WO2020211984A1 - Procédé et appareil de traitement d'un mélange gazeux - Google Patents

Procédé et appareil de traitement d'un mélange gazeux Download PDF

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Publication number
WO2020211984A1
WO2020211984A1 PCT/EP2020/025175 EP2020025175W WO2020211984A1 WO 2020211984 A1 WO2020211984 A1 WO 2020211984A1 EP 2020025175 W EP2020025175 W EP 2020025175W WO 2020211984 A1 WO2020211984 A1 WO 2020211984A1
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Prior art keywords
gas
gas mixture
absorption
starting
carbon dioxide
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PCT/EP2020/025175
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English (en)
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Marcus Guzmann
Constantin Maniut
James Mercer
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Linde Gmbh
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Publication of WO2020211984A1 publication Critical patent/WO2020211984A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1462—Removing mixtures of hydrogen sulfide and carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1475—Removing carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1418—Recovery of products
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1468—Removing hydrogen sulfide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/50—Carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
    • B01D2252/20—Organic absorbents
    • B01D2252/202—Alcohols or their derivatives
    • B01D2252/2021—Methanol
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2256/00—Main component in the product gas stream after treatment
    • B01D2256/16—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/30—Sulfur compounds
    • B01D2257/302—Sulfur oxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/50—Carbon oxides
    • B01D2257/504—Carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/02—Other waste gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Definitions

  • the invention relates to method for treating a starting gas mixture comprising hydrogen sulphide and carbon dioxide, the starting gas mixture being produced involving a Claus process, and to a corresponding apparatus according to the preambles of the independent claims.
  • Corresponding methods and embodiments are e.g. disclosed in US 4,684,514 A, disclosing a method which removes water concurrently with the condensation of sulphur and which can be operated at high pressure, and in US 2013/0071308 A1 , relating to a method and a plant for recovering sulphur from a sour gas containing hydrogen sulphide and carbon dioxide wherein the carbon dioxide is compressed and at least a part of the carbon dioxide is injected into an oil well.
  • the present invention may also be concerned with producing carbon dioxide which can be used accordingly.
  • the Claus process originally only mixed hydrogen sulphide or a corresponding sour gas mixture with oxygen and passed the mixture across a pre-heated catalyst bed. It was later modified to include a free-flame oxidation upstream the catalyst bed in a so- called Claus furnace. Most of the sulphur recovery units (SRU) in use today operate on the basis of a correspondingly modified process. If, in the following, therefore, shorthand reference is made to a“Claus process” or a corresponding apparatus, this is intended to refer to a free-flame modified Claus process as just described.
  • hydrogen sulphide in the gas mixture which is fed to the Claus furnace is oxidized, preferably quantitatively, to sulphur dioxide which is subsequently, typically in several catalytic stages, converted to elementary sulphur.
  • the latter is condensed and typically withdrawn in liquid form.
  • oxygen enrichment is a well-known economic and reliable method of debottlenecking existing Claus sulphur recovery units with minimal capital investment.
  • Oxygen enrichment is, however, as described in detail below, not limited to retrofitting existing Claus sulphur recovery units but can likewise be advantageous in newly designed plants.
  • The“term oxygen enrichment” shall, in the following, refer to any method wherein, in a Claus sulphur recovery unit or in a corresponding method, at least a part of the air introduced into the Claus furnace is substituted by oxygen or a by gas mixture which is, as compared to ambient air, enriched in oxygen or, more generally, has a higher oxygen content than ambient air.
  • Oxygen or oxygen enriched gas mixtures for Claus sulphur recovery units can be, in general, provided by cryogenic air separation methods and corresponding air separation units (ASU) as known from the prior art, see e.g. Haering, H.-W.,“Industrial Gases Processing,” Wiley-VCH, 2008, especially chapter 2.2.5,“Cryogenic
  • oxygen or gases enriched in oxygen in comparison to atmospheric air can also be produced using non-cryogenic methods, e.g. based on pressure swing adsorption (PSA), particularly with desorption pressure levels below atmospheric pressure (Vacuum PSA, VPSA).
