United States
Environmental Protection
Agency
Municipal Environmental Research'
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-215 Oct. 1981
Project Summary
Modification of Spill Factors
Affecting Air Pollution:
Volume II. The Control of the
Vapor Hazard from Spills of
Liquid Rocket Fuels
J. S. Greer, S. S. Gross, R. H. Hiltz, and M. J. McGoff
The hypergolic rocket fuels, hydra-
zine and nitrogen tetroxide, are
volatile hazardous materials of special
interest to the Air Force. Through
monitoring of ongoing U.S. Environ-
mental Protection Agency (EPA)
programs, the Air Force has maintained
cognizance of the developing state of
the art in spill control. This Air Force
supplement to the basic EPA program
was a preliminary evaluation of the
potential of cooling and foam covers
to mitigate the vapor hazard from
hydrazine and nitrogen tetroxide.
Coolants exhibited some control
over vapor release from the hypergolic
fuels. Liquid nitrogen was the most
effective material. Logistics were
considered a major disadvantage for
the anticipated spill scenarios.
Foams using commercial agents
were beneficial with hydrazine, but
they were not effective against nitro-
gen tetroxide. Modified foam systems
incorporating acrylic resins were more
effective. They were able to maintain
hydrazine concentrations at or below
0.5 ppm. Some control was also
exhibited with nitrogen tetroxide, but
there was intermittent vapor release
through the foam.
Based on the results of this study,
the acrylic foams are judged to offer a
promising approach to the control of
the vapor hazard from hydrazine and
nitrogen tetroxide.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory, Cincin-
nati, OH. to announce key findings of
the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Liquid rocket propellants present one
class of volatile hazardous chemicals,
and their toxic hazard is well recognized.
The Air Force has monitored the
evolving state of the art in spill control
for its application to their particular
situations. Successes in controlling
vapor hazards with aqueous foams and
by cryogenic cooling led the Air Force to
undertake an investigation of these
techniques as mechanisms to control
the vapor hazard from spilled rocket
fuels.
A program was instituted for the
specific purpose of investigating cooling
and aqueous foam blankets to mitigate
the vapor hazard of hydrazine and
nitrogen tetroxide. This study was
primarily a survey and was not intended
to develop a total system fully. The goal
was to use the existing state of the art to
the fullest extent.
-------
Discussion of Results
Each technique was pursued inde-
pendently for each of the propellant
materials. The program used a series of
laboratory tests to evaluate the various
methods and materials for vapor sup-
pression. Vapor concentrations above
the two fuel materials were measured
using detector tubes. Tests in which the
concentrations exceeded the maximum
limit of detector tubes (about 35 ppm)
were considered failures.
The coolant portion of the study
investigated water ice, dry ice, liquid
COz and liquid nitrogen. For nitrogen
tetroxide, only liquid nitrogen was able
to reduce the vapor concentration below
the detector tube limit. To maintain the
low vapor level, fairly large quantities of
nitrogen were required with fairly
frequent make up indicated. Water ice
had an immediate but small effect that
persisted only as long as the ice
remained. As liquid forms, it reacts to
form nitric acid. The heat of formation
more than offsets the cooling effects.
The addition of coolants to hydrazine
did reduce vapor levels below the limits
of the detector tubes, but they were not
able to approach the threshold limit
value. Wet ice produced the slowest
reduction of vapor concentration with
hydrazine, but it also achieved the
lowest vapor concentration ultimately.
This result was due to the accompany-
ing dilution as the ice melted.
The evaluation of foam systems
initially considered commercially avail-
able foam agents. Representative
materials of protein, fluoroprotein,
aqueous film-forming foams (AFFF),
and polar solvent and surfactant foams
were selected based on the character-
istics identified in a previous EPA
program.
None of the materials selected were
able to exercise any control over the
vapor release rate of nitrogen tetroxide.
In contrast, nearly all were able to
reduce substantially the vapor concen-
tration above hydrazine. These levels
varied from 2 to 20 ppm, depending on
the foam type. The duration of control
also varied as a function of foam type.
A third type of foam system was also
tested based on previously developed
acrylic modified foams that gel when
used on ammonia or amine materials.
The gelled foam forms a stable barrier
with a low permeation of hydrazine
vapor. The drainage mixes with the
hydrazine and gels the top liquid layer.
The two layers, foam and gel, were able
to reduce the vapor concentration to
less than 0.5 ppm.
The acrylic foam formulations were
also beneficial in reducing vapor release
from nitrogen tetroxide. They were not
able to give continuous control, how-
ever. The vapor build-up beneath the
foam layer resulted in intermittent
vapor pulses (breathing).
A series of polymeric materials was
tested alone and in combination with
the acrylic modifier in an effort to
improve the control over nitrogen
tetroxide. Within the time limit of this
program, no major improvements over
the original MSA formulations were
found.
Conclusions
The study results showed that coolants
should be rejected as a method of
controlling the vapor hazard from spilled
liquid hydrazine or nitrogen tetroxide.
Tests showed some reduction in vapor
release, but when this was equated
with the volume of coolant material
required and the logistics involved for
projected scenarios, cooling was nol
considered to be a viable approach.
Aqueous foam systems offered sig-
nificant benefits for hydrazine. Several
commercially available agents were
able to reduce vapor levels to the 2- to 5-
ppm range. None of the agents were
effective against nitrogen tetroxide.
Acrylic modified aqueous foams
(developed previously for ammonia and
similar materials) were shown to be
effective for hydrazine. Foam layers
reduced vapor levels to the 0.5-ppm
range. These agents also had some
positive effects on nitrogen tetroxide.
This study concluded that acrylic
modified foams offered the best mech-
anism to control the vapor hazard from
the two types of rocket propellant
materials.
The full report was submitted in
partial fulfillment of Contract No. 68-
03-2648, Task 9B, by MSA Research
Corporation under subcontract to
Rockwell International under sponsor-
ship of the U.S. Environmental Pro-
tection Agency.
J. S. Greer, S. S. Gross. R. H. Hiltz, and M. J. McGoff are with MSA Research
Corporation. Evans City, PA 16033.
John E. Brugger is the EPA Project Officer (see below).
The complete report, entitled "Modification of Spill Factors Affecting Air Pollu-
tion: Volume II. The Control of the Vapor Hazard from Spills of Liquid Rocket
Fuels," (Order No. PB 82-108 390; Cost: $6.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at.-
OH and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Edison, NJ 08837
•ft U.S GOVERNMENT PRINTING OFFICE, 1981 —559-017/7397
-------
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
RETURN POSTAGE GUARANTEED
PS 0000329
U & ENVIK PROTECTION
REGION 5 LIBRARY
230 3 DEARBORN "
CHICAGO IL
AGENCY
STREET
606Q4
------- |