COMPOSITION AND METHOD OF SCALE CONTROL IN REGULATED EVAPORATIVE SYSTEMS

Abstract

This invention pertains to an anti-scaling composition comprising a blend of a polyamino acid; an anionic carboxylic polymer; and a polymaleic acid. The blend is able to effectively stabilize calcium salts that lead to scale formation in evaporative systems. This three-component blend shows high levels of efficacy in acidic high conductivity waters found in many evaporative systems such as sugar and bio-refining.

Claims

1. A method for controlling, preventing and/or inhibiting the formation of calcium, magnesium, oxalate, sulfate, and phosphate scaling and/or deposits in a regulated evaporative system comprising; adding to the regulated evaporative system a mixture comprising a) a polyamino acid; b) an anionic carboxylic polymer; c) and a polymaleic acid; wherein the polyamino acid, anionic carboxylic polymer, and polymaleic acid has residence time together and is added to the regulated evaporative system premixed, simultaneously or sequentially and in any order.

2. The method according to claim 1, wherein the polyamino acid, anionic carboxylic polymer and polymaleic acid are premixed prior to being added to the regulated evaporative system.

3. The method of claim 3, wherein the calcium and/or magnesium scale is from oxalates and phosphates.

4. The method of any one of claims 1-4, wherein the composition comprises a polyamino acid in an amount of from about 2 ppm to about 100 ppm by weight regulated evaporative system, can be from about 3 ppm to about 50 ppm by weight regulated evaporative system, and may be from about 5 ppm to about 10 ppm by weight regulated evaporative system.

5. The method of any one of claims 1-5, wherein the polyamino acid has an average molecular weight ranging from about 500 g/mol to about 10,000 g/mol, can be from about 1,000 to about 5,000 g/mol, and may be from about 1,000 g/mol to about 4,000 g/mol.

6. The method of any one of claims 1-6, wherein the polyamino acid is a sodium or potassium salt.

7. The method of claim 6 or 7, wherein the polyamino acid is polyaspartate.

8. The method of any one of claims 1-8, wherein the anionic carboxylic polymer has an average molecular weight ranging from about 500 g/mol to about 20,000 g/mol and can be from about 1,000 g/mol to about 50,000 g/mol.

9. The method of any one of claims 1-9, wherein the composition comprises an anionic carboxylic polymer in an amount of from about 2 ppm to about 100 ppm by weight regulated evaporative system, can be from about 3 ppm to about 50 ppm by weight regulated evaporative system, and may be from about 5 ppm to about 10 ppm by weight regulated evaporative system.

10. The method of any one of claims 1-10, wherein the anionic carboxylic polymer is selected from at least one of homopolymers, copolymers, terpolymers and tetrapolymers

11. The method of any one of claims 1-11, wherein the anionic carboxylic polymer is selected from the group consisting of acrylic/sulfonic polymers, acrylic/maleic copolymers, phosphinocarboxylic, acryl/maleic/sulfonated styrene, acrylic/ethoxylate/acrylamide, maleic/ethylacrylate/vinyl acetate and mixtures thereof.

12. The method of any one of claims 1-12, wherein the polymaleic acid has an average molecular weight of from about 200 g/mol to about 1,500 g/mol and can be from about 300 g/mol to about 1,000 g/mol.

13. The method of any one of claims 1-13, wherein the composition comprises polymaleic acid in an amount of from about 2 ppm to about 100 ppm by weight regulated evaporative system, can be from about 3 ppm to about 50 ppm by weight regulated evaporative system, and may be from about 5 ppm to about 10 ppm by weight regulated evaporative system.

14. The method of any one of claims 1-14, wherein the total concentration of the composition added to the regulated evaporative system is from about 0.1 ppm to about 500 ppm based on active solids and may be from about 1.0 ppm to about 50.0 ppm based on active solids.

15. The method of any one of claims 1-13, wherein the composition optionally contains citric acid, sodium phosphate, tartaric acid, gluconic acid, and/or small organic acids.

