AU2006271759A1 - Integrated process for producing hydrocarbons - Google Patents

Description

WO 2007/009951 PCT/EP2006/064266 INTEGRATED PROCESS FOR PRODUCING HYDROCARBONS The present invention relates to a mEthod to start a process for producing normally gaseous, normally liquid, and optionally normally solid hydrocarbons from a hydrocarbonaceous feedstock. In particula.r, the present 5 invention relates to a method to start arn integrated, highly efficient, low cost process providing operational flexibility for the production of hydroca.rbons, in particular at remote locations as well a& at off-shore platforms. 10 Various processes are known for the conversion of (gaseous) hydrocarbonaceous feedstocks, Especially methane, natural gas and/or associated ga.s, into liquid products, especially methanol and liquid hydrocarbons, particularly paraffinic hydrocarbons. In this respect, 15 reference is often made to remote locations and/or off shore locations, where no direct use of the gas is possible. Transportation of the gas, e.g. through a pipeline or in the form of liquefied natural gas, is not always practical and/or economical. This holds true even 20 more in the case of relatively small gas production rates and/or fields. Re-injection of gas adds to the cost of oil production, and may, in the case of E.ssociated gas, result in undesirable effects on crude oil production. Burning of associated gas has become an undesirable 25 option in view of depletion of hydrocarbon sources and air pollution. In addition to gaseous feEdstocks, also liquid and/or solid feedstocks may be usEd. For instance, residual oil streams, heavy oil streams as tar sand WO 2007/009951 PCT/EP2006/064266 -2 extract, peat, brown coal, coal, biomass (straw, wood, etc.) and municipal waste streams may be used. WO 02/060841 relates to an integrated process for producing hydrocarbon products and energy in which FT 5 steam (that is, steam produced by heat exchange between the reaction medium in a Fischer-Tropsch reaction and water) is superheated via a further heat exchange step against hot flue gas produced in a gas turbine generator. The Fischer-Tropsch process is one process used for the 10 conversion of hydrocarbonaceous feedstocks into gaseous, liquid and/or solid hydrocarbons. The feedstock is converted in a first step into a mixture of hydrogen and carbon monoxide (often referred to as synthesis gas or syngas). The syngas is then converted in a second step 15 over a suitable catalyst at elevated temperature and pressure into paraffinic carbons ranging from methane to high molecular weight molecules comprising up to 200 carbon atoms, or, under particular circumstances even more. The Fischer-Tropsch reaction is very exothermic 20 with the reaction temperature usually being controlled by indirect heat exchange of the reaction medium with water, the water being converted to saturated steam (called FT steam). As well as hydrocarbon products 2.nd FT steam the Fischer-Tropsch process also produces a light product 25 stream (also referred to as off gas, or tail gas) comprising unconverted synthesis gas, light hydrocarbon products (Ci-C 4 hydrocarbons, C 2

