Process for improving the volatilization rate of silver in acid leaching residue

Abstract

The present application relates to a kind of process for improving the volatility of silver in acid leaching residue, belong to the valuable metal recovery technical field of zinc smelting slag material, the present application includes two main steps of melting and blowing volatilization, in the blowing step, by adding high-sulfur pulverized coal, and the control of temperature and air utilization coefficient, improve the volatility of silver;The present application will be the three implementation steps of drying and dehydrating of acid leaching residue, melting and heating, blowing volatilization be completed in one fuming furnace, use the sulfur in acid leaching residue and the sulfur of high-sulfur pulverized coal as silver volatilization sulfidation agent, silver is volatilized into zinc suboxide fume, reduce the equipment investment, not additional volatilization silver sulfidation agent, and the volatility of silver can be improved to more than 80%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of valuable metal recovery of zinc smelting slag materials, and particularly relates to a volatile silver technology for smelting furnace blowing and acid leaching slag. BACKGROUND

[0002] Silver is associated in zinc concentrates, and after the boiling roasting desulfurization of the zinc concentrates, the conventional leaching of zinc and cadmium elements from the zinc calcine, the silver is enriched in the acid leaching slag.

[0003] The recovery and utilization of silver enriched in the acid leaching slag is achieved by the existing technology of ore dressing or smelting furnace volatilization.

[0004] The ore dressing method is to separate the liquid and solid of the acid leaching slurry, and then the filter residue is slurried and floated to float the silver into silver concentrate, and the slurry after silver selection is separated again, and the flotation tailings are volatilized into lead and zinc in a rotary kiln or a smelting furnace. The silver recovery rate of this method is relatively high, about 75-80%; but this method needs to separate the liquid and solid of the slurry twice, and the process is long, the facilities are many, the plant occupies a large area, and the investment and maintenance cost are high; and the organic reagent used for floating silver will enter the solution, affecting the electrowinning efficiency of zinc sulfate solution.

[0005] The smelting furnace volatilization method is to directly put the dried acid leaching slag into a smelting furnace to volatilize lead, zinc, silver and other metals into zinc suboxide dust, and the separation of silver and valuable metals and other impurities is poor, and the silver volatilization rate is only 60-70%, and the remaining silver is lost in the water-quenched slag of the smelting furnace. SUMMARY

[0006] In order to overcome the problems in the background art, the present application provides a process for improving the volatilization rate of silver in acid leaching slag, which uses a smelting furnace volatilization method to treat acid leaching slag, and the volatilization rate of silver can be increased to more than 80%, and the drying, melting and volatilization of the acid leaching slag material are completed in one smelting furnace, the equipment investment is less, the process is simple, the volatilization rate of silver can reach more than 80%, and the entire process does not need to add silver volatilization agent.

[0007] To achieve the above purpose, the present application is realized by the following technical scheme:

[0008] The process for improving the volatilization rate of silver in acid leaching slag comprises the following steps:

[0009] (1) Melting and heating

[0010] The hot air and high-sulfur pulverized coal are continuously fed from the tuyere of the smelting furnace to heat and melt the acid leaching slag in the smelting furnace;

[0011] (2) Blowing and volatilization

[0012] Continue to feed hot air and high-sulfur pulverized coal, control the air utilization coefficient to be 0.8-0.95, control the temperature in the furnace and maintain a weak reducing atmosphere, and volatilize the silver into zinc suboxide dust.

[0013] Further, the hot slag after the previous roasting is reserved in the smelting furnace as the smelting pool, and the cold acid leaching slag is fed into the smelting furnace through the metering belt, and the heat of the hot slag in the smelting pool is used to dry and dehydrate the cold acid leaching slag.

[0014] Further, after the roasting, the hot air is stopped, the high-sulfur pulverized coal is fed in, and the hot slag is discharged, and a certain amount of hot slag is reserved in the smelting pool of the fuming furnace, and the mass ratio of the discharged hot slag to the reserved hot slag is 100-125:75-100, and after the discharged hot slag is quenched by water, it is sold to a cement plant to produce slag cement.

[0015] Further, in step (1), the mass ratio of the cold acid leaching slag to the reserved hot slag in the furnace is 125-150:75-100.

