NL2024499B1

NL2024499B1 - Gas treatment device, combination of the gas treatment and a non-gas-fired incinerator, and method for treating gas contaminated with at least one contaminant

Info

Publication number: NL2024499B1
Application number: NL2024499A
Authority: NL
Inventors: Adriaan De Vos Willem; Noorlander Willem
Original assignee: Wim En Wim B V
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-09-08

Abstract

The invention relates to a gas treatment device, comprising: - a container for receiving an amount of purging agent therein, said container being provided with a gas inlet to and a gas outlet from the container, and being provided with a purging agent inlet to and a purging agent outlet from the container, - measuring means for measuring a contaminant concentration in gas, arranged downstream of the gas inlet of the container, and - discharging means, configured for discharging at least a part of the purging agent through the purging agent outlet when the contaminant concentration measured with the measuring means is above a threshold value. The invention further relates to a combination of a gas treatment device according to the invention and a non-gas-fired incinerator, downstream of the purging agent outlet of the container, for incinerating the purging agent discharged through the purging agent outlet, and to a method for treating gas contaminated with at least one contaminant.

Description

GAS TREATMENT DEVICE, COMBINATION OF THE GAS TREATMENT AND A NON- GAS-FIRED INCINERATOR, AND METHOD FOR TREATING GAS CONTAMINATED WITH AT LEAST ONE CONTAMINANT

FIELD OF THE INVENTION The invention relates to a gas treatment device comprising a purging agent.

The invention further relates to a combination of a gas treatment device and an incinerator, and to a method for treating gas contaminated with a contaminant.

19 BACKGROUND OF THE INVENTION Many industrial processes result in the contamination of a gas, such as air, by contaminants. such as VOCs, which contaminants may be either a liquid and/or a gas. In order to avoid emission of these contaminants, such industrial processes are often carried out in a protected (e.g. closed) production space, typically provided with a gas exhaust, in order to expel the contaminated gas from the production space and post-process contaminated gas in a controlled manner in order to at least reduce the amount of contamination in the expelled gas. An example of such an industrial process is the process of spray-painting e.g. of vehicles, which is typically carried out in a spray-painting booth in order to avoid emission of the contaminants released during the process.

Currently, post-processing may involve a process in which the contaminated gas expelled from the production space is passed through an amount of purging agent. An example of a typical purging agent is active carbon, also known as activated carbon, activated or active charcoal, typically supplied in the form of a filter. Contaminants such as VOCs will bind to the purging agent, either by adsorption (such as chemisorption or physisorption) and/or absorption, thereby cleaning the contaminated gas to a certain extent. However, purging agents, in particular active carbon filters, will become saturated during this binding process, therefore requiring regeneration and/or replacement. Regeneration is carried out with a regenerating means, which may be toxic at already fairly low concentrations and/or short exposures itself, such is the case with ozone, which is used for regeneration of active carbon. Furthermore, both regeneration of the filter and replacement of the filter require interrupting the process carried out in the production space. The regeneration or replacement itself, as well as the consequences thereof to the process carried out in the production space, make this process expensive to such an extent that it may not be considered economically feasible.

An alternative known post-processing process involves the step of incinerating the gas expelled from the production space in a rotating gas-fired incinerator. In this step, it is required to add an additional gas as well as oxygen to the gas expelled from the production space, in order to start the incineration. Moreover, the ratio between each of the input components to the incinerator is important in order to convert the contaminants into substances which can be emitted freely. This makes this process very difficult to control and thereby expensive as well.

SUMMARY OF THE INVENTION It is therefore an object of the invention reduce or even obviate the above-mentioned disadvantages.

This object is achieved by providing a gas treatment device, comprising: - a container for receiving an amount of purging agent therein, said container being provided with a gas inlet to and a gas outlet from the container, and being provided with a purging agent inlet to and a purging agent outlet from the container; - measuring means for measuring a contaminant concentration in gas. arranged downstream of the gas inlet of the container, and - discharging means, configured for discharging at least a part of the purging agent through the purging agent outlet when the contaminant concentration measured with the measuring means is above a threshold value.

