B.A.R.C-530
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03
GOVERNMENT OF INDIA
ATOMIC ENERGY COMMISSION
WATER CHEMJSTRY STUDIES - I!f
USE OF HYDRAZrNE FOR SCAVENGING DISSOLVED
OXYGEN IN HIGH TEMPERATURE WATER - A REVIEW
H S. Mahal and K. S. Venkateswarlu
Chemistry Division
BHABHA ATOMIC RESEARCH CENTRE
X
, BOMBAY, INDIA_
11971
.i
B . A . R . C. ^530
S
'.
O
GOVERNMENT OF INDIA
ATOMIC ENERGY COMMISSION
WATER CHEMISTRY STUDIES - i n
USE OF HYDRAZINE FOR SCAVENGING DISSOLVED
OXYGEN IN HIGH TEMPERATURE WATER - A REVIEW
H. S. Mahal and K. S. Venkateawarlu
Chemistry Division
BHABHA ATOMIC RESEARCH CENTRE
BOMBAY, INDIA
1971
WATER CHEMISTRY STUDIES - III :
TJSE OF HYDRAZINE FOR SCAVENGING DISSOLVED
OXYGEN IN HIGH TEMPERATURE WATER - A REVIEW
H. S. Mahal and K. S. Venkateswarlu
In water-cooled reactors, in order to minimise corrosion,
it is essential to keep the dissolved oxygen content in coolant water
at a very low level.
deoxygenated.
Different procedures exist by which water is
One of the more promising methods involve the uee of
hydrazine (N^H^). In view of the importance of this procedure for the
operation of high temperature water loops, Reactor Engineering Division, Bhabha Atomic Research Centre, is contemplating to use it.
As
such it is considered desirable that the available information on this
topic be put together in the form of a report for ready reference.
ADVANTAGES OF THE USE OF HYDRAZINE
(1) One of the advantages of using hydrazine is that tts decomposition and oxidation products do not increase the dissolved
solid content of the water.
Hydrazine reacts with oxygen to give
nitrogen and water.
(2) 1% of hydrazine solution gives a pH = 9. 9. As the reaction is alkaline, this is an advantage because stainless steel and
carbon steel do not corrode in alkaline medium.
Moreover, in the
long run we may have to add less of alkali to maintain the pH at about
IP, and this amounts to saving in operational costs.
-2-
(3) With hydrazine treatment, the pH rises a little due to the
formation of ammonia and due to this rise in pH, the pick-up of Fe and
Cu in water drops to low levels, indicating lesser corrosion.
Straub
8c Ongman have shown that for a pH = 8-9 no iron or copper goes into
solution.
(4) Since it is a powerful reducing agent, it reacts with other
oxidising agents. Chlorine and hypo-chlorous acid rapidly and quantitatively oxidise hydrazine to N 2 - Theoretically, 1 ppm N,H^ reacts
with 2. 23 ppm of chlorine.
(5) The reaction is catalysed by metal surfaces. This is
important Bince the r saction proceeding more rapidly at the surface of
the metal pipe than in the bulk ox the liquid, provides protection to the
metal against pitting by the oxygen.
In view of the above advantages, hydrazine has been suggested
for nearly complete scavenging of dissolved oxygen in nuclear reactor
feed water. For example, the dissolved oxygen content of high temperature water in Reactor Engineering Division's primary pump
testing loop should not exceed 20 ppb and hydrazine is to be employed
to achieve this. It is to be noted that when the coolant under consideration is D2Qf it would be preferable to deoxygenate it by deutrazine, N 2 D 4 rather than N 2 H 4 as the use of- N 2 H 4 will lead to isotopic
dilution of D->O.
-3REACTIONS OF KYDRAZINE IN BOILER WATER
Hydrazine hydrate and its salts have found their greatest
use in boiler feed-waters as oxygen scavengers.
