WO2018040097A1

WO2018040097A1 - Composition and method for controlling, preventing and/or reducing formation of inorganic scale, and use of composition

Info

Publication number: WO2018040097A1
Application number: PCT/CN2016/098065
Authority: WO
Inventors: Fengyang LI; Yan Xu; Kaiyi XU; Lan XIAO
Original assignee: Kemira Oyj; Kemira (Asia) Co., Ltd.
Priority date: 2016-09-05
Filing date: 2016-09-05
Publication date: 2018-03-08
Also published as: CN109661378A

Abstract

Provided is a composition for controlling, preventing and/or reducing the formation of inorganic scale and/or deposits in an aqueous system. The composition comprises a copolymer of phosphinic acid and (meth) acrylic acid or its salt (s), a polycarboxylic acid or its salt (s), at least one monomeric phosphonate comprising phosphonic acid groups, at least one corrosion inhibitor comprising amine groups, and at least one chelating agent. Further disclosed is use of the composition in an aqueous system having water hardness as calcium carbonate in the range of 50–1500 ppm.

Description

COMPOSITION AND METHOD FOR CONTROLLING, PREVENTING AND/OR REDUCING THE FORMATION OF INORGANIC SCALE, AND USE OF COMPOSITION

TECHNICAL FIELD

The invention relates to a composition for controlling, preventing and/or reducing the formation of inorganic scale and/or deposits in an industrial aqueous system and its use according to the preambles of the enclosed independent claims.

BACKGROUND OF ART

Scaling of undesired, sparingly-soluble inorganic salts onto process surfaces is a major problem in several industrial processes. Scaling occurs when a solution contains more dissolved solute than it is possible for saturated solution and salt precipitates spontaneously from the aqueous phase, generally onto different surfaces in the process environment and forms scale. For example, when water is heated or cooled scale is typically formed on heat transfer equipment, such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. The formation of scale on heated surfaces causes the heat transfer coefficient to decline with time. Often the only option is to shut down the process and perform a cleanup. Scaling may also cause equipment failures, production losses, costly repair and higher operating costs. Changes in pH may also lead to scaling.

Carbonate salts, especially calcium carbonate, is common inorganic compound found in process scales. Solubility of carbonate scale (CaCO3) reduces with increasing temperature. Currently, most of carbonate scale inhibitors in the market for aqueous processes work at temperatures less than 100℃. Furthermore, conventional scale inhibitors are not effective in temperaturesranging from 120 to 250℃, but they may degrade at high temperatures. In addition, the few available scale inhibitors in the market which are suitable for temperature conditions higher than 100 ℃, have pH less than 2, even less than 1. Thus, the serious side effect caused by these scale inhibitors is increased corrosion risk. Further, the conventional scale inhibitors are not effective at high water hardness of the aqueous system.

Various industries, such as oil exploitation and refinery, geothermal resource production, coal gasifiers, have strong need for scale inhibitor, especially for carbonate scale inhibitor, which could tolerate harsh process conditions and elevated temperatures without exposing the process equipment for increased corrosion risk.

SUMMARY

An object of this invention is to minimise or even totally eliminate the disadvantages existing in the prior art.

An aim of the invention is to provide a stable composition for controlling, preventing and/or reducing the formation of inorganic scale at elevated temperatures and/or environments with high water hardness.

It is especially an object of the present invention to provide a composition that effectively also reduces the risk for corrosion when reducing the scale formation.

In order to achieve among others the objects presented above, the invention is characterized by what is presented in the characterizing parts of the enclosed independent claims.

Some preferred embodiments of the invention will be described in the other dependent claims.

The embodiments and advantages mentioned in this text relate, where applicable, both to the product, the method as well as to the uses according to the invention, even though it is not always specifically mentioned.

A typical composition according to the invention for controlling, preventing and/or reducing the formation of inorganic scale and/or deposits in an aqueous system comprises

- a copolymer of phosphinic acid and (meth) acrylic acid or its salt (s) ,

- a polycarboxylic acid or its salt (s) ,

- at least one monomeric phosphonate comprising at least one phosphonic acid group, or its salt (s) ,

- at least one corrosion inhibitor comprising amine groups, and

- at least one chelating agent.

Typical use according to present invention of the inventive composition is for controlling, preventing and/or reducing the formation of inorganic scale and/or deposits in an aqueous system having water hardness as calcium carbonate in the range of 50 –1500 ppm.

