U.S. patent application number 09/984435 was filed with the patent office on 2002-04-25 for oxygen scavenger and boiler water treatment chemical.
Invention is credited to Shimura, Yukimasa, Taya, Shiro.
Application Number | 20020046976 09/984435 |
Document ID | / |
Family ID | 27464337 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020046976 |
Kind Code |
A1 |
Shimura, Yukimasa ; et
al. |
April 25, 2002 |
Oxygen scavenger and boiler water treatment chemical
Abstract
A boiler water treatment chemical includes a heterocyclic
compound with N-substituted amino group, or the salt thereof, and
alkaline agent and/or water soluble polymer.
Inventors: |
Shimura, Yukimasa; (Tokyo,
JP) ; Taya, Shiro; (Tokyo, JP) |
Correspondence
Address: |
KANESAKA AND TAKEUCHI
1423 Powhatan Street
Alexandria
VA
22314
US
|
Family ID: |
27464337 |
Appl. No.: |
09/984435 |
Filed: |
October 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09984435 |
Oct 30, 2001 |
|
|
|
08975000 |
Nov 20, 1997 |
|
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Current U.S.
Class: |
210/749 ;
210/750 |
Current CPC
Class: |
C02F 1/20 20130101; C23F
11/149 20130101; C23F 11/10 20130101 |
Class at
Publication: |
210/749 ;
210/750 |
International
Class: |
C02F 001/68 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 1996 |
JP |
H8-318140 |
Mar 17, 1997 |
JP |
H9-63579 |
May 28, 1997 |
JP |
H9-138468 |
Oct 21, 1997 |
JP |
H9-288490 |
Claims
What is claimed is:
1. A boiler water treatment chemical including a heterocyclic
compound with N-substituted amino group, or the salt thereof, and
alkalic agent and/or water soluble polymer.
2. A boiler water treatment chemical according to claim 1, further
including neutral amine.
3. A boiler water treatment chemical according to claim 1, wherein
the heterocyclic compound with N-substituted amino group is
1-aminopyrrolidine, 1-amino-4-methylpiperazine, 1-aminopiperidine,
1-aminohomopiperidine,1,4-diaminopiperazine, N-aminomorpholine, or
morpholinobyguanide, and wherein the salt thereof is water soluble
salt of said heterocyclic compounds and aliphatic carboxylic acid
such as succinic acid, glutaric acid, adipic acid, gluconic acid,
glycollic acid, lactic acid, malic acid, tartaric acid, or citric
acid, or polycarboxylic acid such as polyacrylic acid.
4. A boiler water treatment chemical according to claim 1, wherein
the alkalic agent is sodium hydroxide, potassium hydroxide, sodium
carbonate, or potassium carbonate.
5. A boiler water treatment chemical according to claim 1, wherein
the water soluble polymer is polyacrylic acid, polymaleic acid,
polymethacrylate acid, copolymer of acrylic acid and acrylic amide,
copolymer of acrylic acid and hydroxyallyloxypropanesulfonic acid,
copolymer of acrylic acid and 2-acrylamide-2-methylpropanesulfonic
acid, or the salt thereof.
6. A boiler water treatment chemical according to claim 2, wherein
the neutral amine is one or more among cyclohexylamine,
2-amino-2-methyl-1-propanole, monoethanolamine, diethanolamine,
morpholine, monoisopropanolamine, dimethylethanolamine,
diethylethanolamine, dimethylpropanolamine, and
dimethylpropilamine.
7. A boiler water treatment chemical according to claim 1, wherein
the ratio of the heterocyclic compound with N-substituted amino
group or the salt thereof and the alkalic agent and/or water
soluble polymer is set as follows in weight: i) when the
heterocyclic compound with N-substituted amino group or the salt
thereof and the alkalic agent are used together, heterocyclic
compound with N-substituted amino group or salt thereof: alkalic
agent=1:0.01-20; ii) when the heterocyclic compound with
N-substituted amino group or the salt thereof and the water soluble
polymer are used together, heterocyclic compound with N-substituted
amino group or salt thereof: water soluble polymer=1:0.01-20; and
iii) when the heterocyclic compound with N-substituted amino group
or the salt thereof and the alkalic agent and the water soluble
polymer are used together, heterocyclic compound with N-substituted
amino group or salt thereof: alkaline agent: water soluble
polymer=1:0.01-20:0.01-20.
8. A method of using an oxygen scavenger, comprising: adding to
boiler water an effective amount of an oxygen scavenger including,
as an effective component, a heterocyclic compound with
N-substituted amino group, or the salt thereof, and alkaline agent
and/or water soluble polymer.
9. A method of using an oxygen scavenger according to claim 8,
wherein said oxygen scavenger further includes neutral amine.
10. A method of using an oxygen scavenger according to claim 8,
wherein the heterocyclic compound with N-substituted amino group is
1-aminopyrrolidine, 1-amino-4-methylpiperazine, 1-aminopiperidine,
1-aminohomopiperidine,1,4-diaminopiperazine, N-aminomorpholine, or
morpholinobyguanide, and wherein the salt thereof is water soluble
salt of said heterocyclic compounds and aliphatic carboxylic acid
such as succinic acid, glutaric acid, adipic acid, gluconic acid,
glycollic acid, lactic acid, malic acid, tartaric acid, or citric
acid, or polycarboxylic acid such as polyacrylic acid.
11. A method of using an oxygen scavenger according to claim 8,
wherein the alkaline agent is sodium hydroxide, potassium
hydroxide, sodium carbonate, or potassium carbonate.
12. A method of using an oxygen scavenger according to claim 8,
wherein the water soluble polymer is polyacrylic acid, polymaleic
acid, polymethacrylate acid, copolymer of acrylic acid and acrylic
amine, copolymer of acrylic acid and hydroxyallyloxypropanesulfonic
acid, copolymer of acrylic acid and
2-acrylamide-2-methylpropanesulfonic acid, or the salt thereof.
13. A method of using an oxygen scavenger according to claim 9,
wherein the neutral amine is one or more among cyclohexylamine,
2-amino-2-methyl-1-propanole, monoethanolamine, diethanolamine,
morpholine, monoisopropanolamine, dimethylethanolamine,
diethylethanolamine, dimethylpropanolamine, and
dimethylpropilamine.
