METHOD AND DEVICE FOR REDUCING THE OXYGEN CONTENT OF HEATING WATER

Description

[0001] The invention relates to a method for reducing the oxygen content of the heating water in a heating system.

[0002] The invention also relates to a device for reducing the oxygen content of the heating water in a heating system.

[0003] In heating and cooling circuits, introduced oxygen is considered the main cause of corrosion damage. While salts and limescale can be easily removed from the fill and make-up water using ion exchange cartridges for softening or demineralization, the oxygen content in the water remains unaffected.

[0004] Various methods are known to remove dissolved oxygen from water to prevent corrosion damage. Physical methods, such as thermal degassing or vacuum degassing, are very complex in terms of equipment. The addition of chemical organic or inorganic oxygen scavengers, such as sodium sulfite, generally increases the conductivity of the system water significantly and thus fundamentally increases the risk of corrosion. Electrochemical processes, in which oxygen reduction occurs at preferably large cathode surfaces, are also complex in terms of equipment, as potentiostatic control is required, and measures for sludge removal and venting (gas formation) must be implemented. Furthermore, depending on the system, so-called secondary oxygen is generated at the anode, which must be separated.

[0005] From GB 788,112, a method for removing oxygen from oxygen-containing liquids, particularly water, is known, as is desirable, for example, for the operation of steam boilers or for use in chemical laboratories. For this purpose, the liquid is passed through an ion exchange resin containing oxygen-consuming materials. Insoluble substances in the liquid, such as metal oxides or metal hydroxides, are proposed as oxygen-consuming materials. The ion exchanger can be a cation exchanger, for example, in the sodium or proton form, an anion exchanger, or a mixture of both. The oxygen is not removed by an ion exchange process; the ion exchanger merely serves as a carrier for the oxygen-consuming material.A disadvantage is that the reaction between the oxygen-consuming materials and the oxygen dissolved in the liquid proceeds relatively slowly. This is especially true at low temperatures, such as those typically found in fresh water supplied to a system. Consequently, a large proportion of the oxygen remains in the water even after treatment, which can lead to corrosion of system components.

[0006] German patent DE 10 2005 036 356 A1 discloses a water treatment device for a heating system. Ion exchange elements are stored in a container, and a corrosion inhibitor is stored in an adjacent chamber of the container or in an additional container. To at least partially demineralize the heating water, the water treatment device is flowed through by the incoming fresh water when the heating system is filled. During this process, the pH value of the water is also adjusted to a desired value. The corrosion inhibitor, which can be in the form of molybdate or an oxygen scavenger, releases chemical components into the water, thereby at least reducing the corrosion of system components. However, as previously explained, the addition of chemical oxygen scavengers increases the conductivity of the heating water, which can lead to an increased risk of corrosion.

[0007] From DE 10 2008 003 327 A1, a water treatment device for a heating system is known, comprising a demineralization and softening unit containing ion exchange elements and a downstream pH stabilization unit. The pH stabilization unit has a water-filled container in which a pH stabilizer is arranged to stabilize the pH value created by the ion exchange elements. To fill a heating system, the demineralization and softening unit with the downstream pH stabilization unit is connected to the fresh water inlet of the heating system and the fresh water flows through it. During this process, the water is at least partially demineralized, its pH value is adjusted, and the pH value is stabilized.

[0008] DE 10 2009 022 437 A1 describes a device for treating water conveyed through pipes to prevent corrosion of the water pipes. For this purpose, the water is passed through a mixed-bed electrode designed as a fixed bed, which, in addition to phosphate particles providing corrosion protection, also contains electrically conductive particles to increase the electrode surface area. By applying a direct current voltage, the pH value of the water can be adjusted and the solubility of the phosphates used, preferably sparingly soluble ones, can be influenced, thus enabling the targeted introduction of phosphate into the water.

[0009] From DE 10 2013 102 426 A1 a method and a device for adjusting the pH value of the heating water of a heating system are known.

[0010] In this process, the heating water is circulated through a demineralization unit, which includes a mixed-bed element, and demineralized. The release of OH⁻ from the anion exchanger initially raises the pH of the heating water, allowing it to be adjusted to a desired pH level. To lower the pH, the heating water is circulated through the demineralization unit and the mixed-bed element until the anion exchanger is exhausted. The pH is then lowered by the release of H⁺ from the cation exchanger. The mixed-bed element is located in a bypass line to the main flow of the heating circuit and is therefore only subjected to a portion of the circulating heating water.

[0011] DE 10 2014 103 163 A1 discloses a control device that enables the pH value of heating water to be adjusted to suitable values ​​by specifying the materials of the components used in the heating system, in order to at least minimize their corrosion, using a demineralization unit containing a cation exchanger and an anion exchanger. The demineralization unit of the water treatment system is connected in a bypass to the heating water circuit of the heating system, so that a partial flow of the heating water circulates through the demineralization unit. Through this cyclical treatment, the pH value of the heating water can be brought close to the desired range. Further relevant documents are CA 622 245 A, EP 0 065 687 A2, GB 788 112 A, and DE 10 2017 105435 A1.

[0012] The object of the invention is to provide a method by which oxygen can be removed from the heating water of a heating system with minimal equipment and without having to add oxygen binders to the heating water.

[0013] It is also an object of the invention to provide an easy-to-use and cost-effective device with which oxygen can be removed from the heating water of a heating system.

