A smelting process for the gradient reduction of iron oxides from sulphated slags

Abstract

The present application relates to the technical field of metal material recycling, and discloses a smelting process for gradient reduction of iron oxide in sulfuric acid residue, comprising: feeding the mixture of sulfuric acid residue and reducing agent into a reduction furnace; controlling the generation of lattice stress and inducing the generation of micro-crack channels in the phase change process in the low-temperature section, and adjusting the periodic pressure pulsation of the reducing gas to drive the reciprocating convection of the gas in the channels to discharge impurities; making the reducing gas penetrate to the core in the medium-temperature section; generating a metastable state floatzite thin layer by adjusting the hydrogen-oxygen potential energy when transitioning to the high-temperature section; and completing the metallization reduction in the high-temperature section. The present application utilizes the phase change self-pore creation and pressure pulsation pumping mechanism to eliminate the diffusion back pressure in the reduction process, block the coating of the liquid silicate on the channels, suppress the material sticking and ring formation, and improve the quality of the reduction products.

Description

Technical Field

[0001] This invention relates to a smelting process for gradient reduction of iron oxides in sulfuric acid slag, belonging to the field of metal material recycling technology. Background Technology

[0002] The current mainstream process mixes sulfuric acid slag with a carbon-containing reducing agent and feeds it into a rotary kiln or shaft furnace for reduction. The sulfuric acid slag has dense iron oxide particles and is accompanied by silicate gangue. In direct reduction, the diffusion rate of reducing gas into the material is the rate-limiting factor, and increasing the temperature or reducing agent concentration is a common method. At high temperatures, the ferric oxide on the surface of the sulfuric acid slag is rapidly reduced to elemental iron and micro-melted and welded to form a dense iron shell. The iron shell hinders the penetration of reducing gas into the core, resulting in sandwich slag. The core has a low metallization rate, and premature metallization of the surface increases the thermoplasticity of the material, causing ring formation in the reduction furnace. Simply increasing the temperature or concentration cannot eliminate the contradiction between diffusion limitation and material adhesion.

[0003] Improving the lining structure of the reduction furnace or adjusting the roller arrangement can improve the physical accumulation morphology of the material, but it is difficult to reach the microscopic evolution mechanism of reduction kinetics. It lacks the ability to create microscopic channels inside the material and the dynamic control of the potential energy gradient at the phase interface. It cannot break through the technical dilemma of blocked reducing gas permeation and high-temperature interface adhesion. For example, Chinese invention patent with authorization announcement number CN102627321B discloses a method for preparing titanium dioxide from titanium slag obtained by direct reduction of titanium iron oxide. The slag phase after reduction is treated by hydrochloric acid leaching. This scheme focuses on the later purification of product components and belongs to the static purification at the end of the reduction product. At the level of dynamic control of the reduction process, it cannot induce the generation of interconnected microcrack networks inside the particles to eliminate diffusion back pressure. It lacks a real-time suppression mechanism for the liquid phase coating phenomenon in the reduction transition stage. Before the material enters the high-temperature metallization section, the inside is in a dense and confined state.

[0004] Therefore, the technical problem to be solved by this invention is how to provide a smelting process for gradient reduction of iron oxides in sulfuric acid slag, which constructs diffusion channels by controlling phase transformation and suppresses material adhesion in high-temperature zones. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A smelting process for gradient reduction of iron oxides in sulfuric acid slag, comprising the following steps: step The sulfuric acid residue material is mixed with a carbon-containing reducing agent according to... to The carbon-oxygen ratio is physically mixed and then fed into a reduction furnace with multiple independently controlled temperature zones. step In the first reduction section, the ambient temperature is controlled at... to The volume percentage of carbon monoxide introduced is to The first reducing gas controls the transformation of ferric oxide phase to magnetite phase in sulfuric acid residue material; the lattice stress is generated by the difference in unit cell volume between ferric oxide and magnetite, and interconnected microcrack channels are induced inside the particles of sulfuric acid residue material. step During the operating cycle of the first reduction section, the amplitude of adjusting the supply pressure of the first reducing gas is... to The periodic pulse fluctuations; utilizing the instantaneous internal-to-external pressure gradient generated inside the microcrack channel by the pulse fluctuations, the gas inside the microcrack channel generates reciprocating convection in and out of the particle core, and discharges the vaporized metal impurities to the outside of the particle. step In the second reduction section, the ambient temperature is controlled at... to The volume percentage of carbon monoxide introduced is to The second reducing gas allows the reducing gas in the microcrack channel to continuously penetrate into the particle core; step During the transition from the second reduction stage to the third reduction stage, by adjusting the hydrogen-oxygen potential energy ratio in the reducing atmosphere, a metastable flostenite layer with an atomic thickness is generated at the interface between the gangue component and elemental iron in the particles of sulfuric acid slag material. This layer is used to block the coating and penetration of liquid silicate on the wall of the microcrack channel. step In the third reduction section, the ambient temperature is controlled at... to Then, a third reducing gas is introduced to complete the final metallization reduction.

