Patent Application
20210246020
This invention relates generally to a method of using a system for generating hydrogen gas. More particularly, the present invention relates to a chemical method of in-situ on-demand hydrogen gas generation.
Fuel cells usually use Hydrogen gas as the fuel. Hydrogen is usually stored at high pressure. Transportation of hydrogen with pipelines or tankers is expensive and unsafe. Logistics of hydrogen availability is considered to be a bottle-neck against wide-spread deployment of fuel cells.
This invention provides a method to produce hydrogen in-situ and on-demand near the fuel cell. A set of chemical reactions happen when water is dripped on a mixture of solid chemical compounds and hydrogen is released as a result. Hydrogen thus produced can be pressurized, if necessary, and provided to fuel cells. The rate of water-drip can be regulated so as to control the H2 generation rate.
Generation of Hydrogen by reaction of alkali metals and their hydrides with water is known in chemistry text books.
U.S. Pat. No. 9,985,308 to Iftime, et al. uses encapsulants enclosing metal hydrides for controlling the rate of reaction.
In one example, Group I alkali metals, such as Lithium, produce 1 mole of H2 for every 2 moles of metal used.
2Li+2H2O→2LiOH+H2 (1)
In another example, Group II alkali metals, such as Calcium, produce 1 mole of H2 for every 1 moles of metal used.
Ca+2H2O→Ca(OH)2+H2 (2)
Group I alkali metal hydrides, such as LiH, produce 1 mole of H2 for every 1 mole of metal hydride used.
LiH+H2O→LiOH+H2 (3)
Group II alkali metal hydrides, such as CaH2, produce 2 moles of H2 for every 1 mole of metal hydride used. See equation 4 below.
In the examples above, 0.5 to 2 moles of H2 is produced for each mole of alkali metal or alkali metal hydride used.
The energy density—defined as the ratio of weight of hydrogen generated to the moles of the solid reactant is of primary concern in many applications, such as military, mobile applications, and biomedical applications.
The present disclosure provides a chemistry that produces more than 2 moles of H2 per mole of metal or metal hydride.
A method of using a system for generation of hydrogen gas is disclosed. The system comprises a tank, a pump, a first tube, a second tube, one or more capsules, a tank sensor assembly, and a processing system. The method comprises the steps of preparing one or more capsules; placing the one or more capsules in the tank; supplying a wet reactant to the tank; and collecting hydrogen gas from the tank.
A Stoichiometric ratio of Aluminum powder and Ca(OH)2 powder are mixed and put inside a capsule. The capsules are made out of water-soluble materials. Water-soluble materials are widely available from pharmaceutical industry. In a predetermined size of a capsule, x grams of Aluminum powder and y grams of Ca(OH)2 ground granules are placed in capsules. The stoichiometric ratio of x:y is determined by the chemical reaction in Equation 6. The ratio may be shifted left or right depending on the desired rate of reaction. The capsules are placed in a tank or a bottle. Water is injected with a metered pump into the tank or bottle.
In another implementation, the dry reactant powders are mixed with an ionic liquid with limited hydrophilicity to the consistency of a slurry. When water is added to such slurry, the film of such ionic liquid controls the amount of water that transgresses to the dry reactants, thus controlling the rate of reaction. One example of such limited hydrophilicity ionic liquids is the class of ionic liquids containing the cation bis(trifluoromethanesulfonyl)imide [(CF3SO2)2N]− otherwise known in the field as TFSI or NTF2, are abbreviations for the cation. Many amine-based anions can be attached to this cation that serve the purpose of limited hydrophilicity. One such example is BMIM, which has a chemical formula: 1-Butyl-3-methylimidazolium. The full ionic liquid is therefore BMIM-NTF2.
The generated H2 is optionally provided to a fuel cell, which generates electrical energy by taking oxygen from the atmosphere and combining it with hydrogen electrochemically. The generated H2 is optionally provided to skin or digestive track of a patient.
If the generated hydrogen is used in a fuel cell, it is important to control the rate of generation of hydrogen so that the fuel cell is not starved for or has an excess of hydrogen gas when it is serving its electrical load. In one example, generation of hydrogen is controlled in the following manner:
The flow of water activates the reaction. Firstly, the polymeric wall of the capsule material dissolves in water, exposing the solid reactants to water, allowing the hydrogen gas generation to take place.
The reactions are exo-thermic. Unless the rate of water input is controlled, the system may heat up to boiling and create a hazardous condition. Besides, the copious amount of hydrogen gas produced by unregulated addition of water may not be immediately consumed by the fuel cell, resulting in surplus hydrogen gas escaping through the fuel cell output port—thus resulting in wastage of the fuel.
On the other hand, the fuel cell usually services an electrical load. If the load requirement is lower than the power than can be generated by the produced Hydrogen, then again, the surplus H2 will flow out of the fuel cell output port, resulting in wastage of fuel.
Therefore, the process of addition of water must be controlled as a function of the reactant temperature (Th), and the Fuel cell load voltage (V) and Fuel cell load current (I).
In examples of the present disclosure, a one-way valve 123 is disposed at an upstream location of the inlet hole 114 so that wet reactant flows through the one-way valve 123, through the inlet hole 114, then entering the tank 110. The one-way valve 123 prevents fluid or air flowing from the tank 110 to the pump 120.
In examples of the present disclosure, a one-way valve 125 is disposed at an upstream location of the second end 139 of the second tube 124 so that generated hydrogen from the tank 110 flows through the one-way valve 125 to the second end 139 of the second tube 124. The one-way valve 125 prevents fluid or air flowing from the second end 139 of the second tube 124 to the tank 110.
