Wayne Seames

An initial study of the fine fragmentation fly ash particle mode generated during pulverized coal combustion

The emission of ambient particulate matter that is less than 2.5 μm in aerodynamic diameter from commercial coal combustion sources may represent a greater risk of inhalation into human and animal respiratory systems than emission of larger particles. In addition, there is lower removal efficiency in flue gas particle collection equipment for these smaller particles that may also increase deposition in the downwind environment and subsequent migration into the water table. Recent results suggest that pulverized coal fly ash particle formation is best described as a tri-modal particle size distribution that includes a submicron fume region, a fine fragmentation region centered at approximately 2.0 μm diameter, and a bulk fragmentation region. A fundamental understanding of the mechanisms leading to the formation of the fine fragmentation region and of how this formation influences toxic trace metal partitioning is an important step to mitigating the environmental impact of coal combustion. Results are presented related to some of the factors related to this issue. An extensive SEM examination of fly ash particles in the fine fragmentation region indicates that these particles appear to have a much larger effective surface area compared to supermicron particles due to irregularities such as fractures, stretching, and shedding. These particles also appear to be more reactive with oxy-anion trace elements, such as arsenic and selenium, which may be important in understanding the dominant mechanism related to trace element partitioning during pulverized coal combustion.

Impacts of Biodiesel on Pollutant Emissions of a JP-8–Fueled Turbine Engine

Abstract The impacts of biodiesel on gaseous and particulate matter (PM) emissions of a JP-8–fueled T63 engine were investigated. Jet fuel was blended with the soybean oil-derived methyl ester biofuel at various concentrations and combusted in the turbine engine. The engine was operated at three power settings, namely ground idle, cruise, and takeoff power, to study the impact of the biodiesel at significantly different pressure and temperature conditions. Particulate emissions were characterized by measuring the particle number density (PND; particulate concentration), the particle size distribution, and the total particulate mass. PM samples were collected for off-line analysis to obtain information about the effect of the biodiesel on the polycyclic aromatic hydrocarbon (PAH) content. In addition, temperature-programmed oxidation was performed on the collected soot samples to obtain information about the carbonaceous content (elemental or organic). Major and minor gaseous emissions were quantified using a total hydrocarbon analyzer, an oxygen analyzer, and a Fourier Transform IR analyzer. Test results showed the potential of biodiesel to reduce soot emissions in the jet-fueled turbine engine without negatively impacting the engine performance. These reductions, however, were observed only at the higher power settings with relatively high concentrations of biodiesel. Specifically, reductions of ∼15% in the PND were observed at cruise and takeoff conditions with 20% biodiesel in the jet fuel. At the idle condition, slight increases in PND were observed; however, evidence shows this increase to be the result of condensed uncombusted biodiesel. Most of the gaseous emissions were unaffected under all of the conditions. The biodiesel was observed to have minimal effect on the formation of polycyclic aromatic hydrocarbons during this study. In addition to the combustion results, discussion of the physical and chemical characteristics of the blended fuels obtained using standard American Society for Testing and Materials (ASTM) fuel specifications methods are presented.

An assessment of acid wash and bioleaching pre-treating options to remove mercury from coal

Abstract The United States Environmental Protection Agency is expected to begin regulating the release of vapor-phase mercury from coal-fired power plants in the year 2007. Chemical pre-treatment methods were investigated for mercury removal effectiveness from pulverized low-sulfur North Dakota lignite coal. More limited results were obtained for a pulverized high-sulfur Blacksville bituminous coal. A two-step acid wash treatment showed removal rates of 60–90%, compared to one-step treatments with concentrated HCl, which yielded removals of 30–38%. Removal effectiveness is similar for first step solvents of water, pH 5.0 acid, or pH 2.0 acid followed by concentrated HCl as the second step solvent, and is independent of first step incubation time. Neither of two bacterial strains, Thiobacillus ferrooxidans and T. thiooxidans , was found effective for mercury removal.

