Method for preparing active calcium oxide by using carbide slag

Abstract

The application discloses a method for preparing active calcium oxide by using carbide slag, which comprises the following steps: screening the particle size of the carbide slag raw material by using an airflow classifier, adding an ammonium citrate solution into a stirring tank to obtain a sulfur-removed carbide slag mixture, performing solid-liquid separation on the sulfur-removed carbide slag mixture, and then feeding the solid-liquid separated carbide slag mixture into a continuous sintering furnace for staged sintering, wherein the continuous sintering furnace is sequentially provided with a first temperature zone and a second temperature zone along the material conveying direction, the sintered material is cooled to room temperature, and the activity of the material is detected by using a pH-temperature combined detection device; by accurately grading the core particle size section of the carbide slag, the application significantly improves the recovery rate of the target particles, reduces the production loss, deeply removes the impurities of the carbide slag, improves the product purity, guarantees the product activity and strength, and improves the product qualified rate through standardized and accurate detection, and the production link has environmental protection and safety.

Description

Technical Field

[0001] This invention relates to the field of airtightness testing technology, specifically a method for preparing active calcium oxide using carbide slag. Background Technology

[0002] The steel industry is a pillar industry of the national economy, but its production processes, such as sintering and converters, generate large amounts of sulfur-containing flue gas, making it a key area for air pollution control. According to GB 28662-2012 "Emission Standard of Air Pollutants for Iron and Steel Sintering and Pelletizing Industry" and subsequent revisions, the SO2 concentration in the flue gas from the outlet of sintering machines and converters in iron plants must be strictly controlled at 50 mg / m³. 3 In some environmentally sensitive areas, the concentration is further reduced to 30 mg / m³. 3 From the perspective of flue gas characteristics, desulfurization in ironworks mainly faces two typical scenarios: desulfurization of sintering machine flue gas and desulfurization of converter flue gas. Desulfurization of sintering machine flue gas requires the desulfurization system to have the ability to quickly respond to concentration fluctuations and resist dust interference. Currently, the mainstream approach is to use semi-dry or dry desulfurization processes. Desulfurization of converter flue gas requires the desulfurizing agent to have the characteristics of high temperature resistance, easy transportation, and no impact on subsequent flue gas recovery. Dry injection process has become the mainstream choice because it does not generate wastewater and is suitable for intermittent operating conditions. Regardless of the scenario, the performance (and cost) of the desulfurizing agent are the core factors that determine the economy and environmental protection of the desulfurization system. Currently, most desulfurization systems in ironworks rely on purchased quicklime as the core desulfurizing agent. The high overall cost of desulfurizing agents increases the burden on enterprises. The inherent performance defects of quicklime make it difficult for desulfurization systems to stably cope with changes in flue gas characteristics. At the same time, while iron plants produce desulfurization slag, chemical workshops such as PVC and acetylene also produce a large amount of calcium carbide slag. Calcium carbide slag is a strongly alkaline solid waste. The traditional treatment method is open-air storage or landfill, which requires the construction of seepage prevention ponds. Moreover, the leachate is prone to polluting the soil and groundwater. In addition, the quicklime desulfurization slag has a large amount of residual CaO and contains a large number of impurities. Only a small portion can be recycled for sintering batching, and the majority of the remainder needs to be transported off-site for landfilling. This not only wastes resources but also increases dust pollution during transportation. Furthermore, quicklime is made by high-temperature roasting of limestone, which has high energy consumption and carbon emissions, and does not meet the dual carbon targets. Existing desulfurization technologies in iron plants face multiple challenges, including high costs, unstable efficiency, solid waste accumulation, and excessive carbon emissions. The industry urgently needs an integrated technical solution that can achieve low-cost self-production of desulfurizing agents, coordinated disposal of solid waste, stable desulfurization efficiency, and low carbon emissions. To this end, we propose a method for preparing active calcium oxide using carbide slag. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing active calcium oxide using carbide slag, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution, comprising the following steps: (1) Grading pretreatment: The carbide slag raw material is screened by an air classifier to collect carbide slag particles of 45-106μm. The outlet of the air classifier is connected to the inlet of the mixing tank through a closed conveyor belt. (2) Environmental desulfurization treatment: Add ammonium citrate solution to the mixing tank and stir for 30 minutes at 60-80℃ to obtain a desulfurized carbide slag mixture. The amount of ammonium citrate solution is 1-3% of the mass of the carbide slag particles collected in step (1), and the concentration is 5-8%. The mixing tank is equipped with a temperature sensor and a heating jacket. The probe end of the temperature sensor extends into the material inside the mixing tank. The heating jacket is wrapped around the outer wall of the mixing tank and electrically connected to the temperature control unit. (3) Low-temperature segmented sintering: The calcium carbide slag mixture after desulfurization in step (2) is subjected to solid-liquid separation, and then the calcium carbide slag mixture after solid-liquid separation is sent into a continuous sintering furnace for segmented sintering. The continuous sintering furnace is set with a first temperature zone and a second temperature zone in sequence along the material conveying direction. The first temperature zone and the second temperature zone are separated by heat insulation baffles and the material is continuously conveyed by a conveyor belt. (3.1) Sintering in the first temperature zone: Inert nitrogen gas is introduced into the first temperature zone, and the temperature is raised to 500-600℃ at a heating rate of 5℃ / min, and held for 2 hours. The inert nitrogen gas is connected to the gas inlet of the first temperature zone through a nitrogen generator and a pipeline. The purity of the inert nitrogen gas is ≥99.9%, and the gas inlet rate is 0.5-1m. 3 / h; (3.2) Sintering in the second temperature zone: After the material enters the second temperature zone from the first temperature zone, a composite additive is added to the second temperature zone, and the temperature is raised to 700-750℃ and held for 1.5h. The composite additive is a mixture of nano-SiO2 and Mg(OH)2 in a mass ratio of 3:1. The dosage is 0.5-1% of the mass of the desulfurized carbide slag mixture. The composite additive is sprayed onto the surface of the material through a quantitative addition device. The quantitative addition device is installed above the conveyor belt between the first and second temperature zones. (4) Finished product post-processing: Cool the sintered material in step (3) to room temperature, use a pH-temperature combined detection device to detect the activity of the material, and collect finished products with an activity of ≥420 Nml. The pH-temperature combined detection device includes a pH electrode, a temperature sensor and a data processing unit. The detection ends of the pH electrode and the temperature sensor are both inserted into a 1% concentration of the finished product aqueous solution, and both are electrically connected to the data processing unit. The data processing unit calculates the activity based on the detected pH value and temperature.

