MXPA99006323A - An organic multifunctional composition for the treatment of water with high silica content and stability rating, for colling towers - Google Patents

Abstract

La presente invención se refiere a un paquete multifuncional de productos químicos para tratamiento de aguas de enfriamiento con alto contenido de sílice eíndice de estabilidad, mediante los cuales es posible mantener bajo control los problemas de corrosión, incrustación, ensuciamiento, dispersión, formación de lodos y crecimiento microbiológico, permitiendo operar a elevados ciclos de concentración el agua de repuesto, con lo cual se obtiene un alto nivel de eficiencia y amplias ventajas técnicas, económicas y ecológicas.

Description

MULTIFUNCTIONAL ORGANIC COMPOSITION FOR THE TREATMENT OF WATER WITH HIGH SILICA CONTENT AND STABILITY INDEX, FOR COOLING TOWERS.

DESCRIPTION TECHNICAL FIELD OF THE INVENTION The present invention relates to a water-soluble organic multifunctional composition, which has a high efficiency for the chemical treatment of water of cooling towers with high silica content and stability index, which allows to maintain an adequate control of corrosion, incrustation and dispersion in the heat exchange equipment, also avoiding the tendency to fouling the process equipment, as well as the control of bacterial growth. It also favors the reduction of contamination with heavy metals from the effluents of the refinery and chemical plants, since it is a multifunctional product whose chemical composition is totally organic and biodegradable.

BACKGROUND OF THE INVENTION The water used in cooling towers contains cations, such as calcium, magnesium, sodium, potassium, etc. and various anions such as bicarbonates, carbonates, sulphates, phosphates, silicates, etc. When these anions and cations are combined in concentrations where the solubility of their reaction products is exceeded, they precipitate. The solubility of the components present varies for the following reasons: concentration of salts, changes in pH, and temperature; as well as by the introduction of additional ions that form insoluble compounds with the ions already present in the solution.

These reaction products precipitate on the surfaces of the cooling system, forming deposits, whose accumulation prevents effective heat transfer, interferes with the flow of water, facilitates corrosive processes and bacterial growth. This is a big problem in the cooling tower systems, as the stoppages are increased by cleaning and removing deposits.

Likewise, corrosion in heat exchange equipment and interconnection lines increases operating costs due to stoppages and maintenance, which significantly reduces the useful life of the aforementioned equipment.

For the control of corrosion, incrustation and dispersion of inorganic materials, as well as microbiological control, the following products have been previously used: CORROSION CONTROL.

For the control of this phenomenon caused by the presence of dissolved oxygen in the recirculating water, as well as by the presence of other pollutants coming from the main process such as: ac. sulfhídrico, hydrocarbons, ammonia, etc., have been used various compounds based on chromium and zinc, which showed a satisfactory behavior in this application, however the frequent use of these products has caused pollution problems in receiving bodies such as: rivers and lagoons, for which the elimination of chromium compounds has been recommended and the consumption of zinc-based compounds has been restricted, concentrating in this case the concentration to values lower than 2.0 ppm in the tributaries of refineries and chemical plants.

CONTROL OF INCRUSTATION.

To avoid the formation of deposits of encrusting salts of low solubility, chelate-type compounds such as ac have been used. ethylene diamine tetraacetic, ac. triacetic nitrile and its salts that favor the solubilization of calcium and magnesium compounds; likewise to reduce the tendency to crystallization and deposit formation of these compounds, various compounds have also been used, such as ac. amino trimethylene phosphoric, ac. hydroxyethylidene diphosphonic and polymers of low and medium molecular weight based on ac. acrylic and acrylamide.

CONTROL OF ENSUCIAMIENTO.

The presence of dissolved salts, organic matter and various pollutants in the water used in the cooling systems, cause the gradual formation of hard and adherent bacteriological deposits mainly on the metallic surfaces of heat exchange equipment, reducing the efficiency of these and causing severe problems of clogging, corrosion and fouling.

To keep under control the formation of deposits of organic and inorganic materials such as clays, mud, silt, natural polymeric materials, such as tannins and lignin derivatives (lignosulfonates) have been used; however, these mentioned compounds have as their main drawback their high susceptibility to chemical or biological degradation, which further reduces their efficiency. At present, non-ionic biodispersants are used that keep the organic matter in suspension and reinforce the action of the oxidizing and non-oxidizing biocides.

MICROBIOLOGIC CONTROL.

