SURFACTANT BASED SMALL MOLECULES FOR REDUCING
ALUMINOSILICATE SCALE IN THE BAYER PROCESS
Background of the Invention
The invention relates to compositions, methods, and apparatuses for
improving treatment and inhibition of scale in various industrial process streams, in
particular certain surfactant based small molecules that have been found to be
particularly effective in treating aluminosilicate scale in a Bayer process stream.
As described among other places in US Patent 6,814,873 the contents
of which are incorporated by reference in their entirety, the Bayer process is used to
manufacture alumina from Bauxite ore. The process uses caustic solution to extract
soluble alumina values from the bauxite. After dissolution of the alumina values
from the bauxite and removal of insoluble waste material from the process stream
the soluble alumina is precipitated as solid alumina trihydrate. The remaining
caustic solution known as "liquor" and / or "spent liquor" is then recycled back to
earlier stages in the process and is used to treat fresh bauxite. It thus forms a fluid
circuit. For the purposes of this application, this description defines the term
"liquor". The recycling of liquor within the fluid circuit however has its own
complexities.
Bauxite often contains silica in various forms and amounts. Some of
the silica is unreactive so it does not dissolve and remains as solid material within
the Bayer circuit. Other forms of silica (for example clays) are reactive and dissolve
in caustic when added into Bayer process liquors, thus increasing the silica
concentration in the liquor. As liquor flows repeatedly through the circuit of the
Bayer process, the concentration of silica in the liquor further increases, eventually
to a point where it reacts with aluminum and soda to form insoluble aluminosilicate
particles. Aluminosilicate solid is observed in at least two forms, sodalite and
cancrinite. These and other forms of aluminosilicate are commonly referred to, and
for the purposes of this application define, the terms "desilication product" or
"DSP".
DSP can have a formula of 3(Na2 Al20 3'2Si0 2'0-2 H20 ) · 2NaX
where X represents OH , CI , C0 3
2- , S0 4
2- . Because DSP has an inverse solubility
(precipitation increases at higher temperatures) and it can precipitate as fine scales
of hard insoluble crystalline solids, its accumulation in Bayer process equipment is
problematic. As DSP accumulates in Bayer process pipes, vessels, heat transfer
equipment, and other process equipment, it forms flow bottlenecks and obstructions
and can adversely affect liquor throughput. In addition because of its thermal
conductivity properties, DSP scales on heat exchanger surfaces reduce the efficiency
of heat exchangers.
These adverse effects are typically managed through a descaling
regime, which involves process equipment being taken off line and the scale being
physically or chemically treated and removed. A consequence of this type of regime
is significant and regular periods of down-time for critical equipment. Additionally
as part of the descaling process the use of hazardous concentrated acids such as
sulfuric acid are often employed and this constitutes an undesirable safety hazard.
Another way Bayer process operators manage the buildup of silica
concentration in the liquor is to deliberately precipitate DSP as free crystals rather
than as scale. Typically a "desilication" step in the Bayer process is used to reduce
the concentration of silica in solution by precipitation of silica as DSP, as a free
precipitate. While such desilication reduces the overall silica concentration within
the liquor, total elimination of all silica from solution is impractical and changing
process conditions within various parts of the circuit (for example within heat
exchangers) can lead to changes in the solubility of DSP, resulting in consequent
precipitation as scale.
Previous attempts at controlling and/or reducing DSP scale in the
Bayer process have included adding polymer materials containing three alkyloxy
groups bonded to one silicon atom as described in US patent 6,814,873 B2, US
published applications 2004/0162406 Al, 2004/0011744 Al, 2005/0010008 A2,
international published application WO 2008/045677 Al, and published article Max
HTTM Sodalite Scale Inhibitor: Plant Experience and Impact on the Process, by
Donald Spitzer et. al., Pages 57-62, Light Metals 2008, (2008) all of whose contents
are incorporated by reference in their entirety.
Manufacturing and use of these trialkoxysilane-grafted polymers
however can involve unwanted degrees of viscosity, making handling and dispersion
of the polymer through the Bayer process liquor problematic. Other previous
attempts to address foulant buildup are described in US Patents 5,650,072 and
5,314,626 both of which are incorporated by reference in their entirety.
Thus while a range of methods are available to Bayer process
operators to manage and control DSP scale formation, there is a clear need for, and
utility in, an improved method of preventing or reducing DSP scale formation on
Bayer process equipment. The art described in this section is not intended to
constitute an admission that any patent, publication or other information referred to
herein is "prior art" with respect to this invention, unless specifically designated as
such. In addition, this section should not be construed to mean that a search has been
made or that no other pertinent information as defined in 37 C.F.R. § 1.56(a) exists.
