Simultaneous production of hydrogen and sulfuric acid by partial oxidation of sulfur.

Abstract

A system and method for producing hydrogen, comprising: converting sulfur vapor and oxygen gas into sulfur monoxide in a first zone of a furnace; injecting water into a second zone of the furnace; converting the sulfur monoxide and water into hydrogen gas and sulfur dioxide in the second zone; discharging furnace exhaust gas (including hydrogen gas) from the furnace; condensing the sulfur vapor in the furnace exhaust gas into liquid sulfur in a condenser (heat exchanger) downstream of the furnace; and discharging the liquid sulfur from the condenser to a container.

Description

[Technical Field]

[0001] (Priority Claim) This application claims priority to U.S. Patent Application No. 17 / 946,145, filed September 16, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to the partial oxidation of elemental sulfur in a furnace to produce hydrogen gas as a product. [Background technology]

[0003] Hydrogen sulfide can be a by-product of natural gas processing and sulfur-containing crude oil refining. Other industrial sources of hydrogen sulfide can include pulp and paper manufacturing, chemical manufacturing, waste disposal, etc. In certain instances, hydrogen sulfide can be considered a precursor to elemental sulfur.

[0004] Sulfur recovery may refer to the conversion of hydrogen sulfide (HS) to elemental sulfur in a sulfur recovery unit (SRU), such as a Claus system. The most common technology for sulfur recovery is the Claus system, which may be referred to as a Claus process, Claus plant, Claus unit, etc. A Claus system includes a thermal reactor (e.g., a furnace) and multiple catalytic reactors to convert HS to elemental sulfur and remove (recover) the elemental sulfur.

[0005] Hydrogen is commercially produced from fossil fuels, etc. Hydrogen can be produced, for example, by hydrocarbon reforming or water electrolysis. Hydrogen is produced by coal gasification, biomass gasification, water electrolysis, or reforming or partial oxidation of natural gas or other hydrocarbons.

[0006] Natural gas reforming is the most common source of hydrogen production. Bulk hydrogen is typically produced by steam reforming of natural gas (methane). Conventional steam reforming involves heating natural gas (e.g., to 700°C to 1100°C) in the presence of steam and a nickel catalyst. This endothermic reaction produces carbon monoxide and hydrogen. The carbon monoxide gas can be subjected to a water-gas shift reaction to obtain additional hydrogen.

[0007] The produced hydrogen can be a feedstock for chemical processes such as ammonia production, aromatization, hydrodesulfurization, and hydrocarbon hydrogenation or hydrocracking. The produced hydrogen can be a feedstock for electrochemical processes such as fuel cells. Summary of the Invention

[0008] One aspect relates to a method for producing hydrogen, comprising: converting sulfur vapor and oxygen gas to sulfur monoxide in a first zone of a furnace; injecting water into a second zone of the furnace; converting the sulfur monoxide and water to hydrogen gas and sulfur dioxide in the second zone; and discharging a furnace exhaust gas from the furnace, wherein the furnace exhaust gas comprises hydrogen gas and sulfur dioxide. The method also comprises condensing the sulfur vapor in the furnace exhaust gas to liquid sulfur in a condenser (heat exchanger) downstream of the furnace; discharging the liquid sulfur from the condenser to a container; and discharging a process gas from the condenser to a quench tower, wherein the process gas comprises hydrogen gas and sulfur dioxide. The method also comprises absorbing sulfur dioxide from the process gas with sulfurous acid in the quench tower; and discharging hydrogen gas from the process gas from the quench tower.

[0009] Another aspect relates to a method for producing hydrogen, comprising converting sulfur vapor and oxygen gas to sulfur monoxide in a first zone of a furnace and converting sulfur monoxide and water to hydrogen gas and sulfur dioxide in a second zone of the furnace, with water being injected into the second zone. The method includes cooling furnace gas from the second zone in a heat exchanger section of the furnace using liquid sulfur as a cooling medium, vaporizing the liquid sulfur in the heat exchanger section into sulfur vapor that is fed to the first zone, and discharging furnace exhaust gas from the furnace, the furnace exhaust gas comprising hydrogen gas and sulfur dioxide. The method also includes condensing the sulfur vapor in the furnace exhaust gas into liquid sulfur in a condenser (heat exchanger) downstream of the furnace and discharging the liquid sulfur from the condenser to a container.

[0010] Yet another aspect relates to a hydrogen production system including a furnace that converts sulfur vapor and oxygen gas into sulfur monoxide in a first zone of the furnace and receives water injected into a second zone of the furnace and converts the sulfur monoxide and water into hydrogen gas and sulfur dioxide in the second zone. The hydrogen production system includes a condenser heat exchanger that receives furnace exhaust gas from the furnace, condenses the sulfur vapor in the furnace exhaust gas into liquid sulfur, discharges the liquid sulfur to a container, and discharges a process gas including hydrogen gas and sulfur dioxide to a quench tower. The hydrogen production system includes a quench tower that absorbs sulfur dioxide from the process gas into sulfurous acid and discharges hydrogen gas.

[0011] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram of the reaction schedule associated with sulfur combustion and other reactions in a furnace. [Figure 2] 1 is a plot of the change in Gibbs free energy as a function of temperature. [Figure 3] FIG. 1 is a diagram of the list of reactions considered. [Figure 4]1 is a plot of an example of an operating temperature determination of a furnace that combusts sulfur vapor to produce hydrogen gas. [Figure 5] 1 is a diagram of the overall reaction in the furnace consuming sulfur vapor and water to produce H2 and SO2. [Figure 6] FIG. 1 is a diagram of a hydrogen production system that may produce hydrogen gas as a product and sulfuric acid as a co-product. [Figure 7] FIG. 1 is a block flow diagram of a method for producing hydrogen gas, which may further include producing sulfuric acid as a co-product. DETAILED DESCRIPTION OF THE INVENTION

