CA1336353C - Reformer with low fired duty - Google Patents
Reformer with low fired dutyInfo
- Publication number
- CA1336353C CA1336353C CA000580887A CA580887A CA1336353C CA 1336353 C CA1336353 C CA 1336353C CA 000580887 A CA000580887 A CA 000580887A CA 580887 A CA580887 A CA 580887A CA 1336353 C CA1336353 C CA 1336353C
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- G—PHYSICS
- G07—CHECKING-DEVICES
- G07C—TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
- G07C9/00—Individual registration on entry or exit
- G07C9/20—Individual registration on entry or exit involving the use of a pass
- G07C9/28—Individual registration on entry or exit involving the use of a pass the pass enabling tracking or indicating presence
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- General Physics & Mathematics (AREA)
- Hydrogen, Water And Hydrids (AREA)
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Abstract
A reformer furnace and method for reforming hydrocarbons are described. The feed stream is heated in the presence of reforming catalyst both in a tube convection portion and a radiant section of the reformer furnace. The catalyst tubes may have an extended surface in the tube convection portion to enhance heat transfer within the convection portion.
Description
~ 1 33635~
The present invention relates in general to the tubes used in hydrocarbon reforming processe~ and particularly to processes wherein a hydrocarbon is reformed to obtain hydrogen.
The production of hydrogen from natural gas and other hydrocarbons is well known in the art. Generally, natural gas, such as methane, or other hydrocarbons, and water in the form of steam, are combined in a series of chemical reactions to produce hydrogen in a catalyst-filled tube. The following two chemical reactions are the principal reactions involved in the process:
Reforming Reaction CH4 + H20 -. CO ~ 3~2 ~ 97,000 Btu/mole Shift Reaction CO + ~2 ,~ C2 + H2 + 16,500 Btu/mole The field of the present invention relates gPn~r~lly to the heating surface of catalyst tubes in ~team reforming heaters commonly u~ed in ammonia and hydrogen plants to produce hydrogen.
The endothermic reforming reaction takes place by reacting ~ome portion of hydrocarbon feed with steam to produce hydrogen and carbon monoxide in cataly~t-filled tubes ~n steam reforming furnace~. Previously, all of the required heat '. ~
_ _ _ imparted to the steam reformer tubes took place in the radiant section of the furnace where the entire tube was exposed to radiant heat from the burner flame.
The total fired heat liberation is proportional to the amount of radiant heat required. Typically less than half of the heat released is imparted to the catalyst-filled tube by thermal radiation. The balance of the heat is carried by the flue gases leaving the radiant section and is recovered in various coils located in the convection section where flue gas flow~ transverse to the horizontal tubes that make up the convection coils of the steam reforming furnace. The various convection coils used to recover heat from the flue gases include: the combined hydro-carbon feed plus steam preheat coil, other process preheat coils, boiler feedwater coil, fuel preheat coil, combustion air prehéat coil, and the superheated steam coil. The alternative to using the above coil~ for cooling the convection flue gases is to pass the hot flue gases directly to the atmosphere, thereby losing the energy contained in the hot flue gas.
To reduce the heat load in the radiant section, the combined hydrocarbon feed plus steam is typically preheated to very high temperatures in the convection coils before passing to the radiant section of the furnace, thereby requiring construction from expensive alloy material for the combined hydrocarbon feed plus steam preheat coil and crossover piping interconnecting with the catalyst-filled tubes.
For primary reformers using high temperature gas turbine exhaust for combustion air, combustion air preheaters cannot be used to recover heat from the convection flue gases. Instead, coils for boiler feedwater preheating, steam generation, and steam superheating are the only viable means of recovering ~ 1 336353 maximum heat ~rom flue gases. This heat recovery may require either using steam drivers in the plant for equipment which could otherwise be operated at lower capital cost with electric motors or exporting excess steam production to unfavorable local markets.
Fig. 1 illustrates a conventional reformer with a furnace 10 having burners 12 located therein. Tube 40 is filled with catalyst 45 and runs the height of the furnace 10. A
process fluid mixture enters through process inlet 5 and is preheated by flue gas 92 within a convection section 20 before being injected into tube 40. The fluid mixture travels through the catalyst-filled tube 40 and exits to a manifold 80 and process outlet 85. The fluid mixture within tube 40 is heated almost completely by radiant heat transfer within furnace 10.
The flue gas 92 exiting through stack convection section 20 is at a very hiqh temperature. Some of the heat value within flue gas 92 is recovered by pre-heating the fluid mixture in exchanger tube 70 in stack convection section 20. Other heat is recovered by making steam by running fluid through exchanger tubes 90 also positioned in stack convection section 20.
An object of this invention is to reduce the fired duty and consequently the heat load of the convection flue gases to suit overall,plant requirements. This invention may also increase the heat absorbed in the catalyst tubes as a percentage of the total heat fired in the furnace. The reduced fired duty and increased heat absorption also allow the hydrocarbon feed plus steam preheat temperature to be reduced, which permits more economical alloys to be used for the preheater exchanger.
1 ~36353 Further, this amount of reduction may be varied to allow balancing the steam production to the plant consumption.
Toward the fillfilment of these and other objectives, the reforming furnace tubes of the present invention allow additional heat to be imparted to the catalyst tubes by convection from the heat bearing flue gases leaving the radiant section. Thus by extracting more heat from the flue gases leaving the reforming section, the reforming section efflciency is increased and the fired liberation is reduced. In addition the heat input to other services in the stack convection section is reduced.
- Accordingly, in one of its aspects, the present invention provides a reformer furnace comprising a radiant section containing burners, a tube convection portion through which hot flue gas from said radiant section exhausts, and at least one tube therein adapted to contain reforming catalyst, said tube having a first end and a second end, said ffrst end positioned in said tube convection portion and said second end positioned within said radiant section, said first end of said tube having an extended suri:àce to enhance convection heat tr~n ~fer In another of its aspects, the present invention provides a method for the production of hydrogen from a hydrocarbon stream in a steam reforming furnace for a hydrogen or ammonia plant, said furnace having a radiant section and a convection section, the width of the furnace in the convection section being substantially narrower than the width of the radiant section to provide enhanced velocity to the flue gas, the furnace contain ng a plurality of reforming catalyst-con~ining single pass tubes, the portion of each of said tubes within said furnace _ ~-- 3 - 1 ~36353 being filled with reforming catalyst, comprising the steps of preheating the hydrocarbon stream, introducing, heating and reacting the hydrocarbon stream and steam in said tubes within said convection section of the furnace wherein a portion of the catalyst-filled tubes have an extended surface integral with or attached to an outer surface of said tubes within the convection section to enhance convection heat transfer to the hydrocarbon stream within the catalyst-filled tube and thereafter heating the hydrocarbon stream in said radiant section of the furnace in another portion of said tubes having a substantially bare outer surface within the radiant section thereby ca.using the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas through the furnace.
In yet another of its aspects, the present invention provides a method for the production of hydrogen which comprises reacting a vaporized hydrocarbon with steam in a vertical tube containing steam reforming catalyst, said tube having two sections, one section of said tube has a substantially bare outer wall and receives heat largely by radiation from a radiant section of the furnace, and the other section of tube has extended surface and receives heat largely by convection from flue gases leaving the radiant section of the furnace.
