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  • Post
    Chemically active bed material in fluidiced-bed combustion and related processes for CO2 mitigation
    (2022) Lindberg, Catrin; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Rydén, Magnus; Eliasson Störner, Felicia
    There are two technologies of fluidized bed combustion that recently have been developed with attempt to increase the fuel conversion and enable more efficient CO2 mitigation. These methods are called Oxygen carrier aided combustion (OCAC) and Chemical looping combustion (CLC), which both uses oxygen carrying bed material. Research have been done on both synthetic and naturally occurring oxygen carriers. Expensive synthetic materials might not be suitable when operating wilt solid fuels. These expensive materials are not attractive when operating with solid fuel, since the process implies formation of ashes and the material have to be replaced with fresh material. Researcher are currently looking for alternative materials that can be used in OCAC and CLC, which have to be cheap, accessible at large quantities and available at close distance. attention have been payed to material streams from the metallurgical industries. This study has investigated two potential materials as oxygen carriers which both are available in large quantities in the metallurgical industries in north Europe to a lower price than synthetic materials. Magnetite fines is an industrial slag product from LKAB and copper smelter slag is a by-product from Boliden AB. Experiments have been done in a lab- scale fluidized bed reactor to investigate the materials reactivity with oxygen as well as fuel conversion of syngas and methane fuel for CLC configuration. Experiments were also done for OCAC configuration to investigate the materials potential to move the combustion reactions down in the bed. Furthermore, the physical properties of each material were investigated visually to identify any significant changes during operation. Results from this study shows that magnetite fines and copper smelter slag are reactive with syngas and moderate reactive with methane in CLC configuration. Magnetite fines shows no tendency for agglomeration and sintering which was expected due to the high content of FeO and low concentration of other components commonly causing this affects. However, copper smelter slag showed tendency for agglomeration after visual inspection of the material. Further research is however necessary to fully understand how the physical properties of the materials are affected when operating as oxygen carriers in CLC and OCAC. Lab-scale experiments with longer operational time and investigation of the physical properties and changes in chemical composition are interesting for further research.
  • Post
    3D Radiative Transfer Modeling of the Red Supergiant NML Cyg
    (2021) Hirvonen, Per; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; De Beck, Elvire; De Beck, Elvire; Andrews, Holly
    Red supergiants are bright but cool massive stars that have depleted their core hydrogen supply and have started fusing heavier elements. These evolved stars ex perience a strong mass loss through a slow moving stellar wind that results in an extended circumstellar envelope with a rich chemistry. The circumstellar envelopes of red supergiants will eventually enrich the interstellar medium, influencing the formation and evolution of the next generation of stars and planets. Understanding the mass loss of massive evolved stars is a key component in understanding both the evolution of individual stars and the chemical evolution of the universe. We analyze carbon monoxide emission around the red supergiant NML Cyg ob served with the ground based JCMT 15 meter and Onsala 20 meter telescopes, as well as the HIFI instrument aboard the Herschel Space Observatory. The line pro files have complex shapes, suggestive of multiple components in the stellar outflow. 3D radiative transfer modeling is used to recreate the observed line profiles. We con clude that it is possible to recreate the observed line profiles by using one spherical component and three directed outflows.
  • Post
    Development of A drone based Hydro carbon sensor for gas flux measurements from oil and gas production
    (2022) Bandodkar, Sumedh; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Mellqvist, Johan; Conde, Vladimir; Mellqvist, Johan
    Air pollution is considered the single largest environmental health risk worldwide due to its enormous impact on climate change and human health. It takes an adverse toll not only on human morbidity and mortality, but also affects the geographical distribution of many infectious diseases and natural disasters due to the result ing climate change. Corrective actions to reduce air pollution and its impact on the ecosystem thus require a good understanding of its sources, concentration of the pol lutants and their interaction with the atmosphere. A light weight, Unmanned Aerial Vehicle (UAV)-borne system has been developed to measure emissions of harmful trace gases like Sulphur Dioxide (SO2), Nitrogen Dioxide (NO2), a wide range of Volatile Organic Compounds (VOCs), and Particulate Matter (PM2.5, PM10), with the main application areas being ship emissions and oil refineries. The device is also equipped with auxiliary sensors to detect wind intensity and direction as well as am bient parameters such as temperature, humidity, altitude, positional co-ordinates; all in real-time. The data is relayed to the controller location by means of a ra dio transceiver to enable on-site analysis and logging of measured parameters. The objective of the work was to: a) Characterize effect of EMI on the small sensor outputs and implement corrective measures for diminishing it, b) Calibrate the sen sors for different gas concentrations in a controlled environment so as to obtain a linear relationship and determine the cross-sensitivity for SO2 and NO2 at different concentrations, c) Calibrate the Photo-ionization detector (PID) sensor against a reference and obtain the concentration curve in terms of sensor sensitivity, and d) Design an efficient, light-weight system with carefully weighed trade-offs between sensors used, their size, dimensions, power consumption and overall performance. A remarkable mitigation of EMI is achieved after implementing the corrective measures. The calibrated system was tested in a field campaign where more than a hundred ships were measured over a span of seven days. The results were used to calculate fuel sulfur content (FSC) and fuel NOx content, which is discussed in detail in the results section.