16. The method of any one of claims 1-14, wherein the pH of the regulated evaporative system is from about 1.0 to about 9.0; can be from about 2.5 to about 7; and may be from about 3.0 to about 5.0.

17. The method of claim 15, wherein the pH of the regulated evaporative system is from about 3.0 to about 5.0.

18. The method of any one of claims 1-16, wherein the temperature of the regulated evaporative system is from about 5 C. to about 175 C.; and can be from about 40 C. to about 80 C.

19. The method of any one of claims 1-17, wherein the regulated evaporative system comprises heat exchangers and/or evaporating equipment.

20. The method of any one of claims 1-18, wherein the regulated evaporative system is selected from the group consisting of regulated food process for direct or indirect food consumption; bio-refinery and fuel ethanol processes; sugar processing; fruit and vegetable juice concentrating processes; and food, alcohol and fermentation processes.

21. The method of claim 19, wherein the alcohol or fermentation process comprises beer, wine and concentrate liquors.

22. The method of claim 19, wherein the regulated food processes comprise milk and dairy processes.

23. A composition for controlling, preventing and/or inhibiting the formation of scale and/or deposits in an regulated evaporative system comprising; a) a polyaspartic acid in an amount of from about 2 ppm to about 100 ppm by weight regulated evaporative system; b) an anionic carboxylic polymer in an amount of from about 2 ppm to about 100 ppm by weight regulated evaporative system; and c) a polymaleic acid in an amount of from about 2 ppm to about 100 ppm by weight regulated evaporative system.

Description

DRAWINGS

[0020] FIG. 1, shows a general schematic of the main features of the procedure for determining Cycles of Concentration (COC).

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to a composition and method to remove, clean, prevent, and/or inhibit the formation of calcium, magnesium, oxalate, sulfate, and phosphate scale and deposits in an aqueous system. Furthermore, it relates to a method for controlling the formation of scale in aqueous systems and inhibiting scale deposition on surfaces such as heat exchanger and evaporator equipment.

[0022] In one embodiment a composition comprising a polyamino acid, an anionic carboxylic polymer, and a polymaleic acid is added to an aqueous system for controlling scaling. The composition can be added to an aqueous system premixed, simultaneously or sequentially. For example, the chemicals can be blended together or pre-mixed prior to introduction into the aqueous system, or the polyamino acid, anionic carboxylic polymer and polymaleic acid can be added separately, simultaneously, or they can be added sequentially at various points in a system as long as the chemicals can come into contact with or have residence time with each other in the system. The chemicals can also be added in any order.

[0023] In another embodiment, component (a) of the scale inhibitor composition is a polyamino acid, such as polyaspartic acid. This includes polyaspartic salts and derivatives of polyaspartic acid such as the anhydrides used to form polyaspartic acid. The polyamino acid can also comprise a copolymer of aspartic and succinct monomer units. The polyamino acids can have molecular weights ranging from about 500 grams per mole (g/mol) to about 10,000 g/mol, can be from about 1,000 g/mol to about 5,000 g/mol, and may be from about 1,000 g/mol to about 4,000 g/mol. The polyamino acid can be used as a salt, such as sodium or potassium salt.

[0024] In another embodiment, component (b) is an anionic carboxylic polymer or salt thereof, such as polyacrylic acid. The anionic carboxylic polymer can be produced by the polymerization of one or more monomers and can include one or more homopolymers, copolymers, terpolymers or tetrapolymers, etc. In addition, the anionic carboxylic polymer typically has an average molecular weight of from about 500 g/mol to about 20,000 g/mol and can be from about 1,000 g/mol to about 50,000 g/mol. These polymers and their method of synthesis are well known in the art.

