Patent Application
20100077888
The present invention is directed to the production of an iron powder commodity used in a wide variety of applications such as sintered components, magnetic products, chemical and pharmaceuticals, printing, welding, and others. The iron powder commodity is produced by de-oiling nanoparticle and ultrafine particle iron-bearing solids contained in hot strip mill (HSM) sludge generated in a steelmaking operation. More specifically, this invention is directed to de-oiling magnetic and non-magnetic nanoparticle and ultrafine particle iron-bearing solids contained within HSM sludge to produce a high value iron powder commodity. Oils and greases (hydrocarbons) used as coolants and lubricants during HSM operations adhere to the iron-bearing particles contained in the HSM sludge, making it impossible to recover the valuable iron-bearing particles as a powder without first treating the sludge to remove the oils and greases.
Accordingly, it is a first object of the present invention to produce an iron powder commodity.
It is another object of the present invention to produce an iron powder commodity separated into nanoparticle iron-bearing solids and into and ultrafine particle iron-bearing solids.
It is another object of the present invention to produce an iron powder commodity separated into magnetic iron-bearing solids and into non-magnetic particle iron-bearing solids.
It is another object of the present invention to produce an iron powder commodity using an environmentally friendly, green industry process to de-oil HSM sludge.
It is another object of the present invention to provide an environment friendly green industry de-oiling process that recovers hydrocarbon products from HSM sludge in addition to producing an iron powder commodity.
A still further object of the invention is to provide a de-oiling process that eliminates undesirable emissions into the atmosphere during the de-oiling of HSM sludge.
Other objects and advantages of the present invention will become apparent as a description thereof proceeds.
In satisfaction of the foregoing objects and advantages, the present invention treats HSM sludge in a reactor chamber purged with an inert gas. The reactor chamber temperature is raised so that water in the mixture creates a steam surge that erupts through the oily HSM sludge. The erupting steam surge dehydrates the sludge and removes or frees any viscid hydrocarbons that adhere to surfaces of the nanoparticle and ultrafine particle iron-bearing solids contained in the HSM sludge. The temperature within the inert gas filled reactor chamber is further elevated to vaporize the hydrocarbons, and the inert gas, steam, and hydrocarbon vapors are vented as an off-gas from the reaction chamber. The vented off-gas is separated into inert gas recycled back into the de-oiling process, water, and at least one hydrocarbon product. The remaining, de-oiled iron-bearing particles are discharged from the reactor chamber as an iron powder commodity.
High purity iron powders are used in many different applications. Almost 80% of global iron and steel powder is converted into sintered components that offer design freedom, almost 100% material utilization, and other benefits. The automotive industry is the main user of such sintered components, and the material is used to manufacture transmission and engine parts including bushings and bearings. State of the art sintered components comprise highly complex designs and meet the industry's demands for strength and tolerances. A modern automobile contains on average 22 pounds (10 kg) of sintered components.
Outside the automotive sector, sintered components include power tools, appliances, air-conditioners, computers, lawnmowers, locks, and pumps. These are just a few examples.
Other high purity iron powder applications, where the powder comprises either ultrafine or nanometer size iron particles, include the electrical industry where soft magnetic composites (SMC) are used, for example, in motor and electrical machine designs; the chemical and pharmaceutical industries for products such as magnetic paints, ferric/ferrous chloride in water purification, oxygen-absorbing “active packs” that preserve food freshness, and polymers used in injection-molded or extruded components; the friction industry for products such as brake system components, clutch facing, and the like; the printing industry for use in electrophotographic imaging where ultrafine iron powders deliver important characteristics such as soft magnetic properties, proper particle size distributions, low density, good flow, powder morphology, and electrical qualities; the welding and surfacing industry to provide improved welding electrodes and high quality thermal surfacing; the ceramic industry, particularly in glazing; and in the instance of nanometer size particles, the iron powder is used as a catalyst and drug carrier, in electromagnetic-wave absorption, ferrofluids, high density magnetic recordings, magnetic pastes, among other applications.
