Dear all,
I am designing an Ultrafiltration (UF) membrane coupled with a CSTR. It is desired to utilized a dead end stirred reactor. The main purpose is to separate the enzyme used from the final product stream in the enzymatic hydrolysis of sucrose. Therefore, how would a UF membrane be normally installed? Is there a design handbook which i could follow ?
Thank you in advance and any help would be highly appreciated!
I have no experience with enzyme separation, but a lot of experience using membrane filtration to separate unreacted sugars from the reaction products, such as hydroxymethyl furfural, for example. Due to the very large molecular size of enzymes (several thousands daltons), a separation from sucrose (342 da), glucose and fructose(both 180 da) by ultra-filtration should be very easy and efficient.
The difficulty to pilot that separation is that you would need membrane-filtration equipment, which very few labs have, and which can be on the expensive side. I cannot tell you more on the costs without knowing at which size you are planning to operate.
I would install the UF equipment on a recycling loop, from and to the CSTR. I do not know the concentrations at which you are planning to operate, but let's suppose here that you can achieve a 90% Recovery rate in UF (i.e. the flow of the Permeate is 90% that of the Feed). The UF-Retentate, 10% of the UF Feed flow, would contain nearly 100% of the enzyme dissolved in the Feed, and a tiny bit more than 10% of the sugars. That Retentate coming out of the UF plant under pressure (typically 5-10 bars) could be readily sent back to the CSTR. You could even use that potential energy (pressure) to hydraulically stir the CSTR, by injecting it through so-called mixing nozzles. Whether that can be enough to avoid the use of a mechanical mixer depends on the Reactor's dimensions.
THE UF-Permeate would contain unreacted sucrose, and obviously your hydrolysis products (glucose + fructose). You could even devise a second filtration step, this time through a NF membrane, to separate the unreacted sucrose, from the smaller molecular-size hydrolysis product. This is however more delicate to achieve.
As to sizing the UF membrane, count on a flux rate of 30-40 liters per m2 and per hour. So, should you want to produce 1000 l/h of your sugar solution (i.e. the UF Permeate), you should install approximately 30 m2 of UF membrane. Hollow-fiber modules could also be considered for that application.
I hope these considerations helped you.
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