[0006] Preferably, in the execution step At the same time, obtain the real-time rotation speed of the reduction furnace. inner diameter of the reduction furnace And according to the rotation speed With inner diameter Calculate the radial tumbling cycle of sulfuric acid residue in the reduction furnace. The pulsation period of the periodic pulse fluctuation of the first reducing gas is set as follows: By adjusting the control frequency of the induced draft system, and The following relationship must be satisfied: ,in, This is the pressure fluctuation cycle of the first reducing gas. The radial tumbling cycle of sulfuric acid residue material in the reduction furnace is used to enhance the exchange efficiency of reciprocating convection by utilizing the mechanical shear force generated by the sulfuric acid residue material during the tumbling process.

[0007] Preferably, in the execution step At that time, by intermittently increasing the partial pressure of carbon monoxide in the first reducing gas to trigger the Budow reaction, nanoscale carbon seeds are deposited in situ on the wall of the microcrack channel; the nanoscale carbon seeds are used to react with the generated carbon dioxide in the subsequent second and third reduction stages to regenerate carbon monoxide.

[0008] Preferably, at the junction of the first reduction section and the second reduction section, a locally regulated airflow with a temperature lower than that of the first reduction section is introduced to perform instantaneous thermal shock treatment on the particle surface of the sulfuric acid residue material; the thermal shrinkage radial stress and lattice stress generated by the thermal shock treatment are superimposed on the spatial vector to guide the microcrack channel to extend to the depth of the particle core.

[0009] Preferably, in step In this process, by adjusting the oxygen potential of the first reducing gas, the conversion rate of the ferric oxide phase is controlled to be no less than [a certain percentage]. And ensure that the oxygen potential of the reducing atmosphere in the second reduction stage is lower than that in the first reduction stage.

[0010] Preferably, using steps The pulse fluctuations generated in the process discharge the vaporized zinc and lead impurities from the sulfuric acid slag particles, preventing the metal impurities from condensing and blocking the walls of the microcrack channels.

[0011] Preferably, the material filling rate in the reduction furnace is maintained at to Between them, and at the connection points of the first reduction section, the second reduction section and the third reduction section, physical sealing partitions are provided to maintain the chemical potential gradient in different reduction regions.

[0012] Preferably, in the execution step At that time, by introducing water vapor of varying partial pressure into the reduction furnace, the reducing atmosphere is... The potential energy ratio is controlled below the critical point where the stearite and gangue components undergo a eutectic reaction.

[0013] Preferably, the sulfuric acid residue material enters the step Previously, multi-stage sieving was performed to extract particles with a diameter of [missing value]. to The material components are fed into the reduction furnace.

[0014] Preferably, the metallization rate of the reduced iron powder produced by the smelting process is not less than Furthermore, the slag discharged from the third reduction stage remains in a solid, loose state, without any ring-forming or sticking phenomenon.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In the iron oxide gradient of sulfuric acid slag, the difference in unit cell parameters generated by the transformation of hematite to magnetite is utilized to induce lattice stress at a controlled phase transformation rate in the low-temperature region and form a microcrack network inside the particles. The dense slag structure is transformed into a connected pore structure, and the reduction kinetics are changed from diffusion-restricted to interface reaction-restricted, thus avoiding the formation of a dense iron shell by reducing gas only reacting on the particle surface.

[0016] 2. Periodically adjust the volume percentage of carbon monoxide in the reducing atmosphere. Utilize the instantaneous accumulation of carbon dioxide, a reduction product, in the microcrack channels to generate an inward-outward pressure gradient. This drives the vaporization of zinc and lead metal impurities deep within the particles to be discharged to the outside of the particles with the airflow. This prevents impurities from condensing and forming a shell on the pore walls, maintains the unobstructed flow of microcrack channels throughout the entire process, achieves the removal of harmful elements, and ensures that the reducing gas in the medium- and high-temperature stages continuously reaches the core area of ​​the particles.

[0017] 3. During the transition from medium to high temperature, the hydrogen-oxygen potential energy ratio of the reducing atmosphere is adjusted to induce an atomically thick metastable flostenite layer at the interface between the gangue components and elemental iron within the slag particles. This thin layer occupies the chemically active sites of the gangue components, blocking the eutectic reaction between elemental iron and silica and alumina to form a low-melting-point silicate liquid phase. The microcrack walls maintain dry solid phase characteristics during the high-temperature reduction stage, preventing the liquid phase from covering the channels and causing reduction stall, reducing the thermoplasticity of the material in the high-temperature zone, and avoiding the formation of agglomeration rings in the reduction furnace. Attached Figure Description

[0018] Figure 1 This is a flow chart of the multi-stage gradient reduction process of sulfuric acid slag iron oxide in this invention; Figure 2 This is a graph showing the kinetic response of periodic pressure pulsation and impurity removal in this invention. Figure 3 This is a control architecture diagram of the multi-field coupled gradient reduction smelting system of the present invention. Detailed Implementation

[0019] To make the technical solutions, features and advantages claimed in this invention clearer, the invention will be described in detail below with reference to specific embodiments. The following embodiments are intended to explain the invention and not to limit the scope of protection of the invention.

