WO2020211983A1 - 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
WO2020211983A1
WO2020211983A1 PCT/EP2020/025174 EP2020025174W WO2020211983A1 WO 2020211983 A1 WO2020211983 A1 WO 2020211983A1 EP 2020025174 W EP2020025174 W EP 2020025174W WO 2020211983 A1 WO2020211983 A1 WO 2020211983A1
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Prior art keywords
gas mixture
carbon dioxide
gaseous
steps
group
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PCT/EP2020/025174
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English (en)
Inventor
Marcus Guzmann
Constantin Maniut
James Mercer
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Linde Gmbh
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Publication of WO2020211983A1 publication Critical patent/WO2020211983A1/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
    • B01D53/1481—Removing sulfur dioxide or sulfur trioxide
    • 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
    • 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
    • B01D53/26—Drying gases or vapours
    • B01D53/265—Drying gases or vapours by refrigeration (condensation)
    • 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • 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
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/48—Sulfur compounds
    • B01D53/50—Sulfur oxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B17/00—Sulfur; Compounds thereof
    • C01B17/02—Preparation of sulfur; Purification
    • C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
    • C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
    • 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
    • B01D2252/10—Inorganic absorbents
    • 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
    • B01D2256/22—Carbon dioxide
    • 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
    • B01D2257/80—Water
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Definitions

  • the invention relates to a method for treating a starting gas mixture comprising carbon dioxide, sulphur dioxide and water, the starting gas mixture being produced involving a Claus process operated with oxygen enrichment, 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, relating to 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.
  • 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
  • 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 (at least) carbon dioxide, sulphur dioxide and water, the starting gas mixture being produced involving a Claus process operated with oxygen enrichment, 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. Further background of the invention
  • sour gas mixture refers, in the language as used herein, to a gas mixture containing at least hydrogen sulphide and 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 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.
  • the present invention avoids the need of basically all components of a tail gas treatment, independently which specific method variant is used.
  • the present invention can be used to substitute a sulphur dioxide hydrogenation step involving a classical reducing gas generator and a catalytic stage subsequent thereto, as well as a physical solvent/amine system for removing hydrogen sulphide. If the Claus process is operated with an excess of hydrogen sulphide, the elements of a quench and amine section of which are used in such cases can be eleminated.
  • the present invention proposes to use an untreated, particularly a non-hydrogenated tail gas from a Claus process operated with oxygen enrichment as a starting gas mixture for a separation process that particularly produces a fraction predominantly or exclusively comprises carbon dioxide.
  • This fraction preferably can be used as a further attractive product of the method, e.g. for purposes of enhanced oil recovery or other purposes like food and beverage uses, desalination or the production of liquid carbon dioxide (LIC).
  • LIC liquid carbon dioxide
  • tail gas processing units such as a sulphur dioxide hydrogenation step, a corresponding catalytic stage and a sulphur condenser, a quench column, an absorbing unit (including a regeneration system) for removal of hydrogen sulphide can be dispensed of.
  • the present invention provides a method for treating a starting gas mixture comprising carbon dioxide, sulphur dioxide and water, the starting gas mixture being produced including a Claus process operated using oxygen enrichment.
  • the starting gas mixture may, as it contains sulphur dioxide, particularly be a tail gas of the Claus process which is not subjected to a hydrogenating treatment in a tail gas treatment unit.
  • the starting gas mixture may be formed using recycle streams from the inventive method and, for forming the starting gas mixture, particularly hydrogen sulphide which was previously contained in the tail gas mixture, may be converted to sulphur dioxide.
  • the starting gas mixture may also comprise other components like, but not limited to, carbon monoxide, hydrogen, carbonyl sulphide and carbon disulphide.
  • the starting gas mixture may also comprise hydrogen sulphide.
  • a starting gas mixture is, in the language as used herein, produced“including” 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 be a tail gas of the Claus process, as mentioned.
  • the term“Claus process” is indended to refer to any type of process that produces sulphur from a sulphur compound and furthermore produces a gas mixture including carbon dioxide, sulphur dioxide and/or hydrogen sulphide.
  • the term“Claus process” is not limited to the classical Claus processes described above in relation to the expert literature. It may include any number of catalytic stages, e.g. one, two, three or more catalytic stages.
  • the starting gas mixture may also be produced from or include such a tail gas. In all cases, 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 method comprises forming a fraction predominantly or exclusively containing carbon dioxide, this fraction being later herein also referred to a“carbon dioxide product.”