In yet another of its aspects, the present invention provides a method for the production of hydrogen which comprises (a) reacting a vaporized hydrocarbon with steam in a steam reforming furnace for a hydrogen or ammonia plant, said furnace containing a pl~lrality of steam reforming catalyst-cont~ining single pass vertical tubes each having two sections, the portion of each of said tubes within said furnace being filled with steam -4a-.~
~ 3363~;3 ~rolllflng catalyst, wherein the step of reacting comprises (1) introducing and heating the hydrocarbon and steam largely by convection in a first section of said tubes filled with steam reforming catalyst, the first section having an extended surface integr~l with or attached to an outer surface of said tubes, and (2) heating the hydrocarbon and steam in a second steam reforming catalyst filled section of said tubes largely by radiation from a radiant section of the furnace, the second section of said tubes having substantially bare outer walls thereby causing the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas along the first section of said tubes by providing a substantially narrowed furnace ~vidth.
In still yet another of its aspects, the present invention provides a reforming furnace for producing hydrogen, comprising a radiant section cont~ining burners, a tube convection section connected to and aligned vertically with respect to said radiant section such that hot flue gas from the radiant section exhausts through said tube convection section, a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes extending from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tube portion, said first tube portion being the portion of the reaction tube posi~ioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube yortion and the second tube portion contain reforming catalyst, the first tube portion including extended surface means integral with or attached to an outer surface thereof for enh~ncing convection heat transfer within the tube convection section and means for -4b-- , . ..
.
separating said radiant section from said tube convection section whereby during furnace operation, heat transfer in the tube convection section is predomin~ntly convective and heat transfer in the radiant section is predominantly radiant, said separating means including parallel furnace side walls in the tube convection section having a width between the side walls substantially narrower than the width between side walls of the furnace in the radiant section.
In another aspect of its aspects the present invention provides a reforming furnace for producing hydrogen, comprising a lower radiant section cont~ining burners positioned along furnace side walls, an upper tube convection section connected to and aligned vertically above said radiant section, said tube convection section constructed and arranged such that hot flue gas from said radiant section exhausts through said tube convection section, a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes PYt~nding from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tub,~ portion, said first tube portion being the portion of the reaction tube positioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube portion and the second tube portion contain reforming catalyst, means for enhancing convection heat transfer within the tube convection section comprising radially outwardly eYten(ling heat transfer elements integral with or attached to an outer surface of said first tube portion, means for isolating the tube convection section from radiant heat produced in the radiant section and means for providing enhanced velocity to the flue gas in said tube convection section, comprising parallel ;: ~
~ . ~
vertical furnace side walls in the tube convection section with a distance between the parallel side walls in the tube convection section being less than that between the furnace side walls in the radiant section.
Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:
Fig. 1 schematically illustrates a refi~rmer furnace of the prior art;
Fig. 2 schem~tic~lly illllstr~tes a reformer furnace according to the present invention having a tube convection portion;
Fig. 3 is a cross sectional view of Fig. 2 taken along the line 3-3;
Figs. 4a and 4b are detailed views of a studded extended surface section of the catalyst-filled tube of Fig. 2; and Fig. 5 is a perspective view of an alternative extended surface section of Fig. 4 comprised of fins.
The pl~relled embodiments will now be described with reference to the drawings. Figure 2 illustrates a reformer furnace 110 having a radiant sectio 122 and a tube convection portion 125.
-4d--~ ~ ~36353 The integral radiant-convection reformer tubes of the present invention are vertical catalyst tube~ 140 with top inlet 107 and bottom outlet 182. The bottom of tube 140 which is in the radiant section 122 is substantially bare and located adjacent the burners 112. The top of the tube 140 contains the extended outer surface 150, and is located between two parallel walls 130, extending from the top of the radiant section 122. A
~eries of vertical catalyst-filled tubes are arranged in a straight line and since Fig. 1 illustrates a side view of the furnace, only one tube 140 is shown. Within the radiant section 122 are the burners 112, which supply the heat input for the furnace 110. The radiant heat from burners 112 impacts upon the bare walls of catalyst tubes 140. Tube 140 is filled with catalyst 145 which is supported in the tube on a catalyst support plate 142.
The tube convection portion 125 of the reformer furnace 110 has a reduced width through which exiting flue gas 192 must pass out of furnace 110. The tube convection portion 125 has two parallel walls 130, 130 which are much closer to the tube 140 than the walls of the radiant section 122. As such, the velocity of flue gas exiting through the tube convection portion 125 is much higher because of ~he reduced area through which flue gas 192 must travel, thereby increasing the convection heat transfer from the flue gas 192 to the fluid in the catalyst-filled tube 140.
The tubes 140 may have an extended surface 150 in the tube convection portion 125 to further enhance heat transfer.
Over a length "D" between the parallel walls 130, the extended surface 150 may be comprised of a series or a plurality of studs ~ 1 336353 152 attached-to the outer surface of tube 140 and extending radially outward therefrom.
Combustion gases from the radiant section 122 pass between the parallel walls 130, which contain the extended surface portion 150 of the catalyst-filled tubes 140. Convection heat from the flue gas 192 is efficiently imparted to the tubes 140 via the extended surface 150. Some additional heat is also transferred to the tubes 140 by radiation from the flue gas 192 and radiation from the parallel walls 130. After passing through ~7 the catalyst-tube convection section 125, the flue gas 192 goes to a conventional horizontal tube convection section 120 (which may include preheater exchanger tubes 170 and recovery exchanger tubes 190 for example) and up stack 121 as shown in Figure 2.
The basic process has a fluid mixture entering the furnace 110 at a process inlet 105 and passing through a series of heat exchanger tubes 170 located within stack 120. The fluid mixture is preheated by the flue gas 192 before the mixture enters the catalyst-filled tube 140. As the fluid mixture travel~ through the catalyst-filled tube 140, it is first heated by convection within the tube convection portion 125 where high velocity combustion gases from the radiant section 122 impact the extended surface 150 on tube 140. The fluid mixture within tube 140 thereby under goes substantial heating in the presence of catalyst even before entering the radiant section 122. Within the radiant section 122, tube 140 has a substantially bare outer wall and the fluid mixture within tube 140 is heated primarily through radiant heat transfer. Once the fluid mixture has passed through the radiant section 122, it leaves the furnace 110 through esit line 182 and enters manifold 180 in which the fluid ' -~ 1 ~36353 mixture from all the catalyst-filled tubes 140 is combined and exits through process outlet 185.
Figure 3 is a cross-sectional top view of the furnace 110 of figure 2. Figure 3 illustrates that furnace 110 has many catalyst-filled tubes 140, running the length thereof. Each of the catalyst-filled tubes 140 has an extended surface 150 within the radiant section 122 (see also Figure 2). A typical reformer furnace may have 150 or more reformer tubes. The catalyst-filled tubes 140 are positioned between the two parallel walls 130, 130. Fluid from tubes 140 exit through exit line 182 into manifold 180, combining and exiting out the process outlet 185.
The catalyst-tube convection portion 125 of tube 140 has an extended surface 150. Figs. 4a and 4b illustrate details of extended surface lS0. Extended surface lS0 is comprised of a series or plurality of studs 152 attached to the outer surface of the tube 140 and extending radially outward therefrom. The studs 152 are arranged in planes 155 which are spaced a distant of "d"
apart. Each plane 155 has approximately 30 studs 152 positioned around the circumference of tube 140.
The combination of stud size, quantity, shape, and spacing of the extended surface section 150 exposed to flue gases leaving the radiant section 122 and their enclosure may be varied to achieve the desired heat absorption characteristic within the catalyst-tube convection portion 125.
