Patent Application
20120028786
Steel refining plants routinely produce a large amount of steel slags as a by-product of steelmaking. Steel slags typically contain silica (SiO2) and calcium oxide (CaO). The silica mainly comes from raw iron ore. The calcium oxide is added into a furnace to remove silica and alumina from raw steel ore and remains in steel slags. The similarity between the chemical compositions of steel slag and portland cement allows certain types of steel slags to be used as a raw material of construction cement. Other suitable slag applications include paving material and sand compaction pile.
Thus, known recycles of steel slags are limited to applications in the field of construction and civil engineering. Other applications, however, for further utilization of steel slags is possible.
Example embodiments relate to a method of fabricating a cordierite article comprising determining relative percentages of SiO2, Al2O3, and MgO included in one or more steel slags. Based on the determined percentages, a starting mixture from said one or more steel slags is prepared. The starting mixture is molded into a desired shape and the molded starting mixture is sintered. In one embodiment, the sintered mixture is composed, at least in part, of cordierite.
According to one embodiment, the starting mixture is molded to include one or more elongated limbs that define one or more air channels extending in the axis direction of the one or more elongated limbs. The starting mixture may be molded into a honeycomb shape. In one embodiment, the one or more steel slags may include one or more blast furnace slags and/or one or more converter slags.
In another aspect, the starting mixture is prepared by mixing a plurality of steel slags each selected from the group consisting of one or more blast furnace slags, one or more converter slags and one or more electric furnace slags. In another aspect, the starting mixture is molded by extrusion. In one embodiment, the one or more steel slags include a carbide selected from the group consisting of silicon carbide, aluminum carbide, magnesium carbide. In another aspect, the one or more steel slags include a forming agent.
In another aspect, wherein the starting mixture is molded into a plurality of elongated cylindrical filter elements; wherein each of the molded plurality of elongated cylindrical filter elements are sintered; and the method further includes joining the plurality of elongated cylindrical filter elements with one another. In another aspect, the elongated cylindrical filter elements are joined in a side-by-side fashion such that each of the filter elements defines one or more air channels between neighboring filter elements.
Example embodiments relate to a method of fabricating a cordierite article comprising: determining relative percentages of SiO2, Al2O3, and MgO included in one or more steel slags; selecting, based on the determined percentages, at least one of the one or more steel slags; molding the selected one or more steel slags; sintering the molded one or more steel slags.
In another aspect, the sintered one or more steel slags consist of cordierite. In another aspect, the one or more steel slags include at least one of blast furnace slag, converter slag, and electric furnace slag. In another aspect, the starting mixture is molded to include one or more elongated limbs that define one or more air channels extending in the axis direction of the one or more elongated limbs.
Example embodiments relate to a cordierite article comprising a cordierite body, wherein the cordierite body is fabricated from a starting material including at least one of one or more steel slags selected from the group consisting of one or more blast furnace slags, one or more converter slags and one or more electric furnace slags. In another aspect, the cordierite body is formed to include one or more elongated limbs that define one or more air channels extending in the axis direction of the one or more elongated limbs. In another aspect, the cordierite body is formed into a honeycomb shape.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
Blast furnace slag: any type of steel slag which can be produced in any blast furnace during or as a result of refining process of iron ore.
Converter slag: any type of steel slag which can be produced in any converter furnace during or as a result of the process of refining pig iron into steel.
Electric furnace slag: any type of steel slag which can be produced in any electric furnace during or as a result of the process of refining molten metal mixture into steel.
Steel slag: any type of slag produced during or as a result of steel refining process in any type of furnace. Steel slag includes at least furnace slag, converter slag and electric furnace slag.
One aspect of this disclosure is based on the inventor's observation that the chemical compositions of steel slags are similar to that of cordierite represented by 2MgO-2Al2O3-5SiO2 and, therefore, steel slags can be used to fabricate a cordierite article suitable for a particulate filter. For example, a Diesel Particulate Filter (“DPF”) can be fabricated by using starting materials that come from steel slags. Such a cordierite is economically advantageous as compared to conventional particulate filters that are generally manufactured from expensive raw materials.
Example embodiments of this disclosure relate to a cordierite article suitable for use as a particulate filter body. Such a cordierite article may be fabricated from one or more types of steel slags that may be obtained from various types of furnaces. Example embodiments of this disclosure also relate to a method for fabricating such a cordierite article using steel slags as a starting material.
As described hereinafter, the filter body 102 is fabricated from a starting material that comes from or contains steel slags and formed into a honeycomb shape which may consist of a plurality of polyhedral cells 108. In one embodiment, each of the polyhedron cells 108 may be formed into a square shape in cross section, as shown in
Because of its relatively low density, the molten furnace slag floats on the surface of the molten pig iron in the blast furnaces 202 and 222. The molten furnace slag is tapped off from the blast furnaces 202 and 222 for subsequent treatments. In one embodiment, the molten blast furnace slag is rapidly cooled by applying pressurized water as the slag runs from blast furnaces 202 and 222 into a cooling yard. This rapid cooling process causes the blast furnace slags 204 and 224 to become granulated. In another embodiment, the molten blast furnace slag is poured into a cooling yard without rapid cooling. In the cooling yard, the slags are slowly cooled by air and water sprinkling. These cooled and solidified blast furnace slags 204 and 224 are piled up in a cooling yard located adjacent to each of the blast furnaces 202 and 222.
