The refinery can be used to process items and fluids. It has one item and one fluid input slot, with one item and 3 fluid output slots.

However, by default only one fluid output slot is active. The enable the other 2 output slots, add refinery tank modules above. These are also multiblocks that need to be assembled with machine cores. They need to line up with the refinery itself to connect. The output fluids of the output tank 2 and 3 can be extracted from the modules, not the main refinery block.

When no module is active/used, the remaining fluid is instead used for the initial output. This means the item and fluid output of the first slot is doubled. If only one module is installed, the second fluid output amount is doubled instead. This is only the case if there would be more than 1 fluid to be output in the first place.