Fig. 5 illustrates an alternative embodiment of extended surface 160 comprised of a plurality of fins 165 longitudinally attached alonq the outer surface of tube 140 and extending radially outward therefrom. Again the size, orientation, and spacing of fins 165 are chosen to achieve the desired heat absorption characteristics. Though two particular designs for the extended-surface 150 have been described, other designs may be selected by those skilled in the art to achieve the desired heat trans~er characteristics, given the description and disclosure set forth herein.
The catalyst-tube convection portion 125 may also include baffles (not shown) to enhance convection heat transfer to tube 140.
Though Figs. 2 and 3 have been described to have a substantially vertically oriented tube 140, other orientations may be employed. Figs. 2 and 3 illustrates the inlet to the tube 140 on the top of furnace 110, alternatively the inlet to the catalyst tube may be at the bottom and the outlet at the top. In such a case, it would be more suitable to have the radiant portion of the tube at the top and convection portion of the tube at the bottom. In some cases, it may be desirable to have the inlet at the top, outlet at the bottom, and the convection portion at the bottom. A feature of the invention is the combination of a radiant ~ection and a convection portion in a single catalyst tube.
The temperature of the flue gases leaving the catalyst tube portion of this invention can be reduced to approximately 1200 to 1500F versus 1700 to 1900F in current state-of-the-art furnaces, without substantially increasing the catalyst volume or bare tube surface. As a result, the quantity of fuel required per unit of production may be reduced by up to approximately 25 percent.
The overall cost of the reforming furnace using integral radiant-convection catalyst-filled tubes can be significantly less than for those that do not employ this invention. Lower material cost is achieved by the lower flue gas temperature.
~ 1 336353 9-- .
Typically the preheat exchanger tubes (such as tubes 70 in Fig. 1) are exposed to flue gas at a temperature of 1700 to 1900F. Such a temperature requires more expensive alloy tube construction as compared to tubes (such as tubes 170 in Fig. 2) of the present invention which are exposed to a lower temperature of 1200 to 1500F.
Examples will now be described comparing the present invention to processes of the prior art. The examples compare processes of reformers for a typical 1500 short tons per day ammonia plant. The examples are summarized in Table 1.
Hydrocarbon Feed Furnace Turbine ~otal Plu~ Steam Burner Fuel Fuel Preheat Input Consumption Consumption Consumption Q Q Q Q
Example MMBtu/hr MMBtu/hr MMBtu/hr MMBtu/hr Energy Ab~orbed Other Feed Flue Ga3 Radiant ~ Stack Recovery Inlet Exit Temp. Temp. Flue Convection Gas Coil~
Temp.From Rad. GaY entry Q Exit Q
to TubeSection to Stack MMBtu/hr Temp MMBtu/hr 1150F 1850F 1850F 137 350F t79 ~ lo This example is for a typical 1500 short tons per day ammonia plant according to current technology as in Fig. 1. The reforming furnace contains 152 catalyst-filled tubes of 5.75 inches ID by 39.49 feet high. About 36.5 feet of the catalyst tube height is in the radiant zone. Hydrocarbon feed enters the process inlet 5 and is preheated in exchanger tubes 70 at a heat input rate of 44 MMBtu/hr. The feed enters the catalyst-filled tubes 140 at a temperature of 1025F. The feed i8 then heated in furnace 10 at an absorption rate of 154 MMBtu/hr which is entirely in a radiant section since this example has no convection section. Fuel consumption is 302 MMBtu/hr for the burners 12 and 191 MMBtu/hr. for the gas turbine (not shown) which supplies air for the combustion process. Total fuel consumption is 493 MMBtu/hr. The combustion gases leave the combustion zone and enter the convection section 20 at a temperature of 1850F. Within convection ~ection 20, the gases preheat the hydroca~bon feed in exchanger tubes 70. Further heat is recovered in eYrh~n~er tubes 90 at a rate of 203 MMBtu/hr.
The flue ga~ to the ~tack then exits at 350F.
This example illustrates a 1500 short tons per day ammonia plant according to the present invention as illustrated in Fig. 2. The number and diameter of the cataly-Qt tubes i5 the same as in Example 1. The length of the tubes is increased to 42.06 feet with 29.94 feet of the tube length in the radiant section 122. Tubes 140 have 7.27 feet of extended surface 150 which comprises the convection section 125 of the catalyst-filled tubes 140. The extended surface 150 ~refer to Figs. 4a ~ b) is ~ 1 336353 Il--comprised of studs 152 of 3/8 inches diameter by 3/4 inches high with 30 studs 152 per plane 155 around the circumference of the tube 140. The planes 155 are spaced 1/2 inch apart "d" for the full 7.27 foot height ~D" of the convection section 125. The same results can be o~tained with other types of extended surface.
Referring to Table 1, the hydrocarbon feed is preheated at a rate of 44 MM Btu/hr in exchanger tubes 170. The feed enters the catalyst-filled tubes 140 at 1025F. The feed is heated in furnace 110 at an absorption rate of 154 MM Btu/hr, some of which occurs in the radiant section 122 and the remainder in the catalyst-tube convection portion 125. Fuel consumption is 230 MM Btu/hr at the burner~ 112 and 191 MM Btu/hr for the gas turbine Inot shown). Total fuel consumption is 421 MM Btu/hr.
The combustion gases exit the radiant section 122 and enter the catalyst-tube convection portion 125 at 1850F. The flue ga~ 192 enters convection section 20 at 1470F. Within convection section 20, the flue gas 192 preheats the hydrocarbon stream in exchanger tubes 170. Further heat is recovered in exchanqer tubes 190 at a rate of 131 MM Btu/hr. The flue gas to the stack exits at 350F.
In this example in which the temperature entering the catalyst tube is 1025F (the same as in Example 1), the fuel to the reformer is reduced by about 24 percent. The total fuel to the reformer plus gas turbine is reduced by about 15 percent.
This example is for a conventional reformer similar to that of Example 1 except that the inlet temperature is raised from 1025F to 1150F to reduce the overall fired duty. In this _ _ _ _ ~ 1 336353 case, there are 124 catalyst tubes of 6.0 inc~e~ ID by 39 feet high.
Referring to Fig. 1 and Table 1, feed enters inlet 5 and is preheated in exchanger tubes 70 at a heat input rate of 61 MMBtu/hr. The feed enters the catalyst-filled tube 40 at 1150F
and i8 then heated in furnace 10 at an absorption rate of 137 MMBtu/hr which is entirely in a radiant section since this example has no catalyst-tube convection portion. Fuel consumption is 274 MMBtu/hr for the burners 12 and 191 for the gas turbine (not shown) for a total fuel consumption of 465 MMBtu/hr.
The combustion gases leave the combustion zone and enter convection section 20 ~the flue gas 92) at a temperature of 1850F. The flue gas 92 preheats the hydrocarbon feed in exchanger tubes 70. Further heat is recovered at a rate of 179 MMBtu/hr in exchanger tubes 90. Flue gas to the stack exits at 350F.
Comparing the process conditions for the integral radiant-convection catalyst-filled tube of Example 2 with e 3, the present invention as shown in Example 2 reduces the fuel to the reformer by 16 percent and reduces the~ total fuel required by 9 percent over Example 3.
In this example, the hydrDcarbon feed plus steam temperature entering the catalyst-filled tubes is 125F less for the inteqral radiant-convection catalyst-filled tube of Example 2, thus achieving two objectives simultaneously: tl) a substantially lower cost for the hydrocarbon feed plus steam coil and (2) reducing the fuel firing required for the reforming reaction.
~ 1 33~353 ThuS, a furnace and process are disclosed which reform hydrocarbons to obtain a gas containing substantial amounts of hydrogen. While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that other modifications are possible without departing from the inventive concepts herein. The invention, therefore, it not to be restricted except as in the appended claims.
