5 replies to this topic

[easrikrishna]

Hello Friends,

 

This is srikrishna from india. i am working at biodiesel company in india as a chemical engineer. actually i need a help for biodiesel simulation in Hysys. any vegetable oil consists of Different fatty acid compositions such as Palmitic, Oleic, stearic, linoleic etc. so i have added All components to the list. but i strucked at reaction set. there  we must give stochiometric ratios. stochiometric ratios for oil is (-1), methanol is (-3), biodiesel (1) and glycerin(1). but these values failed for Balance. it shows balance error. Is these values correct or..? whether the hysys library contains oil sepeartely as single compound...?

 

please help me in this case.

 

Thank you very much

 

easrikrishna@gmail.com

[thorium90]

Can you show what are the reactions you have input into hysys? If possible a screenshot of the error?

[ravion143]

Please provide some more information on your feed and biodiesel production method (acid, base, supercritical etc) for a more specific answer

 

In the reaction the number of "biodiesel" molecules should be 3. This is produced from the triglyceride portion of your feed oil. The free fatty acid (FFA)is another component within the feed oil, and it all depends on your source. Used cooking oils and oils from animal fats etc have a high FFA content which react in side reactions to form the soaps and other contaminants. Where as virgin oils have low FFA contents and pose less of a problem.

 

 

The fatty acid methyl ester (FAME, biodiesel fuel) depends on the alcohol used and also on the feedstock oil, the model oil is triolein used in many simulations and methyl oleate (oleic acid) as the FFA, for your simulation i suggest you used the full composition of the feedstock that you have and make sure you write the reactions for each reaction and side reactions.

 

The reaction on the free fatty acids (FFAs) depends on the operating conditions.

 

I suggest you look up the try of transesterification process you are planning to employ, there are a variety of options and a selection includes:

 

1 step acid catalyzed transesterification

1 step alkali catalyzed transesterification

2 step pre acidatalysed esterification followed by alkali catalyzed transesterification

supercritical transesterification.

 

and find the downsides and side reactions for each so you can fully simulate your process. 

Edited by ravion143, 07 April 2013 - 08:53 AM.

[easrikrishna]

Glad to see ur replies. coming to the topic,  first i am trying to enter base catalysed transesterifiction of Biodiesel process. here i give you the composition of Palm Oil and Palm Methyl ester( biodiesel).  i have given input of these components and selected NRTL as  fluid Package and tried to set a reaction between these components. but it shows that Balance error at Stochiometry. even i did this for entering individual reactions. but its vain. and there will be side reaction may occur between FFA and catalyst. here the alcohol is methanol and catalyst is NAOH ( actually we use sodium methylate as catalyst but its not available in Simulation.). And i have not found Triolein in sumulation.

  Palm Oil  Palm Oil BioDiesel Myristic (C14:0) 1.0 0.93      m-myristate Pamitic (C16:0) 45.0

44.56

m-palmitate

Stearic (C18:0) 4.0

4.44

m-stearate

Oleic (C18:1) 40.0

39.48

m-oleate

Linoleic (C18:2) 10.0

10.38

m-linoleate

Linolenic (C18:3) 0.0

0.21

m-linoliniate

  100.0 100.00

 

I think these information is suffiecient. even u need more of that i am glad to provide you.

 

i find difficulties in Reaction Set only, please help me in this case.

 

Thank you very much.

 

Krishna

 

easrikrishna@gmail.com

[ravion143]

The hysys biodiesel library contained triolein as an oil so make sure you have that package added and active so you can check for other oils and components from there. If you do not have access to the oils then you need to create within the program by knowing the structure and physical properties.

 

The list you provided looks like a list of the fatty acid chain lengths and the relative composition. 3 of these acid chains would be part of 1 triglyceride molecule and the way of presenting the information on the triglycerides is in the form of percentage of fatty acid chain lengths. It is not the actual triglyceride that you need to be using in your reaction. The fatty chain content can be interpreted as the percentage composition of the type or triglyceride. For example, palmitic and oleic acid content:

 

44.56% of the total number of fatty acid chains chains are 16 carbon long chains with no double bonds (C16:0, palmitic acid), this could be represented by using an approximation 45% of the oil being modeled as tripalmitin (the triglyceride of 3 palmitic acid fatty chains, C₅₁H₉₈O₆).

 

39.48% of the fatty acid chains are 18 carbons long with 1 double bond (C18:1, oleic acid), which can be represented as 40% of your feed as triolein (triglyceride of 3 oleic acid chains, C57H104O6).

 

And so on, you can see how you build up that information in to useable components within the process.

 

Each triglyceride will then react within your system with  3 molecules of methanol to produce 3 molecules of the ester of the acid (biodiesel). In these two cases you would get 3 methyl oleate molecules from 1 triolein molecule (from the oleic acid chains) and 3 methyl palmate molecules from 1 tripalmitin molecule (from the palmitic acid chains).

 

 

The feed may also contain a small amount of Free fatty acids. 5-15% for palm oil if i remember correctly. These acids will not be incorporated within the triglyceride (oil) molecules and are referred to as free because of this. These produce the problems with the catalysed biodiesel production, reducing yield by reacting with the catalyst and increasing separation costs. The amount of oil would need to be adjusted to account for this so the composition of oil above would need to be reduced by the percentage of FFA within the feed. Then the free fatty acids will also need to be included within the reaction sets and those undesired side reactions also inputted as well with all the kinetic data with it, the reaction extent etc.

 

If you provide me with an image of your current reactions and components you are using then that might help me understand a bit more what your problem is.

 

Below is an images below show the reaction of 1 triglyceride molecule with methanol and also the location of the biodiesel database within the program.

 

 

I hope this helps, if you need anything clearing just ask.

Edited by ravion143, 08 April 2013 - 06:30 AM.

[easrikrishna]

Hi,

Thank u so much.i am glad to get some knowledge from you. and i have not found  triolien or triglycerides in Hysys simulation library. but i have created a hypothetical compounds with structures and physical properties but when i come to set a reaction , i found some difficulties. First is the reaction is not balancing..  and second is to create second reaction that is Soap Formation.

 

 

if u can give ur mail id.. i will just forward you the screenshots...this may find a solution to me.

 

 

Thank u very much..