Introduction to resource cycle science and engineering

1, cleaner production

Cleaner production refers to the continuous application of comprehensive preventive environmental strategies in production processes and products to reduce the risks to human beings and the environment.

Cleaner production refers to the adoption of production methods and measures that can not only meet people's needs, but also rationally utilize natural resources and energy and protect the environment.

As far as the production process is concerned, cleaner production includes canceling raw materials and energy, eliminating toxic raw materials, and reducing the quantity and toxicity of all emissions and wastes before they leave the production process.

For products, cleaner production strategy aims to reduce the impact of products on human beings and the environment in the whole production cycle.

Cleaner production includes three aspects: 1. Clean energy. Clean conventional energy; B. using renewable energy; C. developing new energy sources; Development of new energy and various energy-saving technologies. The production process is clean. Including using as little or no toxic and harmful raw materials as possible, producing non-toxic and harmless intermediate products and reducing or eliminating various dangerous factors in the production process. 3. The product is clean. This product saves raw materials and energy, uses renewable energy or secondary energy as much as possible, and reduces the use of expensive and scarce resources. The packaging, use function and service life of the product are designed reasonably, and the product has been recovered and can be recycled as raw materials, which is easy to handle, degrade and pollution-free.

Theoretical support system for cleaner production: 1. Conservation and equilibrium theory. The material elements in the ecosystem have always been conserved, and they can neither increase or decrease for no reason, nor be absent for no reason, but just change from one form to another. 2. Innovative theory. As far as enterprise production is concerned, the "new combination" of production factors and production conditions has never been introduced into the production system.

Step 2 compost fertilizer

Domestic waste composting technology has the same technical principle as straw composting technology, which is a biochemical process of degradation and transformation of organic matter under the action of microorganisms, and in this process, waste reduction is realized.

According to different composting conditions, it can be divided into aerobic composting and anaerobic composting. Aerobic composting is generally called aerobic composting because it has shorter time, better fertilizer efficiency and less odor than anaerobic composting.

Because the composition of domestic waste is complex, only degradable organic matter can play a role in the composting process, such as metals, plastics, broken glass, ceramics and so on. Garbage must be separated and removed before composting, and the separated garbage can be composted separately or mixed with sludge or agricultural waste from urban sewage treatment plants.

The finished fertilizer after composting shall meet the following standards: 1. Organic matter content is greater than. 2. The finished fertilizer is harmless to the environment, and bacteria, eggs and weed seeds have been killed. 3. This fertilizer is brown or yellowish brown in appearance, odorless and loose in texture.

Agricultural waste compost is scattered, generally treated on the spot, with low degree of mechanization and large proportion of open-air compost. Ventilation adopts the way of turning over the pile, and generally does not control the temperature.

The scale of domestic waste composting is large. Although there is open-air composting, large-volume fermentation bins are mostly used in large-scale production, and the temperature and ventilation can be controlled by instruments.

Aerobic composting process of domestic waste: 1. Pretreatment. It mainly includes sorting, crushing and adding conditioner. After removing non-compostable substances, the garbage is crushed to a particle size of 12-60mm, and then the water content and C/N ratio are adjusted.

Structure regulator and energy regulator are added. 2. Main fermentation. It is the heating stage and high temperature stage of composting process, and forced ventilation 4- 12d is usually adopted. 3. Post-fermentation. For the non-technical cooling stage and after-ripening fertilizer conservation stage, natural ventilation is enough, which generally lasts for 20-30 days. 4. Post-processing. Further sort and remove impurities such as metals, plastics and broken glass that are not completely removed in the pretreatment stage, and further crush compost products if necessary.

5. Deodorize. In the process of fermentation, anaerobic reaction may occur in a certain period of time or in a certain area, resulting in smelly gas, so deodorization is needed. The common deodorizing device is compost filter.

The operation modes of composting mainly include static aerobic composting (one-time feeding, no feeding until the end of composting), intermittent aerobic dynamic composting (intermittent feeding and discharging) and continuous aerobic dynamic composting (continuous feeding and discharging).

3. Compost incineration

Garbage incineration refers to the process that organic components in garbage are fully oxidized and release heat in an incinerator with a temperature of 800- 1000℃ in the presence of oxygen. The heat released by garbage incineration can be converted into steam by boiler, and then into electric energy by steam turbine and generator. In this process, garbage reduction and biomass energy recycling can be realized.