[0014] The problem relating to the method of the invention is solved by passing the heating water through a strongly basic anion exchanger containing a reducing agent during circulation operation, and by at least partially removing the oxygen contained in the heating water from the anion exchanger by reaction with the reducing agent during the circulating flow of the heating water. The reducing agent is an oxygen-consuming chemical. When the heating water is brought into contact with the reducing agent, some of the oxygen dissolved in the heating water is removed by reaction with the reducing agent. During circulation operation, the heating water is repeatedly passed through the anion exchanger containing the reducing agent, with some of the oxygen being removed from the heating water in each cycle.This ensures that oxygen is completely or almost completely removed from the heating water, even at relatively slow reaction rates between the reducing agent and the oxygen. Because the anion exchanger carrying the reducing agent is integrated into the heating water circuit, warm heating water is supplied. The comparatively high water temperature significantly increases the reaction rate between the reducing agent and the oxygen compared to treating cold fresh water, such as that supplied when filling or topping up the heating system. Depending on the reducing agent used, the high temperature may even be the only factor enabling the reaction, resulting in improved oxygen removal.Removing oxygen from the heating water significantly reduces corrosion of heating system components, especially components made of carbon steel.

[0015] To implement the invention, a strongly basic anion exchanger (for example, Purolite A-MB 400-OH) loaded with a reducing agent, such as sodium sulfite, can be used. With such an anion exchanger, effective oxygen removal from the circulating water is possible. In the reaction with the dissolved oxygen in the heating water, the sulfate ion is converted to sulfate. The sulfate has a high selectivity with respect to the anion exchanger and thus remains largely on the exchange resin. This has the advantage that the conductivity of the treated water is not significantly increased. In circulating operation at temperatures of 40 to 60 °C, the residual oxygen content can be reduced to less than 0.02 mg / L within a very short time using such a device.

[0016] To comply with the common guidelines for circulating water (e.g., VDI 2025, AGFW FW 510, SWKI BT 102, ÖNORM H 5195-1), it is advantageous to raise the pH value to the alkaline range (8.2 to 10.0). According to the invention, this is achieved by either partially loading the strongly basic anion exchanger, such as the one mentioned above, with the reducing agent or by adding the reducing agent in its OH- form. It is particularly advantageous if the anion exchanger is present in the OH- form to a concentration of 5% to 10%.

[0017] In circulating systems with uncontrolled oxygen ingress, such as heating systems with diffusion-open underfloor pipes, open expansion tanks located above the system, or insufficient pressure maintenance, oxygen constantly enters the heating water. The continuous oxygen removal process using the reducing agent introduced into the system removes this oxygen from the heating water. This method can therefore be particularly advantageous in heating systems that are not sealed against corrosion.

[0018] The ion exchanger loaded with reducing agent can be easily and cost-effectively integrated into a heating water circuit without requiring complex equipment. A further advantage is that no oxygen-binding chemicals are added to the heating water.

[0019] It can be advantageous to direct a main flow of the heating water, or a branched bypass of the main flow, through the anion exchanger containing the reducing agent. With the cation exchanger and / or anion exchanger positioned in the main flow, the heating water passes completely by the reducing agent in each cycle. This achieves a significant reduction in oxygen content within just a few cycles, and thus quickly. If the anion exchanger is fed by a branched bypass of the heating water, only a portion of the heating water is supplied to the reducing agent in each cycle. An advantage of this arrangement is that the flow resistance within the main flow of the heating water circuit is not increased by the cation or anion exchanger. The anion exchanger can therefore be designed for smaller flow rates.To replace the anion exchanger, only the bypass flow needs to be interrupted, while the heating water can continue to circulate in the main flow. Therefore, the operation of the heating system does not need to be interrupted to replace the anion exchanger.

[0020] The heating water can flow through the anion exchanger until the desired water quality is achieved. Afterwards, the flow through the bypass can be interrupted, or the anion exchanger can be removed from the main flow. This makes it possible to connect the anion exchanger to the heating water circuit only temporarily. Criteria for assessing water quality include, in particular, the oxygen content, conductivity, and / or pH value of the heating water. The heating water is preferably passed through the anion exchanger until the oxygen content, conductivity, and / or pH value of the heating water are within the desired target range.

[0021] If the heating water is passed through the anion exchanger containing the reducing agent, and if the anion exchanger is present in the OH form to a volume fraction of preferably 5 to 10%, then oxygen can be removed from the heating water by reaction with the reducing agent. Simultaneously, the heating water is alkalized by the release of OH⁻ into the heating water, preferably in accordance with the VDI 2035 heating water guideline. This allows for precise adjustment of the heating water's pH value. By selecting a suitable pH value, corrosion of heating system components can be further reduced. For example, the pH value can be adjusted to a target range of 8.2 to 9.0, which is suitable for operating heating systems containing aluminum components.

[0022] According to the invention, the heating water is passed through a mixed-bed cartridge after the anion exchanger or after the cation exchanger, and / or the heating water is passed through a mixed-bed cartridge in the main flow or bypass flow. The mixed-bed cartridge used in the circulating water allows for the removal of potential byproducts. Depending on the ion exchanger used and the reducing agent, various byproducts, such as iron(III) ions / hydroxide in the case of an iron-ion-loaded cation exchanger or sulfate in the case of an anion exchanger loaded with sulfite ions, can be introduced into the heating water. Iron(III) hydroxide can lead to sludge formation within the heating system, while sulfate has an adverse effect on corrosion. These and similar byproducts can be removed from the heating water using the mixed-bed cartridge.The mixed-bed cartridge can be installed directly downstream of an anion exchanger in the main or secondary flow of the heating water circuit. In this case, the heating water only flows through it when the anion exchanger is also being traversed. However, the mixed-bed cartridge can also be installed and operated independently of the anion exchanger within the heating circuit, for example, in the main or secondary flow.