[0016] Further, in step (1), the melting and heating time is 15-20 min.

[0017] Further, in step (2), the temperature in the furnace is controlled to be 1200-1300℃.

[0018] Further, in steps (1) and (2), the hot air temperature is 500-700℃.

[0019] Further, during the roasting and volatilization process, the tail gas after dust collection is treated by the ammonia acid method to obtain low-concentration sulfur dioxide gas.

[0020] Further, the high-sulfur pulverized coal used has the following components in mass percentage: C: 50-60%, V: 15-20%, A: 25-30%, and S: 0.8-1.5%.

[0021] Further, the acid leaching slag has the following main components in mass percentage: H2O: 10-20%, Pb: 2-10%, Zn: 10-20%, S: 7-10%, Fe: 18-25%, SiO2: 7-12%, and CaO: 5-8%, and the Ag content is 100-300g / t.

[0022] Further, the acid leaching slag is the cold material after the acid leaching of the zinc calcine.

[0023] The beneficial effects of the present application are as follows:

[0024] Compared with the existing fuming furnace volatilization technology, the application does not need to add silver volatilization agent, realizes silver volatilization by using acid leaching residue and high-sulfur pulverized coal, increases the silver volatilization rate to more than 80%, reduces the loss of silver into the water-quenched slag of the fuming furnace, and improves the economic benefit. The high-sulfur pulverized coal is used as a source of volatilization heat, and by controlling the air utilization coefficient, a weak reducing atmosphere required for silver volatilization is provided for the fuming furnace. The sulfur in the high-sulfur pulverized coal is effectively utilized as a silver volatilization agent. The entire volatilization process does not need to add additional silver volatilization agent, and the silver volatilization can be realized. Compared with the existing fuming furnace silver volatilization technology, the silver volatilization rate can be increased by 10-25%.

[0025] The application can obtain a high silver recovery rate without silver flotation of the acid leaching residue, saves one-time investment of the acid leaching slurry filtration plant and filtration facilities, reduces the maintenance cost, avoids the introduction of organic reagents for silver flotation into zinc electrowinning, improves the current efficiency of zinc electrowinning, and reduces the production cost of zinc electrowinning.

[0026] The application does not need an additional acid leaching residue drying process, and the drying and dehydration, melting, and volatilization of the acid leaching residue are completed in one fuming furnace. The volatilization of valuable metals and silver is carried out synchronously, and the efficient volatilization of silver is completed in one fuming furnace. The device investment is small, and the process is simple. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and beneficial effects of the application clearer, the technical scheme of the application will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments of the application, other embodiments obtained by those skilled in the art without creative labor also belong to the protection scope of the application.

[0028] The process for improving the silver volatilization rate of the acid leaching residue includes the following steps:

[0029] (1) Dry the cold acid leaching residue in the furnace

[0030] Taking a fuming furnace with a treatment capacity of 30 t / furnace as an example, 20-25 t of hot molten slag from the previous furnace is discharged, 15-20 t of hot molten slag from the previous furnace is reserved in the fuming furnace, and 25-30 t of cold acid leaching residue is metered and added. During the addition of the cold acid leaching residue, the heat of the hot molten slag from the previous furnace completes the drying and dehydration of the cold acid leaching residue.

[0031] The cold acid leaching residue is the leaching residue of the zinc calcine after acid leaching. The main components of the acid leaching residue are H2O 10-20%, Pb 2-10%, Zn 10-20%, S 7-10%, Fe 18-25%, SiO2 7-12%, and CaO 5-8% by mass percentage. The Ag content is 100-300 g / t.

[0032] (2) Melting and heating

[0033] The hot air and high-sulfur pulverized coal are continuously fed from the tuyere of the roaster, and the acid leaching residue in the roaster is heated and melted, and the heating and melting time is 15-20 min.

