Method for comprehensive recovery of copper smelting gypsum slag

Abstract

The application discloses a comprehensive recovery method of copper smelting gypsum slag, which is characterized by the following steps: transporting desulfurization gypsum slag generated in a copper smelting process to the vicinity of a multi-gun top-blown converter, adding the gypsum slag with a water content of 1-30 wt% into the converter through a top cold material system, and replacing part or all of the limestone flux in a continuous blowing process. By controlling the parameters such as the gypsum slag addition amount, the blowing slag temperature, the calcium-iron ratio and the boiler inlet flue gas composition, the copper smelting waste heat and the reaction environment in the converter are utilized to decompose the gypsum slag into calcium oxide and sulfur dioxide, which enter the slag phase and the flue gas acid-making system respectively. The application not only realizes the resource utilization of the copper smelting gypsum slag, significantly reduces the solid waste discharge and treatment cost, but also effectively expands the temperature regulation means of the multi-gun top-blown converter, reduces the dependence on the residual anode in the smelting process, and has significant economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of copper smelting technology, and specifically relates to a comprehensive method for recycling gypsum slag from copper smelting. Background Technology

[0002] Gypsum slag is a common byproduct of smelting processes. In copper pyrometallurgical processes, the acid production system typically generates large quantities of desulfurized gypsum slag to treat sulfur dioxide in the smelting flue gas. For example, in the stepwise treatment of chemical waste acid, desulfurized gypsum and neutralized gypsum are produced sequentially. Taking a company with a cathode copper production capacity of 300,000 tons as an example, approximately 50,000 tons of such gypsum slag are generated annually. These gypsum slags mainly include desulfurized gypsum, phosphogypsum, fluorogypsum, citric acid gypsum, salt gypsum, titanium gypsum, etc., and are rich in sulfur and calcium resources. my country is a sulfur-deficient country with a high dependence on sulfur imports, making the recovery of sulfur resources from gypsum slag of great significance. Simultaneously, the calcium in gypsum slag can be used as a flux to replace limestone in smelting slag formation.

[0003] However, due to the poor quality of copper smelting gypsum slag, it inevitably carries small amounts of heavy metal ions (such as As, Pb, Zn), fluorides, and chloride ions from flue gas, making it difficult to use in the production of high-quality building materials or as a cement retarder. Currently, the vast majority of copper smelting enterprises rely on landfill disposal for their gypsum slag, which not only occupies land but also incurs high disposal costs. The selling price to external parties is often negative, resulting in a huge waste of resources.

[0004] On the other hand, in copper matte smelting processes, with the widespread adoption of side-blown smelting-multi-lance top-blown smelting and flash smelting, calcium-iron slag has become one of the mainstream slag types. In existing technologies, the calcium flux required for slag formation is mainly limestone or quicklime. Some studies have proposed using gypsum to replace limestone for slag formation; for example, patent CN106367613A discloses a slag formation process for matte smelting, but no industrial application has been observed. Furthermore, existing multi-lance top-blown furnace processes suffer from excess heat, often requiring the addition of residual electrodes to regulate the heat balance. If the supply of residual electrodes is insufficient, production load must be reduced. Therefore, how to utilize the smelting system's own conditions to achieve short-process, low-cost recovery of calcium and sulfur resources from gypsum slag, while simultaneously addressing the problem of limited heat balance control methods in multi-lance top-blown furnaces, has become a pressing technical challenge in this field. Summary of the Invention

[0005] In view of the problems of high landfill costs and resource waste in existing technologies for gypsum slag disposal, as well as the limited means of temperature control in multi-gun top-blown furnaces, this invention provides a comprehensive recovery method for gypsum slag in copper smelting, which realizes short-process and low-cost recovery of calcium and sulfur resources in gypsum slag.

