Feedstock Blending in a Continuously Fed Gasifier

Abstract

Imported oil, nuclear and coal now contribute about 55% of the energy the USA consumes, and those forms of energy are under environmental, social and legal scrutiny. There are limits to which non-“clouded” natural gas and renewables can replace these sources. This has motivated the CCTL to pursue R&D on blending domestically available fuels in thermal reactors to produce more useful gaseous or liquid fuels. Feedstock blending results with batch-fed indirectly heated gasifiers (IHGs) were reported at the three previous Turbo Expo meetings. This is a progress report on initial work with a continuously fed IHG scaled to potentially give a gaseous output suitable for a 5–20 kW microturbine or a reciprocating engine. An electric tube furnace is now used rather than a combustor fueled by the residual char or part of the gaseous or liquid output. Some novel features of this current effort are: a) Biomass blends are auger-fed through a reactor tube fabricated out of available components to simulate a conical shape, b) The output gas is filtered and partially cooled by the incoming biomass feedstock, c) The system has been designed to facilitate feedstock blending studies, d) A trap and external heat exchanger condenses the residual tar, water vapor, and volatile metals, e) The char-ash is collected and stored in a pressure vessel, f) Gas output volume is measured with an orifice dividing system and respirometer. The results of runs in a semi-continuously fed system with various biomass particle sizes and with various blends of biomass and coal are presented. The fate of volatile metals contained in the input feedstock is assessed. With the completion of an external hopper-feeder and the replacement of the electric tube furnace by an output gas or charcoal combustor, a later application to microturbines is within reach.