Modelling the cement process and cement clinker quality

Abstract

This paper presents a recently developed simulation model that can be used as a tool for evaluating sustainable development measures for cement and lime production processes. Examples of such measures are introducing new combustion technologies such as oxy-fuel combustion, using biomass fuel and using alternative materials in the raw material feed. One major issue when introducing process changes is the need to maintain product quality. In some ways, oxygen-enriched air combustion resembles oxy-fuel combustion. The model results were validated and found to be consistent with full-scale operational data for normal running conditions and for a full-scale test with oxygenenriched air. The model shows, for example, that with an additional 1500 m 3 /h of oxygen, fuel addition at the calciners can increase up to 108% and the raw material feed rate can increase up to 116% for a process with a raw meal feed of 335 . 5 t/h. IntroductionIt is important to understand how changing the atmosphere in a kiln influences clinker quality. This is especially the case considering that future scenarios for the cement industry include carbon capture and storage and oxy-fuel combustion (Barker et al., 2009;WBCSD and IEA, 2009; Zeman, 2008). This paper describes the influence of oxygen-enriched air combustion on the clinker production process and clinker quality. Increased oxygen addition locally increases the concentration of oxygen in the process. The introduction of oxy-fuel combustion techniques will change the composition of the process gases more significantly due to a drastic increase in carbon dioxide (CO 2 ) concentration.Simulation models are tools that will aid the cement industry of today and help continue its development towards sustainability in the future. Models for simulating carbon dioxide emissions and conserving material and fuel resources, as well as implementing energy efficiency measures, have been described by Schneider et al. (2011) andSorrentino (2011). Carbon dioxide emissions in cement productionOwing to the environmental impact of carbon dioxide emissions, carbon-dioxide-intensive industries must strive to decrease emissions. The cement industry emitted a total of 1514 Mt of carbon dioxide in 2009, which corresponds to 4 . 7% of the total global carbon dioxide emissions from fossil fuel burning (Boden and Andres, 2012). Cement is used nearly without exception in concrete. Concrete is the world's most used construction material and its use has increased threefold since 1970, and production of both cement and concrete is expected to increase even further in the future (WBCSD and IEA, 2009). Manufacturers of clinker and cement must enact environmental measures but at the same time maintain the production of good-quality cement while preserving stable running conditions in the manufacturing process.Oxygen enrichment and oxy-fuel combustion A simplified illustration of oxygen-enriched air combustion is shown in Figure 1. The idea is to add highly concentrated oxygen to the process, with the aim of increasing the...

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