Title of Invention

A PROCESS FOR THE PREPARATION OF HYDROGEN AND CARBON MONOXISE RICH SYNTHESIS GAS

Abstract The present invention relates to a process for the preparation of hydrogen and carbon monoxide rich synthesis gas by steam reforming of a hydrocarbon feedstocl( in presence of a steam reforming catalyst supported as thin film on a tubular reactor, comprising steps of (a) passing a process gas of prereformed hydrocarbon through a tubular reactor (14) being provided with a thin film of steam reforming catalyst and being heated by burning of fuel, thereby obtaining a partially steam reformed gas t effluent and a hot flue gas; (b) passing the effluent from the tubular reactor (14) to a fixed bed steam reforming catalyst; and (c) withdrawing from the fixed bed a product gas of the hydrogen and carbon monoxide rich synthesis gas.
Full Text The present invention is directed to a process for the preparation of hydrogen and carbon monoxide rich synthesis gas by steam reforming of a hydrocarbon feedstock in contact with catalyzed hardware.
The term catalyzed hardware is used for a catalyst system where a layer of catalyst is fixed on a surface of another material, e.g. metallic surfaces. The other material serves as the supporting structure giving strength to the system. This allows to design catalyst shapes which would not have sufficient mechanical strength in itself. The system herein consists of tubes on which a thin layer of reforming catalyst is placed on the inner wall.
Synthesis gas is produced from hydrocarbons by steam reforming by the reactions (l)-(3) :

State of the art steam reforming technology makes use of reforming catalyst in the form of pellets of various sizes and shapes. The catalyst pellets are placed in fixed bed reactors (reformer tubes). The reforming reaction is endothermic. In conventional reformers, the necessary heat for the reaction is supplied from the environment outside the tubes usually by a combination of radiation and convec¬tion to the outer side of the reformer tube. The heat is transferred to the inner side of the tube by heat conduc¬tion through the tube wall, and is transferred to the gas phase by convection. Finally, the heat is transferred from the gas phase to the catalyst pellet by convection. The catalyst temperature can be more than 100°C lower than the inner tube wall temperature at the same axial position of the reformer tube.

EP Patent No. 0124226 discloses a steam reforming process whereby hydrocarbons are steam reformed in a bayonet tube steam reformer with heat supplied by indirect heat exchange with a hot gas flowing on the outer tube shell side, and hot product gas being withdrawn from the tube side of the inner tube of the bayonet tube steam reformer. Steam reforming catalyst is in this process supported on tube side of the inner tube of the bayonet.
EP Patent No. 0440258 discloses a steam reforming process in which heat from a product stream of reformed gas is utilized to supply heat required for the endothermic reforming reactions in a process gas of hydrocarbons and steam by indirect heat exchange between the product gas and process gas.
EP Patent No. 0437059 discloses a steam forming a hydrocarbon in heated auxiliary tubes followed by steam reforming in furnace reformer tubes heated by combustion of a fuel, and passing the reformed product gas stream past the exterior of the auxiliary tubes, thereby supplying heat to the auxiliary tubes and cooling the reformed product gas stream.
The above mentioned disclosures do not mention a steam reforming process utilising a tubular reactor provided with a thin film of steam reforming catalyst and being heated by burning of fuel, followed by passing the effluent from the tubular reactor to a fixed bed of steam reforming catalyst.

It has been found that heat transport is more efficient when catalyzed hardware is used in the steam reforming process. The heat transport to the catalyst occurs by conduction from the inner tube wall. This is a much more efficient transport mechanism than the transport by convection via the gas phase. The result is that the temperatures of the inner tube wall and the catalyst are almost identical (the difference below 5°C). Furthermore, the tube thickness can be reduced, see below, which makes the temperature difference between the inner and outer side of the reformer tube smaller. It is hence possible to have both a higher catalyst temperature and a lower tube temperature, all other conditions being the same when replacing the conventional reformer tubes with catalyzed hardware tubes. A low outer tuber wall temperature is desirable since it prolongs the lifetime of the tube. A high catalyst temperature is advantageous since the reaction rate increases with temperature and since the equilibrium of reaction (3) is shifted to the right hand side resulting in a better utilisation of the feed.
Accordingly, the present invention provides a process for the preparation of hydrogen and carbon monoxide rich synthesis gas by steam reforming of a hydrocarbon feedstock in presence of a steam reforming catalyst supported as thin film on a tubular reactor, characterized in that (a) passing a process gas of prereformed hydrocarbon through a tubular reactor being provided with a thin film of steam reforming catalyst and being heated by burning of fuel, to produce a partially steam reformed gas effluent and a hot flue gas; (b) passing the effluent from the tubular reactor to a fixed bed steam reforming catalyst; and (c) withdrawing from the fixed bed a product gas of the hydrogen and carbon monoxide rich synthesis gas.

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Pressure drop in the catalyzed reformer tube is much lower than in the conventional case for the same tube diameter. This enables the use of reactor tubes with a smaller diameter and still maintaining an acceptable pres¬sure drop. Smaller tube diameter results in an increased tube lifetime, tolerates higher temperatures and reduces the tube material consumption.
Finally, the catalyst amount is reduced -when using catalyzed hardware reformer tubes compared to the conven¬tional reformer with a fixed bed of reforming catalyst.
Fig. 1 shows the front-end of a plant producing syngas. Feed 2 is preheated, desulphurized in unit 4, mixed with process steam 6, and further heated before entering an adiabatic prereformer 8. The effluent stream from prere-former 8 is further heated in loop arranged in flue gas channel 12 and send to the tubular-reformer 14, where conversion of methane to hydrogen, carbon monoxide, and carbon dioxide occurs. The processing of effluent gas downstream from the tubular reformer depends on the use of the product.
Catalyzed hardware can be used in two of the units shown in Fig. 1:
1. In the preheater coil 10 for heating the prerefor¬mer effluent gas before entering the tubular reformer 14.

