Mathematical Modeling and Experimental Studies of Thermal Reactions of Coal

Author: Jain, Ravi

Year: 1980

Degree: Dissertation (Ph.D.)

Advisor: Gavalas, George R.

Committee Member: Unknown, Unknown

Option: Chemical Engineering

DOI: 10.7907/HAV6-QD05

Abstract

This dissertation discusses theoretical and experimental research on coal pyrolysis.

In the theoretical part, a mathematical model based on coal's chemical structure and its reactions is developed for computer simulation of pyrolysis. Firstly, the important organic functional groups of carbon, hydrogen and oxygen in medium and high rank coals are organized into a conceptual model for coal's chemical structure. Using the principles of thermochemistry of free radicals as guidelines, the important categories of chemical reactions in coal pyrolysis are postulated. A set of 41 series-parallel reactions represents the chemical change. It is concluded that there is no a priori distinction between volatiles and non-volatiles in a coal. They are both formed from the same chemical structure, and are basically an inevitable consequence of each other's formation.

For the purpose of mathematical modeling, coal is considered to be a population of randomly distributed functional groups on a matrix. A scheme based on statistical transformations is devised to compute concentrations of reacting configurations before and during pyrolysis. The rates of reactions are expressed in terms of these concentrations. Differential equations governing the rate of change of state variables with pyrolysis time are formulated and numerically integrated on the computer. Pyrolysis results are predicted in terms of the state variables.

The dependence of the yield and composition of volatiles on (a) transport parameters like particle size and pressure, and (b) kinetic parameters like time, temperature and time-temperature history, is investigated experimentally. Gaseous products are analyzed using chromatography, while tar is characterized by GPC, NMR and elemental analysis.

Basic research on coal helps in developing a general "theory" about its structure and chemical behavior. It enhances our ability to meet process, economic and environmental goals in coal's industrial utilization.

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