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Technologies > Glass Furnace Technology > MGP Waste Testing

Manufactured Gas Plant Waste Testing
Many wastes share common characteristics with contaminated river sediment and municipal sludge, both effectively treated with Minergy's vitrification technologies. In March 2003, based on these successes and the similarities in the feedstocks, testing was conducted on Manufactured Gas Plant (MGP) waste in support of a grant to Dr. Gregory Kleinheinz at the University of Wisconsin Oshkosh.

The testing occurred in three phases, including a series of laboratory tests, a series of crucible melts and a demonstration melt in a commercial-scale unit. The laboratory series was performed to determine the overall chemical and physical characteristics and to predict melting temperatures. The crucible melts were performed to verify the viscosity of the waste when in a molten state. Finally, the commercial-scale demonstration melt was performed to substantiate the behavior of the molten material in a large melter process, and to determine throughput predictions for full-scale operation.

Laboratory Tests
A total of four samples were received for preliminary evaluation. A general description of the samples is shown in Table 1 below. [Note in table the use of bgs = below ground surface.]  

Table 1. Physical description of samples

The ITR sample was collected August 2002. All of the TTP samples were collected December 2002.

Mineral Analysis
To predict the melting properties of the material, all of the samples were prepared and analyzed for mineral composition. The samples were ground to 400 mesh and analyzed using X-ray fluorescence (XRF) methods. The XRF results are reported in the common oxide form and are summarized in Table 2.

Table 2. XRF mineral analysis results for MGP samples

Crucible Melts
A total of five crucible melts were performed in an oxy-fuel fired furnace with 8 cubic feet of internal volume and a heat input rating of 165,000 Btu/hr of maximum heat input. The furnace has a maximum operating temperature of approximately 2800 degrees Fahrenheit. Melts were performed in 2000cc fused silica crucibles capable of withstanding temperatures of 2800 degrees Fahrenheit.

Test Procedures
The MGP waste was added to the crucible and loaded into an idle (< 1800 degrees Fahrenheit) furnace. After the crucible temperature stabilized, the furnace temperature was raised. The crucible melts demonstrated that all MGP waste successfully melted into glass and also confirmed acceptable viscosity at typical melter operating temperatures. The molten glass from each crucible was poured off into a water bath to form an aggregate product.

Commercial Demonstration Melt
The third phase of this study processed a batch of MGP waste material in Minergy's GFT melter. The melter's normal rating is three glass tons per day. The melter can accept up to 9 mmBtu/Hr of heat input, and is intended to operate at a temperature of 2500 to 2800 degrees Fahrenheit. The melter has 10 feet, 2 inches of melting area, and is fired with a combination of natural gas and pure oxygen (oxy-fuel combustion). The system consists of a melter, aggregate quench tank, aggregate recovery screw, an oxygen and natural gas supply and control system, an exhaust fan, a water-cooled packed tower, and instrumentation necessary to collect all process critical data.

The oxy-fueled GFT melter proved capable of processing MGP waste with high destruction efficiencies, low operating costs, low emissions and creation of highly inert glass aggregate.

Glass Aggregate Qualities
The melter yielded glass aggregate product within 30 minutes of initiating testing. Qualitative analysis by Minergy indicated that the glass was of the same gradation and hardness as glass aggregates produced by its other vitrification processes.

Chemical analysis of the initial MGP mixture and the final glass aggregate using gas chromatography, coupled with a mass selective detector (GC-MS), revealed that the process had successfully destroyed the PAHs present in the initial material. This group of compounds was chosen for analysis due to their prevalence in the starting material and their propensity to be carcinogenic, teratogenic, and/or mutagenic. They are among the most problematic and long-lived compounds in the starting MGP material. Analysis performed was EPA Method 8270C. All analysis was performed by an EPA certified laboratory. A detailed list of analytes and concentrations are provided in Table 3. There was no sign of secondary products requiring additional mitigation.

Table 3. Polyaromatic hydrocarbon (PAH) analysis of beginning MGP mixture and final glass aggregate product.

The full report is available for download from our Library.

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