14. A method of using an oxygen scavenger according to claim 8,
wherein the ratio of the heterocyclic compound with N-substituted
amino group or the salt thereof and the alkalic agent and/or water
soluble polymer is set as follows in weight: i) when the
heterocyclic compound with N-substituted amino group or the salt
thereof and the alkalic agent are used together, heterocyclic
compound with N-substituted amino group or salt thereof: alkalic
agent=1:0.01-20; ii) when the heterocyclic compound with
N-substituted amino group or the salt thereof and the water soluble
polymer are used together, heterocyclic compound with N-substituted
amino group or salt thereof: water soluble polymer=1:0.01-20; and
iii) when the heterocyclic compound with N-substituted amino group
or the salt thereof and the alkalic agent and the water soluble
polymer are used together, heterocyclic compound with N-substituted
amino group or salt thereof: alkaline agent: water soluble polymer
1:0.01-20:0.01-20.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a divisional patent application of U.S. patent
application Ser. No. 09/404,202 filed on Sep. 23, 1999, which is a
divisional patent application of U.S. patent application Ser. No.
08/975,000 filed on Nov. 20, 1997.
FIELD OF THE INVENTION AND RELATED ART
[0002] The present invention relates to an oxygen scavenger, and
more particularly to an oxygen scavenger which can effectively
remove dissolved oxygen in water and, in particular, is useful in
inhibiting the corrosion in a boiler system by removing dissolved
oxygen in feed water. In addition, the present invention relates to
boiler water treatment chemical including such an oxygen scavenger
and descaling chemicals.
[0003] Dissolved oxygen in feed water contributes corrosion in
components of a boiler system, such as a boiler main body, a heat
exchanger and an economizer arranged in an upstream of the boiler
main body, and a steam and condensate piping arranged in a
downstream of the boiler main body. To inhibit the corrosion in the
boiler system, dissolved oxygen in feed water should be removed by
deoxidizing treatment of the feed water of the boiler.
[0004] Conventionally, chemical treatment or physical treatment has
been applied for the removal of dissolved oxygen. As for the
chemical treatment, a method of adding an oxygen scavenger such as
hydrazine (N2H4), sodium sulfite (Na2SO3), hydroxylamine group, or
saccharide into the boiler water has been widely employed. Proposed
in JPB S59-42073 and JPA H6-23394 is an agent containing
hydroxylamine group and neutral amine.
[0005] However, the safety for humans of hydrazine is doubtful and
thus the handling of hydrazine is at stake.
[0006] Since the reaction between sodium sulfite and oxygen is too
rapid, sodium sulfite dissolved in water and stored in a tank
reacts with oxygen in air before it is added in feed water, thereby
reducing the concentration of effective component thereof.
Therefore, there is a problem that sodium sulfite sometimes does
not produce sufficient effect of dissolved oxygen removal. Since
the feed water treated with sodium sulfite contains sulphate ion as
a reaction product of the sodium sulfite and oxygen, there is
another problem that the corrosion and scale in a boiler system are
easily caused.
[0007] There is also a problem that hydroxylamine group generates
acid such as nitric acid when the hydroxylamine group is added in
feed water and reacts with oxygen in the boiler, thereby reducing
corrosion inhibition effect for the boiler main body.
[0008] Saccharide has disadvantages in that it is difficult to
measure the residual concentration in boiler water and thus
difficult to control the right amount to be added, and saccharide
gives odor to the steam.
[0009] Using azo compound as an oxygen scavenger has been already
proposed. For example, 2,2-azobis (N,N'-dimethlene isobuthy
amidine) 2,2-azobis (isobuthyl amide)uE2 hydrate, 4,4-azobis
(4-cyano caproic acid), and 2,2-azobis (2-amidino propane)uEHCI
have been proposed.
[0010] Each of these azo compounds provides high efficiency of
dissolved oxygen removal. However, azo compounds have disadvantages
in producing various organic matters such as formic acid and acetic
acid in a boiler drum and the steam and thereby adversely affecting
the steam quality and the steam purity.
SUMMARY OF THE INVENTION
[0011] It is the first object of the present invention to provide a
novel oxygen scavenger which can efficiently remove dissolve oxygen
in boiler feed water while providing high safety for humans.
[0012] It is the second object of the present invention to provide
an oxygen scavenger having a heterocyclic compound with
N-substituted amino group as an effective component which can
adequately exhibit the deoxidization effect not only for feed water
lines, a boiler main body, or steam and condensate lines for high
temperature water, but also for feed water lines for low
temperature water.
[0013] It is the third object of the present invention to provide a
novel chemical for treating boiler water which can exhibit
corrosion inhibition effect to both a boiler main body and a piping
for the steam and condensate.
[0014] It is the fourth object of the present invention to provide
a boiler water treatment chemical which has high corrosion
inhibition effect by a heterocyclic compound with N-substituted
amino group and exhibit excellent corrosion inhibition effect and
scale inhibition effect as a state of a solution which contains
component agents.
[0015] In an oxygen scavenger of a first aspect, the effective
component thereof consists essentially of a heterocyclic compound
having N-N bond in a ring thereof.
[0016] In an oxygen scavenger of a second aspect, the effective
component thereof consists of a heterocyclic compound having
N-substituted amino group or its water soluble salt.
[0017] In an oxygen scavenger of a third aspect, the effective
component thereof consists of the following heterocyclic compound:
1
[0018] (wherein a, b are integers between 0 and 5 to satisfy a
relation "2.ltoreq.a+b.ltoreq.5").
[0019] In an oxygen scavenger of a fourth aspect, the effective
component thereof consists essentially of a heterocyclic compound
represented by the following formula: 2
[0020] (wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 may be the same
or different from each other and each designates any one of
hydrogen, lower alkyl group having 1-8 carbon atoms, and aryl group
also having 1-8 carbon atoms, and X designates any one of hydrogen,
amino group, alkyl group or dialkylamino group having 1-8 carbon
atoms, and lower alkyl group or aryl group having 1-8 carbon
atoms).
[0021] In an oxygen scavenger of a fifth aspect, the effective
component thereof consists essentially of azodicarbonamide.
[0022] The oxygen scavengers of the first through fifth aspect may
be prepared by combining two or more kinds of components.
[0023] The amount of the effective component of each aspect is not
limited and can be altered to suitably correspond to the
concentration of dissolved oxygen in water as a subject. Normally,
the amount is, however, between 0.001 and 1000 mg, preferably
between 1 and 300 mg relative to 1 lit. of feed water.
[0024] An oxygen scavenger of a sixth aspect includes a
heterocyclic compound with N-substituted amino group, or the salt
thereof, and a hydroxybenzene derivative.
[0025] In the oxygen scavenger of the sixth aspect, because of the
catalysis of the hydroxybenzene derivative, the heterocyclic
compound with N-substituted amino group or the salt thereof can
exhibit the excellent deoxidization effect even in feed water lines
for low temperature water.
