communicated with the lower half of the water scrubber 4. In the middle of this section of the pipeline, a fan 11 is also provided, and the air volume of the fan 11 is: 20000m 3 / h, the total wind pressure is 18KPa, and the suction force of the fan forms a negative pressure of 200-300Pa in the defoaming tower 3. The rising phosphoric acid tail gas collides with the filler of the wire mesh defoamer 14 and adheres to the filler surface, and the small droplets formed by part of the phosphoric acid mist in the tail gas settle under the action of gravity and other resistances, further reducing the concentration of phosphoric acid mist in the phosphoric acid tail gas.

[0030] The water washing tower 4 in this embodiment has a tower height of 12m and a tower diameter of 3.5m. Among them, the fiber demister 15 (manufacturer is Nanjing Jianghan Petrochemical Equipment Co., Ltd.) is located at a tower height of 9m, a length of 2000mm, and a processing capacity of 1500m 3 / h. The spray device 9 is located at a height of 8m. The spray device 9 is a shower head sprayer (manufacturer: Hangzhou Aoke Environmental Equipment Co., Ltd.), and the spray density is 15m 3 / (m 2·h), the water pressure is 80-100Kpa, the nozzle has a total of 121 holes, the aperture is 0.5mm, and it is made of stainless steel. The spray device 9 is connected to the outlet end of the hydraulic pump 2 10 through a pipeline, and the inlet end of the hydraulic pump 2 10 is connected to the alkali liquid collection tank 13. The hydraulic pump 2 10 extracts the alkali liquid and sends it to the spray device 9. After the spray device 9 is sprayed, the alkali liquid flows through the packing layer 16 and then falls back to the alkali liquid collection tank 13, thereby forming a circulation of the alkali liquid. The packing layer 16 is located at a tower height of 8m, and the packing height is 1800mm. The packing is an ordinary ceramic ring packing, which is a ceramic saddle ring (the manufacturer is Rongfeng Ceramics Co., Ltd., Pingxiang City, Jiangxi Province). The bottom of the water washing tower 4 is the alkali liquid collection tank 13, and the water washing tower 4 is connected to the defoaming tower 3 through the alkali liquid treatment tank but is not connected. The top of the water washing tower 4 is connected with a pipeline, which is connected to the lower part of the demister tower 5. A fan 12 is also arranged in the middle of the pipeline. The air volume of the fan 12 is 25000m3 / h, and the total air pressure is 22Kpa. Through the suction of the fan 12, a negative pressure of 220-350Pa is formed in the water washing tower 4. The phosphoric acid tail gas and the alkali solution are mixed with gas and liquid and heat and mass transfer is carried out on the packing layer 16 of the water washing tower 4. The concentration of phosphoric acid mist in the phosphoric acid tail gas is reduced by acid-base neutralization and physical diffusion. When the phosphoric acid tail gas with phosphoric acid mist rises at a certain speed through the fiber demister 15, due to the inertia of the rising phosphoric acid mist, the phosphoric acid mist collides with the filaments in the fiber demister 15 and is attached to the surface of the filaments. The diffusion and gravity sedimentation of the phosphoric acid mist on the surface of the filaments form larger droplets that flow along the filaments to the intersection of the two filaments. The wettability of the filaments, the surface tension of the liquid and the capillary action of the filaments make the droplets grow larger and larger until the aggregated droplets are large enough that the gravity generated by themselves exceeds the combined force of the rising force of the gas and the surface tension of the liquid. The droplets then separate and fall from the filaments. After the phosphoric acid tail gas passes through the fiber demister 15, it basically does not contain phosphoric acid mist of large particle size, thereby further reducing the concentration of phosphoric acid mist in the phosphoric acid tail gas.

[0031] The demisting tower 5 in this embodiment has a tower height of 7m and a tower diameter of 2.8m, wherein an electrostatic demister 17 (manufacturer is Lianyungang Huifeng Equipment Manufacturing Co., Ltd.) is located at a tower height of 5m, with an operating voltage of 80KV and an operating current of 500mA. The phosphoric acid mist in the tail gas is further removed by the electrostatic demister 17, and then the phosphoric acid tail gas is discharged through the exhaust pipe 6 in compliance with the standards.

[0032] The alkali liquid collecting pool 13, the alkali liquid in the alkali liquid collecting pool in this embodiment is a 10wt% caustic soda solution, and the water level of the alkali liquid collecting pool is about 0.6-1m higher than the connecting part of the defoaming tower 3 and the water washing tower 4.

