阅读说明：本技术 一种湿法磷酸及其衍生产品的有害元素脱除方法及设备 (Method and equipment for removing harmful elements in wet-process phosphoric acid and derivative products thereof ) 是由 陈彬 项双龙 彭学江 杨阳 胡黔 于 2019-09-03 设计创作，主要内容包括：本发明涉及湿法磷酸处理技术领域,具体是一种湿法磷酸及其衍生产品的有害元素脱除方法及设备。本发明选用五硫化二磷作为脱砷剂分别加入到湿法磷酸萃取槽和湿法磷酸陈化槽,进行两级有害元素脱除反应,使其中的砷以不溶性化合物As<Sub>2</Sub>S<Sub>3</Sub>形式最终进入磷石膏渣场,在脱砷的同时,使湿法磷酸及其衍生产品中的Cr、Pb、Cu等重金属阳离子有害元素也同时得到脱除,提升湿法磷酸及其衍生产品的品质,减少所得磷肥中的有害元素,并将副产的硫化氢气体作为萃取尾气中碘分子还原剂,减少了碘回收系统中液体SO<Sub>2</Sub>原料消耗,减少萃取尾气冒红烟视觉污染,回收碘分子资源。(The invention relates to the technical field of wet-process phosphoric acid treatment, in particular to a method and equipment for removing harmful elements in wet-process phosphoric acid and a derivative product thereof. The invention selects phosphorus pentasulfide As a dearsenization agent to be respectively added into a wet-process phosphoric acid extraction tank and a wet-process phosphoric acid aging tank to carry out two-stage removal reaction of harmful elements, SO that arsenic in the phosphorus pentasulfide is finally introduced into a phosphogypsum slag yard in the form of an insoluble compound As2S3, heavy metal cation harmful elements such As Cr, Pb, Cu and the like in the wet-process phosphoric acid and derivative products are simultaneously removed while dearsenization is carried out, the quality of the wet-process phosphoric acid and the derivative products thereof is improved, the harmful elements in the obtained phosphate fertilizer are reduced, and a byproduct hydrogen sulfide gas is used As an iodine molecule reducing agent in extraction tail gas, SO that the consumption of liquid SO2 raw materials in an iodine recovery system is reduced, the visual pollution of red smoke emitted by extraction.)

1. A method for removing harmful elements from wet-process phosphoric acid and derived products thereof is characterized by comprising the following steps:

(1) Adding phosphorus pentasulfide into a wet-process phosphoric acid extraction tank, filtering after full reaction, allowing filter residues to enter a phosphogypsum slag field, transferring filtrate into a wet-process phosphoric acid aging tank, and collecting gas escaped in the reaction process;

(2) Adding phosphorus pentasulfide into a wet-process phosphoric acid aging tank, filtering after full reaction, returning filter residues to a wet-process phosphoric acid extraction tank to continue the step (1), using filtrate for phosphoric acid concentration and phosphate fertilizer production, and collecting gas escaping in the reaction process;

(3) And (3) using the gas collected in the steps (1) and (2) to reduce iodine molecules in the wet-process phosphoric acid and the fluosilicic acid.

2. The method for removing harmful elements from wet-process phosphoric acid and its derivative products according to claim 1, wherein the addition of phosphorus pentasulfide is a sufficient addition of phosphorus pentasulfide.

3. the method for removing harmful elements from phosphoric acid and its derivatives by wet process according to claim 1, wherein the filtration in step (1) is performed by a three-stage counter-current washing rotary table type filter, and the arsenic-removed waste residue is added to the phosphogypsum residue.

4. The method for removing harmful elements from wet-process phosphoric acid and the products derived therefrom according to claim 1, wherein the step (3) for reducing iodine molecules in the wet-process phosphoric acid and the fluosilicic acid is to reduce the iodine molecules to iodide ions by using the collected gas as a reducing agent for extracting iodine molecules in an tail gas from an iodine recovery system in a wet-process phosphoric acid production system.