[0005] Preferably, the classification accuracy of the air classifier in step (1) is ±2μm, the air velocity is 15-20m / s, the inlet of the air classifier is connected to the carbide slag raw material silo through a screw conveyor, the outlet of the raw material silo is sealed to the inlet of the screw conveyor, and the outlet of the screw conveyor is sealed to the inlet of the air classifier. By adopting the above technical solutions, the high-precision air classifier ensures particle size uniformity, reduces impurity contamination, and improves product purity, thereby optimizing subsequent reaction efficiency. At the same time, by optimizing the airflow speed, the classification efficiency and raw material recovery rate are balanced, reducing raw material waste. The use of a screw conveyor can stably and accurately control the feeding, avoiding overload or underload of the classifier. Meanwhile, the overall enclosed structure can solve the problems of dust pollution and raw material moisture.

[0006] Preferably, the stirring rate of the stirring tank in step (2) is 200-300 r / min, a paddle agitator is fixedly installed on the stirring shaft, the outlet of the stirring tank is connected to the inlet of the solid-liquid separation device through a pipe with a valve, and the solid-liquid separation device is a horizontal centrifuge. By adopting the above technical solutions and optimizing the stirring system, the desulfurization reaction is ensured to be uniform and thorough, reducing sulfur residue. At the same time, the use of a horizontal centrifuge can improve separation efficiency, reduce solid moisture content, and reduce subsequent sintering energy consumption.

[0007] Preferably, in step (3), the length of the first temperature zone of the continuous sintering furnace is 2m-3m, and the length of the second temperature zone is 1.5m-2.5m; the conveyor belt is a high-temperature resistant stainless steel mesh belt, the conveying speed of the conveyor belt is 0.1-0.2m / min, and the drive motor of the conveyor belt is linked with the temperature control unit of the sintering furnace; By adopting the above technical solutions, the temperature zone length is precisely matched with the heat preservation requirements, carbonaceous impurities are completely decomposed, blackening and activity reduction of the finished product are avoided, and the segmented sintering is thoroughly completed, thereby ensuring product purity and strength. At the same time, the linkage between the conveyor belt drive motor and the sintering furnace temperature control unit can avoid batch defects caused by temperature fluctuations, reduce rework losses, reduce operational complexity, and reduce human operation errors.

[0008] Preferably, a flow regulating valve is installed on the pipeline between the nitrogen generator and the air inlet of the first temperature zone in step (3.1). The flow regulating valve is electrically connected to the pressure sensor of the first temperature zone. When the pressure of the first temperature zone exceeds 0.12 MPa, the flow regulating valve automatically reduces the air intake to maintain the pressure at 0.1-0.12 MPa. By adopting the above technical solutions, the inert atmosphere in the first temperature zone is kept stable, which enables the directional decomposition of carbonaceous impurities, avoids oxidation side reactions, improves carbon decomposition efficiency, shortens the redundant heat preservation time, and can also accurately control the amount of nitrogen used, avoid nitrogen waste, reduce consumable costs, and avoid the risk of sealing failure and leakage caused by excessive pressure, thus ensuring the safe operation of the equipment.

[0009] Preferably, the nano-SiO2 particle size of the composite additive in step (3.2) is 20-50nm, the purity of Mg(OH)2 is ≥98%, and the additive quantitative addition device includes a silo, a screw feeder and an atomizing nozzle. The outlet of the silo is connected to the screw feeder, the outlet end of the screw feeder is connected to the atomizing nozzle, the spray direction of the atomizing nozzle is towards the material on the surface of the conveyor belt, and the atomizing nozzle is linked with the temperature sensor of the second temperature zone. By adopting the above technical solutions, optimizing composite additives, and efficiently filling with nano-SiO2, the compressive strength of the finished product is significantly improved. High-purity Mg(OH)2 is used for deep desulfurization, reducing the lower limit of sulfur residue. At the same time, the additive quantitative addition device can achieve precise control of the amount of additives and uniform coverage, avoiding waste and local failure. The atomized spraying method greatly improves the utilization rate of additives and avoids ineffective loss.

[0010] Preferably, the pH electrode accuracy of the pH-temperature combined detection device in step (4) is ±0.01pH, and the temperature sensor accuracy is ±0.1℃. The 1% concentration of the finished aqueous solution is prepared by: crushing the sintered and cooled material to a particle size ≤10μm, taking 1g of the crushed material and adding it to 99mL of deionized water, stirring at 25℃ for 5min to obtain the detection solution. The data processing unit has a built-in activity calculation formula: Activity (Nml) = K×(pH value - 12.0)×(20℃ / detection temperature), where K is a correction coefficient, with a value of 100-105. By adopting the above technical solutions and utilizing high-precision testing equipment, the accuracy of activity detection is improved, avoiding false positives and false negatives. At the same time, standardized test solution preparation ensures batch testing consistency, eliminates result fluctuations caused by operational differences, and provides high data comparability. It also enables coordinated correction of pH and temperature to ensure that activity data truly reflects product performance.