  • Post
    Chemical looping gasification for production of aviation fuel with negative emissions: Full chain process modeling and techno-economic analysis
    (2022) Saeed, Muhammad Nauman; Shahrivar, Mohammad; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Mattisson, Tobias; Soleimani, Amir
    The greenhouse gases from the conversion of fossil fuels are the main culprits for the increase in the planet's temperature which is reflected in the global warming context. The aviation sector is more dependent on fossil fuels as there is less possibility to find a viable alternative for fuel requirements for this sector. Chemical Looping Gasification with biomass as a fuel combined with downstream Fischer-Tropsch (FT) synthesis for aviation fuel production is a possible way to decarbonize transportation sectors like aviation. Chemical Looping Gasification (CLG) is like indirect gasification in a circulating fluidized bed, except that instead of inert bed material, particles containing metal-oxides, called oxygen carriers (OCs) are used as the bed material. CLG process has advantage of unnecessary use of an expensive and energy-intensive air separation unit (ASU). Also, due to the presence of a more oxidizing environment in CLG and the catalysing property of OC, the tar yield drops substantially resulting in improved syngas yield and better biomass to syngas conversion compared to the conventional gasification processes. Moreover, all produced CO2 is concentrated in the fuel reactor, with no or limited emissions from the air reactor. This means that it could be a very good process for combined fuel production and capture of CO2, something which would result in net-negative emissions. The study is based on modeling the full chain process of biomass to liquid fuel (BtL) using Aspen Plus software. The model is designed for a gasifier load of around 80 MWth and includes drying of biomass followed by a CLG unit using different oxygen carriers (LD slag and Ilmenite). The circulation rate of an oxygen carrier is adjusted to achieve the desired autothermal CLG operation with temperature of 935oC in the fuel reactor (FR). The resulting syngas from CLG goes through syngas cleaning and conditioning units to meet the requirements for FT synthesis. The steam to biomass ratio is adjusted to 0.7 to achieve an H2/CO ratio of 2.1 before the FT reactor. In the FT reactor with cobalt as a catalyst and at temperature of 220oC, the syngas gets converted into hydrocarbons with carbon numbers ranging from 1 to 40 using the Anderson-Schulz-Flory distribution. Since the aim of the model is to produce aviation fuel, the FT synthesis process combined with a reformer in the recycle loop is adjusted for maximizing the yield of paraffin with carbon numbers ranging from 8 to 16. Based on the optimized model, the clean syngas after syngas cleaning units has an energy content of 8.68 MJ/Nm3 (LHV basis) with a cold-gas efficiency of 77.86 %. FT synthesis model with a reformer estimates an FT crude production of around 647 bbl/day with 154 kilo-tonne of CO2 captured every year and conversion efficiency of biomass to FT-crude of 38.98 %. The calculated levelized cost of fuel (LCOF) is 35.19 $ per GJ of FT crude, with an annual plant profit (cash inflow) of 11.09 M$ and a payback period of 11.56 years for the initial investment.
  • Post
    Foreign aid and energy: Analyzing energy aid’s impact on sub-Saharan African countries’ electrification development
    (2022) Zhang, Handan; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Savvidou, Georgia; Hartvigsson, Elias
    Despite the continued flows of foreign aid on energy development to the sub-Saharan African region, more than half of the population lacks access to electricity. Achieving Sustainable Development Goal 7 and providing clean energy requires further development aid in the region. However, aid’s role in development has so far been inconclusive. Research on the impact that finance flows in different energy sectors, such as energy generation and energy policy, hasn’t gained much attention, mainly due to the lack of disaggregated data available until now. This research thus tries to look into energy aid’s impact on electrification rate through energy sub-sectoral aid data. This study uses two regression models to study aid’s impact on energy development in sub-Saharan African regions. An ordinary least squares model was built to analyze energy aid’s impact on the electrification rate with other macroeconomic factors such as economic growth, inflation, and trade openness, as well as countries’ governance scores. An autoregressive distributed lag model is used to study sector-specific aid’s impact on electrification rate in different country groups based on income. Results from the ordinary least squares model confirm aid’s inconclusive role in energy development but prove that an increase in inflation rate is correlated with higher electrification rate changes. Trade openness showed no significance, while governance changes indicate a positive relationship with changes in the electrification rate. The panel autoregressive distributed lag model found that aid’s impact differs among country groups. The electrification rate in the two lower income groups correlated with different energy aid. In comparison, only the electrification rate in the past period correlated with electrification in higher-income country groups. This study calls for future research to look into countries that receive large blocks of energy aid but shows little development, as well as countries that, despite receiving low amounts of energy aid, they have increased electrification rates, to understand what other factors influence the increase in electrification rate in SSA countries.