Brief Summary of the Invention
To satisfy the long-felt but unsolved needs identified above, at least
one embodiment of the invention is directed towards a method for reducing siliceous
scale in a Bayer process comprising the step of adding to a Bayer liquor an
aluminosilicate scale reducing amount of a non-polymeric reaction product resulting
from the reaction of: a) a surfactant and b) a GPS.
The non-polymeric reaction product may be a resultant from the
reaction of items further comprising one item selected from the group consisting of
at least one: hydrophobe, amine binder, epoxide binder, and any combination
thereof. The GPS may be 3- glycidoxypropyltrimethoxysilane. The surfactant may
be one selected from the group consisting of: ethoxylated fatty alcohols, ethoxylated
fatty amines, fatty amines, G12A7, G12A4, G17A3, G9A6, G9A8, 18M20, 18M2,
16M2, DPD, OPD, OLA, and any combination thereof. The
epoxide binder may be a molecule according to formulas (I), (II), and any
combination thereof:
(I) (P)
The hydrophobe may be a C8-C10 aliphatic glycidyl ether. The reaction product
may have a molecular weight of less than 500 daltons. The reaction product may be
according to the formula illustrated in FIG. 1, FIG. 2, and/or may be Product P,
Product U, and/or Product HS.
The reaction product may be formed at least in part according to one
of the methods selected from the group consisting of Methods: I, II, III, IV, V, VI,
VII, VIII, IX, X, XI, XII, and XIII, and any combination thereof. The amine binder
may be one selected from the list consisting of: tetraethylenepentamine and
ethylenediamine .
Additional features and advantages are described herein, and will be
apparent from the following Detailed Description.
Brief Description of the Drawings
A detailed description of the invention is hereafter described with
specific reference being made to the drawings in which:
FIG. 1 is an illustration of the formula of reaction product X.
FIG. 2 is an illustration of the formula of reaction product BB.
FIG. 3 is a first table of Formula types used in the invention.
FIG. 4 is a second table of Formula types used in the invention.
FIG. 5 is a third table of Formula types used in the invention.
FIG. 6 is a fourth table of Formula types used in the invention
FIG. 7 is an illustration of SEM (Scanning Electron Microscope)
analysis demonstrating the efficacy of the invention.
For the purposes of this disclosure, like reference numerals in the
figures shall refer to like features unless otherwise indicated. The drawings are only
an exemplification of the principles of the invention and are not intended to limit the
invention to the particular embodiments illustrated.
Detailed Description of the Invention
The following definitions are provided to determine how terms used
in this application, and in particular how the claims, are to be construed. The
organization of the definitions is for convenience only and is not intended to limit
any of the definitions to any particular category.
"Polymer" means a chemical compound comprising essentially
repeating structural units each containing two or more atoms. While many polymers
have large molecular weights of greater than 500, some polymers such as
polyethylene can have molecular weights of less than 500. Polymer includes
copolymers and homo polymers.
"Small molecule" means a chemical compound comprising
essentially non-repeating structural units. Because an oligomer (with more than 10
repeating units) and a polymer are essentially comprised of repeating structural
units, they are not small molecules. Small molecules can have molecular weights
above and below 500. The terms "small molecule" and "polymer" are mutually
exclusive.
"Foulant" means a material deposit that accumulates on equipment
during the operation of a manufacturing and/or chemical process which may be
unwanted and which may impair the cost and/or efficiency of the process. DSP is a
type of foulant.
"Amine" means a molecule containing one or more nitrogen atoms
and having at least one secondary amine or primary amine group. By this definition,
monoamines such as dodecylamine, diamines such as hexanediamine, and triamines
such as diethylenetriamine, are all amines.
"GPS" is glycidoxyalkyltrimethoxysilane which includes 3-
glycidoxypropyltrimethoxysilane, one possible formula for GPS can be represented
by the structure:
"Ethoxylated Alcohol" means an alcohol according to the formula:
R— (EO) n-OH
wherein EO is an ethoxy group (-OCH2CH2-) and n is an integer within the range 1-
50.
Ethoxy lated Amine" means an amine according to the formula:
R
wherein EO is an ethoxy group (-OCH2CH2-) , m is an integer within the range 1-
50 , and n is an integer within the range 1-50.
"G12A7" means a C12-C14 non-ionic alcohol ethoxylate surfactant,
a representative example of which is Teric G12A7 sold by Huntsman.
"G12A4" means a C12-C14 non-ionic alcohol ethoxylate surfactant,
a representative example of which is Teric G12A4 sold by Huntsman.
