Co-injection of hydrogen and biomass in ironmaking for decarbonisation
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- NEWSOUTH INNOVATIONS PTY LTD
- Filing Date
- 2023-11-17
- Publication Date
- 2026-07-22
Smart Images
Figure 1.1
Abstract
Description
[0001] Co-injection of hydrogen and biomass in ironmaking for decarbonisation
[0002] Field of the invention
[0003] The present invention relates to a method for co-injecting a carbonaceous material and a fuel gas into a blast furnace, as well as a lance for co-injecting thereof.
[0004] Background to the invention
[0005] As the dominant facility of ironmaking, accounting for over 70 pct of pig iron production, the blast furnace is one of the largest CO2 emission contributors. In the ironmaking process, the traditional fuels are all carbon sources like metallurgical coke and pulverised coal for the purpose of heating and iron ore reduction. In one known implementation, pulverised coal injection (PCI) consists of injecting pulverised coal or coal powders through tuyeres to the furnace for combustion and production of reducing gases. Coal injection in this manner partially replaces coke inside said furnace, thereby remarkably cutting down on coke use, and thus environmental impact and / or costs for the additional coking step. However, the application of PCI in blast steel-making still yields a high-carbon impact as the process still requires a substantial input of (albeit non-coked) coal, similarly derived from non-sustainable fossil fuels.
[0006] One known method of reducing the total fossil fuel used in steel-making is by injecting carbonaceous material derived from biomass. Chemical, physical and mechanical properties of raw biomass do not enable their efficient use in the steel industry, with exception of the reducing gas production by gasification prior to furnace injection.
[0007] One such method is that disclosed in Chinese application number CN 1 14774599, which utilises biomass in the form of a treated pulverised charcoal for injection into a blast furnace via a tuyere alongside the main heated blast. In this implementation, a dehydrated, deoxidised and hydrogenated “biomass hydrogen-rich micro-powder” is prepared by a “coking-like” process of flash evaporation and pyrolysis of charcoal to produce a carbon-rich powder. This powder is subsequently injected into a tuyere alongside a CO2 conveying gas, selected to maintain reduction potential inside the furnace, after which the pre-treated and volatile powder ignites in the raceway. i Charcoal conversion behaviour under the blast furnace raceway simulating conditions is comparable or even better than that for PCI. Particularly at high injection rate, charcoal conversion behaviour becomes more favourable due to the partial compensation of oxygen in the blast from the charcoal macropores.
[0008] The use of biomass in this regard requires extensive pre-treatment of the biomass materials such as charcoal to improve its their energy density and product quality such that they meet to requirements for blast furnace injection. Moreover, while the biomass in this regard is useful in directly replacing pulverised coal injection, the pre-treatment still requires significant thermal energy (usually derived from fossil fuel sources) to allow for auto-ignition inside the raceway.
[0009] Moreover, while pre-treatment of biomass promotes improvements to the blast furnace based steel-making, including but not limited to higher carbon content, calorific value, apparent density, lower oxygen content, better grindability, the prior treatment of biomass is significant to the detriment of solid iron product yield.
[0010] Considering the above, it is clear that a careful balance must be struck between the above aspects - namely the solid product yield causes the loss in blast furnace operation efficiency and vice versa, when biomass injection is considered. If biomass addition is to become widely adopted, another source of thermal energy is required to improve the efficiency and sustainability of biomass or charcoal preparation prior to its combustion to form reducing gases.
[0011] Hydrogen is a climate-friendly fuel with the highest energy content per unit mass among all fuels. Furthermore, green hydrogen is treated as a carbon-free fuel, as it is sourced from water electrolysis powered by renewable generation. Hydrogen is a strong reducing agent and has strong combustibility and diffusivity. It is regarded as a promising clean fuel for many industrial fields towards zero CO2 emission. The above advantages make hydrogen a superior substitute for carbon-based raw materials in multiple carbon-intensive industries, including iron- and steel-making.
[0012] The utilization of hydrogen in blast furnaces has been seen as a future replacement for these carbon-derived fuels, including both coke and / or pulverised coal, providing thermal energy for ignition of carbon-additives and reducing overall carbon dioxide emissions from blast furnace steel-making. In Liu, Yiran; Hu, Zhongjie; and Shen, Yansong; “CFD Study of Hydrogen Injection in Blast Furnaces: Tuyere Co-injection of Hydrogen and Coal”; Metallurgical and Materials Transactions B, 52B, pp. 2971 -2991 , two main types of hydrogen metallurgy in the art are identified. These include hydrogen injection into blast furnaces to replace coal and coke by means of tuyere injection (option 1 : co-injection of hydrogen / coal through tuyeres; option 2: full hydrogen injection through tuyeres); or direct shaft injection of said materials / gases to the furnace. The tuyere injection is regarded as the most feasible in the art, as it only requires slight modifications on the blast furnace and its operation - namely the provision of a consumable lance for carrying and injecting hydrogen and coal via separate fluid channels.
[0013] The co-injection of hydrogen / coal is considered as a transition technology towards full hydrogen steel-making. In this regard, the exothermic nature of coal combustion means that its injection compensates for the calory / heat loss experienced by the endothermic hydrogen reactions in the blast furnace. Moreover, this compensatory nature allows sufficient reaction heat and reductive materials to be injected into the furnace without solely relying on unstable and costly hydrogen supplies. Overall, coal-hydrogen co-injection is the best known and most practiced method in the art for balancing between CO2 emission reduction, reaction kinetics and operational cost.
