Magnesium slag harmless disposal method and disposal system

Abstract

The application discloses a harmless treatment method and treatment system for magnesium slag, which comprises the following steps: utilizing the residual heat and / or external heat of the magnesium slag, and performing an oxidation decarburization reaction on the magnesium slag in the presence of oxygen-containing gas; the oxygen content of the oxygen-containing gas is greater than or equal to 15 wt%; the volume of the oxygen-containing gas is 50 to 100 times of the volume of the magnesium slag; and the temperature of the oxidation decarburization reaction is greater than or equal to 500 DEG C. The method can effectively utilize the residual heat of high-temperature magnesium slag to perform the oxidation decarburization, solve the problem that strong reducing substances, residual carbon and other impurities are enriched in the magnesium slag due to the magnesium smelting process, especially the magnesium smelting raw material, and the toxic and harmful gases such as CO, H2S and CH4 are released in the resource utilization process of the magnesium slag, effectively accelerate the rapid decomposition of the impurities such as residual carbon in the magnesium slag, obtain homogeneous impurity-removed magnesium slag, improve the utilization level and efficiency of the magnesium slag, and promote the large-scale utilization of the magnesium slag.

Description

Technical Field

[0001] This invention belongs to the field of waste residue treatment technology, specifically relating to a method and system for the harmless treatment of magnesium slag. Background Technology

[0002] Magnesium and magnesium alloys possess excellent physicochemical properties, including low density, good damping performance, and large hydrogen storage capacity, making them promising candidates for applications in aerospace, transportation, and electronics (3C) industries. With the rapid development of the global economy and technology, international demand for magnesium is constantly increasing. Leveraging its energy and resource advantages, my country has become the world's largest producer of primary magnesium, accounting for over 80% (900,000 tons) of global production. The Pidgeon process is a widely adopted magnesium smelting technology in my country. For every 1 ton of magnesium produced, approximately 5 to 7 tons of magnesium smelting residue, magnesium slag, are generated. The national magnesium slag discharge is nearly 4.5 to 6.3 million tons, and the large accumulation of magnesium slag seriously threatens the environment and human health. Therefore, the problem of how to treat magnesium slag on a large scale in a harmless manner and utilize it as a resource urgently needs to be solved.

[0003] In recent decades, research on the application of magnesium slag, both domestically and internationally, has mainly focused on cement concrete, building materials, desulfurization, and fertilizer production. However, most applications remain at the experimental or small-scale stage. Furthermore, due to the low activity and expansive properties of magnesium slag, its utilization cost is also high.

[0004] A patent with publication number CN113957269A proposes a method for producing magnesium pellets and smelting magnesium that can stabilize β-C-(2)S in magnesium slag. This method stabilizes β-C-(2)S in the high-temperature magnesium slag discharged after magnesium smelting through source treatment, resulting in modified magnesium slag that does not pulverize and has high activity. This provides a new approach for the large-scale treatment and recycling of magnesium slag solid waste. However, this method does not address the problem of toxic and harmful gases released from the decomposition of internal impurities during the application of magnesium slag, leading to significant safety and environmental risks in applications such as coal mine backfilling. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method and apparatus for the harmless treatment of magnesium slag. This method effectively utilizes the waste heat from high-temperature magnesium slag for oxidation and decarbonization, solving the problem of the accumulation of strong reducing substances, residual carbon, and other impurities in magnesium slag due to the magnesium smelting process, especially the raw materials used in magnesium smelting. This prevents the release of toxic and harmful gases such as CO, H2S, and CH4 during the resource utilization of magnesium slag. The method effectively accelerates the rapid decomposition of residual carbon and other impurities within the magnesium slag, resulting in homogeneous, impurity-free magnesium slag, improving the utilization level and efficiency of magnesium slag, and promoting the large-scale utilization of coal slag.

[0006] There is limited research on the release of gases from magnesium slag and its resource utilization. Current studies only indicate that magnesium slag produces ammonia when it comes into contact with water. However, this invention discovered that a slurry made from finely ground magnesium slag mixed with water releases CO within 4 hours, accompanied by the consumption of O2.

[0007] In response to the above-mentioned phenomenon of rapid CO release from magnesium slag, this invention studies the possible carbon sources of CO: 1) the reaction of reactive alkali metals remaining in high-temperature magnesium slag in contact with air with carbon dioxide to generate C (formulas (1-1) to (1-5)); 2) the C remaining in ferrosilicon in magnesium slag raw materials.

[0008] CO2 + 4Na → 2Na2O + C (1-1)

[0009]

[0010] Considering that the CO release process is accompanied by O2 consumption, the present invention further limits the source of CO to the oxidation reaction of C or carbon compounds (1-6).

[0011] C + O₂ → 2CO (1-6)

[0012] Furthermore, the formation of CO from elemental C and O2 requires high-temperature conditions. After studying the entire production process of modified magnesia slag-based cementitious materials, this invention determined that only two stages involve high temperatures: the stage where the modified magnesia slag exits the reduction furnace and the grinding stage. The temperature of the modified magnesia slag exiting the reduction furnace is approximately 1250℃. After being spread out and allowed to cool naturally for 24 hours, it drops to 60℃. At this stage, the temperature is relatively high, and the surface residual carbon is largely oxidized to CO2. Simultaneously, the modified magnesia slag is solid and walnut-shaped, and there may be unoxidized residual carbon inside. During the grinding process, due to collisions between steel balls and between the steel balls and the tank wall, the instantaneous temperature can reach up to 800℃. Based on calculations using the HSC Chemistry 5 program, reactions (1-7) can occur at temperatures above 600℃, causing iron to be oxidized by CO2 to generate CO, while reactions (1-8) can occur at temperatures above 400℃, causing FeO to be reduced by C to generate CO. In addition, some literature indicates that under the catalysis of FeO and active Fe, carbon and carbon-metal atom compounds react with O2 in the air at room temperature to generate CO.