AdaftlB
(2)
h a v e
Leicester* *> and
reported that the reaction between hydrazino
r^
oxygen in cold distilled water or at room temperatures may be nonexistent, or very very slow.
Leicester states that there is some
evidence to show that if water and hydrazine are in very pure state,
hydrazine and the dissolved oxygen reaction may not occur at all.
Experiments in glass vessels phow that heat, pH or catalyst is
required to initiate the reaction between hydrazine and dissolved
oxygen in water.
Hydrazine is a reducing agent and reacts with dissolved
oxygen to give nitrogen and water.
i
N 2 H 4 + O2
» N 2 + 2H2O
......
(1)
The main factors in determining the rate of the process
are excess of hydrazine, initial concentration of dissolved O 2 , the
temperature and pH of the medium.
In practice, the reaction is not
so simple but nevertheless the equation describes the net result of
oxygen removal.
As at high temperatures hydrasine gives ammonia,
it is desirable that the reaction between hydrazine and oxygen should
be completed before the feed water enters the boilers
3N 2 H 4 — —
> 4NH3 + N 2
(2)
However, under the conditions existing in boilers, reaction
(1) should predominate.
If the concentration of N 2 H 4 is considerably
-4-
in excess, then the decomposition ye action (2) occurs.
Another reaction of N H. which is of interest, particularly
when starting hydrazine treatment, if thfct with metal oxides, e.g.«
N 2 H 4 + 6Fe 2 O 3
»N 2 + 2H2O + 4Fe 3 O 4
(3)
During the reaction of hydrazine with ferric oxide, which ie present
in water and on the metal surface, more of hydrazine is consumed in
the first period of hydrazine treatment, requiring an initial dosage
that is greater than that necessary after the boiler is conditioned.
Stones^) gives three mechanisms which will explain the
reaction between hydrazine and oxygen:
1) Homogeneous Reaction, occurring in the solution as a
simple bimolecular reaction represented by the following equation:
N2H4 + O2
> N 2 + 2H2O
(4)
2) Surface adsorption reaction, a heterogenous reaction
after adsorption on the Butrface of metal ions
j
* N 2 + 2H2O
. . . . (5)
adsorbed
3) Heterogenous Reaction, in which the ferric oxide in the
boiler and feed lines is reduced by N 2 H 4 to ferroso-ferric oxide
which is then converted to the ferric state by dissolved oxygen
{the process is cyclic and continuous),
4Fe 3 O 4
-5The experimental work of Gilbert^, Wickert*5) and Audrieth^ shows
that at and near the saturation concentration of O-, the reaction between N2H^ and O 2 ia not instantaneous.
It has been shown that during N 2 H 4 treatment of water, NHappears in the superheated steam of high pressure boilers and in the
condensates of drains and turbines. The appearance of NH3 is the
result of the thermal decomposition of excess N-H^ in qteam according
to equation1 (2).
The decomposition of N 2 H 4 between 140°-240°C has been investigated and it is found that the results can be extrapolated to higher
temperatures with a fair degree of accuracy' ' '. The reaction obeys
the equation
log
c
.
Co
kr
2.303
where k = velocity constant of the reaction, C = concentration of
videcomposed N 2 H 4 and CQ = its initial concentration, and ***= time
of decomposition. IfC,C o , % are measured, then k can be calculated for various temperatures. It is seen from the-above that the
time required for the decomposition of half of the N 2 H 4 does not
depend oa the initial concentration of the compound
f
,
.
2
0.693
k
This conclusion is of practical significance since after obtaining
reliable data concerning the half-time of large amounts of N 2 H 4 , it
is possible to calculate its residual concentration after passing
through steam super-heater.
chemical analysis.
method gives
This problem has not yet been solved by
Processing of the date according to the above
7 1 at various temperatures of interest as given below;
TABLE I
Time required for the decomposition
of half of the hydrazine
(*ZTl )
Temperature in °C
16O°C
^
200°C.
