CN103768910A - Method and device for synergistic purification of SO2 and heavy metals in smelting flue gas - Google Patents

Abstract

The invention discloses a method and device for synergistic purification of SO ₂ and heavy metals in smelting flue gas, belonging to the technical field of air pollution; the method uses (NH ₄ ) ₂ S solution as an absorbent to absorb and purify SO ₂ and heavy metals (Hg, As, Pb, Cd, Zn, etc.); the smelting flue gas after dust removal treatment is passed into the secondary ammonium sulfide solution absorption tower, and the SO ₂ and heavy metals in the gas are absorbed and purified by the absorbent, and the heavy metals are precipitated in the form of solid sulfide , recycled after filtration; SO ₂ is converted into NH ₄ HSO ₃ and (NH ₄ ) ₂ S ₂ O ₃ and remains in the absorption liquid. After the absorption reaction, the absorption liquid is neutralized, oxidized, evaporated and crystallized to obtain a solid mixture of (NH ₄ ) ₂ SO ₄ and (NH ₄ ) ₂ S ₂ O ₃ , which can be directly sold as fertilizer. The invention has simple process, easy operation, high desulfurization efficiency and low cost, and is suitable for industrial application.

Description

Method and device for synergistic purification of SO2 and heavy metals in smelting flue gas

technical field

The invention relates to a method and device for synergistic purification of _SO2 and heavy metals in smelting flue gas, belonging to the technical field of air pollution.

Background technique

Non-ferrous metals mostly form sulfide ores with sulfur, such as sphalerite, galena, chalcocite, goethite, etc., which are important raw materials for the metallurgical industry. In the non-ferrous smelting industry, there are generally two metallurgical processes, pyromethod and hydromethod, and most of them now use pyromethods to treat metallurgical ores. In the process of pyrometallurgy, the sulfide ore undergoes high-temperature roasting to separate sulfur and metals, and the sulfur is converted into sulfur dioxide and discharged with the roasting flue gas. In the exhausted flue gas, in addition to _SO2 , it also contains heavy metals and toxic non-metals, heavy metals There are mercury (Hg), arsenic (As), lead (Pb) cadmium, (Cd), zinc (Zn) and so on. These substances are released into the air and diffused, or brought into desulfurization products, pollute the air, soil and water, and cause harm to the environment.

At present, the treatment of smelting flue gas generally adopts smelting flue gas desulfurization to produce acid or other sulfur products:

(1) The gaseous pollutants in the smelting flue gas are mainly sulfur dioxide, and the flue gas with a sulfur dioxide concentration of more than 2% can be made into sulfuric acid by the contact method, but the concentration of SO ₂ in the tail gas of acid production is still high, and it is difficult to meet the increasingly stringent requirements. environmental requirements. If the flue gas contains mercury, a special mercury removal device must be installed during the purification process, which increases the investment cost.

(2) There are dozens of sulfur dioxide removal technologies for industrial applications, among which the limestone-gypsum wet desulfurization technology is the most mature and widely used. It is not feasible to simply copy the coal-fired flue gas desulfurization process. There are also some wet desulfurization methods, although the desulfurization effect is very good, but there are problems such as solid waste generation, large equipment investment, high energy consumption, and complicated post-processing, such as the Chinese invention patent with application number 200910244547. method", which has a high removal rate of SO ₂ and mercury vapor, and can also remove heavy metals such as lead, but there is a problem with the treatment of solid waste desulfurization ash; the application number is 201110091281.2 Chinese invention patent "flue gas desulfurization and denitrification Heavy metal removal integrated method and special equipment", the integrated device realizes the integrated purification function of flue gas desulfurization, denitrification and heavy metal removal, and the by-products are ammonium sulfate and ammonium nitrate, which are chemical fertilizer components. However, there are problems that the composition of the mixed absorption liquid is complex, which increases the investment cost, and the removal effect of heavy metals is general.

(3) In 1983, Outokumpu proposed the method of using Na ₂ S solution to absorb SO ₂ to produce sulfur element. When the pH value is too high, H ₂ S gas will be released in the flue gas absorbing SO ₂ , so adjust the pH value of Na ₂ S with a flue gas scrubbing solution with a pH value of 2-5 before absorption. The types of substances contained in the washing liquid are the same as the main types of substances in the solution obtained after Na ₂ S absorbs SO ₂ . After the reaction is completed, the mixed liquid enters the high-pressure reactor, and the self-oxidation-reduction reaction occurs at 160°C to generate S element and Na ₂ SO ₄ , and then regenerates Na ₂ SO ₄ with BaS, and the obtained Na ₂ S is returned to the absorption stage for recycling, and BaSO ₄ Reduction with C to obtain BaS returns to the Na ₂ SO ₄ regeneration stage. In 1997, Shu Yude and others improved the sodium sulfide method. Unlike Outokumpu, the pH value of the Na ₂ S solution was not adjusted in the absorption stage, and two-stage absorption was adopted; the reduction stage was added to the absorption solution by adding concentrated H ₂ SO ₄ and Na ₂ S react with the components in the solution at 50-60°C to produce simple S, and the H ₂ S gas released during the reduction phase is absorbed by Na ₂ S.

