Gas separation: processes – With control responsive to sensed condition
Reexamination Certificate
1998-09-14
2001-01-09
Bushey, C. Scott (Department: 1724)
Gas separation: processes
With control responsive to sensed condition
C095S010000, C095S020000, C095S029000, C095S280000, C055S283000, C055S292000, C055S293000, C055S302000
Reexamination Certificate
active
06171366
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to providing fluid/particle separators and gas cleaning devices and/or gas cleaning systems such as, for instance, electrostatic precipatators (ESP), bag filters (BF), spray dryer absorbers (SDA), evaporative coolers, cyclones, venturi scrubbers, dry systems, humidified dry systems, semi-dry systems, wet systems, combined systems, mechanical separators and the like, with vibration means coupled with control means capable of varying the frequency and amplitude of the vibrations being generated. More particularly, the present invention is directed to control systems and methods for controlling vibration inducing or generating devices utilized to clean and/or operate components of such separator and gas cleaning systems. The systems utilize controllers having input both supplied directly from sensors mounted at spaced surface portions, zones or on components within such devices, and indirectly from additional sensors for measuring operating parameters such as, for instance, pressure differential between inlets and outlets of such systems and/or flow characteristics into and out of such systems or through filtering materials associated with such systems as well as power, voltage, and current conditions of motors associated with fans, blowers, pumps and other equipment associated with such separator and filtering devices for purposes of creating control signals to the generating devices for varying vibration frequencies and amplitudes for developing resonant frequency conditions at various zones and/or on various components of such systems and devices to thereby optimize the operation thereof. Additionally, the controllers may be programmed to provide control signals using previously accumulated data concerning operating characteristics of the same or similar devices or systems.
HISTORY OF THE RELATED ART
Many gas cleaning devices require vibration means either to clean surfaces such as, for instance, the collecting plates of electrostatic precipitators, and the bags of bag filters, or to clean surfaces where non-desired build-up occurs such as, for instance, the wall of a spray dryer absorber, or to vibrate particles suspended in the gases to be cleaned such as, for instance, droplets to be evaporated in an evaporative cooler, particles to absorb gaseous pollutants in a spray dryer absorber, and agglomeration of fine particles with coarser particles. Such vibration means are operated at fixed vibration frequency and amplitude even if they operate periodically according to a sequence that can be automatically adjusted on the basis of the gas cleaning device operation (for instance, the pressure drop of a bag-type dust filter).
Heretofore there have been numerous control systems developed for gas cleaning devices of the type set forth above for periodically cleaning the interior surface areas of such devices. Some conventional systems are simply timed systems which are effective to terminate the normal operations of such devices in order to effect a cleaning cycle. During the cleaning cycle, various mechanical and/or air current and/or acoustical devices are utilized to establish vibrations of the surfaces within the system to loosen or discharge accumulated particulate material including dust, solid particles, water or liquid droplets and the like. Such vibration generators, however, are operated at fixed vibration frequencies and amplitudes. Unfortunately, such timed periodic cleaning systems are not effective for optimizing the cleansing of the various interior surface areas or components associated with such separators or cleaning devices. For instance, in a conventional bag-type dust filter, the surface characteristics of bags and the particulate material to be removed therefrom differs substantially from the surface characteristics of adjacent walls of the filter housing and the particulate material collected thereon. The vibration frequency created by mechanical or air current or acoustical devices affects each of these surfaces differently. That is to say, each surface area within the filter system has a different resonance frequency which is dependent on its structure and which is also affected by the particulate build-up thereon. Thus, each surface reacts differently at a given frequency. Therefore, during a timed cleaning cycle, the extent of cleaning of surface areas having different surface characteristics and having different particulate build-up varies greatly from one component to another component of the system. Under such circumstances, it may be necessary to prolong unreasonably the cleaning cycle to ensure that each of the components and surface portions of a particular filter, or other separator, are effectively cleaned.
To enhance the efficiency of cleaning systems, some prior art devices have utilized real time condition monitors for controlling the operation of cleaning devices. A number of prior art cleaning systems incorporate pressure transducers which are mounted on opposite sides of a filter so that a difference in pressure may be determined between the upstream and downstream sides of the filter. When a condition is sense such that the pressure drop reaches a predetermined level, the control system activates the cleaning equipment, either mechanical or with air current or acoustical, in order to initiate a cleaning cycle of the components of the system. Again, such real time monitoring of pressure conditions does not account for the difference in surface characteristics nor the difference in material build-up upon the various components of the system and, once a cleaning cycle has been initiated, the cycle is normally maintained for an averaged period of time to effect a general cleaning of the system. Such an averaged cleaning cycle may not be adequate to clean some elements of the system, and, again, the vibration generators used in such systems are operated at a fixed frequency and amplitude. An example of such control systems are disclosed in U.S. Pat. No. 4,277,255 to Apelgren.
Additional improvements have been made with respect to computer controlled systems for cleaning particle separators and related equipment. U.S. Pat. No. 5,427,596 to Jorgenson et al., discloses a diagnostic control system for dust collectors which utilizes a micro-processor which interfaces with various sensors and software programming to monitor and control operation of the collector and cleaning system. The patent discloses that various operating parameters of a filter system are continuously monitored and compared with internal software to give immediate indications of conditions of filters and other components of the collector. Such input sensors include motor current sensors, filter pressure drop sensors, internal temperature sensors and the like. Signals received from these sensors are processed to determine operating conditions and failures within the collector. Operation of the collector including cleaning cycles is thus controlled by the data received and by internal software programming. However, as with other prior art cleaning systems, there has been no provision made for monitoring various components or zones of the collector for purposes of determining the exact resonance conditions of spaced elements so as to vary vibration frequencies and amplitudes of generators used to create vibrations used to dislodge material build-up within the collector. The control system also does not control vibration frequencies based upon conditions which include the build-up of material on the various surfaces exposed to vibrations during a cleaning cycle. Therefore, the control system does not effectively control nor vary vibration frequencies and amplitudes for purposes of cleaning the different surfaces within the collector.
Additionally in the field of gas absorption, U.S. Pat. No. 4,535,209 to Pfoutz discloses enhancement of gas/solid particles reaction through acoustics in a semi-dry system. A sonic horn vibrates the sprayed slurry droplets. But again the frequency of the sonic horn, selected case by case, does
Gallo Frank
Vicard Jean-Francois
Bushey C. Scott
Dowell & Dowell , P.C.
Lab, S.A.
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