Process of purifying hydrogen fluoride from fluorosilicic acid using a direct steam injector

Abstract

The present disclosure relates to a method of producing purified hydrogen fluoride using directly injected steam. The steam may either be injected upstream of a second reactor or into the second reactor directly. A first liquid-rich product and steam may react to produce a second gas-rich product and a second liquid-rich product. The second gas-rich product and sulfuric acid may be fed to an absorption tower to produce a fourth gas-rich product comprising purified hydrogen fluoride.

Description

Attorney Docket No. IR4890 WO-PCTPROCESS OF PURIFYING HYDROGEN FLUORIDE FROM FLUOROSILICIC ACID USING A DIRECT STEAM INJECTORTECHNICAL FIELD

[0001] The present disclosure generally relates to a method of purifying hydrogen fluoride (HF) from fluorosilicic acid (FSA) using direct steam injection. Specifically, hydrogen fluoride may be produced from a reaction comprising fluorosilicic acid and sulfuric acid. The liquid product of this reaction may be mixed with steam to produce a vapor stream comprising mostly HF and water, where the vapor stream purified through an absorption tower where a gaseous product comprising crude HF can exit the absorption tower and be sent for final purification, thereby forming what may be termed anhydrous hydrogen fluoride (aHF) in the art.BACKGROUND

[0002] Hydrogen fluoride finds uses across many different technology areas, especially as a precursor to organofluorine compounds such as fluorocarbons and fluoropolymers. Industrial applicability is highly dependent on the purity of the HF. Highly pure or anhydrous HF has the most diverse applicability because it reacts readily, and little refining is required needed before using HF. On the other hand, water laden hydrofluoric acid (HF A) has limited industrial applicability as it is only weakly acidic in dilute solutions.

[0003] As such, the purity of HF is critical to determining its feasibility as a reactant. Many known methods of producing HF either do not yield a high enough purity HF or produce relatively low purity HF at some point. If HF is not produced at a high enough concentration, the result is water laden HFA and additional processing must be undertaken to further refine the acid which incurs large additional manufacturing costs. Additionally, many processes fail to optimally rework off-specification HF or very wet HF resulting in large quantities of unused HF.

[0004] When producing HFA from a fluorosilicic acid solution, the stream is highly corrosive and hot, and because of this, the heat exchangers used to heat the solution are costly and have a high rate of failure. To reduce costs and failures, the reduce the number or the size of heat exchangers may be decreased by using direct steam injection as the heating mechanism. Direct steam injection may reduce the capital costs required to create a hydrofluoric acid production system.Attorney Docket No. IR4890 WO-PCTSUMMARY

[0005] The inventors discovered an improved method of producing HF. For example, the method may include reacting fluorosilicic acid and sulfuric acid within a first reactor to produce a first gasrich product and a first liquid-rich product, where the first liquid-rich product may include sulfuric acid, hydrogen fluoride, and water. Method may also include mixing the first liquid-rich product with steam, where the mixing occurs upstream or within a second reactor. Method may furthermore include reacting the first liquid-rich product and steam to produce a second gas-rich product and a second liquid-rich product. Method may in addition include feeding the second gasrich product and sulfuric acid in an absorption tower to produce a fourth gas-rich product having purified hydrogen fluoride.

[0006] The described implementations may also include one or more of the following features. Method where an auxiliary heat exchanger is configured to heat the first liquid-rich product and is located upstream of the location at which the steam is mixed with the first liquid-rich product. Method where a ratio of a heat from the auxiliary heat exchanger to the first liquid-rich product to a heat from the steam to the first liquid-rich product ranges from 0 and 0.01. Method where a concentration of the hydrogen fluoride of the second liquid-rich product ranges from about between 3 wt% to 5 wt% of HF in the second liquid-rich product. Method where the mixing of the steam and the first liquid-rich product occurs upstream of the second reactor. Method where the mixing of the steam and the first liquid-rich product occurs within the second reactor. Method where a mixer is located within the second reactor to facilitate the mixing of the steam and the first liquid-rich product. Method where the mixer is a mixing tee or a static mixer. Method where an auxiliary heat exchanger is configured to heat the first liquid-rich product and is located upstream of the location at which the steam is mixed with the first liquid-rich product. Method where a ratio of a heat from the auxiliary heat exchanger to the first liquid-rich product to a heat from the steam to the first liquid-rich product ranges from 0 and 0.01.

[0007] For example, the method may include reacting fluorosilicic acid and sulfuric acid within a first reactor to produce a first gas-rich product and a first liquid-rich product, where the first liquid-rich product may include sulfuric acid, hydrogen fluoride, and water. Method may also include mixing the first gas-rich product and sulfuric acid in a first absorption tower to produce a third gas-rich product and a second liquid-rich product. Method may furthermore include reacting the third gas-rich product with water in a hydrolysis reactor to produce a recycle stream havingAttorney Docket No. IR4890 WO-PCTfluorosilicate acid, water, and silicon dioxide. Method may in addition include feeding the recycle stream to the first reactor. Method may moreover include mixing the first liquid-rich product with steam, where the mixing occurs upstream or within a second reactor. Method may also include reacting the first liquid-rich product and steam to produce a second gas-rich product and a third liquid-rich product. Method may furthermore include feeding the second gas-rich product and sulfuric acid in a second absorption tower to produce a fourth gas-rich product having purified hydrogen fluoride.

[0008] The described implementations may also include one or more of the following features. Method where the silicon dioxide of the recycle stream is filtered from the recycle stream upstream of the first reactor. Method where the steam is mixed with the first liquid-rich product such that a combined solution having the first liquid-rich product and the steam may include a temperature of about 150C. Method where a concentration of the hydrogen fluoride of the second liquid-rich product ranges from about between 3 wt% to 5 wt% of HF in the second liquid-rich product. Method where the mixing of the steam and the first liquid-rich product occurs upstream of the second reactor. Method where the mixing of the steam and the first liquid-rich product occurs within the second reactor. Method where a mixer is located within the second reactor to facilitate the mixing of the steam and the first liquid-rich product. Method where the mixer is a mixing tee or a static mixer. Method where a steam quality of the directly injected steam may be less than 50%.

