Gas Dehydration in Concurrent Flow

On gas fields with small debit, direct-flow spray absorbers that consist of several stages connected in series (see Fig. 2.19, a) are frequently used for the dehydration of gas from moisture, as the gas is being prepared for transportation. Each stage consists of a contact chamber and a separator. The absorbent (DEG) with the flow rate q is injected through the atomizer into the contact chamber. 

Because the size of the drops formed in the process of spraying depends on their velocity relative to the gas stream, injection is usually performed against the gas flow, which promotes formation of smaller drops due to secondary breakup. At first, drops move against the flow for a while then the flow drags them along. 

During their contact with the gas, drops absorb the water vapor contained in the gas. After that, the gas-liquid flow enters the separator, where the liquid phase gets separated from the gas. In order to determine the parameters of any single stage of the process, it is necessary to know the dynamics of the absorption process, and the efficiency of drop capture in the separator. The present section will consider the dynamics of mass exchange between DEG drops and a humid gas. For simplicity, it is supposed that the separator completely catches all drops, and that all stages of the absorber are identical. 

Consider the absorption of moisture from a gas flow by absorbent drops. Let gas containing water vapor with mass concentration pgo (kg/m ) arrive at the entrance to the contact chamber. Denote through pg] the concentration of vapor in the gas at the exit from the contact chamber. It should be noted that mass concentration values are taken at operating conditions. Define the dehydration factor as the ratio between the amount of water vapor extracted from the gas in the contact chamber, and the amount of water vapor at the entrance to the chamber  

The primary goal consists in the determination of the dependence of r/ on the parameters describing the gas and the absorbent, and on geometrical dimensions of the contact chamber. Direct the x-axis along the contact chamber axis, so that X = 0 corresponds to the entrance cross-section. Assume that the absorbent is atomized in the gas flow and forms drops of identical radius equal to the stable radius of drops in a turbulent flow  

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