It has surprisingly been found that it is possible to remove contaminants from a contaminated gas more effectively with such a gas treatment device. In the device according to the invention, an amount of solid, granular and/or particulate purging agent may be provided in the container, and a contaminated gas may subsequently be directed through the container and the purging agent provided therein from the gas inlet towards the gas outlet, thereby resulting in binding of the contamination to the purging agent, either by adsorption (such as chemisorption or physisorption) and/or absorption, thereby cleaning or purging the contaminated gas. Purging agent in the container will be able to bind the contaminants by adsorption and/or absorption until a moment in time when it becomes fully saturated, after which moment in time it will no longer be able to bind further contaminants. In order to avoid the occurrence of or shorten such a situation as much as possible, the invention provides measuring means, which allow the contaminant concentration at a position downstream of the gas inlet after passage of purging agent provided in the container, to be measured. This makes it possible to determine the moment in time at which the most saturated purging agent in the container has become saturated to a certain extent, e.g. fully saturated, (i.¢. when the contaminant concentration is above the threshold value) when observing the concentration above this threshold value, and to control the discharging means to discharge at least a part of the purging agent through the purging agent outlet, in order to reduce the average saturation of the purging agentin the container. The part discharged by the discharging means preferably comprises just fully saturated purging agent.

The gas travels through the container from the gas inlet towards the gas outlet. In order to arrive at a suitable contact time, the gas inlet and the gas outlet are preferably not the same. Instead, it 1s preferred to space apart the gas inlet and the gas outlet, in order to obtain effective contact between the contaminated gas with the active carbon within the container. For instance, the gas inlet and gas outlet may be provided in different walls of the container.

While it is possible to discharge all of the purging agent through the purging agent outlet when measuring a contaminant concentration above the threshold value with the measuring means, it is preferred to release just a part of the purging agent contained in the container, preferably just fully saturated purging agent.

The purging agent may be any agent or mixture of agents suitable for purging a contaminated gas, selected by a person skilled in the art by the contaminant to be purged. For instance, the purging agent may comprise sawdust.

However, in a very preferred embodiment of the gas treatment device the purging agent is or comprises active carbon, and the contaminant concentration measured by the measuring means is the concentration of volatile organic components (VOC) in the gas.

It is possible to use the gas treatment device according to the invention for cleaning a variety of gases. However, the gas treatment device has been in particular been found useful for removal of volatile organic components (VOCs) from a gas. In such a case, active carbon is a suitable purging agent.

In the following, when using the terms “purging agent’ and ‘contaminant concentration’, active carbon and the concentration of VOCs are in all cases to be considered a very preferred specific embodiment of those terms, respectively.

In a preferred embodiment of the gas treatment device, the device further comprises supplying means, configured for supplying fresh purging agent through the purging agent inlet for replacing the discharged purging agent.

It is preferred to replace at least a part of the purging agent discharged through the purging agent outlet, by supplying fresh purging agent through the purging agent inlet of the container, either before, during and/or after discharging the aforementioned purging agent from the purging agent outlet. Preferably, the supplying and/or discharging means are configured for keeping the volume of purging agent in the container substantially constant.

The purging agent inlet and the purging agent outlet are preferably spaced apart from each other in order to make it easier to introduce fresh purging agent through the purging agent inlet while discharging more saturated purging agent from the purging agent outlet. Preferably, the purging agent outlet is arranged in the bottom of the container, in order to allow the purging agent inthe container to flow towards the purging agent outlet under the influence of gravity, or another position to achieve a similar effect. For the same reason, the purging agent inlet may be arranged at or near the top of the container. The purging agent inlet may be configured to be opened concurrently with or shortly after opening of the purging agent outlet.

In another preferred embodiment of the gas treatment device. the measuring means comprise a sensor arranged closer to the gas outlet than to the gas inlet.

It is preferred to have measuring means which comprise a sensor, which is arranged closer to the gas outlet than to the gas inlet. In this way, it is possible to obtain a more reliable picture of the contaminant saturation in the container (such as calorific value when the purging agent comprises active carbon), making it easier to discharge saturated, e.g. fully saturated purging agent at the right time.

The device may be provided with a plurality of sensors, of which one, a plurality or all may be arranged closer to the gas outlet than to the gas outlet. Arrangement of sensors at different locations makes it possible to measure the contaminant concentration in the gas passed through the purging agent in the container, and thereby the contaminant saturation of this purging agent in a reliable way, and makes it also possible to correct for malfunctioning sensors.

In a further preferred embodiment of the gas treatment device, the sensor is arranged in or downstream of the gas outlet.

