Apparatus for preparing an alkali metal hypochlorite solution

Abstract

Device for producing an alkali metal hypochlorite solution comprising a housing (1), a brine container (3) for a saturated brine solution, a water supply (2), an electrolysis cell (7) and a power connection (8) for transmitting a current through the electrolysis cell (7), wherein the brine container (3) and the water supply (2) are coupled to the electrolysis cell (7) via a pump (16), characterized in that the brine container (3) and the water supply (2) each have an outlet valve (14, 15), wherein a predefined current through the electrolysis cell (7) can be set by controlling the opening times of the outlet valves (14, 15) and the volume flow through the pump (16), which is connected downstream of the outlet valves (14, 15).

Description

[0001] The invention relates to a device for producing an alkali metal hypochlorite solution, comprising a housing, a brine tank for a saturated brine solution, a water supply, an electrolysis cell, and a power connection for transmitting current through the electrolysis cell, wherein the brine tank and the water supply are coupled to the electrolysis cell via a pump. The invention further relates to a method for producing an alkali metal hypochlorite solution, in particular a sodium hypochlorite solution, wherein water and a saturated brine solution are supplied to an electrolysis cell. BACKGROUND OF THE INVENTION

[0002] The effectiveness of alkali metal hypochlorite solutions, especially sodium hypochlorite solutions, as oxidative disinfectants has been known for a long time. When sodium hypochlorite reacts with various germs, it decomposes into water and sodium chloride through oxidation, a process that is harmless to humans, animals, and the environment. This type of water chlorination is already widely used, for example, in drinking water treatment for cities and municipalities. However, this requires large systems that are not suitable for mobile use. Large systems therefore often cannot be used where they are needed, such as for disinfecting wells and cistern water, or especially in disaster areas. Transporting ready-made sodium hypochlorite solutions to such locations is also fraught with numerous obstacles.The two most serious disadvantages for transport are hypochlorite's instability to UV light and its sensitivity to excessively high storage temperatures (> 20 °C). Since a low concentration of less than 2.5% sodium hypochlorite is generally sufficient for complete disinfection, this implies that over 97.5% of the finished solutions are water, resulting in avoidable environmental pollution during transport compared to on-site production.

[0003] A mobile device and method for producing alkali metal hypochlorite solution are disclosed, for example, in WO 2006 / 077016 A1. The device described therein comprises a single electrolysis cell and various means for supplying a brine solution of water and saturated sodium chloride solution to the electrolysis cell. Parameters such as current intensity or brine concentration, or flow rate of the metering pumps for saturated brine solution and / or water supply, are kept constant to limit the concentration of hypochlorite produced during electrolysis. However, this device does not offer the possibility of regulating the flow rate of the brine solution and the water supply.

[0004] The disclosure in DE 37 04 955 A1 specifically describes the control electronics of a device comprising a brine dosing pump, a controlled power supply, an electrolysis cell, and auxiliary and supplementary components in a compact unit for the production of sodium hypochlorite. The brine concentration within the electrolysis cell is determined by evaluating the voltage across the electrodes and the current flowing through them, as these can vary depending on the conductivity of the mixture. Based on this, a signal proportional to the conductivity is generated, which is then used to control a dosing pump for saturated brine solution. The control system is a PLC (Programmable Logic Controller) in conjunction with appropriate sensors. This necessitates regular maintenance, which makes its use impractical, especially in remote and disaster areas.

[0005] Furthermore, CN 215 481 318 U discloses a device which also includes a power supply, a control system, a saline solution device, an electrolysis cell, a water mixing system, and a drug storage tank. In this device, the electrolysis cell is connected to the saline solution device and the water mixing system via piping, and an outlet of the electrolysis cell is connected to the drug storage tank. A metering pump is arranged at another outlet of the drug storage tank, through which the sodium hypochlorite solution can be dispensed. The control system ensures that the water quantity is monitored in real time and that the operating status of the system and the dispensed quantity of sodium hypochlorite solution can be adjusted. The concentration of sodium hypochlorite in the electrolysis cell is regulated solely by the water supply. The device therefore addresses the same problem as in WO 2006 / 077016 A1.Furthermore, the system still suffers from the aforementioned disadvantages of PLC control.