The tail gas produced by garbage combustion contains dioxin, sulfide, nitrogen oxides, smoke and other pollutants, which need to be purified and reach a certain standard before being discharged into the atmosphere. Therefore, the flue gas treatment device is also an important part of the garbage incineration power generation system.

Factors affecting the incineration process of domestic waste: the nature of domestic waste (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 (widely used in China, which is a more complete incineration method of garbage combustion and more thorough destruction of harmful substances), rotary kiln incinerator (suitable for garbage with refractory substances or large moisture change range, but with small treatment capacity and great difficulty in ash treatment).

Removal of flue gas from incineration: 1. Removal of particulate matter. Neutral settling chamber, cyclone, spray tower, Venturi scrubber, electrostatic precipitator and bag filter can be selected. The dust collector can not only remove dust, but also remove volatile heavy metals, chlorides, sulfates or oxides, dioxins and other organic pollutants adsorbed in the dust. 2. Removal of acid gas pollutants. Alkaline liquor can be used as absorbent for wet washing, dry detergent can also be used for absorption, and gaseous pollutants can also react with alkali liquor to generate solid substances and be removed. 3. Removal of nitrogen oxides. Non-catalytic reduction method, selective catalytic reduction method, oxidation absorption method or absorption reduction method can be selected. 4. Removal of dioxins. Dioxins can be absorbed and concentrated in a fixed bed of activated carbon or activated coke, and then completely oxidized into CO2, HCl, HF and other substances. Dioxins adsorbed in ash can be removed in the dust removal device, and the release of dioxins can also be reduced by increasing the combustion temperature and making the garbage burn fully.

4. Remanufacturing and disassembly

Remanufacturing industry refers to a series of technical measures to repair and transform waste products based on product life cycle theory, with recycling of waste products as the goal, environmental protection, high-quality material saving, high efficiency and energy saving as the criterion, and advanced production technology as the means.

Remanufacturing technology is a high-tech repair of waste products, so that the size, shape and surface quality of parts can be restored to the quality of brand-new parts, even exceeding the quality of brand-new parts, and a brand-new product can be formed after assembly.

It not only reduces the environmental pollution of products or equipment, but also reduces the cost of production input.

The remanufacturing process includes disassembly, cleaning, inspection, processing, parts testing, assembly, running-in test of the whole machine, painting and packaging.

Remanufacturing disassembly process is the general name of all technologies and methods used to disassemble waste products and re-understand the assembly process of products. Remanufacturing disassembly includes two steps: disassembly and assembly.

Remanufacturing disassembly is the systematic disassembly of its components from the assembly, without requiring damage to the target components. Dismantling can be divided into destructive dismantling and non-destructive dismantling.

According to the degree of disassembly, it can be divided into complete disassembly, partial disassembly and target disassembly.

Remanufacturing disassembly process methods can be divided into: knocking disassembly method (using the impact energy generated when a hammer or other heavy object knocks or installs parts for disassembly and separation), pulling disassembly method (using a special ejector for disassembly of parts), pressing disassembly method (using a hand press and a voltage machine for static disassembly), temperature difference method (using the characteristics of material expanding with heat and contracting with cold) and destruction method (during disassembly and welding).

Remanufacturing assembly refers to the whole technological process of assembling qualified remanufactured disassembled parts, parts that can be used directly and other new parts that are replaced after scrapping into parts, parts or remanufactured products according to the technical requirements and accuracy specified by remanufactured products, and achieving the accuracy and usability specified by remanufactured products. The specific assembly processes are: interchange method, matching method, repair method and adjustment method.

5, remanufacturing cleaning

Surface cleaning of parts is an important process in the remanufacturing process, which is not only the premise of testing the dimensional accuracy, geometry, roughness, surface performance, wear and adhesion of parts, but also the basis of remanufacturing parts.

The basic requirements of the cleaning process include: 1. Thoroughly remove the oil and paint on the surface of the workpiece. 2. Thoroughly remove the machine oil scale and scale inside the workpiece. 3. Ensure that the workpiece will not be deformed or the metallographic structure will change due to high temperature during cleaning. 4. Ensure that the workpiece will not be corroded by chemicals. 5. Ensure that the residue and waste liquid generated in the cleaning process do not pollute the environment.