The present invention relates in general to the tubes used in hydrocarbon reforming processe~ and particularly to processes wherein a hydrocarbon is reformed to obtain hydrogen.
The production of hydrogen from natural gas and other hydrocarbons is well known in the art. Generally, natural gas, such as methane, or other hydrocarbons, and water in the form of steam, are combined in a series of chemical reactions to produce hydrogen in a catalyst-filled tube. The following two chemical reactions are the principal reactions involved in the process:
Reforming Reaction CH4 + H20 -. CO ~ 3~2 ~ 97,000 Btu/mole Shift Reaction CO + ~2 ,~ C2 + H2 + 16,500 Btu/mole The field of the present invention relates gPn~r~lly to the heating surface of catalyst tubes in ~team reforming heaters commonly u~ed in ammonia and hydrogen plants to produce hydrogen.
The endothermic reforming reaction takes place by reacting ~ome portion of hydrocarbon feed with steam to produce hydrogen and carbon monoxide in cataly~t-filled tubes ~n steam reforming furnace~. Previously, all of the required heat '. ~
_ _ _ imparted to the steam reformer tubes took place in the radiant section of the furnace where the entire tube was exposed to radiant heat from the burner flame.
The total fired heat liberation is proportional to the amount of radiant heat required. Typically less than half of the heat released is imparted to the catalyst-filled tube by thermal radiation. The balance of the heat is carried by the flue gases leaving the radiant section and is recovered in various coils located in the convection section where flue gas flow~ transverse to the horizontal tubes that make up the convection coils of the steam reforming furnace. The various convection coils used to recover heat from the flue gases include: the combined hydro-carbon feed plus steam preheat coil, other process preheat coils, boiler feedwater coil, fuel preheat coil, combustion air prehéat coil, and the superheated steam coil. The alternative to using the above coil~ for cooling the convection flue gases is to pass the hot flue gases directly to the atmosphere, thereby losing the energy contained in the hot flue gas.
To reduce the heat load in the radiant section, the combined hydrocarbon feed plus steam is typically preheated to very high temperatures in the convection coils before passing to the radiant section of the furnace, thereby requiring construction from expensive alloy material for the combined hydrocarbon feed plus steam preheat coil and crossover piping interconnecting with the catalyst-filled tubes.
For primary reformers using high temperature gas turbine exhaust for combustion air, combustion air preheaters cannot be used to recover heat from the convection flue gases. Instead, coils for boiler feedwater preheating, steam generation, and steam superheating are the only viable means of recovering ~ 1 336353 maximum heat ~rom flue gases. This heat recovery may require either using steam drivers in the plant for equipment which could otherwise be operated at lower capital cost with electric motors or exporting excess steam production to unfavorable local markets.
Fig. 1 illustrates a conventional reformer with a furnace 10 having burners 12 located therein. Tube 40 is filled with catalyst 45 and runs the height of the furnace 10. A
process fluid mixture enters through process inlet 5 and is preheated by flue gas 92 within a convection section 20 before being injected into tube 40. The fluid mixture travels through the catalyst-filled tube 40 and exits to a manifold 80 and process outlet 85. The fluid mixture within tube 40 is heated almost completely by radiant heat transfer within furnace 10.
The flue gas 92 exiting through stack convection section 20 is at a very hiqh temperature. Some of the heat value within flue gas 92 is recovered by pre-heating the fluid mixture in exchanger tube 70 in stack convection section 20. Other heat is recovered by making steam by running fluid through exchanger tubes 90 also positioned in stack convection section 20.
An object of this invention is to reduce the fired duty and consequently the heat load of the convection flue gases to suit overall,plant requirements. This invention may also increase the heat absorbed in the catalyst tubes as a percentage of the total heat fired in the furnace. The reduced fired duty and increased heat absorption also allow the hydrocarbon feed plus steam preheat temperature to be reduced, which permits more economical alloys to be used for the preheater exchanger.
1 ~36353 Further, this amount of reduction may be varied to allow balancing the steam production to the plant consumption.
Toward the fillfilment of these and other objectives, the reforming furnace tubes of the present invention allow additional heat to be imparted to the catalyst tubes by convection from the heat bearing flue gases leaving the radiant section. Thus by extracting more heat from the flue gases leaving the reforming section, the reforming section efflciency is increased and the fired liberation is reduced. In addition the heat input to other services in the stack convection section is reduced.
- Accordingly, in one of its aspects, the present invention provides a reformer furnace comprising a radiant section containing burners, a tube convection portion through which hot flue gas from said radiant section exhausts, and at least one tube therein adapted to contain reforming catalyst, said tube having a first end and a second end, said ffrst end positioned in said tube convection portion and said second end positioned within said radiant section, said first end of said tube having an extended suri:àce to enhance convection heat tr~n ~fer In another of its aspects, the present invention provides a method for the production of hydrogen from a hydrocarbon stream in a steam reforming furnace for a hydrogen or ammonia plant, said furnace having a radiant section and a convection section, the width of the furnace in the convection section being substantially narrower than the width of the radiant section to provide enhanced velocity to the flue gas, the furnace contain ng a plurality of reforming catalyst-con~ining single pass tubes, the portion of each of said tubes within said furnace _ ~-- 3 - 1 ~36353 being filled with reforming catalyst, comprising the steps of preheating the hydrocarbon stream, introducing, heating and reacting the hydrocarbon stream and steam in said tubes within said convection section of the furnace wherein a portion of the catalyst-filled tubes have an extended surface integral with or attached to an outer surface of said tubes within the convection section to enhance convection heat transfer to the hydrocarbon stream within the catalyst-filled tube and thereafter heating the hydrocarbon stream in said radiant section of the furnace in another portion of said tubes having a substantially bare outer surface within the radiant section thereby ca.using the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas through the furnace.
In yet another of its aspects, the present invention provides a method for the production of hydrogen which comprises reacting a vaporized hydrocarbon with steam in a vertical tube containing steam reforming catalyst, said tube having two sections, one section of said tube has a substantially bare outer wall and receives heat largely by radiation from a radiant section of the furnace, and the other section of tube has extended surface and receives heat largely by convection from flue gases leaving the radiant section of the furnace.
In yet another of its aspects, the present invention provides a method for the production of hydrogen which comprises (a) reacting a vaporized hydrocarbon with steam in a steam reforming furnace for a hydrogen or ammonia plant, said furnace containing a pl~lrality of steam reforming catalyst-cont~ining single pass vertical tubes each having two sections, the portion of each of said tubes within said furnace being filled with steam -4a-.~
~ 3363~;3 ~rolllflng catalyst, wherein the step of reacting comprises (1) introducing and heating the hydrocarbon and steam largely by convection in a first section of said tubes filled with steam reforming catalyst, the first section having an extended surface integr~l with or attached to an outer surface of said tubes, and (2) heating the hydrocarbon and steam in a second steam reforming catalyst filled section of said tubes largely by radiation from a radiant section of the furnace, the second section of said tubes having substantially bare outer walls thereby causing the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas along the first section of said tubes by providing a substantially narrowed furnace ~vidth.
In still yet another of its aspects, the present invention provides a reforming furnace for producing hydrogen, comprising a radiant section cont~ining burners, a tube convection section connected to and aligned vertically with respect to said radiant section such that hot flue gas from the radiant section exhausts through said tube convection section, a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes extending from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tube portion, said first tube portion being the portion of the reaction tube posi~ioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube yortion and the second tube portion contain reforming catalyst, the first tube portion including extended surface means integral with or attached to an outer surface thereof for enh~ncing convection heat transfer within the tube convection section and means for -4b-- , . ..
