A harmless resource utilization method of suspending roasting sulfur-containing cyanide tailings

Abstract

A harmless resource utilization method of suspending roasting sulfur-containing cyanide tailings belongs to the field of safe disposal of hazardous waste. The two-stage roasting method is adopted, the reaction conditions such as roasting atmosphere, temperature and holding time in the suspending roasting process are adjusted, and the sintered tile meeting GB / T21149-2019 ''Sintered Tile'' is obtained. The removal of toxic cyanide is realized, and the solidification of sulfide and heavy metal is realized, wherein the removal rate of cyanide and the solidification rate of heavy metal are all more than 99%, and the sulfur solidification rate is more than 90%. The method can realize the harmless and resource disposal and utilization of cyanide tailings in one step, and has the advantages of environmental protection, economy and social benefits.

Description

Technical Field

[0001] This invention belongs to the field of safe disposal of hazardous waste, specifically relating to a method for the harmless resource utilization of sulfur-cyanide tailings from suspension roasting. Background Technology

[0002] Cyanide slag is a solid waste product resulting from gold extraction. Because the gold grade is only at the g / t level, the yield of cyanide slag is 100%. Due to the presence of toxic and harmful substances, including cyanide ions, thiocyanate ions, copper cyanide complexes, iron cyanide complexes, zinc cyanide complexes, and other cyanides, as well as heavy metals, cyanide slag was classified as hazardous waste on August 1, 2016. Furthermore, under the increasing global environmental awareness and the pressure of resource scarcity, research on the resource utilization of cyanide slag is an urgent need for sustainable development.

[0003] Existing literature reveals that current secondary resource utilization of cyanide tailings mainly focuses on the secondary extraction of gold and silver, flotation recovery of sulfides, and degradation of cyanides. However, these methods generally result in the generation of secondary tailings and pollution, failing to achieve direct, harmless resource disposal of cyanide tailings. Cyanide tailings sintered tiles represent a potential resource utilization pathway. During the roasting process, cyanides in the cyanide tailings can be decomposed at high temperatures, thereby reducing environmental risks. Furthermore, during the tile manufacturing process, metal elements in the cyanide tailings can be solidified within the tile body, enabling the recovery and utilization of metal resources. However, this method still requires overcoming technical challenges related to tile body strength, cyanide and sulfide emissions, and feasibility verification in industrial applications.

[0004] Patent CN112608133A provides a method for the harmless resource utilization of cyanide gold extraction tailings. The method involves mixing gold tailings, Laiyang clay, refractory clay, calcined talc, calcite, dolomite, charred gemstone, bauxite, diopside, and potassium-sodium feldspar in a specific ratio to form a batch. The batch, along with 0.25-0.35% sodium tripolyphosphate and 0.8-1 times the weight of water, are added to a ball mill and ground until the residue on a 250-mesh sieve is below 0.5%. The slurry is then spray-dried, granulated, powdered, and pressed into brick blanks. These brick blanks are then fired at 1100-1120℃ for 90-105 minutes. This method does not consider the secondary pollution caused by SO2 generation during the roasting of sulfur-containing cyanide tailings.

[0005] Patent CN116371890A provides a method for the resource utilization and harmless treatment of gold cyanide tailings. The method involves feeding the dehydrated cyanide tailings into a suspension furnace for preheating, dehydration, and oxidative roasting to obtain decyanated tailings. The decyanated tailings are then cooled and smelted in an electric furnace into slag and pig iron. This method only achieves the removal of cyanide and pretreatment of the cyanide slag. A secondary roasting or smelting of the product is required, resulting in high costs and a still relatively large amount of tailings, thus failing to effectively achieve the goal of resource utilization of the cyanide tailings. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of secondary pollution and insufficient resource utilization during the disposal of cyanide tailings, and to provide a method for the harmless resource utilization of sulfur-containing cyanide tailings by suspension roasting. This method utilizes two-stage roasting to degrade cyanide and suppress SO2 generation, while simultaneously producing qualified sintered tiles that meet the standards of GB / T21149-2019 "Sintered Tiles", thus achieving the harmless resource utilization of cyanide tailings.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for the harmless resource utilization of sulfur-containing cyanide tailings from suspension roasting includes the following steps:

[0009] 1. After uniformly mixing the sulfur-containing cyanide tailings with Laiyang clay, spray-drying, granulating, grinding, and pressing the mixture to obtain sintered billets, which are then fed into a suspension roasting oxidation furnace system. The amount of Laiyang clay added is ≤ 15% of the mass of the sulfur-containing cyanide tailings.