[0014] However, hydrogen-coal co-injection remains inadequate in view of the rapid need for decarbonisation in key industries in view of global climate change. According to the WMO (World Meteorological Organization), the concentration of greenhouse gases in the atmosphere reached 400ppm in 2015 and passed 413ppm by 2020. A speedy transition to full hydrogen-steel making, and thus the reduction of coke and / or coal additions are required in the effort to stabilise the concentration of greenhouse gases at a generally acknowledged critical threshold of 450ppm.
[0015] Moreover, the fundamental issue with the widespread use of hydrogen in industrial use, including steel-making is the fact that hydrogen production is overwhelmingly “black”, i.e. sourced by hydrocarbon of fossil fuel sources, rather than “green” hydrogen sourced from renewable sources such as water electrolysis. Accordingly, there is a need in the art for a solution to provide an intermediate technology and / or method for transitioning towards the incorporation of hydrogen to conventional blast furnaces without significant or costly modification.
[0016] In light of the above, such an intermediate technology should combine the cost-effectiveness and reaction kinetics of hydrogen-coal co-injection, while reducing or alleviating fossil fuel use for improved sustainability. Accordingly, it is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative, preferably a method for economic blast steel-making that provides a useful intermediate technological step to full hydrogenisation with significant reductions to fossil-fuel use and carbon- intensiveness.
[0017] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
[0018] Summary of the invention
[0019] In a first aspect of the present invention, there is provided a method of making steel, comprising: a. injecting non-carbon or carbon-neutral fuels comprising at least one combustible gas and a solid carbonaceous material to a tuyere; b. combusting at least a part of said at least one combustible gas; c. blowing said non-carbon or carbon-neutral fuels, including combustion products of said at least one combustible gas, with a blasting flow into a furnace such that said fuels make contact with furnace charge material; and d. reducing said blast furnace charge material alongside said solid carbonaceous material to produce slag and molten steel, wherein said at least one combustible gas and solid carbonaceous material are coinjected to said tuyere through a lance in fluid communication thereto, said lance comprising a first and second channel adapted to flow said solids and gas respectively to adjacent outlets thereof in fluidic communication with said tuyere.
[0020] The at least one combustible gas is a necessary co-injectant for the generation and provision of thermal energy for the purposes of devolatilising the solid carbonaceous material for its eventual combustion in the raceway, and thus the in- situ production of reducing gases such as CO2 and CO for iron reduction. Naturally, the combustion of said gases in an exothermic reaction also supplements thermal energy inside the blast furnace, and is particularly useful in supporting the overall endothermic reaction kinetics of the iron-reduction. Moreover, the significant thermal input provided by the exothermic combustion is beneficial in supporting both the thermal and flow dynamics inside the cohesive, liquid and hearth zones of the furnace stack.
[0021] Accordingly, the at least one combustible gas is selected based on its combustion kinetics, thermodynamics, autoignition temperature and ease of sourcing and / or handling. In this regard, the at least one combustible gas comprises hydrogen in some embodiments. This may include hydrogen gas, hydrocarbon gases such as methane, propane and butane, or a mixture thereof including gas combinations such as syngas.
[0022] In another embodiment, the at least one combustible gas comprises hydrogen gas. For this embodiment, the flow of at least one combustible gas is not limited to hydrogen, and can include non-combustible conveying gas such as nitrogen, air and / or argon. Preferably, the at least one combustible gas comprises hydrogen gas (H2) at concentrations between 1 to 100 vol%. Preferably, hydrogen gas comprises at least 20 vol%. In another embodiment, the hydrogen gas comprises approximately 20 vol% and nitrogen comprises approx. 80 vol.%.
[0023] The at least one combustible gas is adapted to combust upon contact with the blast flow (heated to approx. 1 150 to 1350 deg. C) in the tuyere, such that a flame can be maintained at the tip of the injection lance in communication thereto. In this regard, the at least one combustible gas is selected such that its autoignition temperature is below that of the heated blast, but above a range practical for injection into a blast furnace. Hydrogen gas in this regard is a feasible choice, as autoignition occurs in the presence of oxygen at 585 deg. C and above, meaning that a flame for its combustion in the presence of a heated blast flow is self-generating and relatively easy to maintain.
[0024] The solid carbonaceous material comprising the non-carbon or carbon- neutral fuels is directed towards solid combustible materials that are not sourced from fossil fuel sources and / or require less pre-processing prior to injection into blast furnaces when compared to existing carbonaceous materials including coke, pulverised coal and / or pellets. In some embodiments, this solid carbonaceous material is sourced from a sustainable source such as an organic source. Accordingly, in some embodiments, this solid carbonaceous material is an organic material.
[0025] More preferably, this solid carbonaceous material is biomass, generally accepted in the art to be derived from plant-based materials such as wood, wood residues agricultural residues, and waste from industry, farms and households. In particular, biomass products such as charcoal (bio-charcoal in this case) or ash is preferred for injection into the blast furnace. In some examples where the calorific values are similar, bio-charcoal can replace part of the coke-charge in a 1 :1 replacement ratio, while torrefied biomass materials, another form of treated biomass, can yield a 0.4:1 coke replacement ratio upon tuyere injection.
