METHOD AND SYSTEM FOR NANOMATERIAL PRODUCTION

Abstract

The invention is concerned with a method for combined production of nanomaterials and heat. The method comprises feeding at least one precursor material and a fuel into a combustion unit for the generation of heat and nanoparticles, whereby the precursor material is combusted to be decomposed and oxidized in a sufficient temperature. The heat generated in the combustion of the fuel and the precursor material is recovered by using at least one heat exchanger. The combusted fuel is cooled down and the nanoparticles generated in the form of oxides in the combustion are collected. The system of the invention for combined production of nanomaterials and heat comprises a combustion unit, means for feeding at least one precursor material, fuel and oxidizer into the combustion unit for combustion, a heat exchanger for recovering heat from the combustion unit, and for cooling the combusted fuel, and means for collecting nanomaterials in the form of oxides from the combustion of the precursor material(s).

Claims

1. Method for combined production of nanomaterials and heat, the method comprising the steps of a) feeding at least one precursor material and a fuel into a combustion unit (11) for the generation of heat and nanoparticles, whereby the precursor material is combusted to be decomposed and oxidized in a sufficient temperature, b) recovering the heat generated in the combustion of the fuel and the precursor material using at least one heat exchanger (12), c) cooling down the combusted fuel, and d) collecting the nanoparticles generated in the form of oxides generated in the combustion.

2. Method of claim 1, wherein step a) is preceded by dissolving said at least one precursor material in the fuel in one or more separate containers (4, 7) or mixers before feeding them into the combustion unit (11).

3. Method of claim 1 or 2, wherein compressed air is fed to the combustion unit (11) for dispersion a mixture of precursor material and liquid fuel into small droplets.

4. Method of any of claims 1-3, wherein Silver nitrate (AgNO.sub.3) is dissolved in a solution of the precursor material to be fed into the combustion unit (11).

5. Method of claim 1, wherein said at least one precursor material and fuel are fed separately into the combustion unit (11).

6. Method of claim 5, wherein said fuel is a liquid fuel and said at least one precursor material is fed by spraying in the form of droplets of a solution of the precursor material.

7. Method of claim 5, wherein said fuel is a gaseous and said at least one precursor material is fed in the form of droplets of a solution of the precursor material or suspended in a gas as solid particles.

8. Method of any of claims 1-7, wherein said at least one precursor material is selected from sulphates, chlorides, nitrates, carbonates, and hydroxides of Lithium (Li), Titanum (Ti), Nickel (Ni), Manganese (Mn), Cobolt (Co), Aluminum (Al), Iron (Fe), Phosporus (P), Silver (Ag), Silicon (Si), Carbon (C), Niobium (Nb), Zinc (Zn), and Sulphur (S), and Titanium tetraisopropoxide (TTIP).

9. Method of any of claims 1-8, wherein the fuel is ethanol, methanol, propanol, natural gas, liquefied natural gas, LNG, or hydrogen, acetylene, methane, or propane.

10. Method of any of claims 1-9, wherein the oxidizing of the precursor material is performed by feeding an oxidizer into the combustion unit (11), such as air, a gas containing more oxygen than air, or pure oxygen gas (O.sub.2).

11. Method of any of claims 1-10, wherein the nanoparticles generated in the form of oxides from the combustion of the precursor material(s) consist of Lithium-Titanium oxide, Li.sub.2TiO.sub.3 or Li.sub.4Ti.sub.5O.sub.12, LTO), Lithium Nickel Manganese Cobalt Oxides (LiNi.sub.xMn.sub.yCo.sub.zO.sub.2, Li-NMC), Lithium Iron Phosphate (LiFePO.sub.4, LFP), Lithium Manganese Oxide (LMO, LiMn.sub.2O.sub.4, Li.sub.2MnO.sub.3, LiMnO.sub.2, and/or Li.sub.2MnO.sub.2, and/or different composites, (LMO).

12. Method of claim 11, wherein a stoichiometric ratio of Lithium/Titanium of 4:5 is used in the precursor feed for forming Li.sub.4Ti.sub.5O.sub.12.

13. Method of claim 12, wherein nanosized LTO articles of Li.sub.4Ti.sub.5O.sub.12 with a size of 30-50 nm is produced optionally together with Ag nanoparticles with a size of 1-3 nm on the surface of the LTO particles.

14. Method of any of claims 1-11, wherein the combustion temperature used is sufficient to cause decomposition and reaction of the precursor materials, such as 1000-2500? C.

