GB2604413A

GB2604413A - Sprayers and methods of disinfection

Info

Publication number: GB2604413A
Application number: GB2112291.6A
Authority: GB
Inventors: Nuno Manuel; Guthrie Callum; Guthrie Duncan
Original assignee: Vapourtec Ltd
Current assignee: Vapourtec Ltd
Priority date: 2020-12-09
Filing date: 2021-08-27
Publication date: 2022-09-07
Anticipated expiration: 2041-08-27
Also published as: GB202019362D0; GB2604413B; GB202112291D0

Abstract

A hand-held sprayer 1 having: a nozzle assembly 20 for directing a spray of atomized fluid; a fluid storage 12; an electrochemical flow reactor 50 having an inlet in fluid communication with the fluid storage 12 and an outlet in fluid communication with the nozzle assembly 20, the electrochemical flow reactor 50 being arranged to cause an electrochemical reaction in an input fluid from the fluid storage 12 and produce an output fluid; a pump 14 arranged to pump liquid from the fluid storage 12 to the electrochemical flow reactor 50; and a controller 18 arranged to control the electrochemical flow reactor 50 so as to provide a predetermined concentration of an active agent in the output fluid. There is also a method of disinfecting a surface, including the steps: supplying salt water to an electrochemical flow reactor 50; controlling the reactor to form a predetermined concentration of hypochlorous acid at an output from the reactor; atomising the hypochlorous acid formed in the reactor; and directing the atomized hypochlorous acid to the surface.

Description

SPRAYERS AND METHODS OF DISINFECTION

Field of the Invention

The present invention relates to sprayers and methods of disinfection. it is particularly, but not exclusively, concerned with sprayers that have an electrochemical flow reactor to enable generation of their own active agent and methods of disinfection which use an electrochemical flow reactor.

Background of the Invention

Coronavirus Disease 2019 (COVID-19) is a novel virus. It causes severe acute respiratory syndrome. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent responsible for a surface-to-surface communicable disease that had infected approximately 40 million persons as of 17 October 2020. All persons and business responsible for the safety of the public or employees need options to limit and control the spread of the virus between persons in public areas. There is a need for effective means to disinfect the surfaces in public areas.

COVTD-19 is an enveloped, positive-sense, single-stranded RNA virus approximately 60 to 140 nm in diameter. Transmission occurs through touch or aerosol spreading of the virus. A common pathway of spreading this virus is through respiratory aerosols from an infected person. During speech, humans emit thousands of oral fluid droplets per second that can remain airborne for 8 to 14 minutes. COVID-19 is detectable for up to 3 hours in surface aerosols, for up to 4 hours on copper, for up to 24 hours on cardboard, and for up to 2 to 3 days on plastic and stainless steel. There is therefore a need to disinfect surfaces potentially exposed to COVID-19 to prevent onward transmission.

On contact with the virus, a disinfectant agent changes the protective protein coat, which loses its structure and aggregates, forming clumps of proteins with other viruses. On contact, the mechanism of disinfection involves the destroying of the cell wall of microbes or viruses, allowing the disinfectant to destroy or inactivate them.

Disinfectants, such as hypochlorite, alkalis, oxidizing agents, alcohols and aldehydes, are all effective against viruses within a relatively short period of contact. Currently, the World Health Organisation together with other Environmental Protection Agencies have recommended numerous disinfectants against COVID-19 including hypochlorous acid (HOC]).

An ideal disinfectant and sanitizer must be non-toxic to surface contact, non-corrosive, effective in various forms, and relatively inexpensive. Due to its effectiveness against viruses, its non-toxic and non-corrosive properties, HOC1 is slowly becoming the disinfectant of choice against coronaviruses in public areas.

HOC] is normally made by combining non-iodinated salt, water, and electrolysis. Once made the solution is not particularly stable and must be stored with care. The active ingredient is known as available frcc chlorine (AFC). HOC1 solutions arc less stable when exposed to UV radiation, sunlight, or contact with air or when the temperature of the solution is elevated greater than 25°C. HOCI solutions should therefore be stored in cool, dark places, and contact with air should be minimized.

Any disinfectant needs to be dispensed to the surfaces to be treated. Many products exist [hr dispensing liquids for disin reefing surfaces. Most aim to create a line spray (sometimes termed a mist) of liquid droplets, typically between 50 and 100 um in diameter and allow these droplets to fall evenly onto the target surfaces to deactivate all viruses present on contact.

Existing systems for dispensing can be grouped into a number of technologies as discussed further below.

Converted paint sprayers -These use high pressure pumps to force the liquid through a small nozzle. Sometimes electrostatics are used to improve the surface contact efficiency of the mist when dispensed.

Converted mosquito misting systems -These systems use high-flowrate fans to generate a powerful vortex to create the fine mist. The advantage of this technology is the high levels of reliability since high pressure and small nozzles are not required. The disadvantage is a high power consumption, typically 1.5 kW to 2.5 kW which does not lend itself to battery powered equipment.

High temperature vapour-driven systems -These systems have been seen in use extensively in China for disinfecting outside areas. A hydrocarbon thel is burnt in a heat exchanger where the disinfectant (normally hypochlorite-based) is atomized, the vapour is forced through a nozzle and dispensed onto surfaces. These systems are not used in many countries due to the hazardous operating temperatures.

All of the existing systems use pre-mixed disinfectants that are dispensed through the nozzle system.

Most systems, such as the popular sprayers manufactured by Victory Innovations Co of Minnesota, USA, dispense a pre-manufactured solution of HOC1. The cost of such solutions in October 2020 is typically GBP 40 (USD 50) for 5 litres. The equipment dispenses the pre-made solution at a typical llowrate of 100 ml/min and so can cost c. (iBP 40/USD 50 per hour to operate based on consumables only.

In addition to the running costs, there are administrative and logistical challenges associated with storage of supplies of pre-manufactured HOC1 at suitable locations to enable the filling of the sprayers close to the point of use.

Further, pre-manufactured solutions of HOC] are normally manufactured using batch reactors and therefore require a high salt concentration in the starting solution of salt water in order to make the solution sufficiently conductive to produce sufficient quantities of HOC1. A substantial portion of this salt concentration will remain in the final product as it is not all reacted. Testing of commercially available HOCL solutions sold for use in sprayers has shown salt concentrations of between 10 and 15g / litre.

However, spraying surfaces with solutions with a mist with a high salt concentration is generally undesirable as if surfaces are regularly sprayed, then salt deposits will build up on the surface and may need to be separately washed off with fresh water. Further, exposure to high concentrations of salt water can lead to corrosion of metal surfaces and is also generally undesirable for food.

Many commercial sprayers of the "converted paint sprayer" type use high velocity jets directed through small orifices in the nozzles to create fine droplets. These small apertures arc prone to blocking when, after use, water evaporates from residual solution leaving salt deposits in the apertures.

An object of the present invention is to provide sprayers and methods of disinfecting which are able to make their own active agent in a contemporaneous fashion. in particular an object of the present invention is to provide a disinfection device and a method of disinfecting which does not require pre-manufactured HOC].