[0026] In this regard, the bio-charcoal used in said preferred embodiment provides a calorific value of at least 18 MJ / kg, similar to that of coke particles. Furthermore, said biomass particles can be pulverised and / or milled to mean diameters up to 300 pm, with maximum diameters of 500 pm - sizes akin to that of pulverised coal or coke particles in the deadman zone of the furnace hearth adjacent to the raceway. This provides a similar gas and liquid permeability to the comminuted coke particulates found in the lower sections of the furnace (particularly the liquid and deadman zones) - combined with the biomass density of at least 500 kg / m3.
[0027] As with known methods for pulverised coal injection and hydrogen-coal coinjection, the proposed invention seeks to inject the carbonaceous material, including biomass materials such charcoal and torrefied biomass by entraining them in a conveying gas. The carbonaceous solids of various forms, including but not limited to pellets and pulverised particulates, are entrained and injected by a flow of inert conveying gases such as nitrogen gas, air and CO2. By its operational nature, the conveying gas mass flow rates are adjusted to ensure effective entrainment and solids carrying capacity. In one embodiment, the conveying gas mass flow rate is set to be proportional to that of the desired solids injection rate - approximately 3 to 4 % by mass.
[0028] Accordingly, the person skilled in the art would appreciate that said biocharcoal would have favourable thermal and flow characteristics once injected into the furnace, such that minimal modifications to the equipment or operational conditions are required for charcoal -injection via tuyeres.
[0029] In embodiments where hydrogen gas comprises the at least one combustible gas, a flame front temperature of 500 to 2000 deg. C is desired for devolatilising and gasifying the solid carbonaceous material. If biomass materials, particularly biocharcoal or ash are used, a flame front of 600 to 1600 deg. C at 0.05 to 0.3 m from the lance tip is desired for rapid devolatilisation and gasification prior to its own combustion in the raceway.
[0030] The thermal input from the combustion of the devolatilised and gasified biomass is such that the raceway adiabatic flame temperature (RAFT) from the tuyere is between 1900 and 2300 deg. C. This results in top gas temperatures escaping the furnace to be approx. 95 to 200 deg. C - typical operational temperatures for coked or pulverised coal injected blast furnace operation.
[0031] In another aspect of the present invention, there is provided a system for injecting non-carbon or carbon-neutral fuels to a steel-making furnace, comprising: a lance comprising a first channel adapted to flow solid carbonaceous material and a second channel adapted to flow at least one combustible gas; apertures of said first and second channels forming a lance tip in fluid communication with a tuyere for co-injecting said solid carbonaceous material and combustible gas to a blasting flow; and tuyeres for injecting said non-carbon or carbon-neutral fuels with a blasting flow into said furnace such that said fuels contact furnace charge material in a raceway, wherein said lance and lance tip are adapted to combust said at least one combustible gas in the presence of said blasting flow.
[0032] In one embodiment, said combustion heats said solid carbonaceous material to aid devolatilisation thereof, before injection into the furnace raceway.
[0033] The apparatus used for co-injecting the at least one combustible gas and the solid carbonaceous material is known to influence crucial operational parameters for injection-based blast steel-making (e.g. PCI steel-making) - namely, injection speed, injection flow rate, flame front size and raceway temperature. One said factor that influences the economics and robustness of the invention is the design of the lance used to inject said non-carbon or carbon-neutral fuels, and how it is used.
[0034] In known methods for co-injecting coal and hydrogen to a tuyere, both singlelance and dual-lance methods are common. The former implementation utilises a single lance comprising two channels for separately flowing said at least one combustible gas and said solid carbonaceous fuel, bringing reservoirs thereof into injecting fluid communication with the tuyere. By contrast, dual-lance solutions utilise a single lance for each of the combustible gases and the carbonaceous solids. Certain advantages exist for either solution, including the ease of identifying issues and replacing dual-lances, as well as the improved coal combustion achieved by the proximity of the hydrogen combustion to the coal-feed in a single-lance solution.
[0035] The present invention utilises a single-lance solution, wherein a lance comprising two separate fluid channels is penetratingly placed in a tuyere such that the apertures of said lance are adapted to inject the combustible gas and carbonaceous solids into the blast flow prior to or adjacent to the tuyere’s mouth into the furnace. To maximise mixing of the injected materials, and thus the devolatilisation, gasification and burn-out of the carbonaceous solids, certain embodiment of the system place the lance mouth, and thus the fluid channel apertures in the centre of the tuyere cross-section. In another embodiment of the lance used in the present invention, there is provided an inner and an outer annular wall extending along its length, such that said first channel is formed inside said inner annular wall and said second channel is formed between said inner and outer annular walls. The arrangement of the walls is such that the first channel forms a tubular fluid channel surrounded by an annular second fluid channel. In some embodiments, the inner and outer walls, and thus the first and second channels formed thereby, can be coaxial in arrangement.
[0036] In a preferred method of using either the coaxial or non-coaxially arranged lance, the at least one combustible gas flows through said second channel formed between an inner and outer annular wall extending along its length of said lance, and said solid carbonaceous material flows through said first channel formed inside said inner annular wall.