The existing methods have the following problems: (1) The existing technology only recovers high-concentration SO ₂ in the flue gas, and does not consider the simultaneous removal of low-concentration SO ₂ and heavy metals; (2) The solid waste generated after absorbing and purifying sulfur dioxide is difficult to recycle use. (3) The sodium sulfide method absorbs sulfur dioxide, which has problems such as complex post-treatment, large investment, and high energy consumption, and is difficult to apply industrially.

Contents of the invention

Aiming at the problems of high concentration of _SO2 in smelting flue gas, large fluctuations in gas volume, and containing multiple heavy metals such as Hg, As, Cd, Pb, Zn, etc., the purpose of the present invention is to propose a synergistic purification method for _SO2 and heavy metals in smelting flue gas The method and device adopt (NH ₄ ) ₂ S solution absorption method to simultaneously remove SO ₂ and Hg, As, Cd, Pb, Zn, etc., specifically including the following steps:

(1) After preliminary dedusting of the smelting flue gas, further cool the flue gas temperature to below 50°C;

(2) Fully contact the cooled flue gas with an atomized ammonium sulfide solution with a pH value between 7 and 3, absorb SO ₂ and metal oxides in the SO ₂ smelting flue gas, and purify the flue gas Discharge after deep heavy metal removal;

(3) After the rich solution that has absorbed _SO2 and heavy metals passes through press filtration, the precipitate of heavy metal sulfide in the solution is filtered, and the filter residue is collected and returned to the smelting furnace, and ammonia water, ammonium carbonate, and ammonium bicarbonate are added to the filtrate One of them is neutralized, and the pH value is adjusted to 5.8~6.5 to obtain a neutralized solution;

(4) The neutralized solution is oxidized by passing it into air at a temperature of 40°C~50°C or adding hydrogen peroxide with a mass percentage concentration of 27.5%~50% at room temperature for oxidation, and adding ammonia water and ammonium carbonate to the oxidized solution 1. One of ammonium bicarbonate adjusts the pH value to 5.8~6.5 to obtain the oxidized solution;

(5) Evaporate and concentrate the oxidized solution at 45°C~50°C to 40%~60% of the volume of the original solution, then cool to 20°C~30°C for crystallization, separate and obtain a mixture of ammonium sulfate and ammonium thiosulfate and Concentrate.

The mass percent concentration of the ammonium sulfide solution described in step (2) of the present invention is 8%-25%.

Another object of the present invention is to provide SO in the smelting flue gas The device used for the synergistic purification method of heavy metals, the device includes exhaust fan _I1 , absorption tower I2, circulation liquid storage tank I3, circulation pump I4, nozzle pipe I5, absorption tower II6 , circulation storage tank II7, circulation pump II8, nozzle II9, mist eliminator 10, fixed bed catalytic heavy metal removal device 11, ammonium sulfide storage tank 12, filter pump 13, filter press 14, neutralization tank 15, ventilation Machine II 16, oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22, exhaust fan 1 is connected with absorption tower I2, absorption tower I2, circulation liquid storage tank I3, circulation pump Ⅰ4, nozzle Ⅰ5 are connected in sequence in circulation, absorption tower Ⅱ6, circulating liquid storage tank Ⅱ7, circulation pump Ⅱ8, nozzle Ⅱ9 are connected in sequence in sequence, absorption tower Ⅰ2, absorption tower Ⅱ6, mist eliminator 10, fixed bed catalytic heavy metal removal device 11 The ammonium sulfide storage tank 12 is connected to the circulation storage tank II7, the circulation storage tank II7 is connected to the circulation storage tank I3, the circulation storage tank I3 and the circulation storage tank II7 are connected to the filter pump 13 at the same time, and the filter pump 13. Filter press 14, neutralization tank 15, oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22 are connected in sequence, exhaust fan II 16 is connected to oxidation tank 17, and liquid storage Tank 18 is connected to centrifuge 22 .