[0026] A seventh aspect provides a chemical for treating boiler
water including a heterocyclic compound with N-substituted amino
group and neutral amine.
[0027] An eighth aspect provides a boiler water treatment chemical
including a heterocyclic compound with N-substituted amino group,
or the salt thereof, and alkaline agent and/or water soluble
polymer.
BRIEF DESCRIPTION OF THE DRAWING
[0028] FIG. 1 is a graph showing results of examples 36, 37 and
comparative examples 6 through 8; and
[0029] FIG. 2 is a graph showing results of examples 45 through 49
and a comparative example 21.
PREFERRED EMBODIMENTS
[0030] 1. First Aspect
[0031] In an oxygen scavenger of a first aspect, the effective
component thereof consists of a heterocyclic compound having N-N
bond in a ring thereof. Included as such a heterocyclic compound is
preferably at least of one of the followings: 3
[0032] The above heterocyclic compounds may be used alone or in
combination.
Examples 1 through 10
[0033] Effect of the oxygen scavenger of the first aspect has been
tested as follow.
[0034] Softened water saturated with oxygen in air at the room
temperature was fed into a steam generator test autoclave and the
autoclave was operated to generate steam under the following
conditions:
[0035] Temperature: 185.degree. C., Pressure: 1 MPa, Amount of
Evaporation: 12 liters/hr, and Blow Rate: 10%.
[0036] The generated steam was completely condensed to produce
condensed water. Then, the dissolved oxygen concentration in the
condensed water was measured by a dissolved oxygen meter. Thus
obtained value was used as data of a comparative example 1.
[0037] On the other hand, steam was generated under the same
conditions except that the oxygen scavenger was added in the feed
water. Then, the dissolved oxygen concentration in the condensed
water of the steam was also measured. The difference between thus
obtained value and the data of the comparative example 1 was
calculated as an amount of extraction and the ratio of the
extraction to the data of the comparative example was calculated as
an extraction ratio (%).
[0038] As for each example 1 through 10, the heterocyclic compound
shown in Table 1 was dissolved in the aforementioned softened water
to prepare aqueous solution with a predetermined concentration,
then the aqueous solution was fed into the feed water by a fixed
displacement pump, and the concentration of the heterocyclic
compound to the feed water was controlled to be as shown in Table
1.
[0039] The results are shown in Table 1.
1 TABLE 1 Concentration of Heterocyclic compound dissolved oxygen
Concentration in in flocculated Amount of removal Rate of removal
Kind feed water (mg/L) water (mg/L) (mg/L) (%) Example 1
1,3-dimethyl-5-pyrazolone 45 2.00 6.25 75.8 Example 2
1,3-dimethyl-5-pyrazolone 80 0.50 7.75 93.9 Example 3 urazol 20
3.60 4.65 50.4 Example 4 urazol 40 0.50 7.75 93.9 Example 5
6-azauracil 45 2.35 5.90 71.5 Example 6 6-azauracil 90 0.40 7.85
95.2 Example 7 3-methyl-5-pyrazolone 40 1.75 6.50 78.8 Example 8
3-methyl-5-pyrazolone 80 0.35 7.90 95.8 Example 9
3-methyl-5-pyrazoline-5-on 40 1.75 6.50 78.8 Example 10
3-methyl-5-pyrazoline-5-on 80 0.40 7.85 95.2 Comparative None 0
8.25 -- -- Example 1
[0040] 2. Second Aspect
[0041] In an oxygen scavenger of a second aspect, the effective
component thereof consists of a heterocyclic compound having
N-substituted amino group or water soluble salt thereof. Included
as such a heterocyclic compound is preferably at least one of the
followings: 4
[0042] As the salt thereof, for example, water soluble salt of the
aforementioned heterocyclic compounds and aliphatic carboxylic acid
such as succinic acid, glutaric acid, adipic acid, gluconic acid,
glycollic acid, lactic acid, malic acid, tartaric acid, or citric
acid, or polycarboxylic acid such as polyacrylic acid is preferably
employed, but the salt thereof is not limited thereto.
[0043] The above heterocyclic compounds or the salts thereof may be
used alone or in combination.
Examples 11 through 21
[0044] The deoxidizing treatment was made in each example in the
same manner as the above examples 1 through 10 except using the
heterocyclic compound shown in Table 2 as the effective component
of the oxygen scavenger to have the concentration of the
heterocyclic compound in the feed water as shown in Table 2. The
results are shown in Table 2.
2 TABLE 2 Concentration of Heterocyclic compound dissolved oxygen
Concentration in in flocculated Amount of removal Rate of removal
Kind feed water (mg/L) water (mg/L) (mg/L) (%) Example 11
N-aminomorpholine 25 1.60 6.65 80.1 Example 12 N-aminomorpholine 50
0.45 7.80 94.5 Example 13 N-aminomorpholine 85 0.35 7.90 95.8
Example 14 1-amino-4-methylpiperazine 40 1.10 7.15 86.7 Example 15
1-amino-4-methylpiperazine 80 0.40 7.85 95.2 Example 16
N-aminohomopiperidine 40 1.20 7.05 85.5 Example 17
N-aminohomopiperidine 80 0.45 7.80 94.5 Example 18
1-aminopyrrolidine 40 0.95 7.35 89.1 Example 19 1-aminopyrrolidine
80 0.45 7.80 94.5 Example 20 1-aminopiperidine 40 0.95 7.30 88.5
Example 21 1-aminopiperidine 80 0.40 7.85 95.2 Comparative None 0
8.25 -- -- Example 1
[0045] 3. Third Aspect
[0046] In an oxygen scavenger of a third aspect, the effective
component thereof consists of the following heterocyclic compound:
5
[0047] Included as such a heterocyclic compound are preferably at
least one of the followings: 6
[0048] The above heterocyclic compounds may be used alone or in
combination.
Examples 22 through 27
[0049] The deoxidizing treatment was made in each example in the
same manner as the above examples 1 through 10 except using the
heterocyclic compound shown in Table 3 as the effective component
of the oxygen scavenger to have the concentration of the
heterocyclic compound as shown in Table 3. The results are shown in
Table 3.
