SE449485B - PROCEDURE FOR INHIBITING THE BUILDING OF THE FLAVOR OR SOLID PROVISIONS IN A WATER BASED SYSTEM AND COMPOSITION FOR IMPLEMENTATION OF THE PROCEDURE - Google Patents

Description

10 449 485 2 Sludge and paving stone deposits significantly reduce heat transmission capacity by sedimentation at low flow or 'flow points in the system and restricts the circulation of 'the water and insulate it from the heating surfaces. In addition to heating transmission and fluid flow are disturbed, corrosion is facilitated metal surfaces during deposition, since corrosion regulatory means can not come into contact with the surfaces of one effective way. The deposits also harbor bacteria.

Removal of the deposits can cause costly stoppages or interruptions and shutdowns of the system. Water at the relatively high temperatures prevailing in steam generating boilers as well hard water is especially prone to scale formation. Extremely severe scale deposits can cause localized overheating and breakage of boilers.

Since external treatments of the feed water to indu- radiation systems such as softening, coagulation and filtration do not satisfactorily removes solids and sub- punches that form solids, have different internal chemicals treatments have been used for the purpose of preventing and removing stone and sludge in water-based systems. The chemical treatment usually involves the combined use of a precipitator. agent and a solid conditioner to maintain the solid material in the boiling water in a suspended state for effective removal. The precipitating chemicals that commonly used for calcium salts are soda ash and sodium phosphates. Magnesium is precipitated by the alkalinity in the boiler or the boiler water as magnesium hydroxide.

A variety of polycarboxylates and other water-soluble, polar polymers - such as acrylate polymers have been used as solid substance conditioners in industrial water systems. The presence of small quantities of these polymers improves flowability for the precipitated sludge and results in the formation of amorphous, brittle and serrated precipitates instead of hard, dense ones crystals that form scale on surfaces. The finely dispersed solids the particles remain suspended and are removed from the system by partly by the water flow or by so-called blowing down.

The precipitation of scale-forming compounds can be prevented by inactivation of their cations with chelating sequestrants so that the solubility of their u 115 w 449 485 3 reaction products are not exceeded. Various nitrogen-containing compounds compounds such as ethylenediaminetetraacetic acid and nitrilotriacetic acid. acid has been used as a chelating agent in water treatment.

Phosphonates are widely used in water treatment as precipitation inhibitors and they are effective in threshold amounts which is significantly lower than the stoichiometric amount required for chelating or sequestering of the scale the cation.

U.S. Pat. Nos. 3,666,664 and 3,804,770 disclose paving inhibitors. which contain nitrilotriacetic acid or ethylenediamine tetraacetic acid and an organic aminomethylene phosphonate. Before- preferably the composition also contains a polymer such as a water-soluble sulfoxy-free polar addition polymer. The preferred The water-soluble anionic polymers are maleic anhydride and non-sulfonated styrene copolymers of U.S. Pat. No. 2,723,956 and U.S. Pat. No. 3,549,538, in which the copolymers are used with a nitrite compound, especially a nitrilotricarboxylic acid salt, which stensinhibitor. d U.S. Pat. No. 3,959,167 discloses a composition for inhibiting or prevent the accumulation of paving stones or the like on heating surfaces in a water-based system. The composition contains comprises an acrylic polymer, a water-soluble chelating agent, which may be nitrilotriacetic acid or ethylenediaminetetraacetic acid acid, and an organophosphonic acid, which may be aminotri (methylene- phosphonic acid) or a hydroxyalkylidene diphosphonic acid, such as oxyethylidene diphosphonic acid.

