Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering (MCM'21)
Prague, Czech Republic Virtual Conference – August, 2021
Paper No. HTFF 142
DOI: 10.11159/htff21.142

The Effect of Particles Surface Temperature Distribution in Numerical
Modelling Of High Scale Combustion and Gasification Chambers
Ewa Karchniwy1,2, Adam Klimanek1, Sławomir Sładek1, Andrzej Szlęk1, Agnieszka Korus1,
Wojciech Adamczyk1
1

Department of Thermal Engineering, Silesian University of Technology
Konarskiego 22, 44-100 Gliwice, Poland{ewa.karchniwy; adam.klimanek; slawomir.sladek; andrzej.szlek; agnieszka.korus; wojciech.adamczyk}@polsl.pl2
Department of Energy and Process Engineering, Norwegian University of Science and Technology
Kolbjørn Hejes vei 1B, NO-7491 Trondheim, Norway

Extended Abstract
Solid fuels are common source of energy in global primary energy and electricity production. Numerical modelling ofcombustion and gasification chambers is an important stage of a design and optimisation of existing facilities. To better
reproduce real conditions, it is essential to improve numerical models. In the presented work the influence of a char particlesurface temperature distribution on the particles dispersion has been analyzed. The flow of species between the particle
surface and surrounding gas, so called Stefan flow, is uniform for the entire particle surface when uniform particle reactivity
is assumed. However, a structure of real char particles in non-uniform due to the distribution of pores and ash. Previous
research [1, 2] have shown that temperature distribution on the particle surface is non-uniform with standard deviation oftemperature up to 400K. This can lead to additional force resulting from varied Stefan flow around the particle.
Based on measured surface temperature distributions, numerical model has been developed and described in [3]. It has
been shown that a non-negligible force can occur especially in high temperature regions where reactivity and surface
temperature variances are high. The purpose of this work is to examine the influence of non-uniform Stefan flow aroundparticles in real scale combustion and gasification systems.
A real scale boiler OP-430 has been simulated using the developed numerical model in order to examine the influenceof surface temperature variances in combustion conditions. OP-430 is a tangential, middle-sized boiler producing 430 t/h ofsteam at 532ᵒC and 12,7 MPa. A detailed description of the boiler geometry and operating conditions can be found in [4].
The gasification chamber considered in the paper was Shell Coal Gasification Process (SCGP) gasifier which is a one-stage,entrained-bed facility with nominal power of 300 MW. All details including geometry and work conditions can be found in[5].
All simulations were performed using commercial software Ansys Fluent. The 3-dimensional steady state, Reynoldsaveraged Navier–Stokes (RANS) model has been used. The model included momentum, energy and species transportequations. The realizable k-ε model was used for turbulence. Solid particles were treated as a discrete phase using Lagrangianreference frame, and stochastic tracking was employed to account for the influence of turbulence on the particles dispersion.
The additional force resulting from non-uniform reactivity and Stefan flow was calculated and included in the particle force
balance equations using User Defined Function (UDF). Heterogeneous reactions were analyzed using kinetic-diffusion
model.
Based on performed simulations it can be concluded that the influence of additional particle force on global parameterssuch as temperature and gas species profiles is insignificant. Differences are local and can be found mainly in hightemperature regions where reactions reach the diffusion regime. However, slightly higher dispersion of particles can beobserved in the reaction zone. This effect is less noticeable in the case of the gasification reactor due to the lower temperatureof the process.

Acknowledgements
The research has received funding from the Opus 13 Research Programme operated by the Polish National Science
Center in the frame of Project Contract No UMO-2017/25/B/ST8/00957. This support is gratefully acknowledged.

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