Bio-Crude Production from Protein-Extracted Grass Residue through Hydrothermal Liquefaction

In the present study, the protein-extracted grass residue (press cake) was processed through hydrothermal liquefaction under sub and supercritical temperatures (300, 350 and 400 °C) with and without using a potassium carbonate catalyst. The results revealed that bio-crude yield was influenced by both temperature and the catalyst. The catalyst was found to be effective at 350 °C (350 Cat) for enhancing the bio-crude yield, whereas supercritical state in both catalytic and non-catalytic conditions improved the quality of bio-crude with reasonable HHVs (33 to 36 MJ/kg). The thermal behaviour of bio-crude was analysed and higher volatile contents (more than 50% under the range of 350 °C) were found at supercritical conditions. The overall TOC values in the residual aqueous phase varied from 22 to 38 g/L. Higher carbon loss was noticed in the aqueous phase in supercritical conditions. Furthermore, GCMS analysis showed ketones, acids and ester, aromatics and hydrocarbon with negligible nitrogen-containing compounds in bio-crude. In conclusion, the catalytic conversion of grass residue under subcritical conditions (350 Cat) is favourable in terms of high bio-crude yield, however, supercritical conditions promote the deoxygenation of oxygen-containing compounds in biomass and thus improve HHVs of bio-crude.

CO2 power cycle chemistry in the CV Řež experimental loop

Power cycles using carbon dioxide in a supercritical state (sc-CO2) can be used in both the nuclear and non-nuclear power industry. These systems are characterized by their advantages over steam power cycles, e. g., the sc-CO2 turbine is more compact than the steam turbine with a similar performance. The parameters and lifespan of the system are influenced by the purity of the CO2 in the circuit, especially the admixtures, such as O2, H2O, etc., cause the enhanced structural materials to degrade. Therefore, gas purification and purity control systems for the sc-CO2 power cycles should be proposed and developed. The inspiration for the proposal of these systems could stem from the gas, especially the CO2-cooled nuclear reactors operation. The first information concerning the CO2 and sc-CO2 power cycle chemistry was gathered in the first period of the project and it is summarized in the paper.

The Challenge of Monitoring Impurity Content of CO2 Streams

Carbon capture and storage has gained increased attention during the last decade, and several full-scale projects are currently being planned. From economic and public acceptance point of view it is important to ensure that the transportation system is operated in a safe manner, avoiding threats such as corrosion or formation of solid matters. Thus, routine chemical analyses are required to ensure that the CO2 stream complies with the required specifications. The CO2 will usually be transported in the liquid or supercritical state (high pressure), which makes the practicalities around chemical analyses difficult. Phase transition from liquid or supercritical state to gaseous state may also introduce several physiochemical effects that may affect the analyses. This paper discusses technical and practical challenges with CO2 stream analyses experienced in a joint industry project that studied corrosion and chemical reactions in a simulated CO2 transport system.

The Challenge of Monitoring Impurity Content of CO2 Streams

Carbon capture and storage has gotten increased attention during the last decade, and several full-scale projects are currently being planned. This requires transportation of large quantities of CO2 from the capturing plant to the end point. From economic and public acceptance point of view it is important to ensure that the transportation system is operated in a safe manner. Thus, avoiding threats like corrosion or formation of particles are important. It is therefore required to monitor that the transported CO2 fulfils the required specifications, and in practice this means that the impurity content of the CO2 must be analysed. CO2 will in most cases be transported in the liquid or supercritical state (high pressure), which makes the practicalities around chemical analysis more difficult. Phase transition from liquid or supercritical state to gaseous state may also introduce several physiochemical effects that may affect the analysis. This paper discusses technical and practical challenges with such types of analysis. Most of this work is based on experience that was gained during development of analytical system for dense phase CO2 in a joint industry project that studied corrosion and chemical reactions in a simulated CO2 transport system.

Supercritical Carbon Dioxide Fluid and Its Application to Rankine Cycle

Supercritical CO2 has been given much attention to be a working fluid in a power cycle due to its unique properties. The supercritical CO2 solar Rankine cycle system was designed and developed by using the benefit of supercritical state of CO2 to generate electric power and supply heat energy in environmentally friendly manner. The development of main components in the system are introduced and discussed particularly by focusing on the properties of CO2 for obtaining higher performance. The properties of CO2 in near critical region are also discussed in this chapter. Operating the power cycle in the supercritical region of CO2 enhances the heat transfer in energy exchanging process and improves the cycle efficiency.