U.S. Pat. Nos. 4,255,259 and 4,306,991 disclose a composition to inhibit scale in aqueous systems, which comprises a copolymer of styrene sulfonic acid and maleic anhydride or maleic acid and a water-soluble phosphonic acid or salts hence. Various phosphonic acids including hydroxyethylidene diphosphonic acid, nitrilotri (methylenephosphonic acid) and other amino-methylene- phosphonic acids can be used. ' U.S. Pat. No. 5,650,937 discloses a composition for cooking or boiler water treatment, which contains a sulfonated polystyrene as dispersants and sludge conditioners and a optionally chelating agents such as nitrilotriacetic acid, ethylenediaminetetraacetic acid or their sodium salts. 4 The method of the invention for inhibiting formation of paving stones or solid deposits in a water-based system is characterized by the addition to the system of paving stone inhibitors quantities of the following components, separately or together, a) a copolymer of maleic acid or maleic anhydride and styrene sulfonic acid or a water-soluble salt thereof, which polymer has a molar ratio of styrene sulfonic acid to maleic acid or maleic anhydride of from about 1: 1 to about 4: 1 and a molar cooling weight of from about 1,000 to 25,000; b) an organic phosphonate of the general formula: R \ (cnzcnz) f-if n R Il wherein R is 9 -cH2--1 |> + oH, OH n is from 0 to 6, and x is from 1 to 6, or with the general men formula: w HO-P-C-P-OH of* H X OH wherein X is -OH or -NH 2, and R is an alkyl group having from 1 to carbon atoms, or a water-soluble salt thereof; and c) an aminocarboxylate chelating agent having the general for eln _ m RNE7 (CH2) x_å] 2 wherein x is 1 or 2, R represents - (CH 2) X - Z or -CHZCHZNE- (CH2) x-Z] and each group Z represents separately a group ~ COH, or a water-soluble salt thereof; wherein the composition has a weight ratio of copolymer to phosphonate of from about 10: 1 to about 1:10 and a weight ratio aminocarboxylate to copolymer of from about 50: 1 to about 1:10.

Correspondingly, the composition is characterized according to the invention that it includes a) from about 0.1 to 100 parts by weight of a copolymer of maleic acid or maleic anhydride and styrene sulfonic acid or a _ _......._. ~. »-...-.._-...-.-._....__._._ _ f: 449 485 , s water-soluble salt thereof, which copolymer has a molar content of containing styrene sulfonic acid to maleic acid or maleic acid anhydride of from about 1: 1 to about 4: 1 and a molecular weight of from about 1,000 to 25,000; ~ b) from about 0.1 to 100 parts by weight of an organic phosphonate with the general formula: :> 1v {(cr12cn2) x-Iš R n wherein R is R 1? -cHZ-glion-one, oH n is from 0 to 6, and x is from 1 to 6, or with it general formula: I 9 * f 1? Ho- P-c- P-on 1 1- Ho x on wherein X is -OH or -NH 2, and R is an alkyl group having from 1 to 5 carbon atoms, or a water-soluble salt thereof; and c) from about 0.1 to 100 parts by weight of an aminocarboxylate g-chelating compound of the general formula: RN |: - (cnzlx-zjz wherein x is 1 or 2, R represents- (CH 2) X -Z or -CH 2 CH 2 N [; (CH 2) X -Z] and each group Z a group -COOH, or a water-soluble salt thereof.

According to the present invention, surprisingly, good inhibition of deposition and formation of scale, shell or fixed provisions, in particular those containing ciumr and magnesium phosphates and silicates and iron oxide, on the metallic structures in industrial water systems.

The composition and procedure are effective when used in water at high temperatures and pressure in steam generating boilers 449 485 and the copolymer remains soluble in high hardness water and alkalinity. The invention exhibits the threshold effect of inhibition of the formation of metallic salt crystals and a preventing their adhesion to heat transfer surfaces at low treatment levels.

The chelating compounds used according to the above The present invention are water-soluble aminocarboxylates. The preferred aminocarboxylate chelating compounds are ethylenediaminetetraacetic acid and nitrilotriacetic acid. With others words in these preferred compounds are x 1 and all three Z the calves are the same. Nitrilotriacetic acid is a special drawn chelating agent.

According to the present invention, water soluble are used amino-alkylenephosphonic acids, hydroxy- or amino-alkylidene phosphonic acids phonic acids or their water-soluble salts. The preferred the compounds are amino-tri (methylenephosphonic acid), hydroxyethylidene- 1,1-diphosphonic acid and its water-soluble salts. Hydroxyethyl the 1,1-diphosphonic acid is especially preferred. Others suitable Phosphonic acids of these formulas include ethylenediaminetetra (metal tylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), triethylenetetraminehexa (methylenephosphonic acid), hexamethylenediamine tetra (methylenephosphonic acid), amino- propylidene diphosphonic acid, hydroxypropylidene diphosphonic acid, aminoethylidene diphosphonic acid, hydroxybutylidene diphosphonic acid and hydroxyhexylidene diphosphonic acid.

The aqueous solution used in the present invention the copolymer of maleic acid or maleic anhydride and styrene sulfonic acid or water-soluble salts thereof can prepared by copolymerization of maleic acid or maleic anhydride with styrene sulfonic acid or an alkali metal metal salt thereof. Conventional addition polymerization methods in the presence of light or free radical initiators can be used turned. Another way of preparing the copolymers is to copolymerize the maleic and styrene monomers and sulfonate the copolymer by conventional methods, such as with a sulfur trioxide-organic phosphorus compound as described in US 3 O72_618. The degree of sulfonation can vary but mainly complete sulfonation is preferred.

