Chemistry: fischer-tropsch processes; or purification or recover – Liquid phase fischer-tropsch reaction
Reexamination Certificate
2002-01-30
2004-01-06
Parsa, J. (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Liquid phase fischer-tropsch reaction
C518S702000, C518S712000, C060S039010, C060S039010
Reexamination Certificate
active
06673845
ABSTRACT:
THIS INVENTION relates to the production of hydrocarbon products. It relates in particular to an integrated process for producing hydrocarbon products and energy.
According to a first aspect of the invention, there is provided an integrated process for producing hydrocarbon products and energy, which process includes
reforming a hydrocarbonaceous gaseous feedstock to synthesis gas;
exothermally reacting the synthesis gas at elevated temperature and pressure, and in the presence of a Fischer-Tropsch catalyst, to produce a range of hydrocarbon products of differing carbon chain lengths:
controlling the reaction temperature by indirect heat exchange of a reaction medium, comprising synthesis gas and hydrocarbon products, with water, with the water being converted to steam (‘FT steam’);
burning a combustible gas in a combustion chamber of a gas turbine generator, to form combusted gas, and expanding the combusted gas through an expansion chamber of the gas turbine generator to form hot flue gas, while generating electrical energy by means of the gas turbine generator; and
superheating at least some of the FT steam by means of at least some of the hot flue gas, thereby producing superheated FT steam.
The FT steam may be at a medium pressure between about 800 kPa(a) and about 3000 kPa(a)
The reforming of the hydrocarbonaceous gaseous feedstock to synthesis gas may be effected in a synthesis gas production stage. The synthesis gas comprises at least CO, H
2
and CO
2
, and is at an elevated temperature.
The process may then include, prior to reacting the synthesis gas, cooling the synthesis gas by indirect heat exchange with water, with the water being converted to steam (‘Syngas steam’).
The process may also include feeding the cooled synthesis gas, as a feedstock, to a hydrocarbon synthesis stage in which the exothermal Fischer-Tropsch reaction of the synthesis gas is effected. A vapour phase comprising light hydrocarbon products and unreacted synthesis gas, a liquid phase comprising heavier liquid hydrocarbon product, and an aqueous phase comprising water and any soluble organic compounds formed during the reaction of the synthesis gas, may be produced in the hydrocarbon synthesis stage. The vapour phase, the liquid phase and the aqueous phase may then be withdrawn from the hydrocarbon synthesis stage.
The gas turbine generator constitutes, or forms part of, an electricity generation stage. The hot flue gas is thus withdrawn from the electricity generation stage.
The superheating of the FT steam may thus be effected in a heat exchange stage. If desired, high pressure steam (‘HP steam’) having a pressure between 3000 kPa(a) and 12000 kPa(a) may also be generated in the heat exchange stage by means of hot flue gas. The HP steam may, if desired, be superheated. When HP steam is generated, a portion thereof may, if desired, be used a process steam in the hydrocarbon synthesis stage.
The process may include feeding at least some of the superheated FT steam into an energy generation stage, which may comprise a steam turbine. The superheated FT steam is then directed into the steam turbine which thereby generates electrical and/or mechanical energy.
Thus, according to a second aspect of the invention, there is provided an integrated process for producing hydrocarbon products and energy, which process Includes
in a synthesis gas production stage, reforming a hydrocarbonaceous gaseous feedstock to synthesis gas comprising at least CO, H
2
and CO
2
, with the synthesis gas being at elevated temperature, and cooling the synthesis gas by indirect heat exchange with water, with the water being converted to steam (‘Syngas steam’):
feeding tho cooled synthesis gas, as a feedstock, to a hydrocarbon synthesis stage;
in the hydrocarbon synthesis stage, exothermally reacting the synthesis gas at elevated temperature and pressure, and in the presence of a Fischer-Tropsch catalyst, to produce a range of hydrocarbon products of differing carbon chain length; controlling the reaction temperature by indirect heat exchange of a reaction medium comprising the synthesis gas feedstock and the hydrocarbon products with waters with the water being converted to steam (‘FT steam’); and producing a vapour phase comprising light hydrocarbon products and unreacted synthesis gas, a liquid phase comprising heavier liquid hydrocarbon products, and an aqueous phase comprising water and any soluble organic compounds formed during the reaction of the synthesis gas;
withdrawing the vapour phase, the liquid phase and the aqueous phase from the hydrocarbon synthesis stage;
in an electricity generation stage comprising a gas turbine generator, burning a combustible gas in a combustion zone or chamber of the gas turbine generator, to form combusted gas, and expanding the combusted gas through an expansion chamber of the gas turbine generator to obtain hot flue gas, with electrical energy being generated by the gas turbine generator;
withdrawing the hot flue gas from the electricity generation stage;
in a heat exchange stage, using the hot flue gas to superheat at least some of the FT steam and/or to generate high pressure steam (‘HP steam’) having a pressure between 3000 kPa(a) and 12000 kPa(a) and, optionally, superheating the HP stream;
feeding at least some of the superheated steam into an energy generation stage comprising, for example, a steam turbine;
when the HP steam is generated, optionally using a portion thereof as process steam in the hydrocarbon synthesis stage;
in the energy generation stage, generating electrical and/or mechanical energy by meant of the steam turbine into which the superheated steam is directed.
The reforming of the hydrocarbonaceous gas, ie of the hydrocarbonaceous gaseous feedstock, to synthesis gas is thus effected by reacting the hydrocarbonaceous gas with steam and/or oxygen at high temperature, ie high temperature reforming is employed. Typically, the conversion may be effected by means of steam reforming, which does not require the use of oxygen, autothermal reforming, in which the hydrocarbonaceous material reacts with oxygen in a first reaction section, whereafter an endothermic steam reforming reaction takes place adiabatically in a second reaction section; ceramic oxygen transfer membrane reforming, in which oxygen required for the reforming reaction is transported through an oxygen permeable membrane into a reaction zone; plasma reforming in which the reforming reaction is driven by an electrically generated plasma; non-catalytic partial oxidation; or catalytic partial oxidation. If desired, two or more of these conversion mechanisms or technologies may be combined, eg to optimize thermal efficiency, or to obtain an optimized or beneficial synthesis gas composition. A lower temperature prereforming step may be employed before the high temperature reforming takes place, and is particularly useful for preventing carbon formation by thermal decomposition when higher carbon number hydrocarbons are present in the feedstock.
The hydrocarbonaceous gaseous feedstock may, in particular, be natural gas, or a gas found in association with crude oil, and which comprises mainly CH
4
and other hydrocarbons. An initial cooling step may be used to knock out condensable hydrocarbons prior to the gas being subjected to the reforming. The synthesis gas will then contain, in addition to CO, H
2
and CO
2
, also some unreacted CH
4
and inert gases.
The oxygen may be obtained from a cryogenic air separation plant in which air is compressed and separated cryogenically into oxygen and is nitrogen. At least a portion of the electrical energy and/or the mechanical energy produced in the electricity generation stage and/or in the energy generation stage, may be used as a power source for said cryogenic air separation plant.
The process may include preheating the hydrocarbonaceous gaseous feedstock prior to feeding it into the reformer. Typically, it may be preheated then in excess of 400° C. The preheating may be affected in a gas fired furnace, which may be fired using a portion of the hydrocarbonaceous
(Sasol Technology (Proprietary) Limited)
Ladas & Parry
Parsa J.
LandOfFree
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