Methods, systems and devices for making cold bonded agglomerates

Abstract

There are provided methods, systems and processes for forming cold bonded agglomerates in the form of pellets, briquettes or compacts from iron oxide materials, such as iron ore concentrates. The cold bonded agglomerates have sufficient strength and durability to be handled and shipped without significant damage. Forming the iron ore concentrate product into agglomerates facilitates the shipment and handling of the product and places the product in a form that is suitable for use by a wider variety of iron making customer facilities. There are also provided methods, systems and devices for handling greenballs as they cure, and before they have gained sufficient strength for significant handling, stockpiling or shipping.

1 . A method for making a cold bonded agglomerate including iron oxide, comprising:
 mixing a particulate iron oxide material with a hydraulic bonding agent to provide a solids mixture;   introducing the solids mixture into a first rotating pelletizer;   spraying water onto the solids mixture as it resides in the first rotating pelletizer at a rate effective to cause the development of greenballs in the first rotating pelletizer;   recovering generally spherical green balls from the first rotating pelletizer;   passing the greenballs through a size classifier to provide an oversize fraction, and undersize fraction and an on size fraction; and   subjecting the on size fraction to conditions effective for the greenballs to cure as individual cold bonded agglomerates.   
     
     
         2 . The method in accordance with  claim 1 , further comprising conveying the undersize fraction into the first rotating pelletizer or into a second rotating pelletizer. 
     
     
         3 . The method in accordance with  claim 1  wherein the particulate iron oxide material comprises iron ore concentrate. 
     
     
         4 . The method in accordance with  claim 1  wherein the hydraulic bonding agent comprises a member selected from the group consisting of ordinary Portland cement (OPC) and ground Portland cement clinker (GPCC). 
     
     
         5 . The method in accordance with  claim 1  wherein the solids mixture further comprises an additive selected from the group consisting of wheat gluten binder, wheat starch, corn starch binder, bentonite, organic polymer binder, burnt lime, hydrated lime, quick lime, slack lime, active MgO lime, and burnt MgO lime. 
     
     
         6 . The method in accordance with  claim 1  wherein the water is sprayed in an amount effective to promote curing of the hydraulic bonding agent. 
     
     
         7 . The method in accordance with  claim 1  wherein the first rotating pelletizer is selected from the group consisting of a balling drum and a balling disk. 
     
     
         8 . The method in accordance with  claim 1 , further comprising:
 delivering the oversize fraction to a shredder to convert the oversize fraction to a shredded material; and   introducing the shredded material into the first rotating pelletizer, the second rotating pelletizer or a third rotating pelletizer.   
     
     
         9 . The method in accordance with  claim 1  wherein said subjecting comprises charging the on size fraction into a curing device in accordance with  claim 21 . 
     
     
         10 . The method of  claim 9  wherein the curing device is operable to prevent exposure of the greenballs to greater than a one pound of compressive force from any direction. 
     
     
         11 . The method of  claim 10  wherein the greenballs are allowed to cure in the curing device for at least 8 hours. 
     
     
         12 . The method in accordance with  claim 1  wherein the iron oxide material comprises a filter cake from a wet high intensity magnetic separation system. 
     
     
         13 . A method for making a cold bonded agglomerate feed material including iron oxide, comprising:
 feeding into a curing device a plurality of generally spherical greenballs; the greenballs comprising an iron oxide material, a hydraulic bonding agent and water; wherein the curing device defines a greenball flow path and is configured to allow movement of the greenballs through the flow path for a period of time sufficient for the greenballs to become at least partially cured;   passing a flow stream of the greenballs along the flow path to produce partially cured cold bonded agglomerates; and   discharging the partially cured cold bonded agglomerates from the flow path;   wherein the flow path is configured to prevent the flow stream from having a vertical depth of more than about ten inches at any single point of the flow path.   
     
