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Anthropogenic CO 2 emissions are considered the major contributor of greenhouse gas emissions worldwide. The mitigation of this kind of CO 2 emissions relies on a portfolio of alternatives where CO 2 absorption appears as the nearest approach to be applied at industrial scale. Researchers have been focused on developing new formulations of solvents to make more competitive CO 2 absorption as a carbon capture and storage (CCS) technology. In this sense, this chapter summarizes both the conventional solvents and the most recent investigations on this field. Chemical absorption is more suitable for a lot of industrial process due to the flue gas conditions: ambient pressure, low CO 2 concentration and large volume. Therefore numerous novel solvents came up in recent years and they are further discussed in this chapter. The most recent solvents, their mechanisms and kinetics and the advantages and disadvantages are also included. Finally, physical solvents are adequate in high CO 2 partial pressure applications and they are reported in the last section. Although physical absorption field is constrained to high-pressure flue gas, physical solvents provided higher performance in CO 2 separation process and their characteristics are also summarized.

BACKGROUND Carbon capture and storage is considered one of the pillars that should support greenhouse gas (GHG) emission mitigation by 2050. In this sense, partial oxy‐combustion emerges as a promising alternative. Its advantages rely on the production of a higher CO2 concentration flue gas than these provided by conventional air‐firing processes. The use of higher CO2 concentrations should improve the solvent kinetic and the CO2 cyclic capacity. RESULTS The kinetic behaviour of two representative sterically hindered amines, namely 2‐amino‐2‐methyl‐1‐propanol (AMP) and isophrondiamine (IF), were studied under partial oxy‐combustion conditions in a laboratory‐scale semi‐batch reactor. The CO2 concentration varied from 15%v/v to 60%v/v. The kinetic enhancement experienced by AMP at high CO2 concentration was slightly >60%, instead of 70–80% for IF. AMP also improved its CO2 absorption capacity by 24.7%, from 15%v/v to 60%v/v, almost doubled the improvements achieved by monoethanolamine (MEA). In the case of IF experiments, the CO2 loading increased ≈10% from 15%v/v to 60%v/v CO2 and it changed from 1.10 to 1.34 mol CO2 mol–1 solvent, representing a >20% increase. CONCLUSIONS The presence of higher CO2 concentrations accelerated CO2 absorption and provided higher CO2 absorption rates. In addition, the evolution of the CO2 loading also exhibited higher values in the experiments using higher CO2 concentration flue gas. The steric hindrance causes a hybrid behaviour in these solvents, between both fast and slow kinetic solvents. The kinetic rates observed using AMP were slightly higher than MEA, but lower than IF which showed the fastest kinetics. © 2020 Society of Chemical Industry

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This work evaluates and selects the best sequence of operations for the pretreatment of greenhouse agricultural wastes (GAW) derived from the main greenhouse crops of the west of Almeria (Spain), such as tomatoes, peppers, cucumbers, eggplants, zucchinis, watermelons and melons, before recovering its potential energy in a cement plant located in this province. In this research, a set of operations are proposed to reduce the chlorine percentage and the moisture content presented in this kind of waste, for its use as an alternative fuel in this production facilities. A washing of the waste under optimal conditions may reduce the chlorine content by approximately 50.0% of the original value and increase the lower calorific value by 8.0%. Drying the waste with a hot gas stream could produce a recoverable waste with a moisture content lower than 3.0%, which enables its temporary storage while avoiding its degradation. The use of an adequate amount of conditioned GAW can provide a substitute up to 51% of the conventional fossil fuel currently employed in the daily operation of the facility evaluated, leading to a reduction of the CO2 emissions associated with the decrease in the fossil fuel consumption.