[0009] As used herein, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings, which comprise a part of this specification, illustrate several embodiments and, together with the description, serve to explain the principles disclosed herein.

[0011] FIG. 1 is a diagram of the apparatus according to one embodiment.

[0012] FIG.2 is a diagram of the apparatus according to one embodiment.

[0013] FIG.3 is a diagram of the apparatus according to one embodiment.

[0014] FIG. 4 shows a block flow diagram of an anhydrous hydrogen fluoride process, such as one within which an apparatus according to one or more embodiments can be disposed.

[0015] FIG. 5 shows a less granular description of the FSA Concentration step from FIG. 4.Attorney Docket No. IR4890 WO-PCT

[0016] FIG. 6 shows a less granular description of the STF Production sub-portion of the STF Production / HF Generation step from FIG. 4.

[0017] FIG. 7 shows a less granular description of the HF Generation sub-portion of the STF Production / HF Generation step from FIG. 4.

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and, together with the description, serve to explain the disclosed embodiments. The drawings are not necessarily to scale. Certain dimensions and / or relative placement of objects, for example, may be exaggerated for purposes of clearer illustration.DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTSFirst Reaction Tower

[0019] An aqueous FSA solution / slurry may be introduced into a first reactor and may be mixed with sulfuric acid. The FSA solution can comprise from about 20 to about 50 mass percent of FSA based on the total mass of the FSA solution / slurry (abbreviated herein as “solution,” without any intent to limit). The concentration of sulfuric acid in the sulfuric acid solution / slurry may be greater than about 90 wt%. In some embodiments, the sulfuric acid solution / slurry may be greater than about 94 wt%. In particular, the sulfuric acid solution / slurry may be greater than about 96 wt%.

[0020] In some embodiments, the temperature of the first reactor can range from about 160°F to about 250°F, such as, for example, from about 170°F to about 230°F, and from about 175°F to about 225°F. In some embodiments, the first reactor may comprise at least one reactor. In particular, the first reactor may comprise a plurality of reactors.

[0021] Within the first reactor, the FSA solution and sulfuric react according to at least Formula (1) below.Formula (1)Although reactions disclosed herein, such as in Formula (1), are shown with fluorosilicic acid only in its H2SiFe form, the ordinary skilled artisan should understand that other SiF4precursors may be present (e. , including but not necessarily limited to salts, hydrates, and the like, as well as combinations thereof), in addition or alternatively to the H^SiFe form represented in each formula / reaction scheme.

[0022] After reacting in the first reactor, a first gas-rich product and a first liquid-rich product can be produced. The first gas-rich product may comprise at least SiF4, H2O, and HF. After exiting a gas outlet of the first reactor, the first gas-rich product can be fed into a first absorption tower.Attorney Docket No. IR4890 WO-PCTThe first liquid-rich product may comprise at least HF, SiF4, and water. After exiting a liquid outlet of the first reactor, the first liquid-rich product can be fed to a second reactor. The first liquid-rich product may be fed to the second reactor using a pump.

[0023] In some embodiments, the first reactor may comprise at least one reaction tower or distillation column.

[0024] Description of the components and processing units are made with respect to Figure 3. For example, in Figure 3, “R.n” corresponds to the nthreactor, “Abs.n” corresponds to the nthabsorption tower, “R.Hydr” corresponds to the hydrolysis reactor, “Strip” corresponds to the stripper column, “L.n” corresponds to the nthliquid-rich product, and “G.n” corresponds to the nthgas-rich product. Moreover, the chemical species listed by each of the gas and liquid rich products in Figure 3 is not necessarily exhaustive — additional chemical species may be present.First Absorption Tower

[0025] After exiting a gas outlet of the first reactor, the first gas-rich product can be fed into a first absorption tower. Within the first absorption tower, water and HF of the first gas-rich product can be removed using sulfuric acid as a scrubber. Upon scrubbing the first gas-rich product with sulfuric acid, a third gas-rich product at least comprising SiF4 can be produced. The third gas-rich product may be fed to hydrolysis reactors.Hydrolysis Reactor

[0026] In the hydrolysis reactor, the SiF4 of the third gas-rich product can be converted to a hydrolysis product at least comprising FSA and SiCh. The reaction within the hydrolysis reactor occurs according to at least Formula (2) below.3SIF4+ H2Q 2H2StF6+ SiO2Formula (2)

[0027] The hydrolysis reactor may comprise one or a plurality of hydrolysis reaction vessel(s). In some embodiments, both the third gas-rich product and a fresh FSA solution can be fed to an inlet of the hydrolysis reactor. In some embodiments, the third gas-rich product and fresh FSA solution can be fed into a first hydrolysis reaction vessel of the hydrolysis reactor, and fresh FSA can be fed into each of the remaining hydrolysis reaction vessels of the hydrolysis reactor.

[0028] The last hydrolysis reaction vessel can comprise an outlet comprising the hydrolysis product. Once exiting the outlet of the last hydrolysis reaction vessel, the SiO2 of the hydrolysis product may be filtered from the hydrolysis product to produce a filtered hydrolysis product. TheAttorney Docket No. IR4890 WO-PCTfiltered hydrolysis product can comprise at least FSA. The filtered hydrolysis product may be fed to an inlet of the first reactor.

[0029] Because hydrolysis of STF to FSA typically also produces silica (SiCh), the concentrated FSA stream may include a combination (slurry) with silica. The silica, to the extent present, can be filtered out in the filtration section. The concentrated FSA (CFSA), which can be very low in silica content, if not mostly silica-free, can be sent to the STF Production / HF Generation section. The silica, to the extent present, can be washed and can be a separate product stream or sent for disposal. The FSA wash stream, typically less dilute than “concentrated FSA,” can be sent back to the FSA concentration step for recovery.

