WO2025165712A1

WO2025165712A1 - An improved silicon tetrafluoride reactor

Info

Publication number: WO2025165712A1
Application number: PCT/US2025/013311
Authority: WO
Inventors: Andrew R. Goddard; Jay F. Miller; Steven G. Schon
Original assignee: Arkema Inc
Current assignee: Arkema Inc
Priority date: 2024-01-30
Filing date: 2025-01-28
Publication date: 2025-08-07
Anticipated expiration: 2026-07-30

Abstract

The present disclosure relates to a system for the production of silicon tetrafluoride. In one implementation, a reactor is configured to at least convert fluorosilicic acid (FSA) into silicon tetrafluoride at a reaction zone. A separator receives the products of the reactor and is configured to separate the products into at least a gaseous stream and a liquid stream. At least one additional reactor is configured receive the at least a liquid stream of the reactor and configured to yield a refined product at a reaction zone. At least one additional separator is configured to separate the refined product into at least a gaseous stream and a liquid stream at a separating zone. Finally, a washer is configured to receive and wash the gaseous stream of the product and the gaseous stream of the refined product at a washing zone, wherein the washer yields a purified silicon tetrafluoride product.

Description

AN IMPROVED SILICON TETRAFLUORIDE REACTOR

Field

[0001] The present disclosure generally relates to an apparatus for the production of silicon tetrafluoride (SiF4 or STF). Embodiments of the present disclosure relate to an apparatus for ensuring a greater degree of separation of silicon tetrafluoride from liquid sulfuric acid (SA), hydrogen fluoride (HF), and H2O. Additionally, embodiments of the present disclosure relate to an apparatus for improving the degree of separation of liquid components and gaseous components in the absorber.

Background

[0002] STF gas is versatile and finds uses across many different industries. STF can be used as a precursor in the production of silanes, pure silica, silicon, and silicon nitride. Additionally, STF finds use as an etchant in semiconductor fabrication processes. STF can also be hydrolyzed to produce fluorosilicic acid (FSA), which in turn can be reacted to form more STF and HF.

[0003] One problem with known reactor systems is the low conversion resulting from the reaction of FSA into STF. Additionally, many known reactor systems also produce undesirably high amounts of hydrofluoric acid (HF) and water present in the final STF product. At high enough concentrations of these impurities, undesirable side reactions may occur thereby degrading the purified STF gas. Impurities like these can pose issues for the production of highly purified silicon from purified STF. Additionally, the SA-HF- H2O liquid stream exiting the reactor can have a high amount of unreacted FSA or entrained STF.

[0004] When employing the decomposition of FSA to produce HF and STF gas, the liquid stream can contain unreacted FSA and entrained STF which will react in the HF process producing undesirable operational issues. For example, entrained STF can react in the HF process to produce silica in lines and vessels leading to the vent or scrubber system.

Summary

[0005] The inventors discovered a solution in the form of an improved reactor design for producing STF free or substantially free from impurities and a liquid stream comprising H2SO4, H2O, HF free or substantially free from STF. In one embodiment, the present disclosure is directed to an apparatus for the preparation of a purified silicon tetrafluoride product, comprising: an initial reactor configured to yield an initial product, an initial separator configured to separate the initial product into at least one initial gaseous stream and at least one initial liquid stream; at least one intermediate reactor configured to receive the at least one initial liquid stream and configured to yield an intermediate product in a reaction zone; at least one intermediate separator configured to separate the intermediate product into at least one intermediate gaseous stream and at least one intermediate liquid stream; and an absorber configured to receive and wash the at least one initial gaseous stream and the at least one intermediate gaseous stream to yield the purified silicon tetrafluoride product, wherein the temperature of at least one of the initial reactor and the initial separator is greater than the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator.

[0006] In some embodiments, the temperature of at least one of the initial reactor and the initial separator ranges from about 160°F to about 250°F. In some further embodiments, the temperature of at least one of the initial reactor and the initial separator ranges from about 170°F to about 230°F. [0007] In some embodiments, the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about 170°F to about 280°F. In some further embodiments, the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about 180°F to about 260°F.

