Paul M. Lemieux

Mutagenicity and chemical analysis of emissions from the open burning of scrap rubber tires.

The Salmonella mutagenicity assay and chemical analyses were used to evaluate the emissions from the open burning of scrap rubber tires that had been cut into either of two sizes, CHUNK or SHRED. A wide variety of polycyclic aromatic hydrocarbons was detected in the particulate organics. The mutagenic emission factor for the open burning of scrap rubber tires (approx. 8 x 10 to the power 7 revertants/kg of tire burned) was 3-4 orders of magnitude greater than the values for the combustion of oil, coal, or wood in utility boilers; it was most similar to values for the open burning of wood or plastic. These results demonstrate for the first time that the open burning of scrap rubber tires produces a high mutagenic emission factor, posing potential environmental and health effects. (A)

Role of combustion and sorbent parameters in prevention of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran formation during waste combustion.

The research uses experimental data and a statistical approach to determine the effect of combustion- and sorbent-injection-related parameters on the mechanism of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD and PCDF, respectively) formation and prevention in waste combustors. The operation of a pilot-scale combustor was varied to effect different regimes of oxygen (O2), hydrogen chloride (HCl), and chlorine (Cl2) concentration; temperature; residence time; quench rate; and sorbent injection. Stepwise regression analyses determined the predictive parameters for four models of PCDD, PCDF, the total of PCDD and PCDF yield, and the partitioning between PCDD and total yield. (Copyright (c) 1993 Amercian Chemical Society.)

Characterization of air pollutants emitted from a simulated scrap tire fire

Discarded automobile tires have become a concern to the general public, largely because the growing number of stockpile fires has focused attention on the potentially harmful combustion products as well as products of incomplete combustion (PICs) emitted into the atmosphere from uncontrolled burning of scrap tires. This paper describes a small-scale combustion study that was designed to collect, identify, and quantify the products emitted during the simulated open combustion of scrap tires. During the study, it was found that total estimated emissions of semivolatile organics ranged from 10 to 50 g/kg of tire material burned. Alkyl-substituted mono- and polyaromatic hydrocarbons were the predominant emission products identified. Elevated levels of zinc and lead were also measured.

Variables Affecting Emissions of PCDD/Fs from Uncontrolled Combustion of Household Waste in Barrels

Abstract The uncontrolled burning of household waste in barrels has recently been implicated as a major source of airborne emissions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). A detailed, systematic study to understand the variables affecting emissions of PCDD/Fs from burn barrels was performed. The waste composition, fullness of the barrel, and the combustion conditions within the barrel all contribute significantly to determining the emissions of PCDD/Fs from burn barrels. The study found no statistically significant effect on emissions from the Cl content of waste except at high levels, which are not representative of typical household waste. At these elevated Cl concentrations, the impact of Cl on PCDD/F emissions was found to be independent of the form of the Cl (inorganic or organic). For typical burn conditions, most of the PCDD/F emissions appear to be associated with the later stages of the burn when the waste is smoldering. Polychlorinated biphenyls (PCBs) were also measured for a subset of the tests. For the nominal waste composition, the average emissions were 76.8 ng toxic equivalency units (TEQ)WHO98 /kg of waste com busted, which suggests that uncontrolled burning of household waste could be a major source of airborne PCDD/Fs in the United States.

Application of Pulse Combustion to Solid and Hazardous Waste Incineration

Abstract A bench-scale Rotary Kiln Incinerator Simulator was retrofitted with a frequency-tunable pulse combustor in order to enhance the efficiency of combustion. The pulse combustor excites pulsations in the kiln and increases the completeness of combustion by promoting better mixing within the system. One phenomenon that is unique to batch-fed incineration systems, and rotary kilns in particular, is the formation of transient “puffs,” or plugs of unburned material that are formed when the instantaneous bed waste release rate is greater than the available local stoichiometric oxygen supplied from the primary burner. It is hypothesized that the additional mixing induced by the pulse combustor can reduce gas-phase stratification and enhance transport of available oxygen into the local fuel-rich zones of the puff. Tests were performed using toluene (C7H8) sorted onto a ground corn cob sorbent and placed in cardboard containers. The burner was operated in a non-pulse mode as a baseline condition, and then i...

Priority Pollutant Pah Analysis of Incinerator Emission Particles Using Hplc and Optimized Fluorescence Detection

The U.S. Environmental Protection Agency has investigated particle emissions from the incineration of various waste feeds. Emission particles from the incineration of municipal, medical/pathological, plastic and mixed wastes were captured and subsequently tested for biological activity. An ion-exchange fractionation of emission extracts yielded a base/neutral subfraction that contained a large portion of the total biological activity found. This subfraction was known to contain nonpolar neutrals, such as polycyclic aromatic hydrocarbons (PAHs), some of which are known mutagens and carcinogens. A modified version of U.S. EPA Method 610 for PAHs was utilized to quantify 15 of the 16 priority-pollutant PAHs found in emission particle extracts. Modification of Method 610 consisted of time-programmed excitation and emission wavelength selection for fluorescence detection. Only the PAH acenaphthylene, which has a low fluorescence intensity, could not be quantified at the desired levels using optimized fluorescent detection. PAH detection limits from 0.001 to 0.07 ng/mL extract were obtained. Emission rates based upon extractable organic matter, stack gas, mass of combusted waste and heating potential were calculated for each PAH and incinerator.