Due to the high degree of contamination of the recirculation water in the cooling towers, the growth of various microorganisms such as bacteria, algae, fungi, yeasts, etc., which promote the formation of deposits of organic material on the heat exchange surfaces and connection lines, as well as in specific cases, the corrosion below these deposits in the form of pitting (pitting) as those that occur in the case of reducing sulphate bacteria.

To prevent the growth of the aforementioned microorganisms, compounds such as chlorine have been used, in combination with brominated biocides, quaternary ammonium salts and other organic compounds that have limited efficiencies under certain conditions, so that in some cases specific biocides are required. such is the case of aldehyde-type oxidant biocides that keep microbiological growth under control.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multifunctional package of "All Organic" chemicals for the treatment of cooling water with high silica content and stability index, by means of which it is possible to keep under control the problems of corrosion, scaling, dispersion, sludge formation and microbiological growth, allowing to obtain high efficiency and extensive technical, economic and ecological advantages.

The composition object of the present invention has a highly satisfactory behavior for the control of corrosion, fouling and fouling problems that generally occur in cooling systems with high silica content and stability index.

The product IMP-TE-511 contains in its formulation two organic corrosion inhibitors of the phosphonocarboxylic type and salts derived from the triazole. With the continuous use of these products at dosages in the range of 20-80 ppm it is possible to keep under control the corrosion rates for the parts made of carbon steel and yellow metals, such as: copper and copper alloys; less than 5 mpa for carbon steel and less than 0.5 mpa for admiralty. It additionally presents as an ecological advantage that it does not contain zinc-chromium, thus complying with the specifications established by the Ministry of the Environment, without the above resulting in a lower efficiency in terms of protection against corrosion.

For the control of the formation of encrusting salts on the metallic surfaces of the cooling systems, the formulation object of the present invention contains a mixture of two derivatives of phosphonic type, reinforcing this effect with a terpolymer of low molecular weight specific for silica of last generation, obtaining efficiencies of inhibition to the incrustation of calcium as calcium carbonate and silica as such by more than 90% in laboratory and pilot plant tests.

The non-ionic type biodispersant is applied together with the oxidizing and non-oxidizing biocides, which increases the penetrating power of the chlorine, reinforcing its bactericidal action, resulting in a greater dispersion of the organic matter in the cooling systems.

To maintain microbiological control, a pair of non-oxidizing aldehyde-type biocides that inhibit the growth of bacteria, algae, fungi and yeasts are used.

The objectives of the present invention are: 1. To provide a fully water soluble multifunctional chemical composition that successfully inhibits fouling, corrosion, fouling and biological growth in cooling water systems with high silica content and stability index due to low alkalinity and total hardness, which presents a characteristic main that does not add heavy metals, since it is a completely organic product. 2. It allows the saving in the consumption of spare water to the cooling towers, up to 55% reached a greater number of concentration cycles without presenting incrustation, corrosion and fouling problems. 3. Ecologically the water coming from purges in cooling towers when applying the IMP-TE-511 will not contain heavy metals, because the chemical composition of this is "All Organic". 4. In waters that contain high hardness and high concentration of silica it manages to effectively disperse these materials, preventing their precipitation and thus preventing them from depositing on metal surfaces, reducing fouling in cooling systems by up to 20%, which makes it possible to avoid plant shutdowns not foreseen, continuing with the production programs and having a significant saving by cleaning in the heat exchange equipment.

. The non-oxidizing aldehydic biocides contained in IMP-TE-511 maintain a total bacterial count of less than 300,000 col / ml. and a reducing bacterial sulfate count of less than 8 col / ml.

The composition of the present invention is presented in a liquid, amber color, pungent odor with the following composition: COMPONENT% WEIGHT Hydroxy phosphonocarboxylic acid 5-45 Triazole 2-18 Organic polymer K-T-7800 5-35 l-Hydroxyethylidene 1,1, diphosphonic acid 2-45 Monoethanolamine 2-50 Sodium hydroxide 10-70 Demineralized water 5-50 It contains 5-45% by weight of hydroxy phosphonocarboxylic acid, 2-18% by weight of triazole both used as corrosion inhibitors, of 5-35% by weight of organic polymer KT-7800, of 2-45% by weight of 1-hydroxyethylidene 1,1, diphosphonic acid, 2-50% by weight of monoethanolamine, 10-70% by weight of sodium hydroxide and 5-50% by weight of demineralised water.

The hydroxy phosphonocarboxylic acid compound present in the formulation promotes the formation of a protective film, with a thickness of several molecules, on the metal surfaces which constitutes a mechanical and electrochemical barrier that passivates the metal against corrosive attack. This film has a high degree of thermal stability and oxidation and is not easily removed.