15. Method of any of claims 1-14, wherein a layer of carbon is provided on the nanoparticles by means of an incomplete combustion.

16. Method of any of claims 1-15, wherein at least part of the recovered heat is utilized for other industrial processes or for warming of buildings.

17. Method of any of claims 1-16 wherein at least part of the recovered heat is converted to electricity, preferably by means of a steam generator.

18. System for combined production of nanomaterials and heat comprising a) a combustion unit (11), b) means for feeding at least one precursor material, fuel and oxidizer into the combustion unit for combustion, c) a heat exchanger (12) for recovering heat from the combustion unit (11), and for cooling the combusted fuel, d) means (13) for collecting nanomaterials in the form of oxides from the combustion of the precursor material(s).

19. System of claim 18, wherein the combustion unit (11) is an industrial heat plant, wherein heat is generated and utilized for other industrial processes or for warming of buildings.

20. System of claim 18, wherein the combustion unit (11) is an industrial power plant, wherein heat and electricity are produced.

21. System of claim 20, wherein the industrial power plant is a Combined Heat and Power, CHP, plant.

22. System of any of claims 18-21, wherein the combustion unit (11) comprises a burner (8) for liquid fuel.

23. System of any of claims 18-21, wherein the combustion unit (11) comprises a burner (8) for gaseous fuel, such as a ring burner (8), where several individual burner heads form a ring.

24. System of any of claims 18-23, wherein the means (13) for collecting the nanomaterials is a bag filter (13) or an electrostatic precipitator or other filtering equipment or a cyclone or a scrubber.

Description

FIGURES

[0059] FIG. 1 is a schematic view of a first embodiment of the invention for producing heat and metal oxide nanoparticles

[0060] FIG. 2 is a schematic view of a second embodiment of the invention for producing heat and metal oxide nanoparticles

DETAILED DESCRIPTION

[0061] FIG. 1 is a schematic view of a first embodiment of the invention for producing heat and metal oxide nanoparticles.

[0062] As a whole, reference number 1, marked with dotted lines, represents the precursor material input needs for the nanoparticle production part of the invention, which optionally can be placed in a separated space or container, whereas reference number 2, also marked with dotted lines, represents the input needs of the heat generation part of the invention, which optionally can be in another separated space or container.

[0063] A fuel, which in the embodiment of FIG. 1, consists of liquid ethanol, is fed from a fuel tank 3 into a buffer tank 4 having a mixer.

[0064] A precursor material, which in this embodiment is assumed to be solid Lithium nitrate (LiNO.sub.3), is fed from a (LiNO.sub.3) powder storage 5 into the buffer tank 4 to be dissolved in the ethanol, where it forms a stable solution without solid precipitation.

[0065] Then a liquid Titanium tetraisopropoxide (TTIP) precursor is mixed with the ethanol and lithium nitrate solution just before entering a burner 8. For this reason, it is practical to first feed the ethanol and lithium nitrate solution to another tank with a mixer 7, before adding the Titanium tetraisopropoxide (TTIP) precursor from a storage 6 into it in said tank with the mixer 7, which e.g. can be a static pipe mixer or a tank with a mixer. It is important for the burner operation that all precursors are fully dissolved and stay in the solution and no precipitates are formed.

[0066] Other embodiments of the invention might use only one precursor material, whereby the tank and mixer 7 is not necessary or then more than one precursor materials might be fed into the same buffer tank 4.

[0067] In addition, AgNO.sub.3 can be dissolved in the precursor solution and fed into the burner with the LiNO.sub.3 and TTIP to enhance the performance of the LTO nanomaterial in the battery to be produced.

[0068] The AgNO.sub.3 can also be added before adding the TTIP, whereby it can be mixed into the ethanol in the same buffer tank, wherein LiNO.sub.3 is added into the ethanol.

[0069] The ethanol-LiNO.sub.3-TTIP solution is then fed into a combustion unit having a burner 8, wherein the ethanol-LiNO.sub.3-TTIP precursor material is combusted.

[0070] The flame temperature that is provided in the burner 8 by means of ignition gas is typically nearly 2000? C., usually 1800-2100? C., resulting in the decomposition of the LiNO.sub.3 and TTIP and formation of metallic Li and Ti in an oxidising environment. Li, Ti and oxygen will then react to form Li.sub.4Ti.sub.5O.sub.12 (LTO). The formation of Li.sub.4Ti.sub.5O.sub.12 is sensitive to the molar ratio of lithium and titanium in the precursor. For example, a stoichiometric ratio of Li/Ti, i.e. 4:5, could be used. The firmed Li.sub.4Ti.sub.5O.sub.12 can be used directly as an anode material in Li-ion batteries.

