How and why liquefy gases

Liquefaction of natural gas is called its transfer to the liquid state under the influence of temperatures, which are smaller in comparison with the critical one. This process allows its reservation and savings for later use, as well as for organizing transportation by any type of transport. The substance is often used in the form of alternative fuels in motor vehicles, in the processing of metals, in mobile power plants and so on. Among other things, in many private homes you can find a boiler on liquefied gas. The cost of creating plants for its production depends on the location of the development, as well as the type and composition of the extracted raw materials. Now the most promising of them are floating, because transportation through the construction of submarine gas pipelines is often unrealistic.

Preparation and start of liquefaction

The technological diagrams of those plants used for liquefaction differ from each other, primarily by the refrigerating cycle. His choice is primarily affected by the composition and pressure of the gas, which comes here. These parameters, in turn, are influenced by several factors, including: the time of year, the place of extraction and even the term of its development. Before you start liquefying gases and directing them to the installation, you must clean them of acidic impurities and drain them. At the starting phase of the process, hydrocarbons are massively emitted from the raw materials, among them high-boiling naphthenic, aromatic and paraffinic. Otherwise, the valves and apparatus equipment may become plugged. To effectively and efficiently liquefy gases, it must be remembered that a large number of heavy hydrocarbons in their composition lead to a high liquefaction temperature and low energy costs. If there is nitrogen in their composition, this leads to an increase in volatility and energy consumption.

Cascade method and refrigeration cycles

At the heart of industrial methods of liquefaction lies the principle of evaporation of liquids, the process of adiabatic gas expansion, and also the Joule-Thomson effect. Liquefied natural gas is formed due to the use of several refrigeration units (hence the media). In this case, the medium, which is characterized by a lower boiling point, condenses under pressure due to the evaporation of a higher boiling neighbor. This method is the most common and is known as cascade liquefaction. In most cases, the refrigerant at the first stage is propane (sometimes ammonia), and on the second - ethylene. Thus, the liquefaction of natural gas is carried out in this case under the influence of evaporated ethylene. With regard to refrigeration cycles, which are based on the above-mentioned Joule-Thomson effect, they are distinguished both with single and double throttling, and also with pre-cooling due to a special flow and foreign agent.

Liquefaction with large installations

You can also liquefy gases by using a single-flow cascade cycle. Here, the refrigerant is a multicomponent mixture, which includes nitrogen with hydrocarbons. This method, together with its modifications, is used most often in large installations, whose productivity ranges from two to five million cubic meters of finished product per day. Liquefying gases in this way is beneficial in terms of relatively low energy costs. On the other hand, a single-flow cascade cycle requires a lot of metal-consuming equipment.