3 TABLE 3 Concentration of Heterocyclic compound dissolved oxygen
Concentration in in flocculated Amount of removal Rate of removal
Kind feed water (mg/L) water (mg/L) (mg/L) (%) Example 22
2,3-diaminopyridine 250 3.60 4.65 56.4 Example 23
2,3-diaminopyridine 400 2.15 6.10 73.9 Example 24
2-amino-3-hydroxypyridine 40 2.35 5.90 71.5 Example 25
2-amino-3-hydroxypyridine 55 0.75 7.50 90.9 Example 26
2-amino-3-hydroxypyridine 65 0.50 7.75 93.9 Example 27
2-amino-3-hydroxypyridine 140 0.10 8.15 98.8 Comparative None 0
8.25 -- -- Example 1
[0050] 4. Fourth Aspect
[0051] In an oxygen scavenger of a fourth aspect, the effective
component thereof consists of a heterocyclic compound represented
by the following formula: 7
[0052] In this effective component of the oxygen scavenger of the
lo fourth aspect, for example, methyl group is preferably used as
lower alkyl group having 1-8 carbon atoms designated with R.sub.1,
R.sub.2, R.sub.3, R.sub.4 and phenyl group or tolyl group is
preferably used as aryl group also having 1-8 carbon atoms. In
addition, methyl group or aminomethyl group is preferably used as
alkyl group or dialkylamino group having 1-8 carbon atoms
designated with X.
[0053] Included as such a heterocyckic compound is preferably at
least one of the followings: 8
[0054] The above heterocyclic compounds may be used alone or in
combination.
Examples 28 through 34
[0055] The deoxidizing treatment was made in each example in the
same manner as the above examples 1 through 10 except using the
heterocyclic compound shown in Table 4 as the effective component
of the oxygen scavenger to have the concentration of the
heterocyclic compound in the feed water as shown in Table 4. The
results are shown in Table 4.
4 TABLE 4 Concentration of Heterocyclic compound dissolved oxygen
Concentration in in flocculated Amount of removal Rate of removal
Kind feed water (mg/L) water (mg/L) (mg/L) (%) Example 28
5-aminouracil 30 3.00 5.25 63.6 Example 29 5-aminouracil 50 1.30
6.95 84.2 Example 30 5-aminouracil 90 1.10 7.15 86.7 Example 31
5,6-diamino-1,3-dimethyluracil 35 2.00 5.25 63.6 Example 32
5,6-diamino-1,3-dimethyluracil 50 0.95 7.30 88.5 Example 33
5,6-diamino-1,3-dimethyluracil 70 0.45 7.80 94.5 Example 34
5,6-diamino-1,3-dimethyluracil 100 0.35 7.90 95.8 Comparative None
0 8.25 -- -- Example 1
[0056] 5. Fifth Aspect
[0057] In an oxygen scavenger of a fifth aspect, the effective
component thereof is azodicarbonamide (NH2CON=NCONH2).
[0058] Azodicarbonamide has an advantage in maintaining the purity
of generated steam without changing water quality in the boiler
because the azodicarbonamide does not produce any organic matter
such as formic acid or acetic acid.
Example 35, Comparative Examples 2 through 5
[0059] The deoxidizing treatment was made in this example and each
comparative example in the same manner as the above examples 1
through 10 except adding the azo compound shown in Table 5 as the
effective component of the oxygen scavenger to have the
concentration of 150 mg/L in the feed water. The results are shown
in Table 5.
[0060] Main products in the generated steam and main products in
the autoclave are analyzed, respectively. The results are also
shown in Table 5.
5 TABLE 5 Concentration of dissolved oxygen Amount of Rate of in
flocculated removal removal Main product in Azo compound water
(mg/L) (mg/L) (%) Main product in steam autoclave Example 35
azodicarbonamide 0.35 7.90 95.8 carbon dioxide, ammonia --
Comparative No added 8.25 -- -- -- -- Example 1 Comparative
2,2-azobis(N,N'- 1.05 7.20 87.3 acetone, methylamine, formic acid,
acetic Example 2 dimethyleneisobuthylamidine) isopropyl alcohol
acid, isopropyl alcohol Comparative
2,2-azobis(isobuthylamide).multidot.- 2hydrate 0.25 8.00 97.0
acetone, carbon dioxide, formic acid, acetic Example 3 isopropyl
alcohol, ammonia acid, isopropyl alcohol Comparative
4,4-azobis(4-cyanocaproic acid) 0.35 7.90 95.8 carbon dioxide
various organic acid Example 4 Comparative 2,2-azobis(2-amidino
propane)HCl 0.45 7.85 95.2 acetone, isopropyl alcohol, formic acid,
isopropyl Example 5 ammonia alcohol
[0061] As apparent from Table 5, all of the azo compounds provide
high rates of dissolved oxygen removal. In particular,
azodicarbonamide generates no organic acid changing the water
quality of the feed water in the autoclave which corresponds to a
boiler drum so that azodicarbonamide is preferably used as oxygen
scavenger for feed water of the boiler.
[0062] 6. Sixth Aspect
[0063] An oxygen scavenger of a sixth aspect includes a
heterocyclic compound with N-substituted amino group, or the salt
thereof, and a hydroxybenzene derivative.
[0064] In the oxygen scavenger of the sixth aspect, because of the
catalysis of the hydroxybenzene derivative, the heterocyclic
compound with N-substituted amino group or the salt thereof can
exhibit the excellent deoxidization effect even in feed water lines
for low temperature water.
[0065] The heterocyclic compound with N-substituted amino group is
preferably at least one of 1-aminopyrrolidine,
1-amino-4-methlpiperazine, 1-aminopiperidine,
1-aminohomopiperidine, 1,4-diaminopiperazine, N-aminomorholine, and
morholinobyguanide. As the salt thereof, for example, water soluble
salt of the aforementioned heterocyclic compounds and carboxylic
acid such as succinic acid, gluconic acid, glutaric acid, adipic
acid, glycollic acid, lactic acid, malic acid, tartaric acid or
citric acid or polycarboxylic acid such as polyacrylic acid is
preferably employed, but the salt thereof is not limited thereto.
These heterocyclic compounds and the salts thereof may be suitably
used alone or in combination.
[0066] As the hydroxybenzene derivative, hydroquinone,
2,3-dimethyl-1,4-hydroquinone, catechole, 4-tert-buthyl catechol,
pyrogallol, 1,2,4-hydroxybenzene, gallic acid, 2-aminophenol,
2,4-diaminophenol,4-aminophenol may be employed, but the
hydroxybenzene derivative is not limited to these. The
hydroxybenzene derivative may also be suitably used alone or in
combination.
[0067] Though the oxygen scavenger of the sixth aspect can be
prepared by mixing the heterocyclic compound with N-substituted
amino group or the salt thereof and the hydroxybenzene derivative,
these may be separately injected.
[0068] The amount of the oxygen scavenger of the sixth aspect can
be altered to suitably correspond to the concentration of dissolved
oxygen and other water conditions in feed water of a boiler system
as a subject. Normally, the heterocyclic compound with
N-substituted amino group or the salt thereof and the
hydroxybenzene derivative are, however, each added by between 0.001
and 1000 mg, preferably between 0.01 and 300 mg, more preferably
between 0.02 and 100 mg relative to 1 lit. of feed water.
