Note: Descriptions are shown in the official language in which they were submitted.
1~1425
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an integrated process for
producing hydrogen rich gas in a reformer furnace, reformer
furnaces and furnace structure. More specifically, the
invention relates to a reformer furnace operating under pressure
on both the process and heat side. The invention has
particular application for producing hydrogen rich gas for
commercial size coal gasification plants.
Description of the Prior Art
Recently, considerable interest has been generated
in producing gas for energy requirements by coal gasification.
Certain commercial size coal gasification plants demand large
quantities of hydrogen rich gas. Hydrogen rich gas is also
currently used on a large scale in the commer~ial synthesis
of ammonia.
Large amounts of gaseous hydrogen and carbon monoxide
mixture~, commonl~ referred to as synthesis gas, are currently
required for use in commercial size plants producing methanol
from natural gas or light hydrocarbons.
The hydrogen rich gas and synthesis gas required
for commercial applications are produced by reformer furnaces.
2he commercial reforming process is carried out in a reformer
furn~ce wherein a stream of hydrocarbon and steam is passed
through the furnace tubes which are filled with catalyst, such
as nickel oxide. The reforming reaction is commonly carried
out in the tempe~ature range of 1000F. to 15~0F. or lower.
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The conventional hydrocarbon reforming furnace is
a radiant type furnace wherein the heat source is derived from
the combustion of a hydrocarbon fuel and air at atmospheric
pressure. ~he present state of the art radiant type reformRr
furances are very large and expensive and require considerable
fuel.
Furnaces which operate under pressure also exist.
One such furnace is disclosed in United St~tes Patent No.
3,582,296 (June 1, 1971~. Basic~lly, the furance t~erein is
desi~ned to operate with'the pres'sure difference'between the
process stream and the high-temperature heating gas as small
as possible. The furnace is dèsigned to provide heat~ng
essentially by radiation and rely on bringing the combustion
gas in the heating zone as clqse as possibIe to the'theoretical
co~bustion flame temperature. Another furnace designed to
operate under pres~u,re is the compact convecti~e reactor
sho~n in United States Patent No. 3,688,494 tSeptember 5, 1972~.'
; SUMMARY OF THE INVENTIO~
It is an object of this invention to provide a
xefoxmer furnace and process for providing hydrogen rich'gas
'or s~nthesis gas.
~; ~ It is a urther object of the invention to provtde a
; ~ ' furnace which operates under pressure on bot~'the'~rocess and
co~hustion side and whic~ provides heat to the process side
essentially ~y convection.
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Another object of the invention is to provide a
furnace which can be used as the reformer furance in an
integrated system for reforming hydrocarbon feed into hydrogen.
Thus, the furance of this invention is d~signed to
avoid heating of the process tubes by radiation from the
furnace burner. A single burner preferably, or alternatively
a plurality of burners, are located centrally at the bottom of
the furnace in one combustion chamber. The combustion chamber
is provided with a semi-spherical perforated shieid to allow
the hot combustion gases to traveI from the combustor to the
process tubes but prevent flame impingement on the proce~s
tubes and prevent direct exposure of rad~ant heat from the
burner to the process tubes. The process t~be~assembly is
comprised of a tube sheet mounted at a reIatively high'elevation
in the furnace, process tubes which extend from the tube sheet
and a large center tube in which'the proces's tubes terminate.
The process tubes are provided with'small diameter inlet and
outlet sections on each end and a verY long center section.
I~n the reformer furnace embodiment the center section is filled
~ith catalyst. The tube sheet is of san~wich construction.
The furnace is provided with insulation in the form
of a plurality of aligned eng~gin~ jac~ets. 'Each jacket is
separated from th,e vessel wall to define a small annular space
which is ~dapted to receiye relatiuely cool purge'gas haYing
a pressure slightly greater than that of the interior of the
furnace.
The process of the invention is directed to the use
of flue gas in the furnace as a system recycle medium. Flue
gas discharged from the furnace is used to heat the'system
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furnace hydrocarbon feed. In addition, a portion of the flue
gas is recompressed and recycled to the furnace for mixing
with combustion fuel and compressed air. Another portion of
the flue gas is fed to the turbine of an air compressor to
assist in driving the turbine.
