Process for forming liquid hydrocarbon product

Abstract

A method of forming a liquid hydrocarbon product, the method comprising: providing a feed gas comprising a compound of elemental carbon, hydrogen, and oxygen; generating a synthesis gas from the feed gas, the synthesis gas comprising carbon monoxide, hydrogen, and steam; cooling the syngas below the dew point to form an aqueous condensate having a carbonaceous gas dissolved therein and a water-lean syngas; passing the aqueous condensate to a first stripper and stripping the aqueous condensate with steam to transfer carbonaceous gas from the aqueous condensate to the steam, thereby forming a stripped aqueous condensate and a first stripper effluent steam; passing the water-lean syngas to a Fischer-Tropsch unit to form a liquid hydrocarbon product and co-produced water, the co-produced water having carbonaceous species dissolved therein; passing the co-produced water to a second stripping column and stripping the co-produced water with the first stripping column effluent steam to transfer carbonaceous materials from the co-produced water to the first stripping column effluent steam, thereby forming stripped co-produced water and a second stripping column effluent steam; and recycling the second stripper effluent steam to the feed gas.

Description

Technical Field

[0001] The present invention relates to a process for forming a liquid hydrocarbon product. Background Art

[0002] The Fischer-Tropsch process uses chemical reactions to convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. These reactions occur in the presence of a metal catalyst, typically at temperatures between 150°C and 300°C and pressures between one atmosphere and several tens of atmospheres. The Fischer-Tropsch process produces a variety of hydrocarbons, ideally having the formula (C n H 2n+2 ). A more useful reaction to produce alkanes is as follows:

[0003] (2n+1)H2+nCO→C n H 2n+2 +n H2O

[0004] wherein n is typically from 1 to 100. The formation of methane (n=1) is undesirable. In addition to the formation of alkanes, competing reactions also produce small amounts of olefins as well as alcohols and other oxygenated hydrocarbons. The Fischer-Tropsch reaction is a highly exothermic reaction with a standard reaction enthalpy (ΔH) of -165 kJ / mol combined CO.

[0005] The synthesis gas (syngas) feed to the Fischer-Tropsch unit can be derived from a variety of feedstocks; for example, natural gas via steam reforming and / or autothermal reforming, municipal solid waste and biomass via high temperature gasification, or carbon dioxide and hydrogen via the reverse water gas shift reaction. The latter source is advantageous because it utilizes carbon dioxide that might have been destined for release into the atmosphere.

[0006] WO2022 / 079408A1 discloses the use of an autothermal reverse water gas shift unit in a hydrocarbon synthesis process. Process condensate is recovered from the reverse water gas shift unit, and co-produced water is recovered from the hydrocarbon synthesis (Fischer-Tropsch) unit. The process condensate and co-produced water are stripped separately to reduce their organic contaminants, reduce the burden of downstream water treatment, and return carbon to the process. Such processes require large amounts of steam. Therefore, the energy requirements and water requirements of the process are high. In addition, the water content of the stripping effluent, at least from the stripped process condensate, is high, which means that not all of the stripping effluent can be recycled back to the process. This results in a loss of carbon efficiency in the process. Different examples of stripping condensate or Fischer-Tropsch water are disclosed in WO2021175785A1 and WO2021185865A1, respectively.

[0007] The present invention seeks to address at least some of the problems associated with the prior art or at least provide a commercially acceptable alternative solution thereto. Summary of the invention

[0008] The present disclosure relates to a method for forming a liquid hydrocarbon product, the method comprising:

[0009] providing a feed gas comprising a compound of elemental carbon, hydrogen, and oxygen;

[0010] generating a synthesis gas from the feed gas, the synthesis gas comprising carbon monoxide, hydrogen and steam;

[0011] cooling the syngas to below a dew point to form a water-containing condensate and a water-depleted syngas, the water-containing condensate having carbonaceous gases dissolved therein;

[0012] passing the aqueous condensate to a first stripper and stripping the aqueous condensate with steam to transfer carbon-containing gases from the aqueous condensate to the steam, thereby forming a stripped aqueous condensate and a first stripper effluent steam;

[0013] passing the water-depleted syngas to a Fischer-Tropsch unit to form a liquid hydrocarbon product and co-produced water, the co-produced water having carbonaceous matter dissolved therein;

[0014] passing the co-produced water to a second stripper and stripping the co-produced water with the first stripper effluent steam to form stripped co-produced water and second stripper effluent steam; and

[0015] The second stripper effluent vapor is recycled to the feed gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of one embodiment of a method according to the invention is depicted.

