Patent Application
20110167798
1. Field of the Invention
The present disclosure generally relates to emission control systems. The present disclosure more specifically relates to sequestering emissions from an engine during operation.
2. Description of Related Art
The major components of engine exhaust are nitrogen, water vapor, and carbon dioxide. For example, 100 grams (g) of exhaust gas may include approximately 73 g of nitrogen gas, 12 g of water vapor, 14 g of carbon gas dioxide, and 1 g of trace pollutants. Water vapor can be condensed from exhaust gas according to standard techniques and safely returned to the environment. Trace pollutants can be removed using emissions control systems. Nitrogen, without the carbon dioxide, could be safely returned to the atmosphere. Carbon dioxide, which is a greenhouse gas, could be stored instead of released to the atmosphere. Unfortunately, a problem with returning nitrogen to the atmosphere without the carbon dioxide is that it is difficult to separate nitrogen gas from carbon dioxide gas and typically requires large amounts of energy. There is also a problem with storing carbon dioxide gas, in that tanks having large volumes are required for handling, transportation, and storage.
As a ship consumes fuel during a voyage, the weight and balance changes to a point that the ship may become unstable. Formerly, ships added ballast in the form of seawater to fuel tanks to replace the consumed fuel. The seawater was discharged from the fuel tanks to take on new fuel when the ship reached port. Unfortunately, some fuel was inevitably discharged along with the seawater ballast. This pollution has become an unacceptable form of pollution. Currently, the practice of mixing seawater and fuel in tanks is largely outlawed in most jurisdictions. Separate tanks are now required for seawater ballast and for fuel. Unfortunately, the ballast tanks require a substantial volume within the ship that could otherwise be used for cargo. Moreover, the requirement of separate ballast and fuel tanks inevitably results in a shift in the weight and balance for the ship as fuel is consumed in a fuel tank at a first position on the ship while a ballast tank is filled with seawater at a second position on the ship. This increases the difficulty in designing a fuel/ballast system for achieving optimal weight and balance in all axes for various configurations of fuel consumption. Consequently, the total load and operating envelope of a ship are decreased.
In an embodiment of the presently claimed invention, a liquefied natural gas (LNG) tank provides natural gas for burning in an engine. Exhaust emitted from the engine includes nitrogen gas, water vapor, and carbon dioxide. The exhaust gas may be cooled using heat exchange techniques, for example, reverse flow heat exchangers. Water may be separated from the exhaust gas using condensation techniques. Carbon dioxide may be separated from the remaining nitrogen. For example, a heat exchanger in combination with a turbo charger may be used to liquefy the carbon dioxide gas at high pressures and separate the liquid carbon dioxide from nitrogen gas. The liquid carbon dioxide may be sequestered or used industrially. Separated carbon dioxide gas may be further cooled to solid carbon dioxide and stored in the LNG tank, replacing the LNG burned in the engine. The solid carbon dioxide in the LNG tank may be used as ballast. Alternatively, the solid carbon dioxide may be sequestered using storage technology or used industrially.
In an embodiment of the presently claimed invention, a LNG system is provided for producing power and sequestering emitted carbon dioxide. The system comprises an engine configured to use natural gas for fuel and to emit an exhaust gas including carbon dioxide. The system also includes a LNG tank configured to store LNG and solid carbon dioxide. The system further comprises a first reverse flow heat exchanger in fluid communication with the engine. The first reverse flow heat exchanger is configured for exchanging heat between cold natural gas and carbon dioxide. The exchanged heat may be used to warm the cold natural gas for fuel for the engine and to cool the carbon dioxide to cold carbon dioxide. A second reverse flow heat exchanger may be further included in the system. The second reverse flow heat exchanger may be in fluid communication with the first reverse flow heat exchanger and LNG in the LNG tank. The second reverse flow heat exchanger is configured for exchanging heat between the LNG and the cold carbon dioxide. The exchange of heat may be used to provide heat to the LNG for a phase change from liquid natural gas to cold natural gas and to remove heat from the cold carbon dioxide. The removal of heat from the carbon dioxide provides for a phase change of the carbon dioxide from gas to solid. The solid carbon dioxide may be stored in the LNG tank. The system also includes a refrigerator configured to receive a portion of the cold natural gas from the LNG tank. The refrigerator may be used to condense the cold natural gas to LNG for storage in the LNG tank. The refrigerator may use energy from the engine for condensing the cold natural gas to LNG.
