Patent Application
20200399723
This invention relates to the fields of steel-making and bag house dust remediation.
Steel industries produce significant amount of bag house dust from electric arc furnaces (EAFs). EAF dust is formed during steelmaking operations from metal oxidation and volatilization at high processing temperatures, and collected as dust in bag houses. Because EAFs typically rely on scrap metal for their charge, the composition of the dust correlates with the chemistry of the metallic charge used, and can vary from one melt to the next. Iron is the primary component of steel, and bag house dust from steel mills consequently includes high concentrations of iron oxide (40-60%). Zinc oxide and metals including manganese, calcium, magnesium, silicon, lead, copper, chromium, aluminum, mercury, and their compounds are also present in bag house dust.
From the global crude steel output of 1.62 billion tons reported by the World Steel Association, the international trade body for the iron and steel industry, about 406 million tons were produced by EAF mills in 2015. Approximately 15 to 20 kg of dust is formed per ton of EAF-produced steel, which corresponds to approximately 3-4 million tons of EAF bughouse dust produced per year.
Disposal of EAF bughouse dust at landfill disposal sites is becoming increasingly expensive, as industrial disposal sites become more scarce and remote from the point of origin. Increasing disposal costs and more restrictive environmental legislation have led to the search for economically viable methods to recycle bag house dust. Onsite recycling of bag house dust in the EAF is limited because its high oxide content has a negative impact on the melting process. Successful recycling will reduce disposal costs and extract valuable metal components which would otherwise be disposed of. There is a need in the industry for an improved process for recycling of bag house dust.
The present disclosure provides a method for recycling materials present in EAF bag house dust. Inventors have found that combining bag house dust with a carbon source in briquettes or pellets provides a composition that may be used as a feedstock in steel making furnaces, including electric arc and basic oxygen furnaces.
In some embodiments, a solid composition in the form of a briquette or pellet is provided, the solid composition is adapted for use as a feed stock in steel making furnaces and comprises a carbon source and a bag house dust comprising iron oxide and at least 1% zinc by weight. In some aspects, the solid composition does not include a non-carbonaceous iron reducing agent. Non-limiting examples of non-carbonaceous iron reducing agents include ferrous chloride and ferrous sulfate. In some embodiments, the solid composition carbon source comprises greater than 90% carbon by weight, preferably greater than 80% carbon. In some aspects, the solid composition carbon source is selected from the group consisting of anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, molasses, decanter sludge, petrochemical waste coke, aluminum smelter spent pot lining or combinations thereof. In some aspects, the bag house dust iron oxide is iron (II) oxide (FeO), iron (III) oxide (Fe2O3), iron (HMI) oxide (Fe3O4, Fe5O6, Fe5O7), or mixtures thereof, preferably Fe2O3. In some embodiments, the bag house dust zinc is zinc oxide (ZnO), or any other zinc-containing oxide, zinc ferrite, or mixtures thereof. In some aspects, the solid composition comprises 0 to 15% of an additive. In some aspects, die additive is selected from the group consisting of lime, calcium chloride, silica, limestone, clay, iron and/or steel grindings, iron and/or steel borings, iron and/or steel turnings, or combinations thereof. In some embodiments, the bag house dust comprises greater than 30% by weight iron oxide. In further embodiments, the bag house dust comprises from greater than 0 to 70% by weight iron oxide. Some aspects of the disclosure are directed towards making a solid composition in the form of a briquette or pellet.
In some aspects, a briquette or pellet adapted for use as a recycled feed stock in electric arc and/or basic oxygen furnaces is provided, the briquette or pellet comprising 60 to 90% by weight of a bag house dust comprising iron oxide and zinc, 3 to 20% by weight of a carbon source, and 0 to 15% by weight additive. In some aspects, the briquette or pellet does not include a non-carbonaceous iron reducing agent. Non-limiting examples of non-carbonaceous iron reducing agents include ferrous chloride and ferrous sulfate. In some embodiments, the briquette or pellet carbon source comprises greater than 90% carbon by weight, preferably greater than 80% carbon. In some aspects, the briquette or pellet carbon source is selected from the group consisting of anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, molasses, decanter stodge, or combinations thereof. In some aspects, the briquette or pellet bag house dust iron oxide is iron (II) oxide (FeO), iron (III) oxide (Fe2O3), iron (II,III) oxide (Fe3O4, Fe5O6, Fe5O7), or mixtures thereof, preferably Fe2O3. lit some embodiments, the briquette or pellet bag house dust zinc is zinc oxide (ZnO), or any other zinc-containing oxide, zinc ferrite, or mixtures thereof. In some aspects, the briquette or pellet additive is selected from the group consisting of lime, calcium chloride, silica, limestone, clay, iron and/or steel grindings, iron and/or steel borings, iron and/or steel turnings, or combinations thereof. In some embodiments, the bag house dust comprises greater than 30% by weight iron oxide. In further embodiments, the bag house dust comprises 30 to 70% by weight iron oxide. Some aspects of the disclosure are directed towards making a briquette or pellet adapted for use as a recycled feed stock in electric arc and/or basic oxygen furnaces.
