EnerTech's Method of Converting Biosolids to a Usable Fuel: The Emerging Technology of Biosolids Carbonization

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Abstract:

EnerTech's patented SlurryCarb™ process chemically converts Biosolids into a high-energy solid fuel. The technology can produce significant savings in both operating and capital costs. Commercial installations of the process are currently under development.

Simplicity of operation is key to the SlurryCarb™ technology. Biosolids are brought to a central manufacturing facility where up to 25% solid material is processed as a pumpable slurry. Biosolids are first subjected to nominal pressure to observe the saturated steam curve before adding heat. Upon reaching the desired reaction pressure and temperature without the presence of oxygen, the molecular structure of Biosolids is reconfigured so that the reacted product becomes extremely hydrophobic and is able to be dewatered to a solids content in excess of 50%. This dewatered reacted product is concentrated in carbon and has had removed over 80% of the original water present in the original Biosolids without evaporation. It is then pelletized to form a fuel that is up to 8000 Btu/lb. The fuel is exported to a customer and utilized as a renewable fuel.

The SlurryCarb™ technology is not pyrolysis or not the Zimpro process as it neither creates oil, gas or oxidizes the organic material in Biosolids. The goal of the process is to remove the water and isolate the carbon that is found in Biosolids. First, up to 25% solid Biosolids are received. Biosolds are then continuously pumped and pressurized above their saturated steam pressure to prevent boiling when heated above its normal boiling point. The slurry maintains a liquid state throughout processing and thermal energy inputs for the evaporation of water are minimized. By flowing through heat exchangers, the temperature of the pumpable slurry is raised to the desired reaction temperature. At the heated temperature and pressure, the slurry is molecularly rearranged with the cellular structure of sludge ruptured and carbon dioxide gas being split off from the solid waste, a step called “carbonization.” This reaction significantly reduces the size and improves the uniformity of the Biosolids molecules that also lose their affinity for water. This reaction is stopped short of pyrolysis into hydrocarbon liquids or gasses. After partial cooling and depressurization, the carbonized product is then dewatered via conventional equipment to up to 60% solids, dried, and finally pelletized. The filtrate from dewatering is pretreated to the standards of the local wastewater treatment plant.

The product fuel is then transported to the customer (85% less volume than the original Biosolids) and is combusted in conventional infrastructure and considered a renewable fuel.

Through operating experience and detailed design, the economics for the SlurryCarb™ technology are established. Because the technology avoids the evaporation of water, the economics are extremely compelling and competitive with current methods employed by the industry.

EnerTech has built a 20 ton per day facility with Mitsubishi in Japan. It has a demonstration facility in Atlanta, Georgia. The Company with its partners is developing a project near Los Angeles and a project near New York City. In both cases, the permit cycle has begun, the development team has been determined, and a user for the fuel established. In this paper, the project will discuss the project near Los Angeles.

Document Type: Research Article

DOI: http://dx.doi.org/10.2175/193864704784342965

Publication date: January 1, 2004

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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