Shell’s gas-to-liquids (GTL) technology converts natural gas into high-quality liquid products that would otherwise be made from crude oil. These products include transportation fuels (such as aviation fuel and diesel), motor oils, process oils, and the ingredients for everyday necessities like detergents and cosmetics.(1) GTL products are colorless, odorless, and contain almost none of the impurities like sulfur, aromatics, and nitrogen containing compounds that are found in crude oil. There is a high flexibility in the product slate, viz. types and amounts of fuels and nonfuel products that can be made using GTL technology. The current GTL process consists of the following steps: (1) converting natural gas into synthesis gas, i.e., mixture of carbon monoxide (CO) and hydrogen (H₂); (2) Fischer–Tropsch synthesis, i.e., conversion of synthesis gas into highly paraffinic wax; and (3) upgrading of Fischer–Tropsch wax into final hydrocarbon products in a hydroprocessing step or steps, which can include hydrocracking, hydro-isomerization, and/or hydrogenation.(2,3) As the world transitions to a lower-carbon energy system, GTL technology could be an enabler for making a variety of low-carbon products (such as low-carbon aviation fuel, low-carbon diesel for heavy-duty transportation, chemicals, and specialties with low carbon intensity) by replacing (a part of) the hydrocarbon feedstock with the (intermittent) renewable H₂ and carbon dioxide (CO₂) as feedstock (Figure 1). This mixture, converted to synthesis gas, can be subsequently introduced into Fischer–Tropsch synthesis (going through steps 2 and 3 of the conventional GTL process).(4,5) Sources of CO₂ could include CO₂-rich off gas from internal recycles, concentrated point sources (e.g., from cement, steel, fertilizer, or fermentation plants), or direct air capture (DAC).(5−7) Technology building blocks for the conversion of CO₂ to CO can include CO₂ electrolysis (CO₂ → CO + 0.5O₂), reverse water gas shift (CO₂ + H₂ → CO + H₂O), all-electric thermochemical redox conversion of CO₂ and water to syngas, dry reforming (CH₄ + CO₂ → 2CO + 2H₂), and methanation (CO₂ + 4H₂ → CH₄ + 2H₂O) followed by the partial oxidation of methane (CH₄ + 0.5O₂ → CO + 2H₂).(5,8−11) Figure 1. Schematic of a future gas-to-liquids–power-to-liquids (GTL–PTL) process comprising H₂O and CO₂ electrolyzers integrated with conventional Fischer–Tropsch synthesis. Depending on the availability of intermittent renewable power, H₂, and CO, the natural gas feed can be dialed up or down yielding a hybrid GTL–PTL process. Renewable H₂ and CO₂ could be used as the only feedstocks to the process, which will be termed PTL (power-to-liquids) throughout this Viewpoint, or they can be coprocessed along with a natural gas feed in a so-called “hybrid” GTL–PTL process. In such a hybrid, or coprocessing, approach, (intermittent) renewable H₂ is utilized as much as possible during the times when renewable power is available (such as during the day for solar power and during periods of high wind intensity for wind power, while natural gas is utilized as much as possible during the times when renewable power is not available, like in conventional GTL). This approach reduces the need for costly electricity storage in batteries or as H₂ and CO, which is required for PTL. Natural gas becomes a way of addressing the intermittency of renewables in hybrid GTL. Compared to PTL, the renewable element of a hybrid GTL plant is much more flexible, bringing such concepts closer to commercialization and fitting in well with intermittent renewable power or H₂. In this Viewpoint we focus on the integration of the CO₂ electrolysis block (an emerging technology option) into PTL and hybrid GTL–PTL lineups. Starting with the early seminal work of Hori et al. in the 1980s and 1990s,(9) the electrolysis of CO₂ (low-temperature membraneless, anion or cation exchange polymer membrane-based, or high-temperature solid oxide-based) to molecules such as CO, formic acid, ethylene, and ethanol has received significant research interest.(12) In particular the electrolysis of CO₂ to CO has recently come of age through the work of several startups and electrolyzer companies (Opus 12, Dioxide Materials, Air Company, Sunfire, Lectrolyst, Siemens, Haldor Topsoe, Avantium, etc.) improving its technological readiness level (TRL) from 1 to 3 (per the API 17 N scale).