Proper selection of Random Packing can take you to the maximum performance and perfect solution for the particular operation. It will ease the research for the selection of random packing.

Random packing is used in many applications as solvent recovery, stripping operations, refineries, chemical plants and in absorption operation also. Its effectiveness, easy replacement, availability, affordability and its usability in corrosive applications makes it to stands out.

What is random packing?

Random Packing is directly dumped into the distillation column to achieve the required surface area where fluids contacts with each other to get efficient mass transfer operation. It’s used in distillation, stripping, carbon dioxide scrubbing and Liquid-liquid extraction.

Basically, Random packing are used to allow contact between 2 fluids such as liquid with gas or with liquid-liquid contact. The packing selected should offer large surface area to achieve optimum surface area and effective mass transfer.

Types of Random Packing

Large Sized Random packing has s higher capacity but, its efficiency gets lower while small sized packing offers better efficiency but can’t use for higher capacity. That’s why, proper selection of packing matters where both conditions such as efficiency and capacity should be economical and well balanced.

a) Raschig Ring-

Raschig Ring is first generation packing which was designed with basic structures. Its height is equivalent to its diameter and it is mainly made up of metal. As it’s a first generation packing its efficiency is low, low capacity, and cost is higher comparatively. Mostly it is used in corrosive applications such as carbon/graphite or ceramic material based construction. It lacks internal support known as “fingers.”

b) Pall Ring-

It is very similar to Raschig ring but with “fingers”. They also have same height and diameter as Raschig rings. It is commonly used in the distillation and absorption services mostly. Pall rings are having internal drips which increases the capacity efficiency to almost double compared to Raschig rings. Punching on the sides creates the internal drips in the pall rings.

c) IMTP Saddle Ring-

Saddle rings stands out in the segment as it has different sizing and aspect ratio. It has low aspect ratio which means height less than the diameter. When its dumped in the column, it settles in a way that it offers maximum flat surfaces parallel to liquid and vapors generated in the column.

More the surface area more will be the capacity with effective contact surface area. Due to this higher surface area, Saddle Rings offer higher efficiency and capacity than the Pall Ring Packing. It is called as high performance saddle rings.

They are commonly used in sour water stripping, atmospheric and high-pressure distillation, demethanizers, deethanizers, quench towers, acid gas removal, and main fractionators.

Where to use Random packing?

• Small diameter towers

It is impossible to install trays in towers with a diameter less than 0.9m (3feet). In such cases, Packing can be dumped directly into column and Packing will be the most reliable and efficient choice.

• Processes with Low-pressure drop

Used when pressure drop in packing towers is way too lower than in tray towers. Trays have a free area of about 5% to 10% of the tower cross space while that of packing is more than 50%.

• Corrosive applications

Random packing comes in a range of materials such as plastic, ceramic and metal which are resistant to corrosive fluids.

• Increasing capacity of towers

If the tower with trays has low capacity, it can be upgraded with random packing to upgrade the capacity.

Factors need to be consider while selecting a random packing

Before choosing the random packing, factors and characteristics of packing need to be checked and verified as,

• It should meet the process requirement.

• Need to check whether the direct replacement of an already existing packing is suitable with the process or not.

• Selection of the process familiar packing and its performance in the process.

• Experience with a certain packing with a specific application.

• Can it be used in a licensed process or not.

These are some factors need to be properly verified before selecting a random packing. More the specifically characteristics checked, better will be your selection for your process. Each and every factor like measurement, voids, wetting rate, surface area, efficiency, and density should be more specific which decides the overall performance of the selected packing.

There are some specific characteristics are listed below which must be checked for your process application.

1. The Surface Area

Efficiency of the packing is depending on surface area. Higher the surface area more will be the efficiency with respect to increased vapor contact. Therefore, the efficiency increases with lower packing size.

2. Uniform spreading surface

The vapor-liquid contact enhances the efficiency where the vapor-liquid contact can be enhanced by the uniform spreading surface. Pall ring and Raschig rings of equal size has similar surface area, but latter has a better spread surface as compared to the former, and hence latter is more efficient.

3. An uniform distribution

Random packing rings that can be fixed together with their counterpart can lower the efficiency when they form channels. Packing should also drain fluids freely to prevent liquid settling pockets as it was common with the older saddle type of packing. So the uniform distribution of the fluids also matters to maintain the performance.

4. The rate wetting

Minimum stability means the lower wetting rate. Dewetting of the packing surface occurs when the liquid on the surface of packing is interrupted or disturbed by falling liquid. When packing surface DE wets it causes a decrease in efficiency.

5. Voids in the packing

High voids means lower the pressure drop in vapor flow and higher will be the capacity as there is more space is available for vapors. Capacity increases with the particle size of the packing. The suitable size of packing should be selected with well-balance between efficiency and capacity.

6. The material used in random packing

Metal packing’s are unbreakable, offer higher capacity, turndown and efficiency comes in different shapes and they have a higher resistance to compression.

Ceramic packing’s work best in applications where high chemical inactivity, corrosive applications and high-temperature resistance are required. They offer low capacity, are breakable and are available only with specific shapes and not in popular geometries.

The most affordable packing’s are those made of plastics material mainly of polypropylene, but they can’t withstand higher temperature as above 122⁰C (250⁰F) depending on the grade. They can be degrade in applications of such oxidizing environment and solvents. That’s why they are kind of unsuitable for such applications. They have poor wet ability hence lower efficiency.

7. Friction

Capacity is higher in random packing when friction is minimized by using open shape which has aerodynamic characteristics.

8. Strength

Packing must have strength to bear load which is applied on it in the working conditions. It should resist mechanical damage so that it can last longer.

S-Cube Mass Transfer Pvt. Ltd.

Concluding on guide, it clarifies about how to choose affordable random packing for particular process for new installation or replacing old one, corrosive or for fouling applications.

S-Cube Mass Transfer Pvt. Ltd. is the India’s leading Random Packing manufacturer and supplier. We are delivering patented technology for Distillation and Column Internals as your process solution. Follow this guide to ensure you get maximum efficiency of your random packing.

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The Ultimate Guide on how to choose Random Packing