Typical method according to the present invention for controlling, preventing and/or reducing the formation of inorganic scale and/or deposits in an aqueous system comprises adding a composition according to the present invention to an aqueous system.

Now, it has been surprisingly found that the composition according to the present invention is able to provide synergetic advantages in harsh process conditions, e.g. high temperature and high pressure, which are prevailing e.g. oil and mining industry and coal gasification. The composition is not only capable of effectively reducing or eliminating the scale formation on the surfaces of process equipment at high process temperatures, but it is also effective in aqueous environments having high water hardness. Further, it has been observed that the composition does not subject the process equipment for corrosion in the same degree as at least some of the known solutions. The composition of the invention may further function as dispersant for the foreign particles present in the aqueous system.

It has been unexpectedly observed that the composition according to the present invention is able to control scale formation in industrial aqueous systems, for example, in heat exchangers and evaporative equipment such as those found in regulated markets. The composition of the invention may be used for removing, cleaning, preventing, and/or inhibiting the formation of scale, for example calcium, magnesium, oxalate, sulphate and phosphate scale, in an industrial aqueous system. These systems have unique demands for scale inhibitors due to the high conductivity and high level of insoluble material in the aqueous phase. In addition, the composition according to the invention is thermally stable, maintaining its stabilizing power at elevated temperatures for prolonged periods of time, even for several hours.

The composition according to the invention is able to provide several advantages simultaneously, such as high temperature tolerance, high carbonate scale inhibition effect, good stability against unwanted degradation, and good bio-degradation property. The present composition is a kind of environmentally beneficial “greenish” scale and corrosion inhibitor. It may be widely used in the harsh temperature and pressure conditions, such as desalination plant of flash vaporization equipment, low pressure boiler, crude oil evaporation, petroleum pipeline, or industrial circulating cool water systems.

DETAILED DESCRIPTION

The composition comprises a copolymer of phosphinic acid and (meth) acrylic acid. The term (meth) acrylic acid encompasses also those salts of (meth) acrylic acid that are suitable for formation of the copolymer. The copolymer of phosphinic acid and (meth) acrylic acid may have a weight average molecular weight MW less than 1000 g/mol, preferably in a range of 500 –1000 g/mol. The molecular weights are determined by usingknown chromatographic methods, such as gel permeation chromatography (GPC) employing size exclusion chromatographic columns with polyethylene oxide (PEO) calibration.

According to one embodiment of the invention the amount of the copolymer of phosphinic acid and (meth) acrylic acid in the composition isin the range of 5 –90 weight-％, preferably in the range of 40 –80 weight-％calculated from the total weight of the active constituents in the composition, as dry.

The composition further comprises a polycarboxylic acid or its salt (s) . According to one embodiment of the invention the polycarboxylic acid is selected from poly (meth) acrylic acid, or a copolymer of (meth) acrylic acid and maleic acid, itaconic acid or lactic acid. According to one preferred embodiment of the invention the polycarboxylic acid is a copolymer of (meth) acrylic acid and maleic acid or any suitable salt (s) thereof.

The polycarboxylic acid may have a weight average molecular weight MW less than 5000 g/mol, preferably in a range of 1000 –5000 g/mol. The molecular weights are determined by using gel permeation chromatography (GPC) .

According to one embodiment of the invention the amount of the polycarboxylic acid or its salt (s) in the composition may be in the range of 1 –30 weight -％, preferably 5 –25 weight-％, calculated from the total weight of the active constituents in the composition, as dry.

According to one preferable embodiment of the invention the sum of the amounts of the polycarboxylic acid and the copolymer of phosphinic acid and (meth) acrylic acid in the composition isin the range of 5 –90 weight-％, preferably 20 -80 weight-％and more preferably 40 –70 weight-％, calculated from the total weight of the active constituents as dry in the composition. The summed up amount of the polycarboxylic acid and the copolymer of phosphinic acid and (meth) acrylic acid is dependent on the process conditions of the application and can be adjusted for each application for optimal results, if desired.

