Hyungwoong Ahn

New momentum and energy balance equations considering kinetic energy effect for mathematical modelling of a fixed bed adsorption column

It was aimed to derive rigorous momentum and energy balance equations where the change of kinetic energy in both spatial and temporal domains of a fixed-bed adsorption column was newly taken into account. While the effect of kinetic energy on adsorption column dynamics is negligible in most cases, it can become more and more influential with an adsorption column experiencing a huge pressure drop or with the gas velocity changing abruptly with time and along the column. The rigorous momentum and energy balance equations derived in this study have been validated with two limiting cases: (1) an inert gas flow through a packed column with a very high pressure drop and (2) blowdown of an adiabatic empty column. The new energy balance including the kinetic energy effect paves a way for simulating with an improved accuracy a Rapid Pressure Swing Adsorption process that inherently involves a very high pressure drop along the column and requires very high pressure change rates for column blowdown and pressurisation.

Adsorption Breakthrough Dynamics of Zeolites for Ethylene Recovery from Fluid Catalytic Cracking Fuel-gas

The adsorption dynamics of zeolite 13X, 10X and 5A beds was investigated for recovering ethylene (C2H4) from fluidized catalytic cracking fuel-gas. As a feed gas, a ternary mixture (CH4 : C2H4 : C2H6) and a model FCC fuel-gas (CH4 : C2H4 : C2H6 : C3H6 : N2 : H2) were used for breakthrough experiments. In the ternary mixture, the concentration profiles showed similar patterns in all zeolite beds. C2H4 showed higher adsorption affinity than the others in all zeolites and zeolite 5A had the highest adsorption capacity of C2H4. In the six-component mixture, the breakthrough curves in the zeolite 5A bed showed similar patterns to the results of the ternary mixture. Although weak adsorbates could be removed during the adsorption step, CH4 and N2 imparted a steric hindrance to the initial stage of C2H4 adsorption in the zeolite 5A bed. Since vacuum desorption contributed to producing a high purity of C2H4, a pressure vacuum swing adsorption process was recommended to recover C2H4.