"G17A3" means a C16-C18 straight chain non-ionic alcohol
ethoxylate surfactant, a representative example of which is Teric G17A3 sold by
Huntsman.
"G9A6" means a C9-C11 straight chain non-ionic alcohol ethoxylate
surfactant, a representative example of which is Teric G9A6 sold by Huntsman.
"G9A8" means a C9-C11 straight chain non-ionic alcohol ethoxylate
surfactant, a representative example of which is Teric G9A8 sold by Huntsman.
8M20" means a C18-C22 alkyl amine ethoxylate surfactant, a
representative example of which is Teric 18M20 sold by Huntsman.
"18M2" means a C18-C22 alkyl amine ethoxylate surfactant, a
representative example of which is Teric 18M2 sold by Huntsman.
"16M2" means a C16-C18 alkyl amine ethoxylate surfactant, a
representative example of which is Teric 16M2 sold by Huntsman.
" A 5" means tallow alkyl amine ethoxylate surfactant, a
representative example of which is Agnique TAM5 sold by Cognis.
"DPD" means dodecyl-l,3-propanediamine
"EGDGE" means ethylene glycol diglycidylether
"OPD" means oleyl-l,3-propanediamine
"E " means epichlorohydrin
"OA" means octylamine
"ED" means ethylenediamine
"OLA" means oleylamine
"TEPA" means tetraethylenepentamine
"AGE" means C8-C10 aliphatic glycidyl ether
"Alkyloxy" means having the structure of OX where X is a
hydrocarbon and O is oxygen. It can also be used interchangeably with the term
"alkoxy". Typically in this application, the oxygen is bonded both to the X group as
well as to a silicon atom of the small molecule. When X is C i the alkyloxy group
consists of a methyl group bonded to the oxygen atom. When X is C2 the alkyloxy
group consists of an ethyl group bonded to the oxygen atom. When X is C3 the
alkyloxy group consists of a propyl group bonded to the oxygen atom. When X is
C4 the alkyloxy group consists of a butyl group bonded to the oxygen atom. When X
is C5 the alkyloxy group consists of a pentyl group bonded to the oxygen atom.
When X is C6 the alkyloxy group consists of a hexyl group bonded to the oxygen
atom.
"Monoalkyloxy" means that attached to a silicon atom is one
alkyloxy group.
"Dialkyloxy" means that attached to a silicon atom are two alkyloxy
groups.
"Trialkyloxy" means that attached to a silicon atom are three
alkyloxy groups.
"Synthetic Liquor" or "Synthetic Spent Liquor" is a laboratory
created liquid used for experimentation whose composition in respect to alumina,
soda, and caustic corresponds with the liquor produced by recycling through the
Bayer process.
"Bayer Liquor" is actual liquor that has run through a Bayer process
in an industrial facility.
"Separation" means a mass transfer process that converts a mixture
of substances into two or more distinct product mixtures, at least one of which is
enriched in one or more of the mixture's constituents, it includes but is not limited to
such processes as: Adsorption, Centrifugation, cyclonic separation, density based
separation, Chromatography, Crystallization, Decantation, Distillation, Drying,
Electrophoresis, Elutriation, Evaporation, Extraction, Leaching extraction, Liquidliquid
extraction, Solid phase extraction, Flotation, Dissolved air flotation, Froth
flotation, Flocculation, Filtration, Mesh filtration, membrane filtration,
microfiltration, ultrafiltration, nanofiltration, reverse osmosis, Fractional distillation,
Fractional freezing, Magnetic separation, Precipitation, Recrystallization,
Sedimentation, Gravity separation, Sieving, Stripping, Sublimation, Vapor-liquid
separation, Winnowing, Zone refining, and any combination thereof.
"Thickener" or "Settler" means a vessel used to effect a solid-liquid
separation of a slurry, often with the addition of flocculants, the vessel constructed
and arranged to receive a slurry, retain the slurry for a period of time sufficient to
allow solid portions of the slurry to settle downward (underflow) away from a more
liquid portion of the slurry (overflow), decant the overflow, and remove the
underflow. Thickener underflow and thickener overflow are often passed on to
filters to further separate solids from liquids.
In the event that the above definitions or a description stated
elsewhere in this application is inconsistent with a meaning (explicit or implicit)
which is commonly used, in a dictionary, or stated in a source incorporated by
reference into this application, the application and the claim terms in particular are
understood to be construed according to the definition or description in this
application, and not according to the common definition, dictionary definition, or the
definition that was incorporated by reference. In light of the above, in the event that
a term can only be understood if it is construed by a dictionary, if the term is defined
by the Kirk-Othmer Encyclopedia of Chemical Technology , 5th Edition, (2005),
(Published by Wiley, John & Sons, Inc.) this definition shall control how the term is
to be defined in the claims.
