CN106999884A - Gas Atomization of Molten Materials Using By-Product Off-Gas - Google Patents

Abstract

A metallurgical process and system for gas atomization of molten slag and/or molten metal from a metallurgical furnace is integrated with an off-gas management process and apparatus,thereby feeding the off-gas to a gas atomization apparatus for atomizing the molten slag and/or the molten metal. The use of by-product off-gas for atomizing molten slag and/or molten metal presents several advantages, including the elimination of off-gas management and treatment equipment, the concentration and raising of heat by atomization to increase heat recovery, the prevention of oxidation of atomized particulate product, and the reduction of CO₂And (4) releasing. The process for preparing a granular product comprises: feeding molten material and by-product off-gas to a dispersion device; the gas is contacted with the molten material in a dispersion apparatus, wherein the molten material is dispersed and solidified by contact with the gas to form a granular product.

Description

Gas Atomization of Molten Materials Using By-Product Off-Gas

Cross References to Related Applications

This application claims priority to and benefit of U.S. Provisional Patent Application No. 62/053,170, filed September 21, 2014, the contents of which are incorporated herein by reference.

technical field

The present disclosure relates to metal production processes and facilities, and in particular to the use of by-product off-gases to gas atomize molten materials such as slag and/or metal in such processes and facilities.

Background technique

In facilities that produce molten materials such as metals, gas (waste or air) is transferred from one part of the process to another for one of the following purposes:

(1) release exhaust gases from the process equipment, thereby maintaining a clean working environment around the process equipment; and/or

(2) To heat or cool process equipment.

In either case, the exhaust gas:

A) Carrying particles;

B) can have a wide range of composition (e.g. air-like, oxygen-free (N ₂ , H ₂ O, CO ₂ ), fuel-rich (CO, H ₂ ) or sulfur-rich (SO ₂ ));

C) According to the process of discharging exhaust gas, it can be cold exhaust gas or hot exhaust gas.

In all cases, the gases used or generated in these processes must be transferred in and out of the process via rotating equipment (such as induced draft fans, blowers or compressors), which needs to be purchased to achieve the purpose. Consequently, most metallurgical facilities have many such rotating devices.

Beyond that, unless the gas is cryogenic and clean, gases produced by metallurgical applications must be combusted and/or cooled and/or cleaned through exhaust gas treatment systems because these by-product gases are useless. These gas treatment systems are expensive and thus add significantly to the cost of the metallurgical extraction plant, accounting for approximately 30-50% of the plant operating capital expenditure. Therefore, there is a need to reduce or eliminate possible exhaust gas management equipment, while maintaining a good working environment in the plant and maintaining exhaust emission targets.

Furthermore, little energy is recovered from the gaseous by-products because the gas is dispersed throughout the device and the temperature is too low for economical energy recovery. Thus, the opportunity to recover low level heat in the smelter is lost.

Ultimately, the use of by-product gases from metallurgical applications could not be identified, and for this reason, by-product gases are wastefully vented to the atmosphere through the aforementioned expensive off-gas treatment systems, due to lack of a concentrated and sufficient thermal mass without heat recovery.

For example, in FeNi furnaces, cooling air is wastefully vented to the atmosphere without energy recovery; and secondary calcination and slagging fumes are similarly wastefully vented to the atmosphere through the secondary baghouse cleaning system. Since no use has been found for these by-product gases, they must be treated with expensive exhaust management equipment before being released into the atmosphere.

Similarly, in FeCr smelters, _CO2 -rich furnace off-gases are cooled and vented wastefully to the atmosphere without energy recovery or utilization of the properties of the off-gases. Again, this is because no use has been found for these off-gas products, so these gases are wastefully vented into the atmosphere through costly off-gas treatment systems without value recovery.

