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Granular Iron (granular + iron)

Distribution by Scientific Domains
Engineering66%

Selected Abstracts

Effects of Mixing Granular Iron with Sand on the Kinetics of Trichloroethylene Reduction

GROUND WATER MONITORING & REMEDIATION, Issue 2 2009
Erping Bi
A substantial cost of granular iron permeable reactive barriers is that of the granular iron itself. Cutting the iron with sand can reduce costs, but several performance issues arise. In particular, reaction rates are expected to decline as the percentage of iron in the blend is diminished. This might occur simply as a function of iron content, or mass transfer effects may play a role in a much less predictable fashion. Column experiments were conducted to investigate the performance consequences of mixing Connelly granular iron with sand using the reduction kinetics of trichloroethylene (TCE) to quantify the changes. Five mixing ratios (i.e., 100%, 85%, 75%, 50%, and 25% of iron by weight) were studied. The experimental data showed that there is a noticeable decrease in the reaction rate when the content of sand is 25% by weight (iron mass to pore volume ratio, Fe/Vp = 3548 g/L) or greater. An analysis of the reaction kinetics, using the Langmuir-Hinshelwood rate equation, indicated that mass transfer became an apparent cause of rate loss when the iron content fell below 50% by weight (Fe/Vp = 2223 g/L). Paradoxically, there were tentative indications that TCE removal rates were higher in a 15% sand + 85% iron mixture (Fe/Vp = 4416 g/L) than they were in 100% iron (Fe/Vp = 4577 g/L). This subtle improvement in performance might be due to an increase of iron surface available for contact with TCE, due to grain packing in the sand-iron mixture. [source]

Degradation of TCE with Iron: The Role of Competing Chromate and Nitrate Reduction

GROUND WATER, Issue 3 2000
Oliver Schlicker
This study evaluates the potential of using granular iron metal for the abiotic removal of the organic ground water pollutant trichloroethene (TCE) in the presence of the common inorganic co-contaminants chromate and nitrate, respectively. Our long-term column experiments indicate a competitive process between TCE dechlorination and reductive transformation of chromate and nitrate, which is reflected in a significantly delayed onset of TCE dechlorination. Delay times and therefore the ranges of the nonreactive flowpaths increased with increasing experimental duration, resulting in a migration of the contaminants through the iron metal treatment zone. The present investigation also indicates that the calculated migration rates of TCE and the added cocontaminants chromate and nitrate are linearly related to the initial content of the cocontaminants. With an average pore water velocity of 0.6 m/d and a surface area concentration of 0.55 m2/mL in the column, the calculated migration rates varled between 0.10 cm/d and 5.86 cm/d. The particular similarity between the values of TCE migration and the migration of the strong oxidants chromate and nitrate and the long-term steady state of the TCE dechlorination in the absence of the chromate and nitrate indicates that these competitive transformations are the driving force for the gradual passivation of the granular iron due to the buildup of an electrically insulating Fe(III)-oxyhydroxide. Based on these passivation processes, general formulae were developed that allow a simplified approximation of breakthrough times for the contaminants TCE, chromate, and nitrate. [source]

Effects of Mixing Granular Iron with Sand on the Kinetics of Trichloroethylene Reduction

GROUND WATER MONITORING & REMEDIATION, Issue 2 2009
Erping Bi
A substantial cost of granular iron permeable reactive barriers is that of the granular iron itself. Cutting the iron with sand can reduce costs, but several performance issues arise. In particular, reaction rates are expected to decline as the percentage of iron in the blend is diminished. This might occur simply as a function of iron content, or mass transfer effects may play a role in a much less predictable fashion. Column experiments were conducted to investigate the performance consequences of mixing Connelly granular iron with sand using the reduction kinetics of trichloroethylene (TCE) to quantify the changes. Five mixing ratios (i.e., 100%, 85%, 75%, 50%, and 25% of iron by weight) were studied. The experimental data showed that there is a noticeable decrease in the reaction rate when the content of sand is 25% by weight (iron mass to pore volume ratio, Fe/Vp = 3548 g/L) or greater. An analysis of the reaction kinetics, using the Langmuir-Hinshelwood rate equation, indicated that mass transfer became an apparent cause of rate loss when the iron content fell below 50% by weight (Fe/Vp = 2223 g/L). Paradoxically, there were tentative indications that TCE removal rates were higher in a 15% sand + 85% iron mixture (Fe/Vp = 4416 g/L) than they were in 100% iron (Fe/Vp = 4577 g/L). This subtle improvement in performance might be due to an increase of iron surface available for contact with TCE, due to grain packing in the sand-iron mixture. [source]

Construction of a permeable reactive barrier in a residential neighborhood

REMEDIATION, Issue 4 2002
Peter Richards
In June 2001, the Massachusetts Department of Environmental Protection (DEP) installed a permeable reactive barrier (PRB) within a roadway in Needham, Massachusetts, to treat a plume of chlorinated solvents migrating toward two public water-supply wells located in the adjacent town of Wellesley, Massachusetts. The solvents originated from an electronics manufacturer located approximately 2,300 feet upgradient of the roadway and 5,200 feet upgradient of the public supply wells. Chlorinated solvents, primarily trichloroethene (TCE), had migrated past the roadway to within 300 feet of the public supply wells. Two contaminant transport models prepared by the DEP's design contractor and the EPA indicated that the plume would reach the well field if no response actions were taken. To mitigate the future impact to the municipal well field, the DEP decided to install a PRB composed of zero-valent granular iron across the path of the plume along Central Avenue in Needham. Though several dozen PRBs have been installed at sites worldwide and the technology is no longer considered innovative, the application of the technology in a roadway that receives 17,000 vehicles per day within a residential neighborhood is unique and presented difficulties not typically associated with PRB installations. The Needham PRB was also one of the first zero-valent iron PRBs installed using the slurry trench method to treat chlorinated compounds. © 2002 Wiley Periodicals, Inc. [source]

Metallurgical Characteristics and Effectiveness of Metallic Charges in Electric Arc Furnace

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2006
Cheng-Wu Du
The use of direct reduced iron (DRI), hot metal, cold pig iron, decarburized granular iron, iron carbide, and complex metal charges to replace scrap metal as the feedstock to an electric arc furnace not only resolves the lack of scrap supply, but is also very helpful in diluting the residual elements in the scrap, thus improving the quality of the steel. It has now become possible to produce high-quality steel in an electric arc furnace. In this paper, the characteristics and effectiveness of various metallic charges for use in an electric arc furnace (EAF) are discussed. [source]