Cold oxidation in gaseous phase

Details Cold oxidation in gaseous phase Cold oxidation in gaseous phase

1991-09-06

1994-05-10

Niebling, John

Chemistry: electrical and wave energy

Processes and products

Electrostatic field or electrical discharge

204165, 204169, 204170, 588205, 588212, 588227, H05F 300

Patent

active

053104617

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND AND FIELD OF INVENTION

In a large number of industrial processes one can observe the emission towards the atmosphere of gaseous flows containing organic solvents from painting, spraying, drying processes, furnaces and so on. The conditioning technologies available nowadays to solve this problem, since the regulations enforced by the various regional authorities state particularly low limits, may be summarized in two families:


Adsorption on Activated Carbon

It has the following drawbacks: it is impossible to find commercial activated carbons adapted to systematically adsorb different types of solvents present in the same flow;--possible desorption of a solvent already fixed in a flow which does not include it;--difficulty in regenerating said carbons with the resulting problem of their disposal as "toxic wastes";--in case said carbons get saturated with flammable solvents and problems for the/intrinsic safety of the plant itself.


Thermal After-Burning

The drawbacks experienced are the following:--it is necessary to raise the temperature of the flow by an outside fuel addition with particularly high associated operation costs;--possible formation of positively toxic chemical compounds within the flow, caused by high temperatures.


SUMMARY OF THE INVENTION

Taking the above into account, the Applicant has provided a new treatment suited to remove the above drawbacks, with the purpose of reaching the following benefits:--low operating costs measured in terms of the energy needed to destroy the solvents (by oxidation). The oxidation takes place at ambient temperature (approximately 20.degree. C.);--approximately uniform effectiveness in the oxidation of both aromatic and aliphatic organic compounds;--no production of solid toxic wastes;--no generation of gaseous positively toxic compounds, or more toxic than the substances to be destroyed.


BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view of the processing unit useful for the claimed treatment.
FIG. 2 is a chromatographic representation of the concentrations of waste gases present in a sample of effluent gas prior to the oxidation treatment of the present invention as described in the experimental Example below.
FIG. 3 is a chromatographic representation of the concentrations of waste gases present in a sample of effluent gas after the oxidation treatment of the present invention as described in the experimental Example below.


DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The gaseous matter carrying the organic solvents to be destroyed enters, at a temperature ranging from 180.degree. C. to 40.degree. C., the processing unit, shown schematically in the attached FIG. 1, which substantially comprises two stages:


First Stage, or Ionizing Stage

This portion substantially comprises metal plates 1 lying parallel to the flow and spaced apart from each other in such a way as to maximize the corona discharge generation. The plates are subjected to high voltages ranging from 15000 to 30000 V and from 500 to 1500 Hz in frequency, provided by a high voltage generator 3 in order to enhance the ionizing effect on the gaseous flow. The spacing between the plates is such as to get the highest possible electrical field intensity allowable for the gaseous flow subject to treatment. The plate length is related to the flow velocity, in that it determines the effective processing time. The electronic apparatus is provided with all the automatic controls and safety features necessary to make the plant operation safe and reliable.


Second Stage, or Catalytic Stage

The solvents carried by the gaseous substance undergo a first destructive treatment, while proceeding through the ionizing stage, for about 50% of the upstream contents. Free radicals are formed, in particular, which are able to develop their reactivity while contacting catalyst 2 comprised of oxides of metals such as Cr, V and metals of Group VIII, such as for instance Fe, Ni, and so on, whereby oxidation of the remaining portion takes place. The final result of this operati

REFERENCES:
patent: 4438706 (1984-03-01), Boday et al.
patent: 4834962 (1989-05-01), Ludwig

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