Method and device for corrosion protection

Abstract

Method for the treatment, in particular remediation, of a water installation system, wherein at least a partial stream of the water is passed over cross-linked silica which has a loss on ignition at 1000°C of more than 6%, preferably more than 7%, in particular of 7% to 9% (analogous to FCK-AV ‘Loss on Ignition’ (2012-12)).

Description

Field of invention

[0001] The invention relates to a method and a device for corrosion protection, which can be used in water-carrying pipes and installation systems for both repair and preventative corrosion protection. The method forms a silicate-containing layer on the inner walls of water-carrying pipes and installations, which minimizes corrosion. Background of the invention

[0002] The use of silicate- and phosphate-containing inhibitor solutions for water-bearing systems is well-known as corrosion protection. In this way, a silicate-containing protective layer can be effectively formed on metal pipes, for example in drinking water distribution networks, especially in domestic installations, made of galvanized steel, unalloyed steel, or low-alloy steel.

[0003] German patent application DE 10 2014 003 770 A1 proposes that, to improve the efficacy of an inhibitor solution, it be thermally activated immediately before use. However, this procedure is complex. German patent application EP 1 780 310 A2 describes a method in which a third dosing solution is prepared from two solutions immediately before use. This procedure is also complex.

[0004] Furthermore, such inhibitor solutions are usually added to the water using a dosing pump. This is complex and requires, in particular, measuring the flow rate to adjust the dosage.

[0005] Document DE 27 51 671 A1 describes a corrosion-inhibiting water treatment agent containing alkali disilicate.

[0006] The document DE 10 2012 211 903 A1 describes the treatment of drinking water for water-bearing installations, in which the water is treated with a corrosion inhibitor.

[0007] Document DE 43 21 883 A1 shows a concentrate in the form of a solution containing silicate and phosphate as corrosion protection for drinking water pipes.

[0008] Document DE 35 08 562 C1 describes a method for the chemical cleaning or corrosion protection of water-carrying pipes using a solution of phosphates and silicates. Object of the invention

[0009] In contrast, the invention is based on the objective of providing a method and a device for corrosion protection that reduces the aforementioned disadvantages of the prior art. In particular, it should enable the simple production of a silicate-containing protective layer. Summary of the invention

[0010] The object of the invention is already solved by a method for treating, in particular rehabilitating, a water installation system for corrosion protection of water-carrying pipes and installation systems, and by a device designed for this purpose according to one of the independent claims.

[0011] Preferred embodiments and further developments of the invention can be found in the subject matter of the dependent claims, the description and the drawings.

[0012] The invention relates to a method for the treatment, in particular the rehabilitation, of a water installation system, wherein at least a partial flow of the water is passed over cross-linked silica.

[0013] The process is used in particular for the treatment of drinking water pipes in drinking water distribution networks, especially in house installations made of galvanized steel, unalloyed steel and / or low-alloy steel, i.e. with a mass fraction of the alloy components of a maximum of 5%.

[0014] The process can be used particularly in cooling and heating systems with pipes made of the above materials.

[0015] Preferably, a cartridge filled with cross-linked silica is connected in a bypass of the water flow. A portion of the water is passed through the cartridge, dissolving some of the silica.

[0016] Silicate forms in the water, which has a corrosion-protective effect on the aforementioned materials.

[0017] The partial flow via the cartridge is adjusted so that, after mixing with the main flow, the desired concentration of silicate and / or phosphate is achieved.

[0018] According to another embodiment of the invention, the cartridge can also be switched to full current.

[0019] The use of cross-linked silica enables the provision of a silicate-forming substance as a solid.

[0020] This significantly simplifies the dosage and / or handling.

[0021] In particular, the dosage can be adjusted, for example, via the flow rate, which, in the case of flowing water, for example, passes through a bypass in which the cartridge is connected.

[0022] The need for a costly dosing pump can be avoided.

[0023] Furthermore, the cross-linked silicic acid has an almost unlimited shelf life and only needs to come into contact with the water to release silicic acid and the associated silicate formation in the water to be treated.

[0024] The cross-linked silicic acid releases silicon when passing through water, whereby in the following, in accordance with the invention, quantities relating to silicon are calculated as SiO2.

