Four typical sludge discrimination

1. Electroplating wastewater and electroplating sludge with excessive heavy metals:

Electroplating sludge is a hazardous waste, and the waste category often belongs to HW17, HW21, HW22, and HW23. Electroplating wastewater with excessive heavy metals belongs to the scope of prevention and control of wastewater pollution and is included in wastewater management. It is not applicable to the scope of the Law of the People’s Republic of China on the Prevention and Control of Environmental Pollution by Solid Wastes and is not classified as hazardous waste. Although excessive wastewater is not included in hazardous waste management, according to the “Two High Judicial Interpretation” (2016 edition), if a type of heavy metal (such as lead, mercury, chromium, cadmium, or arsenic) in wastewater exceeds the standard by 3 times, or two types of heavy metals (such as If nickel, copper, zinc, manganese or vanadium exceeds the standard by more than 10 times, in addition to administrative punishment, it will be investigated for criminal responsibility.

2. Sludge produced by domestic sewage treatment plant:

It is a solid waste and is not classified as hazardous waste. According to the document [2005] No. 157 of the Central Office [2010], in the process of transfer management, this type of waste “refers to the management of hazardous wastes and establishes a system for sludge transfer and joint order.” According to the definition of hazardous waste management, this type of sludge does not belong to Hazardous waste, but to improve the management level, especially to strengthen the management of the account, to prevent leakage and illegal dumping during transportation. However, the sludge produced in the sewage treatment process of industrial enterprises is often classified as hazardous waste due to its leaching toxicity, or other toxic and hazardous substances and other dangerous characteristics. The judgment method is mainly based on enterprise environmental assessment, industry rules and materials. Source, expert identification, attribute identification, etc.).

3. Fly ash from domestic waste incineration:

Belongs to hazardous waste (HW18). However, after meeting the requirements of Section 6.3 of the Domestic Waste Landfill Pollution Control Standard (GB16889-2008), the landfill into the domestic waste landfill is not included in the management of hazardous waste; in another case, after pretreatment, To meet the relevant requirements of the “Cement Kiln Cooperative Disposal Solid Waste Pollution Control Standards” (GB30485-2013), the collaborative disposal process is also included in the scope of exemption management.

4. Sludge generated during the sewage treatment process of medical institutions:

Most are hazardous waste. The Medical Waste Management Regulations (Order No. 380 of the State Council) stipulates that “medical waste refers to direct or indirect infection, toxicity and other hazards arising from medical, preventive, health care and other related activities of medical and health institutions. Waste.” The National List of Hazardous Wastes stipulates that “medical waste is classified as hazardous waste. The classification of medical waste is carried out in accordance with the Catalogue of Medical Wastes.” “Catalogue of Medical Wastes” (Wu Wei Fa [2003] No. 287) “Infectious waste” includes “other items contaminated by blood, body fluids and excretions of patients”, and grid slag, sediment sludge and septic tank sludge generated in the sewage treatment process of medical institutions shall be included in this category.

If a medical institution is specially designed for the wastewater treatment process and has made a property determination for the sludge, if the management considers that the sludge should be included in the hazardous waste management, the final determination should be made through the hazardous waste identification procedure. .

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Treatment of ore dressing wastewater and oily wastewater

1. Mineral processing wastewater
The ore dressing wastewater has the characteristics of large water volume, high suspended solid content and many types of harmful substances. Its harmful substances are heavy metal ions and mineral processing chemicals. Heavy metal ions include copper, zinc, lead, nickel, antimony, cadmium, and arsenic and rare elements.

The flotation reagents added during the beneficiation process are as follows: collectors such as xanthate (RocssMe), black medicine [(RO) 2PSSMe], white medicine [CS (NHC6H5) 2]; inhibition of punishment, such as cyanide salt ( KCN, NaCN), water glass (Na2SiO3); foaming agent, such as turpentine, cresol (C6H4CH30H); active penalties, such as copper sulfate (CuS04), heavy metal salts; vulcanizing agents, such as sodium sulfide; Such as sulfuric acid, lime, etc.

The ore dressing wastewater can effectively remove suspended solids from the wastewater through the tailings dam, and the content of heavy metals and flotation reagents can also be reduced. If the emission requirements are not met, further treatment should be carried out. Commonly used treatment methods include lime neutralization method and roasting dolomite adsorption method for heavy metals removal; ore adsorption method and activated carbon adsorption method for main flotation reagents; The cyanide wastewater can be chemically oxidized.

2, oily wastewater
Oily wastewater mainly comes from petroleum, petrochemical, steel, coking, gas generating stations, mechanical processing and other industrial sectors. The oil-contaminated substances in the wastewater have a relative density of less than 1 except for the relative density of heavy tar of 1.1 or more. Oils are usually present in three states in wastewater.

Floating oil, oil droplets larger than 100μm, easy to separate from the wastewater.
Disperse the oil, the oil droplets have a particle size between 10 and 100 μm, and float in water.
Emulsified oil, oil droplet size less than 10μm, difficult to separate from wastewater.

Because the oil concentration in the wastewater discharged by different industrial sectors varies greatly, such as wastewater generated during the refining process, the oil content is about 150~1000mg/L, the tar content in the coking wastewater is about 500~800mg/L, and the gas is discharged from the gas station. The tar content can reach 2000~3000mg/L.

