What Is Liquation?

Liquefaction refers to the process by which a substance changes from a gaseous state to a liquid state, exothermic to the outside world. There are two ways to achieve liquefaction, one is to reduce the temperature, and the other is to compress the volume. The critical temperature is the highest temperature at which a gas can be liquefied. Because the volume of the gas usually becomes a few thousandths after being liquefied, which is convenient for storage and transportation, in reality, some gases (such as ammonia and natural gas) are usually liquefied. Because these two gases have higher critical points, Therefore, at normal temperature, it can become a liquid, while other gases such as hydrogen and nitrogen have a low critical point, and must be deeply cooled while being pressurized, which is called liquefaction.

Material

1. Two main methods of liquefaction: Method 1: Reduce the temperature (all gases and all temperatures); Method 2: Compress the volume (certain temperature of certain gases <normal temperature, special temperature must be reduced first and then the volume>)

2. Any gas can be liquefied when the temperature drops sufficiently low;

Compared with gas, liquefaction can reduce the volume (the volume is 1/1000 of the gas volume), which is convenient for storage and transportation.

Gases that are easily liquid: ammonia (NH ₃ ), chlorine (Cl ₂ ), sulfur trioxide (SO ₃ ), etc.

The process by which a substance changes from a gaseous state to a liquid state. Liquefaction is the reverse process of vaporization, in which gas molecules attract each other and condense into a liquid. The substance emits heat during liquefaction. Gases below the critical temperature can be liquefied. Liquefaction can be achieved by pressure or cooling, or a combination of pressure and cooling. Gases with a critical temperature above or close to room temperature, such as ether, chlorine, ammonia, sulfur dioxide, carbon dioxide and certain hydrocarbons, can be liquefied by compression at room temperature. Gases with very low critical temperatures, such as oxygen, nitrogen, hydrogen, and helium, must be cooled below their critical temperature, and then liquefied by isothermal compression. These very low-temperature gases did not have the ability to liquefy in the first half of the 19th century, when they were once called permanent or true gases. When people realized the fact that matter has a critical temperature, they worked hard to improve the low temperature technology, and finally all the gases were liquefied. Liquid hydrogen was first obtained from 1884 to 1885. The last gas to be liquefied was helium, which was converted to a liquid by K. Onus in 1908 in Leiden, the Netherlands. In 1928, helium was solidified again. Gases with high critical temperatures are liquefied by compressing them in a compressor and condensing them in a heat exchanger. Commercially, the method of gas liquefaction is to cool the highly compressed gas to room temperature through a throttling process, and then adiabatic throttling several times until it is cooled to liquefaction. More advanced and efficient refrigerators are reciprocating or turbine-type expanders or expanders. In these devices, compressed gas is either expanded in a cylinder with a piston, or adiabaticly expanded in a turbine. Work is cooled and liquefied. The liquefaction of gases such as hydrogen and helium is of great significance to the development of modern science and technology. For example, liquid hydrogen and oxygen are high-energy fuels and combustion aids commonly used in modern rockets and jet engines. Liquid oxygen is also used in blasting projects. Air liquefaction can be used in a technique for separating various constituents of air. ^[1]