Water washing

This page is Work In Progress and therefore may not be complete.

Water washing is a way to remove soap from reacted biodiesel. Typically this involves mist spraying water over the biodiesel, or bubbling air through water with the biodiesel floating on top.

Water prewash is a form of water washing, although this is done in the processor before the glycerol is drained off.

Basic wash tank

Basic wash tank.

Water washing is a way to remove soap from reacted biodiesel. Typically this involves mist spraying water over the biodiesel, or bubbling air through water with the biodiesel floating on top.

Water prewash is a form of water washing, although this is done in the processor before the glycerol is drained

GL wash tank

'GL never overflowing' wash tank.

Originally designed by Graham Laming and dubbed 'The never overflowing wash tank’, this design automatically drains the same volume of water as is being introduced.

This simple layout automatically keeps the level in the tank fixed. As you add water via a spray or mist head, it passes through the biodiesel, taking methanol, soap and glycerol with it, and then collects in the bottom of the tank, where it is forced up, by the weight of biodiesel on top of it, through a drain pipe, to drain off as much water as is added. It is arranged in a way which prevents it from siphoning uncontrollably.

The biodiesel outlet tube on the left is bent over with a U joint, to prevent water from entering the biodiesel drain pipe during washing.

Fill the tank with water first, to about ½ way between the biodiesel drain tube and the bottom of the tank. This should be around 15% of the tank capacity.

Caution: This system will work so long as the wash water can freely pass through the drain tube. Therefore, do not use this system in winter, where freezing of either the biodiesel or the water may occur. Use a large bore drain pipe to minimise the risk of it becoming blocked.

Bubble wash tank

Bubble wash tank.