Showing papers in "Industrial & Engineering Chemistry Process Design and Development in 1981"
748 citations
TL;DR: In this paper, the kinetics of wood pyrolysis into gas, tar, and char were investigated in the range of 300 to 400 degrees Celcius at atmospheric pressure.
Abstract: The kinetics of wood pyrolysis into gas, tar, and char was investigated in the range of 300 to 400 degrees Celcius at atmospheric pressure. An experimental system which facilitates the monitoring of the actual sample temperature, collection of gas and tar, and measurement of the sample weight loss as a function of time was developed. It has been found that, in the range investigated, wood decomposition into gas, tar, and char can be described by three parallel first-order reactions as suggested by Shafizadeh and Chin (1977). The activation energies for these reactions are 88.6, 112.7 and 106.5 kJ/mol, respectively, and their frequency factors defined on a mass basis are 8.61 x 10 to the power of 5, 2.47 x 10 to the power of 8, and 4.43 x 10 to the power of 7 min-1. The composition of the pyrolysis products was also analyzed. It was found that the gas consists mainly of carbon dioxide, carbon monoxide, oxygen, and C3 + compounds with trace amounts of methane, ethylene, and acetylene. The tar consists of seven compounds with levoglucosan accounting for more than half. The char was analyzed by elemental analysis and it was found that its carbon content increases withmore » increasing reactor temperature. (Refs. 12).« less
351 citations
TL;DR: In this article, electron microprobe techniques were used to examine the deposition patterns of nickel, vanadium, iron, and coke in 1/16 in. extrudate (unspecified) catalysts aged in hydrotreating pilot plants.
Abstract: Deposition patterns of nickel, vanadium, iron, and coke in 1/16 in. extrudate (unspecified) catalysts aged in hydrotreating pilot plants were examined by electron microprobe techniques. Iron deposited mostly on the outer catalyst surface; coke deposited in an outer annulus initially and then its levels in the catalyst interior increased linearly with time; and nickel and vanadium deposited in the interior in a manner consistent with diffusion-limited demetalation. With increasing temperature or hydrogen partial pressure, nickel and vanadium deposition occurred nearer the catalyst surface. The metals distribution in the catalyst varied with crude source. The metals diffused further into catalysts with larger pores. The distribution of deactivation processes in the catalyst bed suggested that poisoning of surface sites and pore plugging both take place and that the rate at which pore plugging moves through the bed depends on the extent of surface poisoning and on the axial distribution of the metal deposits along the reactor length. The tests were conducted with six feedstocks containing 1.7-4.3% sulfur, 29-630 ppm vanadium, 8-48 ppm nickel, and 3-15% iron.
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107 citations
TL;DR: Thesis (Ph.D.) as mentioned in this paper, Mass. Institute of Technology, Dept. of Chemical Engineering, 1980, Boston, Massachusetts, United States of America, USA, USA.
Abstract: Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1980.
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TL;DR: In this article, the devolatilization reactions of feedlot manure were studied by a thermogravimetric analyzer and the effects of size fraction, heating rate, and purge gas rate on the thermogram characteristics were analyzed statistically.
Abstract: The devolatilization reactions of feedlot manure were studied by a thermogravimetric analyzer The effects of size fraction, heating rate, and purge gas rate on the thermogram characteristics, such as the total weight percent devolatilized and the temperature at which the maximum rate of weight loss occurred, were analyzed statistically The total weight percent devolatilized was mainly influenced by the size fraction, while the temperature at which the maximum rate of devolatilization occurred was mainly affected by the heating rate The devolatilization data were fitted to a multireaction model, and the kinetic parameters were determined The mean value of the activation energy, E, and the standard deviation of the activation energy, sigma, were analyzed statistically to assess their dependence on the heating rate, size fraction, and purge gas rate E was not affected by any of these variables, while sigma was affected by the heating rate and the purge gas rate
TL;DR: This article showed that calcite in the presence of coal decomposes to lime and CO/sub 2/ at lower temperatures than it will when pyrolyzed alone, probably due to lime-catalyzed secondary cracking reactions, while the latter results from base catalysis of a step in the decomposition of the phenolic groups.
