Patent Application
20080307794
The present disclosure relates to “alternative fuels,” and more particularly to the use of guanidine-based fuels in operating combustion engines and furnaces.
Fossil fuels are generally known to be produced in large quantities today with common acceptance in view of its recognized high energy density and present availability and acceptable cost of production. Accordingly, diesel and/or gasoline fuels have been commonly employed as the fuels of choice for various engine applications. However, given that the availability of fossil fuels may diminish, a portion of the industry has more recently begun to explore alternative fuels.
Hydrogen has received some attention as an alternative fuel. Various representatives of the industry, however, have suggested that neither compressed gaseous hydrogen nor its liquefied elemental form may likely be deemed sufficiently economical, practical and safe for offering hope as a viable alternative fuel.
Carbon chemistry based approaches for alternative fuels have likewise been receiving some attention in applications for diesel and spark-ignition engines. For example, “bio-diesel fuels” may be known as an alternative fuel for diesel engines that is usually derived from various vegetable oils treated with ethanol or methanol. For spark-ignition engines, on the other hand, ethanol and methanol may be recognized more directly as the alternative fuels. These various carbon chemistry based alternative fuels may also be know for powering other forms of combustion engines such as turbines. While offering a possible alternative, the carbon chemistry based alternative fuels, however, has been critiqued due to various considerations, which include for example the viability of their supplies, which could ultimately depend on surplus of agricultural and organic waste. Further, the production costs of such carbon chemistry based alternative fuels may also affect its acceptance as a viable alternative fuel.
Ammonia (NH3) may be known as yet another type of alternative fuel that is nitrogen-based. As may be recognized, at least herein by way of this disclosure, it can offer an energy density of about 5.0 kWhr/kg for the fuel alone, which is greater than the incentive target of 3.0 kWhr/kg (total storage system) recently proposed to the industry for the year 2015. Ammonia may be liquefied at modest pressure (−10 atmospheres) and in an ambient temperature for a density of about 0.65 kg/l, which in turn may be further quantified for a volume energy density of about 3.25 kWhr/l (i.e., for the fuel alone). Storage containers may be readily available for storage of the ammonia for its integration with vehicles of combustion engines.
When using ammonia for powering combustion systems, a low flame propagation velocity of the ammonia relative to that of conventional fuels may require some design consideration. Some within the industry may simply limit use of ammonia fuels to applications capable of accommodating the low flame velocity. For example, it may be employed in slow internal combustion engine applications or in alternative turbine applications. As recognized herein, therefor, the rate of fuel burn for such applications is not as stringent as may otherwise be required for fast internal combustion engines, wherein the fuel may be expected to burn before a piston travels down the cylinder. In the context of turbines, however, it may be understood that the fuel burn simply serves to provide and maintain a pressure within a given pressure vessel from which gasses may operatively flow to spin a turbine. Accordingly, a fuel-air mixture for combustion may have a relatively long period of time for reaction before having to exit and spin the turbine.
Others may choose instead to enhance the combustion or rate of flame velocity of the ammonia. In a particular example, a portion of the ammonia may be cracked to form hydrogen and nitrogen. The hydrogen may then be used to accelerate flame propagation of the remaining ammonia composition. Where the hydrogen remains mixed with the remaining ammonia, it will serve to accelerate the flame propagation in the mixture given that the flame propagation of hydrogen is quite fast so as to ignite the surrounding ammonia. In another case, the hydrogen may be separated from the ammonia, e.g., by means of a semi-permeable membrane. Subsequently, the extracted hydrogen may be injected into a combustion chamber when a piston is near its top-dead-center position wherein the ammonia is compressed together with the air. Upon injection, the hydrogen can assist ignition, which may be effected by either the compression itself (as a “diesel mode”) or by spark (as a “gasoline mode”) depending upon the compression ratio operability of the internal combustion engine.
One draw-back to ammonia fuel systems, however, concerns the highly toxic nature of ammonia. Anhydrous ammonia is an extremely toxic substance. As a gas, its immediate danger to health and life, IDHL, threshold is merely 500 parts per million by volume in ambient air. Assuming a density of ambient air of approximately 1 kg/m3 and a molecular weight for ammonia of 17 compared to more than 28 for the air, each kilogram of ammonia that escapes from a storage tank could render more than 3200 m3 of air uninhabitable. A quantity of ammonia sufficient to fuel an automobile or a truck, say for example an equivalent to 60 gallons of gasoline, might require storing more than 342 kg ammonia. Accidental rapture of an ammonia fuel storage tank of such size could, thus, produce a lethal and slowly rising cloud tilling as much as 1,000,000 m3 of air.
Urea has also been proposed as another possible alternative fuel. It may be known as a relatively safe material for the storage of ammonia. The ammonium may be subsequently released from the urea by way of reaction (1) below:
CO(NH2)2+H2O→2NH3+CO2 (1)
The energy density of aqueous forms of urea solution may generally be understood below the density of that for pure solid urea which is about 1.34 kg/l. Accordingly, the energy density per unit volume of such urea-based fuel may be understood to fall below volumetric energy density targets as proposed for the industry and market.