Furthermore, _CO2 emissions from metallurgical plants are an environmental issue and all metals producers are under pressure to reduce greenhouse gas emissions. For this purpose, carbon dioxide reforming units have been used to convert the _CO2 -rich waste gas into a mixture of hydrogen and carbon monoxide (synthesis gas), which can then be processed in different processes (e.g. upstream dryers, calciners, furnaces or pre-reduction units) used as fuel. However, for such a thermally favorable reforming process, the _CO2 -enriched gas needs to be preheated above about 900 °C, implying additional operating costs.

Carbon dioxide is just one example of an emission gas that can cause environmental concern. Emissions from metallurgical facilities can include a variety of other undesirable constituents, including gases and particulate solids whose release to the environment is of concern. Further, reducing or removing these undesired constituents from off-gases from metallurgical facilities often requires expensive equipment and processes. Examples of undesired gases that may be contained in off _- gases from metallurgical facilities include _CO2 , sulfur _- containing species such as SO2, SO3 and H2S, nitrogen oxides (NOx ₎ such as NO and NO2, phosphorus _- containing gases , fluorides (eg HF and SiF ₄ ) and/or organic substances such as furans and dioxins. Examples of undesired particulate solids include dust, which often must be removed from the exhaust.

Slag is another by-product of metal production processes carried out in metallurgical furnaces. Slag typically comprises a mixture of metal oxides and silica and produces slag in amounts ranging from about 10% to several times the amount of metal produced by the process.

Molten slag is periodically tapped from the furnace, usually allowing it to air cool and solidify, with heat loss to the environment. Much of the slag produced by these processes is continuously discharged as waste. Recently, however, there has been interest in the use of granulated slag in various commercial products, and equipment and processes have been developed for the granulation and processing of slag to produce granulated products such as proppants and capping particles in oil and gas production .

A particularly promising process and apparatus for converting slag to granular products by gas atomization is described in commonly assigned U.S. Provisional Patent Application No. 62/007,180 and U.S. Provisional Patent Application No. 62/007,284, filed June 3, 2014 made public. According to the disclosed process, molten slag from a furnace is directly and economically converted into a variety of granular products by gas atomization using ambient air fed to the atomization device via a conventional air blower.

But there remains a need for simpler and more economical process equipment to treat by-products such as slag and off-gas to alleviate at least some of the above-mentioned problems.

Summary of the invention

In one embodiment, there is provided a method for preparing a granular product comprising: (a) providing molten material; (b) supplying molten material to a dispersing device; (c) supplying a gas to a dispersing device, wherein, The gas is a by-product off-gas; (d) contacting the gas with molten material in a dispersing device, wherein the molten material is dispersed and solidified by contact with the gas to form said granular product.

In another embodiment, there is provided a system for producing a granular product comprising: (a) a metallurgical furnace containing molten material selected from one or more molten metals and molten slag; (b) a metallurgical furnace located proximate to the metallurgical furnace Gas atomization equipment; (c) a gas supply system for supplying by-product exhaust gas to the gas atomization equipment; (d) a molten material supply system for transferring molten material from the metallurgical furnace to the gas atomization equipment.

Brief description of the drawings

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is part of a flow diagram of a process according to a first embodiment herein; and

Figure 2 is part of a flow diagram of a process according to a second embodiment herein.

Detailed description of the invention

The following is a detailed description of metallurgical processes and installations, including processes and equipment for gas atomization of molten slag and/or molten metal, and in which at least one waste gas management process is integrated with at least one gas atomization process, and with these Process-related equipment.

The inventors have discovered that by-product gases from metallurgical processes can be used for gas atomization of slag and metals from metallurgical furnaces to bring about one or more of the following advantages:

A. The exhaust gas management equipment is omitted, and the exhaust gas treatment facilities are concentrated to the part that only needs to be atomized for molten slag and/or molten metal.

B. Eliminate furnace, metal tapping, calcining transfer, dust control, and reduce equipment fans. Conversely, atomizing fans can extract gases from these processes and use them for atomization.

C. Eliminate operating expenses related to the use of furnaces, metal slag removal, calcination transfer, dust control, and equipment blower reduction compared to systems using air atomized slag and/or metals.

