UA124441C2 - METHOD OF OBTAINING HYDROGEN - Google Patents

Abstract

The invention relates to methods for producing hydrogen by electrolysis, methods for hydrogen purification, separation, concentration and reduction of hydrogen. The present invention also relates to methods of purifying streams from sulfur-containing and nitrogen-containing substances and concomitantly producing sulfur or sulfuric acid. To obtain hydrogen, provide stream A, which contains at least one reducing substance, and the concentration of unsaturated hydrocarbons in stream A is lower than 100 ppm, and a single-phase stream of liquid B containing water, bromine and bromic acid, and mass the proportion of bromic acid in stream B does not exceed 62 wt.%. These streams are introduced into contact to obtain bromic acid from bromine. After contacting streams A and B receive a liquid stream containing water, bromic acid and residual bromine, which is single-phase, where the molar ratio of bromine and bromic acid is less than or equal to 1, and the side stream containing at least one non-oxidized bromine substance, separated. The obtained single-phase liquid stream is directed to the cell to convert at least part of the bromic acid to bromine and hydrogen, and the potential in the cell does not exceed 1.23 V relative to the standard hydrogen electrode. The resulting liquid stream is redirected to the first stage, and the temperature at each stage in which bromine is present is maintained below 80 ° C.

Description

methods of cleaning streams from sulfur-containing and nitrogen-containing substances and concomitant production of sulfur or sulfuric acid. To produce hydrogen, stream A containing at least one reducing agent is provided, wherein the concentration of unsaturated hydrocarbons in stream A is lower than 100 ppm, and a single-phase liquid stream B containing water, bromine, and bromic acid, wherein the mass the proportion of bromic acid in stream B does not exceed 62 wt.95. The specified streams are brought into contact with the production of bromic acid from bromine. After contact of streams A and B, a liquid stream containing water, bromic acid and residual bromine is obtained, which is single-phase, where the molar ratio of bromine to bromic acid is less than or equal to 1, and a side stream containing at least one non-bromine-oxidized substance, separate

The resulting single-phase flow of liquid is sent to the electrolyzer to convert at least part of the bromic acid to bromine and hydrogen, and the potential in the electrolyzer does not exceed 1.23 V relative to the standard hydrogen electrode. The resulting liquid flow is redirected to the first stage, and the temperature in each stage in which bromine is present is maintained below 80 °C.

In ShNk Soya Sh

The invention belongs to methods of obtaining hydrogen by electrolysis of an aqueous solution of bromic acid; also methods of hydrogen purification, separation, concentration and recovery of hydrogen, as well as methods of purification of streams from sulfur-containing and nitrogen-containing compounds.

The method of obtaining hydrogen

Hydrogen can be obtained from several sources, such as fossil fuels, biomass, water and even H25, or extracted from natural gas (natural hydrogen). Recent scientific and technical work has highlighted the possibility that commercially valuable low-cost natural hydrogen may exist in many places around the world. According to forecasts, the demand for hydrogen will increase significantly in the coming decades. According to the Hydrogen Council (ref:/puagodepsoipsiisot/lmr-sopiep/irioad5/2017/11/Nuagodep-zsaiipd-ir-Nuigodep-Soishpsii. rai), the adoption of hydrogen as one of the central pillars of deep decarbonization of the transport, industrial and energy sectors is potentially could result in a 10-fold increase in hydrogen demand, increasing from 8 EJ (2015) to nearly 80 EJ by mid-century. Today, the largest share (48 95) in hydrogen production is occupied by steam methane reforming (SMR), followed by catalytic reforming of liquid hydrocarbons (30 90) and coal gasification (18 95). Currently, the conversion of fossil fuels into hydrogen produces a significant amount of CO2 as a by-product. In general, global production of hydrogen at current levels leads to the emission of approximately 500 million tons of CO" per year (IEA,

Tesppoiosdu VNoadtar: Nudgodep apa Biye!yi Seiyiye, 2015). Global production of hydrogen from water electrolysis is gaining momentum and could increase significantly in the long term as large-scale renewable electricity becomes more readily available.

However, this technology consumes a huge amount of electricity per mole of hydrogen, requires significant water resources, does not use co-produced oxygen, and requires a large capital investment (uses a precious metal such as iridium). However, in all mentioned hydrogen production technologies, separation, purification and compression of hydrogen are required.

Possible methods of hydrogen separation and recovery are: (1) adsorption with a pressure difference (APD): this technology relies on the differences in the adsorption properties of gases to separate them under pressure and is a way to obtain pure hydrogen; (2) hydrogen-permeable membranes: they are generally divided into three classes - polymeric

From membranes, inorganic (non-metallic porous or non-porous) membranes and dense (non-porous) metallic membranes; (3) chemical-cyclic and advanced adsorption systems with hydride-type materials; (4) cryogenic or low-temperature technologies for the separation of gases based on the difference in their boiling points: the application of this technology for the separation of Hg requires cooling the gas to cryogenic temperatures of -200 "C.

The choice of the most suitable hydrogen production technology depends on the quality of available raw materials, the required purity of hydrogen and production capacity. In many cases, the subsequent use of hydrogen requires a high-pressure flow, which can only be done with the help of gas compressors. A proven method of hydrogen compression is the use of piston compressors. Widely used in oil refineries, they are the basis of oil processing. Reciprocating compressors are usually available in both oil-lubricated and non-lubricated; for high pressure (350-700 bar) non-lubricated compressors are preferred to avoid contamination of hydrogen by lubricant.

