Development of ceramsite produced by solid waste production

In recent years, China’s ceramsite raw material structure has undergone important changes, the proportion of solid waste ceramsite has increased significantly, and the market share of urban construction waste ceramsite and sludge ceramsite has increased significantly. At present, in addition to the more mature fly ash ceramsite and sludge ceramsite, various other solid wastes such as coal gangue, tailings, steel slag, and even fly ash after incineration of domestic garbage have all industrialized production of ceramsite manufacturers.

(1) Sludge ceramsite
The use of sludge to make ceramsite is a hot spot in the industry’s recent development. The country increased the production capacity of ceramsite with sludge as raw material by more than 2 million cubic meters last year alone. The sludge currently mainly comes from river and lake dredging sludge, municipal sewage sludge, and industrial enterprise sludge. Because all localities have certain economic compensations for sludge disposal. For example, Shanghai 300-500 yuan per ton, Zhejiang Ningbo 200-300 yuan per ton, Taizhou 150-250 yuan per ton, Huzhou 150-250 yuan per ton, Jiangsu Nanjing 250 yuan per ton. At present, most ceramsite manufacturers are using or trying sludge to produce ceramsite, and have achieved certain economic and social benefits.

(2) Tailings ceramsite
There are 12,655 tailings ponds in my country, and tailings have become the largest solid waste output and stockpiled in my country, which has caused serious environmental problems and huge safety hazards. Although the land was covered and re-cultivated after the storage was closed, the land area was far from enough to make up for the area occupied by the tailings pond in the early stage, causing the loss of land resources. Using tailings to prepare ceramsite is one of the important ways to utilize tailings as a resource.

(3) Steel slag ceramsite
The slag firing ceramsite technology effectively overcomes the problem of late expansion of steel slag and cannot be used for building materials. It reduces the firing temperature of ceramsite by taking advantage of the iron-rich characteristics of steel slag, which is lower than that of shale clay ceramsite. The need to mine natural stone and mineral resources is an emerging technology worth promoting for energy saving and emission reduction.

(4) Coal gangue ceramsite
Coal gangue is a by-product of coal mining and is one of the largest industrial solid wastes in my country. The large accumulation of coal gangue not only wastes land, but also pollutes the environment, and can even cause serious geological disasters. Therefore, the problem of rational utilization of coal gangue needs to be solved urgently. The use of coal gangue to prepare ceramsite not only solves the pollution problem of coal gangue, but also makes reasonable use of industrial solid waste and turns waste into treasure, which has certain social, economic and environmental benefits. At present, many coal mining enterprises, the following resource utilization companies, are conducting research and development of coal gangue ceramsite.

(5) Ceramsite made from domestic waste fly ash
With the rapid development of China’s social economy and the acceleration of urbanization and the rapid improvement of people’s living standards, the amount of garbage generated in the process of urban production and life has also increased rapidly. Domestic garbage occupies land, pollutes the environment, and is harmful to people’s health. The impact of this has become more obvious. The massive increase in municipal solid waste has made it more and more difficult to dispose of waste. The resulting environmental pollution and other issues have gradually attracted widespread attention from all walks of life. The use of domestic waste for incineration power generation is a common disposal method, and a large amount of waste incineration fly ash will be produced every year. This kind of fly ash is a hazardous waste, and how to carry out subsequent treatment has become another topic. The fly ash ceramsite is produced with waste incineration fly ash as the main raw material. After the harmless treatment, the leaching toxicity of heavy metals meets the control indicators of relevant national standards. The performance of the ceramsite product meets the requirements of GB/T17431.1, realizing the harmlessness of fly ash. , Resource disposal, has made a significant contribution to the promotion of the industry’s technology, and made the ceramsite industry have the functions of resource utilization and safe disposal of hazardous waste.