2. In the tubular reformer 14.
Below is presented the results obtained for the plant in Fig. 1 when catalyzed hardware is used in the above two units. The catalyst used for the catalyzed hard¬ware is the R-67R nickel steam reforming catalyst available from Haldor Topsoe A/S. The results are compared with the conventional case.
The purpose of the preheater coil is to use the heat content in the flue gas for preheating of the process gas before it enters the tubular reformer. The flue gas is used for preheating of process gas and for preheating of the combustion air for the tubular reformer (not shown in Fig. 1). However, the heat content of the flue gas is larger than what can be used for these purposes and the remaining heat is used for steam production. It will be an advantage, if a larger amount of the heat content in the flue gas can be transferred to the process gas. This will reduce the necessary amount of fuel in the tubular reformer, and it will reduce the size of the reformer since a smaller amount of heat is to be transferred in the unit.
The conventional preheater is limited by the risk of carbon formation by decomposition of methane. This sets an upper limit for the tube wall temperature, which can be accepted. Fixing a layer of catalyzed hardware on the inner tube wall 6 of the preheater coil 10 (as shown in Fig. 2) results in a decrease of both the tube wall temperature and the process gas temperature. This enables the transfer of a higher duty in the coil without having a higher tube tem¬perature .
The preheater coil used in the calculation consists of 8 tubes in which the process gas flow inside the tubes. The flue gas flows on the outer side. The flow pattern is cross flow/co-current. Fig. 2 shows the layout for one tube. The two cases with and without catalyzed hardware are summarised in Table 1. It is apparent that the transferred

duty (heat energy) is 49% higher in the catalyzed hardware case compared to the conventional case. The catalyst layer thickness in the catalyst hardware case is 1.0 mm.

The effective tube length is the length of the tube inside the flue gas channel.
The conventional tubular reformer consists of a number of tubes which is filled with catalyst pellets. The process gas flows inside the tubes. The tubes are placed in a furnace which is heated by combustion of a fuel.
In the catalyzed hardware case the catalyst pellet filled tubes are replaced with a number of tubes with a layer of catalyzed hardware on the inner tube wall. The catalyst layer thickness is 0.25 mm. An additional adiabatic reforming fixed bed reactor is placed downstream

from the tubular reactor since the conversion of methane in the catalyzed hardware tubular reformer is inferior to the conventional case. This reactor is called post reformer. The catalyst used in the post reformer is the RKS-2 nickel steam reforming catalyst available from Haldor Topsoe A/S.
The two cases are summarised below in Table 2. It is seen that catalyst consumption is decreased by a factor 11.5, and that material consumption for the tubes in the tubular reformer is decreased 24% in the catalyzed hardware case compared to the conventional case.

A flow scheme of a process according to the inven¬tion is shown in Fig. 3. The numbers in the triangles refer to the table below in which the overall figures for the process are compared. The fuel consumption is decreased by 7.4% in the catalyzed hardware case compared to the conven¬tional case.





WE CLAIM;
1. A process for the preparation of hydrogen and carbon monoxide rich synthesis gas by steam reforming of a hydrocarbon feedstock in presence of a steam reforming catalyst supported as thin film on a tubular reactor, characterized in that (a) passing a process gas of prereformed hydrocarbon through a tubular reactor (14) being provided with a thin film of steam reforming catalyst and being heated by burning of fuel, to produce a partially steam reformed gas effluent and a hot flue gas; (b) passing the effluent from the tubular reactor (14) to a fixed bed steam reforming catalyst; and (c) withdrawing from the fixed bed a product gas of the hydrogen and carbon monoxide rich synthesis gas.
2. The process as claimed in claim 1 wherein said process gas of prereformed hydrocarbon is first passed through a tubular reactor (14) with a thin film of steam reforming catalyst supported on wall of the reactor in heat conducting relationship with hot flue gas from the subsequent process step (a).
3. The process as claimed in claim 1, wherein the fixed bed steam reforming catalyst is operated at adiabatic condition.
4. The process as claimed in claim 1, wherein the steam reforming catalyst is selected from nickel, ruthenium and a mixture of the two.

5. A process for the preparation of hydrogen and carbon monoxide rich synthesis gas substantially as herein described with reference to the accompanying drawings.

Documents:

117-mas-1998 abstract duplicate.pdf

117-mas-1998 abstract.pdf

117-mas-1998 claims duplicate.pdf

117-mas-1998 claims.pdf

117-mas-1998 correspondence others.pdf

117-mas-1998 correspondence po.pdf

117-mas-1998 description (complete) duplicate.pdf

117-mas-1998 description (complete).pdf

117-mas-1998 drawings.pdf

117-mas-1998 form-19.pdf

117-mas-1998 form-2.pdf

117-mas-1998 form-26.pdf

117-mas-1998 form-4.pdf

117-mas-1998 form-6.pdf

117-mas-1998 petition.pdf


Patent Number 201017
Indian Patent Application Number 117/MAS/1998
PG Journal Number 8/2007
Publication Date 23-Feb-2007
Grant Date 19-Jun-2006
Date of Filing 19-Jan-1998
Name of Patentee M/S. HALDOR TOPSOE
Applicant Address NYMOLLEVEJ 55, DK-2800 LYNGBY
Inventors:
# Inventor's Name Inventor's Address
1 JENS ROSTRUP-NIELSEN FURESOVEJ 27, DK-2830 VIRUM
2 PETER SEIER CHRISTENSEN GLASVEJ 7, 1. TV., DK-2400 COPENHAGEN NV BRONSHOJ
PCT International Classification Number C01B 03/38
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/035,396 1997-01-22 U.S.A.