CN112370951A - Method and system for removing arsenic from smelting flue gas by wet method - Google Patents
Method and system for removing arsenic from smelting flue gas by wet method Download PDFInfo
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Abstract
The invention belongs to the technical field of flue gas dearsenification, and particularly relates to a method and a system for removing arsenic from smelting flue gas by a wet method. The smelting flue gas wet-method arsenic removal method comprises the following steps: subjecting the smelting flue gas to high-concentration sulfuric acid washing so as to remove most of sulfur trioxide; subjecting the flue gas after the high-concentration sulfuric acid washing to low-concentration sulfuric acid washing so As to remove most of As2O3(ii) a Wherein the mass fraction of the sulfuric acid in the high-concentration sulfuric acid is more than 40%, and the mass fraction of the sulfuric acid in the low-concentration sulfuric acid is less than 20%. The method for removing arsenic from smelting flue gas by a wet method provided by the invention has the advantages of small amount of hazardous waste residues, small medicament consumption, low treatment cost and high purity of main arsenic products.
Description
Technical Field
The invention belongs to the technical field of flue gas dearsenification, and particularly relates to a method and a system for removing arsenic from smelting flue gas by a wet method.
Background
In the pyrometallurgical process of arsenic-containing metal ore (As percent is more than or equal to 0.5 percent), most of arsenic in the concentrate enters flue gas, and the arsenic is removed before the flue gas enters an acid making system so As to avoid adverse effects on the subsequent acid making production and reduce the production of arsenic-containing waste acid of a flue gas purification system.
The prior nonferrous smelting flue gas dearsenification technology comprises a dry method dearsenification technology and a wet method dearsenification technology, wherein the dry method arsenic collecting technology is used for desublimating arsenic trioxide into solid state through flue gas shock cooling operation and then entering a cloth bag dust collector to complete gas-solid separation to obtain relatively pure As2O3. The efficiency of the dry process for removing arsenic from flue gas can reach more than 90%, the residual 10% of arsenic in the flue gas enters a subsequent flue gas purification system and enters waste acid to be sent to a wastewater treatment system, and the process of depositing arsenic by sulfuration and treating by a ferric limestone salt process generally reaches the standard.
But due to the presence of a certain amount of SO in the smelting flue gas3The dew point temperature of the flue gas is about 200 ℃, and the flue gas is in the working temperature range of the quench tower, so a large amount of condensed acid in the tower is condensed together with arsenic trioxide, and the problems of cloth bag blockage of a dust remover, equipment corrosion and the like are caused. Similar enterprises generally adopt a method of spraying alkali liquor (NaOH or CaO) in a tower to condense and separate out As2O3While removing SO in the flue gas3However, they are all problematic to varying degrees: SO removal by NaOH3High cost of medicament, and adopts CaO to remove SO3A large amount of calcium sulfate generated is mixed into As2O3The product reduces the purity of the arsenic trioxide product, brings a lot of difficulties for subsequent treatment, and has high treatment cost of hazardous waste. Meanwhile, the dry arsenic removal process has the characteristics that the requirements on dust removal equipment and operation conditions are very high: the dust collector has a large number of cloth bags, only one cloth bag leaks to cause the arsenic removal effect of the system to be greatly reduced, and a large amount of As2O3When the flue gas enters a flue gas washing system, the arsenic content in the washing waste acid can be greatly increased, the arsenic content is easily over the treatment capacity of a wastewater treatment system, the arsenic content in the wastewater is discharged beyond the standard, the whole system needs to be stopped and overhauled, and a damaged cloth bag needs to be replaced; in addition, the production is affected by the problems of blockage of a cloth bag of the dust collector and the like due to the operation reason. In conclusion, the dry process has high failure rate and high operation cost, and has great influence on the economic benefit of enterprises.
The conventional wet dearsenization method generally adopts dilute acid multistage washing and electric defogging purification to meet the requirement of subsequent flue gas acid making, arsenic-containing washing liquid is recycled or discharged after reaching the standard through two-stage treatment of sulfuration arsenic precipitation and limescale salt, arsenic sulfide slag and gypsum neutralization slag are produced, and the arsenic sulfide slag is generally qualified according to dangerous solid wastes. The arsenic removal rate of the process can reach more than 99 percent, and the wastewater can be discharged up to the standard, and the process has the defects that: the first investment cost is high; the second vulcanizing agent (generally industrial sodium sulfide) has high agent cost; the purity of the industrial sodium sulfide used in the third step is only 65%, a large amount of impurities enter arsenic sulfide slag, and the subsequent treatment of dangerous waste slag is high in cost and difficulty. The arsenic sulfide slag generated in the fourth step is dangerous solid waste, the arsenic grade is low and is only 30%, the slag amount is large, and the disposal cost of the dangerous waste is high.