Invention principle:

₍ 1) The principle of synergistic purification of SO ₂ and heavy metal pollutants in smelting flue gas: SO ₂ reacts with oxygen and some heavy metal oxides to form insoluble matter, which promotes the removal of heavy metal substances; The liquid phase absorption conversion has a catalytic effect, and the reaction chemical equation is as follows:

SO ₂ + H ₂ O → H ₂ SO ₃

H ₂ SO ₃ + (NH ₄ ) ₂ S → (NH ₄ ) ₂ SO ₃ + H ₂ S

H ₂ S + (NH ₄ ) ₂ S → NH ₄ HS

2H ₂ S + SO ₂ → 3S + 2H ₂ O

S + (NH ₄ ) ₂ SO ₃ → (NH ₄ ) ₂ S ₂ O ₃

(NH ₄ ) ₂ SO ₃ + 0.5O ₂ → (NH ₄ ) ₂ SO ₄

(NH ₄ ) ₂ SO ₃ + SO ₂ + H ₂ O→ 2NH ₄ HSO ₃

(NH ₄ ) ₂ S + HgO + H ₂ O → HgS↓+ 2NH ₄ OH

SO ₂ + 0.5O ₂ + HgO → HgSO ₄ ↓

(NH ₄ ) ₂ S + CdO + H ₂ O → CdS↓+ 2NH ₄ OH

4(NH ₄ ) ₂ S + As ₂ O ₃ + 3H ₂ O → As ₂ S ₃ ↓+ 3NH ₄ OH + NH ₄ HS

(NH ₄ ) ₂ S + PbO + H ₂ O → PbS↓+ 2NH ₄ OH

SO ₂ + 0.5O ₂ + PbO → PbSO ₄ ↓

(NH ₄ ) ₂ S + ZnO + H ₂ O → ZnS↓+ 2NH ₄ OH

NH ₄ OH + SO ₂ → NH ₄ HSO ₃

(2) Neutralization of the absorption filtrate: After the absorption liquid is led out of the absorption tower, the solution contains a relatively high concentration of NH ₄ HSO ₃ and (NH ₄ ) ₂ S ₂ O ₃ , and the absorption liquid is soaked with ammonia water, ammonium carbonate or One kind of ammonium hydrogen neutralizes all the NH ₄ HSO ₃ in the absorption liquid into (NH ₄ ) ₂ SO ₃ and adjusts the pH value to 5.8~6.5. The reaction process is as follows:

NH ₃ + NH ₄ HSO ₃ = (NH ₄ ) ₂ SO ₃

or

NH ₄ HCO ₃ + NH ₄ HSO ₃ = (NH ₄ ) ₂ SO ₃ + CO ₂ + H ₂ O

(3) Oxidation: The content of ammonium thiosulfate in ammonium sulfate produced by this method is very high, which is not suitable for the production of pure ammonium sulfate products. Ammonium sulfite is further oxidized into ammonium sulfate to make mixed fertilizers of ammonium sulfate and ammonium thiosulfate There are two ways to oxidize ammonium sulfite solution:

① Hydrogen peroxide oxidation: Oxidation with hydrogen peroxide will not bring in other impurities, and the oxidation effect is good. Due to the strong oxidation of hydrogen peroxide, some ammonium thiosulfate will be oxidized. The reaction equation is as follows:

(NH ₄ ) ₂ SO ₃ + H ₂ O ₂ = (NH ₄ ) ₂ SO ₄ + H ₂ O

(NH ₄ ) ₂ S ₂ O ₃ + 4H ₂ O ₂ = 2NH ₄ HSO ₄ + 3H ₂ O

After the oxidation reaction is completed, because the thiosulfate radical is partially oxidized to generate hydrogen ions, the pH value of the solution decreases. At this time, it is necessary to add ammonia, ammonium carbonate or ammonium bicarbonate to adjust the pH value to the range of 5.8~6.5.

②Air oxidation method: Using the principle of easy oxidation of ammonium sulfite, ammonium sulfite is oxidized into ammonium sulfate with air. The ammonium sulfite produced by this method contains (NH ₄ ) ₂ S ₂ O ₃ which has a catalytic oxidation effect and has a catalytic oxidation effect on sulfurous acid. Oxidation of ammonium is favorable and the reaction is as follows:

(NH ₄ ) ₂ SO ₃ + 0.5O ₂ = (NH ₄ ) ₂ SO ₄

(NH ₄ ) ₂ S ₂ O ₃ + H ₂ O + 2O ₂ = 2NH ₄ HSO ₄

The air oxidation is relatively slow, so the temperature of the solution needs to be increased to 40°C~50°C, and the aeration device is used for aeration oxidation or the oxidation tower is sprayed from top to bottom for oxidation, that is, the contact area between oxygen and the solution is increased, and the oxidation speed is accelerated. The oxidation reaction is carried out; after oxidation, add ammonia water, ammonium carbonate or ammonium bicarbonate to adjust the pH value to the range of 5.8~6.5.

(4) Concentration by evaporation: When the concentrated solution of ammonium thiosulfate is higher than 50°C, it is easy to decompose to produce sulfur and ammonium sulfite. In order to avoid the decomposition of ammonium thiosulfate, mix the ammonium sulfate obtained after oxidation with ammonium thiosulfate The liquid was evaporated and concentrated to 40%~60% of the original volume at 45°C~50°C. The response is as follows:

(NH ₄ ) ₂ S ₂ O ₃ = S + (NH ₄ ) ₂ SO ₃

(5) Put the concentrated mixture of ammonium sulfate and ammonium thiosulfate into the crystallization tank to cool and crystallize at 20°C~30°C, and continuously separate the crystallization mother liquor in a centrifuge to obtain ammonium sulfate and thiosulfate with a water content of 3~5%. Ammonium sulfate crystallization, in which ammonium thiosulfate has strong hygroscopicity, is not easy to crystallize and precipitate, and part of it is left in the concentrated solution, so the obtained crystal is a mixture mainly of ammonium sulfate, and the concentrated solution after crystallization is returned to evaporate and concentrate or directly used as Liquid fertilizer for sale.

