TECHNICAL FIELD

The invention relates to a method for treatment of a fluid and a fluid treatment device according to the appended claims.

BACKGROUND

Devices for treatment of fluid, such as salt water desalination devices are known. These known devices generate fresh water obtained by boiling saltwater. These de- vices comprise a vessel, which is intended to receive salt water and to discharge fresh water in vapour or steam condition and to discharge salt concentrate. The ves- sei includes heating elements for boiling the salt water present in the vessel and for generating the vapour or steam of fresh water.

Another known device for treatment of fluid is a water desalination device that in cludes a vessel, which is provided with heating elements. A salt layer comprising M9 ₃ (R0 ₄ ) _2*h ^» H ₂ q, is supported in an upper part of the vessel by a perforated partition wall, wherein the heating elements are disposed to heat the salt layer and are con nected to an energy source. The device further comprising a dosabie salt water sup ply pipe, a vapour discharge pipe and a dosabie discharge pipe connected to the vessel. The vessel is charged with salt water through the salt water supply pipe. The salt layer binds water and forms a crystal hydrate. Remaining salt water is collected and discharged from the vessel through the discharge pipe. The salt layer is heated by the heating elements, whereby the water of the crystal hydrate is released as va pour. The vapour is collected through the vapour discharge pipe and finally the va- pour is cooled to obtain desalinated water.

A method for treatment of fluid is also known in which the formation of crystal hy drates is used in order to purify seawater. The crystals are separated from the sus pension and are washed with water. Thereafter the crystals are molten in order to ob tain fresh water and liquid salt. A further known method for treatment of fluid is the separation of ethanol from a low- grade ethyl-alcohol solution. Ethanol, such as bio-ethanol, may be produced by bio chemical processes, such as fermentation of a mixture of water and sugars. By fer- mentation of the mixture, a mash is produced, comprising i.a. a solution, having a low concentration of ethyl-alcohol. Usually, bio-ethanol is obtained by a fermentation of a C-6 sugar/water solution having a low concentration. By extracting high-grade alco hol from the low-grade solution, a useful product is obtained, which can be used as fuel. The liquid mixture or solution from which the ethanol is extracted may be useful in different applications.

SUMMARY

Despite known solutions in the art for treatment of fluid, it is desired to develop a method for treatment of a fluid and a fluid treatment device, which produce a large volume of treated fluid in a short period of time and which require a reduced energy input. Also, it is desired to develop a method and a device for treatment of a large volume of water based liquid, such as seawater, which produce a large volume of fresh water in a short period of time and which require a reduced energy input.

An object of the invention is therefore to achieve a method for treatment of a fluid and a fluid treatment device, which produce a large volume of treated fluid in a short pe riod of time and which require a reduced energy input. Another object of the invention is to achieve a method and a device for treatment of a large volume of water based liquid, such as seawater, which produce a large volume of fresh water in a short period of time and which require a reduced energy input.

These objects are achieved with the above-mentioned method and device for treat- ment of a fluid according to the appended claims.

According to an aspect of the invention a method for treatment of a fluid in a fluid treatment device comprising at least one container for holding a fluid absorbing salt crystal substrate; a fluid supply station for bringing fluid in contact with the salt crystal substrate; and at least one heating station for releasing treated fluid from the salt crystal substrate, wherein the method comprises the steps of: conveying the at least one container with the salt crystal substrate to the fluid supply station; supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal substrate binds fluid and forms a crystal hydrate; conveying the at least one container with the salt crystal substrate to the at least one heating station; and heating the at least one container with the salt crystal substrate in the at least one heating station for releas- ing treated fluid from the salt crystal substrate. According to a further aspect of the invention a fluid treatment device, comprising at least one container for holding a fluid absorbing salt crystal substrate; a fluid supply station for bringing fluid in contact with the salt crystal substrate; and at least one heating station for releasing treated fluid from the salt crystal substrate, wherein the device further comprises: a conveying means for conveying the at least one con- tainer with the salt crystal substrate to the fluid supply station and to the at least one heating station; a fluid supplying means for supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal substrate binds fluid and forms a crystal hydrate. Such method for treatment of a fluid and a fluid treatment device produce a large vol- ume of treated fluid in a short period of time and require a reduced energy input. The method and device may treat a large volume of water based liquid for producing a large volume of fresh water in a short period of time, requiring a reduced energy in- put.