[0017] Figure 2 A flow chart depicting another embodiment of the method according to the invention is shown. DETAILED DESCRIPTION

[0018] In a first aspect, the present disclosure relates to a method of forming a liquid hydrocarbon product, the method comprising:

[0019] providing a feed gas comprising a compound of elemental carbon, hydrogen, and oxygen;

[0020] generating a synthesis gas from the feed gas, the synthesis gas comprising carbon monoxide, hydrogen and steam;

[0021] cooling the syngas to below a dew point to form a water-containing condensate and a water-depleted syngas, the water-containing condensate having carbonaceous gases dissolved therein;

[0022] passing the aqueous condensate to a first stripper and stripping the aqueous condensate with steam to transfer carbon-containing gases from the aqueous condensate to the steam, thereby forming a stripped aqueous condensate and a first stripper effluent steam;

[0023] passing the water-depleted syngas to a Fischer-Tropsch unit to form a liquid hydrocarbon product and co-produced water, the co-produced water having carbonaceous matter dissolved therein;

[0024] passing the co-produced water to a second stripper and stripping the co-produced water with the first stripper effluent steam to transfer carbonaceous matter from the co-produced water to the first stripper effluent steam to form stripped co-produced water and second stripper effluent steam; and

[0025] The second stripper effluent vapor is recycled to the feed gas.

[0026] Unless expressly indicated to the contrary, each aspect or embodiment as defined herein may be combined with any other aspect or embodiment. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0027] Advantageously, recycling the second stripper effluent steam to the feed gas can improve the carbon efficiency of the process. In contrast to the aqueous condensate and co-produced water, the second stripper effluent steam is in gaseous form, typically at high pressure, which means that it can be reintroduced into the feed gas without requiring any significant pre-heating and / or pressurization steps. Thus, the energy efficiency of the process can be improved.

[0028] Compared with the co-produced water formed in the Fischer-Tropsch unit, the water-containing condensate tends to be relatively "clean" or pure due to the synthesis gas generation step. In other words, it tends to contain lower levels of carbonaceous gases and / or carbonaceous substances. This means that the first stripper effluent steam can be used for stripping "dirtier" or more seriously polluted co-produced water. By using the first stripper effluent steam to strip the co-produced water, the method requires less steam than the conventional method in which the water-containing condensate and the co-produced water are stripped in separate stripper units (i.e., in parallel). Therefore, compared with the conventional method, the water requirement and energy requirement of the method can be reduced. In addition, in the conventional method using "parallel" stripping, the water-containing stripper effluent steam can have a relatively low concentration of organic matter and a relatively high concentration of steam. This may mean that the water-containing stripper effluent steam is not suitable for recycling to the feed gas, especially in the absence of energy-intensive further processing steps, but must be disposed of, thereby causing waste treatment costs and causing organic matter or carbon compounds to be lost from the process. In other words, the process of the present invention enables the recycling of substantially all of the organic matter contained in both stripper effluent streams.

[0029] Compared to the alternative method in which the aqueous condensate and the co-produced water are combined and then stripped in a single stripper unit, the method of the present invention can produce a final stripper effluent steam (i.e., the second stripper effluent steam) with a higher organic concentration. This can make it more suitable for recycling to the feed gas for the synthesis gas generation step. In addition, the method of the present invention can produce two stripped products, i.e., a stripped aqueous condensate and a stripped co-produced water. This is beneficial because the stripped aqueous condensate derived from the synthesis gas generation step may be "cleaner" (having a lower chemical oxygen demand, COD) than the stripped co-produced water derived from the Fischer-Tropsch reaction. This means that the stripped aqueous condensate can be more easily processed. Therefore, the overall water treatment burden of the method can be reduced.