[0034] (3) Blowing volatilization

[0035] The hot air and high-sulfur pulverized coal are continuously fed, the air utilization coefficient is controlled to be 0.8-0.95, the temperature in the furnace is controlled to be 1200-1300 DEG C and a weak reducing atmosphere is maintained, the silver is volatilized in the form of Ag2S in the early stage of blowing by using the sulfate in the acid leaching residue, the amount of high-sulfur pulverized coal is increased in the middle and late stages of the reaction, and the amount of hot air is adjusted to make the air utilization coefficient continue to be 0.8-0.95, the silver is continuously volatilized in the form of Ag2S by using the sulfur in the high-sulfur pulverized coal, in the middle and late stages of the reaction, the sulfate in the acid leaching residue is basically completely volatilized, if the amount of high-sulfur pulverized coal is not increased, the silver volatilization rate will be reduced, the applicant has verified through a large number of experiments that if the amount of high-sulfur pulverized coal is not increased in the middle and late stages, the silver volatilization rate will be reduced by about 7%. At the same time of silver volatilization, lead and zinc in the acid leaching residue are also volatilized synchronously. The volatilized Pb and Zn steam is oxidized in the upper part of the roaster by relying on the air supply of the third tuyere. After being collected by the waste heat boiler, the surface cooler and the bag dust collector, silver-containing secondary zinc oxide dust is obtained, and the tail gas after dust collection is treated by the ammonia acid method to obtain low-concentration sulfur dioxide gas.

[0036] The temperature and reducing atmosphere in the furnace are controlled by adjusting the size of the air utilization coefficient (actual air consumption oxygen amount / theoretical air consumption oxygen amount). The larger the air utilization coefficient value, the more complete the pulverized coal combustion, and the higher the temperature in the furnace. However, after the value is increased, the CO2 partial pressure is increased, the CO concentration is reduced, and the reducing ability is weakened. When the air utilization coefficient value is small, the fuel heat effect is reduced, the temperature in the furnace is reduced, but the CO concentration in the furnace is increased, and the reducing ability is enhanced. Therefore, the air utilization coefficient is controlled to be 0.8-0.95, and the high temperature and weak reduction conditions in the roaster are maintained.

[0037] The sulfate in the acid leaching residue is decomposed by heat to release sulfur dioxide gas, and at high temperature and in the presence of carbonaceous reducing agent, elemental sulfur is generated, and the reaction formula is as follows:

[0038] C + SO2 = CO + 1 / 2 S2 (1)

[0039] 4C + 2SO2 = 4CO + S2 (2)

[0040] When the molten slag and the furnace gas contain elemental sulfur, the silver will react with sulfur to generate Ag2S, and the chemical reaction equation is:

[0041] 4Ag + S2 = 2Ag2S (3)

[0042] The standard Gibbs free energy of reaction (3) is △G°=-187400+79.5T (298-1115K), and the Gibbs free energy of the reaction is -98.758kJ at 1115K (842℃), which is a larger negative value, indicating that the reaction is easy to proceed. At the working temperature of 1200-1300℃, the vapor pressure of Ag2S is increased, which provides good conditions for the volatilization of silver.

[0043] In the early stage of volatilization, the sulfates in the acid leaching residue are mainly relied on, and in the middle and late stages of volatilization, the S in the high-sulfur pulverized coal is mainly relied on to produce elemental sulfur. As long as the sulfidation agent for producing elemental sulfur continuously exists, the silver can maintain a high volatilization rate.

[0044] The high-sulfur pulverized coal has a composition of C (carbon content): 50-60%, V (volatile matter): 15-20%, A (ash content): 25-30%, and S (sulfur content): 0.8-1.5% by mass percentage.

[0045] The A (i.e. ash content) in the composition of the high-sulfur pulverized coal is mainly SiO2, and the ash obtained after the combustion of the high-sulfur pulverized coal adjusts the proportion of Fe, SiO2 and CaO in the acid leaching residue, without the need for additional addition of a slagging agent.

[0046] The S in the high-sulfur pulverized coal enables the silver to continue to volatilize into the fumes in the middle and late stages of the blowing, thereby improving the volatilization rate of the silver.

[0047] (4) Slag discharging

[0048] After the blowing is completed, the hot air and the pulverized coal are stopped, and 20-25t of hot molten slag is discharged, and 15-20t of hot molten slag is left in the smelting pool of the fuming furnace. After the discharged hot molten slag is quenched by water, it is sold to a cement plant for the production of slag cement.

[0049] In steps (2) and (3), the temperature of the hot air is 500-700℃.