Guanidine has been proposed as yet another type of nitrogen-based alternative fuel. See International Publication No. WO 2005/108289 A2 published Nov. 17, 2005 (from International Appl. No, PCT/US2005/015920, filed May 3, 2005). Such guanidine based alternative has been recognized with a capability of reducing overall emissions of greenhouse gases. It may also be recognized with the possibility of alleviating some other concerns associated with fossil fuels, such as various problems and risks associated with the extraction and delivery of fossil fuels. For example, the conventional fuels are known to pose possible carcinogenic risks. Accordingly, they have often required expensive procedures for clean-up when spilled, Guanidine, on the other hand, may be characterized in liking with a fertilizer, if accidentally spilled, therefore, it may be readily addressed by a procedure that may be as simple as washing it away with water.
According to an embodiment of the invention, a guanidine based fuel delivery system and method of powering a combustion engine or furnace may be operable to supplying a guanidine-based composition consisting substantially of water, ethanol and guanidine into a reactor chamber. Guanidine and water of the guanidine-based composition may react in the reactor chamber to produce ammonia and carbon dioxide. The products from the reactor chamber may be delivered to a combustion chamber of the combustion based energy conversion system and combusted therein. A controller may control the injecting of product from the reacted composition into the combustion chamber according to at least one attribute of the group consisting of: a level of power predetermined for desired operation of the combustion based energy conversion system, a performance parameter of the combustion based energy conversion system determined during operation thereof, and a concentration determined for at least one of the reactants/products in the reactor chamber and the reactants/products from the combustion chamber.
According to another embodiment, a method of energy conversion may comprise supplying a composition comprising guanidinium borohydride and reacting the composition with water and forming hydrogen, ammonia, carbon dioxide and boric acid. At least a portion of the ammonia and hydrogen resulting from the reaction may then be oxidized for releasing energy, while forming water and nitrogen.
In another embodiment, a fueling system may comprise a mixture container to receive guanidine from a guanidine source and ethanol from an ethanol source. First and second metering devices may be variably operable by electrical signaling to meter guanidine from the guanidine source and ethanol from the ethanol source respectively to the mixture container. A controller may be operable to determine a concentration of the ethanol in the ethanol source and to affect at least one of first and second control signals to the first and second metering devices respectively for establishing a ratio of the guanidine to ethanol delivery to the mixture container based on the concentration of ethanol determined.
In yet a further embodiment, an engine control system may comprise an analysis module operable to analyze the composition of a guanidine/ethanol based fuel that is to power an engine, and a control driver operable to adjust at least one of the engine parameters based on the analysis to affect the efficiency for the fuel burn in the engine.
Subject matter for embodiments of the present invention may be further understood by reference to the following detailed description when read with reference to the accompanying drawings, in which:
In accordance with an embodiment of the present invention, referencing
Further referencing
Reactor 102, with reference to
In a further embodiment, a thermal relationship may be configured between (i) combustion chamber 104 and (ii) the fluid intake for the reactor chamber and/or perhaps even relative to the walls of the reactor-chamber 102 directly. In yet a further embodiment, a portion of the previously produced product from the reacted composition may be held in reserve and subsequently retrieved and burned for specific purposes of heating the fuel composition in the reactor. For example, during a cold start procedure, the reserved product (such as ammonia or perhaps even hydrogen obtained by cracking) may be retrieved and burned to heat the reactor.
In a further embodiment, reactor 102 may also include an electrical heater element 374 that may be operable to further heat reactants of the fuel composition within the reactor. When additional heat may be needed to heat the composition, electrical energy may be supplied to the heater element. For example, during a cold-start of the engine or furnace, heater element may be activated for heating the guanidine-based fuel composition and facilitate the reaction of guanidine with water. During normal operation, on the other hand, the electrical energy supplied to heat the reactor may be reduced or regulated to sustain a target temperature as may have been predetermined for desired rate of reaction in the reactor and production of product from the reacted composition.
Further referencing
In the case of an enzyme, on the other hand, it may comprise an enzyme capable of facilitating the reaction of guanidine and water. In a particular embodiment, it may comprise arginase and urease. The arginase may catalyze the reaction of guanidine with water to from ammonia and urea; while the urease may facilitate the reaction of urea with water for the formation of ammonia and carbon dioxide. These enzymes may catalyze the reaction at a temperature of between about 0° C. and about 60° C. Such enzyme can be provided in a filter within the tank which may be operable to prevent the enzyme from leaving but be permeable to the gases formed. More typically, however, the enzyme is immobilized on the replaceable cartridge 370 which may be defined at least in part by a substrate of ion exchange resin, ceramic or polymeric materials.