(10,13,14) However, further improvement of the TRLs of CO₂ to CO electrolysis to 4 and beyond will require the design and testing of scaled systems integrated with both upstream CO₂ capture units and downstream syngas processing unit such as GTL. While some early work on the topic of integrating CO₂ electrolysis into process flow schemes (as the basis for preliminary techno-economic analysis) are available,(7,8,15−18) they can be nontrivial for real-world industrial (brownfield or greenfield) implementation, thus serving as the focus of this work. The electrolysis of CO₂ to CO can be integrated into a GTL–PTL process scheme in several ways (Figures 2 and 3). To minimize process upsets, maximize the carbon efficiency as well as energy efficiency, and minimize capital costs, techniques/design rules to handle intermittency, recycle off-gases, prevent inert (N₂, argon) buildup, and utility (heat/steam) integration with the exothermic Fischer–Tropsch (FT) synthesis need to be considered. There are three types of off-gases in a GTL–PTL process, coming from (1) FT synthesis containing unconverted CO and H₂ from syngas, light hydrocarbons (C₄ minus), and CO₂; (2) the products upgrading section containing light (C₄ minus) saturated hydrocarbons (paraffins); and (3) flue gas obtained when natural gas or off-gas is used as fuel gas for utilities resulting in a CO₂-rich stream. Figure 2. Power-to-liquids (PTL) process scheme based on low-temperature CO₂ electrolysis and Fischer–Tropsch (FT) synthesis representing (a) an option to recycle the off-gases using an oxy-combustion (oxy-burner) unit or solid oxide fuel cell and (b) an option to recycle the off gases using a gasifier (here denoted by the Shell gasification process, i.e., SGP). Blocks in dashed red show optional blocks required to handle intermittency and enable a continuous production facility. “S” block represents the unit operation (e.g., amine scrubbing, hydroxide scrubbing, membranes, pressure swing adsorption, etc.) required to remove the excess CO₂ from the CO₂ electrolyzer cathode exhaust. Note that HC in the off-gas denotes hydrocarbons. For inerts rejection (“bleed”) and CO recovery, a CO-PSA (carbon monoxide PSA) can be used. Similar integration schemes can be considered for the high-temperature coelectrolysis of CO₂ and H₂O in solid oxide electrolyzers with the additional input or recycle (from exothermic Fischer–Tropsch synthesis and/or exothermic SGP) of steam being required. Variations of the process scheme can also include CO₂ being fed to the CO₂ electrolyzer as loaded onto a solvent in the form of carbonate, bicarbonate, or carbamate. In such a scheme, the CO₂ is regenerated in situ in the CO₂ electrolyzer followed by conversion to CO and the lean solvent being recycled back to the CO₂ capture step. Figure 3. Hybrid GTL–PTL lineups based on low temperature CO₂ electrolysis and FT synthesis representing (a) an option to recycle the off-gases using an oxy-combustion (oxy-burner) unit or solid oxide fuel cell and (b) an option to recycle the off-gases using a gasifier (here denoted by the Shell gasification process, i.e., SGP). Overall scheme coprocesses renewable feed (renewable power, CO₂, and H₂O) and fossil (natural gas) feed to address intermittency and storage issues. Blocks in dashed red show optional blocks required to handle intermittency and enable a continuous production facility. “S” block represents the unit operation (e.g., amine scrubbing, hydroxide scrubbing, membranes, pressure swing adsorption, etc.) required to remove the excess CO₂. For inerts rejection (“bleed”) and CO recovery, a CO-PSA (carbon monoxide PSA) can be used. Note that HC in the off-gas denotes hydrocarbons. Similar integration schemes can be considered for the high-temperature coelectrolysis of CO₂ and H₂O in solid oxide electrolyzers with the additional input or recycle (from exothermic Fischer–Tropsch synthesis or exothermic SGP) of steam being required. Oxygen from the CO₂ electrolyzer can be sent to the liquid O₂ storage, similar to O₂ from water electrolyzer. Battery storage can be used along with, or instead of H₂ storage, to power water electrolyzer as well as CO₂ electrolyzer. Variations of the process scheme can also include CO₂ being fed to the CO₂ electrolyzer as loaded onto a solvent in the form of carbonate, bicarbonate, or carbamate. In such a scheme, the CO₂ is regenerated in situ in the CO₂ electrolyzer followed by conversion to CO and the lean solvent being recycled back to the CO₂ capture step. In PTL process schemes (Figure 2), intermittent renewable power (solar or wind) can be used to drive CO₂ and H₂O electrolysis, producing CO and H₂. The CO₂ feed can be sourced from the air using a DAC unit or from point sources. Delivery of the CO₂ feed to the electrolyzer can be in two forms, i.e., either (i) as a gas wherein CO₂ is first captured using a solid sorbent or a liquid solvent, regenerated thermally or electrochemically,(19,20) and then fed to the electrolyzer for conversion to CO, or (ii) as loaded onto a liquid solvent in the form of bicarbonate, carbonate, carbamates, etc., which is then fed to the electrolyzer for in situ regeneration of the CO₂ followed by conversion to CO.(21−23) However, given CO₂ is the reacting species for electrolysis to CO,(24) it is still unclear whether this single-electrolyzer concept will be advantageous over a separate CO₂ regeneration step followed by a separate conversion step from a capital cost perspective. Consider CO₂ regeneration is rate-limiting for the direct reduction of bicarbonate/carbonate electrolytes; hence, for a combined process, one will need a large (and expensive as catalyst coated) electrolyzer for CO production instead of a large regeneration (electrodialysis) unit plus a small electrolyzer for a two-step process. Hence, to simplify the scope of the discussion in this Viewpoint, we describe integration schemes assuming the CO₂ delivered to the electrolyzer is in the form of a gas. To allow for the continuous operation of the PTL process, i.e., when solar or wind electricity is unavailable, battery storage, CO₂ storage, H₂ storage, and/or CO storage might be needed. To increase the overall efficiency, unconverted CO₂ from the outlet of the CO₂ electrolysis can be separated from the CO stream (as indicated by block “s” in Figure 2) by means of amine scrubbing, hydroxide scrubbing, membranes, pressure swing adsorption (PSA), or other separation technology blocks, and recycled back to the inlet of the CO₂ electrolyzer. Off-gas from FT synthesis and the products upgrading section can be burnt thermochemically in an oxy-burner or electrochemically in a solid oxide fuel cell (SOFC) for higher efficiency, with the resulting CO₂ routed to the CO₂ electrolyzer inlet and the power generated being used to run the H₂O electrolyzer, CO₂ electrolyzer, DAC unit, and/or charging batteries (Figure 2a). O₂ for oxy-combustion can be supplied from the anode of the H₂O electrolyzer and/or CO₂ electrolyzer. For anion exchange membrane-based low-temperature CO₂ electrolyzers producing mixed streams of CO₂ and O₂ at the anode,(25) the anode exhaust can be fed to the oxy-combustion unit, generating clean CO₂ streams which can then be recycled back to the CO₂ electrolyzer inlet and thus avoiding safety issues related to the handling of pure O₂. Another option for recycling off-gases from the FT synthesis or products upgrading section would be to first separate the CO₂ and recycle to the CO₂ electrolyzer while routing the remaining hydrocarbon stream to a gasification unit (here denoted by SGP or Shell gasification process)(26) to make more synthesis gas (CO + H₂) as shown in Figure 2b. Note that it is highly likely that the off-gas from the FT unit would require a bleed or a separation unit such as pressure swing adsorption (PSA) before recycle to prevent the buildup of inerts such as N₂ (potentially coming from DAC or leakages) in the overall process. For energy integration, the heat or steam produced in the exothermic FT synthesis can be used to supply heat/steam or power to the H₂O electrolyzer, CO₂ electrolyzer, CO₂ capture unit, and separation units and/or for charging batteries. Similar integration can be considered with the high-temperature coelectrolysis of CO₂ and H₂O in SOECs with the additional input of steam being required, which can be recycled from