Gas phase reaction system using anhydrous ammonia removes nitrogen dioxide. System consists of ammonia injection and mixing section, reaction section /reactor/, and scrubber section. All sections are contained in system ducting

Metzler, A. J.

Slough, J. W.

English

NASA Technical Reports Server

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NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Antipollution System to Remove Nitrogen Dioxide Gas 
The problem: 
A combustor test facility, developed for an ad-
vanced combustor research program, utilized an 
oxidant-rich hydrazine-nitrogen tetroxide rocket as 
a gas generator to simulate high enthalpy inlet flow
The solution: 
A gas-phase reaction system utilizes ammonia 
(NH 1 ) as the reactant to remove the NO,. Anhydrous 
ammonia was selected on the basis of its effective-
ness in remo Ing NO, from rocket exh'ust emissions 
and its practicality for use in a higli-olume-flo 
system. 
The system consists of: (I) an ammonia injection 
and mixing section: (2) a reaction section (reactor); 
and (3) a scrubber section. All three sections are con-
tained
	 thin the system ducting. 
Hole 
Spacer
Steam Orifice 12 Holes 
NH3 Orifice 
Distribution of Injection Locations	 Detail of Injector Construction 
Figure 1. Ammonia-Steam Injector 
conditions to the combustor. The high propellant 
flow rate was 45.4 kg/sec (100 lb/see), and the ex-
haust was pumped to the atmosphere through a stack. 
The exhaust emissions contained sufficient NO2, 
even from 5-sec test runs, to form large reddish-
brown clouds which dispersed slowly and could drift 
and settle over nearby populous areas. Although the 
concentration of NO, in the drifting cloud was low, 
concern over possible effects on the adjoining com-
munities dictated that the NO level in the exhaust 
emissions be reduced essentially to zero and that the 
eases emitted from the stack be benign. 
I his document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights. 
How it's done: 
The efficiency of NO removal depends on both the 
reaction time and the ammonia concentration. The 
system design optimized the NO - NH 1
 reaction 
by providing long reaction time and excess ammonia 
beyond that required for stoichiometry. 
The ammonia injection and mixing section (see 
Fig. 1) consists of a manifold system with multiple 
injectors to insure rapid and uniform injection and 
distribution of ammonia gas across the flow stream 
of the nitrogen-dioxide-containing gas. Liquid am-
https://ntrs.nasa.gov/search.jsp?R=19710000391 2020-03-17T02:30:18+00:00Z
Spray 1 Bar E F/I Mesh
Spray Bar C 
1i	 A	 Sum[
Pump 
Exhaust Stack
To Drain 
Figure 2. Exhaust-Stack Scrubber System 
monia flow is metered and controlled ahead of the 
manifolds. The injector-mixer design may incor-
porate an auxiliary system to provide steam flow at 
the point of Injection to insure the complete 
vaporization of the ammonia at the injection point. 
Steam is provided at each injection point through 
a separate manifold as shown in the figure detail. 
Ammonia is injected into the stream through the 
annular clearance provided around the steam line, 
and flows normal to the steam jets. The reactor is a 
contained volume which provides the required reac-
tion time for the components. Reactor length and 
diameter may be complementarily adjusted to provide 
the required residence time within the duct system.
The scrubber section, Figure 2, is a high-surface-
contact-area water curtain device through which 
the reactor flow is forced. Its action is three-fold: 
(I) Solid reaction products are washed from the gas 
stream; (2) excess ammonia gas is absorbed by the 
ater and removed from the gas stream; and (3) the 
ater is recirculated and excess NH is absorbed, 
resulting in a solution capable of removing any 
unreacted nitrogen dioxide which might have passed 
the reactor. 
Gases from the reactor enter the scrubber at A 
and are forced to the outer periphery of a deflector 
B. In this region, the gas contacts the highly atomized 
spray from multiple spray nozzles on spray bar C, 
located to effectively distribute liquid spray through-
out the annular area around the periphery of B. A 
dewatering mesh at D removes atomized liquid 
and provides surface contact area. Second stage 
spray bars at E and a mesh at F serve the same 
purpose as their counterparts, C and D. Spray 
water is collected in sump G, returned to the pump 
inlet and recirculated to the spray bar manifold. 
Notes: 
I. At least 99% of the NO2 initially present was re-
moved, and the exhaust from the stack was white. 
2. Requests for further information maN he directed 
to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B71-10393 
Patent status: 
No patent action is contemplated by NASA. 
Source: A. J. Metzler and J. W. Slough

Lewis Research Center

(LEW- l 1297)
. 
Bud 71-10393	 (ateer\ 04


Antipollution system to remove nitrogen dioxide gas

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