The main way for cement kiln to co-process sludge or into future sludge treatment!

According to the technical level and development trend of the target industry, the cement kiln co-processing sludge is the best way to dispose of sludge. In the future, sludge cement kiln treatment will be the main treatment method for sludge treatment.

First, the significance of sludge treatment

If the sludge is not treated in time, it will lead to a large backlog of sludge in the sewage treatment plant, which may cause a total collapse of the sewage treatment system, which will make the efforts to control the river for many years to be lost. Therefore, the construction of sludge treatment and disposal facilities is an indispensable part of urban infrastructure construction and an important environmental protection project for thousands of households.

Second, the status quo and process of co-processing of cement kiln

2.1 Status of sludge treatment

2.1.1 Current status of sludge treatment in cement kiln

The traditional treatment methods of sludge mainly include land use, landfill and incineration. With the improvement of environmental requirements, traditional methods cannot meet environmental protection requirements. Sludge disposal is moving towards harmlessness, reduction and resource utilization. The use of cement kiln to co-process sludge is an economically viable resource treatment.

Related studies have shown that the chemical properties of municipal sludge are basically similar to those used in cement production. Compared with ordinary Portland cement, the cement produced by sludge and sludge incineration ash is similar in terms of particle size and relative density, and is also good in stability, expansion density and curing time. The treatment of municipal sludge by cement rotary kiln not only has the characteristics of volume reduction and reduction of incineration method. Moreover, the residue after combustion is calcined and solidified, and becomes a part of cement clinker. It is a kind of cement production route that has the best of both worlds without secondary treatment.

2.1.2 Principle of cement co-processing incineration

The experimental results show that the optimal sludge addition method for cement kiln co-processing sludge is to be added to the decomposition furnace. The maximum dosage of sludge should be controlled in 6% cement plant rotary incinerator under normal operating conditions. The temperature is 1450 degrees Celsius, the residence time of the material in the furnace is 30 to 40 minutes, and the residence time of the smoke generated during combustion in the furnace temperature above 1300 degrees Celsius is greater than 4 seconds. The harmful organic matter in the sludge in the kiln can be fully burned, the incineration rate can be 99.999%, and organic pollutants such as dioxins are completely decomposed.

2.1.3 Disposal plan

There are two general methods for disposing waste in cement kilns:

One is to add ingredients from the raw mill. Generally, inorganic wastes such as fly ash and slag are disposed by this method, and the advantage is that after the raw material homogenization ingredients are controllable, the influence on the clinker firing system is small. However, due to the high temperature in the raw mill (about 200 ° C), it may cause the volatilization of organic pollutants in the sludge, so the addition of raw material ingredients has not been widely adopted.

The second is to add from the preheater decomposition furnace. Although this disposal scheme has certain adverse effects on production, it is suitable for the disposal of materials containing organic pollutants (especially volatile organic pollutants). Because the sludge contains a certain amount of volatile matter, it is selected to be added from the preheater decomposing furnace, and at the same time, the gas flow rate above the shrinkage chamber of the soot chamber is considered to be fast, and finally the sludge addition point is selected above the sludge chamber.

The sludge enters the cement rotary kiln from the kiln exhaust chamber, and the gas (>800 °C) residence time is more than 20s, which can completely ensure the complete combustion and complete decomposition of organic pollutants in the sludge. Under the high temperature conditions of the cement kiln, the organic pollutants in the sludge are rapidly evaporated and vaporized, and the high-temperature airflow is in full contact with the alkaline materials with high temperature, high fineness, high concentration, high adsorption and high uniformity, effectively suppressing The discharge of acidic substances makes the organic chemical components such as SO2 and Cl and the inorganic salts fixed.

The clinker rate control index has no change before and after treatment. After the initial batching calculation, after adding about 6% of sludge, the alkali can be partially offset by the method of reducing the alkali content of other raw materials, so that the cement clinker can be made. The medium sodium equivalent reached the requirement of internal control index ≤0.8%. In order to ensure the quality of cement products, reduce the impact of sludge moisture on the cement kiln working conditions, reduce the cost of sludge disposal, and consider the cement production plan and quality and safety hazards, in the general disposal process, according to less than 6% of sludge added The amount is disposed.

2.2 Process route

The entire sludge transport system consists of a sludge storage system, a pumping system and a PLC automatic control system.

