A method for increasing the production capacity of magnetite powder and sulfuric acid by incorporating pyrite into copper smelting.

Abstract

This invention belongs to the field of comprehensive utilization technology of metallurgical and chemical resources, and discloses a method for increasing the production capacity of magnetite powder and sulfuric acid by incorporating pyrite into copper smelting. This method optimizes the heat release rate, SO2 generation kinetics, and iron oxide phase transformation pathway by constructing a gradient incorporation mechanism for pyrite and a furnace-based oxygen potential directional oxidation control system. Its key features include: dynamically controlling the pyrite incorporation rate, particle size, and carrier gas oxygen concentration in stages based on real-time feedback from molten pool temperature, flue gas SO2 concentration, and slag FeO activity; creating a reducing microenvironment of logpO2≈-11 at the slag-matte interface to promote Fe3O4 crystal nuclei growth; and optimizing flue gas cooling and sulfuric acid inlet stability. This invention not only achieves simultaneous improvement in the production capacity of magnetite powder and sulfuric acid but also ensures the stability and efficiency of the main copper smelting process, providing an engineering-feasible technical path for the comprehensive utilization of resources in copper smelting enterprises.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of metallurgical and chemical resources, and relates to a method for increasing the production capacity of magnetite powder and sulfuric acid by adding pyrite to copper smelting. Background Technology

[0002] In the non-ferrous metals metallurgy sector, copper pyrometallurgical processes have long relied on copper sulfide concentrate as the primary raw material. The smelting process not only affects metal recovery efficiency but also profoundly impacts the comprehensive utilization of associated resources. In recent years, with the deepening of resource comprehensive utilization policies and the advancement of the circular economy concept, how to ensure the efficient extraction of the primary metal copper while simultaneously increasing the production capacity of by-products such as magnetite powder and industrial sulfuric acid has become a key path for copper smelting enterprises to optimize their process structure and improve economic efficiency.

[0003] Pyrite (mainly FeS2) is a secondary resource rich in iron and sulfur. It is widely introduced into copper smelting systems to supplement smelting heat energy through its exothermic oxidation properties and to provide high-concentration SO2 flue gas for subsequent acid production systems. At the same time, it promotes the enrichment of iron elements in the form of magnetic oxides, which facilitates recycling.

[0004] In existing technologies, pyrite is typically added to the smelting furnace in a single batch, designed to simplify the feeding process and improve operational continuity. This method did achieve some initial utilization of sulfur resources in the early, extensive production stages and played a supporting role in maintaining the molten pool temperature.

[0005] Pyrite undergoes a rapid oxidation reaction in a high-temperature, oxygen-rich environment: 2FeS2 + 7O2 → 2FeO + 4SO2, releasing a large amount of heat and generating SO2 gas. Theoretically, this can simultaneously meet the heat balance requirements and the supply of raw materials for acid production. However, as modern copper smelting places higher demands on process stability, energy consumption control, and environmental emissions, the inherent defects of this one-time investment model are becoming increasingly apparent, especially in terms of dynamic operating condition control, where irreconcilable technical contradictions are exposed.

[0006] The instantaneous and concentrated oxidation of pyrite leads to a sharp increase in oxygen potential in local areas of the furnace, triggering multiple nonlinear coupling effects. First, the large amount of heat released in a short period of time causes a sudden rise in the temperature of the molten pool, disrupting the original thermal field distribution and easily inducing intensified furnace lining erosion or even local nodule formation. Second, the violent oxidation reaction consumes a large amount of oxygen, causing drastic fluctuations in the oxygen partial pressure at the melt interface, which disrupts the phase equilibrium between copper matte (Cu-Fe-S phase) and slag (FeO-SiO2 system), thereby affecting the copper recovery rate and the copper content in the slag. The pulsed peak of SO2 generation rate far exceeds the design capacity of the acid production system, not only causing large fluctuations in flue gas concentration and a decrease in conversion efficiency, but also potentially triggering environmental exceedance risks.

[0007] Iron tends to form Fe2O3 rather than the target product Fe3O4 under a strong oxidizing atmosphere. The latter requires specific oxygen potential window (logpO2≈-10~-12, 1200°C) to be stably precipitated through the disproportionation of FeO or a reducing atmosphere. A single-feed operation cannot achieve spatiotemporal decoupling of the oxidation process, thus hindering the kinetic pathway of magnetite powder formation, resulting in an actual recovery rate far lower than the theoretical potential. Summary of the Invention

[0008] To achieve the aforementioned objectives, this invention provides a method for enhancing the production capacity of magnetite powder and sulfuric acid by incorporating pyrite into copper smelting. This method achieves synergistic optimization of heat release rate, SO2 generation kinetics, and iron oxide phase transition pathways during smelting by constructing a gradient incorporation mechanism for pyrite and a directional oxidation control system for oxygen potential within the furnace. This significantly improves the recovery rate of magnetite powder and the quality of industrial sulfuric acid feed gas while ensuring stable operation of the copper smelting process.