The advantages of the present invention are as follows:

(1) Synergistic purification and removal of SO ₂ and heavy metal oxides in smelting flue gas: SO ₂ promotes the removal of heavy metal oxides, and heavy metal oxides have a catalytic effect on the liquid phase absorption and transformation of SO ₂ ;

(2) The SO ₂ and heavy metal removal efficiency in the smelting flue gas is high, the flue gas can be discharged up to the standard, the desulfurization efficiency is ≥99%, and the SO ₂ content in the outlet flue gas is ≤50mg/m ³ ; mercury, arsenic, cadmium, lead, The removal efficiency of zinc and five heavy metals is more than 90%, Hg≤0.012mg/m ³ , As≤0.1mg/m ³ , Cd≤0.1mg/m ³ , Pb≤0.1mg/m ³ , Zn≤0.1 in the outlet flue gas The nitrogen content of mg/ ^m3 mixed fertilizer is ≥20%, the comprehensive recovery rate of mercury is greater than 80%, and the comprehensive recovery rate of lead, arsenic, cadmium and zinc is greater than 70%;

(3) The mixed fertilizer of ammonium sulfate and ammonium thiosulfate produced from _SO2 in smelting flue gas has high desulfurization rate and low operating cost, while the ammonium sulfate fertilizer added with ammonium thiosulfate can inhibit soil nitrification and maintain soil The effect of medium nitrogen content, high economic value, easy storage and transportation; the concentrated solution after crystallization can be used directly as liquid fertilizer, spraying on crops can effectively prolong the use time of pesticides, and at the same time help crops to absorb nitrogen and sulfur Efficient absorption of elements, therefore, the present invention is a key technology to solve smelting flue gas purification and resource utilization, and can bring good economic benefits to enterprises;

(4) The present invention can recycle heavy metals in smelting flue gas, realize resource utilization of metal sulfides, and avoid secondary pollution caused by heavy metal discharge from smelting flue gas and its transfer to waste water.

Description of drawings

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

In the figure: 1-exhauster fan Ⅰ, 2-absorption tower Ⅰ, 3-circulation liquid storage tank Ⅰ, 4-circulation pump Ⅰ, 5-nozzle pipe Ⅰ, 6-absorption tower Ⅱ, 7-circulation liquid storage tank Ⅱ, 8 -Circulation pump II, 9-Nozzle II, 10-Mist eliminator, 11-Fixed bed catalytic heavy metal removal device, 12-Ammonium sulfide storage tank, 13-Filter pump, 14-Filter press, 15-Neutralization tank , 16-exhauster fan II, 17-oxidation tank, 18-liquid storage tank, 19-circulation pump III, 20-evaporator, 21-crystallization tank, 22-centrifuge.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention is not limited to the content described.

Example 1

In this example, zinc smelting flue gas is used as the treatment object. In zinc smelting flue gas, SO ₂ : 4-8%, Hg: 5 mg/m ³ , As: 1-5 mg/m ³ , Pb: 5-8 mg/m ³ , Cd: 2~7 mg/m ³ , Zn: 20~30 mg/m ³ ; specifically include the following steps:

(1) After preliminary dedusting of the smelting flue gas, further cool the flue gas temperature to 50°C;

(2) Fully contact the cooled flue gas with the atomized ammonium sulfide solution with a pH value of 7 to absorb the SO ₂ smelting flue gas and absorb the metal oxides in the flue gas, and the purified flue gas is fixed The bed catalytic heavy metal removal device is discharged after deep heavy metal removal, and the mass percentage concentration of the ammonium sulfide solution is 8%;

(3) After the rich solution that has absorbed _SO2 and heavy metals passes through press filtration, the precipitate of heavy metal sulfide in the solution is filtered, and the filter residue is collected and returned to the smelting furnace, and ammonia water is added to the filtrate for neutralization to adjust the pH value To 5.8, obtain the neutralized solution;

(4) The neutralized solution is oxidized by introducing air at a temperature of 40°C, and the oxidized solution is added with ammonia water to adjust the pH value to 5.8 to obtain the oxidized solution;

(5) Evaporate and concentrate the oxidized solution at 45°C to 40% of the volume of the original solution, then cool to 20°C to crystallize, and separate to obtain a mixture and concentrate of ammonium sulfate and ammonium thiosulfate.

