Note: Descriptions are shown in the official language in which they were submitted.
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PREVENTING OR REDUCING SCALE IN WET-PROCESS
PHOSPHORIC ACID PRODUCTION
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to formulated reagents and methods for
preventing or
reducing scale formation in and/or on production equipment at the different
stages of
the phosphoric acid production process.
[0003] 2. State of the Art
[0004] Although phosphoric acid can be prepared by three routes ¨ the
thermal
process, the wet process, and the dry kiln process - the wet process is the
most
commonly-used process in phosphoric acid production. In the process, calcium
phosphate rocks, which contain mostly calcium phosphate, are cleaned in the
wash
plant and grinded in the Ball mill before fed into a series of reactors for
digestion with
sulfuric acid along with recycled phosphoric acid from the process. The
digestion
temperature typically ranges from 40 C to 80 C. After completing the reaction
series,
the process stream is washed with evaporator condensate while being forced
through a
filter.
[0005] After digestion, the reaction slurry is filtered to separate
phosphoric acid
from Gypsum (calcium sulfate). The filtered, crude phosphoric acid is then
sent to
Clarifiers and Evaporators for further purification and concentration. The
purified
phosphoric acid is either sent out as Merchant Grade Acid (MGA) or continued
to
make 69% P205 Super Phosphoric Acid (SPA). The Gypsum is washed and dried
before being sold for commercial uses. Some of the crude phosphoric acid is
concentrated to 44% (P205) before sent for Monoammonium Phosphate (MAP),
Diammonium Phosphate (DAP) and ammonium phosphate-sulfate (APS) production.
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[0006] Due to the supersaturated nature of the acid and the impurities in
the
phosphate ores, the concentration steps with respect to P205 render several
side
reactions, causing scale formation in and/or on the equipment at different
stages of the
phosphoric acid production. For example, fluorosilicate is one of the more
common
scale species found in phosphoric acid production. It can be depicted by the
following
equations:
Ca5F(PO4)3 + 5H2SO4 + 5nH20 ¨,.. 3H3PO4 + 5CaSO4-nH20 + HF
6HF + Si02 -).. H2SiF6 + 2H20
H2SiF6 -DP- 2H+ + SiF62- K+ +
or Na ______________________________________ ' K2SiF6 or Na2SiF6
[0007] More than 12-15 other types of scaling species can be found
throughout the
phosphoric acid production process and they pose significant challenges for
the
industry. Plants normally have to shut down production every few weeks to
physically clean up the scale using high pressure water and/or mechanical
means. The
economic impact for the scale-related issues is substantial, and the industry
is in need
of a more efficient scale prevention technology than the existing physical
means of
post scale formation removal.
[0008] Conceptually, there are two basic types of approaches scale removal
from
the phosphoric acid production process ¨ namely, the physical method and the
chemical method. There are several options for the physical method. In
addition to
the previously mentioned mechanical and water wash method, magnetic separation
(Wang, Chuhua; Benson, Robert F.; Martin, Dean F. Enhanced solubility of
sodium
fluorosilicate scale by magnetic treatment, Florida Scientist (1998), 61(1),
17-25) and
ultrasonic methods (Pandey, A. D.; Mallick, K. K.; Pandey, P. C.; Varma, S.
Prevention of scale deposition on heat exchanger surfaces by use of high
intensity
ultrasonic waves during concentration of wet process phosphoric acid,
Fertiliser
News (1983), 28(6), 45-8) have also been used as part of the physical
approach.
Another approach still, is available by using physically smoothed piping in
phosphoric acid production (See DE 3039187).
[0009] With regard to the chemical method, this approach is normally done
by
adding reagents to change the degree of supersaturation, either to induce
precipitation
before filtration, or to prevent scale from forming. This is the preferred
approach
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because it requires a limited amount of capital investment and does not alter
the
existing process in the phosphoric acid plants. It also does not require a
large amount
of reagent and is therefore considered both environmental, and to have a
minimal
impact downstream.
[0010] However, most of the existing work addressing the scale problem in
phosphoric acid production plants is based on the work for addressing scale
issues in
water boiler system. Some examples for scale treatment in boiler water are
such as
copolymers of acrylic acid and 2-acrylamido-2-methylpropane sulfonic acid
(AMPS)
(EP0271035). These polymers were reported to reduce the amount of silica gel
adhering to the wall of the testing bottles. Other systems such as polyamine,
phosphonic acid and carboxylic acid based monomers and polymers have also
shown
effectiveness in scale removal in boiler water system (See, e.g., GB2424876,
JP2002263690, and EP0677485).
[0011] Because water boiler systems differ vastly from the wet-process
phosphoric
acid production environment, this system does not provide the best model for
use in
the phosphoric acid production process. The water boiler systems usually have
mild
condition with a pH in the range of 8 to 9, and a low concentration of
dissolved salts.
The wet-process phosphoric acid production environment, by contrast, normally
contains harsh conditions with a low pH and a high solid content.
Additionally, the
scale in phosphoric acid plants have much more complicated components ¨
containing more than 15 known species, such as Na2SiF6, K2SiF6, CaSiF6.2H20,
CaF2, MgF2, Ca504.2H20 (Gypsum), MgSiF6.6H20, Mgo8A115F6.XH20 (wherein X
is a variable integer), MgH2P607, Ca504, Al(P03)3, NaK2A1F6, Ca3(A1F6)2.4H20,
MgNaA1F6.2H20, Ca4SO4A1SiF13.10H20 (see for example, A. William Frazier, James
R. Lehr, and Ewell F. Dillard, Environmental Science 8. Technology, 11, 1007,
1977). Moreover, different phosphoric acid plants experience different types
of
scale, and even within one plant, the type of scale can differ greatly from
one location
of the process to the other. Due to the complexity of the scale forming
issues, it is a
great challenge to develop scale inhibition reagents for use in preventing
and/or
reducing scale in phosphoric acid plants.
[0012] For example, in a typical 52% phosphoric acid production, a 60 torr
vacuum is applied in a boiler and 85 C phosphoric acid is circulating and
heated up
by a heat exchanger at 130 C. During this evaporation process, some scale is
formed
either at the boiler or at the heat exchanger. However, the scale formed at
the boiler
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can be different than that formed at the heat exchanger. The slow forming
scale such
as that formed at the heat exchanger, contain mostly magnesium fluoro-
aluminates;
while the fast forming scale such as that formed on pipes, contain mostly
sodium or
potassium fluorosilicate.
[0013] Yet, there is very little information in addressing the phosphoric
acid plant
scale issue in an industrial setting. Even for academic studies, the results
are
scattered. For example, several articles mention reagents for fluorosilicate
inhibition
in phosphoric acid production. (See L. Yang, Zhang Y., Huang, Y. Chemical
Industry
and Engineering (China), (2002), V 19(1), 1). Chinese patent CN1762857
discloses
that mixtures of phosphonic acids, polymers, and pesticides can effectively
reduce the
scale formation in wet-process phosphoric acid production. U.S. Patent No.
5,120,519 discloses that high molecular weight polyacrylamide and polyacrylic
acid
can prevent scale from adhering on the surface of the phosphate rock and
phosphoric
acid. However, the use of most of these chemicals is not new and has been
applied in
the water treatment system for scale control, and the mechanism of these
reagents is
based mostly on their dispersant effect.
