Chemistry: fischer-tropsch processes; or purification or recover – Treatment of feed or recycle stream
Reexamination Certificate
1999-09-03
2001-01-30
Richter, Johann (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Treatment of feed or recycle stream
C518S703000, C518S704000, C518S700000, C060S670000, C060S039350
Reexamination Certificate
active
06180684
ABSTRACT:
The present invention relates to a processing and converting a hydrocarbonous gas, particularly natural gas in an integrated plant for the preparation of useful products, including chemical reaction products and mechanical or electrical power, as well as an integrated process plant for the accomplishment of such a process.
By the term <<hydrocarbonous gas>> in the present context and the appending claims is understood hydrocarbon compositions consisting of hydrocarbon components substantially existing in a gaseous form at standard pressure and temperature conditions.
Natural gas is an important part of numerous petrochemical reservoirs and can find utilization as starting materials for further refined products in the form of pure hydrocarbons and in the form of oxidized derivatives thereof. Further, natural gas can be used for the production of power such as electrical power or mechanical power.
In many instances the natural gas reservoirs are situated at remote sites from the established natural gas markets where the utilization thereof, as mentioned above, takes place. This is e.g. the case in Europe, where the petrochemical sources are situated at the sea bottom far away from the European continent.
As a consequence thereof it will not be economical to transport the gas through pipelines to the users, the pipeline systems being long and expensive to install and later also to maintain.
For this reason the options of converting natural gas to other transportable and useful products will be considered, such as e.g. synfuel (synthetically prepared engine fuels in liquid form) and electrical power. Depending on whether the further handling of the gas takes place at an offshore production platform or at the site of entering the ground, it is—provided that the further useful products are to be prepared at one and the same geographical site—economical to evaluate the integration benefits which may be achieved by a suitable connection of the various kinds of plants for the abovementioned purposes.
Natural gas substantially consists of methane admixed with other gaseous hydrocarbons, CO
2
and gaseous sulphur compounds such as H
2
S and lower mercaptanes.
When the methane is preheated to a temperature of the order 800° C. and then is supplied with oxygen in a reforming step, oxygenated products of the methane are formed primarily in the form of CO and H
2
. This gas composition is called <<synthesis gas>>. Such a synthesis gas may alternatively be prepared by reacting the hydrocarbonous material with aqueous vapour under pressure and at high temperatures according to the scheme:
CH
4
+H
2
O→CO+3H
2
.
When the synthesis gas is formed by partial oxidation, energy is released in the form of heat. This heat may be recovered from this step and optionally transferred to mechanical or electrical power.
The synthesis gas may then be reacted in a further step to methanol and dimethyl ether or in a Fischer-Tropsch synthesis to straight alkanes and/or alkenes of a higher molecular weight than the prevailing hydrocarbons of the natural gas.
The products of the reaction step of carbon monoxide and hydrogen gas is the product called <<synfuel>>(synthetic fuel) and being the intended product of the process. The chemical composition of the product will depend on the preparation method and the operation conditions. The term synfuel thus covers products such as methanol, dimethyl ether, mixtures of methanol and dimethyl ether, other oxygenates, Fischer-Tropsch hydrocarbons and further processed products thereof, among others lubricants which may be prepared from the heavier Fischer-Tropsch hydrocarbonous fractions.
Furthermore, non-reacted gas and side products may be recovered as a separate stream and may be recycled to the reforming step or used as fuel for the production of power.
The conversion of synthesis gas is e.g. disclosed in G. A. Mills, <<Status and opportunities for conversion of synthesis gas to liquid fuels>>, Fuel, vol. 73(8) pp 1243-1279, (1994).
The Norwegian publication 179 169 discloses a process of converting natural gas to a normally liquid, carbonous compound such as methanol and/or dimethyl ether and/or liquid hydrocarbons of gasoline quality and/or olefins. The process avoids requirement of vapor reforming and/or adiabatic reforming of natural gas to synthesis gas using a substantially pure oxygen. The synthesis gas may be prepared at an operative pressure which is useful for converting the gas to methanol and/or dimethyl ether without recompression of the synthesis gas. The exhaust gas from the overhead has, subsequent to the conversion of the crude product methanol/DME and/or conversion to liquid hydro-carbons of gasoline quality, generally a BTU-capacity which is required for the use as fuel gas for the power supply being required for the operation of the required gas compression facilities used in the process. This renders the operation of the plant more economical and a process useful at remote sites. Particularly claim
4
of the publication for opposition states that air is introduced in the compressor unit of the gas turbine, the residual gas balance from the synfuel production including unreacted H
2
, CO and methane, being introduced through the fuel entrance of the <<expander-driver>> unit of the gas turbine as a fuel for this part of the air from the outlet of compressed air from the gas turbine being lead to the entrance of a gas compressor driven by the gas turbine for compressing natural gas being introduced through the entrance to a gas compressor operated by a gas turbine and compressed to an enhanced end-pressure, the end-compressed air being heated to a higher temperature, the compressed natural gas being heated to a high temperature, the compressed gases being used in an adiabatic reaction yielding a reformed gas stream having a temperature of 982-1371° C.
U.S. Pat. No. 5,177,114 claims the same priority as the Norwegian publication No. 179169 and does not appear to differ be substantially therefrom.
U.S. Pat. No. 4,927,856 combines the production of electrical power, hydrogen gas production and methanol in an integrated system and discloses a corresponding process. The electricity is formed in turbines run by heated gas from a pressurized fuel source, and the electricity is then used in an electrolysis unit converting water, optionally condensed from the source gas, to hydrogen gas which is subsequently reacted with hydrocarbon oxides of the source gas under the formation of methanol.
U.S. Pat. No. 5,245,110 discloses the preparation of an oxygen enriched gas composition in an apparatus comprising a gas turbine, an oxidation separation plant in a fluid connection with the turbine air compressor and means for maintaining an appropriate mass balance-tolerance between the turbine compressor unit and the turbine power production unit.
In U.S. Pat. No. 5,284,878 methanol is produced by reacting a CO-rich synthesis gas in the presence of a powder methanol synthesis catalyst suspended in an inert aqueous phase reactor system. Unreacted CO-rich synthesis gas is recycled to the reactor. Preferably the process is integrated with a carbon gasification system for the production of electrical power in which one part of the unreacted synthesis gas is used as a fuel, and part of the methanol product is used as further fuel in periods of an increased demand.
U.S. Pat. No. 4,296,350 discloses the production of mechanical and electrical power combined with synthesis or fuel gas in a partial oxidation process by integration combustion and steam turbines. The side product evaporated prior to condensed natural gas is brought through pipelines to the gas consumers. The conversion of the synthesis gas to synfuel is not disclosed.
U.S. Pat. No. 4,359,871 discloses a process and an apparatus for the cooling of natural gas.
When gas recovered from petrochemical reservoirs at the sea bottom in arctic wafers is brought ashore to a land based plant, in arctic regions, problems arise and conditions which are
Halmo Terje M.
Hansen Roger
Martinsen Alf S.
Schanke Dag
Den Norske Stats Oljeselskap A.S.
Fish & Richardson P.C.
Parsa J.
Richter Johann
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