The composition comprises further at least one monomeric phosphonate comprising at least one phosphonic acid group. The monomeric phorphonate may also comprise any suitable salt (s) thereof. The monomeric phosphonate may be selected from hydroxyethylene diphosphonic acid (HEDP) , amino tris (methylenephosphonic acid) (ATMP) , 2-phosphonobutane-1, 2, 4, -tricarboxylic acid (PBTC) , diethylenetriaminepenta (methylene phosphonic acid) (DTPMPA) , hexamethylenediamine tetramethylenephophonic acid (BHMTPMPA) , polyamino polyether methylene phosphonic acid (PAPEMP) or any combination of them. According to one preferable embodiment the monomeric phosphonate is 2-phosphonobutane-1, 2, 4, -tricarboxylic acid (PBTC) , diethylenetriaminepenta (methylene phosphonic acid) (DTPMPA) , hexamethylenediamine tetramethylenephophonic acid (BHMTPMPA) , polyamino polyether methylene phosphonic acid (PAPEMP) or any combination of them. According to one preferred embodiment, the monomeric phosphonate is a combination of 2-phosphonobutane-1, 2, 4, -tricarboxylic acid (PBTC) and diethylenetriaminepenta (methylene phosphonic acid) (DTPMPA) , or a combination of 2-phosphonobutane-1, 2, 4, -tricarboxylic acid (PBTC) and polyamino polyether methylene phosphonic acid (PAPEMP) , or polyamino polyether methylene phosphonic acid (PAPEMP) .

The total amount of the monomeric phosphonate (s) may be in the range of 10 -30 weight -％, calculated from the total weight of the active constituents in the composition, as dry.

The composition comprises further at least one corrosion inhibitor comprising amine groups. The amount of the corrosion inhibitor may be in the range of 0.5 –10 weight -％, calculated from the total weight of the active constituents in the composition, as dry. According to an embodiment of the invention the corrosion inhibitor is selected from diethyl hydroxylamine (DEHA) , octadecylamine, hexadecylamine, cyclohexylamine, methoxypropylamine, other fatty alcohol amines or any combination of them. According to one preferred embodiment the corrosion inhibitor is diethyl hydroxylamine (DEHA) .

The composition comprises further at least one chelating agent. According to one embodiment of the invention the chelating agent is a monomeric carboxylic acid. The term "monomeric carboxylic acid" is here understood to encompass aliphatic saturated and unsaturated carboxylic acids, as well as aromatic carboxylic acids, hydroxycarboxylic acids and aminocarboxylic acids. Examples of monomeric carboxylic acids include salicylic, fumaric, benzoic, glutaric, lactic, citric, malonic, acetic, glycolic, malic, adipic, succinic, aspartic, phthalic, tartaric, glutamic, pyroglutamic, gluconic acid, and any mixtures thereof. According to one preferred embodiment of the invention the chelating agent is selected from citric acid, succinic acid, gluconic acid, maleic acid, malic acid or their salts or any combination of them.

According to an embodiment of the invention, pH of the composition is >3, preferably >4 and more preferably in the range of 4 –6, measured in a 1 ％aqueous solution. Thus, the composition is less corrosive and so e.g. the maintenance costs of the equipment may be decrease.

The composition according to the invention tolerates high hardness of water. The composition according to the present invention is especially suitable for use in industrial aqueous system shaving water hardness as calcium carbonate in the range of 50 –1500 ppm, preferably 100 –1200 ppm, more preferably 200 –1000 ppm. In addition, the composition according to the invention tolerates high temperatures, i.e. it is effective also in high temperatures so it can be added to the industrial aqueous systems having temperature of the aqueous phase higher than 100 ℃. The temperature of the aqueous phase in the aqueous system may be at least 100 ℃, preferably at least 120 ℃, more preferably at least 200 ℃, even more preferably at least 250 ℃. According to one preferred embodiment, the temperature of the aqueous phase is in the range of 120 –280 ℃. The aqueous system may have a pressure between 6 –60 bar at the location where the composition is dosed.

The composition according to the invention may also improve water reuse, since the composition may improve water quality and increase water recycle times. Thus, also total water consumption may be reduce in the process where the composition of the invention is used.

The composition according to the invention may be used in desired dose, depending on the nature of the inorganic scale and/or other conditions in the aqueous system where it is used. For example, according to one embodiment of the invention the addition of the composition may be in the range of 5 –100 ppm, preferably 5 –70 ppm, and more preferably 5 –50 ppm.

