• Energy Research

Abstract This work investigates base and part load operation of natural gas combined cycle power plant integrated with post-combustion CO2 capture plant and selective exhaust gas recirculation scheme. Decarbonizing of natural gas combined cycle power plant is complex due to the higher flue gas flow rate with the least CO2 content ~ 3–4 vol% with residual 20% O2 and 77% N2 content. Therefore, the effect of series, parallel and hybrid selective exhaust gas recirculation is examined, a concept where selectively CO2 can be recycled back and mixed into the ambient air to the inlet feed of the compressor thereby reducing the flue gas flow rate and enhancing CO2 content at the inlet of capture plant. The study is novel in a way that part-load performance at 80, 60 and 40% for parallel and hybrid scheme of selective exhaust gas recirculation is analyzed through process simulation in Aspen Plus for 606 MW commercial-scale natural gas combined cycle power plant coupled with an amine-based CO2 capture plant. It is found that the simulation results of power plant and CO2 capture plant model agrees well with the experimental results. Further, the performance results show the viability of base and part load operation of natural gas combined cycle power plant integrated with CO2 capture plant by enhancing the CO2 concentration for hybrid configuration to approximately 19 vol%. For parallel configuration, CO2 content increases to around 13–14 vol% at 70% recirculation ratio in comparison to 6.6 vol% for simple EGR at 35% ratio. It is found that the selective exhaust gas recirculation offers more stable combustion by maintaining O2 content at 19 vol% at combustor inlets for parallel and hybrid cases and the flue gas flow rate reduces to 68 and 70%, respectively thus reducing the size of the capture plant. The specific reboiler duty for hybrid, parallel, and series configuration reduces to 3.19, 3.25, and 3.31 MJ/kg CO2, respectively in comparison to 3.54 MJ/kg CO2 for base case natural gas combined cycle power plant coupled with MEA-based CO2 capture unit. Whereas for 80 to 40% load change, the specific reboiler duty drops from 1.78% to 1.14% for parallel and hybrid configurations, respectively. In conclusion, hybrid selective exhaust gas recirculation configuration shows less efficiency penalty from base load to 40% part load and results in a decrease in specific reboiler duty in comparison to parallel configuration. Therefore, the study is innovative in an aspect that part-load performance at 80, 60 and 40% is performed, and results show a similar pattern as of baseload operation.

This study is carried out for a comparative screening of three groups of biomasses; soft or non-woody (peanut shell); intermediate woody (walnut shell) and hard woody (pine wood) for the development of adsorbents/activated carbons for post-combustion CO2 capture (over N2 balance). Three different groups of biomass residues are selected to study the role and nature of the material in adsorption and selection of the raw material for CO2 adsorbents synthesis for future researches because of the hot issue of anthropogenic CO2 emissions. The adsorption isotherms studied by the thermal gravimetric analyser (TGA) revealed that CO2 adsorption capabilities are in the range of 2.53–3.92 mmol/g (over N2 balance) at 25 °C. The newly synthesised activated carbons (ACs) exhibited a fast rate of adsorption as 41–94% in the initial 2 min. Porous surface development with catalytic KOH activation is seen clearly through SEM surface morphological analyses and mathematically confirmed from SBET ranges from 146.86 to 944.05 m2/g. FTIR and XRD peaks verify the generation of basic or inorganic O2-rich moieties that help in acidic CO2 capture. It has also been observed from adsorption isotherms that the order of higher adsorption groups is as; peanut shell > pine wood > walnut shell, while the best activation mass ratio (sample/KOH) is 1:3. The synthesised low cost ACs with an amount of 1.93 US$ per kg production could help to overcome the environmental hazards and problems caused by CO2 and biomass waste.

Abstract The solar photovoltaic cells received special attention during the past few years due to their rapid renewability consideration, particularly in international airports because of sustainability and high cost of fossil fuel. The present study aims to evaluate the feasibility performance of a novel 12 MWp capacity solar photovoltaic (PV) power plant at Doncaster Sheffield Airport, UK and to develop a mathematical model to provide a greater understanding of glare from solar panels and subsequently outline methods to avoid its effects. SISIFO and Global Solar Atlas software (GSA) simulations were used to obtain the results. Results reported that the proposed plant produced average energy of 1,034.31 MWh monthly and 12,411.69 MWh annually. The maximum electricity production was observed in May, June, and July as 1,772.71, 1,872.32, and 1,818.25 MWh, with 20.51, 21.67, and 21.04% of Capacity Utilization Factor (CUF), respectively. The average energy yield per month was achieved as 2585.74 kWh/kWp with an average performance ratio of 82.59%. Results also showed that 12 MWp PV plant at DSA reduced an average CO2 emission of 10,562,270 kg (11,642.90 tons) annually. The results revealed that glaring is very unlikely to occur throughout the year; however, winter period produced the lowest trajectory of reflected light. Overall, the proposed solar plant at Doncaster Sheffield airport (DSA) was found to be feasible and generates almost double electricity of overall energy demand (6,951.55 MWh) at Doncaster Sheffield airport. However, it is recommended that the excessive produced energy during summer could be transfer into the national grid, which would be returned during the winter season to facilitate PV plant.

