(380au) Numerical Verification and Validation of the Biomass Pyrolysis and Gasification inside a Bench Scale Reactor with Mfix-TFM

Numerical
verification and validation of the biomass pyrolysis and gasification inside a
bench scale reactor with MFiX-TFM

Yupeng Xu^1,2, 
Mehrdad Shahnam¹, Andrea Porcu³, Alberto Pettinau³, 
Bhima S Sastri⁴, William Rogers¹

1.
National Energy Technology Laboratory, Morgantown, WV 26505, USA

2.
West Virginia University Research Corporation, Morgantown, WV 26506, USA

3.
Sotacarbo Sustainable Energy Research Center, Carbonia, Italy

4.
U.S. Department of Energy, Washington D.C., USA

Abstract

Biomass is a
widely available renewable energy source, which could be an alternative fuel
source to fossil fuels to alleviate environmental problems. Biomass
gasification is a promising approach for combined heat and power generation and
for the production of various products such as fuels and chemicals. Gas-solid
fluidized-bed offers excellent mixing, heat and mass transfer between solid
particles and fluidizing gas, thus is one of the most interesting technologies.

This work shows
the result of an experimental and numerical comparison for biomass gasification
as part of a research collaboration between Sotacarbo Sustainable Energy
Research Center, Carbonia, Italy and National Energy Technology Laboratory (NETL),
Morgantown, WV, USA. A bench-scale fluidized bed, shown in Figure 1, was used
at Sotacarbo research center to gasify cypress biomass from Sardinian woods. The
proximate, ultimate and calorimetric analyses of the fuel were carried out at
Sotacarbo laboratories according to the international standards. A SympaTEC
QICPIC particle analyzer was used to characterize the Cypress biomass and
Olivine sand particles at NETL. Pyrolysis kinetics was measured through thermogravimetric
analysis at Sotarcarbo. In the experimental activity, biomass feedstock is
injected through a hopper via a screw feeder located at the lower side of the
reactor. A small amount of N2 at room temperature is injected to aid the
feeding process. The fluidizing gas (N2 or air) is injected through the bottom
of the gasifier. The bed material consists of Olivine sand particles, to help
with the fluidization of biomass particles and heat distribution in the bed.
Various conditions are tested and the complete and accurate experimental
data provide a benchmark dataset for CFD verification and validation.

Simulations are
conducted using the U.S. Department of Energy’s Multiphase Flow with Interphase
eXchanges code, MFIX.  The Eulerian-Eulerian, Two Fluid Model in MFiX, (MFiX-TFM)
has been used to simulate the drying, pyrolysis, combustion and gasification of
the biomass particles.  Additionally, homogenous oxidation reactions such as
CO, H2 and CH4 oxidation reactions and water gas shift reactions are included.  Syngas
composition at the outlet of the gasifier is compared with the experimental
results.  Figure 2 shows the comparison between the simulation results and the
measurements for one of the conditions under consideration, where very good
agreement is observed.

Fig.1. Direct
comparison between simulation and experiments

Fig.2. Detailed
comparison between the instantaneous pyrolysis vapor between experiment and
simulation