[0013] Fe + CO₂ = FeO + CO (temperature above 600 ℃) (1-7)

[0014] FeO + C = Fe + CO (temperature above 400 ℃) (1-8)

[0015] Based on the above analysis, there are two possible stages for CO gas generation: ① Generation occurs during the grinding stage of the magnesium slag-based cementitious material. Residual carbon in the magnesium slag reacts with oxygen in the air under the high-temperature impact of the grinding steel balls to generate CO. Some CO escapes into the air, while the remaining CO is adsorbed by the cementitious material. During the preparation of the filling material, the adsorbed CO desorbs and escapes, causing CO levels to exceed limits. ② Generation occurs during the preparation of the filling material. Under the catalytic action of FeO and active Fe in the magnesium slag, carbon and carbon-metal atom compounds in the slurry state react with H2O and O2 in the air to generate CO.

[0016] Based on the above analysis, this invention is further verified by conducting the following three experiments:

[0017] ① CO gas measurement experiment during the grinding stage of magnesium slag-based cementitious materials

[0018] The test method includes: grinding the magnesium slag-based cementitious material in a sealed small mill for half an hour, then inserting a CO analyzer into the sealed small mill to measure the CO content. The test results show that the CO concentration in the sealed small mill is between 50 and 300 ppm.

[0019] ②Gas adsorption-desorption experiment of magnesium slag-based cementitious materials

[0020] The test method for gas adsorption-desorption experiment includes: obtaining mixed raw materials according to the ratio of 75% magnesium slag + 20% fly ash + 5% desulfurization gypsum, grinding 5.0 kg of the mixed raw materials for 35 min, and detecting CO through a four-in-one gas detector. The results show that CO was generated during grinding.

[0021] Take 2.5 kg of the above-ground mixed raw materials from step ② and place them in a sealed oven. Bake at 105℃ for 12 hours. Use a four-in-one gas detector to test the gas. No harmful gases such as CO were detected.

[0022] ③Gas determination experiment for slurry preparation of magnesium slag-based cementitious materials.

[0023] Take 2.5 kg of the above-mentioned ground mixed raw materials from ②, add water and mix to obtain mortar. Seal and cure in a plastic bag for 24 hours to obtain hardened mortar. Detect the CO concentration with a four-in-one gas detector. The result shows that the gas concentration exceeds the detector's range, indicating that CO is being released. Combined with ②, it can be seen that CO is released during both the grinding stage and the mortar preparation stage.

[0024] However, grinding is not enough to completely release the CO in the magnesium slag, and CO gas is still generated in the ground magnesium slag-based cementitious materials.

[0025] Based on the above verification results, this invention further investigated the sources of CO in the raw materials, which mainly include magnesium slag, fly ash and desulfurized gypsum, which are the raw materials for magnesium slag-based cementitious materials, as well as calcined white (MgO·CaO), ferrosilicon (FeSi75), fluorite powder (CaF2) and optimizers, which are the raw materials for smelting metallic magnesium.

[0026] The raw materials, magnesium slag, fly ash, and desulfurized gypsum, were ground for 30 minutes and then mixed with water to obtain a slurry. After curing and CO measurement, the water content in the slurry was 25% by mass. The measurement results are shown in Table 1. The results show that desulfurized gypsum does not produce CO, fly ash produces very little CO, while magnesium slag rapidly produces a large amount of CO after 24 hours of curing. Therefore, it can be determined that the CO released by the modified magnesium slag-based filling material mainly comes from magnesium slag.

[0027] In the raw materials for magnesium smelting, the proportions of calcined white precipitate (MgO·CaO), ferrosilicon (FeSi75), fluorite powder (CaF2), and optimizers are 82.2%–82.7%, 16.1%, 0.9%–1.2%, and 0.3%, respectively. CO sources were determined through raw material grinding gas detection experiments. Considering that ferrosilicon (FeSi75) grinding generates dense dust in the space, the ambient temperature rises during equipment operation, and heat and sparks are generated by collisions, compression, and friction between ferrosilicon and the equipment, three conditions for dust explosion are met, making a dust explosion highly likely. Therefore, to avoid the potential dangers of ferrosilicon grinding, four groups were set up: a "ferrosilicon + clinker" grinding group, a "ferrosilicon + calcined white precipitate" grinding group, a clinker grinding group, and a calcined white precipitate grinding group. The experimental results are shown in Table 2. The results show that the release of harmful gases is caused by residual ferrosilicon.

[0028] Table 1. Experimental release of CO gas from raw materials used in the preparation of modified magnesium slag-based cementitious materials (ppm).

[0029]

[0030] Table 2. Detection Experiment of CO Release from Slurry Preparation of Raw Materials in Magnesium Smelting

[0031]

[0032] As mentioned above, both the magnesium slag used in magnesium slag-based cementitious materials and the magnesium slag produced by smelting metallic magnesium contain CO. The sources of CO include ferrosilicon in the raw materials, as well as the reduction furnace and grinding stage from which the magnesium slag-based cementitious materials are prepared. Based on this, the present invention discovers that the harmless disposal method for magnesium slag can be based on decarbonization treatment of magnesium slag. By utilizing the residual heat and / or external heat of the magnesium slag, under the condition of the presence of oxygen-containing gas, the magnesium slag is subjected to an oxidative decarbonization reaction to remove the harmful gases therein.

[0033] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for harmless disposal of magnesium slag, characterized in that it includes using the residual heat and / or external heat of the magnesium slag to carry out an oxidative decarbonization reaction on the magnesium slag in the presence of oxygen-containing gas; the oxygen content of the oxygen-containing gas is ≥15wt%, the volume of the oxygen-containing gas is 50 to 100 times the volume of the magnesium slag; and the temperature of the oxidative decarbonization reaction is ≥500℃.

[0034] The above-mentioned method for harmless disposal of magnesium slag is characterized in that the magnesium slag is the slag from the Pidgeon process for metallic magnesium smelting.

[0035] The above-mentioned method for harmless disposal of magnesium slag is characterized in that the method specifically includes:

[0036] The magnesium slag is fed into the reaction system, and high-temperature oxygen-containing gas is introduced to obtain the reaction system.

[0037] The magnesium slag waste heat and / or external heat are used for oxidation and decarbonization reaction, and the reaction is monitored. When the reaction sufficiency conditions are met, harmless magnesium slag is obtained. The monitored indicators include the oxygen content of the inlet gas, the oxygen content of the outlet gas, and the temperature of the reaction system. The reaction sufficiency conditions include: the reaction system temperature ≥ 500℃, and the difference between the oxygen content of the inlet gas and the oxygen content of the outlet gas < 5% for a duration ≥ 10 min.

