What regulations should be met for the pulverized coal preparation system of the cement plant production line?

The pulverized coal preparation system of the cement production line should be selected according to the process requirements of the kiln and the types of coal, coal quality and moisture. For the preparation of pulverized coal, a grinding system with drying should be used.

Cement production line pulverized coal preparation system design should meet the following requirements

(1) The position of the pulverized coal preparation system shall be determined according to the characteristics of the coal and the process layout requirements, and may be arranged near the kiln tail or the kiln head;

(2) The capacity of the raw coal bunker should meet the needs of coal mill production, the unloading should be smooth, and the feed equipment under the bin should use a quantitative feed scale;

(3) The capacity of the coal powder bin should meet the needs of the kiln production, and the coal powder bin should be unloaded smoothly;

(4) The coal feeding equipment, the dynamic pollinator returning pipe and the discharging part of the coal powder shall be provided with a wind lock device;

(5) All the ducts and rollers of the pulverized coal preparation system should reduce the turning, and when the turning is required, the pulverized coal should be prevented from accumulating;

(6) When using the spoke type grinding machine, the iron removal and metal detection alarm device shall be installed before the raw coal is put into the grinding;

(7) The process equipment and air duct of the pulverized coal preparation workshop shall be insulated;

(8) The external moisture of coal powder should not exceed 1.5%, and the fineness should be determined according to the coal quality and volatile matter content.

The safety and explosion-proof design of the coal powder preparation system of the cement production line shall comply with the following provisions.

(1) The coal mill, dust collector and coal powder bin shall be equipped with a pressure relief valve;

(2) The form of the pressure relief valve should be automatically opened and closed;

(3) The length of the short pipe before the pressure relief valve should not exceed 10 times the short pipe equivalent diameter;

(4) The short pipe before the pressure relief valve shall be straight pipe, and the angle with the horizontal plane shall not be less than 60;

(5) The area of ​​the pressure relief valve on the inlet and outlet pipes of the mill shall not be less than the cross-sectional area of ​​the pipeline;

(6) The calculation of the total area of ​​the pressure relief valve on the pulverized coal storage bin shall comply with the relevant provisions of the current national standard “Guide for Dust Explosion Pressure Relief”) GB/T 15605;

(7) The pressure relief valve shall be provided with an inspection and maintenance platform;

(8) The temperature monitoring device shall be provided for the coal mill inlet and outlet; temperature and carbon monoxide monitoring and automatic alarm devices shall be provided on the coal powder bin and dust collector;

(9) The inlet and outlet pipes of the system dust collector shall be provided with a quick shut-off valve that is automatically closed in the power-off state;

(10) Gas fire extinguishing system shall be provided for coal mill, coal powder bin and coal mill dust collector;

(11) All process equipment, air ducts, coal powder silos and slides in the coal powder preparation workshop shall have grounding measures;

(12) Preparation of pulverized coal When using the residual heat of the firing system as the drying heat source, a dust-reducing facility should be installed before the human coal grinding.

The dust collection design of the coal powder preparation system of the cement production line shall meet the following requirements

(1) Dust collector equipment should use special dust collector for coal mill, dust collection equipment should have measures such as anti-combustion, explosion-proof and anti-static;

(2) The temperature of the gas entering the dust collector should be higher than the dew point temperature of 25.

In summary, the coal powder supply kiln and the decomposition furnace system should be separately equipped with a metering coal feeding device. Two pulverized coal bins should be set up, and a load cell should be provided. The pulverized coal conveying should be pneumatically conveyed.

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Optimization measures for rotary kiln process in cement plant

In recent years, coal resources have become tense and price costs have risen. In order to save costs, cement plants have to reduce the quality of raw fuels, coupled with the gradual decline in limestone grades, resulting in simultaneous reductions in the output and quality of rotary kiln systems. In order to improve this situation, through in-depth analysis and research, the cement plant rotary kiln process has been optimized and improved, and the effect is remarkable.

First, main equipment configuration of cement production line and production before optimization and transformation

The main equipment of these two cement production lines is: double series cyclone preheater + TDF furnace, rotary kiln, high temperature fan, grate cooler and kiln burner. The main problems exist are as follows:

1. With the decline of the local limestone grade, the w(SiO2) value in the milled limestone is as high as 6.5%; the volatiles in the raw coal decrease, the moisture and ash increase, and the calorific value decreases. As a result, the heat consumption of the system clinker is as high as 870×4.18kJ•kg-1; the moisture of the coal powder entering the kiln is large (about 3%); the temperature of the exhaust gas in the kiln head is high. In addition, yellow clinker often appears in clinker, f-CaO fluctuates greatly, low weight rise, clinker clinking is poor, flying sand is serious, and 28d strength is not high.

2. The kiln tail chamber and the decomposition furnace are easy to crust, and the kiln is often thick and thick at 37~44m. When the kiln has a long thick kiln skin, the kiln tail often leaks; even if the raw material feed rate drops to 120t/h, there is still a large amount of leakage at the kiln tail. Leakage at the end of the kiln will adversely affect the service life of the kiln seal, while polluting the environment and increasing the labor intensity of employees.

3. The preheater collapses frequently, often causing the three-stage cylinder to block the material, and the kiln condition is unstable. For this reason, in the three-stage tube feeding tube which is easy to block the material, a compressed air tube is inserted as a material to guide the material, and although the blocking material is relieved, there is often a phenomenon of blocking material.

