Plasma metal melting furnace using auxiliary gas

Abstract

A melting furnace system for melting metals, including but not limited to aluminum and aluminum alloys, includes a plasma gas supply and an auxiliary gas system. The plasma gas supply supplies plasma gas to a melting chamber of a melting furnace of the melting furnace system. The auxiliary gas system supplies auxiliary gas into the melting chamber and an emission control gas to exhaust gases from the melting chamber. A method of melting metal with the melting furnace system includes supplying metal into the melting chamber, supplying plasma gas to the melting chamber to heat the melting chamber, and supplying auxiliary gas to the melting chamber.

Description

[Technical Field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 374,119, filed August 31, 2022, entitled PLASMA METAL MELTING FURNACE WITH ADDITIONAL GASES, the contents of which are incorporated herein by reference in their entirety.

[0002] This application relates to systems and methods for melting metallic materials, such as, but not limited to, aluminum scrap materials. More particularly, this application relates to plasma-fueled furnaces for melting metallic materials. [Background technology]

[0003] Metallic materials (such as, but not limited to, scrap material made of aluminum or aluminum alloys) can be recycled by melting the metallic material using a melting furnace and casting the molten metal for reuse. Conventional melting furnaces typically use natural gas to generate combustion gases (e.g., using burners) and direct the combustion gases into the melting chamber of the melting furnace. The combustion gases are hot and heat the walls of the melting furnace, the ceiling of the melting furnace, the molten aluminum, and / or the solid aluminum, thereby producing molten aluminum or molten aluminum. The combustion gases are typically vented from the melting chamber to the atmosphere, and furnace pressure can be controlled by controlling the rate at which the combustion gases are vented. Conventional natural gas-fired melting furnaces can be resource-intensive in providing the desired heat input to the melting chamber. Summary of the Invention

[0004] The embodiments protected by this patent application are defined by the claims below, rather than by this Summary. The Summary is a high-level overview of various embodiments and introduces some of the concepts further described in the Detailed Description section below. The Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the entire specification of this patent application, any or all of the drawings, and appropriate portions of each claim.

[0005] According to certain embodiments, a melting furnace system includes a plasma gas supply for supplying plasma gas to a melting chamber of a melting furnace of the melting furnace system, and an auxiliary gas system for supplying an auxiliary gas into the melting chamber and for supplying an emission control gas to exhaust gases from the melting chamber.

[0006] According to some embodiments, the melting furnace system includes a plasma gas supply for supplying plasma gas to a melting chamber of a melting furnace of the melting furnace system. The melting furnace system can also include an auxiliary gas system. The auxiliary gas system includes an auxiliary gas supply for supplying auxiliary gas to the melting chamber. In certain embodiments, the auxiliary gas is configured to control furnace pressure in the melting chamber.

[0007] According to various embodiments, a method of melting metal with a melting furnace system includes supplying metal into a melting chamber of a melting furnace of the melting furnace system, supplying a plasma gas to the melting chamber to heat the melting chamber, and supplying an assist gas to the melting chamber.

[0008] The various embodiments described herein may include additional systems, methods, features, and advantages that may not necessarily be explicitly disclosed herein, but will become apparent to one of ordinary skill in the art upon review of the following detailed description and the accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within this disclosure and protected by the accompanying claims.

[0009] This specification refers to the accompanying drawings in which: In the drawings, the use of like reference numerals in different figures is intended to indicate like or similar components. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 illustrates a melting furnace system according to an embodiment. [Figure 2] FIG. 1 illustrates another melting furnace system according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Described herein are systems and methods that utilize plasma to melt metallic materials, such as, but not limited to, aluminum and aluminum alloys.