[0013] Aspects of the present disclosure relate to the production of hydrogen (H) and sulfuric acid (HSO) from sulfur (S). In particular, in a furnace, sulfur monoxide (SO) is produced from the partial combustion (partial oxidation) of elemental sulfur vapor, and the SO is contacted with water (H0) at a temperature (e.g., in the range of 802°C to 1608°C) that promotes the water-gas shift of SO to sulfur dioxide (SO) and inhibits the disproportionation of SO. The overall reaction produces H and SO, both of which are emitted in the furnace exhaust gas. H (H-rich gas) can be separated from SO by quenching the exhaust gas with cooled acidic water, which absorbs the SO, leaving the H-rich gas for recovery. The SO-absorbed water is oxidized to sulfuric acid in the oxidation tower using oxygen from air introduced into the oxidation tower as sulfurous acid. A dilute aqueous sulfuric acid solution exits the oxidation tower. The dilute sulfuric acid is sent to a water treatment unit, such as reverse osmosis (RO), electrodialysis, and / or distillation, to concentrate and recover the sulfuric acid. Clean water separated from the dilute sulfuric acid during concentration may be used as the water supply to the furnace for the furnace water-gas shift reaction to produce H. The concentrated sulfuric acid can be monetized or injected into the furnace to facilitate the combustion of oxygen and SO.

[0014] The produced H2 can be utilized in the transportation and energy sectors, as a feedstock for chemical processes, and the like. Embodiments herein can supply H2 to these applications (and others) by partial oxidation (partial combustion) of elemental S vapor to produce SO2 and water-gas shift of SO2 to H2 and SO2. This production of H2 can occur in a sulfur recovery plant or sulfur recovery unit (SRU), in certain implementations. Furthermore, the furnace for performing the partial oxidation and water-gas shift can be a Claus-type furnace.

[0015] By way of background, reactions for hydrogen production in a conventional Claus reactor that are considered include the following:

[0016] Partial combustion of methane (CH4) followed by water-gas shift reaction of carbon monoxide (CO) to H2 and carbon dioxide (CO2):

[0017]

number

[0018] Methane steam reforming (with water-gas shift of CO):

[0019]

number

[0020] Partial combustion of hydrogen sulfide (HS) followed by the water-gas shift reaction of SO:

[0021]

number

[0022] Although partial combustion of hydrogen sulfide is thermodynamically feasible at operating temperatures below 2000°K, the product of partial combustion, SO, can be difficult to maintain and SO can be readily oxidized (combusted) to SO. This fact is primarily due to the high energy gain of the system when H2S is completely oxidized to SO2.

[0023] To address this issue, embodiments of the present technology involve partial combustion of S vapor within a specific temperature range that facilitates the desired reactions (including partial combustion of S). The partial combustion of sulfur vapor preferably produces the desired SO. The water-gas shift reaction of SO then occurs to produce the desired H, as described with respect to FIG. 1.

[0024] Furthermore, as described below, the operating temperature of the furnace (sulfur burner) for the partial combustion of S vapor (and for the water-gas shift reaction of SO) may be, for example, within the range of 802°C to 1608°C, 1100°C to 1350°C, 1150°C to 1300°C, or 1180°C to 1280°C, and may be, for example, about 1233°C.

[0025] Figure 1 shows reactions associated with sulfur combustion, such as in a Claus furnace (sulfur burner), during the production of H2. Sulfur (sulfur vapor) combustion, sulfur (sulfur vapor) partial combustion, and the water-gas shift reaction of sulfur monoxide are shown. Disproportionation of sulfur monoxide to S and SO2 may be an identified side reaction. To understand the potentially destructive impact of this side reaction, the change in Gibbs free energy of the reaction (Figure 3) was calculated as a function of temperature using the enthalpy of formation and entropy of formation provided by the National Institute of Standards and Technology (NIST). See P.J. Linstrom and W.G. Mallard, Eds., NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg, MD, 20899, https: / / doi.org / 10.18434 / T4D303, (retrieved May 2022). The results are presented in Figure 2.

[0026] Figure 2 plots ΔG (change in Gibbs free energy) in kilojoules per mole (kJ / mol) as a function of temperature in Kelvin (K). Data for each reaction shown in Figure 3 is plotted in Figure 2. This plot (graph) in Figure 2 indicates whether the reaction at a given temperature is equilibrium or non-equilibrium (0 ≠ ΔG ∀T), and whether it is a forward reaction (0 < ΔG and JPEG2025529522000004.jpg1122 ), or the reverse reaction (0 > ΔG and JPEG2025529522000005.jpg1020 ), ΔG is the change in Gibbs free energy, T is temperature in Kelvin, and ∀ is the mathematical symbol for "for all..." Figure 2 also shows the change in Gibbs energy (Gibbs free energy) of the considered reaction as a function of temperature.

[0027] Figure 3 lists the reactions considered. VapElemental liquid sulfur is expressed as S Liq HSt is the complete combustion of H2S. HSp is the partial combustion of H2S. St is the complete combustion of elemental sulfur vapor. Sp is the partial combustion of elemental sulfur vapor. SLt is the complete combustion of elemental liquid sulfur. SLp is the partial combustion of elemental liquid sulfur. AntiDisP is the prevention of disproportionation of SO. SS Rx is the water-gas shift reaction of SO.

[0028] The partial combustion of sulfur vapor and the complete combustion of sulfur vapor have similar Gibbs energies. Therefore, these two reactions usually have the same probability of occurring. The equilibrium can be further promoted by adding excess sulfur vapor. The addition of excess sulfur vapor may be sufficient to shift the reaction to partial combustion of sulfur vapor (instead of complete combustion of sulfur vapor), thus preferably producing the desired SO (instead of SO) upon combustion. The generated SO can be almost instantly converted to SO (and H) via the water-gas shift reaction. SO can be an extremely reactive species. Disulfur dioxide (SO) can be an unstable intermediate in the disproportionation reaction of SO.

[0029] SO can be produced (via partial combustion of S vapor) over a relatively wide temperature range in the furnace (445°C (718°K) to 1727°C (2000°K)). However, the competing disproportionation reaction of SO consumes SO at temperatures below 1075°K. To solve this problem, the operating temperature of the furnace may be set above 1075°K. Furthermore, the SO water-gas shift reaction is reversed at temperatures above 1881°K. Therefore, the operating temperature may be set below 1881°K. Thus, the operating temperature in the furnace may be set, for example, within the range of 1075°K to 1881°K.