A further object of the present invention is to provide sprayers which are not prone to blocking.

A further object of the present invention is to provide sprayers and methods of disinfecting with HOCI which do not result in salt deposits on the surfaces being treated.

Aspects of the present invention aim to provide a disinfection device which satisfies one or more of the above objects.

Summary of the Invention

At their broadest, aspects of the present invention provide hand-held sprayers and methods of disinfecting a surface which use an electrochemical flow reactor, for example to produce an active disinfectant agent.

A first aspect of the present invention provides a hand-held sprayer having: a nozzle assembly for directing a spray of atomized fluid; a fluid storage; an electrochemical flow reactor having an inlet in fluid communication with the fluid storage and an outlet in fluid communication with the nozzle assembly, the electrochemical flow reactor being arranged to cause an electrochemical reaction in an input fluid from the fluid storage and produce an output fluid; a pump arranged to pump liquid from the fluid storage to the electrochemical flow reactor; and a controller arranged to control the electrochemical flow reactor, wherein the controller is arranged to control the electrochemical flow reactor so as to provide a predetermined concentration of an active agent in the output fluid.

By including an electrochemical flow reactor within the sprayer, it is possible for the sprayer to create its own active agent, for example an active disinfectant agent. The active agent can then be dispensed as fine droplets from the nozzle.

As the sprayer can produce its own active agent, the fluid stored in the fluid storage does not need to be, or contain, an active agent. This may allow a more stable or less hazardous precursor to the active agent to be stored in the fluid storage, making storing, supplying and/or refilling the sprayer easier and/or more convenient. This may also allow the sprayer to be operated much more cheaply than buying batch-produced active agent.

For example, the fluid may be salt water and the storage may be for containing a solution of salt water. Electrolysis of the salt water solution produces hypochlorous acid (HOCI) which contains active free chlorine (AFC) as a disinfectant agent. In a preferred embodiment, when the sprayer is in use or ready for use the fluid storage contains a solution of salt water. The salt in the salt water may be at a concentration of between 0.2 g / litre to 20 g / litre. Preferably the salt water is at a concentration o15 g / litre or less.. Certain embodiments use salt water at a concentration of around 2.5 g / litre.

Using a lower concentration salt solution can help to prevent blocking of the sprayer, and reduce the need to clean the sprayer, particularly in the nozzle and in the reactor. Blocking typically arises due to excess solution remaining on thc surfaces of the sprayer, particularly exposed surfaces such as the inner and outer surfaces of the nozzle, after use and the water evaporating to leave a solid salt residue. If the starting solution of salt water is of lower concentration, then the amount of salt deposited in this way can be reduced and the effects on subsequent operation of the sprayer reduced accordingly.

Further, as indicated above, in the case of HOCI, dispensing pre-produced HOCI can cost GBP 40/USD 50 per hour at October 2020 prices. In contrast using salt water can reduce 30 the cost of consumables to under GBP 0.25/USD 0.33 per hour.

Salt water is much more easily stored and transported to the location of intended use than pre-manufactured HOC. It is &so more easy and safe to dispose of if there is excess after use.

Preferably the controller is arranged to control one or more of the current supplied to the electrochemical flow reactor; the voltage across the electrochemical flow reactor; and the flow rate of fluid through the electrochemical flow reactor, in order to provide the predetermined concentration of the reagent in the output fluid. More preferably the controller is arranged to control one of the voltage or the current. In such arrangements the flow rate is preferably maintained substantially constant.

Preferably the sprayer further comprises a sensor arranged to detect an operating characteristic of the electrochemical flow reactor and produce an output relating to said operating characteristic, wherein said controller is arranged to receive said output and to control the electrochemical flow reactor based on said output. For example the sensor may be arranged to detect one or more of the voltage, current and flow rate, whilst the controller controls one o r those operating characteristics which is not detected.

In certain embodiments the controller is arranged to control the electrochemical flow reactor by: a. supplying a first predetermined current through the reactor; b. measuring the voltage across the reactor; c. determining the desired current through the reactor for the measured voltage and the predetermined concentration; d. supplying the determined desired current to the reactor; and 0. repeating steps b. to d. periodically.

The inventors have determined that the main factors which may result in a change in the concentration of active agent which is output from an electrochemical flow reactor (such as input concentration, input flow rate and available reactor area) give rise to a substantially similar lit between voltage and current across/through the reactor for a given output concentration. Therefore by setting one of these parameters and measuring the other, convergence on a steady state reaction which outputs the desired concentration of active agent can be achieved.

The step of determining may be achieved by way of a look-up table, or by way of a stored mathematical relationship, either or both of which may be stored in a memory connected to or forming part of the controller. The entries in the look-up table or the mathematical relationship may be determined for a selection of desired output concentrations of active agent for a particular reactor design in advance, either empirically or theoretically.

In other embodiments the controller may be arranged to control the electrochemical flow rcactor in the same manner, but by supplying determined voltages and measuring the current.

In certain embodiments the electrochemical flow reactor has three electrodes: a first, common electrode which is arranged between two second electrodes and, in use, the first electrode and the second electrodes have opposite polarity. For example, in certain configurations the common electrode is a plate having two opposite planar sides, and each of said sides operates as an electrode in conjunction with a respective one of the second electrodes.

Such a configuration of electrodes in the reactor can allow a reactor which is relatively small and compact and therefore suitable for usc in a handheld device, whilst still providing the necessary electrode area.

Preferably the total area of the two sides of the common electrode is the same as the total area of the second electrodes so that there is an equal surface area of each polarity of electrode within the reactor.

In certain embodiments the spacing between electrodes of opposite polarity in the electrochemical flow reactor is between 0.25mm and 3mm. More preferably the spacing is between 0.5mm and 2mm. Certain embodiments have a spacing of about lmm.

Smaller electrode spacing can allow effective concentrations of active agent to be achieved with relatively low concentrations of input fluid. For example, when using salt solution to generate HOCl/active chlorine, it is possible to achieve 150ppm free chlorine (which is a highly effective concentration) using an input salt solution having just 2.5WI of salt.

Whilst smaller electrode spacings are generally more advantageous electrically, too small a spacing can cause the reactor to be prone to blocking or the formation of a solid bridge between the electrodes due to deposits from the solution (e g limescale where hard water is used to make up the salt solution). The advantages of lower concentration input solutions have been discussed above.

In certain embodiments the controller and electrochemical flow rcactor arc arranged to provide a current density between electrodes in the electrochemical flow reactor of between 10 mA/cm2 and 100 mA/cm2. The current density required to achieve the desired output concentration can be optimised for the specific electrode design. In conjunction with the electrode spacing, the current density can determine the necessary input concentration of fluid to achieve the desired output concentration of active agent.

The sprayer may further include a fan arranged to cause a flow of air through the nozzle assembly. The flow of air can be used to entrain and distribute the active agent produced by the reactor in order to Tenn a spray.

Preferably the sprayer is further arranged to atomize fluid which has passed through the electrochemical reactor, thereby forming a fine mist of droplets of the active agent for disinfection of a surface to which the spray is directed by the nozzle assembly.

