Distillation: processes – separatory – Convective distillation with normally gaseous medium – e.g. – air
Reexamination Certificate
1998-12-17
2001-09-18
Manoharan, Virginia (Department: 1764)
Distillation: processes, separatory
Convective distillation with normally gaseous medium, e.g., air
C159S047100, C159SDIG001, C203S013000, C203S014000, C203S100000, C423S391000, C423S584000
Reexamination Certificate
active
06290820
ABSTRACT:
BACKGROUND OF THE INVENTION
In the field of aerospace propulsion, the widespread use of traditional hypergolic rocket engine propellants, such as hydrazine and nitrogen tetroxide, are being eliminated. Presently, there is a movement toward the development of inexpensive rocket engine fuel systems that use non-toxic propellants. High test hydrogen peroxide/kerosene offers similar performance per unit volume as Liquid Oxygen (LOX) and kerosene for Single Stage To Orbit (SSTO) vehicles. High test hydrogen peroxide has been employed as a rocket engine oxidizer for over half a century, and has been used in military rocket-assisted aircraft systems, due to the ease of handling and storing.
Rocket engines traditionally employ a chemical redox process requiring both an oxidizer and a fuel source to generate energy and hot gasses for propulsion. It is known that some oxidizers generate toxic gasses during the redox process. Therefore, an interest in alternative oxidizers that do not generate toxic gasses is of growing importance. Hydrogen peroxide is a leading candidate for use as an environmentally friendly oxidizer source.
Rocket engines are capable of consuming vast amounts of hydrogen peroxide. For example, it is predicted that some rocket engines may require over 1 million pounds of hydrogen peroxide per rocket launch. Thus, the market for highly concentrated hydrogen peroxide within the next 5-10 years could reach over 26 million pounds per year for the U.S. military market alone. These estimates are based upon current use by the Air Force and Navy in rocket propulsion and airborne laser applications. To date, there is a limited supply of hydrogen peroxide in necessary concentrations for rocket propulsion, and current engine developments are hindered by the high cost of obtaining sufficiently concentrated hydrogen peroxide, which at this time, is predominantly satisfied by importation.
Liquid oxygen, a cryogenic liquid has frequently been utilized, but presents many problems. For example, a common problem with liquid oxygen in rocket engines is that of “hard-start,” wherein inadequate ignition is provided to the fuel stream. Thus, a mixture of liquid oxygen and fuel can collect and ignite inside the rocket engine thereby causing the disintegration of the engine and launch vehicle. Rocket engines employing highly concentrated hydrogen peroxide can avoid this hazard entirely as hydrogen peroxide engines typically decompose the hydrogen peroxide into hot steam and oxygen gas, which is then mixed with the fuel. Propellants cannot accumulate in the engine due to the onrush of decomposed hydrogen peroxide gas. Previous methods of concentrating hydrogen peroxide have been accomplished by using an inert working gas and vacuum system within a fluorinated reaction vessel, see for example, Tillotson et al., U.S. Pat. No. 5,621,847. However, systems such as the one described in Tillotson et al., are not very economical as the design requires use of a vacuum. Also, such systems do not have the capability of using air to evaporate water from a dilute solution.
SUMMARY OF THE INVENTION
Thus, a need exists to provide inexpensive solutions in sufficient concentration that can be employed in rocket engine propulsion systems and other military and civilian applications. The apparatus and method described herein provides inexpensive concentrated solutions, such as hydrogen peroxide, at previously unavailable quantities, relatively quickly. This may have a profound impact on the U.S. space industry, where over a dozen new space start-ups have begun within the last five years.
The present invention provides an apparatus for concentrating a dilute solution. The apparatus includes a fluid dryer, a pump for compressing and moving a working fluid through the fluid dryer, a mass transfer device maintained at ambient pressure that is in fluid communication with the fluid dryer, and a heating source which is in contact with at least a portion of the mass transfer device. Preferably, the working fluid employed in the apparatus is air and the dilute solution is a dilute hydrogen peroxide solution. The apparatus of the invention may also include a pre-filter in fluid communication with the fluid dryer, and a spent working fluid transfer tube in fluid communication with the mass transfer device. Additionally, the apparatus may include a condenser in fluid communication with the spent working fluid transfer tube.
The apparatus of invention may further include a first transfer pump for moving a dilute solution into the mass transfer device. The dilute solution may be contained in a storage tank, wherein the storage tank is in fluid communication with the first transfer pump. The apparatus may further include a second transfer pump for moving a concentrated solution from the mass transfer device. The concentrated solution may be moved to a collection tank as the collection tank is in fluid communication with the second transfer pump. Additionally, the apparatus may include a third transfer pump for moving a purified solution from the condenser. The purified solution may be moved to a collection tank as the collection tank is in fluid communication with the third transfer pump. The apparatus of the invention may also include a combination flowmeter/valve wherein the flowmeter valve is in fluid communication with the fluid dryer and the mass transfer device.
A fluid dryer employed in the apparatus of the invention may be a cryogenic chiller, a refrigerated chiller, a desiccant dryer or an air/water vapor separating membrane. A mass transfer device employed in the apparatus of the invention may be a bubble column reactor plate, a structured packing air stripping column, a randomly dumped packing air stripping column or a falling film evaporator. A heating source used with the apparatus includes a heater and a heating medium. Preferably, the heating medium is water and is maintained at a temperature of about 70° C. to about 90° C. Preferably, the apparatus of the invention includes components described above and excludes an evacuating component.
A method for concentrating a dilute solution of the invention is also provided. The method includes (a) providing an apparatus that contains a fluid dryer, a pump for compressing and moving a working fluid through the fluid dryer, a mass transfer device in fluid communication with the fluid dryer, and a heating source which is in contact with at least a portion of the mass transfer device, (b) drying the working fluid to yield a low dewpoint working fluid, and (c) contacting the low dewpoint working fluid with the dilute solution to yield a concentrated solution.
Preferably, the contacting step, step (c) in the method, is carried out at ambient pressure. More preferably, the dilute solution is a dilute hydrogen peroxide solution. Most preferably, the dilute hydrogen peroxide solution has a concentration of less than 80% by weight percent, and a concentrated hydrogen peroxide solution has a concentration of at least 80% by weight percent. Typically, the method of the invention employs a low dewpoint working fluid that preferably has a dewpoint of about −40° C. to about −75° C.
Another method for concentrating a dilute solution of the invention is also provided. The method includes (a) providing an apparatus that contains a fluid dryer, a pump for compressing and moving a working fluid through the fluid dryer, a mass transfer device in fluid communication with the fluid dryer, and a heating source which is in contact with at least a portion of the mass transfer device wherein the working fluid is air, (b) drying the working fluid to yield a low dewpoint working fluid, and (c) contacting the low dewpoint working fluid with the dilute solution at ambient pressure to yield a concentrated solution.
Yet another method for concentrating a dilute solution of the invention is also provided. The method includes (a) providing an apparatus having a fluid dryer, a pre-filter having an inlet and an outlet wherein the outlet of the pre-filter is in fluid communication with the flu
Iowa State University & Research Foundation, Inc.
Manoharan Virginia
Mueting Raasch & Gebhardt, P.A.
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