[0020] This invention discloses a smelting process for gradient reduction of iron oxides from sulfuric acid slag. By establishing multiple independent temperature-controlled zones within the reduction furnace, and utilizing the lattice stress associated with phase transformation to create diffusion channels, coupled with a pressure pulsating pumping mechanism and phase interface steady-state control, efficient reduction and impurity removal of sulfuric acid slag are achieved. In the material preparation stage, the sulfuric acid slag is pre-treated with multi-stage sieving to extract particles with a particle size of [missing information]. to The material components are fed into the reduction furnace; the sulfuric acid slag material and carbon-containing reducing agent are mixed according to... to The carbon-to-oxygen ratio is physically mixed; the material filling rate in the reduction furnace is maintained at [value missing]. to Between these sections, and at the connections between the first, second, and third reduction sections, physical seals are installed to maintain the chemical potential gradients within different reduction regions; within the first reduction section, the ambient temperature is controlled at... to The volume content of carbon monoxide introduced is to The first reducing gas is used; in this stage, hematite in the sulfuric acid slag material transforms into magnetite, that is, ferric oxide transforms into magnetite; the difference in cell volume between ferric oxide and magnetite generates lattice stress, and induces interconnected microcrack channels within the particles of sulfuric acid slag material; to guide the microcrack channels to extend to the particle core depth and inhibit fine particle pulverization, a locally regulated airflow with a temperature lower than the ambient temperature of the first reduction stage is introduced at the junction of the first and second reduction stages to perform instantaneous thermal shock treatment on the surface of the material particles, and crack propagation is achieved by superimposing the thermal shrinkage radial stress and lattice stress in the spatial vector; by intermittently increasing the partial pressure of carbon monoxide in the first reducing gas to trigger the Fidol reaction, nanoscale carbon seeds are deposited in situ on the walls of the microcrack channels; the nanoscale carbon seeds are used to react with the generated carbon dioxide in the subsequent reduction stage to regenerate carbon monoxide and provide reduction potential energy for the particle core region.

[0021] During the first reduction stage operation cycle, the amplitude of adjusting the supply pressure of the first reducing gas is... to The periodic pulse fluctuations; the pulse amplitude of 2kPa to 5kPa set here is not intended to overcome steady-state seepage resistance, but to utilize the compressibility of the gas and the volume effect of the microcrack channels to generate a breathing effect. When the external pressure is at the peak of the pulse wave, the reducing gas is forced into the open microcracks pre-created by the lattice stress; when the pressure rapidly switches to the trough, the instantaneous pressure difference between the microcrack cavity inside the particle and the external environment is much greater than the conventional diffusion driving force. This pressure difference is sufficient to overcome the viscosity of high-viscosity metal vapor on the pore wall, thereby driving the vaporized zinc and lead impurities deep in the pore to be discharged in the form of convection; at this time, the real-time rotation speed of the reduction furnace is obtained. inner diameter of the reduction furnace And according to the rotation speed With inner diameter Calculate the radial tumbling cycle of sulfuric acid residue in the reduction furnace. The pressure pulsation period of the first reducing gas is set to... By adjusting the control frequency of the induced draft system, and The following relationship must be satisfied: The physical basis for setting this ratio range lies in the evolution of the porosity of the particle layer within the rotary kiln. During each tumbling cycle R, the material rises and collapses with the kiln body. At the moment of collapse, the particle layer is in a loose, expanding state, at which point the porosity reaches its peak. By controlling P / R between 0.6 and 0.8, it is ensured that the peak of the pressure pulsation can capture the time window when the material layer is in a loose state, thereby minimizing the macroscopic resistance of the reducing gas entering the particle gaps and achieving high-frequency, effective gas-solid contact. The pulse fluctuations generate an instantaneous pressure gradient within the microcrack channel, driving the gas within the channel to generate reciprocating convection in and out of the particle core, and discharging vaporized zinc and lead impurities to the outside of the particles, preventing metal impurities from condensing and blocking the channel walls. In the second reduction section, the ambient temperature is controlled at... to The volume content of carbon monoxide introduced is to The second reducing gas; the reducing gas continuously permeates into the particle core along the microcrack channels, completing the phase reduction; by adjusting the oxygen potential of the first reducing gas, the conversion rate of the ferric oxide phase is controlled to be no less than And ensure that the oxygen potential of the reducing atmosphere in the second reduction stage is lower than that in the first reduction stage.

