The purpose of this thesis study is to assess the feasibility of using a fiber sorbent module system to remove t-butyl mercaptan (TBM), a common odorant, from pipeline grade natural gas. Odorants such as mercaptans are added to natural gas for safety reasons, but their combustion products are corrosive and decrease the lifetime of the turbines in which they are combusted. Therefore, it is desirable to remove the odorants to extend this lifetime. A TBM removal system attached to a 840 MW natural gas-fueled combined cycle power plant unit such as the one at Plant McDonough-Atkinson (Smyrna, GA) must process gas at a flow rate of approximately 180,000 standard cubic feet per minute. A single 85 MW GE 7EAQ gas turbine has a flow rate of approximately 15,000 standard cubic feet per minute, and will serve as the basis for a system design and process analysis study. The concentration of odorants in natural gas is typically 10 ppm or less. For the purposes of this study, the upper limit of 10 ppm TBM will be used. Zeolite 13X was selected as the model adsorbent for this study due to its high sorption capacity for mercaptans and its ease of incorporation into both fibers and pellets. Design calculations were performed to optimize and determine the feasibility of fiber modules for TBM removal, as well as assess their advantages over conventional pellet packed beds. An understanding of how critical parameters such as heat and mass transfer resistances, pressure drop, and capital and operating costs are affected by design specifications such as sorbent and bed dimensions, allows an optimal design for the needs of the model turbine to be found. Based on these design equations, a fiber sorbent module configuration that selectively and continuously removes TBM from natural gas is developed

<p>This thesis describes a new type of biosensor, which reports the presence of a target by generating a smell that can be easily detected by the human nose. This approach is radically different from, but complementary to, colorimetric based reporting and it paves the way for the development of multi-sensory biosensors that can be used in a variety of fields, such as diagnostic device, food processing and environmental monitoring</p> <p>Biosensors typically consist of two parts: a bio-recognition element and a signal transducer. The biorecognition element is the component that can specifically interact with its cognate target, while the transducer produces a signal that can be easily identified. The key element of the smell generating biosensor is the enzyme tryptophanase (TPase), which was used as the signal transducer. This enzyme uses either L-tryptophan or S-methyl-L-cysteine as substrates, to produce either indole or methyl mercaptan as final products- both molecules are easily detectable by the human nose. Proof-of-concept for this biosensor was achieved by performing an enzyme-linked immunosorbent assay (ELISA) on magnetic beads with detection of IgG from rabbit serum (the target) in a sample and reporting the presence of the target through the generation of a smell (either indole or methyl mercaptan, depending on the substrate used).</p> <p>The potential use of TPase for biosensing was further expanded by creating a bienzyme system that allows specifically detecting of adenosine-5’-triphosphate (ATP) and reporting its presence by generating a smell. This bienzyme system is based on the fact that TPase activity is greatly affected by the concentration of pyridoxal phosphate (PLP)- which acts as a cofactor that modulates enzyme activity. The enzyme pyridoxal kinase PKase catalyzes the phosphorylation of pyridoxal to PLP in the presence of ATP. The more ATP presents, the more PLP is produced per unit time. If this occurs in the presence of TPase, larger concentrations of ATP in samples will result in higher amounts and faster rates of PLP formation, leading to increased activity of TPase, hence faster generation of either indole or methyl mercaptan is achieved. This bienzyme was used for the detection of DNA molecules with a specific sequence as well as for the detection of microbial cells through smell generation.</p> <p>Most widely used biosensors require immobilization of the biologically active elements on a stable surface. Paper, being a cheap and easy accessible substrate, was used for fabrication of the olfactory-based biosensor. Poly(N-isopropylacrylamide-co-vinylacetic acid) (PNIPAM-VAA) microgels with functional groups present on their surface were modified by biotinylation and loaded with streptavidin/avidin (to be prepared as a platform for further biomolecule immobilization). The microgels were then used as a supporter for the bienzyme system on filter paper to construct a paper-based smell-generating biosensor, which opens the way for the creation of printable smell-reporting printable bio-inks.</p> / Doctor of Philosophy (PhD)

No description available.

Le méthanethiol est un intermédiaire clé dans la synthèse de la méthionine, un acide aminé largement utilisé dans l'industrie agro-alimentaire. / Methanethiol is a key intermediate in methionine synthesis, an amino-acid which is widely used in food-processing industry.

The polymerization of methyl methacrylate (MMA) was investigated in this dissertation. Selected kinetic models from the literature were reviewed, and two new, generalized models of diffusion-limited effects (gel- and glass effects), derived from the current models were proposed and tested for bulk and solution polymerization of MMA in batch and semi-batch reactors, under isothermal and non-isothermal conditions. The newly proposed models include the capability of modeling termination by combination, radical transfer to monomer and depropagation reaction. The new and previous models were compared with experimental data of bulk and solution polymerizations of MMA, under a selection of non-steady state processes conditions (initiator and monomer feed, step changes in temperature) and compositions (initiator and chain transfer agents, regarding both type and dosages). The particular case of a non-isothermal bulk polymerization was also investigated. A simulation program (Reactormodel) was developed in Matlab, and its algorithm is provided. / Sem resumo.

No description available.