Iron ore reducing and melting apparatus providing plasma assisted hydrocarbon cracking

Abstract

An iron ore reducing and melting apparatus comprising a blast furnace said furnace comprising: -at least one gas injector on the tuyere level adapted to introduce methane gas into the furnace, -at least one heater adapted to heat the methane gas to be introduced into the furnace to above 500 °C; -at least one oxygen gas injector port on the tuyere level adapted to provide oxygen gas comprising at least 80 vol.-% oxygen.

Description

[0001] IRON ORE REDUCING AND MELTING APPARATUS PROVIDING PLASMA ASSISTED HYDROCARBON CRACKING

[0002] BACKGROUND

[0003] In a typical blast furnace , a hot blast ( i . e . air which is heated to about 1200 ° C ) is blown into the blast furnace as a blast gas from a tuyere . As a result , oxygen in the hot blast reacts with coke or pulverized coal to produce thermal energy and the reducing agents carbon monoxide (CO ) and hydrogen ( H2) gases . These carbon monoxide and hydrogen gases reduce iron ore charged into the blast furnace . In addition, carbon dioxide and steam are produced during the reduction reaction of the iron ore .

[0004] However , there is a desire to reduce carbon dioxide emissions .

[0005] Important carbon dioxide emission reduction in blast furnaces can be achieved when changing from hot blast to gas comprising more than 80 vol . -% oxygen . This approach allows to inj ect high amounts of auxiliary fuel at the tuyere level , which can help to reduce the coke requirement and finally the carbon dioxide production of the furnace . Ideally these auxiliary fuels are lean in carbon, such as for example methane , hydrogen, and others .

[0006] Nevertheless , not having the high temperature and flow rate provided by the hot blast anymore will require to burn a substantial amount of coke and possibly pulverized coal ( PCI ) together with substantial amounts of cold oxygen to produce the flame temperature , when simultaneously inj ecting carbon lean fuels such as methane , hydrogen, or others required to transfer the heat to the solid charge for its direct reduction and melting of the iron and the slag phase . In the lower part of a blast furnace , i . e . in the reducing atmosphere , there will be only the combustion or partial oxidation ( 2C+O2--> 2 CO ) of carbon containing species which can supply the required heat levels . In addition, hydrogen cannot be oxidized and thus hydrogen components are cooling the flame temperature rather than heating it . Promising auxiliary fuels replacing other fuels to be used at tuyere level with respect to carbon dioxide emission reduction of the blast furnace process are hydrocarbons like, for example, methane, and fuels like hydrogen gas .

[0007] However, it was observed that methane and other hydrocarbons tend to crack when heated up in hydrogen resulting in the production of carbon and / or soot particles which results in operational problems of the heaters .

[0008] Therefore, it is an object of the invention to provide an iron ore reducing and melting apparatus as well as method of operating an iron ore reducing and melting apparatus addressing the above discussed issues .

[0009] SUMMARY

[0010] The invention solving the above described problem is defined by the appended claims .

[0011] Disclosed is an iron ore reducing and melting apparatus comprising a blast furnace said furnace comprising: at least one gas injector on the tuyere level adapted to introduce methane gas into the furnace, at least one heater adapted to heat the methane gas to be introduced into the furnace to above 500 °C; at least one oxygen gas injector port on the tuyere level adapted to provide oxygen gas comprising at least 80 vol.-% oxygen.

[0012] The methane gas can comprise at least 10 vol.-%, 20 vol.-%, 30 vol.- %, 40 vol.-%, 50 vol.-%, 60 vol.-%, 70 vol.-%, 75 vol.-%, 80 vol.-%, 90 vol.-%, or 95 vol.-% methane or pure methane. The remainder of the methane gas can be nitrogen, carbon monoxide, hydrogen, hydrocarbons which are not methane, water, and / or carbondioxide, or mixtures thereof . For example , the methane gas can be natural methane gas or regenerative methane gas produced in the iron ore reducing and melting apparatus or produced by integrating gases from the reducing and melting apparatus which are not produced in the furnace .

[0013] The oxygen gas can comprise 80 % or more , preferably 90 % or more , 95 or more or 100% by volume percent pure oxygen . The remainder of the oxygen gas other than oxygen maybe carbon monoxide , carbon dioxide , hydrogen, hydrocarbons ( other than methane ) , water / vapor and / or nitrogen .

[0014] It has been surprisingly found that when methane gas is heated to temperatures above 500 ° C and ( at least partially) cracked, the produced carbon and soot particles will help to achieve the required flame temperature in the conditions of the raceway . In fact , this process has the effect of reducing the requirement for coke and or PCI burning , specifically since the hydrogen resulting from the hydrocarbon cracking ( as well as the remaining hydrocarbon and possibly other gases being part of the gas ) are also heated, thereby helping to achieve the required flame temperature . Additionally, the carbon and soot particles will burn ( i . e . at least be partially oxidized ) within the furnace in the raceway at the required high temperatures together with the inj ected oxygen gas further increasing the flame temperature .

[0015] The iron ore reducing and melting apparatus may also contain at least one gas inj ector on the shaft level adapted to introduce methane gas into the furnace . The total amount of methane gas being supplied to the iron ore reducing and melting apparatus may be divided between the at least one gas inj ector on the tuyere level and the at least one gas inj ector on the shaft level . The amount of the methane gas being supplied to the at least one gas inj ector on the tuyere level may be more than 50% , 60% , 70% , 80% , or 90 & , or may be 100% of the total amount of methane gas being supplied to the iron ore reducing and melting apparatus and thus the amount of the methane gas being supplied to the at least one gas inj ector on the shaft level may be less than 50% , 40% , 30% , 20% , or 10% , or may be 0% of the total amount of methane gas being supplied to the iron ore reducing and melting apparatus .