In the Bayer process for manufacturing alumina, bauxite ore passes
through a grinding stage and alumina, together with some impurities including
silica, are dissolved in added liquor. The mixture then typically passes through a
desilication stage where silica is deliberately precipitated as DSP to reduce the
amount of silica in solution. The slurry is passed on to a digestion stage where any
remaining reactive silica dissolves, thus again increasing the concentration of silica
in solution which may subsequently form more DSP as the process temperature
increases. The liquor is later separated from undissolved solids, and alumina is
recovered by precipitation as gibbsite. The spent liquor completes its circuit as it
passes through a heat exchanger and back into the grinding stage. DSP scale
accumulates throughout the Bayer process but particularly at the digestion stage and
most particularly at or near the heat exchanger, where the recycled liquor passes
through.
In this invention, it was discovered that dosing of various types of
small molecule based products can reduce the amount of DSP scale formed. The
small molecules are reaction products of surfactants with GPS and optionally also
with one or more of: hydrophobes, amine binders, epoxide binders, and any
combination thereof. FIG. 1 and FIG. 2 show representative structures of small
molecules constituted by combinations of surfactant, GPS and epoxide binder (FIG.
1) and surfactant, GPS, epoxide binder and amine binder (FIG.2) and which are
examples of the possible reaction product combinations encompassed by this
embodiment. In at least one embodiment of the invention, an effective concentration
of the small molecule product is added to some point or stage in the liquor circuit of
the Bayer process, which minimizes or prevents the accumulation of DSP on vessels
or equipment along the liquor circuit.
As described in US Patent 8,545,776 the small molecule DG12 is an
example of a small molecule which is a reaction product of a surfactant and GPS.
Similarly small molecule TG14 also in US Patent 8,545,776, and the various small
molecules such as GEN1, GEN2, and GEN3 are described in US Published Patent
Applications 2011/0212006 and 2012/0148462 are reaction products of some of
these items. In at least one embodiment the invention excludes TG14, DG12,
GEN1, GEN2, and GEN3.

In at least one embodiment the reaction product is formed at least in
part by allowing two or more of the reactants to contact each other for a period of
time between 1 minute and 55 days, and/or by allowing the reactants to contact each
other at a temperature of between 20°C and 500°C. The invention encompasses
adding any of some or all the reactants to the reaction simultaneously and/or in any
sequential order. Any portion of the reaction may occur within one or more of: a
liquid medium, a water medium, in the presence of acid and/or base, and or under
acidic, basic, or neutral conditions. Any portion of the reaction may occur at least in
part in the presence of one or more catalysts.
In at least one embodiment the surfactant includes but is not limited
to one selected from the list consisting of: ethoxylated fatty alcohols, ethoxylated
fatty amines, fatty amines, G12A7, G12A4, G17A3, G9A6, G9A8, 18M20, 18M2,
16M2, DPD, OPD, OLA, and any combination thereof. FIG. 3, FIG. 4, FIG 5 and
FIG. 6 are tables illustrating some of the possible reaction product combinations
encompassed by this embodiment.
In at least one embodiment the epoxide binder is according to one or
more of the formulas (I) and (II):
(I) (II)
In at least one embodiment the hydrophobe is a C8-CIO aliphatic
glycidyl ether. The hydrophobe may be may be described as a linear or branched,
aromatic or aliphatic hydrocarbon chain which may optionally contain an ether
linkage or additional functional end group such as an epoxide which allows the
hydrophobe to be reacted with and attached to other molecules. The hydrocarbon
chain may consist of between 3 and 50 carbon atoms
In at least one embodiment the hydrophobe is according to formula
(III) where R' is a linear or branched hydrocarbon chain containing at least 3 carbon
atoms:
(III)
In at least one embodiment, the amine binder is selected from a linear
or branched, aliphatic or cycloaliphatic monoamines, diamines, triamines,
butamines, and pentamines. The total number of carbon atoms in the amine is
preferred to be less than 30 and more preferred to be less than 20. In at least one
embodiment the amine is selected from a list consisting of: tetraethylene pentamine,
ethylene diamene, and any combination thereof.
In at least one embodiment, an amine small molecule is reacted with
both 3-glycidoxypropyltrialkoxysilane (GPS) and a hydrophobic molecule to form a
DSP inhibition composition. The hydrophobic molecule is an amine-reactive
compound having an amine-reactive functional group such as glycidyl, chloro,
bromo, or isocyanato groups. Besides the amine-reactive group, the hydrophobic
molecule has at least one C 3-C22 hydrophobic carbon chain, aromatic or aliphatic,
linear or branched.
