PROCESS FOR PREPARING LIQUID HYDROCARBONS USING THE FISHER-TROPSCH PROCESS INTEGRATED IN REFINERIES

Abstract

The present invention relates to a process for preparing liquid hydrocarbons by means of the Fischer-Tropsch process integrated in refineries, comprising in particular the recycling of streams from the steam reforming hydrogen production process as the feedstock for the Fischer-Tropsch process.

Description

PROCESS FOR PREPARING LIQUID HYDROCARBONS USING THE FISHER-TROPSCH PROCESS INTEGRATED IN REFINERIES FIELD OF INVENTION

[0001] This invention relates to a process for preparing liquid hydrocarbons using the Fischer-Tropsch process integrated in refineries. BACKGROUND OF THE INVENTION

[0002] The Fischer-Tropsch synthesis reaction has garnered considerable attention due to its technological and scientific significance. This interest stems from its role in converting hydrocarbons into high-quality, high-value-added liquid products. The reaction involves the catalytic hydrogenation of carbon monoxide (CO) to produce liquid hydrocarbons, such as gasoline, diesel, and lubricants, from synthesis gas. Since the invention of the original process by Franz Fischer and Hans Tropsch, numerous refinements and adjustments have been made.

[0003] Essentially, the Fischer-Tropsch reaction for converting synthesis gas, which consists of a mixture whose main components are H2 and CO, can be characterized by the overall reaction scheme: H2+ CO-»-CH2-+ H2O.

[0004] The hydrocarbons produced in the Fischer-Tropsch reaction range from methane to paraffinic hydrocarbons containing more than 100 carbon atoms.

[0005] The Fischer-Tropsch reaction can be carried out in various types of reactors, including traditional fixed, fluidized or moving bed reactors, the three-phase slurry bubble, and more recently, the so-called micro or "millichannel" reactors (stacked multichannel reactor).

[0006] Currently, there are industrial complexes in operation in South Africa based on the large-scale FischerTropsch route (with an installed capacity of 7,500,000 tons / year) that produce chemicals, linear olefins, gasoline, diesel and lubricants in Malaysia (capacity of 500,000 tons / year), and in Qatar.

[0007] In general, the Fischer-Tropsch process has four main sections: synthesis gas generation; gas purification; Fischer-Tropsch synthesis; and product treatment. Almost 60 to 70% of the Fischer-Tropsch process capital cost is associated with the synthesis gas production stage, whether it is produced from natural gas or coal. The Fischer-Tropsch synthesis portion comprises almost 20% of the costs, and refining operations about 10%. Refining operations include hydrotreating, hydroisomerization for diesel production, and hydrocracking to convert heavy fractions.

[0008] In fact, the high capital cost of implementing the Fischer-Tropsch process has limited its use to strategic situations for reducing dependence on foreign oil, or for valuing natural gas in remote regions or those with a large overproduction surplus. As an example, for a 50,000 barrel / day FT unit using coal (12,000 tons / day) and biomass (1,412 tons / day), the estimated investment is US$5.8 billion. / RL / rn / Lznz / q / Yi

[0009] The literature on Fischer-Tropsch catalysts and processes is extensive, with nearly 4,000 publications in 1954 and a similar number of patents. However, despite its widespread recognition, the potential for innovation in the Fischer-Tropsch process remains high. Recent patents relate, for example, to the use of the gas separated from the liquid products ("tail gas") as fuel, feedstock for the synthesis gas production section, recovery of light hydrocarbons, or other components.

[0010] Furthermore, the integration of processes aimed at reducing Fischer-Tropsch costs and achieving greater energy efficiency is revealed. Document US 2016 / 0293985 describes an integration of the Fischer-Tropsch process with the synthesis gas production process using the solid oxide fuel cell method.

[0011] Document US 2016 / 0003480, in turn, teaches the integration of Fischer-Tropsch gasification processes, and joint generation.

[0012] In particular, with regard to the integration of Fischer-Tropsch processes with refining processes, there are several routes taught in the state of the art.

[0013] United States Patent 9,328,291 teaches the use of heavy fractions generated in a refinery (bitumen, heavy oil, or coke) for the production of synthesis gas by the gasification process, and their use in the Fischer-Tropsch process.

