Abstract:
A method for volatile compound (VC) mitigation in a syngas production process is provided. This method includes providing a hydrocarbon reforming syngas production plant, this plant includes a reformer system comprising a primary fuel and oxidant stream, where part of this system is at low pressure, a steam inlet stream, and a primary combustion system for providing heat to the reformer system and producing a reformer flue gas stream, and a gaseous vent stream mainly composed of water and containing VC. This method also includes introducing at least a portion of the vent stream into one or more of the following: the primary fuel and oxidant stream; the steam inlet stream; the reformer flue gas stream.

Description:
BACKGROUND 
       [0001]    The present invention relates to a method to mitigate and reduce the volatile compound emissions (Volatile Organic Compounds (VOC) and other volatile compounds) of a Steam Methane Reformer (SMR) plant by routing the contaminated streams to the furnace and by using the heat of the furnace to destroy the organic compounds. Steam Methane Reformers are used to produce Synthesis Gas (syngas) from Methane and Steam and can be adjusted to produce pure hydrogen, methanol or other products. These endothermic reactions occur at high pressure and temperature releasing a lot of heat. Part of this heat is used to produce steam required by the process in one or more boilers. 
         [0002]    To produce steam, the boiler will need high quality water which is usually mixed with condensates from the process and sent to a deaerator to remove oxygen, dissolved CO2 and other impurities. The process condensates will sometimes contain volatile organic and volatile inorganic compounds coming from the plant process, which might have been absorbed by the water during condensing. Typically those volatile compounds such as, but not limited to, methanol or ammonia would be stripped from the water and vented to the atmosphere by the deaerator. Other vent streams containing volatile compounds (e.g. vent stream from boiler blowdown drum, process condensate stripper) can be treated similarly. 
         [0003]    In order to protect our environment, more and more states and countries have new legislation limiting and reducing atmospheric rejects by industrial plants. The first regulations were focusing on sulfuric acid or nitric oxides but today regulations are now implemented on volatile compound emissions (VOC &amp; Other). The proposed invention describes how the heat from the furnace of an SMR could be used to destroy those pollutants and reduce the environmental impact of the plant. 
       SUMMARY 
       [0004]    The present invention is a method for Volatile Compound (VC, which includes VOC and other volatile compounds) mitigation in a syngas production process. This method includes providing a hydrocarbon reforming syngas production plant, this plant includes a reformer system comprising a primary fuel and oxidant stream, where part of this system is at low pressure, a steam inlet stream, and a primary combustion system for providing heat to said reformer system and producing a reformer flue gas stream, and a gaseous vent stream mainly composed of water and containing VC. This method also includes introducing at least a portion of said vent stream into one or more of the following: said primary fuel or oxidant stream; said steam inlet stream; said reformer box; said reformer flue gas stream. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0005]      FIG. 1  is a schematic representation of one embodiment of the present invention, indicating the VC containing stream being injected into the convective section of the heat recovery device. 
           [0006]      FIG. 2  is a schematic representation of one embodiment of the present invention, indicating the VC containing stream being injected into the radiant section of the reformer unit. 
           [0007]      FIG. 3  is a schematic representation of one embodiment of the present invention, indicating the VC containing stream is combined with an ambient air stream, introduced into convection section where it is preheated, then combined with a fuel stream, and then introduced into the reformer through burners, where it is combusted. 
           [0008]      FIG. 4  is a schematic representation indicating a vertical VC containing stream injection manifold, in accordance with one embodiment of the present invention. 
           [0009]      FIG. 5  is a schematic representation indicating a horizontal VC containing stream injection manifold, in accordance with one embodiment of the present invention. 
           [0010]      FIG. 6  is a schematic representation indicating the blow down from the heat recovery device, in accordance with one embodiment of the present invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0011]    The invention provides a number of technical solutions for using the heat of the reformer to destroy the volatile compounds (VC), which can be implemented in order to destroy the volatile compounds without a dedicated thermal or catalytic oxidizer. 