[0069] The effect ratio of the heterocyclic compound with
N-substituted amino group or the salt thereof and the
hydroxybenzene derivative in the oxygen scavenger of the sixth
aspect is heterocyclic compound with N-substituted amino group or
salt thereof hydroxybenzene derivative=1 : 0.001-10 (ratio in
weight). When the hydroxybenzene derivative is less than the ratio,
the effect improved by using the hydroxybenzene derivative
according to the present invention, i.e. the improved effect of the
deoxidization to low temperature water can not be sufficiently
provided. On the other hand, when the hydroxybenzene derivative is
more than the ratio, the treatment cost becomes higher relative to
the increase in the effect.
[0070] The oxygen scavenger of the sixth aspect is dissolved in
water in such a manner that the acescent hydroxybenzene derivative
is neutralized by the heterocyclic compound having basic
N-substituted amino group. When it is difficult to dissolve the
oxygen scavenger, adding alkali such as caustic soda (NaOH)
improves the solubility of the oxygen scavenger.
[0071] Though the oxygen scavenger of the sixth aspect includes the
heterocyclic compound with N-substituted amino group or the salt
thereof and the hydroxybenzene derivative if necessary, another
oxygen scavenger or corrosion inhibitor such as hydrazine, sodium
sulfite, succinic acid or gluconic acid or furthermore dispersant,
chelate compound, descaling chemicals, or the mixture of some among
these may also be added.
[0072] The oxygen scavenger of the sixth aspect can be effectively
used in boiler systems of various types such as low pressure,
medium pressure, and high pressure boiler systems and is not
restricted at all by the boiler pressure, the boiler type, or the
kind of feed water.
Examples 36, 37, Comparative Examples 6 through 8
[0073] After filling 1 lit. of softened water of Atsugi-city's tap
water into an Erlenmeyer flask and controlling pH to be 9.0 by
using NaOH, it was agitated two hours in a constant-temperature
water bath at 60.degree. C. in such a manner as to be saturated by
oxygen in air. The concentration of dissolved oxygen at this point
was measured by a dissolved oxygen meter ("MOCA3600" manufactured
by Obisfair Co., Ltd.) with the result that it was 4.75 mg/L.
[0074] After adding chemicals by the respective amounts shown in
Table 6 into the water in the Erlenmeyer flask and sufficiently
agitating them, the resultant solution was poured into three furan
bottles of 200 ml capacity and the furan bottles were capped
without space therein and then returned into the
constant-temperature water bath at 60.degree. C. to cause the
reaction of the solution. The furan bottles were taken out from the
constant-temperature water bath one at a time with the passage of
predetermined periods (5, 10, 20 minutes) and the concentrations of
dissolved oxygen in the solution were measured by the dissolved
oxygen meter. The residual rate of dissolved oxygen in each sample
solution was calculated from the ratio of the concentration of
dissolved oxygen after adding the chemicals to that before adding
the chemicals. These operations were rapidly performed in
nitrogen-atmosphere.
[0075] The results are shown in Table 6 and FIG. 1.
[0076] As apparent from the results, it is found that the
deoxidization reaction is significantly speeded up by using
hydroquinone (HQ) as a hydroxybenzene derivative with
1-aminopyrrolidine (APY) or 1-amino-4-methylpiperazine (AMPI) as a
heterocyclic compound with N-substituted amino group.
6 TABLE 6 Concentration of dissolved oxygen Agent added after
addition of agent (mg/L) and its concentration Just (mg/L) after 5
min. 10 min. 20 min. Ex. APY AMP I HQ addition later later later
Ex. 36 100 -- 2 4.75 0.78 0.18 0.08 37 -- 100 2 4.75 2.01 0.96 0.58
Co. 6 100 -- -- 4.75 3.69 3.33 3.12 7 -- 100 -- 4.75 3.86 3.63 3.52
8 -- -- 2 4.75 4.43 4.33 4.31 (Notes) Ex.: Example Co.: Comparative
Example APY: 1-aminopyrrolidine AMPI: 1-amino-4-methylpiperazine
HQ: Hydroquinone
[0077] 7. Seventh Aspect
[0078] A seventh aspect provides a chemical for treating boiler
water including a heterocyclic compound with N-substituted amino
group and neutral amine.
[0079] The essential components of the chemical of this aspect are
the heterocyclic compound with N-substituted amino group and the
neutral amine.
[0080] The heterocyclic compound with N-substituted amino group
exhibits the excellent deoxidization effect by reacting with
dissolved oxygen in boiler water so as to inhibit the corrosion in
a boiler main body.
[0081] The chemical has the following useful functions in addition
to the aforementioned functions of the heterocyclic compound with
N-substituted amino group.
[0082] The heterocyclic compound with N-substituted amino group has
volatility characteristics and excellent reduction ability relative
to iron. In other words, the heterocyclic compound has functions of
inhibiting the oxidation of iron, that is, inhibiting the corrosion
of iron.
[0083] Therefore, steam condensate generated from boiler water
treated with the chemical of the seventh aspect is deprived of the
characteristics of corroding a piping through which the steam
condensate passes because of the aforementioned functions of the
heterocyclic compound which is included in the steam condensate. In
addition, the steam condensate is held in a pH range of neutral or
alkaline because of the functions of the neutral amine which is
also included in the condensate, thereby inhibiting the corrosion
of the piping through which the condensate passes.
[0084] That is, the chemicals of this aspect can exhibit the
corrosion inhibition effect in both the boiler main body and the
steam and condensate piping.
[0085] Any compound which can exhibit the functions and effects as
mentioned above may be employed as the heterocyclic compound with
N-substituted amino group. For example, N-aminomorpholine,
1-aminopyrrolidine, 1-amino-4-methylpiperazine,
1,4-diaminopiperazine, 1-aminopiperidine, 1-aminohomopiperidine,
morpholinobiguamide may be preferably employed and water soluble
salt of the aforementioned heterocyclic compounds and carboxylic
acid such as succinic acid, gluconic acid, glutaric acid, adipic
acid, glycollic acid, lactic acid, malic acid, tartaric acid or
citric acid, polycarboxylic acid such as polyacrylic acid are also
preferably employed. Moreover, these heterocyclic compounds and the
salts thereof may be suitably used alone or in combination.