Additional objectives, advantages and novel features of the invention will be apparent to one skilled in the art from the following details, and through exercising the inven- tion. While the invention is described below, it should be apparent that the invention may not be limited to the specifically described details. One skilled in the art, having access to the teachings herein, will recognize additional applications, modifications and incorporations in other areas, which are within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Below is a description of, as examples, preferred embodiments with reference to the enclosed drawings, in which:

Fig. 1 schematically illustrates a fluid treatment device in a side view according to an embodiment, Fig. 2 schematically illustrates a fluid treatment device in a view from above accord- ing to an embodiment,

Figure 3a illustrates a flow chart of a method for treatment of a fluid according to an embodiment; and

Figure 3b illustrates a flow chart of a method for treatment of a fluid according to an embodiment.

DETAILED DESCRIPTION

The need of fluids, such as fresh water in household and industrial applications in- creases. Depending on different climate conditions the availability of fresh water may vary. The availability of water based liquid, such as seawater is however often satis- fying, but the salinity and/or unwanted substances in the seawater often make sea- water unsuitable in household and industrial applications.

Therefore a method for treatment of fluids has been developed in which a large vol- ume of treated fluid may be produced in a short period of time and which requires a reduced energy input. This method may treat a large volume of water based liquid, such as seawater for producing a large volume of fresh water in a short period of time, requiring a reduced energy input.

According to an aspect, the method for treatment of a fluid in a fluid treatment device, comprising at least one container for holding a fluid absorbing salt crystal substrate; a fluid supply station for bringing fluid in contact with the salt crystal substrate; and at least one heating station for releasing treated fluid from the salt crystal substrate, wherein the method comprises the steps of: conveying the at least one container with the salt crystal substrate to the fluid supply station; supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal substrate binds fluid and forms a crystal hydrate; conveying the at least one container with the salt crystal sub- strate to the at least one heating station; and heating the at least one container with the salt crystal substrate in the at least one heating station for releasing treated fluid from the salt crystal substrate.

The feature of conveying the at least one container with the salt crystal substrate to the fluid supply station enables and facilitates treatment of large volumes of fluids. Several containers with the salt crystal substrate may be conveyed to the fluid supply station at the same time and/or in sequence. In the fluid supply station the fluid is supplied to the salt crystal substrate, so that the salt crystal substrate binds fluid and forms a crystal hydrate. The fluid may be any water based liquid, aqueous fluid or liq uid, such as seawater, water from a lake, water from a river, water from sewage or drainage, or rainwater. The seawater may contain salt, such as aCI or any other type of salt. The seawater may contain substances, such as hazardous substances. The seawater may also contain objects, such as wood pieces and metal pieces. A large volume of fluid to be treated may be supplied to the containers with the salt crystal substrate, since several containers with the salt crystal substrate may be con- veyed to the fluid supply station. If the fluid to be treated is seawater containing salt, the salt crystal substrate in the containers absorbs the water of crystallisation, where- with pure desalinated water is bound to the salt, which therewith forms a crystal hy- drate. The remainder of the supplied saltwater delivered to the fluid supply station will have a higher salt concentration. The containers with the salt crystal substrate are thereafter conveyed to the heating station. Depending on the number of containers with salt crystal substrate more than one heating station may be needed. Alterna- tively, the heating station may be large enough to housing several containers with the salt crystal substrate. In the heating station the containers with the salt crystal sub- strate are heated, so that fluid is released from the salt crystal substrate. Heating the containers with the salt crystal substrate causes said salt crystal sub- strate to emit the fluid that the salt absorbing the water of crystallisation has earlier bound to itself to form a hydrate. The fluid restored from the hydrate is emitted in va- pour form in the heating station. If the fluid to be treated is seawater containing salt, pure or fresh water is released from the salt crystal substrate in the heating station. Heating the containers with the salt crystal substrate causes said salt crystal sub- strate to emit the pure or fresh water that the salt absorbing the water of crystallisa- tion has earlier bound to itself to form a hydrate. The water restored from the hydrate is emitted in vapour form in the heating station. A further fluid treatment process can be carried out upon completion of a preceding fluid treatment process.

