Claims
- 1. A system for controlling emissions created by spraying a heated liquid paving composition from at least one nozzle of a moving vehicle onto a pavement surface, comprising:
- a vacuum hood positionable adjacent said at least one nozzle and above said pavement surface, said vacuum hood having at least one inlet and at least one outlet;
- a mechanism communicating with said at least one outlet to create a partial vacuum within the vacuum hood and draw air containing said emissions through said at least one inlet; and
- apparatus for receiving said air and extracting said emissions therefrom.
- 2. The system of claim 1 wherein:
- said mechanism comprises a fan.
- 3. The system of claim 1 wherein:
- the vacuum hood has a forward end and a rearward end; and
- said at least one inlet comprises a primary opening adjacent said forward end.
- 4. The system of claim 3 wherein:
- the vacuum hood has a flap adjacent said at least one inlet.
- 5. The system of claim 4 wherein:
- said flap is flexible and extends downwardly from the underside of the vacuum hood.
- 6. The system of claim 1 wherein:
- the vacuum hood extends transversely across the vehicle.
- 7. The system of claim 1 wherein:
- said apparatus for receiving air and extracting emissions therefrom comprises a filter structure.
- 8. The system of claim 7 wherein:
- said filter structure has at least one preliminary stage to extract relatively large particulate matter and at least one subsequent stage for extracting extremely fine particulate emissions.
- 9. The system of claim 1 for use in controlling emissions created by spraying a heated asphalt-rubber composition.
- 10. The system of claim 1 for use in controlling emissions created by spraying heated pavement grade oil containing a synthetic polymer.
- 11. The system of claim 10 wherein:
- said filter means comprises at least one preliminary stage to extract relatively large particulate matter and at least one subsequent stage for extracting extremely fine particulate emissions.
- 12. A method for controlling emissions created by spraying a heated liquid paving composition from at least one nozzle of a moving vehicle onto a pavement surface, comprising:
- providing a vacuum hood adjacent said at least one nozzle and above the pavement surface, the vacuum hood having at least one inlet and at least one outlet;
- spraying the heated liquid paving composition from said at least one nozzle as said vehicle moves;
- creating a partial vacuum within the vacuum hood to draw air containing emissions from the spraying operation through said at least one inlet;
- extracting said emissions from said air; and
- exhausting to the atmosphere said air from which said emissions have been extracted.
SUMMARY OF THE INVENTION
This application is a continuation of Application Ser. No. 08/000,748 filed Jan. 5, 1993, now U.S. Pat. No. 5,297,893.
In recent years, asphalt paving oil mixed with recycled rubber has emerged as a preferred paving material because of its superior physical properties and its potential as a solution to a major environmental problem: the disposal of scrap automobile and truck tires. A popular process for the use of such material is described in U.S. Pat. No. 3,891,585 and U.S. Pat. No. 4,069,182, both issued to Charles H. McDonald, the specifications of which are hereby incorporated by reference. According to a current form of this process, recycled crumb rubber obtained from scrap automobile tires is mixed with paving grade liquid asphalt (usually AR 4000) at a temperature of approximately 400 degrees F. (199 degrees C.) to form a jellied composition of "asphalt-rubber" which is sprayed at 385-400 degrees F. (189-199 degrees C.) in quantities of approximately 0.55-0.65 gallons per square yard (2.5-2.9 liters per square meter) of pavement or used as a binder in hot mix asphalt (HMA).
A thick cloud of visible emissions is released into the air when hot asphalt-rubber is sprayed onto a pavement surface. These emissions result from the hot liquid coming into contact with the surrounding air and then contacting the pavement itself, both of which are much cooler than the liquid. The emissions produced in applying asphalt-rubber are much greater than those produced by spraying most other materials because non-rubberized materials are typically applied in smaller quantities and/or at lower temperatures. In contrast to asphalt-rubber, a tack coat of conventional paving grade oil is applied in quantities of only approximately 0.05-0.10 gallons per square yard (0.2-0.4 liters per square meter), and conventional prime coat oil is applied at temperatures of only approximately 150-180 degrees F. (63-82 degrees C.).
Although emissions from the spraying of asphalt-rubber compositions have not been shown to be harmful medically, they do present an "opacity" problem at the point of application due to more stringent air quality regulations adopted in recent years. This was investigated by Roberts Environmental Services of West Covina, California and is discussed in a document entitled "The Asphalt-Rubber Producers. Group Ambient Air Sampling Program" (Jun. 1989), which reports opacity readings of up to 90% at locations downwind of mobile asphalt-rubber operations.
Prior efforts to reduce emissions in the asphalt industry have focussed on devices for collecting emissions from substantially stationary sources, such as delivery trucks as they are being filled with hot mix asphalt (HMA), or on complex machines which mill, rejuvenate and reapply asphalt pavement in a slow, relatively enclosed process known as asphalt heater scarification/recycling. These systems have not been proposed for mobile spraying operations, however, and are not suitable for liquid asphalt-rubber applications.
Therefore, it is desirable in many instances to reduce or eliminate emissions from a mobile asphalt-rubber application process.
A large proportion of the emissions produced by spraying heated liquids onto a pavement surface are collected efficiently and inexpensively by the system and method of the present invention without disrupting the continuity of the spraying process or affecting the quality of the treated surface. This is accomplished with a vacuum hood mounted to a distributor vehicle behind a row of nozzles through which the liquid is sprayed. A fan or other mechanism draws emissions-containing air away from the area of the nozzles and passes it through a filter or other suitable apparatus where the emissions are removed. The efficiency of the collection process is enhanced in a preferred embodiment of the invention by placing the hood directly behind the spray nozzles at a location above and out of contact with the pavement surface, and providing the hood with a large primary opening adjacent its forward end. A secondary opening, which may be a slot, may then be provided a suitable distance behind the primary opening to collect secondary emissions produced as the liquid cools. In a further embodiment, a flap is provided behind these openings to maximize the collection of visible emissions directly behind the nozzles.
The structure of the filter is specifically adapted to extract emissions of the type created by hot-spray applied materials, such as asphalt-rubber, in a high volume system. It preferably has an extremely fine stage preceded by at least one coarser stage. The coarser stage extracts relatively large particulate matter from the air stream and prevents it from clogging the final stage.
Accordingly, a system and a method for controlling emissions created-by spraying liquid from at least one nozzle of a moving vehicle onto a pavement surface involve: a vacuum hood mountable to the vehicle at a location adjacent the nozzle and having at least one inlet and at least one outlet; a fan or older mechanism communicating with the outlet to create a partial vacuum within the vacuum hood and draw air containing emissions through the inlet; and apparatus for receiving the air and extracting emissions therefrom. In a preferred embodiment, the vacuum hood is located behind the nozzle and is adjustable in a vertical direction. It may also have a primary opening adjacent its forward end and a transverse auxiliary opening in the form of a slot behind the primary opening. In a further embodiment, the vacuum hood has a flap extending downwardly from its underside at a location behind its inputs and transversely across the width of the vehicle. The vacuum may also have a main portion extending substantially across the vehicle and at least one side portion movable relative to the main portion between a stowed position in which it is disposed alongside the vehicle and an operating position in which it, extends outwardly from the vehicle in line with the main portion.
US Referenced Citations (1)
| Number |
Name |
Date |
Kind |
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5161910 |
O'Konek |
Nov 1992 |
|
Continuations (1)
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Number |
Date |
Country |
| Parent |
748 |
Jan 1993 |
|
Patent Grant
5342143
