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Closed Loop Oxygen Generation System

IP.com Disclosure Number: IPCOM000212154D
Publication Date: 2011-Nov-02
Document File: 5 page(s) / 97K

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The IP.com Prior Art Database

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Robert Desmond: ATTORNEY

Abstract

ABSTRACT In many manmade enclosed cabins or bounded areas, requirement of continuous supply of fresh oxygen and removal of carbon dioxide is a big challenge. In certain cases where fresh oxygen supply by ventilation is impossible, either oxygen has to be stored in tanks or has to be generated onboard. The existing technologies for generating onboard oxygen utilize external resources, e.g. water in electrolysis technology and chlorates in chemical oxygen generator technology need to be continuously replenished by external means. This paper proposes onboard oxygen generation by converting carbon dioxide (CO2) present in an enclosed area into oxygen (O2) by a closed loop system of Bosch reactor and Solid Oxide Electrolysis Stack. 1. Introduction Human survival in enclosed cabins or bounded areas is primarily dependent on the percentage of oxygen in the air. Presence of carbon dioxide (CO2) is another factor that affects the health and performance of the occupants. Occupational Safety and Health Administration (OSHA) recommends the acceptable levels of oxygen to be between 19.5% - 23.5 % and limits CO2 exposure level to 0.5 % for a prolonged period. Today commonly used technology for onboard generation of oxygen is water electrolysis. The electricity required for electrolysis is normally generated using solar panel or any other available power generating sources. The water for electrolysis is supplied from external sources. There is a need to generate oxygen onboard without depending on external resources. Some of the prior art in the area of oxygen generation systems for enclosed cabins are discussed below. • Patent US7572530 discloses the use of solid oxide regenerative fuel cell system to supply power in a fuel cell mode and to generate metabolic oxygen in an electrolysis mode. • Patent JP3022990 teaches production of oxygen in a closed space such as a submarine by separating and recovering CO2 in a gas by membrane separation, adsorption separation, ion exchange separation, etc., and supplying the CO2 to a reactor composed of a plant growing in a culture liquid to effect photosynthesis. In general, none of the techniques available in the state of the art offer self sufficient closed loop oxygen generation system that operates by utilizing only the available resources. The proposed technique offers system that is self sufficient and utilizes onboard CO2 to generate oxygen. 2. Proposed solution for onboard oxygen generation The proposed closed loop oxygen generation system involves a CO2 conversion system. CO2 can be generated by human metabolism or may be drawn in from any CO2 rich atmosphere. The end products of the conversion process are gaseous oxygen and solid carbon. The closed loop oxygen conversion system consists of a Bosch reactor. It involves direct catalytic conversion of carbon dioxide to carbon and water at higher temperatures. CO2 + H2 Catalyst CO + H2O --------- (1) CO + H2 Catalyst C(S) + H2O -------- (2) The generated solid carbon deposited in the disposable receiver at the discharge of the reactor is discarded The water vapor exhausted from the Bosch reactor is directed into Solid Oxide Electrolysis Stack (SOES) to generate oxygen and hydrogen. The oxygen is generated at the anode side of the electrolysis stack and separated from the cathode by the solid oxide electrolyte. The oxygen is compressed and stored in a pressure vessel for later use in the enclosed cabins. SOES Cathode Reaction H2O + 2e- O 2- + H2¬¬ ------------- (3) SOES Anode Reaction O2- 0.5O 2 + 2e-¬¬ ------------- (4) The hydrogen generated in the cathode of the SOES is compressed and transferred to Bosch reactor for the reduction of carbon dioxide and carbon monoxide (see reactions 1 and 2) The advantage of integrating Bosch reaction and SOES is that both the reactors operate at the similar temperatures. Designing and operating the close loop cycle at thermal equilibrium becomes simpler. The existing technologies for generation of oxygen in enclosed cabins requires valuable supplies from the earth such as water for electrolysis system and chlorate for chemical oxygen generator. The proposed system of closed loop oxygen generation recycles the CO2 that is generated in the enclosed areas and thus reducing the dependency on external resources. 3. Design features of the proposed closed loop oxygen generation system The closed loop system includes a Bosch reactor where the input to the reactor is CO2. Exothermic reaction in the presence of catalyst and hydrogen from the SOES reduces the CO2 into solid carbon. Solid carbon generated in the Bosch reactor should be removed periodically to avoid clogging of the catalyst and filters. The process further generates intermediate carbon monoxide (CO) that is toxic to humans. CO thus generated is reduced by the H2 produced in the SOES reactor. After reduction of CO, the end products from the Bosch reaction that remain are H2O (vapor) and solid carbon. H2O (vapor) is sent to SOES for generating oxygen. Figure 1 provides the graphical representation of the closed loop oxygen generation system. Figure 1. Closed loop oxygen generation system. The SOES of the closed loop system uses power (electricity) from any external source (such as but not limited to photovoltaic cells) as its input. This electricity is used to sustain the electrochemical reaction in the SOES that splits the H2O (vapor) from the Bosch reactor into oxygen and hydrogen at temperatures in the range of 600 to 800°C. The oxygen generated from the SOES will be stored in an oxygen tank, while the hydrogen generated from the SOES will be redirected into the Bosch reactor to support the Bosch reaction. The Bosch reaction has the potential to generate carbon monoxide (see reaction 1) which is toxic in nature. However, in combination with SOES issue of CO is nullified. Since the operation of SOES is insensitive to CO and the permeability of H2O (vapor), hydrogen, carbon monoxide and carbon dioxide through the solid oxide electrolyte is near zero, any carbon monoxide transferred along with the H2O (vapor) from the Bosch reactor to the cathode of the SOES returns to back to the Bosch reactor for further reduction. 4. Advantages of the proposed solution The proposed solution is a closed loop system for oxygen recycling wherein no other byproduct is generated from the system. The CO2 is completely recycled and converted into oxygen. • The resources required to generate oxygen are carbon dioxide and electricity. No additional chemicals are required for the normal operation of the system. • Single gas phase products are generated from SOES and Bosch reactor; gas separation/conditioning devices are not required in the system. • Improved thermal management – the exhaust from the Bosch reactor can be directly introduced into the solid oxide electrolysis stack since both devices could be operated at similar temperature and integrated together. • Pure oxygen generation – the oxygen is generated at the anode side of the SOES and separated from the cathode by solid oxide electrolyte thus the gaseous oxygen generated is of at most purity.