If there are known solutions to this technical problem, what or in what way are previous solutions lacking?

In APT methods, impurities (СНа, СО», СО, Н2О, etc.) in the gas stream are removed in adsorbent layers. Adsorbents are usually made of molecular sieves, activated alumina or silica gel, depending on the nature of the impurities. Impurities are adsorbed at a higher partial pressure and desorbed at a lower pressure. Adsorption of Neo compared to other gases and light hydrocarbons is not very significant; therefore it is obtained as highly purified. The adsorbent layer or layers are regenerated by reducing the pressure from the raw gas to the pressure of the tail gas and subsequently by purging part of the obtained NO. The process of adsorption due to the above reason is known in industry as pressure difference adsorption (PDA). This method is more suitable for high concentration hydrogen flow. Usually, depending on the tail gases, about 60-85 No is obtained if a high purity of 99.9 95 is desired.

Hydrogen recovery reduces the content of heavy hydrocarbons (HHC) and should be used as a way to avoid the phenomenon of condensation. The main limitation of the APT approach is the ratio of hydrogen recovery to hydrogen purity; unreduced hydrogen must either be returned or lost.

Membrane flows can be used to extract hydrogen from highly concentrated flows with a purity of more than 80 95. This technology is very sensitive to impurities, especially to the presence of Na5, H2gO, C3-hydrocarbons. Typically, about 9595 Ne is recovered with a purity greater than 9095. Membrane separation is not efficient enough and is not suitable for obtaining pure hydrogen. The presence of impurities limits their service life.

For metal hydrides, the main problem is limited specific adsorption capacity, which will require a huge amount of material for separation, and high sensitivity to impurities. The best achievable limit of adsorption is about 0.07 kg of Ne" per kg of material.

The cryogenic process is a low-temperature separation process that uses the difference in boiling points (relative volatilities) of the components of the raw materials to perform the separation. Does not have a very high relative volatility compared to hydrocarbons. Therefore, the cryogenic process has been used for many years to recover H»5 from gaseous wastes of refineries and petrochemical industries.

For the production of He from feed streams containing low-boiling impurities such as

СО and M», a СНa washing column is used, which washes impurities from the He stream. The content of CO" and water must be reduced to less than 1 ppm by passing the raw material stream through a gas dehydration system. CO is removed in the amine treatment column to a level of 100 ppm.

The cryogenic process is thermodynamically more efficient than other ways of improving H." A high recovery factor in the range of 92-98 95 is easily achieved at a purity of 95 95, and losses with increasing hydrogen purity are smaller than for membrane systems.

The main disadvantage of all discussed processes is the high cost, high energy requirement, moderate hydrogen recovery rate and the need to calculate the design for highly concentrated H flows.

A higher content of Neo in the raw material favors membrane and APT methods, and a lower content of Neg favors cryogenic separation. Streams with 75-90 rpm. 95 are not the most cost-effective to clean with an APT or membrane method, with the choice depending on flow, pressure, and pretreatment requirements. Cryogenic separation technology is applicable for large flows from 30-75 06.95 No. The higher the SN content in the stream, the more Joule-Thomson cooling is available for the cryogenic method.

If it is not formed as a result of steam reforming of SNa (natural gas) or oil, c

There are no heavier hydrocarbons from the gaseous reforming product. The gaseous product of reforming mainly consists of Hg, CO, CO" and M2. The H?e stream can only be cleaned with an APT system, as it is the only process that can remove the above components easily and completely.

If the NO stream is a gaseous waste from an oil refinery, then the content of heavier hydrocarbons (Se) is an important factor in the development of all three methods. Membrane systems will remove these components, but higher concentrations increase the retentate condensation temperature, making system reliability more dependent on the proper operation of the pretreatment system. APT systems will remove heavier hydrocarbons, but higher concentrations result in larger systems with poorer recovery due to difficulty removing these impurities from the adsorbents. The concentration of heavier hydrocarbons in the feed to the cryogenic plant must be limited to avoid freezing in the process, which makes this system also more dependent on the operation of the pretreatment plants.

Due to its high boiling point, benzene is of particular concern in membrane and cryogenic processes.

If the gas stream contains H25 and MO;x that must be removed, the membrane process is not suitable because H25 has a relatively high permeation rate and will exit with the resulting

Not. If Ne»b is present in concentrations exceeding several hundred ppm, then the APT method is advantageous, since the cryogenic process requires a separate system for removing Neoo.

Changes in concentration in raw materials

If there is a gradual change in the quality of the feedstock, it will affect the performance of all separation technologies. Thus, the flexibility of the treatment system must be sufficient to respond to changes in the quality of the raw material, with a response time that does not cause interruptions in the process. The APT method is the most flexible of the three considered in terms of its ability to maintain Hg purity and recovery under changing conditions. As the concentration of the impurity in the raw material increases (at a constant pressure of the raw material), the partial pressure of the impurity also increases. An increase in the partial pressure of the impurities usually leads to an increase in the amount of the impurity that would be adsorbed. Thus, this method is largely self-compensating, and even relatively large changes in the concentrations of impurities in the feedstock have little effect on the purity of the hydrogen, but reduce the recovery rate.

In membrane methods, an increase in the concentration of an impurity in the raw material tends to cause an increase in the concentration of this particular impurity in the product. Product purity can be maintained for small changes in feed composition by adjusting the feed to permeate pressure ratio. However, the relatively strong effect of product purity on recovery for these systems means that recovery cannot be significantly affected. The response time of membrane systems is essentially instantaneous, and corrective action has immediate results, but operators have less time to react.

