Characterization of quicklime as raw material to hydrated lime: Effect of temperature on its characteristics Rajeb Salem Hwidi, Tengku Nuraiti Tengku Izhar, Farah Naemah Mohd Saad, Omar S. Dahham, N. Z. Noriman, and Z. Shayfull
Citation: AIP Conference Proceedings 2030, 020027 (2018); doi: 10.1063/1.5066668 View online: https://doi.org/10.1063/1.5066668 View Table of Contents: http://aip.scitation.org/toc/apc/2030/1 Published by the American Institute of Physics
Characterization of Quicklime as Raw Material to Hydrated Lime: Effect of Temperature on Its Characteristics Rajeb Salem Hwidi1, Tengku Nuraiti Tengku Izhar1,a), Farah Naemah Mohd Saad1, Omar S. Dahham2,b), N Z Noriman2,c) and Z Shayfull3,4) 1
School of Environmental Engineering, Universiti Malaysia Perlis, Kompleks Pusat Pengajian Jejawi 3, Arau 02600, Perlis, Malaysia. 2 Center of Excellence Geopolymer and Green Technology (CEGeoGTech), Faculty of Engineering Technology (FETech), Universiti Malaysia Perlis (UniMAP), Level 1 Block S2, UniCITI Alam Campus, Sungai Chucuh, Padang Besar, 02100, Perlis, Malaysia. 3 School of Manufacturing Engineering, Universiti Malaysia Perlis, Kampus Tetap Pauh Putra, 02600 Arau, Perlis, Malaysia. 4 Green Design and Manufacture Research Group, Centerof Excellence Geopolymer and Green Technology (CEGeoGTech), Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysia a)
Corresponding author:
[email protected] b)
[email protected] c)
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Abstract. In this work, the quicklime (CaO) was produced from the thermal decomposition of the limestone (CaCO3) using a lab kiln at 700, 900 and 1100 °C temperature. Furthermore, the effect of these different temperature on the mineralogical, chemical, physical and morphological properties of the produced CaO were investigated using X-Ray Fluorescence (X-RF), X-Ray Diffraction (X-RD), Fourier-Transform Infrared Spectroscopy (F-TIR) and Scanning Electron Microscope (SEM). Results show that the CaO content has slightly increased as temperature increases indicating that the purity of sample increased. FTIR shows that all samples have strong characteristic bands at 1,472 cm-1 and also at 912 cm-1, which are belong to the two different elongation modes of C-O bonds. However, the samples show O-H bond at 3,696 - 3698 cm-1 due to the low concentration of Ca(OH)2 in the sample. Several distinctive peaks are observed in XRD results indicating that the presence of calcite and quartz in the samples. The increase of temperature improved the particles size distribution of the samples and appeared more homogeneous. However, some relief lines on the surfaces of CaO particles are observed as high temperature (1100 °C) uses.
INTRODUCTION Lime (calcium oxide) is one of the most raw materials used widely for many process industries, such as environmental protection, constructions, chemical processes, steel manufacture and others. In year 2002, about 116,000 thousand metric tones of the calcium oxide (CaO) were produced in the world. The consumption of CaO by major end users was as follows: 36 % for metallurgical applications, 27 % for environmental applications, 24 % for chemical and industrial applications and 13 % for construction applications [1]. In general, the quicklime (calcium oxide CaO) can be produced through the thermal decomposition process of the Limestone powder (calcium carbonate CaCO3) [2]. The thermal decomposition of CaCO3 was widely studied over the years. At high temperature carbone dioxide (CO2) is released and CaO is produced as shown in Equation 1.
Green Design and Manufacture: Advanced and Emerging Applications AIP Conf. Proc. 2030, 020027-1–020027-7; https://doi.org/10.1063/1.5066668 Published by AIP Publishing. 978-0-7354-1752-6/$30.00
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CaCO3 (S) → CaO (S) + CO2 (g)
(1)
The formation of CaO from the thermal decomposition of CaCO 3 can be affected by some factors such as the textural and microstructural properties of CaCO 3 and the intrinsic chemical reactivity. In contrast, the partial pressure of the gas phase has a strong effect on the formation of CaO. An increase of the partial pressure of CO 2 deals with the increase of the initial calcination temperature [3]. In the literature, there are numerous studies regarding factors that can influence the quality of quicklime. These factors are the calcination temperature, calcination rate, fuel quality, raw material characteristics and pressure acquired in kilns [4]. In our current work, the effects of kiln temperature on the mineralogical, chemical, physical and morphological properties of the produced quicklime were investigated using X-Ray Fluorescence (X-RF), X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (F-TIR) and Scanning Electron Microscope (SEM).