[0008] In some embodiments, the purified silicon tetrafluoride product produced by the apparatus described herein comprises at least 99 wt% of silicon tetrafluoride, such as, for example, at least 99.1 wt% of silicon tetrafluoride, at least 99.2 wt% of silicon tetrafluoride, at least 99.3 wt% of silicon tetrafliioride, at least 99.4 wt% of silicon tetrafluoride, at least 99.5 wt% of silicon tetrafluoride, at least 99.6 wt% of silicon tetrafluoride, at least 99.7 wt% of silicon tetrafluoride, at least 99.8 wt% of silicon tetrafluoride, and at least 99.9 wt% of silicon tetrafluoride. In some further embodiments, the purified silicon tetrafluoride product comprises less than 10,000 ppm fluorosilicic acid, such as, for example, less than 5,000 ppm, less than 1,000 ppm, less than 500 ppm, less than 100 ppm, less than 50 ppm, or less than 10 ppm of fluorosilicic acid.

[0009] In another embodiment, the present disclosure is directed to an apparatus for the preparation of a purified silicon tetrafluoride product, comprising: an initial reactor configured to yield an initial product, an initial separator configured to separate the initial product into at least one initial gaseous stream and at least one initial liquid stream; at least one intermediate reactor configured to receive the at least one initial liquid stream and configured to yield an intermediate product in a reaction zone; at least one intermediate separator configured to separate the intermediate product into at least one intermediate gaseous stream and at least one intermediate liquid stream; and an absorber configured to receive and wash the at least one initial gaseous stream and the at least one intermediate gaseous stream to yield the purified silicon tetrafluoride product, wherein a concentration silicon tetrafluoride in the at least one initial gaseous stream is greater than a concentration of silicon tetrafluoride in at least one intermediate gaseous stream. [0010] In some further embodiments, the temperature of at least one of the initial reactor and the initial separator ranges from about 160°F to about 250°F. In some further embodiments, the temperature of at least one of the initial reactor and the initial separator ranges from about 170°F to about 230°F.

[001 1] In some embodiments, the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about 170°F to about 280°F. In some further embodiments, the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about 180°F to about 260°F.

[0012] In some further embodiments, the purified silicon tetrafluoride product produced by the apparatus described herein comprises at least 99 wt% of silicon tetrafluoride, such as, for example, at least 99.1 wt% of silicon tetrafluoride, at least 99.2 wt% of silicon tetrafluoride, at least 99.3 wt% of silicon tetrafluoride, at least 99.4 wt% of silicon tetrafluoride, at least 99.5 wt% of silicon tetrafluoride, at least 99.6 wt% of silicon tetrafluoride, at least 99.7 wt% of silicon tetrafluoride, at least 99.8 wt% of silicon tetrafluoride, and at least 99.9 wt% of silicon tetrafluoride. In some further embodiments, the purified silicon tetrafluoride product comprises less than 10,000 ppm of fluorosilicic acid, such as, for example, less than 5,000 ppm, less than 1,000 ppm, less than 50 ppm, or less than 10 ppm of fluorosilicic acid.

[0013] As used herein, the singular forms “a,’’ “an,” and “the” include plural reference unless the context clearly dictates otherwise. Brief Description of the Drawings

[0014] The accompanying drawings, which comprise a part of this specification, illustrate several embodiments and, together with the description, explain the invention disclosed herein.

[0015] FIG. 1 shows a flow diagram of an apparatus according to one embodiment.

[0016] FIG. 2 shows a flow diagram of an apparatus according to another embodiment.

[0017] FIG. 3 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.

[0018] FIG. 4 shows a less granular description of the FSA Concentration step from FIG. 3.

[0019] FIG. 5 shows a less granular description of the STF Production sub-portion of the STF

Production/HF Generation step from FIG. 3.

[0020] FIG. 6 shows a less granular description of the HF Generation sub-portion of the STF Production/HF Generation step from FIG. 3.

