Process using fly ash to create chunks of raw material for iron or steel mill activities.

Abstract

A process of preparing for reuse small particles of one or more waste products produced from iron or steel mill activities, comprising the steps of creating a blend of one or more waste products with a blending system, the blend including a predetermined proportion of each of the one or more waste products, combining fly ash and the blend with a liquid in a mixing container to create a mixture, adding a predetermined amount of moisture reduction additive to the mixture, adjusting the amount of the liquid in the mixture to achieve a predetermined moisture and time before set up occurs, mixing the mixture continuously until set up occurs and an agglomeration forms, casting the agglomeration onto a surface, dividing the agglomeration into predetermined size chunks, removing particles of less than the predetermined size from the agglomeration. The chunks produced according to this process.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/432,478, filed Jan. 13, 2011.

BACKGROUND

Many iron and steel mill activities have negative environmental impact. Mills have waste generating activities that create problems related to landfills, air and water pollution. These streams of waste present problems for which a solution is necessary. Combustion of coal produces several distinct byproducts referred to as Coal Combustion Products (“CCP”). These CCPs include fly ash, bottom ash, and boiler slag. Several million tons of these CCPs are disposed of in landfills every year, which only adds to the negative environmental impact that iron and steel mills already impose.

When making iron, raw materials like iron ore, coke and limestone are mixed and heated in a blast furnace. There, carbon monoxide produced from the burning coke reduces the iron ore to iron. Gangue in the iron ore reacts with the limestone to produce slag. The slag is often removed as a waste product of the iron making activity and transported for further processing which creates fine material that is then moved to a landfill.

Also during the iron making activity, small particles of metallic materials are produced that are considered waste product, mainly due to the fact that it is not practical to recover these particles and re-introduce them as raw material. These small particles may be dust from the dust catcher of the blast furnace, scaled metal particles from finishing processes, and wet sludge from water treatment, to name a few examples. These particles are too small for reuse as raw materials in the iron making activity and are therefore hauled away and deposited in landfills.

Attempts have been made to develop methods of grouping together these small particles into larger-sized pieces that could then, in the case of a blast furnace, be dumped into the top of the blast furnace for reuse. For example, sintering and briquetting have both been utilized to try to fashion usable pieces of material from the small particles. These attempts have, thus far proved to be economically or otherwise unfeasible for various reasons. Sintering, for example, creates stack emission air polluting problems due to the burning of the particles. Briquetting, as another example, requires dry and uniformly sized materials, and so requires additional process steps to achieve these requirements.

Information relevant to attempts to address these problems can be found in U.S. Pat. Nos. 5,556,457 (Terza) and 5,395,441 (Bogdan). However, each one of these references suffers minimally from one or more of the following disadvantages: 1) set up time of the resultant product is too long, 2) high temperature is required for set up, 3) these solutions do nothing to alleviate the accumulation of CCPs, such as fly ash, in the world's landfills.

For the foregoing reasons, there is a need in the industry for a process that produces a product that sets up rapidly and in low heat situations, and helps alleviate the accumulation of Coal Combustion Products and waste products from iron or steel mill activities in the environment.

SUMMARY

The present invention is directed to a chemical process of recovering waste products from an iron or steel-making activity, and a product made by the process. The product produced by the process sets up rapidly and in low heat situations, so that a large-sized agglomeration can be produced quickly. After set-up, the agglomeration can be divided into chunks of suitable size for use as raw material in the iron or steel-making activity. The inventive process helps alleviate the accumulation in the environment of Coal Combustion Products and waste products resulting from iron or steel mill activities.

A chemical process of preparing for reuse small particles of one or more waste products produced from iron or steel mill activities, and product made thereby, having the steps and features of the present invention comprises, first creating a blend of one or more waste products with a blending system, the blend includes a predetermined proportion of each of these one or more waste products. Then, combining fly ash and the blend with a liquid in a mixing container to create a mixture. Next, adding a predetermined amount of moisture reduction additive to the mixture. Then, adjusting the amount of the liquid in the mixture to achieve a predetermined moisture and time before set up occurs. Then, mixing the mixture continuously until set up occurs and an agglomeration forms. Then, casting the agglomeration onto a surface and then dividing the agglomeration into predetermined size chunks. Next, removing particles of less than the predetermined size from the agglomeration. The foregoing process will result in a product that can be used as charge in a blast furnace, for example.

Importantly, the process uses the pozzolan fly ash because of fly ash's chemical characteristics, such as its rapid set up time when mixed with water and without heating.

These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawing where FIG. 1 shows the steps of an embodiment of the present invention.

DESCRIPTION

Definitions.

“Waste Product” refers to small size particles of material containing iron, carbon, alumina, magnesium, calcium or revert material such as bag-house dust, coke breeze, mill scale, bauxite fines, pellet fines, hammer mill fines, and the like. “Set up” refers to the characteristic of having been brought into a state of high plasticity. “Iron or steel mill activity” refers to metal processing activities of various types including, for example, steel making, iron making, foundry activities, and gold product manufacturing.

Overview.

As shown in FIG. 1, a process according to the present invention of preparing for reuse small particles of one or more waste products produced from iron or steel mill activities, comprises the steps of creating a blend of one or more waste products with a blending system 1, the blend including a predetermined proportion of each of the one or more waste products; combining fly ash 4 and the blend with a liquid 3 in a mixing container to create a mixture 2; adding a predetermined amount of moisture reduction additive 6 to the mixture 5; adjusting the amount of the liquid in the mixture to achieve a predetermined moisture and time before set up occurs; mixing the mixture continuously until set up occurs and an agglomeration forms 7; casting the agglomeration onto a surface 8; dividing the agglomeration into predetermined size chunks 9; removing particles of less than the predetermined size from the agglomeration 10. The process will necessarily produce chunks for use as raw material 11.

