Kinetics Of Coal Liquefaction Research Articles

Kinetics of coal liquefaction during heating-up and isothermal stages

Direct liquefaction of Shenhua bituminous coal was carried out in a 500 ml autoclave with iron catalyst and coal liquefaction cycle-oil as solvent at initial hydrogen of 8.0 MPa, residence time of 0–90 min. To investigate the liquefaction kinetics, a model for heating-up and isothermal stages was developed to estimate the rate constants of both stages. In the model, the coal was divided into three parts, easy reactive part, hard reactive part and unreactive part, and four kinetic constants were used to describe the reaction mechanism. The results showed that the model is valid for both heating-up and isothermal stages of liquefaction perfectly. The rate-controlled process for coal liquefaction is the reaction of preasphaltene plus asphaltene (PAA) to oil plus gas ( O + G). The upper-limiting conversion of isothermal stage was estimated by the kinetic calculation.

96/05921 A novel reactor system for studying the kinetics of coal liquefaction and related processes at very short reaction times

96/05921 A novel reactor system for studying the kinetics of coal liquefaction and related processes at very short reaction times

96/04794 Kinetics of coal liquefaction at very short reaction times

96/04794 Kinetics of coal liquefaction at very short reaction times

Kinetics of coal liquefaction at very short reaction times

Kinetics of coal liquefaction at very short reaction times

96/01379 Mechanism and kinetics of coal liquefaction

96/01379 Mechanism and kinetics of coal liquefaction

Kinetics of Coal Liquefaction: Interpretation of Data

The communication addresses the following questions: How should one interpret experimental data on the kinetics of coal liquefaction? What theoretical validity resides in a rate equation for liquefaction? What deductions about chemical mechanism can be deduced from the form of the rate equation?

95/01037 Enhancement of coal liquefaction kinetics: Effect of a multicomponent mixture on the attributes of an optimal chain-transfer solvent

95/01037 Enhancement of coal liquefaction kinetics: Effect of a multicomponent mixture on the attributes of an optimal chain-transfer solvent

A kinetic investigation of coal liquefaction at short reaction times

Coal liquefaction kinetics have been studied at very short reaction times (less than 250 seconds) in order to emphasize the initial underlying physical and chemical processes involved. These studies were made possible by the use of a continuous flow stirred tank reactor (CSTR) which avoids the problems of slow heat up and cool down associated with the massive equipment required for running high-temperature and high-pressure liquefaction reactions. Preliminary physical (NMR and ESR) and chemical analytical results are presented on the coal liquids and reaction residues from Illinois No. 6 hv bituminous and Wyodak Black Thunder subbituminous coals. ESR results showed that radical concentration in the solid residue changed during coal liquefaction. These changes were accompanied by changes in the NMR-derived aromaticity. The rate of decrease of organic-based radicals was different for Wyodak Black Thunder and Illinois No. 6 coals, perhaps indicating a different mechanism for the quenching of radicals in these bituminous and subbituminous coals. NMR spectra of the liquid products indicated that the initially produced material was relatively aromatic, and that subsequent products had lower aromatic content. This is consistent with secondary hydrogenation of the primary liquefaction products. Finally, the total oxygen contents of the coal residues decreased gradually during the first three minutes of coal liquefaction at 390°C. A corresponding decrease in the hydroxyl content of these residues was also noted.

Kinetics of liquefaction of coal catalyzed by coal minerals

This work describes the development of a fundamental engineering understanding of the kinetics of coal liquefaction using a semiempirical kinetic model for SRC-II coal liquefaction, and experimental data for liquefaction of several bituminous, subbituminous, and lignite coals in the presence of iron pyrite catalysts. The study establishes the applicability of one kinetic model to the liquefaction of widely different coals catalyzed by iron-sulfur catalysts in the coal minerals and/or iron pyrite catalysts. The source of the iron-sulfur catalyst has no effect, whereas H/sub 2/S has a strong inhibitive effect on the rate of hydrogenation reactions.

