A systematic investigation of the performance of copper-, cobalt-, iron-, manganese-, and nickel-based oxygen carriers for chemical looping combustion technology through simulation studies

The Integrated Gasification Combined Cycle coupled with chemical looping combustion (IGCC-CLC) is one of the most promising technologies that allow generation of cleaner energy from coal by capturing carbon dioxide (CO2). It is essential to compare and evaluate the performances of various oxygen carriers (OC), used in the CLC system; these are crucial for the success of IGCC-CLC technology. Research on OCs has hitherto been restricted to small laboratory and pilot scale experiments. It is therefore necessary to examine the performance of OCs in large-scale systems with more extensive analysis. This study compares the performance of five different OCs – copper, cobalt, iron, manganese and nickel oxides – for large-scale (350–400 MW) IGCC-CLC processes through simulation studies. Further, the effect of three different process configurations: (i) water-cooling, (ii) air-cooling and (iii) air-cooling along with air separation unit (ASU) integration of the CLC air reactor, on the power output of IGCC-CLC processes – are also investigated. The simulation results suggest that iron-based OCs, with 34.3% net electrical efficiency and ~100% CO2 capture rate lead to the most efficient process among all the five studied OCs. A net electrical efficiency penalty of 7.1–8.1% points leads to the IGCC-CLC process being more efficient than amine based post-combustion capture technology and equally efficient to the solvent based pre-combustion capture technology. The net electrical efficiency of the IGCC-CLC process increased by 0.6–2.1% with the use of air-cooling and ASU integration, compared with the water- and air-cooling cases. This work successfully demonstrates a correlation between the reaction enthalpies of different OCs and power output, which suggests that the OCs with higher values of reaction enthalpy for oxidation (ΔHr, oxidation) with air-cooling are more valuable for the IGCC-CLC

The range and level of impurities in CO2 streams from different carbon capture sources

For CO2 capture and storage deployment, the impact of impurities in the gas or dense phase CO2 stream arising from fossil fuel power plants, or large scale industrial emitters, is of fundamental importance to the safe and economic transportation and storage of the captured CO2. This paper reviews the range and level of impurities expected from the main capture technologies used with fossil-fuelled power plants in addition to other CO2 emission-intensive industries. Analysis is presented with respect to the range of impurities present in CO2 streams captured using pre-combustion, post-combustion and oxy-fuel technologies, in addition to an assessment of the different parameters affecting the CO2 mixture composition. This includes modes of operation of the power plant, and different technologies for the reduction and removal of problematic components such as water and acid gases (SOx/NOx). A literature review of data demonstrates that the purity of CO2 product gases from carbon capture sources is highly dependent upon the type of technology used. This paper also addresses the CO2 purification technologies available for the removal of CO2 impurities from raw oxy-fuel flue gas, such as Hg and non-condensable compounds. CO2 purities of over 99% are achievable using post-combustion capture technologies with low levels of the main impurities of N2, Ar and O2. However, CO2 capture from oxy-fuel combustion and integrated gasification combined cycle power plants will need to take into consideration the removal of non-condensables, acid gas species, and other contaminants. The actual level of CO2 purity required will be dictated by a combination of transport and storage requirements, and process economics

Energy and exergy analysis of chemical looping combustion technology and comparison with pre-combustion and oxy-fuel combustion technologies for CO2 capture