307.7
Sees
41
sees
250°C
6.5
seca
300°C
1.5
sees
The plot of log Ifck
of N-H 4 against the absolute textiperature
indicates that It U • ivereely proportional to the latter.
The data can
be 'extrapolated to higher temperatures also. It will be seen that
under the actual existing operating conditions of this equipment (high
pressure steam generators with steam superheating), negligibly small
traces of N_H. are present in the superheated steam.
Theoretically, in order to scavenge 1 PP m of O^ from
boiler water, 1 ppm of hydrazine i s required provided the efficiency
and purity are 100%, but this i s not usually the case, so excess
N , H . is required in practice.
-7AMMONIA FORMATION
It has already been mentioned that traces of N7H4 and NH3
in the condensate are an advantage since they help to maintain the
pH = 8-9. Above 350°C, decomposition of hydrazine further raises
the pH. Thug, if the concentration of N 2 H 4 is considerably in excsea
of that required to react with dissolved oxygen, then a part of it decomposes to give ammonia.
The low copper and iron pick-up is probably due to the
increase of pH of the condensate and suggests that if O? and CO2 are
low, ammonia is effective in reducing the amount of metal pick-up' "'.
Leicester^ 1 ' has shown that in an Italian plant'the ratio of
°2
:
^2^4 a t
tne t
^me
of
starting it was 1: 1.5, later on it was reduced
to 1 : 1.2 and even under these conditions, the reducing cycle was
maintained, while the pK rose from 8. 8 - 9.1 in the condensate due
to the presence of 0.1 ppm of NH3.
'
HYDROGEN FORMATION
In some tests with the experimental boiler. Jaeklhr
'
observed that hydrogen is also one of the decomposition products of
N 2 H 4 at 1500 p. s. i. The addition of 0.5 ppm of N ^ to the feedwater caused an increase of 6 ppb of dissolved hydrogen in the steam,
corresponding to about 10% of hydrogen added as hydrazine. There
is also data concerning the decomposition of N2H4 at temperature
269* - 637°C with evolution of hydrogen'3'
-8-
2
4
2 N H
3
+ 2N 2 + 3H2
(8)
In an operating reactor, due to radlolysis of water, molecular hydrogen is formed in the coolant. It is assumed that the additional H 2 from
N 2 H 4 is very much less than the radiolytic yield.
THE VARIABLES IN N 2 H 4 REACTION WITH OXYGEN - TEMPERATURE,
PRESSURE, pH, CATALYSTS
The reaction between hydrazine and oxygen at room temperatures is very very slow, but at higher temperatures the rate increases.
Upto 70°C the reaction rate increases to slighly more than double
every 10°C.
Ellis and Mor eland* ' performed the experiments on the
reaction between N 2 Hj and oxygen at 20 C using pure water. A 10%
excess N-H^ was used. The experiments were performed in all glass
apparatus. The rates of reaction were also determined at 35°C and
51°C. Over this temperature range, there is a Bmall increase in the
rate with temperature. Though the rate is approximately doubled tor
every 10°C rise in temperature, It ia still low. Even at 51°C, only
60% of the O2 reacts after 10 hours. Assuming the reaction rate to
be doubled for every 10°C rise, at 170°C the time would be only a
few seconds.
Influence of pH
The pH of the water also affects the rate of reaction between
N 2 H 4 and oxygen. The rate is higher between pH 9 and 11 than below
-9-
9 and falls abruptly beyond pH 11. At pH 10. 5, the rate of reaction is
maximum. Also, the rate of reaction at pH 9 is nearly half of thak at
pH 10.5. A marked increase in the rate is seen -when the pH la
increased from 7 to 9. With increase in pH to 11, the rate falls off to
an intermediate value. This is in agreement with the findings of Gordon,
who found N 2 H. to be a most effective reducing agent in the pH range
9-10. B. This fact is important since the boiler feed waters are controlled in this pH range. The primary coolant in RAPP is also maintained at pH 10. However, the rates are still low and further modifications are necessary to increase them. The purity of water also
affects the rate of reaction. The reaction is much slower as the
purity of water increases.