Disclosure of Invention
Aiming at the problems of the smelting flue gas treatment technology of the arsenic-containing metal ore, the invention provides a method and a system for removing arsenic from the smelting flue gas by a wet method, wherein the method and the system are safe and environment-friendly, low in failure rate, small in amount of dangerous waste residues, high in purity of main arsenic products, low in production cost and low in subsequent treatment cost.
Specifically, the invention provides the following technical scheme:
a method for removing arsenic from smelting flue gas by a wet method comprises the following steps:
subjecting the smelting flue gas to high-concentration sulfuric acid washing so as to remove most of sulfur trioxide;
subjecting the flue gas after the high-concentration sulfuric acid washing to low-concentration sulfuric acid washing so As to remove most of As2O3；
Wherein the mass fraction of the sulfuric acid in the high-concentration sulfuric acid is more than 40%, and the mass fraction of the sulfuric acid in the low-concentration sulfuric acid is less than 20%.
The present invention utilizes As2O3High-acid washing and dilute acid washing are sequentially carried out on the arsenic-containing smelting flue gas under the solubility difference of different sulfuric acid concentrations, low-arsenic high-acid waste liquid and high-arsenic dilute acid waste liquid are respectively produced, and more than 90% of SO in the flue gas3Entering low-arsenic high-acid waste liquid with more than 90 percent of As2O3And introducing the high arsenic diluted acid waste liquid. The high arsenic dilute acid waste liquid can be further subjected to a circulating cooling crystallization process to produce pure As2O3Crystallization, lowThe arsenic high acid waste liquid is treated by the process of sulfuration and arsenic precipitation plus lime ferric salt to produce a small amount of arsenic sulfide slag and neutralized gypsum slag.
Preferably, in the method, the smelting flue gas is a pyrometallurgical flue gas of the arsenic-containing non-ferrous metal ore.
Preferably, in the method, the mass fraction of the sulfuric acid in the high-concentration sulfuric acid is 40-90%, and preferably 45-65%;
and/or the low-concentration sulfuric acid washing is graded gradient washing, preferably, the mass fraction of sulfuric acid in the low-concentration sulfuric acid used in the first washing is 10-15%, and the mass fraction of sulfuric acid in the low-concentration sulfuric acid used in the later washing is 0-5%.
Preferably, the method further comprises:
cooling and crystallizing at least part of the washing liquid after washing with the low-concentration sulfuric acid, and filtering to obtain As2O3And (4) crystallizing.
Preferably, the method further comprises:
sequentially cooling, crystallizing and settling at least part of washing liquid after the high-concentration sulfuric acid washing, and collecting precipitates;
adding liquid for size mixing to the precipitate so As to obtain As2O3Slurry;
the As is2O3The slurry is mixed with at least part of the washing liquid washed by the low-concentration sulfuric acid, and then heating and stirring are carried out until As is2O3The solid is dissolved and then filtered to obtain the As-containing2O3A solution;
the said As is contained2O3Cooling and crystallizing the solution, and filtering to obtain As2O3Crystallizing;
further preferably, the temperature of the heating treatment is 80-100 ℃, and the stirring intensity is 150-250 r/min.
Preferably, in the method, the flue gas temperature after the high-concentration sulfuric acid washing is 120-140 ℃;
and/or the low-concentration sulfuric acid washing is graded gradient washing and cooling, wherein the temperature of the flue gas after the first washing is reduced to 60-75 ℃, and the temperature of the flue gas after the last washing is reduced to below 40 ℃.
Preferably, in the method, the ratio of the flow rate of the washing liquid to the flow rate of the flue gas in the high-concentration sulfuric acid washing is 4-6L/Nm3；
And/or when the low-concentration sulfuric acid is used for washing, the ratio of the flow of the washing liquid to the flow of the flue gas is 6-10L/Nm3。
Preferably, the method further comprises:
and sending the flue gas washed by the low-concentration sulfuric acid into an electric demister for purification treatment.
