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ABSTRACT: This study compares three conventional methods of natural gas (Associated Natural Gas) dehydration to carry out the dehydration process and suitability of use on the basis of energy requirement. These methods are Triethylene Glycol (TEG) absorption, solid desiccant adsorption and condensation. Analyses performed were based on dehydration of Natural Gas saturated with 10^sup 3^Nm^sup 3^/h water content at a temperature range of -10° C to 30°C, and gas pressure variation between 7MPa and 20MPa. This analysis and study showed that energy required for all three processes decreases with increase in pressure, but condensation dehydration requires the least energy at high pressures. Results obtained shows that, both at high pressures and low pressures, TEG dehydration is most suitable and in cases where very low T^sub dew^ is required, solid desiccant adsorption is preferable. In conclusion, the findings in this paper will aid natural gas process design engineers to decide on what method to use base on energy consumption and on the physical and chemical properties of the final products. © JASEM
http://dx.doi.org/10.4314/jasem.v20i2.4
Keywords: Dehydration, Absorption, Desiccant, Condensation, Triethylene Glycol (TEG)
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Natural gas usually contains significant amount of water vapour. Changes in temperature and pressure condense this water vapour, altering the physical state from gas to liquid and then to solid. This water must be removed to protect the system from corrosion and hydrate formation. The distribution specification set the allowable water concentration in natural gas by specifying the dew point temperature (Tdew) of natural gas (NG) Tdew as -7°C at 4 MPa, and Tdew for hydrocarbons is 0OC for NG at the operating pressures (NET4GAS, 2011). This value is equivalent to roughly 5gH2O/m3 NG at 4MPa. The Water content, which NG at saturation can contain, is dependent on the temperature and pressure within the pipeline and storage facility. The average value of H2O in Natural gas is five times higher than requested (GPSA Data Book, 2004).
The distribution specifications depend on the geographic region in which they are applied. For example, in Nigeria water Tdew should be below 4°C for NG at 4MPa, which means that the NG can contain more than twice as much water vapors as in Europe (Netusil and Ditl, 2012).
The water content of NG...