【Daily Question No. 293】October 26, 2018
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【Daily Question No. 293】October 26, 2018: Briefly describe the impact of changes in space velocity on production. A higher space velocity results in a larger processing capacity, but the degree of reaction decreases. Reducing the space velocity increases the residence time of the reactants within the catalyst, thereby increasing the degree of reaction. However, a lower space velocity leads to a reduced processing capacity; too low a space velocity can promote cracking reactions, reduce product yield, increase hydrogen consumption, and cause more carbon deposition on the catalyst. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) Correct: 3 wealth, Incorrect: 1 wealth ； Mass posting of posts – rated based on the lowest score ； Replies that are unrelated to the answer are considered spam and will be deleted immediately. For management purposes, if you need to view content from a few days ago, please go to https://bbs.hcbbs.com/home.php?mod=space&uid=3862647&do=thread&view=me&from=space through the summary post below
Volume space velocity: the volume of feed per hour (liquid (LHSV) or gas (GHSV)) divided by the volume of catalyst loaded. Weight space velocity (WHSV): the weight of feed per hour (liquid or gas) divided by the weight of catalyst loaded. Additionally, space velocity can also be expressed as actual space velocity or effective space velocity; in industrial radial reactors, the catalyst in the sealing layer must be removed after it is loaded, as this portion of the catalyst does not participate in the reaction. Therefore, the concept of effective space velocity exists: it is the total weight of the catalyst minus the weight of the catalyst in the sealing layer, and this value is used as the actual or effective weight for calculating space velocity. Physical meaning: The physical quantity processed per unit time per unit reaction volume. The higher the air velocity, the greater the production capacity of the reactor.
A high space velocity results in a large processing capacity, but the reaction depth decreases. Reducing the space velocity increases the residence time of the reactants within the catalyst, thereby enhancing the reaction depth. However, lowering the space velocity reduces the processing capacity; an excessively low space velocity promotes cracking reactions, lowers the yield of products, increases hydrogen consumption, and leads to more carbon deposition on the catalyst.
A high space velocity results in a large processing capacity but reduces the reaction depth. Reducing the space velocity increases the residence time of the reactants in the catalyst, thereby increasing the reaction depth. However, this reduction in space velocity leads to a decrease in the processing capacity; an excessively low space velocity promotes cracking reactions, reduces the yield of products, increases hydrogen consumption, and causes more carbon deposition on the catalyst.
Reaction space velocity refers to the amount of gas processed per unit volume of catalyst per unit time under specified conditions. The unit is simplified to h^-1. Space velocity reflects the processing capacity of the unit. There are two ways to express the air velocity: volume air velocity and mass air velocity. The value of the space velocity affects the selectivity and conversion rate of the methanol synthesis reaction.
A high space velocity can increase the production capacity of the device, but an excessively high space velocity results in incomplete reaction. The opposite.
Volumetric flow rate is the volume of material that passes through the reactor volume per unit time. Air velocity reflects the processing capacity of the device. Industrially, higher space velocities are desired, but the space velocity is limited by the reaction temperature. Depending on catalyst activity, feedstock properties, and reaction depth, the space velocity varies over a wide range (0.5–10 h). Heavy oils and oils obtained through secondary processing generally use lower space velocities; during hydrorefining, reducing the space velocity can increase the desulfurization rate, denitration rate, and olefin saturation rate.
A high space velocity results in a large processing capacity, but the reaction depth decreases. Reducing the space velocity increases the residence time of the reactants within the catalyst, thereby enhancing the reaction depth. However, lowering the space velocity reduces the processing capacity; an excessively low space velocity promotes cracking reactions, lowers the yield of products, increases hydrogen consumption, and leads to more carbon deposition on the catalyst.
A high space velocity results in a large processing capacity, but the reaction depth decreases. Reducing the space velocity increases the residence time of the reactants within the catalyst, thereby enhancing the reaction depth. However, lowering the space velocity reduces the processing capacity; an excessively low space velocity promotes cracking reactions, lowers the yield of products, increases hydrogen consumption, and leads to more carbon deposition on the catalyst.
Increasing the space velocity reduces the residence time of the feed material in the catalyst bed, resulting in less reaction depth and poorer product purification； By reducing the space velocity, the residence time of the feedstock in the catalyst bed increases, resulting in greater reaction depth and better purification effects; however, this also increases the likelihood of coking. Therefore, hydrogenation production should select an appropriate space velocity based on the properties of the catalyst and feedstock
Volumetric flow rate is the volume of material that passes through the reactor volume per unit time. Air velocity reflects the processing capacity of the device. Industrially, higher space velocities are desired, but the space velocity is limited by the reaction temperature. Depending on catalyst activity, feedstock properties, and reaction depth, the space velocity varies over a wide range (0.5–10 h). Heavy oils and oils obtained through secondary processing generally use lower space velocities; during hydrorefining, reducing the space velocity can increase the desulfurization rate, denitration rate, and olefin saturation rate.