Second, the main problem analysis

The tight resources of limestone and bituminous coal have caused the quality of the raw fuel entering the plant to decrease, which has caused a series of problems. If the raw material is easily burnt, it is difficult to burn. If the coal quality deteriorates, the flame burning speed in the kiln is slow, the flame is dispersed, the high temperature is not concentrated, and the system working conditions are unstable; then the clinker is poor in material and the cooling effect is poor, resulting in kiln head exhaust gas and cooling clinker temperature. High; after the pulverized coal combustion, the preheater outlet temperature is high (up to 385 °C ± 10 °C), the temperature difference between the cylinders is small, and the heat exchange efficiency is low. Therefore, the heat consumption of the mature material is high, the strength of the clinker is lowered, the amount of the mixed material is decreased, the wearability is deteriorated, and the output of the cement mill is decreased, thereby greatly increasing the production cost of the enterprise. Therefore, the change in the quality of the raw fuel is the main reason.

In addition, the cement production line has been put into production for 5 years, the strength of the refractory material in the three air ducts has dropped significantly, and the top of the air duct is often red out. The emergency treatment is for the back casting, which causes the accumulation of refractory materials and fine clinker in the third duct to increase the third wind. The increase of pipe resistance and wind speed leads to unbalanced wind in the preheater system; in addition, the air leakage in each system is serious, and the circulation in the preheater is increased, which causes the airflow of the preheater to be disordered and collapsed frequently.

Third, the response measures

1. Strengthen contact with suppliers of limestone and bituminous coal, take pre-tests before entering the factory, strictly control the quality of raw materials into the factory, and reject the raw materials with poor quality. At the same time, strengthen the stacking management of the plant site, do a good job in the use of raw materials, and increase the stock level of the limestone homogenization warehouse, the coal homogenization warehouse and the raw material homogenization warehouse, and increase the sampling frequency of each process. , to achieve pre-control, improve the predictability of ingredients, and stabilize the chemical composition of raw materials.

2. Improve the burning speed of kiln coal powder and the burning rate of coal powder in the kiln tail decomposing furnace. The factors affecting the burning speed of pulverized coal mainly include moisture, ash, fixed carbon, fineness, and performance of the burner. According to the characteristics of low calorific value, high water content and low volatile content of coal powder, the countermeasures adopted are:

(1) Replace the damaged lifting plate in the drying chamber of the coal grinding system, reduce the average ball diameter of the second bin, clean the accumulated dust and accumulated materials of each pipe, etc., in order to increase the ventilation of the coal grinding system and ensure the fineness of the coal powder. The degree (80μm sieve) is controlled within 5%, and the moisture is controlled within 1.8%, which creates conditions for the full combustion of pulverized coal.

(2) In the case of the same process conditions such as equipment configuration, raw materials, and ingredients, the performance of the burner will affect the quality of the clinker. In order to reduce the amount of primary air, increase the utilization of high temperature secondary air, enhance the thrust of the burner, strengthen the carrying of the secondary air, increase the mixing of pulverized coal and combustion air, and increase the adjustment means for the air volume and wind speed of each channel. Increasing the burning rate, improving the thermal efficiency of the kiln system, making the flame shape and temperature field easy to control as needed, meeting the requirements of the current coal quality, and knowing more and replacing the new burner through multiple manufacturers. Compared with the old burner, the new burner has a shorter structure in the structure; the cross-sectional area of ​​the outer and inner ducts is smaller; the cross-sectional area of ​​the coal duct is larger. Therefore, after the new burner is put into use, it can increase the speed difference between the primary wind and the coal wind and the secondary air, so that the coal powder is fully mixed and has the ability to carry the high temperature secondary air, improve the adaptability to the coal quality, and promote the flame. More complete and more active, the pulverized coal is burned more completely, which improves the thermal strength of the kiln firing zone.

(3) Carefully inspected all aspects of the wind that affect the system to better adjust the process wind of the kiln system; cleaned the ventilation holes of the air chambers, pipes and rafts of the grate cooler to improve 篦The cooling effect of the cold machine reduces the temperature of the clinker and raises the secondary air temperature; cleans the accumulated material in the third air duct, and replaces the refractory material in the third air duct to ensure the air volume and wind speed of the third air duct. In addition, the air leakage points are thoroughly sealed and leaked, which can control the collapse phenomenon of the preheater system.

(4) Improve the heat exchange effect of the preheater system and reduce the heat consumption of the clinker. 80% of the heat exchange in the preheater is completed in the pipeline, and 20% is completed in the cyclone; the heat exchange efficiency is mainly affected by the dispersibility of the material in the pipeline, the dust collection efficiency of each cylinder, and the airflow of each cylinder. The speed difference of the material, the performance of the raw meal powder and other factors. In order to improve the heat exchange efficiency of the preheater, targeted transformation and adjustment measures were carried out:

First, the feeding angle of each sprinkling bin in the preheater is increased, and a material dispersing device is installed on the dispersing plate to forcefully disperse the material to improve the speed difference and dispersion effect of the material in the pipeline and the airflow;

The second is to increase the height of the inner cylinder of C4 and C5 to improve the dust collection efficiency of the two-stage cyclone;

The third is to check the clearance of each flap valve in the cutting tube and adjust the counterweight of the flap valve to ensure smooth and wind-locking effect during normal production.