Catalysts
Copper salts and activated carbon are the best catalysts in
increasing the rate of reaction between N_H4 and oxygen. The reaction
is catalysed at the surface. This is important since the reaction proceeding more rapidly at the surface of the metal than in the bulk of t h e ^
solution protects the metal from pitting by oxygen attack. . The effect
of N2Hg is to reduce the O 2 concentration at the metal surface.
Ferric oxide also acts as a catalyst in the N 2 H 4 /O 2 reaction.
Ferric oxide is first reduced by the N 2 H 4 to ferrosoferric oxide (black)
and O 2 is removed by oxidising the magnetite back to hematite. This
is ; supported by the fact that some two weeks are required even when
using 100% excess N 2 H 4 before the latter can be detected in the boiler
-10water. It appears that this time is required for the N_H - to reduce
all the ferric oxide in the system to Fe^O. and only after this reaction
is completed, it is possible for the excess to build up a residual and
also produce NH3. Discontinuation of N2H^ addition even for long
periods still results in the complete deoxygenation of the steam. The
probable explanation is that the reduced iron oxides continue to remove
O, to such times till they are reoxidised.
The catalytic effect of metal ions Cu ++ , Fe + + , Co**, Nl ++ #
Cr + + + , and Mn++ (added as sulphates) in concentrations giving 1 ppm
of the metallic ions has been studied. Usually hasiness develops in
the reaction flasks after the addition of hydrazine, presumably due to
the formation of an insoluble reduced complex. The presence of 1
ppm of either Cu ++ or Co"*"*" ions gives a great increase in the rate of
reaction; the reaction is completed in 4 hours at 20°C.
Heterogenoua Catalysts
Here a solid insoluble meterial is immersed in solutions BO
as to present a relatively large area to the reactants. With Cu
gauze, the reaction with O2 is complete in 5 hours at 20°C. The
effect of glass wool is interesting because it gives a considerable
increase in the fate of reaction. It suggests that the reaction is
catalysed at the surface and that the increase in the rate is due to
the large surface area.
-11Copper Column
In water containing 40% N2H4 and Na 3 PO 4 , to bring the pH
to 9-10 when passed through a glass column of 1 inch diameter packed
with bright Cu turnings to a height of 55 cm., the reaction occurs
rapidly but less BO compared to activated carbon. The time of contact is varied by varying the flow-rate.
The quantitative results are
summarised in Table II.
TABLE II
Results of Experiments Using Copper Column
Temp. °C
Rate of flow
cm/Bee
Estimated
time of
contact, sec.
O content
2
of H_O
emerging
mg/1
% O,
removed
20
0.12
324
0.4
95
23
0.25
156
4.6
40
38
0.33
120
1.5
75
As mentioned before, activated carbon is also used to remove
oxygen dissolved in water in presence of ^ H ^ . It has beeh shown
that the grade of activated carbon has little influence on the reaction
between oxygen and N 2 H 4 . Some typical results given in Table IH show
that the reaction is complete in 90 sec. at 20°C and in 9 sec. at 42°C.
Addition of a trace of CoSO4 does not increase the reaction. In Germany
and Italy, activated carbon is used for O 2 /N 2 H 4 reaction in the deoxygenation of boiler feed-waters.
-12TABLE HI
Results of Experiments using Carbon Column
Rate of
Length of
column, cm . Temp. flow
°C. cm/sec
EBtimated1 O, content
time of
ofH 2 O
emerging
contact,
mg/1
sec.