The raw sludge produced by the water treatment plant is loaded into the cement plant by the automobile and poured into the closed sludge storage bin. At the same time, the odor in the sludge storage bin is discharged through the pipeline to the fan inlet of the grate cooler, and acts as a fan. The lower row is burned in the rotary kiln. The sludge enters the feeding end of the paste pump through the discharge gate and the variable frequency feed screw, and continuously enters the sludge conveying pipeline under the extrusion of the two plungers of the paste pump, and is uniformly sent into the furnace high temperature zone through the middle feeder of the kiln. combustion. The adjustment of the delivery volume can be achieved by adjusting the rotational speed of the feed screw and the flow rate of the paste pump. All control is controlled by PLC microcomputer, and can be networked with the furnace control system. The sludge conveying volume can be remotely steplessly adjusted, and the whole process can be unattended.

Third, cement kiln synergistic treatment of sludge advantages

The landfill and composting of sludge requires a large amount of land occupation, and there are secondary pollution hazards and geological risks. Specially built incinerators have high investment, high energy consumption, and will produce hazardous waste such as fly ash and slag, and it is difficult to completely decompose harmful gases. In contrast, cement kiln co-processing sludge technology has many advantages in terms of harmlessness, comprehensive utilization of resources and economy;

1. Finally converted into cement clinker products, no waste left;

2. The cement kiln has large heat capacity, high temperature and stability, completely eliminates harmful gases, and can process sludge in large quantities;

3. Do not occupy land resources;

4. Make full use of primary energy and resources;

5. The investment period is short and the construction period is short.

Fourth, the conclusion

In short, according to the current industrial technology level and development trend, cement kiln co-processing sludge is the best way to dispose of sludge, and environmental protection and cement industry have also paid great attention. Now some cement companies are actively exploring accumulation. Operating experience. In the future, sludge cement kiln treatment will be the main treatment method for sludge treatment.

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Suspension calcination lime will be the next stage of rotary kiln lime production

Rotary kiln lime production line is a semi-automatic lime production line composed of several separate equipment. The main power part is industrial power consumption. The operation principle belongs to batch production of chemical reaction industry. It belongs to the sunrise industry in the current building materials industry. Domestic lime kiln manufacturers have made China’s lime kiln technology rank first in the world through continuous research and development and improvement. Luoyang Building Material and Architectural Design and Research Institute is not satisfied with the existing kiln lime production technology. The Suspension Calcination lime production technology independently developed has changed the existing rotary kiln calcination technology. It not only maintains the advantages of the existing lime kiln technology, but also solves the shortcomings of the rotary kiln such as large area and large heat loss. It is one of the most advanced production technology at present. In view of two different production processes, the main equipment components are introduced respectively.

  • The main components of rotary kiln lime production line are as follows:

Preheater: Preheater, as its name implies, preheat limestone raw materials. The whole wind power system of limestone kiln moves towards the kiln tail through the kiln head. The inlet and outlet of the lime kiln are at the kiln tail (kiln top), so the preheater of the lime rotary kiln will be installed at the kiln tail. The limestone will be heated to about 800 degrees Celsius through the kiln tail gas to volatilize limestone impurities and reach lime. The surface of the stone is decomposed preliminarily.

Rotary kiln: Calcination core equipment of lime kiln production line, which can heat lime to 1250 degrees Celsius so that calcium carbonate in limestone can be quickly decomposed into calcium oxide and carbon dioxide.

Cooler: Calcium oxide decomposed from the lime rotary kiln is still in a high temperature and red-hot state. The temperature of lime is reduced to no more than 60 degrees Celsius by means of cold air heat transfer. At the same time, the cold air is replaced by hot air and returned to the lime rotary kiln.

  • The main components of suspension calcining lime production line are as follows:

Three-stage suspension preheating system: through the first cyclone preheater, the second preheating ascending flue, the second cyclone preheater, the third preheating ascending flue and the third cyclone preheater, the suspended powdery limestone is preheated by the exhausted hot air.

Calcinator system: CaCO_3 is decomposed into CaO and CO_2 after thorough decomposition of calcination temperature in the calciner. Activated lime after calcination enters the cyclone separator with hot air flow.

Multi-stage cyclone cooling system: the separated active lime powder flows through the pipeline into the graded cooling device, through heat exchange and cooling with the incoming air, enters the ash outlet tube, and is fed into the finished product warehouse. After preheating in this stage, the air enters the roaster for combustion.

Advanced technology is the power source to promote the development of lime industry. Luoyang Building Material and Architectural Design and Research Institute is constantly studying and innovating. The production process of suspension calcined lime will certainly bring lime production to a new stage.

