Classifications

• • 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
  • B01J8/06—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 in tube reactors; the solid particles being arranged in tubes
  • B01J8/062—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 in tube reactors; the solid particles being arranged in tubes being installed in a furnace
• • 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
  • C01B3/38—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
  • C01B3/384—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 the catalyst being continuously externally heated
• • 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
  • C01B2203/0811—Methods of heating the process for making hydrogen or synthesis gas by combustion of fuel
• • 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
• • 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
  • C01B2203/0866—Methods of heating the process for making hydrogen or synthesis gas by combination of different heating methods

Definitions

• This invention relates to combustion heating appar ⁇ atus for fluids, and has particularly advantageous applica ⁇ tion to the process of steam reforming of hydrocarbons.
• the steam reforming process consists of heating a mixture of a hydrocarbon feedstock with steam in the presence of a solid catalyst.
• the catalyst generally used is nickel, in finely divided form and dispersed on the surface of porous support bodies made of alumina.
• Dependent upon the application, the process may be carried out at any pressure up to 40 bar or even more with known apparatus.
• the •temperature of the process stream reaches its maximum as it leaves the catalyst bed, this temperature being limited in practice by the corresponding metal temperature at which adequate mechanical properties of the containing duct .can be relied upon. Typically, these temperatures are about 850°C and 900°C respectively.
• the product stream consists of a mixture of hydrogen, carbon oxides, steam, and methane, together with any inert components such as nitrogen which may be present.
• the product composition may approach quite closely the equilibrium composition for the conditions at exit from the catalyst bed.
• the steam reforming process is of great industrial importance. Among its applications are the production of hydrogen and reducing gases for metallurgical and fuel refining processes, and for fuel cells, and the manufacture of synthesis gases for conversion to ammonia, ethanol, and other chemicals and fuels.
• the catalyst is normally contained within a number of identical tubes, typically of 0.12 m outside diameter and more than 12 in length, suspended within a refractory lined furnace box which is heated by burners.
• the main deficiency of the conventional reformer furnace is that it is wasteful in its use of energy. Typically, less than half of the heat released by the burners goes to provide reaction heat. This part of the heat is directly useful, since it is potentially available as fuel value of the end products.
• the balance of the heat goes to heat up the exiting process and flue gas streams and the surroundings; and while a high proportion of this is usually recovered to process heat, and steam raising, large costs and large losses of work potential are involved in such recovery. In particular, only some 25% of heat transferred to a steam system is recovered as work. Work is also lost as a result of an undesirably high frictional pressure drop through the catalyst bed. This has to be accepted in conventional reformer practice, because the cost penalty of using more numerous or wider tubes to reduce the pressure drop is too high.
• recupera ⁇ tive reformer tubes have found very few applications so far, probably because of considerations of cost and of access to replace the catalyst. It may be however, that in the context of a radically new .reformer design the recuperative ' • •-5 reformer tube arrangement will have significant advantages.
• Pressurisation of the combustion space of a steam reformer is also known, for instance from USP 3,958,951. Advantages include size reduction, and the possibility of recovering work by expansion of combustion product gas. However, up to the present, pressurised combustion reformers have not been used in large scale applications, probably because the proposed designs have been considered to be too complicated.
• an object o ⁇ f the present invention is to provide an improved combustion heating apparatus for fluids e.g. for carrying out steam reforming, with a higher thermal efficiency and lower cost than is achieved by the known kinds of apparatus.
• combustion heating apparatus of the kind in which the fluid is passed through a heated zone, which zone is heated by a combustion zone to which air and fuel is fed, characterised in that said fluid is passed through said heated zone in multiple substantially parallel streams, in that there is a heated zone for each stream, in that there is an associated combustion zone for each heated zone and in that the associated heated and combustion zones are arranged one within another with a high degree of radial symmetry.
• each individual heated zone through which a fluid stream passes is provided with its own combustion zone or chamber and, where required for steam reforming, catalyst zone or ⁇ chamber, the combination being preferably concentric.
• further beneficial features of the invention may include: 0 a) ensuring a substantially equal heat release between parallel streams, and, b) ensuring a controlled distribution of heat release within each combustion chamber.
• Figure 1 is a fragmentary sectional view of one form of combustion chamber
• Figure 2. is a fragmentary sectional view of another form of combustion chamber.
• Figures 3 and 4 are enlarged, contour views of turbulence-promoting shapes
• Figures 5 and 6 are enlarged, contour views of catalyst bodies.
• flue gas may be recirculated axially by the jet action of incoming air (a) and fuel (f) at the burner nozzle 1. Circulation along the length of the chamber is promoted by a baffle 2 which divides the chamber into separate channels 3 and 4 for forward and reverse flow. 2.
