Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 281-286).

Thesis (Ph. D.)--Washington State University, December 2006. / Includes bibliographical references.

No description available.

Thesis (Ph. D.)--Stanford University, 1991. / "May 1991." Includes bibliographical references (p. 201-219).

Volatile organic compounds (VOCs) and carbon monoxide are considered the main greenhouse gas pollutants from either automotive engines or stationary sources. The increased concentration of these pollutants in air severely affects human health and causes changes in earth climate and vegetation growth rates. Ethylene is one of the VOCs closely related with photocatalytic pollution when it reacts with nitrogen oxides in the presence of sun light to form ground-level ozone. It is also responsible for quick repining of fruits and vegetables. Carbon monoxide, on the other hand, is a poisonous gas mainly released by vehicle emissions, and when inhaled in high concentrations, it causes severe health problems related to the respiratory system leading to significant rates of deaths annually in Europe and North America. Globally, The World Health Organization (WHO) estimates that seven million people die yearly due to poor air quality-related reasons which urges current and future stringent regulations to control air pollution emissions. In the past four decades, several equipment modifications and processes have been studied for reducing these emissions. Among them is the phenomenon of Electrochemical Promotion of Catalysis (EPOC) which was first reported in the early 1980s. EPOC has been successfully shown to convert automotive, indoor and industrial air pollutants such as VOCs, CO and nitrogen oxides (NOx) to harmless gases. It involves reversible changes in the catalytic properties of catalysts deposited on solid electrolytes when a small electric current or potential is applied. More recently, it was demonstrated that EPOC can be thermally induced without any electrical polarization, in analogy to the well-known phenomenon of metal-support interaction, by using noble metal nanocatalysts supported on ionically conducting materials such as yttria-stabilized zirconia (YSZ). The objective of this research is to gain deeper understanding of the factors affecting metal-support interaction between the active metal and the support to enhance their catalytic activity for environmentally-important reaction systems; specifically, ethylene and carbon monoxide oxidation as well as hydrogen fuel purification by carbon monoxide methanation. First, the activity of platinum nanoparticles deposited on carbon black, which is a conventional support used in catalysis, is studied. The effect of particle size of four Pt/C nanoparticles synthesized using a modified reduction method for ethylene (C2H4) complete catalytic oxidation is investigated. These catalysts show high activity towards C2H4 oxidation which is found to be a strongly size-dependent reaction. Full conversion of 1000 ppm C2H4 is achieved over the smallest nanoparticles (1.5 nm) at 100oC while higher temperature 170oC is required to completely oxidize ethylene over the largest nanoparticle (6.3 nm). The second stage of this research compares the catalytic activity of platinum and ruthenium nanoparticles when deposited on ionic or mixed ionic conductive vs. non ionic conductive supports for CO and VOCs oxidation. The Pt and Ru nanoparticles are deposited on yttria-stabilized zirconia (8% Y2O3-stabilised ZrO2), cerium (IV) oxide (CeO2), samarium-doped ceria (SDC), gamma-alumina (γ-Al2O3), carbon black and on novel perovskite group Sm1-xCexFeO3 (x = 0, 1, 5) resulting in ≤ 1 wt. (weight) % of Pt and Ru on each support. It is found that the nanocatalysts deposited on ionic conductive or mixed ionic conductive supports outperformed the catalysts deposited on non ionic conductors due to strong metal-support interaction that greatly affects the electronic and catalytic properties of the catalysts. The enhanced catalytic activity towards CO and C2H4 oxidation reactions is shown by earlier catalytic activity and complete conversion, lower activation energies, greater turnover frequencies and higher intrinsic rates per active surface area. To further investigate the effect of ionic conductivity of the supports and the exchange of O2- (oxygen vacancy) between the support and the catalyst surface, complete oxidation of pollutants is studied in the absence of oxygen in the gas phase. For the first time, complete oxidation of CO and C2H4 in an oxygen-free environment at low temperatures (< 250oC) is achieved, which represents the main novel finding in this research. The idea of pollutant removal in the absence of oxygen is extended to a practical reaction for fuel cells application which is hydrogen fuel purification from CO impurities at temperatures < 100oC. Moreover, the effect of particle size, pollutant concentration, operating conditions and support nature in the absence of oxygen in the gas feed is studied. It is proposed that the metal nanoparticles and the solid electrolyte form local nano-galvanic cells at the vicinity of the three-phase boundary where the anodic reaction is CO or C2H4 oxidation and the cathodic reaction is the surface partial reduction of the support. A systematic catalyst reactivation process is suggested and the catalytic activity of these nano-catalysts is studied which can be further investigated for air pollution control applications such as in vehicle catalytic converters, indoor air quality units and power plant emissions.

