6 Matching Results

Search Results

Advanced search parameters have been applied.

EM-21 ALTERNATIVE ENHANCED CHEMICAL CLEANING PROGRAM FOR SLUDGE HEEL REMOVAL

Description: Preliminary studies in the EM-21 Alternative Chemical Cleaning Program have focused on understanding the dissolution of Hematite (a primary sludge heel phase) in oxalic acid, with a focus on minimizing oxalic acid usage. Literature reviews, thermodynamic modeling, and experimental results have all confirmed that pH control, preferably using a supplemental proton source, is critical to oxalate minimization. With pH control, iron concentrations as high as 0.103 M have been obtained in 0.11 M oxalic acid. This is consistent with the formation of a 1:1 (iron:oxalate) complex. The solubility of Hematite in oxalic acid has been confirmed to increase by a factor of 3 when the final solution pH decreases from 5 to below 1. This is consistent with literature predictions of a shift in speciation from a 1:3 to 1:1 as the pH is lowered. Above a solution pH of 6, little Hematite dissolves. These results emphasize the importance of pH control in optimizing Hematite dissolution in oxalic acid.
Date: December 18, 2009
Creator: Hay, M.; King, W. & Martino, C.
Partner: UNT Libraries Government Documents Department

HIGH-LEVEL WASTE GLASS FORMULATION MODEL SENSITIVITY STUDY 2009 GLASS FORMULATION MODEL VERSUS 1996 GLASS FORMULATION MODEL

Description: This document presents the differences between two HLW glass formulation models (GFM): The 1996 GFM and 2009 GFM. A glass formulation model is a collection of glass property correlations and associated limits, as well as model validity and solubility constraints; it uses the pretreated HLW feed composition to predict the amount and composition of glass forming additives necessary to produce acceptable HLW glass. The 2009 GFM presented in this report was constructed as a nonlinear optimization calculation based on updated glass property data and solubility limits described in PNNL-18501 (2009). Key mission drivers such as the total mass of HLW glass and waste oxide loading are compared between the two glass formulation models. In addition, a sensitivity study was performed within the 2009 GFM to determine the effect of relaxing various constraints on the predicted mass of the HLW glass.
Date: December 7, 2009
Creator: JD, BELSHER & FL, MEINERT
Partner: UNT Libraries Government Documents Department

SLUDGE CHARACTERIZATION AND SRAT SIMULATIONS USING A NITRITE-FREE SLUDGE SIMULANT

Description: Understanding catalytic hydrogen generation is fundamental to the safe operation of the Defense Waste Processing Facility (DWPF) Chemical Process Cell (CPC). Two Sludge Receipt and Adjustment Tank (SRAT) simulations were completed at the Aiken County Technology Laboratory (ACTL) of the Savannah River National Laboratory (SRNL) using a nitrite-free starting simulant. One simulation was trimmed with Rh and Hg and the other with Ru and Hg. The two noble metals were trimmed at the upper end of the recent Rh-Ru-Hg study. Mercury was trimmed at 1.5 wt% in the total solids. Excess acid comparable in quantity to that in the recent Rh-Ru-Hg matrix study was used. In spite of the favorable conditions for hydrogen generation, virtually no hydrogen production was observed during either SRAT simulation. The Rh test result confirmed the postulated significance of nitrite ion to the catalytic reactions producing hydrogen in CPC testing with normal DWPF sludge simulants. As for Ru, however, previous testing has shown that Ru activated for hydrogen generation only after nitrite destruction. Therefore, Ru could have potentially been catalytically active from the start of the nitrite-free SRAT test, but no such activity was seen. The nitrite-free Ru test result suggests that the intermediate form detected in the bead-frit melter feed preparation Ru solubility profiles was some form of nitro-Ru complex. The nitro-Ru complex is apparently not catalytically active for hydrogen generation but is a precursor to the catalytically active form (presumably a different complex not involving nitrite ligands). Removing nitrite ion from the system prevented the Ru catalyst precursor from forming and consequently blocked formation of the catalytically active form. These results, along with the results of a simulation in which sodium nitrite was metered into the SRAT to prevent ligand substitution reactions that occur during nitrite destruction from occurring in order to reduce hydrogen ...
Date: December 17, 2009
Creator: Koopman, D.
Partner: UNT Libraries Government Documents Department

A Modern Interpretation of the Barney Diagram for Aluminum Solubility in Tank Waste

Description: Experimental and modeling studies of aluminum solubility in Hanford tank waste have been developed and refined for many years in efforts to resolve new issues or develop waste treatment flowsheets. The earliest of these studies was conducted by G. Scott Barney, who performed solubility studies in highly concentrated electrolyte solutions to support evaporator campaign flowsheets in the 1970's. The 'Barney Diagram', a term still widely used at Hanford today, suggested gibbsite ({gamma}-Al(OH){sub 3}) was much more soluble in tank waste than in simple sodium hydroxide solutions. These results, which were highly surprising at the time, continue to be applied to new situations where aluminum solubility in tank waste is of interest. Here, we review the history and provide a modern explanation for the large gibbsite solubility observed by Barney, an explanation based on basic research that has been performed and published in the last 30 years. This explanation has both thermodynamic and kinetic aspects. Thermodynamically, saturated salt solutions stabilize soluble aluminate species that are minor components in simple sodium hydroxide solutions. These species are the aluminate dimer and the sodium-aluminate ion-pair. Ion-pairs must be present in the Barney simulants because calculations showed that there was insufficient space between the highly concentrated ions for a water molecule. Thus, most of the ions in the simulants have to be ion-paired. Kinetics likely played a role as well. The simulants were incubated for four to seven days, and more recent data indicate that this was unlikely sufficient time to achieve equilibrium from supersaturation. These results allow us to evaluate applications of the Barney results to current and future tank waste issues or flowsheets.
Date: December 16, 2009
Creator: Reynolds, J. G. & Reynolds, D. A.
Partner: UNT Libraries Government Documents Department

Design and Implementation of Energized Fracture Treatment in Tight Gas Sands

Description: Hydraulic fracturing is essential for producing gas and oil at an economic rate from low permeability sands. Most fracturing treatments use water and polymers with a gelling agent as a fracturing fluid. The water is held in the small pore spaces by capillary pressure and is not recovered when drawdown pressures are low. The un-recovered water leaves a water saturated zone around the fracture face that stops the flow of gas into the fracture. This is a particularly acute problem in low permeability formations where capillary pressures are high. Depletion (lower reservoir pressures) causes a limitation on the drawdown pressure that can be applied. A hydraulic fracturing process can be energized by the addition of a compressible, sometimes soluble, gas phase into the treatment fluid. When the well is produced, the energized fluid expands and gas comes out of solution. Energizing the fluid creates high gas saturation in the invaded zone, thereby facilitating gas flowback. A new compositional hydraulic fracturing model has been created (EFRAC). This is the first model to include changes in composition, temperature, and phase behavior of the fluid inside the fracture. An equation of state is used to evaluate the phase behavior of the fluid. These compositional effects are coupled with the fluid rheology, proppant transport, and mechanics of fracture growth to create a general model for fracture creation when energized fluids are used. In addition to the fracture propagation model, we have also introduced another new model for hydraulically fractured well productivity. This is the first and only model that takes into account both finite fracture conductivity and damage in the invaded zone in a simple analytical way. EFRAC was successfully used to simulate several fracture treatments in a gas field in South Texas. Based on production estimates, energized fluids may be required when drawdown ...
Date: December 31, 2009
Creator: Sharma, Mukul & Friehauf, Kyle
Partner: UNT Libraries Government Documents Department