Modeling the Effect of Shale Heterogeneities on Hazardous Waste Transport in Deep Well Disposal Systems.

The transport of hazardous wastes in heterogeneous confining layers was evaluated using numerical simulations. The expected configuration of the confining layers was defined by Monte Carlo techniques assuming a binary random structure composed of pure sand and pure shale zones. Flow and solute transport in the generated configuration was determined via a finite element model. The effective permeability under saturated steady-state flow was dominated by shale permeability for higher shale fractions ($\u3e$0.65) and by sand permeability for lower shale fraction ($\u3c$0.4). The results agreed well with the numerical result of Desbarats (1987) and the analytical results of Dagan (1979). The effective vertical permeabilities were found to be dependent on shale size and anisotropy. Application of the techniques to a well in Jefferson Parish, Louisiana suggested that a mean advective penetration into confining layer using the injection pressure as an upper bound to the driving pressure was only 3m over 10,000 years. Transport calculations assuming a constant pressure driving force over 10,000 years suggested solute transport was controlled by hydrodynamic dispersion (dispersion + diffusion) rather than advection for higher shale fractions. Transport calculations assuming active injection for only the first 100 years suggested solute transport was controlled by diffusion for higher shale fraction. Buoyancy effects associated with salinity and temperature variations were negligible for solute transport through confining layers with a shale permeability less than 0.01 md. The results of solute transport of hazardous wastes in heterogeneous confining layers suggested that confining layers greater than 300 ft in thickness with shale fractions of greater than 0.65 and shale permeabilities of less than 0.01 md would be expected to contain injected wastes for 10,000 years

Evaluation on Recovery of Glass and Plastics from Compact Fluorescent Lamps (CFLs) by Air Separation Unit

Compact Fluorescent Lamps (CFLs) are composed of glass, plastic, non-ferrous metal, ferrous metal, paper, plastic, rubber, and so on. In order to separate glass and plastic among CFLs components, air separation unit is applied using the difference in specific gravity. Since specific gravities of glass, plastic, non-ferrous metals, rubber, etc. were widely spread, it can be separated by the different specific gravity between 0.40 and 4.36. In air separation unit, particle size and air speed are controlled to recover glass and plastics among the components of CFLs. In other words, it can be removed paper and vinyl to recover glass and plastics. The specific gravities of paper and vinyl in CFLs are 0.45 and 0.88, respectively. And the specific gravities of glass and plastics are almost similar to be 2.2 - 2.6. In air separation unit, the used particle size of the components from CFLs is less than 6 mm. Since phosphor powder and ferrous metals are recovered prior to the air separation unit, the components are not involved those materials. By utilizing a vertical and zigzag type of air separation unit, thereafter, recovery of glass and plastics is estimated with changing air speed. As the air speed increased from 3.08 m/s to 6.75 m/s, separation efficiency of glass and plastics increased from 42.0% to 99.3%. Due to the experimental results of air separation unit, it can find that paper and vinyl from the components of CFLs be efficiently removed by the air separation unit

Evaluation of Energy Consumption in the Mercury Treatment of Phosphor Powder from Spent Fluorescent Lamps Using a Thermal Process

In a pilot-plant-scale thermal mercury treatment of phosphor powder from spent fluorescent lamps, energy consumption was estimated to control mercury content by the consideration of reaction kinetics. Mercury content was analyzed as a function of treatment temperature and time. The initial mercury content of the phosphor powder used in the thermal process was approximately 3500 mg/kg. The target mercury content in the phosphor powder thermal process of the phosphor powder was 5 mg/kg or less at 400 °C or higher because the target mercury content was recommended by Minamata Convention and Basel Convention. During thermal processing, the reaction rate was represented by a first order reaction with the Arrhenius equation. The reaction rate constant increased with temperature from 0.0112 min−1 at 350 °C to 0.0558 min−1 at 600 °C. The frequency factor was 2.51 min−1, and the activation energy was 6509.11 kcal/kg. Reaction rate constants were used to evaluate the treatment time required to reduce mercury content in phosphor powder to be less than 5 mg/kg. The total energy consumption in a pilot-plant-scale thermal process was evaluated to determine the optimal temperature for removing mercury in phosphor powder