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Status and development trend of sludge treatment and disposal

The current status of sludge treatment and disposal in my country is:

(1) Reduction aspect

The sludge produced by the sewage treatment facilities of each unit is basically dehydrated, but the sludge digestion technology and the remaining sludge reduction technology are rarely used;

(2) Stabilization

Due to its advantages in nature, scale, technology, economy, etc., urban living sewage treatment plants generally perform necessary stabilization of sludge, mainly alkali stabilization. Enterprise point source facilities generally do not stabilize sludge;

(3) Recycling

At present, the utilization of various types of sludge in my country is still in the initial stage of exploration.

Most of the sludge from urban sewage treatment plants is disposed of in landfills. Among them, some are specialized landfills, and some are mixed landfills with municipal waste. A small part is used for agricultural disposal, including returning to the field after stabilization and returning to the field after composting. Some are also incinerated. The amount of sludge from enterprise point source facilities is relatively small and the cost of disposal is relatively high. Basically, it is handled by the enterprise itself.

Depending on the nature of the sludge, the disposal methods are more diverse.

In general, the state of sludge treatment and disposal in my country is still in its infancy, and there is still a big gap with the international advanced level. With the continuous progress of environmental protection technology, China’s sludge treatment and disposal technology will gradually catch up with the development trend of international sludge disposal, from landfilling to incineration, land utilization, building materials utilization and other comprehensive utilization methods. .

With the increase in the amount of urban sewage discharge and the increase in treatment rate in my country, the output of sludge has increased significantly, and the treatment and disposal of sludge is facing new challenges. Therefore, there is an urgent need to seek solutions based on my country’s national conditions and the characteristics of sludge. The sludge should be turned into usable materials under the principles of “reduction, stabilization, harmlessness, and resource utilization” to realize resource recycling and promote the development of circular economy. As the country attaches great importance to environmental protection and increases its investment, sludge treatment and disposal technology will surely be further developed and improved.

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Brief Introduction to the Technology of Increasing Production of Preheater

Introduction to the technology of upgrading the production of the preheater of Luoyang Building Material and Architectural Design and Research Institute Co., Ltd.:

1. Transformation of kiln to increase speed
According to the requirement of increasing the output, without changing the diameter and length of the rotary kiln, by increasing the speed of the rotary kiln, so as to increase the firing output;

2. Reformation of calciner
By enlarging the diameter of the calciner and increasing the height of the calciner, the volume of the calciner is increased;

3. Expansion and transformation of smoke chamber
Increase the flow size of the smoke chamber, replace the dispersing disc to increase the feed volume, modify the kiln tail seal, and reduce the air flow;

4. Expansion and resistance reduction transformation
Enlarge the size of the inlet and outlet, reduce the wind speed, and reduce the resistance; increase the volume, increase the gas-solid heat exchange time; optimize the length of the inner cylinder, and reduce the outlet temperature;

5. Cross flow transformation
Through the transformation of the preheaters C1 and C2, the air outlet of the cyclone is changed to the lower air outlet, which increases the heat exchange time between the material and the wind, and forms the cross-flow heat exchange of the two-stage cyclone, thereby improving the heat exchange efficiency;

6. Reduce heat loss transformation
Adopt new nano material heat insulation board and nano heat insulation coating to reduce the heat dissipation of the cyclone and kiln shell.

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Thinking on the utilization of sludge resources under the epidemic situation

The resource utilization of sludge in the epidemic has always been a bottleneck. There are two key influencing factors: one is that the content of heavy metals in the sludge is unstable and may exceed the standard; the other is that the content of antibiotics in the sludge is relatively high. In fact, this third influencing factor still exists in sludge: microplastics.

The first is recognized by everyone. Due to the wide range and uncertainty of sewage sources, the content and types of heavy metals have obvious risks to the use of sludge land. This makes the policy for sludge agricultural use in the country unable to pass. Both limit the agricultural use of sludge—it has always been considered the best resource utilization direction of sludge, which can make full use of N, P, and Ka. However, it is also due to the prevention of heavy metals from the use of sludge land that the hazards of antibiotics and microplastics on land use have been paid attention to. Otherwise, these two unforeseen long-term hazards will be overshadowed by the short-term benefits of a large amount of sludge land use .