Therefore, the treatment of oily wastewater should first use the grease trap to recover the oil or heavy oil. The treatment efficiency is 60%~80%, and the oil content in the effluent is about 100~200mg/L. The emulsified oil and dispersed oil in the wastewater are difficult. Treatment should prevent or mitigate emulsification.

First, pay attention to reduce the emulsification of oil in wastewater during the production process;
Second, in the process of treatment, minimize the number of times the pump is used to lift the wastewater, so as not to increase the degree of emulsification. The treatment method usually uses air flotation and demulsification.

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What wastes are produced in industry

1. Heavy metal wastewater
Heavy metal wastewater mainly comes from wastewater discharged from mines, smelting, electrolysis, electroplating, pesticides, medicine, paints, pigments and other enterprises. The type, content and form of heavy metals in wastewater vary with different production companies.

The principle of heavy metal wastewater treatment is:
The most fundamental is to reform the production process, no need to use less heavy metals; secondly, use reasonable process, scientific management and operation, reduce the amount of heavy metals and the amount of waste water, and minimize the amount of wastewater discharged. Heavy metal wastewater should be treated in situ at the place of production, and different other wastewaters should be mixed to avoid complicating the treatment. It should not be discharged directly into urban sewers without treatment, so as to avoid the expansion of heavy metal pollution.

The treatment of heavy metal wastewater can usually be divided into two categories:
The first is to convert the heavy metal in the dissolved state into an insoluble metal compound or element, which is removed from the wastewater by precipitation and floating. Applicable methods such as neutralization precipitation method, sulfide precipitation method, floating separation method, electrolytic precipitation (or floating) method, diaphragm electrolysis method, etc.;

The second is to concentrate and separate the heavy metals in the wastewater without changing the chemical form. The applicable methods include reverse osmosis, electrodialysis, evaporation and ion exchange. These methods should be used singly or in combination depending on the quality of the wastewater, the amount of water, and the like.

2. Metallurgical wastewater
The main features of metallurgical wastewater are large water volume, various types, and complex and variable water quality. Classified according to the source and characteristics of wastewater, there are mainly cooling water, pickling wastewater, washing wastewater (dust removal, gas or flue gas), slag wastewater, coking wastewater, and wastewater that is condensed, separated or overflowed from production.

The trend of metallurgical wastewater treatment development is:
Develop and adopt new technologies and technologies that use no or little water and no pollution or less pollution, such as dry quenching, coking coal preheating, direct desulfurization and denitrification from coke oven gas, etc.; Recycling useful materials and heat energy in waste water and waste, reducing material fuel loss; comprehensively balancing and streamlined use according to different water quality requirements, improving water quality stabilization measures, continuously improving water recycling rate; developing new treatment process suitable for metallurgical wastewater characteristics And technology, such as the use of magnetic treatment of steel wastewater. It has the advantages of high efficiency, small footprint, convenient operation and management.

3. Acid and alkali wastewater
Acidic wastewater mainly comes from steel plants, chemical plants, dye factories, electroplating plants and mines, which contain various harmful substances or heavy metal salts. The acid mass fraction varies widely, from less than 1% at low and greater than 10% at high.

Alkaline wastewater mainly comes from printing and dyeing factories, leather factories, paper mills, oil refineries and so on. Some of them contain organic bases or inorganic bases. The mass fraction of the base is higher than 5%, and some are less than 1%. In addition to acid and alkali, acid-base wastewater often contains acid salts, basic salts and other inorganic and organic substances.

Acid-base wastewater is highly corrosive and needs to be properly treated before it can be discharged.

The principle of treating acid and alkali wastewater is:
High-concentration acid-base wastewater should be recycled in priority. According to water quality, water quantity and different process requirements, plant or regional scheduling should be carried out as much as possible. If it is difficult to reuse, or the concentration is low, the water volume is large. The method of recovering acid and alkali.
Low-concentration acid-base wastewater, such as washing water in the acid washing tank and rinsing water in the alkali washing tank, should be neutralized.

For neutralization treatment, the principle of waste treatment should be considered first. For example, acid or alkali wastewater neutralizes each other or neutralizes acidic wastewater with waste alkali (slag), and neutralizes alkaline wastewater with waste acid. In the absence of these conditions, a neutralizing agent treatment can be employed.

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How to deal with toxic wastewater

The toxic waste water mainly includes cyanide-containing wastewater, phenol-containing wastewater and mercury-containing wastewater.

Cyanide-containing wastewater
Cyanide-containing wastewater mainly comes from electroplating, gas, coking, metallurgy, metal processing, chemical fiber, plastics, pesticides, and chemical industries.

Cyanide-containing wastewater is a kind of toxic industrial wastewater. It is unstable in water and easy to decompose. Inorganic cyanide and organic cyanide are highly toxic substances. People can cause acute poisoning by ingestion. The lethal dose of cyanide to human body is 0.18g, and the potassium cyanide is 0.12g. The mass concentration of cyanide in fish to death is 0.04~0.1mg/L.