Organic solvent production plants emit waste gases containing volatile organic compounds (VOCs) which are usually harmful to the environments and public healths. Plant managers are obligated to control the VOC emission to meet regulations at reasonable costs. A solvent plant located in southern Taiwan emits VOC-containing gas streams from some distillation columns and storage vessels with a total ventilation gas flow rate of 2.6-3.6 m3/min which contains VOCs with concentrations of less than 1,000 mg C/m3. Due to a concern of plant¡¦s safety, the plant managers constructed a full-scale biofilter for eliminating a part of the VOCs and the associated odors in the waste gas. This study aimed to investigate the effects of operation parameters such as EBRT (empty bed retention time) of the gas through the biofiltration media and organic loading to the media on the VOC removal efficiency. The biofilter is constructed of RC (reinforced concrete) with outer dimensions of 8.45 mL ¡Ñ 3.30 mW ¡Ñ 3.00 mH. The filter was also instrumented with inverters for control of speed of induced fans, and with thermometers, hygrometers, and wind speed meters. Fern chips with a total packing volume of 36 m3 was used as the biofiltration media. After inoculation with suitable microorganisms, the waste gas was introduced to the filter for VOC elimination. Nutrients (urea, milk, and a phosphate salt) and water were supplemented to the media on a daily basis. The investigation period is July, 2008 to May, 2010. In the period, THC (total hydrocarbon) concentrations for the influent and effluent gases to and from the reactor were daily measured. In addition, on a weekly basis, compositions of the VOCs in gas samples were detected by a gas chromatography equipped with a flame ionization dector (FID). On the same time basis, pH, COD (chemical oxygen demand), SS (suspended solids) in a sample of the trickled liquid from the media was analyzed. Media pH and moisture content were also analyzed for understanding the environmental conditions around the microorganisms for the VOC degradation. Results indicated that the media was in conditions of pH = 4.5-7.0, moisture = 11-61 % in the experimental phase. Trickled liquid had low COD and SS contents which can be easily treated by the existing wastewater unit in the plant, or be recycled to the media. Avarage THC, NMHC (nonmethane hydrocarbon), and VOCs were 71, 73, and 79%, respectively, with gas EBRTs of 4.2-6.3 min. With media pH of 4-5 and moisture contents 51-57%, over 90% of the influent VOCs coulb be eliminated. However, nearly dried media (moisture around 10%) had VOC removal efficiencies of lower than 30%. Nutrition tests indicate that the VOC removal efficiency was nearly proportional to milk supplementation rate. Removal of ethnaol and acetic could easily be removed with an efficiency of over 97% while 2-pentane was only 74%. Odor intensities of the treated gas could be controlled to <1,000 (dilutions to threshold) according to 3 test data.

Abstract Biological processes have been proven to be economical and effective for control of VOCs with concentration of <1,000 mg C/m3. This study armed to develop a biofilter packed only with fern chips for the removal of airborne isopropyl alcohol (IPA). A three-stage down-flow biofilter (2.2 m in height and 0.4 m¡Ñ0.4 m in cross-sectional area) was constructed for the performance test. The first stage serviced as a humidifier for the incoming gas and the following two stages, both packed with fern chips with a packing space of 0.30 m ¡Ñ 0.40 m ¡Ñ0.40 m, as trickling bed biofilters for the VOC removal. Air with a nearly constant IPA concentration of 100 mg/Am3 (@ an average temperature of 34 oC) and a flow rate in the range of 100-400 L/min was fed to the reactor in Phase I test. The flow rate gave an empty bed retention time (EBRT) in the range of 12-48 s for the gas flowing through the two bed media. Solutions of urea-N, phosphate-P, and milk powder were supplied daily to the fern chips for the microbial nutrition in Phase I experiment which lasted for 26 days. Following the Phase, Phase II test operated with a constant EBRT of 12 s and without any nutrient supplementation for 30 days. Experimental results show that with an influent gas temperature of 29-40oC (average 34 oC) and relative humidity of 43-93% (average 73%), with a proper moistening of the bed media, the effluent gas could achieved a temperature of 26-35oC (average 29 oC) and a relative humidity of 98%. The proceeding medium experienced a greater moisture variation (12-68%, average 38%) than that (65-82%, average 72%) of the following one. The former and the latter media had pH in the range of 6.11-7.78 (average 6.77) and 6.13-7.36 (average 6.59), respectively. With no additional nutrient supplementation for 30 days, approximately 98% of the influent IPA of 100 mg/m3 could be removed at the EBRT of as short as 12 s which corresponded to a loading of 60 g IPA/m3.h.