[0033] The above-mentioned phosphorus removal treatment process for tail gas from yellow phosphorus phosphoric acid production is used to remove most of the acid mist in the tail gas of phosphoric acid produced in the thermal phosphoric acid process, and specifically comprises the following steps:

[0034] S1, phosphoric acid tail gas enters the spray tower 2 from the air inlet pipe 1 at the top of the spray tower 2 for primary deacidification, the atomizing spray gun 7 atomizes the sprayed alkali solution, and the atomized particle size is 1-10um. The atomized alkali solution reacts and settles with the phosphoric acid mist in the phosphoric acid tail gas; the particulate matter and phosphoric acid mist in the phosphoric acid tail gas condense with the water vapor sprayed by the atomizing spray gun, and then increases in the spray tower and sinks into the alkali solution collection pool. The phosphoric acid tail gas after preliminary cleaning flows into the defoaming tower through the bottom of the spray tower. In the process of flowing into the defoaming tower, the phosphoric acid tail gas will transfer heat and mass with the alkali solution collection pool, and a small amount of phosphoric acid mist can be removed.

[0035] S2. After the primary deacidification, the phosphoric acid tail gas flows into the defoamer tower 3. The phosphoric acid tail gas passes through the wire mesh defoamer 14 in the defoamer tower 3 for secondary deacidification. Under the suction of the fan 11, there is a negative pressure of about 200 Pa in the defoamer tower 3. The negative pressure decreases from top to bottom, so that the phosphoric acid tail gas passes through the wire mesh defoamer 14 in the defoamer tower 3 from bottom to top. The flow rate of the phosphoric acid tail gas in the defoamer tower 3 is about 0.5m 3 / s, during this process, the phosphoric acid mist in the rising phosphoric acid tail gas collides with the filler of the wire mesh demister 14 and is attached to the filler surface, and droplets formed by part of the phosphoric acid mist in the tail gas settle under the action of gravity and other resistances.

[0036] S3, the phosphoric acid tail gas after the secondary deacidification flows into the water washing tower 4 for the third deacidification, the spray device 9 in the water washing tower 4 sprays out alkali solution, and the phosphoric acid tail gas and the alkali solution are mixed and heat and mass transferred in the packing layer 16; after the phosphoric acid tail gas passes through the packing layer 16 and the spray device 9, the phosphoric acid tail gas passes through the fiber demister 15, and the phosphoric acid mist in the phosphoric acid tail gas gathers and settles on the filaments in the fiber demister 15, flows through the packing layer 16, and then enters the alkali solution collection tank 13.

[0037] S4. The phosphoric acid tail gas after the three acid removals flows into the demister 5, passes through the electrostatic demister 17, and undergoes the fourth acid removal. The phosphoric acid tail gas passing through the electrostatic demister 17 is discharged into the atmosphere through the exhaust pipe 6 at the top of the demister 5.

[0038] Example 2

[0039] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 2 is different from Example 1 in that the filler of the packing layer 16 in the water washing tower 4 is changed into a modified ceramic ring filler. The preparation process of the modified ceramic ring filler is: 100 kg of ceramic rings are placed in 600 kg of a mixed acid solution of 15wt% sulfuric acid and 12wt% hydrochloric acid and soaked for 6 hours, washed with water, and then the ceramic ring filler is added to 1100 kg of a 25wt% polyvinyl alcohol aqueous solution and soaked for 12 hours to obtain the modified ceramic ring filler.

[0040] Example 3

[0041] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 3 is different from that in Example 1 in that the two-layer filler of the wire mesh demister 14 in the demister tower 3 is changed into a single-layer filler.

[0042] Example 4

[0043] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 4 is different from that in Example 1 in that the height of each layer of filler in the wire mesh demister 14 of the demister tower 3 is changed to 180 mm.

[0044] Example 5

[0045] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 5 is different from that in Example 1 in that the height of each layer of filler in the wire mesh demister 14 of the demister tower 3 is changed to 160 mm.

[0046] Example 6

[0047] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 6 is different from that in Example 1 in that the spray density of the spray device 9 in the water washing tower 4 is changed to 13m 3 / (m 2 h).

[0048] Example 7

[0049] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 7 is different from that in Example 1 in that the spray density of the spray device 9 in the water washing tower 4 is changed to 18m 3 / (m 2 h).

[0050] Example 8

[0051] A yellow phosphorus phosphoric acid tail gas treatment device. The difference between the yellow phosphorus phosphoric acid tail gas treatment device in Example 8 and Example 1 is that the packing height of the packing layer 16 in the water washing tower 4 is changed to 2400 mm.

