Method for producing organic soil conditioner by using biomass bamboo reed to treat red mud

Abstract

The invention belongs to the technical field of solid waste resource utilization and environmental governance, and discloses a method for producing an organic soil conditioner by using biomass bamboo reed to treat red mud, and the method for producing the organic soil conditioner by using biomass bamboo reed to treat red mud comprises the following specific steps: S1, bamboo reed pretreatment and crushing; s2, pickling and dealkalizing the red mud; s3, mixed pyrolysis and iron element magnetization; s4, magnetic separation and iron powder collection; s5, purifying and utilizing the biomass gas; s6, pretreatment of a mixture obtained after iron separation; and S7, preparing the land improver. Through cooperative treatment of the biomass bamboo reed and the red mud, efficient recovery of iron elements is achieved, the conversion rate is 85%-95%, the calorific value of the biomass gas is increased to 3000 kcal / m < 3 > and increased by 150%, the organic soil conditioner capable of preserving moisture and fertility is prepared, fine utilization of resources is ensured through the multi-link process, 70%-85% of natural gas can be replaced by the biomass gas, and the environment-friendly and energy-saving effect is achieved. And a solid waste treatment-resource recovery-ecological restoration industrial chain is formed, and the method has both environmental and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization and environmental governance, and specifically relates to a method for producing an organic soil conditioner by treating red mud with biomass reed bamboo. Background Art

[0002] As a perennial grass plant, Phragmites australis is widely distributed in the subtropical and warm regions of the world. It has strong environmental adaptability and can grow in barren land, swamps, riverbeds, river banks, sandy wastelands or ordinary wilderness. Under warm climate and sufficient irrigation conditions, the average annual dry matter yield in the second to third year can reach 5-8 tons per mu. It is a biomass resource with great development potential.

[0003] Red mud is a polluting waste residue produced when alumina is extracted in the aluminum industry. It mainly comes from the residue of alumina production from bauxite. Every ton of alumina produced will be accompanied by 1.2-1.5 tons of red mud. It is strongly alkaline and contains a variety of heavy metals and other harmful substances. It has complex properties, fine particles and is sticky. At present, red mud is mainly treated by stacking, which not only occupies a large amount of land resources, but also may cause soil alkalinization, groundwater pollution and other environmental problems if it is randomly stacked, posing a serious threat to the ecological environment. In this context, exploring methods for efficiently utilizing reed biomass and treating red mud is of great significance to solving the environmental problems of red mud and realizing resource recycling. Summary of the Invention

[0004] The object of the present invention is to provide a method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis, so as to solve the problems raised in the above background technology.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis. The specific steps of the method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis are as follows:

[0006] S1: Pretreatment and crushing of Phragmites australis: After harvesting, the perennial Phragmites australis are firstly removed of impurities and preliminarily screened to ensure the purity of the raw materials. They are then crushed using professional machinery and the ash is filtered simultaneously to reduce the particle size to ≤5mm. After crushing, they are sent to the drying equipment for drying. The temperature is controlled to keep the moisture content less than 10%. After drying, the particle size and moisture content are quality inspected to ensure that they meet the process standards.

[0007] S2: Red mud acid washing and de-alkali treatment: The red mud raw material is first subjected to simple physical screening to remove larger particle impurities, followed by acid washing and de-alkali treatment. The red mud is rinsed with citric acid solution. The pH value is monitored in real time during rinsing and stopped when it reaches 7-9. This step can reduce the alkaline substances in the red mud and reduce the risk of subsequent equipment corrosion. After rinsing, the red mud pH value is tested to ensure that it meets the process requirements;

[0008] S3: Mixed pyrolysis and iron magnetization: Dry biochar and treated red mud are accurately weighed and mixed in a mass ratio of 1:3-1:5, and then put into pyrolysis equipment. The temperature is set at 500-600℃ and the time is 60-120 minutes. During pyrolysis, the fixed carbon in the biochar reacts with the red mud Fe2O3. The iron magnetization conversion rate is 85%-95%, and Fe3O4 elemental iron is generated to obtain a mixture. The temperature is strictly controlled during the process to ensure sufficient reaction.

[0009] S4: Magnetic separation and iron powder collection: The mixture after pyrolysis is cooled to room temperature and enters the electromagnetic separator for magnetic separation. The magnetic field strength is set to 1.4-1.8T. The magnetic field is used to separate the magnetic magnetite powder, metallic iron powder and other mixtures. The selected iron powder is collected and packaged and can be sold directly to the steel mill. After separation, the iron powder is tested for purity to ensure that the quality meets the steel mill's requirements;

[0010] S5: Biomass gas purification and utilization: Biomass reed and red mud are co-pyrolyzed to produce biomass natural gas with a calorific value of 1200-3000kcal / m 3 , which can be used as a roasting energy source for alumina plants. The fuel gas is first dusted by a high-temperature bag filter or a cyclone separation system, and then purified by an electric coke capture system to remove tar. After purification, it can be mixed with natural gas for combustion, accounting for more than 70%. During use, the calorific value and impurities are monitored in real time to ensure safety.

[0011] S6: Pretreatment of the mixture after iron separation: The mixture after magnetic separation needs to be initially crushed and screened. By controlling the parameters of the crushing equipment, the particle size of the mixture is made uniform, which is conducive to the subsequent production of land improvement agent. After crushing, the mixture is screened and the particle size of the mixture is tested after screening to ensure that its particle size meets the process standard requirements;

[0012] S7: Preparation of soil conditioner: Weigh 40% of the pretreated red mud-biochar mixture, add 30% of humic acid coated with sodium alginate to enhance the water retention and fertilizer slow-release effect, then add 3% nitrogen, 7% phosphorus, 10% potassium and 10% apple pomace in sequence, stir evenly at room temperature and dehydrate to make red mud organic soil conditioner, and finally test its composition and performance to ensure that it meets the improvement requirements.