[0014] Accordingly, the compositions and methods presently available for
preventing and/or reducing scale in the phosphoric acid production process
require
further improvement. Compositions and formulations that effectively prevent
and/or
reduce scale, thereby enabling the phosphoric acid production plant to run
longer
without shutting down to remove scale would be a useful advance in the art and
could
find rapid acceptance in the industry.
SUMMARY OF THE INVENTION
[0015] It has now been discovered that certain formulated, water-soluble,
functional organic reagents are useful for preventing and/or inhibiting
multiple
species of scale formation in and/or on production equipment at various stages
of the
wet-process phosphoric acid production. Such formulated reagents extend the
production time for making phosphoric acid by reducing the frequency of the
washing/shut down time to remove scale, thereby improving the overall
productivity
of the equipment and plant.
[0016] Accordingly, in one aspect, the invention provides methods for
preventing
or reducing at least one species of scale in a wet-process phosphoric acid
production
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process by adding at one or more steps of the phosphoric acid production
process an
effective amount of a scale inhibiting reagent chosen from one or more of:
i) a phosphonic acid derivative chosen from: phenylphosphonic acid;
phosphonoacetic acid; hydroxyethylamino-di(methylene phosphonic acid) (HEMPA);
and mixtures thereof;
ii) sulfonic acid or a corresponding derivative chosen from: sulfosuccinic
acid; 5-sulfosalicylic acid hydrate; 4-sulfophthalic acid; N-(1,1-dimethy1-2-
hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPS 0); 3-amino-4-
hydroxybenzenesulfonic acid; 1-dodecanesulfonic acid sodium salt; 3-
sulfopropyl
acrylate potassium salt; 4-hydroxybenzenesulfonic acid solution; 4,5-
dihydroxynaphthalene-2,7-disulfonic acid disodium salt; hydroquinonesulfonic
acid
potassium salt; and mixtures thereof;
iii) a carboxylic acid derivative chosen from:
a compound according to Formula 1:
R2
HOR1
OH (1)
wherein R1 is chosen from H or OH; and R2 is chosen from: ¨COOH; a
C1-C6 carboxyalkyl or a C2-C6 carboxyalkenyl group; and
tartaric acid; and mixtures thereof;
iv) a phosphite derivative;
v) a polysaccharide comprising a sulfate, sulfonic acid or carboxylic acid
functional group;
vi) a copolymer comprising a first repeating unit containing a functional
group chosen from (i) ¨ (iv) and a second repeating unit having a sulfonic
acid or
carboxylic acid functional group;
vii) a polymer or copolymer having a low critical solution temperature
phase transition (LCST) from 30 C to 100 C; and
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viii) a reagent comprising a blend of an organic acid, a polyamine, and a
sugar acid. In certain embodiments, the reagent can also be blended with
various
polymers, which are known to those skilled in the art to which the invention
pertains.
[0017] These and other objects, features and advantages of this invention
will
become apparent from the following detailed description of the various aspects
of the
invention taken in conjunction with the accompanying Examples.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
[0018] As summarized above, the present invention is based in part on the
use of
water-soluble functional organic reagents for use in preventing or reducing
scale
formed in and/or on the production equipment in the phosphoric acid production
process.
[0019] Definitions
[0020] As employed above and throughout the disclosure, the following terms
are
provided to assist the reader. Unless otherwise defined, all terms of art,
notations and
other scientific or industrial terms or terminology used herein are intended
to have the
meanings commonly understood by those of skill in the chemical arts. In some
cases,
terms with commonly understood meanings are defined herein for clarity and/or
for
ready reference, and the inclusion of such definitions herein should not
necessarily be
construed to represent a substantial difference over the definition of the
term as
generally understood in the art unless otherwise indicated. As used herein and
in the
appended claims, the singular forms include plural referents unless the
context clearly
dictates otherwise.
[0021] Throughout this specification, the terms and substituents retain
their
definitions. A comprehensive list of abbreviations utilized by organic
chemists (i.e.
persons of ordinary skill in the art) appears in the first issue of each
volume of the
Journal of Organic Chemistry. The list, which is typically presented in a
table entitled
"Standard List of Abbreviations" is incorporated herein by reference.
[0022] As used herein the term "phosphonic acid derivative," "sulfonic acid
derivative," and "carboxylic acid derivative" refer to compounds having a
functional
phosphonic acid, sulfonic acid, or carboxylic acid group, respectively, in the
compound. Where a phosphonic acid or sulfonic acid appear together with a
carboxylic acid in the same compound, the compound will be termed a phosphonic
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acid derivative or sulfonic acid derivative as the case may be. For example,
sulfosuccinic acid is considered a sulfonic acid derivative for purposes of
this
application. Similarly, phosphonoacetic acid and 2-phosphonobutane-1,2,4-
tricarboxylic acid (PBTCA) are considered phosphonic acid derivatives for
purposes
of this application.
[0023] As used herein, the term "alkyl" means a straight or branched chain
hydrocarbon containing from 1 to 12 carbon atoms. Representative examples of
alkyl
include, but are not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl,
sec-butyl,
iso-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl,
2,2-
dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, n-octyl, n-nonyl, n-decyl, etc.
[0024] The term "alkenyl" means a straight or branched chain hydrocarbon
containing from 2 to 12 carbons and containing at least one carbon-carbon
double
bond formed by the removal of two hydrogens. Representative examples of
alkenyl
include, but are not limited to, ethenyl, 2-propenyl, 2-methyl-2-propenyl, 3-
butenyl,
4-pentenyl, 5-hexenyl, 2-heptenyl, 2-methyl-1-heptenyl, 3-decenyl, etc.
[0025] The term "carboxy" means a ¨CO2H group.
[0026] The term "carboxyalkyl" means a carboxy group, as defined herein,
appended to the parent molecular moiety through an alkyl group, as defined
herein.
Representative examples of carboxyalkyl include, but are not limited to,
carboxymethyl, 2-carboxyethyl, and 3-carboxypropyl.
[0027] The term "carboxyalkenyl" means a carboxy group, as defined herein,
appended to the parent molecular moiety through an alkenyl group, as defined
herein.
[0028] The term "copolymer" as used herein refers to a polymer composed of
two or
more different units, wherein the units are linked randomly or in repeating
sequences,
or in blocks, or as side chains off the main chain. Accordingly, a phosphonic
acid
derivative copolymer, for example, refers to a copolymer having a phosphonic
acid
derivative unit (i.e., a first unit) linked randomly or in repeating sequence
with one or
more different unit (i.e., a second unit). Those of ordinary skill in the art
will
appreciate that there are a variety of different units (monomers or polymers)
known to
them that could be used as a second unit to form a copolymer according to the
invention. Sulfonic acid copolymer or sulfonic acid derivative copolymers,
etc. are
similarly formed.
[0029] As used herein, and as would be understood by the person of skill in
the art,
the recitation of "a reagent" or "scale inhibiting reagent" is intended to
include salts
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and solvates of that reagent as well as any stereoisomeric form, or a mixture
of any
such forms of that reagent in any ratio.
[0030] When the reagents of the present invention are basic, salts may be
prepared
from acceptable non-toxic acids including inorganic and organic acids.
