Technics
Materials Center for Combustion Turbines
A New Cure for Medical Waste
Holt Nominated to ASME Board of Governors
Materials Center for Combustion Turbines
Electric power companies now have a potentially even brighter future thanks to the technical support offered by the Materials Center for Combustion Turbines (MCCT) at SwRI. The MCCT was established by the Electric Power Research Institute (EPRI) to provide expertise in all areas of combustion turbine materials technology. The joint SwRI/EPRI facility is available only to EPRI members. SwRI, however, continues to offer its services in turbine materials technology to all interested parties.
The center was created to address the technical and material problems that have arisen as more utilities install combined cycle turbines. Combined cycle (combustion and steam) systems are more efficient than steam turbines or combustion turbines alone, and have low emissions. These factors, along with a readily available supply of cheap natural gas and low capital costs, have helped combined cycle plants become the leading source of new electric capacity in the U.S. and abroad. However, widespread use of combustion turbines has given rise to numerous materials-related problems as manufacturers compete to meet the utilities’ demands for turbines that are more efficient and can operate at higher temperatures. To cope with advances in turbine technology and the associated costs, utility operators seek advice that is independent from that of equipment manufacturers and repair vendors.
SwRI engineers and scientists can help EPRI members understand the new technology and solve related problems through a wide range of MCCT services including investigations of turbine component failures, analyses of repair procedures, development of nondestructive evaluation methods for measuring hot section component degradation, analysis and specification of protective coatings for turbine blades and other components, and development of life prediction and life assessment tools to help achieve maximum value from turbine operation.
“Since the MCCT was established in 1993, SwRI engineers and scientists have made significant contributions in several areas of combustion turbine materials technology that have resulted in substantial savings to EPRI member utilities,” notes Dr. Gerald R. Leverant, director of the MCCT and of the Power Generation Materials Department at SwRI.
For example, a materials evaluation of a cracked second-stage bucket from an EPRI-member utility revealed that cracking had not entered the base metal as originally believed, but was confined to an internally oxidized layer along the leading edge of the bucket. The MCCT therefore recommended refurbishing the three sets of second-stage buckets instead of replacing them, saving the utility an estimated $1.8 million dollars.
“Activities at the MCCT are not confined to hardware testing and analysis,” explains Dr. Henry L. Bernstein, assistant director of the MCCT. “Engineers have also developed software packages that allow utility operators to determine the need for component replacement or maintenance without costly downtime and with greater reliability.” The Advisor on Blade Coatings (ABC) software offers recommendations about generic coatings on the basis of user input regarding turbine type, environment, and operating conditions. An EPRI-member utility used ABC to select a coating for new combustion turbine blades in four units. The coating should double the life of the blades and save the utility an estimated $3.6 million.
REMLIF, an expert system computer program that predicts the remaining life of blades and vanes in gas turbines, was developed by MCCT personnel specifically to evaluate first-stage blades and vanes of General Electric MS7001B, E, and EA gas turbines. REMLIF analysis of a set of first-stage blades from the Anchorage Municipal Light and Power Company proved that little damage had occurred to the blades. That evaluation saved an estimated $560,000 in avoided outage costs. In a collaborative program with EPRI and KEMA, an EPRI foreign affiliate member located in The Netherlands, MCCT engineers are developing a REMLIF code for GE Frame 6 gas turbines.
New research at the MCCT includes developing a coating durability model that could be integrated into both REMLIF and ABC, as well as nondestructive evaluation methods to determine the condition of coatings on-line. “These developments should allow utilities to realize savings in both downtime and new component acquisition,” says Leverant.
The MCCT is available to any member of EPRI. For more information contact the EPRI Materials Center for Combustion Turbines, c/o Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas, 78228-0510, or phone (800) 456-6842.
A New Cure for Medical Waste
Engineers at SwRI are testing the efficacy of an innovative medical waste treatment system manufactured by Med Compliance Services (MCS) of El Paso. The system first shreds the material, reducing its volume, then disinfects the waste by exposure to a chlorine dioxide solution. The chemical treatment system, called the Encore-2100, is an alternative to incineration, traditionally used to dispose of medical waste but threatened by upcoming federal regulations.
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The U.S. Environmental Protection Agency (EPA) estimates that 3.4 million tons of waste are produced annually by health care facilities in the United States. Hospitals are the single largest generator of that waste, contributing more than 70 percent of the annual total in the form of contaminated dressings, biopsy specimens, laboratory wastes, needles and syringes, and blood and blood products. Over 3,000 hospitals now employ incineration as a primary means of medical waste disposal.
