The aim of this work is to study the effect of Egyptian limestone microstructure on the activation energy required for the onset of its calcination. Limestone samples were investigated for their bulk density, apparent porosity, crushing strength, microstructure and chemical composition by applying transmitted light microscopy, SEM and X-ray fluorescence methods respectively. The samples were calcined for 0·25–1 h at 800–950°C. The activation energy of calcination was calculated from the Arrhenius equation. Triple junction fractures detected after calcination are mainly attributed to euhedral–subhedral calcite crystals in the sparite matrices of their limestone samples. Samples with higher ‘grain’ content and lower bulk density show relatively lower activation energy and rate of lime crystallite growth. This is due to the original ‘grain’ channel pores and the formation of triple junction fractures during calcination, which facilitate transfer of hot gases and diffusivity of the evolved CO2. It is finally concluded that calcination of limestone is a temperature, chemical and microstructure dependent process.
ChengC, SpechtE: ‘Reaction rate coefficients in decomposition of lumpy limestone of different origin’, Thermochim. Acta, 2006, 449, 8–15.
2.
KoyuncuÜ: ‘A kinetic study for the sorption of SO2 on calcined limestones’, Master's dissertation, METU, Ankara, Turkey, 1985.
3.
DoguG, DoguT:‘Kinetics of capture of sulphur dioxide and applications to flue gas desulfurization’ in ‘Chemical reactor technology for environmentally safe reactors and products’(, de LassaH J, et al..); 1992, Dordrecht, Kluwer Academic Publishers.
4.
KhraishaYH, DugwellDR: ‘Coal combustion and limestone calcination in a suspension reactor’, Chem. Eng. Sci., 1992, 47, 993–1006.
5.
ArI, DoguG: ‘Calcination kinetics of high purity limestone’, Chem. Eng. J., 2001, 83, 2.
6.
Kirk-Othmer: ‘Kirk-Othmer encyclopedia of chemical technology’, Vol. 14, 3rd edn, 361; 1981, Hoboken, NJ, John Wiley & Sons.
7.
MoffatW, WalmsleyMRW: ‘Improving energy efficiency of a lime kiln’, Proc. Joint SCENZ/FEANZ/SMNZI Conf., Hamilton, New Zealand, July 2004, 17–24.
8.
MoffatW, WalmsleyMRW: ‘Understanding lime calcination kinetics for energy cost reduction’, Proc. 59th Appita Conf., Auckland, New Zealand, May 2006, 16–19.
9.
StanmoreBR, GilotP: ‘Review – calcination and carbonation of limestone during thermal cycling for CO2 sequestration’, Fuel Process. Technol., 2005, 86, 1707–1743.
10.
AdanezJ, García-LabianoF, FierroV: ‘Modelling for the high-temperature sulphation of calcium-based sorbents with cylindrical and platelike pore geometries’, Chem. Eng. Sci., 2002, 57, 13, 2381–2393.
11.
FengK, LombardoS: ‘Kinetic analysis from dilatometry and mass spectrometry measurements of the decomposition and sintering of calcium carbonate’, J. Ceram. Process. Res., 2002, 3, (3), 101–108.
12.
TrikkelA, KuusikR: ‘Modelling of decomposition and sulphation of oil shale carbonates on the basis of natural limestone’, Oil Shale, 2003, 20, (4), 491–500.
13.
TrikkeA: ‘Estonian calcareous rocks and oil shale ash as sorbents for SO2’, PhD thesis, Tallinn Technical University, Tallinn, Estonia, 2001.
14.
DoguT: ‘The importance of pore structure and diffusion in the kinetics of gas–solid noncatalytic reactions: reaction of calcined limestone with SO2’, Chem. Eng. J., 1981, 21, 213–222.
15.
HuangJ.-M, DaughertyKE: ‘Lithium carbonate enhancement of the calcination of calcium carbonate: proposed extended-shell model’, Thermochim. Acta, 1987, 118, 135–141.
16.
HuangJ.-M, DaughertyKE: ‘Inhibition of the calcination of calcium carbonate’, Thermochim. Acta, 1988, 130, 173–176.
17.
MurthyMS, HarishBR, RajandamKS, KumarKYAP: ‘Investigation on the kinetics of the thermal decomposition of calcium carbonate’, Chem. Eng. Sci.1994, 13, 2198–2204.
SoltanAM, KahlWA, WendchauM, HazemM: ‘Calcination microstructural behaviour of mud-supported limestones’, Miner. Process. Extr. Metall., to be published.
20.
ChengJ, ZhouJ, JiuL, ZhouZ, HuangZ, CaoX, ZhaoX, CenK: ‘Sulfur removal at high temperature during coal combustion in furnaces: a review’, Prog. Energy Combust. Sci., 2003, 29, 381–405.
21.
García-LabianoF, AbadA, de DiegoF, GayánP, AdánezJ: ‘Calcination of calcium-based sorbents at pressure in a broad range of CO2 concentrations’, Chem. Eng. Sci., 2002, 57, (13), 2381–2393.
22.
KhinastJ, KrammerG, BrunnerC, StaundingerG: ‘Decomposition of limestone: the influence of CO2 and particle size on the reaction rate’, Chem. Eng. Sci., 1996, 51, (4), 623–634.
23.
AnthonyEJ, GranatsteinDL: ‘Sulphation phenomena in fluidized bed combustion systems’, Prog. Energy Combust. Sci., 2001, 27, 215–236.
24.
BorgwardtRH: ‘Calcination kinetics and surface area of dispersed limestone particles’, AIChE J., 1985, 31, (1), 103–111.
MilneCR, SilcoxGR, PershingDW, KirchgesnerDA: ‘Calcination and sintering models for application to high temperature, short-time sulfation of calcium-based sorbent’, Ind. Eng. Chem. Res., 1990, 29, 139–152.
27.
AckeF, PanasI: ‘Activation energy for calcination of lime stone by means of a temperature programmed reaction technique’, Thermochim. Acta, 1997, 303, 151–154.
28.
StrougoA, HaggagMAY, FarisM, AzabM: ‘Eocene stratigraphy of the Beni-Suef area’, Ain Shams Sci. Bull. B, 1984, 24B, 177–192.
29.
StrougoA: ‘Mokattamian stratigraphy of eastern Maghagha-El-Fashn district’, Mid. East Res. Cent. Ain Shams Univ., Sci. Res. Ser., 1986, 6, 33–58.
30.
BoukharyMA, Abdel MalikW: ‘Revision of the stratigraphy of the Eocene deposit in Egypt’, Neues Jahrb. Geol. Palaeontol. Mh., 1983, 6, 321–337.
31.
RaflaS, El-AbdKT, Hassab-AllahM, SolimanM: ‘Exploration of cement raw materials in Gabal Libni and Lassafa areas, North Libni’, EGSMA Int. Rep., 1983, 62, 90.
32.
‘Standard test methods for chemical analysis of limestone, quicklime and hydrated lime’, C25-06, ASTM International, West Conshohocken, PA, USA, 2006
33.
BaldoJB, RichardCB: ‘Grain growth of the lime and periclase phases in a synthetic doloma’, J. Am. Ceram. Soc., 1988, 71, (9), 720–725.
34.
KarklitAK: ‘Sintering of dolomites’, Ref. Ind. Ceram., 1997, 38, 9–10.
