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.

Novel CO2/N2 Foam Concept and Optimization Scheme for Improving CO2-foam EOR Process

Nitrogen and Carbon dioxide are the most common gases utilized in enhanced oil recovery (EOR) techniques. Most of the gas injection process suffers from the gravity override and viscous fingering resulting in lower oil recovery. Foam is introduced in enhanced oil recovery (EOR) to mitigate these problems encountered during gas flooding. When it comes to the CO2-gas injection the CO2-becomes supercritical at a typical reservoir condition giving it difficulty to form CO2-foam at reservoir condition. The CO2-foam has a common problem to become weaker above its supercritical conditions of 1100 psi and 31°C. As a result, the advantages of using CO2 foam are diminished due to the weakness of CO2-foam at supercritical conditions and results in a lower recovery. However, CO2-foam can be generated by replacing a portion of CO2 with N2 gas. It lacks the understating of mixture properties and its effect on EOR. This study evaluates the performance of CO2/N2 foam at supercritical conditions for EOR. It aims to improve recovery under supercritical conditions by using N2/CO2 mixture foam and optimize the foam quality and CO2/N2 ratio. The results from the experiments showed that the CO2/N2 foam flooding recovered an additional oil of Original Initial Oil in Place (OIIP) indicating that foam flooding succeeded in producing more oil than pure CO2-foam injection processes. Also, the results of foam flooding at different foam quality and CO2/N2 ratio significantly affected the performance and recovery of the process. Hence it is necessary to optimize the CO2/N2 foam parameters flooding process which is affected by the parameters such as foam quality and CO2/N2 ratio. The study also shows an experimental approach for optimizing CO2/N2 foam parameters. The concept of adding N2 to CO2 is a novel way of generating CO2 foam at supercritical conditions. Although investigators are trying different ways to generate the strong and stable CO2- foam, adding N2 to CO2 can be considered to be the easiest way for foam generation as CO2 is always having some impurities in the form of other gases and N2 can be considered as one of such gas helps in generating the foam.

ROLE OF INLET BOUNDARY CONDITIONS ON FUEL-AIR MIXING AT SUPERCRITICAL CONDITIONS

Advanced engine design and alternative fuels present the possibility of fuel injection at purely supercritical conditions in diesel engines and gas turbines. The complex interactions that govern this phenomenon still need significant research, particularly the boundary conditions for fuel injection are critical for accurate simulation. However, the flow inside the injector itself is often omitted to reduce the computational efforts, and thus, velocity, mass flux, or total pressure is specified at the injector exit (or domain inlet), often with simplified velocity profiles and turbulence levels. This simplified inlet boundary treatment has minimal effects on results for conventional fuel injection conditions, however, the validity of this approach at supercritical conditions has not been assessed. Comprehensive real-gas and binary fluid mixing models have been implemented for computational fluid dynamic (CFD) analysis of fuel-air mixing at supercritical conditions. The model is verified using prior CFD results from the literature. The model is used to investigate the effects of the shape of axial velocity and mass fraction profiles at the inlet boundary with the goal to improve the comparison of predictions to experimental data. Results show that the boundary conditions have a significant effect on the predictions, and none of the cases match precisely with experimental data. The study reveals that the physical location of the inlet boundary might be difficult to infer correctly from the experiments and highlights the need for high-quality, repeatable measurements at supercritical conditions to support the development of relevant high-fidelity models for fuel-air mixing.