In one particular aspect the present invention provides
a process for generating hydrogen rich gas comprising the
steps of:
~ a) passing a mixture of hydrocarbon feed and steam
through reformer tubes of a furnace having catalyst therein
and operating at pressures between 200 psia and 600 psia,
the reformer tubes being disposed in a convection section of
the furnace;
(b) heating the hydrocarbon-steam feed while in the
reformer tubes to a temperature in the range between 1000F
! and 1550F by convection heat, the heating being effected by
at least one burner in a burner section of the furnace;
(c) substantially preventing radiant heat from the
furnace burner section from exposure to the hydrocarbon-
steam feed in the reformer tubes; and
(d) maintaining the pressure of the combustion gases inthe convection section of the furnace above 100 psia.
In another particular aspect the present invention
provides a process for producing raw ammonia synthesis gas
comprising:
(a) passing a mixture of hydrocarbon feed and steam
through reformer tubes of a furnace having catalyst therein
and operating at pressure between 450 psia and 550 psia, the
reformer tubes being disposed in a convection section of the
~ .
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` ~urnace;
(b) heating the hydrocarbon-steam feed while in the
reformer tubes to a temperature in the range be~ween 1000F
and 1550F by convection heat, the heating being effected
by at least one burner in a burner section of the furnace;
(c) substantially preventing radiant heat from the
furnace burner section from exposure to the hydrocarbon-steam
feed in the reformer tubes;
(d) maintaining the pressure in the convection section
of the furnace between 100 psia and 230 psia;
(e) preheating the steam-hydrocarbon feed mixtures by
passing it in heat exchange relationship with flue gas from
the furnace;
(f) generating steam for the steam-hydrocarbon mixture
by passing water in heat exchange relationship with the flue
gas from the furnace;
(g) generating compressed air by passing flue gas from
the furnace and hot combustion gases through the turbine
side of a turbine air compressor;
(h) generating electical power by driving an electrical
generator having a common drive shaft with the turbine air
compressor;
(i) diverting a portion of the compressed air and
reformed effluent from step (a) to a secondary reformer; and
(;) injecting waste process steam into the turbine side
of the turbine air compressor along with the flue gases from
the furnace.
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`
DESCRIPTION OF THE DRA~INGS
The invention will be better understood when considered
with the attached drawings of which:
Figure 1 is a sectional elevational drawing of the
furnace of the present invention depicted as particularly
suited for use as a reformer furnace;
Figure 2 is a drawing of an alternate embodiment of the
furnace of the present invention;
Figure 3,:which appears on the sheet of drawings
additionally including Figure 6, is a sectional plan view
taken through line 3-3 of Figure 1 showing the web construction
of the tube sheet;
Figure 4 is an enlarged partial sectional elevation
showing the burner structure and the structure of the
insulation jackets of the furnace of Figure l;
! Flgure 5, which appears on the sheet of drawings
additionally including Figure 8, is a sectional plan view
taken through line 5-5 of Figure l;
Figure 6, which appears on the sheet of drawings
additionally including Figure 3, is a drawing of the
furnace of Figure 2 showing the temperature gradient during
reforming operation'
Figure 7 is a schematic diagram of the overall system
of the furnace; and
Figure 8, which appears on the sheet of drawings
additionally including Figure 5, is an enlarged detailed
drawing of a modification of the tube sheet assembly in
Figure 1.
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.
DESCRIPTION_OF THE PRE~ERRED EMBODIMENT
The furnace of the present invention is suitable for
many applications. The particular furnace of the present
invention can be used in virtually every service where
catalytic and non-catalytic cracking is desired However, the
invention will be described in detail as a reformer furance
wherein catalytic cracking occurs.
The reformer furnace 2 of the subject invention,
as best seen in FIGURE 1, is comprised essentially of three
main sections, the vessel shell assembly 4, the process tube
assembly 6 and the combustion section 8.
The vessel shell assembly 4 consists of the outer
shell 9, the insulation jackets 10 and the purge gas chambers
12 defined by the outer surface of the jacket 10 and the inner
surface of the shell 9. As best seen in FIGURES 1 and 4, each
refractory jacket 10 is configured cylindrically or in the
configuration of the inside wall of the vessel shell 9~ and is
joined to the vessel wall at one end, preferably the upper end.