[0006] Documents US 2016 / 265123 A1, US 2014 / 124378 A1 and US 10,183,876 B2 disclose an electrolysis cell arrangement, a device for carrying out electrolysis and a water treatment system with electrolysis cells.

[0007] Furthermore, document US 10,280,526 B2 discloses a system for producing a sterilization solution. The system comprises an electrolysis cell, a water softener tank (or an external water supply), a brine tank, various valves, a positive displacement pump, and a control unit that manages the common positive displacement pump and the valves. The positive displacement pump is configured to selectively supply the sodium chloride salt solution from the brine tank to either the electrolysis cell or the water softener tank. The electrolysis current is proportional to the salt concentration, so the current indicates whether new solid sodium chloride should be added to the brine tank. Since the entire system is under line pressure, the positive displacement pump must pump the sodium chloride salt solution against this line pressure when supplying it to the electrolysis cell. A production valve then regulates the flow of the sodium chloride salt solution and water mixture to the electrolysis cell.The production valve cannot regulate the mixture between the sodium chloride salt solution and water. Due to the line pressure, the mixing accuracy between the sodium chloride salt solution and water is reduced, as the positive displacement pump must continuously counteract the water pressure. Furthermore, the increased need for regulation increases the likelihood of pump malfunction, which accelerates pump wear. As a result of a pump malfunction, no brine-water mixture can be delivered to the electrolysis cell, and consequently, no reaction to form a sodium hypochlorite solution can occur within the electrolysis cell. BRIEF DESCRIPTION OF THE INVENTION

[0008] Against this background, the invention aims to provide a device and a method for producing an alkali metal hypochlorite solution, enabling the production of such a solution with a sufficiently constant concentration for technical applications using a minimal, trouble-free, pressure-independent, and low-maintenance design. Furthermore, the device should be suitable for continuous operation and exhibit the lowest possible energy consumption.

[0009] This problem is solved by a device for producing an alkali metal hypochlorite solution, in particular a sodium hypochlorite solution, comprising a housing, a brine tank for a saturated brine solution, a water supply, an electrolysis cell and a power connection for transmitting a current through the electrolysis cell, wherein the brine tank and the water supply are coupled to the electrolysis cell via a pump, characterized in that the brine tank and the water supply each have an outlet valve, wherein a predefined current through the electrolysis cell can be set by controlling the opening times of the outlet valves and the volume flow by the pump, which is connected downstream of the outlet valves.

[0010] Preferably, the pump is located downstream of the outlet valves.

[0011] The mixture of water from the water supply and saturated brine solution from the brine tank, which is fed to the electrolysis cell, is hereinafter referred to as the brine-water mixture.

[0012] The opening times of the outlet valves can be controlled by electronic control units suitable for managing the system. This control of the outlet valves ensures a constant concentration of the alkali metal hypochlorite solution in the electrolysis cell. Specifically, the opening times of the outlet valves in the brine tank and the water supply can be regulated to maintain a constant ratio of water to saturated brine solution flowing towards the pump. This allows for continuous operation, thus increasing the system's range of applications.

[0013] The pump can be a dosing pump. The dosing pump can regulate a constant flow rate of water and / or saturated brine solution by adjusting its speed. This ensures precise control of the flow rate. Adjusting the flow rate via the dosing pump guarantees that the brine-water mixture is completely converted as it passes through the electrolysis cell.

[0014] Furthermore, a brine-water mixing tank can be positioned between the pump and the electrolysis cell. This tank ensures a homogeneous brine-water mixture, thus allowing the use of a smaller electrolysis cell. This is because practical experience has shown that the more uniform the brine-water concentration is at the electrolysis cell's inlet, the more efficiently it operates.

[0015] In one embodiment, a water tank is interposed between the water supply and the associated outlet valve. This water tank can include a level sensor with an inlet valve, preferably a float switch with a solenoid valve. The float switch with solenoid valve enables the tank to be filled regularly. Furthermore, the water tank is designed to have both a water inlet and a water outlet, whereby in one embodiment the water inlet and outlet can be the same line. The water tank also includes a vent with an overflow, ensuring that both the tank and the system are only under ambient pressure. This also ensures that the suction side of the pump remains pressure-free.The absence of pressure minimizes the risk of a pipe break and improves the pump's delivery performance, as it is no longer dependent on the existing water line pressure and therefore remains constant.

[0016] The water supply can be equipped with at least one water softener upstream, which prevents limescale deposits. This significantly increases the lifespan of the electrolysis cell and can improve the quality of the finished product.

[0017] In one embodiment, a fuel filter is installed upstream of the pump in both the water and salt lines. The fuel filter serves to protect the pump valves from particles and thus prevent clogging.

[0018] In one embodiment, the water supply is arranged on the side of the housing opposite the power connection when viewed vertically. This arrangement places the power supply line at the highest point of the housing, while the water supply and overflow lines are located at the lowest point. This prevents damage caused by moisture.

[0019] A two-phase main switch can be connected downstream of the power supply, with the main switch leading to at least two separate power supplies, preferably two 12 V DC power supplies, one of which can be connected to the circuit of the electrolysis cell and the other to the circuit of the remaining electronics. The division into two power supplies prevents an irregular power supply to the electronics. An irregular power supply to the electronics would result from the power supply to the electrolysis cell, as its power can fluctuate depending on the concentration and leads to a very high current in the electrolysis cell, especially during start-up.

[0020] Furthermore, the device can comprise at least two, preferably three, separate modules, which are independently interchangeable. The three modules are an electrolysis module, an electronics module, and a wet cell. In contrast to WO 2006 / 077016 A1, the device according to the invention is modular in design, which offers the advantages of easy assembly and maintenance, and consequently, increased sustainability and recyclability.

[0021] In one embodiment, the housing is modularly expandable. This results in increased flexibility, as modules can be added and removed. Furthermore, the device can be adapted to future modifications or technological developments.

[0022] The electronic module monitors and controls all process-relevant parameters. It also enables the regular transmission of key parameters, such as duty cycle, electrolysis cell current, pump speeds, etc. This cloud-based transmission is made possible by the control electronics, which include a communication module, preferably an IoT communication module. Unlike the device in DE 37 04 955 A1, the device according to the invention incorporates IoT technology, which allows for remote maintenance and monitoring of the system and billing of consumption. In the event of a malfunction, a fault message is automatically transmitted, and the system can be shut down via the communication module, thus preventing any damage to the user or owner in the event of a malfunction.

[0023] In one embodiment, the brine tank includes a level sensor with an inlet valve, preferably a float switch with a solenoid valve. The brine tank can also include an overflow and be connected to the water supply. Sufficient time is always allowed for the water in the brine tank to become completely saturated with salt. Furthermore, the brine tank can have different shapes and be arranged on the housing of the device in various embodiments. In one embodiment, the brine tank is arranged on an outer surface of the housing.

[0024] One particular embodiment provides an additional, preferably cuboid, housing with an integrated brine tank, which may itself be cuboid in shape. However, the brine tank and the additional housing are not limited to such a regular shape. A cuboid design offers the advantage, among others, that the brine tank and the water tank can be integrated into a single component. This saves space and significantly simplifies the system's construction. Furthermore, the cuboid design facilitates a more modular design.

[0025] To minimize the need to refill the salt tablets required to achieve a saturated brine solution for operation, the brine tank can be installed as a separate unit. This allows for unlimited refilling of the salt tablets. This can also offer the advantage of significantly reducing the frequency of maintenance required.

[0026] A gas separator can be placed downstream of the electrolysis cell to remove the hydrogen produced during the process.

[0027] The device for producing an alkali metal hypochlorite solution consumes less than 200 W during operation. Therefore, one version of the housing incorporates a photovoltaic module with a buffer storage unit. This version can also include a rechargeable battery that can be charged via the photovoltaic module. Alternatively, the battery can be installed in place of the power supply. This allows the device to operate independently of a stable power grid, making it particularly suitable for use in developing countries, disaster areas, and earthquake and flood zones.

[0028] The invention also relates to a process for producing an alkali metal hypochlorite solution, in particular a sodium hypochlorite solution, comprising the steps (i) Supplying water and a saturated brine solution to an electrolysis cell and (ii) converting the brine-water mixture into alkali metal hypochlorite solution, water and hydrogen in the electrolysis cell, characterized in that a predefined current through the electrolysis cell is set by regulating the opening times of outlet valves and the volume flow by a pump which is connected downstream of the outlet valves, whereby the regulation is carried out by means of control electronics.

[0029] This method can preferably be carried out with the aforementioned device and accordingly shares features with the previously described device. DETAILED DESCRIPTION OF THE INVENTION

[0030] Further details of the invention are explained with reference to the figures and figure descriptions. Fig. 1 shows a schematic representation of the device according to the invention. Fig. 2 shows an embodiment of the device according to the invention. Figs. 3a and 3b each show a further embodiment of the brine tank and the water tank of the device according to the invention.

[0031] Fig.1 Figure 1 shows a schematic representation of the device according to the invention for carrying out the method according to the invention. The device comprises a housing 1 (for clarity only shown in the following sections). Fig. 2 (as shown), a water supply 2, a brine tank 3 for a saturated brine solution, a brine-water mixing tank 5, an electrolysis cell 7, a power connection 8, preferably an AC connection, with power supplies 18, 18' for transmitting current through the electrolysis cell 7, control electronics 9 for controlling the system, a gas separator 20 for removing hydrogen, and a collection tank 6 for collecting the alkali metal hypochlorite solution. Furthermore, in the illustrated embodiment, the device includes a water tank 4, which is connected to the water supply 2 via an inlet valve 13. The same applies to the brine tank 3, which is also connected to the water supply 2 via an inlet valve 11. A level sensor 10, 12 measures the water level of each respective tank 3, 4 and regulates the respective inlet valve 11, 13 with respect to this parameter.Instead of the power connection 8 with the power supplies 18, 18' for transmitting current through the electrolysis cell 7 or in addition to it, a (not shown) accumulator can be provided which can be charged via a photovoltaic module.

[0032] The two containers 3, 4 in Fig. 1 Each outlet valve 14, 15 is connected downstream. The outlet valves 14, 15 are connected to a pump 16, preferably a metering pump. The pump 16 is further coupled to the optional brine-water mixing tank 5, which is coupled to the electrolysis cell 7. The electrolysis cell 7 and the outlet valves 14, 15 are electrically connected to the control electronics 9, so that the opening times of the outlet valves 14, 15 are regulated depending on the current within the electrolysis cell 7, with a setpoint range for the current. Furthermore, the setpoint range of the current is adjustable depending on the desired concentration of alkali metal hypochlorite solution. The pump 16 continuously draws in brine or fresh water, depending on which outlet valve 14, 15 is open, and then directs it into the brine-water mixing tank.The optional brine-water mixing tank serves to give the brine and water time to mix.

[0033] Within the electrolysis cell 7, the brine-water mixture is converted into alkali metal hypochlorite solution, water, and hydrogen. A gas separator 20 is connected downstream of the electrolysis cell 7 to remove the hydrogen. A collection vessel 6 is arranged downstream of the gas separator, into which the alkali metal hypochlorite solution is directed.

[0034] The process for producing an alkali metal hypochlorite solution, in particular a sodium hypochlorite solution, comprises, firstly, the supply of a saturated brine solution and water to an optional brine-water mixing tank 5, wherein the resulting brine-water mixture is subsequently supplied to the electrolysis cell 7, the concentration of which is adjusted via outlet valves 14, 15 and a pump 16. Secondly, the process comprises the conversion of the brine-water mixture into alkali metal hypochlorite solution, water, and hydrogen in the electrolysis cell 7. The volumetric flow rate of the saturated brine solution and the water is controlled by the control electronics 9, which regulates the outlet valves 14, 15 depending on the current within the electrolysis cell 7, thus determining the flow of the two solutions into the pump 16 and subsequently into the brine-water mixing tank 5 and then into the electrolysis cell 7.

[0035] The Fig. 2 shows further elements that the device according to the invention comprises and also explains further functions of the elements already mentioned. Thus, in Fig.2 The modular structure is shown, comprising a wet cell 21, an electronics module including the power connection 8, power supplies 18, 18' and main switch 22, and a control module including the control electronics 9 with communication module 19. These modules can be replaced independently. Furthermore, in Fig. 2 The aforementioned brine tank 3 and water tank 4 are also arranged modularly, as they are shaped like a cuboid and mounted in the housing of the wet cell 21.

[0036] The water supply 2 is located on the side opposite the power connection 8 in relation to the housing 1. This means that the power supply is located at the highest point of the housing 1, while the water supply and drainage are located at the lowest point of the housing 1.

[0037] Furthermore, a two-phase main switch 22 is connected downstream of the power connection 8, the main switch 22 leading to at least two separate power supplies 18, 18', preferably two 12 V DC power supplies. One of the two power supplies 18, 18' supplies the circuit of the electrolysis cell 7 with power, while the other power supply 18, 18' supplies the circuit of the remaining electronics with power. The control electronics 9 with integrated communication module 19 is part of the circuit of the remaining electronics and processes all process-relevant parameters. The communication module 19 integrated into the control electronics 9 also regularly transmits the core parameters.

[0038] The gas separator 20 is arranged in the housing 1 in such a way that it removes the hydrogen produced in the electrolysis cell 7 from the housing 1.

[0039] The Fig. 3a, 3bEach diagram shows a possible design variant for how the brine tank can be installed or attached to the system. For example, it is possible to connect the brine tank 3 to the water tank 4 when installed.

Claims

1. Device for producing an alkali metal hypochlorite solution comprising: • a housing (1), • a brine tank (3) for a saturated brine solution, • a water supply (2), • an electrolysis cell (7) and • a power connection (8) for transmitting a current through the electrolysis cell (7), wherein the brine tank (3) and the water supply (2) are coupled to the electrolysis cell (7) via a pump (16), characterized by the fact that The brine tank (3) and the water supply (2) each have an outlet valve (14, 15), whereby a predefined current through the electrolysis cell (7) can be set by controlling the opening times of the outlet valves (14, 15) and the flow rate by the pump (16), which is connected downstream of the outlet valves (14, 15).

2. Device according to claim 1, characterized by the fact that The opening times of the outlet valves (14, 15) can be controlled via a control electronics (9) which is suitable for controlling the system.

3. Device according to claim 1 or 2, characterized by the fact that a brine-water mixing tank (5) is connected between the pump (16) and the electrolysis cell (7).

4. Device according to claims 1 to 3, characterized by the fact that the pump (16) corresponds to a dosing pump and a constant volume flow of brine-water mixture can be controlled via the speed of the dosing pump.

5. Device according to claims 1 to 4, characterized by the fact that A water reservoir (4) is connected upstream of an outlet valve (15), the reservoir comprising a level sensor (12) with an inlet valve (13).

6. Device according to claims 1 to 5, characterized by the fact that the water tank (4) includes a vent with overflow.

7. Device according to any one of claims 1 to 6, characterized by the fact that the device comprises at least two separate modules, wherein the modules comprise an electrolysis module, a control module and a wet cell (21) and these are independently interchangeable.

8. Device according to any one of claims 1 to 7, characterized by the fact that The control electronics (9) include a communication module (19).

9. Device according to any one of claims 1 to 8, characterized by the fact that the brine tank (3) includes a level sensor (10) with an inlet valve (11).

10. Device according to any one of claims 1 to 9, characterized by the fact that the brine tank (3) can be connected to the water supply (2).

11. Device according to any one of claims 1 to 10, characterized by the fact that The housing (1) in one version comprises an additional housing with an integrated brine tank (3).

12. Device according to any one of claims 1 to 11, characterized by the fact that A gas separator (20) is connected downstream of the electrolysis cell (7).

13. Device according to any one of claims 1 to 12, characterized by the fact thatthe housing (1) comprises a photovoltaic module with buffer storage, wherein the photovoltaic module is connected to an accumulator which can be connected to the circuit of the electrolysis cell (7) and to the circuit with the rest of the electronics.

14. Method for producing an alkali metal hypochlorite solution comprising the steps (i) supplying water and a saturated brine solution to an electrolysis cell (7) and (ii) converting the brine-water mixture into alkali metal hypochlorite solution, water and hydrogen in the electrolysis cell (7), characterized by the fact that A predefined current through the electrolysis cell is set by regulating the opening times of outlet valves (14, 15) and the volume flow by a pump (16) which is connected downstream of the outlet valves (14, 15), whereby the regulation is carried out by means of control electronics (9).

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