[0016] Injecting more methane gas on the tuyere level than on the shaft level has been found to assist in reducing the requirement for coke and or PCI burning.

[0017] The at least one gas heater can be adapted to heat the methane gas to 500 °C - 2600 °C, 600 °C - 2600 °C, 700 °C - 2600 °C, 800 °C - 2600 °C, 900 °C - 2600 °C, 1000 °C - 2600 °C, 1100 °C - 2600 °C, 1200 °C - 2600 °C, 1300 °C - 2600 °C, 1400 °C - 2600 °C, 1500 °C - 2600 °C, 1600 °C - 2600 °C, 1800 °C - 2600 °C, 2000 °C - 2600 °C, or 2100 - 2200 °C.

[0018] Heated methane gas is methane gas at the above disclosed temperatures.

[0019] The iron ore reducing and melting apparatus can be adapted to heat the methane gas by contacting the methane gas directly with the at least one heater or by contacting the methane gas with another gas, like hydrogen gas or transfer gas, heated by the at least one heater.

[0020] It was found that at these temperatures the burning of the carbon and soot particles in the raceway with oxygen gas especially in presence of hydrogen gas is particularly efficient. This temperature level is well suited to reduce requirement for coke burning in the raceway of the furnace with oxygen and therefore reduces the carbondioxide footprint .

[0021] The at least one heater can be adapted to operate at an electric power of 100 - 1000 kwh / t, 150 - 900 kwh / t, or 200 - 700 kwh / t of hot metal. Preferentially, two or three heaters are used to provide in sum a power of 200 - 700 kwh / t of hot metal.

[0022] The electric power is suitable for heating the gas to the desired temperatures .

[0023] The at least one heater can be an electrically driven heater. Electrically driven heaters provide advantages with regard to energy output , overcall control and maintenance over other heaters

[0024] Alternatively, the at least one heater can be a heater using chemical energy .

[0025] The at least one electrically driven heater can be an electric resistance heater .

[0026] Electric resistance heaters are especially simple in maintenance .

[0027] The at least one heater can be a plasma torch .

[0028] A plasma torch is an electrically driven device capable of heating gas to the physical state of plasma . Plasma torches can provide high gas temperatures , unattained by conventional heating systems . Moreover plasma torches allow a flexible operation with regard to flowrates and temperature . In addition, it is compact technology having a low volumetric footprint . Thus , plasma torches are especial suitable for achieving the required heating temperatures .

[0029] A plasma torch can be especially ( energy) efficient in providing the desired temperatures and is especially efficient when heating a gas from an already high temperature to an even higher temperature which is almost not efficiently possible with standard technologies .

[0030] The plasma torch can be an electrode-comprising or electrodeless plasma torch .

[0031] In an electrodeless plasma torch, the plasma is inductively ignited, thus no electrodes are needed . Such devices are especially useful in the apparatus and method of the disclosure since no electrodes can be clogged or covered by soot or other debris .

[0032] Electrodeless plasma torches can be microwave (MW) plasma and radiofrequency ( RE) plasma torches . The plasma torch can also be an electrode-comprising plasma torch . The electrodes can be graphite electrodes .

[0033] The electrodes of electrode comprising plasma torches can be used directly in the gas stream to be heated producing an arc directly in the gas stream between the electrodes .

[0034] Electrode-comprising plasma torches are very energy efficient in providing the required temperatures to the gas which is to be inj ected into the furnace .

[0035] When the plasma torch is an electrode-comprising plasma torch, the iron ore reducing and melting apparatus can further comprise a plasma torch electrode exchanging / amendment device adapted to automatically replace at least one used or eroded electrode of the plasma torch with an unused electrode / amend the used electrode with at least one new electrode .

[0036] When the plasma torch is an electrode-comprising plasma torch, the iron ore reducing and melting apparatus can further comprise an electrode paste column or paste feeder .

[0037] The at least one plasma torch electrode exchanging / amendment device may further comprise a magazine for unused electrodes .

[0038] The at least one plasma torch can be an alternating current plasma torch .

[0039] For example , the alternating current plasma torch can be a 3-phase alternating current plasma torch, having 3 or a multiplicity of 3 electrodes .

[0040] The at least one plasma torch can be a 3 phase alternating current plasma torch which is adapted to provide a ( gas ) velocity within the arc perimeter of the plasma torch of 1 -120 m / s , preferably 5 -60 more preferably 18 to 60 m / s . The inter-electrode distance of the plasma torch, particularly of the 3-phase alternating current plasma torch can be adj ustably employing moving inclined electrodes . The inter-electrode distance may be 0-150 mm, 10-100 mm, or 20-80 mm. The adj ustability allows for easy plasma ignition and higher plasma controllability and thus , stability .

[0041] Alternating current plasma torch, particularly the 3-phase alternating current plasma torch can have 3 or a multiplicity of 3 electrodes ( e . g . 3 , 6 , 9 , 12 , 15 , 18 , 21 electrodes ore more ) . A higher number of electrodes can improve the control of the plasma and increase the plasma torch power .

[0042] The apparatus can further comprise power supplies powering the at least one plasma torch or torches .

[0043] Preferably, one power supply powers 1-5 , 1-3 , or 1 of the at least one plasma torches .

[0044] Use of multiple plasma torches powered by multiple power supplies of up to 30 MW ( one power supply drives at least one plasma torch) has advantages over using one power supply of total capacity equal to the summation of the capacities of all low-capacity power supplies . The flickering imposed to the electrical grid by plasma torch operation fluctuation in the former case is way less severe than in the latter .

[0045] It can be advantageous to use a power supply with up to 5 times the power of the individual plasma torch in combination with each respective plasma torch to provide a stable operation .