The cryogenic process is less flexible than the other two processes. Particular attention should be paid to the high freezing point components that are removed in the pretreatment system, as failure to remove these contaminants can lead to plugging of the heat exchangers. Changes in the concentration of raw material components with lower boiling points directly affect the purity of the product. It does not affect recovery much.

None of these techniques are economical for hydrogen recovery from dilute waste streams.

The method of cleaning sulfur-containing streams.

To use the electrolysis of bromic acid as a method of obtaining hydrogen, it is necessary to provide a reducing agent for the repeated production of bromic acid from bromine. One of the practically available reducing agents can be sulfur or sulfur-containing substances, hydrogen sulfide, and sulfur-containing organics. The source of sulfur-containing reducing agents is, in particular, natural gas; biogas; waste gases from

Refineries, incineration plants, coal-fired power plants, metallurgical plants; flue gases, exhaust gases, etc.

The treatment of streams containing H25 or other sulfur-containing compounds is now carried out in principle by two main approaches: (1) amine washing followed by the Klaus process. This method includes three stages: first, Na5, present in the streams, is adsorbed in an amine or a mixture of amines, and the purified ("sweet") gas stream is removed from the installation; then the formed saturated amine solution is sent to the desorption stage, where a gaseous stream saturated with Negb5 is formed, and the unsaturated amine is returned to the first stage; finally, Ne5 reacts with air in the Klaus furnaces to produce sulfur and water vapor;

(2) adsorption of pollutants on filters containing activated carbon as the main component; this commercial solution requires disposal of filters saturated with H»e25 after use; (3) Halogen cycles (M/01994001205А1 - with the help of catalytic oxidation of НВг to Вг?г,

OSH5B2O090028767A1 - oxidation of carbon-containing and sulfur-containing materials by halogens, i5B5433828A - oxidation of Нег5 and С52 in flue gases by bromine with subsequent electrolysis of НГ)

What or in what way is the previous decision lacking?

Amine wash/Claus method is energy intensive, capital intensive and only economical at high scale. Amine is an expensive consumable that must be gradually replaced due to thermal degradation. In addition, the presence of 5-organic compounds reduces efficiency and increases cleaning costs. The resulting elemental sulfur is of low quality, which hinders the possibility of its sale. It is worth noting that this solution is not economically justified for biogas processing, since the scale of biogas production is too small, and its delivery to treatment facilities requires either expensive transportation or investments in the entire pipeline network, which will significantly harm the capabilities of remote small biogas producers. Adsorption by carbon filters will require further infrastructure for the treatment of spent filter material.

The disadvantage of halogen cycles lies in the multiphase system of reactions. Bg2 is poorly soluble in water, and directing a two-phase system into an electrolytic cell destabilizes this system.

Moreover, the two-phase system will form an emulsion and will significantly reduce the efficiency of the oxidation process. For example, the reaction with water and bromine in I55433828A will be extremely difficult due to the separation of C52 phases, an aqueous solution of Na and water, and bromine. It should be noted that the process consumes a huge amount of water, and water must be added constantly.

It is not enough to recycle the reaction medium.

Technical task

This invention is aimed at solving several problems, the main of which is the optimization of the process of electrolysis of a solution of bromic acid in water in the presence of bromine to obtain hydrogen. Solving this problem leads to the creation of an optimal method of hydrogen production by electrolysis of a solution of bromic acid in water, as well as solving related problems - providing optimal methods for the simultaneous disposal of a number of reducing agents, which in turn solves the task of cleaning various streams from such reducing agents and producing related products by oxidation such restorers.

Solving the problem

The task is solved by taking into account the unique discovery of the inventors in the conditions of electrolysis, which became the basis of this invention. Namely, that the electrolysis of bromic acid in the water/bromic acid/bromine system is most effective in maintaining the single-phase system, i.e., that the resulting bromine does not form a separate liquid phase that separates from water. The inventors found that bromine dissolves in an aqueous solution of bromic acid, without forming a separate liquid phase, in a molar ratio to bromic acid not exceeding 1 (bromine:bromic acid "1). Conducting electrolysis under such conditions, it is possible to use more economical conditions for obtaining hydrogen, which are provided by the electrolysis of an aqueous solution of bromic acid compared to the electrolysis of water.

Useful results of the invention

The main technical result of this invention is the provision for the first time of a method of obtaining hydrogen by electrolysis of an aqueous solution of bromic acid in a single-phase system. An additional useful result is the concomitant utilization of reductants, necessary for the reduction of bromine and the formation of bromic acid to complete the cycle of reactions on which this method is based. A derivative technical result from the utilization of reductants is the accompanying purification of flows (in particular, flows of saturated hydrocarbons and CO2). Also, one of the additional technical results of this invention is the recovery of hydrogen from streams where hydrogen is present in small concentrations. And finally, one of the additional technical results is obtaining some oxidation products that are useful in themselves, in particular sulfuric acid or sulfur (or its condensed forms).

POSSIBILITY OF IMPLEMENTING THE INVENTION

Detailed description of the invention

In this section, the proposed invention will be described in terms of its best, preferred and most preferred embodiments.

