Patent Application
20160326040
This disclosure is related to a process for creating glass-making-quality granulated slag, an additive for the making of glass into flat sheets and containers.
The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Slag is a by-product of the creation of iron and other metals from ore. Slag is a mixture of stony products, metal fragments including iron and alumina, silica, and other materials. One common use of ground granulated blast furnace slag is the production of blended cements, using properties of the slag to improve upon the properties of common Portland cement.
Another, less-utilized use for slag is the production of glass products. However, glass products using slag as an ingredient are sensitive to alumina and silica contaminants. Glass made with contaminated slag can cause pocks, voids, and other weaknesses. Further, slag particle size can affect the quality and ease of manufacture of glass products. Particles that are too large can weaken the glass. Particles that are too small or are essentially slag dust are very difficult and/or hazardous to deal with as they tend to create a cloud of particles in the air upon delivery and handling at the glass maker's facility.
Methods to create slag particles in particular size range include taking an already cooled slag and crushing the slag.
Glass-making-quality granulated slag particles can be defined within a certain particle size range. A process for forming glass-making-quality granulated slag includes collecting a molten slag flow, cold-water quenching the molten slag flow to create a granulated slag flow, drying the granulated slag flow, and size-screening the granulated slag flow to separate conforming glass-making-quality granulated slag from the granulated slag flow. The process can include using at least one magnetic device to separate ferrous contaminants from the granulated slag flow.
One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which:
A unique process has been developed to utilize a special type of blast furnace slag called glass-making-quality granulated slag coming from an exemplary iron making facility. For the purposes of this disclosure, an embodiment of the glass-making-quality granulated slag can be labeled or described by the product name Vitrafine™. This glass-making-quality granulated slag has most of the metal and alumina contaminants removed and has been selected/sorted for particles in a conforming contaminant range.
An exemplary process for creating conforming glass-making-quality granulated slag from a flow of untreated slag. In a first step of the exemplary process, the process begins with collecting the slag and determining slag chemistry appropriate for production of the desired glass-making-quality granulated slag.
An exemplary sub-set of steps to collect and certify molten slag from a blast furnace creating iron is provided. The molten slag is tapped from a notched hole in the bottom of the furnace and begins to flow down a ceramic trough in a liquid state of approximately 2500 degrees Fahrenheit which is verified by the operator. The trough is made up of various hard, heat and wear-resistant materials cast in a U-shape and sloped to promote gravity flow. Attention to the chemical and physical properties as well as when replacement and repair of these runners take place is critical. At repair and replacement time the hardened minerals loosen from the runner and increase in the slag product contaminating it when it is water quenched. The chemistry of the slag must be examined to determine whether the slag is a conforming unprocessed slag capable of being utilized for glass-making-quality granulated slag. If large concentrations of contaminants are determined to be present, whether from the iron making process or from the runner, the product is determined to be non-conforming slag and aborted for other purposes.
In a next step of the exemplary process, beginning a sub-set of process steps which can be labeled the quenching steps, the slag must be provided from the smelting process in a temperature range of between 2,500° F.-2600 ° F.
Once the molten blast furnace slag reaches the cooling box sprays, which provide ten (10) times the water volume to slag, it causes the slag to expand and crystallize into what is called granulated slag. The liquid slag is water-quenched instantly into a solid state. Adequate water flow and substantially cold water ideally in the range of 150° F.-170° F. is important to generate adequate generation of slag particles in the desired size and shape range. The coolant water needs to be below 200° F. to be effective. Knowledge of the slag temperature and replacement water volume is critical to the cooling water temperature. Low temperatures do not produce the proper product for further processing at the plant and will have to be aborted.
Attention is required of the cooling water temperature so as to have a consistent quenching of the slag for further processing in the plant. The amount of water circulation change needs to be monitored from that which is relieved as steam and that which is evacuated to the water treatment facility and returned as cooled replacement water.
The granulated slag, wet from the quenching process, goes through a rotating drum to be dewatered and then is transported to a dewatering silo. In an optional stage, the quenched slag mixed with water can be filtered or screen separated, removing undersized particles from the slag mixture while the slag particles are still mixed with the quenching water. In this way, many fine particles are removed with the water going to the water treatment facility which removes many contaminated fines that do not meet the separation criteria.
In a next step of the exemplary process, a quality check can be performed upon the quenched slag from the previous step. Visual acceptance is first utilized as discolored material is the sign of an inferior product. In one embodiment, samples of the granulated slag are taken and reviewed by a laboratory to determine a number of contaminants in the sample. If the slag meets the noted criteria it is considered acceptable for plant processing and the quenching steps can be considered complete. Upon determination of required quality parameters of the slag from the blast furnace granulation process, the slag is labeled as premium granulated slag, stockpiled, and ready for processing in the Vitrafine™ plant.
In a next step of the exemplary process, the stockpiled premium granulated slag dewaters further in the stockpile for several days before being loaded by an exemplary end-loader to a plant reservoir called a bin.
In a next step of the exemplary process, beginning a sub-set of process steps which can be labeled as plant operation steps, a first plant operation step is introduction into an exemplary natural gas rotary drum dryer moisture. This dried slag flow can optionally be screened at this point, for example, with a particle screen, for grossly oversized particles.