% o2
removed
600
0.1
>98
20
0.09
0.55
90
0.1
>98
29
16
1.67
9
4.8
40
29
20
10
2.4
70
29
20
32
0.9
90
29
42
1.48
0>8
1.67
•29
20
1.38
11
10
42
1.51
18
1.67
100
20
100
0.15
>97
1.0
87
3.3
2.0
65
9
3.0
60
* using 200% excess N 2 H 4
@ Water had 2 ppm Cu++
Note: 0.1 mg O /I is the lower limit of the method of analysis used.
Ellis'
is
t has likewise reported that, When the feed temperature
< 100°C and oxygen concentration is high, deoxygenation can be*
achieved using the theoretical amount of N~HJ and passing the water
through a carbon bed as catalyst to accelerate the reaction. The use
of a filter containing a special active carbon for catalysing reaction,
is also recommended. The carbon assumes the function of an autof egulaior, absorbing the excess N-H^ and restoring it when there i s
deficiency. Furthermore, the filter extracts any Cu in suspension
in the water and therefore a carbon filter, is recommended where the
Cu content is high.
-13How much Excess N2H4 can be Employed - The Place of Addition
In his paper on 'boiler feed water treatment and oxygen
scavenger' Ellis*
' mentions that in a high pressure boiler, because
of the high temperature of the boiler feed water, hydrazine reacts
rapidly with oxygen. After thermal deaeration, 50 to 300% excess hy«drazine above the theoretical amount is added to the feed and thus a
small excess is maintained in the boiler.
Zanchi describes the results obtained at Taveiszan'o,Power
Station using cylindrical shell boilers generating steam at approximately 1800 p. B, i. and 520°C. Copper was present In the circuit. The
feed water after deaeration contained 0. 01 ppm O2 and approximately
400% excess hydrazine was added at 130°C. The exact amount of NgH.
added was varied to give a pH 8. 5 in the feed water. A residual of
5 ppm of Na2SO3 was maintained in the boiler.
Using photometric O-toluidine method, no O2 was detected in
the saturated and superheated steam; also there was no hydrazine in
the steam and NH 3 content was 0.1 - 0.2 ppm. The boiler had 0. 02
ppm copper and in the steam less than 0. 002 ppm copper. The Fe
content was 0. 02 - 0. 03 ppm in the circuit.
Practical experience in the use of hydrazine for boiler feed
water treatment has shown that the amount of hydra*lne added should
not exceed three times the amount of oxygen content of the deaerated
feed water. Initially hydrazine is consumed by any Fe 2 O 3 present.
So the initial hydr&zime dosage must be higher than that when the
-14boiler 1B conditioned. It is necessary to maintain"a certain residual
value in the boiler once it is conditioned, The maximum residual..
varies from boiler to boiler ranging from 0. 05 to 0. 25 ppm with a
typical value of 0.1 ppm. The corresponding hydrasine addition
ranges from 0. 005 to 0. 03 ppm hydrazine in tha boiler feed water.
(3)
According to Stones , initially hydrazine reacts with
and CuO as follows:
,
2 - * Z,4 ,
4CuO
+ N2H4
N
£,
,+ 2H,O
2 + 4Fe,O,
34
^ N 2 + 2H 2 O + 2Cu 2 O
I-v •
-..(9)
j
No further reduction of FeJO^ takes place. These reactions account
for the fact that on starting-up a high pressure boiler even when using
100% excess hydrazine, some two weeks pass before a residual of the
deoxidant is found in the boiler.
The addition of N-Hg 100% in excess of the oxygen value to
a boiler (at Duston) of 625 psi resulted in a fairly rapid rise of NH3 ,
concentration and thus in an increase in the pH of the condensate,
while a 50% excess of hydrazine just maintained a hydrazine residu'al
in the boiler and resulted in a lower NH-j concentration in the steam*
without affecting the pH and metal pick-up. When 700% excess of
hydrazine was used, there was an increase in (1) N^Hi boiler residual,
(2) increased NH- concentration, and (3) presence of small amounts
of hydrazine in the saturated steam.