[0046] Moreover, using multiple power supplies of up to 30 MW gives better controllability and flexibility : when a power supply fluctuates or crashes , there is no disturbance propagation to the whole system and the furnace may keep running without severe issues since the other power supplies can collectively provide the power input of the crashed power supply . In addition, one or more spare power supplies can be installed online and in case of failure of a main power supply, a switching over to the spare one assures steady-state operation at full power . During the next planned maintenance shift , the repair can be done , thereby, a production loss never occurs .

[0047] Yet , high number of power supplies lead to high cost , high power losses and high space requirements , thus , an optimum number of power units has to be selected . In the furnace as defined above at least 10 power units and up to 70 power units , most preferably 18 -52 power units are used .

[0048] The plasma torches can be 3 phase AC plasma torches which are adapted to provide a ( gas ) velocity within the arc perimeter of the plasma torch of 1 -120 m / s , preferably 5- 60 more preferably 18 to 60 m / s . Within these ranges the optimal conditions for heating the gas are provided . In case that not all gas to be heated can pass through this perimeter , the remainder of the gas to be heated will be supplied outside of this perimeter .

[0049] In addition it is provided a plasma torch and a method of using that plasma torch that reduces the thermal load on the wall lining surrounding the plasma torch .

[0050] Thus , the apparatus , e . g . the plasma torches , can be adapted to split the incoming gas into two streams . In particular, the configuration of the plasma torch provides a first stream flowing centrally through the arc created by the plasma torch and a second stream flowing peripherally around the arc .

[0051] The central stream can flow through the plasma arc and will be heated to very high temperature . The second stream, which can be inj ected shortly upstream or downstream of the plasma arc , is orientated in such way that it acts as a protection of the refractory lined walls of the plasma burner chamber from the heat of the central high temperature stream . This reduces the thermal load on the wall lining . It is possible that the gas passing through the plasma area and the surrounding gas are of different nature. It might for example be that the gas passing through the plasma is a methane containing gas whereas the gas second stream flowing peripherally around the arc is hydrogen gas. Also vice versa or other combinations are possible.

[0052] Alternatively, the plasma torch can be a direct current plasma torch (e.g. having 2 or a multiplicity of 2 electrodes) .

[0053] Direct current plasma torch have a stable arc, which might be swirling between the (fixed) electrodes.

[0054] Direct current plasma torches have the advantage that they are rather compact in size, i.e. do not require substantial amounts of space.

[0055] Direct current plasma torch can have 2 or a multiplicity of 2 electrodes (e.g. 2, 4, 6, 8, 12, 14, 16, 18, 20) . A higher number of electrodes can improve the control of the plasma and increase the plasma torch power.

[0056] The ore reducing and melting apparatus may further comprise a supply of a thermal transfer gas or hydrogen gas and the at least one plasma torch is adapted to heat the thermal transfer gas or hydrogen gas. Furthermore, the iron ore reducing and melting apparatus is adapted to heat the methane gas with the heated thermal transfer gas.

[0057] Due to this heat transfer mechanism direct contact between the methane gas and the arc is avoided and the application of direct current torches in the heating of methane gas is improved.

[0058] For example, direct current plasma torches (e.g. with permanent electrodes) may not allow for direct integration of methane gas as the plasma gas since the production of carbon particles and or soot may block the plasma torch and or disturb the formation of the arc. However, indirect heating may also be useful when using other types of plasma torches ( e . g . with consumable electrodes , other AC and DC torches ) .

[0059] The thermal transfer gas in the sense of the disclosure is a gas that does not react chemically or to very low degree with electrodes . For example , the thermal transfer gas may comprise nitrogen and / or argon amongst other gases .

[0060] The electrodes of the DC plasma torch might be cooled or uncooled electrodes and may be of different materials such as predominantly be built of copper or graphite .

[0061] In case of cooled copper we talk about permanent electrodes . In case of graphite we talk about consumable uncooled electrodes . In the latter case an electrode feeding mechanism will be foreseen to compensate for the graphite consumption .

[0062] The at least one plasma torch can have an electric power rating of 1 to 10 MW, preferably of 2 to 6 MW, most preferably of 4 to 5 MW .

[0063] Thus the iron ore reducing and melting apparatus may further comprise first and second dehydration devices for removing water from a gas stream exiting the furnace . The iron ore reducing and melting apparatus may further comprise a methane gas generation device for producing regenerative methane . For example , the methane gas generation device may provide a methane gas starting from hydrogen and carbon monoxide and / or carbon dioxide generated in the iron ore reducing and melting apparatus and optionally supplemented with those gases from external sources .

[0064] The iron ore reducing and melting apparatus may further comprise an oxygen supply device configured for inj ecting oxygen at the tuyere level of the smelting furnace via an oxygen gas inj ector , or an oxygen inj ection port .

[0065] The iron ore reducing and melting apparatus may further comprise an oxygen gas heater . The iron ore reducing and melting apparatus according to any of the above claims, wherein an oxygen injection port is arranged within the gas injector for injecting methane.

[0066] The oxygen gas heater or the iron ore reducing and melting apparatus can be adapted to provide oxygen via the oxygen port at a temperature of 20°C to 800 °C, 100°C to 800 °C, 200°C to 800 °C, 300°C to 800 °C.

[0067] The iron ore reducing and melting apparatus may further comprise a powdered coal injector port, an injector port for tar, an injector port for oil, an injector port for plastic or / and an injector port for other auxiliary fuels .

[0068] It has been found that these temperatures are especially useful for reaching the desired burning temperatures of coal particles .

[0069] The iron ore reducing and melting apparatus may further comprise at least one second methane gas heater upstream of each respective at least one first heater, wherein the at least one second heater is adapted to heat the methane to 450°C - 550°C or 500°C. This first and / or the second gas heater may be electrically driven or also by burning a fuel as for example a steel plant gas or a mixture thereof as for example blast furnace gas.