[0014] Document US 2010 / 0108568 teaches the integration of hydrocracking, oligomerization, alkylation and hydrotreating with the Fischer-Tropsch process, with the intention of producing aviation kerosene.

[0015] Document EP 2487225 teaches the use of the naphtha fraction produced in the FischerTropsch process as a raw material for the synthesis gas generation unit, in order to maximize the production of middle distillates (diesel and aviation kerosene).

[0016] In addition, methods for producing synthesis gas for use in FischerTropsch processes with alternative processes for steam reforming are described.

[0017] US patent 6043288 discloses a process for producing synthesis gas by reacting a gaseous hydrocarbon stream with oxygen and, optionally, steam. This process can be broadly classified as autothermal reforming when a catalyst is used, or partial oxidation when a catalyst is absent. These processes are industrially inconvenient because they utilize O2, which is expensive to produce.

[0018] Patent application Pl 0508327-3 discloses a process for producing a hydrogen-rich stream from streams containing a low concentration of hydrogen, using one or more reverse selective membranes that are permeable to carbon dioxide, and thus concentrate the stream in the other components. The gas containing a low concentration of hydrogen can come from a Fischer-Tropsch section.

[0019] Therefore, despite the fact that there are numerous specialized citations and descriptions of Fischer-Tropsch processes in the literature, there is still a need to provide a process that uses a low-cost raw material to produce Fischer-Tropsch derivatives in small-scale units, and its integration with existing refinery units. BRIEF DESCRIPTION OF THE INVENTION

[0020] This invention relates to a process for preparing liquid hydrocarbons by means of the Fischer-Tropsch process integrated with existing hydrogen generation units, comprising in particular the recycling of streams arising from the hydrogen generation process by steam reforming. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The detailed description presented below refers to the attached figures:

[0022] Figure 1 represents a simplified flow diagram of the steam reforming hydrogenation process.

[0023] Figure 2 presents a simplified flow diagram of the integration of the Fischer-Tropsch process with a steam reforming hydrogen generation unit.

[0024] Figure 3 illustrates the effect of the pressure and temperature used in the Fischer-Tropsch section in the production of liquid by-products using the blowdown gas from a steam reforming production unit, according to this invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] This invention relates to a process for preparing liquid hydrocarbons by means of the Fischer-Tropsch process integrated into hydrogen generation units, comprising in particular the recycling of streams arising from the steam reforming hydrogen generation process as the feedstock in the small-scale Fischer-Tropsch process.

[0026] As shown in Figure 1, the hydrogen generation process begins with the supply of a hydrocarbon stream as the initial feedstock, which can be natural gas, liquefied petroleum gas (LPG), refinery gas, or naphtha (stream 1), along with some of the hydrogen produced in the unit itself (stream 2), into a pretreatment reactor containing catalyst and fixed-bed adsorbents. The main function of this reactor is to remove organic and inorganic sulfur-containing compounds.

[0027] However, depending on the type of raw material, this reactor may also have the functions of chloride and olefin removal.

[0028] Typical operating conditions involve pressures ranging from approximately 10 kgf / cm2 (0.98 MPa) to approximately 40 kgf / cm2 (3.92 MPa), and temperatures in the range of approximately 250°C to 400°C, containing CoMo / alumina or NiMo / alumina type catalysts in different forms.

[0029] The mixture of hydrocarbon feedstock, recycled hydrogen, and steam (stream 3) generated in the unit itself in heat recovery sections feeds the first reformer. This equipment consists of a furnace containing a set of tubes, generally 101.2 mm in diameter and between 8 and 12 m high, within which is a fixed-bed catalyst containing nickel on a refractory support, such as alumina, calcium aluminate, or magnesium, which drives the main reforming (1) and shunting (2) reactions, exemplified in / RL / rn / Lznz / q / Yi below: CnH2m+ nH2O -► nCO + H2(m+n) (1) CO + H2O CO2 + H2(2)

[0030] Steam is fed to the process in excess of the stoichiometry of reactions (1 and 2) in order to prevent coke buildup on the catalyst. Typical operating conditions in the primary reformer section are temperatures between approximately 450°C and 550°C (tube inlet) and 800°C to 950°C (tube outlet), pressures between approximately 10 kgf / cm² (0.98 MPa) and 40 kgf / cm² (3.92 MPa), and steam-to-coal ratios between 2 and 5 mol / mol. Reactions (1 and 2) are sufficiently endothermic at equilibrium, so the necessary heat is supplied by burning fuel, most of which is the so-called "purge gas" (stream 10), supplemented by external fuel, which is generally natural gas or refinery gas.

