Introduction to Resource Cycle Science and Engineering
1. Cleaner Production
Cleaner production refers to the continuous application of comprehensive preventive environmental strategies to the production process and products , in order to reduce risks to humans and the environment.
Cleaner production refers to production methods and measures that can not only meet people's needs, but also rationally use natural resources and energy and protect the environment.
As far as the production process is concerned, cleaner production includes the elimination of raw materials and energy, the elimination of toxic raw materials and the reduction of the quantity and toxicity of all emissions and waste before they leave the production process.
For products, cleaner production strategies aim to reduce the impact of products on humans and the environment throughout the entire production cycle.
Cleaner production includes three aspects: 1. Clean energy. (a Cleaning of conventional energy; b Utilization of renewable energy; c Development of new energy; d Development of new energy and various energy-saving technologies) 2. Clean production process. This includes using as little or no toxic and hazardous raw materials as possible, producing non-toxic and harmless intermediate products, and reducing or eliminating various risk factors in the production process. 3. Product cleaning. The product saves raw materials and energy during use, uses renewable energy or secondary energy as much as possible, and reduces the use of expensive and scarce resources. The packaging, use functions and service life of the product are reasonably designed. The product has been recycled and can be used as raw materials. Easy to handle, degrade and pollution-free.
Theoretical support system of cleaner production: 1. Conservation and balance theory. The material elements in the ecosystem are always conserved. They cannot increase or decrease without reason, nor can they be absent without reason. They just transform from one form to another. 2. Innovation theory. As far as enterprise production is concerned, an unprecedented "new combination" of production factors and production conditions is introduced into the production system.
2. Composting
The technical principles of domestic waste composting technology and straw composting technology are the same. They are both biochemical processes that degrade and transform organic matter under the action of microorganisms. Here, Waste reduction is achieved in the process.
According to different composting conditions, it can be divided into aerobic composting and anaerobic composting. Since aerobic composting takes less time than anaerobic composting, has better fertilizer efficiency, and has less odor, generally domestic waste composting refers to aerobic composting.
Due to the complex composition of domestic waste, only degradable organic matter can play a role in the composting process. Therefore, metals, plastics, broken glass, ceramics, etc. in the garbage must be sorted and removed before composting. The waste can be composted alone or mixed with sludge from municipal sewage treatment plants or agricultural waste and then composted.
The finished fertilizer after composting should meet the following standards: 1. The organic matter content is greater than. 2. The finished fertilizer must not be harmful to the environment, and pathogens, pest eggs, weed seeds, etc. have been killed. 3. The fertilizer is brown or dark brown in appearance, has no odor and has a loose texture.
Because agricultural waste compost is relatively scattered, it is usually processed on-site. The degree of mechanization is low. Open-air composting accounts for a large proportion. Ventilation uses the method of turning the pile, and temperature control is usually not carried out.
Domestic waste composting is larger in scale. Although there is also open-air composting, it is more common to use large-scale fermentation bins for large-scale production. Both temperature and ventilation can be controlled by instruments.
Domestic waste aerobic composting process: 1. Pretreatment. It mainly involves sorting, crushing and adding conditioners. After removing non-compostable materials, crush the garbage to a particle size of 12-60mm. Then adjust the moisture content and C/N ratio, and add structural conditioners and Energy conditioner. 2. Main fermentation. It is the heating stage and high temperature stage of the composting process. It usually uses forced ventilation and lasts for 4-12 days. 3. Post-fermentation. For the non-process cooling stage and the post-ripening and fertilizer-preserving stage, natural ventilation is enough, which generally lasts 20-30 days. 4. Post-processing. Further sorting is performed to remove metal, plastic, broken glass and other impurities that were not completely removed during the pre-treatment stage, and the compost product can be further crushed if necessary.
5. Deodorization. During the fermentation process, anaerobic reactions may occur part of the time or in some areas, producing odorous gases. Therefore, deodorization treatment should be carried out. The commonly used deodorization device is a compost filter.
The main operating methods of composting include static aerobic composting (one-time feeding, no more feeding before the end of composting), intermittent aerobic dynamic composting (intermittent feeding and discharging) and continuous composting. Aerobic dynamic composting (continuous feed and discharge).