[0006] This invention is achieved through the following technical solution: A method for comprehensive recovery of gypsum slag from copper smelting includes the following steps: S1: Transfer the desulfurized gypsum or neutralized gypsum produced by the copper smelting acid production system to the intermediate silo of the multi-gun top-blown smelting furnace, and control the moisture content of the gypsum slag entering the furnace to 1-30 wt%; In step S1, the gypsum slag can be directly transferred and stored, or it can be preliminarily air-dried or dried according to the moisture content to meet the moisture content requirements of the furnace.

[0007] S2: After the gypsum slag is metered from the intermediate silo, it is added into the furnace through the cold material feeding system of the multi-gun top blown furnace as a slag-forming flux to replace part or all of the limestone. S3: During the blowing process, the waste heat from blowing is used to decompose gypsum slag into calcium oxide and sulfur dioxide. By controlling the amount of gypsum slag added, the oxygen lance air volume, and the oxygen concentration, the blowing slag temperature is controlled at 1240–1300℃, the slag contains 15–35 wt% copper, the calcium-to-iron ratio in the slag is 0.2–0.5, the magnetic iron content in the slag is not higher than 60%, and the sulfur dioxide concentration in the boiler inlet flue gas is controlled to be not higher than 30% and the oxygen concentration not higher than 5%, thereby achieving the recovery and utilization of calcium and sulfur resources in the gypsum slag. Through precise control of process parameters, efficient decomposition of gypsum slag under favorable low-oxygen and low-sulfur dioxide partial pressure conditions is ensured, while also guaranteeing production safety.

[0008] The gypsum decomposition and slag-forming reaction involved in this invention are as follows: CaSO4·2H2O = CaSO4 + 2H2O; 2CaSO4 = 2CaO + 2SO2 + O2; CaSO4+ 2FeS + 3O2= CaO·Fe2O3+ 3SO2; CaO + Fe2O3 = CaO·Fe2O3; CaO + SiO2 = CaO·SiO2.

[0009] Based on the above reactions, the partial pressure conditions of low sulfur dioxide and low oxygen concentrations are favorable for the direct decomposition of calcium sulfate. The relatively low oxygen concentration (typically below 30%) in multi-lance top-blown furnaces, coupled with the continuous emission of sulfur dioxide from the flue gas system, provides favorable thermodynamic and kinetic conditions for the efficient decomposition of gypsum slag, making it more adaptable than furnace types such as smelting furnaces and flash furnaces.

[0010] Preferably, in step S2, the rate at which gypsum slag is added is adjusted according to the furnace temperature and the target calcium-iron ratio, and the amount added is 0-10 t / h.

[0011] Preferably, in step S2, the gypsum residue is added into the furnace through the existing residual electrode inlet, limestone inlet, or newly added special silo of the multi-gun top-blown furnace.

[0012] Preferably, in step S3, gypsum residue completely replaces limestone as a calcium flux.

[0013] Preferably, in step S3, the temperature of the blowing slag is controlled at 1260–1300°C.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention utilizes waste heat from smelting to achieve online recovery of calcium and sulfur resources from gypsum slag. Calcium is converted into calcium oxide and enters the slag to replace limestone, while sulfur is converted into sulfur dioxide and enters the flue gas acid production system. This significantly reduces the amount of gypsum slag that needs to be landfilled and the associated treatment costs, achieving resource utilization and waste reduction of solid waste. Industrial trials have verified that the addition of gypsum slag has no negative impact on key indicators such as copper content and sulfur content in the smelting slag, and the produced copper plating exhibits stable quality, with the smelting slag properties meeting the requirements of subsequent processes.

[0015] 2. The decomposition of gypsum slag into the furnace is an endothermic reaction, which can effectively absorb the excess heat in the blowing process, realize the rapid and precise adjustment of the furnace temperature, reduce the dependence of multi-gun top-blown furnaces on residual electrode cooling, broaden the means of temperature control, and enhance the stability and continuity of production.

