A method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag

Abstract

The present invention belongs to the technical field of smelting solid waste material treatment, and specifically relates to a method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag. Specifically, it comprises the following steps: the smelting slag is first treated with microwave activation, and then mixed with a reducing agent and an additive in proportion and fed into a batching area, and then fed into a chain plate for drying; the dried material is fed into a high-temperature roasting, and valuable metals such as zinc and indium are reduced and volatilized into the flue gas; a bag filter collects valuable metal oxides such as zinc and indium volatilized in the flue gas; and sulfur-containing flue gas is discharged by waste heat utilization and desulfurization to meet emission standards. This method improves the activity of valuable metals such as valuable zinc and indium in hazardous waste slag through microwave activation, has a high recovery rate of valuable metals, and realizes the resource utilization of solid hazardous waste slag.

Description

Technical Field

[0001] The invention relates to the technical field of smelting solid waste material treatment, in particular to a method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag. Background Art

[0002] Zinc smelting mixed hazardous waste slag contains rich metal resources. If it is abandoned, it will cause a waste of valuable metal resources, which is not conducive to the comprehensive recycling of resources. The existing methods for recovering valuable metals from zinc smelting hazardous waste slag mainly include wet leaching, flotation and pyrometallurgy. Wet leaching is mainly divided into acid leaching and alkaline leaching. Although the leaching rate is high, the production cycle of the process is long, and the leached wastewater is difficult to treat, and the equipment is easily corroded. Flotation can be used to recover precious metals such as gold and silver from zinc smelting hazardous waste slag, but it cannot effectively recover valuable metals such as zinc and indium from smelting slag. During pyrometallurgical treatment, valuable metals volatilize into the flue gas in the form of metal oxides. The recovered smoke can be used for subsequent smelting. However, due to the complex composition of hazardous waste slag, in order to make zinc volatilize into the flue gas as much as possible, the use of coke is large, the energy consumption is high, and the enterprise cost is high. Therefore, it is of great significance to find a method that can both reduce the production cost of the enterprise and improve the recovery rate of valuable metals in smelting slag. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag, so as to solve the problems of high disposal cost, insufficient reaction and the like caused by the zinc smelting process.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme, a method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag, the main chemical composition and mass percentage of the mineral raw material hazardous waste slag are: Zn 4.32% ~ 5.67%, In0.056% ~ 0.10%, Fe 3.52% ~ 4.27%, water 23.60% ~ 26.47%, the specific steps are as follows:

[0005] (1) Place the hazardous waste residue in a microwave oven and heat it for activation. The microwave frequency is 4 GHz, the heating temperature is 200°C to 500°C, and the holding time is 3 to 5 minutes;

[0006] (2) The activated hazardous waste residue is mixed in the ratio of hazardous waste residue: reducing agent: additive = 10:2.5-3.5:1 and then sent to the batching area, and then sent to the chain plate for drying through the feeding device;

[0007] (3) The dried material is placed in a rotary kiln and roasted at a temperature of 1050-1100°C for 2-3 hours. The zinc and indium in the mixed slag are reduced and volatilized into the flue gas. The rotary kiln flue gas volume is 48495.7-49595.1Nm 3 / h, the outlet flue gas temperature is 650℃~750℃;

[0008] (4) The valuable metals such as zinc and indium volatilized in the flue gas enter the smoke in the form of metal oxides and are collected by bag filters for comprehensive recovery;

[0009] (5) Sulfur-containing flue gas is discharged after waste heat utilization, desulfurization and demisting.

[0010] In the step (2), the reducing agent is a mixture of anthracite and coke, and the mixing ratio is 1:0.2-0.3.

[0011] The additive in step (2) is active lime.

[0012] The main chemical components and mass percentages of the kiln slag in step (3) are: Zn 0.10%-0.25%, In 0.012%-0.018%, Fe 15.10%-25.72%, CaO 10.99%-13.65% and SiO2 12.94%-13.42%.

[0013] The flue gas outlet temperature of the settling chamber in step (3) is 550°C to 600°C.

[0014] The main chemical components and mass percentages of the smoke in step (4) are Zn 50.96% to 55.89% and In 0.34% to 0.38%.

[0015] The step (5) adopts a wet desulfurization process, and the material used is gypsum.

[0016] The beneficial effects of the present invention are:

[0017] 1. By finely grinding the zinc smelting hazardous waste slag, heating it up and storing it in a microwave environment, the zinc and iron compounds in the zinc smelting hazardous waste slag are quickly heated, and the iron-zinc compounds that are difficult to volatilize and dissolve are quickly converted into volatile iron oxides and zinc oxides. The iron oxides and zinc oxides can absorb microwaves, which is beneficial to subsequent oxidation roasting.