  • PSA pressure swing adsorption
  • VPSA desorption pressure levels below atmospheric pressure
  • tail gas treatment unit a so-called tail gas treatment unit
  • sulphur dioxide is partially converted to hydrogen sulphide so that the resulting ratio sulphur dioxide and hydrogen sulphide stochiometrically results in a 100% conversion by synproportionation to elemental sulphur.
  • reducing gas generators can be arranged in a tail gas treatment unit.
  • a reducing gas generator is classically also operated with air and a fuel gas and represents a further furnace in the whole process. It can be operated using oxygen enrichment as well.
  • tail gas treatment While several alternatives for tail gas treatment are known from the prior art, they often proof as unsatisfactory, particularly in cases when carbon dioxide is to be recovered from the tail gas.
  • a tail gas In an oxygen enriched operation of a Claus process, less or no nitrogen is present in the tail gas, as no such nitrogen is introduced into the Claus furnaces as a part of combustion air. Therefore, such a tail gas generally can be seen as an attractive source of carbon dioxide, e.g. for Enhanced Oil Recovery (EOR) in which the carbon dioxide is used to facilitate oil extraction from oil wells, particularly in the third (tertiary) stage of oil recovery.
  • EOR Enhanced Oil Recovery
  • carbon dioxide produced accordingly may also e.g. put to food and beverage uses or can be used for desalination or the production of liquid carbon dioxide (LIC).
  • An object of the present invention is to provide improved methods of this kind, particularly in view of reducing capital and operating expenses.
  • the present invention provides a method for treating a starting gas mixture comprising hydrogen sulphide and carbon dioxide, the starting gas mixture being produced involving a Claus process, and to a corresponding apparatus according to the preambles of the independent claims.
  • Advantageous embodiments of the present invention are the subject of the dependent claims and of the description that follows.
  • sour gas mixture refers, in the language as used herein, to a gas mixture containing at least hydrogen sulphide and optionally carbon dioxide and other known sour gases in a common an amount of at least 50%, 75%, 80% or 90% by volume, these numbers relating to the content of one of these compounds or to a common content of several ones of these components. Further components besides sour gases may be present in a sour gas mixture as well, particularly water, hydrocarbons, benzene, toluene and xylenes (BTX), carbon monoxide, hydrogen, ammonia and mercaptans.
  • a sour gas mixture of the kind mentioned can particularly be obtained when“sweetening” natural gas or other gas mixtures, particularly including scrubbing processes as known from the art.
  • the term“desulphurisation” as used herein shall refer to any process including conversion of a first sulphur compound comprising sulphur at a lower oxidation stage, which is contained in a sour gas mixture, to a second sulphur compound comprising sulphur at a higher oxidation stage in a first reaction step, and particularly further including forming elementary sulphur from the second sulphur compound in a second reaction step, the elementary sulphur particularly being obtained in liquid state.
  • the first sulphur compound may be hydrogen sulphide and the second sulphur compound may be sulphur dioxide.
  • the first reaction step may particularly include combusting the first sulphur compound and the second reaction step may particularly include using a suitable catalysis reaction as generally known for the Claus process.
  • a mixture of components may be rich or poor in one or more components, where the term“rich” may stand for a content of more than 75%, 80%, 85%, 90%, 95%, 99%, 99.5% or 99.9% and the term“poor” for a content of less than 25%, 20%, 15%, 10%, 5%, 1 %, 0.5% or 0.1%, on a molar, weight or volume basis.
  • a sour gas mixture with a hydrogen sulphide content of more than 80% is generally referred to as“rich” while a sour gas mixture containing less hydrogen sulphide is generally referred to as“lean.”
  • a mixture may also be, in the language as used herein, enriched or depleted in one or more components, especially when compared to another mixture, where“enriched” may stand for at least 1 , 5 times, 2 times, 3 times, 5 times, 10 times or 100 times of the content in the other mixture and“depleted” for at most 0.75 times, 0.5 times, 0.25 times, 0.1 times, or 0.01 times of the content in the other mixture.
  • pressure level and“temperature level” are used herein in order to express that no exact pressures but pressure ranges can be used in order to realise the present invention and advantageous embodiments thereof.
  • Different pressure and temperature levels may lie in distinctive ranges or in ranges overlapping each other. They also cover expected and unexpected, particularly unintentional, pressure or temperature changes, e.g. inevitable pressure or temperature losses.
