A method for efficiently recovering gold and silver from waste graphite crucibles used in gold and silver smelting

Abstract

The present invention provides a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles. The method includes: classifying and crushing waste graphite crucibles according to gold smelting and silver smelting respectively, and finely grinding them to obtain crucible slag; subjecting the crucible slag to primary enrichment by a spiral chute to obtain pre-enriched slag and tailings; subjecting the pre-enriched slag to two-stage fine sand shaking table concentration to obtain gold / silver-rich slag; adding an oxidant to the gold / silver-rich slag for oxidative roasting to obtain ashed slag; subjecting the ashed slag to high-temperature and high-pressure strong alkali leaching to obtain alkali leached slag; subjecting the alkali leached slag to dilute acid leaching for deep impurity removal to obtain gold / silver highly enriched crude gold / silver powder. This method uses a combined beneficiation and metallurgy process for deep impurity removal and continuous enrichment of gold and silver, overcoming the problems in the traditional process of waste gold and silver smelting graphite crucible slag, such as refractory fire smelting due to a large amount of carbonaceous gangue, insufficient oxidative roasting, "gold robbing" of carbonaceous substances in wet leaching, high unit energy consumption or large water consumption, etc., and effectively realizing the recovery of gold and silver dispersed in the gaps of waste gold and silver smelting graphite crucibles.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste recycling, and particularly relates to a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles. Background Art

[0002] In the gold and silver metallurgy industry, medium (high)-frequency induction furnaces are generally used for operations such as gold and silver smelting, refining, and casting. Generally, high-density graphite crucibles, graphite-clay crucibles, or graphite-silicon carbide crucibles are used as melting furnaces. During the use of these crucibles, they will be subjected to mechanical erosion by gold and silver liquids, internal pressure, flux corrosion, high-temperature oxidation, etc., resulting in the gradual peeling off of the dense layer or glaze layer on the inner lining surface. The molten gold and silver liquid enters the pores or gaps of the crucible wall in the form of fine particles. In gold and silver metallurgy, whether it is graphite, graphite-clay, or graphite-silicon carbide, they all belong to refractory carbonaceous gangue components. During pyrometallurgy, carbonaceous substances will greatly increase the melting point of the slag, affect the fluidity of the slag, and reduce the metal recovery rate. During hydrometallurgical extraction, due to the strong "gold-robbing" effect of carbonaceous substances, a small amount of carbon, especially organic carbon, will significantly reduce the gold and silver leaching rate. Therefore, theoretically, gold and silver raw materials containing carbonaceous substances are usually subjected to oxidative roasting to oxidize the carbonaceous substances, eliminating the adverse effects of the high melting point of carbonaceous substances on pyrometallurgy and the "gold-robbing" effect on hydrometallurgy.

[0003] Currently, there is little research or application on recovering gold, silver, or other valuable metals from waste graphite crucibles used in metal smelting. CN108823416B discloses a method for extracting gold and silver from clay graphite crucible slag. This method makes the crucible slag react with a sulfuric acid / hydrofluosilicic acid mixed solution first, then calcines at 900 - 1000 °C, and finally separates gold and silver by leaching with acid and aqua regia respectively; CN109055767A discloses a method for extracting gold and silver from clay graphite crucible slag by alkali roasting. This method is aimed at the same crucible slag as CN108823416B, and uses alkali roasting, water washing, and acid washing, and finally separates gold and silver by leaching with acid and aqua regia respectively. However, both of the above methods directly target a large amount of graphite-clay crucible slag, either removing impurities by wet method first or by pyrometallurgical method first, and the impurity removal effect is not good, and the highest impurity removal rate is only 42.69%. Moreover, a large amount of wastewater is generated when removing impurities by wet method first, and the energy consumption is huge when removing impurities by pyrometallurgical method first; in addition, the amount of enriched slag after impurity removal is still large. At this time, directly performing silver separation with nitric acid and gold separation with aqua regia, on the one hand, there is the "gold-robbing" of unoxidized carbonaceous substances, and on the other hand, gold and silver production practices show that trace amounts of gold and silver (the impurity content is as high as 99.95%) are difficult to effectively recover by gold separation with aqua regia or silver separation with nitric acid, and there is still a lot of gold and silver residue in the gold separation slag and silver separation slag.

[0004] Regarding the recovery of gold and silver from waste gold and silver smelting graphite crucibles, if the waste graphite crucible slag is directly smelted, it will be difficult to melt due to the excessive content of graphite (the melting point of graphite is 3652 °C); if all the crucible slag is oxidized and roasted, there will be problems such as a large amount of roasting treatment, low ashing efficiency, insufficient oxidation, and high unit energy consumption; if a wet process is adopted, due to the "gold-robbing" effect of carbonaceous substances, it is difficult to effectively recover relatively low-content gold and silver from a large amount of graphite carbon powder; if a conventional pyrometallurgical-wet process is used, there will be common problems faced by both methods at the same time. Therefore, under the existing process equipment conditions, gold and silver smelting enterprises hardly have an effective method to systematically recover the dispersed gold and silver in waste gold and silver smelting crucibles.