The device used in the synergistic purification method of _SO2 and heavy metals in the smelting flue gas described in this embodiment includes an exhaust fan I1, an absorption tower I2, a circulation storage tank I3, a circulation pump I4, a nozzle pipe I5, an absorption tower II6, and a circulation storage tank. Liquid tank Ⅱ7, circulating pump Ⅱ8, nozzle pipe Ⅱ9, mist eliminator 10, fixed bed catalytic heavy metal removal device 11, ammonium sulfide storage tank 12, filter pump 13, filter press 14, neutralization tank 15, exhaust fan Ⅱ16, Oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22, exhaust fan 1 is connected with absorption tower I2, absorption tower I2, circulation liquid storage tank I3, circulation pump I4, spray Pipe I5 is connected in circulation in sequence, absorption tower II6, circulating liquid storage tank II7, circulation pump II8, nozzle II9 are connected in sequence in circulation, absorption tower I2, absorption tower II6, mist eliminator 10, fixed bed catalytic heavy metal removal device 11 are connected in sequence, The ammonium sulfide liquid storage tank 12 is connected with the circulation liquid storage tank II7, the circulation liquid storage tank II7 is connected with the circulation liquid storage tank I3, the circulation liquid storage tank I3 and the circulation liquid storage tank II7 are connected with the filter pump 13 at the same time, the filter pump 13, pressure Filter 14, neutralization tank 15, oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22 are connected successively, exhaust fan II 16 is connected with oxidation tank 17, liquid storage tank 18 and The centrifuges 22 are connected, as shown in FIG. 1 .

The use method of the device described in this embodiment: the flue gas is sucked into the absorption tower I2 through the exhaust fan I1, and the ammonium sulfide solution enters the circulating liquid storage tank I3 and the circulating liquid storage tank II7 from the ammonium sulfide storage tank 10 in sequence In the process, the ammonium sulfide solution in the circulation storage tank I3 is pumped out by the circulation pump I4, sprayed and atomized by the nozzle I5, and then fully contacts with the cooled flue gas, and the flue gas absorbed in the absorption tower I2 enters the absorption tower II6 Absorb again, the absorption process is the same as in the absorption tower I2, the absorbed flue gas enters the mist eliminator 10 through the top of the absorption tower II6 for demisting, and the flue gas is discharged through the fixed bed catalytic heavy metal removal device 11 for deep heavy metal removal; The rich liquid that has absorbed _SO2 and heavy metals flows into the circulating liquid storage tank I3 and circulating liquid storage tank II7 and is mixed with the ammonium sulfide solution for reuse. When the pH of the rich liquid in the liquid storage tank reaches 3, part of the rich liquid enters the filter pump 13, and then Add ammonium sulfide solution to the liquid storage tank to adjust the pH value of the solution to 7, and the filtrate filtered by the filter pump 13 enters the neutralization tank 15, adds ammonia water for neutralization, adjusts the pH value to 5.8, and collects the filter residue and returns it to the smelting furnace, send the neutralized solution to the oxidation tank 17 and pass air into it for oxidation, then add ammonia water to adjust the pH value to 5.8, send the oxidized solution to the evaporator 20, and concentrate it to the volume of the original solution at 45°C 40%, put it into the crystallization tank 21 and cool to 20°C to crystallize, and separate it with a centrifuge 22 after crystallization to obtain ammonium sulfate and ammonium thiosulfate mixed fertilizer and concentrated solution, and the concentrated solution is returned to the evaporation tank 18.

Through the method described in this example, the flue gas desulfurization efficiency is 99.5%, the SO ₂ content in the outlet flue gas is 20 mg/m ³ ; the removal efficiency of mercury, arsenic, cadmium, lead, and zinc is 94%, and the outlet flue gas Hg is 0.01 mg/m ³ , As is 0.05 mg/m ³ , Cd is 0.01 mg/m ³ , Pb is 0.07 mg/m ³ , and Zn is 0.08 mg/m ³ . The nitrogen content of the mixed fertilizer is 23.6%, reaching According to the quality standards of fertilizer products, the resource recovery rate of lead is 66%, and the comprehensive recovery rate of mercury is 75%.

Example 2

This example takes lead smelting flue gas as the treatment object, SO ₂ in lead smelting flue gas: 8~12%, Hg: 2~5mg/m ³ , As: 1~5mg/m ³ , Pb: 35~45mg/m ³ , Cd: 1~3 mg/m ³ , Zn: 1~5 mg/m ³ specifically include the following steps:

(1) After preliminary dedusting of the smelting flue gas, further cool the flue gas temperature to 40°C;

(2) Fully contact the cooled flue gas with the atomized ammonium sulfide solution with a pH value of 7 to absorb the SO ₂ smelting flue gas and absorb the metal oxides in the flue gas, and the purified flue gas is fixed The bed catalytic heavy metal removal device is discharged after deep heavy metal removal, and the mass percentage concentration of the ammonium sulfide solution is 25%;