  • Values expressed for pressure levels in bar units are absolute pressure values.
  • Oxygen enrichment which was already mentioned hereinbefore, can also eliminate the need for fuel gas co-firing in the Claus furnace which is classically required to maintain the correct temperature for contaminant destruction, for example for destruction of benzene, toluene and xylenes (BTX) in the sour gas mixture. Whether or not a corresponding co-firing is required particularly depends on the hydrogen sulphide content of the sour gas mixture treated and whether a sufficient temperature and a stable flame can be obtained by burning the sour gas mixture alone. As, when using oxygen enrichment is used, oxygen is less diluted with nitrogen, the energy density and therefore the combustion temperature is higher.
  • oxygen enrichment entails replacing part or all of the air fed to the Claus furnace by air enriched in oxygen or pure oxygen.
  • the volumetric flow through the Claus sulphur recovery unit decreases, allowing more of the sour gas mixture to be fed to the system. This results in an increased sulphur production capacity without the need for significant modifications to existing equipment or major changes to the process plant pressure profile.
  • Oxygen enrichment can also have advantages in plants where the acid gas mixtures obtained are lean and contain benzene, toluene and xylenes. Such plants classically require feed gas and/or combustion air preheating and the use of fuel gas co-firing and have not, historically, been considered for oxygen enriched operation.
  • a particular advantage of oxygen enrichment is, as also mentioned hereinbefore, that the tail gas downstream a tail gas treatment unit is less“diluted” with nitrogen from the combustion air classically used in the reaction furnace of the Claus process and potentially in the reducing gas generator of the tail gas treatment unit. If little or no additional nitrogen is introduced into the process, the main component of the sour gas mixture after desulphurisation, e.g. carbon dioxide, can be obtained in a simpler and more cost-effective way as no cryogenic separation of nitrogen and carbon dioxide is necessary. This is specifically the case when the carbon dioxide is to be used for purposes like enhanced oil recovery or fracking in which no absolute purity is necessary.
  • treatment of a tail gas of a Claus process may involve a removal of hydrogen sulphide, much like in a conventional gas treating plant. That is, a so- called amine unit is typically utilised for removing hydrogen sulphide using chemical based solvents. Solvents for the amine unit are often selected in view of selectivity towards hydrogen sulphide.
  • Solvents for the amine unit are often selected in view of selectivity towards hydrogen sulphide.
  • Flexsorb solvents are well known due to high selectivity they offer at low pressures.
  • the chemical solvents are usually amine- based systems that rely on chemical reactions to bind the hydrogen sulphide. In other words, classical methods involve using a chemical absorption process in order to remove hydrogen sulphide.
  • a physical absorption step is used to remove hydrogen sulphide at a relatively low pressure from the tail gas or from a gas mixture obtained from the tail gas.
  • a process based on cold methanol or a different polar organic solvent not chemically reacting with the hydrogen sulphide preferably a so-called Rectisol process
  • Rectisol process and other physical absorption methods are known per se and e.g. described in G. Hochgesand, Ind. Eng. Chem. 1970, 62, 7, 37-43, or a plethora of publications subsequent thereto.
  • the physical absorption method is performed at a pressure level substantially below that classically used for such processes, particularly for the Rectisol process.
  • A“physical” absorption particularly is based on a non-covalent association of molecules to be absorbed and absorbing molecules (absorbent). In contrast to“chemical” absorption, no covalent binding is involved here.
  • tail gas treatment particularly the hydrogenation of sulphur dioxide
  • the inventive method can easily be separated off in the inventive method and can e.g. be recycled to the Claus process, particularly together with hydrogen sulphide which is recycled anyway.
  • the present invention provides a method for treating a starting gas mixture comprising hydrogen sulphide and carbon dioxide, the starting gas mixture being produced involving a Claus process, wherein the method comprises a gas conditioning step and a gas separation step.
  • a starting gas mixture is, in the language as used herein, produced“involving” a Claus process if it contains at least some compounds which were previously produced or converted in the Claus process.
  • the starting gas mixture may particularly a tail gas of the Claus process remaining after sulphur dioxide was converted at least in the predominant part to elementary sulphur and the elementary sulphur was removed.
  • the starting gas mixture may also be produced from or include such a tail gas.