5. The method for removing harmful elements from wet-process phosphoric acid and its derivative products according to claim 4, wherein the collected gas in step (3) is used as a reducing agent for extracting iodine molecules in tail gas in an iodine recovery system in a wet-process phosphoric acid production system to reduce the iodine molecules into iodine ions, and the method comprises the following specific steps: dissolving the collected gas in water, adding SO2 to prepare an absorption liquid-SO 2 aqueous solution, catalytically oxidizing iodine ions in the iodine-containing dilute phosphoric acid and the fluosilicic acid into iodine molecules, blowing the iodine molecules in the dilute phosphoric acid and the fluosilicic acid into the prepared absorption liquid-SO 2 aqueous solution in a gas phase for reaction by an air extraction blowing-out method, and reducing the iodine molecules into the iodine ions through SO 2.

6. the method for removing harmful elements from phosphoric acid and its derivatives by wet process as claimed in claim 5, wherein said absorbing solution-SO 2 aqueous solution is SO2 aqueous solution with concentration of 2% -10%.

7. The method for removing harmful elements from phosphoric acid and its derivative products by wet process according to claim 5, wherein the iodine molecules in the diluted phosphoric acid and fluosilicic acid are blown into the prepared absorption liquid-SO 2 aqueous solution in gas phase for reaction, and the temperature is controlled to be 20-50 ℃ during the reaction.

8. The method for removing harmful elements from wet-process phosphoric acid and the products derived therefrom according to claim 5, wherein the concentration of iodide ions in the absorbing solution-SO 2 aqueous solution is controlled to be 30-70 g/L.

9. The method for removing harmful elements from phosphoric acid and its derivatives by wet process as claimed in claim 5, wherein the iodine molecules are reduced to iodide ions and then put into solution, and then oxidant is introduced to oxidize the iodide ions to iodide molecules again, and the iodide products are obtained by liquid-solid separation.

10. The equipment used in the method for removing harmful elements in wet-process phosphoric acid and the products derived therefrom according to claims 1 to 9, which is characterized by comprising a phosphorus pentasulfide bin, a phosphorus pentasulfide metering and conveying system, a rotary table filter, a dilute phosphoric acid clarifying tank, a dilute phosphoric acid storage tank, a dilute phosphoric acid concentrating and removing system, a fluorine tower of a fluorine absorption system for extracting fluorine by wet-process phosphoric acid, a device for producing iodine-containing fluosilicic acid by the fluorine absorption system for extracting fluorine by wet-process phosphoric acid, an iodine oxidation-reduction-enrichment-oxidation recovery device and a system behind the fluorine absorption system for extracting fluorine by wet-process phosphoric acid, wherein the phosphorus pentasulfide bin is respectively connected with the phosphoric acid extracting tank and the dilute phosphoric acid clarifying tank through the phosphorus pentasulfide metering and conveying; the bottom of the wet-process phosphoric acid extraction tank is connected with a rotary table filter, the mixture at the bottom is sent to the rotary table filter for filtering, the upper part of the wet-process phosphoric acid extraction tank is connected with a fluorine tower of a fluorine absorption system for extracting fluorine by wet-process phosphoric acid, and the generated H2S gas is sent to a fluorine tower; the rotary table filter is connected with a filter residue phosphogypsum deslagging field and a dilute phosphoric acid clarifying tank, filter residue flows to the filter residue phosphogypsum deslagging field, and filtrate flows to the dilute phosphoric acid clarifying tank; the bottom of the dilute phosphoric acid clarifying tank is connected with the wet-process phosphoric acid extraction tank for conveying the bottom sediment back to the wet-process phosphoric acid extraction tank, the upper part of the dilute phosphoric acid clarifying tank is connected with a dilute phosphoric acid storage tank for conveying clear liquid to the dilute phosphoric acid storage tank, the top of the dilute phosphoric acid clarifying tank is connected with a fluorine tower of a wet-process phosphoric acid extraction fluorine absorption system, and the generated H2S gas is conveyed to a fluorine tower; the dilute phosphoric acid storage tank is connected with the dilute phosphoric acid concentration removal system, and dilute phosphoric acid is sent to be concentrated; the lower part of a fluorine tower of the wet-process phosphoric acid extraction fluorine absorption system is connected with an iodine oxidation-reduction-enrichment-oxidation recovery device for producing the iodine-containing fluosilicic acid by the wet-process phosphoric acid extraction fluorine absorption system so as to recover iodine molecular resources; the upper part is connected with a system behind the wet-process phosphoric acid extraction fluorine absorption system to recover tail gas.