The invention also provides a system for the wet arsenic removal of smelting flue gas, which is suitable for implementing the method for the wet arsenic removal of smelting flue gas, and comprises the following steps:
the high-acid washing tower is sequentially connected with one or more stages of dilute acid washing towers and electric demisters in series behind the high-acid washing tower;
a high-acid circulation tank is circularly connected with the high-acid washing tower, and is sequentially connected with a high-acid cooling tank, a high-acid settling tank, a filter, a size mixing tank, an arsenic dissolving tank and a cooling crystallization system in series;
and a dilute acid circulating groove is arranged in circulating connection with the dilute acid washing tower and is connected with the arsenic dissolving groove.
Preferably, in the above system, the high acid scrubber is a U-shaped scrubber.
The invention has the following beneficial effects:
the method for removing arsenic from smelting flue gas by a wet method provided by the invention has the advantages of small amount of hazardous waste residues, small medicament consumption, low treatment cost and high purity of main arsenic products. Compared with NaOH dry arsenic removal process, the agent has lower cost, only needs a small amount of vulcanizing agent to process 10 percent of the total arsenic content of the flue gas and process SO in the flue gas3The cost of the lime is greatly reduced compared with that of NaOH; compared with CaO dry dearsenization, the invention mainly contains As of arsenic products from cooling crystallization process2O3Has less impurities and high purity, and can be directly sold as a productThe deepening treatment can be continued, and the subsequent treatment process is simple and low in cost; compared with the conventional wet-process arsenic-precipitating sulfurization process, the dosage of the sulfurizing agent is greatly reduced, the cost of the agent is obviously reduced, the same amount of arsenic is treated, and the main product As of the process is2O3Compared with arsenic sulfide slag, the purity is high, the yield is low, and the subsequent treatment cost is greatly reduced.
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FIG. 1 is a schematic diagram of a smelting flue gas wet dearsenification system, wherein the smelting flue gas wet dearsenification system comprises an A-high acid washing system, a B-dilute acid washing system, a C-electric fog system, a D-low arsenic waste liquid treatment system and an E-high arsenic waste liquid treatment system.
FIG. 2 is a process flow diagram of wet dearsenification of smelting flue gas in example 1, wherein a-process water, b-arsenic-containing smelting flue gas, c-arsenic sulfide slag, d-neutralized lime slag, e-lead slag, f-arsenic trioxide crystals, a 1-U-shaped washing tower, a 2-high acid circulation tank, a 3-high acid cooling tank, a 4-high acid settling tank, a 5-low arsenic waste liquid treatment system, a 6-first filter, a 7-filter cake size mixing tank, an 8-arsenic dissolving tank, a 9-first dilute acid washing tower, a 10-second dilute acid washing tower, an 11-third dilute acid washing tower, a 12-dilute acid cooler, a 13-dilute acid settling tank, a 14-second filter, a 15-rapid cooling reactor, a 16-high efficiency crystallizer, a 17-crystallization settling tank, 18-a third filter, 19-primary electric demisting, 20-secondary electric demisting and 21-an electric demisting water washing tank.
Detailed Description
The invention provides a system for removing arsenic from smelting flue gas by a wet method, which consists of a flue gas washing system and an arsenic-containing waste liquid treatment system, wherein the flue gas washing system removes arsenic and SO in the flue gas3And other impurities to meet the requirements of the subsequent acid making process, and the solubility difference of arsenic at different sulfuric acid concentrations and temperatures is utilized to remove SO in the flue gas3Mainly concentrates in low-arsenic waste liquid, arsenic (more than 90 percent) in the smoke is mainly concentrated in high-arsenic waste liquid; the arsenic-containing waste liquid treatment system is used for treating low-arsenic waste liquid and high-arsenic waste liquid generated by the flue gas washing system by different processes according to the characteristics of the waste liquid, and removing arsenic, sulfuric acid and other impurities. The low-arsenic waste liquid is treated by conventional arsenic-lime ferric salt sulfurization precipitation process to produce small amount of sulfurizedArsenic slag (hazardous waste) and neutralized gypsum slag (general solid waste); the high arsenic waste liquid is treated by a circulating cooling crystallization process to produce pure As2O3And (4) crystallizing. The process has the advantages of small amount of hazardous waste residues, low medicament consumption, low treatment cost, high purity of main arsenic products and the like.