[0009] The method of this invention includes the following steps: First, a multi-parameter real-time feedback system based on molten pool temperature, flue gas SO2 concentration, and slag phase FeO activity is established in the main reaction zone of copper smelting; second, a phased feeding strategy for pyrite is dynamically planned based on the feedback signal, dividing the total feeding amount into three time intervals: initial ignition stage, steady-state strengthening stage, and final tempering stage, and setting the feeding rate, particle size distribution, and carrier gas oxygen concentration for each stage; third, a local reducing microenvironment control unit is set in the slag-matte interface region of the smelting furnace, and the interface oxygen partial pressure is precisely controlled at the target window of logpO2=-11±0.5 (based on 1200°C) by injecting carbon-containing reducing agent or adjusting the secondary air ratio; finally, the generated high-temperature flue gas is rapidly cooled to below 400°C by a waste heat boiler and then introduced into the acid production system to ensure that the SO2 concentration fluctuation is less than ±8%, meeting the inlet gas stability requirements of the dual-contact acid production process.

[0010] The multi-parameter real-time feedback system consists of a molten pool infrared thermometer array, an online flue gas analyzer, and an automatic slag sampling-spectroscopy device. The molten pool infrared thermometer array is positioned on the side wall of the smelting furnace at a height of 300-500 mm from the slag surface, with a sampling frequency higher than 1 Hz, used to monitor the temperature field distribution on the melt surface. The online flue gas analyzer employs non-dispersive infrared and ultraviolet differential absorption spectroscopy composite detection technology to simultaneously measure SO2, O2, and CO concentrations, with a response time of less than 2 seconds. The automatic slag sampling-spectroscopy device performs periodic sampling every 15 minutes, followed by water quenching and rapid cooling before being sent to an X-ray fluorescence spectrometer to determine the FeO content, and combines this with a thermodynamic database to invert the current oxygen potential state of the slag phase.

[0011] In a preferred embodiment of the present invention, the total amount of pyrite added accounts for 12% to 18% of the dry weight of the copper concentrate, and its particle size is controlled by screening so that ≥85% can pass through a 200-mesh sieve, and the moisture content is ≤0.5%. The initial ignition section lasts for the first 10 minutes of the smelting cycle, with an addition rate of 25% of the total rate. Pyrite particles are carried into the upper oxidation zone of the molten pool by nitrogen gas, and the oxygen volume fraction in the carrier gas is controlled at 21%. The steady-state strengthening section covers the 11th to 70th minutes of the smelting cycle, with the addition rate increased to 60% of the total rate. Pyrite is carried by oxygen-enriched air (oxygen volume fraction 32%), and the injection position is moved down to the middle stirring zone of the molten pool to enhance the solid-liquid mass transfer efficiency. The final conditioning section is the last 20 minutes of the smelting cycle, with the addition rate reduced to 15% of the total rate. Pyrite is transported by low-oxygen carrier gas (oxygen volume fraction 15%), and interface reduction regulation is simultaneously initiated to suppress Fe. 2+ Excessive oxidation promotes the growth of Fe3O4 crystal nuclei.

[0012] The localized reducing microenvironment control unit comprises eight sets of reducing agent spray guns arranged in a ring around the slag line area of ​​the smelting furnace. Each set of spray guns is equipped with an independent flow control valve and a pulse modulator. The reducing agent is anthracite powder with a particle size of 5-15 μm, a fixed carbon content ≥75%, and volatile matter ≤8%. The injection pressure is maintained at 0.35-0.45 MPa, and the single-set injection flow rate is 1.2-1.8 kg / min. The injection timing is synchronized with the final addition of pyrite and is adjusted in a closed loop based on the FeO activity feedback of the slag sample: when the FeO activity is higher than 0.65, the injection flow rate increases by 10%; when the FeO activity is lower than 0.55, the injection flow rate decreases by 10%; maintaining the FeO activity of the slag phase stable in the range of 0.58 to 0.62, corresponding to an oxygen partial pressure logpO2≈-11.0±0.3.

