HOT TOPIC HOUR

Six Mercury Decision Guides discussed in the Hot Topic Hour February 11

Mercury removal requirements are relatively new except for waste incineration. There is great progress in providing cost-effective solutions in six different industries. McIlvaine has a Mercury Decision Guide in each industry. The guides were displayed and used in the discussions yesterday. Following is a summary.

E = experience, P = potential

H = high, M = medium, L = low, U = unknown

Ionic liquids are promising three times the capability of carbon beds for removing mercury from natural gas. The question is whether they can also be used for exhaust gas.

There were a number of contributions from participants. Michael Pealer of Calgon Carbon sees a steady and growing market for activated carbon in U.S. power plants with smaller markets in waste-to-energy. Cement is a market with some growth potential. With PRB coal it is now possible to meet the mercury requirements with as little as 2 lbs/MMacf of the new carbons. This is in contrast to requirements of 10 pounds or more with older carbons. Whereas activated carbon could not even meet the limits with high mercury and use of an ESP, now the limit can be achieved at, in some cases, 20 lbs/MMacf.

Scott Miller and Matt McCune of Montrose say that the sorbent trap is being more widely selected for compliance measurement and is also cost-effective. Relative to the question of whether sorbent traps report higher mercury levels than do CEMs, the answer is that they are generally within 20 percent when side by side measurements are made. McIlvaine has reported findings of higher mercury readings for sorbent traps due to particulate mercury. This is more likely to occur when the system has an ESP rather than a fabric filter.

Geetha Srinivasan of Queens University in Belfast, described the research which led to the ionic liquid coating of packings for mercury removal from natural gas. The product is being offered by Clariant which reports that experience shows 3-to-4 times the mercury capture per unit volume than achieved with carbon pellets. The technology would appear to also be suitable for coal-fired boilers.

Charlie Alack of Semi-Bulk Systems, explained two options for conveying storage and injection of PAC into the scrubber. The carbon in the scrubber slurry captures the mercury. A hydrocyclone then separates the spent carbon.

Jeff Kolde of W. L. Gore, reviewed the experience with the Gore absorption module for mercury removal from coal-fired boilers and sludge incinerators. The technology is very cost- effective for removal of modest quantities of mercury. It therefore works well after a wet scrubber which captures some of the mercury. Twenty-three systems are now installed in coal- fired boilers and sewage sludge incinerators.

For new sewage sludge incinerators that need 99 percent removal, the carbon bed may still be the best approach. The question posed was whether the use of bromine chemicals in the sewage sludge venturi scrubber could provide enough capture to make the tail end Gore module cost- effective. The answer was that this combination has not yet been pursued.

 The Decision Guides are continually updated. They are found in the following publications:

The Decision Guides are also found in the N056 Mercury Air Reduction Market.

They appear in N032 Industrial Air Plants and Projects.  (This service also includes the Fabric Filter, Scrubber, and Precipitator Knowledge Systems. The Decision Guides appear in the Knowledge System as indicated above