In its most preferred embodiment, the technical solution of this invention is a method of obtaining hydrogen in which:

Zo (a) provide stream A, which contains at least one substance - a reducing agent, and a single-phase stream of liquid B, which contains water, bromine and bromic acid; (b) bring the specified streams into contact under conditions sufficient for the reaction of the components of stream A with bromine from stream B to produce bromic acid from bromine; (c) separate a side stream containing at least one non-oxidizable bromine substance; (d) obtain a liquid stream from step (b), wherein said liquid stream contains essentially water, bromic acid and residual bromine, and which is single-phase; (d) direct the specified flow of liquid from stage (d) to an electrolyzer to convert at least part of the bromic acid to bromine and hydrogen; and (e) receiving the liquid stream from stage (d) and redirecting it to stage (a).

As a substance that is not oxidized by bromine, in stage (c), we mean either the non-oxidizable component of stream A, or the product of the oxidation of the reducing agent from stream A by bromine incapable of further oxidation by bromine under the conditions of implementation of the method according to the invention, or both options.

In preferred embodiments of the method according to the invention, the separation of the side stream in stage (c) can occur, in particular, by means of decantation (when the streams of liquids do not mix), or the side stream is gaseous and thus facilitates its separation; also, the side stream may be aqueous and require, in particular, distillation for its separation.

In certain embodiments, the side stream in step (c) is further washed and dried, and optionally, at least one oxidation product of the reducing agent is separated from stream A.

In part of the preferred embodiments, the specified stream A in the method according to the invention contains as a reducing agent hydrogen in the amount of at least 500 ppm. other forms of hydrogen in flow A can be contained in amounts from 100 ppm. up to 90 95 by mass.

In other embodiments of the invention, the specified stream A can contain as a substance - reducing agent ammonia, nitrogen-containing organic compounds, amines and/or amides in the amount of at least 500 c.m. Accordingly, the side stream specified in stage (c) may contain nitrogen. In a separate embodiment of this invention, the above-mentioned flow A contains as a reducing agent carbon monoxide in an amount of at least 10 ppm.

In many preferred embodiments of this invention, the specified flow A contains sulfur-containing compounds or sulfur in a concentration of not less than 1 ppm as a reducing agent. A sulfur-containing compound, according to this embodiment, can be Со52, На5, 50», СО5, dimethyl sulfide, dimethyl disulfide, methyl mercaptan and/or ethyl mercaptan.

In the most preferred embodiments of the method according to the present invention, at least one product of the oxidation of the reducing agent from stream A is separated from the liquid stream at stage (d). This separation from the liquid stream at stage (gu) can be carried out by distillation or extraction.

In the preferred embodiments of the previous version of the invention, the above-mentioned oxidation product of the reducing agent is sulfur or// forms of condensed sulfur. In other embodiments of this variant of the present invention, the specified oxidation product is sulfuric acid. In the preferred embodiment of this variant of the method according to the invention, at stage (a) additionally provide stream C containing water.

In some preferred embodiments of the invention, flow A is gaseous. In these embodiments, the gaseous stream A can be provided under a pressure of 0.5 to 60 atmospheres. In these or other acceptable embodiments of the invention, the gaseous stream after extraction in stage (c) is additionally washed and dried using a molecular sieve or distillation. In another preferred embodiment of the present invention, the specified gaseous stream essentially contains CO. In other preferred embodiments, this gaseous stream contains essentially methane and/or other saturated hydrocarbons. In a separate embodiment of the invention, the gaseous stream may contain nitrogen.

In many preferred embodiments of the method according to the present invention, water is additionally added at stage (d).

In all preferred embodiments of the method according to the invention, the mass fraction of bromic acid in stream B does not exceed 62 95 wt. In more preferred embodiments of the present invention, the mass fraction of bromic acid in stream B does not exceed 48 95 wt.

In the most preferred embodiments of the method according to the present invention, the molar ratio of bromine to bromic acid in stream B is less than or equal to 1.

Also, in the most preferred embodiments of this invention, the potential in the electrolyzer does not exceed 1.23 V relative to a standard hydrogen electrode.

In some embodiments of the present invention, it is possible to additionally recover the thermal energy released in the reaction of the reducing agent with bromine.

In other embodiments of this invention, it is possible to additionally recover electrical energy in the same or another electrolytic cell (electrolyzer).

In some embodiments of the present invention, a water-miscible organic solvent and water-miscible compounds are additionally added to stream B. Such water-miscible organic solvents or compounds can be, in particular, methanol, acetone, acetic acid, nitromethane, sulfolene (butadiene sulfone), dimethylsulfoxide, dimethylformamide, acetonitrile, propionitrile, and/or ionic liquids, in particular, imidazolium, pyrrolidinium, pyridinium salts , such as bromides or sulfates.

In most preferred embodiments of the present invention, the concentration of unsaturated hydrocarbons in stream A is lower than 100 ppm. In some embodiments of the method according to the present invention, after the contact of stream A with bromine and bromic acid, but before electrolysis, a stage of removal of bromides and dibromides formed from olefins during such a reaction is carried out. In particular, such removal is carried out by distillation and subsequent decomposition, in particular by thermal decomposition.

Also, in most preferred embodiments of the method according to the present invention, the temperature at each stage in which bromine is present is maintained below 80 °C.

In some separate embodiments of the method according to the present invention, stream A is additionally concentrated before stage (a). In other separate embodiments of the method according to the present invention, the indicated liquid flow from stage (c) is concentrated, in particular, by extractive rectification using, in particular, concentrated solutions of bromides of alkaline earth metals or sulfuric acid before being fed into the electrolyzer.

Industrial suitability

This section is devoted to examples of the use of various embodiments of the proposed invention.