AROMATIZATION OF PROPYLENE OVER HZSM-5: A DESIGN OF EXPERIMENTS (DOE) APPROACH

Aromatization of propylene was performed in a continuous reactor over HZSM-5 catalysts. A full-factorial design of experiments (DOE) methodology identified the effects of temperature (400°–500°C), Si:Al ratio (50–80), propylene feed concentration (8.9–12.5 mol.%), and catalyst amount (0.2–1.0 g) on propylene conversion as well as the yields of benzene, toluene, p-xylene, o-xylene (BTX), and total BTX. The Si:Al ratio and amount of the HZSM-5 catalyst influenced all of the responses, while temperature affected all the responses except the yield of p-xylene. An increase in feed concentration significantly increased the yields of benzene, toluene, and total BTX. An interaction between propylene feed concentration and catalyst amount influenced the yields of benzene, toluene, and total BTX. This interaction indicated that a higher feed concentration promotes aromatization at higher catalyst concentrations. By contrast, the interaction of Si:Al ratio with propylene feed concentration was found significant for p-xylene and o-xylene yields, but not for benzene and toluene, suggesting that xylenes are synthesized on different sites than those for benzene and toluene. These interaction effects demonstrate how the use of DOE can uncover significant information generally missed using traditional experimental strategies.

Method development for the characterization of biofuel intermediate products using gas chromatography with simultaneous mass spectrometric and flame ionization detections

Accurate analytical methods are required to develop and evaluate the quality of new renewable transportation fuels and intermediate organic liquid products (OLPs). Unfortunately, existing methods developed for the detailed characterization of petroleum products, are not accurate for many of the OLPs generated from non-petroleum feedstocks. In this study, a method was developed and applied to the detailed characterization of complex OLPs formed during triacylglyceride (TG) pyrolysis which is the basis for generating one class of emerging biofuels. This method uses gas chromatography coupled simultaneously with flame ionization and mass spectrometry detectors (GC-FID/MS). The FID provided accurate quantification of carbonaceous species while MS enabled identification of unknown compounds. A programed temperature vaporizer using a 25 °C, 0.1 min, 720 °C min(-1), 350 °C, 5 min temperature program is employed which minimizes compound discrimination better than the more commonly utilized split/splitless injector, as verified with injections at 250 and 350 °C. Two standard mixtures featuring over 150 components are used for accurate identification and a designed calibration standard accounts for compound discrimination at the injector and differing FID responses of various classes of compounds. This new method was used to identify and quantify over 250 species in OLPs generated from canola oil, soybean oil, and canola methyl ester (CME). In addition to hydrocarbons, the method was used to quantify polar (upon derivatization) and unidentified species, plus the unresolved complex mixture that has not typically been determined in previous studies. Repeatability of the analytical method was below 5% RSD for all individual components. Using this method, the mass balance was closed for samples derived from canola and soybean oil but only ca. 77 wt% of the OLP generated from CME could be characterized. The ability to close the mass balance depended on sample origin, demonstrating the need for an accurate quantification method for biofuels at various stages of production.

Recovery of CO2 from Monoethanolamine using a Membrane Contactor

The technical feasibility of using polymeric membranes to recover CO2 from saturated monoethanolamine was investigated. A lab-scale system was built to study the performance of several common polymeric porous membranes for the recovery of CO2 from saturated aqueous MEA solution (15% wt) using a thermal swing process. Compositional, structural, and surface morphological characterization was carried out on the membranes before and after this process. The results showed polypropylene and polytetrafluoroethylene porous membranes outperformed polyester, polyamide, polyvinylidene fluoride, polysulfone, and cellulose acetate. The major component of mass transfer resistance was found to be the liquid boundary layer at the surface of the membrane. Membrane wetting and fouling were found to significantly deteriorate membrane performance.

Extraction of Fatty Acids from Noncatalytically Cracked Triacylglycerides with Water and Aqueous Sodium Hydroxide

A study was performed to determine the effectiveness of extracting short-chain fatty acids (SCFAs) from noncatalytically cracked canola oil using neutral and basic aqueous solutions. A detailed quantitative analysis was performed to determine the composition of the cracking reactor organic liquid product (OLP) before and after extraction. We have demonstrated that water alone can be used to completely extract C2 and C3 monocarboxylic acids, while partially extracting acids up to C6. The degree of extraction can be slightly increased by increasing temperature and, for some acids, by using multiple extraction stages. A basic solution (1 M NaOH) was found to extract a wider range of acids—up to C8—and this was independent of the temperature or number of stages. While this method was not capable of reducing the acid number of the OLP to within the specifications for fuel, it could be used to extract a narrow range (C2 to C5) of biobased carboxylic acids. As such, this method could serve as one step in a process to produce biobased carboxylic acids, replacing acids currently produced from non-renewable sources.