Accordingly, ultrafine and nanometer size iron powders are high value commodities. In the steelmaking industry, HSM sludge contains the finest iron-bearing particle size waste material generated in the various steel mill operations. For example, the coarsest iron-bearing waste material is mill scale, where the particles typically measure about ¼-inch×10 mesh. Mill scale waste is generally recycled back into the steelmaking process through a sinter plant. A chemical analysis of iron-bearing mill scale solids shows the material comprises about 73% Fe by weight, mostly in the form of oxides: FeO, Fe2O3, and Fe3O4, and the remainder in the form of Fe metal. Some steel mill waste water streams generate iron-bearing sludges that contain finer sized iron-bearing particles as compared to mill scale solids. Due to the finer particle size, such finer particle size sludges contain higher concentration levels of hydrocarbon matter that prevents recycling the sludge back into the steelmaking process through a sinter plant. This is because the higher amounts of hydrocarbons clog the sintering operation and generate unacceptable levels in VOC emissions. Such steelmaking sludge can now be de-oiled using the process taught in the above-mentioned priority patent U.S. Pat. No. 7,531,046 incorporated herein in its entirety by reference. The de-oiled iron-bearing particles are suitable for either recycling as a steelmaking revert, or they are sold as a raw material in non-steelmaking applications. The chemical analysis of such de-oiled sludge particles is similar to the above-mentioned composition for mill scale.
The highest or finest quality iron-bearing particles generated in steelmaking operations are found in HSM waste water streams. HSM waste water is collected in large settling basins where long sedimentation times clarify the water. The clarified water is recycled back into the steelmaking operation, and the settled sludge, containing nanoparticle and ultrafine particle iron-bearing solids, is periodically removed from settling basins, loaded onto trucks and/or railroad cars, and transported to a landfill for disposal. Such landfilled, hydrocarbon laden sludge has an increasing potential for causing an environmental disaster as continuing amounts of sludge are dumped onto a landfill. Even in instances where the landfill includes an impermeable membrane barrier, extensive academia studies have shown that, at sometime in the future, the landfilled sludge will permeate the membrane barrier and contaminate ground waters.
The iron-bearing particles in HSM sludge are extremely fine sized, ranging between about 150 mesh or 100 microns (μ) and about 150 nanometers (nm). Chemically, HSM sludge particles or solids are similar to the coarser mill scale particles, about 73% Fe by weight, mostly in the form of oxides: FeO, Fe2O3, and Fe3O4, and the remainder in the form of Fe metal. Both mill scale and HSM sludge contain the oils and grease used in steel mill operations. However, because HSM sludge comprises ultrafine nanoparticle iron-bearing solids, the entrained solids have high surface nominally, about 20,000+ cm2/gram and greater as compared about 100 cm2 for mill scale, and therefore, the HSM sludge has a higher oil/grease content than mill scale ranging between about 2% and 15% hydrocarbon matter by weight with an average of about 4% hydrocarbon matter by weight. Mill scale contains less than 0.5% oil/grease by weight.
A typical integrated steel mill with a 4 million tons/year steel production rate generates about 5,000 tons/year HSM sludge on a dry basis. That is after the sludge is dredged from the settling basins and deposited in a landfill. As a result of such past sludge disposal practice, the high value iron particles contained in HSM sludge, i.e. iron powder, was either not recognized by steelmakers or not recoverable, and this valuable commodity was lost in landfill disposal. The present invention recognizes the value of the nanoparticle and ultrafine particle iron-bearing solids contained in HSM sludge, and it provides means to recover that value in the form of an iron powder commodity as taught in the following disclosure of the preferred embodiments.
Definitions:
As used herein, iron powder commodity means de-watered and de-oiled HSM sludge comprising ultrafine and nanoparticle solids in the form oxides: FeO, Fe2O3, and Fe3O4, and in the form of Fe metal.
