Reburning technique may lead to acid rain reduction in US and USSR by Don Rittner Reducing pollutants that are the cause of acid rain is a priority in a unique experiment being conducted by the U.S. EPA and involving the Soviet Republic of the Ukraine. The program is designed to reduce by 50% or more Nitrogen Oxides (NOx) from incomplete burning processes in boilers used by power plants using a technique known as "Reburning." According to Robert E. Hall, who heads up a group at the Environmental Protection Agency (EPA) called the Combustion Research Branch, recent passage of the 1990 Clean Air Act amendments highlights the need for establishing commercially viable technologies for reducing concentrations of NOx , a known culprit in acid rain production. These gases combine with water vapor in the atmosphere and produce nitric acids. NOx also is known to contribute to the formation of ground level ozone which helps create smog, leads to forest damage, and is the cause of serious respiratory health problems in humans. According to research by Hall and others, electric utility power plants account for about one-third of the NOx and two-thirds of the SOx (Sulfur Oxides) emissions in the Unite States alone. Cyclone fired boilers, while representing about 9% of coal-fired generating capacity, emit about 14% of the NOx that utility boilers produce. There are hopes that "reburning' may be part of the solution to substantially reduce these noxious emissions. The reburn process, according to Hall, starts by creating a second combustion or 'reburn' zone downstream from the main burner in a boiler. Combustion gases that result from burning a fossil fuel in the main combustion zone, move to the 'reburn' zone where additional fuel, in this case, natural gas, is injected, he said. The injection of additional fuel creates a fuel-rich zone in which the NOx formed in the main combustion zone are converted to molecular nitrogen and water vapor which occur naturally in the atmosphere. Any unburned fuel leaving the reburn zone is subsequently burned to completion in a downstream burnout zone where additional air is injected, he added. Reburning is especially good for cyclone-fired boilers and other wet-bottom boilers since low NOx burners and most other low NOx combustion technologies used on conventional boilers are not applicable to cyclone-fired and wet-bottom boilers, Hall said. The overall goal of the program is to successfully demonstrate a 50% or more reduction in NOx emission from boilers using the reburning technology. The first tests were done during the summer of 1990 on a 108 megawatt cyclone boiler, known as Niles Unit No. 1, owned by Ohio Edison. The results of that test reduced NOx levels ranging from 30 to 70% during parametric testing showing that NOx reductions in the 50-60% range are possible with acceptable boiler operation. Longer termed tests are scheduled for the fall of 1991 and 1992. While the first set of tests reduced much of the NOx, when the reburn was off a slagging problem developed due to recirculated flue gas that kept the burners cool, according to Hall. After running additional tests, it was determined that recirculated flue gas to get good mixing was not necessary and instead installed a water cooled burner in the reburn zone. Further tests are scheduled this week with long term tests taking place over a period of four and nine months. Continual use of the reburn system will depend on these tests and the cost of natural gas. The success of this project has broader implications. For the last 13 years, a joint U.S/USSR committee for cooperation in the field of environmental protection has sponsored meetings of a working group on stationary source air pollution control technology. In 1988, the 11th working group, meeting in Moscow, agreed to the first major air pollution control research project with its goal to implement a NOx control technology on a large 300 megawatt coal fired boiler in the Soviet Union. The Soviet Union is in the process of developing NOx emission level standards for electric utility boilers to help reduce air pollution in that country. During the summer of 1991, Hall and others visited the host site in the Ukraine for final arrangements of the test on a 300 megawatt boiler that is a opposed wall-fired, wet bottom type, according to Hall. The location of the test is the Ladyzhinskaya Power Station in the Ukrainian city of Vinnitsa. There are six 300 megawatt coal fired boilers in the plant. The US side provided the Soviets with a preliminary design for an in-furnace NOx control system while the Soviets did the final detail design, fabrication, installation and testing of the system. The US side will assist in the evaluation. Recently back from another visit of the site, Hall said the site is undergoing a major overhaul on the nose of the furnace system and the installation of the reburn equipment has been postponed until next spring. The boiler should be online for testing in August, 1992. The Ukrainians have indicated an interest in testing the other boilers and as many as 35 additional ones throughout the USSR if the tests are successful. In any event, the successful implementation of reburn systems could lead to a serious reduction in NOx emissions that could further reduce the threat of acid rain. Contact Robert E Hall, 919-541-2477; fax is 919 541-0554. Copyright 1991, Don Rittner ---------- Don Rittner is the author of EcoLinking: Everyone's Guide to Online Information (Peachpit Press), a columnist for Environment News Service, and Host of America Online's Environmental