Suitable acid
addition salts for the reagents of the present invention include acetic,
benzenesulfonic
(besylate), benzoic, camphorsulfonic, citric, ethenesulfonic, fumaric,
gluconic,
glutamic, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic,
mandelic,
methanesulfonic, mucic, nitric, pamoic, pantothenic, phosphoric, succinic,
sulfuric,
tartaric acid, p-toluenesulfonic, and the like. When the reagents contain an
acidic side
chain, suitable acceptable base addition salts for the reagents of the present
invention
include metallic salts made from aluminum, calcium, lithium, magnesium,
potassium,
sodium and zinc or organic salts made from lysine, N,N'-
dibenzylethylenediamine,
diethanolamine, and ethylenediamine.
[0031] All numbers expressing quantities of ingredients, reaction
conditions, and
so forth used in the specification and claims are to be understood as being
modified in
all instances by the term "about." Accordingly, unless indicated to the
contrary, the
numerical parameters set forth in the specification and attached claims are
approximations that may vary depending upon the desired properties sought to
be
obtained by the present invention. Additionally, each numerical parameter
should be
construed in light of the number of significant digits and ordinary rounding
approaches.
[0032] Scale from the phosphoric acid production process forms on heat
exchangers, evaporators, concentrators, and pipes during the repetitive
flashing/cooling/concentrating process of the phosphoric acid production
process. A
scale inducing system was set up to mimic this process, whereby hot or cold
water is
fed through a stainless steel tube while the tube is submerged in hot
phosphoric acid
solution. The temperature gradient and free flowing solid causes the formation
of
scale on the outside of the tube. This system is the basis for the
corresponding
Examples provided herein, and it also uses a control flask under identical
environment
for comparison to the sample flask.
[0033] Methods
[0034] In a first aspect, the invention provides methods for preventing or
reducing
at least one species of scale in a wet-process phosphoric acid production
process by
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adding at one or more steps of the phosphoric acid production process an
effective
amount of a scale inhibiting reagent chosen from one or more of:
i) a phosphonic acid derivative chosen from: phenylphosphonic acid;
phosphonoacetic acid; hydroxyethylamino-di(methylene phosphonic acid) (HEMPA);
and mixtures thereof;
ii) sulfonic acid or a corresponding derivative chosen from: sulfosuccinic
acid; 5-sulfosalicylic acid hydrate; 4-sulfophthalic acid; N-(1,1-dimethy1-2-
hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPS 0); 3-amino-4-
hydroxybenzenesulfonic acid; 1-dodecanesulfonic acid sodium salt; 3-
sulfopropyl
acrylate potassium salt; 4-hydroxybenzenesulfonic acid solution; 4,5-
dihydroxynaphthalene-2,7-disulfonic acid disodium salt; hydroquinonesulfonic
acid
potassium salt; and mixtures thereof;
iii) a carboxylic acid derivative chosen from:
a compound according to Formula 1:
R2
HOR1
OH (1)
wherein R1 is chosen from H or OH; and R2 is chosen from: ¨COOH; a
C1-C6 carboxyalkyl or a C2-C6 carboxyalkenyl group; and
tartaric acid; and mixtures thereof;
iv) a phosphite derivative;
v) a polysaccharide comprising a sulfate, sulfonic acid or carboxylic acid
functional group;
vi) a copolymer comprising a first repeating unit containing a functional
group chosen from (i) ¨ (iv) and a second repeating unit having a sulfonic
acid or
carboxylic acid functional group;
vii) a polymer or copolymer having a low critical solution temperature
phase transition (LCST) from 30 C to 100 C; and
viii) a reagent comprising a blend of an organic acid, a polyamine, and a
sugar acid.
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[0035] In one embodiment, the species of scale prevented or inhibited from
forming during the phosphoric acid production process includes, but is not
limited to,
one or more of: Si2F6; Na2SiF6; K2SiF6; CaSiF6/2 H20; CaF2; MgF2; CaSO4/2 H20;
MgSiF6/6 H20; MgosAli 5F6/X H20 (wherein X is an integer ranging from 2 to
20);
MgH2P607; CaSO4; Al(P03)3; NaK2A1F6; Ca3(A1F6)2/4 H20; MgNaA1F6/2 H20; and
Ca4SO4A1SiF13/10 H20.
[0036] In some embodiments, the scale inhibiting reagent can be added at
any step
of the phosphoric acid production process, which steps are well known to those
skilled in the art. An overall view of the manufacture of phosphates and
phosphoric
acid is treated by Becker in Phosphates and Phosphoric Acids, Marcel Dekker,
Inc.
1989; and by Stack in Phosphoric Acid, Part 1 and Part 2, Marcel Dekker, inc.
1968.
In certain embodiments, for example, the adding step occurs at one or more of
the
milling step; the digesting step; the filtering step; the clarifying step; and
the
condensation/evaporation step of the phosphoric acid production process. In
one
embodiment, the adding step occurs after the digesting step of the phosphoric
acid
production process. In another embodiment, the adding step occurs at the
condensation/evaporation step of the process. In still other embodiments, the
scale
inhibiting reagent can be added to any of the piping connecting the various
stages of
the phosphoric acid production process. This is sometimes referred to as the
"interstitial piping" or "process flow pipeline".
[0037] The scale inhibiting reagent(s) may be intermixed in the phosphoric
acid
production process in various ways, e.g., in a single stage, in multiple
stages,
sequentially, in reverse order, simultaneously, or in various combinations
thereof. For
example, in one embodiment, the scale inhibiting reagent is added to form a
pre-mix,
then intermixed with the phosphoric acid. In another embodiment, the scale
inhibiting
reagent is formed in situ by separately inter-mixing the components of the
reagent
with the phosphoric acid. Accordingly, the scale inhibiting reagent (such as
those
embodied by Examples 16-26 and 42) can either be added to the phosphoric acid
production process as a single component or as individual components anywhere
along the process. Various modes of addition will be found to be effective.
[0038] The scale inhibiting reagents that are in liquid form (such as with
water, oil
and/or alcohol) may be formulated in various ways, e.g., the solid reagent may
be
suspended (e.g., colloidal suspension), dispersed and/or slurried in the
liquid, and/or
the reagent may be suspended, dispersed, slurried and/or dissolved in the
liquid. In
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one embodiment, the reagent is added separately to the phosphoric acid
solution. In
another embodiment, the reagent is premixed and added together to the
phosphoric
acid solution.