[0016] 3. This invention hardly changes the main process and equipment of existing multi-gun top-blown furnaces. It can be implemented by adding simple transfer and metering devices, with low investment and quick results. The gypsum slag has a wide range of adaptable moisture content (1-30%), dries quickly after entering the furnace and only floats on the surface of the melt, resulting in low safety risks. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings. In the embodiments, unless otherwise specified, the technical means used are all conventional technical means in the art. Furthermore, in the following embodiments, other impurities and water are not included in the chemical element composition of substances other than gypsum, the mass of the added mineral is the mass after drying, and all components are expressed in mass percentage (wt%).

[0019] The limestone composition is CaCO3 94.05%, MgCO3 0.76%, and other components 5.19%. The residual electrode composition is Cu 99.20%, Fe 0.06%, Pb 0.18%, Fe 0.05%, and other components 0.51%. Example 1

[0020] A comprehensive recovery method for gypsum slag from copper smelting, the process flow is as follows: Figure 1 As shown.

[0021] The hot copper matte feed rate of the multi-gun top-blown furnace is 55.5 t / h, and its composition is Cu 72.63%, S 19.97%, Fe 4.38%, SiO2 0.06%, Pb 1.48%, Zn 0.73%, with the balance being other components.

[0022] The gypsum residue used consisted of 79.05% CaSO4, 15.01% H2O, and the remainder being other components.

[0023] The original process parameters were: limestone addition 1.4t / h, residual electrode addition 10t / h.

[0024] In this implementation, gypsum slag is added at a rate of 1.0 t / h, the residual anode addition rate is adjusted to 8 t / h, and the limestone addition rate is adjusted to 1.0 t / h, partially replacing the limestone. The total air volume of the oxygen lance is 40,000 m³ / h. 3 / h, oxygen concentration is 28%.

[0025] The furnace reaction was normal, the furnace condition was stable, and slag and copper discharge was smooth. A significant increase in sulfur dioxide and residual oxygen concentrations was observed in the flue gas at the boiler inlet 1.5 hours after the addition of gypsum slag, a normal phenomenon. The final output was 8.2 t / h of smelting slag and 48.7 t / h of copper smelting. The copper smelting composition was 98.27% Cu, indicating excellent quality. The smelting slag composition was 29.23% Cu, 29.57% Fe, 6.26% CaO, and 0.21% S, with a magnetic iron content of 32.57%. No increase in sulfur content was observed in the slag, indicating complete gypsum decomposition. This embodiment achieved comprehensive recovery of gypsum slag from copper smelting and observed that adding one ton of gypsum slag could reduce the furnace temperature by 5–10°C. Example 2

[0026] A comprehensive recovery method for gypsum slag from copper smelting, the process flow is as follows: Figure 1 As shown.

[0027] The hot copper matte feed rate of the multi-gun top-blown furnace is 53.7 t / h, and its composition is Cu 73.81%, S 19.82%, Fe 2.92%, SiO2 0.08%, Pb 1.53%, Zn 0.91%, with the balance being other components.

[0028] The gypsum residue used consisted of 66.38% CaSO4, 28.85% H2O, and the remainder was other components.

[0029] The original process parameters were: limestone addition 0.9t / h, residual electrode addition 7t / h.

[0030] In this implementation, gypsum slag is added at a rate of 2.1 t / h, the residual anode addition rate is adjusted to 4 t / h, and the limestone addition rate is adjusted to 0, completely replacing the limestone. The total air volume of the oxygen lance is 34,000 m³ / h. 3 / h, oxygen concentration is 30%.

