So this is what the actual tower equipment and its internals look like!

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Usually we only see tower structures in books, but what do they really look like? The actual appearance of the tower equipment: The string screen tray assemblies that are to be installed; the two-channel trays installed in certain sections of the tower; the tray support grid components; the structured packing used in towers with a diameter of 1.425 m; the auxiliary scraper belts that are already installed before leaving the factory; the support grids and the filling bed above them; the channel-type liquid distributors that are to be installed; the channel-type distributors installed in the various sections of the tower; the liquid transfer from the annular channels to the liquid distributors. What are the components of tower equipment? Apart from the various types of internal components, the other components of tower equipment are more or less similar. It mainly includes the following parts: 1. Tower body – The tower body is the outer shell of the tower equipment. A common tower structure consists of cylinders with equal diameter and wall thickness, along with elliptical end caps that serve as the top and bottom covers. It includes a cylinder, end caps (mainly elliptical heads), and connecting flanges. In addition to considering the operating pressure (internal or external pressure) and temperature, wind loads, seismic loads, and eccentric loads must also be taken into account, as well as requirements regarding strength, stiffness, and stability during pressure testing, transportation, and lifting. The tower is composed of several tower sections, each containing a certain number of trays, and the sections are connected to each other using flanges. 2. Internal tray elements: The internal components of a tower include trays, packing, and support devices, among others. Plate towers, integral tray types: classified by assembly method into fixed-spacing tray towers ； Overlapped tray. (1) Spaced tube tray: Several trays within the same tray section are supported and fixed to the supports inside that section using spacing tubes and tie rods; the spacing tubes serve to support the trays and maintain the distance between them. The gap between the tray and the tower body is sealed with soft packing and compressed by a compression ring, as shown in the figure. The height increases as the tower diameter increases. (2) Overlapped trays: A set of supports is welded to the lower part of the tower section; the bottom tray is supported on these supports, and subsequent trays are installed one after another. The spacing between the trays is maintained by the supports beneath them, and the level of the trays can be adjusted using three adjustment screws. The gap between the tray and the tower wall is also sealed with soft packing, which is compressed by a compression ring. Segmented trays have a larger diameter, which facilitates their manufacturing, installation, and maintenance. They are inserted into the tower through manholes and welded to the tray support members on the inner wall of the tower. Welded as a single cylinder, without segmented towers. 3. Internal liquid dropping pipes: The structural types of liquid dropping pipes are circular and arc-shaped. Circular liquid dropping pipes are used in situations where the liquid load is low, the tower diameter is small, and foam formation is unlikely to occur (a), (b), (c)). In the arc-shaped type, only a small portion of the cross-section is used for effective liquid dropping. The downcomer of a monolithic tray is generally welded directly to the tray sheet. The downcomers of segmented trays come in vertical and inclined types; the connection between these downcomers and the tower body can be either foldable or welded in place. 4. Liquid receiving trays: These trays ensure a liquid seal at the outlet of the downcomers and are located on the tray itself. There are two types: flat and concave. Flat receiving trays are used in situations where materials tend to polymerize. It can prevent dead zones from forming on the tray. Figure (a) shows a detachable flat liquid receiving tray. The concave liquid receiving tray provides cushioning for fluid flow; it is used when the pressure drop between the liquid flow tube and the liquid receiving tray exceeds 25 mm of water column, or when an inclined liquid flow tube is used. It can reduce the liquid level at the tray inlet, allowing for a smoother flow of liquid and facilitating better bubbling in the tray inlet area. The depth of the concave liquid receiving tray is generally greater than 50 mm, but not more than one-third of the plate spacing; otherwise, the plate spacing should be increased. 5. Internal liquid seal disk and overflow weir: The liquid seal disk is installed at the downcomer of the lowest tray in the tower or tower section in order to ensure a liquid seal at the outlet of the downcomer. Tear hole: Used for draining liquid during shutdown. Overflow weirs are classified into inlet weirs and outlet weirs based on their location. Inlet weir: A flat liquid receiving plate that ensures a liquid seal in the downcomer, allowing the liquid to flow evenly into the lower trays while reducing the impact of the liquid flow in the horizontal direction; it is located at the entrance where the liquid flows in. Outlet weir: Maintains the liquid level on the tray and ensures uniform distribution of the fluid. The maximum overflow rate at the outlet weir is < 100–130 m3/(h·m). Determine the length of the outlet weir. Single-stream tray: outlet weir length Lw = (0.6～0.8)Di, where Di is the inner diameter of the tower ； Two-stream tray: outlet weir length Lw = (0.5～0.7)Di. Outlet weir height hw: Determined by factors such as material properties, tower type, liquid flow rate, and tray pressure drop. 6. Internal packing, support devices, liquid distributor; Classification of packing: Packing in packed towers: Bulk packing ； Regular packing. Bulk packing material: It is usually installed in a random pile, but it can also be arranged neatly. Particulate bodies with a certain shape structure, also known as granular fillers. Bulk packing: Ring-shaped ； saddle shape ； Annular saddle-shaped. Support device for the packing: Installed at the bottom of the packing layer. Function: Prevent the filler from passing through the support