(408e) High Resolution Simulations of a Coal Gasifier

Integrated Gasification Combined Cycle (IGCC) is a promising technology for meeting the growing demand for power using fossil fuel resources, while economically controlling the emission of CO2 and other pollutants. The centerpiece of an IGCC system is the gasifier, which converts coal or other carbonaceous materials such as biomass into syngas, a mixture of CO and H2. The syngas can be used for the production of liquid fuels and chemicals or for power generation. In an IGCC system the syngas is shift converted into a mixture of CO2 and H2, CO2 is captured and stored, and H2 is used for power generation.

A reliable gasifier is critical for the commercial viability of IGCC. The gas-solids multiphase flow such as occurring in the gasifier is known to make the design of commercial-scale units using traditional scale-up methods difficult. Multiphase computational fluid dynamic (CFD) models are being developed at NETL to address that challenge, and this presentation discusses the potential for using high-resolution CFD simulations for gasifier design. A gasifier model based on the code MFIX was ported to several high performance computing (HPC) platforms ranging from Cray XT series to clusters with high bandwidth, low latency interconnects (e.g., Infiniband). MFIX is based on a continuum multiphase flow model that considers gas and solids to form interpenetrating continua. Low resolution simulations of a commercial scale gasifier with a validated MFIX model revealed interesting physical phenomena with implications on the gasifier design, which prompted the study presented here. To be predictive, the simulations need to model the spatiotemporal variations in gas and solids volume fractions, velocities, temperatures with any associated phase change and chemical reactions. These processes occur at various time- and length-scales requiring very high spatial resolution and large number of iterations with small time-steps. We were able to perform perhaps the largest known simulations of gas-solids reacting flows, providing detailed information about the gas-solids flow structure and the pressure, temperature and species distribution in the gasifier. Simulations were conducted with up to 6032 computational cores with a 10 million cells grid resolution. Porting the code to run on 1000's of cores instead of 10's or 100's of cores required changes in the code algorithm, parallelization methods, and the method of writing the output. This presentation will discuss the experiences in porting and running the code on HPC, the results of the high resolution simulations, and the prospects of using such high resolution simulations for scale-up.