[0030] The process forms a liquid hydrocarbon product. As used herein, the term "liquid hydrocarbon" may encompass species formed from carbon and hydrogen that are liquid at room temperature and pressure. Hydrocarbons typically include alkanes and typically contain 5 to 30 carbon atoms per molecule. The process preferably includes: recovering the liquid hydrocarbon product.

[0031] The method comprises providing a feed gas comprising a compound of the elements carbon, hydrogen and oxygen. For the avoidance of doubt, the feed gas contains each of the elements carbon, hydrogen and oxygen. However, the compounds contained in the feed gas may contain only one, only two or all three of these elements. For example, the feed gas may contain carbon dioxide (CO2) and hydrogen (H2), and / or methane (CH4) and steam (H2O).

[0032] The method includes: generating synthesis gas from a feed gas, the synthesis gas including carbon monoxide (CO), hydrogen (H2) and steam (H2O). As discussed in more detail below, generating the synthesis gas may include, for example, a reverse water gas shift reaction and / or a steam reforming reaction and / or a partial oxidation reaction.

[0033] As used herein, the term "reverse water gas shift reaction" may encompass the reaction of carbon dioxide and hydrogen to form carbon monoxide and steam, i.e.

[0034]

[0035] As used herein, the term "steam reforming reaction" may encompass the reaction of methane and steam to form carbon monoxide and hydrogen, i.e.,

[0036]

[0037] As used herein, the term "partial oxidation" may encompass the reaction of methane and molecular oxygen to form carbon monoxide and hydrogen, i.e.,

[0038]

[0039] The method of the present invention includes: cooling the synthesis gas to below the dew point to form a water-containing condensate and a water-depleted synthesis gas. As used herein, the term "dew point" can encompass the temperature at which the gas must be cooled to reach water vapor saturation assuming constant pressure and temperature. Cooling to below the dew point results in the formation of a water-containing condensate. The water-containing condensate has a carbon-containing gas (i.e., a gas of one or more carbon-containing compounds) dissolved therein. Such carbon-containing gas may include, for example, one or more of carbon monoxide, carbon dioxide, and methane.

[0040] The method comprises: conveying the water-containing condensate to a first stripping tower and stripping the water-containing condensate with steam. As used herein, the term "stripping" may encompass a physical separation process in which one or more components are removed from a liquid stream by a vapor stream. Suitable stripping equipment is known in the art. Stripping is usually carried out in a packed tower or a plate tower, but may also be carried out in, for example, a spray tower, a bubble tower and / or a centrifugal contactor. Stripping is usually carried out at an elevated temperature and / or pressure. Suitable elevated temperatures and pressures are known in the art. Stripping can transfer carbonaceous gas from the water-containing condensate to steam, thereby forming a stripped water-containing condensate and a first stripping tower effluent steam. Stripping typically transfers most of the carbonaceous gas from the water-containing condensate to steam, more typically at least 50% by mass carbonaceous gas, more typically at least 75% by mass, even more typically at least 90% by mass, even more typically at least 95% by mass, even more typically substantially all of the carbonaceous gas.

[0041] The method also includes: sending the water-depleted syngas to a Fischer-Tropsch unit to form a liquid hydrocarbon product and co-produced water. Fischer-Tropsch units are known in the art. The Fischer-Tropsch process uses a collection of chemical reactions to convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. These reactions occur in the presence of a metal catalyst, typically at a temperature of 150°C to 300°C and a pressure of one atmosphere to several tens of atmospheres. The Fischer-Tropsch process produces a variety of hydrocarbons, ideally having the formula (C n H 2n+2 ). A more useful reaction to produce alkanes is as follows:

[0042] (2n+1)H2+nCO→C n H 2n+2 +n H2O

[0043] Where n is typically between 1 and 100.

