Lin He

Parameters of Solvent Extraction for Bitumen Recovery from Oil Sands

Solvent extraction was applied in the separation of oil sands and considered as a promising technology. Results in this study indicated that the factors such as the volume of solvent to mass of oil sand (v/m), solvent aromatic content (the amount of aromatic hydrocarbons in the solvent), and the polarity of the solvent significantly influenced the oil sands bitumen recovery. A value of v/m greater than 5 was proposed in the extraction. The bitumen recovery increased with the increase of the solvent aromatic content. In addition, an appropriate polarity of the solvent with the range from 1.5 to 3.0 was suggested in the solvent selection. Hence, results demonstrated that the solubility of the composite solvent of n-heptane and toluene was less than the sum of the single ones. This study provided useful guidance for the solvent selection in the subsequent works.

Recovery and purification of ionic liquids from solutions: a review

With low melting point, extremely low vapor pressure and non-flammability, ionic liquids have been attracting much attention from academic and industrial fields. Great efforts have been made to facilitate their applications in catalytic processes, extraction, desulfurization, gas separation, hydrogenation, electronic manufacturing, etc. To reduce the cost and environmental effects, different technologies have been proposed to recover the ionic liquids from different solutions after their application. This review is mainly focused on the recent advances of the recovery and purification of ionic liquids from solutions. Several methods for recovery of ionic liquids including distillation, extraction, adsorption, membrane separation, aqueous two-phase extraction, crystallization and external force field separation, are introduced and discussed systematically. Some industrial applications of ionic liquid recovery and purification methods are selected for discussion. Additionally, considerations on the combined design of different methods and process optimization have also been touched on to provide potential insights for future development of ionic liquid recovery and purification.

Synthesis and application of hydrophilically-modified Fe3O4 nanoparticles in oil sands separation

Nanoparticles have been reported to be a promising candidate for the separation of heavy oil from its host rocks surface. These nanoparticles (NPs) are often dispersed and stabilized in the solution by some surfactants during the unconventional oil ores processing. Herein, the PEG600–KH560 (PK) has been grafted onto Fe3O4 NP surfaces, obtaining a kind of hydrophilically-modified recyclable nanoparticle. Results show that these NPs (averaged at around 16 nm for single sphere) could be well dispersed in water (no settling in 72 h), forming PK-Fe3O4 nanofluids (NFs) at 0.2 wt%. These PK-Fe3O4 NFs are found to be able to be quickly separated from the dispersions by an external magnetic field, and returning back to stable NFs when the magnetic field disappears and by shaking. The PK-Fe3O4 NFs have been further used for the enhancement of heavy oil recovery from oil sands. The floatation results show that the PK-Fe3O4 NFs could improve oil recovery by at least 12% compared with the traditional hot water extraction process (HWEP). After the extraction, up to 70% of the PK-Fe3O4 NPs could be directly recycled from the solution for further use. The rest of the NPs are left in the oil phase and attached on the residual solid surface. However, the efficiency of the PK-Fe3O4 NPs is found to be decreased when the recycling times exceed 5 due to the adsorption of oil components. A mechanistic study shows that the hydrophilic PK-Fe3O4 NPs could be adsorbed on the mineral surface, making the surface more hydrophilic. The hydrophilic surface and the agitation disturbance helps the liberation process of bitumen from the solid surfaces. On the other hand, when adding the PK-Fe3O4 NPs into the heavy oil–water system, the oil–water interface is found to be highly modified by the NPs, resulting in significant reduction of the oil–water interfacial tension. The above findings suggest that the PK-Fe3O4 NPs combined the surface-active role (surfactant) and the nano-size role (adsorption) together, which facilitates its role in oil sands separation.

Evaluation and determination of soil remediation schemes using a modified AHP model and its application in a contaminated coking plant

Soil remediation has been considered as one of the most difficult pollution treatment tasks due to its high complexity in contaminants, geological conditions, usage, urgency, etc. The diversity in remediation technologies further makes quick selection of suitable remediation schemes much tougher even the site investigation has been done. Herein, a sustainable decision support hierarchical model has been developed to select, evaluate and determine preferred soil remediation schemes comprehensively based on modified analytic hierarchy process (MAHP). This MAHP method combines competence model and the Grubbs criteria with the conventional AHP. It not only considers the competence differences among experts in group decision, but also adjusts the big deviation caused by different experts preference through sample analysis. This conversion allows the final remediation decision more reasonable. In this model, different evaluation criteria, including economic effect, environmental effect and technological effect, are employed to evaluate the integrated performance of remediation schemes followed by a strict computation using above MAHP. To confirm the feasibility of this developed model, it has been tested by a benzene workshop contaminated site in Beijing coking plant. Beyond soil remediation, this MAHP model would also be applied in other fields referring to multi-criteria group decision making.

Conversion of low-grade heat from FCC absorption-stabilization system to electricity by organic Rankine cycles: Simulation and optimization

In this study, the organic Rankine cycle (ORC) is applied to be integrated into the fluid catalytic cracking (FCC) absorption-stabilization system to extract and convert the low-grade process heat to electricity. This newly integrated system is simulated by the Aspen Plus software. For the simulation, eleven different dry and isentropic working fluids are selected to investigate the energy conversion performance of the incorporated ORC system. It is found that, the performance depends highly on the operational parameters, such as mass flow rate and the evaporation pressure of the working fluids, outlet temperature of the process stream. After optimization, the working fluids R124 and R227ea are determined to be the best candidates due to their highest output net work in HCT (high critical temperature) and LCT (low critical temperature) working fluids, respectively. A further optimization has been conducted based on the economic evaluations (i.e., electricity production cost (EPC) and total annual profit (TAP)). Results show that, for the HCT working fluids, the use of working fluid of R245fa allows the EPC to be the lowest, while the application of R124 obtains the highest TAP. For the LCT working fluids, R227ea is the best choice due to its lowest EPC and highest TAP.