Question

what is the effect of air flowrate and stirrer speed on oxygen mass transfer in an aerobic process?

What are the potential impacts this might have on an industrial scale?

and how can the condition be improved?

Answer 1

The flowrate increase decreases mass trasnfer due to less residence time in tank which decreases the contact time between liquid and oxygen gas. The stirrer speed directly enhances the oxygen tranfer rate as high stirrer spedd increases the mxiing hence more intimate contact betwene liwuid and gas which increase rate of mass transfer

High stirrer speed results in high power consumption per unit volume and at large scale excess power usage becomes uneconomical Thus needs to be optimised by appropriate condition of mass transfer rate. High flow rates decarease the residence time and hence low mass trasnfer rate results in low oxggen concentration which needs then a recycle stream to compensate for it hence increases pumping and piping cost

To improve such conditions stirrer speed need to be adjusted at optimum and high pressure spargers should be used to enhance natural mixing inside tank and flowrate can be kept at optimum level using flow control measuring devices

for any doubts pelase write to me in comments