Conveying the at least one container with the salt crystal substrate to the fluid supply station and to the heating station will make it possible produce a large volume of treated fluid. The fluid to be treated may already been brought to the fluid supply sta- tion before the containers with the salt crystal substrate are conveyed to the fluid supply station. In this situation the containers with the salt crystal substrate may bath in the fluid to be treated and the fluid supply station will have function similar to a bathtub. Alternatively, the fluid to be treated may enter the fluid supply station after the containers with the salt crystal substrate have been conveyed to the fluid supply station. The containers with the salt crystal substrate may in this situation be show- ered with the fluid to be treated. After the fluid has been supplied to the salt crystal substrate in the fluid supply station and the salt crystal substrate has bounded fluid and formed a crystal hydrate, the containers with the salt crystal substrate are con- veyed to the at least one heating station. When the containers with the salt crystal substrate are leaving the fluid supply station another container or a number of other containers with salt crystal substrate may be conveyed to the fluid supply station. At the same time as the first containers with the salt crystal substrate are heated in the heating station, the containers with the salt crystal substrate in the fluid supply station are supplied with fluid, so that the salt crystal substrate binds fluid and forms a crystal hydrate. In a further step, after the containers with the salt crystal substrate have been heated in the heating station, they may be conveyed to the fluid supply station at the same time as the containers with the salt crystal substrate, which have been supplied with fluid in the fluid supply station, are conveyed to the heating station. This way, a large volume of treated fluid may be produced in a short period of time. Only the crystal hydrate need to be heated after having bound pure or fresh fluid from the supplied fluid to be treated. Therefore, less heat is required to obtain the same amount of pure or fresh fluid than that required if all the fluid supplied should be heated. The substrate of salt crystals is present in the containers during the entire process of treatment of fluid. In the fluid supply station, the salt crystal substrate will still be present in the containers, even though the salt crystal substrate has bounded fluid and formed a crystal hydrate. Therefore, the salt crystal substrate can be con- sidered to be equal to the crystal hydrate. In other words, the salt crystal substrate in the containers has bounded fluid and formed a crystal hydrate, so that the containers comprise crystal hydrate after fluid has been supplied to the salt crystal substrate in the fluid supply station. Thus, after the fluid has been supplied to the salt crystal sub- strate in the fluid supply station and the salt crystal substrate has bounded fluid and formed a crystal hydrate, the containers with the crystal hydrate are conveyed to the at least one heating station. When the containers with the formed crystal hydrate are leaving the fluid supply station another container or a number of other containers with salt crystal substrate may be conveyed to the fluid supply station. At the same time as the first containers with the formed crystal hydrate are heated in the heating sta- tion, the containers with the salt crystal substrate in the fluid supply station are sup- plied with fluid, so that the salt crystal substrate binds fluid and forms a crystal hy- drate. In a further step, after the containers with the formed a crystal hydrate have been heated in the heating station, they may be conveyed to the fluid supply station at the same time as the containers with the formed a crystal hydrate, which have been supplied with fluid in the fluid supply station, are conveyed to the heating sta- tion. This way, a large volume of treated fluid may be produced in a short period of time. Only the crystal hydrate need to be heated after having bound pure or fresh fluid from the supplied fluid to be treated. Therefore, less heat is required to obtain the same amount of pure or fresh fluid than that required if all the fluid supplied should be heated. Thus, the method may comprise the steps of: conveying the at least one container with the salt crystal substrate to the fluid supply station; supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal sub- strate binds fluid and forms a crystal hydrate; conveying the at least one container with the crystal hydrate to the at least one heating station; and heating the at least one container with the crystal hydrate in the at least one heating station for releasing treated fluid from the crystal hydrate. According to an example the method comprising the further step of: collecting the re- leased fluid from the salt crystal substrate. Heating the containers with the salt crystal substrate causes said salt crystal sub- strate to emit the fluid that the salt absorbing the water of crystallisation has earlier bound to itself to form a hydrate. The fluid restored from the hydrate is emitted in va- pour form in the heating station. If the fluid to be treated is seawater, the water re- stored from the hydrate is emitted in water vapour form in the heating station. The re- leased fluid or water vapour from the salt crystal substrate or the crystal hydrate is collected and may after cooling be collected as pour or fresh fluid or water.

According to an example the method comprising the further step of: cleaning the at least one container with the salt crystal substrate after supplying the fluid to the salt crystal substrate in the fluid supply station and before heating the at least one con- tainer with the salt crystal substrate in the at least one heating station.

The fluid to be treated may contain substances, such as hazardous substances, and also objects, such as wood pieces and metal pieces. Therefore, the containers with the salt crystal substrate are cleaned after the fluid has been supplying to the salt crystal substrate in the fluid supply station. The cleaning may take place in the fluid supply station or after the containers with the salt crystal substrate or the crystal hy drate has left the fluid supply station and during the conveying of the containers with the salt crystal substrate or the crystal hydrate to the heating station. During the cleaning process any substances, such as hazardous substances, and objects, such as wood pieces and metal pieces are removed from the containers with the salt crys- tal substrate or the crystal hydrate.

According to an example, heating the at least one container with the salt crystal sub- strate in the at least one heating station for releasing treated fluid from the salt crystal substrate comprises: heating the at least one container with the salt crystal substrate in at least two steps at two different temperatures. The heating of the container with the salt crystal substrate or the crystal hydrate may be performed at a first temperature under a first predetermined period of time and at a second temperature under a second predetermined period of time. The first tem- perature may be lower than the second temperature. The first and second period of times may be equal or they may be different. The first and second temperatures and the first and second period of times may depend on the type of salt crystal substrate, the weight and volume of salt crystal substrate and the number of containers with the salt crystal substrate or the crystal hydrate that should be heated. According to an example, conveying the at least one container with the salt crystal substrate to the fluid supply station and to the at least one heating station comprises conveying the at least one container with the salt crystal substrate on a track.