[0030] The SiCh filtration step may be performed by any standard filtration method, e.g., filter press, belt filter, rotating or non-rotating pressure filters, dead end filters, or the like, or a combination thereof. The basic operation for the filter can be to separate FSA from silica formed in the hydrolysis of STF to FSA, thereby increasing concentration of FSA in the process. Typically, a concentrated FSA (CFSA) stream can comprise a CFSA (typically predominantly liquid phase) portion and a cake (typically predominantly solid phase) portion. The cake portion may contain silica but may also contain some FSA “trapped” in the cake. This cake may be washed to remove any “trapped” FSA, which FSA-containing “wash” effluent can be recycled by sending it back to the FSA Concentration step. Washing of the cake can advantageously reduce losses of FSA to the cake. When utilized, washing can be batch-wise, or continuous, in a one step or multi-step counter current fashion, or the like.Second Reaction Tower

[0031] After exiting a liquid outlet of the first reactor, the first liquid-rich product can be fed to an inlet of a second reactor. In some embodiments, upstream of the second reactor, the first liquid rich product and the sixth liquid rich product can be mixed to form a mixed product, which can fed to an inlet of the second reactor (or they can alternatively be individually fed to an inlet of the second reactor and combined therein).

[0032] In some embodiments, steam can be combined with the mixed product at or upstream of the second reactor.

[0033] The steam can be fed to the second reactor such that the combined solution comprising the first liquid-rich product and the steam at a temperature of at least about 125°C e.g., at least about 150°C, at least about 175°C, or at least about 200°C; in particular, at least about 150°C).Attorney Docket No. IR4890 WO-PCT

[0034] In some embodiments, the steam and mixed product may be combined within the second reactor. In some embodiments, the mixing within the second reactor may be facilitated using a mechanical mixer. In some embodiments, the steam can be introduced into the second reactor through a plate comprising a plurality of holes or a sintered charcoal fdter.

[0035] In some embodiments, the steam can be combined with the mixed product prior to entering the inlet of the second reactor. For example, the steam may be combined with the mixed product using at least one of a mixing tee, static mixer, an injector, and an eductor.

[0036] In some embodiments, combining the steam with the mixed product may induce a phase change when the pressure of the steam is greater than a predetermined value. When the phase combined steam and mixed product is in a liquid phase, a pressure reducing valve or orifice may be implemented upstream of the second reactor to reduce the pressure.

[0037] In other embodiments, the combining the steam with the mixed product may induce substantially no phase change, due to the pressure of the steam being below the predetermined value. In such an embodiment, the combined steam and mixed product may be maintained at a substantially constant pressure, thereby allowing a portion of the combined steam and mixed product to vaporize, including any heating needed to increase to a vaporizing temperature range.

[0038] After the combined solution comprising the first liquid-rich product and the steam is raised to a desired temperature, a second gas-rich product, such as comprising HF and some H2O, can be produced in a second reactor. The second gas-rich product can be fed from a gas outlet of the second reactor to a second absorption tower.

[0039] In some embodiments, the second liquid-rich product may be fed to a stripper column. As shown in Fig. 2, the second liquid-rich product may additionally or alternatively be directed recycled from the second reactor back to the first reactor. Alternatively, as shown in Fig. 1, the second liquid-rich product may not be directly recycled from the second reactor back to the first reactor, perhaps instead being sent to waste.

[0040] In some embodiments, the second reactor may comprise at least one reactor. In particular, the second reactor may comprise a plurality of reactors. In some embodiments, the second reactor can comprise or be a flash drum.Second Absorption Tower

[0041] After exiting a gas outlet of the second reactor, the second gas-rich product can be fed into a second absorption tower. Within the second absorption tower, water and HF of the secondAttorney Docket No. IR4890 WO-PCTgas-rich product can be removed from the second gas-rich product, such as using sulfuric acid as a scrubber. Upon scrubbing the second gas-rich product with sulfuric acid, a fourth gas-rich product at least comprising HF and a fourth liquid-rich product at least comprising sulfuric acid, H2O, and HF can be produced. The fourth gas-rich product may be sent for final purification. The fourth liquid-rich product may be fed to a stripper column.

[0042] In some embodiments, the second absorption tower can comprise or be an HF absorption tower.Stripper Column

[0043] The fourth liquid-rich product may be fed to a stripper column, where HF can be removed from the fourth liquid-rich product. The stripper column can produce a fifth liquid-rich product and a fifth gas-rich product. The fifth gas-rich product can exit the stripper column from an outlet and can be fed to a cooler to produce a cooled fifth product. The cooled fifth product may be fed to at least one of: the stripper column, a drying column, and another process. When the cooled fifth product is sent to the stripper column, the cooled fifth product may be sent to a sump of the stripper column and / or can be used to cool the stripper column receiver. When the cooled fifth product is sent to the drying column, the cooled fifth product can remove water from the fourth gas-rich product, which can further increase the concentration of HF in the fourth gas-rich product, inter alia. When the cooled fifth product is sent to another process, in some embodiments, a sulfuric acid-containing portion of the cooled fifth product may be used in a phosphate rock / phosphoric acid production process.

[0044] A portion of the cooled fifth product, such as equal to the sum of the mass of sulfuric acid that enters the first reactor and the mass of water that enters the first reactor in the FSA stream, can either be sent to waste or to a phosphoric acid process which produces phosphoric acid from phosphate rock.

[0045] To remove HF from the fourth liquid-rich product, the stripper column can use steam and / or air (in particular, both). In some embodiments, the fourth liquid-rich product, steam, and air can be mixed within the stripper column. A fifth gas-rich stream comprising the fourth liquidrich product, steam, and air can exit an outlet of the stripper column and can be fed to a drying column.Drying ColumnAttorney Docket No. IR4890 WO-PCT

[0046] The fifth gas-rich product can enter the drying column through an inlet of the drying column. In some embodiments, sulfuric acid may also be introduced into the drying column through the same inlet or through separate inlets. In some embodiments, the sulfuric acid can be virgin or fresh sulfuric acid. Alternatively, the sulfuric acid can be sent to the drying column from the cooled fifth product of the stripper column.