In certain embodiments the nozzle assembly ancUor the fan are arranged to cause said flow of air to generate a vortex so as to atomize fluid which has passed through the electrochemical reactor.

The sprayer preferably further includes a power supply arranged to supply power to the reactor, the pump and the fan. The power supply is preferably self-contained within the sprayer thereby enabling hand-held and independent operation of the sprayer and may he detachable for charging separately from the sprayer.

In certain embodiments, the controller may additionally be arranged to control the activation of the reactor in response to a user input (such as the squeezing of a trigger), the operation of the pump, the operation of the centrifugal fan or any combination thereof In certain embodiments, the pump may be arranged to pump liquid at a constant flow rate. If there is a constant flow rate of liquid through the reactor, the concentration of the active agent can be varied by controlling the current and/or voltage used for the electrochemical cell. Pumping at a constant rate may be important to provide for a consistent size of atomised droplets.

The pump may be a positive displacement pump.

The pump may be arranged to provide a liquid flow rate of between 50m1/min and 150 ml/min.

In certain embodiments a simplified pumping process may be used. For example, rather than actively pumping liquid from the fluid storage, a pump may be arranged to apply a small over-pressure to the fluid storage and, in combination with a fixed orifice to allow fluid to leave the fluid storage, this can achieve the desired flow to the reactor.

The nozzle assembly may include a plurality of vanes which are arranged to generate the vortex by guiding the air flow from the fan in a circular pattern.

The nozzle assembly may include a fluid aperture through which fluid from the output of the electrochemical reactor is supplied and wherein said plurality of vanes are arranged around the aperture so as to generate a vortex in the vicinity of aperture.

The nozzle arrangement is preferably arranged to reduce the likelihood of blocking. For example, this may be achieved by using a nozzle assembly where the energy required to divide the fluid into tiny droplets is provided by a high velocity vortex which may be produced by constraining a high flowrate of ambient air to adopt a circular motion across the face of a fluid aperture having a relatively large diameter. In this way an aperture, or plurality of apertures, of between 1.0 and 2.5 mm in diameter can be used and the fluid pressure may be less than 0.1 bar (gauge pressure).

By contrast if the fluid was atomized by forcing the fluid through a small orifice under high pressure, the size of the aperture would typically need to be in the range 0 05 mm to 0.15 mm and the fluid pressure required would be in the range 5 to 20 bar.

A nozzle with a larger diameter aperture may thus be advantageous in reducing and preferably preventing blocking of the aperture when excess solution remains on the surfaces of the aperture after use and subsequently dries leaving a salt residue.

The fan is preferably a centrifugal fan. Centrifugal fans can generate high speeds of air flow which may be useful for atomising the fluid produced by the reactor to produce small droplets whilst allowing a relatively large aperture.

The nozzle assembly and/or centrithgal fan are preferably arranged to produce atomized droplets with an average diameter of between 20 um and 120 um, preferably about RO um.

Controlling the air flow and the fluid flow rates may allow a consistent size distribution of atomised droplets to be produced.

The sprayer of this aspect may include any combination of some, all or none of the above-described preferred and optional features.

A second aspect of the present invention provides a method of disinfecting a surface, the method including the steps of: supplying salt water to an electrochemical flow reactor; controlling the reactor to form a predetermined concentration of hypochlorous acid at an output from the reactor; atomising the hypochlorous acid formed in the reactor; and directing the atomized hypochlorous acid to the surface.

Electrolysis of salt water produces hypochlorous acid (HOC1) which contains active free chlorine (AFC) as a disinfectant agent.

As indicated above, in the case of HOC], dispensing pre-produced HOCI can cost (BP 40/USD 50 per hour at October 2020 prices. In contrast using salt water can reduce the cost of consumables to under GBP 0.25/USD 0.33 per hour.

Salt water is much more easily stored and transported to the location of intended use than pre-manufactured HOC1. It is also more easy and safe to dispose of if there is excess after use.

By using an electrochemical flow reactor, it is possible for the hypochlorous acid to be produced on demand as it is needed for disinfection. As the sprayer can produce its own active agent, the consumable fluid for thc disinfection method does not need to be, or contain, an active agent. This may allow a more stable or less hazardous precursor to the active agent to be stored/transported for the disinfection, making storing and/or supplying the consumable for the method easier and/or more convenient.

Preferably the step of controlling includes controlling one or more of the current supplied to the electrochemical flow reactor; the voltage across the electrochemical flow reactor; and the flow rate of fluid through the electrochemical flow reactor, in order to provide the predetermined concentration of the hypochlorous acid. More preferably the step of controlling controls one of the voltage or the current. In such arrangements the flow rate is preferably maintained substantially constant.

Preferably the method further comprises the step of detecting an operating characteristic of the electrochemical flow reactor, wherein the step of controlling controls the electrochemical flow reactor based on said detected operating characteristic. For example the one or more of the voltage, current and flow rate may be detected, whilst one of those operating characteristics which is not detected is controlled.

In certain embodiments the step of controlling includes: a. supplying a first predetermined current through the reactor; b. measuring the voltage across the reactor; c. determining the desired current through the reactor for the measured voltage and the predetermined concentration; d. supplying the detennined desired current to the reactor; and e. repeating steps b. to d. periodically.

The inventors have determined that the main factors which may result in a change in the concentration of active agent which is output from an electrochemical flow reactor (such as input concentration, input flow rate and available reactor area) give rise to a substantially similar fit between voltage and current across/through the reactor for a given output concentration. Therefore by setting one of these parameters and measuring the other, convergence on a steady state reaction which outputs the desired concentration of active agent can be achieved.

In other embodiments the controller may be arranged to control the electrochemical flow reactor in the same manner, but by supplying determined voltages and measuring the 20 current.

In certain embodiments the step of controlling controls the reactor to provide a current density between electrodes in the reactor of between 10 mA/cm2 and 100 mA/cm2. The current density required to achieve the desired output concentration can be optimised for the specific electrode design. In conjunction with the electrode spacing, the current density can determine the necessary input concentration of fluid to achieve the desired output concentration of active agent.

Current densities in the above range can allow effective concentrations of active agent to be achieved with relatively low concentrations of input fluid. For example, when using salt solution to generate HOC/active chlorine, it is possible to achieve 150ppm free chlorine (which is a highly effective concentration) using an input salt solution having just 2.5g/1 of salt. The advantages of lower concentration input solutions have been discussed above.

In certain embodiments the method further includes the step of mixing a buffer into the salt water. The buffer acts to keep the pH of the solution within a desired range despite the change in chemical composition caused by the reaction(s) in the reactor. For example, the production of HOC1 causes the pIl of the solution to decrease (i.e. the solution becomes more acidic). However, the balance between the respective components of the solution may be adversely affected by changes in pH and so the buffer ensures maintenance of the pH within a desired range and thus can contribute the output of a desired concentration of active agent.

In certain embodiments the buffer and the amount of buffer is selected arranged to maintain the pH of the output hypochlorous acid solution in the range o14 to 6.5.