In an embodiment of the presently claimed invention, a method is provided for storing carbon dioxide emitted from a natural gas engine. In this method, natural gas may be received from a LNG tank and burned in the natural gas engine to produce exhaust gas which includes carbon dioxide and nitrogen. The method includes compressing and cooling the exhaust gas to a liquid carbon dioxide temperature. The method further includes separating the liquid carbon dioxide from the nitrogen and decompressing the separated carbon dioxide. The method also includes exchanging heat between the decompressed carbon dioxide and the LNG. The exchange of heat may be used to heat the LNG to cold natural gas and to cool the decompressed carbon dioxide to below solid carbon dioxide temperature. The solid carbon dioxide is stored in the LNG tank. The method also includes providing a first portion of the cold natural gas to the natural gas engine and condensing a second portion of the cold natural gas to LNG. The condensed liquefied natural LNG may be returned to the LNG tank for storage.
In an embodiment of the presently claimed invention, a LNG system is described for providing power and sequestering emitted carbon dioxide. The system includes an engine configured to use natural gas for fuel and a LNG tank configured to store LNG and solid carbon dioxide. The engine may emit an exhaust gas including carbon dioxide gas. The system further includes a first reverse flow heat exchanger in fluid communication with the engine. The first reverse flow heat exchanger may be configured for exchanging heat between cold natural gas and the emitted carbon dioxide gas. The exchange of heat may be used to warm the cold natural gas to be used for fuel for the engine and to cool the emitted carbon dioxide gas to cold carbon dioxide. The system also includes a separator in fluid communication with the first reverse flow heat exchanger. The separator may be configured to receive the exhaust gas including nitrogen and the cold carbon dioxide from the first reverse flow heat exchanger and to separate the cold carbon dioxide from the nitrogen. A second reverse flow heat exchanger is also provided. The second reverse flow heat exchanger is in fluid communication with the cold carbon dioxide from the separator and LNG in the LNG tank. The second reverse flow heat exchanger may be configured for exchanging heat between the LNG and the cold carbon dioxide. The heat exchange may be used to provide heat to the LNG for a phase change from LNG to cold natural gas. The heat exchange may also be used to remove heat from the cold carbon dioxide for a phase change from gas to solid carbon dioxide. The solid carbon dioxide may be stored in the LNG tank. The system further includes a refrigerator that is configured to receive a portion of the cold natural gas from the LNG tank. The refrigerator may condense the portion of cold natural gas to LNG and provide the LNG to the LNG tank.
In an embodiment of the presently claimed invention, a method is provided for storing ballast in a ship. The method includes removing LNG from a LNG tank and burning the removed LNG in an engine to produce energy for driving the ship. Exhaust gas emitted by the engine includes carbon dioxide gas and nitrogen gas. The method further includes separating the carbon dioxide gas from nitrogen gas in the exhaust gas using a compressor to compress the exhaust gas, a turbine to drive the compressor, and a heat exchanger. The method also includes cooling the carbon dioxide gas to produce solid carbon dioxide, and storing the solid carbon dioxide in the LNG tank. The solid carbon dioxide may serve as ballast in place of the removed LNG.
