How can you stop coconut oil from solidifying at temperatures below 23
degrees celcius? I need to be able to apply this to large quantities
of coconut oil (100 litres)and the oil must remain edible after the
treatment or process.

You'll need to mix it with something.  Perhaps as little as 1:100 with
a light no flavor oil like canola?

It is a natural property of coconut oil...that is, it freezes at those
temperatures.  Not much you can do about it except decrease the
purity.