The step of atomizing may include generating a vortex of air flow around a fluid aperture. A centrifUgal Can may be used to produce a high flowrate of ambient air and may constrain this ambient airstream to adopt a circular motion across the face of a nozzle having a relatively large aperture. In this way a nozzle with an aperture of between 1.0 and 2 5 mm in diameter can be used whilst still providing finely atomized (average droplet size of around 80 pm) hypochlorous acid to the surface.

A nozzle with a larger diameter aperture may be advantageous in reducing and preferably preventing blocking of the aperture when excess solution remains on the surfaces of the aperture after use and subsequently dries leaving a salt residue.

The step of atomizing may produce atomized droplets with an average diameter of between 20 pm and 120 pm, preferably 80 pm. Controlling the air flow and the fluid flow rates may allow a consistent size distribution of atomised droplets to be produced.

The salt in the salt water may be at a concentration of between 0.2 g / litre to 10 g / litre. Preferably the salt water is at a concentration of 5 g / litre or less. Certain embodiments use salt water at a concentration of around 2.5 g / litre.

Using a lower concentration salt solution can help to prevent Hocking of the apparatus used to deliver the hypochlorous acid to the surface, and reduce the need to clean the apparatus. Blocking typically arises due to excess solution remaining on the surfaces of the apparatus, particularly exposed surfaces, after use and the water evaporating to leave a solid salt residue. If the starting solution of salt water is of lower concentration, then the amount of salt deposited in this way can be reduced and the effects on subsequent operation of the apparatus reduced accordingly.

The salt water may be supplied at a constant flowrate, and so the concentration of the active agent can be varied by controlling the constant current used for the electrochemical cell. Supplying the salt water at a constant rate may be important to provide for a consistent size of atomised droplets.

The salt water may be supplied at a rate of between 50m1/min and 150 ml/min. Depending on the current supplied to the electrochemical reactor, this can produce AFC concentrations ranging between less than 50 ppm and over 200 ppm.

The method may further include the step of controlling the rate of supply of salt water and/or the current supplied to the reactor in order to control the concentration of the hypochlorous acid produced. This may allow a desired strength of an active agent in the atomized fluid to be achieved. For example, this may depend on the surface to be disinfected. 45 ppm of AFC is considered as a safe level for disinfecting foods that might be eaten, but higher levels may be desired for surfaces which are not foods or likely to be in contact with food, but are, for example, considered higher risk.

The method of this aspect may use a sprayer according to the first or third aspect described above and below, including some, all or none of the above-described preferred and optional features of that aspect, but need not be.

The method of this aspect may include any combination of some, all or none of the above-described preferred and optional features.

A third aspect of the present invention provides a hand-held sprayer having: a nozzle assembly for directing a spray of atomized fluid; a fluid storage; an electrochemical flow reactor having an inlet in fluid communication with the fluid storage and an outlet in fluid communication with the nozzle assembly; a pump arranged to pump liquid from the fluid storage to the electrochemical flow reactor; and a fan arranged to cause a flow of air through the nozzle assembly, wherein the nozzle assembly and/or the fan are arranged to cause said flow of air to generate a vortex so as to atomize fluid which has passed through the electrochemical reactor.

For example, the fluid may be salt water and the storage may be for containing a solution of salt water. Electrolysis of the salt water solution produces hypochlorous acid (1-100) which contains active free chlorine (AFC) as a disinfectant agent. In a preferred embodiment, when the sprayer is in use or ready for use the fluid storage contains a solution of salt water. The salt in the salt water may be at a concentration of between 0.2 g / litre to 20 g / litre. Preferably the salt water is at a concentration oil0 g / litre or less..

Certain embodiments use salt water at a concentration of around 5 g / litre.

Using a lower concentration salt solution can help to prevent blocking of the sprayer, and reduce the need to clean the sprayer, particularly in the nozzle. Blocking typically arises due to excess solution remaining on the surfaces of the sprayer, particularly exposed surfaces such as the inner and outer surfaces of the nozzle, after use and the water evaporating to leave a solid salt residue. If the starting solution of salt water is of lower concentration, then the amount of salt deposited in this way can be reduced and the effects on subsequent operation of the sprayer reduced accordingly.

Further, as indicated above, in the case of HOC!, dispensing pre-produced HOC1 can cost GBP 40/USD 50 per hour at October 2020 prices. In contrast using salt water can reduce the cost of consumables to under GBP 0.25/USD 0.33 per hour.

Salt water is much more easily stored and transported to the location of intended use than pre-manufactured HOC1. It is also more easy and safe to dispose of if there is excess after 10 use.

The sprayer preferably further includes a power supply arranged to supply power to the reactor, the pump and the fan. The power supply is preferably self-contained within the sprayer thereby enabling hand-held and independent operation of the sprayer and may be detachable for charging separately from the sprayer.

Preferably the sprayer further includes a controller arranged to control the supply of current to the electrochemical flow reactor. The controller may alternatively or additionally be arranged to control the activation of the reactor in response to a user input (such as the squeezing of a trigger), the operation of the pump, the operation of the centrifugal fan or any combination thereof In certain embodiments the controller is arranged, on actuation of the sprayer, to supply current to the electrochemical flow reactor in the opposite polarity to the previous actuation of the sprayer. This can assist in preventing the reactor from becoming clogged by deposition on one of the electrodes as any deposition will be at least partially reversed on the subsequent use.

The controller may be arranged to receive an input from a user. The controller may be arranged to control the current supplied to the electrochemical flow reactor depending on the input from the user. For example, the controller may be arranged to supply current at one of a plurality of pre-set levels depending on the input from the user. This may allow the user to specify a desired strength of an active agent in the atomized fluid and the controller to control the electrochemical reactor accordingly.

In certain embodiments the pump may be arranged to pump the salt water solution at a constant flowrate, and so the concentration of the active agent can be varied by controlling the constant current used for the electrochemical cell. Pumping at a constant rate may be important to provide for a consistent size of atomised droplets.

In certain embodiments the pump may be a positive displacement pump.

By way of example, when using a salt solution with a salt concentration of 5g/1 to producc HOC1 and a flow rate through the reactor of 80 ml/min, a current of 1300 mA is used to give AFC o1200 ppm, 480 mA is used to give AFC of 100 ppm and 200 mA is used to give 45 ppm. 45 ppm is considered as a safe level for disinfecting foods that might be eaten.

The electrochemical flow reactor may have a flow path and two electrodes in contact with the flow path, wherein the total area of each electrode in contact with the flow path is between 500 and 600 mm2 The pump may he arranged to provide a liquid flow rate of between 50m1/min and 150 ml/min.

The nozzle assembly and/or centrifugal fan are preferably arranged to produce atomized droplets with an average diameter of between 20 [un and 120 um, preferably about 80 Rm.

A further aspect of the present invention provides a method of disinfecting a surface, the method including the steps of: supplying salt water to an electrochemical flow reactor; supplying current to the reactor to form hypochlorous acid; atomizing the hypochlorous acid formed in the reactor; and directing the atomized hypochlorous acid to the surface.

