Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Utilizing subatmospheric or superatmospheric pressure during...
Reexamination Certificate
2001-03-30
2003-04-08
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Utilizing subatmospheric or superatmospheric pressure during...
C205S343000, C205S637000, C205S638000, C205S639000, C204S252000, C204S263000, C204S264000, C204S265000, C204S266000, C204S276000, C429S047000, C429S047000, C429S047000, C422S129000, C422S212000, C422S255000, C422S305000
Reexamination Certificate
active
06544400
ABSTRACT:
BACKGROUND OF THE INVENTION
A critical need exists for safe portable hydrogen sources. Fuel cells that transform chemical energy to electrical energy by reacting gas or liquids in the presence of an electrolyte, electrodes and a catalyst, are currently limited in use and performance by the fuel supply.
Our previous patents, U.S. Pat. No. 4,673,624 “Fuel Cell” and U.S. Pat. No. 5,631,099 “Surface Replica Fuel Cell, and U.S. Pat. No. 5,759,712 “Surface Replica Fuel Cell for Micro Fuel Cell Electrical Power Pack”, described a method of forming a fuel cell that efficiently utilizes expensive catalysts, is easily mass produced, and is packaged for portable electronics. When fuel cells can utilize hydrogen as the fuel they can obtain superb power performances. There are many other applications that would benefit from a safe portable pure source of hydrogen; these include jewelry-welding torches, miniature-welding torches. A co-pending patent application, U.S. Ser. No. 09/208,745, describes how the MICRO-FUEL CELL™ can be packaged in portable electronics. A co-pending patent application U.S. Ser. No. 09/210,792 describes how the non-bipolar fuel cells can be packaged to form larger power supplies.
Hydrogen generators have been explored by Millennium Cell (1 Industrial Way West, Eatontown, N.J. 07724). They use pumping of NaBH
4
+H
2
O+NaOH solutions, hereafter referred to as “fuel” throughout this document, on contact with Ru catalytic surfaces to produce hydrogen and sodium borate by hydrolysis. They also use electrically heated catalytic surfaces and control mechanisms for production of hydrogen from the fuel. The principal concept is that these techniques work well with large-scale systems, but are unsuitable for small devices where active systems are cost and size prohibitive. Also, the larger systems use gravitational orientation to function, while small and portable systems often need to work in any position.
An advance in hydrogen sources is described in U.S. Pat. No. 5,804,329 utilizing a process of hydrolyzing a mixture of NaBH
4
, NaOH and H
2
O in contact with a cobalt catalyst by acidifying the solution. Other systems are described in U.S. Pat. No. 3,133,837 and U.S. Pat. No. 3,649,360 to extract hydrogen from chemical hydrides such as calcium hydride, lithium hydride, magnesium hydride, and sodium hydride meter-out water to the hydrides and produce hydrogen. The particular problem with simply making hydrogen by a controlled mixture is that the reaction is typically highly exothermic and can proceed violently, or form intermediate compounds. The general experience with these sources is that they can be unsteady or require active control systems.
The process described in U.S. Pat. No. 5,804,329 utilizes a base such as NaOH dissolved in water to stabilize the dissolved NaBH
4
. The highly basic environment inhibits the spontaneous hydrogen evolution from NaBH
4
dissolved in water. When the solution makes contact with a catalyst such as cobalt or ruthenium, or is acidified, hydrogen is evolved at a steady regular rate. Thus, the basic mechanism for a controllable hydrogen source is in place if the contact between the catalyst and the solution is controlled. One focus of the present invention is to build a small portable packaged system that has this control mechanism based on consumption feedback.
Applications for this hydrogen source to provide hydrogen to small fuel cells for power applications include devices that are currently powered by batteries, especially rechargeable batteries. The present invention addresses a host of problems existing in the art.
