Biodiesel reactor design is both varied and inventive. As most users are of the home variety, designs have emerged that suit the users needs, budgets and abilities. The growth of the Internet has enabled these designs to spread easily and allow other users to mimick the designs and worry less about how biodiesel is made and more about making it.
Designs and procedures have emerged that have become recognised within the community with names such as "Appleseed" and the "World Famous Dr Pepper Technique (Pat Pend)" where the author reminds users that "...after producing in excess of 53,459 litres of biodiesel in any calander year using this process, please make royality check out to Tilly From Paradise and send it to me through your favourite Numbered Swiss bank account." Good one Tilly...146 litres a day in a two litre processor!
World Famous Dr Pepper Technique (Pat Pend)
I believe we'll start our discussion today with "test sized batches" as described by the "World Famous Dr Pepper Technique (Pat Pend)". The full procedure can be found here. This technique describes making biodiesel in small 1 Litre test batches in a 2 litre (approx) glass bottle.
Practising batches in test sizes is a fundamental skill that should not be over looked. It should be the first batch you ever make and the first thing you do before every larger batch. The reasons are as follows. The test batch contains all of the skills and techniques needed in larger batches and is a valuable way of determining oil suitability, possible water contamination, floors in technique and to a lesser extent titration levels. Also by doing test batches in smaller quantities you will minimise wastage due to failure (or spending wasted time trying to correct mistakes.)
An adendum to this procedure worth noting since this article first inception, is the fact that Gas Chronometer tests show that although one 10 second shake produces very useable Biodiesel it is in fact not of ASTM standard. It appears that to produce ASTM quality fuel (high quality fuel) requires at least four - 5 second shakes over the space of an hour... Tilly From Paradise
The limitations for this design are its size, but given that it is only for training and testing this is not really an issue.
The Appleseed Processor
The appleseed processor is a "open source" closed design system. Put simply, the plans that describe a system that is entirely "closed to the atmosphere" and are freely available for use and redistribution. The difinitive webpage on Appleseed design can be found here.
The system is based on a hot water tank and takes advantage of the components needed/desireable for Biodiesel reactor design;
a closed vessel that holds upwards of 100 litres (depending on the system and needs),
a 2400w or greater heater with thermostat,
natural drainage due to the design of the inner vessel,
piping both at the top and the bottom of the vessel,
insulation.
Having these components in one unit saves time and money. Of particular benefit are the built in heater (often upwards of 3500w...yipee), thermostat and insulation. As well as having the added benefits of reduced spillage and risk of injuries.
This system typically relies on a water pump (around the 2000 lt\hr mark) to pump the oil/methoxide mix from bottom to top and also to pump from one vessel to another by way of ball valve to open and close pipes to and from mixing and settle/washing tanks.
The challenges of this design are introducing solid feedstock, viewing the internals of the system and dealing with the problem were you to have it set solid. Some users bypass this last problem by decanting into a settling tank with the added advantage of freeing the reactor for another batch after the mixing phase.
The Cone Bottom Processor
The Cone Bottom Biodiesel Processor is as it suggests. It is a vessel with a cone shaped bottom. This can be a high density plastic mould or a 44 gallon drum with a cone shaped addition. The top and bottom of the drum is removed and the cone is welded into place at the bottom. A ball valve sits at the bottom of the cone to control flow. The cone bottom allows for collection and easy decanting of the glycerine after the mixing/seperation phase of Biodiesel Production. The cone design is freely available on the web and enables users to manufacture their own processor using a 44 gallon drum. Also this scales very well. Imagine welding another 44 gallon drum on top of the first one...
This system often has a mechanical mixer in the form of a electric motor and paddle, positioned at the top used to stir the methoxide in to the oil. Another variation on this is a electric pump used to mix from the bottom to the top of the reactor. This also allows for decanting into other tanks for seperation/washing.
The limitations of this system are the physical height this system will/can grow to. This system may weigh upwards of 50kg and usually is not portable. A 44 gallon drum with at least 30cm of cone plus height enough to decant into a 20 litre drum put the minimum height of this system at around 1.8Mts. You may literally need a step ladder to load feedstock and methanol into this system is you aren't better organised.
This system however can allow for a closed design to minimise fumes and methanol loss. The plumbing can allow for endless variations for pumping to and from this vessel and others and can very importanly can pump methoxide into the mix. This is a definite safety advantage.
Also having the pump on hand means we can reduce the amount of manual handling we need to do.
Other Processors
Other types of processors may include smaller drums with paint stirers that may or may not have a collection point at the bottom with a tap at the bottom to allow for easy seperation of glycerine and biodiesel.
My personal favourite is the 25 litre HPDE drum filled with 20 litres of oil and 4 litres of methoxide. There is a tap at the bottom to drain the glycerine off after seperation. This same drum can then be used for washing/settling and bubble drying. This particular small system is cheap but not scaleable. It is easy to handle, is portable, see-through and can suit users who may use up 100 litre a month.
This method however involves lots of manual handling and is usually grossly inefficient. It may suit starters or users with low useage requirements but tends to be a bit messy as lots of transferring of materials is required. Also the mixing of the methoxide and the oil is manual. Requires hand shaking or "soccer balling" of the container. Oil loses heat rapidly so can result in incomplete conversion or incomplete conversion times. (60 mins at 50C, 120 mins at 40C, 360 at 30C). A towel can be wrapped around the drum/processor to reduce heat loss. If you can keep it at or around 45-50C for the hour, then 3-4 10 second shakes are all that is required for fairly good conversion, although I have no tests to back this up.
This wraps up our exploration of Biodiesel processors. If you feel there are any further points that deserve discussion please contact me from .
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