Questions regarding one-way conversion rates.

Reply 1# ripp: The one-way conversion rate refers to the conversion rate of the feedstock, calculated based on the materials at the inlet and outlet of the reactor (there is only one reactor), without taking into account any recycle stream. The overall conversion rate takes into account the recycle stream; it is the raw material conversion rate calculated based on the materials at the inlet and outlet of the reactor (which is a single reactor). Generally, the overall conversion rate is definitely higher than the one-way conversion rate; should they be calculated against each other...? No, haha. The conversion rates under different circulation ratio conditions don’t seem meaningful to me. It depends on the selectivity, that is, the amount of target product produced. The level of cycling should be determined primarily based on the requirements regarding selectivity; if increasing the number of cycles can promote the formation of the target product, then such an increase should be made, but the energy consumption associated with cycling also needs to be taken into account. Otherwise, cycling should not be used.

Reply to 1# ripp: It depends on the production requirements to decide whether to add a circulation volume

This is also closely related to the choice of reactor type; for example, when a PFR plug-flow reactor is used, if the recycle ratio becomes high enough, it behaves like a CSTR completely mixed-flow reactor, thereby significantly reducing the conversion rate of the feedstock. The material circulation in the reactor is essentially a form of material backmixing, which has an adverse effect on the reaction. However, during the design process, implementing a loop is equivalent to increasing the processing volume of the reactor, which in turn increases the amount of material that can be processed per unit time, thereby improving the conversion rate of the raw materials. You’d better try running it with a simulation software like Hysis or something.

This post was last edited by zilch325 on 2011-3-31 at 10:11. The overall conversion rate is set manually; it essentially represents the utilization rate of the raw materials you wish to achieve. For example, in the case of Fischer-Tropsch synthesis, you want a conversion rate of 98% for the entire syngas stream; in other words, considering the cycle, 98% of the syngas should be converted into oil. The one-way conversion rate is related to the catalyst, reactor, reaction conditions, etc. Under the given conditions, it can be considered to reflect the catalyst's activity. For example, in the case of no circulation, the one-pass conversion rate for a fixed-bed FT is 30–40%. Generally, it is difficult to increase the one-way conversion rate, as there are many limiting factors such as catalyst activity, reaction temperature, reactor design, and so on. Reaching a higher overall conversion rate is relatively easy; all that is needed is to increase the circulation volume. But in many cases, a high overall conversion rate is not required; it is mainly a matter of economic considerations, not a technical issue.