System and method for conveying material

Abstract

The invention relates to a system for conveying material comprising a tube comprising a first vertical section, a second vertical section, a horizontal section and means for feeding gas to the tube. The upper end of the first vertical section is arranged above the upper end of the second vertical section. The invention also relates to a method for conveying material from a lower pressure to a higher pressure.FIG. 1

Description

Full specification SYSTEM AND METHOD FOR CONVEYING MATERIALFIELD OF THE INVENTIONThe present invention relates to a system and method for conveying material from a lower pressure to a higher pressure.  BACKGROUND OF THE INVENTIONConveying material from a lower pressure to a higher pressure is energy consuming. The reason being that often such systems comprise pumps, which require energy. Often material needs to be fed to pressurised reactors or storage vessels. These often contain explosive gases. Thus, it is hazardous to use systems comprising moving parts, such as pumps, as a spark may be formed between the moving parts. Further, reactors and storage vessels often need to be isolated from their outside environment, such that nothing except the material to be conveyed is exchanged between the inside and outside of the reactor or storage vessel. As such, systems that allow the transport of certain materials in a controlled direction while sealing the environment to which the material is transported from the outside is needed. Some examples of equipment used to seal the environment of one space from another include valves. However, a valve does not provide the freedom to convey only certain components while keeping other components separate. Also, valves usually cannot be used to feed material continuously. Further, a valve contains moving parts and, thus, the above issue related to moving parts is also an issue when using a valve.  As such, there exists a need for systems for conveying material that overcome the above challenges.  SUMMARYAccording to a first aspect a system for conveying material is provided, the system comprising:a. a tube comprising a first vertical section comprising a first upper end and a first lower end, a second vertical section comprising a second upper end and a second lower end, and a horizontal section; andb. means for feeding gas to the tube;wherein the first upper end is arranged above the second upper end.  According to a second aspect, a method for conveying material from a lower pressure to a higher pressure is provided, the method comprising: a. feeding material to a first end of a tube;b. feeding gas to the tube through means for feeding gas ; andc. conveying the material to a pressurised reactor, silo, bin or the like through a second end of the tube;wherein the gas is fed to the tube in an amount to create a particle Froude number (Frp) of between 0.02 and 0.12, or between 0.03 and 0.1, in the horizontal cross-section of the tube with the largest area.  BRIEF DESCRIPTION OF THE DRAWINGSThe accompanying drawing, which is included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawing:Figure 1 shows a side view of a system for conveying material. Figure 2a shows a top view of a system for conveying material.Figure 2b shows end views of a system for conveying material. DETAILED DESCRIPTIONIt is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims. System for conveying material According to a first aspect and as seen in figure 1, a system for conveying material is provided, the system comprising:a. a tube comprising a first vertical section (101) comprising a first upper end (102) and a first lower end (103), a second vertical section (104) comprising a second upper end (105) and a second lower end (106), and a horizontal section (107); andb. means for feeding gas (108) to the tube;wherein the first upper end (102) is arranged above the second upper end (105).  A tube may refer to a long hollow round cylinder of a durable material for holding or transporting material. The cylinder may be bent to form a L-, U-, or S-shape or anything in between.  The first vertical section (101) and the second vertical section (104) according to the first aspect may be parallel to each other, and the horizontal section (107) may connect the first vertical section (101) and the second vertical section (104) through the first lower end (103) and the second lower end (106). The connection between the first lower end (103) and the horizontal section (107) as well as the second lower end (106) and the horizontal section (107) may be rounded for smooth transfer of material.  The horizontal section (107) may be oriented substantially horizontally and the vertical sections (101, 104) substantially vertically when the system for conveying material is in use. Alternatively, the horizontal section (107) may be oriented substantially horizontally, and the vertical sections (101, 104) may be slightly tilted, such that the vertical sections (101, 104) deviate from the vertical direction with 45° to 60°. The vertical sections (101, 104) may be tilted for improved flowability of material or because of the space where the system is to be placed.  For the avoidance of doubt, “vertically” may mean the direction of gravity and “horizontally” may mean the direction that is perpendicular to the vertical direction. The horizontal section (107) may have the length of 1 m to 3 m. The first vertical section (101) may be at least 3 m, or 4 m, or 5 m longer than the second vertical section (104). It has been found that these dimensions provide optimal conditions for conveying fine particles (109) having a density of around 2500 to 4800 kg / m3 from one end of the system to the other end of the system through gravity.  