-C

4 olef.ns and some oxygenates) as well as some carbon dioxide and inerts such as nitrogen and argon. It is observed that normally 30 gaseous hydrocarbons are e.g. hydrocarbons which are gaseous at ambient conditions (20 OC, 1 bar). Examples are saturated Ci-C 4 hydrocarbons. Normally liquid hydrocarbons are liquid at ambient conditions WO 2007/009951 PCT/EP2006/064266 -3 (20 *C, 1 bar). Examples are saturated C5-n-C 15 , as well as C 5 -i-C 18 compounds. Normally solid hydrocarbons are solid at ambient conditions (20 OC, 1 bar). Examples are saturated n-C 15 and higher normal hydrocarbons, as well 5 as most i-C 20 -compounds. It is an object of the present invention to provide a method to start up a process for producing hydrocarbon products from a hydrocarbonaceous feedstock, which start up method has low (operational) costs and provides 10 operational flexibility in an integrated system comprising a hydrocarbon synthesis reaction and associated utilities. It is another object of the invention to provide an integrated process for producing hydrocarbons products 15 and energy. For the purposes of describing the invention the terms Fischer Tropsch (FT) steam, medium pressure (MP) steam and high pressure (HP) steam are defined as follows: 20 FT steam has a pressure in the range of from 15 to 40 bar and a saturated temperature of frcm 200 to 250 OC; MP steam is (usually) FT steam which is further heated in the range of 20-150 OC, preferably 50-120 oC, more preferably 70-90 OC, above the FT steam temperature, 25 such that it is unsaturated FT steam having a pressure in the range of from 15 to 40 bar and a temperature of from 220 OC to 400 oC, preferably in the rangE 250 OC-370 OC, more preferably in the range 280 OC-330 CC; and HP steam has a pressure in the range of from 55 to 30 150 bar and is preferably superheated with respect to MP steam by 10-100 oC, preferably by about 5.0 OC, such as being in the range 230 OC-500 *C, preferably in the range 260 0 C-470 OC, more preferably in the range WO 2007/009951 PCT/EP2006/064266 -4 280 OC-40 OC, and even more preferably in the range 330 OC-380 oC. It is observed that MP steam may also be produced by pressure reduction of HP steam. 5 Accordingly, the present invention provides a method to start up a process for the production of normally gaseous, normally liquid, and optionally normally solid hydrocarbon products from a hydrocarbonaceous feedstock comprising the steps of 10 (1) producing high pressure (HP) steam, preferably HP superheated steam, by means of at least one gas turbine generator and optionally one or more boilers fed with a hydrocarbonaceous feedstock; (2) reducing the pressure of at least ]part of the HP 15 steam produced according to step 1 to medium pressure (MP) steam; (3) using at least part of the MP steam produced according to step 2 to drive a compressor; (4) using the compressor to drive one cr more means for 20 compressing and optionally separating an oxygen containing gas; (5) using at least part of the oxygen containing gas to convert a hydrocarbonaceous feedstock into synthesis gas; (6) converting the synthesis gas produced according to 25 step 5 exothermally to a range of normally gaseous, normally liquid, and optionally normally solid hydrocarbon products in a Fischer-Tropsch reaction; (7) controlling the reaction temperature of step 6 by indirect heat exchange of the reaction medium with water, 30 the water being converted to saturated steam ( FT steam); (8) separating the hydrocarbon products produced in step 6 into a light product stream (comprising any unconverted syngas and at least part of the normally WO 2007/009951 PCT/EP2006/064266 -5 gaseous hydrocarbon products) and a heavy product stream (comprising the normally liquid and optionally normally solid hydrocarbon products); (9) feeding at least part of the light product stream 5 to one or more gas turbine generator(s) to form combusted gas and expanding said combusted gas through an expansion chamber of the gas turbine generator(s) to form hot flue gas and energy; (10) heating boiler feed water by heat exchange with the 10 hot flue gas to produce additional high pressure (HP), preferably superheated, steam; (11) cooling and/or condensing at least a part of the HP steam produced in step 10 in a heat exchanger against at least part of the FT steam produced in step 7 to produce 15 additional MP steam for use in generating electrical and/or mechanical energy for steps 1 to 10; and optionally (12) reducing the pressure of at least part of the superheated HP steam produced in step 10 to medium 20 pressure (MP) steam for use in earlier steps. Preferably the gas turbine generator(s) and/or the boiler(s) of step 1 includes one or more gas turbine heat recovery steam generators (HRSG). A HRSG is a steam generator known in the art, and is commonly a downstream 25 part of a gas turbine generator or a boiler. It can be separate or integral with a generator or boiler. Usually the heat recovery comprises several heat exchangers, e.g. a heater to convert water into saturated steam, a superheater to convert saturated steam into unsaturated 30 steam and an economiser, to heat up boiler feed water to its boiling point. Preferably one or more duct burners are present to increase the steam productivity.