[0022] During the transition from the second to the third reduction stage, the hydrogen-oxygen potential energy ratio in the reducing atmosphere is adjusted by introducing a method to regulate the partial pressure of water vapor; thus, the reducing atmosphere... The potential energy ratio is controlled below the critical point for the eutectic reaction between putrescite and gangue components. To establish the criterion for the formation of a metastable putrescite thin layer in the high-temperature region, the system executes a phase interface steady-state maintenance procedure based on heat flux density sensing. This involves using an infrared thermometer array installed outside the reduction furnace shell to acquire real-time thermal intensity data of the material particle surface. The controller dynamically adjusts the steam injection space velocity based on the deviation between the thermal intensity data and the theoretical latent heat of phase transformation at the eutectic point, maintaining the local oxygen potential at the phase interface at the upper edge of the putrescite stable region. During the residence time from the second reduction section to the third reduction section, the volume percentage of steam is controlled within a certain range. to Within this range, a layer of thickness is induced at the interface between elemental iron and silicate gangue. to The ferrous oxide transition zone in the interval blocks the capillary penetration of liquid silicate into the particle surface, causing the material particles to... The high-temperature reduction zone described above still maintains the characteristics of a solid bulk material. In actual operation, since this nanoscale thin layer cannot be observed in real time through physical sampling, the system indirectly controls it by establishing a chemical potential window based on gas-solid reaction equilibrium. Specifically, the controller has pre-stored the iron-ferrous oxide-ferroolitic equilibrium phase diagram curves corresponding to the sulfuric acid slag components, and maintains the local oxygen potential at the reaction sites. Located 0.2 to 0.5 orders of magnitude above the iron / steatite equilibrium line, thickness self-locking is achieved using the self-limiting property of phase transformation kinetics; when the infrared thermography array monitors the rate of change of thermal intensity on the surface of the material particles... When abnormal fluctuations occur, indicating a shift in the latent heat of phase transformation at the interface, the system adjusts the vapor space velocity to change the hydrogen-oxygen activity ratio of the interface boundary layer, thereby limiting the growth rate of the flosite layer to between 10-20 nm per minute. This ensures that the layer thickness remains stable at 300-500 nm during the transition from the second to the third reduction stage. The system is pre-set with a metastable window function calculated based on the Fe-O-Si ternary phase diagram. The intensity of thermal radiation on the surface of particles is obtained by an infrared thermometer array at a sampling frequency of 20Hz and converted into real-time temperature. Calculate the rate of change of surface thermal intensity This is compared with the critical heat flux density of phase change calibrated based on thermal equilibrium gradient experiments. Compare, if the deviation is The controller retrieves the water vapor coupling gain coefficient λ preset in the ROM, and uses the formula... Real-time updates of actuator airspeed enable closed-loop compensation of the hydrogen-oxygen potential energy ratio γ, locking the γ value within the flosite stability domain. The upper limit is negatively offset within a narrow range of 0.1 to 0.2 to compensate for the non-uniformity of heat transfer caused by furnace rotation, where α is the emissivity correction factor calibrated based on the Stefan-Boltzmann law; within the third reduction stage, the ambient temperature is controlled at... to A third reducing gas is then introduced to complete the final metallization reduction; the metallization rate of the reduced iron powder produced by this smelting process is not less than... Furthermore, the discharged slag showed no signs of clumping or sticking.

[0023] Example 1: In the treatment of total iron content of Zinc content is And contains In the smelting process of high-density sulfuric acid slag from silicate gangue, the porosity of the material is lower than that of silicate gangue due to the high-temperature process in the early stage. When the reducing ambient temperature is At this point, a layer of elemental iron rapidly forms on the particle surface. This iron shell blocks the penetration of reducing gas into the particle core, causing a delay in the reduction reaction of internal iron oxides and resulting in insufficient metallization. The product, along with the surface micro-melted elemental iron reacting with silicate gangue to produce liquid-phase adhesion, triggers ring formation on the inner wall of the reduction furnace. Using the gradient reduction process described above, the particle size is... to The sulfuric acid residue material in the interval and the carbon-containing reducing agent are according to The carbon-to-oxygen ratio is physically mixed and fed into a reduction furnace, where the controlled temperature is set to [temperature value missing] in the first reduction section. And introduce carbon monoxide with a volume content of The first reducing gas, used within this temperature range Towards The lattice volume difference caused by the phase transformation generates interconnected microcrack channels within the particles, while the real-time rotation speed of the reduction furnace is simultaneously acquired. for and the inner diameter of the reduction furnace for The radial tumbling cycle of the material is calculated based on the material's movement trajectory. for The pressure pulsation cycle is adjusted by regulating the airflow frequency. Locked to ,at this time and The ratio is , in to The process range, in which The pressure pulsation period is expressed in units of 1. , The radial tumbling cycle of the material, in units of , The speed of the reduction furnace is expressed in units of _____. , This refers to the inner diameter of the reduction furnace, in units of... The dynamic pressure gradient generated by the pressure pulse drives the reducing gas to reciprocate convection within the microcrack channel, removing gaseous zinc impurities from the interior of the particles.