[0038] The above-mentioned method for harmless treatment of magnesium slag is characterized in that the method for determining the oxidation decarbonization reaction time includes: setting the holding times at 850-1150℃, 610-850℃, and 500-610℃ as t1, t2, and t3, respectively; the decarbonization amount Y = A1*t1 + A2*t2 + A3*t3; the units of t1, t2, and t3 are min; and A1, A2, and A3 are the CO removal amounts per unit time within the corresponding temperature range, in ppm / min; the unit of decarbonization amount Y is ppm.

[0039] The above-mentioned method for harmless treatment of magnesium slag is characterized in that the oxidation and decarbonization reaction time is 0.5h to 5h.

[0040] The above-mentioned method for harmless treatment of magnesium slag is characterized in that the method further includes: heat recovery of the tail gas generated by the oxidation decarbonization reaction.

[0041] The above-mentioned method for harmless treatment of magnesium slag is characterized in that the method further includes: monitoring the temperature of the magnesium slag after harmless treatment, and discharging the magnesium slag after harmless treatment when the temperature of the magnesium slag after harmless treatment is ≤200℃.

[0042] The above-mentioned method for harmless treatment of magnesium slag is characterized in that utilizing the residual heat of the magnesium slag and / or providing external heat specifically includes: providing external heat when the temperature inside the reaction system drops to 500℃~550℃ and the difference between the oxygen content of the inlet gas and the oxygen content of the outlet gas is ≥5%.

[0043] The above-mentioned method for harmless treatment of magnesium slag is characterized in that the high-temperature oxygen-containing gas is an oxygen-containing gas with a temperature of 300-400℃.

[0044] In addition, the present invention also provides a magnesium slag harmless treatment system that applies the above-mentioned magnesium slag harmless treatment method, characterized in that it includes a reaction system, a heat preservation system, a heat replenishment system, an air supply and tail gas treatment system, a high-temperature magnesium slag waste heat recovery system and a monitoring system.

[0045] The reaction system includes a reaction chamber for the oxidation and decarburization of magnesium slag.

[0046] The insulation system is used to keep the reaction system warm;

[0047] The heating system is used to selectively provide heat to the reaction system;

[0048] The gas supply and exhaust gas treatment system includes an intake system, an exhaust system, and an exhaust gas waste heat recovery and treatment system. The intake system provides oxygen-containing gas to the reaction system. The exhaust system discharges the gas produced after the reaction in the reaction system. The exhaust gas waste heat recovery and treatment system includes an exhaust gas waste heat recovery system and an exhaust gas treatment system. The exhaust gas waste heat recovery system can recover heat from the gas discharged from the exhaust system. The exhaust gas treatment system can treat the low-temperature exhaust gas discharged from the exhaust gas waste heat treatment system.

[0049] The high-temperature magnesium slag waste heat recovery system is used to cool down the magnesium slag and recover heat after the decarburization reaction.

[0050] The monitoring system is used to monitor the system's operating status and operating parameters.

[0051] Compared with the prior art, the present invention has the following advantages:

[0052] 1. The harmless treatment method and system for magnesium slag of the present invention can effectively utilize the waste heat of high-temperature magnesium slag for oxidation and decarbonization, solving the problems caused by the accumulation of strong reducing substances, residual carbon and other impurities in magnesium slag due to magnesium smelting process, especially magnesium smelting raw materials, which leads to the release of toxic and harmful gases such as CO, H2S and CH4 during the resource utilization of magnesium slag. It can effectively accelerate the rapid decomposition of residual carbon and other impurities inside magnesium slag, obtain homogeneous impurity-free magnesium slag, improve the utilization level and efficiency of magnesium slag, and promote the large-scale utilization of coal slag.

[0053] 2. This invention creatively discovers that the reason for the release of gases such as CO during the resource utilization of magnesium slag is the residual ferrosilicon in the magnesium smelting process. Based on this, a method for harmlessly treating magnesium slag based on the self-heating oxidation and decarburization of magnesium slag is proposed. The amount of CO released from the harmlessly treated magnesium slag is significantly lower than that before the treatment.

[0054] 3. Preferably, the treatment system of the present invention includes a horizontal reactor and a horizontal cooling furnace. The system, which includes a horizontal reactor and a horizontal cooling furnace connected in series, performs harmless treatment on the magnesium slag to be treated, realizes the removal of residual carbon and the recovery of waste heat in the magnesium slag. The magnesium slag to be treated is turned over in the horizontal reactor and undergoes an oxidation and decarbonization reaction with oxygen-containing gas. Then it enters the cooling furnace to be turned over and cooled, which has the characteristics of sufficient contact of reactants and high reaction efficiency.

[0055] 4. Preferably, another treatment system of the present invention achieves the harmless treatment of magnesium smelting slag by including a closed treatment whole formed by a connected reaction furnace and a cooling furnace, which can effectively solve the problem of CO release during the resource utilization of magnesium slag and remove impurities such as residual carbon in magnesium slag.

[0056] 5. The magnesium slag harmless treatment method and system of the present invention have the characteristics of high degree of harmlessness of magnesium slag and high operation efficiency, low smoke emission and no environmental pollution. It can effectively promote the large-scale recycling and utilization of magnesium slag in my country and promote the sustainable development of the magnesium metal industry.

[0057] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0058] Instruction manual illustrations

[0059] Figure 1 This is a schematic diagram of the system structure in Example 2.

[0060] Figure 2 This is a schematic diagram of the system structure in Example 3.

[0061] Figure 3 This is a schematic diagram of the system structure in Example 4.

