Search

Calcium looping is a promising CO2 capture technology due to reduced energy and economic penalties compared to mature solvent scrubbing technologies. It also can enable negative CO2 emissions when biomass is used to drive the sorbent regeneration process in the calciner. However, the trade-off between the energy, economic and environmental performance under different biomass co-firing fractions in the calciner and process operating scenarios has not yet been well understood. This study examined the potential for transforming a 580 MWel coal-fired power plant into a negative CO2 emitter via retrofit of calcium looping with biomass co-firing in the calciner. High-fidelity process models were developed in Aspen Plus and used to analyse the effect of biomass co-firing fraction, CO2 capture rate in the carbonator, and the fraction of flue gas fed to the carbonator on the techno-economic performance indicators. The results revealed that co-firing 30% biomass with coal in the calciner was sufficient for the retrofitted process to achieve negative CO2 emissions (−3.9 gCO2/kWelh). In this scenario, the levelized cost of electricity was 5% lower (81.1 €/MWelh) than that in the reference retrofit scenario without biomass co-firing (85.4 €/MWelh) at a carbon tax of 100 €/tCO2. Further improvement to the techno-economic performance was achieved by reducing the amount of CO2 captured in the carbonator by reducing either the CO2 capture rate (81.1 €/tCO2) or the amount of flue gas processed (80.4 €/tCO2). Although this was achieved at the expense of the increased specific CO2 emissions to 65.2 gCO2/kWelh and 109.0 gCO2/kWelh, respectively, the net specific emissions were still about 90% lower than those of the unabated host plant (792.3 gCO2/kWelh). This study demonstrated that depending on design priorities, biomass co-firing in the calciner can transform the existing coal-fired power plants into negative CO2 emission technologies or improve the process techno-economic viability. [ABSTRACT FROM AUTHOR]

Abstract Calcium looping combustion (CaLC) is a new class of low CO 2 emission technologies for thermochemical conversion of carbonaceous fuels that can help achieve the emissions reduction targets set out in the Paris Agreement. Compared to mature CO 2 capture technologies, which cause net efficiency penalties higher than 7% points, CaLC results in a net efficiency penalty of 2.9% points. However, a thorough economic assessment of CaLC needs to be undertaken to evaluate its economic viability. The levelised cost of electricity is commonly used to assess the economic performance of clean energy systems. However, this method does not account for commercially important parameters, such as tax, interest, and depreciation charges. This study aimed to improve the reliability and accuracy of economic assessments of clean energy systems by implementing the net present value (NPV) approach. This approach was applied to assess the economic performance of two concepts of the CaLC-based power plant with either the conventional steam cycle (SC) or the supercritical CO 2 cycle (s-CO 2) for heat utilisation along with the bottom-up approach to total capital cost estimation. A parametric study for both concepts was also conducted to assess the impact of the key thermodynamic parameters on the economic performance. Although the s-CO 2 case with revised assumptions was shown to result in a 1%-point lower net efficiency compared to the SC case, its break-even cost of electricity was lower by 0.81 €/MWh. Further improvements of the techno-economic performance can be sought by optimisation of the s-CO 2 cycle structure. Highlights • CaLC-based power plant was assessed using NPV approach. • Bottom-up cost estimation method based on CaLC plant equipment scale was derived. • Bottom-up cost method principals can be used for other clean power systems. • Case study of CaLC plant with steam and supercritical CO 2 cycles was evaluated. • Implementing supercritical CO 2 cycle into CaLC power plant improved the economic performance. [ABSTRACT FROM AUTHOR]

• Acceleration of the development of a the indirectly heated carbonate looping process. • Detailed process description of the 300kWth pilot plant. • Demonstration in close by semi-industrial conditions for cement and lime. • First-of-a-kind application of waste derived fuels in an IHCaL facility for delivering heat for calcination. The indirectly heated carbonate looping process (IHCaL) is a promising technology for decarbonizing the lime and cement industry. Advantages of the IHCaL are the synergy with these industries using same solid materials and the avoidance of an air separation unit (ASU), since no technical pure oxygen is necessary in this capture process. Former pilot tests showed the feasibility of the IHCaL for applications in the power plant sector. However, the integration of the IHCaL into cement and lime plants, as well as the usability of spent sorbents as educts in these processes, has not yet been proven in industrially relevant conditions. In this study, the modification of an existing 300 kW th pilot plant for demonstrating the IHCaL process are described, aiming in accelerating the demonstration in an industrially relevant environment for cement and lime industries. A flue gas circulation system and a solid fueling system into the combustor, allowing the heat generation for the calcination with e.g. waste derived fuels, have been designed and installed. Results gained during the operation with the modified reactor configuration, are presented in order to assess the performance of the new components in the framework of the IHCaL configuration. The external combustor was operated while co-firing propane with either dried lignite or waste derived fuels. The carbonator was fluidized with a real flue gas from the external combustor, having CO 2 concentrations between 11 and 18 vol-% dry. The results, obtained within more than 200 h of continuous testing with modified reactor configuration, show a good hydrodynamic behavior and adequate reactor performance, while providing a sound basis for further improvement and up scaling of the technology. [ABSTRACT FROM AUTHOR]