[0030] As described below, the operating temperature of the furnace (sulfur burner) for the first zone of the furnace and the second zone of the furnace may be within a range including, for example, 802°C to 1608°C, 1100°C to 1350°C, 1150°C to 1300°C, or 1180°C to 1280°C, and may be a specific value, for example, about 1233°C.

[0031] As shown in Figures 1 and 3, complete combustion of elemental sulfur vapor can be the conversion of sulfur vapor and oxygen gas to sulfur dioxide, and partial combustion of sulfur vapor can be defined as the conversion of sulfur vapor and sub-stoichiometric oxygen gas to sulfur monoxide.

[0032] Figure 4 is a plot of an example of the operating temperature determination of a furnace that burns sulfur vapor to produce hydrogen gas. R 2 is 1. The common area above the two lines is grayed out, but the intersection of the two lines is significant as it represents (determines) the beneficial or optimal temperature. The plot in this implementation shows that the beneficial or optimal operating temperature is 1506°K. The operating temperature of the furnace may be set, for example, within the range of 1075°K to 1881°K. Thus, FIG. 4 shows 1506°K as the beneficial or optimal temperature in the operating temperature range of 802°C (1075°K) to 1608°C (1881°K).

[0033] Figure 5 shows the overall reaction in the furnace to produce H2 (and SO2), which shows that water and sulfur vapor are consumed.

[0034] 6 illustrates a hydrogen production system 100 that can produce hydrogen gas as a product and sulfuric acid as a co-product (e.g., in stream 128). The hydrogen gas produced (e.g., in stream 124) can be utilized as a product or can be further processed to be utilized as a product.

[0035] The hydrogen production system 100 includes a furnace (vessel) that burns elemental sulfur vapor to produce hydrogen gas. The furnace may be referred to as a sulfur burner and may be a Claus-type furnace that uses sulfur instead of acid gas supplied to the furnace. The furnace vessel may have a combustion chamber with a first zone 101a and a second zone 101b separated by an internal baffle within the combustion chamber. The furnace may operate at temperatures ranging from 802°C (1075°K) to 1608°C (1881°K), for example. The furnace vessel may include a heat exchanger section 101c, which may be referred to as a boiler or waste heat boiler (WHB), that cools the furnace gas (and recovers heat from the furnace gas). The furnace configuration may be the same as or similar to a Claus furnace. The furnace may be referred to as a reactor, Claus-type furnace, or sulfur burner. Generally, acid gas or H2S is not supplied to the furnace. Although hydrogen production system 100 may be located in a sulfur recovery plant, system 100 is generally not an SRU or Claus system, and elemental sulfur is generally not produced, although again, reactors 101a / 101b (and 101c) may be the same as or similar to a typical Claus reactor, but fed with elemental sulfur vapor instead of acid gas or HS.

[0036] During operation, elemental sulfur vapor 111 and oxygen gas (O2) 112 are supplied to the furnace for combustion in the first zone 101a. Within the furnace, the sulfur vapor 111 is partially combusted (partial combustion, partial oxidation) with less than stoichiometric oxygen gas (O2) 112 in at least the first zone 101a. Partial combustion of sulfur vapor is herein referred to as O2 + 2S with less than stoichiometric O2 relative to the S vapor. Vap →It can be defined as 2SO.

[0037] Sulfuric acid 113 may be fed to the furnace for combustion in the first zone 101a. The sulfuric acid 113 may be recycled sulfuric acid, as described below. The amount of sulfuric acid 113 fed to the furnace may be relatively small compared to the amount of sulfur vapor 111 fed to the furnace.

[0038] In an implementation, the inlet section of the furnace mixes the flows 111, 112, 113 (e.g., in a nozzle) and ignites the mixture into the furnace flame, causing it to combust in the first section 101a of the furnace combustion chamber.

[0039] In the first zone 101a, the reaction of partial combustion (partial oxidation) of elemental sulfur vapor 111 may be O + 2S → 2SO, as previously described and shown in Figure 1. The furnace gas (combustion gas) with the produced SO flows from the first zone 101a to the second zone 101b.

[0040] Water 129 may be injected into the second zone 101b of the furnace for the water-gas shift reaction of SO to produce the desired hydrogen gas. The SO water-gas shift reaction is HO + SO → H + SO. The water-gas shift reaction of SO may be similar (at least in principle) to the water-gas shift reaction of carbon monoxide (CO).

[0041] The SO water-gas shift reaction produces hydrogen gas, which is supplied as a product by hydrogen production system 100. The SO water-gas shift reaction (and reverse disproportionation of SO) occurs at a temperature in the range of 802°C to 1608°C. The operating temperature of the furnace (including first zone 101a and / or second zone 101b) may be specified as a temperature within that range. This operating temperature of first zone 101a or second zone 101b, or both, may be, for example, 1100°C to 1350°C, 1150°C to 1300°C, or 1180°C to 1280°C, e.g., about 1233°C.

[0042] The overall reaction in the furnace (sulfur burner), including the partial combustion (partial oxidation) of sulfur vapor in the first zone 101a and the water-gas shift reaction of SO in the second zone 101b, can be characterized as 2H2O + O2 + 2S → 2H2 + 2SO2. See Figure 5.

[0043] Furnace gases (combustion gases, reaction gases) (including produced hydrogen gas) from a second zone 101b of the furnace (e.g., a Claus-type furnace or sulfur burner) flow through and are cooled in the furnace heat exchanger section 101c. The furnace gases cooled in the heat exchanger section 101c may be discharged from the furnace (e.g., from the heat exchanger section 101c) as furnace exhaust gas 114 at a temperature, for example, less than 315°C. The furnace exhaust gas 114 comprises hydrogen gas produced in the second zone 101b via the water-gas shift reaction of SO. The furnace exhaust gas 114 may comprise H, SO, and unreacted S vapor.

[0044] The heat exchanger in the heat exchanger portion 101c of the furnace may be a shell-and-tube heat exchanger. In implementations, the furnace vessel wall may be or function as the shell of the shell-and-tube heat exchanger. Heat transfer from the furnace gases to the cooling fluid may occur through the tube walls of each of the plurality of tubes. In certain implementations, the furnace gases from the second zone 101b to be cooled flow through the tubes (tube side) of the heat exchanger, and the cooling medium flows on the outside of the tubes (shell side).