  • the starting gas mixture must not be produced exclusively in the Claus process and may also comprise components from other sources. Not all the tail gas of a Claus process must, on the other hand, be used according to the present invention.
  • the“gas conditioning step” and the“gas separation step” are mentioned herein merely for reasons of reference, and that these steps must not be clearly be separated from each other.
  • the gas conditioning step and the gas separation step not necessarily have to be performed in different units of a corresponding apparatus and media used in one of these steps can be used in the other as well. Particularly, this refers to heat transfer streams like steam.
  • the gas conditioning step is rather a step preparing the starting gas mixture for separation, essentially leaving the gas composition unchanged, while the gas separation step operates under the conditions provided by the gas conditioning step and performs a substantial separation of the starting gas mixture.
  • the gas separation step comprises at least partially separating the hydrogen sulphide from the starting gas mixture.
  • the gas conditioning step comprises providing the starting gas mixture at an absorption pressure level of 4 to 10 bar (abs.) and at an absorption temperature level of -30 to -50 °C
  • the gas separation step comprises a physical absorption at the absorption pressure level and at the absorption temperature level using an absorption liquid and generating at least two fractions, one of which predominantly or exclusively comprising carbon dioxide.
  • carbon dioxide may more easily dissolve or be absorbed in the absorption liquid used, e.g. in“cold” methanol at the absorption pressure and temperature levels.
  • the absorption liquid loaded with mostly carbon dioxide can be withdrawn from the absorption column at a position below a position at which the absorption liquid loaded with hydrogen sulphide may be withdrawn.
  • carbon dioxide may be stripped, resulting in the fraction predominantly or exclusively comprising carbon dioxide (also referred to as“carbon dioxide fraction” hereinafter).
  • hydrogen sulphide may be stripped, resulting in a further fraction which contains predominantly or exclusively hydrogen sulphide (also referred to as“hydrogen sulphide fraction” hereinafter).
  • Hydrogen like carbon monoxide and other non-polar compounds that may be present in the starting gas mixture as well, preferably stay in the gas phase, the gas phase forming a yet further fraction poor in or free from carbon dioxide and hydrogen sulphide and containing hydrogen (also referred to as“hydrogen fraction” hereinafter).
  • a separation between a carbon dioxide fraction, a hydrogen sulphide fraction and a hydrogen fraction is possible.
  • Each of these fractions may contain further components, if they are contained in the starting gas mixture.
  • sulphur dioxide may be contained the hydrogen sulphide fraction and this fraction may be recycled to the Claus process wherein the hydrogen sulphide may be converted to sulphur dioxide.
  • This sulphur dioxide, and the sulphur dioxide recycled to the Claus process from the hydrogen sulphide fraction may be converted to elementary sulphur. Therefore, a tail gas treatment by hydrogenation, which is classically used to remove sulphur dioxide can be dispensed of according to the present invention.
  • the absorption pressure level at which the starting gas mixture is provided i.e.
  • the absorption temperature level at which the starting gas mixture is provided, i.e. to which it is cooled, in the gas conditioning may preferably be between -35 to -50 °C, particularly ca. -40 °C or ca. -45 °C.
  • Advantages of this approach include that less energy is required for compression, as compared to classical physical absorption processes, and that the equipment used for the physical absorption does not need to withstand higher pressures, reducing capital expenses.
  • the gas separation step used according to the present invention preferably provides a fraction predominantly or exclusively comprising hydrogen sulphide which can be recycled to a point upstream. Depending on the composition of the starting gas mixture, this fraction may comprise further components as well. If a Claus process is used, as is the case according the present invention, this fraction can be at least partially introduced into the Claus furnace, for example.
  • the physical absorption is performed, as mentioned, preferably using a cold polar organic solvent, particularly methanol, a mixture of several different solvents or one or more solvents and additives. However, none of the compounds used in the physical absorption preferably chemically bind with the carbon dioxide or the hydrogen sulphide, at least not covalently.
  • the carbon dioxide and the hydrogen sulphide are preferably driven out of such the solvent or solvent mixture used in the physical absorption, or parts thereof, respectively, particularly in a regeneration unit or step.
  • the starting gas mixture may be provided as an unhydrogenated tail gas of the Claus process or as a gas mixture produced from the tail gas in a tail gas treatment unit involving a hydrogenation.
