Steam generating electrode boiler

Abstract

An electrode boiler (100) is provided for generating pressurised steam comprising an electric power source (140), a bundle (110) of elongated channels (113), a water supply (130), and a steam outlet (115). Each channel comprises a first electrode (111) and a second electrode (112), both coupled to the electric power source (140). The water supply (130) is fluidly coupled to a first end of the channels (113) and configured to at least partly submerge the electrodes (111, 112) in water (200). The steam outlet (115) is fluidly coupled to a second end of the channels (113) and configured to release steam generated when an electric current flows through the water (200) between the first electrode (111) and the second electrode (112).

Description

[0001] STEAM GENERATING ELECTRODE BOILER

[0002] Field of the Invention

[0003] This invention relates to an electrode boiler for generating pressurised steam using electrodes submerged in water for passing a current through the water between the electrodes .

[0004] Background of the invention

[0005] In many industries, there is a need for generating high pressure saturated and superheated steam. The generated steam may be used for providing mechanical power or as an ingredient for a specific production process. Typical industries where such steam generation is used include the oil and gas industry, the refining of ores in, e.g. , the aluminium and steel industry, or the production of hydrogen from steam methane.

[0006] Historically, boilers for generating the pressurised steam often use fossil fuels to provide the energy needed to turn water into steam. More recently, there has been a move to less carbon intensive technologies to achieve the same. One example of a fossil free steam boiler is an electrode-based e-boiler wherein electrodes are submerged in a vessel filled with water. When driving an electric current through the electrodes, the resistance of the water itself generates the heat needed for generating steam. With current technology and properly reinforced vessels, steam can be generated at pressures up to about 85 bar. However, partly because of the high pressure the vessel needs to be able to withstand, these e-boilers can be relatively large and expensive. Furthermore, the steam output they can generate is highly dependent on the design of the e-boiler and difficult to scale up or down when circumstances ask for this.

[0007] It is an aim of the current invention to overcome at least some of the disadvantages of the known e-boiler.

[0008] Summary of the Invention

[0009] In view of this aim and according to an aspect of the invention, an electrode boiler is provided for generating pressurised steam. The electrode boiler comprises an electric power source, a bundle of elongated channels, a water supply, and a steam outlet. The elongated channels in the bundle each comprise a first electrode and a second electrode, both coupled to the electric power source. The water supply is fluidly coupled to a first end of the channels and configured to at least partly submerge the first electrode and the second electrode in water. The steam outlet is fluidly coupled to the other, second end of the channels and configured to release steam generated when an electric current flows through the water between the first electrode and the second electrode.

[0010] By using a bundle of narrow channels, each having their own submerged electrodes for generating only a portion of the generated steam, instead of a single large vessel wherein all steam is generated, an inherently far more robust e-boiler is provided. The shared or adjoining walls of two neighbouring channels in the bundle are subject to equal or similar steam pressures from both sides of said walls, while in the previously used large vessels pressure is exerted on the vessel walls in an outward direction only. As a result, the channel bundle provides for a cheaper design with a smaller footprint. This channel bundle can be used for providing similar or greater amounts of steam at a similar or higher pressure as already possible with the previously known e-boilers with their large, heavily reinforced vessels. Another advantage of the use of a bundle of channels, instead of a single large vessel, is that this significantly decreases the start-up time for the required heating power as the heat generation is localized in each channel which gives a significant advantage in start-up. Furthermore, the now presented electrode boiler allows to easily and quickly add or enable a second, third, or further bundle of elongated channels with corresponding first and second electrodes to provide additional steam generating capacity when needed. In contrast, it would be very difficult to adjust a capacity of the vessel included in the prior art e-boilers described above.

[0011] In an embodiment, the first electrode and the second electrode are both arranged within the respective channel and at a distance from an inner wall thereof. 'At a distance' herein means that the electrodes are separate from the wall such that the water they are submerged in flows around the full circumference of the electrodes. When both connected to the activated power source, the water wherein the electrodes are at least partly submerged closes the circuit and the electrical resistance provided by the water causes the water to heat to the point of changing phase and turning into steam.