D. Concentration of heat from the above process and enhancement of this heat by slag and/or metal atomization to provide more economical slag and molten metal heat (energy) recovery.

E. Generate exhaust gas with high temperature (relative to air with lower temperature) for processing units requiring heat (drying unit, water preheating, etc.).

F. Eliminate waste gas treatment systems and capital expenditures associated with granulation and atomization, as high temperature waste gas can already be reused in processes already equipped with such equipment. A specific example is drying in FeNi rotary kiln electric furnace (RKEF) equipment.

G. Atomize the metal or slag into pellets or powder using an inert gas to prevent their oxidation.

H. Improved metal recovery efficiency compared to existing slag crushing, sorting and screening operations, and reduced or eliminated use of such by-product reprocessing equipment.

I. If _CO2 -enriched waste gas from the process is used for atomization: A) a portion of the carbon-containing gaseous species can be dissolved in the molten material (since dispersion increases the specific surface area and thus enhances dissolution); and B) is rich in The temperature of the _CO2 gas will increase due to contact with the molten material, which facilitates a reforming process with less or without any additional preheating.

It can be appreciated that the above advantages lead to a more significant cost reduction compared to the prior art, which results in:

- energy recovery from slag is more feasible;

- energy recovery from smelting waste gases is more feasible;

- Significant reduction in smelter costs by reducing or eliminating currently used off-gas, slag and metal processing systems;

- Reducing greenhouse gas emissions from smelters in a more cost-effective manner.

Figure 1 is a part of a flow diagram of a process according to a first embodiment of the invention. The flowchart illustrates in part a process and system for producing metals by a metallurgical furnace 10 comprising a plurality of electrodes 12 for providing heat to create and maintain a layer of molten metal 14 and a layer of molten slag within the furnace chamber 16. FIG. 1 shows that the furnace includes a slag tap 18 in communication with the molten slag layer 16 and a molten metal tap 20 in communication with the molten metal layer 14 .

Molten slag is periodically discharged from the furnace 10 through a slag tap 18 directly into a movable slag container or slag runner or runner from which the molten slag is transferred to another area of the plant. During transportation, the slag remains in a molten state. The delivery of slag in the slag container or launder is indicated by arrow 22 in FIG. 1 .

The furnace 10 in Figure 1 is at least partially cooled by air. More specifically, the bottom wall and lower side walls of the furnace 10 are cooled by air. In known processes and systems, furnace cooling air is provided to the furnace by fans or blowers. However, processes and systems according to the present embodiments omit such fans or blowers.

As will be appreciated, the air cooling the furnace heats up as it cools the bottom and side walls of the furnace. In Fig. 1, the exhausted cooling air streams from the bottom wall and the lower side walls of the furnace are indicated by arrows 24 and 26, respectively. In typical processes and systems, heated cooling air is vented to the atmosphere.

The system according to this embodiment also includes a gas atomization device 28 to atomize the molten slag and produce slag particles suitable for commercial products such as proppants and/or capping particles. A gas atomization device 28 is located adjacent to the metallurgical furnace 10 and receives molten slag from the furnace 10 through a slag container or launder, as indicated by arrow 22 .

The molten slag is atomized within the device 28 by air flow from an induced draft (ID) fan 30 , wherein the supply of atomizing gas from the ID fan 30 to the gas atomizing device 28 is indicated by arrow 32 in FIG. 1 . When the airflow supplied by the ID fan 30 contacts the falling stream of molten slag in the atomization chamber of the gas atomization device 28, the molten slag simultaneously separates into liquid droplets and cools into a solid state, thereby forming a solid that falls to the bottom of the atomization chamber Slag particles.