  • the inventive method comprises that the starting gas mixture is enriched in carbon dioxide and depleted in sulphur dioxide and water in a first group of method steps forming an intermediate gas mixture, the first group of method steps including compressing, cooling, condensating and drying steps, and in that the intermediate gas mixture is at least partially submitted to a second group of method steps, the second group of method steps including absorbing steps in which liquid carbon dioxide is used to absorb sulphur dioxide from the intermediate gas mixture, the liquid carbon dioxide being formed from carbon dioxide contained in the intermediate gas mixture after treatment in the absorbing steps.
  • the classical tail gas treatment of a Claus process can be dispensed of. While the Claus process can, in terms of the energy balance, be considered to represent a heat exporter (due to waste heat of the Claus furnace, for example), classical Claus tail gas treatment is heat consumer which consumes large parts, if not all, of the energy that is exported by the actual Claus process. In contrast to this, waste energy of the Claus process can be used, in the inventive method, for other purposes.
  • the present invention is used in connection with a Claus process which is operated using oxygen enrichment, i.e. if the Claus furnace is supplied with oxygen that is contained in a fluid stream which is enriched in oxygen when compared to atmospheric air or which is substantially pure oxygen.
  • a carbon dioxide product can be provided without cryogenic separation of nitrogen.
  • Oxygen enrichment in a Claus process does therefore form part of the present invention.
  • the starting gas mixture comprises carbon dioxide in a concentration sufficient to perform the inventive separation while, if a corresponding starting mixture comprises a lower concentration of carbon dioxide, a classical e.g. amine based carbon capture can be more economical to produce a carbon dioxide product fraction.
  • the tail gas from the Claus process which can be used as the starting gas mixture may, in an illustrative example, contain only 20.8 mol-% carbon dioxide, the rest of the main components are water (67.5 mol-%), carbon monoxide (6 mol-%), sulphur dioxide (2.2 mol-%), hydrogen (3.3 mol-%) and traces of carbonyl sulphide and carbon disulphide in combination.
  • the starting gas mixture may comprise 15 to 25 mol-% carbon dioxide, 1 to 5 mol-% sulphur dioxide and 60 to 70 mol-% water.
  • the first group of method steps includes subjecting the starting gas mixture to a first cooling step at a first pressure level and from a first temperature level to a second temperature level, forming a first condensate and a first gaseous remainder, subjecting at least a part of the first gaseous remainder to a compression step from the first pressure level to a second pressure level, forming a second condensate and a second gaseous remainder, subjecting at least a part of the second gaseous remainder to a further cooling step to a third temperature level, forming a third condensate and a third gaseous remainder, subjecting at least a part of the third gaseous remainder to a drying step obtaining a dried gas mixture, and using at least a part of the dried gas mixture as the intermediate gas mixture which is subjected to the second group of method steps.
  • the starting gas mixture is, in other words, in the first group of method steps firstly cooled and then compressed using an adequate compressor system designed for this type of media.
  • a condensate (the“first” condensate) is formed which already contains carbon dioxide and sulphur dioxide dissolved in water.
  • the carbon dioxide content is already increased at this point.
  • the subsequent compression of the gaseous remainder (“first” gaseous remainder) with availability of at least or exceeding 30 ton per hour is preferably realized using several, e.g. three, compression stages with intercooling.
  • more condensate is generated, additional sulphur dioxide being also removed in the liquid condensate and the carbon dioxide concentration further raises.
  • the first gaseous remainder may comprise 50 to 60 mol-% carbon dioxide, e.g. ca. 54.7 mol-% carbon dioxide
  • the second gaseous remainder and the dried gas mixture may each comprise 65 to 75 mol-% carbon dioxide and less sulphur dioxide and water than the starting gas mixture.
  • the second gaseous remainder may comprise ca. 70.4 mol-% carbon dioxide.
  • the starting gas mixture is provided at a first pressure level which is 0 to 1 bar (g), e.g. at a slight overpressure of 50 mbar (g).
  • the second pressure level may be 20 to 30 bar.
  • the second pressure level preferably is at least 22 bar (g) but due to efficiency reasons is preferably not above 27 bar (g).
  • the first temperature level, at which the starting gas mixture is provided is 200 to 300 °C, e.g. at least 240 °C, and the second temperature level and the third temperature level each are 0 to 60 °C, preferably below 50 °C.