[0023] Preferably, the mixed-bed cartridge can also be arranged in a further side stream of the main stream or in a further side stream of the side stream. It can also be provided that a switching device is assigned to the further side stream. With this switching device, the heating water flow can be controlled so that it is selectively: is only carried by the main current or the side current, is carried in parallel by the main current or the side current and the further side current, or is only carried by the further side current.

[0024] Such a switching device can, for example, be formed by a 3-way valve.

[0025] It is also conceivable to use a switching device that works in such a way that the heating water flow can be controlled so that it is optionally is only carried by the main current or the side current, or only by the further side current.

[0026] Such a switching device can, for example, be formed by a 2-way valve.

[0027] To remove byproducts introduced into the heating water during oxygen removal, the heating water can be passed through a filter, particularly a depth filter, after the anion exchanger, and / or the heating water can be passed through a filter, particularly a depth filter, in the main or bypass flow. The filter can be integrated into the heating water circuit as an alternative to, or in addition to, a mixed-bed cartridge. The filter can be located directly after an anion exchanger in the main or bypass flow of the heating water circuit. In this case, the heating water only flows through it when the anion exchanger is also being traversed. However, the filter can also be located and operated independently of the anion exchanger within the heating circuit, for example, in the main or bypass flow.

[0028] A high reaction rate between the oxygen dissolved in the heating water and the reducing agent can be promoted by passing the heating water through the anion exchanger in the heating system's flow line. The heating water in the flow line is at a high temperature. This high temperature significantly increases the reaction rate between the oxygen and the reducing agent, or, depending on the specific reagent used, may even enable the reaction in the first place. This results in the efficient removal of oxygen from the heating water.

[0029] The object of the invention relating to the device is solved by arranging an anion exchange cartridge through which the heating water flows in a main stream or a side stream of a heating water circuit of the heating system, by having the anion exchange cartridge have a strongly basic anion exchanger and by loading the anion exchanger with a reducing agent for oxygen.

[0030] Additionally or alternatively, the anion exchange cartridge can also be integrated into a fresh water supply line. The heating system's water circuit can be initially filled or topped up with fresh water via this supply line. In this way, oxygen is removed from the supplied fresh water during the initial filling and / or topping up of the heating water circuit. However, the efficiency with which oxygen can be removed from the fresh water is somewhat lower compared to integrating the anion exchange cartridge directly into the heating circuit, preferably into the flow line. As described above, the high water temperature in the flow line improves efficiency. Nevertheless, even with integration into the fresh water supply line, a noticeable reduction in oxygen content can occur.In particular, it has been shown that the oxygen content of the supplied fresh water can be reduced by approximately 80%. Less oxygen directly translates to a reduction in magnetite sludge formation. Magnetite sludge is a corrosion product in the heating water circuit. Therefore, integrating the system into the fresh water supply prevents the significant accumulation of magnetite sludge in the heating water circuit during initial filling and / or refilling.

[0031] The heating water is circulated through the anion exchange cartridge, thereby coming into contact with the reducing agent. As described in the process, the oxygen contained in the heating water reacts with the reducing agent and is thus removed. The heating water is advantageously directed through the anion exchange cartridge during circulation. This allows the oxygen to be removed from the heating water over several cycles. Even with relatively slow reaction rates between the oxygen and the reducing agent, this enables the complete or near-complete removal of dissolved oxygen from the heating water. Since the anion exchange cartridge is not located in a fresh water inlet of the heating system, but rather within the heating water circuit, it is constantly exposed to the flow of warm heating water.The comparatively high temperatures of the heating water, compared to an arrangement of the ion exchange cartridges in a fresh water inlet of the heating system, lead to a noticeable increase in the reaction rate between the oxygen and the reducing agent, which also contributes to the efficient removal of oxygen from the heating water. Certain redox reactions, required depending on the reducing agent used, are only made possible by the increased water temperature. The heating system cannot be designed to be corrosion-resistant. Such a corrosion-resistant heating system may have diffusion-open underfloor heating pipes, open expansion tanks located at the top, or insufficient pressure maintenance. In such heating systems, oxygen enters the heating water uncontrollably.By placing the ion exchange cartridge with the reducing agent in the circulating water, the oxygen introduced into the heating water during operation of the heating system is advantageously removed.

[0032] Oxygen can be efficiently removed from the heating water in a circulating heating system if the reducing agent used on the cation exchanger is a chemical with an oxidation state different from its maximum oxidation state, preferably a reducing agent in the form of ferrous iron. The oxygen dissolved in the heating water can accept electrons from the reducing agent adsorbed on the cation exchanger. This process oxidizes the reducing agent. Advantageously, the reducing agent oxidized to a higher oxidation state has the same or preferably a higher affinity for the cation exchanger than the reducing agent present in the lower oxidation state. This prevents the reducing agent from being released into the heating water in large quantities.

[0033] A cation exchanger (not according to the invention) can simply be loaded with divalent iron.

[0034] When heating water containing dissolved oxygen is supplied to a cation exchanger in its iron form, the oxygen reacts with the divalent iron according to the reaction equation: 4 Fe²⁺ + O₂ + 2 H₂O → 4 Fe³⁺ + 4 OH⁻

[0035] According to the selectivity series for ion exchange resins, the trivalent iron formed has a higher affinity for the cation exchanger than divalent iron, so it remains predominantly bound to the cation exchanger and is released only in small amounts into the heating water. Sludge formation in the heating water, for example through the formation of iron(III) hydroxide, can thus be avoided or at least reduced.

