PP Raschig Ring

Product Model	Bulk Ring Fill Series
Category	PP Molded Products
Reference Price	Price on request

Hot Customizable for Working Conditions 11 Technical Parameters

Product Overview

PP Raschig rings are a structurally simple ring-shaped bulk packing, featuring thin-walled hollow cylinders with heights equal to their diameters, molded from polypropylene. During use, a large number of Raschig rings are randomly stacked in the packing layer of scrubbing towers, absorption towers, and regeneration towers. Waste gas and absorbent flow through the voids between the rings and the inner holes of the rings, completing the mass transfer and purification process.

Raschig rings are an early-developed and widely applied classic packing type, characterized by simple structure, easy processing, and low cost. The ring structure allows both the interior and surface of the packing to participate in gas-liquid contact. Randomly stacked packing forms tortuous flow paths, extending the residence time of gas within the packing layer. The PP material is resistant to acid, alkali, and salt corrosion, lightweight, and not easily broken, making it suitable for treating corrosive exhaust gases and offering significant advantages over metal packing in applications prone to rust.

Xicheng Environmental supplies PP Raschig rings in multiple diameter specifications. Smaller specifications result in more packing units per unit volume and larger specific surface area, but also increased resistance. Larger specifications offer higher throughput and resistance to blockage, making them suitable for dusty or sticky gas streams. Selection should be based on tower diameter, gas treatment capacity, and purification requirements to determine the packing specification and loading height.

Working Principle

The purification effect of Raschig ring packing comes from the thorough contact between the gas and liquid phases on the packing surface. Absorbent is sprayed downward from above the packing layer, forming a liquid film on the ring surface and filling part of the internal space. Waste gas rises from below through the tortuous channels formed by the randomly stacked packing, continuously contacting the wetted ring wall liquid film, where pollutants in the gas phase are absorbed or neutralized by the liquid phase, achieving gas purification.

A large number of randomly stacked Raschig rings provide a specific surface area far greater than that of an empty tower. The more developed the liquid film and the larger the gas-liquid contact area, the more thorough the mass transfer. The hollow structure of the ring ensures a high voidage, allowing gas to pass through multiple paths via the inner holes and inter-ring voids, resulting in high throughput and low resistance. The PP material is not corroded by the absorbent, maintains stable wettability, ensures uniform liquid film distribution, and retains the packing shape and void structure over long-term operation.

Structural Composition

Each Raschig ring is a thin-walled cylindrical tube with equal diameter and height, open at both ends and hollow in the middle, with a smooth wall surface. Plastic Raschig rings are molded from molds, ensuring uniform wall thickness, round ring bodies, and consistent dimensional accuracy in batch production. The ring wall can be smooth, or modified products with windows or ribs on the wall surface may be used to improve internal surface wetting and liquid distribution.

The packing layer consists of tens of thousands of randomly stacked individual Raschig rings, supported by grating plates or porous plates at the bottom, and sometimes limited by pressure plates at the top if necessary. Randomly interlocking Raschig rings form numerous void channels. During loading, wet or dry methods are used to ensure uniform density throughout the layer, avoiding voids and wall flow. When packing layers of different specifications are stacked, support members are installed between layers.

Specification Model Table

The following table provides a general comparison of Raschig ring specifications and their applicable characteristics. Specific dimensions should be based on actual products and selection calculations.