In at least one embodiment, the amine molecule is selected from
linear or branched, aliphatic or cycloaliphatic monoamines or diamines. The total
number of carbon atoms in the amine is preferred to be less than 30 and more
preferred to be less than 20.
In at least one embodiment the amine is selected from a list
consisting of: isophoronediamine, xylenediamine, bis(aminomethyl)cyclohexane,
hexanediamine, C,C,C-trimethylhexanediamine, methylene bis(aminocyclohexane),
saturated fatty amines, unsaturated fatty amines such as oleylamine and soyamine,
N-fatty-l,3-propanediamine such as cocoalkylpropanediamine,
oleylpropanediamine, dodecylpropanediamine, hydrogenized
tallowalkylpropanediamine, and tallowalkylpropanediamine and any combination
thereof.
In at least one embodiment the reaction product is Product P, which
is a reaction product of GPS with a surfactant having a formula of:
In at least one embodiment the reaction product is Product U, which
is a reaction product of GPS with a surfactant and a hydrophobe having a formula
of:
In at least one embodiment the reaction product is Product X, which
is a reaction product of GPS with a surfactant, a hydrophobe and an epoxide binder
having a formula illustrated in FIG 1.
In at least one embodiment the reaction product is Product BB, which
is a reaction product of GPS with a surfactant, a hydrophobe, an epoxide binder and
an amine binder having a formula illustrated in FIG 2.
In at least one embodiment the reaction conditions results in the
formation of two or more of the aforementioned and incorporated reaction products.
In at least one embodiment the composition introduced to address DSP contains one,
two, or more of the aforementioned and incorporated reaction products.
In at least one embodiment the resulting surfactant based small
molecules are added to a dilute caustic solution prior to addition to the process
stream.
These small molecules reduce the amount of DSP scale formed and
thereby prevents its accumulation on Bayer process equipment.
The effectiveness of these small molecules was unexpected as the
prior art teaches that only high molecular weight polymers are effective. Polymer
effectiveness was presumed to depend on their hydrophobic nature and their size.
This was confirmed by the fact that cross-linked polymers are even more effective
than single chain polymers. As a result it was assumed that small molecules only
serve as building blocks for these polymers and are not effective in their own right.
(WO 2008/045677 [0030]). Furthermore, the scientific literature states "small
molecules containing" . . . "[an] S 1-O 3 grouping are not effective in preventing
sodalite scaling".... because ... "[t]he bulky group" ... "is essential [in] keeping the
molecule from being incorporated into the growing sodalite." Page 57 9 Light
Metals 2008, (2008). However it has recently been discovered that in fact, as further
explained in the provided examples, small molecules such as those described herein
are actually effective at reducing DSP scale.
It is believed that there are at least three advantages to using a small
molecule-based inhibitor as opposed to a polymeric inhibitor with multiple repeating
units of silane and hydrophobes. A first advantage is that the smaller molecular
weight of the product means that there are a larger number of active, inhibiting
moieties available around the DSP seed crystal sites at the DSP formation stage. A
second advantage is that the lower molecular weight allows for an increased rate of
diffusion of the inhibitor, which in turn favors fast attachment of the inhibitor
molecules onto DSP seed crystals. A third advantage is that the lower molecular
weight avoids high product viscosity and so makes handling and injection into the
Bayer process stream more convenient and effective.
In at least one embodiment DSP scale is addressed using one or more
of the compositions and/or methods of application described in US Patent
Applications 13/035,124, 13/403,282, 13/791,577, 14/011,051, US Patents
5,314,626, 6,814,873, 7,390,415, 7,442,755, 7,763,698, International Patent
Applications WO 02/070411, WO 2008/045677, WO 2012/115769, and US
Published Patent Applications 2004/0162406, 2004/0011744, 2010/0256317,
2011/0076209, 2011/0212006, and 2012/0148462.
EXAMPLES
The foregoing may be better understood by reference to the following
examples, which are presented for purposes of illustration and are not intended to
limit the scope of the invention. In particular the examples demonstrate
representative examples of principles innate to the invention and these principles are
not strictly limited to the specific condition recited in these examples. As a result it
should be understood that the invention encompasses various changes and
modifications to the examples described herein and such changes and modifications
can be made without departing from the spirit and scope of the invention and
without diminishing its intended advantages. It is therefore intended that such
changes and modifications be covered by the appended claims.
A number of reaction products were produced using the reactants
listed in FIG. 3, FIG. 4, and FIG. 5 according to the various methods described
below. The mass of surfactant added to all reactions was 5 g. Masses of other
reactants were calculated from the mole ratios described in Figures 3, 4 and 5..