[0031] The reformer effluent process gas (stream 4) is a mixture of CH4, CO, CO2, H2, and steam, with a composition close to thermodynamic equilibrium. Under reformer outlet conditions of approximately 840°C, pressure of approximately 25.2 kgf / cm2 (2.47 MPa), and steam / coal ratio of approximately 3.0 mol / mol, the dry basis (%v / v) composition of the reformer effluent is 70.2% H2, 12.3% CO, 8.9% CO2, and 8.4% CH4. This gas is cooled with steam generated from boiler water and then fed to the “Change” reactor (stream 5).

[0032] The changeover reactor generally contains a catalyst based on iron, chromium, and copper oxides (“high-temperature changeover”) and catalyzes the CO conversion reaction (reaction 2). Typical operating conditions are temperatures between approximately 330°C (inlet) and 450°C (outlet), and pressures between approximately 10 kgf / cm² (0.98 MPa) and 40 kgf / cm² (3.92 MPa). The reactor effluent composition (stream 6) is a mixture of CH₄, CO, CO₂, H₂, and steam, with a composition close to thermodynamic equilibrium. For a reactor outlet temperature of approximately 425°C, a pressure of approximately 24.4 kgf / cm2 (2.39 MPa), and a steam / coal ratio of approximately 3.0 mol / mol in the reformer, the dry basis (%v / v) composition of the exchange reactor effluent is 72.5% H2, 3.5% CO, 16.0% CO2, and 7.8% CH4.

[0033] Next, the effluent stream from the changeover reactor (stream 6) is cooled to typical temperatures of approximately 20°C to 45°C and sent to a condensate separation vessel, where an aqueous stream (stream 7) and a gaseous stream (stream 8) are generated. The aqueous stream can be treated and recycled in the unit's steam generation system or sent to the refinery's boiler water treatment plants. The gaseous stream (stream 8) is then sent to the pressure swing adsorption (PSA) section for separation and recovery of the hydrogen produced in the process.

[0034] The PSA section consists of several reactors containing adsorbent material in beds comprised of alumina, activated carbon, and zeolites. These beds allow the separation of a high-pressure hydrogen stream with a purity of over 99.99% from a low-pressure gas stream containing the so-called purge gas (stream 10), composed of CH4, CO, CO2, and H2, which is returned to the reformer as fuel. The composition of the purge gas is generally 25 to 35% H2, 35 to 55% CO2, 10 to 30% CH4, and 8 to 15% CO.

[0035] Purge gas is produced in large quantities. For example, for a small-scale hydrogen production unit (550,000 Nm3 / d), a typical volumetric ratio of purge gas to hydrogen produced would be 0.64 (Nm3 / Nm3), meaning that approximately 350,000 Nm3 / day of purge gas would be produced. Larger-scale hydrogen generation units using the steam reforming process can achieve values ​​on the order of 3,500,000 Nm3 / d of hydrogen produced, which corresponds to more than 2,000,000 Nm3 / d of associated purge gas, which, in the current technology, is a byproduct used as fuel in the unit.

[0036] Therefore, the purpose of this invention is to provide a process for preparing liquid hydrocarbons by the small-scale Fischer-Tropsch process integrated into refinery units, preferably existing refinery units, employing the recycling of the gas stream from the steam reforming hydrogen generation process, preferably a gas stream coming from the PSA section of the steam reforming hydrogen generation process, such as purge gas, as the feedstock in the Fischer-Tropsch process, wherein the carbon dioxide content is at least 20% and the hydrogen content is preferably less than 50% v / v.

