This paper describes the formation of a phosphorous belite solid solution and its impact on alite formation. A subsolidus phase relation for the ternary system silicon dioxide-calcium oxide-phosphorus pentoxide (SiO 2 -CaO-P 2 O 5 ) is reported. The ternary system is based on Rietveld refinements of X-ray diffraction patterns from experimental tests. The overall picture is based on known phase diagrams, relevant Rietveld refinements models, stoichiometric relationships as a function of increasing phosphorus pentoxide concentration and vacancy theories for solid solutions of phosphate belites. A tool is developed for predicting the chemistry of the product as well as the chemistry during heating when producing Portland cement clinker. A thermodynamic database for phase chemistry calculations of clinkering reactions has been created and evaluated. Suitable compounds and solution species have been selected from the thermochemical database included in FactSage software. Some solution compositions have been uniquely designed to allow for the proper prediction of the cement clinker chemistry. The calculated results from the developed database for heating raw materials in cement clinker production and cooling of the product are presented in this paper. The calculated results provide a good prediction of the phases and quantities formed during heating and non-equilibrium cooling. The prediction of the amounts of alite, belite and aluminoferrite phases in the product according to the Scheil method is good. The temperature interval for the existence of all of the major phases is relevant. The thermodynamic data for a solution phase of alite with substituting ions of primarily magnesium oxide and phosphorus pentoxide would improve the predictability of the developed database.

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Based on modified Bogue calculations, steelmaking slags were combined in order to produce a belite-rich clinker activated with sulphoaluminate. The experiments were conducted on two different mixtures based on steelmaking slags together with additives, namely MixA and MixB. The objective of the present study was to investigate the hydraulic properties of the specimens, using conduction calorimetry, X-ray diffraction and differential scanning calorimetry, and also to measure the mechanical strength of the specimens when hydrated for 2 and 28 days. The compressive strength was satisfactory in relation to the estimated compositions. Both mixtures behaved the same with regard to heat development as well as the amount of ettringite formed during the first 24 h of the hydration.

In the present study, slags from the steelmaking industry are described and considered as a potential raw material within the field of sulphoaluminate belite cement. The objective of the study was to investigate the possibility of using a substantial amount of steelmaking slags as raw meal in the manufacture of a sulphobelitic clinker. A further aim was to compare the influence of different slags in relation to the formation of sulphoaluminate and the other clinker phases required. The behaviour of high temperature reactions was investigated by using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out through X-ray powder diffraction, and scanning electron microscopy. Three different mixtures and a single ladle slag were prepared using modified Bogue calculations, which are characterised by the assessment of a potential phase composition in order to produce belite-rich cement activated with sulphoaluminate. The results so far prove that steelmaking slags have the potential to be used as raw material, since sulphoaluminate along with polymorphs of dicalcium silicate and ferrite phases were detected after firing at 12008C in an air atmosphere.

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...