Hydrogen production by electrochemical conversion of hydrogen sulfide

Abstract

A reactor is configured to electrochemically convert hydrogen sulfide to produce hydrogen. The reactor includes a first shell, a second shell, a hydrogen-permeable electrode, and a check valve. The first shell defines a first chamber. The first shell defines a first inlet for water, a second inlet for hydrogen sulfide, and a first outlet for hydrogen sulfide. The second shell defines a second chamber isolated from the first chamber. The second chamber stores hydrogen molecules. The hydrogen-permeable electrode is at least partially disposed within the first chamber. The hydrogen-permeable electrode is permeable to hydrogen atoms originating from the hydrogen sulfide. The check valve allows flow of hydrogen molecules, formed from the hydrogen atoms that have permeated into the hydrogen-permeable electrode, into the second chamber while preventing flow of hydrogen molecules back out from the second chamber through the check valve.

Description

Attorney Ref. : 38136-2816WO 1HYDROGEN PRODUCTION BY ELECTROCHEMICAL CONVERSION OF HYDROGEN SULFIDECLAIM OF PRIORITY

[0001] This application claims priority to U.S. Patent Application No.19 / 018,892 filed on January 13, 2025, the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD

[0002] This disclosure relates to conversion of hydrogen sulfide, and in particular, conversion of hydrogen sulfide to produce hydrogen.BACKGROUND

[0003] Hydrocarbons extracted from a reservoir can contain various impurities. Hydrocarbons that are contaminated with significant amounts of sulfur compounds, such as hydrogen sulfide, is considered sour, while hydrocarbons that are contaminated with little or negligible amounts of sulfur compounds is considered sweet. Hydrogen sulfide, in particular, is highly poisonous, corrosive, and flammable. Therefore, the presence and handling of hydrogen sulfide is not only an operational concern (with respect to equipment and piping corrosion) but also a safety concern. The hydrocarbon refining processes can include processes that remove such impurities from the raw hydrocarbons, for example, before the hydrocarbons are transformed into vanous products.SUMMARY

[0004] This disclosure describes technologies relating to conversion of hydrogen sulfide to produce hydrogen. The subject matter described in this disclosure can be implemented in particular implementations, so as to realize one or more of the following advantages. The described apparatuses and methods convert hydrogen sulfide, which is poisonous, corrosive, and flammable, into hydrogen, which is a value-added, useful, and highly sought commercial product. The described apparatuses and methods take advantage of spontaneously occurring corrosion reactions to electrochemically convert hydrogen sulfide into hydrogen. Because the reactions are spontaneous, the described apparatuses and methods require minimal energy to operate. The reactions take place at moderate conditions of pressure and temperature, whichAttorney Ref. : 38136-2816WO 1allow for the use of readily available and relatively inexpensive materials of construction (for example, in comparison to high temperature and / or high pressure service materials).

[0005] The details of one or more implementations of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.DESCRIPTION OF DRAWINGS

[0006] FIG. 1 is a schematic diagram of an example apparatus for conversion of hydrogen sulfide to produce hydrogen.

[0007] FIG. 2 is a flow chart of an example method for conversion of hydrogen sulfide to produce hydrogen.

[0008] FIG. 3 is a flow chart of an example method for operating the apparatus of FIG. 1.DETAILED DESCRIPTION

[0009] The world is undergoing an energy transition to remediate the climate unbalance caused by excessive use of fossil fuel. Greenhouse gas (GHG) emissions are considered a main culprit causing an increase in global warming. One method of combating global warming is to reduce carbon dioxide and methane emissions. Another method is to capture carbon dioxide that has already been released into the atmosphere and process the captured carbon dioxide to be in a nonreactive condition. In order to accomplish the target of zero carbon emissions, there is a growing trend to replace fossil fuels with clean energy sources, such as renewable produced electricity and hydrogen, which is considered a clean fuel. Some example types of hydrogen that can be produced in a sustainable manner include green hydrogen, blue hydrogen, and gray hydrogen. Green hydrogen is produced from water using renewable energy sources, such as solar power and wind energy. Blue hydrogen is produced from fossil fuels with no associated carbon emissions. Gray hydrogen is produced from fossil fuels with associated carbon emissions. However, these types of hydrogen (e.g., green, blue, and gray) require valuable resources to generate the hydrogen. In the case of green hydrogen, water is used. In the cases of blue and green hydrogen, fossil fuels are used.

[0010] This disclosure describes electrochemical conversion of hydrogen sulfide (H2S), which is a harmful chemical, to produce hydrogen (H2), which is a value-added,Attorney Ref. : 38136-2816WO 1useful, and highly sought commercial product. A reactor holds an aqueous solution that is saturated with hydrogen sulfide. The portion of the reactor holding the aqueous solution saturated with hydrogen sulfide can be referred to as the reactor side chamber (RSC). The ThS-saturated aqueous solution undergoes electrochemical corrosion reactions of hydrogen sulfide in water with carbon steel (specifically iron), which originates from consumable electrodes that are disposed within the reactor. The electrochemical corrosion reactions result in hydrogen atoms (H°), which permeate into an annulus of each electrode. The hydrogen atoms then recombine, thereby producing hydrogen molecules (H2), for example, inside the annulus of each electrode which can then transfer to a second chamber of the reactor due to pressure difference. The second chamber which collects produced hydrogen molecules can be referred to as the product side chamber (PSC). Iron sulfide (FeS) precipitates from the electrochemical corrosion reactions as a byproduct and may accumulate at the bottom of the reactor. The hydrogen sulfide partial pressure in the RSC can be maintained at a slightly positive value (for example, about 103.4 kilopascals (kPa)) in comparison to atmospheric pressure in order to ensure continuous saturation of the aqueous solution with hydrogen sulfide and to avoid air ingress into the reactor. In some implementations, the temperature in the RSC is maintained at an operating temperature of about 35 degrees Celsius (°C). In some implementations, a backpressure regulator is included to maintain a pressure of about 689.5 kPa inside the PSC. The temperature in the PSC may. in some cases, be left uncontrolled, for example, at ambient temperature.

[0011] FIG. 1 is a schematic diagram of an example apparatus 100 for conversion of hydrogen sulfide to produce hydrogen. The apparatus 100 is a reactor configured to electrochemically convert hydrogen sulfide into hydrogen. The apparatus 100 includes a first shell 110, a second shell 120, and a barrier 130. The first shell 110, the second shell 120, and the barrier 130 make up a reactor vessel of the apparatus 100. The first shell 110 and the barrier 130 define a first chamber 110a (RSC) of the apparatus 100. The second shell 120 and the barrier 130 define a second chamber 120a (PSC) of the apparatus 100. The first chamber 110a and the second chamber 120a are isolated from each other. For example, the barrier 130 isolates the first chamber 110a from the second chamber 120a and isolates the second chamber 120a from the first chamber 110a. During operation, the apparatus 100 can be vertically oriented, and the first chamber 110a can be positioned below the second chamber 120a with respect to gravity. TheAttorney Ref. : 38136-2816WO 1apparatus 100 includes a hydrogen-permeable electrode 132. The hydrogen-permeable electrode 132 is coupled to the barrier 130 and extends into the first chamber 110a. As shown in FIG. 1, the apparatus 100 can include a bundle of hydrogen-permeable electrodes 132. The apparatus 100 includes a check valve 134. In implementations in which the apparatus 100 includes multiple hydrogen-permeable electrodes 132, the apparatus 100 includes a corresponding plurality of check valves 134 (that is, a check valve 134 for each of the hydrogen-permeable electrodes 132).