[0086] Any compound capable of making the boiler water after
treatment and the steam condensate neutral or alkaline may be
employed as the neutral amine, the other essential component of the
chemical. For example, cyclohexylamine,
2-amino-2-methyl-1-propanol, monoethanolamine, diethanolamine,
morpholine, monoisopropanolamine, diethylethanolamine,
dimethylpropanolamine, dimethylethanolamine, and
dimethylpropylamine may be preferably employed. These may be
suitably used alone or in combination.
[0087] The chemical of the seventh aspect is prepared by mixing the
heterocyclic compounds and the neutral amine as mentioned
above.
[0088] The mixing ratio thereof can be determined to suitably
correspond to the concentration of dissolved oxygen and other water
conditions in feed water of a boiler system as a subject. However,
the heterocyclic compounds and the neutral amine are normally each
added by between 0.001 and 1000 mg, preferably between 0.01 and 300
mg, more preferably between 0.02 and 100 mg relative to 1 lit. of
feed water.
[0089] Though the essential components of the chemical of the
seventh aspect are the heterocyclic compound with N-substituted
amino group and the neutral amine, another known oxygen scavenger
or corrosion inhibitor such as hydrazine, sodium sulfite, succinic
acid or gluconic acid or furthermore the known dispersant, chelate
compound, descaling chemicals, or the mixture of some among these
may also be added.
[0090] The chemical of the seventh aspect can be effectively used
in boiler systems of various types such as low pressure, medium
pressure, and high pressure boiler systems and is not restricted at
all by the boiler pressure or the type of feed water.
Examples 38 through 44, Comparative Examples 9 through 20
[0091] After feeding softened water of Atsugi-city's tap water
which has been saturated by oxygen in air at 40.degree. C. into an
experimental electric boiler with a capacity of 5 liters and the
boiler was operated to generate steam under the following
conditions:
[0092] Temperature: 183.degree. C., Pressure: 1 MPa, Amount of
Evaporation: 12 liters/hr, and Blow Rate: 10%.
[0093] The steam was cooled to produce condensate. The condensate
was cooled to 50.degree. C. and then fed into a column. Previously
disposed in the column and the aforementioned experimental electric
boiler were test pieces made of steel (SS400 of Japanese Industrial
Standard) each having a length of 50 mm, a width of 15 mm, and a
thickness of 1 mm. The test pieces were dipped in said condensate
96 hours.
[0094] The amounts of corrosion of the respective pieces were
measured to calculate the corrosion rates in the boiler water and
the condensate. The resultant values were indexes representing the
degree of corrosion of the pieces caused by the boiler water
without chemical treatment. The results are shown in Table 8 as a
comparative example 9.
[0095] It should be noted that the concentration of nitrate ion and
the concentration of nitrite ion in the boiler water after the
operation were measured and the results are also shown in Table
8.
[0096] The chemical components shown in Table 7 were dissolved in
softened water mentioned above in such a manner as to have the
respective indicated concentrations in the softened water and then
supplied to the boiler by using a fixed displacement pump.
7 TABLE 7 Concentration of each component (mg/L) Heterocyclic
compound Neutral amine Hydroxylamine group 1-amino 2-amino-2-
diethylhyd isoproxylhyd N-amino 1-amino -4-methyl cyclohexyl
methyl-1- monoethanol -roxylamine -roxylamine -morpholine
-pyrrolidine -piperazine -amine propanol -amine Comparative Example
10 36 -- -- -- -- -- -- -- Comparative Example 11 -- 36 -- -- -- --
-- -- Comparative Example 12 36 -- -- -- -- 30 -- -- Comparative
Example 13 36 -- -- -- -- -- 30 -- Comparative Example 14 36 -- --
-- -- -- -- 30 Comparative Example 15 -- 36 -- -- -- 30 -- --
Comparative Example 16 -- 36 -- -- -- -- 30 -- Comparative Example
17 18 18 -- -- -- 30 -- -- Comparative Example 18 -- -- 36 -- -- --
-- -- Comparative Example 19 -- -- -- 36 -- -- -- -- Comparative
Example 20 -- -- -- -- 36 -- -- -- Example 38 -- -- 36 -- -- 30 --
-- Example 39 -- -- 36 -- -- -- 30 -- Example 40 -- -- 36 -- -- --
-- 30 Example 41 -- -- -- 36 -- 30 -- -- Example 42 -- -- -- 36 --
-- 30 -- Example 43 -- -- -- -- 36 30 -- -- Example 44 -- -- -- --
36 -- 30 --
[0097] As for condensate of steam generated from the softened water
in which the chemical components are dissolved, the corrosion test
was made under the same conditions as that of the aforementioned
comparative example 9 to calculate the corrosion rate of test
coupons.
[0098] In addition, the concentration of nitrate ion and the
concentration of nitrite ion in the boiler water after the
operation were measured. The results are shown in Table 8.
8 TABLE 8 Corrosion rate of test piece (mdd) Concentration of
nitric ion and nitrite In boiler In condensed ion in boiler water
water water nitric ion nitrite ion Comparative Example 9 10.5 143.5
not detected not detected Comparative Example 10 2.0 48.3 2.3 3.1
Comparative Example 11 2.3 39.4 3.5 4.2 Comparative Example 12 2.0
29.2 2.8 3.6 Comparative Example 13 1.8 34.6 2.7 2.9 Comparative
Example 14 1.7 33.3 1.9 3.3 Comparative Example 15 2.4 26.4 4.3 4.1
Comparative Example 16 2.6 28.6 5.2 4.5 Comparative Example 17 2.1
24.3 3.4 3.8 Comparative Example 18 1.0 30.3 not detected not
detected Comparative Example 19 1.2 23.5 not detected not detected
Comparative Example 20 0.9 21.6 not detected not detected Example
38 0.8 8.4 not detected not detected Example 39 1.0 9.3 not
detected not detected Example 40 0.7 9.1 not detected not detected
Example 41 1.1 9.5 not detected not detected Example 42 0.9 9.8 not
detected not detected Example 43 0.8 11.3 not detected not detected
Example 44 1.0 12.5 not detected not detected
[0099] As apparent from Table 7 and Table 8, the following facts
are found.
[0100] 1) The chemicals including hydroxyamine groups (comparative
examples 10 through 17) are not convenient for inhibiting the
corrosion of the boiler because nitrate ion and nitrite ion are
produced in the boiler water.
[0101] 2) Using the heterocyclic compound with N-substituted amino
group alone reduces the corrosion rate of iron in the boiler water
and does not produce nitrate ion and nitrite ion in the boiler
water. Since, however, the corrosion rate of iron in the condensate
is still large so that the corrosion in the steam and condensate
piping will be caused, the heterocyclic compound is not
convenient.