In some aspects of the disclosure, a steel product selected front the group of flat products and long products is provided, the steel product comprising <99% by weight unrecycled iron, >1% by weight iron derived from recycled bag house dust in the form of a briquette or pellet; the recycled bag house dust comprising <99% by weight iron oxide, >1% by weight zinc, a carbon source. In some embodiments, the recycled bag house dust comprises 0-15% of an additive. In some aspects, the recycled bag house dust does not include a non-carbonaceous iron reducing agent. Non-limiting examples of non-carbonaceous iron reducing agents include ferrous chloride and ferrous sulfate. In some embodiments, the recycled bag house dust carbon source is selected from the group consisting of anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, molasses, decanter sludge, or combinations thereof. In some aspects, the recycled bag house dust iron oxide is iron (II) oxide (FeO), iron (III) oxide (Fe2O3, iron (II,III) oxide (Fe3O4, Fe5O6, Fe5O7), or mixtures thereof preferably Fe2O3. In some embodiments, the recycled bag house dust zinc is zinc oxide (ZnO), or any other zinc-containing oxide, zinc ferrite, or mixtures thereof.
Some aspects of the disclosure are directed towards a method of making a steel product comprising die steps of obtaining a solid composition in the form of a briquette or pellet, introducing the solid composition into an electric arc furnace or basic oxygen furnace, operating said electric arc furnace or basic oxygen furnace to produce molten steel, and processing the molten steel from the electric arc furnace or basic oxygen furnace into a steel product. In some aspects, the solid composition comprises a carbon source and a baghouse dust comprising iron oxide and at least 1% zinc by weight. In further embodiments, the solid composition comprises 60 to 90% by weight of a bag house dust comprising iron oxide and zinc, 3 to 20% by weight of a carbon source, and from 0 or greater than 0 to 15% by weight additive. In some embodiments, the iron oxide comprises 30 to 70% by weight of the bag house dust. Additives include lime, calcium chloride, silica, limestone, clay, iron and/or steel grindings, iron and/or steel borings, iron and/or steel turnings, and the like. In some aspects, the briquette or pellet does not include a non-carbonaceous iron reducing agent. Non-limiting examples of non-carbonaceous iron reducing agents include ferrous chloride and ferrous sulfate. In some embodiments, the carbon source is selected from the group consisting of anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, molasses, decanter sludge, or combinations thereof. In some aspects, the iron oxide is iron (II) oxide (FeO), iron (III) oxide (Fe2O3). iron (KIM oxide (Fe3O4, Fe5O6, Fe5O7 or mixtures thereof preferably Fe2O3. In some embodiments, the zinc is zinc oxide (ZnO), or any other zinc-containing oxide, zinc ferrite, or mixtures thereof.
The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically.
The terms “a” and “an” are defined as one or more unless this disclosure explicitly requires otherwise.
The term “substantially” is defined as being largely but not necessarily wholly what is specified (and include wholly what is specified) as understood by one of ordinary' skill in the art, in any disclosed embodiment, the term “substantially” may be substituted with “within [a percentage] of” what is specified, where the percentage includes 0.1, 1, 5, and 10 percent.
The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a briquette that “comprises,” “has,” “includes” or “contains” one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, an element of a system or composition that “comprises,” “has,” “includes” or “contains” one or more features possesses those one or more features, but is hot limited to possessing only those one or more features.