The main treatment measures for cyanide-containing wastewater are:
Reform the process to reduce or eliminate the effluent containing cyanide. If the cyanide-free plating method is used, the industrial wastewater in the electroplating workshop can be eliminated.
Waste water with high cyanide content should be recycled, and waste water with low cyanide content should be purified before being discharged. The recovery methods include acidification aeration-alkali absorption method, steam desorption method, and the like.

The treatment methods include alkaline chlorination method, electrolytic oxidation method, pressurized hydrolysis method, biochemical method, bio-iron method, ferrous sulfate method, air stripping method, and the like. Among them, the alkaline chlorination method is widely used, the ferrous sulfate method is not thorough and unstable, and the air blowing method not only pollutes the atmosphere, but also fails to meet the discharge standard. Less used.

Phenolic wastewater
The phenol-containing wastewater mainly comes from the industrial sectors such as coking plants, gas plants, petrochemical plants, and insulating materials plants, as well as the production process of petroleum cracking to ethylene, synthetic phenol, polyamide fiber, synthetic dyes, organic pesticides and phenolic resins. The phenol-containing wastewater mainly contains a phenol-based compound, which is a protoplasmic poison that can coagulate the protein.

Mercury-containing wastewater
Mercury-containing wastewater mainly comes from non-ferrous metal smelters, chemical plants, pesticide plants, paper mills, dye factories and thermal instrumentation plants. The toxicity of various mercury compounds varies greatly. For example, methylmercury, methylmercury is easily absorbed into the human body, is not easily degraded, and excretion is slow and easily accumulates in the brain.

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The basic way of industrial waste heat utilization

The use of industrial waste heat utilization is an important way to improve the economy and save fuel. There are various waste heats in the production process of thermal power plants. For example, boiler waste heat, deaerator exhaust and steam seal steam exhaust heat. This type of waste heat belongs to the heat transfer of the working medium. Usually, while recovering heat, it will also recover some of the remaining heat of the working fluid. They only use heat, and there is no recovery of the working fluid, for example, the heat lost by the generator. The heat removed by the oil cooler and the waste heat of the boiler exhaust, etc., such waste heat is pure heat recovery.

The availability and value of waste heat is determined by both its production and quality. The amount of waste heat refers to the amount of residual heat. The quality of waste heat refers to the grade of waste heat, which can be characterized by its temperature, pressure and medium carrying heat. The higher the residual heat grade, the greater the quantity and the greater the availability and value.

The availability and value of waste heat is not equal to the effect of waste heat utilization. The former refers to the quality and nature of the waste heat itself. It only indicates the availability of waste heat, but does not indicate the effectiveness of waste heat utilization. The latter is not determined by the quality of the waste heat itself, but also depends on the location, environment, and method of utilization of waste heat, that is, the objects and conditions for the use of waste heat.

Industrial waste heat mainly includes: waste heat of flue gas, waste heat of cooling medium, chemical reaction heat of waste steam waste heat, high temperature product and residual heat of slag, and waste heat of combustible waste gas and waste. From the perspective of economy, it is necessary to combine the process production to design the overall system layout and comprehensively utilize energy to improve the efficiency of the waste heat utilization system equipment.

Industrial waste heat utilization technology

According to the characteristics of energy transfer or conversion of waste heat resources in the process of utilization, the current domestic industrial waste heat utilization technology can be divided into heat exchange technology, heat work conversion technology, and waste heat refrigeration heating technology.

Heat exchange technology heat

The exchange technology is the most direct and efficient economic method for recovering waste heat from the industry. This technology does not change the form of waste heat energy. It only transfers the waste heat energy directly to the energy consumption process of its own process through heat exchange equipment, reducing primary energy consumption. The main utilization methods include partition wall heat exchange, waste heat boiler, regenerative heat exchange, and heat transfer of heat pipes.

Thermal power conversion technology

The use of thermal power conversion technology can improve the grade of waste heat. It is another important technology for recycling industrial waste heat. According to the classification of working fluids, the heat work conversion technology can be divided into traditional steam turbine power generation technology with water as working fluid and low boiling point work. Quality organic working power generation technology.

At present, the main industrial applications are water-based working fluids, low-temperature steam turbine power generation systems consisting of waste heat boilers + steam turbines or expanders.

Refrigeration and heating technology

Compared with traditional compression refrigeration units, absorption or adsorption refrigeration systems can use low-cost energy and low-grade thermal energy to avoid power consumption. They have significant power-saving and environmental benefits, and have been widely used.

The absorption type waste heat refrigeration unit has high refrigeration efficiency and is suitable for waste heat recovery of large-scale heat. The adsorption refrigeration system has a simple structure, no noise, no pollution, and can be used for bumping and oscillating occasions, and is more suitable for utilizing small heat waste heat recovery or for cogeneration systems.

The heat pump consumes a part of high-quality energy (electric energy, mechanical energy or high-temperature heat energy) as compensation. The heat of the low-temperature residual heat source is “pumped” to the high-temperature heat medium through the thermal cycle of the refrigerator. The heat pump technology is often used to recover slightly higher than the environment. The waste heat of temperature (30~60 °C) achieves the purpose of energy saving and consumption reduction.

In summary, the industrial waste heat is large and wide, but there are certain applicable conditions. According to different types of waste heat, temperature and residual heat, combined with production conditions, process flow, internal and external energy demand, enterprises should choose suitable waste heat utilization. Ways to achieve the goal of reducing energy consumption and improving efficiency.