[0012] The first shell 110 can have a generally hemispherical shape. In some implementations, the first shell 110 includes a cylindrical portion capped with a hemispherical end. The first shell 110 defines a water inlet 112, an H2S inlet 114, and an H2S outlet 116. The water inlet 112 is configured to receive water for receiving into the first chamber 110a. Water can flow into the first chamber 110a via the water inlet 112. The H2S inlet 114 is configured to receive hydrogen sulfide for receiving into the first chamber 110a. Hydrogen sulfide can flow into the first chamber 110a via the H2S inlet 114. For example, water can flow into the first chamber 110a via the water inlet 112, and hydrogen sulfide can be flowed into the first chamber 110b via the H2S inlet 114. During operation, the H2S inlet 114 can be located below the water inlet 112 (the water inlet 112 can be positioned above the H2S inlet 114) with respect to gravity7. Because the H2S inlet 114 is located below the water inlet 112 with respect to gravity and because hydrogen sulfide is in a vapor state while the water is in a liquid state, the hydrogen sulfide introduced into the first chamber 110b can bubble up through the water residing in the first chamber 110b. As the hydrogen sulfide bubbles through the water within the first chamber 110b, the hydrogen sulfide can dissolve into the water within the first chamber 110b. A sufficient amount of hydrogen sulfide can be flowed into the first chamber 110b via the H2S inlet 114 to saturate the water residing within the first chamber 110b. The water saturated with hydrogen sulfide is also referred to as aqueous hydrogen sulfide. The H2S outlet 116 is configured to discharge hydrogen sulfide from the first chamber 110a. In some implementations, an excess amount of hydrogen sulfide is flowed into the first chamber 110b via the H2S inlet 114 to bubble through the water and ensure that the w ater residing within the first chamber 110b becomes saturated with hydrogen sulfide. Excess hydrogen sulfide that has bubbled through the water can accumulate within a vapor space of the first chamber 110b. The excess hydrogen sulfide can flow out of the first chamber 110b via the H2S outlet 116. In some implementations,Attorney Ref. : 38136-2816WO 1the apparatus 100 includes a pressure sensor 117. The pressure sensor 117 can be coupled to the H2S outlet 116. The pressure sensor 117 can be configured to measure an operating pressure of the vapor space of the first chamber 110b.

[0013] In some implementations, the first shell 110 defines a liquid outlet 118. The liquid outlet 118 can be configured to discharge liquid (such as aqueous hydrogen sulfide) from the first chamber 110a. The apparatus 100 can include a filter 118a directly upstream of the liquid outlet 118. The filter 118a can, for example, be a mesh screen designed to prevent solids (such as FeS precipitate 136) from exiting the apparatus 100 through the liquid outlet 118. The filter 118a can define pores that are sized to prevent solids from exiting the first chamber 11 Oathrough the liquid outlet 118 while allowing fluid (such as aqueous hydrogen sulfide) to exit the first chamber 110a through the liquid outlet 118. In some implementations, the pores defined by the filter 118a have an average pore diameter in a range of from about 1 micrometers (pm) to about 10 pm. In some implementations, the filter 118a is made of an alloy that includes nickel, chromium, and molybdenum. For example, the filter 118a is made of Hastelloy C-276, which is an alloy that includes molybdenum, chromium, iron, tungsten, and nickel. In some implementations, the alloy that makes up the filter 118a includes from about 15 wt.% to about 17 wt.% molybdenum. In some implementations, the alloy that makes up the filter 118a includes from about 14.5 wt.% to about 16.5 wt.% chromium. In some implementations, the alloy that makes up the filter 118a includes from about 4 wt.% to about 7 wt.% iron. In some implementations, the alloy that makes up the filter 118a includes from about 3 wt.% to about 4.5 wt.% tungsten. In some implementations, the alloy that makes up the filter 118a includes from about 49 wt.% to about 63.5 wt.% nickel. In some implementations, the first shell 110 defines a solids outlet 119. The solids outlet 119 can be configured to discharge solids (such as FeS precipitate 136) from the first chamber 110a. While the apparatus 100 operates to generate hydrogen, the solids outlet 119 may be closed.

[0014] The second shell 120 can have a generally hemispherical shape. In some implementations, the second shell 120 includes a cylindrical portion capped with a hemispherical end. The second shell 120 is configured to store hydrogen molecules. The second shell 120 can include a hydrogen outlet 122. The hydrogen outlet 122 is configured to discharge hydrogen from the second chamber 120a. In some implementations, the apparatus 100 includes a pressure sensor 123. The pressure sensorAttorney Ref. : 38136-2816WO 1123 can be coupled to the hydrogen outlet 122. The pressure sensor 123 can be configured to measure the operating pressure within the second chamber 120a and / or the operating pressure of the hydrogen flowing out of the second chamber 120a via the hydrogen outlet 122. The first shell 110 and the second shell 120 are made of a material that is resistant to hydrogen damage, such as blistering due to exposure to aqueous hydrogen sulfide, hydrogen induced cracking (HIC) due to exposure to aqueous hydrogen sulfide, stress-oriented HIC due to exposure to aqueous hydrogen sulfide, sulfide stress corrosion cracking due to exposure to aqueous hydrogen sulfide, and hydrogen embrittlement due to hydrogen exposure at high temperatures. In some implementations, the first shell 110 and the second shell 120 are made of stainless steel. For example, the first shell 110 and the second shell 120 are made of chrome-plated Grade 316 stainless steel. As another example, the first shell 110 (defining the RSC) is made of glass-lined low alloy carbon steel, and the second shell 120 (defining the PSC) is made of bare low alloy carbon steel. In cases in which the operating pressure within the first chamber 110a (RSC) is close to ambient pressure, the first shell 110 can optionally be made of glass or another material (such as polyvinyl chloride) that is lined with glass.