In the context of the present invention, seventeen embodiments are now described. Embodiment 1 is a solid composition adapted for use as a feed stock in steel making furnaces. The solid composition contains a baghouse dust containing iron oxide and at least 1% zinc by weight; and a carbon source, wherein said solid composition is in the form of a briquette or pellet. Embodiment 2 is the solid composition of embodiment 1, wherein the product does not contain either or both of ferrous chloride and ferrous sulfate amount that alters the properties of the composition as a feed stock in steel making furnaces. Embodiment 3 is the solid composition of embodiments 1 or 2, wherein the carbon source contains greater than 50% carbon by weight. Embodiment 4 is the solid composition of either of embodiments 1 to 3, wherein the carbon source is selected front the group consisting of anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, tar, molasses, decanter sludge, and combinations thereof. Embodiment 5 is the solid composition of either of embodiments 1 to 4, wherein the iron oxide is iron (II) oxide (FeO), iron (III) oxide (Fe2O3), iron (0,01) oxide (Fe3O4, Fe5O6, Fe5O7), or mixtures thereof preferably Fe2O3. Embodiment 6 is the solid composition of either of embodiments 1 to 5, wherein the zinc is zinc oxide (ZnO), or any other zinc containing oxide, zinc ferrite, or mixtures thereof. Embodiment 7 is the solid composition of either of embodiments 1 to 6, further containing from greater than 0% up to 15% by weight of an additive. Embodiment 8 is the solid composition of embodiment 6, wherein the additive is selected from the group consisting of lime, calcium chloride, silica, limestone, clay, iron and/or steel grindings, iron and/or steel borings, iron and/or steel turnings, and combinations thereof. Embodiment 9 is the solid composition of either of embodiment 1 to 8, wherein the baghouse dust contains greater than 30% iron oxide by weight. Embodiment 10 is the solid composition of either of embodiment 1 to 9, wherein the baghouse dost contains 30% to 70% iron oxide by weight.
Embodiment 11 is a briquette or pellet adapted for use as a recycled feed stock in electric arc and/or basic oxygen furnaces, the briquette or pellet containing: 60 to 90% by weight of a bag house dust containing iron oxide and zinc, wherein the iron oxide contains 30 to 70% by weight of the bag house dust; 3 to 20% by weight of a carbon source; and 0 to 15% by weight additive. Embodiment 12 is the briquette or pellet of embodiment 11, wherein the product does not contain either or both of ferrous chloride and ferrous sulfate. Embodiment 13 is the briquette or pellet of embodiment 11 or 12, wherein the carbon source contains greater than 50% carbon by weight. Embodiment 14 is the briquette or pellet of either of embodiment 11 to 13 wherein the carbon source is selected from the group consisting of anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, tar, molasses, decanter sludge, and combinations thereof. Embodiment 15 is the briquette or pellet of either of embodiment 11 to 14, wherein the additive is selected from ‘the group consisting of lime, calcium chloride, silica, limestone, clay, iron and/or steel grindings, iron and/or steel borings, iron and/or steel turnings, and combinations thereof. Embodiment 16 is the briquette or pellet of either of embodiment 11 to 15, wherein the iron oxide is iron (II) oxide (FeO), iron (III) oxide (Fe2O3), iron (II,III) oxide (Fe3O4, Fe5O6, Fe5O7), or mixtures thereof preferably Fe2O3. Embodiment 17 is the briquette or pellet of either, of embodiment 11 to 16, wherein the zinc is zinc oxide (ZnO), or any other zinc-containing oxide, zinc ferrite, or mixtures thereof.
The feature or features of one embodiment may be applied to other embodiments, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments. Any embodiment of any of the disclosed container assemblies and compositions can consist of or consist essentially of rather than comprise/include/contain/have, any of the described elements and/or features and/or steps. Thus, in any of the claims, the term “consisting of or “consisting essentially of can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb. Details associated with the embodiments described above and others are presented below.
Various features and advantageous details are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, are given by way of illustration only, and not by way of limitation. Various substitutions, modifications, additions, and or rearrangements will become apparent to those of ordinary skill in the art from this disclosure.
In the following description, numerous specific details are provided to provide a thorough understanding of the disclosed embodiments. One of ordinary skill in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
The present disclosure provides methods and compositions that make use of the steel-making waste by-product, bag house dust. The bag house dust contains valuable materials such as iron and zinc, primarily in the form of oxides. High oxide content in the bag house dust oxide precludes direct use of bag house dust in industrial steel furnaces. In the methods and compositions disclosed herein, the bag house dust is combined with a carbon source and optionally an additive, and molded into briquettes or pellets. Without wishing to be bound by theory, the carbon source is believed to act as an in situ reducing agent that assists in transformation of metal oxides to useful metals. The briquettes or pellets may be employed as a source of iron, zinc, and/or carbon in iron, zinc, or steelmaking processes.
