Subject: new FGD decision tree allows suppliers
to create a bigger market
FGD Decisions is a new and comprehensive service which will allow utilities and A/Es to methodically consider each important issue and they make decisions relative to the selection of systems, components and services to reduce SO2 emissions. Suppliers have the opportunity to provide input to the displayed material and to network with the utility users. It could, therefore, modify the way products and services are purchased.
This comprehensive decision tree system would cost millions of dollars to duplicate. Since McIlvaine is making a very low cost introductory offer it should be easily justified even by suppliers with modest FGD potential. For more information, click on: http://www.mcilvainecompany.com/FGDdecbroch/Default.htm .
More Analysis Needed on Major FGD Issues
FGD is the biggest near-term investment for most utilities. A few percent savings in capital or operating cost is significant.
There are numerous unresolved issues which need to be addressed. There is the inclination to select a forced oxidation limestone system with gypsum quality wallboard production without much analysis. There is an argument that you can save money by eliminating the oxidation and disposing of a calcium product other than wallboard quality material.
The potential for using lime instead of limestone in wet systems is also generally unexplored. One recent bid request gave the suppliers the option to quote lime or limestone. But they all opted to quote limestone. Analyses show that under certain conditions lime is more than competitive.
The choice of spray towers vs. tray towers vs. sump scrubbers is potentially important. Claims of significant energy savings for a given efficiency are being made for one vs. the other. There is even the question of the fineness of the limestone grind needed for each system. Two stage scrubbers may offer advantages. The argument is that two stages of trays provide higher efficiency with less slurry flow and energy cost.
Pre-scrubbers to remove mercury and produce hydrochloric acid offer a big potential. The cost of the pre-scrubber is offset by downstream cost reductions.
What about alkaline flyash scrubbing followed by a wet precipitator (WESP)? An alternative to dry scrubbers is to use a wet scrubber to collect the flyash and SO2 and follow the unit with a WESP for more fine particle removal. Sherburne Station is operating in this mode, although not with a design that is ideal.
The whole question of sludge fixation and disposal is not fully explored. Decades ago there was all sorts of work on construction uses for the FGD/flyash sludges. A new one popped up in the form of a product (gypsum) to remove sodium from reclaimed wastewater.
The circulating fluid bed dry scrubber appears to have some advantages over the more popular spray drier. If that is so, why are utilities considering only spray driers?
There are hundreds of choices when it comes to components. Is there an alternative such as a drum filter for the belt filter for gypsum dewatering? Should the slurry pump be rubber lined or hard metal? How important are mist eliminators in meeting total particulate guarantees?
The whole grinding circuit for limestone has many variations starting with the stone size delivered by the material supplier down to the actual size used in the scrubber.
Why are resin lined scrubbers popular in Japan, rubber lined scrubbers popular in Europe and nickel alloy scrubbers popular in the U.S.? The answer is the tendency to use what worked last time rather than what is most economical. With a quadrupling of nickel prices in just four years, this can be a costly mistake.
What fabric should be selected for bags for dry FGD? Choices include PPS, PTFE laminates and acrylic. Cost and performance differences need careful scrutiny.
Many complex choices must be made in the selection of optimization and instrumentation systems. Is response time for an SO2 instrument significant in minimizing reagent consumption?
The even bigger issue as to end products is not being debated. It is being addressed by government sponsored projects for innovative technology (Powerspan, Airborne, Enviroscrub, etc.). This means decades between conception and commercialization. The Philadelphia Electric MgO scrubbers were up and running at Eddystone within a few years after the idea was first proposed. But back in the 1970s the utilities and suppliers were moving ahead without relying on the government to fund new technologies.
FGD Decisions explores all these issues continually and will be encouraging the maximum amount of input from suppliers, utilities, researchers, A/Es and others.
McIlvaine is making this new service available free-of-charge to any subscriber to the Utility Environmental Upgrade Tracking System as a way to introduce this radically new and efficient system. To learn more just click on: http://www.mcilvainecompany.com/FGDdecbroch/Default.htm .
Bob McIlvaine
847-784-0012