Cement Energy and Environment

Table-2 Chemical analysis of samples collected during the studies on loss free basis I Material Sample Kiln Feed Fan deposit Vl 1 h stage Cyclone gas outlet Si02 21.55 22.28 AI203 5.54 16.98 Fe20a 4.43 19.3 CaO 66.30 38.77 MgO 1.21 1.30 S03 0.29 0.29 Na20 0.23 0.22 K20 0.51 0.75 Cl· 0.005 0.097 Hence, in order to ensure the validity of this assumption , all the samples, namely the preheater kiln feed , fan outlet and fan deposition samples, were also subjected to thermal characterization using TG-DSC (Figure 4-6). The analysis showed that calcite is getting decomposed endothermically at 859.9 and 831.90C respectively. Considering typical range of temperature in which the calcite is known to decompose (i.e. around 800-8700C) these two samples (preheater kiln feed and fan 1200 1100 ~ 1000 ~ m .3 000 roo 600 lOO - .000 - l!lO 100 10 19.17 5.43 4.34 68.13 1.88 0.25 0.35 0.36 0.086 outlet) can be said to have usual thermal behaviour. A small temperature peak at 4880C in figure 4 indicates the presence of clay particles (Kaolinite) since typical dehydration range of Kaolinite is known to exist between 480-5000C [9]. Similarly temperature peak at 895.20C in figure 4 shows an indication of exothermic phase transformation of Kaolinite to Mullite (AI2Si205) indicating change in crystal structure of the compound [9, 10, 11]. 2-Theta · Scale !iY;I< FonC.O""Ol,AC,.,.,. l tJ>I! :rrtl1h '>CI«d !:l.n 100CXI' Er~ 60 000' SIEfl 0 0~0 ' · Sop <tre 4 • Tenp 2~ 'C iltotml· Ti"" ""-""' 0\ · 2-11•'"• 10009' Thtn HXW C..>fll"f [.4 ~aeons ~h01!JDI~1"0~3J O~IIn'"Wr I OS86rJ CfW> 91" C..CO'l Y !iOOO% dol>; I "'1,1 ~4()1; 0 Utf!.ifl · 1045rJ a ...,""' s.m v 500011.-d<t>y 1 \IVL I S<llli o llcFUJ< CE84 r1 "l!m~ 'Yfl f!'XD l 6D00ttt. d • ri'( I 1M.. 1fA08 G lAcPOr ') 4 141!6rJ N.l~f111• ¥ f~ Y ~00,._ d•bt I "--. 1 ..... (1) 0 1>0038tC! •ao1nctl14·Ail5!20'>1QHI4 t 5000~ d•bv 1 1M.. 11>40~·0 ~cP!:F 1 Figure 3: X-ray diffraction patterns of the fan deposit sample containing considerable amount of Kaolinite (AI2(SiOs)(OH)4) and anhydrite (CaS04) in addition to expected compounds namely calcite, quartz, free lime and hematite. Figure 6 representing thermal behaviour of fan deposition sample demonstrate remarkably different behaviour compared to the other two samples. Figure 7 for example compares the thermal characteristics of. all the samples considered in the study indicating recognizable differential behaviour of the samples. The endothermic peak at 775.2°C corresponds to decomposition of calcite present in the sample. The sample indicates the loss of water molecules from Kaolinite at 494.7°C endothermically and phase transformation of Kaolinite to Mullite at 873.5°C exothermically. This thermal behaviour can thus be assumed to be supporting the