[0044] The co-produced water formed as a result of the Fischer-Tropsch reaction has carbonaceous matter (carbonaceous compounds) dissolved therein. Such carbonaceous matter may include, for example, one or more of carbon monoxide, carbon dioxide, methane, alcohols, and carboxylic acids.

[0045] The method also includes: conveying the co-produced water to the second stripper and stripping the co-produced water with the first stripper effluent steam to transfer carbonaceous matter from the co-produced water to the first stripper effluent steam, thereby forming stripped co-produced water and the second stripper effluent steam. As discussed above, suitable stripper equipment is known in the art. The first stripper and the second stripper may be the same or different. Stripping is usually carried out at an elevated temperature and / or pressure. Stripping usually transfers most of the carbonaceous matter from the aqueous condensate to the steam, more usually at least 50% by mass of the carbonaceous matter, more usually at least 75% by mass, even more usually at least 90% by mass, even more usually at least 95% by mass, even more usually substantially all of the carbonaceous matter.

[0046] The method also includes: recycling the second stripper effluent steam to the feed gas. As discussed above, the second stripper effluent steam can be combined with the feed gas without any significant pressurization and / or heating steps due to being a high pressure gas. The carbonaceous materials (such as one or more of carbon monoxide, carbon dioxide, methane, alcohols and carboxylic acids) in the second stripper effluent steam can be converted into synthesis gas.

[0047] The generation of synthesis gas from the feed gas preferably comprises converting at least a portion of the feed gas into carbon monoxide. Usefully, the reaction for converting the feed gas into carbon monoxide uses steam. The use of steam in these reactions advantageously reduces catalyst deactivation.

[0048] Preferably, the feed gas comprises carbon dioxide and hydrogen; and converting at least a portion of the feed gas to carbon monoxide comprises subjecting the feed gas to a reverse water gas shift reaction. The reverse water gas shift reaction is particularly suitable for converting at least a portion of the feed gas to carbon monoxide. At least some of the hydrogen may remain in the synthesis gas, i.e., it is not converted to water in the reverse water gas shift reaction. This enables it to be used in a subsequent Fischer-Tropsch reaction. Since the reverse water gas shift reaction uses carbon dioxide, it can utilize carbon dioxide produced by combustion, which might otherwise be emitted to the atmosphere.

[0049] The reverse water gas shift reaction is preferably an autothermal reverse water gas shift reaction, an electrically heated reverse water gas shift reaction or a plasma heated reverse water gas shift reaction. Such reactions are particularly suitable.

[0050] The reverse water gas shift reaction is preferably carried out using a catalyst comprising nickel, more preferably wherein the catalyst comprises 3 wt % to 20 wt % nickel expressed as NiO on a refractory metal oxide support based on the total weight of the reverse water gas shift catalyst. Such catalysts may enable the reverse water gas shift reaction to be carried out at reduced temperature and / or pressure and / or in high yield and / or with high selectivity. In addition, such catalysts are active for converting carbonaceous matter in the second stripper effluent vapors into synthesis gas by steam reforming.

[0051] The reverse water gas shift reaction is preferably carried out at a temperature of at least 700° C. Such temperatures may lead to particularly high yields.

[0052] In an alternative arrangement, the feed gas comprises methane and steam; and converting at least a portion of the feed gas to carbon monoxide comprises subjecting the feed gas to a steam reforming reaction. The steam reforming reaction is particularly suitable for converting at least a portion of the feed gas to carbon monoxide.

[0053] The steam reforming reaction is preferably carried out using a catalyst comprising nickel.

[0054] Steam reforming is preferably carried out at a pressure of 15 to 55 bar and / or a temperature of 750 to 1100° C. Such conditions may lead to particularly high yields and / or selectivities.

[0055] The steam reforming reaction preferably includes one or more stages of adiabatic steam reforming, combustion steam reforming, gas heated reforming, electrically heated reforming, and autothermal steam reforming.

[0056] Preferably, the mass (or molar) ratio of steam to aqueous condensate in the first stripping column is from 0.1:1 to 0.5:1, more preferably from 0.2:1 to 0.4:1, even more preferably from 0.25:1 to 0.35:1, yet even more preferably about 0.3:1. Lower levels of steam may result in less efficient stripping. Higher levels of steam may increase the cost of the process without significantly increasing stripping efficiency.