As used herein, ultrafine particles refers to iron-bearing particles measuring between about 100 microns (μ) down to about 1(μ).
As used herein, nanoparticle or nanosize refers to iron-bearing particles measuring less than about 1,000 nanometers (nm) to about 100 (nm).
Referring again to
In the preferred embodiment, showing an exemplary batch de-oiling process, after a predetermined amount of the analyzed HSM sludge 2 is fed into the reactor vessel 3, the reactor vessel is sealed. A hot inert gas purge is fed into sealed reactor vessel 3 by way of line 4 that extends from an inert gas supply 5. In this example, the inert gas is nitrogen heated to about the boiling point temperature of a particular hydrocarbon contained in the sludge within the sealed reactor vessel. However, it should be understood that any heated inert gas, such as nitrogen, argon, etc. may be used as a purge without departing from the scope of the present invention.
Reactor vessel 3 may include a stirring mechanism 6 housed within its sealed interior chamber 3a. If provided, the stirring mechanism 6 is operated during at least part of the heating cycle to expose all surfaces of the ultrafine and nanomicron particles in the HSM sludge 2. The temperature within chamber 3a is raised to 200-250° F. (93-121° C.) so that the water contained in the HSM sludge is vaporized. This creates a steam surge that erupts through the mixture and removes or frees the hydrocarbons clinging to the surfaces of the ultrafine and nanomicron iron-bearing solids contained in the sludge. The temperature within the sealed chamber is elevated toward a maximum boiling point temperature (target temperature) determined for the hydrocarbons contained in the HSM sludge, for example 800°-1000° F. (427°-538° C.), and the freed hydrocarbons, as well as any suspended hydrocarbons in the mixture, are vaporized. During the heating cycle, the nitrogen gas purge provides an inert gas atmosphere that prevents ignition of the gases evolved from the heated hydrocarbons.
As temperature within sealed chamber 3a is raised to about 212° F. (100° C.), an erupting steam surge is generated. The steam surge erupts from the oily mixture and it removes or frees any hydrocarbons clinging to the solid particles and dehydrates the mixture. During this initial phase of the heating cycle, a small amount of hydrocarbons may vaporize and the hydrocarbon concentration in the mixture 2 may actually increase slightly as the water is converted to steam. When the water concentration falls to near zero, the chamber temperature begins to rise through a range of one or more effective temperature levels to a target temperature and one or more hydrocarbons are vaporized within the sealed chamber as the temperature increases. When the sealed chamber temperature reaches target temperature, the hydrocarbon concentration in the mixture falls to about 0.01 to 0.04% by weight or 100 to 400 ppm, leaving behind a valuable de-oiled and de-watered iron powder.
Referring again to the drawing FIGURE, during the initial heating step of the de-oiling process, when it is determined that the steam surge has removed or freed the hydrocarbons clinging to the nanoparticle and ultrafine particle iron-bearing solids, valve 7 is operated to open sealed chamber 3a. The opened valve purges the hot gases from the vessel, for example, nitrogen, hydrocarbon vapors, and steam as a hot off-gas discharged through gas line 8 attached to reactor vessel 3. Such gas purge determination may be made by operating valve 7 in response to a pressure or a temperature measurement within sealed chamber 3a. A continuous emissions monitor (CEM) 9 samples the off-gas. When the monitor shows the amount of hydrocarbon vapor in the off-gas suddenly falls to virtually zero, the de-oiling process is discontinued. Chamber 3a is purged with hot nitrogen gas to prevent a premature phase change before the off-gas reaches condenser 12. The dry, de-oiled, iron powder 20 is discharged from reactor vessel 3 as a commodity, or it is discharged for downstream beneficiating into Fe oxides and Fe metal, and/or into ultrafine and nanoparticle fractions.
