EP1536882A1 - Autothermal method comprising periodic flow reversal - Google Patents

Autothermal method comprising periodic flow reversal

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Publication number
EP1536882A1
EP1536882A1 EP03757758A EP03757758A EP1536882A1 EP 1536882 A1 EP1536882 A1 EP 1536882A1 EP 03757758 A EP03757758 A EP 03757758A EP 03757758 A EP03757758 A EP 03757758A EP 1536882 A1 EP1536882 A1 EP 1536882A1
Authority
EP
European Patent Office
Prior art keywords
regeneration
fixed bed
temperature
phase
reactor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03757758A
Other languages
German (de)
French (fr)
Inventor
Gerhart Eigenberger
Bernd Glöckler
Gregorius Kolios
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Evonik Operations GmbH
Original Assignee
Eigenberger Gerhart
Glockler Bernd
Kolios Gregorius
Evonik Degussa GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eigenberger Gerhart, Glockler Bernd, Kolios Gregorius, Evonik Degussa GmbH filed Critical Eigenberger Gerhart
Publication of EP1536882A1 publication Critical patent/EP1536882A1/en
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • B01J8/0285—Heating or cooling the reactor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • B01J8/0207—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid flow within the bed being predominantly horizontal
    • B01J8/0221—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid flow within the bed being predominantly horizontal in a cylindrical shaped bed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • B01J8/04—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds
    • B01J8/0403—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds the fluid flow within the beds being predominantly horizontal
    • B01J8/0423—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds the fluid flow within the beds being predominantly horizontal through two or more otherwise shaped beds
    • B01J8/0438—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds the fluid flow within the beds being predominantly horizontal through two or more otherwise shaped beds the beds being placed next to each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • B01J8/04—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds
    • B01J8/0496—Heating or cooling the reactor
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C01B3/12—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide
    • C01B3/16—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents by reaction of water vapour with carbon monoxide using catalysts
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    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/38—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/46—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using discontinuously preheated non-moving solid materials, e.g. blast and run
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00026—Controlling or regulating the heat exchange system
    • B01J2208/00035—Controlling or regulating the heat exchange system involving measured parameters
    • B01J2208/00044—Temperature measurement
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00106—Controlling the temperature by indirect heat exchange
    • B01J2208/00309—Controlling the temperature by indirect heat exchange with two or more reactions in heat exchange with each other, such as an endothermic reaction in heat exchange with an exothermic reaction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00327—Controlling the temperature by direct heat exchange
    • B01J2208/00336—Controlling the temperature by direct heat exchange adding a temperature modifying medium to the reactants
    • B01J2208/00353—Non-cryogenic fluids
    • B01J2208/00371—Non-cryogenic fluids gaseous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00389—Controlling the temperature using electric heating or cooling elements
    • B01J2208/00398—Controlling the temperature using electric heating or cooling elements inside the reactor bed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00389—Controlling the temperature using electric heating or cooling elements
    • B01J2208/00415—Controlling the temperature using electric heating or cooling elements electric resistance heaters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00504—Controlling the temperature by means of a burner
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00017—Controlling the temperature
    • B01J2208/00522—Controlling the temperature using inert heat absorbing solids outside the bed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00191—Control algorithm
    • B01J2219/00193—Sensing a parameter
    • B01J2219/00195—Sensing a parameter of the reaction system
    • B01J2219/002—Sensing a parameter of the reaction system inside the reactor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00243—Mathematical modelling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/18—Details relating to the spatial orientation of the reactor
    • B01J2219/182—Details relating to the spatial orientation of the reactor horizontal
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    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
    • C01B2203/0227—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
    • C01B2203/0233—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being a steam reforming step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0283—Processes for making hydrogen or synthesis gas containing a CO-shift step, i.e. a water gas shift step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/08—Methods of heating or cooling
    • C01B2203/0805—Methods of heating the process for making hydrogen or synthesis gas
    • C01B2203/0838—Methods of heating the process for making hydrogen or synthesis gas by heat exchange with exothermic reactions, other than by combustion of fuel
    • C01B2203/0844—Methods of heating the process for making hydrogen or synthesis gas by heat exchange with exothermic reactions, other than by combustion of fuel the non-combustive exothermic reaction being another reforming reaction as defined in groups C01B2203/02 - C01B2203/0294
    • 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
    • Y02P20/10—Process efficiency
    • Y02P20/133—Renewable energy sources, e.g. sunlight

Definitions

  • the invention relates to an autothermal process for coupling endothermic and exothermic reactions in reactors with periodic flow reversal.
  • these can be high-temperature reactions.
  • thermodynamic equilibrium endothermic synthesis reactions often require high temperatures of 500 to 1000 ° C in order to proceed with a sufficiently high conversion.
  • Typical examples are dehydrogenation and steam reforming of hydrocarbons to produce synthesis gas.
  • the gaseous or vaporous starting materials must first be heated to the reaction temperature and then the required enthalpy of reaction must be supplied to them at high temperature.
  • the heat required for this is provided by an exothermic accompanying reaction, usually a combustion reaction.
  • the present application extends the state of the art laid down in PCT / EP00 / 10928 by concrete inventive configurations for the above-mentioned asymmetrical case in which one endothermic reaction in a cyclical change with an exothermic accompanying reaction in a catalytic fixed bed reactor with periodic change of the flow direction is to be carried out.
  • the invention is based on the following concept: If gaseous or vaporous feedstocks for an endothermic reaction at low temperature are introduced into an adiabatic catalyst bed which is uniformly preheated to a sufficiently high temperature T ma ⁇ , a pronounced temperature which migrates in the direction of flow develops. and turnover front, in which a turnover is reached which corresponds to the equilibrium turnover at the temperature T ma ⁇ .
  • Low temperature is understood to mean the ambient temperature or a temperature which is above or at the temperature at which the substances in question are gaseous or vaporous.
  • a sufficiently high temperature T ma ⁇ is understood to mean a temperature at which the endothermic reaction is so rapid that it largely takes place in a manner controlled by equilibrium and at the same time the equilibrium conversion is sufficient for technical applications.
  • the production phase of the endothermic reaction lasts as long as the reaction front is in the active part of the catalyst bed.
  • the fixed bed cools down in the production phase.
  • the production phase must be followed by a regeneration phase in which the catalyst bed is heated up again to the original uniform temperature T max .
  • the regeneration takes place according to the invention in that a regeneration stream with a low temperature is fed continuously to the reactor during the regeneration phase in countercurrent to the production phase, the
  • Production time corresponds to ⁇ ⁇ .
  • This regeneration gas stream is supplied with heat at several discrete points arranged over the length of the catalytically active region and distributed over the flow cross-section such that the original temperature profile is set again at the end of the regeneration phase.
  • the distance between the feed points is' about to be selected so long as a pure temperature front during the duration of the regeneration passes through the catalyst bed.
  • a further embodiment results if the inlets already have a high temperature.
  • the reaction mixture continuously enters the front end of the reactor and is heated by the fixed bed to the temperature T ma ⁇ necessary for the required conversion, where T m a is greater than or equal to a minimum preheating temperature T j. and reacts in a catalytically active part of the fixed bed, whereby the fixed bed cools down.
