Thermal Exploitation of Wastes with Lignite for Energy Production

Abstract

The thermal exploitation of wastewood with Greek lignite was investigated by performing tests in a laboratory-scale fluidized bed reactor, a 1-MW th semi-industrial circulating fluidized bed combustor, and an industrial boiler. Blends of natural wood, demolition wood, railroad sleepers, medium-density fiberboard residues, and power poles with lignite were used, and the co-combustion efficiency and the effect of wastewood addition on the emitted pollutants were investigated. Carbon monoxide, sulfur dioxide, and oxides of nitrogen emissions were continuously monitored, and, during the industrial-scale tests, the toxic emissions (polychlorinated dibenzodioxins and dibenzofurans and heavy metals) were determined. Ash samples were analyzed for heavy metals in an inductively coupled plasma-atomic emission spectroscopy spectrophotometer.Problems were observed during the preparation of wastewood, because species embedded with different compounds, such as railway sleepers and demolition wood, were not easily treated. All wastewood blends were proven good fuels; co-combustion proceeded smoothly and homogeneous temperature and pressure profiles were obtained. Although some fluctuations were observed, low emissions of gaseous pollutants were obtained for all fuel blends. The metal element emissions (in the flue gases and the solid residues) were lower than the legislative limits. Therefore, wastewood co-combustion with lignite can be realized, provided that the fuel handling and preparation can be practically performed in large-scale installations.

Co-combustion of Bituminous Coal and Pickling Sludge in a Drop-Tube Furnace: Thermodynamic Study and Experimental Data on the Distribution of Cr, Ni, Mn, As, Cu, Sb, Pb, Cd, Zn, and Sn

“…These substances can be released into the environment through flue gas, fly ash, and bottom ash during the co-combustion process in suspensionfiring boilers; secondary pollution may occur if improper disposal methods are used. Co-combustion experiments using different waste fuels have been performed to study heavy metal emission characteristics, including co-combustion of sewage sludge in a scaled drop-tube furnace, 6 in a circulating fluidized bed incinerator, 7 and in a pulverized coal boiler; 8,9 cocombustion of solid recovered fuel in an entrained flow reactor, 10 in a pulverized coal-fired power station, 11 and in a drop-tube furnace; 12 co-combustion of refuse-derived fuel in a fluidized bed pilot; 13 and co-combustion of waste wood in a laboratory-scale fluidized bed reactor 14 and in a bubbling fluidized bed boiler. 15 In general, the heavy metal content in waste materials has a large impact on heavy metal emissions from fly ash, bottom ash, and flue gas during the co-combustion process in boilers.…”