Gas separation: apparatus – Electric field separation apparatus – With control means responsive to sensed condition
Reexamination Certificate
2000-03-23
2001-09-18
Chiesa, Richard L. (Department: 1724)
Gas separation: apparatus
Electric field separation apparatus
With control means responsive to sensed condition
C055S523000, C055SDIG003, C096S069000, C096S070000, C096S073000, C096S100000, C204S290010
Reexamination Certificate
active
06290757
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to nitrogen purification and, more particularly, to a nitrogen purification device employing a honeycomb ceramic structure that purifies nitrogen by removing oxygen from a gaseous nitrogen source.
Purified nitrogen is utilized in a variety of modern applications. Three conventional supplies of nitrogen gas include liquid nitrogen dewars, gas cylinders of nitrogen, and a nitrogen supply generated by passing air through bundles of semi-permeable membranes. All three of these sources of purified nitrogen have disadvantages. Specifically, nitrogen source dewars and cylinders are typically vendor-based products that are subject to cost fluctuations, supply shortages, and shipping and handling difficulties. The membrane based generators suffer from low flow rates, relatively low purity levels, relatively high initial cost, and relatively high maintenance costs. Accordingly, there is a need for a nitrogen generation scheme that overcomes the above-noted shortcomings associated with conventional nitrogen sources.
BRIEF SUMMARY OF THE INVENTION
This need is met by the present invention wherein an improved nitrogen purification scheme is provided. In accordance with one embodiment of the present invention, a nitrogen purification device is provided comprising a source gas, a set of gaseous nitrogen passages, a set of oxygen disposal passages, an electroded oxygen conducting ceramic membrane, an electrical power source and nitrogen purification control circuitry. The source gas comprises gaseous nitrogen. The gaseous nitrogen passages define respective source nitrogen input openings and purified nitrogen output openings. The set of oxygen disposal passages defines disposed oxygen output openings. The electroded oxygen conducting ceramic membrane defines a plurality of electrode surfaces disposed in the gaseous nitrogen passages and the oxygen disposal passages, the oxygen disposal passages being separated from respective ones of the set of gaseous nitrogen passages by the electroded oxygen conducting ceramic membrane. The electrical power source is coupled to the electroded oxygen conducting ceramic membrane and arranged such that the electroded surfaces comprise cathodes in the gaseous nitrogen passages and anodes in the oxygen disposal passages. The nitrogen purification control circuitry is arranged to optimize current and voltage generated by the power source as a function of nitrogen purity of gas passing through the purified nitrogen output openings.
The nitrogen purification device may further comprise an oxygen sensor in fluid communication with the purified nitrogen output openings, and the control circuitry may be arranged to optimize current and voltage generated by the power source as a function of a signal generated by the oxygen sensor. The control circuitry may be arranged to optimize current and voltage generated by the power source by switching from a current control mode to a voltage control mode when the oxygen sensor signal indicates a decrease in oxygen content below a predetermined level. The predetermined level is preferably between about 1000 ppm and about 200 ppm.
The oxygen conducting ceramic membrane may comprise a ceramic body defining the set of gaseous nitrogen passages and the set of oxygen disposal passages may be in the form of first and second sets of substantially parallel passages. The nitrogen purification device may further comprise a mass flow regulator coupled to at least one set of the first and second sets of substantially parallel passages. And, the nitrogen purification control circuitry may be further arranged to control the mass flow regulator to optimize a mass flow ratio &eegr; of gasses moving through the first and second sets of substantially parallel passages, where &eegr; represents the following ratio:
η
=
R
1
R
2
where R
1
represents a flow rate of a nitrogen source gas in the set of gaseous nitrogen passages and R
2
represents a flow rate of disposed oxygen in the oxygen disposal passages. The mass flow regulator may be arranged to establish the mass flow ratio &eegr; between about 0.2 and 2.0. The mass flow regulator may comprise a draft fan coupled to the set of oxygen disposal passages.
The nitrogen purification device may further comprise turbulence inducing inserts arranged in the set of gaseous nitrogen passages. The nitrogen purification device may further comprise a source gas comprising air and/or a source gas comprising a gas with a nitrogen purity level of about 97%. A plurality of gaseous nitrogen passages are preferably exclusively dedicated to individual ones of the oxygen disposal passages. Additionally, the oxygen conducting ceramic membrane may comprise a ceramic body defining the set of gaseous nitrogen passages and the set of oxygen disposal passages in the form of first and second sets of substantially parallel passages. A selected set of the first and second sets of passages preferably include inter-passage channels formed in the ceramic body between adjacent ones of the selected set of passages. The inter-passage channels may be arranged proximate selected ones of the opposite passage ends. The selected set of passages and the inter-passage channels are arranged to define a flow path extending through the selected set of passages. The flow path reverses direction following passage through the inter-passage channels.
Each of the passages defines opposite passage ends. The opposite ends of the gaseous nitrogen passages may be open and the opposite ends of the oxygen disposal passages may be closed. The oxygen disposal passages may include inter-passage channels formed in the ceramic body between adjacent ones of the oxygen disposal passages. The source nitrogen input openings may be coupled to a source of air or a source of gas with a nitrogen purity level of about 97%. The nitrogen purification device may further comprise at least one disposed oxygen output port coupled to the oxygen disposal passages.
Each of the passages define opposite passage ends and the opposite ends of the oxygen disposal passages may be open while the opposite ends of the gaseous nitrogen passages are closed. The gaseous nitrogen passages may include inter-passage channels formed in the ceramic body between adjacent ones of the gaseous nitrogen passages.
The oxygen conducting ceramic membrane preferably comprises a ceramic body defining the set of gaseous nitrogen passages and the set of oxygen disposal passages in the form of first and second sets of substantially parallel passages. Each of the passages define opposite passage ends. The opposite ends of a selected set of the passages are preferably open and the opposite ends of a remaining set of the passages are preferably closed. The set of closed passages include inter-passage channels formed in the ceramic body between adjacent ones of the closed passages. The nitrogen purification device further comprises at least one closed passage input port coupled to the closed set of passages and at least one closed passage output port coupled to the set of closed passages. The closed passage input port, the closed passages, and the closed passage output port collectively define a closed passage flow path extending from the closed passage input port to the closed passage output port. The closed passage input port may be coupled to a source of gaseous nitrogen while the open passages are coupled to a source of air and the nitrogen purification device is arranged such that the closed passage output port passes purified nitrogen. The nitrogen purification device may further comprise a draft fan coupled to the open passages. The closed passage input port may be coupled to a source of air while the open passages are coupled to a source of gaseous nitrogen, and the nitrogen purification device is arranged such that the closed passage output port passes oxygen enriched air. The nitrogen purification device may further comprise a draft fan coupled to the closed passage output port.
In accordance with another embodiment of the present inv
CeramPhysics, Inc.
Chiesa Richard L.
Killworth, Gotiman, Hagan & Schaeff LLP
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