Packed tower

The principle behind selecting redistributors is that, as the condensate flows downward through a certain height of packing, it tends to flow along the tower walls, which affects the heat and mass transfer between the gas and liquid phases on the surface of the packing and ultimately impacts the efficiency of the tower. Therefore, a conical redistributor is installed at intervals corresponding to a certain height of packing (usually 3–5D), in order to direct the liquid flowing along the tower walls toward the center.

Most importantly, there is the issue of the wall effect in the tower (fluids tend to flow toward the tower walls, as these areas have a higher porosity and thus less resistance to flow). A liquid collector is used to collect liquid and then redistribute it. I remember it being something like a round disc with many holes in it.

As the liquid flows downward through the packing layer, it tends to concentrate toward the tower wall, resulting in an increasing flow rate of liquid near the wall; this phenomenon is known as wall flow. The wall flow effect causes uneven distribution of the gas-liquid phases in the packing layer, thereby reducing the mass transfer efficiency. Therefore, when the packing layer is high, it is necessary to divide it into sections and install redistribution devices in between, whose function is to prevent wall flow from occurring. The liquid redistribution device consists of a liquid collector and a liquid redistributor. The liquid that flows down from the upper packing is collected by the liquid collector and then sent to the liquid redistributor, where it is redistributed before being sprayed onto the lower packing. Forms of redistributors: there are disc type, trough type, and frustum type, etc.

The main function of the redistributor should be to improve material efficiency

The commonly used liquid collectors are the vented liquid collector and the baffle-type liquid collector. The structure of the riser-type liquid collector is similar to that of the tray-type gas-liquid distributor, except that it lacks a liquid distribution mechanism. A baffle-type liquid collector is a common liquid collection device in towers. While collecting the liquid, it can be extracted in the liquid phase. The baffle-type liquid collector features complete collection with very low gas-phase resistance. It is a device placed beneath the packing layer, used to collect the liquid in the tower whose distribution uniformity no longer meets the requirements, so that it can be redistributed or withdrawn via a side stream. The baffle-type design allows for the complete collection of liquid; its resistance is negligible, and it has little impact on the uniformity of gas distribution. It features a large free area and low gas resistance, usually below 2.5 mm of liquid column, making it highly suitable for vacuum operations

The main goal is to reduce wall flow, ensure uniform distribution of the liquid, and thus facilitate good gas-liquid contact.

Primarily, liquid is collected through multiple liquid collectors in the packed tower, which helps to reduce wall effects and redistribute the liquid flow, thereby achieving a relatively ideal mixing effect between the gas and liquid phases. Based on our practical applications, sometimes choosing the right type and size of liquid collector allows for better results, even at the cost of some filler space

Very detailed, thank you! It would be perfect if pictures of installing the bottom ring and the vertical ring could be provided

It’s available in books on principles of chemical engineering; you can refer to them!

The liquid flows downward through the packing layer, creating a wall flow. Wall flow causes uneven distribution of the gas-liquid phases, thereby reducing mass transfer efficiency. Therefore, for the higher sections of the packed tower, a redistribution device is installed in the middle; its purpose is to prevent wall flow from occurring.