Abstract:
A station for dispensing liquid natural gas (LNG) and hydrogen to vehicles features a bulk tank which receives LNG from a tanker truck. LNG from the bulk tank may be directed to either an LNG conditioning and dispensing portion of the station or a hydrogen production and dispensing portion of the station. The latter includes a heat exchanger for warming the LNG and a steam reformer which produces hydrogen and carbon dioxide from the warmed LNG. The hydrogen is compressed and then either stored or dispensed to a vehicle powered by a fuel cell. The carbon dioxide may optionally be further processed and stored for future use.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority from U.S. Provisional patent application Ser. No. 60/298,476, filed Jun. 15, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to fuel cell refueling stations, more particularly, to liquid natural gas dispensing stations that are modified to additionally provide hydrogen to fuel cell vehicles.  
           [0003]    In order to protect the environment and air from harmful chemicals, the government has set maximum allowable harmful fuel emissions for vehicles in the United States. These requirements are forcing vehicle manufacturers to design vehicles that run on fuels other than gasoline and diesel fuel or consider alternative types of engines, such as electric engines. This has led to the design of vehicles that use fuel cells that run on pure hydrogen. When pure hydrogen is mixed with oxygen in the vehicle, water, heat and electricity are produced, ideally without emitting other chemicals that are harmful to the air or the environment.  
           [0004]    Fuel cell technology is so promising that a public-private partnership between the U.S. Department of Energy (DOE) and the nation&#39;s major automakers was recently formed to promote the development of hydrogen as a primary fuel for cars and trucks. The new parnership/program, called FeedomCAR (CAR stands for Cooperative Automotive Research), includes Ford, General Motors and DaimlerChrysler and focuses on technologies to enable mass production of affordable, hydrogen-powered fuel cell vehicles and the hydrogen supply infrastructure to support them.  
           [0005]    While fuel cell vehicles are already being tested and used, a standard infrastructure that efficiently provides fuel for these vehicles throughout the country has not been developed yet. Hydrogen is not found naturally and must be separated or stripped from a source chemical to obtain pure hydrogen. However, no general agreement exists as to which source chemical to use to obtain hydrogen. A number of different source chemicals are known, including natural gas (methane or CH 4 ), methanol, ethanol and even diesel fuel and gasoline.  
           [0006]    The expense of building the infrastructure depends heavily on which source chemical is used. The easiest way to build an infrastructure would be to modify the substantial existing gasoline and diesel fuel infrastructure to provide hydrogen. Existing facilities could be fitted with devices for converting gasoline or diesel fuel to hydrogen. The fuel cell vehicles could then refuel at existing gas stations. Gasoline and diesel fuel, however, are very inefficient sources, providing merely 50% hydrogen for every pound of gasoline or diesel fuel. In addition, converting these fuels and purifying the hydrogen requires special low sulfuric chemicals, adding to the cost of the conversion.  
           [0007]    Additionally, no consensus exists as to when to convert the source chemical into hydrogen along the process of supplying the hydrogen fuel. Hydrogen can be converted and purified at a plant and then supplied to the refueling stations (“upstream” conversion). However, supplying hydrogen to the refueling station can result in very high shipping costs because pure hydrogen is less dense or takes up more volume than hydrogen still bonded within the source chemicals. In other words, a tanker truck full of a source chemical will typically provide substantially more hydrogen than a tanker truck full of liquid hydrogen by itself.  
           [0008]    The hydrogen could also be produced by supplying the source chemical to the vehicle and providing mini plants on the vehicles for converting the source chemical to hydrogen on the vehicles (“downstream” conversion). This configuration, however, requires a reformer that strips the hydrogen from the source chemical on each vehicle. The size restrictions on the reformer and the complexity of the design of the vehicle to implement this will drive the cost of the vehicle to unreasonable levels.  
           [0009]    Due to these considerations, the DOE has recently indicated that it would cast its investment on promoting a hydrogen infrastructure based on steam reformation at the service station as opposed to fuel cell vehicles powered by hydrogen reformed onboard the vehicle.  