[0013] Preferably, the pretreatment and crushing of reed bamboo in S1 refers to the removal of impurities and preliminary screening after harvesting perennial reed bamboo to ensure the purity of the reed bamboo raw materials, followed by crushing with professional machinery, and filtering ash simultaneously during the crushing process to control the particle size of the crushed reed bamboo to ≤5mm. After the crushing is completed, the reed bamboo is sent to a drying equipment for drying. By controlling the drying temperature and time, the moisture content of the reed bamboo is reduced to <10%, providing biomass raw materials that meet the requirements for subsequent processes. After drying is completed, the particle size and moisture content of the reed bamboo are quality inspected to ensure that the process standards are met.

[0014] Preferably, the red mud acid washing and de-alkali treatment in S2 refers to taking red mud raw materials, first performing simple physical screening to remove larger particle impurities, and then performing acid washing and de-alkali operations, and using citric acid solution to rinse the red mud. During the rinsing process, the pH value of the red mud is monitored in real time. When the pH value reaches 7-9, the rinsing is stopped. This step is intended to reduce the alkaline substances in the red mud and reduce the corrosion risk of subsequent equipment. After the rinsing is completed, the pH value of the red mud is tested to ensure that it meets the process requirements.

[0015] Preferably, the specific steps of mixed pyrolysis and iron element magnetization in S3 are as follows:

[0016] Step 1: Material Proportioning and Mixing: Dried biochar with a moisture content of less than 10% and red mud after acid washing and de-alkali treatment with a pH of 7-9 are accurately weighed on an electronic scale at a mass ratio of 1:3-1:5. A twin-shaft paddle mixer is used for three-dimensional tumbling stirring. The speed is controlled at 20-30 r / min and the mixing time is ≥15 minutes. Sampling tests are performed to ensure that the material particle size distribution is uniform and the coefficient of variation CV is ≤5% to avoid inadequate pyrolysis reaction due to local agglomeration.

[0017] Step 2: Start and stop the pyrolysis equipment and set parameters: pre-start the pyrolysis furnace temperature control system, heat the furnace to 200 ° C for 30 minutes to remove residual moisture in the equipment, then feed the mixed material into the furnace at a uniform rate of ≤ 5kg / min, set a staged temperature control program, heating stage: heat to 500 ° C at a rate of 10 ° C / min, hold for 10 minutes to stabilize the thermal field, constant temperature stage: maintain a core reaction temperature of 500-600 ° C, adjust the holding time to 60-120 minutes according to the material amount, cooling stage: turn off the heating system, introduce inert gas N2 to circulate in the furnace to cool down to below 100 ° C;

[0018] Step 3: Magnetization reaction monitoring and product collection: The temperature curve is recorded in real time through the built-in thermocouple with an accuracy of ±1°C and the intelligent temperature controller in the furnace. When the temperature fluctuates by more than ±5°C, the alarm system is automatically triggered. During the reaction, the reducing gas CO produced by the pyrolysis of biochar accounts for 25-35%, and H2 accounts for 8-12%, which reacts with Fe2O3 in red mud to undergo solid-phase reduction reaction. The reaction formula is as follows: 3Fe2O3+CO→2Fe3O4+CO2, Fe3O4+4CO→3Fe+4CO2. The CO2 generation rate is monitored by an online gas analyzer to judge the reaction progress. When the CO2 concentration in the tail gas is <1% for 30 consecutive minutes, the reaction is determined to be complete. The cooled product is transported to the buffer bin via a screw conveyor, and the biomass gas produced during the pyrolysis process is collected simultaneously, with a gas volume of about 150-200m 3 / t raw materials.

[0019] Preferably, the magnetic separation and iron powder collection in S4 refers to the mixture after pyrolysis being cooled to room temperature and then entering an electromagnetic separator for magnetic separation. The magnetic field strength is set to 1.4-1.8T, and the magnetic field is used to separate the magnetic magnetite powder and metallic iron powder from the mixture of biomass carbon and other by-products. The selected iron powder is collected and packaged and can be sold directly to the steel mill. The purity of the separated iron powder is tested to ensure that its quality meets the requirements of the steel mill.

[0020] Preferably, the specific steps of biomass gas purification and utilization in S5 are as follows:

[0021] Step 1: Preliminary dust removal of biomass gas: The temperature of the biomass gas generated by pyrolysis is about 500-600℃. It first enters the high-temperature filter bag dust collector. The filter material is ceramic fiber with a temperature resistance of ≥800℃. The gas flow rate is maintained at ≤0.8m / min. Solid particles ≥10μm are removed through bag filtration. A cyclone separation system is configured with an inlet wind speed of 18-22m / s and a pressure drop of 800-1200Pa as a bypass backup. When the filter bag pressure difference is greater than 1500Pa, it automatically switches to the cyclone dust removal mode. After dust removal, the gas temperature drops below 400℃ and the particulate matter content is ≤50mg / Nm 3 , meeting the requirements of subsequent decoking process;

[0022] Step 2: Tar deep purification and quality control: After preliminary dust removal, the gas enters the electric coke capture system with an operating voltage of 30-40kV and an electric field strength of 1.2-1.5kV / cm. The high-voltage electrostatic field charges and aggregates the tar droplets, achieving a tar removal efficiency of ≥95% and a final tar content of ≤10mg / Nm 3 The purified gas enters the buffer tank with a volume of 500-1000m 3 , real-time monitoring of the component H2S≤20mg / Nm through the online gas analyzer 3 , CO≤10% and calorific value, low calorific value ≥1200kcal / m 3 When the calorific value fluctuates by more than ±10%, the natural gas blending ratio is automatically adjusted to ensure that the biomass gas ratio remains stable in the range of 70%-85%;

[0023] Step 3: Mixed combustion and safety monitoring: The purified gas and natural gas are mixed in a set ratio through a venturi mixer and then transported to the burner of the alumina plant roaster. During the combustion process, the flame monitor has a response time of less than 50ms and detects the combustion status in real time. The pressure transmitter is configured with an accuracy of ±0.5% FS to monitor the gas pipeline pressure, with an operating pressure of 0.05-0.1MPa, and an emergency shut-off valve is set with a closing time of less than 1s. When the O2 content in the gas is detected to be greater than 1% and the calorific value is less than 1000kcal / m 3When the system is in operation, the system will automatically trigger the sound and light alarm and cut off the fuel supply to ensure the safe operation of the roaster.

