A Pneumatic driven chemical injection system is a system that usually has a high pressure piston pump suitable for transferring all kind of chemicals from a storage tank to a injection point e.g. a flowline or process line.
The pump can be operated with a manual adjustable pneumatic timer with which the flowrate of the injection pump can be adjusted. The actual flow rate can be digitally measured with a positive displacement meter and displayed with a flow computer (actual flow and totalized volume). These systems are often used for very low flow and high pressure. Very important is to match the material and seal selection with the chemicals. In some situations that will mean that exotic materials will be required like e.g. Hastelloy C-276. But in most cases 316SS will be good enough.