COPPER DIVISION: Intermittent Control System

Horne’s atmospheric discharges are much less than they used to be, but whether they will exceed the regulated limits in ground level air depends on the local weather conditions. Over 25 years, Horne has perfected its self-imposed weather monitoring system, called the Intermittent Control System (ICS), so it can run the smelter at maximum efficiency while protecting ambient air quality.

There are seven air-sampling stations that record SO2 concentrations, as well as an automated weather station staffed by meteorologists and technicians. Instruments measure the daily convective period, mechanical and thermal turbulence, wind speed and direction, and the temperature profile up to 500 metres above ground level.

If there is a potentially critical situation, the computer notifies a staff member who decides whether to shut down part or all of the smelter. “In a typical year we have to shut down about 10% of our production capacity to keep the SO2 emissions below the norms,” says Peter Godbehere, superintendent of business development, “We have had no more than one to three exceedances [>0.5 ppm SO2 hourly] per annum since the acid plant opened.”