Technical Field

the invention relates to the technical field of wet-process phosphoric acid treatment, in particular to a method and equipment for removing harmful elements in wet-process phosphoric acid and a derivative product thereof.

Background

At present, in the production process of phosphate fertilizer, because concentrated phosphoric acid contains a certain amount of arsenic (about 50-60 ppm), the content of arsenic in phosphate fertilizer products is about 80ppm, and a certain gap exists between the arsenic content in I type product execution standards and the arsenic content in foreign product quality execution standards, wherein the As% is less than or equal to 0.005, and the As% is less than or equal to 0.002.

At present, the industrial dearsenification of phosphoric acid and its derivative products is mainly used for dearsenification of food-grade or electronic-grade related products, the dearsenification objects are mostly thermal phosphoric acid and its related products or wet phosphoric acid purified acid and its related products, and researches or industrial experiments for directly dearsenifying wet phosphoric acid and its derivative products are rarely reported. Most of the products are dearsenized in phosphoric acid, and most of the methods are to dearsenize phosphoric acid to obtain the required products or to reproduce subsequent products.

Therefore, it is urgent to find a method and equipment for removing harmful elements from wet-process phosphoric acid and its derivatives, which can fully remove the harmful elements such as arsenic in the production process of wet-process phosphoric acid, reduce the content of the harmful elements such as arsenic in the prepared phosphate fertilizer, and have simple operation, no introduction of new impurities and no generation of three wastes.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a method for removing harmful elements from wet-process phosphoric acid and a derivative product thereof, which comprises the following steps:

A method for removing harmful elements from wet-process phosphoric acid and its derivative products comprises the following steps:

(1) Adding phosphorus pentasulfide into a wet-process phosphoric acid extraction tank, filtering after full reaction, allowing filter residues to enter a phosphogypsum slag field, transferring filtrate into a wet-process phosphoric acid aging tank, and collecting gas escaped in the reaction process;

(2) Adding phosphorus pentasulfide into a wet-process phosphoric acid aging tank, filtering after full reaction, returning filter residues to a wet-process phosphoric acid extraction tank to continue the step (1), using filtrate for phosphoric acid concentration and phosphate fertilizer production, and collecting gas escaping in the reaction process;

(3) And (3) using the gas collected in the steps (1) and (2) to reduce iodine molecules in the wet-process phosphoric acid and the fluosilicic acid.

Preferably, the phosphorus pentasulfide is added in a sufficient amount. Sufficient phosphorus pentasulfide can fully remove harmful elements of heavy metal cations such As As, Cr, Pb, Cu and the like in wet-process phosphoric acid and derivative products thereof.

and (2) filtering in the step (1) by using a three-stage countercurrent washing rotary table type filter, wherein the arsenic-removing waste residue is doped into the phosphogypsum filter residue.

Preferably, the step (3) for reducing iodine molecules in wet-process phosphoric acid and fluosilicic acid is to reduce iodine molecules into iodine ions by using the collected gas as a reducing agent for extracting iodine molecules in tail gas in an iodine recovery system in a wet-process phosphoric acid production system. Further preferably, in the step (3), the collected gas is used as a reducing agent for extracting iodine molecules in tail gas in an iodine recovery system in a wet-process phosphoric acid production system, and the iodine molecules are reduced to iodide ions, and the specific steps are as follows: dissolving the collected gas in water, adding SO2 to prepare an absorption liquid-SO 2 aqueous solution, catalytically oxidizing iodine ions in the iodine-containing dilute phosphoric acid and the fluosilicic acid into iodine molecules, blowing the iodine molecules in the dilute phosphoric acid and the fluosilicic acid into the prepared absorption liquid-SO 2 aqueous solution in a gas phase for reaction by an air extraction blowing-out method, and reducing the iodine molecules into the iodine ions through SO 2.

Preferably, the absorbing liquid-SO 2 aqueous solution is SO2 aqueous solution with the concentration of 2% -10%, the temperature is controlled to be 20-50 ℃ in the reaction process, and the concentration of iodide ions in the absorbing liquid-SO 2 aqueous solution is controlled to be 30-70 g/L. The condition is the optimal process condition for reducing and absorbing the iodine molecules.