Through the optimization and transformation of the above measures, the operating conditions of the rotary kiln system in the cement production line are stabilized, the number of occurrences of system process failures is reduced, the environmental pollution and the labor intensity of the employees are reduced, the output of the rotary kiln system is improved, and the quality is also significantly improved. In general, the transformation of the cement plant was more successful and has the significance of promotion.

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How is sludge treated?

Food industry wastewater

The food industry has a wide range of raw materials and a wide variety of products. The amount of water and water quality discharged from wastewater are very different.

The main pollutants in the wastewater are: solid materials floating in the wastewater, such as vegetable leaves, peels, minced meat, bird feathers, etc.; substances suspended in the wastewater are oils, proteins, starches, colloids, etc.; acids dissolved in the wastewater , alkali, salt, sugar, etc.; mud and other organic matter entrained in raw materials; pathogenic bacteria and so on.

The waste water of the food industry is characterized by high content of organic substances and suspended solids, easy to be spoiled, and generally no major toxicity. The hazard is mainly to make the water body eutrophication, causing the death of aquatic animals and fish, causing the organic matter deposited on the bottom to produce odor, deteriorating water quality and polluting the environment.

In addition to proper pretreatment according to the characteristics of water quality, wastewater treatment in food industry should generally adopt biological treatment. If the effluent water quality is very high or because the organic matter content in the wastewater is high, a two-stage aeration tank or a two-stage biological filter, or a multi-stage biological turntable, or a combination of two biological treatment devices, or an anaerobic can be used. In series with aerobic.

Pesticide wastewater

There are many varieties of pesticides, and the water quality of pesticide wastewater is complicated. Its main features are:

The concentration of pollutants is high, and the chemical oxygen demand (COD) can reach tens of thousands of milligrams per liter. It is highly toxic. In addition to pesticides and intermediates, wastewater contains toxic substances such as phenol, arsenic and mercury, as well as many substances that are difficult to degrade. It has a foul smell and is irritating to the human respiratory tract and mucous membranes; water quality and water volume are unstable.

Therefore, the pollution of pesticide wastewater to the environment is very serious. The purpose of pesticide wastewater treatment is to reduce the concentration of pollutants in the wastewater of pesticide production, improve the recycling rate, and strive to achieve harmlessness. The treatment methods of the pesticide wastewater include activated carbon adsorption method, wet oxidation method, solvent extraction method, distillation method and activated sludge method.

However, the development of new pesticides with high efficiency, low toxicity and low residue is the development direction of pesticides. Some countries have banned the production of organochlorine and organic mercury pesticides such as 666, and actively researched and used microbial pesticides. This is a new way to fundamentally prevent pesticide wastewater from polluting the environment.

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How industrial waste is treated?

Printing and dyeing industrial wastewater

The printing and dyeing industry uses a large amount of water. Generally, it consumes 100 to 200 tons of water per 1 t of textiles for printing and dyeing, of which 80% to 90% is discharged by printing and dyeing wastewater. Commonly used treatment methods are recycling and harmless treatment.

Recycle and re-use:

The wastewater can be recycled separately according to the characteristics of water quality, such as the separation of bleaching and smelting wastewater and dyeing printing wastewater. The former can be used for convection washing and multi-use, reducing emissions;

The recovery and utilization of lye is usually carried out by evaporation method. If the amount of lye is large, it can be recovered by three-effect evaporation. The amount of lye is small, and it can be recovered by evaporation of the film;

Dye recovery, such as Shilin dye can be acidified into cryptic acid, as colloidal particles. Suspended in the residual liquid, filtered by precipitation and recycled.

Harmless treatment:

The physical treatment methods include a precipitation method and an adsorption method. The precipitation method mainly removes suspended matter in the wastewater; the adsorption method mainly removes dissolved pollutants and discoloration in the wastewater.

The chemical treatment methods include a neutralization method, a coagulation method, and an oxidation method. The neutralization method is to adjust the pH in the wastewater, and also to reduce the color of the wastewater; the coagulation method is to remove the disperse dyes and colloidal substances in the wastewater; the oxidation method is to oxidize the reducing substances in the wastewater to precipitate the sulfur dyes and the vat dyes.

Biological treatment methods include activated sludge, biological turntables, biological drums, and biological contact oxidation methods. In order to improve the quality of the effluent water, to meet emission standards or recycling requirements, it is often necessary to use several methods for joint treatment.

Paper industry wastewater

The papermaking wastewater mainly comes from the two production processes of pulping and papermaking in the paper industry. Pulping is to separate the fibers in the plant material, make a slurry, and then bleach; papermaking is to dilute, shape, press, and dry the slurry to make paper. Both processes discharge large amounts of wastewater.

The wastewater produced by pulping is the most polluted. The waste water discharged during washing is dark brown, called black water. The concentration of pollutants in black water is very high. The BOD is as high as 5~40g/L, which contains a lot of fiber, inorganic salt and pigment. The wastewater discharged from the bleaching process also contains a large amount of acid and alkali substances. The waste water discharged from the paper machine, called white water, contains a large amount of fibers and fillers and rubbers added during the production process.

The treatment of paper industry wastewater should focus on increasing the recycling rate, reducing water consumption and wastewater discharge, and actively exploring various reliable, economical and adequate treatment methods for utilizing useful resources in wastewater. For example, the flotation method can recover fibrous solid materials in white water, the recovery rate can reach 95%, and the clarified water can be reused; the combustion method can recover sodium hydroxide, sodium sulfide, sodium sulfate and other sodium salts combined with organic substances in black water.

