Turbulent Non-Stationary Reactive Flow in a Cement Kiln

The reduction of emissions from large industrial furnaces critically relies on insights gained from numerical models of turbulent non-premixed combustion. In the article <i>Mitigating Thermal NOx by Changing the Secondary Air Injection Channel: A Case Study in the Cement Industry</i>, th...

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Main Authors: Marco Talice, Franjo Juretić, Domenico Lahaye
Format: Article
Language:English
Published: MDPI AG 2022-06-01
Series:Fluids
Subjects:
Online Access:https://www.mdpi.com/2311-5521/7/6/205
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author Marco Talice
Franjo Juretić
Domenico Lahaye
author_facet Marco Talice
Franjo Juretić
Domenico Lahaye
author_sort Marco Talice
collection DOAJ
description The reduction of emissions from large industrial furnaces critically relies on insights gained from numerical models of turbulent non-premixed combustion. In the article <i>Mitigating Thermal NOx by Changing the Secondary Air Injection Channel: A Case Study in the Cement Industry</i>, the authors present the use of the open-source OpenFoam software environment for the modeling of the combustion of Dutch natural gas in a cement kiln operated by our industrial partner. In this paper, various model enhancements are discussed. The steady-state Reynolds-Averaged Navier-Stokes formulation is replaced by an unsteady variant to capture the time variation of the averaged quantities. The infinitely fast eddy-dissipation combustion model is exchanged with the eddy-dissipation concept for combustion to account for the finite-rate chemistry of the combustion reactions. The injection of the gaseous fuel through the nozzles occurs at such a high velocity that a comprehensive flow formulation is required. Unlike in <i>Mitigating Thermal NOx by Changing the Secondary Air Injection Channel: A Case Study in the Cement Industry</i>, wave transmissive boundary conditions are imposed to avoid spurious reflections from the outlet patch. These model enhancements result in stable convergence of the time-stepping iteration. This in turn increases the resolution of the flow, combustion, and radiative heat transfer in the kiln. This resolution allows for a more accurate assessment of the thermal NO-formation in the kiln. Results of a test case of academic interest are presented. In this test case, the combustion air is injected at a low-mass flow rate. Numerical results show that the flow in the vicinity of the hot end of the kiln is unsteady. A vortex intermittently transports a fraction of methane into the air stream and a spurious reaction front is formed. This front causes a transient peak in the top wall temperature. The simulated combustion process is fuel-rich. All the oxygen is depleted after traveling a few diameters into the kiln. The thermal nitric oxide is formed near the burner and diluted before reaching the outlet. At the outlet, the simulated thermal NO concentration is equal to 1 ppm. The model is shown to be sufficiently mature to capture a more realistic mass inflow rate in the next stage of the work.
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spelling doaj.art-5bb91450635547adbc16de4cb4bbeb622023-11-23T16:37:04ZengMDPI AGFluids2311-55212022-06-017620510.3390/fluids7060205Turbulent Non-Stationary Reactive Flow in a Cement KilnMarco Talice0Franjo Juretić1Domenico Lahaye2PM2 Engineering, 09127 Cagliari, ItalyCreative Fields Ltd., 10000 Zagreb, CroatiaDelft Institute of Applied Mathematics, Faculty of Electrical Engineering, Mathematics and Computer Science, Technical University of Delft, 62628 Delft, The NetherlandsThe reduction of emissions from large industrial furnaces critically relies on insights gained from numerical models of turbulent non-premixed combustion. In the article <i>Mitigating Thermal NOx by Changing the Secondary Air Injection Channel: A Case Study in the Cement Industry</i>, the authors present the use of the open-source OpenFoam software environment for the modeling of the combustion of Dutch natural gas in a cement kiln operated by our industrial partner. In this paper, various model enhancements are discussed. The steady-state Reynolds-Averaged Navier-Stokes formulation is replaced by an unsteady variant to capture the time variation of the averaged quantities. The infinitely fast eddy-dissipation combustion model is exchanged with the eddy-dissipation concept for combustion to account for the finite-rate chemistry of the combustion reactions. The injection of the gaseous fuel through the nozzles occurs at such a high velocity that a comprehensive flow formulation is required. Unlike in <i>Mitigating Thermal NOx by Changing the Secondary Air Injection Channel: A Case Study in the Cement Industry</i>, wave transmissive boundary conditions are imposed to avoid spurious reflections from the outlet patch. These model enhancements result in stable convergence of the time-stepping iteration. This in turn increases the resolution of the flow, combustion, and radiative heat transfer in the kiln. This resolution allows for a more accurate assessment of the thermal NO-formation in the kiln. Results of a test case of academic interest are presented. In this test case, the combustion air is injected at a low-mass flow rate. Numerical results show that the flow in the vicinity of the hot end of the kiln is unsteady. A vortex intermittently transports a fraction of methane into the air stream and a spurious reaction front is formed. This front causes a transient peak in the top wall temperature. The simulated combustion process is fuel-rich. All the oxygen is depleted after traveling a few diameters into the kiln. The thermal nitric oxide is formed near the burner and diluted before reaching the outlet. At the outlet, the simulated thermal NO concentration is equal to 1 ppm. The model is shown to be sufficiently mature to capture a more realistic mass inflow rate in the next stage of the work.https://www.mdpi.com/2311-5521/7/6/205non-premixed turbulent combustionrotary cement kilnradiative heat transferthermal NO formationOpenFoam software toolbox
spellingShingle Marco Talice
Franjo Juretić
Domenico Lahaye
Turbulent Non-Stationary Reactive Flow in a Cement Kiln
Fluids
non-premixed turbulent combustion
rotary cement kiln
radiative heat transfer
thermal NO formation
OpenFoam software toolbox
title Turbulent Non-Stationary Reactive Flow in a Cement Kiln
title_full Turbulent Non-Stationary Reactive Flow in a Cement Kiln
title_fullStr Turbulent Non-Stationary Reactive Flow in a Cement Kiln
title_full_unstemmed Turbulent Non-Stationary Reactive Flow in a Cement Kiln
title_short Turbulent Non-Stationary Reactive Flow in a Cement Kiln
title_sort turbulent non stationary reactive flow in a cement kiln
topic non-premixed turbulent combustion
rotary cement kiln
radiative heat transfer
thermal NO formation
OpenFoam software toolbox
url https://www.mdpi.com/2311-5521/7/6/205
work_keys_str_mv AT marcotalice turbulentnonstationaryreactiveflowinacementkiln
AT franjojuretic turbulentnonstationaryreactiveflowinacementkiln
AT domenicolahaye turbulentnonstationaryreactiveflowinacementkiln