[0057] By operating the first stripper within the above range, the mass (or molar) ratio of the first stripper effluent steam to the co-produced water in the second stripper can be 0.2: 1 to 0.6: 1, preferably 0.3: 1 to 0.5: 1, more preferably 0.35: 1 to 0.45: 1, even more preferably about 0.4: 1. Lower levels of first stripper effluent steam may result in less efficient stripping. Higher levels of first stripper effluent steam may increase the cost of the process without significantly increasing stripping efficiency.

[0058] The first stripper is preferably operated at a higher pressure than the second stripper. The first stripper is more preferably operated at a pressure of 100 kPa to 200 kPa higher than the pressure of the second stripper. This can make it easier to transfer the first stripper effluent vapor to the second stripper due to the pressure drop that may occur in the first stripper.

[0059] The first stripper and the second stripper are preferably operated at a pressure of 1500kPa to 5500kPa. Such pressures may be particularly suitable for transferring carbonaceous gases from water-containing condensates to steam and / or for transferring carbonaceous substances from co-produced water to the first stripper effluent steam. In addition, the use of such pressures causes the second stripper effluent steam to be at a pressure suitable for being incorporated into the feed gas without having to undergo a significant pressurization step, which will reduce the energy efficiency of the method. When using the reverse water gas shift reaction to produce synthesis gas, a lower pressure is preferably used, such as 1500kPa to 3000kPa. When using the steam reforming reaction to produce synthesis gas, a higher pressure is preferably used, such as 3000kPa to 5500kPa.

[0060] The method may further comprise: conveying the stripped aqueous condensate to a demineralized water plant to produce water for use in generating steam. Since the stripped aqueous condensate tends to be relatively "clean", it may be conveyed to the demineralized water plant without any substantial pretreatment steps. The generated steam is preferably used in the first stripping column or for heat exchange with components of the feed gas or for heat exchange within a Fischer-Tropsch unit.

[0061] The method may further comprise: conveying the stripped co-produced water to a water treatment unit to produce a water effluent stream. Such a water effluent stream may be sufficiently "clean" for subsequent treatment.

[0062] The carbonaceous gas dissolved in the aqueous condensate and / or the carbonaceous material dissolved in the co-produced water preferably comprises carbon dioxide and / or carbon monoxide and / or organic compounds (e.g., water-soluble organic compounds). It may be beneficial to recycle such species in the second stripper effluent steam, as such species may be employed in the synthesis gas generation step. For example, such species are typically converted to synthesis gas in a reverse water gas shift unit or a steam reformer unit.

[0063] The molar ratio of hydrogen to carbon monoxide in the water-depleted synthesis gas is preferably from 1.8 to 2.2. Such a ratio is particularly suitable for the subsequent Fischer-Tropsch reaction.

[0064] The Fischer-Tropsch unit is preferably operated at a temperature of 150° C. to 300° C. Lower temperatures may result in the production of disadvantageously low levels of liquid hydrocarbons. Higher temperatures may increase the energy cost of the process without significantly increasing the level of liquid hydrocarbons produced, and may increase the formation of undesirable by-products.

[0065] The Fischer-Tropsch unit preferably comprises a catalyst comprising cobalt, iron and / or ruthenium, preferably cobalt. Such catalysts may be particularly effective in catalysing the Fischer-Tropsch reaction and / or allow the reaction to proceed advantageously at low temperatures to produce alkanes and / or to proceed advantageously in high yields.

[0066] The liquid hydrocarbon product preferably comprises alkanes.Alkanes may be particularly desirable products.

[0067] One or more of the compounds in the feed gas may originate from the gasification of biomass and / or municipal waste.

[0068] In a preferred embodiment, the second stripper effluent steam can be directly recycled to the feed gas. In other words, the second stripper effluent steam can be recycled to the feed gas without any substantial further processing steps. In an alternative preferred embodiment, before the second stripper effluent steam is recycled to the feed gas, the second stripper effluent steam can be sent to a reverse enrichment reactor to convert the hydrocarbons with two or more carbon atoms contained in the second stripper effluent steam into methane. Methane can be more easily converted to carbon monoxide in the synthesis gas generation step.