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What are the soil remediation processes?

With the continuous development and progress of the society, people’s use of resources has been continuously improved, and even excessive exploitation of resources has led to continuous changes in the environment, showing a terrible situation of linear decline. Let’s take a look at the relevant information on soil remediation.

Soil remediation definition

Soil remediation refers to the physical, chemical and biological methods of transferring, absorbing, degrading and transforming contaminants in the soil to reduce their concentrations to acceptable levels or to convert toxic and harmful contaminants into harmless substances. Fundamentally, the principles of contaminated soil remediation processes can include:

(1) changing the existing form of pollutants in the soil or the way of combining with the soil, reducing its mobility and bioavailability in the environment;

(2) Reduce the concentration of harmful substances in the soil. China’s soil pollution has threatened the sustainable use of land resources and the ecological security of agricultural products. The country’s farmland contaminated by organic pollutants has reached 36 million hectares. The types of pollutants include petroleum, polycyclic aromatic hydrocarbons, pesticides, organic chlorine, etc.; the area of ​​serious oil contaminated land caused by oilfield exploitation is 10,000 hectares, and the petroleum refining industry It also pollutes large areas of land.

In the petroleum sewage irrigation area, the content of polycyclic aromatic hydrocarbons in the surface layer and the bottom layer exceeds 600 mg/kg, causing serious pollution of crops and groundwater. The country’s heavy metal contaminated land reached 20 million hectares, of which more than 700,000 hectares of heavily polluted land, of which 130,000 hectares were forced to abandon arable due to excessive cadmium content. Because of this, the research on contaminated soil remediation is undergoing a transition from laboratory research to a practical stage, and is about to enter a period of rapid and comprehensive governance.

Soil remediation process

Thermodynamic repair technology: the use of heat conduction, thermal blankets, hot wells or hot walls, or thermal radiation, radio wave heating, etc. to achieve the repair of contaminated soil.

Thermal desorption repair technology: heating the soil contaminated by organic matter to the boiling point of organic matter above the organic matter in the adsorbed soil volatilized into a gaseous state and then separated. Thermal desorption technology is one of the most advanced pollution treatment technologies in the world. The main treatment targets are pesticide-contaminated soil, oil-field oily waste, and tank bottom sludge. The operation principle is to utilize the thermal instability of the organic matter in the polluted waste, realize the separation of the pollutant and the soil through the indirect heating method of non-incineration, and can completely separate the solid phase, the oil phase, the water phase and the gas phase in the waste. Most of the recycling is fundamentally harmless, so the technology is widely used in oil field waste disposal operations around the world.

 Incineration method: Incinerate contaminated soil in an incinerator to make high molecular weight harmful substances? Volatile and semi-volatile, decomposed into low molecular smoke. After dedusting, cooling and purification, the flue gas reaches the discharge standard.

Landfill method: use waste as a mud to apply sludge to the soil. Adjust soil nutrient, humidity and pH by fertilizing, irrigating, adding lime, etc. Maintain aerobic degradation of pollutants in the upper layer of soil. For soil pH and humidity can be measured with a soil acidity meter, soil EC values ​​can be measured with a soil EC meter to see the soil improvement effect.

Chemical leaching: The chemical/biochemical solvent that promotes the dissolution or migration of pollutants in the soil environment is used to push the eluent into the contaminated soil layer under gravity or by head pressure, and then contain the pollutants. The solution is extracted from the soil for separation and wastewater treatment techniques.

Composting method: using traditional composting method, accumulating contaminated soil, mixing pollutants with organic matter, straw, wheat straw, wood chips and bark, etc., relying on the action of microorganisms in the composting process to degrade the soil. Organic pollutants.

Phytoremediation: The use of agricultural techniques to improve the chemical and physical constraints that are unfavorable for plant growth, making it suitable for planting, and directly or indirectly absorbing, volatilizing, separating, and degrading by planting preferred plants and their rhizosphere microorganisms. Contaminants, restore and rebuild natural ecological environment and vegetation landscape.

Infiltration reaction wall: It is an in-situ treatment technology. In the shallow soil and groundwater, a wall with permeability and reactive materials is constructed. When the polluted water passes through the wall, the pollutants and the reaction materials in the wall occur. Physical and chemical reactions are removed and removed.

Bioremediation: A controlled or spontaneous process that uses organisms, especially microbes, to catalyze the degradation of organic contaminants to repair contaminated environments or eliminate contaminants in the environment. Among them, microbial remediation technology utilizes microorganisms, indigenous bacteria, foreign bacteria and genetic engineering bacteria to convert and degrade pollutants by metabolizing pollutants, and is mainly used for degradation of organic pollutants in soil. By changing various environmental conditions such as nutrition, redox potential, and co-metabolism matrix, microbial degradation is enhanced to achieve the purpose of treatment.

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What are the industrial sludge treatment options?

In industrial wastewater treatment, municipal wastewater and industrial sludge treatment, the amount of sludge produced is about 0.3% to 0.5% of the total treatment (97% water content). The composition of the sludge is complex, containing parasitic eggs, heavy metals and pathogenic microorganisms, which must be treated to prevent secondary pollution to the environment.