[0012] In a different embodiment, the first electrode is formed by an electrically conductive inner wall of the respective channel, and the second electrode is arranged within the respective channel at a distance from the inner wall. Because the inner wall functions as an electrode, only a single additional electrode needs to be installed within each channel. This also allows the single additional electrode to be installed centrally within the channel, therewith minimising the risk of the two electrodes coming into contact with each other and caus ing a short-circuit that may damage the equipment .

[0013] Preferably, the bundle of elongated channels is formed as a monolithic unit . 'Monolithic' is herein defined as being formed or cast as a single unitary piece , such that the bundle of elongated channel s does not need any j oints or seams to be held together . The unitary, seamles s character of the monolithic unit contribute s to its strength and its ability to withstand high pres sure s from the steam generated ins ide the channels . For example , the monolithic unit may be made of a ceramic material , or of a metal , such as aluminium, copper , ca st iron , or stainle ss steel . The bundle may be coated with high- temperature res istant ceramic or polytetrafluoroethylene for protection against live electric shocks .

[0014] If the monolithic unit is made of an electrically conductive metal , its inner walls may be used a s one of the two electrodes between which the steam is generated . If a ceramic material is used for making the monolithic unit , the inner walls of the channels may be partly or fully coated by an electrically conductive material to allow using the inner wall a s one of the electrodes .

[0015] In preferred embodiment s , the electrode boiler further comprises a controller , coupled to the electric power source and / or the water supply to control the operation thereof . The controller may be controlled by software , based on predetermined control programs . User commands and sensor input may be used as input for the control programs for the power source and / or the water supply .

[0016] For example , the electrode boiler may further comprise a water level sensor for monitoring a water level in the channels , and the controller is coupled to the water level sensor and configured to control the water supply in dependence of the water level . This way, it i s ensured that the channels are always filled with liquid water up to the appropriate level , keeping the first and second electrodes at least partly submerged and allowing steam to be generated at the preferred rate and pres sure .

[0017] As a further example , the electrode boiler may further compris ing a salinity sensor for monitoring a salinity of the water in the channels , and the controller is coupled to the salinity sensor . The electrical resistance of the water between the electrode s is determined by the salts and mineral s dis solved therein . The electrical resistance of the water determines how the electric power provided by the electric power source generates the steam . For the optimal functioning of the electrode boiler , it is therefore preferred to be able to accurately control the salinity level of the water . While steam i s being generated, the salinity of the water increases . Accordingly, it i s useful to continuously or repeatedly monitor the salinity level and to ta ke appropriate mea sures to adj ust the salinity level when needed or desired .

[0018] One way of adj usting the salinity level of the water may be to configure the controller to control the water supply in dependence of the salinity . By adding fresh water with a relatively low level of salinity, the overall salinity level of the water is reduced . Another way of adj usting the salinity level of the water may be to configure the controller to control a salt di spenser in dependence of the salinity . When operating the salt dispenser to add an amount of salts to the water , the salinity level of the water is increased . Very preci se control over the salinity level of the water can be achieved by continuously monitoring the salinity level using the salinity sensor and operating the water supply and the salt di spenser to add water and / or salt s to the system in dependence of the measured salinity levels .

[0019] In some embodiments , the controller may be configured to selectively supply power to the f irst electrodes and / or the second electrodes of a subset of the channel s . The amount of steam being generated and the pres sure of the generated steam depends on the number of channel s that i s activated by powering the re spective electrodes of those channels .

[0020] More precise control of the steam generation rate , pres sure , and temperature may be achieved by controlling the current and / or voltage of the electric power sent through the electrode s . In an exemplary embodiment of the electrode boiler according to the invention , the power source is configured to provide an alternating current at a voltage of about 15 -25 kV. In some embodiment s , the voltage may be adj ustable within a predetermined voltage range .

[0021] Brief Description of the Drawings

[0022] Figure 1 schematically shows an electrode boiler according to an embodiment of the invention .

[0023] Figure 2 schematically shows a cros s section of a bundle of elongated channels for use in the electrode boiler of Figure 1 .

[0024] Figure 3 schematically shows a cros s section of a different bundle of elongated channels for use in the electrode boiler of Figure 1 .

