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US 11,828,028 B1Granted
Method for processing up to 100% RAP in an asphalt plant
AssigneeStansteel Corporation
InventorsLeonard A. Loesch, Steven W. Elam
Life of this patent
Estimating the term…
Abstract
A method for producing asphalt using a high percentage of RAP (recycled asphalt pavement) in the total aggregate raw material. A counterflow rotary drum dryer is used to dry the raw material. The extent of the burner flame in the dryer is limited such that the RAP does not come into direct contact with the flame. The hot gases leaving the dryer pass to a wet scrubber.
Claims20
A method for producing asphalt, comprising the steps of:
- heating raw aggregate material in a counterflow drum dryer that rotates about a longitudinal axis, wherein the raw aggregate material is greater than 50% RAP by weight and flows through said counterflow drum dryer in a downstream direction, from an inlet end to an outlet end, with said heated raw aggregate material exiting said counterflow drum dryer through an outlet opening;
- wherein said counterflow drum dryer includes veiling flights from adjacent said inlet end toward said outlet end, wherein said veiling flights cause said raw aggregate material to be picked up and dropped as said counterflow drum dryer rotates, to create a veiling zone, and wherein said veiling flights terminate upstream of said outlet opening to define a non-veiling zone extending upstream of said outlet opening for at least two feet;
- providing a combustion chamber and a burner, with said combustion chamber having an outlet end adjacent to the outlet end of the counterflow drum dryer, and said burner generating a flame directed in an upstream direction toward the outlet end of the counterflow drum dryer, and controlling the flame so that the flame terminates short of the outlet end of the combustion chamber and terminates short of the outlet end of the counterflow drum dryer and avoids contacting the raw aggregate material, wherein said burner generates a hot air stream flowing upstream through the counterflow drum dryer, said hot air stream picking up moisture, volatile gases and dust as the hot air stream flows through the counterflow drum dryer;
- said hot air stream then exiting the counterflow drum dryer and flowing to a wet scrubber which sprays water over the hot air stream, cooling the hot air stream and condensing volatile gases.
1 more element
An asphalt production plant for producing asphalt from Reclaimed Asphalt Pavement (RAP), the asphalt production plant comprising:
- a bin array storing raw aggregate material and comprising at least one bin storing RAP material;
- a conveyer for transporting the raw aggregate material including RAP material;
- a Counterflow Drum Dryer (CDD) having an inlet end adapted to receive aggregate material greater than 50% RAP by weight from the conveyor, the CDD further comprising an outlet end defining an outlet opening adapted to discharge treated aggregate material from the CDD, the CDD further comprising a set of veiling flights disposed from adjacent said inlet end toward the CDD outlet end;
- wherein the CDD rotates about a longitudinal axis and causes the raw aggregate material to flow through the CDD in a downstream direction, from the inlet end to the outlet end of the CDD;
- wherein the set of veiling flights define a veiling zone in which the raw aggregate material is picked up and dropped as the CDD rotates, and wherein the set of veiling flights terminate upstream of the CDD outlet opening to define a non-veiling zone extending upstream of the CDD outlet opening for at least two feet;
- a combustion chamber (CC) having a combustion chamber outlet end operatively coupled with the CDD outlet end;
- a burner configured to generate a flame, project the flame in the combustion chamber, and project the flame in an upstream direction toward the CDD outlet end, the burner and combustion chamber being configured so that the generated and projected flame terminates short of both the CC outlet end and the CDD outlet end to ensure the flame does not directly contact raw aggregate material in the counterflow drum dryer;
- wherein the burner generates a hot air stream exiting the combustion chamber and flowing upstream through the counterflow drum dryer and heating the raw aggregate material as it travels downstream and exits the counterflow drum dryer through the CDD outlet opening;
- wherein, the hot air stream picks up moisture, volatile gases and dust as the hot air stream flows through and exits the counterflow drum dryer;
- and
- a wet scrubber configured to receive and spray water over the hot air stream exiting the counterflow drum dryer, thereby cooling the hot air stream and condensing volatile gases.
8 more elements
Dependencies are inferred from the claim text.