3. Compost incineration
Garbage incineration refers to incineration in an incineration furnace with a furnace temperature of 800-1000°C in the presence of oxygen, so that the organic components in the garbage are fully The process of oxidizing and releasing heat. The heat released by waste incineration can be converted into steam through boilers, and then converted into electrical energy by steam turbines and generators. In the process, waste reduction and biomass energy recycling are achieved.
The exhaust gas produced after garbage burning contains dioxins, sulfides, nitrogen oxides, smoke and other pollutants. It needs to be purified and reaches certain standards before it can be discharged into the atmosphere. Therefore, flue gas treatment The device is also an important part of the waste incineration power generation system.
Factors that affect the domestic waste incineration process: the properties of domestic waste (referring to particle size, calorific value and moisture content), residence time, turbulence, temperature and air excess coefficient.
The main forms of incinerators: grate incinerator (the most widely used in the world, suitable for large-scale centralized garbage treatment), fluidized bed incinerator (the most widely used in China, is An incineration method that burns garbage more fully and destroys harmful substances more thoroughly), rotary kiln incinerator (suitable for difficult-to-burn substances, or garbage with a large moisture variation range, but the processing capacity is small and ash processing is difficult).
Removal of flue gas generated by incineration: 1. Removal of particulate matter. You can choose neutral settling chamber, cyclone dust collector, spray tower, Venturi scrubber, electrostatic precipitator and bag dust collector. The dust removal device can not only remove ash, but also remove volatile heavy metals, chlorides, sulfates or oxides. , as well as organic pollutants such as dioxins adsorbed in the ash. 2. Removal of acidic gaseous pollutants. Alkali liquid can be used as the adsorbent for wet cleaning, dry detergent can also be used for absorption, and gaseous pollutants can also be removed by reacting with alkali liquid to form solid substances. 3. Removal of nitrogen oxides. Non-catalytic reduction method, selective catalytic reduction method, oxidation absorption method or absorption reduction method can be used. 4. Removal of dioxin. Dioxins can be first adsorbed and concentrated using a fixed bed of activated carbon or activated coke, and then completely oxidized into CO2, HCl, HF and other substances. Dioxins adsorbed in the ash can be removed in a dust removal device or Reduce the release of dioxin by increasing the combustion temperature and allowing the garbage to be fully burned.
4. Remanufacturing and dismantling
The remanufacturing industry is guided by the product life cycle theory, aims at recycling and reusing waste products, and is environmentally friendly, high-quality, material-saving, A general term for a series of technical measures such as the repair and transformation of waste products based on the principle of high efficiency and energy saving, using advanced production technology as a means.
Remanufacturing technology is a high-tech repair of used products, restoring the size, shape, surface quality and other properties of parts to the quality of brand-new parts, or even exceeding the quality of brand-new parts, and forming a new product after assembly Products,
not only reduce the environmental pollution of products or equipment, but also reduce the cost of production input.
The remanufacturing process includes: disassembly, cleaning, testing, processing, parts testing, assembly, complete machine running-in test, painting and packaging, etc.
The remanufacturing and disassembly process is the collective name for all the process technologies and methods used in the disassembly and reassembly process of used products. Remanufacturing and disassembly includes two steps: disassembly and assembly. .
Remanufacturing and disassembly is the systematic removal of component parts from the assembly, requiring no damage to the target parts. Disassembly is divided into two types: destructive disassembly and non-destructive disassembly.
According to the degree of disassembly, it can be divided into complete disassembly, partial disassembly and target disassembly.
Remanufacturing and disassembly process methods can be divided into: dismantling method (using the impact energy generated by hammers or other heavy objects when knocking or installing parts to disassemble and separate parts), and pulling and dismantling methods (using the impact energy generated by hammers or other heavy objects when knocking or installing parts). A method of manual disassembly using a special puller to disassemble parts), pressure disassembly method (a static disassembly method using a hand press or a voltage machine), temperature difference method (using the thermal expansion and contraction properties of the material) Heating and containing parts to achieve disassembly) and destruction method (destructive disassembly is performed when low-value parts must be destroyed to preserve core value parts during disassembly and welding).