  • a regeneration stream with the desired maximum temperature T max is passed through the catalytically active fixed bed until the entire catalytically active area has again reached the maximum temperature T max .
  • Figures 2a and 2b Diagrams of the temperature and turnover curve in the method according to the invention
  • Figure 3 Diagrams for changing the
  • Figure 4 a reactor structure.
  • FIGS. 1 a and 1 b show, using the example of steam reforming of methane and assuming a reaction conversion determined only by the temperature, how the temperature front spreads through the catalyst bed starting from temperature profile 1 or 1 ′.
  • the length coordinate of the catalyst bed is designated z and is given in meters.
  • the temperature rises very quickly from a base temperature TB to the preheating or maximum temperature T max in the fixed bed, while the turnover increases accordingly.
  • An implicit determination equation is given below for the asymptotic final value of the base temperature in a sufficiently long catalyst bed.
  • the higher the preheating temperature T max the slower the front moves and the lower the base temperature T B ( Figure lb).
  • the minimum preheating temperature Ti of the catalyst bed from which a pronounced front is formed under the conditions mentioned, follows from the condition: d 2 x
  • X is the equilibrium conversion of the endothermic reaction which depends on the reaction temperature T. Its gradient
  • Velocity of migration of a fictitious, dissipation-free thermal front which is an inert gas flow with the same
  • the fixed bed reactor should be as in FIG. 2 be sketched.
  • the fixed bed consists of a catalytically active zone and an inert edge zone, which are arranged one behind the other in the direction of flow.
  • the catalytically active zone can also be preceded by a short inert zone.
  • the temperature profile at the beginning of the production phase (state 1) has an increasing one
  • the subsequent inert bed prevents the sales from falling again as the temperature drops.
  • the outlet temperature is constantly at the level of the inlet temperature during this time interval. This prevents sensible heat from being discharged from the reactor.
  • the heat storage capacity of the fixed bed made of catalyst and inert material is largely exhausted and the outlet temperature would then rise (state 2).
  • the dashed lines show the temperature and turnover curves at the end of the production phase.
  • the dotted lines in between represent profiles at times between states 1 and 2.
  • the peripheral zone can also contain a catalyst for a desirable subsequent reaction. However, it must not catalyze the main endothermic reaction.
  • a typical example in the case of steam reforming of methane would be the replacement of the inert peripheral zone with a water gas shift catalyst, in which CO and water vapor are increasingly converted into CO 2 and hydrogen as the temperature drops.
  • the regeneration of the bed from state 2 to state 1 is required to implement an efficient cyclic process.
  • the process conditions during the regeneration phase must meet the following requirements:
  • the profile of the maximum temperature T max is set by regulating the local heat input via temperature sensors which are installed in the vicinity of the feeds and downstream in the direction of the regeneration current.
  • the heat input can z. B. by in the Catalyst bed installed heating elements or by hot gas feed.
  • a solution is particularly preferred in which a reactant for an exothermic reaction is admixed to the regeneration gas stream at the feed points, which reacts automatically at the prevailing temperature and takes place completely, e.g. B. a catalytic combustion.
  • FIG. 3 schematically shows the configuration of a fixed bed reactor with temperature-controlled side feed of a reactant required for the regeneration and the basic change in the temperature fronts during the regeneration time.
  • the temperature controller is labeled TC. It can be seen how the temperature fronts generated at the feed points replenish the broken temperature profile and at the same time a shift of the temperature profile flanks takes place at the entry and exit of the (inert) bed to the starting position.
  • FIG. 4 shows a possible reactor structure according to the invention using the example of steam reforming of methane.
  • the reactor 1 contains an axially structured fixed bed with the inert edge zones 2 and 4 and the catalytically active zone 3, which is filled with a suitable reforming catalyst.
  • Four distributors 5 for feeding an additional stream are integrated in the reactor 1.
  • the distributors are supplied by axially guided supply lines that have good thermal contact with the surrounding fixed bed.
  • the distance between the distributors corresponds to the distance that a fictitious thermal front would cover during the regeneration phase.
  • Thermocouples 6 are installed in the vicinity of the distributors and are used to regulate the temperature of the reactor.
  • the reactor 1 is mixed with a mixture 7 of technically relevant feed composition
  • the distributors 5 are supplied with a fuel 9, for example methane, or the exhaust gas of a pressure swing adsorption system for hydrogen purification.
  • the throughput in the supply lines is set by means of control valves 10 so that the temperature of the measuring points is regulated to 1000 K.
  • a fuel-containing main stream 8 can also be fed to the reactor during the regeneration phase, in which an oxygen-containing gas, e.g. B. air is added.
  • the cyclic process described is characterized by a high level of energy efficiency, since the inlet and outlet take place (relatively) cold in both the production and regeneration period and the high temperature required for the endothermic reaction remains completely in the reactor.
  • Ti is the temperature that the catalyst bed reached at the end of the production phase.
  • An endothermic reaction can advantageously be carried out in the manner described.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
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  • General Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)

Abstract

The invention relates to a method for carrying out endothermic reactions in an autothermal manner in adiabatic fixed bed reactors (4), alternating cyclically between a production phase for the endothermic reaction and a regeneration phase for the heat supply. According to said method, during the production phase, a low-temperature reaction mixture (7) enters the front end of the reactor, is heated to the necessary temperature Tmax for the required conversion, whereby Tmax is greater than or equal to a minimum pre-heating temperature Tr, reacts in a catalytically active part of the fixed bed, simultaneously cooling the fixed bed and then exits the reactor via a rear, inert zone that is located downstream of the catalytically active part, or exits an additional catalytic fixed bed. During the regeneration phase, a low-temperature regeneration flow (8) is supplied to the rear end of the reactor and is drawn off at the front end, the overall heat capacity m pcPR?tR of the regeneration flow m R over the regeneration period ?tR corresponding to 70 to 300 %, preferably 80 to 120 % of the corresponding overall heat capacity m pcPR?tR of the reaction mixture over the production period ?tP. Heat is supplied to several discrete (5) points that are located along the length of the catalytically active zone and distributed over the flow cross-section in such a way that an original temperature profile is re-established at the end of the regeneration phase.

Description

AUTOTHERMES VERFAHREN MIT PERIODISCHER STROMUNGSUM EHR AUTOTHERMAL PROCESS WITH PERIODIC FLOW EHR
Beschreibungdescription
Die Erfindung betrifft ein autothermes Verfahren zur Kopplung endothermer und exothermer Reaktionen in Reaktoren mit periodischer Strömungsumkehr. Insbesondere kann es sich hierbei um Hochtemperaturreaktionen handeln.The invention relates to an autothermal process for coupling endothermic and exothermic reactions in reactors with periodic flow reversal. In particular, these can be high-temperature reactions.
