U.S. patent application number 09/752728 was filed with the patent office on 2001-12-06 for process and reactor for the preparation of hydrogen and carbon monoxide rich gas.
This patent application is currently assigned to Haldor Topsoe A/S. Invention is credited to Christensen, Thomas S., Primdahl, Ivar I..
Application Number | 20010048912 09/752728 |
Document ID | / |
Family ID | 22640174 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048912 |
Kind Code |
A1 |
Primdahl, Ivar I. ; et
al. |
December 6, 2001 |
Process and reactor for the preparation of hydrogen and carbon
monoxide rich gas
Abstract
Process for suppression of soot formation in the preparation of
hydrogen and/or carbon monoxide rich gas by partial oxidation of a
hydrocarbon feedstock, comprising the steps of in a reactor with an
upper and a lower portion, arranging at least on surface of the
reactor upper portion catalytic material being active in steam
reforming of hydrocarbon; introducing the feedstock and an oxygen
containing atmosphere into the upper portion of the reactor;
partially oxidizing the feedstock with oxygen in the upper portion
of the reactor; and contacting a part of the partially oxidized
feedstock with the reforming catalyst in the reactor upper
portion.
Inventors: |
Primdahl, Ivar I.;
(Copenhagen, NV, DK) ; Christensen, Thomas S.;
(Lyngby, DK) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
Haldor Topsoe A/S
|
Family ID: |
22640174 |
Appl. No.: |
09/752728 |
Filed: |
January 3, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60175427 |
Jan 11, 2000 |
|
|
|
Current U.S.
Class: |
423/418.2 ;
423/651 |
Current CPC
Class: |
C01B 2203/143 20130101;
C01B 2203/82 20130101; C01B 2203/142 20130101; C01B 3/382 20130101;
C01B 3/36 20130101 |
Class at
Publication: |
423/418.2 ;
423/651 |
International
Class: |
C01B 031/18; C01B
003/26 |
Claims
1. Process for suppression of soot formation in the preparation of
hydrogen and/or carbon monoxide rich gas by partial oxidation of a
hydrocarbon feedstock, comprising the steps of in a reactor with an
upper and a lower portion, arranging at least on surface of the
reactor upper portion catalytic material being active in steam
reforming of hydrocarbon; introducing the feedstock and an
oxygen-containing atmosphere into the upper portion of the reactor;
partially oxidising the feedstock with oxygen in the upper portion
of the reactor; and contacting a part of the partially oxidised
feedstock with the reforming catalyst in the reactor upper
portion.
2. The process of claim 1, wherein the partially oxidised feedstock
from the upper portion of the reactor is further contacted with a
steam reforming catalyst arranged in the lower portion of the
reactor.
3. The process of claim 1, wherein the hydrocarbon feedstock and
the oxygen containing atmosphere is mixed in a burner before
introduction into the upper portion of the reactor.
4. Use of a process according to anyone of the preceding claims in
the suppression of soot formation in a process for the preparation
of synthesis gas.
5. Use of a reactor being provided at least on surface of upper
portion of the reactor with a catalyst being active in steam
reforming of hydrocarbons for partial oxidation and/or autothermal
steam reforming of a hydrocarbon feedstock with reduced soot
formation.
Description
[0001] The present invention is directed to the preparation of
hydrogen and carbon monoxide rich gas. In particular, the invention
relates to a process and reactor for the preparation of such gas by
autothermal catalytic reforming of a hydrocarbon feedstock.
[0002] Hydrogen and carbon monoxide rich gases are mainly used as
synthesis gas in the production of ammonia and methanol or other
organic compounds.
[0003] The gases find further employment during steel production
and as fuel or town gas.
[0004] Industrial preparation methods most usually comprise
autothermal catalytic reforming and non-catalytic partial oxidation
of hydrocarbons.
[0005] During partial oxidation a hydrocarbon feedstock is
combusted together with air, oxygen, or oxygen enriched air in a
burner mounted at the top of a reaction vessel. Oxygen is, thereby,
supplied in amounts, which are less than the amount required for
complete combustion, and hydrogen and carbon monoxide are produced
in an effluent gas mainly by flame ignition reactions:
C.sub.nH.sub.m+n/.sub.2O.sub.2nCO+m/.sub.2H.sub.2 (1)
C.sub.nH.sub.m+n/.sub.2O.sub.2nCO.sub.2+m/.sub.2H.sub.2O (2)
[0006] Both reactions are strongly exothermic for all
hydrocarbons.
[0007] Partial oxidation is typically employed in the gasification
of heavy oils, where the temperature in the gas raises during the
combustion to 1000-1500.degree. C., which is high enough to give a
sufficient low content of unconverted hydrocarbons in the
combustion effluent gas. Lighter feedstocks ranging from natural
gas to naphtha fractions with a boiling point up to 200.degree. C.
are conventionally treated by autothermal catalytic reforming of
the feedstock.
[0008] During this process, only a part of the hydrocarbon
feedstock is oxidized with an oxygen containing atmosphere by the
above flame reactions (1, 2). Residual hydrocarbons in the gas
stream from the combustion are then catalytic steam reformed by the
endothermic reaction:
C.sub.nH.sub.m+nH.sub.2OnCO+(m/.sub.2+n)H.sub.2 (3)
[0009] Necessary heat for the endothermic steam reforming reaction
is, thereby, provided by the exothermic flame reactions (1, 2).
[0010] Somewhat lower combustion temperatures are used during
autothermal catalytic reforming, which is operated at a typical
temperature of about 900-1400.degree. C. Steam is added to the feed
in order to moderate the flame temperature and increase hydrocarbon
conversion in the burner effluent gas.