the exothermic FT synthesis and/or exothermic gasification process (SGP) or renewably generated using electric steam generators. In contrast, for hybrid GTL–PTL process schemes (Figure 3), renewable feed (electrons as well as CO₂ and H₂O), whenever available (during the day for solar or during periods of high wind intensity for wind power), is coprocessed with fossil natural gas feed to handle intermittency as well as run through periods of low renewable power availability. In such a scheme, the CO₂ and H₂O electrolyzers operate in sync (intermittently) on renewable power without the need for expensive large-scale batteries, producing CO and H₂. Meanwhile, the fossil natural gas-based GTL process operates 24/7 with the electrolyzers supplying the additional CO and H₂ whenever they are produced. As a result, compared to PTL schemes, extra syngas (CO/H₂) storage could be downsized or completely avoided, which also translates to lower overcapacity of renewable power generation and smaller scale of CO₂ electrolyzer and water electrolyzer, all of which can reduce capital investment. Similar to the PTL schemes, unconverted CO₂ from the outlet of the CO₂ electrolyzer can be separated from the CO stream and recycled back to its inlet. Off-gas from FT synthesis and the products upgrading section can be burnt thermochemically in an oxy-burner or electrochemically in a SOFC for power with the resulting CO₂ routed to the CO₂ electrolyzer (Figure 3a) or recycled to the gasification unit to make CO and H₂ after first separating the excess CO₂ (Figure 3b). O₂ for oxy-combustion or gasification can be optionally supplied from the anode of the H₂O electrolyzer and/or CO₂ electrolyzer. Also, the extra O₂ available from the H₂O and CO₂ electrolyzers could be sent to available liquid oxygen storage, thereby downsizing the air separation unit compared to a conventional GTL lineup. To avoid buildup of N₂ or argon (coming from the air separation unit (ASU), direct air capture (DAC), or natural gas feed) in the process, the off-gas from the FT unit will likely require a bleed stream or a separation unit (such as a PSA) to remove the excess inerts before recycling. Also similar to PTL lineups, heat and/or steam from the exothermic FT synthesis or gasification can be used for supplying heat/steam or power to the H₂O electrolyzer, CO₂ electrolyzer, CO₂ capture unit, direct air capture (DAC) unit, or separation units. Similar integration schemes can be considered with the high-temperature coelectrolysis of CO₂ and H₂O in SOECs with the additional input of steam being required, which can be recycled from the exothermic FT synthesis and/or gasification section or renewably generated using electric steam generators. In summary, although much progress has been made in the field of CO₂ electrolysis to progress the technology from TRL 1 to 3, process integration strategies such as the PTL and hybrid GTL–PTL archetype lineups described in this work will be critical toward maturing it beyond TRL 4, thus making the technology a credible option to enable the energy transition. Also, as shown in this work, design rules to minimize process upsets, maximize the carbon as well as energy efficiency, minimize capital costs, handle intermittency, recycle off-gases, and prevent inerts buildup need to be incorporated. As next steps, further plant-level optimization of the process schemes proposed in this work will be needed to select the most credible option(s) and optimally size the equipment. This should be followed by demonstration activities at a relevant (kilowatt or megawatt) scale to further derisk the technology in a real-world setting. Views expressed in this Viewpoint are those of the authors and not necessarily the views of the ACS. The authors declare the following competing financial interest(s): The authors are employed by Shell. This work is related to the field of GTL (gas-to-liquids) technology within Shell. The authors gratefully acknowledge Dr. HP Calis, Dr. Albert Harvey, Dr. Clara F. Heuberger, Dr. Fu Xiao, Dr. Abhinav Verma, Marco Smaling, Dr. Ronald Wolf, Dr. Esther van Soest-Vercammen, Robert Schouwenaar, and Dr. Paul Corbett for their critical review of the manuscript. This article references 26 other publications.