1. The flue gas washing system comprises a high-acid washing circulating system, a dilute acid washing circulating system and an electric defogging system, wherein the arsenic-containing flue gas is treated by the flue gas washing system and is sent to the acid making system after meeting the requirements of the acid making process.
The high-acid washing circulating system comprises a high-acid washing tower, a high-acid circulating tank, a high-acid washing liquid settling tank, a high-acid cooling tank and the like. The system adopts a high-concentration sulfuric acid solution (the concentration of sulfuric acid is 40-90%, referred to as high acid for short) for cyclic washing. The temperature of the flue gas is reduced from 350-300 ℃ to about 120 ℃ in the washing process, wherein SO3Dissolved into high-acid cleaning solution, and As in the flue gas2O3At this temperature, As is precipitated out2O3Together with the fumes, are removed in the washing systems of the stages, about 30% of which enter the high-acid washing liquid (only a small amount of As in the case of high acidity)2O3Dissolved into the wash liquor, mostly As2O3In the form of solid insolubles and smoke dust in the washing liquid), 70% enters the washing liquid of the subsequent dilute acid washing system. The high-acid washing liquid is partially opened (the acid balance of the system is maintained), the high-acid washing liquid is cooled to below 40 ℃ in a high-acid cooling tank for crystallization, then the high-acid washing liquid enters a settling tank, the upper clear liquid of the settling tank contains less than 5g/L of arsenic, the high-acid washing liquid is mixed with part of electric fog washing water and sent to a low-arsenic waste liquid treatment system, underflow concentrated slurry rich in solid insoluble arsenic and smoke dust is sent to filtration, and filter cakes are subjected to size mixing and then enter a dilute acid washing system arsenic dissolving tank.
The dilute acid washing circulating system consists of a multistage washing tower, a dilute acid settling tank and the like, and the concentration of the circulating acid in the system is below 20 percent. Residual As in the flue gas after high-acid washing2O3And the smoke dust enters the dilute acid washing liquid in the washing process, and meanwhile, the dilute acid washing liquid is partially opened in the circulating process (the arsenic balance and the water balance of the system are maintained) and is sent to an arsenic dissolving tank.
Arsenic dissolving tank treatment from high acid scrubbingUnder the condition of controlling the temperature in the tank, solid insoluble arsenic is dissolved in dilute acid at 80-100 ℃ and then filtered, the filter cake is lead slag (sold) coming from smoke insoluble substances, and high-arsenic filtrate (with the As concentration of 25-30 g/L) is sent to be cooled and crystallized to produce As2O3。
The electric demisting system consists of two stages of electric demisters, an electric demisting washing water tank and a water pump and is used for removing acid mist and fine particles in the washing and purifying flue gas, one part of electric mist washing water is sent to the high-acid washing system to supplement water lost in the heat insulation evaporation process, and the rest part of water is mixed with the supernatant of the high-acid settling tank and sent to the low-arsenic waste liquid system for treatment.
2. The arsenic-containing waste liquid treatment system is used for treating arsenic-containing waste liquid generated by a flue gas washing system and comprises a low-arsenic waste liquid treatment system and a high-arsenic waste liquid treatment system.
The low-arsenic waste liquid treatment system is used for treating supernatant liquid of a settling tank of a high-acid washing system, the arsenic concentration of the part of waste liquid is low (the As concentration is below 5 g/L), and the part of waste liquid is treated by adopting a process of depositing arsenic by sulfuration and two-stage lime iron salt to produce a small amount of arsenic sulfide slag (dangerous solid waste slag, wherein the As content is below 10 percent of the total arsenic content of the system) and neutralized gypsum slag (common solid waste slag).
The high-arsenic waste liquid treatment system is used for treating high-arsenic filtrate (80-100 ℃, the As concentration is 25-30 g/L) produced by filtering slurry in an arsenic dissolving tank, reducing the temperature of the washing liquid from 80 ℃ to 35 ℃ in a rapid cooling reactor, and utilizing As2O3Has the characteristic of poor solubility at different temperatures, is crystallized and separated out in a high-efficiency crystallizer, and the crystal slurry is sent to be filtered to produce high-purity As2O3And (4) crystallizing. The crystallization mother liquor (35 ℃, the As concentration is below 15 g/L) returns to the dilute acid washing system. As precipitated by crystallization2O3The purity is more than 99 percent, the requirement of GB26721 is met, and the arsenic content is more than 90 percent of the total arsenic content of the system.
