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How should the filler in the tower be selected?

2024-7-15

The requirements of packing tower for packing are reflected in the following aspects:

(1) The specific surface area at is larger, and the specific surface area at refers to the surface area of 32mm per unit packing volume of the filler;

(2) can provide a large fluid flow, that is, the selected structural filler should be open, so that the space in the dead Angle area is small and the effective voidage is large;

(3) The liquid redistribution performance is good;

(4) the filler should have sufficient mechanical strength, especially non-metallic filler;

(5) Low price;

Types and characteristics of fillers

Industrial fillers are divided into granular fillers and structured fillers according to shape and structure:

(A) particle packing is generally wet or dry bulk packing. There are mainly the following types: lacey ring packing, pall ring packing, step ring packing and other ring packing; Arc saddle packing, ring torque saddle packing and other saddle-shaped packing.

(2) structured packing with a certain geometric shape, neatly stacked, industrial use is mostly corrugated packing, its advantages are compact structure, high mass transfer efficiency, large processing capacity, but it is not easy to deal with large viscosity or suspended materials, and high cost.

Taking the above factors into consideration, I choose the step ring filler in this design process.

Packing size

The size of filler directly affects the operation of tower bottom and equipment investment. Practice has proved that the ratio of tower diameter (D) to packing outer diameter (d) has a lower limit, if the diameter ratio is lower than this lower limit, the void ratio of packing near the tower wall is large and uneven, and the air flow is easy to short circuit and liquid wall flow increase.

Lower limit of diameter ratio of various fillers:

Lacing ring 20-30 (* minimum 8-10)

Bauer Ring 10-15 (* minimum 8)

Step ring 15 (* minimum 8)

For a certain column diameter, the packing that meets the lower limit of diameter ratio may have several sizes, and the performance and economic factors of the packing should be considered comprehensively.

General recommendation: When D≤300, select 25 mm filler;

300mm  D  900mm, choose 25-38mm filler. D  900mm, choose 50 70mm filler. However, 50mm filler is commonly used in large towers, but the increase in flux cannot compensate for the reduction in cost.

Selection of filler material

The filler material is selected according to the corrosiveness of the material system, operating temperature, corrosion resistance of the material, and comprehensive consideration of the performance of the filler and economic factors.

(1) Ceramics have corrosion resistance and heat resistance, but the quality is brittle, fragile, and the price is cheap.

(2) Metal Metal materials are mainly carbon steel, stainless steel, aluminum and aluminum alloy.

(3) Plastics mainly include polypropylene, polyethylene, polyvinyl chloride, etc., plastics have good corrosion resistance and low heat resistance, but they have cold brittleness and poor surface wettability.

Generally speaking, when the operating temperature is high but there is no significant corrosion, metal fillers are selected; Low temperature selection of plastic filler; The material system is corrosive and the operating temperature is high, it is appropriate to use ceramic filler. Considering that the design is to use water to absorb the SO2 absorption liquid, which is weakly acidic and has a certain corrosiveness, while taking into account the economic rationality and absorption efficiency, polyethylene step ring is selected.