中文翻译：

---

将CO ₂电解整合到气-液-电-液工艺中

壳牌的天然气制油（GTL）技术将天然气转化为高质量的液体产品，而这些产品原本是由原油制成的。这些产品包括运输燃料（例如航空燃料和柴油），机油，加工油以及清洁剂和化妆品等日常必需品的成分。（1）GTL产品是无色无味的，几乎不含诸如硫的杂质原油中发现的芳烃，芳烃和含氮化合物。产品板岩具有高度的灵活性，即。可使用GTL技术制造的燃料和非燃料产品的类型和数量。当前的GTL工艺包括以下步骤：（1）将天然气转化为合成气，即一氧化碳（CO）和氢气（H ₂）; （2）费-托合成，即将合成气转化为高度链烷烃的蜡；（3）随着世界过渡到低碳能源，在一个或多个加氢处理步骤中将费托蜡升级为最终烃产品，其中包括加氢裂化，加氢异构化和/或加氢。（2,3）系统中，GTL技术可以通过替换（一部分）来制造各种低碳产品（例如低碳航空燃料，用于重型运输的低碳柴油，化学品和低碳强度的特种产品） （间歇）可再生H ₂和二氧化碳（CO ₂）作为原料（图1）。转化为合成气的混合物可以随后引入费托合成（通过常规GTL工艺的步骤2和3）。（4,5）CO _2的来源可能包括来自内部的富含CO _2的废气回收，集中点源（例如，来自水泥，钢铁，化肥或发酵厂的）或直接空气捕获（DAC）。（5-7）将CO ₂转化为CO的技术基石可以包括CO ₂电解（ CO ₂ →CO + 0.5O ₂），水煤气变换（CO ₂ + H ₂ →CO + H ₂ O），CO _2的全电热化学氧化还原和水制合成气，干重整（CH ₄ + CO ₂ →2CO + 2H ₂）和甲烷化（CO ₂ + 4H ₂ →CH ₄ + 2H ₂ O），然后甲烷部分氧化（CH ₄ + 0.5O ₂ →CO + 2H ₂）。（5,8-11）图1.未来的气-液-动力-液（GTL-PTL）工艺示意图，该工艺包括与传统的Fischer集成的H ₂ O和CO ₂电解槽–合成。取决于间歇性可再生能源的可用性，H ₂以及CO，可以向上或向下拨入天然气原料，以产生GTL-PTL混合工艺。可再生的H ₂和CO ₂可以用作该过程的唯一原料，在此观点中将被称为PTL（动力至液体），也可以将它们与天然气原料一起在所谓的“混合” GTL-PTL过程。在这种混合或协同处理方法中，（间歇）可再生H ₂在可再生能源可用的时候（例如白天用于太阳能和风力高风强度的时期）尽可能多地利用天然气，而在可再生能源被利用的时候尽可能多地利用天然气。不可用，就像常规GTL中一样）。这种方法减少了对电池或以PTL所需的H ₂和CO进行昂贵的电存储的需求。天然气成为解决混合GTL中可再生能源间歇性的一种方式。与PTL相比，混合GTL工厂的可再生能源要灵活得多，这使这种概念更接近于商业化并与间歇性可再生能源或H ₂很好地契合。在这种观点下，我们专注于CO ₂的整合电解块（一种新兴的技术选择）进入PTL和混合GTL-PTL阵容。从Hori等人的早期开创性工作开始。在1980年代和1990年代，（9）将CO ₂（基于低温无膜，基于阴离子或阳离子交换聚合物的膜，或基于高温固体氧化物的电解）电解成诸如CO，甲酸，乙烯和乙醇受到了广泛的研究兴趣。（12）尤其是CO ₂的电解通过几家初创公司和电解器公司（Opus 12，Dioxide Materials，Air Company，Sunfire，Lectrolyst，Siemens，Haldor Topsoe，Avantium等）的合作，CO的发展已成熟，其技术准备水平（TRL）从1到3（按API 17 N等级）。（10,13,14）但是，将CO ₂到CO电解的TRL进一步提高到4甚至更高，将需要设计和测试与两个上游CO ₂集成在一起的规模化系统捕集单元和下游合成气处理单元（例如GTL）。