U.S. patent application number 10/542776 was filed with the patent office on 2006-08-17 for thermal liquids providing glass corrosion protection especially for solar systems.
Invention is credited to Frank Hillerns, Claudius Kormann, Ladislaus Meszaros, Bernd Wenderoth, Horst Zollner.
Application Number | 20060180793 10/542776 |
Document ID | / |
Family ID | 32602814 |
Filed Date | 2006-08-17 |
United States Patent
Application |
20060180793 |
Kind Code |
A1 |
Wenderoth; Bernd ; et
al. |
August 17, 2006 |
Thermal liquids providing glass corrosion protection especially for
solar systems
Abstract
A heat transfer liquid concentrate comprises, in addition to at
least one glycol, a) from 0.05 to 10, preferably from 0.1 to 5, %
by weight of one or more aliphatic amines of the formula (I),
##STR1## where R.sup.1 to R.sup.3 may be identical or different and
are hydrogen, optionally branched C.sub.1-C.sub.9-alkyl or
C.sub.1-C.sub.9-hydroxyalkyl, b) from 0.005 to 3, preferably from
0.01 to 1, % by weight of one or more silicates which may have been
stabilized, c) from 0 to 3% by weight of one or more corrosion
inhibitors selected from the group consisting of the
hydrocarbon-triazoles and of the hydrocarbon-thiazoles, d) from 0
to 5% by weight of one or more alkali metal, ammonium or
substituted ammonium molybdates and e) from 0 to 1% by weight of
one or more polymeric hard water stabilizers. The concentrates, if
required after prior dilution with water, are particularly suitable
for use in solar plants in which a heat transfer liquid is in
direct contact with the glass of the solar plant.
Inventors: |
Wenderoth; Bernd; (Birkenau,
DE) ; Kormann; Claudius; (Schifferstadt, DE) ;
Zollner; Horst; (Harthausen, DE) ; Meszaros;
Ladislaus; (Mutterstadt, DE) ; Hillerns; Frank;
(Hamburg, DE) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
32602814 |
Appl. No.: |
10/542776 |
Filed: |
January 21, 2004 |
PCT Filed: |
January 21, 2004 |
PCT NO: |
PCT/EP04/00447 |
371 Date: |
July 20, 2005 |
Current U.S.
Class: |
252/387 |
Current CPC
Class: |
C09K 5/10 20130101; C09K
5/20 20130101 |
Class at
Publication: |
252/387 |
International
Class: |
C23F 11/00 20060101
C23F011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 21, 2003 |
DE |
103 02 093.4 |
Claims
1-18. (canceled)
19. A heat transfer liquid concentrate comprising, in addition to
at least one glycol, from 0.05 to 10% by weight of one or more
aliphatic amines of the general formula (I), ##STR3## where R.sup.1
to R.sup.3 may be identical or different and are hydrogen,
straight-chain or branched C.sub.1-C.sub.9-alkyl or
C.sub.1-C.sub.9-hydroxyalkyl, from 0.005 to 3% by weight of one or
more silicates which may have been stabilized, from 0 to 3% by
weight of one or more corrosion inhibitors selected from the group
consisting of the hydrocarbon-triazoles and of the
hydrocarbon-thiazoles, from 0 to 5% by weight of one or more alkali
metal, ammonium or substituted ammonium molybdates and from 0 to 1%
by weight of one or more polymeric hard water stabilizers; and
wherein the concentrate contains no borate.
20. The concentrate as claimed in claim 19, wherein the component
c) is present in an amount of from 0.01 to 3% by weight.
21. The concentrate as claimed in claim 20, wherein the component
c) is present in an amount of from 0.05 to 1% by weight.
22. The concentrate as claimed in claim 19, wherein, in the amine
of the formula (I), R.sup.1 to R.sup.3 are selected from hydrogen,
linear and branched alkyl radicals with 1 to 9 carbon atoms and
linear and branched alkyl radicals with 1 to 9 carbon atoms with at
least one hydroxyl substituent.
