Metal Structured Packing is made of perforated plate with channel corrugation on surface, and remains structure feature of metal wire gauze packing.
Metal Structure tower packing strengthens uniform liquid distribution and surface wetting ability, which increases mass transfer efficiency.Metal structured packing has feature of specific surface large, void ratio high and weight light; Gas path obliquity small and regular, pressure drop low; Radial diffusion good, gas liquid contact sufficient.
Metal Structured Packing Advantages
| Packed columns |
Trayed columns |
| Lower pressure drop leads to significant power savings. (Greater than 5% reduction in power is possible.) |
Higher pressure drop, but shorter columns. |
| High turndown capability. (Down to 40% of design capacity is possible.) |
Limited turndown for efficient operation. (60-70% of design capacity is typical.) |
| Enables pure argon production by distillation, therefore eliminating need for a pure hydrogen source. |
Can be used for high-pressure distillation. |
Metal Structured Packing Advantages
1. The pressure drop of the structured packing is significant
Since the gas-liquid two-phase membrane contact in the structured packing is different from the bubbling contact of the two phases in the sieve tray, the pressure drop of the packed tower is only 1/4 to 1/6 of the sieve tray. For example, the operating resistance of the tower on the structured packing is 3.5-4.2 kPa, the operating pressure at the bottom is only 35-45 kPa, the lower tower is still still using the sieve tray tower, and the operating resistance is not changed, so the operating pressure of the lower tower is correspondingly reduced by 0.05~ 0.06 MPa, generally 0.44 to 0.48 MPa, so that the shaft power of the air compressor can be reduced by 5% to 7%.
2. High efficiency of structured packing separation
The lower the operating pressure of the upper column, the greater the separation of oxygen, nitrogen and argon, especially the separation of oxygen and argon. Generally, the extraction rate of oxygen can be increased by 1% to 3%, and the extraction rate of argon can be increased by 5%. 10%, practice has proved that the oxygen extraction rate of air separation equipment has reached more than 99%, and the extraction rate of argon has reached more than 80%.
The extraction rate of the distillation column depends to a large extent on the amount of expansion air entering the upper column, especially for the extraction rate of argon, so the isentropic efficiency of the turboexpander and the supercharging of the supercharger are continuously improved. The ratio is the key to increasing the extraction rate of the distillation column.
3. The regular packing has a small liquid holding capacity
The volume of the structured packed column is generally only 1% to 6% of the column volume, while the holding capacity of the sieve column is 8% to 10% of the column volume. The small liquid holding capacity means that the liquid stays in the tower for a short time and the operating pressure drop is small, which is beneficial to the operation of the variable working condition. The structured packing tower can be designed in the range of 40% to 120%. The oxygen production of the upper tower of the 12000m3/h air separation plant of Shanggang No. 5 Plant can be adjusted within the range of 9000~14000mm3/h, and the operating load range is only 75%~117%.
4. Regular packing gap is large
The structured packing has a void ratio of more than 95%. In the sieve tray tower, the orifice plate area accounts for 80% of the tower section, and the opening ratio is 8% to 12%, which are far less than the void ratio of the filler layer. For the same load, the tower of the packed tower is smaller than the sieve tower; in general, the cross-sectional area is only about 70% of the sieve tower, which is advantageous for large-scale air separation equipment.
5. The device startup time is greatly shortened
The starting process of the air separation equipment is no product output operation, so shortening the starting time is one of the ways to save energy and reduce consumption of the air separation equipment. The starting time of the air separation equipment refers to the time required to start the expansion machine to the oxygen output. After the completion of the packing, the amount of liquid held during normal rectification is greatly reduced, and the start-up time of the air separation plant is greatly shortened. After the conventional packing is used in the upper tower, the amount of liquid held during normal rectification is greatly increased. After the descent, the start-up time of the air separation plant is greatly shortened, and the general start-up time only takes 26 to 30 hours.
6. The oxygen content in the argon fraction is about 90%.
To reduce directly to 1~2×10-4% by cryogenic rectification, the theoretical plate number of the rectification column needs about 180 pieces, the sieve plate plate needs about 300 pieces, and the resistance is up to about 100 kPa. Obviously, the crude argon is It is impossible to discharge the outside of the tower, and the height of the structured packing is about 45m. The resistance is only 14 to 16 kPa, so the realization of the full rectification argon process is possible.
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