Abstract:
An apparatus for decreasing steam methane reformer (SMR) tube temperature is provided. The apparatus can include an SMR furnace, a monitoring system in communication with the SMR furnace and a water source in fluid communication with the SMR furnace. The SMR furnace includes a plurality of SMR tubes disposed within the SMR furnace. The monitoring system is configured to monitor the temperature of at least a plurality of SMR tubes and compare the temperature against a first predetermined value, and the water source is configured to introduce water to an SMR tube that has a temperature above the first predetermined value, such that the temperature of the SMR tube is reduced.

Description:
TECHNICAL FIELD OF INVENTION 
       [0001]    The present invention relates to an apparatus for reducing the tube temperature of a steam methane reformer (SMR). 
       BACKGROUND 
       [0002]    During normal operation of a steam methane reformer (SMR), some portion of the catalyst tubes may experience unexpectedly higher temperatures. Therefore, on account of the small number of tubes, the overall burner power has to be reduced and/or the steam to carbon ratio has to be increased to bring the temperature down; however, both of these methods globally affect plant efficiency. Additionally, predicting which tubes will be affected by this problem cannot be easily done since the tubes affected by this problem can vary. Therefore, a solution with which the temperature of each tube can be controlled independently has been sought to date, but no practical approach has been found. 
       SUMMARY 
       [0003]    The present invention is directed to an apparatus that satisfies at least one of these needs. The present invention is directed to an apparatus that satisfies the need to reduce temperature of particular SMR tubes. Certain embodiments of the present invention relate to introducing water into an individual tube that is affected by abnormally high temperatures in order to reduce the temperature of the tube, such that the temperature is below a given threshold temperature. Embodiments of the invention allow the plant to run more efficiently because the burner and steam to carbon changes are not necessary. 
         [0004]    In one embodiment, an apparatus for decreasing steam methane reformer (SMR) tube temperature can include an SMR furnace, a monitoring system in communication with the SMR furnace and a water source in fluid communication with the SMR furnace. The SMR furnace includes SMR tubes disposed within the SMR furnace. The monitoring system is configured to monitor the temperature of at least a plurality of SMR tubes and compare the temperature against a first predetermined value, and the water source is configured to introduce water to an SMR tube that has a temperature above the first predetermined value, such that the temperature of the SMR tube is reduced. 
         [0005]    In one embodiment, each SMR tube can include a feed inlet, a mixing zone, and a reaction zone. In one embodiment, the feed inlet is configured to receive the hydrocarbon feed, the mixing zone is configured to mix the hydrocarbon feed with water, and the reaction zone containing a reforming catalyst is configured to reform the hydrocarbon feed into hydrogen and carbon monoxide. 
         [0006]    Optional embodiments can also include:
       a header disposed within the SMR furnace and in fluid communication with the water source and at least a portion of the plurality of SMR tubes, wherein the header is configured to distribute water to more than one SMR tube,   a valve downstream the water source and upstream the SMR furnace, wherein the valve is configured to control the flow of water from the water source to the SMR furnace,   a water tube for each SMR tube, wherein the water tube is configured to introduce water to the mixing zone of the SMR tube,   a nozzle disposed on an end of the water tube, wherein the nozzle is configured to disperse the water into water droplets that are effective to provide cooling to the SMR tube,   wherein the water droplets have droplet sizes less than 500 microns,   wherein the water droplets have droplet sizes less than 100 microns,   wherein the nozzle is configured to atomize the water, such that the water droplets are of sufficiently small diameters such that the water droplets do not adversely affect catalyst performance within the reaction zone of the SMR tube,   wherein air is used to atomize the water,   wherein natural gas is used to atomize the water,   a high surface area foam disposed in the SMR tube between the mixing zone and the reaction zone, the high surface area foam configured to improve vaporization of the water, thereby reducing the risk of adversely affecting catalyst performance within the SMR tube,   wherein the first predetermined value is the maximum operating temperature rating of the tube, preferably 10° C. less than the first predetermined value,   wherein the monitoring system is configured to compare the temperature of each measured SMR tube against a second predetermined value, such that water flow from the water source to the SMR tube is reduced or stopped once the monitored temperature falls below the second predetermined value,   wherein the second predetermined value is the same as the first predetermined value, preferably 10° C. less than the first predetermined value,   wherein the water is demineralized water, and   wherein the water originates from the same water source as steam used in the SMR furnace.       
 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0022]    These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention&#39;s scope as it can admit to other equally effective embodiments. 
           [0023]      FIG. 1  illustrates an embodiment of the present invention. 
           [0024]      FIG. 2  illustrates a top view of an embodiment of the present invention. 
           [0025]      FIG. 3  illustrates an embodiment of the present invention. 
           [0026]      FIG. 4  illustrates comparative data for certain embodiments of the present invention. 
           [0027]      FIG. 5  illustrates increased pressure drop as a function of inlet velocity. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]    While the invention will be described in connection with several embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all the alternatives, modifications and equivalence as may be included within the spirit and scope of the invention defined by the appended claims. 
         [0029]    Certain embodiments of the present invention provide a straightforward approach in that water, preferably demineralized, is introduced directly, preferably by injection, into a particular SMR tube in order to reduce the SMR tube temperature. 
         [0030]    In one embodiment, water, preferably demineralized water can be introduced into a particular tube in order to reduce that tube&#39;s temperature. Demineralized water is typically available in the SMR plant to supply clean feedwater to the boilers for the steam production for the steam reforming process. In one embodiment, the water used for temperature regulation can be supplied directly from the plant&#39;s demineralized water source or from any returned condensate if the plant produces any excess steam that is not otherwise valorized. In a preferred embodiment, the water entering the SMR tube vaporizes prior to coming into contact with SMR tube catalysts. 