Production of metallic iron powder requires particle size distribution control, i.e. beneficiation, depending on the final product specifications. Size distribution control of particles in the range of, for example, less than about 25 microns is not feasible by simple screening techniques used in commercial operations, particularly with dry screening. Therefore, the beneficiating apparatus may include a grinder, for example, a ball grinder 19 or other suitable means such as a crusher, a magnetic separator 21 with high/low intensity magnetic fields that separate the iron powder into Fe oxides 22 and Fe metal 23, and it may include a high/low pressure pneumatic cyclone 24 whereby the pressure differential separates the iron powder into ultrafine and nanoparticle fractions 25 and 26 respectfully. The beneficiation apparatus may be used in any suitable order that separates the iron powder particles into desired fractions without departing from the scope of the present invention. For example, optional grinding 19 may precede either magnetic separation 21 or cyclone separation 24, or grinding 19 may follow either magnetic separation 21 or cyclone separation 24. In addition, magnetic separation 21 may either precede or follow particle size separation in the cyclone separation 24. In the event grinding or crushing follows cyclone separation, only the coarse product fraction in the cyclone underflow 26 is subjected to grinding. The nanoparticle or ultrafine fractions in the cyclone overflow 25 are discharged either as an iron powder commodity or for further separation into magnetic and non-magnetic particles,
One exemplary mechanism for magnetic separation of dry, de-oiled HSM sludge, containing nanoparticle, ultrafine particle, and coarse particle iron-bearing solids includes pneumatic pumping across a magnetic field. In such an arrangement, where the metallics are the magnetic fraction and where, for example, Fe2O3, is the non-magnetic fraction, the dry de-oiled iron product is pneumatically pumped along a plastic pipe or duct and across the magnetic field where the magnetic fraction is concentrated or collected for sequential removal as a magnet iron powder commodity, and where the non-magnetic fraction passes through the magnetic field and is discharged for collection as a non-magnet iron powder commodity. Varying the magnetic field strength will change the product weight distribution and composition as required.
The use of cyclones operated at 40 to 60 psi inlet pressure can separate the iron powder into a nanoparticle iron powder commodity, an ultrafine particle iron powder commodity, and a coarser iron-bearing product distribution. Variations in the cyclone inlet pressure can yield changes in the product size distributions. For example, the higher the pressure in the cyclone overflow the finer the fraction or product, and the lower the pressure in the cyclone underflow the coarser the fraction or product. It should be understood, however, that any suitable beneficiating mechanism may be used to separate the iron-bearing powder into Fe oxides and Fe metal fractions and into nanoparticle and ultrafine particle fractions without departing from the scope of the present invention.
As further illustrated in
In addition to separation into various fractions, beneficiation may also include baghouse air separation to collect the different distribution or fractions discharged from the magnetic separator 21 and the pneumatic cyclone 24. The baghouse mechanism would feed specific product size distribution into bags or suitable sealed containers for shipping.
Referring again to the de-watering and de-oiling side of the process, in some instances, where the off-gas contains suspended particulate matter, it may be desirable to feed the off-gas through an optional baghouse 10, shown in dotted lines, before the hot off-gas is sent to the condenser 12. Such baghouse apparatus may comprise any suitable filter arrangement well known in the art without departing from the scope of the present invention. For example, the baghouse may include an arrangement of mechanical filters, an electrostatic precipitator system, or other suitable means. However, in instances where the de-oiling process does not produce suspended particulate matter in the off-gas discharge the hot gas does not need to be cleaned in a baghouse. In such case, the hot off-gas is fed directly from reactor vessel 3 to condenser 12. If a baghouse is provided, the suspended particulate matter or dust 18, which comprises essentially iron-bearing particles, may be recycled back into the de-oiling process to recover the suspended particulate.
The hot gases from baghouse 10 are fed downstream through gas line 11 to condenser 12 where the gas is separated into nitrogen recycled back to the inert gas purge supply 5 through return line 13 for reuse in the de-oiling process, into hot water that is discharged through line 15 to a cooling tower 14, and into a condensate that is fed along line 16 to separator 17 that isolates condensate substances into water and hydrocarbon products using any suitable means well known in the art. The waters discharged from separator 17 and cooling tower 14 are suitable for direct discharge to the environment.