The bag house dust is mixed with, a carbon source and molded into briquettes or pellets. The carbon source carbon source may be anthracite, graphite, coal, coke, petcoke, coal tar pitch, tar, molasses, decanter sludge, or combinations thereof. In some aspects, the carbon source and bag house dust are combined in a weight ratio ranging from 0.03:1 to 0.18:1, with carbon as the major weight constituent of the carbon source. In one embodiment, the briquettes or pellets comprise a 0.06:1 weight ratio of carbon source to bag house dust.
One or more additives may optionally be included in the pellets or briquettes, including lime, calcium chloride, silica, limestone, day, iron and/or steel grindings, iron and/or steel borings, iron and/or steel turnings, and the like. The pellets or briquettes may include an optional binder. The pellets or briquettes may include one or more non-carbonaceous reducing agents. In preferred embodiments, non-carbonaceous reducing agents are excluded from the pellets or briquettes.
The pellets or briquettes may be employed in a steelmaking process wherein the bag house dust iron oxide is used as an iron source for the production of steel. The pellets or briquettes may be combined with recycled iron or steel, unrecycled iron, or a metal ore.
In a briquette or pellet-making process, bag house dust is combined with a carbon source and shaped into briquettes or pellets. The bag house dust, carbon source, optional additive, and optional binder are combined in a mixing apparatus. In some embodiments, the carbon source acts as a binder. The binder, if added, will be sufficient to bind together the carbon source and the BHD to be formed into briquettes via the chosen processing technique. Typically, the binder will be present in an amount of from 1 to 20% by weight of the mixture of BHD, carbon source and the binder. Preferred binders include hydrocarbon binders such as, e.g., corn starch, cellulose, and the like. Water may be optionally added to the mixture to create a slurry.
The relative amounts of bag house dust, carbon source, and optional components (additive, binder, and water) may be adjusted in order to improve the adherence of the mixture and/or the strength of the briquette or pellet product. The mixture may be mixed at room temperature, or it may be subjected to heating conditions.
The mixture is formed into briquettes or pellets using any molding or shaping method known in the art. Exemplary methods include extrusion and pelletizing. The shaped briquette or pellet may be further coated with additional bag house dust mixture and subsequently molded or shaped.
The shaped briquette or pellet may be heated in an oven. The oven may be used to remove water, increase binding, and/or cause at least a portion of the metal oxide content to be reduced. The oven may be provided with a stream of oxygen or an oxygen-containing gas or in inert atmosphere such as Ar and N. The briquettes or pellets may be used immediately or may be aged prior to using. Aging of the briquettes or pellets may be accomplished at ambient temperature or under elevated temperature.
The briquettes or pellets may be used in iron or steel-making furnaces. The briquettes or pellets may be used in other processes, for example, the briquettes or pellets may be used in a Midrex and HYL processes or any other reduction technology whereby the iron oxide is reduced in the absence of melting. The briquettes or pellets may be used as an aggregate and added to concrete. The briquettes or pellets may be used to enhance zinc content in zinc distillation or extraction methods. The recycling of bag house dust may provide financially advantageous environmental protection credits for waste reduction and/or recycling of iron and zinc oxides.
Baghouse dust (BHD) briquettes containing carbon as a reductant in briquettes containing carbon as a reductant in a 1.6:1 molar ratio of carbon to Fe2O3 The BHD briquettes were prepared by mixing 10 wt % carbon with 90 wt % BHD along with water. The wet mixture was then pressed into briquettes with a roller press cold briquetting machine. The BHD was provided by SABIC, and was obtained from an electric arc furnace. The chemical composition of an exemplary, non-limiting BHD analyzed by X-ray fluorescence spectrometry (XRF) used in accordance with the present invention is provided below in Table 1:
The briquettes of Example 1 were subjected to reduction at 1100° C. and analyzed. Analysis of the as-received and reduced briquettes was performed by x-ray diffraction (XRD) for phase identification, and x-ray fluorescence (XRF) spectrometry to determine approximate elemental composition. The nominal compositions of the reduced BHD briquettes is summarized in the Table 2 below:
Reduction of a sample briquette was carried out in a vertical tube furnace under flowing argon gas (flow rate of 150 mL/min). One briquette was weighed, and then suspended (using Kanthal wire) at the top of the furnace while the furnace was heating up. The furnace was taken from room temperature to 1100° C. at a rate of 5° C. per minute, where it was held for one hour, before being cooled to room temperature also at a rate of 5° C. per minute. Upon reaching 1100° C., the briquette was lowered into the hot zone of the furnace, and the exhaust gasses were directed to an infrared gas analyzer, which recorded the concentrations of CO, CO2, CH4, H2, and O2. After the furnace had fully cooled down, the briquette was removed from the furnace and weighed again.