[0013] In another preferred embodiment of the present invention, the pyrite feeding system adopts a dual-channel screw feeding mechanism. The main channel is used for conveying conventional particle size pyrite, while the auxiliary channel integrates a high-frequency vibrating screen and an air classifier, which can remove coarse particles that cannot pass through a 100-mesh screen and ultrafine powders that can pass through a 325-mesh screen online, ensuring that the standard deviation of the particle size distribution of the material entering the molten pool is ≤15μm. The feeding rate is controlled by a metering screw driven by a variable frequency motor, with an accuracy of ±0.5%, and communicates in real time with the central control system via the PROFIBUS-DP protocol to achieve dynamic matching between the feeding rate and the smelting load.

[0014] The directional oxidation control also includes the optimized design of the oxygen lance layout within the smelting furnace. Based on traditional top-blown or side-blown oxygen lances, this invention adds two obliquely inserted auxiliary oxygen lances. The nozzle axis of these auxiliary lances forms a 35° angle with the horizontal plane, and the insertion depth reaches 400 mm below the molten pool surface. This is used to create a localized high-oxygen-potential vortex zone downstream of the pyrite injection point, accelerating the initial oxidation and dissociation of FeS2 while preventing a general jump in oxygen potential in the main reaction zone. The oxygen flow rate of the auxiliary oxygen lances is independently controllable, ranging from 50 Nm³. 3 / h to 120Nm 3 The auxiliary oxygen lance is dynamically adjusted according to the SO2 rise rate of the flue gas: when d[SO2] / dt>0.8% / s, the auxiliary oxygen lance is turned off; when d[SO2] / dt<0.3% / s, it is turned on up to 80 Nm. 3 / h.

[0015] In the method described in this invention, the formation mechanism of the magnetic powder depends on the disproportionation reaction of FeO under a specific oxygen potential: 3FeO → Fe3O4 + Fe. This reaction is thermodynamically spontaneous in the range of logpO2 = -10.5 to -11.5, but requires a sufficiently long holding time to complete crystal growth.

[0016] Regarding sulfuric acid production capacity, this invention achieves a smoother SO2 generation rate curve through gradient introduction. Under typical operating conditions, the flue gas SO2 concentration stabilizes between 10.5% and 12.2%, with the standard deviation of fluctuation decreasing from 1.8% in the traditional process to 0.6%, meeting the requirement of ≤±10% for inlet gas concentration fluctuation in the dual-contact sulfuric acid production method. The inlet temperature of the first stage of the converter is controlled at 410°C±5°C, and the SO2 conversion rate at the outlet of the fourth stage reaches over 99.85%, with the tail gas SO2 emission concentration below 200 mg / m³. 3 It is better than the limit of the "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industry" (GB25467-2010).

[0017] The implementation of the method described in this invention does not alter the main structure of the existing smelting furnace; only modular modifications are required at the levels of the feeding system, oxygen lance configuration, and control system. The control system adopts a three-layer architecture: the bottom layer is a PLC execution unit responsible for the switching and adjustment of the feeder, oxygen valve, and spray lance; the middle layer is a process optimization server running a dynamic scheduling algorithm based on a mechanistic model, with real-time feedback parameters as input and setpoints for each execution unit as output; the top layer is a human-machine interface providing process curve visualization and anomaly warning functions. The core of the dynamic scheduling algorithm is the oxygen potential-heat balance coupling equation:

[0018] ；

[0019] ;

[0020] in, To accumulate heat in the molten pool, The instantaneous incorporation rate of pyrite. The enthalpy change for the FeS2 oxidation reaction is -1780 kJ / mol. The reaction efficiency coefficient is taken as 0.85. For heat dissipation coefficient, The surface area of ​​the furnace body. The average temperature of the molten pool. For ambient temperature; in the second formula , , , The regression coefficients, identified from historical data, are used for real-time estimation of oxygen partial pressure. The controller uses... Maintain within ±5MW and Find the optimal solution with the goal of approaching -11. sequence.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This invention fundamentally solves the problem of multiple imbalances in heat, mass, and phase caused by traditional one-time feeding by deconstructing the pyrite incorporation process into a time-controllable gradient stage and coupling it with the directional regulation of interfacial oxygen potential. This method not only achieves simultaneous improvement in the production capacity of magnetite powder and sulfuric acid but also ensures the stability and efficiency of the main copper smelting process. Detailed Implementation

[0023] This invention provides a method for improving the production capacity of magnetite powder and sulfuric acid by incorporating pyrite into copper smelting. The core of this method lies in constructing a gradient incorporation mechanism of pyrite and a directional oxidation control system for oxygen potential in the furnace. This enables the synergistic optimization of heat release rate, sulfur dioxide generation kinetics, and iron oxide phase transformation pathway during the smelting process. As a result, the recovery rate of magnetite powder and the quality of industrial sulfuric acid feed gas are significantly improved while ensuring the stable operation of the copper smelting process.