General conditions for carrying out methods according to the invention

This invention is based on the features discovered by the inventors of the electrolysis of hydrogen bromide in an aqueous solution: 2NVI - N»e same Vi: (the potential in the electrolyzer does not exceed 1.23 V relative to the standard hydrogen electrode)

This process, as the inventors discovered, takes place effectively only when there is a single liquid phase. According to the inventors, a solution of bromine in aqueous bromic acid exists without the formation of a second liquid phase only under certain conditions: the ratio of bromine to bromic acid is less than or equal to one.

The inventors of this invention also discovered that there are some other limitations of single-phase and process efficiency: the mass fraction of bromic acid in water cannot exceed 62 95 (and the amount of bromine in relation to water does not matter, because it binds to bromic acid). The most optimal value for the concentration of bromic acid in water is 48 wt. 96, which coincides with the concentration of the azeotropic solution of bromic acid.

Another important parameter is the temperature: although bromine begins to pass into the gas phase already at 60 "C, it is at a temperature of 80 "C, as the inventors discovered, that the stratification of the flow and the transition of bromine into the gas phase occurs; starting from this temperature, it becomes very difficult to control the process from a technical point of view.

Among other important conditions for the efficient implementation of the methods according to the invention, it should be noted that the concentration of unsaturated hydrocarbons in stream A of the raw material, which is fed into the reaction with bromine dissolved in aqueous bromic acid, must be lower than 100 ppm. Unsaturated hydrocarbons (olefins) in contact with bromine and bromic acid form bromide and dibromide derivatives, which accumulate in the system and create problems during electrolysis, reducing its efficiency. If necessary, removal of bromides and dibromides formed from olefins during such a reaction is carried out. In particular, such removal can be carried out before the electrolysis stage; for the removal of these substances can be used, in particular, distillation and further decomposition, for example, thermal.

In order to maintain the single phase of the reaction liquid in the methods according to the present invention, some organic solvents or liquids that are miscible with water can also be added to stream B, in particular methanol, acetone, acetic acid, nitromethane, sulfolene (butadiene sulfone), dimethylsulfoxide, dimethylformamide, acetonitrile, propionitrile , and/or ionic liquids, in particular imidazolium, pyrrolidinium, pyridinium salts, such as bromides or sulfates. An ordinary specialist in this field, if he wishes or if necessary, will be able to conduct simple experiments and optimize the composition of stream B, modifying it with the content of water-miscible organic solvents or water-miscible liquids.

One of the main examples of the use of the proposed invention is the method of returning and extracting hydrogen from gas streams.

The method of the invention is a low-cost and low-carbon way of recovering and obtaining high-purity hydrogen from streams that may contain complex mixtures of hydrogen, CO, CO."

Nob5, 05", alkanes, nitrogen, nitrogen oxides, ammonia and noble gases, and hydrogen in such streams can be contained in amounts from 100 ppm. up to 90 95 by mass.

As you know, hydrogen easily reacts with bromine already at room temperature:

Ne yak Vi - 2NVI with the formation of hydrogen bromide, which is then reduced back to bromine by electrolysis with the capture of low concentration hydrogen from the stream. Thus, in this process, hydrogen is both a reducing agent and a product, which this method is aimed at obtaining.

The method according to the invention can also be used for cleaning CO2 streams for their further transportation, since in many cases the amount of H2 is a very critical parameter.

The recovery of hydrogen in this solution is close to 100 95. This solution is not sensitive to changes in gas concentration and composition. This technique is suitable even for the recovery of traces of hydrogen.

This method can be used for: (a) small, mobile installations for biorefineries; (b) small devices for extracting H»e from the flow of СО»5; (c) large-scale stationary installations for additional recovery of He from streams after separation installations by APT, membrane and cryogenic separation; (d) large-scale stationary installations for the treatment of natural gas coming from reservoirs located in large hubs or in the immediate vicinity of natural gas reservoirs; (d) large-scale stationary plants for the treatment of waste gases from refineries, waste incineration plants, coal-fired power plants, metallurgical plants, flue gases and exhaust gases.

A method of processing a sulfur-containing stream to obtain hydrogen from water with the co-oxidation of sulfur-containing compounds to sulfuric acid and a method of purifying sulfur-containing streams

In this family of methods, the reductant used for the regeneration of bromic acid spent on electrolysis is sulfur or sulfur-containing compounds such as C52, H25, 50", CO5, 60 dimethyl sulfide, dimethyl disulfide, methyl mercaptan and/or ethyl mercaptan. The sulfur source stream in step (1) may be a gaseous stream or a liquid stream containing at least one

C-containing compound.

Depending on the amount and nature of the available reducing agent (sulfur or sulfur-containing compounds), conditions (in particular temperature), excess water and the ratio between the reducing agent and bromine, different chemical reactions can occur and different products can be formed, for example:

But I'm Vig - 2NVI 4 5 (passes at low temperature)

Ng5 i 4Vi2 - 4H2gO - 8Nhg i NobOx (an excess of bromine is necessary, water is consumed; this reaction takes place at 80 "С)

З - ЗВи2 - 4Н2О - Н25О» and 6НВг (necessary excess of bromine)

ЗО» i Vi2 - 2Н2О NO 4 2НВг

Sat» i 2ВИ2 - 2Н2О - СО» i ANVI 4 25

С52 и 8ВИ2 - 10Н2О - СО» и - 16НВг и 2Н2505 (an excess of bromine is required, water is consumed)