Preferably, after the iodine molecules are reduced into iodine ions and enter the solution, an oxidant can be introduced to oxidize the iodine ions into iodine molecules again, and the iodine product is obtained through liquid-solid separation. More preferably, 30 percent of H2O2 is used as an oxidant, the dosage of the oxidant is 105 to 120 percent of the theoretical addition amount, the reaction temperature is 10 to 40 ℃, and the reaction time is 10 to 30min

Preferably, the iodine ions in the iodine-containing dilute phosphoric acid and the fluosilicic acid are catalytically oxidized into iodine molecules, and specifically, 30% H2O2 oxidant with the volume fraction of 0.5% -3.0% is added, the reaction temperature is 60-90 ℃, and the reaction time is 10-30 min. The condition is the optimal process condition for the catalytic oxidation of iodide ions.

Preferably, the gas-liquid volume ratio in the air extraction process is 80-150, and the reaction temperature is 65-95 ℃. The condition is the optimal process condition for air extraction of iodine molecules.

At present, the industrial dearsenification of phosphoric acid and its derivative products is mainly used for dearsenification of food-grade or electronic-grade related products, the dearsenification objects are mostly thermal phosphoric acid and its related products or wet phosphoric acid purified acid and its related products, and researches or industrial experiments for directly dearsenifying wet phosphoric acid and its derivative products are rarely reported. Most of the products are dearsenized in phosphoric acid, most of the methods are to dearsenize phosphoric acid to obtain the required products or reproduce subsequent products, and the dearsenization methods are mainly divided into the following methods:

The technical principle of harmful element removal is as follows:

as is present in concentrated phosphoric acid in the form of H3AsO4 or H3AsO3, both of which react with S2-to form the insoluble compound As2S3, which is reacted As follows:

HAsO+HS＝HAsO+S↓+HO

2HAsO+3HS＝AsS↓+6HO

Wherein H3AsO4 reacts with H2S to generate H3AsO3, and then H3AsO3 can react with H2S to generate insoluble As2S3 precipitate, which indicates that the content of H3AsO4 in phosphoric acid can influence the demand of H2S.

In dearsenification of phosphoric acid, P2S5 reacts in the presence of water as follows:

PS+HO＝HPO+HS

P2S5 generates H3PO4 and H2S in the presence of water, generates a compound H2S containing S2 < - >, and does not introduce other impurities, so P2S5 is an excellent dearsenization agent. However, concentrated phosphoric acid contains a certain amount of Cr, Pb, Cu, etc., and these heavy metal cations and S form insoluble precipitates, and the reaction is as follows:

2Cr+3S＝CrS↓

Cu+S＝CuS↓

Pb+S＝PbS↓

therefore, while removing arsenic, part of heavy metal cations can be removed, i.e. the content of other heavy metal ions can affect the consumption of P2S 5.

However, during the reaction, H2S generated by the decomposition of P2S5 is hardly soluble in water, the solubility in water is only 0.58g/100g of water, and the solubility in phosphoric acid is lower, so that after P2S5 is added into the reaction solution system, a part of H2S gas may overflow.

The technical principle of reducing and absorbing gas-phase iodine molecules is as follows:

H2S is used as a reducing agent to react with iodine molecules blown out from dilute phosphoric acid and fluosilicic acid as follows:

4I+HS+4HO＝HSO﹢8HI

Taking Kaiyang phosphate ore as an example, in a wet-process phosphoric acid process, about 60% of associated iodine resources enter dilute phosphoric acid, about 25% enter an extraction tail gas washing and absorbing system, wherein the dilute phosphoric acid contains about 40mg/kg of iodine, and the extraction tail gas washing and absorbing solution-fluosilicic acid contains about 25mg/kg of iodine. The method comprises the steps of catalytically oxidizing iodine ions in 23 percent (P2O5) dilute phosphoric acid and 10 percent fluosilicic acid into iodine molecules by using H2O2 as an oxidant, blowing the iodine molecules in the dilute phosphoric acid and the fluosilicic acid into an absorption liquid-SO 2 aqueous solution in a gas phase manner by an air extraction blowing-out method, reducing the iodine molecules into the iodine ions by using an SO2 reducing agent, introducing the H2O2 oxidant into the absorption liquid after the concentration of the iodine ions in the absorption liquid reaches a certain value, oxidizing the iodine ions into the iodine molecules again, and carrying out liquid-solid separation to obtain the iodine product. The process of recovering the phosphorus ore associated iodine comprises the working procedures of catalytic oxidation of iodide ions, air extraction of iodine molecules, reduction and absorption of the iodine molecules and separation of iodine products.