[0024] Preferably, the pretreatment of the mixture after iron selection in S6 refers to the preliminary crushing and screening of the mixture after magnetic separation and iron selection, so that the particle size of the mixture is uniform, which is convenient for the subsequent production of land conditioner. During the crushing process, the parameters of the crushing equipment are controlled to ensure that the particle size of the mixture meets the requirements. After screening, the particle size of the mixture is tested to ensure that it meets the process standards.

[0025] Preferably, the specific steps of preparing the soil conditioner in S7 are as follows:

[0026] Step 1: Weighing and pretreatment of core materials: weighing the red mud biochar mixture, using an electronic belt scale to accurately weigh the pretreated red mud biochar mixture, with a particle size of ≤2mm and a moisture content of <15%, so that it accounts for 40% of the land improver, and the mass fraction is controlled at ±0.5%; humic acid coating treatment: humic acid is weighed at a 30% addition amount, with a purity of ≥90%. A spray coating process is used to evenly spray a sodium alginate solution with a concentration of 2-3% on the surface of the humic acid particles in an atomization form, with an atomization pressure of 0.3-0.5MPa, and dried in a fluidized bed at a temperature of 60-80°C for 10-15 minutes to form a slow-release coating layer with a thickness of 0.1-0.3mm, so that the humic acid dissolution rate is ≤30% within 24 hours;

[0027] Step 2: All components are mixed and stirred: Nutrient addition: nitrogen, N ≥ 46% urea, 3%, phosphorus, P2O5 ≥ 64% superphosphate, 7%, potassium, K2O ≥ 60% potassium chloride, 10%, and apple pomace, moisture content ≤ 20%, crushed to particle size ≤ 3mm, 10%, to ensure that the purity of each raw material meets agricultural standards; stirring and mixing at room temperature: all materials are put into a double-shaft paddle mixer with a volume of 5-10m 3 , speed 15-20r / min, stirring time ≥20 minutes, sampling to test the uniformity coefficient of variation CV ≤ 8% of the mixture to ensure uniform distribution of nitrogen, phosphorus and potassium nutrients;

[0028] Step 3: Dehydration and molding: The stirred mixture is dehydrated by a plate and frame filter press at a working pressure of 0.6-0.8 MPa and a centrifugal dehydrator at a speed of 1500-2000 r / min to reduce the moisture content of the modifier to 25%-30%, forming a plastic granular structure.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. The present invention uses the method to synergize the treatment of biomass reed bamboo and red mud. On the one hand, red mud, as alkaline waste residue from the aluminum industry, contains Fe2O3 and Al2O3, which are dealkalized by acid washing and pyrolysis reaction, which not only realizes the magnetic recovery of iron elements with a conversion rate of 85%-95%. The separated iron powder can be directly used for steelmaking, but also can be used as a catalyst for biomass pyrolysis, increasing the calorific value of biomass gas converted from reed bamboo from 1200kcal / m 3 Increased to 3000kcal / m 3 , H2 production rate increased by 46%, significantly improving energy conversion efficiency. On the other hand, the biochar generated after the crushing and pyrolysis of reed bamboo is combined with red mud residue, and an organic soil conditioner is made by adding humic acid, nitrogen, phosphorus and potassium components. The fixed carbon of reed bamboo and the minerals in red mud can be reused, realizing the two-way conversion of "solid waste-resources" and reducing dependence on traditional chemical raw materials.

[0031] 2. The present invention realizes refined resource recovery and product performance enhancement through multi-link process control. In the pyrolysis stage, the staged temperature control program heats up at 10℃ / min to 500℃ and maintains the constant temperature at 500-600℃ for 60-120 minutes. Combined with CO and H2 reduction reaction, it ensures that the iron element is fully magnetized and generates Fe3O4 and elemental iron. At the same time, through magnetic separation, the magnetic field strength is 1.4-1.8T, which realizes high-purity recovery of iron powder and meets the requirements of steel mills. The biomass gas is dust-removed by high-temperature filter bags, and the particulate matter is ≤50mg / Nm 3 , and electric coke capture treatment, tar content ≤ 10mg / Nm 3 After that, it can be mixed with natural gas at a ratio of 70%-85% as a roasting energy source for alumina plants to reduce fossil fuel consumption. In the preparation of soil conditioners, the sodium alginate-coated humic acid process has a dissolution rate of ≤30% in 24 hours. Combined with the addition of apple pomace, the product is given water-retaining and fertilizer-retaining, slow-release and synergistic properties. At the same time, the calcium and sodium components in the red mud reduce the oxygen content of the tar by 76% through catalytic decarboxylation reaction, further improving the resource utilization rate of the overall process and the economic value of the product.

