tag:blogger.com,1999:blog-8964719845369935777.post2907732034577145221..comments2024-03-29T09:05:29.819-04:00Comments on Chemjobber: Process Wednesday: pH adjustments on scaleChemjobberhttp://www.blogger.com/profile/15932113680515602275noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-8964719845369935777.post-77764345434421009182013-02-14T10:26:09.217-05:002013-02-14T10:26:09.217-05:00Biopharma does this at scale (2500 - 12000L). You ...Biopharma does this at scale (2500 - 12000L). You actually want to minimize number of ports in a pressure vessel to minimize the number of leaks and in the case of biopharma, the points of entry where contaminants can skunk your batch. <br /><br />It ends up being a mixing problem more than anything, agitator design helps but is expensive and you have to know the CFD software reasonably well. Then shear is an issue, in biopharma we add shear protectants and antifoam to deal with it. Blessedly I have not had to deal with titration of anything particularly viscous. <br /><br />Depending on how you are titrating, if you are using carbonate based buffering you can have some % CO2 in the overlay gas to help control a bit. Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-28647443856221899202013-02-14T08:46:05.144-05:002013-02-14T08:46:05.144-05:00Would it not be advantageous for the larger reacto...Would it not be advantageous for the larger reactors to have multiple dosing ports located at different sections/depths of the reactor (all fed through a single loop)? Maybe this is already the case. 15 min. feedback on a 1000 gal tank doesn't seem too bad, but still. How big of a concern is localized concentration at such scale?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-82998643579645621212013-02-13T11:30:23.875-05:002013-02-13T11:30:23.875-05:00pH adjustments at large scale can be problematic a...pH adjustments at large scale can be problematic at times where often entails straightforward engineering issues that are mentioned. However the process chemist may be able to help modulate certain control elements by good selection of the acid or base and possibly concentration variables during lab studies. HCl and NaOH are favored, for legitimate reasons, but on occasion a weaker acid or base choice can provide refined control that may be more forgiving. I have used H3PO4 or AcOH as acids and K2CO3 as base (CO2 evolution manageable with little foaming) in plant settings to avoid over shooting a critical pH range that was hard to achieve with more common choices (with Patience was a luxury did not have).Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8964719845369935777.post-22660466165658930742013-02-13T10:44:09.406-05:002013-02-13T10:44:09.406-05:00Selecting the sampling point in tanks that contain...Selecting the sampling point in tanks that contain 100s or 1000s gallons of solution is crucial in getting an accurate pH measurement. In a 1000-gal tank with a good recirculating pump, our minimum wait time to get a homogeneous solution was 15 min.George Goreckinoreply@blogger.com