[0025] Preferably, cross-linked silica is used in the form of a silica gel in the form of an aqueous, porous, amorphous modification of silicon dioxide (SiO2).

[0026] Instead of cross-linked silicic acid and silica gel, the terms "amorphous silicon dioxide", "polysilicic acid" and "silicic acid dioxide" are often used.

[0027] It has been found that, at least when selecting a material with high moisture content and / or a high proportion of silanol groups, such a high solubility can be achieved that sufficient silicon release is obtained.

[0028] The inventors hypothesize that a hydrolysis reaction is necessary to dissolve cross-linked silica. The dissolution rate thus depends on the hydrolysis rate, which in turn depends on the modification of the silicon dioxide. For modifications, especially highly heated silicon dioxide with a framework structure containing many Si-O-Si bonds, the energy requirement is higher, as these bonds must first be cleaved. Therefore, modifications with a high water content and / or a high loss on ignition are preferred.

[0029] When cross-linked silica comes into contact with water, less polymerized or unpolymerized silica is released (e.g., monosilicic acid, disilicic acid).

[0030] For example: SiO 2 (s) + 2 H2O ⇌ Si(OH) 4 (aq)

[0031] Silica is a weak acid. Therefore, it only slightly alters the pH value and conductivity of the treated water.

[0032] The cross-linked silica used for the invention can be produced, for example, as follows.

[0033] Possible starting materials for cross-linked silica are aqueous solutions of alkali silicate, e.g. sodium silicate, from which an amorphous silica is precipitated by the addition of an acid.

[0034] The precipitated silica is filtered off, washed and dried.

[0035] Preferably, the silica is not heated above 250 °C during drying, as otherwise the silanol groups may be cleaved off.

[0036] According to the invention, the cross-linked silica has a loss on ignition at 1000°C of over 6%, preferably over 7% (analogous to FGK-AV “Loss on Ignition” (2012-12)). The loss on ignition is therefore determined according to FGK-AV “Loss on Ignition”, only at a slightly lower temperature of 1000°C. In particular, the loss on ignition is between 7% and 9%.

[0037] Loss on ignition is a measure of the proportion of silanol groups.

[0038] As explained above, silicic acids contain a certain amount of water chemically bound in the form of silanol groups. This amount is determined by the loss on ignition at 1000 °C. The loss on ignition can be determined based on the original substance, but is calculated using the substance dried at 105 °C.

[0039] Preferably, the silica has a loss on drying of over 30%, preferably over 40%, particularly preferably over 50%, and especially a loss on drying of 55 to 65%. The loss on drying can be determined according to DIN EN ISO 787-2 - 1995-04.

[0040] It has been found that silica can be heated to about 130 °C and dried without a significant decrease in solubility.

[0041] According to a preferred embodiment of the invention, the silica has a specific surface area of ​​over 300 m². 2 / g, preferably over 700 m 2 / g, especially preferred above 800 m 2 / g, especially between 820 and 1000 m 2 / G.

[0042] The specific surface area can be determined according to the BET method according to DIN ISO 9277-2017-07.

[0043] Silica is preferably used, which has a solubility at 25 °C (in deionized water) of over 80 mg / l, preferably over 100 mg / l, and particularly preferably over 150 mg / l. In particular, the solubility is between 140 and 180 mg / l (calculated as SiO2).

[0044] The solubility can be determined by stirring a sufficient quantity of silicic acid, which is so large that it does not dissolve completely, in 25 °C warm water until saturation is reached.

[0045] The silica and / or the optionally present phosphate can be in the form of granules, in particular with a mean grain size of 0.5 to 3.0 mm.

[0046] In another embodiment, the silica can also be in powder form or preferably as a porous block of interconnected particles.

[0047] The internal structure of silica consists of a large network of interconnected microscopic pores with a high content of silanol groups, which can attract and retain water through physisorption and capillary action. This gives the material sufficient solubility in water.

[0048] This is achieved by using a silica that has a high specific surface area and a high proportion of silanol groups (characterized by a high loss on ignition at 1000 °C).

[0049] Preferably, the cartridge is filled with synthetically produced silica.