23. The concentrate as claimed in claim 22, wherein R.sup.1 to
R.sup.3 are selected from hydrogen, linear and branched alkyl
radicals with 3 or 4 carbon atoms and linear and branched alkyl
radicals with 3 or 4 carbon atoms which have at least one hydroxyl
substituent.
24. The concentrate as claimed in claim 19, wherein the amine
carries an alkyl radical having at least one hydroxyl
substituent.
25. The concentrate as claimed in claim 19, wherein the silicate of
component b) is stabilized.
26. The concentrate as claimed in claim 25, wherein the silicate is
stabilized by organosilicophosphonates and/or
organosilicosulfonates.
27. The concentrate as claimed in claim 19, wherein component b)
contains an alkali metal silicate, the silicate being stabilized,
if required, with orthophosphates.
28. The concentrate as claimed in claim 19, wherein component c)
contains a mixture of at least two hydrocarbon-thiazoles, a mixture
of at least one hydrocarbon-triazole and one hydrocarbon-thiazole
or a mixture of at least two different hydrocarbon-triazoles.
29. The concentrate as claimed in claim 19, wherein component d)
contains sodium molybdate.
30. The concentrate as claimed in claim 19, wherein component e)
contains at least one hard water stabilizer based on one or more
compounds from the group consisting of polyacrylic acid, polymaleic
acid, acrylic acid/maleic acid copolymers, polyvinylpyrrolidone,
polyvinylimidazole, vinylpyrrolidone/vinylimidazole copolymers and
copolymers of unsaturated carboxylic acids and olefins.
31. The concentrate as claimed in claim 19, wherein furthermore one
or more soluble magnesium salts of organic acids, one or more
hydrocarbazoles and/or one or more quaternized imidazoles are
present.
32. The concentrate as claimed in claim 19, wherein the pH is from
6 to 11.
33. The concentrate as claimed in claim 19, wherein the freezing
point depressant contains at least one compound from the group
consisting of the lower alkylene glycols and derivatives thereof,
higher glycols and glycol ethers, monoethers of glycols,
1,3-propanediol and glycerol.
34. The concentrate as claimed in claim 19, wherein the freezing
point depressant is present in the concentrate in an amount of
>75% by weight.
35. The concentrate as claimed in claim 19, wherein the freezing
point depressant comprises 1,2-propylene glycol or a mixture of
1,2-propylene glycol with one or more other polyalcohols, the
mixture containing at least 85% by weight of 1,2-propylene
glycol.
36. A ready-to-use aqueous heat transfer liquid comprising water
and from 10 to 90% by weight of a heat transfer liquid concentrate
as claimed in claim 19.
37. A method of transferring heat in a solar plant comprising using
in the solar plant a heat transfer liquid concentrate as claimed in
claim 19.
38. The method as claimed in claim 37, comprising bringing the heat
transfer liquid concentrate into direct contact with glass of the
solar plant.
39. A method of transferring heat in a solar plant comprising using
in the solar plant a ready-to-use heat transfer liquid as claimed
in claim 36.
40. The method as claimed in claim 39, comprising bringing the heat
transfer liquid concentrate into direct contact with glass of the
solar plant.
Description
[0001] The present invention relates in particular to borate-free
concentrates based on glycols with glass corrosion protection for
heat transfer liquids, in particular for solar plants, comprising
amines and, if required, stabilized silicates and
hydrocarbon-thiazoles and hydrocarbon-triazoles; further corrosion
inhibitors and other components may also be present. The present
invention furthermore relates to ready-to-use aqueous heat transfer
liquids which are based on said concentrates, and their use in
solar plants.
[0002] Concentrates for heat transfer liquids, in particular for
solar plants, generally contain alkylene glycols, especially
1,2-propylene glycol or ethylene glycol, as the main component. For
use in solar plants, they are diluted with water and, in addition
to preventing freezing, should ensure good heat transfer. Alkylene
glycol/water mixtures are, however, very corrosive at the high
temperatures occurring in intense sunlight and in particular those
occurring when the plant is not operating; the various metals, for
example copper, brass, steel, cast iron (gray cast iron), lead,
tin, chromium, zinc, aluminum, magnesium and alloys thereof and
solder metals, for example tin solder (soft solder), which in
principle can occur in the heat transfer circulation of solar
plants therefore have to be adequately protected from various types
of corrosion, for example pitting, crevice corrosion, erosion or
cavitation. A large number of individual chemical substances is
known from the prior art for use as corrosion inhibitors for metals
in such systems.
