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Section 3: Various Commonly Used Columns. Columns: (1) What are columns? Columns are important manufacturing devices that are widely used in industries such as chemical and petroleum processing. Its shape is that of an upright cylindrical container; its height is much greater than its diameter. It looks like a tower from the outside, which is why it is commonly referred to as a tower-shaped vessel. (2) The main function of the tower: to provide an opportunity for thorough contact between the gas and liquid phases, enabling mass and heat transfer processes in chemical production to take place rapidly and efficiently, as well as to allow for the timely separation of the gas and liquid phases after they come into contact. For example, towers are commonly used in unit operations such as the distillation, absorption, extraction, purification, dust removal, and cooling of materials. When a tower is used as a reaction device, it is called a reaction tower. When used as a distillation apparatus, it is called a distillation tower. Working principle of the shell-and-tube synthesis tower: Ø The shell-and-tube synthesis tower adopts a tube-in-shell structure. The catalyst is loaded in the tube side, while boiler water is added to the shell side; heat is removed after boiling. The reaction temperature is regulated by controlling the pressure of the boiling water in the reactor’s shell side. The operating temperature ranges from 190–210 °C, and the operating pressure is 1–3 MPa. This type of tower catalyst bed has a small temperature difference, operates more stably, and achieves a high conversion rate; it can also produce medium-pressure steam as a by-product. However, since the shell side occupies a large amount of space, the catalyst loading capacity is low (only 35%). To address the issue of thermal expansion stresses, such towers must use special stainless steel materials with two different coefficients of expansion. The tubes need to be imported, which results in a long supply cycle and high equipment costs. Ø In recent years, to meet the demands of large-scale production, Lurgi has developed combined synthesis units that consist of shell-and-tube reactors and tube-type reactors in series. These units utilize water cooling and air cooling for heat transfer respectively; the preheated gas exits from the top and enters the catalyst bed inside the shell-and-tube reactor where it reacts. Boiler feed water is passed outside the tubes, where it boils and absorbs heat. The gas exiting the reactor then goes to the catalyst bed at the upper part of the tube-type reactor to continue reacting. The gas exiting the tube-type reactor regains some heat, and after its temperature drops, it enters a separator for separation. The gas is recycled as circulating gas; due to the use of series-connected synthesis towers, the amount of gas that needs to be recycled is relatively small, which helps to save energy consumption. The Lurgi process utilizes the reaction heat to generate medium-pressure steam, enabling effective energy recovery; it offers better economic efficiency and operational reliability. Ø Larger production facilities can significantly reduce product investment and costs. The enlargement of equipment has become a trend in the industrial development of our country. The core equipment for synthesis is the synthesis tower. Choosing a stable, energy-efficient, high-yield, and cost-effective synthesis tower is crucial for manufacturers. Considering aspects such as operation, structure, materials, and maintenance, the basic requirements for a synthesis tower are: 1. Good stability and reliable structure ； 2. Operationally, the catalyst temperature needs to be easy to control and flexible to adjust ； The conversion rate of the synthesis reactor is high ； Catalysts feature high production efficiency, as well as high activity and stability ； Reaction heat that can be recovered as high-grade energy ； The gas is evenly distributed in the bed layer ； Pressure decreases. 3. The catalyst can be easily heated and reduced, with thorough reduction achieved ； 4. Gas can pass through the catalyst layer evenly, with low resistance and high ethylene glycol yield ； 5. Stable operation and easy adjustment, capable of adapting to changes in various operating conditions ； 6. The catalyst is easy to load and unload, and its manufacturing, installation, and maintenance are simple ； 7. The connections and insulation of various internal components are appropriate, allowing them to move freely within the tower and preventing the generation of thermal stress. Basic structure of the tower: 1. Packing 2. Support grating 3. Liquid collector 4. Liquid collection ring 5. Multi-stage trough-type liquid distributor 6. Packing compression ring 7. Support grating 8. Steam inlet pipe 9. Tower bottom 10. Loop to the reboiler 11. Skirt 12. Base ring Section 4: Several commonly used distillation tower packings – Raschig ring packing, Pall ring packing, stepped ring packing, rectangular saddle ring packing, stainless steel corrugated wire mesh packing