Used Tires as Fuel in Clinker Production: Economic and Environmental Implications

Abstract

This work analyzes how gases emitted during the manufacture of clinker vary in a cement plant using two types of fuel: petroleum coke and unusable tires (UTs). This study is based on a case study using real time data on more than 40 process variables. Gases are analyzed from two points of the production process: from the sintering kiln, where the main focus of emissions to the atmosphere is by chimney, and from the preheater. The variation of CO and NOx depending on the oxygen and fuel type is studied. The SO2 levels are also analyzed and a decrease was observed when using the UTs. The quality of the clinker is compared according to the fuel type. The results are analyzed, on the one hand, by the quality of the clinker, determined by the content of the majority (C3S, alite) and minority (free CaO) phases, and, on the other hand, by the kiln sintering temperature, the most influential parameter in the productive process. It is verified that the clinker quality is maintained regardless of the type of fuel used. Therefore, the use of UTs as fuel could generate important economic and environmental benefits for cement companies.

The value of different recycling technologies for waste rubber tires in the circular economy—A review

“…As waste rubber tires form a cheap alternative to the usual heat sources, typically oil, gas or petroleum coke, they are a welcomed addition to the heat process by most cement manufacturers. A recent economic and environmental assessment of using waste tires as fuel in cement clinker production reported a cost reduction of around 25%, when a combination of 40% scrap tires and 60% petroleum coke was used instead of 100% coke (Castañón et al, 2021). Additionally, in the same study and using the same test conditions, a reduction of 17% NO x , 28% SO 2 and up to 60% CO at the exit of the kiln was observed, showing that there is also potential environmental benefit when cement kilns are operated efficiently.…”

“…Additionally, in the same study and using the same test conditions, a reduction of 17% NO x , 28% SO 2 and up to 60% CO at the exit of the kiln was observed, showing that there is also potential environmental benefit when cement kilns are operated efficiently. There is another technological advantage of using waste tires as fuel in cement kilns, as it is not necessary to remove the metal reinforcements in the tires prior to incineration as they can partially replace the iron additions used as a flux in the composition of cement raw mix (Castañón et al, 2021). Further research is required, however, to fully determine all the potential environmental implications of using tires as fuel and under which conditions EU limits, e.g., 500 mg/Nm 3 NO x and 50 mg/Nm 3 SO 2 according to Directive 2010/75/EU for cements kilns co-incinerating waste, can be met.…”

An Overview of the Utilization of Common Waste as an Alternative Fuel in the Cement Industry

“…Nevertheless, the supply of coal is predicted to be in short supply in the near future in order to achieve the goal of halving CO 2 emissions by 2030 and reaching net zero emissions by 2050. On top of that, the cement industry is very vulnerable to fuel price fluctuations [9]. As a result of the energy-intensive characteristics of cement production processes, escalating fuel prices, and fuel shortages, the cement industry is forced to search for alternative fuel (AF) sources [9][10][11].…”

“…On top of that, the cement industry is very vulnerable to fuel price fluctuations [9]. As a result of the energy-intensive characteristics of cement production processes, escalating fuel prices, and fuel shortages, the cement industry is forced to search for alternative fuel (AF) sources [9][10][11]. Adopting wastes as an AF in the cement industry is another viable approach to reduce CO 2 emissions and preserve natural fossil fuel, as well as cost savings.…”

Multi-Case Study on Environmental and Economic Benefits through Co-Burning Refuse-Derived Fuels and Sewage Sludge in Cement Industry

“…Moreover, calcium oxide present in the raw material feed neutralizes and captures acid gases such as HCl, HF, and SO 2 formed during combustion [18]. Ash, a solid residue after combustion, is completely absorbed in the clinker structure, constituting approximately 3.5-4% of its mass [19,20]. Thus, this process allows for both the simultaneous recovery of thermal energy from the organic part of the alternative fuel and material recycling from the mineral part as a valuable component of the raw material set [21].…”