• Market Assessment and Demonstration Lignite FBC Ash in Flowable Fill Applications
• Ash Based Grout Injection for Subsidence Control at Shamrock Mine
• PFBC Ash Management Evaluation and Demonstrations
• SYNAG - Technology Application

Market Assessment and Demonstration Lignite FBC Ash in Flowable Fill Applications

Background
Montana-Dakota Utilities operates fluidized bed combustor burning North Dakota lignite in a sand bed.  The ash material can't be used in conventional ash applications such as ready-mix concrete and therefore represents a liability and cost to the generation of power at the Heskett Station.  WRI and MDU conducted preliminary tests that indicated that there was a potential and market for the use of both the ash and sand in flowable fill applications in the Bismarck-Mandan area.  However, several geotechnical and environmental performance issues remained unsolved that needed to be verified prior to the commercial deployment of the resultant flowable fill product, termed ReadyFill™.

Description
The project involved both product development and product demonstration, including:

• Product development that included mix design, environmental compatibility testing and geotechnical performance evaluations under seasonal climatic conditions.  Mix designed addressed the proportions of Heskett ash and waste sand from the fluidized bed combustor operation.  Both excavatable structural grade flowable fills were designed.
• Product demonstration included the construction of a commercial-scale batch plant at a site centrally located between two of the ready-mix concrete suppliers in Bismarck, North Dakota in order to produce quantities of Ready-Fill product for full-scale field demonstrations.  Demonstrations of the ReadyFill product included excavatable, structural, and niche applications.

The results of the project have been presented at the International Conference on Fluidized Bed Combustion and the International Symposium on Management and Use of Coal Combustion Products (CCPs)

Preliminary Results

• Developed a cost-effective and customized performance flowable fill product (Ready-Fill™) for excavatable and structural applications.  Ready-Fill utilizes fluidized bed combustion ash from the lignite-fired Heskett plant and waste sand fines, small amounts of cement and water.
• Developed a 'Field Simulator' for evaluating the environmental impact of ash-based products on adjacent soils and ground water.  The field simulator use flex-wall permeates to assess impact on adjacent soils and leachate quality.  The simulator can be pressurized to assess decades of permeate passing through the flowable fill material in a matter of months of testing.
• Demonstrated the performance of Ready-Fill in full scale field applications.  A total of seven demonstrations covering structural, excavatable, and niche applications.  For example, structural base for coal unloading facility at Heskett plant, excavatable trench bedding for utilities, erosion control, base material for residential patios are a few of the demonstrations.

Status
Ready-Fill was commercially marketed in the Bismarck-Mandan area of North Dakota.  Ready-Fill was wholesaled to the three Ready Mix concrete suppliers who in turn retailed the product.  The price of Ready-Fill was approximately 75% of the cost of other commercially available fill materials.

Ash Based Grout Injection for Subsidence Control at Shamrock Mine

Background
It has been estimated that some 50,000 acres along the Front Range in Colorado are underlain by abandoned underground mines, which are potentially susceptible to subsidence.  The potential for subsidence represents a detriment to the development of the surface property associated with these mined areas.  The Shamrock mine in Weld County, Colorado is an example of one of abandoned underground mines.  The geotechnical and environmental performance of ash-based grouts for this application need to be developed and demonstrated prior to commercial operations can be permitted.

Objectives
The overall objective of the project is to evaluate the environmental and geotechnical issues associated with the use of ash-based grouts for subsidence control in flooded underground mines.

Description
The project is composed of a number of phases that address the geotechnical and environmental issues associated to the use of ash-based grouts for subsidence control in the flooded underground Shamrock Mine.  Phase I Laboratory-scale Geotechnical and Environmental Evaluations examined the environmental and geotechnical issues associated with ash-based grout injected into the Shamrock Mine.  Grouts were developed and tested in flumes designed to stimulate mine conditions.  Phase II Acquisition of Permitting Information was designed to acquire the information required to obtain a permit for an in-situ pilot-scale demonstration of the ash0based grout injection process.  Phase III Field-Scale Above Ground Mine Simulation was designed to address an above ground full-scale injection of the process and to monitor water quality and geotechnical performance of the grout.  Phase IV In-Situ Pilot Scale Demonstration was designed as a full-scale in-situ injection of the grout into the Shamrock Mine using full-scale equipment and the developed injection plan.  Phase VI Demonstration Monitoring was designed to conduct long-term (multi-year) monitoring of the water quality and grout performance.

