| OCR Text |
Show of 1500° to 20000F while the centr~l spout temperature can be varied from 2000° to 3000 0F. The hot zone thus formed is localized and very distinct in terms of temperature and size, and can be altered by changing the gas flow distribution. This feature is the key to it's ability to produce and control the rate of vitrification of solid residue in the fluidized bed. The ability of the fluidized bed to produce solid wastes that meet leachability standards has been demonstrated in coal gasification tests. As an example, contaminated soils and sludges fed into the fluidized bed undergo rapid gasification/combustion, producing gaseous components. The large inorganic fraction i s softened and oxidized in the hot zone, producing glassy, essentially non-leachable, environmentally benign agglomerates. These agglomerates are ejected from the fluidized bed through the classification zone via a terminal velocity mechanism. This solid product is expected to meet the EPA standards for leachability (TCLP) and should be suitable for normal disposal in landfills or for return to the site as fill. Additives or fluxes, such as calcium carbonate and sodium carbonate, may be added to this stage of the incinerator to help the agglomeration process as well as for capture of any sulfur and chlorine present in the waste being treated. Because of the large volume of R&D activity being conducted for various in-situ treatment methods, a considerable amount of information is available on the physical and chemical properties of the various soil types encountered at contaminated sites. In-situ vitrification (ISV) research has determined that most soils melt in the range of 2200° to 3l000F.[2-4] It is therefore expected that the first stage of the incinerator will be able to vitrify the majority of soils. Previous work by IGT and others in the areas of gasification, combustion, and incineration has shown that metals volatilized in gasifiers and combustors are closely associated with fine particulates carried over in the flue gas. Collection and return of fine particulate from the flue gas back to the fluidized bed will increase the quantity of metals captured in the vitrified solids discharged from the bottom of the fluidized bed. The addition of flue-gas cooling upstream of the cyclone will further increase metals capture in the discharge by partially condensing the more volatile metal vapors, a portion of which will be returned to the bed with the captured fines. Second Stage -- Cyclonic Incinerator The cyclonic combustor, shown in Figure 3, is the second incinerator stage where flue gas from the fluidized bed is further combusted at temperatures of 1600° to 22000F. Either secondary air or a natural gas/air mixture is fed to this incinerator stage as needed. The cyclonic combustor provides sufficient residence time at operating conditions to oxidize all carbon monoxide (CO) and organic compounds to CO2 and water vapor, giving a combined ORE greater than 99.99%. The -5- INSTITUTE o F GAS TEe H N 0 LOG Y |