[0011] Preferably, before the classification pretreatment in step (1), the process further includes a carbide slag raw material drying step: the carbide slag raw material is fed into a hot air dryer and dried at 80-100℃ for 1-2 hours until the raw material moisture content is ≤5%. The outlet of the hot air dryer is connected to the inlet of the air classifier in step (1) through a closed screw conveyor, and the exhaust port of the hot air dryer is connected to a bag filter. The outlet of the bag filter is connected back to the inlet of the hot air dryer through a pipe. By adopting the above technical solutions, the moisture content of raw materials can be precisely controlled, laying a solid foundation for the stable operation of subsequent processes. By adding a carbide slag raw material drying process at the front end of the "grading pretreatment", the smooth operation of the air classifier can be ensured, equipment blockage and downtime can be reduced, the uniformity of desulfurization reaction can be improved, and the consumption of reagents can be reduced. At the same time, the use of a recirculating bag filter greatly improves the utilization rate of raw materials, reduces material waste, and lowers the cost of environmental protection treatment.

[0012] Preferably, after solid-liquid separation in step (2), a solid washing step is also included: the solid material obtained by solid-liquid separation is sent into a washing tank, deionized water is added for washing, the amount of deionized water is 2-3 times the mass of the solid material, and solid-liquid separation is performed again after stirring for 10-15 minutes. The outlet of the washing tank is connected to the solid-liquid separation device, and the solid outlet of the solid-liquid separation device is connected to the feed port of the continuous sintering furnace in step (3) through a belt conveyor. The surface of the belt conveyor is covered with a heat insulation layer, and the temperature inside the heat insulation layer is maintained at 50-60℃. By adopting the above technical solutions, residual reagents can be deeply removed, improving the purity and environmental friendliness of the finished product, avoiding sintering side reactions and product contamination. The use of secondary solid-liquid separation can enhance impurity retention, and the setting of deionized water can avoid external pollution and extend the storage period of the finished product. At the same time, the heat preservation design of the belt conveyor reduces sintering energy consumption and furnace temperature fluctuations, saves operating costs, and ensures product uniformity.

