Advantages of structured packing

1. The separation efficiency of structured packing is high, and the extraction rate of distillation tower is high. There are two kinds of extraction rates of oxygen and nitrogen in the equipment. Because of the extraction rate of the equipment and the capacity of air separation equipment. It is difficult to measure the characteristics of high separation efficiency of structured packing due to the production of liquid products and other factors. The extraction rate of distillation column, especially the extraction rate of argon, is more representative of the design level of air separation equipment. Based on the actual measurement, the new air separation equipment has been put into operation. The oxygen extraction rate of the distillation column has reached over 99%, and the argon extraction rate has reached 79%.

The operation value of the oxygen content in the waste nitrogen of the upper tower is the main index of the distillation column extraction rate. According to the actual measurement, the oxygen content in the waste nitrogen can be less than 0.1%, even 150-200x10-4%.

The high separation efficiency of the structured packing upper column and the crude argon column is the result of their greatly reduced operating pressure. The lower the operating pressure, the better the separation of oxygen, nitrogen and argon, especially the separation of oxygen and argon. In general, the extraction rate of oxygen can be increased by 1% ~ 3% and that of argon by 5% ~ 10%.

To a great extent, the extraction rate of distillation tower also depends on the amount of expansion air entering the upper tower, especially the extraction rate of argon. Therefore, the key to improve the extraction rate of distillation tower is to continuously improve the isentropic efficiency of turbine expander and the supercharger's supercharging ratio.

2. The gap of regular packing is large, the production capacity is large, and the diameter of tower is reduced, which is convenient for transportation

The void ratio of regular packing can reach more than 95%. In the sieve plate tower, the area of the orifice plate accounts for 80% of the cross section of the tower, while the opening rate is about 8-12%, which is far less than the air drop rate of the packing layer. For the same load, the diameter of the packed tower is smaller than that of the sieve plate tower; in general, the cross section area is only about 70% of the sieve plate tower, which is conducive to transportation for large air separation equipment.

3. Regular packing has less liquid holding capacity, larger ratio of operating liquid to gas and elasticity, and rapid changing conditions

The operation load of the sieve plate tower is limited by the leakage of the sieve hole and the flooding speed, while the packing tower is limited by the flooding speed, so their operation load can be changed in a large range. The design load range of the packing tower can be up to 40% - 120%. The oxygen output of the upper tower of the packing can be adjusted in the range of 9000-14000mm3 / h according to the regulation of 12000m3 / h air separation equipment of Shanghai No.5 Steel works, and the operation load range is only 75％～117％。

Because the liquid holding capacity of packed tower is only 1% - 6% of the tower volume, while the liquid holding capacity of sieve plate tower is 8% - N% of the tower volume, and the liquid holding capacity is less, which means that the liquid stays in the tower for a short time, the operation pressure drop is small, and it is also conducive to the operation under variable conditions, but it should be verified in the actual operation under variable conditions in the future.

4. The start-up time of the device is greatly shortened

The start-up process of the air separation plant is no product output operation, so shortening the start-up time is one of the ways to save energy and reduce consumption of the air separation plant. The start-up time of the air separation plant refers to the time required from the start-up of the expander to the output of oxygen. After the existing integral packing is used in the upper tower, the amount of liquid held in the normal distillation is greatly reduced, which greatly shortens the start-up time of the air separation plant.