[0047] Upon mixing of the sulfuric acid and fifth gas-rich product within the drying column, a sixth gas-rich product and a sixth liquid-rich product can be produced. The sixth gas-rich product can be fed from an outlet of the drying column to a third absorption tower. The sixth liquid-rich product may be fed to the first reactor and / or second reactor.Third Absorption Tower

[0048] The sixth gas-rich product can be fed to an inlet of the third absorption tower. In some embodiments, sulfuric acid can be fed into the inlet of the third absorption tower. In some embodiments, the sixth gas-rich product and sulfuric acid can be fed into the same inlet or into separate inlets.

[0049] The sulfuric acid can absorb HF from the sixth gas-rich product. From the third absorber, a seventh gas-rich product and seventh liquid-rich product can be produced. The seventh gas-rich product can comprise H2O, air, and non-condensables. The seventh gas-rich product may be sent to a scrubber. In some embodiments, the seventh gas-rich product can pass through a vent system, e.g., downstream of the third absorption tower and upstream of the scrubber.

[0050] The seventh liquid-rich product can comprise sulfuric acid and HF. In some embodiments, the seventh liquid-rich product can be fed to the second absorption tower to recover the HF from the seventh liquid-rich product, and the sulfuric acid can be eventually sent to the first reactor.Direct Steam Injection

[0051] The steam may be used to heat the mixed product, which can then be fed to the second reactor. Additionally or alternatively, steam may be injected directly in the second reactor to heat the contents thereof. In some embodiments, by heating the mixed product prior to entering the second reactor, the steam can provide sufficient sensible and / or latent heat to vaporize most of the HF and some of the water prior to their entry into the second reactor, or alternatively the pressure can be controlled so that sensible heat is transferred to the mixed product without significant latent heat (substantially no phase change). A sensible heat refers to the heat which causes a change inAttorney Docket No. IR4890 WO-PCTtemperature of the substances, but not a phase change. Latent heat refers to the heat which causes a change in the phase of a substance, but not a temperature change. By heating the contents within the second reactor by directly injecting steam, HF and water can be vaporized within the second reactor.

[0052] In some embodiments, an auxiliary heat exchanger may or may not be used in addition to the steam injection. In particular, when utilized, an auxiliary heat exchanger may be employed in conjunction with the steam injection. If employed, the auxiliary heat exchanger may advantageously be located downstream of where the first liquid product and sixth liquid product are mixed. If one or more auxiliary heat exchangers is employed, the auxiliary heat exchanger may be located upstream or downstream of the location at which the steam is injected. In particular, if an auxiliary heat exchanger is employed, the auxiliary heat exchanger can advantageously be located upstream of the location at which the stream is injected.

[0053] The auxiliary heat exchanger may provide heat to the mixed product prior to entering the second reactor. In some embodiments, the auxiliary heat exchanger may be employed for starting up the HF production process. In certain embodiments, the auxiliary heat exchanger may be employed on standby to provide heat to the mixed product. In certain embodiments, the auxiliary heat exchanger may be employed to reduce the amount and / or temperature of steam necessary to heat the mixed product, e.g., since it will have already been heated to a certain extent by the auxiliary heat exchanger. In some embodiments, the auxiliary heat exchanger may provide some or all the sensible heat and / or a small amount of latent heat to the mixed product. In some embodiments, the direct steam may provide some sensible and some latent heat to the mixed product, or the direct steam may provide all the latent heat.

[0054] In some embodiments, the ratio of the heat of the indirect steam from the auxiliary heat exchanger to the heat of direct steam from the directly injected steam can be from 0 to 0.1, such as from 0 to 0.01 or from 0 to 0.001. The heat from the indirect steam can transferred via the auxiliary heat exchanger to the mixed product. The heat from the direct steam can be transferred via direct contact between the injected steam and the mixed product.

[0055] In some embodiments, the duty of heat from the direct steam can be from 10% to 100% of the total steam required to vaporize the requisite amount of HF and water.

[0056] In some embodiments, a steam quality of the directly injected steam may be less than 50%, such as less than 25%, less than 10%, less than 5%, or even about 0%. In some embodiments,Attorney Docket No. IR4890 WO-PCTthe directly injected steam can comprise superheated steam. In other embodiments, the directly injected steam can comprise wet steam. A steam quality is defined as defined as the mass of the vapor portion of the steam divided by the total mass of the steam ( / .<?., % = mvapor / mtotai).

[0057] After heating and reacting the components in the second reactor, a second gas rich product can be produced, which is at least partially vaporized, and can be fed to the second absorption tower. In some embodiments, a valve or orifice plate may be located downstream of the second reactor and upstream of the second absorption tower. The second gas rich product may be pressurized to ensure little to no vapor or flash across the valve or orifice plate upon leading the second gas rich product to the second absorption tower.

[0058] In some embodiments, the fourth liquid rich product can be sent from the second absorption tower to second stripper column, located downstream the second absorption tower and upstream the first reactor. The stripped fourth liquid rich product can then be fed to the first reactor. Alternatively, the stripped fourth liquid rich product may be fed to an STF generator reactor or a pump prior to being fed to the first reactor.

[0059] In some embodiments, the temperature of the directly injected steam may range from 250°F to 600°F, such as from 300°F to 550°F or from 300°F to 400°F.

[0060] In some embodiments, the steam can be directly injected into the second reactor using a pressure valve. If a pressure valve is used, the pressure of directly injected steam can range from ~15 psig to -150 psig, such as from -50 psig to -100 psig. Alternatively, the steam can be directly injected into the second reactor without a pressure valve. If a pressure valve is not used, the pressure of directly injected steam can ranges from about -25 inches of water to -15 psig.

