JPH05104093A - Method for controlling silica/silicate deposition in water system using 2-phosphonobutane-1,2,4- tricarboxylic acid and anionic polymer - Google Patents

Abstract

PURPOSE: To make it possible to effectively control the deposition of silica/ silicate in a water system by adding an effective amt. of 2- phosphonobutane-1,2,4-tricarboxylic acid or its salt to the water system.

CONSTITUTION: The deposition of the silica/silicate in the water system is controlled by adding the effective amt. of the 2-phosphonobutane-1,2,4-tricarboxylic acid or its salt to the water system. The term 'water system' signifies the inclusion of a cooling water system, boiler water system, desalting system, gas scrubber water system, blast furnace water system, reverse osmosis system, evaporator system, paper making system, mining system, etc. The term 'control of the deposition of the silica/silicate' signifies the inclusion of the suppression of silica polymn., threshold precipitation suppression, stabilization, dispersion, solubilization and/or reduction of the grain sizes of calcium silicate, magnesium silicate and silicon ions at the time of silica and silicate.

COPYRIGHT: (C)1993,JPO

Description

Detailed Description of the Invention

[0001]

Silica / silicate precipitation in aqueous systems, such as those containing boilers, cooling towers, persalt geothermal brine, remains a problem. Traditionally, by softening and draining the makeup water to the system to be treated,
Or both have controlled precipitation. Once precipitation occurs, mechanical removal or washing with ammonium fluoride or hydrofluoric acid is a common control method. clearly,
Mechanical or chemical cleaning requires downtime and increases energy and labor costs.

PH affects the ionization of silanol groups,
Therefore, it affects the polymerization rate. Silica is produced first,
Then, it is considered that a three-dimensional network structure is formed. Eventually, the condensation causes the colloidal particles to grow. At pH7,
Nucleation and grain growth are significantly faster. The pH of cooling water is generally 6.0 to 8.5, and the water temperature is generally about 30 to 70 ° C.
Is. Geothermal brines generally have a pH of 4.0 to 6.0 and brine temperatures of about 100 ° to 210 ° C.

It is known to use cationic polymers or cationic surfactants as silica scale inhibitors in persalt geothermal brines (Harrar, JE.
Et al., "Final Report on Testing of Patented Chemical Additives as Antiscale Agents for Persalt Geothermal Brine", January 1980, Lawreuce Livermore Laboratory; Harrar, JE.
Et al., "Online test of organic additives for suppressing silica precipitation from persalt geothermal brine, IV, final test of candidate additives", February 1980, Lawreuce Livermore Laborator
ies; Harrar, JE et al. "Study of scale formation and scale inhibitors in the Salton Sea geothermal field" Corrosion / 8
0, Paper No. 225, International Corrosion Forum, 3 March 1980 (dedicated solely to material protection and performance).
~ 7th, Chicago, Illinois).

[0004] Pending Calgon, US Patent Application No. 290,798 also uses phosphonates and anionic polymers such as hexamethylenediaminetetra (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid). Disclosed is controlling silica deposition. Pending Calgon US Patent Application No. 19
No. 0,621 discloses the use of phosphonates such as 2-phosphonobutane-1,2,4-tricarboxylic acid and maleic acid / dimethyldiallylammonium chloride type polymers to control silica precipitation.

US Pat. No. 3,928,196 discloses the use of copolymers of 2-acrylamido-2-methylpropyl sulfonic acid and acrylic acid as scale inhibitors.

US Pat. No. 4,640,793 discloses the use of a mixture containing a carboxylic acid / sulfonic acid polymer and a phosphonate as a scale and corrosion inhibitor.

US Pat. No. 4,618,448 discloses the use of polymers encapsulating unsaturated carboxylic acids, unsaturated sulfonic acids and unsaturated polyalkylene oxides as scale inhibitors.

Japanese Patent Application No. 57-084794 discloses the use of homopolymers of allyl acid and allyl polyethylene glycol as scale inhibitors.

European Patent Application No. 84301450.
7 discloses a carboxylic acid / sulfonic acid copolymer in combination with an organic phosphonate as a scale inhibitor.