[0025] In another embodiment, monomers that can provide the source for the carboxylic functionality for the anionic carboxylic polymer include acrylic acid, methacrylic acid, carboxy-methyl inulin, crotonic acid, isocrotonic acid, fumaric acid, and itaconic acid. Numerous co-monomers can be polymerized with the monomer containing the carboxylic functionality. Examples such as vinyl, allyl, acrylamide, (meth) acrylate esters, and hydroxyl esters such as hydroxypropyl esters, vinyl pyrrolidone, vinyl acetate, acrylonitrile, vinyl methyl ether, 2-acrylamido-2-methyl-propane sulphonic acid, vinyl or allyl sulphonic acid, styrene sulphonic acid, and combinations thereof. The molar ratio of carboxylic acid functionalized to co-monomer can vary over a wide range, such as from about 99:1 to 1:99, and can be from about 95:5 to 25:75.

[0026] It is also possible to employ anionic carboxylic polymers that contain a phosphonate or other phosphorous containing functionality in the polymer chain, preferably phosphino polycarboxylic acids such as those disclosed in U.S. Pat. No. 4,692,317 and U.S. Pat. No. 2,957,931, incorporated herein by reference.

[0027] In another embodiment, component (c) is polymaleic acid (PMA) and is also known as hydrolyzed polymaleic anhydride (HPMA) and may be used interchangeably through the application. Polymaleic acid can have an average molecular weight of from about 200 g/mol to about 1,500 g/mol and can be from about 300 g/mol to about 1,000 g/mol.

[0028] Other optional components or additives include phosphonobutane tricarboxylic, polyphosphates, phosphates, hydroxyethylidene diphosphonic acid, amino tri(methylene phosphonic acid), citric acid, gluconic acid, and other small organic acids.

[0029] The three components, polyamino acid, anionic carboxylic polymer, and polymaleic acid, can be considered the active ingredients of the three component compositions of the current invention. The amounts of these three ingredients together are referred to as active agents or actives. Therefore, concentrations and amounts of the polymers used herein are based on active solids.

[0030] The effective ratio of polyamino acid to anionic carboxylic polymer to polymaleic acid is from 1:9:1 to 9:1:9, can be from 1:3:1 to 1:1:1 and may be 1.7:1:1.4. The compositions have an effective pH range of from about 1 to about 9, can be from about 1 to about 6, and may be from about 1 to about 5. The composition functions over a wide range of temperatures of from about 5 C. to about 175 C. The three-component composition can be added to the regulated evaporative system at a dosage of from about 0.1 ppm to about 500 ppm, can be from about 1.0 ppm to about 50 ppm, and may be from 0.1 ppm to about 15 ppm based on total active solids.

[0031] The following examples illustrate specific embodiments of the invention. It is likely that many similar and equivalent embodiments of the invention will also apply outside of those specifically disclosed. One skilled in the art will appreciate that although specific compounds and conditions are outlined in the following examples, these compounds and conditions are not a limitation on the present invention.

EXAMPLES

[0032] The invention has been described with reference to a preferred embodiment, those skilled in the art will understand that changes can be made and equivalent substitutions made for certain components without departing from the scope of the invention. Additionally, modifications may be made to adapt to specific conditions or materials without departing from the scope thereof. Additionally, any future changes in the regulations pertaining to the restricted dosage limits fall within the scope of this invention. It is intended that the invention not be limited to a particular embodiment disclosed but that the invention will include all embodiments falling with the scope of the claims.

Example 1

[0033] Calcium oxalate is one of the main scale forming compounds in the targeted applications. Example 1, describes the efficiency of the present invention against calcium oxalate compared with each individual polymer and a blend of polyaspartic acid and polyacrylic acid as described in patent application US 2015/0251939 (WO 2015/134048 A1). The dosages are given in ppm as active solids for each polymer product. The test method used in the current study is described as follows:

Test Method

[0034] The test measurement was performed using a control unit to reproduce the recirculation process of a regulatory system. The control unit used in each of the following examples was a Druckmessgerat Haas V2.2 measurement and control unit (DMEG), manufactured by Franz-Josef Haas (see FIG. 1).