The outside wall 14 of each jacket is of a diameter smaller
than the diameter of the inside of the vessel shell 9 to define
the purge gas chamber 12 associated with each insulation
jacket 10. The purge gas chamber 12 is provided with means
to maintain the proper distance between the insulation jacket
10 and the outer wall of the shell 9. The means for separation
can take any form but one particularly suitable form is a bar
11 arranged in a spiral from top to bottom of the purge gas
chamber 12. Each chamber 12 terminates in an annular opening
13 to provide communication between the chamber 12 and the
furnace interior. Each chamber 12 is provided with a separate
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purge gas inlet 20 through which purge gas enters at a
pressure slightly higher than the pressure on the combustion
gas side of the reformer furnace 2~ In practice, the purge
gas is cooled flue gas from the furnace 2. Each insulation
jacket 10 is provided with refractory corbelling 16 to limit
any excessive deflection of the outer process tubes and to
prevent channeling of the flue gas in the furnace 2.
The reformer tube assembly 6 is comprised of the
tube sheet 22, reformer tubes 24 and central tube 26. The
central tube 26 is axially disposed within the reformer
furance 2 and extends upwardly through the top of the furnace
2. The upper end of the central tube 26 is the furnace outlet
27 for the process fluid. In practice, the center tube 26
is secured to the upper opening 28 in the furnace 2 by any
appropriate means such as welding. The tube sheet 22, as
best seen in FIGURES 1 and 3, is formed of an upper sheet 34,
a lower sheet 36 and an internal web assembly 38. The tube
sheet 22 is provided with a centrally disposed opening 30
. which conforms to the contour of the center tube 26 and is
secured thereto for support by a strength weld which attaches
the upper sheet 34 of the tube sheet to the center tube 26.
Additional support is provided by attachment of the tube sheet
22 to the inside of the furnace by means such as an elongated
support section 32. The support section 32 is continuous and
is sealed at both the furnace wall and the tube sheet 22.
Thermal baffles 40 are also provided to protect the tube
sheet 22 from the hot flue gases. The tube sheet 22 is
provided with aligned holes 42 and 44 in the upper sheet 34
and the lower sheet 36, respectively.
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The reformer tubes 24 are p~ovided with a large
central section 50, inlet tube sections 46 and outlet tube
sections 48. The ~arge central section 50 comprises by far
the greatest portion of each reformer tube 24 and is the only
section filled with catalyst. The inlet tubes 46 extend from
the upper surface of the top tube sheet 34 through the holes
44 in the lower tube sheet 36 and are secured by strength weld
to the top tube sheet 34 of the tube sheet assembly 22. The
diameter of the inlet tube section 46 is considerably smaller
than that of the reformer tube central section 50. Thus,
close spacing of the reformer tube center section 50 is
afforded with attendant minimization of the flue gas restriction
near the flue gas outlet and minimization of heat transfer to
the heat process stream in the inlet tube sect~ons 46 where
catalyst is not present.
The outlet tube sections 48 of the reformer tubes 24
are also considerably smaller in diameter than the center
section 50 of the reformer tubes. As best seen in FIGURE 5,
the outlet tube sections 48 are contoured to extend to and
into the central tube 26 in a somewhat helical or skew pattern.
The skew pattern of the outlet tube sections 48 affords an
inherent thermal expansion means for the reformer tubes 24.
The small size of the outlet tube 48 a~ain minimizes interference
with the flow of combustion gases allowing minimally restricted
access to the central sections 50 of the process tubes 24
containing the catalyst and minimizing the amount of heat
transfer to the outlet tube 46 wherein catalyst is not present.