Endotherme Synthesereaktionen benötigen aus Gründen des thermodynamisehen Gleichgewichts häufig hohe Temperaturen von 500 bis 1000°C, um mit ausreichend hohem Umsatz abzulaufen. Typische Beispiele sind Dehydrierungen sowie die Dampf- Reformierung von Kohlenwasserstoffen zur Erzeugung von Synthesegas. Das bedeutet, dass die gas- oder dampfförmig vorliegenden Edukte zunächst auf Reaktionstemperatur aufgeheizt werden müssen und ihnen dann die benötigte Reaktionsenthalpie bei hoher Temperatur zugeführt werden muss. In aller Regel wird die dafür benötigte Wärme über eine exotherme Begleitreaktion, meist eine Verbrennungsreaktion, bereitgestellt. Dabei kommt einer möglichst direkten thermischen Kopplung der endothermen Synthese mit der exothermen Begleitreaktion sowie einer effizienten Wärmeintegration des Gesamtsystems entscheidende wirtschaftliche Bedeutung zu. Idealerweise sollten alle an der endothermen und der exothermen Reaktion beteiligten Edukte dem Reaktionssystem „kalt", d.h. bei Umgebungstemperatur bzw. bei einer Temperatur knapp oberhalb einer möglichen Kondensation zugeführt und alle entstehenden Produkte bei vergleichbar niedrigen Temperaturen abgeführt werden, so dass die für die Reaktion benötigte Zone hoher Temperatur vollständig im Reaktor verbleibt. Eine solche Reaktionsführung wird als „autotherm" bezeichnet. Aus dem Stand der Technik ist beispielsweise die PCT/EP00/10928 bekannt, die die autotherme Kopplung endothermer und exothermer Reaktionen beschreibt. Demnach ist ein optimales Verfahren insbesondere durch Gegenstromführung von Prozessgasen mit gleichen Wärmekapazitätsströmen in den Wärmetauschzonen der Reaktorschaltung und durch die örtlich verteilte Dosierung von Edukten der exothermen Reaktion gekennzeichnet .For reasons of thermodynamic equilibrium, endothermic synthesis reactions often require high temperatures of 500 to 1000 ° C in order to proceed with a sufficiently high conversion. Typical examples are dehydrogenation and steam reforming of hydrocarbons to produce synthesis gas. This means that the gaseous or vaporous starting materials must first be heated to the reaction temperature and then the required enthalpy of reaction must be supplied to them at high temperature. As a rule, the heat required for this is provided by an exothermic accompanying reaction, usually a combustion reaction. Thereby, a direct thermal coupling of the endothermic synthesis with the exothermic accompanying reaction as well as an efficient heat integration of the overall system is of crucial economic importance. Ideally, all of the starting materials involved in the endothermic and exothermic reaction should be fed to the reaction system “cold”, ie at ambient temperature or at a temperature just above a possible condensation, and all the products formed should be removed at comparatively low temperatures, so that those required for the reaction Zone of high temperature remains completely in the reactor. Such a reaction procedure is referred to as "autothermal". For example, PCT / EP00 / 10928 is known from the prior art, which describes the autothermal coupling of endothermic and exothermic reactions. Accordingly, an optimal process is characterized in particular by countercurrent flow of process gases with the same heat capacity flows in the heat exchange zones of the reactor circuit and by the locally distributed metering of educts of the exothermic reaction.
Darüber hinaus sind aus dem Stand der Technik asymmetrische Fahrweisen mit periodischem Wechsel der Strömungsrichtung bekannt, wobei ein Zyklus aus einer endothermen Produktionsphase mit Durchströmung des Reaktors in einer Richtung und einer exothermen Regenerationsphase mit Durchströmung in Gegenrichtung besteht. Für diesen Fall existieren bisher keine überzeugenden Konzepte. Die Unzulänglichkeiten der Reaktionsführung führen entweder zu exzessiven Maximaltemperaturen {M. S . Kulkarnl and M. P. Dudukovlc : Ind. Eng. Chem . Res . , 37, 770- 781 (1998) ) oder zu einer technisch uninteressanten Reaktorleistung (G. Kollos and G. Elgenberger: Chem . Eng. Sei . , 54, 2637-2646 (1999) ) .In addition, asymmetrical modes of operation with a periodic change in the flow direction are known from the prior art, a cycle consisting of an endothermic production phase with flow through the reactor in one direction and an exothermic regeneration phase with flow through in the opposite direction. No convincing concepts exist for this case so far. The inadequacies of the reaction either lead to excessive maximum temperatures {M. S. Kulkarnl and M. P. Dudukovlc: Ind. Eng. Chem. Res. , 37, 770-781 (1998)) or to a technically uninteresting reactor performance (G. Kollos and G. Elgenberger: Chem. Eng. Sei., 54, 2637-2646 (1999)).
Es ist nun Aufgabe der vorliegenden Erfindung, das Verfahren aus dem Stand der Technik in vorteilhafter Weise weiterzubilden .It is an object of the present invention to further develop the prior art method in an advantageous manner.
Die Aufgabe wird hierbei gelöst durch ein Verfahren mit den Merkmalen des Anspruchs 1 bzw. 12.The object is achieved here by a method having the features of claims 1 and 12, respectively.
Vorteilhafte Ausgestaltungen der Erfindung finden sich in den Unteransprüchen .Advantageous embodiments of the invention can be found in the subclaims.
Die vorliegende Anmeldung erweitert den in PCT/EP00/10928 niedergelegten Stand der Technik um konkrete erfinderische Ausgestaltungen für den o. a. asymmetrischen Fall, in dem eine endotherme Reaktion im zyklischen Wechsel mit einer exothermen Begleitreaktion in einem katalytischen Festbettreaktor mit periodischem Wechsel der Strömungsrichtung durchgeführt werden soll.The present application extends the state of the art laid down in PCT / EP00 / 10928 by concrete inventive configurations for the above-mentioned asymmetrical case in which one endothermic reaction in a cyclical change with an exothermic accompanying reaction in a catalytic fixed bed reactor with periodic change of the flow direction is to be carried out.
Die Erfindung beruht auf folgendem Konzept: Werden gas- oder dampfförmige Einsatzstoffe für eine endotherme Reaktion mit niedriger Temperatur in ein adiabates Katalysatorbett eingeleitet, das einheitlich auf eine ausreichend hohe Temperatur Tmaχ vorgeheizt ist, so entwickelt sich eine ausgeprägte, in Strömungsrichtung wandernde Temperatur- und Umsatzfront, in der ein Umsatz erreicht wird, der dem Gleichgewichtsumsatz bei der Temperatur Tmaχ entspricht. Dabei soll unter niedriger Temperatur die Umgebungstemperatur oder eine Temperatur verstanden werden, die oberhalb oder bei der Temperatur liegt, bei der die betreffenden Stoffe gas- bzw. dampfförmig sind. Als ausreichend hohe Temperatur Tmaχ wird eine Temperatur verstanden, bei der die endotherme Reaktion so schnell ist, dass sie weitgehend gleichgewichtskontrolliert abläuft und gleichzeitig der Gleichgewichtsumsatz für technische Anwendungen ausreicht.The invention is based on the following concept: If gaseous or vaporous feedstocks for an endothermic reaction at low temperature are introduced into an adiabatic catalyst bed which is uniformly preheated to a sufficiently high temperature T ma χ, a pronounced temperature which migrates in the direction of flow develops. and turnover front, in which a turnover is reached which corresponds to the equilibrium turnover at the temperature T ma χ. Low temperature is understood to mean the ambient temperature or a temperature which is above or at the temperature at which the substances in question are gaseous or vaporous. A sufficiently high temperature T ma χ is understood to mean a temperature at which the endothermic reaction is so rapid that it largely takes place in a manner controlled by equilibrium and at the same time the equilibrium conversion is sufficient for technical applications.