[0039] In one
embodiment, the concentration of the scale inhibiting reagent added
to the phosphoric acid production process is from 10 to 5000 g per ton of
phosphoric
acid (e.g., 10 g/ton, 20 g/ton, 30 g/ton, 40 g/ton, 50 g/ton, 60 g/ton, 70
g/ton, 80 g/ton,
90 g/ton, 100 g/ton, 110 g/ton, 120 g/ton, 130 g/ton, 140 g/ton, 150 g/ton,
160 g/ton,
170 g/ton, 180 g/ton, 190 g/ton, 200 g/ton, 210 g/ton, 220 g/ton, 230 g/ton,
240 g/ton,
250 g/ton, 260 g/ton, 270 g/ton, 280 g/ton, 290 g/ton, 300 g/ton, 310 g/ton,
320 g/ton,
330 g/ton, 340 g/ton, 350 g/ton, 360 g/ton, 370 g/ton, 380 g/ton, 390 g/ton,
400 g/ton,
410 g/ton, 420 g/ton, 430 g/ton, 440 g/ton, 450 g/ton, 460 g/ton, 470 g/ton,
480 g/ton,
490 g/ton, 500 g/ton, 510 g/ton, 520 g/ton, 530 g/ton, 540 g/ton, 550 g/ton,
560 g/ton,
570 g/ton, 580 g/ton, 590 g/ton, 600 g/ton, 610 g/ton, 620 g/ton, 630 g/ton,
640 g/ton,
650 g/ton, 660 g/ton, 670 g/ton, 680 g/ton, 690 g/ton, 700 g/ton, 710 g/ton,
720 g/ton,
730 g/ton, 740 g/ton, 750 g/ton, 760 g/ton, 770 g/ton, 780 g/ton, 790 g/ton,
800 g/ton,
810 g/ton, 820 g/ton, 830 g/ton, 840 g/ton, 850 g/ton, 860 g/ton, 870 g/ton,
880 g/ton,
890 g/ton, 900 g/ton, 910 g/ton, 920 g/ton, 930 g/ton, 940 g/ton, 950 g/ton,
960 g/ton,
970 g/ton, 980 g/ton, 990 g/ton, 1000 g/ton, 1200 g/ton, 1400 g/ton, 1600
g/ton, 1800
g/ton, 2000 g/ton, 2200 g/ton, 2400 g/ton, 2600 g/ton, 2800 g/ton, 3000 g/ton,
3200
g/ton, 3400 g/ton, 3600 g/ton, 3800 g/ton, 4000 g/ton, 4200 g/ton, 4400 g/ton,
4600
g/ton, 4800 g/ton, 5000 g/ton of phosphoric acid). In another embodiment, the
concentration of the scale inhibiting reagent added to the phosphoric acid
production
process is from 50 to 300 g/ton of phosphoric acid. In a preferred embodiment,
the
concentration of the scale inhibiting reagent added to the phosphoric acid
production
process is 100 g/ton of phosphoric acid.
[0040] The
treatment times and effective amounts may vary, depending in many
cases on the nature of the scale formation rate and/or the species of the
scale. For
example, if the scale is formed within 30 minutes of the treatment, the
overall
treatment time may be just one hour. If the scale is not formed within 4 hours
of the
treatment, the overall treatment time may be over one day. One of ordinary
skill in
the art would be able to determine the applicable treatment time and effective
amount
through no more than routine means.
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[0041] In one embodiment, the scale formed in the phosphoric acid
production
process is prevented or reduced from 5 to 180 days, depending on the amount
and
type of scale.
[0042] The pH of the phosphoric acid, although not adjusted, should not be
altered
by a value of 1 after the addition of the reagent for treatment. The preferred
pH of the
phosphoric acid should be in the range of 1-5 before starting the method of
the
invention. In case the pH of the phosphoric acid dropped below 1, it can be
adjusted
by sodium hydroxide or soda ash. In case the pH of the phosphoric acid rose
above 5,
it can be adjusted by addition of sulfuric acid or phosphoric acid.
[0043] In one embodiment, the scale inhibiting reagent is a phosphonic acid
derivative chosen from: phenylphosphonic acid; phosphonoacetic acid;
hydroxyethylamino-di(methylene phosphonic acid) (HEMPA); and mixtures thereof.
[0044] In another embodiment, the water-soluble, functional organic scale
inhibiting reagent is sulfonic acid or a sulfonic acid derivative chosen from:
sulfosuccinic acid; 5-sulfosalicylic acid hydrate; 4-sulfophthalic acid; N-
(1,1-
dimethy1-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPS 0); 3-
amino-4-hydroxybenzenesulfonic acid; 1-dodecanesulfonic acid sodium salt; 3-
sulfopropyl acrylate potassium salt; 4-hydroxybenzenesulfonic acid solution;
4,5-
dihydroxynaphthalene-2,7-disulfonic acid disodium salt; hydroquinonesulfonic
acid
potassium salt; and mixtures thereof.
[0045] In still another embodiment, the scale inhibiting reagent is a
carboxylic acid
derivative chosen from:
a compound according to Formula 1:
R2
HOW
OH (1)
wherein R1 is chosen from H or OH; and R2 is chosen from: ¨COOH; a Ci-C6
carboxyalkyl or a C2-C6 carboxyalkenyl group; and
tartaric acid; and mixtures thereof.
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[0046] In certain embodiments, the scale inhibiting reagent can be a
carboxylic
acid derivative chosen from: 3,4-dihydroxyhydrocinnamic acid; 3,4-
dihydroxybenzoic
acid; gallic acid; caffeic acid; and mixtures thereof.
[0047] In another embodiment, the scale inhibiting reagent can be a
phosphite
derivative such as, but not limited to, tannic phosphite.
[0048] In another embodiment, the scale inhibiting reagent can be a
polysaccharide
containing a sulfate, sulfonic acid or carboxylic acid functional group. In
certain
embodiments, the polysaccharide contains a sulfate functional group and is
carrageenan. While "carrageenan" is used generally to describe the different
members of the family, one of skill in the art will appreciate that the family
includes
multiple varieties of carrageenan, and as used herein the general terms shall
refer to
all those that contain a sulfated functional group as part of the structure.
In preferred
embodiments, a commercially available form of carrageenan, such as iota,
kappa, or
lambda, is used.
[0049] In other embodiments, the polysaccharide scale inhibiting reagent
useful
for the present invention will contain a carboxy functional group and can be
alginic
acid, or corresponding salts thereof. In another embodiment, the
polysaccharide
containing a carboxy functional group can be carboxymethyl cellulose. In
certain
embodiments the carboxymethyl cellulose useful as a scale inhibiting reagent
has a
molecular weight of from 2 kDa to 100 kDa (e.g.,2 kDa; 5 kDa; 7 kDa; 10 kDa;
15
kDa; 20 kDa; 25 kDa; 30 kDa; 40 kDa; 45 kDa; 50 kDa; 55 kDa; 60 kDa; 65 kDa;
70
kDa; 75 kDa; 80 kDa; 85 kDa; 90 kDa; 95 kDa; 100 kDa). In one embodiment, a
carboxymethyl cellulose scale inhibiting reagent is preferred to have a
molecular
weight of from 10 kDa to 75 kDa. In another embodiment, a molecular weight of
carboxymethyl cellulose of from 10 kDa to 30 kDa is preferred.
