Modeling study of carbonate decomposition in LLNL's 4TU pilot oil shale retort

Lawrence Livermore National Laboratory's (LLNL) 4 tonne-per-day oil shale Pilot Retort (4TU-Pilot) has been modeled to study the degree of carbonate decomposition occurring in the process. The modeling uses a simplified version of the processes occurring in the retort to allow parametric studies to be performed. The primary focus of the work is on the sensitivity of computed carbonate decomposition to the assumed manner in which solid material leaves the retort. It was found that for a variety of assumptions about solid passage and evolution within the process the computed carbonate decomposition varied by only a few percent. It was also determined that using available kinetic expressions based on literature data led to a consistent underestimate of the carbonate decomposition, from 12-17% low on an absolute basis and on a relative basis as much as a factor of seven times too low. A simplified kinetic expression based on limited data from laboratory experiments on the same shale as used in the 4TU-Pilot run was also employed and found to match the pilot results fairly well.