In a contactor, a countercurrent flow of wet NG and TEG is arranged. The industrial absorption dehydration process proceeds in a glycol contactor (a tray column or packet bed). The water content of the gas can be calculated using the following equation : 20, Chapter 20, in the GPSA Data Book, 12 th Edition. With increasing pressure of the gas the water content decreases, and with increasing temperature the water content in the gas increases. The water content of NG at saturation is dependent on temperature and pressure. For example, in Nigeria water T dew should be below 4☌ for NG at 4 MPa, which means that the NG can contain more than twice as much water vapors as in Europe. As was stated above, the distribution specifications depend on the geographic region in which they are applied. This value for water is equivalent to roughly 0,131 g H2O/m S 3 of NG at 4 MPa. T dew for water is -7☌ for NG at 4 MPa, and T dew for hydrocarbons is 0☌ for NG at the operating pressures.
In Europe, the concentration of water and higher hydrocarbons is specified by their dew point temperature (T dew). This amount should be lower than 7 lbs/MMcft, which is equivalent to 0,112 g H2O/m S 3. In the US and Canada, the amount of allowable water in the gas is specified in units: pounds of water vapor per million cubic feet (lbs/MMcft). The directive for gas distribution sets the allowable concentration of water and concentration of higher hydrocarbons. In the case of depleted oil field UGSs, vapors of higher hydrocarbons also contaminate the stored gas. The exact temperature varies with the location of the UGS and with the time of year.Ī disadvantage of UGSs is that during storage the gas become saturated by water vapors. The temperature of the gas usually ranges from 20 - 35☌. Distribution sites from UGS normally begin at 7 MPa. The output gas pressure depends on further distribution. The pressure inside increases as the gas is being injected, and decreases when gas is withdrawn. Generally, the allowable pressure of stored gas inside a UGS is up to 20 MPa.
The important parameters describing the appropriateness of UGS use are storage capacity, maximum injection/withdrawal performance, and gas contamination during storage. Each of these types possesses distinct physical characteristics. There are three types of UGSs: (1) Aquifers, (2) Depleted oil/gas fields, and (3) Cavern reservoirs (salt or hard rock). According to the latest update, over 0,7∙10 9 m s 3 of additional storage capacity will come on stream in Europe by 2020. Their total maximum technical storage capacity is around 10 9 m s 3. Nowadays there are approximately 135 UGSs inside the European Union. Underground Gas Storages (UGS) are the most advantageous option for storing large volumes of gas. Reserves smooth seasonal peaks and also short-term peaks of NG consumption. NG is stored in summer periods, when there is lower demand for it, and is withdrawn in the winter periods, when significant amounts of NG are used for heating. Secondly, NG storage enables the maximum capacity of distribution lines to be exploited. With this in mind, national strategic reserves are created. Firstly, it can reduce dependency on NG supply. There are two basic reasons why NG storage is important. The theme of natural gas (NG) dehydration is closely linked with storage of natural gas.
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