[0012] Plasma-based systems have not traditionally been used in melting furnace systems for a variety of reasons. For one, furnace pressure within the melting chamber of a melting furnace is a critical control factor during the melting process. In typical combustion systems, a positive pressure is maintained within the furnace to prevent air intrusion, which can adversely affect the melting process. As an example, during the melting of aluminum or aluminum alloys, air intrusion can result in the formation of aluminum oxide. However, because plasma-based burners operate at higher temperatures than conventional combustion burners, they must be operated at lower flow rates to achieve comparable heat output within the chamber (e.g., suitable for melting metals in a melting furnace). Such low flow rates of plasma-based burners make it difficult to control the furnace pressure within the melting chamber. For another, certain types of plasma gases pose other challenges. For example, inert diatomic plasma gases, such as plasma argon and plasma nitrogen, require very high temperatures to acquire the ability to radiatively transfer heat, and upon cooling below these temperatures, the plasma gases recombine into their original, non-radiative molecular form. As another example, plasma carbon dioxide can improve heat transfer to temperatures lower than those of inert diatomic plasma gases, but plasma carbon dioxide produces excessive amounts of carbon monoxide (CO), a toxic substance.

[0013] The systems and methods described herein may employ a supply of plasma gas and a supply of auxiliary gas. Optionally, the systems and methods described herein may employ an emission control gas. The plasma may provide heating to the melting chamber of the melting furnace, which may provide enhanced heating compared to traditional techniques due to the radiative properties of the plasma gas. In optional embodiments, the plasma gas may be a mixture of gases, including, but not limited to, plasma carbon dioxide. In certain embodiments, the auxiliary gas may provide control of furnace pressure within the melting chamber, thereby enabling the melting furnace system to reduce and / or prevent unwanted air intrusion into the melting chamber. In various embodiments, the emission control gas may include exhaust gas from the melting chamber. Optionally, the emission control gas may be atmospheric air and / or other suitable gas for controlling emission gases. In certain embodiments, the emission control gas may introduce oxygen into the exhaust gas from the melting chamber, which, when the plasma gas is plasma carbon dioxide, may enable the complete combustion of carbon monoxide to carbon dioxide. Various other benefits and advantages may be realized by the systems and methods provided herein, and are not limited to the aforementioned advantages.

[0014] FIG. 1 illustrates a melting furnace system 100 according to an embodiment. As illustrated in FIG. 1, the melting furnace system 100 includes a melting furnace 102 having a melting chamber 104. During the melting process, as described in more detail below, a solid metal material 106 is melted to form molten metal 108, which can then be used as needed. Note that the particular melting furnace 102 and melting chamber 104 illustrated are not intended to be limiting.

[0015] The melting furnace system 100 includes one or more plasma burners 110 that generate and deliver plasma gas into the melting chamber 104, thereby heating the melting chamber 104 and any contents therein via radiant heating from the plasma gas. In the illustrated embodiment, the melting furnace system 100 includes two plasma burners 110A and 110B, with the flow of plasma gas from each plasma burner 110A, 110B represented by arrows 113. The exemplary locations of the plasma burners 110A and 110B in FIG. 1 are not limited to their particular locations. Additionally, in other embodiments, any number of plasma burners may be used as desired.

[0016] The plasma gas supplied by the plasma burner 110 can be any type of plasma gas as desired and / or suitable for melting the metallic material 106. By way of non-limiting example, the plasma gas can be plasma nitrogen, plasma argon, and / or plasma carbon dioxide. In one non-limiting example, the plasma gas can be plasma carbon dioxide to enhance radiative heating at lower temperatures. In certain embodiments, multiple plasma gases can be used to heat the melting chamber 104. In such embodiments, each plasma gas can be supplied separately. By way of non-limiting example, plasma burner 110A can supply plasma carbon dioxide, and plasma burner 110B can supply plasma nitrogen. Various other combinations of plasma gases can be used in other melting furnace systems as desired.

[0017] In addition to one or more plasma burners 110 for supplying plasma gas, the melting furnace system 100 includes an auxiliary gas system 111, which includes one or more auxiliary gas supplies 112 for supplying auxiliary gas into the melting chamber 104. In the embodiment illustrated in FIG. 1, the melting furnace system 100 includes three auxiliary gas supplies 112A-C, with the flow of auxiliary gas from each auxiliary gas supply 112A-C represented by arrows 115. In other embodiments, the melting furnace system 100 can include any number of auxiliary gas supplies as needed. Additionally, the auxiliary gas supplies 112A-C are not limited to their particular locations.