[0037] One major benefit of selecting hydrogen specifically and flowing it through said second channel is the lance cooling effect obtainable during co-injection operation. As per typical hydrogen injection steel-making methods known in the art, the proposed invention utilises a combustible gas comprising hydrogen gas injected into the tuyere at approximately 25 deg. C up to its autoignition temperature of 585 deg. C. Considering the hot blast flow is typically preheated to approximately 1 150 to 1350 deg. C, there is a significant thermal difference between the tip of said lance exposed to the heated blast flow and the hydrogen flow to be heated. Accordingly, there is a significant thermal drive to convectively transfer heat from the lance walls to the flowing hydrogen gas - causing noticeable cooling of the lance tip exposed inside said tuyere.
[0038] Moreover, the thermal conductivity and specific heat capacity of the lance material and hydrogen gas respectively affects this lance cooling effect. In particular, hydrogen gas has a significantly high specific heat capacity, which indicates the ability for hydrogen gas flowing through the second channel to convectively remove heat per one degree of temperature increase. Accordingly, the temperature increases in the hydrogen gas caused by its contact with the heated metallic lance tip, mixing with the hot blast flow and subsequent ignition adjacent to said lance aperture makes hydrogen well suited for removing heat from said lance and alleviating or preventing temperature-related degradation of said lance. The lance used in these embodiments are designed such that this lancecooling effect occurs via convection of the combustible gas flow of a subsonic speed. Both the overall cross-section of each lance, and thus the cross-sectional surface area of the two channels therein, is sized to enable such lance cooling in each lance at total furnace-wide co-injection rates of up to 35 kg of combustible gas per tonne of hot metal (kg / tHM) and up to 250 kg / tHM of carbonaceous solids injection across lance-tuyere arrangements.
[0039] This lance-cooling effect is active whether the hydrogen gas flows through the inner tubular channel or the outer annular channel. However, the person skilled in the art would appreciate that the cooling effect on the lance’s outer wall, and thus the thermal damage alleviation thereto can be maximised by flowing hydrogen gas through an outer, annular second channel.
[0040] The above lance-cooling effect is designed to reduce or prevent the temperature-related degradation of the lance and lance-tips in particular. Coal- injected or hydrogen-coal co-injected blast furnaces known in the art use consumable lances that are easily replaced when the lance tip becomes degraded by relatively short- to medium-term high temperature exposure in the tuyere. The continuous lance-cooling effect brought on by the subsonic flow of a combustible gas comprising hydrogen gas makes such as lance effectively reusable - allowing a longer operational lifespan and prevents costly maintenance or furnace down-time for lance replacements.
[0041] As discussed above, the co-injected combustible ignites to form a high- temperature flame front when injected into the tuyere and comes into contact with the heated blast flow. The blast flow through the blowpipe in the invention is enriched with oxygen to facilitate the above combustion reaction, while also providing sufficient oxygen for the standard blast furnace coke oxidation and iron reduction reactions. In one example, the blast gas is enriched with oxygen by the stoichiometric proportion required for complete combustion of said combustible gas.
[0042] For example, where the at least one combustible gas comprises an approximate 80:20 vol. % nitrogen to hydrogen gas mixture, the oxygen composition of the blast flow gas is also raised to up to 40 vol. % to accommodate the additional combustion of the hydrogen gas.
[0043] As discussed above, the combustion of combustible gases, including hydrogen, create a significant de-oxygenated flame front of very high temperatures (approx. 1200 to 1600 deg. C) inside the tuyere, projecting from the lance tip. Exposure of the co-injected solid carbonaceous materials such as biomass results in devolatilisation. This is followed by thermal cracking, whereby the volatile materials such as light permanent gases (including H2, CO, CO2, CH4, H2O, NH3) and tar (e.g condensable hydrocarbon vapours) are released thereform, leaving devolatilised char solids.
[0044] Without wishing to be bound by the theory of modelling reaction mechanism inside a blast furnace, the in-situ devolatilisation reaction in relation to biomass material, for example, can be represented in competing models each represented by the following chemical equations 1 and 2: Equation 1 Equation 2
[0045] Both above equations represent a faction (a of the original injected biomass, namely the volatile materials (VMs) separating from the devolatilised and carbon- enriched char materials at a rate determined by reaction rate constant Kv. Both Kv constants are exponentially temperature-dependent, such that at the high flame-front temperatures discussed above, the devolatilisation reactions play a substantial role in preparing the charred carbonaceous solids for combustion or gasification once in the presence of the heated blast flow.
[0046] Moreover, the fact that the devolatilisation reaction is exponentially temperature dependent means that the provision of a high temperature heat source in the form of a combusting gas adjacent to the lance tip results in the effective catalysation of said in-situ devolatilisation. Accordingly, the devolatilisation of said solid carbonaceous material in some embodiments is substantially rate dependent on the combustion of said at least one combustible gas. For embodiments utilising biomass, this in-situ devolatilisation reaction is in direct contrast to existing biomass-injected blast steel-making, whereby biomass pretreatment is performed prior to its injection into the tuyere or the furnace. The in-situ devolatilisation driven by the combustion of the co-injected hydrogen is both efficient and effective by comparison to the costly, energy consuming and bulky prior processes required in the latter existing solution.
