CS242278B1 - Means for progressive alkaline treatment of aqueous circulation cooling systems - Google Patents

Abstract

The invention belongs to the field of metal corrosion protection and solves the corrosion protection of steel and other metals in heat exchange systems with an aqueous cooling medium. The agent for progressive alkaline treatment of aqueous circulating cooling systems according to the invention contains 1 to 20 wt. % ethane-1-hydroxy-1,1-diphosphonic acid, 0.1 to 5 wt. % 1,2,3-benzotriazole, 1 to 10 wt. % sodium ammonium salt of acrylate polymer, 1 to 15 wt. % N,N-dimethylformamide, 1 to 10 wt. % sodium hydroxide, 40 to 80 wt. % aqueous condensate. The effectiveness of the agent can be further increased by adding 0.1 to 15 wt. % alkylamine salt (compound of phosphoric acid with alkanolamines with 2 to 8 carbon atoms in the chain, preferably triethanolamine phosphate). The agent for progressive alkaline treatment of water circulation cooling systems is continuously maintained in water heat exchange media at a concentration of 20 to 100 g per 1 m3.

Description

The invention belongs to the field of corrosion protection of metals and solves the corrosion protection of steel and other metals in heat exchange systems with an aqueous cooling medium.

The composition for the progressive alkaline treatment of the aqueous circulation cooling systems according to the invention comprises 1 to 20% by weight. % ethane-1-hydroxy-1,1-diphosphonic acid, 0.1 to 5 wt. % 1,2,3-benztriazole, 1 to 10 wt. % sodium ammonium salt of acrylate polymer, 1 to 15 wt. % N, N-dimethylformamide, 1 to 10 wt. % sodium hydroxide, 40 to 80 wt. aqueous condensate. The activity of the composition can be further increased by the addition of 0.1 to 15% by weight. alkylamine salts (phosphoric acid compound with C 2 -C 8 alkanolamines in the chain, preferably triethanolamine phosphate).

The composition for the progressive alkaline treatment of aqueous circulation cooling systems is continuously maintained in aqueous heat exchange media at a concentration of 20 to 100 g per m ³ .

The invention relates to a composition with corrosion inhibiting, dispersing and sequestering action for the progressive alkaline treatment of the heat exchange environment of steel systems containing also materials of the medium, aluminum, zinc and their alloys in circulating cooling circuits.

The influence of water heat exchange medium on steel systems leads to corrosion of steel and other metals. The corrosion proceeds evenly, but due to the formation of deposits of insoluble substances such as insoluble salts, mainly calcium carbonate, dust, clay, sand, corrosion products, biomass, it is uneven in nature, most often through corrosion, but also worsens the hydraulic resistance of water flow in pipelines thus increasing the thermal resistance on the heat exchange surfaces.

To prevent the corrosion effect of aqueous heat exchange media on steel systems, corrosion inhibitors based on chromates, nitrites, silicates, phosphates, molybdates and zinc salts are added to these media. These compositions are capable of suppressing the corrosion of steel (but not Cu, Al, Zn and their alloys) to various extents, nor do they suppress the growth of the layers by deposition, and therefore cannot prevent the increase of hydraulic and thermal resistance and hence uneven forms of corrosion.

In addition, some known corrosion inhibitors are also harmful to health, for example chromates, nitrites, and at the same time do not safely suppress corrosion of the steel unless their required minimum concentration in the aqueous medium is maintained.

Therefore, dispersant additives such as cellulose and its derivatives, polyacrylates, polyacryamides and the latest synthetic polymers such as e.g. copolymer of ethylene oxide and propylene oxide and others.

Sequestering agents are known for suppressing the formation of solid deposits which, by forming non-stoichiometric complexes, prevent the formation of insoluble salts and the formation of their layers on the steel surfaces. Inhibitors of these deposits primarily include polyphosphates, natural polymers such as lignin and tannin.

The most commonly used polyphosphate programs to date have the disadvantage that in systems with longer residence times, high operating temperatures and higher pH values, the polyphosphate is retrogradable to orthophosphate, resulting in sticky calcium orthophosphate deposits.

The drawbacks of the prior art in this field are largely eliminated by the composition for the progressive alkaline treatment of aqueous circulating cooling systems with corrosion inhibiting, dispersing and sequestering effect for the aqueous circulating cooling circuits according to the invention, which consists of 1 to 20% by weight. % phosphonate (ethane-1-hydroxy-1,1-diphosphonic acid), from 0.1 to 5 wt. % 1,2,3-benztriazole, from 1 to 10 wt. % aqueous solution of sodium ammonium salt of acrylate polymer, from 1 to 15 wt. % Of N, N-dimethylformamide, from 1 to 10 wt. % sodium hydroxide, from 0.1 to 15 wt. % alkylamine salts (phosphoric acid compound with C 2 -C 8 alkanolamines), from 40 to 80 wt. aqueous condensate.

