• Support renewable grid balancing. • Create skilled industrial employment. • Reduce dependence on fossil imports. Integration into existing fuel logistics significantly lowers infrastructure transition costs compared to hydrogen refuelling networks. Strategic role in mobility transition While electrification will dominate passenger mobility in urban areas, renewable liquid fuels offer strategic value for: • Heavy-duty transport. • Remote and rural mobility. • Emergency services. system, where vapour and liquid traffic are hydraulically segregated within the same shell. Vapours from the flash zone rise freely into the rectification section, while liquid streams are directed to the stripping section. Vapours generated in the stripping section are prevented from entering the rectification zone by the partition and are instead routed to dedicated overhead condensation systems. This enables independent control of stripping and rectification, effectively transforming a single column into a dual-zone system without major structural changes or vessel replacement. • Aviation and maritime sectors. • Legacy vehicle decarbonisation. Rather than replacing electrification, CO₂- derived fuels complement it within a diversified energy portfolio. Conclusion The ZCT Solutions process engineering team continues to work on the improvement and innovation of CCC technologies. By combining these technologies with established synthesis processes, such as FT, it is possible to produce renewable fuels that are fully compatible with existing vehicles and fuel supply infrastructure. Techno-economic assessments consistently selected pumparound duties to stripper condensers, resulting in improved preheat levels, reduced furnace duty, and lower NOx emissions, while also minimising maintenance requirements of radiant coils under high-sulphur show that CO₂-derived e-fuels remain more expensive than fossil fuels on a per- litre basis under current conditions. ZCT’s CCC technology reduces GHG emissions and converts CO2 to valuable products. Its main advantage over other carbon capture technologies, such as carbon capture and For revamp scenarios in Indian refineries, this configuration allows existing column shells to be retained, with optional addition of a flash drum where required, enabling implementation within typical 30-45 day shutdown windows without exceeding turnaround constraints. Heat integration is further enhanced by shifting • Thermodynamic framework: The Peng-Robinson equa- tion of state was selected as the fluid package for modelling, as it is highly recommended for predicting the pressure-vol- ume-temperature (PVT) behaviour of liquid and gas phases in petroleum processes. This equation of state provides accu- racy for hydrocarbon systems operating across wide pres- sure and temperature ranges typical of refinery operations. • Stabiliser column convergence criteria were established to meet stream specifications: a) C₅+ content in the FG is ≤0.1 wt%; b) HCl content in the stabiliser bottom stream is ~ 0 ppm (zero tolerance for corrosive species). service. Overall, the configuration achieves seamless integration within existing hardware while delivering enhanced energy efficiency and operational flexibility, making it well-suited for brownfield revamp applications. Subsequently, the model predictions were validated against the actual plant conditions (operating case), con- firming the accuracy of DHA lab analysis and the selected thermodynamic fluid package. Further, Figure 2 presents a comparative analysis of the stabiliser feed composition between the base case and the current operating case, with differences expressed as delta wt% (Δ wt%). The analysis indicates that the current stabiliser feed is lighter by approximately 1.5 wt% compared to the base case feed composition. Despite this shift, the stabiliser column restore pressure losses across the stripper and associated circuits, enabling its reuse within the CDU-VDU system. Depending on the achieved pressure level, the recovered steam can be reutilised for VDU stripping and, upon further boosting, for CDU stripping requirements, thereby reducing fresh steam demand. The core modification lies in the introduction of the partition and associated nozzle 0 -5 10 5 15 ∆wt% (base feed-operating feed) detailed hydrocarbon analysis (DHA) along with relevant operating data, including temperature, pressure, flow rates, and steam consumption. Figure 2 Difference of DHA composition from base case stabiliser feed with operating case feed, wt% • LPG stripper convergence was performed to ensure compliance with LPG product specifications: a) C₅+ content in the LPG product is ≤2.0 wt%; b) HCl content in the LPG product is ≤6 ppm. -10 iC4 nC4 iC5 nC5 22 DMB 23 DMB 2MP 3MP nH MCP CH C7+