[0045] Liquid sulfur may be the cooling medium in the heat exchanger of heat exchanger section 101c. The liquid sulfur (coolant) is on the opposite side of the heat exchanger to the furnace gas. In cooling the furnace gas received from second zone 101b, heat exchanger section 101c may vaporize the liquid sulfur (coolant) with heat from the furnace gas (through the tube walls) to produce sulfur vapor 111 that is sent as feed to the furnace. As previously mentioned, elemental sulfur vapor 111 may be supplied for partial combustion of sulfur vapor 111 in first zone 101a to produce SO that is subjected to water-gas shift in second zone 101b.

[0046] Liquid sulfur 131 may be pumped from a vessel 104 (e.g., a sulfur pit) containing liquid sulfur to supply the heat exchanger section 101c with a cooling medium (liquid sulfur). The liquid sulfur 131 may be pumped from the vessel 104 via a pump 130 (e.g., a centrifugal pump) through a heat exchanger 102 that heats the liquid sulfur 131 to produce preheated liquid sulfur 132 (with the same composition as the liquid sulfur 131) that is supplied to the heat exchanger section 101c. The heat exchanger 102 (e.g., a shell-and-tube heat exchanger, a plate-fin heat exchanger, etc.) may be a cross-exchanger that heats the liquid sulfur 131 with heat from the furnace exhaust gas 114 discharged from the heat exchanger section 101c. The heat exchanger 102 may be called an economizer when recovering heat from the furnace exhaust gas 114.

[0047] The furnace exhaust gas 114 exits the heat exchanger 102 as cooled furnace exhaust gas 115. The composition of the cooled furnace exhaust gas 115 is generally the same as the furnace exhaust gas 114. Again, the furnace exhaust gas 114 / 115 may have H, SO, and unreacted S vapor.

[0048] The heat exchanger 102 cools the furnace exhaust gas 114 while heating the liquid sulfur 131 with heat from the furnace exhaust gas 114, and discharges cooled furnace exhaust gas 115. The cooled furnace exhaust gas 115 flows from the heat exchanger 102 to the condenser 103 heat exchanger.

[0049] The cooling medium (cooling fluid) flowing through the condenser 103 (e.g., a shell-and-tube heat exchanger) may be water, such as demineralized water, steam return water, or boiler feed water. The condenser 103 may vaporize the incoming liquid water (cooling fluid) into steam 116, e.g., low-pressure steam of less than 150 pounds per square inch gauge (psig), which is discharged from the condenser 103, in cooling the furnace exhaust gas 115.

[0050] The condenser 103 may cool (remove heat from) the furnace exhaust gas 115 to reduce the temperature of the furnace exhaust gas 115 and condense elemental sulfur vapor in the furnace exhaust gas 115. The condensed sulfur may be discharged from the condenser 103 as liquid elemental sulfur 117 to a vessel 104 (sulfur receiver), such as a sulfur pit.

[0051] The sulfur pit may be a sulfur receiver, container, vessel, or the like. The sulfur receiver or sulfur pit may be a storage vessel where condensed sulfur is received, accumulated, and stored. The sulfur pit may temporarily house elemental sulfur extracted from an SRU or similar system and transported for further processing or to a transportation system, etc. As previously mentioned, liquid sulfur 131 / 132, which becomes sulfur vapor 111 for combustion in the furnace, may be from vessel 104. Thus, condensed sulfur as liquid sulfur 117 in the furnace exhaust gas 115 (sent to vessel 104) may be pumped from vessel 104 for combustion as vapor in the first zone 101a of the furnace. Liquid sulfur (other than liquid sulfur 117) may be added to vessel 104. This additional liquid sulfur may constitute consumption of sulfur vapor 111 in the furnace. In the case of a hydrogen production system 100 located in a sulfur recovery plant, one or more SRUs may discharge elemental liquid sulfur to vessel 104. On the other hand, the additional liquid sulfur added to vessel 104 can come from another source.

[0052] The furnace exhaust gas 115 (minus the elemental sulfur 117) exits the condenser 103 as process gas 118. The temperature of the process gas 118 exiting the condenser 103 may be less than 165°C and may be less than the temperature of the cooled furnace exhaust gas 115 entering the condenser 103. The process gas 118 may include H and SO produced in the water-gas shift reaction of SO in the second zone 101b of the furnace. The process gas 118 may include residual elemental sulfur, such as relatively small amounts of S vapor and / or entrained liquid S.

[0053] The process gas 118 may flow from the condenser 103 to the quench tower 105. Heat tracing 119 may be disposed along the conduit carrying the process gas 118 to the quench tower 105 to prevent or reduce sulfur deposition (from elemental S) in the process gas 118. The heat tracing 119 may be, for example, electric tracing or steam tracing that generates heat to maintain the temperature of the process gas 118 flowing through the conduit. The electric tracing may be an electric heating element (electric tracing heating cable) that extends in physical contact along the length of the conduit and generates heat. The steam tracing may be a relatively small diameter pipe through which steam is routed to heat the conduit and maintain the temperature of the process gas 118. The conduit may be covered with insulation to retain heat loss from the conduit. The heat tracing 119 may be a component of a heat tracing system.

[0054] The process gas 118 enters the quench tower 105 (e.g., at the bottom of the quench tower 105) and flows upward through the quench tower 105 (e.g., a vertical vessel) countercurrently to the aqueous sulfurous acid solution 122, which flows downward through the quench tower 105. The aqueous sulfurous acid solution 122 may be cooled (e.g., to 60°C) in a cooler 107 and may be a relatively dilute sulfurous acid solution in water, and thus may be referred to as cooled acid water. In the quench tower 105, contact between the gas 118 and the sulfurous acid solution 122 cools the gas, e.g., to 60°C. The quench tower 105 vessel may have packing or trays within the vessel to increase contact between the gas (flowing upward through the tower 105) and the sulfurous acid solution 122 (flowing downward through the tower 105). The sulfurous acid solution 122 may be referred to as a quench medium. Residual elemental S in the process gas stream 118 can be converted to soluble polythionic acids in the presence of excess sulfurous acid. Thus, little or no sulfur solids may accumulate in the quench tower 105.

