Abstract
There is an absolute need to adopt innovative technologies to improve energy efficiency with minimum possible environment emission and conservation of natural resources. Oxygen-enriched combustion is one of the latest technologies that may improve combustion efficiency depending on the exhaust gas temperature and percentage of oxygen in the combustion air. Cement industry is responsible for approximately 8% of the global anthropogenic CO2 emissions (IPCC, 2006) and the cement market is expected to grow with increased industrialization and urbanization. In typical cement manufacturing process, 60% of CO2 emissions are due to the transformation of limestone to lime (the calcination process) and rest 40% is due to fuel combustion in pyro processing. The air is used as an oxidizing agent content in industrial combustion processes that has maximum nitrogen component (78–79%) by volume. The chemically inert nitrogen dilutes the reactive oxygen and carries away some of the energy in the hot combustion exhaust gas during the air-fuel combustion process. An increase in oxygen in the combustion air can reduce the energy loss in the exhaust gases and increase the fuel combustion efficiency. Oxygen enrichment is helpful in curbing gaseous emission. By increasing oxygen content in air, N2 content is limited that leads to less NOx in exhaust gases. In this condition exhaust gases are more CO2 rich that are partially recirculate along with combustion air. In CO2 rich exhaust gases, water vapour is removed though condensation process and remaining CO2 is captured through CCS technology.
Highlights
Oxygen is required for any combustion process and ambient air is the most common source of oxygen that contains about 79% Nitrogen by volume
Oxygen-enriched combustion technology can improve the fuel combustion conditions of cement production, increase flame temperature, shorten the time needed for combustion and achieve complete combustion enabling cement plants to increase the flame radiation heat ability of a material and improving the whole system’s thermal
Flame temperature can rise by 200–300 °C when oxygen content increases by 4–5%
Summary
Combustion is a chemical process in which a substance reacts rapidly with oxygen and releases heat as product. The nitrogen contained in air inhibits fuel from reacting with oxygen. This results in a flame temperature below that attainable with pure oxygen (Schorcht et al 2013). Oxygen enrichment which is known as increased O2% in combustion air. This improves the overall combustion process and the resulting heat transfer increases flame temperature and the amount of available heat (Eriksson 2015). Overall gas flow rates are reduced and thermal efficiency increases by substituting pure oxygen either for a portion or total combustion air (Gao et al 2017). It can be understood that for the air/methane reaction, there are 10.5 volumes of combustion products, compared to only three volumes of combustion products for the oxygen/methane flame. The adiabatic flame temperature of the oxygen/methane flame is roughly 800 °C higher than the air/methane flame due to the elimination of nitrogen
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