Oxy-Coal Combustion: Submicrometer Particle Formation, Mercury Speciation, And Their Capture

Energy is the issue of great importance at the present. Coal, the cheapest and the most abundant reserve fossil fuel, is currently one of the most widely used energy source globally and will continue to be in the foreseeable future. The use of coal has also posed many world-wide environmental challenges, including the control of particulate matter, mercury, and trace metals, and carbon oxide: CO2) emissions. The rising of CO2 level in the atmosphere due to burning of fossil fuels is one of the major factors contributing to the global climate change. Capturing CO2 from coal combustion exhaust has been receiving significant attention; however, the volume fraction of CO2 in conventional coal combustion system: with air) ranges only 13%-15%, making it difficult to cost-effectively design the systems. Oxy-coal combustion or O2/CO2 recycled coal combustion is one of the promising techniques to overcome the limitation of low CO2 concentration in the exhaust. Before this technology can be employed, the effects of oxy-coal combustion on the pollutants associated with coal combustion, including fine particle, gaseous mercury and heavy metal emissions, need to be established. In addition, the influences of oxy-coal combustion on the performance of the current pollution control technologies, such as an electrostatic precipitator: ESP), need to be addressed. This dissertation investigated two aspects of coal combustion process:: 1) pollutant formation, specifically submicrometer particles and mercury, and: 2) pollutant control. The first part of dissertation addresses the impact of oxy-coal combustion on the formation submicrometer particles and the speciation of gaseous mercury. The second part focuses on the performance of two pollutant control technologies, including an ESP for capturing submicrometer particles and nano-structured TiO2 with UV irradiation for mercury capture. The findings presented here can be broadly divided into three parts. The first part reports the influence of oxy-coal combustion on submicrometer particle formation and capture using an ESP. The second part addresses the impacts of oxy-coal combustion on mercury speciation. The third part investigates the performance of nano-structured sorbent for capturing mercury and controlling heavy metal emissions from combustion process. The findings presented here can be used as a guideline for proper operation and control of pollutants generated from both oxy-coal and conventional combustion systems

Removal of Humic Acid by Photocatalytic Process: Effect of Light Intensity

Humic acid is commonly found in natural water as it is one of the by-products from decomposition of plants and animal residues. In a conventional water treatment process, which chlorine is common used as a disinfectant, the presence of humic acid could lead to the formation of carcinogenic substances, such as trihalomethanes and haloacetic acids. Thus, removal of humic acid from raw water before disinfection process is necessary. Photocatalytic reaction using Titanium Dioxide (TiO2) as a catalyst is one of the most effective techniques for degrading humic acid. The efficiency of this process depends on several factors; and, one of these factors is light intensity. This research investigated the effect of light intensity (35, 225 and 435 µW/cm2) and studied kinetic of photocatalytic degradation of humic acid, using commercial TiO2 Degussa P25 as a photocatalyst. Concentration of humic acid in water was monitored using UV254 absorbance and concentration of total organic compound was measured using a Total Organic Carbon Analyzer (TOC) every 30 min. The results showed that the removal efficiency of humic acid increased with increasing light intensity and then becoming asymptotic. At light intensity of 435 µW/cm2 and initial humic acid concentration of 4 mg/L with TiO2 loading of 100 mg/L was found to have highest removal efficiency, nearly 95% of humic acid measured by UV254; however, the removal efficiency of total organic compound was found only 20%. The photocatalytic degradation rate of humic acid was followed by Langmuir - Hinshelwood (L-H) kinetic models, and the reactivity constant kL–H values for the light intensity of 35, 225 and 435 µW/cm2 were found as 0.049, 0.152 and 0.178 mg L-1 min-1, respectively