[0061] In some embodiments, a ratio of the flow rate of the mixed product to the flow rate of total steam into the second reactor may range from about 100 to about 3, such as from about 80 to about 5 or from about 40 to about 5.

[0062] In some embodiments, a percentage defined by the flow of water of the directly injected steam divided by the flow of the mixed product may range from about 3% to about 100%. Additionally or alternatively, the mixed product may comprise from about 60 wt% to about 90 wt% sulfuric acid. Further additionally or alternatively, the mixed product may comprise from about 0 wt% to about 10 wt% HF.

[0063] In some embodiments, the direct injection of the steam may occur in-line in a pipe or in a tank.Attorney Docket No. IR4890 WO-PCT

[0064] In some embodiments, the injected steam may induce a phase change to the combined steam and mixed product, when the steam comprises a sufficient pressure. In such embodiments, a flash valve may be employed to vaporize the combined steam and mixed product upstream of the second reactor. Additionally, pipe line sizes may be smaller in such embodiments.

[0065] In other embodiments, the injected steam may induce substantially no phase change to the combined steam and mixed product. In such embodiments, a flash valve may not be necessary, as the combined steam and mixed product comprise a vaporized portion, and the directly injected steam can be controlled by flow rate and / or by the temperature of the second reactor.

[0066] In some embodiments, the water content from the directly injected steam can flow primarily out of the second reactor in the second liquid rich product which can be fed into the stripper column.Example

[0067] The flows and concentrations in this Example are not limiting but are representative for the purposes of this example. All percentages given below are weight percents.

[0068] A stream containing -42% fluorosilicic acid in water flows to the first reactor at -138 gpm. Sulfuric acid also flows to the first reactor from the third liquid-rich product from the first absorption tower (e.g., a STF generation column) at about 93 gpm (which also contains the water vaporized in first reactor), the fourth liquid-rich product of the second absorption tower (e.g., HF generator column) at about 95 gpm (also containing HF and water). The above-mentioned streams are mixed in the first reactor at about 100°C, which allows the Formula (1) reaction to take place. The first gas-rich product from the first reactor is sent to the first absorption tower (STF generation column) which removes any water from the gaseous stream, producing a third gas-rich product comprising primarily SiF4 (aka silicon tetrafluoride or STF) gas to be sent to the concentration section for hydrolysis to convert the STF to fluorosilicic acid (aka FSA, typically H2SiFe), which may optionally be sent back to the first reactor.

[0069] First liquid-product of the first reactor, optionally with a sixth-liquid rich product comprising sulfuric acid stream resulting from the drying column, is pumped to the second reactor. Steam, at approximately 25000 pounds / hr, may be added directly to this stream, or steam may be added directly to the second reactor. Steam can be added by way of a mixing tee, static mixer, directly into the second reactor by a steam distribution system, or by any other effective and facileAttorney Docket No. IR4890 WO-PCTmethod. Optionally, a mixer may be employed in the second reactor to ensure good mixing of the first liquid-rich product, sixth liquid-rich product, and steam.

[0070] The steam increases the temperature of the second reactor to about 300°F or about 150°C, wherein a second gas-rich product is formed comprising HF and water. In some embodiments, the temperature is at least about 125°C, at least about 150°C, at least about 175°C, or at least about 200°C.

[0071] This second gas rich product goes to the second absorption tower (HF generation column) where sulfuric acid absorbs water from the HF producing a fourth gas-rich product comprising HF, about 9000 pounds / hr, which goes to the final purification operations. The amount and concentration of HF after final purification can depend on the chilling temperature and size of the condenser in the purification system of the final purification and thus can vary. The second liquid-rich product from the second reactor contains sulfuric acid, water and about 3-5% HF.

[0072] The HF of the second liquid-rich product is stripped by steam and air in the stripper column. The fifth liquid-rich product of the stripper is cooled, where some of the fifth liquid-rich product is sent back to the stripper. A portion of the cooled fifth product, ideally about equal to the sum of the mass of sulfuric acid that enters the first reactor and the mass of water that enters the first reactor in the FSA stream, is sent either to waste or to a process that produces phosphoric acid from phosphate rock. The remainder of the fifth liquid rich product is sent to the drying column.

[0073] The fifth gas-rich product from the stripper is dried by sulfuric acid in the drying column. Optionally, depending on the size and temperature of the purification operation, HF may be recycled to the drying column. The water in the fifth gas-rich stream is removed by mixing the fifth gas-rich stream with the cooled fifth product in the drying column thereby producing the sixth liquid-rich product which is sent back to the second reactor via a pumping system. The HF from the sixth gas-rich product of the drying column is sent to the third absorption tower, which flows at about 90 gpm on a sulfuric acid basis, to recover the HF in the seventh liquid-rich product. Air and other non-condensables of the seventh gas-rich product are passed through the vent system to the scrubber with only up to trace amounts of HF. The seventh liquid-rich product comprising HF-sulfuric acid stream is sent to the second absorption tower (HF generator column) to recover the HF and allow the sulfuric acid to flow to the first reactor.Attorney Docket No. IR4890 WO-PCTProcess Context

[0074] In phosphate rock, typically about 3-4% fluoride can be present. In past commercial phosphate processing, when fluoride is present, it has often been seen as an undesirable contaminant. Thus, when phosphate rock is processed, particularly to phosphoric acid, the fluoride may end up as fluorosilicic acid (FSA; H^SiFe). Some phosphoric acid manufacturers have sold FSA to drinking water treatment facilities or converted it to higher value products such as silicon tetrafluoride (STF). These product lines are not growing rapidly and some have gone away in the US. Another higher value product that can be made from FSA is hydrogen fluoride (HF) which can be produced in the anhydrous state (AHF).