[0036] To soften the heating water in addition to removing oxygen, the cation exchange cartridge can be equipped with a sodium cation exchanger in which a portion of the sodium ions are replaced by a reducing agent, preferably ferrous ferrous ferric (Fe²⁺). The oxygen dissolved in the heating water is removed by reaction with the ferrous ferric ferric, while the water is softened by replacing the calcium and magnesium ions present in the heating water with sodium ions. This method of softening advantageously does not alter the pH value of the heating water.Such a cation exchanger, existing partly in sodium and partly in iron form, can be produced by first replacing all or nearly all hydrogen atoms with sodium, starting with a cation exchanger existing in its hydrogen form, and then replacing some of the sodium with divalent iron (Fe²⁺). This process exploits the fact that polyvalent ions have a higher affinity for the cation exchange material; that is, Fe²⁺ has a greater affinity for the cation exchange material than Na⁺. With appropriate process control, Na⁺ can therefore be partially replaced by Fe²⁺.

[0037] To soften typical heating water and remove dissolved oxygen, it has proven advantageous for the cation exchanger to contain 10 to 50% sodium in the reducing agent by volume. This ratio between sodium and reducing agent content ensures that approximately equal volumes of water can be softened and oxygen-free.

[0038] According to the invention, sulfite ions are provided as a reducing agent at the anion exchanger. Sulfite ions are oxygen-consuming. Upon contact with the heating water, they react with the oxygen dissolved in the heating water, reducing the oxygen and oxidizing the sulfate ion SO₃²⁻ to the sulfate ion SO₄²⁻. Advantageously, the sulfate ion has a higher affinity for the anion exchanger than the reduced form of sulfite. This prevents the circulating water from being excessively burdened with the oxygen-consuming chemical. The reaction between the oxygen and the sulfate ion can proceed, for example, according to the reaction equation 2 Na₂SO₃ + O₂ → 2 Na₂SO₄. The reaction of the sulfite with the oxygen only occurs at higher temperatures. Since the reducing agent is advantageously arranged in the circulation of the warm heating water, the reaction can take place.

[0039] Preferably, the anion exchanger may be configured in which a proportion of hydroxide ions (OH⁻) are replaced by ions of the reducing agent, preferably by sulfite ions (SO₃²⁻). In addition to reducing the oxygen present in the heating water by reaction with the reducing agent, the heating water can be alkalized by exchanging dissolved anions for hydroxide ions. In this way, the pH value of the heating water can be specifically controlled, and, in combination with a cation exchanger, demineralization of the heating water can be achieved.

[0040] In order to remove approximately the same amount of oxygen and alkalize heating water using an anion exchange cartridge, it may be necessary for the anion exchanger to be present in the OH form with the reducing agent to a volume fraction of 5 to 10%.

[0041] According to the invention, a mixed-bed cartridge is arranged downstream of the anion exchange cartridge, and / or a filter, preferably a depth filter, and / or a mixed-bed cartridge are arranged downstream of the cation exchange cartridge. The mixed-bed cartridge or a filter can remove potential byproducts from the heating water, such as those that may arise during the reaction of oxygen with the reducing agent. For example, iron(III) hydroxide formed in the cation exchange cartridge can be removed by the downstream mixed-bed cartridge, thereby preventing or at least reducing sludge formation within the heating system. Similarly, sulfate formed in the anion exchange cartridge, which has unfavorable corrosion properties, can be removed by the downstream mixed-bed cartridge.

[0042] Advantageously, the heating water is first softened and then the oxygen is removed reductively. To enable this to happen in the preferred sequence, the cation exchange cartridge (not according to the invention) can be used as

[0043] The system is designed as a two-chamber or multi-chamber system, in which a cation exchanger in the sodium form is arranged in a chamber that is forward in the direction of flow and in a chamber that follows in the direction of flow the cation exchanger loaded with the reducing agent.

[0044] Particularly preferably, the oxygen is first removed from the heating water by reductive action, and the heating water is then alkalized to retain any sulfate released into the heating water or to exchange it for OH⁻ ions. To enable this in the preferred sequence, the anion exchange cartridge can be designed as a two-chamber or multi-chamber system, with the anion exchanger loaded with the reducing agent arranged in a chamber leading upstream in the flow direction, and an anion exchanger in OH⁻ form arranged in a chamber downstream in the flow direction.

[0045] Separation of the chambers of the cation exchange cartridge and / or the anion exchange cartridge can be achieved by separating the chambers of the cation exchange cartridge and / or the anion exchange cartridge from each other by a filter disc, preferably a filter disc made of sintered material. Preferably, the heating water is filtered as it passes through the filter disc. Advantageously, the cation exchange cartridge and / or the anion exchange cartridge, and thus the filter discs, are integrated into the heating water circuit and are circulated through by the heating water.

[0046] Easy installation of the cation exchange cartridge and / or the anion exchange cartridge in a heating circuit is facilitated by the fact that each cartridge has a water inlet and outlet connection. These connections allow for simple integration into the heating system's piping. If the cation exchange cartridge and / or the anion exchange cartridge are connected to the heating water circuit via a bypass, the water flow through the bypass can be interrupted, for example, by means of appropriately designed valves, such as for maintenance purposes. In this way, the ion exchange cartridges can be replaced without interrupting the heating system's operation.