Electrolysis of salt water produces hypochlorous acid (HOC]) which contains active free chlorine (AFC) as a disinfectant agent.

Salt water is much more easily stored and transported to the location of intended use than pre-manufactured II0C1. It is also more easy and safe to dispose of if there is excess after use.

By using an electrochemical flow reactor, it is possible for the hypochlorous acid to be produced on demand as it is needed for disinfection. As the sprayer can produce its own active agent, the consumable fluid for the disinfection method does not need to be, or contain, an active agent. This may allow a more stable or less hazardous precursor to the active agent to be stored/transported for the disinfection, making storing and/or supplying the consumable for the method easier and/or more convenient.

The step of atomizing may include generating a vortex of air How around a fluid aperture. A centrifugal fan may be used to produce a high flowrate of ambient air and may constrain this ambient airstream to adopt a circular motion across the face of a nozzle having a relatively large aperture. In this way a nozzle with an aperture of between 1.0 and 2 5 mm in diameter can be used whilst still providing finely atomized (average droplet size of around 80 pm) hypochlorous acid to the surface.

The step of atomizing may produce atomized droplets with an average diameter of between 20 pm and 120 pm, preferably SO pm. Controlling the air flow and the fluid flow rates may allow a consistent size distribution of atomised droplets to be produced.

The salt in the salt water may be at a concentration of between 0.2 g / litre to 20 g / litre. Preferably the salt water is at a concentration oil0 g / litre or less. Certain embodiments use salt water at a concentration of around 5 g / litre.

Using a lower concentration salt solution can help to prevent blocking of the apparatus used to deliver the hypochlorous acid to the surface, and reduce the need to clean the apparatus. Blocking typically arises due to excess solution remaining on the surfaces of the apparatus, particularly exposed surfaces, after use and the water evaporating to leave a solid salt residue. If the starting solution of salt water is of lower concentration, then the amount of salt deposited in this way can be reduced and the effects on subsequent operation of the apparatus reduced accordingly.

The salt water may be supplied at a rate of between 50m1/min and 150 ml/min. Depending on the current supplied to the electrochemical reactor, this can produce AFC 20 concentrations ranging between less than 50 ppm and over 200 ppm.

The method may further include the step of changing the polarity of the current supplied to the reactor on each actuation of the reactor. This can assist in preventing the reactor from becoming clogged by deposition on one of the electrodes as any deposition will he at least partially reversed on the subsequent use.

The method of this aspect may use a sprayer according to the first or third aspect described above, including some, all or none of the above-described preferred and optional features of that aspect, but need not be.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows a disinfectant sprayer according to an embodiment of the present invention; Fig. 2 shows, schematically, the internal components and connections of the disinfectant sprayer of Fig. 1 and their connections; Fig. 3 shows the exterior of an electrochemical reactor block used in disinfectant sprayers according to embodiments of the present invention; Fig. 4 is an exploded view of the electrochemical reactor block of Fig. 3; Figs. SA and 5B are, respectively, end and side sections of the nozzle assembly used in disinfectant sprayers according to embodiments of the present invention; Fig. 6 is an exploded view of the nozzle assembly of Figs. SA and 5B; Fig. 7 shows the exterior of an electrochemical reactor block used in disinfectant sprayers according to embodiments of the present invention; Fig. 8 is an exploded view of the electrochemical reactor block of Fig. 7; Fig, 9 is a graph showing the relationship between the current and voltage in an electrochemical reactor depending on variations in flow-rate, salt concentration and active electrode area; and Fig. 10 is a graph showing the form in which available chlorine in a solution is present depending on the pH of the solution.

Detailed Description

Fig. 1 shows a disinfectant sprayer 1 according to an embodiment of the present invention.

The main parts of the sprayer I are labelled in Fig. 1 and will be described in further detail below and illustrated in the other figures.

The sprayer 1 has a detachable tank assembly 10 which stores the salt water which is processed by the sprayer 1 to produce HOC. The tank assembly 10 has an inlet (not shown) to allow filling of the internal storage tank. The tank capacity in the embodiment shown is 2.5 litres but anything between 1 litre and 3 litres is practical for a hand-held device. Tn other embodiments, the tank assembly 10 may be an integral part athe sprayer. A tank capacity of 2.5 litres gives 30 minutes of continuous dispensing of disinfectant at typical flow rates. If more that this is required the tank may be provided in a separate backpack, which may, for example, carry up to 12 litres, with the salt water delivered to the sprayer 1 by a tube.

A handle 12 is provided for a user to hold the sprayer 1. It will be appreciated from the relative dimensions that the sprayer 1 is intended to be a hand-held portable device that a user can operate in either single-handed or two-handed operation. A trigger 14 is arranged on the front of the handle so that it can be conveniently squeezer by a user to start dispensing of the disinfectant from nozzle assembly 20.

Battery pack 30 is provided beneath the handle to enable cordless operation of the sprayer 1. The battery pack is detachable using clip 31 for charging. Alternatively, a charging socket may be provided so that the battery pack 30 can be connected to a charger by plugging it in (which may include slotting the sprayer into a dedicated storage/charging station in which the battery pack 30 is automatically engaged with contacts for charging).

A centrifugal fan 40 provides a high velocity air flow which is used in the nozzle assembly 10 to atomize the HOCI produced in the sprayer before it is dispensed.

A user interface/display 16 allows certain parameters of the sprayer 1 to be adjusted by the user andJor provides feedback to the user on the settings, remaining charge etc..

Fig. 2 shows, schematically, the electrical and fluidic connections within the sprayer 1. A controller 18 which, in this embodiment, is a microcontroller with pre-configured and programmed electronics, controls the operation of the various electrical components of the sprayer 1, as well as taking inputs from and providing outputs to the user interface/display 16. A power source 32 (typically a battery housed in the battery pack 30) is connected to the controller which controls the supply of power from the power source 32 to the other components. In the present embodiment the power source is a 4 Ahr 18V battery. This gives the sprayer 3 hours of continuous operation between charges.

A switch 15 is mechanically coupled to the trigger I 4 so that squeezing of the trigger causes the switch to be closed and triggers operation of the sprayer 1.

Tank 12 in the tank assembly 10 holds the salt water solution which, on actuation is pumped by a pump 14 through feed line 13 and supplied to the electrochemical flow reactor assembly 50. The salt solution used can bc from 0.2 g / litre to 20 g / litre and is preferably 5 g/litre or thereabouts.

The pump 14 provides a fixed liquid flow rate of between 50 ml/min and 150 ml/min, preferably between 75 mUmin and 125 ml/min, ideally about 80 mUmin.

The electrochemical flow reactor assembly 50 includes an electrochemical flow reactor in which the salt water from the tank 12 passes along a flow path between electrodes 51, 52.

The electrochemical reactor may have a structure and configuration similar to that shown in GB 2,578,292A, the contents of which are hereby incorporated by reference in their entirety.

The HOC1produced by the electrochemical flow reactor passes along a second feed line 17 to the nozzle assembly 20. The air flow from the centrifugal fan 40 atomizes the HOC at the nozzle assembly 20 and expels it through the nozzle aperture 23.