In examples of the present disclosure, the tank sensor assembly 160 is disposed in the tank 110. The tank sensor assembly 160 comprises a first temperature sensor measuring the temperature in the tank 110, a second temperature sensor measuring the temperature of the first dry reactant, a third temperature sensor measuring the temperature of the second dry reactant, a flow sensor to measure a flow rate of the incoming wet reactant entering the tank 110, and a gas sensor to measure the amount of hydrogen gas generated.
The second end 139 of the second tube 124 optionally deliver hydrogen gas to a compressor 192, skin 194 of a patient, a digestive track 196 of a patient, or a fuel cell 198. Because of being optional, the compressor 192, the skin 194 of a patient, the digestive track 196 of a patient, and the fuel cell 198 are shown in dashed lines. The compressor 192 increases the pressure of the hydrogen gas.
The one or more capsules 140 contains predetermined dry reactants. In examples of the present disclosure, the one or more capsules 140 are water-soluble. In one example, the one or more capsules 140 comprises a first capsule 142 and a second capsule 144. The first capsule 142 contains calcium hydride. The second capsule 144 contains aluminum.
In another example, the one or more capsules 140 comprises a first capsule 500 of
In still another example, the one or more capsules 140 comprises a first capsule 400 of
In examples of the present disclosure, powdered calcium hydride is thoroughly mixed with powdered Aluminum in weight ratio of 42:65 to create a fuel mixture. The stoichiometric ratio according to Equation 6 is 42:54. The surplus amount of Aluminum is provided to increase the rate of reaction of the 2nd step described as Equation 5. Average size of calcium hydroxide powder is 10 micron. Average size of aluminum powder is 1 micron. The advantage of smaller powder size is to increase overall powder surface areas, with a controlled overall powder weight, for reaction.
In one embodiment of the present disclosure, the fuel mixture is used as is in the reaction chamber with water.
In another embodiment of the current disclosure, the fuel mixture is further mixed with the ionic liquid BMIM-NTF2 so as to form a slurry. The weight ratio of calcium hydroxide:aluminum:BMIM-NTF2 is 42:65:25. The slurry is to be dispensed under a dynamic pressure into the reaction chamber for reaction with water.
In yet another embodiment of the current disclosure, the fuel mixture is encapsulated in water soluble capsules, to be used in the reaction chamber for reaction with water.
In examples of the present disclosure, the hydrogen inlet 232 connects to the second end 139 of the second tube 124 of the system 100 of
In examples of the present disclosure, the fuel cell sensor assembly 258 is disposed in the vessel 220. The fuel cell sensor assembly 258 comprises a temperature sensor to measure the temperature in the vessel 220, a plurality of gas flow sensors to measure a flow rate of the incoming hydrogen, a flow rate of the outgoing hydrogen, a flow rate of the incoming oxygen, and a flow rate of the outgoing oxygen.
In the implementation of the control of the generation of H2 and the fuel cell application, electrical measurements of “Th value” 322, “V value” 324, and “I value” 326 are conditioned as necessary and then fed to into the processor 300. Here, “Th value” 322 is a temperature measured in the tank 110 of
An example of the logic implementation when the ambient temperature is 25 degrees C. is:
If (Th<35 degrees C. AND V<0.8 Volt): Turn Pump ON
If (Th>60 degrees C. OR V>1.1): Turn Pump OFF
If (V×I)>Pmax: Turn Pump OFF
Here, Pmax is the maximum allowable power.
In examples of the present disclosure, the condition 342 is used to control the flow rate of the incoming wet reactant into the tank 110 of
In block 602, one or more capsules 140 of
In block 604, the one or more capsules 140 of
In block 606, a wet reactant is supplied to the tank 110 of
In examples of the present disclosure, the reaction process consists of a two-step reaction of mixture of an alkaline (Group II) metal hydride and a Group III metal, such as aluminum. All solid reactants are preferably in powder form, reacting with water.
In examples of the present disclosure, the alkaline metal hydride is Calcium Hydride. Other alkaline and alkali metals whose hydrides that will also work include Lithium, Sodium, Magnesium, and Potassium.
In the first reaction step, CaH2 reacts with water to generate H2 gas and Calcium Hydroxide Ca(OH)2. Ca(OH)2 is soluble in water and makes the water alkaline. In the second reaction step, Ca(OH)2 reacts with aluminum powder to produce even more H2 gas.
1st reaction step: CaH2+2H2O→Ca(OH)2+2H2 (4)
2nd reaction step: Ca(OH)2+2Al+4H2O→Ca(AlH2O3)2+3H2 (5)
The resultant chemical reaction is:
CaH2+2Al+6H2O→Ca(AlH2O3)2+5H2 (6)
Thus, for each mole of Calcium Hydride, 5 moles of Hydrogen are generated. This is far higher than 0.5-2 Moles of H2 per mole of metal or hydride. The addition of Aluminum power is considered a small cost to pay for this additional hydrogen yield, since Aluminum is far cheaper than hydrides. Block 606 may be followed by block 608.
In block 608, the generated hydrogen gas is collected through the second tube 124 of
Those of ordinary skill in the art may recognize that modifications of the embodiments disclosed herein are possible. For example, a number of capsules in the tank 110 may vary. Other modifications may occur to those of ordinary skill in this art, and all such modifications are deemed to fall within the purview of the present invention, as defined by the claims.
The disclosure made in the U.S. Pat. No. 9,985,308 to Iftime, et al., and the disclosure made in International Patent Application No. WO2003016165A1 to Scott, et al. are hereby incorporated by reference.