During remanufacturing cleaning, cleaning liquid is smeared on the surface of waste parts by cleaning equipment, and pollutants such as grease, rust, dirt, scale and carbon deposit attached to the surface of waste parts are removed by mechanical, physical, chemical or electrochemical methods, so that the surface of waste parts can reach the required cleanliness. Disassembled parts of waste products are classified according to shape, material, category and damage degree, and then cleaned by 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 solutions, and there are manual and mechanical cleaning methods. 2. Remove scale. Generally, chemical removal methods are adopted, including phosphate removal method, alkali solution removal method and pickling method. 3. Remove rust. The main methods are mechanical method, chemical pickling method and electrochemical etching method. 4. Remove carbon deposits. Commonly used are mechanical method, chemical method and electrolytic method.

Remanufacturing cleaning technology: 1. Thermal cleaning technology. Thermal energy can promote various cleaning methods. 2. Pressure cleaning technology. Jet cleaning technology is superior to jet cleaning in that the pressurized cleaning liquid is sprayed through the nozzle to impact the surface of the cleaning object. 3. Friction grinding cleaning technology. It is a method to clean the surface of parts or products by gas sandblasting and liquid sandblasting. 4. Ultrasonic cleaning technology. In the ultrasonic environment, the process of cleaning the grease on the surface of the blank is called ultrasonic cleaning. 5. Electrolytic cleaning technology. Electrolytic cleaning is a cleaning method to remove dirt on metal surface by electrolysis. 6. Chemical cleaning technology. Chemical cleaning is a method of using one or more chemicals to remove dirt on the inner or outer surface of equipment.

6. Lead storage battery

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-hydrogen batteries and lithium batteries.

The battery can be reused through the reverse reaction mechanism of electric energy conversion, but it must obey the second law of thermodynamics. In each charge-discharge cycle, Junhui will dissipate a certain amount of effective components, and with the accumulation of cycles, the discharge characteristics will become worse. When the deteriorated discharge characteristics can not meet the use requirements, the battery loses its use value and becomes a waste battery.

Recovery method of lead-acid battery: Lead-acid battery is bulky and highly toxic, which is the earliest among all kinds of batteries and has perfect technology. The sludge phases of waste lead-acid batteries are mainly PbSO4 _ 4, PbO _ 2, PbO, Pb, etc. Among them, PBO _ 2 is the main component, accounting for 465,438+0%-46% and 24%-28% in the positive electrode filler and mixed filler respectively. Therefore, the reduction effect of PbO2 has an important influence on the whole recovery process, and its reduction process includes pyrometallurgical method and wet method. Pyrolysis is to reduce PbO _ 2 and other components such as PbSO4 _ 4 _ 4 and PbO in sludge to Pb in metallurgical furnace. However, it will produce secondary pollutants such as SO2 and high-temperature Pb dust, with high energy consumption and low utilization rate, so it will be phased out. Wet method is to reduce PbO2 into low-priced lead compounds by adding reducing agent under the condition of solution. Among reducing agents, it is ideal to add ferrous sulfate to sulfuric acid solution to reduce lead oxide.

The recovery process is as follows:

7. Lithium battery

Metal lithium is a precious metal resource, and lithium batteries have high recycling value. The varieties and types of disposable lithium batteries and lithium-ion batteries are constantly changing, that is, the chemical composition and structure of batteries are also constantly changing, which makes it more difficult to recycle waste lithium batteries than other mature and stable waste batteries. Lithium ion batteries have long service life and short time to market.

Laboratory recycling process of disposable lithium batteries: the crushed lithium batteries are screened to obtain negative lithium electrodes. Because metallic lithium reacts with water quickly when it is dissolved in water, it releases a lot of heat to generate hydrogen and water-soluble lithium hydroxide. Yin Ge cannot directly dissolve waste lithium batteries in water or acid. The experiment shows that the reaction can be carried out safely by using isobutanol aqueous solution, and colleagues in the reaction can introduce carbon dioxide gas to generate lithium carbonate precipitate with uniform purity. After standing and separating the precipitate, hydrochloric acid is added to dissolve the precipitate, and high-purity lithium metal can be obtained by electrolysis. Manganese metal in the positive electrode can be obtained by acid dissolution and electrolysis. This method has yet to be verified by productive experiments.

8. Fly ash

Fly ash is a kind of clayey volcanic ash discharged from coal combustion. Refers to the powdery residue in the flue gas during boiler combustion, which is referred to as ash or fly ash for short. It also includes the bottom slag discharged from the bottom of the boiler, which is called slag for short.