[0018] The auxiliary gas supplied by each auxiliary gas supply 112A-C can be used to control the furnace pressure within the melting chamber 104, as described in more detail below. Various gases and / or gas mixtures can be used as the auxiliary gas as desired. By way of non-limiting example, the auxiliary gas can be carbon dioxide, recycled exhaust gas (e.g., gas released from the melting chamber 104), and / or various other suitable auxiliary gases and / or mixtures of auxiliary gases, as desired.

[0019] One or more exhaust pipes 114 or other suitable conduits may be provided for venting exhaust gases from the melting chamber 104. Flow into the exhaust pipe 114 is represented by arrow 116, and flow of exhaust gases out of the exhaust pipe 114 is represented by arrow 118. In various embodiments, the melting furnace system 100 includes a pressure controller 120. The pressure controller 120 may at least partially control the flow rate of exhaust gases out of the exhaust pipe 114, thereby at least partially controlling the furnace pressure within the melting chamber 104. In the embodiment illustrated in FIG. 1 , the pressure controller 120 is a slidable door 122, the movement of which is represented by arrow 124. However, in other embodiments, the pressure controller 120 may be any of a variety of other suitable devices or mechanisms for controlling the flow rate of exhaust gases out of the exhaust pipe 114.

[0020] In some cases, the melting furnace system 100 includes a controller 126, which may include one or more processing units and / or one or more memory devices. The processing unit of the controller may be any suitable processing device or combination of devices. Such devices may include, but are not limited to, one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, other electronic units, and / or combinations thereof. The one or more memory devices of the controller 126 may be any machine-readable medium accessible by a processor. Such machine-readable media may include, but are not limited to, any type of long-term, short-term, volatile, non-volatile, or other storage medium. The memory devices are not limited to any particular type or number of memories or the type of medium on which the memories are stored. Furthermore, as disclosed herein, the terms “storage medium,” “storage,” or “memory” may refer to one or more memories for storing data. Such memory may include read-only memory (ROM), random-access memory (RAM), magnetic RAM, core memory, magnetic disk storage media, optical storage media, flash memory devices, and / or other machine-readable media for storing information. The term "machine-readable medium" encompasses, but is not limited to, portable or non-removable storage devices, optical storage devices, wireless channels, and / or various other storage media capable of storing or conveying instruction(s) and / or data.

[0021] In certain embodiments, the controller 126 may optionally include an associated user interface. Such a user interface may include, but is not limited to, a graphical user interface. In such cases, the controller 126 may obtain information from a user and / or provide information to a user. In such embodiments, the user interface may be located on the controller 126 itself or may be located remotely from the controller 126 (e.g., without limitation, at another location within the melting furnace system 100). Additionally or alternatively, the controller 126 may optionally include various communication modules. In such cases, the controller 126 may receive information and / or transmit information as needed. Non-limiting examples of communication modules may include systems and mechanisms enabling wired and / or wireless communication (e.g., industrial Ethernet, Profibus, near field communication, cellular communication, Wi-Fi, Bluetooth, Bluetooth Low Energy (BLE), etc.).

[0022] The controller 126 may be communicatively coupled to one or more components of the melting furnace system 100, including, but not limited to, one or more of the plasma burners 110, gas supplies for one or more of the plasma burners 110, flow regulators for one or more of the auxiliary gas supplies 112, and / or the pressure controller 120. Optionally, one or more sensors may be provided within the melting chamber 104 and / or to provide information regarding furnace pressure and / or exhaust gases, as otherwise needed. The controller 126 may then control one or more components of the melting furnace system 100 based on such information.

[0023] As described above, the flow rate of plasma gas into the melting chamber 104 may be relatively low. In such cases, the flow rate of the auxiliary gas may be controlled (e.g., by the controller 126, by an operator, and / or in any other desired manner) to control the furnace pressure within the melting chamber 104. In certain embodiments, the flow rate of the auxiliary gas may be controlled to maintain a positive furnace pressure within the melting chamber 104. This may reduce and / or prevent undesired air ingress into the melting chamber (e.g., via the exhaust 114). By way of non-limiting example, the flow rate of the auxiliary gas into the melting chamber 104 may be increased if the furnace pressure falls below and / or decreases, and the flow rate of the auxiliary gas into the melting chamber 104 may be maintained and / or decreased if the furnace pressure is above the threshold. In embodiments having multiple auxiliary gas supplies 112, the auxiliary gas supplies 112 may be controlled together, or each auxiliary gas supply 112 may be controlled independently. In some embodiments, the furnace pressure is optionally further controlled by controlling the pressure controller 120. As a non-limiting example, the pressure controller 120 can be controlled to increase the furnace pressure by restricting the flow of exhaust gas from the exhaust line 114. Various other controls of the auxiliary gas and / or the pressure controller 120 can be implemented as needed to control the furnace pressure. Thus, the melting furnace system 100 can beneficially use the plasma gas for radiant heating while still providing the desired furnace pressure within the melting chamber 104.