Die Produktionsphase der endothermen Reaktion dauert so lange, wie sich die Reaktionsfront im aktiven Teil des Katalysatorbettes befindet. In der Produktionsphase kühlt das Festbett ab.The production phase of the endothermic reaction lasts as long as the reaction front is in the active part of the catalyst bed. The fixed bed cools down in the production phase.
Der Produktionsphase muss sich eine Regenerationsphase anschließen, in der das Katalysatorbett wieder auf die ursprüngliche einheitliche Temperatur Tmax aufgeheizt wird. Die Regeneration erfolgt erfindungsgemäß dadurch, dass dem Reaktor während der Regenerationsphase kontinuierlich ein Regenerationsstrom mit niedriger Temperatur im Gegenstrom zur Produktionsphase zugeführt wird, wobei dieThe production phase must be followed by a regeneration phase in which the catalyst bed is heated up again to the original uniform temperature T max . The regeneration takes place according to the invention in that a regeneration stream with a low temperature is fed continuously to the reactor during the regeneration phase in countercurrent to the production phase, the
Gesamtwärmekapazität mP cPRAtR des Regenerationsstroms mR über der Regenerationsdauer AtR in etwa der entsprechenden Gesamtwärmekapazität mP cPPAtP des Reaktionsgemischs über derTotal heat capacity m P c PR At R of the regeneration current m R over the regeneration period At R roughly the corresponding one Total heat capacity m P c PP At P of the reaction mixture over the
Produktionsdauer Δ^entspricht . Diesem Regenerationsgasstrom wird an mehreren diskreten, über der Länge des katalytisch aktiven Bereichs angeordneten Stellen Wärme so zugeführt und über dem Strömungsquerschnitt verteilt, dass das ursprüngliche Temperaturprofil am Ende der Regenerationsphase wieder eingestellt wird. Dabei ist ' der Abstand zwischen den Einspeisestellen etwa so lang zu wählen, wie eine reine Temperaturfront während der Dauer der Regeneration durch das Katalysatorbett wandert.Production time corresponds to Δ ^. This regeneration gas stream is supplied with heat at several discrete points arranged over the length of the catalytically active region and distributed over the flow cross-section such that the original temperature profile is set again at the end of the regeneration phase. The distance between the feed points is' about to be selected so long as a pure temperature front during the duration of the regeneration passes through the catalyst bed.
Eine weitere Ausgestaltung ergibt sich, sofern die Zuläufe bereits eine hohe Temperatur besitzen. Dabei tritt während der Produktionsphase kontinuierlich Reaktionsgemisch am vorderen Ende des Reaktors ein, wird durch das Festbett auf die für den geforderten Umsatz notwendige Temperatur Tmaχ aufgeheizt, wobei Tma größer oder gleich einer Mindestvorheiztemperatur Tj. ist, und reagiert dabei in einem katalytisch aktiven Teil des Festbetts, wodurch sich das Festbett abkühlt. Während der Regenerationsphase wird ein Regenerationsstrom mit der gewünschten Maximaltemperatur Tmax solange durch das katalytisch aktive Festbett geleitet, bis der ganze katalytisch aktive Bereich wieder die Maximaltemperatur Tmax angenommen hat .A further embodiment results if the inlets already have a high temperature. During the production phase, the reaction mixture continuously enters the front end of the reactor and is heated by the fixed bed to the temperature T ma χ necessary for the required conversion, where T m a is greater than or equal to a minimum preheating temperature T j. and reacts in a catalytically active part of the fixed bed, whereby the fixed bed cools down. During the regeneration phase, a regeneration stream with the desired maximum temperature T max is passed through the catalytically active fixed bed until the entire catalytically active area has again reached the maximum temperature T max .
Weitere Vorteile und Merkmale der Erfindung ergeben sich aus den übrigen Anmeldungsunterlagen und insbesondere der nachfolgenden Beschreibung von Ausführungsbeispielen des Verfahrens. Die Erfindung soll nun im Folgenden anhand einer Zeichnung näher erläutert werden. Dabei zeigen:Further advantages and features of the invention result from the other application documents and in particular from the following description of exemplary embodiments of the method. The invention will now be explained in more detail below with reference to a drawing. Show:
Figur la und lb: Diagramme zum Temperaturverlauf während derFigure la and lb: Diagrams of the temperature profile during the
Produktionsphase der endothermen Reaktion;Production phase of the endothermic reaction;
Figur 2a und 2b: Diagramme zum Temperatur- und Umsatzverlauf beim erfindungsgemäßen Verfahren; Figur 3: Diagramme zur Veränderung desFigures 2a and 2b: Diagrams of the temperature and turnover curve in the method according to the invention; Figure 3: Diagrams for changing the
Temperaturprofils während der Regenerationsphase;Temperature profile during the regeneration phase;
Figur 4: einen Reaktoraufbau.Figure 4: a reactor structure.
Die Figuren la und lb zeigen am Beispiel der Dampfreformierung von Methan und unter der Annahme eines nur von der Temperatur bestimmten Reaktionsumsatzes, wie sich die Temperaturfront ausgehend vom Temperaturprofil 1 bzw. 1' durch das Katalysatorbett ausbreitet. Die Verläufe sind dabei für zwei unterschiedliche Temperaturen von Tmaχ = 1000K (Figur la) und Tma = 1500K (Figur lb) dargestellt. Dabei ist die Längenkoordinate des Katalysatorbettes mit z bezeichnet und in Metern angegeben. In der Front steigt die Temperatur sehr schnell von einer Basistemperatur TB auf die Vorheiz- bzw. Maximaltemperatur Tmax im Festbett an, während der Umsatz entsprechend zunimmt. Für den asymptotischen Endwert der Basistemperatur in einem hinreichend langen Katalysatorbett wird nachfolgend eine implizite Bestimmungsgleichung angegeben. Je höher die Vorheiztemperatur Tmax, desto langsamer wandert die Front und desto tiefer sinkt die Basistemperatur TB (Figur lb) .FIGS. 1 a and 1 b show, using the example of steam reforming of methane and assuming a reaction conversion determined only by the temperature, how the temperature front spreads through the catalyst bed starting from temperature profile 1 or 1 ′. The curves are shown for two different temperatures of T ma χ = 1000K (figure la) and Tma = 1500K (figure lb). The length coordinate of the catalyst bed is designated z and is given in meters. In the front, the temperature rises very quickly from a base temperature TB to the preheating or maximum temperature T max in the fixed bed, while the turnover increases accordingly. An implicit determination equation is given below for the asymptotic final value of the base temperature in a sufficiently long catalyst bed. The higher the preheating temperature T max , the slower the front moves and the lower the base temperature T B (Figure lb).