.
separating said radiant section from said tube convection section whereby during furnace operation, heat transfer in the tube convection section is predomin~ntly convective and heat transfer in the radiant section is predominantly radiant, said separating means including parallel furnace side walls in the tube convection section having a width between the side walls substantially narrower than the width between side walls of the furnace in the radiant section.
In another aspect of its aspects the present invention provides a reforming furnace for producing hydrogen, comprising a lower radiant section cont~ining burners positioned along furnace side walls, an upper tube convection section connected to and aligned vertically above said radiant section, said tube convection section constructed and arranged such that hot flue gas from said radiant section exhausts through said tube convection section, a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes PYt~nding from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tub,~ portion, said first tube portion being the portion of the reaction tube positioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube portion and the second tube portion contain reforming catalyst, means for enhancing convection heat transfer within the tube convection section comprising radially outwardly eYten(ling heat transfer elements integral with or attached to an outer surface of said first tube portion, means for isolating the tube convection section from radiant heat produced in the radiant section and means for providing enhanced velocity to the flue gas in said tube convection section, comprising parallel ;: ~
~ . ~
vertical furnace side walls in the tube convection section with a distance between the parallel side walls in the tube convection section being less than that between the furnace side walls in the radiant section.
Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:
Fig. 1 schematically illustrates a refi~rmer furnace of the prior art;
Fig. 2 schem~tic~lly illllstr~tes a reformer furnace according to the present invention having a tube convection portion;
Fig. 3 is a cross sectional view of Fig. 2 taken along the line 3-3;
Figs. 4a and 4b are detailed views of a studded extended surface section of the catalyst-filled tube of Fig. 2; and Fig. 5 is a perspective view of an alternative extended surface section of Fig. 4 comprised of fins.
The pl~relled embodiments will now be described with reference to the drawings. Figure 2 illustrates a reformer furnace 110 having a radiant sectio 122 and a tube convection portion 125.
-4d--~ ~ ~36353 The integral radiant-convection reformer tubes of the present invention are vertical catalyst tube~ 140 with top inlet 107 and bottom outlet 182. The bottom of tube 140 which is in the radiant section 122 is substantially bare and located adjacent the burners 112. The top of the tube 140 contains the extended outer surface 150, and is located between two parallel walls 130, extending from the top of the radiant section 122. A
~eries of vertical catalyst-filled tubes are arranged in a straight line and since Fig. 1 illustrates a side view of the furnace, only one tube 140 is shown. Within the radiant section 122 are the burners 112, which supply the heat input for the furnace 110. The radiant heat from burners 112 impacts upon the bare walls of catalyst tubes 140. Tube 140 is filled with catalyst 145 which is supported in the tube on a catalyst support plate 142.
The tube convection portion 125 of the reformer furnace 110 has a reduced width through which exiting flue gas 192 must pass out of furnace 110. The tube convection portion 125 has two parallel walls 130, 130 which are much closer to the tube 140 than the walls of the radiant section 122. As such, the velocity of flue gas exiting through the tube convection portion 125 is much higher because of ~he reduced area through which flue gas 192 must travel, thereby increasing the convection heat transfer from the flue gas 192 to the fluid in the catalyst-filled tube 140.
The tubes 140 may have an extended surface 150 in the tube convection portion 125 to further enhance heat transfer.
Over a length "D" between the parallel walls 130, the extended surface 150 may be comprised of a series or a plurality of studs ~ 1 336353 152 attached-to the outer surface of tube 140 and extending radially outward therefrom.
Combustion gases from the radiant section 122 pass between the parallel walls 130, which contain the extended surface portion 150 of the catalyst-filled tubes 140. Convection heat from the flue gas 192 is efficiently imparted to the tubes 140 via the extended surface 150. Some additional heat is also transferred to the tubes 140 by radiation from the flue gas 192 and radiation from the parallel walls 130. After passing through ~7 the catalyst-tube convection section 125, the flue gas 192 goes to a conventional horizontal tube convection section 120 (which may include preheater exchanger tubes 170 and recovery exchanger tubes 190 for example) and up stack 121 as shown in Figure 2.
The basic process has a fluid mixture entering the furnace 110 at a process inlet 105 and passing through a series of heat exchanger tubes 170 located within stack 120. The fluid mixture is preheated by the flue gas 192 before the mixture enters the catalyst-filled tube 140. As the fluid mixture travel~ through the catalyst-filled tube 140, it is first heated by convection within the tube convection portion 125 where high velocity combustion gases from the radiant section 122 impact the extended surface 150 on tube 140. The fluid mixture within tube 140 thereby under goes substantial heating in the presence of catalyst even before entering the radiant section 122. Within the radiant section 122, tube 140 has a substantially bare outer wall and the fluid mixture within tube 140 is heated primarily through radiant heat transfer. Once the fluid mixture has passed through the radiant section 122, it leaves the furnace 110 through esit line 182 and enters manifold 180 in which the fluid ' -~ 1 ~36353 mixture from all the catalyst-filled tubes 140 is combined and exits through process outlet 185.
Figure 3 is a cross-sectional top view of the furnace 110 of figure 2. Figure 3 illustrates that furnace 110 has many catalyst-filled tubes 140, running the length thereof. Each of the catalyst-filled tubes 140 has an extended surface 150 within the radiant section 122 (see also Figure 2). A typical reformer furnace may have 150 or more reformer tubes. The catalyst-filled tubes 140 are positioned between the two parallel walls 130, 130. Fluid from tubes 140 exit through exit line 182 into manifold 180, combining and exiting out the process outlet 185.
The catalyst-tube convection portion 125 of tube 140 has an extended surface 150. Figs. 4a and 4b illustrate details of extended surface lS0. Extended surface lS0 is comprised of a series or plurality of studs 152 attached to the outer surface of the tube 140 and extending radially outward therefrom. The studs 152 are arranged in planes 155 which are spaced a distant of "d"
apart. Each plane 155 has approximately 30 studs 152 positioned around the circumference of tube 140.
The combination of stud size, quantity, shape, and spacing of the extended surface section 150 exposed to flue gases leaving the radiant section 122 and their enclosure may be varied to achieve the desired heat absorption characteristic within the catalyst-tube convection portion 125.
Fig. 5 illustrates an alternative embodiment of extended surface 160 comprised of a plurality of fins 165 longitudinally attached alonq the outer surface of tube 140 and extending radially outward therefrom. Again the size, orientation, and spacing of fins 165 are chosen to achieve the desired heat absorption characteristics. Though two particular designs for the extended-surface 150 have been described, other designs may be selected by those skilled in the art to achieve the desired heat trans~er characteristics, given the description and disclosure set forth herein.
The catalyst-tube convection portion 125 may also include baffles (not shown) to enhance convection heat transfer to tube 140.
Though Figs. 2 and 3 have been described to have a substantially vertically oriented tube 140, other orientations may be employed. Figs. 2 and 3 illustrates the inlet to the tube 140 on the top of furnace 110, alternatively the inlet to the catalyst tube may be at the bottom and the outlet at the top. In such a case, it would be more suitable to have the radiant portion of the tube at the top and convection portion of the tube at the bottom. In some cases, it may be desirable to have the inlet at the top, outlet at the bottom, and the convection portion at the bottom. A feature of the invention is the combination of a radiant ~ection and a convection portion in a single catalyst tube.