The composition according to the present invention may be used at any process stage of suitable application, where there is a risk for inorganic scale formation. According to one embodiment of the invention the composition according to the present invention may be used for reducing or eliminating the formation of inorganic scale, such as calcium carbonate scale, in the aqueous system of a desalination plant of flash vaporization equipment, a low pressure boiler, crude oil evaporator, petroleum pipeline, an industrial circulating cool water system, a heat exchanger or a coal gasifier at high temperature, typically in a temperature of the system being above 100 ℃, more typically above 120 ℃ and even the systems having temperature above 250℃.

According to one embodiment of the invention the composition comprises a copolymer of phosphinic acid sodium salt and acrylic acid (CAS 71050-62-9) , sodium salt of poly (acrylic acid-co-maleic acid) (CAS 52255-49-9) , 2-phosphonobutane-1, 2, 4, -tricarboxylic acid (PBTC) , diethylenetriaminepenta (methylene phosphonic acid) (DTPMPA) , diethyl hydroxylamine (DEHA) and citric acid.

According to a second embodiment of the invention the composition comprises a copolymer of phosphinic acid sodium salt and acrylic acid (CAS 71050-62-9) , sodium salt of poly (acrylic acid-co-maleic acid) (CAS 52255-49-9) , polyamino polyether methylene phosphonic acid (PAPEMP) , diethyl hydroxylamine (DEHA) and sodium gluconate.

EMBODIMENTS

EXPERIMENTAL

Test method for inhibition rate

Solution A: cationicCaCl₂ liquid

Solution B: anionic NaHCO₃ liquid

Blank sample: 50mL solution A + 50 mL solution B

Reference sample: 50 mL solution A + 50 mL deionized water

Test sample: 50mL solution A + suitable amount of test solution +50 mL solution B

After all the chemicals of each samplesare added into respective bottles, the bottles are shaken well. Then, the bottles are put into the water bath at 80 ℃for 24h. The bottles are taken out from the water bath. The solution from each bottle is filtered and Ca²⁺ concentration in the filtrates are determined using inductively coupled plasma (ICP) instrument.

Calculation of inhibition rate (％) :

wherein

X2 is Ca²⁺ of reference sample, mg/L,

X3 is Ca²⁺of blank sample, mg/L,

X4 is Ca²⁺of test sample of a scale inhibitor, mg/L.

Example

Some examples of the scale inhibitor compositions according to the invention are listed in Table 1.

Table 1. Compositions, amounts of the constituents are given as weight-％, calculated from the total weight of the active constituents in the composition, as dry.

	Formula 1	Formula 2	Formula 3
POCA	63	42	63
AA-MANH-2SEM	7	28	7
PBTC	10	10	-
DTPMPA	10	10	-
PAPEMP	-	-	20
DEHA	2	2	5
Citric acid	8	8	-
Gluconate sodium	-	-	5

POCA is copolymer of phosphinic acid sodium salt and acrylic acid (CAS: 71050-62-9) .

AA-MANH-2SEM is 2-propenoic acid, polymer with 2, 5-furandione, sodium salt (CAS 52255-49-9) .

PBTC, DTPMPA and PAPEMP are organic phosphonates.

DEHA is diethyl hydroxylamine.

Reference 1, reference 2 and reference 3 are commercial products.

Scale inhibition rate isdetermined after 240 ℃ treatment for 1 h, 2 h, 3 h in the hydrothermal synthesis reactor, wherein Ca hardness is 600 mg/L. The dosage of the scale inhibition composition was 12 ppm. The results are presented in Table 2.

Table 2. Thermal stability test. Scale inhibition rate (％) after 0, 1, 2, 3 hours at 240 ℃ in the hydrothermal synthesis reactor.

	0 h	1 h	2 h	3 h
Formula 1	93.6	93.0	91.1	88.9
Formula 2	94.3	93.4	88.1	86.7
Formula 3	94.8	92.8	80.1	78.8
Reference 1	94.6	90.7	67.3	65.1
Reference 2	90.6	74.6	66.8	60.1
Reference 3	77.5	62.3	60.3	43.1

The results of the scale inhibition rate after 3 hours treatment at 240 ℃ are presented in Table 3. The test was carried at different dosages of the scale inhibitor and also water hardness varied.

Table 3. Scale inhibition rate (％) after 3 hours at 240 ℃ in the hydrothermal synthesis reactor.

As shown in Tables 2 and 3, the composition according to the invention is stable even at high temperatures and inhibition rate stays good. The behaviour is better than reference compositions.

Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.

