[Weekly Topic] June 20-27, 2011
Thread Content
What are the main criteria for the stratified and zoned design in the converter design for coal-to-methanol production, as well as its advantages and disadvantages? Note: 1. If participants offer rewards of varying degrees, please feel free to speak up. 2 In accordance with the forum rules, please do not use hidden replies; otherwise, no scores will be given.
1. The layered or segmented design of the shift converter is mainly due to the fact that the shift reaction is an exothermic reaction; the gas exiting from one section or layer is cooled before entering the next section or layer, thereby reducing the temperature in that layer or section and facilitating the progress of the shift reaction in the forward direction. 2. Shift converter: The shift converter is designed with layers or sections mainly because the shift reaction is an exothermic reaction. By dividing it into two to three layers or sections, it is possible to better control the temperature at the hot spots within the converter, preventing overheating and thus protecting the catalyst.
The main criteria for the stratified and segmented design in converter design are conversion rate and conversion depth； The advantage is reduced methanation and prevention of heat accumulation. The disadvantage is that the converter is difficult to manufacture, as stratification must be arranged inside it.
First, it is necessary to understand what layers are and what segments are. Those with inter-stage coolers are called segmented, while those without them are called stratified. Our low-temperature transformer is divided into upper and lower layers, with no heat exchange channel in between.
Some higher temperatures result in a faster reaction rate, while some lower temperatures lead to a higher conversion rate; both are achievable
In the furnace replacement design, the layering and segmentation are primarily determined based on the water-to-vapor ratio of the shift process and the concentration of CO after the shift； The main advantages are preventing heat accumulation and overheating of the bed during production, as well as reducing methanation.
Layering and segmentation are both used in single-reactor systems. In layering, the upper layer consists of a protective agent while the lower layer contains the catalyst; the protective agent in the upper layer serves to protect the catalyst below. Segmentation is employed to prevent the furnace temperature from rising too high, as this would make it difficult to control the temperature
Reply to 1# sxtblo: First, the layered or segmented design of the shift converter is mainly due to the fact that the shift reaction is an exothermic reaction. The gas exiting between sections or layers is cooled before entering the next section or layer, which reduces the temperature in that layer or section and thus promotes the shift reaction to proceed in the forward direction. Second: The layered or segmented design of the shift converter is due to the fact that the shift reaction is an exothermic reaction. By dividing it into two to three layers or sections, it is possible to better control the temperature at the hot spots within the shift converter, preventing it from overheating and thus protecting the catalyst.
Many things have been said by those upstairs, but some of the key issues haven’t been clarified. The purpose of the layered design of the converter is to ensure uniform distribution of gas within the catalyst layer； The purpose of the segmented design of the converter is to adjust the catalyst layer temperature to bring it close to the optimal reaction temperature.
The transformation reaction is a gas-solid phase catalytic reaction, which raises the issue of an optimal reaction temperature. To bring the actual temperature close to this value and thereby achieve a high conversion rate, a stepwise cooling method is employed, with cold agents (steam in this case) being added to achieve this goal. However, the onset temperature for the catalytic reaction in low-temperature conversion is already low, and the properties of the catalyst itself are taken into account by using a layered approach to bring the actual temperature close to the optimal temperature curve, while also considering heat accumulation, reaction depth, and gas-phase distribution.
1. To approach the optimal temperature curve, it provides the necessary space for adding a cold shock medium. 2. Similar to the purpose of filler stratification, it redistributes the gas to prevent bias flow in the entire catalyst layer.