You can easily bring them to your local recycling park for further processing. They can also be processed by specialised waste companies, such as Van Gansewinkel.
We do not currently process faulty, empty or expired fire extinguishers ourselves.
We would also like to note that there is a difference between an expired fire extinguisher (usually older than 20 years) and an non-inspected fire extinguisher. As long as a fire extinguisher has not expired (this can be deduced from the production date on the device or the expiry date on the label, depending on the model), you can have the device re-inspected.