At present, one of the larger raw materials consumed by the iodine recovery device of wet-process phosphoric acid is sulfur dioxide, and the sulfur dioxide is generally purchased from bottled liquid sulfur dioxide, the concentration of the sulfur dioxide is 99.9 percent, and the pressure of a gas cylinder is 0.3-0.5MPa, and each bottle of sulfur dioxide gas is about 1 ton. Liquid sulfur dioxide is decompressed by the buffer tank and then is introduced into a using point of the device by a pipeline to enter a system for use. In order to avoid safety and environmental protection risks, the stock is not more than 20 tons. When the field is used up, the forklift is transported from the storage warehouse to the field for replacement. At present, no liquid sulfur dioxide producer in Guizhou province needs to purchase outside provinces, field production interruption is caused when long-distance transportation is carried out or the producer cannot supply goods in time, and on the other hand, bottled liquid sulfur dioxide is high in concentration and pressure, belongs to a pressure container, and is high in transportation and internal storage safety and environmental protection risks. The price of the adopted liquid sulfur dioxide is higher, and the purchase price of the liquid sulfur dioxide in the market is 5700 yuan per ton.

Because sulfur dioxide in the iodine recovery device is mainly used for reducing iodine molecules in wet-process phosphoric acid and fluosilicic acid, and the requirements on the purity and concentration of the sulfur dioxide are low, H2S gas collected in the invention is used as a reducing agent to react with iodine molecules blown out from dilute phosphoric acid and fluosilicic acid to obtain iodine ions, SO that the consumption of liquid SO2 raw materials is reduced, and the visual pollution of red smoke emitted by extraction tail gas is reduced.

the equipment used in the method for removing harmful elements from the wet-process phosphoric acid and the derived products thereof comprises a phosphorus pentasulfide bin, a phosphorus pentasulfide metering and conveying system, a rotary table filter, a dilute phosphoric acid clarifying tank, a dilute phosphoric acid storage tank, a dilute phosphoric acid concentrating removal system, a fluorine tower of a fluorine absorption system for extracting fluorine from the wet-process phosphoric acid, a device for removing iodine, oxidizing, reducing, enriching and oxidizing recovery iodine from iodine-containing fluosilicic acid produced by the fluorine absorption system for extracting fluorine from the wet-process phosphoric acid, and a system behind the fluorine absorption system for extracting the wet-process phosphoric acid, wherein the phosphorus pentasulfide bin is respectively connected with the wet-process phosphoric acid extracting tank and the dilute phosphoric acid clarifying tank through the phosphorus penta; the bottom of the wet-process phosphoric acid extraction tank is connected with a rotary table filter, the mixture at the bottom is sent to the rotary table filter for filtering, the upper part of the wet-process phosphoric acid extraction tank is connected with a fluorine tower of a fluorine absorption system for extracting fluorine by wet-process phosphoric acid, and the generated H2S gas is sent to a fluorine tower; the rotary table filter is connected with a filter residue phosphogypsum deslagging field and a dilute phosphoric acid clarifying tank, filter residue flows to the filter residue phosphogypsum deslagging field, and filtrate flows to the dilute phosphoric acid clarifying tank; the bottom of the dilute phosphoric acid clarifying tank is connected with the wet-process phosphoric acid extraction tank for conveying the bottom sediment back to the wet-process phosphoric acid extraction tank, the upper part of the dilute phosphoric acid clarifying tank is connected with a dilute phosphoric acid storage tank for conveying clear liquid to the dilute phosphoric acid storage tank, the top of the dilute phosphoric acid clarifying tank is connected with a fluorine tower of a wet-process phosphoric acid extraction fluorine absorption system, and the generated H2S gas is conveyed to a fluorine tower; the dilute phosphoric acid storage tank is connected with the dilute phosphoric acid concentration removal system, and dilute phosphoric acid is sent to be concentrated; the lower part of a fluorine tower of the wet-process phosphoric acid extraction fluorine absorption system is connected with an iodine oxidation-reduction-enrichment-oxidation recovery device for producing the iodine-containing fluosilicic acid by the wet-process phosphoric acid extraction fluorine absorption system so as to recover iodine molecular resources; the upper part is connected with a system behind the wet-process phosphoric acid extraction fluorine absorption system to recover tail gas.

