Coal Cleaning Program for 1994-1995
- Dewatering of Fine-Size Clean Coal Slurries
- Removal of Hazardous Trace Elements from Coal
- Wastewater Treatment
- Recovery of Clean Coal from Waste Ponds
- Advanced Fine-Coal Dewatering Technique
Contact: B.K. Parekh
Associate Director, Coal Cleaning Program
The original emphasis of the Coal Cleaning Program was concerned with research relating to advanced processes for coal cleaning, with the primary focus on column flotation. The scope of the program has broadened considerably, using a base of expertise in separations and surface chemistry to develop novel technologies and to improve existing ones for the recovery, handling and dewatering of fine particles. As well as active research in trying to resolve immediate or near-term problems faced by the coal, utility, and other industries, concerted efforts are being made to diversify and develop technologies for the resolution of problems in wastewater treatment.
Two current projects are concerned with dewatering of fine-size clean coal slurries:
The first project, sponsored by DoE, deals with the evaluation of high pressure filtration technology, and identifying the optimum filter operating conditions. Laboratory findings have been tested on a pilot scale (1 ton/hr) high-pressure filter unit at two coal preparation plants, processing two fine-size particles: the first plant processed finer than 150 micron size coal. Using high pressure filtration tech-no logy, a 14 % moisture filter cake was obtained compared to 24 % currently obtained at the plant. The second plant processed finer than 74 micron size slurry, which is difficult to dewater using the con-conventional equipment. High pressure filtration provided a 24 % moisture filter cake. Both results were acceptable to industry.
The second project consists of pilot-scale testing of a novel dewatering approach developed at the CAER, which involves a modification of the surface property of coal by treating it with a combination of metal ions and surfactant mixture. The modified coal slurry will then be dewatered using high pressure, centrifuge, and vacuum filter tech-technologies. The studies are being conducted using a clean-coal slurry obtained from the commercial KENFLOTE column flotation units developed at the CAER and employed at the Powell Mountain Coal Company's Mayflower Preparation Plant.
In a DoE sponsored project, pilot scale column flotation studies were conducted to obtain an ultra clean coal product containing less than 2 % ash and less than 1 % sulfur. The process is now being tested at the rate of two tons per hour at the Amax R & D Center at Golden, CO. The product will be tested as a coal-water slurry in advanced combustion systems to replace fuel oil.
Currently, a project sponsored by DoE under the auspice of the Appalachian Clean Coal Technology Consortium, is involved with destabilization of the column flotation froth product. The project will utilize novel chemical and mechanical approaches to achieve the objective of breaking down the bubbles.
In a project sponsored by the DoE EPSCoR program, a combination of physical and chemical approaches is being evaluated for the removal of hazardous trace elements from coal, while achieving 90 % combustible recovery. The techniques under investigation include a combination of column flotation and hydrothermal treatment.
Wastewater Treatment: Research is being continued to develop a novel approach for the treatment of industrial waste waters, where the contaminants can be flocculated prior to separation and removal. Successful investigations have been made for the removal of dye substances from textile manufacturing process waters, and waste products from the effluent of the paper and pulp industry.
Recovery of Clean Coal from Waste Ponds: In an industry-sponsored project, an experimental program is being carried out to develop a flow sheet for the recovery of clean coal from inactive waste ponds.
Froth, oil, and column flotation -- the most effective processes available for cleaning coal finer than 0.5 mm (28 mesh) -- share the same serious drawback: their end-product contains 80% moisture. Most U.S. coal companies, therefore, have been reluctant to use these advanced fine-coal cleaning technologies, particularly since an economical process to dewater the coal does not currently exist.
This project will attempt to demonstrate an efficient and economical fine clean coal dewatering process. If successful, it will be an important step in the U.S. Department of Energy's program to show that ultraclean coal can be effectively dewatered to 20% or lower moisture content using either conventional or advanced techniques.
The University of Kentucky Center for Applied Energy Research (UKCAER) will develop and test a novel surface modification technique -- which uses the synergistic effect of combining metal ions with surfactants -- to dewater ultrafine coal at the proof-of-concept (POC) scale of between one and two tons per hour. This novel coal surface modification approach will use vacuum, centrifuge, and hyperbaric filtration techniques on both high-sulfur and low-sulfur clean coal. The POC testing will be performed at the Powell Mountain Coal Company's Mayflower Preparation Plant.
Coal represents 94% of proven U.S. fossil fuel reserves and 70% of proven global fossil fuel reserves, but burning coal for power generation produces harmful SOx, NOx, and CO2 emissions. It is in the Nation's interest to invest in clean coal technologies to maximize the use of this abundant resource while minimizing its negative impacts on the environment. DOE's Clean Fuels from Coal Program addresses this priority and seeks to provide a long-term alternative to imported oil as well.
The goal of the Advanced Fine-Coal Dewatering project is to develop a technique that can achieve a 20% or lower moisture level in the fine clean coal product. Additionally, by providing a detailed technical and economic evaluation of the advanced dewatering process, this project seeks to promote this new process and encourage coal companies to install it in their plants.
University of Kentucky - (Primary Project Partner & Main Site)
Center for Applied Energy Research
Powell Mountain Coal Company
Mayflower Preparation Plant
St. Charles, VA
Andritz Ruthner, Inc.
(laboratory dewatering tests/pilot-scale tests using the hyperbaric pressure filtration unit at the Powell Mountain Coal Company)
A recent survey co-conducted by the U.S. Department of Energy identified the dewatering of fine clean coal as the number-one priority of the Nation's coal industry.
If the advanced dewatering process demonstrated in the University of Kentucky (UKCAER) project is adopted by U.S. coal companies and used in a large number of coal preparation plants, it will have a strong socioeconomic impact. First, it will provide monetary benefits to the coal industry by enabling it to recover extra coal. Second, because most of the coal will be recovered, solid waste discharge from the preparation plants will be significantly r educed. This technology will indirectly reduce land pollution.
This technology will also lessen U.S. dependence on imported oil, thereby increasing the Nation's energy security.
Center for Applied Energy Research
U.S. Department of Energy