environment

The ability to detect contaminated feedwater or steam before it can corrode the internals of a turbine or HRSG and cause a forced outage is worth millions. One knock against cation conductivity monitoring—still the most common technique for the early detection of contamination—is the difficulty of interpreting conductivity readings when the plant’s makeup contains significant levels of organics or CO2. Here are the pros and cons of cation conductivity monitoriting and some alternative monitoring methods.

This February, a federal appeals court tossed out the Clean Air Mercury Rule and its cap-and-trade program and ordered that mercury be regulated more stringently as a hazardous air pollutant. Adding insult to injury, the court made its ruling effective one month later. While the EPA regroups, state energy and environmental regulators will have an opportunity to look closely at recent power plant permits for guidance. This article reviews the technology options and regulatory approach for mercury control used on recently permitted and currently operating coal-fired plants.

On a larger scale, the North American coalfired generating industry has been scrambling for economically viable ways to retrofit existing infrastructure with carbon capture and sequestration (CCS) solutions.Power producer TransAlta Corp. Recently announced it will partner with technology developer Alstom on a project to develop an extensive CCS facility in Alberta, Canada.

Engineers in Wales have reportedly developed a filtration system that converts carbon dioxide emissions into a waste product that can be converted by genetically modified algae into biodiesel.

The system, called a Greenbox, could replace the muffler on a conventional exhaust although it is too large to fit onto an existing car exhaust. It could also be used for larger vehicles or even buildings, its creators suggest.

Prior to 1990, little reliable data was available on mercury concentrations in coal plants' stack gas or anywhere within the plant gas stream. The ERA attempted to change that by developing an emissions inventory known as the 1999 Information Collection Request (ICR). The ICR collected basic information on all 1,140 coal-fired utility boilers in the U.S., and more detailed information as well. The detailed data included analyses of coal's calorific value and its mercury, chlorine, sulfur, moisture, and ash content. Also included were analyses of total and speciated (elemental and oxidized) mercury in the inlet and outlet flue gases of 81 units representing a cross-section of the various types of boilers and fuels used in the U.S.

No single technology will work for every coal-fired power plant. The mercury control options under investigation can be classified into six broad categories:

• Sorbent injection involves injecting a material, usually in powdered form, that adsorbs mercury upstream of a particulate collector such as a baghouse or electrostatic precipitator (ESP). Activated carbon injection currently represents one of the most promising controls on the horizon. It is the only technology that is close to being commercialized.

Burning coal in the U.S. is a tough job that continues to get tougher. Every few years, the federal government decides that coal-fired power plants must reduce their emissions of yet another pollutant. First came limits on NOX, SO2, and particulates, which required plants to install cleaner burners, scrubbers, and baghouses or electrostatic precipitators. The latest air-quality nemesis to show up on the radar screen is mercury. But the difference this time is that regulations for removing it are coming not just from Washington but from states as well.

By Dr. Robert Peltier, PE, Editor-in-Chief of POWER

A power plant that gasifies coal, produces hydrogen, and seguesters carbon is the DOES answer to the question, "How will the U.S. reduce its greenhouse gas emissions without signing the Kyoto Protocol?" But unproven technologies, an aggressive schedule, and the energy industry's historical inability to cost-share raise questions about the program. Is this just another pie-in-the-sky federal boondoggle or the coal-fired plant of the future?

By Dr. Robert Peltier PE, Editor-in-Chief POWER