At present, a large number of unsettled sludge has become a heavy burden for sewage treatment plants. How to treat the sludge with large output and complex composition properly and safely to make it harmless, resource-resourced and reduced, has been widely used. attention.

At present, the commonly used sludge treatment schemes include: concentration, sludge conditioning, anaerobic digestion, dehydration, composting and other treatment technologies. As for aerobic digestion, wet oxidation, disinfection, thermal drying, incineration, low temperature pyrolysis, etc. stage.

Industrial sludge type and characteristics

First, urban sludge

The amount of sludge produced by urban sludge is moderate, generally accounting for about 0.1% of the total volume of domestic sewage treatment, but the total amount is large, the organic matter content is high, and the water content is high, generally reaching 95% to 99%, even after dehydration. Still 60%~80%, there are a lot of pathogens and parasites, which are easy to rot and stink, very unstable.

Second, petrochemical sludge

The composition of petrochemical sludge is complex and contains different kinds of heavy metals. Generally, petroleum sludge contains oil, has high viscosity and high water content, generally up to 96%~99%, and still 70%~85% after mechanical dehydration. The volume and mass are still large, the organic matter content is small, and the calorific value is low.

Third, printing and dyeing sludge

The printing and dyeing mud production is large, the total sludge volume accounts for 0.3%~1.0% of the total volume of the sewage, and the water content is high, generally up to 96%~99%. After mechanical dehydration, there are still 55%~85%, and the volume and quality are still relatively good. Large, printing and dyeing sludge generally has a higher inert content, while organic matter, pathogenic bacteria and other content are less, the calorific value is also lower, and the general heavy metal content is high.

Fourth, paper sludge

Papermaking sludge ash is relatively large, generally can reach 50%~70%, so the calorific value is relatively low and the water content is high, generally reaching 95%~99%. Even after dehydration, the water content is still 60%~80%. And it contains a lot of fiber.

Five, tannery sludge

The tanning industry produces a large amount of mud. Generally, it can produce 40-80 tons of sludge per ton of wastewater per day. The organic matter content is high. Due to the large amount of fur and blood pollution generated during the leather treatment process, the organic matter content is very high and there are many toxic substances. The content of S2- and trivalent chromium is high, and the conversion of trivalent chromium to hexavalent chromium has carcinogenic effects.

Sixth, electroplating sludge

The electroplating sludge contains cyanide and heavy metals such as hexavalent chromium, copper, zinc, cadmium and nickel. The chemical treatment of electroplating wastewater is the main source of sludge. The electroplating sludge has low organic content and low calorific value.

Industrial sludge conventional treatment method

(1) Sludge concentration method: concentrated by gravity, concentrated by centrifugation and concentrated. The gravity concentration method has the advantages of high sludge storage capacity and simple operation, and is one of the most commonly used methods for sludge volume reduction.

(2) Sludge adjustment method: sludge adjustment treatment can reduce the hydrophilicity of sludge and improve the dehydration efficiency. Commonly used adjustment methods include chemical adjustment method and thermal regulation method. The thermal regulation method, the water-freezing-melting method, and the addition of an inert substance are in the experimental research stage.

(3) Anaerobic digestion: Sludge anaerobic digestion is currently the most commonly used sludge stabilization treatment process, with medium temperature digestion (32~C~35~c) and high temperature digestion. With the advancement of technology.

(4) Sludge dewatering method: The water content after sludge dewatering can generally be reduced to 70%~80% to reduce the volume of sludge. Commonly used dehydration methods include natural drying and mechanical dehydration. Currently, the commonly used mechanical dewatering machines include vacuum filters, plate and frame filter presses, belt filter presses and centrifuges.

(5) Composting method: Composting is a comprehensive treatment technology of harmless, volume reduction and stabilization. The mixed microbial community decomposes organic matter in a humid environment, and the high temperature generated during the composting process can effectively kill Dead pathogenic microorganisms and various parasitic eggs are a comprehensive treatment technology that is harmless, volume-reducing and stable.

Research progress in industrial sludge treatment

1. Sludge reduction technology: The sludge reduction mechanism has become a research hotspot. The principle is to make the sludge as far as possible in the sewage treatment system. The main methods of research are:

(1) Study sludge biological volume reduction technology, using thermophilic bacteria or micro-animals to reduce excess sludge.

(2) The excess sludge is treated by a membrane bioreactor.

2. Sludge volume reduction technology: sludge volume reduction is studied from sludge concentration and dewatering. After sludge concentration and dewatering, its volume is greatly reduced, reducing transportation costs and subsequent disposal costs.

In terms of sludge concentration:

(1) Bioflocculation The remaining sludge from the secondary settling tank is mixed with the raw water and returned to the primary sedimentation tank. The flocculation performance of the activated sludge is used to improve the sedimentation effect of the primary sedimentation tank, and at the same time, the activated sludge is concentrated;

(2) Concentrating the sludge by air flotation and bio-floating method, such as using the gas generated by the reverse digestion of the sludge to make the sludge float and concentrate;

(3) Improve the structure of the concentration equipment and increase the concentration efficiency.