The risks of antibiotics and microplastics have been mentioned in few people in recent years. This is because the content of sludge is relatively small, but the characteristics of its accumulation in the human body are the same as those of heavy metals, and it also brings diseases to the human body. The uncertainty is much higher than that of heavy metals. Therefore, for some non-industrial cities’ sludge, composting and other land-use resourceization processes, the potential risks of antibiotics and microplastics poisoning the land cannot be avoided. China has always been the country with the largest per capita use of antibiotics, and the per capita use is 5 times that of the West. After passing through the digestive system and urinary system, it enters the sewage treatment plant. The sludge has the highest enrichment; the microplastics in the sewage plant sludge The main source is domestic washing sewage, which then enters the sewage treatment plant. Most of it is retained in the sludge due to the adsorption characteristics of the biochemical sludge, and some is discharged with the factory water. Therefore, antibiotics and microplastics can be directly absorbed and accumulated by plants after the sludge land is used, and finally enter the human food chain.

China has a large population and dense population, and the iterative spread of pollutants should be strictly controlled. Therefore, the resource utilization of sludge should be developed in the direction of biomass fuel. Through the sludge pyrolysis carbonization process, the pollution of heavy metals, antibiotics and microplastics is stopped here.

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Little knowledge about inorganic sludge and organic sludge

1. Where does the inorganic sludge come from?
Inorganic sludge exists in minerals, stone processing industries, municipal construction slurry, desulfurization and denitrification products of thermal power plants, etc.

2. How can we quickly distinguish the organic content of sludge?
1). The simplest and most direct method is to use the moisture content detector to measure the moisture content.
Take 3 grams of mud sample and put it in the tray to see the size. The large volume of sludge can basically be judged to be due to the presence of more organic substances such as suspended solids and fungi. The small size indicates that the inorganic content is high.

2). Look at the feel after drying
The original bulky sludge is severely reduced after drying, and it feels hard and brittle after being crushed with fingers, which can be judged as sludge with high organic content. If it feels soft, the organic content is medium. After drying, the volume does not change much, and it becomes ash after being crushed by fingers, which can basically be judged as inorganic sludge with very low organic matter.

3. How to distinguish the organic matter content of sewage?
The sewage we come into contact with is generally concentrated or precipitated sewage after anaerobic or aerobic treatment. The sewage has been treated by physicochemical or oxidation. You can use a measuring cup to fill the sewage and use time to analyze the state of the sewage, mud, moisture layer, and organic matter. High-content sewage is not easy to stratify or is very slow, medium-level sewage has slight stratification or obvious stratification, and inorganic sewage stratifies very quickly or the bottom of the sludge is not easy to agitate after sedimentation.

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Questions and answers on basic knowledge of sludge drying

Q: What types of sludge are generated by industry?
A: Sludge is a strange existence, divided by industry, including municipal, chemical, smelting, food processing, metal processing, pharmaceutical, printing and dying sludge, etc. It is not only to distinguish the types of sludge, but also to choose a reasonable treatment method from the analysis of the nature of the sludge. From a geographical point of view, taking municipal living sludge as an example, people in different regions have different living environments, conditions, and habits, and the nature of living sludge varies.

The rainwater in Jiangsu and Zhejiang is relatively abundant. A large amount of rainwater mixed with dust, soil, weeds, etc. flows into the pipe network of the sewage treatment unit together with sewage, forming a blend with municipal sewage. Therefore, the organic matter content of domestic sewage in these areas is low, generally around 50%. In areas such as Inner Mongolia, Ningxia, and Tibet, domestic sewage and rainwater generated from eating habits are relatively low, and the organic content of sewage is about 60%, and the organic matter in the pharmaceutical industry and food processing and breeding industry is even higher.