Continuing with further reference to
The reaction of guanidine therein with water can be described by the following equation (2):
CN3H5+2H2O→3NH3+CO2(+96.3kJ/mol) (2)
The reaction and release of energy from guanidine may be accomplished in two steps. In the first step, guanidine reacts with water to from ammonia and urea. The urea may then react with water to form ammonia and carbon dioxide, hi operation, this reaction may be performed at a temperature ranging between about 50° C. and about 240° C. and a pressure ranging between about 1 ambient atmosphere and about 50 standard atmospheres. It may be noted that the first reaction is exothermic while the second reaction is endothermic. The endothermic reaction may take place at a relatively low temperature (˜100° C.), so the heat needed for this step can be obtained from the waste heat that is normally exhausted to the environment from the engine, turbine, or boiler. In some applications, it may be augmented from other sources such as the combustion or oxidization of hydrogen, or perhaps even sourced from a heating element energized by electrical energy such as a battery as may be utilized to assist an initiation of the reaction.
Returning with reference to
In operation according to an embodiment of the invention, the controller 120 may be preconfigured or programmed to be operable to adjust a valve or similar fluid regulator device of delivery means 160 between fuel storage 103 and combustion chamber 104. For example, assuming that the exhaust is determined to contain too much nitrous oxides, the controller in turn may adjust the delivery means to the combustion chamber to provide additional gas thereto for potential excess ammonia so as to allow for the removal of the nitrous oxides by the residual ammonia in the exhaust.
In a further embodiment, the controller may sense a concentration of one of the components of the guanidine, ethanol and water composition in the fuel container 101 and responsive thereto, act to effect recovery of water from the exhaust system by water vapor recovery means (not shown). The recovered water, in turn, may then be recycled to the fuel container 101 or alternatively reactor 102 for purposes of affecting a refinement of the stoichiometric ratios between the guanidine and water portion of the guanidine-based composition. Accordingly, the exhaust resulting from the combustion chamber 104 may be kept within a more acceptable range of ammonia emissions and/or nitrous oxide emission.
In accordance with a particular example, a guanidine-based fuel may be referenced relative to a solution in liking with an E85 type fuel, which may reference a fuel type of 85% ethanol. Generally, the customary ethanol applications required ethanol of nearly 200 proof (100%) purification, so as to prevent possible phase separation of the solution by residual waters therein when it is mixed with the customary hydrocarbon-based liquid fuels. But, such purification processes may be recognized as impacting resulting fuel cost.
It may be understood, however, that purification levels may be more readily obtained at purification levels of 160 to 190 proof. With addition of guanidine and/or urea encapsulated guanidine, the residual water in of the lower proof ethanol may react with the guanidine to form ammonia. The ammonia produced from the addition of the guanidine to the 180-proof ethanol in turn may be completely dissolved at near atmospheric pressure and 25° C. within the remaining ethanol.
In further examples of higher water concentrations, a larger pressure may be employed to dissolve the ammonia within the ethanol, assuming that all of the water is consumed by the reaction with the guanidine. Upon combustion, the ammonia will react with oxygen to yield nitrogen and water with the release of energy. Accordingly, it may be recognized that the added expense associated with the production of the more customary ethanol may be reduced in the absence of the additional steps otherwise required to produce the purified forms of ethanol.
In a further embodiment of the present invention, referencing
In a particular embodiment of operation, controller 220 may sense via sensor 130 nitrous oxide in the exhaust from combustion chamber 106. Responsive to sensing the nitrous oxide, the controller may enable a valve between the gas collection chamber 205 and the path of the exhaust for enable release of a finite amount of ammonia into the exhaust system, such into ammonia and nitrous oxide reaction chamber 106 disposed in the exhaust path from the combustion chamber 104. The added ammonia may serve to react the nitrous oxide with the ammonia to produce nitrogen and water. This water, in turn, may then be recovered if desired for recycling into the reactor.
In a further embodiment, the controller responsive to sensing an increase of nitrous oxide in the exhaust may act to lower the internal operating temperature of the combustion engine, which may serve to lower the nitrous oxide emissions.
For recovery of water from the exhaust, various water recovery embodiments may be used. For example, such water recovery systems may incorporate available water removal membranes, filters, cold traps and/or gas expansion exhaust manifold designs.
In accordance with a further embodiment of the invention, referencing
In a particular example, 180 proof ethanol (90% ethanol by volume) may be sensed in the ethanol source. In may be understood therefore a litter of such may comprise 900 mL of ethanol and ˜100 mL H2O per liter. Stoichioraetricaliy, the 90% ethanol solution with 10% water may be shown with about 90 gm H2O/(0.9 liter). Complete hydrolysis with guanidine may be calculated as: 90 gm/18 gm= 5.0 moles H2O for reacting with about 5.0/2=2.5 moles guanidine. This quantity of guanidine may be determined as representative of 2.5*59 gm/mole=147 gm. At a density of 1.32, the volume of the guanidine would be 112 mL, so one could therefore add such amount of guanidine to the ethanol (for ˜11% guanidine by volume) for a stoichiometric mixture.
While certain exemplary features of the embodiments of the invention have been illustrated and described above, it may be understood that various modifications, substitutions, changes and equivalents may now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such embodiments and changes as fall within the spirit of the invention.
This non-provisional application claims priority and benefit of U.S. Provisional Application Ser. No. 60/813,388 filed Jun. 14, 2006, and U.S. Provisional Application Ser. No. 60/903,439 filed Feb. 25, 2007, each of which are hereby incorporated by reference in their entirety.