US Pat. No. 4,510,059 discloses the use of carboxylic acid functional ampholytic polyelectrolytes to reduce silica deposits in aqueous systems.

US Pat. No. 4,432,879 discloses 2-phosphonobutane-1,2 for dispersing solids such as clay containing China clay (Al ₃ O _{3 .2H 2 O.2SiO 2} ) in an aqueous system. , 4-tricarboxylic acid and methacrylic acid /
Disclosed is the use of 2-acrylamido-2-methylpropyl sulfonic acid polymer. No silica / silicate threshold suppression has been identified or proposed.

US Pat. No. 4,532,047 discloses a method for inhibiting the formation of amorphous silica scale using a polypolar organic compound and a sulfur borate source.

US Pat. No. 4,584,104 discloses a method of inhibiting amorphous silica scale formation using a source of orthoborate ions.

We have used 2-phosphonobutane-1,2,4-tricarboxylic acid or its salts, alone or preferably in combination with a water-soluble anionic polymer, to precipitate silica and silicates in aqueous systems. I found a way to control. This anionic polymer is preferably prepared from at least one carboxylic acid component alone or in combination with at least one sulphonic acid component and optionally with at least one polyalkylene oxide component. Terpolymers are preferred.

The 2-phosphonobutane-1,2,4-tricarboxylic acid or its salt is an effective inhibitor in itself.
This compound and its salts suppress silica precipitation in aqueous systems. Thus, when this compound is added to water containing silica and hardness components at a pH of about 9.0, the compound suppresses the formation of silicates and their deposition on the surface in contact with the water to be treated. For example, 2-phosphonobutane-
About 10 mg / l of 1,2,4-tricarboxylic acid at a dose of about 20 mg / l in 2 cycles, without SiO ₂ 250-280 mg / l and hardness 180-20 without substantial precipitation on the system surface.
It was shown to keep 0 mg / l effective. Further, the anionic polymer is generally 2-phosphonobutane-1,2,4-
It has also been found to enhance the potency of tricarboxylic acids. Sources of borate and morphudate can also be used to increase silica inhibition.

The present invention relates to A) 2-phosphonobutane-1,2,4-tricarboxylic acids or salts thereof, optionally B) water soluble, in aqueous systems containing silica or prone to silica / silicate precipitation. A method of controlling silica / silicate precipitation in the above aqueous system, which comprises adding an effective amount of a composition comprising a cationic anionic polymer. If used, the polymer B) is a homopolymer of acrylic acid, a homopolymer of methacrylic acid, a polymer of acrylic acid and methacrylic acid, hydrolyzed polyacrylamide, a homopolymer of maleic acid or its anhydride, and acrylic acid and / or Or methacrylic acid and allyl polyalkylene glycol, methallyl polyalkylene glycol, polyalkylene glycol acrylate or methacrylate, and polyalkylene oxide such as methoxyallyl polyalkylene glycol, 2-hydroxypropyl acrylate, vinyl sulfonic acid, vinyl phosphonic acid, acetic acid. Vinyl, ethyl vinyl ether, acrylamide, ethyl acrylate, ethyl methacrylate, 2-acrylamide-
2-methylpropyl sulfonic acid, 2-methacrylamido-2-methylpropyl sulfonic acid, styrene sulfonic acid, sulfoalkyl acrylate, sulfoalkyl methacrylate, allyl sulfonic acid, methallyl sulfonic acid,
It is selected from the group consisting of polymers consisting of 3-methacrylamido-2-hydroxypropylsulfonic acid and at least one other polymerizable unsaturated water-soluble monomer selected from the group consisting of salts thereof. Blends of the above polymers and their water-soluble salts can also be used.

The use of anionic polymers is optional,
Its use is also preferred. Methods for making the above polymers are well known in the water treatment art. Also, many of the above polymers are commercially available from various suppliers.

