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    Mongabay, a leading resource for news and perspectives on environmental and conservation issues related to the tropics, has launched Tropical Conservation Science - a new, open access academic e-journal. It will cover a wide variety of scientific and social studies on tropical ecosystems, their biodiversity and the threats posed to them. Tropical Conservation Science - March 8, 2008.

    At the 148th Meeting of the OPEC Conference, the oil exporting cartel decided to leave its production level unchanged, sending crude prices spiralling to new records (above $104). OPEC "observed that the market is well-supplied, with current commercial oil stocks standing above their five-year average. The Conference further noted, with concern, that the current price environment does not reflect market fundamentals, as crude oil prices are being strongly influenced by the weakness in the US dollar, rising inflation and significant flow of funds into the commodities market." OPEC - March 5, 2008.

    Kyushu University (Japan) is establishing what it says will be the world’s first graduate program in hydrogen energy technologies. The new master’s program for hydrogen engineering is to be offered at the university’s new Ito campus in Fukuoka Prefecture. Lectures will cover such topics as hydrogen energy and developing the fuel cells needed to convert hydrogen into heat or electricity. Of all the renewable pathways to produce hydrogen, bio-hydrogen based on the gasification of biomass is by far both the most efficient, cost-effective and cleanest. Fuel Cell Works - March 3, 2008.


    An entrepreneur in Ivory Coast has developed a project to establish a network of Miscanthus giganteus farms aimed at producing biomass for use in power generation. In a first phase, the goal is to grow the crop on 200 hectares, after which expansion will start. The project is in an advanced stage, but the entrepreneur still seeks partners and investors. The plantation is to be located in an agro-ecological zone qualified as highly suitable for the grass species. Contact us - March 3, 2008.

    A 7.1MW biomass power plant to be built on the Haiwaiian island of Kaua‘i has received approval from the local Planning Commission. The plant, owned and operated by Green Energy Hawaii, will use albizia trees, a hardy species that grows in poor soil on rainfall alone. The renewable power plant will meet 10 percent of the island's energy needs. Kauai World - February 27, 2008.


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Monday, September 15, 2008

Researchers design more efficient fluidized bed for biomass gasification


Scientists from the Carlos III University of Madrid (UC3M) have developed a new system that improves the efficiency of the conversion process of biomass to gas that will contribute to the production of renewable energy.

One of the challenges that chemical engineers face is placing solid materials in contact with gases to generate certain reactions. One of the options is to use a fluidized bed, consisting of a vertical cylinder with a perforated plate inside where solid particles are introduced using pressurised air.

This way, the solid particles are suspended, and behave much like boiling water. Solids behaving like a liquid depend on the speed of the air stream, making it key to achieving the desired behaviour. With insufficient air, the particles don’t move, but with too much the opposite happens, and they are carried away by the air stream.

Fluidized beds have important environmental applications because they allow the gasification of biomass to produce energy in an efficient manner. That is, producing fuel gas from crushed biomass which can then be used for energy production.

According Mercedes de Vega from the Energy System Engineering Group of the department of Thermal and Fluid Engineering of the UC3M, using fluidised beds as chemical reactors allows for a more efficient conversion by achieving high mixing degrees and high exchange rates of mass and heat.

According to the researchers, this renewable energy source has great potential, especially in processes of co-combustion, direct combustion, and gasification. The applications are mainly industrial, open to be used in motors for the production of electricity, in gas turbines, drying processes, as well as in the pharmaceutical industry for the treatment of powder.

Greater efficiency
The study analyses the behaviour of a new bed designed with a rotating base (illustration, click to enlarge). The base consists of a perforated plate where holes represent just 1% of its total area. The study evaluates the performance of this new design, considering the increase in pressure and the quality of the fluidisation:
:: :: :: :: :: :: :: ::

It also analyses the effect of the rotation speed of the perforated plate on the performance of the fluidised bed. This type of beds can usually present problems such as agglomeration of solid particles and points of high temperature.

But one of the most important conclusions determined that the rotating perforated plate reduces these problems by maintaining a very uniform fluidisation. The researchers now propose, for future investigations, to study different rotation speeds over a hundred revolutions per minute, and to alter the configuration of the holes in the plate.

Celia Sobrino, co-author of the study, states that the new rotating distribution plate produces smaller bubbles inside the fluidised bed and distributes them better, while improving the efficiency of the conversion in gasification applications.

References:

C. Sobrino, J.A. Almendros-Ibañeza, D. Santana and M. de Vega, "Fluidization of Group B particles with a rotating distributor", Powder Technology, doi: 10.1016/j.powtec.2007.05.014

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