Accordingly, depending on the need in specific products for the concentration of the reducing agent, the possibility of supplying bromine and water, this method can be used for the production of hydrogen, splitting water to obtain hydrogen, converting sulfur-containing waste into sulfur or sulfuric acid, for desulfurization of gas streams (removal of C52, H25, 50", СО5) of different nature (natural gas; biogas; waste gases from refineries, incineration plants, coal-fired power plants, metallurgical plants; flue gases, exhaust gases) on various scales. These can be: (a) large-scale stationary plants for the production of hydrogen 3 water using sulfur-containing compatible feedstocks from natural gas reservoirs, biogas plants, waste gases from oil refineries, sulfur wastes, waste incinerators, coal-fired power plants, metallurgical plants, flue gases and exhaust gases; (b) large-scale stationary plants for the treatment of waste gases from refineries, waste incineration plants, coal-fired power plants, metallurgical plants, flue gases and exhaust gases (c) large-scale stationary plants for the treatment of natural gas coming from reservoirs located in large hubs or in the immediate vicinity from tanks

From natural gas; (d) large-scale stationary installations for biogas purification located in large centers; (e) conversion of sulfur-containing waste at oil refineries and gas plants into sulfuric acid and hydrogen, which are easier to transport; (i) small-scale mobile on-site biogas purification plants for remote biogas producers; (g) small-scale devices for private composting;

The method according to the invention is a simple and low-carbon way of cleaning sulfur-containing streams (where sulfur is present in the form of He5, Сbo2, СО5, sulfur or 5-organic), including in remote locations with joint production of high-value products: hydrogen, sulfuric acid or sulfur; the invention offers a technology that can easily be scaled up or down, depending on specific requirements, and adjusted to produce sulfur or sulfuric acid when water is added.

In addition to the purification of sulfur and sulfur-containing compounds, the methods of the present invention can be used to purify streams of carbon monoxide and ammonia and some nitrogen-containing substances.

When using carbon monoxide (at a minimum concentration of 10 ppm) as a reducing agent for the reduction of bromine, carbon dioxide is obtained, which can also be collected as a useful product, according to methods known to a person skilled in the art.

As nitrogen-containing compounds as reducing agents in stream A according to this invention, such substances as ammonia, nitrogen-containing organic compounds, amines and/or amides in the amount of at least 500 ppm can be used. As a product in reactions with similar reductants, molecular nitrogen is formed: 2МНз -- ЗВиИ2 - 6НВг -- M2 which can also be collected as a useful product, by methods known to specialists in this field.

Given that the essence of this invention is a radical improvement in the efficiency of the electrolysis of bromic acid in water due to an unexpected discovery of the inventors of this invention, the description of the invention focuses on the disclosure on which this invention is based. The direct detailed implementation of the methods described above on a domestic, small or large industrial scale, materials, equipment, conditions for performing reactions and actions, which do not relate to the disclosure of this invention and have long been well known to specialists in this field, have not been included in this description, because it is not the essence of this invention. Any specialist in this field, having familiarized himself with the disclosure of this invention, will be able to use his knowledge and information available in the state of the art to apply the methods of this invention on any scale without involving additional invention.

In the next section, the possibility of implementing the methods according to this invention was tested and proved in experimental laboratory examples.

Experimental examples

Bromine-containing mixtures for Examples 1-3 were made using azeotrope HB»g (48 wt. 9b), liquid Vig and distilled water.

Example 1.

Gas mixture (1) containing 97 vol. 95 SNae and Z vol. 95 Na5 was used as a raw material for the reaction, and a monophasic solution containing water, HBg and Bi2 (52 mab. bo, 43 wt. o and 5 wt. bo, respectively) was used for the oxidation reaction of Na5 to Hg5O". As a reactor, the installation presented in the drawing was used, which includes a vessel made of Pyrex glass (3), equipped with a temperature controller, a heating element, a Liebig refrigerator and a mechanical stirrer (4), covered with a layer of polytetrafluoroethylene (PTFE). The supply of raw gas was carried out through a PTFE tube connected to a Bronckhorst mass flow regulator (2), calibrated for the indicated gas mixture using an external flow meter.

The reaction was carried out at 55-60 "С, 1000 g of a single-phase solution was loaded into the reactor, and the mechanical stirrer was maintained at 400 rpm throughout the experiment.

The flow of the raw gas mixture was maintained for 10 hours at a flow rate of 2 L/h, and the Liebig cooler was continuously flushed with water to avoid unwanted losses of liquid products due to evaporation.

Gas samples collected at the exit from the refrigerator down into the reactor were collected with a gas-tight syringe every 2 hours of the experiment and analyzed using gas chromatography. Only traces of He were detected in all the collected initial samples, which confirmed that the oxidation of He5 with the help of VI: took place.

Vi2 4 H25 4. 4H2O -». Н2БОх 4 8НВг

After the end of the reaction, the liquid in the reactor was cooled and analyzed by available analytical methods. According to the results of gravimetric analysis, the total amount of Н25О4 was 2.55 g, which indicated an almost complete conversion of Не5 to Не25Ох.

Example 2.

A gas mixture containing 97 vol. 95 SN" and Vol. 95 Na5 was used as a raw material for the reaction, and a monophasic solution containing water, HBg and HB2 (53 wt. 95, 27 wt. 95 and 20 wt. 95, respectively) was used for the oxidation reaction of Na5 to Hg5O. As a reactor, an installation was used, which included a vessel made of pyrex glass, equipped with a temperature controller, a heating element, a Liebig refrigerator and a mechanical stirrer covered with a layer

PTFE. Feed gas was supplied through a PTFE tube connected to a Bronckhorst mass flow controller calibrated for the indicated gas mixture using an external flow meter.

