An existing biogas plant in Hammel near Aarhus, Denmark has taken delivery of what is probably the largest tank for glycerin in the country. Supplied by Germany-based Erich Stallkamp ESTA GmbH, via its Danish distribution partner Biogas Teknik A/S, the 4 500m³ fully insulated digester is made from long-lasting stainless steel.
The project is part of an existing 2 MW biogas plant being constructed by Danish partners Biogas Teknik A/S. The diameter of the new biogas tank is 25 m with a height of almost 9 m. It is constructed with stainless steel shell plates in a segment-like design. At the height of almost 9 m, seven rings of the shell plates are necessary. The lower five rings are made from stainless steel 1.4462 and the upper two rings from stainless steel 1.4571 to prevent corrosion.
The digester is covered with a stainless steel roof pillared by a central support. Being composed of an inner and outer screwed element, the outer ring is attached to the top of the tank, whereas, the inner ring is posted higher. Thus, a decline of 10° occurs. The roof is designed for insulation and cladding. It is completed by two inspection openings.
The basis for the fermentation process is glycerin with a pH value between 3.5 and 8 and it is a by-product from biodiesel production. Having a density of 1.3 kg/l, the glycerin is heated up to 52°C. Glycerin is a sought after feedstock for anaerobic digestion (AD) plants as almost all is converted by bacteria into biogas. The yield is four to five times higher than for maize silage.
of a digester. It has as two gas-tight wall bushings, two working platforms with ladders
and three submersible motor agitators in stainless steel (photo courtesy Erich Stallkamp).