The preferred polymers for use as component B) in the compositions and methods of the present invention are homopolymers of acrylic acid or methacrylic acid, and (i) unsaturated monomonomers selected from the group consisting of acrylic acid and methacrylic acid. About 35 to about 95% by weight of carboxylic acid,
Preferably about 50 to about 90% by weight; (ii) about 5 to about 65 unsaturated sulfonic acids selected from the group consisting of 2-acrylamido-2-methylpropyl sulfonic acid and 2-methacrylamido-2-methylpropyl sulfonic acid. %, Preferably about 10 to about 50% by weight; and, optionally, (iii) a polymer of polymers consisting of 0 to about 40%, preferably 0 to about 30% by weight unsaturated polyalkylene oxide. To be elected.

Any water-soluble unsaturated polyalkylene oxide compound can be used as (iii) in the preferred polymers. Examples include, but are not limited to, allyl polyalkylene glycol, methallyl polyalkylene glycol, polyalkylene glycol acrylate, polyalkylene glycol methacrylate and methoxyallyl polyalkylene glycol. Preferred unsaturated polyalkylene oxide compounds are unsaturated polyethylene compounds, their unsaturated polypropylene equivalents and their ether derivatives. More preferably, unsaturated polyethylene compounds are used. It is also possible to use polyether mixtures formed from unsaturated polyethylene oxide and other polyalkylene oxides such as propylene oxide or butylene oxide. Unsaturated polyether chains can be blocked with alkyl, aralkyl, sulfonate or phosphonate groups, metals or ions, or unblocked.

The most preferred unsaturated polyalkylene oxide compounds for use as component (iii) have the formula CH ₂ = CH-
CH ₂ (OCH ₂ CH ₂ ) _n OH or CH ₂ = CH-CH ₂ (OCH ₂ CH ₂ ) _n OCH ₃
An allyl polyethylene glycol having the formula: where n is 5-10, and the formula:

[Chemical 2] Where R and R ¹ can be the same or different and are selected from the group consisting of H, C ₁ -C ₃ lower alkyl, preferably CH ₃ , and x is 1-20. Selected from the group consisting of polyethylene glycol acrylate or methacrylate. The most preferred component has the formula:

[Chemical 3] (Wherein x is 1 to 10, preferably 3 to 7).

The above preferred polymers are commercially available from Calgon Corporation, Pittsburgh, PA. Alternatively, such polymers can be made by free radical polymerization methods well known in the art. See U.S. Pat. No. 4,680,135.

The most preferred polymers for use as component B) in the compositions and methods of this invention are acrylic acid homopolymers and salts thereof, about 35 to 95% by weight acrylic acid, preferably about 50 to about 90% by weight. , 2-acrylamido-2-methylpropyl sulfonate, a copolymer of about 5 to about 65% by weight, preferably about 10 to about 50% by weight, eg TRC-233 ™, acrylic commercially available from Calgon Corporation. acid,
A terpolymer consisting of 2-acrylamido-2-methylpropionic acid and polyethylene glycol monomethacrylate and salts thereof, such as TRC-271 ™, commercially available from Calgon Corporation. If a terpolymer is used, the most preferred terpolymer is about 50 to about 80 wt% acrylic acid or its salt, about 10 to about 30 wt% 2-acrylamido-2-methylpropyl sulfonic acid or its salt, polyethylene glycol monomethacrylate. It comprises about 5 to about 15% by weight.

The molecular weight of the above polymers is not critical, but it is preferably about 1,000,000 or less when measured by light scattering or gel permeation chromatography. More preferably, the molecular weight is about 100,
000 or less, most preferably about 50,000 or less. This polymer was added to 2-phosphonobutane-1,2,4
It can be applied to the system to be treated as part of an aqueous solution which simultaneously contains tricarboxylic acid or its salts.

When using polymer B), A) vs. B)
Should be about 1:10 to about 10: 1, preferably about 1: 3 to about 3: 1.

Furthermore, when using polymer B), a molybdate-containing composition, to which a molybdate ion source or borate ion source can be added, is a composition containing molybdate ions such as calcium ions, magnesium ions and SiO _2. It does not contain molybdate ions as it solubilizes the species more than expected. Any molybdic acid or borate ion source can be used. The preferred source of molybdate ion is ammonium molybdate and the preferred source of borate ion is US Pat. Nos. 4,504,104 and 4,532,047.
No. (referenced herein). When used as a source of molybdate or borate ions and component C), the weight ratio of component A) to component C) is about 1:
It should range from 5 to about 5: 1. Molybdate and borate sources are commercially available.

