Final Report: Novel Process for the Management and Mitigation of Tar and Oil Byproducts From Solid Waste GasificationEPA Contract Number: EPD05046
Title: Novel Process for the Management and Mitigation of Tar and Oil Byproducts From Solid Waste Gasification
Investigators: Boardman, Richard D.
Small Business: Emery Energy Company
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2005 through August 31, 2005
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2005) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Waste , Small Business Innovation Research (SBIR)
Emery Energy Company, LLC, developed a novel, noncatalytic concept for separation and treatment of light and heavy hydrocarbons (tars and oils) that are inherently produced when municipal solid waste (MSW), biomass waste residuals, waste tires, and coal are gasified. Emery’s device, the Emery Entrainment Reactor (E2R), is based on enhancements of Emery’s earlier concepts and has the potential to improve overall gasification efficiency, simplify gasification operations, and reduce costs. This results in reducing overall gasifier system complexity by mitigating traditional downstream syngas cleanup unit operations and costs. The E2R will extend Emery’s fixed-bed gasifier capabilities to embrace a wider range of fuel types and synthesis gas conversion options.
A prototype of Emery’s novel pyrolysis gas treatment device was designed, fabricated, and assembled for testing at the existing Emery Gasifier Test Facility near Salt Lake City, Utah. All testing was in accordance with the research plan provided to the U.S. Environmental Protection Agency (EPA). The new E 2R exploits only nonmoving components and is based Emery’s knowledge and experience in process fluid dynamics, pyrolysis, and gasification reaction kinetics. The E2R was constructed with multiple instrumentation ports for accumulating test data such as flow velocities, system pressures and temperatures, and gas mixture compositions in the device. This first prototype was sized for integration with one of Emery’s test gasifier pilot plants for “hot” reacting flow demonstration under Phase II. Under the Phase I effort, cold flow testing and gas mixing studies were completed to verify that fluid mechanics and other performance criteria meet the technical and functional requirements, including entrainment and treatment of the hot pyrolysis gases from the main body of fuel within the gasifier.
An EPA Method 2F protocol 3-D flow measurement probe was used to determine velocity fields in the E2R as a function of fluid flows and configuration and position variations. These measurements were evaluated to determine whether the E2R is applicable to a continuum of solid wastes ranging from MSW to waste tires (i.e., fuels with relatively high oxygen content to fuels with low/no oxygen content). Standard gas infrared analyzers were used to measure gas mixing (i.e., mixture fractions).
The experimental data were evaluated to determine the suitability of the E 2R for application in Emery’s solid waste gasifiers. Results provided basic entrainment and mixing ratios that were used to verify application of the tar mitigation device for MSW and waste tires. These two wastes feedstocks are diametrically different. MSW has a high moisture content, high noncombustibles (ash) content, high oxygen content, approximately 75 percent volatiles (including the moisture), and less than 10 percent fixed carbon. Consequently, MSW has a low heating value and is difficult to convert to energy using any other technology than “mass burn” for steam generation. Waste tires, however, have little moisture and little chemically bound oxygen. Waste tires have about 65 percent volatiles, 30 percent fixed carbon, and up to twice the heating value of MSW. The flow data obtained in Phase I verified that the new component can be operated to enhance the gasification of both fuel types, potentially mitigating the need for typical downstream tar management processes, including tar crackers and quench systems. Material and energy balance and gasifier modeling results based on the flow measurements predict that a tar-free, medium-quality syngas, with a heating value of 120-140 Btu/scf (lower heating value basis) can be produced in a 100 ton/day modular gasifier unit. The size of this unit is the anticipated modular commercial size amenable for various industrial heating, drying, steam, and electrical power applications in a wide number of locations in the United States and throughout the world. Multiple modules can be used in parallel to achieve desired waste mitigation and/or gaseous fuel supply volumes.
The E2R efficiency and power requirements were calculated and compared to alternative gasifier systems that use downstream tar crackers, steam reforming, or autothermal reforming to manage the tars and oils that are produced from small-scale, fixed- and fluid-bed gasifiers. The parasitic load of the E2R is projected to be approximately 0.5-1 percent of the net available productive energy. This is favorable compared to tar crackers that may require syngas preheating and impurities removal prior to feeding the synthesis gas to catalytic treatment beds.
Adjustment of flow patterns in the E2R were manipulated by relatively minor changes of the device components and operating parameters. Therefore, a single design can be used to match a variety of gasifier feedstocks and operating conditions—affording a highly fuel-flexible system. This is particularly important for waste feedstocks because both daily and seasonal variations are anticipated. Furthermore, this apparatus helps reduce the financial risk associated with single fuel gasifiers.
Experimental testing showed that the E2R will perform its intended function. Both capital and operating costs appear favorable for the new technology, which can be fitted to either fixed-bed or fluidized-bed gasifiers. Scalability of the E2R and final verification of its performance requires integration and operation in conjunction with a gasifier test facility. This, hopefully, will be completed under the Phase II effort.
Application of the gasifier enhancement has been discussed with various entities currently considering and/or actively developing waste-to-energy projects. Commercial applications appear promising, pending ultimate demonstration of the E2R technology on an actual gasifier.