Supercritical Carbon Dioxide Treatment Of Oil-based Drilling Solid Waste Research

With the rapid development of shale oil and gas exploration, waste pollutants are also growing. The waste oil-based drilling fluid is one of the main pollutants.Waste oil-based drilling mud is rich in various kinds of additives and petroleum substances. Its high concentration of pollutants, if not handled properly, will pollute the environment.National hazardous waste directory has been including in hazardous waste category (number HW08). "National Cleaner Production Promotion Law" and "solid waste pollution prevention law" also requires explicitly that innocent treatment must be carried out.As a kind of high effective and clean separation technology, supercritical fluid extraction technology holds prominent status in separation and extraction of the product. In this thesis, the optimal conditions of extracting waste oil-based drilling fluid with supercritical carbon dioxide were investigated.First,the effect of different factors (extracting pressure, extracting temperature, and extracting time) on the waste oil-based drilling cutting has been investigated by utilizing the single factor experiment and orthogonal experiment.In this part, the lowest residual oil rate 0.748% was achieved when the extracting pressure, extracting temperature, extracting temperature was 25 MPa,50?,and 100 min respectively, indicating an optimal treatment efficiency.Meanwhile, we analyzedthe properties ofraffinate with commercially available 0# diesel as a reference.There were no significant differences in the boiling point range and physical properties between extraction diesel and 0# diesel with distillation range analysis.Infrared analysis showed that the composition and structure of extraction are basically same as commercial 0# diesel, which explained that the supercritical carbon dioxide extraction technology has a small damage to diesel in waste oil-based drilling.GC-MS analysis showed that the extractions of diesel 81 compoundswere identified in the extractions of diesel by GC-MS, including alkanes, alkenes, alcohols, aldehydes, and unsaturated fatty acids.In this study,the solubility of diesel in supercritical carbon dioxide was studied with associated models. The improved Chrastil equation was advanced. Considering the associated number k changed with temperature and density, it was expressed as a function of the temperature and density in theimproved Chrastil equation. And the average relative error for improved Chrastil equation was 0.43%, which shows that the fitting result was better than that of Chrastil equation.The studies in this thesis provide some basic data for the utilization of extracted diesel and a new idea for treatment of the waste oil-based drilling fluids and solid waste.The improved solubility equation in this thesis may be further extended to other solid waste-supercritical CO2 system. These theoretical research resultsalso provide an important guidance for enlarging extraction process with supercritical CO2.