     
         14 . The method in accordance with  claim 13  where the curing device further includes a discharge opening for discharging the partially cured cold bonded agglomerates from the flow path, and a conveyor configured to receive the partially cured cold bonded agglomerates from the flow path and convey the partially cured cold bonded agglomerates to the discharge opening. 
     
     
         15 . The method in accordance with  claim 14  wherein the conveyor is configured to prevent the partially cured cold bonded agglomerates conveyed thereon from having a vertical depth of more than about twenty inches at any single point of the conveyor. 
     
     
         16 . The method in accordance with  claim 13  wherein the period of time that a respective greenball resides in the flow path is at least about eight hours. 
     
     
         17 . The method in accordance with  claim 13  wherein the period of time that a respective greenball resides in the flow path is at least about sixteen hours. 
     
     
         18 . The method in accordance with  claim 13  wherein the flow path extends from the inlet to the outlet. 
     
     
         19 . The method in accordance with  claim 13  wherein the flow stream of the greenballs provides for motion of the respective greenballs in the flow stream relative to other greenballs in the flow stream, and wherein the relative motion is not interrupted for any period of more than eight hours between said feeding of the respective greenballs and said discharging of the respective partially cured cold bonded agglomerates. 
     
     
         20 . The method of  claim 13  wherein, in the flow path, the greenballs are not subjected to greater than one pound of compressive force from any direction. 
     
     
         21 . The method of  claim 13 , further comprising, before said feeding, forming greenballs in an agglomerating device selected from the group consisting of a disk pelletizer, a drum pelletizer, a compactor, and a high pressure briquetter. 
     
     
         22 . A curing device for producing partially cured cold bonded agglomerates, comprising:
 an inlet for receiving a charge of generally spherical greenballs, wherein the inlet is configured to prevent a dropping of the greenballs any distance greater than ten inches;   an outlet for discharging partially cured cold bonded agglomerates, the outlet positioned at a location lower than the inlet; and   a channel defining a flow path for said greenballs, the channel having a floor oriented at a slope of at least two degrees measured from horizontal upon which the greenballs travel along the flow path from the inlet to the outlet;   wherein the channel is configured to prevent the flow stream from having a vertical depth of more than about ten inches at any single point of the flow path.   
     
     
         23 . The device in accordance with  claim 22  wherein the flow path comprises a non-linear flow path. 
     
     
         24 . The device in accordance with  claim 22 , further comprising a system for delivering moisture to the flow path. 
     
     
         25 . The device in accordance with  claim 24  wherein said system comprises a humidifier system. 
     
     
         26 . The device in accordance with  claim 24  wherein said system comprises a water delivery system effective to deliver a spray of water onto the greenballs in at least one region of the flow path. 
     
     
         27 . The device in accordance with  claim 22 , wherein the curing device comprises a bin having a cylindrical outer wall, a central column and a stationary helically shaped floor affixed to the outer wall and the central column, the floor having a downward slope of not less than two degrees measured from horizontal, said curing device allowing gentle movement of the greenballs through the curing device in a spiral trajectory from the inlet to the outlet at a controlled mass flow rate such that each of the greenballs resides in the curing device for at least eight hours. 
     
     
         28 . The device in accordance with  claim 22 , wherein the curing device comprises a bin having an outer wall that defines an internal chamber, and multiple sloped floors positioned within the chamber in a generally stacked relationship with a space therebetween, each one of the sloped floors sloping in a direction that is generally opposite of the slope of the floor or floors adjacent to it; wherein the lower end of each floor is separated from the outer wall and defines a space between the floor and the outer wall near the lower end of the floor to allow greenballs supported by said floor to drop to the next lower floor through said space; wherein the flow path is defined by the outer wall and the multiple sloped floors and allows gentle movement of the greenballs through the curing device in a generally zigzag pattern from the inlet to the outlet at a controlled mass flow rate such that each of the greenballs resides in the curing device for at least eight hours.