WO2013059280A2

WO2013059280A2 - Dehalogenation of inorganic minerals prior to vitrification

Info

Publication number: WO2013059280A2
Application number: PCT/US2012/060558
Authority: WO
Inventors: Thomas J. Baudhuin
Original assignee: Minergy Corporation Limited
Priority date: 2011-10-18
Filing date: 2012-10-17
Publication date: 2013-04-25
Also published as: WO2013059280A3

Abstract

A process for recovering a hydrogen halide from an industrial byproduct including a halide is disclosed. The process can include the steps of: contacting the industrial byproduct with sulfuric acid to form a slurry including a sulfate and a hydrogen halide; heating the slurry to drive off a gas phase including the hydrogen halide; condensing water and the hydrogen halide in the gas phase to form a hydrohalic acid; drying the slurry to form solids including the sulfate; melting the solids in a furnace to form a molten material; capturing gases including sulfur dioxide from the furnace; passing the gases over a catalyst to convert at least a portion of the sulfur dioxide in the gases to sulfur trioxide; condensing water and the sulfur trioxide in the gases to form sulfuric acid; and quenching the molten material to form a glass.

Description

Dehalogenation Of Inorganic Minerals Prior To Vitrification

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority from U.S. Patent Application No.

61/548,516 filed October 18, 201 1.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0003] The invention relates to the pre-treatment of materials prior to high temperature processing and vitrification.

2. Description of the Related Art

[0004] Vitrification of waste material initially was focused on radioactive materials and materials heavily contaminated with toxic metals. More recently, the vitrification of high volume industrial wastes has been performed on larger, commercial scale projects. The economics of scale for larger dedicated purpose, high volume waste streams can improve economics, and coupled with increasing costs and poor sustainability of continued land filling operations provide cases for economically viable vitrification system investments.

[0005] Several waste streams such as the solid waste from air emissions control equipment and spent pot liner from the production of aluminum from bauxite can have significant levels of chloride and fluoride based salts in the overall waste make up. The chloride and fluoride salts can be extremely problematic after the introduction into a high temperature melting furnace. The first issue can be the formation of an immiscible floating layer of salt on top of the balance of mineral oxides. This layer can quickly attack furnace refractory, and also acts as a barrier to heat transfer for fuel fired type furnace designs.

Furthermore, some of the chloride and fluoride salts can decompose and form fluoride gas, hydrofluoric acid, chloride gas and hydrochloric acid. The

aforementioned gases are very corrosive and can drastically reduce the operating life of furnace refractory and of gas treatment systems. The gases are also toxic, and require complete removal from the other melting furnace off gases generated. This process produces another waste stream that requires disposal, thereby diminishing the benefits of the operation.

[0006] What is needed therefore is a process for dehalogenation of inorganic minerals prior to vitrification.

SUMMARY OF THE INVENTION

[0007] The invention relates to the pre-treatment of materials prior to high temperature processing and vitrification of inorganic oxide minerals into a glass (amorphous atomic structure) that is highly resistant to breakdown and leaching of trace heavy metals into the environment. An advantage of the pre-treatment step is to remove halogens (e.g., chlorine and fluorine) from the raw materials prior to the introduction of the materials into the melting process.

[0008] The invention blends a specific amount of sulfuric acid with a given volume of fluorinated or chlorinated inorganic minerals to generate hydrofluoric acid (HF) and/or hydrochloric acid (HCI) that can be liberated from the mixture by vaporization. The HF and HCI can be recovered and recycled into a useful byproduct.

[0009] The pre-treated raw material now containing sulfate-based inorganic minerals is then mixed with fluxing materials, and introduced into a high temperature, refractory lined melting furnace. As the temperature of the feed material increases, high temperature mineral reactions greatly favor the volatilization of the sulfur dioxide (SO₂) gas from the sulfate based inorganic minerals. The sulfur dioxide gas is vented from the melting furnace along with the balance of the gaseous byproducts of combustion (CO₂ and H₂0).

[0010] The gaseous byproducts are conditioned and cleaned from

contaminants and are then passed over an oxidation catalyst to convert the sulfur dioxide (SO₂) gas into sulfur trioxide (SO₃). The sulfur trioxide is cooled and then contacted with water which is also condensing out of the gas stream to form sulfuric acid (H₂SO₄). The sulfuric acid is then recycled back to the

dehalogenation step which reduces or eliminates the need to purchase sulfuric acid. [001 1] In summary, the process includes: (a) a pre-treatment step involving the formation of a slurry from the use of sulfuric acid and water to form a slurry and to displace the halogenated fraction of the raw material into the liquid in the form of a hydrogen halide in solution with the water; (b) evaporating the liquid portion of the slurry and capturing the hydrogen halide containing liquid and converting them into useful byproducts; (c) taking the remaining dry fraction from the evaporation step, adding fluxing materials, and feeding the mixture into a high temperature melting furnace operating in a temperate range of 2300°F to 2900°F; (d) liberating S0₂ from the decomposition of sulfate minerals in the furnace; (e) converting the sulfur dioxide gases emitted from the high

temperature glass melting furnace, and converting the gas into sulfur trioxide; (f) capturing the sulfur trioxide and converting it to sulfuric acid for either reuse in step (a) as described above, or for sale as a usable byproduct.

