Optimization of Oxygen-based CFBC Technology with 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

On the Flexibility of Coal-fired Power Plants with Integrated Ca-looping CO2 Capture Process

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

Amine-impregnated Alumina Solid Sorbents for CO2 Capture. Lessons Learned

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

Optimized Ca-looping thermochemical energy storage under dynamic operation for concentrated solar power

The massive deployment of renewable energy sources and carbon capture technologies are required to achieve net zero emissions target by 2050. Calcium Looping (CaL) is a promising Thermochemical Energy Storage (TCES) system which improves the dispatchability of Concentrating Solar Power (CSP) plants. CaL TCES configurations found in literature focus on a steady-state analysis of thermal-to-electric efficiency of the CSP plants. In this work, the operation of the CaL TCES system for a CSP plant is economically optimized taking into account the seasonal and daily variations of solar resource and electricity prices. The defined methodology determines the operating performance of the CaL TCES which maximize the economic incomes of the CSP and the daily profiles of energy production and storage for representative days of the different seasons/periods of the year. Results show that it is possible to obtain good economic results and operate the CSP + storage for a daily maximization of incomes. Obtained results are also useful for the final design of the system and for the definition of the size required for the storage equipment

Operation maps in calcium looping thermochemical energy storage for concentrating solar power plants

Calcium Looping (CaL) process used as thermochemical energy storage system in concentrating solar plants has been extensively investigated in the last decade and the first large-scale pilot plants are now under construction. Existing research focuses on improving global efficiencies under steady-state and single modes of operation: energy storage or energy retrieval. However, TCES systems will operate under different operation points to adapt the load of its reactors to the solar availability and the energy demand from the power cycle. A thorough analysis of the operation modes provides an extremely large number of potential situations to operate the system. In this study, operation maps which maximize thermal energy availability and energy storage efficiency are defined. Furthermore, a novel approach for the management of partially carbonated solids is examined to reduce the circulation of inert material in the system based on preliminary experimental results which allows for a partial separation of carbonated solids. Two threshold scenarios are analysed: (i) no solids separation as considered in most CaL TCES studies and (ii) ideal total solids separation. The aims of this work are to set methodological criteria to define the optimal operation map and to assess the effect of partially carbonated solids separation on the energy penalties and equipment size. The inclusion of a solid separation stage leads to a maximum increase of energy storage efficiency of 26 % and a size reduction between 53 and 74 % of those heat exchangers affected by solids streams

An operational approach for the designing of an energy integrated oxy-fuel CFB power plant

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

Energy Integration of High and Low Temperature Solid Sorbents for CO2 Capture

It is crucial to reduce the energy penalties related to CO2 capture processes if CCS is to be implemented at industrial scale. In this context, gas-solid sorption has become a relevant technology. The absence of large amounts of water when using dry solid sorbents and their high heat capacity reduce the energy requirements in the gas-solid sorption CO2 capture process. Depending on the sorbent composition, the gas-solid sorption process carries out at high or low temperatures. High temperature sorbents allow the utilization of waste energy while energy requirements in low temperature processes will be less demanding. This study is focused on the assessment and comparison of the final energy penalty of low-temperature (amine impregnated alumina-based solid particles) and high-temperature solid sorbents capture process (calcium oxide)

Power to Gas projects review: Lab, pilot and demo plants for storing renewable energy and CO2

Power to Gas (PtG) processes have appeared in the last years as a long-term solution for renewable electricity surplus storage through methane production. These promising techniques will play a significant role in the future energy storage scenario since it addresses two crucial issues: electrical grid stability in scenarios with high share of renewable sources and decarbonisation of high energy density fuels for transportation. There is a large number of pathways for the transformation of energy from renewable sources into gaseous or liquid fuels through the combination with residual carbon dioxide. The high energy density of these synthetic fuels allows a share of the original renewable energy to be stored in the long-term. The first objective of this review is to thoroughly gather and classify all these energy storage techniques to define in a clear manner the framework which includes the Power to Gas technologies. Once the boundaries of these PtG processes have been evidenced, the second objective of the work is to detail worldwide existing projects which deal with this technology. Basic information such as main objectives, location and launching date is presented together with a qualitative description of the plant, technical data, budget and project partners. A timeline has been built for every project to be able of tracking the evolution of research lines of different companies and institutions

Power to Gas technology under Spanish Future Energy Scenario

Power to Gas (PtG) has been pointed out in the last years as a promising energy storage technology to smartly manage the renewable intermittent power generation that limits the operational flexibility of the network. In this work, we present a prospective study for the Spanish case, in which the implementation potential of PtG technology is evaluated in terms of the estimated renewable surpluses. We found that the annual surplus for the year 2050 would vary between 1.4 TWh and 5.2 TWh, and the PtG capacity required would be in the range 7.0 - 13.0 GW, depending on the renewable production pattern considered

Methodology for dimensioning the socio-economic impact of power-to-gas technologies in a circular economy scenario

Innovative and sustainable energy technologies are needed in the transition of energy toward a circular economy. Because of the use of renewable energy and carbon utilization, power-to-gas could be a cutting-edge technology that supports the circular model in future sustainable energy markets. However, this technology faces new technical and socio-economic challenges. The use of power-to-gas is limited because of barriers that limit the mobilization of investment capital. In addition, social and economic impacts on the territories in which these facilities are located are under study. In this context, the aims of this paper are: (i) To explore the determinants and barriers for power-to-gas technology to enhance the understanding of investment in innovative energy technologies; and (ii) to support effective policymaking and energy companies’ decision-making processes. This study defines and measures, from a circular economy perspective, the main impacts of the deployment of this technology on a territory in terms of volume of investment, employment generation, and CO2 capture. The study also provides a simplified methodology to contribute to the analysis of the use of power-to-gas. Finally, it improves the knowledge of the socio-economic impact of this cutting-edge technology for the transition of energy to a zero-emission scenario