Numerical Experimentation and Validation of Shrinking Particle - Gas Reaction in a Pilot Plant Downer Reactor

ABSTRACT

Downer reactors have been the choice for catalytic reactions necessitating control on intermediates, short residence time and high solid loading. The noncatalytic gas-solid reactions exhibit different hydrodynamics due to continuous variation of particle morphology during the reaction. This study addresses the challenges with numerical experimentation of reactive gas-solid system possessing shrinking particle characteristics and verification with the results from pilot scale test facility. Petcoke with ash content about 0.322% by weight is selected to justify the shrinking particle characteristics during combustion. The particle size ranges from 2 µm to 130 µm with an average size of 60 µm. The powder is cohesive with Hausner ratio of 1.43 and occupies cohesive regime in the Geldart’s classification.

Ansys Fluent v19.0R1 is employed in simulating the reaction with a shrinking particle model and the kinetic parameters deduced with the help of TGA has been incorporated in the numerical model as well. The optimum multiphase interaction parameters using numerical experiments established with coupled CFD-RSM method also been included. The simulation tests are conducted for the same experimental conditions with the pilot plant test facility. The temperature profile and concentration profile are obtained for different solid/gas loading ratios and compared with the experimental data obtained with the pilot plant test facility. The study establishes the significance of appropriate drag models along with the interacting parameters for reliable and robust simulation. The simulation model presented here can be used for design and analysis of the performance of a downer reactor for reactive systems with shrinking particle characteristics.

KEYWORDS:

• Downer reactor
• pilot plant test facility
• shrinking gas particle reaction
• simulation
• validation

Highlights

• The modelling of ultrafine cohesive shrinking particle-gas reaction characteristics is studied in the downer reactor with petcoke as the raw material.

• Gas-solid reaction follows shrinking particle model (SPM) is applied among the available gas-solid reaction models with ANSYS Fluent.

• Deduced kinetics of petcoke-air reaction following SPM with an Activation energy, E_a =175.8743 kJ/mol, and pre-exponential factor, k_o = 3E08 m/min has also been accounted in the model.

• The experimental pilot scale test facility is setup to carry out ultrafine cohesive shrinking particle reaction.

• The simulation results are then validated against the pilot plant experimental data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.