EXPERIMENTAL Sample Location The limestone (CaCO3) was used as a main material in this work. CaCO3 was obtained from Bukit Keteri area, Chuping, 02450 Kangar, Perlis, Malaysia, 6.5035795,100.26139 GPS coordination.
Sample Preparation In order to prepare quicklime (CaO), limestone (CaCO3) was burned at three different temperatures at 700, 900 and 1100 °C using lab kiln. After that, lab grinder was used to prepare the size of CaO samples. After grinding, the ground CaO samples were sieved at 75 μm. The sieved samples were examined using Particle Size Analyzer (PSA) Model Malvern Mastersizer 2000 as shown in Figure 1.
FIGURE 1. Particle size distribution of CaO sample
SAMPLE CHARACTERIZATION After preparation of CaO samples, the mineralogical, chemical, physical and morphological properties of the hydrated lime samples were characterized and evaluated using X-ray fluorescence (X-RF) spectrometry, X-ray diffraction (X-RD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electronic Microscopy (SEM) attached with Energy Dispersive X-ray analysis (EDS) respectively.
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X-Ray Fluorescence (X-RF) X-rays fluorescent (XRF) test was performed using XRF spectrometer (Model MiniPAL 4 Brand: PANanalytical PW4030). The purpose of this test is to identify the elemental composition of the CaO samples based on the principle of individual atoms. When the CaO samples are irradiated using X-rays, it measures the wavelengths of individual component of the fluorescent emission produced by the samples.
X-Ray Diffraction (X-RD) X-RD test was performed to study the mineralogical properties of CaO samples using CuKα radiation, 0.02° step size, 3 s counting time, 10° b 2θ b 90° range and Rietveld refinement method (X′Pert MPD - PANalytical X-ray B.V.). The CaO samples were pressed in stainless steel holder and then the Quantitative mineralogical evaluation was carried out to obtain a high quality diffraction data, linked with ease of use and flexibility to quickly switch to different applications.
Fourier Transform Infrared Spectroscopy (FTIR) FTIR spectroscopy model Perkin Elmer 2000 was used in this work. CaO samples were prepared by thin KBr disc method at room temperature. After samples preparation, they were scanned from 4000 to 400 cm−1 with resolution of 0.4 cm−1.
Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM-EDS) The morphological properties and elemental chemical composition of the CaO samples were examined using SEM-EDS model LEO Stereoscan 440. Before test, the samples were coated using an extremely thin layer of gold (1.5 - 3 nm) using sputter coater machine to prevent the electrostatic charging as well as to avoid the poor resolution of the image during test. The test was performed at 1000x magnification.