Hydroxy-terminated surfactants
Method I : A mixture of surfactant (di-hydroxy terminated) and
hydrophobe was stirred and heated at 65°C. A solution of NaOH (50% in water) was
added and the mixture left for 30 min at 65°C. Glycidoxypropyltrimethoxysilane
was then added and the mixture left for 2 h at 65°C. The reaction mixture was
cooled then diluted to 5 % w/w in 20 g/L NaOH solution.
• NaOH was added at 2 molar equivalents to that of added epoxide.
• For A - O products, Method I was used excluding incorporation of
hydrophobe.
Amino-terminated surfactants
Method II: Surfactant was stirred and heated at 65°C. Hydrophobe
was added and the mixture left for 30 min at 65°C.
Glycidoxypropyltrimethoxysilane was then added and the mixture left for 2 h at
65°C. The reaction mixture was cooled then diluted to 5 % w/w in 20 g/L NaOH
solution.
• For products P and Q, Method II was used excluding incorporation of
hydrophobe.
Method III: Surfactant was stirred and heated at 65°C. Epoxide
binder was added and the mixture left for 30 min at 65°C.
Glycidoxypropyltrimethoxysilane was then added and the mixture left for 2 h at
65°C. The reaction mixture was cooled then diluted to 5 % w/w in 20 g/L NaOH
solution.
Method IV: A mixture of surfactant and amine binder was stirred and
heated at 65°C. Epoxide binder was added and the mixture left for 30 min at 65°C.
Glycidoxypropyltrimethoxysilane was then added and the mixture left for 2 h at
65°C. The reaction mixture was cooled then diluted to 5 % w/w in 20 g/L NaOH
solution.
• Products EE and FF were allowed to react for 60 min at 65°C prior to
addition of the glycidoxypropyltrimethoxysilane.
Method V: A mixture of surfactant and amine binder was stirred and
heated at 65°C. Epoxide binder was slowly added to the mixture then left for 2 h
total at 65°C. Glycidoxypropyltrimethoxysilane was then slowly added and the
mixture left for 1 h total at 65°C. The reaction mixture was cooled then diluted to 5
% w/w in 20 g/L NaOH solution.
Method VI: A mixture of surfactant, amine binder and DMSO was
stirred and heated at 65°C. Epoxide binder was slowly added to the mixture then
left for 3 h total at 65°C. Glycidoxypropyltrimethoxysilane was then slowly added to
the mixture. After 30 min a sample was taken from the reaction mixture and added
slowly to a stirred 20 g/L NaOH solution, diluting the sample to a concentration of
13.3% w/w.
Method VII: A mixture of surfactant and amine binder was stirred
and heated at 65°C. Epoxide binder was slowly added to the mixture then left for 30
min total at 65°C. Glycidoxypropyltrimethoxysilane was then slowly added to the
mixture. After 19 min a sample was taken from the reaction mixture and added
slowly to a stirred 20 g/L NaOH solution, diluting the sample to a concentration of
10 w/w.
Method VIII: A mixture of surfactant and amine binder was stirred
and heated at 65°C. Epoxide binder was slowly added to the mixture then left for 1
h total at 65°C. Glycidoxypropyltrimethoxysilane was then slowly added to the
mixture. After 15 min a sample was taken from the reaction mixture and added
slowly to a stirred 20 g/L NaOH solution, diluting the sample to a concentration of
10 w/w.
Method IX: A mixture of surfactant, amine binder and DMSO was
stirred and heated at 65°C. Epoxide binder was slowly added to the mixture then
left for 1 h total at 65°C. Glycidoxypropyltrimethoxysilane was then slowly added to
the mixture and the mixture left for 1 h. The reaction mixture was cooled then
diluted to 10 % w/w in 20 g/L NaOH solution.
Method X: A mixture of surfactant, amine binder and DMSO was
stirred and heated at 65°C. Epoxide binder was slowly added to the mixture then
left for 3 h total at 65°C. Glycidoxypropyltrimethoxysilane was then slowly added to
the mixture. After 16 min a sample was taken from the reaction mixture and added
slowly to a stirred 20 g/L NaOH solution, diluting the sample to a concentration of
11.8%.
Method XI: The reaction mixture from Method X was left at 65°C for
a further 44 min post sampling, cooled then diluted to 11.8 %w/w in 20 g/L NaOH
solution.
Method XII: A mixture of surfactant, amine binder and DMSO was
stirred and heated at 65°C. Epoxide binder was slowly added to the mixture then
left for 2 h and 2 min total at 65°C. Glycidoxypropyltrimethoxysilane was then
slowly added to the mixture. After 20 min a sample was taken from the reaction
mixture and added slowly to a stirred 20 g/L NaOH solution, diluting the sample to a
concentration of 11.8%.
