The kinetic experiments were carried out in a continuous stirred tank reactor. Practically important ranges of SRC‐II reactor temperature (444–466°C), pressure (10.4–20.8 MPa), nominal slurry residence time (0.54–1.62 h), coal concentration in the feed slurry (25–35 wt%), and inorganic mineral matter concentration (4.75–13.43 wt%) were covered in a total of 43 experimental runs. In each of the experimental runs, the feed slurry was formulated by using vacuum tower bottoms from SRC‐II pilot plants using the same feed coal (Powhatan No. 5), to obtain feed compositions similar to those obtained in SRC‐II pilot‐plant recycle operation.
The kinetic model considers the overall conversion to be achieved in two stages. The first stage is the instantaneous dissolution of coal and in the rate controlled second stage all the reactive organic components in the liquid phase are initially assumed to react, each yielding components lighter than itself. The distribution of products in each reaction stage is considered to be independent of the operating conditions. The best rate controlled (second stage) reaction scheme and values of the unknown parameters are obtained by minimizing the overall difference (i.e. for all the components over all the runs) between the measured and model predicted mass fractions of the various components in the reactor. This analysis identifies the reaction of solvent refined coal (pyridine soluble organic matter boiling above 482°C) to be the only significant reaction in the second stage and its rate is determined to be ‐rSRC = 1.567 × 105 exp (‐79.16/RT) · p0.28 H 2 · XASH, kg/L h. Overall error in this analysis yielding the reaction scheme, rSRC and values of product distribution coefficients for both the reaction stages is less than 8% absolute i.e. ±4%.