Said composition is added to the aqueous heat exchange medium at a concentration of 20 to 100 g. m ^-3 .

As a multi-component mixture of synthetic organic corrosion inhibitors including specific sediment control agents, this formulation provides double corrosion control. At the anode it is provided by the action of an azole inhibitor (1,2,3benztriazole - a specific inhibitor of Cu, Al, Zn and their alloys) and at the cathode it is provided by a phosphonate (ethane-1-hydroxy-1,1-diphosphonic acid), where phosphonic acid part of the inhibitor, in addition to acting as a cathode corrosion inhibitor, also has a strong chelating component which ensures the stability of water hardness at high temperatures (200 to 250 ° C), long residence times (100 hours) and high pH values (pH = 10.5 to 11); wherein the phosphonate is substantially stable under the given conditions, thereby providing the possibility of higher concentration and also helps to remove iron oxides from the cooling system together with the anionic dispersant (sodium ammonium acrylate polymer).

The composition provides control of deposits, thereby allowing the cooling water treatment program to operate in neutral and alkaline ranges, while providing selective control of calcium carbonate deposits (by adjusting the crystalline lattice structure). It is not affected by chlorine or process impurities such as hydrogen sulfide or hydrocarbons.

The composition has a self-passivating capability without the need for hardening ions. It can also be used in systems where calcium concentrations are insufficient for proper phosphate film formation.

Said mode of operation using said composition at higher densities ensures a relatively high reduction in the cost of chemical treatment of the circulation cooling ducts, saving of make-up water and saving of energy necessary for pumping and cooling of the aqueous heat exchange medium.

The invention and its effects are explained in more detail by the following examples.

Example 1

Correction using 50 g of the product. m ^{-3 of} water of composition 12% wt. % ethane-1-hydroxy-1,1-diphosphonic acid, 5 wt. % sodium hydroxide, 1 wt. % sodium ammonium salt of acrylate polymer, 3 wt. % N, N-dimethylformamide, 0.5 wt. 1,2,3-benztriazole and the remainder water condensate, reduced steel corrosion by 92% and the formation of deposits resulting from impurities and calcium salts by 94%.

Example 2

Adjustment using the composition in an amount of 50 g. m ^-3 water with a composition of 12 ° / o wt. % ethane-1-hydroxy-1,1-diphosphonic acid, 5 wt. % sodium hydroxide, 1 wt. % sodium ammonium salt of acrylate copolymer, 3 wt. % N, N-dimethylformamide, 0.5 wt. % 1,2,3-benztriazole, 10 wt. triethanolamine phosphate and the remainder aqueous condensate, reduced corrosion by 94% and reduced the formation of deposits resulting from impurities and calcium salts by 95%.

The invention is intended for use in steel systems of water heat exchange environments in the chemical, food, pharmaceutical, metallurgical industry but mainly in power engineering.

Claims (2)

242278 of 50 g. M-3 water of 12% by weight. ethane-1-hydroxi-1,1-diphosphonic acid, 5 wt. sodium hydroxide, 1 wt. % sodium ammonium salt of acrylate polymer, 3 wt. N, N-dimethylformamide, 0.5% w / w 2,3,3-benztriazole and the remainder aqueous condensate, reduced the corrosion of steel by 92% and the formation of sediments resulting from impurities and calcium salts by 94%. Example 2 Treatment with a composition of 50 gm-3 water of 12% by weight. ethane-1-hydroxi-1,1-diphosphonic acid, 5 wt. sodium hydroxide, 1 wt. % sodium ammonium salt of acrylate copolymer, 3 wt. N, N-dimethylformamide, 0.5% w / w 2,3,3-benztriazole, 10% w / w. phosphorous triethanolamine and the remainder aqueous condensate, reduced corrosion by 94% and reduced the formation of debris resulting from impurities and calcium salts of 95%. The invention is intended for use in steel systems of water heat exchange environments in the chemical, food, pharmaceutical and metallurgical industries, but mainly in the energy sector. E R E D E R I D E The means for the progressive alkaline treatment of aqueous circulating cooling systems is characterized in that it comprises from 1 to 20 wt. % ethane-1-hydroxy-1,1-diphosphonic acid, 0.1 to 5 wt. 1,2,3-benztriazole, 1 to 10 wt. a sodium ammonium salt acrylate polymer, 0.1 to 15 wt. DESCRIPTION OF THE INVENTION An alkylamine salt - a phosphoric acid compound with alkanolamines having 2 to 8 carbon atoms in the chain, preferably triethanol amine, 1 to 15 wt. Ν, Ν-dimethylformamide, 1 to 10 wt. sodium hydroxide and the remaining aqueous condensate.