[0037] Figure 2 shows a process for the preparation of liquid hydrocarbons using the Fischer-Tropsch process integrated into refining units, in which the blowdown gas from the PSA section of the steam reforming hydrogen production unit (stream 12) is recycled as the sole feedstock in the Fischer-Tropsch process. This gas is compressed to a typical pressure ranging from approximately 0.5 kgf / cm² (0.049 MPa) to 4 kgf / cm² (0.39 MPa) to 40 kgf / cm² (3.92 MPa). Optionally, a portion of the blowdown gas stream is left uncompressed (stream 13) and sent to the reformer to compress the fuel. Next, the compressed purge gas is fed into the Fischer-Tropsch reactor, where it comes into contact with a catalyst, converting H2 and CO into liquid products containing hydrocarbons, such as gasoline, diesel, and lubricants (stream 15).

[0038] The liquid fraction (stream 15) comprises a mixture of liquid hydrocarbons ranging from the naphtha to wax distillation range, called synthetic oil, which may also contain varying amounts of oxygenated compounds and water. This stream can be sent to a dedicated separation process, where gasoline, diesel, and lubricant fractions are obtained. Because they are sulfur-free, they can comprise the final refinery liquid byproduct stream through direct blending. Alternatively, synthetic oil can be processed in existing refinery units when the objective is to reduce fixed investment.

[0039] In a preferred option, where the objective is low fixed investment, the liquid products generated in the Fischer-Tropsch section are initially separated into an aqueous stream and an oily stream, which are then sent to existing units in the refinery, preferably to the distillation, hydrotreating, and effluent treatment sections. As an example, the oily stream (synthetic oil) is returned to the refinery's distillation unit, with the distilled fractions comprising the feedstock for the gasoline, diesel, and lubricant hydrotreating units. The aqueous stream can be sent to the refinery's existing acid water unit for proper disposal. For someone experienced in the matter, various other schemes for processing synthetic oil in an existing refinery are possible, depending on the type and characteristics of the existing units. The unconverted gaseous fraction containing light hydrocarbons generated in the process, with a molecular weight less than or equal to pentane, known as "tail gas," is, in a preferred option, returned to the hydrogen generation process to comprise the reformer fuel (stream 14). In an alternative option, the tail gas can be sent to a light hydrocarbon recovery section.

[0040] The Fischer-Tropsch reaction can be carried out in well-known and widely used reactors, such as fixed-bed reactors (multitubular fixed bed or moving bed, “slurry bed”, circulating fluidized bed (CFB), and fixed fluidized bed (FFB). Compact reactors (“stacked multichannel reactor”) that are of the “milli-” or “microchannel” type are particularly suitable for the production capacities sought in the present invention.

[0041] The Fischer-Tropsch reaction preferably uses a catalyst containing cobalt oxide on support types including alumina, titanium, aluminates, silica, zirconia, or a mixture thereof, and may also contain noble metals such as Pt, Re, or Ru as promoters. It operates at temperatures between approximately 180 and 300°C, preferably from approximately 190°C to 250°C, and pressures between approximately 4 kgf / cm² (0.39 MPa) and 30 kgf / cm² (2.94 MPa). This arrangement is particularly suitable for the production of diesel and waxes with low production of oxygenates as reaction byproducts. The cobalt-based catalyst for the Fischer-Tropsch step also contains selected noble metals such as Pt, Re, or Ru as promoters. It may also preferably contain copper as a promoter to favor the "exchange" reaction, zeolites to reduce the wax content, or a combination thereof. Alternatively, the catalyst in the Fischer-Tropsch section may be iron oxide-based and may contain silica, copper, noble metal, and alkali metal promoters selected from potassium oxide (K₂O), copper oxides, silica, zinc oxide, or a combination thereof. In this case, the section preferably operates at temperatures between approximately 250°C and 400°C, more preferably between approximately 300°C and 350°C.

[0042] The Fischer-Tropsch section may contain one or more reaction stages, depending on whether the objective is to reduce fixed costs or maximize production from liquid products, respectively.

[0043] The Fischer-Tropsch section must contain catalyst regeneration means for coke removal, generally by passing dilute air at temperatures between approximately 200°C and 400°C, and reducing the catalyst with H2 and / or dilute purge gas. The use of N2 or steam for dilution is particularly desirable.