[0062] Explanation of reference numerals in the attached figures

[0063] 11—Reactor body; 12—Insulation layer; 13—Reactor feed inlet;

[0064] 14—Reactor feed inlet; 151—First temperature sensor;

[0065] 152—First gas parameter sensor; 16—Reactor inlet;

[0066] 17—Reactor outlet; 191—Reactor exhaust dust removal device;

[0067] 192—Reactor waste heat recovery device; 193—Reactor exhaust fan;

[0068] 110—Reaction furnace insulation cover; 21—Cooling furnace discharge port; 22—Cooling furnace outlet;

[0069] 231—Second gas parameter sensor; 232—Second temperature sensor;

[0070] 241—Cooling furnace blower; 242—Cooling furnace vent pipe;

[0071] 243—Airflow meter; 25—Cooling furnace exhaust port; 26—Cooling furnace air inlet;

[0072] 311—Intake dust removal device; 312—Intake heating device; 313—Intake exhaust fan;

[0073] 314—Inlet vent pipe; 51—Conveyor belt; 52—Lifting device;

[0074] 53—Storage bin; 54—Support frame;

[0075] 61—Reactor head section; 621—Storage hopper cavity; 622—Storage hopper conveying pipe;

[0076] 63—Inlet of horizontal reactor; 64—Insulation cover; 65—Outlet of reactor;

[0077] 67—Emergency air hose with switch;

[0078] 69—Oxygen content detector for reactor gas; 610—Reactor temperature detector;

[0079] 611—Reactor exhaust port; 612—Reactor dust removal device;

[0080] 613—Reactor waste heat recovery device; 614—Reactor exhaust fan;

[0081] 615—Reactor body section; 616—Reactor tail section;

[0082] 617—Heating component; 71—Cooling furnace head section; 72—Cooling furnace inlet;

[0083] 73—Discharge port of horizontal cooling furnace;

[0084] 74—Air inlet of horizontal cooling furnace;

[0085] 75—Cooling furnace temperature detector;

[0086] 761—Cooling furnace blower; 762—Heating device; 763—Air volume measuring instrument;

[0087] 77—Oxygen content detector for cooling furnace gas; 78—Cooling furnace body section;

[0088] 79—Cooling furnace tail section; 81—Material pipeline; 91—Base;

[0089] 92—Support roller; 93—Tire; 94—Ring gear;

[0090] 95—Reduction wheel; 96—Drive unit; 97—Jacket;

[0091] 98—Support structure; 99—Conveyor belt; 910—Material lifting device;

[0092] 911—Storage Warehouse. Detailed Implementation

[0093] Example 1

[0094] This embodiment provides a method for the harmless disposal of magnesium slag, including using the waste heat and / or external heat of the magnesium slag to carry out an oxidative decarbonization reaction on the magnesium slag in the presence of oxygen-containing gas; the oxygen content of the oxygen-containing gas is ≥15wt%, the oxygen-containing gas can be air or oxygen, and the volume of the oxygen-containing gas is 50 to 100 times the volume of the magnesium slag, for example, 50 times, 80 times or 100 times; the temperature of the oxidative decarbonization reaction is ≥500℃.

[0095] The magnesium slag is the slag from the Pidgren process of smelting metallic magnesium. The Pidgren process smelting slag is the magnesium slag obtained through the Pidgren process (silicothermic reduction process) of smelting metallic magnesium, and includes high-temperature magnesium slag, low-temperature magnesium slag, and / or stockpiled ambient-temperature magnesium slag produced by the Pidgren process.

[0096] Furthermore, the aforementioned methods for the harmless treatment of magnesium slag specifically include:

[0097] The magnesium slag is fed into a reaction system, and a high-temperature oxygen-containing gas is introduced to obtain a reaction system; the high-temperature oxygen-containing gas is an oxygen-containing gas with a temperature of 300-400℃; the oxygen-containing gas is air or oxygen.

[0098] The magnesium slag waste heat and / or external heat are used to carry out an oxidation decarbonization reaction, and the reaction is monitored at the same time. When the reaction sufficiency conditions are met, harmless magnesium slag is obtained. The monitored indicators include the oxygen content of the inlet gas, the oxygen content of the outlet gas, and the temperature of the reaction system. The reaction sufficiency conditions include: the reaction system temperature ≥ 500℃, and the difference between the oxygen content of the inlet gas and the oxygen content of the outlet gas < 5% for a duration ≥ 10 min.

[0099] Furthermore, the method also includes heat recovery of the tail gas generated by the oxidation decarbonization reaction, specifically including: recovering heat from the exhaust gas by using a waste heat recovery device after dust removal.

[0100] Furthermore, the method also includes: monitoring the temperature of the harmlessly treated magnesium slag; when the temperature of the harmlessly treated magnesium slag is ≤200℃, discharging the harmlessly treated magnesium slag; the temperature of the harmlessly treated magnesium slag can also be kept ≤200℃ by introducing fresh air into the container containing the harmlessly treated magnesium slag, using air flow to remove the heat from the harmlessly treated magnesium slag, for example, by cooling the container, and the air used as the cooling medium participates in the continuous treatment of harmless treatment of magnesium slag as an oxygen-containing gas after cooling, or the air used as the cooling medium participates in the continuous treatment of harmless treatment of magnesium slag as an oxygen-containing gas after cooling and dust removal and heating.

[0101] Specifically, utilizing the residual heat of the magnesium slag and / or providing external heat includes: providing external heat when the temperature inside the reaction system drops to 500℃~550℃ and the difference between the oxygen content of the inlet gas and the oxygen content of the outlet gas is ≥5%; the provision of external heat includes heating using an external heating device, which includes an electric heater.

[0102] In addition to determining the oxidative decarburization reaction time using reaction sufficiency, this invention also provides a method for determining the oxidative decarburization reaction time, including: setting holding times of 850–1150℃, 610–850℃, and 500–610℃ as t1, t2, and t3, respectively; the decarburization rate during each holding time is measured by CO release, and the decarburization amount Y = 40*t1 + 45*t2 + 80*t3; the units of t1, t2, and t3 are min; and the unit of decarburization amount, i.e., CO release, is ppm. When the rate of introducing high-temperature oxygen-containing gas is 1 m / s to 2 m / s, t1 = t2 / 2 = 3*t3 / 2; when the mass percentage of ferrosilicon in the pellets is 16%, A1 is 40 ppm / min, A2 is 45 ppm / min, and A3 is 80 ppm / min; the CO equivalent of carbon in the magnesium slag is 3500 ppm; for every 1% increase in the mass percentage of ferrosilicon in the pellets, the oxygen-containing gas increases by 50 m. 3 The heat preservation time is increased by 1 hour.

[0103] According to the above determination method, the specific oxidative decarbonization reaction time is 0.5h to 5h.

[0104] In this embodiment, the discharged magnesium slag after harmless treatment was ground for 30 minutes and then mixed with water to obtain a slurry. After curing and CO determination, the water content in the slurry was 25% by mass. The test results are shown in Table 3.