Q: Can you distinguish the nature of sludge from the organic matter content of sludge?
A: The nature of sludge is complex, and there are many classification methods. However, from the perspective of sludge analysis, the determination of the nature of sludge and the content of organic matter is an inevitable process for the service of subsequent processes. By identifying the nature of sludge and the content of organic matter, we can accurately select the type of agent used and the type of treatment.

Q: What is the organic matter content of sludge in various industries?
A: Organic sludge refers to sludge with organic matter as the main component. The main features are high organic content, perishable odor, fine particles, small specific gravity, high water content, and sludge often contains many phytonutrients, parasitic eggs, pathogenic microorganisms and so on. The industries with high organic content of sludge are pharmaceutical, food, animal husbandry, etc.; the organic sludge with medium content exists in municipal sewage, printing and dyeing industries; the industries with low organic content of sludge include chemical industry, river dredging and so on.

It should be noted that this is to distinguish the nature of sludge from the perspective of theory or industry experience. In actual operation, the properties of sludge produced by different sections, environments, and seasons of sewage treatment plants in different industries are diverse and complex. Therefore, the specific sludge properties must be distinguished in combination with actual conditions and experimental results.

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Sludge turned into a new material for environmental protection — brick making

“In addition to incineration of power generation and fertilizer production, dirty and smelly sludge can also be transformed into an environmentally friendly building material through automated production.” The construction of a comprehensive sludge production line allows more sludge to be comprehensively utilized. New technologies open up new ways of ecological governance.

“Slimy and smelly sludge is originally a pollutant and harms the environment, but it becomes a resource after harmless drying, and has a variety of uses.” Sludge drying is a key link, not only energy consumption and high cost , And improper handling will cause secondary pollution. If the kiln waste heat is used to achieve drying treatment in a sealed environment, good results can be achieved with waste treatment and energy saving.

Into the sludge brick production plant, you can’t smell the smell of sludge, only see one after another closed workshop, even the conveyor belt for material transportation is also installed in accordance with environmental standards Closed facilities. In the production workshop of the sludge storage tank, the black-pressed sludge was transported by a fully enclosed professional vehicle the night before. Enter the aging warehouse and aging. The aged materials are refined into mud. After various processes such as brick extruder, blank cutting machine, ring blank conveying machine, yard robot, etc., they finally enter the tunnel kiln for drying, preheating, roasting, Cool and burn into bricks.

In recent years, with the increase in the number of sewage treatment plants and the expansion and upgrading, the sewage treatment capacity has also increased significantly, and the resulting sludge volume has also increased.

According to environmental protection requirements, the scientific and standardized harmless treatment standards for sewage sludge are becoming more and more strict. In the past, simple harmless landfills are no longer applicable, and sludge disposal has embarked on the road of comprehensive utilization of resources . The brick and tile factory made sludge into ecological and environmentally friendly building materials through new technologies, which reduced the land and natural resource consumption occupied by the sludge landfill, and achieved the effects of saving energy, protecting the environment, improving economic benefits, and realizing solid waste disposal. “Win-win” approach.

All processes and processes for the comprehensive utilization of sludge disposal resources have corresponding environmental protection disposal facilities in operation. At present, 700 tons of sludge can be absorbed every day, and the comprehensive utilization rate of sludge reaches more than 99%. Under the high temperature firing of 950℃-1050℃, the organic matter in the sludge is carbonized, and the harmful heavy metals are solidified in the brick, which will not cause secondary pollution. The flue gas has been harmlessly treated in advance to achieve zero emissions, and the odor is sent to the terminal by the negative pressure pumping system for dust removal, deodorization and other treatments to meet the purification standard.

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Case Study: 3x140MW Biomass Coupling Retrofitting in a UK Power Plant

A British power plant is located in Ashington, England. In March 1972, a power plant in the United Kingdom was put into operation as a supporting power plant for local smelters. The installed capacity of the power plant is equipped with 3 pulverized coal furnace units, each equipped with a 140MW steam turbine generator, for a total of 420MW. The smelter needs 310 MW of electricity load, and the excess is sold to the British National Grid Corporation. After the smelter is sealed, all the electricity is sold to the grid.