[0044] The blowdown gas fed to the Fischer-Tropsch process from a natural gas steam reforming unit comprises methane, hydrogen, carbon monoxide, and carbon dioxide, wherein, preferably, the carbon dioxide content is at least 20% and the hydrogen content is preferably less than 50% v / v. More specifically, the blowdown gas composition generally contains 25 to 35% H2, 35 to 55% CO2, 10 to 30% CH4, and 8 to 15% CO, with a H2O ratio between approximately 1.2 and 5.5 mol / mol.

[0045] This invention allows the integration of the small-scale Fischer-Tropsch process into existing refinery units, without alterations to the existing hydrogen unit, and without the need for distillation and treatment sections for products and effluents of the Fischer-Tropsch unit. In a scenario where it is desired to reduce fixed process costs, a high degree of blowdown gas conversion is not desirable, since in this situation it would be necessary to replace the reformer burners that use blowdown gas to burn another fuel, such as natural gas.

[0046] One option that is particularly useful for existing hydrogen production units that are operating below their rated capacity, and consequently have excess capacity in the PSA system to reduce the H2:CO ratio of the purge gas, is to reduce the inlet temperature of the shift reactor until CO escape is observed. For high-temperature shift catalysts (HTS), the temperature can be adjusted between approximately 280°C and 300°C so that there is CO escape and a consequent reduction in the F^CO ratio.

[0047] The following examples show the different embodiments of this invention. Examples Example 1

[0048] This example illustrates the process configuration according to this invention. An industrial hydrogen production unit using the steam reforming process, with a capacity of 1,100,000 Nm3 / d of 99.99% H2 operating at the "design" capacity shown in Table 1, produces 1099.12 kmol / h of purge gas with the composition described in Table 1, according to the prior art. The purge gas, according to this invention, can be sent to the small-scale Fischer-Tropsch unit, which operates at 200°C, a pressure of 5 bar (0.5 MPa), and with a cobalt-based catalyst. The gaseous fraction resulting from the Fischer-Tropsch process can be returned to the reformer as fuel and supplemented with natural gas to provide the heat of reaction required for the steam reforming step. The process allows the production of a mixture containing approximately 487.5 kg / h of gasoline, 46.1 kg / h of diesel, and 0.2 kg of paraffins, which can be returned to the refinery's distillation section for cost reductions, preferably, or separated and purified. The aqueous fraction resulting from the Fischer-Tropsch process (condensate) can preferably be sent to the refinery's effluent treatment section, or to the acid water section. Table 1: Production of liquid derivatives from the Fischer-Tropsch process using purge gas from a hydrogen production unit by steam reforming. Condition / Variable Unit Design Invention Comment Natural gas raw material discharge Kmol / h 751.443 751.443 1 Steam raw material discharge Kmol / h 2684.875 2684.875 18 H? Recycled Kmol / h 35.747 35.747 2 V / C Ratio Mol / mol 3.5 3.5 Hs / Raw Material Ratio Mol / mol 0.047 0.047 Reformer Outlet Temperature °C 850 850 4 Reformer Outlet Pressure Kgf / cm2 22.5 22.5 4 Reformer Effluent (bsp) 4 CO % v / v 12.50 12.50 CO2 % v / v 9.37 9.37 H2 % v / v 73.33 73.33 ch4 % v / v 4.56 4.56 n2 % v / v 0.25 0.25 Reformer Inlet Temperature °C 371 371 5 HTS Outlet Temperature °C 428 428 5 HTS Effluent (bsp) 6 CO % v / v 3.68 3.68 CO2 % v / v 16.47 16.47 h2 % v / v 75.42 75.42 ch4 % v / v 4.20 4.20 n2 % v / v 0.23 0.23 H2 production Nm3 / d 1,100,000 1,100,000 16 Purge gas discharge (3) Kmol / h 1099.117 841.8 12 Composition of “[...] gas 12 14 12o 14 CO % v / v 10.71 2.80 CO2 % v / v 48.01 62.69 h2 % v / v 28.57 14.81 oh4 % v / v 12.24 17.27 n2 % v / v 0.47 0.61 C2H6 % v / v 0 0.88 C3H8 % v / v 0 0.57 C4Hw % v / v 0 0.61 Fuel for the [...] Kg / h 3176 3905 17 Condensation of the section of [...] Kmol / h 1522 1522 15 Fischer-Tropsch production 15 Gasoline Kg / h - 487.5 Diesel Kg / h - 46.1 Paraffins Kg / h - 0.2.