RESULTS AND DISCUSSIONS Table 1 shows the chemical composition of CaO samples at 700, 900 and 1100 °C respectively. It is clearly observed that the main composition of all samples was the calcium oxide (CaO) at 97.56-97.97 wt.% indicating that the sample was high purity of lime [5]. However, the silica composition at 0.9-0.96 wt.% constituted the common impurity. The amount of silica in the samples usually depends on the nature of samples place; low silica content refers to high purity of sample. In contrast, the high content of the calcium oxide in the samples presents an improvement factor; therefore cement is considered as the major contributing source to airborne particulate matter in these factories and environs. This has a strong influence on the environment, which should be of interest to the government well as to the environmental protection agency. The existence of magnesium oxide (0.01-0.06 wt%) in the CaO sample is considered as a witness to the existence of trace amount of smectite [5, 6]. It is observed that there is also a trace amount of Fe2O3, Al2O3 and SrO elements in the sample. The chemical compositions of CaO samples are slightly altered as temperature increases. It is observed that the calcium oxide content increased wit h the increase of temperature indicating that the purity of CaO sample increased. By contrast, some of elements content decreased as temperature increase due to the thermal decomposition of these elements at high temperature. TABLE 1. The chemical composition of CaO sample at (a) 700 °C, (b) 900 °C and (c) 1100 °C Chemical Compounds Weight % (a) Weight % (b) Weight % (c)
Mg MgO 0.06 0.05 0.01
Al Al2O3 0.36 0.35 0.3
Ca CaO 97.56 97.66 97.97
Ti TiO2 0.13 0.13 0.11
Mn MnO 0.07 0.06 0.06
Fe Fe2O3 0.39 0.38 0.34
Cu CuO 0.068 0.042 0.01
Sr SrO 0.092 0.091 0.08
Ru RuO2 0.37 0.36 0.23
Si SiO2 0.96 0.92 0.9
Total 100 100 100
The FTIR bands of CaO samples at 700, 900 and 1100 °C are shown in Figure 2a, b and c respectively. The characteristic band at 3,696 - 3698 cm-1 in all spectra corresponded to O-H bond due to the low concentration of
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Ca(OH)2 in the sample. The O-H is a remaining component of the carbonation process [7]. The relatively strong intensity bands at 1,472 cm-1 and the bands at 912 belong to the two different elongation modes of C-O bonds whereas the characteristic bands at 2,569, and 787 cm-1 are considered the harmonic vibrations of the elongation modes mention earlier. The low intensity bands at 2909 cm-1 probably corresponding to carbonate C=O group from carbonate ion. Another low intensity band is shown at 1839 cm-1 which is also related to the C=O bonds. The band at 742 cm-1 is probably due to the Ca–O bonds [7].
FIGURE 2. Response FTIR spectra of CaO sample at (a) 700 °C, (b) 900 °C and (c) 1100 °C
Figure 3a, b and c show the XRD diffractograms of the CaO samples at 700, 900 and 1100 respectively. Generally, all samples showed distinctive peaks at 3.85–3.86 A ̊ (102), 3.03 A ̊ (100), 2.84 A ̊ (006), 2.49 A ̊ (110), 2.28 A ̊ (113), 2.09 A ̊ (202), 1.97 A ̊ (108), 1.87 A ̊ (116) and 1.60 A ̊ (212) indicating that the existence of calcite in the samples. Moreover, all samples have also exhibited further peaks prevailing at 3.33–3.34 A ̊ (101), 1.54 A ̊, (211), 1.37 A ̊ (203) and 1.28 A ̊ (104) due to the existence of quartz [5]. Detailed clay mineralogy was identified and investigated by the characteristic reflections according to Moore and Reynolds [8].
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FIGURE 3. Diffractograms of the CaO sample at (a) 700 °C, (b) 900 °C and (c) 1100 °C
The morphology of the CaO samples at 700, 900 and 1100 °C were examined using the scanning electron microscope attached with energy dispersive x-ray spectroscopy, and the micrographs of these samples are shown in Figures 4a, b, c and Table 2 respectively. It is found that all samples present amorphous like particles. The edges of particles are not well defined and their shape is more to round shape. However, the inset shows some relief lines on the surfaces of CaO particles at high temperature (1100 °C). These lines might be formed during high temperature calcination process followed by a cooling process, which in turn caused a thermal shock resulting these cracks on the surface of particles [7]. The samples had some pores and the appearance of continuous matrix like it was made of attached particles. Furthermore, the size distribution of particles seems homogeneously dispersed, particularly the sample at high temperature. This was proved earlier by using particle size distribution as shown in Figure 1. The existence of Ca, C, and O as main elements proves the significance of carbonate phases, in the samples (Table 2).
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(a)
(b)
(c) FIGURE 4. SEM-EDS of CaO samples at (a) 700 °C, (b) 900 °C and (c) 1100 °C TABLE 2. Elemental analysis of CaO sample. Element CK OK Ca K Pt K
Weight% 10.6 45.07 35.87 9.00 Total = 100
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Atomic % 18.22 61.31 19.47 1.00
CONCLUSIONS In this work, it can be concluded that the quicklime was successfully produced from the limestone using three different temperature at 700, 900 and 1100 °C. The higher temperature showed higher purity as well as higher particle size distribution. However, high temperature (1100 °C) caused a thermal shock for the samples resulting some cracks on the surface of CaO particles
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