(3) After the rich solution that has absorbed _SO2 and heavy metals passes through press filtration, the precipitate of heavy metal sulfide in the solution is filtered, and the filter residue is collected and returned to the smelting furnace, and ammonium carbonate is added to the filtrate for neutralization to adjust the pH Value to 6.5, obtain the solution after neutralization;

(4) The neutralized solution is oxidized by passing through hydrogen peroxide with a mass percentage concentration of 27.5% at a temperature of 50°C, and the oxidized solution is added with ammonium carbonate to adjust the pH value to 6.5 to obtain an oxidized solution;

(5) Evaporate and concentrate the oxidized solution at 50°C to 60% of the volume of the original solution, then cool to 30°C to crystallize, and separate to obtain a mixture and concentrate of ammonium sulfate and ammonium thiosulfate.

The device used in the synergistic purification method of _SO2 and heavy metals in the smelting flue gas described in this embodiment includes an exhaust fan I1, an absorption tower I2, a circulation storage tank I3, a circulation pump I4, a nozzle pipe I5, an absorption tower II6, and a circulation storage tank. Liquid tank Ⅱ7, circulating pump Ⅱ8, nozzle pipe Ⅱ9, mist eliminator 10, fixed bed catalytic heavy metal removal device 11, ammonium sulfide storage tank 12, filter pump 13, filter press 14, neutralization tank 15, exhaust fan Ⅱ16, Oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22, exhaust fan 1 is connected with absorption tower I2, absorption tower I2, circulation liquid storage tank I3, circulation pump I4, spray Pipe I5 is connected in circulation in sequence, absorption tower II6, circulating liquid storage tank II7, circulation pump II8, nozzle II9 are connected in sequence in circulation, absorption tower I2, absorption tower II6, mist eliminator 10, fixed bed catalytic heavy metal removal device 11 are connected in sequence, The ammonium sulfide liquid storage tank 12 is connected with the circulation liquid storage tank II7, the circulation liquid storage tank II7 is connected with the circulation liquid storage tank I3, the circulation liquid storage tank I3 and the circulation liquid storage tank II7 are connected with the filter pump 13 at the same time, the filter pump 13, pressure Filter 14, neutralization tank 15, oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22 are connected successively, exhaust fan II 16 is connected with oxidation tank 17, liquid storage tank 18 and The centrifuges 22 are connected, as shown in FIG. 1 .

The use method of the device described in this embodiment: the flue gas is sucked into the absorption tower I2 through the exhaust fan I1, and the ammonium sulfide solution enters the circulating liquid storage tank I3 and the circulating liquid storage tank II7 from the ammonium sulfide storage tank 10 in sequence In the process, the ammonium sulfide solution in the circulation storage tank I3 is pumped out by the circulation pump I4, sprayed and atomized by the nozzle I5, and then fully contacts with the cooled flue gas, and the flue gas absorbed in the absorption tower I2 enters the absorption tower II6 Absorb again, the absorption process is the same as in the absorption tower I2, the absorbed flue gas enters the mist eliminator 10 through the top of the absorption tower II6 for demisting, and the flue gas is discharged through the fixed bed catalytic heavy metal removal device 11 for deep heavy metal removal; The rich liquid that has absorbed _SO2 and heavy metals flows into the circulating liquid storage tank I3 and circulating liquid storage tank II7 and is mixed with the ammonium sulfide solution for reuse. When the pH of the rich liquid in the liquid storage tank reaches 4, part of the rich liquid enters the filter pump 11, and then Add ammonium sulfide solution to the liquid storage tank to adjust the pH value of the solution to 7. The filtrate filtered by the filter pump 13 enters the neutralization tank 15, adds ammonium carbonate for neutralization, adjusts the pH value to 6.5, and collects the filter residue and returns it to the smelting furnace, the neutralized solution is sent to the oxidation tank 17, and the mass percentage concentration is 27.5% hydrogen peroxide for oxidation, and then ammonium carbonate is added to adjust the pH value to 6.5, and the oxidized solution is sent to the evaporator 20, at 50 Concentrate to 60% of the volume of the original solution at ℃, put it into the crystallization tank 21 and cool to 30 ℃ to crystallize, and separate it with a centrifuge 22 after crystallization to obtain ammonium sulfate and ammonium thiosulfate mixed fertilizer and concentrated solution, the concentrated solution is in a liquid state Fertilizers for sale.

Through the method described in this example, the flue gas desulfurization efficiency is 99.7%, the SO ₂ content in the outlet flue gas is 35 mg/m ³ ; the removal efficiency of mercury, arsenic, cadmium, lead, and zinc is 95%, and the outlet flue gas Hg is 0.011mg/m ³ , As is 0.03mg/m ³ , Cd is 0.06mg/m ³ , Pb is 0.06mg/m ³ , Zn is 0.01mg/m ³ ; the nitrogen content of the mixed fertilizer is 25.3%, The quality standard of fertilizer products has been met, the recycling rate of lead is 80%, and the comprehensive recovery rate of mercury is 96%.

