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Author: David Gorman Publisher: ISBN: Category : Languages : en Pages : 55
Book Description
Supercritical water technology has the potential to enable the safe and complete destruction of hazardous chemical compounds, including chemical waste and chemical warfare agents. While the underlying technology shows promise, quantitative determination of chemical kinetic rates under these conditions are needed to facilitate the design of full scale technology. Collecting these needed data requires a versatile reactor capable of determining chemical decomposition rates. Critical parameters include temperature, residence time, and catalytic wall effects. The literature shows significant differences in the published chemical kinetic rates, which is at least partially attributed to variations in reactor design. To determine best practices, existing reactor designs, components, and technologies, as well as some promising new technologies, are reviewed. From this overview, a reactor specialized for the gasification of organic compounds was designed featuring in situ Raman monitoring of the effluent stream. In addition to the design of the reactor, some basic processing techniques for Raman baseline signal subtraction are discussed, along with preliminary results for organic compounds decomposition. With the reactor completed, the rapid determination of chemical kinetic rates in supercritical water becomes possible for a wide range of reagents and operating conditions.
Author: David Gorman Publisher: ISBN: Category : Languages : en Pages : 55
Book Description
Supercritical water technology has the potential to enable the safe and complete destruction of hazardous chemical compounds, including chemical waste and chemical warfare agents. While the underlying technology shows promise, quantitative determination of chemical kinetic rates under these conditions are needed to facilitate the design of full scale technology. Collecting these needed data requires a versatile reactor capable of determining chemical decomposition rates. Critical parameters include temperature, residence time, and catalytic wall effects. The literature shows significant differences in the published chemical kinetic rates, which is at least partially attributed to variations in reactor design. To determine best practices, existing reactor designs, components, and technologies, as well as some promising new technologies, are reviewed. From this overview, a reactor specialized for the gasification of organic compounds was designed featuring in situ Raman monitoring of the effluent stream. In addition to the design of the reactor, some basic processing techniques for Raman baseline signal subtraction are discussed, along with preliminary results for organic compounds decomposition. With the reactor completed, the rapid determination of chemical kinetic rates in supercritical water becomes possible for a wide range of reagents and operating conditions.
Author: Khaled Khalili Publisher: ISBN: Category : Chemical detectors Languages : en Pages : 88
Book Description
In the upgrading of heavy feeds, it is essential to avoid the onset formation of mesophase, which is considered a precursor for coke formation. The formation of this aromatic dense phase leads to serious problems such as catalyst deactivation, limiting the vacuum residue conversion, and fouling in the reactors and the downstream equipment; subsequently, a costly mechanical removal will be necessary to remove the coke. Therefore, tracking of the mesophase formation at in-situ conditions is important step towards avoiding the onset formation of carbonaceous mesophase. In this work, a fiber-coupled in-situ Raman hot reactor was designed, constructed and validated. The system has been developed as on-line chemical sensor to track evolution of the two graphitization Raman bands associated with the mesophase formation, namely the 1575cm-1 band and the band located near 1340cm-1. The operation of the system is based on acquiring real-time backscattered Raman spectra from a hot stage reactor running at high temperature and sometimes high-pressure conditions. The outcome of this system has been validated using non-reactive and reactive systems. In terms of non-reactive systems, the spectra of some common solvents such as toluene and 1-methylnapthalene have been acquired using this system and then compared with the published spectra; excellent spectral matching in the range of ± 5cm-1 is observed. On the other hand, the hydro-desulfurization reaction of benzothiophene using 1-methylnapthalene as a solvent has been used as a model reaction for system validation. This reaction has been conducted ex-situ and in-situ at the same experimental conditions i.e. 290° C and 2.5 MPa of hydrogen pressure. The GC/MS analysis of the ex-situ shows hydrodesulphurization of benzothiophene and formation of ethylbenzene, which is in agreement with the well-known chemistry of this reaction; in addition, a considerable hydrogenation of the solvent was observed in the products of the ex-situ runs, which confirms the hydrogenation capability of the used catalyst. The spectral data, which have been acquired during the in-situ runs, have been preprocessed using the airPLS algorithm to remove the fluorescence background from the spectra that have been then analyzed using multivariate PCA analysis. The PCA analysis confirms the evolution of the Raman bands associated with ethylbenze formation and the decline of the Raman bands attributed to benzothiophen; moreover, the PCA analysis also shows a concomitant decrease of the aromatic content of the mixture via hydrogenation of aromatic rings which confirms the hydrogenation of the solvent that have been observed in the ex-situ runs.