Homogeneous Mercury Oxidation under Simulated Flue Gas of Oxy-coal Combustion

This study investigated the effects of oxy-coal combustion on Hg-oxidation by HCl using simulated flue gas. Experiments were conducted with different carrier gases that one might find in oxy-coal combustion and conventional coal combustion. The extents of Hg-oxidation in pure CO2, pure N2 and air were also studied for comparison. Our experimental results demonstrated that CO2 weakly assisted Hg-oxidation by HCl; however, its significance was outweighed by the presence of O2. For all carrier gases, the presence of NO or H2O inhibited Hg-oxidation. The inhibitory effects strongly depended on concentrations of NO, but not moisture content. The synergistic inhibitory effects were shown when both NO and H2O were present together. The extents of Hg-oxidation were not significantly different for O2-N2, O2-N2-CO2 and O2-CO2 gas mixtures for all conditions investigated in this study

Comparison of diversity and community structure of aquatic insects based on habitat class in Johor

Aquatic insects had been well used as a tool in monitoring water quality and this study is aimed to gauge their potential in Johor. The rapid development in the state of Johor may cause pollution to water resources that require a more efficient water quality monitoring program. The objectives of this study were to (i) collect, identify, determine and produce aquatic insect diversity data in selected rivers in Johor, (ii) relate the presence of aquatic insect diversity with some of the physical features of rivers in Johor. Seven sampling areas were selected based on their importance to local communities and geographical distribution: Taman Negara Johor Endau Rompin (PETA) (TNJER-PETA), Taman Hutan Lagenda Gunung Ledang (THLGL), Hutan Lipur Soga Perdana (HLSP), Hutan Lipur Gunung Belumut (HLGB), Hutan Lipur Sungai Bantang (HLSB), Hutan Lipur Gunung Pulai 1 (HLGP1) and Sungai Sayong Pinang. Insect samples were collected using a kick net method and slight modifocation made according to type of microhabitats. A total of 11,647 individuals of aquatic insects consisting of 68 families from nine orders were sampled. About 69% of insects collected were indicators of good water quality; among them are families Hydropsychidae from order Trichoptera, Baetidae from Order Ephemeroptera, and Simuliidae from Order Diptera. Based on family diversity analyzed using Shannon Index (H’), TNJER- PETA is recorded having the highest index (H’= 3.215) followed by HLSP (H’= 2.791) and HLGB (H’= 2.482). Comparison made and based on physical characteristics, the study sites were classified into three categories (i) the most preferred sites by aquatic insects (HLSB, THLGL, HLGP1, and HLGB), (ii) intermediate preferred sites (TNJER-PETA and HLSP) and (iii) least preferred site (Sg. Sayong). In conclusion, community structure of benthic organisms were influenced by many factors such as presence of variety of microhabitat, predation, surrounding environments, food availability, physical and chemical characteristics of water. Moreover, higher heterogeneity of habitat promote high abundance and diversity of aquatic insects. Any changes happened that involves human interference in the habitats, will affect the abundance of aquatic insects. Last but not least, results suggested that the quality of river water in Johor can be monitored using insects as biological indicators due to the abundance, distribution, and rapid response of aquatic insects to environmental conditions

Pool boiling of water-Al2O3 and water-Cu nanofluids on horizontal smooth tubes

Experimental investigation of heat transfer during pool boiling of two nanofluids, i.e., water-Al2O3 and water-Cu has been carried out. Nanoparticles were tested at the concentration of 0.01%, 0.1%, and 1% by weight. The horizontal smooth copper and stainless steel tubes having 10 mm OD and 0.6 mm wall thickness formed test heater. The experiments have been performed to establish the influence of nanofluids concentration as well as tube surface material on heat transfer characteristics at atmospheric pressure. The results indicate that independent of concentration nanoparticle material (Al2O3 and Cu) has almost no influence on heat transfer coefficient while boiling of water-Al2O3 or water-Cu nanofluids on smooth copper tube. It seems that heater material did not affect the boiling heat transfer in 0.1 wt.% water-Cu nanofluid, nevertheless independent of concentration, distinctly higher heat transfer coefficient was recorded for stainless steel tube than for copper tube for the same heat flux density

A review on boiling heat transfer enhancement with nanofluids

There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement

Seasonal Ammonia Emissions from a Free-Stall Dairy in Central Texas

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