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I am planning to use partial vacuum in two parts of the processing WVO into biodiesel to remove unwanted water more quickly.
Before adding to the Reactor, the WVO is cleansed and purified as much as possible to remove contamination that will hinder the transestification process. So the WVO is filtered to remove particulate materials, it is left to stand to let any free water gravitate to the bottom of the container so that it can be decanted, but any water held in suspension is not removed. So we can heat the WVO to drive off the water by "boiling", but this takes time and energy and heats the WVO to a temprature that then requires it to be cooled before adding the Acid/Methoxide, particulaly the Methoxide.
So having a partial vacuum over the filtered and heated WVO during its drying phase allows a much lower temperature to be utilized to drive off any water held in suspension. The net result of this is that (1) the WVO does not need to be cooled before further processing, which means that (2) time is not wasted on unnecessary heating and cooling so that the processing takes place in less time and (3) money is not wasted on unnecessary heating costs.
Again, after the washing of the biodiesel to remove any residual hydroxide, soap or methanol the biodiesel needs to have any excess water in it removed. Settling and decantation removes the free water that will gravitate to the bottom of the tank, but the suspended water needs to be "boiled off". This can be done by spraying the biodeisel to enhance the evaporation of the water, but this produces some oxidation of the biodeisel, an unwanted reaction.
So heat is usually used with the attendant issues listed above and again using a partial vacuum allows a lower temperature to be used with the attendant benefits.
So, using partial vacuum has real benefits.
However, producing it is usually considered expensive - think vacuum pumps.
A cheaper and equally efficient method to produce partial vacuum is to use an Aspirator, a device usually associated with laboratories. It uses Bernoulli's Principle better know as the Venturi Effect in a fitting that is attached to a tap and uses the flow of water through a venturi with the vacuum produced via the suction produced by the low pressure within the venturi.
Look up "Aspirator" in Google and you will find info and pictures
There is an added advantage in using a Aspirator. When drying either the WVO or the biodeisel, one may not wish to vent any fumes to atmosphere, in which case a condensor and associated condenate capture container would be used in-line before the vacuum pump or the Aspirator. Condensors need to have a flow of cooling water run through them for maximum efficiency, and so a happy win-win solution can be found for both needs of running water.
To conserve water use within the condesor and operate the aspirator at the same time as the condenser so as to extract unwanted water from either WVO or washed biodiesel, a tank of 100-200 litres of water could be used to provide the fluid required by both devices: The water could be pumped from the storage tank through the condenser for cooling purposes, but then be used to produce the partial vacuum in the Aspirator - being discharged through air to the storage tank for settling before re-use. This discharge through the air back into the storage tank would provide partial cooling of the water through evaporative losses which would aid the effectiveness of the condenser. The partial vacuum produced by the Aspirator would allow any suspended water to boil out at close to 60o C thus “drying” the WVO or the washed biodiesel fairly rapidly. It would entail the use of a small water pump to circulate the water, but this is more sustainable than just wasting water for hours on end to work both devices.
Sorry to be so wordy, but I think there is some merit in thinking about the whole process in terms of efficiency.
I await any thoughts
Quentin
Before adding to the Reactor, the WVO is cleansed and purified as much as possible to remove contamination that will hinder the transestification process. So the WVO is filtered to remove particulate materials, it is left to stand to let any free water gravitate to the bottom of the container so that it can be decanted, but any water held in suspension is not removed. So we can heat the WVO to drive off the water by "boiling", but this takes time and energy and heats the WVO to a temprature that then requires it to be cooled before adding the Acid/Methoxide, particulaly the Methoxide.
So having a partial vacuum over the filtered and heated WVO during its drying phase allows a much lower temperature to be utilized to drive off any water held in suspension. The net result of this is that (1) the WVO does not need to be cooled before further processing, which means that (2) time is not wasted on unnecessary heating and cooling so that the processing takes place in less time and (3) money is not wasted on unnecessary heating costs.
Again, after the washing of the biodiesel to remove any residual hydroxide, soap or methanol the biodiesel needs to have any excess water in it removed. Settling and decantation removes the free water that will gravitate to the bottom of the tank, but the suspended water needs to be "boiled off". This can be done by spraying the biodeisel to enhance the evaporation of the water, but this produces some oxidation of the biodeisel, an unwanted reaction.
So heat is usually used with the attendant issues listed above and again using a partial vacuum allows a lower temperature to be used with the attendant benefits.
So, using partial vacuum has real benefits.
However, producing it is usually considered expensive - think vacuum pumps.
A cheaper and equally efficient method to produce partial vacuum is to use an Aspirator, a device usually associated with laboratories. It uses Bernoulli's Principle better know as the Venturi Effect in a fitting that is attached to a tap and uses the flow of water through a venturi with the vacuum produced via the suction produced by the low pressure within the venturi.
Look up "Aspirator" in Google and you will find info and pictures
There is an added advantage in using a Aspirator. When drying either the WVO or the biodeisel, one may not wish to vent any fumes to atmosphere, in which case a condensor and associated condenate capture container would be used in-line before the vacuum pump or the Aspirator. Condensors need to have a flow of cooling water run through them for maximum efficiency, and so a happy win-win solution can be found for both needs of running water.
To conserve water use within the condesor and operate the aspirator at the same time as the condenser so as to extract unwanted water from either WVO or washed biodiesel, a tank of 100-200 litres of water could be used to provide the fluid required by both devices: The water could be pumped from the storage tank through the condenser for cooling purposes, but then be used to produce the partial vacuum in the Aspirator - being discharged through air to the storage tank for settling before re-use. This discharge through the air back into the storage tank would provide partial cooling of the water through evaporative losses which would aid the effectiveness of the condenser. The partial vacuum produced by the Aspirator would allow any suspended water to boil out at close to 60o C thus “drying” the WVO or the washed biodiesel fairly rapidly. It would entail the use of a small water pump to circulate the water, but this is more sustainable than just wasting water for hours on end to work both devices.
Sorry to be so wordy, but I think there is some merit in thinking about the whole process in terms of efficiency.
I await any thoughts
Quentin
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