[0031] The reaction inside the furnace was normal, and the furnace conditions were stable. The flue gas at the inlet of the blowing boiler showed a significant increase one hour after the addition of gypsum slag. The final output was 4.4 t / h of blowing slag and 43.4 t / h of copper leaching. The composition of the blowing slag was Cu 23.07%, Fe 35.72%, CaO 8.56%, S 0.22%, and magnetic iron content 42.73%. The sulfur content in the slag was stable, indicating complete gypsum decomposition. This embodiment achieved complete replacement of limestone with gypsum slag, and the addition of each ton of gypsum slag reduced the furnace temperature by 6–10℃. Example 3

[0032] A comprehensive recovery method for gypsum slag from copper smelting, the process flow is as follows: Figure 1 As shown.

[0033] The hot copper matte feed rate of the multi-gun top-blown furnace is 62.5 t / h, and its composition is Cu 70.38%, S 20.57%, Fe 6.40%, SiO2 0.09%, Pb 0.66%, Zn 0.30%, with the balance being other components.

[0034] The gypsum residue used consisted of 84.33% CaSO4, 8.56% H2O, and the remainder was other components.

[0035] The original process parameters were: limestone addition 2.4t / h, residual electrode addition 16t / h.

[0036] In this embodiment, gypsum slag is added at a rate of 5.0 t / h, the residual anode addition rate is adjusted to 8 t / h, and the limestone addition rate is adjusted to 0, completely replacing the limestone. The total air volume of the oxygen lance is 46,000 m³ / h. 3 / h, oxygen concentration is 26%.

[0037] The reaction inside the furnace was normal, and the furnace condition was stable. The flue gas at the inlet of the blowing boiler showed a significant increase 0.5 hours after the addition of gypsum slag. The final output was 9.7 t / h of blowing slag and 50.4 t / h of copper leaching. The composition of the blowing slag was Cu 21.60%, Fe 41.10%, CaO 12.76%, S 0.20%, and magnetic iron content 45.19%. The sulfur content in the slag was stable, and the gypsum was completely decomposed. This embodiment achieved complete replacement of limestone with gypsum slag at a relatively large addition rate; the addition of each ton of dried gypsum slag reduced the furnace temperature by 4–9°C.

[0038] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for comprehensive recovery of gypsum slag from copper smelting, characterized in that, Includes the following steps: S1: Transfer the desulfurized gypsum or neutralized gypsum produced by the copper smelting acid production system to the intermediate silo of the multi-gun top-blown smelting furnace, and control the moisture content of the gypsum slag entering the furnace to 1-30 wt%; S2: After the gypsum slag is metered from the intermediate silo, it is added into the furnace through the cold material feeding system of the multi-gun top blown furnace as a slag-forming flux to replace part or all of the limestone. S3: During the blowing process, the waste heat from blowing is used to decompose gypsum slag into calcium oxide and sulfur dioxide. By adjusting the amount of gypsum slag added, the oxygen lance air volume and oxygen concentration, the blowing slag temperature is controlled at 1240-1300℃, the slag contains 15-35wt% copper, the calcium-iron ratio of the slag is 0.2-0.5, the magnetic iron content of the slag is not higher than 60%, and the sulfur dioxide concentration in the boiler inlet flue gas is controlled not higher than 30% and the oxygen concentration is not higher than 5%, thereby realizing the recovery and utilization of calcium and sulfur resources in gypsum slag.

2. The method for comprehensive recovery of copper smelting gypsum slag according to claim 1, characterized in that: In step S2, the rate at which gypsum slag is added is adjusted according to the furnace temperature and the target calcium-iron ratio, and the amount added is 0-10 t / h.

3. The method for comprehensive recovery of copper smelting gypsum slag according to claim 1, characterized in that: In step S2, gypsum slag is added into the furnace through the existing residual electrode inlet, limestone inlet, or newly added special silo of the multi-gun top-blown furnace.

4. The method for comprehensive recovery of copper smelting gypsum slag according to claim 1, characterized in that: In step S3, gypsum residue completely replaces limestone as a calcium flux.

5. The method for comprehensive recovery of copper smelting gypsum slag according to claim 1, characterized in that: In step S3, the temperature of the blowing slag is controlled at 1260-1300℃.

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