An improved method to produce silicon tetrafluoride from fluorosilicic acid

Abstract

The present disclosure relates to a method or producing silicon tetrafluoride from fluorosilicic acid. In one implementation, a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid are reacted in a pressure regulator to produce an outgoing liquid stream comprising silicon tetrafluoride. The outgoing liquid is then fed into at least one separator which outputs at least one gas stream containing silicon tetrafluoride and at least one liquid stream. The at least one gas stream is fed into at least one additional separator which separates the at least one gas stream into at least one stream of purified silicon tetrafluoride gas. In some implementations, the at least one liquid stream is recycled back into the at least one separator.

Description

AN IMPROVED METHOD TO PRODUCE SILICON TETRAFLUORIDE FROM FLUOROSILICIC ACIDTechnical Field

[0001] The present invention generally relates to an improved method to produce silicon tetrafluoride from fluorosilicic acid. In particular, and without limitation, the present invention relates to a method where fluorosilicic acid begins decomposition before introduction into a flash drum or silicon tetrafluoride reactor. The present disclosure seeks to maximize the extent of silicon tetrafluoride’s reaction and to maximize the liquid-gas separation to form the liquid product.Background

[0002] Silicon tetrafluoride gas is versatile and finds uses across many different industries. Silicon tetrafluoride (SiF4) can be used as a precursor in the production of silanes, pure silica, silicon, and silicon nitride. Additionally, silicon tetrafluoride finds use as an etchant in semiconductor fabrication processes.

[0003] Traditionally, silicon tetrafluoride was prepared by thermally decomposing an alkali or alkaline earth metal fluorosilicate. Another known method of preparing silicon tetrafluoride involves reacting a stream of sulfuric acid with fluorosilicic acid to yield a gaseous stream of hydrofluoric acid and silicon tetrafluoride. Later, the gas stream is washed with concentrated sulfuric acid to recover a highly purified silicon tetrafluoride gas.

[0004] One problem with known methods is the remarkably low conversion of fluorosilicic acid into silicon tetrafluoride. Many known methods also produce undesirably high amounts of hydrofluoric acid and water present in the final product. Specifically, when separating gaseous products from liquid ones, an undesirably high amount of gaseous product becomes entrained in the liquid product. Such entrainment leads to undesirably high levels of silicon tetrafluoridebeing siphoned off with the liquid product instead of separating with the purified silicon tetrafluoride gas. These decreased silicon tetrafluoride yields thereby reduce the overall purified silicon tetrafluoride gas.Summary

[0005] The inventors have discovered an improved method of producing silicon tetrafluoride from fluorosilicic acid. In one embodiment, the present disclosure is directed to a method for producing silicon tetrafluoride from fluorosilicic acid, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulated volume to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator.

[0006] In another exemplary embodiment, the present disclosure is a method comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulated volume to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator, converting the at least one stream of purified silicon tetrafluoride gas into at least one of fluorosilicic acid and hydrofluoric acid.

[0007] In another exemplary embodiment, the present disclosure is a method for producing silicon tetrafluoride from fluorosilicic acid, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulating valve to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator.

[0008] In one embodiment, the at least one separator comprises a flash drum or a reactive separator comprising a quiescent volume in a vessel which allows vapor to separate from liquid.

[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 shows a diagram of a system according to one embodiment.

[0012] FIG. 2 shows a block flow diagram of an anhydrous hydrogen fluoride process, such as one within which a system according to one or more embodiments can be disposed.

[0013] FIG. 3 shows a less granular description of the FSA Concentration step from FIG. 2.

[0014] FIG. 4 shows a less granular description of the STF Production sub-portion of the STFProduction / HF Generation step from FIG. 2.

[0015] FIG. 5 shows a less granular description of the HF Generation sub-portion of the STF Production / HF Generation step from FIG. 2.

[0016] The accompanying drawings, which are incorporated in and constitute apart 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, for example, may be exaggerated for purposes of clearer illustration.Detailed Description of the Illustrative Embodiments

[0017] Generally to begin the process, at least two streams are introduced into a pressure regulated volume. One stream may contain fluorosilicic acid and the other stream may contain sulfuric acid. In some embodiments, at least one of the streams are pumped into the pressure regulated volume. In some embodiments, the stream containing fluorosilicic acid comprises a high concentration of fluorosilicic acid. The fluorosilicic acid solution can comprise from about 25 to about 50 mass percent of fluorosilicic acid based on the total mass of the fluorosilicic acid solution, such as, for example, from about 30 to about 48 mass percent and from about 35 to about 47 mass percent. In some embodiments, the stream containing sulfuric acid comprises a high concentration of sulfuric acid. In some embodiments, a high concentration of sulfuric acid ranges from about 70 to 100%, such as, for example, from about 75 to about 99%, from about 80 to about 98%, and from about 85 to 96%, and from about 83 to about 87%.

