RU2118666C1 - method of producing lead from lead sulfide - Google Patents

Abstract

FIELD: nonferrous metallurgy. SUBSTANCE: in a method of producing lead including melting lead-containing materials in presence of alkali metal salts and isolating molten lead, lead sulfate is charged into carbonate salt melt (additionally containing alkali-earth metal carbonates) at ratio (0.28-0.42):1 and temperature 800 to 1200 C, after which mixture is aged for 2-4 h. EFFECT: enhanced process efficiency. 2 cl, 1 tbl

Description

 The method relates to non-ferrous metallurgy, in particular to methods for producing lead from sulfide raw materials.

There is a method of extracting lead from sulfide concentrates by sublimation [1]. According to this method, a concentrate containing Pb - 72, Fe - 5, S - 14, SiO ₂ - 3, CaO - 3, Al ₂ O ₃ - 3, was heated by flue gases 1100 ^o C. When this was sublimated 97% of lead in the form of sulfide . Oxygen was metered into the gas to convert part of the lead to oxide. The latter, interacting with sulfide, gave metallic lead. Upon cooling the gas to a temperature of 1000 ^o C, the metal condenses. Cooling was carried out by irrigation with a refrigerant, preferably molten lead.

 The disadvantages of this method are the large amount of gases, the need to use oxygen enriched air, and the need to use molten lead for irrigation. Therefore, a large amount of dusty gases and the entrainment of metal with them are formed, they must be cleaned, dust must be returned to the process and, as a consequence, environmental degradation.

 A known method of producing metallic lead by direct fusion [2]. The metal is obtained from lead-containing materials by oxidative smelting and subsequent reduction of the melt, the resulting oxides. Recovery is carried out using a solid carbon-containing reagent present in the melt. A solid carbonate-containing material, such as limestone, dolomite or soda ash, is also required in the melt.

 However, the method requires the use of reducing agents, in addition, limestone together with impurities forms slags.

 The specified method is similar to the method of smelting in a Kaldo furnace [3].

The process is designed to process pure and complex (copper-containing) concentrates of lead and lead-containing dusts. The advantage, according to the authors, is high productivity and autogenous smelting, and environmental protection. Caldo furnace with a diameter of 3.6 m and a length of 6 m is lined with chromomagnesite brick, it rotates smoothly at a speed of 0-30 rpm, tilted at an angle of 28 ^o .

Experimental melts were conducted on 2 concentrates containing 76.4 and 66.1% of lead and 13.6 and 16.3% of sulfur, respectively. The process is two-stage; first, draft lead is obtained due to reaction melting and slag with 50% lead. Slag is reduced with coke to a lead content of 1-2%. The melting speed is 600-1000 kg / min, the amount of dust is 15-20%. Consumption per 1 g of concentrate O ₂ 115-125 m ³ , coke 26-31 kg.

 The disadvantages of this method include the high energy consumption for oxygen production, the consumption of scarce coke, the need for cooling and cleaning gases from dust and their recycling.

 Known low-temperature, not polluting the environment with sulfur oxides, a method for separating lead from a material containing lead sulfide in a boiler [4].

 To isolate lead, for example, from galena concentrate (lead gloss), lead is autogenously melted in a boiler, an alkali metal in a free state, for example, metallic sodium, is added in an amount sufficient to reduce lead sulfide to metal, a concentrate is added to the melt and the components are mixed. Sodium quickly and exothermically reduces sulfide to metallic lead to form matte containing sodium sulfide, which floats to the surface of metallic lead.

To impart fusibility and fluidity, fluxes are added to the matte. The process is conducted in a steel boiler at T ≤ 650 ^o C. In the process, sulfur dioxide is not released into the atmosphere.

The disadvantage of this process is that they use an expensive reducing agent, metal sodium (for at least 0.222 kg per 1 kg of lead) for recovery. In addition, matte is formed, which must be processed in an additional process. The use of steel equipment at 650 ^o C will lead to its rapid corrosion.

 The closest in technical essence is the method of processing dust lead production / 5 / smelting with a reducing agent and sodium sulfate, characterized in that in order to reduce operating costs, as a source of sodium sulfate use sludge from the production of sodium sulfide in the amount of 45-65% by weight dust, with the ratio of sludge to reducing agent (3.3 - 4.3): 1.

The finished mixture is fed to the surface of the bath furnace, heated to 1150-1180 ^o C. the charge Loading speed of 230 kg per 1 m ^{2 of the} furnace. Smelting products are discharged from the furnace as they accumulate.

 The disadvantages of this method are: the need to use a reducing agent in an amount of 16-18% by weight of the dust; waste sulfate used (30% sodium sulfate, 55% soda ash, the rest is oxides of aluminum, silicon, iron) in the form of sludge, single use, i.e. pour out of the furnace in the form of matte-slag phase, which goes either to the dump or for further processing; a large amount of gases and sublimates (37-37.6%) of the total loaded into the furnace is released.