Preliminary Results

• Developed ash-based grouts composed of various ashes including dry flue gas desulfurization ash that were capable of being injected into flooded underground mines with minimal dispersion into water.  The ash-based grouts met the strength requirements and gained strength under water.
• Developed a mine simulator flume capable of simulating the impact of ash-based grout injection in flooded underground mines.  The mines simulator is capable of assessing dispersion of the grout in the mine water, penetration of the grout around debris in the mine, consolidation of the grout, and impact of grout on mine water quality.
• Develop a mine injection plan, whereby ash contaminated mine water is used in the grout formulation and thereby minimizing the impact to ground water resources.  The plan takes into account the use of ground water flow rates and direction and the spacing and sequence of grout injection wells.  The grout injection plan involves pumping the grout into the mine on 25-foot spacing and the displaced mine water would be used in the grout production and/or used for surface needs.

Status

• Project is complete.  Project goals met.
• Development of a mine simulator flume capable of simulating the impact of ash-based grout injection in flooded underground mines.  The mine simulator is capable of assessing dispersion of the grout in the mine water, penetration of the grout around debris in the mine, consolidation  of the grout, and impact of grout on mine water quality.
• Development of a mine injection plan, whereby ash contaminated mine water is used in the grout formulation and thereby minimizing the impact to ground water resources.  The plan takes into account the use of ground water flow rates and direction and the spacing and sequence of grout injection wells.
  
  

PFBC Ash Management Evaluation and Demonstrations

Background
One of the main emphases for the U.S. DOE is the development of advanced power systems that offer higher efficiencies (greater than 45%) and thereby lower the cost of electricity (COE).  DOE and industry have spend millions on the engineering and power cycle side of this development and this effort addresses the ash side of these developments.  Foster Wheeler Energy International, Inc., a major developer of the PFBC technology, has proposed to demonstrate the technology at the Lakeland Electric and Water McIntosh Station.  This 170 MW PFBC would provide the first commercially available PFBC ash for marketing and use in the central Florida area.  Western Research Institute and Foster Wheeler Development Corporation have completed a project for US DOE that defines potential ash management options for the ashes from advanced power systems such as PFBC systems.

Objectives
The objective for this project is to determine the technical reuse options for circulating pressurized fluidized bed combustion (PFBC) ashes in construction, agricultural, and reclamation applications through laboratory-scale and pilot-scale testing.

Description
The project addressed ash use evaluations of PFBC ashes generated at the Foster Wheeler Energia Oy 10MW pilot facility at Karhula Finland burning low sulfur Powder River Basin coal, eastern bituminous medium sulfur coal and Illinois Basin high sulfur coal.  The results of the testing have indicated that the PFBC ash is an excellent material in commercially mature applications, including:

• Use in cement product as a replacement for gypsum;
• Use as an engineered fill and embankment material;
• Use as a soil stabilization agent;
• Use as a feedstock in the production of synthetic aggregate according to the AET process;
• Use as a soil amendment for agriculture and reclamation of problem acidic and sodic soils.

The results of these investigations have been widely published and presented at national and international meetings, such as in the Journal FUEL, proceedings of the International Conference on Fluidized Bed Combustion, and American Coal Ash Association Symposium.

Preliminary Results

• Testing confirmed that PFBC ash could be used in a number of construction applications, including as a feedstock for cement manufacturing as a replacement for gypsum and as a pozzolan addition; as a compacted and flowable fill material; as a stabilizing agent for soil and road base stabilization; and as a feedstock in the manufacture of synthetic aggregate.  Greenhouse tests have confirmed the use of PFBC ash as a soil amendment in agriculture and reclamation, providing neutralization of acidic soils and texture modification enhancing root penetration.
• Results of testing have been applied to ash from combustion of gasifier char generated by advanced power systems, such as that being developed at the Power System Development Facility in Wilsonville, Alabama.

Status

• Testing confirmed that PFBC ash could be used in a number of construction applications, including as a feedstock for cement manufacturing as a replacement for gypsum and as a pozzolan addition; as a compacted and flowable fill material; and a stabilizing agent for soil and road base stabilization; and as a feedstock in the manufacture of synthetic aggregate.  Greenhouse tests have confirmed the use of PFBC ash as a soil amendment in agriculture and reclamation, providing neutralization of acidic soils and texture modification enhancing root penetration.
• Results of testing have been applied to ash from combustion of gasifier char generated by advance power systems, such as that being developed at the Power System Development Facility in Wilsonville, Alabama.
• Results of testing have been published in the Journal FUEL, proceedings of the International Conference on Fluidized Bed Combustion, and American Coal Ash Association Symposium.
  
  

The overall goal of the multi-year project is to commercialize the SYNAG™ technology in a range of applications.

Western Research Institute, through the support of the U.S. DOE NETL, has developed the SYNAG™ process for the production of synthetic aggregate from coal combustion ashes. Based on cold bonding techniques, the SYNAG ™ process is capable of producing ASTM and AASHTO normal-weight and lightweight construction aggregate. The objective is to verify through pilot-scale and field-scale demonstrations the technical and economic viability of the SYNAG™ process to produce ASTM and AASHTO grade construction aggregate for use in construction.