[0015] The barrier 130 is intermediate of the first shell 110 and the second shell 120. The barrier 130 separates the reactor vessel into the first chamber 110a and the second chamber 120a. The barrier 130 is made of a material that is resistant to hydrogen damage. In some implementations, the barrier 130 is made of stainless steel. In some implementations, the barrier 130 is made of an alloy that includes nickel, chromium, and molybdenum. For example, the barrier 130 is made of Hastelloy C-276, which is an alloy that includes molybdenum, chromium, iron, tungsten, and nickel. In some implementations, the alloy that makes up the barrier 130 includes from about 15 weight percent (wt.%) to about 17 wt.% molybdenum. In some implementations, the alloy that makes up the barrier 130 includes from about 14.5 wt.% to about 16.5 wt.% chromium. In some implementations, the alloy that makes up the barrier 130 includes from about 4 wt.% to about 7 wt.% iron. In some implementations, the alloy that makes up the barrier 130 includes from about 3 wt.% to about 4.5 wt.% tungsten. In some implementations, the alloy that makes up the barrier 130 includes from about 49 wt.% to about 63.5 wt.% nickel.Attorney Ref. : 38136-2816WO 1

[0016] In some implementations, the apparatus 100 includes a seal 135a disposed between the first shell 110 and the barrier 130. In some implementations, the apparatus 100 includes a seal 135b disposed between the second shell 120 and the barrier 130. The seals 135a, 135b are configured to prevent leakage of fluid (such as molecular hydrogen and hydrogen sulfide) out of the apparatus 100. In some implementations, the seals 135a, 135b are made of an elastomeric material. For example, the seals 135a, 135b can be made of a fluorine rubber (a fluorocarbon-based fluoroelastomer, FKM), a perfluoroelastomer (FFKM), or a copolymer of tetrafluoroethylene and propylene (TFE / P). The seals 135a, 135b can be included in cases where the first shell 110, the second shell 120, and the barrier 130 are distinct components that are coupled together. In cases in which the second shell 120 (defining the PSC) and the barrier 130 are welded together, the seal 135a may not be necessary. In cases in which the second shell 120 (defining the PSC) and the barrier 130 are formed as a unitary body (e.g., one continuous component, as opposed to distinct components coupled together), the seal 135a may not be necessary.

[0017] The hydrogen-permeable electrode 132 is coupled to the barrier 130. The hydrogen-permeable electrode 132 extends from the barrier 130 and into the first chamber 110a. At least a portion of the hydrogen-permeable electrode 132 is disposed within the first chamber 110a. No surface of the hydrogen-permeable electrode 132 is exposed to the second chamber 120a. Gaseous hydrogen is produced from reactions involving the hydrogen-permeable electrode 132 and the aqueous hydrogen sulfide residing within the first chamber 110a. Under operation of the apparatus 100, at least a portion of the hydrogen-permeable electrode 132 is submerged in the aqueous hydrogen sulfide. The hydrogen-permeable electrode 132 is configured to. in response to exposure to water and hydrogen sulfide (e.g., the aqueous hydrogen sulfide), undergo a spontaneous corrosion reaction to produce iron sulfide and hydrogen atoms. The hydrogen-permeable electrode 132 includes iron (Fe). Within the first chamber 110a, the iron of the hydrogen-permeable electrode 132 can undergo an oxidation half-reaction (represented by Equation 1) to form iron cations (Fe2+) and electrons (e“).Fe -> Fe2++ 2e“ (1)

[0018] Within the first chamber 110a, the hydrogen sulfide (dissolved in the water) can dissociate into hydrogen cations (H+) and bisulfide anions (HS ) which is represented by Equation 2. Within the first chamber 110a, the bisulfide anions canAttorney Ref. : 38136-2816WO 1dissociate into additional hydrogen cations and sulfide anions (S2’) which is represented by Equation 3. The sulfide anions can react with the iron cations (represented by Equation 4) to produce iron sulfide. The iron sulfide 136 produced from Equation 4 precipitates out of solution and may adhere to surfaces within the apparatus 100 (for example, a surface of the hydrogen-permeable electrode 132 and / or an inner surface of the first shell 110 defining the RSC).H2S H++ HS“ (2) HS-«-> H++ S2-(3) Fe2++ S2“ FeS (4)

[0019] In the aqueous hydrogen sulfide, a reduction half-reaction (represented by Equation 5) can occur, which can result in the formation of hydrogen atoms which may adhere to surfaces within the apparatus 100 (for example, the surface of the hydrogen-permeable electrode 132 and / or the inner surface of the first shell 110). In various chemical environments, the hydrogen atoms produced rapidly undergo a recombination reaction (represented by Equation 6) to form hydrogen molecules.H++ e--> H° (5) 2H° - H2(6)

[0020] Within the first chamber 110a, however, the recombination reaction (Equation 6) is retarded by the presence of the iron sulfide layer. The formation of the iron sulfide layer can result in a longer lifetime (and in turn, a larger concentration) of the individual hydrogen atoms adsorbed (ads) on the surface of the hydrogen-permeable electrode 132, which allows them to be absorbed (abs) into the matrix of the hydrogen-permeable electrode 132 (represented by Equation 7). Due to its very small size, atomic hydrogen is very soluble in materials, such as carbon steel. Due to the concentration gradient at the surface of the hydrogen-permeable electrode 132, hydrogen atoms can quickly diffuse into the matrix of the hydrogen-permeable electrode 132.H(ads) H°abs:)(7)

[0021] The hydrogen-permeable electrode 132 defines an inner bore 132a. The hydrogen-permeable electrode 132 is configured to allow hydrogen atoms (H°abs)) to diffuse into the inner bore 132a. The hydrogen atoms produced within the first chamber 110a diffuse into the inner bore 132a of the hydrogen-permeable electrode 132. Within the inner bore 132a, the hydrogen atoms (H°) will spontaneously combine to formAttorney Ref. : 38136-2816WO 1hydrogen molecules (H2) (Equation 6). The inner bore 132a is configured to store hydrogen molecules that have formed from the combining of hydrogen atoms. The inner bore 132a is in fluid communication with the check valve 134. The check valve 134 is in fluid communication with the second chamber 120a. The inner bore 132a of the hydrogen-permeable electrode 132 is in fluid communication with the second chamber 120a via the check valve 134. The hydrogen molecules (H2) residing within the inner bore 132a of the hydrogen-permeable electrode 132 can flow through the check valve 134 and into the second chamber 120a. The second chamber 120a can store the hydrogen molecules. The check valve 134 is configured to prevent flow of fluid (such as hydrogen) out of the second chamber 120a through the check valve 134. Because no surface of the hydrogen-permeable electrode 132 is exposed to the second chamber 120a and the check valve 134 prevents backflow of hydrogen molecules from the second chamber 120a back into the inner bore 132a of the hydrogen-permeable electrode 132 through the check valve 134, hydrogen molecules can migrate from the hydrogen-permeable electrode 132 into the second chamber 120a but cannot migrate from the second chamber 120a into the hydrogen-permeable electrode 132. The overall electrochemical reactions that involve Equations 1-7 are represented by Equations 8 and 9. Equation 8 represents the spontaneous corrosion reaction of iron (present in the hydrogen-permeable electrode 132) with water and hydrogen sulfide (water saturated with dissolved hydrogen sulfide, also referred to as aqueous hydrogen sulfide), which produces iron sulfide precipitate 136 and hydrogen atoms. Equation 9 represents the recombination reaction of hydrogen atoms to form hydrogen molecules."> > >

