What are the ways to dry sludge
What are the ways to dry sludge
The main drying modes currently used are: traditional thermal sludge drying and solar sludge drying.
(1) Drum drying process. Using natural gas or biogas as energy and air as the heat transfer medium, the wet sludge and part of the dried sludge particles are mixed in the mixer, and the airflow takes it into the drum dryer. The sludge is followed by the drum dryer. The airflow rotates forward at a stable speed and transfers from the inner cylinder to the outer cylinder, and the sludge is gradually dried into particles. The process is divided into direct heating and indirect heating. Directly heated drum dryers rely on very complex monitoring systems to maintain. The indirect heating drum dryer must be operated in a strict inert environment. Due to the uneven internal temperature and heat distribution, it is easy to cause dust accumulation and overheating in the small environment, which will cause great dangers.
(2) . The sludge does not require pretreatment and is directly sent to the fluidized bed dryer. The fluidizing gas is blown into the entire bottom section of the fluidized bed dryer uniformly to form a fluidized layer inside. As the sludge gradually dries, its density decreases, rises to the upper part, and then is pumped out of the fluidized bed with the gas pumped from the upper part. Because the composition of the sludge determines its fluidization characteristics, the treatment system is very sensitive to changes in the composition of the sludge, which often causes the heat exchange in the fluidized bed to fail to proceed smoothly, the fluidized bed and pipes are worn out seriously, and the system consumes energy. Also higher.
(3) Disc drying process. First use an external heat source to heat an oil furnace, and then transfer the heat energy to the drying plate through the oil body. Disk dryers are divided into horizontal disk dryers and vertical multi-disk dryers. Horizontal disc dryers can only use steam as a standard heating medium. The tower crane is constructed as a fixed body, forming a horizontal shell. Its internal rotating part consists of a tubular hollow shaft, on which some empty disks are fixed, and the disks are filled with steam, etc., and some mixing blades are used for conveying materials. The heat medium enters the disk through the central axis and is distributed to the rotating body at the same time. The disadvantage of this method is that the dry product contains a large amount of dust, a separate granulation system must be added, and the equipment is very easy to wear. The vertical multi-disc dryer uses the special evaporation curve of the sludge to prepare hard particles of the sludge, so that the sewage treatment plant can achieve the discharge of sewage up to the standard while being safe and free of secondary pollution and saving energy. In addition, there are disc type, belt type, sunlight type, flash type and other drying processes, but currently they are rarely used in large-scale projects. The drying equipment in Europe and the United States is technically very mature, with high safety, compact equipment layout, small footprint, high automatic control level, simple operation and operation, and conforms to the popular trend of industrialization.