Experimental study and CFD modeling of NOx reduction and reductive gas formation in deep reburning of cement precalciner

Li, Dan; He, Xiaolong; Peng, Xueping; Chen, Changhua; Li, Zhenshan

doi:10.1016/j.fuproc.2022.107183

Cited by 18 publications

(5 citation statements)

References 47 publications

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“…However, for simulations, their fixed concentrations were required in feed to assess the importance of the HCN–NO reaction in the reduction of NO to N 2 . Therefore, for simulations, we selected a typical condition in the exhaust gas of a cement kiln, where the NO concentration is found near 1200 ppm . For HCN, since its amount in the flame will be variable and would highly depend on the amount and type of SPL being cofired and fuel–air mixing, different amounts of HCN in the feed that represent different amounts of SPL cofiring with coal were used, as explained later.…”

Section: Results and Discussionmentioning

confidence: 99%

NO_x Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

Padole,

Raj

2024

Ind. Eng. Chem. Res.

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NO x emission from cement kilns is generally high due to the presence of fuel-bound nitrogen in the fuel (coal) and high temperatures in the combustion zone. To reduce the reliance on coal, spent pot lining (SPL, a carbon-rich waste from aluminum production plants) is cofired with coal in cement kilns. An unexpected advantage of this cofiring is the reduced NO x emission from the kiln, which is thought to occur due to the high cyanide content of SPL that may initiate NO x reduction reactions. This study focuses on investigating the potential of HCN that is released from SPL and its tautomer, HNC, to reduce NO to N2 under cement kiln conditions. A detailed reaction mechanism for the possible reactions of HCN and HNC with NO to form a variety of products (N2, HCO, HO2, HNN, O2, CO, N2O, and OH) through different pathways is developed. The reaction energetics are found using CBS-QB3 and B3LYP levels of theory, and the reaction kinetics are calculated using the transition state theory and RRKM. Through reaction pathway analyses and reactor simulation, the major products of the HCN–NO interaction and the most preferred pathways for reactant consumption and product formation are identified, which indicate N2 and HCO to be the major products of their reactions.

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Section: Results and Discussionmentioning

confidence: 99%

NO_x Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

Padole,

Raj

2024

Ind. Eng. Chem. Res.

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“…As computational fluid dynamics (CFD) continues to evolve, an increasing number of scientists have worked digital models to investigate the mechanisms and processes involved in the reduction and generation of NOx. − M. J. Kwon et al numerically investigate the details of NOx reduction in a mid/large-sized combustion system employing a new novel FIR burner, which thoroughly studies with emphasis on the effects of buoyancy and thermal radiation predicts the effects of buoyancy and thermal radiation. At present, there is a growing body of research focused on the creation of open-source computational models for combustion, which are leading to increasingly accurate predictions of flame behavior that more closely align with experimental observations.…”

Section: Challenges Research Gaps and Perspectivesmentioning

confidence: 99%

Review and Perspectives of Novel Flue-Gas Internal Recirculation Combustion Technology for Low Nitrogen Emission: Fundamentals, Performance, Method, and Applications for Conventional Fossil Fuels and Sustainable e-Fuels

Zhu

Wang

2023

Energy Fuels

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Novel flue-gas internal recirculation (FIR) is gaining increasing attention owing to its overwhelming stable combustion and nitrogen oxide (NOx) reduction advantages. This paper aims to reveal the nitrogen reduction mechanisms in the exciting new FIR methods and discuss the main FIR techniques in terms of combustion performance. In particular, the basic concept and the nitrogen reduction mechanism of FIR are first introduced. Besides, three main categories of FIRs are reviewed in accordance with the characteristics and operation status of different devices. The analysis of 16 FIR systems suggests that the recirculation space, effective recirculation rate, and combustion ignition limit must be considered during the design process, in order to balance NOx reduction and combustion efficiency. The integrated FIR and external FIR can achieve NOx emission reductions of at least 20% and 15.5%−20%, respectively. The embedded FIR exhibits more outstanding NOx emission reduction performance, with NOx reduction ratios of up to 26.09%−65%. In addition, the influence elements of FIR on combustion efficiency and nitrogen reduction are also discussed. In conclusion, strategies aimed at enhancing the combustion performance of novel FIR burners are thoroughly delineated, and the challenges that need to be addressed are succinctly highlighted in a forward-looking perspective. This review is expected to clarify the NOx reduction and combustion characteristics of current FIR techniques and suggest a development direction for FIR design.