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part I: Theory

AbstractBased on the concept of reactions in a continuum, a mathematical model has been developed to simulate coal liquefaction kinetics. In an excess hydrogen donor environment, the rate‐limiting reactions are considered to be irreversible cracking reactions involving cleavage of carbon and oxygen linkages. Concurrent evolution of a wide spectrum of products, with an initial rapid formation of species of high carbon and oxygen contents, followed by progressively slower reactions leading to lower carbon and oxygen content species is predicted. Simple lumping functions are employed to obtain conventional lumped pseudocomponents (preasphaltenes, asphaltenes, and oils). Parameter analysis has been carried out.

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part II: Comparison with experiments on catalyzed and uncatalyzed liquefaction of coals of different rank

AbstractExperimental kinetic data for three Australian coals are compared with predictions from the mathematical model developed in Part I. For these coals, as well as data reported for North American coals, the model is found to show good agreement, using the characteristic molecular weight as the only parameter. The effects of reaction time and temperature are coupled via a severity index that arises in the model as a dimensionless reaction time. The model is also shown to be applicable when catalysts are present. The product distribution for a particular coal seems to be a function only of the conversion even in the presence of catalysts, as long as the chemical reaction controls the rate of liquefaction.

Kinetics of coal liquefaction under supercritical conditions

Kinetics of coal liquefaction under supercritical conditions

On the measurement of coal liquefaction kinetics

AbstractCoal liquefaction kinetic rate constants play an important role in the design and operation of liquefaction reactors. The objectives of this work are to present a comparative review of the measurement techniques which have appeared in the recent literature, and to analyse briefly some of the kinetic models used in the measurements of the rate constants. A mathematical technique to analyse multicomponent‐multireaction kinetic schemes using the data obtained from autoclave (closed) and continuous stirred tank reactors (CSTR, open) is discussed.

Continuous reaction mixture model for coal liquefaction kinetics

The complex reactions taking place in the coal liquefaction process have been described in terms of a continuous reaction mixture with the molecular weight as a single state variable. A kinetic model, based on this approximation as well as on simple fission of molecules, has been developed. The resulting mathematical models, giving the amount of coal undissolved and the MW distribution of the species produced at a given time in a batch reactor, is amenable to the solution of an integrodifferential equation.

Role of vapor‐liquid equilibrium in evaluation of coal liquefaction kinetics

AbstractThe role of vapor liquid equilibrium in the coal liquefaction process and its effect on the process kinetics were studied. Available experimental data were analyzed by inclusion of vapor‐liquid equilibrium in an existing model to study its effect on the kinetics. The analysis showed that due to liquid vaporization, a significant increase in the slurry residence time occurs. In the range of operating variables investigated, the actual slurry residence time was observed to be higher by a factor of 1.14 to 1.41.Model simulations for some typical operating conditions (717‐737 K, 13.8‐20.7 MPa) showed the wt. fraction of liquid vaporized to be in the range of 0.1 to 0.3. This is seen to be in agreement with published data on the volatility of typical coal liquids. This study has shown that consideration of vapor‐liquid equilibrium in the kinetics and design of coal liquefaction process can be of importance, especially at high temperatures, where vaporization would be significant.

Kinetics of coal liquefaction: effect of catalyst, H2 concentration and coal type

Abstract A process for dry coal hydrogenation—liquefaction has been developed that permits short residence times (seconds) and achieves notably high space rate utilization factors. The purpose of the work reported here is to identify more precisely the process variables that determine space rate utilization factors, and to express them in a kinetic scheme, in the hope of establishing more effective control of these variables in the process. A kinetic analysis of work done in a 3 mm i . d . × 1 m long reactor is presented. Some data from a 4.5 mm i . d . × 34 m long reactor is also included. A correlation of hydroaromatic, catalyst and hydrogen concentration is considered. Parameters considered important for an optimum space rate utilization factor are both chemical and physical in nature. Of special importance are heat transfer, catalyst concentration and hydrogen concentration. A large space rate utilization factor is important from the standpoint of reduced reactor volume.