[0012] These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic showing an apparatus according to the invention for the pre-treatment of materials prior to high temperature processing and vitrification of the pretreated materials into a glass.

[0014] Figure 2 is a schematic showing an apparatus according to the invention for the high temperature processing and vitrification of the pretreated materials into a glass.

[0015] Like reference numerals will be used to refer to like parts from Figure to Figure in the following description of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0016] The invention provides a process for recovering a hydrogen halide from an industrial byproduct including at least one of a halide, a hydroxyhalide, or an oxyhalide. The treated industrial byproduct, which has lower levels of the halide, hydroxyhalide, or oxyhalide, can then be vitrified. In the process, the industrial byproduct is contacted with an amount of sulfuric acid to form a slurry including a sulfate and a hydrogen halide. The sulfuric acid used can have a concentration of 10% to 50% by mass. The slurry is heated to drive off a gas phase including the hydrogen halide. Water and the hydrogen halide in the gas phase are then condensed to form a hydrohalic acid. Preferably, a concentration of the halide, the hydroxyhalide, or the oxyhalide in the industrial byproduct is a minimum of 5% on a mass basis.

[0017] The slurry can be dried to form solids including the sulfate, and then the solids can be melted in a furnace to form a molten material. In one version of the process, the solids are melted at a temperate range of 2300°F (1260°C) to 2900°F (1593°C). A fluxing material, such as silica or a silicate, can be added before melting the solids. Gases which include sulfur dioxide can be captured from the furnace. Gases from the furnace can be treated to remove residual hydrogen halide from the gases. Also, gases from the furnace can be treated to remove particulates from the gases. The treated gases can be passed over a catalyst to convert at least a portion of the sulfur dioxide in the gases to sulfur trioxide. Preferably, the gases are reheated before passing the gases over the catalyst. Water and the sulfur trioxide in the gases can then be condensed to form sulfuric acid. The gas phase can be treated to remove particulates before condensing the hydrogen halide in the gas phase. The condensed sulfuric acid can be recycled for combining with the amount of sulfuric acid added to the industrial byproduct. The molten material can be quenched to form a glass.

[0018] The slurry can be thickened before heating the slurry, and a liquid can be removed from the slurry, and the liquid can be added with the amount of sulfuric acid to the industrial byproduct. Particle sizes of the industrial byproduct above a predetermined size can be removed from the industrial byproduct before contacting the industrial byproduct with the amount of sulfuric acid. For example, particle sizes of 100 microns or above can be removed from the industrial byproduct such that a majority (preferably 95% or more) of the particles are 99 microns or less.

[0019] The hydrogen halide can be hydrogen fluoride, hydrogen chloride, hydrogen bromide, or hydrogen iodide. The hydrohalic acid can be hydrofluoric acid, hydrochloric acid, hydroiodic acid, or hydrobromic acid. When the hydrohalic acid is hydrofluoric acid, the hydrofluoric acid can be blended with aluminum hydroxide to make aluminum fluoride, or blended with sodium hydroxide to make sodium fluoride, or blended with sodium fluoride and aluminum fluoride to produce cryolite.

[0020] The industrial byproduct can include a metal halide selected from the group consisting of sodium fluoride, calcium fluoride, sodium chloride, and calcium chloride. The sulfate can be selected from the group consisting of sodium sulfate and calcium sulfate.

[0021] In one version of the invention, the industrial byproduct is a spent pot liner. The spent pot liner can be thermally treated at a temperature of 1200°F (649°C) to 1600 (871 °C) prior to contacting the spent pot liner with the amount of sulfuric acid. In another version of the invention, the industrial byproduct is a material from an acid gas removal system.