Abstract: This paper presents results on the pretreatment of coal with calcite (CaCO/sub 3/) and lime (CaO). These minerals have already been shown to influence fluidized-bed pyrolysis, steam gasification, and CO/sub 2/ gasification of coal. Addition of CaCO/sub 3/ or CaO to coal reduces the high temperature yield of hydrocarbon products and increases the yield of CO in rapid coal pyrolysis. The former effect is probably attributable to lime-catalyzed secondary cracking reactions, while the latter results from base catalysis of a step in the decomposition of the phenolic groups. Calcite in the presence of coal decomposes to lime and CO/sub 2/ at lower temperatures than it will when pyrolyzed alone.
TL;DR: In this article, a mathematical model was developed to describe the gasification of biomass in a fluid-bed reactor, and a preliminary attempt was made to compute the gas composition and yields of gas, liquid, and solid products assuming that the water-gas shift reaction was the only gas-phase reaction.
Abstract: A mathematical model was developed to describe the gasification of biomass in a fluid-bed reactor. The model was simplified, applied to the gasification of feedlot manure, and a preliminary attempt was made to compute the gas composition and yields of gas, liquid, and solid products assuming that the water-gas shift reaction was the only gas-phase reaction. The governing equations were solved by using a software interface. Although the predicted and experimental values agreed reasonably well, the comparison suggested that cracking and reforming reactions involving the volatiles produced during devolatilization should be included in the model. An approximate calculation of the gas yields and liquid yields incorporating the thermal cracking reactions of the heavy volatiles compared more favorably with the data. 22 refs.
TL;DR: Controlled cracking in the liquid phase of n-hexadecane, 6-methyleicosane, 1-phenyldodecane, and C21-C27 paraffins was studied in a stainless steel microreactor between 350 and 440 C for residence times varyin from 0.5 to 4 h at nitrogen or hydrogen pressures of 20 bar as mentioned in this paper.
Abstract: Controlled cracking in the liquid phase of n-hexadecane, 6-methyleicosane, 1-phenyldodecane, and C21-C27 paraffins was studied in a stainless steel microreactor between 350 and 440 C for residence times varyin from 0.5 to 4 h at nitrogen or hydrogen pressures of 20 bar. Cracking occurred according to a molecular mechanism, but its kinetic data such as the order of reaction and the activation energy were similar to those of radical type cracking. The rate of formation of cracked gases was extremely small and the experimental and simulated compositions of the cracked liquids, based on a molecular type scission, agreed very well. This type of cracking is very interesting for visbreaking of heavy oils.
TL;DR: In this paper, the effect of inhibitors on natural gas hydrate-formation conditions appears to be more accurate than that currently used for injecting inhibitor into a natural gas stream, using existing hydrate parameters and data from the literature.
Abstract: This method for predicting the effect of inhibitors on natural gas hydrate-formation conditions appears to be more accurate than that currently used for injecting inhibitor into a natural gas stream. Incorporating existing hydrate parameters and data from the literature, analysts can predict the effects of KCl, CaCl/sub 2/, CH/sub 3/OH, and C/sub 2/H/sub 5/OH inhibition of pure gas hydrates. The extension to other inhibitors and gas mixtures is straightforward. Work is proceeding to extend the measurements to simulated natural gases with methanol and glycol inhibitors.
TL;DR: In this paper, the minimum reflux conditions and the number of stages and feed tray location for complex distillation columns are calculated via shortcut methods for ordinary and thermally coupled columns.
Abstract: Shortcut Methods for Complex Distillation Columns: Part 1 -Minimum Reflux This two-part paper presents in detail the theory for calculating via shortcut methods the minimum reflux conditions and the number of stages and feed tray location for ordinary and thermally coupled columns. Nonadjacent key components are permitted. In this paper, part 1, the approximations made to estimate minimum reflux are similar to earlier methods such as those by Underwood and Colburn. However, some novel manipulations lead to particularly simple equations requiring only a few minutes to use, particularly for ordinary distillation columns. Several example problems demonstrate that the method compares favorably with these other approaches.