         [0012]    As defined in this document, volatile compounds (VC), includes, but is not limited to, regulated volatile organic compounds, and other volatile compounds both organic and inorganic. This also includes, but is not limited to, ammonia and amines. 
         [0013]    One solution is to route the VC-containing stream, composed mostly of water and VC, to the convection section (also called waste heat recovery section) of the plant. In order to ensure the full destruction of the VC, the higher the flue gas temperature at the injection point, the better. A preferred embodiment of this solution would be to inject the contaminated stream into the flue gas duct between the exit of the furnace and the first coil of the waste heat recovery section. In order to ensure high destruction efficiency the flue gas temperature should be above 750° C. and preferably above 850° C. The injection system could be designed with an injection grid located horizontally or vertically, co-current or counter current of the flue gas flow. The preferred solution would be to have a counter flow injection to minimize the impact on the downstream coils in the waste heat section. Additionally the invention could include the mixing of the vent with steam to avoid any condensation in the lines prior to and at the injection point. 
         [0014]    In another embodiment of the solution, the contaminated stream would be injected in the bottom of the furnace in one or more places in the flue gas tunnels. Temperature at the injection point should be in the range of 1000° C. to 1060° C. In order to ensure the full destruction of the VC, beside the high temperature a sufficient residence time is important. The preferred distance to allow the maximum destruction of the VC would be ⅔ rd  of the furnace length away from the flue gas exit. This would provide enough residence time to ensure destruction efficiency over 99%. The injection point should be carefully designed to avoid any impact on the refractory bricks of the flue gas tunnel and should ensure no liquid carry-over into the firebox. 
         [0015]    In another embodiment, the contaminated stream may be injected on one or several side of the furnace at one or several locations. In the preferred solution the vent would be injected low enough not to disturb the burners flames but high enough to allow enough residency in the box and destruction of the VC. Tube protections would have to be engineered to avoid spraying the vent directly on the tubes and therefore cooling down the tubes, reducing the efficiency of the process reactions and leading to potential tube damage due to the water. 
         [0016]    In another embodiment, the contaminated stream could be injected from the top of the furnace either in the fuel system of the burners or in a separate injection point. If injected in the fuel system a protection system would have to be put in place to ensure that no liquid water is sent to the burners. 
         [0017]    The invention provides a number of technical solutions that could be implemented in order to destroy the volatile compounds without a dedicated thermal or catalytic oxidizer. 
         [0018]    Turning now to  FIG. 1 , hydrocarbon reforming syngas production plant  100  is presented. Reformer feed stream  101  and steam stream (steam inlet stream)  103  are introduced into the catalyst tubes of reformer unit  104 . Reformer unit  104  may be a Steam Methane Reformer (SMR) or an Autothermal Reformer (ATR). Hydrocarbon fuel (primary fuel) and oxidant stream  102  is introduced into the primary combustion system  114  in the shell side of reformer  104 , where they are combusted thereby providing the temperature and heat required for the reforming process. The products of this combustion exit the shell side of reformer  104  as SMR flue gas stream  106 . 
         [0019]    Reformer feed stream  101  and steam stream (steam inlet stream)  103  are converted into syngas stream  105 , which exits reformer  104  and proceeds to downstream cleanup, cooling and utilization (not shown). The SMR flue gas stream  106  then enters heat recovery device  107 , where it indirectly exchanges heat with boiler feed water stream  112 , thereby producing steam stream  103 , and with the SMR flue gas stream exiting as cool flue gas stream  110 . The two major sections of system  100  comprise a radiant section  108 , and a convection section  109 , with the convection section primarily comprised of heat exchange tubes. 
         [0020]    Most of the dissolved oxygen, as well as other non-condensable gases, in boiler feed water stream  112  are removed in deaerator  111 . The dissolved oxygen stream also contains volatile compounds (VC) which exit deaerator  111  in VC containing stream (gaseous vent stream)  113 . In one embodiment, VC containing stream  113  is introduced into convective section  109  of heat recovery section  107 . The idea would be to introduce the VCs into a section of the system wherein the pressure is relatively low and wherein the temperature and residence time are sufficiently high to destroy the VCs. By relatively low, it is understood that the pressure should be less than 2 bar, preferably less than 1.5 bar and could even be below atmospheric pressure. 
