Gas separation: processes – With control responsive to sensed condition – Pressure sensed
Reexamination Certificate
1999-12-20
2001-10-09
Smith, Duane S. (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
Pressure sensed
C055S337000, C055S338000, C055S342000, C055S343000, C055S344000, C055S385200, C055SDIG001, C095S268000, C096S397000, C096S421000, C451S088000
Reexamination Certificate
active
06299667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and a device for removing dust from areas with high dust loading.
2. Description of the Related Art
Areas with high dust loading can be found, for example, in blast jet chambers. Government regulations do not permit dust produced by jet blasting of workpieces which consists, for example, of removed rust, scales, paint coverings or abrasives, to enter the environment in the produced concentration and create an environmental hazard. For this reason, the aerosols generated in the blast jet chambers are treated as spent air and drawn off. By employing suitable methods, the spent air is subsequently separated from the solid constituents and dust, respectively, and exhausted to the surroundings, containing only a small residual dust fraction. The air volume to be treated depends on the number of the air changes necessary for providing sufficient visibility in the jet chamber. Accordingly, the number of the air changes is very high in comparison with the number of air changes required for controlling the air quality in conventional office and work areas.
Importantly, the pressure in blast jet chambers should always be slightly lower than the ambient pressure to prevent dust from uncontrollably escaping into the surroundings through leaks in the chamber. The slightly lower pressure guarantees that an air currents eaters the chamber from the outside at all times.
Air filters in the form of, for example, cartridge filters are suitable to separate the air and the dust particles and to attain a small residual dust fraction of approximately 1 mg/m
3
. The cartridge filters have the characteristic feature that the pressure drop increases with increasing filtration efficiency.
The energy consumption for cleaning the air is therefore determined by the pressure drop across the filter and the air flow through the filter. The energy consumption can become very high if the desired high separation efficiency requires a large pressure drop and the large exhaust air volume to be cleaned requires a large number of air changes.
A conventional method and device for removing fine dust particles is described, for example, in DE 43 00 830 C2. An essential feature is a here that the volume of fresh air is essentially equal to the air volume which is drawn off with the exhaust air and subsequently filtered by a fine filter.
SUMMARY OF THE INVENTION
It is an object of the invention to remove dust particles from areas with a high dust loading using a less complex apparatus and less energy while complying with the regulatory requirements for exhausting a residual dust fraction into the surroundings.
According to an aspect of the invention, the volume of exhaust air is separated into at least two partial flows. With this approach, it is not necessary to reduce the residual dust contents of the entire exhaust air volume exhausted from the area with high dust loading. Instead, the residual dust contents of only one of the partial exhaust air flows exhausted to the surroundings is reduced, while the dust particle fraction of the remaining exhaust air flow is reduced only to a point where it satisfies parameters for re-introduction into the chamber space. This recirculating air flow is subjected to significantly less stringent requirements with respect to the degree of separation than the exhaust air flow which is exhausted into the surroundings.
Accordingly, a device according to the invention produces both a recirculating air flow and an exhaust air flow. For this purpose, compressors or preferably blowers are arranged in the space loaded with dust, which move the partial flows to the separators which separate the airborne particles, such as filters, electrical or cyclone separators.
Moreover, the space loaded with dust particles is preferably provided with control devices which control the power consumption of the compressors or blowers using pressure sensors and/or optical measuring devices.
Advantageously, the energy consumption can be reduced depending on the ratio of the partial flows.
Advantageous embodiments of the method and the device are described in the dependent claims.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
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patent: 93 00 580 U1 (1993-01-01), None
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patent: 43 00 830 C2 (1994-07-01), None
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Darby & Darby
KF Strahltechnik Dresden
Smith Duane S.
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