WO 2007/009951 PCT/EP2006/064266 -6 In the above method the high pressure (HP) steam is at a pressure between 55 and 150 bar and at a temperature of 330 to 380 *C and/or the medium pressure (MP) steam is at a temperature of 280 to 330 OC. 5 The process according to the invention has the advantage of providing considerable flexibility at the start up of a process for the production of hydrocarbons products from a hydrocarbonaceous feedstcck where downstream energy and steam (FT steam) are not available 10 at the time of start up. In addition, the present invention allows more flexibility in the design of a hydrocarbon synthesis plant. In most cases, the cooling system of a hydrocarbon synthesis plant will produce saturated steam. For 15 instance, a very generally used cooling system is a thermo-syphon system in which hot boiler feed water is introduced at a low level in a reactor. Heart of the water is converted into steam, and at the top cf the reactor a mixture of steam and water is transferred to the so 20 called steam drum. Steam is removed from the steam drum, and the water, together with make-up boiler feed water, is returned to the reactor. The saturated steam thus produced needs to be heated as quickly as possible to avoid condensation in the lines. Thus, the saturated 25 steam needs to be converted into unsatura.ted steam at a location close to the hydrocarbon synthesis reactor. This can relatively easily be done by a steam/steam heat exchanger which is fed with high pressurE, preferably superheated, steam. Such a heat exchanger is relatively 30 small when compared with for instance a cas turbine with a heat recovery steam generator and associated equipment. Thus, the use of superheated high pressure steam, preferably slightly superheated to e.g. .25 oC, made by WO 2007/009951 PCT/EP2006/064266 -7 gas turbines, makes it possible to locate the gas turbines at a more suitable location, generally being separate or distal to the reactor, and still heat the saturated hydrocarbon conversion steam close to the 5 hydrocarbon synthesis reactor. This still overcomes the problems caused by the formation of (large amounts of) condensate in the reactor exit lines or pipes. For start up, it is preferable that the gas turbine generator(s) and any boiler(s) run at full capacity. Once 10 the overall system is operational, the generator operation may be reduced to (and maintained at) a much lower steam production level in the event that it should be necessary to re-engage it in order to generate more steam. 15 When a natural gas fired boiler(s) is used for the start up of the process for producing hydrocarbon products from a hydrocarbonaceous feedstcck, it can help provide the necessary steam for the generation of power to start the overall process. After the start up of the 20 process the boiler may be maintained in hot standby mode for emergency situations and still operate at low cost. With the hydrocarbon production process in use the boiler may be fired with any suitable fuel source, for example Fischer-Tropsch off gas instead of natural gas. However, 25 a boiler cannot generate electricity, and thus is less flexible. In the above method the gas turbine generator of step 9 is preferably that at least one gas turbine generator of step 1. Preferably the heat exchange in step (vi) is 30 done in a condensing mode to maximise the efficiency of the total process. The present invention also provides an integrated process for producing normally gaseous, normally liquid, WO 2007/009951 PCT/EP2006/064266 -8 and optionally normally solid hydrocarbon products and energy comprising the steps of: (i) converting a hydrocarbonaceous feedstock into syngas; 5 (iia) converting in a Fischer Tropsch reaction at least part of the syngas of step (i) exothermically to normally gaseous, normally liquid, and optionally normally solid hydrocarbon products; (iib) producing saturated FT steam by indirect heat 10 exchange of the reaction medium with water; (iii) separating the reaction products produced in step (iia) into a heavy product stream (comprising the normally liquid and optionally normally gaseous hydrocarbon products) and a light product stream 15 (comprising any unconverted syngas and at least part of the normally gaseous hydrocarbon products); (iv) cooling and/or feeding fuel to one or more gas turbine generators and burning it to for hot flue gas and energy; 20 (v) producing high pressure (HP), preferably superheated, steam by heat exchange of water against the hot flue gas from step (iv); and (vi)cooling and/or condensing at lea3t part of the HP (superheated) steam from step (v) in a heat exchanger 25 against at least part of the FT steam frcm step (iib) to form MP steam. Optionally, part of the HP superheated steam from step (v) may be depressurised (reduced in pressure) to produce medium pressure (MP) steam. The a.bove step (vi) 30 is carried out in a condensing steam modE. The condensed steam (or condensate) may be re-used as boiler feed water.

