Grantee Research Project Results
2007 Progress Report: The Fining Behavior of Selectively Batched Commercial Glasses
EPA Grant Number: X832541C003Subproject: this is subproject number 003 , established and managed by the Center Director under grant X832541
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Center for Environmental and Energy Research (CEER)
Center Director: Earl, David A.
Title: The Fining Behavior of Selectively Batched Commercial Glasses
Investigators: Carty, William
Institution: Alfred University
EPA Project Officer: Aja, Hayley
Project Period: September 1, 2006 through February 1, 2008
Project Period Covered by this Report: September 1, 2006 through February 1, 2007
RFA: Targeted Research Center (2006) Recipients Lists
Research Category: Targeted Research
Objective:
The fining behavior of a selectively batched generic float glass is being investigated. In previous studies selective batching techniques utilizing two granules of different chemical composition have shown up to an 80% reduction in batch free times for SLS and E-glass melts. Our goal is to develop a fast fining process that utilizes selective batching technologies. Shortened batch free times lead to the reduction of CO2, while a fast fining process could help reduce dependence on saltcake. For each ton of flat or float glass produced in the United States, 1.5 Kg of SOx is emitted into the earth’s atmosphere. The use of selective batching technologies also inherently reduces NOx emissions through reduced fuel use. It was originally proposed that by tailoring the size of void spaces between granules, large gas bubbles could be generated and used to sweep smaller intra-granular bubbles to the surface.
Progress Summary:
Many methods of granulation are known to exist and have been investigated for the selective batching of common commercial glasses, these include; spray drying, pan pelletizing, pin mixing and finally high intensity mixing. Erich high intensity mixers were found to yield the desired size and density granules while conserving energy over the other most desirable method- spray drying. Granule #1’s chemistry is 73.17 SiO2·26.45·Na2O·0.26 K2O·0.12 Al2O3 and is mixed from fine ground silica, dense soda ash, potash and EPK. Granule #2’s chemistry is 70.50 SiO2·20.93 CaO·8.57 MgO and is mixed from fine ground silica, calcium carbonate and dolomitic limestone.
The granulation process uses high and low speed settings on the rotor of an Eirich R-07 mixer. The process for producing dense, narrowly distributed granules involves an initial low speed, dry mix for homogeneity followed by high speed liquid addition mixing. A high speed granulation step followed by low speed growth and dusting steps completes the process. The size of the final granule produced is a delicate balance between water content and the duration of granulation/growth mixing steps. A variety of granule sets were prepared including one variety of generic E-glass two varieties of generic SLS glass and finally the float glass composition melted in this study. The granules were characterized using optical microscopy and granule size/distribution weight measurements.
The study’s main mode of investigation has been melting intermediate (2 Kg) sized batches and cutting cross sections into the melts to count and compare bubble populations. These populations are expressed as a function of vertical position in the crucible. A total of 32 crucibles will have been investigated this way, leading to plots of bubble diameter as a function of height in the crucible (figure 1).
Figure 1. An example bubble plot showing the vertical bubble population, this plot is for a selectively batched melt after three hours in the furnace at 1350°C. The size of the circle is proportional to the size of the bubble.
Glass chemistry and density as a function of melt time have been verified using ICP chemical analysis and helium pycnometry, respectively. Using the Vogel-Fulcher-Tammann equation, viscosity estimates were made from the chemical analysis results of each final glass. The viscosity of each melt at the 5 hour mark was also measured using a hot stage microscope. Viscosity data support batch segregation theory within the conventionally batched melts while suggesting a more uniform, homogenous melt evolves in selectively batched trials.
Within the many steps of any fining operation one of the first steps is the growth and rise of the largest bubbles in the melt. Selective batching allows for the initiation and completion of this step faster than conventional melting by avoiding the inherent high viscosity pockets associated with a melt undergoing batch segregation, while simultaneously achieving lower batch free times.
Future Activities:
A re-melt at higher temperatures is underway to try and resolve a greater difference in fining behaviors between conventional and selective batching methods. Concentric granulation combines the two-granule system into a single-granule system with a core and crust of different chemistries and is the next step in developing selective batching technologies.
Supplemental Keywords:
Selective Batching, NOX, SOX, CO2, Granulation, Batch Free Time, Fining, Green House Gas, Hot Stage Microscope, Vogel-Fulcher-Tammann,Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
X832541 Center for Environmental and Energy Research (CEER) Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
X832541C001 Microarray System for Contaminated Water Analysis
X832541C003 The Fining Behavior of Selectively Batched Commercial Glasses
X832541C004 The Use of Fly Ash in the Production of SiAlON based Structural Ceramics
X832541C005 Separation and Purification of Hydrogen From Mixed Gas Streams Using Hollow Glass Microspheres
X832541C006 Magnesium Rich Coatings for Corrosion Control of Reactive Metal Alloys
X832541C008 Tunneled Titanate Photocatalysts for Environmental Remediation and Hydrogen Generation
X832541C009 Material and Environmental Sustainability in Ceramic Processing
X832541C010 Robust, Spectrally Selective Ceramic Coatings for Recycled Solar Power Tubes
X832541C011 Recycling of Silicon-Wafers Production Wastes to SiAlON Based Ceramics with Improved Mechanical Properties
X832541C012 Emissions Reduction of Commercial Glassmaking Using Selective Batching
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.