虽然有关整合CO _2的一些早期工作可以电解成工艺流程方案（作为初步技术经济分析的基础）（7、8、15-18），对于现实世界中的工业（棕地或绿地）实施来说，它们可能是不平凡的，因此成为这项工作。可以通过几种方式将CO ₂电解为CO集成到GTL-PTL工艺方案中（图2和3）。为了最大程度地减少工艺问题，最大程度地提高碳效率和能源效率，最小化资本成本，处理间歇性，回收废气，防止惰性（N ₂，氩气的积累，以及与放热费托合成（FT）合成的效用（热/蒸汽）集成。有三种类型的尾气在GTL-PTL过程中，从（1）FT合成含未转化的CO和H未来₂从合成气，轻质烃（C ₄负），和CO ₂ ; （2）产品升级区，含轻（C ₄减）饱和烃（链烷烃）；（3）当将天然气或废气用作公用事业的燃料气体时产生的烟道气，产生富CO _2的物流。图2.基于低温CO ₂的液体动力（PTL）处理方案电解和费-托（FT）合成代表（a）使用氧燃烧（氧气燃烧器）单元或固体氧化物燃料电池再循环废气的选项，以及（b）使用a再循环废气的选项气化炉（此处由壳牌气化工艺表示，即SGP）。红色虚线框显示处理间断并启用连续生产设施所需的可选框。“ S”块代表从CO _2中去除多余的CO ₂所需的单元操作（例如，胺洗涤，氢氧化物洗涤，膜，变压吸附等）电解阴极废气。注意，废气中的HC表示烃。为了防止惰性气体（“渗出”）和回收CO，可以使用CO-PSA（一氧化碳PSA）。对于固态氧化物电解槽中的CO ₂和H ₂ O的高温共电解，可以考虑采用类似的集成方案，并需要额外的输入或蒸汽循环（来自费托合成和/或SGP放热）。处理方案的变化也可以包括CO ₂被供给至CO ₂电解槽如装载到在碳酸盐，碳酸氢盐，或氨基甲酸酯的形式的溶剂。在这样的方案中，CO ₂被再生原位中的CO ₂电解槽，然后转化为CO，将稀溶剂循环回CO ₂捕集步骤。图3.基于低温CO ₂电解和FT合成的混合GTL–PTL阵容，表示（a）使用氧气燃烧（氧气燃烧器）单元或固体氧化物燃料电池再循环废气的选项，以及（b）使用气化炉（此处用壳牌气化工艺，即SGP表示）再循环废气的选择。总体方案共处理可再生饲料（可再生能源，CO ₂和H ₂O）和化石（天然气）饲料来解决间歇性和存储问题。红色虚线框显示处理间歇性和启用连续生产设施所需的可选框。“ S”方框代表去除过量CO ₂所需的单元操作（例如，胺洗涤，氢氧化物洗涤，膜，变压吸附等）。为了防止惰性气体（“渗出”）和回收CO，可以使用CO-PSA（一氧化碳PSA）。注意，废气中的HC表示烃。对于CO ₂和H _2的高温共电解，可以考虑类似的集成方案固体氧化物电解槽中的O需要额外的蒸汽输入或循环（通过费托合成或SGP放热）。与来自水电解槽的O ₂相似，可以将来自CO ₂电解槽的氧气发送到液体O ₂存储器。电池储存器可以与H ₂储存器一起使用或代替H ₂储存器使用，以为水电解槽以及CO ₂电解槽供电。处理方案的变化也可以包括CO ₂被供给至CO ₂电解槽如装载到在碳酸盐，碳酸氢盐，或氨基甲酸酯的形式的溶剂。在这样的方案中，CO ₂被再生原位中的CO ₂电解槽，然后转化为CO，将稀溶剂循环回CO ₂捕集步骤。在PTL工艺方案（图2）中，间歇性可再生能源（太阳能或风能）可用于驱动CO ₂和H ₂ O电解，产生CO和H ₂。可以使用DAC单元从空气中或从点源中获取CO ₂进料。将CO ₂进料输送到电解器可以采用两种形式，即（i）作为气体，其中CO ₂首先使用固体吸附剂或液体溶剂捕获，通过热或电化学方式进行回收（19,20），然后供入电解槽转化为CO，或（ii）以碳酸氢盐，碳酸盐的形式负载到液体溶剂上，氨基甲酸酯等，然后将其送入电解槽中以原位再生CO _2，然后转化为CO。（21-23）然而，考虑到CO ₂是电解生成CO的反应物种，（24）从资本成本的角度来看，这种单电解槽的概念是否优于单独的CO ₂再生步骤和随后的单独转化步骤，尚不清楚。