[0055] In the quench tower 105, the H2 in the process gas can be separated from the SO2 in the process gas 118 by absorbing the SO2 into sulfurous acid 122. The SO2 absorbed in water can produce sulfurous acid.

[0056] Hydrogen gas 124 may be discharged upward from quench tower 105. In implementations, hydrogen gas 124 may be a product of hydrogen production system 100. Hydrogen gas 124 may be utilized as a product or may be processed to purify hydrogen gas as a product.

[0057] In the quench tower 105, the sulfurous acid 122 may become more concentrated as it absorbs SO. However, makeup water 120 added to the aqueous sulfurous acid solution 121 discharged from the tower 105 may maintain dilution of the sulfurous acid. The aqueous sulfurous acid solution 121 may be discharged from the bottom of the quench tower 105 (e.g., as a bottoms stream). Makeup water 120 may also be added to the sulfurous acid 121 (e.g., to constitute the water in the portion 123 of the sulfurous acid 121 sent to the oxidation tower 108). The sulfurous acid 121 may be sent to the top of the quench tower 105 via pump 106 through a cooler 107 heat exchanger (e.g., an air cooler using ambient air as a cooling medium). The cooler 107 may cool (reduce the temperature of) the sulfurous acid 121 (e.g., to a temperature below 60°C) to produce sulfurous acid 122 that enters the top of the quench tower 105 and flows downwardly through the quench tower 105. The composition of the sulfurous acid 121 entering the cooler 107 may be the same as the composition of the sulfurous acid 122 exiting the cooler.

[0058] A portion 123 of the aqueous sulfurous acid solution 121 (e.g., upstream of the cooler 107) may be sent to the oxidation tower 108 vessel (e.g., a tower or vertical vessel). The portion 123 of the aqueous sulfurous acid solution 121 may be a representative portion of the sulfurous acid solution 121 in that the portion 123 has the same composition as the sulfurous acid solution 121 discharged from the pump 106. The portion 123 of the aqueous sulfurous acid solution 121 may enter the top of the oxidation tower 108 and flow downward within the oxidation tower 108 in a countercurrent direction to the air 126 flowing upward through the oxidation tower 108. The air 126 may be introduced into the bottom of the oxidation tower 108 via a blower 108 (e.g., a centrifugal fan). In implementations, the blower 109 may receive ambient air and exhaust it with the air 126.

[0059] In oxidation tower 108, oxygen gas in air 126 can oxidize aqueous sulfurous acid solution (HSO) to sulfuric acid (HSO). Oxidation tower 108 vessel may have packing or trays within the tower to increase contact between the air (flowing upward within tower 108) and the sulfurous acid 123 flowing downward within tower 108. Overhead gas 125 (e.g., air substantially depleted of oxygen) emerging upward from oxidation tower 108 can generally be air 126 minus O gas from air 126 utilized (consumed) in the oxidation of HSO to HSO. Thus, overhead gas 125 can be N gas containing some O gas (e.g., 2-4% O by volume).

[0060] The aqueous sulfuric acid solution 127 can be discharged from the bottom of the column 108 (e.g., as a bottoms stream) and sent through the membranes of the membrane system 110. The membrane system can include a container that holds the membranes. The membranes can be nanofiltration (NF) membranes, reverse osmosis (RO) membranes, etc., within the associated membrane system 110. Membrane treatment of acidic aqueous wastes is well known in the mining industry. Polymeric membranes are applicable for sulfuric acid recovery. One example of an applicable polymeric membrane is TFC-HR (thin film composite polyamide membrane) from Koch Membrane Systems, available from Koch Industries, Inc., headquartered in Wichita, Kansas, USA. Another example of an applicable polymeric membrane is HYDRACoRe70pHT (sulfonated polyethersulfone membrane) from Hydranautics, a division of Nitto Denko Corporation, headquartered in Osaka, Japan. Yet another example is Desal KH (piperazine-based polyamide membrane) available from Suez Waters USA Inc., headquartered in Revose, Pennsylvania USA.

[0061] The membranes of membrane system 110 output sulfuric acid 133 (e.g., more concentrated than the influent sulfuric acid 127) as a retentate and relatively pure or clean water 129 as a permeate. A portion 128 (e.g., relatively concentrated) of the sulfuric acid 133 may be removed as a useful product. Another portion 113 of the sulfuric acid 133 may be fed (e.g., conveyed via a conduit) to a furnace to enrich the furnace (e.g., first zone 101a) with oxygen, aspects of which may be described in U.S. Pat. No. 4,826,670, U.S. Patent Application Publication No. 2022 / 0177306, and U.S. Patent Application Publication No. 2022 / 0199908, all three of which are incorporated herein by reference in their entireties. Portions 113, 128 may have the same composition (same concentration of sulfuric acid in water).

[0062] Conventional techniques for producing H2 either produce carbon dioxide CO2 (such as in hydrocarbon steam reforming) or are slow (such as in water electrolysis) and produce relatively small amounts of H2.

[0063] In this embodiment, a novel series of reactions (partial combustion of S vapor and water-gas shift of SO) is used in a furnace to produce hydrogen and sulfur dioxide. Hydrogen can be isolated from the furnace exhaust gas as a product. Sulfur dioxide can be converted to sulfuric acid downstream. The additional product, sulfuric acid, can be monetized and / or sent to the furnace (e.g., a Claus-type furnace) to enrich the furnace with oxygen. Thus, this technology addresses H production from the partial combustion of S vapor and the water-gas shift of SO, achieving the production of hydrogen and sulfuric acid from sulfur. The production of intermediate SO comes from the partial combustion of sulfur vapor, which is not readily available for combustion of sulfur liquids or hydrogen sulfide.

[0064] The H2 and sulfuric acid production process can be performed on-site with an existing SRU (and / or SRU tail gas processing). The elemental sulfur starting material can be available from the SRU. Again, the sulfuric acid can be monetized and / or utilized to enrich the furnace with oxygen.

[0065] 7 is a method 700 for producing hydrogen gas. The method may further include producing sulfuric acid as a co-product. In implementations, the method may be for the co-production of hydrogen gas and sulfuric acid.