storage (CCS) and carbon capture and utilisation (CCU), is that it not only captures CO2 but also creates fuels for use in transportation. This results in a significant reduction of costs. In the transition to net-zero mobility, CO₂-to-fuel systems should not be viewed as a competitor to electrification but as a complementary solution within a diversified energy portfolio. While battery-electric vehicles will dominate high-efficiency urban road transport, synthetic fuels provide a pragmatic decarbonisation pathway for existing combustion engines and sectors that are difficult to electrify. ZCT’s technology aligns with the objectives of the Paris Agreement, adopted in 2015, a legally binding international treaty aimed at significantly reducing GHG emissions. Under the agreement, countries are required to submit updated, increasingly ambitious Nationally Determined Contributions (NDCs) every five years, detailing their plans to reduce GHG emissions, pursue net-zero pathways, and enhance climate resilience. Ultimately, the significance of CO₂-derived fuels lies in their conceptual shift: carbon is no longer treated solely as waste, but as a recyclable industrial resource. By closing the carbon loop from capture to fuel tank, synthetic fuel technologies demonstrate how emissions can be transformed from a liability into an asset, advancing both climate objectives and industrial resilience. sections within the existing configuration, enabling improved control over vapour-liquid traffic and separation behaviour. Operating conditions, including pressure, temperature, and flow rates, were maintained in line with the existing base case, with product yields held within ±1% for consistent comparison. The broad product distillation ranges and specifications considered for the base case are presented in Tables 1 and 2 . The configuration incorporates steam-free Simulations were carried out with operating case feed over a range of decreasing stabiliser column pressure from 18 kg/cm²(g) to 14 kg/cm²(g) to evaluate the feasibility of operating the column at reduced pressure and to assess its impact on product quality and steam consumption. Based on the simulation results (Table 1), it was observed that operating the stabiliser column at 18 kg/cm²(g) is Nabeel Ataimisch N.Ataimisch@zero-carbon.at vacuum stripping section. Moreover, the remaining steam is routed to the overhead ejector condenser, ensuring a balanced and stable vacuum circuit. Case study: Revamp of Bombay High unit The proposed configuration is demonstrated for a CDU-VDU processing Bombay High crude in a typical ~8 MMTPA refinery, representing a common operating scenario in Indian refineries. The scheme integrates partition- based segregation of rectification and stripping However, operating a column at low pressure increases the overhead vapour load, which can lead to higher duty requirements for downstream equipment, including the air cooler (AC-02), cooling water heat exchanger (E-02), and chiller (E-03). To address this, simulations were performed at reduced pressure and by adjusting the reflux ratio to achieve proper hydrocarbon separation and meet product specifications, while ensuring that the downstream sections‘ heat duty remained within acceptable limits. The key oper - ating parameters captured during the operating case and low-pressure simulation are tabulated in Table 1 . Results and discussion pressure of 20 kg/cm²(g) has been maintained for the oper - ating case. A feed with a higher proportion of low-boiling components requires lower stabiliser column pressure for efficient separation, thereby reducing the reboiler duty required to vaporise the lighter fractions. Thus, based on the feed composition analysis, it was observed that there is significant potential for energy saving by optimising the stabiliser column at a lower pressure. Figure 3 Relationship between stabiliser pressure reduc- tion on reboiler steam consumption and its effect on prod- uct quality specification Minimal modifications for maximum gains Figure 3 highlights the minimum modifications needed for a quick payback. It focuses on nozzle additions, tray adjustments, and partition plates in CDU and VDU, which can be implemented during routine annual turnarounds of 20-30 days without major shutdowns. The concept is also independently applicable to the VDU, enabling a low-modification, quick-fix implementation where required. This approach leverages existing infrastructure to deliver immediate Opex savings, avoiding extensive capital-intensive overhauls. In this configuration, no additional flash drums are envisaged, and a minimum ejector system is required to boost steam pressure for the 14 18 16 Pressure (kg/cm g) 21 12 14 Meeting product spec Pressure < 18 kg/cm g >Increased chiller duty >Retro t required to meet product spec 16 20 18 22 0.15 0.19 0.23 0.31 0.27 0.35 Stabili s er reboiler steam Exchanger chiller duty
THE FCCU IN TRANSITION How refiners can turn challenges into opportunities beyond 2030
Strategies to enhance the profitability of unit operations
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