In the exemplary embodiment of
CH4+2O2+8N2→CO2+2H2O+8N2
According to the above chemical equation, for every 1 mole of methane (16 g CH4), 2 moles of oxygen gas (32 g O2) are consumed in a combustion reaction. Ambient air includes approximately 4 moles of nitrogen gas for each 1 mole of oxygen. Thus, 8 moles of nitrogen (224 g N2) are mixed with the 2 moles of oxygen in ambient air 266 and are introduced together into the engine during combustion. The output of the above combustion reaction is hot exhaust gas 264 comprising a mixture of 1 mole of carbon dioxide (44 g CO2), 2 moles of water vapor (36 g H2O), and 8 moles of nitrogen gas. The 224 g of N2 that was taken into the engine as part of the ambient air is expelled in the exhaust and mixed with the 44 g of carbon dioxide and 36 g of water vapor.
Thus, the components of the hot exhaust gas 264 include about 224 g nitrogen gas, 44 g carbon dioxide gas, and 36 g water vapor. Generally, additional byproducts are produced in the above combustion reaction. Examples include oxides of nitrogen (NOx), oxides of sulfur (SOx), hydrocarbons (HC), particulate matter (PM), and other emission gasses such as carbon monoxide (CO) and etc. For simplicity, however, these gasses may be ignored.
While
The regenerative heater 250 and the environmental cooler 240 may be used for cooling the hot exhaust gas 264 from engine exhaust temperatures to ambient temperature. Water may also be condensed out of the exhaust using the regenerative heater 250 and the environmental cooler 240. For simplicity, +300° C. may be treated as engine temperature or hot exhaust temperature. Also for simplicity, +40° C. may be treated as ambient temperature and +80° C. may be treated as warm temperature. However, ambient temperature may range from about 0° to +80° C. Engine temperature and engine exhaust temperature may range from +80° to +500° C. Warm exhaust, warm carbon dioxide, warm nitrogen, and/or warm fuel may be at a temperature between hot engine temperature and ambient temperature.
The regenerative heater 250 is configured to exchange heat between the engine temperature exhaust gas 264 (including carbon dioxide) and warm fuel 252, for cooling the hot exhaust gas 264 and further heating the warm fuel 252. The regenerative heater 250 may receive the engine temperature exhaust gas 264 from the engine 260 at about +300° C. and warm fuel 252 from the environmental cooler 240 at about +80° C. The heat exchange in the regenerative heater 250 may be used to cool the exhaust gas to about +80° C. for output to the environmental cooler 240 as warm exhaust gas 254. The heat exchange may be used to further heat the warm fuel 252 to about +300° C. for output to the engine 260 as hot fuel 262.
The environmental cooler 240 is configured to exchange heat between the warm exhaust gas 254 and the fuel 242. The environmental cooler 240 may also be used to condense water vapor from the warm exhaust gas 254. The environmental cooler 240 may receive the warm exhaust gas 254 at about +80° C. from the regenerative heater, and may receive the fuel 242 at about −45° C. from the heat exchanger 230. The heat exchange in the environmental cooler 240 may be used to condense most of the water vapor out of the warm exhaust gas 254 for output as water 246. The water 246 may be returned to the environment. The heat exchange in the environmental cooler 240 may be used further to cool the warm exhaust gas 254 from about +80° C. to about +40° C. for output to the heat exchanger 230 as ambient temperature exhaust gas 244. Since most of the water has been removed, the ambient temperature exhaust gas 244 output to the heat exchanger 230 includes about 224 g of nitrogen gas and 44 g of carbon dioxide gas. The heat exchange may be used to heat the fuel 242 from about −45° C. to about +80° C. for output to the regenerative heater 250 as fuel 252.
While cooling the hot exhaust gases has been described as being performed in two steps, more or fewer steps may be used for cooling the hot exhaust gases to about ambient temperature.
While fuel may be used for cooling the hot exhaust gas 264 from engine exhaust temperature to ambient temperature, other techniques that may be understood by persons having ordinary skill in the art may be used for cooling the exhaust and heating the fuel. For example, the environmental cooler 240 and/or the regenerative heater 250 may use cold water and/or air for cooling the exhaust gas 264 and/or warm exhaust gas 254 to ambient temperature.