Carbon capture with subsequent compression and storage is a promising possibility for the reduction of CO2 emissions from coal-fired power generation. A very efficient post-combustion CO2 capture technology is the carbonate looping process. To further increase the process efficiency, a new concept is considered where the heat for calcination is transferred from an external combustor to the calciner by means of heat pipes. Some thermodynamic evaluations for a retrofit of a coal-fired host plant with the indirectly heated carbonate looping process and cold flow model tests of a 300-kWth test facility that will be erected in 2013 in Darmstadt are presented. [ABSTRACT FROM AUTHOR]

Abstract: CO2 capture by solid sorbents through uptake–regeneration cycling is a promising option for high temperature removal of CO2 from combustion gases and synthesis/fuel gases. The present study investigates the influence of regeneration atmosphere and temperature on the CO2 uptake capacity during repeated cycling of CaO-based solid sorbents. The sorbents were synthesised to contain 75 and 85% w/w of active phase (CaO) and binder (Ca12Al14O33) and were then subjected to cycling tests with repeated CO2 uptake and release in a thermogravimetric analyser TGA for up to 200 cycles. Test conditions were chosen to test high temperature CO2 capture at 600°C in an atmosphere containing 14 and 25% v/v CO2 (N2 balance). Three different regeneration conditions were tested: [(a)] mild condition: regeneration at 900°C in 14% CO2 or 100% N2; [(b)] moderate condition: regeneration at 1000°C in 14% CO2; and [(c)] severe condition: regeneration at 1000°C in 86% CO2. Hydration of the sorbent during synthesis and prolonged carbonation prior to the cycling tests significantly improved the stability of the uptake capacity. Interestingly, the pretreated 75% w/w CaO synthetic sorbent maintained a good uptake capacity up to the 150th cycle under severe regeneration conditions and even showed continuously increasing CO2 uptake capacity throughout the 150 cycle test with 25% CO2. The 75% w/w CaO sorbent is thus an interesting candidate for future work on high temperature CO2 capture. [Copyright &y& Elsevier]

Abstract: A novel process for conversion of hydrocarbons to H2 has been examined. The process, sorption enhanced chemical-looping reforming, involves three interconnected reactor vessels. In the reforming reactor, hydrocarbon fuel is partially oxidized with oxygen provided via a solid oxygen carrier such as NiO. Resulting CO is shifted instantly to CO2 via sorption enhanced water–gas shift, facilitated by the capturing of CO2 with a solid CO2 sorbent such as CaO. Ni and CaCO3, are regenerated downstream in separate reactors. The process produces H2, CO2 and N2 of reasonable purity in separate streams, without need for additional gas separation equipment. The characteristics of the process have been examined by thermodynamic calculations and by process modeling. At 1bar it could produce >2.8mol H2 with a purity of >98vol.% for each mol CH4 added as fuel, while capturing >95% of added carbon as CO2. Increasing the pressure reduces the performance due to lower conversion of CH4. Involved reactions have also been examined in a fluidized-bed reactor at 600–750°C, with particles of NiO and CaO as bed material and CH4 mixed with steam as fuel. The CH4 conversion was incomplete but the results fitted with theory and gas with a H2/(H2 +CO+CO2) ratio of more than 98% was produced at 600°C. [Copyright &y& Elsevier]

• A 1 MWth carbonate looping plant was operated in steady state for > 2000 h. • A carbonator efficiency > 80 % was obtained under a variety of operating conditions. • A calciner efficiency > 90 % was achieved 30 K above equilibrium temperature. Carbon capture and utilization/storage is an effective means to reduce CO 2 emissions from power and energy intensive industries. Carbonate looping is a 2nd generation post-combustion CO 2 capture technology using solid sorbents that form carbonates when reacting with CO 2. This technology has economic benefits caused by the low efficiency penalty and the low cost of the sorbent. Autothermal continuous operation of this process at high CO 2 capture rates has been successfully proven in several pilot plants up to 1.7 MW th. The 1 MW th pilot plant in Darmstadt has been operated for more than 2000 h with long periods of steady-state conditions, which allows the evaluation of the performance of the reactor system during long-term operation. This paper presents complementary results of these pilot tests focussing on the performance of the carbonator and calciner reactors. A high carbonator efficiency above 80 % is possible in the temperature range of 650–675 °C with a specific solid inventory above 700 kg/m2 combined with either a high sorbent looping ratio of 16 mol Ca /mol CO2 or a high make-up ratio of 0.13 mol Ca /mol CO2. A calcination efficiency of 90 % can be achieved by a calciner space time above 6 min, if the calciner temperature is 30 K above the equilibrium temperature at the prevailing CO 2 concentration. Heating of the sorbent entering the calciner consumes almost half of the thermal fuel input. [ABSTRACT FROM AUTHOR]