In the gas treatment device according to the mvention, purging agent is discharged and new purging agent may be supplied. A sensor arranged within the container may be exposed to forces due to this discharge and/or supply which may damage the sensor. Therefore, it may be more desirable to arrange at least one. a plurality and possible all of the sensors of the measuring means at a location which is not in direct contact with the purging agent in the container. Arrangement in or downstream of the gas outlet is therefore preferred. A sensor arranged downstream of the gas treatment device is preferably arranged directly downstream of the gas treatment device, e.g. in a tubing directly connecting the gas outlet with a further piece of processing equipment.

In another preferred embodiment of the gas treatment device, the gas inlet, gas outlet, purging agent inlet and purging agent outlet are arranged for in use obtaining a saturation gradient in the purging agent, the saturation increasing from the purging agent inlet towards the purging agent outlet.

It is preferred to design the gas treatment device and more in particular to choose the position of the gas inlet, gas outlet, purging agent inlet and purging agent outlet, for in use obtaining a saturation gradient in the purging agent (such as VOC saturation, in the case of purging of VOCs from gas with active carbon). This may mean or additionally mean that, when choosing a plurality of, preferably equally spaced, locations within the container, with each following location being closer to the purging agent outlet than the previous location, each following location also makes the probability of full saturation of the purging agent at this following location higher than at the direct previous location. The gradient is preferably a smooth ascending gradient of saturation. Various types of flow within the container are conceivable in order to achieve such a gradient, such as countercurrent or crossflow of the purging agent.

5 However, in a preferred embodiment of the gas treatment device, the container comprises a gas-permeable and purging agent-impermeable inner and outer wall, arranged surrounding a cavity and spaced apart from each other, wherein the purging agent outlet is below the purging agent inlet, seen in a direction along the inner wall.

In such a gas treatment device, the gas inlet and gas outlet are formed by the opposing inner and outer walls. The gas-permeability of the inner and outer walls makes it possible to let the gas enter and leave the container over a large surface area and thereby distribute more evenly within the volume of the container. At the same time, purging agent is not able to pass the inner and outer wall, and thereby stays in the container. Preferably, gas is forced through the container from the outer wall through the container and thereafter through the inner wall, consequently implying the outer wall to form the gas inlet and the inner wall to form the gas inlet. By choosing the position of the purging agent outlet below the purging agent inlet, seen in a direction along the inner wall, purging agent in the container moves towards the purging agent outlet when using the discharging means. In combination with the provision of the gas inlet and gas outlet as a gas-permeable inner and outer wall of the container, this makes it possible to, after an initial start-up phase, build a saturation gradient within the container. In yet another embodiment of the gas treatment device, at least one of the inner wall and the outer wall is cylindric. Cylindrical walls make it easier for a gas to pass the inner and/or outer wall, compared to other designs. For that reason, preferably both of the inner and outer wall are cylindric. In this case, the cylindric inner and outer wall are preferably concentric, making it easier to achieve an equal saturation level in a radial direction as seen from the center of the container. In another embodiment of the gas treatment device, the device further comprises rotating means for rotating at least one cylindric wall around its axis. Rotation of one or preferably both of the walls makes it possible to further homogenize the saturation level within the container in the tangential direction. In yet another preferred embodiment of the gas treatment device, the container is adapted for receiving, or is loaded with purging agent in bulk. As mentioned, it 1s known to treat contaminated gasses with active carbon filters which are provided in the form of one or more cartridges, which cartridge(s) is or are, when required, replaced as a whole. However, the container according to the invention is preferably adapted to receive purging agent, and active carbon in particular, in bulk, or loaded with this purging agent in bulk. This makes it easier to gradually replace the purging agent in the container, maximizing the efficiency. Furthermore, purging agent in a bulk is cheaper than cartridges comprising active carbon.

The object of the invention is further achieved by providing a combination of a gas treatment device according to the invention and a non-gas-fired incinerator, downstream of the purging agent outlet of the container, for incinerating the purging agent discharged through the purging agent outlet.

The purging agent discharged through the purging agent outlet of the container of the gas treatment device is preferably post-processed in an incinerator, downstream of the purging agent outlet of the container. When the purging agent comprises active carbon for purging VOCs from gas, incineration converts the active carbon mainly into carbon dioxide (CO:), nitrogen oxide (NO,). water (H;0) and heat.