The heat exchanger 230 is configured exchange heat between the ambient temperature exhaust gas 244 and cold fuel 232, and further to exchange heat between the ambient temperature exhaust gas 244 and cold nitrogen gas 236. The heat exchanger may receive ambient temperature exhaust gas 244 at about +40° C. from the environmental cooler 240, and cold fuel 232 at about −163° C. from the LNG tank 210. The heat exchanger may receive cold nitrogen gas 236 at approximately −70° C. from the separator 220. The heat from the ambient temperature exhaust gas 244 may be transferred to the cold nitrogen gas 236 and the fuel 232 to cool the ambient temperature exhaust gas 244 to about −70° C. The cooled exhaust gas may be output to the separator 220 as cold exhaust gas 234.
Approximately 36 joules of heat energy may be transferred to about 8 moles or 224 g of cold nitrogen gas 236 from the ambient temperature exhaust gas 244 in the heat exchanger 230. The transferred heat may be used to warm the about 8 moles of cold nitrogen gas 236 from about −70° C. to about +40° C. About 8 moles of warmed nitrogen gas may be returned to ambient air in the environment as nitrogen gas 238. A portion of the nitrogen gas 238 may be provided to the air/nitrogen mixer 280 for mixing with ambient air and/or oxygen. The air/nitrogen mixer 280 may provide ambient air 266 to the engine 260.
Approximately 4 joules of heat energy may be transferred from the ambient temperature exhaust gas 244 to about 1 mole of cold fuel 232 in the heat exchanger 230. The transferred heat may be used to warm the about 1 mole of cold fuel 232 from about −163° C. to about −45° C. The warmed fuel may be output as fuel 242 to the environmental cooler. The 36 joules and 4 joules of transferred heat are set forth for illustration purposes. The actual amount of heat energy may be more or less depending on input temperatures and rates of flow of the various gases and efficiency of the heat exchanger 230.
The separator 220 is configured to separate nitrogen from carbon dioxide. The separator 220 may use fractional distillation and heat exchange techniques, as described elsewhere here. The separator may receive cold exhaust gas 234 from the heat exchanger 230 at a temperature of about −70° C. The cold exhaust gas 234 includes about 1 mole of carbon dioxide and about 8 moles or 224 g of nitrogen. The separator 220 may output about 1 mole of cold nitrogen gas 236 to the heat exchanger 230 at about −70° C. The separator 220 may output about 1 mole of cold carbon dioxide gas 216 to the LNG tank 210 at about −70° C.
The LNG tank 210 is configured to store LNG 212 and solid carbon dioxide 218 or dry ice at a temperature of about −170° C. and a pressure of about 4-5 psi above 1 atmosphere (ATM). The LNG tank 210 may receive the 1 mole of cold carbon dioxide gas 216 from the separator 220 at about −70° C. The carbon dioxide gas 216 may be cooled from a gas at about −70° C. gas to a solid at about −170° C. (dry ice) for storing in the LNG tank. As discussed above, 1 mole of carbon dioxide has a mass of about 44 g. In cooling 44 g of carbon dioxide from −70° C. gas to −170° C. solid, about 30 joules of heat energy are released from the carbon dioxide.
The LNG 212 inside the LNG tank 210 may be used for some or all of the further cooling of the cold carbon dioxide gas 216 to solid carbon dioxide 218. For example, the 30 joules of heat energy released from the cold carbon dioxide gas 216 may be used to warm about 130 g of liquid methane from about −170° C. to about −163° C. and to cause a phase transition of LNG 212 to methane gas 214 at about −163° C. This can result in the conversion of about 130 g of LNG 212 to methane gas 214 inside the LNG tank. The 130 g of methane gas 214 may be released from the LNG tank 210. About 16 g of the methane gas 214 may be provided to the heat exchanger as the cold fuel 232. About 114 g of the methane gas 214 may be provided to the refrigerator 270 as recycle gas 272. The recycle gas 272 may be cooled to LNG at about −170° C. using the refrigerator 270 and output to the LNG tank 210 as liquid methane 274. Energy for operating the refrigerator 270 may be provided by the engine 260. The solid carbon dioxide 218 has a higher density than LNG 212 so the solid carbon dioxide 218 will tend to settle to the bottom of the LNG tank 210.