[0066] In block 702, the method includes converting sulfur vapor and oxygen gas to sulfur monoxide in a first zone of the furnace. The first zone may be an initial zone of a combustion chamber of the furnace vessel. The sulfur vapor and oxygen gas may be supplied to the first zone from outside the furnace, or the sulfur vapor and oxygen gas may be supplied separately, mixed in the initial part of the furnace (e.g., via a nozzle), and introduced (and ignited) into the first zone for partial combustion of the sulfur vapor. The conversion of the sulfur vapor and oxygen gas to sulfur monoxide in the first zone may be due to partial combustion of the sulfur vapor. Partial combustion of the sulfur vapor may be defined as the conversion of the sulfur vapor and oxygen gas to SO, where the combustion uses less than stoichiometric oxygen gas relative to the sulfur vapor.

[0067] At block 704, the method includes converting sulfur monoxide and water in a second zone of the furnace to hydrogen gas and sulfur dioxide. The SO may flow from the first zone to the second zone. The method may include injecting water into the second zone. The water may be injected into the second zone from outside the furnace. The conversion of the SO and water to H and SO in the second zone may be a water-gas shift reaction of SO. The produced hydrogen gas may be recovered downstream as a product. The produced SO may be utilized downstream to produce sulfuric acid as a product.

[0068] In block 706, the method may include cooling the kiln gas in a heat exchanger portion of the furnace after the second zone (e.g., 101c in FIG. 6). The method includes exhausting kiln exhaust gas from the furnace, the kiln exhaust gas comprising hydrogen gas and sulfur dioxide produced in the second zone of the furnace.

[0069] The method may include supplying liquid sulfur from a vessel (e.g., the vessel of block 708) to the heat exchanger section as a cooling fluid. Thus, the method may include cooling kiln gases from the second zone in the heat exchanger section of the furnace using the liquid sulfur as a cooling medium. Cooling the kiln gases through the heat exchanger section vaporizes the liquid sulfur into sulfur vapor, which is supplied to the first zone. Thus, the method may include vaporizing the liquid sulfur in the heat exchanger section into sulfur vapor, which is supplied to the first zone.

[0070] Supplying the liquid sulfur may involve pumping (via a pump) the liquid sulfur from a container. Supplying the liquid sulfur may include flowing the liquid sulfur from the container through a cross-exchanger (heat exchanger) external to the furnace to a heat exchanger portion of the furnace and heating the liquid sulfur in the cross-exchanger with heat from the furnace exhaust gas, and discharging the furnace exhaust gas from the furnace includes discharging the furnace exhaust gas from the furnace through the cross-exchanger to a condenser.

[0071] At block 708, the method includes condensing elemental sulfur vapor in the furnace exhaust gas to elemental liquid sulfur in a condenser. The condenser is a heat exchanger downstream of the furnace. The method includes discharging the liquid sulfur from the condenser to a container (e.g., a sulfur pit) and discharging a process gas from the condenser to a quench tower. The process gas includes hydrogen gas and sulfur dioxide from the furnace exhaust gas. The process gas may be the furnace exhaust gas minus the condensed sulfur vapor that is discharged as liquid sulfur from the condenser.

[0072] At block 710, the method includes absorbing sulfur dioxide from the process gas with sulfurous acid in a quench tower and discharging hydrogen gas from the process gas from the quench tower. In implementations, the hydrogen gas may be discharged from the quench tower as a product. The hydrogen gas may be discharged upward from the quench tower.

[0073] The method may include discharging sulfurous acid (aqueous sulfurous acid solution) from the quench tower. The method may include recycling a portion of the discharged sulfurous acid to the quench tower as a quench medium and feeding another portion of the discharged sulfurous acid to the oxidation tower.

[0074] In block 712, the method may include oxidizing sulfurous acid (within the oxidation tower) to sulfuric acid using oxygen from air injected into the oxidation tower. The method may include discharging a bottoms stream having sulfuric acid from the bottom of the oxidation tower through a membrane system including a membrane. The method may include discharging water from the membrane as a permeate and discharging sulfuric acid from the membrane as a retentate, wherein the sulfuric acid concentration in the retentate is higher than the sulfuric acid concentration in the bottoms stream. In an implementation, injecting water into a second zone of the furnace (block 704) may include injecting water discharged from the membrane as a permeate into the second zone. The method may include supplying at least a portion of the retentate to the furnace for combustion in a first zone of the furnace, or supplying at least a portion of the retentate as a sulfuric acid product (e.g., discharged from a hydrogen production system), or a combination thereof. The method may include supplying at least a portion of the retentate as a sulfuric acid product discharged from the hydrogen production system.

[0075] One embodiment is a method for producing hydrogen, comprising: converting sulfur vapor and oxygen gas to sulfur monoxide in a first zone of a furnace; injecting water into a second zone of the furnace; converting the sulfur monoxide and water to hydrogen gas and sulfur dioxide in the second zone; and exhausting a furnace exhaust gas from the furnace, the furnace exhaust gas comprising hydrogen gas and sulfur dioxide. The conversion of the sulfur vapor and oxygen gas to sulfur monoxide in the first zone can be partial combustion of the sulfur vapor or can involve partial combustion of the sulfur vapor. The conversion of the sulfur monoxide and water to hydrogen gas and sulfur dioxide in the second zone can be a water-gas shift reaction of the sulfur monoxide or can involve a water-gas shift reaction of the sulfur monoxide. The operating temperature of at least one of the first and second zones can be in the range of 802°C to 1608°C, or, for example, in the range of 1100°C to 1350°C.

[0076] The method includes condensing sulfur vapor in the furnace exhaust gas to liquid sulfur in a condenser (heat exchanger) downstream of the furnace, discharging the liquid sulfur from the condenser to a container, and discharging a process gas from the condenser to a quench tower, the process gas comprising hydrogen gas and sulfur dioxide. The method also includes absorbing sulfur dioxide from the process gas with sulfurous acid in the quench tower, and discharging hydrogen gas from the process gas from the quench tower.