[0024] When the material transitions from the second reduction section to the third reduction section, the ambient temperature changes from... Upgraded to The generated microcrack channels guide the reducing gas to permeate into the particle core, and regulating water vapor is introduced to... When the potential energy ratio is below the critical point of the eutectic reaction between elemental iron and gangue components, a metastable flostenite layer with atomic-level thickness is formed at the phase interface. This thin layer blocks the penetration and spreading of liquid silicate on the walls of microcrack channels, allowing the material to maintain its solid-state bulk characteristics in the high-temperature region. The measured metallization rate of the final reduced iron powder is [missing information]. Furthermore, there is no slag residue adhering to the inner wall of the reduction furnace.

[0025] Example 2: The experiment was conducted in a three-section horizontal furnace with multiple independent temperature control functions, wherein the temperature control accuracy of each section was maintained at... It is also equipped with a data acquisition frequency of The pressure monitoring unit; the total iron content of the original sulfuric acid slag material used in the experiment was... The initial porosity is During the trial operation, the servo frequency of the induced draft system was adjusted and an amplitude was superimposed in the air path. High-frequency pressure disturbances were used to simulate flow field fluctuations under industrial conditions; the experimental group was run according to the steps of claim 1, wherein the temperature of the first reduction section was set to... The carbon-oxygen ratio is set to .

[0026] The core parameter settings follow the ratio of the pressure pulsation period to the tumble period. The decision-making logic, ratio Used to balance the removal efficiency of internal metal impurities in particles with the dust load of the reduction furnace exhaust gas; when the real-time rotation speed of the reduction furnace is obtained. Fluctuations occur, causing the radial tumbling cycle of the material calculated based on the material's movement trajectory to be affected. When corresponding changes occur, the system adjusts the pressure pulsation period proportionally. To maintain the intensity of the pulsation; if the ratio Below The dynamic pressure gradient within the microcrack channel is insufficient to overcome the gas diffusion resistance; if the ratio Higher than Excessive pressure impact can cause an imbalance in the stress distribution on the surface of material particles. The experimental setup includes multiple sample groups to verify the technical effect. The experimental group adopts a complete gradient reduction procedure. Control group 1 removes the pressure pulsation pumping step, control group 2 removes the lattice reconstruction pore step in the first reduction stage, and control groups 3 and 4 are respectively compared with the ratio of Table 1 records the comparison data of key indicators under different test conditions, set outside the preset range.

[0027] Table 1: Validation Data of Gradient Reduction Process for Sulfuric Acid Residue

[0028] in, The pressure pulsation period is expressed in units of 1. ; The radial tumbling cycle of the material, in units of ; The value represents the residual zinc mass fraction in the reduced product, expressed in units of... ; A dimensionless parameter reflecting the degree of connectivity of pores within particles; Metallization rate of the product, in units of Analysis of the data in Table 1 shows that in control group 2, which lacks the first reduction phase transformation pore-forming process, the microcrack connectivity rate inside the particles is... Only This leads to a decrease in the amount of residual zinc after reduction. achieve Furthermore, material agglomeration was observed; in contrast, the experimental group, which combined phase change pore formation with pressure pulsation pumping, achieved a higher microcrack connectivity rate. achieve Final metallization rate achieve Although control group 4 had a lower residual zinc content, its pulverization rate exceeded the process limit. The data reflects that the interconnected pore network established by the gradient reduction process is the foundation for improving metallization rate, and is limited by... The range achieves a balance between impurity removal efficiency and material physical stability.

[0029] Example 3: This example combines Figures 1 to 3 A description of a smelting process for gradient reduction of iron oxides from sulfuric acid slag, such as... Figure 1 As shown, the main process flow begins in the material mixing and proportioning unit, where sulfuric acid slag and reducing agent are physically mixed at a carbon-oxygen ratio of 1.0 to 1.2. The mixture then enters the low-temperature phase transformation pore-forming unit, where microcracks are induced by lattice stress within a temperature range of 650°C to 750°C. This unit also receives pulse drives of 2 kPa to 5 kPa from a periodic pressure pulsation module to pump out impurities. The treated material then enters the medium-temperature core permeation unit at 850°C to 950°C, allowing reducing gas to permeate into the core. In the metastable interface control unit, the H2 / H2O ratio in the atmosphere is adjusted by the hydrogen-oxygen potential energy regulation module, generating an atomic-level floatite thin layer at the interface to block the liquid phase. Finally, the material enters the high-temperature metallization reduction unit at 1050°C to 1150°C to complete the final metallization, producing high-metallization-rate iron powder and reduction products in a solid bulk state.