[0052] Example 9

[0053] A yellow phosphorus phosphoric acid tail gas treatment device. The difference between the yellow phosphorus phosphoric acid tail gas treatment device in Example 9 and Example 1 is that the packing height of the packing layer 16 in the water washing tower 4 is changed to 2600 mm.

[0054] Example 10

[0055] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in Example 10 is different from that in Example 1 in that the interval between the spray tower 2 and the defoaming tower 3 is changed to 3.5m.

[0056] Embodiment 11

[0057] A yellow phosphorus phosphoric acid tail gas treatment device. The yellow phosphorus phosphoric acid tail gas treatment device in Example 11 is different from that in Example 1 in that the operating voltage of the electrostatic precipitator 17 is changed to 60KV.

[0058] Example 12

[0059] A yellow phosphorus phosphoric acid tail gas treatment device. The difference between the yellow phosphorus phosphoric acid tail gas treatment device in Example 12 and Example 1 is that the operating voltage of the electrostatic precipitator 17 is changed to 40KV.

[0060] Comparative Example 1

[0061] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in comparative example 1 is different from that in embodiment 1 in that: no demister is used in comparative example 1, that is, the phosphoric acid tail gas is directly discharged from the top of the water washing tower 4. Accordingly, the treatment process of the yellow phosphorus phosphoric acid tail gas treatment device in comparative example 1 becomes:

[0062] S1, phosphoric acid tail gas enters the spray tower 2 from the air inlet pipe 1 at the top of the spray tower 2 for primary deacidification, the atomizing spray gun 7 atomizes the sprayed alkali solution, and the atomized particle size is 1-10um. The atomized alkali solution reacts and settles with the phosphoric acid mist in the phosphoric acid tail gas; the particulate matter and phosphoric acid mist in the phosphoric acid tail gas condense with the water vapor sprayed by the atomizing spray gun, and then increases in the spray tower and sinks into the alkali solution collection pool. The phosphoric acid tail gas after preliminary cleaning flows into the defoaming tower through the bottom of the spray tower. In the process of flowing into the defoaming tower, the phosphoric acid tail gas will transfer heat and mass with the alkali solution collection pool, and a small amount of phosphoric acid mist can be removed.

[0063] S2. After the primary deacidification, the phosphoric acid tail gas flows into the defoamer tower 3. The phosphoric acid tail gas passes through the wire mesh defoamer 14 in the defoamer tower 3 for secondary deacidification. Under the suction of the fan 11, there is a negative pressure of about 200 Pa in the defoamer tower 3. The negative pressure decreases from top to bottom, so that the phosphoric acid tail gas passes through the wire mesh defoamer 14 in the defoamer tower 3 from bottom to top. The flow rate of the phosphoric acid tail gas in the defoamer tower 3 is about 0.5m 3 / s, during this process, the phosphoric acid mist in the rising phosphoric acid tail gas collides with the filler of the wire mesh demister 14 and is attached to the filler surface, and droplets formed by part of the phosphoric acid mist in the tail gas settle under the action of gravity and other resistances.

[0064] S3, the phosphoric acid tail gas after the secondary deacidification flows into the water washing tower 4 for the third deacidification, the spray device 9 in the water washing tower 4 sprays out alkali solution, and the phosphoric acid tail gas and the alkali solution are mixed and heat and mass transferred in the packing layer 16; after the phosphoric acid tail gas passes through the packing layer 16 and the spray device 9, the phosphoric acid tail gas passes through the fiber demister 15, and the phosphoric acid mist in the phosphoric acid tail gas gathers and settles on the filaments in the fiber demister 15, flows through the packing layer 16, and then enters the alkali solution collection tank 13.

[0065] Comparative Example 2

[0066] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in comparative example 2 is different from that in embodiment 1 in that: the water washing tower 4 in comparative example 2 is not provided with a packing layer 16. Accordingly, step S3 in the treatment process of the yellow phosphorus phosphoric acid tail gas treatment device in comparative example 2 is changed to:

[0067] The phosphoric acid tail gas after the secondary deacidification flows into the water scrubber 4 for the third deacidification. The spray device 9 in the water scrubber 4 sprays alkali solution, and the rising phosphoric acid tail gas directly contacts the alkali solution. Part of the phosphoric acid mist in the phosphoric acid tail gas directly settles, thereby reducing the concentration of the phosphoric acid mist. After the phosphoric acid tail gas passes through the spray device 9, the phosphoric acid tail gas passes through the fiber demister 15, and the phosphoric acid mist in the phosphoric acid tail gas gathers and settles on the filaments in the fiber demister 15, flows through the packing layer 16, and then enters the alkali solution collection tank 13.

