Abstract:
This invention relates to an apparatus and method for the production and storage of hypochlorite, typically sodium hypochlorite, and hydrogen integrating a method of electrochemical power generation using said hydrogen. A brine solution is supplied to an electrolytic cell(s) where hypochlorite and hydrogen gas are evolved. The hypochlorite and hydrogen are separated and then stored or used directly. The hydrogen is transferred from the storage system to, or used as it is separated by, a proton exchange membrane fuel cell (PEMFC) device that produces electrical energy.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention is in the field of chemical production, more is more specifically directed to an apparatus and method for producing two chemical products, hypochlorite for use as a sanitizing solution and hydrogen as an energy source or an industrial product.  
       BACKGROUND OF THE INVENTION  
       [0002]     Chlorine in the form of hypochlorite, typically sodium hypochlorite, has been used in the field of water treatment for over a century. Traditionally however it has been chlorine gas that has been primarily used as a chlorine source for disinfecting water. The transportation of chlorine gas has become a safety concern in recent years. Sodium hypochlorite as an alternative source of chlorine is relatively safe to transport but much more costly per unit of available chlorine as it is mostly water.  
         [0003]     On-site sodium hypochlorite generation has been used as a relatively safe and cost efficient way of providing chlorine for water treatment applications. Sodium hypochlorite is made by reacting sodium chloride and water in the presence of a DC current according to the following equation 1: 
 
NaCl+H 2 O+2e − →NaOCl+H 2  
 
         [0004]     Previous systems of on-site sodium hypochlorite generation have vented away the H 2  produced into the atmosphere.  
         [0005]     Greenhouse gas (GHG) emissions have been identified as a contributor to deleterious environmental effects. Fossil fuel consumption is a major source of GHG emissions. As a result new technologies have emerged to provide energy without the negative GHG by-products. One of these new technologies is hydrogen fuel cells or Proton Exchange Membrane Fuel Cells (PEMFC).  
         [0006]     A hydrogen fuel cell is used to convert stored chemical energy into electrical energy. Typically a fuel cell includes a cathode flow field plate, a gas diffusion layer, a membrane electrode assembly, a second gas diffusion layer, and an anode flow field plate. Each flow field plate has an inlet and an outlet connected by open-faced channels that provide a means of distributing reactant gases to the membrane electrode assembly. The membrane electrode assembly typically includes a solid electrolyte sandwiched between a cathode catalyst and an anode catalyst.  
         [0007]     Operation of the fuel cell involves the input, flow and output of an anode reactant gas and a cathode reactant gas on their respective flow field plates. As these gases pass through the channels of their respective flow field plates they are forced to pass through their respective gas diffusion layers. In passing through these layers the gases will come into contact with their respective catalyst layers.  
         [0008]     The anode catalyst helps the anode reactant gas separate into reaction intermediates. Reaction intermediates include ions and electrons. Only the ions may pass through the solid electrolyte of the membrane electrode assembly to come into contact with the catalyst layer on the cathode side of the fuel cell. The cathode catalyst interacts with the cathode reactant gas and the reaction intermediates converting the cathode reactant gas into the chemical product of the fuel cell reaction. The chemical product passes through the gas diffusion layer back to the cathode flow field plate and is transferred along the channels of the plate to its outlet.  
         [0009]     The solid electrolyte is a barrier to the flow of the electrons created as reaction intermediates at the anode catalyst. The electrons can flow from the anode side to the cathode side of the membrane electrode assembly if the two sides are electrically connected using an external load between the anode flow field plate and the cathode flow field plate. The anode reaction in this case is an oxidation reaction as electrons are released at the anode catalyst. Conversely the cathode reaction is a reduction reaction where electrons are consumed. The specific anode (A), cathode (B), and overall fuel cell reaction (C) are represented as: 
 
H 2 →2H + +2e −   (A) 
 
½O 2 +2H + +2e − →H 2 O  (B) 
 
