•The catalytic effect of potassium doping on soot oxidation is studied in oxy-fuel combustion.•The catalysis extent is affected by potassium type, doping concentration, oxygen concentration, ...atmosphere.•The catalytic role of potassium in oxy-fuel combustion is lower than that in air combustion.•The promotion degree of potassium doping presents the minimum value around at 15% O2 concentration.•These observations strongly approve the hypothesis that potassium as the oxygen carrier.
In oxy-fuel combustion, switching from nitrogen to carbon dioxide atmosphere with higher oxygen concentration will affect the oxidation rate of soot, and it was observed in our recent study on soot emission from biomass pyrolysis that potassium (K) crystals are embedded in soot and its precursor clusters. In this study, the effects of K-doping (KCl and K2SO4) and O2 concentration on soot oxidation in O2/CO2 atmosphere are studied using thermogravimetric analysis (TGA), and the extent of catalysis is compared with that in O2/N2 atmosphere. The delays on start, peak and end temperatures of soot oxidation are observed in O2/CO2 atmosphere. However, increase in O2 concentration which promotes oxidation significantly reduces the delay. All the K-doping cases results in accelerated soot oxidation rate, but catalytic role of the K-doping in O2/CO2 is significantly lower than that in O2/N2 because the CO2-enriched environment inhibits the performance of potassium as oxygen carrier. The accelerating degree from K-doping is also affected by the potassium type, doping mass and oxygen concentration. KCl acts as a better, more efficient doping agent than K2SO4 with the increase in doping mass. The catalytic effect of K2SO4 will not change and even decrease at 375μmol(K)/g(soot) for K2SO4 while the catalytic role of KCl keeps increasing even at 600μmol(K)/g(soot) for KCl. In O2 concentration range of 5–30%, the accelerating degree from K-doping presents the minimum value around 15%. This phenomenon strongly approves the hypothesis that potassium as the oxygen carrier and accelerating the oxygen transportation, because in the cases of without K-doping and at a high O2 concentration there is no additional active site for more O2 adsorption thus inducing the slow accelerating degree. The kinetic analysis indicates the first order reaction for soot oxidation and also a good compensation relation between apparent activation energy E and logarithmic frequency factor A. E is generally reduced with the atmosphere changing from O2/N2 to O2/CO2, with K-doping, and with O2 concentration decreasing. This study is beneficial to demonstrate the mechanism of how potassium doping and oxygen concentration affect soot oxidation rate in oxy-fuel combustion environment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
A pressurized drop tube furnace was used to study the pyrolysis behavior of bituminous and lignite coal at elevated pressure. Experiments were conducted at the pressure range from 1 to 10 atm in 100% ...N2 or 100% CO2 atmosphere. The volatile yields, char morphology, swelling ratio, and pore structure were discussed in detail. The results show that the pressure, atmosphere and coal rank could effect on the volatile releasing and char evolution significantly. In N2 atmosphere, the total volatile yields of YL and NM coal decrease as the pressure elevated, while in CO2 atmosphere, the mass release of NM coal increases at high pressure contributed by the reaction of CO2 with organic macromolecule inside the particles; different with bituminous coal, no significant swelling behavior is found with the increase of pressure; the BET surface area of YL char decreases as the pressure increases, while for lignite coal, in N2 atmosphere and at high pressure, less macro pores are formed, which could contribute to the BET surface area. While in CO2 atmosphere, the CO2-macromocular organic reaction would promote the volatile releasing, and the BET surface area decreases significantly at high pressure.
•Char gasification increases from 0.55% to 4.25% at elevated pressure.•Volatile releasing of lignite is enhanced significantly in CO2 atmosphere.•No significant swelling is found for lignite char.•BET surface area of produced char is susceptible to the atmosphere and pressure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
As a vital power propulsion device, gas turbines have been widely applied in aircraft. However, fly ash is easily ingested by turbine engines, causing blade abrasion or even film hole blockage. In ...this study, a three-dimensional turbine cascade model is conducted to analyze particle trajectories at the blade leading edge, under a film-cooled protection. A deposition mechanism, based on the particle sticking model and the particle detachment model, was numerically investigated in this research. Additionally, the invasion efficiency of the AGTB-B1 turbine blade cascade was investigated for the first time. The results indicate that the majority of the impact region is located at the leading edge and on the pressure side. In addition, small particles (1 μm and 5 μm) hardly impact the blade’s surface, and most of the impacted particles are captured by the blade. With particle size increasing, the impact efficiency increases rapidly, and this value exceeds 400% when the particle size is 50 μm. Invasion efficiencies of small particles (1 μm and 5 μm) are almost zero, and the invasion efficiency approaches 12% when the particle size is 50 μm.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The Conferences on Sustainable Development of Energy, Water and Environment Systems (SDEWES) at the beginning of the 21st century have become a significant venue for researchers to meet, and ...initiate, discuss, share, and disseminate new ideas in various disciplines of sustainable development. In 2002, the first conference was organised in Dubrovnik, Croatia and since then, 10 more successful conferences were realised. Following the success of international conferences in Dubrovnik, the organizing committees decided to organize the main conference and regional conferences all over the world in even years. In 2016, the second regional SDEWES conference, namely the 2nd South East European Conference on Sustainable Development of Energy, Water and Environment Systems, was held June 15–18 in Piran/Portorose, Slovenia while the 11th SDEWES conference was organised in Lisbon, Portugal on September 4–8. There were 10 special sessions dedicated to various sustainability topics organised in both conferences.