[0047] According to a preferred embodiment of the invention, the anion exchange cartridge can be connected to the flow line of the heating water circuit. The heating water reaches its highest temperature in the flow line. By arranging the anion exchange cartridge loaded with the reducing agent in the flow line of the heating system, high reaction rates between the reducing agent and the oxygen dissolved in the heating water can be achieved due to the high water temperatures. The oxygen can thus be removed from the heating water quickly and completely. Reducing agents that only react with oxygen when thermal energy is supplied can also be used.However, depending on the anion exchange material used, care must be taken to ensure that the temperature of the supplied water does not exceed 65 °C, or does not exceed it permanently, as there is a risk that the exchange resin used will be damaged, and in particular that regeneration of this resin will no longer be possible.

[0048] The invention will be explained in more detail below with reference to exemplary embodiments illustrated in the drawings. The drawings show: Fig. 1 shows a highly schematic representation of a heating system with an ion exchange cartridge connected in a shunt circuit, and Fig. 2 shows a highly schematic representation of another embodiment of a heating system.

[0049] Figure 1Figure 1 shows a highly schematic representation of a heating system 10 with an ion exchange cartridge 22 connected in a bypass circuit. A heating water circuit 11 of the heating system 10 forms a flow 16 and a return 13. A fresh water connection 12 is provided on the heating water circuit 11 for filling the heating system 10 or for topping up the heating water. A heat exchanger 14, a first pump 15, and a radiator 17 are integrated into the highly simplified heating water circuit 11. The heat exchanger 14 transfers thermal energy, which is supplied, for example, by a gas or oil boiler, to the heating water. The heating water is pumped by the first pump 15, in a flow direction 30 indicated by an arrow, via the flow 16 to the radiator 17. The radiator 17 represents other radiators and serves to heat a building.The cooled heating water from radiator 17 is routed back to heat exchanger 14 via return pipe 13.

[0050] The ion exchange cartridge 22 is designed as a multi-chamber cartridge, specifically a two-chamber cartridge. It has a front chamber 22.1 and a subsequent chamber 42.2. The front chamber 22.1 and the subsequent chamber 22.2 are separated from each other by a filter disc 22.3. On the inlet side, the ion exchange cartridge 22 is connected to the flow line 16 of the heating system 10 via a first shut-off valve 20 and a second pump 21. The second pump 21 causes the heating water from the flow line 16 of the heating system to be pumped to the ion exchange cartridge 22 in the direction of flow 30, indicated by an arrow. Downstream of the ion exchange cartridge 22, a mixed-bed cartridge 23 is arranged. On the outlet side, the mixed-bed cartridge 23 is connected to the flow line 16 of the heating system 10 via a second shut-off valve 24.

[0051] With the help of the second pump 21, heating water from the flow 16 of the heating circuit 11 is pumped through the two chambers 22.1, 22.2 of the ion exchange cartridge 22, the filter disc 22.3 arranged between them and the subsequent mixed bed cartridge 23 and then fed back to the flow 16 of the heating circuit 11 via the second shut-off valve 24.

[0052] In a first embodiment, the ion exchange cartridge 22 is designed as a cation exchange cartridge (not according to the invention).

[0053] In the front chamber 22.1, a strongly acidic sodium cation exchanger is arranged. This sodium cation exchanger serves, in a known manner, to soften the heating water passing through it. In the subsequent chamber 22.2, a cation exchanger loaded with a reducing agent is provided. The reducing agent is designed to remove oxygen from the heating water. For this purpose, the hydrogen ions of the strongly acidic cation exchanger have been at least partially replaced by ions of the reducing agent, in this case, Fe²⁺ ions. When the heating water softened in the front chamber 22.1 is brought into contact with the reducing agent in the subsequent chamber 22.2, the oxygen dissolved in the heating water is reduced by the reducing agent, and the reducing agent is oxidized accordingly. In this case, the divalent iron ion Fe²⁺ is oxidized to the trivalent iron ion Fe³⁺.In this process, the oxygen dissolved in the heating water is broken down according to the reaction equation 4 Fe 2+< + O 2 + 2 H 2 O → 4 Fe 3+< + 4 OH -<.

[0054] In another embodiment, the ion exchange cartridge 22 is configured as an anion exchange cartridge. A strongly basic anion exchanger, loaded with a reducing agent to remove oxygen from the heating water, is arranged in the front chamber 22.1. In this case, the reducing agent consists of sulfite ions SO₃²⁻. These partially replace the OH groups of the anion exchanger arranged in the front chamber 22.1. When the heating water comes into contact with this reducing agent, the dissolved oxygen is reduced, and the sulfite ions SO₃²⁻ are oxidized to sulfate ions SO₄²⁻. The oxygen is thus removed from the heating water. An OH-form anion exchanger is filled into the subsequent chamber 22.2. The heating water is alkalized by exchanging the anions present in the heating water for hydroxide ions provided by the anion exchanger.The heating water can thus be both freed from oxygen and alkalized in accordance with the VDI 2035 heating water guideline.

[0055] Advantageously, the ion exchange cartridge 22 is arranged in the circulation of the heating water circuit 11. The heating water is thus passed through the ion exchange cartridge 22 in each cycle. This ensures that the oxygen is completely or almost completely removed from the heating water, even at comparatively slow reaction rates between the oxygen and the reducing agent. Since the ion exchange cartridge 22 is connected to the flow pipe 16 of the heating system 10, the heating water passing through the ion exchange cartridge 22 has a comparatively high temperature. This high temperature advantageously increases the reaction rate between the oxygen and the reducing agent. This is particularly relevant for the reaction of oxygen with sulfite, as this reaction requires heat.