[0069] The invention will now be described with reference to the accompanying drawings. It will be appreciated by those skilled in the art that the drawings are illustrative and that other equipment items may be required in a commercial device, such as feedstock barrels, pumps, vacuum pumps, compressors, gas recycle compressors, temperature sensors, pressure sensors, pressure relief valves, control valves, flow controllers, level controllers, collection tanks, storage tanks, etc.

[0070] refer to Figure 1, a water-containing process condensate stream 10 recovered from a synthesis gas generation unit (not shown) is first heated by exchanging with the process condensate stripper bottoms from line 14 in a heat exchanger 12 and fed to the top of a first stripper 18 via line 16. The first stripper contains structured packing to enhance the removal of dissolved gases from the water-containing process condensate. The heated process condensate passes downwardly through the first stripper 18, where it is contacted with high-pressure steam fed to the bottom of the first stripper via line 20. The high-pressure steam strips carbonaceous gases from the heated process condensate. The stripped liquid process condensate stream 14 recovered from the bottom of the first stripper 18 is first cooled by exchanging with the first stripper feed in a heat exchanger 12 and then cooling against cooling water or air in one or more additional heat exchangers 22 for output to a water treatment unit (not shown). The stripped aqueous condensate can be fed to a demineralized water unit for purification and use in the process. The first stripper effluent steam is recovered from the top of the first stripper 18 and fed to the bottom of the second stripper 26 via line 24. The Fischer-Tropsch co-produced water stream from the Fischer-Tropsch synthesis unit (not shown) fed via line 28 is first heated by exchanging with the second stripper bottoms from line 32 in a heat exchanger 30 and fed to the top of the second stripper 26 via line 34. The bypass 36 around the heat exchanger 30 is used to control the inlet temperature of the second stripper 26. The second stripper contains structured packing to enhance the removal of dissolved substances from the co-produced water. The heated co-produced water passes downward through the second stripper 26, where it contacts the first stripper effluent steam fed via line 24. The first stripper effluent steam strips carbonaceous substances from the co-produced water. The stripped co-produced water stream 32 is first cooled by exchange with the second stripper feed in heat exchanger 30 and then cooled against cooling water or air cooling in one or more additional heat exchangers 38 for output to a water treatment unit (not shown) for further purification. The second stripper effluent steam containing carbonaceous materials is recovered from the top of the second stripper 26 and fed to a syngas generation unit (not shown) via line 40 for recycling to the syngas generation unit feed gas.

[0071] refer to Figure 2 , showing the Figure 1 However, in Figure 2In the embodiment of the present invention, bypass 36 is omitted and a heat exchanger 50 and a gas-liquid separator 52 are used to condense a portion of the second stripper effluent vapor and separate the stripper effluent condensate, which is returned to the vicinity of the top of the second stripper 26 by a pump via line 54. The remaining second stripper effluent vapor is recovered from the gas-liquid separator 52 and fed to a syngas generation unit (not shown) via line 56 for recycling to the syngas generation unit feed gas.

[0072] The process according to the invention allows a higher recovery of carbonaceous materials from an aqueous stream compared to alternative processes using a single stripping column or two stripping columns operating in parallel.

[0073] The invention will now be described with reference to the following non-limiting Examples and Comparative Examples.

[0074] Example

[0075] according to Figure 1 The method is designed to provide a steam stream to a reverse enrichment vessel in an upstream synthesis gas generation unit. In the synthesis gas generation unit, the reverse enrichment vessel provides a feed comprising carbon dioxide, hydrogen and methane to an autothermal reverse water gas shift reactor (rWGS unit) operating at about 30 bar, which provides a synthesis gas comprising carbon monoxide and hydrogen after separation of a water-containing condensate for use in a Fischer-Tropsch synthesis reaction to produce liquid hydrocarbons. The Fischer-Tropsch reaction produces a co-produced water stream as a by-product.

