Apparatus for silicon nitride precursor solids recovery
Reference Number: N 03-03
Inventors: Crosbie, Gary M.; Predmesky, Ronald L.; Nicholson, John M.
Owner: NISTAC
USPTO Link:5403563
Invention Summary
In accordance with the invention, method and apparatus are provided for collecting
solids, such as reaction product solids, entrained in a gas flow comprising condensable
vapor. In the case of a gaseous outflow from a reaction situs during a reaction, the
gaseous outflow comprises vapor condensable at a reduced temperature, that is, at
a condensation temperature lower than the temperature at which it exits the reaction
vessel. The gaseous outflow is passed from an outlet of the reactor vessel to a static
mixer heat exchanger. The static mixer heat exchanger has a static mixer cooling chamber
defining a flow path for the gaseous outflow between the inlet and an outlet. Static
mixer surfaces are provided in the flow path of the static mixer cooling chamber for
capturing the entrained solids in a condensate formed of the aforesaid condensable
vapor. Specifically, the static mixer heat exchanger further provides cooling means
for maintaining the static mixer surfaces at a temperature not greater than the aforesaid
reduced temperature at which the condensable gas condenses. Entrained reaction product
solids in a gaseous outflow contact, and are thereby captured in, the condensate formed
on the static mixer surfaces. The condensate and the reaction product solids captured
therein can be collected, for example, for return to the reactor vessel or for other
processing.
The present invention provides advantages in collecting or recovering reaction product
solids which may otherwise be lost or which would otherwise require different, more
expensive or difficult collection methods and apparatus. Such collection of reaction
product solids will in many instances increase the effective reaction product yield,
thereby improving the efficiency of the production process.
In addition, in those embodiments of the invention wherein the condensate formed
in the static mixer heat exchanger comprises reactant for the ongoing reaction, the
return of the condensate, with the recovered reaction product solids, can further
improve the efficiency of the production process. This is particularly true where
the reactant in the condensate would otherwise be lost or require more expensive or
difficult collection and return apparatus.
The method and apparatus of the invention are particularly advantageous in preferred
embodiments of the invention, discussed further below, wherein silicon nitride precursor
solids are entrained in a gaseous outflow from a reaction situs during an ongoing
reaction. The static mixer heat exchanger can treat gaseous outflow from the reaction
situs anaerobically, including steps of receiving the gaseous outflow, forming a condensate
of a condensable vapor in the gaseous outflow to capture entrained solids, and returning
the condensate, optionally through intermediate fluid communication means, to the
reaction situs or other receiving point for further processing. In such preferred
embodiments the invention is particularly advantageous in that the entrained solids
comprise reaction product, thus directly enhancing process yield, and the condensate
returned with the solids to the ongoing reaction is usable reactant.