Extraction of Fatty Acids from Noncatalytically Cracked Triacylglycerides Using Aqueous Amines

It has been reported that a basic aqueous solution was effective in extracting short chain C2–C6 fatty acids from noncatalytically cracked triacylglyceride oils. However, the extraction efficiency was not optimal over the entire range (C2–C12) of acids present in the cracking reactor organic liquid product (OLP). Therefore, an additional study was performed to explore the efficiency of solvent extraction using aqueous amines for this application. Based on the screening of several amines, two tertiary amines, trimethyl amine (TMA), and dimethyl ethanolamine (DMEA), were selected and evaluated. The extraction conditions were optimized with respect to several factors: temperature, amine concentration, and the amine-to-OLPratio (amine/OLP). Under optimal conditions, both TMA and DMEA were effective in extracting a wide range of organic acids, with TMA removing 93% of total acids and DMEA removing 100% of total acids. The amine/OLP was found to be a significant factor, as was the concentration of the amine solution. Temperature was not found to be a significant factor over the range studied. These results provide a basis for the development of a scalable, continuous process to produce a variety of C2–C12 fatty acids from biological sources.

Comparison of Coal Ash Particle Size Distributions from Berner and Dekati Low Pressure Impactors

This article presents the differential mass size distributions of coal combustion particulate matter (PM) determined with the Berner low-pressure impactor (BLPI, Hauke Model 25-4/0.015) and a newer generation of low pressure impactor, the Dekati low-pressure impactor (DLPI, Dekati Ltd Model 6281). The collection characteristics of the BLPI and DLPI are compared and cutoff diameters are calculated. Samples were collected in the post-combustion zone of a 19 kW vertical downflow combustor from two coal types. Both BLPI and DLPI represent a tri-modal distribution and give statistically similar characterizations of the coal ash particle size distribution. Distributions generated from DLPI data have higher fractions of submicron particles compared to those generated from BLPI data. The DLPIs two additional stages may provide greater resolution in the submicron region than the BLPI.

Biofiltration of gasoline and diesel aliphatic hydrocarbons

The ability of a biofilm to switch between the mixtures of mostly aromatic and aliphatic hydrocarbons was investigated to assess biofiltration efficiency and potential substrate interactions. A switch from gasoline, which consisted of both aliphatic and aromatic hydrocarbons, to a mixture of volatile diesel n-alkanes resulted in a significant increase in biofiltration efficiency, despite the lack of readily biodegradable aromatic hydrocarbons in the diesel mixture. This improved biofilter performance was shown to be the result of the presence of larger size (C9-C12) linear alkanes in diesel, which turned out to be more degradable than their shorter-chain (C6-C8) homologues in gasoline. The evidence obtained from both biofiltration-based and independent microbiological tests indicated that the rate was limited by biochemical reactions, with the inhibition of shorter chain alkane biodegradation by their larger size homologues as corroborated by a significant substrate specialization along the biofilter bed. These observations were explained by the lack of specific enzymes designed for the oxidation of short-chain alkanes as opposed to their longer carbon chain homologues. Implications: Biological removal of petroleum hydrocarbons from contaminated air has not become a widely used technology due to its low efficiency. This paper presents the analysis of this problem using bench-scale experiments and provides several reasons for the low biodegradation efficiency of gasoline. The results reported suggest that gasoline removal efficiency strongly depends on the substrate composition, with aromatic hydrocarbons being removed preferentially. The study also opens up a new perspective for the efficient biofiltration of diesel hydrocarbons as opposed to gasoline, as higher molecular weight n-alkanes of diesel were removed readily. By contrast, low-molecular-weight n-alkanes of gasoline turned out to be poor substrates for biofiltration, and the biological reasons for this phenomenon were suggested.