Method XIII: The reaction mixture from Method XII was left at 65°C
for a further 40 min post sampling, cooled then diluted to 11.8 %w/w in 20 g/L
NaOH solution.
RESULTS: Test 1 Bottle Test Method
Assessment of inhibition of DSP formation used test conditions
similar to those previously used and published. To a stirred sample of plant spent
liquor, a small volume of concentrated sodium metasilicate pentahydrate solution
was added slowly so as to increase the amount of silica in the liquor (typically the
concentration was increased by approximately 1 g/L as Si0 2) . This "spiked" liquor
was then split into batches of 500 mL for treatment by addition of the appropriate
inhibitor at the desired dose. One batch of spiked liquor was kept as untreated
liquor.
Each of the treated batches was then sub-sampled to deliver duplicate
samples which were individually placed into 250 mL Nalgene polypropylene bottles
and placed into a rotating water bath at 95°C. Duplicate untreated control samples
were also included. After heating for 3 hours, the bottles were removed from the
bath and the solids were collected by filtration, washed with hot water and dried in
the oven at 110°C. After drying the resulting mass of DSP solids precipitated was
weighed. The efficacy of the treatment was determined by comparing the mass of
DSP precipitated from the individual treated samples to the untreated control
samples in the same test.
Results are presented as a percent calculated as: (Average mass
treated / Average mass untreated) x 100. A value of 100% means no effective
inhibition (same mass as untreated) while a value less than 100% indicates some
inhibitory activity. Lower numbers indicate more effective inhibition.
Type 1.1 Ethoxylated Alcohol Surfactant / Siloxane
Table 1% Sodalite Precipitated
A* 78 73
A* 66 57
B 72 6 1
C 72 6 1
D 69 45
E 70 6 1 6 1
*test repeated under the same test conditions as previous
Type 1.2 Ethoxylated Amine Surfactant / Siloxane
Table 2: % Sodalite Precipitated
0 30 4
*test repeated under the same test conditions as previous
Type 1.3 Fatty Amine Surfactant / Siloxane
Table 3: % Sodalite Precipitated
Type 2.1 Ethoxylated Amine Surfactant / Siloxane / Hydrophobe
Table 4: % Sodalite Precipitated
*test repeated under the same conditions as previous
Type 2.2 Fatty Amine Surfactant / Siloxane / Hydrophobe
Table 5: % Sodalite Precipitated
*test repeated under the same conditions as previous
Type 3.1 Fatty Amine Surfactant / Siloxane / Epoxide Binder
Table 6: % Sodalite Precipitated
*test repeated under the same conditions as previous tests
Type 4.1 Fatty Amine Surfactant / Siloxane / Amine Binder / Epoxide
Binder
Table 7: %Sodalite Precipitated
*test repeated under the same conditions as previous
RESULTS: Test 2 Bottle Test Method
Test 2 conditions were similar to those of Test 1 but were designed to
assess the effect on the initial formation of DSP solids from solution. As a result, a
shorter holding time for the precipitation step and an increased initial concentration
(higher "spike") of silica in the liquor was used in this method. Data is again
presented as a percent of mass precipitated compared to an undosed control sample.
Type 4.2 Fatty Amine Surfactant / Siloxane / Pentamine binder / Epoxide
Binder
Table 8: % Sodalite Precipitated
Table 9: % Sodalite Precipitated
SK 70 27
SL 7 2
SM 77 0 0
SN 156 37
SO 24 14
SP 97 77 3.6 0
SQ 82 62 1.5 0
SR 69 28
ST 78 33 2 0
SU 74 77 0 0
sv 30 4
sw 56 27 0.5
sx 4 1 2
AS 70 12
BS 40 3.3
c s 32 0
DS 40 0
ES 18 0
FS 55 24
GS 50 12
HS 3 1 0
Type 4.3 Fatty Monoamine Surfactant / Siloxane / Pentamine binder / Epoxide
binder
Table 10: %Sodalite Precipitated
Dose (ppm)
Product
20 40
LL 44 42
MM 47 4 1
Test 2 - Surfactant-based Molecules versus Gen2 and Gen 3
Table 11: % Sodalite Precipitated
Results in table 11 above demonstrate the surprising difference between the
inhibitory effects of previously identified small molecule inhibitors (Gen 2 and Gen
3 products) and surfactant based products (DD and HS). The latter are effective in
eliminating DSP formation at doses as low as 30ppm. However, for the Gen2 and
Gen 3 products some DSP precipitation still occurs under these test conditions even
at doses greater than lOOOppm. Given the efficacy of the Gen 2 and Gen 3 products
under test 1 conditions, such a result is unexpected and novel.