Incinerators by themselves are known to a person skilled in the art and are, as mentioned, currently used for directly incinerating contaminated gasses. In contrast to this, in the combination according to the invention, the purging agent. such as active carbon, may have a high calorific value when incinerated. Active carbon with a relatively high calorific value does not require, in contrast to the incineration of contaminated gas, the addition of additional gasses in order to fire the incinerator.

In an embodiment of the combination, the combination further comprises a heat exchanger, for heating a gas flow using heat originating from the incineration of the purging agent discharged through the purging agent outlet, said gas flow preferably comprising gas from the gas outlet of the container.

The aforementioned heat released in the step of incineration in the incinerator may for instance be used to heat a gas flow, thereby utilizing the products of the incineration more effectively. More specifically, the treatment of the contaminated gas in the gas treatment device according to the invention may have cleaned the gas to such an extent that it may be suitable for further use in a process. This process may require the cleaned gas to be brought to an increased temperature. At least a part and possibly all of the heat released in the incinerator according to the invention is preferably used to at least provide a part of the heat necessary to bring the gas to such a temperature.

In another preferred embodiment of the combination, the combination further comprises storage means, for storing the purging agent discharged from the container, downstream of the container and upstream of the incinerator.

It is preferred to provide the combination with such a storage means for storing the purging agent. such as active carbon, discharged from the container. The storage means may for instance comprise a receptacle. A storage means makes it possible to choose the moment in time for incineration of the active carbon discharged from the container, independent from the discharge itself. In other words, the steps of binding of contaminants to the purging agent {such as active carbon) in the container and subsequent incineration in the incinerator are more or less disconnected from each other. The storage means typically has a volume larger than the volume of the container in order to provide a suitable capacity for such a disconnection, ¢.g. at least twice as large, maybe even at least five times larger or maybe even at least ten times larger.

For instance, it is possible to clean contaminated gasses with the gas treatment device during the summer season, and to store the discharged purging agent in the storage means, waiting for the winter season to start incinerating it in the incinerator, after which the heat is transferred to e.g. a central heating system, such as by means of a heat exchanger.

In a preferred embodiment of the combination, the combination further comprises a dust filter, upstream of the container. Dust may adversely impact binding of contaminants by purging agents, in particular active carbon. Therefore, it is preferred to provide a dust filter in order to prevent dust from getting into contact with the purging agent in the container. Such dust filters are known to a person skilled in the art, and may for instance be provided in the form of a replaceable cartridge.

In another embodiment of the combination, the combination further comprises a production space, such as a spray-painting booth, said production space being provided with a gas exhaust in fluid connection with the gas inlet of the gas treatment device.

The gas treatment device according to the invention is in particular suitable as a means for treating gasses from one or more production spaces. An example of such a production space is a spray-painting booth, which is typically used for spray-painting of e.g. vehicles. A dust filter, if present, may for instance be provided as a part of the gas exhaust of the production space.

In a preferred embodiment of the combination the production space further comprises a gas inlet configured for receiving gas treated with the gas treatment device, said combination thereby forming an at least partially closed circuit.

In order to replace the contaminated gas expelled from the production space, it is necessary to introduce fresh air into the production space. As mentioned, the treatment of the contaminated gas in the gas treatment device according to the invention may have cleaned the gas to such an extent that it may be suitable for further use in a process. Such a process may be carried out in a production space. Introducing a part or all of the gas cleaned by the gas treatment device into the same production space as the production space from which the contaminated gas was exhausted for treatment in the gas treatment device may be preferred, thereby forming an at least partially closed circuit.

Before reintroduction into the production space, the gas may be heated to a temperature according to specification, e.g. 20 °C when the production space is a spray-painting booth. The heat for this heating may be provided by contacting the cleaned gas with heat released in the incinerator.

The object of the invention is further achieved by providing a method for treating gas contaminated with at least one contaminant, comprising the steps of: a) passing the contaminated gas through an amount of purging agent in a container; b) measuring the contaminant concentration in the contaminated gas passed through the amount of purging agent, and c) discharging at least a part of the purging agent from the container when step b) results in a contaminant concentration measured above a threshold value.

In the method an amount of purging agent is provided in a container, and a contaminated gas is directed through the container and the purging agent provided therein from the gas inlet towards the gas outlet. This results in binding of the contamination to the purging agent, thereby cleaning or purging the contaminated gas. Measuring means measure the contaminant concentration at a position downstream of the gas inlet, i.e. after passage of at least some of the purging agent provided in the container and are configured to control the discharge means to discharge at least a part of the purging agent through the purging agent outlet when observing the contaminant concentration above the threshold value in order to reduce the saturation of the purging agentin the container. This method may be carried out continuously or by batch processing.