[0022] The invention also provides a vitrification process comprising the steps of contacting an industrial byproduct including an unoxidized metal with an amount of sulfuric acid to form a slurry including a sulfate of the metal; drying the slurry to form solids including the sulfate; melting the solids in a furnace to form a molten material; and quenching the molten material to form a glass. The solids can be melted at a temperate range of 2300 ( 260°C) to 2900°F (1593°C). A fluxing material can be added before melting the solids. Preferably, the sulfuric acid has a concentration of 10% to 50% by mass. The unoxidized metal can be aluminum or iron. Gases which include sulfur dioxide can be captured from the furnace. Gases from the furnace can be treated to remove residual hydrogen halide from the gases. Also, gases from the furnace can be treated to remove particulates from the gases. The treated gases can be passed over a catalyst to convert at least a portion of the sulfur dioxide in the gases to sulfur trioxide. Preferably, the gases are reheated before passing the gases over the catalyst. Water and the sulfur trioxide in the gases can then be condensed to form sulfuric acid. The gas phase can be treated to remove particulates before condensing the hydrogen halide in the gas phase. The condensed sulfuric acid can be recycled for combining with the amount of sulfuric acid added to the industrial byproduct that includes an unoxidized metal.

[0023] In one example embodiment, the invention provides a process for recovering hydrogen fluoride from an industrial byproduct. The process comprises: (1a) contacting the industrial byproduct with a measured amount of sulfuric acid, water plus any recycled liquid remaining from step (1 b) below and allowing the proper amount of time for the reaction to finish; (1 b) thickening the solids into a slurry from the solution and retaining the liquid fraction for step (1 a); (1 c) heating the thickened slurry to drive off water vapor and hydrogen fluoride; (1d) condensing the water vapor and hydrogen fluoride into an aqueous hydrofluoric acid solution; (1e) feeding the dry solids remaining after the heating process in step (1c) and into a high temperature furnace to melt the material; (1f) capturing the gases from the high temperature furnace, cleaning the gases and passing them through a catalyst engineered to convert the sulfur dioxide in the gas to sulfur trioxide; (1 g) cooling the gases and condensing water vapor and sulfur trioxide to form a sulfuric acid and water mixture; and (1 h) recycling the acid created in step (1 h) to step (1a).

[0024] Hydrofluoric acid recovered in the method can be used to: (a) blend with aluminum hydroxide to make aluminum fluoride, or (b) blend with sodium hydroxide to make sodium fluoride, or (c) blend with sodium fluoride and aluminum fluoride in a controlled proportions to produce the synthetic mineral cryolite (Na3AIF₆).

[0025] In another example embodiment, the invention provides a process for recovering hydrogen chloride from an industrial byproduct. The process comprises: (2a) contacting the industrial byproduct with a measured amount of sulfuric acid, water plus any recycled liquid remaining from step (2b) and allowing the proper amount of time for the reaction to finish; (2b) thickening the solids into a slurry from the solution and retaining the liquid fraction to step (2a); (2c) heating the thickened slurry to drive off water vapor and hydrogen chloride; (2d) condensing the water vapor and hydrogen chloride into an aqueous hydrochloric acid solution; (2e) feeding the dry solids remaining after the heating process in step (2c) into a high temperature furnace to melt the material; (2f) capturing the gases from the high temperature furnace and passing them through a catalyst engineered to convert the sulfur dioxide in the gas to sulfur trioxide; (2g) cooling the gases and condensing water vapor and sulfur trioxide to form a sulfuric acid and water mixture; and (2h) recycling the acid created in step (2h) to step (2a).

[0026] In still another example embodiment, the invention provides a method for processing spent pot liner (a waste byproduct) from the production of aluminum metal from bauxite. The method comprises: (3a) contacting the spent pot liner with a measured amount of sulfuric acid, water plus any recycled liquid remaining from step (3b) below and allowing the proper amount of time for the reaction to finish; (3b) thickening the solids into a slurry from the solution and retaining the liquid fraction for step (3a); (3c) heating the thickened slurry to drive off water vapor and hydrogen fluoride; (3d) condensing the water vapor and hydrogen fluoride into an aqueous acid solution; (3e) feeding the dry solids remaining after the heating process in step (3c) into a high temperature furnace to melt the material; (3f) capturing the gases from the high temperature furnace, cleaning said gases and passing them through a catalyst engineered to convert the sulfur dioxide in the gas to sulfur trioxide; (3g) cooling the gases and condensing water vapor and sulfur trioxide to form a sulfuric acid and water mixture; and (3h) recycling the acid created in step (3h) to step (3a). The spent pot liner can be thermally treated at a temperature of 1200°F to 1600°F for the purpose of reducing the carbon content of the mixture prior to treating the spent pot liner in accordance to the method.