[0077] The method may include cooling furnace gases in a heat exchanger section of the furnace after the second zone and supplying liquid sulfur from a container to the heat exchanger section as a cooling fluid. Cooling the furnace gases through the heat exchanger section vaporizes the liquid sulfur into sulfur vapor that is supplied to the first zone. In this case, supplying liquid sulfur may include flowing liquid sulfur from the container through a cross-exchanger external to the furnace to the heat exchanger section of the furnace and heating the liquid sulfur in the cross-exchanger with heat from the furnace exhaust gas. Discharging furnace exhaust gases from the furnace includes discharging furnace exhaust gases from the furnace through the cross-exchanger to a condenser.

[0078] The method may include discharging sulfurous acid from the quench tower (the sulfurous acid is an aqueous sulfurous acid solution); supplying a portion of the sulfurous acid discharged from the quench tower to an oxidation tower; and oxidizing the sulfurous acid to sulfuric acid in the oxidation tower using oxygen from air injected into the oxidation tower. In this case, the method may include discharging a sulfuric acid-containing bottoms stream from the oxidation tower through a membrane system including a membrane; discharging water from the membrane as a permeate; and discharging sulfuric acid from the membrane as a retentate. The retentate has a higher concentration of sulfuric acid than the bottoms stream. Injecting water into a second zone of the furnace may include injecting the water discharged from the membrane as a permeate into the second zone.

[0079] Another embodiment is a method for producing hydrogen, comprising: converting sulfur vapor and oxygen gas to sulfur monoxide in a first zone of a furnace; and converting sulfur monoxide and water to hydrogen gas and sulfur dioxide in a second zone of the furnace, where water is injected into the second zone. The method includes cooling furnace gas from the second zone in a heat exchanger section of the furnace using liquid sulfur as a cooling medium, vaporizing the liquid sulfur in the heat exchanger section into sulfur vapor that is fed to the first zone, and discharging furnace exhaust gas from the furnace, the furnace exhaust gas comprising hydrogen gas and sulfur dioxide. The method also includes condensing the sulfur vapor in the furnace exhaust gas into liquid sulfur in a condenser (heat exchanger) downstream of the furnace, and discharging the liquid sulfur from the condenser to a container.

[0080] The method may include discharging a process gas from the condenser to a quench tower, the process gas comprising hydrogen gas and sulfur dioxide, absorbing sulfur dioxide from the process gas with sulfurous acid (aqueous sulfurous acid solution) in the quench tower, and discharging hydrogen gas as a product from the quench tower. The method may include oxidizing the sulfurous acid (from the quench tower) to sulfuric acid using air in an oxidation tower, and discharging a bottoms stream comprising sulfuric acid from the oxidation tower through a membrane system comprising a membrane. The method may include discharging water from the membrane as a permeate, discharging sulfuric acid from the membrane as a retentate, the retentate having a higher concentration of sulfuric acid than the bottoms stream, and providing at least a portion of the retentate as a sulfuric acid product discharged from the hydrogen production system.

[0081] Yet another embodiment is a hydrogen production system including a furnace that converts sulfur vapor and oxygen gas to sulfur monoxide in a first zone of the furnace and receives water injected into a second zone of the furnace, converting the sulfur monoxide and water to hydrogen gas and sulfur dioxide in the second zone. The conversion of the sulfur vapor and oxygen gas to sulfur monoxide in the first zone can be partial combustion of the sulfur vapor or can involve partial combustion of the sulfur vapor. The conversion of the sulfur monoxide and water to hydrogen gas and sulfur dioxide in the second zone can be a water-gas shift reaction of the sulfur monoxide or can involve a water-gas shift reaction of the sulfur monoxide. The hydrogen production system includes a condenser heat exchanger that receives furnace exhaust gas from the furnace, condenses the sulfur vapor in the furnace exhaust gas into liquid sulfur, discharges the liquid sulfur to a container, and discharges a process gas containing hydrogen gas and sulfur dioxide to a quench tower. The hydrogen production system includes a quench tower that absorbs sulfur dioxide from the process gas with sulfurous acid and discharges hydrogen gas.

[0082] The furnace may have a heat exchanger section after the second zone that cools furnace gases in the furnace and vaporizes liquid sulfur as a cooling medium into sulfur vapor that is supplied to the first zone, the heat exchanger section being configured to receive liquid sulfur from the vessel. The hydrogen production system may include a cross-exchanger that heats the liquid sulfur from the vessel using furnace exhaust gas discharged from the furnace.

[0083] The hydrogen production system may include an oxidation tower that receives the sulfurous acid discharged from the quench tower, oxidizes the sulfurous acid to sulfuric acid using air, and discharges a bottoms stream containing sulfuric acid. The hydrogen production system may include a membrane system that receives the bottoms stream and discharges water as a permeate from the membrane and sulfuric acid as a retentate from the membrane, the retentate having a higher concentration of sulfuric acid than the bottoms stream. The water injected into the second zone of the furnace may be the water discharged from the membrane as a permeate or may include the water discharged from the membrane as a permeate. The membrane may be configured to discharge at least a portion of the retentate to the furnace for combustion in the first zone, or to discharge at least a portion of the retentate as a sulfuric acid product, or a combination thereof.

[0084] Although several implementations have been described, it will nevertheless be understood that various modifications may be made without departing from the spirit and scope of the disclosure.

Claims

1. converting sulfur vapor and oxygen gas into sulfur monoxide in a first zone of the furnace; injecting water into a second zone of the furnace; converting said sulfur monoxide and said water to hydrogen gas and sulfur dioxide in said second zone; Discharging furnace exhaust gas from the furnace, the furnace exhaust gas comprising the hydrogen gas and the sulfur dioxide; condensing sulfur vapor in the furnace exhaust gas into liquid sulfur in a condenser downstream of the furnace, the condenser comprising a heat exchanger; Discharging the liquid sulfur from the condenser into a vessel; Discharging a process gas from the condenser to a quench tower, the process gas comprising the hydrogen gas and the sulfur dioxide; absorbing the sulfur dioxide from the process gas with sulfurous acid in the quench tower; Discharging the hydrogen gas from the process gas from the quench tower; A method for producing hydrogen, comprising:

2. 2. The method for producing hydrogen according to claim 1, wherein converting sulfur vapor and oxygen gas to sulfur monoxide in the first zone comprises partial combustion of the sulfur vapor, and converting the sulfur monoxide and water to hydrogen gas and sulfur dioxide in the second zone comprises a water-gas shift reaction of the sulfur monoxide, and an operating temperature of at least one of the first zone and the second zone is in the range of 802°C to 1608°C.