[0050] In order to more clearly illustrate the present application, the following examples are used for detailed description. Example 1

[0051] The acid leaching residue used in this example has a composition (wt%) of H2O 19.63, Pb 9.08, Zn 15.36, Ag 109g / t, S 7.32, Fe 18.46, SiO2 11.25, and CaO 7.83; and the high-sulfur pulverized coal has a composition (wt%) of C 59.13, V 15.10, A 29.15, and S 0.86.

[0052] The hot slag of 15 tons after the end of the previous blowing is reserved in the smelting pool of the fuming furnace as the smelting pool, the cold acid leaching slag of 25 tons is fed in through the metering belt, the feeding belt is stopped after the end of feeding; the hot air and high-sulfur pulverized coal are continuously fed in from the tuyere to melt the acid leaching slag, the temperature of the hot air is 500 DEG C, the amount of the high-sulfur pulverized coal is 2 tons per hour, the acid leaching slag is melted and heated to 1150 DEG C, the melting and heating time is 15 minutes; the high-sulfur pulverized coal of 2 tons per hour is continuously fed in during the blowing and volatilization, the hot air is continuously fed in, the air utilization coefficient is controlled to be 0.8, the temperature in the furnace is controlled to be 1250 DEG C and a weak reducing atmosphere is maintained, the amount of the high-sulfur pulverized coal is adjusted to be 4 tons per hour in the middle and late stages of the reaction, and the amount of the hot air is increased to continuously maintain the air utilization coefficient to be 0.8; after the end of the blowing, the feeding of the hot air and the pulverized coal is stopped, the hot slag of 20 tons is discharged, the hot slag of 15 tons is reserved in the smelting pool of the fuming furnace, after the discharged hot slag is water quenched, it is sold to a cement plant to produce slag cement. The water quenched slag contains Ag 25 g / t, lead 0.04%, and zinc 0.85%, the volatilization rate of silver is 81.65% based on the water quenched slag, the volatilization rate of lead is 99.65%, and the volatilization rate of zinc is 95.57%.

[0053] Comparative Example 1 (reducing volatilization temperature)

[0054] The raw materials and treatment process of the present comparative example are the same as those of Example 1, the difference lies in that the volatilization temperature is reduced, the process control of the present comparative example is as follows:

[0055] The hot slag of 15 tons after the end of the previous blowing is reserved in the smelting pool of the fuming furnace as the smelting pool, the cold acid leaching slag of 25 tons is fed in through the metering belt, the feeding belt is stopped after the end of feeding; the hot air and high-sulfur pulverized coal are continuously fed in from the tuyere to melt the acid leaching slag, the temperature of the hot air is 500 DEG C, the amount of the high-sulfur pulverized coal is 2 tons per hour, the acid leaching slag is melted and heated to 1150 DEG C, the melting and heating time is 15 minutes; the high-sulfur pulverized coal of 2 tons per hour is continuously fed in during the blowing and volatilization, the hot air is continuously fed in, the air utilization coefficient is controlled to be 0.8, the temperature in the furnace is controlled to be 1250 DEG C and a weak reducing atmosphere is maintained, the amount of the high-sulfur pulverized coal is adjusted to be 4 tons per hour in the middle and late stages of the reaction, and the amount of the hot air is increased to continuously maintain the air utilization coefficient to be 0.8; after the end of the blowing, the feeding of the hot air and the pulverized coal is stopped, the hot slag of 20 tons is discharged, the hot slag of 15 tons is reserved in the smelting pool of the fuming furnace, after the discharged hot slag is water quenched, it is sold to a cement plant to produce slag cement. The water quenched slag contains Ag 25 g / t, lead 0.04%, and zinc 0.85%, the volatilization rate of silver is 81.65% based on the water quenched slag, the volatilization rate of lead is 99.65%, and the volatilization rate of zinc is 95.57%. Example 2

[0056] The acid leaching residue used in this example has the following composition (%wt): H2O 10.52, Pb 2.39, Zn 19.86, Ag 296 g / t, S 9.89, Fe 24.92, SiO2 7.06, CaO 5.86; the high-sulfur pulverized coal has the following composition (%wt): C 51.63, V 18.94, A 28.69, S 1.42.

