Drying Technology
Keywords:sludge drying treatment、urban sewage treatment plants
With the surge of sewage treatment capacity, the amount of sludge increases significantly. China's sludge is 38.2 million tons in 2015, 41.04 million tons in 2016 and is expected to exceed 50 million tons in 2020. Sludge is rich in organic matter, nitrogen, phosphorus, potassium and other nutrients, which has obvious utilization value. The high moisture content of sludge is the key to the development of sludge treatment technology. At present, the common methods of sludge disposal are landfill, composting and incineration. Due to the high content of heavy metals and other harmful substances in sludge, there are problems in sludge composting.
The instability of sludge leads to the problem that sludge cannot be piled up during landfill, resulting in excessive land use and increasing shortage of land resources. Incineration method has gradually become the mainstream method because of its advantages of reduction and recycling. Sludge incineration usually requires pretreatment such as sludge dehydration or thermal drying to improve the calorific value of sludge. Sludge drying uses heat energy to evaporate water, greatly reducing sludge volume, storage and disposal costs, and removing pathogens. Due to microbial cracking, hydrolysis of macromolecular organic matter such as fat and protein and release of volatile substances in the drying process, the sewage contains a large amount of ammonia nitrogen, volatile organic compounds, heavy metals and oils, which cannot be directly discharged into the sewage treatment plant.
The treatment of urban domestic sludge is required to comply with the four principles of "reduction, harmlessness, stabilization and recycling". The heat energy generated in the process of sludge incineration can be used for power generation, self-produced steam circulation is used for sludge drying, and the burned ash is used for making ceramic tiles, floor tiles, water mud blending materials, etc. Taking the EPC project of sludge drying and incineration project undertaken by Beijing Jingcheng environmental protection Co., Ltd., including 240 t / D centralized sludge drying and incineration project in Wenzhou and 750 T / D sludge drying and incineration treatment project in Shanghai Zhuyuan (the moisture content of dewatered sludge is about 80%) as an example, the single machine commissioning, subsystem commissioning, load linkage commissioning The commissioning and troubleshooting are introduced respectively.
The carrier gas of the dryer is recycled. After dedusting and washing, the carrier gas is sent to the carrier gas inlet of the dryer by the centrifugal fan. The surface of a section of carrier gas pipeline with a length of about 22 m is not insulated. A large temperature drop is formed between the carrier gas at this section and the carrier gas at the outlet of the dryer, and the condensate carried by the circulating carrier gas is precipitated, Flowing into the dryer consumes equipment heat and reduces the ambient temperature required for the normal operation of the dryer, which greatly affects the moisture content and output of dry mud.
After the process line of sludge drying incineration project is determined, the selection and configuration of various equipment is the key. The commissioning process can inspect the equipment from
Confirm and correct the logical relationship of interlocking, interlocking and delay required by the automatic operation of the whole line and the working reliability of automatic instruments. After a set of mature sludge drying incineration process is determined, the correct selection of equipment and paying attention to the commissioning of different contents in different stages can provide a greater guarantee for the smooth completion of the project. Various potential problems in heat load operation will be exposed in the trial operation stage, and the deviation can be corrected by applying the right medicine to the case.
① Clarify the commissioning purpose and operation process of each step, and the actual operation of the emergency plan is required;
② The conveying link of controlled dry sludge into the furnace to prevent air from entering the furnace with sludge;
③ According to the characteristics of internal viscosity and external dryness of semi dry sludge, the conveying equipment that does not destroy the shape of sludge mass is selected;
④ For self sliding granular dry materials, such as fluidized bed sand and granular coal, tests shall be conducted to obtain the angle of the pipeline or chute
Degree to prevent pipe blockage or accumulation;
⑤ After washing, the circulating carrier gas of the dryer restores the temperature of the return carrier gas pipeline;
⑥ It is suggested to decide whether to spray tungsten carbide coating on the blade according to the specific conditions and requirements of the project, and the coating results shall be evaluated thirdly
