Dawid P. Hanak

A review of developments in pilot-plant testing and modelling of calcium looping process for CO2 capture from power generation systems

A nearly complete decarbonisation of the power sector is essential to meet the European Union target for greenhouse gas emissions reduction. Carbon capture and storage technologies have been identified as a key measure in reducing the carbon-intensity of the power sector. However, no cost-effective technology has yet been developed on a commercial scale, which is mostly due to high capital cost. Moreover, the mature technologies, such as amine scrubbing or oxy-combustion technologies, impose a high projected efficiency penalty (8–12.5% points) upon integration to the power plant. The calcium looping process, which is currently being tested experimentally in bench- and pilot-scale plants worldwide, is regarded as a promising alternative to the chemical solvent scrubbing approach, as it leads to the projected efficiency penalty of 6–8% points. The calcium looping concept has been developing rapidly due to the introduction of new test facilities, new correlations for process modelling, and process configurations for improved performance. The first part of this review provides an overview of the bench- and pilot-plant test facilities available worldwide. The focus is put on summarising the characteristics and operating conditions of the test facilities, as well as extracting the key experimental findings. Additionally, the experimental data suitable for validation or verification of the process models are presented. In the second part, the approaches to the carbonator and the calciner reactor modelling are summarised and classified in five model complexity levels. Moreover, the model limitations are assessed and the needs for modelling baselines for further process analyses are identified. Finally, in the third part the approaches for the integration of calcium looping to the power generation systems and for the improvement of the process performance are identified and evaluated. This review indicates that calcium looping integration resulted in the projected efficiency penalty of 2.6–7.9% points for the coal-fired power plants and 9.1–11.4% points for the combined-cycle power plants. Also, it was found that the calcium looping process can be used to develop a novel high-efficiency (46.7%LHV) coal-fired power generation system, making this technology even more promising compared to the other CO2 capture technologies.

Calcium looping with inherent energy storage for decarbonisation of coal-fired power plant

Implementation of carbon capture and storage, nuclear power stations and wide utilisation of renewable energy sources have been identified as capable of reducing around 42% of the energy sector’s cumulative CO2 emissions between 2009 and 2050. In scenarios assuming high shares of renewable energy sources in the energy portfolio, energy storage technologies and the remaining power generating assets would be required to flexibly balance energy supply and demand. With nuclear power plants operating at base load, this task would be handled by flexible fossil fuel power plants with CO2 capture. However, mature CO2 capture systems were shown to impose high efficiency penalties (8–12.5% points) and are better suited for base-load operation. An emerging calcium looping process, which has also been considered for energy storage, has been found to offer lower efficiency penalties (5–8% points). This study presents a concept of the calcium looping process with inherent energy storage for decarbonisation of the coal-fired power plant. Analysis has revealed that the possible routes for energy storage in this process include CaO/CaCO3 solids storage, CaO/Ca(OH)2 solids storage and cryogenic O2 storage systems. Comparison of the CaO/CaCO3 storage and cryogenic O2 storage systems revealed that implementation of the latter would result in higher turndown of the entire system and would offer higher energy density. Also, the hydration reaction was found to improve the energy density of the CaO/CaCO3 energy storage system by 57.4%, from 307.2 kWth h m−3 to 483.6 kWth h m−3. Economic evaluation of the proposed concepts revealed that application of the cryogenic O2 storage system in the calcium looping CO2 capture process has the potential to increase the profitability of the integrated system, even over the reference coal-fired power plant without CO2 capture.

An experimental investigation of the combustion performance of human faeces

Highlights • Dry human faeces have a Higher Heating Value (HHV) of 24 MJ/kg.• Faeces combustion was investigated using a bench-scale downdraft combustor test rig.• Combustion temperature of 431–558 °C was achieved at air flow rate of 10–18 L/min.• Fuel burn rate of 1.5–2.3 g/min was achieved at air flow rate of 10–18 L/min.• Combustion temperature of up to 600 ± 10 °C can handle 60 wt.% moisture in faeces.

Conceptual energy and water recovery system for self-sustained nano membrane toilet

Highlights • Energy and water recovery system from human excreta is modelled in Aspen Plus.• The Nano Membrane Toilet is proven to be a self-sustained system.• Up to 87% of total amount of water fed to the system can be recovered.• Net power output of the entire system is similar to the USB port peak power (2–6 W).• The specific net power output varies between 23.1 and 69.2 Wh/kgsettledsolids.

PROCESS MODELLING AND TECHNO-ECONOMIC ANALYSIS OF NATURAL GAS COMBINED CYCLE INTEGRATED WITH CALCIUM LOOPING

Calcium looping is promising for large-scale CO2 capture in the power generation and industrial sectors due to the cheap sorbent used and the relatively low energy penalties achieved with this process. Because of the high operating temperatures the heat utilisation is a major advantage of the process, since a significant amount of additional power can be generated from it. However, this increases its complexity and capital costs. Therefore, not only the energy efficiency performance is im- portant for these cycles, but also the capital costs must be taken into account, i. e. techno-economic analyses are required in order to determine which parameters and configurations are optimal to enhance technology viability in different integration scenarios. In this study the integration scenarios of calcium looping and natural gas combined cycles are explored. The process models of the natural gas combined cy- cles and calcium looping CO 2 capture plant are developed to explore the most promising scenarios for natural gas combined cycles-calcium looping integration with regard to efficiency penalties. Two scenarios are analysed in detail, and show that the system with heat recovery steam generator before and after the capture plant exhibited better performance of 49.1% efficiency compared with that of 45.7% when only one heat recovery steam generator is located after the capture plant. However, the techno-economic analyses showed that the more energy efficient case, with two heat recovery steam generators, implies relatively higher cost of electrici- ty, 44.1 €/MWh, when compared to that of the reference plant system (33.1 €/MWh). The predicted cost of CO 2 avoided for the case with two heat recovery steam gener- ators is 29.3 € per tonne of CO2.

Rate-based Modelling of Chilled Ammonia Process (CAP) for CO2 Capture

Abstract Chilled ammonia process (CAP) has been identified as a promising alternative to the monoethanolamine based capture process for post-combustion CO 2 capture. Therefore, a full-scale rate-based CAP capture plant model has been developed. First, the aqueous NH 3 process was modelled in Aspen Plus and validated with pilot-plant data. The model was modified to meet the CAP operating conditions, and then scaled-up to process the flue gas from 660 MW el coal-fired power plant. The full-scale rate-based CAP model showed a substantial performance improvement through reducing the energy requirement for solvent regeneration by 27 % compared to the reference MEA process.