Monday, July 30, 2012

Waste to Energy: Micro-Channel Fischer Tropsch

Sierra Energy plans to build a municipal waste to liquid fuels plant in Northern California, based upon the scalable microchannel Fischer Tropsch technology developed by Velocys / Oxford Catalysts.

The microchannel FT technology can affordably convert any carbonaceous form of matter -- from biomass to coal to natural gas to municipal waste, etc. -- to high quality diesel fuel and other high value chemicals.
The waste-to-liquids process involves two main operations: production of a synthesis gas (syngas) using a gasifier; followed by FT synthesis. The resulting FT product can then be upgraded via hydrocracking and fractionation to produce a range of liquid hydrocarbon fuels. The fuels produced can be directly substituted for conventional fuels, and are generally of higher quality than those derived by conventional means.

In the commercial demonstration, which will be hosted by SacPort Biofuels, the gasification will be carried out using Sierra Energy’s proprietary FastOx waste gasification process. The FT synthesis will be carried out using Velocys’ microchannel FT reactor technology. Sierra Energy intends to use this commercial demonstration as the basis for the design of a turn-key, waste gasification system called the FastOx Pathfinder.

The FastOx gasifier is a simple derivative of the blast furnace, specifically designed to convert waste; waste is fed into the top of the gasifier while oxygen and steam are injected into the bottom. The injection of oxygen and steam is one of Sierra Energy’s patented innovations. The waste passes through four reaction zones as it descends in the gasifier:
Drying occurs when the hot syngas produced at the bottom of the gasifier rises and passes through the waste in the top zone of the unit, drying the waste as it passes.

Devolatization is where the majority of the organic matter is driven off into syngas.

Partial oxidation occurs when carbon-containing materials in the waste react with the injectors. This reaction creates high temperatures in the range of 4,000 °F, allowing for the thorough conversion of remaining carbon into syngas.

Melting of inorganic compounds results from the high temperatures occurring in the partial oxidation zone. These compounds collect at the bottom of the unit and are continuously removed as inert stone (slag) and recycled metals.

While California's government is attempting to promote this nifty technology for waste to liquids, a more economical use at this time would be on offshore oil platforms and at stranded gas wells -- to reduce the level of natural gas flaring and to make economical use of stranded and offshore gas.

This technology would also work well for decentralised biomass to liquids (BTL) production on a local and regional level -- once the infrastructures for collection and densification of biomass are developed.

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