[0057] The hot smelting residue 20 t left in the smelting pool of the fuming furnace after the end of the blowing of the upper furnace is used as the smelting pool, the cold acid leaching residue 30 t is fed into the smelting pool through a metering belt, the feeding belt is stopped after the end of feeding; the hot air and the high-sulfur pulverized coal are continuously fed into the tuyere, the temperature of the hot air is 700 ℃, the amount of the high-sulfur pulverized coal is 2 t / h, the acid leaching residue is melted and heated to 1150 ℃, the melting and heating time is 20 min; the high-sulfur pulverized coal 2 t / h is continuously fed in during the blowing and volatilization, the hot air is continuously fed in, the air utilization coefficient is controlled to be 0.95, the temperature in the furnace is controlled to be 1300 ℃ and a weak reducing atmosphere is maintained, the amount of the high-sulfur pulverized coal is adjusted to be 4 t / h in the middle and late stages of the reaction, and the amount of the hot air is increased to continuously maintain the air utilization coefficient to be 0.95; after the end of the blowing, the feeding of the hot air and the pulverized coal is stopped, 25 t of hot smelting residue is discharged, 20 t of hot smelting residue is left in the smelting pool of the fuming furnace, after the discharged hot smelting residue is water quenched, it is sold to a cement plant to produce slag cement. The water quenched slag contains Ag 52 g / t, Pb 0.03%, and Zn 1.02%, the volatilization rate of silver is 85.94%%, the volatilization rate of lead is 98.99%, and the volatilization rate of zinc is 95.89% based on the water quenched slag.

[0058] Comparative Example 2 (increasing the air utilization coefficient)

[0059] The raw materials and the process used in this comparative example are the same as those in Example 2, the difference is that the air utilization coefficient is increased to 1.05 during the blowing and volatilization, and the specific process is as follows:

[0060] The hot slag of 20 tons left in the smelting pool of the fuming furnace after the end of the blowing of the upper furnace is used as the smelting pool, the cold acid leaching slag of 30 tons is fed into the smelting pool through a metering belt, the feeding belt is stopped after the feeding is completed; the hot air and high-sulphur pulverized coal are continuously fed into the tuyere, the temperature of the hot air is 700°C, the amount of the high-sulphur pulverized coal is 2 tons per hour, the acid leaching slag is melted and heated to 1150°C, the melting and heating time is 20 minutes; the blowing and volatilization is continued while the high-sulphur pulverized coal of 2 tons per hour is continuously fed in, the hot air is continuously fed in, the air utilization coefficient is controlled to be 1.05, the temperature in the furnace is controlled to be 1300°C and a weak reducing atmosphere is maintained, the amount of the high-sulphur pulverized coal is adjusted to be 4 tons per hour in the middle and late stages of the reaction, and the amount of the hot air is increased to continuously maintain the air utilization coefficient to be 1.05; after the end of the blowing, the feeding of the hot air and the pulverized coal is stopped, the hot slag of 25 tons is discharged, the hot slag of 20 tons is left in the smelting pool of the fuming furnace, after the discharged hot slag is quenched with water, it is sold to a cement plant to produce slag cement. The quenched slag contains Ag 116 g / t, lead 0.03%, and zinc 2.84%, the volatilization rate of silver is 68.65% based on the quenched slag, the volatilization rate of lead is 98.99%, and the volatilization rate of zinc is 88.56%. It can be seen that when the air utilization coefficient is increased, the volatilization rate of lead is not affected, but the volatilization rates of silver and zinc are reduced, which greatly affects the volatilization rates of silver and zinc.

[0061] When the air utilization coefficient is 1.05, the atmosphere in the furnace is weakly oxidizing, which reduces the generation of elemental sulphur in the middle and late stages of the blowing, thereby affecting the volatilization of silver; the volatilization of zinc also requires a reducing atmosphere, and when the air utilization coefficient is 1.05, the volatilization of zinc is also affected.

[0062] Comparative Example 3 (using low-S pulverized coal)

[0063] The raw materials and processes used in the present comparative example are the same as those in Example 2, except that low-S pulverized coal is used, the composition of the pulverized coal is (%wt): C 58.78, V 16.49, A 26.76, and S 0.19.