At state 315, the carbon dioxide gas is separated from the nitrogen gas. The carbon dioxide gas and the nitrogen gas may be separated, for example, using the separator 220 to produce cold carbon dioxide gas 216 and cold nitrogen gas 236. The temperature of the separated carbon dioxide gas and nitrogen gas at state 315 is about −70° C.
During the transition 316 from state 315 to state 318, carbon dioxide gas undergoes a cooling from −70° C. to −79° C. A negligible amount of energy is release during the transition 316 for cooling 44 g of carbon dioxide. At state 318, the carbon dioxide gas is in equilibrium with solid carbon dioxide at about −79° C.
During the transition 320 from state 318 to state 322, the separated carbon dioxide undergoes a phase change from gas to a solid. The temperature does not change during the transition 320. Approximately 26 joules of heat energy are released during the transition 320 for the phase change. At state 322, the separated carbon dioxide is a solid. During the transition 324 from state 322 to state 326, solid carbon dioxide is cooled from −79° C. to −170° C. Approximately 5 joules of heat energy are released during the transition 324. At state 326, the carbon dioxide is a solid and methane is a liquid at about −170° C. Solid carbon dioxide may be stored in LNG at state 326. A portion or all of the transitions 316, 320, and 324 may take place inside the LNG tank 210.
During the transition 328 from state 326 to 330, about 130 g of methane is warmed from −170° C. to −163° C. At least 2 joules of energy are used to warm the methane −170° C. to −163° C. During the transition 332 from state 330 to state 334, the 130 g of methane undergoes a phase change from liquid to gas. The temperature does not change during the transition 332. At least 28 joules are required for the phase change of transition 332. The transitions 328 and 332 may take place inside the LNG tank 210. The approximately 30 joules of energy released during the transitions 316, 320 and 324 may be used to provide the 30 joules to perform the temperature change transition 328 and phase change transition 332. That is, energy released from the temperature change and phase change of 44 g of carbon dioxide may be absorbed in a temperature change and phase change of 130 g of methane.
At state 334, 114 g of the 130 g of methane may be refrigerated to liquid methane at −170° C., and returned to the LNG tank 210. This refrigeration step may be performed, for example, using the refrigerator 270. This refrigeration step is omitted from the phase diagram 300 for clarity. During the transition 336 from state 334 to state 338, 16 g of methane (the remainder of the 130 g of methane) are warmed from −163° C. to −70° C. At least 4 joules of energy are used to warm the 16 g of methane from −163° C. to −70° C. The transition 338 may be performed in the heat exchanger 230.
At state 315, 44 g of carbon dioxide gas was separated from 224 g of nitrogen gas. The transition of the nitrogen gas from the state 315 to state 338 is omitted for clarity. The 224 g of nitrogen gas and 16 g of methane may undergo at transition 340 from state 338 to state 342. The nitrogen gas may be maintained separate from the methane gas. Energy released in the transition 312 may be provided for the transition 340, for example, using the environmental cooler 240 and/or the heat exchanger 230. At state 342, the nitrogen gas may be released to the environment. While the state 338 and 342 may be at about the same position on the phase diagram as states 315 and 310 respectively, the states 338 and 342 are illustrated in
The separation heat exchanger 420 is configured exchange heat between the hot compressed exhaust gas 234 and cold separated nitrogen gas 436, and further to exchange heat between hot compressed exhaust gas 234 and liquid carbon dioxide 432. The heat exchanger may receive hot compressed exhaust gas 424 at about +110° C. from the compressor 414, and cold separated nitrogen gas 436 at about −40° C. from the separator tank 430. The heat exchanger may receive liquid carbon dioxide 432 at about −40° C. from the separator tank 430. The heat from the hot compressed exhaust gas 424 may be transferred to the cold separated nitrogen gas 436 and the liquid carbon dioxide 432 to cool the hot compressed exhaust gas 234 to about −40° C. for output as cold compressed exhaust gas 434. The cold compressed exhaust gas 434 includes liquid carbon dioxide and cold nitrogen gas. The cold compressed exhaust gas 434 may be provided to the separator tank 430.