[0013] Compared with the prior art, the beneficial effects of this application are: This invention uses an air classifier to accurately classify the core particle size range of carbide slag, significantly improving the recovery rate of target particles and reducing production losses. Compared with traditional landfill or brick-making methods, it greatly improves the utilization rate of carbide slag, allowing fine powder <45μm to be used as a binder for sintered ore and coarse particles >106μm to be used as a carrier for blast furnace pulverized coal, with no secondary solid waste, thus enabling the full utilization of by-products for secondary revenue generation. This invention utilizes a combination of ammonium citrate desulfurization and secondary washing to deeply remove impurities from carbide slag, thereby improving product purity, ensuring product activity and strength, and enhancing product qualification rate through standardized and precise testing. This invention employs low-temperature segmented sintering, which greatly reduces energy consumption; heat preservation and conveying reduce preheating energy consumption; nitrogen closed-loop control eliminates the need for additional drying and molding processes; thus optimizing energy consumption and significantly reducing operating costs. This invention, through the use of ammonium citrate and composite additives, eliminates the emission of toxic gases, achieves a washing water recovery rate of ≥70%, requires only a small amount of fresh water to be added, and results in zero wastewater discharge. Combined with a fully enclosed conveying system, no additional dust removal facilities are needed, making the entire production process environmentally friendly and safe. The present invention has a simple overall process, automated control, reduced personnel and labor costs. The continuous dual-temperature zone linkage sintering furnace and sealed conveyor are used in combination to greatly shorten the production cycle and increase the production capacity, solving the problems of "large batch differences and complicated operation" in the prior art. Compared to existing technologies that are only suitable for the single industrial application of calcium carbide production, this invention breaks through the limitations of existing technologies and meets the needs of automotive paint, medical desiccants, power plant desulfurization, steel desulfurization and sintered ore binders. Compared to existing technologies, this invention achieves multiple breakthroughs through systematic innovation throughout the entire process: full utilization of solid waste, product quality improvement, energy consumption reduction, environmental compliance, and broadening of application scenarios. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of a method for preparing active calcium oxide using carbide slag according to the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figure 1 The present invention provides a technical solution comprising the following steps: (1) Grading pretreatment: The carbide slag raw material is screened by an air classifier to collect carbide slag particles of 45-106μm. The outlet of the air classifier is connected to the inlet of the mixing tank through a closed conveyor belt. The classification accuracy of the air classifier in step (1) is ±2μm, and the airflow velocity is 15-20m / s. The high classification accuracy of the air classifier ensures the uniformity of particle size, reduces the mixing of impurities, and improves the purity of the product, thereby optimizing the efficiency of subsequent reactions. The feed inlet of the air classifier is connected to the carbide slag raw material silo through a screw conveyor. The discharge outlet of the raw material silo is sealed to the feed inlet of the screw conveyor, and the discharge outlet of the screw conveyor is sealed to the feed inlet of the air classifier. The use of a screw conveyor can stably and accurately control the feeding, avoid overloading or underloading of the classifier, and the overall closed structure can solve the problems of dust pollution and raw material moisture. By optimizing the airflow velocity, the classification efficiency and raw material recovery rate are balanced, and raw material waste is reduced. Before the classification pretreatment in step (1), the process also includes a carbide slag raw material drying step: the carbide slag raw material is fed into a hot air dryer and dried at 80-100℃ for 1-2 hours until the raw material moisture content is ≤5%. The outlet of the hot air dryer is connected to the inlet of the air classifier in step (1) through a closed screw conveyor, and the exhaust port of the hot air dryer is connected to a bag filter. The outlet of the bag filter is connected back to the inlet of the hot air dryer through a pipeline. By adding a carbide slag raw material drying process at the front end of the "classification pretreatment", the air classifier can be ensured to operate smoothly, reduce equipment blockage and shutdown, improve the uniformity of desulfurization reaction, and reduce reagent consumption. At the same time, the use of a back-connected bag filter greatly improves the raw material utilization rate, reduces material waste, reduces environmental protection treatment costs, and can accurately control the raw material moisture content, thus laying a solid foundation for the stable operation of subsequent processes. (2) Environmental desulfurization treatment: Add ammonium citrate solution to the mixing tank and stir for 30 minutes at 60-80℃ to obtain a desulfurized carbide slag mixture. The amount of ammonium citrate solution is 1-3% of the mass of the carbide slag particles collected in step (1), and the concentration is 5-8%. The mixing tank is equipped with a temperature sensor and a heating jacket. The probe end of the temperature sensor extends into the material inside the mixing tank. The heating jacket is wrapped around the outer wall of the mixing tank and electrically connected to the temperature control unit. The stirring rate of the mixing tank in step (2) is 200-300 r / min. A paddle agitator is fixedly installed on the stirring shaft. The diameter of the paddle is 1 / 3-1 / 2 of the inner diameter of the mixing tank. The stirring system is optimized to ensure that the desulfurization reaction is uniform and thorough and to reduce sulfur residue. The outlet of the mixing tank is connected to the inlet of the solid-liquid separation device through a pipe with a valve. The solid-liquid separation device is a horizontal centrifuge with a rotation speed of 1000-1500 r / min. Using a horizontal centrifuge can improve the separation efficiency, reduce the solid moisture content, and reduce the energy consumption of subsequent sintering. (3) Low-temperature segmented sintering: The calcium carbide slag mixture after desulfurization in step (2) is subjected to solid-liquid separation, and then the calcium carbide slag mixture after solid-liquid separation is sent into a continuous sintering furnace for segmented sintering. The continuous sintering furnace is set with a first temperature zone and a second temperature zone in sequence along the material conveying direction. The first temperature zone and the second temperature zone are separated by heat insulation baffles and the material is continuously conveyed by a conveyor belt. In step (3), the length of the first temperature zone of the continuous sintering furnace is 2m-3m, and the length of the second temperature zone is 1.5m-2.5m. The temperature zone length is precisely matched to the heat preservation requirements, and carbonaceous impurities are completely decomposed to avoid blackening of the finished product and decrease in activity. This ensures thorough sintering in segments, thereby guaranteeing the purity and strength of the product. The conveyor belt is a high-temperature resistant stainless steel mesh belt, and the conveying speed of the conveyor belt is 0.1-0.2m / min. The drive motor of the conveyor belt is linked with the temperature control unit of the sintering furnace. The linkage between the drive motor of the conveyor belt and the temperature control unit of the sintering furnace can avoid batch non-conformity caused by temperature fluctuations, reduce rework losses, reduce operational complexity, and reduce human operation errors. (3.1) Sintering in the first temperature zone: Inert nitrogen gas is introduced into the first temperature zone, and the temperature is raised to 500-600℃ at a heating rate of 5℃ / min, and held for 2 hours. The inert nitrogen gas is connected to the gas inlet of the first temperature zone through a nitrogen generator and a pipeline. The purity of the inert nitrogen gas is ≥99.9%, and the gas inlet rate is 0.5-1m. 3 / h; A flow regulating valve is installed on the pipeline between the nitrogen generator and the air inlet of the first temperature zone in step (3.1). The flow regulating valve is electrically connected to the pressure sensor of the first temperature zone. The flow regulating valve can accurately control the amount of nitrogen used, avoid nitrogen waste, and reduce the cost of consumables. When the pressure of the first temperature zone exceeds 0.12MPa, the flow regulating valve automatically reduces the air intake to maintain the pressure at 0.1-0.12MPa. At the same time, it avoids the risk of sealing failure and leakage caused by excessive pressure, ensures the safe operation of the equipment, ensures the stability of the inert atmosphere in the first temperature zone, enables the directional decomposition of carbonaceous impurities, avoids oxidation side reactions, improves carbon decomposition efficiency, and shortens the heat preservation time. (3.2) Sintering in the second temperature zone: After the material enters the second temperature zone from the first temperature zone, a composite additive is added to the second temperature zone, and the temperature is raised to 700-750℃ and held for 1.5h. The composite additive is a mixture of nano-SiO2 and Mg(OH)2 in a mass ratio of 3:1. The dosage is 0.5-1% of the mass of the desulfurized carbide slag mixture. The composite additive is sprayed onto the surface of the material through a quantitative addition device. The quantitative addition device is installed above the conveyor belt between the first and second temperature zones. The composite additive in step (3.2) has a nano-SiO2 particle size of 20-50nm and a Mg(OH)2 purity of ≥98%. The nano-SiO2 is efficiently filled, significantly improving the compressive strength of the finished product. The high-purity Mg(OH)2 deeply desulfurizes and reduces the lower limit of sulfur residue. The additive quantitative addition device includes a silo, a screw feeder and an atomizing nozzle. The outlet of the silo is connected to the screw feeder, and the outlet end of the screw feeder is connected to the atomizing nozzle. The spray direction of the atomizing nozzle is towards the material on the surface of the conveyor belt, and the atomizing nozzle is linked with the temperature sensor of the second temperature zone. The additive quantitative addition device can achieve precise control of the amount of additive and uniform coverage, avoiding waste and local failure. The atomized spraying method greatly improves the utilization rate of the additive and avoids ineffective loss. Step (2) after solid-liquid separation also includes a solid washing step: the solid material obtained from solid-liquid separation is sent into a washing tank, deionized water is added for washing, the amount of deionized water is 2-3 times the mass of the solid material, and solid-liquid separation is performed again after stirring for 10-15 minutes. The outlet of the washing tank is connected to the solid-liquid separation device, and the solid outlet of the solid-liquid separation device is connected to the feed port of the continuous sintering furnace in step (3) through a belt conveyor. The surface of the belt conveyor is covered with a heat insulation layer, and the temperature inside the heat insulation layer is maintained at 50-60℃. The use of secondary solid-liquid separation can enhance the interception of impurities. The setting of deionized water can avoid external pollution and extend the storage period of finished products. At the same time, the heat insulation design of the belt conveyor reduces sintering energy consumption and furnace temperature fluctuation, saves operating costs, and ensures product uniformity. (4) Finished product post-processing: Cool the sintered material in step (3) to room temperature, use a pH-temperature combined detection device to detect the activity of the material, and collect finished products with an activity of ≥420 Nml. The pH-temperature combined detection device includes a pH electrode, a temperature sensor and a data processing unit. The detection ends of the pH electrode and the temperature sensor are both inserted into a 1% concentration of the finished product aqueous solution, and both are electrically connected to the data processing unit. The data processing unit calculates the activity based on the detected pH value and temperature. The pH electrode accuracy of the pH-temperature combined detection device in step (4) is ±0.01pH, and the temperature sensor accuracy is ±0.1℃. By using high-precision detection equipment, the accuracy of activity detection is improved, and the situation of false positives and false negatives is avoided. The 1% concentration of the finished product aqueous solution is prepared in the following way: the sintered and cooled material is crushed to a particle size ≤10μm, 1g of the crushed material is added to 99mL of deionized water, and stirred at 25℃ for 5min to obtain the detection solution. The data processing unit has a built-in activity calculation formula: activity (Nml) = K×(pH value-12.0)×(20℃ / detection temperature), where K is the correction coefficient, with a value of 100-105. By standardizing the detection solution preparation, the consistency of batch detection is ensured, the result fluctuation caused by operational differences is eliminated, the data comparability is high, and the synergistic correction of pH and temperature is achieved to ensure that the activity data truly reflects the product performance.