In a very preferred embodiment of the method, the purging agent is or comprises active carbon, and the contaminant concentration measured by the measuring means in step b) is the concentration of volatile organic components (VOC) in the gas.

In an embodiment of the method, the steps b) and c) are carried out concurrently with step a).

The steps b) and ¢) allow the method according to the invention to be carried out during step a), making it possible to realize a process which may be continuous, as opposed to batch processing, although batch processing is also possible.

In a further embodiment of the method, the method further comprises the step d) of supplying fresh purging agent through a purging agent inlet for replacing the at least partly discharged purging agent, which step d) is preferably carried out concurrently with step a).

As mentioned, it is preferred to replace at least a part of the purging agent discharged through the purging agent outlet, by supplying fresh purging agent through the purging agent inlet of the container, either before, during and/or after discharging more saturated purging agent (which may have a higher calorific value than the fresh purging agent, such as when the purging agent comprises active carbon) from the purging outlet. Replacement makes it also possible to realize a continuous process, as opposed to batch processing. although batch processing is also possible.

In another embodiment of the method, step a) is carried out at ambient temperature.

The method according to the invention allows for cleaning or purging without bringing the gas to a temperature higher than ambient temperature, e.g. between 20 and 25 °C, thereby making the method cheaper and safer.

In another embodiment of the method, the container moves, in particular rotates, while step a) is carried out.

In vet another embodiment of the method, the method further comprises the step ¢) of incinerating the purging agent discharged without gas-firing.

As mentioned in relation to the combination, the incineration of purging agent may not require gas-firing in order to start the incineration, especially when the purging agent discharged has a relatively high calorific value, e.g. when the purging agent comprises active carbon for I5 purging VOCs from gas.

In a preferred embodiment of the method. the method further comprises the step f) of heating a gas flow with heat originating from step €), said gas flow preferably comprising gas from the gas outlet of the container.

As mentioned, the heat released in the step €) of incineration in the incinerator may for instance for a step f) of heating a gas flow, thereby utilizing the products of the incineration more effectively.

In another preferred embodiment of the method, at least a part of the purging agent originates from plant material, such as wood.

It is preferred to use purging agent which originated from plant material, such as wood, ¢.g. in the form of sawdust and/or converted to active carbon, in order to remove contaminants from the gas bv binding processes such as adsorption and/or absorption. Plant materials such as wood, are able to convert carbon dioxide into food using energy from light by photosynthesis. The method according to the invention may involve a step involving the release of carbon dioxide, e.g. the step €) of incineration. Choosing purging agent originating from plant material thereby only produces carbon dioxide which previously had been converted from carbon dioxide, thus reducing the carbon footprint of the method and making it preferred over other sources of active carbon.

For clarity, it is observed that any embodiment or implementation discussed hereinabove is applicable to any of the aspects (e.g. gas treatment device, combination, method) covered in the present application. Consequently, the hereinabove descrnibed method are preferably carried out in the hereinabove described device and/or combination.

BRIEF INTRODUCTION OF THE FIGURES These and other aspects of the invention will be further elucidated with reference to the figures, which are purely diagrammatical in nature and not drawn to scale, wherein: Fig. 1 shows a schematic diagram of an example of a combination according to the prior art Fig. 2 shows a schematic diagram of an embodiment of a combination according to the invention.

Fig. 3 shows an embodiment of a method according to the invention.

Fig. 4 shows a perspective view of a gas treatment device according to the invention.

Fig. 5 shows a cross section of the gas treatment device according to Fig. 4.

DETAILED DESCRIPTION OF ILLUSTRATES EMBODIMENTS In the following, the illustrated embodiments are intended for explanation and illustration of the invention, the scope of the invention being defined by the claims.

In Fig. 1, a combination 100 according to the prior art is shown. In this combination 100, a gas contaminated by the process carried out in a production space 101, is either cleaned or purged by passing the gas through a active carbon filter 102 from a gas inlet 103 to a gas outlet 104, or by Incineration in an incinerator 105, which also requires introduction of a further gas 106, as well as oxygen, to start the incineration, resulting in exhaust 107. When the filter 102 in this prior art arrangement is saturated, it is either replaced by a new filter or regenerated by means treating it with ozone.