Conveying the containers with the salt crystal substrate may be performed on a track, such as a railway track or a monorail. The track may also be a road, such a concrete road. The containers with the salt crystal substrate may be arranged on railway cars or on wheeled trailers. Conveying the at least one container with the salt crystal sub- strate to the fluid supply station, supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal substrate binds fluid and forms a crystal hy- drate, conveying the at least one container with the salt crystal substrate or the crys tal hydrate to the at least one heating station and heating the at least one container with the salt crystal substrate or the crystal hydrate in the at least one heating station for releasing fluid from the salt crystal substrate or the crystal hydrate may be per- formed along the track. The track may be endless and may have a shape as a circle or an oval, such as an ellipse. A number of railway cars or on wheeled trailers loaded with containers containing the salt crystal substrate may be driven on the track.

When one car or trailer has been conveyed into the fluid supply station another car or trailer may be situated at the heating station. According to an example, heating the at least one container with the salt crystal sub- strate in the at least one heating station for releasing fluid from the salt crystal sub- strate is performed by solar energy. Electrical energy transformed from solar energy generated by solar cells can be used to heat the containers with the salt crystal substrate or the crystal hydrate in the heat- ing station. Other renewable energy sources may be used, such as wind power and water power. Different types of renewable energy sources may be used in combina- tion for generating power to the heating station. The heating may also be performed in combination with conventional energy sources.

According to an example the fluid absorbing salt crystal substrate comprising

Mg3(P0 ₄ ) _2* n ^» H ₂ 0.

A suitable fluid absorbing salt crystal substrate that absorbs water and other fluids of crystallisation is one that has a dissolution index of not higher than 10 ²⁴ Above this dissolution index the need to add new crystals becomes greater. A fluid absorbing salt crystal substrate comprising Mg ₃ (P0 ₄ ) _2* n*H ₂ 0 wherein n=12-22 may be used for the method according to the present disclosure. However, it may also be possible to use a fluid absorbing salt crystal substrate comprising Mg ₃ (P0 ₄ ) _2* n*H ₂ 0 wherein n=0-22. Thus, the method may be used for expelling water from Mg ₃ (P0 ₄ ) _2* n*H ₂ 0, n= 0-22. According to an example the fluid to be treated is seawater.

The seawater may contain salt, such as NaCi or any other type of salt. The seawater may contain substances, such as hazardous substances. The seawater may also contain objects, such as wood pieces and metal pieces. However, the method ac~ cording to the present disclosure may treat the seawater in order to achieve pure wa- ter or fresh water. The pure water or fresh water may be distiiiated water with a high grade of purity.

Also a fluid treatment device has been developed in which a large volume of treated fluid may be produced in a short period of time and which fluid treatment device re- quires a reduced energy input. This fluid treatment device may treat a large volume of seawater for producing a large volume of fresh water in a short period of time, re- quiring a reduced energy input. The fluid treatment device comprising at least one container for holding a fluid ab- sorbing salt crystal substrate; a fluid supply station for bringing fluid in contact with the salt crystal substrate; and at least one heating station for releasing treated fluid from the salt crystal substrate, wherein the device further comprises: a conveying means for conveying the at least one container with the salt crystal substrate to the fluid supply station and to the at least one heating station; a fluid supplying means for supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal substrate binds fluid and forms a crystal hydrate. The container may comprise a perforated container made of steel, plastic, tissue or another suitable material that allows the fluid to be treated to enter through the perfo rated walls of the container. The container should also allow pure or fresh fluid to leave the container through the perforated walls. However, the container should be configured to hold the fluid absorbing salt crystal substrate and thus prevent the fluid absorbing salt crystal substrate to escape from the container. The device may be provided with a conveying means for conveying the at least one container with the salt crystal substrate to the fluid supply station and to the at least one heating station. The conveying means may comprise suspension means for suspending the con- tainer in a wire, such as a traverse. The conveying means may alternatively comprise a stand for arranging the container on a movable train car or on a wheeled trailer.

