Module 4b Absorbers

MCEN 4131/ Preliminaries VOC project assignment Project night this Thurs 5-6:30 Party Thurs Apr The Sink

MCEN 4131/ Review Adsorption:process in which pollutant molecules separate themselves from the gas phase and attach themselves to the surface of a solid material Isotherm: describes equilibrium between the mass that is adsorbed on the adsorbent material and the concentration in the gas phase Design parameters for a fixed bed adsorber –Saturation time (breakthrough time) –Adsorption zone velocity –Adsorption zone thickness –Regeneration

MCEN 4131/ What is absorption? Process in which pollutant molecules separate themselves from the gas phase and becomes dissolved in a liquid phase Some gases very soluble in water, exploit and contact air with water, use Henry’s Law To work need high solubility and good mass transfer

MCEN 4131/ Counterflow Packed Tower Tower containing packing increases surface area of liquid film Quiz Question: What makes good packing? a. Thermally conductive material b. Light-weight c. High liquid holdup

MCEN 4131/ Counterflow Packed Tower Tower containing packing increases surface area of liquid film Water injected into top of tower

MCEN 4131/ Counterflow Packed Tower Tower containing packing increases surface area of liquid film Water injected into top of tower Gas comes in at bottom and flows up

MCEN 4131/ Mass Transfer… …from gas to liquid is important Two-film theory Mole fraction Gas-liquid interface Packing Bulk gas y GAS FILM LIQUID FILM ON PACKING Bulk liquid x P T y i =H i x i Distance Quiz Question: A major assumption in the two-film theory is: a. Both films are moving in opposite directions b. Diffusion is major transport phenomena in films c. The gas and liquid are in equilibrium at interface d. Liquid can be treated as water, gas as air