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and, together with the description, 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

[0022] The apparatus comprises a plurality of reactors configured to convert reactant FSA into products HF and STF and a plurality of separators configured to separate the products and reactants into liquid and gaseous streams.

First Reactor

[0023] FIG. 1 shows an exemplary embodiment of the improved STF reactor. First, an FSA solution and a sulfuric acid solution are fed into a reaction zone where they are caused to react with each other. In some embodiments, the initial concentration of aqueous FSA can range from about 8 to about 50%, such as, for example, from about 15 to about 40%, and from about 20 to about 30%. In some embodiments, the sulfuric acid is a concentrated sulfuric acid. The concentrated sulfuric acid used in the process may have a concentration ranging from about 90 to 100%, such as, for example, from about 92 to about 98%, and from about 93 to about 97.

[0024] The FSA solution and sulfuric acid solution may be fed into the reaction zone continuously, semi-continuously, or in batches. The FSA solution and sulfuric acid solution may be fed into the reaction zone under a turbulent or laminar regime. In one embodiment the FSA solution and concentrated sulfuric acid are under a turbulent flow regime within the reaction zone.

[0025] The temperature of the reactor depends on the amount of water present in the reaction zone. In some embodiments, the temperature of the reaction zone ranges 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 reactor operates at a pressure ranging from about 7.5 psia to about 50 psia, such as from about 10 psia to about 45 psia.

[0026] The reactants undergo the following conversion of FSA into HF and silicon tetrafluoride (SiF4 or STF) according to the following formula:

[0027] Operating the reactor under the embodiments described above yields an initial product comprising STF, with relatively small amounts of HF in the gas phase after the absorber.

Separator

[0028] Next, the initial product is to be separated into an initial gaseous stream comprising STF and an initial liquid stream comprising sulfuric acid. The reactor can be fitted to encompass the reaction and the separation areas, or these can be separate. In an embodiment, the reactor has the separator configured such that the liquid stream exits from the bottom and the gaseous stream exits from the top. In some embodiments, the initial gaseous stream comprises mostly STF. This separation can occur using any equipment for gas/liquid separation. The gas/liquid separation may a continuous, semi-continuous or batch process. In some embodiments, the separation occurs using an open area of the reactor, packed tower, spray tower, or film tower.

[0029] To separate into the initial gaseous stream and the initial liquid stream, the separator may be operated at a reduced temperature. In one embodiment, the separator operates at a temperature ranging from about 10-150°F, such as from about 10 to 50°F below the reactor temperature.

[0030] In some embodiments, the initial gaseous stream exits the separator at a point located above the vertical midpoint of the separator. While exiting the separator, the initial gaseous stream may contain amounts of HFA and water vapor.

[0031] In some embodiments, the initial liquid stream exits at a point located below the vertical midpoint of the separator. While exiting the separator, the initial liquid stream may contain amounts of STF and unreacted FSA. While exiting the separator, the liquid stream may have none or a low amount of unreacted FSA and/or none or a low amount of entrained STF. [0032] In some embodiments, the initial reactor and initial separator are a single unit. When the initial reactor and initial separator are a single unit, the unit may comprise at least one bubble column reactor, trickle bed reactor, or fluidized bed reactor. In other embodiments, the initial reactor and initial separator comprise separate units for reacting and separating.

Intermediate Reactorfs) [0033] In some embodiments, the aqueous sulfuric acid is fed into at least one intermediate reactor. In some embodiments, each of the at least one intermediate reactor has an intermediate reaction zone. In some embodiments, the intermediate reaction zone temperature of the additional reactors is greater than the reaction zone temperature of the initial reactor. In certain embodiments, the temperature of the intermediate ranges from about 5 to about 30 °F, such as from about 10 to about 25 °F, greater than the temperature of the first reactor.