[0030] like Figure 2 As shown, this two-dimensional coordinate graph uses time (in minutes) as the horizontal axis, the left vertical axis represents pressure pulsation (in kPa), and the right vertical axis represents impurity content (in wt%). The solid line in the graph depicts the pressure pulsation as a periodic sawtooth oscillation waveform within the range of -2 kPa to 2.5 kPa. Simultaneously, the dashed line representing zinc impurity content decreases over time from above 0.8 wt% to below 0.2 wt%, and the dotted line representing lead impurity content shows a synchronous decreasing trend. Figure 3 As shown, the core node of this smelting system is a multi-stage gradient reduction rotary kiln containing low-temperature, medium-temperature, and high-temperature sections. Its top is connected to the batching and feeding terminal to receive the mixed material input, and its bottom is connected to the unloading and separation terminal to output the finished product. A process intelligent control server is configured on the left side of the system, which is connected to the core node through a real-time monitoring and speed adjustment module, and has a built-in tumbling cycle coupling calculation module to control the pulsation frequency. It is also connected to an infrared and pressure array for data acquisition. A dynamic atmosphere control station is set up on the right side of the system, which delivers pulsating airflow and water vapor to the core node. The control station is equipped with a pressure pulsation generator to remove impurities and a hydrogen-oxygen potential energy regulating valve to block the formation of liquid phase.

[0031] Example 4: In the inner diameter for And real-time rotation speed for In the operation scenario of a reduction furnace, in order to solve the problem of pressure pulsation mismatch caused by the dynamic tumbling characteristics of materials, the system obtains the material deflection angle through a displacement sensor. The controller is used to execute the parameter calibration program according to the formula. Determine the radial tumbling cycle of the material According to the formula Output pressure pulsation cycle control command, where The radial tumbling cycle of the material, in units of , The real-time rotation speed of the reduction furnace is expressed in units of 1000 rpm. , This refers to the inner diameter of the reduction furnace, in units of... , The dynamic deflection angle of the material within the reduction furnace, measured in units of... , The pressure pulsation period is expressed in units of 1. When the material is driven by gravity to produce radial displacement, the system drives the induced draft fan to generate a response similar to that of the material via frequency conversion commands. The matched periodic pressure difference dynamically adjusts the gas convection rate in the microcrack channels inside the particles with the tumbling frequency, ensuring that the reducing gas reaches the particle core in each tumbling cycle, while maintaining the ambient temperature. for During the transition from the second reduction stage to the third reduction stage, in order to block the physical path of high-temperature eutectic liquid phase formation, the system executes a process based on the hydrogen-oxygen potential ratio. The self-calibration procedure involves the controller monitoring the composition of the reducing atmosphere in real time via a mass spectrometer and adjusting the opening of the steam injection valve to achieve the correct hydrogen-oxygen potential ratio. Locked in by formula Within a defined interval, To recreate the atmosphere and The volume percentage of content, and These are thermodynamic constants related to the eutectic kinetics of iron silicate. The absolute temperature of the ambient temperature, in units of . Under this controlled atmosphere, a metastable flotite isolation layer remains at the interface between elemental iron and gangue components within the sulfuric acid slag particles. This metastable flotite isolation layer blocks the penetration and spreading of liquid silicate on the walls of microcrack channels, preventing the particles from... The high-temperature zone above remains in a bulk state. The system retrieves the eutectic equilibrium constant of fir olivine calibrated based on the Kulikov thermodynamic database, setting coefficients A=2.86 and B=5240. Here, coefficients A and B are based on the specific alkalinity of the silicate gangue contained in the sulfuric acid slag in this embodiment (i.e., The empirical constants, corrected for the mass ratio, are as follows: coefficient B corresponds to the extrapolated standard enthalpy change of formation for the iron silicate formation reaction, while coefficient A reflects the liquidus slope correction value introduced by trace amounts of alumina and magnesium oxide in the material. A discriminant function constructed using these two constants can accurately determine the critical temperature at which this batch of material undergoes eutectic melting under a specific reduction potential; the controller provides feedback via a mass spectrometer. and Using mole fraction as the input vector, the real-time reduction potential of the current atmosphere is calculated. Simultaneously acquire the uniformity of the material layer measured by the thermocouple array embedded inside the furnace lining. If the calculated value γ is different from the threshold When the Euclidean distance is less than 0.03, the proportional-integral-derivative control command of the steam injection valve is triggered, and the output is changed from... It is determined that the driving water vapor partial pressure increases at a slope of 0.5 kPa / s until γ returns to 10% below the safety envelope. The self-calibration frequency and the rotary kiln tumbling cycle R satisfy a 1:5 ratio relationship, which counteracts the oxygen potential disturbance at the gas-solid reaction interface caused by the fluctuation of gangue content in the material entering the furnace.

