Chemical apparatus and process disinfecting – deodorizing – preser – Control element responsive to a sensed operating condition – Control element is fluid pressure sensitive
Patent
1980-07-03
1982-06-01
Richman, Barry
Chemical apparatus and process disinfecting, deodorizing, preser
Control element responsive to a sensed operating condition
Control element is fluid pressure sensitive
422186, 422198, 422209, 4221863, 423579, 423648R, G05D 1602, B01J 1912, C01B 1300, C01B 306
Patent
active
043327753
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the production of hydrogen using solar energy to dissociate water.
PRIOR ART
It has already been proposed to dissociate directly water flowing over a surface heated by concentrated solar radiation, and collect the hydrogen and oxygen.
The state of the art in this field may be illustrated by the following publications:
(1) The article by E. A. Fletcher, entitled: "Hydrogen and Oxygen from Water", and published in the review "Science", Vol. 197, Sept. 9, 1977, pages 1050-1056.
(2) U.S. Pat. No. 4,053,576 to E. A. Fletcher.
(3) U.S. Pat. No. 4,019,868 to D. E. Sebacher.
(4) The article by T. Nakamura entitled: "Hydrogen Production from Water utilising Solar Heat at high Temperatures" and published in the review "Solar Energy", Vol. 19, pages 467-475, by Pergamon Press in 1977.
(5) Belgian Pat. No. 845,009 to the C.G.E.
The article by E. A. Fletcher mentioned in (1) above describes more particularly the following:
Direct concentration of solar radiation onto a molecular diffusion porous membrane (operating under Knudsen flow conditions).
Dissociation of water by passage through the membrane thus heated directly by the concentrated solar radiation.
Partial separation of hydrogen and oxygen by selective molecular diffusion in this membrane.
Compression of the vapours enriched in H.sub.2 and O.sub.2 respectively, after having cooled the vapours to a low temperature, and separation by H.sub.2 O by condensation so as to recover H.sub.2 and O.sub.2 under pressure.
Preheating of the water to be dissociated, by counter-current heat exchange with the vapours enriched in H.sub.2 and O.sub.2 and superheated by passage through the said membrane.
Use of a refractory porous membrane formed from ThO.sub.2.
OUTLINE OF THE INVENTION
The main advantage of using concentrated solar radiation to effect the direct dissociation of water is that in principle it enables high thermodynamic yields at high temperature to be obtained.
This advantage is however restricted by the refractory construction materials at present available. In fact, at the present time there are no refractory materials which would be capable of withstanding very high temperatures, for example of 3000.degree. K. or above, as well as chemical attack and mechanical constraints at such high temperatures.
Consequently, one problem that needs to be solved in this case is to ensure as far as possible compatibility between the collection of the heat energy, the dissociation of the water, and the separation of the dissociated products.
Thus, for example, it is possible to operate at 2500.degree. K. under a reduced pressure of 0.1 atmosphere so as to provide an acceptable degree of dissociation of the order of 20%. At the same time this also enables the thermal and mechanical constraints to which the heated refractory materials are subjected to be reduced.
However, the mass flux of a gas diffusing across a porous wall increases as a function of the pressure difference across this membrane, with the result that the operation of the generator at very low pressures reduces the flow rate of the gas that is consequently separated. It is nevertheless possible to take account of this reduction during separation by molecular diffusion, as will be seen hereinafter.
In addition, in order to ensure a good collection efficiency of the concentrated solar radiation, of the order of 80% for example, the surface absorbing this concentrated radiation should not re-emit an excessive amount of the absorbed energy, i.e. it should re-emit at most 20% for such a collection efficiency of 80%.
Nevertheless, the radiation flux re-emitted by a wall heated to 2500.degree. K. is of the order of 200 W/cm.sup.2. Consequently, a collection efficiency of 80% would only be achieved if the incident concentrated radiation flux I.sub.mc were equal to 1000 W/cm.sup.2, which corresponds to a concentration 10,000 times greater than that of the solar radiation.
Consequently, assuming that the solar concentrator intercepts the solar radiation over a surface
REFERENCES:
patent: 4019868 (1977-04-01), Sebacher et al.
patent: 4053576 (1977-10-01), Fletcher
patent: 4071608 (1978-01-01), Diggs
patent: 4233127 (1980-11-01), Monahan
Fletcher, E. A. et al.; "Hydrogen and Oxygen from Water"; Science, vol. 197, 9/77, pp. 1050-1056.
Nakamura T.; "Hydrogen Production from Water Utilizing Solar Heat at High Temperatures", Solar Energy; vol. 19, pp. 467-475.
Genequand Pierre
Gross Daniel M.
Battelle (Memorial Institute)
Dunson Philip M.
Richman Barry
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