July 14, 2011

expert reaction to the industrial explosion in Lincolnshire

Five people were killed in an explosion at a factory in Boston, Lincolnshire, which was believed to have been used as an illegal alcohol distillery.

Emeritus Professor Hans Michels, Department of Chemical Engineering and Chemical Technology at Imperial College London, said:

“There is a lot of speculation that the facility was being used as an alcohol factory. If that turns out to be the case, I would say the following:

“Brewing high concentration alcohol, like the base material for vodka, is a simple process of heating natural products such as potatoes, wheat, rye, sugar or sugar extracts until they start to give off their alcoholic vapours. These are a whole bunch of different products, which have to be separated out to make sure that you get the purest possible alcohol, that is not contaminated with other volatile compounds, some of which are very ‘unhealthy’.

“As all the different products have different boiling points, one does this by ‘fractional distillation’. The more carefully one does this, the better one is able to pick off the various products one by one and the purer each of these will be. The only substance one can’t get out of the alcohol ‘fraction’ completely is water, but as the alcohol produced is too concentrated for human consumption and needs to be diluted with water afterwards, that is not a problem. The problem is contamination with other products by inferior distillation. After dilution the product is given its special taste and flavour by additives, which are immaterial to the issues of today.

“The process is carried out by slowly increasing the temperature of the base liquid at the bottom of equipment from which the alcohol has to be extracted as a vapour from a column above the vessel at the bottom. As the alcohol boils close to 80 degrees C, the base liquid may at that point be closer to 100 degrees. The liquids are also invariably very flammable. So if something goes wrong, for instance the equipment with the boiling base liquid or the one that collects the alcohol breaks, one has a hot liquid coming out, which gives off very flammable vapours which will very quickly find an ignition source, certainly cause an intense fire and almost certainly an explosion. If the alcohol still is large, that will be a very big fire and a powerful explosion.”