[0027] In yet another example embodiment, the invention provides a method for processing fly ash produced in acid gas removal systems connected to incinerators combusting chlorinated materials. The method comprises: (4a) contacting the fly ash with a measured amount of sulfuric acid, water plus any recycled liquid remaining from step (4b) and allowing the proper amount of time for the reaction to finish; (4b) thickening the solids into a slurry from the solution and retaining the liquid fraction to step (4a); (4c) heating the thickened slurry to drive off water vapor and hydrogen chloride; (4d) condensing the water vapor and hydrogen chloride into an aqueous acid solution; (4e) feeding the dry solids remaining after the heating process in step (4c) into a high temperature furnace to melt the material; (4f) capturing the gases from the high temperature furnace and passing them through a catalyst engineered to convert the sulfur dioxide in the gas to sulfur trioxide; (4g) cooling the gases and condensing water vapor and sulfur trioxide to form a sulfuric acid and water mixture; and (4h) recycling the acid created in step (4h) to step (4a).

[0028] Sulfuric acid (H₂S0₄) is a strong acid that can substitute a chloride salt with a sulfate-based salt, or a fluoride based salt with a sulfate-based salt.

[0029] Spent pot liner, a waste from the production of aluminum from bauxite, is a waste that contains a known amount of both sodium fluoride, and calcium fluoride. The following reactions take place when a properly proportioned mixture of sulfuric acid and water mixture are blended with the spent pot liner:

CaF₂ + H₂S0₄ -» CaS0₄ + 2HF

2NaF + H₂S0₄ - Na₂S0₄ + 2HF

Preferably, the sulfuric acid is added to the spent pot liner such that the molar ratio of sulfuric acid to calcium fluoride is 1 : 1 , and the molar ratio of sulfuric acid to sodium fluoride is 1 :2.

[0030] Flue gases from an incinerator that combusts chlorine containing waste materials can be scrubbed with lime (CaO) based reagents. The resulting byproduct which is captured in a particulate collection system is a mixture of ash from the incinerated waste and salts formed in the scrubbing operation. In lime- based systems, the two common forms of chloride salts that are found in the ash are calcium chloride and calcium hydroxychloride. The following reactions take place when a properly proportioned mixture of sulfuric acid and water mixture are blended with the incinerator ash:

CaCI₂ + H₂S0₄ - CaS0₄ + 2HCI

CaOHCI + H₂S0₄ - CaS0₄ + HCI + H₂0

Preferably, the sulfuric acid is added to .the ash such that the molar ratio of sulfuric acid to calcium chloride is 1 :1 , and the molar ratio of sulfuric acid to calcium hydroxychloride is 1 :1. [0031] Flue gases from an incinerator that combusts chlorine containing wastes materials can be treated using a dry sorbent injection technology that uses sodium based reagents such as sodium bicarbonate or sodium

sesquicarbonate. The resulting byproduct which is captured in a particulate collection system is a mixture of ash from the incinerated waste and salts formed in the scrubbing operation. The ash contains a portion of sodium chloride formed when HCI in the flue gas reacted with the dry sorbent. The treatment of this ash with sulfuric acid produces the following reaction:

2NaCI + H₂S0₄ -» Na₂S0₄ + 2HCI

Preferably, the sulfuric acid is added to the ash such that the molar ratio of sulfuric acid to sodium chloride is 1 :2.

[0032] Not all reactions from the treatment of the raw materials form hydrogen halides, however they still can be beneficial to the overall process. Many waste materials like recycling process residue, and incinerator bottom ash can contain a fraction of unoxidized metal, such as iron or aluminum. Unoxidized iron can be detrimental to the melting furnace in the vitrification process because it melts into a liquid that is denser than the surrounding molten pool in the furnace. The heavy droplets fall to the bottom of the liquid bath damaging the refractory lining and potentially filling the furnace over time. Since the sulfuric acid is not selective in the case iron, the following reaction occurs:

2Fe + 3H₂S0₄ Fe₂(SO₄)₃ + 3H₂

Preferably, the sulfuric acid is added to the ash such that the molar ratio of sulfuric acid to iron is 3:2.

[0033] Free metallic aluminum, often found in spent pot liner, while not recognized as being significantly problematic in the vitrification furnace, will react when blended with sulfuric acid with the resulting reaction:

2AI + 3H₂S0₄ -= AI₂(S0₄)₃ + 3H₂

Preferably, the sulfuric acid is added to the ash such that the molar ratio of sulfuric acid to aluminum is 3:2.

[0034] Looking at Figure 1 , there is shown an apparatus according to the invention for the pre-treatment of materials prior to high temperature processing and vitrification of the pretreated materials into a glass. Raw material 10, which is generally a waste material from a process, and is characterized by a significant content of halogenated inorganic salts such as common salt (NaCI), calcium chloride (CaCI) or sodium fluoride (NaF), or calcium fluoride (CaF₂) or a combination of these salts. In the preferred embodiment of the invention, the raw material should be dry or have a minimum amount of free moisture. The raw material should also be free of or contain a low concentration of organic material and free carbon. As a guideline, the concentration of the halogenated salts in the raw material is preferably a minimum of 5% on a mass basis, and with more preferable concentrations greater than 10%. The raw material may or may not require a sizing step 11. The preferred material size is less than 100 micron. If the raw material size already meets the sizing requirements it can be bypassed directly via bypass line 12 to reaction tank 13.