[0050] In a further embodiment, the water-soluble, functional organic scale
inhibiting reagent is a co-polymer comprising a first repeating unit
containing a
phosphonic acid derivative, a sulfonic acid derivative, a carboxylic acid
derivative, or
a phosphite derivative, and a second repeating unit chosen from any suitable
polymer
including, but not limited to: polyethyleneimine-epoxy-hydroxysuccinate;
acrylamide/acrylate copolymer (CYANAMER P-70 available from Cytec Industries
Inc., Woodland Park, NJ); allyl sulfonic acid/maleic anhydride copolymer
(CYANAMER P-80 available from Cytec Industries Inc., Woodland Park, NJ);
poly-diallyl dimethyl ammonium chloride (SUPERFLOC C587 available from
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Cytec Industries Inc., Woodland Park, NJ); poly-dimethylamine epichlorohydrin
ethlenediamine (SUPERFLOC C573 available from Cytec Industries Inc.,
Woodland Park, NJ); poly(4-styrenesulfonic acid); phosphinopolycarboxylic
acid;
acrylic acid/acrylate/sulfonate co-polymer; polyacrylic acid (PAA); sodium
polyacrylate (PAAS); methoxyphenyl maleamic acid (MPMA); maleic anhydride
acrylic acid polymer (MA-AA); AA-MA-acrylamido-methyl-propane sulfonate
polymer (AMPS) hypophosphorous acid quadripolymer; AA-AMPS multipolymer;
AA-acrylate copolymer T-225; and acrylic acid-2-methyl propanesulfonic acid
acrylic
polymer; and mixtures thereof. One of ordinary skill in the art would
understand and
appreciate that equivalent structures to the second repeating units referenced
immediately above can be achieved either by copolymerization or by post
reaction of
a polymer, such as by hydrolysis. In certain embodiments, any of the reagents
and/or
co-polymers can be further blended with a suitable polymer such as those
described
herein.
[0051] In still another embodiment of the invention, the scale inhibiting
reagent
can be chosen from a polymer or copolymer having a low critical solution
temperature phase transition (LCST) from 30 C to 100 C (e.g, 30 C; 32 C;
35 C;
37 C; 40 C; 45 C; 50 C; 55 C; 60 C; 65 C; 70 C; 75 C; 80 C; 85 C;
90 C;
95 C; 100 C) . In one embodiment, a scale inhibiting reagent having a LCST
of
from 30 C to 100 C can include a poly(ethylene glycol)-block-poly(propylene
glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) copolymer. Those of ordinary
skill in the art will understand that for polymers or copolymers, LCST is
dependent
upon polymer degree of polymerization, polydispersity, and branching.
Accordingly,
the ratio of poly(ethylene glycol) units to poly(propylene glycol) units will
be
determined by whether the resulting LCST is in the appropriate and desired
range as
described herein.
[0052] In another embodiment, the scale inhibiting reagent having a LCST of
from
30 C to 100 C can include poly(n-isopropylacrylamide) (NIPAM). In some
embodiments, the NIPAM can be copolymerized with acrylic acid such that the
ratio
of acrylic acid (AA) : NIPAM can range from 20:80 to 80:20. In a specific
embodiment, the ratio of AA:NIPAM can be 50:50. It will be understood by those
of
skill in the art that copolymerizing acrylic acid with NIPAM will generally
increase
the hydrophillicity of the copolymer and that an increased hydrophillicity
will result
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in an increased LCST temperature. Accordingly, the ratio of acrylic acid to
NIPAM
is able to be modified so it can be within the LCST range as described herein.
[0053] In another embodiment, the scale inhibiting reagent is a blend
comprising
an organic acid, a polyamine, and a sugar acid. Organic acids suitable for use
in a
blend reagent of the instant invention include those known to one of skill in
the art. In
one embodiment, the organic acid of the reagent blend is a phosphonic acid
chosen
from: phenylphosphonic acid; phosphonoacetic acid; hydroxyethylamino-
di(methylene phosphonic acid) (HEMPA); amino-tri(methylene phosphonic acid)
(ATMPA); 1-hydroxyethylidene-1,1-diphosphonic acid (HEDPA);
diethylenetriamine-penta(methylene phosphonic acid) (DTPMP); ethylenediamine
methylene phosphonic acid (EDTMP); hydroxyl ethane phosphonothyl acetic acid
(HPAA); and phosphonobutane-1,2,4-tricarboxylic acid (PBTCA).
[0054] Polyamines suitable for use in a reagent blend of the instant
invention
include those known to one of skill in the art. In some embodiments, the
polyamine
of the reagent blend can be poly-diallyl dimethyl ammonium chloride (SUPERFLOC
C587 ) or poly-dimethylamine epichlorohydrin ethylenediamine (SUPERFLOC
C573 ).
[0055] Sugar acids suitable for use in a reagent blend of the instant
invention
include those known to one of skill in the art. In certain embodiments, the
sugar acid
is chosen from: glyceric acid; xylonic acid; gluconic acid; ascorbic acid;
neuraminic
acid; ketodeoxyoctulosonic acid; glucuronic acid; galacturonic acid; iduronic
acid;
tartaric acid; mucic acid; saccharic acid; and mixtures thereof.
[0056] In a particular embodiment, the reagent comprises a blend that can
include
1-hydroxyethylidene-1,1-diphosphonic acid (HEDPA), poly-diallyl dimethyl
ammonium chloride (SUPERFLOC C587 ), and gluconic acid. While the ratio of
components in the reagent blend necessary to reduce or prevent scale can be
readily
determined by those of ordinary skill in the art with no more than routine
experimentation, a preferred ratio of components is 1:1:1.
[0057] In certain embodiments, particularly preferred reagents for use in
the
methods of the invention include, for example, one or more of phosphonoacetic
acid;
tannic phosphite; hydroxyethylamino-di(methylene phosphonic acid) (HEMPA);
sulfonic acid; sulfosuccinic acid; 5-sulfosalicyclic acid hydrate; N-(1,1-
dimethy1-2-
hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPS 0); 3-sulfopropyl
acrylate potassium salt; 1-dodecanesulfonic acid sodium salt; 4-
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hydroxybenzenesulfonic acid solution; 4,5,-dihydroxynaphthalene-2,7-disulfonic
acid
disodium salt; 3,4-dihydroxyphenylacetic acid; 3,4-dihydroxyhydrocinnamic
acid;
3,4-dihydroxybenzoic acid; tartaric acid; polyethyleneimine-epoxy-
hydroxysuccinate;
carrageenan; alginic acid; carboxymethyl cellulose; PEG-PPG-PEG copolymers;
NIPAM; AA:NIPAM; blend of 1-hydroxyethylidene-1,1-diphosphonic acid
(HEDPA), poly-diallyl dimethyl ammonium chloride (SUPERFLOC C587 ), and
gluconic acid; and mixtures thereof.
[0058] In certain embodiments, the method can further include one or more
step of
flocculating the phosphoric acid with a flocculating agent thereby removing
the scale-
causing metal ions from the phosphoric acid; treating the phosphoric acid with
a
precipitation agent; and filtering the phosphoric acid. Typical agents for use
with
these additional steps are known to those of ordinary skill in the art.