The hydroxy phosphonocarboxylic acid active component of the present invention has the following formula: OH The compound with chemical structure of the group of triazoles whose chemical formula is shown below, works by reacting with copper and its alloys, giving rise to an insoluble polymer complex.

This complex promotes the formation of a protective layer or film on the surface of yellow metals such as copper with a thickness of several molecules, which constitute a mechanical and electrochemical barrier against corrosive attack. This layer or film possesses a high degree of thermal and oxidative stability and is not easily removed.

The low molecular weight organic terpolymer K-T-7800 present in the composition object of the invention works by dispersing the particles that are in solution, inhibiting the precipitation of calcium carbonate salts and silica as such specifically.

The phosphonated active component present in this invention has the following structural chemical formulation.

OR The usefulness of this compound is that it is an extremely effective stabilizer for aqueous solutions supersaturated, especially with calcium carbonate, but also with calcium sulphate and other salts or hydroxides which are difficult to dissolve.

The mechanism of action of this inhibitor supposes an adsorption of the same in the points of growth of the crystals, giving origin to a deformation of the same one and avoiding an ordered crystallization.

Another of the phosphonated compounds present in the invention has the following chemical formula.

HO OH OH I I I HO - P - C - P - OH II I II OR CH3 O This compound has properties as a sequestrant, manifesting itself in an ability to form metal ion complexes at stoichiometric concentrations, it also has properties as a dispersant of solid materials and inhibition of precipitation, as well as as a high thermal stability due to its resistance to decomposition in aqueous solutions under conditions of high temperature and extreme pH conditions.

EXAMPLES EXAMPLE 1 In a 1 liter glass vessel provided with cooling jacket and mechanical stirring, 180.0 g were placed. of demineralized water and 200.0 g. of hydroxy phosphonocarboxylic acid 50% by weight, this mixture had a pH of about 1.69.

Then 100 g were added. of l-hydroxyethylidene 1,1-diphosphonic acid at 60% by weight and 200 g. of the K-T-7800 terpolymer without variation in temperature and pH.

Subsequently, 41.6 g was slowly added. of Monoethanolamine, observing gas evolution and a small increase in temperature. Then 187.0 g were slowly added. of 50% sodium hydroxide, an increase in temperature was observed until approximately 70 ° C was reached, therefore a cooling system was required without suspending the agitation and as a consequence the pH of the solution was increased by more than 12, It was important to keep stirring and cooling until a temperature below 30 ° C was reached, at which time 50 g was added. of Triazole and 41.4 g. of demineralized water.

During the procedure it was necessary to make sure to maintain the agitation in the container, as well as to prevent the temperature of the contents of the container from exceeding 80 ° C. In addition, the addition of a new reagent was done when the contents of the container were at a temperature below 30 ° C.

A product with the following characteristics was obtained: Appearance Dark brown liquid (amber). Specific gravity, at 20/4 ° C 1.35 Brookfield viscosity, cPs at 20 ° C 200 max. APHA color 14 pH of the 1% solution 12 EXAMPLE 2 In a 1 liter glass vessel provided with cooling jacket and mechanical stirring, 350.0 g were placed. of demineralized water and 200.0 g. of hydroxy phosphonocarboxylic acid 50% by weight, this mixture had a pH of approximately 2.69.

Then 100 g were added. of l-hydroxyethylidene 1,1, diphosphonic acid at 60% by weight and 180 g. of the K-T-7800 terpolymer without variation in temperature and pH.

Subsequently, 41.6 g was slowly added. of Monoethanolamine, observing gas evolution and a small increase in temperature. Then 87.0 g were slowly added. of 50% sodium hydroxide, an increase in temperature was observed until approximately 70 ° C was reached, therefore a cooling system was required without suspending the agitation and as a result the pH of the solution was increased by approximately 10, it was important keep stirring and cooling until a temperature lower than 30 ° C was reached, at that time 30 g was added. of Triazole and 11.4 g. of demineralized water.

During the procedure it was necessary to make sure to maintain the agitation in the container, as well as to prevent the temperature of the contents of the container from exceeding 80 ° C. In addition, the addition of a new reagent was done when the contents of the container were at a temperature below 30 ° C.

A product with the following characteristics was obtained: Appearance Dark brown liquid. Specific gravity, at 20/4 ° C 1.20 Brookfield Viscosity, cPs at 20 ° C < 200 Color APHA 9 pH of the solution 1% 10.0 EXAMPLE 3 In a 1 liter glass vessel provided with cooling jacket and mechanical stirring, 125.0 g were placed. of demineralized water and 220.0 g. of hydroxy phosphonocarboxylic acid 50% by weight, this mixture had a pH of about 1.29.

