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Desulphurisation of biogas using metal alloy foam
On the winning side economically and ecologically(PresseBox) ( München, )
Biogas, which is produced during the microbiological breakdown of organic matter, contains substances including hydrogen sulphide, in addition to the actual energy source methane. As hydrogen sulphide has corrosive properties and is harmful to the environment, it is usually filtered out before biogas is used to generate electrical energy, in vehicle operation or to feed gas supply networks. In the event that non-desulphurised biogas is used in combined heat and power plants, a robust, sulphur-resistant oxidation catalyst is required for the after-treatment of waste gases. Innovative systems can be realised for both applications with the aid of open porous metal alloy foam from Alantum Europe GmbH.
Environmentally-friendly fine desulphurisation with cost savings up to 50%
To bring biogas to the same quality level as natural gas, a fine desulphurisation process takes place. This typically involves the use of active carbon with potassium iodide. However, the sulphur-saturated substrates must then be disposed of as hazardous waste. This is not only to the detriment of the environment, but also generates high costs.
As part of a project supported by the Federal Ministry for the Environment, Alantum Europe GmbH is working with the Fraunhofer Institutes for Ceramic Technologies and Systems (IKTS) and for Manufacturing Technology and Advanced Materials (IFAM) as well as Lehmann Maschinenbau GmbH on the development of a reclaimable filter system. Substrate is a metal alloy foam which, just like the wood chips or pellets used in the past, has an iron oxide coating. The reaction of hydrogen sulphide with the coating results in the formation of iron sulphide on the foam. However, unlike wood, the high temperature-resistance of the metal foam allows numerous thermal regeneration cycles. During the regeneration iron oxide and elemental sulphur is formed on the surface of the porous structure. The sulphur can be output by a thermal after-treatment process and may be re-used commercially, e.g. in the production of artificial fertiliser.
The ability of the metal foam filter to regenerate up to ten times offers a number of ecological advantages. Additionally, the open-pored structure of the metal foam allows it to absorb a greater quantity of hydrogen sulphide then conventional systems, thus reducing the size of the desulphurisation unit or allowing it to demonstrate longer cycle duration. These advantages help to reduce the cost of removing one kilogramme of sulphur from €16 - 20 to around €10. This will almost certainly help to lower the price of biogas, which until now has been relatively high when compared to natural gas.
Innovative sulphur-resistant oxidation catalyst
A further project involves the development of an innovative catalyst for the treatment of sulphurous waste gases from biogas combustion in pilot injection gas engines and Otto gas engines, which are used in combined heat and power plants. Alantum is working on this project in collaboration with Wieland Edelmetall GmbH, LGA Immissions- und Arbeitsschutz GmbH and the Precious Metals & Metals Chemistry Research Institute (FEM). The project aims to develop a robust, sulphur-resistant oxidation catalyst. The precious metals platinum and palladium, which are required for waste gas after-treatment, are deposited on the metal foam as a nanofilm by means of direct metallisation.
The open porous structure of the metal alloy foam causes permanent deflection of sulphurous waste gases in the catalyst. Compared to extruded, ceramic substrates, the result is a micro-turbulence over the entire reaction surface. Combined with the large reactive surface of the metal foam, a highly-efficient waste-gas purification process is achieved. In turn, this facilitates a 20% reduction in component volume, resulting in a similar reduction in precious metal usage and a significant cost reduction. In addition, the platinum and palladium can be recovered from the metal surface of the foam more easily and in a more environmentally-friendly manner than from a ceramic surface.
Perfectly adapted to suit any application
Metal foam is produced with a fully open-pored nickel and iron-based structure in a patented process. The pore size is defined to 450, 580, 800 and 1200 µm. An additional advantage of Alantum's material is its ability to be shaped easily, which is preserved even after the coating process. The metal alloy foam can be cut, moulded, bent, coiled and stacked. This makes it perfectly adaptable to suit any application and any required installation space.
Further information can be found at www.alantum.com.
Contacts for editorial staff:
SCHULZ. PRESSE. TEXT., Doris Schulz, Journalist (DJV), Martin-Luther-Strasse 39,
70825 Korntal, Germany, Telephone: +49 (0)711 854085, Fax: +49 (0)711 815895,
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