Background
The method is characterized in that a waste circuit board and low-grade impure copper are mixed as main raw materials, flue gas treated by a pyrometallurgical smelting process is adopted, washing liquid generated by liquid alkali absorption contains sulfur, bromide, fluoride and other components, wherein the concentration of fluorine and bromine is high, the concentration of fluorine is about 300-600 mg/L, the bromine content is 4000mg/L, the recovered bromine in the washing liquid has high economic value, usually, a double-effect evaporation process is adopted to recover bromine salt in the washing liquid, but the washing liquid contains high fluorine ions, so that the bromine salt cannot be directly fed into double-effect evaporation equipment for treatment, otherwise, the equipment is greatly corroded, and the recovered bromine salt quality is influenced by high fluorine content.
The conventional lime defluorination and calcium removal process is influenced by the pH value, when the pH value is more than 10, the defluorination efficiency is obviously reduced, and the lime defluorination is repeatedly carried out after the PH value is adjusted back. The invention is realized by a section of Ca (OH)2-CaCl2The fluorine removal by the PAM-PAC combined method solves the problem, and the further fluorine removal by the polyferric sulfate-PAM-PAC combined method at the second stage solves the problem that the PH value is adjusted back to F and is continuously increased.
Disclosure of Invention
The invention aims to remove high-content fluorine from the recovered washing liquid and ensure the quality of bromine salt. The fluorine content in the washing liquid is reduced by improving the pretreatment process of the washing liquid, and the treated washing liquid enters a double-effect evaporation system, so that double-effect evaporation equipment can be protected, and the quality of bromine salt can be effectively improved. Compared with the conventional calcium removal process after lime fluorine removal, the process is better, and the fluorine content of the bromine salt can be reduced to be below 0.1 percent.
A process for recovering bromine salt from the washed liquid of fume includes such steps as absorbing the waste gas containing bromide, fluoride and chloride with 30% liquid alkali to generate an absorption liquid containing bromide, chloride and fluoride, delivering the washed liquid to the pre-treating system of washed liquid, delivering the supernatant to dual-effect evaporating regulating pool, filtering by plate-frame liquid press, and pumping it to dual-effect evaporating system. The pretreatment is mainly to remove fluoride in the washing liquid, and the steam used by the double-effect evaporation system comes from a waste heat boiler.
The method comprises the following steps:
the flue gas is generated by using waste circuit boards and low-grade impure copper as main raw materials and limestone, quartz stone and coke as auxiliary materials through pyrogenic process treatment.
The absorption liquid is subjected to defluorination pretreatment, a two-stage defluorination method is adopted, and a first-stage defluorination process comprises the following steps: using Ca (OH)2-CaCl2Removing fluorine by using a PAM polyacrylamide-PAC polyaluminium chloride combination method; two-stage defluorination process: fluorine removal is carried out by using a polymeric ferric sulfate-PAM-PAC combined method.
A first-stage defluorination process: using Ca (OH)2-CaCl2PAM-PAC combinations using Ca (OH)2-CaCl2And (4) removing by a PAM-PAC combined method, conveying the washed liquid to a first-stage defluorination reaction tank, adding lime emulsion, and controlling the pH value to be 10.0.
Adding CaCl2The amount of the solution added is the Ca content of the coagulated solution2+The content is 45-50 mg/L. PAC and PAM medicaments are added simultaneously, wherein the adding amount of the PAC coagulant is 100mg/L, and the adding amount of the PAM flocculating agent is 5.0 mg/L. Controlling the solution to coagulate and react for 25-30 min, and then putting the solution into a first-stage defluorination sedimentation tank for natural sedimentation.
And after the natural settling time of the solution in the first-stage defluorination settling tank is more than or equal to 5.0 hours, performing second-stage defluorination.
Two-stage defluorination process: the fluorine is removed by using a polymeric ferric sulfate-PAM-PAC combined method, and the two-stage fluorine removal process also adopts an intermittent treatment mode.
The possible reactions of polymeric ferric sulphate with fluoride ions are as follows:
Fe3++6F-=FeF6 3-Fe3++5F-=FeF5 2-
Fe3++4F-=FeF4 -Fe3++3F-=FeF3
conveying the supernatant of the first-stage defluorination sedimentation tank to a second-stage defluorination reaction tank, and adding acid (HCl or H) after the tank is full2SO4) Adjusting the pH value to 6.0-7.5, and stirring for 3-5 min.