[0034] Similar to the initial reactor, an intermediate gaseous product of the at least one intermediate reactor feeds into at least one intermediate separator for separating the intermediate product into at least one intermediate gaseous stream and at least one intermediate liquid stream. In some embodiments, the intermediate gaseous stream comprises mostly STF. In some embodiments, the intermediate liquid stream comprises mostly sulfuric acid, HF and water. The at least one intermediate separation can occur using any known equipment for gas/liquid separation. In some embodiments, the at least one intermediate separation occurs using an open section of the reactor, packed tower, spray tower, or film tower. The gas/liquid separation may be a continuous, semi-continuous, or batch process.

[0035] In some embodiments, the at least one intermediate reactor and the at least one intermediate separator are a single unit. When the at least one intermediate reactor and the at least one intermediate separator are a single unit, the unit may comprise at least one reaction vessel with stirred or not stirred, bubble column reactor, trickle bed reactor, or fluidized bed reactor. In other embodiments, the at least one intermediate reactor and the at least one intermediate separator comprise separate units for reacting and separating.

Absorber [0036] In some embodiments, the initial gaseous stream and the at least one intermediate gaseous stream are fed to an absorber. In some embodiments, washing of the gas in the absorber occurs using sulfuric acid. In some embodiments, the sulfuric acid is a concentrated sulfuric acid. In some embodiments, the sulfuric acid used in the process can have a concentration ranging from about 80 to 100 wt% based on the total weight of the sulfuric acid solution, such as from about 92 to about 97 wt% based on the total weight of the sulfuric acid solution. In some embodiments the concentrated sulfuric acid enters the washing zone at a temperature at or below ambient temperature.

[0037] Without being bound to a particular theory, adequate gas-liquid contact is required for washing the gaseous streams. In some embodiments, the initial gaseous stream and the at least one intermediate gaseous stream are separately fed the washer. In some embodiments, the initial gaseous stream and the at least one intermediate gaseous stream are mixed and then fed into the washer. In some embodiments, the initial gaseous stream and the at least one intermediate gaseous stream are fed below a vertical midpoint of the washer. In some embodiments, the washer is a packed tower or a tray tower.

[0038] After absorbing the initial gaseous stream and the at least one intermediate gaseous stream, the absorber outputs a purified STF gaseous product and a final liquid stream. In some embodiments, the final liquid stream is introduced into a reboiler to produce a reboiled gaseous stream. In some embodiments, the reboiled gaseous stream comprises at least one of hydrofluoric acid, water, STF, and sulfuric acid. In some embodiments, the reboiled gaseous stream is fed back into the washer. In some embodiments, the reboiled gaseous stream is fed below a vertical midpoint of the washer. [0039] In some embodiments, the absorption column is operated without a reboiler. In this case, the liquid stream from the bottom of the column is either mixed with the FSA solution and fed to the STF generator, or the stream is sent directly to the STF generator where it mixes with FSA.

[0040] The apparatus is configured to produce purified STF product. In some embodiments, the purified STF product comprises at least 95 wt% of STF, such as, for example, at least 99 wt% of STF, at least 97 wt% of STF, and at least 99.9 wt% of STF. In some further embodiments, the purified STF product comprises at least 99 wt% of silicon tetrafluoride, such as, for example, at least 99.1 wt% of silicon tetrafluoride, at least 99.2 wt% of silicon tetrafluoride, at least 99.3 wt% of silicon tetrafluoride, at least 99.4 wt% of silicon tetrafluoride, at least 99.5 wt% of silicon tetrafluoride, at least 99.6 wt% of silicon tetrafluoride, at least 99.7 wt% of silicon tetrafluoride, at least 99.8 wt% of silicon tetrafluoride, and at least 99.9 wt% of silicon tetrafluoride. In some further embodiments, the purified silicon tetrafluoride product comprises less than 10000 ppm of fluorosilicic acid, such as, for example, less than 5000 ppm, less than 1000 ppm, less than 50 ppm, or less than 10 ppm of fluorosilicic acid.

[0041] In some embodiments the purified STF product is the final product. In other embodiments, the purified STF product is hydrolyzed to produce FSA, which in turn can be reacted to form more STF and HF.