[0032] 3. The present invention has significant advantages in carbon reduction, cost reduction and soil remediation through this process. The acid washing and alkali removal of red mud can reduce the pH to 7-9, eliminating the risk of alkaline pollution. Biomass gas replaces natural gas in the pyrolysis process, which can reduce fossil energy consumption by more than 70% and reduce carbon emissions. The iron powder separated by magnetic separation is directly sold to steel mills. Biomass gas is used as industrial energy, and soil conditioners are used to repair saline-alkali land or barren soil, forming an "solid waste treatment-resource recovery-ecological restoration" industry chain to achieve diversified economic benefits. Experimental data show that after adding red mud, the calorific value of biomass gas increases by 150%, and the tar content decreases by 50%. At the same time, the nitrogen, phosphorus and potassium nutrients in the conditioner are evenly distributed, with a coefficient of variation CV≤8%, which can effectively improve soil fertility and reduce the use of chemical fertilizers. The overall process not only solves the environmental risks of red mud storage, but also provides low-cost, high-performance raw materials and energy for agriculture and industry, which is in line with the concept of circular economy and green development. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, the embodiment of the present invention provides a method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis. The specific steps of the method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis are as follows:

[0036] S1: Pretreatment and crushing of Phragmites australis: After harvesting, the perennial Phragmites australis are firstly removed of impurities and preliminarily screened to ensure the purity of the raw materials. They are then crushed using professional machinery and the ash is filtered simultaneously to reduce the particle size to ≤5mm. After crushing, they are sent to the drying equipment for drying. The temperature is controlled to keep the moisture content less than 10%. After drying, the particle size and moisture content are quality inspected to ensure that they meet the process standards.

[0037] S2: Red mud acid washing and de-alkali treatment: The red mud raw material is first subjected to simple physical screening to remove larger particle impurities, followed by acid washing and de-alkali treatment. The red mud is rinsed with citric acid solution. The pH value is monitored in real time during rinsing and stopped when it reaches 7-9. This step can reduce the alkaline substances in the red mud and reduce the risk of subsequent equipment corrosion. After rinsing, the red mud pH value is tested to ensure that it meets the process requirements;

[0038] S3: Mixed pyrolysis and iron magnetization: Dry biochar and treated red mud are accurately weighed and mixed in a mass ratio of 1:3-1:5, and then put into pyrolysis equipment. The temperature is set at 500-600℃ and the time is 60-120 minutes. During pyrolysis, the fixed carbon in the biochar reacts with the red mud Fe2O3. The iron magnetization conversion rate is 85%-95%, and Fe3O4 elemental iron is generated to obtain a mixture. The temperature is strictly controlled during the process to ensure sufficient reaction.

[0039] S4: Magnetic separation and iron powder collection: The mixture after pyrolysis is cooled to room temperature and enters the electromagnetic separator for magnetic separation. The magnetic field strength is set to 1.4-1.8T. The magnetic field is used to separate the magnetic magnetite powder, metallic iron powder and other mixtures. The selected iron powder is collected and packaged and can be sold directly to the steel mill. After separation, the iron powder is tested for purity to ensure that the quality meets the steel mill's requirements;

[0040] S5: Biomass gas purification and utilization: Biomass reed and red mud are co-pyrolyzed to produce biomass natural gas with a calorific value of 1200-3000kcal / m 3 , which can be used as a roasting energy source for alumina plants. The fuel gas is first dusted by a high-temperature bag filter or a cyclone separation system, and then purified by an electric coke capture system to remove tar. After purification, it can be mixed with natural gas for combustion, accounting for more than 70%. During use, the calorific value and impurities are monitored in real time to ensure safety.

[0041] S6: Pretreatment of the mixture after iron separation: The mixture after magnetic separation needs to be initially crushed and screened. By controlling the parameters of the crushing equipment, the particle size of the mixture is made uniform, which is conducive to the subsequent production of land improvement agent. After crushing, the mixture is screened and the particle size of the mixture is tested after screening to ensure that its particle size meets the process standard requirements;

[0042] S7: Preparation of soil conditioner: Weigh 40% of the pretreated red mud-biochar mixture, add 30% of humic acid coated with sodium alginate to enhance the water retention and fertilizer slow-release effect, then add 3% nitrogen, 7% phosphorus, 10% potassium and 10% apple pomace in sequence, stir evenly at room temperature and dehydrate to make red mud organic soil conditioner, and finally test its composition and performance to ensure that it meets the improvement requirements.

[0043] The specific surface area of biochar is 300-500m 2 / g, the Ca and Fe elements in red mud are loaded on the carbon surface in the form of nanoparticles; alkaline red mud can neutralize the acidity of biochar, forming a pH buffer system of pH 7.5-8.5, and at the same time solidify heavy metals Pb and Cd; this process achieves the dual goals of improving biochar performance and harmless utilization of red mud through the synergistic pyrolysis of reed bamboo and red mud. It has the characteristics of low cost and significant environmental benefits, and is a typical technical path combining desertification control with circular economy.

[0044] Among them, the pretreatment and crushing of reed bamboo in S1 refers to the removal of impurities and preliminary screening after harvesting perennial reed bamboo to ensure the purity of the reed bamboo raw materials, followed by crushing with professional machinery, and simultaneous filtration of ash during the crushing process to control the particle size of the crushed reed bamboo to ≤5mm. After the crushing is completed, the reed bamboo is sent to the drying equipment for drying. By controlling the drying temperature and time, the moisture content of the reed bamboo is reduced to <10%, providing biomass raw materials that meet the requirements for subsequent processes. After drying is completed, the particle size and moisture content of the reed bamboo are quality inspected to ensure that the process standards are met.

[0045] After harvesting perennial Phragmites australis, impurities are removed and preliminary screening is carried out to ensure the purity of the raw materials. Then, it is crushed by professional machinery and the ash is filtered simultaneously to make the particle size ≤5mm. After crushing, it is sent to the drying equipment for drying. The temperature is controlled to make the moisture content less than 10%. After drying, the particle size and moisture content of the Phragmites australis are quality inspected to ensure that they meet the process standards and provide qualified biomass raw materials for subsequent processes.