[0003] The prior art includes a number of patents and patent
applications in which heat transfer liquids for solar plants
containing effective corrosion inhibitor formulations for metals
are described, some of which are mentioned below.
[0004] DE 195 25 090 A1 describes heat transfer liquids for
preventing the deposition of solids in the solar absorbers
comprising 1,2-propylene glycol, polyethylene glycol having a molar
mass of 400 and water, in which borax, silicate, dicarboxylic
acids, sodium benzoate, benzotriazole, tolutriazole, sodium nitrate
or sodium nitrite is used as a corrosion inhibitor.
[0005] EP 0 971 013 A1 describes aqueous heat transfer media for
solar plants, which contain tri- and/or tetraethylene glycol,
1,2-propylene glycol and/or ethylene glycol, comprising a content
of borates, silicates, mono- or dicarboxylic acids, sodium
benzoate, benzotriazoles, tolutriazoles, nitrites or nitrates as
corrosion inhibitors.
[0006] EP 0 109 377 A2 claims a solar collector which contains a
heat transfer liquid comprising monoethylene glycol or glycerol,
water, formic acid and a quaternary ammonium salt.
[0007] EP 0 092 687 B1 describes an aqueous corrosion-inhibiting
heat transfer composition which is also suitable for solar systems
and contains an alcohol, for example ethylene glycol or propylene
glycol, and an organosiloxane/silicate copolymer and, in the
absence of nitrite, contains at least one nitrate salt.
Furthermore, known corrosion inhibitors for metals, such as
molybdate, borate, phosphate, benzoate, hydroxybenzoate, nitrite,
tolutriazole, mercaptobenzothiazole and benzotriazole may be
present.
[0008] For solar plants, there are now newer solar collectors
comprising special glass, for example comprising special
borosilicate glasses, in which the heat transfer liquid no longer
flows through metal tubes inside evacuated glass tubes but directly
through the glass tubes. The internal surfaces of the glass tubes
through which the heat transfer liquids flow can suffer corrosive
attack, which leads to opacity and, associated with this, reduced
energy absorption from sunlight. The heat transfer liquids of the
prior art which are available on the market are still in need of
substantial improvement in this respect.
[0009] The problems of glass corrosion are not described and have
not been solved to date by the known prior art mentioned above.
[0010] It is an object of the present invention to provide novel
concentrates and heat transfer liquids to be prepared therefrom for
solar plants. These are intended to be in particular solar plants
in which the heat transfer liquid is directly in contact with the
glass, for example the glass tubes. The liquids to be provided
should no longer have the disadvantages of glass corrosion of the
prior art.
[0011] We have found that this object is achieved by heat transfer
liquid concentrates with glass corrosion protection, in particular
for solar plants, comprising, in addition to at least one glycol,
[0012] a) from 0.05 to 10, preferably from 0.1 to 5, % by weight,
based on the total amount of the concentrate, of one or more
aliphatic amines of the general formula (1), ##STR2## [0013] where
R.sup.1 to R.sup.3 may be identical or different and are hydrogen,
straight-chain or branched C.sub.1-C.sub.9-alkyl or
C.sub.1-C.sub.9-hydroxyalkyl, [0014] b) from 0.005 to 3, preferably
from 0.01 to 1, % by weight, based on the total amount of the
concentrate, of one or more silicates which, if required, have been
stabilized, [0015] c) from 0 to 3, preferably from 0.01 to 3, in
particular from 0.05 to 1, % by weight, based on the total amount
of the concentrate, of one or more corrosion inhibitors selected
from the group consisting of the hydrocarbon-triazoles and the
hydrocarbon-thiazoles, [0016] d) from 0 to 5, preferably from 0.01
to 1, % by weight, based on the total amount of the concentrate, of
one or more alkali metal, ammonium or substituted ammonium
molybdates and [0017] e) from 0 to 1, preferably from 0.1 to 0.5, %
by weight, based on the total amount of the concentrate, of one or
more polymeric hard water stabilizers.
