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<br /> Comprehensive Review of <br /> S olid W aste Collection and Disposal Options <br /> <br /> <br />v2.1 167 10/22/12 <br />used to achieve a different balance of the gaseous by-products, mainly the production of a <br />hydrogen (H)-rich gas with smaller quantities of carbon monoxide (CO), methane (CH4) and <br />carbon dioxide (CO2). The refined gas, primarily H and CO, is termed syngas and has many <br />direct applications such as powering a turbine to produce electricity and potentially for use as a <br />feedstock to produce alternative vehicular fuel (ethanol), or other chemical compounds. Most of <br />these processes require an external heat source under normal operating conditions. This is <br />usually hot, clean air that captures heat from the downstream gas combustion process. <br /> <br />A basic gasification process is shown in Exhibit 12-6. Gasification processes have attracted <br />much interest because the process is inherently more efficient than a combustion-based process, <br />the syngas is a relatively clean energy source and the plant may generate less troublesome air <br />emissions overall. <br /> <br />Exhibit 12 -6. Basic Gasification Process <br /> <br /> <br /> <br />A relatively recent development for solid waste conversion using the gasification process, that <br />employs a unique heating source, is known as a plasma arc converter. Although there are many <br />variations, a typical plasma arc converter uses an array of plasma torches to generate <br />temperatures in the reactor of more than 5,000C. This extremely high temperature, coupled <br />with a gasification environment has shown potential in small laboratory test units to achieve a <br />very high efficiency in decomposing the organic fraction of the waste to syngas, while <br />generating a slag material from the inert fraction. The slag has potential for use as a substitute <br />ingredient in potentially many building materials, including concrete structural elements (e.g., <br />wall panels and blocks, etc.) and asphalt. <br /> <br />A plasma is an ionized gas that results when a basic gas, such as nitrogen or air is passed through <br />an electrical arc struck between two electrodes. The electrodes are constructed into a torch that <br />directs the plasma arc. The intense heat created by the arc can be used to treat many materials,