With the trend towards decoalization in the UK power industry, the number of coal-fired power plants operating in the UK has decreased from more than 50 at peak to 8 in 2016. By 2019, the proportion of coal-to-electricity in the UK will be only 1.9%, and by 2020 only The remaining 2 coal-fired power plants operate intermittently. As one of the smallest power plants still operating in the UK, the main reason for this power plant to avoid being shut down is to follow the development trend and realize the conversion from coal to biomass fuel.

As one of the larger investment projects in the field of biomass power generation in the UK in recent years, this coal-fired power plant has experienced two stages of its biomass power generation, from close to 1% coal mill coupling in 2004, to 100 after 2017 % Biomass fuel conversion.

In 2003, as the United Kingdom began to encourage large-scale coal-fired power plants with biomass-coupled power generation, this plant also began its biomass-coupled power generation process. In 2004, the power plant adopted a biomass direct combustion coupling technology route with the lowest cost and the lowest biomass coupling ratio-coal mill coupling, that is, biomass fuel and coal are powdered together in the coal grinding mechanism. The plant uses 3 different biomass fuels: sawdust, biomass pellets and olive residue. In 2004, about 11,000 tons of biomass fuel were used, and the biomass coupling ratio was less than 1%.

In 2016, the power plant began the conversion of 100% biomass fuel for three 140MW pulverized coal furnace units. After the design, manufacture and equipment supply transformation of its biomass fuel delivery system were completed, this power plant became a 3*140MW pure biomass fuel-fired power plant, consuming approximately 1.4 million tons of biomass fuel annually. Since the conversion of biomass fuel, due to the clean combustion characteristics of biomass fuel, the NOx emissions of boilers have been reduced by 2/3, and the SOx emissions have been reduced by more than 90%.

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What are the possible directions and possibilities for China’s biomass energy industry

Unlike the particularity of garbage and livestock manure, biomass fuel for agricultural and forestry waste is most likely to move to a large-scale, high-efficiency, low-cost large-scale coal-fired power plant biomass-coupled power generation model.

In terms of technology and operation, because European countries have nearly 20 years of experience in large-scale coal-fired power plant biomass-coupled power generation, we can absorb and digest it and get out of the high-efficiency low-cost biomass power generation route that suits my country’s national conditions.

In terms of electricity market, in 2019 Finland has less than 1% of China’s electricity and Denmark has less than 0.5% of China’s electricity, and the population of both countries is only more than 5 million. In a country where the population and power supply are much smaller than China, no matter which mode of biomass power generation is used, it will not have much impact on its industry and country, and even if Finland and Denmark are small European countries, Also after 2000, the route of coupled biomass power generation was selected. For a large country like China, hundreds of low-efficiency, high-cost, small-scale solid waste treatment biomass power plants operate continuously at full load, for a long time, and with high subsidies, while a larger number of high-parameter high-efficiency Coal-fired power plants operate or shut down at low loads, which is itself a low-efficiency mix of power resources.

In terms of biomass fuel, according to China’s agricultural and forestry waste biomass resources equivalent to 460 million tons of standard coal, 10% of the amount is processed in the mode of small solid waste. The power consumption of standard coal is 470g/kwh, which can provide 97.87 billion yuan to the power grid. KWh, and the current state financial subsidies for all biomass power generation categories are only 14.24 billion kWh. Equivalent to the amount of biomass fuel, it is only 6.694 million tons of standard coal calorific value biomass fuel, which is less than 1.5% of the country’s total agricultural and forestry waste. More biomass fuels cannot be sold to biomass power plants after they are collected, or cannot be subsidized in time after being sold for power generation.

In terms of power structure, according to data released by the National Energy Administration, coal power in my country’s power structure will still exceed 2/3 in 2019, compared with 29.1% in Germany, 23.5% in the US, 1.9% in the UK, and 0.3% in France. my country’s power structure requires a higher proportion of clean and renewable energy, not just wind power and solar energy.