[0056] Ion exchangers are used to bring oxygen-consuming chemicals into contact with the heating water as reducing agents. When used with a strongly acidic cation exchanger, the oxygen-consuming chemicals have an oxidation state below their maximum oxidation state. The oxygen dissolved in the heating water can then accept electrons from the oxygen-consuming chemical. Advantageously, the more highly charged ion after the oxidation reaction exhibits a higher affinity for the cation exchanger than the less charged ion, as can be seen in the selectivity series for ion exchange resins. In the case of an iron-loaded cation exchanger, the Fe³⁺ ion formed has a higher affinity for the cation exchanger than the original Fe²⁺ ion.This prevents Fe 3+< from entering the heating water in larger quantities, for example in the form of iron(III) hydroxide, and leading to sludge formation there.

[0057] Even in an anion exchanger using sulfite ions (SO₃²⁻) as a reducing agent, the sulfate ions (SO₄²⁻) formed by oxidation advantageously exhibit a higher affinity for the anion exchanger than the reduced form of sulfite. This prevents the heating water from becoming excessively burdened with the oxygen-consuming chemicals.

[0058] An acidic, preferably strongly acidic, cation exchanger existing in its hydrogen form can be converted to the iron form, for example, using iron(II) sulfate. In this process, 2H⁺ ions are replaced by the oxidation-sensitive or oxygen-consuming Fe²⁺ ion. It is conceivable that the strongly acidic cation exchanger already exists in its sodium form before conversion to the iron form, so that in one embodiment an ion exchange cartridge 22 can be produced which easily reduces the oxygen content of the heating water and simultaneously softens it. By converting a portion of the ion exchange resin to the iron form and leaving a portion in the sodium form, calcium and magnesium can be removed from the water by exchange for sodium, similar to a conventional water softener, and oxygen can be removed from the water at the same time. The ion exchange cartridge can then also be designed as a single-chamber cartridge.Advantageously, multivalent ions exhibit a higher affinity for the exchange material. The cation exchanger can thus first be converted into its sodium form and subsequently partially converted into the iron form by partially replacing the monovalent Na+ ions with divalent Fe2+ ions. Preferably, such a cation exchanger exists in the sodium form to a volume fraction of 10 to 50%. In this way, approximately the same amount of heating water can be softened and oxygen-free with one cation exchange cartridge. Both the oxygen removal capacity and the softening capacity are exhausted after approximately the same amount of treated heating water at this volume ratio, thus preventing premature replacement of the cation exchange cartridge due to premature exhaustion of one of the reactants.

[0059] Accordingly, when using a basic ion exchanger in which the basic groups are only partially replaced by, for example, sulfite ions, alkalization of the system water to be treated, as defined in the VDI 2035 heating water guideline, can be achieved in addition to the oxygen consumption effect. Advantageously, the anion exchanger contains the reducing agent in the OH form at a volume fraction of 5 to 10%, so that the oxygen removal and alkalization capacity is exhausted with approximately the same amount of treated heating water. Here, too, it is conceivable to design the ion exchange cartridge 22 as a single-chamber cartridge.

[0060] The cation exchange cartridges (not according to the invention) and the anion exchange cartridges, which are provided with a reducing agent for oxygen removal, are preferably designed as single-bed cartridges. Byproducts formed during oxygen removal, such as iron(III) hydroxide in the cation exchanger, which can lead to sludge formation, or sulfate in the anion exchanger, which has an adverse effect on corrosion, can be removed by the Figure 1 The inline process shown, for example, is filtered out by the filter disc 22.3 or removed from the heating water by the downstream mixed-bed cartridge 23. It is conceivable, alternatively or additionally to the filter disc 22.3 or the mixed-bed cartridge 23, to use a Figure 1To integrate a filter (not shown), in particular a depth filter, into the heating water circuit 11. The filter can be integrated into the bypass of the heating water circuit downstream of the ion exchange cartridge. The filter removes the byproducts generated during oxygen removal.

[0061] The mixed-bed cartridge 23, which is either connected downstream of the ion exchange cartridge 22 or inserted at any point in the system water circuit, is advantageous because, depending on the composition of the system water, more or less iron ions can be displaced by the ion exchange cartridge 22, which is designed for oxygen reduction. The oxygen-binding effect nevertheless takes place within the heating water circuit.

[0062] The ion exchange cartridge 22 preferably has a water inlet connection (not shown) and a water outlet connection (also not shown). The ion exchange cartridge 22 can therefore be easily disconnected from the heating water circuit 11 for replacement, and a new ion exchange cartridge 22 can be connected to the heating water circuit 11.

[0063] Figure 2 Figure 10 shows a further embodiment of a heating system according to the invention. This embodiment of a heating system is based on the design variant according to Figure 10. Figure 1 This document builds upon, or further develops, the existing design. Identical parts are numbered with the same reference numbers, so that reference can be made to the preceding explanations to avoid repetition. Therefore, the following discussion will focus primarily on the differences between the two design variants.

[0064] How Figure 1As shown, the heating system 10 has an ion exchange cartridge 22 connected in parallel. A heating water circuit 11 of the heating system 10 forms a flow 16 and a return 13. A fresh water connection 12 is provided on the heating water circuit 11 for filling the heating system 10 or for topping up the heating water.