[0049] (1) Composition of natural gas (%v / v): CH4 = 89.85; C2He = 8.04; C3Hs = 0.42; CO2 = 0.69 and N2 = 1.0; Cp of fuel gas = 0.501 kcal / kg°C; (2) Cobalt-based catalyst, temperature of 200°C and pressure of 5 bar and assuming an 80% conversion of the CO contained in the purge gas; (3) For the purposes of the invention, purge gas means the residual gas that emerges from the Fischer-Tropsch section. The streams refer to the numbering shown in Figure 2. Example 2

[0050] In this example, the process conditions (steam / carbon ratio) of the steam reforming section were adjusted for increased production of liquid byproducts, in accordance with this invention. Table 2: Production of liquid derivatives from the Fischer-Tropsch process using purge gas from a hydrogen production unit by steam reforming. Condition / Variable Unit Design Invention Current Natural gas feedstock discharge Kmol / h 751.443 715.66 1 Steam feedstock discharge Kmol / h 2684.875 2301.348 18 Recycled H2 Kmol / h 35.747 35.747 2 V / C ratio Mol / mol 3.5 3.00 H2 / feedstock ratio Mol / mol 0.047 0.047 Reformer outlet temperature °C 850 850 4 Reformer outlet pressure Kgf / cm2 22.5 22.5 4 Reformer effluent (bs) 4 CO %v / v 12.50 15.08 CO2 %v / v 9.37 9.29 H2 %v / v 73.33 80.52 ch4 %v / v 4.56 6.56 n2 %v / v 0.25 0.29 Inlet temperature of the [...] °C 371 300 5 Outlet temperature of HTS °C 428 353 5 HTS effluent (bs) 6 CO %v / v 3.68 6.43 CO2 %v / v 16.47 15.88 H2 %v / v 75.42 72.23 ch4 %v / v 4.20 7.77 n2 %v / v 0.23 0.26 H2 production Nm3 / d 1,100,000 860.859 16 Purge gas discharge (3) Kmol / h 1,099.117 947 Purge gas composition 12 14 12o 14 CO %v / v 10.71 5.00 CO2 %v / v 48.01 63.72 H2 %v / v 28.57 2.0 ch4 %v / v 12.24 25.54 Table 2: (Continued) n2 %v / v 0.47 1.04 c2h6 %v / v 0 1.24 C3H8 %v / v 0 0.88 C4H10 %v / v 0 0.61 Fuel for the [...] Kg / h 3176 17 Condensation of the section of [...] Kmol / h 1522 1265 Fischer-Tropsch production 15 Gasoline Kg / h - 826.3 Diesel Kg / h - 137.3 Paraffins Kg / h - 1.5

[0051] (1) Composition of natural gas (%v / v): CH4 = 89.85; C2H6 = 8.04; C3Hs = 0.42; CO2 = 0.69 and N2 = 1.0; Cp of fuel gas = 0.501 kcal / kg°C; (2) Cobalt-based catalyst, temperature of 200°C and pressure of 5 bar and assuming an 80% conversion of the CO contained in the purge gas; (3) For the purposes of the “invention”, purge gas means the residual gas that arises from the Fischer-Tropsch section. Example 3

[0052] In this example, according to this invention, the process conditions (pressure and temperature) of the Fischer-Tropsch section were altered, and the impact on the production of liquid byproducts was quantified. The unit data are those presented under the “design” condition in Table 1, and the results are shown in Figure 3.

[0053] As can be seen from the invention described herein, the solution of the present invention provides an increase in the production of liquid hydrocarbons with low investment, by integrating a small-scale Fischer-Tropsch process into existing hydrogen generation, distillation, and hydrotreating units in the refinery. Therefore, it is possible to obtain high-quality, sulfur-free liquid fuels, reducing vehicle emissions.