Specification Tendency	Specific Surface Area	Applicable Characteristics
Small Diameter	Larger	High purification requirements for relatively clean gas
Medium Diameter	Medium	General acid-alkali gas scrubbing
Large Diameter	Smaller	High throughput, anti-blocking, dusty gas

Product Features

PP Raschig rings feature a mature structure, are economical and durable, and are a common bulk packing for acid-alkali gas scrubbing towers. Key features include:

Classic ring structure, high throughput, low pressure drop
PP injection molded, resistant to acid, alkali, and salt corrosion, does not rust
Lightweight, low labor intensity for loading and replacement
Smooth wall surface, resistant to scaling and blockage, easy to clean
Low cost, ample supply, low replacement cost
Multiple diameter specifications, adaptable to different tower diameters and gas flows
Not easily broken, low transport and loading loss

Material	PP Polypropylene
Molding Process	Injection Molding
Appearance	Elevated Hollow Circular Ring
Filling Method	Improperly stacked loading
Corrosion resistance performance	Acid-alkali-resistant
Installation Location	Tower packing layer
Support Component	Grid Plate / Perforated Plate
Purpose	Packed tower
Color	Porcelain White / Transparent
Structural Features	Large gap, high flow rate
Outer Diameter Specification	Multiple size options available

Application Industries

Mass Transfer Packing for Acid-Base Exhaust Scrubbers in Electroplating Industry
Filler for Hydrogen Chloride and Ammonia Absorption Towers in Chemical Enterprises
Filler for Acid-Base Vent Purification Towers in Semiconductor and PV Factories
Acid Mist Purification Tower Filler Layer for Metallurgical Pickling Lines
Reaction Tail Gas Absorption and Solvent Scrubbing Filler for Pharmaceutical Plants
Odor Spray Scrubber Filler for Wastewater Treatment Plants
Filler for Small Scale Filler Towers in Laboratory Fume Treatment

Typical Process Location

Larox Ring is installed in the packing layer of the middle section of scrubbing towers and absorption towers, located between the upper and lower layers of spray pipes or below the spray pipes, supported by a grating at the bottom. The exhaust gas enters from below the packing layer, rises through the Larox Ring bed, while the absorbing liquid sprays downward from above. The gas and liquid come into countercurrent contact in the voids of the packing, and the purified gas continues to rise through a demisting layer for discharge.

During the equipment loading process, after the tower body and support grating are installed, Larox Ring is poured from the manhole or the top of the tower and leveled to the design height. After leveling the surface, the upper pressure plate and spray device are installed. When replacing the packing, the manhole is opened to remove the old packing, inspect the grating and tower wall, and then re-load the packing. The quality of packing loading directly affects gas-liquid distribution and purification efficiency. It should be avoided to have local voiding and uneven density. Before loading, confirm that the ring diameter matches the tower diameter, ensure the Larox Ring is clean and free of fragments, and use wet loading or batch loading to minimize damage and bridging. The bed surface should be leveled and the loading height controlled. During operation, liquid distribution is observed through sight glasses, blockage is judged by pressure drop, and the packing is cleaned regularly. Broken, deformed, and heavily clogged old rings are screened out, and new rings are added and leveled again to ensure uniform gas-liquid contact across the entire cross-section.

Packing specifications should be selected based on tower diameter, gas flow rate, and purification requirements. As a general rule, packing diameter should not exceed a certain proportion of the tower diameter; using large packing in small towers can lead to severe wall flow and uneven distribution. For clean gas with high purification requirements, smaller specifications can be selected, offering larger specific surface area and sufficient mass transfer. For dusty or adhesive-containing gas, or when low pressure drop and high flow rate are required, larger specifications should be chosen for their strong anti-clogging capability. Common engineering practice involves calculating packing specifications and bed height based on empty tower gas velocity and liquid-to-gas ratio.

Under the same specifications and loading conditions, the structured packing has a more complex configuration, typically featuring a higher specific surface area and voidage, leading to more thorough gas-liquid contact and higher efficiency, but at a slightly higher price. The Raschig ring, on the other hand, has a simpler structure, high throughput, strong anti-blocking and anti-fouling capabilities, is cost-effective, and has low replacement costs. When the gas is dirty, contains solid or viscous substances, or when economic reliability is prioritized, Raschig rings are often used with appropriately increased specifications. For cleaner gas requiring higher purification efficiency, structured packing can be employed to enhance mass transfer performance. The two types of packing can also be combined in layers within the same tower: the lower section near the inlet uses large-scale anti-blocking packing, while the upper section employs high-efficiency packing for fine treatment, balancing anti-blocking and efficiency. Actual performance also depends on spray distribution, packing height, and gas-liquid ratio. Selection should be based on pollutant concentration and compliance requirements, with reference to similar project packing configurations when necessary.

