Chemistry of inorganic compounds – Hydrogen or compound thereof – Elemental hydrogen
Reexamination Certificate
1999-04-15
2001-05-22
Langel, Wayne (Department: 1754)
Chemistry of inorganic compounds
Hydrogen or compound thereof
Elemental hydrogen
C252S373000, C423S652000
Reexamination Certificate
active
06235262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the production of hydrogen rich gas by autothermal steam reforming of a hydrocarbon process gas, wherein the hydrogen rich gas being withdrawn from the autothermal steam reforming process at elevated pressure is depressurized in a gas turbine for generation of valuable power.
2. Description of the Related Art
Autothermal steam reforming is a well-known process for the preparation of hydrogen rich synthesis gas. The process is conventionally performed in a combustion reactor with a top combustion zone, and a bottom catalyst zone. In the combustion zone, hydrocarbon feedstock is partially oxidized with an oxygen-containing atmosphere. Partially oxidized effluent from the combustion zone is subsequently subjected to steam reforming in the presence of a steam reforming catalyst arranged in fixed bed manner in the bottom part of the reactor. Typical operation conditions in the above process are 850° C. and 2-4 MPa at steam to carbon ratios above 1, depending on the desired product gas.
A problem with autothermal steam reforming is formation of soot in the substoichiometric combustion of hydrocarbons. In particular, at low steam/carbon ratios in the feed gas to the autothermal reformer, soot is formed markedly in the combustion zone.
In a number of industrial applications, a low steam to carbon ratio is required in the feed gas. Thus, in the manufacture of synthesis gas, steam to carbon ratios below 1 are advantageous to obtain the optimum hydrogen to carbon monoxide ratio in the product gas.
Several attempts to reduce soot formation at low steam to carbon ratios in autothermal reforming have been made in the past, including specific burner designs and control of operation conditions.
In co-pending European Patent Application No. 99102386, a process for soot free autothermal catalytic steam reforming is described, wherein formation of soot is avoided by controlling the operation pressure within a certain range depending on the adiabatic gas temperature of the reformed feed stock and the steam to carbon ratio. It was, furthermore, found that operation pressures above 3.5 MPa allow soot free reforming at a very low steam to carbon ratio.
The disadvantages of operating at high operation pressure in the autothermal steam reforming process are the expense involved in compressing the feed gas and the pressure of produced synthesis gas, which, for applications in subsequent process units, will be typically required at a lower pressure.
SUMMARY OF THE INVENTION
It has now been found that substantial amounts of energy used in the compression of feed gas to an autothermal reformer operating without formation of soot at low steam/carbon ratios are regained when the synthesis gas being withdrawn from the reformer at high pressure is depressurized in a turbine, as the autothermal reformer combined with the turbine constitute a gas turbine generating power.
Accordingly, the present invention provides a process for the production of hydrogen rich gas by soot free autothermal steam reforming of a hydrocarbon process gas, wherein the hydrogen rich gas being withdrawn from the autothermal steam reforming process at an elevated pressure is depressurized in a gas turbine for generation of valuable power.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.
REFERENCES:
patent: 4725381 (1988-02-01), Pinto
patent: 4822521 (1989-04-01), Fuderer
patent: 5740667 (1998-04-01), Bhattacharyya et al.
patent: 6025403 (2000-02-01), Marler et al.
John H. Perry'sChemical Engineers' Handbook, Fourth Edition (1963), McGraw-Hill Book Co., pp. 24-74 through 24-76; (No Month).
Haldor Topsoe A/S
Langel Wayne
Ostrolenk Faber Gerb & Soffen, LLP
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