[0022] The formation of the iron sulfide layer promotes the absorption of hydrogen atoms into the steel matrix of the hydrogen-permeable electrode 132, followed by diffusion and permeation. The presence of iron sulfide can slow down the recombination reaction (Equation 6), which can allow for additional time for the hydrogen to exist in atomic form (H°) as opposed to molecular form (H2). The hydrogen-permeable electrode 132 is made of a material that does not trap hydrogen atoms (e.g., is permeable to hydrogen atoms) while being resistant to damage by exposure to hydrogen molecules. For example, the hydrogen-permeable electrode 132 is made of hydrogen-induced cracking (EHC)-resistant carbon steel. In someAttorney Ref. : 38136-2816WO 1implementations, the hydrogen-permeable electrode 132 is made of American Petroleum Institute (API) 5L Grade X52 steel. In some implementations, the hydrogen-permeable electrode 132 includes from about 0.11 wt.% to about 0.28 wt.% carbon. In some implementations, the hydrogen-permeable electrode 132 includes from about 0.27 wt.% to about 0.45 wt.% silicon. In some implementations, the hydrogen-permeable electrode 132 includes from about 1.1 wt.% to about 1.5 wt.% manganese. In some implementations, the hydrogen-permeable electrode 132 includes from about 0.003 wt.% to about 0.3 wt.% sulfur. In some implementations, the hydrogen-permeable electrode 132 includes from about 0.006 wt.% to about 0.3 wt.% phosphorus. In some implementations, the hydrogen-permeable electrode 132 includes from about 0.003 wt.% to about 0.15 wt.% molybdenum. In some implementations, the hydrogen-permeable electrode 132 includes up to about 0.01 wt.% or up to about 0.1 wt.% vanadium. In some implementations, the hydrogen-permeable electrode 132 includes up to about 0.06 wt.% of a total combined content of niobium and vanadium. In some implementations, the hydrogen-permeable electrode 132 includes up to about 0.15 wt.% of a total combined content of niobium, vanadium, and titanium. In some implementations, the hydrogen-permeable electrode 132 includes up to about 0.5 wt.% copper. In some implementations, the hydrogen-permeable electrode 132 includes up to about 0.5 wt.% nickel. In some implementations, the hydrogen-permeable electrode 132 includes up to about 0.5 wt.% chromium. A remainder of the chemical makeup of the hydrogen -permeable electrode 132 is iron.

[0023] Because the check valve 134 prevents hydrogen from escaping the second chamber 120a through the check valve 134, hydrogen molecules can accumulate within the second chamber 120a. In some implementations, the check valve 134 is made of an alloy that includes nickel, chromium, and molybdenum. For example, the check valve 134 is made of Hastelloy C-276, which is an alloy that includes molybdenum, chromium, iron, tungsten, and nickel. In some implementations, the alloy that makes up the check valve 134 includes from about 15 wt.% to about 17 wt.% molybdenum. In some implementations, the alloy that makes up the check valve 134 includes from about 14.5 wt.% to about 16.5 wt.% chromium. In some implementations, the alloy that makes up the check valve 134 includes from about 4 wt.% to about 7 wt.% iron. In some implementations, the alloy that makes up the check valve 134 includes from about 3Attorney Ref. : 38136-2816WO 1wt.% to about 4.5 wt.% tungsten. In some implementations, the alloy that makes up the check valve 134 includes from about 49 wt.% to about 63.5 wt.% nickel.

[0024] The amount of hydrogen molecules that have accumulated within the second chamber 120a can be determined based on the operating pressure within the second chamber 120a. In some implementations, the apparatus 100 includes a pressure port 124. The pressure port 124 can be configured to couple to a pressure sensor, a pressure relief valve, a backpressure regulator, or any combinations of these. The pressure relief valve is a safety measure that prevents overpressure in the apparatus 100. The pressure sensor coupled to the pressure port 124 can be configured to measure the operating pressure within the second chamber 120a. Under normal operation, the pressure relief valve is closed. The pressure relief valve coupled to the pressure port 124 can be configured to open in response to the operating pressure within the second chamber 120a reaching a specified threshold pressure for relieving pressure from the second chamber 120a.

[0025] In some implementations, as shown in FIG. 1, the apparatus 100 includes a recirculation pump 140. The recirculation pump 140 can be in fluid communication with the first chamber 110a. The recirculation pump 140 can be configured to circulate the aqueous hydrogen sulfide through the first chamber 110a. For example, the aqueous hydrogen sulfide flows from the first chamber 110a to the recirculation pump 140, and the recirculation pump 140 flows the aqueous hydrogen sulfide back to the first chamber 11 a.

[0026] In some implementations, as shown in FIG. 1, the apparatus 100 includes a heater 150. The heater 150 can be configured to maintain an operating temperature of the aqueous hydrogen sulfide within the first chamber 110a. For example, the heater 150 is configured to maintain the aqueous hydrogen sulfide within the first chamber 110a at an operating temperature in a range of from about 30 degrees Celsius (°C) to about 40 °C (such as about 35 °C). In some implementations, as shown in FIG. 1, the heater 150 is located downstream of the recirculation pump 140. In such implementations, the aqueous hydrogen sulfide flows from the first chamber 110a, through the recirculation pump 140, through the heater 150, and back to the first chamber 110a. Having the heater 150 located downstream of the recirculation pump 140 as opposed to upstream of the recirculation pump 140 can reduce the chances of cavitation, which can damage the recirculation pump 140. The apparatus 100 canAttorney Ref. : 38136-2816WO 1include a filter 150a upstream of the outlet for the aqueous hydrogen sulfide flowing to the recirculation pump 140. The filter 150a can, for example, be a mesh screen designed to prevent solids (such as FeS precipitate 136) from exiting the apparatus 100 through the outlet to the recirculation pump 140. The filter 150a can define pores that are sized to prevent solids from exiting the first chamber 110a and entering the recirculation pump 140, while allowing fluid (such as aqueous hydrogen sulfide) to exit the first chamber 110a and enter the recirculation pump 140. In some implementations, the pores defined by the filter 150a have an average pore diameter in a range of from about 1 micrometers (pm) to about 10 pm. In some implementations, the filter 150a is made of an alloy that includes nickel, chromium, and molybdenum. For example, the filter 150a is made of Hastelloy C-276. which is an alloy that includes molybdenum, chromium, iron, tungsten, and nickel. In some implementations, the alloy that makes up the filter 150a includes from about 15 wt.% to about 17 wt.% molybdenum. In some implementations, the alloy that makes up the filter 150a includes from about 14.5 wt.% to about 16.5 wt.% chromium. In some implementations, the alloy that makes up the filter 150a includes from about 4 wt.% to about 7 wt.% iron. In some implementations, the alloy that makes up the filter 150a includes from about 3 wt.% to about 4.5 wt.% tungsten. In some implementations, the alloy that makes up the filter 150a includes from about 49 wt.% to about 63.5 wt.% nickel.