[0059] Other Embodiments
[0060] 1. A method for reducing or preventing scale in a wet-process
phosphoric
acid production process, the method comprising:
adding at one or more step of the phosphoric acid production process an
effective amount of a scale inhibiting reagent chosen from one or more of:
i) a phosphonic acid derivative chosen from: phenylphosphonic acid;
phosphonoacetic acid; hydroxyethylamino-di(methylene phosphonic acid)
(HEMPA); and mixtures thereof;
ii) sulfonic acid or a corresponding derivative chosen from:
sulfosuccinic acid; 5-sulfosalicylic acid hydrate; 4-sulfophthalic acid; N-
(1,1-
dimethy1-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPS 0);
3-amino-4-hydroxybenzenesulfonic acid; 1-dodecanesulfonic acid sodium
salt; 3-sulfopropyl acrylate potassium salt; 4-hydroxybenzenesulfonic acid
solution; 4,5-dihydroxynaphthalene-2,7-disulfonic acid disodium salt;
hydroquinonesulfonic acid potassium salt; and mixtures thereof;
iii) a carboxylic acid derivative chosen from:
a compound according to Formula 1:
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R2
HOW
OH (1)
wherein R1 is chosen from H or OH; and R2 is chosen from: ¨COOH;
a Cl-C6 carboxyalkyl or a C2-C6 carboxyalkenyl group; and
tartaric acid; and mixtures thereof;
iv) a phosphite derivative;
v) a polysaccharide comprising a sulfate, sulfonic acid or carboxylic
acid functional group;
vi) a copolymer comprising a first unit containing a functional group
chosen from (i) ¨ (iv) and a second unit having a sulfonic acid or carboxylic
acid functional group;
vii) a polymer or copolymer having a low critical solution temperature
phase transition (LCST) from 30 C to 100 C; and
viii) a reagent comprising a blend of an organic acid, a polyamine, and
a sugar acid.
[0061] 2. A method according to embodiment 1, wherein the species of
phosphoric acid scale is chosen from one or more of: Si2F6; Na2SiF6; K2SiF6;
CaSiF6/2 H20; CaF2; MgF2; CaSO4/2 H20; MgSiF6/6 H20; Mgo8A115F6/X H20;
MgH2P607; CaSO4; Al(P03)3; NaK2A1F6; Ca3(A1F6)2/4 H20; MgNaA1F6/2 H20; and
Ca4SO4A1SiF13/10 H20, wherein X is an integer ranging from 2 to 10.
[0062] 3. A method according to embodiment 1 or embodiment 2, wherein the
adding step occurs at one or more stage of the wet-process phosphoric acid
production
process chosen from: the milling stage; the digesting stage; the filtering
stage; the
condensation/evaporation stage; and the clarifying stage.
[0063] 4. A method according to any one of the preceding embodiments,
wherein the adding step occurs at any of the interstitial piping of the
phosphoric acid
production process.
[0064] 5. A method according to any one of the preceding embodiments,
wherein the adding step is performed in a single stage, in multiple stages,
sequentially, in reverse order, simultaneously, or in combinations thereof.
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[0065] 6. A method according to any one of the preceding embodiments,
wherein the scale inhibiting reagent is added as a single component or in
individual
components.
[0066] 7. A method according to any one of the preceding embodiments,
wherein the reagent is added directly to the phosphoric acid production
process or
premixed with a solvent chosen from: water; oil; alcohol; and mixtures
thereof.
[0067] 8. A method according to any one of the preceding embodiments,
wherein the compound according to Formula (1) is chosen from: 3,4-
dihydroxyphenylacetic acid; 3,4-dihydroxyhydrocinnamic acid; 3,4-
dihydroxybenzoic
acid; gallic acid; caffeic acid.
[0068] 9. A method according to any one of the preceding embodiments,
wherein the polysaccharide is chosen from: carrageenan; alginic acid; and
carboxy
methyl cellulose.
[0069] 10. A method according to embodiment 9, wherein the carboxy methyl
cellulose has a molecular weight of from 2 kDa to 100 kDa.
[0070] 11. A method according to embodiment 10, wherein the molecular
weight
is from 10 kDa to 75 kDa.
[0071] 12. A method according to embodiment 10 or embodiment 11, wherein
the
molecular weight is from 10 kDa to 30 kDa.
[0072] 13. A method according to any one of the preceding embodiments,
wherein the reagent is a copolymer formulation and wherein the second
repeating unit
contains a functional group chosen from: polyethyleneimine-epoxy-
hydroxysuccinate;
acrylamide/acrylate copolymer (CYANAMER P-70 ); allyl sulfonic acid/maleic
anhydride copolymer (CYANAMER P-80 ); poly-diallyl dimethyl ammonium
chloride (SUPERFLOC C587 ); poly-dimethylamine epichlorohydrin
ethlenediamine (SUPERFLOC C57310); poly(4-styrenesulfonic acid);
phosphinopolycarboxylic acid; acrylic acid/acrylate/sulfonate copolymer;
polyacrylic
acid (PAA); sodium polyacrylate (PAAS); methoxyphenyl maleamic acid (MPMA);
maleic anhydride acrylic acid copolymer (MA-AA); AA-MA-acrylamido-methyl-
propane sulfonate polymer (AMPS) hypophosphorous acid quadripolymer; AA-
AMPS multipolymer; AA-acrylate copolymer T-225; and acrylic acid-2-methyl
propanesulfonic acid acrylic polymer; and mixtures thereof.
[0073] 14. A method according to any one of the preceding embodiments,
wherein the polymer or copolymer having a low critical solution temperature
phase
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transition is chosen from: polyethyleneglycol-polypropyleneglycol-
polyethyleneglycol (PEG-PPG-PEG) copolymers; poly-n-isopropyl polyacrylamide
(NIPAM); and copolymers of acrylic acid-poly-n-isopropyl polyacrylamide
(AA:NIPAM).
[0074] 15. A method according to embodiment 14, wherein the ratio of
acrylic
acid monomer:poly-n-isopropyl polyacrylamide monomer is from 20:80 to 80:20.
[0075] 16. A method according to embodiment 14 or embodiment 15, wherein
the
ratio of acrylic acid monomer:poly-n-isopropyl polyacrylamide monomer is
50:50.
[0076] 17. A method according to any one of the preceding embodiments
wherein
the organic acid of the reagent blend is a phosphonic acid derivative chosen
from:
phenylphosphonic acid; phosphonoacetic acid; hydroxyethylamino-di(methylene
phosphonic acid) (HEMPA); amino-tri(methylene phosphonic acid) (ATMPA); 1-
hydroxyethylidene-1,1-diphosphonic acid (HEDPA); diethylenetriamine-
penta(methylene phosphonic acid) (DTPMP); ethylenediamine methylene phosphonic
acid (EDTMP); hydroxyl ethane phosphonothyl acetic acid (HPAA); and
phosphonobutane-1,2,4-tricarboxylic acid (PBTCA).
[0077] 18. A method according to embodiment 17, wherein the polyamine is
poly-diallyl dimethyl ammonium chloride (SUPERFLOC C587 ) or poly-
dimethylamine epichlorohydrin ethylenediamine (SUPERFLOC C573 ).
[0078] 19. A method according to any one of the preceding embodiments,
wherein the sugar acid is chosen from: glyceric acid; xylonic acid; gluconic
acid;
ascorbic acid; neuraminic acid; ketodeoxyoctulosonic acid; glucuronic acid;
galacturonic acid; iduronic acid; tartaric acid; mucic acid; saccharic acid;
and
mixtures thereof.
[0079] 20. A method according to any one of the preceding embodiments,
wherein the reagent blend comprises 1-hydroxyethylidene-1,1-diphosphonic acid
(HEDPA), poly-diallyl dimethyl ammonium chloride (SUPERFLOC C587 ), and
gluconic acid.