[0018] 2. By finely grinding the zinc smelting hazardous waste slag and then treating it with microwaves, more cracks can be formed on the surface of the material under the microwave field, increasing the contact with the air during the subsequent roasting process and improving the roasting efficiency.

[0019] 3. The melting point of SiO2 in zinc smelting hazardous waste slag is 1713℃, but the temperature in the rotary kiln cannot melt SiO2, resulting in poor slag activity. Active lime is added as a regulator. Active lime can combine with SiO2 to form a low melting point (<1200℃) compound, which is sufficient to melt in the blast furnace to form slag with good fluidity, which is convenient for subsequent cleaning.

[0020] 4. The use of anthracite and coke for synergistic roasting fully utilizes the characteristics of coal's fast reaction speed, low cost, good coke permeability, more complete combustion during coal-coke synergistic roasting, and uniform temperature in the furnace. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described in detail below in conjunction with the embodiments. It is obvious that the embodiments described in the present invention are only a part of the embodiments. Based on the embodiments of the present invention, the embodiments obtained by those skilled in the art without creative work all belong to the protection scope of the present invention.

[0022] Example 1

[0023] This embodiment is an example of the method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag. The main chemical components and mass percentages of the zinc smelting hazardous waste slag are: Zn 4.32%, In 0.056%, and the processing capacity is 250t / d. The method comprises the following steps:

[0024] (1) Place the hazardous waste residue in a microwave oven and heat it for activation. The microwave frequency is 4 GHz, the heating temperature is 200°C, and the holding time is 3 min;

[0025] (2) The activated hazardous waste residue: reducing agent: active lime is mixed in a ratio of 10:2.5:1 and sent to the batching area, and then sent to the chain plate for drying through the feeding device. The mixture of anthracite and coke has a mixing ratio of 1:0.2;

[0026] (3) The dried material is placed in a rotary kiln for high-temperature roasting at a temperature of 1050-1100°C for 2 hours. The zinc and indium in the mixed slag are reduced and volatilized into the flue gas;

[0027] (4) Valuable metals such as zinc and indium volatilized in the flue gas enter the smoke in the form of metal oxides and are collected by bag filters for comprehensive recovery;

[0028] (5) Sulfur-containing flue gas is discharged after waste heat utilization, desulfurization and demisting;

[0029] Using the above test method, the product contains 51.29% Zn, 20t / d of output, and 94.98% recovery rate; 0.34% In, 37t / d of output, and 89.86% recovery rate.

[0030] Example 2

[0031] This embodiment is another example of the method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag. The main chemical components and mass percentages of the zinc smelting hazardous waste slag are: Zn 5.07%, In 0.093%, and the processing capacity is 280t / d; the method comprises the following steps:

[0032] (1) Place the hazardous waste residue in a microwave oven and heat it for activation. The microwave frequency is 4 GHz, the heating temperature is 350°C, and the holding time is 4 min.

[0033] (2) The activated hazardous waste residue: reducing agent: active lime = 10:3:1 is mixed and sent to the batching area, and then sent to the chain plate for drying through the feeding device. The mixture of anthracite and coke has a mixing ratio of 1:0.3;

[0034] (3) The dried material is placed in a rotary kiln for high-temperature roasting at a temperature of 1050-1100°C for 2.5 hours. The zinc and indium in the mixed slag are reduced and volatilized into the flue gas;

[0035] (4) Valuable metals such as zinc and indium volatilized in the flue gas enter the smoke in the form of metal oxides and are collected by bag filters for comprehensive recovery;

[0036] (5) Sulfur-containing flue gas is discharged after waste heat utilization, desulfurization and demisting.

[0037] By using the above test method, the product contains 54.23% Zn, 25t / d of output, and 95.50% of recovery rate; and 0.33% In, 70t / d of output, and 88.71% of recovery rate.

[0038] Example 3

[0039] This embodiment is another example of the method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag. The main chemical components and mass percentages of zinc smelting hazardous waste slag are: Zn 5.67%, In 0.010%, and the processing capacity is 300t / d. The method comprises the following steps:

[0040] (1) Place the hazardous waste residue in a microwave oven and heat it for activation. The microwave frequency is 4 GHz, the heating temperature is 500°C, and the holding time is 5 min;

[0041] (2) The activated hazardous waste residue: reducing agent: active lime = 10:3.5:1 is mixed and sent to the batching area, and then sent to the chain plate for drying through the feeding device. The mixture of anthracite and coke has a mixing ratio of 1:0.3;

[0042] (3) The dried material is placed in a rotary kiln for high-temperature roasting at a temperature of 1050-1100°C for 3 hours. The zinc and indium in the mixed slag are reduced and volatilized into the flue gas;

[0043] (4) Valuable metals such as zinc and indium volatilized in the flue gas enter the smoke in the form of metal oxides and are collected by bag filters for comprehensive recovery;

[0044] (5) Sulfur-containing flue gas is discharged after waste heat utilization, desulfurization and demisting.

