Process and apparatus for measuring gaseous fixed nitrogen species
First Claim
1. An improved process for measuring the total concentration of fixed nitrogen species, including NO, NO2, NH3 and HCN, in a gaseous mixture involving the steps of contacting said gaseous mixture with a conversion catalyst at elevated temperature and in the presence of excess elemental oxygen and thereby converting said fixed nitrogen species to NO and measuring the resulting NO concentration and calculating therefrom said total concentration of gaseous fixed nitrogen species, in which the improvement comprises the combined steps of:
- (a) reducing the pressure of said gaseous mixture to about 0.03 MPa or below;
(b) preheating said gaseous mixture from step (a) to a temperature in the range of about 700°
-1100°
K in a non-catalytic preheat zone; and
(c) contacting said preheated gaseous mixture from step (b) with said conversion catalyst at a temperature in the range of about 800°
-1100°
K. for a sufficient time to convert substantially all of said gaseous fixed nitrogen species to NO.
3 Assignments
0 Petitions
Accused Products
Abstract
Process and apparatus for measuring total fixed gaseous nitrogen species, including NH3, NO, NO2, HCN and organic amines in gaseous mixtures. The process involves catalytic conversion at elevated temperature of all fixed nitrogen species to nitric oxide, NO, followed by chemiluminescent measurement of the resulting NO concentration. The improvement features of the process are the use of a reduced pressure gaseous sample flow to prevent N2 poisoning of the heated platinum catalyst and a preheat step of the reduced pressure gaseous mixture in an inert, non-catalytic quartz preheater prior to catalytic conversion to prevent loss of some species, such as NH3, through premature catalyzed reaction with NO and subsequent loss from the system as N2.
374 Citations
20 Claims
-
1. An improved process for measuring the total concentration of fixed nitrogen species, including NO, NO2, NH3 and HCN, in a gaseous mixture involving the steps of contacting said gaseous mixture with a conversion catalyst at elevated temperature and in the presence of excess elemental oxygen and thereby converting said fixed nitrogen species to NO and measuring the resulting NO concentration and calculating therefrom said total concentration of gaseous fixed nitrogen species, in which the improvement comprises the combined steps of:
-
(a) reducing the pressure of said gaseous mixture to about 0.03 MPa or below; (b) preheating said gaseous mixture from step (a) to a temperature in the range of about 700°
-1100°
K in a non-catalytic preheat zone; and(c) contacting said preheated gaseous mixture from step (b) with said conversion catalyst at a temperature in the range of about 800°
-1100°
K. for a sufficient time to convert substantially all of said gaseous fixed nitrogen species to NO. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. An improved process for measuring the total concentration of fixed nitrogen species, including NO, NO2, NH3 and HCN, involving the steps of contacting a gaseous mixture, containing one or more of said species with a conversion catalyst at elevated temperature and in the presence of excess elemental oxygen and thereby converting said fixed nitrogen species to NO and measuring the resulting NO concentration by NO chemiluminescence and calculating therefrom said total concentration of gaseous fixed nitrogen species, in which the improvement comprises the combined steps of:
-
(a) reducing the pressure of said gaseous mixture to about 0.001 to 0.030 MPa; (b) preheating said gaseous mixture from step (a) to a temperature in the range of about 800°
-1000°
K in a fused quartz vessel; and(c) contacting said preheated gaseous mixture from step (b) with platinum gauze at a temperature in the range of about 800°
-1000°
K for a sufficient time to convert substantially all of said gaseous fixed nitrogen species to NO.
-
-
11. An improved apparatus for measuring the total concentration of fixed nitrogen species in a gaseous mixture, including NO, NO2, NH3 and HCN, involving a means for introducing said gaseous mixture into said apparatus, a catalytic converter for converting said fixed nitrogen species in said gaseous mixture at elevated temperature to NO and an NO detector for measuring the resulting NO concentration in which the improvement comprises the combined elements of:
-
(a) means for reducing the pressure of said introduced gaseous mixture to about 0.03 MPa and below; and (b) a non-catalytic preheater for preheating said reduced pressure gaseouse mixture in the temperature range of about 700°
-1100°
K, prior to contacting said catalytic converter. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. An improved apparatus for measuring the total concentration of fixed nitrogen species in a gaseous mixture, including NO, NO2, NH3 and HCN, involving a means for introducing said gaseous mixture into said apparatus, a platinum gauze catalytic converter for converting said fixed nitrogen species in said gaseous mixture at elevated temperature to NO and an NO chemiluminescence detector for measuring the resulting NO concentration, in which the improvement comprises the combined elements of:
-
(a) vacuum means for reducing the pressure of said introduced gaseous mixture to about 0.03 MPa and below; and (b) a quartz preheater for preheating said reduced pressure gaseous mixture in the temperature range of about 700°
-1100°
K prior to contacting said platinum gauze catalytic converter.
-
Specification