Claims

A composition for controlling, preventing and/or reducing the formation of inorganic scale and/or deposits in an aqueous system comprising the followings as active constituents:

- a copolymer of phosphinic acid and (meth) acrylic acid or its salt (s) ,

- a polycarboxylic acid or its salt (s) ,

- at least one monomeric phosphonate comprising at least one phosphonic acid group, or its salt (s) ,

- at least one corrosion inhibitor comprising amine groups, and

- at least one chelating agent.
The composition according to claim 1, characterized in that the copolymer of phosphinic acid and (meth) acrylic acid has a weight average molecular weight MW less than 1000 g/mol, preferably in the range of 500–1000 g/mol, determined by using gel permeation chromatography (GPC) .
The composition according to claim 1 or 2, characterized in that the polycarboxylic acid is selected from poly (meth) acrylic acid, or a copolymer of (meth) acrylic acid and maleic acid, itaconic acid or lactic acid, preferably a copolymer of (meth) acrylic acid and maleic acid or any suitable salts thereof.
The composition according to any of the preceding claims, characterized in that the polycarboxylic acid has a weight average molecular weight MW less than 5000 g/mol, preferably in the range of 1000–5000 g/mol, determined by using gel permeation chromatography (GPC) .
The composition according to any of the preceding claims, characterized in that the monomeric phosphonateis selected from selected from hydroxyethylenediphosphonic acid (HEDP) , amino tris (methylenephosphonic acid) (ATMP) , 2-phosphonobutane-1, 2, 4, -tricarboxylic acid (PBTC) , diethylenetriaminepenta (methylene phosphonic acid) (DTPMPA) , hexamethylenediamine tetramethylenephophonic acid (BHMTPMPA) , polyamino polyether methylene phosphonic acid (PAPEMP) or any combination of them.
The composition according to any of the preceding claims, characterized in that the corrosion inhibitor is selected from diethyl hydroxylamine (DEHA) , octadecylamine, hexadecylamine, cyclohexylamine, methoxypropylamine, other fatty alcohol amines or any combination of them.
The composition according to any of the preceding claims, characterized in that the chelating agent is selected from citric acid, succinic acid, gluconic acid, maleic acid, malic acid or their salts or any combination of them.
The composition according to any of the preceding claims, characterized in that the sum of the amounts of the polycarboxylic acid and the copolymer of phosphinic acid and (meth) acrylic acid is in the range of 5–90 weight-％, preferably 20-80 weight-％ and more 40–70 weight-％, calculated from the total weight of the active constituents in the composition, as dry.
The composition according to any of the preceding claims, characterized in that the amount of the copolymer of phosphinic acid and (meth) acrylic acidisin the range of 5–90 weight-％, preferably in the range of 40–80 weight-％, calculated from the total weight of the active constituents in the composition, as dry.
The composition according to any of the preceding claims, characterized in that the amount of the polycarboxylic acid or its salt (s) is in the range of 1–30 weight-％, calculated from the total weight of the active constituents in the composition, as dry.
The composition according to any of the preceding claims, characterized in that the total amount of the monomeric phosphonate (s) is in the range of 10 -30 weight-％, calculated from the total weight of the active constituents in the composition, as dry.
The composition according to any of the preceding claims, characterized in that the amount of the corrosion inhibitor is in the range of 0.5–10 weight-％, calculated from the total weight of the active constituents in the composition, as dry.
The composition according to any of the preceding claims, characterized in that pH of the composition is > 3, preferably > 4, measured in a 1 ％ aqueous solution.
Use of composition according to any of preceding claims 1 to 13 for controlling, preventing and/or reducing the formation inorganic scale and/or deposits in an aqueous system having water hardness as calcium carbonate in the range of 50–1500 ppm.
Use according to claim 14, characterized in that temperature of the aqueous phase in the aqueous system is at least 100℃, preferably at least 120℃, more preferably in the range of 120–280℃.
Use according to claim 14 or 15, characterized in that the aqueous system is the aqueous system of a desalination plant of flash vaporization equipment, a low pressure boiler, crude oil evaporator, petroleum pipeline, an industrial circulating cool water system, a heat exchanger or a coal gasifier.
A method for controlling, preventing and/or reducing the formation inorganic scale and/or deposits in an aqueous system, the method comprising adding a composition according to any of claims 1 to 13 to an aqueous system.
The method according to claim 18, characterized in that the addition of the composition is in the range of 5–100 ppm, preferably 5–70 ppm, and more preferably 5–50 ppm.