[0070] In this way the power requirement of the first methane heater, especially of a plasma torch, can be reduced.

[0071] The at least one gas injector can also be adapted to provide hydrogen gas .

[0072] For example, hydrogen gas, oxygen gas and / or methane gas can be heated by separate heaters and optionally be partially or completely mixed in the at least one gas injector before being injected into the furnace . Alternatively, a different at least one gas injector is used for each of the gas types hydrogen gas, oxygen gas, methane gas.

[0073] The hydrogen gas mainly comprises hydrogen and carbon monoxide. The hydrogen gas may comprise more the 50 % (vol / vol) of hydrogen and carbon monoxide, the remainder being, for example, water, carbon dioxide hydrocarbons, and / or nitrogen. The hydrogen gas may have a (CO+H2) / (CO2+H2O) in % (vol / vol) that is bigger than 7, 8, or 9. The ( (CO+H2) / (CO2+H2O ) ) -ratio may be 6-80, 7-30, or 8-12.

[0074] Thus, the iron ore reducing and melting apparatus may further comprise at least one hydrogen gas injector adapted to provide hydrogen gas. Thus the hydrogen gas injector can be provided separate from the at least one (methane) gas injector.

[0075] The iron ore reducing and melting apparatus can be adapted to heat via the at least first heater, in particular at least one electrical heater, even more preferred at least one AC or DC plasma torch, methane gas, hydrogen gas, a gas comprising methane gas and hydrogen gas, or transfer gas .

[0076] Methane gas, hydrogen gas, a gas comprising methane gas and hydrogen gas, or transfer gas prior to being injected into the at least one heater can be preheated by a respective dedicated (pre-) heater as described above.

[0077] The iron ore reducing and melting apparatus is optionally adapted to mix the gas provided by the at least one heater with further methane gas, hydrogen gas, or gas comprising methane gas and hydrogen gas via respective dedicated ports.

[0078] The iron ore reducing and melting apparatus can be adapted to inject oxygen gas into the blast furnace via an oxygen gas injector port. In this way, the oxygen gas joins the gas heated by the at least one heater or the gas heated by the at least one heater and mixed with further gases as described above. The oxygen gas prior to being inj ected into the blast furnace can be preheated by an oxygen gas heater as described above .

[0079] The iron ore reducing and melting apparatus can further comprise at least one sensor adapted to analyze the composition of the gas at the top level . The sensor can be inside the furnace within the top level or can be connected to a piping which retrieves gas from the top level of the furnace .

[0080] The sensor can be of an electrochemical , catalytic bead (pellistor ) , photoionization, infrared point , infrared imaging, semiconductor , or ultrasonic type . The sensor of the semiconductor type can be a metal- oxide-semiconductor sensor . The sensor can be comprised in a gas chromatograph .

[0081] The at least one sensor can be adapted to detect a CO , C02 , or / and H2 concentration of the gas . The at least one sensor can also be adapted to detect a H20 , N2 , or / and CH4 or / and other hydrocarbon concentrations in the gas .

[0082] The iron ore reducing and melting apparatus may further comprise a gas inj ector regulating device configured to adapt the composition of the gas and / or the volume of the gas inj ected by the first and / or second gas inj ectors based on the determined gas composition and / or temperature at the top level .

[0083] The gas inj ector regulating device may also adapt the power supply to the at least one electrical heater based on the determined gas composition at the top level and / or temperature at the top level .

[0084] The gas inj ector regulating device may also be configured to adapt the composition of the gas and / or the volume of the gas inj ected and / or the temperature of the gas inj ected by the first and / or second gas inj ectors based on the composition and / or temperature of the hot metal outputted by the apparatus and the hot metal production rate . To determine the composition of the hot metal outputted by the apparatus and the hot metal production rate , the apparatus comprises further sensors positioned at the hot metal outlet of the furnace configured to determine the composition of the hot metal and / or to determine the volume of the hot metal .

[0085] The apparatus as defined above has the advantage that the oxygen consumption during hot metal production can be reduced and thus the CO2 emissions be reduced.

[0086] The hydrogen gas can comprise 30-100 % (vol / vol) hydrogen, optionally further comprising CO 10-70 % (vol / vol) with less than 35%, 10 % or 5% (vol / vol) of gaseous compounds that are not CO or H2.

[0087] The iron ore reducing and melting apparatus may further comprise at least one heater for heating hydrogen gas .

[0088] The heater can be any heater as described above, especially all above described electrical heaters.

[0089] The iron ore reducing and melting apparatus may further comprise a hydrogen gas injector (separate from the injectors for the other gases ) .

[0090] Alternatively or in addition, hydrogen gas may be injected by the

[0091] (methane) gas injector.

[0092] The apparatus, preferentially, the at least one hydrogen heater can be adapted to heat the hydrogen gas to 750 °C - 2600°C, 1000 °C - 2300 °C, or 1250 - 2200 °C-. The at least one hydrogen heater can be adapted to provide the heated gas at the tuyere level to the furnace.

[0093] The apparatus may also comprise an injection port for other fuels (e.g. pulverized coal) than those described above and this port may be separate or integrated with the at least first gas injector.

[0094] Disclosed is also a method for operating a furnace for reducing and melting iron ore comprising the steps of:

[0095] - heating a methane gas to 500 °C - 2600 °C by at least one heater; - injecting the methane gas into the furnace at tuyere level;

[0096] - injecting an oxygen gas comprising at least 80 vol.-% oxygen into the furnace at tuyere level .