The central tube 26 of the tube assembly 6 is
essentially a straight tube for conveying the process fluid
emanating from the process tubes 24 out of the furnace 2
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through outlet 27. The central tube 26 is provided ~ith a
thermal shroud 29 to shield the lower portion of the central
' tube 26 from the hot combustion gases. The thermal shroud 29
extends do~n~ardly from the central tu~e 26 at a location
a40ye.the botto,m, of the central section 50 of the process
tuhes. A cylindrically shaped flow diverter 25 ts also
provided in the interior of the lo~er portion of the central
tube 26. The flow diYerter 25 is arranged to dow~wardly-
diyert the flo~ of process fluid fro~ the outlet tube sections
' lO 48 of the reformex tubes 24. Thus, process~ flu~d flowtng
from the outlet tube sections 48 flows o,ver and ~mpinges on the
inside surface of the bottom of the central tube 26. This
desi~n further protects the lo~er portion of the central tu~e 26
f~om da~a~e due to the hot com~uStion gases.
Tube guides 31 a~e ar~anged on the central tube 26
and extend out~ardly from the centr~l tube 26 ~nto the area
of the prQcess tubes 24. The tube guides 31 function si~ilar ,
to the corbeling 16 to proyide both a means for pre~enting
excess,iye de~lection of the process tubes 24 and for preyent~ng
channeling af the furnace combust on gas. Addit~onally a
' m,ultiplicity of circular ~asher type spacer rings 75 a,re ~elded
to ~he p,rocess tubes 24 outer periphery ~n staggered
arr~ngement to prevent excessive~defIection and ~ibration of
the process tubes.
The com~ustion section 8 of the furnace ~s comprised
preferably of a single burner 52 arranged in a venturi or
conyerging-diverging section 54 ~nd a plurality of fixed curved
. . .
blades 56 to direct the combustion gas leaving the burner 52
in a spiral path to facilitate uniform mixing of fuel, air and
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flue gas. The combustion section 8 is also provided With a
partial semi-spherical member 58 or igloo which spans the
furnace just above the burner section 52. The igloo 58 is
formed of refractory material and is provided with a plurality
of openings 60 intermediate the furnace wall and the center
of the igloo 58 to allow passage of the hot combustion gases
to the area directly below the reformer tubes 24. The igloo
58 has arranged on top of it a cylindrical refracto~y member
64 which serves the dual function of protecting the lower end
of the center pipe 26 from direct exposure to the hottest
combustion gases and as a receptac.le for weighted members such
as ceramic balls 65 which counterbalance any lift force
imposed by the hot combustion gases below the igloo 58. The
igloo or partial semi-spherical member 58 prevents radiant
heat from the burner section 8 from reaching the process tubes
24. The only radiation which the process tubes 24 can
experience is the small amount of radiation from the combustion
gases themselves. The bottom contour of the partial semi-
spherical member 58 can be streamlined as best shown in the
Figure 1 to reduce the pressure drop through and lifting force
on me~ber 58 caused by the flow of combustion gases.
The furnace 2 is also provided with an upper chamber
66 which is sealed from the convection section by the tube sheet
22 and center tube 26. The upper chamber 66 is an inlet chamber
for the hydrocarbon feed. The hydrocarbon feed is ~ntroduced
into the upper section 66 through inlet opening 68 and passes
. directly to the process tube inlet tube sections 46.
The furnace 2 is also provided with a flue gas
outlet 70 located just below the tube sheet 22 and just above
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the section 50 of the reformer tubes containing catalyst.
The embodiment of FIGURE 2 is virtually identical
to that of FIGURE 1 with all like parts having like numbers.
The only difference is the addition of a heat exchanger unit
72. The heat exchanger 72 is located within the central tube
26 and is preferably comprised of bayonet tubes 74, an inlet
section 76 and an outlet section 78. The heat exchanger ~ubes
72 can carry any fluid but preferably hydrocarbon feed for the
reformer furnace is carried. The hot effluent from the reformer
tubes passes upwardly around the tube 74. The flue gas, air,
water or other fluid to be heated enters the heat exchanger
inlet 76, flows downwardly around the outer concentric chamber
of the bayonet tubes 72 and upwardly through the inner concentric
chamber of the bayonet tubes 72 to the heat exchanger outlet
78. The process fluid from the reformer tubes 24 thereby
transfers heat to the fluid inside the tubes 74 and is
coincidently cooled.