[0011] Similar to the partial oxidation process, hydrocarbon feed
mixed with steam is burnt with an oxygen containing atmosphere at
the top of a reactor. Residual hydrocarbons in the combusted gas
are then steam reformed in the presence of a catalyst arranged as
fixed bed in a lower portion of the reactor. Heat for the
endothermic steam reforming reactions is supplied by the hot
effluent gas from the combustion zone in the upper reactor portion
and above the catalyst bed. As the combustion gas contacts the
catalyst, the temperature in the gas cools to 900-1100.degree. C.
by the steam reforming reactions in the catalyst bed.
[0012] In operating the above processes, suitable hydrocarbon feed,
if necessary after preheating, is introduced into a burner mounted
at the top of a reactor and burnt with oxygen containing
atmosphere. In order to protect the reactor shell against the high
temperatures arising during the exothermic oxidation reactions,
industrial reactors are provided with a temperature resistant and
insulating refractory lining on the inner wall of the reactor
shell.
[0013] The lining materials must be able to withstand high
temperature exposure and be suited to resistant erosion by hot
gases. At present, refractory materials most commonly used in
industrial reactors of the above types contain more than 90%
alumina.
[0014] A general problem in the preparation of synthesis gas by the
above processes is formation of soot in the combustion zone at
critical process conditions, such as low steam/carbon ratios in the
feedstock to the processes.
[0015] A further problem is related to start-up of the burner for
the partial oxidation of the feedstock, which requires preheating
of the feedstock and the reactor to high temperatures.
[0016] It has now been found that the above problems in partial
oxidation and autothermal catalytic reforming processes are
substantially avoided when performing steam reforming reactions on
the surface surrounding the combustion zone of hydrocarbon
feedstock. Those reactions proceed in the combustion effluent gas
when a suitable catalyst is arranged on the surface at least in the
portion of the reactor, which surrounds the hot combustion
zone.
[0017] A theoretical explanation for the reduced soot formation may
be that precursor molecules participating in the formation of soot
are reduced or reacted by steam reforming reactions proceeding on
the catalysed surface adjacent to the combustion zone. An increased
hydrogen concentration by the steam reforming process occurring in
this region results furthermore in improved ignition property of
the feed oxygen mixture and start-up of the process at less severe
conditions.
[0018] Pursuant to the above finding, this invention provides a
process for suppression of soot formation in the preparation of
hydrogen and/or carbon monoxide rich gas by partial oxidation of a
hydrocarbon feedstock, comprising the steps of
[0019] in a reactor with an upper and a lower portion, arranging at
least on surface of the reactor upper portion catalytic material
being active in steam reforming of hydrocarbon;
[0020] introducing the feedstock and an oxygen-containing
atmosphere into the upper portion of the reactor;
[0021] partially oxidising the feedstock with oxygen in the upper
portion of the reactor; and
[0022] contacting a part of the partially oxidised feedstock with
the reforming catalyst in the reactor upper portion.
[0023] A reactor being useful in carrying out the process according
to the invention comprises within a pressure shell a refractory
lining on an inner wall of the shell,
[0024] an upper portion adapted to receive a hydrocarbon feedstock
and an oxygen containing atmosphere, and to partially oxidise the
feedstock with oxygen, and
[0025] a reforming catalyst arranged in the upper portion of the
reactor.
[0026] In operating a specific embodiment of the inventive process
and reactor, a hydrocarbon feedstock preheated to about
400-700.degree. C. is introduced into a burner mounted at the top
of a refractory lined reactor. In the burner, the feedstock is
mixed with steam and oxygen containing atmosphere in an amount
providing a process gas with an oxygen/carbon mole ratio of
preferably between 0.5 and 0.7 and a steam/carbon mole ratio of
preferably between 0.5 and 1.5.
[0027] Typical hydrocarbon feedstock suited for the process will
range from methane to naphtha fractions with a boiling point up to
200.degree. C., including natural gas, LPG and primary reformed
gas, when operating the process under autothermal catalytic
reforming conditions. The process gas is discharged from the burner
into a combustion zone in the upper reactor portion, where part of
the hydrocarbons in the gas are reacted with oxygen to carbon
oxides and hydrogen by flame ignition reactions (1) and (2) as
mentioned herein before.
[0028] Depending on the desired composition of the final product
gas, oxygen may be supplied from air or oxygen enriched air as in
the preparation of ammonia synthesis gas or from oxygen for the
production of oxosyn-thesis gas and reducing gas, where nitrogen is
unwanted in the product gas. During hydrocarbon oxidation the
temperature in the combustion zone raises to 900-1500.degree.
C.
[0029] By the endothermic steam reforming reaction (3) proceeding
in the gas on the surface adjacent to combustion zone,
concentration of hydrogen in recirculated combustion gas is
increased and content of soot precursor molecules decreased.
[0030] The actual increase of hydrogen concentration depends,
thereby, on the amount of hydrocarbons and steam in the gas from
the combustion zone and the activity and amount of reforming
catalyst in the upper reactor portion.
[0031] Catalysts suited for this purpose comprise the well-known
reforming catalysts of Group VIII in the Periodic Table, including
nickel and/or cobalt, which for sufficient soot reduction and flame
ignition improvements are loaded in an amount of between 1
g/m.sup.2 and 0.1 g/cm.sup.2 on the lining surface by conventional
impregnation or coating techniques.
[0032] When the process takes place at autothermal catalytic
reforming conditions, the effluent gas from the combustion zone is
further passed through a fixed bed of conventional nickel and/or
cobalt reforming catalyst arranged in the lower portion of the
reactor. By passage through the catalyst bed, residual hydrocarbons
in the gas are further steam reformed to hydrogen and carbon
monoxide.
* * * * *