|Reactor system process and instrumentation. Inset shows more detail on the reactor vessel. Source: Purdue University. Click to enlarge.|
Researchers at Purdue University have developed a facility aimed at learning the chemical kinetic processes in coal and biomass gasification to improve thermodynamic efficiency and reduce the environmental impact of the technology. The research is part of work to develop a system for generating large quantities of synthetic liquid fuel from agricultural wastes, other biomass or coal via a gasification pathway.
Other aims are to learn how to generate less carbon dioxide than conventional synthetic-fuel processing methods while increasing the yield of liquid fuel by adding hydrogen into the coal-and-biomass-processing reactor, a technique pioneered by Rakesh Agrawal, Purdue’s Winthrop E. Stone Distinguished Professor of Chemical Engineering. (Earlier post.)
A major focus is to be able to produce a significant quantity of synthetic fuel for the US air transportation system and to reduce our dependence on petroleum oil for transportation. We want to show that our system is flexible for using coal and biomass. The aim is to create a sustainable synthetic fuel economy. What’s daunting is the size of the problem—how much oil we need—how much energy we need.—Jay Gore, the Reilly University Chair Professor of Combustion Engineering at Purdue
Findings published last year showed carbon dioxide might be reduced by 40% using the technique. New findings will be detailed in a research paper being presented during a January 2011 meeting of the American Institute of Aeronautics and Astronautics in Orlando.
The optically accessible entrained flow coal-gasifier is designed for maximum operating pressures and temperatures of 1 MPa (10 bar, 145 psi) and 1400 K (1,127 °C. The 2-meter tall gasifier comprises five subsystems:
- optical diagnostics;
- steam generator;
- coal feeder;
- external heaters; and
- gas sampling and analysis.
Tunable diode laser absorption spectroscopy (TDLAS) is used for optical diagnostics of the gasification process. A stoichiometric H2-O2 flame generates superheated steam—the gasifying agent. A novel variable feed-rate pressurized feeder is used to inject pulverized coal or biomass into the reactor. Radiant heaters provide the 15 kW of external heating needed to sustain the endothermic coal gasification reaction. Product gases are sampled at the reactor exit and are analyzed using a gas chromatograph to determine the dry major species concentrations.
The stainless steel reactor borrows technology from aerospace applications, including a spark igniter used in space shuttle engines. Materials inside the spark igniter may briefly reach temperatures of up to 3,000 °C.
It’s a modular design, so the optical diagnostics part can be moved to various points to analyze how the gasification proceeds.—Robert Lucht, the Ralph and Bettye Bailey Professor of Combustion in Mechanical Engineering
The work is funded by the US Air Force Office of Scientific Research.