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Amine solvents are one of the main options for post-combustion CO2 capture applications. The main drawback of the carbon capture processes is the required energy to regenerate the solvent once it has reacted with the CO2. When applied to a power plant, the energy requirement has an important impact on the net efficiency of the overall system. Several solvents, i.e., monoethanolamine (MEA), diethanolamine (DEA), methyl diethanolamine (MDEA), and many others have been proposed to overcome this drawback. Regeneration temperature and heat duty reduction are considered to be the significant objectives. Moreover, enhancement of the amine''s concentration and its working capacity without the impact on the other variables are important. In this work, different types of amines with a wide range of heat duty and regeneration temperatures under the same set of assumptions are calculated and compared. The effect of both variables on the energy penalty caused by carbon capture is measured. A review of amines and their effects on the net efficiency of the overall system (power plant, chemical absorption, CO2 compression) are conducted and analyzed. As expected, the impact of heat duty is greater than the modification of regeneration temperature. The effect of reducing 1 GJ/ton CO2 in the heat duty is similar to the effect of reducing the regeneration temperature from 40 degrees C to 25 degrees C.

One of the main challenges associated with utilisation of the renewable energy is the need for energy storage to handle its intermittent nature. Power-to-Gas (PtG) represents a promising option to foster the conversion of renewable electricity into energy carriers that may attend electrical, thermal, or mechanical needs on-demand. This work aimed to incorporate a stochastic approach (Artificial Neural Network combined with Monte Carlo simulations) into the thermodynamic and economic analysis of the PtG process hybridized with an oxy-fuel boiler (modelled in Aspen Plus®). Such approach generated probability density curves for the key techno-economic performance indicators of the PtG process. Results showed that the mean utilisation of electricity from RES, accounting for the chemical energy in SNG and heat from methanators, reached 62.6%. Besides, the probability that the discounted cash flow is positive was estimated to be only 13.4%, under the set of conditions considered in the work. This work also showed that in order to make the mean net present value positive, subsidies of 68 €/MWelh are required (with respect to the electricity consumed by PtG process from RES). This figure is similar to the financial aids received by other technologies in the current economic environment.

A promising hybridization which increases the chances of deployment of Power to Gas technology is found in the synergy with oxycombustion of biomass. This study assesses the efficiency of an energy integrated system under different sizes and potential applications. District heating and industrial processes are revealed as the most suitable potential applications for this hybrid technology. Global efficiency of the combined system may be increased through thermal energy integration. The relative increment of efficiency achieved for those designs which avoid the requirement of an air separation unit and for those which completely consumed the generated CO2, are 24.5% and 29.7% respectively. A 2 MWth district heating case study is also analysed, revealing that 81.2% of the total available heat from the PtG–oxy system could be integrated raising the global efficiency up to 78.7% at the adequate operational point. Further ‘full-fuel-cycle’ analysis will be required prior to decide the interest of the concept under a specific scenario in comparison to other available energy storage technologies.

The application of Amine-impregnated Alumina Solid Sorbent Carbon Capture is a suitable option to increase CO2 capture efficiency and to reduce by several percentage points the efficiency penalty of CCS in power plants. These sorbents require less regeneration energy due to the reduction in water content and the higher heat capacity of solids. The objective is to demonstrate that the use of amine-impregnated alumina solid sorbents is a suitable option to increase CO2 capture efficiency and to reduce several percentage points the efficiency penalty caused by the capture system in the power plant. The proposed innovative sorbent consists in amines supported on high surface area and high porosity solid materials, such as alumina and silica-alumina. Good results have been achieved. Important high porosity support makes possible to obtain high CO2 capture capacities over 50 mg CO2/g of sorbent. As a consequence, the combination of this CCS option with a coal power plant may reduce the efficiency penalty down to 7 efficiency points. This figure could make feasible the impregnated amine solid sorbent as a future and promising option for CO2 capture.

O2GEN project was running during more than three years and it was successfully finished in January 2016. The main target was to develop the 2nd generation oxyfuel circulating fluidized bed (CFB) power plants based on higher oxygen concentrations with the aim of decreasing flue gas recirculation and the energy penalty. Remarkable advances have been achieved in Air Separation (ASU) and Compression and Purification Units (CPU) reducing significantly their energy consumption. CFB boiler concept was proposed by scaling-up from past designs. No special drawbacks were found regarding combustion, heat transfer and emissions. Finally, a process integration methodology was applied and overall efficiency was increased by heat integration. Energy penalty was reduced from 10.5 to 7.3 efficiency points. The new power plant lay-out avoids technical restrictions in the use of complex heat exchangers and facilitates the operational flexibility of the system.

In order to increase the overall net electric efficiency and consequently to decrease the energy penalty in oxy-fired systems, heat integration configurations must be proposed. Coupling among the Air Separation Unit (ASU), the Compression and Purification Unit (CPU) and flue gases leaving the boiler becomes critical to obtain good efficiency figures. Many solutions have tried to show outstanding efficiency results but practical proposals are necessary to develop the technology. The use of flue gases waste energy to recycle flue gases heating up, oxygen preheating and increasing temperature of feedwater to steam cycle has been proposed to surpass the efficiency reduction. Nevertheless, care should be taken as potential problems would appear if only theoretical analysis is carried out. This work deals with a suitable and flexible design to increase the overall efficiency of an oxy-fuel combustion power plant working with high O2 concentration. Waste energy has been integrated avoiding any potential risk/damage into a new designed steam cycle. Applied solutions try to use lower cost proven materials in heat exchangers and simple equipment designs avoiding gas-gas heaters. Novel arrangements are presented, such as indirect heat exchangers, plastic heaters or different configurations integrating high pressure feedwater and low pressure condensate mass flows. Finally, results are compared with a previously optimized power plant design without operational restrictions and just a slight reduction in power plant net efficiency (less than 1%) was observed between both concepts.

The share of renewable energy production is growing quickly. The output and variability of renewable power will force to fossil fuel power plants to adapt its electricity production to variable demand. In a future scenario, with CO2 capture systems installed in power plants, the variable performance will affect not only to fossil fuel power plant but also to the CO2 capture behavior. The knowledge of part load performance of fossil fuel power plants with CO2 capture systems will be essential in a near future. This paper analyzes the integration between Ca-looping cycles and power plants to foresee the requirements derived from a flexible operation. With this goal, the performance of the integrated system under different load scenarios is studied. An integration scheme designed for nominal load is proposed under different load scenarios at steady state, to study their performance. Then, for each load scenario, the optimum integration is designed, to quantify the minimum energy penalty of each specific load level. Finally, a comparative analysis of the general integration against the optimum one for each scenario is performed.