[0075] Another advantage of colocation of AHF facilities with phosphate rock processing (phosphoric acid manufacturing) facilities is that there is overlapping infrastructure present. For instance, AHF processes typically utilize large amounts of sulfuric acid (SA). Large phosphate rock processing (phosphoric acid manufacturing) facilities typically have sulfuric acid plants at the site. Additionally, AHF processes typically make use of high concentration SA to produce a more dilute (e.g., about 70%) stream that cannot easily be stored (it can be used or disposed of). Phosphoric acid processes can typically use the dilute SA stream in their production processes.

[0076] FIG. 4 shows a block diagram of an overarching AHF process. The process contains 4 granular steps: concentration; filtration; STF production / HF generation; and AHF purification.

[0077] Typically, the FSA concentration step may not be a simple concentration operation, e.g., boiling off water to concentrate FSA, for several reasons. One can be that FSA may break down on concentration, and another can be that, when HF is formed from FSA, STF is generally formed at the same time. The STF should typically be recovered, or else -67% of the potential fluoride atoms would be lost. One way to recover STF is to hydrolyze it, such as to FSA and / or silica. The hydrolyzed FSA can be reincorporated into the FSA stream, thereby further concentrating it.

[0078] Because hydrolysis of STF to FSA typically also produces silica (SiO2), the concentrated FSA stream may include a combination (slurry) with silica. The silica, to the extent present, can be filtered out in the filtration section. The concentrated FSA (CFSA), which is very low in silica content, if not mostly silica-free, can be sent to the STF Production / HF Generation section. The silica, to the extent present, can be washed and can be a separate product stream or sent for disposal. The FSA wash stream, typically less dilute than “concentrated FSA,” can be sent back to the FSA concentration step for recovery.Attorney Docket No. IR4890 WO-PCT

[0079] The CFS A can be reacted in an STF reactor, e.g., with SA as a catalyst, to produce STF, which can then be recycled to the concentration section. Along with the STF, HF is typically generated. The HF can be in (or combined with) SA, and typically also water, either in liquid or gaseous form. If liquid, that combined HF / SA / water stream can be vaporized. In gaseous form, the HF / SA / water stream can be scrubbed, with a crude HF portion (see, e.g., FIG.7) typically sent to purification. The remaining SA / water may have any residual HF removed for recovery, if desired, after which it may additionally or alternatively be sent back to phosphate rock processing / phosphoric acid manufacturing process, particularly if colocated.

[0080] The purification section in FIG. 4 can typically include one or a series of distillation columns to remove heavies e.g., water and SA), lights (e.g., STF, air), any optionally any undesired by-products. In some embodiments, such as when water content is desired to be reduced to extremely low levels (such as in the ultimate formation of AHF), an additional water removal step may be broadly encompassed within the purification section as well. The final, purified, AHF can be seen as a product, and is represented in FIG. 4 as being sent to storage, although it may be piped elsewhere for immediate use as an alternative to shorter- and / or longer- term storage.

[0081] FIG. 5 shows further detail of the FSA Concentration box / step from FIG. 4. In an embodiment, it is shown as a countercurrent operation in which FSA (typically at least partially in liquid phase) can be concentrated by counterflow of STF (typically at least partially in gaseous phase), represented here as the STF input to FSA Concentration from FIG. 4. Although four (4) reactors are exemplified in FIG. 5, the ordinary skilled artisan should understand that there may be more or fewer reactors present in this FSA Concentration step. Exactly at which reactor in a multi-reactor process each feed and recycle stream may enter is typically flexible, but the general idea is that FSA-based and / or predominantly liquid phase inputs can typically enter upstream in concentration on the FSA / liquid phase flow path and typically flow in the FSA / liquid phase flow direction, while STF-based and / or predominantly (solid and / or) gaseous phase inputs can typically enter downstream on the FSA / liquid phase flow path (upstream on the STF / gas phase counterflow path) and typically flow opposite the FSA / liquid phase flow direction.

[0082] The “SiF4” input shown entering Reactor 1 is meant to represent the same stream as the “STF” flow between STF Production / HF Generation box / step and FSA Concentration box / step from FIG. 4 - it can flow counter to the FSA / liquid phase flow. The feed FSA, which may beAttorney Docket No. IR4890 WO-PCTfrom a colocated phosphate rock processing / phosphoric acid manufacturing process, is shown as entering via Reactor 3 - it can flow in the same direction as the FSA / liquid phase flow.

[0083] At each stage (in each reactor), some STF can be converted into FSA, with the reactors being present in number and operated at conditions such that a vast majority (typically almost all the STF) can be consumed (e.g., such that only trace amounts are “lost” to the scrubber). Water is shown as entering Reactor 4, flowing in the FSA / liquid phase flow direction opposite the STF / gas phase counterflow, with a goal of converting as much of the STF as possible into FSA. Some of the water, along with whatever FSA is converted in Reactor 4, can be sent to Reactor 3, where the feed FSA is shown to enter, and also where any optional recycle from the SiCh fdtration step that may contain FSA (from the SiOs fdtration box / step in FIG.4, described as an “FSA wash stream,” but which is not specifically shown as an effluent stream) is shown as entering in FIG. 5.

[0084] A remaining portion of the water entering Reactor 4, in tandem with non-neutral pH byproducts of the STF-to-SFA / -SiC>2 reaction, can optionally be a side stream from Reactor 4 (and / or from any one or more of the other Reactors) and can be sent for neutralization, as desired. Additionally, though not shown, air (such as from a scrubber) may be an additional (gas phase) input to one or more of the Reactors e.g., to Reactor 4), which air may be a recycle of the “trace SiF4-air to scrubber” (gas phase) effluent shown as exiting from Reactor 4.

[0085] From Reactor 3 to Reactor 2 to Reactor 1, as exemplified in FIG. 5, some quantity of STF can be converted into FSA, which can progressively increase the concentration of FSA. In some embodiments, the FSA concentration can increase significantly, e.g. to about 45 wt%, until CFSA, represented as an effluent exiting Reactor 1 (most downstream on the FSA / liquid phase path) can be sent to filtration.