         [0031]      FIG. 1  illustrates a general process overview of an embodiment of the invention. SMR furnace  10  receives hydrocarbon steam mixture  12  and produces syngas  4  and hot stream  16 . As noted previously, some SMR tubes (not shown) within SMR furnace will exceed the desired operating temperature. In order to combat this issue, monitoring system  20  monitors the temperature of each SMR tube in order to identify any tubes that are running too hot. In the event an SMR tube is running hot, monitoring system can then initiate a sequence that will allow for water from water source  30  to be introduced to SMR tubes within SMR furnace  10 . In the embodiment shown, monitoring system  20  communicates (e.g., wired or wireless communication) with water source  30  and/or valve  32  to allow for the flow of water  42 . Monitoring system  20  continues to monitor the temperatures, and once the temperature of the affected SMR tube is below a desired value, monitoring system initiates a sequence to either stop the introduction of water to SMR furnace  10  or send a reduced amount of water that is effective for maintaining the tube&#39;s temperature below the desired value. It should be noted that use of a valve is not intended to limit the invention, as a person of ordinary skill in the art will recognize other methods of controlling flow of water can be utilized. 
         [0032]    In another embodiment, rather than taking the temperature of all of the tubes, a smaller subset of temperatures can be taken, preferably, those areas of tubes that exhibit higher temperatures than normal. 
         [0033]    In one embodiment, the flow rate of the incoming water  42  is determined by the upstream pressure. However, those of ordinary skill in the art will recognize that other methods for determining the flow rate can also be used, for example, flow meters. 
         [0034]      FIG. 2  depicts a top view of a water distribution system  1 . In the embodiment shown, header  66  carries water  42  to SMR tubes  50 , which can be aligned in rows. In one embodiment, the flow rate at which the water is introduced to header  66  depends on the pressure of the system. Water  42  introduced to water distribution system  1  is usually readily available elsewhere in the plant operation. In one embodiment, each SMR tube  50  has its own valve  33  to control the flow of water to SMR tube  50 . In one embodiment, check valves  35  can be installed to help improve the overall safety of the device. While  FIG. 2  only shows two rows of SMR tubes  50 , those of ordinary skill in the art will recognize that there can be more than two rows. 
         [0035]      FIG. 3  provides a cross sectional view of SMR tube  50  in accordance with an embodiment of the invention. Hydrocarbon steam mixture  12  enters SMR tube  50  via feed inlet  60  before entering mixing zone  62 . Hydrocarbon steam mixture  12  then travels down the length of SMR tube  50  coming into contact with catalyst  76 , wherein the reforming reaction takes place. In the event SMR tube  50  exceeds a desired temperature, water  42 , originating from water source  30 , is introduced to mixing area  62  via water tube  44 . In one embodiment, water tube  44  can vary in length. In an optional embodiment, SMR tube  50  can include a nozzle  56  that is configured to create small water droplets within mixing zone  62  to help improve overall water contact and speed up the cooling process. In one embodiment, insulation  52  can be utilized in top of SMR tube  50  to help reduce heat transfer through the top of SMR tube  50 . Insulation holder  54  can also be included to provide support for insulation  52 , and in certain embodiment, it can provide a seal from outside SMR tube  50 . 
         [0036]    In an optional embodiment, SMR tube  50  can also include foam  70 , which helps to vaporize the water such that water droplets are prevented from making contact with catalyst  76 . Advantageously, foam  70 , in conjunction with operating conditions (e.g., temperature and pressure), provide sufficient surface area for evaporation of water droplets. In the embodiment shown, foam holder  74  provides support for foam  70 , while ceramic fiber seal  72  provides a seal, such that substantially all of the water droplets are forced through foam  70 . Orifice plate  75  can also be provided in order to control the pressure drop across foam  70 . In one embodiment, foam  70  can be high surface area metallic foam or high surface area ceramic foam. 
         [0037]    In one embodiment, nozzle  56  introduces water  42  before water  42  enters mixing area  62 . Nozzle  56  may atomize water  42 , which helps to further preserve the stability of SMR tube  50  by preventing liquid water droplets from harming catalyst performance in the lower part of SMR tube  50 . The atomization process can make use of any acceptable gas, for example air or natural gas; however, use of natural gas is preferred since its use in the atomization process enables the steam and carbon ration to remain constant. In one embodiment, harm to the catalyst can be identified by a substantial pressure drop across SMR tube  50 . 
         [0038]      FIG. 4  represents the impact of introducing a small amount of water to the high temperature SMR tube. As shown in  FIG. 1 , a relatively small amount of water (10-30 ml/s) can effectively reduce the tube temperature. In one embodiment, the water can be introduced by injection. Depending on the water injection methodology (i.e., additive or replacement), water can be added to the total flowrate (NG/steam+water) of a particular tube or water can displace a specific amount of steam at the inlet. As depicted in  FIG. 4 , the former method produces a greater temperature drop, which makes the addition of fluid to the total flow rate more effective in temperature reduction. 
       EXAMPLES 
       [0039]      FIG. 5  is a graphical representation depicting pressure drop across various foams as a function of inlet velocity. As seen in  FIG. 5 , as inlet velocity is increased, the pressure drop across the foam also increases (this is shown by each individual line). Additionally,  FIG. 5  shows that increasing the density of the foam increases the pressure drop across the foam. Therefore, pressure drop is directly related to both foam density and inlet velocity. It is preferred to select a foam having a low pressure drop and while maintaining a high vaporization potential. 
         [0040]    Table I includes collected data, which includes resulting droplet sizes as a function of various pressures and capacities for various spray pattern types. Based on the data in Table I, higher spraying pressures yields smaller droplet sizes, with lower flow rates (at the same pressures) having smaller droplet sizes. Additionally, hydraulic spraying yields droplet sizes that are generally higher than atomizers. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Droplet Size by Spray Pattern at Various Pressures and Capacities 
               