However, under the auspices of the Clean Air Act Amendments, the EPA has issued a proposed rule, which should be finalized by April 15, 1996, that would impose stringent pollution control requirements on medical waste incinerator operators to reduce potential toxic emissions such as dioxins and metals. Implementation of the control measures is expected to significantly increase equipment and operating costs, making on-site incineration economically impractical for many hospitals. Some waste treatment industry representatives estimate that the proposed rule could force the closure of up to 80 to 90 percent of existing medical waste incinerators.
James Scott, a senior research engineer at the Institute and a certified industrial hygienist, has led the effort to design test protocols for and perform third-party, independent testing of the Encore-2100 to assess its compliance with efficacy standards established by the EPA and a consortium of state medical waste regulators. Environmental Health Management Systems, South Bend, Indiana, provided microbiology consultation to MCS during development of the Encore-2100 system.
“The Encore-2100, with a maximum production rate of 2,000 pounds per hour, is designed to effectively and safely treat infectious waste so the processed material can be disposed of in a conventional solid waste landfill,” says Scott. “Two specially configured industrial shredders in series reduce waste volume significantly and enhance contact between all the waste components and the chlorine dioxide solution, which is introduced during and after shredding.”
The chemical disinfection solution is provided by a patented chlorine dioxide generator system made by the Rio Linda Chemical Company in Sacramento, California. Chlorine dioxide — a powerful disinfecting agent commonly used to treat drinking water and wastewater — can be generated through a reaction involving sodium hypochlorite, hydrochloric acid, and sodium chlorite solution, or by mixing gaseous chlorine and sodium chlorite solution. In the Rio Linda system, the chemicals react on a molecular basis, under vacuum, to create gaseous chlorine dioxide. A unique feature of the system is its single ejector, which serves both to create a vacuum bringing the premeasured chemicals together to form gaseous chlorine dioxide, and then to introduce the gas into an aqueous solution.
The disinfecting solution is removed from the waste using a helipress, then recirculated and returned to the desired concentration prior to reuse in the treatment process. Release of airborne contaminants is controlled by a high-efficiency particulate air filter and by scrubber units.
Scott explains that the Institute designed two test protocols to measure the effectiveness of the Encore-2100.
“One protocol tests the system relative to EPA requirements for sanitizing inanimate, non-food contact surfaces. This part of the study is being conducted in accordance with EPA Good Laboratory Practice standards. The second protocol subjects the Encore-2100 to national standards developed by a consortium of state medical waste regulators, the State and Territorial Association of Alternate Treatment Technologies.” To satisfy these standards, the system must demonstrate a 99.9999 percent reduction in selected microorganism species representing vegetative bacteria, viruses, fungi, parasites, and tubercle mycobacteria. In addition, the process must demonstrate a 99.99 percent reduction in bacterial spores, a highly resistant microorganism form of Bacillus bacterium.
Stringent quality assurance controls were incorporated to encompass all aspects of the study: sources and culturing of the microorganisms, processing of waste through the Encore-2100, and microbiological analyses of the samples. Quality assurance documents generated during the study validate the sample results and allow complete reproduction of the experimental tests. SwRI has collected more than 150 samples from the Encore-2100. The first commercial unit is scheduled to be installed and operating at an existing MCS facility in Albuquerque, New Mexico, this fall.
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Dr. Amos Holt |
Holt Nominated to ASME Board of Governors
Dr. Amos Holt, vice president of SwRI’s Nondestructive Evaluation Science and Technology Division, has been nominated to the national Board of Governors of the American Society of Mechanical Engineers (ASME).
The board oversees ASME fiduciary operations. Holt will assist in the review and approval of policies and procedures during a term lasting from 1996 until 1999.
An ASME member for 14 years, Holt was named a Fellow in 1993. He is currently senior vice president of the ASME Council on Engineering and a member of the Council Coordination Committee. Other national ASME offices and assignments he has held include vice president of the Materials and Structures Committee, vice chairman of the Council on Engineering, chairman of the Council of Engineering Long Range Planning Committee, chairman of the Nondestructive Evaluation Engineering and Science Division, and chairman of the Technology Executives Conference Committee.
Published in the Fall 1995 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Joe Fohn.