[0005] To recover some of the gold and silver dispersed in waste gold and silver smelting graphite crucibles, usually only the inner wall surface of the crucible can be manually cleaned and then washed to recover a small amount of gold and silver. Most of the dispersed gold and silver still remain in the crucible wall, with a gold or silver content as high as 200 - 450 g / t. These gold and silver dispersed in the crucible wall can only be sold to non-ferrous smelters together with the crucible after being converted at a low pricing coefficient of 10% - 25% for gold and 5% - 10% for silver, and gradually recover the dispersed and lost gold and silver by being used as a small amount of reduction smelting additive. However, for gold and silver smelting enterprises, the total recovery rate of gold or silver is only 5% - 25%, and the gold and silver cannot be effectively recycled, resulting in the wasteful loss of valuable resources.

[0006] In order to solve the deficiencies of the existing methods for recovering dispersed gold and silver in waste gold and silver smelting graphite crucibles, the present invention provides a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles, which is efficient, simple, economically feasible, environmentally friendly, and has strong adaptability. Summary of the Invention

[0007] In view of the above problems, the present invention provides a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles. According to the principle of continuous enrichment in the extraction of precious metals, a combined beneficiation and smelting process is adopted to deeply remove a large amount of impurity components such as graphite, and obtain gold and silver products that are highly enriched and convenient for conventional refining and purification processes, so as to achieve the efficient recovery of the dispersed and lost gold and silver in waste gold and silver smelting crucibles.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions:

[0009] A method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles, comprising the following steps:

[0010] (1) Classification pretreatment, crushing and fine grinding of the crucibles: Classify and recycle gold and silver according to the crucibles used for gold smelting and silver smelting. Clean the gold or silver attached to the inner wall of the gold or silver smelting crucible, transfer it to a sandblasting machine for wet crushing (spray water while crushing to reduce dust), and send the crushed slag to a ball mill for fine grinding to obtain crucible slag;

[0011] (2)Pre-concentration by spiral chute: The crucible slag obtained in step (1) is slurried and fed into the spiral chute for primary separation to remove most of the graphite carbon powder and other substances. The spiral chute concentrate and middlings obtained are the pre-concentrated slag, and the spiral chute tailings are sold externally.

[0012] (3)Two-stage fine sand shaking table concentration: The pre-concentrated slag obtained in step (2) is fed into the first-stage shaking table for separation. The first-stage concentrate and middlings are fed into the second-stage shaking table for re-selection. The second-stage concentrate produced is the gold-rich slag or silver-rich slag. The second-stage middlings are returned to the first-stage shaking table for re-selection to further recover gold and silver. The tailings from the two-stage shaking tables are sold externally.

[0013] (4)Oxidative roasting and ashing of gold-rich and silver-rich slag: The gold-rich slag or silver-rich slag obtained in step (3) is dried, potassium nitrate is added, and it is sent to a muffle furnace for oxidative roasting to fully ash the carbonaceous substances and other substances, obtaining the ashed slag.

[0014] (5)High-temperature and high-pressure strong alkali leaching: The ashed slag obtained in step (4) is added to a sodium hydroxide solution, a small amount of potassium nitrate is added, and it is introduced into an autoclave for high-temperature and high-pressure leaching to dissolve as much acidic argillaceous substances such as SiO2 and Al2O3 in the slag as possible, and the alkali leached slag is separated.

[0015] (6)Deep impurity removal by dilute acid leaching: The alkali leached slag obtained in step (5) is leached with dilute hydrochloric acid to make all metal oxides such as CaO, Fe2O3, MgO, and K2O enter the solution. After filtration, crude gold powder or crude silver powder is obtained. The crude gold powder is incorporated into the process of separating gold with aqua regia for purification, and the crude silver powder is melted into an anode plate and incorporated into the process of electrolytic refining of silver.

[0016] Preferably, in step (1), the fine grinding time of the ball mill is 1.5 - 3 h, and the particle size of the crucible slag with -0.074 mm accounts for more than 85%.

[0017] Preferably, in step (2), the spiral chute is a single-head chute, with a cross-sectional width of 25 - 30 cm, a transverse inclination angle of 9 - 12°, 5 - 8 blade turns, a feed rate of 200 - 300 kg / h, a feed concentration of 15% - 25%, and the intercepting valve adjusts the intercepting amplitude according to the distribution of the concentrate and middlings ore belts.

[0018] Preferably, in step (3), the shaking table is a two-stage fine sand shaking table, with a screen surface of 60 - 88 grooves, a transverse slope of 1.5 - 3.5°, a longitudinal slope of 0.5 - 1.5°, a feed rate of 100 - 200 kg / h, a feed concentration of 25% - 35%, and a flushing water of 15 - 35 L / min; among them, the stroke of the first-stage shaking table is 12 - 15 mm, the stroke frequency is 250 - 280 times / min, the stroke of the second-stage shaking table is 8 - 12 mm, and the stroke frequency is 300 - 340 times / min.

