Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece Breakthrough adsorption study of activated carbons for CO 2 separation from flue gas Mohammed K. Al Mesfer ⁎ , Mohd Danish Chemical Engineering Department, College of Engineering, King Khalid University, Abha 61411, Saudi Arabia ARTICLE INFO Keywords: Granular activated carbon Flue gas Breakthrough time Adsorption ABSTRACT Granular activated carbons (GACs) were used to separate carbon dioxide (CO 2 ) from N 2 -CO 2 feed gas mixture employing a fixed bed column. Two grades of GAC (GAC-1 and GAC-2) were used as an adsorbents. The ad- sorbents were characterized using Micromeritics ASAP surface analyzer and a scanning electron microscope. The parameters considered for examining the breakthrough responses of GACs were the initial concentration of CO 2 in feed, temperature, and feed flow rate. It was observed that breakpoint time decreases with increased column temperature and with the gas feed rate for GAC-1 and GAC-2. For both types of activated carbons, the break- through time (t b ) slightly decreases with increased initial CO 2 concentration (vol. %) from 1% to 2% in feed. It was suggested that longer breakthrough time contributes to a higher adsorption capacity of an adsorbents. The adsorption breakthrough occurs early for GAC-2 compared with GAC-1 when the bed was subjected to the same temperature of 25 °C because of the superior surface characteristics of GAC-1. A longer breakthrough time of 1640 sec for GAC-1 was observed compared with a slower breakthrough time of 760 s for GAC-2 at a constant bed temperature of 25 °C subjected to a feed rate of 3 L/min (C feed = 5%). It was concluded that GAC-1 breakthrough was delayed compared with that of GAC-2 when the column was controlled to the same initial concentration of CO 2 in the feed. The breakthrough periods of 960 s and 270 s were observed at an initial CO 2 concentration of 2% in feed for GAC-1 and GAC-2, respectively. The maximum CO 2 adsorption capacity of 25.39 g/kg adsorbent was estimated at a CO 2 partial pressure of 0.048 bars for GAC-1. 1. Introduction Among all greenhouse gases, carbon dioxideis the substantial con- tributor to global warming. The rising level of atmospheric CO 2 is one of the most pressing environmental concerns of our age [1,2].The combustion of fossil fuels contributes to 81% of the world’s commercial energy and releases 30 × 10 12 kg of CO 2 annually [3]. Power genera- tion will account for almost half of the increase in global CO 2 emission between 2000 and 2030 [4]. The primary sources of carbon dioxide emissions are industrial and thermoelectric power plants, accounting for 45% of the world’s CO 2 emissions [5]. An increase in average global temperature by more than 2 °C will lead to serious consequences; thus it is suggested that greenhouse gases be minimized to 50% by 2050 [6].The CO 2 emissions can be captured by any one of three processes: post-combustion, pre-combustion, and oxy-fuel combustion methods, depending on the layout of given facility [7–10]. Physical and chemical absorption, membrane-based adsorption, and cryogenic separation are the foremost technologies used for carbon dioxide capture [11–13]. An absorption study using dilute amine solutions for CO 2 capture from a mixture of CO 2 and air has been conducted. In that study, a significantly higher adsorption capacity of 0.982 mol/mol amine was obtained for diethanol amine in comparison with monoethanolamine [14]. Post- combustion capture is the most feasible process for power plants on a short time scale [15–18]. A significant number of adsorbents have been employed for CO 2 capturing [19,20]. Adsorption is a well-accepted technology to capture CO 2 from flue gas of post-combustion emissions [21,22]. Various in- vestigators have employed mass balance equations to estimate the ad- sorption capacity of the adsorbents. The specific equilibrium capacity of CO 2 at a designated temperature and CO 2 partial pressure was esti- mated (Eq. (1)) by using the following mass balance to the adsorption bed [21]: ∫ = ⎡ ⎣ ⎢ − − − ⎤ ⎦ ⎥ q m (F F ) y PƐV ZRT y PV ZRT ad 0 t CO ,in CO ,out CO ,feed CO ,feed d s 2 2 2 2 (1) where q denotes the specific CO 2 adsorption capacity of the adsorbent, m ad is the mass of adsorbent in the bed, F CO ,in 2 and F CO ,out 2 , are the molar flow rate of CO 2 at inlet and outlet of the bed, t s is the time https://doi.org/10.1016/j.jece.2018.06.042 Received 14 March 2018; Received in revised form 31 May 2018; Accepted 19 June 2018 ⁎ Corresponding author. E-mail address: almesfer@kku.edu.sa (M.K. Al Mesfer). Journal of Environmental Chemical Engineering 6 (2018) 4514–4524 Available online 23 June 2018 2213-3437/ © 2018 Elsevier Ltd. All rights reserved. T