[0010] 2. After setting the atmosphere, calcination temperature, heating rate and holding time of the suspension calcination oxidation system, the sintered billet is sintered in the suspension calcination oxidation furnace using a two-stage calcination method; wherein, the system atmosphere is one or a mixture of water vapor and air; the calcination temperature is 280-1180℃; the heating rate is 3-15℃ / min; and the holding time is 0-60min.

[0011] 3. Press the suspended calcined billet into shape to obtain sintered tiles with a water absorption rate of 2-5% and a flexural strength of 28-58MPa, which meet the product quality requirements of GB / T21149-2019 "Sintered Tiles".

[0012] In step 1, the sulfur-containing cyanide tailings include one or more of the following: gold concentrate cyanide tailings produced in gold smelting, pretreated cyanide tailings, whole sludge cyanide tailings, and high-silica tailings after flotation of gold concentrate cyanide tailings; the main elements include Si, S, Fe, Pb, Zn, Cu, K, Na, Ca, Al, Mg, Mn, Ti, As, Cd, Ni, C, and N; wherein the sulfur content accounts for 0.1%-25% of the mass of the cyanide tailings, the total cyanide content is 80-5000 mg / kg, and the total heavy metal content is 5-30 g / kg.

[0013] In step 1, the moisture content of the sulfur-containing cyanide tailings is ≤17%, and the particle size is ≤250μm.

[0014] In step 1, the cyanide-containing substances in the thiocyanate tailings include free cyanide, thiocyanate, ferric cyanide complex, copper cyanide complex, zinc cyanide complex, and lead cyanide complex.

[0015] In step 2, the first stage of roasting is a mixture of water vapor and air, with a water vapor concentration of 5-35%, a roasting temperature of 280-450℃, a heating rate of 3-15℃ / min, and a holding time of 0-3min; the second stage of roasting is in air, with a roasting temperature of 1050-1180℃, a heating rate of 8-15℃ / min, and a holding time of 1-60min.

[0016] In step 3, the pressure during the pressing process is 3-18 MPa.

[0017] Preferably, during the suspension roasting process of cyanide tailings, the degradation products of cyanide include NO. x CO x The total cyanide content after roasting is ≤0.5mg / kg, and the removal rate is >99%.

[0018] Preferably, the sulfur solidification rate is defined as the percentage of sulfur element in the cyanide tailings before and after suspension roasting. In step 1, the sulfur solidification rate of the cyanide tailings after roasting is >90%.

[0019] Preferably, the heavy metal solidification rate is defined as the percentage of the ratio of heavy metal elements in the cyanide tailings before and after suspension roasting. In step 1, the heavy metal solidification rate of the cyanide tailings after roasting is >99%.

[0020] Preferably, the sintered tiles formed by roasting and pressing cyanide tailings have a water absorption rate of 2-5% and a flexural strength of 28-58 MPa.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention provides a method for the harmless resource utilization of sulfur-containing cyanide tailings from suspension roasting. Employing a two-stage roasting process, by adjusting reaction conditions such as roasting atmosphere, temperature, and holding time during suspension roasting, sintered tiles conforming to GB / T21149-2019 "Sintered Tiles" are obtained. Highly toxic cyanide is removed, while sulfides and heavy metals are simultaneously solidified. The removal rate of cyanide and the solidification rate of heavy metals both exceed 99%, and the sulfur solidification rate is >90%. This method can achieve the harmless and resource-based disposal and utilization of cyanide tailings in one step, possessing environmental, economic, and social benefits. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments.

[0024] It should be noted that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] The sulfur-containing cyanide tailings in the embodiments of the present invention are tailings after direct cyanidation of gold concentrate, tailings after roasting or biological pretreatment for cyanidation of gold, tailings obtained by whole-sludge cyanidation for gold extraction, and high-silica tailings after cyanide slag is recovered by flotation for sulfide recovery.

[0026] In this embodiment of the invention, the sulfur-containing cyanide tailings have a moisture content of ≤17%, and no drying is required during roasting.