Carbon dioxide (CO2) emitted from conventional coal-based power plants is a growing concern for the environment. Chemical looping combustion (CLC), pre-combustion and oxy-fuel combustion are promising CO2 capture technologies which allow clean electricity generation from coal in an integrated gasification combined cycle (IGCC) power plant. This work compares the characteristics of the above three capture technologies to those of a conventional IGCC plant without CO2 capture. CLC technology is also investigated for two different process configurations—(i) an integrated gasification combined cycle coupled with chemical looping combustion (IGCC–CLC), and (ii) coal direct chemical looping combustion (CDCLC)—using exergy analysis to exploit the complete potential of CLC. Power output, net electrical efficiency and CO2 capture efficiency are the key parameters investigated for the assessment. Flowsheet models of five different types of IGCC power plants, (four with and one without CO2 capture), were developed in the Aspen plus simulation package. The results indicate that with respect to conventional IGCC power plant, IGCC–CLC exhibited an energy penalty of 4.5%, compared with 7.1% and 9.1% for pre-combustion and oxy-fuel combustion technologies, respectively. IGCC–CLC and oxy-fuel combustion technologies achieved an overall CO2 capture rate of ∼100% whereas pre-combustion technology could capture ∼94.8%. Modification of IGCC–CLC into CDCLC tends to increase the net electrical efficiency by 4.7% while maintaining 100% CO2 capture rate. A detailed exergy analysis performed on the two CLC process configurations (IGCC–CLC and CDCLC) and conventional IGCC process demonstrates that CLC technology can be thermodynamically as efficient as a conventional IGCC process

Comparative assessment of gasification based coal power plants with various CO2 capture technologies producing electricity and hydrogen

Seven different types of gasification-based coal conversion processes for producing mainly electricity and in some cases hydrogen (H2), with and without carbon dioxide (CO2) capture, were compared on a consistent basis through simulation studies. The flowsheet for each process was developed in a chemical process simulation tool “Aspen Plus”. The pressure swing adsorption (PSA), physical absorption (Selexol), and chemical looping combustion (CLC) technologies were separately analyzed for processes with CO2 capture. The performances of the above three capture technologies were compared with respect to energetic and exergetic efficiencies, and the level of CO2 emission. The effect of air separation unit (ASU) and gas turbine (GT) integration on the power output of all the CO2 capture cases is assessed. Sensitivity analysis was carried out for the CLC process (electricity-only case) to examine the effect of temperature and water-cooling of the air reactor on the overall efficiency of the process. The results show that, when only electricity production in considered, the case using CLC technology has an electrical efficiency 1.3% and 2.3% higher than the PSA and Selexol based cases, respectively. The CLC based process achieves an overall CO2 capture efficiency of 99.9% in contrast to 89.9% for PSA and 93.5% for Selexol based processes. The overall efficiency of the CLC case for combined electricity and H2 production is marginally higher (by 0.3%) than Selexol and lower (by 0.6%) than PSA cases. The integration between the ASU and GT units benefits all three technologies in terms of electrical efficiency. Furthermore, our results suggest that it is favorable to operate the air reactor of the CLC process at higher temperatures with excess air supply in order to achieve higher power efficiency

Sulfur trioxide formation/emissions in coal‐fired air‐ and oxy‐fuel combustion processes: a review

In oxy‐fuel combustion, fuel is burned using oxygen together with recycled flue gas, which is needed to control the combustion temperature. This leads to higher concentrations of sulfur dioxide and sulfur trioxide in the recycled gas, which can result in the formation of sulfuric acid and enhanced corrosion. Current experimental data on SO3 formation, reaction mechanisms, and mathematical modelling have indicated significant differences in SO3 formation between air‐ and oxy‐fuel combustion for both the wet and dry flue gas recycle options. This paper provides an extensive review of sulfur trioxide formation in air‐ and oxy‐fuel combustion environments, with an emphasis on coal‐fired systems. The first part summarizes recent findings on oxy‐fuel combustion experiments, as they affect sulfur trioxide formation. In the second part, the review focuses on sulfur trioxide formation mechanisms, and the influence of catalysis on sulfur trioxide formation. Finally, the current methods for measuring sulfur trioxide concentration are also reviewed along with the major difficulties associated with those measurements using data available from both bench‐ and pilot‐scale units