A 20 kg/hr ritual-money combustion chamber and a 20 Am3/min (@35oC) wet scrubber were setup for performance tests on the removal of TSP (total solid particulates) from the combustion flue gas. Test results indicate that (1) TSP in the flue gas ranged from 93-157 (avg. 126) and 127-182 (avg. 157) mg/m3 (@35oC) at gas drawing rates (QG) of 13.1 and 26.3 m3/min (@35oC), respectively, and ritual-money combustion rates of 14.2-16.3 (avg. 15.3) kg/hr. The lower gas drawing rate gave lower TSP concentrations in the flue gas. TSP removal efficacy varied linearly with the liquid scrubbing rate (QL) and a 70% TSP removal was achieved at a QL of 60 L/min which is equivalent to a scrubbing-liquid intensity of 4.0 L/m2.s over the scrubber cross section. (2) Visual smoke intensity in the exit of the scrubber chimney was not apparent with a combustion rate of 16 kg/hr, scrubbing intensity of 4.0 L/m2.s, and gas drawing rates of 13.1 and 26.3 m3/min. (3) Scrubbing water consumptions of 1.2-2.4 L were estimated for a combustion of 1 kg ritual money. (4) Pertinent design parameters of a scrubber for 70% TSP removal from the flue gas are (a) liquid/gas ratio (QL/QG) = 3-6 L liquid/(m3 gas @30oC); (b) superficial gas velocity over the scrubber cross section (UG) = 0.6-1.2 m/s; (c) superficial liquid velocity over the scrubber cross section (UL) = 0.004 m/s; and (d) a gas-liquid contacting length of 0.70 m. Results also show that the combustion exit gas odor concentration (D/T, dilution times to threshold) could be removed from 309 to 232 by the scrubber at operation conditions of QG = 13.1 and 26.3 m3/min, and QL = 60 L/min. Results also show that parts of CO2, CO, and NO could be removed by the scrubbing liquor, and there was no significant removal for NO2 and SO2 by the scrubber. By spraying KClO3 on a homemade wood pulp ritual money at a dosage of 3 wt.%, it shows that it burned more rapidly and with more smoke emission than a non-sprayed sample. Experiments also show that FeCl3 (15mg/L) was a satisfactory coagulant for enhancing the coagulation and sedimentation of the suspended solids (SS) in the wasted scrubbing liquor (known as Gray water). By the coagulant, SS in the Gray water with a pH of 7.0 could be removed from 100 to < 10 mg/L. XRD (X-Ray Diffraction) examination of a bottom ash sample indicates that the ash has an elemental composition of O, Na, Al, and Si of 49.9, 11.8, 23.8, and 15.1%, respectively. SEM (Scanning Electron Microscope) analysis indicates that the collected fly ash and the bottom one have particle sizes of 20-110 (mostly 45-60 nm) and 50-300 (average 250) nm, respectively.

Thesis (Ph. D.)--University of California, Riverside. / Includes bibliographical references.

Air quality legislation in South Africa is entering a transformation phase, shifting the concept of atmospheric emission control towards pollution prevention and emission minimisation through a more integrated approach. This transformation, along with public pressure and increased foreign trade, is providing industries with incentives to consider their effect on the environment and to take action where required. To assist South African industries in determining what air pollution control technologies are best suited to power plants, gasification and refining processes in South Africa; an assessment of air pollution control technologies used in other countries was carried out. This assessment concluded that the best available technologies for power plants to control air emissions are electrostatic precipitators, low-NOx burners, selective catalytic reduction systems and wet flue gas desulphurisation (limestone) systems. For gasification processes it was found that the main air pollution contributor is the gas handling and treatment process. Releases from this process are controlled through dust collection, wet scrubbing, conversion of sulphide compounds, sulphur recovery and the incineration of final vent gases before release to the atmosphere. For refining processes the catalytic cracking unit is normally the largest single air emission source and controlling emissions from this unit avoids controlling multiple minor sources. Emissions from this unit are controlled via wet scrubbing, selective catalytic reduction systems and carbon monoxide boilers. An assessment of the financial effects associated with air pollution control at power plants was conducted by completing a cost analysis. This analysis demonstrated that by increasing capital expenditure on control technologies by R 1,7 billion, the external costs associated with producing electricity can be reduced by almost R 3,4 billion. Formulation of external cost factors for South African conditions, and the development of a software database for the information obtained from the different countries, will promote future technology selections. / Dissertation (MASTER OF ENGINEERING(Environmental Engineering))--University of Pretoria, 2007. / Chemical Engineering / unrestricted