In terms of sludge dewatering:

(1) Pretreatment of sludge before chemical pretreatment (chemical conditioning, heat treatment, freezing method, panning method, etc.)

(2) Using biological engineering methods to improve the properties of the sludge, such as using lysing rain to destroy the micelles to improve the dewatering performance of the sludge;

(3) Exploring new agents for improving sludge dewatering performance, such as adding surfactants;

(4) Improve the working efficiency of the traditional sludge dewatering machine and study the new sludge dewatering equipment.

3, the stability of the sludge: the purpose of stability is to degrade the perishable organic matter in the sludge, reduce the amount of liquids and solids, reduce pathogenic bacteria, eliminate odor. The main methods of sludge stabilization include anaerobic digestion, aerobic digestion, wet oxidation, low temperature pyrolysis, and composting.

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The harm of leachate in MSW incineration plant

There are a lot of kitchen waste, high moisture content and low calorific value in China’s urban domestic waste. During incineration, fresh waste must be stored in the waste storage pit for 3-5 days for fermentation and ripening, so as to achieve the purpose of draining water and increasing calorific value, so as to ensure the normal operation of the subsequent incinerators. According to the pollution control standard for domestic waste incineration (gbi8485-200, the water drained in this process is called as “Leachate” is characterized by high concentration of pollutants, great change in water quality, strong odor, yellow brown or gray brown. Leachate is the last link of garbage treatment. Many factors lead to the fact that leachate treatment has not been concerned by the public, the media and the whole society, and has become a forgotten corner.

The COD of landfill leachate is several times or even dozens of times higher than that of landfill leachate, and the amount of landfill leachate accounts for the vast majority of the process wastewater in the waste incineration plant. Compared with the discharge standard data, it is found that the pollutant discharge concentration in the landfill leachate discharge standard is higher than that in the waste incineration plant, so the difficulty of leachate treatment in the waste incineration plant will be much higher than that in the landfill leachate treatment. As a special industry, the leachate in the garbage chushao plant is a kind of sewage with high concentration, complex composition and difficult degradation, and its treatment difficulty is more difficult than that of other industries. According to the purpose of relaxing the discharge standard of special industries such as sugar making, chemical industry and monosodium glutamate stipulated in the integrated wastewater discharge standard, whether the discharge standard of the garbage incineration plant should be properly relaxed is worth while. Otherwise, the treatment difficulty and cost will be too high for many incineration plants to bear.

At present, the treatment of landfill leachate is a research hotspot and a difficulty in the field of environmental protection in China. Landfill leachate is a kind of sewage with high pollution and strong odor. When the landfill incineration plant is put into operation without solving the problem of leachate treatment, it will produce new secondary pollution. In the absence of economic and reliable technology at present, part of the garbage incineration plants that have been put into operation use to transport the leachate to the urban sewage treatment plant for mixed treatment with domestic sewage, not to mention the high cost. It needs 80-100 yuan less), which is also an illegal activity of pollutant transfer, the same as the behavior of secretly discharging sewage to the urban sewage pipe network. However, some plants use the method of private drainage to directly discharge the leachate into the surface water such as the ocean and rivers, which seriously pollutes the environment. Some manufacturers use the process with high operating cost, which only runs when the environmental protection department checks, and directly discharges these practices in the rest of the time, which will seriously pollute the environment. It is suggested that when the environmental protection department approves and accepts the leachate treatment of the waste incineration plant, corresponding clauses should be added to strictly prohibit the leachate from being transported to the urban sewage treatment plant, and refer to the automatic online monitoring of flue gas requirements in the waste incineration plant. Cod automatic on-line monitoring system is added at the drainage outlet of the system.

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Stabilization treatment of waste incineration slag

Curing / stabilizing treatment

Before filling, it is usually necessary to solidify and stabilize the incineration ash flow, which can not only reduce the impact of leaching of toxic heavy metals in the ash on the geological environment, but also ensure the engineering safety.

(1) curing. Solidification is a process in which hazardous wastes are mixed and contained in dense emotional base materials by physical and chemical methods to stabilize them. The mechanism of solidification treatment is very complex, which is still under research and development. Some of them are the process of chemical transformation or introduction of hazardous waste into a stable lattice; some are the process of inclusion of hazardous waste with emotional materials; some have both of the above two processes. The commonly used curing agents are mainly cement, lime, gypsum, silicate, pozzolanic ash and asphalt, etc. Good results have been achieved in the solidification treatment of MSW incineration ash with cement and asphalt. The cement solidified body of incineration ash is mainly used in subgrade, river dam, etc. and has long-term stability problems. The stability of heavy metals in the solidified body may be reduced due to the decomposition of water-soluble sulfur segment salt, organic acid and organic matter.

(2) chemical stabilization. According to the types of heavy metals contained in the waste, the stabilizers can be gypsum, bleaching powder, sodium thiosulfate, sodium sulfide and organic stabilizers. In recent years, the application of heavy metal chelating agent is developing rapidly. It is a kind of water-soluble chelating polymer. Its parent polymer has hydrophilic chelating group and reacts with heavy metal ions to form water-insoluble polymer complex.