The relative proportions of styrene sulfonate and Maleic anhydride depends on the degree of bovine stenosis inhibition '10 449 485 7 as desired. The copolymer usually contains from about 10 to about 90 mole percent of the sulfonate. In general, molar holding styrene sulfonate units to maleic acid or 1 maleic anhydride derived units from about 1: 1 to about 4: 1 and especially from about 1: 1 to about 3: 1.

The average molecular weight of the copolymer is not critical, as long as the polymer is water soluble. Generally in- This means that the molecular weight is from about 1000 to about 000 and especially from about 6000 to about 10,000.

The aminocarboxylates, phosphonates and copolymers was usually used in the form of an alkali metal salt and usually as the sodium salt. Other suitable water-soluble salts include contains potassium, ammonium, zinc and lower amine salts. The free the acids can also be used and all acidic hydrates do not need replaced, nor does the cation need to be the same for them which has been replaced. Thus, the cation can be any of or a mixture of NH 4, H, Na, K, etc. The copolymer is converted to the water-soluble salts by conventional means methods. c g Although it is possible to add each of the components separately to a water-based system, it is common more appropriate to add them together in the form of a_ composition. The composition of the present invention comprises from about 0.1 to about 100, preferably from about 2 to about 6, parts by weight of the copolymer; from about 0.1 to about 100, preferably from about 0.5 to about 5, parts by weight of the phosphonate and from about 0.1 to about 100, preferably from about 0.5 to about 5, by weight. parts of the aminocarboxylate. The polymer and phosphonate were used in weight ratios that are usually between about 10: 1 and about 1:10, preferably from about 4: 1 to about 1: 4, and especially about 1: 1. In general, aminocarboxylate and the copolymer in weight ratios of from about 50: 1 to about 1:10, preferably from about 30: 1 to about 10: 1 and especially around 1821. The ratio of aminocarboxylate to phosphorus is usually from about 50: 1 to about 5: 1, preferably wise from about 20: 1 to about 5: 1 and especially from about : 1 to about 8: 1. 449 485 The compositions can be added as dry powders and are allowed to dissolve during use, but are normally used in the form of aqueous solutions. The solutions contain usually from about 0.1 to about 70% by weight of the component and preferably contains from about 1 to about 40% by weight. The solutions can be prepared by adding the components to water in any order.

The amount of composition added to the water is a substochiometric amount that is effective in * inhibit scale and sludge and depend on the nature of the based systems to be addressed. Phosphonate and aminocarboxy- the dosage depends to some extent on the amounts of hard causative and headstone-forming compounds which are being in the system. The copolymer dosage depends to some extent on concentration of suspended solids and excipient existing levels of solid material in the system. Composi- is usually added to the aqueous system in an amount of from about 0.01 to about 500 parts per million (ppm) and preferably from about 0.1 to about 50 parts per million of system water.

The compositions of the present invention may include or add to water containing other components agents commonly used in water treatment, such as alkali, lignin derivatives, other polymers, tannins, other phospho- nats, biocides and corrosion inhibitors. The composition can introduced at any place where it is rapidly and efficiently actively mixed with the water in the system. The treatment chemicals is usually added to the additive or feed water lines through which water enters the system. Typically one was used injector calibrated to deliver a predetermined amount periodically or continuously to the additive water (so-called water).

The present invention is particularly useful in determining action of alkaline boiling or boiling water, such as feed, smiles the additive water in a steam-generating boiler. Such forehead systems is usually operated at a temperature of from about 148 to about 336 ° C and a pressure of from about 0.34 to about 13.8 MPa overpressure. 449 485 The composition and method of the present invention invention is illustrated by the following examples, in which parts refer to parts by weight, unless otherwise stated.

EXAMPLES 1 AND 2 Aqueous solutions of a composition containing some hydroxyethylidene diphosphonic acid, some nitrilotriacetic acid acid and three or six parts of a sodium styrene copolymer pure sulfonate and maleic anhydride were prepared. Treatment the solutions also contain sodium phosphate, sodium sulphate, sodium sodium sulfite, sodium hydroxide and sodium chloride in amounts such as are sufficient to give the boiler water composition shown below in Table I. Solutions containing the same amounts of the action chemicals and the same parts of each component of the composition was also prepared.

