EP2536977B1

EP2536977B1 - Use of a catalytic heater for drying and/or curing

Info

Publication number: EP2536977B1
Application number: EP11709317.9A
Authority: EP
Inventors: Knud Jørgen RASMUSSEN; Knut Thorbjørn Næss RASMUSSEN
Original assignee: Netek Ir System AS
Current assignee: Netek Ir System AS
Priority date: 2010-02-16
Filing date: 2011-02-16
Publication date: 2015-04-08
Anticipated expiration: 2031-02-16
Also published as: DK2536977T3; DK201000130A; WO2011100970A3; WO2011100970A2; EP2536977A2; DK177389B1

Description

Technical field of the invention

The present invention relates to the use of a heater for drying and/or curing a coating of a coated, inner surface of a tank.

Background of the invention

When exploiting the energy resources of the underground on offshore oil production facilities, the material which is brought to the surface is a mixture of crude oil, gas, sea water, mud, sand and gravel. In order to be able to fractionate the crude oil of this mixture into the various typically fractions, the crude oil must first be separated from the solid and the aqueous phases into a hydrocarbon fraction.
This separation of the crude oil from the solid and the aqueous phases takes place in large separation tanks located on the oil production facility. For economical reasons, these separation tanks are typically made of steel. Normally an oil production facility comprises many separation tanks in order to cope with the huge amount of material that has to be separated.
Due to the harsh and corrosive environment at sea it is necessary to coat these steel tanks with an interior and exterior coating in order to avoid corrosive disintegration of the tanks. Accordingly, the tanks are usually coated on the inside and on the outside with an epoxy coating.
Despite being coated on the inside, the presence of moving mud, sand and gravel in the interior of the tank has the consequence that the inside coating of the tanks will be subject to abrasive actions which eventually will lead to exposure of the bare metal underneath. When the bare metal of the tank is exposed, the corrosive action will set in immediately. Accordingly, from time to time it will be necessary to recoat the interior of a tank. The frequency of the necessity to recoat the interior of a tank is usually once every fourth year.
GB503027 discloses a method of lining vats and tanks with a resin which can be hardened by heat treatment, where the interior may be heated by electric heaters suspended from the roof of the tank.
The full process of dismantling the piping, sandblasting the interior of the tank, cleaning the interior and application of a new internal coating and allowing this coating to cure may have a duration of seven or eight days. Although the curing process presently takes place with the aid of electrical heating, the duration of the present curing process alone may amount to six to seven days.
Although an oil production facility comprises several separation tanks, the shut-off of one separation tank for a whole week leads to a decreased production rate for this week. For a mid-size type of oil production facility having 3 - 4 separation tanks, the shut off of one separation tank for one day may impose a reduced production of up to 50,000 barrels of crude oil. With a price of crude oil of US$ 60 per barrel, this reduced production corresponds to a reduced turnover of US$ 21,000,000 in respect of one recoating process lasting seven days. Hence, the necessity of shutting off one separation tank for seven days represents a problem for the oil company due to the huge loss in income.
One solution to this problem could be to supply the oil production facility with larger or a greater number of separation tanks. However, this is not a feasible solution due to the fact the amount of available space for such extra tanks on an oil production facility is highly limited.
In order to avoid the reduced production rate due to maintenance of the oil tanks, another solution is needed.
Accordingly, there is a need for a solution which provides the consequence that the overall amount of reduced production rate of the oil production facility due to maintenance of a single separation tank, is diminished. In this respect, the term "overall amount of reduced production rate" shall include the shut off time necessary when that single separation tank is shut off as well as the frequency with which that single separation tank needs to be shut off due to maintenance work.

Brief description of the invention

This need is met with the various aspects according to the present invention.
A heater for generating heat by catalytic oxidation of gaseous hydrocarbon may comprise:

an arrangement 2 of one or more panels 4;
wherein one or more of said panels each comprising:
- an enclosure 6 comprising a heat radiating front surface 8, and a back surface 10;
- a catalyst pad 12, said catalyst pad comprising a catalyst capable of catalytically oxidising a hydrocarbon exothermically;
- a heat insulating material 16 arranged between said catalyst pad and said back surface;
- means 18 for supplying and distributing gas to said panel;
- wherein two points (P1,P2) exist on said one or more heat radiating front surfaces 8 of said one or more panels of said heater; said points (P1,P2) defines initial points of two normal vectors (v1,v2) respectively of said surfaces, wherein the mutual angle, α between said two normal vectors (v1,v2) lies within the range of 70 -180°.