Example 3

This example takes nickel smelting flue gas as the treatment object, SO ₂ in nickel smelting flue gas: 0.8~2.0%, Hg: 1~4mg/m ³ , As: 3~5mg/m ³ , Pb: 10~25mg/m3 ³ , Cd: 1~3 mg/m ³ , Zn: 2~6 mg/m ³ ; specifically include the following steps:

(1) After preliminary dedusting of the smelting flue gas, further cool the flue gas temperature to 30°C;

(2) Fully contact the cooled flue gas with an atomized ammonium sulfide solution with a pH value of 6 to absorb SO ₂ smelting flue gas and absorb metal oxides in the flue gas, and the purified flue gas is fixed The bed catalytic mercury removal device is discharged after deep heavy metal removal, and the mass percentage concentration of the ammonium sulfide solution is 15%;

(3) After the rich solution that has absorbed SO ₂ and heavy metals passes through press filtration, the precipitate of heavy metal sulfide in the solution is filtered, and the filter residue is collected and returned to the smelting furnace, and ammonium bicarbonate is added to the filtrate for neutralization and adjustment When the pH value reaches 6, a neutralized solution is obtained;

(4) The neutralized solution is oxidized by passing through hydrogen peroxide with a mass percentage concentration of 50% at a temperature of 45°C, and adding ammonium bicarbonate to the oxidized solution to adjust the pH to 6.2 to obtain an oxidized solution;

(5) Evaporate and concentrate the oxidized solution at 48°C to 20% of the volume of the original solution, then cool to 25°C for crystallization, and separate the mixture and concentrated solution of ammonium sulfate and ammonium thiosulfate.

The device used in the synergistic purification method of _SO2 and heavy metals in the smelting flue gas described in this embodiment includes an exhaust fan I1, an absorption tower I2, a circulation storage tank I3, a circulation pump I4, a nozzle pipe I5, an absorption tower II6, and a circulation storage tank. Liquid tank Ⅱ7, circulating pump Ⅱ8, nozzle pipe Ⅱ9, mist eliminator 10, fixed bed catalytic heavy metal removal device 11, ammonium sulfide storage tank 12, filter pump 13, filter press 14, neutralization tank 15, exhaust fan Ⅱ16, Oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22, exhaust fan 1 is connected with absorption tower I2, absorption tower I2, circulation liquid storage tank I3, circulation pump I4, spray Pipe I5 is connected in circulation in sequence, absorption tower II6, circulating liquid storage tank II7, circulation pump II8, nozzle II9 are connected in sequence in circulation, absorption tower I2, absorption tower II6, mist eliminator 10, fixed bed catalytic heavy metal removal device 11 are connected in sequence, The ammonium sulfide liquid storage tank 12 is connected with the circulation liquid storage tank II7, the circulation liquid storage tank II7 is connected with the circulation liquid storage tank I3, the circulation liquid storage tank I3 and the circulation liquid storage tank II7 are connected with the filter pump 13 at the same time, the filter pump 13, pressure Filter 14, neutralization tank 15, oxidation tank 17, liquid storage tank 18, circulation pump III 19, evaporator 20, crystallization tank 21, centrifuge 22 are connected successively, exhaust fan II 16 is connected with oxidation tank 17, liquid storage tank 18 and The centrifuges 22 are connected, as shown in FIG. 1 .

The use method of the device described in this embodiment: the flue gas is sucked into the absorption tower I2 through the exhaust fan I1, and the ammonium sulfide solution enters the circulating liquid storage tank I3 and the circulating liquid storage tank II7 from the ammonium sulfide storage tank 10 in sequence In the process, the ammonium sulfide solution in the circulation storage tank I3 is pumped out by the circulation pump I4, sprayed and atomized by the nozzle I5, and then fully contacts with the cooled flue gas, and the flue gas absorbed in the absorption tower I2 enters the absorption tower II6 Absorb again, the absorption process is the same as in the absorption tower I2, the absorbed flue gas enters the mist eliminator 10 through the top of the absorption tower II6 for demisting, and the flue gas is discharged through the fixed bed catalytic heavy metal removal device 11 for deep heavy metal removal; The rich liquid that has absorbed _SO2 and heavy metals flows into the circulating liquid storage tank I3 and circulating liquid storage tank II7 and is mixed with the ammonium sulfide solution for reuse. When the pH of the rich liquid in the liquid storage tank reaches 4, part of the rich liquid enters the filter pump 11, and then Add ammonium sulfide solution to the liquid storage tank to adjust the pH value of the solution to 6. The filtrate filtered by the filter pump 11 enters the neutralization tank 15, adds ammonium bicarbonate to neutralize, and adjusts the pH value to 6. The filter residue is recovered in a concentrated manner and returned to Smelting furnace, the neutralized solution is sent to the oxidation tank 17, and the hydrogen peroxide with a mass percentage concentration of 50% is oxidized, then ammonium carbonate is added to adjust the pH value to 6.2, and the oxidized solution is sent to the evaporator 18. Concentrate to 20% of the volume of the original solution at 48°C, put it into the crystallization tank 21 and cool to 25°C to crystallize, and separate it with a centrifuge 22 after crystallization to obtain ammonium sulfate and ammonium thiosulfate mixed fertilizer and concentrate, and return the concentrate to To the evaporation tank 18.