In a preferred embodiment, the high-acid washing tower is a U-shaped washing tower, the inside of the U-shaped washing tower is lined with an anti-corrosion brick, and a sprayer is arranged inside the U-shaped washing tower.
In a preferred embodiment, the diluted acid washing tower adopts a combined arrangement scheme of a reverse spray washer, a packed tower and a reverse spray washer.
In a preferred embodiment, each stage of electric defogging can adopt a plurality of parallel modes so as to improve the working efficiency.
In a preferred embodiment, the low-arsenic waste liquid treatment system adopts a combined arrangement scheme of mature general waste acid treatment plants, namely, sulfuration dearsenization, neutralization gypsum slag and lime ferric salt.
The invention specially develops a U-shaped washing tower for high-acid washing, a rapid cooling reactor and a high-efficiency crystallizer for crystallizing dilute acid high-arsenic waste liquid, and utilizes As at different acidity and different temperatures2O3Poor solubility to SO in the scrubbing solution3And As2O3The treatment is respectively carried out, so that the amount of dangerous solid waste arsenic sulfide slag can be greatly reduced, the cost of a vulcanizing agent is reduced, sodium ions entering a washing system are reduced, and meanwhile, the As is recovered by utilizing a cooling crystallization process2O3Without addition of other agents, As2O3The product has high purity, and is beneficial to subsequent further treatment.
In a preferred embodiment, as shown in fig. 1, the arsenic-containing flue gas treatment process of the present invention comprises a high-acid washing system a, a dilute-acid washing system B, an electric spraying system C, a low-arsenic waste liquid treatment system D, and a high-arsenic waste liquid treatment system E:
high-temperature arsenic-containing flue gas (300-350 ℃) firstly enters a high-acid washing tower, and is subjected to adiabatic evaporation circulating washing by using sulfuric acid with the concentration of more than 40%, the temperature of the flue gas is reduced to 120-140 ℃, and As in the flue gas2O3At the temperature, about 30 percent of the SO in the flue gas is crystallized and separated out, enters high-acid washing circulating liquid (a small amount of the SO is dissolved, and most of the SO exists in a solid insoluble substance form)3Dissolving into high-acid circulating washing liquid. And (3) opening a 10% high-acid circulating washing liquid to a high-acid crystallizer to further reduce arsenic content in the washing liquid, then sending the washing liquid to a high-acid settling tank, sending smoke dust and undissolved solid arsenic to underflow, pumping to remove filter pressing, mixing filter cakes, sending the filter cakes to an arsenic dissolving tank of a dilute acid washing system B, and returning the filtrate to the high-acid settling tank. Supernatant of the high-acid settling tank and part of electric fog washing water are mixed and sent to a low-arsenic waste liquid treatment system D to neutralize the process by adopting arsenic sulfide and limescaleMainly producing neutralized gypsum slag and a small amount of arsenic sulfide slag;
the flue gas enters a dilute acid washing system B at the temperature of 120-140 ℃ after passing through a high acid washing tower, dilute acid with the concentration of below 15% is adopted for circular washing, residual smoke dust particles, arsenic dust and other impurities in the flue gas enter washing liquid after three-stage dilute acid washing, and 10% of dilute acid washing liquid is sent to an arsenic dissolving tank in an open circuit mode. The dilute acid washing system adopts circulating water for indirect cooling, and finally the temperature of the flue gas is reduced to below 40 ℃;
slurry from a filter cake size mixing tank of a high-acid system and open-circuit dilute acid washing liquid enter an arsenic dissolving tank, the arsenic dissolving tank is provided with a jacket to accompany heat to maintain the temperature in the tank not higher than 100 ℃, solid insoluble arsenic is dissolved in the tank and then enters a dilute acid settling tank, underflow is subjected to filter pressing, and a filter cake is insoluble smoke dust particles (the main component is lead insoluble salt and generally called lead slag) from flue gas and is subjected to selling treatment; the high-arsenic filtrate is sent to a rapid cooling system of a high-arsenic waste liquid treatment system E, the temperature of the solution is rapidly cooled from the temperature of not higher than 100 ℃ to 35 ℃ through cooling water, then the solution is sent to a cooling crystallization system, and in the cooling crystallization system, due to the poor solubility at different temperatures, a large amount of As2O3Crystallization is separated out, and As is produced after the crystal slurry is filtered2O3A crystal;
the arsenic concentration of the crystallization mother liquor is reduced to below 15g/L and then the crystallization mother liquor returns to a dilute acid washing system B;
the flue gas is washed by dilute acid and is cooled forcibly to the temperature below 40 ℃, the flue gas enters an electric fog system C, two-stage electric demisting is carried out to remove acid fog and fine particles in the flue gas, then the flue gas meets the requirements of an acid making process and is sent to the acid making system, part of electric fog washing water is sent to each stage of washing system to supplement water evaporated in washing liquid, and the rest part of electric fog washing water is sent to a high-acid settling tank and is mixed with supernatant liquid of the high-acid settling tank to be treated by a low-arsenic waste liquid treatment system D.