In operation, the furnace 2 of FIGURES 1 and 2 is
provided with hydrocarbon feed through inlet 68 which then
passes through the reformer inlet tubes 46 to the central section
50 of the reformer tube where catalyst is present. The principal
reforming occurs in the catalyst section. The reformed gas or
effluent leaves the catalyst bed in the central tube section 50
and for a short duration passes through the reformer outlet
tubes 48 to the bottom of the central tube 26 and thereafter
upwardly to the top of the furnace 2 and out for further
processing. The heat necessary to carry out the reformer
reaction is provided by a combination of recycled flue gas and
combustion gas generated by fuel and compressed air. The flue
gas enters the combustion chamber area 8
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through line 113, best seen in FIGURES 1 and 7, at approximately
1,050F. and 155 psia. Recycle of flue gas to the combustion
chamber 8 serves the purpose of controlling the combustion
temperature and supplying a portion of the combustion heat.
Gaseous fuels such as methane, natural gas or other fuel gases
or light liquid fuels such as light naphtha, enters the burner
52 through line 105 at approximately 70F. and 155 psia. Air
for combustion with the gaseous fuel enters through line 104
at about 700F. and 155 psia. The recycled flue gas from line
113 and the combustion products from burner 52 are then spirally
directed ~through the igloo 58 into the sections of the furnace
in contact with the reformer tubes 24. As best seen in FIGURE 6,
a temperature gradient from approximately 2250F. at the bottom
of the furnace 2 to 1200F. at the flue gas outlet occurs.
Pressure of the combustion gas can be between 100 psia to 230
psia and preferably between 100 psia to 180 psia and particularly
between 145 and 155. The pressure on the process side is
somewhat higher. The hydrocarbon feed enters the furnace (2) at
about 300 psia and preferably at 250 psia although pressure of
up to 550 psia have been found acceptable without modification
of the basic furnace structure and the reformed effluent exits
from the termination of the center pipe 26 at a pressure about
50 psia lower than the pressure at which the hydrocarbon feed
enters the furnace. It is possible to increase the outlet
process pressure even beyond 550 psia by a modification of the
tube sheet assembly as shown in Figure 8. The height and
vertical thickness of the web (38a) are increased. It has been
found that increasing the tube-shell differential pressure from
about 200 psi to about 450 psi and somewhat higher an increase
of 25% in thickness and 40~ increase
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10914Z5
in vertical height are necessary. In addition, layers of thin
thermal sheets or foils (121) are inserted between the thermal
baffle (40) and webs (38a). In this embodiment of the tubing
sheet (22), webs (38a) have been tapered at the two ends to
provide sufficient clearance between the weld at the two ends
of the webs (38a~ and the inlet tubes (4~). The insertion of the
thin~ thermal sneets suppresses free-convective ana radiant heat
transfer from the flue gas to process stream across the tube
sheet assembly ~22) thereby jreducing the axial temperature
gradient across the tube sheet assembly ~22) and thus preventing
excessive thermal stresses and deformation.
The temperature gradient over the furnace is shown in
FIGURE 6. The temperature ranges shown are for the combustion
gas side.
As best seen in FIGURE 7, the system of the present
invention uses the hot flue gas from the fu~nace to heat the
hydrocarbon feed-steam mixture, generate steam and to driYe the
turbine for producing the necessary compressed air for the
burning operation. The flue gas line 112 passes through the hot
side of heat exchanger 80 to heat the steam-hydrocarbon feed in
line 114 ~hich terminates in furnace inlet 68. After exiting
from the heat exchanger 80, the flue gas passes through the hot
side of heat exchanger 82 wherein hydracarbon feed from line 108
is heated. The heated hydrocarbon feed passes through the cold
side of the heat exchanger 82 and is ultimately introduced into
the steam-hydrocarbon feed line 114. The flue gas is then split
after leaYing the hot side of heat exchanger 82 and one portion
is passed through line 113 to heat exchanger 86 to generate steam
from process water which passes through'the cola side of heat exchanger 86.