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“…Flow rate / (Kiln Cross -Sectional Area) (13) A = (πDs 2 /4) -( 4πr 2 ) = 11.3 m 2 Vg = (292679 * (1/3600) * (1/11.3) = 7.2 m/s Several main and secondary reactions (tables 3 and 4) result from the direct contact of the raw materials with the going air within the furnace. Considering that the equations are written steadily, the value of ∂ / ∂t in relations 11 and 12 is zero and is modified as follows for each solid, gas, and fuel species (Li et al, 2022;Spang, 1972). The rate constant of the reaction is calculated from the Arenos equation as follows (Spang, 1972): Ki = Ai exp (-Ei / RTs) , i = H2O, CaO (18) KF = (3/ rF) AF exp (-EF / RTg) (19) Here, Ts and Tg represent the solid and gas temperatures in this equation.…”

Section: The Equation Of Movement Of Particlesmentioning

confidence: 99%

“…Various conditions, such as temperature, pressure, time, and fuel, affect the concentration of the gases produced by the kiln. Thus, the mass balance is a function of the length and time in the kiln, shown as follows (Li et al, 2022): ∂Ci / ∂t = Ri -Vg ∂Ci / ∂z , i = CO2, CO, N2, H2O, O2 (11) ∂Cj / ∂t = Rj -Vs ∂Cj / ∂z , j = CaO, CaCO3 (12) In up equations, Vg and Vs represent gas and raw materials velocity entering the kiln, respectively. Also, Ci and Cj are gas and raw material concentrations entering the kiln, respectively, and Ri is the reaction rate constant.…”

Section: The Equation Of Movement Of Particlesmentioning

confidence: 99%

Investigation of Cement Kiln Process for Reducing Environmental Emissions

Hashemi

2023

Preprint

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The cement industry is one of the world's most important strategic industries, essential to every country's economic and infrastructure development. Also, its production is recognized as one of the growth indicators for any country. In cement production, the rotary cement kiln is one of the main components that play a significant role in producing environmental pollutants such as NOX, VOC, CO, and CO2. Hence, this research aims to determine the concentration of pollutants gases and investigate ways to reduce their emissions, especially carbon monoxide, in different conditions in the cement kiln process. The rotary kiln is a Horizontal cylinder inclined with a relatively gentle slope, in which the raw materials with air flow have direct and counter contact. For this purpose, the kiln process was modeled and optimized using the equations of transfer phenomena, operational variables, and chemical reactions. Also investigated were primary and secondary reactions resulting from incomplete combustion. Results demonstrated that increasing excess air from 0–30% decreases exhaust gas concentration. Also, if the extra air is raised to 30%, the kiln performance efficiency and the combustion flame model do not show significant variations, and the CO mass fraction decreases.

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Experimental study and CFD modeling of NOx reduction and reductive gas formation in deep reburning of cement precalciner

Cited by 18 publications

References 47 publications

NO_x Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

NO_x Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

Review and Perspectives of Novel Flue-Gas Internal Recirculation Combustion Technology for Low Nitrogen Emission: Fundamentals, Performance, Method, and Applications for Conventional Fossil Fuels and Sustainable e-Fuels

Investigation of Cement Kiln Process for Reducing Environmental Emissions

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Experimental study and CFD modeling of NOx reduction and reductive gas formation in deep reburning of cement precalciner

Cited by 18 publications

References 47 publications

NOx Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

NOx Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

Review and Perspectives of Novel Flue-Gas Internal Recirculation Combustion Technology for Low Nitrogen Emission: Fundamentals, Performance, Method, and Applications for Conventional Fossil Fuels and Sustainable e-Fuels

Investigation of Cement Kiln Process for Reducing Environmental Emissions

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Product

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NO_x Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions

NO_x Reduction in a Cement Kiln with Spent Pot Lining: A Reaction Kinetics Study on HCN–NO and HNC–NO Interactions