The present invention will be described in further detail with reference to specific examples, but the scope of the present invention is not limited thereto.
The experimental procedures used in the following examples are conventional unless otherwise specified. The experimental raw materials and the related equipments used in the following examples are commercially available unless otherwise specified.
Example 1
As shown in fig. 2, the arsenic-containing flue gas treatment process of the embodiment includes a high-acid washing system, a dilute acid washing system, an electric defogging system, a low-arsenic waste liquid treatment system, and a high-arsenic waste liquid treatment system.
(1) High acid washing system: the arsenic-containing smelting flue gas b is subjected to adiabatic evaporation and temperature reduction and SO removal in a U-shaped washing tower 1 (sulfuric acid circulation washing with concentration of about 50 percent)3(liquid-gas ratio 5L/Nm3) The temperature of the flue gas is reduced from about 350 ℃ to 120 ℃, and about 30 percent of As in the flue gas2O3Desublimation and precipitation into the washing liquid, only a small amount of As due to solubility limitation2O3Dissolved, containing a large amount of undissolved As2O3The solid high-acid washing slurry enters a high-acid circulating tank 2, then 10% of the solid high-acid washing slurry enters a high-acid cooling tank 3 in an open way, the solid high-acid washing slurry is cooled to below 40 ℃ and crystallized and then enters a high-acid settling tank 4, supernatant in the settling tank 4 enters a low-arsenic waste liquid treatment system 5, underflow slurry is sent to a first filter 6 for filtration, and filter cakes enter a filter cake size mixing tank 7 for size mixing and then are sent to an arsenic dissolving tank 8 of a dilute acid washing system.
(2) A dilute acid wash system: the flue gas (the temperature is 120 ℃) which is washed by high acid in the U-shaped washing tower 1 enters a first-stage dilute acid washing tower 9 (the liquid-gas ratio is 8L/Nm)3) And a second-stage diluted acid washing tower 10 (liquid-gas ratio is 8L/Nm)3) And a three-stage diluted acid washing tower 11 (liquid-gas ratio is 5L/Nm)3) And (2) circularly washing by using dilute acid with the concentration of below 15% (specifically: 15% of first-stage dilute acid washing tower, 8% of second-stage dilute acid washing tower and 3% of third-stage dilute acid washing tower), and residual smoke particles and As in flue gas after three-stage dilute acid washing2O3And other impurities enter dilute acid circulating washing liquid, the dilute acid circulating washing liquid is forcibly cooled by cooling circulating water in a dilute acid cooler 12, and the temperature of the flue gas is finally reduced to be below 40 ℃. 10 percent of dilute acid circulating washing liquid in the first-stage dilute acid washing tower 9 is sent to the arsenic dissolving tank 8 in an open circuit.
