Patent Application
20180179448
The present invention relates to a novel composition of matter having application for use as an electrode, reducing agent, and carbon source in metallurgical processes and the method for its manufacture.
Carbon serves an important role in the refining and manufacturing of several metals including aluminum, silicon, and carbon steel.
Aluminum metal is produced from aluminum oxide in the Hall-Héroult process, in which the aluminum oxide is electrolyzed in a molten mixture of cryolite with calcium fluoride. A consumable carbon anode serves the dual role of an electric current source for the process and a source of carbon to react with oxygen produced in the process to form carbon dioxide.
Silicon metal is produced in a similar fashion from silicon dioxide in an electric arc furnace using carbon electrodes. The carbon electrodes are oxidized by the oxygen in the silicon dioxide, reducing the silicon and leaving pure silicon metal.
In steel production, the carbon is utilized in the form of coke, which is burned as fuel and used as a reducing agent for the conversion of iron into steel. Coke is produced from metallurgical coals using a process which requires low levels of sulfur, phosphorous, and ash to prevent the addition of impurities in the coal to the coke product. Petroleum coke is a solid residue produced in oil refining which is resembles coke. However, it contains too many impurities to be useful in metallurgical manufacturing process.
Although only three examples are listed, carbon is used in a broad range of metallurgical applications including, but not limited to the production of titanium, zinc, copper, silver, gold, and many other applications. All of these applications utilize carbon as a fuel or reducing agent and produce CO2 as a byproduct. If the carbon is derived from coal, or other fossil sources, the released CO2 represents an increase in atmospheric CO2 levels.
U.S. Pat. No. 3,215,522 A, “Silicon Metal Production” issued to August M. Kuhlmann on Nov. 2, 1965, describes a method of silicon metal production which uses electrodes made from coke, coal, and wood chips in an electric arc furnace. However, carbonaceous materials with fewer fines and low iron content are preferred over the materials disclosed by Kuhlmann.
US Patent Application Publication No. 20110150741 A1, published Jan. 23, 2011, now abandoned, by Lang et al. for “Production of Silicon by Reacting Silicon Oxide and Silicon Carbide, Optionally in the Presence of a Second Carbon Source” describes an improved method of silicon production utilizing a mixture of silicon oxide and silicon carbide with a secondary carbon source. The carbon source can include wood, or plant matter and charcoal, preferable low in boron and phosphorous.
U.S. Pat. No. 1,996,643 A, for “Improved Electrode and Method of Making Same” issued to De Pree, on Apr. 2, 1935, discloses a method for producing electrodes for a steel making process. In De Pree's process, carbon, graphite, or graphitized carbon are bound with rosin and oil to produce an electrode which will withstand oxidation at high temperatures.
Kuhlmann and Lang both focus on methods of silicon production and list preferred properties of carbonaceous electrode material. De Pree shows a method for producing resistant electrodes from a combination of a carbon material and pitch binders. None of the above patents describe a method for producing a carbon material with targeted properties for metallurgical processing; although, they do explain the properties of the used carbon being of significant importance. They also do not address a need for renewable materials or materials which have a negligible impact on atmospheric CO2 levels.
In view of the foregoing, it is apparent that a need exists for a new and useful material which has properties similar to existing electrodes and cokes, but with targeted physical properties and which can be produced renewably and without the emission of fossil carbon dioxide or other pollutants into the environment.
The novel material and manufacturing processes herein described are complementary to the prior art and represent significant improvements thereto. In an embodiment, the present invention provides a method for the creation of a novel composition of carbon to be used in metallurgical processes through the pyrolysis of biomass particles under special treatment conditions to create specific properties targeted for use as a metallurgical carbon.
In another embodiment, a system is disclosed for carbon production which is integrated with the metallurgical process to provide increased efficiency and manufacturing costs reductions.
These and other advantages and novel features of the present invention will become apparent from the following description of the invention and appended claims.
It should be noted that the present description is by way of instructional examples, and the concepts presented herein are not limited to use or application with any single method and/or apparatus for the production of a metallurgical carbon material. Hence, while the method of producing a novel carbon material of the present invention may be used in connection with a selected metallurgical precursor in the manufacturing of a preselected metal in a metallurgical refining unit such as a furnace. the details of the innovation described herein are for the convenience of illustration and explanation with respect to exemplary embodiments, and the principles disclosed may be applied to other types and applications of the production of metallurgical carbons from biomass feedstocks without departing from the scope hereof.
Referring now to
Once the feedstock had been dried, sized, and otherwise prepared, at step 18, it is introduced to a carbonization reactor 20 where it is thermally decomposed or pyrolyzed at a sufficiently high temperature to drive off volatile carbon and create the high purity, highly fixed solid carbon structure or carbon coke 22. The carbonization or pyrolysis of the biomass at a preselected temperature of between approximately 350° C. and approximately 750° C. under atmospheric pressure for a preselected time of between one and twenty minutes will yield a carbon material which has a predetermined structure, size and density for the specific application. This structure may be created via any number of pyrolysis processes known in the art, including external heating, steam pyrolysis, or staged pyrolysis as described in Applicant's U.S. Pat. No. 9,505,984 B2 (the “'984 patent”). Any cost effective method for the carbonization would be suitable for this process. The carbon material may then be added directly to the steelmaking process at step 23 or processed further as will be discussed in greater detail below.