[0018] In some embodiments, once the two streams are introduced into the pressure regulated volume, they react to produce an outgoing product comprising silicon tetrafluoride along with HF, sulfuric acid, and water that was in the FSA stream or in the sulfuric acid. In some embodiments, the pressure regulated volume comprises a pressure valve or orifice plate. In some embodiments, the pressure and temperature of the pressure regulated volume are configured suchthat the product comprises liquid. The temperature of the pressure regulated volume may range from about 60°C to about 120°C, such as, for example, from about 70°C to about 110°C and from about 80°C to about 105°C. The pressure of the pressure regulator volume may range from about 10” water column to about 60 psig, such as, for example, from 20” water column to about 50 psig and from about 1 psig to about 40 psig. In some embodiments, the pressure of the pressure regulator volume may range from about 10” water head pressure to about 20” water head pressure.

[0019] In some embodiments, the product is mostly liquid by weight. In some embodiments, a residence time is selected or predetermined for the fluororsilicic acid and sulfuric acid in the pressure regulator such that the silicon tetrafluoride yield is about 100%. In some embodiments, a residence time is selected or predetermined for the fluororsilicic acid and sulfuric acid in the pressure regulator such that the silicon tetrafluoride yield is less than 100%. The residence time of the pressure regulated volume may be from about 1 minute to about 60 minutes, such as, for example, from about 5 minutes to about 45 minutes, from about 10 minutes to about 45 minutes, from about 15 minutes to about 45 minutes, and from about 15 minutes to about 30 minutes.

[0020] In some embodiments, the pressure regulated volume comprises pipe or vessel, wherein the pressure is controlled by a pressure regulator or orifice plate or the like.

[0021] Once an adequate silicon tetrafluoride yield is obtained, the outgoing product comprising silicon tetrafluoride is introduced into at least one separator. In some embodiments, the outgoing product is introduced to an upper region of the at least one separator. In some embodiments, the at least one separator comprises at least one reactive separator. In some embodiments, the at least one reactive separator undergoes at least the decomposition reaction of fluorosilicic acid into silicon tetrafluoride using sulfuric acid. In an embodiment, the feed to theseparator is a pipe with holes at 45 degrees angles downwards allowing the gaseous STF to disengage from the liquid sulfuric acid, HF and water.

[0022] In some embodiments, the produced silicon tetrafluoride is an intermediate product and is further processed to produce fluorosilicic acid and hydrofluoric acid.

[0023] In some embodiments, the at least one separator produces at least one outgoing gas stream and at least one outgoing liquid stream. In some embodiments, the at least one outgoing gas stream comprises silicon tetrafluoride. In some embodiments, the at least one outgoing liquid stream comprises at least one of sulfuric acid, water, and hydrofluoric acid.

[0024] In some embodiments, the at least one outgoing gas stream is fed into a washer or absorber to produce a purified gaseous stream comprising silicon tetrafluoride. In some embodiments, the washer also produces a liquid stream comprising hydrofluoric acid, sulfuric acid and water. In some embodiments, the at least one outgoing gas stream is fed to a point close to or at the bottom of the washer. In some embodiments, the washer is a packed tower or a tray tower. In some embodiments, concentrated sulfuric acid is fed to a point close to or at a top of the washer. In some embodiments, the concentrated sulfuric acid used in the process can have a concentration ranging from about 90 to 100 wt% based on the total weight of the sulfuric acid solution, such as, for example, from about 92 to about 98 wt%, from 92 to 96%, from 94 to 98 wt%, and from 94 to 96 wt%.

[0025] The washer may be operated at a temperature below room temperature, such as, for example, from about 0°C to about 50°C, from about 10°C to about 40°C, and from about 15°C to about 35°C.

[0026] In some embodiments, the at least one outgoing liquid stream is fed into a reboiler. In some embodiments, the reboiler comprises a heat exchanger. In some embodiments, once the atleast one outgoing liquid stream is reboiled, the reboiled stream is reintroduced into the at least one separator. In some embodiments, the reboiled stream is fed into the at least one separator by a pipe comprising holes angled at about 45 degrees downwards, which allows the gaseous STF to disengage from the liquid sulfuric acid, HF and water.Process Context

[0027] 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; ILSiFe). 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).

[0028] 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.

[0029] FIG. 2 shows a block diagram of an overarching AHF process. The process contains 4 granular steps: concentration; filtration; STF production / HF generation; and AHF purification.

[0030] 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.

[0031] Because hydrolysis of STF to FSA typically also produces silica (SiO ), 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.

[0032] The CFSA 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.5) 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.

[0033] The purification section in FIG. 2 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. 2 as being sent to storage, although it may be piped elsewhere for immediate use as an alternative to shorter- and / or longer- term storage.