RESULTS: Test 3 - Metal coupon test
Test 3 conditions were the same as test 2 however, metal coupons
were included in the bottles and small amounts of DSP were precipitated onto the
surface of the metal. As shown in FIG. 6, SEM analysis of coupon tests using the
invention shows that significant amounts of DSP were precipitated onto the
untreated coupon, as well as those treated with extreme doses (lOOOppm) of GEN2
and GEN3 products. However, on the coupon subjected to liquor treated with the
surfactant based inhibitor (KK) at relatively low dose (lOOppm) significantly less
DSP was deposited. This indicates substantial and surprising efficacy of the
surfactant based small molecule in inhibiting the formation of DSP scale.
Table 2.15 Treatment of liquor exposed to metal coupons in test method 3.
While this invention may be embodied in many different forms, there
are described in detail herein specific preferred embodiments of the invention. The
present disclosure is an exemplification of the principles of the invention and is not
intended to limit the invention to the particular embodiments illustrated. All patents,
patent applications, scientific papers, and any other referenced materials mentioned
herein are incorporated by reference in their entirety. Furthermore, the invention
encompasses any possible combination of some or all of the various embodiments
mentioned herein, described herein and/or incorporated herein. In addition the
invention encompasses any possible combination that also specifically excludes any
one or some of the various embodiments mentioned herein, described herein and/or
incorporated herein.
The above disclosure is intended to be illustrative and not exhaustive.
This description will suggest many variations and alternatives to one of ordinary
skill in this art. All these alternatives and variations are intended to be included
within the scope of the claims where the term "comprising" means "including, but
not limited to". Those familiar with the art may recognize other equivalents to the
specific embodiments described herein which equivalents are also intended to be
encompassed by the claims.
All ranges and parameters disclosed herein are understood to
encompass any and all subranges subsumed therein, and every number between the
endpoints. For example, a stated range of " 1 to 10" should be considered to include
any and all subranges between (and inclusive of) the minimum value of 1 and the
maximum value of 10; that is, all subranges beginning with a minimum value of 1 or
more, (e.g. 1 to 6.1), and ending with a maximum value of 10 or less, (e.g. 2.3 to
9.4, 3 to 8, 4 to 7), and finally to each number 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10
contained within the range. All percentages, ratios and proportions herein are by
weight unless otherwise specified.
This completes the description of the preferred and alternate
embodiments of the invention. Those skilled in the art may recognize other
equivalents to the specific embodiment described herein which equivalents are
intended to be encompassed by the claims attached hereto.
Claims
1. A method for reducing aluminosilicate containing scale in a Bayer process
comprising:
adding to a Bayer liquor an aluminosilicate scale reducing amount of a nonpolymeric
reaction product resulting from the reaction of:
a surfactant
and a GPS.
2. The method of claim 1 in which the non-polymeric reaction product resulting
from the reaction of items further comprising one item selected from the group
consisting of at least one: hydrophobe, amine binder, epoxide binder, and any
combination thereof.
3. The method of claim 1 wherein the GPS is 3-
glycidoxypropyltrimethoxysilane.
4. The method of claim 1 wherein the surfactant is one selected from the group
consisting of: ethoxylated fatty alcohols, ethoxylated fatty amines, fatty amines,
G12A7, G12A4, G17A3, G9A6, G9A8, 18M20, 18M2, 16M2, DPD, OPD, OLA,
and any combination thereof.
5. The method of claim 2 wherein the epoxide binder is a molecule according
to formulas (I), (II), and any combination thereof:
(I) (P)
6. The method of claim 2 wherein the hydrophobe is a C8-C10 aliphatic
glycidyl ether.
7. The method of claim 1 wherein the reaction product has a molecular weight
of less than 500 daltons.
8. The method of claim 2 wherein the reaction product is according to the
formula illustrated in FIG. 1.
9. The method of claim 2 wherein the reaction product is according to the
formula illustrated in FIG. 2.
10. The method of claim 1 wherein the reaction product is Product P.
11. The method of claim 2 wherein the reaction product is Product U.
12. The method of claim 2 wherein the reaction product is Product HS
13. The method of claim 1 wherein the reaction product was formed at least in
part according to one of the methods selected from the group consisting of Methods:
I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, and XIII, and any combination thereof.
14. The method of claim 2 wherein the reaction product was formed at least in
part according to one of the methods selected from the group consisting of Methods:
I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, and XIII, and any combination thereof.
15. The method of claim 2 wherein the amine binder is one selected from the list
consisting of: tetraethylenepentamine and ethylenediamine.