(3) High arsenic liquid water disposal system: slurry from a filter cake slurry mixing tank 7 of a high-acid washing system and open-circuit washing liquid of a dilute acid system enter an arsenic dissolving tank 8, and 80-1 ℃ of the slurry and the open-circuit washing liquid in the tankSolid insoluble arsenic in the slurry is dissolved at the temperature of 00 ℃ (specifically 85 ℃), then the dissolved solid insoluble arsenic enters a dilute acid settling tank 13, the bottom flow is sent to a second filter for filter pressing, the filter cake is insoluble particulate matter lead slag e from smoke dust, the filtrate is high arsenic dilute acid, the filtrate and the supernatant of the dilute acid settling tank 13 are sent to a rapid cooling reactor 15, the temperature of the solution in the rapid cooling reactor 15 is rapidly reduced from 80 ℃ to 35 ℃, then the solution enters a high-efficiency crystallizer 16, and As2O3Crystallizing and separating out, filtering the crystal slurry by a crystal settling tank 17 (increasing the concentration of crystal substances and facilitating the next step of filtration) and a third filter 18 to produce As2O3The dry-based purity of the crystal f is more than or equal to 98 percent, and the crystal f meets the requirement of GB 26721. The supernatant in the crystallization settling tank 17 is returned to the first-stage dilute acid washing tower 9 after the arsenic concentration is reduced to below 15 g/L.
(4) Low arsenic liquid waste treatment system: the supernatant from the high-acid settling tank 4 is high-acid low-arsenic waste liquid, the supernatant is mixed with low-acid low-arsenic electric fog washing water and contains 2-5 g/L of arsenic, a conventional mature wastewater treatment process (arsenic sulfide precipitation and limescale salt neutralization method) is adopted, neutralized gypsum slag d and a small amount of arsenic sulfide slag c are produced after treatment, and return water returns to a high-acid washing system to serve as washing liquid supplementing water.
(5) Electric defogging system: the temperature of the flue gas is reduced to below 40 ℃ after the flue gas is washed by dilute acid, the flue gas enters a first-stage electric demisting system 19 and a second-stage electric demisting system 20 which are connected in series to remove acid mist and fine particles in the flue gas, then the flue gas meets the requirements of an acid making process and is sent to an acid making system, part of electric mist washing water in an electric mist removing and washing water tank 21 is sent to each stage of washing system to supplement water evaporated in washing liquid, and the rest part of the electric mist washing water is sent to be mixed with the supernatant of a high-acid settling tank 4 to be treated by a low.
In this embodiment, the U-shaped scrubber 1 is integrally divided into left and right parts, which are connected together by a transverse gas passage at the bottom, and the overall form is U-shaped. The whole tower is made of a steel shell, a lead plate and acid-resistant bricks from the outside to the inside in sequence. The top parts of the left tower and the right tower are provided with at least 1 layer of spray heads. The flue gas enters from the top of the left tower of the U-shaped washing tower and is in downstream contact with the washing liquid sprayed by the spray head at the top of the left tower, so that the purposes of pre-cooling and washing the flue gas are achieved. Then, the flue gas enters the right tower through the transverse gas channel and is in countercurrent contact with the washing liquid sprayed by the spray head at the top of the right tower, so that the mass transfer and heat transfer are enhanced, and the flue gas is fully evaporated in a heat insulation way. Then, the flue gas is discharged from the top of the tower and enters a lower-level flue gas washing system. To prevent clogging, the column is generally not packed.
In this embodiment, the rapid cooling reactor 15 is a special device for improving cooling efficiency and ensuring rapid cooling of the high arsenic solution to the crystallization temperature. The rapid cooling reactor 15 mainly comprises a stirring device, a reactor shell, a cooling jacket, a cooling coil and the like. Besides, the cooling device also comprises necessary accessories, such as a baffle plate, a liquid inlet pipe, a cooling liquid connecting pipe, a liquid outlet pipe and the like.
All parts of the rapid cooling reactor 15 which are contacted with the solution are made of stainless steel groove materials, and the shell which is not contacted with the solution can be made of carbon steel;
a spiral pipe is arranged in a cooling jacket of the rapid cooling reactor 15 to avoid short circuit of cooling liquid;
the cooling coil of the rapid cooling reactor 15 adopts a double-helix design, and fins are designed on the outer wall of the coil to increase the cooling speed;
baffle plates are uniformly arranged in the rapid cooling reactor 15 to enhance the disturbance of liquid;
the rotating speed of the stirring device of the rapid cooling reactor 15 is more than 300 r/min.
In this embodiment, the high-efficiency crystallizer 16 ensures that the high-arsenic solution is stabilized at the crystallization temperature with small energy consumption. The high-efficiency crystallizer 16 mainly comprises a stirring device, a reactor shell, a cooling jacket and the like. Besides, the cooling device also comprises necessary accessories, such as a baffle plate, a liquid inlet pipe, a cooling liquid connecting pipe, a liquid outlet pipe and the like.