[0024] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0025] Example 1: Total pyrite content 15% (based on dry copper concentrate); gradient blending (25% in ignition section, 60% in strengthening section, and 15% in conditioning section); oxygen potential logpO2 = -11; slag temperature 1220℃; SiO2 / FeO molar ratio 1.2; magnetic separation with a magnetic field strength of 0.25T.

[0026] Preparation process: Real-time feedback of multiple parameters → staged addition of pyrite → interfacial oxygen potential regulation → flue gas cooling for acid production → magnetic separation of slag to recover magnetite powder.

[0027] Example 2: The total amount of pyrite added is 12%, and the rest of the formula and process are the same as in Example 1;

[0028] Preparation process: Same as in Example 1.

[0029] Example 3: The total amount of pyrite added is 18%, and the rest of the formula and process are the same as in Example 1;

[0030] Preparation process: Same as in Example 1.

[0031] Example 4: Oxygen potential logpO2 = -11.5, the rest of the formulation and process are the same as in Example 1;

[0032] Preparation process: Same as in Example 1.

[0033] Example 5: Oxygen potential logpO2 = -10.5, the rest of the formulation and process are the same as in Example 1;

[0034] Preparation process: Same as in Example 1.

[0035] Example 6: SiO2 / FeO molar ratio 1.1, other formulations and processes are the same as in Example 1;

[0036] Preparation process: Same as in Example 1.

[0037] Example 7: SiO2 / FeO molar ratio 1.3, other formulations and processes are the same as in Example 1;

[0038] Preparation process: Same as in Example 1.

[0039] Example 8: The flow rate of the reducing agent in the final conditioning stage is increased by 15%, and the rest of the formulation and process are the same as in Example 1;

[0040] Preparation process: Same as in Example 1.

[0041] Comparative Example 1: No gradient addition, 15% pyrite added at once; the rest of the formulation and process are the same as in Example 1;

[0042] Preparation process: Same as in Example 1 (without the step-by-step addition).

[0043] Comparative Example 2: No localized reducing microenvironment regulation, oxygen potential fluctuates naturally; the rest of the formulation and process are the same as in Example 1;

[0044] Preparation process: Same as in Example 1 (no reducing agent spraying step).

[0045] Test method:

[0046] Production capacity and recovery rate test: After magnetic separation, the magnetic powder recovery rate is calculated by weighing; Fe3O4 content is detected; SO2 concentration and fluctuation range in flue gas are monitored to calculate sulfuric acid production capacity.

[0047] Smelting stability test: Determine copper recovery rate and copper content in slag; record furnace lining erosion rate; monitor molten pool temperature fluctuation.

[0048] Environmental protection and energy consumption testing: Detecting SO2 emission concentration in exhaust gas; calculating the comprehensive energy consumption per unit of copper smelting.

[0049] The test data comparisons are shown in Table 1 and Table 2.

[0050] Table 1 Comparison of Magnetite Powder Recovery Rate, Fe3O4 Content, and SO2 Concentration

[0051] ;

[0052] Table 2 Comparison of SO2 fluctuation range, copper recovery rate, and copper content in slag

[0053] ;

[0054] Examples 1-8 show that the recovery rate of magnetite powder is ≥82% and the content of Fe3O4 is ≥92%, which is far superior to the comparative examples. Comparative example 1 has no gradient addition and the heat release is out of control. Comparative example 2 has no oxygen potential regulation and the iron oxide phase transformation is abnormal, which confirms that the core process is the key to performance improvement.

[0055] Increasing the amount of pyrite (Examples 2→1→3) leads to a simultaneous increase in magnetite recovery rate and SO2 concentration; Fe3O4 formation is stable within the oxygen potential range of -10.5 to -11.5; optimizing the SiO2 / FeO molar ratio can reduce slag viscosity and promote grain growth.

[0056] In the example, the copper recovery rate was ≥98.5%, the copper content in the slag was ≤0.45%, and the furnace condition fluctuated little; in the comparative example, due to uncontrolled reaction, the copper recovery rate decreased, the copper content in the slag increased, and the furnace lining erosion intensified.

[0057] The example shows that the flue gas SO2 fluctuation is ≤±8%, which is suitable for acid production systems and significantly increases sulfuric acid production capacity. The process is compatible with existing smelting equipment, reduces energy consumption, meets environmental standards, and has the potential for large-scale application.

