P. S. T. Sai
Indian Institute of Technology Madras, India
P. S. T. Sai is a professor in Chemical Engineering at Indian Institute of Technology Madras. He has been actively involved in teaching and research for the past 32 years. His research interests include fluidization, reaction engineering and air pollution control. He has published over 80 research papers. His paper entitled “Esterification of ethanol with sulfuric acid: A kinetic study” was awarded as the best paper published in The Canadian Journal of Chemical Engineering in 2001. He also received Chemical Weekly Award, IIChE NRC Award and. Kuloor Memorial Award in 2012. He has handled many industrial projects and one of them is development of an equipment for simultaneous removal of particulates and SO2 from effluent gaseous streams.
Coal gasification is one of the best ways to convert the char into the synthesis gas. This process has proved to be very effective in Internally Circulating Fluidized Bed (ICFB) gasifier. In ICFB, there occurs gas bypassing from draught to annulus region and vice versa. In the present work, the effects of gas bypassing through the orifices on product gas compositions in both annulus and draught tube is studied following the modeling reported in literature.
The same modeling is applied to a coal of inferior quality and the conversion and product gas compositions at different temperatures and the effects of various parameters are studied. The number of circulations a particle should undergo, total gas yield and solid circulation rate inside the reactor is studied at different temperatures for different conversion levels. In addition, the effects of coal feed rate, particle size, and O2 to coal and H2O to coal mass ratio is studied on number of circulations, total gas yield and solid circulation rate.
The optimum operating conditions are also obtained to achieve a specified conversion with minimum number of circulations and maximum gas yield per kg of coal per pass through sequential optimization. For a mixture of particle of different sizes, the conversion and product gas composition in annulus region are studied and compared with uniform size particles. The product gas composition depends strongly on operating parameters such as O2/coal and H2O/coal mass ratio and gas bypassing values through the orifice.
Figure 1: Composition of product gas in annulus region at different temperatures