Evaluation of coal devolatilization concept. Final report

The objective of this test program was to evaluate the concept of increasing gas heating value from an air-blown entrained gasifier by feeding some or all of the coal to a devolatilizer vessel downstream of the gasifier. It was further required that the increase in heating value should be accomplished without the production of tar or soot. A pilot plant was constructed consisting of a one foot diameter gasifier and an eighteen inch I.D. by eight feet high devolatilizer. A total of 43 test runs were conducted using an Eastern Bituminous coal as well as a western sub-bituminous coal. Three modes of operation were employed; all coal fed to the gasifier, all coal fed to the devolatilizer, and a 50 to 50 split between the two. Analysis of the pilot plant data yielded the following general results: The highest heating value gases were generated when all of the coal was fed to the gasifier; unacceptably large tar quantities were generated when half or all of the coal was fed to the devolatilizer; and tar content of the gas was negligibly small when all of the coal was fed to the gasifier. Heat losses were considerably higher than anticipated. Without modification there appears to be no way to operate so as to significantly lower heat losses. It is recommended that the pilot gasifier be redesigned with the aid of the thermal model. This step, together with the addition of an externally fired air heater to the facility will reduce heat losses to those representative of a commercial installation.