Production of renewable chemicals and energy from waste biomass

With the rapid growth of world population and developing industries, the production of wastes has dramatically increased in the past decades. Due to environmental concerns and limited landfill space, the disposal of wastes has been subjected to strict regulations. Beneficial uses of wastes such as recycling/reuse, land applications, energy production, and resource recovery have been advocated greatly. This thesis presents the utilization of two types of solid waste: lignin and waste paper/plastic. Through thermochemical conversion, wastes can be converted to chemicals and energy. This aims at reducing the energy dependence on fossil fuels while achieving effective waste management. Lignin is the main byproduct from pulping and paper industry and is usually combusted to provide the heat for the pulping process. However, its poly-methoxylated phenylpropane structure makes lignin a potential natural source for phenolic and aromatic chemicals. Obtaining high yield of chemicals from lignin is a challenge due to its complex structure and unreactive nature. In this thesis, the pyrolysis of lignin extracted from maple wood and a β-O-4 oligomeric lignin model compound is presented. Advanced analytical techniques were utilized to obtain a comprehensive characterization of pyrolysis products. The results show that carbon concentrated solid char is the major pyrolysis product for both extracted lignin and β-O-4 oligomeric lignin model compound. Reaction chemistry is proposed based on a free radical reaction mechanism. Additionally, a new coal combustion technology utilizing Re-Engineered FeedstockTM (ReEF), was evaluated for pulverized coal combustion emission control. The ReEF consists of non-recyclable fibers/plastics and commercialized flue gas desulfurization (FGD) sorbent. This novel feedstock is combusted to produce energy while capturing the sulfur dioxide generated during coal combustion. It is demonstrated that up to 85% of sulfur dioxide reduction was achieved when co-firing coal with ReEF in a lab scale fluidized bed combustor. Through the kinetics study, combustion of waste fibers/plastics accelerates the sorbent sintering in ReEF which leads to a lower total sulfur uptake compared with pure FGD sorbent. However, the time of maximum reaction rate of sorbent sulfation is delayed in ReEF which indicates the ReEF can prevent the sorbent from early time sulfation. The application of ReEF will have positive impacts on the environment and society by supplementing coal combustion, reducing greenhouse gas emissions, and minimizing wastes that will go to landfill

The inert gas effect on the rate of evaporation of zinc and cadmium

An experimental study has been made to investigate the effect of argon and helium on the rate of evaporation of zinc and cadmium under one atmosphere pressure at temperatures ranging from 500⁰C to 850⁰C. The experimental results were compared with the maximum rates calculated using the effusion formula as well as with values obtained using three different types of equations based on kinetic theory, diffusion theory, and empirical data. The rate of evaporation in this study appeared to be diffusion controlled. Equations have been derived for expressing the rate of evaporation of zinc and cadmium in both argon and helium as functions of temperature of the liquid zinc and cadmium. It was found that the rates of evaporation of zinc and cadmium were higher in helium than in argon, with the difference increasing with increasing temperature. it was also found that the experimental results obtained in argon agree with the calculated values better than those obtained in helium, possibly due to slight oxidation of the cadmium --Abstract, page iii

Atom Interferometry with up to 24-Photon-Momentum-Transfer Beam Splitters

We present up to 24-photon Bragg diffraction as a beam splitter in light-pulse atom interferometers to achieve the largest splitting in momentum space so far. Relative to the 2-photon processes used in the most sensitive present interferometers, these large momentum transfer beam splitters increase the phase shift 12-fold for Mach-Zehnder (MZ-) and 144-fold for Ramsey-Borde (RB-) geometries. We achieve a high visibility of the interference fringes (up to 52% for MZ or 36% for RB) and long pulse separation times that are possible only in atomic fountain setups. As the atom's internal state is not changed, important systematic effects can cancel.Comment: New introduction. 4 pages, 4 figure

Extended cavity diode lasers with tracked resonances

We present a painless, almost-free upgrade to present extended cavity diode lasers (ECDLs), which improves the long term mode-hop free performance by stabilizing the resonance of the internal cavity to the external cavity. This stabilization is based on the observation that the frequency or amplitude noise of the ECDL is lowest at the optimum laser diode temperature or injection current. Thus, keeping the diode current at the level where the noise is lowest ensures mode-hop free operation within one of the stable regions of the mode chart, even if these should drift due to external influences. This method can be applied directly to existing laser systems without modifying the optical setup. We demonstrate the method in two ECDLs stabilized to vapor cells at 852 nm and 895 nm wavelength. We achieve long term mode-hop free operation and low noise at low power consumption, even with an inexpensive non-antireflection coated diode.Comment: 5 pages, 6 figure

Continual Causal Effect Estimation: Challenges and Opportunities

A further understanding of cause and effect within observational data is critical across many domains, such as economics, health care, public policy, web mining, online advertising, and marketing campaigns. Although significant advances have been made to overcome the challenges in causal effect estimation with observational data, such as missing counterfactual outcomes and selection bias between treatment and control groups, the existing methods mainly focus on source-specific and stationary observational data. Such learning strategies assume that all observational data are already available during the training phase and from only one source. This practical concern of accessibility is ubiquitous in various academic and industrial applications. That's what it boiled down to: in the era of big data, we face new challenges in causal inference with observational data, i.e., the extensibility for incrementally available observational data, the adaptability for extra domain adaptation problem except for the imbalance between treatment and control groups, and the accessibility for an enormous amount of data. In this position paper, we formally define the problem of continual treatment effect estimation, describe its research challenges, and then present possible solutions to this problem. Moreover, we will discuss future research directions on this topic.Comment: The 37th AAAI conference on artificial intelligence Continual Causality Bridge Progra