Composition of fly ash: SiO2 _ 2 _ 2 and Al _ 2O _ 3 are the main components, and the rest are small amounts of Al2O3, CaO, MgO, Na2O, K2O and SO3.

According to the content of CaO in fly ash, fly ash can be divided into high calcium ash and low calcium ash. Generally, the CaO content above 20% is called high calcium ash, and its quality is better than that of low calcium ash. Most coal-fired power plants in China

When burning bituminous coal, the content of CaO in fly ash is low, which belongs to low calcium ash, but the content of Al2O3 is generally high and the ignition loss is also high.

The mineral composition of fly ash mainly includes amorphous phase and crystalline phase. The amorphous phase is mainly glass, accounting for about 50%-80% of the total fly ash. Most of them are solid melts formed by SiO2 _ 2 _ 2 and Al _ 2O _ 3, and most of them form hollow microspheres. In addition, unburned fine carbon particles also belong to amorphous phase. The crystalline phase of fly ash mainly includes quartz sand, mullite, feldspar, mica, magnetite and pyrite. Single crystalline phase in fly ash is extremely rare, and it is often wrapped by glass phase.

Fly ash particles are usually divided into two types according to their shapes: bead particles and slag particles. Beads include floating beads, hollow precipitation beads, dense precipitation beads and iron-rich glass beads. Slag particles include sponge glass slag particles, carbon particles, obtuse-angled particles, fragments and agglomerated particles.

Physical properties of fly ash: it is gray or grayish white powder.

The activity of fly ash includes physical activity and chemical activity. Physical activity is the sum of particle effect and micro-aggregate effect of fly ash. Chemical activity refers to the coagulation and hardening characteristics of fly ash 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 _ 2 and Al _ 2O _ 3 in vitreous body, the higher the activity. The activity of fly ash is potential and needs to be stimulated to play out. The commonly used excitation methods are mechanical grinding, hydrothermal synthesis and alkali excitation.

Fly ash contains useful components such as iron, aluminum, hollow microspheres and unburned carbon, and contains many rare metal elements, so extracting these useful components from fly ash has great economic value.

(1) to extract iron. Coal contains pyrite, hematite, limonite and other minerals. When coal burns, one of them

After high-temperature incineration, part of iron oxide is reduced to Fe3O4 and granular iron, which can be directly separated by magnetic separation.

Mechanical separation and extraction of this magnetic iron oxide. Magnetic separation can be divided into wet magnetic separation and dry magnetic separation. At present, most power plants use wet magnetic separation.

(2) extracting Al2O3. The methods of extracting aluminum include limestone sintering, hot acid leaching, chlorination and direct welding.

And other processes. The technological process of extracting alumina from limestone by sintering mainly includes sintering and cooking.

The material is crushed, dissolved, carbonized and calcined.

(3) extracting glass beads. According to the physical and chemical characteristics, the microbeads in fly ash can be divided into floating beads, settling beads and magnetic beads. Extract trace amounts

The methods of bead separation can be roughly divided into dry mechanical separation and wet mechanical separation.

Dry mechanical separation process is as follows:

Wet mechanical separation of microbeads is a process combining flotation, magnetic separation and gravity separation in China.

The density of floating beads is less than that of water, so water can be used as the medium to make use of the difference between floating beads and other particles.

Floating beads are separated from other particles by flotation. (flotation)

Magnetic beads in fly ash are the reduction of iron-containing minerals in coal in carbon and carbon monoxide during high temperature combustion of boilers.

Under this action, some iron particles are formed and some are reduced to Fe3O4. Therefore, according to the magnetic

Magnetic beads are classified according to their magnetic differences with other particles. (magnetic separation)

When floating beads, magnetic beads and carbon particles are selected from fly ash, only precipitated beads and a small amount of monomers are left.

There are great differences in density, shape, particle size and surface properties. Different grades of pearl precipitation products can be obtained by gravity separation, flotation or classification plus enrichment and separation.

(4) extracting carbon. When power plant boilers burn anthracite and inferior bituminous coal, because pulverized coal cannot be completely burned,

Increase the carbon content of fly ash to reduce the carbon content of fly ash and make full use of coal resources.

Coal ash is usually treated by carbon extraction. Generally, flotation and electrostatic separation are used to extract carbon.

Floating carbon extraction is suitable for fly ash discharged by wet method. This method makes use of the hydrophilicity of fly ash and coal particles.