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Traditional Vertical Kiln Process Lime and Suspension Calcination Process Lime

The traditional lime calcining process is the lime shaft kiln. At present, the lime production enterprises are affected by many factors such as investment, site and so on. At present, the lime shaft kiln is one of the most preferred preparation processes. With the progress of science and technology and the development of the times, the lime industry is also constantly seeking new solutions. Luoyang Building Material and Architectural Design and Search Institute will gradually enter the public’s vision by using mature cement preheater technology for reference and developing a new suspension calcining active lime technology. Following is a comparative introduction of two different lime calcination processes, so that you can have a simple understanding of the two processes.

  • Summary of vertical kiln lime technology:

The loader loads the qualified raw fuel into the limestone bin and the coal bin respectively, and then transports it to the mixing bin through the conveyor belt. The raw fuel is weighed accurately by electronic scale according to the set value. The mixture is evenly fed by vibrating feeder, and then transported to the hopper on the top of the furnace by hoisting truck. The distribution in the furnace is completed by the spiral case distributor on the top of the furnace. The burden moves downward slowly by self-weight and passes through the preheating zone, the forging zone and the cooling zone one after another. In the process of burden decreasing, there is complex heat exchange with the hot rising gas flow, accompanied by the decomposition of limestone and the growth of lime grains. When the whole process is completed, it is also cooled by combustion-supporting air to 40-60 C, and then unloaded by the unloader to the finished product belt outside the furnace without air leakage. Lime is transported to finished silo by multi-bucket hoist. If screening is required, the first screening is carried out and then loaded into a block ash bin and a fly ash bin.

  • Summary of Suspension Calcination lime technology:

Limestone is crushed and grinded to a certain fineness by its good grindability, and then fed into the suspension calcination system according to the required feeding amount. The Suspension Calcination system of active lime consists of three-stage suspension preheating system, fluidized calciner and multi-stage cyclone cooling system. Feed raw meal is preheated by preheating system to 600 C and calcined in suspension fluidized calciner. Limestone powder is heated and decomposed to form lime powder here. After separation by gas separator, about 900 C flue gas enters the preheating system for raw meal powder. The burned lime powder is cooled by multi-stage cyclone cooling system. The cooled products are sent to storage for intensive packaging (or bulk loading). After leaving the factory, the air is heated to about 400 C and enters the calciner to be used as combustion-supporting air. The flue gas discharged after dust removal meets the discharge standard.

Although the traditional vertical kiln production process has less investment, the inherent shortcomings are also the problems faced by major lime production enterprises, such as: 1. Limestone particle size is limited, raw meal burning rate is high; 2. higher operating level requirements; 3. If the fuel contains high sulfur, the finished product contains high sulfur. If these problems need to be solved, we have to rely on new technology and process, Suspension Calcination lime production process, not only can solve the above problems, but also can meet the current high-yield, low-consumption, environmental protection and energy saving and related national policy requirements, promote the iterative upgrading of the industrial chain.

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Waste heat utilization technology of lime kiln

To improve the thermal efficiency of the kiln, we should not only reduce the heat loss of the kiln, but also make rational use of the waste heat generated in the kiln production process. The waste heat generated in the production process of lime kiln is mainly waste gas from kiln, heat dissipation of kiln body and physical heat of lime from kiln. The sum of these waste heat accounts for 40%-50% of the heat consumption of kiln. Therefore, the rational utilization of waste heat is very important for energy saving and consumption reduction, and for improving the thermal efficiency of kilns.

Cement waste heat utilization

1. Utilization Technology of Waste Heat from Kiln Exhaust Gas

Lime kiln exhaust temperature is high, the amount of flue gas is large, direct emissions will cause a large amount of energy waste. In practice, in order to protect downstream dust collectors and dust removal fans, it is often necessary to incorporate a large number of cold air to cool down, further increase the load of the fan, and waste a lot of electric energy. Therefore, making full use of waste heat from kiln exhaust gas is an important way to save energy and reduce consumption. At present, there are several ways to utilize waste heat from kiln exhaust gas:

(1) Preheating combustion-supporting air, fuel and biomass with exhaust gas from kiln. The high-temperature flue gas discharged from lime kiln can be preheated by heat exchange for combustion-supporting air and fuel, which can not only reduce the exhaust gas temperature, but also increase the physical sensible heat of the gas entering the kiln, increase the combustion temperature and reduce fuel consumption, thus saving energy and reducing consumption. This method has been widely used in rotary kilns and various vertical kilns. In addition, the physical sensible heat of kiln exhaust gas can be used to preheat raw meal to the greatest extent by formulating a reasonable feeding and discharging system. For example, according to the operation characteristics of double-chamber shaft kiln, reasonable setting of the feeding times of each calcination cycle can ensure that the added materials can absorb the sensible heat of the exhaust gas in the calcination cycle evenly without the phenomenon of excessive temperature of the exhaust gas.

