Besides reducing air loss as much as possible, reducing equipment resistance to increase air volume and reducing loss of running cooling, incomplete loss of heat exchange and leakage as much as possible to reduce expansion air volume, here, mainly from the angle of adjusting the rectification working condition, analyze the method of adjusting the output:
1) the liquid level should be stable. The stability of liquid oxygen level marks the cooling balance of the equipment. If the liquid oxygen level is high and low, it is very difficult to adjust the purity. Reasonably adjust the expansion amount and the opening degree of liquid-air and liquid-oxygen regulating valve to make the liquid-oxygen surface stable.
2) adjust the purity of liquid air and liquid nitrogen. Rectification in the lower tower is the foundation of the upper tower. The change of the amount of liquid nitrogen and liquid nitrogen will affect the purity of liquid nitrogen and the reflux ratio of the distillation section of the upper tower. If the amount of liquid nitrogen is too small, although the nitrogen purity is very high, but the recirculation liquid provided for the distillation section is too small, the purity of nitrogen will be reduced. At this time, due to the low oxygen concentration in the liquid, the purity of oxygen will decrease and the output of oxygen will decrease. Therefore, the best rectification working condition of the lower tower should be to increase the amount of extraction as much as possible under the condition that the purity of liquid nitrogen meets the requirements. On the one hand, it provides more recirculation fluid for the distillation section of the upper tower; on the other hand, it increases the oxygen concentration in the liquid and reduces the distillation burden of the upper tower, so that it is possible to increase the oxygen production. What needs to be explained here is that liquid nitrogen regulating valve should be used to adjust the purity of liquid nitrogen, instead of the liquid nitrogen return valve of the lower tower. The return valve should be fully open under normal circumstances.
3) adjust the rectification working condition of the upper tower, and strive to improve the average nitrogen purity. The average nitrogen purity marks the oxygen loss rate. And the average nitrogen purity depends on the purity of sewage nitrogen, because the amount of sewage nitrogen accounts for a large proportion. The purity of polluted nitrogen is also mainly guaranteed by providing the required liquid nitrogen from the lower tower. At present, the rectification working condition of the tower is normal while the purity of dirt and nitrogen is still too low, it may be due to the reduction of the rectification efficiency of the upper tower (for example, the tower block or leakage); or the expansion air volume is too large; or the amount of oxygen taken out is too small and the purity is too high, which will increase the amount of rising steam and decrease the reflux ratio. To improve the rectification working condition of the upper tower, it is mainly to control the amount of oxygen and nitrogen taken out. On the one hand, the amount of taking out the two should be appropriate; on the other hand, the valve opening degree should be moderate, so as to reduce the pressure of the upper tower as much as possible, which is beneficial to the rectification and improve the purity of the nitrogen.