Each of the pig irons from the blast furnaces 202 and 222 is poured into corresponding converter furnaces 206 and 226 where the pig irons are further refined into molten steel. During this refining process in the converter furnaces 206 and 226, converter slag is produced as a by-product and poured into corresponding cooling yards each adjacent to the converter furnaces 206 and 226. Also used for steelmaking are electric furnaces 210 and 230, each of which produces electric furnace slag as a by-product of the process of refining scrap metal into steel. The produced converter slag and electric furnace slag contain a large percentage of lime (CaO), silica (SiO2), alumina (Al2O3) and manganese oxides (MgO). As with the blast furnace slags 204 and 224, the converter slag and electric furnace slag are rapidly or slowly cooled. The cooled converter slags 208 and 228 and electric furnace slags 212 and 232 are piled up in respective cooling yards.
In one embodiment, carbon dioxide may be injected in at least one of the blast furnace slags 204, converter slags 208 and 228 or electric furnace slags 212 and 232 before performing a cooling treatment to facilitate the carbonation of each steel slag. The carbonization of lime, silica, alumina and manganese oxides contained in each slag may stabilize the trapping efficiency and improve the durability of a resulting filter made from the carbonized slags. As a result of the injection of carbon dioxide, the resulting blast furnace slags 204, converter slags 208 and 228 or electric furnace slags 212 and 232 may include at least one of silicon carbide, aluminum carbide and magnesium carbide. In one embodiment, the carbonation treatment may utilize carbon dioxide emitted in the steelmaking processes in each of the blast furnaces 202 and 222, converter furnaces 206 and 226 and electric furnaces 210 and 230, which facilitates the reduction of CO2 emission from each furnace.
In one embodiment, a forming agent such as sodium hydrogen carbonate (NaHCO3) or ammonium carbonate ((NH4)2CO3) may be injected into at least one of the blast furnace slag, converter slag and electric furnace slag before cooling treatment so that larger number of pores can be formed in a resulting filter. The large porosity increases the trapping efficiency of the resulting filter.
In an example operation 302, samples of each of the blast furnace slags 204, 224, converter slags 208, 228 and electric furnace slags 212, 232 are taken to determine, for example, the relative weight percentages of the components of each sample. The weight per unit volume of each sample may be measured using any known method in the art, such as Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) or X-ray Diffraction (XRD). Samples may also be taken from different slags produced by different furnaces than the blast furnaces 202 and 222, converter furnaces 206 and 226 and electric furnaces 210 and 230.
Based on the measured weight per unit volume of each sample, the relative weight percentages of each component, such as SiO2, Al2O3, MgO and CaO, are determined. The determined weight percentages may be stored in the format shown in table 402 in
In an example operation 304, based on the records stored in table 402, one or more appropriate steel slags are selected from those stored in table 402 such that the weight percentages of the selected steel slag is similar to that of the stoichiometric cordierite composition. In another embodiment, an optimal mixture of steel slags selected from table 402 is determined such that the weight percentages of the mixed steel slags is similar to that of the stoichiometric cordierite composition. Given the stoichiometric cordierite composition of 2MgO-2Al2O3-5SiO2, the stoichiometric weight percentages of cordierite composition is 51.4% SiO2, 34.9% Al2O3, and 13.7% MgO. Despite its large amount in each steel slag, CaO may be ignored in determining an optimal proportion of steel slags to be used in a cordierite filter because it is not a component of cordierite.
In one embodiment, to obtain a filter body consisting of cordierite, a starting slag mixture may contain (i) SiO2 and Al2O3 each of which is within, for example, 15% on either side of their stoichiometric weight proportions and (ii) MgO which is within 5% on either side of its stoichiometric weight proportion. That is, the starting slag mixture may contain from about 36-66% by weight SiO2, 20-50% by weight Al2O3 and 9-19% by weight MgO. This weight percent ranges of SiO2, Al2O3, and MgO may be hereinafter referred to as a “first acceptable range.” In one embodiment, one or more steel slags including SiO2, Al2O3, and MgO whose weight percentages are within the first acceptable range are selected in order to obtain a starting slag mixture. In another embodiment, an optimal mixture proportion of steel slags is determined such that the weight percentages of SiO2, Al2O3, and MgO included in the mixed steel slags are within the first acceptable range. In accordance with the determined proportion, one or more selected steel slags are mixed or blended to form a starting powder mixture by use of any method commonly used in the art. Accordingly, a starting slag mixture is prepared by selecting one or more appropriate steel slags or determining an optimal mixture proportion of steel slags based on the recorded relative weight percentages of SiO2, Al2O3, and MgO.