(2) Drying materials with waste gas from kiln. The lime kiln with pulverized coal as fuel is usually equipped with a special pulverized coal preparation system, which requires a lot of heat to dry pulverized coal. On the one hand, the exhaust gas from lime kiln has large amount of flue gas, high temperature and enough heat to meet the needs of coal powder preparation, on the other hand, the oxygen content is low, which can ensure the safety of coal powder preparation system. Therefore, the use of lime kiln tail gas as a drying medium for pulverized coal has been widely used. In addition, in some factories and mines, the kiln exhaust gas is used for blast furnace slag drying and powder making, as well as for orchid charcoal drying, which has achieved comprehensive benefits of energy saving and environmental protection.

(3) Utilizing the exhaust gas from kiln to provide heating and bathing in the factory area through high-efficiency flue gas-water heat exchanger. Heat pipe type flue gas-soft water heat exchanger was used to recover waste heat from tail gas of lime rotary kiln. That is to say, a heat pipe type flue gas-soft water heat exchanger is set up on the tail pipe line between the preheater and the dust collector of rotary kiln. Soft water is used as the heat medium to heat the tail gas of rotary kiln through the heat pipe type flue gas-soft water. Most of the hot soft water after heat transfer is directly used for heating in the plant area, and a small part is used for the secondary heat transfer of soft water-bath water, which is supplied by the heat exchange station and recycled. After cooling, the exhaust gas is sent to the dust collector for purification, and then discharged into the atmosphere by the smoke exhauster. The advantages of this scheme are low requirement for flue gas temperature, high heat transfer efficiency, large heat recovery, simple system configuration, stable and reliable operation.

(4) Utilizing the waste gas from kiln to develop waste heat power generation technology. Luoyang Building Material Architectural Design and Research Institute is exploring waste heat power generation technology suitable for lime kiln, drawing on the successful experience of waste heat power generation of cement kiln. The waste gas temperature of cement kiln is relatively high, and high thermal efficiency can be obtained by using double pressure steam system. However, the waste gas temperature of lime kiln is relatively low, which belongs to pure low temperature waste heat. Therefore, the waste heat power generation of lime kiln still needs a lot of theoretical demonstration and experimental research. For large and medium-sized lime rotary kilns with exhaust gas greater than 100,000 Nm3/h, the development of waste gas waste heat power generation has entered the stage of demonstration project. The technical scheme of using waste heat to generate low parameter steam to drive kiln tail flue gas exhauster by steam turbine has also been determined.

2. Recycling and Utilization of Heat Dissipation from Lime Kiln

The heat dissipation of lime kiln body mainly dissipates into the atmosphere in the form of radiation heat, which not only wastes energy, but also affects the surrounding environment. However, due to the wide distribution of the heat dissipation surface of the lime kiln body and the large number of auxiliary equipment around the kiln body, it is difficult to recover and utilize the radiation heat of the kiln body. At present, the economy and rationality of the technical scheme are still in the stage of research and demonstration when the kiln body radiation heat is replaced by hot water for heating and bathing.

3. Utilization of waste heat of lime from kiln

The physical heat of the lime from the kiln is determined by the lime cooling system of the kiln. If the cooling effect is good, the temperature of the lime from the kiln is low, and more heat is brought into the kiln again by the cooling air to participate in combustion. Therefore, the structure of cooling belt or cooling device of lime kiln plays an important role in the utilization of waste heat of lime from kiln. By optimizing and improving the vertical cooler system of rotary kiln and improving the air distribution system of cooling air, the cooling effect of the cooler can be significantly improved and the discharge temperature can be reduced. In the shaft kiln system, taking the double-chamber shaft kiln as an example, its lime cooling device adopts central and peripheral annular cooling, and the central cooling air cap adopts tower structure to ensure uniform and smooth ventilation, so that the cooling air can better absorb the physical sensible heat of lime.

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Wuhan customers come to our design institute to exchange views on sludge treatment projects

On May 30, Wei, General Manager of Wuhan Mingchuangxinghai Eco-technology Co., Ltd. and two of them visited and visited our institute. They exchanged and discussed with the leaders of our Institute on the project of producing ceramsite from sludge wastes.

