Process description of the fermentation line

MT-Energie biogas technology is based on a two-step, steady feed on-going system. As a rule, at least three containers are necessary: a fermenter, a secondary fermenter and a storage for fermentation material. (see picture on the right: site plan of a biogas plant)

The process deviates from the classical defintion of a two-step plant, as the fermenter as well as the secondary fermenter have the same environmental conditions for bacteria. The setting conditions can be recapulated in a way that the fermentor is of a close-to oxygen-void atmosphere, whilst the substrate holds a mesophilic temperature of about 40°-42° and a neutral-range pH-value (6,7-7,2).

site plan of a biogas plant

So, a stringent seperation of hydrolysis and the formation of acid on the one hand, and the formation of acetic acid and methane on the other hand is not done. In fact, maximal gas exploitation is warranted by these two steps. With the second step 20% of the possible gas earnings are achieved, making sure, the amortisation of the second step is always assured.

All organic materials can function as substrates. These can be waste materials the food industry produces, dungs or renewable raw materials from agricultural businesses or anything similar. At the moment silage in used in great quantities in Germany, as its use is the focus of attention in regard to the renewable energy laws in Germany.

The continuing solid feeds induction is conducted by the MT-Fortis®. With the help of the pushing floor container the feed is directed towards the filling pieces with as little movement and resulting energy consumption as possible. The pushing floor container is placed on a weighing bars, so that all data of the feeding process can be documented by the system control. Potential liquid feeds are induced by a direct liquid feed-in.

It is feasable to run a MT-Energie biogas plant on solid feed only, enabling agricultural farms having no access to liquid manure to run a profitable plant.

The fermentation containers consist of acid proof prestressed or in-situ concrete with doubled concrete reinforcement. Diameter and height are dependant of the particular circumstances. Facilities are offered starting from 250 kWel. Fermenters and secondary fermenters are insulated with styrofoam along the sides and styrodur on the bottom. To allow for weather protection walls are cladded with aluminum profiled sheeting.(see picture, right “container rim from above”)

The technical outfit of the individual containers is basically similar. The agitators are in fact submersible motor agitators, which can be adapted in height and angle as needed. Part of the agitator works in a horizontal fashion and at least one agitator works in a vertical fashion to avoid deposits.( see picture, right “inside view of container with agitator”)

Within the fermenter, the heater has the largest dimension, as through the feed-in fresh substratum of cold material is constantly added. The non-corrosive wall heater made out of PE-pipes is mounted at a distance of 10cm to the walls, to avoid stress cracks. The storage container, the so-called fermentation product strorage, is neither insulated nor cladded and does not have a heater. Inspite of the little amount of left-over gas, this third container is equally covered to provide for an additional gas collector and desulphurisation chamber. 

container rim from above 

inside view of container with agitator 

The substratum moves from one particular container to another via an overflow or via the pumping system. An automated pumping system allows substratum to be transported from one container to any other container as needed. The eccentric screw pump is positioned in the pump room, along with the system control and the control box positioned between two containers, resulting in a work shop, which is space-and material saving, yet holding all regulatory elements needed. (see picture, right "Pump room")

The desulphurisation is handled by bacteria which inhabitate a net underneath the container´s foil covering. Before the gas is currented in a block heat power plant, it is cooled down and dried. Part of the incidential warmth, which occurs during the incineration is reintroduced into the fermation process. The rest can be used externally.

Pump room