[0035] A sulfuric acid (H₂S0₄) solution and water mixture is feed from tank 41 at a controlled rate proportional to the raw material flow. The preferred sulfuric acid concentration may range from 10% to 50% by mass depending on the properties of the waste material processed and the water content of the

thickened slurry leaving the centrifuge device 19 via line 21. If the sulfuric acid concentration available exceeds the desired concentration, it can be diluted with water from supply line 9. The reaction tank may either be a batch process or a continuous process depending on the reaction rates. The proportion of the raw material to acid feed rate is adjusted to optimize the yield of the reaction. The solids in the reaction tank are stirred and suspended by mixer 14. Several typical reactions that occur in the mixing tank 14 include, but are not limited to the examples given previously herein. The status of the reaction is monitored by instrumentation 15 which can include (but is not limited to) pH, density, conductivity, and ion exchange chromatography.

[0036] Both hydrogen chloride and hydrogen fluoride have a strong affinity to water, and do not evolve as a gas as long as the temperatures remain low. The reacted products are discharged into thickening tank 16, where the solids migrate to the bottom of the tank and are extracted via underflow conduit 18. The solids are further thickened with centrifuge 19. The liquid fraction of the slurry fed to the dryer 22 will be an aqueous mixture of hydrogen halides and water. The thickened solids are discharged via line 21 to dryer 22, while the clear water discharge fraction of the centrifuge is directed back to back into the top of the thickening tank via line 20. In the preferred embodiment of the invention, the water entering the system that is mixed with the sulfuric acid is equal to the water leaving the system as a fraction of the thickened slurry leaving the system via line 21. If excess water enters the system, then the excess water overflows tank 16 and drains via line 17 requiring additional water treatment.

[0037] Dryer 22 is heated by an external source of energy. That energy may take the form of steam or thermal heat transfer fluid and enters the dryer heating coils 22H via line 23, and exits as condensate or cooled thermal heat transfer fluid via line 24. The water and hydrogen halide is vaporized and is exhausted from the dryer via line 25 to particulate capture device 26. The particulate capture device 26 is preferably an electro static precipitator. Captured particulate is discharged from the collection device 26 via line 27b and is blended back with the dried product discharged from the dryer 22 via line 27a. Lines 27a and 27b combine into line 27c.

[0038] A particulate free vapor mixture of water and halogen gas exits the electrostatic precipitator 26 via line 28 and enters the bottom of condensing tower 29. The condensing tower 29 is partially filled with packing media 30, and the vapor flow is upward and countercurrent to the down flowing liquid mixture of water and hydrogen halide. The liquid enters the condensing tower 29 and is sprayed evenly over the packing media 30 by spray manifold 31. The sprayed liquid is colder and will have a vapor pressure lower than entering vapor, allowing both the water and hydrogen halide vapor to condense to a liquid. The

condensed aqueous mixture is collected in sump 32. A portion of the mixture is pumped with pump 33 to heat exchanger 34 where the fluid is cooled before it enters the spray manifold 31. The concentration of hydrogen halide in the water is controlled by adding additional make-up water to the system via line 35. The non condensable gas, primary air that has leaked into the dryer is removed via vent port 36. Excess liquid exits sump overflow via line 37 into storage tank 38 and can be pumped to another process for further processing via conduit 39. The hydrogen halide and water mixture can be used as a raw material in the chemical industry. Additional steps may be required depending on user specifications for the hydrogen halide.

[0039] Turning now to Figure 2, there is shown an apparatus according to the invention for the high temperature processing and vitrification of the pretreated materials into a glass. Depending on the chemical make up of the dried and treated solids 47, additional fluxing agents may be required. It is highly desirable that the finished product after the vitrification process be an amorphous state. The amorphous state is defined by a lack of crystalline structure, and a significantly lower potential to leach any heavy metals into the environment. A key ingredient to achieving the amorphous state is the content of silica (Si0₂). Silica and potentially other fluxing agents are added via line 48 into line 27c (from Fig. 1) which supplies dried and treated solids 47. The rate of flux addition is used to optimize furnace temperature influence on the molten glass viscosity characteristic. Flux addition also impacts product quality, as defined by its heavy metal leachability, after the product has been quenched.