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Physical Properties of Municipal Solid Waste

As municipal solid waste (MSW) is a mixture of heterogeneous and diverse substances, it does not have its own specific internal structure and external characteristics as a single substance, so it does not have specific physical properties. Its physical properties often vary with the properties and proportions of its constituents.

In the process of management and disposal of municipal solid waste, three physical properties are often involved: bulk density, void fraction and moisture content.

(1) bulk density. In the natural state, the mass per unit volume of municipal solid waste is called its bulk density, expressed as kg/m3 or t/m3. The bulk density of garbage varies with the composition of garbage, compaction degree, biochemical degradation process and the way of cleaning and handling. Therefore, the bulk density of garbage can be divided into natural bulk density, loading bulk density of garbage truck and landfill bulk density. The bulk density of garbage is one of the important characteristics of garbage. It is an indispensable parameter for selecting and designing storage containers, collecting and transporting machines or pipelines, calculating and determining the size of disposal structures and landfills. By analyzing the survey data of refuse bulk density provided by 12 cities in China in 1990, it is concluded that the natural bulk density of refuse is (0.53 + 0.26) t/m3, the loading capacity of garbage truck is about 0.8 t/m3, and the landfill bulk density is 1 t/m3. Generally speaking, large cities with developed economy and high living standards have high content of light organic matter and low bulk density, which is about 0.45t/m3; while small and medium-sized cities, especially northern cities, have high content of heavy inorganic matter (mainly ash) and high bulk density, which is about 0.6-0.8t/m3. The Natural bulk density of garbage in some small and medium-sized cities in the North even reaches 1.0t/m3. The bulk density of garbage in industrial developed countries is 0.10-0.15t/m3, that in middle-income countries is 0.20-0,40t/m3 and that in low-income countries is 0.250-0.50t/m3.

(2) Void fraction. Void fraction is the proportion of void volume between materials in garbage to garbage storage volume. It is a characterization parameter of garbage ventilation capacity and is related to garbage bulk density. The void fraction of garbage with small bulk density is generally larger. The larger the void ratio, the larger the void between the material and the material, the larger the ventilation cross-section area of the material, the smaller the flow resistance of the air correspondingly, and the more conducive to the ventilation of garbage. Therefore, void fraction is widely used in compost oxygen supply ventilation and resistance calculation of forced ventilation of refuse in incinerator and determination of parameters of ventilator; the main factors affecting void fraction are material size, material strength and moisture content. The smaller the material size, the more voids; the better the material structure strength, the larger the average void volume, which will lead to the increase of the void fraction of garbage. Water will occupy the voids of materials and affect the structural strength of materials, resulting in the reduction of voids.

(3) Water content. Moisture is an important parameter in garbage disposal. Its value directly affects the normal process of landfill, refuse composting and incineration. In the process of garbage separation, moisture in garbage will also affect the screening of garbage, air separation and material transportation.
The pyrolysis and gasification process developed by Luoyang Building Materials Architectural Design and Research Institute can directly treat the original unsorted garbage, and even the garbage with high moisture content can be directly treated for power generation.
The moisture content of municipal solid waste is defined as the moisture content of the unit mass waste. It is a relatively changeable physical quantity expressed by the mass fraction (%). The moisture content of a certain component of municipal solid waste often changes with the change of humidity in the air, and is related to the moisture content of man-made mixed people. The variation range is 11% – 53% (typical value is 15%, 40%). According to the investigation, the main factors affecting the moisture content of garbage are the content of animals and plants and inorganic substances in garbage. When the content of plants and animals in garbage is high and the content of inorganic substances is low, the moisture content of garbage is high, whereas the moisture content of garbage is low, that is, the moisture content of garbage is proportional to the organic content.