• either the air (a), or the fuel (f) may be introduced gradually through the radiant surface of a porous wall 5 of the combustion chamber. The resulting extensive flame zone can be stablised close to the wall by turbulence-promoting shapes.
• Catalytic bodies can also be incorporated, so as to maintain the flame reaction at conditions unfavourable to stable non-catalytic combustion.
• Figures 3 and 4 illustrate examples of turbulence-promoting shapes
• Figures 5 and 6 show examples of catalyst bodies one comprising spaced catalytic metal gauze discs G and the other having an enclosing catalytic metal spiral S. These bodies may also be shaped to function as turbulence promoters.
• the basic geometry of the catalyst and combustion chambers may be any one of at least three possible configurations:
• the catalyst may be contained in tubes, with a combustion chamber around each tube.
• Combustion may take place within tubes, with the catialyst either in a surrounding annulus, or in a continuous space containing other combustion tubes. In the latter case, provided the flow through the catalyst bed is axial rather than transverse, the feature of substantial radial axial symmetry can be preserved.
• the catalyst may be in an annular space between inner and outer combustion tubes.
• the porous wall arrangement is generally preferred over the jet recircu- lation arrangement because: a) heat distribution is directly controlled b) less space is required c) reliability is potentially higher, since none of the components is required to operate at such high temperatures as occur in the throat of a conventional burner nozzle.
• Figures 7a and 7b are elevation and plan views respectively of the first embodiment of apparatus
• Figure 8 is an enlarged cross-sectional view of one tube/combustor unit of the apparatus shown in Figure 7, and
• Figures 9 and 10 are sectional elevations of the second and third embodiments of apparatus.
• the heating apparatus is a steam reformer intended to operate with near atmospheric combustion pressure.
• the apparatus comprises a group of some 40 identical tube/combusion units 6 arranged around central inlet and outlet process ducts 7 and 8. Fuel is distributed via a pipe manifold 9. Air and flue gas duct connections are respectively at 10 and 11. Referring to
• FIG. 8 one tube/combustor unit 6 is shown with a part of surrounding structure common to all units.
• Hydrocarbon and steam feed mixture enters at 12 and is heated against reformed gas in a recuperative exchanger 13. It then flows downward through a catalyst bed 14. Reformed gas returns upward through a thin-walled tube 15, giving up heat to the catalyst bed before leaving at 16.
• the tube 15 is formed to have fluted surfaces, and is fitted with an internal restricting cylinder 17.
• the catalyst tube has an outside diameter of 0.12m and it is packed with catalyst over a height of 10 m. In respect of throughput, outside surface, and weight, it is comparable with a conventional reformer tube, but average heat flux is lower because of the recuperated heat supplied from the central tube 15.
• Fuel entering at 18 is preheated against flue gas in a helical coil 19, and enters the combustion chamber 20, in this embodiment via a porous wall 5 as described herein, before flowing through a bed of ceramic pellets 21 to ensure an even flow distribution.
• Flue gas is partly cooled in a convection heating section 24 by exchange with the inlet portion 14 of a cata- lyst tube 14'.
• Catalyst bodies are located in the section
• Flue gas is then further cooled against incoming air in a recuperative exchanger- 25 before flowing at low velocity through a plenum chamber 26 to the edge of the cylindrical outer casing of the apparatus.
• a recuperative exchanger- 25 is further cooled in an outer recuperator 27 which is common to the group of tube/combustor units, before exiting at 28. These units are suspended from above and are free to expand without restraint.
• the second embodiment is in the form of a pressurised combustion heater for delivering product gas at a high temperature.
• the steam reforming reaction is carried out within a bed 30 of catalyst resting on a perforated grid 31 and filling a continuous space outside a number of identical heating tubes, such as 32, and within the pressure enclosure 33.
• process gas enters at a port 34, flows upwardly through a bed 30, where reaction takes place, and leaves at a port 35.
• Fuel gas supplied at 36 is segregated from product gas by a baffle 37 and is drawn into extensions 38 of the heating tubes 32. Gaps in the baffle 37 ensure that only a small pressure difference exists across the wall of the heating tubes 32.
• baffle 37 and tube extensions 38 are omitted.
• the third embodiment is a variant of the second embodiment, and is suited to the case where it is desired to recuperate heat from the product gas. Like parts have, therefore, been given the same reference numerals.
• the steam reforming reaction is carried out within a number of identical beds such as 46, each resting on a grid 47, and filling a space between a heating tube 32 and a catalyst container 48.
• process gas flows upwardly through the beds 30, then downwardly through the gaps between the catalyst containers 48, before leaving at a port 49.
• the catalyst containers may be circular or hexagonal in cross- section, and they may be corrugated or ribbed to provide rigidity and to improve recuperative heat transfer. Their cross-section is reduced at 50, so as to form a plenum chamber for the outlet gases.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Inorganic Chemistry (AREA)
• Hydrogen, Water And Hydrids (AREA)

Applications Claiming Priority (2)

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• 1984
  • 1984-01-25 GB GB848401989A patent/GB8401989D0/en active Pending
• 1985
  • 1985-01-23 AU AU38870/85A patent/AU3887085A/en not_active Abandoned
  • 1985-01-23 EP EP19850900703 patent/EP0169227A1/de not_active Withdrawn
  • 1985-01-23 WO PCT/GB1985/000032 patent/WO1985003281A1/en unknown

Non-Patent Citations (1)

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