The diameter of the first vertical section (101), the second vertical section (104) and the horizontal section (107) may be the same or the sections may all have different diameters. The diameter may also vary within one section such that the first vertical section (101), second vertical section (104) and horizontal section (107) are tapered. In one embodiment, the sections have the same diameter, and the diameter is 0.3 m to 2 m, or 0.4 m to 1.5 m, or 0.5 m to 1 m. It has been found that it is beneficial to have such a diameter as this diameter provides the optimal conditions for conveying fine particles (109) having a density of around 2500 to 4800 kg / m3 from one end of the system to the other end of the system through gravity.  The means for feeding gas (108) according to the first aspect may be arranged in the horizontal section (107). The means for feeding gas (108) may be arranged such that gas (110) is fed across the whole horizontal length of the horizontal section (107) in a continuous line or at certain intervals. The means for feeding gas (108) may be arranged substantially in the middle of the horizontal section (107) and cover about 1 / 3 of the length of the horizontal section (107) in a continuous line or at certain intervals. In one embodiment, the means for feeding gas (108) is arranged such that the gas (110) is fed vertically upwards in the horizontal section (107). The means for feeding gas (108) may also be arranged such that the gas (110) is fed vertically upwards but deviating from the direction perpendicular to the direction in which the horizontal section (107) extends. This may be the case if the horizontal section (107) is placed on a sloping surface.  It has been found that the above means for feeding gas (108) gives the added utility of at least partially sealing the environment between the two ends of the system for conveying material. The fed gas (110) is preferably mainly conveyed in the direction of material that is fed through the system for conveying material. However, some gas (110) may also escape to the direction from which material is fed. Importantly, the gas (110) ensures that gas from outside the system does not enter the system. Accordingly, the environment on one side of the system for conveying material may be kept separated from the environment on the other side of the system, even when continuously feeding material through the system.  The system for conveying material according to the first aspect may be configured to convey material from a lower pressure to a higher pressure, wherein the difference between the lower pressure and the higher pressure may be at least 0.5 bar, or at least 0.8 bar, or at least 1 bar, or at least 1.2 bar. The difference between the lower pressure and the higher pressure may be 0.5 to 1.2 bar, or 0.8 to 1.1 bar, or 1 bar. The inventors have surprisingly found that the dimensions of the system for conveying material disclosed herein provide optimal conditions for feeding material across a pressure difference of up to 1.2 bar without the use of any external power source. The conditions even allow the transport of fine particles (109) having a density of about 2500 to 4800 kg / m3. The system for conveying material according to the first aspect may be configured to allow movement of solid or liquid material substantially in one direction only. It has been found that the configuration of the system for conveying material ensures that material may be fed in a controlled manner in a desired direction.  In one embodiment, the system for conveying material comprises no moving parts. It is beneficial to provide a system devoid of any moving parts as the environment to which material is fed may comprise an easily ignited medium.  The system for conveying material according to the first aspect may further comprise a solids conveyor on top of the first upper end (102) of the first vertical section (101) for feeding solid material to the tube.  The solid conveyor may comprise a belt, apron, flight or screw conveyor. The solid conveyor may be configured to convey solids to be transported through the system for conveying material to the top of the first upper end (102) of the first vertical section (101). This ensures that a sufficient amount of material is present in the first vertical section (101) for maintaining the pressure difference between the two ends of the system.  In one embodiment, the solids conveyor is the only moving part in the system for conveying material.  The means for feeding gas (108) to the tube according to the first aspect may comprise a nozzle grid, perforated plates or a set of single nozzles. In one embodiment, the means for feeding gas (108) is configured to feed gas (110) in an amount to create a certain particle Froude number Frp in the horizontal cross-section of the tube with the largest area (112). The means for feeding gas (108) may configured to feed gas (110) in an amount to create a certain particle Froude number Frp above the entrance of the fed gas (110). The Froude number Frp should hereby be between 0.02 and 0.12, or between 0.03 and 0.1 and is defined as . Umean is the actual volume flow of the feeding gas (110) (m3 / s) divided by the flow through area (m2) in the horizontal cross-section of the tube with the largest area (112). ρs is the density of the fine particles (109) (kg / m3) and ρg is the density of the feeding gas (110) in the vertical section (kg / m3). g is the gravitational constant (m / s2) and d80 the characteristic particle diameter, i.e. 80% of the particles are smaller than this diameter (m).  