.,
Kot" *) has mentioned that from the experience gained during
the operation of electrical power plants where N,H. treatment of water
-15was employed, it w t i found that only the decomposition of hydrasine
with the evolution of NH3 was of any practical importance.
To sum up, good results in the removal of oxygen are
achieved when N 2 H 4 is introduced in amounts 2-3 times that of the
residual oxygen remaining in the water after deaeratien. The excess
of hydrazine should be maintained at a level 0. 02 - 0. 03 mg/litre.
In order to protect N 2 H 4 from oxidation by air the container
1B sealed with Teflon lining which is removed when the container is to
be filled or emptied. Filling of the container with N2H4.H2O
or its
emptying is carried out by gravity flow or N, pressure. Prior to
N9H4 treatment of the water the internal surfaces of the feed circuit
and steam generators is cleaned for any deposits of Fe and Cu oxides.
AH connecting parts, fittings and containers of the dosage device for
the introduction of N 2 H 4 (Fig. 1) must be checked for leaks. Before
the introduction of N 2 H 4 , a number of feed water samples is taken for
the determination of O 2 , Fe and Cu oxides aad sometimes NH3. From
the results obtained, the first portions of N 2 H 4 to be added is calculated.
Hydrazine treatment of water is carried out in two stages,
or continuously; First, an increased (provisional) amount of hydrasine
solution is added to achieve a "saturation of the system" followed by
the introduction of normal amount of the reagent serving for the nearly
complete removal of oxygen.
The increased (provisional) amount of N 2 H 4 Is calculated f«**a
the oxygen content and the content of Fe(m) and Cu{ll) oxtdea in the
-16deaerated feed water before N2H^ treatment. For calculation, the
following formula is used:
g; = 3cj + 0. 3c 2 + 0. 15c 3
. . . (10)
gi = the increased provisional amount of N9H4 mg/1;
c. = concentration of O2 in the feed water before the introduction'of
N2H4; c, = concentration of Fe^O, mg/1, c , = concentration of
CuO mg /I.
REAGENTS CONTAINING N 2 H 4 GROUPING
Hydrazine salt of dinaphthyl methane disulphonic acid was
used in some instances as (a) this material was alkaline'in nature
and did not affect the pH control of the boiler, (b) it is a very active
dispersing agent and thus assists in fluidiuing any solids in the boiler,
(c) in view of the catalytic effect of the ion exchange resins on the
N 2 H 4 - O2 reaction, it was thought that sulphonated naphthyl radical
of this compound might assist the reaction, and (d) the dry meterial
had approximately 11-15% available l^H^. It is also highly soluble in
cold water. Initial tests by using sufficient amount of this compound
to give 200 - 300% excess of hydrazine, showed that the amount of
oxygen removed at the feed pump (at 150°F), increased from 60 to 80%
and in the boiler water from 86 to 91%. At 203°F, the oxygen removed at the feed pump discharge showed an increase from 81 and in the boiler water from 94 - 96%. Table IV gives percentage
removal of O_.
TABLE IV
Summarized Results of Pilot-Plant Boiler Tests
__.__«>——__••—.••—._.•._.—
_ ..
l rial
Series
No.
I
— — . — . - _ _ — • - _ _ . —
— ••—>•——.•-
.
—
_
—
.
_
—
_
— _ — _ »
—
_»—.—.—.—.—I — . — . — — . — . _ _ . _
Conditions of trial.
