Catalytic fuel deoxygenation system

Abstract

A fuel system for an energy conversion device includes a deoxygenator system with a reducing system and an active metal catalyst system downstream thereof. The reducing system injects a reducing agent such as hydrogen into the liquid hydrocarbon fuel which contains the dissolved oxygen. The liquid hydrocarbon fuel with the dissolved oxygen is thereby enriched with the reducing agent prior to communication to the active catalyst system which reactively consumes the free oxygen dissolved within the liquid hydrocarbon fuel.

Description

BACKGROUND OF THE INVENTION

The present invention relates to stabilizing fuel by deoxygenation, and more particularly to catalytic deoxygenation.

Fuel is often utilized in aircraft as a coolant for various aircraft systems. The presence of dissolved oxygen in hydrocarbon jet fuels may be objectionable because the oxygen supports oxidation reactions that yield undesirable by-products. Dissolution of air in jet fuel results in an approximately 70 ppm oxygen concentration. When aerated fuel is heated between 350° F. and 850° F. the oxygen initiates free radical reactions of the fuel resulting in deposits commonly referred to as “coke” or “coking.” Coke may be detrimental to the fuel lines and may inhibit combustion. The formation of such deposits may impair the normal functioning of a fuel system, either with respect to an intended heat exchange function or the efficient injection of fuel.

Various conventional fuel deoxygenation techniques are currently utilized to deoxygenate fuel. Typically, lowering the oxygen concentration to 2 ppm is sufficient to overcome the coking problem.

One conventional Fuel Stabilization Unit (FSU) utilized in aircraft removes oxygen from jet fuel by producing an oxygen pressure gradient across a membrane permeable to oxygen. The FSU includes a plurality of fuel plates sandwiched between oxygen permeable membranes and porous substrate plates disposed within a housing to extract oxygen from the fuel by a pressure differential across the membrane. Although effective, the fuel plate FSU may be relatively difficult and expensive to manufacture.

Accordingly, it is desirable to provide for the effective deoxygenation of hydrocarbon fuel in an uncomplicated and robust system.

SUMMARY OF THE INVENTION

The fuel system for an energy conversion device according to the present invention includes a deoxygenator system which includes a reducing system and an active catalyst system downstream thereof. The reducing system injects a reducing agent such as hydrogen into the liquid hydrocarbon fuel which contains the dissolved oxygen. The liquid hydrocarbon fuel with the dissolved oxygen is thereby enriched with the reducing agent prior to communication to the active catalyst system which reactively consumes the free oxygen dissolved within the liquid hydrocarbon fuel.

The present invention therefore provides for the effective deoxygenation of hydrocarbon fuel in an uncomplicated and robust system.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a general schematic block diagram of an energy conversion device (ECD) and an associated fuel system employing a fuel deoxygenator in accordance with the present invention; and

FIG. 2 is a flow chart illustrating operation of the fuel deoxygenator system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a general schematic view of a fuel system 10 for an energy conversion device (ECD) 12. A deoxygenator system 14 receives liquid fuel F from a reservoir 16 such as a fuel tank. The fuel F is typically a liquid hydrocarbon fuel such as jet fuel. The ECD 12 may exist in a variety of forms in which the fuel, at some point prior to eventual use for processing, for combustion or for some form of energy release, acquires sufficient heat to support autoxidation reactions and coking if dissolved oxygen is present to any significant extent in the fuel.

One form of the ECD 12 is a gas turbine engine, and particularly such engines in high performance aircraft, however, other ground vehicles and power stations will likewise benefit from the present invention. Typically, the fuel also serves as a coolant for one or more sub-systems in the aircraft and becomes heated as it is delivered prior to combustion.

A heat exchange system 18 represents a system through which the fuel passes in a heat exchange relationship. It should be understood that the heat exchange system 18 may be directly associated with the ECD 12 and/or distributed elsewhere in the fuel system 10. The heat exchange system 18 may alternatively or additionally include a multiple of heat exchanges distributed throughout the system.

As generally understood, fuel F stored in the reservoir 16 normally contains dissolved oxygen, possibly at a saturation level of approximately 70 ppm. A fuel pump 20 draws the fuel F from the reservoir 16 into the fuel circuit 17. The fuel pump 20 communicates with the reservoir 16 via a fuel reservoir conduit 22 and a valve 24 to a fuel inlet 26 of the deoxygenator system 14. The pressure applied by the fuel pump 20 assists in circulating the fuel F through the deoxygenator system 14 and other portions of the fuel system 10. As the fuel F passes through the deoxygenator system 14, oxygen is selectively removed.

The deoxygenated fuel Fd flows from a fuel outlet 30 of the deoxygenation system 14 via a deoxygenated fuel conduit 32, to the heat exchange system 18 and to the ECD 12 such as the combustor of a gas turbine engine. A portion of the deoxygenated fuel may be recirculated, as represented by recirculation circuit 33 to either the deoxygenation system 14 and/or the reservoir 16. It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit from the instant invention.