The separator tank 430 is configured to allow liquid carbon dioxide to accumulate at the bottom and cold nitrogen gas to accumulate at the top. Cold separated nitrogen gas 436 may be removed from the top of the separator tank 430 and provided to the heat exchanger 420 for cooling the hot compressed exhaust gas 424. In cooling the hot compressed exhaust gas 424, the nitrogen gas is heated to hot compressed nitrogen gas 426 at about +110° C. and provided to the second turbine 416. The hot compressed nitrogen gas 426 may be used to drive the second turbine 416 and is output from the second turbine 416 as cold nitrogen gas 236 at about 1 ATM and −70° C. Similarly, the liquid carbon dioxide 432 may be removed from the bottom of the separator tank 430 and provided to the heat exchanger 420 for cooling the hot compressed exhaust gas 424. In cooling the hot compressed exhaust gas 424, the liquid carbon dioxide is heated to hot compressed carbon dioxide gas 422 at about +110° C. and provided to the first turbine 412. The hot compressed carbon dioxide gas 422 may be used to drive the first turbine 412 and is output from the turbine as cold carbon dioxide gas 216 at about 1 ATM. Power from the first turbine 412 and the second turbine 416 may be used to drive the compressor 414.
As discussed elsewhere herein, heat released in cooling the carbon dioxide from about −70° C. to about −170° C. turns LNG 212 into a gas, generating methane bubbles 520. The methane bubbles 520 collect at the top of the tank as cold methane gas 214. A portion of the methane gas 214 may be provided as fuel 232 to the engine 260, via the heat exchanger 230. Another portion of the methane gas 214 may be refrigerated a using the refrigerator 270 and returned to the LNG tank 210 as liquid methane 274.
Solid carbon dioxide 218 may be stored in the LNG tank 210 as ballast to replace LNG 212 that is consumed as fuel in the engine 260. As discussed elsewhere herein, about 44 g of carbon dioxide are produced for each 16 g of methane consumed. The 16 g of LNG 212 may be replaced in the LNG tank 210 by the 44 g of solid carbon dioxide. The volume of 16 g of LNG 212 is about 32-40 cc. The volume of 44 g of solid carbon dioxide 218 is about 28-31. Thus, volume of the LNG 212 plus solid carbon dioxide stored in the LNG tank 210 remains approximately constant or decreases as LNG 212 is used for fuel. However, the weight of the ballast in the form of solid carbon dioxide 218 at the bottom of the LNG tank 210 increases at a ratio of about 2.75:1 dry ice: LNG respectively (i.e., 44 g ballast: 16 g fuel). The increased weight of the ballast replacing the consumed fuel enhances stabilization of the ship. Moreover, the solid carbon dioxide 218 forms ballast at the bottom of the LNG tank 210 which is an advantageous location for stabilizing a ship. Using solid carbon dioxide 218 as ballast in the LNG tank 210 to replace the consumed fuel reduces or eliminates the need for separate tanks to hold seawater ballast to replace the consumed fuel.
Various examples of temperatures, pressures, energy transfers and amounts of fuel are provided in this description for methane, carbon dioxide, nitrogen, and water. These examples are for illustrating the processing of carbon dioxide from engine exhaust to dry ice and sequestration of the dry ice inside an LNG tank. However, these temperatures, pressures, energy transfers and amounts should not be considered in a limiting sense. Other temperatures, pressures, energy transfers and amounts may be used without departing from the invention.