[0025] These drawings depict one or more implementations in accordance with the present teachings , by way of example only, not by way of limitation . In the figure s , like reference numerals refer to the same or s imilar element s . Detailed Description of the Drawings

[0026] Figure 1 schematically shows an electrode boiler 100 according to an embodiment of the invention . The electrode boiler 100 comprises an electric power source 140 , a bundle 110 of elongated channels 113 ( see Figures 2 and 3 ) , a water supply 130 , and a steam outlet 115 . In other embodiment s , two or more of such bundles 110 may be provided . The elongated channels 113 in the bundle 110 each comprise a first electrode 111 and a second electrode

[0027] 112 ( see Figure s 2 and 3 ) , both coupled to the electric power source 140 . A controller 150 may be coupled to the electric power source 140 to control the supply of electric power to the electrodes 111 , 112 of the channels

[0028] 113 .

[0029] The water supply 130 is fluidly coupled to a first end of the channels 113 and configured to at least partly submerge the first electrode 111 and the second electrode 112 in water 200 . Thi s may, for example , be achieved by placing the bundle 110 in a reservoir 120 that is partly filled with water 200 , such that the first end of the channel s 113 is located under the water level 220 . When using the water supply 130 to add water to the reservoir , the water level 220 rises , and the water level within the channel s 113 ri ses accordingly . The reservoir 120 may further comprise a drain 135 that can be operated to relea se some of the water 200 and lower the water level 220 . The electrodes 111 , 112 inside the channel s 113 are positioned such that they are at least partly submerged when the electrode boiler 100 is in use . Optionally, the bundle 110 can be moved up and down to adj ust the water level inside the channels 113 without adj usting the water level 220 in the reservoir 120 .

[0030] A water level sensor 160 may be provided for monitoring the water level 220 in the reservoir and / or in the channels 113 . The controller 150 is coupled to the water level sensor 160 to monitor the water level 220 . The controller may further be configured to control the water supply 130 , the drain 135 , and / or the vertical movement of the bundle 110 in dependence of the measured water level 160 . This way, it is ensured that the channel s 113 are always filled with liquid water 120 up to the appropriate level , keeping the first and second electrode s 111 , 112 at least partly submerged and allowing steam to be generated at the preferred rate and pres sure . Additionally, the controller 150 may be configured to switch of f the electrodes 111 , 112 for safety reasons when the water level 220 drops below the level at which the electrodes 111 , 112 are sufficiently submerged .

[0031] The steam outlet 115 is fluidly coupled to the not submerged, second end of the channels 113 for releas ing the steam that is generated when an electric current flows through the water between the first electrode 111 and the second electrode 112 . From the steam outlet 115 , the generated steam can be pas sed on to further technical installations that ma ke use of the pres surised steam generated by the electrode boiler 100 .

[0032] Figure 2 schematically shows a cros s section of a bundle 110 of elongated channels 113 for use in the electrode boiler 100 of Figure 1 . Figure 3 schematically shows a cros s section of a different bundle 110 of elongated channels 113 for use in the electrode boiler 100 of Figure 1 . By using a bundle 110 of narrow channel s 113 instead of a single large ve s sel wherein all steam i s generated, an inherently far more robust e-boiler 100 i s provided . Each channel 113 has its own submerged electrodes 111 , 112 for generating a portion of the generated steam . The shared or adj oining wall s 115 of two neighbouring channels 113 in the bundle 110 are subj ect to equal or similar steam pressures from both sides of said walls 115. The resulting channel bundle 110 provides for a low cost design with a relatively small footprint. This channel bundle 110 can be used for providing similar or greater amounts of steam at a similar or higher pressure as already possible with the previously known e-boilers with their large, heavily reinforced vessels. Furthermore, the now presented electrode boiler 100 allows to easily and quickly add or enable a second, third, or further bundle 110 of elongated channels 113 with corresponding first and second electrodes 111, 112 to provide additional steam generating capacity when needed.

[0033] In the embodiment shown in Figure 2, the first electrode 111 and the second electrode 112 are both arranged within the respective channel 113 and at a distance from an inner wall 115 thereof. 'At a distance' herein means that the electrodes 111, 112 are separate from the wall 115 such that the water 200 they are submerged in flows around the full circumference of the electrodes 111, 112. When both connected to the activated power source 140, the water 200 wherein the electrodes 111, 112 are at least partly submerged closes the circuit and the electrical resistance provided by the water 200 causes the water 200 to heat to the point of changing phase and turning into steam. In general, the electrodes 111, 112 may be made of any suitable electrically conductive metal.