WO 2007/009951 PCT/EP2006/064266 -9 The gas turbine generator(s) of step (iv) includes one or more gas turbine heat recovery steam generators (HRSG). A HRSG is a steam generator known in the art, and is commonly a downstream part of a gas turbine generator. 5 It can be separate or integral with a generator. The fuel for the gas turbine generator may be any suitable combustible substance known in the art, including a hydrocarbonaceous feedstock or at least part, possibly all, of the light product steam produced 10 according to step (iii). Preferably there is a common steam header for all the MP steam in the present invention. Preferably the heat exchange in step (vi) is done in a condensing mode to maximise efficiency. 15 The invention is described in further detail below with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a Fischer-Tropsch process and some supporting utilities for producing hydrocarbons from a hydrocarbonaceous feedstock using the 20 claimed start up method. During normal production operation of a Fischer Tropsch synthesis plant electricity for various purposes is generally provided by means of one or more generators known in the art. Such a generator will typically be kept 25 running constantly. Where a HRSG is employed a readily usable source of HP steam will be available. This HP steam source may be utilised during start up (for example to power a compressor for an air separation unit) when other sources of steam are not yet available. 30 The process for production of hydrocarbon products from a hydrocarbonaceous feedstock, utilising the start up method of the present invention, shall now be described with reference to Figure 1. The following WO 2007/009951 PCT/EP2006/064266 - 10 description relates to a single train of production, but it will be appreciated that multiple trains (i.e. with multiple ASUs, gasification units etc) may be employed in which the different trains may be started in series. 5 The hydrocarbon production process begins with the conversion of a hydrocarbonaceous feedstock into syngas (i) by means of catalytic reforming, auto thermal reforming, partial oxidation and/or combinations thereof in the appropriate apparatus fed by a hydrocarbonaceous 10 feedstock such as natural gas, coal or biomass and, where necessary, oxygen and/or steam. The syngas is converted (ii) exothermically at elevated temperat-ures and pressures in the presence of a suitable Fischer-Tropsch catalyst to a range of hydrocarbon products. The reaction 15 temperature may be controlled by indirect heat exchange of the reaction medium with water (indicated in Figure 1 as boiler feedwater (BFW)) which is converted into steam (herein after referred to as FT steam). The Fischer-Tropsch products are converted (iii) into 20 a heavy product stream which is drawn off, and a light product stream (or off-gas). Preferably a major part of the light gas is recycled to the syngas production process. In this way an optimum carbon efficiency is obtained. For instance 20 - 90% of the light product is 25 recycled, especially 40 - 80%. At least part of the light product stream is fed to a combustion chamber of a gas turbine generator (iv), and/or the burners of a HRSG, to form combusted gas, which is subsequently combusted through an expansion chamber to form hot flue gas while 30 at the same time generating electricity or driving a compressor (for example for powering an ASU). Boiler feedwater is heated by heat exchange against the hot flue gas to produce HP superheated steam in a series of heat WO 2007/009951 PCT/EP2006/064266 - 11 exchangers, in Figure 1 designated (va), (vb) and (vc). For example, (va) may be an economiser, (vb) an evaporator and (vc) a superheater. The HP steam is condensed in a heat exchanger against at least part of 5 the FT steam produced by heat exchange with the FT reaction medium in order to superheat the FT steam. Thereafter, at least part of the superheated FT steam is fed to steam turbines to generate electricity and/or mechanical power. For example, turbines driven by the 10 superheated FT steam may be used to drive compressors in steps (i), (ii) and/or (iii). Optionally, a hydrocarbonaceous feed (ix) may be used to feed a fired heater in the production of HP superheated steam ((v) above). 15 Optionally, part of the superheated HP steam may be depressurised to MP steam (x) where insufficient FT steam from step (iii) is available. The depressurising step may be carried out via an appropriate valve. As a further option, hydrocarbonaceo-us feed may be 20 fed (xi) to the gas turbines in case of insufficient light product stream from step (iii) is available. At start up energy in the form of a hydrocarbonaceous feedstock, for example natural gas, is available while the alternative energy sources of off-gas and FT steam 25 are not available until the FT synthesis is underway. The start up method of the invention is controlled and safe not only under fresh start conditions, b.t also under re start conditions. The start up method of the invention also provides flexibility for quick response to changing 30 conditions, in particular via step (x) whereby HP steam is converted to MP steam to provide electrical or mechanical power for other components within the system.

WO 2007/009951 PCT/EP2006/064266 - 12 The present invention facilitates a Fr process in which FT steam is heated by indirect heat exchange (step (vi)) to produce MP steam. In essence, the reaction temperature in the FT reactor is controlled by heat 5 exchange with water being converted to saturated FT steam. The FT steam is primarily used as feed for a steam turbine (iv) which thereby generates electrical and/or mechanical energy. However, in order to prevent excessive condensation in the steam turbines the FT steam needs to 10 be superheated. According to the invention, the FT steam is superheated by indirect heat exchange by means of condensation of HP steam (see step (vi)). The superheated temperature of the HP steam is such that the temperature after isoenthalpic depressurisation of the HP steam to 15 the FT steam pressure, is equal to or higher than the temperature of the superheated FT steam. It is noteworthy that the heat exchange process taking place in step (vi) involves cooling or condensing HP steam against saturated FT steam as opposed to a heat 20 exchange process which involves heat transfer from flue gas to the FT steam stream. The superheated HP steam is produced in a heat recovery steam generator utilising hot flue gas. The hot flue gas in turn originates from the expansion chamber of 25 a gas turbine generator and/or from a burner integrated within the heat recovery steam generator. Appropriate selection of the HP pressure and superheat temperature may be made in order to ensure that the heat recovery steam generator operates under 30 conditions suitable to provide energy to superheat the FT steam during steady state operations, as well as to provide MP steam in the situation where insufficient or no FT steam is available (for example at start up).