[0040] The dried and treated (and optionally fluxed) solids 47 enter melting furnace 46. The furnace design and construction can be patterned after a glass melting furnace. The inner lining of refractory is selected based on its corrosion resistance to the material that is processed in the furnace 46. To reduce the rate of heat loss from the furnace 46 to the surrounding environment, a layer of insulating fire brick followed by an additional layer of insulating blanket are often utilized. In the preferred embodiment of the invention, heat energy is introduced by combusting a fuel inside the furnace. Other methods of adding heat may include but are not limited to electrical resistance, electrical induction and electric plasma arc heating. In most cases, a fuel such as natural gas will have the lowest cost and environmental impact. Natural gas is introduced via line 45 and is introduced into the furnace 46 in a controlled ratio to oxygen introduced via oxygen line 44. Oxy-fuel burner 49 is more energy efficient and emits a significantly lower volume of off gas, which is highly preferred over using the oxygen contained in air. The rate of fuel firing is established to maintain a constant furnace temperature in the preferred range of 2400°F (1315°C) to 2800°F (1538°C). The flow rate of oxygen to the furnished is established by the oxygen necessary to complete stoichiometric combustion of the fuel, plus any residual combustible material in the feed material, plus a reserve margin of oxygen known as excess oxygen. In the preferred embodiment of the invention, an oxygen excess of no less than 2% and no greater than 7% would be typical.

[0041] The dried, treated and fluxed solids 47 are introduced into the furnace 46 and exposed to the high radiant heat flux of the furnace 46. The temperature of the material rises and numerous chemical reactions occur, as defined below, as the solids are rapidly heated.

[0042] The temperature of the feed material increases until it melts into the pool of molten material 50. The molten material 50 drains from the furnace via line 51 into quench tank 52. The quench tank 52 is filled with water 53, and the rapid cooling causes the molten glass to quickly solidify and fracture into a amorphous solid, that is often called frit or flit glass. The overall process of heating, melting and quenching material into an amorphous, leach resistant product is often called vitrification to those skilled in the art. The quenched product is extracted from the quench tank by means of mechanical conveyance, dewatered, and can be shipped out as a product 54.

[0043] During the melting process, the following reactions to the sulfate minerals occur:

Na₂(S0 ) + Si0₂ -» Na₂Si0₃ + S0₂ + ½ 0₂

Na₂(S0₄) + 2Si0₂ -» Na₂Si₂0₃ + S0₂ + ½ 0₂

Na₂(S0₄) + Al₂0₃ -> 2NaAI0₂ + S0₂ + ½ 0₂

Ca(S0₄) + Si0₂ CaSi0₃ + SO₂ + ½ 0₂

AI₂(S0₄)₃ + Si0₂ AI₂Si0₅ + 3S0₂ + 1 ½ 0₂

[0044] The products of combustion from the oxy-fuel burner 49 are H₂0 and C0₂. The S0₂ liberated by the above reactions together with the oxy-fuel combustion products and exit from the furnace via refractory insulated duct 55. The expected range of S0₂ in the furnace gases is 2% to 15% on a wet volume basis. The exiting gas temperature will be approximately equal to the operating temperature of the furnace. The gas is first cooled by cooling water stream 56, which is finely atomized and dispersed in the hot gas stream in gas quencher 57. The flow of cooling water is such that all of the water is vaporized, and that no liquid phase water or water droplets remain in the gas stream prior to the next pre-treatment step. The desired temperature of the gas stream exiting the quencher is preferably 750°F (399°C) or lower at the point the gases enter particulate removal device 58. The particulate removal device 58 is preferably an electro-static precipitator. Captured particulate is discharged from the device via line 59 as a byproduct. Depending on the chemical and physical properties, it may be permissible to blend the byproduct back into the raw feed stream 0 at the start of the treatment process.

[0045] The particulate free gas exiting the collector via line 60 may still contain a residual amount of the hydrogen halide gases due to chemical reactions that did not proceed to 100% in the initial acid treatment stages. The hydrogen chloride and hydrogen fluoride have a strong affinity for water, while the balance of the gases CO₂ and SO2 have a very low absorption potential. The gases then enter packed scrubbing tower 61 , where they are further cooled, as they contact the cooling water flowing in packing 64, until they reach the adiabatic saturation temperature. In the preferred embodiment of the invention, the adiabatic saturation temperature is expected to be less than 200°F (93°C), but greater than 150°F (65°C). Cooling water is distributed by a spray nozzle header 66 onto the top of the packing. The cooling water flows down through the packing 64, assisted by gravity, to the bottom of the scrubber tower 61 , and out drain conduit to pump 62. Acid levels are prevented from building up by maintaining a blow-down flow 63 and make up water is added via line 65 to balance blow-down and evaporation loss.

[0046] The hydrogen halide free gases exit via conduit 67, and enter reheater 68. The gases can be heated by several different methods. In the preferred embodiment of the invention, a gaseous fuel such as natural gas 69, is combusted with the support of combustion air 70, in direct contact with the gases. The gases exit the reheat burner section and proceed to the catalytic converter 72 via line 71. The preferred temperature of the gases at this point is 700°F (371 °C) to 825°F (440°C).