In a typical installation, the gas input to the gas atomization device 28 is instead passed through an air blower (not shown, but instead of an ID fan), and may include air at ambient temperature and pressure. However, in the process and system according to the present embodiment, the gas input to the ID blower 30 includes exhaust gas discharged from the furnace bottom wall and/or lower side wall, as indicated by arrows 24 and/or 26 . This exhaust air cannot be fed to the blowers used in existing air atomizing equipment because they are hot and unclean. In this embodiment, the gas input to the ID blower 30 comprises the combined exhaust gas from the bottom and lower side walls of the furnace, so Figure 1 shows arrows 24 and 26 combined to form arrow 34, which represents the input to the ID blower 30 exhaust. As will be appreciated, the exhaust gas supplied by the ID blower 30 to the gas atomization device 28 includes heat extracted from the furnace, and is therefore at a temperature above ambient temperature.

According to this embodiment, the ID blower 30 used to supply the exhaust gas to the gas atomizing device 28 also draws air into the furnace cooling system. This makes it possible to dispense with any fans supplying cooling air to the furnace 10, thereby reducing capital and operating costs. In addition, the use of exhaust gas for atomization enables the elimination of a separate exhaust gas treatment system for the exhaust gas, further reducing capital and operating costs.

Thus, in this embodiment, the air circulation in the furnace air cooling system and the exhaust gas circulation to the gas atomizing device are provided by the same ID fan 30 . It should be understood that the ID blower 30 may not necessarily be located between the furnace 10 and the gas atomizing device 28 , but may be located upstream of the furnace 10 so as to blow cooling air to the furnace walls and heated air to the gas atomizing device 28 .

In FIG. 1 , the solid slag particles produced by the gas atomizing device 28 are represented by box 36 and their removal from the gas atomizing device 28 is represented by arrow 38 .

The exhaust gas used for atomization is exhausted by the gas atomization device 28 as slag granulated waste gas, indicated by box 40 , and the removal of the exhaust gas from the gas atomization device 28 is indicated by arrow 42 . The exhaust gas 40 contains heat extracted from the side and bottom walls of the furnace, as well as heat extracted from the molten slag. Thus, using the exhaust gas from the furnace cooling system in the gas atomization apparatus 28 increases the heat in the exhaust gas so that it can be used for energy transfer in downstream process equipment. For example, the hot exhaust gas 40 from the gas atomization device 28 may be treated to recover heat therefrom, or it may be supplied to other processing units requiring heat, such as drying units, water preheating units, etc. These other processing units are represented by box 44 in the figure.

While the above description relates to an embodiment in which the exhaust gas used for atomization is air from the furnace cooling system and in which molten slag is the material being atomized, this is not necessarily the case. For example, Figure 2 shows a part of a process flow diagram according to a second embodiment, where the exhaust gases instead comprise exhaust gases from the interior of the furnace and/or from a fume and dust collection hood. The first and second embodiments have many of the same components, and these same components are identified with the same reference numerals in FIG. 2 . Furthermore, the above description of these same components also applies to the second embodiment unless otherwise stated below.

The embodiment of FIG. 2 includes a metallurgical furnace 10 as described above, and also includes an exhaust gas port 50 for exhausting by-product exhaust gases from the interior of the furnace 10 . Exhaust furnace exhaust gases are indicated by arrow 52 in FIG. 2 . In this embodiment, at least a portion of the furnace exhaust may be collected in the fume and dust collection hood 54 and withdrawn therefrom for delivery to the gas atomization device 28 via the ID blower 30 . To this end, FIG. 2 shows arrows 56 , 58 , 34 to indicate the exhaust gas flow from the fume and dust capture hood 54 to the ID blower 30 .

At least a portion of the exhaust gases exiting the furnace 10 may be routed by the ID blower 30 directly to the gas atomization device 28 rather than being collected in the hood 54 . To this end, FIG. 2 shows arrows 52 , 60 , 58 , 34 to represent the exhaust gas flow from the exhaust port 50 to the ID blower 30 . It should be understood that all or a portion of the exhaust gas may be collected in the hood 54 prior to being delivered to the gas atomizing device 28, and/or all or a portion of the exhaust gas may be delivered directly from the furnace 10 to the gas atomizing device (via the ID blower 30) , or any combination thereof.

