초록 ▼

An HMA plant has a catalytic reactor which can effectively and reliably reduce VOC and NOx emissions produced during plant operation. The reactor effectiveness is enhanced by exhausting the gas stream from a primary dryer of the plant at a sufficiently high temperature for effective catalytic reacti

An HMA plant has a catalytic reactor which can effectively and reliably reduce VOC and NOx emissions produced during plant operation. The reactor effectiveness is enhanced by exhausting the gas stream from a primary dryer of the plant at a sufficiently high temperature for effective catalytic reaction. Since withdrawal of gases from the dryer at these elevated temperatures necessarily reduces the effectiveness of the dryer, overall plant efficiency is maintained by using the treated gas stream from the catalytic reactor to heat further the aggregate in a secondary dryer, which is preferably a finishing dryer/mixer such as a fixed sleeve dryer drum coater. Poisoning of the catalyst is avoided by removing at least a large portion of the dust in the gas stream via a high efficiency cyclone prior to introducing the gas stream into the catalytic reactor. Ammonia or urea may if desired also be injected into the gas stream prior to its introduction into the catalytic reactor.

대표청구항 ▼

A method comprising: (A) heating and partially drying virgin asphalt aggregate in a primary dryer; (B) removing a gas stream from said primary dryer; then (C) treating said gas stream with a catalyst thereby to reduce VOC and NOx levels in said gas stream; and then (D) further heating and drying sai

A method comprising: (A) heating and partially drying virgin asphalt aggregate in a primary dryer; (B) removing a gas stream from said primary dryer; then (C) treating said gas stream with a catalyst thereby to reduce VOC and NOx levels in said gas stream; and then (D) further heating and drying said virgin aggregate with said treated gas stream in a finishing dryer.