The height of the packing layer is determined based on the inlet concentration of pollutants, the required purification efficiency, and the mass transfer performance of the packing itself. The higher the inlet concentration and the stricter the emission requirements, the more mass transfer units are needed, and the taller the bed becomes. Packing height is not always better; excessive bed height increases bed resistance and fan energy consumption. When liquid distribution is poor, wall flow and channel flow occur, further increasing packing height offers limited efficiency improvement. In engineering practice, the total height is often divided into several sections, each controlled within a reasonable height, with liquid redistributors installed between sections to evenly distribute liquid flowing down the walls across the cross-section. Design calculations determine the height of each section and the total height based on material balance and gas-liquid mass transfer, with a certain margin reserved. Once determined, the number of packing layers should not be arbitrarily added or removed on-site. If adjustment is necessary, it should be based on recalculations considering measured resistance and outlet concentration.

The plastic Raschig rings themselves are acid and alkali resistant and insoluble. Under normal operating conditions, there is no fixed replacement period. Whether to replace them depends primarily on the actual condition of the packing. When the packing is heavily broken, deformed, crystallized, severely blocked by sludge, and the effective specific surface area decreases, leading to a continuous increase in tower resistance and a reduction in purification efficiency, and cannot be restored after rinsing, it should be replaced in batches or as a whole layer. Strengthening the filtration of the circulating liquid, controlling dust and crystalline materials entering the tower, and regularly rinsing the packing and water tank can significantly extend the service life of the packing. Daily records of changes in tower resistance, circulating liquid turbidity, and outlet concentration should be kept as a basis for determining cleaning and replacement. During replacement, remove the old packing, inspect the support grating and spray nozzles, and then refill according to specifications. For towers with varying degrees of aging and blockage, the most severely affected sections can be replaced first to gradually restore overall performance.

Before loading, check if the bottom grating plate or porous plate is secure, if the gaps are smaller than the minimum filler size, if the support rings and pressure plates are complete, and ensure the tower is clean of debris. For dry loading, evenly spread the filler from the manhole and spread it in batches to avoid local accumulation and voids. For wet loading, first fill the tower with water to the bed height, then slowly pour the filler to reduce breakage and bridging using the water's cushioning effect, and drain the water after loading. During the loading process, avoid stepping directly on the filler; if entry is necessary, use wooden planks or specialized platforms to distribute weight. After completing the entire layer, level the surface with a rake to ensure uniform height and consistent density, paying close attention to filling near the tower wall to prevent wall flow and gas short-circuiting. Finally, install and secure the upper pressure plate or pressure screen to prevent the filler from being blown or fluidized during operation.

For minor blockages, online flushing can be performed by increasing the rinsing flow rate and extending the rinsing duration using the spray system. Alternatively, after shutdown, high-pressure water can be used from the manway to flush the packing layer from top to bottom, dislodging crystals, dust, and sludge, which are then discharged into the sump with wastewater. Soluble salt crystals can be cleaned by circulating dilute acid or dilute alkali corresponding to the medium for immersion cleaning to enhance dissolution. However, the suitability of the cleaning fluid concentration and temperature for the tower, packing, and sealing components must be verified first. After cleaning, the tower should be thoroughly rinsed with clean water. If the blockage is severe, resistance remains high even after flushing, or the packing is aged, broken, or hardened, the packing should be removed for a comprehensive cleaning of the tower, grating, and nozzles. New packing should then be installed to restore the purification capacity. During packing removal, inspect the tower wall, support rings, and spray pipes. Reinstall the packing, spread it evenly, and secure the pressure plates. Maintain regular rinsing and resistance records for routine management.

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