[0018] The novel concentrates for heat transfer liquids can be used
in conventional solar plants, but in particular in newer systems
comprising special glass, in which the heat transfer liquid no
longer flows through metal tubes inside evacuated glass tubes but
directly through the glass tubes, with the result that particular
protection of the internal glass surfaces from opacity due to
corrosion is required.
[0019] We have found that effective corrosion prevention in solar
plants, in particular those with direct contact between the heat
transfer liquid and the glass, for example the glass tubes, can be
achieved by the combination of the amines used according to the
invention with silicates, i.e. the components a) and b).
[0020] All amounts stated in the present application relate to the
total amount of the concentrate.
[0021] In a preferred embodiment, R.sup.1 to R.sup.3 are selected
from hydrogen, alkyl radicals with 2 to 9 carbon atoms and alkyl
radicals with 1 to 9 carbon atoms which have one or more hydroxyl
substituents. In particular, R.sup.1 to R.sup.3 are selected from
hydrogen and alkyl groups with 3 or 4 carbon atoms and alkyl
radicals with 3 or 4 carbon atoms which have one or more hydroxyl
substituents.
[0022] Examples of preferred amines are ethylamine, propylamine,
isopropylamine, n-butylamine, isobutylamine, sec-butylamine,
tert-butylamine, n-butylamine, n-pentylamine, n-hexylamine,
n-heptylamine, n-octylamine, isononylamine, diethylamine,
di-n-propylamine, diisopropylamine, di-n-butylamine,
diisobutylamine, triethylamine, diisopropylamine,
butyldiethanolamine and mono-, di- and triethanolamine.
[0023] For the purposes of the present invention, alkyl-substituted
amines in which at least one alkyl radical carries at least one
hydroxyl substituent are particularly preferred.
[0024] Diisopropanolamine or butyldiethanolamine is particularly
preferably used for component a).
[0025] In a further preferred embodiment, the component b) contains
at least one alkali metal silicate, particularly suitable silicates
being those described in EP-A 0 189 527. Examples are alkali metal
orthosilicates, alkali metal metasilicates, alkali metal
tetrasilicates and alkali metal silicates. The sodium salts are
preferred. In particular, sodium metasilicate is used.
[0026] The alkali metal silicate is furthermore preferably
stabilized by conventional organosilicophosphonates, for example
according to EP-A 0 189 527 or DE-OS 29 12 430, or conventional
organosilicosulfonates, for example according to EP-A 0 061 694, in
conventional amounts. Silicates stabilized by
organosilicophosphonates are particularly preferred.
[0027] The organosilicophosphonates disclosed in EP-A 0 189 527 and
DE-OS 29 12 430 and the organosilicosulfonates disclosed in EP-A 0
061 694 are an important component of the present invention and are
hereby incorporated by reference in the present Application. In a
further preferred embodiment, the component c) is a mixture of at
least two hydrocarbon-thiazoles, a mixture of at least one
hydrocarbon-triazole and one hydrocarbon-thiazole or a mixture of
at least two different hydrocarbon-triazoles. Examples of preferred
hydrocarbon-thiazoles are benzothiazole and
2-mercaptobenzothiazole.
[0028] A mixture of at least two different hydrocarbon-triazoles is
preferably used. These are selected in particular from
benzotriazole, tolutriazole and 1H-1,2,4-triazole.
[0029] In a further preferred embodiment, the component d) contains
sodium molybdate, in particular sodium molybdate dihydrate.
[0030] In a further preferred embodiment, the component d) contains
at least one hard water stabilizer based on polyacrylic acid,
polymaleic acid, acrylic acid/maleic acid copolymers,
polyvinylpyrrolidone, polyvinylimidazole,
vinylpyrrolidone/vinylimidazole copolymers and copolymers of
unsaturated carboxylic acids and olefins.
