A digester mixer system consists of a digester tank, the contents of which are mixed through effectively designed mixers. For effective mixing, these systems are designed with options, such as a gas mixing system, where the contents are mixed through the bio-gas generated and are recycled through properly sized compressors.
The gas mixing system involves various gas lances that are installed all over the tank area and extend deep into the tank from the roof of digester tank. In another type of system, the lances can be positioned directly on the floor of tank thereby avoiding long lances. Both these types of systems have their specific advantages and the selection of a particular system depends on the requirement of client. The bio gas systems are designed and provided with different types of fail safe devices to avoid any accident in view of inflammable conditions around the Digestion area due to the possibilities of leakage of bio-gas.
Anaerobic digestion is a sludge stabilization process, which is based on biological processes to degrade composite organic substances in the absence of dissolved or free oxygen. The biological method of anaerobic digestion involves 3 separate stages in which the solids present in the sewage sludge are brought in contact with an existing consortium of microorganisms, which first hydrolyzes, then ferments and lastly gasifies the original long chain of organic substances.
The requirement for both a suitable environment for the proliferation of the right kind of microorganisms and the required adequate contact and interaction of the microorganisms mass with the incoming solids in the raw sewage sludge has rendered a necessity for efficient mixing systems. The efficient mixing systems help in maximizing the yield of suitable intermediate products and gas production.
There are various types of digestion mixing systems available in the market today and the selection and performance evaluation of them has been of considerable importance for consulting engineers and plant operators. The effectiveness of digester mixing systems can be evaluated on the basis of three factors –
- Solid Concentration Profile
- Temperature Profile
- Tracer Dispersion Test
Primarily designed for sludge treatment, digester mixers have found their uses in various applications, including –
- Digester mixing of municipal and industrial waste
- Deep-tank mixing of high-viscosity liquids
- Two-phase anaerobic digestion systems
- New or retrofit projects