Sludge conditioning and paving stone inhibitory properties for these solutions were evaluated in a small laboratory boiler; which had three removable tubes as described in the Procedure dings of the Fifteenth Annual Water Conference, Engineers Society of Western Pennsylvania, pp. 87-102 (1954). Feeding water net for the laboratory boiler was prepared by diluting tap water from Lake Zurich, Illinois, with distillation water to 40 ppm total hardness as CaCO3 and additive of calcium chloride to provide a ratio of elements to tartar calcium to magnesium of 6 to 1. Feed water and the chemical treatment solutions were fed to the boiler in a holding 3 volumes of feed water per 1 volume of solution, which gives a total hardness in the feed water of 30 ppm 'CaCO3. Pannstens- the experiments for all treatment solutions were performed by adjusting the boiler inflation to 10% of the boiler feed water, giving approximately 10 concentrations of boiler salt solutions, and adjusting the composition of the treatment the solution to form a boiler water after these 10 concentrations with the composition shown in Table I.

ZS I ss 449 485 1 '' lo TABLE I Sodium hydroxide as NaOH 258 ppm Sodium carbonate as Na2CO3 120 ppm = Sodium chloride as NaCl 681 ppm Sodium sulfite as Na2SO3 7 50 ppm Sodium sulfate as Na 2 SO 4 819 ppm Silica as S102 less than 1 ppm Iron such as Fe less than 1 ppm Phosphate as P04 at 10-20 ppm The paving tests were carried out for 45 hours each at one boiler pressure of 2.8 MPa overpressure. At the end of the experiment, the removal the boiler tubes were separated from the boiler and the boiler stone or the deposit present at 15.2 cm of the central length of each tube was removed by scraping, collected in a weighed ampoule and weighed. The results of the experiments are reported in a table II. ' TABLE II Dosage of Pannstens- additive reduction Experiment no. Additives in Feed (ppm) (%) 1 Styrene sulfonate and 0.5 66.1 maleic anhydride copolymer (I) 2 Hydroxyethylidene- _. 0.5 20.0 phosphonic acid (II) 4 Nitrilotriacetic acid - 1.0 _ 6.0 (III) p_ - s 1 + 11 + 111 0.5 95.5 (3: 1: 1 active) 6 I + 11 + 111 9.5 ”. 96.0 - (6: 1: 1 active] Comparison results for 'paving stone' reported in table II illustrates that the composition and the process of the present invention provides an inhibition of paving stone formation which is considerably larger than that of is obtained when the components are added separately. .hrs _449 485 ll EXAMPLE 3 The same laboratory boiler was used to study the efficacy the activity of the composition of the present invention and each of its components as additives then it to prevent the formation of new paving stones or the removal of those of existing pavers in an already paved boiler.

The boiler was first driven so that the headstone formed on the tubes and the boiler water surfaces. Amount of calcium phosphate (hydroxyapatite) - The paving stone was determined during several experiments.

After removing the boiler, the boiler was turned off removal of a tube sample and determination of the initial one the amount of paving stones on the tubes. The operation continued in more than 45 hours using feed or feed water containing 30 ppm (as CaCO 3) total hardness and treatment the additive. Other boiler water chemicals such as those used written in Examples 1 and 2 were also used. Boiler water pressure was 2.8 MPa overpressure and the boiler water concentration was ten times.

The headstone deposited on the test tubes was 5.98 grams (on average) during the first step (removal of paving stones) and an additional 8.99 grams during the second step, where any additive treatment (zero test) was not performed. The results of the experiments are reported in Table III.

TABLE III Dose additive- Tartar- Tartar- ~ funds in Feed formation reduction Attempt (ppm) speed (%) Nr. Additive 7 (g / m2) 1 blank test (no additive - 96.67 - average) 2 styrene sulfonic acid and 2 (0.75) 100.8 maleic anhydride (I) 3 Hydroxyethylidene diphosphono- 3 16.3 83.1 acid (II) 4 Nitrilotriacetic acid (III) 3 39.14 59.5 I + II + III (3: 1: 1 2 (6.99) 107.2 active) - 449 485 12 The results show the surprisingly good efficiency for the composition and method of the present invention finning when it comes to removing existing paving stones. we!

Claims (19)