[0047] In practice, the increased carbonaceous solids temperatures adjacent to the high temperature flame front means that a larger fraction of said injected particles devolatilises and burns out in the raceway. This directly results in the earlier and increased generation of conventional blast furnace gases such as CO and CO2 used for reducing the iron ore charged in the furnace. Moreover, by effectively catalysing the devolatilisation and subsequent combustion of the charred solids, the injection of hydrogen alongside biomass makes the injection of the latter more efficient and practically feasible.
[0048] The “burn-out” of the carbonaceous material once injected in the furnace is achieved by the temperature-driven chemical consumption of its carbon-enriched and devolatilised solids to form reducing solids. This chemical consumption predominantly takes two pathways inside a blast furnace - namely oxidation and gasification. Without wishing to be bound by the theory behind modelling the precise chemical dynamics inside a blast furnace, the reactions underpinning the competing models of the biomass oxidation and gasification can each be represented by the formulae below: k
[0049] Char oxidation <pChar + O2-> 2(<p - 1)CO + (2 - <p)CO2Equation s k
[0050] Char gasification (1) Char + CO22CO Equation 4 k
[0051] Char gasification (2) Char + H2O -> CO + H2Equation s
[0052] In light of the heated, oxygen-enriched blast flow, the predominant mode of carbon consumption in the blast furnace is oxidation. As shown in one such reaction process exemplified by Equation 3 above, the oxygen supplied in the heated blast flow reacts with the carbon-enriched char to generate a stoichiometric mixture of reductants CO and CO2. Both are active reductants inside a blast furnace, useful for reducing iron oxides to form pig iron or steel.
[0053] The other two pathways involve a comparatively direct gasification reaction that only occurs under high temperature conditions, such those in hydrogen flame front or in a blast raceway. In this regard, the reactants that the devolatilised carbonaceous solids react with are both possible combustion products of fuel combustion - namely carbon dioxide (CO2) and water (H2O). In this regard, the at least one combustible gas can be selected such that said combustion products thereof gasify at least part of the solid carbonaceous material in the raceway. As exemplified by Equations 4 and 5, it is clear that combustion of combustible gases such as methane and hydrogen gas at the lance tip results in the subsequent promotion of gasification and generation of reducing gases for steel-making.
[0054] With respect to the latter water-based gasification reaction, such as that disclosed in Equation 5, the generation of hydrogen gas (H2) as a result means that further exothermic combustion of said reaction is product to re-form a water molecule is possible - provided that stoichiometrically sufficient oxygen gas and heat remains in the furnace. Accordingly, a chain reaction of hydrogen-based gasification and water recombination further along the raceway and further into the hearth of the furnace is preferred and can be facilitated by the co-injection of hydrogen-containing gases and biomass materials.
[0055] This chain-effect caused by the co-injection of hydrogen via a lance that promotes immediate combustion and devolatilisation of biomass propagates both thermal energy and the consumption of carbon, as well as increasing the amount of heat available for reduction further inside the furnace. This synergistic effect results in improved process efficiency, improved carbon burn-out and supplements carbon utilisation of the blast furnace.
[0056] Accordingly, in another aspect of the present invention , there is also provided a method of using the system disclosed herein, comprising the steps of: a. flowing said solid carbonaceous material and said at least one combustible gas through said first and second channel of said lance; b. injecting said solid carbonaceous material and said at least one combustible gas to said blasting flow through adjacent outlets of said first and second channels; c. combusting at least part of said at least one combustible gas in the presence of said blasting flow; d. devolatilising at least part of said solid carbonaceous material with heat generated from said combustion; e. blowing said at least one combustible gas, combustion products thereof and said carbonaceous material to said blast furnace and contacting said furnace charge therewith in a raceway; and f. reducing said furnace charge to produce molten steel and slag.
[0057] Definitions
[0058] In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of the invention only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one having ordinary skill in the art to which the invention pertains.
[0059] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.
[0060] As used herein, the phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of’ (or variations thereof) appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. As used herein, the phrase “consisting essentially of” limits the scope of a claim to the specified elements or method steps, plus those that do not materially affect the basis and novel characteristic(s) of the claimed subject matter.
[0061] With respect to the terms “comprising”, “consisting of”, and “consisting essentially of’, where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of” or, alternatively, by “consisting essentially of”.
[0062] Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”. The examples are not intended to limit the scope of the invention. In what follows, or where otherwise indicated, “%” will mean “volume %”, “ratio” will mean “volume ratio” and “parts” will mean “volume parts”.
[0063] The term ‘substantially’ as used herein shall mean comprising more than 50% by volume, mass or weight, according to the context is it used, unless otherwise indicated. Preferably, it is meant to mean more than 75%. Even more preferably, it is meant to mean more than 90%. Most preferably, it is meant to mean 100% or close to 100%.
[0064] The recitation of a numerical range using endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1 , 1 .5, 2, 2.75, 3, 3.80, 4, 5 etc.).
[0065] The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.
[0066] It must also be noted that, as used in the specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. The prior art referred to herein is fully incorporated herein by reference.
[0067] Although exemplary embodiments of the disclosed technology are explained in detail herein, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the disclosed technology be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The disclosed technology is capable of other embodiments and of being practiced or carried out in various ways.