Fig. 3 shows the exterior of the electrochemical flow reactor assembly 50, whilst Fig. 4 shows the components of the electrochemical flow reactor assembly 50 in an exploded form. A housing 54 and lid 60 seal the electrochemical flow reactor in the assembly. An input port 58 and an output port 59 are provided for connection to the feed lines 13 and 17 which supply salt water to the electrochemical flow reactor and take the HOCI produced to the nozzle assembly respectively. Electrical connectors 56,57 are provided for supplying an electrical current to the electrode plates 51, 52 which form the reactor.

Inside the electrochemical flow reactor assembly 50, a flow path element 53 is sandwiched between the electrode plates 51 and 52. The flow path element 53 may be an impermeable membrane formed, for example, from polytetrafluorocthylenc (PTFE) or a perfluoroalkoxy alkanc (PEA) and defines a flow path from an inlet point to an outlet point. In the preferred embodiment a short wide flow path was round to be adequate to produce HOO at 200 ppm concentration. However, in alternative embodiments, the flow path could be a convoluted path (for example cut into it by laser machining) forming a relatively long channel within the overall size of the reactor unit maintaining a narrow residence time distribution.

The flow path forms a reaction chamber which runs from the inlet, which is in communication with the input port 58 to the outlet, which is in communication with the outlet port 59. The reaction chamber is bounded on either side of the membrane by the electrode plates 51, 52 making the reaction chamber suitable for carrying out electrochemical reactions as fluid passes through the reaction chamber from the inlet to the outlet.

The electrodes used in the electrode plates 51, 52 are manufactured with mixed metal oxide coatings on a 1 mm thick base metal of pure titanium. Three alternative oxide arrangements have been tested, each giving similar performance: ruthenium and iridium oxides, iridium and tantalum oxides or ruthenium mixed with both iridium and tantalum oxides. The currently preferred coating is ruthenium and iridium oxides of'6 um thickness.

The exposed area of each electrode e. the total area in contact with the flow path) is 500 nun2.

The sprayer 1 is preferably configured so that, in normal use, the electrochemical reactor is oriented close to vertical with the inlet at the bottom and outlet at the top. This orientation can help to prevent build-up of gas in the reactor.

The reactor can be operated at voltages between 2.5 V and 14 V and with currents between 0.1 A and 3 A. Preferably, when using a supply solution with 5 g / litre of salt, the reactor is operated at 6 V and 1300 mA to achieve an output o1200 ppm of AFC. Control of the current allows control of the rate of reaction in the reactor and thus the concentration of AFC produced.

The voltage and current supplied to the electrochemical now reactor is monitored to ensure correct manufacture of the AFC. Warning indicators on the display 16 notify the user if the voltage is out of tolerance or if the current is out of range. The display 16 also includes a button to allow the user to choose the concentration of AFC dispensed. Pressing the button allows the user to cycle between a number of choices, in this embodiment, selecting on of 45 ppm, 100 ppm or 200ppm AFC. Lights on the display 16 indicate the concentration selected at the current time.

Figs. 5A, 5B and 6 show the nozzle assembly 20 in more detail. Fig. 5A is an end view of the nozzle assembly, whilst Fig. 5B is a sectional view along the plane C-C shown in Fig 5A. Fig. 6 is an exploded view to show the components of the nozzle assembly in more detail.

The nozzle assembly 20 includes a nozzle base 21 and a nozzle cap 22. The nozzle cap 22 which has the aperture 23 is separate from the base 21 to allow assembly of the nozzle assembly 20 and is secured in place by screw-fixings 24.

The HOC solution is fed from the electrochemical reactor 50 by a tube (not shown) connected to the interior end 33 of a central pipe 29 and to outlet 34 at the exterior end of the pipe 29.

A static circular vane plate 25 is mounted on supports 26 which are evenly spaced around the circumference of the base 21. In the embodiment shown there are three supports 26. Whilst three supports 26 are considered optimal to reduce the contact area between the supports 26 and the vane plate 25 whilst preventing twisting of the vane plate 25, more could be used.

The vane plate 25 has a plurality of vanes 27 (in this case 6, but more or fewer could be used) which are formed perpendicular to the plane of the vane plate 25, and a plurality of corresponding holes 28 formed in between each pair of vanes 27. The vanes are arranged to guide the airflow driven by the pressure generated by the centrifugal fan 40 through the holes 28 and around the outside of the plate 25 to generate a vortex on the outer side of the plate 25 before the air exits the nozzle assembly 20 through the aperture 23.

The vanes 27 force the airflow generated by the fan 40 (not shown in Fig. 5B) and supplied to the internal end of the nozzle assembly 20 to move in a circular motion around the outlet 34 of the pipe 29. The air flow is accelerated by the progressively decreasing cross sectional area caused by the shape of the nozzle cap 22. The rotation of the air stream combined with the high velocity of the airflow across the surface of the outlet 34 causes the HOC1 solution to be atomised into tiny droplets and carried by the airstream as it exits the nozzle through the aperture 23.

The centrifugal fan 40 thus combines with the nozzle assembly 20 to produce the mist of HOC. The nozzle assembly 20 requires a high static pressure to allow the air to attain sufficient velocity to generate the fine droplet distribution. The centrifugal fan 40 used in this embodiment is manufactured by Sanyo Denki and has part number 9B MC24P2G001.

It provides a maximum static pressure of 1950 Pa and has a maximum flowrate of 1.85 m3/min.

The nozzle can generate droplets from 20 pm to 120 um in average diameter, preferably SO um. The droplet size is mainly determined by the velocity of the air flow in the vortex around the exit port and the rate of fluid flow out of the nozzle. By keeping both the fluid flow rate through the reactor and the speed of the centrifugal fan 40 constant, a consistent droplet size distribution can be achieved.

A large number of small droplets are desirable to achieve good surface coverage however if the droplets are too small, the AFC will be reduced due to the high surface area to volume ratio. Tiny droplets may also he carried away by air currents and not fall onto and disinfect the intended surface. Droplets of about SO pm have been found to have the preferred properties balancing between surface coverage, activity and deliverability.

In a further development, the switch 15 and/or the controller IS may be con figured to activate the electrochemical reactor in opposite polarity in each activation. This can help to prevent the electrochemical reactor from blocking due to deposition of solids from the reaction on one of the electrodes.

An electrochemical reactor block 50' used in a further embodiment of a sprayer is shown in Figs. 7 and 8. Fig. 7 shows the exterior of the electrochemical reactor block 50', whilst Fig. 8 shows an exploded view of the components of the electrochemical reactor block 50'.

A housing 54' and a cap 60' seal the electrochemical flow reactor in the assembly. The housing 54' and cap 60' are made from ABS. An input port 58 and an output port 59 are provided for connection to the feed lines 13 and 17 which supply salt water to the electrochemical flow reactor and take the 1-IOC1 produced to the nozzle assembly respectively. Electrical connectors 56, 57, 57' arc provided for supplying an electrical current to the electrode plates 51, 52, 52' which form the reactor.

