After the completion of a sewage plant, about 120 tons of dewatered sludge (75% moisture content) are produced every day, and the urban sewage sludge has secondary pollution after long-term stacking; Urban sewage sludge also contains about 50% organic matter. After appropriate process treatment, the sludge will be harmless and resourceful, and the harm can be changed into protection.
After years of work, we have developed high-temperature aerobic fermentation of urban sewage sludge to make the sludge harmless. Then we can prepare bio organic fertilizer and organic and inorganic compound fertilizer according to the needs of the factory, and develop complete sets of equipment for sludge harmless and recycling. According to the needs of the factory, we now provide the design scheme of a fertilizer plant with a daily treatment of 120 tons of dewatered sludge, a daily production of 119 tons of finished fertilizer and an annual output of 41000 tons of finished fertilizer after harmless treatment (i.e. fermentation).
This scheme only includes one process, that is, the aerobic composting process is used to treat sludge, and the fermented sludge is used to make organic fertilizer.
Aerobic composting fermentation this process is mainly composed of dewatered sludge with moisture content of 75% and industrial waste fly ash, backfill and deodorant as adjusting agent, which are mixed in a certain proportion into the mixer. The materials are evenly transported to the horizontal fermentation bin through the distributor, and the materials are fully aerobic fermented through forced ventilation in the fermentation bin. At the same time, the materials are evenly fermented through stirring by the dumper and pushed forward. After ten days of fermentation, the moisture content of the material has been reduced to 27%. Part of the dried material is recycled as backfill, and part is directly exported as finished fertilizer. This fertilizer can be used as soil agent. Due to the aspects of urban lawn, flower planting, landscaping, desert vegetation, barren mountain greening, etc., it can also be used as field fertilizer to make full use of the advantages of high organic composition of the fertilizer. Farmers add different amounts of N and n according to their own soil conditions P. The application effect of K fertilizer has been tested in the field for three consecutive years in Hebei Province, and the effect is obvious. It can increase the yield of Wheat by 1596 and corn by 5%. Then it can be used to make high-quality yueba. After a certain shape and exquisite packaging, it can be sold in shopping malls, which is mainly used for family flower breeding. In order to prevent the environmental pollution caused by the odor in the fermentation process, the odor extraction pipeline is arranged in the fermentation bin, and the odor treatment tank is arranged outside the bin.
1、 Design index and requirements:
The annual output of finished fertilizer is:
41000 tons of organic and inorganic fertilizers were prepared by sludge fermentation
Daily treatment capacity of dewatered sludge: 120 tons
The hygienic index of the product shall meet the hygienic standard of high-temperature composting.
2、 Technical basis
Through more than ten years of painstaking research, we have developed urban sludge aerobic composting technology and key mechanized composting equipment, such as special sludge mixer, chain dumper, distributor, deodorization tank, air dryer, multi screw conveyor, bin transfer machine, special granulation machine for sludge composting, etc. the designed complete set of sludge composting equipment has reliable operation, convenient management and high degree of automation. It has been successfully applied in the sludge fertilizer making demonstration project of Tangshan western suburb sewage plant and Tianjin petrochemical fertilizer making project, and achieved considerable economic and social benefits. At the same time, the demonstration project of "harmlessness of sludge in 500000 T / D sewage treatment plant" of the State Planning Commission and the phase II expansion of sludge fertilizer production project of Tangshan Xijiao sewage plant were also designed.
The following are our Tangshan sludge fertilizer project, Tianjin Petrochemical Sludge fertilizer project, Qinhuangdao sludge fertilizer project, Tangshan sludge fertilizer phase II project, etc.
1. Tangshan sludge fertilizer project
2. Tianjin Petrochemical Sludge fertilizer project
3. Qinhuangdao mud fertilizer project
3、 Process route and design.
1. Process route: aerobic composting process
Sludge fertilizer making process is divided into aerobic fermentation and anaerobic fermentation. Anaerobic fermentation will produce odor due to the production of methane and other metabolites. At the same time, it has high equipment investment, complex operation and management and strict requirements. It is suitable for the treatment of liquid sludge of large sewage plants. Because China generally adopts medium temperature anaerobic fermentation treatment, the sludge temperature is 30-40 ℃, although it can achieve the purpose of volume reduction, it can not be directly returned to the field. The sludge after mechanical dehydration is mainly prepared by aerobic fermentation. In the aerobic fermentation process, the organic matter in the sludge is transformed into humus rich in plant nutrients through the biological metabolism of aerobic microorganisms. The final metabolites of the reaction are C02, H20 and heat. A large amount of heat maintains the continuous high temperature of the material, reduces the moisture content of the material, effectively removes pathogens, parasite eggs and weed seeds, and reduces the sludge The purpose of stabilization, harmlessness and recycling. By comparison, the equipment investment and operation energy consumption of aerobic fermentation are 1 / 3 lower than that of anaerobic fermentation, which is an energy-saving and efficient composting process. At the same time, due to its few equipment and simple operation and management, it is especially suitable for sludge treatment. Therefore, the project adopts the sludge aerobic fermentation process. As China's rural areas need quick acting fertilizer and bio organic fertilizer is not easy to promote in the vast rural areas, the fertilizer produced from the composting bin can be directly put on the market or further processed to prepare organic-inorganic compound fertilizer. The project adopts high-temperature aerobic composting technology, which is an efficient biochemical reaction process that uses bioenergy to completely mature and degrade sludge.