  • the third gaseous remainder may still comprise up to 5,000 vppm water, preferably up to 2,000 vppm water, more preferably up to 1 ,000 or 600 vppm water, the dried gas mixture preferably only comprises less than 20 vppm water according to the present invention.
  • the purpose of the second group of method steps, including a liquefaction is firstly to increase the carbon dioxide content level to at least 95 mol-%, more preferably more than 98,5 mol-% or even more preferably 99,9 mol-%, which is the content of carbon dioxide in the fraction“predominantly or exclusively containing carbon dioxide” which is formed according to the present invention.
  • the purification of the carbon dioxide must be completed, as elucidated below.
  • the absorbing steps used in the second group of method steps include a first absorbing step using a first absorption column in which a first liquid bottom product and a first gaseous overhead product is formed, and a second absorbing step using a second absorption column in which a second liquid bottom product and a second gaseous overhead product is formed, at least a part of the intermediate gas mixture being supplied to the first absorbing step at least a part of the first gaseous overhead product being supplied to the second absorbing step, at least a part of the second gaseous overhead product being liquefied, and the liquid carbon dioxide used in the absorbing steps being formed from a part of the liquefied second gaseous overhead product.
  • the absorbing step reduces the amount of sulphur dioxide and traces of carbonyl sulphide/carbon disulphide present in the intermediate gas mixture.
  • the intermediate gas mixture is preferably routed through a highly efficient direct contact liquid carbon dioxide wash unit, referred to as an“absorption column” hereinbefore.
  • Absorption columns usable according to the present invention are known from the art per se.
  • Liquid carbon dioxide used in the first (and also in the second) absorption step is preferably high purity liquid carbon dioxide generated after the liquefaction, as described below.
  • intermediate gas mixture is reduced to 0 °C or less, more preferably even -10 °C or less, and secondly the sulphur dioxide concentration is greatly reduced.
  • the liquid carbon dioxide/sulphur dioxide mixture will then concentrate itself in the sump of the carbon dioxide absorption column, yielding the“first” bottom product. This is preferably withdrawn and treated in a waste treatment step or system as described below.
  • the first bottom product preferably comprises ca. 40 mol-% carbon dioxide, 58 mol-% sulphur dioxide, but also traces of carbon monoxide, hydrogen and carbonyl sulphide. Due to the high concentration of carbon dioxide, an additional handling of the bottom product formed in the first absorption step (“first bottom product”) is required and will be described below.
  • the overall flowrate of the first bottom product may preferably comprise ca. 1% of the flow rate (e.g. estimated in kg/h) of the intermediate gas mixture entering the first absorption step.
  • the first overhead product preferably has a carbon dioxide content of 70 to 75 mol-%, e.g. ca. 70.4 mol-% to 73 mol-%, while the sulphur dioxide content may preferably be reduced to 12 to 15 mol-%, e.g. ca 14.2 mol-%.
  • the concentration of all other components like non-condensable hydrogen and carbon monoxide may remain mainly unchanged.
  • the second absorption step serves the purpose of further reducing sulfur components presented in the intermediate gas mixture.
  • the first overhead product or a part thereof is therefore routed through a second highly efficient direct contact liquid carbon dioxide wash unit, referred to as“second” absorption column herein.
  • additional streams may be contacted with the first overhead product: a liquid carbon dioxide stream, preferably equal at an flowrate with the liquid carbon dioxide stream used in the first direct contact wash unit, a gaseous carbon dioxide stream from a recycling compressor unit subsequent to the waste treatment system and a second liquid carbon dioxide stream with an average carbon dioxide purity of e.g. 84 mol-% purity provided as an a e.g. 87.5/12.5 split of a stream formed from the second bottom product, the rest of which being provided to the waste treatment system, like the first bottom product.
  • a liquid carbon dioxide stream preferably equal at an flowrate with the liquid carbon dioxide stream used in the first direct contact wash unit
  • a gaseous carbon dioxide stream from a recycling compressor unit subsequent to the waste treatment system and a second liquid carbon dioxide stream with an average carbon dioxide purity of e.g. 84 mol-% purity provided as an a e.g. 87.5/12.5 split of a stream formed from the second bottom product, the rest of which being provided to the waste treatment system, like the first bottom product.
