LPG production flowchart
Justification of the advisability of Liquefied Petroleum Gas (technical mixture of propane and butane) production.
The table contains a simplified flowchart of the composition and properties of the hydrocarbon mixture extracted from the borehole. The level of concentration of each component can vary significantly depending on the field and stage of its exploitation.
Natural gas fraction requires the simplest refining and bringing the dew point to a desired level. Simply put, it means that in the cold no products in liquid and solid phases will appear in the gas pipe, which is undesirable for the exploitation of the water pipe system.
Methane that got into the gas pipe requires odorization as it does not have its own odor. After the addition of an odorant (substance with a strong “gas” odor), methane is fully ready to use as fuel for heaters and automobiles since its Motor Octane number, as is evident from the flowchart, equals 110 units.
Now — regarding the release of a fraction of LPG (technical mixture of propane and butane). After the separation of the main “commercial” methane, what is left is a mixture of hydrocarbons. It is composed of methane itself as well as nitrogen, carbon dioxide, propane, butane, isobutane and the components up to C6+ inclusive. Usage of the aforementioned mixture is possible only at the field as it is not transportable. Meaning, it is combustion for personal needs and TORCH. Since personal needs do not require large quantities of fuel, almost all of it is burned. It is harmful to the environment.
On our plant, the mixture is compressed up to 2.0 MPa on the compressor, then it is cooled to -20 degree Celsius in the refrigerator and gets sent into the first separator, where the process of separation of methane, nitrogen and, partly, carbon dioxide takes place. Next, the liquid phase gets into the first column K1. Here, the processes of separation of the fractions of pentane and hexane from the column’s cube as well as the increase in propane and butane’s concentration in the reflux reservoir take place. Then, after pressure reduction, the mixture gets into the separator K2 — and from its cube we get the final product that, upon odorization, meets all the requirements of GOST.