[0097] The methane gas can be heated to 800 °C - 2600 °C, 900 °C - 2600 °C, 1000 °C - 2600 °C, 1100 °C - 2600 °C, 1200 °C - 2600 °C, 1300 °C - 2600 °C, 1400 °C - 2600 °C, 1500 °C - 2600 °C, 1600 °C - 2600 °C, 1800 °C - 2600 °C, 2000 °C - 2600 °C, or 2100 - 2200 °C.

[0098] The oxygen gas can be injected at a temperature of 20°C to 800 °C, 100°C to 800 °C, 200°C to 800 °C, 300°C to 800 °C.

[0099] The method may also utilize a iron ore reducing and melting apparatus containing at least one gas injector on the shaft level adapted to introduce methane gas into the furnace. The method may comprise dividing the total amount of methane gas being supplied to the iron ore reducing and melting apparatus between the at least one gas injector on the tuyere level and the at least one gas injector on the shaft level. The amount of the methane gas being supplied to the at least one gas injector on the tuyere level may be more than 50%, 60%, 70%, 80%, or 90&, or may be 100% of the total amount of methane gas being supplied to the iron ore reducing and melting apparatus and thus the amount of the methane gas being supplied to the at least one gas injector on the shaft level may be less than 50%, 40%, 30%, 20%, or 10%, or may be 0% of the total amount of methane gas being supplied to the iron ore reducing and melting apparatus.

[0100] Injecting more methane gas on the tuyere level than on the shaft level has been found to assist in reducing the requirement for coke and or PCI burning.

[0101] The methane can be heated prior to being heated by the first heater by at least one second methane heater to 500°C.

[0102] The at least one heater can be a heater as defined above. In particular, the at least one heater can heat a thermal transfer gas or hydrogen gas, the heated thermal transfer gas or hydrogen gas being brought into contact with the methane, and the heated thermal transfer gas heating and possibly cracking the methane.

[0103] The thermal transfer gas can comprise at least 10, 30, 50, 70, 90 vol.-% of pure nitrogen the remainder being other gases.

[0104] The thermal transfer gas can comprise at least 10, 30, 50, 70, 90 vol.-% of pure argon the remainder being other gases.

[0105] The thermal transfer gas can comprise at least 10, 30, 50, 70, 90 vol.-% of pure argon and pure nitrogen the remainder being other gases.

[0106] The method may further comprise injecting hydrogen gas into the furnace at tuyere level .

[0107] The method may involve the use of any of the apparatuses and conditions as described above in relation to the iron ore reducing and melting apparatus .

[0108] Disclosed is also a system comprising an apparatus as described above and a computer-based control or regulation system, wherein the system is adapted to perform the method as described above.

[0109] BRIEF DESCRIPTION OF FIGURES

[0110] Figure 1 schematically illustrates an iron ore reducing apparatus according to the disclosure.

[0111] Figure 2 schematically illustrates a further iron ore reducing apparatus according to the disclosure.

[0112] DESCRIPTION OF THE DISCLOSURE

[0113] Description of the figures Figure 1 schematically illustrates an iron ore reducing and melting apparatus 1 as disclosed in this application. Each of the elements of the apparatus, especially, the devices, generators etc. are also separately disclosed. In addition, the apparatus 1 as disclosed can comprise any number of the illustrated devices, generators etc.

[0114] The object is the heating of a methane gas by help of an heater, especially a plasma torch in order to achieve a certain temperature level . At this temperature level the methane may be cracked in carbon particles and hydrogen (CH4--> C + 2 H2 ) .

[0115] The arrows with solid lines symbolize piping and the direction of the flow of material within the apparatus 1.

[0116] The apparatus 1 comprises a blast furnace 2. The blast furnace 2 from bottom to top comprises a hearth 11, a region comprising the tuyeres, i.e. a tuyere level 12, a shaft region comprising the shaft level 14, and a top level 15.

[0117] On the tuyere level 12, at least one methane gas injector 8 is installed. The methane gas injector 8 is used to inject methane gas into the blast furnace 2.

[0118] The at least one methane gas injector can comprise or be connected to a methane gas heater 19, i.e. an electrically driven heater, preferentially a plasma torch (9) . In Figure 1 the methane gas heater 19 is shown separated from the methane gas injector 8.

[0119] On the tuyere level 12, at least one hydrogen gas injector 6 is installed. The hydrogen gas injector 6 is used to inject hydrogen gas into the blast furnace 2.

[0120] The at least one hydrogen gas injector 6 can comprise or be connected to a hydrogen gas heater 18, e.g. an electrically driven heater, preferentially a plasma torch (9) . In Figure 1 the hydrogen gas heater 18 is shown separated from the hydrogen gas injector 8. Alternatively, the at least one hydrogen gas injector 6 and the at least one methane gas injector 8 can be combined into one gas injector as explained with reference to figure 2 below. The combined gas injector may also be used for PCI or the injection of other fuels.

[0121] The tuyere level 12 (or region) can also be used to inject oxygen into the blast furnace 2 via at least one oxygen gas injector 10. The at least one oxygen gas injector 10 can comprise or be connected to an oxygen gas heater 20, e.g. an electrically driven heater. In Figure 1 the oxygen gas heater 20 is shown separated from the oxygen gas injector 10.

[0122] Alternatively, the at least one hydrogen gas injector 6 and the at least one methane gas injector 8 can be combined into one gas injector (as illustrated below with respect to figure 2) comprising a methane gas injection port 7 and a hydrogen injection port 5. The combined gas injector may also be used for PCI or the injection of other fuels.

[0123] A lock hopper 16 is used to provide material (e.g. coke, ore, and optionally fluxes) to the interior of the blast furnace while securing that the pressure conditions in the blast furnace 2 are maintained. Alternatively, the blast furnace 2 may be open at the top lacking a lock hopper 16 and be in direct contact with the atmosphere.