The neutralization method adjusts the pH value of the wastewater; the coagulation sedimentation or flotation method can remove the suspended solids in the wastewater; the chemical precipitation method can decolorize; the biological treatment method can remove the BOD, and is effective for the kraft paper wastewater; the wet oxidation treatment of the sulfite pulp wastewater success. In addition, reverse osmosis, ultrafiltration, electrodialysis and other treatment methods are also used at home and abroad.

Dye production wastewater

Dye production wastewater contains acids, bases, salts, halogens, hydrocarbons, amines, nitros and dyes and their intermediates, and some also contain pyridine, cyanide, phenol, benzidine and heavy metals such as mercury, cadmium, chromium and so on. These wastewaters are complex, toxic and difficult to handle. Therefore, the treatment of dye production wastewater should be based on the characteristics of the wastewater and its discharge requirements, and appropriate treatment methods should be selected.

For example, the removal of solid impurities and inorganic substances, coagulation method and filtration method can be used; the removal of organic matter and toxic substances mainly adopts chemical oxidation method, biological method and reverse osmosis method; decolorization can generally adopt a process composed of coagulation method and adsorption method. In the process, the heavy metal can be removed by ion exchange or the like.

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Environmental impact of municipal waste solutions

With the acceleration of urbanization and the improvement of residents’ living standards, the number of municipal  waste solution has increased. In recent years, municipal solid waste has grown at an annual rate of 8% to 10%, and the growth of urban domestic waste has become a potential factor restricting the sustainable development of various countries. How to properly manage urban domestic waste is of great significance to China and the world. Urban living garbage is complex and large in quantity, and it is one of the main sources of pollution in the environment. The landfill gas generated by landfill degradation is a greenhouse gas. About 3% to 4% of the annual anthropogenic greenhouse gas emissions are from methane in landfill gas.

At present, the most common methods of domestic garbage disposal are landfill and incineration. About 80% of the existing waste disposal implementation is landfill. Due to the characteristics of domestic garbage and economic development, landfill will remain the main disposal method for municipal domestic garbage in the future for a long time to come. In recent years, waste incineration technology has caused great concern to all sectors of society because of the harmlessness, reduction and resource level of waste disposal. Incineration power generation technology has become an emerging industry with great development potential. The National Development and Reform Commission has identified municipal solid waste incineration power generation as a key support industry.

1. Landfill treatment

Economic and technical analysis: Landfill treatment is a commonly used treatment method. It can handle all kinds of garbage, and the method is simple and saves investment. Therefore, this method is widely used in countries all over the world. From uncontrolled landfill to sanitary landfill, including drainage and landfill, compressed landfill, and landfill.

The landfill treatment method firstly prevents the liquid leaching and rainwater runoff from the waste from polluting the groundwater. The general specification requires that the elevation at the lowest point of the backfill should be more than 3.3 m above the water table, and the lower part of the backfill should have an impervious rock or clay layer. Otherwise, an impervious layer such as clay, asphalt or plastic film should be set up. Secondly, the landfill should be provided with an exhaust port to allow methane and other gases released during the decomposition of anaerobic microorganisms to escape in time to avoid explosion.

Impact on the environment: After the backfilling, it is generally not suitable to build houses on it within 20 years to avoid structural damage caused by uneven subsidence of the backfill, but it can be used for green space, farmland and pasture. For landfill disposal, try to use natural or artificially excavated depressions, such as waste clay pits, waste quarries, and waste pits after development resources. Landfilling in the pit is conducive to restoring the landform and maintaining the ecological balance. However, if backfilling in large areas of depressions, harbors, valleys, etc., it is necessary to consider whether it will destroy the ecological environment. The biggest advantage of landfill is that its processing cost is relatively low. However, it has a large land resource. At the same time, landfill disposal will also cause serious environmental problems. The most important thing is malodor and methane emission. And landfill leachate, landfill leachate is a highly toxic substance, so its pollution is very serious. If the anti-seepage measures are not good, or the landfill leachate is out, the treatment will be bad, which will cause serious pollution to groundwater, surface water and soil, and bring serious environmental problems.

2. Composting treatment

Economic and technical analysis: Waste composting is a method of treating and utilizing garbage. It uses microorganisms such as bacteria, yeasts, fungi and actinomycetes present in garbage or soil to cause biochemical reactions in the garbage to be degraded (digested). ), forming a substance similar to corrosive soil, used as a fertilizer and used to improve the soil. According to the principle of bacterial decomposition, the garbage composting technology is divided into high temperature (good) oxygen method and low temperature anaerobic method composting.

According to the composting method, it is divided into open-air composting method and mechanical composting. The composting operation is generally divided into 4 steps:

(1) Pretreatment, removing large and inorganic impurities, and dividing the waste crushing sieve into a homogeneous shape. The optimum moisture content of the homogeneous garbage is 45-60%, and the carbon to nitrogen ratio is about (20-30): 1. Can be mixed with sludge or manure when it is not needed;

(2) Bacterial decomposition (or fermentation), under the appropriate conditions of temperature, moisture and oxygen, aerobic or anaerobic microorganisms rapidly multiply, and the waste begins to decompose, converting various organic matter into harmless fertilizer;

(3) It is decomposed, stable and fat, and can be applied after it is completely decomposed;

(4) Storage or disposal, storage of fertilizers, and disposal of fertilizers for landfill disposal.