A heating system 200 may comprise one or more of the heaters 100 according to the above description, wherein said one or more heaters being mounted on an axle 22; said heating system furthermore comprising suspension means 42 for suspending said one or more heaters via suspension of said axles; said suspension means furthermore comprises attaching means 44 attaching said axle to said suspension means.
The present invention relates according to claim 1 to a use of a heater for drying and/or curing a coating of a coated surface 78 of a structure.
The different aspects of the invention according to the present application have surprisingly shown to provide substantial reductions in the maintenance time necessary under which a separation tank is put out of service for recoating the interior. Furthermore, the different aspects of the invention according to the present application provide for substantially increased strengths of the applied coatings of the interior of a separation tank for use on an oil production facility.
The use of the heater according to the present invention provides for considerably reduced shut off periods in the situation wherein a separation tank on an oil production facility has to be taken out of service due to maintenance work in the form of recoating the interior of such a separation tank.
Whereas the prior art electrical heaters to a great extent provides for an indirect heating in that they heat the air present in the interior of a tank and subsequently, that air by diffusion heats the walls of the tank, it has surprisingly been found that the heater according to the first aspect and the heating system according to the second aspect provides for a much more profound direct heating of the coating of the walls of the tank without much heating of the air inside the tank.
In fact it is possible for a person to move around inside the tank in the initial stage of the use according to the present invention without being burned or without experiencing any unpleasant heat, although the heater provides for a heating effect resulting in the coating of the walls of the tank being heated to a temperature of above 100 °C.
It is believed that this direct heating process according to the present invention will provide for a situation in which the applied coating to be cured will be cured homogenously in the sense that the interior of the coating cures approximately at the same speed as the outer parts of the coating.
Hence the use and the process according to the present invention provides for a complete curing during the time at which heat is provided by the heating system, i.e. during a time span of only a couple of hours. This is in deep contrast to the electrical heating systems according to the prior art in which no complete curing can be accomplished during the time (up to 24 hours) at which heat is provided electrically. In the prior art process, it has been found that a not insignificant degree of curing takes place after the heating process has been terminated. A part of this curing process thus takes part after the tank has been brought into service once again. As the coating at this point in time is not fully cured, it is inevitably that the coating exhibits some undesirable soft characteristics, which in turn leads to faster abrasion of that partly cured coating.

Brief description of the figures

Fig. 1a is a cross-sectional plan view of an arrangement of three panels of a heater used according to a first aspect of the present invention. The three panels are arranged in an arrangement corresponding to a three-sided geometrical prism.
Fig 1b is a perspective view of the heater of fig. 1a.
Fig. 2a is a cross-sectional plan view of an arrangement of four panels of a heater used according to a first aspect of the present invention. The four panels are arranged in an arrangement corresponding to a four-sided geometrical prism.
Fig 2b is a perspective view of the heater of fig. 2a.
Fig. 3a is a cross-sectional plan view of an arrangement of five panels of a heater used according to a first aspect of the present invention. The five panels are arranged in an arrangement corresponding to a five-sided geometrical prism.
Fig 3b is a perspective view of the heater of fig. 3a.
Fig. 4a is a cross-sectional plan view of an arrangement of six panels of a heater used according to a first aspect of the present invention. The six panels are arranged in an arrangement corresponding to a six-sided geometrical prism.
Fig 4b is a perspective view of the heater of fig. 4a.
Fig. 5a is a cross-sectional plan view of an arrangement of seven panels of a heater used according to a first aspect of the present invention. The seven panels are arranged in an arrangement corresponding to a seven-sided geometrical prism.
Fig 5b is a perspective view of the heater of fig. 5a.
Fig. 6a is a cross-sectional plan view of an arrangement of seven panels of a heater used according to a first aspect of the present invention. The seven panels are arranged in an arrangement corresponding to a seven-sided geometrical prism.
Fig 6b is a perspective view of the heater of fig. 6a.
Fig. 7a is a cross-sectional plan view of an arrangement of a panel of a heater , which doesnot form part of the present invention having a cylindrical shape.
Fig 7b is a perspective view of the heater of fig. 7a.
Fig. 8 is a perspective view of a panel making up the heater used according to a first aspect of the present invention and showing various parts of that panel.
Fig. 9 is a perspective view of one embodiment of a heating system according to a first aspect comprising a heater and two beams.
Fig 10 is a perspective view showing an embodiment corresponding to the one of fig. 9 arranged within a tank.
Fig. 11 is a perspective view of another embodiment of heating systems according to a first aspect arranged within a tank and comprising one pivot joint and a girder.
Fig. 12 is a perspective view of another embodiment of heating systems according to a first aspect comprising arranged within a tank and comprising two pivot joints and a girder.
Fig. 13 is a depiction of simplified geometrical shapes corresponding to various configurations of arrangements of one or more panels making up a heater according to the present invention. Fig. 13 shows that three points (P1,P2,P3) being initial points of normal vectors (v1,v2,v3) exist on the sides of such geometrical shapes in such a way that the mutual angle α, between any two of these three vectors (v1,v2,v3) lies within the range of 70 -180°.
Fig. 14 is a plan view of another embodiment of a heating system according to a first aspect and comprising two pivot joints and a girder, wherein each girder is suspended in a hoist mechanism.
Fig. 15 is a plan view of the embodiment of the heating systems according to fig. 14 and arranged within a tank.
Fig. 16 is a perspective view illustrating a process of arranging a heating system within a tank by use of a wheeled cart.
Fig. 17 is a perspective view illustrating a wheeled cart useful for moving a heater in the process of arranging a heating system within a tank.

Detailed description

The present invention relates in a first aspect to the use of a heater 100 for generating heat by catalytic oxidation of gaseous hydrocarbon; said heater comprising:

an arrangement 2 of one or more panels 4;
wherein one or more of said panels each comprising:
- an enclosure 6 comprising a heat radiating front surface 8, and a back surface 10;
- a catalyst pad 12, said catalyst pad comprising a catalyst 14 capable of catalytically oxidising a hydrocarbon exothermically;
- a heat insulating material 16 arranged between said catalyst pad and said back surface;
- means 18 for supplying and distributing gas to said panel.