H 2 +½O 2 →H 2 O  (C) 
 
         [0010]     To increase the electrical output, a plurality of fuel cells can be arranged in series to form a fuel cell stack. In a stack arrangement one side of a flow field plate functions as the anode flow field plate for one fuel cell while the other side of the flow field plate functions as the cathode flow field plate for another fuel cell.  
         [0011]     Referring now to  FIG. 1  illustrating a hypochlorite production system  100  disclosed in U.S. Pat. No. 6,468,412. The system includes an electrolyzer  106  that requires a source of brine  102  which may be either a synthetic source such as a salt saturator  102  or a natural source such as sea water. The brine is metered by a pump  104  into the electrolyzer  106  containing electrolytic cell  105  where electrolysis occurs. The electrolytic cell  105  contains cathodes and anodes. A separate softened water supply may be provided to the electrolyzer to optimize the brine concentration within. The resultant hypochlorite solution is transferred past product outlet  109  and travels through solution line  110  to storage tank  111 .  
         [0012]     Hydrogen gas, produced in addition to hypochlorite in the electrolyzer  106 , passes with the hypochlorite solution through solution line  110  into the storage tank  111  where it separates from the liquid product. In other embodiments some separation may occur in the electrolyzer  106  itself with a gas vent connected to the top of the electrolyzer  106  allowing for the flow of hydrogen gas directly into the storage tank. The storage tank is provided with a vent  112  that allows the hydrogen to exit the system into the atmosphere. An air blower  116  may also be connected to the storage tank to provide a forced flow of air to purge the hydrogen in the storage tank into atmosphere. In further embodiments a fan may be attached to individual electrolyzers  106 . Hydrogen is thus not collected for future utility.  
         [0013]     UK Patent Application No. 2,068,016 discloses an electrolyzer with electrolytic cell assembly  200  as shown in  FIG. 2 . The electrolyzer casing  210  is typically cylindrical and is sealed on its end flanges with removable covers  201 , and gaskets  205 . Electrically non-conductive partitions  209  are spaced evenly along the length of tie rod  214 . Spacer  213  is fitted over the tie rod  214  and abuts the partitions  209 . Titanium electrode support blocks  211  are secured on both sides of the partitions  209 . Conductor studs  204  and  215  are connected on opposite flanges of the electrolyzer. Brine inlet and product outlet are not shown. Product or brine passageway  212  exists between the circumference of the partition  209  and the electrolyzer casing.  
         [0014]     The electrolytic cell assembly encompasses anode plates  206  and cathode plates  207 . Both anode and cathode plates  206   207  are aligned in parallel and spaced alternately in fixed increments. Clamping washers  202  are inserted to between successive anode and cathode plates. Electrode plates and washers are assembled over rods that are not shown and are secured using clamping nuts  208 .  
         [0015]     Referring now to  FIG. 3  illustrating further parts of the electrolyzer  300  of  FIG. 2 . This particular schematic shows a hydrogen vent port  301  where evolved hydrogen from the gas zone  302  is removed and product discharge connection  308  where hypochlorite from electrolyte zone  303  are both under atmospheric pressure with the overflow trap  307  regulating the level of product in the electrolyzer to the approximate level in the discharge connection. The gas bleed orifice  309  provides an additional route with which to remove evolved hydrogen. Hydrogen is not shown to be collected.  
         [0016]     Referring now to  FIG. 4 , a prior art proton exchange membrane fuel cell  400  is reviewed in U.S. Pat. No. 6,569,298. The proton exchange membrane fuel cell is comprised of a centrally located membrane electrode assembly  401 , which includes an anode electrode layer  404 , a cathode electrode layer  408 , an electrocatalyst layer  405  between the anode electrode and the membrane electrode assembly, and an electrocatalyst layer  407  between the cathode electrode  408  and the membrane electrode assembly  401 .  
         [0017]     The electrocatalyst layers  405  and  407  promote the desired electrochemical reaction. The polymer membrane electrode or electrolyte  406  readily permits the flow of ions between the anode electrode layer  404  and the cathode electrode layer  408  but is relatively impermeable to gases and electrons.  
         [0018]     During the operation of the proton exchange membrane fuel cell  400 , hydrogen flows through channels  403  that are part of the anode flow field plate  402 . The hydrogen is forced to travel through anode electrode layer  404  leading to contact with electrocatalyst layer  405 . The contact of hydrogen with electrocatalyst layer  405  yields electrons and hydrogen ions in an oxidation reaction. These hydrogen ions will then migrate through the electrolyte  406 . The reaction at electrocatalyst layer  405  is given by: 
 