WO 2007/009951 PCT/EP2006/064266 - 13 From the above discussion it will be apparent that operation of an integrated FT process requires flexibility between external energy sources (such as natural gas) and light FT products (off-gas) on the fuel 5 side, and optimal flexibility between FT steam and MP steam production on the steam side for reliable operation and start up/shut down reasons. The present invention provides such operational flexibility. The means for providing additional heat or heating 10 serves to assist the provision of steam by the heating or superheating of water by the exhaust flue gases. The additional heat or heating could be provided by any suitable means, including one or more burners, such as duct burners known in the art. The means is located in a 15 suitable position, for example, in the direct vicinity of the heat exchangers. The means may be powered by any suitable fuel source, including for example, the fuel source(s) (such as syngas) used for the gas turbine or other parts of the hydrocarbon synthesis plant. Such 20 means may be operable at different conditions, e.g. temperature, at different locations. The means for compressing and optionally separating an oxygen containing gas is suitably one or more air separation units known in the art. 25 The hydrocarbonaceous feed stock is suitably methane, natural gas, associated gas or a mixture of

C

1

.

4 hydrocarbons. The feed comprises mainly, i.e. more than 90 v/v%, especially more than 94%,

C

1

_

4 hydrocarbons, especially comprises at least 60 v/v 30 percent methane, preferably at least 75%, more preferably 90%. Very suitably natural gas, associated gas, or coal bed methane is used. Suitably, any sulphur in the feedstock is removed.

WO 2007/009951 PCT/EP2006/064266 - 14 The normally liquid hydrocarbons mentioned in the present description are suitably C 4