The heater according to the first aspect is characterised in that two points (P1,P2) exist on said one or more heat radiating front surfaces 8 of said one or more panels of said heater; said points (P1,P2) defines initial points of two normal vectors (v1,v2) respectively of said surfaces, wherein the mutual angle, α between said two normal vectors (v1,v2) lies within the range of 70 -180°.
Accordingly, the first aspect relates to a heater. The heater is useful for drying and curing purposes which requires that IR radiation is radiated in a wide range of different spatial directions.
As set out above the heater of the first aspect comprise one or more panels. The heater comprises an arrangement of panels which provides for radiation of IR electromagnetic radiation in a wide range of different spatial directions. This result may be provided by the arrangement comprising one panel, such as a one panel having a cylindrical surface. Alternatively, the heater comprises more than one panel, such as three or more panels having surfaces corresponding to a geometrical prism.
Fig. 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a and 7b show arrangements 2 of different configurations of the panels 4 making up the heater according to a first aspect.
Each panel of the heater comprises an enclosure 6 comprising a heat radiating front surface 8, and a back surface 10. The enclosure may comprise a metal box wherein a substantial part of one side is lacking. The enclosure thereby comprises a front surface and a back surface. Typically, the front surface and the back surface of the panel are arranged opposite to each other. The heat radiating front surface is that surface of the heater from which the substantial part of IR radiation emits, hence the term "heat radiating front surface".
By the term "the surface from which a substantial part of IR radiation emits" shall be interpreted to be that surface of the panel from which 50% or more of the total intensity of IR radiation emitted from said panel emits. Preferably the term "the surface from which a substantial part of IR radiation emits" shall be interpreted to mean that surface of the panel from which 55% or more, such as 60% or more, e.g. 65% or more, for example 70% or more, such as 75% or more, e.g. 80% or more, for example 85% or more, or 90% or more, such as 95% or more of the total intensity of IR radiation emitted from said panel, emits.
The IR radiation provided by the heater originates from a catalytically oxidation of a gaseous hydrocarbon taking place. Accordingly, to effect this process the panel comprises a catalyst pad 12. The catalyst pad comprising a catalyst capable of catalytically oxidising said hydrocarbon exothermically. The catalyst pad preferably comprises a heat resistant material of thin, long-fibres which has been impregnated with a catalyst. A heat resistant material made of mineral wool and having long fibres may prove to be a suitable material for the catalyst pad.
The catalyst pad preferably defines a surface which is arranged in a metal box (making up the enclosure of the panel) wherein a substantial part of one side is lacking in such a way that the lacking part of the one side of the metal box exposes the catalyst pad.
When a hydrocarbon gas molecule, such as a propane or methane molecule comes into contact with the surface of the catalyst, a chemical reaction will take place. This chemical reaction will split the hydrocarbon molecule into carbon dioxide and water. During this reaction, heat will be generated and this heat will thus be radiated from the heat radiating surface of the panel of the heater. Such catalytically reactions of gaseous hydrocarbons are known per se.
In order to prevent that or in order to reduce the amount of heat in the form of IR electromagnetic radiation emitting from other surfaces of the panel than the heat radiating front surface, the panel comprises a heat insulating material 16 arranged between said catalyst pad and said back surface.
In one embodiment of the first aspect, the heat insulating material 16 may be replaced by a reflecting surface provided on the inside of the enclosure of the panel. Such a reflecting surface may provide reflection of the electromagnetic IR radiation emitted on the surface of the catalyst in such a way that the electromagnetic IR radiation directed towards the inside of the enclosure eventually will be reflected so as to emit from the inside of the enclosure in a direction passing the heat radiating front surface, thereby reducing the heat dissipated in the material of the enclosure and thereby increasing the intensity of electromagnetic IR radiation emitted through the heat radiating front surface.
In another embodiment such a reflecting surface provided on the inside of the enclosure of the panel may be combined with a heat insulating material 16.
The panel of the heater comprises means for supplying and distributing gas to said panel. Accordingly a hydrocarbon gas can be supplied to a panel of the heater of the first aspect and that gas can be distributed inside said panel with the view to present on the heat radiating surface where it will come into contact with the catalyst.
Fig. 8 shows a panel 4 for use in the heater 200 according to the first aspect. The panel comprises an enclosure 6 having a back surface 10 and a heat radiating front surface 8. The enclosure comprising a catalyst pad 12 impregnated with a catalyst, a heat insulation material 16 and tubing 18 for supplying and distributing a gaseous hydrocarbon within the catalyst pad.
In order for the heater according to the first aspect to be able to emit IR radiation in a wide range of different spatial directions, the heater comprises the technical feature that:

two points (P1,P2) exist on said one or more heat radiating front surfaces 8 of said one or more panels of said heater; said points (P1,P2) defines initial points of two normal vectors (v1,v2) respectively of said surfaces, wherein the mutual angle, α between said two normal vectors (v1,v2) lies within the range of 70 - 180°.