An effective amount of 2-phosphonobutane-1,2,4-tricarboxylic acid or salt thereof should be added to the aqueous system to be treated. The term "effective amount" as used herein is the amount required to control silica / silicate precipitation in the aqueous system to be treated. Generally, an effective amount is in the range of about 0.1 to about 200 ppm active ingredient, preferably about 1 to 200 ppm, based on the total weight of the aqueous system to be treated.

As used herein, the term "control of silica / silicate precipitation" refers to inhibition of silica polymerization, inhibition of limiting precipitation, stabilization, dispersion, solubilization, and / or silica, silicates, especially calcium silicates. It is meant to include particle size reduction of magnesium silicate and silicon ions. Clearly, the additives of the present invention are inhibitors of marginal silicate precipitation, but at the same time are believed to stabilize, disperse and solubilize silica and silicates. Therefore, the present inventors have found that 2-phosphonobutane-1,2,4-tricarboxylic acid and its salts, alone or in combination with a specific polymer, and optionally a source of morbutene acid or borate ions, under severe operating conditions. It has been found to suppress, minimize or prevent silica precipitation, and this specification describes this finding without attempting to describe a particular mechanism by which silica / silicate precipitation is prevented or suppressed. Is intended.

As used herein, the term "aqueous system" is meant to include cooling water systems, boiler water systems, desalination systems, gas scrubber water systems, blast furnace water systems, reverse osmosis systems, evaporator systems, papermaking systems, mining systems and the like. Meaning, but not limited to.

The use of 2-phosphonobutane-1,2,4-tricarboxylic acids or salts thereof, by themselves, reduces, suppresses and / or reduces silica / silicate precipitation under severe saturation and / or temperature conditions. Alternatively, it is essential to the method in terms of prevention.

The polymers of this invention are commonly available when used. Sources of molybdate and borate ions are also commonly available.

The compositions disclosed herein effectively control silica / silicate precipitation in aqueous systems having high alkalinity, high calcite saturation, and / or high pH values. Such conditions are often formed as the concentration cycle increases. Therefore, the 2-phosphonobutane of the present invention
The 1,2,4-tricarboxylic acid composition provides silica / silicate protection under severe conditions where conventional silica control agents may not be effective.

The composition can be added to the system to be treated by any suitable means and the components can be added separately or in combination. The preferred method of addition is via the makeup water stream.

In addition, other conventional water treatment agents can be used with the polymer, including corrosion inhibitors such as tolyltriazole.

[0034] To illustrate the suppression of the silica / silicate deposition by use of the present composition by following examples. The following examples do not limit the scope of the invention in any way.

The following compounds were tested in this example:
PBTA is 2-phosphonobutane-1,2,4-tricarboxylic acid and is commercially available from Mobay as Bayhibit AM. PMA is poly (maleic anhydride) and is commercially available as Belclene 200 from Ciba Geigy. Ammonium molybdate is the source of MoO ₄ ²⁻ . AA / HPA is a copolymer of acrylic acid and 2-hydroxypropyl acrylate
42 commercially available from National Starch. PAA is a sodium-neutralized acrylic acid homopolymer having a weight average molecular weight of about 2200, manufactured by Calgon Corporation.
Commercially available from. AA / AMPSA / POE
Is 60 / of acrylic acid / 2-acrylamido-2-methylpropyl sulfonic acid having a weight average molecular weight of about 8200 as measured by gel permeation chromatography (GPC).
40 w / w polymer, commercially available from Calgon Corporation. AA / AMPSA / POE is acrylic acid, 2-acrylamido-2-methylpropyl sulfonic acid and formula:

[Chemical 4] 70/20 of polyethylene glycol methacrylate
/ 10 (w / w / w) polymer, Calgon Corpora
commercially available from tion.

Test Method The following procedure was used to evaluate the ability of the composition to prevent the formation and precipitation of calcium silicate and magnesium silicate.