  • a tail gas treatment unit can be used in order to convert traces or residuals of sulphur dioxide to hydrogen sulphide by hydrogenation, i.e. producing the starting gas mixture from the tail gas in the tail gas treatment unit at least includes hydrogenating sulphur-containing compounds to hydrogen sulphide.
  • this may include usage of a reducing gas generator in order to adjust the hydrogen content, or may also entail introducing hydrogen from external sources. However, as mentioned below, this may not be necessary according to the invention, as here sufficient amounts of hydrogen may be present already.
  • the starting gas mixture may include sulphur dioxide and other compounds which are not hydrogenated to hydrogen sulphide. They are thus transferred into the hydrogen sulphide fraction and may be recycled into the reaction furnace of the upstream Claus process.
  • the present invention is particularly advantageous in connection with oxygen enrichment, particularly because this results in carbon dioxide being easily obtainable from the tail gas.
  • a gas mixture comprising a higher oxygen content than atmospheric air or pure oxygen is provided to oxidise hydrogen sulphide in the Claus process.
  • the term“pure” oxygen shall also refer to gas mixtures containing more than 90, 95, 98, 99 or 99,5 vol.-% of oxygen.
  • Operating the process under oxygen enrichment may also have further advantages, as also mentioned below.
  • the tail gas is produced comprising hydrogen in the Claus process.
  • the hydrogen may be separated off and may e.g. be used in hydrodesulfurization steps generating sour gases which then may be converted in the Claus process. Hydrodesulfurization is a process known from the prior art per se. Reference is made to expert literature.
  • the tail gas comprises very substantial amounts, i.e. 5 to 35 vol.-%, of hydrogen, even if no reducing gas generator is present.
  • This hydrogen is at least in part, preferably completely, transferred to the subsequent method steps and therefore the starting gas mixture comprises at least a part of the hydrogen contained in the tail gas. Therefore, in the separation step, this hydrogen can be separated off and it can be used in upstream method steps such that no external hydrogen needs to be provided.
  • purifying carbon dioxide according to the present invention the remaining off gas been found to be very rich in hydrogen, with a content of typically more than 90 vol.-%.
  • This hydrogen being made available purely by the purification of the carbon dioxide, can optionally be utilized in the method and as such avoids the installation of the reducing gas generator or alternatively an external hydrogen source like a steam reformer.
  • the fraction at least predominantly comprises carbon dioxide can be used as a gas product which is used for enhanced oil recovery.
  • the fraction predominantly or exclusively comprising hydrogen can, as mentioned, preferably used in upstream method steps, i.e. for hydrodesulfurisation, or can be combusted, and the fraction predominantly or exclusively comprising hydrogen sulphide can be recycled.
  • conditioning the starting gas mixture upstream of the separation step and/or the separation step comprises a first compression and/or the fraction which predominantly or exclusively comprises carbon dioxide is further compressed in a second compression.
  • the first compression is the one which is performed upstream the physical absorption and which is performed at the pressure used therein.
  • compression heat i.e. compression heat from the first and/or the second compression can advantageously be utilised in generating steam, thereby recovering substantial amounts of energy.
  • the first compression may be performed to the absorption pressure level used in the physical absorption step.
  • the second compression for the application in enhanced oil recovery may particularly be performed to a pressure as high as 200 bar (g) or more. Therefore, substantial amounts of compression heat are generated.
  • this heat may be withdrawn.
  • a heat transfer medium may be used to this purpose, absorbing the heat energy from the compression stage(s).
  • This heat transfer medium may be used to preheat water in a steam generation system, actually boiler feed water. Due to the preheating of the boiler feed water, less thermal energy is required to generate steam, reducing the overall energy demand.
  • the embodiment just mentioned may be used in connection with the production of carbon dioxide in an amount of 190,000 Nm3/h (normal cubic meters per hour) at 2 bar (abs.) wherein no substantial amounts of other gaseous or liquid products are provided, as they are preferably recycled.
  • An air separation process may be optimized to minimize energy consumption and includes supply of the process air at one, two or more pressure levels.
  • the main air compressor in this unit may be of the axial-radial type with a high isentropic efficiency in its axial stage.
