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_______________________________________________________________ _______________________________________________________________ Report Information from ProQuest October 16 2014 14:28 _______________________________________________________________ 16 October 2014 ProQuest Tabla de contenido 1. Managing Emissions During Hazardous-Waste Combustion....................................................................... 1 Bibliografía...................................................................
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   _______________________________________________________________     _______________________________________________________________    Report Information from ProQuest October 16 2014 14:28  _______________________________________________________________    16 October 2014ProQuest  Tabla de contenido 1. Managing Emissions During Hazardous-Waste Combustion.......................................................................1Bibliografía........................................................................................................................................................1216 October 2014iiProQuest  Documento 1 de 1   Managing Emissions During Hazardous-Waste Combustion Enlace de documentos de ProQuest   Resumen: As one of the most controversial options for treating hazardous wastes, combustion systems thattreat or use some form of hazardous waste as a primary or supplemental fuel source have undergone intensescrutiny, regulation and public opposition over the last two decades. Yet, hazardous-waste combustiontechnologies fill an essential niche in assuring that both the toxicity and volume of certain waste streams arereduced to safe and manageable levels in accordance with legislative mandates in a number of countries. At theheart of many corporate and government policies regarding the prioritization of waste-management options lieswhat has been termed the waste-management hierarchy. This hierarchy defines a set of priorities to helpdefine how best to manage existing or potential waste streams, and states a strong preference for eliminatingwaste at the source prior to its generation. Nitrogen oxides are formed during combustion and must becontrolled through proper system design and operation. Texto completo: Headnote Proper system selection and design ensures that waste volume and toxicity are reduced to safe levels, and thatemissions meet legislative requirements As one of the most controversial options for treating hazardous wastes, combustion systems that treat or usesome form of hazardous waste as a primary or supplemental fuel source have undergone intense scrutiny,regulation and public opposition over the last two decades. Yet, hazardous-waste combustion technologies fillan essential niche in assuring that both the toxicity and volume of certain waste streams are reduced to safeand manageable levels in accordance with legislative mandates in a number of countries. Table 1 summarizes the many types of combustion technologies that can be used to process a number of hazardous and toxic waste streams. The table also discusses how most of these wellestablished combustiontechnologies can be adapted to suit the characteristics of a wide array of toxic and hazardous wastes streams. Waste-management hierarchy At the heart of many corporate and government policies regarding the prioritization of waste-managementoptions lies what has been termed the waste-management hierarchy. 1 This hierarchy defines a set of prioritiesto help define how best to manage existing or potential waste streams, and states a strong preference for eliminating waste at the source prior to its generation (for more on the benefits of pollution prevention, see CE,July, pp. 59-63). This type of policy, adopted by both both governments and companies, has led to significantreductions in the total volume of wastes produced over the past decade.2 After source reduction has been considered, the waste-management hierarchy states that recycling and reuseoptions are the next preference, followed by treatment or disposal methods that are considered to beenvironmentally safe. For example, the authors' firm recently helped a chemical facility to significantly reduce a solvent discharge toits wastewater-treatment plant, using a recycling and reuse approach. The solvent was present in a processvent stream that was being pumped and compressed by steam jet ejectors. This practice caused the solvent tobe lost to the wastewatertreatment system via the ejector condensate. The existing steam jet ejectors werereplaced with liquidring vacuum pumps employing the solvent as the seal fluid. With this change, the solventcondensed from the process vent now collects in the vacuum pump separator and is returned to storage for reuse. Clearly, processes that can be designed to produce a higher yield, and hence a greater percentage of productwith less byproduct waste, are intuitively desirable, from both a business and an environmental perspective.However, at some point, the tions of technology and economics affect the final manufacturing alternatives, and 16 October 2014Page 1 of 12ProQuest  in all but the rarest situations, some amount of waste will unavoidably be generated. When these wastes arehazardous or toxic, proper waste-management technologies must be employed to ensure that post-treatmentresidues can be safely disposed of, and that any final emissions pose no environmental threat. A number of countries have recognized that waste combustion technologies that are properly designed,equipped with appropriate emission-control systems, and operated responsibly by trained personnel play a keyrole in maintaining environmental quality. In the U.S. for example, when the U.S. Environmental ProtectionAgency (EPA) established the Land Disposal Restrictions Program, incineration formed the basis of both thetechnologyand performance-based requirements for many organic streams containing hazardous wastes thatare regulated under the federal hazardous-waste program [I]. Over the past few years, a number of U.S. hazardous-waste-combustion (HWC) facilities, both onsite andcommercial third-party units, have been upgraded to meet new federal emissions standards.3 Today, a number of complex risk-assessment studies suggest that these upgraded facilities pose minimalhuman health or environmental impact. Nonetheless, HWCs remain the subject of intense opposition, and manyinstallations may be forced to further upgrade their systems, depending on the outcome of additional U.S.federal regulation.4 Regulations vary by country Hazardous-waste incinerators and other waste-combustion systems are regulated differently in differentcountries. While some countries have specific standards for these process operations, other countries regulatewaste-combustion systems and their emissions under general air emissions programs. Table 2 summarizes therelevant regulations relating to hazardous-waste-combustion emissions for a selection of countries. Whilestandards vary worldwide, the U.S. and European Union programs are often used as references for thedevelopment of new standards elsewhere. Control approaches Table 3 lists the pollutants that are commonly encountered in combustion systems, and shows the possiblecontrol methods, which are discussed in detail below. For most combustion systems, hot fluegas producedduring the combustion step usually requires further treatment, to remove residual gaseous and particulatepollutants. The temperature of the gas stream leaving the combustion zone is high (typically above 800°C), andis typically quenched to a lower temperature before it is subjected to further treatment (for more on quenchingfluegas to control particulate emissions, see CE, August, pp. 183-188). This cooling can be done by installing awasteheat boiler to either generate steam or hot water, or preheat combustion air that is injected into the unit topromote oxidation. In cases where heat recovery is not used, the gases are instead quenched to the adiabatic saturationtemperature by the injecting water into the stream. The gases then pass from the quench system throughsubsequent treatment systems, such as particulate and/or acid-gas-removal devices, for further cleanup (Figure1). Controlling nitrogen oxides Nitrogen oxides (NOx) are formed during combustion and must be controlled through proper system design andoperation. There are generally two contributors to NOx formation during combustion: * Conversion of nitrogen contained in the combustion air - this is usually referred to as thermal NOx * Conversion of chemically bound nitrogen compounds that are contained in the feed - this is commonly referredto as chemical NOx Thermal NOx is controlled by minimizing flame temperature, typically through the use of low-NOx burners.Chemical NOx formation can be controlled using staged combustion. The first stage of the combustor operateswith sub-stoichiometric oxygen levels at high temperatures. Excess air is then added to complete combustion of carbon monoxide and residual hydrocarbons in the second stage. Two other methods of NOx control could be appropriate, depending on the application. These include: 16 October 2014Page 2 of 12ProQuest
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