In the event the HSM mixture 2 comprises certain amounts of nanoparticle and ultrafine particle iron-bearing solids, water, and a particular single hydrocarbon, for example a light oil, a single heating cycle raises the chamber temperature through a temperature range that includes the steam surge temperature and a target temperature suitable for vaporizing the single hydrocarbon, in this instance 550° F. (288° C.) for the light oil. As the chamber temperature is elevated from ambient temperature to the target temperature, the above-mentioned steam surge removes any oil clinging to the solid particle surfaces. As the temperature approaches target temperature, the light oil begins to vaporize, and complete vaporization of the oil is realized at target temperature. The heating cycle is discontinued when the CEM 9 indicates that there are no hydrocarbon vapors evolving from the heated mixture. The reactor vessel 3 is then purged with hot nitrogen gas from supply 5 and the condensate from condenser 12 is fed along line 16 to a separator 17 where the condensate is separated into water and light oil hydrocarbon product, and the dry de-oiled iron powder commodity is discharged from vessel 3.
When HSM sludge 2 comprises certain amounts of nanoparticle and ultrafine particle iron-bearing solids, water, and two or more particular hydrocarbons, i.e. light oil and grease from rolling mill stands, the de-oiling process includes a first and a second heating cycle. The first heating cycle includes the temperature that generates the steam surge within the oily mixture to free sticky or viscid hydrocarbons from the solid particle surfaces, and a lowest, or first, effective temperature for vaporizing one of the hydrocarbons contained in the oily mixture. In this instance, the first effective temperature is an exemplary 550° F. (288° C.), the boiling point temperature for the light oil. The off-gas is fed to condenser 12, and the condensate is fed along line 16 to a separator 17 where it is separated into water and a light oil or first hydrocarbon product. When the CEM 9 indicates an absence of hydrocarbon vapors in the off-gas, chamber 3a is purged with hot nitrogen gas to remove any remaining oil vapors, and a dry de-oiled iron powder commodity is discharged from vessel 3.
The process continues with the second or next successive heating cycle that raises the chamber temperature to the next higher effective temperature corresponding with a boiling point temperature for one of the hydrocarbons contained in the oily mixture, in this instance the grease having an exemplary boiling point temperature of about 1050° F. (566° C.). During the second heating cycle, off-gas from reactor vessel 3 may be fed either along lines 8 or 11 to an optional or second condenser 12x. In such an alternate embodiment, condensate from the second condenser 12x is fed along line 16x to a second separator 17x where the condensate is separated into water and a grease or last hydrocarbon product. When the CEM 9 indicates an absence of hydrocarbon vapors in the off-gas, chamber 3a is purged with hot nitrogen gas to remove any remaining gases and vapors.
Where HSM sludge 2 comprises certain amounts of nanoparticle and ultrafine particle iron-bearing solids, water, and at least three different hydrocarbons, for example light oil, heavy oil, and grease, the de-oiling process comprises at least three heating cycles. The first heating cycle is operated to raise the chamber temperature through the steam surge temperature range to the lowest effective temperature for vaporizing one of the hydrocarbons contained in the oily mixture as heretofore described above Example 2.
After the first heating cycle, condensate is separated into water and a first hydrocarbon product using condenser 16 and separator 17, chamber 3a is purged with hot nitrogen, and a second or next successive heating cycle step raises the chamber 3a temperature to a next higher effective temperature for vaporizing one the hydrocarbons contained in the oily mixture. In this example, the chamber temperature is raised to the predetermined boiling point temperature for the heavy oil, about 675° F. (357° C.). During the second heating cycle step, off-gas from reactor vessel 3 may be fed to an optional, or second condenser 12x. The condensate from the second condenser 12x is fed along line 16x to the second separator 17x where the condensate is separated into water and a heavy oil or at least a second hydrocarbon product. When the continuous emission monitor 9 indicates an absence of evolved oil vapors in the off-gas, chamber 3a is purged with hot nitrogen gas to remove any remaining heavy oil vapors. The de-oiling process may include multiple successive heating cycles between the first heating cycle and target temperature depending on the number of different hydrocarbons contained in the oily mixture.