• __,__.-._._.-,-,-._,_.-._._._,_.-_.._____-___.-_,_-_-_._.___.__.._-._Oxygen, scavenger
0~ in feedTemp, of
used
water ppm
feed water
°F
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
_
N Z H 4 .H 2 O
0.02
150
31
55
Dihydrazine Phosphate
0.0Z
150
32
55
m
N Z H 4 .H 2 O
0.20
150
60
84
IV
DihydraKixte Phosphate
0.20
150
58
86
V
VI
N 2 H 4 .%O
N,H_. R2O + activated-
0.20
203
81
94
II
2 4
VU
Yin
charcoal
°-
2 0
1 5
°
7 2
^0
N2H4Mltofdinapthyl.
methane disolphonilc
acid
-do-
0.20
203
" • » • » • »
Percentage of
Original O-> removed
_----«.___« A. ___________
Sampled at Sampled at
Feedpump boiler guage
discharge
glass
86
r
/6
-4
t
-18PLANT EXPERIENCE ON F e 2 O 3 AS CATALYST
Leicester' ' Las mentioned that oxide films, on the surface
of a solid or on suspended particles in solution, may provide the
necessary sites for N^H^ - C*2 reaction.
In a pilot-plant boiler at. the Admirality Materials Laboratory, experiments were conducted at 500 p. s. i. g, -and It was observed
that the N2H4 - O, reaction is dependent on surface properties. It
would appear that the initial reaction machanism might well be between,
hydrazine and Fe2O^ ( thereby reducing iron to the ferrous condition and
this is followed by the reoxidation of ferrous to ferric by dissolved
oxygen of the feed water. This would certainly seem to be the case in
the example quoted, as a change from red coloration of ferric oxide
to the black colour of the ferrous oxide was observed after the addition
of N^H.. When the hydrazine addition was stopped, removal of d i s solved C*2 continued until the ferrous oxide in suspension in the boiler
water had become fully oxidised to the original ferric state. This is
a typical case where the presence of a suspension of iron oxide in the
feed water may provide a large oxide surface area to catalyze the
N,H . reaction with dissolved oxygen.
HAZARDS AND SAFETY PRECAUTIONS
1) Hydrazine should be stored in a cool place (<40°C)
to prevent possible fires or explosions from the vapours.
2) The feed solution should be added to a stainless steel
tank filled with water.
-193) Rusty containers should not be used as hydrazine may react
violently with Fe 2 O 3 .
4) Inhaling of sharp irritating vapours (>100 ppm) should
be avoided.
5) Rubber gloves, goggles, mask or other protective equipment should be used to prevent solution or vapours from coining into
contact with skin.
6) Affected skin should be washed with soap immediately
after flushing with water. Some individuals get dermatitis even on
contact with small amounts of N2H4.
7) N2H . reacts exothermically and often violently with many
oxidising agents, and contact with these should be avoided.
8) The area of metal exposed to hot N^H^ vapour should be
kept to a micimum.
9) The equipment should be flushed well with water before
opening for repairs.
10) Freshly fabricated equipment should be treated well with
diluted N 2 H 4 to deactivate catalytic surfaces.
-20REFERENCES
1. Leicester; Trans A. S. M. E. 7<3, 273(1956)
2. Adams; Trans. A.S. M.E. 78, 273 (1956).
3. Stones; Chem & Ind. 120-8 (1957)
4. Gilbert; J. Am. Chem. Soc. 51., 2744 (1929)
5. Wickert; Arch. MetaU-Kunde 3_, 113(1949)
6. Audrieth; Ind. Engg. Chem. 43, 1774 (1951)
7. Straub; Combustion J_, 34 (1957)
8. Woodward; Power No. 11, 80(1956)
9. Alexander and Rununel; Trans. A. S. M.E. 72» 519(1950)
10. Jacklin; Trans. A.S.M.E. 78, 273 (1956)
11. Kot; Water and water treatment in Nucl. power plant p. 98
12. Ellis & Moreland; Chem. Process Engg. p.47 (1956)
13. Ellis; Chem. Process Engg. p. 81 (1955)
Condensate
input
Discharge of solution
-*-into water treatment
tank
Fig.1 Diagram of the Installation for the introduction of Hydrazine.
t
1 Portable tank, capacity30Ut.
2. Dosage tank with 1-5 ttr each.
3. Glass liquid level indicators.
4 Plunger type dosage device.