Phosphate is also used to stabilize the incinerator slag. The principle is that it can react with heavy metals to form metal tristate phosphate and apatite minerals that are stable in nature. These substances have high stability for pH and eh, so as to reduce the leaching of heavy metals in the slag. Generally speaking, the reaction mechanism has two ways: surface adsorption and deposition / replacement. The specific process is related to the physical and chemical characteristics of phosphate (such as solubility), concentration and existing form of heavy metals and many other factors. The results show that phosphate can react with more than 30 elements to produce more than 300 minerals that are stable in nature, which are often used to control the pollution of Ca2 +, Cd2 +, Cu2 +, Pb2 + and Zn2 + in natural land system, especially Pb2 +.

In addition, studies have shown that (M. A. Soreness et al. , 2001). When FeSO4 solution is used to treat the incineration ash, most of the salts in the ash are dissolved, and there is amorphous ferrite deposition on the surface, while the heavy metals can be well fixed due to surface adsorption or direct physical combination in the ferrite.

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What are the requirements for the burning of clinker in the cement factory production line?

The clinker burning part of the cement factory production line mainly consists of: preheater system, decomposition furnace, bypass windproof system, kiln tail high temperature fan, exhaust gas treatment system, rotary kiln, firing system, etc. What are the requirements? Let’s take a closer look!

The preheater system should be arranged in accordance with the following regulations:

(1) Under the premise of meeting the production requirements of the production line of the cement factory, it should be arranged compactly, occupy a small area, and the height of the preheater tower should be low;

(2) In addition to the main platform of each layer, the preheater tower shall be provided with a platform in the place where the skin is to be cleaned, operated and maintained, such as preheater and decomposing furnace, and a safe operation space shall be reserved;

(3) The position on the floor of each floor should be temporarily placed with refractory materials during maintenance;

(4) The compressed air system piping should be connected to the main platform of each layer of the preheater tower;

(5) The kiln tail tower should be equipped with a cargo elevator.

The preheater system shall be designed in accordance with the following regulations:

(1) The preheater system shall be arranged in a single row or in a double row according to the production capacity, and a five or six stage preheater shall be adopted;

(2) The technical performance of the preheater should meet the following requirements:

a. The separation efficiency of the top-stage cyclone of the preheater should not be lower than 92%;

b. The sealing performance of the system should be good, and the air lock device should be flexible;

c. The air duct and the material pipe of the preheater shall have measures to absorb thermal expansion;

The selection and design of the decomposition furnace should meet the following requirements:

(1) The furnace type and furnace structure parameters should be determined according to the original and fuel properties;

(2) The residence time of the gas in the decomposition furnace can be determined according to the type of the decomposition furnace and the original and fuel properties; the fuel should be completely burned in the decomposition furnace, the gas residence time should be greater than 5 s; the apparent decomposition rate of the human kiln material should reach 92%. the above;

(3) The proportion of coal used in the decomposing furnace should be 55%~65% of the total coal consumption; when the bypass is used, the proportion of coal used in the decomposing furnace should be adjusted according to different air release amounts.

The design of the bypass air release system shall comply with the following regulations:

(1) When the content of harmful components in raw meal and clinker exceeds the provisions of Article 5. 6. of this specification, the bypass system shall be added to the firing system. The proportion of the air release from the bypass ventilation system shall be based on the type of harmful components and The content is determined;

(2) The bypass air release quenching chamber shall be provided at the location where the dust concentration is the smallest in the airflow;

(3) The temperature of the venting gas is about 1100, and should be cooled to below 450 after passing through the quenching chamber;

(4) The venting gas should be mixed with cold air and then enter the bag dust collector, and discharged after the treatment reaches the standard;

(5) The return ash received by the bag filter should be sent to the bypass blast kiln for storage and proper disposal.

The selection and arrangement of the kiln high temperature fan should meet the following requirements:

(1) The fan efficiency should be greater than 80%, the fan should be resistant to temperature, wear and abrasion; the wind volume, wind pressure and maximum temperature of the fan should be adapted to the most unfavorable working conditions of the system, and the air volume and wind pressure should be 10 % of reserve;

(2) The fan speed control should select the frequency conversion speed regulation mode;

(3) The air inlet of the fan can be equipped with a regulating valve;

(4) When the high-temperature fan is arranged in the open air, rain-proof facilities should be added to the fan transmission part.

The exhaust gas treatment system shall be designed in accordance with the following regulations:

(1) The exhaust gas discharged from the system should be used for waste heat utilization, and the exhaust gas should be discharged after cooling and dust collection;

(2) The exhaust gas treatment system should use a bag type dust collector;

(3) High temperature wind cooling measures should be sprayed with kiln tail pipe, or humidification tower, air cooler and cold air can be used;

(4) The air duct, humidification tower and dust collector of the exhaust gas treatment system shall adopt insulation measures;

(5) Exhaust gas treatment The arrangement of hot air ducts should be compact and reasonable, and should not be arranged horizontally;

(6) The ash return conveying equipment of the humidification tower and the dust collector should have a reserve capacity of 1.5 times;

(7) The ash return of the exhaust gas treatment system shall be set to the facility for feeding the raw material homogenization tank or the kiln ash silo, or directly to the kiln feeding system; the factory with the bypass venting system shall be closed to the bypass venting To return to ash, the treatment plan should be implemented at the same time;

(8) The exhaust gas chimney outlet diameter should be determined according to the chimney outlet flow rate, and the outlet flow rate can be 1Om/s~16m/s. Exhaust gas monitoring and chimney height shall comply with the relevant provisions of the current national standard “Cement Industry Air Pollutant Emission Standards” GB 4915.

