There are three ways to configure the liquid air in the condensing evaporator of the crude argon column: one is that all the liquid air in the main tower passes through it, and after partial evaporation, the vapor and liquid air are sent back to the upper tower together. In this way, the cold source of condensing evaporator is sufficient, which is beneficial to the working condition of crude argon, but has great influence on the main tower;DEAR Air separation unit.Before the appearance of liquid air, the flow rate of central pumping or circulation should be appropriate, and there should be considerable room for adjustment. Generally, the intermediate temperature should not be lower than - 100 ℃. Before and after the appearance of liquid air, cool the main engine thoroughly as soon as possible, so that liquid oxygen can appear as soon as possible after the appearance of liquid air. It will not evaporate quickly after throttling to the upper tower due to liquid air.The distribution of boiling section and preheating section is reasonable. If the liquid oxygen level is too low or too high, the heat transfer performance will become worse. If the liquid oxygen level is too low (H < 0.2), there is a long dry vapor zone on the upper part of the tube, so that the heat transfer area of the tube is not fully utilized; if the liquid level is too high (H > 0.7), the liquid oxygen in the boiling zone may be taken out and the liquid film section with the best heat transfer effect cannot be formed, and the boiling intensity will be weakened.
For 1000m3 / h such a small low-pressure air separation plant, when producing gaseous products, the required expansion air volume has reached 28% of the processing air volume, and it can not all enter the tower to participate in distillation. If some liquid products are to be produced, more expansion air will be needed, and more expansion air will be bypassed to the heat exchanger.Where the liquid layer is thin, the resistance is small, the amount of steam rising from the small hole is more; where the liquid layer is thick, the resistance is large, the amount of steam passing through is less, or even No. The distillation process of air on the fractionator tray depends on the mass transfer and heat transfer between the rising steam and the liquid on the tray. The more the gas and liquid contact on the tray, the more perfect the distillation process will be, and the more conducive to the separation of oxygen and nitrogen.Condensation is the reverse process of evaporation. For pure matter, the condensation temperature is also called liquefying temperature, which is equal to the evaporation temperature under the same pressure. The saturation temperature can unify them.
DEAR Air separation unit.When the boiling point difference between rare gases and impurities is large, the method of segregation can be used to separate them. For example, nitrogen can be separated from neon and helium to obtain crude neon and helium.During operation, due to incomplete heating at the valve, or water entering at the valve packing, the valve will be frozen at low temperature, or the valve will be closed too tightly at room temperature, resulting in thread biting. In order to prevent the valve from sticking, the rising rod structure and thick tooth trapezoidal thread should be adopted in the design;DEAR Air separation unit.High heat transfer efficiency, large heat transfer area per unit volume, about 2500 m3 / m3. Moreover, due to the direct heat exchange between cold and hot fluids, it is basically a stable heat transfer process, which can ensure the stability of working conditions in the tower. The temperature of air flow and packing in the accumulator will change periodically with the switching time, which is an unstable heat transfer process.