 An object of the present invention is to simplify the process, reduce the amount of waste in the form of slag and sublimates, and eliminate the use of a reducing agent.

The problem is solved in that in the melt of carbonates containing carbonates of sodium, potassium, calcium and (or) magnesium, lead sulfide (galena) is loaded, kept at a temperature of 800-1200 ^o C (preferably at 840-1080 ^o C) for 2-4 h and metal lead is recovered, while the mass fraction of lead sulfide in the melt should be maintained in the range of 0.28 - 0.42.

New in this method is the production of lead from lead sulfide without the addition of a reducing agent, while the highest recovery is obtained in the temperature range of 900-1050 ^o C (above 80%).

 The advantage of this method is its simplicity, the absence of slag, the possibility of producing liquid lead, the absence of lead sublimates, the overall reduction of sublimates, the possibility of organizing a continuous process, and the elimination of the use of a reducing agent.

Lead sulfide can be continuously or periodically loaded into the molten salt, and lead is also continuously or periodically removed from the furnace. At the same time, the molten mixture of carbonates itself is constantly in the furnace for an indefinitely long time with a small amount of salt additions to compensate for evaporation losses (2-3 kg from 1 m ² per hour).

 The technical result achieved in the present method, when implemented, is to reduce the amount of exhaust gas, fuel economy, simplification of the process.

Example 1. 45 g of K ₂ CO _{3 were} loaded into a beryllium oxide crucible, 37 g of Na ₂ CO _{3 were} placed in a closed cell, the cell was evacuated, and filled with helium. The cell was connected to the atmosphere through a water trap with sulfuric acid. The cell, in turn, was installed in a resistance shaft furnace with celite heaters.

The temperature in the furnace was maintained with an accuracy of ± 5 ^° C. The cell was heated in the furnace to 890 ^° C. After the salt mixture was melted, 35 g of PbS was charged through the gate. At 862 ^° C, intense gas evolution was observed. When the temperature decreased to 780 ^o C, gas evolution ceased. For 4 hours, the cell was kept at 800-869 ^o C (average 841 ^o C). Then the furnace was turned off, the cell was cooled and metal lead was separated - 21.42 g. The total weight of carbonates and lead was 97.18 g, the initial weight was 117 g. Lead recovery was 70.75%. The results of other experiments are summarized in table. 1.

At temperatures below 840 ^o C, productivity drops sharply, as well as recovery.

At temperatures above 1200 ^o C the evaporation of carbonates and lead dramatically worsen performance. So, at 880 ^{o the} evaporation of carbonates is 0.35 g / cm ² • h, then at 1118 - 1.78 g / cm ² • h. At 1200 ^o C - 2.5 g / cm ² • h.

 With a mass ratio of raw materials to molten salts of less than 0.28, productivity decreases, with a ratio above 0.42, the melt thickens.

 In all examples, the processing of sulfides in molten carbonates without the use of a reducing agent leads to a decrease in the consumption of salts by at least 20 times, a decrease in the yield of slag and sublimates.

List of references
1. Pat. 65806. Finland. Claim 04.16.80 N 801213, publ. 07/10/84. MKI C 22 B 13/02 "Method for the recovery of lead from sulfide concentrates by sublimation".

 2. Application EPO (EP) N 0153913 publication 850904 N 36 MKI 4. C 22 B 13/02. Method for the production of metallic lead by direct fusion.

 3. Processing of lead concentrates in the Kaldo furnace. Verarbeitung von Bleikonzentraten in Kaldoofen. Petersson Stig. Lindkvist Goren "Erzmetall", 1982, 35, N. 189-191. (German. Ed. Eng.).

 4. Application EPO (EP) N 0038124 publication 31.10.21 N 42 MKI C 22 B 13/06. C 01 G 21/00, C 22 B 7/04, 5/04. "A low-temperature non-polluting sulfur oxide method for the separation of lead from a material containing lead sulfide in a boiler."

 5. Auth. testimonial. USSR N 804705 "Method for processing dust from lead production" MKI C 22 B 7/02. Claim 04/26/79. Publ. 02.15.81 Bull. N 6.

Claims (2)

1. A method for producing lead, comprising melting lead-containing materials in the presence of alkali metal salts and extracting molten lead, characterized in that lead sulfide is used as lead-containing materials, which are loaded into a carbonate salt melt when it is related to a salt melt of 0.28-0. 42: 1, a temperature of 800 - 1200 ^o C and then incubated for 2 to 4 hours  2. The method according to p. 1, characterized in that the lead sulfide is loaded into a carbonate salt melt, optionally containing alkaline earth metal carbonates.

Images