And after the reaction is finished, adding a polymeric ferric sulfate solution, wherein the adding amount is 450-500 mg/L. PAC and PAM medicaments are added simultaneously, wherein the adding amount of the PAC coagulant is 100mg/L, and the adding amount of the PAM flocculating agent is 5.0 mg/L. And controlling the coagulation and reaction time for 25-30 min, and then placing the mixture into a two-stage defluorination sedimentation tank for natural sedimentation.
And after the natural settling time of the solution in the second-stage defluorination settling tank is more than or equal to 5.0 hours, conveying the supernatant of the settling tank to a double-effect evaporation regulating tank, filtering by a plate-frame type hydraulic press, and then feeding into a double-effect evaporation system by a feeding pump.
The steam required by the double-effect evaporation system is generated by a waste heat boiler and is conveyed through a pipeline to evaporate the heat required by salt.
The invention has the beneficial effects that:
the invention recovers the bromine salt through double-effect evaporation after the two-stage defluorination pretreatment of the washed liquid, obviously reduces the corrosive damage of the washed liquid to double-effect evaporation equipment, ensures that the fluorine content in the recovered bromine salt is lower than 0.1 percent, effectively improves the quality of the bromine salt, reduces the discharge of waste water while realizing the reutilization of effective components in the waste water, and is beneficial to the environmental protection.
Example 1
The method comprises the steps of carrying out pyrogenic smelting by using waste circuit boards and low-grade impure copper as main raw materials and limestone, quartz stone and coke as auxiliary materials, passing smelted flue gas through a high-efficiency pipeline type reaction desulfurizing tower, and obtaining acidic Substances (SO) in the flue gas2HBr, HCl, HF, etc.) is dissolved in the lye sprayed from the top of the desulfurization tower. The alkali liquor with dissolved acid substances circulates in the desulfurizing tower, and the washing liquid is obtained when the concentration of the concentrated solution reaches the discharge set value.
The washing liquid contains 300-600 mg/L of fluorine, the fluorine content in the wastewater passing through the first-stage fluorine removal reaction tank is 40-50 mg/L, the fluorine removal efficiency is up to 90%, and the effect is very obvious.
And (3) through a two-stage defluorination process, further reducing the fluorine content in the washed liquid to 25-40 mg/L, conveying the treated supernatant to a double-effect evaporation regulating pool, filtering by a plate-frame type hydraulic press, and then feeding into a double-effect evaporation system by a feeding pump. The steam used by the double-effect evaporation system is sourced from a waste heat boiler. The fluorine content in the recovered bromine salt is lower than 0.1 percent, and all heavy metals are far less than the 'hazardous waste identification Standard leaching toxicity identification' (GB)
5085-.
The first stage defluorination process comprises the following steps: delivering the washed solution to a first-stage defluorination reaction tank, adding lime emulsion to control the pH to be 10.0, and then adding CaCl2The amount of the added solution is the Ca in the coagulated solution2+The content is 50 mg/L; PAC and PAM medicaments are added simultaneously, wherein the adding amount of the PAC coagulant is 100mg/L, and the adding amount of the PAM flocculating agent is 5.0 mg/L; controlling the solution to coagulate and react for 25-30 min, and then placing the coagulated reaction mixture into a first-stage defluorination sedimentation tank for natural sedimentation for more than 5.0 h;
and a second-stage defluorination process: conveying the supernatant of the first-stage defluorination sedimentation tank to a second-stage defluorination reaction tank, adding acid hydrochloric acid or sulfuric acid to adjust the pH value to 6.0-7.5, and stirring for 3-5 min; then adding 5 wt% of polymeric ferric sulfate solution, wherein the adding amount is 500 mg/L; PAC and PAM medicaments are added simultaneously, wherein the adding amount of the PAC coagulant is 100mg/L, and the adding amount of the PAM flocculating agent is 5.0 mg/L; controlling the coagulation and reaction time to be 25-30 min, and then placing the coagulation reaction mixture into a second-stage defluorination sedimentation tank for natural sedimentation for more than 5.0 h; and then, conveying the supernatant in the second sedimentation tank to a double-effect evaporation regulating tank, filtering by a plate-frame type liquid pressing machine, pumping into a double-effect evaporation system, and recovering bromine salt.