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Source and Composition of Municipal Domestic Waste

The main components of municipal solid waste include kitchen waste, waste paper, waste plastics, waste fabrics, waste metal, waste glass and ceramic fragments, brick and tile residue, waste batteries, waste household appliances, etc. They mainly come from urban households, urban commerce, catering industry, Hotel industry, tourism, service industry, municipal sanitation industry, transportation industry, street cleaning garbage, construction waste, culture and education. Sanitation and administrative institutions, industrial enterprises, sewage sludge treatment and other scattered garbage (Note: The garbage treatment system developed by Luoyang Building Materials Architectural Design Research and Development can cover the above-mentioned various types of garbage and dispose of them).
The main factors affecting the composition of municipal solid waste are the quality of life and habits of residents, season, climate and so on. Municipal solid waste (MSW) comes mostly from residents’living and consumption, municipal construction and maintenance, commercial activities, urban landscaping and suburban farming, production, medical treatment and tourism and entertainment places, including general garbage, kitchen waste of human and animal manure, sludge, garbage residue and dust. Regarding the factors mentioned above, it is usually recommended to find a professional company to dispose of the waste. Luoyang Building Material Architectural Design and Research Institute is a professional research institute, which has made a long-term in-depth research and engineering development on garbage gasification and power generation technology. The garbage gasification technology developed now has the characteristics of high efficiency and continuity, gas De-Coking and purification, automatic control of one-key operation, strong adaptability, modular design, zero emission and waste heat utilization. It is one of the earliest professional research institutes in China.
Municipal solid waste (MSW) is produced in large quantities and is increasing rapidly. The main sources of MSW are listed in Table 1-1. Statistics show that the production of municipal solid waste is directly proportional to the size of the city, the growth rate of the population and the living standard of the city residents. In different regions, the composition of municipal solid waste is different due to the unbalanced development of industry, the different degree of urban modernization, and the influence of habits, but it can be divided into inorganic and organic substances in general. Detailed classification can be found in Table 1-2.

Table 1-1 Composition Sources of Municipal Solid Waste

Sources of municipal solid waste Composition of municipal solid waste
Resident Life Food garbage, waste paper, glass, metal, plastic porcelains, ash, plants, electricity, yellow stool, miscellaneous soil, etc.
Commercial and municipal office Ditto. There are also building materials waste, flammable, infectious, radioactive waste, automobiles, tires, batteries, electrical appliances, appliances, etc.
City Slope Construction and Maintenance Dirty soil, debris, branches and leaves, dead agricultural sticks, vegetables, fruits, weeds, stools, dead livestock, etc.
Medical treatment Metals, radioactive materials, dust, sludge, building materials for appliances, cotton yarn, etc.

Table 1-2 Urban Domestic Waste Classification Table

Classification of Municipal Domestic Waste Item Composition of Municipal Solid Waste
Inorganic substances Glass Fragments, bottles, tubes, mirrors, instruments, balls, toys, etc.
Metal Fragments, wire, cans, parts, toys, pots, etc.
Brick and tile Stones, tiles, cement blocks, cylinders, porcelains, lime flakes
Organic compound stove ash Slag, dust, etc
Other Waste electric filtration, gypsum, etc.
Plastic Films, bottles, tubes, bags, toy shoes, tapes, wheels, etc.
Papel type Packing cartons, stationery, toilet paper, newspapers, cigarette paper, etc.
Fibers type Worn clothes, cloth shoes, etc
Organic compound Vegetables, fruits, animal corpses and hair, waste, bamboo and wood products, etc.
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Technical comparison between biomass direct combustion power generation and biomass gasification power generation

Biomass direct combustion power generation technology refers to the direct injection of biomass into the boiler for combustion, heating and gasification of water, and the high temperature and high pressure steam generated to drive the steam turbine to work, and finally drive the engine to generate electricity.

Biomass gasification power generation technology is to convert various low calorific value solid biomass into gas, extract hydrocarbon materials, convert them into biomass gas, and then enter the gas generator set to generate electricity after purification and cooling.

The Luoyang Building Material and Architectural Design and Research Institute has researched and developed the material gasification power generation units as the research object. After years of painstaking research, it has developed a modular and efficient biomass gasification power generation units with many patented technologies. It has opened up new avenues for the comprehensive utilization of biomass.

Technical comparison between biomass direct combustion power generation and biomass gasification power generation

Technical comparison between biomass direct combustion power generation and biomass gasification power generation.