The temperature of the flue gases leaving the catalyst tube portion of this invention can be reduced to approximately 1200 to 1500F versus 1700 to 1900F in current state-of-the-art furnaces, without substantially increasing the catalyst volume or bare tube surface. As a result, the quantity of fuel required per unit of production may be reduced by up to approximately 25 percent.
The overall cost of the reforming furnace using integral radiant-convection catalyst-filled tubes can be significantly less than for those that do not employ this invention. Lower material cost is achieved by the lower flue gas temperature.
~ 1 336353 9-- .
Typically the preheat exchanger tubes (such as tubes 70 in Fig. 1) are exposed to flue gas at a temperature of 1700 to 1900F. Such a temperature requires more expensive alloy tube construction as compared to tubes (such as tubes 170 in Fig. 2) of the present invention which are exposed to a lower temperature of 1200 to 1500F.
Examples will now be described comparing the present invention to processes of the prior art. The examples compare processes of reformers for a typical 1500 short tons per day ammonia plant. The examples are summarized in Table 1.
Hydrocarbon Feed Furnace Turbine ~otal Plu~ Steam Burner Fuel Fuel Preheat Input Consumption Consumption Consumption Q Q Q Q
Example MMBtu/hr MMBtu/hr MMBtu/hr MMBtu/hr Energy Ab~orbed Other Feed Flue Ga3 Radiant ~ Stack Recovery Inlet Exit Temp. Temp. Flue Convection Gas Coil~
Temp.From Rad. GaY entry Q Exit Q
to TubeSection to Stack MMBtu/hr Temp MMBtu/hr 1150F 1850F 1850F 137 350F t79 ~ lo This example is for a typical 1500 short tons per day ammonia plant according to current technology as in Fig. 1. The reforming furnace contains 152 catalyst-filled tubes of 5.75 inches ID by 39.49 feet high. About 36.5 feet of the catalyst tube height is in the radiant zone. Hydrocarbon feed enters the process inlet 5 and is preheated in exchanger tubes 70 at a heat input rate of 44 MMBtu/hr. The feed enters the catalyst-filled tubes 140 at a temperature of 1025F. The feed i8 then heated in furnace 10 at an absorption rate of 154 MMBtu/hr which is entirely in a radiant section since this example has no convection section. Fuel consumption is 302 MMBtu/hr for the burners 12 and 191 MMBtu/hr. for the gas turbine (not shown) which supplies air for the combustion process. Total fuel consumption is 493 MMBtu/hr. The combustion gases leave the combustion zone and enter the convection section 20 at a temperature of 1850F. Within convection ~ection 20, the gases preheat the hydroca~bon feed in exchanger tubes 70. Further heat is recovered in eYrh~n~er tubes 90 at a rate of 203 MMBtu/hr.
The flue ga~ to the ~tack then exits at 350F.
This example illustrates a 1500 short tons per day ammonia plant according to the present invention as illustrated in Fig. 2. The number and diameter of the cataly-Qt tubes i5 the same as in Example 1. The length of the tubes is increased to 42.06 feet with 29.94 feet of the tube length in the radiant section 122. Tubes 140 have 7.27 feet of extended surface 150 which comprises the convection section 125 of the catalyst-filled tubes 140. The extended surface 150 ~refer to Figs. 4a ~ b) is ~ 1 336353 Il--comprised of studs 152 of 3/8 inches diameter by 3/4 inches high with 30 studs 152 per plane 155 around the circumference of the tube 140. The planes 155 are spaced 1/2 inch apart "d" for the full 7.27 foot height ~D" of the convection section 125. The same results can be o~tained with other types of extended surface.
Referring to Table 1, the hydrocarbon feed is preheated at a rate of 44 MM Btu/hr in exchanger tubes 170. The feed enters the catalyst-filled tubes 140 at 1025F. The feed is heated in furnace 110 at an absorption rate of 154 MM Btu/hr, some of which occurs in the radiant section 122 and the remainder in the catalyst-tube convection portion 125. Fuel consumption is 230 MM Btu/hr at the burner~ 112 and 191 MM Btu/hr for the gas turbine Inot shown). Total fuel consumption is 421 MM Btu/hr.
The combustion gases exit the radiant section 122 and enter the catalyst-tube convection portion 125 at 1850F. The flue ga~ 192 enters convection section 20 at 1470F. Within convection section 20, the flue gas 192 preheats the hydrocarbon stream in exchanger tubes 170. Further heat is recovered in exchanqer tubes 190 at a rate of 131 MM Btu/hr. The flue gas to the stack exits at 350F.
In this example in which the temperature entering the catalyst tube is 1025F (the same as in Example 1), the fuel to the reformer is reduced by about 24 percent. The total fuel to the reformer plus gas turbine is reduced by about 15 percent.
This example is for a conventional reformer similar to that of Example 1 except that the inlet temperature is raised from 1025F to 1150F to reduce the overall fired duty. In this _ _ _ _ ~ 1 336353 case, there are 124 catalyst tubes of 6.0 inc~e~ ID by 39 feet high.
Referring to Fig. 1 and Table 1, feed enters inlet 5 and is preheated in exchanger tubes 70 at a heat input rate of 61 MMBtu/hr. The feed enters the catalyst-filled tube 40 at 1150F
and i8 then heated in furnace 10 at an absorption rate of 137 MMBtu/hr which is entirely in a radiant section since this example has no catalyst-tube convection portion. Fuel consumption is 274 MMBtu/hr for the burners 12 and 191 for the gas turbine (not shown) for a total fuel consumption of 465 MMBtu/hr.
The combustion gases leave the combustion zone and enter convection section 20 ~the flue gas 92) at a temperature of 1850F. The flue gas 92 preheats the hydrocarbon feed in exchanger tubes 70. Further heat is recovered at a rate of 179 MMBtu/hr in exchanger tubes 90. Flue gas to the stack exits at 350F.
Comparing the process conditions for the integral radiant-convection catalyst-filled tube of Example 2 with e 3, the present invention as shown in Example 2 reduces the fuel to the reformer by 16 percent and reduces the~ total fuel required by 9 percent over Example 3.
In this example, the hydrDcarbon feed plus steam temperature entering the catalyst-filled tubes is 125F less for the inteqral radiant-convection catalyst-filled tube of Example 2, thus achieving two objectives simultaneously: tl) a substantially lower cost for the hydrocarbon feed plus steam coil and (2) reducing the fuel firing required for the reforming reaction.
~ 1 33~353 ThuS, a furnace and process are disclosed which reform hydrocarbons to obtain a gas containing substantial amounts of hydrogen. While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that other modifications are possible without departing from the inventive concepts herein. The invention, therefore, it not to be restricted except as in the appended claims.
Claims (39)
1. A reformer furnace comprising:
a radiant section containing burners;
a tube convection portion through which hot flue gas from said radiant section exhausts; and at least one tube therein adapted to contain reforming catalyst, said tube having a first end and a second end, said first end positioned in said tube convection portion and said second end positioned within said radiant section, said first end of said tube having an extended surface to enhance convection heat transfer.
a radiant section containing burners;
a tube convection portion through which hot flue gas from said radiant section exhausts; and at least one tube therein adapted to contain reforming catalyst, said tube having a first end and a second end, said first end positioned in said tube convection portion and said second end positioned within said radiant section, said first end of said tube having an extended surface to enhance convection heat transfer.
2. A reformer furnace as in Claim 1 wherein said tube convection portion has two substantially parallel walls with said first end of said tube positioned therebetween.
3. A reformer furnace as in Claim 1 wherein the extended surface of the first end of said tube is comprised of a plurality of studs attached to the outer surface of said first end and extending radially outward therefrom.
