JPH0478495A - Scale inhibitor - Google Patents

Abstract

PURPOSE:To obtain a scale inhibitor having a significant effect especially to silica-based scale by incorporating a specified compd. obtd. by allowing an aliphatic amine to react with ethylene oxide. CONSTITUTION:This scale inhibitor contains a compd. obtd. by allowing as aliphatic amine to react with ethylene oxide and represented by formula I (where R is 12-18C alkyl or alkenyl and each of n1 and n2 in an arbitrary integer of >=1 but 10<=n1+n2<=80). This scale inhibitor has superior power especially to silica-based scale as well as to Ca-based scale and Mg-based scale.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a water-based scale inhibitor.

<Conventional Technology> In recent years, from the perspective of effective use of water sources, recycling of cooling water and the like has been progressing in factories and other facilities to reduce the amount of water used. Accordingly, water becomes highly concentrated, and as a result, in such water systems, so-called scale components such as calcium, magnesium, and silica are concentrated, causing problems such as scale adhesion to heat transfer surfaces such as heat exchangers. . When scale builds up, it not only reduces the heat exchange rate but also causes problems such as tube blockage and corrosion, which in the worst case can lead to interruption of operation. Such scale failures occur not only in cooling water systems, but also in boiler water systems and geothermal power generation water systems. In particular, silica scale is hard and has low thermal conductivity, which is a big problem.

Conventionally, phosphorus compounds, polyacrylic acid, polymaleic acid, or water-soluble salts thereof have been used as agents to prevent such scale, but these alone have little effect on silica scale. In addition, quaternary ammonium compounds (JP-A-57-11039B), polyacrylamide (JP-A-61-107997), glyoxal (JP-A-61-293597), etc. are used as silica-based scale inhibitors. has been proposed, but its effectiveness is not sufficient.

<Problems to be solved by the invention> The present invention solves the problems of the conventional techniques, and has a scale prevention effect superior to that of the conventional techniques.
The purpose of the present invention is to provide a scale inhibitor that exhibits an excellent effect particularly on silica scale.

<Means for solving the problems> The scale inhibitor according to the present invention, which has been made to achieve the above object, has the general formula (I) (CHzCHzO) F obtained by reacting an aliphatic amine with ethylene oxide.
l, H/R-N
(I)\(CHz CH20) -z H (In the formula, R is an alkyl group or alkenyl group having 12 to 18 carbon atoms, nl5nz is 10≦n, 10nz≦8, respectively
(any integer greater than or equal to 1 within the range of 0). Note that a compound in which both ethylene oxide and propylene oxide are reacted instead of reacting only ethylene oxide also has a certain degree of scale prevention effect, but the compound of formula (I) in which only ethylene oxide is reacted has a certain degree of scale prevention effect. This provides a better scale prevention effect.

The above compound alone exhibits unprecedented scale prevention effects, but it can also be used in conjunction with acrylic acid polymers and copolymers, maleic acid polymers and copolymers, and sulfonic acid polymers and copolymers. Even better effects can be obtained by using at least one selected from the group consisting of combinations.

Examples of aliphatic amines used in the present invention include laurylamine, cecyamine, oleylamine, and stearylamine.

The reaction product of aliphatic amine and ethylene oxide can be obtained by reacting a specified amount of aliphatic amine and ethylene oxide at a temperature of 130 to 180° C. in the presence of a caustic catalyst. The scale inhibitor of the present invention is a compound in which the degree of polymerization of ethylene oxide in formula (I) (the sum of n and n2 in general formula (I)) is 10 to 80. 15 to 30 is particularly excellent in terms of scale prevention effect.

Also 1, the acrylic acid polymer and copolymer used,
Maleic acid polymers and copolymers, sulfonic acid polymers and copolymers include polyacrylic acid, polymaleic acid, styrene sulfonic acid (all of the above are homopolymers), acrylic acid-acrylamide copolymers, and methacrylic acid. - There are water-soluble salts such as acrylamide copolymers, maleic acid-isobutylene copolymers, maleic acid-styrene sulfonic acid copolymers, and their sulfur/lium salts, potassium salts, etc. Or use two or more types together. These polymers or copolymers can be easily polymerized by known methods. The molecular weight of these polymers or copolymers is preferably 200 to 1000, preferably 500 to 30,000.

When the above polymer or copolymer is used in combination with the compound of formula (I), each may be added separately to the water, but each drug may be mixed in advance at a predetermined ratio to form a single agent. It is convenient to do so because handling and addition operations become easier.

The mixing ratio when mixing each drug to form a single drug is determined by the formula (I
) compound:polymer and/or copolymer-9:1 to 4:6 (weight ratio; the same applies hereinafter), preferably 8:2 to 5:5.