[0019] Preferably, in step (4), potassium nitrate is added in an amount of 2% - 5% by weight of the rich gold slag, and the mixture is evenly spread with a thickness of 0.5 - 2.0 cm, and calcined for 3 - 6 h under the conditions that the working temperature of the muffle furnace is 600 - 900 °C and the furnace door is opened 2 - 5 cm.

[0020] Preferably, in step (5), the ashed slag is mixed with a sodium hydroxide solution with a concentration of 2 - 5 mol / L according to a liquid-solid ratio of 4:1 - 6:1, and 1.0% - 2.5% by weight of potassium nitrate is added as a catalyst. The total pressure in the autoclave is controlled at 2.0 - 5.0 Mpa, the oxygen partial pressure is 0.1 - 0.5 Mpa, the reaction temperature is 140 - 180 °C, and the reaction time is 1 - 2.5 h. After cooling, filtration and washing, the alkali-leached slag is obtained.

[0021] Preferably, in step (6), the alkali-leached slag is mixed with dilute hydrochloric acid with a molar mass of 3 - 5 mol / L according to a liquid-solid ratio of 2:1 - 5:1, and the temperature is controlled at 50 - 70 °C, the stirring speed is 200 - 300 r / min, and the reaction time is 1 - 2 h. After filtration and washing, crude gold powder or crude silver powder is obtained.

[0022] Advantages of the present invention:

[0023] (1) The present invention adopts a combined beneficiation and smelting process to deeply remove a large number of impurity components such as graphite in the gold and silver smelting crucible slag, and obtains highly enriched gold and silver products that are convenient for conventional refining and purification processes, effectively solving the problem that gold and silver smelting enterprises could not efficiently recover dispersed gold and silver from waste gold and silver smelting graphite crucibles before.

[0024] (2) The present invention uses the characteristic that the density of gold and silver is much greater than that of graphite powder to remove impurities by gravity separation. The impurity removal rate is as high as 95.29%, and the gold and silver enrichment ratio can reach 110 times. The separation effect is remarkable, solving the problems such as difficult refractory in pyrometallurgy, insufficient oxidation roasting, "gold robbing" of carbonaceous matter in hydrometallurgical leaching, high unit energy consumption or large water consumption caused by a huge amount of carbonaceous gangue in the traditional process of waste gold and silver smelting graphite crucible slag, and obtaining a preliminary enrichment of gold and silver that is convenient for metallurgical process treatment.

[0025] (3) According to the principle of continuous enrichment in the extraction of precious metals, the present invention adopts oxidation roasting and ashing, high-temperature and high-pressure alkali leaching, and acid leaching to further deeply remove impurities. The impurity removal rate is as high as 98.53%, the cumulative enrichment of gold is 2560 times, and the cumulative enrichment of silver is 1897 times. The comprehensive recovery rate of gold is increased from 10% - 25% to 92.89%, and the comprehensive recovery rate of silver is increased from 5% - 10% to 88.62%, effectively realizing the efficient recovery of gold and silver, and the economic benefits are remarkable.

[0026] (4) The combined beneficiation and smelting process of the present invention is efficient, simple, has strong adaptability, is environmentally friendly and economically feasible, and has wide reference and promotion value for gold and silver smelting enterprises to recover gold and silver from carbonaceous matter resources. Description of the Drawings

[0027] Figure 1 This is a process flow schematic diagram of a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles of the present invention. Detailed implementation manners

[0028] In order to make the technical problems and technical solutions solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] As Figure 1 shown, a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles, the specific steps include:

[0030] (1) Classification pretreatment, crushing and fine grinding of crucibles: Classify and recycle gold and silver according to the crucibles for gold smelting and the crucibles for silver smelting. After cleaning the inner wall of the gold (silver) smelting crucible with a shovel to remove the attached gold (silver), add water while adding it to a hammer crusher for crushing (spraying water to reduce dust). The crushed slag is sent to a ball mill for fine grinding for 1.5 - 3 hours to obtain crucible slag with a particle size of -0.074 mm accounting for more than 85%. After mixing well several times, spread it out flat to a slag layer thickness of about 3 cm and conduct repeated riffle sampling. Analyze the gold (silver) and main impurity components of the samples.

[0031] (2) Pre-concentration by spiral chute: Slurry the crucible slag and water at a weight ratio of 1:3 - 1:6, and then introduce it into the feeding box at the top of the spiral chute. The rotation speed of the stirring paddle in the box is 300 r / min. Control the opening of the valve at the bottom of the box to make the slag slurry swirl from top to bottom. The feeding amount is 200 - 300 kg / h. The transverse inclination of the chute is 9 - 12°, and the number of blade turns is 5. Adjust the intercepting amplitude of the intercepting valve at the end of the chute according to the distribution of the concentrate and middling ore belts. The mixture of the spiral chute concentrate and middling ore is the pre-concentrated slag. The tailings are filtered and dried to obtain spiral chute tailings for external sale. The filtrate and tail liquid are discharged into the sedimentation pond for reuse.