[0034] In a different embodiment, shown in Figure 3, the first electrode 111 is formed by an electrically conductive inner wall 115 of the respective channel 113, and the second electrode 112 is arranged within the respective channel 113 at a distance from the inner wall 115. Because the inner wall 115 functions as an electrode 111, only a single additional electrode 112 needs to be installed within each channel 113. As can be seen in the schematic drawing shown in Figure 3, this also allows the single additional electrode 112 to be installed centrally within the channel 113, therewith minimising the risk of the two electrodes 111, 112 coming into contact with each other and causing a short-circuit that may damage the equipment .

[0035] Preferably, the bundle 110 of elongated channels 113 is formed as a monolithic unit. 'Monolithic' is herein defined as being formed or cast as a single unitary piece, such that the bundle 110 of elongated channels 113 does not need any joints or seams to be held together. The unitary, seamless character of the monolithic unit further contributes to its strength and its ability to withstand high pressures from the steam generated inside the channels 113. For example, the monolithic unit may be made of a ceramic material, or of a metal, such as aluminium, copper, cast iron, or stainless steel. The bundle 110 may be coated with high-temperature resistant ceramic or polytetrafluoroethylene for protection against live electric shocks .

[0036] If the monolithic unit is made of an electrically conductive metal, its inner walls 115 may be used as one of the two electrodes 111, 112 between which the steam is generated. If a ceramic material is used for making the monolithic unit, the inner walls 115 of the channels 113 may be partly or fully coated by an electrically conductive material to allow using the inner wall 115 as one of the electrodes 111, 112.

[0037] The controller 150 of the electrode boiler 110 may be controlled by software, based on predetermined control programs. User commands and sensor input may be used as input for the control programs for, e.g. , the power source 140, the water supply 130, or the drain 135. The electrode boiler 100 may further comprise a salinity sensor 170 , coupled to the controller 150 , for monitoring a salinity of the water 200 in the channels 113 . The electrical resistance of the water 200 between the electrodes 111 , 112 i s determined by the salts and minerals dis solved therein . The electrical resi stance of the water 200 determines how the electric power provided by the electric power source 140 generates the steam . For the optimal functioning of the electrode boiler 100 , it i s therefore preferred to be able to accurately control the salinity level of the water 200 . While steam is being generated, the salinity of the water 200 increases . Accordingly, it is useful to continuously or repeatedly monitor the salinity level and to take appropriate measures to adj ust the salinity level when needed or desired .

[0038] One way of adj usting the salinity level of the water may be to configure the controller 150 to control the water supply 130 in dependence of the mea sured salinity level . By adding fresh water with a relatively low level of salinity, the overall salinity level of the water 200 is reduced . Another way of adj usting the salinity level of the water 200 may be to conf igure the controller 150 to control a salt dispenser 180 in dependence of the measured salinity . When operating the salt dispenser 180 to add an amount of salts to the water 200 , the salinity level of the water is increased . Very precise control over the salinity level of the water 200 can be achieved by continuous ly monitoring the salinity level us ing the salinity sensor 170 and operating the water supply 130 and the salt dispenser 180 to add water and / or salt s to the system in dependence of the measured salinity levels .

[0039] In some embodiments , the controller 150 may be configured to selectively supply power to the f irst electrodes 111 and / or the second electrodes 112 of a subset of the channels 113. The amount of steam being generated and the pressure of the generated steam depends on the number of channels 113 that is activated by powering the respective electrodes 111, 112 of those channels 113. The proposed configurations are modular and provide significant flexibility, i.e. being able to size up the system based on local (renewable) energy availability and process constraints (including voltagecurrent limitations) .

[0040] More precise control of the steam generation rate, pressure, and temperature may be achieved by controlling the current and / or voltage of the electric power sent through the electrodes 111, 112. In an exemplary embodiment of the electrode boiler 100 according to the invention, the power source 140 is configured to provide an alternating current at a voltage of about 15-25 kV. In some embodiments, the voltage may be adjustable within a predetermined voltage range.