In the step of creating a blend, a blending system is used, such as a metering system or a bedding and blending system, to create the blend.

In the step of combining fly ash and the blend with a liquid, the fly ash, blend and liquid, water is preferred but other liquids or combinations of liquids may be appropriate, are added to a mixing unit, such as a screw mixer, drum mixer, cement mixer, pug mill mixer, paddle wheel mixer, or other similar mixer.

In the step of adding a moisture reduction additive, an appropriate amount should be added, this is done, for example, in case the waste products are introduced with natural moisture, for instance if the waste products came from an open landfill and were subjected to rains.

In the step of adjusting the amount of the liquid, this is done to minimize the total moisture content and set up time of the mixture.

In the step of mixing the mixture, continuous agitation is applied to the mixture by the mixer for approximately 10 minutes.

In the step of casting the agglomeration onto a surface, the surface can be a conveyor system that transports the agglomeration and makes the agglomeration available for sizing.

In the step of dividing the agglomeration, the agglomeration is formed into appropriately sized chunks, depending on the target mill activity, by cutting and shearing, fracturing, molding, crushing, or other similar size reducing process which reduces the size of the agglomeration.

In the step of removing particles, the fine particles that resulted primarily from dividing the agglomeration are removed by screen filtering or other similar procedure.

The inventive process necessarily produces chunks that can be stored for later reuse or transported directly to the target mill activity location.

Example 1

This Prospective Example Demonstrates how the Process can be Carried Out

A bin is at least partly filled with water treatment sludge which is of benefit to a blast furnace process because of its affect on density and chemical characteristics of an agglomeration. The water treatment sludge is blended at a moisture content which is required to achieve the desired chemical composition for compatibility with the blast furnace process. Fly ash, water, and calcium carbonate are added to the blend to create a mixture. The fly ash percentage changes as carbon content and oil concentration of the mixture varies in order to obtain up to a 5,000 psi final strength of the agglomeration. This mixture is placed in a screw mixer. Additional water or moisture reducer may be added at this point to regulate a total moisture content and affect the set up time of the mixture. Mixing is carried out for about 10 minutes creating an agglomeration of fly ash, water, and sludge. The agglomeration is then discharged onto a moving belt. The agglomeration is cut and sheared into 2.5 inch chunks before the agglomeration cures. The agglomeration chunks are then screened to eliminate undesirable fines that result from the cutting and shearing. The resulting chunks are then moved to storage or directly to a recycling unit.

Although the present invention has been described in considerable detail with the reference to certain preferred versions thereof, other versions are possible. For example, there can be a plurality of waste products used, not just a single waste product. Or a curing accelerator can be added to the process if it is desirable to decrease the time to cure. Such a curing accelerator will be one selected from the group consisting of sodium carbonate, sodium silicate, calcium chloride, potassium silicate and aluminum silicate. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

Claims

1. A process for converting small particles of one or more reusable waste products into an agglomeration, the one or more reusable waste products being produced from iron or steel mill activities, the process comprising:

(a) creating a blend of one or more waste products with a blending system, the blend including a predetermined proportion of each of the one or more waste products;

(b) combining fly ash and the blend with a liquid in a mixing container to create a mixture;

(c) adding a predetermined amount of moisture reduction additive to the mixture;

(d) adjusting an amount of the liquid in the mixture to achieve a predetermined moisture and time before set up occurs;

(e) mixing the mixture continuously until set up occurs and an agglomeration forms;

(f) casting the agglomeration onto a surface;

(g) dividing the agglomeration into predetermined size chunks;

(h) removing particles of less than the predetermined size from the agglomeration.

2. The process according to claim 1 further comprising:

(a) adding a curing accelerator to the mixture prior to forming the agglomeration, the curing accelerator being selected from the group consisting of sodium carbonate, sodium silicate, calcium chloride, potassium silicate and aluminum silicate.

3. The chunks produced according to the process of claim 1.

4. A process for converting small particles of one or more reusable waste products into an agglomeration, the one or more reusable waste products being produced from iron or steel mill activities, the process comprising:

(b) creating a blend of one or more waste products with a blending system, the blend including a predetermined proportion of each of the one or more waste products;

(c) combining fly ash and the blend with a liquid in a mixing container to create a mixture;

(d) adding a predetermined amount of moisture reduction additive to the mixture;

(e) adjusting an amount of the liquid in the mixture to achieve a predetermined moisture and time before set up occurs;

(f) adding a curing accelerator to the mixture prior to forming the agglomeration, the curing accelerator being selected from the group consisting of sodium carbonate, sodium silicate, calcium chloride, potassium silicate and aluminum silicate.

(g) mixing the mixture continuously until set up occurs and an agglomeration forms;

(h) casting the agglomeration onto a surface;

(i) dividing the agglomeration into predetermined size chunks;

(j) removing particles of less than the predetermined size from the agglomeration.

5. The chunks produced according to the process of claim 4.

6. A process for converting small particles of one or more reusable waste products into an agglomeration, the one or more reusable waste products being produced by a metal-processing activity, the process comprising:

(a) measuring a first amount and a second amount of a first and second reusable waste product, respectively;

(b) blending the first amount and the second amount together to produce a uniform mixture;

(c) adding fly ash and liquid to the mixture;

(d) mixing the mixture continuously until the mixture starts to set-up;

(e) casting the mixture onto a surface to form an agglomeration; and

(f) after the agglomeration sets-up, divide the agglomeration into pieces sized for reintroduction into the metal-making activity.

7. The pieces produced according to the process of claim 6.