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"The Warnqvest Test and re-processing
Over the last several years, a procedure has gained in popularity which uses the dropout amount from a warnqvest test to calculate the amount of chemicals required to reprocess or perform the second stage of a 2 stage reaction.
This method involves measuring the percent of dropout in the warnqvest test and then treating this as the percent of oil with a zero titration remaining from the initial reaction to be reprocessed.
An Example
You have a 40 litre batch of oil that you react and find that when you then perform a 10/90 version of the Warnqvest test you have 3ml of dropout.
3ml dropout is 30% of the 10ml warnqvest test sample, so you then calculate the un-reacted oil remaining to be reacted in the second stage as 30% of 40 litres.
30% of 40 litres is 12 litres.
Because all of the FFA's have been converted into soap in the first stage, you treat this remaining 12 litres of oil to be reacted as if it were new oil with a zero titration.
When reacting oil with a zero titration, most people will use 5g NaOH/ 8g KOH mixed into 200ml methanol for every litre of oil being reacted.
In the above example, you have calculated that there is 12 litres of oil remaining to be reacted.
The KOH amount required in the reprocess is 8g X 12= 96g KOH
The methanol amount required in the reprocess is 200ml X 12= 2400ml Methanol
This method has been proven to be quite reliable in performing a second stage reaction that does produce biodiesel that subsequently passes the Warnqvest test.
Recent testing posted to another thread on this forum has demonstrated what everyone has suspected for years, there is NOT a 1 to 1 correlation between dropout and conversion in the Warnqvest test.
People have asked why the above procedure works so well at reprocessing if there is not a 1 to 1 correlation between dropout and unreacted oil.
Some preliminary information
Most people want to make very high conversion biodiesel that will pass the Warnqvest test while spending as little money as possible.
Testing has shown that the formula of 5g NaOH/ 8g KOH and 200ml methanol is about the least amount of chemicals you can use to react a litre of zero titration oil in a single stage that will probably pass the Warnqvest test.
If you use more chemicals than 5g NaOH/ 8g KOH and 200ml methanol, this will give you even higher conversion and a more reliable pass on the Warnqvest test.
For instance, a few weeks ago I made a litre of biodiesel from new oil using about 16g KOH and 250ml methanol.
This turned out to be extremely high conversion biodiesel, but it also cost more to produce. I would not use this formula for my daily driving biodiesel.
Why the above procedure works so well if there is not a 1 to 1 correlation
Recent testing has shown that the Warnqvest test actually has more dropout than would be the case if there were a 1 to 1 correlation.
In other words, the above procedure overstates the amount of oil remaining to be reacted and as a consequence, if you use the above procedure, you end up using more than 5g NaOH/8g KOH and 200ml methanol for every litre of oil remaining to be reacted.
This results in a very high likelihood that you will pass the warnqvest test after reprocessing using this procedure."
Over the last several years, a procedure has gained in popularity which uses the dropout amount from a warnqvest test to calculate the amount of chemicals required to reprocess or perform the second stage of a 2 stage reaction.
This method involves measuring the percent of dropout in the warnqvest test and then treating this as the percent of oil with a zero titration remaining from the initial reaction to be reprocessed.
An Example
You have a 40 litre batch of oil that you react and find that when you then perform a 10/90 version of the Warnqvest test you have 3ml of dropout.
3ml dropout is 30% of the 10ml warnqvest test sample, so you then calculate the un-reacted oil remaining to be reacted in the second stage as 30% of 40 litres.
30% of 40 litres is 12 litres.
Because all of the FFA's have been converted into soap in the first stage, you treat this remaining 12 litres of oil to be reacted as if it were new oil with a zero titration.
When reacting oil with a zero titration, most people will use 5g NaOH/ 8g KOH mixed into 200ml methanol for every litre of oil being reacted.
In the above example, you have calculated that there is 12 litres of oil remaining to be reacted.
The KOH amount required in the reprocess is 8g X 12= 96g KOH
The methanol amount required in the reprocess is 200ml X 12= 2400ml Methanol
This method has been proven to be quite reliable in performing a second stage reaction that does produce biodiesel that subsequently passes the Warnqvest test.
Recent testing posted to another thread on this forum has demonstrated what everyone has suspected for years, there is NOT a 1 to 1 correlation between dropout and conversion in the Warnqvest test.
People have asked why the above procedure works so well at reprocessing if there is not a 1 to 1 correlation between dropout and unreacted oil.
Some preliminary information
Most people want to make very high conversion biodiesel that will pass the Warnqvest test while spending as little money as possible.
Testing has shown that the formula of 5g NaOH/ 8g KOH and 200ml methanol is about the least amount of chemicals you can use to react a litre of zero titration oil in a single stage that will probably pass the Warnqvest test.
If you use more chemicals than 5g NaOH/ 8g KOH and 200ml methanol, this will give you even higher conversion and a more reliable pass on the Warnqvest test.
For instance, a few weeks ago I made a litre of biodiesel from new oil using about 16g KOH and 250ml methanol.
This turned out to be extremely high conversion biodiesel, but it also cost more to produce. I would not use this formula for my daily driving biodiesel.
Why the above procedure works so well if there is not a 1 to 1 correlation
Recent testing has shown that the Warnqvest test actually has more dropout than would be the case if there were a 1 to 1 correlation.
In other words, the above procedure overstates the amount of oil remaining to be reacted and as a consequence, if you use the above procedure, you end up using more than 5g NaOH/8g KOH and 200ml methanol for every litre of oil remaining to be reacted.
This results in a very high likelihood that you will pass the warnqvest test after reprocessing using this procedure."
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