[0124] On the shaft level 14 the blast furnace can also comprise at least one by-product injector 4, which can be used to inject by-product gas into the upper shaft level / region. The CO2 content of by-product gas may be partially or fully captured.

[0125] Alternatively or in addition, the blast furnace may also comprise at least injector port for injecting coke oven gas, methane, H2, NH3, further hydrogen gas, or other similar gases, which can be used to inject those gases into the lower shaft level / region (not illustrated in the figure ) .

[0126] The heating temperature (supply temperature) of the methane gas achieved by the methane gas heater 19 is preferably above 500°C, e.g. in the range of 500°C to 2600°C. The heating temperature ( supply temperature ) of the oxygen gas , if heated, is preferably in the range of 100 ° C to 800 ° C .

[0127] During the process methane , oxygen, and possibly hydrogen gas are inj ected at the tuyere level . Other fuels including coke and PCI coal can also be inj ected, for example , at the tuyere level . It was observed that methane when heated up tends to crack and react to carbon and soot particles and hydrogen respectively .

[0128] When methane is heated to temperatures above 500 ° C , for example , with an electrical heater like a plasma torch 2 aspects are observed : whereas the inj ection of methane into the furnace and its subsequent combustion with the inj ected oxygen leads to a certain increase in temperature , to about 500 ° C, the thermal energy liberated in the raceway by the partial combustion of carbon and soot particles together with the oxygen in the raceway of the furnace ( in or after the outlet of the inj ector ) will help much more in achieving the desired flame temperature and thus lower the requirement for PC and / or coke burning . Thus , the effect of the carbon particles from the methane cracking in the raceway is similar to the effect of PCI inj ection according to following chemical reaction : 2 C + 02 — > 2CO AH=-221 kJ .

[0129] Second due to the elevated temperature of the cracked methane ( cracked and / or uncracked ) less coke needs to be burnt to achieve the high flame temperature required to melt the iron ore in the furnace .

[0130] Thus , by inj ecting hot and at least partially cracked methane together with oxygen in the reductive environment inside the blast furnace at tuyere level the iron ore provided in the blast furnace can be melted and reduced to metal .

[0131] During the reduction reaction of the ore material , carbon dioxide , carbon monoxide and hydrogen may be generated and then discharged from the head of the blast furnace as a by-product gas . In addition, water vapor may condense due to the expansion and cooling of the blast furnace by-product gas which is the by-product gas discharged from the head of the blast furnace as it returns to normal pressure . The condensate is then removed through a first dehydration device 21 .

[0132] The methane gas can be and / or can be provided from different sources , for example , NG, COG, coal gas , synthetically produced methane by methanation, methanation using steel plant off gases as for example , using the blast furnace gas to recover components like CO , C02 and / or hydrogen, and . bio-methane .

[0133] Figure 2 schematically illustrates a further iron ore reducing and melting apparatus 24 as disclosed in this application . Each of the elements of the apparatus , especially, the devices , generators etc . are also separately disclosed . In addition, the apparatus 24 as disclosed can comprise any number of the illustrated devices , generators etc .

[0134] Basically the apparatus 24 of figure 2 only differs from apparatus 1 of figure 1 in that at least some of the gases are combined before being inj ected into a port 7 . The oxygen gas may be added approximately at the entrance port to the methane and / or hydrogen gas . The oxygen gas cannot be added further upstream since it might directly burn with the gas producing very high temperatures .

[0135] The main obj ect remains to heat methane gas outside the blast furnace to a certain temperature ( at least 500 ° C as described above ) . This can be achieved by directly heating methane gas or a gas comprising methane gas and hydrogen gas by a heater 19 . Alternatively, methane gas maybe heated by contacting methane gas or a gas comprising methane gas and hydrogen gas via a different gas ( e . g . transfer gas , hydrogen gas ) .

[0136] Thus , the iron ore reducing and melting apparatus 24 heats via the first heater 19 , in particular at least one electrical heater, even more preferred at least one AC or DC plasma torch, methane gas , hydrogen gas , a gas comprising methane gas and hydrogen gas , or transfer gas . Methane gas, hydrogen gas, a gas comprising methane gas and hydrogen gas, or transfer gas prior to being injected into the at least one heater can be preheated by a respective dedicated (pre-) heater 22.

[0137] The iron ore reducing and melting apparatus mixes the gas provided by the at least one heater 19 with further methane gas, hydrogen gas, or gas comprising methane gas and hydrogen gas via a port (not illustrated) .

[0138] Further methane gas, hydrogen gas, a gas comprising methane gas and hydrogen gas, or transfer gas prior to being mixed with the gas provided by the heater 19 can be preheated by a dedicated (pre-) heater 23.

[0139] The iron ore reducing and melting apparatus injects oxygen gas into the blast furnace via an oxygen gas injector port (not illustrated) . Thus, the oxygen gas joins the gas heated by the at least one heater 19 or the gas heated by the at least one heater and mixed with further gases as described above.

[0140] The oxygen gas prior to being injected into the blast office can be preheated by an oxygen gas heater 20.

[0141] Reference examples and examples of the disclosure

[0142] To better illustrate the disclosure, several cases have been deeply investigated. The details of the cases are presented in Table 1.

[0143] To highlight how varying temperatures influence the key parameters in the process such as coke, electricity and 02 consumptions, the calculations have been performed for two different temperatures: 600°C and 1200°C.

[0144] Furthermore, for the shaft gas injection, two positions along the shaft are considered: the upper part and lower part. The selected position depends upon the availability of the gases in the plant. In the absence of COG, methane, H2, NH3, hydrogen gas, or other similar gases, a preheated by-product gas can be used for injection. Since this gas may contain certain levels of C02and H20, it is injected into the cooler upper part of the shaft to minimize unwanted reactions of H20 and C02with coke. The primary purpose of injecting this gas is only to maintain the top gas temperature above 100°C.