[0027] The main material composition and mass percentage of the gold concentrate cyanide tailings used in this embodiment of the invention are as follows: 10-30% Si, 20-25% S, 20-40% Fe, 0.3-0.7% Pb, 0.2-0.5% Zn, 0.3-0.4% Cu, 2-3% K, 0.5-2% Na, 0.3-0.5% Ca, 8-11% Al, 0.3-0.6% Mg, 0.1-0.3% Mn, and 0.05-0.1% Ti; the main material composition and mass percentage of the pretreated cyanide tailings used are as follows: 10-15% Si, 1-3% S, 30-50% Fe, 0.1-0.3% Pb, 0.1-0.2% Zn, 0.05-0.2% Cu, 1-3% K, 1-2% Na, 10-13% Al, and 1-2% Ti. The main material composition and mass percentage of the cyanidation tailings used are as follows: 50-60% Si, 0.1-0.5% S, 5-7% Fe, 0.01-0.05% Pb, 0.01-0.02% Zn, 0.01-0.02% Cu, 5-8% K, 5-8% Na, and 15-20% Al. The main material composition and mass percentage of the high-silica tailings used are as follows: 40-50% Si, 8-12% S, 5-7% Fe, 0.1-0.2% Pb, 0.05-0.2% Zn, 0.02-0.05% Cu, 2-5% K, 5-8% Na, 12-15% Al, 0.3-1% Mg, 0.1-0.2% Mn, and 0.5-0.3% Mg. Ti; The main material composition and mass percentage of the Laiyang clay used are: 15.2% Al2O3, 63.5% SiO2, 0.5% Na2O, 1.5% K2O, 4% MgO and 3.8% CaO.

[0028] The technical solution of the present invention will be further described below with reference to preferred embodiments.

[0029] Example 1

[0030] The total cyanide content of the sulfur-cyanide tailings is 4730 mg / kg, the S content is 24.8%, the Cu content is 0.3%, the Pb content is 0.07%, the Zn content is 0.5%, the As content is 0.1%, and the moisture content is 17%.

[0031] 435g of sulfur-containing cyanide tailings and 65g of Laiyang soil were mixed to prepare the ingredients; the ingredients were spray-dried to obtain powder with a moisture content of 7%, pressed into shape to obtain a billet, and placed in a suspension roasting oxidation furnace system for a first-stage roasting. The system was heated to 280°C at a rate of 3°C / min, the atmosphere was water vapor, and the holding time was 0min.

[0032] After the first stage of roasting, the second stage of roasting, which contains thiocyanate tailings, is initiated. The system is set with a heating rate of 8℃ / min, a roasting temperature of 1050℃, an air atmosphere, and a holding time of 1min.

[0033] The total cyanide content, sulfur content, heavy metal content, water absorption rate, and flexural strength of the roasted products were tested and calculated. The total cyanide content in the samples of sulfur-containing cyanide tailings treated for harmless resource utilization was ≤0.5 mg / kg, with a removal rate >99%, meeting the relevant requirements for pollution control of cyanide slag utilization in the "HJ 943-2018 Technical Specification for Pollution Control of Cyanide Slag in the Gold Industry"; the heavy metal leaching concentration was 41 mg / L, with a solidification rate >99%, meeting the limit requirements of the "GB18598-2019 Standard for Pollution Control of Hazardous Waste Landfill"; the sulfur content was 2.3%, with a sulfur solidification rate of 90.73%; the water absorption rate of the sintered tiles was 5%, and the flexural strength was 37 MPa, meeting the product quality requirements of GB / T21149-2019 "Sintered Tiles".

[0034] Example 2

[0035] The total cyanide content of the sulfur-containing cyanide tailings is 83 mg / kg, the S content is 2.4%, the Cu content is 0.1%, the Pb content is 0.15%, the Zn content is 0.1%, the As content is 1.5%, and the moisture content is 16%.

[0036] 435g of sulfur-containing cyanide tailings and 65g of Laiyang soil were mixed to prepare the ingredients; the ingredients were spray-dried to obtain powder with a moisture content of 5%, pressed into shape to obtain a billet, and placed in a suspension roasting oxidation furnace system for a first-stage roasting. The system was heated to 450℃ at a rate of 3℃ / min, the atmosphere was water vapor, and the holding time was 3min.

[0037] After the first stage of roasting, the second stage of roasting, which contains thiocyanate tailings, is initiated. The system is set to a heating rate of 15℃ / min, a roasting temperature of 1080℃, an air atmosphere, and a holding time of 30min.