This special issue is based primarily upon a collection of 35 papers selected from among 538 scientific contributions presented at the 2nd SEE and 11th SDEWES Conferences. Moreover, this editorial summarises SDEWES published articles that have addressed and identified problems or provided the background for the research that is reported in the current special issue. The main topics of the selected papers address sustainable combustion technologies, renewable energy sources and sector integration, including the integration of renewable technologies in the urban environment, the integration of heat, cold, electricity and fuel production in buildings and industrial applications, heat exchangers and heat exchanger networks, the development and integration of energy storage for concentrated solar power plants, and sectorial integration of bioenergy resources and biorefineries with a particular focus on system integration for efficient and low-carbon systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•Numerical model for fuel disintegration was presented.•Fuel liquid and vapour were calculated.•Good agreement with experimental data was shown for various combinations of injection and chamber ...pressure.
This research investigates high pressure diesel fuel injection into the combustion chamber by performing computational simulations using the Euler–Eulerian multiphase approach. Six diesel-like conditions were simulated for which the liquid fuel jet was injected into a pressurised inert environment (100% N2) through a 205μm nozzle hole. The analysis was focused on the liquid jet and vapour penetration, describing spatial and temporal spray evolution. For this purpose, an Eulerian multiphase model was implemented, variations of the sub-model coefficients were performed, and their impact on the spray formation was investigated. The final set of sub-model coefficients was applied to all operating points. Several simulations of high pressure diesel injections (50, 80, and 120MPa) combined with different chamber pressures (5.4 and 7.2MPa) were carried out and results were compared to the experimental data. The predicted results share a similar spray cloud shape for all conditions with the different vapour and liquid penetration length. The liquid penetration is shortened with the increase in chamber pressure, whilst the vapour penetration is more pronounced by elevating the injection pressure. Finally, the results showed good agreement when compared to the measured data, and yielded the correct trends for both the liquid and vapour penetrations under different operating conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
•The products and contents of DMF pyrolysis and fuel-lean combustion and the characteristics of SNCR for DMF combustion products were studied.•The products of largest concentration in DMF pyrolysis ...are H2, CO, HCN and CH4.•HCN, N2O and NO are generated as the mainly N-containing species in DMF’s fuel-lean combustion, and NO concentration increases with the increase of temperature or equivalence ratio.•With a lower temperature of 850 °C and high NSR ratio, SNCR has obvious effect on NO removal of the products from DMF combustion, while N2O removal rate is low.
An experimental investigation was conducted on N,N-dimethylformamide (DMF) pyrolysis at medium-temperature followed by extremely fuel-lean combustion. Furthermore, the NH3-SNCR (Selective non-catalytic reduction) method was studied to control NOx produced in DMF oxidation. Jet-stirred reactors (JSRs) were used in experimental investigation, because the uniform gas-phase mixing state formed by high-speed turbulence in JSR makes the validation of detailed models easier. The major gaseous species produced by pyrolysis, oxidation, and SNCR, namely H2, N2, CO, CO2, NOx, N2O, HCN, and CxHy, are quantified because the mechanism of NOx reduction will be elaborated using these species. The results show that the main nitrogen-containing pyrolysis products are HCN and N2, taking up 65% and 25% of DMF nitrogen, while carbon-containing pyrolysis products are mostly CO, CH4 and HCN. The HCN concentration increases significantly by 42.13% as pyrolysis time increases from 1.5 to 7 s. In oxidation, HCN and N2O concentration peaks are at 650 °C and 750 °C respectively, and NO concentration increases as temperature enhances when it is over 800 °C. A higher ratio of NO/N2O concentration was shown in oxidation of the higher equivalence ratio. The de-NOx efficiency of NH3-SNCR on oxidation flue gas peaked in range 825–875 °C, and as the NH3/NO ratio increased to more than 2.5, NO removal rate tended to reach the maximum of about 50%. The N2O removal rate rose significantly as temperature exceeded 900 °C in SNCR. The results shows the feasibility of NO emission control with DMF containing VOCs incineration in current industrial applications·NH3-SNCR at 825–875 °C shows significant de-NOx effect, but not a proper solution to limit N2O emission at the same time. This study could provide guidance for designing and optimizing the incinerator parameters and its de-NOx system, as well as provide validation data for future chemical kinetic model capable of predicting DMF combustion.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The utilization of biomass combustion for electricity generation has grown an importance and popularity. However, effective management of ash produced during biomass combustion is a major challenge. ...To analyze the ecological risk of heavy metals and ash characteristics in biomass ash, an inductive coupled plasma emission spectrometer (ICP) and X-ray diffraction (XRD) were used. The effects of temperature (20 °C, 40 °C, 60 °C), stirrer time (1h, 2h, 3h), and water-ash ratio (1:1, 2:1, 3:1) on potassium extraction were studied. The results show that the ecological risk index (RI) values of the fly ash and slag samples are very high, and all samples have very high risk (VHR) mainly due to Cd higher toxicity than other heavy metals. The main constituents of slag are aluminosilicate and SiO2, whereas fly ash contains CaSO4, KCl, SiO2, and KAlSi3O8. The fly ash from straw-fired biomass boiler contains more potassium, making it the most suitable raw material for the actual potassium extraction. In addition, temperature and stirrer time have little effect on potassium solubility while the effect of water-ash ratio is significant. Therefore, the most cost-effective potassium extraction method is water washing at room temperature with a stirrer time of about 1 h, a water-ash ratio of about 2:1, and leaching fly ash multiple times with incorporating the water recycling.
