FGD Wastewater Treatment will be the Hot Topic on September 3rd at 10 a.m. CDT (Chicago time)
Over the next 12 years owners of coal-fired power plants will spend $200 billion dollars to add FGD systems to existing and new coal-fired power plants. The decision on which FGD technology to install will be shaped by the need or desire to be “carbon capture ready.” If SO2 concentrations in stack gases as low as 10 ppm are deemed to be necessary to ensure good operation of a carbon capture scrubber, then this will be an important parameter in scrubber selection. Since it will be difficult for dry scrubbers to meet these limits, wet scrubbers will be the most probable choice. However, the choice of wet FGD technology can introduce another regulatory problem.
Concurrently with the regulations that will require FGDs, states are tightening surface water discharge limits on trace metals and salts to meet National Pollutant Discharge Elimination System (NPDES) requirements for surface water discharge. Most FGDs discharge purge or wastewater that is a slurry of water, dissolved solids, and suspended solids laden with heavy metals and salts. Therefore, in developing plans to install wet limestone FGDs, utilities must also develop a strategy for the associated wastewater treatment system for the scrubber purge stream. But it is not an easy task to design an FGD wastewater treatment system that meets or exceeds regulations because the quantity and composition of FGD discharge water varies widely based on the boiler rating, scrubber type, the efficiency of flyash removal, the efficiency of the dewatering system and the composition of the coal, limestone and make-up water used. Coal contributes acidic gases, such as chlorides, fluorides and sulfate as well as volatile metals, such as arsenic, mercury, selenium, boron, cadmium and zinc which must be removed before discharge into any surface water. Limestone contributes clay minerals such as aluminum to the FGD wastewater and the clays tend to contribute the inert fines that are among the reasons wastewater is purged from the scrubber.
The following speakers will discuss the advantages and disadvantages of the currently available options and the latest state-of-the-art technologies for treating, minimizing or eliminating the wastewater that is generated by wet FGD systems.
Dr. Tom Higgins, Technology Fellow and Vice President, CH2M HILL will present the top 10 lessons he has learned from characterizing, developing, testing, designing, and troubleshooting treatment technologies for FGD wastewaters. These will include evaluation of developing treatment technologies for mercury and selenium removal. This will include current understanding of wastewater characterization, impacts of scrubber technologies, effects of treatment technologies on each other, and selection of specific equipment for achieving low level effluent limits.
Anna I. Casasús, Ph.D., Research and Development Director, Mazyck Technology Solutions, LLC will describe the Silica-Titania Composites (STC) for mercury removal from water to below 10 ppt developed by Mazyck Technology Solutions, LLC (MTS). MTS has obtained mercury concentrations below 1.3 ppt when evaluating its proprietary sorbent, Silica-Titania Composites (STC), for mercury removal from ash pond water from a coal-fired power plant. These Hg levels would be in compliance with the Great Lakes Initiative, which will be enforced in parts of the U.S. in 2010. MTS continues to evaluate and optimize the STC for Hg removal from water from a number of coal-fired power plants and expects to carry out a pilot-scale study in the near future.
William (Bill) Shaw, Senior Process Engineer at HPD, a Veolia Water Solutions & Technology company will discuss recent developments with the ZLD evaporation-crystallization processes for FGD scrubber waste. Conventional ZLD evaporation-crystallization processes for FGD scrubber waste streams have required pretreatment of the wastewater with lime-soda ash softening to replace the calcium, magnesium, and heavy metal ions in the wastewater with sodium ions so that a crystalline solid can be produced. A new ZLD process for FGD scrubber blowdown is operated at low pressure. Lowering the operating pressure allows water from the waste stream to evaporate at lower temperatures. Upon concentration of the waste stream at low temperature, dissolved solids will precipitate and crystallize at relatively low concentration. The low process temperature utilized eliminates the need to soften the feed brine to the ZLD process, saving the cost of chemicals and sludge disposal.
Joe Lally, Regional Technical Manager for Evonik Industries in Houston, Texas will discuss TMT 15, a heavy metal precipitant for separating heavy metals from effluents. TMT 15 offers advantages in safety and handling as well as having excellent eco-toxilogical properties. The presentation will touch on the chemistry and application notes ranging from reactions with acid, precipitable metals, addition points and rates and performance versus pH.
Brian Heimbigner, Business Development Manager for Integrated Solutions at Siemens Water Technologies will discuss established processes for FGD wastewater treatment systems and what the future might hold. Siemens Water Technologies (SWT) has been fortunate to be involved in 14 individual FGD wastewater treatment systems (WWTS) projects, of which 11 of them will be operational by the end of 2009. Since the primary objectives for most plants with WWTS are the reduction of TSS and Hg along with pH adjustment prior to discharge, a physical chemical treatment system has been common to all of the FGD WWTS supplied by Siemens. Each one has some resemblance to others, but each one has also needed to be custom designed for the specific plant’s wastewater characteristics. In certain states, selenium reduction has been a requirement and has been met by specialized biological treatment following the physical chemical system. In other states, total nitrogen is regulated more tightly and a different type of biological system has followed the physical chemical treatment. What does the future hold? Only the USEPA and state regulatory agencies have those answers. However, it appears requirements could get tighter and affect other contaminants which might focus not only on FGD WW, but also on other plant WW including ash pond water and cooling tower blowdown.
To register for the “Hot Topic Hour” on Thursday, September 3, 2009 at 10:00 a.m. CDT, click on: http://www.mcilvainecompany.com/brochures/FGDnetoppbroch/Default1.htm .
Bob McIlvaine
847 784-0012 ext. 112