Bench-scale studies on the simultaneous formation of PCBs and PCDD/Fs from combustion systems

The presence of endocrine disrupting chemicals (EDCs) in the environment has wide-ranging potential ecological and health impacts on animals and humans. A significant amount of experimental and theoretical work has been performed the examining formation and control of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), which account for only part of the EDCs being emitted from combustion devices. Generally accepted mechanistic theories for PCDD/F formation propose heterogeneous reactions in the cooler regions of the combustor involving gas-phase organic precursors (such as chlorobenzenes or chlorophenols), a chlorine donor [such as hydrogen chloride (HCl)], and a flyash-bound metallic catalyst (such as copper chloride). There is evidence that some other proposed EDCs, including polychlorinated biphenyls (PCBs), are formed through a similar mechanistic pathway as PCDD/Fs. In addition, there is evidence that certain important steps in the catalytic reaction between the copper catalyst and the organic precursors may suggest a common rate limiting step for the heterogeneous formation of the previously mentioned EDCs. This paper reports on a bench-scale experimental study to characterize a newly built reactor system that was built to: produce levels and distributions of PCDD/F production similar to those achieved by previous researchers; verify similar responses to changes in independent variables; examine the hypothesis that PCB formation rates exhibit trends similar to PCDD/F formation rates as reactor variables are changed; and begin to explore the dependence of PCB formation on temperature and precursor type. The reactor system has been built, and initial reactor characterization studies have been performed. Initial experiments yielded results that support the hypothesis of a similar formation mechanism of PCBs and PCDD/Fs in combustors. Initial experiments uncovered potential deficiencies with the reactor system and the experimental procedures and have suggested corrective action to improve the experimental system.

Enhanced formation of dioxins and furans from combustion devices by addition of trace quantities of bromine

Past pilot-scale experimental studies have shown a dramatic increase in the formation of certain chlorinated products of incomplete combustion (PICs) caused by the addition of trace amounts of bromine (Br). Emissions of trichloroethylene and tetrachloroethylene, generated as PICs from the fuel-lean combustion of methylene chloride, were enhanced by up to 3 orders of magnitude by introducing Br in the form of methylene bromide at a constant halogen molar input rate with a 1:10 Br/chlorine (Cl) molar ratio. The two chlorinated PICs in question are both potential ring growth precursors, which could lead to enhanced formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs). The experiments described in this paper expand on this earlier work by examining the effect of trace amounts of Br on the formation of PCDDs/PCDFs, in addition to other chlorinated, brominated, and mixed bromo-chloro organic PICs.

Research on emissions and mitigation of POP's from combustion sources

The environmental consequences of persistent organic pollutants (POPs) are of increasing concern due to the serious health effects on animals and humans including reproduction, development and immunological function. Several major classes of POPs, including polycyclic aromatic hydrocarbons (PAHs), chlorobenzenes, chlorinated dioxins and chlorinated furans, have been identified as products of incomplete combustion (PICs) produced in trace levels in combustion systems. A wide variety of combustion processes, ranging from power plants, industrial boilers, industrial furnaces and incinerators, to home heating devices, are believed to be potential sources of POPs. Full-scale combustion facilities can be significant sources of POPs due to the large mass flow of flue gas released from a plant. Total emissions of POPs from small combustion devices, such as wood stoves and residential oil furnaces, can also be significant due to the large numbers of existing units near high population areas. It becomes increasingly important to understand the formation of POPs from different combustion processes to identify sources of POPs and to develop strategies for their prevention and mitigation. Research on POP emissions from combustion sources conducted by EPA is largely driven by the need for regulating the emissions of hazardous air pollutants as required by Title III of the 1990 Clean Air Act Amendments and by the Resource Conservation and Recovery Act. This paper provides a summary of EPAs research on emissions and control of POPs from combustion sources with emphasis on source characterization and measurement, formation and destruction mechanisms, formation prevention and flue gas cleaning. Laboratory experiments conducted to examine the PAH emissions from a wide variety of combustion processes, ranging from pulverized coal utility boilers to wood stoves, have shown that they exhibit widely different emission characteristics. Waste incineration research conducted by the National Risk Management Research Laboratory, Air Pollution Prevention and Control Division (NRMRL/APPCD) has also shown that complex mechanisms, including physical mixing and chemical kinetics, are involved in the formation of chlorinated PICs. Research has also indicated that the formation of ultra-trace levels of chlorinated-dioxins and -furans in combustion/incineration processes includes the complex interaction of several factors including temperature, chlorine content and catalyst. The beneficial effect of sulfur and sorbents for dioxin formation prevention is demonstrated. This Laboratorys effort to develop and evaluate state-of-the-art technologies for on-line measurements of PAHs, volatile PICs, dioxins and furans is also discussed. The promising potential of applying artificial-intelligence-based control systems for improving combustion processes operating conditions as a POP prevention approach is demonstrated.

Minimization of transient emissions from rotary kiln incinerators

Abstract Transient emissions of organics can occur from rotary kiln incinerators when drums containing liquid wastes bound on sorbents are introduced in a batch-wise fashion. Physical processes controlling the release of waste from the sorbent material are greatly affected by the rotation speed of the kiln and the kiln temperature. Local partial pressure of oxygen influences the rate of oxidation of the puff formed inside the kiln. These physical and chemical phenomena can be exploited to effect control of transient emissions by oxygen enrichment, where this is accomplished in either a steady or a dynamic mode. Experimental results from a pilot-scale rotary kiln incinerator simulator were combined with a theoretical model in order to explore the potential of minimizing transient emissions through changes in kiln rotation speed, kiln temperature, steady oxygen enrichment, and oxygen enrichment in a dynamic mode. Results indicated that transient organic emissions could indeed be minimized by changes in thes...