preferably, the wet-process phosphoric acid extraction tank consists of a reaction tank and a digestion tank, wherein the reaction tank consists of one to six zones, and the digestion tank consists of seven to nine zones. The district sets up a stirring rake in the extraction tank, the district sets up the limit groove that the cooling ground paste got into, six districts set up the limit groove of ground paste axial-flow pump interface, two three district upper portions respectively set up a mixed tee bend interface, six districts set up the overflow mouth that the ground paste got into the digestion tank, one district to two districts, two districts to three districts, three district to four districts, four districts to five districts, five districts to six districts, seven districts to eight districts, partition wall sets up the gate-type opening that the extraction reaction ground paste circulated between eight districts to nine districts, each district's inside lining rubber slab barrier, the outer lining carbon brick anticorrosive coating of rubber slab. And waste gas outlets are arranged at the upper parts of the three zones and the four zones.

preferably, a low-level flash cooling circulating pump is further arranged in a sixth area of the reaction tank in the wet-process phosphoric acid extraction tank.

preferably, the phosphorus pentasulfide bin is connected with the three areas and the four areas of the wet-process phosphoric acid extraction tank through a phosphorus pentasulfide metering and conveying system.

preferably, the bottom of the dilute phosphoric acid clarifying tank is connected with the third zone of the wet-process phosphoric acid extraction tank.

Preferably, the bottom of the wet-process phosphoric acid extraction tank is connected with the rotary table filter through a slurry pump.

preferably, the bottom of the dilute phosphoric acid clarifying tank is connected with the wet-process phosphoric acid extraction tank through a slurry pump.

Preferably, the dilute phosphoric acid storage tank is connected with the dilute phosphoric acid de-concentration system through a phosphoric acid pump.

Preferably, the device for producing iodine-containing fluosilicic acid through the wet-process phosphoric acid extraction fluorine absorption system, namely the iodine oxidation-reduction-enrichment-oxidation recovery device, comprises an iodine ion-containing fluosilicic acid settling tank and an iodine recovery system.

Compared with the prior art, the invention has the technical effects that:

(1) The invention selects phosphorus pentasulfide As dearsenization agent to be respectively added into a wet-process phosphoric acid extraction tank and a wet-process phosphoric acid aging tank to carry out two-stage harmful element removal reaction, so that arsenic in the phosphorus pentasulfide finally enters a phosphogypsum slag yard in the form of insoluble compound As2S 3.

(2) The invention can remove the harmful elements of heavy metal cations such as Cr, Pb, Cu and the like in the wet-process phosphoric acid and the derivative products thereof at the same time of arsenic removal, improve the quality of the wet-process phosphoric acid and the derivative products thereof and reduce the harmful elements in the obtained phosphate fertilizer.

(3) The byproduct hydrogen sulfide gas in the arsenic removal process is used as an iodine molecule reducing agent in the extraction tail gas, SO that the consumption of liquid SO2 raw materials in an iodine recovery system is reduced, the visual pollution of red smoke emitted by the extraction tail gas is reduced, and iodine molecule resources are recovered.

drawings

FIG. 1 is a process flow diagram of the present invention;

Fig. 2 is a block diagram of the apparatus of the present invention.

Detailed Description

The technical solution of the present invention is further defined below with reference to the specific embodiments, but the scope of the claims is not limited to the description.

