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Mini CHP plant with Stirling motor
© SOLO Kleinmotoren GmbH

Fuel cell system with FLOX® reformer for domestic energy supply
© WS Wärmeprozesstechnik GmbH
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And new fields of application...

Lean gases can be utilised

Various research projects are examining how landfill gas, coalmine gas, biogas, sewage gas, product gas, or wood gas, can be used in an energy-efficient manner with low emissions. This work often involves lean gases with a low energy content compared to natural gas. Furthermore, in many cases the fuel quality often fluctuates in the short term, e.g. with gases from production processes, or over a longer term, e.g. with landfill gases. Today, lean gases are often still burnt off, so that climate-damaging methane does not escape into the environment. FLOX burners deal with low-energy gases better than conventional burners do, and with flameless oxidation, fluctuating fuel quality does not immediately cause problems with flame stability.

In the European research project BIO-PRO, burners are being developed for biorefineries. These are systems which convert biomass into fuels, chemicals, and even foodstuffs. In these processes, solid, liquid, and gaseous residues arise. To enable combustion of solid fuels as well, researchers at the University of Stuttgart are investigating the use of FLOX burners with various pregasifiers.
For clean combustion of lean gases, the conversion of the nitrogen compounds contained in many lean gases must be kept within tight limits. In the laboratory, it has been shown that this is possible. Now it needs to be confirmed on an industrial scale. To this end, alongside constructive approaches, the development of a new type of burner controller is being promoted. If this project succeeds in producing the required confirmation, this technology can be offered on a commercial basis in the future. Together with the University of Bochum, the Gaswärmeinstitut (Gas-Fired Thermal Energy Institute) in Essen, Germany, is developing new burners and combustion chamber concepts for micro gas turbines. Here, it is possible to use lean gases which only have a third of the heating value of natural gas. In so doing, the levels of nitrogen oxide and carbon monoxide fall well short of the TA Luft threshold values for the combustion of landfill gas, biogas, and wood gas in gas turbines.

On-site hydrogen production

To date, hydrogen is mainly produced industrially. Consumers satisfy their requirements by means of pressure cylinders or hydrogen pipelines. Now, natural gas can be used to cover these requirements on site. This is made possible by modular reformers, which are approximately as efficient as large-system reformers are. The reformers are based on conventional steam reforming from natural gas. The temperatures of around 800 °C which this requires are provided by FLOX burners. Due to a new type of heat management, the reformers achieve energy conversion efficiencies of over 80%. In the future, this technology could enable broad implementation of PEM fuel cells.

Two product series have been developed to date. One version for industrial implementation is already marketable, with hourly capacities of 50 to 400 Nm³. The reformer has a modular structure. The capacity can be adapted to the application in an economical manner via the number of reformer tubes. Several reformers have already been commissioned and, for example, are supplying a hydrogen filling station at Munich Airport. A second series, which is compact, should enable the use of fuel cell stacks for domestic power supply. Here too, the prototypes are already achieving conversion efficiency of over 80%. Before a market launch, work is still being done towards maximisation of efficiency, operational safety, and optimisation of gas purification.

Mini combined heat and power plant

For decentralised combined heat and power generation, SOLO Kleinmotoren GmbH has developed a marketable Stirling motor. This engine, with an electrical capacity of 9kW, is suitable for hotels, swimming pools, schools, hospitals, residential buildings, or businesses. It can be operated using different heat sources. For natural gas operation, a FLOX burner with air preheating is provided.

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