CORROSION PROTECTION METHODS

Description

Field of the invention

[0001] The invention relates to a corrosion protection method that can be used in water pipes and installation systems as corrosion protection, both for rehabilitation and preventive purposes. The method forms a silicate-containing layer on the inner walls of water 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 for corrosion protection. This can be used to effectively form a silicate-containing protective layer on metal pipes made of galvanized steel, unalloyed steel, or low-alloy steel, for example, in drinking water distribution networks, especially in domestic installations.

[0003] The published patent application DE 10 2014 003 770 A1 proposes that an inhibitor solution be thermally activated immediately before use to improve its effectiveness. However, this procedure is complex. The published patent application EP 1 780 310 A2 describes a process 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 1 517 496 describes a method for protecting pipeline systems by adding colloidal silica. Document WO 2008 / 064504 A1 describes a microporous filter material containing silica and basic metal oxides for separating viruses and bacteria. Document CH 569 504 A5 shows a filter containing silica gel and carbon. Document EP 2 456 327 A1 describes a method for producing water enriched with natural orthosilicic acid to achieve improved bioavailability. Object of the invention

[0006] The invention, in contrast, is based on the object of providing a corrosion protection method that reduces the aforementioned disadvantages of the prior art. In particular, it should be possible to produce a silicate-containing protective layer in a simple manner. Summary of the invention

[0007] The object of the invention is already achieved by a method for treating, in particular renovating, a water installation system for corrosion protection for water-carrying pipes and installation systems with the features of claim 1.

[0008] Preferred embodiments and further developments of the invention can be found in the subject matter of the dependent claims, the description and the drawings.

[0009] The invention relates to a method for treating, in particular renovating, a water installation system, wherein at least a partial flow of the water is passed over cross-linked silica.

[0010] According to the invention, the method is used for treating drinking water pipes in drinking water distribution networks, in particular in domestic 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%.

[0011] The process can also be used in particular in cooling and heating systems with pipes made of the above-mentioned materials.

[0012] Preferably, a cartridge filled with cross-linked silica is placed in a bypass of the water flow. A partial flow of water is passed through the cartridge, dissolving some of the silica.

[0013] Silicate forms in the water, which protects the above-mentioned materials from corrosion.

[0014] The partial flow through the cartridge is adjusted so that after mixing with the main flow the desired concentration of silicate and / or phosphate is achieved.

[0015] According to another embodiment of the invention, the cartridge can also be switched to full flow.

[0016] The use of cross-linked silica enables the provision of a silicate-forming substance as a solid.

[0017] This makes dosing and / or handling much easier.

[0018] In particular, the dosage can be adjusted, for example, via the volume flow, which, when water is flowing, for example, through a bypass into which the cartridge is connected.

[0019] The costly use of a dosing pump can be dispensed with.

[0020] Furthermore, the cross-linked silica has an almost unlimited shelf life and only needs to come into contact with the water to release silica and the resulting silicate formation in the water to be treated.

[0021] The cross-linked silica releases silicon when passing through water, whereby in the following, quantities of silicon are calculated as SiO 2 in accordance with the invention.

[0022] The preferred cross-linked silica used is a silica gel in the form of a water-containing, porous, amorphous modification of silicon dioxide (SiO 2 ).

[0023] Instead of cross-linked silica and silica gel, the terms "silica gel", "amorphous silicon dioxide", "polysilicic acid" and "silicic acid dioxide" are often used.

[0024] 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 achieved.

[0025] The inventors suspect that a hydrolysis reaction is necessary for the dissolution of 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 because these bonds must first be cleaved. Therefore, modifications with a high water content and / or a high loss on ignition are preferred.

[0026] When the cross-linked silica comes into contact with water, less polymerized or non-polymerized silica is released (e.g. monosilicic acid, disilicic acid).

[0027] For example: SiO 2 (s) + 2 H 2 O Si(OH) 4 (aq)

[0028] Silica is a weak acid, so it only slightly changes the pH and conductivity of the treated water.

[0029] The crosslinked silica used for the invention can be prepared, for example, as follows.

[0030] Possible starting materials for the 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.

[0031] The precipitated silica is filtered off, washed and dried.

[0032] Preferably, the silica is not heated above 250°C during drying, as otherwise the silanol groups can be split off.

[0033] According to a preferred embodiment of the invention, the crosslinked silica has a loss on ignition at 1000°C of 3% to 30%, preferably 5% to 25%, particularly preferably over 6% to 15%, preferably over 7% to 10%, in particular between 7 and 9% (analogous to FGK-AV "Loss on ignition" (2012-12)). The loss on ignition is thus determined according to FGK-AV "Loss on ignition," only at a slightly lower temperature of 1000°C.

[0034] The loss on ignition is a measure of the proportion of silanol groups.

[0035] As mentioned above, silicas contain a certain amount of chemically bound water in the form of silanol groups. This 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 based on the substance dried at 105 °C or 110 °C. The loss on ignition thus refers to a sample pre-dried at 105 °C or 110 °C.

[0036] The silica preferably has a drying loss of more than 30%, preferably more than 40%, particularly preferably more than 50%, and in particular a drying loss of 55 to 65%. The drying loss can be determined according to DIN EN ISO 787-2 - 1995-04.

[0037] It has been found that silica can be heated to about 130 °C or even to about 145 °C and dried without significantly reducing its solubility.

[0038] According to a preferred embodiment of the invention, the silica has a specific surface area of ​​more than 300 m 2 < / g, preferably more than 700 m 2 < / g, particularly preferably more than 800 m 2 < / g, in particular between 820 and 1000 m 2 < / g.

[0039] The specific surface area can be determined according to the BET method according to DIN ISO 9277-2017-07.

[0040] Preferably, silica is used which has a solubility at 25 °C (in deionized water) of more than 80 mg / l, preferably more than 100 mg / l, and particularly preferably more than 150 mg / l. In particular, the solubility is between 140 and 180 mg / l (calculated as SiO 2 ).

[0041] The solubility can be determined by stirring a sufficient amount of silica, which is so large that it does not dissolve completely, in 25 °C warm water until saturation is reached.

[0042] The silica and / or the optionally present phosphate can be formed as a granulate, in particular with an average grain size of 0.5 to 3.0 mm.

[0043] In another embodiment, the silica can also be present as a powder or as a preferably porous block of interconnected particles.

[0044] 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 effects. This gives the material sufficient solubility in water.

[0045] 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).

[0046] The cartridge is preferably filled with synthetically produced silica.

[0047] Substances registered as silica, in particular under CAS No. 112926-00-8, 7631-86-9, 1343-98-2, 7699-41-4, 63231-67-4 or 10193-36-9, can be used.

[0048] The silica forms silicate, which precipitates and forms a protective layer on surfaces, especially on the inner walls of metal pipes.

[0049] This can reduce corrosion, particularly in galvanized drinking water pipes.

[0050] Furthermore, as stated above, the water can be used to fill heating or cooling circuits. This applies particularly to circuits with pipes made of unalloyed and low-alloyed ferrous materials.

[0051] The cartridge used for dosing preferably contains 20 to 10,000 ml, particularly preferably 100 to 1,000 ml, of cross-linked silica.

[0052] 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.

[0053] Furthermore, a polyphosphate, especially sodium calcium polyphosphate, can be added to the water.

[0054] The chain-like polymers of a phosphate are commonly referred to as polyphosphates. The degree of condensation of the polyphosphate is preferably at least 4.

[0055] The phosphate(s) may be present as a solid.

[0056] For example, a phosphate granulate can be mixed with a granulate of cross-linked silica in a cartridge.

[0057] According to another embodiment of the invention, the phosphate(s) and the cross-linked silica are present in separate chambers.

[0058] By means of an adjustable or design-dependent volume flow ratio through the chambers, a uniform degradation of both components as well as the desired ratio of silicate to phosphate can be achieved despite possibly different solubilities of phosphate and silica.

[0059] The components silica and orthophosphate provide corrosion protection by forming a dense and homogeneous protective layer on the inside of the pipe.

[0060] The polyphosphate component serves to refine water by complexing iron(III) ions formed by corrosion processes, thus eliminating the yellow to rust-brown color of the water and making the water appear clear and colorless.

[0061] This is particularly important at the beginning of a renovation project, until the corrosion inhibitors silicate and orthophosphate take effect.

[0062] In addition, 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 from completely precipitating in the front area of ​​the water distribution network.

[0063] Furthermore, the polyphosphate component stabilizes the hardness of the water.

[0064] In particular, the risk of black biofilm formation on the outlet fittings has been significantly reduced because the phosphate content can be kept as low as possible.

[0065] 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.

[0066] According to one embodiment of the invention, the water is adjusted to a silicate concentration of 0.5 to 15 g / m 3< , preferably 1 to 12 g / m 3< .

[0067] According to one embodiment of the invention, the method is used for the rehabilitation of a water installation system, wherein a higher amount, in particular at least twice the amount, of silicon and / or phosphate is supplied as the rehabilitation dose than in a subsequent maintenance dose.

[0068] During maintenance dosing, the phosphate concentration can be adjusted to 0.3 to 1.3 g / m³, and even to 0.6 to 0.7 g / m³. This can reliably prevent the formation of black biofilms.

[0069] According to the invention, the water is passed through an alkalizing filter material.

[0070] For this purpose, the container according to the invention comprises one or a mixture of at least two of the materials selected from the group consisting of carbonates and / or metal and / or semi-metal oxides.

[0071] Furthermore, the container may, for example, contain at least one or a mixture of at least two of the materials selected from the group consisting of Dolomites, semi-calcined dolomites, carbonates, in particular calcium carbonate and / or magnesium carbonate, oxides, in particular metal and / or semi-metal oxides, in particular calcium oxide and / or magnesium oxide and / or magnesium hydroxide and / or alkali hydroxides and / or alkaline earth hydroxides.

[0072] The alkalizing filter material can be in the form of a solid and, in particular, as a granulate.

[0073] Preferably, the alkalizing filter material increases the pH of the water by at least 0.05, particularly preferably at least 0.2 (compared to the pH of the water passed over the cross-linked silica without the alkalizing filter material).

[0074] It has been shown that, depending on the raw water, alkalizing filter material can increase the solubility of cross-linked silica, leading to improved silicate formation.

[0075] Furthermore, increasing the pH value reduces corrosion.

[0076] The simultaneous addition of silicate and the alkalization of the water creates a synergistic effect that increases corrosion protection.

[0077] In addition, alkaline drinking water can also have a positive effect on human health, and some people also prefer alkalized drinking water.

[0078] The alkalizing material can be used, in particular, as a solid. For example, it can be in the form of granules, particularly with an average grain size of 0.5 to 3.0 mm.

[0079] The disclosure further relates to a device for corrosion protection for water-carrying pipes and installation systems, which is designed in particular to carry out the method described above.

[0080] The device comprises a container, preferably designed as a replaceable cartridge, through which water can be conducted, the container being filled with a cross-linked silica.

[0081] Furthermore, the container can be filled with an ortho- and / or a polyphosphate.

[0082] In particular, the container may be filled with the substances previously described in connection with the process.

[0083] Furthermore, the device can comprise at least one throttle valve. The throttle valve can be used to adjust the volume flow in a bypass and thus the volume flow ratio between the main and partial flow. This allows for easy adjustment of the dosage.

[0084] It is also possible to adjust the dosage of silicate and phosphate separately using at least two throttle valves.

[0085] The container may have at least two chambers to allow the phosphate and the cross-linked silica to flow through separately.

[0086] The volume flow ratio through the chambers, which is adjustable or predetermined by the design, can be used to compensate for different solubility of silica and phosphate.

[0087] According to the invention, the container is also filled with an alkalizing filter material, in particular with at least one of the materials described above. The amount of alkalizing filter material is preferably at least 5% by weight of the crosslinked silica. Brief description of the drawings

[0088] The subject matter of the invention will be explained in more detail below with reference to an embodiment. Fig. 1 is a schematic view of a water installation system which is treated with a method according to the invention. Fig. 2 is a schematic view of a corrosion protection device designed as a cartridge. Fig. 3 is a flowchart of an embodiment of the invention. Detailed description of the drawings

[0089] Fig. 1 shows a schematic view of a water installation system.

[0090] The water installation system comprises at least one water pipe 1 through which water, in particular drinking water, flows.

[0091] A partial flow is passed through a bypass 2 through a cartridge 3, which in this embodiment is filled with cross-linked silica, an orthophosphate and a polyphosphate.

[0092] For the various components, the cartridge 3 comprises the chambers 4a - 4c. The chambers 4a - 4c can be arranged either side by side (4a opposite 4 and 4c) or one behind the other (4b and 4a).

[0093] Preferably, the bypass water is passed in a separate partial flow over the chamber 4a filled with silica.

[0094] The ratio of released silicate to phosphate can be determined by the design-related volume flow ratio of chamber 4a to chambers 4b and 4c, which are filled with polyphosphate and orthophosphate.

[0095] 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 present in the bypass 2, e.g. in order to apply a higher dosage in a remediation phase than in a subsequent maintenance phase.

[0096] Fig. 2shows schematically the structure of an embodiment of a cartridge 3, which can be used, for example, in the bypass of a water installation system.

[0097] The cartridge 3 comprises a housing 6 with an inlet 8 and an outlet 9.

[0098] In this embodiment, the water is fed into the cartridge 3 via the downpipe 10.

[0099] The interior comprises two chambers 4a, 4b, which are formed by an axially extending partition wall 7.

[0100] Chamber 4a is filled with cross-linked silica and chamber 4b is filled with at least one phosphate.

[0101] The ratio of silicate and phosphate enrichment can be set by adjusting the size of the chambers 4a, 4b, the design-related volume flow ratio through the chambers 4a, 4b and the amount of filling.

[0102] The water flows through the chambers 4a and 4b, divided into two partial streams, and is brought together in the mixing chamber 11 before leaving the cartridge via the outlet 9.

[0103] If the cartridge 3 is inserted into a bypass, the water from the drain 9 is fed into the main stream.

[0104] The cartridge 3 itself may comprise a throttle valve (not shown) to adjust the volume flow ratio between the main and secondary flow.

[0105] It is also conceivable to make the volume flow ratio between the individual chambers 4a, 4b adjustable so that the ratio of silicate to phosphate enrichment can be changed (not shown).

[0106] Fig. 3 shows in a flowchart the steps of the method according to an embodiment of the invention for renovating an installation system.

[0107] A cartridge is provided which is filled with cross-linked silica as well as an ortho- and a polyphosphate.

[0108] The cartridge is inserted into a bypass of the water installation system.

[0109] The volume flow through the bypass is adjusted via at least one throttle valve in such a way that the phosphate content (total PO 4 ) in a remediation phase is 1.3 to 6.7 g / m 3< and the silicate content is 5.9 to 15 g / m 3<.

[0110] After the remediation has been completed, the dosage is reduced by reducing the bypass flow through the cartridge so that the phosphate content is 0.6 to 1.3 g / m 3 and the silicate content is 1.2 to 5.8 g / m 3 .

[0111] The invention made it possible to provide a simple and safe system for the rehabilitation of water installation systems. List of reference symbols:

[0112] 1Water pipe 2Bypass 3Cartridge 4a,4b,4cChamber 5Throttle valve 6Housing 7Partition 8Inlet 9Drain 10Downpipe 11Mixing chamber

Claims

1. A method for treating, in particular rehabilitating, a water installation system, wherein at least a partial flow of the water is passed through a container filled with a cross-linked silica which is provided as a solid, and wherein the water is passed through an alkalizing filter material that contains one or a mixture of at least two of the materials selected from the group consisting of carbonates and / or metal oxides and / or semi-metal oxides, and wherein a pipeline made of galvanized, low-alloy or unalloyed iron material is treated.

2. The method according to the preceding claim, characterized in that a phosphate is added to the water, in particular an orthophosphate, in particular magnesium phosphate, especially magnesium triphosphate, and / or calcium phosphate.

3. The method according to the preceding claim, characterized in that the phosphate is provided as a solid.

4. The method according to any one of the preceding claims, characterized in that a polyphosphate is added to the water, in particular sodium calcium polyphosphate.

5. The method according to the preceding claim, characterized in that the cross-linked silica exhibits a loss on ignition at 1000 °C of 3 % to 30 %, preferably of 5 % to 25 %, more preferably of more than 6 % to 15 %, still more preferably of more than 7 % to 10 %, especially between 7 % and 9 % (analogous to FGK-AV "Loss on ignition" (2012-12)).

6. The method according to any one of the preceding claims, characterized in that a cross-linked silica with a loss on drying of more than 30 %, preferably more than 40 %, preferably more than 50 %, in particular a loss on drying of 55 to 65 %, is used.

7. The method according to any one of the preceding claims, characterized by using a cross-linked silica with a specific surface area of more than 300 m2 / g, preferably more than 700 m2 / g, particularly preferably more than 800 m2 / g, in particular between 820 and 1000 m2 / g (BET procedure according to DIN ISO 9277-2017-07), and / or with a solubility at 25 °C of more than 80 mg / l, preferably more than 100 mg / l, and most preferably more than 150 mg / l.

8. The method according to any one of the preceding claims, characterized in that the water is adjusted to a phosphate concentration of 0.2 to 8.0 g / m3, preferably 0.3 to 7.0 g / m3, and to a silicate concentration of 0.5 to 15 g / m3, preferably 1 to 12 g / m3.

9. The method according to the preceding claim, characterized in that the water is treated with a maintenance dosage for the water installation system, by adjusting the phosphate concentration to between 0.3 and 1.3 g / m3, preferably 0.6 to 0.7 g / m3.

10. The method according to any one of the preceding claims, characterized in that the alkalizing filter material comprises dolomite, semi-calcined dolomite, calcium carbonate and / or magnesium carbonate, calcium oxide and / or magnesium oxide and / or magnesium hydroxide and / or alkali hydroxides and / or alkaline earth hydroxides.

11. The method according to any one of the preceding claims, characterized in that the cross-linked silica and / or the phosphate and / or the alkalizing filter material are in solid form, in particular in the form of granules, especially with an average grain size of 0.5 to 3.0 mm.