[0027] In some implementations, the apparatus 100 includes a temperature sensor 152. The temperature sensor 152 can be configured to measure an operating temperature of the aqueous hydrogen sulfide prior to entering the heater 150. The temperature sensor 152 can be communicatively coupled to the heater 150. The temperature sensor 152 can transmit a signal that represents the measured operating temperature of the aqueous hydrogen sulfide. The heater 150 can provide heating duty to the aqueous hydrogen sulfide to maintain the aqueous hydrogen sulfide at a specified target operating temperature. In some implementations, the specified target operating temperature is about 34 °C, about 35 °C, or about 36 °C. Maintaining the operating temperature of the aqueous hydrogen sulfide residing within the first chamber 110a at the specified target operating temperature (for example, about 35 °C) can improve the permeation flux of hydrogen (e.g., hydrogen atoms) into the inner bore 132a of the hydrogen-permeable electrode 132. Maintaining the operating temperature of the aqueous hydrogen sulfide residing within the first chamber 110a at the specified targetAttorney Ref. : 38136-2816WO 1operating temperature (for example, about 35 °C) can reduce the rate of corrosion, for example, of the first shell 110 which is already made of a material that is resistant to corrosion.

[0028] In some implementations, the apparatus 100 includes an access port 160. During operation of the apparatus 100, the access port 160 is closed. The access port 160 can, for example, be opened to access internal components (such as the hydrogen-permeable electrode 132) of the apparatus 100. In some implementations, the access port 160 includes a sight glass (e.g., a glass window) that allows for visual observation of the first chamber 110a and internal components (such as the hydrogen-permeable electrode 132) of the apparatus 100. For example, a user can monitor the state of internal components of the apparatus 100 during operation of the apparatus 100. As another example, the user can monitor a liquid level (for example, of the aqueous hydrogen sulfide solution) within the first chamber 110a during operation of the apparatus 100.

[0029] In some implementations, the apparatus 100 includes an access manhole 170. During operation of the apparatus 100, the access manhole 170 is closed. The access manhole 170 can, for example, be opened to access internal components (such as the hydrogen-permeable electrode 132) of the apparatus 100. In some cases, the access manhole 170 has a larger diameter in comparison to the access port 160. The access manhole 170 can be opened, for example, to perform maintenance on the apparatus 100, to remove iron sulfide precipitates 136 that have accumulated at the bottom of the apparatus 100, to flush out liquid from the apparatus 100, or any combinations of these.

[0030] As the hydrogen-permeable electrode 132 corrodes by exposure to the aqueous hydrogen sulfide, hydrogen atoms (H°) are produced, and the walls of the hydrogen-permeable electrode 132 get thinner. The hydrogen atoms permeate through the walls of the hydrogen-permeable electrode 132 and combine within the inner bore 132a of the hydrogen-permeable electrode 132, forming hydrogen molecules (H2). Pressure within the inner bore 132a builds due to accumulation of hydrogen gas. As the pressure difference between the inner bore 132a and the second chamber 120a increases, the check valve 134 opens, allowing flow of hydrogen molecules from the inner bore 132a into the second chamber 120a. For example, a pressure difference of about 1 pound per square inch (psi) (7 kilopascals (kPa)) differential or greater can cause the check valve 134 to open, while the check valve 134 remains closed for a pressure difference less than about 1 psi (7 kPa) differential. As described previously, closure of the checkAttorney Ref. : 38136-2816WO 1valve 134 prevents flow of fluid from the second chamber 120a into the inner bore 132a of the hydrogen-permeable electrode 132, while opening of the check valve 134 allows flow of fluid from the inner bore 132a into the second chamber 120a. As hydrogen gas accumulates in the second chamber 120a, pressure within the second chamber 120a increases. The pressure within the second chamber 120a can, for example, be monitored by pressure gauge 123. A backpressure regulator can be coupled to the pressure port 124. The backpressure regulator can be set to open at a specified pressure threshold. For example, the specified pressure threshold at which the backpressure regulator is set to open can be about 100 psi gauge (psig) (689.5 kPa gauge (kPag)). In such cases, when the pressure within the second chamber 120a reaches about 100 psig (689.5 kPag), the backpressure regulator can open, and excess hydrogen gas can flow out of the second chamber 120a through the backpressure regulator to ensure that the pressure within the second chamber 120a does not exceed about 100 psig (689.5 kPag). The excess hydrogen gas exiting the second chamber 120a through the backpressure regulator can be, for example, collected in a gas cylinder. The process of hydrogen generation can continue until the pressure within the second chamber 120a ceases to support flow of hydrogen into the second chamber 120a. This can occur, for example, once hydrogen production ceases.

[0031] A possible reason the production of hydrogen gas ceases includes the development of an iron sulfide layer / film on the external surface of the hydrogen-permeable electrode 132, which can reduce the surface area of the hydrogen-permeable electrode 132 being exposed to the aqueous hydrogen sulfide, thereby inhibiting the corrosion reaction of the hydrogen-permeable electrode 132 and preventing additional production of hydrogen atoms to combine and form hydrogen molecules. In such cases, the external surface of the hydrogen-permeable electrode 132 can be cleaned to remove the iron sulfide deposition, such that the external surface of the hydrogen-permeable electrode 132 can be exposed to the aqueous hydrogen sulfide for allowing the corrosion reactions to occur. Another possible reason the production of hydrogen gas ceases includes the corrosion of the hydrogen-permeable electrode 132 to a point where the walls of the hydrogen-permeable electrode 132 become too thin to support pressure within the inner bore 132a of the hydrogen-permeable electrode 132. If the walls of the hydrogen-permeable electrode 132 become too thin to support pressure within the inner bore 132a of the hydrogen-permeable electrode 132, then sufficient pressure within theAttorney Ref. : 38136-2816WO 1inner bore 132a is prevented from accumulating to allow flow of hydrogen molecules from the inner bore 132a into the second chamber 120a through the check valve 134. For example, the pressure within the inner bore 132a may not be sufficient to open the check valve 134 if the walls of the permeable electrode 132 become too thin even when additional hydrogen molecules are being produced. The corrosion reactions involving the hydrogen-permeable electrode 132 to produce hydrogen atoms results in wall thickness reduction, so wall thinning of the hydrogen-permeable electrode 132 is expected over time. Once the walls of the hydrogen-permeable electrode 132 have become too thin, the hydrogen-permeable electrode 132 should be replaced. The condition of the hydrogen-permeable electrode 132 can be monitored, for example, visually through the access port 160.

[0032] In order to clean or replace the hydrogen-permeable electrode 132, the hydrogen sulfide is removed from the first chamber 110a. The hydrogen sulfide can be removed from the first chamber 110a, for example, by purging with an inert gas (such as nitrogen). The inert gas can be injected into the inlet 114 to purge the aqueous hydrogen sulfide from the first chamber 110a. Purging the inert gas into the inlet 114 and out of the outlet 116 can ensure removal of any residual hydrogen sulfide from these ports. The inert gas used to purge the first chamber 110a and exiting the outlet 116 can be passed through a scrubber to remove hydrogen sulfide before disposal (for example, release into the atmosphere). An additional measure that can be taken to ensure neutralization of potential residual hydrogen sulfide within the first chamber 110a after purging with the inert gas can include injection of a caustic soda solution (for example, 15% sodium hydroxide) into the first chamber 110a via the inlet 112. The recirculation pump 150 can be operating and circulating fluid through the first chamber 110a during purging and neutralization. The purged, neutralized solution can be drained from the first chamber 110a via the outlet 118. Remaining liquid can be drained from the first chamber 110a via the outlet 119. Once the first chamber 110a has been drained of liquid, solids residing in the first chamber 110a can be removed, for example, by opening the access manhole 170 and removing such solids through the opened access manhole 170.