The effect on the environment:

The composting treatment has a long cycle, a large area and poor sanitary conditions; the products produced by composting are farmyard manure, the fertilizer efficiency is poor, and the sales are relatively difficult.

3. Incineration treatment

Economic and technical analysis: Waste incineration treatment refers to the process in which combustibles in waste are burned with oxygen in an incinerator. The essence is the chemical reaction of carbon, hydrogen, sulfur and other elements with oxygen. After the waste is incinerated, heat is released, and at the same time, smoke and solid residue are generated. The heat is recovered, the flue gas is purified, and the residue is digested. This is an indispensable process for incineration. The incineration treatment technology is characterized by large processing capacity, good volume reduction, and complete harmlessness. The heat generated by the incineration process can be used to generate electricity to realize the energyization of waste. Therefore, it is a waste treatment technology commonly used in developed countries. Garbage can be oxidized and decomposed by incineration to remove toxicity, recover energy and obtain by-products. Almost all organic waste can be treated by incineration. For inorganic, organic mixed solid waste, if the organic matter is a toxic and hazardous substance, it is generally best to use incineration. The incineration method is suitable for treating garbage with more combustibles. By incineration, care must be taken not to cause secondary pollution of the air. Incineration is a waste disposal technology that destroys the heat of waste utilization. However, it is only possible to recycle waste with thermal energy, and waste incineration is scientific and reasonable.

The effect on the environment:

(1) The destruction of available resources in garbage during incineration is a waste of resources;

(2) Incineration treatment has certain requirements for the low calorific value of garbage, and no garbage can be incinerated;

(3) The flue gas generated by incineration must be purified, and the purification technology is difficult and the operation cost is high;

(4) One-time investment in incineration equipment is high and the operating cost is high.

4. Pyrolysis

Organic solid waste → gas (H2, CH4, CO, CO2) + liquid (organic acid, aromatic hydrocarbon, tar, etc.) + solid (carbon black, slag, etc.)

Economic and technical analysis: Pyrolysis is a combustion process under anoxic or anaerobic conditions. It is an endothermic decomposition reaction under low electrode potential reduction conditions, also known as dry distillation or carbonization process (gas engineering, and coking is heat) Solution process).

The difference between pyrolysis and incineration can be summarized in the table below.

  Incineration Pyrolysis
Thermal effect Exothermic, oxidizing Endothermic, reduction
Reaction product Carbon dioxide, water Combustible low molecular compound
Release method and application The heat generated can only be used nearby (power generation, heating water or steam generation) Produces fuel oil and gas, can be stored and transported over long distances

Environmental impact: It converts organic matter from solid waste into storage energy such as fuel gas, fuel oil, and carbon black. Pyrolysis is an anoxic decomposition that produces less exhaust gas and, accordingly, less exhaust gas, which helps to reduce environmental air pollution. Most of the harmful components such as sulfur and heavy metals in the waste are fixed in the carbon black. The trivalent chromium is not converted to hexavalent chromium because it is maintained under reducing conditions. The amount of nitrogen oxides produced is small.

In order to make urban garbage disposal resources, the following points should be achieved:

(1) Strengthen the classification and recycling of municipal waste. The classification and recycling of municipal waste is an important prerequisite for realizing urban waste recycling. The mixed recycling of urban garbage has increased the difficulty of harmlessness, reduction and resource treatment of garbage, resulting in a waste of a large amount of resources. In order to promote the classification and recycling of garbage, garbage containers with different signs should be placed in residential areas, commercial, cultural and entertainment centers, and corresponding systems and reward and punishment measures should be formulated to ensure that residents consciously classify and place garbage to realize classified collection of garbage.

(2) Strengthen the recycling of waste materials and promote the development of the old goods market.

(3) Strengthen the management of urban garbage resources. To recycle urban garbage, we must first change the garbage management system of government and enterprise integration, and establish a municipal solid waste management system that is compatible with the market economy. Secondly, we must establish an information management system for urban waste recycling and improve management capabilities. Technicalization of urban waste treatment to improve the technical level of harmless, reduced and resourced urban waste treatment
.
The traditional landfill method takes up land and forms secondary pollution, which does not meet the requirements of harmlessness. Incineration costs are high and resource utilization is low. Urban waste has complex composition, high water content and less combustibles. Therefore, the garbage disposal is suitable for the comprehensive treatment technical route of garbage sorting, recycling, organic fermentation, fertilizer, and combustibles for heat generation. The comprehensive treatment technology of waste recycling involves many fields such as machinery, chemical industry, biology, electronics, etc. Therefore, it is more important to improve the technology integration capability.

(4) Vigorously develop urban waste recycling technology. Faced with the challenge of garbage, many scientists have suggested that high-tech should be applied in full, turning waste into treasure and benefiting from garbage. Science and technology are the primary productive forces, and the recycling of urban waste is largely related to resource-based technologies.

Advances in science and technology can increase the types of wastes that can be utilized and their utilization depth, and improve the comprehensive utilization rate, thereby promoting the rapid development of the waste resource industry. Therefore, it is very necessary to strengthen the research of garbage resource technology and provide hardware support for urban garbage resource.

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How industrial waste is treated?