XRD patterns were analyzed by using the QualX software package (See A. Altomare, N. Corriero, C. Cuocci, A. Falcicchio, A. Moliterni, and R. Rizzi, “QUALX2.0: a qualitative phase analysis software using the freely available database POW_COD,” J. Appl. Crystallogr., vol. 48, no. 2, pp. 598-603, April 2015). The patterns were filtered to remove the broad carbon peak present around 20=25°, and major peaks were identified from the filtered pattern. The search-match database was restricted to elements listed in Table 1, in addition to carbon and oxygen in order to account for oxides and carbides that may have been present. The phases that best accounted for the peaks were selected manually.
Data gathered from the infrared gas analyzer is plotted in
The data suggests that the rate of reduction is quite fast. The infrared (IR) spectrometer data is particularly useful for determining the total amount of CO, CO2, and H2 produced by integration of the curves.
The mass loss of the briquette was significant (initial mass=13.7 g, final=9.2 g). The inside surface of the furnace tube was also coated with a gray powder, which was analyzed by scanning electron microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) and found to zinc-contain primarily zinc. The XRF results (Table 3, which shows the approximate ratios of Ca, Fe, and Zn, normalized to 100%) show an almost complete loss of zinc in the final product.
XRD of an unreduced ground briquette shows in
XRD on the reduced briquette as shown in
This suggests that the briquette has been fully reduced by the reductant in about 1 hour or less at 1100° C. The presence of austenite is likely due to the presence of significant amounts of manganese. If all manganese was reduced as well, the resulting iron should contain ˜5 weight percent manganese given the composition in Table 1. Manganese is an ausenite stabilizer as can be seen from, e.g., the phase diagram in FIG. 4 of the ASM Handbook, Volume 3, Alloy Phase Diagrams (1998). It is believed, without being bound to any theory, that the presence of dicalcium silicate is likely due to interactions between the CaO and SiO2, as silica was not detected in the unreduced sample's XRD pattern because it was either not present in sufficient quantities or was amorphous.
From the data, it can be concluded that reduction was rapid at the tested furnace temperature of 1100° C., resulting in complete reduction of the iron and near-complete removal of zinc by reduction of zinc oxide to metallic zinc, that evaporated out of the briquette.
The BHD of Example 1 having the composition shown in Table 1 above process was premixed with anthracite as a carbon source according to the procedure and ratios described in Example 1 above and shaped into pellets/briquettes using the method of Example 1.
Experiments were conducted to evaluate the use of BHD and the aforementioned carbon briquettes in the EAF. Different experiments were conducted with varying temperature and time. The summary of experimental result shown in table −1
Steps for conducting the experiment of Example 2 are described below in Table 3 with reference to Table 4:
The results in Table 4 show that the four set of experiments conducted with varying temperature (1200° C. and 1400° C.) and holding time 10 and 15 min) result show that acceptable amounts of reduction occur in all cases (76.55 to 80.69% reduction).
At 1200° C. and 10 min holding time metallization varies from 76.55% to 77.35% whereas with 15 min holding time metallization varies from 79.69% to 79.83%.
In case of 1400° C. and 10 min holding time metallization varies from 79.02% to 81.76% whereas with 15 min holding time metallization varies from 80.03% to 80.69%.
The claims are not to be interpreted as including means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for” respectively.
This application claims the benefit of US. Provisional Patent Application No. 62/504,496 filed May 10, 2017, hereby incorporated by reference in its entirety for all lawful purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2018/053262 | 5/10/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62504496 | May 2017 | US |
