For molecular sieve adsorption purification process, the adsorption capacity of molecular sieve is related to temperature. The lower the temperature is, the larger the adsorption capacity is. For a certain size of adsorber, the working cycle can be long, or for a certain adsorption cycle, the designed adsorber volume can be small, so it is also required to pre cool the air to the lowest possible temperature. In the nitrogen water precooler, the cooling capacity of nitrogen is fully recovered and utilized to cool the air.DEAR Air separation unit.In many processes occurring in nature, some processes can proceed spontaneously in one direction, but not vice versa. There are two gases with the same temperature and pressure on both sides of a container. After the partition in the middle is pulled out, the two gases will mix spontaneously and evenly. However, to separate them, work must be consumed.The refrigeration capacity of throttling effect is due to the decrease of pressure, volume expansion and the increase of potential energy of molecular interaction, resulting in the decrease of kinetic energy of molecular motion and the decrease of gas temperature, which makes it have a certain ability to absorb heat. For the whole air separation unit, the air pressure when entering the unit is high, and the pressure when leaving the air separation unit is low. Theoretically, the temperature can be reheated to the temperature when entering the unit. At this time, the enthalpy value of the low pressure gas is greater than the enthalpy value at the inlet, and the enthalpy difference between the low pressure gas and the inlet gas is the refrigeration capacity of throttling effect, no matter whether the pressure drop is generated in the throttle valve or not.
DEAR Air separation unit.The temperature of liquid oxygen at the bottom of the upper tower is about - 180 ℃. In the process of gasification, it exchanges heat and mass with the liquid on the tray. The nitrogen component evaporates and the gas temperature decreases. When the gas passes through dozens of trays and rises to the top of the tower, the gas has reached pure nitrogen and the temperature drops to the same level as the liquid temperature (- 193 ℃). Therefore, the formation of the lowest temperature in the tower is the result of liquid throttling expansion and gas-liquid heat and mass exchange.DEAR Air separation unit.Under certain conditions, especially under high pressure, oxygen may react with carbon in steel when encountering friction, impact and spark. Therefore, according to the pressure and laying method, except for the requirements shown in table 40, a stainless steel pipe (gb2270-80) or copper pipe with a length of more than 5 times the outer diameter of the pipe and no less than 1.5m shall be used at the downstream side of the pressure or flow control valve group Stainless steel pipe shall also be used for the oxygen release pipe section with working pressure greater than 0.1MPa at the downstream side of the oxygen release valve.
In order to condense the required amount of nitrogen, it is necessary to increase the pressure of the lower tower to increase the heat transfer temperature difference, which will increase the energy consumption of the air separation unit. Neon and helium purge pipes are installed on the top of condensing evaporator. During operation, it is necessary to open neon and helium purge valves regularly to discharge them. When air liquefies in the liquefier, there will also be accumulation of neon and helium non condensable gases, so neon and helium purging pipes are installed on the upper part of the liquefier for regular discharge.Nitrogen water precooler is widely used in all low pressure air separation units. It mainly makes use of the unsaturation of the water in the polluted nitrogen to make part of the water evaporate. When the water evaporates, it absorbs the latent heat of vaporization to reduce the cooling water temperature. Then it is used to cool the processing air and reduce the temperature of the air entering the tower. Therefore, it includes air cooling tower and water cooling tower.
Medium pressure blow off: after high pressure blow off, close the main inlet valve of high pressure air and open the blow off valve of oil-water separator. Install high pressure and medium pressure gauges, install and close throttle-1 valve. Close the blow-1 and blow-2 valves, then open the main inlet valve of high pressure air and close the blow off valve.DEAR Air separation unit.In order to prevent the pipeline from freezing and cracking in winter, insulation measures must be taken for some outdoor detection pipelines with liquid medium. In places with low ambient temperature, steam or electric heating can be used for insulation. In general, the pipeline can be wrapped with asbestos rope and other insulation materials for thermal insulation;DEAR Air separation unit.For the internal compression process, the liquid oxygen is compressed to the required pressure in the device and then reheated and gasified in the high-pressure heat exchanger. If the compression pressure of liquid oxygen is lower than the critical pressure (for example, the pressure of oxygen for steelmaking is 3.0MPa), there is a gasification stage in which the heat is absorbed and the temperature remains unchanged, and then the superheating stage when the gas temperature rises.
