Drying Technology
Keywords: sludgedryercompany；sludgewastewatertreatment
With the continuous increase of my country's population, secondary pollution of sewage and sludge has followed. Due to the presence of organic pollutants, heavy metals, parasites, germs, and corrosive substances in the sludge, it will seriously affect the ecological environment if not properly treated. Under normal circumstances, sludge treatment mainly includes reclamation, landfill, incineration, land use and other forms. However, in recent years, due to the country's gradual restrictions on sludge composting and landfill, it is forbidden to put sludge into the sea. Therefore, the main method of sludge treatment today is incineration. Incineration treatment can carbonize the organic matter in the sludge, completely kill pathogens, reduce the volume of sludge to the greatest extent, and greatly reduce the impact of sludge on the ecological environment.
The sludge volume can be effectively reduced by carrying out sludge drying, which can usually be reduced by more than 4 times to produce stable, sterile and odorless protozoa. The dried sludge products have a wide range of uses, not only for Fertilizers, soil conditioners, etc., can also replace part of the energy. The sludge drying equipment is divided according to the medium and the contact mode, which can be divided into two forms: direct heating and indirect heating. Among them, direct heating, also known as convection drying, mainly uses hot air to directly contact the sludge, thereby evaporating the moisture on the sludge surface.
This method has high utilization rate and can increase the solid content of sludge. from25% to more than 85%, but because it is in direct contact with the sludge, the heat transfer medium is extremely susceptible to sludge pollution, and the waste gas needs to be discharged through harmless treatment. The direct drying equipment is mainly a rotary drum dryer. However, due to the relatively high cost of direct drying tail gas treatment, tail gas recycling technology can be used for treatment, that is, the tail gas is transferred back to the hot blast stove.and the rest will be discharged again after being heated by a regenerative thermal oxidizer. Indirect heating does not directly contact the sludge, but the heat transferred from the surface of the heat source heating the container contacts the sludge, so as to achieve the purpose of drying. This method can avoid contact with heat medium
It avoids the separation of medium and sludge, but the heat transfer efficiency and evaporation rate are relatively poor, the decomposition of organic substances in the sludge is not thorough enough, and a separate heat source system is required, which will greatly increase the maintenance cost.
Sludge incineration needs to be carried out at a very high temperature. In an environment with sufficient oxygen, the organic matter in the sludge is burned and converted into nitrogen dioxide, carbon dioxide, water vapor and other gases. The incineration products are mainly flue gas and Ash. Incineration technology can decompose all organic substances, completely kill pathogens, improve the stability of heavy metals, and the sludge volume after incineration is only 1/10 of the volume of mechanically dewatered sludge. Sludge incineration equipment mainly includes stepped incinerators, multi-stage incinerators, etc. There are two forms of incineration after drying and direct incineration. Among them, the initial investment of post-drying incineration equipment is relatively large, but the treatment cost is relatively low. From a long-term perspective and a safety perspective, the economical and applicability of post-drying incineration is very high.
The cost caused by different dry incineration processes is different. Essentially, sludge treatment costs mainly include equipment costs and operating costs. For example, for fluidized bed incinerators, domestic equipment is about 25% to 50% cheaper than international equipment. Therefore, domestic incineration equipment can be mainly considered. For sludge generated in special industries, it is necessary to select a sludge treatment technology with strong applicability according to the characteristics of the sludge, which can reduce the cost of sludge treatment, improve the efficiency of thermal energy utilization and reduce operating losses.