[0024] FIG. 2 illustrates another melting furnace system 200 according to an embodiment. The melting furnace system 200 is substantially similar to the melting furnace system 100, but includes an auxiliary gas system 211. The auxiliary gas system 211 is substantially similar to the auxiliary gas system 111, except that the auxiliary gas system 211 further includes an emission control gas supply 228. The emission control gas supply 228 supplies an emission control gas into the exhaust gas (i.e., the mixture of plasma gas and auxiliary gas) exhausted from the melting chamber 104. The flow of the emission control gas is represented by arrows 230 in FIG. 2. The emission control gas can be a variety of gases suitable for controlling the emission gas. In certain embodiments, the emission control gas may contain free oxygen and / or may be a gas with a molecular structure having free oxygen. In one non-limiting example, the emission control gas may be atmospheric air. In other embodiments, the emission control gas may be the same as the auxiliary gas. The emission control gas introduced into the exhaust gas can completely combust carbon monoxide to carbon dioxide when the plasma gas is plasma carbon dioxide. In other words, the emission control gas can be used to control the emission gas to minimize or reduce the emission of carbon monoxide and / or other harmful gases. In certain embodiments, the emission control gas can be controlled as needed to control the furnace pressure. As a non-limiting example, the emission control gas can be supplied at various flow rates, which in turn can control the rate at which the mixed gas exits the melting chamber 104, and therefore the furnace pressure.

[0025] As illustrated in Figure 2, the auxiliary gas system 211 includes a return supply 232. The return supply 232 returns at least a portion of the exhaust gas exiting the exhaust line 114 to one or more of the auxiliary gas supplies 112 for use as the auxiliary gas. In the embodiment of Figure 2, the return supply (represented by dashed line 232) includes exhaust gas mixed with an emission control gas, although in other embodiments this is not required. By way of non-limiting example, the return supply 232 can be provided in the melting furnace system 100 to return exhaust gas (e.g., without the emission control gas) to one or more of the auxiliary gas supplies 112.

[0026] Referring back to FIG. 1 , a method for melting a solid metal material 106 with a melting furnace system 100 to produce molten metal 108 includes providing the solid metal material 106 in a melting chamber 104. The method includes providing a plasma gas to the melting chamber 104 using a plasma supply, such as one or more plasma burners 110, to heat the melting chamber. The method includes providing an auxiliary gas to the melting chamber 104 using one or more auxiliary gas supplies 112. In various embodiments, the method includes controlling the furnace pressure by controlling the auxiliary gas provided by the one or more auxiliary gas supplies 112. Various other processes can be implemented and are not limited to the control processes described above.

[0027] A list of exemplary embodiments is provided below. Such list includes at least some of the explicitly listed ones as "exemplary," which further describes various exemplary embodiments consistent with the concepts described herein. These examples are not intended to be mutually exclusive, exhaustive, or limiting. The present disclosure is not limited to these example illustrations, but rather encompasses all possible modifications and variations within the scope of the appended claims and their equivalents.

[0028] Example 1. A melting furnace system comprising: a plasma gas supply for supplying plasma gas to a melting chamber of a melting furnace of the melting furnace system; and an auxiliary gas system configured to supply auxiliary gas into the melting chamber and configured to supply an emission control gas to exhaust gases from the melting chamber.

[0029] Example 2. The melting furnace system of any preceding or subsequent example or combination of examples, further comprising the melting furnace defining the melting chamber, the melting furnace further comprising an exhaust pipe for exhausting the mixture of the plasma gas and the auxiliary gas from the melting chamber as the exhaust gas.

