A HIGH-PRESSURE DROP-TUBE FACILITY FOR COAL COMBUSTION STUDIES

A number of processes, including coal gasification, combined cycles an d heat engines, are being used or developed that combust coal at eleva ted pressures. While practical research is being conducted on the use of coal in these applications, little is known about the basic nature of high-pressure coal combustion. The few studies that have examined t he effect of pressure on these reactions during the past 25 years have been limited by experimental apparatus (shock tubes) and have produce d conflicting results. A need clearly exists for well-characterized fa cilities that can be used for high-pressure coal combustion research. This paper describes the design and characterization of an elevated pr essure drop-tube facility. This unique facility consists of a high-pre ssure drop-tube reactor, a tar/char/gas separation and collection syst em, an optical pyrometer and support equipment. The electrically heate d, computer controlled reactor was shown to provide the following capa bilities: pressure from 1 to 15 atm, wall and gas temperatures from 10 00 to 1700 K, controllable temperature profile along the reaction tube length, particle residence times from 30 to 1000 ms, variable gas com positions of inert and oxidizing gases, and optical access ports for i n situ diagnostics. Characterization of the reactor over the range of design operating conditions verified the suitability of the reactor fo r coal combustion experiments. Results from a series of char oxidation tests are also presented, demonstrating the wide range of possible ex perimental conditions; these oxidation experiments spanned a broader r ange of conditions than other known work.