[0065] In the area of ​​this fresh water connection 12, another ion exchange cartridge 22 is arranged. Additionally or alternatively, it can also be provided that another mixed-bed cartridge 23 is integrated into the fresh water supply line.

[0066] The construction of the further ion exchange cartridge can again be as described above or specified in the claims. To avoid repetition, reference is therefore made to the preceding statements and the claims.

[0067] The further mixed-bed cartridge 23 can be designed as described above or specified in the claims. The mixed-bed cartridge serves to at least partially demineralize the fresh water that passes through the mixed-bed cartridge 23. For the sake of brevity, reference is made to the above statements.

[0068] However, it is particularly preferred that the further ion exchange cartridge 22 together with a further mixed bed cartridge 23 are integrated into the fresh water supply line, wherein the further mixed bed cartridge 23 is preferably arranged downstream of the further ion exchange cartridge 22 in the direction of flow.

[0069] In the highly simplified representation of the heating water circuit 11, a heat exchanger 14, a first pump 15, and a radiator 17 are integrated. The heat exchanger 14 transfers thermal energy, supplied, for example, by a gas or oil boiler, to the heating water. The heating water is pumped by the first pump 15, following a flow direction 30 indicated by an arrow, via the supply line 16 to the radiator 17. The radiator 17 represents other radiators and serves to heat a building. From the radiator 17, the cooled heating water is returned via the return line 13 to the heat exchanger 14.

[0070] A bypass is derived from the heating water circuit 11. Preferably, the bypass is branched off from the flow 16 coming from the heat exchanger 14.

[0071] The parallel argument can, as mentioned above, also refer to Figure 1The system described is designed to be shut off or opened by means of two shut-off valves 20 in relation to the heating water circuit 11. In the opened state, the heating water can circulate in parallel through the flow and the bypass.

[0072] To transport the heating water in the bypass, a pump 21 is again provided. Furthermore, a depth filter 25 can optionally be used, which can be arranged upstream or downstream of the pump 21 in the direction of flow.

[0073] Preferably, the depth filter 25 is arranged downstream of the pump 21. Particularly preferably, the depth filter 25 is arranged upstream of a mixed bed 23 or upstream of the ion exchange cartridge 22 in the direction of flow.

[0074] How Figure 2As can be further seen, a first secondary bypass 27 is integrated into the secondary bypass. A mixed-bed cartridge 23 is inserted in the area of ​​this first secondary bypass 27. This mixed-bed cartridge 23 can be designed as already described above or specified in the claims. The mixed-bed cartridge serves to at least partially demineralize the heating water that passes through the mixed-bed cartridge 23. To avoid repetition, reference is made to the above statements. The first secondary bypass 27 has two shut-off valves 24. By means of these shut-off valves 24, the mixed-bed cartridge 23 can be disconnected from the secondary by means of the main bypass. This makes it possible to replace the mixed-bed cartridge 23, for example, when it is exhausted.

[0075] Furthermore, a control device can be provided, which in this case is designed in the form of a 3-way valve 26. By means of the 3-way valve 26, the first secondary bypass 27 can be coupled to the secondary bypass in such a way that, depending on the position of the 3-way valve 26, the flow of the heating water takes place via the first secondary bypass 27 or bypassing this first secondary bypass 27.

[0076] The 3-way valve 26 can preferably be an electrically controlled 3-way valve 26.

[0077] Preferably, a measuring device can be provided that determines the conductivity of the heating water in the heating water circuit 11. If the measuring device signals an undesirably high conductivity of the heating water, the three-way valve 26 is controlled by a control unit by means of a switching signal so that the flow of the heating water occurs via the first secondary bypass 27. The heating water then flows through the mixed-bed cartridge 23. In the mixed-bed cartridge 23, the heating water is at least partially demineralized. This reduces the conductivity. The three-way valve 26 can remain switched until the conductivity returns to its desired value. Then the three-way valve 26 is switched and the heating water continues to flow via the secondary bypass, for example to an ion exchange cartridge 22.

[0078] The use of the additional bypass 27, the mixing bed 23 and the 3-way valve 26 is an option that is not mandatory in the embodiment shown. Figure 2 must be present.

[0079] The secondary bypass also includes a second secondary bypass 28. This second secondary bypass 28 is connected to the primary bypass via a 3-way valve 26. The ion exchange cartridge 22 is integrated into this second secondary bypass 28.

[0080] The construction of this ion exchange cartridge can again be as described above or specified in the claims. To avoid repetition, reference is therefore made to the preceding statements and the claims.

[0081] Depending on the position of the 3-way valve 26, the circulation of the heating water in the bypass can be controlled so that the heating water is either routed via the second bypass 28, or that the heating water is routed in the bypass, bypassing the second bypass 28. This makes it possible to switch the ion exchange cartridge 22 on or off as needed.

[0082] Preferably, it can be provided that the heating water flows through the ion exchange cartridge 22 loaded with the reducing agent (and, if necessary, also through the upstream depth filter 25) for a predetermined period of time, for example several hours per day.

[0083] Preferably, the heating water is not passed through the mixed-bed cartridge 23 and the ion exchange cartridge 22 simultaneously. Then, depending on the desired operating mode, either the mixed-bed cartridge 23 or the ion exchange cartridge 22 can be disconnected from the bypass circuit.

[0084] Of course, it is also conceivable that both the mixed bed cartridge 23 and the ion exchange cartridge 22 are flowed through simultaneously.