[0045] By using the above test method, the product contains 55.89% Zn, 28t / d of output, and 92.00% of recovery rate; and 0.37% In, 7t / d of output, and 86.33% of recovery rate.

[0046] Comparative Example 1

[0047] This embodiment is a comparative example of the method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag described in the present invention. The difference between the comparative example and Examples 1, 2, and 3 is that microwave activation treatment is not used. The main chemical components and mass percentages of zinc smelting hazardous waste slag are: Zn 5.34%, In 0.085%, and the processing capacity is 290t / d; the following steps are included:

[0048] (1) Mix the waste slag and char in a weight ratio of 5:2 and send them to the batching area, and then send them to the chain plate for drying through the feeding device. The anthracite particle size of 3 to 6 mm accounts for 75%;

[0049] (2) After drying, the material is placed in a rotary kiln and calcined at a temperature of 1070°C to 1100°C. The zinc and indium valuable metals in the mixed slag are reduced and volatilized into the flue gas and separated. The amount of flue gas in the rotary kiln is 48670.7Nm 3 / h, the main chemical components and mass percentages of the slag are: Zn 0.11%, In 0.018%, Fe 20.08%, CaO 13.54% and SiO212.56%;

[0050] (3) The valuable metals such as zinc, lead, cadmium and indium volatilized in the flue gas enter the smoke dust in the form of metal oxides, and are collected by bag filter after cooling in the settling chamber. The flue gas outlet temperature of the settling chamber is 550℃~580℃. The main chemical components and mass percentages in the smoke dust are Zn and In.

[0051] (4) The gypsum produced by waste heat utilization, desulfurization and desulfurization of sulfur-containing flue gas meets the requirements of "Flue Gas Desulfurization Gypsum" GB / T37785-2019 and is sold externally. The desulfurized flue gas meets the emission standards of GB 25466-2016.

[0052] By using the above test method, the product contains 50.96% Zn, 24t / d of output, and 78.98% of recovery rate; and 0.38% In, 50t / d of output, and 77.07% of recovery rate.

[0053] It can be seen from the comparative test results that after microwave activation treatment, the zinc recovery rate is higher than 92.00%, the indium recovery rate is as high as 89.86%, and the recovery rate of hazardous waste slag without microwave activation treatment is only 78.98%, and the recovery rate of valuable metals is improved.

Claims

1. A method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag, characterized in that: The main chemical components and mass percentages of the zinc smelting hazardous waste slag are: Zn 4.32% to 5.67%, In 0.056% to 0.10%, Fe 3.52% to 4.27%, and water 23.60% to 26.47%. The specific steps are as follows: (1) Place the hazardous waste residue in a microwave oven and heat it for activation. The microwave frequency is 4 GHz, the heating temperature is 200°C to 500°C, and the holding time is 3 to 5 minutes; (2) The activated hazardous waste residue is mixed in the ratio of hazardous waste residue: reducing agent: additive = 10:2.5-3.5:1 and then sent to the batching area, and then sent to the chain plate for drying through the feeding device; (3) The dried material is placed in a rotary kiln and roasted at a temperature of 1050-1100°C for 2-3 hours. The zinc and indium in the mixed slag are reduced and volatilized into the flue gas. The rotary kiln flue gas volume is 48495.7-49595.1Nm 3 / h, the outlet flue gas temperature is 650℃~750℃; (4) The valuable metals such as zinc and indium volatilized in the flue gas enter the smoke in the form of metal oxides and are collected by bag filters for comprehensive recovery; (5) Sulfur-containing flue gas is discharged after waste heat utilization, desulfurization and demisting.

2. A method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag according to claim 1, characterized in that: In the step (2), the reducing agent is a mixture of anthracite and coke, and the mixing ratio is 1:0.2-0.

3.

3. The method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag according to claim 1, characterized in that: The additive in step (2) is active lime.

4. The method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag according to claim 1, characterized in that: The main chemical components and mass percentages of the kiln slag in step (3) are: Zn 0.10%-0.25%, In 0.012%-0.018%, Fe 15.10%-25.72%, CaO 10.99%-13.65% and SiO2 12.94%-13.42%.

5. The method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag according to claim 1, characterized in that: The flue gas outlet temperature of the settling chamber in step (3) is 550°C to 600°C.

6. A method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag according to claim 1, characterized in that: The main chemical components and mass percentages of the smoke in step (4) are Zn 50.96% to 55.89% and In 0.34% to 0.38%.

7. The method for improving the recovery rate of valuable metals in zinc smelting hazardous waste slag according to claim 1, characterized in that: The step (5) adopts a wet desulfurization process, and the material used is gypsum.