No abstract

There are global efforts to reduce the impacts from climate change by limiting increases in temperature to 1.5 °C until 2030, and achieve carbon neutrality by 2050. Thus, it is necessary to design new neutral processes and systems that can meet the varying and growing demands of the population in terms of energy, water and food. One of the main carbon emitters and contributors to climate change is the energy industry, which primarily uses oil and natural gas as an energy source. Fortunately, alternative resources are available such as renewable energies that assemble various environmental and economic benefits. However, more work is necessitated to efficiently utilise these resources by designing, analysing, and optimising existing and new renewable energy-based processes. Therefore, this study proposes a net negative carbon emissions energy system that utilises waste biomass as a feedstock. A biomass based integrated gasification combined cycle combined with a post combustion carbon capture unit by means of chemical absorption is designed and analysed. Two different chemical solvents are used for comparison: Monoethanolamine (MEA) and potassium carbonate. The proposed integrated system is modelled and simulated in Aspen Plus software, and is analysed thermodynamically in terms of energy and exergy efficiencies. A sensitivity analysis is also conducted to assess the effect of varying operating conditions such as flowrate, and temperature of the lean solvent, and the pressure inside the stripper. At design conditions with 80% carbon capture, the system generates 419 kW of electricity and operates at -0.32 kg/kWh of CO2 for both the potassium carbonate and MEA systems.

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The settling characteristics of carrot and plastic cylindrical particles has been investigated. the settling velocities in hindered and unhindered environments have been determined for particles of different diameters and aspect ratios. In settling studies using single particles, there was an initial increase in falling velocity with increasing aspect ratio. However, for aspect ratios above 2:1, the settling velocity reached a constant value, which then began to decrease as a function of the particle length. the results for particles subjected to hindered settling did not correlate well with existing literature except for low aspect ratio systems. Wall effects were studied and observed for particles with aspect ratios greater than 4.25:1. Fluidization data were compared with the results from settling tests for similar systems, and it was observed that the terminal falling velocity of a particle is mainly affected by drag only, but in fluidization, the transportation velocity is influenced by a combination of drag, wall and interparticle effects.