Remanufacturing assembly is to assemble parts with qualified performance after remanufacturing dismantling and processing, parts that can be directly used, and other new parts that have been scrapped and replaced according to the technical requirements and accuracy specified for remanufactured products. Components, parts or remanufactured products, and the entire process to achieve the accuracy and performance specified in the remanufactured products. The specific assembly processes include: interchange method, matching method, repair method, and adjustment method.
5. Remanufacturing cleaning
Cleaning the surface of parts is an important process in the remanufacturing process. It is not only to detect the surface dimensional accuracy, geometry, roughness, surface properties, The premise of abrasion, wear and adhesion, etc., and is the basis for remanufacturing parts.
The basic requirements of the cleaning process include: 1. Completely remove oil and paint on the surface of the workpiece. 2. Thoroughly remove the oil scale and scale inside the workpiece. 3. Ensure that the workpiece does not deform or change its metallographic structure due to high temperature during the cleaning process. 4. Ensure that the workpiece is not corroded by chemical substances. 5. Ensure that the residue of the cleaning process, The waste liquid does not pollute the environment.
During remanufacturing cleaning, cleaning equipment is used to apply cleaning fluid to the surface of used parts, and mechanical, physical, chemical or electrochemical methods are used to remove grease, rust, dirt and scale attached to the surface of used parts. , carbon deposits and other dirt, and make the surface of scrap parts reach the required cleanliness. The disassembled parts of used products are classified according to shape, material, category, damage, etc. and then cleaned using corresponding methods.
1. Remove oil stains. Chemical methods and electrochemical methods are mainly used. Organic solvents, alkaline solvents and chemical cleaning agents are commonly used cleaning fluids. The cleaning methods include manual and mechanical methods. 2. Remove scale. Chemical removal methods are generally used, including phosphate removal, alkali solution removal and acid cleaning. 3. Remove rust. The main methods include mechanical method, chemical pickling method and electrochemical acid etching method. 4. Remove carbon deposits. Mechanical methods, chemical methods and electrolytic methods are often used.
Remanufacturing cleaning technology: 1. Thermal cleaning technology. Thermal energy has a good promotion effect on various cleaning methods. 2. Pressure cleaning technology. Jet cleaning technology sprays pressurized cleaning fluid through a nozzle to impact the surface of the cleaning object. The cleaning method is more advanced than jet cleaning. 3. Friction and grinding cleaning technology. It is a method of cleaning the surface of parts or products using gas sandblasting and liquid sandblasting methods. 4. Ultrasonic cleaning technology. In an ultrasonic environment, the process of cleaning grease on the surface of the blank is called ultrasonic cleaning. 5. Electrolytic cleaning technology. Electrolytic cleaning is a cleaning method that uses electrolysis to remove dirt from metal surfaces. 6. Chemical cleaning technology. Chemical cleaning is a method of using one or several chemicals to remove dirt from the inside or outside surfaces of equipment.
6. Lead-acid batteries
Dry batteries are divided into primary batteries and secondary batteries. Primary batteries mainly include zinc carbon batteries, alkaline manganese batteries, and button batteries such as mercury oxide and silver oxide. Secondary batteries mainly include nickel-cadmium batteries, nickel-metal hydride batteries and lithium batteries.
The battery can achieve re-energy storage operation through the reverse reaction mechanism of electric energy conversion, so it can be reused. However, subject to the second law of thermodynamics, Junhui uses a certain amount of effective components in each charge-discharge cycle. Dissipation and discharge characteristics deteriorate with the accumulation of cycles. When the degraded discharge characteristics cannot meet the usage requirements, the battery loses its use value and becomes a waste battery.
Lead-acid battery recycling and treatment methods: Lead-acid batteries are larger in size and lead is highly toxic, so among all types of batteries, they are the earliest to be recycled and the process is relatively complete. The sludge phases of spent lead-acid batteries are mainly PbSO4, PbO2, PbO, Pb, etc., of which PbO2 is the main component. It accounts for 41%-46% and 24%-28% of the mass of the positive electrode filler and mixed filler. Therefore, the reduction effect of PbO2 has an important impact on the entire recycling technology, and its reduction processes include fire method and wet method. The fire method is to reduce and smelt PbO2 into Pb together with other components PbSO4, PbO, etc. in the sludge in a metallurgical furnace. However, due to the production of secondary pollutants such as SO2 and high-temperature Pb dust, high energy consumption and low utilization rate, it will be gradually eliminated. The wet method is to add a reducing agent under solution conditions to reduce and convert PbO2 into a low-valent lead compound. Among the reducing agents, it is ideal to add FeSO4 to sulfuric acid solution to reduce PbO2.
