Glossary of Terms

Acid plant

A smelter’s acid plant collects the sulfur dioxide from the sinter plant and converts it into sulfuric acid, which is sold to fertilizer manufacturers.

Alloy

A mixture of metals.

Baghouse

A facility at a smelter used to capture dust from smelting and refining operations. The dust is recycled back into the smelting process.

Finished grade lead

Material that has been smelted and refined for delivery to customers. Doe Run’s lead is 99.99 percent pure.

Lead concentrate

After the raw ore is screened, crushed and ground at the mills, it is chemically treated in a flotation process to separate metal-containing mineral from the waste rock (tailings) and from each other. The resulting material is called lead concentrate.

Lead milling

The process that extracts most, but not all, of the desirable mineral from the lead ore.

NAAQS

National Ambient Air Quality Standards; air quality standards set by the Environmental Protection Agency (EPA). The National Ambient Air Quality Standard for lead is 1.5 µg/m³ of air (averaged over a three-month period).

NOV

Notice of Order Violation; action taken by the state when it believes that one or more of its orders has not been complied with.

Polymetallic ore

Ore that contains lead, zinc, copper, silver and other metals. Lead concentrates from Doe Run mining operations are transported to the Herculaneum smelter complex for treatment, while non-lead concentrates are sold.

Processed lead

Finished grade lead that is sold to customers.

Sinter

The two- to four-inch chunks of solid material that result from roasting the sulfur away from the lead concentrate. This material becomes feed to the blast furnace.

SIP

State Implementation Plan; a plan prepared by state government and approved by the EPA outlining how a company or community plans to reduce emissions during a specific time period (often three years). The goal is to get the concentration of certain materials measured in the air within EPA standards.

Slag

A byproduct of smelting. Slag is a glassy, sand-like material containing small amounts of lead, zinc, copper and other materials.

Tailings

Tailings and chat are leftover rock created from two different milling processes. Tailings and chat both contain a high level of limestone. Chat is coarser material, while tailings have the consistency of fine sand. Tailings have been used as agricultural lime.

TRI

Toxic Release Inventory; a list of materials maintained and updated annually by manufacturers and filed with the EPA as required under Title III of the Superfund Amendments and Reauthorization Act (SARA) of 1986.