Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 148 (2016) 718 – 725
4th International Conference on Process Engineering and Advance Materials
Carbon Dioxide Adsorption on Sawdust Biochar Hazimah Madzakia,*, Wan Azlina Wan AB KarimGhania, NurZalikhaRebitanima, AzilBahariAliasb a
Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia b Faculty of Chemical Engineering, Universiti Technology MARA Malaysia,43450 Shah Alam, Serdang, Selangor , Malaysia
Abstract Biochar has been acknowledged for its unique property which makes it potential candidates as adsorbent for carbon dioxide (CO 2) in the flue gas system. In this study, the properties of raw sawdust biochar (SB) and amine treated sawdust biochar (NSB) are being compared. Ultimate analysis was performed using elemental analyzer to determine the carbon, hydrogen, nitrogen and sulfur contents in the adsorbent. Physiochemical characterization has been performed to characterize the biochar properties. Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) were used to evaluate the functional groups and surface area of the biochar. Thermogravimetric analyzer (TGA) was used to discover the thermal properties, reactivity during adsorption. During the adsorption study, it was observed that raw sawdust biochar gasified at 850 °C gave the highest adsorption of 0.47 kg CO2/kg biochar at temperature of 30 °C. The incorporation of nitrogen functionalities onto the carbon surface may cause decrement of surface area of carbon. © 2016 2016 The TheAuthors. Authors.Published © Published by Elsevier Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing of ICPEAM 2016. Peer-review under responsibility of the organizing committee of ICPEAM 2016 Keywords: Biochar; carbon dioxide; amine; thermogravimetric; flue gas
1.Introduction Extensive studies are currently being performed to reduce the discharge of CO2 to the atmosphere. Countless organizations are finding alternatives to reduce the CO2 concentration and considering methods to control the emissions of this greenhouse gases. The energy generated from the combustion of fossil fuels is one of the major sources of the greenhouse gasses [1]. In Malaysia CO2 emission has increase rapidly since 1980 and this number is expected to increase massively in years to come. The amount of CO2 emission in 1980 shows an emission of 25 million metric tons of CO2 and increased to 160 million metric tons of CO2 by 2006 which contributes to 540% increase from the initial amount in 1980 [2]. Monoethanolamine (MEA) solvent is widely used in the flue gas which involves introducing the gas stream to an aqueous amine solution which reacts with the CO2 in the gas by an acid-base neutralization reaction. A problem that the industry is facing with the usage of amine in the flue gas system is the degradation of the amine as it is being recycled continuously. Other than the byproducts created by degradation of amine which reduces the adsorption capacity of CO2, amine also accelerates the corrosion process inmachines involved [3]. One promising method to handle the carbon dioxide uptake is by using activated carbon which hasadsorptive properties such as microporous structure and high surface area [4]. Other than these criterions, the surface chemistryalso plays a role in the effectiveness of the adsorption process [5]. In this paper, the treatment of biochar is focused on MEA treatment to incorporate nitrogen component to the biochar structure. * Corresponding author. Tel:+603-89466287; fax: +603-86567120. E-mail address:
[email protected]
1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ICPEAM 2016
doi:10.1016/j.proeng.2016.06.591
Hazimah Madzaki et al. / Procedia Engineering 148 (2016) 718 – 725
2. Materials and Methodology 2.1 Preparation of sawdust biochar Sawdust biochar adsorbent used was derived from a lab scale air blown gasifier reactor operated at 850 °C to generate energy. The samples are grounded to diameter of 500μm and dried overnight at 90 °C to remove any moisture present. The biochar is separated into two parts of raw and chemically treated sample for the CO2 adsorption capacity study. The samples were treated with monoethanolamine (MEA) and the sample was stirred for 20 minutes. The treated sample was then dried at 100 °C for 24 hours [6]. The raw biochar sample is identified as SB while the amine treated sample is regarded as NSB. 2.2 Adsorbent Characterization Ultimate analysis was performed using CHNS elemental analyzer to determine the carbon, hydrogen, nitrogen and sulfur contents in the adsorbent. Brunauer-Emmett-Teller (BET) surface area of the biochar was analyzed using an automatic Quantacome AS1WinTM – Automated Gas Sorption Data Analyzer. Mettler Toledo TGA/SDTA851 (USA) Thermal Gravimetric Analyzer (TGA) was used to check the stability of the sample. Fourier Transform Infrared Spectroscopy (FTIR) is used to identify the chemical composition of char by recording the infrared spectrum of respective samples. The compositions of the sample can be recognized by analyzing the spectra with the relative intensities of a functional group. 2.3 Isothermal Adsorption Tests The isothermal carbon dioxide (CO2) adsorption analyses were carried out at temperature 30 °C to evaluate the adsorption capacity of the char sample using EXSTAR 6000 Thermal Gravimetric Analyzer (TGA). It is used to measure reactivity of carbonaceous material with CO2. Around 10 mg of sample is placed in crucible before being placed in the conveyer. The sample is then heated up to desired temperature of 30 and 70 °C in 100 ml/min nitrogen flow. The sample is held at this temperature until the weight of sample is stabled (10 to 20 minutes). Gas is then switched to CO 2 at 100 mL/min to measure CO2 adsorption and change back to nitrogen flow of 100 mL/min for desorption test. 3. Results and Discussion 3.1 Characterization of sawdust biochar. The difference characteristics of the sawdust samples can be seen from the results of the ultimate analysis in Table 1. SD750 gives the highest amount of carbon content of 97.3 %, followed by SD850 of 93.4 % and SD450 of 82. 3%. SD450 and NSD850 have the highest moisture content of 10.27 % and 9.18 wt% respectively. The high volatile matter content of the biochar is due to the decomposition of cellulose, hemi cellulose and lignin. The high moisture, volatile and ash content may be due to the plant origin of the biochar samples [8]. It is foreseen that the treatment with monoethanolamine (MEA) will increase the nitrogen contents of the biochar sample and hence further improve the CO2 adsorption. The observation of the nitrogen percentage is essential to verify the impregnation of amine onto the surface of biochar at which the nitrogen content will increase after amine treatment. All raw biochar has low value of nitrogen contents of