[0086] The SiCh filtration step may be performed by any standard filtration method, e.g., filter press, belt filter, rotating or non-rotating pressure filters, dead end filters or the like. The basic operation for the filter can be to separate FSA from silica formed in the hydrolysis of STF to FSA, thereby increasing concentration of FSA in the process. Typically, a concentrated FSA (CFSA) stream can comprise a CFSA (typically predominantly liquid phase) portion and a cake (typically predominantly solid phase) portion. The cake portion may contain silica but may also contain some FSA “trapped” in the cake. This cake may be washed to remove any “trapped” FSA, which FSA-containing “wash” effluent can be recycled by sending it back to the FSA Concentration step.Attorney Docket No. IR4890 WO-PCTWashing of the cake can advantageously reduce losses of FSA to the cake. When utilized, washing can be batch-wise, or continuous, in a one step or multi-step counter current fashion, or the like.

[0087] The STF Production / HF Generation section (box / step) of the process (from FIG. 4) can be broken into two sub-sections, namely STF Production and HF Generation, as shown in FIG.6.The CFSA from the SiCh Filtration step can be sent as an input stream to the STF reactor. To ensure a relatively high conversion and / or a relatively quick reaction, sulfuric acid can also advantageously be added to the STF reactor, as represented in FIG. 6 by two inputs (“Optional recycled SA streams” and “SA with HF & water”). The CFSA can be converted into HF and STF in the STF reactor, such as under relatively hot and acidic conditions. Represented in FIG. 6 as an overhead (predominantly vapor phase), an outlet of the STF reactor can comprise mostly STF (typically gas phase), but may contain some amounts of HF and / or water. The SA, HF, and water output from the STF Reactor is shown as being sent to the HF Generation sub-section, which can be seen in further detail in FIG. 7.

[0088] The HF and / or water can be transformed / removed in the STF column by the addition of SA (represented in FIG. 6 as “concentrated SA” in counterflow). The (counterflowed) SA that is not consumed in the STF column can be sent to the STF reactor (shown as bottoms) as a source of SA in the STF reactor, optionally with entrained HF and / or water, if they are not separated out from the unconsumed SA.

[0089] As shown in FIG. 7, along with generating crude HF, the HF Generation sub-section also aims to achieve good recovery of HF from the SA via the HF flash tank. Indeed, an SA, HF, and water stream (output from the STF Reactor in FIG. 6) can be heated to produce a predominantly vapor-phase stream that is represented as an input to an HF Flash Tank, where pressure (and / or temperature) can be altered to separate components remaining in a vapor phase (represented as top effluent from the HF Flash Tank) from components remaining in / transforming to a condensed (e. , liquid) phase (represented as bottom effluent from the HF Flash Tank; identified in FIG. 7 as “SA / HF / water”).

[0090] The (typically liquid phase) SA stream (represented as bottoms in FIG. 7) from the HF Flash Tank can contain HF, which optionally can be recovered, e.g., using a stripper column to remove HF, which can involve (counter)flow of air and / or steam (as shown in FIG. 7). The SA from this column can typically be dilute and can advantageously be recycled, such as to a dryer, and / or sent out to a colocated phosphate rock processing / phosphoric acid manufacturing processAttorney Docket No. IR4890 WO-PCT- FTG. 7 shows sending a portion of dilute SA to both, although needs may alternatively dictate all “dilute SA” being used by either application, to the exclusion of the other, as desired. The air stream from the stripper column can typically entrain HF and water, represented as the overhead of the stripper and effluent to the dryer in FIG.7. In two columns (represented in FIG.7 as a dryer and an absorber), or alternatively in a single column (not shown), the air, HF, and water can be scrubbed to recover any HF, with the resulting air (shown as the overhead effluent from the absorber in FIG. 7) optionally being sent to the scrubber. When two columns are used, as shown in FIG. 7, SA (bottoms from the dryer column) may be sent back to the HF Flash Tank and / or to the STF Reactor from FIG.6 (not shown) and SA (bottoms from the absorber column) can be sent to the HF Column and / or to the STF Reactor from FIG. 6 (not shown). Although “concentrated SA” is shown as the input to the absorber in FIG. 7, using the two-column dryer / absorber option, the SA may not be concentrated (e.g, may be at one of a variety of dilutions) or may be the feed to a single column representing the dryer plus the absorber. Optionally, the temperature of any SA stream can be adjusted, as desired / needed. The “SA with HF & water optionally to STF reactor,” shown as the bottoms effluent from the HF Column in FIG. 7, represents at least one of the “Optional recycled SA streams” from FIG. 6.Additional Embodiments

[0091] Additionally, or alternatively, the following embodiments should be understood to be included within and at least partially representative of the present disclosure.

[0092] Embodiment 1 : A method of producing purified hydrogen fluoride, may include: reacting fluorosilicic acid and sulfuric acid within a first reactor to produce a first gas-rich product and a first liquid-rich product, where the first liquid-rich product may include sulfuric acid, hydrogen fluoride, and water; mixing the first liquid-rich product with steam, where the mixing occurs upstream or within a second reactor; reacting the first liquid-rich product and steam to produce a second gas-rich product and a second liquid-rich product; and feeding the second gas-rich product and sulfuric acid in an absorption tower to produce a fourth gas-rich product may include purified hydrogen fluoride.

[0093] Embodiment 2: The method of Embodiment 1, where a temperature of the first reactor is about 100°C.

