Up to now, gas processing and gas feeding have only been possible for biogas plants within the MW range. However, with the “Zeven model” we are entering a new era: We are going to process 250 Nm³/h of raw biogas. This intelligent concept allows profitable processing for biogas plants with a power range much below 1.0 MWel.
The “Zeven model” describes a combined plant where a CHP with approx. 400 kW of electrical power generates sufficient high-temperature heat in order to power a processing plant with a capacity of approx. 250 Nm³ of raw gas per hour.
The processing technology is non-pressurised amine washing by MT-Biomethan GmbH, which requires approximately the above amount of heat. Since the CHP of the biogas plant produces the entire process energy, the plant operator has permanent control over the processing consumption costs, which are independent from electricity price variations on the energy markets. This is a decisive advantage compared to physical processing technologies, which require electricity as their process energy.
Furthermore, the motor exhaust heat is used for maintaining the digestion temperature in the biogas plant’s digesters so that here, too, an own heat source is available. Due to the intelligent interconnections between the raw gas plant, CHP, heat decoupling and processing plant, the CHP can be operated all year round with a heat usage of far above 70 percent.
Also, the feeding process renders a significant savings potential. Due to the small raw gas amount, the produced biomethane can be fed into the local medium-pressure supply grid. As compared to a connection to a high-pressure grid, the expenses for gas compression are far less.
For small plants, the specific value of the processing costs is higher than for larger plants. However, this is compensated for by savings regarding transport and balancing costs. For the feeding into consumer grids, the disadvantage of the higher specific costs of a small plant is quickly made up for. Therefore, the efficiency of this kind of gas processing can be compared to that of large processing plants from 700 Nm³ of raw gas per hour. This way, farmers with plant sizes from 800 kWel can produce biomethane both sustainably and economically.