The reaction was carried out at 55-60 "С, 1000 g of a single-phase solution was loaded into the reactor, and the mechanical stirrer was maintained at 400 rpm throughout the experiment.

The flow of the raw gas mixture was maintained for 10 hours at a flow rate of 10 L/h, and the Liebig cooler was continuously flushed with water to avoid unwanted losses of liquid products due to evaporation.

Gas samples collected at the exit from the refrigerator down into the reactor were collected with a gas-tight syringe every 2 hours of the experiment and analyzed using gas chromatography. In all the collected initial samples, only traces of Ne, which were detected

BO confirmed that the oxidation of Не5 with the help of ВИ: took place.

After the end of the reaction, the liquid in the reactor was cooled and analyzed by available analytical methods. According to the results of gravimetric analysis, the total amount of Н25О4 was 12.97 g, which indicated an almost complete conversion of Не5 to Н25Ох.

Example 3.

A gas mixture containing 97 vol. 95 SN" and Vol. 95 Но5 was used as a raw material for the reaction, and a monophasic solution containing water, НВг and Ві2 (52 wt. 95, 43 wt. 95 and 5 wt. 95, respectively) was used for the oxidation reaction of На5 to Нг5О". As a reactor, an installation was used, which included a vessel made of Pyrex glass, equipped with a temperature controller, a heating element, a Liebig refrigerator, and a mechanical stirrer covered with a layer of PTFE. Feed gas was supplied through a PTFE tube connected to a Bronckhorst mass flow controller calibrated for the indicated gas mixture using an external flow meter.

The reaction was carried out at 55-60 "С, 1000 g of a single-phase solution was loaded into the reactor, and the mechanical stirrer was maintained at 400 rpm throughout the experiment.

The flow of the raw gas mixture was maintained for 10 hours at a flow rate of 6 L/h, and the Liebig cooler was continuously flushed with water to avoid unwanted losses of liquid products due to evaporation.

Gas samples collected at the exit from the refrigerator down into the reactor were collected with a gas-tight syringe every 30 minutes of the experiment and analyzed using gas chromatography. At the initial period of the experiment, only traces of Nob were detected in the initial samples, while after 8 h, the intensity of the He5 peak in C increased. At this point, the color of the liquid in the reactor gradually changed from orange-red to yellow, indicating that Vig2 was almost completely consumed.

Example 4.

The liquid product obtained in Example 3 was placed in a distillation unit with a round bottom flask, a dephlegmator and a refrigerator. The liquid was diluted with 100 ml of distilled water, as part of the water was consumed during the reaction with He5, and was distilled at a temperature of 124-127 "C for b hours in a well-ventilated fume hood. The total amount of almost colorless liquid collected in the receiver flask was 1072 g, and the amount of liquid residue with a higher boiling point in the round-bottom flask was 33 g. This residue was analyzed for sulfuric acid by gravimetric analysis. The total amount of Na25O4 was found to be 7.63 g, indicating almost complete conversion of Neg5 on He50Ox during Example 3. The analysis of the specified distillate showed that it is an 8.2 M solution of NVUG, close to the azeotrope (8.89 M).

Example 5.

A specially designed electrolysis unit was used to decompose NVHg into He and Vi. 600 ml of solution containing 48 wt. 95 Ng in water was passed through the electrolysis unit using a peristaltic pump with a PTFE surface. The liquid output from the electrolysis unit was collected in a glass vessel; the gaseous output was released into the hood

Out of the closet. The total duration of electrolysis was 7 min., the average voltage during the run was 1.02 V, the average current was 82 A. The voltage during the experiment was stable. The liquid products were analyzed for the content of VIi2g and HBg by titration and gravimetric analysis. Analysis showed the final content of HB" and Vi" 44 wt. 9b and 4 wt. 95, respectively.

Example 6.

An individually designed electrolysis unit containing a Nafion membrane was used as a reactor. A gas mixture (СНа/Нег 95/5 vol.) and a monophase solution that included water, НГ and Ви2 (52 wt. 95, 43 wt. 90 and 5 wt. 95, respectively) were used as raw materials. Feed gas was supplied through a PTFE tube connected to a Bronckhorst mass flow controller calibrated for the indicated gas mixture using an external flow meter. The liquid phase was fed by a syringe pump. The flow of the specified gas mixture was set at 5 l/h, the experiment was conducted for 2 hours. The average cell voltage was 0.96 V, and the average current was 0.6 A.

Example 7 is comparative.

A specially designed electrolysis unit was used to decompose the model mixture, which includes water, HB" and Bi (35 wt. 95, 28 wt. 95, and 36 wt. 95, respectively). 100 g of the indicated solution was connected in a closed circulation to a cell for electrolysis and recirculated through this cell with an average flow rate of 15 ml/min. The average voltage during the run was 1.03 V, the average current was 39 A. After about 5 minutes of the experiment, a clear formation of a second layer at the bottom of the flask was observed, which corresponded to the conversion of about 35 mol. 905 NVh, that is, the molar ratio NVh/Vg" is less than 1. At this moment of the experiment, the voltage began to increase and reached a value of 1.34V at the point 6.5 min.; eventually, the 1.34 V cell potential was accompanied by the formation of bubbles at the anode, which were assumed to be oxygen produced by water decomposition.

