Effect of pulsations on black liquor gasification. Progress report, July--September 1995

Abstract

The objective of this study is to investigate the use of pulse combustion to provide the energy required for the endothermic gasification of black liquor in a fluidized bed. In this process it is critical that the temperature remain in the small window above the gasification temperature but below the smelting temperature of the inorganic salts in the black liquor. Pulse combustors have been shown to have high heat transfer rates between the hot combustion products and the combustor tailpipe. Similarly, fluidized beds have high heat transfer rates within the bed itself, promoting temperature uniformity throughout. By combining a pulse combustor with a fluidized bed as the means of supplying energy to the gasification process we take advantage of the high heat transfer rates associated with each.Typical analysis of the gasified black liquor shows there is a large percentage of combustible gases in the products of the gasification process (approximately 70%). The potential exists, therefore, for using this fuel mixture to fire the pulse combustor This makes the entire process more efficient and may be necessary to make it economically feasible.The overall goals of this study are to determine: (1) which is the limiting heat transfer rate in the process of transferring the heat from the hot combustion products to the pipe, through the pipe, from the tailpipe to the bed and then throughout the bed; i.e., whether increased heat transfer within the pulse combustor will significantly increase the overall heat transfer rate; (2) whether the temperature distribution in the bed can be maintained within the narrow temperature range required by the process without generating hot spots in the bed even if the heat transfer from the pulse combustor is significantly increased; and (3) whether the fuel gas produced during the gasification process can be used to efficiently fire the pulse combustor.