The fluid supply station and the heating station may be arranged on a path defined by the conveying means. The fluid supplying means for supplying fluid to the salt crystal substrate in the fluid supply station may comprise a pipe system for transport- ing the fluid to be treated from a reservoir, a sea, a lake, a river, water from sewage or drainage, or rainwater depending on the type of fluid to be treated. The pipe sys- tem may comprise a pump for generating a fluid flow in the pipe system. The pipe system may comprise a valve for regulating the fluid flow. The pipe system may corn- prise a nozzle for showering the container with the fluid absorbing salt crystal sub- strate. The pipe system may comprise a connecting pipe to the fluid supply station for filling a tank with the fluid to be treated. The tank may be provided with a discharge pipe for discharging fluid from the tank. A valve for opening and closing the discharge pipe may be arranged on the discharge pipe. The discharged fluid is collected in a vessel. The discharged fluid may be taken care of in a separate treatment plant in an environment friendly process. The heating station for releasing fluid from the salt crystal substrate may comprise a heating device for heating the container with the fluid absorbing salt crystal substrate. The heating device may be an electrical heating device which may be provided with electrical energy. The heating device may a warm air element, which may be provided with electrical energy. The warm air element may be provided with a fan, which may circulate heated air in the heating station. The heating device may be enclosed in a housing, which forms the heating station.

The container is configured to contain the substrate of salt crystals is present in the containers during the entire process of treatment of fluid. In the fluid supply station, the salt crystal substrate will still be present in the containers, even though the salt crystal substrate has bounded fluid and formed a crystal hydrate. After the fluid has been supplied to the salt crystal substrate in the fluid supply station and the salt crys- tal substrate has bounded fluid and formed a crystal hydrate, the containers with the crystal hydrate are configured to be conveyed to the at least one heating station. Thus, the fluid treatment device may comprise at least one container for holding a fluid absorbing salt crystal substrate; a fluid supply station for bringing fluid in contact with the salt crystal substrate to form a crystal hydrate; and at least one heating sta- tion for releasing treated fluid from the crystal hydrate, wherein the device further comprises: a conveying means for conveying the at least one container with the salt crystal substrate to the fluid supply station and the crystal hydrate to the at least one heating station; a fluid supplying means for supplying fluid to the salt crystal substrate in the fluid supply station, so that the salt crystal substrate binds fluid and forms a crystal hydrate. According to an example the device further comprising a collecting means for collect- ing the released fluid from the at least one heating station.

The fluid restored from the hydrate is emitted in vapour form in the heating station. If the fluid to be treated is seawater, the water restored from the hydrate is emitted in water vapour form in the heating station. The released fluid or water vapour from the salt crystal substrate is collected in a collecting mean. The collecting means may comprise a cooling means. The cooling means may comprise a heat exchanger for cooling the fluid or water vapour. The fluid or water vapour may after cooling be col- lected as pour or fresh fluid or water in a vessel or the pour or fresh fluid or water may be feeded or transported in to an external pipeline. Before the fluid or water va- pour enter the cooling means the fluid or water vapour may pass a filter in order to remove any unwanted substances in the fluid or water vapour. According to an example the device further comprising a cleaning means for cleaning the at least one container with the salt crystal substrate.

The cleaning means may comprise a vapour pipe system comprising a collector for vapour, a valve for regulating the vapour flow and a nozzle for showering the con- tainer with the fluid absorbing salt crystal substrate. Vapour may be collected from the collecting means of the heating station.

According to an example the heating station comprises a heating device for heating the at least one container with the salt crystal substrate in at least two steps at two different temperatures.

The heating device for heating the at least one container with the salt crystal sub- strate may be at least one heating element. A first set of heating elements may be configured for heating the at least one container with the salt crystal substrate at a first temperature. A second set of heating elements may be configured for heating the at least one container with the salt crystal substrate at a second temperature. Further sets of heating elements may be configured for heating the at least one con- tainer with the salt crystal substrate at other temperatures. The heating device may be an electrical heating device which may be provided with electrical energy. Thus the heating device may be an electrical heating element. The electrical heating ele- ment may be a warm air element. The warm air element may be provided with a fan, which may circulate heated air in the heating station. The sets of heating elements may be enclosed in different housings, which form the heating station. In a first hous- ing the first set of heating elements may be configured for heating the at least one container with the salt crystal substrate at a first temperature. In a second housing second set of heating elements may be configured for heating the at least one con- tainer with the salt crystal substrate at a second temperature. Further housings may be arranged with further sets of heating elements may be configured for heating the at least one container with the salt crystal substrate at other temperatures. The heat- ing station may comprise a heating device for heating the at least one container with the crystal hydrate in at least two steps at two different temperatures. According to an example the conveying means comprises a track for conveying the at least one container to the fluid supply station and to the at least one heating sta- tion.

