Environmentally clean, affordable power is the goal of research at NETL,
and coal gasification is one of the technologies that will make a
difference. "There are two issues with coal," says Jack Halow, director
of NETL's simulation and multi-phase flow analysis division. "As a
solid, it's difficult to transport compared to liquids and gas, and
fundamentally it's difficult to remove contaminants from a solid. Once
it's gasified, you can pipe it wherever you want, and in the gas phase,
it's much easier to separate and remove the environmental contaminants."
In recent studies using LeMieux, PSC's terascale system,
NETL researchers under the direction of project managers
James Longanbach and Daniel Cicero carried out 3D
simulations of the transport reactor from the Power System Development
Facility in Wilsonville, Alabama. PSDF is a U.S.
Department of Energy demonstration plant for advanced
electric-power technologies, and the PSDF transport reactor
is a "circulating fluidized-bed" that can operate as a coal
In this plant-sized technology - the reactor unit is 80 feet tall - coal
and recycled material feed into the lower part of the gasifier, called
the mixing zone, where the coal combusts at high temperature and
pressure. Hot gas and unburnt solids rise from the mixing zone into the
riser. At the top of the riser, unburnt solids are collected and fed
back into the bottom of the mixing zone. Eventually coal converts with
nearly 100 percent efficiency into gas.
Among the research tools NETL has developed is simulation
software called MFIX
(Multiphase Flow with Interphase Exchanges), which
realistically models the gas and particle dynamics, chemical
reactions and heat transfer involved in coal gasification
and other power-generating combustion processes. "Capturing
the correct hydrodynamics in a circulating fluidized bed,"
says NETL consulting engineer Chris Guenther, who
coordinated the MFIX computations, "is critical."
In this study, the NETL researchers simulate the flow as it moves from
the mixing zone into the riser. They track the hydrodynamics of both the
gas and solid phases along with heat transfer between the two phases and
production of gas species, such as methane, carbon monoxide and carbon
dioxide. "Design engineers," says Guenther, "want to see how design
changes affect the hydrodynamics and the chemistry, which isn't readily
available from experiments. With simulations, design changes can be
tested at a fraction of the cost of building and doing experiments with
a scale model."
The transport reactor (green) at The Power Sytems
Development Facility, a DOE supported experimental
plant in Wilsonville, Alabama. NETL simulations
complement testing and development at this plant-sized