By implementing the above method, the flue gas desulfurization efficiency is 99.8%, the SO ₂ content in the outlet flue gas is 40 mg/m ³ ; the removal efficiency of mercury, arsenic, cadmium, lead, and zinc is 92%, and the Hg in the outlet flue gas is 0.011mg/m ³ , As 0.06mg/m ³ , Cd 0.04mg/m ³ , Pb 0.08mg/m ³ , Zn 0.02mg/m ³ ; the nitrogen content of the mixed fertilizer is 24.1%, reaching the level of chemical fertilizer products According to the quality standard, the recycling rate of lead is 78%, and the comprehensive recycling rate of mercury is 96%.

Claims (3)

1. _SO in a smelting flue gas and heavy metal synergistic purification method, it is characterized in that comprising the steps: (1) After preliminary dedusting of the smelting flue gas, further cool the flue gas temperature to below 50°C; (2) Fully contact the cooled flue gas with an atomized ammonium sulfide solution with a pH value between 7 and 3 to absorb SO ₂ and metal oxides in the SO ₂ -containing smelting flue gas, and the purified The flue gas is discharged after deep heavy metal removal; (3) After the rich solution that has absorbed _SO2 and heavy metals passes through press filtration, the precipitate of heavy metal sulfide in the solution is filtered, and the filter residue is collected and returned to the smelting furnace, and ammonia water, ammonium carbonate, and ammonium bicarbonate are added to the filtrate One of them is neutralized, and the pH value is adjusted to 5.8~6.5 to obtain a neutralized solution; (4) The neutralized solution is oxidized by passing it into air at a temperature of 40°C~50°C or adding hydrogen peroxide with a mass percentage concentration of 27.5%~50% at room temperature for oxidation, and adding ammonia water and ammonium carbonate to the oxidized solution 1. One of ammonium bicarbonate adjusts the pH value to 5.8~6.5 to obtain the oxidized solution; (5) Evaporate and concentrate the oxidized solution at 45°C~50°C to 40%~60% of the volume of the original solution, then cool to 20°C~30°C for crystallization, separate and obtain a mixture of ammonium sulfate and ammonium thiosulfate and Concentrate. 2. The method for synergistic purification of SO ₂ and heavy metals in smelting flue gas according to claim 1, characterized in that: the mass percent concentration of the ammonium sulfide solution in step (2) is 8% to 25%. 3. The device used in the method for synergistic purification of _SO2 and heavy metals in smelting flue gas according to claim 1, characterized in that: the device includes exhaust fan I (1), absorption tower I (2), circulating liquid storage tank I (3 ), circulating pump Ⅰ (4), nozzle Ⅰ (5), absorption tower Ⅱ (6), circulating liquid storage tank Ⅱ ( 7), circulating pump Ⅱ ( 8), nozzle Ⅱ ( 9 ), demister ( 10), fixed bed catalytic heavy metal removal device (11), ammonium sulfide storage tank (12), filter pump (13), filter press (14), neutralization tank (15), exhaust fan II (16), oxidation Tank (17), liquid storage tank (18), circulating pump III (19), evaporator (20), crystallization tank (21), centrifuge (22), exhaust fan (1) and absorption tower I (2) Connection, absorption tower Ⅰ (2), circulating liquid storage tank Ⅰ (3), circulating pump Ⅰ (4), nozzle Ⅰ (5) are connected in sequence, absorbing tower Ⅱ (6), circulating liquid storage tank Ⅱ (7) , circulating pump II (8), and nozzle II (9) are connected in sequence, and absorption tower I (2), absorption tower II (6), demister (10), and fixed-bed catalytic heavy metal removal device (11) are connected in sequence , the ammonium sulfide storage tank (12) is connected with the circulation storage tank II (7), the circulation storage tank II (7) is connected with the circulation storage tank I (3), the circulation storage tank I (3) and the circulation storage tank Liquid tank II (7) is connected with filter pump (13) at the same time, filter pump (13), filter press (14), neutralization tank (15), oxidation tank (17), liquid storage tank (18), circulation pump III (19), evaporator (20), crystallization tank (21), and centrifuge (22) are connected in sequence, exhaust fan II (16) is connected to oxidation tank (17), liquid storage tank (18) and centrifuge (22 ) are connected.

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