METHOD FOR PROCESS-INTEGRATED OXYGEN SUPPLY OF A HYDROGEN CIRCULATION ENGINE COMPRISING RECIRCULATION OF A NOBLE GAS

Abstract

A method for supplying hydrogen-operated internal combustion engines with oxygen, wherein an inert gas is cycled. An economical local supply of pure oxygen for a closed-cycle hydrogen engine with argon cycling is realized by separating the oxygen from the atmosphere without relying on the useful work of the engine. OSM ceramics and exhaust gas heat and low oxygen partial pressure of the exhaust gas are used to generate oxygen. Two reactors filled with OSM ceramics are used, these reactors being alternately purged with exhaust gas and regenerated with air. Losses of inert gases and the entry of atmospheric nitrogen are avoided by intermediate purging with steam. The steam is generated by the heat of the exhaust gas or exhaust air. A mixture of water vapor, inert gas and oxygen is formed during purging. Subsequently, the oxygen content in the gas phase is markedly increased since water vapor is condensed out.

Claims

1. A method for operating a closed-cycle hydrogen engine with an oxidizer gas comprising oxygen and an inert gas not participating in the combustion, the method comprising: cycling a gas mixture, and separating a combustion-product water by condensing out, by performing the steps of: alternatingly operating, in two phases, at least two reactors, each filled with oxygen-storage material to obtain oxygen needed for combustion directly from air surrounding the closed-cycle hydrogen engine, including: in a first phase, filling the at least two reactors with air so that oxygen contained in the air is stored in the oxygen-storage material, and in a second phase purging the at least two reactors which were enriched with the oxygen in the oxygen-storage material with the gas mixture expelled from the combustion engine so that the gas mixture is enriched with the oxygen stored in the oxygen-storage material; separating water from the oxygen-enriched gas mixture resulting from the second phase by condensing the water out to produce the oxidizer gas containing the oxygen and the inert gas; supplying the oxidizer gas to the closed-cycle hydrogen engine.

2. The method according to claim 1, wherein an OSM ceramic with a composition Ca.sub.0.5Sr.sub.0.5Fe.sub.0.5Mn.sub.0.5O.sub.3-δ synthesized from individual oxides and carbonates by solid state reaction is used.

3. The method according to claim 1, wherein any desired purge time of the at least two reactors is adjustable by a bypass valve and the oxygen to be stored in the oxygen-storage material is accordingly adjustable in any desired manner.

4. The method according to claim 1, wherein the gas mixture supplied for cycling after the second phase has an exhaust gas heat which is utilized for generating low-pressure steam.

5. The method according to claim 1, wherein an oxygen-depleted air results in the first phase and has a heat which is utilized for generating low-pressure steam.

6. The method according to claim 1, wherein a membrane gas storage for storing the oxidizer gas is contained in the circuit and serves to homogenize a mixture of the oxidizer gas and enables a reliable starting of the closed-cycle hydrogen engine.

7. The method according to claim 1, further comprising using switchover valves for switching between the first and second phases, inputs to the at least two reactors are arranged upstream of the at least two reactors and outputs of the at least two reactors are arranged downstream of the at least two reactors, wherein the inputs and outputs of the at least two reactors during the first phase are switched to outputs and inputs of the at least two reactors in the second phase.

8. The method according to claim 1, wherein losses of inert gas and entry of atmospheric nitrogen are prevented by means of an intermediate purge with low-pressure steam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the following, the invention will be described in more detail referring to an embodiment example with the aid of a drawing. The drawing shows:

[0023] FIG. 1 a functional diagram for illustrating the method according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0024] The method for the oxygen supply of a closed-cycle hydrogen engine 1 with fuel performance of 100 kW is shown schematically in FIG. 1. The exhaust gas of the closed-cycle hydrogen engine 1 is fed directly via a switchover valve to a first reactor 4 which is filled with an OSM ceramic. A mixed oxide with the composition Ca.sub.0.5Sr.sub.0.5Fe.sub.0.5Mn.sub.0.5O.sub.3-δ which was synthesized from the individual oxides and carbonates by solid state reaction is used as OSM ceramic. A mixture is prepared with 25 vol % of an organic pore forming agent, plasticized with the addition of organic binders and floating agents and extruded to form thin rods with a diameter of approximately 2 mm. The extrudates are sintered at 1420° C. for 4 hours and then broken into pieces of 1 to 3 cm length. The first reactor 4 and a second reactor 5 are filled in each instance with 15 kg of the granulate with an open porosity of 27 to 30 vol %. When the first reactor 4 is purged with the recycle gas for 20 seconds, approximately 100 standard liters of oxygen are released from the OSM ceramic due to the low oxygen partial pressure of the hydrogen/argon mixture and the rising temperature in the first reactor 4. During the purging in the first reactor 4, the OSM ceramic is regenerated in the second reactor 5 to which air is fed via a further switchover valve 3. The recycle gas which is enriched with the oxygen in the first reactor 4 is guided via the further switchover valve 3 and from the latter via an outgoing collection line for recycle gas 6 through a first heat exchanger 15 of a low-pressure steam generator 8 in which a portion of the exhaust gas heat is used to generate steam (<110° C., <0.5 bar).