Die Mindest-Vorheiztemperatur Ti des Katalysatorbettes, ab der sich unter den genannten Voraussetzungen eine ausgeprägte Front ausbildet, folgt aus der Bedingung: d2xThe minimum preheating temperature Ti of the catalyst bed, from which a pronounced front is formed under the conditions mentioned, follows from the condition: d 2 x
= 0 dT2 = 0 dT 2
Dabei ist X der von der Reaktionstemperatur T abhängige Gleichgewichtsumsatz der endothermen Reaktion. Sein GradientX is the equilibrium conversion of the endothermic reaction which depends on the reaction temperature T. Its gradient
. ist bei der Temperatur Ti maximal. dT, is maximum at temperature Ti. dT
Die Reaktionsfront erreicht asymptotisch einen konstanten Temperaturhub Tmax —TB und eine konstante Wanderungsgeschwindigkeit wR . Für die Basistemperatur TB gilt die folgende implizite Beziehung: dX _ X(Tmax )-X(TB ) dT TB max ~ * B und für wR die Beziehung:The reaction front asymptotically reaches a constant temperature rise T max -T B and a constant one Migration speed w R. The following implicit relationship applies for the base temperature T B : dX _ X (T max ) -X (T B ) dT T B max ~ * B and for w R the relationship:
Darin symbolisiert ΔTad die adiabate Temperaturabsenkung derIt symbolizes ΔT ad the adiabatic lowering of the temperature
Reaktionsmischung bei Vollumsatz und wτ dieReaction mixture at full conversion and w τ die
Wanderungsgeschwindigkeit einer fiktiven, dissipationsfreien thermischen Front, die ein inerter Gasstrom mit derselbenVelocity of migration of a fictitious, dissipation-free thermal front, which is an inert gas flow with the same
Wärmekapazität wie der Prozessstrom hervorrufen würde. wτ ergibt sich aus der folgenden Beziehung: sτ m- c wτ = -*- = sτ —Heat capacity as the process current would cause. w τ results from the following relationship: s τ m- cw τ = - * - = s τ -
Δt (m ■ c)Δt (m ■ c)
Darin bedeuten:Where:
-dt : Die Dauer einer Prozessphase. sτ : Die Strecke, um die eine ideale thermische Front im-dt: The duration of a process phase. s τ : The distance by which an ideal thermal front in the
Zeitintervall - twandert.Time interval - wanders.
• m : Massenstrom des Prozessgases. cp : Spezifische Wärmekapazität des Prozessstroms. (m-c) : Wärmekapazität des Festbettes.• m: mass flow of the process gas. c p : Specific heat capacity of the process stream. (mc): heat capacity of the fixed bed.
Das in Figur 1 a) und b) gezeigte und vorstehend charakterisierte Verhalten kennzeichnet die Produktionsphase der endothermen Reaktion. Ihr muss erfindungsgemäß eine Regenerationsphase folgen, in der das ursprüngliche Temperaturprofil wiederhergestellt wird.The behavior shown in FIG. 1 a) and b) and characterized above characterizes the production phase of the endothermic reaction. According to the invention, it must be followed by a regeneration phase in which the original temperature profile is restored.
Für den erfindungsgemäßen Prozess, bestehend aus einem zyklischen Wechsel zwischen Produktions- und Regenerationsphase sollte der Festbettreaktor wie in Figur 2 skizziert aufgebaut sein. Das Festbett besteht aus einer katalytisch aktiven Zone und einer inerten Randzone, die in Strömungsrichtung hintereinander angeordnet sind. Der katalytisch aktiven Zone kann zusätzlich auch eine kurze inerte Zone vorgelagert werden. Das Temperaturprofil zu Beginn der Produktionsphase (Zustand 1) besitzt eine aufsteigendeFor the process according to the invention, consisting of a cyclical change between the production and regeneration phases, the fixed bed reactor should be as in FIG. 2 be sketched. The fixed bed consists of a catalytically active zone and an inert edge zone, which are arranged one behind the other in the direction of flow. The catalytically active zone can also be preceded by a short inert zone. The temperature profile at the beginning of the production phase (state 1) has an increasing one
Flanke im Zulaufbereich, ein Plateau bei T = Tmax (hier bei ca.Flank in the inlet area, a plateau at T = T max (here at approx.
1000 K) bis zum Ende der katalytisch aktiven Schicht und in der inerten Randzone eine abfallende Flanke, gefolgt von einem Plateau auf dem Niveau der Zulauftemperatur (hier bei ca. 400 K) . Dieser Verlauf ist durch die durchgezogene Linie dargestellt.1000 K) to the end of the catalytically active layer and a falling edge in the inert edge zone, followed by a plateau at the level of the inlet temperature (here at approx. 400 K). This course is shown by the solid line.
Dabei ist die Entwicklung der Temperaturverläufe (obere Darstellung) und der Umsatzverläufe (untere Darstellung) während der Produktionsphase unter den obigen Bedingungen und unter Voraussetzung eines effizienten Wärmetauschs zwischen Gas und Festbett sowie einer schnellen Reaktionskinetik gezeigt. Wie die zeitlich aufeinander folgenden Temperatur- und Umsatzprofile zwischen dem Anfangszustand 1 und dem Endzustand 2 zeigen, wird über der gesamten Dauer der Produktionsphase am Austritt der katalytisch aktiven Zone die geforderte Maximaltemperatur Tmax und damit der geforderteThe development of the temperature profiles (top illustration) and the sales profiles (bottom illustration) during the production phase under the above conditions and under the assumption of an efficient heat exchange between gas and fixed bed and fast reaction kinetics is shown. As the chronologically successive temperature and conversion profiles between the initial state 1 and the final state 2 show, the required maximum temperature T max and thus the required temperature over the entire duration of the production phase at the outlet of the catalytically active zone
Endumsatz erreicht. Die sich anschließende inerte Schüttung verhindert, dass mit der jetzt absinkenden Temperatur auch der Umsatz wieder absinkt. Gleichzeitig liegt während dieses Zeitintervalls die Austrittstemperatur konstant auf dem Niveau der Eintrittstemperatur. Damit wird das Austragen fühlbarer Wärme aus dem Reaktor verhindert. Am Ende der Produktionsphase ist die Wärmespeicherkapazität des Festbettes aus Katalysator und Inertmaterial weitgehend erschöpft und die Austrittstemperatur würde anschließend ansteigen (Zustand 2) . Die gestrichelten Linien zeigen die Verläufe von Temperatur und Umsatz am Ende der Produktionsphase. Die dazwischen liegenden punktierten Linien stellen Profile zu zwischen den Zuständen 1 und 2 liegenden Zeitpunkten dar. Anstelle der inerten Randzone, in der die Temperatur zum Ausgang des Reaktors abfällt, kann die Randzone auch einen Katalysator für eine wünschenswerte Folgereaktion enthalten. Er darf allerdings die endotherme Hauptreaktion nicht katalysieren. Ein typisches Beispiel wäre im Fall der Dampfreformierung von Methan der Ersatz der inerten Randzone durch einen Wassergas-Shift-Katalysator, in dem mit fallender Temperatur zunehmend CO und Wasserdampf in C02 und Wasserstoff umgewandelt werden.Final sales reached. The subsequent inert bed prevents the sales from falling again as the temperature drops. At the same time, the outlet temperature is constantly at the level of the inlet temperature during this time interval. This prevents sensible heat from being discharged from the reactor. At the end of the production phase, the heat storage capacity of the fixed bed made of catalyst and inert material is largely exhausted and the outlet temperature would then rise (state 2). The dashed lines show the temperature and turnover curves at the end of the production phase. The dotted lines in between represent profiles at times between states 1 and 2. Instead of the inert peripheral zone, in which the temperature drops at the outlet of the reactor, the peripheral zone can also contain a catalyst for a desirable subsequent reaction. However, it must not catalyze the main endothermic reaction. A typical example in the case of steam reforming of methane would be the replacement of the inert peripheral zone with a water gas shift catalyst, in which CO and water vapor are increasingly converted into CO 2 and hydrogen as the temperature drops.