[0035] A constant volume flow of 2 [I/h] of a stoichiometric mixture prepared from a solution of calcium chloride di-hydrate and sodium oxalate in de-mineralized water was passed through a spiral metal capillary (length: 1 meter (m), inner diameter: 1.1 millimeter (mm) and placed in a heating bath at 40 C. The calculated calcium oxalate concentration was 110 milligram per liter (mg/L); calcium was added in a fivefold stoichiometrical ratio of oxalate. The pH of a calcium chloride di-hydrate solution was adjusted to 2.0 and the scale prevention polymers, i.e. PASP, PAA, PMA and combinations thereof, were added to the solution of calcium chloride di-hydrate followed by the sodium oxalate. However, the order is not of particular relevance and and the scale inhibition compositions could be added to the carbonate solutions or added to the solution of calcium chloride di-hydrate and sodium oxalate.

[0036] In this study, the individual polymers (PAA, PASP, and PMA), two-component blends of a) polyacrylic acid (PAA) with polymaleic acid (PMA); b) polyaspartic acid (PASP) with polymaleic acid (PMA); and c) polyacrylic acid (PAA) with polyaspartic acid (PASP), and three-component blend comprising PAA, PASP and PMA, were added to the solution of calcium chloride di-hydrate followed by sodium oxalate in de-mineralized water at 10 ppm total active solids. The dosages of the individual chemicals in the two-component and three-component blends can be found in Table 1, as ppm active solids.

TABLE-US-00001 TABLE 1 Dosages of Antiscaling Compositions PAA PASP PMA Total PAA 10 10 PASP 10 10 PMA 10 10 PAA + PMA 4.8 5.2 10 PMA + PASP 6.1 3.9 10 PAA + PASP 3.7 6.3 10 PAA + PASP + PMA 2.6 4.5 2.9 10

[0037] A solution of calcium chloride di-hydrate, with and without anti-scaling polymers was mixed with sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water and pumped in a circuit from a flask through a capillary in the water bath, through a cooler and back to the flask. In the water bath a heat exchange occurred and the temperature of the solution increased. The solution was then passed through a cooler unit where an adjusted air flow from below caused evaporation of the solution. During the study, samples of the solution of calcium chloride di-hydrate, with and without anti-scaling polymers, sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water were taken and filtered through a 0.45 m filter and concentration determinations of chloride and calcium, magnesium and phosphate were made.

[0038] Cycles of Concentration (COC) were calculated by dividing the analyzed concentration of a compound by the initial concentration. The chloride concentration describes the effective concentration of the system as the solubility of chloride is high. A loss of calcium by precipitation as calcium oxalate will result in a deviation of the COC for chloride and the COC for calcium. In this way, the maximum obtainable COC without scaling can be determined for each product at the equal dosage. The results can be seen in Table 2.

TABLE-US-00002 TABLE 2 Cycles of Concentration Maximum Cycles of Concentration (COC) Polyaspartic acid (PASP) 1.5 Polyacrylate (PAA) 1.4 Polymaleic acid (PMA) 1.6 Two-Component Blend (PAA + PMA) 1.5 Two-Component Blend (PMA + PASP) 1.6 Two-Component Blend (PASP/PAA) 2.3 Three Component Blend (PASP/PAA/PMA) 2.7

[0039] As it can be seen the maximum COC reached with the three-component blend was significantly higher than with the individual polymers and the two-component blends. Although the same amount of anti-scaling composition was added to the system, the COC measured was higher than would have been expected from the results of the single polymer products and a synergistic anti-scaling effect is clearly seen with the three-component polymer blend.

Example 2

[0040] This study evaluated the efficiency of a three-component anti-scaling composition comprising PASP, PAA and PMA, at inhibiting calcium carbonate deposition in comparison with each of the individual polymers (PASP, PAA and PMA), and two-component blends consisting of a) polyacrylic acid (PAA) with polymaleic acid (PMA); b) polyaspartic acid (PASP) with polymaleic acid (PMA); and c) polyacrylic acid (PAA) with polyaspartic acid (PASP) were included in this study. The dosages are given in ppm as total active solids for each product.