[0025] Further, the low-pressure steam generator 8 can be heated via a separate further heat exchanger 16 with the oxygen-depleted exhaust air which is alternately guided from the second reactor 5 or from the first reactor 4 via the collection line for exhaust air 7. After passing through the first heat exchanger 15 of the low-pressure steam generator 8, the gas mixture of the collection line for recycle gas 6 comprising water vapor, argon and oxygen is subsequently guided through an air-cooled condenser 9 so that the water vapor is condensed out. The liquid water is introduced in the liquid phase of the low-pressure steam generator 8, and accumulating excess water is let off via an overflow. The recycle gas comprising argon and oxygen is stored intermediately in a membrane gas storage 12 at approximately atmospheric pressure and is guided back again from the latter to the closed-cycle hydrogen engine 1. The membrane gas storage 12 serves to improve homogenization of the recycle gas, since fluctuating oxygen contents can occur therein. The oxygen partial pressure in the membrane gas storage 12 is constantly monitored by an oxygen sensor 14 and moved to the preadjusted desired value in that the purge time with recycle gas is increased in the first reactor 4 and/or second reactor 5 when the oxygen content is too low and decreased when the oxygen content is too high. The membrane gas storage 12 also serves for restarting the system after stoppage without external gas supply.

[0026] In order that no argon is lost when the feed of recycle gas to the first reactor 4 is switched to the second reactor 5 or when the feed of recycle gas to the second reactor 5 is switched to the first reactor 4, low-pressure steam is metered into the recycle gas at the end of the purge process, i.e., shortly before switching over, via a steam metering valve for recycle gas 10 which is connected on the input side to the low-pressure steam generator 8, so that residual gas remaining in the first reactor 4 or second reactor 5 is flushed out with low-pressure steam into the collection line for recycle gas 6. At the same time, the second reactor 5 or first reactor 4 in the regeneration cycle with air is purged with low-pressure steam at the end of the cycle via a valve for fresh air 11 connected on the input side to the low-pressure steam generator 8 in order to remove the residual air from the second reactor 5 or first reactor 4 in the collection line for exhaust air 7 so that no extraneous gases or residual air remains in the second reactor 5 or first reactor 4 or subsequently reaches the recycle gas. After this phase of purging with low-pressure steam, the two switchover valves 2 and 3 are switched simultaneously so that the supply of recycle gas is diverted from the first reactor 4 to the second reactor 5 or from the second reactor 5 to the first reactor 4, and the air feed from the second reactor 5 to the first reactor 4 or from the first reactor 4 to the second reactor 5 is carried out simultaneously.

[0027] As has already been mentioned above, more oxygen can be generated in the recycle gas than is required for the combustion of a determined amount of hydrogen. The oxygen content in the recycle gas is adjusted in a simple manner by varying the purge time of the first reactor 4 or of the second reactor 5 with the recycle gas. A bypass valve 13 is used for this purpose and allows the purge time of the first reactor 4 or of the second reactor 5 with the recycle gas to be varied at will. It is advantageous that a regeneration time deviating from the purge time with recycle gas can be used for the regeneration of the second reactor 5 or first reactor 4 with air. In this way, it can be ensured that the OSM ceramic is sufficiently loaded with oxygen.

REFERENCE NUMERALS

[0028] 1 closed-cycle hydrogen engine [0029] 2 switchover valve [0030] 3 further switchover valve [0031] 4 first reactor with OSM bed [0032] 5 second reactor with OSM bed [0033] 6 collection line for recycle gas [0034] 7 collection line for exhaust air [0035] 8 low-pressure steam generator [0036] 9 condenser [0037] 10 steam metering valve for recycle gas [0038] 11 valve for fresh air [0039] 12 membrane gas storage [0040] 13 bypass valve [0041] 14 oxygen sensor [0042] 15 first heat exchanger [0043] 16 further heat exchanger