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Many issues face coal fired utilities with respect to environmental demands, some based on current and future regulations and others based on local pressures. These include increasingly stringent control of criteria pollutants, anticipated federal and state requirements for mercury and HAP control, plume visibility, disposal issues and future climate change considerations.

For western utilities water use issues play an especially prominent role.

The J-Power/Isogo repowering project replaced two vintage coal fired units, and within the same site limits, more than doubled generation capacity to 2x600MW with ultrasupercritical boilers fitted with SCR, ESPs, and advanced generation ReACT™ technology. The controls provide exceptionally low emissions from the high efficiency coal fired boiler plant, which ranks Isogo as the cleanest coal fired power plant in the world in terms of emissions intensity. Emissions levels at Isogo are at levels equivalent to natural gas fired power plants.

Regenerative Activated Coke Technology (ReACTtm) is an integrated multi-pollutant control approach provides SOx, NOx, and Hg adsorption on activated coke with regeneration of the activated coke sorbent and has 1% of the water use of conventional WFGD.

ReACTtm, which is both mature (having origins in German technology in the 1960s) and fully commercial on coal fired utilities (to 600MW scale in Japan), is available in the United States through a recent license agreement between J-Power Entech and Hamon Research-Cottrell.

[CICIND Report Vol. 27, No. 1] -- Over the past 6 years electric utilities in the United States have under taken a program of retrofitting Wet Flue Gas Desulphurization (WFGD) Systems at coal-fired power plants throughout the country. These projects have been initiated due to a variety of environmental regulations, settlement agreements and permitting conditions. These retrofit projects, along with the construction of several new coal-fired power plants, have resulted in the construction of over 70 new concrete chimneys with over 100 flues or liners. Because of the excellent corrosion resistance and relative cost advantage of Fiberglass Reinforced Plastic (FRP) Chimney Liners (also known as Glass Reinforced Plastic (GRP) Chimney Liners) the overwhelming majority (approximately 90%) of the chimney liners were constructed of FRP.

[CICIND Report Vol. 25, No. 1] -- This paper explores various aspects of breeching entries for chimneys serving Wet Flue Gas Desulphurization (WFGD) systems. The advent of WFGD systems in the 1970’s resulted in the lowing of flue gas temperatures in power plants. Prior to WFGD, or scrubbers, most chimneys operated in a dry condition above or near the sulfuric acid dew point. The flue gas leaving a WFGD is wet and saturated. Flue gas reheat can be used to raised the flue gas temperature and help solve problems relating to liquid entrained in and condensing out of the flue gas, however due to problems and cost associated with reheat, more and more WFGD installations do not have any type of reheat and allow the wet saturated flue gas to directly enter the chimney, creating what is commonly know as a wet stack (Figure 1). This has now become the almost exclusive application following a WFGD in the United States.

This paper describes the design of a chimney with a GRP liner with several design features to accommodate both low and high temperature operation following an FGD system with continuous bypass capability, including a highly ventilated annulus, and a special high temperature resin for use in the GRP laminate. The chimney also incorporates a large construction opening to accommodate erection of the GRP liner sections with structural components to provide performance equivalent to a similar chimney with a normal sized opening.

Operational variations have an impact on the stack, often increasing corrosion and deterioration. Chimneys and stacks appear to be relatively stable components in an industrial plant. However, they are not immune to the impacts of changing plant operations. During their lifespans, chimneys may be exposed to a variety of changes, including variations in plant production, energy requirements, and environmental regulations. For instance, in some cases, new environmental regulations may require an extension in chimney height, a modification that alters the stress conditions of an existing structure.

Chimneys are often overlooked when plant maintenance and repair programs are developed. Chimneys are basically passive structures with few mechanical parts that require maintenance attention to keep them functional. Because of this, it is easy to overlook them - but doing so can be costly.

Chimneys and stacks have only one function: dispersing flue gas into the atmosphere. In the process of fulfilling that function, they are exposed to harsh environments, both inside and outside. Flue gas, with its abrasive and corrosive characteristics, can damage the structural materials of the chimney or liner. Climatic conditions, ranging from high winds to extreme cold, place extreme stress on the structure itself.

Chimney annulus pressurization is not uncommon in the power industry. Many new chimneys have pressurization fans already existing and operating; however, many older chimneys built with brick linings do not have an annulus pressurization system.
After years of service, these brick liners show signs of normal cracking, and flue gases under positive pressure tend to permeate through the brickwork into the annulus. This causes deterioration of mortar joints and corrosion of lining bands and other metal components within the annulus. It also can cause spalling of concrete on the inside face of the chimney column.