Plant says new mercury controls installed on kiln stacks; DEQ compliance plan in place

Company representatives updated the community on efforts to reduce mercury emissions from the plant’s kiln operations and described a technology‑focused compliance approach agreed with state regulators.

A company presenter said mercury occurs in phosphate ore and volatilizes in the kiln, entering the kiln gas stream that is routed through environmental controls at the north end of the plant. The presenter traced the company’s work from a pilot test begun about 2014 using an impregnated fabric media developed by W.L. Gore & Associates to capture mercury, through a DEQ compliance agreement, to full‑scale installation on all four kiln gas trains completed in 2024.

Under the state‑level agreement described by the company, DEQ and the company agreed to a technology‑based compliance approach (the presenter called it an application of best available control technology principles for mercury) rather than a single numerical emission limit for stack mercury. The company said the permit includes operational monitoring and demonstration of correct operation rather than direct continuous measurement of mercury in the hot gas stream, which the presenter described as technically difficult.

The presenter described the Gore‑based fabric media as part of a system that ultimately traps and transfers mercury into a wash stream; that wash stream is processed alongside other SO2‑control wastes, dewatered, and placed in the company’s lined landfill at the north end of the site. The presenter said the company has a Title V air permit and manages compliance with DEQ, which holds primacy for the state program.

Company staff said baseline emission discussions with DEQ and EPA had included an earlier numeric year‑limit concept (the presenter cited a historical reference point of roughly 746 pounds per year tied to feed rates), but the current compliance path emphasizes technology deployment and operational monitoring. The presenter described removal efficiency as variable with kiln feed chemistry and operation; operational controls are in place and the company said it will continue working with regulators as federal and state requirements evolve.

Questions from attendees covered monitoring, filter life and disposal, and the scale of company investment; the presenter said some historic control projects were “tens of millions” of dollars and that the company has installed multiple controls over decades. The presenter said the mercury control work is part of a continuing program of environmental controls that the facility has implemented since the 1980s.