[0050] Substances registered as silica, in particular under CAS numbers 112926-00-8, 7631-86-9, 1343-98-2, 7699-41-4, 63231-67-4 or 10193-36-9, may be used.

[0051] The silicic acid forms silicate, which precipitates and forms a protective layer on surfaces, especially on the inner wall of metal pipes.

[0052] This can reduce corrosion, especially in galvanized drinking water pipes.

[0053] Furthermore, as explained above, the water can be used for filling heating or cooling circuits. This applies in particular to circuits with pipes made of unalloyed and low-alloy ferrous materials.

[0054] Preferably, the cartridge used for dosing contains 20 to 10,000 ml, particularly preferably 100 to 1000 ml, cross-linked silica.

[0055] According to a further development of the invention, a phosphate, in particular an orthophosphate, in particular magnesium phosphate, in particular magnesium triphosphate and / or calcium phosphate, is added to the water.

[0056] Furthermore, a polyphosphate, in particular sodium calcium polyphosphate, can be added to the water.

[0057] The chain-like polymers of a phosphate are commonly referred to as polyphosphate. The degree of condensation of the polyphosphate is preferably at least 4.

[0058] The phosphate(s) can exist as a solid.

[0059] Thus, a phosphate granule can be present as a mixture with a granule of cross-linked silica in a cartridge.

[0060] According to another embodiment of the invention, the phosphate(s) and the cross-linked silica are present in separate chambers.

[0061] By adjusting the volume flow ratio through the chambers, or by adjusting the design, a uniform degradation of both components and the desired ratio of silicate to phosphate can be achieved despite potentially different solubilities of phosphate and silica.

[0062] The components silica and orthophosphate provide corrosion protection by forming a dense and homogeneous protective layer on the inside of the pipe.

[0063] The polyphosphate component serves to purify the water by complexing iron(III) ions formed by corrosion processes, thus eliminating the yellow to rust-brown coloration of the water and making the water appear clear and colorless.

[0064] This is particularly important at the beginning of a renovation project, until the corrosion inhibitors silicate and orthophosphate take effect.

[0065] Furthermore, the polyphosphate component causes the corrosion protection components to be carried into the rear areas of the water distribution network and prevents them from reacting with the calcium and magnesium ions present in the water and precipitating out completely in the front area of ​​the water distribution network.

[0066] Furthermore, the polyphosphate component stabilizes the water's hardness.

[0067] In particular, the risk of black biofilm formation on the outlet fittings could be significantly reduced, as the phosphate content can be kept as low as possible.

[0068] The mass ratio of silicate to phosphate, i.e. the sum of all phosphates, is preferably between 2.0 and 10.0, particularly preferably between 3.0 and 6.0 and most preferably between 4.0 and 5.0.

[0069] According to one embodiment of the invention, the water is treated to achieve a silicate concentration of 0.5 to 15 g / m³. 3 , preferably from 1 to 12 g / m³ 3 , set.

[0070] According to one embodiment of the invention, the method is used for the rehabilitation of a water installation system, wherein a higher quantity, in particular at least twice the quantity, of silicon and / or phosphate is supplied as the rehabilitation dose than in a subsequent maintenance dose.

[0071] During maintenance dosing, the phosphate concentration can be reduced to 0.3 to 1.3 g / m³. 3 , especially even down to 0.6 to 0.7 g / m³ 3 , can be adjusted. This can reliably prevent the formation of black biofilms.

[0072] The invention further relates to a device for corrosion protection of water-carrying pipes and installation systems, which is particularly designed for carrying out the method described above.

[0073] The device comprises a container, preferably designed as an interchangeable cartridge, through which water can be conducted, wherein the container is filled with a cross-linked silica.

[0074] Furthermore, the container may be filled with orthophosphate and / or polyphosphate.

[0075] In particular, the container may be filled with the substances previously described in connection with the process.

[0076] Furthermore, the device can include at least one throttle valve. The throttle valve allows the flow rate in a bypass, and thus the flow rate ratio between the main and partial flows, to be adjusted. This allows for simple dosing control.

[0077] It is also conceivable to adjust the dosage of silicate and phosphate separately using at least two throttle valves.

[0078] The container can have at least two chambers to allow the phosphate and the cross-linked silica to flow through separately.

[0079] The volume flow ratio through the chambers, which is adjustable or predetermined by the design, can compensate for any differences in the solubility of silica and phosphate. Brief description of the drawings

[0080] The subject matter of the invention will be explained in more detail below with reference to an exemplary embodiment. Fig. Figure 1 is a schematic view of a water installation system which is treated using a method according to the invention. Fig. Figure 2 is a schematic view of a corrosion protection device designed as a cartridge. Fig. Figure 3 is a flowchart of an embodiment of the invention. Detailed description of the drawings

[0081] Fig. Figure 1 shows a schematic view of a water installation system.

[0082] The water installation system includes at least one water pipe 1 through which water, in particular drinking water, flows.

[0083] A partial flow is directed via a bypass 2 through a cartridge 3, which in this embodiment is filled with cross-linked silica, an orthophosphate and a polyphosphate.

[0084] The cartridge 3 contains chambers 4a - 4c for the various components. The chambers 4a - 4c can be arranged either side by side (4a opposite 4 and 4c) or one behind the other (4b and 4a).

[0085] Preferably, the bypass water is passed in a separate partial flow through chamber 4a filled with silica.

[0086] The ratio of silicate to phosphate released can be determined via the design-related volume flow ratio of chamber 4a to chambers 4b and 4c, which are filled with polyphosphate and orthophosphate.

[0087] In this embodiment, the volume flow ratio between the main flow and the bypass, and thus the release of silicate and phosphate, can be adjusted via the throttle valve 5 located in the bypass 2, e.g. to make a higher dosage in a remediation phase than in a subsequent maintenance phase.

[0088] Fig. Figure 2 schematically shows the structure of an exemplary embodiment of a cartridge 3, which can be used, for example, in the bypass of a water installation system.

[0089] The cartridge 3 comprises a housing 6 with an inlet 8 and an outlet 9.

[0090] In this embodiment, the water is directed into the cartridge 3 via the downpipe 10.

[0091] The interior comprises two chambers 4a, 4b, which are formed by an axially extending partition 7.

[0092] Chamber 4a is filled with cross-linked silica and chamber 4b is filled with at least one phosphate.

[0093] The ratio of silicate and phosphate enrichment can be precisely adjusted by the size of chambers 4a, 4b, the design-related volume flow ratio through chambers 4a, 4b and the amount of filling.

[0094] The water, divided into two partial streams, passes through chambers 4a and 4b and is combined in the mixing chamber 11, before exiting the cartridge via outlet 9.

[0095] If the cartridge 3 is inserted into a bypass, the water from outlet 9 is fed into the main flow.

[0096] The cartridge 3 itself may include a throttle valve (not shown) to adjust the volume flow ratio between main and bypass flow.

[0097] It is also conceivable to design the volume flow ratio between the individual chambers 4a, 4b to be adjustable, so that the ratio of silicate to phosphate enrichment can be changed (not shown).

[0098] Fig. Figure 3 shows in a flowchart the steps of the procedure according to an embodiment of the invention for refurbishing an installation system.

[0099] A cartridge is provided which is filled with cross-linked silica as well as orthophosphate and polyphosphate.

[0100] The cartridge is inserted into a bypass of the water installation system.

[0101] The flow rate through the bypass is adjusted via at least one throttle valve so that the phosphate content (total PO4) during a remediation phase is between 1.3 and 6.7 g / m³. 3 and the silicate content is 5.9 to 15 g / m³ 3 amounts.

[0102] After remediation, the dosage is reduced by decreasing the bypass current via the cartridge so that the phosphate content is between 0.6 and 1.3 g / m³. 3 and the silicate content 1.2 to 5.8 g / m³ 3 amounts.

[0103] The invention made it possible to provide a simple and safe system for the renovation of water installation systems. Reference symbol list: 1 water pipe 2 Bypass 3 cartridges Chambers 4a, 4b, and 4c 5 Throttle valve 6 cases 7 Partition wall 8 Inlet 9 Procedure 10 downpipe 11 Mixing chamber

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