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industrial processes because of the inherent variability of the industrial process operations, such as in primary steelmaking [65]. The main strategies proposed for power plants with a carbon capture system can be summarized as follows:

       Allowing the thermal power plant to follow load changes. The capture unit follows the power plant load change [58, 59].

       Varying the CO2 capture rate, depending on CO2 costs and electricity prices [51]. In such case, the solvent regeneration is variable, using the large amount of loading capacity and large inventories of solvent as CO2 storage [66]. At times with high electricity prices, the steam is used for power production, while the regeneration takes place at low electricity prices.

       Turning on‐and‐off the capture unit or flue gas bypass. The flue gases sent to the capture unit are bypassed to the stack of the power plant so that partial or no CO2 is being captured. Part of the flue gas is vented to the atmosphere. This allows part of the steam used for solvent regeneration to be used for power production in the steam turbine. This option might be viable in scenarios in which CO2 emission costs or prices are low.

       Providing solvent storage to decouple plant operation from the capture unit. The capture rate is kept constant and the solvent is stored in tanks. The regeneration energy is shifted to times when electricity prices are low. Solvent storage can incur in significant capital expenditure required for solvent storage, which could be favorable in scenarios with high CO2 emission costs.

1.4 CO₂ Capture in the Industrial Sector

      The industrial sector was responsible for almost 25% of the CO₂ emissions in 2014. CO₂ is emitted on the fuel combustion, intrinsic reactions and indirectly on the use of electricity. IEA predicted a required reduction on the CO₂ emissions of 3–6 Gt/yr to achieve the 2 degrees scenario (2DS) or B2DS. Although other measures such as increasing energy efficiency, developing new production process, using renewable energy or fuel switching, will reduce CO₂ emissions, still there is a significant amount of CO₂ from the process that can be only reduced through CO₂ capture [20]. To achieve the B2DS, the contribution of CCS is estimated as 23%.

      All the available CO₂ capture technologies can be potentially installed in industrial facilities. However, while certain industries would have similar or even more favorable characteristics for the implementation of carbon capture utilisation and storage (CCUS) compared to power plants, the design of CO₂ capture systems must be tailored for each facility. The heat and energy integration will be site specific and, together with the composition and CO₂ emission stacks, will impact on the optimum capture rate and the CO₂ avoidance cost.

An exhaustive description of the integration of certain CO₂ capture technologies in the cement sector can be found, for example, in Refs. [67, 68]. A large scale chemical absorption system will be installed in the Norcem Brevik facility, after other technologies (solid sorbents and membranes) were tested at smaller scale [6]. Oxyfuel has been included in the Front End Engineering Design (FEED) studies within the European climate research alliance (ECRA) project and the LEILAC project will test the Calix technology (direct separation) [7]. Other technologies, such as chilled ammonia, membrane‐based capture combined with liquefaction, and calcium looping were studied, for example, in the CEMCAP project at modeling scale [69]. Moreover, partial capture configurations for several industries are being studied by the CO2STCAP project [70] and the CLEANKER project will scale up the calcium looping up to a TRL of 7.⁶

The peculiarity of the steelmaking sector is the heterogeneity of production processes that will be more or less dependent on the electricity grid. At large scale, the most significant project is the Al Reyadah in Abu Dhabi, where CO₂ is captured in the steam methane reforming (SMR) for H₂ production to be used in a direct reduction iron (DRI) process. A recent cost review identified promising CO₂ capture solutions for this sector, perhaps at lower TRL and potentially with less accurate cost figures [71]. Other projects are advancing on CO₂ capture technologies applied to the steelmaking sector. For example, the C4U project will test high‐temperature solid sorbents, aiming to reach a TRL of 7 once the demonstration facility is fully operational. Additionally, the STEPWISE project will advance on the testing of the sorption‐ enhanced water gas shift technology, reaching a TRL of 7 once it operates successfully, while the 3D project will test an advanced solvent in a steel mill.⁷

      Other sectors such as refining, hydrogen, natural gas, heavy oil, fertilizer productions, and waste‐to‐energy are important and are being considered for further study, for example, by the CSLF.

1.5 Conclusions

      In this chapter, the main CO₂ capture systems applied to the industrial and power sectors have been described, covering a wide range of TRLs. Chemical absorption as post‐combustion arrangement was further discussed, including advanced process configurations and its integration in the power plant and electricity grid.

Based on the information from the literature, Figure 1.12 aims to provide an overview of the current TRLs of the different CO₂ capture technologies applied to the power and industrial sectors. Note that differences on the TRL definitions from different sources can impact on the TRL assessment. Additionally, several systems can vary and it would be reflected in their TRL. For example, chemical absorption systems have reached their maximum TRL when commercial solvents are used. However, emerging solvents might be at a much lower TRL. Similar limitations of those estimations can be seen, for example, in the use of different absorbents, different types of membranes or using novel O₂ separation process for oxyfuel. Moreover, in the case of the industrial sector, the TRL is also dependent on the industry. For example, while a system has been tested within a cement production facility, it might not have been used in the iron and steel production environment. In addition, in some industries, there could be a wide range of production processes, which impact on the CO₂ emitted and composition of the flue gas, and will be considered when assessing the TRL at the relevant environment.

Figure 1.12 Review of current TRL of different CO₂ capture technologies. *The prediction of the TRL of fuel cells is based on the project implemented in Alabama by ExxonMobil and Fuel Cell Energy partnership using MCFC. **SEWGS = Sorption‐enhanced water gas shift. This prediction is based on the expected outcome of the STEPWISE project. ***The prediction of the calcium looping technology on the industrial sector is based on the expected outcome of the CLEANKER project. ****Oxyfuel is considered here as the combustion with almost pure oxygen. Other configurations of, for example, chemical looping, cryogenics, membranes (oxygen separation), among others, can be considered as part of the oxy‐combustion technologies.

References

      1 1 Masson‐Delmotte, V., Zhai, P., Pörtner, H.‐O. et al. (eds.) (2018). IPCC, 2018: summary for policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the Impacts of Global Warming of 1.5°C Above Pre‐industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change. Geneva, Switzerland, 32 pp.: World Meteorological Organization.

      2 2 Giannaris, S., Jacobs, B., Srisang, W. et al. (2019). Heat integration analysis and optimization for a post combustion CO2 capture retrofit study of SaskPower's Shand Power Station. Int. J. Greenhouse Gas Control 84: 62–71.

      3 3 Rock, L., McNaughton, C., Black, A. et al. (2017). Assessment of CO2 levels prior to injection across the quest sequestration lease area. Energy Procedia 114: 2836–2846.

      4 4 Allam, R., Martin, S., Forrest, B. et al. (2017). Demonstration of the Allam

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