           [0010]    The DOE has also indicated that the hydrogen infrastructure will likely be built around steam reformation of natural gas at fueling stations. Natural gas is attractive because it has the highest carbon-to-hydrogen ratio of any hydrocarbon. In other words, reformation of natural gas gives you more of what you want (hydrogen) with less of what you don&#39;t want (carbon). In addition, natural gas contains few contaminants and reforming it is a cost effective and established technology. Because of this, the majority of commercial hydrogen used in the U.S. today is produced by reforming natural gas and virtually every commercially operating fuel cell in the world is powered by hydrogen produced by natural gas.  
           [0011]    The U.S. has over 1.3 million miles of transmission and distribution lines carrying natural gas to almost every part of the country. As a result, the focus on natural gas reformation has been on stations that receive natural gas from pipelines. For example, The SunLine Transit Agency in Thousand Palms, Calif. has constructed a fueling station for buses equipped with fuel cell engines. The station obtains natural gas from a preexisting natural gas pipeline network, reforms it into hydrogen gas, compresses the hydrogen gas and dispenses the compressed hydrogen gas into storage tanks onboard a bus.  
           [0012]    There are disadvantages, however, in relying on a pipeline to provide natural gas to the station. For example, a station that does not require access to a natural gas pipeline offers more flexibility with regard to location. In addition, there is significant additional cost and maintenance associated with the plumbing and equipment necessary to connect the station to the natural gas pipeline. Furthermore, a disruption in piping the natural gas to the station, such as due to a pipe leak or other problem, would interrupt the fueling capability of the station.  
           [0013]    Liquid natural gas (LNG) dispensing stations exist for supplying natural gas for dispensing a diesel/natural gas mixture or natural gas by itself that reduces harmful emissions from trucks with modified combustion engines. The conventional LNG dispensing station generally has a bulk storage tank that receives LNG from a tanker truck. The bulk storage tank is connected to a pump in a sump, which in turn is connected to a dispensing device as known in the art. These known systems, however, do not provide a way of supplying pure hydrogen or converting LNG to hydrogen.  
           [0014]    Accordingly, a main object of the present invention is to provide an infrastructure that converts a source chemical to pure hydrogen at a point, and with a source material, that reduces shipping costs and the cost to provide refueling stations in order to fuel vehicles.  
           [0015]    It is another object of the present invention to provide a relatively simple and inexpensive infrastructure with refueling stations that provide a source chemical that converts to pure hydrogen at an efficient high rate while substantially reducing waste material.  
         SUMMARY OF THE INVENTION  
         [0016]    The present invention is directed to a system for producing hydrogen and fueling vehicles which use hydrogen to produce power via fuel cells. The system includes a centralized liquid natural gas production facility from which a tanker truck receives LNG. The tanker truck delivers the LNG to a refueling station that includes a bulk tank containing a supply of the LNG. Means may exist for the refueling station to contact the centralized liquid natural gas production facility so that LNG may automatically be reordered and dispatched. The refueling station has the capability to condition and dispense the LNG from the bulk tank to a use device such as an LNG-powered vehicle.  
           [0017]    A heat exchanger is also in communication with the bulk tank and receives LNG from the bulk tank so as to warm it. The warmed LNG is directed to a steam reformer where hydrogen gas and carbon dioxide are produced. The hydrogen is then compressed in a compressor and either dispensed to the vehicle or stored. CO 2  from the reformer may be filtered out and exhausted.  
           [0018]    In an alternative embodiment, CO 2  from the reformer is directed to the heat exchanger of the refueling station and then a storage container so that the CO 2  is cooled by the liquid natural gas flowing through the heat exchanger and liquid CO 2  is formed in the heat exchanger and stored in the storage container for future use. A compressor is in circuit between the reformer and the heat exchanger so that the CO 2  from the reformer is compressed prior to entering the heat exchanger.  