This means that the heater according to the first aspect is capable of radiating heat in the form of IR radiation in at least two different direction, viz. the direction of vector v1 and the direction of vector v2 respectively, wherein the mutual angle between these two directions lies within the range of 70 - 180°. In practice though, the heat in the form of the IR radiation will radiate in a more dispersed manner because the IR radiation typically will spread out in an emission angle of approximately 21° on each side of the normal vector (v1 or v2) of the heat emitting surface. At angles greater than approximately 21° on each side of the normal vector (v1 or v2) of the heat emitting surface, it has been found that the IR radiation is emitted in a more diffuse manner.
The heater according to the first aspect is very well suited for curing newly applied coatings, such as epoxy coatings inside a tank, e.g. a separation tank for an oil production facility because it provides for faster curing of the coating as well as improved tensile strength and thus improved quality of the applied coating.
In a preferred embodiment, the heater according to the first aspect comprises the feature that three points (P1,P2,P3) exist on said one or more heat radiating front surfaces 8 of said one or more panels of said heater; said points (P1,P2,P3) defines initial points of three normal vectors (v1,v2,v3) respectively of said heat radiating front surfaces, wherein the mutual angle, α between any two of said three normal vectors (v1,v2,v3) lies within the range of 70 -180°.
Fig. 13 shows that three points (P1,P2,P3) being initial points of normal vectors (v1,v2,v3) exist on the sides of such geometrical shapes in such a way that the mutual angle α, between any two of these three vectors (v1,v2,v3) lies within the range of 70 -180°.
Examples of arrangements of panels having this configuration are shown in Fig. 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a and 7b.
This embodiment has the advantage that the radiating heat in the form of IR radiation will be radiated in at least three different directions, viz. the direction of vector v1, the direction of vector v2, and the direction of vector v3 respectively. In this way the heat in the form of IR radiation can be radiated in directions spanning a range of at least 140° (70° + 70°). Such an embodiment will provide for even better curing when the heater is used for curing a coating of the interior of a tank because the spatial distribution of radiating IR electromagnetic waves are spread even more.
In a preferred embodiment of the invention, the mutual angle, α between the two vectors (v1,v2) or between any two of the three vectors (v1,v2,v3) of the heat radiating surfaces of the heater according to the first aspect lies within the range of 70 - 175°, such as 75 - 170°, for example 80 - 165°, such as 85 - 160°, e.g. 90 - 155°, such as 95 - 150°, for example 100 - 145°, such as 105 - 140°, such as 110 - 135°, such as 115 - 130°, for example 120 - 125°. Each of these limited ranges represents preferred embodiments of the heater.
It is preferred that the mutual angle, α between the two vectors (v1,v2) or between any two of the three vectors (v1,v2,v3) of the heat radiating surfaces of the heater according to the first aspect of the present invention lies within the range of 70 - 160°. Examples of arrangements of panels having this configuration are shown in Fig. 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a and 7b.
In another embodiment, the arrangement 2 of the panels of the heater according to the first aspect, the panels 4 may be arranged around a central axis 20. Examples of arrangements of panels having this configuration are shown in Fig. 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a and 7b.
This is preferred because this embodiment will provide for the possibility of having an even spatial emission of IR radiation emitted from the heat emitting surfaces of the panels of the heater.
The heater may comprise an axle. Such an embodiment provides for the possibility to have the heater making rotational movements, thereby improving the evenness of the spatial distribution of the IR radiation.
The axle may essentially coincide with a central axis 20 of said heater.
The panels 4 of the heater are arranged in an arrangement 2 essentially corresponding to the sides of a geometrical prism. This embodiment provides for an even spatial distribution of the radiated electromagnetic IR waves.
In a preferred embodiment of this embodiment of the heater according to the present invention, the geometrical prism is a polygonal prism having n sides, wherein n is 3 or more, such as 3, 4, 5, 6, 7 or 8. Such embodiments provides for a simple and yet effective heater. Examples of arrangements of panels having this configuration are shown in Fig. 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a and 6b.
In a preferred embodiment of the present invention, the catalyst 14 comprises or consists of a metal selected from the group comprising: platinum, palladium and rhodium, vanadium and iridium.
Such metal/alloys have shown to be capable of efficiently catalytically oxidising a gaseous hydrocarbon in the desired way.
In a preferred embodiment of the invention, one or more of said panels 4 are provided with preheating means, such as electrical preheating means, in order to facilitate initiation of the catalytically oxidation of the hydrocarbon by virtue of activation of the catalyst.
It is preferred that said preheating means are capable of heating the catalyst pad to a temperature of approximately 110 °C in case the hydrocarbon gas is propane and of approximately 160 °C in case the hydrocarbon gas is natural gas or methane.
For safety reasons it is preferred that the heater according to the first aspect of the present invention itself or one or more of said panels 4 making up the heater is provided with safety shut off gas valve(s). Such a valve enables shutting off the supply of gas to the panel or the heater in case of e.g. a malfunction which may otherwise result in overheating of the panel(s).
In an embodiment of the invention, one or more of the heat radiating front surfaces 8 of the heater are planer or having a curved geometrical shape, e.g. a shape corresponding to part of a cylinder surface. An example of such an embodiment is shown in fig. 7a and 7b.
A planer heat radiating front surface of the panel provides for easier and less expensive manufacturing costs. However, if the heat radiating front surfaces are curved, still more increased dispersion angels of the emitted electromagnetic IR waves can be obtained.
In a preferred embodiment of the present invention, the means for supplying gas 18 comprises tubing and/or manifolds of the heater. The tubing and/or manifolds provide for delivery of the gaseous hydrocarbon.
In a preferred embodiment of the present invention, the means for distributing gas 18 comprises tubing and/or one or more perforated distribution plates arranged in the heater. Fig. 8 shows such a panel comprising tubing.
Such an embodiment provides for very good distribution of the gaseous hydrocarbon in the catalyst mat.