  • the steam demand of the main air compressor aspiring ambient air at e.g. 35 °C may be 150 t/h at 25 bar (abs.) at a temperature of 450 °C.
  • This required steam mass flow rate to drive the main air compressor corresponds to a similar feed water volume with a feed condensate temperature of 40.3 °C.
  • the condensate exit temperature level is e.g. at about 165 °C.
  • the sulphur recovery unit used in this example may produce superheated high-pressure steam at 25 bar (abs.) and 450 °C with a mass flow of about 35,900 t/h, saturated at 42 bar (abs.) and 370 °C. Due to a heat integration between the air separation unit and the sulphur recovery unit according to the present invention, the sulphur recovery unit may produce an increased volume of high-pressure steam.
  • the gain in steam mass flow in the present example could be up to 30 t/h and as such quite significant with reference to a steam flow required to operate the air separation unit. This steam can be at 25.5 bar (abs.) and 450 °C.
  • a content of the hydrogen sulphide in the starting gas mixture is preferably 50 ppm to 10 vol.-% and a content of the carbon dioxide in the starting gas mixture is preferably 40 to 90 vol.-%.
  • the starting gas mixture can, as frequently mentioned, particularly be the tail gas of a Claus process or a gas mixture which is obtained from such a tail gas using the processes mentioned before.
  • a number of different advantageous options is available for the individual processes comprised by the gas conditioning step. This can e.g. comprise compressing the starting gas mixture to the absorption pressure level and cooling the starting gas mixture to the absorption temperature level thereafter.
  • the cooling may be performed using a cooling system in which a nitrogen coolant is expanded and compressed and/or using a fluid stream produced in an air separation unit.
  • a nitrogen coolant is expanded and compressed and/or using a fluid stream produced in an air separation unit.
  • the latter can e.g. be an oxygen or oxygen rich stream withdrawn from the air separation unit in order to be fed into the Claus furnace for the oxygen enriched operation envisaged in an embodiment of the present invention.
  • the injection of water into the Claus furnace results in the benefit that the water molecule is thermally decomposed into hydrogen and oxygen.
  • the oxygen can react with the hydrogen sulphide and results in the same effect such as oxygen enrichment.
  • the same desired effect of oxygen enrichment such as e.g. debottlenecking, can be achieved with less oxygen being introduced, as water is introduced into the reaction furnace (flame) that in situ generates the oxygen being available as reactant.
  • the starting gas mixture comprises water and the gas conditioning step comprises drying the starting gas mixture.
  • a drying can be particularly involve using molecular sieve adsorbers known from the prior art or, if sufficient, condensation cooling.
  • the water content of the starting gas mixture is particularly reduced to less than 100, less than 50 or less than 20 ppm by volume.
  • the cooling may comprise at least two cooling steps and preferably the drying is performed between at least two of the at least two cooling steps.
  • the present invention also relates to an apparatus for treating a starting gas mixture comprising hydrogen sulphide and carbon dioxide, the starting gas mixture being produced involving a Claus process.
  • the apparatus comprises a gas
  • the conditioning unit and a gas separation unit comprising a separator adapted to at least partially separate the hydrogen sulphide from the starting gas mixture.
  • the gas conditioning unit is adapted to provide the starting gas mixture at an absorption pressure level of 4 to 10 bar (abs.) and at an absorption temperature level of -30 to -50 °C, and that the separator adapted to at least partially separate the hydrogen sulphide from the starting gas mixture in the gas separation unit is adapted for physical absorption of at least a part of the hydrogen sulphide at the absorption pressure level and at the absorption temperature level.
  • Figure 1 illustrates a method according to an embodiment of the invention.
  • a sour gas stream A is supplied to a Claus process 1 which is, for illustrative purposes only, shown as a method step separate from tail gas treatment 2.
  • the Claus process 1 and the tail gas treatment 2 can also be performed in a common apparatus exchanging media and energy.
  • the tail gas treatment 2 can also be omitted.
  • the Claus process 1 is operated using oxygen enrichment, and therefore, an air separation 3 is present as well.
  • the air separation 3 can be performed cryogenically or non-cryogenically.
  • a stream B of pure oxygen or air enriched in oxygen is provided to the Claus process 1 and used as described.