[0071] Another Lithium-Titanium oxide, Li.sub.2TiO.sub.3, LTO) for producing a cathode material for Lithium-ion batteries Li.sub.2TiO.sub.3 can be formed by changing the Li/ti ratio in the fed precursor solution.

[0072] The oxidizing environment is achieved by feeding air with e.g. an air fan 9 thus oxidizing the precursor materials and the ethanol to produce heat. Instead of air, a gas containing more oxygen than air can be used, even pure oxygen gas O.sub.2. The heat is mainly a result of the combustion of the fuel but partly from the chemical reaction and decomposition of the precursor materials. In this case the decomposition/reactions LiNO.sub.3 consumes heat and the decomposition/reactions of TTIP produces heat.

[0073] In the burner 8, compressed air 10 is used to disperse the ethanol fuel-(Li, Ti) precursor mixture into small droplets (mist, droplets preferable below 100 ?m). A part of the air is usually consumed by the oxidation reaction of the precursor materials. The burner is a liquid fuel burner, by means of which the mixture of air and fuel/precursor droplets is ignited to burn at a high temperature to decompose the precursors into Li/Ti oxides and the ethanol fuel forms CO.sub.2 and H.sub.2O.

[0074] There is a boiler 11 in the combustion unit in connection with the burner 8, which boiler 11 consists of a furnace in which the fuel and precursor mixture is burned, and further, the boiler 11 consists of heat surfaces (not shown) to transmit heat from the combustion products as recovered by a heat exchanger 12 is used to recover the heat and cool the flue gas resulting from the combustion.

[0075] In this example, only heat is produced but the invention can also be used in connection with a power plant that produce both heat and power, for example by means of steam superheating, wherein a heat recovery steam generator works as a boiler, i.e. as an energy recovery heat exchanger that recovers heat from the hot gas stream being the result of the combustion. It produces steam that can be used to drive a steam turbine or is used as process steam in industrial processes.

[0076] Thus, in this embodiment, a heating plant, which typically is used to produce heat, has been expanded to produce LTO nanomaterial simply by dissolving its precursors in ethanol. Now both heat as well as LTO nanoparticles are produced in this power plant to give additional value for the heat production.

[0077] For the high electrochemical performance of the LTO in Li-ion batteries at high charge and discharge rates, it is important that it is composed of nanosized LTO primary particles, preferably with a size of 30-50 nm, to achieve short electronic and ionic conduction pathways. Ag nanoparticles with a size of 1-3 nm on the surface of the LTO particles (30-50 nm) will further enhance the electronic and ionic conductivity of the LTO particles, which improves the LTO nanomaterial performance in Li-ion batteries.

[0078] The produced LTO nanoparticles are filtered by a filtering unit 13 such as with normal bag house filters that are typically used in power plants for fuel gas cleaning and collected in a LTO container 14. The cleaned exhaust gas is led out to air through a stack 15.

[0079] Also, an electrostatic filter could be used. Thanks to the heat exchanger, which is situated before the filtering unit, the exhaust gas has been cooled down thus enabling collecting of the nanoparticles.

[0080] This is an inventive and advantageous part of the invention compared to prior art, wherein exhaust gases in power plants are cooled down by e.g. air, wherein the price for the filter bag is many times higher since it has to be dimensioned for a very big amount of gas.

[0081] Thus, the heat exchanger(s) used in the invention has two functions. In addition to heat recovery, it cools down the exhaust gas to a suitable temperature (preferable below) 200? ? C. for flue gas cleaning systems.

[0082] FIG. 2 is an architecture view of a second embodiment of the invention for producing heat and metal oxide nanoparticles.

[0083] In this example the fuel used is Hydrogen (H.sub.2) gas, which is led from storage 3 to be burned by e.g. a ring burner 8, where several individual burner heads form a ring. Any gas burner, however, could be used for producing a controlled flame by mixing the fuel gas, here hydrogen, with an oxidizer such as the ambient air or supplied oxygen, and allowing for ignition and combustion.

[0084] Droplets of a water solution of e.g. inorganic sulphates of different metals, such as Li.sub.2SO.sub.4, NiSO.sub.4, MnSO.sub.4, and CoSO.sub.4 are sprayed into the middle of the burner ring from storages 5 (not distinguished in the figure). Instead of or in addition to Li.sub.2SO.sub.4, a useful Li-precursor is LiNO.sub.3. The droplet size can be of the order of 10-100 micrometers.