[0094] Embodiment 3 : A method of producing purified hydrogen fluoride, may include: reacting fluorosilicic acid and sulfuric acid within a first reactor to produce a first gas-richAttorney Docket No. IR4890 WO-PCTproduct and a first liquid-rich product, where the first liquid-rich product may include sulfuric acid, hydrogen fluoride, and water; mixing the first gas-rich product and sulfuric acid in a first absorption tower to produce a third gas-rich product and a second liquid-rich product; reacting the third gas-rich product with water in a hydrolysis reactor to produce a recycle stream may include fluorosilicate acid, water, and silicon dioxide; feeding the recycle stream to the first reactor; mixing the first liquid-rich product with steam, where the mixing occurs upstream or within a second reactor; reacting the first liquid-rich product and steam to produce a second gasrich product and a third liquid-rich product; and feeding the second gas-rich product and sulfuric acid in a second absorption tower to produce a fourth gas-rich product may include purified hydrogen fluoride.

[0095] Embodiment 4: The method of Embodiment 3, where the silicon dioxide of the recycle stream is filtered from the recycle stream upstream of the first reactor.

[0096] Embodiment 5: The method of any of Embodiments 3-4, where the steam is mixed with the first liquid-rich product such that a combined solution includes the first liquid-rich product and the steam at a temperature of about 150°C.

[0097] Embodiment 6: The method of any of Embodiments 1-5, where an auxiliary heat exchanger is configured to heat the first liquid-rich product and is located upstream of the location at which the steam is mixed with the first liquid-rich product.

[0098] Embodiment 7: The method of any of Embodiments 1-6, where a concentration of the hydrogen fluoride of the second liquid-rich product ranges from about 3 wt% to 5 wt% of HF in the second liquid-rich product.

[0099] Embodiment 8: The method of any of Embodiments 1-7, where the mixing of the steam and the first liquid-rich product occurs upstream of the second reactor.

[0100] Embodiment 9: The method of any one of Embodiments 1-8, where the mixing of the steam and the first liquid-rich product occurs within the second reactor.

[0101] Embodiment 10: The method of any of Embodiments 1-9, where a mixer is located within the second reactor to facilitate the mixing of the steam and the first liquid-rich product.

[0102] Embodiment 11 : The method of Embodiment 10, where the mixer is a mixing tee or a static mixer.Attorney Docket No. IR4890 WO-PCT

[0103] Embodiment 12: The method of any of Embodiments 1-11, where a ratio of a heat from the auxiliary heat exchanger to the first liquid-rich product to a heat from the steam to the first liquid-rich product ranges from 0 and 0.1.

[0104] Embodiment 13: The method of any of Embodiments 1-12, where a steam quality of the directly injected steam is less than 50%.

[0105] The foregoing description has been presented for purposes of illustration. It is not exhaustive and is not limited to precise forms or embodiments disclosed. Modifications and adaptations of the embodiments will be apparent from consideration of the specification and practice of the disclosed embodiments. Moreover, while illustrative embodiments have been described herein, the scope includes any and all embodiments having equivalent elements, modifications, omissions, combinations (e. ., of aspects across various embodiments), adaptations and / or alterations based on the present disclosure. It is intended that the specification and examples be considered as example only.

Claims

Attorney Docket No. IR4890 WO-PCTCLAIMS;What is claimed is:

1. A method of producing purified hydrogen fluoride comprising:reacting fluorosilicic acid and sulfuric acid within a first reactor to produce a first gasrich product and a first liquid-rich product, where the first liquid-rich product comprises sulfuric acid, hydrogen fluoride, and water;mixing the first liquid-rich product with steam, where the mixing occurs upstream or within a second reactor;reacting the first liquid-rich product and steam to produce a second gas-rich product and a second liquid-rich product; andfeeding the second gas-rich product and sulfuric acid in an absorption tower to produce a fourth gas-rich product comprising purified hydrogen fluoride.

2. The method of claim 1, where a temperature of the first reactor is about 100°C.

3. A method of producing purified hydrogen fluoride comprising:reacting fluorosilicic acid and sulfuric acid within a first reactor to produce a first gasrich product and a first liquid-rich product, where the first liquid-rich product comprises sulfuric acid, hydrogen fluoride, and water;mixing the first gas-rich product and sulfuric acid in a first absorption tower to produce a third gas-rich product and a second liquid-rich product;reacting the third gas-rich product with water in a hydrolysis reactor to produce a recycle stream comprising fluorosilicate acid, water, and silicon dioxide;feeding the recycle stream to the first reactor;mixing the first liquid-rich product with steam, where the mixing occurs upstream or within a second reactor;reacting the first liquid-rich product and steam to produce a second gas-rich product and a third liquid-rich product; andfeeding the second gas-rich product and sulfuric acid in a second absorption tower to produce a fourth gas-rich product comprising purified hydrogen fluoride.

4. The method of claim 3, where the silicon dioxide of the recycle stream is filtered from the recycle stream upstream of the first reactor.Attorney Docket No. IR4890 WO-PCT5. The method of any of claims 3-4, where the steam is mixed with the first liquid-rich product such that a combined solution comprises the first liquid-rich product and the steam at a temperature of about 150°C.

6. The method of any of claims 1-5, where an auxiliary heat exchanger is configured to heat the first liquid-rich product and is located upstream of the location at which the steam is mixed with the first liquid-rich product.

7. The method of any of claims 1-6, where a concentration of the hydrogen fluoride of the second liquid-rich product ranges from about 3 wt% to 5 wt% of HF in the second liquid-rich product.

8. The method of any of claims 1-7, where the mixing of the steam and the first liquid-rich product occurs upstream of the second reactor.

9. The method of any one of claims 1-8, where the mixing of the steam and the first liquidrich product occurs within the second reactor.

10. The method of any of claims 1-9, where a mixer is located within the second reactor to facilitate the mixing of the steam and the first liquid-rich product.

11. The method of claim 10, where the mixer is a mixing tee or a static mixer.

12. The method of any of claims 1-11, where a ratio of a heat from the auxiliary heat exchanger to the first liquid-rich product to a heat from the steam to the first liquid-rich product ranges from 0 to 0.1.

13. The method of any of claims 1-12, where a steam quality of the directly injected steam is less than 50%.

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