The track may be a railway track or a monorail. The track may also be a road, such a concrete road. The containers with the salt crystal substrate may be arranged on rail- way cars or on wheeled trailers, which are configured to be driven on the track. The track may be endless and may have a shape as a circle or an oval, such as an el- lipse. A number of railway cars or on wheeled trailers loaded with containers contain- ing the salt crystal substrate may be configured to be driven on the track. The track may be configured to pass through the fluid supply station, the cleaning station, the heating station and any other possible station, such as a service station for the rail- way cars or the wheeled trailers, or a station for loading containers containing the salt crystal substrate on the railway cars or on the wheeled trailers. When one car or trailer has been conveyed into one of the stations, another car or trailer may be situ- ated in another station.

According to an example the device comprises a solar energy generator for generat- ing heat in the at least one heating station. The solar energy generator for generating heat in the at least one heating station may be a solar panel or a set of solar panels comprising solar cells. The solar cells may produce electrical energy, which is transmitted to the heating device in the heat- ing station. The present disclosure will now be further illustrated with reference to the appended figures.

Fig. 1 schematically illustrates a fluid treatment device in a side view according to an embodiment. The fluid treatment device 1 according to the embodiment comprising a container 2 for holding a fluid absorbing salt crystal substrate 4. A fluid supply station 6 is config- ured for bringing fluid 8 in contact with the salt crystal substrate 4. A heating station 10 is configured for releasing treated fluid 12 from the salt crystal substrate 4. A con- veying means 14 is configured for conveying the container 2 with the salt crystal sub- strate 4 to the fluid supply station 6 and to the at least one heating station 10. Ac- cording to the embodiment the conveying means 14 may be a traverse. A fluid sup- plying means 16 is configured for supplying the fluid 8 to the salt crystal substrate 4 in the fluid supply station 6.

The fluid supplying means 16 for supplying fluid 8 to the salt crystal substrate 4 in the fluid supply station 6 may comprise a pipe system 18 for transporting the fluid 8 to be treated from a reservoir 20, a sea, a lake, a river, water from sewage or drainage, or rainwater depending on the type of fluid 8 to be treated. The pipe system 18 may comprise a pump 22 for generating a fluid flow in the pipe system 18. The pipe sys- tem 18 may comprise a valves 24 for regulating the fluid flow. The pipe system 18 may comprise a nozzle 26 for showering the container 2 with the fluid absorbing salt crystal substrate 4, so that the fluid absorbing salt crystal substrate 4 forms a crystal hydrate. The pipe system 18 may comprise a connecting pipe 28 to the fluid supply station 6 for filling a tank 30 of the fluid supply station 6 with the fluid 8 to be treated. The tank 30 may be provided with a discharge pipe 32 for discharging fluid 36 from the tank 30. A discharging valve 34 for opening and closing the discharge pipe 32 may be arranged on the discharge pipe 32. The discharged fluid 36 is collected in a discharging fluid vessel 38.

The heating station 10 for releasing treated fluid 12 from the salt crystal substrate 4 may comprise a heating device 40 for heating the container 2 with the fluid absorbing salt crystal substrate 4 or the crystal hydrate. The heating device 40 may comprise a warm air element 42, which may be provided with electrical energy. The warm air el- ement 42 may be provided with a fan 44, which may circulate heated air in the heat- ing station 10. The heating device 40 may be enclosed in a housing 46, which forms the heating station 10. A collecting means 48 is configured for collecting the released, treated fluid 12 from the heating station 10. The collecting means 48 may comprise a cooling means 50. The cooling means 50 may comprise a heat exchanger 52 for cooling the treated fluid 8 from vapour form to liquid form. The collecting means 48 may comprise a filter 54 in order to remove any unwanted substances in the treated fluid 8.

A cleaning means 56 may be configured for cleaning the container 2 with the salt crystal substrate 4. The cleaning means 56 may comprise a vapour pipe system 58 comprising a vapour collector 60, a vapour valve 62 for regulating the vapour flow and a vapour nozzle 64 for showering the container 2 and the fluid absorbing salt crystal substrate 4 with vapour. The vapour pipe system 58 may be connected to the collecting means 48 of the heating station 10.

A solar energy generator 66 may be configured for generating heat in the heating station 10. The solar energy generator 66 may be a solar panel 68 or a set of solar panels 68 comprising solar cells 70. The solar cells 70 may produce electrical en- ergy, which is transmitted to the heating device 40 in the heating station 10.