[0032] (3) Two-stage fine sand shaking table beneficiation: Feed the pre-concentrated slag into the first-stage shaking table for separation. The screen surface of the first-stage shaking table has 60 - 88 grooves, the transverse slope is 1.5 - 3.5°, the longitudinal slope is 0.5 - 1.5°, the stroke is 12 - 15 mm, the impulse frequency is 250 - 280 times / min, the feeding amount is 100 - 200 kg / h, the feeding concentration is 25% - 35%, and the flushing water is 15 - 35 L / min to obtain the first-stage concentrate, middling ore and tailings;

[0033] The first-stage concentrate and middlings are sent to a second-stage shaking table for re-selection. The second-stage shaking table has a screen surface with 60 - 88 slots, a transverse slope of 1.5 - 3°, a longitudinal slope of 0.5 - 1.5°, a stroke of 8 - 12 mm, a stroke frequency of 300 - 340 times / min, a feed rate of 100 - 150 kg / h, a feed concentration of 20% - 30%, and a flushing water rate of 15 - 20 L / min. Second-stage concentrate, middlings, and tailings are obtained. The second-stage concentrate is filtered and dried to obtain rich gold (silver) slag. The second-stage middlings are returned to the first-stage shaking table for re-selection. The first-stage tailings and the second-stage tailings are mixed, filtered, and dried, and then the shaking table tailings are sold externally. The filtrate and tail liquid are discharged into a sedimentation pond for reuse.

[0034] (4)Oxidative roasting and ashing of rich gold (silver) slag: Potassium nitrate is added at 2% - 5% of the weight of the rich gold (silver) slag and mixed evenly. The paving thickness is 0.5 - 2.0 cm. It is roasted for 3 - 6 h under the conditions that the working temperature of the muffle furnace is 600 - 900°C and the furnace door is opened 2 - 5 cm to obtain ashed slag.

[0035] (5)High-temperature and high-pressure strong alkali leaching: The ashed slag is mixed with a sodium hydroxide solution with a concentration of 2 - 5 mol / L at a liquid-solid ratio of 4:1 - 6:1. Potassium nitrate at 1.0% - 2.5% of the weight of the ashed slag is added as a catalyst. The mixed material liquid is introduced into a stainless-steel high-pressure reactor. The total pressure in the reactor is controlled at 2.0 - 5.0 Mpa, the oxygen partial pressure is 0.1 - 0.5 Mpa, the reaction temperature is 140 - 180°C, and the reaction time is 1 - 2.5 h. After cooling, filtration and washing are carried out to obtain alkali leaching residue, and the filtrate is discharged into a waste water pond.

[0036] (6)Deep impurity removal by dilute acid leaching: The alkali leaching residue is mixed with dilute hydrochloric acid with a molar mass of 3 - 5 mol / L at a liquid-solid ratio of 2:1 - 5:1. The temperature is controlled at 50 - 70°C, the stirring speed is 200 - 300 r / min, and the reaction time is 1 - 2 h. Filtration and washing are carried out to obtain crude gold powder or crude silver powder, and the filtrate is discharged into a waste water pond.

[0037] Specifically, the composition range of the waste gold and silver smelting graphite crucible slag used in the embodiments of the present invention is described:

[0038] (1)The main components of the gold smelting crucible slag are: Au 248.41 g / t, C 76.46%, SiO2 7.62%, Al2O3 2.06%, CaO 5.56%, Fe2O3 0.74%, MgO 1.69%, K2O 0.42%, H2O 4.33%, and others < 1.12%.

[0039] (2) The main components of the silver smelting crucible slag are: Ag 373.84 g / t, C 75.03%, SiO2 9.41%, Al2O3 2.49%, CaO 5.89%, Fe2O3 0.53%, MgO 1.75%, K2O 0.23%, H2O 3.86%, and others <0.81%. Example 1

[0040] In this example, a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles provided by the present invention is adopted to recover the gold in the above-mentioned "gold smelting crucible slag", which specifically includes the following steps:

[0041] (1) Weigh 200.00 kg of gold smelting crucible slag and add 0.8 m of water 3 Mix well. The slurry swirls from top to bottom on the spiral chute at a flow rate of 20 L / min to obtain a mixture of spiral chute concentrate and middlings, which is the pre-concentrated slag. The tailings are filtered and dried to obtain 121.64 Kg of spiral chute tailings, containing 16.92 g / t of gold.

[0042] (2) After adding 200 L of water to the pre-concentrated slag for pulp adjustment, it is sent to a primary shaking table for separation. The feed rate is 100 Kg / h and the flushing water is 25 L / min; the obtained primary concentrate and middlings are adjusted with 50 L of water for pulp and then sent to a secondary shaking table for re-selection. The feed rate is 100 kg / h and the flushing water is 16 L / min; the obtained secondary concentrate is filtered and dried to obtain 1770.52 g of gold-rich slag, containing 2.61% of gold; the secondary middlings are returned to the primary shaking table for re-selection. The tailings of the two-stage shaking table are mixed, filtered, and dried to obtain 56.28 kg of shaking table tailings, containing 10.33 g / t of gold.