In the electrochemical flow reactor of this embodiment, there arc three electrodes: a common anode 51 which is sandwiched between two cathodes 52, 52' (although it will be appreciated that an arrangement with a common cathode and two anodes would be effectively the same). Fluid from the input port 58 flows into the hollow volume 53 within the housing 54' and between the electrode plates 51, 52, 52' to the output port 59.

The electrode plates 51, 52, 52' are supported and held in position in the hollow volume 53 by ABS spacers 65 which also serve to maintain a fixed distance between the electrode plates. Further spacers (not shown) may be provided at the cap end of the electrode plates.

Each electrode plate 51, 52, 52' has a tab 51a extending from one edge. The tabs of each electrode plate are offset from each other along the direction of the edge so as to allow separate electrical connectors 56 to provide electrical connection between the electrode plates and the exterior of the cap 60'. Each electrical connector 56 is formed by a stainless steel pin 61 which is held in place by a pin retainer 64 and urged into contact with the respective tab 51a by a gold plated spring 62. Each electrical connector 56 also has a seal 63 in the form of a nitrile 0-ring to prevent liquid from the reactor from exiting the block 50' through the apertures in the cap 60' provided for the electrical connectors.

The electrode plates 51, 52, 52' are made from grade TA1 titanium coated in a mixed metal oxide (MMO) coating of ruthenium oxide and iridium oxide. The MMO coating is a uniform thickness of 10 um.

The electrode plates 51, 52, 52' are of identical dimensions. Thus the total area of cathode and anode is equal as the two planar surfaces of the common anode 51 are matched to the corresponding planar surfaces of the two cathodes 52, 52'. The total combined surface area of the electrodes in the reactor of this embodiment is 22cm2. This arrangement of electrode plates allows a compact electrochemical flow reactor to be achieved, which is suitable for use in a handheld sprayer, whilst still having the necessary electrode area to be effective.

The spacers 65 ensure that the electrode plates 51, 52, 52' are arranged with a uniform small spacing of lmm. By using a flow reactor with a small electrode spacing and a relatively low current density, it is possible to use a more dilute salt solution than in current devices whilst still achieving desired outputs of active agent. For example using the electrochemical reactor of this embodiment, it is possible to achieve an output of 150ppm free chlorine using a supply salt solution with a concentration of only 2.5g/ with a flow rate of 80m1/min of salt solution and 1.03A current through the reactor.

For the reactor of this embodiment, the current densities required to achieve various concentrations of free chlorine are 20mA/cm= for 45ppm free chlorine, 47mA/cm= for 100ppm free chlorine and 67mA/cm= for 150ppm free chlorine.

Using less concentrated input salt solutions means that the output spray from the sprayer contains less residual salt. This can reduce the undesirable and/or unsightly salt deposits left on the disinfected surface after the residual water in the output evaporates and can mean that the sprayer is suitable for disinfecting foodstuffs.

It will bc apprcciatcd that, apart from thc identified differences in the construction of the electrochemical reactor, the other features of the sprayer of this embodiment may be as described above, including any combination of optional or preferred features.

The controller 18 of the sprayers of embodiments of the invention is configured to maintain a constant concentration of active agent in the output from the electrochemical reactor 50.

In order to ensure consistent function as a disinfectant sprayer, the sprayer needs to produce hypochlorous acid at a consistent, and reliably known, concentration throughout its life and regardless of variations in the functioning of the various components of the spraycr and the input fluids.

In general terms, three factors can affect the concentration of the hypochlorous acid (also referred to as the concentration, typically in parts-per-million (ppm), of "free chlorine) produced in the electrochemical reactors of the present embodiments. These are: a. The area of active electrode in the electrochemical reactor. Over time, and particularly after extensive use, the electrodes of the electrochemical reactor may corrode and/or become contaminated or blocked which reduces the area of electrode which is able to perform the electrochemical reaction to produce the hypochlorous acid/free chlorine.

b. The concentration of salt in the salt solution which is supplied to the electrochemical reactor. Typically, salt solutions will be mixed up by a user in advance of use and so variations/errors in the concentration from the specified or desired levels will arise.

c. The flow rate of the solution passing through the electrochemical reactor. This may vary due to ageing of pump components, accumulation of sediment reducing pump capacity, partial blockages of filters, etc. Fig. 9 shows the relationship between voltage and current for the electrochemical reactor described in the previous embodiment when generating a constant (measured) concentration of free chlorine (in this case 100ppm). The respective plots in Fig. 9 show the variation of voltage and current dependent on changes in the three factors identified above (with all other conditions being kcpt constant in cach case).

A first plot (labelled at the extremities with "99m1/min" and "69.4m1/min") shows the variation in voltage and current in the reactor needed to maintain an output oil00ppm free chlorine based on variation in the flow rate of salt solution through the reactor.

A second plot (labelled at the extremities with "3.5g/T." and "1 g/I: sodium chloride") shows the variation in voltage and current in the reactor needed to maintain an output of 100ppm free chlorine based on variation in the concentration of salt (sodium chloride) in the supply solution.

A third plot (labelled at the right-hand extremity with "55% of electrode area") shows the variation in voltage and current in the reactor needed to maintain an output of 100ppm free chlorine based on variation in the active working area of the electrode.

A standard or ideal operating point is also labelled showing that, with the desired or standard conditions of 100% active electrode area, 2.5g/L sodium chloride concentration and a flow rate of 80m1/min, a current of 1.03A and a voltage of 3.68V is required to produce 100ppm free chlorine.

The inventors have noted that the variation in voltage and current required to maintain an constant concentration of free chlorine substantially follows a similar curve, regardless of whether the variation is in the flow rate, salt concentration or active electrode area. Fig. 9 shows a best-fit curve through the combined data set (dotted line). This best fit curve can also be defined mathematically as: = 2.239 In V -1.873 where I is the current and V is the voltage.

Similar relationships are observed for different output concentrations of free chlorine and similar best fit curves can be defined.

In the devices of the present embodiments, concentrations of 45ppm, 100ppm, 150ppm and 200ppm free chlorine are selectable as described above. The controller 18 is arranged to control thc current and/or voltage supplied to the electrochemical reactor 50 in order to maintain the desired or selected concentration of free chlorine.

In one embodiment the controller is configured to operate by following the process below: a. Set the reactor current to a predetermined starting current. This may be chosen to be the nominal current which would produce the desired/selected concentration if all conditions are exactly as standard. For example, in the reactor of the above embodiment, based on Fig. 9, this current would be 1.03A for 100ppm free chlorine.

b. Measure the cell voltage at the set current.

c. Calculate the desired current for the measured voltage. This may be done by using a look-up table, stored in a memory connected to the controller, which has a series of voltage/current entries with the closest matching entry being selected, or may be calculated by the controller from a known relationship such as that set out above.

d. Set the current to the desired current detennined in step c.

e. Repeat steps b.-d.

By repeating steps b.-d., the controller will progressively arrive at a steady-state position on the voltage-current graph which will reflect the variation in the underlying operating conditions from the standard conditions and ensure a controlled output of the active agent.

Experimentally it is found that the steady-state is typically arrived at in around 6 iterations.