             
          
           
               
                   
                 10 psi (0.7 bar) 
                 40 psi (2.8 bar) 
                 100 psi 7 bar) 
               
             
          
           
               
                 Spray Pattern 
                 Capacity  
                 VMD 
                 Capacity 
                 VMD 
                 Capacity 
                 VMD 
               
             
          
           
               
                 Type 
                 gpm 
                 1 pm 
                 microns 
                 gpm 
                 1 pm 
                 microns 
                 gpm 
                 1 pm 
                 microns 
               
               
                   
               
             
          
           
               
                 Air Atomizing 
                 0.005 
                 0.02 
                 20 
                 0.008 
                 0.03 
                 15 
                 12 
                 45 
                 400 
               
               
                   
                 0.02 
                 0.08 
                 100 
                 8 
                 30 
                 200 
                 — 
                 — 
                 — 
               
               
                 Fine Spray 
                 0.22 
                 0.83 
                 375 
                 0.03  
                 0.1 
                 110 
                 0.05 
                 0.2 
                 110 
               
               
                   
                 — 
                 — 
                 — 
                 0.43 
                 1.6 
                 330 
                 0.69  
                 2.6 
                 290 
               
               
                 Hollow Cone 
                 0.05 
                 0.19 
                 360 
                 0.1 
                 0.38 
                 300 
                 0.16 
                 0.61 
                 200 
               
               
                   
                 12 
                 45 
                 3400 
                 24 
                 91 
                 1900 
                 38 
                 144 
                 1260 
               
               
                 Flat Fan 
                 0.05 
                 0.19 
                 260 
                 0.1 
                 0.38 
                 220 
                 0.16  
                 0.61 
                 190 
               
               
                   
                 5  
                 18.9 
                 4300 
                 10 
                 38 
                 2500 
                 15.8 
                 60 
                 1400 
               
               
                 Full Cone 
                 0.1 
                 0.38 
                 1140 
                 0.19 
                 0.72 
                 850 
                 0.3 
                 1.1 
                 500 
               
               
                   
                 12 
                 45 
                 4300 
                 23 
                 87 
                 2800 
                 35 
                 132 
                 1720 
               
               
                   
               
             
          
         
       
     
         [0041]    The values in Table I are not intended to limit the invention to the pressure ranges or droplet sizes listed. Rather, the contents of Table I are provided for exemplary purposes. 
         [0042]    While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step. 
         [0043]    The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise. 
         [0044]    “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of” or “consisting of” and remain within the expressly defined scope of “comprising”. 
         [0045]    “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary. 
         [0046]    Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur. 
         [0047]    Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range. 
         [0048]    All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.