[0030] Example 3. The melting furnace system of any preceding or subsequent example or combination of examples, further comprising a pressure control device configured to control an exhaust rate of the mixture of the plasma gas and the assist gas from the melting chamber.

[0031] Example 4. The melting furnace system of any preceding or subsequent example or combination of examples, further comprising a controller configured to control the pressure controller based on a detected furnace pressure within the melting chamber.

[0032] Example 5. The melting furnace system of any preceding or subsequent example or combination of examples, further comprising a controller configured to control at least one of the plasma gas supply or the auxiliary gas supply.

[0033] Example 6. The melting furnace system of any preceding or subsequent example or combination of examples, wherein the plasma gas includes at least one of plasma argon, plasma nitrogen, or plasma carbon dioxide.

[0034] Example 7. The melting furnace system of any preceding or subsequent example or combination of examples, wherein the auxiliary gas includes exhaust gas from the melting chamber.

[0035] Example 8. The melting furnace system of any preceding or subsequent example or combination of examples, wherein the auxiliary gas comprises carbon dioxide.

[0036] Example 9. A melting furnace system comprising: a plasma gas supply for supplying plasma gas to a melting chamber of a melting furnace of the melting furnace system; and an auxiliary gas system comprising an auxiliary gas supply for supplying an auxiliary gas to the melting chamber, the auxiliary gas being configured to control furnace pressure within the melting chamber.

[0037] Example 10. The melting furnace system of any preceding or subsequent example or combination of examples, further comprising the melting furnace defining the melting chamber, and an exhaust for exhausting the mixture of the plasma gas and the assist gas from the melting chamber.

[0038] Example 11. The melting furnace system of any preceding or subsequent example or combination of examples, further comprising a pressure control device configured to control an exhaust rate of the mixture of the plasma gas and the auxiliary gas from the melting chamber.

[0039] Example 12. The melting furnace system of any preceding or subsequent example or combination of examples, wherein at least a portion of the mixture of the plasma gas and the auxiliary gas is supplied as the auxiliary gas.

[0040] Example 13. The melting furnace system of any preceding or subsequent example or combination of examples, wherein the plasma gas includes at least one of plasma argon, plasma nitrogen, or plasma carbon dioxide.

[0041] Example 14. The melting furnace system of any preceding or subsequent example or combination of examples, wherein the plasma gas comprises plasma carbon dioxide.

[0042] Example 15. The melting furnace system of any preceding or subsequent example or combination of examples, wherein said auxiliary gas system is further configured to provide an exhaust control gas into exhaust gases from said melting chamber.

[0043] Example 16. A method for melting a metal using a melting furnace system, the method comprising: supplying the metal into a melting chamber of a melting furnace of the melting furnace system; supplying a plasma gas to the melting chamber to heat the melting chamber; and supplying an auxiliary gas to the melting chamber.

[0044] Example 17. The method of any preceding or subsequent example or combination of examples, wherein supplying the plasma gas includes supplying at least one of plasma argon, plasma nitrogen, or plasma carbon dioxide.

[0045] Example 18. The method of any preceding or subsequent example or combination of examples, further comprising supplying an emissions control gas to the emissions gases emitted from said dissolution chamber.

[0046] Example 19. The method of any preceding or succeeding example or combination of examples, wherein said emission control gas comprises atmospheric air.

[0047] Example 20. The method of any preceding or subsequent example or combination of examples, wherein the auxiliary gas comprises carbon dioxide.

[0048] Example 21. The method of any preceding or subsequent example or combination of examples, further comprising controlling the supply of the mixture of the assist gas and the atmospheric air using a controller and based on furnace pressure within the melting chamber.

[0049] Although the subject matter of the embodiments has been described with particularity herein to satisfy statutory requirements, such description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other forms, may include different elements or steps, and may be used in conjunction with other existing or future technologies. Unless the order of individual steps or arrangement of elements is explicitly described, this description should not be construed as suggesting a particular order or arrangement among or between the various steps or elements. In particular, directional references such as "top," "bottom," "upper," "lower," "left," "right," "front," and "rear" are intended to refer to the directions shown and described in the drawing(s) that reference the components and directions. In the drawings and description, like numerals are intended to represent like elements. Throughout this disclosure, reference numerals accompanied by a letter refer to specific instances of an element, while reference numerals without an accompanying letter refer to elements generally or collectively. Thus, by way of example (not shown), device "12A" refers to one example of a type of device that may be collectively referred to as device "12," any one of which may be collectively referred to as device "12." As used in this disclosure, the meanings of "a," "an," and "the" include singular and plural references unless the context clearly dictates otherwise.