H 2 →2H 30  +2e −   (A) 
 
         [0019]     Simultaneously, oxygen flowing through channels  409  that are part of the cathode flow field plate  410  is forced to travel through cathode electrode layer  408 . In the cathode electrode layer the oxygen will combine with any hydrogen ions that have migrated through the electrolyte  406  and electrons from the cathode electrode layer  408  to form water. This electrochemical reaction is given by: 
 
½O 2 +2H + +2e − →H 2 O  (B) 
 
         [0020]     The overall electrochemical reaction for the proton exchange membrane fuel cell  400  is therefore: 
 
H 2 +½O 2 →H 2 O  (C) 
 
         [0021]     A stream of electrons  412  travels from the anode flow field plate  402  through an electrical load  411  to the cathode flow field plate  410  to provide electrons for the reaction occurring at the cathode electrocatalyst layer  407 .  
         [0022]      FIG. 5  shows a further prior art proton exchange membrane fuel cell stack of the invention reviewed in U.S. Pat. No. 6,569,298 and utilizing an internal module for humidification of the reactants  500 . The assembly  500  includes a proton exchange membrane fuel cell stack  504 , an internal module for humidification of the reactants  505 , an electrochemically active region  506 , a water softening or deionization apparatus  501 , a softened water reservoir  502 , and a heat exchanger  508 . In the assembly  500  the softened water can be used for both conditioning of the reactant gases and heat transfer away from the fuel cell stack  204 . To accommodate both functions water is simultaneously injected through the humidification module  505  and through cooling elements  507  positioned along the length of the electrochemically active module  506 .  
         [0023]     A hydrogen fuel stream is delivered to fuel inlet port  509  while a stream of compressed oxidizer is likewise delivered to oxidizer inlet port  510 . The reactants are both distributed to the electrochemically active region  506 . Excess hydrogen and oxidizer exit the proton exchange membrane fuel cell stack  504  respectively through fuel outlet port  511  and oxidizer outlet port  512 . Excess fuel may be re-circulated back into the fuel stream using an appropriate purification and pumping system (not shown).  
         [0024]     Proper temperature management of the proton exchange membrane fuel cell stack  504  is critical maintaining the functionality of the unit. Softened water is injected through coolant inlet port  513  and is circulated through the humidification module  505 , and the cooling elements  507  within the electrochemically active module  506 . The water and adsorbed heat then exits through coolant outlet port  514  and is received by the heat exchanger  508  where the water is cooled to approximately its original temperature.  
         [0025]     The potential difference produced by the fuel cell stack  504  occurs across positive terminal  515  and negative terminal  516 . A DC current may be forced through a power handling module  517  where it could be used directly or subsequently it can be converted into AC current by power-conditioning module  518 .  
         [0026]      FIG. 6  is a schematic view of a prior art proton exchange membrane electrolysis device and hydrogen storage system  600  reviewed in U.S. Pat. No. 6,569,298. The system is generally comprised of an electrolysis stack  601  sandwiched between a cathode plate  606  and an anode plate  605 . A hydrogen manifold  616  is positioned at the cathode plate  606  and an oxygen manifold  617  is positioned at the anode plate  605 . The cathode plate  606  and the anode plate  605  are coupled to a DC power supply  604 . The electrolysis stack  601  is further coupled to a water deionization module  603  that delivers treated water to the electrolysis stack  601 . Treated water is also circulated through the electrolysis stack  601  by a recirculation pump  612  for cooling or other purposes.  