[0046] Among them, the red mud acid washing and de-alkali treatment in S2 refers to taking red mud raw materials, first performing simple physical screening to remove larger particle impurities, and then performing acid washing and de-alkali operations. The red mud is rinsed with citric acid solution. During the rinsing process, the pH value of the red mud is monitored in real time. When the pH value reaches 7-9, the rinsing is stopped. This step is intended to reduce the alkaline substances in the red mud and reduce the corrosion risk of subsequent equipment. After the rinsing is completed, the pH value of the red mud is tested to ensure that it meets the process requirements.

[0047] The red mud raw material is first subjected to simple physical screening to remove larger particle impurities, and then acid washing and de-alkali are carried out. The red mud is rinsed with citric acid solution. The pH value is monitored in real time during the rinsing process and the process is stopped when the pH value reaches 7-9. This step can effectively reduce the alkaline substances in the red mud and reduce the risk of subsequent equipment corrosion. After the rinsing is completed, the pH value of the red mud is tested again to ensure that it meets the process requirements and provide suitable conditions for subsequent mixed pyrolysis and other processes.

[0048] The specific steps of the mixed pyrolysis and iron element magnetization in S3 are as follows:

[0049] Step 1: Material Proportioning and Mixing: Dried biochar with a moisture content of less than 10% and red mud after acid washing and de-alkali treatment with a pH of 7-9 are accurately weighed on an electronic scale at a mass ratio of 1:3-1:5. A twin-shaft paddle mixer is used for three-dimensional tumbling stirring. The speed is controlled at 20-30 r / min and the mixing time is ≥15 minutes. Sampling tests are performed to ensure that the material particle size distribution is uniform and the coefficient of variation CV is ≤5% to avoid inadequate pyrolysis reaction due to local agglomeration.

[0050] Step 2: Start and stop the pyrolysis equipment and set parameters: pre-start the pyrolysis furnace temperature control system, heat the furnace to 200 ° C for 30 minutes to remove residual moisture in the equipment, then feed the mixed material into the furnace at a uniform rate of ≤ 5kg / min, set a staged temperature control program, heating stage: heat to 500 ° C at a rate of 10 ° C / min, hold for 10 minutes to stabilize the thermal field, constant temperature stage: maintain a core reaction temperature of 500-600 ° C, adjust the holding time to 60-120 minutes according to the material amount, cooling stage: turn off the heating system, introduce inert gas N2 to circulate in the furnace to cool down to below 100 ° C;

[0051] Step 3: Magnetization reaction monitoring and product collection: The temperature curve is recorded in real time through the built-in thermocouple with an accuracy of ±1°C and the intelligent temperature controller in the furnace. When the temperature fluctuates by more than ±5°C, the alarm system is automatically triggered. During the reaction, the reducing gas CO produced by the pyrolysis of biochar accounts for 25-35%, and H2 accounts for 8-12%, which reacts with Fe2O3 in red mud to undergo solid-phase reduction reaction. The reaction formula is as follows: 3Fe2O3+CO→2Fe3O4+CO2, Fe3O4+4CO→3Fe+4CO2. The CO2 generation rate is monitored by an online gas analyzer to judge the reaction progress. When the CO2 concentration in the tail gas is <1% for 30 consecutive minutes, the reaction is determined to be complete. The cooled product is transported to the buffer bin via a screw conveyor, and the biomass gas produced during the pyrolysis process is collected simultaneously, with a gas volume of about 150-200m 3 / t raw materials.

[0052] Weigh dry biochar with a moisture content of less than 10% and acid-washed red mud with a pH of 7-9 in a mass ratio of 1:3-1:5, and stir with a twin-shaft paddle mixer at a speed of 20-30r / min for ≥15 minutes to ensure that the material is uniform CV≤5%; second, preheat the pyrolysis furnace to 200℃ and feed the material at a rate of ≤5kg / min, heat and maintain the temperature at 500-600℃ for 60-120 minutes, and cool to below 100℃ with nitrogen; third, monitor the temperature with a thermocouple, use CO and H2 to reduce Fe2O3, determine the reaction is complete based on the CO2 concentration, and collect the product and 150-200m 3 / tBiomass gas.

[0053] Among them, the magnetic separation and iron powder collection in S4 refers to the cooling of the pyrolysis mixture to room temperature and then entering the electromagnetic separator for magnetic separation. The magnetic field strength is set to 1.4-1.8T. The magnetic field is used to separate the magnetic magnetite powder and metallic iron powder from the mixture of biomass carbon and other by-products. The selected iron powder is collected and packaged and can be sold directly to the steel mill. The purity of the separated iron powder is tested to ensure that its quality meets the requirements of the steel mill.

[0054] After the pyrolysis mixture cools to room temperature, it enters the electromagnetic separator with a magnetic field strength of 1.4-1.8T. The magnetic field adsorption characteristics are used to separate the magnetic magnetite powder, metallic iron powder and non-magnetic by-products of biomass carbon. The selected iron powder can be directly supplied to the steel plant after collection and packaging. During the separation process, the purity of the iron powder is tested to ensure that its quality meets the raw material standards of the steel plant, thereby realizing the efficient recovery and reuse of iron resources.

[0055] The specific steps of biomass fuel gas purification and utilization in S5 are as follows:

[0056] Step 1: Preliminary dust removal of biomass gas: The temperature of the biomass gas generated by pyrolysis is about 500-600℃. It first enters the high-temperature filter bag dust collector. The filter material is ceramic fiber with a temperature resistance of ≥800℃. The gas flow rate is maintained at ≤0.8m / min. Solid particles ≥10μm are removed through bag filtration. A cyclone separation system is configured with an inlet wind speed of 18-22m / s and a pressure drop of 800-1200Pa as a bypass backup. When the filter bag pressure difference is greater than 1500Pa, it automatically switches to the cyclone dust removal mode. After dust removal, the gas temperature drops below 400℃ and the particulate matter content is ≤50mg / Nm 3 , meeting the requirements of subsequent decoking process;

