3 replies to this topic

[aok9900]

I have just joined this forum and am very impressed by the level of support students can get. Hoping someone will help me too.

I'm designing a CSTR reactor for my design project.
The reactor is being designed to convert Free Fatty Acids (FFA) into biodiesel. I need to find the volume of the reactor. I'm trying to use the Arrhenius equation to calculate the reaction rate constant but I am not sure where to obtain the values for the Activation energy and the Arrhenius constant for this reaction.

Can someone please guide me towards the solution also please let me know if this is the correct approach to find the volume.

Thanks

[kkala]

I'm designing a CSTR reactor for my design project.
The reactor is being designed to convert Free Fatty Acids (FFA) into biodiesel. I need to find the volume of the reactor. I'm trying to use the Arrhenius equation to calculate the reaction rate constant but I am not sure where to obtain the values for the Activation energy and the Arrhenius constant for this reaction.
Can someone please guide me towards the solution also please let me know if this is the correct approach to find the volume.

You have to search the literature (or even WWW / wikipedia) to find the rate of the relevant reactions. Verify that chemical reaction rate is the controlling one, to use the Arrhenius constant (and activation energy to specify the constant at set reaction(s) temperature); transport processes (e.g. diffusion) often control industrial reactions, probably including esterifications (base or acid catalyst). Technical literature can guide you on these matters, as well as on the average residence time in the reactor (an economical issue that can be probably bypassed through an assumption).
Volumetric flows and average residence time can specify the necessary net volume of the reactor. However there shall be a distribution of feed residence times (some part higher, some lower than normal) affecting reactor performance. In the past this distribution was measured experimentally. I do not know whether the distribution can be predicted theoretically today and assessed. If not, one can increase reactor volume to cover it, using engineering judgment conservatively.
Stirring is another issue to be looked into. Unless you trace examples in literature, you have to find purpose (e.g. to homogenize liquids) and necessary stirring intensity. Chemical Engineering issued a good series on "agitation" some 30 years ago, similar articles must "circulate" today.
Heat transfer can be another issue for the design.
Of course a bio diesel plant has equipment downstream reactor to purify the product (see wikipedia), or even upstream.
If your project is market oriented (e.g. feasibility study) economic data, prices, demand perspective should be looked for.

Edited by kkala, 22 March 2010 - 12:59 PM.

[confused]

Could you guide me on how to start the design of a reactor for ethanol production from a 1000lb/hr corn livefeedstock? will i have to do a CSTR or batch?

[kkala]

Could you guide me on how to start the design of a reactor for ethanol production from a 1000lb/hr corn livefeedstock? will i have to do a CSTR or batch?

Unfortunately I have no experience on the subject, but probably some clarification would probably help others to offer some guidance. What do you mean by "corn live feedstock"? Is it real corn in solid form, which have to be processed to ethanol instead of giving it to animals as food?

Edited by kkala, 06 October 2011 - 09:01 PM.