         [0021]    Turning now to  FIG. 2 , hydrocarbon reforming syngas production plant  200  is presented. Reformer feed stream  201  and steam stream (steam inlet stream)  203  are introduced into the catalyst tubes of reformer unit  204 . Reformer unit  204  may be a Steam Methane Reformer (SMR) or an Autothermal Reformer (ATR). Hydrocarbon (primary fuel) fuel and oxidant stream  202  is introduced into the primary combustion system  214  in the shell side of reformer  204 , where they are combusted thereby providing the temperature and heat required for the reforming process. The products of this combustion exit the shell side of reformer  204  as SMR flue gas stream  206 . 
         [0022]    Reformer feed stream  201  and steam stream (steam inlet stream)  203  are converted into syngas stream  205 , which exits reformer  204  and proceeds to downstream cleanup, cooling and utilization. The SMR flue gas stream  206  then enters heat recovery device  207 , where it indirectly exchanges heat with boiler feed water stream  212 , thereby producing steam stream  203 , and with the SMR flue gas stream exiting as cool flue gas stream  210 . The two major sections of system  200  comprise a radiant section  208 , and a convection section  209 , with the convection section primarily comprised of heat exchange tubes. 
         [0023]    Most of the dissolved oxygen, as well as other non-condensable gases, in boiler feed water stream  212  are removed in deaerator  211 . The dissolved oxygen stream also contains volatile compounds (VC) which exit deaerator  211  in VC containing stream  213 . In one embodiment, VC containing stream  213  is introduced into the radiant section of reformer unit  204 . The idea would be to introduce the VCs into a section of the system wherein the pressure is relatively low and wherein the temperature and residence time are sufficiently high to destroy the VCs. By relatively low, it is understood that the pressure should be less than 2 bar, preferably less than 1.5 bar and could even be below atmospheric pressure. 
         [0024]    Turning now to  FIG. 3 , hydrocarbon reforming syngas production plant  300  is presented. Reformer feed stream  301  and steam stream (steam inlet stream)  303  are introduced into the catalyst tubes of reformer unit  304 . Reformer unit  304  may be a Steam Methane Reformer (SMR) or an Autothermal Reformer (ATR). 
         [0025]    Reformer feed stream  301  and steam stream (steam inlet stream)  303  are converted into syngas stream  305 , which exits reformer  304  and proceeds to downstream cleanup, cooling and utilization. The SMR flue gas stream  306  then enters heat recovery device  307 . The two major sections of system  300  comprise a radiant section  308 , and a convection section  309 , with the convection section primarily comprised of heat exchange tubes. Within heat recovery device  307 , the combined stream indirectly exchanges heat the above combined ambient air stream  302 A and VC containing stream  313 , and with boiler feed water stream  312 , thereby producing steam stream  303 , and with the SMR flue gas stream exiting as cool flue gas stream  310 . 
         [0026]    Most of the dissolved oxygen, as well as other non-condensable gases, in boiler feed water stream  312  are removed in deaerator  311 . The dissolved oxygen stream also contains volatile compounds (VC) which exit deaerator  311  in VC containing stream  313 . A deaerator will typically operate at between 0.4 bar and 0.7 bar, so stream  313  will be at an equivalent low pressure. VC containing stream  313  is combined with ambient air stream  302 A, and the combined stream is introduced into radiant section  308 . In radiant section  308 , the combined stream is in indirect heat exchange with hot flue gas stream  306 , thereby producing preheated oxidant stream  302 A. Preheated oxidant stream  302 A is combined with fuel stream  302 C, which are then introduced into the shell side of reformer  304 , where they are combusted thereby providing the temperature and heat required for the reforming process. The products of this combustion exit the shell side of reformer  304  as SMR flue gas stream  306 . 
         [0027]    The idea would be to introduce the VCs into a section of the system wherein the pressure is relatively low and wherein the temperature and residence time are sufficiently high to destroy the VCs. By relatively low, it is understood that the pressure should be less than 2 bar, preferably less than 1.5 bar and could even be below atmospheric pressure. 