The horizontal cross-section of the tube with the largest area (112) may be the horizontal cross-section of the tube the projection of which onto a horizontal plane has the largest area. As explained above, the horizontal section (107) may be oriented substantially horizontally and the vertical sections (101, 104) substantially vertically when the system for conveying material is in use. Accordingly, the horizontal cross-section of the tube with the largest area (112) may be found in the horizontal section (107), extending between the first lower end (103) and the second lower end (106). The above-mentioned particle Froude number should be achieved because it provides sufficient fluidisation to the material to be conveyed but does at the same time not disturb the process of conveying material from one end of the system to another.  The system for conveying material according to the first aspect may be configured to convey fine particles (109) and to mix the fine particles (109) with gas (110) and to convey the fine particles and gas (111) to a reactor, silo, bin or the like. The configuration of the system for conveying material allows conveying and mixing of fine particles (109) and gas (111) simultaneously. Therefore, the material to be fed does not need to be subjected to an inert medium prior to being fed to the reactor. Instead, the medium used in the reactor as diluent may be used for pre-treating the material simultaneously when the material is fed through the system. The configuration of the system for conveying material also allows feeding material continuously while mixing the fine particles (109) and gas (111) as well as sealing the environment of one end of the system from the other even when conveying material to a pressurised system.  The fine particles (109) according to the first aspect may comprise metal oxides, and / or the gas (110) may comprise water vapour, nitrogen, ammonium or hydrogen and / or the fine particles and gas (111) may be conveyed to a pressurised reactor. The fine particles (109) may consist of metal oxides, and / or the gas (110) may consist of water vapour, nitrogen, ammonium or hydrogen.  The fine particles (109) may have a size of 0.0001 mm to 5 mm, or 0.1 mm to 4 mm, or 1 mm to 3 mm.  The pressurised reactor according to the first aspect may be a fluidised bed reactor for reducing metal oxides. The metal oxides according to the first aspect may comprise iron oxides. The metal oxides may consist of iron oxides. Method for conveying material  The description related to the system above apply to the method below and the description related to the method below apply to the system above.  According to a second aspect, a method for conveying material from a lower pressure to a higher pressure is provided, the method comprising: a. feeding material to a first end (112) of a tube;b. feeding gas (110) to the tube through means for feeding gas (108); andc. conveying the material to a pressurised reactor, silo, bin or the like through a second end (113) of the tube;wherein the gas is fed to the tube in an amount to create a particle Froude number (Frp) of between 0.02 and 0.12, or between 0.03 and 0.1, in the horizontal cross-section of the tube with the largest area (112).  The gas may be fed to the tube in an amount to create a particle Froude number (Frp) of between 0.04 and 0.8, or between 0.05 and 0.6, in the horizontal cross-section of the tube with the largest area (112).  The tube according to the second aspect may comprise a first vertical section (101) comprising a first upper end (102) and a first lower end (103), a second vertical section (104) comprising a second upper end (105) and a second lower end (106) and a horizontal section (107), and wherein the first upper end (102) is arranged above the second upper end (105).  The material fed to the first end (112) of the tube according to the second aspect may comprise fine particles (109). The material fed to the first end (112) of the tube may consist of fine particles (109).  The material according to the second aspect may be conveyed to a pressurised reactor, preferably wherein the pressurised reactor is a fluidised bed reactor for reducing a metal. The material according to the second aspect may be conveyed from a lower pressure to a higher pressure and wherein the difference between the lower pressure and the higher pressure is at least 0.5 bar, or at least 0.8 bar, or at least 1 bar, or at least 1.2 bar. The gas (110) according to the second aspect may be fed to the tube in the horizontal section (107). EXAMPLES This example illustrates conveying solid iron ore of approximately 90 t / h consisting of particles where 80% have a diameter of lower than 1mm and have a density of 3800 kg / m3, through a system described herein.  The pressure at the inlet of the first vertical section was 100 kPa and at the outlet of the second vertical section 370 kPa. The temperature of the particles was 850 °C. To enable smooth transport of the particles, the diameter of the first vertical section was chosen to be 0.6 m and the diameter of the second vertical section 0.6 m. The diameter of the horizontal section was 0.6 m. The height of the first vertical section was 25.6 m and the height of the second vertical section was 3.6 m.  A FrP number of 0.095 was chosen resulting in mean vertical velocity of 0.6 m / s in the horizontal cross-section of the tube with the largest area. At this point the gas density was 0.93 kg / m3 and the pressure 440kPa. 