A third or last heating cycle step elevates chamber temperature to a target temperature that corresponds with the last or highest predetermined boiling point temperature for the hydrocarbons contained in the oily material 2, in this instance, the boiling point temperature for the exemplary grease, about 1050° F. (566° C.). During the last heating cycle, off-gas from reactor vessel 3 may be fed along either line 8 or line 11 to a last optional condenser 12y. Condensate from the last alternative condenser 12y is fed along line 16y to the last optional separator 17y where the condensate is separated into water and a grease, or last hydrocarbon product. When the continuous emission monitor 9 indicates an absence of evolved hydrocarbon vapors in the off-gas, chamber 3a is purged with hot nitrogen gas to remove any remaining gases and vapors, and a dry de-oiled iron powder commodity is discharged from vessel 3.
It should be noted however, that in oily mixtures containing more than one hydrocarbon, the off-gas and condensate generated by the different hydrocarbons during the successive heating cycle steps may be processed in a single condenser and a single separator, for example condenser 16 and separator 17, without departing from the scope of the present invention. However, using the same condenser and separator during successive heating cycle steps may result in producing a blended hydrocarbon product that may require additional downstream refining.
After the last heating cycle step is completed, the dry, de-oiled iron powder is discharged from reactor vessel 3 as heretofore described above, including beneficiation into various fractions. The dried and de-oiled iron powder may be pyrophoric, and accordingly, the discharged ultrafine and nanoparticle solids may be lightly sprayed with water to prevent spontaneous combustion when the solid material is suddenly exposed to the air.
An alternate to the above three examples for de-oiling HSM sludge comprises a single continuous heating cycle that elevates the reactor vessel chamber through a range of effective temperature levels including a first effective temperature, at least one intermediate effective temperature, and a final target temperature at the end of the heat cycle. Referring again to
As the HSM sludge 2 is being de-oiled during the continuous heating cycle, the discharged off-gas is sent to the condenser 12 and recovered nitrogen is recycled back to the inert gas purge supply 5 through line 13. Hot water is discharged to cooling tower 14 through line 15, and the condensate is fed along line 16 to separator 17 where the condensate is separated into water and a blended hydrocarbon product. The collected hydrocarbon product may be refined into different hydrocarbon products using any suitable process known in the art. The discharged water from separator 17 and from cooling tower 14 is suitable for direct discharge to the environment, and a dry de-oiled iron powder commodity is discharged from reactor vessel 3.
Although the present invention is disclosed in terms as being particularly useful for de-oiling HSM sludges, wastewater streams, and the like, it should be understood that the present invention is not limited to use in the steelmaking industry. The de-oiling process of the present invention is global in that the process may be used to de-oil and separate into its various components any industrial, municipal, or environmental oily waste or spill without departing from the scope of the present invention.
As such, the present invention has been disclosed in terms of preferred and alternate embodiments that fulfill each one of the objects set forth above, and the invention provides a new and improved method for de-oiling oily materials and separating the various components of the oily material into useful products. Of course, those skilled in the art may contemplate various changes, modifications, and alterations from the teachings of the present disclosure without departing from the intended spirit and scope of the present invention.
This is a continuation-in-part of application Ser. No. 12/409,571 filed Mar. 24, 2009, which is a continuation of application Ser. No. 11/016,136, filed Dec. 17, 2004 now U.S. Pat. No. 7,531,046 granted May 12, 2009.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11016136 | Dec 2004 | US |
| Child | 12409571 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12409571 | Mar 2009 | US |
| Child | 12473300 | US |