A 2 liter polypropylene flask with side arms was filled to the 1500 ml level with make-up water as described in Table I. By immersing an electrically heated 304 stainless steel heat exchanger in the polypropylene flask,
The temperature of make-up water was controlled and maintained. A refractive index liquid level sensor was placed on the side arm and a constant volume was maintained inside the flask by controlling the solenoid valve on the inflow line from the make-up reservoir.

Through a Teflon tube placed at the bottom of the flask,
Evaporation was achieved by sending filtered dry air or nitrogen at a regulated and measured rate. Make-up water was concentrated to various levels (ie cycle up) by controlling the aeration rate. Set point on pH stat device
Depending on the pH, the pH of the system was controlled by supplying acid or alkali as needed.

After reaching the target enrichment cycle, the cycle was held constant for several days. This simulated the operating procedure normally used in industrial cooling towers. in this case,
Make-up water in the sump was replaced with distilled water to stop further concentration. The make-up water listed in Table I was chosen because it is stable at room temperature and provides sufficient induction period to establish the enrichment process before any mineral precipitation occurs. The pH of the makeup water was adjusted to 8-9 and the flask was kept at the selected pH during the entire cycle up process. Make-up water contained 10 mg / l of the specified inhibitor. Samples were taken at various time intervals, filtered and analyzed for chloride, calcium, magnesium and silica. The concentration cycle was determined based on the chloride concentration in cycle-up water. The expected concentration of other species in solution was then calculated based on the concentration cycle. The amount of precipitation on the heat exchanger was determined by weighing the heat exchanger at the beginning and end of each experiment. The above results are shown in Tables II and II.
Shown in I and IV. Table I Chemical composition of makeup water Total ion concentration (mg / L) Calcium 100 Magnesium 7.5 Sodium 153 Chloride 199 Sulfuric acid 219 Silica 150 ────────────────────── ──────── Table II Silica / silicates at pH 9.0 ± 0.2 with air or nitrogen for cycle up and a constant cycle (1.8-2.0) for 2-3 days. Inhibition ─────────────────────────────────── Inhibitor Cycle% Inhibition Dose increase Precipitation mg / L) Additive (mg / L) vehicle SiO ₂ Ca Mg Bayhibit AM 10 N ₂ 97 72 87 84 10 Air 5 74 31 0 20 Air 15 79 69 11 AA / AMPSA 2 Air * 80 3 62 10 Air 80 88 56 62 10 N ₂ 96 79 88 63 AA / AMPSA / POE 2 Air * 82 3 17 5 Air * 84 0 32 10 Air 29 81 2 0 10 N ₂ 80 84 79 67 PAA 2 Air 49 85 5 17 5 Air 45 72 12 33 10 Air 83 80 25 24 20 Air 32 77 4 4 10 N ₂ 92 78 88 57 AA / HPA 10 Air 5 84 2 40 10 N ₂ 59 71 37 0 PMA 10 N ₂ 62 72 89 15 MoO ₄ 20 N ₂ 59 58 10 7 AA / AMPSA + MoO ₄ 10 / 20 N ₂ 51 75 38 0 Bayhibit AM + MoO ₄ 10/20 N ₂ 77 63 57 7 PAA + MoO ₄ 10/20 N ₂ 62 67 90 0 ───────────────── ─────────────────── * Precipitate weight is higher than the control. Table III Silica / silicate inhibition at a pH of 8.8 ± 0.2, which was maintained for a constant cycle (1.8-2.0) for 7-8 days by using air for cycle-up ─────── ──────────────────────────── Usage amount% suppression Retention in solution (mg / L) Additive (mg / L) precipitation SiO ₂ Ca Mg PBTA 10 85 59 8 0 AA / AMPSA 10 85 88 0 7 AA / AMPSA / POE 10 96 75 86 82 PAA 10 97 37 2 0 PBTA + AA / AMPSA / POE 10/10 94 81 0 10 PBTA + 10 / 10/20 98 83 96 44 AA / AMPSA / POE + 5/5/10 91 83 0 19 MoO ₄ ^-2 PBTA + PAA 10/10 95 100 0 14 PBTA + PAA + MoO ₄ 100 91 100 95 ─── ──────────────────────────────── Table IV Cycle-up air and make-up water ^* , constant for 7-8 days Inhibition of silica / silicate at pH 8.8 ± 2 holding cycle (1.8-2.0) ───────────────────── ────────────── retention of a dose% inhibition solution (mg / L) additives (mg / L) precipitated _{SiO 2 Ca Mg PBTA 10 - 45} 11 0 AA / AMPSA 10 85 65 10 8 AA / AMPSA / POE 10 84 67 21 11 MoO ₄ 20 16 58 3 0 PBTA + MoO ₄ 10/20 69 70 0 9 PBTA + 10/10 95 62 3 21 AA / AMPSA / POE PBTA + 10/10 / 20 96 89 100 100 AA / AMPSA + MoO ₄ ─────────────────────────────────── * Makeup water It gave the alkalinity ^- HCO ₃ of 100mg / l to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susan P. Ray United States, 15108 Pennsylvania, Coraopolis, Oak Heaven Drive 203 (72) Inventor Jiyon Etchi. Weirnik United States, 15204 Pennsylvania, Pittsburgh, Aidon Street 1233