The equipment used for assembling the method for removing harmful elements from wet-process phosphoric acid and the derived products thereof comprises a phosphorus pentasulfide bin, a phosphorus pentasulfide metering and conveying system, a rotary table filter, a dilute phosphoric acid clarifying tank, a dilute phosphoric acid storage tank, a dilute phosphoric acid concentrating and removing system, a fluorine tower of a fluorine absorption system for extracting fluorine by wet-process phosphoric acid, a recovery device for removing iodine and fluosilicic acid by iodine oxidation-reduction-enrichment-oxidation produced by the fluorine absorption system for extracting fluorine by wet-process phosphoric acid, and a rear system of the fluorine absorption system for extracting wet-process phosphoric acid, wherein the phosphorus pentasulfide bin is respectively connected with the phosphoric acid extraction tank and the dilute phosphoric acid clarifying tank through the phosphorus pentasulfide metering and conveying system; the bottom of the wet-process phosphoric acid extraction tank is connected with a rotary table filter, the mixture at the bottom is sent to the rotary table filter for filtering, the upper part of the wet-process phosphoric acid extraction tank is connected with a fluorine tower of a fluorine absorption system for extracting fluorine by wet-process phosphoric acid, and the generated H2S gas is sent to a fluorine tower; the rotary table filter is connected with a filter residue phosphogypsum deslagging field and a dilute phosphoric acid clarifying tank, filter residue flows to the filter residue phosphogypsum deslagging field, and filtrate flows to the dilute phosphoric acid clarifying tank; the bottom of the dilute phosphoric acid clarifying tank is connected with the wet-process phosphoric acid extraction tank for conveying the bottom sediment back to the wet-process phosphoric acid extraction tank, the upper part of the dilute phosphoric acid clarifying tank is connected with a dilute phosphoric acid storage tank for conveying clear liquid to the dilute phosphoric acid storage tank, the top of the dilute phosphoric acid clarifying tank is connected with a fluorine tower of a wet-process phosphoric acid extraction fluorine absorption system, and the generated H2S gas is conveyed to a fluorine tower; the dilute phosphoric acid storage tank is connected with the dilute phosphoric acid concentration removal system, and dilute phosphoric acid is sent to be concentrated; the lower part of a fluorine tower of the wet-process phosphoric acid extraction fluorine absorption system is connected with an iodine oxidation-reduction-enrichment-oxidation recovery device for producing the iodine-containing fluosilicic acid by the wet-process phosphoric acid extraction fluorine absorption system so as to recover iodine molecular resources; the upper part is connected with a system behind the wet-process phosphoric acid extraction fluorine absorption system to recover tail gas.

The wet-process phosphoric acid extraction tank consists of a reaction tank and a digestion tank, wherein the reaction tank consists of one to six zones, and the digestion tank consists of seven to nine zones. The district sets up a stirring rake in the extraction tank, the district sets up the limit groove that the cooling ground paste got into, six districts set up the limit groove of ground paste axial-flow pump interface, two three district upper portions respectively set up a mixed tee bend interface, six districts set up the overflow mouth that the ground paste got into the digestion tank, one district to two districts, two districts to three districts, three district to four districts, four districts to five districts, five districts to six districts, seven districts to eight districts, partition wall sets up the gate-type opening that the extraction reaction ground paste circulated between eight districts to nine districts, each district's inside lining rubber slab barrier, the outer lining carbon brick anticorrosive coating of rubber slab. And waste gas outlets are arranged at the upper parts of the three zones and the four zones.

And a low-level flash cooling circulating pump is arranged in a sixth area of the reaction tank in the wet-process phosphoric acid extraction tank.

And the phosphorus pentasulfide bin is connected with the three areas and the four areas of the wet-process phosphoric acid extraction tank through a phosphorus pentasulfide metering and conveying system.

And the bottom of the wet-process phosphoric acid extraction tank is connected with the rotary table filter through a slurry pump.

and the bottom of the dilute phosphoric acid clarifying tank is connected with the third area of the wet-process phosphoric acid extraction tank.

the bottom of the dilute phosphoric acid clarifying tank is connected with the wet-process phosphoric acid extraction tank through a slurry pump.

The dilute phosphoric acid storage tank is connected with a dilute phosphoric acid concentration removal system through a phosphoric acid pump.

the device for producing iodine-containing fluosilicic acid by the wet-process phosphoric acid extraction fluorine absorption system, which is used for removing iodine, oxidizing, reducing, enriching and oxidizing recovery, consists of an iodine ion-containing fluosilicic acid settling tank and an iodine recovery system.