Related Art
U.S. Pat. No. 3,133,837 uses closed circulation of produced hydrogen to circulate water from the fuel cell to the metal hydride supply to generate more hydrogen. This system is started by an injection of water into the metal hydride supply. Water vapor recovery from the fuel cell is necessary to maintain the performance of this system. Regulation of the hydrogen production in this system is by hydrogen pressure controlling the flow rate of a hydrogen circulation pump. The diffusion time of water to the active decomposition sites causes a delay time in the production, and a subsequent overshoot response. Most of the metal hydride/water decompositions are highly exothermic which can lead to unstable hydrogen production. This system is considered too complex to be used in small portable hydrogen supplies.
U.S. Pat. No. 3,649,360 uses a pressure-controlled interface in a wicking system to deliver water in a pressure-regulated manner to hydrides that decompose to generate hydrogen. In addition, they also describe a membrane separation between the reactants before use as a method of storing the generator. Regulating the water to metal hydrides has been found to be difficult. The diffusion time of water to the active decomposition sites causes a delay time in the production, and a subsequent overshoot response. Most of the metal hydride/water decompositions are highly exothermic which can lead to unstable hydrogen production. A key problem is that the exothermic output increases the decomposition rate and steam production, which in turn involves more of the metal hydride in production. These two effects accelerate and amplify the hydrogen production overshoot and can lead to over-pressurization and explosions.
U.S. Pat. No. 5,702,491 uses the heating of chemical hydrides to generate hydrogen on demand in a portable generator. This thermally regulated and insulated hydrogen generator may have a time response insufficiently fast for small portable devices. The insulation of the generator can keep it from being dense enough to result in a high energy per unit volume needed in small portable devices. If the insulation is made thin and compact, the device will take a large fraction of the output power to run, resulting in low system efficiency.
U.S. Pat. No. 5,509,901 illustrates a pressure responsive device to deliver fluids. A mechanical pressure device such as this could deliver fuel to catalytic reactor. But this system appears to be a very complex mechanical scheme that could be expensive to manufacture, take up a large fraction of the generators volume, and lead to a lower energy per unit volume.
U.S. Pat. No. 5,997,821 presents a gas amplifier device that uses electrochemical generation of gas as the control mechanism. The generated gas is amplified by a mechanical member making contact with chemical reactants to produce product gas with much greater volume than the initiating gas production. The gas production is used to pressurize a fluid and deliver a controlled amount of a liquid or gas, such as medical fluids, fragrances, insecticides, hydrogen, and lubricants. This system depends on an electrical power input to run. Thus without an initiating source of electricity it would not be self-starting. If this device were used to generate hydrogen gas for a device that needs a constant pressure supply of hydrogen, there would need to be an additional coupling between the hydrogen pressure and the electrical input into the electrochemical cell. This may be error prone and expensive for small portable hydrogen generators.
U.S. Pat. No. 5,599,640 describes an alkaline fuel cell that uses NaBH
4
, KBH
4
, LiAlH
4
, KH, NaH, and other hydrides in an alkaline electrolyte (NaOH or KOH) to generate hydrogen. Some of the generated hydrogen is stored in Misch metal hydride alloys such as zirconium alloyed with Mn, Co, Ni, and Al in the anode. The electrolyte of the fuel cell is in common with the alkaline electrolyte and products of the fuel supply. The buildup of products in the fuel supply interferes with the operation of the fuel cell. The alkaline fuel cell if using air as the source of oxygen will absorb carbon dioxide from the atmosphere. Absorption of water in the alkaline electrolyte can cause insoluble precipitates to form inside the electrodes and interfere with the operation of the fuel cell. The position of the electrolyte: In the fuel cell, and critically the oxygen electrode, can be affected by the pr
DeJohn Marc D.
Hockaday Robert G.
Navas Carlos J.
Turner Patrick S.
Vaz Heathcliff L.
Bell Bruce F.
Creighton Wray James
Manhattan Scientifics, Inc.
Narasimhan Meera P.
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