In treating slag flows that include an iron contaminant content, optional plant operation steps can be initiated to remove the iron contaminants. In one exemplary step to achieve separation of iron particles from the slag flow, one or more rare earth rotary drum magnets are in the flow. Magnetic particles are strongly attracted to the drum surface and removed from the slag flow. The iron particles once beyond the magnetic field of the drum magnet are then separated from the drum. for further processing.
The drum magnets are designed to efficiently separate iron particles by placement of the magnetic rare earth magnets within the drum. The magnetic material utilized inside the drums are a specially made magnet that can withstand high heat without losing the magnet properties.
While alumina and other non-ferrous particles are not attracted to the magnetic drums, testing has found that the iron particles removed by the drums tend to also include other contaminants. By separating out the ferrous particles, the other contaminants are largely removed as well.
A next plant operation step includes transferring the dried slag material to a separating device or devices configured to separate conforming slag particles of the desired size and shape from non-conforming particles. In one exemplary configuration to accomplish this separation, a bucket elevator takes the slag to a splitter tube that distributes the material over two exemplary Midwest 4 deck vibratory screens with rubber balls for increased screening capacity that separate specifically sized gradation material into a finished product that is 24 mesh by 140 mesh. Oversized and undersized materials are separated from conforming material, which can then be transported pneumatically to a storage silo for shipping. Material not meeting the specific size can be separated into larger than 24 mesh and smaller than 140 mesh for reprocessing or marketing into other products. In one optional embodiment of the process, the rejected slag material labeled as larger than 24 mesh flows into a crusher device for further size reduction and recirculates back to the screens for separation repeating the separation step of the process. In one exemplary configuration, the crusher device has the capability of changing the rotation speed through a variable speed setting on the motor to minimize crushing the granulated slag to a size smaller than that which is required conforming slag.
In one exemplary process step, the smaller than 140 mesh material is pneumatically delivered to a silo for sales to alternate non-glass manufacturing facilities.
After the separation step, the plant operation steps end and the conforming slag flow from the separation process can be labeled as Vitrafine™ or glass-making-quality granulated slag. Additional testing can be performed to sub-classify the Vitrafine™ or confirm presence of contaminants that would cause a problem in the glassmaking process.
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The disclosed process provides 24 mesh and 140 mesh screens as useful for size-screening conforming slag particles. Other size meshes can be used depending upon the particular requirements of a glass manufacturer, and the disclosure is not intended to be limited to the particular mesh sizes provided. In another example, a large-side dimension for granulated slag particles can be 16 mesh instead of 24 mesh.
A rotary drum rare earth magnet device can be used to remove ferrous material from a granulated slag flow. Rare earth magnets can be sensitive to temperature. Depending upon the specific embodiment of the disclosed process, the temperature of the slag flow being processed by the magnet device can be too high for rotary drum magnet devices known in the art. In one exemplary embodiment, after slag is dried by a natural gas drying station, the temperature of the slag can be up to 300° F. An exemplary high temperature rotating drum and housing magnet capable of processing a flow up to 300° F. is provided with the following characteristics. A device outer housing can include 11 gauge 304 stainless steel construction, 28″×54″×33-⅛″ tall flange to flange with heavy duty predrilled 2″×2″×¼″ carbon steel angle flanges. The high temperature rotating drum and housing magnet can include rare earth Neodymium-Iron-Boron permanent magnet material for operating temperatures to 300° F. The high temperature rotating drum and housing magnet can include a magnetic field designed for high gauss at drum surface and low burden depth applications. The rotating drum can be 18″ diameter×48″ wide and fabricated with ⅛″ thick Nitronic 30 stainless steel for abrasion resistance. In another embodiment, the drum can be made with 3/16″ thick Nitronic 30 stainless steel. In another embodiment, the drum can be made with ⅛″ thick 304 stainless steel. The high temperature rotating drum and housing magnet can include an adjustable feed gate for product flow, wherein a slag flow inlet has fixed diverter to direct product flow over magnet area. A slag flow outlet can have an adjustable splitter for ferrous and non-ferrous product discharge. In one embodiment, a 230/460 Volt, 3 ph ¾ HP motor and reducer with variable frequency drive and controller can be used to drive rotation of the drum. A position of magnet or magnets within the drum can be adjustable for optimum separation. The high temperature rotating drum and housing magnet can include continuous cleaning discharges ferrous contaminants separate from product. In one embodiment, the drum shaft has a ½″ NPT (National Pipe Thread Taper) adjustable cooling air inlet on fixed end and outlet on drive end to assist in internal cooling of magnet assembly. There can be a dust cover on a drum cooling air inlet to avoid contamination within the drum. The cooling air inlet permits a cooling flow to flow through the magnet device and keep the device from overheating. In another exemplary construction, a water cooling flow can be channeled through the magnet device.
The disclosure has described certain preferred embodiments and modifications of those embodiments. Further modifications and alterations may occur to others upon reading and understanding the specification. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.
This disclosure claims the benefit of U.S. Provisional Application No. 62/156,607 filed on May 4, 2015 which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62156607 | May 2015 | US |