The main technical features of mechanized aerobic composting are:
(1) Make full use of bioenergy, save energy consumption, turn harm into benefit, and there is no secondary pollution. The organic matter in the sludge fully reacts with aerobic bacteria under oxidation to release heat, so that the composting material will naturally produce high temperature. No matter what the outdoor temperature is, it can maintain a high temperature of more than 60 ℃. This biochemical reaction process does not require the application of any fuel. Biology can decompose small molecule organics, stabilize the degradation of macromolecular organics, generate organic fertilizers, and dehydrate materials. The aerobic fermentation process does not produce anaerobic gases such as methane and produces a small odor. Due to the continuous high temperature, it kills pathogens and weed seeds and completely makes the sludge harmless. Special additives are used to stabilize and harmless heavy metals in sludge under the action of alkaline medium.
(2) The biological process of high-temperature fermentation can produce high-quality organic fertilizer. Because the sludge is rich in nutrients such as N, P and K, it is stable and mature under the action of aerobic bacteria, which is easy to be absorbed by plants and crops.
(3) The bio organic fertilizer produced in the process of high-temperature aerobic fermentation is easy to be deeply processed and beneficial to the reproduction of microorganisms. It can be processed into bacterial fertilizer, or mixed with nutrients to make compound fertilizer and various soil improvers.
This technology uses fly ash as additive. Fly ash is a kind of solid waste. It is not only cheap, but also can turn waste into treasure. After years of research, it is found that the appropriate application of fly ash has a good effect on the physical and chemical properties of soil:
(1) Reduce clay content in clay and improve soil quality;
(2) Reduce the bulk density of clay;
(3) Increase soil porosity;
(4) Increase the temperature in the soil layer at the depth of 15cm;
(5) Increase soil water content and field water capacity;
(6) Regulating the three aspects of soil;
(7) Reduce the expansion rate of soil;
(8) Increase the content of silicon, copper, molybdenum, zinc, manganese and boron in soil;
(9) Adjust the pH value of soil.
The process flow chart of aerobic composting is shown in Figure 1, with an annual output of 27000 tons of organic compound fertilizer.
2. Process design:
The sludge composting plant mainly includes a composting workshop (A1), a composting workshop (A2), a biological deodorization filter (A3) and a finished product warehouse (A4).
(1) The fermentation workshop (A1) covers an area of 2000 square meters, 50 meters long and 36 meters wide. The mixing part covers an area of 200 square meters, with a length of 20 meters, a width of 10 meters and a height of 10 meters. It is a light steel shed structure.
The composting workshop (A1) of the building has an area of 50m long x 36m wide: 1800m2, which can be light steel structure and 5m high under the beam. The fermentation tank is 1.3m underground and is of reinforced concrete structure. There are 8 horizontal rapid fermentation silos, with the dimensions of length x width x height: 30x5.2x2m. The bottom of the silo is paved with plane tubular two-stage aeration. The top of the warehouse is a closed plant, and the bottom is an underground cement structure, and the operation track and track moving device of the dumper are set. The dewatered sludge, backfill and fly ash enter the primary mixer together, disperse into small particles in the primary mixer, and enter the fermentation bin through the distributor for aerobic fermentation. Carry out aerobic fermentation in the fermentation bin for about 10 days to complete the harmless treatment of sludge. The dumper regularly dumps the materials and moves them from the inlet of the fermentation bin to the outlet. The compost after fermentation is moved to the outlet of the compost bin and transported out by the loader.
(2) The fertilizer making workshop (A2) covers an area of 720 square meters, 36 meters long and 20 meters wide.
The plant can be of light steel structure, and the ground is a cement structure. The compost from the fermentation bin enters the fertilizer production line. After mixing with the chemical fertilizer through the fine mixer, it enters the granulator for granulation. The prepared fertilizer enters the air dryer for drying, and the dried materials are bagged through the bagging machine, which is the finished fertilizer. Using the flat mold high-pressure granulation mechanism, the fertilizer has high strength and uniform particle size. According to the standard requirements of compound fertilizer, the granulated granular fertilizer enters the air dryer to further dehydrate and meet the requirements of commercial fertilizer.
(3) The biological deodorization filter (A3) covers an area of 400 square meters, with a length of 20 meters and a width of 20 meters. It is a reinforced concrete filter. (it can be adopted according to the needs of users)
(4) The finished product warehouse (A4) covers an area of 1080 square meters, 36 meters long and 30 meters wide. It is a simple shed structure.