[0017] The implementation principle of this application is as follows: 1. Raw material specifications and pretreatment This implementation method uses three types of typical calcium carbide slag raw materials (all from different industries in China to ensure the universality of the solution). The basic indicators of the raw materials are shown in Table 1 below: Raw material pretreatment steps: The above raw materials were fed into a QLM-100 hot air dryer. The drying temperature was set to 85℃±2℃ and the drying time was 1.5h±0.1h. The moisture content was monitored in real time by an online moisture content detector until the moisture content of the raw materials was ≤4%. After cooling to room temperature, the raw materials were stored for later use. During the drying process, the exhaust gas was treated by a bag filter. The collected dust was mixed back into the dried raw materials. The raw material loss rate was ≤0.5%.

[0018] 2. Core Equipment and Parameter Settings 3. Preparation of reagents and auxiliaries Ammonium citrate solution: 5%, 7%, and 8% solutions were prepared using analytical grade ammonium citrate and deionized water. After stirring and dissolving, the solutions were filtered through a 0.45μm filter membrane to remove impurities and then sealed and stored in a PE storage tank. The concentration was determined by titration before use.

[0019] Composite additive: Nano SiO2 and Mg(OH)2 are mixed at a mass ratio of 3:1, and deionized water is added to make a suspension with a mass concentration of 20%. The suspension is dispersed for 30 minutes using an ultrasonic disperser to ensure uniformity. Shake well before use.

[0020] II. Operational Procedures for Multiple Implementation Examples Example 1 (Verification of intermediate values ​​of core parameters, corresponding to raw material A) Step 1: Graded Preprocessing Start the air classifier. After the equipment is running stably, feed the pretreated raw material A into the classifier at a rate of 500 kg / h. The particle size analyzer built into the classifier monitors the particle size in real time and collects particles of 45-106 μm, which are labeled as "Classified Material A1". After classification, fine powder <45 μm is labeled as "Fine Powder A", and coarse particles >106 μm are labeled as "Coarse Powder A". "Fine Powder A" and "Coarse Powder A" are collected separately for subsequent resource utilization. Fine Powder A can be used to prepare cement additives, and Coarse Powder A can be used to prepare roadbed materials.

[0021] Step 2: Environmentally friendly desulfurization treatment Add 200 kg of "Grading Material A1" to a 500 L mixing tank, close the feed valve, start stirring, and slowly add 4 kg of 7% ammonium citrate solution into the tank through a metering pump. The amount added is 2% of the mass of the grading material. Turn on the heating jacket, set the temperature to 70℃, and control the temperature in real time through the temperature sensor inside the tank. Stir for 30 minutes. During the stirring process, take a sample every 5 minutes to check the pH value of the solution. The initial pH is ≈6.5, and the pH is ≈7.2 at the end of the reaction to ensure that the sulfur impurities are fully converted into calcium citrate.

[0022] After the reaction is complete, open the discharge valve of the mixing tank and send the mixture into a horizontal centrifuge. Set the speed to 1200 r / min and separate for 15 min. Collect the solid material and label it as "desulfurization material A1". Send the centrifugation mother liquor containing calcium citrate into the wastewater circulation tank for the next preparation of ammonium citrate solution. Use EDTA complexometric titration to detect the sulfur content of "desulfurization material A1" to ensure that the sulfur content is ≤0.05%.

