What are the structural features of the internals in multi-layer insulated shock-type synthesis towers?

Multi-layer insulated quench-type synthesis tower internals: It divides the entire catalyst bed into several sections, with quenching elements placed between these sections. Advantages: Simple structure; apart from the cold and hot gas mixing distributors, there are no other components in each section of the catalyst layer ； Large catalyst loading ； The air flow and temperature distribution are uniform in the same plane, and cold air adjustment is convenient ； The airflow resistance of the entire tower is low. Disadvantage: The cold shock gas only serves to cool down the mixture; it does not participate in the reactions of the catalysts in the upper layers. With each cold shock, the ammonia content in the mixture is diluted, thereby reducing the overall ammonia concentration in the entire tower ； Each bed layer is exposed to fresh gas containing toxic gases, which can thus cause poisoning in all layers simultaneously ； When the net ammonia output is the same, the gas temperature at the outlet of this tower type is slightly lower than that of other tower types; therefore, its heat recovery efficiency is low ； It requires a larger heat exchanger surface area compared to other tower types.

This post was last edited by 654262293 on 2011-12-25 18:41. Found it elsewhere, sharing! The multi-stage cold-quench methanol reactor developed by ICI in the UK is the most commonly used type of reactor in methanol production facilities abroad; it is a fully axial multi-stage cold-quench synthesis reactor. Its simple structure is its unique advantage. The synthesis tower consists of a tower body, multiple bed layers, and a specialized triangular distributor. Diamond-shaped distributors are embedded in the catalytic bed, with one set installed at each level of the bed; a total of three to four sets are installed throughout the tower. It enables the cold shock gas and reaction gas to mix evenly. The catalyst has a large loading capacity and a long service life, typically up to 6 years. The downside is that it involves an adiabatic reaction, resulting in large axial temperature differences within the catalyst bed. To control the temperature of the reactor bed, cold feed gas is used; cold feed gas is injected between various sections of the catalyst bed in order to lower the temperature of the reaction gas. Therefore, the cooling process diluted the methanol content in the reaction gas, affecting the catalyst utilization rate. To prevent the catalyst from overheating, a high space velocity is used; the methanol content in the gas leaving the tower is less than 4%, and the amount of by-product steam is low, making it impossible to recover the high-energy reaction heat. The circulation volume is large, resulting in high tower pressure, typically ranging from 0.1 MPa to 0.4 MPa, which leads to high operating costs. Due to the constraints imposed by friction, its height-to-diameter ratio is small, usually ranging from 2.2 to 4.0; when made larger, its diameter becomes quite large (4–6 meters), which makes transportation difficult ； Due to the simple structure of ICI’s cryogenic methanol synthesis towers, their reliable operation, ease of handling, design flexibility, low material requirements, low investment costs, and ease of scaling up, they remain a major type of tower used in large-scale methanol plants. ICI still holds the record for the largest single-unit capacity; it has several units with a capacity of 3,000 t/d, and it is reported that the largest units currently in use have a capacity of 7,500 t/d. To address the shortcomings of the cold-jet towers, in the 1980s ICI developed two types of cold-tube towers. One of these was the water-cooled tower known as LCM. Unlike methanol synthesis towers of the Ruchi type that use tubular reactors, in this design water flows inside the tubes while the catalyst is placed outside them; this setup allows the expansion issues associated with the tubes to be addressed more effectively through its expansion ring structure. Additionally, it features a radial-flow catalytic bed design, which helps reduce resistance while increasing the heat transfer coefficient. Currently, many large-scale methanol plants around the world use multi-stage quench-type methanol synthesis towers. In recent years, on the basis of what already existed, extensive and diverse improvements and enhancements have been made to cold-jet synthesis towers, resulting in the introduction of a series of improved versions of such towers. The cold-stirred synthesis tower has the following characteristics: ——The synthesis tower has a high production capacity per unit, making it suitable for large or super-large plants. ——The methanol synthesis tower has a simple structure, and the catalyst is easy to install and remove. ——Cold shock is applied using a specially designed distribution system, making temperature control more convenient. ——The high-grade heat energy generated during methanol synthesis cannot be recovered, resulting in a large volume of circulating gas in the synthesis loop. ——There is backmixing between catalyst sections, resulting in a low methanol content at the outlet of the synthesis tower. ——The space-time yield of the catalyst is low, and a large amount of it is required.