[0043] (3) Add 50 g of potassium nitrate to the above gold-rich slag, mix well, spread it out with a thickness of 1.0 cm, and calcine it in a muffle furnace at a constant temperature of 760 °C for 4 h, keeping the furnace door open 3 cm to obtain 581.02 g of ashed slag.

[0044] (4) Mix the above ashed slag with 2.4 L of sodium hydroxide solution with a concentration of 5 mol / L, add 15 g of potassium nitrate, introduce it into a stainless steel autoclave, control the total pressure in the autoclave at 3.5 Mpa, the oxygen partial pressure at 0.4 Mpa, the reaction temperature at 180 °C, and the reaction time at 2 h. After the reaction, cool down, filter, and wash to obtain alkali-leached slag, with a dry weight of 301.18 g.

[0045] (5) Add the above alkali-leached slag to 1.5 L of hydrochloric acid solution with a concentration of 4 mol / L, control the reaction temperature at 60 °C in a glass reaction kettle, react for 1 h, and filter to obtain 76.34 g of crude gold powder, containing 60.45% of gold. This crude gold powder can easily achieve efficient separation, purification, and recovery of gold by the aqua regia method.

[0046] Test results: The removal rate of impurities such as graphite in the gold smelting crucible slag reaches 93.85% through the combined separation of a spiral chute and two-stage fine sand shaking tables. The gold is enriched 105 times, the direct recovery rate of gold is 92.91%, and the separation effect is remarkable. For the gold-rich slag, the impurity removal rate reaches 98.25% after enhanced impurity removal, and the obtained crude gold powder contains 60.45% gold. The cumulative enrichment of gold in the whole process is 2434 times, and the comprehensive recovery rate of gold is 92.89%. It effectively realizes the deep removal of impurities such as graphite in the waste crucibles for gold smelting, as well as the high enrichment and efficient recovery of gold. Example 2

[0047] In this example, a method for efficiently recovering gold and silver from waste graphite crucibles for gold and silver smelting provided by the present invention is adopted to recover the gold in the above-mentioned "gold smelting crucible slag", which specifically includes the following steps:

[0048] (1) Weigh 200.00 kg of gold smelting crucible slag and add 1.2 m 3 of water and mix evenly. The slurry swirls downward from top to bottom on the spiral chute at a flow rate of 30 L / min to obtain a mixture of spiral chute concentrate and middlings, which is the pre-enriched slag. The tailings are filtered and dried to obtain 132.29 kg of spiral chute tailings, containing 25.81 g / t of gold.

[0049] (2) The pre-enriched slag is adjusted to a pulp with 150 L of water and then sent to a first-stage shaking table for separation, with a feed rate of 150 kg / h and a flushing water rate of 30 L / min. The obtained first-stage concentrate and middlings are adjusted to a pulp with 40 L of water and then sent to a second-stage shaking table for re-selection, with a feed rate of 100 kg / h and a flushing water rate of 20 L / min. The obtained second-stage concentrate is filtered and dried to obtain 1562.74 g of gold-rich slag, containing 2.75% gold. The second-stage middlings are returned to the first-stage shaking table for re-selection. The tailings from the two-stage shaking tables are mixed, filtered, and dried to obtain 50.37 Kg of shaking table tailings, containing 13.57 g / t of gold.

[0050] (3) Add 40 g of potassium nitrate to the above gold-rich slag and mix evenly. Spread it out with a thickness of 1.0 cm and roast it in a muffle furnace at a constant temperature of 800 °C for 3.5 h, keeping the furnace door open 4 cm to obtain 547.15 g of ashed slag.

[0051] (4) Mix the above ashed slag with 2.2 L of sodium hydroxide solution with a concentration of 5 mol / L, add 10 g of potassium nitrate, and introduce it into a stainless steel autoclave. Control the total pressure in the autoclave at 3.2 Mpa, the oxygen partial pressure at 0.3 Mpa, the reaction temperature at 160 °C, and the reaction time at 2 h. After the reaction, cool down, filter, and wash to obtain alkali-leached slag, with a dry weight of 293.36 g.

[0052] (5) Add the above alkali-leached slag to 1.5 L of hydrochloric acid solution with a concentration of 4.2 mol / L, control the reaction temperature at 60 °C in a glass reaction kettle, react for 1 h, and filter to obtain 72.09 g of crude gold powder, containing 59.19% gold. This crude gold powder can easily achieve efficient separation, purification, and recovery of gold by the method of separating gold with aqua regia.

[0053] Test results: The removal rate of impurities such as graphite in the gold smelting crucible slag reaches 95.29% through the combined separation of a spiral chute and a two-stage fine sand shaking table. The gold enrichment ratio is 110 times, the direct gold recovery rate is 86.49%, and the separation effect is remarkable. For the gold-rich slag, the impurity removal rate reaches 95.39% after enhanced impurity removal, and the obtained crude gold powder contains 59.19% gold. The cumulative gold enrichment in the whole process is 2383 times, and the comprehensive gold recovery rate is 85.89%. The deep removal of impurities such as graphite in the waste gold smelting crucible, the high enrichment of gold, and the efficient recovery of gold are effectively realized. Example 3

[0054] This example uses a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles provided by the present invention to recover the gold in the above-mentioned "gold smelting crucible slag", and specifically includes the following steps:

[0055] (1) Weigh 316.52 kg of gold smelting crucible slag and add 1.5 m 3 of water and mix evenly. The slurry swirls downward from top to bottom on the spiral chute at a flow rate of 25 L / min to obtain a mixture of spiral chute concentrate and middlings, which is the pre-enriched slag. The tailings are filtered and dried to obtain 196.87 kg of spiral chute tailings, containing 18.79 g / t of gold.