Industrial wastewater refers to wastewater, sewage and waste liquid produced in industrial production processes, which contain industrial production materials, intermediate products and products that are lost with water, and pollutants produced during the production process, summarizing chemical industrial wastewater, printing and dyeing industrial wastewater. 15 kinds of industrial wastewater treatment processes such as paper industry wastewater, dye production wastewater, food industry wastewater and pesticide wastewater.

1. Characteristics and treatment process of desulfurization wastewater from coal-fired power plants

Characteristics of desulfurization wastewater from power plants:

Most desulfurization devices in power plants use flue gas limestone-gypsum wet desulfurization process. The process mainly consists of a limestone slurry preparation system, a gypsum dehydration system, and a desulfurization wastewater treatment system. The water in the slurry of the desulfurization device will be enriched with heavy metal elements and Cl- in the process of continuous circulation. On the one hand, the corrosion of the desulfurization equipment is accelerated, and on the other hand, the quality of the gypsum is affected, and the wastewater needs to be discharged in time.

Power plant desulfurization wastewater treatment process: desulfurization wastewater → waste water tank → wastewater pump → pH neutralization tank → settling tank → flocculation tank → clarifier → water tank → water pump → discharge standard

The desulfurization wastewater treatment system includes three parts: wastewater treatment, dosing and sludge treatment. The wastewater treatment system is mainly composed of waste water tank, triple tank, clarification tank, mud pump, water outlet tank, clean water pump, fan and dewatering machine. In addition to a large amount of Cl-, Mg2+, the impurities in the desulfurization wastewater include: fluoride, nitrite, etc.; heavy metal ions such as Cu2+, Hg2+, etc.; insoluble CaSO4 and fine dust. In order to meet the wastewater discharge standards, a corresponding wastewater treatment device is required.

2. Chemical industry wastewater

The chemical industry wastewater mainly comes from the production wastewater discharged from the petrochemical industry, the coal chemical industry, the acid and alkali industry, the fertilizer industry, the plastics industry, the pharmaceutical industry, the dye industry, and the rubber industry.

The main measures for the prevention and control of chemical wastewater pollution are: first, reform the production process and equipment, reduce pollutants, prevent wastewater discharge, comprehensive utilization and recycling;

The primary treatment mainly separates suspended solids, colloids, oil slicks or heavy oil in water. Water quality and water volume adjustment, natural sedimentation, floating and oil separation methods can be used.
The secondary treatment mainly removes the biodegradable organic solute and some colloids, reduces the biochemical oxygen demand and part of the chemical oxygen demand in the wastewater, and is usually treated by biological methods. A considerable amount of COD remains in the biologically treated wastewater, sometimes with a high color, smell, taste, or high environmental sanitation standards, and further purification is required by a three-stage treatment.

The tertiary treatment is mainly to remove organic pollutants and dissolved inorganic pollutants that are difficult to biodegrade in wastewater. Commonly used methods include activated carbon adsorption and ozone oxidation, and ion exchange and membrane separation techniques can also be used. Various chemical industry wastewaters can be selected according to different water quality, water quantity and post-treatment external drainage quality.

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Deep Dewatering Technology and Analysis

In recent years, sludge dewatering technology has been greatly developed, and technological breakthroughs have focused on the development of conditioning agents before sludge dewatering and the improvement of dewatering machinery and equipment. At present, using sludge chemical conditioning + mechanical dewatering technology, sludge conditioning agent is added to the wet sludge raw mud to destroy the microbial structure of the sludge floc and lyse, and the physical binding water is separated to make the microorganism’s water Separation, eventually converting most of the combined water in the sludge into free water, and then separating the free state water by mechanical dewatering equipment. The sludge dewatering technology has been applied in large scale in the sludge treatment of the tannery sewage treatment plant. The sludge moisture content after treatment can be less than 50%. In order to meet the requirements of sludge subsequent treatment and disposal, it is necessary to further reduce the conventional mechanical dewatered sludge. Moisture content.

The quenching and tempering treatment of sludge is the key link and core technology for deep dewatering of sludge. It can be said that sludge conditioning technology determines the success or failure of sludge deep dewatering project. There are many methods for quenching and tempering domestic sludge. It is common to add dehydrating agent, flocculant or coagulant to the sludge to change the existence and structure of water molecules (mainly interstitial water and capillary water) in the sludge. Conducive to the separation of water and mud under certain conditions. Commonly used conditioning agents are ferric chloride (or ferric sulfate, polymeric ferric sulfate) plus quicklime.

The sludge deep dewatering equipment is mainly a high pressure diaphragm plate frame filter press. By applying pressure from the outside of the sludge, the moisture in the quenched and tempered sludge is leached and separated to obtain a mud cake having a high solid content. There are many domestic equipment manufacturers, and the equipment manufacturing process and quality have been increasingly improved.

Advantages of sludge deep dewatering technology:
The reduction effect is good, the energy consumption is low, the floor space is small, the construction period is short, and the processing time is short.

Disadvantages of sludge deep dewatering technology:
Ferric chloride is highly corrosive, and quicklime is easy to scale. As a result, the high-pressure diaphragm frame filter press has high operation and maintenance costs, stable and insufficient sterilization, slightly odor, and the organic matter content in the sludge is not reduced.

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What are the municipal waste solutions?