[0023] Step 3: Low-temperature segmented sintering Turn on the continuous sintering furnace, set the target temperature of the first temperature zone to 550℃ and the target temperature of the second temperature zone to 720℃, and introduce 99.99% pure nitrogen into the first temperature zone. After the temperature inside the furnace stabilizes, send the "desulfurized material A1" into the sintering furnace through the conveyor belt. The temperature sensor inside the furnace is linked with the speed of the conveyor belt to calibrate and control the speed of the mesh belt to 0.15m / min, ensuring that the material stays in the first temperature zone for 2 hours to decompose carbonaceous impurities. After confirming that the material has entered the second temperature zone by the in-furnace infrared detector, the additive quantitative addition device is started to spray a 20% composite additive suspension onto the surface of the material. The spraying time is synchronized with the time it takes for the material to pass through the second temperature zone to ensure uniform coverage of the additive. After sintering, the material enters the cooling zone with the mesh belt. The cooling medium is room temperature nitrogen. After cooling to room temperature, the material is collected and labeled as "Sintered Material A1". The loss on ignition of the sintered material is then measured.

[0024] Step 4: Finished Product Post-Processing and Inspection The sintered material A1 was fed into a jaw crusher and crushed to a particle size ≤10μm. 1.0000g of the crushed sample was taken and 99.00mL of deionized water was added. The mixture was stirred on a magnetic stirrer for 5min to prepare a 1% mass concentration aqueous solution. The solution was then transferred to the detection cup of the pH-temperature combined detection device. After the temperature stabilized at 20℃, the pH value was measured to be 12.73. According to the built-in formula "Activity (Nml) = 102 × (pH value - 12.0) × (20℃ / detection temperature)", the activity was calculated to be 432Nml.

[0025] Another sample was taken to test the purity. The purity was determined to be 98.7% by EDTA complexometric titration. The compressive strength was tested using a WDW-100 universal testing machine and was 2.7 MPa. The sulfur content was 0.042%. All tests were performed in parallel three times, and the average value was taken. The relative deviation was ≤1.0%. The finished product was marked as "Active Calcium Oxide A1" and met the requirements of active calcium oxide for high-end coatings.

[0026] Example 2 (Verification of low concentration / low dosage parameters, corresponding to raw material B) Key parameter adjustments (differences from Example 1) Pre-treatment for classification: Collect 45-106μm particles of raw material B (labeled "Classified Material B1"); Desulfurization treatment: Ammonium citrate solution concentration 5%, dosage is 1% of the mass of the graded material (200kg graded material plus 2kg solution), stirring temperature 60℃; Sintering treatment: first temperature zone 500℃, second temperature zone 700℃, composite additive dosage 0.5%; Finished product test results Example 3 (Verification of high concentration / high dosage parameters, corresponding to raw material C) Key parameter adjustments (differences from Example 1) Pre-treatment for classification: Collect 45-106μm particles of raw material C (labeled "classified material C1"); Desulfurization treatment: Ammonium citrate solution concentration 8%, dosage is 3% of the mass of the graded material (6 kg solution for 200 kg graded material), stirring temperature 80℃; Sintering treatment: first temperature zone 600℃, second temperature zone 750℃, composite additive dosage 1.0%; Finished product test results III. Comparative Design and Result Analysis Comparative Example 1 (Refer to method CN116199433A, raw material A) Operating steps Raw material pretreatment: Dry raw material A to a moisture content of ≤5% and crush it to a particle size of ≤100μm (without grading and screening); Impurity removal: Add 2% phosphoric acid solution instead of ammonium citrate in this solution, stir at 60°C for 30 minutes, and then centrifuge. Sintering treatment: Under nitrogen atmosphere, the temperature is increased to 750℃ at 5℃ / min and held for 3h. No segmented sintering and no composite additives are used. Finished product testing: Tested using the same method as in Example 1.

[0027] Test results and differential analysis Comparative Example 2 (blank control without composite additives, raw material A) Operating steps It is completely consistent with Example 1, except that no composite additive is added during sintering in the second temperature zone, and all other steps and parameters are the same.

[0028] Test results and differential analysis IV. Handling Abnormal Situations and Verification of Process Stability 1. Case Studies of Handling Abnormal Situations Case 1: Fluctuation in airflow velocity in a classifier Abnormal phenomenon: During the operation of Example 2, the airflow velocity of the air classifier suddenly dropped to 15m / s (lower than the set value of 18m / s), and the particle size analyzer showed that the recovery rate of 45-106μm particles dropped to 85%. Handling measures: Immediately stop feeding, check the blower filter screen, if the filter screen is found to be clogged, clean the filter screen and restart the blower, adjust the airflow speed to 18m / s, and reclassify the collected "graded material B1" to ensure that the particle size is qualified; Results: After secondary classification, the recovery rate rebounded to 96%, and the purity of the final product was 98.1%, which deviated from the target value of 98.2% by 0.1%, with no significant impact.

[0029] Case 2: Temperature fluctuations in sintering furnace Abnormal phenomenon: In Example 3, the temperature in the second temperature zone suddenly rose to 770°C, which is higher than the set value of 750°C, and lasted for 10 minutes; Corrective measures: Immediately reduce heating power, open the cooling nitrogen bypass, and increase nitrogen intake to 1.2 m³ / h. 3 / h, the temperature is reduced to 750℃ within 15 minutes, and the "sintered material C1" produced during this period is sampled and tested separately; Results: The activity of the sample tested alone was 438 N / ml, slightly lower than the target value of 445 N / ml, and the purity was 98.8%, close to the target value of 99.0%. The particle size can be adjusted by subsequent crushing to ensure the finished product is qualified.