Test Method

[0041] A solution of calcium chloride di-hydrate, sodium carbonate and sodium bicarbonate in de-mineralized water is stored in a heatable shaker bath. At increased temperature precipitations of calcium carbonate can form. After a defined period of time the solution is filtered, using a 0.45 mfilter, and calcium concentration is determined in the filtrate. A stabilization value S can be calculated using the following equation, where the residual calcium concentration of the blank test, the residual concentration of the test with product and the initially prepared concentration is included. The higher the stabilization, the more calcium carbonate was kept from precipitating compared with the blank. The following procedure and parameters were applied. A 100 ml sample containing 500 ppm calcium as CaCO.sub.3, 75 ppm CO.sub.3.sup.2 as CaCO.sub.3 and 440 ppm HCO.sub.3.sup. as CaCO.sub.3 were stored for one hour at 80 C. in the shaker bath. The pH of the sample was 8.6. The scale inhibition compositions were added to the calcium chloride dehydrate followed by the sodium carbonate and sodium bicarbonate. However, the order of addition is not particularly relevant and the scale inhibition compositions could be added to the carbonate solutions or added to the solution of calcium chloride di-hydrate, sodium carbonate and sodium bicarbonate.

[0042] The anti-scaling compositions were used at 5 ppm and 10 ppm total active solids. The ratio of the two-component and three-component blends are found in Table 3, and indicates the dosage of the individual compounds as ppm active solids.

TABLE-US-00003 TABLE 3 Dosage 1 Dosage 2 PAA PASP PMA Total PAA PASP PMA Total PAA 5 5 10 10 PASP 5 5 10 10 PMA 5 5 10 10 PAA + PMA 2.4 2.6 5 4.8 5.2 10 PMA + PASP 3 2 5 6.1 3.9 10 PAA + PASP 1.85 3.15 5 3.7 6.3 10 PAA + PASP + 1.3 2.25 1.45 5 2.6 4.5 2.9 10 PMA

[0043] A stabilization value S was calculated using the following equation,

[00001]$\mathrm{Stabilization}.Math..Math.S=\frac{\left({\left[{\mathrm{Ca}}^{2+}\right]}_{\mathrm{with}.Math..Math.\mathrm{product}}-{\left[{\mathrm{Ca}}^{2+}\right]}_{\mathrm{blank}}\right)}{\left({\left[{\mathrm{Ca}}^{2+}\right]}_{\mathrm{initial}}-{\left[{\mathrm{Ca}}^{2+}\right]}_{\mathrm{blank}}\right)}.Math.100.Math.\%$

[0044] wherein [Ca.sup.2+].sub.blank is the residual calcium concentration of the solution of calcium chloride di-hydrate and sodium oxalate in de-mineralized water, [Ca.sup.2+].sub.initial is the residual concentration of the solution of calcium chloride di-hydrate and sodium oxalate in de-mineralized water with anti-scaling product, and [Ca.sup.2+].sub.initial is the initially prepared Ca.sup.2+ concentration of the solution of calcium chloride di-hydrate and sodium oxalate in de-mineralized water. The higher the stabilization, the more calcium carbonate was kept from precipitating out compared to the blank.

[0045] Table 4, indicates the stabilization value S when the system was dosed at 5 ppm and 10 ppm active solids with the anti-scaling compositions. Table 4, also includes a theoretical Stabilization S value in percent, considering the stabilization efficiency of the individual polymers and the respective composition of the two-component and three-component blends. For example, the theoretical Stabilization value of the two-component blend can be calculated as follows: (c1*S1+c2*S2)/(c1+c2)=(1.85*35 +3.15*16)/5=23; wherein c1 and c2 are the anti-scaling chemicals, and S1 and S2 is the stabilization value of the individual anti-scaling chemicals c1 and c2.