The solid carbon dioxide may be removed from the LNG tank 210 and sequestered or used industrially. For example, the solid carbon dioxide may be stored deep under layers of rock. Solid carbon dioxide may be stored at the bottom the ocean. For example, carbon dioxide may be injected into deep-sea formations such as underwater basalt. Below about 500-1,000 feet, carbon dioxide is liquid at seawater temperatures. Thus, solid carbon dioxide would warm to liquid carbon dioxide in the deep sea. Liquid carbon dioxide is denser than seawater and will sink to the bottom of the ocean.
The solid carbon dioxide may be used industrially. Dry ice may be used as a cyclic or non-cyclic refrigerant. For example, dry ice is used in the food industry for transport and storage of foods such as ice cream. Carbon dioxide may be used as a refrigerant in vehicles, freezers and refrigerators. Dry ice can also be used for construction, cleaning, plumbing, insect abatement, scientific experiments.
Solid carbon dioxide may be used as storage for later conversion to carbon dioxide gas. The carbon dioxide gas may be stored in stable carbonate mineral forms using a process referred to as mineral carbonation or mineral sequestration. Limestone is an example of a mineral carbonate. A substantial percentage of the mineral mass in the Earth's crust is able to form stable carbonates with carbon dioxide.
The carbon dioxide gas may be injected into the earth adjacent oil and natural gas wells for enhancing recovery of fuels such as methane, oil and natural gas. The injected carbon dioxide may reduce the viscosity of crude oil adjacent the well which can enhance a flow of oil through the earth toward the well. The injected carbon dioxide may also increase pressure in a well for removing the flow of oil and natural gas. For example, carbon dioxide may be used for enhancing recovery of methane from coal beds. A power plant may be operated on fuel received from a nearby oil or natural gas field. The carbon dioxide produced while generating power may be separated from the exhaust gas. The separated carbon dioxide may be injected into the field for sequestration and enhancing recovery of the fuel. Other emission gasses may be similarly separated. Thus, the power plant may be operated at near zero emissions.
For simplicity and clarity, carbon dioxide separation and sequestration discussions omitted emissions of other components which are typically present in exhaust gas at concentrations of about parts per million. However, these components, such as NOx, SOx, and various hydrocarbons, may be separated and sequestered in a similar manner. For example, NO2 undergoes a phase transition from gas to liquid at about +21° C., butane at about 0° C., propane at about −42° C., ethane at about −89° C., and nitric oxide at about −152° C. These molecules may be separated and stored in liquid form using heat exchange in combination with turbo charger techniques as discussed elsewhere herein. Further, NO2 undergoes a phase transition from liquid to solid at about −21° C. and SO2 at about −75° C. NO2 and/or SO2 may be separated from other exhaust gases, cooled to a solid form, and stored as solids inside a LNG tank a manner similar to that described for carbon dioxide elsewhere herein.
Several embodiments are specifically illustrated and/or described herein. However, it will be appreciated that modifications and variations are covered by the above teachings and within the scope of the appended claims without departing from the spirit and intended scope thereof. For example, LNG engine systems 200 and 600 are described for a ship. However, these systems may be used for other applications, including power plants, land vehicles, aircraft, and etc. For example, the engine 260 may use fuels other than LNG. Various embodiments of the invention include logic stored on computer readable media, the logic configured to perform methods of the invention.
In the foregoing specification, the present invention is described with reference to specific embodiments thereof, but those skilled in the art will recognize that the present invention is not limited thereto. Various features and aspects of the above-described present invention may be used individually or jointly. Features in each of the various illustrations may be used individually or combined with features in other illustrations for illustrating the present invention. Further, the present invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be recognized that the terms “comprising,” “including,” and “having,” as used herein, are specifically intended to be read as open-ended terms of art.
The present application claims the priority and benefit of U.S. patent application No. 61/293,609 titled “Zero-Emissions Engines,” filed Jan. 8, 2010. The disclosures of the above U.S. patent application is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61293609 | Jan 2010 | US |
