Drum mix asphalt plant with fiber filter dust collector

Drum asphalt plant with reduced airborne emission, comprising in combination:

• means providing a heated combined drying and mixing drum which is operative to receive and agitate a quantity of aggregate material, so as to produce airborne particulate material within the drum;
• means for supplying liquid asphalt material to said drying and mixing drum so as to apply said asphalt material to the aggregate material within said drum, whereby hydrocarbon smoke particles are formed in the drum as a consequence of exposing the asphalt material to the heat within the drum,
• exhaust means in communication with said drying and mixing drum and operative to withdraw air including the airborne particulate matter and hydrocarbon smoke particles from said drum;
• air filtering means connected to receive said withdrawn air and having at least one porous fiber filter medium through which the withdrawn air is passed, so as to form on said filter member a dust cake of said particulate matter which absorbs said hydrocarbon smoke particles;
• means operative to remove said dust cake from said filter medium;
• and
• means operative to receive said removed dust cake, which comprises separated nonairborne particulate matter and absorbed hydrocarbon smoke particles, and to return said dust cake to said drying and mixing drum by mixing the dust cake with said liquid asphalt material that is supplied to said drum, so that the dust cake forms part of the mixture of aggregate and asphalt material within the drum without again becoming airborne.

Asphalt plant apparatus, comprising in combination:

• a combined drying and mixing drum supported for rotation on a longitudinal axis;
• burner means disposed at one end of said drying and mixing drum for heating the contents of the drying and mixing drum to an elevated temperature;
• means for admitting aggregate material to said one end of said drying and mixing drum so that the aggregate material is heated by said burner means and agitated by rotation of the drying and mixing drum;
• means for supplying liquid asphalt material to said drying and mixing drum at a location intermediate the ends thereof so as to apply said liquid asphalt to said aggregate material within the drying and mixing drum;
• exhaust means in communication with said drying and mixing drum and operative to withdraw air and airborne particulate matter from the drying and mixing drum;
• fiber filter collector means disposed to receive said air and airborne particulate matter withdrawn from said drying and mixing drum and operative to filter said particulate matter from said air, so that the separated particulate matter is no longer airborne;
• and
• means operative to receive said separated nonairborne particulate matter and to return said separated nonairborne particulate matter to said drying and mixing drum by mixing the separated nonairborne particulate matter with said liquid asphalt material that is supplied to the drying and mixing drum so that the separated nonairborne particulate matter is coated with asphalt and forms part of the mixture of aggregate and asphalt material within the drying and mixing drum without again becoming airborne within the drying and mixing drum.

Asphalt plant apparatus for the continuous preparation of asphalt aggregate mix, comprising:

• a heated mixing drum which is operative to agitate an aggregate material passing through the mixing drum, so as to produce airborne particulate material within the mixing drum;
• means operative to withdraw air and said airborne particulate matter from said mixing drum;
• means operative to separate said particulate matter from said withdrawn air by passing the withdrawn air through a porous dry filter medium;
• and
• means operative to receive said separated particulate matter and to return said separated particulate matter to said mixing drum by mixing the separated particulate matter with liquid asphalt that is supplied to the mixing drum, so that the separated particulate matter is coated with asphalt and cannot again become airborne within the mixing drum.

Asphalt plant apparatus for the continuous preparation of asphalt aggregate mix while reducing the emission of dust and smoke to the ambient atmosphere, comprising:

• a mixing drum which is operative to agitate an aggregate material passing through the mixing drum, so as to produce airborne particulate material within the mixing drum;
• heating means operatively associated with said mixing drum to heat the interior of the mixing drum;
• means in said mixing drum to supply liquid asphalt to said aggregate material at a location within the mixing drum which is at a temperature below the flash point of said asphalt, so as to minimize the production of smoke caused by heating of the liquid asphalt within the mixing drum;
• means operative to withdraw air and said airborne particulate matter from said mixing drum;
• means separate from said mixing drum and operative to separate said particulate matter from said withdrawn air by passing the withdrawn air through a porous dry filter medium;
• and
• means operative to return said separated particulate matter to said mixing drum by mixing the separated particulate matter with said liquid asphalt that is supplied to the mixing drum, so that the separated particulate matter is coated with asphalt and cannot again become airborne within the mixing drum.