[0068] Brief description of the drawings
[0069] The invention will now be described, by way of example with reference to the accompanying drawings, in which:
[0070] Figure 1 a is a cutaway schematic view of a blast furnace comprising a tuyere and a lance for co-injecting a solid carbonaceous material and a combustible gas according to the present invention. Figure 1 b is an enlarged schematic view of said tuyere, including the co-injection lance, and Figure 1 c is a cross-sectional orthographic view of the lance showing the coaxial annular fluid channels for co-injection;
[0071] Figure 2a is an enlarged sectional view of contours in specific heat capacity of co-injected nitrogen gas and a biomass material in a tuyere, while Figure 2b is an enlarged sectional view of contours in specific heat capacity of co-injected hydrogen gas and a biomass material in a tuyere;
[0072] Figure 3a and Figure 3b is an enlarged sectional isothermal view of air and a hydrogen-nitrogen mixture, respectively being co-injected with biomass particles from a lance to a furnace via a tuyere;
[0073] Figure 4a and Figure 4b are graphical representations of biomass consumption and particle temperature, respectively plotted against distance from a lance tip;
[0074] Figure 5a and Figure 5b are enlarged sectional isothermal views of air and hydrogen gas, respectively being co-injected with biomass particles from a lance to a tuyere; Figure 6 is a graphical representation of distance-dependent biomass particle consumption in a tuyere and a furnace raceway;
[0075] Figure 7a and Figure 7b are enlarged sectional views of water molecule molar fraction contours along a tuyere and furnace raceway under air and hydrogen coinjection with biomass, respectively; and
[0076] Figure 8a and 8b are enlarged sectional views of paths taken by hydrogen molecules liberated from the co-injected biomass.
[0077] Detailed description of the invention
[0078] The skilled addressee will understand that the invention comprises the embodiments and features disclosed herein as well as all combinations and / or permutations of the disclosed embodiments and features.
[0079] Example 1 - Lance and Tuyere Structure
[0080] Referring to Figure 1 a, there is shown the internal structure of a blast furnace 100, taken along a symmetry plane. The blast furnace 100 comprises a tuyere 101 in fluid communication with both a blowpipe 102 and an injection lance 103. The tuyere 101 is adapted to inject a heated blast flow to the dripping zone 104 of the blast furnace, forming a raceway 105 adjacent to the deadman zone 106. The injected blast flow also comprises a solid carbonaceous material and at least one combustible gas co-injected by said lance 103 thereto. The combustion of said at least one combustible gas and subsequent devolatilisation of said solid carbonaceous material in tuyere 101 causes gasification and / or reduction of said devolatilised carbonaceous solids in the raceway 105.
[0081] The reducing gases (mixture of carbon oxides and hydrogen) 107 produced therefrom rises through the furnace 100, combining with similar gases from carbon oxidation of the coke layers 108 to reduce the iron ore charged in the iron ore layers 109. The remaining reducing gases escape the furnace in the form of top gas, while the solid charge of coke and iron ore sinks in a counter current manner towards the cohesive zone 1 10 and deadman zone 106 in the lower section of the furnace 100. After filtering through the coke particles of the deadman zone 106, the reduced iron ore separates to form a liquid slag layer 1 11 and molten iron layer 1 12 at the bottom of said furnace 100.
[0082] Referring to Figure 1 b, the lance 103 is tangentially and fittingly placed in a sleeve 113 adjacent to the tuyere cooler 1 14 comprising the blowpipe 102. Lance 103 and blowpipe 102 fluidly communicate with the tuyere 101 penetrating through the blast furnace walls. The tip 1 15 of said lance 103 protrudes into the centre of the tuyere’s cross-section such that co-injectant contact / entrainment with the blast flow is maximised. The tuyere 101 comprises a tuyere aperture 1 16 facing the internal volume of the blast furnace such that it brings the molten iron ore and coke into fluid communication with the oxygen-enriched blast flow.
[0083] The lance 103 is adapted to facilitate combustion of the at least one combustible gas at its tip 1 15 and formation of a flame front adjacent thereto in the tuyere 101 for devolatilising the solid carbonaceous materials co-injected therewith. Referring to Figure 1 c, the lance 103 is comprised of two coaxial cylindrical walls, an outer wall 1 17 and an inner wall 1 18, the space therebetween forming a fluid channel 1 19 adapted to flow the at least one combustible gas. Another inner fluid channel 120 is formed inside the cylindrical inner wall 1 18, adapted to flow the solid carbonaceous materials and a conveying gas.
[0084] Example 2 - Lance Cooling
[0085] In another embodiment of the present invention, at least one combustible gas is flowed through the outer fluid channel 201 of the lance 200. Referring to Figure 2a, contours in the specific heat capacity of materials flowing through the lance 200a show that the nitrogen gas co-injected through outer fluid channel 201 a has a barely higher specific heat capacity when compared to the solid combustible material flowing through the aperture of the inner fluid channel 202a of said lance. By comparison, the flow of hydrogen through said outer fluid channel 201 b of lance 200b in Figure 2b shows a significant increase in specific heat capacity inside said channel, as well as the immediate area adjacent to the apertures of said lance tip 203a. Furthermore, a clear trail of high specific heat capacity can be observed originating from the hydrogen jet at the lance tip 203b, extending out along the blowpipe 204b and towards the furnace internals. This evidences the higher specific heat capacity of the hydrogen gas and the heat-removal capabilities of said gas when employed as said at least one combustible gas. Moreover, the trail of said gases or particles with higher specific heat capacity compared to the blast flow depicts the potential for heat removal from the lance, and thus potential for alleviating thermal-related damage in coaxial biomass-hydrogen coinjection lances.