[0057] Step 2: Tar deep purification and quality control: After preliminary dust removal, the gas enters the electric coke capture system with an operating voltage of 30-40kV and an electric field strength of 1.2-1.5kV / cm. The high-voltage electrostatic field charges and aggregates the tar droplets, achieving a tar removal efficiency of ≥95% and a final tar content of ≤10mg / Nm 3 The purified gas enters the buffer tank with a volume of 500-1000m 3 , real-time monitoring of the component H2S≤20mg / Nm through the online gas analyzer 3 , CO≤10% and calorific value, low calorific value ≥1200kcal / m 3 When the calorific value fluctuates by more than ±10%, the natural gas blending ratio is automatically adjusted to ensure that the biomass gas ratio remains stable in the range of 70%-85%;

[0058] Step 3: Mixed combustion and safety monitoring: The purified gas and natural gas are mixed in a set ratio through a venturi mixer and then transported to the burner of the alumina plant roaster. During the combustion process, the flame monitor has a response time of less than 50ms and detects the combustion status in real time. The pressure transmitter is configured with an accuracy of ±0.5% FS to monitor the gas pipeline pressure, with an operating pressure of 0.05-0.1MPa, and an emergency shut-off valve is set with a closing time of less than 1s. When the O2 content in the gas is detected to be greater than 1% and the calorific value is less than 1000kcal / m 3 When the system is in operation, the system will automatically trigger the sound and light alarm and cut off the fuel supply to ensure the safe operation of the roaster.

[0059] 500-600℃ gas passes through ceramic fiber filter bag for dust removal, flow rate ≤0.8m / min, particulate matter ≤50mg / Nm 3 When the pressure difference exceeds 1500Pa, switch to cyclone dust removal; Second, the electric coke capture system has a voltage of 30-40kV, the decoking efficiency is ≥95%, and the tar is ≤10mg / Nm 3 , the buffer tank monitors the components and automatically adjusts the blended natural gas to a biomass gas ratio of 70%-85%; 3. After mixing with natural gas, it is burned, and the combustion status and pressure are monitored in real time. When the standard is exceeded, the fuel will be cut off within 1 second to ensure safety.

[0060] Among them, the pretreatment of the mixture after iron selection in S6 refers to the preliminary crushing and screening of the mixture after magnetic separation and iron selection, so that the particle size of the mixture is uniform, which is convenient for the subsequent production of land conditioner. During the crushing process, the parameters of the crushing equipment are controlled to ensure that the particle size of the mixture meets the requirements. After screening, the particle size of the mixture is tested to ensure that it meets the process standards.

[0061] The mixture after magnetic separation of iron is initially crushed and screened. By controlling the parameters of the crushing equipment, the particle size of the mixture is made uniform, which is conducive to the subsequent production of land conditioners. After crushing, it is screened and the particle size of the mixture is tested to ensure that its particle size meets the process standard requirements and provide qualified raw materials for the preparation of soil conditioners.

[0062] The specific steps for preparing the soil conditioner in S7 are as follows:

[0063] Step 1: Weighing and pretreatment of core materials: weighing the red mud biochar mixture, using an electronic belt scale to accurately weigh the pretreated red mud biochar mixture, with a particle size of ≤2mm and a moisture content of <15%, so that it accounts for 40% of the land improver, and the mass fraction is controlled at ±0.5%; humic acid coating treatment: humic acid is weighed at a 30% addition amount, with a purity of ≥90%. A spray coating process is used to evenly spray a sodium alginate solution with a concentration of 2-3% on the surface of the humic acid particles in an atomization form, with an atomization pressure of 0.3-0.5MPa, and dried in a fluidized bed at a temperature of 60-80°C for 10-15 minutes to form a slow-release coating layer with a thickness of 0.1-0.3mm, so that the humic acid dissolution rate is ≤30% within 24 hours;

[0064] Step 2: All components are mixed and stirred: Nutrient addition: nitrogen, N ≥ 46% urea, 3%, phosphorus, P2O5 ≥ 64% superphosphate, 7%, potassium, K2O ≥ 60% potassium chloride, 10%, and apple pomace, moisture content ≤ 20%, crushed to particle size ≤ 3mm, 10%, to ensure that the purity of each raw material meets agricultural standards; stirring and mixing at room temperature: all materials are put into a double-shaft paddle mixer with a volume of 5-10m 3, speed 15-20r / min, stirring time ≥20 minutes, sampling to test the uniformity coefficient of variation CV ≤ 8% of the mixture to ensure uniform distribution of nitrogen, phosphorus and potassium nutrients;

[0065] Step 3: Dehydration and molding: The stirred mixture is dehydrated by a plate and frame filter press at a working pressure of 0.6-0.8 MPa and a centrifugal dehydrator at a speed of 1500-2000 r / min to reduce the moisture content of the modifier to 25%-30%, forming a plastic granular structure.

[0066] 1. Use an electronic belt scale to accurately weigh the red mud biochar mixture, with a particle size of ≤2mm, a moisture content of <15%, and a proportion of 40%. Spray the humic acid with a 2-3% sodium alginate solution, with an atomization pressure of 0.3-0.5MPa, and dry at 60-80℃ / 10-15min. The dissolution rate is ≤30%. 2. Add urea and superphosphate nutrients, and simmer for 5-10 minutes. 3 The mixer is stirred at 15-20 r / min for ≥20 minutes (CV≤8%); third, the water content is reduced to 25%-30% through plate and frame filter pressing (0.6-0.8 MPa) and centrifugal dehydration (1500-2000 r / min) to form a granular structure.