[0047] The reheated gases enter catalytic reactor 72. The reactor houses catalyst layers 73a, 73b, 73c and intercooler heat exchangers 74a and 74b. As the SO2 rich gas contacts the first catalyst layer 73a, excess oxygen in the gas reacts to form S0₃ via the following reaction:

2S0₂ + 0₂ -» 2S0₃

[0048] The reaction is exothermic, which increases the gas temperature. The gas phase equilibrium is approached as the temperature increases slowing the rate of reaction. In order to reduce the gas temperature, heat exchanger 74a, is supplied with a continuous controlled flow cooling media from source 74. The cooling media can be steam, air, boiler feedwater or thermal heat transfer fluid. The entering temperature of the cooling fluid should be maintained at a minimum to prevent acid condensation, but below 800°F (427°C) to allow cooling of the gases back down to the optimum temperature prior to entering the second catalyst layer 73b. More of the S0₂ is converted to S0₃ and the gas temperature increases due to the exothermic reaction. Heat exchanger 74b again cools the gases to the same temperature range as the first stage 74a of cooling did. The flow rate of the cooling media supply 73 and cooling media exhaust 75

temperature are precisely controlled to maintain the proper inter-stage

temperatures for optimum catalyst performance. The gases then enter the third stage of catalyst, 73c, and exit the reactor housing in conduit 76. In the preferred embodiment of the invention, three stages of catalysts are used. Depending on a number of both economic and technical factors, more or less layers of catalyst may be utilized provided that some form of cooling is provided between the layers. In the preferred embodiment of the invention, a minimum of 90% of the S0₂ that entered the catalytic reactor 72 is converted to S0₃ at the exit of the catalytic reactor 72. As additional catalyst layers are employed, the fraction of S0₂ converted to SO3 approaches nearly 100%. [0049] The gases furnished in conduit 76 then enter the Wet Sulfuric Acid (WSA) condenser 77. Cooling media 78, preferably air, is provided by fan 79 to cool the hot gases by indirect heat transfer. The air passes over the outside of the heat exchanger tubes 80, and cools the tubes 80. The heated air is exhausted out line 85 and can be utilized as an energy source in an integrated processing facility. As the mixture cools the sulfur trioxide gas combines with the water vapor to form sulfuric acid:

S0₃ + H₂0 - H₂S0₃

[0050] The mixture of sulfuric acid and excess water vapor condense on the inside surface of the tubes. The tubes are preferably made from a material that is highly resistant to acid under a wide range of temperatures such as

borosilicate glass. The. condensed acid and water mixture flows along the inside surface with the assistance of gravity, and drops into sump 81. The sulfuric acid mixture is then pumped by pump 82 through cooling heat exchanger 83 and is discharged to line 84 for transfer back to the sulfuric acid storage tank 41 (see Fig. 1 ). In a situation that the rate of H₂S0₄ production from the WSA process does not satisfy the consumption in the dehalogenation, then additional H₂S0₄ is added to the cycle from outside source 40. It is also conceivable that the H₂S0₄ production exceeds the consumption in the dehalogenation then excess H₂S0₄ is exported via line 43. The non-condensable gases, primary consisting of carbon dioxide, nitrogen, oxygen, and trace amounts of water vapor and S0₂ that were not converted in the catalytic reactor are discharged out vent pipe 86 for further treatment by conventional methods, prior to discharge to the atmosphere.

[0051] Thus, the invention provides a process for dehalogenation of inorganic minerals prior to vitrification.

[0052] Although the invention has been described in considerable detail with reference to certain embodiments, one skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which have been presented for purposes of illustration and not of limitation.

Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein.

Claims

CLAIMS What is claimed is:

1. A process for recovering a hydrogen halide from an industrial byproduct including at least one of a halide, a hydroxyhalide, or an oxyhalide, the process comprising:

(a) contacting the industrial byproduct with an amount of sulfuric acid to form a slurry including a sulfate and a hydrogen halide;

(b) heating the slurry to drive off a gas phase including the hydrogen halide; and

(c) condensing water and the hydrogen halide in the gas phase to form a hydrohalic acid.

2. The process of claim 1 further comprising:

(d) drying the slurry to form solids including the sulfate.

3. The process of claim 2 further comprising:

(e) melting the solids in a furnace to form a molten material.

4. The process of claim 3 wherein:

step (e) comprises melting the solids at a temperate range of 2300°F to 2900°F.

5. The process of claim 3 wherein:

step (e) further comprises adding a fluxing material before melting the solids.

6. The process of claim 3 further comprising:

(f) capturing gases from the furnace, the gases including sulfur dioxide.