[0056] (2) The pre-enriched slag is adjusted to a pulp with 300 L of water and then sent to a first-stage shaking table for separation, with a feed rate of 120 kg / h and a flushing water rate of 25 L / min. The obtained first-stage concentrate and middlings are adjusted to a pulp with 60 L of water and then sent to a second-stage shaking table for re-separation, with a feed rate of 100 kg / h and a flushing water rate of 20 L / min. The obtained second-stage concentrate is filtered and dried to obtain 2809.68 g of gold-rich slag, containing 2.52% gold. The second-stage middlings are returned to the first-stage shaking table for re-separation. The tailings from the two-stage shaking tables are mixed, filtered, and dried to obtain 82.90 Kg of shaking table tailings, containing 8.85 g / t of gold.

[0057] (3) Add 80 g of potassium nitrate to the above gold-rich slag and mix evenly. Spread it out with a thickness of 1.0 cm and roast it in a muffle furnace at a constant temperature of 700 °C for 3.5 h, keeping the furnace door open 4 cm to obtain 958.66 g of ashed slag.

[0058] (4) Mix the above ashed slag with 4 L of sodium hydroxide solution with a concentration of 5 mol / L, add 15 g of potassium nitrate, and introduce it into a stainless steel high-pressure reactor. Control the total pressure in the reactor at 4.0 Mpa, the oxygen partial pressure at 0.4 Mpa, the reaction temperature at 180 °C, and the reaction time at 2.5 h. After the reaction, cool down, filter, and wash to obtain alkali leaching slag, which is dried to a weight of 472.78 g.

[0059] (5) The above alkali leaching residue is added to 2.0 L of hydrochloric acid solution with a concentration of 4.5 mol / L. The reaction temperature is controlled at 70 °C in a glass reaction kettle, and the reaction is carried out for 1 h. After filtration, 110.89 g of crude gold powder is obtained, containing 63.59% gold. The crude gold powder can be easily separated, purified and recycled by the aqua regia method for separating gold.

[0060] Test results: The removal rate of impurities such as graphite in the gold smelting crucible slag reaches 93.75% by the combined separation of a spiral chute and two-stage fine sand shaking tables. The gold is enriched 101 times, and the direct recovery rate of gold is 89.69%. The separation effect is remarkable. For the gold-rich slag, the impurity removal rate reaches 98.53% after enhanced impurity removal, and the obtained crude gold powder contains 63.59% gold. The gold is cumulatively enriched 2560 times in the whole process, and the comprehensive recovery rate of gold is 89.69%. The deep removal of impurities such as graphite in the waste crucible of gold smelting and the high enrichment and efficient recovery of gold are effectively realized. Example 4

[0061] This example adopts a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles provided by the present invention to recover silver from the above "silver smelting crucible slag", and specifically includes the following steps:

[0062] (1) Weigh 300.00 kg of silver smelting crucible slag and add 1.5 m of water 3 Mix well. The slurry swirls downward from top to bottom on the spiral chute at a flow rate of 25 L / min to obtain a mixture of spiral chute concentrate and middlings as pre-enriched slag. The tailings are filtered and dried to obtain 179.89 kg of spiral chute tailings, containing 32.57 g / t of silver.

[0063] (2) Add 300 L of water to the pre-enriched slag and send it to a first-stage shaking table for separation, with a feed rate of 100 kg / h and a water supply rate of 20 L / min. The obtained first-stage concentrate and middlings are adjusted to a pulp with 70 L of water and sent to a second-stage shaking table for re-selection, with a feed rate of 100 kg / h and a water supply rate of 18 L / min. The obtained second-stage concentrate is filtered and dried to obtain 2994.73 g of silver-rich slag, containing 3.21% silver. The second-stage middlings are returned to the first-stage shaking table for re-selection. The tailings of the two-stage shaking tables are mixed, filtered and dried to obtain 94.60 Kg of shaking table tailings, containing 16.74 g / t of silver.

[0064] (3) Add 80 g of potassium nitrate to the above silver-rich slag and mix well. Spread it out with a thickness of 1.0 cm and roast it in a muffle furnace at a constant temperature of 750 °C for 4 h, keeping the furnace door open 4 cm to obtain 1032.39 g of ashed slag.

[0065] (4) Mix the above ashed slag with 4.5 L of sodium hydroxide solution with a concentration of 5 mol / L, add 20 g of potassium nitrate, introduce it into a stainless steel autoclave, control the total pressure in the autoclave at 4.0 Mpa, the oxygen partial pressure at 0.4 Mpa, the reaction temperature at 180 °C, and the reaction time at 2.5 h. After the reaction, cool down, filter and wash to obtain alkali leaching residue, and the dried weight is 526.53 g.