Für die Realisierung eines leistungsfähigen zyklischen Verfahrens ist die Regeneration des Bettes vom Zustand 2 auf den Zustand 1 erforderlich. Erfindungsgemäß müssen dazu die Prozessbedingungen während der Regenerationsphase folgende Voraussetzungen erfüllen:The regeneration of the bed from state 2 to state 1 is required to implement an efficient cyclic process. According to the invention, the process conditions during the regeneration phase must meet the following requirements:
• Die Wärmekapazitäten der während der Regenerationsphase (Index R) und der während der Produktionsphase (Index P) durchgesetzten Prozessströme: ' -cpR -ΔtR bzw. ' -cpP -ΔtP , müssen in etwa gleich sein. Dabei ist für die spezifische Wärmekapazität cp des jeweiligen Gases ein Mittelwert über den durchlaufenen Temperatur- und Konzentrationsbereich anzusetzen.• The heat capacities of the process streams implemented during the regeneration phase (index R) and during the production phase (index P): ' -c pR -Δt R or ' -c pP -Δt P must be approximately the same. An average over the temperature and concentration range passed through must be used for the specific heat capacity c p of the respective gas.
• Es uss ein Wärmeeintrag an örtlich diskreten Stellen im Katalysatorbett erfolgen. Der Abstand der Einspeisestellen soll dabei dem Abstand der Strecke entsprechen, die von einer fiktiven thermischen Front während der Regenationsphase gerade überbrückt wird.• There must be heat input at discrete locations in the catalyst bed. The distance between the feed points should correspond to the distance of the route that is being bridged by a fictitious thermal front during the regeneration phase.
• Das geforderte konstante oder örtlich veränderliche• The required constant or locally variable
Profil der Maximaltemperatur Tmax wird dadurch eingestellt, dass der lokale Wärmeeintrag über Temperatursensoren geregelt wird, die in der Nähe der Einspeisungen und stromabwärts in Richtung des Regenerationsstroms installiert sind.The profile of the maximum temperature T max is set by regulating the local heat input via temperature sensors which are installed in the vicinity of the feeds and downstream in the direction of the regeneration current.
• Der Wärmeeintrag kann dabei z. B. durch in der Katalysatorschüttung installierte Heizelemente oder durch Heißgaseinspeisung erfolgen. Besonders bevorzugt ist eine Lösung, bei der dem Regeneriergasstrom an den Einspeisestellen ein Reaktionspartner für eine exotherme Reaktion zugemischt wird, die bei der herrschenden Temperatur selbständig zündet und vollständig abläuft, z. B. eine katalytische Verbrennung.• The heat input can z. B. by in the Catalyst bed installed heating elements or by hot gas feed. A solution is particularly preferred in which a reactant for an exothermic reaction is admixed to the regeneration gas stream at the feed points, which reacts automatically at the prevailing temperature and takes place completely, e.g. B. a catalytic combustion.
Figur 3 zeigt schematisch die für die Regeneration erforderliche Konfiguration eines Festbettreaktors mit temperaturgeregelter Seiteneinspeisung eines Reaktionspartners und die prinzipielle Veränderung der Temperaturfronten während der Regenerationszeit. Der Temperaturregler ist dabei mit TC gekennzeichnet. Man erkennt, wie die an den Einspeisestellen erzeugten Temperaturfronten das eingebrochene Temperaturprofil wieder auffüllen und gleichzeitig eine Verschiebung der Temperaturprofilflanken am Ein- und Austritt der (inerten) Schüttung in die Ausgangsposition stattfindet.FIG. 3 schematically shows the configuration of a fixed bed reactor with temperature-controlled side feed of a reactant required for the regeneration and the basic change in the temperature fronts during the regeneration time. The temperature controller is labeled TC. It can be seen how the temperature fronts generated at the feed points replenish the broken temperature profile and at the same time a shift of the temperature profile flanks takes place at the entry and exit of the (inert) bed to the starting position.
Figur 4 zeigt einen möglichen erfindungsgemäßen Reaktoraufbau am Beispiel der Wasserdampfreformierung von Methan. Der Reaktor 1 enthält ein axial strukturiertes Festbett mit den inerten Randzonen 2 und 4 und der katalytisch aktiven Zone 3, die mit einem geeigneten Reformierkatalysator gefüllt ist. Im Reaktor 1 sind vier Verteiler 5 für die Einspeisung eines Zusatzstroms integriert. Die Verteiler werden durch axial geführte Zuleitungen versorgt, die einen guten thermischen Kontakt zum umgebenden Festbett haben. Der Abstand zwischen den Verteilern entspricht der Strecke, die eine fiktive thermische Front während der Regenerationsphase zurücklegen würde. In der Nähe der Verteiler sind jeweils Thermoelemente 6 installiert, die zur Temperaturregelung des Reaktors dienen. Während der Produktionsphase wird der Reaktor 1 mit einem Gemisch 7 von technisch relevanter ZulaufZusammensetzungFIG. 4 shows a possible reactor structure according to the invention using the example of steam reforming of methane. The reactor 1 contains an axially structured fixed bed with the inert edge zones 2 and 4 and the catalytically active zone 3, which is filled with a suitable reforming catalyst. Four distributors 5 for feeding an additional stream are integrated in the reactor 1. The distributors are supplied by axially guided supply lines that have good thermal contact with the surrounding fixed bed. The distance between the distributors corresponds to the distance that a fictitious thermal front would cover during the regeneration phase. Thermocouples 6 are installed in the vicinity of the distributors and are used to regulate the temperature of the reactor. During the production phase, the reactor 1 is mixed with a mixture 7 of technically relevant feed composition
( yH2θ •' ycH4 = 3 ' 1 ) und einer Zulauftemperatur von 400K von links nach rechts in der zeichnerischen Darstellung durchströmt. Während der Regenerationsphase wird die Strömungsrichtung umgekehrt und im Hauptstrom 8 wird z. B. ein Sauerstoffhaltiges Gas dem Reaktor zugeführt. Die gesamte Wärmekapazität i ^fh R c pR At R } ) r die mit dem Hauptstrom 8 zugeführt wird, soll dabei in etwa der gesamten Wärmekapazität im c Δt } entsprechen, die während der Produktionsphase mit dem Reaktionsgemisch 7 zugeführt wurde. Die Verteiler 5 werden mit einem Brennstoff 9, beispielsweise Methan oder dem Abgas einer Druckwechsel-Adsorptionsanlage zur Wasserstoffreinigung versorgt. Der Durchsatz in den Versorgungsleitungen wird mittels Regelventilen 10 so eingestellt, dass die Temperatur der Messstellen auf 1000 K geregelt wird. Alternativ kann dem Reaktor während der Regenerationsphase auch ein brennstoffhaltiger Hauptstrom 8 zugeführt werden, in den über die Einspeisungen ein sauerstoffhaltiges Gas, z. B. Luft zugemischt wird.(y H2θ • 'yc H4 = 3 ' 1) and an inlet temperature of 400K from left to right in the drawing. During the regeneration phase, the direction of flow is reversed and in the main stream 8 z. B. fed an oxygen-containing gas to the reactor. The total heat capacity i ^ fh R c pR At R}) r that is supplied with the main stream 8 should correspond approximately to the total heat capacity i mc Δ t } that was supplied with the reaction mixture 7 during the production phase. The distributors 5 are supplied with a fuel 9, for example methane, or the exhaust gas of a pressure swing adsorption system for hydrogen purification. The throughput in the supply lines is set by means of control valves 10 so that the temperature of the measuring points is regulated to 1000 K. Alternatively, a fuel-containing main stream 8 can also be fed to the reactor during the regeneration phase, in which an oxygen-containing gas, e.g. B. air is added.
