3.1 Adsorption of SOx at combustion

The sulfur oxide emissions greatly concerned the thermal boilers and energy sector, and caused more efficient new methods for postcombustion SO2 capture from the stack gas. Among procombustion and postcombustion systems, wet flue gas washing was carried out in higher and wider shower stacks, and lime slurry sorption one, which was used for a gas cleaning separation for many years. The characteristic features of adsorption column provide long life of the sorbents used, low energy consumption, and less effect on the environment. However, sorption column by lime slurries at postcombustion application required distinct preparation of the stack gas fed into the washing tower of SO2 separation so that the flue gas temperature is as low as possible and with a lack of steam in it.

#### 3.1.1 Langmuir model

The gaseous matter reacts with adsorbent and then adsorbs the sorbent in certain amount that is equal to the amount of previous adsorbent that was partially degraded on the surface of the expanded clay, removing aliphatic hydrocarbons and phenols/chlorinated phenols and carbonyl toxins, along with organic matter–related odor substances.

The Langmuir model [25, 26] is the common one sorption explanation for wellknown reacting column packed explaining sequential diffused and concentrated adsorbed matter and kinetics. Although the linear concentration sequentially followed, sequential adsorption packed bed column was usually experimented by various researchers for the sorption diffusion process of fuel carbon materials, and it can also be used for the sorption over leafy composites. The carbon material is soaked in fluid in an ethanol extraction vessel, and after some time, the solute is diffused from the leafy composite substrate matrix and gets adsorbed on the active surface sites, which further mass transfers to the separator vessel in the solvent. The Langmuir extraction model is presented in the following form:

$$\mathbf{Y} = \mathbf{Y}\_{\mathbf{f}}.\mathbf{t} \left(\mathbf{K}\_{\mathbf{L}} + \mathbf{t}\right) \tag{7}$$

where Y is % extraction yield (w/w) and Yf and KL are constants (Yf is the yield at infinite time).

The temperature dependence of the adsorption coefficient is governed by an Arrhenius equation as follows [27]:

$$\mathbf{K}\_{\rm L} = \mathbf{K}\_{\rm 0L} \exp\left(-\mathbf{ERT}\right) \tag{8}$$

where E is the activation energy (kJ/mol), K0L is the pre-exponential coefficient, and R is the universal gas constant.
