Making Use of Glycerin

Glycerin is one of the most important by products of bio diesel. Now making use of it will reduce the actual cost of bio diesel produced in any given unit. The main problems that we face for utilising the Glycerin thus produced are the impurities. One of most problem making impurities is methanol. Other impurities are different salts, soap, water etc. Now there are different ways we can use glycerin in. These can be basically divided into direct use of crude glycerin and purified use. Now let us first consider how we can use it directly.

Direct Use:-
The easiest way to use this glycerin directly is to use it in bio digester's(bio gas plants) The thing to be care full about while using glycerin in bio plants is that it shouldn't be added in large quantities and more importantly it shouldn't be the only input to the plant. If you add a little by little to the plant then experiments have shown that it can increase the production of the plant by up to 10 -15%. This is a major way to utilise the glycerin thus produced. The bio gas can be utilised to power the Bio diesel Plants electricity needs to an extent. The thing to be remembered is that this is fairly easy to do but less rewarding that purifying it and then selling it.

Purifying and Utilising:-
Pure glycerin or glycerol is in great demand world over for different industries from cosmetics to pure industrial applications and some times even in IT industries. The transestirification can yield on average 5% glycerin (crude) for a given batch quantity. Thus around 30 liters of diesel could give you 1 liter fairly pure glycerin. The cost of 1 liter glycerin is around 300 Rs (8$). This price is directly dependent on the purity. Now let us see a process to get fairly pure glycerin.

Take Aqueous solution of glycerol which has to be acidic (if it's not, acidify with H2SO4). It's first treated with fine activated carbon, neutralised with NaHCO3 and boiled down. Majority of solid non organic salts is filtered off and the rest is removed by addition of alcohol followed by filtering. Evaporating clear solution and heating slowly to 180 degree C gives a clear, slightly yellow liquid thick at room temp. This is fairly pure glycerol. Warning, methanol is poisonous. When boiling down glycerol, there are produced acrolein (a poison and a mutagen). All procedures should be therefore done in a well ventilated area. The methanol evaporates at relatively low temperatures. Other methods like Flash distillation or vacuum distillation or chemical purification etc are much more expensive but will yield better quality glycerin.

Another suggestion would be to use ethanol instead of methanol. (A different process altogether)

The glycerin in crude form can be used as a degreaser but the methanol needs to be removed
Letting the by-product stand in an open container for a few weeks will NOT evaporate the methanol as it's often said it will, or not much anyway.
The best way to remove methanol is to heat it, but be care full not to heat it under direct flame.

Glycerin is an alcohol (glycerol) and is used as a preservative in the food industry, as well as a sweetener: it is very sweet, yet it contains no sugar. This makes it an ideal sweetener for patients who cannot take sugar. But this is not a callory free substitute. Do not attempt this until your are 100% sure that all methanol is removed.(we do not recommend this due to the high risk involved from methanol poisoning)

Some links to methods of purifying glycerin:-
http://www.freepatentsonline.com/7126032.html