[0031] In addition to said inhibitor components, for example,
soluble magnesium salts of organic acids, preferably magnesium
benzenesulfonate, magnesium methanesulfonate, magnesium acetate or
magnesium propionate, and furthermore hydrocarbazoles and/or
quaternized imidazoles, as described in DE-A 196 05 509, in
conventional amounts may also be used as further inhibitors.
[0032] The pH of the novel heat transfer concentrates is usually
from 6 to 11, preferably from 7 to 10, in particular from 7.5 to
10. The desired pH is established, as a rule, by adding alkali
metal hydroxide to the formulation. Solid sodium hydroxide or
potassium hydroxide and aqueous sodium hydroxide solution and
potassium hydroxide solution are particularly suitable for
establishing the pH.
[0033] The novel concentrates contain no borate. For the purposes
of the present invention, borate may be present in the heat
transfer liquids or concentrates, but then the advantages according
to the invention are not achieved in most cases. In particular, in
the presence of strongly alkaline borates, greater glass corrosion
is generally to be found, which can assume substantial levels
depending on the composition of the liquid. The borate usually used
is borax (sodium tetraborate).
[0034] The novel heat transfer liquid concentrates preferably
furthermore contain a freezing point depressant which is selected
from alkylene glycols and derivatives thereof. The freezing point
depressant is preferably present in the novel concentrates in an
amount of at least 75, more preferably at least 85, % by
weight.
[0035] First, lower alkylene glycols and derivatives thereof, for
example ethylene glycol and 1,2-propylene glycol, are suitable for
use in the novel concentrates. However, higher glycols and glycol
ethers are also suitable, for example diethylene glycol,
dipropylene glycol, tri- and tetraethylene glycol, polyethylene
glycol, monoethers of glycols, for example the methyl, ethyl,
propyl and butyl ethers of ethylene glycol, propylene glycol,
diethylene glycol and dipropylene glycol. 1,3-Propanediol and
glycerol are furthermore suitable. A single solvent or a mixture of
two or more solvents may be used.
[0036] Ethylene glycol and/or 1,2-propylene glycol are preferably
used, in particular 1,2-propylene glycol.
[0037] In a preferred embodiment, the freezing point depressant is
based on 1,2-propylene glycol or mixtures thereof with other
polyalcohols, at least 85, preferably 90, % by weight of
1,2-propylene glycol being present in the mixture.
[0038] The novel heat transfer concentrates may also contain, in
conventional small amounts, antifoams, preferably in amounts of
from 0.003 to 0.008% by weight, dyes and bitter substances for
reasons of hygiene and safety in the event of swallowing, for
example of the denatonium benzoate type, as further conventional
assistants.
[0039] The present invention also relates to ready-to-use aqueous
heat transfer liquids having a depressed freezing point and the use
thereof in solar plants, which comprise water and from 10 to 90, in
particular from 20 to 60, % by weight of the novel heat transfer
concentrates.
[0040] The novel heat transfer concentrates are distinguished not
only by effective corrosion inhibition of the metals or alloys
listed at the outset and good high-temperature stability but in
particular additionally provide very good protection from glass
corrosion in applications in modern solar plants in which the heat
transfer liquid is in direct contact with the glass of the solar
plant, for example the glass tubes.
[0041] The example which follows illustrates the invention without
restricting it.
EXAMPLES
[0042] The preparation of the novel heat transfer concentrates can
be effected by mixing together the stated components, as described
by way of example below for the novel concentrate 1. TABLE-US-00001
Comparative Comparative Concentrate 1 concentrate A concentrate B %
by weight % by weight % by weight 1,2-Propylene glycol 94 94 94
Polyacrylic acid <0.5 <0.5 <0.5 (Sokalan .RTM. CP 10 S)
Potassium hydroxide <0.3 <0.3 <0.3 solution (50% strength)
Tolutriazole <0.2 <0.2 <0.2 Benzotriazole <0.1 <0.1
<0.1 Sodium molybdate <0.1 <0.1 <0.1 dihydrate
Hydroxyalkylamine <5 <5 <5 Antifoam 40 ppm 40 ppm 40 ppm
(Pluriol .RTM. PE 10100) Borax (sodium -- -- 0.20 tetraborate
10H.sub.2O) Sodium metasilicate 0.20 -- -- (stabilized with
silicophosphonate) Water Remainder Remainder Remainder
[0043] 1,2-Propylene glycol was initially taken, and polyacrylic
acid, potassium hydroxide solution, tolutriazole, benzotriazole,
sodium molybdate dihydrate, the hydroxyalkylamine and antifoam were
added in succession while stirring at room temperature. After
complete dissolution of all starting materials, the sodium
metasilicate diluted beforehand in the ratio 1:9 with water and
stabilized with silicophosphonate was added and stirring was
carried out until a clear, homogeneous liquid was present.
