Performance characteristics of PTFE pall ring

- Jun 17, 2019-

The PTFE pall ring has the advantages of large flux, low resistance, high separation efficiency and high operational flexibility. Under the same pressure reduction, the treatment capacity can be more than 50% larger than the Raschig ring.


The air pre-cooling system generally consists of an air cooling tower, a water cooling tower, a chiller and a water pump. It is disposed between the air compressor and the molecular sieve adsorber to reduce the air temperature and water content of the molecular sieve adsorber. Before the 1990s, air-cooled towers and water-cooled towers often used flow-through trays and downcomer-type large-hole passage trays. In actual operation, the following problems were exposed, such as air cooling tower water, water cooling tower water spraying, and trays. Problems such as large resistance, large refrigeration capacity of the freezer and poor pre-cooling effect. Since the 1990s, polypropylene and Pall ring packing towers have been widely used in air separation equipment manufacturing plants at home and abroad. Some use a small amount (about 2m) of stainless steel Pall ring packing at the bottom of the air cooling tower. The specifications are generally selected from the nominal diameters of DN50, DN70 and DN90.


The air cooling tower and the water cooling tower are filled with a Pall ring and are freely stacked. During mass transfer and heat transfer, the liquid flows down uniformly from the top of the tower, flows in a film along the packing, and the gas contacts the liquid film when it rises through the bottom of the column (the specific surface area of the filler reaches 80-110 m 2 /m 3 ). Heat and mass exchange. The air separation equipment manufactured around the 1970s, the air cooling tower and the water cooling tower also use ceramic Raschig ring packing. Due to the significant improvement of the Raschig ring by the German BASF, although the outer diameter of the ring is equal to the height, it is opened on the ring wall. Two rows of holes with inner tabs. There are 5 windows in each layer. This structure improves the gas-liquid distribution and makes full use of the inner surface of the ring. Compared with the Raschig ring, the processing capacity of the Pall ring can be more than 50%, and the pressure is reduced by half.


Practice has proved that the air pre-cooling system uses the pall ring packed tower and has the following remarkable features compared with the sieve tray tower:


(1) Strong mass transfer and heat transfer capability. The temperature difference between the air temperature of the air cooling tower and the cold water of the upper tower may be less than 1 ° C, and a negative temperature difference of 4 to 5 ° C may be generated between the water outlet temperature of the water cooling tower and the sewage nitrogen temperature of the inlet tower;


(2) Since the stacking void ratio reaches 94~95%, it is not easy to block, and it is not easy to be selected as a foaming entrainment, which is beneficial to the operation under variable working conditions. After the air volume is increased, it is not easy to bring water;


(3) The pressure drop is small, and the resistance per meter of packing is about 10 mm water column;


(4) The water consumption of the air cooling tower can be reduced by 30%;


(5) It can reduce the cooling capacity of the chiller. It can be turned off in winter and the cooling capacity can be reduced by 80% in summer, which makes it possible to realize air precooling system without chiller;


(6) Easy installation and low manufacturing cost;


(7) A relatively low density (0.9 kg/m3), and the product is light in