Repsol YPF

Liquid petroleum gases

Commercial mixtures of hydrocarbons in which butane or propane are predominant are referred to as Liquid Petroleum Gases (LPG).

In their natural state, they are gaseous, whereas in closed containers and at room temperature, a large portion of them are in their liquid phase, occupying a volume that is 250 times less than the space they would occupy in their gaseous state.

GLPs, once they have been extracted as refinery gases or from related natural gas facilities, are compressed until they become liquid and are kept in this state in large storage units that are normally adjacent to refinery or port facilities that are known as terminals.

There are several kinds of storage deposits:

• Pressurised deposits
• Cooled or atmospheric pressure deposits
• Semi-cooled deposits
• Underground deposits: in saline cavities or conventional mining galleries.   

From the terminals, the LPG is transported by boat, tanks travelling both by rail or road, or gas pipelines to the filling plants for its commercial distribution in bottles or bulk deposits.

The high heating power of LPGs in comparison with other commercial gases, offers the advantage that in order to obtain the same amount of overall energy, a lesser diameter is required for the pipes used to distribute the gas in its gaseous phase, although the pressures cannot be higher than a specified value, because otherwise instances of condensation in the pipes would occur.

Its characteristics of high purity and the homogenous nature of its components make it very easy to adjust the required air level for the combustion of these products to be stoichiometric.

Moreover, and this is one of their main features, they are practically devoid of sulphur and other substances such as metals. The area in which it is employed is generally direct heating, and those facilities in which the accessibility of propane gas in deposits, the absence of sulphur and all the benefits that being a gaseous fuel entail, lend it an added value, compared with other fuels.

Its sale is clearly distinguished, depending on the form of storage and distribution, as follows:

• bottled LPG, which is almost exclusively used as domestic fuel for the kitchen, hot water and heating.
  
• LPG stored as a fixed deposit, which is mainly used in the domestic, residential and commercial sectors, and in agriculture and specific industries.
  
• GLP for automotion, to be used as fuel.
  
  

On certain occasions, when the room temperature decreases, the deposit's vaporisation capacity is inadequate for the outflow of propane gas that is demanded, and the use of vaporisers becomes necessary, in which case the latent vaporisation heat level of propane, that is 90 kcal/kg, must be taken into account.