-

24 hydrocarbons, especially C 5

-

20 hydrocarbons, more especially C6- 16 hydrocarbons, or mixtures thereof. These 5 hydrocarbons or mixtures thereof are liquid at temperatures between 5 and 30 C (1 bar), especially at about 20 OC (1 bar), and usually are paraffinic of nature, while up to 24 wt%, preferably up to 12 wt%, of either olefins or oxygenated compounds may be present. 10 Depending on the catalyst and the process conditions used in the Fischer Tropsch reaction, normally gaseous hydrocarbons, normally liquid hydrocarbons and optionally normally solid hydrocarbons are obtained. It is often preferred to obtain a large fraction of normally solid 15 hydrocarbons. These solid hydrocarbons may be obtained up to 85 wt% based on total hydrocarbons, usually between 50 and 75 wt%. The partial oxidation and/or reforming of gaseous feedstocks, producing mixtures of especially carbon 20 monoxide and hydrogen, can take place according to various established processes. These processes include the Shell Gasification Process. A comprehensive survey of this process can be found in the Oil and Gas Journal, September 6, 1971, pp 86-90. 25 The oxygen containing gas used in conversion of hydrocarbonaceous feed into syngas may be air (containing about 21 vol. percent of oxygen), oxygen enriched air, suitably containing up to 70 percent, or substantially pure air, containing typically at least 95 vol.%, usually 30 at least 98 vol.%, oxygen. Oxygen or oxygen enriched air may be produced via cryogenic techniques, but could also be produced by a membrane based process, e.g. the process as described in WO 93/06041. At least initially the WO 2007/009951 PCT/EP2006/064266 - 15 boiler provides a power source for driving at least one air compressor or separator of the air compression/separating unit. To adjust the H 2 /CO ratio in the syngas, carbon 5 dioxide and/or steam may be introduced into the partial oxidation process or combined partial oxidation and reforming process. In this context, the partial oxidation process is defined as including partial oxidation, non catalytic and catalytic, with or without a flame and with 10 or with out steam and/or carbon dioxide injection. The percentage of hydrocarbonaceous feed which is converted in the first step of the process of the invention is suitably 50-99% by weight and preferably 80-98% by weight, more preferably 85-96% by weight. 15 The gaseous mixture, comprising predominantly hydrogen, carbon monoxide and optionally nitrogen, is contacted with a suitable catalyst in the catalytic conversion stage, in which the hydrocarbcns are formed. Suitably at least 70 v/v% of the syngas is contacted with 20 the catalyst, preferably at least 80%, mcre preferably at least 90%, still more preferably all the syngas. In a preferred embodiment, step (ii) represents a Fischer-Tropsch synthesis reaction in which case conversion of the mixture comprising hydrogen and carbon 25 monoxide into hydrocarbons utilises a catalyst known in the art and usually referred to as a Fischer-Tropsch catalyst. Catalysts for use in the Fischer-Tropsch hydrocarbon synthesis process frequently comprise, as the catalytically active component, a metal from Group VIII 30 of the previous IUPAC version of the Periodic Table of Elements such as that described in the 60th Edition of the Handbook of Chemistry and Physics (CPC Press). Particular catalytically active metals include ruthenium, WO 2007/009951 PCT/EP2006/064266 - 16 iron, cobalt and nickel. Cobalt is a preferred catalytically active metal. The catalytically active metal is preferably supported on a porous carrier. The porous carrier may be 5 selected from any of the suitable refractory metal oxides or silicates or combinations thereof known in the art. Particular examples of preferred porous carriers include silica, alumina, titania, zirconia, ceria, gallia and mixtures thereof, especially silica and titania. 10 The amount of catalytically active metal on the carrier is preferably in the range of from 3 to 300 pbw per 100 pbw of carrier material, more preferably from 10 to 80 pbw, especially from 20 to 60 pbw. (pbw - parts by weight). 15 If desired, the catalyst may also comprise one or more metals or metal oxides as promoters. Suitable metal oxide promoters may be selected from Groups IIA, IIIB, IVB, VB and VIB of the (same) Periodic Table, or the actinides and lanthanides. In particular, oxides of 20 magnesium, calcium, strontium, barium, scandium, yttrium. lanthanum, cerium, titanium, zirconium, hafnium, thorium, uranium, vanadium, chromium and manganese are most suitable promoters. Particularly preferred metal oxide promoters for the catalyst used to prepare the waxes for 25 use in the present invention are manganese and zirconium oxide. Suitable metal promoters may be selected from Groups VIIB or VIII of the (same) Periodic Table. Rhenium and Group VIII noble metals are particularly suitable, with platinum and palladium being especially preferred. 30 The amount of promoter present in the catalyst is suitably in the range of from 0.01 to 10C pbw, preferably 0.1 to 40, more preferably 1 to 20 pbw, per 100 pbw of carrier.