Author: Publisher: ISBN: Category : Languages : en Pages : 8
Book Description
Reaction studies have been carried out on the destruction of nitrogen-containing compounds such as ammonium, nitrates, and species containing aromatic nitro functionality. The destruction of ammonium ion in near-critical and supercritical water using Raman spectroscopy is the subject of this presentation. Reaction rates were determined from Raman spectra and from measurements of system pressure. Concentrations of key species in the reactor effluent were determined via off-line assay. The effects of temperature, pressure, and concomitants on reaction rate were determined. The reaction half-life is below ten seconds at 400 C with better than 95% conversion. Oxides of nitrogen were not generated in detectable quantities. The studied system is a model for the destruction of ammonium in municipal wastes.
Author: Kartik Tiwari Publisher: ISBN: Category : Languages : en Pages : 45
Book Description
Supercritical water (sc-H2O) reactors have been used for biomass gasification and the destruction of hazardous waste. Laboratory scale reactors are typically used for development of chemical kinetic rate parameters. These smaller reactors with lower Reynolds numbers often suffer from slow mixing between the reagent and sc-H2O; this slow mixing increases uncertainty in the data required for calculation of chemical kinetic rate parameters. In this study, we present a multiple-jet in crossflow design for a mixing section, which enables rapid mixing of reagents into sc-H2O. A parametric analysis is conducted to establish an optimum jet-to-crossflow velocity ratio (r) for scalar mixing using three-dimensional computational fluid dynamics (CFD) with Detached Eddy Simulations (DES) for resolving turbulence. Kinetic theory models for calculating physical properties of the fluids at the supercritical state are evaluated against data available in published literature. CFD simulations show that mixing can be characterized by three distinct regimes: (i) under-penetrating jets, (ii) weakly penetrating jets, (iii) jets forming counter-rotating vortex pairs (CVPs), and (iv) impinging jets. The best mixing is observed for jets forming CVPs; under-penetrating jets show the worst mixing. The mechanism of mixing in the three configurations is explained. Decomposition of methanol (MeOH) in a continuous-flow sc-H2O reactor is simulated with CFD using global first-order chemical kinetic rate parameters calculated from published experimental data. This numerical modeling sheds insight into the complex physiochemical processes of organic compound decomposition in the supercritical environment. The modeling approach can be used in industrial process optimization and to improve the design of new and existing systems.
Author: R.E. Hayes Publisher: CRC Press ISBN: 1000102041 Category : Science Languages : en Pages : 437
Book Description
This book provides an introduction to the basic concepts of chemical reactor analysis and design. It is intended for both the senior level undergraduate student in chemical engineering and the working professional who may require an understanding of the basics of this subject.
Author: Igor Novosselov Publisher: ISBN: Category : Electronic books Languages : en Pages : 0
Book Description
Supercritical water gasification (SCWG) is an emerging technology with synergistic applications in renewable energy and waste processing. Supercritical water (SCW) functions as a green reaction medium during the gasification process, serving to dissolve and decompose complex organic molecules via ionic, radical, hydrolysis, and pyrolysis reaction mechanisms. Researchers investigate the decomposition of model compounds in order to predict product yields and conversion efficiencies during the gasification of heterogeneous biomass waste, food waste, sewage sludge, and other available feedstocks. Continuous, laboratory-scale reactors are often employed to study reaction kinetics, pathways, and mechanisms. This chapter synthesizes previous work investigating model compound gasification in continuous supercritical water reactors (SCWRs). A summary of continuous reactor design strategies is presented for practical benefit, followed by a discussion on reaction chemistry in the supercritical water environment. Reaction pathways and mechanisms have been investigated for several model compounds, lending insight toward the conditions needed for the complete conversion of real-world feedstocks. Several studies assume first-order reaction kinetics and propose Arrhenius parameters for the decomposition reaction. The first-order rate assumption must be carefully evaluated, and the applicable temperature range must be specified. Opportunities for further research are discussed.
Author: David Gorman
Author: David Gorman
Author: Khaled Khalili
Author: 
Author: Kartik Tiwari
Author: R.E. Hayes
Author: Igor Novosselov
Author: Charles G. Hill
Author: Alfred Ronald Cooper
Author: K. R. Westerterp
Author: James Blake Rawlings