0 The other portion of the,flue gas is delivered throu,gh line 112
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to a burner 88 wherein it mixes with fuel and compressed air
to provide combustion gas to drive-the turbine 90 of the air
compressor 92. Excess energy produced by the turbine 90 can
be used to generate electric power through generator 76 which
is in common drive with turbine 90. Air from line 104 is
compressed preferably in one main stage air compressor 92 and
delivered to high pressure booster compressor 96 for possible
further compression and ultimately to the furnace burner 52.
Compressors 96 and 98 are preferably connected in common drive
with turbine 90 to derive drive power therefrom, but may
alternatively be powered by separate motor or other drive means.
The flue gas from the tubular 90, along with the other hot gas,
passes through heat exchange e~uipment 94 to generate additional
steam for the system. Thereafter, the flue gas is exhausted
to atmosphere.
The effluent emanating from the outlet 27 of the center
tube 26 of the furnace 2 is passed through line 110 and through
the hot side of heat exchanger 100. Flue gas which has exhausted
from the hot side of heat exchanger 86 and then elevated in
pressure by compressor 98 passes through the cold side of heat
exchanger 100 and therein is heated prior to entry into the
furnace 2. The effluent in line 110 ¢an then be used to generate
steam in heat exchanger 102.
The furnace 2 is fired by fuel from line 105 that is
introduced into furnace 2 with compressed air from line la4.
; An example of the furnace and system of the invention
in operation is set forth. Reforming of methane is shown in the
example but it should be understood that higher hydrocarbons
such as propane and also prevaporized normally liquid h~drocarbons
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such as hexane or prevaporized low boiling petroleum fractions
such as naphtha may be catalytically reformed with the system
and furnace of the present invention. Two furnaces are operated
in parallel in this example is as follows:
2-7,000 lbs/hr. or CH4 feed at 100F and 260 psia is
delivered from line 108 to the cold side of heat exchanger 82.
3.96 x 10 6 lbs/hr. of flue gas combined from two identical
furnaces operating in parallel is delivered through line 112 to
the hot side of heat exchanger 82 after initial cooling in heat
exchanger 80. The 207,000 lbs/hr. of CH4 is heated to 417F.
and introduced into line 114 to mix with 835,000 lbs/hr of steam.
The steam-CH4 mixture is elevated to 1000 F, in heat
exchanger 80.
Flue gas from the hot side of heat exchanger 82 is
! split into two portions~ In one portion, 2.43 x 10 6 lbs/hr.
of flue gas i~ delivered to line 113 for recycle to the furnaces
(i.e. 2.43 x 106/2 lbs/hr flue gas to each furnace). Initially
the flue gas in line 113 which is at 913F. passes through the
hot side of heat exchanger 86 wherein it generates 214,000
lbs/hr. of steam at ~17F. and 300 psia for steam-water llne
116.
The flue gas leaves heat exchanger 86 at 600F. and
135 psia and is elevated to 160 psia in compressor 98 and heated
to 1050F. in heat exchanger 100 prior to entering the furnaces.
The other portion of the flue gas from the hot side
of heat exchanger 82 amounts to 1.53 x 106 lbs/hr~ and is
at 913F, and 140 psia, This portion continues in line 112 to
burner 88 wherein it mixes with 35,000 lbs/hr. of CH4 fuel and
0.61 x 106 lbs/hr. of compressed air to drive turbine 90. The
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hot gas entering turbine 90 iS at 1730F, and 140 psia and
upon discharge from the turbine gO is at 950F, and 15 psia.
The gas discharged from turbine 90 is used to
generate 325,000 lbs/hr. of steam at 300 psia in unit 94 for
delivery through line 116 to line 114. The gas leaving the
unit 94 is exhausted to atmosphere.
1.45 x IO6 lbs/hr. of compressed air is delivered
from compressor 92 to compressor g6 at 670F~ and 140 psia,
In compressor 96 the air is elevated to 700F~ and 155 psia,
From compressor 96 the compressed air is delivered in equal
portions through line 104 to the furnace burner 52 of the two
parallel reformer furnaces 2.
41,500 lbs hr. of CH4 fuel at 70F, and 160 psia is
delivered through line 105 to each of the two furnaces 2 at
their furnace burner 52 to combust with the 0,725 x 106 lbs/hr,
of compressed air delivered to each furnace through line 104,
The combustion gases along with the 2.43 x 106 lbs/hr, of
recycled flue gas at 1050F. (1.215 x 106 lbs/hr, to each
furnace) provides the heating service for each of the two
furnaces.