[0076] The steam to aqueous condensate ratio for the first stripper is 0.3:1. Applicants have found that it is beneficial to maximize the steam carryover from the first stripper because this both reduces the chemical oxygen demand (COD) of the stripped aqueous condensate, thereby reducing water treatment requirements, and has a diluting effect on contaminants in the stripped Fischer-Tropsch co-produced water stream. This can be achieved by maximizing the heat transferred in the heat exchanger 12 using a small hot end temperature approach (e.g., about 35°C). The outlet temperature of the heat exchanger 30 (which sets the co-produced water temperature entering the second stripper) is adjusted so that the overhead distillate rate from the second stripper is equal to about 90% of the steam addition required upstream of the de-enrichment vessel. This allows 10% of steam to be added directly to the de-enrichment vessel for additional controllability. Typical specifications for the crude aqueous condensate stream are:

[0077]

[0078] Typical specifications for the crude co-product water stream are:

[0079]

[0080] Using high pressure steam provided by the rWGS unit at 50 bar saturated steam, a steam to condensate ratio of 0.3:1 entering the first stripper and an inlet aqueous condensate temperature of 200°C (equivalent to nearly 35°C in the heat exchanger) resulted in a co-produced water inlet temperature of 145°C (equivalent to nearly 90°C) to the second stripper in order to obtain a suitable amount of steam for the de-enrichment vessel. This resulted in the following with respect to aqueous condensate, co-produced water and process carbon efficiency (compared to not recovering any carbon from the condensate stream via stripping):

[0081] COD reduction of aqueous condensate 95％ Increased water condensate flow 9％ Reduction of COD in produced water 86％ Increase in produced water flow 21％ Improved carbon efficiency 1％

[0082] Comparative Example

[0083] By comparison, to illustrate the improvement of the present invention in allowing integration with the same rWGS unit, the stripping may alternatively be performed in two parallel stripping columns. The heat in both heat exchangers is set to 35°C to minimize steam addition, and the steam to condensate ratio of each column is adjusted to achieve similar COD reduction results (compared to not recovering any carbon from the condensate stream by stripping):

[0084] COD reduction of aqueous condensate 95％ Increased water condensate flow 8％ Reduction of COD in produced water 85％ Increase in the flow of produced water 7％ Improved carbon efficiency 0.9％ Stripping condensed steam (as % of co-produced water flow) 45％

[0085] The overhead of the co-produced water stripper contains most of the organic compounds, so the loss in carbon efficiency is only slight. However, the total overhead steam produced from the two strippers is 370% of the process requirement, which means that the remaining portion of the steam will need to be condensed and sent to water treatment. Therefore, the use of steam, energy and carbon is much less efficient than the present invention. In addition, considering that the stripping duty of the first tower is much lighter than that of the second tower, the two-stage series arrangement effectively allows the same steam to be used for both strippers.

[0086] The above detailed description has been provided by way of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to those of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A method for forming a liquid hydrocarbon product, the method comprising: providing a feed gas comprising a compound of elemental carbon, hydrogen, and oxygen; generating a synthesis gas from the feed gas, the synthesis gas comprising carbon monoxide, hydrogen and steam; cooling the syngas to below a dew point to form a water-containing condensate and a water-depleted syngas, the water-containing condensate having carbon-containing gases dissolved therein; passing the aqueous condensate to a first stripper and stripping the aqueous condensate with steam to transfer the carbon-containing gas from the aqueous condensate to the steam, thereby forming a stripped aqueous condensate and a first stripper effluent steam; passing the water-depleted syngas to a Fischer-Tropsch unit to form a liquid hydrocarbon product and co-produced water, the co-produced water having carbonaceous matter dissolved therein; passing the co-produced water to a second stripper and stripping the co-produced water with the first stripper effluent steam to transfer carbonaceous matter from the co-produced water to the first stripper effluent steam to form stripped co-produced water and second stripper effluent steam; and The second stripper effluent vapor is recycled to the feed gas.

