Modeling of mercury desorption from activated carbon at elevated temperatures under fluidized/fixed bed operations T.C. Ho a, * , Y. Lee a , H.W. Chu b , C.J. Lin c , J.R. Hopper a a Department of Chemical Engineering, Lamar University, Beaumont, TX 77710, USA b Department of Industrial Engineering, Lamar University, Beaumont, TX 77710, USA c Department of Civil Engineering, Lamar University, Beaumont, TX 77710, USA Received 1 November 2004 Available online 28 January 2005 Abstract An effective method for controlling elemental mercury emission is to employ activated carbon (AC) to adsorb mercury from the combustion flue gas. An environmental concern regarding the process is the low sorption capacity of AC. The mercury control practice, therefore, will need a large quantity of fresh AC and generate an equally large quantity of spent AC contaminated with various forms of mercury. A practical solution to this problem is to regenerate the AC for reuse. In this study, an activated carbon mercury sorption/desorption model was developed for simulating the mercury sorption/desorption process at various temperatures under both the fixed and fluidized bed conditions. Mercury sorption experiments were carried out to determine the best-fit model parameter and the parameter-fitted model was then used to simulate the mercury desorption processes under various conditions. The simulation results have indicated that both the desorption temperature and the fluidization condition affect significantly the mercury desorption rates. D 2004 Elsevier B.V. All rights reserved. Keywords: Mercury; Adsorption/desorption; Modeling; Activated carbon; Regeneration 1. Introduction 1.1. Mercury emission control Control of mercury emissions from various combustion sources has attracted great attention due to the toxic nature of mercury and the current and potential regulations. The proposed Clear Skies Act of 2003, introduced in the US House of Representatives as House bill HR 999 and the US Senate as Senate bill S. 485 on February 27, 2003, would create a mandatory program that would dramatically reduce power plant emissions of SO 2 , NO x and Hg by setting a national cap on each pollutant (see EPA website at: http:// www.epa.gov/clearskies/). The 1997 U.S. EPA bMercury Study-Report to CongressQ [1] states that roughly 87% of the estimated 158 tons of annual anthropogenic US mercury emissions are from combustion sources, including waste and fossil fuel combustion. The largest emitters cited are coal utility boilers, municipal waste combustors, industrial boilers, medical waste incinerators, hazardous waste incinerators, and several manufacturing sources such as chlor-alkali and Portland cement manufacturers. Current mercury control technologies are either applicable to only selected emission sources or still under development. Additional research is urgently needed to further develop technologies for univer- sal and optimum mercury emission control. Unlike most other trace elements, mercury is highly volatile and exists almost exclusively in the vapor phase of combustion flue gases, either in the form of elemental mercury or mercury salts such as HgCl 2 , HgO, HgS and HgSO 4 [1]. To protect public health, mercury emission standards of as low as 30 Ag/dscm (dry standard cubic meter) have been imposed and are expected to be even stricter in the future [1]. An effective method for mercury emission control is to employ suitable sorbents to absorb/adsorb mercury from the 0032-5910/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.powtec.2004.11.034 * Corresponding author. Tel.: +1 409 880 8790; fax: +1 409 880 1717. E-mail address: hotc@hal.lamar.edu (T.C. Ho). Powder Technology 151 (2005) 54 – 60 www.elsevier.com/locate/powtec