[0085] During the initial filling of heating system 10, fresh water is introduced into the heating system 10 via the fresh water connection 12. The fresh water first flows through the second ion exchange cartridge 22. In this second ion exchange cartridge 22, oxygen is consumed, and the oxygen is removed from the supplied water (tap water). This results in a significant reduction of the oxygen content. Following the ion exchange cartridge 22, the supplied fresh water flows through the second mixed-bed cartridge 23. Here, the supplied fresh water is at least partially demineralized. The treated water, with its reduced oxygen content and at least partially demineralized state, is then introduced into the heating system. Accordingly, the water has already been treated to optimize corrosion resistance.

[0086] For the sake of completeness, it should be noted here that the invention refers to a heating system 10 in which a further ion exchange cartridge 22 is integrated in the area of ​​the fresh water connection 12 or in the area of ​​the fresh water inlet, and optionally a mixed-bed cartridge 23 is also integrated in the fresh water connection 12 or in the area of ​​the fresh water inlet. In particular, it is conceivable that in such an embodiment of the invention, the use of a bypass, as described in the exemplary embodiments according to the Figure 1 and 2 It has been shown that it has been dispensed with.

[0087] In the embodiment according to the Figure 2After the heating system 10 is filled, the heating water is circulated in the heating water circuit 11. The heating water also flows through the bypass. As it flows through the bypass, the heating water is at least partially and continuously cleaned by the optional depth filter 25. Depending on the switching position of the 3-way valves 26, the heating water can be treated in the mixed-bed cartridge 23 and / or in the ion exchange cartridge 22.

[0088] If a component in the bypass, for example the depth filter 25, the pump 21, or the ion exchange cartridge 22, is to be replaced, the bypass can be separated from the heating water circuit 11 by means of the two shut-off valves 20.

Claims

1. A method for reducing the oxygen content of the heating water in a heating system (10), wherein the heating water is circulated in the heating water circuit of the heating system (10), characterized in that the heating water in the heating water circuit is passed, during circulation operation, through an anion exchanger containing a reducing agent, namely a strongly basic anion exchanger, that the oxygen contained in the heating water is removed from the heating water, at least in part, by reaction with the reducing agent as the heating water circulates through the anion exchanger, that sulfite ions are provided on the anion exchanger as the reducing agent, which, upon contact with the heating water, react with the oxygen dissolved in the heating water, whereby the oxygen is reduced and the sulfite ions are oxidized to sulfate ions, wherein the sulfate ions exhibit a higher affinity for the anion exchanger than the reduced form of the sulfite, that the heating water is passed through the anion exchanger containing the reducing agent, that the anion exchanger is present in the OH form in part, preferably in a volume fraction of 5 to 10%, and that the heating water is passed through a mixed-bed cartridge (23) after the anion exchanger.

2. Method according to claim 1, characterized in that a main stream of the heating water or a secondary stream of the heating water branched off from the main stream is passed through the anion exchanger containing the reducing agent.

3. Method according to claim 2, characterized in that the heating water in the main stream or in the secondary stream is passed through the mixed-bed cartridge (23).

4. Method according to any one of claims 2 to 3, characterized in that the heating water is passed through a filter, in particular a depth filter, after the anion exchanger, and / or that the heating water in the main stream or in the secondary stream is passed through a filter, in particular a depth filter.

5. Method according to any one of claims 1 to 4, characterized in that the heating water in the feed flow (16) of the heating system (10) is passed through the anion exchanger, and / or that fresh water for filling or replenishing the heating system is passed through a cation exchanger and / or the anion exchanger or another anion exchanger.

6. Heating system with a device for reducing the oxygen content of the heating water in the heating system (10), characterized in that an anion exchanger cartridge through which the heating water flows is arranged in a secondary stream of a heating water circuit (11) of the heating system (10) that is branched off from a main stream, that the anion exchanger cartridge comprises a strongly basic anion exchanger, that the anion exchanger is loaded with a reducing agent for oxygen, that sulfite ions are provided as the reducing agent on the anion exchanger, which react with the oxygen dissolved in the heating water upon contact with the heating water, whereby the oxygen is reduced and the sulfite ions are oxidized to sulfate ions, wherein the sulfate ion has a higher affinity for the anion exchanger than the reduced form of the sulfite, that the anion exchanger with the reducing agent is present in the OH form at a volume fraction of 5 to 10%, and that the heating water is passed through a mixed-bed cartridge (23) after the anion exchanger.

7. Heating system according to claim 6, characterized in that a mixed-bed cartridge (23) is arranged downstream of the anion exchange cartridge in the flow direction and / or that a filter, preferably a depth filter, and / or a mixed-bed cartridge (23) is arranged downstream of the anion exchange cartridge in the flow direction.

8. Heating system according to claim 6 or 7, characterized in that the anion exchanger cartridge is designed as a two-chamber system or as a multi-chamber system, that the anion exchanger loaded with the reducing agent is arranged in a chamber (22.1) located upstream with respect to the flow direction, and that an anion exchanger in the OH form is arranged in a chamber (22.2) located downstream with respect to the flow direction, and wherein it may preferably be provided that the chambers of the anion exchanger cartridge are separated from one another by a respective filter disc (22.3), preferably by a respective filter disc made of sintered material.

9. Heating system according to any one of claims 6 to 8, characterized in that the anion exchange cartridge has a water inlet connection and a water outlet connection and / or that the anion exchange cartridge is connected to the feed flow (16) of the heating water circuit (11).