Fig. 2 schematically illustrates a fluid treatment device 1 in a view from above ac- cording to an embodiment. According to this embodiment the conveying means 14 comprises a track 14a for conveying a number of containers 2 to the fluid supply sta- tion 6, a cleaning station 72, to a number of heating stations 10A, 10B, 10C and to a service station 74. The track 14a may be a railway track, a monorail or a road. The containers 2 with the salt crystal substrate 4 may be arranged on railway cars 76 or on wheeled trailers, which are configured to be driven on the track 14a. The track 14a is endless and has a shape of a circle. The track 14a is configured to pass through the fluid supply sta- tion 6, the cleaning station 72, the heating stations 10A, 10B, 10C and the service station 74. When one car 76 or trailer has been conveyed into one of the stations 6, 72, 10A-10C, 74, another car or trailer may be situated in another station. The cars 76 or trailers may be coupled in pairs. More than two cars 76 or trailers may be cou- pled to each other. Each car 76 or trailer may be provided with a propulsion unit (not shown) or the track 14a may be provided with the propulsion unit for propulsion of the cars 76 or trailers.

The fluid supply station 6 comprises the fluid supplying means 16 for supplying fluid 8 to the salt crystal substrate 4 in the fluid supply station 6. The pipe system 18 is con- figured to transporting the fluid 8 to be treated from the reservoir 20, a sea, a lake, a river, water from sewage or drainage, or rainwater depending on the type of fluid 8 to be treated. The pipe system 18 may comprise the pump 22 for generating a fluid flow in the pipe system 18. The pipe system 18 may comprise the valves 24 for regulating the fluid flow. The pipe system 18 may comprise the nozzle 26 for showering the con- tainer 2 with the fluid absorbing salt crystal substrate 4. The pipe system 18 may comprise the connecting pipe 28 to the fluid supply station 6 for filling the cars 76 with the fluid 8 to be treated. The fluid supply station may be provided with a dis- charge pipe 32 for discharging fluid 36 from the fluid supply station 6. A discharging valve 34 for opening and closing the discharge pipe 32 may be arranged on the dis- charge pipe 32. The discharged fluid 36 is collected in a discharging fluid vessel 38.

The heating stations 10A, 10B, 10C for releasing treated fluid 12 from the salt crystal substrate 4 or the crystal hydrate may comprise heating device 40 for heating the containers 2 with the fluid absorbing salt crystal substrate 4. The heating device 40 may comprise a warm air elements 42, which may be provided with electrical energy. The warm air element 42 in each heating station 10A, 10B, 10C may be provided with a fan 44, which may circulate heated air in the respective heating stations 10A, 10B, 10C. Each heating device 40 may be enclosed in a housing 46, which forms each heating station 10A, 10B, 10C.

In the first heating station 10A the warm air element 42 may be configured for heating the containers 2 with the salt crystal substrate 4 at a first temperature. In the second heating station 10B the warm air element 42 may be configured for heating the con- tainers 2 with the salt crystal substrate 4 at a second temperature. In the third heating station 10C the warm air element 42 may be configured for heating the containers 10 with the salt crystal substrate 4 at a third temperature. The first, second and third temperatures may be adapted to the type of the salt crystal substrate 4 used in the process. A collecting means 48 is configured for collecting the released, treated fluid 12 from the heating stations 10A, 10B, 10C. The collecting means 48 may comprise a cooling means 50. The cooling means 50 may comprise a heat exchanger 52 for cooling the treated fluid 8 from vapour form to liquid form. The collecting means 48 may corn- prise filters 54 in order to remove any unwanted substances in the treated fluid 8.

The cleaning station comprises a cleaning means 56, which is configured for clean- ing the containers 2 with the salt crystal substrate 4. The cleaning means 56 may comprise a vapour pipe system 58 comprising a vapour collector 60, a vapour valve 62 for regulating the vapour flow and a vapour nozzle 64 for showering the contain- ers 2 and the fluid absorbing salt crystal substrate 4 with vapour. The vapour pipe system 58 may be connected to the collecting means 48 of the heating station 10. A solar energy generator 66 may be configured for generating heat in the heating station 10. The solar energy generator 66 may be a solar panel 68 or a set of solar panels 68 comprising solar cells 70. The solar cells 70 may produce electrical en- ergy, which is transmitted to the heating device 40 in the heating stations 10A, 10B, 10C.