The controller may repeat the steps at a cycle rate ofbetween 0.1s and 10s, ideally around Is.

The current can be limited to ensure that the system does not enter a run-away situation. In this embodiment the limit is set at 3A. Similarly, if the measured voltage exceeds a certain value (in this embodiment 7.2V), then a cell fault is indicated and the controller stops the operation of the sprayer.

It will be appreciated that, whilst the above description of the operation of the controller has involved setting the current and monitoring the voltage, the opposite arrangement of setting the voltage and measuring the current could be used in an otherwise identical process.

Another important consideration in the effectiveness and/or concentration of the active agent dispersed from the sprayer is the pH of the sprayed solution. Fig. 10 shows the equilibrium balance between C12, HOCI and OCI-in a solution of hypochlorous acid at varying pH. From this it can be seen that, [hr maximum proportions or HOC (and thus maximum free chlorine), the pH of the solution should have a pH of between about 3.5 and 6 and, for consistent output of free chlorine as an active agent, should be maintained in that range.

To achieve a constant pH in the desired range, a buffer of citric acid is added to the salt solution which is used in the sprayers. The buffer is added as 0.4g citric acid per litre of salt solution. Acids other than citric acid may alternatively be used to correct the pH (i.e. Acetic acid).

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

Claims

Claims I. A hand-held sprayer having: a nozzle assembly for directing a spray of atomized fluid; a fluid storage; an electrochemical flow reactor having an inlet in fluid communication with the fluid storage and an outlet in fluid communication with the nozzle assembly, the electrochemical flow reactor being arranged to cause an electrochemical reaction in an input fluid from the fluid storage and produce an output fluid; a pump arranged to pump liquid from the fluid storage to the electrochemical flow reactor; and a controller arranged to control the electrochemical flow reactor, wherein the controller is arranged to control the electrochemical flow reactor so as to provide a predetermined concentration of an active agent in the output fluid.
2. A sprayer according to claim 1 wherein the controller is arranged to control one or more of: the current supplied to the electrochemical flow reactor; the voltage across the electrochemical flow reactor; and the flow rate of fluid through the electrochemical flow reactor, in order to provide the predetermined concentration of the reagent in the output fluid.
3. A sprayer according to claim 1 or claim 2 further comprising a sensor arranged to detect an operating characteristic of the electrochemical flow reactor and produce an output relating to said operating characteristic, wherein said controller is arranged to receive said output and to control the electrochemical flow reactor based on said output.
4. A sprayer according to claim 3 as dependent on claim 2, wherein the controller is arranged to control the electrochemical flow reactor by: a. supplying a first predetermined current through the reactor; b. measuring the voltage across the reactor; c. determining the desired current through the reactor for the measured voltage and the predetermined concentration; d. supplying the determined desired current to the reactor; and e. repeating steps b. to d. periodically.
5. A sprayer according to any one of the preceding claims wherein the electrochemical flow reactor has three electrodes: a first, common electrode which is arranged between two second electrodes and, in use, the first electrode and the second electrodes have opposite polarity.
6. A sprayer according to claim 5 wherein the common electrode is a plate having two opposite planar sides, and each of said sides operates as an electrode in conjunction with a respective one of the second electrodes.
7. A sprayer according to claim 6 wherein the total area of the two sides of the common electrode is the same as the total area of the second electrodes.
8. A sprayer according to any one of the preceding claims wherein the spacing between electrodes of opposite polarity in the electrochemical flow reactor is between 0.25mm and 3mm.
9. A sprayer according to any one of the preceding claims wherein the controller and electrochemical flow reactor are arranged to provide a current density between electrodes in the electrochemical flow reactor of between 10 mA/cm2 and 100 mA/cm2.
10. A sprayer according to any one of the preceding claims further including a fan arranged to cause a flow of air through the nozzle assembly, wherein the nozzle assembly and/or the fan are arranged to cause said flow of air to generate a vortex so as to atomize fluid which has passed through the electrochemical reactor.
11. A sprayer according to any one of the preceding claims further including a power supply arranged to supply power to the reactor, the pump and the fan.
12. A sprayer according to any one of the preceding claims wherein the fluid storage contains a solution of salt water.
13. A sprayer according to any one of the preceding claims wherein the controller is arranged to receive an input from a user and control the electrochemical flow reactor depending on the input from the user so as to provide a desired concentration of the active 5 agent.
14. A sprayer according to any one of the preceding claims wherein the pump is arranged to pump liquid at a constant flow rate.
15. A sprayer according to any one of the preceding claims wherein the pump is a positive displacement pump.
16. A sprayer according to any one of the preceding claims wherein the pump is arranged to provide a liquid flow rate of between 50m1/min and 150 ml/min.
17. A sprayer according to any one of the preceding claims wherein the nozzle assembly includes a plurality of vanes which are arranged to generate a vortex by guiding said air flow in a circular pattern.
18. A sprayer according claim 17 wherein the nozzle assembly includes a fluid aperture through which fluid from the output of the electrochemical reactor is supplied and wherein said plurality of vanes arc arranged around the aperture so as to generate said vortex in the vicinity of aperture.
19. A method of disinfecting a surface, the method including the steps of: supplying salt water to an electrochemical flow reactor; controlling the reactor to form a predetermined concentration of hypochlorous acid at an output from the reactor; atomising the hypochlorous acid formed in the reactor; and directing the atomized hypochlorous acid to the surface.
20. A method according to claim 19 wherein step of controlling includes controlling one or more of: the current supplied to the electrochemical flow reactor; the voltage across the electrochemical flow reactor; and the flow rate of fluid through the electrochemical flow reactor, in order to provide the predetermined concentration of the hypochlorous acid.
21. A method according to claim 19 or claim 20 further comprising the step of detecting an operating characteristic of the electrochemical flow reactor, wherein the step of controlling controls the electrochemical flow reactor based on said detected operating characteristic.
22. A method according to claim 21, wherein the step of controlling includes: a. supplying a first predetermined current through the reactor; b. measuring the voltage across the reactor; c. determining the desired current through the reactor for the measured voltage and the predetermined concentration; d. supplying the determined desired current to the reactor; and 0. repeating steps b. to d. periodically.
23. A method according to any one o I claims 19 to 22 wherein the step of controlling controls the reactor to provide a current density between electrodes in the reactor of between 10 mA/cm2 and 100 mA/cm2.
24. A method according to any one of claims 19 to 23 further including the step of mixing a buffer into the salt water.
25. A method according to claim 24 wherein the buffer is arranged to maintain the pH of the output hypochlorous acid solution in the range o14 to 6.5.
26. A method according to any one of claims 19 to 25 wherein the step of atomising includes generating a vortex of air flow around a fluid aperture.
27. A method according to any one of claims 19 to 26 wherein the salt in the salt water is at a concentration of between 0.2 g / litre to 10 g / litre.
28. A method according to any one or claims 19 to 27 wherein the salt water is supplied at a constant flow rate.
29. A method according to any one of claims 19 to 28 wherein the salt water is supplied at a rate of between 50m1/min and 150 ml/min.