[0085] The oxidizing environment is achieved by feeding the hydrogen gas together with combustion air from a storage 9 thus oxidizing the precursor materials and the hydrogen to produce heat. [0086] (a) The inorganic metal precursors decompose completely in the burner flame achieved by means of ignition gas and then they react and form the desired LiNiMnCoO final product consisting of different oxides of the metals, i.e. Li, Ni, Mn, and Co. They have the general formula LiNi.sub.xMn.sub.yCo.sub.zO.sub.2. (such as LiNiMnCoO.sub.2, and are abbreviated Li-NMC, LNMC, NMC, or NCM). The fractions of the metals can be varied by changing their concentrations in the water solution precursor. [0087] (b) The temperature profile of the particle formation can be varied by modifying the fuel-to-precursor feed rate ratio. Thus, it is possible to achieve conditions where the inorganic metal precursors do not vaporize but react in the droplet phase to form the desired final LiNi.sub.xMn.sub.yCo.sub.2O.sub.2 product. The fractions of the metals can be varied by changing their concentrations in the water solution precursor. In this case the final product is composed of larger particles.

[0088] As in the embodiment of FIG. 1, there is a boiler 11 in the combustion unit in connection with the burner 8, which boiler 11 consists of a furnace in which the fuel and precursor mixture is burned, and further, the boiler 11 consists of heat surfaces (not shown) to transmit heat from the combustion products as recovered by a heat exchanger 12 is used to recover the heat resulting from the combustion.

[0089] The produced Li-NMC particles are collected by normal bag house filters 13 that are typically used in power plants for flue gas cleaning and collected in a Li-NMC container 14. The cleaned exhaust gas is led out to air through a stack 15.

[0090] As in the embodiment of FIG. 1, also here only heat is produced but also electricity could be produced.

[0091] Thus, in this embodiment a heating plant has been expanded to produce Li-NMC material simply by dissolving its precursors in water and spraying the solution into the gas flame, which is typically used to produce heat without metal precursors. Now both heat and Li-NMC particles are produced in this power plant to give added value for the heat production.

EXAMPLES

Example 1

[0092] In a process in accordance with FIG. 1, for example in a 10 MW (fuel power) plant, lithium and titanium precursors can be fed in a stoichiometric ratio (up to 2 moles/litre solution in liquid fuel (e.g. ethanol) to produce LTO nanomaterial.

[0093] A solution of 51 kg/h LiNO.sub.3, 280 l/h TTIP and 1 400 l/h ethanol was combusted to produce 71 kg/h LTO nanomaterial. Silver doping of the particles was achieved by adding AgNO.sub.3 to the precursors.

[0094] LTO material with a primary particle size of 20 nm measured by transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) was produced in a laboratory scale burner. The specific surface area SSA of the formed nanoparticles was 87 m.sup.2/g and the silver (Ag) concentration was 1 wt % measured by Inductive coupled mass spectrometer (ICP-MS).

Example 2

[0095] In a process in accordance with FIG. 2, for example in a 10 MW (fuel power) gas fired power up to 2 moles/litre water solution of Li, Ni, Mn and Co precursors can be sprayed as small droplets (droplet size below 100 ?m) to produce NMC li-ion battery cathode material plant,

[0096] Accordingly, 59 kg/h LiNO.sub.3, 79 kg/h NiSO.sub.4, 26 kg/h MnSO.sub.4 and 27 kg/h CoSO.sub.4 in water solution are fed to produce 83 kg/h NMC622 material.

Example 3

[0097] Lithium titanate (LTO) production in a traditional Light Fuel Oil burner (LFO) burner was tested. A commercial LFO burner was converted to an ethanol burner according to the manufacturer's recommendations.

[0098] A fuel mixture of 49 g/h of Li-nitrate and 260 ml/h of Ti-tetraisopropoxide in 1.3 l/h of ethanol was burned in the modified LFO burner to produce 83 g/h of LTO powder.

[0099] A collected powder sample was analyzed by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) for morphology and chemical composition, an organic carbon and elemental carbon (OC/EC) analyser to determine the elemental carbon (soot) and organic carbon content as well as X-ray powder diffraction (XRD) to analyse the LTO crystal phase.

[0100] The production rate was calculated to be 0.5 g/h with a collection efficiency of 60%.

[0101] As can be seen from this, some particles were lost in the heat exchanger and flue gas lines. The total carbon content of the product was 1.24% of which the organic carbon content was 1.07% and soot 0.15%. The XRD showed that crystalline lithium titanate particles were produced.