考虑CO ₂再生是直接还原碳酸氢根/碳酸根电解质的速率限制；因此，对于组合工艺，将需要大型（且昂贵的催化剂涂层电解槽）来生产CO，而不是大型再生（电渗析）装置以及小型电解槽来进行两步工艺。因此，为了简化该观点中的讨论范围，我们描述了假设输送到电解器的CO ₂为气体形式的集成方案。为了允许PTL过程的连续运行，即当太阳能或风能不可用时，可能需要电池存储，CO ₂存储，H ₂存储和/或CO存储。为了提高整体效率，未转化的CO ₂可以通过胺洗涤，氢氧化物洗涤，膜，变压吸附（PSA）或其他分离技术模块，从CO ₂的出口中分离出电解产物（如图2中的方框“ s”所示） ，然后循环回到CO ₂电解槽的入口。FT合成和产品升级部分产生的废气可以在氧气燃烧器中进行热化学燃烧，或者在固体氧化物燃料电池（SOFC）中进行电化学燃烧以提高效率，并将生成的CO ₂输送至CO ₂电解槽的入口和产生的氢用于运行H ₂ O电解槽，CO ₂电解槽，DAC单元和/或充电电池（图2a）。Ø₂为氧燃烧可以从H的阳极供给₂ ö电解槽和/或CO ₂电解槽。对于基于阴离子交换膜的低温CO ₂电解槽，在阳极产生CO ₂和O _2的混合流，（25）可以将阳极废气送入氧燃烧单元，生成清洁的CO ₂流，然后将其回收到CO ₂电解槽的入口，从而避免了与处理纯O ₂有关的安全问题。FT合成或产品升级部分中的废气再循环的另一种选择是首先分离CO ₂并再循环至CO₂电解槽，同时将剩余的烃流路由到气化单元（此处用SGP或Shell气化过程表示）（26），以制造更多的合成气（CO + H ₂），如图2b所示。请注意，从FT装置排出的废气很可能在再循环之前需要放气或分离装置（例如变压吸附（PSA）），以防止诸如N ₂的惰性气体堆积（可能来自DAC或泄漏）。 ）。对于能量集成，放热FT合成中产生的热量或蒸汽可用于向H ₂ O电解槽，CO ₂电解槽，CO ₂提供热量/蒸汽或功率。捕获单元，分离单元和/或为电池充电。在SOEC中，CO ₂和H ₂ O的高温共电解需要额外的蒸汽输入，可以考虑类似的整合，这些蒸汽可以从放热FT合成和/或放热气化过程（SGP）中回收或可再生地产生使用蒸汽发生器。相比之下，对于混合GTL-PTL工艺方案（图3），可再生原料（电子以及CO ₂和H ₂O）（如果有的话）（在白天使用太阳能或在风力强风期间）与化石天然气进料进行共处理，以处理间歇性问题，并在可再生能源利用率低的时期运行。在这样的方案中，CO ₂和H ₂ O电解器在可再生电力上同步地（间歇地）运行，而不需要昂贵的大型电池来生产CO和H ₂。同时，基于化石天然气的GTL工艺以24/7运行，电解槽在生产时会提供额外的CO和H ₂。结果，与PTL方案相比，额外的合成气（CO / H ₂）可以缩小或完全避免存储，这也意味着可再生能源发电的过剩能力降低，CO ₂电解槽和水电解槽的规模较小，所有这些都可以减少资本投资。与PTL方案相似，可以将CO ₂电解槽出口的未转化CO ₂与CO流分离，然后循环回到其入口。FT合成和产物提纯段的废气可以在氧气燃烧器中进行热化学燃烧，或在SOFC中进行电化学燃烧以发电，将生成的CO ₂输送至CO ₂电解槽（图3a）或循环至气化装置进行生产。首先分离过量的CO后的CO和H ₂₂（图3b）。用于氧燃烧或气化的O ₂可以任选地从H ₂ O电解器和/或CO ₂电解器的阳极供应。同样，可以将H ₂ O和CO ₂电解槽中可用的额外O ₂发送到可用的液氧存储中，从而与传统的GTL系列产品相比，减小了空气分离装置的尺寸。为了避免N _2的积累或氩气（来自空气分离装置（ASU），直接空气捕获（DAC）或天然气进料），来自FT装置的废气可能需要排放流或分离装置（例如PSA）以去除多余的惰性物质，然后再进行回收利用。