  • the second absorption step is preferably also supplied with a stream enriched in carbon dioxide and depleted in sulphur dioxide produced in the waste treatment system using at least a part of the first and the second bottom product, and a stream formed from a part of the second bottom product.
  • the impact of all the streams meeting in the second absorption column unit is more complex, but the impact is again double: Firstly, the feed gas to the second absorption step (at least a part of the first absorption step) is further reduced to temperatures nearing the liquefaction point (-23 °C), this being an important preparation step for the liquefaction, and secondly the sulphur dioxide concentration is reduced to trace levels only (this includes also other sulphur species like carbonyl sulphide/carbon disulphide). The carbon dioxide concentration increases again, e.g. from 70 to 75 mol-% to 75 mol-% to 77 mol-%, e.g. from ca. 73 mol-% to ca. 76.4 mol- %, wherein the amount of non-condensable hydrogen and carbon monoxide remains further on mainly unchanged.
  • the second bottom product still contains large amounts, i.e. 82 to 86 mol-%, e.g. ca. 84 mol-%, of carbon dioxide and therefore additional handling in the waste treatment system is required to recover the carbon dioxide at maximum extent possible or advantageous.
  • the part of the second bottom product not recycled to the second absorption step is therefore preferably sent to the waste treatment system, preferably including a low-pressure rectification system to separate mainly the liquid carbon dioxide by the gaseous sulphur dioxide.
  • the pressure of the corresponding stream may be is reduced to 5 to 6 bar (g), e.g. to 5.5 bar (g) and temperature drops automatically as a result of the isenthalpic process to -40 to -50 °C, e.g.
  • the first liquid bottom product and the second liquid bottom product are treated in the waste handling step, forming a fraction which is recycled to the Claus process.
  • Two phases are generated in the waste handling step due to the expansion mentioned, these particularly being one liquid phase containing mainly carbon dioxide and sulphur dioxide, e.g. ca. 80.5 mol-% carbon dioxide and ca. 18.6 mol-% sulphur dioxide and a gaseous phase containing significantly less sulphur dioxide, e.g. ca. 97.2 mol-% carbon dioxide and only 0.6 mol-% sulphur dioxide.
  • the rest of the components in the gaseous phase are preferably hydrogen and carbon monoxide.
  • Both these streams together with the first bottom product whose pressure may be reduced to the same level, may be forwarded to a further separation system, e.g. a low-pressure rectification system, the liquid phase being the liquid feed at the top of a rectification column in such a system and the gaseous phase being used as the boil-up.
  • a further separation system e.g. a low-pressure rectification system
  • the liquid phase being the liquid feed at the top of a rectification column in such a system and the gaseous phase being used as the boil-up.
  • the reboiler unit of the rectification system will generate enough boil-up to assure a proper sulphur dioxide distillation.
  • the liquid phase of this further separation system contains up to 66 mol-% carbon dioxide, preferably 50 mol-% carbon dioxide, most preferably 20 mol-% carbon dioxide and the rest is represented by sulphur dioxide in the correct balance.
  • the amount of sulphur dioxide concentrated in this stream of 33 mol-%, preferably 50 mol-%, most preferably 80 mol-% and this stream is recycled to the Claus process. Accordingly, the oxygen concentration in the feed to the Claus process is preferably adjusted
  • the gaseous phase of this further separation system has a carbon dioxide
  • Liquefaction and further purification of the second overhead product preferably comprises a liquefaction against liquid carbon dioxide in a ratio of e.g. 45 to 55% and further on in the balance chiller to a vapour/liquid ratio of e.g. 0.4/0.6.
  • the liquid carbon dioxide obtained accordingly may comprise a carbon dioxide concentration of more than 98 mol-%, e.g. ca. 98.3 mol-%, with main impurities like 1.4 mol-% carbon monoxide, 0.1 mol-% hydrogen and traces of sulphur dioxide/carbonyl sulphide/carbon disulphide.
  • the liquefaction step may preferably instead be realized in a rectification unit and a recycle stream may be increased.
  • the final carbon dioxide product may enter a further treatment step described below.
  • a gas phase remaining in the liquefaction step still may contain 40 to 50 mol-%, e.g. 43.5 mol-% carbon dioxide that is preferably recovered.
  • Other components like hydrogen (e.g. ca. 20.4 mol-%) and carbon monoxide (e.g. ca 36 mol-%) may also be present in this stream and have a certain heat value that is preferably reused in the Claus process.