[0066] (5) The above alkali leaching residue is added to 2.0 L of hydrochloric acid solution with a concentration of 4 mol / L. The reaction temperature is controlled at 70 °C in a glass reaction kettle, and the reaction is carried out for 1 h. After suction filtration, 134.71 g of crude silver powder is obtained, containing 70.93% silver. This crude silver powder can be directly melted and cast into an anode plate for electrolytic purification to recover silver.

[0067] Test results: The removal rate of impurities such as graphite in the silver smelting crucible slag reaches 95.17% through the combined separation of a spiral chute and two-stage fine sand shaking tables. The silver enrichment ratio is 88 times, and the direct silver recovery rate is 91.58%. The separation effect is remarkable. For the silver-rich slag, the impurity removal rate reaches 95.50% after enhanced impurity removal, and the obtained crude silver powder contains 70.93% silver. The cumulative silver enrichment in the whole process is 1897 times, and the comprehensive silver recovery rate is 88.62%. It effectively realizes the deep removal of impurities such as graphite in the waste silver smelting crucible, as well as the high enrichment and efficient recovery of silver. Example 5

[0068] This example uses a method for efficiently recovering gold and silver from waste gold and silver smelting graphite crucibles provided by the present invention to recover silver from the above-mentioned "silver smelting crucible slag", and specifically includes the following steps:

[0069] (1) Weigh 400.00 kg of silver smelting crucible slag and add 1.6 m 3 of water and mix evenly. The slurry swirls from top to bottom on the spiral chute at a flow rate of 30 L / min to obtain a mixture of spiral chute concentrate and middlings, which is the pre-enriched slag. The tailings are filtered and dried to obtain 246.51 kg of spiral chute tailings, containing 36.22 g / t of silver.

[0070] (2) The pre-enriched slag is added with 320 L of water and sent to a first-stage shaking table for separation, with a feed rate of 100 kg / h and a water feed rate of 25 L / min. The obtained first-stage concentrate and middlings are adjusted with 80 L of water and sent to a second-stage shaking table for re-selection, with a feed rate of 100 kg / h and a water feed rate of 20 L / min. The obtained second-stage concentrate is filtered and dried to obtain 3714.64 g of silver-rich slag, containing 3.43% silver. The second-stage middlings are returned to the first-stage shaking table for re-selection. The tailings of the two-stage shaking tables are mixed, filtered, and dried to obtain 117.45 Kg of shaking table tailings, containing 17.26 g / t of silver.

[0071] (3) The above silver-rich slag is mixed with 100 g of potassium nitrate, spread out with a thickness of 1.0 cm, and roasted in a muffle furnace at a constant temperature of 700 °C for 4 h, keeping the furnace door open 4 cm to obtain 1173.13 g of ashed slag.

[0072] (4) The above-mentioned ash slag was mixed with 5L of 5mol / L sodium hydroxide solution, and 25g of potassium nitrate was added. The mixture was introduced into a stainless steel high-pressure reactor. The total pressure in the reactor was controlled to be 3.75Mpa, the oxygen partial pressure was 0.35Mpa, the reaction temperature was 180°C, and the reaction time was 2.5h. After the reaction was completed, the slag was cooled, filtered, and washed to obtain an alkaline leached residue with a drying weight of 725.94g.

[0073] (5) The alkaline leaching residue was added into 2.5 L of 4 mol / L hydrochloric acid solution, and the reaction temperature was controlled at 70°C in a glass reactor. The reaction was carried out for 1 h, and 184.61 g of crude silver powder was obtained by filtration, containing 68.42% silver. The crude silver powder can be directly melted into anode plates for electrolysis to purify and recover silver.

[0074] Test results: The removal rate of graphite and other impurities in crucible slag reached 94.64% under the combined separation of spiral chute and two-stage fine sand shaking table, silver was enriched 95 times, and the direct recovery rate of silver was 91.58%, with significant separation effect; the silver-rich slag was enhanced to remove impurities, with an impurity removal rate of 95.03%, and the crude silver powder obtained contained 68.42% silver; the cumulative silver enrichment in the whole process was 1830 times, and the comprehensive silver recovery rate was 87.86%, which effectively achieved the deep removal of impurities such as graphite in the discarded crucibles of silver smelting and the high enrichment and efficient recovery of silver.

[0075] It can be seen from the test results of Examples 1 to 5 that the method for treating the discarded graphite crucible for gold and silver smelting can effectively recover the gold and silver lost in the inner wall of the gold and silver smelting crucible, and the gold recovery rate is increased from 10% to 25% of the original price for sale to 92.89%. The obtained crude gold powder contains 63.59% gold, and the gold is enriched by 2560 times. The subsequent water regia gold metallization method can be used to efficiently purify and recover the gold; the silver recovery rate is increased from 5% to 10% of the original price for sale to 88.62%, and the obtained crude silver powder contains 70.93% silver, and the silver is enriched by 1897 times, and the anode plate can be directly melted and cast for electrolysis to purify and recover the silver.

