Radiant energy – Invisible radiant energy responsive electric signalling – With means to inspect passive solid objects
Reexamination Certificate
2001-05-24
2003-08-05
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
With means to inspect passive solid objects
C250S359100, C250S360100, C250S269600, C250S370050, C250S390040, C250S390050
Reexamination Certificate
active
06603122
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to an apparatus and method to detect the identity and concentration of substances in recyclable materials.
BACKGROUND
The detection of various substances such as water, butane from butane lighters, heavy metals and fertilizers in bulk volumes to be recycled, such as sows, has significant safety and economic significance. Sows are rectangular blocks of scrap aluminum weighing about 1,500-lb. each. Sows and scrap bales are commonly assembled in the aluminum recycling industry, sows being normally formed from a plurality of bales or refined metals. The presence of such substances even in relatively low concentrations can result in violent explosions when the bulk volumes to be recycled are loaded into melting furnaces during a typical recycling process. For example, if the water content exceeds a certain level or if significant levels of oxidizers are present, such as can be provided by butane from butane lighters and ammonium nitrate from fertilizers, catastrophic explosions can result.
Current empirically-derived practices for detecting such substances involve preheating sows for extended periods of time to evaporate an unknown quantities of water and other substances contained within the sow. For example, a typical preheating step can be performed for 6 hours at 700° F. This practice is time-consuming, energy intensive and dependent on closely following stringent operational guidelines derived from empirical experience. The amount of energy consumed for preheating aluminum sows alone is approximately equal to the amount of energy it takes to melt the aluminum sows. Furthermore, investments in and maintenance of preheat furnaces are required to support the moisture evaporation step used in conventional aluminum recycling processes.
Because the moisture level is not measured in conventional aluminum recycling, a preheating step is generally required to remove moisture, whether the moisture level entrapped in the so-called shrinkage cavities of sows is above or below a safe level. This results in the performance of a preheating step in instances when the preheating step may be unnecessary. Preheating practices followed are conservative and result in significant economic costs. Typical shrinkage cavities in 1,500-lb sows can accumulate volumes of water, from sources such as rainfall, in amounts typically from approximately 0.25 to 1.25 gallons (about 1 to 4 liters) per sow.
The existence of contaminating substances, such as lead, in scrap bales can also completely void the quality of the finished product. Accordingly, it is also important to detect and remove these substances, prior to bales being charged into furnaces. Current practice involves manually searching through selected bales to identify certain contaminating substances prior to charging furnaces.
X-rays are generally not useful as applied to contamination detection in bulk volumes, and accordingly are not used for this purpose. X-rays can be used to produce sharp images as well as density-dependant shading of interrogated objects. However, X-rays primarily provide information relating to the bulk properties of an object, and cannot provide substance-specific information. As a result, the application of an X-ray system to a sow to detect moisture cannot determine whether a density difference detected is due to an empty cavity, a cavity filled with water, some potentially explosive compound, or some other cause. Ultrasound techniques, which can be useful when used for crack or flaw detection, cannot be used for contaminant detection because ultrasound typically generates considerable scattering-induced noise and is also incapable of identifying specific substances.
Methods are used between the melt and casting steps to detect and remove hydrogen and unwanted inclusions, the inclusions being mainly oxides of elements such as magnesium and aluminum. The current practice typically used for detecting hydrogen involves use of the so-called Alscan probe, which is based on monitoring the thermal conductivity of a “sipped” sample drawn from a bulk material. For inclusion detection, a Limca probe is utilized which also uses small samples and detects inclusions via, monitoring electrical resistance changes from sipped samples. These techniques are both intrusive techniques which monitor small samples, require expensive equipment and cannot identify specific substances. Thus, current techniques do not provide the ability to assess bulk volumes of material, cannot detect contaminants with specificity, and cannot locate the position of contaminants within a given bulk volume.
A neutron detection system for detection of contaminants contained within a bulk material during recycling includes at least one neutron generator for neutron bombardment of a bulk material. At least one gamma ray detector is provided for detection of gamma rays emitted by contaminants within the bulk material responsive to the neutron bombardment. A structure for analyzing gamma ray data is communicably connected to the gamma ray detector, the structure for analyzing gamma ray data adapted to determine the presence of at least one contaminant in the bulk material.
The system can include a neutron reflector for reflecting at least a portion of neutrons which pass through the bulk material back into the bulk material, the neutron reflector disposed on an end of the bulk material distal to an end of the bulk material which receives an initially incident neutron beam emitted from the neutron generator. The neutron reflector can be made from Be, beryllium oxide and graphite. The system can include a structure for scanning a neutron beam emitted from the neutron generator across a portion of the bulk material to identify portions of the bulk material having contaminants. Discrete locations having contaminants can be identified with a 2-dimensional, or more preferably, with a 3-dimensional description.
The system can include a structure for removing detected contaminants from the bulk material. The structure for removing contaminants can be adapted to direct an energetic beam at discrete locations of the bulk material found to have contaminants. The structure for removing contaminants can be selected from a microwave source, an infrared and an acoustical source. Preferably, the structure for removing contaminants is an ultrasonic source, provided the contaminants are fluid contaminants.
The system can comprise at least two neutron generators, the neutron generators emitting at least two distinct neutron energy spectrums. The first neutron generator can emit neutrons having average energies of least 6 MeV and a second neutron generator can emit neutrons having average energies less than the first neutron generator. The first neutron generator can be a deuterium-tritium (D-T) generator and the second neutron generator can be a deuterium—deuterium (D—D) generator or an isotopic generator.
The bulk material for recycling can be scrap aluminum. The aluminum can be in the form of at least one sow. The structure for analyzing gamma ray data can be adapted to determine the identity, concentration and locations of contaminants in the bulk material.
A neutron detection system includes at least one neutron generator for neutron bombardment of a material, at least one gamma ray detector for detection of gamma rays emitted by the material responsive to the neutron bombardment, and a neutron reflector for reflecting at least a portion of the neutrons which pass through the material back into the material. The neutron reflector is disposed on an end of the material distal to an end of the material which receives an initially incident neutron beam emitted from the neutron generator. A structure for analyzing gamma ray data is communicably connected to the gamma ray detector, the structure for analyzing gamma ray data adapted to determine the presence of at least one substance in the material.
In another embodiment of the invention, a neutron detection system includes at least two neutron generators, the neutron generators emitt
Akerman & Senterfitt
Hannaher Constantine
Moran Timothy
UT-Battelle LLC
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