  • the gas has a low temperature of e.g. ca. -42 °C and a high pressure of e.g. ca. 24.6 bar (g), representing conditions that are ideal for the use of a methanol wash system as a separation step, which is therefore preferably used.
  • two gaseous streams are available, one low pressure and low temperature highly carbon dioxide concentrated stream with 99.9 mol-% carbon dioxide and a synthesis gas stream at high pressure and low temperature gas stream with e.g. ca. 35.9 mol-% hydrogen and 63.4 mol-% carbon monoxide to be reused in the Claus process.
  • heat is transferred in the first group of method steps to a part of the liquefied second gaseous overhead product, forming an evaporated carbon dioxide product.
  • the evaporated carbon dioxide product may be compressed to provide a compressed carbon dioxide product, representing the fraction comprising predominantly or exclusively carbon dioxide as mentioned above.
  • Compression may e.g. be performed to 200 to 300 bar (g), e.g. ca. 240 bar (g) and the compressed stream may be delivered for use in enhanced oil recovery.
  • Other applications can be included, e.g. usage of carbon dioxide for liquid carbon dioxide supply and for the beverage market.
  • the fraction predominantly or exclusively comprising carbon dioxide according to the present invention may at least in part be produced as or processed to a liquid fraction. That is, such a fraction may be withdrawn in liquid form or may be liquefied from a gaseous fraction. Any further processing, like conventional in the art for producing carbon dioxide for food and beverage uses, may also be included.
  • Any compression step in the method of the present invention generates substantial amounts of compression heat. Through the use of one or more heat exchangers, 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 invention 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 used in providing oxygen for oxygen enrichment in the Claus 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.
  • the present invention also relates to an apparatus for treating a starting gas mixture comprising carbon dioxide, sulphur dioxide and water, the starting gas mixture being produced including a Claus process operated with oxygen enrichment, wherein the apparatus comprises means adapted to forming a fraction predominantly or exclusively containing carbon dioxide.
  • means are provided which are adapted to enrich the starting gas mixture in carbon dioxide and deplete the starting gas mixture in sulphur dioxide and water forming an intermediate gas mixture in a first group of method steps including compressing, cooling, condensating and drying steps, and in that means are provided which are adapted to at least partially submit the intermediate gas mixture to a second group of method steps, the second group of method steps including absorbing steps in which liquid carbon dioxide is used to absorb sulphur dioxide from the intermediate gas mixture, the liquid carbon dioxide being formed from carbon dioxide contained in the intermediate gas mixture after treatment in the absorbing steps.
  • Figure 1 illustrates a method according to an embodiment of the invention.
  • a starting gas mixture A comprising carbon dioxide, sulphur dioxide and water is produced including a Claus process 1.
  • a recycling stream B explained below may also be used in forming the starting gas mixture A.
  • a tail gas incinerator 2 to destroy rests of hydrogen sulphide in the tail gas of the Claus process 1 may also be used in the method 100.
  • the method 100 generally comprises forming a fraction predominantly or exclusively containing carbon dioxide.
  • the starting gas mixture A is enriched in carbon dioxide and depleted in sulphur dioxide and water in a first group 10 of method steps forming an intermediate gas mixture C, the first group 10 of method steps including compressing 11 , cooling 12, 13, condensating and drying 14 steps.
  • the intermediate gas mixture C is at least partially submitted to a second group of method steps 20, the second group 20 of method steps including absorbing 21 , 22 steps in which liquid carbon dioxide is used to absorb sulphur dioxide from the intermediate gas mixture C, the liquid carbon dioxide being formed from carbon dioxide contained in the intermediate gas mixture after treatment in the absorbing steps 21 , 22.
  • the first group 10 of method steps includes subjecting the starting gas mixture to a first cooling step 11 at a first pressure level and from a first temperature level to a second temperature level, forming a first condensate and a first gaseous remainder, and subjecting at least a part of the first gaseous remainder to a compression step 12 from the first pressure level to a second pressure level, forming a second condensate and a second gaseous remainder.
  • the first and second condensates are not shown here for reasons of conciseness, and the first cooling step 11 and the compression step 12 are shown as a common block 12, 13.
  • At least a part of the second gaseous remainder remaining after compression 12 is subjected to a further cooling step 13 to a third temperature level, forming a third condensate (again not shown) and a third gaseous remainder.