[0105] Table 3. CO2 determination results of magnesium slag after harmless treatment.

[0106]

[0107] Among them, the average temperature of the oxidation and decarburization reaction of magnesium slag 1 is 900℃ and the reaction time is 2h; the average temperature of the oxidation and decarburization reaction of magnesium slag 2 is 700℃ and the reaction time is 2.5h; the average temperature of the oxidation and decarburization reaction of magnesium slag 3 is 550℃ and the reaction time is 2.5h.

[0108] Example 2

[0109] This embodiment provides a harmless treatment system for magnesium slag. Please refer to [link / reference]. Figure 1 It includes a slag feeding system, a reaction system, a heat preservation system, a supplementary heating system, a gas supply and tail gas treatment system, a high-temperature magnesium slag waste heat recovery system, a monitoring system, and a slag discharge system;

[0110] The slag feeding system includes tools for transporting magnesium slag to be rendered harmless. The slag to be rendered harmless is transported to the reaction system by the slag transport system, which may be, for example, a forklift.

[0111] The reaction system includes a reaction chamber for the oxidation and decarburization of magnesium slag. The reaction system can be a reaction vessel, which includes a reaction vessel inlet, a reaction vessel outlet, a reaction vessel inlet, and a reaction vessel outlet connected to the reaction chamber. The reaction vessel inlet and outlet serve as channels for the magnesium slag to enter and exit the reaction chamber before and after the reaction, while the reaction vessel inlet and outlet serve as channels for oxygen-containing gas to enter and exit the reaction chamber before and after the reaction. Sealing the reaction vessel inlet, outlet, inlet, and outlet achieves a sealed reaction chamber. The reaction vessel can be, for example, a reactor or a rotary kiln. Depending on the discharge rate and the required amount of oxygen-containing gas, the reaction vessel outlet and inlet can be the same port, or the inlet can be part of the outlet. For example, a pipe connected to the reaction chamber within the outlet can be used as the inlet. Alternatively, the reaction vessel outlet and inlet can be set as different ports.

[0112] The insulation system is used to keep the reaction system warm; the insulation system can be an insulation layer installed in the reaction chamber; the insulation layer can be a steel insulation layer or a ceramic insulation layer.

[0113] The heating system is used to selectively provide heat to the reaction system; the heating system can be a device that can conduct heat to the reaction system, such as a solvothermal heating medium or an electric heating medium.

[0114] The air supply and exhaust gas treatment system includes an air intake system, an exhaust system, and an exhaust gas waste heat recovery treatment system.

[0115] The air intake system provides oxygen-containing gas to the reaction system; the air intake system is connected to the reaction system and the oxygen-containing gas source; the air intake system can be a pipe connected to the air inlet of the reaction vessel.

[0116] The exhaust system is used to discharge the gas produced after the reaction in the reaction system; it ensures the airflow path during the reaction process and reduces the resistance to oxygen entry; the exhaust system is connected to the reaction system, and the exhaust system can be a pipe connected to the exhaust port of the reaction vessel.

[0117] The exhaust gas waste heat recovery system includes an exhaust gas waste heat recovery system and an exhaust gas treatment system. The exhaust gas waste heat recovery system can recover heat from the gas discharged from the exhaust system. The heat recovered by the exhaust gas waste heat recovery system can be used to preheat oxygen-containing gas in the intake system. The exhaust gas waste heat recovery system may include an exhaust gas dust removal device, an exhaust gas waste heat recovery device, and an exhaust fan connected in sequence with the exhaust system. The exhaust gas dust removal device can be a bag filter or an electrostatic precipitator, and the exhaust gas waste heat recovery device can be a waste heat boiler.

[0118] The exhaust gas waste heat recovery system can also be connected to both the exhaust system and the intake system to transfer heat from the exhaust gas to the intake system, thereby preheating the oxygen-containing gas in the intake system.

[0119] The exhaust gas treatment system can treat the low-temperature exhaust gas discharged from the exhaust gas waste heat treatment system; the exhaust gas treatment system is connected to the exhaust gas waste heat recovery system and is used to treat the exhaust gas, such as a treatment pool that can absorb exhaust gas.

[0120] The high-temperature magnesia slag waste heat recovery system is used to cool the magnesia slag after the decarburization reaction and recover heat. The recovered heat can be used to improve the insulation system, while also promoting the rapid cooling of the impurity-removed magnesia slag. The high-temperature magnesia slag waste heat recovery system may include a cooling container and a magnesia slag heat recovery unit. The cooling container is connected to the reaction container and has an air inlet, an air outlet, a feed inlet, and a discharge outlet. The magnesia slag heat recovery unit includes a cooling container dust removal device installed at the air outlet of the cooling container. The cooling container dust removal device is connected to the insulation system through a pipeline. After absorbing heat, the gas discharged from the cooling container is cleaned by the cooling container dust removal device and then used to serve the insulation system, thus contributing to the insulation of the reaction container.

[0121] Preferably, the magnesium slag heat recovery unit serves as an air intake system connected to the reaction vessel. During the continuous processing of magnesium slag, the medium that has absorbed heat from the magnesium slag selectively enters the reaction vessel through the magnesium slag heat recovery unit, serving as a source of oxygen-containing gas for the reaction vessel. For example, during the continuous processing of magnesium slag, the cooling medium in the cooling vessel enters the cooling vessel through the cooling vessel air inlet to cool the material. The medium that has absorbed heat from the material enters the dust removal device in the magnesium slag heat recovery unit through the cooling vessel air outlet for dust removal. The dust-removed gas selectively enters the reaction vessel as an oxygen source and / or heat source.

[0122] The slag discharge system is used to discharge the harmlessly treated magnesium slag; the slag discharge system can be, for example, a conveyor belt and a lifting device; the material is transported to the storage silo by the conveyor belt and the lifting device.

[0123] The monitoring system is used to monitor the system's operating status and working parameters; the monitoring system includes a temperature sensor and a gas oxygen content sensor; by monitoring the inlet and outlet oxygen content and the reaction temperature in the reaction vessel, the reaction time is controlled; by monitoring the material temperature in the cooling vessel, the cooled material is discharged.