Claims

1. A system for conveying material comprising:a. a tube comprising a first vertical section (101) comprising a first upper end (102) and a first lower end (103), a second vertical section (104) comprising a second up-per end (105) and a second lower end (106), and a horizontal section (107); andb. means for feeding gas (108) to the tube;wherein the first upper end (102) is arranged above the second upper end (105).  2. The system for conveying material according to claim 1, wherein the first vertical section (101) and the second vertical section (104) are parallel to each other, and the horizontal section (107) connects the first vertical section (101) and the second vertical sec-tion (104) through the first lower end (103) and the second lower end (106).  3. The system for conveying material according to claims 1 or 2, wherein the means for feeding gas (108) is arranged in the horizontal section (107). 4. The system for conveying material according to any preceding claims, wherein the system is configured to convey material from a lower pressure to a higher pres-sure, wherein the difference between the lower pressure and the higher pressure is at least 0.5 bar, or at least 0.8 bar, or at least 1 bar, or at least 1.2 bar. 5. The system for conveying material according to any preceding claims, wherein the system is configured to allow movement of solid or liquid material substantially in one direction only.  6. The system for conveying material according to any preceding claims, wherein the system further comprises a solids conveyor on top of the first upper end (102) of the first vertical section (101) for feeding solid material to the tube.  7. The system for conveying material according to any preceding claims, wherein the means for feeding gas (108) to the tube comprises a nozzle grid, perforated plates or a set of single nozzles. 8. The system for conveying material according to any preceding claims, wherein the system is configured to convey fine particles (109) and to mix the fine particles (109) with gas (110) and to convey the fine particles and gas (111) to a reactor, silo, bin or the like. 9. The system for conveying material according to claim 8, wherein the fine particles (109) comprise metal oxides, and / or the gas (110) comprises water vapour, nitro-gen, ammonium or hydrogen and / or the fine particles and gas (111) are conveyed to a pres-surised reactor.  10. The system for conveying material according to claim 9, wherein the pres-surised reactor is a fluidised bed reactor for reducing metal oxides. 11. The system for conveying material according to claim 9, wherein the metal oxides comprise iron oxides. 12. A method for conveying material from a lower pressure to a higher pres-sure, the method comprising: a. feeding material to a first end (112) of a tube;b. feeding gas (110) to the tube through means for feeding gas (108); andc. conveying the material to a pressurised reactor, silo, bin or the like through a second end (113) of the tube;wherein the gas is fed to the tube in an amount to create a particle Froude number (Frp) of between 0.02 and 0.12, or between 0.03 and 0.1, in the horizontal cross-section of the tube with the largest area (112).  13. The method according to claim 12, wherein the tube comprises a first verti-cal section (101) comprising a first upper end (102) and a first lower end (103), a second vertical section (104) comprising a second upper end (105) and a second lower end (106) and a horizontal section (107), and wherein the first upper end (102) is arranged above the second upper end (105).  14. The method according to claim 12 or 13, wherein the material fed to a first end (112) of the tube comprise fine particles (109).  15. The method according to any of claims 12 to 14, wherein the material is conveyed to a pressurised reactor, preferably wherein the pressurised reactor is a fluidised bed reactor for reducing a metal. 16. The method according to any of claims 12 to 15, wherein the material is conveyed from a lower pressure to a higher pressure and wherein the difference between the lower pressure and the higher pressure is at least 0.5 bar, or at least 0.8 bar, or at least 1 bar, or at least 1.2 bar. 17. The method according to any of claims 13 to 16, wherein the gas (110) is fed to the tube in the horizontal section (107).

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