TRYBIODIESEL - Devon biodiesel factory

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ABOUT BIODIESEL

INTRODUCTION:
This webpage talks about Biodiesel in general and our own fuel in partcular. From 'How its made' onwards is all about our fuel and our factory... its our 'online factory tour' if you like!

BACKGROUND:
Biodiesel is a clean burning bio-fuel, produced from domestic, renewable resources such as waste vegetable oil from restaurants or virgin oilseed crops such as rapeseed.
Biodiesel contains no petroleum but it can be blended, at any level, with normal pump diesel to create a biodiesel blend. It can be used in most diesel engines with no modifications. Biodiesel is simple to use, biodegradable, non toxic, carbon neutral and essentially free of sulphur and aromatics.
In European countries since the mid 1990's and in the UK since 2002 reductions in bio-fuel duty has made the use of bio-diesel economically viable as it is now seen to be the sustainable fuel of the future.
Biodiesel is very different to straight vegetable oil. Both can be used as fuel in diesel engines but Biodiesel is the only clean burning option. On this page I will attempt to explain the chemistry of biodiesel in 'laymans terms' and then go on to explain how our state of the art machinery converts used cooking oil into biodiesel fuel. If you dont want to know the technical stuff then look away now but if you are as intrigued as I am by Biodiesel then what follows will really interest you!

A CHEMISTRY LESSON:
Biodiesel is also known as F.A.M.E. - Fatty Acid Methyl Ester, it is made from used vegetable oil, methanol and sodium hydroxide. The vegetable oil is the feedstock, the methanol is used up in the conversion of the molecules and the sodium hydroxide is the catalyst that makes the reaction happen.
Vegetable oil is a triglyceride. Triglycerides are big fat sticky molecules. Esters are small neat slick molecules. If you imagine that you can see the triglyceride molecules of vegetable oil, imagine that each one is a three legged octopus. It's head is a glycerin molecule (glyceride) and its three (tri) legs are fatty acid ester chains. The large head is the sticky, blobby bit that makes vegetable oil gloopy whilst the legs are the energetic, muscley tentacles that can be used as fuel.
The chemistry of biodiesel is called Transesterification and, in simple terms, the catalyst causes the head of the octopus to be pulled off. The methanol reacts with the head and the legs to create a soup of head-glycerine and leg-esters. The heavy glycerine falls to the bottom of the soup and the esters sit on top. Then its just a case of separating the two liquids.
The amount of catalyst added has a bearing on the conversion efficiency. Too little catalyst results in some of the vegetable oil not converting into biodiesel (an incomplete reaction). Too much catalyst results in a lower yield of biodiesel and the production of soap. In fact, adding lots too much catalyst makes a saponification reaction and vegetable oil gets turned into soap! What we do at TryBiodiesel is add just too much catalyst to our reaction so that we get as close to 100% conversion as possible with just a little soap made. We then have a process to remove the soap as well as one to remove the glycerine, please read on...

HOW ITS MADE:
Now that you have an understanding of what Biodiesel is and the chemistry behind it you are armed with enough knowledge to understand how biodiesel is made. (I will soon add photographs and diagrams to this section to make it better)
Our Biodiesel processor is a hybrid of two Green Fuels Ltd machines with the addition of a few extra bits we have made ourselves. What follows is a list of the components from start to finish with an explanation of what they do:

UCO Storage Tanks and input hopper	This bank of 10 tanks can hold 10,000 litres of UCO (used cooking oil). Each 1000 litre tank has a fill valve and a drain valve and all the fills and all the drains are connected together via a single electric pump. The input hopper is designed so that 20l drums of used oil can be simply upturned on the grid. The used oil then drains through the gauze and gets pumped into the storage tanks. Finally, the output of the electric pump feeds UCO to the preheat tanks.
UCO Preheat Tanks (2x)	These two 205 litre drums are plumbed in so that they fill from the UCO Storage tanks and drain direct to each of the two processor vessels. Each preheat tank has a 4KW electric heater that can raise the temperature of the UCO to around 60C in under and hour. The UCO needs to be at this temperature to make it more runny. The more runny it is and the hotter it is the better the efficiency of the reaction. However, it mustn't be too hot or the methanol will evaporate in the next process! As soon as the UCO is pumped into the processor vessels the two preheat tanks are refilled and the process of heating the UCO starts again.
Processor Vessels (2x) with auto Batch Doser	We have two processor vessels, each can make 150 litres of Biodiesel an hour... meaning that we can theoretically make 300 litres of fuel an hour. Its theoretical as the tanks take time to fill and time to empty. In reality we can probably get 300 litres every 90mins. The process starts by filling the two vessels with hot UCO from the preheat tanks. The processors are then set to recirculate the UCO for 10 minutes. This means that the UCO is sucked out of the bottom of the conical vessel and pumped back in at the top. The point where it is pumped back in has a special mixing jet that sprays the UCO at the back wall of the vessel creating turbulence in the liquid. After 10 minutes has elapsed we take a 1ml oil sample from each vessel and perform a 'titration' test on it. This test establishes just how 'used' the UCO is and works out how much of the catalyst is required to make the transesterification reaction happen. Whilst we titrate the oil samples the two processors are set to suck in the right quantity of methanol. The auto batch doser is air operated and it sucks sodium-methylat from a drum and injects it in measured pulses into the stream of UCO as it exits the mixing jet of each processor. Currently it batches one processor at a time and takes around 15minutes to complete its task. Once we have the titration results the batcher is set and the lefthand processor is started. Again, UCO is sucked from the botttom of the vessel and injected back in, via the mixing jet, at the top of the tank. As soon as the lefthand processor has been dosed, the doser is switched over to the righthand processor and restarted (with the correct titration information) to dose the right hand one. So we have a 15minute gap between starting the left and starting the right processor. The Sodium-Methylat that is dosed into the UCO+Methanol mix is like a premix of methanol and sodium hydroxide (aka Caustic Soda), it is the catalyst referred to in the chemistry section above. After the lefthand processor has completed its 1 hour of agitation (15mins of dosing + 45mins of further mixing) the transesterification is comlete. At this point we perform a quality test (see below) and then the liquid from the processor is pumped into the glycerine separator. 15 minutes later the righthand processor is finished and the liquid from this one goes down the same pipe. The 'liquid' in each processor at this stage is Biodiesel, Glycerine and some Soap. The two empty processors are then refilled with hot UCO and the process starts again.
Glycerine Separator	This air operated, electronically controlled box of tricks is magic! The liquid from the processors enters the separator at one end and flows accross thousands of angled plates. The glycerine drops out of the liquid and forms on the plates before sinking quickly down special channels to a sump in the bottom of the unit. An air-mover on top of the unit creates a partial vacuum in the separator and the hot liquid inside gives up some methanol vapours which get ejected from the box and passed into a filter which catches them. The liquid inside the main section of the separator is now soapy biodiesel sitting on top of heavy glycerine. An electronic sensor monitors the level of glycerine at the bottom of the liquid and switches on an air operated pump to remove the glycerine to a storage tank when the level reaches a certain point. The soapy biodiesel flows over a 'weir' at the other end of the separator and collects in a chamber. When the chamber is full the soapy fuel is pumped out into the buffer tanks. The 'magic' of this piece of equipment is that it is fully automated and just sits there doing its job. We pump the liquid in from the processors and the separator instantly strips out the glycerine pumping glycerine out of one pipe and biodiesel out of the other!
Buffer Tanks (2x)	The buffer tanks simply collect the soapy biodiesel from the glycerine separator and hold it ready for the Amberlite column. The reason we have 2x 1000l buffers connected together is that the column can purify 1440l of biodiesel per 24hr day. It takes around 7.5hrs of processing time for the two processors to make this quantity of fuel so we make the fuel in the daytime and fill the buffers ready for the column to do its job all day and all night.
Amberlite Column	The soapy biodiesel enters the column and is pumped through under slight pressure. The column contains Amberlite BD-DRY which is an ion exchange resin. This resin absorbs soaps and other impurities from the Biodiesel before the fuel is passed through a couple of filters and is ready for sale.
Biodiesel Storage Tanks	These tanks have desicant breathers on them to keep moist air away from the biodiesel fuel. Biodiesel is hygroscopic and absorbs moisture from the air turning it cloudy. Our tanks keep the fuel in tip-top condition before sale.
Delivery Pump	Our Gilbarco Highline Forecourt Pump is trading standards approved under the weights and measures act. We, test it from time to time for accuracy. With its extra long delivery hose we can put the biodiesel from our storage tanks straight into your car or van's fuel tank!

QUALITY CONTROL:
Every batch of our fuel undergoes a simple 'go/no-go' test which looks at the conversion rate of the vegetable oil into biodiesel. We apply this test as soon as the biodiesel has finished its hour in each of the processor vessels. If it passes then the fuel is pumped into the glycerine separator. On the rare occasion that it fails then the fuel is re-processed and then tested again.
We also, from time to time, send our fuel to a lab for testing. We do not currently have the full BS EN14214 suite of tests done as it is not economically viable but are considering EN testing in 2008 as the volume of our business increases.

CONCLUSION:
That completes the factory tour and the explanation of how we make our biodiesel. Should you have any questions that arise from reading this far then please ask. I would be please to show you the machine in action when you visit.