The reduction process is:
7. Lithium battery
Lithium metal is a precious metal resource, and lithium batteries have high recycling value. Whether it is a disposable lithium battery or a lithium-ion battery, because the varieties and types are constantly changing, that is, the chemical composition and structure of the battery are constantly changing, the recycling of waste lithium batteries is more difficult than other mature and stable waste batteries. Lithium-ion batteries have a long service life and a short time to market.
Disposable lithium battery laboratory recycling process: After screening the broken lithium battery, the negative lithium electrode is obtained. When metallic lithium is dissolved in water, it reacts rapidly with water, releasing a large amount of heat to generate hydrogen and water-soluble lithium hydroxide. Yingfei cannot directly dissolve spent lithium batteries in water or acid. Experiments have shown that the reaction can be carried out safely by using an isobutanol aqueous solution. At the same time, carbon dioxide gas is introduced during the reaction to generate a lithium carbonate precipitate of high uniform purity. After the precipitate is left to stand for separation, hydrochloric acid is added to dissolve the precipitate, and then high-purity metallic lithium can be obtained through electrolysis. The metallic manganese in the positive electrode can be obtained through acid dissolution and electrolysis. This method still needs to be verified by productive experiments.
8. Fly ash
Fly ash is a clay-like volcanic ash material emitted by coal combustion. It refers to the powdery residue brought out of the flue gas when the boiler burns, referred to as ash or fly ash. It also includes the bottom slag discharged from the bottom of the boiler, referred to as slag.
The composition of fly ash: SiO2 and Al2O3 account for the majority, and the rest are small amounts of Fe2O3, CaO, MgO, Na2O, K2O, SO3, etc.
According to the CaO content in fly ash, fly ash can be divided into two categories: high calcium ash and low calcium ash. Generally, those with CaO content above 20% are called high calcium ash, and their quality is better than low calcium ash. Most of my country's coal-fired power plants
burn bituminous coal. The CaO content in fly ash is low and it is a low-calcium ash. However, the Al2O3 content is generally high and the loss on ignition is also high.
The mineral composition of fly ash mainly includes two categories: amorphous phase and crystalline phase. The amorphous phase is mainly glass body, accounting for about 50%-80% of the total fly ash. Most of it is a solid solution formed by SiO2 and Al2O3, and most of them form hollow microspheres. In addition, the unburned fine carbon particles also belong to the amorphous phase. The crystalline phases of fly ash mainly include quartz sand, mullite, feldspar, mica, magnetite, pyrite, etc. The crystalline phase existing alone in fly ash is extremely rare and is often surrounded by a glass phase.
Fly ash particles are usually divided into two categories: bead-like particles and slag-like particles according to their shape. The bead-like particles include floating beads, hollow sunken beads, dense sunken beads and iron-rich glass beads. Slag-like particles include sponge-like glass slag particles, carbon particles, obtuse-angle particles, debris and cohesive particles.
The physical properties of fly ash: it is gray or off-white powder.
The activity of fly ash includes physical activity and chemical activity. Physical activity is the sum of fly ash particle effect, micro-aggregate effect, etc. Chemical activity refers to the coagulation and hardening properties of fly ash after being mixed with lime and water. The activity of fly ash is not only determined by its chemical composition, but also closely related to its phase composition and structural characteristics. The more active SiO2 and active Al2O3 the vitreous body contains, the higher the activity. The activity of fly ash is potential and needs to be stimulated to be exerted. Commonly used excitation methods include mechanical grinding, hydrothermal synthesis and alkaline excitation.
Fly ash contains useful components such as iron, aluminum, hollow microspheres and unburned carbon, and contains a variety of rare metal elements. Therefore, it is important to extract these useful components from fly ash. economic value.
(1) Extract iron. Coal contains minerals such as pyrite, hematite, limonite, etc. When coal is burned, part of the iron oxide is reduced to Fe3O4 and granular iron after being burned at high temperature, so it can be directly This magnetic iron oxide is separated and extracted using a magnetic separator
. Magnetic separation is divided into two processes: wet magnetic separation and dry magnetic separation. At present, wet magnetic separation process is mostly used in power plants.