[0034] FIG. 3 shows further detail of the FSA Concentration box / step from FIG. 2. 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. 2. Although four (4) reactors are exemplified in FIG. 3, 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.

[0035] 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. 2 - it can flow counter to the FSA / liquid phase flow. The feed FSA, whichmay be from 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 / Iiquid phase flow.

[0036] 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 SiCb filtration step that may contain FSA (from the SiCb filtration box / step in FIG. 2, described as an “FSA wash stream,” but which is not specifically shown as an effluent stream) is shown as entering in FIG. 3.

[0037] A remaining portion of the water entering Reactor 4, in tandem with non-neutral pH by-products of the STF-to-SFAZ-SiCh 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.

[0038] From Reactor 3 to Reactor 2 to Reactor 1, as exemplified in FIG. 3, 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.

[0039] The SiC 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. 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.

[0040] The STF Production / HF Generation section (box / step) of the process (from FIG. 2) can be broken into two sub-sections, namely STF Production and HF Generation, as shown in FIG. 4. The CFSA from the SiCb 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. 4 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. 4 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 subsection, which can be seen in further detail in FIG. 5.

[0041] The HF and / or water can be transformed / removed in the STF column by the addition of SA (represented in FIG. 4 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.

[0042] As shown in FIG. 5, 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. 4) 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.g., liquid) phase (represented as bottom effluent from the HF Flash Tank; identified in FIG. 5 as “SA / HF / water”).

[0043] The vapor phase effluent from the HF Flash Tank can be scrubbed with SA in the HF Column to remove a considerable amount of water. The resulting (predominantly vapor phase) effluent, represented as the overhead of the HF Column, can advantageously be a crude HF stream that can be sent to purification, such as described vis-a-vis FIG. 2.

[0044] The (typically liquid phase) SA stream (represented as bottoms in FIG. 5) 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. 5). 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 process - FIG. 5 shows sending a portion of dilute SA to both, although needs may alternatively dictateall “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. 5. In two columns (represented in FIG. 5 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. 5) optionally being sent to the scrubber. When two columns are used, as shown in FIG. 5, SA (bottoms from the dryer column) may be sent back to the HF Flash Tank and / or to the STF Reactor from FIG. 4 (not shown) and SA (bottoms from the absorber column) can be sent to the HF Column and / or to the STF Reactor from FIG. 4 (not shown). Although “concentrated SA” is shown as the input to the absorber in FIG. 5, 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. 5, represents at least one of the “Optional recycled SA streams” from FIG. 4.

[0045] With the context of FIGS. 2-5, the following linkages can be made between them and FIG. 1. The “Pressure regulator” and “Flash drum” from FIG. 1 can be encompassed by the STF Reactor from FIG. 4, and the “HF removal column” can correspond to the STF Column from FIG. 3. The “Purified SiF4 gas” exiting the HF removal column from FIG. 1 can correspond to the STF to FSA Concentration stream from FIG. 4, with the “Heat exchanger(s)” plus “HF reboiler” from FIG. 1 corresponding to the “HF Flash Tank” from FIG. 5. The “High concentration H2SO4” input pumped to the Pressure regulator in FIG. 1 can correspond to the“Optional recycled SA streams” from FIG. 4. The “Concentrated HzSiFe” input pumped to the Pressure regulator in FIG. 1 can correspond to the “CFSA” from FIG. 4.Additional Embodiments

[0046] Additionally or alternatively, the following embodiments should be understood to be included within and at least partially representative of the present disclosure.

[0047] Embodiment 1. A method for producing silicon tetrafluoride from fluorosilicic acid, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulated volume to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator.

[0048] Embodiment 2. A method, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulated volume to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator; and converting the at least one stream of purified silicon tetrafluoride gas into at least one of fluorosilicic acid and hydrofluoric acid.

[0049] Embodiment 3. A method for producing silicon tetrafluoride from fluorosilicic acid, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulating valve to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator.

[0050] Embodiment 4. The method according to any one of embodiments 1-3, wherein the at least one separator comprises a flash drum or a reactive separator comprising a quiescent volume in a vessel.

[0051] Embodiment 5. The method according to any one of embodiments 1-2 and 4, wherein the pressure regulated volume comprises a pressure regulating valve.

[0052] Embodiment 6. The method of any one of embodiments 1-5, wherein the outgoing liquid stream comprises mostly liquid.

[0053] Embodiment 7. The method of any one of embodiments 1-6, wherein the at least one liquid stream is fed into a reboiler to produce a reboiled stream comprising hydrofluoric acid.

[0054] Embodiment 8. The method of embodiment 7, wherein the reboiled stream is fed into the at least one separator.