[0032] To meet the engineering requirements for the thermal shock intensity at the outlet of the first reduction section, the system determines the cooling temperature difference of the locally regulated airflow through gradient experiments. The specific operating procedures include injecting regulated airflows of different temperature levels into the interface zone and monitoring the phase transition stress field distribution of the particle core, among which... , The controlled ambient temperature of the first reduction stage, in units of , To locally adjust the injection temperature of the airflow, the unit is... When the experiment will Depend on Upgraded to At this time, the radial stress caused by thermal shrinkage during cooling inside the particle and the lattice volume stress caused by phase transformation are superimposed in the space vector. The measured microcrack density in the core region of the material shows a monotonically increasing trend with increasing temperature difference, while when Continue to increase to The material pulverization index was changed from Increase to Based on this, The work window is locked in to This allows for the generation of a radial crack network that penetrates the core of the particle, while simultaneously inhibiting the breakage of the particle surface.

[0033] For the process specification of in-situ deposition of nanoscale carbon seeds in the first reduction stage, the system executes a process based on the partial pressure of carbon monoxide. The pulse modulation program, i.e., the controller adjusts the flow ratio of the first reducing gas and the diluting inert gas based on the reducing gas composition data fed back by the online gas chromatograph, so that the pulse modulation program in the first reduction section... exist to Sinusoidal fluctuations are generated within the range. At this point, the hematite active sites on the inner wall of the microcrack channel are used as catalytic centers for the Büdow reaction, at a reduction temperature of [temperature missing]. Under certain operating conditions, carbon monoxide in the induced gas phase undergoes a disproportionation reaction and precipitates solid carbon atoms. The deposition rate of solid carbon atoms on the surface of cracks inside the particles is calculated by the controller. The consumption rate change is fed back in a closed loop; when the consumption rate changes relative to the thermodynamic equilibrium value... The instantaneous drop is determined to be the formation of a carbon seed layer, thus providing in-situ reduction power for the subsequent medium-temperature reduction stage without damaging the physical structure of the microcracks.

[0034] Example 5: In the equipment commissioning scenario of a newly built smelting production line, the system executes a pressure balance calibration procedure based on physical sealing isolation. Under no-load conditions in the reduction furnace, a pressure gradient is introduced into the first reduction section. to The leakage coefficient of the physical seal is determined by monitoring the pressure response curves of the second and third reduction sections of the inert gas in the interval. It is a dimensionless parameter; it is used to compensate for changes in the partition gaps caused by the thermal expansion of the furnace body. The controller obtains the real-time temperature of each temperature zone of the furnace body. And calculate the thermal expansion displacement, For the first Real-time temperature of the temperature zone, in units of The gas flow rate under the current operating condition is determined based on the pressure decay slope, and a reference compensation value is output to adjust the frequency of the reducing gas induced draft fan, so as to maintain a constant chemical potential gradient in different reduction regions.

[0035] When the system encounters different batches of sulfuric acid residue material with fluctuating material density, the process executes a material permeability benchmark calibration procedure. Before the material enters the first reduction stage, the pressure loss coefficient of that batch of material is obtained through a fluidization testing device. The controller performs correlation calculations based on the pressure loss coefficient and a preset material porosity model to determine the reduction rate required to induce lattice stress and create pores for the current batch. The actual reduction rate is achieved by adjusting the inlet space velocity of the first reducing gas. and The ratio is at to The constraint interval, where This represents the actual reduction rate, in units of... , Critical reduction rate, in units of This process, while suppressing localized thermal stress on the material surface, allows lattice expansion stress to be uniformly released across the entire radial direction of the particles. Actual measurements show that the deviation in the internal microcrack connectivity of the material calibrated according to this procedure is less than [a certain value] when it enters the second reduction stage. .

[0036] Example 6: When daily output is at In a large-scale gradient reduction smelting scenario using sulfuric acid slag, the system executes a reducing agent matching procedure based on the chemical activity of the materials, that is, obtaining the fixed carbon content of the carbon-containing reducing agent through sampling analysis. ,in It is a percentage of mass; the controller is based on the formula. Issue feeding instructions. This is the feed mass flow rate of the carbon-containing reducing agent, in units of... , This refers to the feed mass flow rate of sulfuric acid residue, in units of... , The reaction ratio coefficient is used to match the distribution density of activated carbon in the furnace mixture with the pore evolution rate generated by the phase transformation, thereby establishing a reduction potential field in the first reduction section.