(2) Extract Al2O3. There are many processes for extracting Al, such as limestone sintering, hot acid leaching, chlorination, and direct welding.
Among them, the technological process of extracting alumina by limestone sintering mainly includes five processes: sintering, self-pulverization of cooked materials, dissolution, carbon separation and calcination.
(3) Extract glass beads. Microbeads in fly ash are divided into floating beads, sinking beads and magnetic beads according to their physical and chemical characteristics. The methods for extracting microbeads can be roughly divided into two categories: dry mechanical sorting and wet mechanical sorting.
The dry mechanical separation process is:
Wet mechanical separation of beads is a combination process of flotation, magnetic separation, gravity separation and other selection methods in China.
The density of the floating beads is smaller than that of water, so the density difference between the floating beads and other particles can be used to separate the floating beads from other particles by flotation using water as the medium.
(Flotation)
The magnetic beads in fly ash are partially formed by the reduction of carbon and CO from the iron-containing minerals in the coal during the high-temperature combustion process of the boiler.
particles, part of which is reduced to Fe3O4. Therefore, magnetic beads can be sorted based on their magnetic differences from other particles. (Magnetic separation)
When the floating beads, magnetic beads and carbon particles are selected from the fly ash, only the sinking beads and a small amount of monomer quartz are left.
They are There are great differences in density, shape, particle size and surface properties, so gravity separation, flotation or classification methods can be used to enrich and separate, to obtain different levels of sunken bead products.
(4) Extract charcoal. When power plant boilers burn anthracite and inferior bituminous coal, the pulverized coal cannot be completely burned,
resulting in an increase in the carbon content in fly ash. In order to reduce the carbon content in fly ash and make full use of coal resources,
As a source, fly ash is often subjected to carbon extraction treatment. Carbon extraction generally uses flotation and electroseparation methods.
Float carbon extraction is suitable for fly ash discharged by wet method. This method uses the hydrophilic surface of fly ash and coal particles
Burning bituminous coal, CaO in fly ash The content is low and it is a low calcium ash, but the Al2O3 content is generally higher and the loss on ignition is also higher.
The mineral composition of fly ash mainly includes two categories: amorphous phase and crystalline phase. The amorphous phase is mainly glass body, accounting for about 50%-80% of the total amount of fly ash. Most of it is a solid solution formed by SiO2 and Al2O3, and most of them form hollow microspheres. In addition, the unburned fine carbon particles also belong to the amorphous phase. The crystalline phases of fly ash mainly include quartz sand, mullite, feldspar, mica, magnetite, pyrite, etc. The crystalline phase existing alone in fly ash is extremely rare and is often surrounded by a glass phase.
Fly ash particles are usually divided into two categories: bead-like particles and slag-like particles according to their shape. The bead-like particles include floating beads, hollow sunken beads, dense sunken beads and iron-rich glass beads. Slag-like particles include sponge-like glass slag particles, carbon particles, obtuse-angle particles, debris and cohesive particles.
The physical properties of fly ash: it is gray or off-white powder.
The activity of fly ash includes physical activity and chemical activity. Physical activity is the sum of fly ash particle effect, micro-aggregate effect, etc. Chemical activity refers to the coagulation and hardening properties of fly ash after being mixed with lime and water. The activity of fly ash is not only determined by its chemical composition, but also closely related to its phase composition and structural characteristics. The more active SiO2 and active Al2O3 the vitreous body contains, the higher the activity. The activity of fly ash is potential and needs to be stimulated to be exerted. Commonly used excitation methods include mechanical grinding, hydrothermal synthesis and alkaline excitation.
Fly ash contains useful components such as iron, aluminum, hollow microspheres and unburned carbon, and contains a variety of rare metal elements. Therefore, it is important to extract these useful components from fly ash. economic value.
(1) Extract iron. Coal contains minerals such as pyrite, hematite, limonite, etc. When coal is burned, part of the iron oxide is reduced to Fe3O4 and granular iron after being burned at high temperature, so it can be directly This magnetic iron oxide is separated and extracted using a magnetic separator
. Magnetic separation is divided into two processes: wet magnetic separation and dry magnetic separation. At present, wet magnetic separation process is mostly used in power plants.