By way of example and not of limitation, the pyrolysis process as described in the '984 patent, produces the desired carbonized structure without the need for external fuel beyond the chemical energy in the biomass feedstock. Additional carbonization by-products such as wood gas 24 are also produced in the pyrolysis process which may have a number of uses, all of which create significant economic advantages and enhanced efficiencies over prior art systems and manufacturing processes.
First, it reduces operating costs since the wood gas may be directed to a combustor 26 as shown at step 28 where it is burned for heat recovery, producing hot gas for biomass drying 30, step 32, a portion of which may be directed to a blast furnace 34 at step 36 for adding heat to the steelmaking process. The need for fuel from extraneous fuel sources, which would otherwise be required to be burned for process heating, is eliminated. Moreover, the excess wood gas produced by carbonization, which does not drive the carbonization process, can be used to produce steam and/or electricity to offset the electrical needs of many metallurgical production and refining processes, to provide heat for biomass drying, and/or to fire a furnace. Hence, a synergistic integration of carbonization and electricity production with a metal refining facility is created.
Second, a substantial environmental benefit is realized by not utilizing fossil carbons for fuel or feedstock in metallurgical processing. No fossil CO2 emissions from the reduction reaction are present; the emissions being substantially if not completely free of any environmentally hazardous compounds or chemicals. Moreover, other heat and/or electrical requirements can be offset using produced wood gas, as noted above.
Referring again to
The dried and sized biomass 58 is introduced via step 60 to a carbonization reactor 62 where it is decomposed at high temperature (between approximately 350° C. and approximately 750° C.) under atmospheric temperature into solid carbon 64 and wood gas 66. The wood gas may be directed to a combustor 68 as shown at step 70 where it is burned for heat recovery, producing hot gas for biomass drying 72, step 74. A portion of the wood gas produced during the carbonization process may also be used to produce steam 76 at step 78 which is directed to an electrical power generator 80 to provide electricity for the aluminum making process at step 84.
The solid carbon 64 produced in the carbonization process at 62 is then introduced into an electrode forming apparatus 86 where it is mixed with a binding material and formed into one or more solid electrodes 90. The electrodes are installed in an aluminum reduction cell at step 94 to provide a reducing agent and an electron sink to process alumina 96 (A12O3) into molten aluminum 98 and carbon dioxide 99 at steps 100 and 101, respectively.
The dried and sized biomass 118 is introduced via step 120 to a carbonization reactor 122 where it is decomposed at high temperature (between approximately 350° C. and approximately 750° C.) under atmospheric temperature into solid carbon as above which is formed into carbon electrodes 124. Wood gas 126 is a by-product of the carbonization process which may be directed to a combustor 128 as shown at step 130 where it is burned for heat recovery, producing hot gas for biomass drying 132, step 134. A portion of the wood gas produced during the carbonization process may also be used to produce steam 136 at step 138 which is directed to an electrical power generator 140 to provide electricity 141 for the silicon making process at step 142.
One or more of the electrodes 124 formed of the carbon are installed in a silicon arc furnace 144 at step 146 to provide a reducing agent and an electron sink to process silica 148 into molten silicon 150, at step 152 and carbon monoxide 154 and carbon dioxide 156 at step 158.
The end product material of the manufacturing processes described above with respect to the embodiments of the processes of the present invention possesses a number of properties and characteristics which overcome the shortcomings of the prior art and make it ideal for use as a metallurgical processing or refining material, a reducing agent, and as a source of metallurgical carbon. The material may be formed into an electrode by incorporating a binder and by submitting the material to a densification process. The material's properties and characteristics include by way of example:
1. a composition of matter, particulate or pelletized material created entirely through the pyrolysis of biomass which has greater than 50% by mass of non-volatile, high purity fixed elemental carbon, the composition of which material may be adjusted for a specific metallurgical application;
2. a sulfur content less than or equal to approximately 1% by mass;
3. an ash content less than or equal to approximately 10% by mass;
4. a content of less than approximately 10 mg/kg of each of the following: antimony, arsenic, barium, cadmium, chromium, cobalt, copper, lead, nickel, mercury phosphorous, boron and selenium;
5. a content of less than approximately 5 μg/kg of any polycyclic aromatic compound;
6. a surface area of between approximately 10 m2/g to approximately 600 m2/g as measured by nitrogen absorption techniques.
7. substantially free of any environmentally hazardous chemicals or components; and
8. the following physical properties which may be adjusted to meet the requirements of a specific metallurgical application, including but not limited to, coking strength, conductivity, density, porosity, surface area and particle size.
Changes may be made to the foregoing methods, devices and systems without departing from the scope of the present invention. It should be noted that the matter contained in the above description should be interpreted as illustrative and not in a limiting sense. The following claim(s) are intended to cover all generic and specific features described herein as well as statement of the scope of the present invention, which, as a matter of language, might be said to fall therebetween.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/438,633, filed Dec. 23, 2016, which is incorporated herein by reference in its entirety as if fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 62438633 | Dec 2016 | US |