4. A reformer furnace as in Claim 1 wherein the extended surface of the first end of said tube is comprised of a plurality of fins attached to the outer surface of said first end and extending radially outward therefrom.
5. A reformer furnace as in any one of Claims 1-4 further comprising baffles in said tube convection portion.
6. A reformer furnace as in any one of Claims 1-4 wherein the width between reformer walls at the tube convection portion is substantially narrower than the width between reformer walls at the radiant section such that the reformer walls at the tube convection portion are close to the extended surface of the catalyst-filled tube enhancing heat transfer to the tube.
7. A reformer furnace as in Claim 3 wherein the plurality of studs are arranged in planes along the length of the tube convection portion with about 30 studs per plane, the planes spaced at about 1/2 inch apart, and the studs having a diameter of about 3/8 inch and a length of about 3/4 inch.
8. A reformer furnace as in any one of Claims 1-4 wherein the furnace has a top and a bottom portion and wherein said tube is oriented substantially vertically, said radiant section being at the bottom of the furnace and said tube convection portion being at the top of the furnace.
9. A reformer furnace as in any one of Claims 1-4 wherein the furnace has a top and a bottom portion and wherein said tube is oriented substantially vertically, said radiant section being at the top of the furnace and said tube convection portion being at the bottom of the furnace.
10. A method for the production of hydrogen from a hydrocarbon stream in a steam reforming furnace for a hydrogen or ammonia plant, said furnace having a radiant section and a convection section, the width of the furnace in the convection section being substantially narrower than the width of the radiant section to provide enhanced velocity to the flue gas, the furnace containing a plurality of reforming catalyst-containing single pass tubes, the portion of each of said tubes within said furnace being filled with reforming catalyst, comprising the steps of:
preheating the hydrocarbon stream;
introducing, heating and reacting the hydrocarbon stream and steam in said tubes within said convection section of the furnace wherein a portion of the catalyst-filled tubes have an extended surface integral with or attached to an outer surface of said tubes within the convection section to enhance convection heat transfer to the hydrocarbon stream within the catalyst-filled tube; and thereafter heating the hydrocarbon stream in said radiant section of the furnace in another portion of said tubes having a substantially bare outer surface within the radiant section thereby causing the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas through the furnace.
preheating the hydrocarbon stream;
introducing, heating and reacting the hydrocarbon stream and steam in said tubes within said convection section of the furnace wherein a portion of the catalyst-filled tubes have an extended surface integral with or attached to an outer surface of said tubes within the convection section to enhance convection heat transfer to the hydrocarbon stream within the catalyst-filled tube; and thereafter heating the hydrocarbon stream in said radiant section of the furnace in another portion of said tubes having a substantially bare outer surface within the radiant section thereby causing the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas through the furnace.
11. A method according to Claim 10 wherein said extended surface comprises a plurality of studs attached to an outer surface of said tubes and extending radially outward therefrom.
12. A method according to Claim 10 wherein said extended surface comprises a plurality of fins attached along an outer surface of said tubes and extending radially outward therefrom.
13. A method according to any one of Claims 10-12 creating turbulence in the convection section of said furnace with baffles.
14. A method according to any one of Claims 10-12 wherein the furnace has a top and a bottom portion in which an inlet to the catalyst tube is at the top, an outlet from the catalyst tube is at the bottom, and the flue gases leave from the top.
15. A method according to any one of Claims 10-12 wherein the furnace has a top and a bottom portion in which an inlet to the catalyst tube is at the bottom, an outlet from the catalyst tube is at the top, and the flue gases leave at the bottom.
16. A method according to any one of Claims 10-12 wherein the furnace has a top and a bottom portion in which an inlet to the catalyst tube is at the top, an outlet from the catalyst tube is at the bottom, and the flue gases leave at the bottom.
17. A method for the production of hydrogen which comprises reacting a vaporized hydrocarbon with steam in a vertical tube containing steam reforming catalyst, said tube having two sections, one section of said tube has a substantially bare outer wall and receives heat largely by radiation from a radiant section of the furnace, and the other section of tube has extended surface and receives heat largely by convection from flue gases leaving the radiant section of the furnace.
18. A method according to Claim 17 wherein the furnace has a top and a bottom portion in which an inlet to the catalyst tube is at the top, an outlet from the catalyst tube is at the bottom, and the flue gases leave from the top.
19. A method according to Claim 17 wherein the furnace has a top and a bottom portion in which an inlet to the catalyst tube is at the bottom, an outlet from the catalyst tube is at the top, and the flue gases leave at the bottom.
20. A method according to Claim 17 wherein the furnace has a top and a bottom portion in which an inlet to the catalyst tube is at the top, an outlet from the catalyst tube is at the bottom, and the flue gases leave at the bottom.
21. A method for the production of hydrogen which comprises (a) reacting a vaporized hydrocarbon with steam in a steam reforming furnace for a hydrogen or ammonia plant, said furnace containing a plurality of steam reforming catalyst-containing single pass vertical tubes each having two sections, the portion of each of said tubes within said furnace being filled with steam reforming catalyst, wherein the step of reacting comprises (1) introducing and heating the hydrocarbon and steam largely by convection in a first section of said tubes filled with steam reforming catalyst, the first section having an extended surface integral with or attached to an outer surface of said tubes, and (2) heating the hydrocarbon and steam in a second steam reforming catalyst filled section of said tubes largely by radiation from a radiant section of the furnace, the second section of said tubes having substantially bare outer walls thereby causing the hydrocarbon and steam to flow through the tubes in a direction countercurrent to the flow of flue gas throuugh the furnace, and (b) enhancing velocity of flue gas along the first section of said tubes by providing a substantially narrowed furnace width.
22. A method according to Claim 21 wherein the extended surface comprises a plurality of studs attached to an outer surface of the tubes and extending radially outwardly therefrom.
23. A method according to Claim 22 wherein the extended surface comprises a plurality of fins longitudinally attached along an outer surface of said tubes and extending radially outward therefrom.
24. A method according to Claim 21 wherein the furnace has a top and a bottom portion in which an inlet to the steam reforming catalyst-containing tubes is at the top, an outlet from the steam reforming catalyst-containing tubes is at the bottom, and the flue gas leaves from the top.
25. A method according to Claim 21 wherein the furnace has a top and a bottom portion in which an inlet to the steam reforming catalyst-containing tubes is at the bottom, an outlet from the steam reforming catalyst-containing tubes is at the top, and the flue gas leaves from the bottom.
26. A method according to any one of Claims 20-25 wherein the width of the furnace is in the tube convection portion is substantially narrower than the width of the radiant section.
27. A reforming furnace for producing hydrogen, comprising:
a radiant section containing burners;
a tube convection section connected to and aligned vertically with respect to said radiant section such that hot flue gas from the radiant section exhausts through said tube convection section;
a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes extending from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tube portion, said first tube portion being the portion of the reaction tube positioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube portion and the second tube portion contain reforming catalyst, the first tube portion including extended surface means integral with or attached to an outer surface thereof for enhancing convection heat transfer within the tube convection section; and means for separating said radiant section from said tube convection section whereby during furnace operation, heat transfer in the tube convection section is predominantly convective and heat transfer in the radiant section is predominantly radiant, said separating means including parallel furnace side walls in the tube convection section having a width between the side walls substantially narrower than the width between side walls of the furnace in the radiant section.
a radiant section containing burners;
a tube convection section connected to and aligned vertically with respect to said radiant section such that hot flue gas from the radiant section exhausts through said tube convection section;
a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes extending from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tube portion, said first tube portion being the portion of the reaction tube positioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube portion and the second tube portion contain reforming catalyst, the first tube portion including extended surface means integral with or attached to an outer surface thereof for enhancing convection heat transfer within the tube convection section; and means for separating said radiant section from said tube convection section whereby during furnace operation, heat transfer in the tube convection section is predominantly convective and heat transfer in the radiant section is predominantly radiant, said separating means including parallel furnace side walls in the tube convection section having a width between the side walls substantially narrower than the width between side walls of the furnace in the radiant section.