[0050] The above-described aspects are merely possible examples of implementations, presented merely for a clear understanding of the principles of the present disclosure. Many changes and modifications can be made to the above-described embodiment(s) without substantially departing from the spirit and principles of the present disclosure. All such modifications and variations are intended to be encompassed herein within the scope of the present disclosure, and all possible claims directed to individual aspects or combinations of elements or steps are intended to be supported by the present disclosure. Moreover, although specific terms are used in this specification and the following claims, they are used in a generic and descriptive sense only and not for the purpose of limiting the described embodiments or limiting the scope of the following claims.

Claims

1. 1. A melting furnace system, comprising: a plasma gas supply for supplying plasma gas to a melting chamber of a melting furnace of the melting furnace system; an auxiliary gas system configured to supply an auxiliary gas into the melting chamber to mix with the plasma gas to form a mixed gas, and configured to supply an emission control gas to exhaust gases from the melting chamber.

2. 2. The melting furnace system of claim 1, further comprising the melting furnace defining the melting chamber, the melting furnace further comprising an exhaust pipe for exhausting the mixed gas from the melting chamber as the exhaust gas.

3. The melting furnace system of claim 2 , further comprising a pressure controller configured to control an exhaust rate of the mixed gas from the melting chamber.

4. The melting furnace system of claim 3 , further comprising a controller configured to control the pressure controller based on a detected furnace pressure in the melting chamber.

5. The melting furnace system of claim 1 , further comprising a controller configured to control at least one of the plasma gas supply or the auxiliary gas supply.

6. The melting furnace system of claim 1 , wherein the plasma gas comprises at least one of plasma argon, plasma nitrogen, or plasma carbon dioxide.

7. The melting furnace system of claim 1 , wherein the auxiliary gas comprises exhaust gas from the melting chamber.

8. The melting furnace system of claim 1 , wherein the auxiliary gas comprises carbon dioxide.

9. 1. A melting furnace system, comprising: a plasma gas supply for supplying plasma gas to a melting chamber of a melting furnace of the melting furnace system; an auxiliary gas system comprising an auxiliary gas supply for supplying an auxiliary gas to the melting chamber, the auxiliary gas being configured to control furnace pressure within the melting chamber.

10. the melting furnace defining the melting chamber; 10. The melting furnace system of claim 9, further comprising an exhaust for exhausting the mixture of the plasma gas and the assist gas from the melting chamber.

11. The melting furnace system of claim 10 , further comprising a pressure controller configured to control an exhaust rate of the mixture of the plasma gas and the assist gas from the melting chamber.

12. The melting furnace system of claim 10 , wherein at least a portion of a mixture of the plasma gas and the auxiliary gas is supplied as the auxiliary gas.

13. 10. The melting furnace system of claim 9, wherein the plasma gas comprises at least one of plasma argon, plasma nitrogen, or plasma carbon dioxide.

14. 14. The melting furnace system of claim 13, wherein the plasma gas comprises plasma carbon dioxide.

15. 10. The melting furnace system of claim 9, wherein the auxiliary gas system is further configured to provide an emission control gas into exhaust gases from the melting chamber.

16. 1. A method of melting metal with a melting furnace system, comprising: providing the metal into a melting chamber of a melting furnace of the melting furnace system; providing a plasma gas into the melting chamber to heat the melting chamber; and supplying an auxiliary gas to the dissolution chamber.

17. 17. The method of claim 16, wherein supplying the plasma gas comprises supplying at least one of plasma argon, plasma nitrogen, or plasma carbon dioxide.

18. 17. The method of claim 16, further comprising supplying an emissions control gas to the exhaust gases emitted from the dissolution chamber.

19. 20. The method of claim 18, wherein the emission control gas comprises atmospheric air.

20. The method of claim 16 , wherein the auxiliary gas comprises carbon dioxide.

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