The US Environmental Protection Agency (EPA) is proposing amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for taconite iron ore processing plants that include new emission standards for mercury as well as revising the existing emission standards for hydrogen chloride and hydrogen fluoride.

Taaconite is a low-grade iron ore containing 20- to 25-percent iron; 99% of the crude iron ore produced in the United States is taconite, according to the US EPA.

Taconite iron ore processing plants separate and concentrate iron ore from taconite to produce taconite pellets, which are 60- to 65-percent iron. Taconite iron ore processing includes crushing and handling of the crude ore, indurating (firing to strengthen and stabilize the pellets), and finished pellet handling.

The Taconite Iron Ore Processing NESHAP applies to each new or existing ore crushing and handling operation, ore dryer, pellet indurating furnace, and finished pellet handling operation at a taconite iron ore processing plant that is (or is part of) a major source of HAP emissions.

There are currently eight taconite iron ore processing plants in the United States: six facilities are located in Minnesota and two are located in Michigan.

Indurating furnaces represent the most significant source of HAP emissions from the Taconite Iron Ore Processing source category. The indurating furnaces are responsible for approximately 99% of total HAP emissions from this source category.

Indurating furnaces emit acid gases, mercury and other metal HAP (e.g., arsenic, chromium, nickel) that are present in the taconite ore and sometimes in the fuel (such as coal) fed into the furnaces, and small amounts of organic HAP (e.g., formaldehyde). The acid gases include HCl and HF and are formed when chlorine and fluorine compounds are released from the raw materials during the indurating process and combine with moisture in the exhaust stream.

Emissions data collected from the exhaust stacks of existing taconite indurating furnaces indicate that mercury (Hg) is emitted; these mercury emissions are not regulated under the existing taconite iron ore processing NESHAP. Therefore, the EPA is proposing new standards that reflect maximum achievable control technology (MACT) for mercury emitted from taconite indurating furnaces.