The distribution plate may comprise a plate-like structure having an inlet for supply of gaseous hydrocarbon. Furthermore the distribution plate is perforated with a number of tiny holes which allows the gas to be distributed into the catalyst mat, whereafter it will flow to the heat radiating surface of the panel. On its way to the heat radiating surface of the panel or on said heat radiating surface the gas will meet a catalyst material, such as platinum, onto which it will be broken down to carbon dioxide and water under the evolution of heat. It is preferred that also the tubing supplying gas to said distribution plate; or taking the place of a distribution plate is provided with perforation holes for better distribution of the gas.
In an embodiment of the invention, one or more of said one or more heaters further comprising ventilation means for supplying air from the surroundings into the enclosure of the one or more of said panels.
In this embodiment the ventilation means may comprise one or more ventilators and/or the ventilation means may be arranged on the back surface(s) of the corresponding panel. Other ventilation means may be used with the same effect.
When no ventilation means are provided on the panel, the exothermic reaction takes place on the heat radiating surface of the panel in that hydrocarbon gas molecules meet oxygen molecules on the surface of a catalyst particle. It has however been found that active supplying air into the interior of a panel e.g. by means of ventilation means will increase the reaction rate and thus the amount of heat generated.
In a preferred embodiment of the heater according to the first aspect of the present invention, one or more of said panels have a design in which the gaseous hydrocarbon is supplied to a heat radiating front surface 8 which is gas permeable.
It is preferred that said one or more of said panels comprising a temperature sensor , such as a thermocouple for measuring the temperature at a predefined point of said one or more panels.
This will allow for controlling that the temperature of the panel and/or the heat radiating front surface does not deviate too much from the desired temperature.
It is furthermore preferred that said one or more of said panels according to embodiments of the invention having individually controllable regulation means for individually regulating the supply of gaseous hydrocarbon to said one or more panels.
Such regulation means may regulate individually the supply of gaseous hydrocarbon to each panel itself, or it may regulate individually the supply of gaseous hydrocarbon to more than one panel, such as e.g. the panel making up one heater.
The regulation may take place on the basis of the temperature of the panel and/or on the temperature of the heat radiating front surface(s) of one or more of such panels.
In order to prevent that more heat than necessary escapes the panel in a direction other than the desired direction, i.e. the direction defined by the heat radiating front surface, the panel is provided with a heat insulating material 16 arranged between said catalyst pad and said back surface. In a preferred embodiment, the heater, the heat insulating material 16 is selected from the group comprising mineral wool and or glass wool.
Such material are inexpensive, easy to handle, and provides for excellent heat insulation. Fig. 8 shows such a panel comprising a heat insulating material 16.
In a preferred embodiment of the invention, the catalyst pad 12 comprises fibrous mat(s) impregnated with said catalyst.
The catalyst pad 12 is arranged between said heat radiating front surface 8 and said back surface 10.
These two embodiments have proven to be an excellent way of providing an effective exothermic catalytic oxidation of the gaseous hydrocarbon.
It is preferred to provide one or more of the panels with means for protection 40 of the heat radiating front surface against impact. Such means for protection may be in the form of a metal lattice.
The heater comprising one or more panels of the above specified kind can easily be assembled from the parts making up the heater, i.e. the enclosure(s), the catalyst pad comprising the catalyst, the heat insulation material, the means for supplying and distributing gas. Individually panels may be fixed to one another with brackets or any other suitable means for assembling the panels.
Alternatively, as the panels per se are commercially available, one may decide to purchase the panels and assemble such panels into the desired configuration of the heater.
The panels per se are commercially available from Netek IR System A/S, Mariager DK-9550, Denmark. Suitable panels are the panels from Netek IR System A/S having the product Nos. The standard panels from Netek IR system A/S and having the following product numbers are very suitable for use as a heater according to the first aspect of the present invention: Model 6.6, Model 6.24, Model 8.8, Model 8.40, Model 8.51, Model 12.12, Model 12.24, Model 12.24, Model 12.36, Model 12.48, Model 12.60, Model 15.30, Model 16.40, Model 16.51, Model 18.24, Model 18.36, Model 18. 48, Model 18.60, Model 18.72, Model 24.24, Model 24.30, Model 24.36, Model 24.48, Model 24.60, Model 24.72. Likewise, the following products numbers corresponding to panels having built in an air ventilation system have proven beneficial for use as a heater according to the first aspect of the present invention: Model 5K, Model 10K, Model 12K, Model 15K, Model 18K, Model 20K, Model 25K, Model 28K.
All the above-mentioned panels are also available as panels fulfilling the ATEX-standard for offshore use. The names of these ATEX-approved panels are given the suffix "EX".
When using the heater according to the first aspect of the present invention for the curing of a coating inside a tank, it is preferred to use the heater in the form of a heating system.
Accordingly, in a second aspects, a heating system 200 comprising one or more of the heaters according to the first aspect, wherein said one or more heaters being mounted on an axle 22; said heating system furthermore comprising suspension means 42 for suspending said one or more heaters via suspension of said axle(s); said suspension means furthermore comprises attaching means 44 attaching said axle to said suspension means.
The second aspect does not form part of the invention.
The axle of the heating system provides for suspending one or more heaters on suspension means. The suspension means serves the purpose of holding the one or more heaters in the desired position in the interior of a tank which is to be subjected to the heating effect of the heaters. The axle is attached to the suspension means by means of attaching means. The attaching means may be a bearing or the like which allows for rotational movement of the axle and hence the heater inside the tank.
In case the heating system comprises more than one heater, the axle of the system may comprise a common axle or may comprise separate axles, which in turn may or may not be connected to each other.
Fig. 9, 10, 11 and 12 shows examples of the heating system according to a second aspect which is not part of the invention.
In one preferred embodiment of the heating system according to the second aspect , the suspension means 42 comprises one or more beams 46 having fixing means 48 for being releasable fixed in the interior of a tank.
