posted December 21, 2014 04:59 AM Hide Post
posted December 20, 2014 03:49 PM
For a while now I have been experimenting with the minimum amount of catalyst required to achieve complete conversion.
My first few tests resulted in KOH amounts between 5.2 and 4.0 gms KOH/litre after glycerol pre-treating (with no KOH added to the glycerol)
After the 4.0 result it was obvious that to try and obtain a 'minimum' result then more stages would be required. Including the pre-wash (lets call this stage one) the 4.0 result needed 4 stages.
Another thought is that I feel that there is more residual catalyst left in the glycerol than most of us realise.
Before I start the description of the process, I am not advocating this as a practical proposition. It is not energy efficient and certainly requires a lot more work, It's really a result of my over enquiring mind.
I used 80 litres of oil that titrated at only 1.3
I pre-treated this with 30 litres of glycerol.
This glycerol had no added KOH, however it had 3 litres of added methanol. The pre-treatment was at 55 degs and mixed for a long time- 2 1/2 hours.
I conducted a 10/90 where the dropout was 8.8 mls (12% conversion)
The next 5 stages were all at 60degs for 1 hour and were as follows;
130gms KOH 3.2 mls dropout.
80 gms 0.8 mls
30 gms 0.4 mls
20 gms 0.2 mls
20 gms zero
This total of 280gms equates to 3.5 gms/litre.
Now, the big question, How much KOH was removed from the glycerol during pre-treatment.
From testing I have done, I came up with the following figures.
72 gms of KOH would be reqd to neutralise the FFA's, and 38 gms would be be reqd for the 12% conversion. A total of 110 gms.
So 30 litres of the glycerol I used contained at least 110 gms KOH. Thats 3.7 gms /litre. I would consider this a large amount.
So the result for complete conversion was;
3.5 gms/litre of actual KOH flake used.
4.88gms/litre including KOH extracted from glycerol.
6 stages over 3 days,I won't be doing another one of these soon!
Before someone asks, from tests I have done previously I have found that 100 litres of oil that titrated at 1.3 required 90 gms of KOH to neutralise. (this is where the 72gm figure came from) |

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