Continuous stirred tank reactors
A frontal loader delivers substrates into a hopper where the inputs are crushed and fed to the horizontal auger. Next, the substrates are transported to the vertical auger.
Supply of substrates
Substrates are fed into the reactor by vertical and inclined augers.
The target temperature inside the reactor is maintained with heating pipes on the inner reactor walls.
Substrates are constantly mixed with inclined and submersible mixers.
Anaerobic bacteria digest the substrates, producing biogas.
Sulfur is removed by means of a biofilter. To create the local aerobic conditions for sulfur-eating bacteria, air is supplied.
Biogas is collected and stored in a gas-holder. Then it is dried, pressurized by a gas compressor, and pumped for combustion into the co-generator.
The classic CSTR technology (Continuous Stirred Tank Reactor) is simple and easily recognizable.
Distinctive features are the diameter of the reactor is greater than the height, heating by pipes on the reactor’s walls, a flexible gas holder above the reactor, sulfur removal by a biofilter from air in the center of the fermenter, mixing with inclined and submersible mixers. Reactors are made of either reinforced concrete or bolted steel panels.
Moisture in a well-functioning CSTR reactor is 93%. The organic dry matter load per m³ of reactor is 2-4 kg. Fermentation occurs in the mesophilic mode of 33° – 40° С.
The technology is most often used for processing manure, dung and stillage. A biogas plant with CSTR technology is often referred to as a “farm-style”. It is easy to maintain, which is especially important in rural areas, but less effective than other technologies. The degree of decomposition is 70% – 75%.
- load of organic dry matter (ODM) 2-4 kg/m³ of the reactor
- heating by pipes on the walls of the reactor
- mesophilic mode 33-40 °C
- substrate supply by pumps or by loaders
- solids content in the reactor 4-7%
- sulfur removal by air using a biofilter
- cooling of biogas in an underground coil