TABLE-US-00004 TABLE 4 Stabilization Values Stabilization Theoretical Stabilization S (%) S (%) 5 parts-per- 10 5 10 million (ppm) ppm ppm ppm PAA 35 59 PASP 16 40 PMA 43 65 PAA + PMA 39 65 39 62 PMA + PASP 34 61 27 50 PAA + PASP 31 59 23 47 PAA + PASP + PMA 35 59 29 52

[0046] The calculated relative increase of the Stabilization value S given in % is shown in Table 5.

TABLE-US-00005 TABLE 5 Relative Increase of Stabilization S Relative Increase of Stabilization S 5 parts-per-million (ppm) 10 ppm PAA + PMA 0 5 PMA + PASP 26 22 PAA + PASP 35 26 PAA + PASP + PMA 21 13

[0047] For the two-component blend of polyacrylic acid with polymaleic acid the Stabilization value S measured corresponds with the theoretical value calculated from the results of the individual compounds. The other compositions show a synergistic stabilization effect and the Stabilization value is clearly higher than the values expected based on the results when the individual compounds were used separately.

Example 3

[0048] In many regulatory systems scale in the form of calcium oxalate and magnesium phosphate is generated. Example 3, compares the efficiency at inhibiting scaling of the present three-component blend with each of the individual polymers found in the blend and also with two-component blends of polyacrylic acid with polymaleic acid, polyaspartic acid with polymaleic acid, and polyacrylic acid with polyaspartic acid. The dosages are given in ppm as active solids for each product in Table 6.

Test Method

[0049] A constant volume flow of 2 [I/h] of a mixture prepared from a solution of calcium chloride di-hydrate, sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water was passed through a spiral metal capillary (length: 1 (m), inner diameter: 1.1 (mm)) placed in a heating bath at 90 C. The initial concentrations of calcium, oxalate, magnesium and phosphate used in this study were as follows: 5 mg/l calcium, 10 ppm oxalate, 230 ppm magnesium, 800 ppm phosphate. The pH was adjusted to 6.0. The scale inhibition compositions were added to the solution of calcium chloride di-hydrate followed by sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water.

[0050] The scale inhibition compositions were added to the solution of calcium chloride di-hydrate followed by sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water at 40 ppm total active solids. The ratio of the two-component and three-component blends were set to regulatory limits. Table 6 indicates the dosage of the anti-scaling compositions as parts-per-million (ppm) active solids.

TABLE-US-00006 TABLE 6 Anti-Scaling Dosages PAA PASP PMA Total PAA 40 40 PASP 40 40 PMA 40 40 PAA + PMA 19 21 40 PMA + PASP 14.8 24.3 15.7 40 PAA + PASP 10.4 25.2 40 PAA + PASP + PMA 10.4 18 11.6 40

[0051] A solution of calcium chloride di-hydrate, with and without anti-scaling polymers was mixed with sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water and pumped in a circuit from a flask through a capillary in the water bath, through a cooler and back to the flask. In the water bath a heat exchange occurred and the temperature of the solution increased. The solution was then passed through a cooler unit where an adjusted air flow from below caused evaporation of the solution. During the study, samples of the solution of calcium chloride di-hydrate, with and without anti-scaling polymers, sodium oxalate, magnesium chloride hexahydrate and di-sodium phosphate dodeca-hydrate in de-mineralized water were taken and filtered through a 0.45 p.m filter and concentration determinations of chloride, calcium, magnesium and phosphate were made.

[0052] The Cycles of Concentration (COC) were calculated as described in Example 1. Results are indicated in Table 7.

TABLE-US-00007 TABLE 7 Maximum Cycles of Concentration Maximum Cycles of Concentration PAA 3.0 PASP 1.9 PMA 2.0 PAA + PMA 2.1 PMA + PASP 2.0 PAA + PASP 2.0 PAA + PASP + PMA 3.0

[0053] The results indicated that a significantly higher COC can be reached by adding a third component to the two-component blend, while keeping the same dosage. The three-component blend surprisingly reaches the performance of the best polymer PAA although a high ratio of the lower performing PMA and PASP is part of the blend.