[0145] If a gas with a high reducing power, defined by a (CO+H2) / (CO2+H2O) ratio above 5, is available or can be produced from existing gases, it is recommended to inject this gas into the lower part of the shaft at high temperatures. This gas can aid in the reduction of iron oxides and further decrease of coke. Additionally, it helps maintain a high top gas temperature .

[0146] However, both shaft gas injection options described above merely serve to optimize the function of the iron or reducing and melting apparatus and present optional features .

[0147] In the following, a summary of the cases is provided:

[0148] Case 1 involves a typical blast furnace operating with Pulverized Coal Injection (PCI) .

[0149] Cases 2 and 3 focus on injecting heated methane gas at 600°C with the upper and lower shaft injections respectively.

[0150] Cases 4 and 5 are about injecting heated methane gas at 1200°C with the upper and lower shaft injections respectively.

[0151] Case 6 is dedicated to evaluate the effect of PCI injection with cracked methane .

[0152]

[0153] As observed, the heated methane gas , combined with additional 02might eliminate the need for a hot blast and PCI inj ection, while also reducing coke consumption . This is because the heated methane cracks into hot H2 and carbon and / or soot . In fact the hot H2 and carbon / soot will provide sufficient reducing power and thermal energy once burned with oxygen in the raceway of the furnace (C+0 . 5 02 ->C0 ) , reducing or even eliminating the requirement of burning of PCI and / or additional coke inside the furnaces ' raceway .

[0154] Plasma torches

[0155] The plasma torches disclosed in this application can be DC or AC plasma torches .

[0156] Alternating current 3-phase plasma torches can show the following characteristics .

[0157] The core of the plasma can reach about 15000K or even higher .

[0158] Graphite electrodes , most preferably, can be used having an outer diameter of 0-150 mm, 10-100 mm, or 20-80 mm.

[0159] An AC voltage of 100V-3000V can be applied . Of note , such a voltage can also be applied in DC torches . Higher voltage , say in the order of kV, is also possible to be applied to reach higher power output , say 2 -8 MW .

[0160] The inter-electrode distance of the plasma torch is adj ustable within the ranges defined above . The adj ustability allows for easy plasma ignition and higher plasma stability .

[0161] The plasma control can be based on visual observation : pictures of the plasma that are continuously captured by a camera are benchmarked against steady-state plasma pictures , using a relevant software . Then, respective changes are imposed ( i . e . inter-electrode distance , voltage amplitude etc . ) in order to retain the plasma in stable regime . Additionally and / or alternatively the control of the plasma can be based on the electric characteristics , tension, current , power phi of the power supply system in the different phases . Using the relation of the different characteristics in the several supply phases may allow to correctly adj ust the electrode positions .

[0162] The plasma torch can operate for weeks or months if spare electrodes are continuously charged in an electrodes magazine . There are 6 arc plasmas taking place each period between the 3 electrodes playing alternatively the role of anode and cathode, one at a time .

[0163] The alternating ignition point of plasma makes it more diffusive, resulting in higher gas volume treatment than direct current plasma torches. Maybe 30% of the gas can be treated per single pass.

[0164] The lifetime of the electrodes, specifically in case of graphite electrodes, can be increased if the reducing gas has low concentrations of oxygenated species, i.e., H20 and C02. Reducing gas may comprise a reductant to oxidant ratio (CO+H2) / (CO2+H2O) in % (vol / vol) that is bigger than 7, 8, or 9. The ( (CO+H2) / (CO2+H2O) ) -ratio may be 6-80, 7- 30, or 8-12.

[0165] A minimum reduction degree of the gas should therefore be maintained and / or the concentration of H2O plus CO2shall be limited to values below 35 vol%, 10 vol%, preferably below 5 vol% .

[0166] Reference Numbers

[0167] 1 : iron ore reducing and melting apparatus

[0168] 2 : blast furnace

[0169] 3: by-product gas injection port

[0170] 4: by-product gas injector

[0171] 5: (hydrogen) gas injection port

[0172] 6: (hydrogen) gas injector

[0173] 7: (methane) gas injection port

[0174] 8: (methane) gas injector

[0175] 9: (oxygen) gas injection port

[0176] 10: (oxygen) gas injector

[0177] 11: hearth

[0178] 12: tuyere level

[0179] 13: belly

[0180] 14: shaft level

[0181] 15: top level

[0182] 16: lock hopper

[0183] 17 : by-product gas heater

[0184] 18: hydrogen gas heater

[0185] 19: at least one gas heater / (first (methane gas heater

[0186] 20: oxygen gas heater

[0187] 21: first dehydration device

[0188] 22: methane / hydrogen / transf er gas (pre) heater

[0189] 23: further methane / hydrogen gas (pre (heater

Claims

1. Claims1. An iron ore reducing and melting apparatus comprising a blast furnace said furnace comprising: at least one gas injector on the tuyere level adapted to introduce methane gas into the furnace, at least one heater adapted to heat the methane gas to be introduced into the furnace to above 500 °C; at least one oxygen gas injector port on the tuyere level adapted to provide oxygen gas comprising at least 80 vol.-% oxygen.

2. Iron ore reducing and melting apparatus according to any of the above claims, wherein the at least one heater is adapted to heat the methane gas to 500 °C - 2600 °C, 600 °C - 2600 °C, 700 °C - 2600 °C, 800 °C - 2600 °C, 900 °C - 2600 °C, 1000 °C - 2600 °C, 1100 °C - 2600 °C, 1200 °C - 2600 °C, 1300 °C - 2600 °C, 1400 °C - 2600 °C, 1500 °C - 2600 °C, 1600 °C - 2600 °C, 1800 °C - 2600 °C, 2000 °C - 2600 °C, or 2100 - 2200 °C.