[0086] Example 3 - Hydrogen Combustion and Devolatilisation
[0087] Comparing Figures 3a and 3b, the co-injection of air (Case 1 ) and at least one combustible gas in the form of a hydrogen-nitrogen mixture with 20.9 vol.% hydrogen (Case 2) alongside biomass materials, respectively show the potential for combustion and the formation of a flame-front when combustive gases are utilised. The combustible hydrogen-nitrogen gas mixture was flowed at 1.92 kg / hr, while the biomass carbonaceous material was injected at a rate of 35 kg / hr. The conveying gas flow rate was also set to 3 to 4% of the mass flow rate of said biomass.
[0088] A flame front of 1200 deg. C to 1600 deg. C can be observed adjacent to the outer fluid channels 301 b of lance 300b in Figure 3b in an embodiment where hydrogen-nitrogen mix gas is co-injected alongside the biomass. By comparison, no equivalent flame-front can be observed in Figure 3a where air is co-injected instead of a combustible fuel gas. Moreover, as observable when comparing Figures 3a and 3b, the thermal profile of particle temperatures in the tuyere and furnace are significantly affected by the injection and combustion of a hydrogen-containing gas. In particular, higher temperature gas and / or particulate plumes further into the furnace can be observed.
[0089] The effect on biomass burn-out and particle temperatures from hydrogen injection and combustion can be observed in Figures 4a and 4b. Referring to the latter graphical representation, a sustained increase in particle temperatures are observed between 0.05 and 0.3 m from the lance tip in an axial direction for Case 2. This increase in temperature is clearly affected by the introduction of additional thermal energy to area surrounding the lance tip from the exothermic combustion of the coinjected hydrogen gas in Case 2. The increased temperature also correlates with the increased biomass consumption across the same distance range from the lance tip, as observed in Figure 4a. The increased consumption of biomass in this regard is representative of the increased thermal exposure experienced by the co-injected biomass and the subsequent the evolution of volatile materials out of this solid matter as a result of the hydrogen combustion.
[0090] This hydrogen combustion flame front can also be observed when comparing the co-injection of air and hydrogen gas alongside biomass in Figures 5a and 5b, respectively. In this regard, said flame front is clearly visible as a highly localised region of higher temperature. The improved devolatilisation and subsequent “burn-out” of the biomass can also be observed in the graphical representation of Figure 6. In particular, an increase in biomass consumption can be observed over 0.6 to 1 .4 m from the lance tip. This suggests that the hydrogen injection and combustion catalyses the devolatilisation process by supplying more heat to the adjacent biomass particles. The observed correlation between the heat released from hydrogen combustion and biomass devolatilisation can be described by Equations 1 and 2, in which the devolatilisation reactions are only dependent on the reaction rate constants that vary exponentially with temperature.
[0091] Example 4 - Biomass gasification
[0092] Again referring to Figure 6, a clear improvement in biomass burnout can be observed further away from the lance tip when hydrogen is co-injected as the at least one combustible gas instead of air alongside said biomass. In this regard, a higher burnout can be observed in Case 2 (hydrogen co-injection) from 1 .70 m to 2.0 m, when 4.13 kg H2 / tHM of hydrogen gas is co-injected with the biomass particles. The increase in burnout occurred towards the end of the raceway, which falls within the typical region of char reactions.
[0093] Contours and particle trajectories at the raceway region elucidate the enhancement in burnout of the biomass particles at the downstream. Referring to Figures 7a and 7b, the water vapour content throughout the whole raceway region is significantly higher in the latter (Case 2) where hydrogen gas was injected at 4.13 kg H2 / tHM. This indicates that the injected hydrogen is rapidly converted to water as soon as it is in contact with oxygen in the tuyere. On the other hand, Figures 8a and 8b display the mass flow paths of hydrogen molecules liberated from the biomass plume and into the raceway. Hydrogen, which is also product of char gasification, as highlighted in Equation 5, can be considered an important indicator to assess the rate of char gasification. A higher intensity of hydrogen gas liberated from the biomass plume can be observed in Figure 8b, suggesting that the high concentration of water vapour in the raceway is favourable for the char gasification reaction. In brief, the co-injection of hydrogen and biomass is beneficial in elevating the char burnout indirectly through the char gasification by water. Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.
[0094] Example 5 - Example Parameters for Co-injection In one example of the present invention, the below operating parameters were used for co-injecting hydrogen and biomass into a running blast furnace with an internal volume of at least 3000m3.
[0095] Table 1 - A list of operating parameters for co-injection of hydrogen and biomass. . Temperature Flow Rate . . . . . .. ..
[0096] Component ,o. .. . Industrial Units
[0097] ( C) (kg / h)
[0098] Blast Air (natural humidity 16 g / / Vm3air)
[0099] Blast Enrichment Oxygen 1230 35920 25.6% total O2 in blast
[0100] Biomass 25 70669 156 kg / t-HM
[0101] Hydrogen gas (100% H2) 25 1355 3 kg / tHM
[0102] Conveying gas (100% N2) 25 4157 Steady-state operation of the blast furnace was achieved under the above parameters for hydrogen and biomass co-injection. The resulting operational conditions observed in the blast furnace is listed below in Table 2. In particular, favourable thermal characteristics were achieved in the raceway, while hot metal production rates typical for the size of blast furnace was maintained.
