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

A number of processes, including coal gasification, combined cycles and heat engines, are being used or developed that combust coal at elevated 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 the effect of pressure on these reactions during the past 25 years have been limited by experimental apparatus (shock tubes) and have produced conflicting results. A need clearly exists for well-characterized facilities that can be used for high-pressure coal combustion research. This paper describes the design and characterization of an elevated pressure drop-tube facility. This unique facility consists of a high-pressure drop-tube reactor, a tar/char/gas separation and collection system, an optical pyrometer and support equipment. The electrically heated, computer controlled reactor was shown to provide the following capabilities: pressure from 1 to 15 atm, wall and gas temperatures from 1000 to 1700 K, controllable temperature profile along the reaction tube length, particle residence times from 30 to 1000 ms, variable gas compositions of inert and oxidizing gases, and optical access ports for in situ diagnostics. Characterization of the reactor over the range of design operating conditions verified the suitability of the reactor for coal combustion experiments. Results from a series of char oxidation tests are also presented, demonstrating the wide range of possible experimental conditions; these oxidation experiments spanned a broader range of conditions than other known work.