[0076] The present invention is described in detail above through specific and preferred embodiments, but those skilled in the art should understand that the present invention is not limited to the embodiments described above, and any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucibles, characterized in that: The following steps are involved: (1) Crucible classification pretreatment, crushing and fine grinding: gold and silver are recovered according to the crucibles for gold smelting and silver smelting. The gold or silver attached to the inner wall of the gold or silver smelting crucible is cleaned out and transferred to a sand blasting machine for wet crushing. The crushed slag is sent to a ball mill for fine grinding to obtain crucible slag; (2) Pre-enrichment in spiral chute: The crucible slag obtained in step (1) is slurried and sent to the spiral chute for preliminary selection to remove most of the graphite, carbon powder and other substances. The spiral chute concentrate and middlings obtained are the pre-enrichment slag, and the spiral chute tailings are sold externally; (3) Two-stage fine sand shaking table selection: the pre-enriched slag obtained in step (2) is sent to the first-stage shaking table for selection, and the obtained first-stage concentrate and middlings are sent to the second-stage shaking table for reselection. The produced second-stage concentrate is gold-rich slag or silver-rich slag, and the second-stage middlings are returned to the first-stage shaking table for reselection to further recover gold and silver. The tailings of the two-stage shaking tables are sold out; (4) Oxidation roasting and ashing of gold-rich or silver-rich slag: drying the gold-rich or silver-rich slag obtained in step (3), adding potassium nitrate and sending it to a muffle furnace for oxidation roasting to fully ashed the carbonaceous matter and other substances to obtain ashed slag; (5) High temperature and high pressure strong alkaline leaching: the ash residue obtained in step (4) is added to a sodium hydroxide solution, a small amount of potassium nitrate is added, and the mixture is introduced into a high pressure autoclave for high temperature and high pressure leaching to dissolve the acidic mud in the residue as much as possible, and the alkaline leached residue is separated; (6) Deep impurity removal by dilute acid leaching: The alkaline leaching residue obtained in step (5) is leached with dilute hydrochloric acid to allow all metal oxides to enter the solution. The crude gold powder or the crude silver powder is filtered to obtain the crude gold powder. The crude gold powder is incorporated into the aqua regia gold purification process. The crude silver powder is melted into anode plates and incorporated into the electrolytic silver refining process.

2. The method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucibles according to claim 1, characterized in that: The ball mill fine grinding time in step (1) is 1.5 to 3 hours, and the crucible slag particle size of -0.074 mm accounts for more than 85%.

3. The method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucible according to claim 1, characterized in that: The spiral chute in step (2) is a single-head chute with a cross-sectional width of 25 to 30 cm, a lateral inclination of 9 to 12°, 5 to 8 blades, a feed rate of 200 to 300 kg / h, and a feed concentration of 15% to 25%. The interception valve adjusts the interception range according to the distribution of the concentrate and middling ore zones.

4. The method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucible according to claim 1, characterized in that: The shaking table in step (3) is a two-stage fine sand shaking table with a screen surface of 60 to 88 slots, a transverse slope of 1.5 to 3.5°, a longitudinal slope of 0.5 to 1.5°, a feed rate of 100 to 200 kg / h, a feed concentration of 25% to 35%, and a flushing water rate of 15 to 35 L / min; wherein the first-stage shaking table has a stroke of 12 to 15 mm and a stroke of 250 to 280 times / min, and the second-stage shaking table has a stroke of 8 to 12 mm and a stroke of 300 to 340 times / min.

5. The method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucible according to claim 1, characterized in that: In step (4), potassium nitrate is added according to 2% to 5% of the weight of the gold-rich slag and mixed evenly, and the mixture is spread to a thickness of 0.5 to 2.0 cm. The mixture is then roasted for 3 to 6 hours in a muffle furnace with an operating temperature of 600 to 900° C. and a furnace door opened 2 to 5 cm.

6. The method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucible according to claim 1, characterized in that: In step (5), the ash residue is mixed with a sodium hydroxide solution having a concentration of 2 to 5 mol / L at a liquid-to-solid ratio of 4:1 to 6:1, and potassium nitrate in an amount of 1.0% to 2.5% by weight of the ash residue is added as a catalyst. The mixture is introduced into an autoclave to control the total pressure in the reactor to 2.0 to 5.0 MPa, the oxygen partial pressure to 0.1 to 0.5 MPa, the reaction temperature to 140 to 180° C., and the reaction time to 1 to 2.5 h. The mixture is cooled, filtered, and washed to obtain the alkaline leached residue.

7. The method for efficiently recovering gold and silver from abandoned gold and silver smelting graphite crucibles according to claim 1, characterized in that: In step (6), the alkali leaching residue is mixed with dilute hydrochloric acid having a molar mass of 3 to 5 mol / L at a liquid-to-solid ratio of 2:1 to 5:1, the temperature is controlled at 50 to 70° C., the stirring speed is 200 to 300 r / min, the reaction time is 1 to 2 h, and the crude gold powder or the crude silver powder is obtained by suction filtration and washing.

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