WO 2007/009951 PCT/EP2006/064266 - 17 The catalytically active metal and the promoter, if present, may be deposited on the carrier material by any suitable treatment, such as impregnation, kneading and extrusion. After deposition of the metal and, if 5 appropriate, the promoter on the carrier material, the loaded carrier is typically subjected to calcination at a temperature of generally from 350 to 750 OC, preferably a temperature in the range of from 450 to 550 *C. The effect of the calcination treatment is to remove crystal 10 water, to decompose volatile decomposition products and to convert organic and inorganic compounds to their respective oxides. After calcination, the resulting catalyst may be activated by contacting the catalyst with hydrogen or a hydrogen-containing gas, typically at 15 temperatures of 200 to 350 *C. The catalytic conversion process may be performed under conventional synthesis conditions known in the art. Typically, the catalytic conversion may te effected at a temperature in the range of from 100 to 600 OC, 20 preferably from 150 to 350 OC, more preferably from 180 to 270 OC, and most preferably from 200 to 250 OC. Typical total pressures for the catalytic conversion process are in the range of from 1 to 20C bar absolute, more preferably from 10 to 70 bar absolute. In the 25 catalytic conversion process mainly (at least 70 wt%, preferably 90 wt% of C 5 + hydrocarbons are formed. Preferably, a Fischer-Tropsch catalyEt is used, which yields substantial quantities of paraffins, more preferably substantially unbranched paraffins. A part may 30 boil above the boiling point range of thE so-called middle distillates, to normally solid hydrocarbons. A most suitable catalyst for this purpose is a cobalt containing Fischer-Tropsch catalyst. The term "middle WO 2007/009951 PCT/EP2006/064266 - 18 distillates", as used herein, is a reference to hydrocarbon mixtures of which the boiling point range corresponds substantially to that of kerosene and gas oil fractions obtained in a conventional atmospheric 5 distillation of crude mineral oil. The boiling point range of middle distillates generally lies within the range of 150 to 360 OC. The higher boiling range paraffinic hydrocarbons, if present, may be isolated and subjected to a catalytic 10 hydrocracking step, which is known per se in the art, to yield the desired middle distillates. The catalytic hydro-cracking is carried out by contacting the paraffinic hydrocarbons at elevated temperature and pressure and in the presence of hydrogen with a catalyst 15 containing one or more metals having hydrogenation activity, and supported on a carrier. Suitable hydro cracking catalysts include catalysts comprising metals selected from Groups VIB and VIII of the Periodic Table of Elements. Preferably, the hydrocrackir.g catalysts 20 contain one or more noble metals from Group VIII. Preferred noble metals are platinum, palladium, rhodium, ruthenium, iridium and osmium. Most preferred catalysts for use in the hydrocracking stage are those comprising platinum. 25 The amount of catalytically active metal present in the hydrocracking catalyst may vary within wide limits and is typically in the range of from 0.05 to 5 parts by weight per 100 parts by weight of the carrier material. Suitable conditions for the catalytic hydrocracking 30 are known in the art. Typically, the hydrocracking is effected at a temperature in the range of from 175 to 400 OC. Typical hydrogen partial pressures applied in WO 2007/009951 PCT/EP2006/064266 - 19 the hydrocracking process are in the range of from 10 to 250 bar. The FT process (step (ii)) may be operated in a single pass mode ("once through") or in a recycle mode. 5 The process may be carried out in one or more reactors, either parallel or in series. In the case of small hydrocarbonaceous feedstock streams, the preference will be to use only one reactor. Slurry bed reactors, ebulliating bed reactors and fixed bed reactors may be 10 used, the fixed bed reactor being the preferred option. The product of the hydrocarbon synthesis and consequent hydrocracking suitably comprises mainly normally liquid hydrocarbons, beside water and normally gaseous hydrocarbons. By selecting the catalyst and the 15 process conditions in such a way that especially normally liquid hydrocarbons are obtained, the prcduct obtained ("syncrude") may transported in the liquid form or be mixed with any stream of crude oil without creating any problems as to solidification and or cryEtallization of 20 the mixture. It is observed in this respect that the production of heavy hydrocarbons, compriEing large amounts of solid wax, are less suitable for mixing with crude oil while transport in the liquid form has to be done at elevated temperatures, which is less desired.

Claims (16)

1. A method to start up a process for the production of normally gaseous, normally liquid, and optionally normally solid hydrocarbon products from a hydrocarbonaceous feedstock comprising the steps of 5 (1) producing high pressure (HP) steam, preferably HP superheated steam, by means of at least one gas turbine generator and optionally one or more boilers fed with a hydrocarbonaceous feedstock.; (2) reducing the pressure of at least -art of the HP 10 steam produced according to step 1 to medium pressure (MP) steam; (3) using at least part of the MP steam produced according to step 2 to drive a compressor; (4) using the compressor to drive one or more means for 15 compressing and optionally separating an oxygen containing gas; (5) using at least part of the oxygen containing gas to convert a hydrocarbonaceous feedstock into synthesis gas; (6) converting the synthesis gas produced according to 20 step 5 exothermally to a range of normally gaseous, normally liquid, and optionally normally solid hydrocarbon products in a Fischer-Tropsch reaction; (7) controlling the reaction temperature of step 6 by indirect heat exchange of the reaction mEdium with water, 25 the water being converted to saturated steam (FT steam); (8) separating the hydrocarbon products produced in step 6 into a light product stream (comprising any unconverted syngas and at least part of the normally gaseous hydrocarbon products) and a heavy product stream WO 2007/009951 PCT/EP2006/064266 - 21 (comprising the normally liquid and optionally normally solid hydrocarbon products); (9) feeding at least part of the light product stream to one or more gas turbine generators to form combusted 5 gas and expanding said combusted gas through an expansion chamber of the gas turbine generator(s) to form hot flue gas and energy; (10) heating boiler feed water by heat exchange with the hot flue gas to produce additional high pressure (HP), 10 preferably superheated, steam; (11) cooling and/or condensing at least a part of the HP steam produced in step 10 in a heat exchanger against at least part of the FT steam produced in step 7 to produce additional MP steam for use in generating electrical 15 and/or mechanical energy for steps 1 to 10; and optionally (12) reducing the pressure of at least part of the additional high pressure (HP), preferably superheated, steam produced in step 10 to medium pressure (MP) steam 20 for use in earlier steps.