[0068] Comparative Example 3

[0069] A yellow phosphorus phosphoric acid tail gas treatment device, the yellow phosphorus phosphoric acid tail gas treatment device in comparative example 3 is different from that in embodiment 1 in that: the fiber demister 15 is not provided in the water washing tower 4 in comparative example 3. Accordingly, step S3 in the treatment process of the yellow phosphorus phosphoric acid tail gas treatment device in comparative example 3 becomes:

[0070] The phosphoric acid tail gas after the secondary deacidification flows into the water scrubber 4 for the third deacidification. The spray device 9 in the water scrubber 4 sprays out alkali solution. The phosphoric acid tail gas and the alkali solution are mixed in gas and liquid and heat and mass transfer is carried out in the packing layer 16. After the phosphoric acid tail gas passes through the packing layer 16 and the spray device 9, the phosphoric acid tail gas passes through the fiber demister 15. The phosphoric acid mist in the phosphoric acid tail gas gathers and settles on the filaments in the fiber demister 15, flows through the packing layer 16, and then enters the alkali solution collection tank 13. The phosphoric acid tail gas passing through the spray device 9 enters the pipeline from the top of the water scrubber 4.

[0071] Performance Testing

[0072] 1. Measurement of the change in the content of phosphoric acid mist in the tail gas and the removal rate of phosphoric acid mist: The acid mist content (mg / m 3), the measurement method is ion chromatography, and the specific reference document is "Ion Chromatography for the Determination of Phosphoric Acid Mist in Waste Gas from Stationary Pollution Sources" (Draft for Comments).

[0073] 2. Determination of phosphoric acid recovery rate: The yellow phosphorus phosphoric acid tail gas treatment devices in Examples 1-12 and Comparative Examples 1-4 were respectively operated for two days, and the phosphoric acid and phosphates in the alkali solution treatment tank 13 and the residual phosphoric acid and phosphates in the demister 5 were collected. The ratio of the sum of the molar amounts of the above phosphoric acid and phosphates to the molar amount of phosphorus pentoxide used in the production and preparation of phosphoric acid is the phosphoric acid recovery rate of the above yellow phosphorus phosphoric acid tail gas treatment device.

[0074] The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] By analyzing Table 1, it can be seen that by comparing Examples 1 and 2, after using the modified ceramic ring filler, the performance of the tail gas treatment device in removing acid mist is significantly enhanced; by comparing Examples 1 and 3, 4, and 5, it can be seen that increasing the number of filler layers and increasing the height in the wire mesh demister can improve the performance of the tail gas treatment device in removing acid mist; by comparing Examples 1 and 6 and 7, it can be seen that increasing the spray density of the spray device in the water scrubber can also enhance the performance of the tail gas treatment device in removing acid mist in the tail gas, thereby improving the recovery rate of phosphoric acid; by comparing Examples 1 and 8 and 9, it can be seen that the height of the filler layer in the water scrubber is appropriately increased, The performance of the tail gas treatment device in removing acid mist in the tail gas can be enhanced, but when the packing layer is too high, it will affect the normal circulation of the tail gas, so that the phosphoric acid tail gas speed will decrease, which is not conducive to the subsequent process of removing phosphoric acid mist, such as the packing layer height increases in Example 9, but the phosphoric acid recovery rate is lower; it can be obtained by comparing Examples 1 and 10 that the interval between the defoaming tower and the spray tower also has a more obvious effect on the performance of the tail gas treatment device in removing acid mist, and the interval is too short, and the phosphoric acid tail gas cannot fully transfer heat and mass with the alkali solution collection pool liquid surface during the process of flowing from the spray tower to the defoaming tower, thereby affecting the performance of the tail gas treatment device in removing acid mist in the tail gas as a whole. It can be obtained by comparing Example 1 and Comparative Examples 1-3 that the main body of the yellow phosphorus phosphoric acid tail gas treatment device of the present invention includes a spray tower, a defoaming tower, a water washing tower and a demisting tower, and a four-stage phosphoric acid mist removal process is carried out, and the change of one of the devices will affect the removal of the overall phosphoric acid mist and the phosphoric acid recovery rate.

