• Energy Research

Abstract The results of carbon dioxide separation from real flue gas using the dual-reflux vacuum pressure swing adsorption (DR-VPSA) technology have been presented. The mobile pilot CO2 separation plant consists of two containers: a processing container and a control container. The processing container includes a flue gas treatment section (which comprises dust removal, cooling, deSOx, deNOx, gas drying and compression units), as well as a CO2 adsorptive separation unit. The adsorption unit is made up of four fixed-bed columns, each divided into two sections, operating in a dual-reflux vacuum pressure swing adsorption mode. Two kinds of activated carbon in the total amount of 540 kg were used as the beds filling. The results from the 8-step reference process with no partition of the adsorbers into the upper and lower sections (as one-step separation process with partial product recirculation), and from the 9-step DR-VPSA process (as two-step separation process) with a division of the adsorbers are presented. In the measurement campaign three different feed gas flow rates and five different times of adsorption step were selected to assess their influence on separation results. The results show the optimal parameters of 100 Nm3/h for feed gas flow rate and 300 sec for adsorption step time for both mentioned processes. The 87.5% of purity, 44.6% of recovery, 11.4 kg/(m3 h) of productivity and 978 kWh/MgCO2 of energy demand for gas compression and vacuum evacuation in the case of optimal parameters of 9-step DR-VPSA technology were obtained. Additionally the results from measurement campaign were compared with those reported by other researchers.

Carbon Capture and Utilization (CCU) is a viable solution to valorise the CO2 captured from industrial plants’ flue gas, thus avoiding emitting it and synthesizing products with high added value. On the other hand, using CO2 as a reactant in chemical processes is a challenging task, and a rigorous analysis of the performance is needed to evaluate the real impact of CCU technologies in terms of efficiency and environmental footprint. In this paper, the energetic performance of a DME and methanol synthesis process fed by 25% of the CO2 captured from a natural gas combined cycle (NGCC) power plant and by the green hydrogen produced through an electrolyser was evaluated. The remaining 75% of the CO2 was compressed and stored underground. The process was assessed by means of an exergetic analysis and compared to post-combustion Carbon Capture and Storage (CCS), where 100% of the CO2 captured was stored underground. Through the exergy analysis, the quality degradation of energy was quantified, and the sources of irreversibility were detected. The carbon-emitting source was a 189 MW Brayton–Joule power plant, which was mainly responsible for exergy destruction. The CCU configuration showed a higher exergy efficiency than the CCS, but higher exergy destruction per non-emitted carbon dioxide. In the DME/methanol production plant, the main contribution to exergy destruction was given by the distillation column separating the reactor outlet stream and, in particular, the top-stage condenser was found to be the component with the highest irreversibility (45% of the total). Additionally, the methanol/DME synthesis reactor destroyed a significant amount of exergy (24%). Globally, DME/methanol synthesis from CO2 and green hydrogen is feasible from an exergetic point of view, with 2.276 MJ of energy gained per 1 MJ of exergy destroyed.

The problem of reducing carbon dioxide emissions from flue gas, particularly from flue gas originating from coal-firing CFB systems, is currently an important challenge. Many centers around the world have tested post-combustion CO2 capture systems. One of these systems, operated using DR-VPSA adsorption technology (dual-reflux vacuum pressure swing adsorption), was tested under the Strategic Project in Poland. The flue gas in this study originated from a supercritical CFB boiler (460 MWe). An important problem involved in capturing CO2 from flue gas is the occurrence of SO2 and NOx. These substances have a negative effect on the CO2 adsorption process. In this study, commercial impregnated activated carbon was used to remove SO2 and NOx from CFB flue gas in the pre-treatment section during the tests of a pilot CO2 capture unit in a large-scale CFB boiler at the Lagisza Power Plant (Poland). The spent activated carbon was analyzed using several different methods (N2 adsorption–desorption isotherms, SEM-EDX, XRD, FTIR, and TG) to evaluate the efficiency of the operation and life span of the adsorbent used in the SO2 and NOx removal unit. The results demonstrate that using commercial impregnated activated carbon in the pre-treatment section ensures sufficient flue gas purification and the removal of sulfur oxides but remains insufficient for nitrogen oxides.

Carbon Capture Utilization and Storage (CCUS) is a set of technologies aimed at capturing carbon dioxide (CO2) emissions from point-source emitters to either store permanently or use as a feedstock to produce chemicals and fuels. In this paper, the potential benefits of CCUS integration into the energy supply sector are evaluated from a Life Cycle Assessment (LCA) perspective by comparing two different routes for the CO2 captured from a natural gas combined cycle (NGCC). Both the complete storage of the captured CO2 and its partial utilization to produce dimethyl ether are investigated. Moreover, the assessment is performed considering the region-specific features of two of the largest CO2 emitters in Europe, namely Italy and Poland. Results shows that the complete storage of the captured CO2 reduces Global Warming Potential (GWP) by ~89% in Italy and ~97%, in Poland. On the other hand, the partial utilization of CO2 to produce dimethyl ether leads to a decrease of ~58% in Italy and ~68% in Poland with respect to a comparable reference entailing conventional dimethyl ether production. A series of environmental trade-offs was determined, with all the investigated categories apart from GWP showing an increase, mainly connected with the higher energy requirements of CCUS processes. These outcomes highlight the need for a holistic-oriented approach in the design of novel implemented configurations to avoid burden shifts throughout the value chain.

Bioadsorbent, obtained as a result of the processing of bio-waste, has recently gained popularity as a material that adsorbs greenhouse gases, mainly carbon dioxide. Bio-waste, mainly residues from food industry operations, is a waste to be landfilled or composted and can be a potential substrate for bioadsorbent production. Bioadsorbents used for carbon capture must, above all, have low production costs and high adsorption efficiency. This review covers popular bioadsorbents that have been tested for their ability to adsorb carbon dioxide. The paper compares bioadsorbent production methods, physicochemical properties, adsorption isotherms, surfaces, and their porosity. There is a lack of data in the literature on the topic of carbon dioxide adsorption on large-scale plants in the target environment. Therefore, further research needs to fill in the gaps to identify the promised potential of these bioadsorbents.

Abstract The results of laboratory and numerical investigations of oxy-combustion flue gas purification for enhanced oil recovery (EOR) as well as storage purposes using the adsorption method were presented. The experimental investigations provided results of purification process and allowed to determine the correction factors for validation and calibration of the elaborated numerical model. In turn, the numerical simulations were used to extensive research on the purification process at different thermodynamic conditions and process configurations, other than applied at laboratory tests. Neither experimental research nor numerical simulations confirmed the possibility of enrichment the oxy-combustion flue gas to meet the conceptual design purity limits of oxygen at the level of 10ppmv (recommended by NETL) for EOR and storage purposes, but the purity of the product was met in the case of higher ones, described in the literature. The conducted analysis of the energy demand shows that the one-stage vacuum-pressure swing adsorption (VPSA) purification process requires about 57 kWh/tCO2 at recovery of 73.58% and product purity of 97.78% when the product is at the ambient pressure, 128 kWh/tCO2 when the product is at 18 bar and 161 kWh/tCO2 at the pressure equals 120 bar. Obtained results were also compared with the literature data.