         [0027]     During operation of the electrolysis device and hydrogen storage system  600 , externally supplied water from a municipal source is fed through the water deionization module  603 . The purified water stream  615  flows to a water storage container  609  and is subsequently fed into the electrolysis device. Water fed into the electrolysis stack  601  is evolved into hydrogen and oxygen at the cathode and anode respectively. A two-phase mixture of hydrogen and water is collected at the hydrogen manifold  616  while a two-phase mixture of oxygen and water is collected at the oxygen manifold  617 . The two-phase mixture of hydrogen and water flows through line  618  where check valve  620  prevents the back-flow of the mixture into the electrolysis stack  601 . A phase separator  614  divides the evolved hydrogen gas from the remaining water where the water portion is returned to the water storage container  609 . Another phase separator  613  divides the evolved oxygen gas from the remaining water having entered the separator through line  619  containing check valve  621  to prevent back-flow. The water portion of the oxygen-water separation is also returned to water storage container  609 .  
         [0028]     The produced hydrogen gas is purified further following the phase separator  614  by condenser  611 . The purified hydrogen is then passed through a hydrogen outlet port  607 , through check valve  622  to a mechanical compression system  623 . The product hydrogen is then accumulated in fuel storage system  624 . In this description the storage system  624  is assumed to comprise a plurality of pressure vessels  625  with a safety relief valve  626 , a control valve  627 , and a dispensing regulator  628  fluidly coupled to the vessels  625 . Burst discs  629  have been illustrated as a safety precaution against over pressurizing the pressure vessels  625 . The product oxygen flows from the phase separator  613  into a condenser  610  to remove residual water and is then routed through oxygen outlet port  608  to leak valve  630 .  
       SUMMARY OF THE INVENTION  
       [0029]     One object of this invention aims to collect the H 2  in during hypochlorite generation for use in a power generating capacity.  
         [0030]     The objective of the present invention is to provide an integrated system for the production, separation and collection of both hypochlorite and hydrogen. In accordance with a preferred embodiment of the invention, an apparatus for producing hypochlorite and generating electrochemical power is provided that comprises: an electrolyzer for generating hypochlorite and hydrogen in fluid communication with a source of brine and in electrical communication with a source of electrical energy, the electrolyzer having an electrolyzer outlet for spent brine solution, generated hypochlorite and hydrogen; a separator for separating spent brine and generated hydrogen and hypochlorite in fluid communication with the electrolyzer outlet; a fuel cell for generating electrochemical power in input fluid communication with a source of oxidizer and output electrical communication with a power handling module; a hydrogen conduit for controllably transporting hydrogen separated by the separator to the fuel cell and a hydrogen storage system; a hypochlorite conduit for removing hypochlorite separated by the separator from the separator; and a brine conduit for transporting brine separated by the separator.  
         [0031]     Another preferred embodiment is directed to a method for producing hypochlorite and generating electrochemical power comprising the steps of: producing hypochlorite and hydrogen in an electrolyzer from brine received from a source of brine; separating in a separator spent brine and generated hydrogen and hypochlorite received from the electrolyzer; generating electrochemical power in a fuel cell using generated hydrogen and an oxidizer received from a source of oxidizer; and directing generated hypochlorite from the separator to a hypochlorite storage.  
         [0032]     In accordance with another aspect of the invention, the apparatus operates in a hypochlorite and hydrogen production mode, with a water softener receiving water from a water source, transferring softened water to salt saturator, transferring brine solution to an electrolyzer or plurality of electrolyzers containing at least one electrolytic cell where hypochlorite and hydrogen are evolved. Separation can occur during and after the production mode both in the electrolyzers and in the final hypochlorite storage tank. Collection of the hypochlorite can occur in a closed top tank where further hydrogen can be separated and then stored usually in pressurized containers. Hypochlorite can be utilized in a water disinfection capacity while the hydrogen can be accessed in a power generation capacity using a variety of control methods. Alternatively the hydrogen can be used in a variety of industrial processes.  
