PDF Publication Title:
Text from PDF Page: 031
2 Theoretical background 18 concentration profile resulting from the diffusion equation is parabolic and symmetric with respect to the particle center [69,71]. The finding suggests that the LDF model can be applied when a single diffusion resistance occurs within the adsorbent particle, or one mass transfer resistance significantly dominates. Therefore, when considering the dynamics of an adsorption column, the LDF model succeeds to describe adsorption processes characterised by a symmetrical breakthrough curve. The model was developed for pure-component adsorption following linear or moderately curved isotherms, where conditions are maintained close to equilibrium [68]. It was shown that for a long column where constant pattern behaviour was established the LDF model was a good approximation for a system that could be described using the Langmuir isotherm [37]. Moreover, with regards to cyclic adsorption processes, when the external concentration changes fast in comparison to the diffusion time, the modification of the LDF equation was proposed, as stated in Eq. 2.2.1-2 [69,70]. wk(t)=MTC (w*(t)−w (t))=D(w*(t)−w (t)) (Eq.2.2.1-2) t LDF k k r2 k k 0 where: Ω is a function of the half-cycle time. The value of Ω increases rapidly for faster cycles. 2.2.2 QDF model The quadratic driving force model of adsorption kinetics can be considered as the LDF approach modified by a concentration-dependent mass transfer coefficient [69,72]. According to QDF, the mass transfer rate of a single adsorbate k into adsorbent particle is estimated as shown in Eq. 2.2.2-1. w (t) =MTC w*(t)2 −w (t)2 =MTC w*(t)+w (t)(w (t)−w (t)) kkkkk* t QDF 2w (t) kk kk (Eq.2.2.2-1) QDF 2w (t) Fig. 2.2.2-1 Comparative column breakthrough curves by LDF and QDF models [37]; here Φ is gas concentration within the adsorber related to feed gas concentrationPDF Image | Modelling and Simulation of Twin-Bed Pressure Swing Adsorption Plants
PDF Search Title:
Modelling and Simulation of Twin-Bed Pressure Swing Adsorption PlantsOriginal File Name Searched:
dissertation_marcinek.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)