Fig. 2 discloses a combination 1 according to the invention. This combination comprises a gas treatment device 2, which is first described. The gas treatment device 2 comprises a container 3 provided with a gas inlet 4 and a gas outlet 5 in suitable walls (including the top and/or bottom wall) of the container 3. The container 3 is further provided with an active carbon inlet 6, and an active carbon outlet 7, arranged in the top wall and bottom wall of container 3, respectively. The container 3 is provided with discharge means for discharging active carbon through active carbon outlet 7, and with supply means for supplying fresh active carbon through carbon inlet 6. A sensor 8 is provided to measure the VOC concentration in the gas. This sensor 8 is closer to the gas outlet 5 than to the gas inlet 4, downstream of the gas outlet 5. The sensor 8 may however also be arranged in the container 3 or in the gas outlet 5.

In use, the container 3 is provided with an amount of active carbon 9, and a contaminated gas is forced from gas inlet 4 towards gas outlet 5. On its way, the gas contacts the active carbon 9, thereby cleaning or purging the gas. The sensor 8 measures the VOC concentration in the gas, and controls the discharge of the active carbon through the active carbon outlet 7 by the discharge means, as well as the supply of fresh active carbon through the active carbon inlet 6 by the supply means. To this end, the sensor 8 may be connected to a controller controlling the discharge means and the supply means. The gas inlet 4 of the gas treatment device 2 is preferably connected to a gas exhaust of a production space 20 which may be similar to production space 101. Gas contaminated by the process in this production space 20 is transferred to the container 3, and is thereby cleaned or purged by the active carbon 9 in the container 3. The clean gas then passes a three-way valve 21, allowing some of the cleaned gas to be released through exhaust 22, and the rest to be passed to a heat exchanger 23 for heating the gas, which will be described hereafter. The heated gas then will be clean enough for reintroduction into the production space 20.

The active carbon 9 discharged through the active carbon outlet 7 of the container 3 is supplied to a storage means 24. When required. the active carbon 9 is subsequently transferred to an incinerator 25, where it is incinerated. This incinerator 24 does not require a further gas stream, due to the high calorific value of the (at least partially) saturated active carbon 9 supplied to the incinerator 25. The incineration mainly converts the active carbon into carbon dioxide (CO), nitrogen oxide (NO), water (HO), exhausted through exhaust 26, and heat. The heat released is preferably transferred to a heat exchanger, such as heat exchanger 23 to heat the gas before reintroduction into the production space 20. Alternatively, the storage means 24 1s omitted, and the active carbon 9 discharged from the container 3 is directly transferred to the incinerator 25.

Fig. 3 discloses a method 30 according to the invention. The method 30 comprises the step 31 of passing the contaminated gas through an amount of active carbon in a container and the step 32 of measuring the concentration of VOCs in the contaminated gas passed through the amount of active carbon. In step 33, it is determined whether the concentration of VOCs in the contaminated gas measured in step 32 is above a threshold value. When this is the case, at least a part of the active carbon from the container is discharged in step 34 and fresh active carbon is supplied through an active carbon inlet for replacing the at least partly discharged active carbon in step 35. When this is not the case, the step 32 is repeated after a suitable period of time, preferably continuously. The method also comprises the step 36 of incinerating the carbon discharged without gas-firmg. Steps 32-36 are preferably carried periodically, and possibly concurrently with step 31.

Fig. 4 and 5 disclose an example 40 of a container 3 according to the invention. The container 40 is annular and comprises a cylindric inner wall 41 and cylindric outer wall 42, spaced apart from inner wall 41, arranged surrounding a cavity 43. Both of the walls 41, 42 are gas- permeable and purging agent-impermeable. They may comprise a fine mesh. The container 40 further has an annular top wall 52 and an annular bottom wall 33, both of which are closed. Together, the inner and outer walls 41, 42 and top and bottom walls 52, 53 form an annular drum.

The container 40 is provided with a purging agent outlet 44 below the purging agent inlet 45, seen in a direction along the inner wall, in this case at the top and bottom of the container 40,

respectively.

The container is further provided with rotating means 46, for rotating at least one of the walls 41, 42 of the container around its common axis 47, as shown by arrow R.

