Air separation equipment is the air liquefaction, rectification, and final separation into oxygen, nitrogen and other useful gases of the gas separation equipment, referred to as air separation equipment. Its minimum operating temperature is 77K. At the end of the 19th century, air was still called “permanent gas”, and later it was found that air can be liquefied at deep low temperatures, and because of the different boiling points of oxygen and nitrogen, oxygen and nitrogen can be separated from the liquefied air. The first commercial oxygen generator was made in 1903, and it was originally only used for gas welding and cutting metal. Nitrogen fertilizer industry needs nitrogen, oxygen generator developed to produce oxygen and nitrogen at the same time, renamed air separation equipment.
Cryogenic air separation plant
1, air separation equipment process freezing method to remove water and CO2. During the cooling process, water and CO2 are precipitated and frozen in the heat exchanger channel. After a certain period of time, the channel is switched, and the frozen impurities are taken away by the backflowing dirty nitrogen gas. According to the different types of heat exchangers, they are divided into regenerators and plate-fin switching heat exchangers. In this way, the switching action is frequent, the start-up operation is more complicated, the technical requirements are high, and the operation cycle is about 1 year;
2, the air separation equipment process according to molecular sieve adsorption purification process. Before the air enters the main heat exchanger, the impurities are cleaned by the adsorber. The long switching cycle of the adsorber greatly simplifies the operation, the amount of pure nitrogen products is no longer limited by the backflow gas requirements, and the operation cycle can reach two years or more, which is more and more widely used.
Low pressure air separation equipment. The whole equipment is composed of four main systems: air compression system, impurity purification and heat exchange system, refrigeration system and liquefaction rectification system. The corresponding mechanical equipment includes air turbine compressor, air cooling tower, turbine expander and fractionating tower. The working principle of the low-pressure air separation equipment is based on the theory of liquefaction cycle and rectification. The incoming air is first passed through the air filter, then compressed and cooled by the air cooling tower of the turbine compressor to a pressure of 0.5 mpa and a temperature of about 303K, and then enters the switching heat exchanger (E1, E2). The two heat exchangers can remove water and carbon dioxide in the air, and carry out heat exchange. The air is cooled to near the liquefaction temperature (101K) and sent to the lower tower, from which part of the air is pumped to the heat exchanger (E2) for heating. The heated air is combined with a small amount of cold air from the lower tower and then entered the turbine expander for adiabatic expansion, generating the required amount of cold, and then sent to the upper tower for rectification. The remaining air is preliminarily distilled in the lower tower. At the bottom, the liquid air with 38% oxygen content is obtained, the pure liquid nitrogen with 99.99% nitrogen content is obtained at the top of the lower tower, and the dirty liquid nitrogen with about 95% nitrogen content is obtained in the middle. The liquefied air, pure liquid nitrogen and polluted liquid nitrogen are extracted from the lower tower through the valve to reduce pressure to about 0.05 mpa, and sent to the upper tower for reflux liquid, where the second deep low temperature rectification is carried out, and the oxygen containing 99.6 ~ 99.8% of high purity oxygen is obtained at the bottom of the upper tower, and the heat exchange is carried out with the air through the heat exchanger (E4, E2, E1), and the temperature is heated to the atmospheric temperature. High purity nitrogen containing 99.999% nitrogen was obtained in the top of the upper tower, and waste nitrogen containing about 96% nitrogen was obtained in the middle of the upper tower. All of the nitrogen was reheated to atmospheric temperature by heat exchangers (E3, E4, E2, E1) and then discharged from the device. The condensing evaporator located between the upper and lower towers is also a heat exchanger, its function is to evaporate the liquid oxygen at the bottom of the upper tower through heat transfer, and condense the gas nitrogen in the lower tower, so it is called the condensing evaporator. After the evaporation of liquid oxygen, part of it is output as a product, and the rest is used as rising steam required for rectification in the upper column. Part of the condensed liquid nitrogen in the lower column is sent to the upper column as the reflux liquid in the upper column, and the other part is the reflux liquid required for the rectification of the lower column. Therefore, the condensing evaporator is one of the indispensable equipment to make the upper and lower tower can play the role of rectification. In addition to the above main equipment, there are adsorbers in the cold box, which can adsorb the impurities carbon dioxide and explosive substances that are not frozen in the heat exchanger (E1, E2). The box is also equipped with a liquid oxygen pump to circulate liquid oxygen and remove explosive substances to ensure the safe operation of the equipment. Heat exchangers, towers, liquid oxygen pumps and turbine expanders operating at low temperatures are housed in cold boxes filled with insulation to reduce cooling loss. The product oxygen and nitrogen from the cold box are then sent to the storage system and turbine compressor to increase the pressure to the required pressure for users to use.
Operating principle of air separation equipment from air to pure oxygen
Air separation equipment, as the name suggests, is a device that uses physical methods to separate oxygen, nitrogen and other components from the air. It is mainly based on the difference of the boiling point of each component in the air, and is separated by low temperature rectification. In this process, the air is first compressed, purified, and then cooled to a liquefied temperature, forming liquid air. Then, using the different boiling points of each component in the liquid air, the oxygen is gradually separated from the other components through multiple evaporation and condensation processes.
In the work flow of air separation equipment, compression and purification are the first steps. After the air is compressed by the compressor, the pressure is significantly increased, and the temperature is also increased. In order to remove impurities such as water vapor and carbon dioxide from the air, it is necessary to cool and purify the compressed air. This step is essential to ensure that the subsequent separation process proceeds smoothly.
This is followed by cooling and liquefaction. The compressed and purified air enters the cooling system, and the temperature of the air is gradually reduced by heat exchange with the refrigerant. When the air temperature drops to its liquefaction temperature, most of the components in the air (mainly nitrogen and oxygen) condense into a liquid state. At this point, the liquid air contains a higher concentration of oxygen.
The final stage is separation and purification. At this stage, liquid air is introduced into the rectification column. The distillation column is provided with multiple layers of trays, each of which has liquid and gas co-existing. Due to the different boiling points of oxygen and nitrogen, the lighter nitrogen evaporates first and rises to the upper tray during rectification, while the heavier oxygen remains in the lower tray. Through multiple evaporation and condensation processes, oxygen is gradually separated from the liquid air and is piped to storage tanks or supplied directly to the user.
The company adopts international advanced low-temperature rectification technology and intelligent control system to achieve efficient and stable operation of air separation equipment. At the same time, the company focuses on environmental protection and energy-saving design, and reduces energy consumption and emissions by optimizing process flow and improving equipment efficiency. These technical advantages make the company’s air separation equipment has a strong competitiveness in the market.