2. The method of claim 1, wherein generating synthesis gas from the feed gas comprises: At least a portion of the feed gas is converted to carbon monoxide.

3. The method according to claim 2, wherein: The feed gas comprises carbon dioxide and hydrogen; and Converting at least a portion of the feed gas to carbon monoxide includes subjecting the feed gas to a reverse water gas shift reaction.

4. The method according to claim 3, wherein the reverse water-gas shift reaction is an autothermal reverse water-gas shift reaction, an electrically heated reverse water-gas shift reaction, or a plasma heated reverse water-gas shift reaction.

5. A method according to claim 3 or claim 4, wherein the reverse water gas shift reaction is carried out using a catalyst comprising nickel, preferably wherein the reverse water gas shift catalyst comprises 3 wt % to 20 wt % nickel expressed as NiO on a refractory metal oxide support, based on the total weight of the reverse water gas shift catalyst.

6. The process according to any one of claims 3 to 5, wherein the reverse water gas shift reaction is carried out at a temperature of at least 700°C.

7. The method according to claim 2, wherein: The feed gas comprises methane and steam; and Converting at least a portion of the feed gas to carbon monoxide includes subjecting the feed gas to a steam reforming reaction.

8. The method of claim 7, wherein the steam reforming reaction is performed using a catalyst comprising nickel.

9. A method according to claim 7 or claim 8, wherein the steam reforming is carried out at a pressure of 15 to 55 bar and / or a temperature of 750°C to 1100°C.

10. The method according to any one of claims 7 to 9, wherein the steam reforming reaction comprises one or more stages of adiabatic steam reforming, combustion steam reforming, gas heated reforming, electric heated reforming and autothermal steam reforming.

11. The process according to any preceding claim, wherein the mass ratio of steam to aqueous condensate in the first stripping column is from 0.1:1 to 0.5:1, preferably from 0.2:1 to 0.4:1, more preferably from 0.25:1 to 0.35:1, even more preferably about 0.3:

1.

12. The process according to any preceding claim, wherein the mass ratio of the first stripper effluent to the co-produced water in the second stripper is from 0.2:1 to 0.6:1, preferably from 0.3:1 to 0.5:1, more preferably from 0.35:1 to 0.45:1, even more preferably about 0.4:

1.

13. The process according to any preceding claim, wherein the first stripping column is operated at a higher pressure than the second stripping column.

14. The method of claim 13, wherein the first stripping column is operated at a pressure 100 kPa to 200 kPa higher than the pressure of the second stripping column.

15. The process according to any preceding claim, wherein the first stripping column and the second stripping column are operated at a pressure of 1500 kPa to 5500 kPa.

16. The method according to any preceding claim, further comprising: The stripped aqueous condensate is conveyed to a demineralized water plant to produce water for use in producing steam, preferably wherein the steam is used in the first stripping column.

17. The method according to any preceding claim, further comprising: The stripped co-produced water is passed to a water treatment unit to produce a water effluent stream.

18. A method according to any preceding claim, wherein the carbonaceous gas dissolved in the aqueous condensate and / or the carbonaceous matter dissolved in the co-produced water comprises carbon dioxide and / or carbon monoxide and / or water-soluble organic compounds.

19. A process according to any preceding claim, wherein the molar ratio of hydrogen to carbon monoxide in the water-depleted synthesis gas is from 1.8 to 2.

2.

20. A method according to any preceding claim, wherein the Fischer-Tropsch unit is operated at a temperature of from 150°C to 300°C.

21. A method according to any preceding claim, wherein the Fischer-Tropsch unit comprises a catalyst comprising cobalt, iron and / or ruthenium, preferably cobalt.

22. A process according to any preceding claim, wherein the liquid hydrocarbon product comprises alkanes.

23. A process according to any preceding claim, wherein one or more of the compounds in the feed gas originates from the gasification of biomass and / or municipal waste.

24. The process according to any preceding claim, wherein the second stripper effluent steam is passed to a reverse enrichment reactor to convert hydrocarbons contained in the second stripper effluent steam into methane before recycling the second stripper effluent steam to the feed gas.

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