  • At least a part of the third gaseous remainder is subjected to a drying step 14, obtaining a dried gas mixture, and at least a part of the dried gas mixture is used as the intermediate gas mixture C which is subjected to the second group 10 of method steps.
  • the absorbing steps 21 , 22 used in the second group 20 of method steps in the method 100 include a first absorbing step 21 using a first absorption column in which a first liquid bottom product D and a first gaseous overhead product E is formed, and a second absorbing step 22 using a second absorption column in which a second liquid bottom product F and a second gaseous overhead product G is formed.
  • At least a part of the intermediate gas mixture C is supplied to the first absorbing step 21
  • at least a part of the first gaseous overhead product E is supplied to the second absorbing step 22
  • at least a part of the second gaseous overhead product G is liquefied
  • the liquid carbon dioxide used in the absorbing steps 21 , 22, shown as streams H1 and H2 are formed from a part of the liquefied second gaseous overhead product G which is treated in a liquefaction and purification step 23 and which is withdrawn therefrom in form of a stream H.
  • a part F1 of the second bottom product is recycled to the second absorption step 22 as described before.
  • the remainder F2 and preferably the first bottom product are submitted to a waste treatment step 24.
  • a stream I rich in sulphur dioxide which is recycled to the Claus process 1
  • a stream K which is rich in carbon dioxide and which submitted to a recompression step 25 and then recycled to the second absorption step 22 are formed.
  • the stream H mentioned before is produced in form of a liquid stream rich in carbon dioxide.
  • a part H3 of this stream, which is not used as described before, is submitted to an energy recovery step 26 and then heated in the cooling step 11 in the first group 10 of method steps. Thereafter, a compression in a compression step 40 is performed.
  • the compressed stream H3 may be used for the purposes described above.
  • a further stream L less rich in carbon dioxide than the stream H is withdrawn from the liquefaction and purification step 23 in gaseous form and subjected to a washing step 30, particularly including a methanol wash.
  • a high pressure stream M rich in carbon monoxide and hydrogen and a low pressure stream N rich in carbon dioxide are formed. Both streams are routed through the energy recovery step 26.
  • the stream M is e.g. used for firing purposes and the stream N is e.g. used as the recycling stream B.

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Abstract

La présente invention concerne un procédé (100) de traitement d'un mélange gazeux de départ comprenant du dioxyde de carbone, du dioxyde de soufre et de l'eau, le mélange gazeux de départ étant produit comprenant un processus Claus (1), le procédé comprenant la formation d'une fraction majoritairement ou exclusivement contenant du dioxyde de carbone. Selon la présente invention, le mélange gazeux de départ est enrichi en dioxyde de carbone et appauvri en dioxyde de soufre et en eau dans un premier groupe (10) d'étapes de procédé formant un mélange gazeux intermédiaire, le premier groupe (10) d'étapes de procédé comprenant la compression (11), le refroidissement (12, 13), la condensation et le séchage (13) étapes, et en ce que le mélange gazeux intermédiaire est soumis au moins partiellement à un deuxième groupe d'étapes de procédé (20), le deuxième groupe (20) d'étapes de procédé comprenant l'absorption (21, 22) étapes dans lesquelles du dioxyde de carbone liquide est utilisé pour absorber le dioxyde de soufre à partir du mélange gazeux intermédiaire, le dioxyde de carbone liquide étant formé à partir de dioxyde de carbone contenu dans le mélange gazeux intermédiaire après traitement dans les étapes absorbantes (21, 22). L'invention concerne également un appareil correspondant.
PCT/EP2020/025174 2019-04-18 2020-04-20 Procédé et appareil de traitement d'un mélange gazeux WO2020211983A1 (fr)

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US20130071308A1 (en) 2011-09-21 2013-03-21 Linde Aktiengesellschaft Co2 recovery using the sure process

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CA2878403C (fr) * 2012-07-06 2020-05-26 Total Sa Procede integre destine a la recuperation de co2 natif d'un gaz acide, comprenant du h2s et du co2

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GB2048708A (en) * 1979-04-18 1980-12-17 Cng Res Co Processes for Separating a Crystallizable Material From at Least one Other Material
US4609388A (en) * 1979-04-18 1986-09-02 Cng Research Company Gas separation process
US4684514A (en) 1985-07-22 1987-08-04 Air Products And Chemicals, Inc. High pressure process for sulfur recovery from a hydrogen sulfide containing gas stream
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