Referring now to
Looking at the example weight percentages recorded in table 402, it can be seen that each of the weight percentages of the blast furnace slags 204, 224 and electric furnace slags 212, 232 are within the first acceptable range. For example, the blast furnace slag 204 contains 34.2% by weight SiO2, 13.0% by weight Al2O3, 7.8% by weight MgO and 41.0% by weight CaO. Accordingly, the weight percentages of three cordierite components are 62.2% by weight SiO2, 23.6% by weight Al2O3, and 14.2% by weight MgO, which is clearly within the first acceptable range. By way of another example, the blast furnace slag 224 contains 36.2% by weight SiO2, 12.3% by weight Al2O3, 7.3% by weight MgO and 39.9% by weight CaO. Accordingly, the weight percentages of three cordierite components is 64.9% by weight SiO2, 22.0% by weight Al2O3, and 13.1% by weight MgO, which is also within the first acceptable range. Similarly, in connection with the electric furnace slags 212 and 132, it is clear from table 402 that the weight percentages of three cordierite components therein are within the first acceptable range.
In another example embodiment, the weight percentages of the converter slags 208 and 228 are out of the first acceptable range. Consequently, the converter slags 208 and 228 can not be used as a starting slag mixture for a particulate filter without being mixed with other slags. Considering that the converter slags 208 and 228 contain relatively lower weight percentage of Al2O3, the converter slags 208 and 228 may be mixed with other types of slag which contain relatively higher weight percentage of Al2O3 to form a starting slag mixture.
In another embodiment, to enhance an absorption efficiency (or trapping efficiency) of the filter 102, a narrower second acceptable range may be selected, wherein a starting slag mixture may contain (i) SiO2 and Al2O3 each of which is within, for example, 10% on either side of their stoichiometric weight proportions and (ii) MgO which is within 3% on either side of its stoichiometric weight proportion. That is, the second acceptable range includes a starting powder mixture containing from about 41-61% by weight SiO2, 25-45% by weight Al2O3 and 11-17% by weight MgO. It can be seen that none of the steel slags in table 402 is within the second acceptable range. However, an example starting slag mixture which is within the second acceptable range may be obtained by mixing the furnace slag 104 and the electric furnace slag 212 in the proportion of 1.0 kg of the furnace slag 104 to 1.0 kg of the electric furnace slag 212. The weight percentages of the mixture becomes 58.5% by weight SiO2, 25.1% by weight Al2O3 and 16.4% by weight MgO, which is within the second acceptable range.
Thus, even though in certain embodiments the weight percentages of an individual steel slag is not within a predetermined acceptable range, in an embodiment a mixture of a plurality of steel slags can achieve the desired weight percentages of SiO2, Al2O3, MgO within the predetermined acceptable range. In one embodiment, different types of slags are mixed to obtain a starting slag mixture within a predetermined acceptable range. Such a mixture of steel slags may be made by mixing one type of the steel slags (e.g., blast furnace slag) with a different type of steel slag (e.g., electric furnace slag). More than two types of steel slags may be mixed to obtain a starting slag mixture. For example, such a starting slag mixture may be made by mixing blast furnace slag, converter slag and electric furnace slag. In another embodiment, a mixture of steel slags may be made by mixing a plurality of the same type of steel slags that are produced by different furnaces (e.g., blast furnace slags 204 and 224 produced respectively by blast furnaces 202 and 222).
In an example operation 306, an organic binder may be added to the starting slag mixture prepared in operation 304 to form a well-mixed binder mixture. Such a binder mixture may be made by use of a mixer or blender.
Next, in an example operation 308, the binder mixture prepared in operation 306 is molded by various methods such as extrusion using a lattice-shaped die to form a presintered honeycomb filter body having substantially the same shape as the filter body 102 illustrated in
In an example operation 310, the molded honeycomb body is sintered. In one embodiment, the sintering process is carried out within a temperature range from 1380 to 1445 degrees Celsius for 3-10 hours. The resulting honeycomb filter body is composed, at least in part, of porous cordierite. The cordierite filter body can trap particles from gases or liquids as they travel through the filter body.
Next, in an example operation 508, the binder mixture prepared in operation 506 may be molded to form a plurality of elongated cylindrical filter elements.
In an example operation 612, the sintered filter elements 708 are joined with one another in a side-to-side fashion by a known joining material such as common organic binder. The plurality of filter elements 608 are arranged such that the axes of the elements 708 are arranged substantially parallel to one another.
In an example operation 804, if one of the steel slags is within a predetermined acceptable weight range (e.g., the first or second acceptable range as described above), the steel slag may be directly introduced into a die to form a honeycomb filter body without solidifying the molten slag by performing cooling treatment. In another embodiment, the steel slag may be formed into an elongated cylindrical shape, similar to that shown in
The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.
As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP10/04856 | 7/30/2010 | WO | 00 | 12/13/2010 |
