Alternative technology for gasifying manure and sewage sludge promising

News - 30 March 2016

Wet biomass, such as sewage sludge and manure, could soon be efficiently convertible into natural gas by means of so-called supercritical water gasification. Onursal Yakaboylu has contributed to the further development of this new technology and obtained his doctorate on this subject at TU Delft on Thursday 17 March.

Wet biomass

Biomass will play an important role in the coming years, together with other sustainable energy sources. Conventional gasification is an excellent conversion technology for dry biomass. However, in the case of wet biomass, such as sewage sludge, animal manure and residues from the food industry, this method is not efficient, since the drying process uses too much energy. An alternative method is anaerobic digestion, although this is a very slow process.

Supercritical

 

A possible viable alternative for wet biomass is the supercritical water gasification process. This process does not require a drying, is fast and under high pressure and temperature converts wet biomass in water into natural gas.

Wet biomass waste streams consist mainly of water, organic compounds and minerals (salts). When wet biomass is pressurised and heated up to conditions above the so-called critical point, the water will reach a state between a liquid and a gas (supercritical state). The properties of water then change dramatically. The water becomes a solvent for the organic components, a reactant and a catalyst, resulting in a rapid and virtually complete conversion of the organic components into gas. The minerals, on the other hand, are no longer soluble in the supercritical water and will crystallise into mineral particles. This makes it possible to separate the minerals in a solid form. Because the waste is almost completely converted, the gas yield and savings on the costs of waste management are substantial.

Pilot plant

Of course, the process must be reliable and efficient for the large-scale commercial application of supercritical water gasification. The Gensos company (a TU Delft spin-off) has improved the technology in recent years and shown that its works in experiments. Yakaboylu’s TU Delft PhD research is part of this ongoing improvement. His dissertation was aimed at modelling the thermodynamic equilibrium, additional experimental research and process modelling. Together with Gensos, he designed, among other things, an innovative new type of experimental configuration, in which a fluidised bed reactor is integrated. Gensos is also currently testing a pilot plant on a commercial scale.

 

More information
For further information please contact dr. ir. Wiebren de Jong, TU Delft tel. +31 15 - 27 894 76 or wiebren.dejong@tudelft.nl.

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