Item Direct combustion power generation technology Biomass gasification power generation technology
Environmental protection Flue gas needs desulfurization and denitrification, and there is a risk of excessive atmospheric pollutants such as NOx and SO2; there is a risk of dioxin exceeding the standard; Clean gas combustion, there is no risk of excessive atmospheric pollutants such as NOx and SO2 in the flue gas; there is no condition for dioxin formation;
Power generation efficiency Biomass gasification power generation is 1.5 times that of direct combustion power generation;
Adaptability to different power generation scales The economic scale of a single machine generally requires not less than 1 MW, but is limited by the concentration of biomass, and the scale of a single machine is generally less than 25 MW; The characteristics of biomass in China are huge, but the distribution is relatively scattered, and collection and transportation are difficult; the scale of single-machine economy is generally not less than 0.5MW; generally, medium-scale (1~5MW) biomass gasification power generation is adopted, and the adaptability is strong;
Reliability of equipment operation The ashing, slag inclusion and high temperature corrosion caused by alkali metals are the three major problems currently existing in biomass direct combustion power generation; The two core technologies are gasification and decoking; the biomass gasification power generation device using Finnish and German technology is reliable in operation;
Ash usage 1) Grass ash can be used as farmyard manure;

2) Part of the raw materials used as building materials;

 1) Broad market prospects with alternative potash;

2) Processed into biomass activated carbon and sold as a high value-added adsorbent products;
Overall evaluation Biomass gasification, as a power generation technology suitable for national conditions, is the development direction for the effective use of biomass energy in China in the future.
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Biomass energy characteristics

Biomass refers to various organisms formed by photosynthesis, including all animals and plants and microorganisms. These organisms are formed directly or indirectly through the photosynthesis of green plants and are converted into conventional solid, liquid and gaseous fuels in green plants. Biomass energy is inexhaustible and inexhaustible. It is a renewable new energy source. Driven by the booming new energy market, biomass energy utilization has received extensive attention, demonstrating enormous resource potential, but biomass power generation still faces many problems. Luoyang Building Material and Architectural Design and Research Institute has faced difficulties and thoroughly studied the problems of the recovery and utilization of biomass energy. The biomass gasification power generation units developed can efficiently utilize biomass energy for gasification and power generation. The biomass gasification power generation device adopts modular design, is convenient for transportation and installation, compact in structure, safe and reliable, stable in operation and strong in adaptability, and opens up a new way to reduce the pollution caused by energy consumption to the environment.

Biomass energy has the following characteristics:
1.Renewability
Biomass is a renewable energy source that is formed by photosynthesis of plants. Biomass energy can guarantee the sustainable use of energy, which is equivalent to wind energy and solar energy;
2. Low pollution
The amount of SO and NO produced by biomass in the combustion process is less, because the sulfur content and nitrogen content are low, so the net carbon dioxide emission to the atmosphere is close to zero, which can effectively reduce the greenhouse effect;
3. Wide distribution
Biomass energy is distributed in every corner of the earth, and areas with biological growth such as leaves and plant stems, especially in areas lacking coal, are an ideal energy supplement;
4. Rich resources
The total amount of biomass fuel is very rich, second only to coal, oil and natural gas. Biomass is the fourth largest energy source in the world. The annual production of biomass energy is equivalent to 10 times the current total energy consumption in the world, far exceeding the total energy demand in the world. Biologists estimate that the ocean produces about 50 billion tons of biomass per year in the ocean; the land produces two to three times as much biomass as the ocean every year; and with the development of agroforestry, especially the promotion of charcoal forests, there will be more and more material resources. By 2020, China’s biomass resources that can be developed into energy are expected to reach 800 million tons.

In the face of such a huge biomass resource, how to develop and utilize it effectively? uoyang Building Material and Architectural Design and Research Institute will give you the most economical and reasonable solution according to the needs of customers. You are welcome to come to our institute for exchange and discussion.

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Relevant Technology and Key Points of Waste Leachate Treatment

Landfill leachate mainly comes from the water holding capacity of garbage itself, the liquid produced by garbage decomposition and the rainwater brought in during garbage collection and transportation. Landfill leachate has the characteristics of high ammonia nitrogen content, high concentration of organic pollutants, high salinity, complex components, large fluctuation range of water quality and quantity, which makes it difficult to treat.

I. Characteristics of Landfill Leachate

1. High concentration of organic pollutants and good biodegradability

The CODcr of landfill leachate is as high as 20 000-60 000 mg/L and BOD5 is 10 000-30 000 mg/L, which belongs to high concentration organic wastewater. Most of the organic compounds in leachate are soluble organic compounds. About 90% of the soluble organic carbon in leachate is composed of short-chain volatile fatty acids. The main components are acetic acid, propionic acid and butyric acid, followed by gray yellow enzymatic acid with polycarboxyl and aromatic carboxyl groups. Therefore, the biodegradability of leachate is better.

2. High concentration of ammonia nitrogen

The concentration of ammonia-nitrogen in leachate can reach 1000-3000mg/L. Nitrogen in leachate mostly exists in the form of ammonia-nitrogen, accounting for 75-90% of total nitrogen.

