Abstract:
A system for separating and storing carbon dioxide (CO2) in exhaust produced by an internal combustion engine. The system uses a scrubber tank containing a carbon dioxide absorbent fluid to capture CO2 in the exhaust. The system also includes a carbon dioxide storage means configured to temporarily store the captured CO2, and a CO2 recovery facility to refine the captured CO2 for future use or prepare the CO2 for permanent storage. The system is intended for installation on vehicles such as automobiles to reduce the amount of CO2 emitted by automobiles into the environment, but could also be used for other applications such as stationary power generators.

Description:
TECHNICAL FIELD OF INVENTION 
     The invention generally relates to a system for separating or capturing carbon dioxide gas from internal combustion engine exhaust and then storing that gas. More particularly, the invention relates to a system using a carbon dioxide absorbent fluid to capture or extract the carbon dioxide gas and then heating the carbon dioxide absorbent fluid to release the carbon dioxide gas so it can be stored or further processed. 
     BACKGROUND OF INVENTION 
     Most internal combustion engine emit carbon dioxide (CO2) as a by-product of an internal combustion process. Some government regulations are directed at reducing emissions of CO2, in particular vehicle related CO2 emissions. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of this invention, a system for separating carbon dioxide gas from internal combustion engine exhaust is provided. The system includes an internal combustion engine, a heat exchanger, a scrubber tank, a pump, and a carbon dioxide storage means. The internal combustion engine is configured to emit exhaust gas when operating. The exhaust gas is characterized as having an elevated temperature and comprises carbon dioxide. The heat exchanger is configured to cool the exhaust gas emitted by the internal combustion engine. The scrubber tank contains a carbon dioxide absorbent fluid and is configured to bubble exhaust gas from the heat exchanger through the carbon dioxide absorbent fluid. By this process carbon dioxide gas is absorbed by the carbon dioxide absorbent fluid. The pump is configured to urge the carbon dioxide absorbent fluid through the heat exchanger so that the carbon dioxide absorbent fluid is heated as the exhaust gas is cooled. Heating the carbon dioxide absorbent fluid releases stored carbon dioxide. The carbon dioxide storage means is configured to store the carbon dioxide released in the heat exchanger. 
     In another embodiment of the present invention, a system for separating carbon dioxide gas from exhaust from an internal combustion engine configured to propel a vehicle is provided. The internal combustion engine is configured to emit exhaust gas when operating. The exhaust gas is characterized as having an elevated temperature and comprises carbon dioxide. The system includes a heat exchanger, a scrubber tank, a pump, and carbon dioxide storage means. The heat exchanger is configured to cool the exhaust gas emitted by the internal combustion engine. The scrubber tank contains a carbon dioxide absorbent fluid and is configured to bubble exhaust gas from the heat exchanger through the carbon dioxide absorbent fluid. By this process carbon dioxide gas is absorbed by the carbon dioxide absorbent fluid. The pump is configured to urge the carbon dioxide absorbent fluid through the heat exchanger so that the carbon dioxide absorbent fluid is heated as the exhaust gas is cooled. Heating the carbon dioxide absorbent fluid releases stored carbon dioxide. The carbon dioxide storage means is configured to store the carbon dioxide released in the heat exchanger. 
     Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagram of a system for separating carbon dioxide gas from internal combustion engine exhaust in accordance with one embodiment; and 
         FIG. 2  is a diagram of a heat exchanger in the system of  FIG. 1  in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     In accordance with an embodiment of a system  10  for separating carbon dioxide gas from internal combustion engine exhaust,  FIG. 1  illustrates a non-limiting example of vehicle  12  equipped with such a system. The system  10  may include an internal combustion engine  14  that may be configured to propel the vehicle  12 . Examples of suitable internal combustion engines include, but are not limited to, gasoline spark ignition engines, compression ignition engines fueled with gasoline or diesel fuel, turbine engines, hybrid combustion/electric engines, and fuel cells such as solid oxide fuel cells. In general, these internal combustion engines emit exhaust gas  16  when operating, and the exhaust gas  16  is generally characterized as having an elevated temperature. The exhaust gas may also include elevated levels of carbon dioxide. While not specifically shown, the exhaust gas will generally be downstream from known engine exhaust after treatment devices such as a catalytic converter. In the non-limiting example shown in  FIG. 1 , the internal combustion engine  14  is generally configured to propel the vehicle  12 . 
     The system  10  may include a heat exchanger  18  configured to cool the exhaust gas  16  emitted by the internal combustion engine  14 , and so cooled exhaust gas  20  is generally passed out of the heat exchanger  18  to a scrubber tank  22 . A more detailed explanation of the heat exchanger  18  is provided below with regard to  FIG. 2 . 
     The scrubber tank  22  is generally configured to contain a carbon dioxide absorbent fluid  24 , hereafter often fluid  24 . The scrubber tank  22  is also configured to bubble cooled exhaust gas  20  from the heat exchanger  18  through the carbon dioxide absorbent fluid  24 , whereby carbon dioxide gas in the cooled exhaust gas  20  is absorbed by the fluid  24 . A suitable material for the fluid is Novec™ HFE7600 produced by 3M Company. It is noted that 3M primarily markets this fluid as a heat transfer medium for use in electronics and other cooling applications. However it was recognized that HFE7600 had a particularly large capacity to absorb CO2 and so may be useful to preferentially capture CO2. 