All parts of the high-efficiency crystallizer 16, which are contacted with the solution, are made of stainless steel groove materials, and the shell, which is not contacted with the solution, can be made of carbon steel;
a spiral pipe is arranged in a cooling jacket of the high-efficiency crystallizer 16 to avoid short circuit of cooling liquid;
baffle plates are uniformly arranged in the high-efficiency crystallizer 16 to enhance the disturbance of liquid;
the rotating speed of a stirring device of the high-efficiency crystallizer 16 is below 300 r/min;
the bottom of the high-efficiency crystallizer 16 is a conical bottom, and the cone angle is not less than 45 degrees;
the bottom of the high-efficiency crystallizer 16 is provided with a compressed air coil which is irregularly blown to prevent crystallization and bonding.
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (9)
1. A method for removing arsenic from smelting flue gas by a wet method is characterized by comprising the following steps:
subjecting the smelting flue gas to high-concentration sulfuric acid washing so as to remove most of sulfur trioxide;
subjecting the flue gas after the high-concentration sulfuric acid washing to low-concentration sulfuric acid washing so As to remove most of As2O3；
Wherein the mass fraction of the sulfuric acid in the high-concentration sulfuric acid is more than 40%, and the mass fraction of the sulfuric acid in the low-concentration sulfuric acid is less than 20%.
2. The method according to claim 1, wherein the mass fraction of sulfuric acid in the high-concentration sulfuric acid is 40-90%, preferably 45-65%;
and/or the low-concentration sulfuric acid washing is graded gradient washing, preferably, the mass fraction of sulfuric acid in the low-concentration sulfuric acid used in the first washing is 10-15%, and the mass fraction of sulfuric acid in the low-concentration sulfuric acid used in the later washing is 0-5%.
3. The method of claim 1 or 2, further comprising:
cooling and crystallizing at least part of the washing liquid after washing with the low-concentration sulfuric acid, and filtering to obtain As2O3And (4) crystallizing.
4. The method of claim 1 or 2, further comprising:
sequentially cooling, crystallizing and settling at least part of washing liquid after the high-concentration sulfuric acid washing, and collecting precipitates;
adding liquid for size mixing to the precipitate so As to obtain As2O3Slurry;
the As is2O3The slurry is mixed with at least part of the washing liquid washed by the low-concentration sulfuric acid, and then heating and stirring are carried out until As is2O3The solid is dissolved and then filtered to obtain the As-containing2O3A solution;
the said As is contained2O3Cooling and crystallizing the solution, and filtering to obtain As2O3Crystallizing;
preferably, the temperature of the heating treatment is 80-100 ℃, and the stirring intensity is 150-250 r/min.
5. The method according to any one of claims 1 to 4, wherein the temperature of the flue gas after the high-concentration sulfuric acid washing is reduced to 120 to 140 ℃;
and/or the low-concentration sulfuric acid washing is graded gradient washing and cooling, wherein the temperature of the flue gas after the first washing is reduced to 60-75 ℃, and the temperature of the flue gas after the last washing is reduced to below 40 ℃.
6. The method according to any one of claims 1 to 5, wherein the ratio of the flow rate of the washing liquid to the flow rate of the flue gas in the high-concentration sulfuric acid washing is 4-6L/Nm3；
And/or when the low-concentration sulfuric acid is used for washing, the ratio of the flow of the washing liquid to the flow of the flue gas is 6-10L/Nm3。
7. The method of any one of claims 1-6, further comprising:
and sending the flue gas washed by the low-concentration sulfuric acid into an electric demister for purification treatment.
8. A system for wet dearsenification of smelting flue gas, the system being adapted to perform the method of any of claims 1-7, comprising:
the high-acid washing tower is sequentially connected with one or more stages of dilute acid washing towers and electric demisters in series behind the high-acid washing tower;
a high-acid circulation tank is circularly connected with the high-acid washing tower, and is sequentially connected with a high-acid cooling tank, a high-acid settling tank, a filter, a size mixing tank, an arsenic dissolving tank and a cooling crystallization system in series;
and a dilute acid circulating groove is arranged in circulating connection with the dilute acid washing tower and is connected with the arsenic dissolving groove.
9. The system of claim 8, wherein the high acid scrubber is a U-shaped scrubber.
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