RU2409523C2 - Method of preventing scaling, corrosion and biogrowth in water supply systems - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves adding hexamethylene diamine tetramethylene phosphonic acid and its metal-containing complexonate to the treated water in molar ratio of 3:1-2:1. The metal-containing complexonate used is a mixture of zinc complexonate and copper complexonate in molar ratio 0.75:0.25-0.5:0.5 respectively.

EFFECT: invention enables to prevent biogrowth, scaling and corrosion in water supply systems and ensures long uninterrupted operation of closed water supply systems and the required quality.

3 tbl, 19 ex

Description

The invention relates to methods for preventing mineral deposits, corrosion and biofouling and can be used in water treatment of closed heating, cooling, recycled water supply systems.

A known method of preventing mineral deposits and biofouling by introducing compositions of organophosphonate IOMS and its copper-containing complex with a molar ratio of 5: 1 ÷ 1: 1 [Russian Patent No. 2133229, IPC6 C02F 5/14, 1999].

The use of the method is effective for suppressing biofouling, but ineffective for simultaneously suppressing scaling and corrosion.

Closest to the proposed method is a method of preventing mineral deposits and corrosion by introducing into the treated water compositions containing hexamethylene diamine tetramethylene phosphonic acid (GMDTF) and its zinc-containing complexonate in their molar ratio 4: 1 ÷ 2: 1 [Russian Patent No. 2238453, C02F 5/14 (2006.01); C23F 11/167 (2006.01); C02F 103/04 (2006.01), 2008].

This method provides a reduction in the consumption of reagents (compositions containing them) while increasing the efficiency of water treatment in order to prevent scaling and corrosion, but is not effective enough to simultaneously suppress biofouling, especially for closed water use systems, the characteristic feature of which is to minimize the amount of fresh water recharge. The lack of effectiveness of the known method against biofouling leads to the development of microflora, because nitrogen and phosphorus, which are part of organophosphonates, and, in particular, GMDTF, are the products of the vital activity of bacteria. Ultimately, by reducing the concentration of GMDTF decreases the effectiveness of the composition to inhibit scaling and corrosion.

The objective of the invention is to increase the efficiency of water treatment in closed water supply systems by increasing the efficiency of suppressing biofouling while increasing the efficiency of suppressing scaling and corrosion.

The problem is solved in that the water is treated by introducing organophosphonates, while hexamethylene diamine tetramethylene phosphonic acid (GMDTF) and a mixture of its zinc and copper complexonates are used as organophosphonates at a molar ratio of GMDTF: a mixture of complexonates of 3: 1 ÷ 2: 1, the ratio of zinc to copper complexonates is 0.75: 0.25 ÷ 0.5: 0.5, respectively.

The claimed method is illustrated by the following examples, carried out in order to study the inhibitory properties, suppress biofouling and scaling.

Examples of corrosion inhibition in comparison with analogue and prototype.

In the “chemically cleaned” water of a clean steel cycle of the steelmaking production of the composition (mg / l): salt content - 479, Cu - 6, suspended solids - 2, alkalinity - 180, Fe - 0.12, Mn - 0.05, Cl - 19, 5, petroleum products - 0.04, sulfates 178, - the composition of GMDTF and its zinc and copper complexes were introduced at a molar ratio of GMDTF: a mixture of complexonates 3: 1-2: 1, the molar ratio of zinc to copper complexonates varied from 1: 0 to 0 : 1, in an amount of 5 mg / l. Hermetically sealed samples were kept in a thermostated cabinet at a temperature of 60 ° C for 14 days. At the end of the exposure, the corrosion rate was measured at a temperature of 20 ° C, with stirring (1.2 m / s) in a non-flowing cell with two-electrode probes made of St.3 steel using an Expert-004 corrosion meter. The braking coefficient was calculated by the formula:

K = a _o / a _j ,

where K is the braking coefficient;

a _o - corrosion rate in the control experiment (without reagent);

a _j is the corrosion rate with the reagent.

The measurement error is not more than 10%.

The data are presented in table 1.

From the data presented in table 1, it can be seen that the use of HMDTF with its zinc and copper complexonates with a molar ratio of zinc and copper complexonates = 0.75: 0.25 ÷ 0.5: 0.5 can significantly reduce the corrosion value, i.e. the effectiveness of corrosion inhibition is higher than corrosion inhibition using only zinc-containing complexonates (example No. 2). Moreover, the use of IOMS only with copper complexonate (example No. 1) increases corrosion (copper is in the series of voltages to the right of hydrogen). The data obtained suggest that the presence of copper complexonates prevents the development of microorganisms that destroy organophosphonate, in this case, HMTDF, and thereby reduce its effectiveness in the composition as a corrosion inhibitor. In this case, an unexpectedly high increase in the drag coefficient (increased inhibitory properties) is manifested when the molar ratio of zinc and copper complexonates = 0.75: 0.25 ÷ 0.5: 0.5 (examples Nos. 4, 5, 6, 7). Outside the specified ratios, the braking coefficient is lower than that of the prototype, i.e. inhibitory properties against corrosion are reduced.

Examples of biofouling prevention in comparison with analogue and prototype.

“Chemically cleaned” water (see the above examples for corrosion inhibition) was infected with microorganisms in the reverse cycle of the Seversky Pipe Plant. The water was introduced into the composition according to examples No. 10-14. The molar ratio, concentration and exposure conditions in accordance with Example 1. At the end of the exposure, the determination of the effectiveness of biofouling prevention was determined by the standard method: the water layer was removed by a siphon, and the number of living microorganisms was visually (under a microscope) determined in the sediment. The data are presented in table 2.

