Characterization and utilization of solid residues generated upon oil and heat production from carbonate-rich oil shale

The utilization of a newly discovered Jordan-origin oil shale was outlined in this work. Both industrial and environmental issues were discussed for better handling the wastes that often generated upon processing of oil shale. Two by-products of oil shale were studied, retorted, and combusted oil shale. The wastes were produced under different conditions. Different analytical techniques (XRF, XRD, proximate analysis, infrared spectroscopy, particle size distribution, TGA/DSC, and ultimate analysis) were used to follow up the physicochemical changes in generated solid residues. Oil shale was rich in carbonate with spent content of 73.2%. Upon processing oil shale, many heavy metals were concentrated in the final residue. The most concentrated metals were Cr, Cu, Co, and V with enrichment factor more than 2.0 in both residues. Compared with raw oil shale, leaching of toxic heavy metals was increased many folds and percentage of extraction was higher than 60% of all metals using HNO₃. Total characteristic leaching tests TCLT, a standard test to stimulate metals elution in the environment, confirmed that retorted oil shale was more toxic when contacted with aquatic environment. TCLT indicated that the released amount of Cr was 4.4 higher than the safe limit set by international agencies. Elemental analysis indicated that H/C ratio of oil shale was 0.11 and hence would be used as low-grade fuel. The maximum content of kerogen was 19%, which is estimated by Soxhlet extraction with methanol. The best utilization of retorted and combusted solid residues was as solid medium for Pb ions and phenol removal from solution. Retorted oil shale has better efficiency toward phenol, while combusted oil shale exhibited better removal for Pb ions. Gross heating value, textural parameters, density, and Si/Al ratio were found useful indicators to assess the best utilization of solid wastes generated upon oil shale processing.