This embodiment of the heating system of the second aspect is shown in fig. 9, 10 and 15.
In the use of this embodiment of the heating system according to the second aspect for heating the interior of a tank, one or more beams are releasably fixed to e.g. opposite sides of the tank's interior. Subsequently, one or more heaters according to the first aspect of the present invention is lowered into the tanks interior. Inside the tank one or more axles is provided to the heater(s) if not already present on the heater(s). Then, the heather is attached to the one or more beams by attaching means which suitably may be one or more bearings or the like.
Accordingly, this embodiment of the system according to the second aspect provides for a very simple set-up in the process of heating the interior of a tank, such as a separation tank used on an oil production facility with the view to cure a newly applied coating, such as an epoxy coating.
In a preferred embodiment of this embodiment said fixing means 48 of said heating system according to the second aspect comprises a telescopic arrangement 50 of the beam(s). Fig. 9 shows one type of a telescopic arrangement 50 of the beams 46.
In a preferred embodiment of this embodiment said fixing means 48 of said heating system according to the second aspect comprises threads 52 for adjusting the lengths of said beams.
Such a telescopic arrangement and/or threads allow for fast and easy attachment of the beams in the tank's interior, and furthermore, such an arrangement provides for flexibility in that it is useful for use in a set of different tanks, wherein each tank differs in internal size.
In a preferred embodiment according to the second aspect, said fixing means comprises magnet(s) arranged at the ends of said beams.
In a preferred embodiment according to the second aspect of the present invention, said fixing means comprises beams having tapered ends.
Such magnets or tapered ends allow for fast and easy attachment of the beams in the tank's interior.
In one preferred embodiment of the heating system according to the second aspect , the heating system comprises 1, 2, 3, 4, 5, 6, 7 or 8 heaters . Examples of such arrangements of panels are shown in fig. Fig. 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 7a and 7b. In theory however, there is no limit on the number heaters applicable in the system.
In essence there is no limit on the number of heater which may be employed in one heating system according to the second aspect of the present invention. However, for the sake of simplicity, the above stated numbers have proven appropriate.
In one preferred embodiment of the heating system according to the second aspect, the attaching means comprises one or more bearings. An example of such an embodiment is shown in fig. 10.
Bearings that attach the axle(s) to the beam(s) have proven very beneficial. However, other means for attaching the axle(s) to the beam(s) may be used instead. Such means may simply comprise U-shaped brackets attached to the beam(s) and having the opening (of the U-shape) pointing upward, wherein the axle may rest so as to prevent a transverse displacement of said axle during a heating process.
In one preferred embodiment of the heating system according to the second aspect , the heating system comprises one heater, wherein said heater is fixed on an axle 22; and wherein said axle is mounted in a bearing, said bearing being connected to a first end 60 of a first pivot joint 62, wherein a second end 64 of said first pivot joint 60 is connected to a girder 66 for lowering into the interior of a tank. Examples of such an embodiment are shown in fig. 11, 12, 14 and 15.
In the use of this embodiment of the heating system according to the second aspect for heating the interior of a tank, a heater mounted on an axle which in turn is connected to a girder is lowered into the tank's interior by lowering the girder into the tank. The axle is mounted in a bearing which allows for a rotational movement of the heater of the heating system. Furthermore, the bearing is connected to a first end of a pivot joint. The second end of the pivot joint is connected to the girder. The pivot joint allows for arranging the heater in the desired orientation within the tank.
Accordingly, also this embodiment of the system according to the second aspect provides for a very simple set-up in the process of heating the interior of a tank, such as a separation tank used on an oil production facility with the view to cure a newly applied coating, such as an epoxy coating.
In one embodiment of the above heating system, the bearing may be omitted. Accordingly, in this embodiment, the axle is directly connected to a first end of said first pivot joint.
In a preferred embodiment, this heating system comprises a second pivot joint 68 which is arranged between said second end 64 of the first pivot joint 60 and said girder 66. Examples of such an embodiment are shown in fig. 12, 14 and 15.
In the heating system comprising two pivot joints it is preferred that said first pivot joint 60 and said second pivot joint 68 being arranged in mutual positions allowing for at least being able to make pivoting movements essentially in the same plane.
Such arrangements provide for better flexibility in arranging the heater in the desired orientation within the tank.
In one embodiment of the heating system according to the second aspect , the heating system comprises means for automatically pivoting said one or more of said pivot joints. Such means for automatically pivoting said one or more of said pivot joints may inter alia comprise pneumatic actuators, electrical motors or hydraulic systems.
It is preferred that the heating system comprising pivot joints furthermore comprises a hoist mechanism 70 for lowering and raising the heater into and out of the interior of a tank 72. Examples of such an embodiment are shown in fig. 14 and 15.
In order to obtain a better spatial distribution of the electromagnetic IR waves, it will be preferred to provide the heating with an actuator for providing rotating the heater(s) around its/their corresponding axle(s). This applies whether the system is an embodiment comprising the beam(s) or is an embodiment comprising the girder.
In one embodiment the actuator is able to rotate the axle(s) in an unrestricted number of degrees in one or in both directions. However, it is preferred that the actuator for rotating the heater(s) around its axle allows for a movement of the axle in one or both direction of 10 - 180°, such as 20 - 170°, e.g. 30 - 160°, such as 40 - 150°, for example 50 - 140°, such as 60 - 130°, e.g. 70 - 120°, such as 80 - 110°, such as 90 - 100°.
The actuator may inter alia be an electrical motor, a pneumatic motor or a hydraulic motor.
In an embodiment of the invention, said heating system further comprising automatically controlling means for controlling the supply of gaseous hydrocarbon on the basis of e.g. a temperature, such as a temperature on the heat radiating front surface of one or more of the panels.
Such an embodiment allows for controlling the amount of energy in the form of IR radiation emitted from the heat radiating from surfaces of one or more of the panels of the heating system.