28. A reforming furnace as in Claim 27 wherein the furnace has a top and a bottom portion and wherein said reaction tubes are oriented substantially vertically, said radiant section being at the bottom portion of the furnace and said tube convection section being at the top portion of the furnace.
29. A reforming furnace as in Claim 27 wherein the extended surface of the first tube portion is comprised of a plurality of studs attached to the outer surface of said first tube portion and extending radially outward therefrom.
30. A reforming furnace as in Claim 29 wherein each of the studs has a diameter of between about 3/8 inch (1 cm) and a length of about 3/4 inch (2 cm).
31. A reforming furnace as in Claim 29 wherein the plurality of studs are arranged in planes along the length of the tube convection portion with about 30 studs per plane, the planes spaced at about 1/2 inch (1.3 cm) apart, and the studs having a diameter of about 3/8 inch (1 cm) and a length of about 3/4 inch (2 cm).
32. A reforming furnace as in Claim 27 wherein the extended surface of the first tube portion is comprised of a plurality of fins attached to the outer surface of said first tube portion and extending radially outward therefrom.
33. A reforming furnace as in any one of Claims 27-32 further comprising baffles in said tube convection section.
34. A reforming furnace as in any one of Claims 27-32 wherein the length of the first tube portion is between 10% and 40% of the total length of the first and second tube portions of the tube.
35. A reforming furnace as in any one of Claims 27-32 wherein the length of the first tube portion is between 15% and 30% of the total length of the first and second tube portions of the tube.
36. A reforming furnace as in any one of Claims 27-32 wherein the width between the furnace side walls of the tube convection section being sufficiently narrower than the width between side walls of the radiant section to inhibit radiant heat from the radiant section from impinging on the first tube portion in the tube convection section and wherein the side walls of said tube convection section and said radiant section being constructed and arranged with a generally right angle transition therebetween to inhibit radiant heat from said radiant section from impinging on the first tube portion in said tube convection section.
37. A reforming furnace as in any one of Claims 27-32 wherein said separating means further comprises the side walls of said tube convection section and said radiant section being constructed and arranged with a generally right angle transition therebetween to inhibit radiant heat from said radiant section from impinging on the first tube portion in said tube convection section.
38. A reforming furnace for producing hydrogen, comprising:
a lower radiant section containing burners positioned along furnace side walls;
an upper tube convection section connected to and aligned vertically above said radiant section, said tube convection section constructed and arranged such that hot flue gas from said radiant section exhausts through said tube convection section;
a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes extending from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tube portion, said first tube portion being the portion of the reaction tube positioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube portion and the second tube portion contain reforming catalyst;
means for enhancing convection heat transfer within the tube convection section comprising radially outwardly extending heat transfer elements integral with or attached to an outer surface of said first tube portion;
means for isolating the tube convection section from radiant heat produced in the radiant section and means for providing enhanced velocity to the flue gas in said tube convection section, comprising parallel vertical furnace side walls in the tube convection section with a distance between the parallel side walls in the tube convection section being less than that between the furnace side walls in the radiant section.
a lower radiant section containing burners positioned along furnace side walls;
an upper tube convection section connected to and aligned vertically above said radiant section, said tube convection section constructed and arranged such that hot flue gas from said radiant section exhausts through said tube convection section;
a plurality of reaction tubes vertically disposed within said furnace, each of said reaction tubes extending from the radiant section through the tube convection section, each of said reaction tubes having a first and a second tube portion, said first tube portion being the portion of the reaction tube positioned in the tube convection section and said second tube portion being the portion of the reaction tube positioned within the radiant section, wherein both the first tube portion and the second tube portion contain reforming catalyst;
means for enhancing convection heat transfer within the tube convection section comprising radially outwardly extending heat transfer elements integral with or attached to an outer surface of said first tube portion;
means for isolating the tube convection section from radiant heat produced in the radiant section and means for providing enhanced velocity to the flue gas in said tube convection section, comprising parallel vertical furnace side walls in the tube convection section with a distance between the parallel side walls in the tube convection section being less than that between the furnace side walls in the radiant section.
39. A reforming furnace as in Claim 38 wherein said means for isolating further comprises the side walls of said tube convection section and said radiant section being constructed and arranged with a generally right angle transition between said radiant section and said tube convection section.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11272787A | 1987-10-23 | 1987-10-23 | |
| US112,727 | 1987-10-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1336353C true CA1336353C (en) | 1995-07-25 |
Family
ID=22345548
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000580887A Expired - Fee Related CA1336353C (en) | 1987-10-23 | 1988-10-21 | Reformer with low fired duty |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU604568B2 (en) |
| CA (1) | CA1336353C (en) |
| WO (1) | WO1989004031A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5070329A (en) * | 1989-12-04 | 1991-12-03 | Motorola, Inc. | On-site communication system with rf shielding having pager identification capability |
| US5363425A (en) * | 1992-06-29 | 1994-11-08 | Northern Telecom Limited | Method and apparatus for providing a personal locator, access control and asset tracking service using an in-building telephone network |
| US8466795B2 (en) | 1997-01-21 | 2013-06-18 | Pragmatus Mobile LLC | Personal security and tracking system |
| FR2812433A1 (en) * | 2000-07-28 | 2002-02-01 | Turquoise Com Internat Lda | METHOD AND DEVICE FOR THE CONTINUOUS PROTECTION AGAINST INTRUSIONS IN POTENTIALLY INHABITED PREMISES |
| US7134595B2 (en) * | 2003-05-30 | 2006-11-14 | Sensormatic Electronics Corporation | People counting system for facility-wide reporting |
| CN110363900B (en) * | 2019-08-16 | 2024-07-02 | 上海工程技术大学 | Gate for rail transit and control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1767598B2 (en) * | 1968-05-28 | 1970-07-02 | Alcorn Combustion Company, New York, N.Y. (V.St.A.) | Tube furnace |
| JPS55154303A (en) * | 1979-05-18 | 1980-12-01 | Toyo Eng Corp | Method and apparatus for steam-reforming hydrocarbon |
| ATE10602T1 (en) * | 1980-09-10 | 1984-12-15 | Varn Products Company Limited | DAMPENING. |
| US4590460A (en) * | 1984-10-03 | 1986-05-20 | Abbott Ralph E | Stairwell security system |
| US4660024A (en) * | 1985-12-16 | 1987-04-21 | Detection Systems Inc. | Dual technology intruder detection system |
| US4682155A (en) * | 1986-01-13 | 1987-07-21 | Central Security Mfg. Corp. | Personnel security system |
| US4684933A (en) * | 1986-05-15 | 1987-08-04 | Rita Ann Gray | Unauthorized personnel detection system |
-
1988
- 1988-10-11 AU AU23631/88A patent/AU604568B2/en not_active Ceased
- 1988-10-21 WO PCT/US1988/003721 patent/WO1989004031A1/en unknown
- 1988-10-21 CA CA000580887A patent/CA1336353C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| WO1989004031A1 (en) | 1989-05-05 |
| AU604568B2 (en) | 1990-12-20 |
| AU2363188A (en) | 1989-04-27 |
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