Inquiry Form for Methanol Recovery or Dehydration

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“Excess Methanol” Vs “Methanol % in biodiesel and glycerin” after separation.
After separation, the Biodiesel typically will contain 2-7vol% un-reacted methanol, which is 35-40% of the total Excess Methanol added to the reaction. 
After separation, the Glycerin typically will contain 20-55vol% un-reacted methanol, which is 60-65% of the total Excess Methanol added to the reaction.

A biodiesel reaction for full completion, requires ~12.9vol% Methanol; so 1000 liters of oil, requires addition of 129 liters of methanol =  129/1000 = 12.9%  for a total batch of 1129 liters.
This volume will make:  1000 liters of biodiesel, plus ~129 liters of Glycerin.
Typically there is an excess amount of methanol added to the process to force reaction to completion.
This excess methanol is what Wintek removes; however- how the customer defines (or tries to explain, will make a big difference). For example if he says there is 40% extra methanol, is that 40%  of the 129 liters, or is that 40(vol or wt)% of the total batch of oil of 1000 liters?
The excess methanol divides between the Biodiesel and the Glycerin at ~35-40vol% in biodiesel and 60-65% in the Glycerol.

So if customer added 100vol% Excess methanol 129 liters of which 35% (0.35 x 129= 45.2 liters) goes into the Biodiesel (45.2 / 1045.2 = 4.3vol%).  So in this case, the feed to Wintek’s removal system would be 4.3vol% methanol in biodiesel.
65% of the Excess Methanol goes with the Glycerin, so 0.65 x 129 = 83.9 liters.  83.9 liters MeOH with 129 liters of Glycerin = 83.9/(129+83.9) = 39.4vol%. So in this case, the feed to Wintek’s removal system would be 39.4vol% methanol in the Glycerin.

Methanol Removal vs Methanol Recovery
Although most manufacturers supply an integrated system to Remove and Recover the excess methanol, there is a big difference between methanol removal and methanol recovery.   The customer should clearly understand what his objectives are because these are two different objectives, and the design of each of these operations are separately affected.  Typically a biodiesel manufacturer is primarily concerned with the removal step, because it is this step which gives him a saleable biodiesel product.  The recovery step affects the customers cost of operation (and emissions), because the amount recovered methanol can typically be reused in the process.

The removal is how much needs to be removed from the biodiesel or the glycerin to meet the customers’ requirements, and is usually specified in the maximum allowable % that can remain. This step is usually done separately on the biodiesel and glycerin after separation, although removal can be performed on the combined stream prior to a centrifuge separation.
Note: By removing and recovering the methanol prior to a water wash, the methanol can be recovered in relatively pure form with a “simple to operate system”. If the removal of the methanol is to be performed after a water wash, the resulting condensate is a mix of methanol and water, which requires a distillation column (much more complex in design, cost and operation). 

In biodiesel, the amount of methanol allowable in final biodiesel product is dictated by ASTM by Flash point. However, this is after the water wash, if used, (which picks up the final traces of methanol and other impurities). In the initial methanol removal step (after separation, but prior to a water wash) a typical maximum allowable remaining is 0.5- 0.1wt%. However to meet the ASTM concentration of less than 0.2 vol% is required.
Note: the removal system design (and cost) is greatly affected by this customer specified %. The design/cost is significantly different if the specification allows 0.2 vol% methanol remaining vs 0.05 vol% methanol remaining.

Methanol Recovery is condensing/collecting the methanol which was removed from the biodiesel or glycerin. By recovering the methanol without water, this can then be reused in the process.  Typical recovery rates is to recover 93-97wt% of the removed methanol. Wintek always designs to “recover as much methanol as practical”. The “recover as much methanol as practical” design is governed by the temperature of the available cooling water or chilled water – the colder the better, but is also affected by the removal requirement (a very stringent removal requirement may reduce the recovery efficiency) .  Also, if the customer has an environmental limitation on vapor emissions, then the design of the recovery system may be more complex.