Mathematical modeling of CO 2 capture in a semi-dry spouted bed reactor M.R. Haghnegahdar, M.S. Hatamipour ⇑ , A. Rahimi Chemical Engineering Department, College of Engineering, University of Isfahan, Isfahan, Iran article info Article history: Received 31 August 2010 Received in revised form 2 June 2011 Accepted 3 June 2011 Available online 22 June 2011 Keywords: Spouted bed Non-isothermal modeling Carbon dioxide capture Hydrated lime abstract In present study, a non-isothermal comprehensive mathematical model is developed for performance analysis of a spouted bed reactor in which CO 2 is removed by using a semi-dry chemical absorption pro- cess. For this aim, based on the hydrodynamic model of streamtube and equations of mass and energy balances for a reactive absorption process, the governing equations for gas and solid phases in three dif- ferent regions of the bed are derived and solved numerically. The effects of variation of different operat- ing parameters and process conditions are investigated and corresponding maximum, minimum and average values of errors are obtained by comparison of the model results with existing experimental ones. Results show that the superficial gas velocity and the approach to saturation temperature have con- siderable effects on CO 2 removal efficiency, while Ca/C molar ratio, inlet concentration of CO 2 and static bed height of reactor do not influence performance of the reactor significantly. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Global expansion of industrial activities, over the past three decades, has caused the concentration of greenhouse gases to rise significantly in the atmosphere. This has contributed to global warming which in turn has resulted in serious environmental problems [1]. CO 2 emission is primarily due to fossil-fuel combus- tion in the commercial, industrial and transportation sectors [2]. Within the many options and actions for mitigation of greenhouse gas emissions, CO 2 capture and sequestration is emerging as a via- ble option to achieve the very deep cuts in emissions that might be needed in the medium term [3]. Various end-of-pipe technologies are therefore tested to remove and recover CO 2 from the flue gas. Among these technologies, chemical absorption has been exten- sively studied and is considered as the best economical method for reducing CO 2 emission from the flue gas [2]. The cost and diffi- culties of solvent recovery and/or waste disposal are the main drawbacks of such processes. With the advantages of high removal efficiency and no waste- water produced, Powder-Particle Spouted Bed (PPSB) process is a feasible technology for controlling acid gas emissions from flue gases. PPSB process involves the continuous injection of slurry of fine sorbent (such as slaked lime or other alkaline powder) into a spouted bed in which coarse particles are spouted with flue gas containing acid gas (such as SO 2 and CO 2 ). The reaction between acid gases and the sorbent, and the drying of the slurry take place in the bed, simultaneously. Finally, the reacted and dried sorbents are entrained out of the bed and then collected by a bag filter [4]. Several experimental investigations have been reported on this kind of reactor and the results confirm that PPSB has the advantage of higher removal efficiency for some gaseous pollutants over some conventional existing processes [4–9]. Mathematical modeling is an attractive and capable technique for performance analysis, designing, scaling up, optimization and prediction of the behavior of the process equipments. However, the performance of powder particle spouted bed reactors have been discussed by a few numbers of mathematical models. The first numerical model was considered by Liu and Kato [8]. Their study was based on the analysis of chemical reaction rate and mass transfer between sorbent particles and flue gas. The predictions of their model were compared with experimental results. The effects of various operating conditions on removal efficiency are also investigated and optimum operating conditions are obtained. Another investigation about PPSB was performed by Moeini and Hatamipour [10]. They compared two isothermal reactor models. The first model, based on the model of Mathur and Lim [11] was a one-dimensional, two phase model. The second one was proposed on the basis of Lim and Mathur [12] hydrodynamic ap- proach. The predictions of models were compared with each other and with the published experimental data of Xu et al. [9]. The re- sults showed that the trend of the predictions of developed models was valid but in some cases they showed a considerable difference with experimental data. Up to now, no study has been reported about the mathematical modeling of CO 2 capture in PPSB reactors. Based on the above mentioned points, and as an extension to our previous studies in this filed, in the present study a heteroge- neous non-isothermal model is developed in order to analyze the heat and mass transfer between the existing phases in a PPSB used 1383-5866/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2011.06.005 ⇑ Corresponding author. Tel.: +98 311 7934047; fax: +98 311 7934031. E-mail address: hatami@eng.ui.ac.ir (M.S. Hatamipour). Separation and Purification Technology 80 (2011) 509–518 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur