DE102018203808A1 - Disinfection of process water in evaporative cooling plants - Google Patents

Abstract

In a method for disinfecting process water and / or components coming into contact with process water in evaporative cooling plants, cooling towers and wet scrubbers, at least one UV irradiation device with at least one UV emitter is provided in components intended for collecting the process water, in particular in a process water tank. In this process, the process water is UV irradiated using the UV irradiation devices, the process water at least one preferably by UV radiation degradable oxidizing agent and / or disinfectant is added and / or the process water at least one chemical that affects the lime-carbonic acid balance is added.

Description

The invention relates to a method for disinfecting process water and / or coming into contact with process water components in evaporative cooling systems, cooling towers and Naßabscheidern.

Evaporative cooling systems and cooling towers are used to dissipate process heat. These are usually cooling systems in which the cooling effect is caused by the evaporation of water.

In such cooling systems, as well as wet scrubbers, there is the problem that propagate there pathogens and can spread from there. There are a number of cases in which a legionellosis disease outbreak is associated with cooling towers.

A common approach to prevent or suppress bacterial contamination of cooling towers is the use of biocides, which are intended to prevent colonization of the plants with the corresponding biological material or dissolve already formed biofilms. However, the use of biocides reduces the resistance of the materials used in the plants to corrosion. In addition, use of biocides is usually associated with significant costs for the corresponding chemicals.

Another problem with the operation of these systems is the occurrence of limescale. These are created by introducing carbon dioxide from the air into the circulating water of the cooling circuit. Depending on the amount of resulting carbon dioxide, this circulating water can then behave corrosive to the materials used in the plants, usually metals, or it can lead to precipitation of poorly soluble lime.

Finally, it has to be taken into consideration that the plants mentioned, in particular the cooling towers, as a rule have large or very large dimensions. As a result, the aforementioned protective measures, for example against microbial contamination or limescale deposition, have to be provided in large volumes. Added to this in this context is that, for example, required electrical equipment due to the water and air currents in such cooling systems can not be installed in the system (cooling tower) itself, but must be accommodated outside.

Accordingly, the invention has the object to provide a method of the type mentioned, which avoids the problems described at least partially. On the one hand, the aim is to reliably prevent or at least keep it under control. On the other hand, it should also be possible to prevent limescale deposits on components of the system. Finally, it should be achieved that the measures proposed according to the invention can be carried out reliably despite the large dimensions of the said systems.

These objects are achieved by the method having the features of claim 1. Preferred embodiments of this method are described in the claims dependent on claim 1. The wording of all claims is hereby expressly incorporated by reference into this description.

As mentioned in the introduction, the invention provides a method for disinfecting process water and / or a method for disinfecting components that come into contact with process water in evaporative cooling systems, cooling towers and wet scrubbers. In this method, at least one UV irradiation device with at least one UV emitter is provided at least in components provided for collecting the process water, wherein such a component is in particular at least one process water tank.

Furthermore, said UV emitters have electrical or electronic ignition devices.

In addition, in the process according to the invention, the process water is UV-irradiated with the aid of the UV irradiation devices, wherein at least one oxidizing agent and / or disinfectant which is preferably degradable by UV radiation is added to the process water. Alternatively or additionally, at least one chemical is added to the process water, which influences the lime-carbonic acid balance (in the process water).

This feature combination of the method according to the invention leaves open various possibilities for the intended disinfection. Thus, the UV irradiation of the process water with the help of the UV irradiation facilities of the germ reduction. With the help of UV radiation activated and / or degraded oxidant / disinfectant disinfection is further enhanced. The chemical affecting the lime-carbonic acid balance preferably maintains the pH of the process water in the acid, which results in that no lime precipitation can take place. Here, lime deposition is prevented not only in the plant itself, but also on the surfaces of the UV irradiation facilities and the corresponding UV lamps.

The fact that the UV emitters themselves have electrical or electronic ignition devices has the advantage that these ignition devices do not have to be accommodated outside the system itself, for example in control cabinets. Accordingly, long cable paths between the electrical equipment with the ignitors and the UV lamps can be avoided because they are often the cause of the poor ignition behavior of the mercury discharge lamps.

In preferred embodiments of the method according to the invention, said ignition devices are arranged on the holder of the UV lamps or integrated in this holder. In this way, no additional components must be provided with the ignition devices, and possibly connected to the UV lamps.

In a further development, in the method according to the invention, the UV irradiation devices are provided with a protective structure, wherein this protective structure is in particular a cage-like protective structure. This protective structure serves to protect the UV irradiation devices against damage, in particular mechanical damage, this protection being advantageous in particular for the comparatively sensitive UV emitters with their casings of glasses.

Preferably, said protective structure comprises at least two stirrups, which span a UV emitter provided in a UV irradiation device in the transverse direction and are arranged spaced apart in the longitudinal direction of the UV emitter.

In further preferred embodiments, the method according to the invention is characterized in that UV irradiation devices are provided not only in at least one process water tank, but preferably in addition to other components of the evaporative cooling systems, cooling towers and wet scrubbers. As a result, not only the process water in the process water tank is disinfected by UV radiation, but also other surfaces of the plant and the process water flowing along these surfaces. As said components, in particular the so-called (cooling) register of the corresponding systems come into question.

In the method according to the invention, it is also advantageous if at least one UV irradiation device is immersed at least partially, preferably completely, in the process water, at least during the UV irradiation. This ensures that the largest possible volume of process water, for example, in a process water tank with the UV radiation can be treated. For this purpose, the corresponding UV irradiation device can be arranged, for example, at the bottom of a process water tank, and preferably fixed. In such embodiments, it then also makes sense to equip such a UV irradiation device with an already described protective structure, in particular against mechanical damage.

Furthermore, embodiments of the method according to the invention are preferred in which at least one UV irradiation device is provided at least during the UV irradiation on the surface of the process water. This then allows for a UV irradiation of the process water surface, and in particular a UV irradiation of the air space directly above the process water surface.

In the method according to the invention, it is possible to add different oxidizing agents or disinfectants, which in particular can be activated and also degraded by the UV radiation of the UV irradiation devices. Particularly preferred here is the use of hydrogen peroxide (H ₂ O ₂ ), whose effect in connection with UV radiation is readily known to the person skilled in the art. In connection with the present invention, it is advantageous that a combination of UV irradiation and the use of chemically completely degradable hydrogen peroxide is an effective and environmentally friendly method for sterilizing said plants and also acts by the combination effect oxidizing organic ingredients and thus the concentration reduced at carbon sources for microorganisms. As a result, the nutrient supply for germs is reduced, which also counteracts a re-germination.

According to the invention, it is also possible to add any chemical which influences the lime-carbonic acid equilibrium in the desired manner. In the invention, at least one complexing agent is preferably used here, in particular citric acid or a phosphonate being added.

All chemicals mentioned, z. As H ₂ O ₂ , citric acid, phosphonate and others, are usually added in the form of aqueous solutions, preferably in commercial concentrations.

As already explained, the process according to the invention can be implemented in different ways, wherein in particular the addition of the oxidizing agent / disinfectant or the addition of the chemical influencing the lime-carbonic acid balance can be varied. Preferably, the substances mentioned are added to the process water at least once a day, in particular between once a day and ten times a day. Within the latter range, addition of oxidant / disinfectant or addition of the lime-carbonic acid equilibrium-affecting chemical between once a day and five times a day is more preferable.

In particular, the addition of the oxidizing agent / disinfectant can be done more frequently than adding the chemical to influence the lime-carbonic acid equilibrium.

In a further development, at least one corrosion inhibitor may be added to the process water or the added substances in the process according to the invention.

Furthermore, the invention also includes an evaporative cooling system, a cooling tower or a wet scrubber, which comprises at least one UV irradiation device in at least one component provided for collecting process water. This component may in particular be a process water tank.

According to the invention, a UV emitter provided in the UV irradiation device has at least one electrical or electronic ignition device.

In the case of the abovementioned devices according to the invention, it is preferred if the abovementioned ignition device is provided on a holder of the UV emitter, in particular integrated in the holder of a UV emitter.

The invention has a number of advantages.

On the one hand, the addition of toxic chemicals (biocides) can be dispensed with. In this way, on the one hand the adverse effect of these chemicals on the materials used in the systems avoided and on the other hand costs are saved by dispensing with these relatively expensive chemicals. Finally, it is also possible to dispense with the addition of further substances which generally have to be used compulsorily when using biocidal chemicals in order to minimize their negative effects (corrosion of materials, build-up of circulating water, etc.).

On the other hand, in the invention, the benefits of a combination of UV irradiation with an oxidizing agent, such as hydrogen peroxide, come fully into play. The hydrogen peroxide is completely degradable, especially when used in small amounts. At the same time it decomposes under the influence of UV radiation in hydroxyl radicals, which act as a strong oxidizing agent, but are short-lived. In this way, the microbial contamination in the corresponding facilities, such as cooling towers, can be controlled very well by the measures according to the invention.

Finally, lime deposits are reliably prevented in the plants by the invention. This applies not only to the usual components of a plant, such as the cooling tower itself, but also for the UV irradiation devices used in the invention. Here, for example, limescale deposits on the quartz envelopes of UV lamps are avoided.

Overall, the measures according to the invention offer a solution which is advantageous in many respects for the disinfection of process water in evaporative cooling plants. Also in terms of cost, the invention provides a real alternative, in particular to the use of biocidal chemicals for the control of biological stress in such facilities.

Finally, it should be mentioned that the invention is particularly advantageous for the aforementioned systems with large dimensions. According to the invention, electric or electronic ignition devices for the UV lamps used are assigned directly to these UV lamps, and are preferably integrated in their holders. As a result, long cable runs between igniters and UV emitters can be avoided. This allows reliable ignition of the UV lamps. Ignition devices that are mounted outside of the actual system, such as the cooling tower, for example, in cabinets, the voltage pulses for the UV lamps due to the large cable lengths are very strong, which sometimes leads to the fact that the UV lamps no longer ignited become.

Further features and advantages of the invention will become apparent from the following description of the examples and the drawings. In this case, the individual features of the invention can be implemented individually or in combination with each other. The examples described below merely serve to further explain the invention without restricting the invention to the disclosure content of the examples.

• 1 die schematische Darstellung eines Kühlturms, der nach dem erfindungsgemäßen Verfahren betrieben wird.

In the drawing shows

• 1 the schematic representation of a cooling tower, which is operated by the method according to the invention.

1 shows a schematic sectional view of a cooling tower 1 , A cooling tower is known to be a facility whose function is the dissipation of waste heat to the environment. As a rule, this waste heat is generated in power plant or industrial processes. The cooling effect is realized by the evaporation of water.

As in 1 is shown, air and water flow in the cooling tower 1 in countercurrent. Part of the water evaporates. The enthalpy withdrawn from the overall system results in a cooling of the (process) water remaining in the system.

Essential components of the cooling tower 1 are in 1 shown graphically or at least indicated in the drawing. These are on the one hand a pool or a tub 2 in which the process water is collected. Next are indicated graphically the registers 3 of the cooling tower 1 , in which the heat transfer takes place, as well as the device 4 to the task of water, which is in this device 4 usually a spray system for the fine distribution of water.

Finally, in 1 another dropper 5 indicated in the drawing, the discharge of water with the air from the cooling tower 1 reduced.

The device 14 shows an example of a fan, with the help of ambient air in the cooling tower 1 is introduced. pump 15 serves to introduce water into the cooling tower, pump 16 serves to promote circulating / process water in the system. By reference 17 the heat exchanger is shown graphically for the entire process.

Next shows 1 another shut-off valve 18 , with the help of deposits in the cooling system (usually inorganic salts), which settle in the (process water) trough 2, from the cooling tower 1 can be removed (so-called desalination).

In operation, this is due to the heat exchanger 17 heated process water over the device 4 (for example, spray system) from the top of the cooling tower 1 about the registers 3 (Heat transfer medium) distributed. At the same time the device blows 14 Ambient air up through the cooling tower 1 , When the warm process water meets the cold air, the air is heated and, as already mentioned, part of the process water evaporates. The process water cooled thereby collects in the (process water) tub 2 , and then returns to the heat source of the process, namely to the heat exchanger 17 back. The heated air leaves the cooling tower 1 at its top, the mist eliminator 5 this serves to remove water droplets from the exhaust air.

As 1 also shows are at the cooling tower 1 according to the invention UV irradiation facilities 6 and 7 intended. Electrical or electronic ignition devices for the UV lamps are integrated in the holders of the UV lamps provided in these UV irradiation devices.

In the UV irradiation device 6 It is a so-called UV immersion heater with an elongated UV lamp 8th Made with a protective structure in the form of ironing 9 that the UV emitter 8th span in the transverse direction, is provided. Next has the UV irradiation device 6 Mounting elements in 1 are not shown in detail. With the help of these mounting elements, the UV irradiation device 6 at suitable locations in the cooling tower 1 be attached.

1 shows an example of an embodiment in the UV irradiation facilities 6 at the bottom of the (process water) tub 2 and on the inner walls of the cooling tower 1 are provided and attached. Overall shows 1 five UV irradiation facilities 6 ,

In the UV irradiation device 7 it is a buoyant facility. Next to the float 11 has UV irradiation device 7 four UV lamps 10 on, with three UV emitters 10 are arranged horizontally and spaced apart at an angle of 120 °. The fourth UV emitter 10 dives vertically into the liquid to be irradiated. This ensures that, on the one hand, the process water itself is UV-irradiated and, on the other hand, the air space above the water surface and the surrounding walls of the cooling tower.

In 1 are graphically three UV irradiation facilities 7 represented, over the surface of the process water distributed more easily such more UV irradiation facilities 7 can be arranged.

Next shows 1 the facilities 12 and 13 , with the aid of oxidant / disinfectant, for example, a hydrogen peroxide solution or at least one chemical that affects the lime-carbonic acid balance, can be added to the process water stream.

The in 1 illustrated cooling tower 1 with its components and components can be operated by the method according to the invention as follows.

The over the device 14 air supply into the cooling tower 1 conditionally mandatory entry of germs and possibly other biological components. The same applies to the water supply via the pump 15 , The corresponding germs can accumulate within the cooling tower and multiply and then in particular on the from the cooling tower 1 discharged air into the environment.

This formation of so-called biofilms in the cooling tower 1 and the discharge of germs from the cooling tower 1 are prevented or significantly reduced by the invention.

On the one hand, the process water in the tub 2 and the container walls in the area of the process water tank 2 through the UV irradiation facilities 6 and 7 in the tub 2 UV-irradiated and disinfected accordingly.

Further, on the other hand, further areas of the container wall and important components of the cooling tower 1 by the addition in the cooling tower 1 arranged UV irradiation facilities 6 UV-irradiated and thus disinfected. Even in the corresponding areas of the cooling tower 1 along-flowing process water is through these additional UV irradiation facilities 6 UV-irradiated.

Additionally, in the invention, oxidant / disinfectant is passed over the device 12 metered into the process water stream. Thus, this oxidizing agent, for example, hydrogen peroxide, in addition to the UV irradiation develops its oxidizing effect. In the case of hydrogen peroxide, the ultraviolet rays of the UV emitters release hydroxyl radicals, which act as strong oxidizing agents and accordingly serve to reduce the germs.

Finally, according to 1 the process water flow through the device 13 Added a chemical that affects the lime-carbonic acid balance to avoid or at least reduce lime deposition.

Finally, as already explained in the description, in the holders / floats of the UV irradiation facilities 6 and 7 already used electrical or electronic ignition devices, so that a cable guide between outside the cooling tower 1 arranged electrical equipment such as cabinets and the UV lamps can be dispensed with.

example 1

A cooling tower, in its construction the cooling tower 1 according to 1 has a capacity of 800 kW and a (process) water volume of 6 m ³ . This cooling tower is operated with a feed water quality of 18 ° German hardness and a circulation rate of 150 m ³ / h.

In this cooling tower are UV irradiation facilities 6 and 7 according to 1 placed so that the interior of the cooling tower is substantially completely illuminated with UV radiation. In addition, 15 ml / m ³ H ₂ O ₂ (oxidizing agent hydrogen peroxide) (as a 35% aqueous solution) is added three times a day to the process water stream. Once a week, an addition of citric acid (chemical to influence the lime-carbonic acid equilibrium) (as a 20% aqueous solution) is carried out at a concentration of 30 ml / m ³ .

With this operation of the cooling tower, microbial contamination of the plant and discharge of germs from the plant could be reliably prevented over longer periods of time.

Example 2

A cooling tower, in its construction the cooling tower 1 according to 1 corresponds, has 2,300 kW of power and a (process) water volume of 7.6 m ³ . This cooling tower is operated with a feedwater quality of 19 ° German hardness and a circulation rate of 220 m ³ / h.

In this cooling tower are UV irradiation facilities 6 and 7 according to 1 placed so that the interior of the cooling tower is substantially completely illuminated with UV radiation. In addition, 15 ml / m ³ H ₂ O ₂ (oxidizing agent hydrogen peroxide) (as a 35% aqueous solution) is added four times a day to the process water stream. Once a day, a concentrate of organophosphonate (lime-carbonic acid balance-controlling chemical) (as a 30% aqueous solution) is added at a concentration of 4 ml / m ³ . In addition, the addition of a corrosion inhibitor occurs at regular intervals.

With this operation of the cooling tower, microbial contamination of the plant and discharge of germs from the plant could be reliably prevented over longer periods of time.

Claims (11)

Method for disinfecting process water and / or components coming into contact with process water in evaporative cooling systems, cooling towers and wet scrubbers, wherein at least one UV irradiation device (6) is provided at least in components intended for collecting the process water, in particular in at least one process water sump (2). 7) with at least one UV emitter (8, 10) is provided, wherein the UV emitters have electrical or electronic ignition devices, and in which the process water using the UV irradiation devices (6, 7) is UV-irradiated, the process water at least one preferably by Ultraviolet radiation degradable oxidizing agent (12) and / or disinfectant is added and / or the process water at least one lime-carbon dioxide balance affecting chemical (13) is added. Method according to Claim 1 , characterized in that the ignition devices are arranged on the holder of the UV lamps or integrated in this holder. Method according to Claim 1 or Claim 2 , characterized in that the UV irradiation devices have a protective structure, preferably a cage-like protective structure, wherein in particular the protective structure comprises at least two brackets (9) which span a UV radiator (8) provided in a UV irradiation device (6) in the transverse direction and are arranged spaced apart in the longitudinal direction of the UV radiator (8). Method according to one of the preceding claims, characterized in that UV irradiation devices are provided in at least one process water sump (2) and preferably additionally to other components of the evaporative cooling systems, cooling towers and wet scrubbers, in particular at their registers. Method according to one of the preceding claims, characterized in that at least one UV irradiation device (6) at least partially, preferably completely immersed in the process water at least during the UV irradiation. Method according to one of the preceding claims, characterized in that at least one UV irradiation device (7) is provided at least during the UV irradiation on the surface of the process water. Method according to one of the preceding claims, characterized in that hydrogen peroxide is added as the oxidizing agent. Method according to one of the preceding claims, characterized in that at least one complexing agent, preferably citric acid or a phosphonate is added as chemical influencing lime-carbonic acid balance. Method according to one of the preceding claims, characterized in that the addition of an oxidizing agent and / or disinfectant and / or a chemical influencing lime-carbonic acid balance takes place at least once a day, preferably between once a day and ten times a day, in particular between once per day and five times a day. Evaporative cooling system, cooling tower or wet scrubber, comprising at least one UV irradiation device in at least one provided for collecting process water component, in particular a process water tank, wherein provided in the UV irradiation device UV emitter has at least one electric or electronic ignition device. Evaporative cooling system, cooling tower or wet scrubber after Claim 10 , characterized in that the ignition device is provided on a holder of the UV lamp, in particular in the holder of a UV lamp is integrated.

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