[0124] Example 3

[0125] Please see Figure 2 This embodiment provides a specific magnesium slag harmless treatment system based on Embodiment 1 and / or 2, including a reactor and a cooling furnace, wherein the cooling furnace is located below the reactor and is connected to the reactor; the reactor and the cooling furnace are erected and fixed by a support 54 commonly used in the art;

[0126] The reactor includes a reactor body 11, an insulation layer 12, a reactor inlet 13, a reactor outlet 14, a reactor air inlet 16, a reactor air outlet 17, a reactor exhaust system, and a first monitoring device for monitoring parameters inside the reactor. The insulation layer 12 is disposed on the inner wall of the reactor body 11. The reactor inlet 13 is located at the upper part of the reactor body 11, and the reactor outlet 14 is located at the lower part of the reactor body 11. A reactor inlet valve and a reactor insulation cover 110 are installed on the reactor inlet 13. The reactor insulation cover 110 covers the reactor inlet 13. The reactor air inlet 16 is located at the lower part of the reactor body 11, and the reactor air outlet 17 is located at the upper part of the reactor body 11. The reactor exhaust system... The reactor is connected to the gas outlet 17 of the reactor; the insulation layer 12 is used to maintain a stable reaction temperature and reduce heat loss inside the reactor; the reactor insulation cover includes a reactor insulation cover body and a reactor insulation cover door opened on the reactor insulation cover body. The reactor insulation cover door is slidably installed on the reactor insulation cover body. The reactor insulation cover door is slidably installed on the reactor insulation cover body by opening a doorway in the reactor insulation cover body, and installing a slide rail and matching pulleys on the edge of the doorway to achieve a sliding connection between the reactor insulation cover door and the reactor insulation cover body; when magnesium slag needs to be fed, the reactor insulation cover door is slidably opened and the reactor feed port valve is opened. After the feeding is completed, the reactor feed port valve and the reactor insulation cover door are closed to form a closed reaction space; the parameters include reaction temperature and gas oxygen content.

[0127] The cooling furnace includes a cooling furnace feed inlet 21, a cooling furnace discharge inlet 22, a cooling furnace air inlet device, a cooling furnace air inlet 26, a cooling furnace exhaust outlet 25, and a second monitoring device for monitoring parameters inside the cooling furnace. The cooling furnace feed inlet 21 is located at the top of the cooling furnace and communicates with the reactor feed inlet 14. The cooling furnace discharge inlet 22 is located at the bottom of the cooling furnace. The cooling furnace air inlet 26 is located at the bottom of the cooling furnace, and the cooling furnace exhaust outlet 25 is located at the top of the cooling furnace. The cooling furnace air inlet device is connected to the cooling furnace air inlet 26. A cooling furnace lower... The feed inlet valve and the cooling furnace feed outlet valve are used to control the rate at which materials enter the cooling furnace; a cooling furnace discharge outlet valve is provided inside the cooling furnace discharge outlet 22; gas is introduced through the cooling furnace air inlet device to cool the materials in the cooling furnace; the parameters include temperature and gas oxygen content; when the first monitoring device shows that the material temperature in the reactor is ≥500℃ and the difference between the oxygen content of the gas discharged from the reactor and the oxygen content of the gas inlet of the second monitoring device is <5%, the material in the reactor is discharged into the cooling furnace; when the second monitoring device shows that the material temperature is ≤200℃, magnesium slag after impurity removal is obtained;

[0128] In this embodiment, the reactor exhaust system includes a reactor exhaust dust removal device 191, a reactor waste heat recovery device 192, and a reactor exhaust fan 193. The inlet of the reactor exhaust dust removal device 191 is connected to the reactor outlet 17, the outlet of the reactor exhaust dust removal device 191 is connected to the inlet of the reactor waste heat recovery device 192, and the outlet of the reactor waste heat recovery device 192 is connected to the reactor exhaust fan 193. The reactor exhaust dust removal device 191 is used to treat the exhaust gas generated in the reactor, and then the waste heat is recovered through the reactor waste heat recovery device 192. The recovered waste heat can supplement the heat of the air inlet heating device 312 or be used for other purposes. The reactor exhaust dust removal device 191 is a commonly used exhaust dust removal device in the art, such as a bag filter or an electrostatic precipitator. The reactor waste heat recovery device 192 can be, for example, a waste heat boiler.

[0129] In this embodiment, the first monitoring device includes a first temperature sensor 151 and a first gas parameter sensor 152. The first temperature sensor 151 is located inside the reactor chamber 11, and the first gas parameter sensor 152 is located on the reactor exhaust device. The first monitoring device can provide real-time feedback on the internal temperature and gas parameters of the reactor, including the oxygen content of the gas.

[0130] In this embodiment, the reactor inlet 16 and the reactor outlet 17 are located on both sides of the reactor body 11.

[0131] In this embodiment, the cooling furnace air intake device includes a cooling furnace blower 241 and a cooling furnace vent pipe 242 installed on the cooling furnace blower 241. The cooling furnace vent pipe 242 is spirally arranged upward along the cooling furnace air inlet 26 inside the cooling furnace, and multiple cooling vent holes are opened on the cooling furnace vent pipe 242. Fresh air is sent into the cooling furnace by the cooling air blower 241, and after cooling the material, it enters the reaction furnace through the cooling furnace exhaust port 25. The cooling furnace air intake device also includes an air volume detector 243 installed on the cooling furnace blower 241.

[0132] In this embodiment, the second monitoring device includes a second temperature sensor 232 and a second gas parameter sensor 231. The second temperature sensor 232 is located inside the cooling furnace, and the second gas parameter sensor 231 is located on the cooling furnace air inlet device.

[0133] In this embodiment, an air intake and heat preservation device is also included. The air intake and heat preservation device is connected to both the reactor air inlet 16 and the cooling furnace exhaust outlet 25. The air intake and heat preservation device is used to introduce oxygen-containing gas from the cooling furnace air inlet into the reactor. This is used to heat the magnesium slag in the furnace while providing abundant oxygen, promoting the oxidation reaction of impurities in the magnesium slag in the reactor. This device is a continuous device for removing impurities and recovering waste heat from magnesium slag. During the first batch of magnesium slag processing, high-temperature oxygen-containing gas at a temperature of 300-400°C can be transported to the reactor through the cooling furnace air inlet to carry out decarburization oxidation reaction with the magnesium slag in the reactor. In subsequent batches of magnesium slag processing, fresh air can be directly introduced through the cooling furnace air inlet to cool the material in the cooling furnace. The fresh air absorbs the heat of the material and enters the reactor as a heat source to supplement the heat for the decarburization reaction in the reactor.

