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Selection of Packing Material in Packed Bed Scrubber

Views: 8     Author: China Xicheng     Publish Time: 2021-06-28      Origin: China Xicheng

Packed bed scrubbers can also be called packed towers, spray towers, etc. They are currently widely used in industrial waste gas treatment. Due to factors such as the composition of the waste gas and installation environment, they need to be customized to be square or round. The composition of the filler added in the scrubber is also different.

Packing layer: The packing layer is placed on top of the defogging layer and spray layer. The main fillers are multi-faceted hollow balls and Raschig rings. The packing layer in the spray tower is used as a mass transfer device for the contact components between the gas and liquid phases. The bottom of the packing tower is equipped with packing support plates, and the packing is placed on the support plates in a random pile. A packing pressure plate is installed above the packing to prevent it from being blown by the rising airflow. The spray liquid of the packed bed scrubber is sprayed onto the packing from the top of the tower through the liquid distributor, and flows down the surface of the packing.

Polyhedral spherical packing inside packed bed scrubber

What is filler

Filling generally refers to materials that are filled in other objects.

In chemical engineering, the filler refers to the inert solid materials installed in the packed tower, such as Pall rings and Raschig rings, etc., whose function is to increase the gas-liquid contact surface and make them mix strongly with each other.

In the field of sewage treatment, it is mainly used in the contact oxidation process, and microorganisms will accumulate on the surface of the filler to increase the surface contact with the sewage and degrade the sewage.

Advantages: simple structure, small pressure drop, easy to use corrosion-resistant non-metallic materials, etc. It is quite suitable for gas absorption, vacuum distillation and processing of corrosive fluids.

Disadvantages: When the tower neck increases, it causes uneven gas-liquid distribution, poor contact, etc., resulting in a decrease in efficiency, which is called the amplification effect. At the same time, the packed tower has disadvantages such as high weight, high cost, troublesome cleaning and maintenance, and large packing loss.

Filler selection criteria

The geometric characteristic data of fillers mainly include specific surface area, porosity, filler factor, etc., which are the basic parameters for evaluating filler performance.

(1) Specific surface area The surface area of the filler per unit volume of the filler is called the specific surface area, denoted by a, and its unit is m2/m3. The larger the specific surface area of the packing, the larger the gas-liquid mass transfer area provided. Therefore, the specific surface area is an important index to evaluate the performance of the filler.

(2) Porosity The void volume per unit volume of the filler is called porosity, expressed in e, and its unit is m3/m3, or expressed in %. The greater the porosity of the filler, the greater the gas passing capacity and the lower the pressure. Therefore, porosity is another important indicator for evaluating the performance of fillers.

(3) Filler factor The ratio of the specific surface area of the filler to the cubic porosity, namely a/e 3, is called the filler factor, expressed as f, and its unit is 1/m. It represents the hydrodynamic properties of the filler, the smaller the f value, the smaller the flow resistance

Material selection of packing

The material of the filler is divided into three categories: ceramic, metal and plastic.

(1) Ceramic filler

Ceramic fillers have good corrosion resistance and heat resistance. Ceramic fillers are cheap and have good surface wetting properties. They are brittle and fragile. It is more common in the process of gas absorption and gas washing.

(2) Metal filler

The metal filler can be made of a variety of materials, and corrosion is the main consideration when choosing.

(3) Plastic packing

Plastic filler materials mainly include polypropylene (PP), polyethylene (PE) and polyvinyl chloride (PVC), etc. Generally, polypropylene is used in China. The plastic filler has good corrosion resistance and can withstand the corrosion of general inorganic acids, alkalis and organic solvents. It has good temperature resistance and can be used below 100°C for a long time.

PP flame retardant Raschig ring

Plastic filler is light in weight, low in price, has good toughness, impact resistance, is not fragile, and can be made into a thin-walled structure. It has large flux and reduced pressure, and is mostly used in devices such as absorption, desorption, and dust removal.

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