Sorbent Traps are One Way to Measure Mercury in Cement Plants

Clean Air Engineering points out that sorbent traps would be one solution for mercury measurement. In their blog they write, “Generally, mercury emissions from cement kilns reflect the amounts of mercury in the feedstock and fuel inputs of the kilns." The EPA assumes that nearly all the mercury entering a kiln eventually leaves as a stack emission. Usually, up to 80 percent of the mercury emissions result from trace contaminants of mercury present in the limestone, which typically comes from a quarry located adjacent to the plant. Mercury is also found as a trace contaminant in the other inputs to the kiln such as silica, alumina, and iron, as well as the coal and petroleum coke used to fuel the kilns.

Since the mercury content of the feed and fuels is believed to vary significantly from day-to-day, cement kilns do not emit mercury uniformly. This variation is compounded in modern preheater and preheater/precalciner kilns that have in-line raw mills. Consequently, short term emission tests would not be expected to provide a good indication of long term mercury emissions from cement kilns. Therefore, the proposed rule will require plants to install either instrument based or sorbent trap based mercury monitoring systems that meet either the requirements of PS-12A or PS-12B. These performance specifications are being added into 40 CFR 60, Appendix B as part of the proposed rule changes (they had been removed after CAMR was vacated.

The EPA states that they “see no technical basis to say that [mercury CEMS or sorbent trap monitoring systems] will not work as well on a cement kiln as they do on a utility boiler. In addition, we are aware that there are 34 cement kilns that have operating continuous mercury monitors in Germany.”

We'll see if the rest of the industry agrees. The proposed rule is currently in the midst of a 60-day comment period that expires on or about June 20. After that, we’ll have to see what, if any changes the EPA makes before publishing the final rule. Stay tuned”…