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Biogas is a green energy calling on more and more leading edge technical
installations. Undoubtedly, the produced kW cost is not yet a competitor against nuclear or fossil fuel energies, but the systems installed are more and more efficient, and their financial profitabilityis increasing. European Biogas electricity production in 2006 was 17,272GWh per year, of which ,7338GWh was by Germany alone. Biogas now represents 1.2% of the annual production of electricity and nearly 10% ofrenewable energy, with an installed power close to 1500MW. This success is also due to efficient regulations, intended to promote renewableenergies. In fact, the German law stipulates the purchase price per kWh by energy distributing companies for 20 years. This price takes into account the ‘green’ nature of the energy and recompenses the operators, based on efficiency, technological innovation and agricultural re-conversion criteria.
Germany built 820 systems in 2006, increasing the total installed production units to 3700 and is the No.1 world biogas based energy producer, and also the technological leader. Ciat has approximately a 35% market share and has acquired significant know-how in gas treatment, enabling it to propose systems adapted to ever widening scopes of application. Two installations produced with theGerman partners of Ciat, Seva AG and Siloxa AG, illustrate this progress.
There are several different types of biogas production systems. Biogas production means production of electricity using a gas engine and an alternator. Process heat can also be recovered, this is called cogeneration. Biogas is a gas produced by the fermentation of animal or vegetable organic matter without oxygen. This so called methanization occurs naturally (in swamps) or spontaneously in waste dumps containing organic waste. It can be artificially produced in digesters when treating purification sludge, industrial organic waste or agricultural crops or can be recovered by sucking mine gas. In all cases, the biogas must be dehumidified and purified before combustion; otherwise it can damage the gas engine.
Biogas is a mixture comprising methane (30 to 70%) and carbon dioxide, with varying quantities of waterand hydrogen sulfide (H2S). Biogas energy is produced from methane andis a renewable form of fossil energy, which is natural gas. Furthermore, biogas systems are highly respectful of the environment. As the contribution of a methane molecule (CH4) to the greenhouse effect is 21times greater than that of CO2, the burning of methane, even though producing CO2, reduces its impact on the environment.
Fermentation of organic waste
Seva has developed forefront know-how for small-sized systems. Out of the 820 installed in Germany in 2006, they produced 170 biogas combustion units, with a total power of 54MW. Furthermore they are present internationally in Europe, United States,Thailand, and Japan. The philosophy at Seva Energie is to make biogasprofitable by offering high production rate systems, operating continuously with limited human intervention and very high reliability.
Ciat has become a recognized standard for the up-line treatment partof gas. As previously mentioned, the humidity is removed from the gas. Steam is condensed by cooling the gas to temperatures between 15 and5°C. This process also eliminates part of the impurities in gas by trapping them in the condensates, which are evacuated. This treatment protects the motor, reducing the maintenance frequency and prolonging its service life. This operation is carried out by an optimized refrigeration unit and heat exchanger set, delivering precisely the cooling power needed.
"What we like at Ciat is that it is always capableof reactively responding with the precise technical solution", explains Klaus Vieth, project leader at Seva. Reliability is also a strong point: "We tried several competitors' systems previously, but we found too many failures, especially in the refrigeration unit, which is located outside".
"For each new development project, we forward our specifications to Ciat, who help us size the components to integratein the best possible manner. They respond quickly, the prices are competitive and there is always a Ciat product corresponding to our need", adds Michael Siemer, Sales Manager at Seva.
The MönninghausenGmbH Biogas system located at Geseke (Germany) illustrates effectively the capacity of Seva to provide profitable solutions. The gas here is produced by the fermentation of organic waste. The installed electrical power is 537kW for a 230Nm3/h approx. biogas flow rate. The systemduty factor is 97%, being 8500 hours per year. This system only requires the presence of a technician for two hours per day. The control system designed by Seva displays the instantaneous operating parametersfrom the Seva office in Emstek and sends telephone alerts or SMSs in case of an operating incident. Shutdowns are thus minimized. The cost per kWh produced is €.0.08. Today, the energy is sold at €0.16. "As a general rule, our customers obtain an investment return in 2 to 4 years", concluded Michael Siemer.
Furthermore, this system consumes70% of the produced heat through sterilization of organic waste beforemethanization, maintaining methanizers at operating temperature, heating of neighbouring buildings and farms. 15% of the biogas energy yield was obtained by heat recovery in Germany in 2006 (equivalent to 1324KTEP/year). Seva is present internationally: Europe, United States, Thailand, and Japan.
Transportable mine gas installation
Siloxa, founded in 1998, is specialized in Biogas treatment; they offer a very wide range of biogas impurity treatment solutions. Biogas saturated in steam contains impurities such as organic silica compounds and hydrogen sulphide which are highly detrimental to gas engine reliability. Other than the corrosion generated by hydrogen sulfide, irreversible damage may be caused by deposits of siloxane in combustion chambers which can cause total shutdown of the engine. Steam creates condensation in the pipeline system. The consequences are corrosion, alteration to valve and measurement instrument calibration and pressure variations.
The system installed by Siloxa at Recklinghausen (4/5 König Ludwig mine shaft) offers a high capacity: 2,400 Nm3/h for an annual electricity production of 20GWh, being the equivalent of 6 large-sized wind turbines. The centre container, fitted with two compressors,sucks up the underground gas at a 400m depth through a shaft. The gasis dehumidified though an exchanger powered by a rooftop refrigerationunit and distributed to the 4 motors in the cogeneration containers.Continuous process, maximum availability and minimum human intervention (1 hour/day) have been key factors since commissioning. As the modules are fully transportable, the entire energy production system can bemoved, when the mine no longer produces sufficient methane.
Jochen Beese, member of the Board of Siloxa AG, explains why Ciat was chosen: "Our systems range from 100m3/h to 4000m3/h. Ciat provides us with extensive experience in choosing solutions and sizing systems. Furthermore, the characteristics of the Ciat equipment are exceptional interms of energy yield".
Marc Schaller, Marketing Manager for the industrial segment at Ciat explains:"Our leading position in Germanyenabled us to work alongside the players in this sector. Ciat's equipment offers several sought-after features. Our experience in the sector and our equipment range allows us to propose a system solution sizedideally over the entire power range. Furthermore, with our mastery in3 technologies, we can propose the 5 main heat exchangers of a cogeneration system".
"Biogas is considered as one of the cleanest green energies and its use will naturally progress across the world. Based on our experience, acquired over several years in partnership withour German customers, we want to share our expertise in other markets. We already have numerous projects or installations completed in Russia, Thailand, England, France, Spain and Turkey, and this is just thebeginning. Numerous countries are copying the German model, offering financial incentives that are sometimes greater", concluded Marc Schaller.
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