     Several known gas scrubber configurations would be suitable for use as or within the scrubber tank  22  to bring the fluid  24  into intimate contact with the cooled exhaust gas  20  to maximize the amount of CO2 removed from the cooled exhaust gas  20 . After the cooled exhaust gas passes through the scrubber tank  22 , scrubbed exhaust gas  26  is emitted by the system  10 . 
     The system  10  may also include a pump  28  configured to urge the fluid  24  through the heat exchanger  18 , wherein the fluid  24  is heated as heat is transferred from the exhaust gas  16  to form cooled exhaust gas  20 . The pump  28  is illustrated as being located between the heat exchanger  18  and the scrubber tank  22 , but it could be located elsewhere in the circulation path of the fluid  24 . As such the location of the pump  28  illustrated is a non-limiting example. 
       FIG. 2  illustrates a non-limiting example of the heat exchanger  18 . While not subscribing to any particular theory, but applying thermodynamic principles of heat conduction to the heat exchanger  18 ; as the exhaust gas  16  passes through the heat exchanger  18 , heat is drawn out of the exhaust gas  16  so cooled exhaust gas  20  exits the heat exchanger  18 . Heat is drawn out of the exhaust gas  16  and transferred to the fluid  24 , whereby the carbon dioxide absorbent fluid  24  releases the carbon dioxide (CO2) gas that was absorbed when the fluid was in the scrubber tank  22 . The arrangement of the system  10  includes an inherent energy-efficiency in that the system  10  uses heat in the exhaust gas  16  for heating the fluid  24  to release the CO2, and so does not need to provide a separate heat source to release the CO2 from the fluid  24 . 
     As suggested by  FIG. 2 , the CO2 generally rises out of the fluid  24  to the top of the heat exchanger  18  and accumulates around a CO2 gas outlet  30 . In one embodiment, the heat exchanger  18  may include a thermostat  32  to help regulate the temperature of the fluid  24  exiting the heat exchanger  18  so that the amount of CO2 removed from the fluid  24  is maximized. It is noted that the heat exchanger  18  is generally configured to keep the exhaust gas  16  and the cooled exhaust gas  20  separated from the fluid  24 , but does facilitate heat transfer from the exhaust gas  16  to the fluid  24 . 
     Referring again to  FIG. 1 , the system  10  may also include a carbon dioxide storage means  34  configured to store the carbon dioxide released by the fluid  24  in the heat exchanger  18 . As suggested by  FIG. 1 , one embodiment of the CO2 storage means  34  may include a compressor  36  and a storage tank  38 . The compressor  36  and the storage tank  38  may be configured to store CO2 in liquid form. Also, the storage tank  38  is preferably sized so that the storage tank  38  does not need to be emptied any more frequently than the fuel tank (not shown) of the vehicle  12  needs to be filled with fuel. 
     The system  10  or the carbon dioxide storage means  34  may also include a carbon dioxide recovery facility  44 , hereafter often facility  44 . The facility is generally configured to empty the storage tank  38 . The facility  44  may be part of a vehicle fueling station so that when the vehicle  12  is refueled, the storage tank  38  can be emptied. The storage tank  38  may be emptied by, for example, coupling the facility  44  to the storage tank  38  via a connection  46  and then operating a valve  48  so the contents of the storage tank  38  can be transferred to the facility  44 . The facility  44  may be simply a larger storage tank that stores the contents from several vehicle storage tanks to await later transfer to a processing facility, or the facility  44  may be equipped to refine the contents received from the storage tank  38  and package carbon dioxide for storage at a permanent storage facility or for use by a consumer of carbon dioxide. The refinement process may also include recovering other chemicals or pollutants present in the storage tank  38 , for example, but not limited to, carbon monoxide, nitric oxides, and unburned hydrocarbons. 
     The system  10  may also include a radiator  40  configured to receive fluid  24  from the heat exchanger  18  and cool the fluid  24  as it flows into the scrubber tank  22 . The cooling by the radiator  40  may be assisted by a fan  42 . It is desirable to cool the fluid  24  as much as possible since the fluid  24  generally is able to absorb more CO2 at lower temperatures, about 25 C for example, than at higher temperatures, 100 C for example. 
     Accordingly, a system  10  for separating and storing carbon dioxide (CO2) gas from exhaust produced by an internal combustion engine  14  is provided. CO2 is produced as the internal combustion engine  14  is operated, for example to propel a vehicle  12  or as a stationary power source. The system  10  removes at least some of the CO2 in the exhaust and stores that CO2 for later use or permanent storage, and so reduces the amount of CO2 released into the environment by the engine  14 . The system  10  is particularly well suited for use on a vehicle because the vehicle regularly visits refueling stations where the storage tank  38  can be emptied. 
     While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.