[0038] The total cyanide content, sulfur content, heavy metal content, water absorption rate, and flexural strength of the calcined product were tested and calculated. The total cyanide content in the samples of sulfur-containing cyanide tailings treated for harmless resource utilization was ≤0.3 mg / kg, with a removal rate >99%, meeting the relevant pollution control requirements for cyanide slag utilization in the "HJ 943-2018 Technical Specification for Pollution Control of Cyanide Slag in the Gold Industry"; the heavy metal leaching concentration was 29 mg / L, with a solidification rate >99%, meeting the limit requirements of the "GB18598-2019 Standard for Pollution Control of Hazardous Waste Landfill"; the sulfur content was 0.2%, with a sulfur solidification rate of 91.67%; the water absorption rate of the sintered tiles was 3%, and the flexural strength was 42 MPa, meeting the product quality requirements of GB / T21149-2019 "Sintered Tiles".

[0039] Example 3

[0040] The total cyanide content of the sulfur-cyanide tailings is 2048 mg / kg, the S content is 15.8%, the Cu content is 0.2%, the Pb content is 0.4%, the Zn content is 0.3%, the As content is 0.5%, and the moisture content is 17%.

[0041] 450g of sulfur-containing cyanide tailings and 50g of Laiyang soil were mixed to prepare the ingredients; the ingredients were spray-dried to obtain powder with a moisture content of 6%, pressed into shape to obtain a billet, and placed in a suspension roasting oxidation furnace system for a first-stage roasting. The system was heated to 300℃ at a rate of 15℃ / min, the atmosphere was a mixture of 80% water vapor and air, and the holding time was 2min.

[0042] After the first stage of roasting, the second stage of roasting, which contains thiocyanate tailings, is initiated. The system is set with a heating rate of 12℃ / min, a roasting temperature of 1150℃, an air atmosphere, and a holding time of 60min.

[0043] The total cyanide content, sulfur content, heavy metal content, water absorption rate, and flexural strength of the calcined product were tested and calculated. The total cyanide content in the sample of the sulfur-containing cyanide tailings after harmless resource utilization was ≤0.2 mg / kg, with a removal rate >99%, meeting the relevant pollution control requirements for cyanide slag utilization in the "HJ 943-2018 Technical Specification for Pollution Control of Cyanide Slag in the Gold Industry"; the heavy metal leaching concentration was 33 mg / L, and the solidification rate was >99%, meeting the limit requirements of the "GB18598-2019 Standard for Pollution Control of Hazardous Waste Landfill"; the sulfur content was 1.5%, and the sulfur solidification rate was 90.5%; the water absorption rate of the sintered tiles was 3%, and the flexural strength was 28 MPa, meeting the product quality requirements of GB / T21149-2019 "Sintered Tiles".

[0044] Example 4

[0045] The total cyanide content of the sulfur-cyanide tailings is 1620 mg / kg, the S content is 6.8%, the Cu content is 0.3%, the Pb content is 0.25%, the Zn content is 0.2%, the As content is 1.2%, and the moisture content is 11%.

[0046] 475g of sulfur-containing cyanide tailings and 25g of Laiyang soil were mixed to prepare the ingredients; the ingredients were spray-dried to obtain powder with a moisture content of 6%, pressed into shape to obtain a billet, and placed in a suspension roasting oxidation furnace system for a first-stage roasting. The system was heated to 400℃ at a rate of 8℃ / min, the atmosphere was a mixture of 80% water vapor and air, and the holding time was 2min.

[0047] After the first stage of roasting, the second stage of roasting, which contains thiocyanate tailings, is initiated. The system is set with a heating rate of 8℃ / min, a roasting temperature of 1180℃, an air atmosphere, and a holding time of 1min.

[0048] The total cyanide content, sulfur content, heavy metal content, water absorption rate, and flexural strength of the calcined product were tested and calculated. The total cyanide content in the samples of sulfur-containing cyanide tailings treated for harmless resource utilization was ≤0.5 mg / kg, with a removal rate >99%, meeting the relevant pollution control requirements for cyanide slag utilization in the "HJ 943-2018 Technical Specification for Pollution Control of Cyanide Slag in the Gold Industry"; the heavy metal leaching concentration was 39 mg / L, with a solidification rate >99%, meeting the limit requirements of the "GB18598-2019 Standard for Pollution Control of Hazardous Waste Landfill"; the sulfur content was 0.6%, with a sulfur solidification rate of 91.18%; the water absorption rate of the sintered tiles was 5%, and the flexural strength was 38 MPa, meeting the product quality requirements of GB / T21149-2019 "Sintered Tiles".

[0049] Example 5

[0050] The total cyanide content of the sulfur-cyanide tailings is 3470 mg / kg, the S content is 24.8%, the Cu content is 0.3%, the Pb content is 0.5%, the Zn content is 0.2%, the As content is 0.9%, and the moisture content is 17%.