  • a fuel gas stream, which can also be used in the Claus process 1 is not shown.
  • the Claus process 1 is operated essentially as described hereinbefore.
  • a tail gas stream C is withdrawn.
  • the tail gas stream C is introduced into the tail gas treatment 2.
  • a hydrogen stream can be provided, which can be a recycle stream as described below.
  • a stream E, representing a starting gas mixture comprising hydrogen sulphide and carbon dioxide is withdrawn from the tail gas treatment 2 and is subjected to a gas conditioning step 10 and, subsequently thereto, to a gas separation step 20. If no tail gas treatment of this kind is present, the tail gas stream C may also be directly submitted to these steps.
  • the gas conditioning step 10 comprises providing the starting gas mixture at an absorption pressure level and at an absorption temperature level described in more detail before. In the embodiment shown here, the gas conditioning step 10 first comprises compressing 11 the starting gas mixture to the absorption pressure level and then cooling 12, 14, the starting gas mixture to the absorption temperature level.
  • the starting gas mixture of stream E comprises water and therefore the gas conditioning step 10 comprises drying 13 the starting gas mixture.
  • the gas conditioning step 10 comprises drying 13 the starting gas mixture.
  • at least two cooling steps are used for the cooling 12, 14 and the drying 13 is performed between these cooling steps.
  • the gas separation step 20 comprises a physical absorption 21 of at least a part of the carbon dioxide and of the hydrogen sulphide at the absorption pressure level and at the absorption temperature level.
  • the starting gas mixture conditioned in the condition step 10 is provided to the gas separation step in the form of a stream F.
  • a stream G rich in or essentially consisting of hydrogen sulphide is formed. This may be recycled to the Claus process. Furthermore, a stream H rich in or essentially consisting of hydrogen is formed. This may be used as the stream D already mentioned before. A stream I rich in or essentially consisting of carbon dioxide is transferred to a compression step 30.
  • Compression heat from the compression step 30, as indicated with K, but any other compression heat as well, may be withdrawn and e.g. be used in a steam system 4.
  • Steam M generated in the steam system 4 from boiler feed water 5 may e.g. be used to operate the air separation 3.
  • a carbon dioxide product stream N is withdrawn which may e.g. be used in enhanced oil recovery.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Treating Waste Gases (AREA)
  • Gas Separation By Absorption (AREA)

Abstract

La présente invention concerne un procédé (100) pour traiter un mélange gazeux de départ comprenant du sulfure d'hydrogène et du dioxyde de carbone, le procédé comprenant une étape de conditionnement de gaz (10) et une étape de séparation de gaz (20), l'étape de séparation de gaz (10) consistant à séparer au moins partiellement le mélange gazeux de départ. Selon l'invention, l'étape de conditionnement de gaz (10) comprend la fourniture du mélange gazeux de départ à un niveau de pression d'absorption de 4 à 10 bars (abs.) et à un niveau de température d'absorption de -30 à -50 °C, et l'étape de séparation de gaz (20) comprend une absorption physique (21) au niveau de la pression d'absorption et au niveau de la température d'absorption à l'aide d'un liquide d'absorption et la génération d'au moins deux fractions, dont l'une contient majoritairement ou exclusivement du dioxyde de carbone. Un appareil correspondant est également décrit dans la présente invention.
PCT/EP2020/025175 2019-04-18 2020-04-20 Procédé et appareil de traitement d'un mélange gazeux WO2020211984A1 (fr)

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GB1905562.3A GB2583137A (en) 2019-04-18 2019-04-18 Method and apparatus for treating a gas mixture
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US20130071308A1 (en) 2011-09-21 2013-03-21 Linde Aktiengesellschaft Co2 recovery using the sure process
WO2014005817A1 (fr) * 2012-07-06 2014-01-09 Total Sa Procédé intégré destiné à la récupération de co2 natif d'un gaz acide, comprenant du h2s et du co2

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US20130071308A1 (en) 2011-09-21 2013-03-21 Linde Aktiengesellschaft Co2 recovery using the sure process
WO2014005817A1 (fr) * 2012-07-06 2014-01-09 Total Sa Procédé intégré destiné à la récupération de co2 natif d'un gaz acide, comprenant du h2s et du co2

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