[0033] In cases where the hydrogen-permeable electrode 132 is observed to be covered by a layer of iron sulfide, and the walls of the hydrogen-permeable electrode 132 appear to be strong / thick enough to maintain pressure (for example, by visual inspection), a cleaning solution can be injected into the first chamber 110a, for example,Attorney Ref. : 38136-2816WO 1via the inlet 112 while the access manhole 180 is closed. The cleaning solution can be, for example, 10% hydrochloric acid. To accelerate the cleaning process, the cleaning solution can be heated to, for example, about 35 °C using the heater 140. In some implementations, the cleaning process proceeds for about 30 minutes. During the cleaning process, the recirculation pump 150 can be operating and circulating fluid through the first chamber 110a. Once the cleaning process concludes, the cleaning solution can be neutralized, for example, by injection of a caustic soda solution (for example, 50% sodium hydroxide). The amount of caustic soda solution injected into the first chamber 110a for neutralization of the cleaning solution can be determined, for example, based on a 1:1 molar ratio of sodium hydroxide present in the caustic soda solution to hydrochloric acid present in the cleaning solution. The neutralized cleaning solution can be drained from the first chamber 110a via the outlet 118. Remaining liquid can be drained from the first chamber 110a via the outlet 119. The first chamber 110a and the hydrogen-permeable electrode 132 can then be rinsed, for example, with distilled water. Once rinsed, the hydrogen-permeable electrode 132 can be inspected. If the hydrogen-permeable electrode 132 is determined to be in adequate condition, the hydrogen-permeable electrode 132 can be reinstalled within the first chamber 110a. If, however, the hydrogen-permeable electrode 132 is determined to be in poor condition (for example, has holes), then the hydrogen-permeable electrode 132 can be replaced by a new electrode. Replacement and reinstallation of the hydrogen-permeable electrode 132 can be performed, for example, through the opened access manhole 170.

[0034] FIG. 2 is a flow chart of an example method 200 for conversion of hydrogen sulfide to produce hydrogen. The apparatus 100 can, for example, be used to implement method 200. At block 202. a hydrogen-permeable electrode (such as the hydrogen-permeable electrode 132) is exposed to water and hydrogen sulfide within a first chamber (such as the first chamber 110a) of a reactor vessel (such as the apparatus 100). Exposing the hydrogen-permeable electrode 132 to water and hydrogen sulfide at block 202 can include exposing the hydrogen-permeable electrode 132 to water that is saturated with dissolved hydrogen sulfide (aqueous hydrogen sulfide). In some implementations, more than 90% (e g., by volume) of the hydrogen-permeable electrode 132 is submerged in the aqueous hydrogen sulfide solution. During operation, the bottom of the hydrogen-permeable electrode 132 is positioned below the EES outlet 116 with respect to gravity. In some implementations, at least 90% (e.g., by volume) of theAttorney Ref. : 38136-2816WO 1hydrogen-permeable electrode 132 is located below the H2S outlet 116 with respect to gravity. In some implementations, the aqueous hydrogen sulfide is circulated through the first chamber 110a by a recirculation pump (such as the recirculation pump 140). In some implementations, the aqueous hydrogen sulfide circulated through the first chamber 110a by the recirculation pump 140 is maintained at an operating temperature in a range of from about 30 °C to about 40 °C (for example, about 35 °C) by a heater (such as the heater 150). As described previously, the hydrogen-permeable electrode 132 includes iron. Exposing the hydrogen-permeable electrode 132 to water and hydrogen sulfide at block 202 results in the iron of the hydrogen-permeable electrode 132 to undergo a spontaneous corrosion reaction with the aqueous hydrogen sulfide to produce iron sulfide (precipitate 136) and hydrogen atoms. At block 204, the hydrogen-permeable electrode 132 allows the hydrogen atoms to diffuse into an inner bore (such as the inner bore 132a) of the hydrogen-permeable electrode 132. The hydrogen atoms that have diffused into the inner bore 132a at block 204 spontaneously combine to form hydrogen molecules. At block 206, a check valve (such as the check valve 134) allows the hydrogen molecules (formed as a result of block 204) to flow from the inner bore 132a through the check valve 134 to a second chamber (such as the second chamber 120a) of the reactor vessel (apparatus 100). At block 208, the check valve 134 prevents hydrogen molecules from flowing back out from the second chamber 120a through the check valve 134. The check valve 134 is a one-way (no return) valve that allows flow of fluid through the check valve 134 in a first direction (into the second chamber 120a) while preventing flow of fluid through the check valve 134 in a second direction that is opposite the first direction (out of the second chamber 120a). At block 210, the hydrogen molecules are flowed out of the second chamber 120a via an outlet (such as the hydrogen outlet 122) of the reactor vessel (apparatus 100).

[0035] FIG. 3 is a flow chart of an example method 300 for operating the apparatus 100. At block 302, water is flowed to a first chamber (such as the first chamber 110a) via a first inlet (such as the water inlet 112). At block 304, hydrogen sulfide is flowed to the first chamber 110a via a second inlet (such as the H2S inlet 114), thereby saturating the water within the first chamber 110a (block 302) with the hydrogen sulfide and exposing a hydrogen-permeable electrode (such as the hydrogen-permeable electrode 132) to the water saturated with hydrogen sulfide (aqueous hydrogen sulfide). In some implementations, the aqueous hydrogen sulfide is circulated through the firstAttorney Ref. : 38136-2816WO 1chamber 110a by a recirculation pump (such as the recirculation pump 140). In some implementations, the aqueous hydrogen sulfide within the first chamber 110a is maintained at an operating temperature in a range of from about 30 °C to about 40 °C (for example, about 35 °C). The operating temperature of the aqueous hydrogen sulfide within the first chamber 110a can be maintained at a desired operating temperature by a heater (such as the heater 150). The iron of the hydrogen-permeable electrode 132 undergoes a spontaneous corrosion reaction in response to exposure to the aqueous hydrogen sulfide (block 304) to produce iron sulfide (precipitate 136) and hydrogen atoms. At block 306, the hydrogen-permeable electrode 132 allows the hydrogen atoms to diffuse into an inner bore (such as the inner bore 132a) of the hydrogen-permeable electrode 132. The hydrogen atoms within the inner bore 132a combine to form hydrogen molecules. At block 308, a check valve (such as the check valve 134) allows the hydrogen molecules to flow from the inner bore 132a through the check valve 134 to a second chamber (such as the second chamber 120a). At block 310, the check valve 134 prevents hydrogen molecules from flowing back out from the second chamber 120a through the check valve 134. At block 312, the hydrogen molecules are flowed out of the second chamber 120a via a hydrogen outlet (such as the hydrogen outlet 122) defined by a second shell (such as the second shell 120).