[0103] Table 2 - Operational conditions of the Blast furnace observed
[0104] Observed Operational Conditions Parameter Value
[0105] Raceway Adiabatic Flame Temperature (°C) 2110
[0106] Top Gas Temperature (°C) 113
[0107] Bosh Gas Volume (A / m3 / h) 540120
[0108] Hot Metal Production (t / day) 10842
[0109] Coke Rate (kg / t-HM) 301
Claims
Claims:1 . A method of making steel, comprising: a. injecting non-carbon or carbon-neutral fuels comprising at least one combustible gas and a solid carbonaceous material to a tuyere; b. combusting at least a part of said at least one combustible gas; c. blowing said non-carbon or carbon-neutral fuels, including combustion products of said at least one combustible gas, with a blasting flow into a furnace such that said fuels make contact with furnace charge material in a raceway; and d. reducing said blast furnace charge material alongside said solid carbonaceous material to produce slag and molten steel, wherein said at least one combustible gas and solid carbonaceous material are co-injected to said tuyere through a lance in fluid communication thereto, said lance comprising a first and second channel adapted to flow said solids and gas respectively to adjacent outlets thereof in fluidic communication with said tuyere.
2. The method according to claim 1 , wherein said at least one combustible gas comprises hydrogen.
3. The method according to claim 2, wherein said combustible gas comprises hydrogen gas.
4. The method according to any one of the preceding claims, wherein said solid carbonaceous material is organic material.
5. The method according to claim 4, wherein said solid carbonaceous material is biomass.
6. The method according to claim 5, wherein said solid carbonaceous material is bio-charcoal.
7. The method according to any one of the preceding claims, wherein said at least one combustible gas is flows through said second channel formed between an inner and outer annular wall extending along its length of said lance, and said solid carbonaceous material flows through said first channel formed inside said inner annular wall, wherein said lance tip is cooled by sub-sonic said flow of said at least one combustible gas through said second channel to alleviate temperature-related degradation.
8. The method according to claim 7, wherein said inner and outer annular walls are coaxial.
9. The method according to claim 7 and claim 8, wherein said lance is reusable.
10. The method according to any one of the preceding claims, wherein devolatilisation of at least part of said solid carbonaceous material is aided by heat generated from said combustion of said at least one combustible gas.1 1 . The method according to claim 10, wherein said devolatilisation of said solid carbonaceous material is substantially rate dependent on the combustion of said at least one combustible gas.
12. The method according to any one of the preceding claims, wherein said at least one combustible gas is selected such that said combustion products thereof gasify at least part of said solid carbonaceous material in said raceway.
13. The method according to claim 12, wherein said gasification comprises oxidising said solid carbonaceous material to generate reductants for reducing said furnace charge material.
14. The method according to claims 12 and 13, wherein said at least one combustible gas comprises hydrogen gas such that said combustion product thereof is water, adapted to produce reducing gases inside said furnace.
15. A lance used in the method according to any one of the preceding claims.
16. A system for injecting non-carbon or carbon-neutral fuels to a steel-making furnace, comprising: a lance comprising a first channel adapted to flow solid carbonaceous material and a second channel adapted to flow at least one combustible gas; apertures of said first and second channels forming a lance tip in fluid communication with a tuyere for co-injecting said solid carbonaceous material and combustible gas to a blasting flow; and tuyeres for injecting said non-carbon or carbon-neutral fuels with a blasting flow into said furnace such that said fuels contact furnace charge material in a raceway, wherein said lance and lance tip are adapted to combust said at least one combustible gas in the presence of said blasting flow.
17. The system according to claim 16, wherein said combustion heats said solid carbonaceous material to aid devolatilisation thereof, before injection into the furnace raceway.
18. The system according to claim 16 or claim 17, wherein said at least one combustible gas comprises hydrogen gas.
19. The system according to any one of claims 16 to 18, wherein said solid carbonaceous material is biomass or bio-charcoal.
20. The lance according to any one of claims 16 to 19, comprising an inner and an outer annular wall coaxially extending along its length, such that said first channel is formed inside said inner annular wall and said second channel is formed between said inner and outer annular walls, wherein said lance tip is cooled by the sub-sonic flow of said at least one combustible gas through said second channel to alleviate temperature-related degradation.21 . The lance according to claim 20, wherein said lance is reusable.
22. The system according to any one of claims 16 to 21 , wherein said tuyere is adapted to inject the combustion products of said at least one combustible gas, such that the devolatilised solid carbonaceous material is gasified in said raceway.
23. A method of using the system according to any one of claims 16 to 22, comprising the steps of: a. flowing said solid carbonaceous material and said at least one combustible gas through said first and second channel of said lance; b. injecting said solid carbonaceous material and said at least one combustible gas to said blasting flow through adjacent outlets of said first and second channels; c. combusting at least part of said at least one combustible gas in the presence of said blasting flow; d. devolatilising at least part of said solid carbonaceous material with heat generated from said combustion; e. blowing said at least one combustible gas, combustion products thereof and said carbonaceous material to said blast furnace and contacting said furnace charge therewith in a raceway; and f. reducing said furnace charge to produce molten steel and slag.