[0064] The hot slag of 20 tons left in the smelting pool of the fuming furnace after the end of the blowing of the upper furnace is used as the smelting pool, the cold acid leaching slag of 30 tons is fed into the smelting pool through a metering belt, the feeding belt is stopped after the end of the feeding; the hot air and the low-S-containing pulverized coal are continuously fed into the tuyere, the temperature of the hot air is 700℃, the amount of the low-S-containing pulverized coal is 2 tons per hour, the acid leaching slag is melted and heated to 1150℃, the melting and heating time is 20 minutes; the low-S-containing pulverized coal of 2 tons per hour is continuously fed in during the blowing and volatilization, the hot air is continuously fed in, the air utilization coefficient is controlled to be 0.95, the temperature in the furnace is controlled to be 1300℃ and a weak reducing atmosphere is maintained, the amount of the low-S-containing pulverized coal is adjusted to be 4 tons per hour in the middle and late stages of the reaction, and the amount of the hot air is increased to continuously maintain the air utilization coefficient to be 0.95; after the end of the blowing, the feeding of the hot air and the pulverized coal is stopped, the hot slag of 25 tons is discharged, the hot slag of 20 tons is left in the smelting pool of the fuming furnace, after the discharged hot slag is quenched with water, it is sold to a cement plant to produce slag cement. The quenched slag contains Ag of 106 g / t, lead of 0.03%, and zinc of 0.97%, the volatilization rate of silver is 71.35% based on the quenched slag, the volatilization rate of lead is 98.99%, and the volatilization rate of zinc is 96.09%. It can be seen that when the low-S-containing pulverized coal is used, the volatilization rates of lead and zinc are not affected, but the amount of the generated elemental sulfur in the middle and late stages of the blowing is insufficient, thereby affecting the volatilization rate of silver and reducing the volatilization rate of silver.

[0065] Finally, it should be pointed out that the above preferred embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application, although the present application has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present application.

Claims

1. A process for improving the volatilization rate of silver in acid leach residue, characterized by, The method comprises the following steps: (1) Melting and heating Hot air and high-sulfur pulverized coal are continuously fed from the tuyere of the roaster to heat and melt the acid leaching residue in the roaster; (2) Blowing and volatilizing The feeding of hot air and high-sulfur pulverized coal is continued, the air utilization coefficient is controlled to be 0.8-0.95, the temperature in the roaster is controlled and a weak reducing atmosphere is maintained, and silver is volatilized into secondary zinc oxide dust; the feeding amount of high-sulfur pulverized coal is increased in the middle and later stages of blowing and volatilizing; The high-sulfur pulverized coal contains S: 0.8-1.5% by mass percentage; the hot air temperature in steps (1) and (2) is 500-700℃.

2. The process for improving the volatilization rate of silver in acid leach residue according to claim 1, characterized by, The hot molten slag after the end of blowing in the last roaster is reserved in the molten pool of the roaster, cold acid leaching residue is fed by a metering belt in each roaster, and the heat of the hot molten slag passing through the molten pool is used to dry and dehydrate the cold acid leaching residue during the feeding process.

3. The process for improving the volatilization rate of silver in acid leach residue according to claim 1 or 2, characterized by, After the blowing is completed, the feeding of hot air and high-sulfur pulverized coal is stopped, the hot molten slag is discharged, the hot molten slag is reserved in the molten pool of the roaster, and the mass ratio of the discharged hot molten slag to the reserved hot molten slag is 100-125:75-100.

4. The process for improving the volatilization rate of silver in acid leaching residue according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the cold acid leaching residue added in each roaster to the reserved hot molten slag in the roaster is 125-150:75-100.

5. The process for improving the volatilization rate of silver in acid leached residue according to claim 1, characterized by, In step (1), the melting and heating time is 15-20 min.

6. The process for improving the volatilization rate of silver in acid leached slag as claimed in claim 1 wherein, In step (2), the temperature in the roaster is controlled to be 1200-1300℃.

7. The process of improving silver volatility in acid leach residue according to claim 2, characterized by, The acid leaching residue is the leaching residue of a zinc calcine after acid leaching.