Check Levenspiel´s book: Chemical reaction engineering. John Wiley & Sons. Chapter 2. Homogeneous reactions. Chapter 3. Batch reactors.

You can get the 3rd Edition pdf download online...

You can use any technique to measure  Disolved oxygen 

Rogelio Valadez-Blanco .The reactioni s not homogeneous,because the compound in the reactor uitilize oxygen to form the product.

2A+oxygen-> Product is an example of my reaction stochiometry.

Hence it involve two different phase to make the product,hence heterogeneous reaction.

Please help me in this

Basically it is not a fermentation as per the definition of fermentation.  You must find out the mass-balance -transfer of oxygen for your process.

The fermentation unit is separate .Here I am only performing oxidation .I know theoretically the stochiometry .But to determine kinetics of this reaction I  have to measure the concentration of A as well as oxygen. But i am not able to measure A,as it is very unstable compound.again I am not getting any literature  regarding estimation of A.

so in this case how i could perform my kinetics? and what would be my rate of reaction?

As it is an heterogeneous system and I can not measure A,I am getting problem to do the kinetics. Kindly help me on this.

Dear Lopa, it seems that the system is a bit more complex than thought. A simple way to know the kinetics of your reactor would be to relate the mass transport paremeters with your reaction.

Regarding your reaction, you say that it is difficult for you to quantify A. That is a real problem. You mentioned that the product is coloured, so I don´t know if you have a colorimeter in your laboratory. That would be a simple way to measure the amount of dye produced in your reactor. If you don´t have a colorimeter you can use an spectrophotometer at a certain wavelength.

On the other hand, the mass transfer rates should be considered as you want to characterise your reaction in terms of the aereation and agitation. I don´t know if with the air flow rates that you use in your reactor, there would be oxygen limitations. If this is not the case, this is what I would do:

For a known "best" initial  substrate concentration (according to your previous experience): 1. Vary the oxygen flow rate and measure the product concentration on time. Plot the kinetic data and try to get the equation to fit the data, for each flow rate condition. 2. Vary the agitation rate, and perform the kinetics as above. For each kinetic data set you have to get the reaction rate. If the curve is not linear, you may try to linearize it... For reporting your results you can use agitation speed or you can also calculate the Re number. You cand perform this experiment as a factorial design.

Examples of studies similar to this are described in Bailey & Ollis, 1986, Biochemical Engineering Fundamentals, Mc Graw Hill. I don´t know if Levenspiel deals with this.

If the oxygen consumption is important, then you need to consider the volumetric mass transfer coefficient (kLa) for oxygen. To do this you need to measure dissolved oxygen in your reactor as it wsa mentioned above. The good thing of this parameter is that it relates the flow rate and the agitation speed.

To get the reaction rate constants of your reaction you need to perform an experiment varying the substrate initial concentration. But this is regularly done at defined conditions of flow rate and agitation. For what I understood you really want to optimize gas flow rate and agitation, so the methods suggested above are more useful.

Thank you for your suggestions.

I have  performed certain experiments on aeration ,agitation and oxidation time.

For agitation I have varied the speed from 0 rpm to 1500 rpm at an interval of 200 rpm.

ex.0,100,300,500,700.........1500 rpm.

For aeration I have varied aeration rate from 0 lpm to 10 lpm at an interval of 1 lpm.

Ex. 0,1,2,3,4,.......10 lpm

For oxidation time I have varied the time from 5 min to 80 minutes.

Ex,5,10,20,40....80 minutes.

Earlier I thought my reaction is mass transfer dependent. 

But with the variation of agitation speed I did not find any change in yield of the dye.

I think it is not mass transfer limited.

But with the variation of aeration speed i found increment  in yield up to 3 lpm from 0 lpm.

Now i want to perform kinetics.As I can not determine reactant conc. A conc.

I think I can determine the rate of production of dye ,plotting the graph between yield of dye at different time.

But for the oxidation time experiment I have fixed the aeration rate of 3 lpm and agitation speed of 700 rpm. and varied the time and measured the yield.

Can you suggest  me do I have to measure mass transfer for this ?and for kinetics what more experiments do i need to perform?

Hi Lopa, if you already define your ideal reactor conditions (aereation and agitation speed), now I suggest that you perform an initial rate experiment. For this you will perform the reaction at different initial concentrations, and measure the product concentration increment with time. For each concentration you will have a plot. Then, for each plot you will select the initial part of it (linear section of the curve), to calculate the inital reaction rate, which is the slope. Finally, you plot the initial reaction rates vs the initial concentrations, to determine the type of reaction kinetics you have. For more informaction about this, you can check Levenspiel book, or a fundamental physical chemistry book (Atkins or another alike).

Thank you very much for your reply! But in every case I have to determine the rate of reaction from rate of product formation,because i can not measure one of the reactant concentration that is A.So I can determine the rate from product .but how can i detrmine the order of the reaction?

Yes, it is ok to perform your kinetics in terms of product formation. You get the order of the reaction plotting the initial reaction rates vs. initial reactant concentrations. Regards!

But I do not know my initial reactant concentrations,remember A I can not  measure ,So how can I measure order of the reaction?

You need to figure out the amount of reactant concentration for each kinetic data point.  Probably you can use the stoichiometry of the reaction that you mentioned above.

Can I talk to you in more detail I need to understand this .Can I have your gmail Id ?