3. High Salt Content

The salt content in leachate is usually more than 10 000 mg/L. Membrane treatment will result in low water yield due to excessive osmotic pressure. It is difficult to start up, low load, unstable operation or even unable to operate because of excessive salt content in ordinary biochemical treatment.

4. Water quantity and water quality fluctuate greatly

The amount of leachate is affected by the type of municipal solid waste collection and transportation system, the composition of refuse, rainfall and other factors. The daily output of leachate is about 5%~40% of the garbage. The variation range of pollutant concentration is 3 to 5 times.

II. Common Technical Routes for Leachate Treatment

1. Biochemical + Advanced Oxidation + Advanced Treatment

Leachate has high concentration of organic pollutants and good biodegradability. Biochemical treatment process is the most thorough and economical process to treat high concentration organic wastewater. It can degrade organic pollutants in a large scale under relatively economic conditions, and at the same time, it can play a role in nitrogen and phosphorus removal, which makes the overall treatment cost of leachate more economical. Because the leachate also contains many refractory macromolecular organic compounds, some “inert COD” which can not be biodegraded and adsorbed will always be retained after biochemical treatment. Engineering practice shows that the CODcr of leachate can be reduced to less than 1000 mg/L by various biochemical treatment processes. The removal rate is very considerable, but the effluent can not meet the discharge standard directly.

2. Biochemical + Membrane Processing

After biochemical treatment, the leachate is further treated by membrane process, which is the most commonly used leachate treatment method at present. The effluent quality of this process is good and can meet the standard of reuse water. It also has a high anti-variability ability for the fluctuation of leachate water quality and quantity, and has a high operational stability. After membrane separation, the effect of pollutants is obvious, and the separated effluent can meet the corresponding national discharge standards. Membrane technology has the advantages of continuous operation, high degree of mechanization and easy management. The instability of water quality has little influence on the effect of membrane treatment.

3. Membrane process or evaporation treatment

The disc-tube reverse osmosis DTRO membrane has the characteristics of good anti-pollution, high flux and long service life. The front end of the disc-tube reverse osmosis DTRO membrane can directly treat the leachate only through sand filtration protection. Even in the case of high turbidity, high SDI value, high salinity and high COD, it can operate economically, effectively and steadily.

MVC evaporation process for leachate treatment has the advantages of fast start-up, low energy consumption, low concentration ratio and small occupation area. The problems of evaporation process are as follows: firstly, the condensate contains volatile hydrocarbons, volatile organic acids and ammonia, which need further treatment to reach the standard, and the cost of treatment is relatively high; secondly, when COD in leachate is relatively high, the content of reactor is easy to foam, which directly affects the quality of effluent and concentration multiple, and can be solved by adding defoamer, and the cost of ammonia-nitrogen conversion is high; When transferred to the condensate and followed by ion exchange treatment, the resin replacement frequency is high.

III. Technical Key Points and Difficulties

1. Accurate prediction of design water quantity and quality

Accurate prediction of design water quantity and quality is the basis of Engineering design. The daily production of landfill leachate should take into account the residence time of garbage in the aggregate pit, main components and local rainfall. The water quantity and quality of landfill leachate can refer to the operation data of garbage in the same area.

2. Biochemical treatment

The COD of landfill leachate is high, and the energy consumption of aeration system is too high when aerobic process is used directly. Therefore, the leachate should be treated by aerobic process after reducing the concentration of organic pollutants through anaerobic reactor.

3. Selection of Membrane System

The selection of membrane system is influenced by the design effluent standard.

In recent years, the environmental protection requirement of newly-built garbage is getting higher and higher. Many newly-built garbage require the reuse of leachate after treatment and the requirement of “zero discharge”, which puts forward higher requirements for the design of leachate treatment system. With the complex composition of landfill leachate and the high concentration of pollutants, it is difficult to treat, and the treatment standard is constantly improving. The treatment of landfill leachate should be considered from the whole landfill, and experts in the field of water treatment are actively exploring more treatment processes of landfill leachate.

Luoyang Building Material and Architectural Design and Research Institute is committed to the innovation and development of technology and equipment in building materials and construction industry. It has a double-level design and Research Institute which integrates scientific research and development, design, general contracting, supervision, technical consultation and technical service of building materials and construction engineering. The garbage gasification power generation technology developed by our institute has high efficiency and continuity, gas De-Coking and purification, automatic control of one-key operation, strong adaptability, modular design, zero emission and waste heat.

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