[0051] 450g of sulfur-containing cyanide tailings and 50g of Laiyang soil were mixed to prepare the ingredients; the ingredients were spray-dried to obtain powder with a moisture content of 6%, pressed into shape to obtain a billet, and placed in a suspension roasting oxidation furnace system for a first-stage roasting. The system was heated to 450℃ at a rate of 5℃ / min, the atmosphere was a mixture of 90% water vapor and air, and the holding time was 1min.

[0052] After the first stage of roasting, the second stage of roasting, which contains thiocyanate tailings, is initiated. The system is set with a heating rate of 12℃ / min, a roasting temperature of 1120℃, an air atmosphere, and a holding time of 15min.

[0053] The total cyanide content, sulfur content, heavy metal content, water absorption rate, and flexural strength of the calcined product were tested and calculated. The total cyanide content in the sample of the sulfur-containing cyanide tailings for harmless resource utilization was ≤0.4 mg / kg, with a removal rate >99%, meeting the relevant pollution control requirements for cyanide slag utilization in the "HJ 943-2018 Technical Specification for Pollution Control of Cyanide Slag in the Gold Industry"; the heavy metal leaching concentration was 21 mg / L, with a solidification rate >99%, meeting the limit requirements of the "GB18598-2019 Standard for Pollution Control of Hazardous Waste Landfill"; the sulfur content was 1.3%, with a sulfur solidification rate of 94.76%; the water absorption rate of the sintered tiles was 3%, and the flexural strength was 58 MPa, meeting the product quality requirements of GB / T21149-2019 "Sintered Tiles".

Claims

1. A method for the harmless resource utilization of sulfur-containing cyanide tailings from suspension roasting, characterized in that, Includes the following steps: Step 1. After uniformly mixing the sulfur-cyanide tailings with Laiyang clay, the mixture is spray-dried, granulated, powdered, and pressed into sintered blanks, which are then fed into the suspension roasting oxidation furnace system. The amount of Laiyang clay added is ≤ 15% of the mass of the sulfur-cyanide tailings. Step 2. After setting the atmosphere, calcination temperature, heating rate and holding time of the suspension calcination oxidation system, the sintered billet is sintered in the suspension calcination oxidation furnace using a two-stage calcination method. Step 3. Press the suspended calcined billet into shape to obtain sintered tiles; In step 2, during the roasting process, the first roasting atmosphere is a mixture of water vapor and air, with a water vapor concentration of 5-35%, a roasting temperature of 280-450℃, a heating rate of 3-15℃ / min, and a holding time of 0-3 min; the second roasting atmosphere is air, with a roasting temperature of 1050-1180℃, a heating rate of 8-15℃ / min, and a holding time of 1-60 min. The sulfur solidification rate of the cyanide tailings after roasting is >90%, the cyanide removal rate is >99%, and the heavy metal solidification rate of the cyanide tailings after roasting is >99%. Sintered tiles have a water absorption rate of 2-5% and a flexural strength of 28-58 MPa. In step 1, the sulfur-containing cyanide tailings include one or more of the following: gold concentrate cyanide tailings produced in gold smelting, pretreated cyanide tailings, whole sludge cyanide tailings, and high-silica tailings after flotation of gold concentrate cyanide tailings; the main elements include Si, S, Fe, Pb, Zn, Cu, K, Na, Ca, Al, Mg, Mn, Ti, As, Cd, Ni, C, and N; The cyanide-containing substances in the sulfur-cyanide tailings include free cyanide, thiocyanate, ferric cyanide complexes, copper cyanide complexes, zinc cyanide complexes, and lead cyanide complexes; In step 1, the sulfur-containing cyanide tailings contain sulfur content of 0.1%-25% of the cyanide tailings mass, total cyanide content of 80-5000 mg / kg, and total heavy metal content of 5-30 g / kg. The moisture content of the sulfur-containing cyanide tailings is ≤17%, and the particle size is ≤250 μm.

2. The method for harmless resource utilization of sulfur-containing cyanide tailings from suspension roasting according to claim 1, characterized in that, In step 3, the pressure during the pressing process is 3~18 MPa.

3. The method for harmless resource utilization of sulfur-containing cyanide tailings from suspension roasting according to claim 1, characterized in that, During the suspension roasting process of cyanide tailings, the degradation products of cyanide include NO. x CO x The total cyanide content after roasting is ≤0.5 mg / kg, including H2.