device and falling down ； Weight of the packing layer during support operations ； Ensure an adequate porosity to allow free passage of both gas and liquid phases. Requirements: sufficient strength and stiffness, simple structure for easy installation, and corrosion resistance. Grid support – Liquid distributor in the packed tower. Function: To distribute the liquid feed and return liquid evenly over the surface of the packing, thereby creating an initial distribution of the liquid. Key design considerations: the density of liquid distribution points, the method of distributing the liquid at these points, and the uniformity of the liquid distribution. This includes the structure of the distributor, the determination of its geometric dimensions, the level height or head pressure, and resistance, among others. Distribution parameters: When D ≤ 400 mm, one spray point is installed for every 30 cm2 of the tower cross-section; when D ≤ 750 mm, one spray point is installed for every 60 cm2 of the tower cross-section; when D ≤ 1200 mm, one spray point is installed for every 240 cm2 of the tower cross-section. For structured packing, where even distribution of the liquid is required, one spray point is installed for every 20–50 cm2 of the tower cross-section. Location: 150–300 mm above the surface of the packing layer. Structural classification: tubular, trough-type, spray-type, and disc-type. The gravity-type tube-type liquid distributor has a funnel-shaped inlet, equipped with a metal wire mesh filter to prevent solid impurities from entering the liquid distributor. The level tube 2 and the liquid distribution tube 3 can be made of round tubes or square tubes. The liquid distribution pipe 4 is generally made of a circular tube, with holes drilled in its bottom to distribute the liquid over the upper part of the packing layer. Grooved liquid distributor: a gravity-type distributor that distributes liquid based on the liquid level (the gravity of the liquid). It is divided into: pore flow type and overflow type. The structure of the spray-type liquid distributor is similar to that of the pressure-type tubular distributor; under liquid pressure, the liquid is distributed over the filler through nozzles (rather than the spray holes of the tubular distributor), as shown in the figure. Early showerheads were rarely used nowadays due to their poor distribution performance. Currently, nozzles are used in place of showerheads to achieve a better distribution effect. Key design elements of the nozzle include its structure, layout, spray angle, liquid flow rate, and installation height. The liquid ejected from the nozzle forms a cone shape; to achieve even distribution, the bases of these cones need to overlap to some extent, with an overlap rate of 30–40%. The nozzle is installed about 300–800 mm above the packing, at an injection angle of approximately 120°. Disk-type liquid distributors are divided into: pore flow type and overflow type ； Disk-type orifice flow liquid distributor structure: Liquid spray holes are provided on the base plate, along with lift pipes. The flow channels for gas and liquid are separated: the gas rises through the gas lift pipe, while the liquid maintains a certain level on the chassis and flows down through the spray holes. The cross-section of the riser can be circular or conical, with a height generally below 200 mm ； Function of the liquid collection redistributor: Eliminate \"wall flow\" and prevent a \"dry cone\"” ； Eliminate the radial concentration difference between gas and liquid. Method: Install liquid collection and redistribution devices between each section of the packing. Function of the gas distributor: to ensure even distribution of gas. Purpose of the packing compression and positioning device: to prevent poor distribution of gas and liquid phases as well as fluidization of the packed material, which can occur when the gas flow rate is high or pressure fluctuations are significant. Packaging compressor: Used for brittle bulk packing materials such as ceramics and graphite. Packing layer limiter: Used for bulk packing made of metal or plastic, as well as various structured packings. It is made of steel rings, grills, and metal mesh; when the diameter of the tower is large, its weight can be increased appropriately. It is made of steel rings, grills, and metal mesh; when the diameter of the tower is large, its weight can be increased appropriately. 7. Supports: The supports of the tower are the connecting elements that secure the tower to its foundation; skirt-type supports are generally used. It must ensure that the tower is positioned in the correct location to function properly. To this end, it should possess sufficient strength and stiffness to bear the weight of the entire tower under various operating conditions, as well as loads caused by wind, earthquakes, and other factors. The most commonly used tower support is the skirt support, also known as a skirt base. 8. Demister: The demister is used to capture liquid droplets carried in the airflow. The use of efficient demisters is essential for recovering precious metals, improving separation efficiency, enhancing the operational conditions of equipment downstream from the tower, and reducing environmental pollution. 9. Nozzles: The nozzles of tower equipment are used to connect the process pipelines, linking the tower equipment with related devices to form a system. Based on their purpose in the process, they are classified into inlet pipes, outlet pipes, inlet air pipes, exhaust air pipes, return pipes, side-line extraction pipes, and instrument connection pipes, etc. Liquid feed (including reflux) pipe 1 – Feed inlet ； 2 – Inlet weir, gas inlet pipe, gas outlet pipe. 10 – Manholes and access holes. Manholes and access holes are generally provided for the purposes of installation, maintenance, inspection, and filling with packing; they have different requirements depending on whether it is a plate tower or a packed tower. 11. Lugs: The transportation and installation of tower equipment, especially as the equipment becomes larger in size, is often a crucial task at factory construction sites. For easy lifting, lifting lugs can be welded to the tower equipment. 12. Hangers: Hangers are installed at the top of the tower to facilitate the transportation of components inside the tower during installation and maintenance. 13. Operation Platform