Forum.e may lead to acid rain reduction in US and USSR by Don Rittner Reducing pollutants that are the cause of acid rain is a priority in a unique experiment being conducted by the U.S. EPA and involving the Soviet Republic of the Ukraine. The program is designed to reduce by 50% or more Nitrogen Oxides (NOx) from incomplete burning processes in boilers used by power plants using a technique known as "Reburning." According to Robert E. Hall, who heads up a group at the Environmental Protection Agency (EPA) called the Combustion Research Branch, recent passage of the 1990 Clean Air Act amendments highlights the need for establishing commercially viable technologies for reducing concentrations of NOx , a known culprit in acid rain production. These gases combine with water vapor in the atmosphere and produce nitric acids. NOx also is known to contribute to the formation of ground level ozone which helps create smog, leads to forest damage, and is the cause of serious respiratory health problems in humans. According to research by Hall and others, electric utility power plants account for about one-third of the NOx and two-thirds of the SOx (Sulfur Oxides) emissions in the Unite States alone. Cyclone fired boilers, while representing about 9% of coal-fired generating capacity, emit about 14% of the NOx that utility boilers produce. There are hopes that "reburning' may be part of the solution to substantially reduce these noxious emissions. The reburn process, according to Hall, starts by creating a second combustion or 'reburn' zone downstream from the main burner in a boiler. Combustion gases that result from burning a fossil fuel in the main combustion zone, move to the 'reburn' zone where additional fuel, in this case, natural gas, is injected, he said. The injection of additional fuel creates a fuel-rich zone in which the NOx formed in the main combustion zone are converted to molecular nitrogen and water vapor which occur naturally in the atmosphere. Any unburned fuel leaving the reburn zone is subsequently burned to completion in a downstream burnout zone where additional air is injected, he added. Reburning is especially good for cyclone-fired boilers and other wet-bottom boilers since low NOx burners and most other low NOx combustion technologies used on conventional boilers are not applicable to cyclone-fired and wet-bottom boilers, Hall said. The overall goal of the program is to successfully demonstrate a 50% or more reduction in NOx emission from boilers using the reburning technology. The first tests were done during the summer of 1990 on a 108 megawatt cyclone boiler, known as Niles Unit No. 1, owned by Ohio Edison. The results of that test reduced NOx levels ranging from 30 to 70% during parametric testing showing that NOx reductions in the 50-60% range are possible with acceptable boiler operation. Longer termed tests are scheduled for the fall of 1991 and 1992. While the first set of tests reduced much of the NOx, when the reburn was off a slagging problem developed due to recirculated flue gas that kept the burners cool, according to Hall. After running additional tests, it was determined that recirculated flue gas to get good mixing was not necessary and instead installed a water cooled burner in the reburn zone. Further tests are scheduled this week with long term tests taking place over a period of four and nine months. Continual use of the reburn system will depend on these tests and the cost of natural gas. The success of this project has broader implications. For the last 13 years, a joint U.S/USSR committee for cooperation in the field of environmental protection has sponsored meetings of a working group on stationary source air pollution control technology. In 1988, the 11th working group, meeting in Moscow, agreed to the first major air pollution control research project with its goal to implement a NOx control technology on a large 300 megawatt coal fired boiler in the Soviet Union. The Soviet Union is in the process of developing NOx emission level standards for electric utility boilers to help reduce air pollution in that country. During the summer of 1991, Hall and others visited the host site in the Ukraine for final arrangements of the test on a 300 megawatt boiler that is a opposed wall-fired, wet bottom type, according to Hall. The location of the test is the Ladyzhinskaya Power Station in the Ukrainian city of Vinnitsa. There are six 300 megawatt coal fired boilers in the plant. The US side provided the Soviets with a preliminary design for an in-furnace NOx control system while the Soviets did the final detail design, fabrication, installation and testing of the system. The US side will assist in the evaluation. Recently back from another visit of the site, Hall said the site is undergoing a major overhaul on the nose of the furnace system and the installation of the reburn equipment has been postponed until next spring. The boiler should be online for testing in August, 1992. The Ukrainians have indicated an interest in testing the other boilers and as many as 35 additional ones throughout the USSR if the tests are successful. In any event, the successful implementation of reburn systems could lead to a serious reduction in NOx emissions that could further reduce the threat of acid rain. Contact Robert E Hall, 919-541-2477; fax is 919 541-0554. Copyright 1991, Don Rittner ---------- Don Rittner is the author of EcoLinking: Everyone's Guide to Online Information (Peachpit Press), a columnist for Environment News Service, and Host of America Online's Environmental Forum.