         [0028]      FIGS. 4 and 5  are illustrative embodiments of two possible ways in which VC containing stream  113  may be introduced into convective section  109  of heat recovery section  107 .  FIG. 4  illustrates a vertical injection manifold, and  FIG. 5  illustrates a horizontal injection manifold. Additional embodiments are envisioned, and are within the ability of one of ordinary skill in the art to develop and implement without undue experimentation. 
         [0029]    As indicated in  FIG. 4 , VC containing stream  113  is introduced into convective section  109  in a vertical injection manifold. This vertical manifold may have forward facing injection ports (A) or rearward facing injection ports (B). These ports may inject VC containing stream  113  at a positive or negative angle to the horizontal, as required for optimum distribution and mixing in SMR flue gas stream  106 . 
         [0030]    VC containing stream  113  may be injected on one or several sides of convective section  109 , at one or several locations. Special care should be taken to protect heat exchangers close to the injection ports to avoid spraying the vent directly on the exchanger tubes and therefore cooling down the tubes, reducing the efficiency and leading to potential tube damage due to the water. 
         [0031]    As indicated in  FIG. 5 , VC containing stream  113  is introduced into convective section  109  in a horizontal injection manifold. This horizontal manifold may have forward facing injection ports (A) or rearward facing injection ports (B). These ports may inject VC containing stream  113  at a positive or negative angle to the vertical as required for optimum distribution and mixing in SMR flue gas stream  106 . Special care should be taken to protect heat exchangers close to the injection ports to avoid spraying the vent directly on the exchanger tubes and therefore cooling down the tubes, reducing the efficiency and leading to potential tube damage due to the water. 
         [0032]    VC containing stream  113  may be injected from near the top of convective section  109 , or at any point above the horizontal midpoint of convective section  109 . 
         [0033]    Turning now to  FIG. 6 , hydrocarbon reforming syngas production plant  600  is presented. Reformer feed stream  601  and steam stream (steam inlet stream)  603  are introduced into the catalyst tubes of reformer unit  604 . Reformer unit  604  may be a Steam Methane Reformer (SMR) or an Autothermal Reformer (ATR). Hydrocarbon (primary fuel) fuel and oxidant stream  602  is introduced into the primary combustion system  614  in the shell side of reformer  604 , where they are combusted thereby providing the temperature and heat required for the reforming process. The products of this combustion exit the shell side of reformer  604  as SMR flue gas stream  606 . 
         [0034]    Reformer feed stream  601  and steam stream (steam inlet stream)  603  are converted into syngas stream  605 , which exits reformer  604  and proceeds to downstream cleanup, cooling and utilization. The SMR flue gas stream  606  then enters heat recovery device  607 , where it indirectly exchanges heat with boiler feed water stream  612 , thereby producing steam stream  603 , and with the SMR flue gas stream exiting as cool flue gas stream  610 . The two major sections of system  600  comprise a radiant section  608 , and a convection section  609 , with the convection section primarily comprised of heat exchange tubes. 
         [0035]    Most of the dissolved oxygen, as well as other non-condensable gases, in boiler feed water stream  612  are removed in deaerator  611 . The dissolved oxygen stream also contains volatile compounds (VC) which exit deaerator  611  in VC containing stream  613 . In one embodiment, the blow down stream  614  from heat recovery device  607  is introduced into a phase separation device  615 , where it is separated into a high solids content waste stream  616  and a vapor stream  617  which may contain VCs. Vapor stream  617  may then be introduced into deaerator  611 , after which VC containing stream  613  is introduced into either the radiant section  608  or the convective section  609  of reformer unit  604 . In one embodiment, VC containing stream  613  is introduced into both the radiant section  608  and the convective section  609  of reformer unit  604 . Vapor stream  617  may then be introduced directly into either the radiant section  608  or the convective section  609  of reformer unit  604 . In one embodiment, vapor stream  617  is introduced into both the radiant section  608  and the convective section  609  of reformer unit  604 .