March 1, 2007

Limestone Quality and Lime Sources were the Focus of Hot Topic Discussions

The Hot Topic Hour on calcium reagents yesterday revealed that there are going to be real challenges in supplying enough of the right quality calcium reagents. To add lime capacity takes several years. Plants need to be permitted and a substantial capital investment is required. Opening up new limestone sources is also not that easy for several reasons including the scarcity of the right quality limestone.

The recording of the session was posted within a few hours of the completion.

The Hot Topic Hours are very popular. There were 30 or more participating in this session and more than 60 last week. One reason is the convenience. Jeff Karloff of Omaha Public Power called just before the meeting to say his group was home snowbound and could each of them have access through their home computers? We provided this access and therefore demonstrated the advantages of telecommuting.

Eric Van Rens of Mississippi Lime was one of the speakers. He managed to step off a plane just in time to start his presentation.

The meeting opened with a quick tutorial on how to analyze all the reagent information. McIlvaine is providing forecasts of lime and limestone consumption for SO₂ removal and also sorbent consumption for SO₃. Displays from this database were provided attendees and are available in the recording.

Substantial information on reagents was added to the FGD Decision Tree in preparation for the Hot Topic Hour. Strangely not many papers have been presented in recent years. As a result we have scanned and posted a number of papers from the early to mid 1990s. Here are the links.

Continuing Decision Process For: Limestone

A study by Illinois State shows that limestone reactivity is variable. Calcite content is one aspect but limestone constituents, including fossil fragments, microcrystalline calcite matrix, sparry calcite content, and non-skeletal grains are also important. Certain compounds such as magnesium carbonate, iron oxides, and other trace and major elements may increase or decrease the capture efficiency.

http://www.icci.org/04final/03-1lasemifgd.pdf

Comparison of various limestones and performance in FGD systems.

http://www.mcilvainecompany.com/FGD_Decision_Tree/subscriber/Tree/DescriptionTextLinks/comparison_on_various_limestones.htm
 

Several papers from the mid 1990s provide analysis of limestone for circulating fluid bed boilers.

http://www.mcilvainecompany.com/FGD_Decision_Tree/subscriber/Tree/DescriptionTextLinks/analysis_of_limestone_for_circul.htm
 

subscriber/Tree/DescriptionTextLinks/Limestone in FGD.pdf

subscriber/Tree/DescriptionTextLinks/Limestone Requirements.pdf

Bill Ellison of Ellison Consultants led off the meeting with a discussion of lime requirements for circulating dry scrubbers (CDS). He also mentioned that an announcement would be made soon on the purchase of a 500 MW single module CDS scrubber.

Mike Schantz of Chemical Lime provided an overview of the national and even international activities of his company and its parent L’hoist. With its new acquisition Chemical Lime can now supply more ground limestone. It is already a major supplier of lime and limestone for FGD. Pictures of Sorbacal compared to conventional lime show a product with much different structure and porosity. This hydrated lime product has been widely used in Europe for higher degrees of SO₃, SO₂, and other pollutant removal.

The use of lime for forced oxidation gypsum at the Huntington plant in Utah is a significant milestone in showing that there is a lower cost option than limestone even if you want to make gypsum.

If you want to go directly to his visual presentation (instead of the recording) it is in the Decision Tree at the following branch

Greg Andersen and Eric Van Rens of Mississippi Lime provided an overview of the company’s activities in supply of calcium in all forms including limestone, hydrated lime, and quick lime in various sizes and purity.

Advantages of dry grinding were also enumerated. One advantage is the ability to provide storage. Wet grinding with ball mills has to be instantaneous. Dry grinding also results in lower capital and operating and maintenance costs.

Hydrated lime is very effective for SO₃ removal. It is a robust material with good handling characteristics and is available in the needed quantities. Their presentation is displayed at

Putt Wetherbee of Florida Rock only briefly referenced the merger with Vulcan which makes for a very large player in the calcium reagent supply field. He advised attendees that finding the optimum limestone supply was not a matter to be taken lightly.

Much more limestone will be needed in the future. But there are problems with production capacity, reserve capacity, and transportation. So planning for limestone purchases should be years ahead of the actual need. Utilities need to work in tandem with the rock suppliers to ensure development of the needed reserves.

Regional grinding of limestone makes lots of sense. It reduces capital costs and simplifies operations for the power plant owners. The problem is that without a regional supply utilities will keep buying their own grinding plants. Without a market no regional grinding facilities will be built. So somewhere along the way there needs to be some coordination.

That leads to some comments received after the session and shown in the following article.  To view the Florida Rock presentation click on

Bob Sommerlad of Loesche had some provocative thoughts. Here is what he emailed us.

 “Super Hot Topic Session!  From my perspective re: dry vs. wet limestone milling, we heard different views; summaries of which are as follow:

• Chemical Lime -- It depends; driven by system suppliers.
• Mississippi Lime -- Go dry!
• Florida Rock -- Go dry!
• Unknown (to me) commentator -- the following utilities are advocating dry as follows:

• TVA -- Issuing RFPs for dry for Kingston and Bull Run
• AEP -- leaning toward dry
• First Energy -- leaning toward dry
• Georgia Power -- ordered dry 

(Editor’s note: We have not confirmed any of the above. However this is an accurate listing of the points made. It is what the legal profession calls “hearsay evidence.”)

Based on the above it seems to me that the people with the most experience in milling calcium products are advocating dry milling. The A/Es appear to be advocating wet because that is the way it's always been done and by the way, make sure you install a redundant wet mill. The systems suppliers, especially the boiler manufacturers who make dry mills, seem to be using wet mills, perhaps because the A/Es specify same.

I think your Lime and Limestone "Hot Topics" uncovered an interesting future debate -- Dry Versus Wet Milling for FGD.  I suggest you invite the System Suppliers (B&W, Babcock Power, Marsulex, etc.), the A/Es (WGI, S&L, B&V, Burns & McDonnell, Shaw, etc.) and the Limestone-Lime suppliers (Chemical Lime, Mississippi Lime, Florida Rock, etc.), and the utilities (Georgia Power, TVA, AEP, First Energy, Duke, etc.) for a "Hot Topic" discussion.”