With the development of urbanization, the amount of garbage generated by the city is increasing, and then a problem is caused  municipal waste solutions. Now people’s living standards have improved, and the use of some high-end durable goods will increase, which will inevitably increase the difficulty of garbage disposal. The common treatment methods and advantages and disadvantages of garbage are as follows:

1. Stacked in the open air. This method simply stacks the garbage on the open space without any processing. Because of the low cost of this method, this method has been used frequently, especially in remote areas. However, the open dumping of garbage will occupy the land. In some places, the garbage dump covers an area of ​​several acres and uses valuable cultivated land. Also, open-air stacking will cause some of the garbage to deteriorate, and the spoiled garbage will emit an unpleasant smell, which will attract flies, which can spread diseases and are harmful to the health of surrounding residents. In addition, some substances containing sulfur will metabolize to produce a highly toxic gas, hydrogen sulfide. When hydrogen sulfide reaches a certain concentration, it will cause irreparable damage. When the concentration is extremely large, it will be life-threatening. When stacked in the open air, the electrolyte of the battery will flow out. The electrolyte of the battery is sulfuric acid, which acidifies the soil and prevents the crop from growing. Because this method has a great damage to the environment, the open-air stacking method is not generally used now.

2. Deep burial method. This method is to dig deep pits to bury the garbage so that it does not occupy the surface space. This method utilizes the decomposer-microbe in the soil, and the garbage can be buried without using the ground space. The microorganisms will also decompose some organic matter and will not attract flies, so some areas will use this method. However, microorganisms can only decompose a part of organic compounds, and organic substances such as polyethylene take four hundred years to decompose. Also, this method makes the waste battery pollute the land more easily. According to research, a button cell will pollute 6 billion liters of water. This is the water consumption of a person for a lifetime! The bacteria will be more harmful in the underground, some in the garbage. Bacteria accelerate in the soil and then enter the groundwater, which can invisibly pollute the water and harm the health of the residents.

3. Traditional incineration method. This method is to incinerate the waste and decompose it. Most of the cities chose this method because the incinerator occupies a small area and the garbage is easily cleaned after incineration. However, some objects cannot be burned, like glass and metal. There is also some organic matter burning to generate toxic gases, such as polyvinyl chloride, burning at 240 ° C – 340 C will decompose hydrogen chloride gas and diolefins containing double bonds, and then carbon burning at 400-470C will release toxic Gases, as well as some organic matter, undergo an addition reaction, making the original non-toxic substances toxic. Also, the battery will rupture at high temperatures, and the material inside is toxic. These toxic substances are discharged into the air with the smoke, and the damage will be even greater.

Because traditional methods have many drawbacks, and with the development of technology, there are many ways to deal with garbage, so we can use modern methods to treat garbage in a harmless way.

1. Fermentation method. For some kitchen waste, the manure can be put into the biogas tank for fermentation. In the biogas tank, the kitchen waste will be decomposed to generate methane, which can be used for power generation, cooking, lighting, etc. The fermented items can be used as fertilizer or feed.

2. High-tech incineration. Traditional incineration can damage the environment, and we can use technology to reduce the hazards of incineration. First, use high-power electromagnets to extract iron, nickel and batteries from the waste for recycling. The garbage is then compressed to make it smaller. The waste is then placed in an incinerator, the organic matter is decomposed at a high temperature of 500 degrees, and the gas is treated harmlessly. Then, the heat generated by the waste combustion is used to generate electricity. This can minimize the harm caused by organic matter, and make full use of the energy generated by combustion, which is less harmful to the environment, and can also reduce the consumption of ore fuel, killing two birds with one stone. However, this method has high technical requirements and high cost, especially for the harmless treatment of gases, so it is suitable for economically developed regions.

3. Reuse method. This method is to reuse the garbage, make the garbage harmless, and produce something that can be reused. This not only handles the garbage, but also generates useful things, which has turned waste into treasure. For metal waste, it can be remelted to make new items, which can reduce the dependence on metal ore in the production process and make full use of resources. It is very suitable to treat polymer organic substances such as plastics in this way because polymer organic substances are difficult to degrade, and incineration pollutes the air. It can be heated to the melting point of the organic matter, and the organic matter is fired into a liquid state and then subjected to purification treatment, and the impurities are removed and re-injected into the mold to form a new product.

Because organic compounds do not undergo chemical reactions during this process, no harmful gases are formed and naturally do not damage the environment. Moreover, most of these high molecular organic compounds are made from ethylene, ethane and propylene extracted from crude oil. Recycling and recycling can reduce the dependence on oil in the production process and achieve green production. This method is also very effective in disposing of used batteries. Waste batteries, whether they are incinerated or stacked or buried, can pollute the environment. If the used batteries are recycled, some of the internal materials can be reused, such as the zinc casing of the battery and the internal carbon electrode. If it is recycled, it not only treats the waste, but also saves resources.

4. High temperature composting of garbage. High-temperature waste compost refers to the method of fermenting and biodegrading waste at a certain temperature to make the garbage harmless. This method is relatively simple, has less investment, and can be garbage-resourced, so it is more popular. However, the problem of garbage composting is that the incoming garbage components need to be controlled, otherwise the quality of composting products will be very difficult to grasp. The sale of garbage compost products also needs to have a better market mechanism. Waste compost is more suitable for areas with high organic matter content in waste components.