           [0019]    In another alternative embodiment, hydrogen gas from the refueling station reformer is routed to the refueling station heat exchanger and cooled by the LNG flowing therethrough prior to traveling to the dispenser. A compressor is in circuit between the heat exchanger and the dispenser so that the hydrogen is compressed after leaving the heat exchanger and before traveling to the dispenser. As an alternative to the compressor, a liquifier may be placed in circuit between the heat exchanger and the dispenser so that the hydrogen is liquified after leaving the heat exchanger and before traveling to the dispenser. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is an illustration primarily in block diagram form showing an embodiment of the fuel cell refueling station and system of the present invention;  
         [0021]    [0021]FIG. 2 is a schematic drawing of a first embodiment of the fuel cell refueling station of the present invention;  
         [0022]    [0022]FIG. 3 is a schematic drawing of a second embodiment of the fuel cell refueling station of the present invention;  
         [0023]    [0023]FIG. 4 is a schematic drawing of a third embodiment of the fuel cell refueling station of the present invention; and  
         [0024]    [0024]FIG. 5 is a schematic drawing of a fourth embodiment of the fuel cell refueling station of the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    As illustrated in FIG. 1, in accordance with the present invention, tanker trucks  10   a,    10   b  and  10   c  are filled with liquid natural gas (LNG) at a centralized LNG production facility  20 . The LNG tanker trucks are then dispatched to refueling stations  100   a,    100   b  and  100   c  so that the LNG bulk tanks at the stations may be refilled. The refueling stations  100   a,    100   b  and  100   c  may optionally include transmitters that communicate via refueling station antennas  30   a,    30   b  and  30   c  and an LNG facility antenna  40  with a receiver at the LNG facility  20  so that the LNG tanker trucks may be automatically and timely dispatched so that the refueling stations may provide uninterrupted service. As an alternative to the antennas  30   a,    30   b,    30   c  and  40 , the automatic dispatching system may be landline-based.  
         [0026]    Referring to FIG. 2, in an embodiment of the present invention, a hydrogen refueling station  100  is built by retrofitting hydrogen processing components onto an already existing LNG dispensing station. The hydrogen refueling station has a bulk cryogenic storage tank  102  for storing liquid natural gas (LNG) typically at −260° F. and approximately 100 psig as known in the art. As described with regard to FIG. 1, the bulk tank  102  is refilled by a tanker truck dispatched from a centralized LNG production facility.  
         [0027]    The bulk tank  102  is connected to a pump in a sump  104 , which in turn is connected to an LNG conditioning and dispensing portion of the station  105 . Examples of LNG conditioning and dispensing systems that are suitable for use as the LNG conditioning and dispensing portion  105  of the station  100  are presented in commonly assigned U.S. Pat. No. 6,354,088 to Emmer et al., U.S. Pat. Nos. 5,421,160 and 5,537,824, both to Gustafson et al., U.S. Pat. Nos. 5,121,609 and 5,231,838, both to Cieslukowski and U.S. Pat. No. 5,228,295 to Gustafson. In addition, the dispensing portion may take the form of currently pending and commonly owned U.S. patent application Ser. No. 09/632,088.  
         [0028]    To implement hydrogen dispensing, the refueling station  100  has a supply line  106  connected to the bulk storage tank  102  that supplies LNG to an ambient air heat exchanger  108  where the temperature of the LNG is raised to 50° F. The warmed LNG is then routed to a hydrogen reformer  110  where the LNG is preferably mixed with steam. While hydrogen reformer  110  is discussed below in terms of a steam reformer, it is to be understood that alternative types of reformers that produce hydrogen from natural gas may be used without departing from the scope of the present invention.  
         [0029]    Reformer  110  produced hydrogen, and waste carbon dioxide, from the inputs of LNG and steam in the presence of a catalyst in accordance with the following endothermic reaction:  
         CH 4 +2H 2 O→CO 2 +4H 2   
         [0030]    In the reformer, the mixture of LNG and steam is passed through a catalytic bed which is typically heated to a reforming temperature of about 1,250° F. to about 1,600° F. Catalysts typically used are nickel catalysts which are deposited on alumina pellets.  
         [0031]    The reformer  110  may be a tubular reformer or a plate-type reformer, both of which are well known in the art. Examples of tubular reformers are presented in U.S. Pat. Nos. 4,810,485 to Marianowski et al., 4,838,897 to Amano et al. and 3,698,957 to Sanderson. Examples of plate-type reformers are presented in U.S. Pat. Nos. 5,997,594 to Edlund et al. and 6,033,634 to Koga. In addition, reformers suitable for use in the station may be obtained from GTI/Mosaic Energy of Des Plaines, Ill.  