From the data presented in table 2 it is seen that GMDTF and its zinc-copper complexonates taken in the stated ratio (examples No. 13 and 14) effectively suppress the vital activity of microorganisms and, accordingly, biofouling. The effectiveness of the proposed method in the claimed range of zinc and copper complexonates = 0.75: 0.25 ÷ 0.5: 0.5 to prevent biofouling is identical to the similar method using only copper-containing complexonates (example No. 10) and significantly exceeds the efficiency of the prototype method (example No. 11).

Examples for the prevention of scaling in comparison with analogue and prototype

"Chemically cleaned" water, of composition and composition containing GMDTF and its zinc-copper complexonates, in accordance with the above examples, was thermostated for 14 days at a temperature of 60 ° C. At the end of the exposure, model supersaturated solutions of calcium sulfate (C = 7.5 g / l) were prepared on this water by mixing equivalent amounts of sodium sulfate and calcium chloride. The calculated concentration of the composition (in terms of GMDTF) was 1.0 mg / L. Crystallization was studied with stirring (Re = 12500) and a temperature of 70 ° C (the effectiveness of the compositions was evaluated by the duration of the induction period). The data are presented in table 3.

From the data presented in table 3, it is seen that the introduction of copper complexonates has a positive effect on the inhibitory properties of the crystallization of calcium sulfate, and, therefore, on the suppression of the formation of salt deposits. Unexpectedly high results were obtained with the claimed molar ratio of zinc and copper complexonates 0.75: 0.25 ÷ 0.5: 0.5, respectively (examples No. 18 and No. 19). The unexpectedly high results are difficult to explain by the simple effect of these complexonates on the process of scaling as such.

From the data presented in tables No. 1-No. 3, it is seen that when using the GMDTF system and its metal-containing complexonates with a molar ratio of GMDTF: metal-containing complexonate = 3: 1 ÷ 2: 1, while zinc and copper are used as the metal when molar the ratio of zinc complexonate: copper complexonate = 0.75: 0.25 ÷ 0.5: 0.5, respectively, in closed water supply systems allows you to get an unexpected result - the inhibition of the development of microflora while effectively inhibiting corrosion and scaling. A comprehensive solution to the problem is achieved, in our opinion, by the fact that the presence of copper complexonate at the stated ratio of a mixture of zinc and copper complexonates interferes with the activity of microorganisms, and therefore, there is no destruction of GMDTF.

The use of the proposed method in water supply systems due to the processing of the proposed reagent will prevent biofouling, scaling and corrosion, ensuring a long and uninterrupted operation of closed water supply systems and with the required quality.

Table 1 Corrosion rate No. p / p Composition The molar ratio of GMDTF: complexonate The molar ratio of zinc and copper complexonates Braking coefficient one IOMS: copper complexonate (analogue) 2: 1 0: 1 0.5 2 GMDTF: zinc complexonate (prototype) 2: 1 1-0 3.4 3 GMDTF: zinc complexonate (prototype) 3: 1 1-0 2.9 four HMDTF: complexonate (according to the invention) 3: 1 0.75: 0.25 3.3 5 HMDTF: complexonate (according to the invention) 3: 1 0.5: 0.5 3.8 6 HMDTF: complexonate (according to the invention) 2: 1 0.75: 0.25 4.1 7 HMDTF: complexonate (according to the invention) 2: 1 0.5: 0.5 4,5 8 GMDTF: complexonate (control) 3: 1 0.25: 0.75 2.5 9 GMDTF: complexonate (control) 2: 1 0.25: 0.75 2.9

table 2 The number of living microorganisms No. p / p Composition The molar ratio of GMDTF: complexonate The molar ratio of zinc and copper complexonates The state of microorganisms 10 IOMS: copper complexonate (analogue) 3: 1 0: 1 100% dead eleven GMDTF: zinc complexonate (prototype) 3: 1 1-0 Everybody is alive 12 GMDTF: complexonate (control) 3: 1 0.25: 0.75 100% dead 13 HMDTF: complexonate (according to the invention) 3: 1 0.5: 0.5 100% dead fourteen HMDTF: complexonate (according to the invention) 3: 1 0.75: 0.25 100% dead Table 3 Crystallization of calcium sulfate No. p / p Composition The molar ratio of GMDTF: complexonate The molar ratio of zinc and copper complexonates Induction period, min fifteen IOMS: copper complexonate (analogue) 2: 1 0: 1 190 16 GMDTF: zinc complexonate (prototype) 2: 1 1-0 120 17 GMDTF: complexonate (control) 2: 1 0.25: 0.75 150 eighteen HMDTF: complexonate (according to the invention) 2: 1 0.5: 0.5 250 19 HMDTF: complexonate (according to the invention) 2: 1 0.75: 0.25 220

Claims (1)

A method for preventing scaling, corrosion and biofouling in water supply systems by introducing hexamethylene diamine tetramethylene phosphonic acid and its metal-containing complexonate into the treated water at a molar ratio of 3: 1 ÷ 2: 1, characterized in that a mixture of zinc complexonate and copper complexonate is used as a metal-containing complexonate with m the ratio of 0.75: 0.25 ÷ 0.5: 0.5, respectively.