[0042] FIG. 2 shows another exemplary embodiment of the improved STF reactor. In this embodiment, a single unit or vessel reacts the reactants to at least produce HF and STF and separates the products into gas and liquid streams. When the reactor and separator are a single unit, the unit may comprise at least one bubble column reactor, trickle bed reactor, or fluidized bed reactor. Process Context

[0043] 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; FhSiFg). 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).

[0044] 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.

[0045] FIG. 3 shows a block diagram of an overarching AHF process. The process contains 4 granular steps: concentration; filtration; STF production/HF generation; and AHF purification.

[0046] 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.

[0047] 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 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.

[0048] 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. 6) 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.

[0049] The purification section in FIG. 3 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. 3 as being sent to storage, although it may be piped elsewhere for immediate use as an alternative to shorter- and/or longer- term storage.

[0050] FIG. 4 shows further detail of the FSA Concentration box/step from FIG. 3. 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. 3. Although four (4) reactors are exemplified in FIG. 4, 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.

[0051] 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. 3 - it can flow counter to the FSA/liquid phase flow. The feed FSA, which may 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/liquid phase flow. [0052] 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 SiO filtration step that may contain FSA (from the SiCh filtration box/step in FIG. 3, described as an “FSA wash stream,” but which is not specifically shown as an effluent stream) is shown as entering in FIG. 4.

[0053] 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.

[0054] From Reactor 3 to Reactor 2 to Reactor 1 , as exemplified in FIG. 4, 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.

[0055] The SiOz 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.

[0056] The STF Production/HF Generation section (box/step) of the process (from FIG. 3) can be broken into two sub-sections, namely STF Production and HF Generation, as shown in FIG. 5. The CFSA from the SiO2 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. 5 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. 5 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. 6.

[0057] The HF and/or water can be transformed/removed in the STF column by the addition of SA (represented in FIG. 5 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.

[0058] As shown in FIG. 6, 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. 5) 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. 6 as “SA/HF/water”).

[0059] 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. 3.

[0060] The (typically liquid phase) SA stream (represented as bottoms in FIG. 6) 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. 6). 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. 6 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. 6. In two columns (represented in FIG. 6 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. 6) optionally being sent to the scrubber. When two columns are used, as shown in FIG. 6, SA (bottoms from the dryer column) may be sent back to the HF Flash Tank and/or to the STF Reactor from FIG. 5 (not shown) and SA (bottoms from the absorber column) can be sent to the HF Column and/or to the STF Reactor from FIG. 5 (not shown). Although

“concentrated SA” is shown as the input to the absorber in FIG. 6, 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. 6, represents at least one of the “Optional recycled SA streams” from FIG. 5.

[0061] With the context of FIGS. 3-6, the following linkages can be made between them and

FIGS. 1-2. The “STF Reactor” from FIG. 5 can encompass the First Reactor plus the Separator plus the At least one additional reactor column from FIG. 1, as well as the First Reactor Column and At least one additional reactor column from FIG. 2. The “Washer” from FIGS. 1 and 2, which were interchangeably referred to in this specification as an “absorber,” can encompass the STF Column from FIG. 5. The “Liquid stream” output from the “Washer” in FIGS. 1 and 2 can be recycled to the First Reactor (FIG. 1) or First reactor column (FIG. 2), linking to the recycle to the “STF Reactor” in FIG. 5, and/or can represent the SA/HF/water stream to HF Generation (input to the HF Flash Tank) in FIG. 6. The “Reactants” in FIG. 2 link to the concentrated FSA (CFSA) and Optional recycled SA streams from FIG. 5.

Additional Embodiments

[0062] Additionally or alternatively, the following embodiments should be understood to be included within and at least partially representative of the present disclosure.