同样类似于PTL系列，放热FT合成或气化产生的热量和/或蒸汽可用于向H ₂ O电解槽，CO ₂电解槽，CO ₂捕集单元，直接空气捕集（DAC）提供热量/蒸汽或动力。单位或分离单位。在CO ₂和H _2的高温共电解中，可以考虑类似的集成方案SOEC中的O需要额外输入蒸汽，可以从放热FT合成和/或气化段回收或使用电蒸汽发生器可再生地产生。总之，尽管在CO ₂领域已经取得了很大进展。电解将技术从TRL 1提升到3，这项工作中描述的过程集成策略（例如PTL和GTL–PTL混合原型）对于将其成熟到TRL 4以上至关重要，因此使该技术成为实现能源使用的可靠选择过渡。此外，如本工作所示，还必须纳入设计规则，以最大程度地减少工艺问题，最大化碳和能源效率，最小化资本成本，处理间歇性，回收废气并防止惰性气体堆积。下一步，将需要对这项工作中提出的工艺方案进行进一步的工厂级优化，以选择最可靠的选项并优化设备的尺寸。在此之后，应进行相关的（千瓦或兆瓦）规模的示范活动，以进一步证明该技术在现实世界中的地位。本观点中表达的观点是作者的观点，不一定是ACS的观点。作者宣告以下竞争性财务利益：作者受壳牌公司聘用。这项工作与壳牌公司的GTL（气液）技术领域有关。作者非常感谢HP Calis博士，Albert Harvey博士，Clara F. Heuberger博士，Fu Xiao博士，Abhinav Verma博士，Marco Smaling，Ronald Wolf博士，Esther van Soest-Vercammen博士，Robert Schouwenaar，和Paul Corbett博士对稿件进行了严格的审查。本文引用了其他26个出版物。本观点中表达的观点是作者的观点，不一定是ACS的观点。作者宣告以下竞争性财务利益：作者受壳牌公司聘用。这项工作与壳牌公司的GTL（气液）技术领域有关。作者非常感谢HP Calis博士，Albert Harvey博士，Clara F. Heuberger博士，Fu Xiao博士，Abhinav Verma博士，Marco Smaling，Ronald Wolf博士，Esther van Soest-Vercammen博士，Robert Schouwenaar，和Paul Corbett博士对稿件进行了严格的审查。本文引用了其他26个出版物。本观点中表达的观点是作者的观点，不一定是ACS的观点。作者声明具有以下竞争利益：作者受壳牌公司聘用。这项工作与壳牌公司的GTL（气液）技术领域有关。作者非常感谢HP Calis博士，Albert Harvey博士，Clara F. Heuberger博士，Fu Xiao博士，Abhinav Verma博士，Marco Smaling，Ronald Wolf博士，Esther van Soest-Vercammen博士，Robert Schouwenaar，和Paul Corbett博士对稿件进行了严格的审查。本文引用了其他26个出版物。Albert Harvey博士，Clara F. Heuberger博士，Fu Xiao博士，Abhinav Verma博士，Marco Smaling博士，Ronald Wolf博士，Esther van Soest-Vercammen博士，Robert Schouwenaar博士和Paul Corbett博士对他们的手稿。本文引用了其他26个出版物。Albert Harvey博士，Clara F. Heuberger博士，Fu Xiao博士，Abhinav Verma博士，Marco Smaling博士，Ronald Wolf博士，Esther van Soest-Vercammen博士，Robert Schouwenaar博士和Paul Corbett博士对他们的手稿。本文引用了其他26个出版物。