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Closed Loop Oxygen Generation System

Dacong Weng

28112 Ridgeforest CT, Rancho Palos Verdes, California, 90275, United States

Stephen Yates

2 Mesa Drive, South Barrington, IL, 60010, United States

Mark Kaiser

301 E. Circle Ave, Prospect Heights, IL, 60070, United States

Dale Winton

United States

ABSTRACT

In many manmade enclosed cabins or bounded areas, requirement of continuous supply of fresh oxygen and removal of carbon dioxide is a big challenge. In certain cases where fresh oxygen supply by ventilation is impossible, either oxygen has to be stored in tanks or has to be generated onboard. The existing technologies for generating onboard oxygen utilize external resources, e.g. water in electrolysis technology and chlorates in chemical oxygen generator technology need to be continuously replenished by external means. This paper proposes onboard oxygen generation by converting carbon dioxide (CO2) present in an enclosed area into oxygen (O2) by a closed loop system of Bosch reactor and Solid Oxide Electrolysis Stack.

1.                 Introduction

Human survival in enclosed cabins or bounded areas is primarily dependent on the percentage of oxygen in the air. Presence of carbon dioxide (CO2) is another factor that affects the health and performance of the occupants. Occupational Safety and Health Administration (OSHA) recommends the acceptable levels of oxygen to be between 19.5% - 23.5 % and limits CO2 exposure level to 0.5 % for a prolonged period.

Today commonly used technology for onboard generation of oxygen is water electrolysis. The electricity required for electrolysis is normally generated using solar panel or any other available power generating sources. The water for electrolysis is supplied from external sources. There is a need to generate oxygen onboard without depending on external resources.

Some of the prior art in the area of oxygen generation systems for enclosed cabins are discussed below.

·         Patent US7572530 discloses the use of solid oxide regenerative fuel cell system to supply power in a fuel cell mode and to generate metabolic oxygen in an electrolysis mode.

·         Patent JP3022990 teaches production of oxygen in a closed space such as a submarine by separating and recovering CO2 in a gas by membrane separation, adsorption separation, ion exchange separation, etc., and supplying the CO2 to a reactor composed of a plant growing in a culture liquid to effect photosynthesis.

In general, none of the techniques available in the state of the art offer self sufficient closed loop oxygen generation system that operates by utilizing only the available resources. The proposed technique offers system that is self sufficient and utilizes onboard CO2 to generate oxygen.

2.       Proposed solution for onboard oxygen generation

The proposed closed loop oxygen generation system involves a CO2 conversion system. CO2 can be generated by human metabolism or may be drawn in from any CO2 rich atmosphere. The end products of the conversion process are g...