Claims (10)

[Claims] 1. An aqueous system containing 2-phosphonobutane-1,2,
A method for controlling silica / silicate precipitation in an aqueous system, which comprises adding an effective amount of 4-tricarboxylic acid or a salt thereof. 2. A) 2-phosphonobutane-1, in an aqueous system,
2,4-tricarboxylic acid or a salt thereof, and B) a homopolymer of acrylic acid or methacrylic acid, and a) an unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, or salts thereof.
% By weight; b) about 5 to 65% by weight of an unsaturated sulfonic acid selected from the group consisting of 2-acrylamido-2-methylpropyl sulfonic acid, 2-methacrylamido-2-methylpropyl sulfonic acid, or salts thereof; c) Unsaturated polyalkylene oxide compound 0 to about 4
0% by weight of polymer; an effective amount of a water-soluble polymer having a weight average molecular weight of less than or equal to about 50,000 is used in a weight ratio of A) to B) of about 1:10 to about 10: A method for controlling silica / silicate precipitation in an aqueous system, characterized in that the addition is performed in the range of 1. 3. The method of claim 2 wherein the weight ratio of A) to B) is from about 1: 3 to about 3: 1. 4. B) is a) 50 to 80% by weight of an unsaturated carboxylic acid compound selected from the group consisting of a) acrylic acid, methacrylic acid, salts thereof, and mixtures thereof; b) 2-acrylamido-2- 10 to 30% by weight of an unsaturated sulfonic acid compound selected from the group consisting of methylpropyl sulfonic acid, 2-methacrylamido-2-methylpropyl sulfonic acid, salts thereof, and mixtures thereof; c) CH ₂ ═CH—CH ₂ (OCH ₂ CH ₂ ) _n OH, CH ₂ = CH-CH ₂ (OCH ₂ CH
₂ ) _n OCH ₃ (where n is 5 to 10), and (Wherein R and R ¹ are each independently H or lower alkyl and x is 1 to 20) and the water-soluble unsaturated polyalkylene oxide compound is selected from the group consisting of 5 to 15% by weight. The method of claim 3 which is a hydrophilic polymer. 5. The method of claim 1, wherein the 2-phosphonobutane-1,2,4-tricarboxylic acid is added in a dose of about 0.1 to about 200 ppm. 6. The method of claim 2 wherein 2-phosphonobutane-1,2,4-tricarboxylic acid is added in a dose of about 0.1 to about 200 ppm. 7. A molybdate or borate ion source as component C) in a weight ratio of A) to C) of about 1: 5.
The method of claim 2 wherein the addition is within the range of about 5: 1 to about 5: 1. 8. The method of claim 7, wherein C) is a molybdate ion source. 9. A molybdate or borate ion source as component C) in a weight ratio of A) to C) of about 1: 5.
5. The method of claim 4, wherein the addition is within the range of about 5: 1. 10. The method of claim 9 wherein C) is a molybdate ion source.