James T. Cobb

Stabilization of Heavy Metal Containing Hazardous Wastes with Byproducts from Advanced Clean Coal Technology Systems

The purpose of this investigation was to evaluate the success of residues from advanced Clean Coal Technology (CCT) systems as stabilization agents for heavy metal containing hazardous wastes. In the context examined here, stabilization refers to techniques that reduce the toxicity of a waste by converting the hazardous constituents to a less soluble, mobile, or toxic form.1 Three advanced CCT byproducts were used: coal waste-fired circulating fluidized bed combustor residue, pressurized fluidized bed combustor residue, and spray drier residue. Seven metal-laden hazardous wastes were treated: three contaminated soils, two air pollution control dusts, wastewater treatment plant sludge, and sandblast waste. Each of the seven hazardous wastes was treated with each of the three CCT byproducts at dosages of 10, 30, and 50% by weight (byproduct:waste). The treatment effectiveness of each mixture was evaluated by the Toxicity Characteristic Leaching Procedure. Of the 63 mixtures evaluated, 21 produced non-hazardous residues. Treatment effectiveness can likely be attributed to mechanisms such as precipitation and encapsulation due to the formation of hydrated calcium silicates and calcium sulfo-alu-minates. Results indicate that these residues have potential beneficial uses to the hazardous waste treatment community, possibly substituting for costly treatment chemicals.

Urban Wood/Coal Co-Firing in the Bellefield Boilerplant

During the third quarter, important preparatory work was continued so that the experimental activities can begin early in the fourth quarter. Authorization was awaited in response to the letter that was submitted to the Allegheny County Health Department (ACHD) seeking an R&D variance for the air permit at the Bellefield Boiler Plant (BBP). Verbal authorizations were received from the Pennsylvania Department of Environmental Protection (PADEP) for R&D variances for solid waste permits at the J. A. Rutter Company (JARC), and Emery Tree Service (ETS). Construction wood was acquired from Thompson Properties and Seven D Corporation. Forty tons of pallet and construction wood were ground to produce BioGrind Wood Chips at JARC and delivered to Mon Valley Transportation Company (MVTC). Five tons of construction wood were milled at ETS and half of the product delivered to MVTC. Discussions were held with BBP and Energy Systems Associates (ESA) about the test program. Material and energy balances on Boiler No.1 and a plan for data collection were prepared. Presentations describing the University of Pittsburgh Wood/Coal Co-Firing Program were provided to the Pittsburgh Chapter of the Pennsylvania Society of Professional Engineers, and the Upgraded Coal Interest Group and the Biomass Interest Group (BIG) of the Electric Power Research Institute (EPRI). An article describing the program appeared in the Pittsburgh Post-Gazette. An application was submitted for authorization for a Pennsylvania Switchgrass Energy and Conservation Program.

Cofiring Wood and Coal to Stoker Boilers in Pittsburgh

The prime objective of the University of Pittsburghs overall wood/coal cofiring program is the successful introduction of commercial cofiring of urban wood wastes into the stoker boilers of western Pennsylvania. Central to this objective is the demonstration test at the Pittsburgh Brewing Company. In this test the project team is working to show that two commercially-available clean wood wastes - tub-ground pallet waste and chipped clearance wood - can be included in the fuel fed daily to an industrial stoker boiler. Irrespective of its economic outcome, the technical success of the demonstration at the brewery will allow the local air quality regulation agency to permit a parametric test at the Bellefield Boiler Plant. The objective of this test is to obtain comprehensive data on all key parameters of this operational boiler while firing wood with coal. The data would then be used for thorough generic technical and economic analyses. The technical analysis would be added to the open literature for the general planning and operational guidance for boiler owners and operators. The economic analysis would gage the potential for providing this stoker fuel commercially in an urban setting and for purchasing it regularly for combustion in an urban stoker boiler.

URBAN WOOD/COAL CO-FIRING IN THE NIOSH BOILERPLANT

During the third quarter, the experimental portion of the project was carried out. Three one-day tests using wood/coal blends of 33% wood by volume (both construction wood and demolition wood) were conducted at the NIOSH Boiler Plant (NBP). Blends using hammer-milled wood were operationally successful and can form the basis of Phase II. Emissions of SO{sub 2} and NOx decreased and that of CO increased when compared with combusting coal alone. Mercury emissions were measured and the mathematical modeling of mercury speciation reactions continued, yielding many interesting results. Material and energy balances for the test periods at the NBP, as well as at the Bellefield Boiler Plant, were prepared. Steps were taken to remove severe constraints from the Pennsylvania Switchgrass Energy and Conservation Project and to organize the supplying of landfill gas to the Bruceton federal complex. Two presentations were made to meetings of the Electric Power Research Institute and the National Energy Technology Laboratory.