Asphalt recycling

• US 4,540,287 A
• Filed: 12/01/1983
• Issued: 09/10/1985
• Est. Priority Date: 12/02/1982
• Status: Expired due to Fees

• Current Assignee: South African Inventions Development Corporation Administration BLDG Scientia Pretoria Transvaal Province South Africa
• Original Assignee: South African Inventions Development Corp.
• Inventors: Voors, Wilhelm P. H., Servas, Vladimiros
• Primary Examiner(s): JENKINS, ROBERT
• Application Number:
  US06/556,891
• Time in Patent Office: 649 Days
• Field of Search: 366/2, 366/7, 366/22, 366/23, 366/24, 366/25, 366/14, 106/281
• US Class Current: 366/7
• CPC Class Codes: E01C 19/1036 for in-plant recycling or for reprocessing, e.g. adapted to receive and reprocess an addition of salvaged material, adapted to reheat and remix cooled-down batches
• CPC Class Codes: E01C 2019/1095 Mixing containers having a parallel flow drum, i.e. the flow of material is parallel to the gas flow

Abstract

This invention provides a hot-mix asphalt recycling processes for reconstituting and upgrading old road materials. In usual hot-mix plants the asphaltic material is heated by a naked flame. Residual bitument in the asphalt is exposed to the naked flame from the burner, which can seriously damage the bitument and render it largely worthless. In order to reduce wastage, the invention provides for heating of aggregate in a heating zone, and supplying of the heated aggregate, usually cold reclaimed asphalt, and suitable binder material to a substantially flame-free mixing zone. By mixing these constituents in that zone, it is possible to produce a usable hot asphalt pavement mix with reduced asphalt wastage.

Claims

1. A method of recycling asphalt, which comprises heating aggregate in a rotating heating zone by a burner flame, supplying the heated aggregate to and introducing reclaimed asphalt and suitable binder material into a rotating, separately rotatable flame-free mixing zone, and there mixing these constituents to produce a usable hot asphalt pavement mix wherein the heated aggregate and flame-free combustion gases from the heated zone pass through the mixing zone also to heat the reclaimed asphalt.

2. A method according to claim 1, wherein the heating zone is inclined for causing aggregate to pass generally downwardly through the heating zone to be heated and to leave it from a bottom region thereof, and wherein combustion gases for heating the aggregate also flow generally downwardly through the heating zone and are guided downwardly into the mixing zone together with the hot aggregate.

3. A method according to claim 2, wherein the aggregate and combustion gases are made to move downwardly through the mixing zone to heat the materials therein.

4. A plant for recycling asphalt, the plant comprising a heating drum rotatable about an axis and provided with a burner at the upper end of the heating drum for heating aggregate, means for controlling heating of said aggregate by said burner;

and a separately rotatable burnerless mixing drum rotatable about a second axis for recovering heated aggregate from the heating drum and which is positioned at a lower level than the heating drum; and

means for supplying reclaimed asphalt and binder material to said mixing drum for mixing with the heated aggregate from the heating drum, wherein the tilt of the heating drum and mixing zone are independently adjustable at downwardly inclined angles, and there is provided a chute so that aggregate can pass downwardly through the heating drum, fall via the chute into the mixing drum, and then pass downwardly through the mixing drum to mix with reclaimed asphalt and binder material.

5. The plant of claim 4, including means for guiding the combustion gases together with the aggregate from the heating drum to the mixing drum.

6. The plant of claim 5, including an extractor for drawing the combustion gases through the mixing drum.

7. A method of producing a hot asphalt pavement mix using recycled asphalt pavement, comprising the steps of

feeding new aggregate into one end of a rotatable heating drum,

tilting the heating drum so that the axis of rotation of the heating drum is inclined downward from the one end of the heating drum,

rotating the heating drum to feed the aggregate downwardly from the one end of the heating drum to its other end,

heating the aggregate by a burner flame in the heating drum,

dropping the heated aggregate from the other end of the heating drum via a chute into one end of a burnerless rotatable mixing drum which is positioned at a lower level from the heating drum,

also feeding recycle asphalt pavement via a hopper and the chute into one end of the mixing drum,

further feeding a suitable binder material into the mixing drum,

tilting the mixing drum so that the axis of rotation of the mixing drum is inclined downwardly from the one end of the mixing drum,

rotating the mixing drum to mix the heated aggregate, recycle asphalt and binder material and to feed the mixture downwardly from the one end of the mixing drum to its other end,

drawing combustion product gases from the heating drum through the chute and through the mixing drum,

said rotating and tilting of the mixing drum being selected independent of the heating drum to provide suitable mixing and feeding of the heated aggregate, recycle asphalt and binder material through the mixing drum, and

said rotating and tilting of the heating drum being selected independent of the mixing drum to provide adequate retention time of the aggregate in the heating drum to provide suitable heating of the aggregate to produce hot asphalt pavement mix from the other end of the mixing drum.

8. A plant for producing a hot asphalt pavement mix using recycled asphalt pavement, comprising

a rotatable heating drum,

means for feeding new aggregate into one end of the rotatable heating drum,

means for tilting the heating drum so that the axis of rotation of the heating drum is inclined downward from the one end of the heating drum,

means for rotating the heating drum to feed the aggregate downwardly from the one end of the heating drum to its other end,

a burner for producing a flame in the heating drum to heat the aggregate therein,

a burnerless rotatable mixing drum which is positioned at a lower level from the heating drum,

a chute for directing heated aggregate falling from the other end of the heating drum into one end of the mixing drum,

a hopper for feeding recycle asphalt pavement into the chute and into one end of the mixing drum,

means for feeding a suitable binder material into the mixing drum,

means for tilting the mixing drum so that the axis of rotation of the mixing drum is inclined downward from the one end of the mixing drum,

means for rotating the mixing drum to mix the heated aggregate, recycle asphalt and binder material and to feed the mixture downwardly from the one end of the mixing drum to its other end,

means for drawing combustion product gases from the heating drum through the chute and through the mixing drum,

said rotating means and said tilting means for the mixing drum being selected independently of the heating drum to provide suitable mixing and feeding of the heated aggregate, recycle asphalt and binder material through the mixing drum, and

said rotating means for the heating drum being selected independent of the mixing drum to provide adequate retention time of the aggregate in the heating drum to provide suitable heating of the aggregate to produce hot asphalt pavement mix at the other end of the mixing drum.