[0055] Embodiment 9. The method of embodiment 8, wherein the reboiled stream is fed into the at least one separator by a pipe comprising holes angled downward at about 45 degrees.

[0056] Embodiment 10. The method of any one of embodiments 1-9, wherein a temperature of the pressure regulated volume ranges from about 60 °C to about 120 °C.

[0057] Embodiment 11. The method of any one of embodiments 1-10, wherein a pressure of the pressure regulated volume ranges from about 1 psig to about 40 psig.

[0058] Embodiment 12. The method of any one of embodiments 1-11, wherein a pressure of the pressure regulated volume ranges from about 10” water head pressure to about 20” water head pressure.

[0059] Embodiment 13. The reactor of any one of embodiments 1-12, wherein one or more aspects of FIGS. 2-5, as harmonized with FIG. 1, are present.

[0060] 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.g., 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

CLAIMSWhat is claimed is:

1. A method for producing silicon tetrafluoride from fluorosilicic acid, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulated volume to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator.

2. The method according to claim 1, wherein the at least one separator comprises a flash drum or a reactive separator comprising a quiescent volume in a vessel.

3. The method according to claim 1, wherein the pressure regulated volume comprises a pressure regulating valve.

4. The method of claim 1, wherein the outgoing liquid stream comprises mostly liquid.

5. The method of claim 1, wherein the at least one liquid stream is fed into a reboiler to produce a reboiled stream comprising hydrofluoric acid.

6. The method of claim 5, wherein the reboiled stream is fed into the at least one separator.

7. The method of claim 6, wherein the reboiled stream is fed into the at least one separator by a pipe comprising holes angled downward at about 45 degrees.

8. The method of claim 1, wherein a temperature of the pressure regulated volume ranges from about 60°C to about 120°C.

9. The method of claim 1, wherein a pressure of the pressure regulated volume ranges from about 1 psig to about 40 psig.

10. The method of claim 1, wherein a pressure of the pressure regulated volume ranges from about 10” water head pressure to about 20” water head pressure.

11. A method, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulated volume to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator; and converting the at least one stream of purified silicon tetrafluoride gas into at least one of fluorosilicic acid and hydrofluoric acid.

12. The method according to claim 11, wherein the at least one separator comprises a flash drum or a reactive separator.

13. The method according to claim 11 , wherein the pressure regulated volume comprises a pressure regulating valve.

14. The method of claim 11, wherein the outgoing liquid stream comprises mostly liquid.

15. The method of claim 11, wherein the at least one liquid stream is fed into a reboiler to produce a reboiled stream comprising hydrofluoric acid.

16. The method of claim 15, wherein the reboiled stream is fed into the at least one separator.

17. The method of claim 16, wherein the reboiled stream is fed into the at least one separator by a pipe comprising holes angled downward at about 45 degrees.

18. The method of claim 11 , wherein a temperature of the pressure regulated volume ranges from about 60°C to about 120°C.

19. The method of claim 11 , wherein a pressure of the pressure regulated volume ranges from about 1 psig to about 40 psig.

20. The method of claim 11 , wherein a pressure of the pressure regulated volume ranges from about 10” water head pressure to about 20” water head pressure.

21. A method for producing silicon tetrafluoride from fluorosilicic acid, comprising: reacting a first stream comprising fluorosilicic acid and a second stream comprising sulfuric acid in a pressure regulating valve to produce an outgoing liquid stream comprising silicon tetrafluoride; feeding the outgoing liquid stream to at least one separator; separating the outgoing liquid stream into at least one gas stream containing silicon tetrafluoride and at least one liquid stream; feeding the at least one gas stream to at least one additional separator; and separating the at least one gas stream into at least one stream of purified silicon tetrafluoride gas using the at least one additional separator.

22. The method according to claim 21, wherein the at least one separator comprises a flash drum or a reactive separator.

23. The method of claim 21, wherein the outgoing liquid stream comprises mostly liquid.

24. The method of claim 21, wherein the at least one liquid stream is fed into a reboiler to produce a reboiled stream comprising hydrofluoric acid.

25. The method of claim 21, further comprising converting the at least one stream of purified silicon tetrafluoride gas into at least one of fluorosilicic acid and hydrofluoric acid26. The method of claim 24, wherein the reboiled stream is fed into the at least one separator.

27. The method of claim 26, wherein the reboiled stream is fed into the at least one separator by a pipe comprising holes angled downward at about 45 degrees.

28. The method of claim 21, wherein a temperature of the pressure regulated volume ranges from about 60°C to about 120°C.

29. The method of claim 21 , wherein a pressure of the pressure regulated volume ranges from about 1 psig to about 40 psig.

30. The method of claim 21, wherein a pressure of the pressure regulated volume ranges from about 10” water head pressure to about 20” water head pressure.

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