Fig. 3a illustrates a flow chart of a method for treatment of a fluid 8 according to an embodiment. The method thus relates to the fluid treatment devices 1 disclosed in figures 1 and 2. The fluid treatment device 1 , comprising at least one container 2 for holding a fluid absorbing salt crystal substrate 4, a fluid supply station 6 for bringing fluid 8 in contact with the salt crystal substrate 4, and at least one heating station 10, 10A, 10B, 10C for releasing treated fluid 12 from the salt crystal substrate 4. The method comprises the steps of: conveying s101 the at least one container 2 with the salt crystal substrate 4 to the fluid supply station 6; supplying s102 fluid 8 to the salt crystal substrate 4 in the fluid supply station 6, so that the salt crystal substrate 4 binds fluid and forms a crystal hydrate; conveying s103 the at least one container 2 with the salt crystal substrate 4 to the at least one heating station 10, 10A, 10B, 10C; and heating s104 the at least one container 2 with the salt crystal substrate 4 in the at least one heating station 10, 10A, 10B, 10C for releasing treated fluid 12 from the salt crystal substrate 4. According to an aspect the heating s104 the at least one container 2 with the salt crystal substrate 4 in the at least one heating station 10, 10A, 10B, 10C for releasing treated 12 fluid from the salt crystal substrate 4 comprises: heating s104 the at least one container 2 with the salt crystal substrate 4 in at least two steps at two different temperatures. According to a further aspect conveying s101 , s103 the at least one container 2 with the salt crystal substrate 4 to the fluid supply station 6 and to the at least one heating station 10, 10A, 10B, 10C comprises conveying s101 , s103 the at least one container 2 with the salt crystal substrate 4 on a track 14a. According to a further aspect heating s104 the at least one container 2 with the salt crystal substrate 4 in the at least one heating station 10, 10A, 10B, 10C for releasing treated fluid 12 from the salt crystal substrate 4 is performed by solar energy. According to a further aspect the fluid absorbing salt crystal substrate 4 comprising MgsiPG^n'hhO. Ac- cording to a further aspect the fluid 8 may be seawater.

Fig. 3b illustrates a flow chart for a method for treatment of a fluid 8 according to an embodiment. The method thus relates to the fluid treatment devices 1 disclosed in figures 1 and 2. The fluid treatment device 1 , comprising at least one container 2 for holding a fluid absorbing salt crystal substrate 4, a fluid supply station 6 for bringing fluid 8 in contact with the salt crystal substrate 4, and at least one heating station 10, 10A, 10B, 10C for releasing treated fluid 12 from the salt crystal substrate 4. The method comprises the steps of: conveying s101 the at least one container 2 with the salt crystal substrate 4 to the fluid supply station 6; supplying s102 fluid 8 to the salt crystal substrate 4 in the fluid supply station 6, so that the salt crystal substrate 4 binds fluid 8 and forms a crystal hydrate; conveying s103 the at least one container with the salt crystal substrate 4 to the at least one heating station 10, 10A, 10B, 10C; heating s104 the at least one container 2 with the salt crystal substrate 4 in the at least one heating station 10, 10A, 10B, 10C for releasing treated fluid 12 from the salt crystal substrate 4; collecting s105 the released and treated fluid 12 from the salt crystal substrate 4; and cleaning s106 the at least one container 2 with the salt crys- tal substrate 4 after supplying s102 the fluid to the salt crystal substrate 4 in the fluid supply station 6 and before heating s104 the at least one container 2 with the salt crystal substrate 4 in the at least one heating station 10, 10A, 10B, 10C. In view of the method steps s101 and s102, it is evident that the salt crystal substrate mentioned in the method steps s103 and s104 is the same salt crystal substrate 4 that has bounded fluid and has been formed to a crystal hydrate in the method step s102. Therefore, it must be clear that the salt crystal substrate will appear in the at least one container through all method steps s101 - s104. In the method step s102 the salt crystal substrate binds fluid and forms a crystal hydrate. Thus, it is evident and clear that the salt crystal substrate is hydrated in and after step s102. The sub- strate 4 of salt crystals is present in the containers 2 during the entire process of treatment of fluid 8. In the fluid supply station 6 and after the containers 2 has left the fluid supply station 6, the salt crystal substrate 4 will still be present in the containers 2, even though the salt crystal substrate 4 has bounded fluid 8 and formed a crystal hydrate. Thus, according to an aspect, the method comprises the steps of: conveying s101 the at least one container 2 with the salt crystal substrate 4 to the fluid supply station 6; supplying s102 fluid 8 to the salt crystal substrate 4 in the fluid supply sta- tion 6, so that the salt crystal substrate 4 binds fluid and forms a crystal hydrate; con- veying s103 the at least one container 2 with the crystal hydrate to the at least one heating station 10, 10A, 10B, 10C; and heating s104 the at least one container 2 with the crystal hydrate in the at least one heating station 10, 10A, 10B, 10C for releasing treated fluid 12 from the crystal hydrate.

The foregoing description of the embodiments has been furnished for illustrative and descriptive purposes. It is not intended to be exhaustive, or to limit the embodiments to the variants described. Many modifications and variations will obviously be appar- ent to one skilled in the art. The embodiments have been chosen and described in order to best explicate principles and practical applications, and to thereby enable one skilled in the art to understand the embodiments in terms of its various embodi- ments and with the various modifications that are applicable to its intended use. The components and features specified above may, within the framework of the embodi- ments, be combined between different embodiments specified.