Analytics.

Analysis of output gases.

For the analysis of effluent gases, we used Adiyepi S with TSO and RIO detectors and ziisaRI Ot columns.

Total sulfate content was analyzed by gravimetric analysis. A solution containing H25O" was introduced into the reaction with an excess of barium chloride. The reaction was carried out at 907 to complete the precipitation, which formed barium sulfate. The precipitate was filtered and calcined at 600 °C for 12 hours before mass measurement.

Ne50" from Vasi" -" VabOgi. I 2NSII

Total bromine content was analyzed by gravimetric analysis. This method is based on the neutralization of HBg by adding an excess of sodium carbonate followed by the addition of silver nitrate and the precipitation of AaHg. All manipulations were carried out at 40 "С and intensive stirring to ensure the completion of the reaction. Then the solid AdHg precipitate was filtered, air-dried and calcined at 400 "С for b hours to ensure the purity of the sample. 2NVg - MagbOz -» 2MavVg and H2O i SO» 2NVg 4 Maon -» MaVg i H2O

Mavg - AdMOz -» MamMoOz - AdVg.

In the case of presence of polybromides (Vggpi1|), the method was modified in such a way that the initial stage included the reduction of Vi? to Vg ions with the help of sodium thiosulfate solution.

The content of molecular bromine, which may be present in the form of polybromides, (Vggp "1) was analyzed using iodometric titration. At the first stage, polybromides were introduced into a reaction with an excess of potassium iodide solution, obtaining molecular iodine. Then the formed iodine was titrated with a solution of sodium thiosulfate with colloidal starch as an indicator.

IVggin | - 2oKI -» 2pKVh k Ve 4 pygo

And2 I -- And"

Is - 252032 -- From I 54O67

The above examples are not meant to limit the proposed invention, but are given solely for the purpose of illustrating the possibility of its implementation. The scope of protection of the proposed invention is set forth in the following section - claims.

Claims (19)

FORMULA OF THE INVENTION 1. A method for obtaining hydrogen, in which: (a) a stream A is provided, which contains at least one reducing substance, and the concentration of unsaturated hydrocarbons in the stream A is lower than 100 ppm, and a single-phase liquid stream B, which contains water, bromine and bromic acid, and the mass fraction of bromic acid in stream B does not exceed 62 wt. 905; (b) bring the specified streams into contact with obtaining bromic acid from bromine; (c) separate a side stream containing at least one non-oxidizable bromine substance; 35 (d) obtain a liquid stream from stage (b), where said liquid stream contains water, bromic acid and residual bromine, and is single-phase, where the molar ratio of bromine to bromic acid is less than or equal to 1; (d) direct the specified flow of liquid from stage (d) to the electrolyzer to convert at least part of the bromic acid to bromine and hydrogen, and the potential in the electrolyzer does not exceed 1.23 V relative to the standard hydrogen electrode; and (e) receiving the liquid stream from stage (d) and redirecting it to stage (a), the temperature of each stage in which bromine is present being maintained below 80 °C. 2. The method according to claim 1, where the indicated stream A contains hydrogen as a reducing agent in an amount of at least 500 ppm. 45 3. The method according to claim 1, where the indicated stream A contains ammonia, nitrogen-containing organic compounds, amines and/or amides in the amount of at least 500 ppm as a reducing agent. 4. The method according to claim 1, where the indicated stream A contains as a reducing agent carbon monoxide in the amount of at least 10 ppm. 5. The method according to claim 1, where the specified stream A contains sulfur-containing compounds or sulfur 50 in a concentration of not less than 1 ppm as a reducing agent. b. The method according to claim 5, where the sulfur-containing compound is C52, Na25, 50", СО5, dimethyl sulfide, dimethyl disulfide, methyl mercaptan and/or ethyl mercaptan. 7. The method according to claim 1, where flow A is gaseous. 8. The method according to claim 1, where at least one product 55 of the oxidation of the reducing agent from stream A is additionally separated from the liquid stream at stage (g). 9. The method according to claim 8, where the indicated separation is carried out by means of distillation or extraction. 10. The method according to claim 9, where the product of oxidation is sulfur and/or forms of condensed sulfur. 11. The method according to claim 10, where the oxidation product is sulfuric acid. 12. The method according to claim 1, where at stage (a) additionally a stream C containing water is provided. 60 13. The method according to any of the preceding clauses, in which water is additionally added at stage (d). 14. The method according to any of the previous items, in which the mass fraction of bromic acid in stream B does not exceed 48 wt. 95. 15. The method according to any of the previous clauses, in which the heat energy released in the reaction of the reducing agent with bromine is additionally recovered. 16. The method according to any of the previous clauses, in which recovery of electrical energy is additionally carried out in the same or another electrolytic cell (electrolyzer). 17. The method according to any of the previous items, in which stream B additionally contains at least one water-miscible organic solvent and/or water-miscible compound selected from the group containing methanol, acetone, acetic acid, nitromethane, sulfolene ( butadiene sulfone), dimethylsulfoxide, dimethylformamide, acetonitrile, propionitrile and/or ionic liquids, in particular imidazolium, pyrrolidinium and/or pyridinium salts. 18. The method according to claim 1 or claim 3, where the indicated side stream in stage (c) additionally contains nitrogen. 19. The method according to claim 1, where the side stream is separated by distillation. 8. s Emission of gas y pru also y y |. that and Ki oi t | y la What U VV ME I A E : KO podnvn z