[0036] As the hydrogen-permeable electrode 132 is corroded by the aqueous hydrogen sulfide and produces hydrogen atoms, the walls of the hydrogen-permeable electrode 132 become thinner with time.EMBODIMENTS

[0037] In an example implementation (or aspect), a reactor comprises: a first shell defining a first chamber, wherein the first shell defines a first inlet configured to receive water, a second inlet configured to receive hydrogen sulfide, and a first outlet configured to discharge hydrogen sulfide; a second shell defining a second chamber isolated from the first chamber, wherein the second chamber is configured to store hydrogen molecules; a hydrogen-permeable electrode at least partially disposed within the first chamber, wherein the hydrogen-permeable electrode is permeable to hydrogen atoms originating from the hydrogen sulfide within the first chamber; and a check valve coupled to the hydrogen-permeable electrode and in fluid communication with the second chamber, wherein the hydrogen-permeable electrode is in fluid communicationAttorney Ref. : 38136-2816WO 1with the second chamber via the check valve which is configured to allow flow of hydrogen molecules, formed from the hydrogen atoms that have permeated into the hydrogen-permeable electrode, into the second chamber, wherein the check valve is configured to prevent flow of hydrogen molecules back out from the second chamber through the check valve.

[0038] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the hydrogen-permeable electrode defines an inner bore configured to store the hydrogen molecules formed from the hydrogen atoms that have permeated into the hydrogen-permeable electrode, wherein the inner bore is in fluid communication with the check valve.

[0039] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the reactor comprises a barrier intermediate of the first chamber and the second chamber, wherein the barrier isolates the first chamber from the second chamber, wherein the hydrogen-permeable electrode and the check valve are coupled to the barrier.

[0040] In an example implementation (or aspect) combinable with any other example implementation (or aspect), during operation, the reactor is vertically oriented with the first chamber positioned below the second chamber with respect to gravity .

[0041] In an example implementation (or aspect) combinable with any other example implementation (or aspect), during operation, the first inlet is positioned above the second inlet with respect to gravity7.

[0042] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the reactor comprises a recirculation pump in fluid communication with the first chamber, wherein the recirculation pump is configured to circulate the water and the hydrogen sulfide through the first chamber.

[0043] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the reactor comprises a heater configured to maintain the water and the hydrogen sulfide within the first chamber at an operating temperature in a range of from about 30 degrees Celsius (°C) to about 40 °C.

[0044] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the first shell defines a third outlet configured to discharge liquid from the first chamber, wherein the first shell defines a fourth outlet configured to discharge solids from the first chamber, wherein the reactor comprises aAttorney Ref. : 38136-2816WO 1filter covering the third outlet, wherein the filter defines a plurality of pores sized to prevent solids from exiting the first chamber through the third outlet while allowing fluid to exit the first chamber through the third outlet.

[0045] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the first shell and the second shell are made of stainless steel resistant to hydrogen damage.

[0046] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the barrier is made of an alloy resistant to hydrogen damage, and the alloy comprises nickel, chromium, and molybdenum.

[0047] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the hydrogen-permeable electrode is made of a hydrogen-induced cracking (HlC)-resistant carbon steel.

[0048] In an example implementation (or aspect), a method for electrochemical conversion of hydrogen sulfide to produce hydrogen comprises: exposing a hydrogen-permeable electrode to water and hydrogen sulfide within a first chamber of a reactor, wherein the hydrogen-permeable electrode comprises iron, wherein the iron of the hydrogen-permeable electrode undergoes a spontaneous corrosion reaction in response to exposure to the water and the hydrogen sulfide to produce iron sulfide and hydrogen atoms, wherein the reactor comprises a second chamber isolated from the first chamber; allowing, by the hydrogen-permeable electrode, the hydrogen atoms to diffuse into an inner bore of the hydrogen -permeable electrode, where the hydrogen atoms combine to form hydrogen molecules; allowing, by a check valve coupled to the hydrogen-permeable electrode, the hydrogen molecules to flow from the inner bore of the hydrogen-permeable electrode through the check valve to a second chamber of the reactor; preventing, by the check valve, hydrogen molecules from flowing back out from the second chamber through the check valve; and flowing the hydrogen molecules out of the second chamber via an outlet different from the check valve.

[0049] In an example implementation (or aspect) combinable with any other example implementation (or aspect), exposing the hydrogen-permeable electrode to water and hydrogen sulfide comprises bubbling an excess amount of the hydrogen sulfide through the water to produce water that is saturated with dissolved hydrogen sulfide and exposing the hydrogen-permeable electrode to the water that is saturated with dissolved hydrogen sulfide.Attorney Ref. : 38136-2816WO 1

[0050] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the method comprises circulating the water that is saturated with dissolved hydrogen sulfide through the first chamber by a recirculation pump.

[0051] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the method comprises maintaining the water that is saturated with dissolved hydrogen sulfide circulated through the first chamber by the recirculation pump at an operating temperature in a range of from about 30 °C to about 40 °C by a heater.

[0052] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the reactor vessel is made of stainless steel resistant to hydrogen damage.

[0053] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the barrier is made of an alloy resistant to hydrogen damage, and the alloy comprises nickel, chromium, and molybdenum.

[0054] In an example implementation (or aspect) combinable with any other example implementation (or aspect), the hydrogen-permeable electrode is made of an HIC -resistant carbon steel.

[0055] In an example implementation (or aspect) combinable with any other example implementation (or aspect), a method of operating the reactor comprises: flowing water to the first chamber via the first inlet; flowing hydrogen sulfide to the first chamber via the second inlet, thereby saturating the water within the first chamber with the hydrogen sulfide and exposing the hydrogen-permeable electrode to the water saturated with hydrogen sulfide, wherein the iron of the hydrogen-permeable electrode undergoes a spontaneous corrosion reaction in response to exposure to the water saturated with hydrogen sulfide to produce iron sulfide and hydrogen atoms; allowing, by the hydrogen-permeable electrode, the hydrogen atoms to diffuse into an inner bore of the hydrogen-permeable electrode, where the hydrogen atoms combine to form hydrogen molecules; allowing, by the check valve, the hydrogen molecules to flow from the inner bore of the hydrogen-permeable electrode through the check valve to the second chamber; preventing, by the check valve, hydrogen molecules from flowing back out from the second chamber through the check valve; and flowing the hydrogen molecules out of the second chamber via a second outlet defined by the second shell.Attorney Ref. : 38136-2816WO 1

[0056] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any subcombination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a subcombination.

[0057] As used in this disclosure, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology7or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

[0058] As used in this disclosure, the term “about” or “approximately” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range.