Further, the amount of the scale inhibitor of the present invention to be added is determined when the compound of formula (I) is used alone, and when the scale inhibitor contains the above polymer and/or copolymer in addition to the compound of formula (I). In either case, the concentration in water is 1.
from 500 ■/A, preferably from 5 to 200 ■/l
It is best to set the amount so that It may be added in either liquid or solid form, but in order to ensure accuracy in the amount added, it is better to add in liquid form.

The scale prevention side of the present invention includes pH 11 regulators such as sodium hydroxide and sodium carbonate, phosphoric acids or their salts such as phosphoric acid compounds, hexametaphosphoric acid compounds, and phosphonic acid compounds, zinc compounds, and molybdenum compounds. In combination with metal compounds normally used as pre-corrosion protection, azole compounds such as benzotriazole and tolyltriazole, chlorine compounds, quaternary ammonium compounds, organic nitrogen sulfur compounds, and disinfectants such as aldehyde compounds. There is no problem with using them or mixing them together.

The compound represented by the general formula (I) obtained by reacting an aliphatic amine with ethylene oxide has a slight cationic property and is effective against not only calcium-based and magnesium-based precipitates in water but also silica-based precipitates. It is thought that it strongly adsorbs ionicly and physically to the surface of objects and suppresses the growth of crystals, thereby preventing the formation of scale.

In addition, acrylic acid polymers and copolymers, maleic acid polymers and copolymers, and sulfonic acid polymers and copolymers used in combination with the above compounds are particularly resistant to the surface of calcium and magnesium precipitates. By using both compounds together for adsorption, it is possible to suppress the crystal growth of not only calcium-based and magnesium-based precipitates, but also the reaction precipitates of calcium and silica, and magnesium and silica, providing an even better synergistic effect. It is thought that then.

<Example> The present invention will be explained in detail below.

Example 1 It has a heat exchanger with a heat transfer area of 0.3n, and the amount of water held is 0.8
- Using an experimental open circulation type cooling device, operation was carried out under the following conditions so that the concentration ratio of the circulating water was 7 times while maintaining the specified amount of the specified chemicals.

Operating conditions Heat exchanger inlet temperature: 30°C Heat exchanger outlet temperature: 45°C Flow rate 1. Orn/s Make-up water quality pH 7.0 Electrical conductivity 210 as/co! silica
50 ■SiO, /A Cal'/um32 ff Ca COt/ I! Magnesium 7.5mgCaCOx/11! After driving,
The silica and calcium concentrations of the circulating water were analyzed.

The types of drugs used are shown in Tables 1 (I) and (2), and the experimental results are shown in Table 2.

Table 1-fl) Chemicals used Table 1-(2) Chemicals used As shown in Table 2, the circulating water to which the scale prevention net of the present invention was added was significantly lower than the comparative example, especially in terms of its silica concentration. It's getting expensive. This means that there is little precipitation or adhesion of silica scale on the heat transfer surfaces of the heat exchangers used, and it can be seen that the scale prevention net of the present invention exhibits excellent effects.

Example 2 Water of the following quality, which had been prepared by concentrating industrial water in advance, was put into a circulation device equipped with a heater with a heat transfer area of 100J and a holding water capacity of 100J, and chemicals specified by the experimental results in Table 2 were added to the water. A predetermined amount was added and the operation was continued for 14 days.

Circulating water quality pH 7.5 Electrical conductivity 1320n/cd Silica 180 [S i Oz/ 1 Calcium 36 (Igca CCh/ 1 Magnesium 126wgCa CO:I/ 7! After the operation, check the rate of scale adhesion on the heater. It was measured.

The results are shown in Table 3 along with comparative examples. Note that in Table 3, the same drug symbols as in Table 1 above indicate the same drugs.

Table 3 Experimental Results Table 3 shows that the scale inhibitor of the present invention exhibits excellent effects.

<Effects> As explained above, the scale inhibitor of the present invention exhibits excellent preventive power not only against calcium-based and magnesium-based scales but also especially against silica-based scales, and only prevents a decrease in the heat exchange coefficient of the heat transfer surface. Instead, it prevents the occurrence of various obstacles and has a great impact on industry.

Claims (1)

[Claims] 1. A scale inhibitor containing a compound represented by the following general formula (I) obtained by reacting an aliphatic amine with ethylene oxide. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R is an alkyl group or alkenyl group having 12 to 18 carbon atoms, and n_1 and n_2 are each 10≦n_1+n_
2. Any integer greater than or equal to 1 in the range of 2≦80) 2. A compound represented by the general formula (I), an acrylic acid polymer and copolymer, a maleic acid polymer and copolymer, The scale inhibitor according to claim 1, further comprising at least one selected from the group consisting of sulfonic acid polymers and copolymers. 3. The scale inhibitor according to claim 1 or 2, wherein the scale is a silica scale.