Der beschriebene zyklische Prozess zeichnet sich durch eine hohe Energieeffizienz aus, da Zu- und Ablauf sowohl in der Produktions- wie in der Regenerationsperiode (relativ) kalt erfolgen und die für die endotherme Reaktion erforderliche hohe Temperatur vollständig im Reaktor verbleibt.The cyclic process described is characterized by a high level of energy efficiency, since the inlet and outlet take place (relatively) cold in both the production and regeneration period and the high temperature required for the endothermic reaction remains completely in the reactor.
Falls die Zuläufe allerdings bereits eine hohe Temperatur besitzen, kann die thermische regenerative Kopplung der endothermen und der exothermen Reaktion auch mit heißen Zuläufen erfolgen. Dabei wird der im endothermen Produktionsschritt erreichbare Umsatz nach wie vor von der zuvor eingestellten Temperatur Tmax der Katalysatorschüttung bestimmt. Ähnlich wie in Fig. 2 findet der Endumsatz in einer steilen Temperaturfront statt, wenn die eingangs abgeleitete Bedingung Tmax > i erfüllt ist.However, if the feeds are already at a high temperature, the thermal regenerative coupling of the endothermic and exothermic reactions can also take place with hot feeds. The conversion achievable in the endothermic production step is still determined by the previously set temperature T max of the catalyst bed. Similar to FIG. 2, the final conversion takes place on a steep temperature front when the condition T max > i derived at the beginning is fulfilled.
Für die Regeneration mit einem auf Tmax vorgeheizten Regenerationsgasstrom ergeben sich allerdings vereinfachte Bedingungen. Dabei kann der Regenerationsstrom auch im Gleichstrom, zweckmäßiger aber im Gegenstrom zum Produktionsstrom geführt werden. Die Zufuhr der gesamten Regenerationswärme erfolgt jetzt über den Reaktorzulauf, sodass keine weiteren Einspeisestellen erforderlich sind. Für die benötigte Wärmekapazität des Regenerationsstroms bei Gegenstromführung gilt dann:For regeneration with a preheated to T max Regeneration gas flow, however, results in simplified conditions. The regeneration stream can also be conducted in cocurrent, but more appropriately in countercurrent to the production stream. The entire heat of regeneration is now supplied via the reactor inlet, so that no further feed points are required. The following then applies to the required heat capacity of the regeneration flow with counterflow:
| m,R cRAtR TW, , Cpbmtp | m, R c R At R TW,, Cpbmtp
Dabei ist Ti die Temperatur, die das Katalysatorbett am Ende Produktionsphase eingenommen hat.Ti is the temperature that the catalyst bed reached at the end of the production phase.
Auf die beschriebene Weise kann eine endotherme Reaktion vorteilhaft durchgeführt werden. An endothermic reaction can advantageously be carried out in the manner described.

Claims

Patentansprücheclaims
1. Verfahren zur autothermen Durchführung endothermer Reaktionen in adiabatischen Festbettreaktoren im zyklischen Wechsel zwischen einer Produktionsphase für die endotherme Reaktion und einer Regenerationsphase für die Wärmezufuhr, dadurch gekennzeichnet, dass während der Produktionsphase kontinuierlich Reaktionsgemisch mit niedriger Temperatur am vorderen Ende des Reaktors eintritt, durch das Festbett auf die für den geforderten Umsatz notwendige Temperatur max aufgeheizt wird, wobei Tmax größer oder gleich einer Mindestvorheiztemperatur Ti ist, dabei in einem katalytisch aktiven Teil des Festbetts reagiert und gleichzeitig das Festbett abkühlt und den Reaktor über eine hintere inerte, dem katalytisch aktiven Teil nachgeschaltete Zone oder ein weiteres katalytisches Festbett verlässt, während der Regenerationsphase kontinuierlich ein Regenerationsstrom mit niedriger Temperatur am hinteren Ende des Reaktors zugeführt und vorne abgezogen wird, wobei die Gesamtwärmekapazität mP cPRAtR des1. Process for the autothermal implementation of endothermic reactions in adiabatic fixed bed reactors in the cyclical alternation between a production phase for the endothermic reaction and a regeneration phase for the supply of heat, characterized in that during the production phase, reaction mixture with low temperature continuously occurs at the front end of the reactor through the fixed bed is heated to the temperature max necessary for the required conversion, where T max is greater than or equal to a minimum preheating temperature Ti, thereby reacting in a catalytically active part of the fixed bed and simultaneously cooling the fixed bed and the reactor via a rear inert, downstream of the catalytically active part Zone or another catalytic fixed bed leaves, during the regeneration phase continuously a regeneration stream with low temperature at the rear end of the reactor and is withdrawn at the front, the total heat capacity ät m P c PR At R des
Regenerationsstroms mR über der Regenerationsdauer ΔtR 70 bis 300%, vorzugsweise 80 bis 120% der entsprechendenRegeneration current m R over the regeneration period Δt R 70 to 300%, preferably 80 to 120% of the corresponding
Gesamtwärmekapazität mPcPPAtP des Reaktionsgemischs über der Produktionsdauer Atpentspricht und an mehreren diskreten, über der Länge des katalytisch aktiven Bereichs angeordneten Stellen Wärme so zugeführt und über dem Strömungsquerschnitt verteilt wird, dass ein ursprüngliches Temperaturprofil am Ende der Regenerationsphase wieder eingestellt wird.Total heat capacity m P c PP At P of the reaction mixture corresponds to the production time At p and heat is supplied at several discrete points arranged along the length of the catalytically active area and distributed over the flow cross-section such that an original temperature profile is set again at the end of the regeneration phase ,
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass dem katalytisch aktiven Teil des Reaktorfestbetts ein inerter Bereich vorgeschaltet wird. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Wärmekapazitäten mlcl der einen oder beider inerten Zone, die Wärmekapazitätsströme wie während Produktion und Regeneration und die Periodendauer von Produktionsphase, Atp , und von Regenerationsphase, AtR . den folgenden Gleichungen genügen:2. The method according to claim 1, characterized in that an inert area is connected upstream of the catalytically active part of the fixed reactor bed. A method according to claim 1 or 2, characterized in that the heat capacities m l c l of one or both inert zones, the heat capacity flows as during production and regeneration and the period of the production phase, At p , and of the regeneration phase, At R. satisfy the following equations:
wobei die Konstanten a, b Werte zwischen 0.1 und 1.0 annehmen und Δtpund ΔtÄ zwischen 0.5 und 30 Minuten liegen. where the constants a, b assume values between 0.1 and 1.0 and Δt p and Δt Ä lie between 0.5 and 30 minutes.