         [0032]    The reformer  110  thus produces hydrogen gas at approximately 150° F. in addition to waste carbon dioxide gas. The waste carbon dioxide is filtered out and exhausted.  
         [0033]    Depending on the device selected for use as reformed  110 , the hydrogen may require further filtration/purification as it could be contaminated with materials that would be detrimental to the electrical chemical reaction that occurs within the fuel cell onboard the vehicle being refueled. More specifically, some trace quantities of unreacted reactants and trace quantities of byproducts such as CO may result from steam reforming. Trace quantities of CO, certain concentrations of CO 2  and, in some cases, unsaturated hydrocarbons and alcohols will poison a fuel cell.  
         [0034]    As a result, the system  100  may optionally be provided with a purifier, indicated in phantom at  111 . As is well known in the art, purifier  111  may include a pressure swing adsorption (PSA) stack arrangement. Alternatively, the purifier may use metallic foils or thin films, also well known in the art.  
         [0035]    The hydrogen gas flows to a high pressure compressor  112  which raises the pressure of the hydrogen gas to 5000 psi. The pressurized hydrogen is either stored in gas storage tubes  114  or flows to a dispenser  116 . A vehicle (not shown) can be connected to the dispenser  116  for receiving a supply of high pressure hydrogen gas.  
         [0036]    Referring to FIG. 3, an alternative embodiment refueling station  200  is shown with features similar to the features of refueling station  100  numbered the same. In this alternative, instead of exhausting the carbon dioxide into the atmosphere or waste removal devices, liquid CO 2  is produced which can be used for dry ice, beverage production or any other known CO 2  application. To provide the liquid CO 2 , the carbon dioxide produced at a reformer  110  is routed to a compressor  204  and is compressed from 100 psig to 300 psig. The pressurized CO 2  is then routed back to a heat exchanger  206  that uses the heat from the CO 2  to warm the LNG first flowing toward the reformer  110 . The exchanger  206  also cools the CO 2  to below its critical temperature, at approximately 90° F., which converts it into liquid before it is stored in a dewar  208  for later dispensing.  
         [0037]    Referring to FIG. 4, in another alternative embodiment, refueling station  300  is a high efficiency station that routes the purified hydrogen from the reformer  110  back to a heat exchanger  302 . At the exchanger  302 , the heat from the hydrogen is used to heat the natural gas before it enters the reformer  110 . The cooled hydrogen then is routed to the high pressure compressor  112  as with refueling station  100 .  
         [0038]    Referring to FIG. 5, a refueling station  400  cools the hydrogen in a heat exchanger  302  as with refueling station  300 , except that the cooled hydrogen then proceeds to a small scale hydrogen liquifier  402 . The liquifier  402  further cools the hydrogen to −420° F. and lowers the pressure to 20 psi. Such liquifiers are well known in the art. A dewar  404  for the liquid hydrogen is then used to store the hydrogen and keep it cool. The hydrogen then flows to a liquid hydrogen dispenser  406  for filling a vehicle (not shown) as needed.  
         [0039]    It will be appreciated that many other configurations of LNG dispensing stations can be retrofitted or built new with a reformer and dispensing mechanisms to provide pure hydrogen. It will also be appreciated that any reformer or conversion device that strips pure hydrogen by cracking natural gas or methane can be used by the refueling station of the present invention to provide the hydrogen.  
         [0040]    The present invention thus offers a number of advantages over the prior art. First, the cost to add on a hydrogen production and dispensing equipment to the existing and growing infrastructure supplying bulk LNG is relatively low. Besides cost, relatively few significant physical restrictions are placed on the reformer at a refueling station, especially compared to a reformer placed onboard a vehicle. Also, for the same size tanker truck, transportation of LNG to the refueling station provides substantially more hydrogen than transporting previously purified liquid hydrogen (approximately one truck of LNG carries the same amount of hydrogen as three trucks of pure liquid hydrogen). Additionally, natural gas is 98% efficient when stripping hydrogen from natural gas leaving very little CO 2  waste compared to methanol that is only 85% efficient. LNG is also relatively safer than the other possible source chemicals because of its high ignition energy.  
         [0041]    While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.