Agitating – Mortar mixer type – Methods
Patent
1986-07-11
1987-11-10
Coe, Philip R.
Agitating
Mortar mixer type
Methods
366 14, 366 25, 432111, B28C 508, B28C 546
Patent
active
047054042
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for processing remixed asphalt materials and to an apparatus for implementing the method.
2. Description for the Background
In known methods for reprocessing used asphalt, a distinction must be made as to whether the processing systems operate with a drying drum operated with counterflow or a drum mixer operated with parallel flow. Drying drums operated with counterflow exhibit better efficiency than the parallel-flow methods with respect to the exchange of heat between the flame and the material to be heated. On the other hand, difficulties arise in the counter flow methods with respect to processing the broken-up used asphalt material.
During this process, hydrocarbons (CH.sub.x) escape from the bitumen in the asphalt, and slight, smoldering combustion produces considerable amounts of carbon monixide (CO). This gas, in spite of an extensive use of filtering devices, escapes into the outside air together with the exhaust gas and produces a considerable pollution of the environment. The legally prescribed minimum emission quantities are generally far exceeded.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method and an apparatus for implementing a method of the above-mentioned type which overcome the above-mentioned drawbacks and assure, in particular, that the manufacturing and reprocessing process can regulate with precision the mixing ratio of used and new components of the material to be processed and the heat balance and the period of dwelling of the material within the system.
DESCRIPTION OF THE INVENTION
This is accomplished in a process of the above-mentioned type by processing, i.e., heating in particular, separately in differently configured drum devices, the portions of used asphalt and new material for the asphalt mixture to be processed or produced wherein the used asphalt component is heated in a drum mixer operated with parallel flow and the new material component to separately heated in a drying drum operated with counterflow. After leaving the respective drum devices, these materials are conducted into at least one further connected mixer where they are further treated with fresh bitumen and filler material possibly being added to the mixer. The exhaust gases of the drum mixer are conducted directly into the drying drum and are there heated further so that the CH.sub.x and CO components contained therein are combusted.
The method according to the invention assures primarily a processing of mixed asphalt favorable to the environment reuses broken-up asphalt. More particularly the used asphalt component which is sensitive to extreme heat is heated to the at least initially maximum possible temperature independently of the new material component in a separate drum device, During this heating process of the used asphalt, the relatively low temperatures of the heating gases cause carbon monoxide (CO) to be released. The CO gas after being transferred to the drum mixer is further heated together with the heating gases developed there and is converted to carbon dioxide (CO.sub.2), and only after this conversion is the gas released to the environment.
Moreover, the above-described process does not require any special conveying or throwing devices within the two drum devices. Rather, generally known conveying devices and conventional drum devices can be employed.
According to the invention, the exhaust gases of the drum mixer are conducted into the interior of the drying drum in the immediate vicinity of the burner flame, via an intake device formed at the frontal face of the drying drum where the burner is disposed.
This type of introduction of the exhaust gases into the interior of the drying drum assures that intimate contact is established with the burner flame, and thus, that the incompletely combusted exhaust gases from the drum mixer are combusted further.
In a further feature according to the invention, the exhaust gases of the drum mixer are positively guided to the burne
REFERENCES:
patent: 4189238 (1980-02-01), Mendenhall
patent: 4387996 (1983-06-01), Mendenhall
patent: 4626198 (1986-12-01), Cohen
Coe Philip R.
Deutsche Asphalt GmbH
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