[0080] 21. A method according to any one of embodiments 17-20, wherein the
ratio of the components of the blend are present at 1:1:1.
[0081] 22. A method according to any one of the preceding embodiments,
wherein the concentration of the reagent is from 10 to 5000 g per ton of
phosphoric
acid.
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[0082] 23. A method according to embodiment 22, wherein the concentration
is
from 10 to 1000 g per ton of phosphoric acid.
[0083] 24. A method according to embodiment 22 or embodiment 23, wherein
the
concentration of the reagent is 100 g per ton of phosphoric acid.
[0084] 25. A method according to any one of the preceding embodiments,
wherein the scale is prevented or reduced for a period of time from 5 to 180
days.
[0085] 26. A method according to any one of the preceding embodiments
further
comprising removing the scale-causing metal ions from the resulting phosphoric
acid.
[0086] 27. A method according to embodiment 26, wherein the removal step is
performed by flocculating the phosphoric acid with one or more flocculating
agent.
[0087] 28. A method according to any one of the preceding embodiments
further
comprising treating the phosphoric acid with one or more precipitation agent.
[0088] 29. A method according to any one of the preceding embodiments
further
comprising filtering the phosphoric acid.
[0089] Examples
[0090] The following examples are provided to assist one skilled in the art
to
further understand embodiments of the present invention. These examples are
intended for illustration purposes and are not to be construed as limiting the
scope of
the embodiments of the present invention or the claims appended hereto.
[0091] Phosphoric acid solutions used for reagent testing are obtained from
phosphoric acid plants such as Agrium, Inc. Canada (Plant A); Prayon, Inc.,
Georgia
(Plant P); and The Mosaic Company, Florida (Plant M) at 28%, 42%, 52% or 69%
P205. ICP and XRD analysis shows the crude phosphoric acids differ greatly in
their
metal components, and this sometimes leads to difficulty in forming scale
within a
reasonable period. Accordingly, the scale formation is sometimes induced with
salts.
In some cases, 0.1% to 10% NaC1, KC1 or MgC12 salts are added to induce
particular
scale formation. These crude samples contained 28% and 69% P205 from Plant A,
30% and 54% P205 from Plant P and 30% P205 from Plant M. These samples are
used
as is or diluted to proper concentration by adding water, or adjusted to more
concentrated solution by adding 86% commercial grade phosphoric acid. In some
cases, 0.1% to 3% NaC1, KC1 or MgC12 salts are also added to induce particular
scale
formation during testing.
[0092] Scale was induced in the following manner:
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[0093] Step 1: Acid preparation - In this step, crude phosphoric acid is
obtained
from phosphoric acid plants and is treated properly (as is, diluting,
concentrating or
adding salt as scale initiator) before placing into the jacket beakers (60 C
to 80 C) for
0.5 to 2 hours.
[0094] Step 2: Testing equipments set up and chemical addition - After the
treatment, proper dosages of the functional organic reagents are added to the
phosphoric acid and agitated using stir bar while being heated by water
circulator at
60 C to 90 C. In the meantime, a 316L stainless steel tube is placed in each
beaker
along with the cover and plastic tubings for water inlet and outlet.
Alternatively, a
graphite tube or a 904L stainless steel tube can be used and the temperature
for the
tube can be 110 C to 130 C.
[0095] Step 3: Scale formation - If a scale inhibiting reagent is used, it
can be
added just before the conditioning (generally the additive is used as a
solution
containing 1-10% of active reagent). This solution is put into the treated
phosphoric
acid in the jacketed beaker and is heated with agitation at 60 C to 80 C for
30
minutes before the tube waster is turned on and kept at that temperature for 2-
12
hours. Two to nine such tests (beakers) are done at one time. At the end of
the test,
the tube is thoroughly rinsed and dried in an oven (80 C) for 1-2 hours.
[0096] Step 4: Weighing and analysis of the scale - Considerable scale is
observed to form on the steel tube. The weight gain of the steel tube is a
measure of
the amount of scaling. The weight of scale formed is expressed as a percentage
of the
average weight that formed on the blanks (i.e, no reagent is used) that were
part of the
same set of tests. Similarly, the total amount of scale is also a measure of
antiscalant
activity and this may be expressed as a percentage of the total weight that
formed in
the blank experiments that were part of the same set of tests. The scale is
also
analyzed by ICP and XRD for metal ion and component information.
[0097] This test method is preferred because other test methods collect
both the
scales and the insolubles, although the insoluble may be free flowing in the
acid
stream in the real plant and thus not contribute as significantly to the scale
growth. In
this test, the scale is collected on the outside surface of the stainless
steel tubes. The
tubes are weighed and compared to the tubes without reagent treatment to
calculate
the scale changes. The reagents are usually prepared in deionized ("DI") water
for
final of 3% concentration for testing. Unless it is stated otherwise, the
maximum
concentration of reagent used in the testing solution is 2000 mg/kg.
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[0098] Care must be taken to ensure all the parameters, such as but not
limited to,
mixing rate, tube temperature, jacket temperature, tube surface quality, tube
volume
submerged, stir bar size and acid quality, are close to one another, so that
the result of
scale inhibition comparison with the control sample will be meaningful.
Example 1
[0099] Four jacketed-beakers are positioned and clamped on top of an
aluminum
tray filled with DI-water over the four corners of the hot plates. The beakers
are
connected in parallel in respect to the water flow from the heating
circulator.
Phosphoric acid (synthetic or crude plant acid sample at 28%) is mixed well
before
evenly dividing into 4 beakers (450-700 g). The beakers are mixed
simultaneously by
stir bars at the same speed. The hot plate is turned on to heat the water bath
to a
temperature of about 90 C. After the mixing in each beaker is stabilized, the
power
of the heating circulator is started. Once the temperature of the circulator
reads about
50-60 C, reagents are then added to the individual beaker (usually to three of
them
with remaining one as control).
[00100] The four pre-weighed U-shape tubes with series connection to tap
water are
then submerged into corresponding beaker. Once the circulator reads about 75
C, the
tap water is turned on to cool the U-shape tubes. The end of the tap water
temperature
coming out of the last U-shape tube is about 25 C. The mixing in each beaker
is
continued and carefully monitored for occasional stops. All tap water and
heating
water connections are monitored frequently for possible leaking and
disconnection.
[00101] After a two hour treatment (or until there is visible scale formed
on the
tubes), the heating for the jacket and cooling water for the tubes are turned
off along
with the stirring and heating for the hot plate. The tubes are disconnected
and rinsed
in a beaker with 500 ml DI water to remove the residual phosphoric acid on the
tubes.
The tubes are then dried in an oven for 1 hour at 80 C and cooled to room
temperature before they are weighed to find out scale weight on the tubes by
the
following equation: Percent scale reduction (increase) = 100x (Wt of scale
w/reagent
¨Wt of scale w/o reagent)/( Wt of scale w/o reagent). ICP analysis and XRD
analysis
is submitted when necessary.
[00102] After the scale study is complete, the beakers are removed with
clamps
attached and used acid solutions are poured into a waste container. The
beakers are
cleaned and returned to their original positions for the next run. The
stainless steel
tubes are cleaned, oven dried, and weighed before being reused for the next
run.