[0041] In exemplary embodiments of an electrode boiler 100 according to the invention, the inlet temperature of the water 200 entering the bundle 110 of elongated channels 113 may be as low as ambient temperature (or even lower) to as high as 500°C. The channels 13 may, for example, have a length of between 1cm and 10m, and a diameter of between 0.1cm and 100cm. The total diameter of the bundle 110 will depend on the number of channels 113 in the bundle 110 and a thickness of the walls between them. Exemplary bundle diameters may be between 10cm and 10m. The resistivity of the water 200 is dependent on the amount and type of salts dissolved in the water and may, for example, be in the range of 10 -5 to 200 Ohm.m, which may be achieved by using deionized water or normal / sea water or by adding some electrolytes. As an example, a modular monolith bundle 110 of radius and length Im (i.e. volume of 3.14 m 3) , and containing roughly 400 channels 113 of radius 5cm. Each channel 113 contains one electrode 112 of radius 2cm. With an aqueous phase resistivity of 80 Ohm.m and voltage supply of 5000V, the unit can produce roughly 857MW of electric power. This much power is equivalent to the endothermic heat requirement of 10 megaton per year of saturated steam production at 100 bar from ambient water. While many possible variations of the electrode boiler 100 have been described above, it will be clear to the skilled person that additional variations and modifications can be made without departing from the scope of the invention as claimed in the appended claims.

Claims

C L A I M S1. An electrode boiler (100) for generating pressurised steam comprising:- an electric power source (140) ;- a bundle (110) of elongated channels (113) , each comprising a first electrode (111) and a second electrode (112) , both coupled to the electric power source (140) ;- a water supply (130) , fluidly coupled to a first end of the channels (113) and configured to at least partly submerge the first electrode (111) and the second electrode (112) in water (200) ; and- a steam outlet (115) , fluidly coupled to a second end of the channels (113) and configured to release steam generated when an electric current flows through the water (200) between the first electrode (111) and the second electrode ( 112 ) .

2. An electrode boiler (100) as claimed in Claim 1, wherein the first electrode (111) and the second electrode (112) are arranged within the respective channel (113) and at a distance from an inner wall (115) thereof.

3. An electrode boiler (100) as claimed in Claim 1, wherein the first electrode (111) is formed by an electrically conductive inner wall (115) of the respective channel (113) , and the second electrode (112) is arranged within the respective channel (113) at a distance from the inner wall (115) .

4. An electrode boiler (100) as claimed in any precedingClaim, wherein the bundle (110) of elongated channels (113) is formed as a monolithic unit.

5. An electrode boiler (100) as claimed in Claim 4, wherein the monolithic unit is made of a metal.

6. An electrode boiler (100) as claimed in Claim 4, wherein the monolithic unit is made of a ceramic material.

7. An electrode boiler (100) as claimed in any preceding Claim, further comprising a controller (150) , coupled to the electric power source (140) and / or the water supply (130) to control the operation thereof.

8. An electrode boiler (100) as claimed in Claim 7, further comprising a water level sensor (160) for monitoring a water level (220) in the channels (113) , wherein the controller (150) is coupled to the water level sensor (160) and configured to control the water supply (130) in dependence of the water level (220) .

9. An electrode boiler (100) as claimed in Claim 7 or 8, further comprising a salinity sensor (170) for monitoring a salinity of the water in the channels (113) , wherein the controller (150) is coupled to the salinity sensor (170) .

10. An electrode boiler (100) as claimed in Claim 9, wherein the controller (150) is configured to control the water supply (130) in dependence of the salinity.

11. An electrode boiler (100) as claimed in Claim 9 or 10, further comprising a salt dispenser (180) for dispensing salts into the water (200) , wherein the controller (150) is coupled to the salt dispenser (180) and configured to control the salt dispenser (180) in dependence of the salinity.

12. An electrode boiler (100) as claimed in any of Claims7 to 11, wherein the controller (150) is configured to selectively supply power to the first electrodes (111) and / or the second electrodes (112) of a subset of the channels ( 113 ) .

13. An electrode boiler (100) as claimed in any preceding Claim, wherein the power source (140) is configured to provide an alternating current at a voltage of about 15-25 kV.

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