[0054] Furthermore, the use of dedicated synthesis gas production units for use as feedstock in Fischer-Tropsch processes, which are costly, is avoided. Since this refers to small-scale production, investment in separation and purification sections is avoided by taking advantage of space in existing refinery sections such as distillation, hydrotreating, and effluent treatment, making the Fischer-Tropsch process economical. In addition, a small-scale Fischer-Tropsch process can undergo unscheduled shutdowns without significant loss of liquid product production, which would not occur in a large-scale complex consisting of synthesis gas generation associated with the Fischer-Tropsch process. High production volumes can be achieved by installing small-scale units in several refineries.

[0055] Countless variations to the scope of protection of this application are permitted. Therefore, it is reinforced that the present invention is not limited to the particular configurations / modes described above.

Claims

1. A process for preparing liquid hydrocarbons by the Fischer-Tropsch process integrated into refining units, wherein it comprises recycling the gas stream from the steam reforming hydrogen generation process as feedstock in the Fischer-Tropsch process, wherein the carbon dioxide content is at least 20% and the hydrogen content is less than 50% v / v.

2. The process according to claim 1, wherein the gas stream of the steam reforming hydrogen generation process is from the PSA section.

3. The process according to claim 1 or 2, wherein the gas stream of the steam reforming hydrogen generation process is a purge gas stream comprising 25 to 35% hydrogen, 35 to 55% carbon dioxide, 10 to 30% methane, and 8 to 15% carbon monoxide.

4. The process according to claim 3, wherein the F^CO ratio is approximately 1.2 and approximately 5.5 mol / mol.

5. The process according to any of claims 1 to 4, wherein the Fischer-Tropsch process comprises: compressing the feedstock, which comes from the steam reforming hydrogen generation process, from a pressure lower than approximately 0.5 kgf / cm2 (0.049 MPa) to approximately 4 to 40 kgf / cm2 (0.39 MPa to 3.92 MPa); feeding said compressed feedstock into a Fischer-Tropsch reactor and contacting it with a catalyst; and optionally, separating the resulting liquid products into an oil stream, comprising liquid hydrocarbons, and an aqueous stream.

6. The process according to any of claims 1 to 5, wherein part of the uncompressed purge gas stream is sent to comprise the reformer fuel.

7. The process according to any of claims 1 to 6, wherein the unconverted residual gas fraction containing light hydrocarbons is returned to the hydrogen generation process with the reformer fuel, or optionally, sent to a light olefins recovery section.

8. The process according to any of claims 1 to 7, wherein the catalyst used in the Fischer-Tropsch reaction is selected from cobalt compounds based on alumina, titanium, aluminos, silica, zirconia, or mixtures thereof.

9. The process according to claim 8, wherein said catalyst further contains noble metals selected from Pt, Re or Ru as promoters.

10. The process according to any of claims 1 to 7, wherein the catalyst used in the Fischer-Tropsch reaction is selected from iron compounds containing, optionally, silica, copper, noble metals and alkali metals promoters selected from potassium oxide, copper oxides, silica, zinc oxide, or a combination thereof.

11. The process according to any of claims 1 to 10, wherein the FischerTropsch reactor is selected from slurry, fluidized, fixed bed, or moving bed reactors, preferably compact “milli” or “microchannel” type reactors.

12. The process according to any of claims 1 to 9, wherein the Fischer-Tropsch reaction temperature is between approximately 180°C and 300°C, preferably between approximately 190°C and 250°C, and pressures between approximately 4 and 30 kgf / cm2 (0.39 and 2.94 MPa).

13. The process according to any of claims 1 to 7 or 10, wherein the Fischer-Tropsch reaction temperature is between approximately 250°C and 400°C, preferably between approximately 300°C and 350°C.

14. The process according to any of claims 1 to 13, wherein the liquid hydrocarbons are gasoline, diesel, lubricants, and the like.

15. The process according to any of claims 1 to 14, wherein the gas stream of the steam reforming hydrogen generation process is from existing refining units.

16. The process according to any of claims 1 to 15, wherein the oil stream containing liquid hydrocarbons obtained in the Fischer-Tropsch process, as defined in claim 5, is recycled in existing refinery sections, preferably in the distillation, hydrotreating and effluent treatment sections.

17. The process according to any of claims 1 to 15, wherein the acid stream generated in the Fischer-Tropsch process, as defined in claim 5, is recycled in the refinery's existing acid water unit.