Due to the variability of the processes carried out in metallurgical furnaces, exhaust gases can have different compositions, as discussed further below. Regardless of the composition of the exhaust gas used for atomization, it should be emphasized that an important aspect of the present invention is the use of induced draft fan 30 to extract exhaust gas (for example from the interior of the furnace or from the bottom of the furnace) and supply the exhaust gas to atomization. This replaces a traditional blower, which sucks in ambient air and blows it out for atomization. This modification applies to all embodiments disclosed herein.

It is also important to emphasize that the use of off-gas for pelletizing purposes results in less oxidation of the molten material than when ambient air is used as the atomizing gas. In this regard, the exhaust gas may be depleted of oxidizing species (eg, oxygen) or may be substantially free of oxidizing species. The degree of oxidation depends on the composition of the exhaust gas, but reductions in oxidation levels can be achieved with various exhaust gases from multiple sources within the system, such as exhaust from the furnace in Figure 2, which may be depleted of oxygen and/or may include a or various gaseous by-products.

Another important aspect of the invention is that the use of exhaust gas for atomization results in an increase in the heat of the exhaust gas. This is an important advantage where it is necessary to recover heat from the exhaust gas or to use the exhaust gas in another process step requiring heat, eg in drying or preheating, and is achieved in all embodiments disclosed herein.

In some embodiments, the exhaust gas supplied to the gas atomization device 28 for atomizing molten metal or slag may carry particles. Use of the method and system as described herein enables a separate exhaust gas treatment system to be dispensed with and the particulate laden exhaust gas supplied to the gas atomization device 28 by the ID blower 30 as described above in the first and second embodiments. The exhaust gas from the gas atomization device 28 is treated as described above.

Another important aspect of the invention is that the atomization of the metal/slag can use _CO2 -enriched waste gas as the atomizing gas. Thus, according to this aspect, not only the atomization of the metal/slag is achieved by using the exhaust gas, but at the same time the _CO2 emissions from the plant are reduced. _CO2 reduction is achieved by partial _CO2 capture from the dissolution of _CO2 in the metal/slag. In addition, the _CO2 -enriched off-gas is heated in the atomization plant, so the off-gas from the atomization plant is sufficiently preheated such that it can be directly (or with minimal preheating) converted into synthesis gas ( CO+ _H2 ). Thus, in this aspect of the invention, the other processing units represented by box 44 include reformers for producing synthesis gas.

Atomization of metals/slags can also be performed with exhaust gases containing one or more other undesirable constituents, defined herein to include gases and particulate solids that are of concern when released into the environment, and typically must be passed through the exhaust treatment to partially or completely remove.

For example, undesired constituents include one or _two gases such as _CO2 , sulfur _- containing species such as SO2, SO3, and H2S, nitrogen oxides (NOx ₎ such as NO and NO2, phosphorus _- containing gases, Fluorides (eg HF and SiF ₄ ) and/or organic substances such as furans and dioxins. The reduction of the concentration of these gases in the off-gas is achieved in the manner discussed above for _CO2 , i.e. by dissolving the undesired components in the molten metal/slag during the formation of said granular products in the physicochemical plant , so that the concentration of the undesired constituents in the hot exhaust gas of the gas atomizing device is lower than the concentration of the undesired constituents in the exhaust gas supplied to the gas atomizing device. This can reduce the need for expensive equipment and processes to remove these undesirable components from the exhaust.

Undesirable components include one or more gaseous organic substances such as furans and dioxins. The reduction of the concentration of these organic substances in the off-gas can be achieved by combusting the organic substances by contacting the molten metal/slag with the organic substances in the presence of oxygen in the off-gas and/or in the metal/slag. Further, at least a part of the gas produced by the combustion of organic matter in the gas atomization device may be dissolved in the molten metal/slag during the formation of the granular product. Thus, the gas atomization device can further serve as an afterburner when some or all of the organic matter is combusted to form carbon dioxide and water.