The design of the rotary kiln should meet the following requirements:

(1) The specifications of the rotary kiln of the cement factory production line shall be determined according to the output of the firing system, the original, fuel conditions, altitude and preheater; decomposition furnace and chiller configuration;

(2) The ratio of the length to diameter of the rotary kiln should be 10~16, the slope of the sinus should be 3.5%~4.0%, and the maximum speed should be 4. Or/min~5.Or/min, the speed range should be 1:10;

(3) The rotary kiln shall be provided with a detection device for the simplified temperature;

(4) The main motor of the rotary kiln should adopt a stepless variable speed motor, and an auxiliary drive should be set. The auxiliary drive should be additionally equipped with a circuit connected to the factory security power supply.

The layout of the rotary kiln shall comply with the following provisions:

(1) The height of the center of the rotary kiln should be determined according to the type and arrangement of the clinker cooler; when there are more than two rotary kiln, the center distance of the two kiln should meet the layout requirements of the kiln head and kiln tail equipment;

(2) The installation dimensions of the rotary kiln shall be determined according to the cold kiln; the horizontal distance between the kiln foundations shall be determined according to the dimensions after thermal expansion; the axial thermal expansion calculation of the kiln shall be based on the center of the belt with the retaining wheel near the transmission. Expansion to both ends; the kiln foundation shall be provided with a joint walkway, and shall be connected with the kiln head platform and the kiln tail platform;

(3) The rotary kiln transmission part may not have factory buildings and special maintenance equipment, but rain protection facilities shall be provided. Insulation facilities shall be provided between the transmission part of the rotary kiln and the kiln cylinder.

The design of the cooling ventilator of the rotary kiln should meet the following requirements:

(1) Rotary kiln firing belt cylinder should be equipped with ventilation cooling system according to equipment requirements;

(2) For rotary kiln belts with air cooling and cooling requirements, an independent ventilation and cooling system shall be designed according to the required air volume and wind pressure requirements of the equipment;

(3) The air cooling of the main drive and other motors in the kiln should be designed according to the requirements of the equipment, and the filtering measures should be taken for the ventilation system.

The design of the tertiary air duct of the decomposition furnace shall comply with the following provisions:

(1) The tertiary air should be taken from the upper casing or kiln cover of the cooler;

(2) The tertiary air duct should be arranged in a slanted “one” shape, otherwise cleaning measures should be taken;

(3) The wind speed in the tertiary air duct should be 25m/s~32m/s.

The configuration of the pulverized coal burner of the firing system shall comply with the following regulations:

(1) Rotary kiln shall adopt multi-channel, low NOx burner; when incinerating alternative fuel, the type of burner shall be adapted to the nature and state of the alternative fuel;

(2) The burner shall be provided with an ignition device, and the length and angle of the burner shall be adjustable;

(3) The ratio of the primary air volume of the multi-channel pulverized coal burner to the theoretical combustion air demand should not exceed 15%, and the ratio of the primary wind to the coal supply wind and the net wind should be determined according to the burner type;

(4) The burner of the decomposition furnace should be determined according to the type of the decomposition furnace and the coal quality, and it is preferable to adopt a multi-layer multi-point arrangement and a staged combustion technique to reduce nitrogen oxides in the flue gas;

(5) The primary fan should be equipped with an accident fan or a backup fan. The kiln head platform shall be provided with equipment for hoisting refractory materials and the stacking position. The inspection and hoisting equipment shall take care of the inspection of the burner.

The configuration of the clinker basket cooler should meet the following requirements:

(1) The heat recovery rate of the basket cooler should not be lower than 72%, and the clinker temperature of the cooler should be less than the ambient temperature plus 65 ‘C;

(2) The amount of cooling water per clinker required for clinker basket cooling shall be determined according to the type of basket cooler;

(3) The residual air of the basket cooler should be fully utilized and can be used for drying or waste heat power generation of raw materials, coal and mixed materials;

(4) The centerline of the basket cooler shall be biased to the side where the material of the center line of the kiln rises;

(5) The dust collection of the residual wind of the clinker basket cooler should be carried out by a bag type dust collector, and a cooling device should be installed before the exhaust gas enters the bag type dust collector.

The above is about the relevant regulations that each part needs to follow during the clinker burning process. After the raw material is preheated and pre-decomposed in the cyclone preheater, the next process is to enter the rotary kiln for clinker firing. In the rotary kiln, the carbonate is further rapidly decomposed and a series of solid phase reactions occur to form equal minerals in the cement clinker. As the temperature of the material rises, the minerals become liquid, and the dissolved in the liquid phase reacts to form a large amount (clinker). After the clinker is fired, the temperature begins to decrease. Finally, the high temperature clinker discharged from the rotary kiln is cooled by the cement clinker cooler to the temperature that can be withstood by the downstream conveying, storage and cement machinery, and the sensible heat of the high temperature clinker is recovered, and the thermal efficiency of the system and the quality of the clinker are improved.

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