5. Sanitary landfill method. This method is different from the deep-buried method mentioned above. The deep-buried method will pollute the environment of the landfill, but the sanitary landfill method will not pollute the environment. No matter which method is used to dispose of the garbage, some waste will be produced, and these wastes can only be landfilled.
Waste sanitary landfills must have facilities to prevent contamination of groundwater, the atmosphere and the surrounding environment, such as bottom lining treatment, biogas collection, landfill leachate and sewage treatment. The anti-seepage coefficient of the bottom lining of the sanitary landfill must be less than 10-7 cm/s. The advantage of landfill sanitary landfill is that the investment cost is low, and the disadvantage is that it takes up a lot of land. In the garbage disposal, it is necessary not only to pay attention to the cost, but also to consider the environment, topography and climate of the area. To proceed from the actual situation, choose the appropriate garbage disposal method according to the situation in this area.

In summary, I think the most suitable garbage disposal solutions for the city are as follows.

(1)Transportation + sanitary landfill

(2)Transportation + incineration + sanitary landfill

(3)Transportation + compost + sanitary landfill

(4)Transportation + Incineration + Composting + Sanitary Landfill

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Sludge lime stabilization technology and analysis of its advantages and disadvantages

By adding a certain proportion of quicklime to the dewatered sludge and uniformly blending, the quicklime reacts with the moisture in the dewatered sludge to form calcium hydroxide and calcium carbonate and release heat. Sludge lime stabilization technology can effectively deodorize, sterilize, inhibit corrosion, dehydration, and passivate heavy metal ions.

The typical process is as follows: sludge with a water content of 80% is sent from the screw conveyor to the silo for temporary storage, and the sludge and quicklime are respectively sent to the material reaction system according to the ratio of mass ratio of 4:1 by the metering and conveying device. In the material reaction system, the sludge and quicklime react and react, so that the temperature in the system is rapidly increased to 100 degrees, and the water in the sludge is evaporated in a large amount to complete the drying and dehydration process of the sludge. The dried sludge is transported to an outdoor stacking shed by a double screw mixer for storage and storage. In order to prevent secondary pollution in the sludge drying process, the treatment of the discharged lime dust and malodorous gas can be realized by adding dust removal and deodorization equipment.

In practical applications, in addition to adding lime, other excipients are often added to enhance the effect. Some of these excipients contain N, increase the production of NH3 gas, strengthen sterilization and facilitate land use; some are strong acid iron and aluminum salts. The reaction temperature is increased and the ratio of solid inorganic components is more suitable for building materials utilization; generally it is acidic, in addition to increasing the exotherm, the pH can be moderately adjusted, and the common effect is to reduce the amount of lime added and save costs.

Advantages of sludge lime stabilization technology:
 Small investment, low operating cost, small floor space, and simple operation and management.
 It can effectively eliminate bacteria and there is no risk of bacterial regeneration.
 The dried product is rich in calcium hydroxide, silica, calcium carbonate and other substances. It can be used as a base material for building materials, road foundation materials, cushion soil for landfills, and backfill for road construction.
 Lime stabilized sludge has a high pH value and can be used as a desulfurizer for incineration equipment.
 Especially suitable for emergency or phased disposal.

Disadvantages of sludge lime stabilization technology:
 Due to the large amount of added lime, the degree of reduction is not high compared to other processes.
 It is strongly alkaline, with low land use value and narrow surface.
 High drug use fees.

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Sludge incineration technology and analysis of its advantages and disadvantages

The sludge incineration technology refers to the conversion of organic matter in the sludge to CO2, H2O, N2, etc. under a certain temperature and sufficient aerobic conditions, and the heat released during the reaction is used to maintain the reaction temperature conditions. Sludge incineration technology is the most thorough sludge treatment method. It removes all organic matter, kills all pathogens, and minimizes sludge volume.

The sludge incineration technology generally adopts a fluidized bed process and is divided into a fixed (bubble) fluidized bed incinerator, a circulating fluidized bed incinerator, and a rotary fluidized bed incinerator. The flue gas from sludge incineration should be treated and meet the relevant regulations of the Domestic Waste Incineration Pollution Control Standard. The ash from sludge incineration and the fly ash collected by dust removal equipment should be collected, stored and transported separately. The state encourages the comprehensive utilization of slag that meets the requirements: fly ash needs to be properly disposed of after identification. The sludge incineration process is widely used in large and medium-sized cities with more developed economies. Generally, the combined use of dry incineration is used to improve the thermal energy utilization efficiency of the sludge.

Advantages of sludge incineration technology:
 Sludge incineration treatment of sludge can achieve “sludge reduction, stabilization and harmlessness” to the greatest extent.
 The ash after sludge incineration can be directly or treated with heavy metal chelating agent and then enter the landfill according to the heavy metal content. It can also be used as building materials or paving.

Disadvantages of sludge incineration technology:
 Large investment and high equipment maintenance cost.
 The sludge itself has a low calorific value and needs to be mixed with domestic garbage and coal, and the running cost is high.
 Exhaust gas emissions are large, which may cause secondary pollution.

The target of sludge treatment is sludge reduction, stabilization, and harmlessness. To be used as a resource is a yearning, and there is a long way to go with reality. It is generally “incapable” and cannot be a goal that must be achieved. Each treatment method has different advantages.

There is no best in the choice of sludge treatment technology, only the most suitable. According to different regions and different sludge types, considering the climate, regional characteristics, construction conditions, etc., it is an ideal choice to combine various processes to achieve the best results.

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