[0079] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A yellow phosphorus phosphoric acid tail gas treatment device, characterized in that: It comprises a spray tower (2), a defoaming tower (3), a water washing tower (4) and a demisting tower (5) which are connected in sequence, and also comprises an alkali liquid collection pool (13); An air inlet pipe (1) is provided at the top of the spray tower (2), an atomizing spray gun (7) is provided inside the spray tower (2), the atomizing spray gun (7) is connected to the outlet end of a hydraulic pump (8) via a pipeline, and the inlet end of the hydraulic pump (8) is connected to an alkali solution collection tank (13); The defoamer tower (3) is provided with a wire mesh defoamer (14); The water washing tower (4) is provided with a packing layer (16), a spray device (9) and a fiber demister (15) in order from bottom to top, the spray device (9) is connected to the outlet end of the second hydraulic pump (10) through a pipeline, and the inlet end of the second hydraulic pump (10) is connected to the alkali liquid collection tank (13); An exhaust pipe (6) is provided at the top of the demisting tower (5), and an electrostatic demisting device (17) is provided in the demisting tower (5); The alkali liquid collection pool (13) is located at the bottom of the spray tower (2), the defoaming tower (3) and the water washing tower (4), and the bottoms of the spray tower (2), the defoaming tower (3) and the water washing tower (4) are connected to the alkali liquid collection pool (13); The filler of the packing layer (16) is a ceramic ring filler, and the filler height is 1500-2400 mm. The ceramic ring filler is a modified ceramic ring filler. The preparation process of the modified ceramic ring filler comprises: placing the ceramic ring in a mixed acid solution of 10-20wt% sulfuric acid and 8-15% hydrochloric acid and soaking it for 5-8h, taking it out and washing it, adding it to a 20-30wt% polyvinyl alcohol aqueous solution and soaking it for 10-15h to obtain the modified ceramic ring filler, wherein the weight ratio of the ceramic ring to the mixed acid solution is 1:5-7, and the weight ratio of the ceramic ring to the polyvinyl alcohol aqueous solution is 1:10-13.

2. A yellow phosphorus phosphoric acid tail gas treatment device according to claim 1, characterized in that: The wire mesh demister (14) has two layers of filler, and the height of each layer is 200-350 mm.

3. The yellow phosphorus phosphoric acid tail gas treatment device according to claim 1, characterized in that: The spraying density of the spraying device (9) is 15-40m 3 / (m 2 h).

4. The yellow phosphorus phosphoric acid tail gas treatment device according to claim 1, characterized in that: The height of the spray tower (2) is 8-12 m, the height of the defoaming tower (3) is 7-10 m, and the interval between the spray tower (2) and the defoaming tower (3) is 4.5-8 m.

5. The yellow phosphorus phosphoric acid tail gas treatment device according to claim 1, characterized in that: The operating voltage of the electrostatic precipitator (17) is 60-90 kV, and the operating current is 200-500 mA.

6. The yellow phosphorus phosphoric acid tail gas treatment device according to claim 1, characterized in that: A fan 1 (11) is provided between the defoaming tower (3) and the water washing tower (4), and a fan 2 (12) is provided between the water washing tower (3) and the demisting tower (4).

7. A treatment process using the yellow phosphorus phosphoric acid tail gas treatment device according to claim 1, characterized in that: The following steps are involved: S1, phosphoric acid tail gas enters the spray tower (2) from the air inlet pipe at the top of the spray tower (2), and the sprayed alkali solution is atomized by the atomizing spray gun (7), and the atomized alkali solution reacts and settles with the acidic components in the phosphoric acid tail gas to perform a deacidification; S2, the phosphoric acid tail gas after the primary deacidification enters the defoamer tower (3), and the phosphoric acid tail gas passes through the wire mesh defoamer (14) in the defoamer tower (3) for secondary deacidification; S3, the phosphoric acid tail gas after the secondary deacidification enters the water washing tower (4) for the third deacidification, the spray device (9) in the water washing tower (4) sprays out alkali solution, and the phosphoric acid tail gas and alkali solution are mixed and heat and mass transferred in the packing layer (16); after the phosphoric acid tail gas passes through the packing layer (16) and the spray device (9), the phosphoric acid tail gas passes through the fiber demister (15), and the acid mist in the phosphoric acid tail gas gathers and settles on the filaments in the fiber demister (15), flows through the packing layer (16), and then enters the alkali solution collection tank (13); S4. After the three times of deacidification, the phosphoric acid tail gas enters the demisting tower (5), passes through the electrostatic demister (17), undergoes the fourth deacidification, and the phosphoric acid tail gas passing through the electrostatic demister (17) is discharged into the atmosphere through the exhaust pipe (6) at the top of the demisting tower (5).

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