Analysis of gas turbine systems for sustainable energy conversion

Increased energy demands and fear of global warming due tothe emission of greenhouse gases call for development of newefficient power generation systems with low or no carbondioxide(CO2) emissions. In this thesis, two different gasturbine power generation systems, which are designed with theseissues in mind, are theoretically investigated and analyzed.Inthe first gas turbine system, the fuel is combusted using ametal oxide as an oxidant instead of oxygen in the air. Thisprocess is known as Chemical Looping Combustion (CLC). CLC isclaimed to decrease combustion exergy destruction and increasethe power generation efficiency. Another advantage is thepossibility to separate CO2without a costly and energy demanding gasseparation process. The system analysis presented includescomputer-based simulations of CLC gas turbine systems withdifferent metal oxides as oxygen carriers and different fuels.An exergy analysis comparing the exergy destruction of the gasturbine system with CLC and conventional combustion is alsopresented. The results show that it is theoretically possibleto increase the power generation efficiency of a simple gasturbine system by introducing CLC. A combined gas/steam turbinecycle system with CLC is, however, estimated to reach a similarefficiency as the conventional combined cycle system. If thebenefit of easy and energy-efficient CO2separation is accounted for, a CLC combined cyclesystem has a potential to be favorable compared to a combinedcycle system with CO2separation. In the second investigation, a solid, CO2-neutral biomass fuel is used in a small-scaleexternally fired gas turbine system for cogeneration of powerand district heating. Both open and closed gas turbines withdifferent working fluids are simulated and analyzed regardingthermodynamic performance, equipment size, and economics. Theresults show that it is possible to reach high power generationefficiency and total (power-and-heat) efficiency with thesuggested system. The economic analysis reveals that the costof electricity from theEFGT plant is competitive with the moreconventional alternatives for biomass based cogeneration in thesame size range (<10 MWe). Keywords:power generation, Chemical Looping Combustion,CO2separation, oxygen carrier, biomass fuel, closedcycle gas turbine, externally fired gas turbineNR 2014080

Preoperativ information till föräldrar - Hur påverkar den?

När ett barn ska opereras upplever såväl barnet som dess föräldrar stress. I en sådan situation kan det vara svårt att fungera som stöd åt sitt barn. Olika faktorer kan underlätta för föräldrarna varav en är information. Problemområde för denna litteraturstudie är preoperativ information till föräldrar. Syftet var att kartlägga hur litteraturen beskriver information till föräldrar och hur informationen påverkar barn och föräldrar. Metoden har följt forskningsprocessen vid en litteraturstudie där fråga, problemformulering, litteratursökning, evaluering, tolkning och rapportering ingår. Efter databassökningar i framför allt PubMed har åtta artiklar valts ut som ligger till grund för resultatet. Resultatet visade att omvårdnadspersonal med hjälp av individuellt anpassad information kan reducera oron hos både föräldrar och barn. Resultatet visar också att den viktigaste informationsvägen fortfarande är den muntliga men att den behöver kompletteras med andra informationsvägar.When a child is due for surgery, the child as well as it’s parents experience stress. In a stresssful situation it can be difficult to function as suppport to one’s child. The area of interest in this review is preoperative information to parents. The aim is to investigate the scientific description of how preoperative information to parents are communicated and how it affects the child as well as it’s parents. The review has followed the scientific procedure described in the following headings: formulating a scientific question, emphasizing a problem, seeking literature, evaluating, interpret and report. After searches in electronic databases, mainly in PubMed, we decided to use eight articles for our result. The result shows that we can reduce anxiety in parents and children by giving them individual preoperative information. Verbal information can never be replaced but needs to be combined by other sorts of information

Denitrogenation (or Oxyfuel Concepts)

Denitrogenation or oxyfuel combustion is ,based on separation of oxygen from nitrogen before combustion. The CO2 obtained is concentrated and easy to isolate after combustion. Oxyfuel combustion has been used in different industrial applications, although technological challenges have to be met for large scale power generation. An important area of improvement of this concept is to be found in the air separation unit, with the help of new technologies like membrane separation technologies, high temperature oxygen adsorption technologies, and improved cryogenic distillation