The use according to the present invention

The present invention relates to use of a heater according to claim 1.
The use relates to drying and/or curing a coating of an inner surface 78 of a tank, such as a separation tank of an oil production facility.

Method for drying and/or curing a coating which does not form part of the invention

A method for drying and/or curing a coating of a coated surface of the interior of a tank may comprise by using a heating system 200 according to the second aspect.
Accordingly, the method for drying and/or curing a coating of a coated surface of the interior of a tank either by using a heating system in the embodiment where the heating system comprises one or more beams or in the embodiment where the heating system comprises a pivot joint and a girder.
The method may make use of the embodiment of the heating system comprising beams for suspending the heater.
The method my comprise the following steps:

i) releasably fixing the suspension means 42 comprising one or more beams 46 to at least one surface 78 of the interior of said tank;
ii) attaching the axle 22 of each of the heaters to at least one attaching means 44 of said suspension means;
iii) optionally preheating the catalyst 14 of the catalyst pad 12 of at least one of the heaters 100 in order to facilitate a catalytic reaction of said catalyst by activation of said catalyst;
iv) supplying a stream of gaseous hydrocarbon to said catalyst pad 12;
v) optionally performing rotational movements of the axle 22 of at least on of the heaters 100 in order to obtain, in the space making up the interior of the tank, an improved spatial distribution of the IR electromagnetic waves emitted from the heat radiating front surface(s) 8 of the corresponding heater.

In this embodiment it is preferred that a wheeled cart 80 is temporarily arranged within the tank 72 for moving the heater into the desired position. A method according to this embodiment is illustrated in Fig. 16.
In this embodiment the stresses exerted on a worker's body is reduced in that he can move the heater on a cart instead of carrying the cart within the tank's interior. An example of the cart itself is depicted in fig. 17.
In another example, the method may make use of the embodiment of the heating system comprising girders and pivot joints.
In this embodiment it is preferred that the method comprises the following steps:

a) lowering the girder 66 comprising the heater into the interior of said tank;
b) optionally pivoting the one or the two pivot joints 62,68 in order to adjust the orientation of the heater;
c) optionally preheating the catalyst of the catalyst pad 12 of at least one of the heaters 100 in order to facilitate a catalytic reaction of said catalyst by activation of said catalyst;
d) supplying a stream of gaseous hydrocarbon to said catalyst pad;
e) optionally performing rotational movements of the axle 22 of at least on of the heaters in order to obtain, in the space making up the interior of the tank, an improved spatial distribution of the IR electromagnetic waves emitted from the heat radiating front surface(s) 8 of the corresponding heather.

A method according to this embodiment is illustrated in Fig. 12.
The method may comprise that air is supplied to the tanks interior by one end of a venting hose 82 being arranged in the tank's interior, and by the other end of said venting hose being connected to a running ventilator 84 thereby supplying air to the interior of said tank 72.
In yet another example, the method may relate to curing a coating, said coating being a polymer coating, such as an epoxy coating, a polyurethane coating, an acrylic coating, a coating of a non-aqueous-solvent based lacquer or a coating of an aqueous-solvent based lacquer.

Examples

The following examples illustrate methods of coating and drying/curing of an epoxy coating applied to a metal surface. The drying/curing process took place outside at a surrounding air temperature of approximately 0 °C.

Example 1 - Manufacture of a heater

This example illustrates a heating system according to the present invention having a preferred configuration. The heating system of this example was made up of four heaters which were arranged "in line" on separate axles by connecting these axles. Each heater comprised four panels each measuring approximately 1530 mm in length and 305 mm in width and 60 mm in depth. The four panels of each heater were arranged in a configuration corresponding to four-sided geometrical prism. Each panel was of a type commercially available as Infracat 12.60 EX from Netek IR System A/S, Mariager, DK-9550, Denmark. The heater comprised two end plates carrying an axle wherein the four panels were attached to the end plates via brackets.

Example 2a - Coating of the interior of a separation tank according to the prior art

A separation tank on an oil production facility was detached from all its supply lines and attached piping etc. The separation tank had an essentially cylindrical form having convex ends (as seen from the outside). The dimension of the separation tank was: length: 9000 mm and diameter: 3000 mm. The interior's original coating was sandblasted so as to remove said original coating. Subsequently a new coating was applied by traditional roll application. The new coating was an epoxy coat of the type Chesterton ARC 855 HT from the supplier Chesterton. The Chesterton ARC 855 HT is available from Jakob Albertsen Komposit A/S, Denmark.
Thereafter, a de-moisturiser and an electrical heater were arranged outside the tank. The de-moisturiser was of the type electric regenerative rotational de-moisturiser having a capacity of 5,000 m³ dry air/h and an effect of 44 kW. The heater was an electrical heater having an effect of 45 kW. The de-moisturized and heated air was blown into the tanks interior via a venting hose.
The tank was left for heating and de-moisturisation for 3 - 4 days at a maximum obtainable coating temperature of 20 °C. Finally, the venting hose of the heater and de-moisturiser was removed from the tank's interior.
This example represents a method of curing a coating according to the prior art.

Example 2b - Preparing tests plates for pull-off tests of steel plates coated in a process corresponding to that of Example 2a

A number of removable steel plates made of the same material as the steel tank of Example 2a were subjected to the same cleaning, coating and curing process as the ones performed in Example 2a. Subsequently, the applied coating of the steel plates was subjected to pull-off tests according to the ISO 4624 standard.