In furnace 2, the 0.521 x 106 lbs/hr. of CH4 and
steam entering each furnace at 1000F, and 250 psia is
reformed over a nickel oxide catalyst by convection from the
hot combustion gases and recycled flue gas to an exit
temperature of 1550F, The inlet pressure of the CH4 feed is
250 psia and the outlet pressure is 200 psia, The pressure
of the combustion gases and recyled flue gas is 155 psia at the
burner 8 and 145 psia at the flue gas exit 70,
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The reformed process fluid is passed in heat exchange
relationship with the recycled flue gas in heat exchanger 100
wherein the process fluid temperature is reduced to 1110F.
The effluent from both reformer furnaces is subsequently
cooled in heat exchanger 102 wherein 296,000 lbs/hr. of steam
is generated for delivery to hydrocarbon-steam line 114.
After leaving the hot side of heat exchanger 102, the reformer
effluent is sent on for further processing,
1,042,000 lbs/hr. of synthesis gas product of the
following composition is produced in this example:
COMPONENTMOL~
CH4 1.42
COz 5.65
CO 8.75
H2 48.85
H2O 35.33
100.00
The hydrocarbon plus CO production is 440 MM SCFD
at 60F.
When the use of the hydrogen rich gas product of
furnace (2) is such that in addition to the hydrocarbon rich
; gas there is a need for compressed air, it is possible to
modify the convective reformer system discussed in this
application to withdraw a portion of the compressed air from
compressor (92) for use elsewhere. The loss of the compressed
air, results in less combustion products to drive turbine 90,
This loss can easily be made up by waste steam in the system
as a whole.
This modification i5 particularly advantageous when
applied to ammonia production,
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Where the H2 rich product of the reformer furnace
is used in ammonia manufacture it is desirable although not
necessary to modify the process heretofore discussed. In
this optional embodiment a portion of the compressed air of
compressor (92) is withdrawn therefrom and fed to a secondary
reformer furnace (117) for an ammonia unit.
The effluent of reformer furnace (2) is fed
through line (110) to become the feed to the secondary reformer.
The combustion products of the secondary reformer (117? are
sent through stream (118) to be further processed in the ammonia
plant. The secondary reformer is of conventional construction
such as that disclosed U.S. Pat. 3,795,485,
By withdrawing air from compressor (92) for use in
the secondary reformer (117), less combustion products are
produced in burners 88 to drive turbine (90) and consequently
to replace this loss, steam is injected into the hot section
of the gas turbine (90). It has been found that there is
sufficient waste steam available in the system to inject in
the gas turbine (90).
Use of the heretofore described modification of
convective reformer system in an integrated ammonia production
facility results in a considerable saving as shown in the
following example for a facility producing 1000 tons/day of
ammonia. The reformer furnace (2) operates at 450 to 550 psia
and the hydrogen rich product of the reformer furnace (2) is
fed through stream (110) at 450 to 550 psia to a secondary
reformer (117) for the production of ammonia synthesis gas.
The secondary reformer (117) operates in a pressure range of
from 450 to 550 psia. Compressor (92) is operated at a rate of
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l,OS0,000 lbs/hr. Compressed,air is sent from the compressor
(92) along line 118 to the secondary reformer (117) at a rate
of 98,600 lbs/hr and enters the secondary reformer at 450-550
psia. Compressed air is sent to the burners (88) at a rate
of 272,000 lbs/hr. The pressure level of the air which is
withdrawn from the compressor for use in the secondary reformer
is 206 psia. The pressure level for the secondary reformer
preferably is 475 psia. ThUs, the pressure ratio for
compression of extracted gas turbine air to secondary reformer
requirements is 2.3. Thus, it has been found that such a unit
has a requirement of 2,100 BHP to compress the air to the
level of 475 psia. When this horse power requirements is
' compared to the 8500 BHP that is normally required to compress
process air in an ammonia facility of this size, one skilled
in the art can perceive a considerable saving.
.
;
.
-19-
bm ~