As shown in figure 5, the interspace between the inner wall 41 and the outer wall 42 and between the top wall 52 and bottom wall 53 may be filled with a purging agent 48.In use, gas is forced to travel from a gas inlet 50 at the exterior of the container 40 through the outer wall 42, then through the purging agent 48 and subsequently through the inner wall 41, entering the cavity 43, which forms or is connected to a gas outlet 51. Although the invention has been elucidated above on the basis of a number of examples, it will be apparent that it not limited thereto.

For instance. the container may have other shapes than a cylindrical shape.

The purging agent may be another purging agent than active carbon.

The invention can be varied in many ways within the scope of the following claims.

Claims

CONCLUSIONS

A gas treatment apparatus comprising: a container adapted to receive or loaded with a quantity of detergent in bulk, the container having a gas inlet to and a gas outlet from the container, and having a detergent inlet to and a detergent outlet from the container; wherein the container comprises a gas-permeable and a detergent-impermeable inner and outer wall surrounding a cavity and spaced apart, the detergent outlet being below the detergent inlet as viewed in a direction along the inner wall, wherein at least one of the inner wall and the outer wall is cylindrical, the gas inlet, the gas outlet, the detergent inlet and the detergent outlet being arranged in use to obtain a saturation gradient in the detergent, which saturation increases from the detergent inlet towards the detergent outlet, measuring means for measuring the concentration of a contaminant in gas, arranged downstream of the gas inlet of the container, and discharge means, arranged for discharging at least a part of the cleaning agent through the cleaning agent outlet when the concentration of a contaminant measured with the measuring means went above a threshold value, supply means adapted to supply fresh cleaning agent through the cleaning agent inlet for replacing the discharged cleaning agent.

- rotation means for rotating at least one cylindrical wall of the container about its axis.

Gas treatment device according to claim 1, wherein the cleaning agent is or comprises activated carbon, and wherein the concentration of a contaminant measured by the measuring means is the concentration of volatile organic compounds (VOC) in the gas.

A gas treatment device according to claim 1 or 2, wherein the measuring means comprise a sensor which is arranged closer to the gas outlet than the gas inlet.

A gas treatment device according to claim 3, wherein the sensor is arranged in or downstream of the gas outlet.

Combination of a gas treatment device according to any one of the preceding claims and a non-gas-fired combustor, downstream of the cleaning agent outlet of the container, for burning the cleaning agent discharged through the cleaning agent outlet.

A combination according to claim 5, further comprising a heat exchanger for heating a gas stream with heat from the combustion of the cleaning agent discharged through the cleaning agent outlet, which gas flow preferably comprises gas from the gas outlet of the container.

A combination according to claim 5 or 6, further comprising storage means for storing the cleaning agent discharged from the container, downstream of the container and upstream of the incinerator.

A combination according to any one of claims 5 to 7, further comprising a dust filter upstream of the container.

A combination according to any one of claims 5 to 8, further comprising a production space, such as a spray booth, which production space is provided with a gas outlet which is in fluid communication with the gas inlet of the gas treatment device.

A combination according to claim 9, wherein the production space further comprises a gas inlet adapted to receive gas treated with the gas treatment device, which combination thereby forms an at least partially closed circuit.

A method for treating a gas contaminated with at least one contaminant, comprising the steps of: a) passing the contaminated gas through a bulk amount of cleaning agent loaded into a container; b) measuring a concentration of a contaminant in the gas passed by the amount of cleaning agent; © discharging at least a portion of the cleaning agent from the container when step b) results in a measured concentration of a contaminant above a threshold value; d) supplying fresh cleaning agent through a cleaning agent inlet to replace the at least partially discharged cleaning agent, the container rotating while performing step a).

A method according to claim 11, wherein the cleaning agent is or comprises activated carbon, and wherein the concentration of a contaminant measured in step b) by the measuring means is the concentration of volatile organic compounds (VOC) in the gas.

A method according to claim 11 or 12, wherein steps b) and c) are performed simultaneously with step a).

A method according to any one of claims 11-13, wherein step d) is performed simultaneously with step a).

A method according to any one of claims 11-14, wherein step a) is performed at room temperature.

A method according to any one of claims 11-15, further comprising the step e) of burning the discharged cleaning agent without firing with gas.

A method according to claim 16, further comprising step f) of heating a gas stream with heat from step e), which gas stream preferably comprises gas from the gas outlet of the container.

A method according to any one of claims 11-17, wherein at least part of the cleaning agent is derived from plant material, such as wood.