AbstractThe objective of this experiment is to analyse the absorption of liquid in gas flow. It is also to determine a relationship between the flowrate of the absorbent and the absorbed. Loading and flooding of the water is also being determine in this experiment. The pressure drop as a function of gas and liquid mass velocities (m3/hour) using flexi glass column packed with Raschig Ring. Air will be use as the function of gas while water will be the function of liquid. The relationship allows future users of the column to determine the possible conditions to achieve the absorption of gas that being desire. The relationship between the absorbent flowrate and concentration change was expected to be linear and have a significant effect on the change in concentration; however, the correlation deviated from the anticipated trend. The data contained outlier points, which when excluded improved the fit of seen correlations. With water as the absorbent, a linear relationship was observed. The water had a higher average of gas concentration change, a lower average percent error, and a lower standard deviation among the calculated k values. Data, good or bad, proved difficult to obtain mostly due to gas analyzer. Calibration of the analyzer took a majority of the time spent in lab, and in the final lab session the analyzer was never able to be calibrated.

IntroductionGas absorption is a widely unit operation in Chemical Engineering. The packed bed represents a workhorse configuration for a wide variety of mass transfer operations such as absorption, distillation and liquid-liquid extraction (LLE). The packed bed will be in contact (mixing) of fluids with mismatched surface area for phase contact that packing offers to increase the amount of momentum transfer, manifested by an increased vapour-phase pressure drop through the column. There are numerous process applications where particular components need to be selectively removed from the gas stream. Type of contacting unit for the feed gas and the absorbing liquid can be tailored to the application along with a high capacity for the absorbed components. This process (absorption process) has been developed by Chemical Engineers as a process that shows high selectivity and capacity as compared to absorbents which do not chemically react with the absorbing series. Examples are the removal of ammonia in the Haber process of ammonia synthesis, separations of acid such as CO2 and H2S from natural gas, and CO separation from gas mixtures with H2.

AimsThis experiment is to examine the air pressure drop across the column as a function of air flow rate for different water flow rates through the column. It is also to determine the Loading and Flooding Points in the column and to model the pressure drop as a function of gas (air) and liquid (water) mass velocities (m3/hour) using flexi glass column packed with Raschig Ring.

Theory Absorption is a mass transfer operation in which a vapour solute A in a gas mixture is absorbed by means of liquid in which the solute is more or less soluble. The gas mixture (Gas Phase) consists of mainly of an inert gas and the solute. The liquid (Liquid Phase) is primarily immiscible in the gas phase; its vaporization into the gas phase is relatively small.Redistribution of soluble gas as solute in the liquid may involve molecular diffusion in a stagnant medium, molecular diffusion in a smoothly flowing medium (laminar), molecular diffusion and mixing in a turbulent flowing medium or mass transfer between phases.Total amount of material transferred increased with time allowed for transfer, area through, which transfer can occur and the driving force (e.g. concentration difference).

KA (CA1 CA2)

The device that is designed to increase the interfacial area for the two phases flow through packing imparts good vapour-liquid contact when a particular type is placed together in numbers, without causing excessive pressure-drop across a packed section.

Properties of packing include low weight per unit volume, large active surface per unit volume, large free cross section and large free volume.

Large free cross section affects the frictional drop through the tower and therefore the power that is required to circulate the gas. Small free cross section means a high velocity for a given throughput of gas, and above certain limiting velocities, there is a tendency to blow the liquid out of the tower. Large free volume is to allow for reaction in the gas phase, this factor may be importance.

Apparatus and Material

Procedure1) U-tube manometer will be filled with water by arranging the values according U-tube arrangement.2) All the values is being set up to operating arrangement before the operation is started.3) The valves is need to be checked carefully before the column is to be use.4) Valve which labelled as VR-3 and VR-4 is being opened and the liquid flow rate is set and the volume of water reservoir must always be greater than the bottom of the reservoir. This is to prevent the air being trapped. Valve VR-4 is adjusted accordingly to avoid this to happen.5) Valve VR-1 is opened and the airflow is being set to 10m3.hour. About 2 minute time is needed to wait and the flow rate of air and water is constant. The pressure drop mmH20 in the mono-tube.6) The gas flow rate is increased by adding 5m3/hour to the column7) Part 4 will be repeat until you reach the flooding point.8) The curve of Ln (V) versus Ln (P/m packing )9) Step 2 to 6 is repeated with different kind of liquid flow rate.

Discussion