Then 100 g were added. of l-hydroxyethylidene 1,1-diphosphonic acid at 60% by weight and 220 g. of the K-T-7800 terpolymer without variation in temperature and pH.

Subsequently, 46.6 g was slowly added. of Monoethanolamine, observing gas evolution and a small increase in temperature. Then 197.0 g were slowly added. of 50% sodium hydroxide, an increase in temperature was observed until approximately 70 ° C was reached, therefore a cooling system was required without suspending the agitation and as a result the pH of the solution was increased up to 12.5, it was important to keep stirring and cooling until a temperature below 30 ° C was reached, at which time 50 g was added. of Triazole and 41.4 g. of demineralized water.

During the procedure it was necessary to make sure to maintain the agitation in the container, as well as to prevent the temperature of the contents of the container from exceeding 80 ° C. In addition, the addition of a new reagent was done when the contents of the container were at a temperature below 30 ° C.

A product with the following characteristics was obtained: Appearance Dark brown liquid (amber). Specific gravity, at 20/4 ° C 1.41 Brookfield viscosity, cPs at 20 ° C > 200 Color APHA 14 pH of the solution 1% 12.5 EXAMPLE 4 In this example, the results of the laboratory-level evaluation of the formulations reported in Example 1 to 3 are shown 1. - INHIBITION TO THE PRECIPITATION OF CaCO3 Method IMP-PE-II-1 In this procedure, 500 ml is measured. of spare water according to the refinery to be studied in this case from Minatitlán, Ver., the selected dosage of inhibitor is added, they are agitated and maintained in heating at 65 - 70 ° C, controlling the pH to the optimum selected in this particular case 8.1 until reaching the volume corresponding to 3 or 5 concentration cycles as appropriate.

Calcium is determined by titration with EDTA.

RESULTS Efficiency at inhibition% Dosage ppm 40 60 80 Example 1 84 89 98 Example 2 55 61 75 Example 3 68 75 87 2. - INHIBITION TO THE PRECIPITATION OF CaSO4 Method NACE-ST-TM-03-74 In this procedure, equal volumes of test solutions a and b are mixed in bottles, the selected dosage of the inhibitor is added, stirred and kept under heating at 71 ° C / 72 hrs.

Calcium is determined by titration with EDTA. Composition of the brines: a) H.l g / I of CaCl2 2H2O 7.5 g / 1 NaCl b) 7.5 g / 1 NaCI 10.66 g / 1 NaSO4 RESULTS Efficiency at inhibition% Dosage ppm 40 60 80 Example 1 91 94 96 Example 2 62 70 82 Example 3 76 78 84 3. - DISPERSION OF CAOLÍN.

ROHM AND HAAS method. In this procedure a test dispersion is prepared, with the following components: 430 ml of a solution containing 200 ppm CaCO3 (CaCl2 as CaCO3) and 0.43 g of coalin (1000 ppm kaolin).

In this procedure, a test dispersion is prepared by mixing 430 ml of a CaCl2 solution equivalent to 200 ppm as CaCO3 0.43 g of kaolin (equivalent to 100 ppm of kaolin) and the dispersing product to be evaluated (0.5% weight). The pH is then adjusted to 7.5 in soda solution, the mixture is stirred in a blender for 10 minutes and the Brookfield viscosity is determined at 20 ° C.

RESULTS Viscosity cPs Example 1 17.2 Example 2 52 Example 3 92 It is observed that Example 1 has a lower viscosity because the clay is better dispersed. 4. - DISPERSION OF IRON OXIDE.

ROHM AND HAAS method. A solution is prepared containing: 200 ppm of CaCl2 as CaCO3 (430 ml) 0.30 of FeO3 (700 mg / 1 Fe2O3) The pH of the test solution is adjusted to 7.5 with soda solution, 60 ppm of the additive to be evaluated is added and the mixture is stirred for 15 minutes.

RESULTS TURBIDEZ, NTU Example 1 90 Example 2 57 Example 3 70 It is noted that Example 1 has a higher turbidity due to the higher iron content it has in suspension.

. - INHIBITION TO CORROSION.

Corrosion Method 83 paper No 281 In this procedure a corrosive solution with the following composition is used.

RESULTS mg / 1 CaCl2.2H2O 442 MgSO4 120 Na2SO4 360 NaHCO3 61 Equivalent to: 17 400 ppm of hardness as CaCO3 10 ppm of alkalinity as CaCO3 The pH is adjusted with soda to 6.5 The carbon steel and admiralty test cores are immersed in the test solution for 20 hrs at room temperature, with constant aeration. The efficiency is deterd by the inhibition by weight difference.