[0030] 2. Process stability verification (72 hours of continuous production) Based on the parameters of Example 1, raw material A was used for continuous production for 72 hours (producing a total of 12 tons of finished product). Samples were taken and tested every 8 hours. The test results are shown in the table below: Conclusion: Within 72 hours of continuous production, the coefficient of variation of key indicators of the finished product was ≤0.5%, indicating that the process has good stability, no obvious parameter drift, and can meet the requirements of industrial continuous production.

[0031] V. Verification of Finished Product Application Scenarios 1. High-end coating applications (fillers for automotive paints) The finished product "Activated Calcium Oxide A1" from Example 1 was added at a dosage of 5% to the automotive paint base material (acrylic resin system). A paint film was prepared according to GB / T1727-1992 "General Method for Preparing Paint Films," and the paint film performance was tested. Pencil hardness: 2H; Adhesion (cross-cut test): Grade 0; Salt spray resistance (5% NaCl solution, 1000h): No rust, no bubbling; Conclusion: Meets the requirements for active calcium oxide in automotive paint.

[0032] 2. Power plant desulfurization applications The finished product "Activated Calcium Oxide C1" from Example 3 was used in the flue gas desulfurization system of a 2×300MW power plant, with the Ca / S molar ratio controlled at 1.05, and the desulfurization effect was tested. SO2 concentration at outlet: ≤20mg / m³ 3 ; Reaction time: 30s; Desulfurization residue moisture content: 25%; Conclusion: The desulfurization process is efficient, fast, and produces minimal desulfurization slag, meeting the requirements of GB13223-2011 "Emission Standard of Air Pollutants for Thermal Power Plants". 3. The ironworks has established a closed-loop solid waste co-processing mechanism within the plant, encompassing "carbide slag - calcium oxide - byproducts". The steel plant's PVC workshop can directly collect calcium carbide slag slurry, which is then dehydrated to a moisture content of less than 15% by the plate and frame filter press in the plant. It utilizes the waste heat of the steel plant to reduce energy consumption, uses the waste heat of the sintering machine to replace electric heating, heats the air through the waste heat exchanger for drying calcium carbide slag, and uses blast furnace gas as fuel for the continuous sintering furnace to replace natural gas. 3.1 Sinter production requires a binder to improve strength, which requires calcium oxide to have low activity and fine particle size to replace traditional quicklime. After classification, fine carbide slag powder with a diameter of <45μm is selected. After drying at 80-100℃ using the residual heat of sintering, it is added at 2%-3% of the mass of sintering materials and mixed with iron ore powder and coke powder for granulation. This increases the drum strength of sintering by 2-3 percentage points, reduces the return rate by 1.5%, and the fine powder does not require high-temperature sintering. 3.2 Blast furnace ironmaking requires flux to adjust slag basicity, necessitating high-purity and high-strength calcium oxide to replace purchased limestone or quicklime. The product from Example 1 of this invention is used, crushed to a particle size of 5-20mm suitable for blast furnace charging, and added to the blast furnace charge batch at 8%-10% of the iron ore mass. This is done in layers with coke and iron ore, reducing slag basicity fluctuations from ±0.08 to ±0.03, and increasing the blast furnace utilization coefficient by 0.05t / (m³). 3 •d) Improved purity and reduced interference from impurities; 3.3 Converter steelmaking requires rapid dephosphorization and desulfurization of slag-forming agents, which necessitates calcium oxide with ultra-high activity and low sulfur content. The finished product from Example 3 of this invention is selected, crushed into fine particles of 1-5mm to increase the contact area with molten steel. It is added in two batches: the first batch accounts for 60% of the total amount and is added 3 minutes after oxygen blowing in the converter to quickly form initial slag; the second batch accounts for 40% of the total amount and is added 6 minutes after oxygen blowing to enhance dephosphorization and desulfurization, shorten slag-forming time, and reduce the converter smelting cycle. 3.4 The integrated wastewater treatment in steel plants requires pH adjustment, necessitating easily soluble and low-cost calcium oxide. Fine calcium oxide powder with a particle size ≤10μm after sintering is selected and prepared into a 5% concentration emulsion at 0.1%-0.2% of the wastewater flow rate. This emulsion is then added to the wastewater network via a static mixer. This stabilizes the sulfur content of the molten steel, improves the steel production qualification rate, reduces the cost of pH adjustment in wastewater treatment, and eliminates the Cl- pollution caused by the use of soda ash. - Residual status.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing activated calcium oxide using carbide slag, characterized in that, Includes the following steps: (1) Grading pretreatment: The carbide slag raw material is screened by an air classifier to collect carbide slag particles of 45-106μm. The outlet of the air classifier is connected to the inlet of the mixing tank through a closed conveyor belt. (2) Environmental desulfurization treatment: Add ammonium citrate solution to the mixing tank and stir for 30 minutes at 60-80℃ to obtain a desulfurized carbide slag mixture. The amount of ammonium citrate solution is 1-3% of the mass of the carbide slag particles collected in step (1), and the concentration is 5-8%. The mixing tank is equipped with a temperature sensor and a heating jacket. The probe end of the temperature sensor extends into the material inside the mixing tank. The heating jacket is wrapped around the outer wall of the mixing tank and electrically connected to the temperature control unit. (3) Low-temperature segmented sintering: The calcium carbide slag mixture after desulfurization in step (2) is subjected to solid-liquid separation, and then the calcium carbide slag mixture after solid-liquid separation is sent into a continuous sintering furnace for segmented sintering. The continuous sintering furnace is set with a first temperature zone and a second temperature zone in sequence along the material conveying direction. The first temperature zone and the second temperature zone are separated by heat insulation baffles and the material is continuously conveyed by a conveyor belt. (3.1) Sintering in the first temperature zone: Inert nitrogen gas is introduced into the first temperature zone, and the temperature is raised to 500-600℃ at a heating rate of 5℃ / min, and held for 2 hours. The inert nitrogen gas is connected to the gas inlet of the first temperature zone through a nitrogen generator and a pipeline. The purity of the inert nitrogen gas is ≥99.9%, and the gas inlet rate is 0.5-1m. 3 / h; (3.2) Sintering in the second temperature zone: After the material enters the second temperature zone from the first temperature zone, a composite additive is added to the second temperature zone, and the temperature is raised to 700-750℃ and held for 1.5h. The composite additive is a mixture of nano-SiO2 and Mg(OH)2 in a mass ratio of 3:

1. The dosage is 0.5-1% of the mass of the desulfurized carbide slag mixture. The composite additive is sprayed onto the surface of the material through a quantitative addition device. The quantitative addition device is installed above the conveyor belt between the first and second temperature zones. (4) Finished product post-processing: Cool the sintered material in step (3) to room temperature, use a pH-temperature combined detection device to detect the activity of the material, and collect finished products with an activity of ≥420 Nml. The pH-temperature combined detection device includes a pH electrode, a temperature sensor and a data processing unit. The detection ends of the pH electrode and the temperature sensor are both inserted into a 1% concentration of the finished product aqueous solution, and both are electrically connected to the data processing unit. The data processing unit calculates the activity based on the detected pH value and temperature.

2. The method for preparing activated calcium oxide using carbide slag according to claim 1, characterized in that: The classification accuracy of the air classifier in step (1) is ±2μm, the airflow velocity is 15-20m / s, the inlet of the air classifier is connected to the carbide slag raw material silo through a screw conveyor, the outlet of the raw material silo is sealed to the inlet of the screw conveyor, and the outlet of the screw conveyor is sealed to the inlet of the air classifier.

3. The method for preparing activated calcium oxide using carbide slag according to claim 1, characterized in that: The stirring rate of the stirring tank in step (2) is 200-300 r / min. A paddle-type stirrer is fixedly installed on the stirring shaft. The outlet of the stirring tank is connected to the inlet of the solid-liquid separation device through a pipe with a valve. The solid-liquid separation device is a horizontal centrifuge.

4. The method for preparing activated calcium oxide using carbide slag according to claim 1, characterized in that: In step (3), the length of the first temperature zone of the continuous sintering furnace is 2m-3m, and the length of the second temperature zone is 1.5m-2.5m; the conveyor belt is a high-temperature resistant stainless steel mesh belt, the conveying speed of the conveyor belt is 0.1-0.2m / min, and the drive motor of the conveyor belt is linked with the temperature control unit of the sintering furnace.

5. The method for preparing activated calcium oxide using carbide slag according to claim 4, characterized in that: A flow regulating valve is installed on the pipeline between the nitrogen generator and the air inlet of the first temperature zone in step (3.1). The flow regulating valve is electrically connected to the pressure sensor of the first temperature zone. When the pressure of the first temperature zone exceeds 0.12 MPa, the flow regulating valve automatically reduces the air intake to maintain the pressure at 0.1-0.12 MPa.

6. The method for preparing activated calcium oxide using carbide slag according to claim 1, characterized in that: The composite additive in step (3.2) has a nano-SiO2 particle size of 20-50nm and a Mg(OH)2 purity of ≥98%. The additive quantitative addition device includes a silo, a screw feeder and an atomizing nozzle. The outlet of the silo is connected to the screw feeder, and the outlet end of the screw feeder is connected to the atomizing nozzle. The spray direction of the atomizing nozzle is towards the material on the surface of the conveyor belt, and the atomizing nozzle is linked with the temperature sensor of the second temperature zone.

7. The method for preparing activated calcium oxide using carbide slag according to claim 1, characterized in that: The pH electrode accuracy of the pH-temperature combined detection device in step (4) is ±0.01pH, and the temperature sensor accuracy is ±0.1℃. The 1% concentration of the finished aqueous solution is prepared as follows: the sintered and cooled material is crushed to a particle size ≤10μm, 1g of the crushed material is added to 99mL of deionized water, and stirred at 25℃ for 5min to obtain the detection solution. The data processing unit has a built-in activity calculation formula: activity (Nml) = K×(pH value-12.0)×(20℃ / detection temperature), where K is a correction coefficient with a value of 100-105.

8. The method for preparing activated calcium oxide using carbide slag according to claim 1, characterized in that: Before the classification pretreatment in step (1), the process also includes a carbide slag raw material drying step: the carbide slag raw material is fed into a hot air dryer and dried at 80-100℃ for 1-2 hours until the raw material moisture content is ≤5%. The outlet of the hot air dryer is connected to the inlet of the air classifier in step (1) through a closed screw conveyor, and the exhaust port of the hot air dryer is connected to a bag filter. The outlet of the bag filter is connected back to the inlet of the hot air dryer through a pipeline.

9. A method for preparing activated calcium oxide using carbide slag according to claim 3, characterized in that: Step (2) after solid-liquid separation also includes a solid washing step: the solid material obtained from solid-liquid separation is sent into a washing tank, deionized water is added for washing, the amount of deionized water is 2-3 times the mass of the solid material, and solid-liquid separation is performed again after stirring for 10-15 minutes. The outlet of the washing tank is connected to the solid-liquid separation device, and the solid outlet of the solid-liquid separation device is connected to the feed port of the continuous sintering furnace in step (3) through a belt conveyor. The surface of the belt conveyor is covered with a heat insulation layer, and the temperature inside the heat insulation layer is maintained at 50-60℃.

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