[0134] The air intake insulation device includes an air intake dust removal device 311, an air intake heating device 312, an air intake exhaust fan 313, and an air intake vent pipe 314. The inlet of the air intake dust removal device 311 is connected to the exhaust port 25 of the cooling furnace, the outlet of the air intake dust removal device 311 is connected to the inlet of the air intake heating device 312, the outlet of the air intake heating device 312 is connected to the inlet of the air intake exhaust fan 313, and the outlet of the air intake exhaust fan 313 is connected to the air intake vent pipe 314. The air intake vent pipe 314 is spirally arranged upward along the air inlet 16 of the reactor and is provided with multiple air holes. The air intake insulation device can effectively realize the uniform diffusion of gas in the reactor after dust removal, purification, and heating, and fully heat and oxidize the magnesium slag in the reactor. The air intake heating device 312 can be, for example, an electric heating device.

[0135] Example 4

[0136] Please see Figure 3 This embodiment provides another specific magnesium slag harmless treatment system based on Embodiment 1 and / or 2, including a horizontal reactor and a horizontal cooling furnace; the horizontal reactor includes a reactor tail section 616, a reactor body section 615, and a reactor head section 61 connected in sequence, the reactor body section 615 being rotatably connected between the reactor tail section 616 and the reactor head section 61; the horizontal cooling furnace includes a cooling furnace head section 71, a cooling furnace body section 78, and a cooling furnace tail section 79 connected in sequence, the cooling furnace body section 78 being rotatably connected between the cooling furnace head section 71 and the cooling furnace tail section 79;

[0137] The tail section 616 of the reactor is directly opposite the head section 71 of the cooling furnace. The horizontal reactor has an angle of 5° to 10° with the ground, and the horizontal cooling furnace has an angle of 5° to 10° with the ground. A heating component 617 for heating the materials in the horizontal reactor is installed inside the tail section 616 of the reactor. The vertical distance from the tail section 616 of the reactor to the head section 71 of the cooling furnace is less than the vertical distance from the head section 61 of the reactor to the tail section 79 of the cooling furnace. The heating component 617 can be a burner.

[0138] The device also includes a support structure 98 for aligning the horizontal reactor and the horizontal cooling furnace with the reactor tail section 616 and the cooling furnace head section 71 facing each other and forming an angle of 5° to 10° with the ground. The support structure can be a steel support structure commonly used in the art, as long as it can support and fix the furnace body.

[0139] The horizontal reactor also includes a jacket 97 sleeved between the reactor tail section 616, the reactor body section 615 and the reactor head section 61, through which the reactor body section 615 is rotatably connected between the reactor tail section and the reactor head section.

[0140] The horizontal reactor is a reaction system for removing residual carbon and other impurities from magnesium slag, and the horizontal cooling furnace is a device for recovering the waste heat from the high-temperature magnesium slag used for impurity removal. The horizontal reactor is driven by a horizontal reactor drive assembly to rotate the reactor body 615 along the long axis of the reactor center, causing the magnesium slag inside the horizontal reactor to tumble circumferentially within the furnace, thereby achieving material oxidation and decarbonization. The horizontal cooling furnace is driven by a horizontal cooling furnace drive assembly to rotate the cooling furnace body along the long axis of the cooling furnace center, causing the material inside the horizontal cooling furnace to tumble circumferentially within the furnace, thereby achieving material cooling.

[0141] The horizontal reactor drive assembly and the horizontal cooling furnace drive assembly are both commonly used drive assemblies in the art that can drive the furnace body or kiln body to rotate. For example, they can be drive assemblies including a base 91, a support roller 92, a tire 93, a gear ring 94, a reduction wheel 95, and a drive device 96. The drive device can be a motor.

[0142] A storage hopper is connected to the furnace head section 61 of the reactor, and a horizontal reactor inlet 63 is opened on the storage hopper. A reactor outlet 65 is opened on the furnace tail section 616 of the reactor. A reactor exhaust port 611 is opened on the furnace head section 61 of the reactor, and a reactor exhaust dust removal and waste heat recovery device is connected to the reactor exhaust port 611.

[0143] The cooling furnace head section 71 is provided with a cooling furnace inlet 72 that communicates with the reactor outlet 65. The cooling furnace tail section 79 is provided with a horizontal cooling furnace outlet 73 and a horizontal cooling furnace air inlet 74. The horizontal cooling furnace air inlet 74 is connected to a cooling furnace air supply device. The reactor outlet 65 and the cooling furnace inlet 72 are connected through a material pipeline 81.

[0144] A cooling furnace inlet valve is installed at the inlet 72 of the cooling furnace.

[0145] In this embodiment, a heat insulation cover 64 is provided on the feed inlet 63 of the horizontal reactor, and the heat insulation cover 64 is hinged to the storage hopper. The storage hopper is a high-temperature resistant storage hopper, which can be a steel storage hopper or a ceramic storage hopper.

[0146] In this embodiment, the storage hopper includes a storage hopper cavity 621 and a storage hopper conveying pipe 622. The storage hopper cavity 621 has an opening at the bottom, and the storage hopper conveying pipe 622 communicates with the opening at the bottom of the storage hopper cavity 621. One end of the storage hopper conveying pipe 622 away from the storage hopper cavity 621 is connected to the furnace head section 61 of the reactor. The connection point of the storage hopper conveying pipe 622 on the furnace head section 61 is located in the lower middle part of the furnace head section 61.

[0147] The reactor is equipped with an insulation layer; the insulation layer prevents heat loss from the furnace and improves the reaction efficiency of magnesium slag in the furnace. The insulation layer can be a ceramic insulation layer.

[0148] In this embodiment, the reactor dust removal and exhaust waste heat recovery device includes a reactor dust removal device 612, a reactor waste heat recovery device 613, and a reactor exhaust fan 614. The reactor waste heat recovery device 613 is located between the reactor dust removal device 612 and the reactor exhaust fan 614, and the reactor exhaust fan 614 is connected to the outside. The reactor waste heat recovery device 613 can be a waste heat boiler or a heat exchanger.