•The ecological risk index values of the fly ash can reach very high risk (VHR) level.•The fly ash in straw-fired boiler is a suitable raw material for potassium extraction.•Room temperature and short stirrer time (about 1 h) are better choices for potassium extraction.•The water-ash ratio has a great influence on the leaching rate of potassium.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work presents multi-objective optimization of an aspirating smoke detection system which uses the pipeline to transport air sample from the sampling points to the analysing module. On the basis ...of 3D computational fluid dynamics simulation it has been shown that the smoke transport will not always take place in the centre of the pipe and that one dimensional analysis is not able to provide information in which layer smoke transport will take place. Consequently, velocity from the layer at the distance of 0.95
R
from the pipe centreline was taken as an input for calculation of the transport time to bind the calculation on the safe side. By employing the multi-objective optimization approach, balancing of specific transport time and volume flow at the sampling points’ location was achieved through pipeline configuration variation with respect to pipe diameters and the position of branches along the main pipe. Objective function was assembled from the flow rate function and transport time function using the weighted sum method. Results for five different values of weight factor have been discussed. After reaching weight factor value of 0.75, configuration reached requested sensitivity, and further increase of weight factor enabled more uniform flow across the network without deterioration of transport time.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Pressurized oxy-combustion (POC) is an emerging technology and has a higher efficiency compared to atmospheric combustion for carbon capture, utilization, and sequestration (CCUS). NOx is one of the ...significant conventional pollutants produced in POC, which has not only a disastrous effect on the environment but also aggravate the corrosion in the CCUS system. Ammonia is one of the primary gaseous precursors for NOx generation in solid fuel combustion. Nonetheless, the evolution of NOx from ammonia oxidation in pressurized combustion is still rarely studied, especially in the oxy-environment. Therefore, it is imperative to study the NOx formation from ammonia oxidation and its control in POC. In this study, first, the formation of NOx from ammonia oxidation in POC is kinetically evaluated. Different parameters are investigated at elevated pressure i.e., the effects of oxy and the air-environment, temperature, H2O, and SO2 concentration, on NOx formation. After that, reburning process is analyzed at high pressure to control the NOx using the actual POC conditions. The results illustrate that the ammonia oxidation temperature continues to decrease as the pressure rises from 1 atm to 10 atm. Pressures larger than 10 atm have no effect on the oxidation of NH3. The NO formation from NH3 oxidation continuously decreases with increasing the pressure, which means that higher pressure inhibits the NOx formation. The NO formation in air is significantly higher than the oxy-environment, due to the significant thermal NOx formation in air environment. The water vapor enhances the NO formation in oxy-environment significantly at 1 atm, however this effect is suppressed by elevated pressure. There is no effect of SO2 on NH3 oxidation and NO formation at both atmospheric and elevated pressure. The NO reduction by reburning process is enhanced from 43% to 76% with a pressure increase from 1 atm to 15 atm. In addition, the conversion of NO to N2 is boosted by elevating the pressure.
•NH3 oxidation starts at lower temperature (950K) at 10 atm compared to 1 atm (1100K).•NO formation from NH3 oxidation decreases with increasing the pressure.•NO reduction by reburning process is enhanced from 43% to 76% at elevated pressure.•The N2 formation from NO is enhanced as the pressure increases from 1 to 10 atm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Thermogravimetric and kinetic analysis of biomass and plastic co-pyrolysis can provide valuable inputs for a better understanding of decomposition mechanisms. Such inputs are important for selecting ...the appropriate process conditions but can also be helpful for process modelling. This work investigates the properties of heterogenous sawdust in a mixture with polypropylene and polystyrene. Thermogravimetric analysis is conducted to determine the decomposition mechanism and kinetic parameters of investigated mixtures and to derive appropriate conclusions regarding their further utilization potential. Co-pyrolysis was performed on mixtures with the following biomass/plastic ratios: 75-25%, 50-50%, 25-75%, over a temperature range of 30-550 °C, at four heating rates 5, 10, 20, and 30 °C/min, with pure argon as a carrier gas. Obtained results were then subjected to comprehensive kinetic and thermodynamic analysis. The primary goal was to determine effective activation energies using model-free methods, pre-exponential factors, and elementary thermodynamic parameters such as changes in enthalpy, entropy, and free Gibbs energy. Finally, the influence of the heating rate and mixture composition was extensively investigated by analyzing calculated parameters.
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