The packed tower, in which two fluids flowing in opposite directions enable a chemical component to be transferred from one fluid phase to the other, occurs in almost all chemical plants. The process may be gas absorption, distillation, solvent extraction or chemical reaction. Knowledge of the characteristics of both fluid flow and of mass transfer in such towers is necessary for both plant operators and designers.
The Armfield Gas Absorption Column has been designed to allow these studies to be made and the instrumentation and layout enables students to follow both the hydrodynamic characteristics in the absence of mass transfer, and also, separately, to advise the performance of the mass transfer process involved in gas absorption. The size of the equipment has been chosen so that teaching exercises may be completed in a typical laboratory class period, while at the same time being capable of demonstrating full-scale plant behavior. Considerable attention is directed towards matters of safety that are of crucial importance in the process industries.
- Description of apparatus:
The equipment consists of a 75 mm diameter column in which there are two lengths of Rasching ring packing material. Pressure tappings are provided at the base, centre and top of the column to determine pressure drops across the column. Sampling points are also provided for the gas at the same three points. The liquid outlet stream and feed solution are also equipped with sampling points. Suitable manometric measurement is included. Water is taken from a sump tank, and pumped to the column via a calibrated flowmeter. Gas is taken from a pressure cylinder (not supplied) through a calibrated flow meter, and mixed with air supplied and monitored from a small compressor in a pre-determined (but variable) mixed ratio. The mixture is fed to the base of the tower, in which a liquid seal is provided. The effluent gas leaves the top of the column and is intended to be exhausted to atmosphere outside the laboratory building.
The apparatus is designed to absorb carbon dioxide/air mixter into an aqueous solution flowing down the column.
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Experiments done on it:
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Experiment A:The objective of this experiment is to measure the absorption of carbon dioxide into water flowing down the packed column, using the gas analysis equipment provided.
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Experiment B:The objective of this experiment is to calculate rate of absorption of carbon dioxide into water from analysis of liquid the solutions flowing down the packed column.
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Experiment C :The objective of this experiment is to calculate rate of absorption of carbon dioxide into caustic soda solutions from analysis of liquid solutions flowing down the packed column.
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Experiment D :The objective of this experiment is to show that the amount of carbon dioxide removed from the air stream equals the amount taken up by a liquid stream of caustic soda solution.
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Experiment E :The objective of this experiment is to determination the Overall Mass Transfer Coefficient (Kog)
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Experiment F :The objective of this experiment is to determine the air pressure differential across the dry column as a function of the air flow rate.
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Experiment G :The objective of this experiment is to examine the air pressure differential across the column as a function of air flow rate for different water flow rates down the column .
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