Alternate: Low Temperature Conductive Drying: Enhancing Thermal Efficiency in Biosolids Treatment

Overview Low temperature, conductive drying represents a novel approach in the pre-treatment of biosolids for plasma synthesis, addressing critical efficiency and sustainability challenges in waste-to-energy processes. This unique drying and dewatering technology substantially reduces moisture content in biosolids, optimizing the energy requirements and operational costs for subsequent plasma synthesis. By lowering water content pre-treatment, LTC Dry enhances thermal efficiency, minimizes energy inputs, and improves syngas quality while reducing waste by-products, contributing to a more effective and environmentally responsible waste-to-energy solution. Process Description The LTC Dry process starts with mechanically dewatered biosolids, typically at 20% dry solids (DS) but accommodating variations from 5% to over 30% DS. Biosolids from multiple wastewater treatment plants (WWTPs) are combined and conditioned through a distinct, predominantly conductive heat transfer process rather than the convective heating used in conventional drying methods. Pre-heated, fully dried biosolids are stored in a vertical silo featuring pillow plate coils that convey necessary thermal energy. These pre-heated solids flow by gravity through a nozzle and enter the initial conveyor section, where they mix with wet cake injected via a progressive cavity pump. A high ratio of dry to wet solids (typically 10:1 to 40:1) ensures efficient mixing without agglomeration, forming dense granules with increased bulk density (45-55+ lbs per cubic foot). Energy transfer and mixing in the first conveyor complete most of the drying. The dry solids are then conveyed to the top of the silo for re-heating, with a takeoff system maintaining equilibrium by removing product equivalent to the input wet cake. This process is executed under high vacuum (down to --14.1 psi) and operates without additional air for drying, which reduces offgas emissions and VOCs. Vapors are directed through a condenser, capturing evaporated water and minimizing VOCs and contaminants, which are managed in an odor control system or blended into syngas-fed power generation downstream. Key Advantages The LTC Dry system's combination of indirect conductive heating, high vacuum operation, and efficient blending of dry and wet biosolids achieves several operational and environmental benefits. Key advantages include: -High Thermal Efficiency: Conductive heating under vacuum minimizes energy consumption and emissions. -Operational Flexibility: The system accommodates diverse heat sources that may not be feasible with traditional methods. -Enhanced Safety and Reliability: Lower operating temperatures and the absence of drying air improve safety and reduce operational risks. -Compact Design: A smaller footprint than traditional drying systems allows for easier integration and reduces installation costs. By effectively pre-treating biosolids, conductive drying significantly improves the performance of thermal destruction technologies, making it a crucial advancement in sustainable waste-to-energy solutions.