[0102] 3) As compared to the above comparative examples, using any
one of the chemicals of the examples does not produce nitrate ion
and nitrite ion in the boiler water and significantly inhibits the
corrosion of iron in both the boiler water and the condensate.
[0103] 8. Eighth Aspect
[0104] A boiler water treatment chemical of an eighth aspect
includes a heterocyclic compound with N-substituted amino group, or
the salt thereof, and alkalic agent and/or water soluble
polymer.
[0105] The heterocyclic compound with N-substituted amino group or
the salt thereof has features of slower deoxidization reaction
under the neutral condition and of higher deoxidization reaction
under the alkaline condition in the case of low temperature water.
Accordingly, using the alkalic agent improves the deoxidization
effect of the heterocyclic compound even in the pipeline for low
temperature water. As a result of this, the deoxidization effect in
the feed water lines is further improved and the amount of iron
entered into the boiler is reduced. Iron entered from the feed
water and iron eluted from the boiler drum adhere as iron oxide
sludge to a heating surface. The iron oxide sludge causes an oxygen
concentration cell or the like so as to contribute the corrosion.
The increase in the corrosion inhibition effect in the feed water
line can reduce such a secondary corrosion.
[0106] Using the water soluble polymer reduces the corrosion,
caused by the iron oxide sludge, by its sludge dispersing function
and, furthermore, can prevent the scaling on the heating surface
even when the hardness components leak from a softener or ion
exchange equipment.
[0107] Since pH of the steam condensate is held to be neutral or
alkaline by using the neutral amine, the corrosion of the pipeline
for the steam condensate (i.e. the steam drain line) is
inhibited.
[0108] As the heterocyclic compound with N-substituted amino group
used in the eighth aspect, 1-aminopyrrolidine,
1-amino-4-methlpiperazine, 1-aminopiperidine,
1-aminohomopiperidine, 1,4-diaminopiperazine, N-aminomorpholine,
and morpholinobyguanide are preferably employed. As the salt
thereof, for example, water soluble salt of the aforementioned
heterocyclic compounds and aliphatic carboxylic acid such as
succinic acid, glutaric acid, adipic acid, gluconic acid, glycollic
acid, lactic acid, malic acid, tartaric acid, or citric acid, or
polycarboxylic acid such as polyacrylic acid is preferably
employed, but the salt thereof is not limited thereto. These
heterocyclic compounds and the salts thereof may be suitably used
alone or in combination.
[0109] As the alkaline agent used in the eighth aspect, sodium
hydroxide, potassium hydroxide, sodium carbonate, and potassium
carbonate are preferably employed, but it is not limited thereto.
These alkaline agents may be suitably used alone or in
combination.
[0110] As the water soluble polymer used in the eighth aspect,
polyacrylic acid, polymaleic acid, polymethacrylate acid, copolymer
of acrylic acid and acrylic amide, copolymer of acrylic acid and
hydroxyallyloxypropanesu- lfonic acid, copolymer of acrylic acid
and 2-acrylamide-2-methylpropanesul- fonic acid, and the salt
thereof are preferably employed, but it is not limited thereto.
These water soluble polymers may be suitably used alone or in
combination.
[0111] As the neutral amine used in the eighth aspect, any compound
capable of making the boiler water and the steam condensate neutral
or alkaline may be employed. For example, cyclohexylamine,
2-amino-2-methyl-1-propanol, monoethanolamine, diethanolamine,
morpholine, monoisopropanolamine, dimethylethanolamine,
diethylethanolamine, dimethylpropanolamine, and dimethylpropilamine
may be preferably employed. These may be suitably used alone or in
combination.
[0112] Though the boiler water treatment chemical of the eighth
aspect can be prepared by mixing the aforementioned heterocyclic
compound with N-substituted amino group or the salt thereof and the
alkalic agent and/or water soluble polymer, and further by mixing
the neutral amine if necessary, these may be separately
injected.
[0113] The amount of the boiler water treatment chemical of the
eighth aspect can be altered to suitably correspond to the
concentration of dissolved oxygen and other water conditions in
feed water of a boiler system as a subject. However, the
heterocyclic compound with N-substituted amino group or the salt
thereof and the alkalic agent and/or water soluble polymer are
normally each added by between 0.001 and 1000 mg, preferably
between 0.01 and 300 mg, more preferably between 0.02 and 100 mg
relative to 1 lit. of feed water.
[0114] Particularly, the alkaline agent is preferably added in such
a manner that pH becomes between 8 and 12, depending on the type of
a boiler.
[0115] When the neutral amine is used with the boiler water
treatment chemical, the preferable amount of the neutral amine is
between 0.01 and 500 mg, particularly between 0.1 and 100 mg
relative to 1 lit. of feed water.
[0116] In the boiler water treatment chemical of the eighth aspect,
the ratio of the heterocyclic compound with N-substituted amino
group or the salt thereof and the alkaline agent and/or water
soluble polymer is preferably set as follows (the ratio is in
weight).
[0117] (1) When the heterocyclic compound with N-substituted amino
group or the salt thereof and the alkalic agent are used
together,
[0118] Heterocyclic compound with N-substituted amino group or Salt
thereof: Alkaline agent=1:0.01-20.
[0119] (2) When heterocyclic compound with N-substituted amino
group or the salt thereof and the water soluble polymer are used
together,
[0120] Heterocyclic compound with N-substituted amino group or Salt
thereof: Water soluble polymer=1:0.01-20.
[0121] (3) When heterocyclic compound with N-substituted amino
group or the salt thereof and the alkaline agent and the water
soluble polymer are used together,
[0122] Heterocyclic compound with N-substituted amino group or Salt
thereof: Alkaline agent: Water soluble
polymer=1:0.01-20:0.01-20.
[0123] Moreover when the neutral amine is used therewith, the
preferable ratio is Heterocyclic compound with N-substituted amino
group or Salt thereof: Neutral amine=1:0.01-20 (ratio in
weight).
[0124] Though the essential components of the boiler water
treatment chemical of the eighth aspect are the heterocyclic
compound with N-substituted amino group or the salt thereof and the
alkaline agent and/or the water soluble polymer and the neutral
amine if necessary, another known oxygen scavenger or corrosion
inhibitor such as hydrazine, sodium sulfite, saccharide, succinic
acid, gluconic acid or amines other than the aforementioned neutral
amine, or furthermore the known dispersant, chelate compound,
descaling chemicals, or the mixture of some among these may also be
added.
[0125] The boiler water treatment chemical of the eighth aspect can
be effectively used in boiler systems of various types such as low
pressure, medium pressure, and high pressure boiler systems and is
not restricted at all by the boiler pressure, the boiler type, or
the type of feed water.
