Chemical & Environmental Engineering Gas Absorption Sample Essay

Assignment 1: Give one industrial graduated table illustration where gas soaking up is used? Gas soaking up is a procedure whereby a contamination ( gas or vapor ) is removed from air or another gaseous watercourse by contact with a fluxing liquid stage. In Oder to increase the surface country available for mass transportation. the operation is about ever conducted inside a tower or column packed with a bed of high surface country make fulling stuff. The operation of the column makes usage of the fact that the contamination is soluble in the liquid stage. and hence has a driving force to fade out in the flowing liqui d. Industrial graduated table gas absorbers are frequently referred to as “scrubbers” because they are often used to clean taint out of the air go outing a works. A common illustration of an industrial – graduated table gas soaking up is the remotion of SO 2 from the air go outing an oil refinery.

Fig 1: Piping and Flow Diagram – Gas Absorber Experiment
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All individuals involved in runing the gas absorber must have on all appro priate personal protective equipment at all times. For illustration: Difficult chapeaus. Splash goggles. Closed -toe. Non-perforated places. Long bloomerss. Long sleeved shirts/ jumper. Heavyweight nitrile baseball mitts. The points required when working with anhydrous ammonium hydroxides cylinder are: Splash shield. Half-mask inhalator with ammonia cylinder. Fortunately the Ammonia smells really strong. so it will be probably to detect it before it reaches risky concentrations. When running a gas absorber. we must foremost find the appropr iate flow rates of incoming gas ( G. L/s ) and liquid ( L. L/s ) . Deluging in counter current -flow gas absorbers occurs when an recess gas flow rate is excessively high. so that it interferes with the downward flow of the liquid through the column. In utmost instances. an upward flow of the liquid through the tower may be observed. Deluging occurs when L/G is excessively low. The force per unit area bead over the column will be rather high when it is flooded.

It is common to run the gas absorbers at an L/G rate Shining Paths ightly higher than ( about 1. 3 ten or more ) the minimal L/G ratio below which deluging occurs. with a much lower ? Pcolumn. The public presentation of the column is frequently optimum someplace within this scope.

If we increase the L/G ratio. the point above which the gas is no longer interfering with the liquid flow rate is called the burden part. Here. we are concerned that the liquid may pool up at the underside of the column because there is deficient gas flow.

Although our gas absorber is a uninterrupted -flow operation. we can quantify its effectivity by specifying a parametric quantity that describes a theoretical figure of separation phases. as if the procedure was broken down into

single batch stairss. For illustration: carry oning the gas soaking up inside a separatory funnel. utilizing clean H2O to pull out ammonia out of a fixed volume of gas. After each extraction of ammonium hydroxide from the gas stage. the water-ammonia mixture was discarded and replaced with clean H2O. The ammonia concentration in the staying gas would diminish after each lavation. but ne’er reach nothing. The figure of lavations could be described as a figure of soaking up phases or transportation phases. For a uninterrupted flow column. the correspondent parametric quantity is the Number of transportation Units ( NTU ) . which is linked to the figure of times the come ining air was scrubbed with clean H2O.

NTU is defined as:

Where: ytop = Concentration of ammonium hydroxide in the gas stage at the top of the column ( go outing ) ybottom = Concentration of ammonium hydroxide in the gas stage at the underside of the column ( come ining ) Y = Concentration of ammonium hydroxide at some height Y from the top of the column. y* = Hypothetical concentration of ammonium hydroxide in the gas stage that would be in equilibrium with the liquid at point Y in the column.

y* might be estimated from Henry’s Law. if the concentration of the solute is low plenty. The tallness of a transportation unit. or HTU. is a step of the efficiency with which the gas absorber is working. If the column achieves mass transportation in a really short length ( HTU is low ) . we have an efficient separation procedure. HTU is really easy to cipher if NTU is known. Let omega be the tallness of the jammed tower subdivision. HTU is given by:

HTU and NTU are of import parametric quantities that might let us to scale up a procedure to industrial propor tions.


J. F. RICHARDSON. J. H. HARKER and J. R. BACKHURST ; 2002. Coulson and Richardson’s CHEMICAL ENGINEERING. Vol 2 ; 5th Edition
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