[0037] When the system encounters a sealing displacement deviation caused by thermal expansion of the inner cylinder of the reduction furnace, the system executes a gas flow path calibration procedure based on the feedback of the sealing isolation torque, that is, the controller obtains the instantaneous pressure difference between the first reduction section and the second reduction section. The mechanical compensation displacement of the physical seal partition was calculated based on the furnace body's coefficient of linear expansion. , Pressure difference, unit: , To compensate for displacement, the unit is... ; By adjusting the output torque of the sealing drive device to maintain the positive pressure at the isolation interface, when a pressure difference is detected The deviation value exceeds At the same time, the exhaust system synchronously adjusts the output frequency of the frequency converter to bring the chemical potential gradient in the reduction zone back to the process value, thereby blocking the cross-zone flow of reducing gas.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A smelting process for gradient reduction of iron oxides from sulfuric acid slag, characterized in that, Includes the following steps: step The sulfuric acid residue material is mixed with a carbon-containing reducing agent according to... to The carbon-oxygen ratio is physically mixed and then fed into a reduction furnace with multiple independently controlled temperature zones. step In the first reduction section, the ambient temperature is controlled at... to The volume percentage of carbon monoxide introduced is to The first reducing gas controls the transformation of ferric oxide phase to magnetite phase in sulfuric acid residue material; the lattice stress is generated by the difference in unit cell volume between ferric oxide and magnetite, and interconnected microcrack channels are induced inside the particles of sulfuric acid residue material. step During the operating cycle of the first reduction section, the amplitude of adjusting the supply pressure of the first reducing gas is... to The periodic pulse fluctuations; utilizing the instantaneous internal-to-external pressure gradient generated inside the microcrack channel by the pulse fluctuations, the gas inside the microcrack channel generates reciprocating convection in and out of the particle core, and discharges the vaporized metal impurities to the outside of the particle. step In the second reduction section, the ambient temperature is controlled at... to The volume percentage of carbon monoxide introduced is to The second reducing gas allows the reducing gas in the microcrack channel to continuously penetrate into the particle core; step During the transition from the second reduction stage to the third reduction stage, by adjusting the hydrogen-oxygen potential energy ratio in the reducing atmosphere, a metastable flostenite layer with an atomic thickness is generated at the interface between the gangue component and elemental iron in the particles of sulfuric acid slag material. This layer is used to block the coating and penetration of liquid silicate on the wall of the microcrack channel. step In the third reduction section, the ambient temperature is controlled at... to Then, a third reducing gas is introduced to complete the final metallization reduction.

2. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, In execution steps At the same time, obtain the real-time rotation speed of the reduction furnace. inner diameter of the reduction furnace And according to the rotation speed With inner diameter Calculate the radial tumbling cycle of sulfuric acid residue in the reduction furnace. The pulsation period of the periodic pulse fluctuation of the first reducing gas is set as follows: By adjusting the control frequency of the induced draft system, and The following relationship must be satisfied: ,in, This is the pressure fluctuation cycle of the first reducing gas. The radial tumbling cycle of sulfuric acid residue material in the reduction furnace is used to enhance the exchange efficiency of reciprocating convection by utilizing the mechanical shear force generated by the sulfuric acid residue material during the tumbling process.

3. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, In execution steps At that time, by intermittently increasing the partial pressure of carbon monoxide in the first reducing gas to trigger the Budow reaction, nanoscale carbon seeds are deposited in situ on the wall of the microcrack channel; the nanoscale carbon seeds are used to react with the generated carbon dioxide in the subsequent second and third reduction stages to regenerate carbon monoxide.

4. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, At the junction of the first reduction section and the second reduction section, a locally regulated airflow with a temperature lower than that of the first reduction section is introduced to perform instantaneous thermal shock treatment on the particle surface of the sulfuric acid residue material; the thermal shrinkage radial stress and lattice stress generated by the thermal shock treatment are superimposed on the spatial vector to guide the microcrack channel to extend to the depth of the particle core.

5. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, In the steps In this process, by adjusting the oxygen potential of the first reducing gas, the conversion rate of the ferric oxide phase is controlled to be no less than [a certain percentage]. And ensure that the oxygen potential of the reducing atmosphere in the second reduction stage is lower than that in the first reduction stage.

6. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, Utilization steps The pulse fluctuations generated in the process discharge the vaporized zinc and lead impurities from the sulfuric acid slag particles, preventing the metal impurities from condensing and blocking the walls of the microcrack channels.

7. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, The material filling rate in the reduction furnace is maintained at to Between them, and at the connection points of the first reduction section, the second reduction section and the third reduction section, physical sealing partitions are provided to maintain the chemical potential gradient in different reduction regions.

8. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, In execution steps At that time, by introducing water vapor of varying partial pressure into the reduction furnace, the reducing atmosphere is... The potential energy ratio is controlled below the critical point where the stearite and gangue components undergo a eutectic reaction.

9. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, sulfuric acid residue material enters the step Previously, multi-stage sieving was performed to extract particles with a diameter of [missing value]. to The material components are fed into the reduction furnace.

10. The smelting process for gradient reduction of iron oxides in sulfuric acid slag according to claim 1, characterized in that, The metallization rate of reduced iron powder produced by the smelting process is not less than Furthermore, the slag discharged from the third reduction stage remains in a solid, loose state, without any ring-forming or sticking phenomenon.

Images