The deoxygenator system 14 includes a reducing system 34 and an active catalyst system 36 downstream thereof. The reducing system 34 injects a reducing agent such as hydrogen into the liquid hydrocarbon fuel which contains the dissolved oxygen. The liquid hydrocarbon fuel with the dissolved oxygen is thereby enriched with the reducing agent prior to communication to the active 1 catalyst system 36. The active catalyst system 36 includes a catalyst such as a platinum or other active catalyst to reactively consume the free oxygen dissolved within the liquid hydrocarbon fuel. The catalytic material may alternatively or additionally be a metal such as but not limited to copper, chromium, platinum, rhodium, iridium, ruthenium, palladium, rhenium and any combination of these materials or a metal multimetallic compound or compounds including transition metal or multimetallic complexes or supported complexes. One such preferred catalyst is a platinum/palladium catalyst on a mildly acidic support optimized with regard to pore structure, surface area, metal dispersion, etc. A worker having the benefit of this disclosure would understand the specific composition of catalyst required to reduce, in the chemical sense, the dissolved oxygen in the fuel.

The catalytic material may be supported on a honeycomb structure disposed within the metal catalyst system 36. Alternatively, the catalytic material may be supported on granules, extrudates, monoliths, or other known catalyst support structures. The active catalyst system 36 may be disposed adjacent heat producing components of the system 10. Preferably, the metal catalyst system is disposed in relatively close proximity with the ECD 12 and most preferably within a housing of the ECD such that heat generated by the ECD 12 elevates the temperature of the active catalyst system 36 to temperatures required to initiate catalytic reactions. The active catalyst system 36 may alternatively be utilized to absorb thermal energy from other systems and/or in conjunction with the heat exchange system 18. The absorbed thermal energy will elevate the temperature of the active catalyst system 36 to temperatures providing optimum operation. Further, it is within the contemplation of this invention to heat the active catalyst system 36 by external systems.

In operation, as the liquid hydrocarbon fuel and the reducing agent from the reducing system 34 are passed through the active metal catalyst system 36, water and thermal energy are produced as byproducts during the deoxygenation process (FIG. 2). A water collection system 38 communicates with the deoxygenator system 14 to receive water therefrom. It should be understood that the water may be collected and/or expelled from the fuel system 10 and the thermal energy may be further utilized within a thermal management subsystem.

Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.

The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.

Claims

1. A fuel system comprising:

a fuel circuit for communicating a liquid hydrocarbon fuel; a reducing system in communication with said fuel circuit for injecting a reducing agent into the liquid hydrocarbon fuel; and an active catalyst system downstream of said reducing system in communication with said fuel circuit to at least partially deoxygenate the liquid hydrocarbon fuel.

2. The fuel system as recited in claim 1, wherein said reducing agent includes hydrogen.

3. The fuel system as recited in claim 1, wherein said active catalyst system includes a metallic compound.

4. The fuel system as recited in claim 1, wherein said active catalyst system includes a metal including at least one of the following materials: copper, chromium, platinum, rhodium, iridium, ruthenium, palladium, silver, nickel, cobalt or rhenium.

5. The fuel system as recited in claim 1, wherein said active catalyst system generates water and thermal energy from the liquid hydrocarbon fuel and the reducing agent.

6. A method of minimizing dissolved oxygen from within a fuel system comprising the steps of:

(1) injecting a reducing agent into a liquid hydrocarbon fuel containing a dissolved oxygen; and

(2) communicating the reducing agent and the liquid hydrocarbon fuel through an active metal catalyst system to minimize the dissolved oxygen within the liquid hydrocarbon fuel.

7. A method as recited in claim 5, wherein said step (1) further comprises the steps of:

injecting hydrogen into the liquid hydrocarbon fuel.

8. A method as recited in claim 5, wherein said step (2) further comprises the steps of:

generating water and thermal energy from the liquid hydrocarbon fuel and the reducing agent.

9. A method of minimizing dissolved oxygen from within a fuel system comprising the steps of:

(1) communicating a liquid hydrocarbon fuel containing a dissolved oxygen from a fuel tank;

(2) injecting a reducing agent into the liquid hydrocarbon fuel;

(3) communicating the reducing agent and the liquid hydrocarbon fuel through an active catalyst system to minimize the dissolved oxygen within the liquid hydrocarbon fuel; and

(4) communicating the liquid hydrocarbon fuel from said step (3) to a gas turbine engine.

10. A method as recited in claim 8, wherein said step (2) further comprises the steps of:

injecting hydrogen into the liquid hydrocarbon fuel.

11. A method as recited in claim 8, wherein said step (3) further comprises the steps of:

generating water and thermal energy from the liquid hydrocarbon fuel and the reducing agent.