[0059] As used in this disclosure, the term “substantially” refers to a majority7of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

[0060] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “0.1% to about 5%” or “0.1% to 5%” should be interpreted to include about 0.1% to about 5%. as well as the individual values (for example, 1%. 2%,Attorney Ref. : 38136-2816WO 13%, and 4%) and the sub-ranges (for example, 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “X to Y” has the same meaning as ■‘about X to about Y,” unless indicated otherwise. Likewise, the statement "X, Y, or Z’’ has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

[0061] Particular implementations of the subject matter have been described. Other implementations, alterations, and permutations of the described implementations are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. In certain circumstances, multitasking or parallel processing (or a combination of multitasking and parallel processing) may be advantageous and performed as deemed appropriate.

[0062] Moreover, the separation or integration of various system modules and components in the previously described implementations should not be understood as requiring such separation or integration in all implementations, and it should be understood that the described components and systems can generally be integrated together or packaged into multiple products.

[0063] Accordingly, the previously described example implementations do not define or constrain the present disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure.

Claims

Attorney Ref. : 38136-2816WO 1CLAIMS WHAT IS CLAIMED IS:

1. A reactor compri sing :a first shell defining a first chamber, wherein the first shell defines a first inlet configured to receive water, a second inlet configured to receive hydrogen sulfide, and a first outlet configured to discharge hydrogen sulfide;a second shell defining a second chamber isolated from the first chamber, wherein the second chamber is configured to store hydrogen molecules;a hydrogen-permeable electrode at least partially disposed within the first chamber, wherein the hydrogen-permeable electrode is permeable to hydrogen atoms originating from the hydrogen sulfide within the first chamber; anda check valve coupled to the hydrogen-permeable electrode and in fluid communication with the second chamber, wherein the hydrogen-permeable electrode is in fluid communication with the second chamber via the check valve which is configured to allow flow of hydrogen molecules, formed from the hydrogen atoms that have permeated into the hydrogen-permeable electrode, into the second chamber, wherein the check valve is configured to prevent flow of hydrogen molecules back out from the second chamber through the check valve.

2. The reactor of claim 1. wherein the hydrogen-permeable electrode defines an inner bore configured to store the hydrogen molecules formed from the hydrogen atoms that have permeated into the hydrogen-permeable electrode, wherein the inner bore is in fluid communication with the check valve.

3. The reactor of claim 2, comprising a barrier intermediate of the first chamber and the second chamber, wherein the barrier isolates the first chamber from the second chamber, wherein the hydrogen-permeable electrode and the check valve are coupled to the barrier.

4. The reactor of claim 3, wherein during operation, the reactor is vertically oriented with the first chamber positioned below the second chamber with respect to gravity.Attorney Ref. : 38136-2816WO 15. The reactor of claim 4, wherein during operation, the first inlet is positioned above the second inlet with respect to gravity.

6. The reactor of claim 5, comprising a recirculation pump in fluid communication with the first chamber, wherein the recirculation pump is configured to circulate the water and the hydrogen sulfide through the first chamber.

7. The reactor of claim 6, comprising a heater configured to maintain the water and the hydrogen sulfide within the first chamber at an operating temperature in a range of from about 30 degrees Celsius (°C) to about 40 °C.

8. The reactor of claim 7, wherein the first shell defines a third outlet configured to discharge liquid from the first chamber, wherein the first shell defines a fourth outlet configured to discharge solids from the first chamber, wherein the reactor comprises a filter covering the third outlet, wherein the filter defines a plurality of pores sized to prevent solids from exiting the first chamber through the third outlet while allowing fluid to exit the first chamber through the third outlet.

9. The reactor of claim 8, wherein the first shell and the second shell are made of stainless steel resistant to hydrogen damage.

10. The reactor of claim 8, wherein the barrier is made of an alloy resistant to hydrogen damage, and the alloy comprises nickel, chromium, and molybdenum.

11. The reactor of claim 8, wherein the hydrogen-permeable electrode is made of a hydrogen-induced cracking (HlC)-resistant carbon steel.

12. A method for electrochemical conversion of hydrogen sulfide to produce hydrogen, the method comprising:exposing a hydrogen-permeable electrode to water and hydrogen sulfide within a first chamber of a reactor, wherein the hydrogen-permeable electrode comprises iron, wherein the iron of the hydrogen-permeable electrode undergoes a spontaneous corrosion reaction in response to exposure to the water and the hydrogen sulfide toAttorney Ref. : 38136-2816WO 1produce iron sulfide and hydrogen atoms, wherein the reactor comprises a second chamber isolated from the first chamber;allowing, by the hydrogen-permeable electrode, the hydrogen atoms to diffuse into an inner bore of the hydrogen-permeable electrode, where the hydrogen atoms combine to form hydrogen molecules;allowing, by a check valve coupled to the hydrogen-permeable electrode, the hydrogen molecules to flow from the inner bore of the hydrogen-permeable electrode through the check valve to a second chamber of the reactor;preventing, by the check valve, hydrogen molecules from flowing back out from the second chamber through the check valve; andflowing the hydrogen molecules out of the second chamber via an outlet different from the check valve.

13. The method of claim 12, wherein exposing the hydrogen-permeable electrode to water and hydrogen sulfide comprises bubbling an excess amount of the hydrogen sulfide through the water to produce water that is saturated with dissolved hydrogen sulfide and exposing the hydrogen-permeable electrode to the water that is saturated with dissolved hydrogen sulfide.

14. The method of claim 13, comprising circulating the water that is saturated with dissolved hydrogen sulfide through the first chamber by a recirculation pump.

15. The method of claim 14, comprising maintaining the water that is saturated with dissolved hydrogen sulfide circulated through the first chamber by the recirculation pump at an operating temperature in a range of from about 30 °C to about 40 °C by a heater.

16. The method of claim 15, wherein the reactor vessel is made of stainless steel resistant to hydrogen damage.

17. The method of claim 15, wherein the barrier is made of an alloy resistant to hydrogen damage, and the alloy comprises nickel, chromium, and molybdenum.Attorney Ref. : 38136-2816WO 118. The method of claim 15. wherein the hydrogen-permeable electrode is made of an HIC-resistant carbon steel.

19. A method of operating the reactor of claim 1, the method comprising:flowing water to the first chamber via the first inlet;flowing hydrogen sulfide to the first chamber via the second inlet, thereby saturating the water within the first chamber with the hydrogen sulfide and exposing the hydrogen-permeable electrode to the water saturated with hydrogen sulfide, wherein the iron of the hydrogen-permeable electrode undergoes a spontaneous corrosion reaction in response to exposure to the water saturated with hydrogen sulfide to produce iron sulfide and hydrogen atoms;allowing, by the hydrogen-permeable electrode, the hydrogen atoms to diffuse into an inner bore of the hydrogen-permeable electrode, where the hydrogen atoms combine to form hydrogen molecules;allowing, by the check valve, the hydrogen molecules to flow from the inner bore of the hydrogen-permeable electrode through the check valve to the second chamber;preventing, by the check valve, hydrogen molecules from flowing back out from the second chamber through the check valve; andflowing the hydrogen molecules out of the second chamber via a second outlet defined by the second shell.

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