TITLE: Solvent Refined Coal (SRC) Process. Effect of Mixing Energy on Hydrogen Reaction Rates in SRC-II Reactors.

AUTHOR: C. P. P. Singh;   Y. T. Shah;   N. L. Carr.

INST.  AUTHOR: Pittsburg and Midway Coal Mining Co., Englewood, CO.

SPONSOR: Department of Energy, Washington, DC.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  Jan 82,  40p.

ABSTRACT:

This study attempted to analyze theoretically the conditions which may lead to hydrogen starvation in SRC-II reactors. Literature correlations for mass transfer coefficients in bubble columns were combined with experimental data from a stirred vessel (CSTR) on the basis of specific power consumption. Specific power consumption, i.e., consumption of mixing energy per unit volume per unit time, is proportional to N exp 3 , where N is the stirred speed, and approximately proportional to superficial gas velocity (Ug) in a bubble column. For operating conditions selected to give maximum practicable reaction rate, i.e., under conditions of highest possibility of hydrogen starvation, results indicate that the fractional decrease in the rate of reaction would be insignificant (<4%) for superficial gas velocity, Ug, above 1 cm/s. Based on this result it can be claimed that in the SRC-II process, hydrogen starvation is unlikely. The rate of reaction was shown to be sensitive to the value of the mass transfer coefficient, K/sub L/a. A decrease in the rate of reaction due to lower value of mass transfer coefficient (K/sub L/a) can be compensated by increasing the gas rate (superficial gas velocity). This shows that the possibility of hydrogen starvation would decrease with increase in the length of SRC-II reactors, since the superficial velocity in a taller reactor will have to be higher. Based on the present study, it is believed that the higher the gas velocity (the longer the reactor) in the large-scale reactor situation, hydrogen reaction rates will not be significantly influenced by mass transfer in normal operation of the reactor.

REPORT  NUMBER: DOE/ET/10104-50

CONTRACT  NUMBER: AC05-76ET10104