7. The process of claim 6 further comprising:

(g) passing the gases over a catalyst to convert at least a portion of the sulfur dioxide in the gases to sulfur trioxide.

8. The process of claim 7 further comprising:

(h) condensing water and the sulfur trioxide in the gases to form sulfuric acid.

9. The process of claim 8 further comprising:

(i) combining the sulfuric acid created in step (h) with the amount of sulfuric acid in step (a).

10. The process of claim 9 further comprising:

0) quenching the molten material to form a glass.

11. The process of claim 6 wherein:

step (f) further comprises treating the gases from the furnace to remove residual hydrogen halide from the gases.

12. The process of claim 6 wherein:

step (f) further comprises treating the gases from the furnace to remove particulates from the gases.

13. The process of claim 7 wherein:

step (g) further comprises heating the gases before passing the gases over the catalyst.

14. The process of claim 1 wherein:

step (c) further comprises treating the gas phase to remove particulates before condensing the hydrogen halide in the gas phase.

15. The process of claim 1 wherein:

step (b) further comprises thickening the slurry before heating the slurry.

16. The process of claim 1 wherein:

step (b) further comprises thickening the slurry before heating the slurry, removing a liquid from the slurry, and adding the liquid with the amount of sulfuric acid in step (a).

17. The process of claim 1 wherein:

step (a) further comprises removing particle sizes of the industrial byproduct above a predetermined size before contacting the industrial byproduct with the amount of sulfuric acid.

18. The process of claim 17 wherein:

the predetermined size is 99 microns, and

particle sizes of 100 microns or above are removed from the industrial byproduct such that a majority of the particles are 99 microns or less.

19. The process of claim 18 wherein:

95% or more of the particles are 99 microns or less.

20. The process of claim 1 wherein:

the hydrogen halide is hydrogen fluoride, and

the hydrohalic acid is hydrofluoric acid.

21. The process of claim 20 further comprising:

blending the hydrofluoric acid with aluminum hydroxide to make aluminum fluoride, or

blending the hydrofluoric acid with sodium hydroxide to make sodium fluoride, or

blending the hydrofluoric acid with sodium fluoride and aluminum fluoride to produce cryolite.

22. The process of claim 1 wherein:

the hydrogen halide is hydrogen chloride, and

the hydrohalic acid is hydrochloric acid.

23. The process of claim 1 wherein:

the industrial byproduct includes a metal halide.

24. The process of claim 23 wherein:

the metal halide is selected from the group consisting of sodium fluoride, calcium fluoride, sodium chloride, and calcium chloride.

25. The process of claim 24 wherein:

the sulfate is selected from the group consisting of sodium sulfate and calcium sulfate.

26. The process of claim 1 wherein:

the industrial byproduct is spent pot liner.

27. The process of claim 26 wherein:

step (a) further comprises thermally treating the spent pot liner at a temperature of 1200°F to 1600°F prior to contacting the spent pot liner with the amount of sulfuric acid.

28. The process of claim 1 wherein:

the industrial byproduct is a material from an acid gas removal system.

29. The process of claim 28 wherein:

the material is ash.

30. The process of claim 1 wherein:

the sulfuric acid has a concentration of 10% to 50% by mass.

31. The process of claim 1 wherein:

a concentration of the halide, the hydroxyhalide, or the oxyhalide in the industrial byproduct is a minimum of 5% on a mass basis.

32. A vitrification process comprising:

(a) contacting an industrial byproduct including an unoxidized metal with an amount of sulfuric acid to form a slurry including a sulfate of the metal;

(b) drying the slurry to form solids including the sulfate;

(c) melting the solids in a furnace to form a molten material; and

(d) quenching the molten material to form a glass.

33. The process of claim 32 wherein:

step (c) comprises melting the solids at a temperate range of 2300°F to 2900°F.

34. The process of claim 32 wherein:

step (c) further comprises adding a fluxing material before melting the solids.

35. The process of claim 32 wherein:

the sulfuric acid has a concentration of 10% to 50% by mass.

36. The process of claim 32 wherein:

the unoxidized metal is aluminum.

37. The process of claim 32 wherein:

the unoxidized metal is iron.

38. The process of claim 32 further comprising:

(e) capturing gases from the furnace, the gases including sulfur dioxide.

39. The process of claim 38 further comprising:

(f) passing the gases over a catalyst to convert at least a portion of the sulfur dioxide in the gases to sulfur trioxide.

40. The process of claim 39 further comprising:

(g) condensing water and the sulfur trioxide in the gases to form sulfuric acid.

41. The process of claim 40 further comprising:

(h) combining the sulfuric acid created in step (g) with the amount of sulfuric acid in step (a).