MASS TRANSFER OPERATION BRANCH - CHEMICAL (5TH SEM )

ABSORPTION WITH CHAMICAL REACTION BARAD MAHUL-- 140453105001 JAIMIN CHAVDA –140453105002 GOHIL ROHIT –140453105004 MISTRY AVI –140453105006 PANCHAL AATISH –140453105009

INRODUCTION Absorption, or gas absorption, is a unit operation used in the chemical industry to separate gases by washing or scrubbing a gas mixture with a suitable liquid . The fundamental physical principles underlying the process of gas absorption are the solubility of the absorbed gas and the rate of mass transfer. One or more of the constituents of the gas mixture dissolves or is absorbed in the liquid and can thus be removed from the mixture. In some systems, this gaseous constituent forms a physical solution with the liquid or the solvent, and in other cases , it reacts with the liquid chemically.

In some systems, this gaseous constituent forms a physical solution with the liquid or the solvent, and in other cases , it reacts with the liquid chemically. The purpose of such scrubbing operations may be any of the following : gas purification (eg , removal of air pollutants from exhausts gases or contaminants from gases that will be further processed) , product recovery , or production of solutions of gases for various purposes. The absorber may be a packed column , plate column , spray column , venturi scrubbers , bubble column , falling films , wet scrubbers ,stirred tanks

TRAY COLUMN

TRAY COLUMNS Tray absorbers are used in applications where tall columns are required, because tall, random-type packed towers are subject to channeling and maldistribution of the liquid streams. Plate towers can be more easily cleaned. Plates are also preferred in applications having large heat effects since cooling coils are more easily installed in plate towers and liquid can be withdrawn more easily from plates than from packings for external cooling. Tray columns are used in a refinery dehexanizer to decrease the benzene content in the naptha feed to the process. This results in lower automobile exhaust emissions.

PACKED COLUMN

PACKED COLUMN Packed columns are used mostly in air pollution control.. The water soluble ethylene gas ishydrolyzed to ethylene gylcol. Packed columns are also used in the chemical ,petrochemical,food, pharmaceutical,paper, and aerospace industries.

Its convincing advantages and disadvantages is following: - Advanges High efficiency of absorption drop Low outlet temperature No need after-cooling Low flow resistance Easy maintenance Disadvanges Restricted by pressure Film breakup Flooding

SPRAY COLUMN

Spray columns are differetal contactors. The liquid stream enters the coloumn through one or more spray nozzles at different heights in the column. The droplets formed provide a large surface area for exposure to the gas stream,with smaller droplets resulting in a greater Exchange area. The liquid and gas streams can flow counter-currently or in paralel. An optimum droplet velocity is essential because low velocity will lead to low contact or turbulence and high velocity may cause flooding.