Introduction to the various components of the liquid nitrogen system

　　In the production of aluminum profiles, the liquid nitrogen cooling mold, whether it is fusion casting or extrusion, requires nitrogen. Today, let’s talk about the preparation of nitrogen-liquid nitrogen system and its equipment principles.
　　The liquid nitrogen system is based on the principle of pressure swing adsorption, using high-quality carbon molecular sieve as the adsorbent, and producing nitrogen from the air under a certain pressure. The purified and dried compressed air is subjected to pressure adsorption and decompression desorption in the adsorber. Because of the aerodynamic effect, the diffusion rate of oxygen in the micropores of carbon molecular sieve is much higher than that of nitrogen. Oxygen is preferentially adsorbed by carbon molecular sieve, and nitrogen is enriched in the gas phase to form product nitrogen. After decompression to normal pressure, the adsorbent desorbs the adsorbed oxygen and other impurities to complete the regeneration. Generally, two adsorption towers are set up in the system, one tower absorbs nitrogen and the other tower desorption regeneration. The PLC program controller controls the opening and closing of the pneumatic valve, so that the two towers can be replaced and cycled to achieve the goal of successively producing high-quality nitrogen. . The whole system consists of the following components: compact air purification components, air storage tanks, and nitrogen buffer tanks.
　　1. Compact air purification components
　　The compressed air supplied by the air compressor is first introduced into the compressed air purification unit. The compressed air is first removed from the pipeline filter to remove most of the oil, water, and dust, and then the freeze dryer is used for further water removal, fine filter oil removal, and dust removal. , And is deeply purified by the ultra-precision filter that follows it. According to the working conditions of the system, a set of compact air degreaser is specially planned to prevent the trace oil from being saturated and provide sufficient maintenance for the carbon molecular sieve. The well-planned air purification components ensure the service life of carbon molecular sieve. The clean air treated by this component can be used for exterior air.
　　2. Air storage tank
　　The effect of the air storage tank is: downdraft pulsation, which has a buffer effect; thereby reducing system pressure fluctuations, so that the compressed air smoothly passes through the compressed air purification components, so as to fully remove oil and water impurities and reduce the load of the subsequent PSA oxygen and nitrogen separation equipment. At the same time, when the adsorption tower is switched, it also supplies the PSA oxygen-nitrogen separation equipment with a lot of compressed air required for rapid pressure increase in a short time, so that the pressure in the adsorption tower will quickly rise to the operating pressure, ensuring that the equipment is reliable and stable run.
　　3. Oxygen and nitrogen separation equipment
　　There are two adsorption towers A and B equipped with dedicated carbon molecular sieve. When clean compressed air enters the inlet end of Tower A and flows to the outlet end through the carbon molecular sieve, O2, CO2 and H2O are adsorbed by it, and the product nitrogen flows out from the outlet end of the adsorption tower. After a period of time, the carbon molecular sieve in Tower A is fully adsorbed. At this time, tower A actively stops the adsorption, the compressed air flows into tower B to absorb oxygen and produce nitrogen, and regenerate the molecular sieve of tower A. The regeneration of the molecular sieve is completed by rapidly lowering the adsorption tower to atmospheric pressure to remove the adsorbed O2, CO2 and H2O. The two towers are replaced for suction and regeneration, complete the separation of oxygen and nitrogen, and successively output nitrogen. The above process is controlled by a programmable controller (PLC). When the nitrogen purity at the outlet end is set to the value, the PLC program will automatically open the vent valve to automatically vent the unqualified nitrogen to ensure that the unqualified nitrogen does not flow to the gas point. When the gas is vented, noise reduction is used to make the noise less than 75dBA.
　　4. nitrogen buffer tank
　　The nitrogen buffer tank is used to balance the pressure and purity of the nitrogen separated from the nitrogen and oxygen separation system to ensure the steady supply of nitrogen. At the same time, after the operation of the adsorption tower is switched, it will recharge part of its own gas to the adsorption tower. On the one hand, it helps the adsorption tower to increase the pressure, and the other also plays a role in maintaining the bed, which plays an extremely important role in the operation of the equipment. Process auxiliary effect.