In our single-drum counterflow system, aggregate and superheated air move in opposite directions. Aggregate enters on the feed-entry end of the drum and travels toward the burner as it's dried. At the burner nose, the dried material passes behind an isolation ring where liquid asphalt. All materials are mixed in the final drum section, and then are discharged and conveyed to the storage silo. Counterflow technology is productive, efficient and environment friendly.
In counterflow drum the liquid asphalt cement, virgin aggregate, and RAP are mixed in a zone removed from the exhaust gas stream, counterflow drum mix plants will likely have organic emissions (gaseous and liquid aerosol) that are lower than parallel flow drum mix plants. However, the available data are insufficient to discern any differences in emissions that result from differences in the two processes. A counterflow drum mix plant can normally process RAP at ratios up to 50 percent with little or no observed effect upon emissions.