[0126] Hereinafter, the eighth aspect will be described in more
detail with some examples and comparative examples.
Examples 45 through 49, Comparative example 21
[0127] Five kinds of testing liquids were prepared by adding sodium
hydroxide as the alkaline agent into 1 lit. of deionized water in
such a manner that respective pHs become 8.0, 9.0, 10.0, 11.0, and
12.0. These were agitated one hours in a constant-temperature water
bath at 60.degree. C. and saturated by oxygen in air. The
respective concentrations of dissolved oxygen were measured by a
dissolved oxygen meter ("MOCA3600" manufactured by Obisfair). After
adding 100 mg of 1-aminopyrrolidine (1-AP) as the heterocyclic
compound with N-substituted amino group and sufficiently agitating
them, the resultant solutions were poured into furan bottles of 200
ml capacity and the furan bottles were capped without space therein
and then returned into the constant-temperature water bath at
60.degree. C. to cause the reaction of the solution. After 20
minutes, the furan bottles were taken out from the
constant-temperature water bath and the concentrations of dissolved
oxygen in the solution were measured by the dissolved oxygen meter.
The residual rate of dissolved oxygen in each testing liquid was
calculated from the ratio of the concentration of dissolved oxygen
after adding the 1-aminopyrrolidine to that before adding the agent
(Examples 45 25 through 49). These operations were rapidly
performed in nitrogen-atmosphere.
[0128] For comparison, the test was made for a testing liquid with
6.8 pH without adding sodium hydroxide in the same manner
(Comparative Example 21).
[0129] The results of this test are shown in Table 9 and FIG.
2.
[0130] As apparent from the results, it is found that using
1-aminopyrrolidine as the heterocyclic compound with N-substituted
amino group and the alkalic agent significantly improves the
deoxidization effect.
9TABLE 9 Concentration Concentration of dissolved of dissolved
Removal oxygen before oxygen after rate of pH of test addding 1-AP
adding 1-AP dissolved Example water (mg/L) (mg/L) oxygen (%)
Example 45 8.0 4.30 3.55 17.4 Example 46 9.0 4.30 2.65 38.4 Example
47 10.0 4.30 1.60 62.8 Example 48 11.0 4.30 1.00 76.7 Example 49
12.0 4.30 0.70 83.7 Comparative 6.8 4.30 4.05 5.8 Example 21
Examples 50 through 55, Comparative Examples 22, 23
[0131] After adding 30 mg of 1- aminopyrrolidine as the
heterocyclic compound with N-substituted amino group into softened
water of Atsugi-city's tap water which has been saturated by oxygen
in air at 40.degree. C., the resultant water were fed into an
experimental electric boiler with a capacity of 5 liters and the
boiler was operated to generate steam under the following
conditions. The operating time was 240 hours.
[0132] Conditions:
[0133] Temperature: 183.degree. C.,
[0134] Pressure: 1 MPa,
[0135] Amount of Evaporation: 11 liters/hr,
[0136] Blow Rate: 10%, and
[0137] Concentration of iron in feed water: 0.5 mg/L.
[0138] Previously disposed in the feed water line, the drum of the
electric boiler, and the steam drain line were test pieces made of
steel (SS400 of Japanese Industrial Standard) each having a length
of 50 mm, a width of 15 mm, and a thickness of 1 mm. The degrees of
corrosion of test pieces were measured to calculate the corrosion
ratios. The results are shown in Table 10. The amount of iron
contained in iron oxide built up (the amount of deposited iron) on
the piece disposed in the boiler drum was measured and the result
was shown in Table 10 (Comparative Example 22).
[0139] The chemical components shown in Table 10 were dissolved in
softened water mentioned above in such a manner as to have the
respective indicated concentrations in the softened water shown in
Table 10 and then fed to the boiler by using a fixed displacement
pump.
[0140] As for condensate of steam generated from the softened water
in which the chemical components are dissolved, the corrosion test
was made under the same conditions as mentioned above to calculate
the corrosion rate of test pieces and the amount of deposited iron
and the results were shown in Table 10 (Examples 50 through 55,
Comparative Example 23).
[0141] As apparent from Table 10, it is found that improved
corrosion inhibition effect and descaling effect can be obtained by
using 1-aminopyrrolidine and the alkaline agent and or the water
soluble polymer, and further using the neutral amine.
10 TABLE 10 Chemicals and its adding rate (mg/L) Iron scale formed
Water Corrosion rate (mdd) on inner surface of soluble Steam dram
boiler dram Example 1.multidot.AP NaOH polymer AMP Feed line In
boiler dram line (mg/cm.sup.2) Example 50 80 5 0 0 20.5 4.1 11.3
0.181 Example 51 30 0 5 0 36.8 4.7 12.7 0.118 Example 52 30 5 5 0
18.8 2.8 13.1 0.104 Example 53 30 5 0 15 17.6 3.9 4.9 0.173 Example
54 30 0 5 15 36.9 4.2 5.8 0.107 Example 55 30 5 5 15 18.2 2.6 5.3
0.097 Comparative 0 0 0 0 81.5 20.3 63.2 0.302 Example 22
Comparative 30 0 0 0 37.2 7.3 12.2 0.221 Example 23 1-AP:
1-aminopyrrolidine water slouble polymer : copolymer of acrylic
acid and hydroxyallyloxypropanepropanesulf- onic acid AMP:
2-amino-2-methyl-1-propanol
[0142] As apparent from the above description, any one of the
oxygen scavengers of the first through fifth aspects of the present
invention can efficiently remove dissolved oxygen in water. When
these are used as an oxygen scavenger for feed water of a boiler,
any one of these can inhibit the corrosion on a boiler main body
and a steam and condensate piping caused by dissolved oxygen.
Therefore, each oxygen scavenger has quite high industrial
utility.
[0143] Further, the fifth aspect provides an oxygen scavenger which
prevents the development of by-product in the boiler so as not to
affect the purity of steam.
[0144] The sixth aspect provides an oxygen scavenger having
improved deoxidization effect in feed water lines for low
temperature water and which is remarkably superior in corrosion
inhibition in a feed water piping as compared with a conventional
one.
[0145] The chemical for treating boiler water of the seventh aspect
exhibits excellent corrosion inhibition effect relative to any of a
boiler main body and steam and condensate lines although the
chemical is one-component agent. This is because the heterocyclic
compounds with N-substituted amino group and the neutral amine are
contained in the chemical.
[0146] The eighth aspect provides a boiler water treatment chemical
having both the excellent corrosion inhibition effect and the
descaling effect although the chemical is one-component agent.
* * * * *