In cases where the undesired constituents comprise particulate solids such as dust, dust particles can be introduced into the granular product during atomization of the molten metal/slag in the gas atomization apparatus. This can reduce the need for expensive equipment and processes to remove dust from the exhaust.

Finally, the invention makes it possible to combine one or more exhaust gas streams into the exhaust gas from the gas atomization device. This enables a reduction in exhaust treatment equipment in the system, resulting in reduced capital and operating expenditures, and this advantage is achieved in all of the embodiments disclosed herein.

In another embodiment, molten metal exiting the furnace 10 through the tap 20 may be passed through the gas atomization device 28 to pelletize instead of slag. In this regard, FIG. 2 includes a dashed line 62 representing the delivery of molten metal from the tap 20 to the gas atomization device 28, wherein the molten metal is pelletized in exactly the same manner as molten slag as described above. In such an embodiment, it will be appreciated that no slag will flow to the gas atomization device 28 as indicated by arrow 22 . It should also be understood that this modification can also be applied to the process flow diagram of FIG. 1 , which is related to the first embodiment.

The composition of the metal exiting furnace 10 will of course depend on the particular metallurgical process being performed therein. For example, where the furnace 10 is a ferronickel smelting furnace, the molten metal discharged through the tap hole 20 may include iron nickel (FeNi). It should be understood, however, that the methods and systems disclosed herein are not limited to any particular metallurgy. For example, the methods and systems disclosed herein can be used to produce pig iron in ironmaking blast furnaces.

Using hot and/or unclean exhaust air for atomization may require an ID blower 30, including a fan with radial blades capable of handling unclean exhaust air, rather than a fresh air blower with backward curved impeller blades. This applies to all embodiments disclosed herein.

In some embodiments, the exhaust gas supplied to the gas atomization device 28 may be substantially free of oxygen. For example, in some embodiments, the exhaust gas may be enriched with gases such as _N2 , _H2O , or _CO2 , which will result in little or no oxidation of the metal contained in the molten slag or molten metal during atomization . For example, furnace off-gases from FeCr smelters are rich in _CO2 , and their use as atomizing gas may be particularly advantageous in the production of pig iron or other metals where oxidation during atomization is to be avoided. In other embodiments, the exhaust may be enriched in fuels such as CO or _H2 , or may be enriched in sulfur _- containing species such as SO2.

Although the invention has been described in connection with certain specific embodiments, the invention is not limited to these specific embodiments. Rather, the invention includes all embodiments possible within the scope of the appended claims.

Claims (31)

