Mass Flow Technology
KEMSTREAM's unique technology
Kemstream has developed a unique and patented injection-atomization technology used as a keystone tool for all its direct liquid injection vaporizers and atomizers. This injection-atomizer is called injection head. The injection head consists of multiple components which are one liquid injector, one mixing chamber, one mixture injector, one connection to a liquid line, one connection to a carrier gas line, one heat sink and one fan. The liquid and mixture injectors are fast and normally closed solenoid valves. They operate in a pulsed regime as fuel injectors. The liquid inlet of the liquid injector is connected to the precursor tank via a liquid line that is maintained at a pressure of typically 4.5 bara (450 kPa). The liquid injector nozzle is plugged into the mixing chamber. A carrier gas line is connected to the mixing chamber and its pressure is maintained constant at typically 3.5 bara (350 kPa). The bottom of the mixing chamber is connected to the inlet of the mixture injector. The nozzle of the mixture injector is plugged into the vaporization chamber. The liquid injector nozzle, the mixing chamber and the mixture injector body are surrounded by a heat sink made of 2 aluminum half-shells. The heat sink is surrounded by a metallic sheet with a fan. The fan blows air on the heat sink to maintain the injection head at room temperature. It allows maintaining the liquid at room temperature as long as it is not injected inside the vaporization chamber thus avoiding potential precursor thermal decomposition and premature solvent evaporation or outgassing in the 2 injectors and in the mixing chamber.
Unique and proprietary injection mode/regime
There always is an offset between the two injectors. As both injectors are pulsing the liquid injector is open when the mixture injector is closed and vice versa (when the mixture injector is open the liquid injector is closed). The liquid injector pulses the cool liquid into the mixing chamber. The mixing chamber blends this liquid with the carrier gas. Finally, the mixture injector injects this mixture in a pulsed regime. The pressure of the carrier gas in the mixing chamber allows a blasting of the carrier gas-liquid mixture. This pulsed flow atomizes the fluid into extremely small droplets and enables a very efficient flash vaporization if the aerosol is delivered in a vaporization chamber. In case of Vapbox DLI vaporizers, the droplets vaporize before touching the internal walls of the vaporization chamber, limiting clogging risks. Thus it is possible to efficiently vaporize thermally unstable compounds without clogging.
The injection head cannot operate without pressurized carrier gas, since the carrier gas pressure and flow are used to blast, atomize and vaporize the liquid in the vaporization chamber. The carrier gas must not react with the liquid/precursor to atomize. Helium is often the best choice as carrier gas but Nitrogen, Argon and Hydrogen may also be used. Reactive gases such as Oxygen should not be used as carrier gas. They can promote unwanted precursor decomposition inside the mixing chamber. They can be used solely if a reaction with the liquid/precursor leading to atomization is excluded.
Very easy maintenance
The injection head can be easily disassembled by the customer for replacing the injectors if this should be required as for instance when the precursor/chemistry is changed and the risk of cross-contamination is to be eliminated.