(2) Extract Al2O3. There are many processes for extracting Al, such as limestone sintering, hot acid leaching, chlorination, and direct welding.
Among them, the technological process of extracting alumina by limestone sintering mainly includes five processes: sintering, self-pulverization of cooked materials, dissolution, carbon separation and calcination.
(3) Extract glass beads. Microbeads in fly ash are divided into floating beads, sinking beads and magnetic beads according to their physical and chemical characteristics.
The methods for extracting microbeads can be roughly divided into two categories: dry mechanical sorting and wet mechanical sorting.
The dry mechanical separation process is:
The wet mechanical separation of beads is a combination process of flotation, magnetic separation, gravity separation and other selection methods in China.
The density of floating beads is less than that of water, so the density difference between floating beads and other particles can be used to separate floating beads from other particles by flotation with water as the medium.
(Flotation)
The magnetic beads in fly ash are partially formed by the reduction of carbon and CO from the iron-containing minerals in the coal during the high-temperature combustion process of the boiler.
particles, part of which is reduced to Fe3O4. Therefore, magnetic beads can be sorted based on their magnetic differences from other particles. (Magnetic separation)
When the floating beads, magnetic beads and carbon particles are selected from the fly ash, only the sinking beads and a small amount of single quartz are left.
They are There are great differences in density, shape, particle size and surface properties, so gravity separation, flotation or classification methods can be used to enrich and separate, to obtain different levels of sunken bead products.
(4) Extract charcoal. When power plant boilers burn anthracite and inferior bituminous coal, the pulverized coal cannot be completely burned,
resulting in an increase in the carbon content in fly ash. In order to reduce the carbon content in fly ash and make full use of coal resources,
As a source, fly ash is often subjected to carbon extraction treatment. Carbon extraction generally uses flotation and electroseparation methods.
Float carbon extraction is suitable for fly ash discharged by wet method. This method is to separate fly ash and coal particles by taking advantage of the difference in their surface hydrophilic properties
way.
Fly ash is used to produce construction materials. It is mainly used to make cement and bricks, and configure ordinary concrete, lightweight concrete, aerated concrete, aggregates, etc. Ashes with poor quality can be used for paving roads, making foundations, and filling materials.
Fly ash is used to produce chemical products. Due to the high content of SiO2 and Al2O3 in fly ash, it can be used to produce chemical products, such as flocculants, molecular sieves, white carbon black, water glass, anhydrous aluminum chloride, aluminum sulfate, etc.
Agricultural utilization of fly ash. There are two ways to utilize fly ash in agriculture: one is to improve soil and increase production in agriculture; the other is to produce fly ash multi-element compound fertilizer suitable for farmland.
9. Phosphogypsum
The calcium sulfate obtained by reacting phosphate rock and sulfuric acid to produce phosphoric acid is called phosphogypsum.
Among the chemical production methods of phosphoric acid, the most important method is to use sulfuric acid to decompose phosphate rock. The main products are phosphoric acid and calcium sulfate. This method is called the sulfuric acid method, also known as the extraction method or wet method. . In my country, the wet dihydrate method is often used to produce phosphoric acid. The reaction equation is:
The composition and properties of phosphogypsum: it is in powder form, with a free water content of 20%-30%, and the color is off-white, gray, The color in the pot is gray yellow, light yellow, light green, etc., and the particle diameter is 5-150um. Phosphogypsum contains a certain amount of impurities, which are divided into soluble impurities and insoluble impurities according to their solubility. Soluble impurities are acids or salts that are not removed during washing, mainly including soluble K+/Na+, etc. Insoluble impurities mainly include unreacted phosphate rock, insoluble fluoride and metals in the form of phosphate complexes. wait.
Various impurity components in phosphogypsum have a great influence on its properties. Specifically, the setting time of phosphogypsum is prolonged and the strength of the hardened body is reduced.
Phosphorus in phosphogypsum mainly comes in three forms: soluble phosphorus, crystalline phosphorus and insoluble phosphorus.
Fluorine in phosphogypsum exists in the form of soluble fluorine and insoluble fluorine such as CaF2 and Na2SiF6. The soluble fluorine has the greatest impact on the performance of phosphogypsum. Insoluble fluorine has basically no impact on the performance of phosphogypsum. .