1. The method for preparing granular product, it comprises: (a) providing molten material; (b) feeding molten material into a dispersion device; (c) supplying gas to the dispersing device, wherein the gas is by-product off-gas; (d) contacting a gas with a molten material in a dispersing device, wherein the molten material is dispersed and solidified by contact with the gas to form said granular product. 2. The method of claim 1, wherein the molten material is molten metal or molten slag resulting from a metallurgical process performed in a metallurgical furnace. 3. The method of claim 2, wherein the molten material is molten metal, and wherein the granular product comprises metal particles. 4. The method of claim 2, wherein the molten material is molten slag, and wherein the granular product comprises slag particles. 5. The method of any one of claims 2-4, wherein the dispersing device comprises a gas atomization device. 6. The method of claim 5, wherein the dispersing device further comprises an induced draft (ID) blower for blowing by-product off-gas into the dispersing device. 7. The method of claim 6, wherein the by-product off-gas comprises gas released from the furnace cooling system, and the ID fan draws gas from the furnace cooling system. 8. The method of claim 6, wherein the by-product off-gas comprises furnace off-gas from inside a metallurgical furnace, and the ID blower draws furnace gas from the furnace. 9. The method of any one of claims 6-8, wherein the gas atomization plant produces hot exhaust gas, and wherein the hot exhaust gas is used in downstream process equipment for energy transfer. 10. The method of claim 9, wherein the downstream process equipment comprises a drying unit or a preheating unit. 11. The method of claim 10, wherein the by-product off-gas supplied to the gas atomization device entrains particles. 12. A method as claimed in any one of claims 3-11, wherein the exhaust gas supplied to the gas atomization device is substantially free of oxygen. 13. The method of any one of claims 1-11, wherein the by-product off-gas is substantially oxygen-free and enriched in one selected from the group consisting of _N2 , _H2O , _CO2 , _CO , _H2 , and SO2. one or more gases. 14. A method as claimed in claim 12 or 13, wherein the molten material atomized using the by-product off-gas is less oxidized than the material atomized using air. 15. The method of claim 1, wherein the dispersing device comprises a gas atomization device; Wherein, the gas atomization equipment produces hot exhaust gas; wherein the exhaust gas supplied to the gas atomization device includes undesired constituents; and Wherein, during the formation of the granular product, the undesired components contained in the exhaust gas supplied to the gas atomization equipment contact the molten material, so that the concentration of the undesired components in the hot exhaust gas is lower than that supplied to the gas atomization equipment. The concentration of undesired constituents in the exhaust air of a plant. 16. The method of claim 15, wherein the undesired constituent is a gas or a particulate solid. 17. The method of claim ₁₅ , wherein the undesired components are _CO2 , sulfur _- containing species such as SO2, SO3 and H2S _; nitrogen oxides selected from NO and NO2, phosphorus _- containing gases ; gaseous organic substances; fluorides (such as HF and SiF ₄ ), and combinations of one or more thereof; and Therein, at least a part of the undesired constituents dissolves in the molten material during the formation of the granular product. 18. The method of claim 16, wherein the gaseous organic substance is selected from the group consisting of furans, dioxins, and combinations thereof; and Therein, at least a part of the gaseous organic substance is combusted and/or dissolved in the molten material during the formation of the granular product. 19. The method of claim 15, wherein the undesired constituents are particulate solids. 20. The method of claim 19, wherein the particulate solid is dust; and wherein, during formation of the granular product, dust is introduced into the granular product. 21. The method of claim 15, wherein the undesired component is _CO2 ; and wherein a portion of the _CO2 in the exhaust gas supplied to the gas atomization device is trapped in the particulate product. 22. A method as claimed in claim 21, wherein the hot off-gas produced by the gas atomization plant is converted into synthesis gas in a downstream reformer. 23. A system for preparing granular products comprising: (a) a metallurgical furnace containing molten material selected from one or more molten metals and molten slags; (b) gas atomization equipment located close to the metallurgical furnace; (c) the gas supply system used to provide by-product exhaust gas to the gas atomization equipment; (d) Molten material supply system for transferring molten material from the metallurgical furnace to the gas atomization equipment. 24. The system of claim 23, wherein the molten material comprises slag, and wherein the molten material supply system comprises a slag container or launder. 25. The system of claim 23 or 24, wherein the dispersing device further comprises an ID blower for blowing by-product off-gas into the gas atomizing device. 26. The system of claim 25, wherein the system further comprises an air cooling system for cooling the furnace. 27. The system of claim 26, wherein the by-product off-gas comprises air released from a furnace air cooling system, and wherein the system further comprises a conduit for transferring the by-product off-gas from the furnace to the gas atomization device . 28. The system of any one of claims 23-25, wherein the by-product off-gas comprises off-gas released from the furnace, and wherein the system further comprises a system for transferring the by-product off-gas from the furnace to the gas atomization equipment piping. 29. The system of claim 28, further comprising a smoke and dust collection hood for collecting exhaust gases released from the furnace, wherein the piping for diverting the by-product exhaust gases to the gas atomization equipment is adjusted to receive exhaust air from the fume and dust collection hood. 30. The system of any one of claims 23-29, wherein molten material atomized by use of by-product exhaust gas is less oxidized than material atomized by air. 31. A product from exhaust gas atomization which is less oxidized than the same product atomized by means of air atomization equipment.