RESULTS Efficiency to corrosion in% Dosage ppm 60 80 Example 1 90 94 Example 2 50 63 Example 3 65 70 As can be seen the formulation reported in example 1 shows better behavior in the tests of inhibition to the incrustation, inhibition to corrosion, dispersion of kaolin and dispersion of iron oxide.

EXAMPLE 5 A cooling tower was built at the pilot plant level to evaluate the product IMP-TE-511 as shown in the following diagram: (see next page) The test conditions were as follows: 1.- Water test medium containing the following characteristics: (ppm as CaCO3) Total hardness 100 Calcium hardness 36 Magnesium hardness 64 Alkalinity at "M" 90.2 Silica 27 Copper 0.03 Iron 0.07 Chlorides 7 Turbidity 5 FTU Suspended solids. 3 Dissolved total solids 176.8 H 7.1 Bact plate count / ml 900,000 Sulfate-reducing bacteria NM P / 100 ml 7 2.- Operating conditions. • Test time 17 days. • Inlet temperature 30 ° C • Exit temperature 42 ° C • System pH 8.0 a. 8.2 • Flow 4 gallons / te • Speed 3 ft / sec.

Results obtained. 9 cycles of concentration were reached in the recirculating water with a slightly corrosive stability index of 6.8 to 7.3 and the following corrosion rates were obtained: Admiralty 0.09 mpa Coal steel 1.89 The characteristics of the water after 9 cycles of concentration were those listed below. (ppm as CaCO3) Total hardness 532 Calcium hardness 245 Magnesium hardness 287 Chlorides 140 Alkalinity at "M" 130 Silica 242 ppm Turbidity 12 FTU Total dissolved solids 948 ppm pH 8.1 Plate count 950 Bact / ml Reducing sulfate bacteria 2 NM P / 100 ml stability index 6.5 The results obtained at the pilot plant level verify the results obtained at the laboratory level, which indicates that the formulation reported in example 1 presents a satisfactory behavior to inhibit the incrustation, corrosion and dispersion to maintain in suspension the solids present in the water of cooling systems that have a high silica content and stability index.

It is also observed that due to the effect of the biodispersant, reinforced by the effect of the microbiocide, an adequate control of microbiological growth is maintained.

A total bacterial count of less than 300,000 col / ml counts for reducing sulphate bacteria less than 8 col / ml is maintained.

Claims (3)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the contents of the following clauses are claimed from our property:

1. An organic multifunctional composition for the treatment of water with high silica content and stability index, for cooling towers, characterized in that it contains 5-45% by weight of hydroxyphosphonocarboxylic acid, 2-18% by weight of triazole both used as corrosion inhibitors, of 5-35% by weight of the organic terpolymer KT-7800, of 2-45% by weight of l-Hydroxyethylidene 1,1, diphosphonic acid, of 2-50% by weight of monoethanolamine, of 10-70 % by weight of sodium hydroxide and 5-50% by weight of demineralized water.

2. A water-soluble multifunctional composition, according to clause 1, characterized in that it inhibits corrosion, fouling, fouling and microbiological growth in water for cooling systems.

3. A multifunctional composition according to clauses 1 and 2, characterized in that due to its organic nature it does not contain heavy metals and therefore does not contribute to increasing the concentration thereof in aqueous effluents of chemical plants and refineries. A multifunctional composition according to clauses 1-3, characterized in that it allows the concentration of solids in cooling waters to be increased up to 9 times, thus contributing to a significant saving in the spare water requirements in these equipments and consequently to a decrease in the electric power consumption of the replacement water dosing equipment. A multifunctional composition according to clauses 1-4, characterized in that it presents a high efficiency of inhibition to scaling even in cooling systems whose recirculation waters contain high concentrations of calcium, magnesium and silica salts. A multifunctional composition according to clauses 1-5, characterized in that it presents a high efficiency of dispersion of solids in cooling systems with high silica content and stability index, which allows to reduce the contamination in the tubes of the exchange exchangers thermal and consequently reduce operating costs for cleaning and maintenance of these equipment. A multifunctional composition according to clauses 1-6, characterized in that it allows microbial growth to be kept under control in cooling water systems with high silica content and stability index, which in turn allows to significantly reduce corrosion and fouling , which occurs below the deposits of organic material in heat exchangers. A multifunctional composition according to clauses 1-7, characterized in that it keeps under control the corrosion in copper pipes and their alloys, as well as the other carbon steel components of the heat exchangers in cooling systems.