2. A method according to claim 1 wherein the high pressure (HP) steam is at a pressure of between 55 and 150 bar and at a temperature of 330 to 380 *C and/or wherein the medium pressure (MP) steam iE at a 25 pressure of between 15 and 40 bar and a temperature of 280 to 330 OC.

3. A method according to either claims 1 and 2 wherein the FT pressure steam is steam produced by indirect heat exchange between water and an exothermic reaction medium, 30 preferably a Fischer-Tropsch reaction medium, and has a pressure in the range of from 15 to 40 bar and a saturated temperature of from 200 to 250 0 C. WO 2007/009951 PCT/EP2006/064266 - 22

4. A method according to any of the precEding claims wherein the generator(s) and any boiler(s) of step (1) includes a heat recovery steam generator.

5. A method according to any of the preceding claims 5 wherein the generator(s) and any boiler(s) of step (1) is initially operated at full capacity and is subsequently reduced to a lower operational level.

6. A method according to any one of the preceding claims wherein the gas turbine generator(s) of step 9 is that at 10 least one gas turbine generator of step 1.

7. An integrated process for producing normally gaseous, normally liquid, and optionally normally solid hydrocarbon products and energy comprising the steps of: (i) converting a hydrocarbonaceous feedstock into 15 syngas; (iia) converting in a Fischer Tropsch reaction at least part of the syngas of step (i) exothermically to normally gaseous, normally liquid, and optionally normally solid hydrocarbon products; 20 (iib) producing saturated FT steam by indirect heat exchange of the reaction medium with watEr; (iii) separating the reaction produces produced in step (iia) into a heavy product stream (comprising the normally liquid and optionally normally gaseous 25 hydrocarbon products) and a light product stream (comprising any unconverted syngas and at least part of the normally gaseous hydrocarbon products); (iv) feeding fuel to a gas turbine generator and burning it to form hot flue gas and energy; 30 (v) producing high pressure (HP), preferably superheated, steam by heat exchange of water against the hot flue gas from step (iv); WO 2007/009951 PCT/EP2006/064266 - 23 and (vi) cooling and/or condensing at: least part of the high pressure (HP), preferably superheated, steam,from step (v) in a heat exchanger against at least part of the FT steam from step (iib) to form MP steam. 5

8. An integrated process according to claim 7 wherein at least part, preferably all, of the fuel is the light product steam produced according to step (iii).

9. An integrated process according to either of claims 7 and 8 comprising the further step of (vii) feeding at 10 least part of the superheated FT steam from step (vi) to steam turbines to generate electrical energy.

10. An integrated process according any of claims 7 to 9 comprising the further step of (viii) feeding at least part of the superheated FT steam from step (vi) to steam 15 turbines to generate mechanical energy, preferably an integrated process wherein the mechanical energy is used to power one or more means for compressing and optionally separating an oxygen containing gas, preferably both processes 20

11. An integrated process according to any of claims 7 to 10 comprising the further step of (ix) supplementing the hot flue gas produced according to step (iv) by means of one or more means for providing additional heat or heating along the path of the hot flue gas. 25

12. An integrated process according to any of claims 7 to 11 comprising the further step (x) of reducing the pressure of part of the HP superheated steam from step (v) to produce medium pressure (MP) steam.

13. An integrated process according to ary of claims 7 to 30 12 employing a start up method according to any of claims 1 to 6.

14. A method according to any one of the preceding claims wherein the conversion of the hydrocarborLaceous feedstock WO 2007/009951 PCT/EP2006/064266 - 24 into syngas involves at least partial oxidation and/or reforming of the feedstock.

15. A method as claimed in any one of claLms 1 to 6 or a process as claimed in any one of claims 7 to 14, further 5 comprising the step of catalytically hydrDcracking higher boiling range paraffinic hydrocarbons of the normally liquid and optionally normally solid hydrocarbon products produced.

16. Hydrocarbon products provided according to any of 10 claims 1 to 15.