Verfahren nach einem der Ansprüche 1 bis 3 , dadurch gekennzeichnet, dass die Menge der Katalysatorschüttung gemäß der Formel: dXMethod according to one of claims 1 to 3, characterized in that the amount of catalyst bed according to the formula: dX
1 + ΔI\ - mpCpp ■ Atp dT bemessen wird, wobei die tatsächliche Menge zwischen 100% und 300%, vorzugsweise zwischen 110% und 150% des Formelwertes beträgt.1 + ΔI \ - mpC pp ■ At p dT, the actual amount being between 100% and 300%, preferably between 110% and 150% of the formula value.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Länge der Katalysatorschüttung zwischen zwei Einspeisestellen für die Wärmezufuhr jeweils so bemessen wird, dass ihre Wärmekapazität mκcκ jeweils zwischen 50 und 100%, zweckmäßigerweise um 90% des durch die Formel: mκcκ = tR mR cPR gegebenen Wertes ausmacht .5. The method according to any one of claims 1 to 4, characterized in that the length of the catalyst bed between two feed points for the heat supply is in each case dimensioned such that its heat capacity m κ c κ in each case between 50 and 100%, expediently by 90% of the the formula: m κ c κ = t R m R c PR of given value.
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass zwischen dem Ende der inerten Zone und der in Strömungsrichtung der Regeneration erste Wärmeeinspeisung eine aktive Katalysatorschüttung der gleichen Länge wie zwischen zwei Einspeisestellen angeordnet wird.6. The method according to claim 5, characterized in that between the end of the inert zone and the first heat feed in the flow direction of the regeneration, an active catalyst bed of the same length as is arranged between two feed points.
7. Verfahren nach einem der Ansprüche 1 bis 6 , dadurch gekennzeichnet, dass die diskrete Wärmezufuhr während der Regenerationsphase durch eine automatische Regelung oder Steuerung so erfolgt, dass die Temperatur jeweils stromabwärts der Wärmezufuhr auf einen vorgegebenen7. The method according to any one of claims 1 to 6, characterized in that the discrete heat supply during the regeneration phase is carried out by an automatic regulation or control so that the temperature downstream of the heat supply to a predetermined
Sollwert Tmax geregelt oder gesteuert wird.Setpoint T max is regulated or controlled.
8. Verfahren nach einem der Ansprüche 1 bis 7 , dadurch gekennzeichnet, dass die Wärmezufuhr während der Regenerationsphase durch eine exotherme Begleitreaktion erzeugt wird, wobei dem Regenerationsstrom an den diskreten Einspeisestellen ein Reaktand zugemischt wird, der mit dem Regenerationshauptstrom exotherm reagiert.8. The method according to any one of claims 1 to 7, characterized in that the supply of heat is generated during the regeneration phase by an exothermic accompanying reaction, wherein the regeneration stream at the discrete feed points is mixed with a reactant which reacts exothermic with the main regeneration stream.
9. Verfahren nach Anspruch 8 , dadurch gekennzeichnet, dass der einzuspeisende Reaktand für die Regenerationsphase vom Festbettende her durch Zuleitungen zugeführt wird und durch Wärmetausch mit dem Regenerationsstrom und/oder dem Festbett aufgeheizt wird.9. The method according to claim 8, characterized in that the reactant to be fed for the regeneration phase is fed from the fixed bed end through feed lines and is heated by heat exchange with the regeneration stream and / or the fixed bed.
10. Verfahren nach einem der Ansprüche 1 bis 9 , dadurch gekennzeichnet, dass Produktions- und Regenerationsphase durch Spülphasen oder Entspannungsphasen getrennt werden, in denen für die folgende Phase störende Komponenten im Gleich- oder Gegenstrom zu der vorherigen Phase aus dem Festbettreaktor entfernt werden.10. The method according to any one of claims 1 to 9, characterized in that the production and regeneration phase are separated by rinsing phases or relaxation phases in which disruptive components for the following phase are removed in cocurrent or countercurrent to the previous phase from the fixed bed reactor.
11. Verfahren nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, dass für die Durchführung einer Folgereaktion bei niedriger Temperatur, insbesondere der Wassergas-Shiftreaktion im Anschluss an die Reformierung, ein katalytisches Festbett eingesetzt wird, das anstelle des inerten Teils dem katalytisch aktiven Teil des Festbettes nachgeschaltet ist.11. The method according to any one of claims 1 to 10, characterized in that for carrying out a subsequent reaction at low temperature, in particular the water gas shift reaction following the reforming, a catalytic fixed bed is used, which catalytically instead of the inert part active part of the fixed bed is connected.
12. Verfahren zur autothermen Durchführung endothermer Reaktionen in adiabatischen Festbettreaktoren im zyklischen Wechsel zwischen einer Produktionsphase für die endotherme Reaktion und einer Regenerationsphase für die Wärmezufuhr, dadurch gekennzeichnet, dass während der Produktionsphase kontinuierlich Reaktionsgemisch am vorderen Ende des Reaktors eintritt, durch das Festbett auf die für den geforderten Umsatz notwendige Temperatur max aufgeheizt wird, wobei Tmax größer oder gleich einer Mindestvorheiztemperatur Ti ist, dabei in einem katalytisch aktiven Teil des Festbetts reagiert und gleichzeitig das Festbett abkühlt und den Reaktor wieder verlässt, und während der Regenerationsphase ein Regenerationsstrom mit der gewünschten Maximaltemperatur Tmax solange durch das katalytisch aktive Festbett geleitet wird, bis der ganze katalytisch aktive Bereich wieder die Maximaltemperatur Tmax angenommen hat. 12. Process for the autothermal implementation of endothermic reactions in adiabatic fixed bed reactors in the cyclical alternation between a production phase for the endothermic reaction and a regeneration phase for the supply of heat, characterized in that during the production phase the reaction mixture continuously enters the front end of the reactor, through the fixed bed onto the for the required conversion temperature m ax is heated, T max being greater than or equal to a minimum preheating temperature Ti, reacting in a catalytically active part of the fixed bed and simultaneously cooling the fixed bed and leaving the reactor, and during the regeneration phase a regeneration stream with the desired The maximum temperature T max is passed through the catalytically active fixed bed until the entire catalytically active area has again reached the maximum temperature T max .
EP03757758A 2002-08-23 2003-08-13 Autothermal method comprising periodic flow reversal Withdrawn EP1536882A1 (en)

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DE10239547A DE10239547A1 (en) 2002-08-23 2002-08-23 Process for autothermally carrying out endothermic high temperature reactions comprises continuously introducing a reaction mixture having a low temperature to the front end of the reactor during the production phase, and further processing
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