3. Iron ore reducing and melting apparatus according to any of the above claims, wherein the at least one heater is adapted to operate at an electric power of 100 - 1000 kwh / t of hot metal.

4. Iron ore reducing and melting apparatus according to any of the above, wherein the at least one heater is an electrically driven heater .

5. Iron ore reducing and melting apparatus according to claim 4, wherein the at least one electrically driven heater is an electric resistance heater.

6. Iron ore reducing and melting apparatus according to claims 4, wherein the at least one heater is a plasma torch, being an electrode-comprising or electrodeless plasma torch.7 . Iron ore reducing and melting apparatus according to claim 6 , wherein the plasma torch is an electrodeless plasma torch, and the electrodeless plasma torch is a microwave (MW) plasma and radiofrequency ( RF) plasma torch .8 . Iron ore reducing and melting apparatus according to claim 6 , wherein the at least one plasma torch is an alternating current plasma torch .9 . Iron ore reducing and melting apparatus according to claim 6 , wherein the at least one plasma torch is a direct current plasma torch .10 . Iron ore reducing and melting apparatus according to claim 8 or9 , further comprising a supply for a thermal transfer gas or hydrogen gas ; wherein the at least one plasma torch is adapted to heat the thermal transfer gas or hydrogen gas ; wherein the iron ore reducing and melting apparatus is adapted to heat the methane with the heated thermal transfer gas or hydrogen gas .11 . Iron ore reducing and melting apparatus according to claims 6-10 , wherein the iron ore reducing and melting apparatus is adapted to split the incoming gas into two streams , in particular , into a first stream flowing centrally through the arc created by the plasma torch and a second stream flowing peripherally around the arc .12 . Iron ore reducing and melting apparatus according to claim 6 , wherein the at least one plasma torch has an electric power rating of 1 to 10 MW, preferably of 2 to 6 MW, most preferably of 4 to 5 MW; or / and further comprise an electrode paste column or paste feeder; or / and further comprising a plasma torch electrode exchanging / amendment device adapted to automatically replace at least one used or eroded electrode of the plasma torch with an unused electrode / amend the used electrode with at least one new electrode; or / and wherein the electrodes are permanent electrodes, preferably copper electrodes, or wherein the electrodes are consumable electrodes, preferably graphite electrodes; or / and wherein the interelectrode distance may be 0-150 mm, 10-100 mm, or 20-80 mm.

13. Iron ore reducing and melting apparatus according to any of the above claims, further comprising an oxygen supply device configured for injecting oxygen at the tuyere level of the smelting furnace via the oxygen injection port, oxygen lance or other specific openings for oxygen injection.

14. Iron ore reducing and melting apparatus according to any of the above claims, wherein said oxygen injection port is arranged within the first injector.

15. Iron ore reducing and melting apparatus according to any of the above claims, wherein the iron ore reducing and melting apparatus is adapted to provide oxygen via the oxygen port at a temperature of 20°C to 800 °C, 100°C to 800 °C, 200°C to 800 °C, 300°C to 800 °C.

16. Iron ore reducing and melting apparatus according to any of the above claims, wherein the iron ore reducing and melting apparatus further comprises at least one second heater upstream of each respective at least one first heater, wherein the at least one second heater is adapted to heat the methane gas to up to 500°C.

17. Iron ore reducing and melting apparatus according to any of the above claims, wherein the at least one first gas injector is also adapted to provide hydrogen gas, or wherein the iron ore reducing and melting apparatus further comprises a hydrogen gas injector adapted to provide hydrogen gas.

18. Iron ore reducing and melting apparatus according to any of the above claims, further comprising a injector port for auxiliary fuels, optionally selected from the group consisting of powdered coal, tar, oil, and plastic.

19. Method for operating a furnace for reducing and melting iron ore comprising the steps of:- heating a methane gas to 500 °C - 2600 °C by at least one heater;- injecting the methane gas into the furnace at tuyere level;- injecting an oxygen gas comprising at least 80 vol.-% oxygen into the furnace at tuyere level.

20. The method of claim 19, wherein the methane gas is heated to 500 °C - 2600 °C, 600 °C - 2600 °C, 700 °C - 2600 °C, 800 °C - 2600 °C, 900 °C - 2600 °C, 1000 °C - 2600 °C, 1100 °C - 2600 °C, 1200 °C - 2600 °C, 1300 °C - 2600 °C, 1400 °C - 2600 °C, 1500 °C - 2600 °C, 1600 °C - 2600 °C, 1800 °C - 2600 °C, 2000 °C - 2600 °C, or 2100 - 2200 °C.

21. The method of claim 19 or 20, wherein the oxygen is injected at a temperature of a temperature of 20°C to 800 °C, 100°C to 800 °C, 200°C to 800 °C, 300°C to 800 °C.

22. The method of any of claims 19 - 21, wherein the methane gas prior to being heated by the first heater is heated by at least one second methane heater to 250°C to 1000°C.

23. The method of any claims 19-22, wherein the at least one heater is a heater as defined in claims 3-9, 11, and 12.

24. The method of any of claims 19 - 23, wherein the at least one heater is a direct current plasma torch or an active current plasma torch and the at least one heater heats a thermal transfer gas or hydrogen gas, the heated thermal transfer gas or hy-drogen gas being brought into contact with the methane gas, and the heated thermal transfer gas heating the methane.

25. The method of any of claims 19 - 14, further comprising injecting hydrogen gas into the furnace at tuyere level.

26. The method according to claims 19-25, further comprising injecting auxiliary fuels into the furnace, the auxiliary fuels optionally selected from the group consisting of powdered coal, tar, oil, and plastic.

Images