Example 3a - Coating of the interior of a separation tank

Example 2a was repeated up to and including the step of application of the epoxy coating. Thereafter, a heating system according to the present invention of the type which is depicted in Fig. 9 was installed in the interior of the tank. Gas hoses and wires for electrical controlling and for supplying electrical power to the preheaters to the system were installed as well.
The preheaters were switched on and allowed for heating for 10 minutes. Thereafter the supply of propane was initiated. The desired operation temperature of 60 - 90 °C (as measured on the coating of the interior walls of the tank) was reached within 5 minutes.
The actuators of the system were switched on so as to achieve a back-and-forth-like rotational movement of the heaters of the system in a rotational window corresponding to 120°. After 1 hour the supply of gas was switched off. The system was removed from the tank's interior.
The thickness of the coating was subsequently controlled and the spots on the interior wall, where the system had occupied a little bit of the surface of the walls and thereby shadowed for full IR radiation of the tank were marked.
Subsequently, these markings were coated with the same type of epoxy coating by the same application means.
The heating system was once again mounted in the tank's interior; this time in a position where the suspensions means did not shadow the newly applied coating.
The start-up procedure of the heating system was repeated and the heating was commenced for 1 hour at a desired operation temperature of 60 - 90 °C (as measured on the coating of the interior walls of the tank).
Finally, the heating system was shut off and removed from the tank's interior.

Example 3b - Preparing tests plates for pull-off of steel plates coated in a process corresponding to that of Example 3a

A number of removeable steel plates made of the same material as the steel tank of Example 2a and 3a were subjected to the same cleaning, coating and curing process as the ones performed in Example 3a. Subsequently, the applied coating of the steel plates were subjected to pull-off tests according to the ISO 4624 standard.

Tests Results

Compared to the test results obtained in respect of the electrical curing method according to the prior art, the pull-off tests performed on the coated steel plates cured according to the present invention exhibited an improved strength of approximately 30%.
This improved strength of the coating obtained by the use and the method according to the third and the fourth aspect of the present invention obviously implies improved abrasive resistance against the rough condition encountered during a separation process on an oil production facility.
Furthermore, it is noted that this improved strength is obtained during a curing process lasting only a couple of hours which is in deep contrast to the several days of curing necessary according to the prior art.
Accordingly, the heater and the heating system according to the first and second aspect provides for huge savings in terms of reduced loss of production rate on an oil production facility due to highly shortened shut-off time of the separation tank.

Claims

Use of a heater for drying and/or curing a coating of a coated surface (78) of a structure,
wherein the structure is a tank (72), and wherein said coated surface of a structure (78) is an inner surface of said tank (72), characterized in that
said heater is configured for generating heat by catalytic oxidation of gaseous hydrocarbon; said heater comprising:
an arrangement (2) of a plurality of panels (4);
wherein each of said panels comprising:
an enclosure (6) comprising a heat radiating front surface (8), and a back surface (10);

a catalyst pad (12), said catalyst pad comprising a catalyst capable of catalytically oxidising a hydrocarbon exothermically;

a heat insulating material (16) arranged between said catalyst pad and said back surface;

means (18) for supplying and distributing gas to said panel;

wherein two points (P1,P2) exist on said heat radiating front surfaces (8) of said panels of said heater; said points (P1,P2) defines initial points of two normal vectors (v1,v2) respectively of said surfaces, wherein the mutual angle, α between said two normal vectors (v1,v2) lies within the range of 70 -180°, and wherein the panels (4) are arranged in an arrangement (2) essentially corresponding to the sides of a geometrical prism.
Use of a heater according to claim 1, wherein three points (P1,P2,P3) exist on said heat radiating front surfaces (8) of said panels of said heater; said points (P1,P2,P3) defines initial points of three normal vectors (v1,v2,v3) respectively of said heat radiating front surfaces, wherein the mutual angle, α between any two of said three normal vectors (v1,v2,v3) lies within the range of 70-180°.
Use of a heater according to claim 1 or 2, wherein the mutual angle, α between said two normal vectors lies within the range of 70 - 175°, such as 75 - 170°, for example 80 - 165°, such as 85 - 160°, e.g. 90 - 155°, such as 95 - 150°, for example 100 - 145°, such as 105 - 140°, such as 110 - 135°, such as 115 - 130°, for example 120 - 125°.
Use of a heater according to any of the claims 1 - 3, wherein said geometrical prism is a polygonal prism having n sides, wherein n is 3 or more, such as 3, 4, 5, 6, 7 or 8.
Use of a heater according to any of the preceding claims wherein the catalyst comprises or consists of a metal selected from the group comprising: platinum, palladium and rhodium, vanadium and iridium.
Use of a heater according to any of the preceding claims, wherein one or more of said panels (4) are provided with preheating means, such as electrical preheating means, in order to facilitate initiation of the catalytically oxidation of the hydrocarbon by virtue of activation of the catalyst.
Use of a heater according to any of the preceding claims wherein said heat radiating front surfaces (8) are plane or having a curved geometrical shape, e.g. a shape corresponding to part of a cylinder surface.
Use of a heater according to any of the preceding claims, wherein said panels comprising a temperature sensor, such as a thermocouple for measuring the temperature at a predefined point of said panels.
Use of a heater according to any of the preceding claims, wherein said panels having individually controllable regulation means for individually regulating the supply of gaseous hydrocarbon to said panels.
Use of a heater according to any of the preceding claims, wherein the means for distributing gas (18) comprises perforated tubing and/or one or more perforated distribution plates arranged in the heater.
Use of a heater according to any of the preceding claims further comprising ventilation means for supplying air from the surroundings into the enclosure of said panels.
Use of a heater according to claim 11, wherein the ventilation means comprises one or more ventilators and wherein the ventilator(s) is/are arranged on the back surface(s) of the corresponding panel.
Use of a heater according to any of the preceding claims, wherein the catalyst pad (12) comprises fibrous mat(s) impregnated with said catalyst, and/or wherein said catalyst pad (12) is arranged between said heat radiating front surface (8) and said back surface (10).
Use of a heater according to any of the claims 1 - 13, further comprising automatically controlling means for controlling the supply of gaseous hydrocarbon on the basis of a temperature, such as a temperature on the heat radiating front surface of said panels.