In the coal power industry, according to data released by the National Energy Administration, the annual utilization hours of coal power in my country in 2019 are less than 4,300 hours. If a coal-fired power plant burns part of the biomass fuel, it will help to increase the utilization hours and load of the coal-fired power plant and improve the power plant’s operating status.

Combined with appropriate industry policies, large-scale coal-fired power plant biomass-coupled power generation will take my country’s biomass power generation industry to a whole new level.

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Thinking about green sustainable restoration of farmland

  • Select the best restoration technology through sustainability evaluation

Different regions in my country have different climatic conditions, soil properties, and sources of farmland pollution, which may lead to different best ways to rehabilitate contaminated farmland. Sustainability assessment can be used to select the best remediation technology. At the same time, when designing a restoration plan for a specific technology, there are also various aspects of sustainability considerations. For example, when solidification or stabilization technology is adopted, it is necessary to prevent the use of passivating agents that damage soil fertility and affect the growth of crops; when using phytoremediation, it is necessary to properly dispose of heavy metal-rich plants to prevent secondary pollution. On the other hand, the experience of farmland restoration in other regions or countries is also worth learning from. For example, Japan is one of the earliest countries to carry out remediation of farmland contaminated soil. Guest soil methods, chemical remediation, plant extraction, and crop rotation are all commonly used remediation methods.

  • Encourage public participation in remediation of farmland contaminated soil

It can be achieved by hiring local farmers to participate in the remediation of farmland contaminated soil, and at the same time it can save remediation expenses and has huge social and economic benefits. Phytoremediation is the most frequently used technology for remediation of farmland contaminated soil in my country. At present, there have been successful cases of farmers participating in remediation, and the goals of pollution remediation and farmers’ income generation have been achieved. There are projects that specifically investigate farmers’ lifestyles and the tendency to grow crop types to design restoration programs that fit farmers’ habits. In addition, farmers can be encouraged to actively participate in restoration through economic subsidies or a combination of energy plant cultivation and restoration.

  • Strengthen pollution prevention

From 1997 to 2014, the proportion of farmland pollution in my country increased from 7.3% to 19.4%. Historical experience shows that pollution prevention is a top priority for sustainable environmental management. Failure to take control measures on pollution sources will cause farmland pollution prevention and control work to continually circulate on the road of pollution first and then treatment, and even fail to achieve the standard of restoration. The Action Plan for Prevention and Control of Soil Pollution puts forward the requirements for strengthening the supervision of pollution sources and doing a good job in preventing soil pollution. However, improving the farmland pollution supervision system requires the joint efforts of multiple departments. For example, in order to promote high-efficiency, low-toxicity and low-residue pesticides, the Ministry of Agriculture needs to promulgate relevant standards and incentive policies.

  • Economic policies promote the remediation of farmland contaminated soil

Most of the farmland pollution in China occurs in economically underdeveloped agricultural areas. Soil restoration of contaminated farmland for the purpose of restoring soil fertility and ensuring crop production does not affect the commercial value of the land. Land appreciation is the main commercial driving force for the restoration of contaminated sites, leading to funding More flows to industrial contaminated sites for remediation, which has hindered the economic recovery of contaminated farmland soil. Case studies have shown that the cost of remediation of farmland contaminated soil can exceed the sum of 30 years of benefits from growing crops in the same area of ​​farmland. However, the importance of repairing large areas of contaminated farmland is self-evident. my country is a country with a large population, and it is extremely important to ensure adequate food supply and food safety at the national level. However, with the development of urbanization, my country’s dependence on food imports has become stronger and stronger. Some studies have shown that my country’s food shortage may reach 100 million tons by 2020. From the perspectives of food safety, increased grain production, and farmers’ income generation, the indirect benefits of farmland contaminated soil remediation are far greater than the direct benefits. Therefore, it is necessary to provide a driving force for remediation of farmland contaminated soil through more economic policy incentives.

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