Gas separation: processes – Electric or electrostatic field – With addition of solid – gas – or vapor
Reexamination Certificate
1998-12-29
2001-05-01
Chiesa, Richard L. (Department: 1724)
Gas separation: processes
Electric or electrostatic field
With addition of solid, gas, or vapor
C095S081000, C096S052000, C096S074000, C096S082000, C096S097000, C204S157300, C323S903000, C361S235000, C422S186040, C422S186150
Reexamination Certificate
active
06224653
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the electrostatic removal of contaminants from air and industrial and domestic gases, and more particularly to the use of a very short duration, high voltage pulsating electrical corona discharge for that purpose. Still more particularly, it provides an improved method and highly effective apparatus for enhancing the capacity of the pulsed corona to modify the molecular structure of, and destroy, pollutants.
2. Prior Art
Prior art systems for removing or destroying pollutants fall generally into one of three categories. One type utilizes catalysts to achieve the desired result. A second employs thermal technology. A third involves some form of electrical discharge in a reaction chamber. Depending on the pollutant and the operative conditions, each has its advantages and deficiencies. For the removal of contaminants from fluids, and particularly gases, the first two suffer from a number of inherent disadvantages. Catalytic converters are usually specific to a particular contaminant and may in fact be impaired or even destroyed by combinations of contaminants or contaminants and ambient conditions. Additionally, they require the input of energy to propel the contaminated gas through the catalytic matrix and to heat the waste stream. Thermal systems, from simple incinerators to esoteric plasma furnaces, tend to be highly inefficient, employing large amounts of fuel or electrical energy-producing resources to heat waste stream temperatures to their operational levels. In operation, they require elaborate containments and controls to handle temperatures ranging from 400° C. to over 6000° C. Commonly, they produce substantial quantities of ash and other solid, frequently hazardous, byproducts the removal and disposal of which in themselves pose a variety of logistical and ecological problems. Electrostatic precipitation devices, while certainly not without limitations, avoid many of the deficiencies inherent in the catalytic and thermal devices and afford a number of significant advantages over the other two types of systems.
Among the electrostatic precipitators, corona discharge reactors are especially well suited to dealing with contaminants in gaseous media. One such electrostatic system in particular shows great promise for removing noxious substances from gases. This device and the method embodied in its use are disclosed in U.S. Pat. Nos. 5,542,967 and 5,601,633. The apparatus includes a reaction chamber through which a stream of the gases to be cleaned passes. An electrode extending axially through the chamber is connected to means for producing a high level pulsating voltage superimposed on a constant direct current. The pulsating high voltage gives rise to a streamer corona discharge within the reaction chamber creating a flow of high-speed electrons which activate and ionize the gas molecules to convert the pollutants into non-noxious aerosols and solid particles. The aerosols and solid particles are removed from the gases in the reaction chamber by the electrostatic conductive field associated with the constant direct-current voltage. In the preferred embodiment of the patented device, a multi-stage Fitch generator is adapted to produce the output current.
The effectiveness of the cleaning process in this device depends on the density and the energy of the electron flow generated by the streamer corona discharge. Both of these parameters rise with increasing pulse amplitude and with increasing steepness of the pulses. The pulse steepness is an important factor because the pulse amplitude that can be achieved without electrical breakdown of the inter-electrode space in the reaction chamber is a function of pulse steepness.
As employed in the patented device, the Fitch generator is particularly well suited to provide pulsating voltages of sufficiently high amplitude and steepness to produce a high density, high energy corona discharge within the chamber. Advantageously, it does so without substantially increasing the temperature within the chamber. Additionally, the Fitch generator is extremely efficient from an energy consumption point of view so that the process may be carried on for long periods of time without consuming excessive amounts of electric power. Still further, in developing, experimenting with, and testing the patented apparatus, we have noted that the electrostatic mechanism (we refer to it as “molecular alteration”) underlying its operation has the potential not only to destroy pollutants and contaminants in both gaseous and liquid environments, but to effect profound changes in the molecular structure and properties of gaseous, liquid, and solid materials as well.
For all of their advantages, precipitators of this type suffer from certain deficiencies. Principal among these is their high degree of unpredictable sensitivity to temperature, humidity, pollutant concentration, and flow rate. By way of example, in dry air at room temperature and levels of 200-500 parts per million we have demonstrated the ability of one such device to destroy as much as 97% of certain pollutants, such as NO
x
. At levels of 500-1,000 parts per million under the same conditions, however, the destruction rate fell to 60% to 73%. In wet air (water vapor content of 5% by volume) and at elevated temperatures (135° C. to 140° C.), the same device consistently removed between 80% and 90% of the NO
x
molecules at levels of more than 1,000 ppm and up to 10,000 ppm while running continuously for sustained periods of time. Similar disparities are noted in the destruction rate with varying concentrations, temperatures, humidities, and flow rates with various organic and inorganic pollutants, such as nitrogen oxides (NO), ammonia (NH
3
), sulfur dioxide (SO
2
), toluene, tetrachloroethylene, and trichloroethylene.
To overcome these inconsistencies and achieve more reliable removal of pollutants, it has been an objective of our efforts to discover methods and means for enhancing the operation of the corona discharge mechanism. Toward this end, we have carried out a program of experimentation to determine the influence of the inert (referred to interchangeably as “noble”) gases, helium, neon, argon, krypton, xenon, and radon, on the corona discharge function. As will be shown, the results demonstrate that, properly utilized, inert gases can profoundly enhance the electrochemical process and substantially and unexpectedly increase the rate and amount of pollutant destruction and removal in waste gases. The subject invention relates generally to our discoveries concerning the utilization of inert gases for this purpose and particularly to novel methods and means utilizing inert gases to enhance the reliability and effectiveness of corona discharge-type electrostatic devices.
While our invention is of broad, general interest in the field of pollution removal by means of electrostatic precipitation, we have identified several areas in which it is of particular utility. In one, the manufacture of semi-conductor chips, various processes are carried out in controlled atmospheres of pure or high concentrations of inert gases. The by-products of these processes contain such highly toxic pollutants as sulfur dioxide (SO
2
), toluene (C
7
H
8
), tetrachloroethylene (C
2
Cl
4
), arsine (AsH
3
), stybine (SbH
3
), phosphine (PH
3
), and the like. In another, the attempted destruction of well-known environmentally noxious wastes by incineration, the off-gases commonly contain dangerous quantities of hazardous organic and chloro-organic compounds, such as, benzene (C
6
H
6
) and chlorobenzene (C
6
H
5
Cl) resulting from incomplete combustion. Our method and apparatus are especially advantageous in these industrial settings. In the former, because the discharge from the manufacturing processes already contains a high concentration of inert gas, in the latter, because the effluent lends itself to electrostatic precipitation with the addition of the necessary concentration of inert gas.
It is an object of the present inve
Kryutchkov Sergei Petrovich
Ponizovsky Aleksander Zalmanovich
Ponizovsky Lazar Zalmanovich
Shvedchikov Adolf Pavlovich
Starobinsky Vladimir Yakovlevich
Chiesa Richard L.
Finkel Robert Louis
Pulsatron Technology Corporation
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