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Lead is the main impurity in the crude crucible . The lead chloride produced by the chlorination refining method removes lead by about 70%. There are generally three ways to treat it: reduction and smelting into crude lead; production of tribasic lead sulfate. ; wet production of yellow dan.
1. Reduction and smelting of lead chloride slag
(1) Process flow. Figure 1.
Figure 1 Lead slag reduction smelting process
(2) Main technical conditions. When the ingredients, the lead chloride slag crushed to less than 10 mm, the amount of slag with 40% to 50% and 6% reduction of limestone powder coal charged reflection smelting reduction furnace, the furnace following reaction occurs:
PbCl 2 +CaCO 3 +C=Pb+CaCl 2 +CO 2 +CO
PbCl 2 +CaCO 3 +CO=Pb+CaCl 2 +2CO 2
The temperature is raised to about 950 ° C, and after the completion of the reaction, the temperature is raised to about 1250 ° C, and the precipitate is precipitated at a high temperature for 4 hours or more, and the lead contained in the slag is 1% or less. Produces crude lead and calcium chloride slag. The crude lead contains 97%-98% lead, which can be directly sent to lead electrolytic refining. Calcium chloride slag can be used to make crude CaCI 2 as oxidant or synthetic white tungsten .
(3) Major equipment. One jaw crusher ; one ball mill ; one 5 m 2 reverberatory furnace; one leaching tank, one concentrating tank, a jacketed enamel reaction kettle; and one tumble dryer.
Second, wet production of Huang Dan
(1) Process flow. as shown in picture 2. Including leaching, purification, crystallization, conversion, drying and other processes.
Figure 2 Process for the production of yellow dans by lead chloride slag
(2) Main technical conditions. Leaching: After the ball slag is ball milled, it is leached with saturated brine, the liquid-solid ratio is 10:1, the leaching temperature is 109 ° C, the leaching solution pH is 3-5, and the leaching solution contains lead higher than 65 g/l.
Purification of copper : Adding Na 2 S or sponge lead to remove copper, the liquid temperature is 90 ° C, and the copper content after copper removal is less than 0.001 g / liter.
Purification and iron removal: adding hydrogen peroxide or sodium hypochlorite to remove iron (sodium hypochlorite is prepared by using chlorine gas into 30% liquid alkali), and the iron content after de-ironing is less than 0.0001 g/l.
Cooling crystallization: using jacketed circulating cold water cooling, mechanical stirring, the solubility of lead chloride in sodium chloride solution decreases with temperature, and PbCl 2 crystals are precipitated. The mother liquor is returned to the leaching.
Conversion: PbCl 2 crystals were washed with distilled water and added to a 30% liquid base. The response is:
PbCl 2 +2NaOH = PbO + 2NaCl + H 2 O
The industrial liquid alkali used first removes iron with MgCl 2 , generally 1 to 5 kg per ton of liquid alkali plus MgCl 2 , after the iron is heated, the liquid alkali is heated to 95 ° C for conversion, and the liquid containing NaOH is not less than 2.5 N after the conversion, so as to avoid Other basic lead salts are formed.
Washing and drying: The alkali-containing PbO is filtered by a centrifuge, and the mother liquor is concentrated to a 30% liquid alkali after filtration, and returned for conversion. The PbO crystals are washed with hot distilled water to a pH of 8, and indirectly heated to 105 ° C with steam, and dried and sieved to form a finished yellow dan.
(3) Major equipment. One ball mill: leaching tank, copper removal tank, iron removal tank, cooling tank, conversion tank, one jacketed enamel reaction kettle; one centrifugal filter; one rotary drum dryer; Several pumps.
(4) Product use. Huang Dan used as a drier in paint: ceramic industry as glaze; used in the production of lead glass with optical glass, optical fiber, electronic vacuum glass, etc.; can also produce lead nitrate, lead acetate, lead chrome yellow; industry.
(5) Quality of output (%). A PbO-containing product is not less than 99, the metal lead is not higher than 0.1, PbO 2 not more than 0.2, nitrate insolubles not higher than 0.2, sieve residue (- 200 days) not more than 0.2; product contains two PbO is not lower than 97, Pb is not higher than 0.3, PbO 2 is not higher than 0.5, nitric acid insoluble matter is not higher than 0.5, and sieve residue (-200 mesh) is not higher than 0.5.
Third, the production of tribasic lead sulfate
(1) Production process. As shown in Figure 3.
Figure 3 Flow chart of the production of three salts of PbCl 3 slag
(2) Main technical conditions. The lead chloride slag is ball milled to -20 mesh leaching, the leaching liquid composition: NaCl 3 20-340 g / liter, HCl 10 ~ 15 g / liter; liquid-solid ratio 8:1; leaching temperature higher than 90 ° C; mechanical stirring; leaching The time is 2 hours; the filtration temperature is higher than 60 °C.
Dilute the crystals; dilute with water, pH 1 to 3; dilute the precipitation time for 24 hours: cool at room temperature, wash the PbCl 2 crystals with water until the pH of the washing water is about 5, and dilute the mixture to concentrate and return to leaching.
Carbonic acid conversion: soda ash equivalent to PhCl 2 crystals 40-405% is dissolved in hot water at 80 °C, and lead chloride crystals are slowly added during stirring to convert, liquid-solid ratio 2:1, conversion temperature above 100 °C, conversion The time is about 2.5 hours, washed to neutrality, and filtered to obtain lead carbonate.
Nitric acid dissolution: The nitric acid was diluted with 3 times of water, and the slurryed lead carbonate was slowly added during stirring to completely dissolve to lead carbonate-free.
Sulfuric acid conversion: Add diluted dilute sulfuric acid, the amount of sulfuric acid is slightly lower than the calculated value, convert to PbSO 4 and wash away the free acid root until the pH is 7 to stop washing.
Solid base was converted to: PbSO 4 slurry into the liquid to solid ratio of 2.5, was added under stirring 40 to 50% NaOH, stirred for 3 hours or base addition was complete, NaOH controlled by analyzing the amount of SO 3 of 7.5% to 8.5%.
Three-salt adjustment: In the solid-base conversion, the product may contain SO 3 too low or too high, so further adjustment is needed; when SO 3 is too low, then sulfuric acid is added. When SO 3 is too high, NaoH is added to adjust production. Qualified products. After centrifugation filtration, the distilled water is washed to remove the sulfate, and then dried in an oven at 150 to 250 ° C, pulverized by a wind mill, and vacuum-filtered.
(3) Major equipment. One ball mill; one leaching tank, dilution tank, carbonic acid conversion tank, nitric acid dissolving tank, sulfuric acid conversion tank, solid alkali conversion tank, using jacketed enamel reactor, mechanical stirring; two centrifuges; one oven; One mill.
(4) Product use. Mainly used as a heat stabilizer for polyvinyl chloride plastics, electrical insulation materials and artificial leather.
(5) Product quality (%). PbO 89±1, SO 3 8±0.5, water content not higher than 0.4, fineness (-200 mesh), 99.5 or more, appearance of white powder.
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