[0063] Embodiment 1. An apparatus for the preparation of a purified silicon tetrafluoride product, comprising: an initial reactor configured to yield an initial product; an initial separator configured to separate the initial product into at least one initial gaseous stream and at least one initial liquid stream; at least one intermediate reactor configured to receive the at least one initial liquid stream and configured to yield an intermediate product in a reaction zone; at least one intermediate separator configured to separate the intermediate product into at least one intermediate gaseous stream and at least one intermediate liquid stream; and an absorber configured to receive and wash the at least one initial gaseous stream and the at least one intermediate gaseous stream to yield the purified silicon tetrafluoride product, wherein (a) the temperature of at least one of the initial reactor and the initial separator is greater than the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator; (b) a concentration silicon tetrafluoride in the at least one initial gaseous stream is greater than a concentration of silicon tetrafluoride in at least one intermediate gaseous stream; or (c) both (a) and (b).

[0064] Embodiment 2. The reactor of embodiment 1, wherein the temperature of at least one of the initial reactor and the initial separator ranges from about 160°F to about 250°F, for example from about 170°F to about 230°F.

[0065] Embodiment 3. The reactor of embodiment 1 or embodiment 2, wherein the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about 170°F to about 280°F, for example from about 180°F to about 260°F.

[0066] Embodiment 4. The reactor of any one of embodiments 1-3, wherein the purified silicon tetrafluoride product comprises at least 99.5 wt% of silicon tetrafluoride, for example at least 99.9 wt% of silicon tetrafluoride. [0067] Embodiment 5. The reactor of any one of embodiments 1-4, wherein the purified silicon tetrafluoride product comprises less than 500 ppm of fluorosilicic acid, for example less than 100 ppm of fluorosilicic acid.

[0068] Embodiment 6. The reactor of any one of embodiments 1 -5, wherein (a) is satisfied but (b) is not satisfied.

[0069] Embodiment 7. The reactor of any one of embodiments 1-5, wherein (b) is satisfied but (a) is not satisfied.

[0070] Embodiment 8. The reactor of any one of embodiments 1 -7, wherein one or more aspects of FIGS. 3-6, as harmonized with FIG. 1 and/or FIG. 2, are present.

[0071] 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

CLAIMS What is claimed is:

1. An apparatus for the preparation of a purified silicon tetrafluoride product, comprising: an initial reactor configured to yield an initial product, an initial separator configured to separate the initial product into at least one initial gaseous stream and at least one initial liquid stream; at least one intermediate reactor configured to receive the at least one initial liquid stream and configured to yield an intermediate product in a reaction zone; at least one intermediate separator configured to separate the intermediate product into at least one intermediate gaseous stream and at least one intermediate liquid stream; and an absorber configured to receive and wash the at least one initial gaseous stream and the at least one intermediate gaseous stream to yield the purified silicon tetrafluoride product, wherein (a) the temperature of at least one of the initial reactor and the initial separator is greater than the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator; (b) a concentration silicon tetrafluoride in the at least one initial gaseous stream is greater than a concentration of silicon tetrafluoride in at least one intermediate gaseous stream; or (c) both (a) and (b).

2. The reactor of claim 1, wherein the temperature of at least one of the initial reactor and the initial separator ranges from about 160°F to about 250°F.

3. The reactor of claim 2, wherein the temperature of at least one of the initial reactor and the initial separator ranges from about 170°F to about 230°F.

4. The reactor of any one of claims 1-3, wherein the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about

170°F to about 280°F.

5. The reactor of claim 4, wherein the temperature of at least one of the at least one intermediate reactor and the at least one intermediate separator ranges from about 180°F to about 260°F.

6. The reactor of any one of claims 1-5, wherein the purified silicon tetrafluoride product comprises at least 99.5 wt% of silicon tetrafluoride.

7. The reactor of claim 6, wherein the purified silicon tetrafluoride product comprises at least 99.9 wt% of silicon tetrafluoride.

8. The reactor of any one of claims 1-7, wherein the purified silicon tetrafluoride product comprises less than 500 ppm of fluorosilicic acid.

9. The reactor of claim 8, wherein the purified silicon tetrafluoride product comprises less than 100 ppm of fluorosilicic acid.

10. The reactor of any one of claims 1-9, wherein (a) is satisfied but (b) is not satisfied.

11 . The reactor of any one of claims 1-9, wherein (b) is satisfied but (a) is not satisfied.