3. cooling furnace gases in the furnace in a heat exchanger portion of the furnace after the second zone; supplying the liquid sulfur from the vessel as a cooling fluid to the heat exchanger section; Including, cooling the furnace gas through the heat exchanger section vaporizes the liquid sulfur into the sulfur vapor that is fed to the first zone; The method for producing hydrogen according to claim 1 .

4. 4. The method for producing hydrogen as described in claim 3, wherein supplying the liquid sulfur comprises flowing the liquid sulfur from the container through a cross exchanger external to the furnace to the heat exchanger portion of the furnace and heating the liquid sulfur in the cross exchanger with heat from the furnace exhaust gas, and discharging the furnace exhaust gas from the furnace comprises discharging the furnace exhaust gas from the furnace through the cross exchanger to the condenser.

5. Discharging the sulfurous acid from the quench tower, the sulfurous acid comprising an aqueous sulfurous acid solution; supplying a portion of the sulfurous acid discharged from the quenching tower to an oxidation tower; oxidizing the sulfurous acid to sulfuric acid in the oxidation tower using oxygen from air injected into the oxidation tower; The method for producing hydrogen according to claim 1 , comprising:

6. Discharging a sulfuric acid-containing bottoms stream from the oxidation tower through a membrane system comprising a membrane; Discharging water as permeate from the membrane; Discharging sulfuric acid from the membrane as a retentate, the retentate having a higher concentration of sulfuric acid than the bottoms stream; The method for producing hydrogen according to claim 5, comprising:

7. 7. The method for producing hydrogen according to claim 6, wherein injecting water into the second zone of the furnace comprises injecting the water discharged from the membrane as a permeate into the second zone, and wherein an operating temperature of at least one of the first zone and the second zone is in the range of 1100°C to 1350°C.

8. 7. The method of claim 6, comprising at least one of: supplying at least a portion of the retentate to the furnace for combustion in the first zone; and supplying at least a portion of the retentate as a sulfuric acid product.

9. converting sulfur vapor and oxygen gas into sulfur monoxide in a first zone of the furnace; converting the sulfur monoxide and water to hydrogen gas and sulfur dioxide in a second zone of the furnace, the water being injected into the second zone; cooling furnace gases from the second zone in a heat exchanger portion of the furnace using liquid sulfur as a cooling medium; vaporizing the liquid sulfur in the heat exchanger section into sulfur vapor that is fed to the first zone; Discharging furnace exhaust gas from the furnace, the furnace exhaust gas comprising the hydrogen gas and the sulfur dioxide; condensing sulfur vapor in the furnace exhaust gas into liquid sulfur in a condenser downstream of the furnace, the condenser comprising a heat exchanger; Discharging the liquid sulfur from the condenser into a vessel; A method for producing hydrogen, comprising:

10. Discharging a process gas from the condenser to a quench tower, the process gas comprising the hydrogen gas and the sulfur dioxide; Absorbing the sulfur dioxide from the process gas with sulfurous acid in the quench tower, the sulfurous acid comprising an aqueous sulfurous acid solution; Discharging the hydrogen gas as a product from the quench tower; The method for producing hydrogen according to claim 9, comprising:

11. oxidizing the sulfurous acid from the quench tower to sulfuric acid using air in an oxidation tower; Discharging the sulfuric acid-containing bottoms stream from the oxidation tower through a membrane system comprising a membrane; The method for producing hydrogen according to claim 10, comprising:

12. Discharging water as permeate from the membrane; Discharging sulfuric acid from the membrane as a retentate, the retentate having a higher concentration of sulfuric acid than the bottoms stream; providing at least a portion of the retentate as sulfuric acid product discharge from a hydrogen production system; The method for producing hydrogen according to claim 11, comprising:

13. a furnace for converting sulfur vapor and oxygen gas into sulfur monoxide in a first zone of the furnace, receiving water injected into a second zone of the furnace and converting the sulfur monoxide and water into hydrogen gas and sulfur dioxide in the second zone; a condenser heat exchanger that receives furnace exhaust gas from the furnace, condenses sulfur vapor in the furnace exhaust gas into liquid sulfur, discharges the liquid sulfur to a vessel, and discharges a process gas comprising hydrogen gas and sulfur dioxide to a quench tower; the quench tower, which absorbs sulfur dioxide from the process gas into sulfurous acid and discharges hydrogen gas; A hydrogen production system comprising:

14. 14. The hydrogen production system of claim 13, wherein converting the sulfur vapor and oxygen gas to sulfur monoxide in the first zone comprises partial combustion of the sulfur vapor, and converting the sulfur monoxide and the water to hydrogen gas and sulfur dioxide in the second zone comprises a water-gas shift reaction of the sulfur monoxide.

15. 14. The hydrogen production system of claim 13, wherein the furnace comprises a heat exchanger portion of the furnace after the second zone that cools furnace gas in the furnace and vaporizes liquid sulfur as a cooling medium into the sulfur vapor that is supplied to the first zone, the heat exchanger portion being configured to receive the liquid sulfur from the container.

16. 16. The hydrogen production system of claim 15, comprising a cross-exchanger that heats the liquid sulfur from the vessel using the furnace exhaust gas discharged from the furnace.

17. 14. The hydrogen production system according to claim 13, further comprising an oxidation tower that receives the sulfurous acid discharged from the quench tower, oxidizes the sulfurous acid to sulfuric acid using air, and discharges a bottoms stream containing the sulfuric acid.

18. 18. The hydrogen production system according to claim 17, comprising a membrane system having a membrane that receives the bottoms stream, discharges water from the membrane as a permeate, and discharges sulfuric acid from the membrane as a retentate, wherein the retentate has a higher concentration of sulfuric acid than the bottoms stream.

19. 20. The hydrogen production system of claim 18, wherein the water injected into the second zone of the furnace comprises the water exiting the membrane as permeate.

20. 20. The hydrogen production system of claim 18, wherein the membrane is configured to at least one of discharge at least a portion of the retentate to the furnace for combustion in the first zone and discharge at least a portion of the retentate as a sulfuric acid product.

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