The application of carbon capture and storage (CCS) and carbon neutral techniques should be adopted to reduce the CO2 emissions from power generation systems. These environmental concerns have renewed interest towards the use of biomass as an alternative to fossil fuels. This study investigates the comparative potential of different power generation systems, including NGCC with and without exhaust gas recirculation (EGR), pulverised supercritical coal and biomass fired power plants for constant heat input and constant fuel flowrate cases. The modelling of all the power plant cases is realized in Aspen Plus at the gross power output of 800 MWe and integrated with a MEA-based CO2 capture plant and a CO2 compression unit. Full-scale detailed modelling of integrated power plant with a CO2 capture and compression system for biomass fuel for two different cases is reported and compared with the conventional ones. The process performance, in terms of efficiency, emissions and potential losses for all the cases, is analysed. In conclusion, NGCC and NGCC with EGR integrated with CO2 capture and compression results in higher net efficiency and least efficiency penalty reduction. Further, coal and biomass fired power plants integrated with CO2 capture and compression results in higher specific CO2 capture and the least specific losses per unit of the CO2 captured. Furthermore, biomass with CO2 capture and compression results in negative emissions.

The deployment of post-combustion CO2 capture on large-scale gas-fired power plants is\ud currently progressing, hence the integration of the power and capture plants requires a\ud good understanding of operational requirements and limitations to support this effort. This\ud article aims to assist research in this area, by studying a micro gas turbine (MGT) integrated\ud with an amine-based post-combustion CO2 capture unit. Both processes were simulated\ud using two different software tools – IPSEpro and Aspen Hysys, and validated against\ud experimental tests. The two MGT models were benchmarked at the nominal condition, and\ud then extended to part-loads (50 and 80 kWe), prior to their integration with the capture\ud plant at flue gas CO2 concentrations between 5 and 10 mol%. Further, the performance of\ud the MGT and capture plant when gas turbine exhaust gases were recirculated was assessed.\ud Exhaust gas recirculation increases the CO2 concentration, and reduces the exhaust gas\ud flowrate and specific reboiler duty. The benchmarking of the two models revealed that the\ud IPSEpro model can be easily adapted to new MGT cycle modifications since turbine\ud temperatures and rotational speeds respond to reaching temperature limits; whilst a\ud detailed rate-based approach for the capture plant in Hysys resulted in closely aligned\ud simulation results with experimental data.\ud

Climate change is the biggest challenge of this century due to the global consequences of human activities on the ecosystem resulting in global warming. The emissions of greenhouse gases, mainly CO2 from the combustion of fossil fuels in the power plant is the main cause of global warming and to mitigate these emissions is the foremost challenge. Nowadays, the most preferred method is post combustion chemical absorption using amine-based solvents. However, high energy requirements for this method restrict its deployment. An efficient approach used for the reduction of the high energy requirement of post combustion CO2 capture process was absorber intercooling. Therefore, this research evaluates the effect of two configurations of intercooled absorber such as “simple” and “advanced” intercoolers for CO2 capture integrated with natural gas combined cycle power plant using aqueous alkanolamines, such as 30 wt.% monoethanolamine and 50 wt.% methyl-diethanolamine and their blends. For pure methyl-diethanolamine case, at lean loading 0.01 intercooling configurations; simple and advanced shows the highest reduction of 21.01% and 22.82% in the specific reboiler duty, respectively in comparison to other blends at the expense of highest liquid solvent flow rate. Simple and advanced intercooling configurations shows optimum results for the case with 40% monoethanolamine and 60% methyl-diethanolamine in a blend with decrease of 9.19% and 17.28% in solvent flow rate and a decrease of 9.42% and 16.83% in specific reboiler duty required for 90% CO2 capture rate, respectively. For pure monoethanolamine case at lean loading 0.2 absorber intercooling does not offer significant results.

Gas turbines are a viable and secure option both economically and environmentally for combined heat and power generation. Process modelling of a micro gas turbine for CO2 injection and exhaust gas recirculation (EGR) is performed. Further, this study is extended to assess the effect of the CO2 injection on the pilot-scale CO2 capture plant integrated with a micro gas turbine. In addition, the impact of the EGR on the thermodynamic properties of the fluid at different locations of the micro gas turbine is also evaluated. The micro gas turbine and CO2 injection models are validated against the set of experimental data and the performance analysis of the EGR cycle results in CO2 enhancement to 5.04 mol% and 3.5 mol%, respectively. The increased CO2 concentration in the flue gas, results in the specific reboiler duty decrease by 20.5 % for pilot-scale CO2 capture plant at 90 % CO2 capture rate for 30 wt. % MEA aqueous solution. The process system analysis for the validated models results in a much better comprehension of the impact of the CO2 enhancement on the process behaviour.