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[00103] Results for various functional organic reagents for preventing or
reducing
scale are shown in Tables A-D below:
[00104] Table A. Test results using single-compound phosphonic acid
derivative
reagents
Examples Reagents Dosage, Percent Scale
mg/kg Reduction vs.
blank
1 Phenylphosphonic 100 -15
acid
2 phosphonoacetic acid 100 -53
[00105] Table B. Test results using single-compound sulfonic acid
derivative
reagents
Examples Reagent Dosage, Percent
mg/kg Scale
Reduction
vs. blank
3 Sulfosuccinic acid 100 -92
4 3-Sulfopropyl acrylate 100 -78
potassium salt
1-Dodecanesulfonic acid 100 -72
sodium salt
6 4- 100 -66
Hydroxybenzenesulfonic
acid solution
7 3-Amino-4- 100 -27
hydroxybenzenesulfonic
acid
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[00106] Table C. Test results using single-compound carboxylic acid
derivative
reagents
Examples Reagent Dosage, Percent
mg/kg Scale
Reduction
vs. blank
8 3,4-Dihydroxyphenylacetic 100 -58
acid
9 3,4-Dihydroxybenzoic acid 100 -42
Gallic acid 100 -10
11 Caffeic acid 100 -17
[00107] Table D. Test results using blend or copolymers as reagents
Examples Reagent Dosage, Percent
mg/kg Scale
Reduction
vs. blank
12 Phosphinopolycarboxylic 100 -9
acid
13 Acrylic 100 -17
acid/acrylate/sulfonate
copolymer
14 P-80 100 -58
poly(4-styrenesulfonic 100 -2.5
acid)
16 Tartaric acid + -33
CYANAMER P80 1:1
17 1-hydroxyethan-(1,1-di- -60
phosphonic acid)(HEDP)
+ polyMA-AA 1:1
18 (HEDP) + polyacrylic acid 1:1 -75
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19 3,4- -35
dihydroxyhydrocinnamic
acid + CYANAMERO
P80 1:1
20 AeroDriO 104 (available -55
from Cytec Industries Inc.
Woodland Park NJ) +
SUPERFLOCO C573
(available from Cytec
Industries Inc. Woodland
Park NJ) 1:1
21 Tartaric acid + -33
SUPERFLOCO C587
(available from Cytec
Industries Inc. Woodland
Park NJ) 1:1
22 3,4- -72
dihydroxyhydrocinnamic
acid + SUPERFLOCO
C587 1:1
23 4,5-dihydroxynaphthalene- -52
2,7-disulfonic acid sodium
salt + CYANAMERO P70
(available from Cytec
Industries Inc. Woodland
Park NJ) 1:1
24 AeroO 865 (available from 1:1 -66
Cytec Industries Inc.,
Woodland Park NJ) +
Tannic phosphite
25 AeroDriO 104 + 1:1 -29
SUPERFLOCO C587
26 P-80 + C-573 1:1 -42
[00108] Example 2
[00109] The testing condition is similar to that for Example 1, but the
phosphoric
acid concentration is increased to 52 %. The test is performed with 55 C tube
temperature and 80 C acid temperature or with 35 C tube temperature and 70 C
acid
temperature in order to increase the temperature difference to enhance scale
formation. In all the tests, 240 rpm to 300 rpm agitation, 1 kg of acid and
100 ppm
(3g of 3% solution) reagents is used. The duration of the tests is between 2
to 6 hours.
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[00110] Results are provided in Table E below:
[00111] Table E. Test results for various reagents at 52% P205
Example Reagent Dosage, Percent
mg/kg Scale
Reduction
vs. blank
27 Tannic phosphite 100 -78%
28 Sulfosuccinic acid 100 -94%
29 1-Dodecanesulfonic acid 100 -67%
sodium salt with
dopamine
30 3,4- 100 -88%
dihydroxyhydrocinnamic
acid
31 hydroxypolyethylenimino 100 -67%
succinate
[00112] A typical experimental process for hydroxypolyethylenimino
succinate is
as follows: 2g disodium cis-epoxysuccinate is synthesized from known procedure
and
is mixed with 8.3g 50% polyethylenimine (PEI) and heated (either neat or in
CH3CN)
and stirred for 4 hr. at 80 C. After cooling, the viscous liquid is treated
with hexanes
after which it was solidified. It is filtered and dried and weighted. The
solid is
dissolved in water for concentration adjustment. The reagent testing results
are
summarized in Table F and reported as percent of scale formed versus blank,
where
no reagent is used.
[00113] Table F. Test results using hydroxypolyethylenimino succinate
Example Reagent Dosage, mg/kg Percent Scale
Reduction vs.
blank
32 hydroxypolyethylenimino 100 -97.5
succinate
[00114] Example 3
[00115] The testing condition is similar to that for Example 1, except the
acid
concentration is 28 % or 42 %, or a synthetically made phosphoric acid
solution to
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match the concentration of scaling species in the acid. The test is performed
with 130
C tube temperature using a recirculation heater with silicone oil. The acid
temperature begins at room temperature, eventually rising to between 90-95 C.
In all
tests, 240 to 300 rpm agitation, 1 kg of acid, and 100 ppm of reagent is used.
The
duration of the tests is from 2 to 6 hours. Results are provided below.
[00116] Table G. Test results for various reagents at 28 % or 42 % P205
Percent Scale
Example Reagent
DosageReduction vs.
(mg/kg)
blank
33 I-Carrageenan 100 -55
34 Alginic acid (sodium salt) 100 -60
35 Carboxy methyl cellulose (10 kDa) 100 -51
36 Carboxy methyl cellulose (30 kDa) 100 -61
Poly(ethylene glycol)-block-poly(propylene
37 glycol)-block-poly(ethylene glycol) 100 -71
(LCST 37 C)
Poly-n-isopropyl polyacrylamide
38 100 -65
(LCST 32 C)
Poly-n-isopropyl polyacrylamide-co-acrylic
39 100-100
acid (80:20 AA:NIPAM)
Poly-n-isopropyl polyacrylamide-co-acrylic
40 100 -86
acid (50:50 AA:NIPAM)
Poly-n-isopropyl polyacrylamide-co-acrylic
41 100 -63
acid (20:80 AA:NIPAM)
1-hydroxyethylidene-1,1-diphosphonic acid
(HEDPA): poly-diallyl dimethyl ammonium
42 100 -59
chloride (SUPERFLOC C587 ):gluconic acid
(1:1:1)
[00117] Various patent and/or scientific literature references have been
referred to
throughout this application. The disclosures of these publications in their
entireties
are hereby incorporated by reference as if written herein to the extent that
such
disclosures are not inconsistent with the invention and for all jurisdictions
in which
such incorporation by reference is permitted. In view of the above description
and the
examples, one of ordinary skill in the art will be able to practice the
disclosure as
claimed without undue experimentation.
[00118] Although the foregoing description has shown, described, and
pointed out
the fundamental novel features of the present teachings, it will be understood
that
various omissions, substitutions, and changes in the form of the processes as
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PCT/US2011/029319
illustrated, may be made by those skilled in the art, without departing from
the scope
of the present teachings. Consequently, the scope of the present teachings
should not
be limited to the foregoing discussion, but should be defined by the appended
claims.
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