Soluble phosphorus, soluble fluorine, crystalline phosphorus and organic matter are the main harmful impurities in phosphogypsum.
Applications of phosphogypsum:
(1) Industrial applications of phosphogypsum
Using phosphogypsum to produce sulfuric acid co-production cement
Using phosphogypsum to produce ammonium sulfate and calcium carbonate
Using phosphogypsum to produce potassium sulfate has one-step and two-step methods
Producing thiourea and calcium carbonate
Extract precious metals and rare earth metals
(2) Application of phosphogypsum in construction
Use as gypsum building materials
Use as cement admixtures
(3) Application of phosphogypsum in highway engineering
Phosphogypsum has strong shear strength and good water stability, so it can be used as a Replace the filling material and the performance is better.
(4) Application of phosphogypsum in agriculture
Phosphogypsum is acidic and contains phosphorus, calcium, sulfur, silicon zinc, magnesium and other nutrients needed for crop growth. It is not only It can be used as a fertilizer based on sulfur and calcium, and can also replace natural gypsum to improve saline-alkali soil.
10. Tailings
Tailings are "waste" discharged by mining enterprises under certain technical and economic conditions, but they are also potential industrial solid waste. When technical and economic conditions When allowed, effective development can begin again.
The comprehensive utilization of tailings mainly includes two aspects: first, the tailings are reprocessed as industrial solid waste to recover useful minerals; the second is the direct utilization of tailings, that is, metal mine tailings are regarded as composite mineral raw materials , for overall utilization.
(1) Extraction of valuable components in tailings
Utilization of iron-containing tailings.
For the recovery of weakly magnetic iron minerals and their associated metals, except for a few gravity separation methods, most of them rely on strong magnetic separation-flotation and gravity separation-magnetic separation-flotation. Selected joint process.
Utilization of tailings containing ferrous metals.
Utilization of A copper tailings. The first is to recover copper and iron from copper tailings; the second is to recover copper, iron and precious metals from copper tailings.
Re-selection of B lead-zinc tailings. One is to recover silver from lead and zinc tailings; the other is to recover non-metallic minerals from lead and zinc tailings.
Recycling of C molybdenum tailings. One is to recover iron from molybdenum tailings; the other is to recover tungsten and other non-metallic minerals from molybdenum tailings.
Recycling of D tin tailings.
Recycling of E tungsten tailings. One is to recover tungsten, bismuth and molybdenum from tungsten tailings; the other is to recover copper and molybdenum from tungsten tailings
ore.
F Gold tailings recycling.
(2) Tailings production of building materials
Tailings brick making: tailings sintered bricks, hydrated synthetic tailings building materials, autoclaved tailings bricks
< p> Tailings produce cementTailings produce ceramic materials
Tailings produce crystallized glass
(3) Tailings are used as underground filling materials
p>Full tailings cemented filling technology
The main aggregate of traditional tailings cemented filling is graded desilted tailings, and the tailings utilization rate is generally only
50 %.
High water solid tailings filling technology
Its essence is that in the tailings cement filling process of metal mines, cement is not used but "high water
speed" is used. "Solidified material" is used as the cementing material, and the whole tailings of the mine dressing plant are used as the filling aggregate. After adding water and mixing according to a certain ratio, a high-water consolidation filling slurry is formed.
11. Develop circular economy
Circular economy refers to the economic process of comprehensive utilization of material resources and waste in accordance with the requirements of cleaner production and the 3R principle.
This definition must grasp the four basic requirements:
The circular economy must comply with the requirements of the ecological economy
The circular economy must follow the 3R principle
p>The circular economy requires the comprehensive utilization of material resources and their wastes, rather than partial utilization or unilateral utilization
The circular economy must focus on the economy rather than recycling
The practical significance of developing a circular economy:
The implementation of a circular economy is a major trend in the current world economic and social development
The implementation of a circular economy is an urgent need for the further development of China's economy
The implementation of circular economy is inevitable to change the unsustainability of my country's current high-growth mode
my country has the possibility of establishing a circular economy
The basic laws of circular economy:
The law of ecological economy
The law of coexistence and unification of two kinds of resources
The law of economic benefit constraints
The law of symmetry of rights and responsibilities