[0149] In this embodiment, the horizontal reactor is equipped with a reactor temperature detector 610 and a reactor gas oxygen content detector 69. The reactor temperature detector 610 is located in the tail section 616 of the reactor, and the reactor gas oxygen content detector 69 is located on the reactor dust removal exhaust waste heat recovery device.

[0150] In this embodiment, a horizontal cooling furnace outlet valve is provided at the outlet 73 of the horizontal cooling furnace.

[0151] In this embodiment, the cooling furnace air supply device includes a cooling furnace blower 761 and a heating device 762 for heating the gas supplied by the cooling furnace blower 761. The cooling furnace blower 761 is connected to the air inlet 74 of the horizontal cooling furnace. The cooling furnace air supply device also includes an air volume measuring instrument 763 installed on the cooling furnace blower 761.

[0152] In this embodiment, the horizontal cooling furnace is equipped with a cooling furnace temperature detector 75 and a cooling furnace gas oxygen content detector 77. The cooling furnace temperature detector 75 is located at the tail section 79 of the cooling furnace, and the cooling furnace gas oxygen content detector 77 is located on the cooling furnace air supply device. The cooling furnace temperature detector 75 can monitor the temperature of the material inside the cooling furnace. When the temperature is ≤200℃, the magnesium slag inside the furnace is discharged through the discharge port of the cooling furnace.

[0153] In this embodiment, the material pipeline 81 is equipped with an emergency gas pipe 67 with a switch and a feed controller for controlling the opening of the reactor outlet 65. The emergency gas pipe 67 with the switch is connected to both the reactor outlet 65 and the cooling furnace inlet 72. The material pipeline 81 connects the reactor and the cooling furnace. On one hand, the material pipeline 81 is used to transport the reacted material in the reactor to the cooling furnace. On the other hand, it is used to transport the gas entering from the horizontal cooling furnace inlet 74 to the reactor as an oxygen supplement to participate in the removal of residual carbon from magnesium slag. The feed controller can be a valve.

[0154] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the invention shall still fall within the protection scope of the present invention.

Claims

1. A method for harmlessly disposing of magnesium slag, characterized in that, This includes utilizing the waste heat and / or external heat of the magnesium slag to carry out an oxidative decarburization reaction on the magnesium slag in the presence of oxygen-containing gas; the oxygen content of the oxygen-containing gas is ≥15wt%, and the volume of the oxygen-containing gas is 50 to 100 times the volume of the magnesium slag; the temperature of the oxidative decarburization reaction is ≥500℃. The method specifically includes: The magnesium slag is fed into the reaction system, and high-temperature oxygen-containing gas is introduced to obtain the reaction system. The magnesium slag waste heat and / or external heat are used for oxidation and decarbonization reaction, and the reaction is monitored. When the reaction sufficiency conditions are met, harmless magnesium slag is obtained. The monitored indicators include the oxygen content of the inlet gas, the oxygen content of the outlet gas, and the temperature of the reaction system. The reaction sufficiency conditions include: the reaction system temperature ≥ 500℃, and the difference between the oxygen content of the inlet gas and the oxygen content of the outlet gas < 5% for a duration ≥ 10 min.

2. The method for harmless disposal of magnesium slag according to claim 1, characterized in that, The magnesium slag is the slag from the Pidgeon process for smelting metallic magnesium.

3. The method for harmless disposal of magnesium slag according to claim 1, characterized in that, The method for determining the oxidation decarbonization reaction time includes: setting the holding times at 850–1150℃, 610–850℃, and 500–610℃ as t1, t2, and t3, respectively; the decarbonization amount Y = A1*t1 + A2*t2 + A3*t3; the units of t1, t2, and t3 are min; and A1, A2, and A3 are the CO removal amounts per unit time within the corresponding temperature range, in ppm / min; the unit of decarbonization amount Y is ppm.

4. The method for harmless disposal of magnesium slag according to claim 3, characterized in that, The oxidation decarbonization reaction time is 0.5h to 5h.

5. The method for harmless disposal of magnesium slag according to claim 1, characterized in that, The method further includes: recovering heat from the exhaust gas generated by the oxidative decarbonization reaction.

6. The method for harmless disposal of magnesium slag according to claim 1, characterized in that, The method further includes: monitoring the temperature of the harmlessly treated magnesium slag, and discharging the harmlessly treated magnesium slag when the temperature of the harmlessly treated magnesium slag is ≤200℃.

7. The method for harmless disposal of magnesium slag according to claim 1, characterized in that, Utilizing the residual heat of the magnesium slag and / or providing external heat specifically includes: providing external heat when the temperature inside the reaction system drops to 500℃~550℃ and the difference between the oxygen content of the inlet gas and the oxygen content of the outlet gas is ≥5%.

8. The method for harmless disposal of magnesium slag according to claim 3, characterized in that, The high-temperature oxygen-containing gas is an oxygen-containing gas with a temperature of 300-400℃.

9. A magnesium slag harmless treatment system applying the magnesium slag harmless treatment method according to any one of claims 1 to 8, characterized in that, It includes a reaction system, a heat preservation system, a heat replenishment system, a gas supply and exhaust gas treatment system, a high-temperature magnesium slag waste heat recovery system, and a monitoring system; The reaction system includes a reaction chamber for the oxidation and decarburization of magnesium slag. The insulation system is used to keep the reaction system warm; The heating system is used to selectively provide heat to the reaction system; The gas supply and exhaust gas treatment system includes an intake system, an exhaust system, and an exhaust gas waste heat recovery and treatment system. The intake system provides oxygen-containing gas to the reaction system. The exhaust system discharges the gas produced after the reaction in the reaction system. The exhaust gas waste heat recovery and treatment system includes an exhaust gas waste heat recovery system and an exhaust gas treatment system. The exhaust gas waste heat recovery system can recover heat from the gas discharged from the exhaust system. The exhaust gas treatment system can treat the low-temperature exhaust gas discharged from the exhaust gas waste heat treatment system. The high-temperature magnesium slag waste heat recovery system is used to cool down the magnesium slag and recover heat after the decarburization reaction. The monitoring system is used to monitor the system's operating status and operating parameters.

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