[0067] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0068] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis, characterized by: The specific steps of the method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis are as follows: S1: Pretreatment and crushing of Phragmites australis: After harvesting, the perennial Phragmites australis are firstly removed of impurities and preliminarily screened to ensure the purity of the raw materials. They are then crushed using professional machinery and the ash is filtered simultaneously to reduce the particle size to ≤5mm. After crushing, they are sent to the drying equipment for drying. The temperature is controlled to keep the moisture content less than 10%. After drying, the particle size and moisture content are quality inspected to ensure that they meet the process standards. S2: Red mud acid washing and de-alkali treatment: The red mud raw material is first subjected to simple physical screening to remove larger particle impurities, followed by acid washing and de-alkali treatment. The red mud is rinsed with citric acid solution. The pH value is monitored in real time during rinsing and stopped when it reaches 7-9. This step can reduce the alkaline substances in the red mud and reduce the risk of subsequent equipment corrosion. After rinsing, the red mud pH value is tested to ensure that it meets the process requirements; S3: Mixed pyrolysis and iron magnetization: Dry biochar and treated red mud are accurately weighed and mixed in a mass ratio of 1:3-1:5, and then put into pyrolysis equipment. The temperature is set at 500-600℃ and the time is 60-120 minutes. During pyrolysis, the fixed carbon in the biochar reacts with the red mud Fe2O3. The iron magnetization conversion rate is 85%-95%, and Fe3O4 elemental iron is generated to obtain a mixture. The temperature is strictly controlled during the process to ensure sufficient reaction. S4: Magnetic separation and iron powder collection: The mixture after pyrolysis is cooled to room temperature and enters the electromagnetic separator for magnetic separation. The magnetic field strength is set to 1.4-1.8T. The magnetic field is used to separate the magnetic magnetite powder, metallic iron powder and other mixtures. The selected iron powder is collected and packaged and can be sold directly to the steel mill. After separation, the iron powder is tested for purity to ensure that the quality meets the steel mill's requirements; S5: Biomass gas purification and utilization: Biomass reed and red mud are co-pyrolyzed to produce biomass natural gas with a calorific value of 1200-3000kcal / m 3 , which can be used as a roasting energy source for alumina plants. The fuel gas is first dusted by a high-temperature bag filter or a cyclone separation system, and then purified by an electric coke capture system to remove tar. After purification, it can be mixed with natural gas for combustion, accounting for more than 70%. During use, the calorific value and impurities are monitored in real time to ensure safety. S6: Pretreatment of the mixture after iron separation: The mixture after magnetic separation needs to be initially crushed and screened. By controlling the parameters of the crushing equipment, the particle size of the mixture is made uniform, which is conducive to the subsequent production of land improvement agent. After crushing, the mixture is screened and the particle size of the mixture is tested after screening to ensure that its particle size meets the process standard requirements; S7: Preparation of soil conditioner: Weigh 40% of the pretreated red mud-biochar mixture, add 30% of humic acid coated with sodium alginate to enhance the water retention and fertilizer slow-release effect, then add 3% nitrogen, 7% phosphorus, 10% potassium and 10% apple pomace in sequence, stir evenly at room temperature and dehydrate to make red mud organic soil conditioner, and finally test its composition and performance to ensure that it meets the improvement requirements.

2. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, wherein: The pretreatment and crushing of reed bamboo in S1 refers to the removal of impurities and preliminary screening after harvesting perennial reed bamboo to ensure the purity of the reed bamboo raw materials, followed by crushing with professional machinery, and simultaneous filtration of ash during the crushing process to control the particle size of the crushed reed bamboo to ≤5mm. After the crushing is completed, the reed bamboo is sent to a drying equipment for drying. By controlling the drying temperature and time, the moisture content of the reed bamboo is reduced to <10%, providing biomass raw materials that meet the requirements for subsequent processes. After the drying is completed, the particle size and moisture content of the reed bamboo are quality inspected to ensure that the process standards are met.

3. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, characterized in that: The red mud acid washing and de-alkali treatment in S2 refers to taking red mud raw materials, first performing simple physical screening to remove larger particle impurities, and then performing acid washing and de-alkali operations. The red mud is rinsed with citric acid solution. During the rinsing process, the pH value of the red mud is monitored in real time. When the pH value reaches 7-9, the rinsing is stopped. This step is intended to reduce the alkaline substances in the red mud and reduce the corrosion risk of subsequent equipment. After the rinsing is completed, the pH value of the red mud is tested to ensure that it meets the process requirements.

4. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, characterized in that: The specific steps of mixed pyrolysis and iron element magnetization in S3 are as follows: Step 1: Material Proportioning and Mixing: Dried biochar with a moisture content of less than 10% and red mud after acid washing and de-alkali treatment with a pH of 7-9 are accurately weighed on an electronic scale at a mass ratio of 1:3-1:

5. A twin-shaft paddle mixer is used for three-dimensional tumbling stirring. The speed is controlled at 20-30 r / min and the mixing time is ≥15 minutes. Sampling tests are performed to ensure that the material particle size distribution is uniform and the coefficient of variation CV is ≤5% to avoid inadequate pyrolysis reaction due to local agglomeration. Step 2: Start and stop the pyrolysis equipment and set parameters: pre-start the pyrolysis furnace temperature control system, heat the furnace to 200 ° C for 30 minutes to remove residual moisture in the equipment, then feed the mixed material into the furnace at a uniform rate of ≤ 5kg / min, set a staged temperature control program, heating stage: heat to 500 ° C at a rate of 10 ° C / min, hold for 10 minutes to stabilize the thermal field, constant temperature stage: maintain a core reaction temperature of 500-600 ° C, adjust the holding time to 60-120 minutes according to the material amount, cooling stage: turn off the heating system, introduce inert gas N2 to circulate in the furnace to cool down to below 100 ° C; Step 3: Magnetization reaction monitoring and product collection: The temperature curve is recorded in real time through the built-in thermocouple with an accuracy of ±1°C and the intelligent temperature controller in the furnace. When the temperature fluctuates by more than ±5°C, the alarm system is automatically triggered. During the reaction, the reducing gas CO produced by the pyrolysis of biochar accounts for 25-35%, and H2 accounts for 8-12%, which reacts with Fe2O3 in red mud to undergo solid-phase reduction reaction. The reaction formula is as follows: 3Fe2O3+CO→2Fe3O4+CO2, Fe3O4+4CO→3Fe+4CO2. The CO2 generation rate is monitored by an online gas analyzer to judge the reaction progress. When the CO2 concentration in the tail gas is <1% for 30 consecutive minutes, the reaction is determined to be complete. The cooled product is transported to the buffer bin via a screw conveyor, and the biomass gas produced during the pyrolysis process is collected simultaneously, with a gas volume of about 150-200m 3 / t raw materials.

5. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, characterized in that: The magnetic separation and iron powder collection in S4 refers to the process of cooling the mixture after pyrolysis to room temperature and then entering an electromagnetic separator for magnetic separation. The magnetic field strength is set to 1.4-1.8T, and the magnetic field is used to separate the magnetic magnetite powder and metallic iron powder from the mixture of biomass carbon and other by-products. The selected iron powder is collected and packaged and can be sold directly to steel mills. The purity of the separated iron powder is tested to ensure that its quality meets the requirements of the steel mills.

6. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, characterized in that: The specific steps of biomass fuel gas purification and utilization in S5 are as follows: Step 1: Preliminary dust removal of biomass gas: The temperature of the biomass gas generated by pyrolysis is about 500-600℃. It first enters the high-temperature filter bag dust collector. The filter material is ceramic fiber with a temperature resistance of ≥800℃. The gas flow rate is maintained at ≤0.8m / min. Solid particles ≥10μm are removed through bag filtration. A cyclone separation system is configured with an inlet wind speed of 18-22m / s and a pressure drop of 800-1200Pa as a bypass backup. When the filter bag pressure difference is greater than 1500Pa, it automatically switches to the cyclone dust removal mode. After dust removal, the gas temperature drops below 400℃ and the particulate matter content is ≤50mg / Nm 3 , meeting the requirements of subsequent decoking process; Step 2: Tar deep purification and quality control: After preliminary dust removal, the gas enters the electric coke capture system with an operating voltage of 30-40kV and an electric field strength of 1.2-1.5kV / cm. The high-voltage electrostatic field charges and aggregates the tar droplets, achieving a tar removal efficiency of ≥95% and a final tar content of ≤10mg / Nm 3 The purified gas enters the buffer tank with a volume of 500-1000m 3 , real-time monitoring of the component H2S≤20mg / Nm through the online gas analyzer 3 , CO≤10% and calorific value, low calorific value ≥1200kcal / m 3 When the calorific value fluctuates by more than ±10%, the natural gas blending ratio is automatically adjusted to ensure that the biomass gas ratio remains stable in the range of 70%-85%; Step 3: Mixed combustion and safety monitoring: The purified gas and natural gas are mixed in a set ratio through a venturi mixer and then transported to the burner of the alumina plant roaster. During the combustion process, the flame monitor has a response time of less than 50ms and detects the combustion status in real time. The pressure transmitter is configured with an accuracy of ±0.5% FS to monitor the gas pipeline pressure, with an operating pressure of 0.05-0.1MPa, and an emergency shut-off valve is set with a closing time of less than 1s. When the O2 content in the gas is detected to be greater than 1% and the calorific value is less than 1000kcal / m 3 When the system is in operation, the system will automatically trigger the sound and light alarm and cut off the fuel supply to ensure the safe operation of the roaster.

7. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, characterized in that: The pretreatment of the mixture after iron selection in S6 refers to the preliminary crushing and screening of the mixture after magnetic separation and iron selection, so that the particle size of the mixture is uniform, which is convenient for the subsequent production of land conditioner. During the crushing process, the parameters of the crushing equipment are controlled to ensure that the particle size of the mixture meets the requirements. After screening, the particle size of the mixture is tested to ensure that it meets the process standards.

8. The method for producing an organic soil conditioner by treating red mud with biomass Phragmites australis according to claim 1, characterized in that: The specific steps of making the soil conditioner in S7 are as follows: Step 1: Weighing and pretreatment of core materials: weighing the red mud biochar mixture, using an electronic belt scale to accurately weigh the pretreated red mud biochar mixture, with a particle size of ≤2mm and a moisture content of <15%, so that it accounts for 40% of the land improver, and the mass fraction is controlled at ±0.5%; humic acid coating treatment: humic acid is weighed at a 30% addition amount, with a purity of ≥90%. A spray coating process is used to evenly spray a sodium alginate solution with a concentration of 2-3% on the surface of the humic acid particles in an atomization form, with an atomization pressure of 0.3-0.5MPa, and dried in a fluidized bed at a temperature of 60-80°C for 10-15 minutes to form a slow-release coating layer with a thickness of 0.1-0.3mm, so that the humic acid dissolution rate is ≤30% within 24 hours; Step 2: All components are mixed and stirred: Nutrient addition: nitrogen, N ≥ 46% urea, 3%, phosphorus, P2O5 ≥ 64% superphosphate, 7%, potassium, K2O ≥ 60% potassium chloride, 10%, and apple pomace, moisture content ≤ 20%, crushed to particle size ≤ 3mm, 10%, to ensure that the purity of each raw material meets agricultural standards; stirring and mixing at room temperature: all materials are put into a double-shaft paddle mixer with a volume of 5-10m 3 , speed 15-20r / min, stirring time ≥20 minutes, sampling to test the uniformity coefficient of variation CV ≤ 8% of the mixture to ensure uniform distribution of nitrogen, phosphorus and potassium nutrients; Step 3: Dehydration and molding: The stirred mixture is dehydrated by a plate and frame filter press at a working pressure of 0.6-0.8 MPa and a centrifugal dehydrator at a speed of 1500-2000 r / min to reduce the moisture content of the modifier to 25%-30%, forming a plastic granular structure.

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