[0058] The method described in this invention solves the problems of thermal imbalance and phase change runaway in traditional processes by gradient introduction and directional control of oxygen potential. Different parameter combinations can achieve synergistic improvement of the production capacity of magnetic powder and sulfuric acid, and are applicable to the comprehensive utilization of copper smelting resources.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for copper smelting with pyrite to enhance the production of magnetite and sulfuric acid, characterized by, The method comprises the following steps: A multi-parameter real-time feedback system based on the bath temperature, flue gas SO2 concentration and slag phase FeO activity is established in the copper smelting main reaction zone; According to the feedback signal, the phased addition strategy of pyrite is dynamically planned, the total addition amount is divided into three time intervals of initial ignition stage, steady-state strengthening stage and final period conditioning stage, and the addition rate, particle size distribution and oxygen concentration of the carrier gas of each stage are set to perform directional oxidation control; A local reducing microenvironment control unit is arranged in the slag-sulfide interface area of the smelting furnace, and the proportion of secondary air is adjusted by spraying carbon-containing reducing agent; The high-temperature flue gas is rapidly cooled by a waste heat boiler and then introduced into an acid making system; The total addition amount of pyrite accounts for 12% to 18% of the dry basis mass of copper concentrate; the initial ignition stage lasts for 10 minutes before the smelting period, the addition rate is 25% of the total rate, and the pyrite particles are carried into the upper oxidation zone of the bath by nitrogen gas; the oxygen volume fraction in the carrier gas is 21%; The steady-state strengthening stage is from the 11th minute to the 70th minute of the smelting period, the addition rate is increased to 60% of the total rate, and the pyrite is injected into the middle stirring zone of the bath by oxygen-enriched air; the final period conditioning stage is the last 20 minutes of the smelting period, and the addition rate is reduced to 15% of the total rate, and the pyrite is transported by a low-oxygen carrier gas; The local reducing microenvironment control unit includes 8 groups of reducing agent lances arranged in a ring in the slag line area of the smelting furnace, each group of lances is equipped with an independent flow control valve and a pulse modulator; the reducing agent is anthracite powder with a particle size of 5-15 μm, a fixed carbon content of ≥75%, a spraying pressure of 0.35-0.45 MPa, and a single group spraying flow of 1.2-1.8 kg / min; the spraying timing is started synchronously with the final period addition of pyrite, and closed-loop adjustment is performed according to the FeO activity feedback of the slag sample: when the FeO activity is higher than 0.65, the spraying flow is increased by 10%; when the FeO activity is lower than 0.55, the spraying flow is reduced by 10%; the FeO activity of the slag phase is maintained stable in the interval of 0.58 to 0.

62.

2. The method of claim 1, wherein, The multi-parameter real-time feedback system includes a bath infrared temperature measurement array, an online flue gas analyzer and a slag sample automatic sampling-spectroscopy combined device; the bath infrared temperature measurement array is arranged at a height of 300-500 mm from the slag surface in the side wall of the smelting furnace; the online flue gas analyzer adopts non-dispersive infrared and ultraviolet differential absorption spectroscopy combined detection technology; the slag sample automatic sampling-spectroscopy combined device performs periodic sampling every 15 minutes, and the quenched slag sample is sent into an X-ray fluorescence spectrometer to measure the FeO content.

3. The method of claim 1, wherein, The pyrite addition system adopts a double-channel spiral feeding mechanism, the main channel is used for conveying conventional particle size pyrite, and the auxiliary channel integrates a high-frequency vibrating screen and an air classifier, which can online remove coarse particles that cannot pass through a 100-mesh screen and ultrafine powder that can pass through a 325-mesh screen, to ensure that the particle size distribution standard deviation σ of the material entering the bath is ≤15 μm.

4. The method of claim 3, wherein, The feeding rate of the double-channel screw feeding mechanism is controlled by a variable frequency motor driven metering screw, with an accuracy of ±0.5%, and communicates with the central control system in real time through PROFIBUS-DP protocol to realize dynamic matching of the feeding rate and the smelting load.

5. The method of claim 1, wherein, The directional oxidation regulation further comprises two auxiliary oblique insertion type oxygen lances added in the smelting furnace, the included angle between the nozzle axis and the horizontal plane is 35°, and the insertion depth is to the position 400mm below the liquid surface of the molten pool, which is used for forming a local high oxygen potential vortex area downstream of the pyrite injection point.

6. The method of claim 5, wherein, The oxygen flow of the auxiliary oxygen lance is independently controllable, ranging from 50 Nm 3 / h to 120 Nm 3 / h, and is dynamically adjusted according to the rising rate of flue gas SO2: when d[SO2] / dt>0.8% / s, the auxiliary oxygen lance is closed; when d[SO2] / dt<0.3% / s, it is opened to 80 Nm 3 / h.