13 449 485 PATENT CLAIMS A process for inhibiting the formation of scale or solid deposits in an aqueous system, characterized in that scale inhibiting amounts of the following components are added to the system, separately or together, a) a copolymer of maleic or maleic anhydride and styrene sulfonic acid or a water-soluble salt thereof, which copolymer has a molar ratio of styrene sulfonic acid to maleic acid or maleic anhydride of from about 1: 1 to approx. 4: 1 and a molecular weight of from approx. 1000 to 25000; b) an organic phosphonate of the general formula: R 1 I / (CH 2 CH 2) or having the general formula: wherein Ho is -OH or -NH 2, and R is an alkyl group having from 1 to S carbon atoms, or a water-soluble salt thereof; and 0 - -on oa X-'CÜ 'W c) an aminocarboxylate-chelating compound of the general formula: Rn -27 and each group Z individually represents a group -COOH, or a water-soluble salt thereof; wherein the composition has a weight ratio of copolymer to 449,485 phosphonates of from about 10: 1 to approx. 1:10 and a weight ratio of aminocarboxylate to copolymer of from approx. 50: 1 to approx. Ino. 1 Process according to Claim 1, characterized in that the weight ratio of copolymer to phosphonate is from approx. 4: 1 to approx. 1: 4. 3. A method according to claim 1 or 2, characterized in that the components are added to the aqueous F system in the form of a composition in an amount of from approx. 0.01 to approx. 500 million parts of system water. _ 4. A process according to any one of claims 1-3, characterized in that the phosphonate is a hydroxyalkylidene phosphonic acid or a water-soluble salt thereof. 5. A process according to claim 4, characterized in that the phosphonate is hydroxyethylidene-1,1-diphosphonic acid or a water-soluble salt thereof. 6. A process according to any one of claims 1-5, characterized in that the aminocarboxylate is nitrilotriacetic acid or a water-soluble salt thereof. 7. A process according to any one of claims 1-6, characterized in that the phosphonate is hydroxyethylidene-1,1-diphonic acid and that the aminocarboxylate is nitrilotriacetic acid. A method according to any one of claims 1-7, characterized in that the water-based system is a steam-generating boiler and that the components are added to the boiler water. 9. Process according to any one of claims 1-8, characterized in that the components are added as a composition in the form of an aqueous solution comprising from approx. Z to approx. 6 parts by weight of the copolymer and from approx. 0.5 to approx. 5 parts by weight each of the phosphonate and aminocarboxylate-chelating agent, and that the composition is added in an amount of from about 0.1 to approx. 50 million parts of system water. 10. A process according to any one of claims 1-9, characterized in that the copolymer is a copolymer of styrene sulfonic acid and maleic anhydride having a molecular weight of from about 6000 to approx. 10,000 and a molar ratio of styrene sulfonate to maleic anhydride of from about 1: 1 to approx. 3: 1. 11. A composition for inhibiting the formation of paving stones f) a or solid deposits in an aqueous system, characterized in that it comprises a) from approx. 0.1 to 100 parts by weight of a copolymer of maleic acid or maleic anhydride and styrene sulfonic acid or a water-soluble salt thereof, which copolymer has a molar ratio of styrene sulfonic acid to maleic acid or maleic anhydride of from about 1: 1 to approx. 4: 1 and a molecular weight of from approx. 1000 to 25000; b) from approx. 0.1 to 100 parts by weight of an organic phosphonate of the general formula: R 1 / (CH 2 CPI 2); x is from 1 to 6, or with the general formula: -OH H 0 II Ho-g- H X_O "FU O °" " And c) from about 0.1 to 100 parts by weight of an aminocarboxylate chelating compound of the general formula: RN 2; (cH 2) X -272 wherein X is 1 or Z R represents - (CH 2) X 2 or -CH 2 CH 2 N [E (CH 2] x 2] and each group Z separately represents a group -COOH, or a water-soluble salt thereof. 12. A composition according to claim 11, characterized in that it has a weight ratio of copolymer to phosphonate of from about 10: 1 to approx. 1:10 and a weight ratio of aminocarboxylate to copolymer of from about 50: 1 to approx. 1:10. 449 485 16 13. A composition according to claim 11 or 12, characterized in that it has a weight ratio copolymer to phosphonate of from about 4: 1 to approx. 1: 4. Composition according to any one of claims 11-13, characterized in that the phosphonate is a hydroxyalkylidene phosphonic acid or a water-soluble salt thereof. 15. A composition according to claim 14, characterized in that the phosphonate is hydroxyethylidene-1,1-diphosphonic acid or a water-soluble salt thereof. Composition according to any one of Claims 11 to 15, characterized in that the aminocarboxylate is nitrilotriacetic acid or a water-soluble salt thereof. Composition according to any one of claims 11-16, characterized in that the phosphonate is the hydroxyethylidene-1,1- -diphosphonic acid and that the aminocarboxylate is nitrilotriacetic acid. Composition according to any one of claims 11-17, characterized in that it is an aqueous solution. 19. A composition according to any one of claims 11-18, characterized in that the composition comprises from approx. 2 to approx. 6 parts by weight of the copolymer and from approx. 0.5 to approx. 5 parts by weight each of the phosphonate and aminocarboxylate.kelate-forming compound.