Energy & Fuels 1993, 7, 928-936
928
A High-pressure Drop-Tube Facility for Coal Combustion Studies Charles R. Monson* and Geoffrey J. Germane Department of Mechanical Engineering, Brigham Young University, Provo, Utah 84602 Received April 8, 1993. Revised Manuscript Received September 14, 1999
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 highpressure 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.
Introduction While most of the current consumption of coal occurs in utility furnaces at atmospheric pressure, several other processes are also being used or developed for either the direct combustion of coal or its conversion into other products. Coal gasification, combined cycles, and heat engines are examples of these other processes that operate at elevated pressures. Practical research is being conducted on the use of coal in these applications, yet little is known about the basic nature of coal combustion at elevated pressure. The few studies that have examined the effect of pressure on char oxidation during the past 25 years have been limited by experimental apparatus (shock tubes) and have produced conflicting This paper describes the design and characterization of an elevated pressure facility for use in high pressure coal combustion research. The controlled conditions required for high temperature, coal devolatilization and char oxidation experiments place great demands on a test facility. Not only must the initial heating rates (104-105K/s) and high particle temperatures (1700-2200K) encountered in pulverized fuel combustors be attained, but reactor temperatures must be controllable over a wide range and it is also desired to maintain constant particle temperature while the particle reacts. The reaction must proceed in a consistent manner, with * Author for correspondence. Present address: GMH Engineering, 336 S. Mountainway Dr., Orem, UT 84058. 0 Abstract published in Advance ACS Abstracts, October 15, 1993. (1) Nettleton, M. A.; Stirling, R. Proc. R. SOC.London, 1971, A322, 207. (2) Park, C.; Appleton, J. P. Combust. Flame 1973,20, 369. (3)Lester, T. W.; Seeker, W. R.; Merklin, J. F. In Eighteenth Symposium on Combustion, Proceedings; The Combustion Institute: Pittsburgh, 1981; pp 1257.
quenching occurring at selected stages during the short time of particle burnoff (
