Biodiesel Processors

Biodiesel Processor

Obviously the next step for those making their own biodiesel on a regular basis is to upgrade to using a biodiesel processor. These mini-batching plants certainly take the labour out of the whole process and allow for making larger quantites if required. However, using a processor should only be considered once you are proficient at making biodiesel by both of the hand batching methods discussed earlier (for SVO and WVO). Always purchase your machine from a reputable manufacturer, and preferably attend a training course run by the manufacturer if possible. Also, enquire about methanol recovery if intending to produce more than 250 litres per day, as this will reduce costs. When using a processor, always wear protective gear and take great care when mixing, just like when hand-batching.


Components of a Processor

Machines will vary greatly from manufacturer to manufacturer and depending upon cost, but to reduce labour, ideally the processor will perform all the stages of biodiesel production:

  • Heating of the vegetable oil
  • Separation of water and fat from the vegetable oil
  • Mixing of the methoxide
  • Housing of the main biodiesel reaction
  • Neutralisation of the biodiesel
  • Drying of the waste oil
  • Water washing of the biodiesel
  • Drying and filtration of the finished biodiesel

What to look for when choosing a biodiesel processor

  • Only use stainless steel vessels. It is chemicaly inert it will not effect the quality of the biodiesel in any way. Mild steel is okay but will eventually corrode. Plastic, HDPE and PVC are not suitable for mixing the reactants as they will corrode and are not fireproof, and yet there are many processors out there using these inadequate materials. Steel will be more expensive, but using lesser materials will be false economy and potentially unsafe. Conical tank bottoms are best to offer maximum separation efficiency.
  • Similarly avoid any plastic pipework, such as braided PVC piping. These will deteriorate with time and will need replacing before they become unsafe.
  • Go for machines where the mixing pump is mounted below the bottom level of the tank. Any higher and the pump will need to be self-priming (one that will clear itself of air and resume pumping without outside attention, something it accomplishes by keeping a reservoir of the liquid being pumped insiode the pump casing itself). These are more expensive and not necessary.
  • The mixing pump should be spark-proof with a full ATEX zone 1 certification (on any electrics and the pump itself). Alternatively, manually operated pumps are safer (but then the idea of a processor is to lessen your workload). Ensure the pump will handle particles in the fluid, as vegetable oil isn't usually filtered beyond 2mm (centrifugal pumps are the best option).
  • The heater that warms the oil should be ATEX rated to zone 0 if it is inside the reactor vessel. The vessel itself should have automatic fluid level sensors (to avoid heaters being left on in empty vessels containing methanol fumes).
  • Only use machines that mix the reactants using a conventional vortex mixer, and not a pump.
  • Avoid machines that mix the methoxide into the hot oil. The methoxide must be added to the reactor vessel before the oil. Even if a temperature gauge is fitted, the oil will tend to be hotter at the top of the tank than at the bottom. If the oil is too hot (more than 65°C) then any added methanol will boil off, potentially causing a pressure build up and subsequent bursting of the vessel (especially if plastic). Combined with non-spark proof motors, this is a serious explosion risk.
  • Features like sample points in the reactor and methanol mixing tanks, and temperature gauges are useful extras to have and well worth paying for.
  • The unit should be bunded at the base by metal plates (often called skid mounted) to catch any spillages that may occur.
  • There should be a top mounted vent on the reactor vessel, allowing a hose to be fed from the processor to the outside in order to vent the processor whilst the reaction takes place between the alcohol and the catalyst. However, methoxide should never be mixed in an open topped vessel so avoid these at all costs.