[0044] The novel concentrate 1 thus obtained and the analogously
prepared comparative concentrates A and B were diluted in the ratio
45:55 with water and tested as in example 1 according to the
invention and as comparative examples A and B in the tests
described below.
A Glass Corrosion
[0045] For the test, borosilicate glass ampoules (dimensions in mm:
14.75.times.0.55) are used. Each container is washed twice with
distilled water and once with doubly distilled water. After drying
for about 1 hour at 150.degree. C., the ampoules are cooled to room
temperature, cleaned on the outside with ethanol and weighed. The
ampoules are then filled with 5.5 ml of test solution, closed with
an aluminum foil and left for 24 hours at 135.degree. C. in an
autoclave (type 112 from KSG Sterilisatoren GmbH, 82140 Olching,
temperature regulation of the thermocouple directly in a test
specimen in each case).
[0046] The containers are removed from the autoclave while taking
the usual precautions and are cooled to room temperature in the
course of one hour. The ampoules are emptied, washed about five
times with distilled water, dried again for about one hour at
150.degree. C., cooled and weighed.
[0047] The test results with example 1 according to the invention
and comparative examples A and B are shown in table 1.
TABLE-US-00002 TABLE 1 Testing of the resistance of borosilicate
glass Example 1 Comp. example A Comp. example B Weight change
Weight change Weight change Glass ampoule [mg] [mg] [mg] 1 +0.1
-0.1 -0.1 2 +0.1 -0.2 -0.3 3 +0.1 -0.2 -0.3 4 +0.2 -0.2 -0.3 5 +0.2
-0.1 -0.3 6 +0.2 -0.3 -0.4 7 +0.1 -0.2 -0.3 8 +0.1 0 -0.4 9 +0.1
-0.4 -0.3 10 +0.2 -0.1 -0.3 11 +0.1 -0.2 -0.4 12 +0.1 -0.3 -0.2 13
+0.2 -0.4 0 14 +0.1 -0.2 -0.3 15 +0.2 -0.2 -0.2 O weight change
+0.1 -0.2 -0.3 pH before 9.7 8.4 9.7 pH after 9.7 8.5 9.6
[0048] The results demonstrate that novel heat transfer liquids,
such as example 1, have substantially improved glass corrosion
prevention compared with the prior art (comparative example); in
example 1, no weight loss was detectable in any of the 15 glass
test specimens. Comparative example B furthermore shows the
corrosive effect of borates on glass.
B Glassware Corrosion Test According to ASTM D 1384-97
[0049] The results of the glassware corrosion test according to
ASTM D 1384-97 furthermore demonstrate that the novel heat transfer
liquids also protect metals from corrosion at least as well as the
prior art.
[0050] Table 2 shows the test results TABLE-US-00003 TABLE 2
Glassware corrosion test according to ASTM D 1384-97 Example 1
Comp. example A Comp. example B Weight change Weight change Weight
change Test specimen [mg/cm.sup.-2] [mg/cm.sup.2] [mg/cm.sup.2]
Copper -1.1 -0.7 -1.4 Soft solder -0.6 -0.9 -67.2 Brass -0.8 -1.0
-2.2 Steel +0.1 -0.3 -0.1 Gray cast iron +0.6 -0.9 -0.6 Cast
aluminum +0.9 -1.5 -1.9 pH before 9.7 8.4 9.7 pH after 9.6 8.6
9.2
* * * * *