Coal combustion and gasification are the processes to utilize coal for production of electricity and many other applications. Global energy demand is increasing day by day. Coal is an abundant source of energy but not a reliable source as it results into high CO 2 emissions. Energy industries are expected to decrease the CO 2 emission to prevent global warming. Coal gasification is a process that reduces the CO 2 emission and emerges as a clean coal technology. Coal gasification process is regulated by several operating parameters. A Number of investigations have been carried out in this direction. A critical review of the work done by several researchers in the field of coal gasification has been compiled in this paper. The effect of several operating parameters such as coal rank, temperature, pressure, porosity, reaction time and catalyst on gasification has been presented here.

A 4.9-m-thick lake sequence, formed due to the landslide damming of a stream in the semiarid Garhwal Himalaya, was studied to understand past monsoonal variations in the region. The Optically Stimulated Luminescence (OSL) chronology indicates that the lake existed between ~ 12 and ~ 7 ka ago. Chronologically constrained trends of sand percent, organic phosphorus (OP), apatite inorganic phosphorus (AIP) and parameters of environmental magnetism were measured in the paleolake profile. Measured proxies indicate that the Indian summer monsoon ameliorated in the early Holocene after 12 ka cooling, and it appears that all the proxies from the lake have captured this globally recognized early Holocene warming. Four phases of wet conditions (intensified monsoon) are recognized at ~ 11.5 ka, ~ 11–10.5 ka, ~ 10–9 ka and ~ 8–7 ka with maximum uncertainties of ~ 1000 years. The wet phases are characterized by high magnetic susceptibility, increased OP and reduced AIP. In an attempt to understand the primary forcing of the sharp fluctuations in monsoonal activity in the region, we show that changes in magnetic susceptibility match variations of residual atmospheric δ14C, suggesting a role for solar variability as an explanation of climatic variability.

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