         [0033]     The system of the present invention will produce two economic products: hypochlorite for use as a sanitizing solution and hydrogen as an energy source. Specifically the invention will allow for the establishment of a basic hydrogen fuel infrastructure in a cost-effective manner in the absence of current demand. An established hydrogen fuel infrastructure may expedite the production and sale of hydrogen fueled vehicles and power generators. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]     Preferred, non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:  
         [0035]      FIG. 1  is a schematic diagram of a prior art hypochlorite production system.  
         [0036]      FIG. 2  is a sectional top view of a prior art electrolyzer with contained electrolytic cell assembly.  
         [0037]      FIG. 3  is a schematic diagram of a prior art electrolyzer.  
         [0038]      FIG. 4  is a sectional view of a prior art proton exchange membrane fuel cell.  
         [0039]      FIG. 5  is a schematic sectional view of a prior art proton exchange membrane fuel cell stack utilizing an internal module for humidification of the reactants.  
         [0040]      FIG. 6  is a schematic view of a prior art electrolysis device and hydrogen storage system.  
         [0041]      FIG. 7  is a schematic diagram of an apparatus for the production, separation, and storage of hypochlorite and hydrogen according to a preferred embodiment of the invention.  
         [0042]      FIG. 8  is a schematic diagram of an apparatus for the production, separation, and storage of hypochlorite and hydrogen integrating a fuel cell according to a preferred embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0043]     The present invention is generally directed to an integrated system for generating both a disinfecting agent and power. Many of the specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 7 and 8  to provide a thorough understanding of such embodiments. One who is skilled in the art will understand, however, that the present invention may have additional embodiments, or that the present invention may be practiced without several of the details described in the following description.  
         [0044]      FIG. 7  is a schematic diagram of an apparatus for the production, separation, and storage of hypochlorite and hydrogen  700  according to a preferred embodiment of the invention. The apparatus  700  is comprised of a brine electrolyzer  703 , a hypochlorite storage and hydrogen separation vessel  704 , and a hydrogen storage system  715 . The internal details and operation of the electrolyzer  703 , the hypochlorite storage and hydrogen separation vessel  704 , and the hydrogen storage system  715  are well known to a person skilled in the relevant art.  
         [0045]     Operation of the apparatus  700  may require water to be delivered to a water deionizer  701 . The source of the water may be either potable or non-potable. The flow rate of the water may be dictated by various factors and may include but not be limited to the level of hypochlorite in the storage vessel  703  or the dosing rate of the metering pump  714 . Once the water has been softened to a sufficient level it is delivered to salt saturator  702  where salt is added to the water to create a brine solution that is input into the electrolyzer  703 . Within the electrolyzer  703  a direct current is applied to cause the brine solution to evolve into hypochlorite and hydrogen in accordance with Equation 1 above. Electrical connections and power conversion devices are not shown but implied.  
         [0046]     In the electrolysis process, hypochlorite and hydrogen are evolved and flow as a two-phase mixture out of the electrolyzer  703  into the hypochlorite storage vessel  704  where phase separation into liquid hypochlorite solution  705  and gaseous hydrogen  706  occurs. Some separation may occur within the electrolyzer  703  itself and any separated hydrogen may be vented out of individual electrolyzers via a vent line  719  directly into the hypochlorite storage vessel  704  to increase the efficiency of any downstream electrolyzers. Additionally, dedicated phase separators and condensers may be employed to purify the hydrogen but are not shown on the diagram. A gas outlet valve  707  allows for evolved hydrogen to be vented to atmosphere in the case of a failure of the hydrogen storage system or the hydrogen fuel cell. A fan that is not shown may be used to purge the system of hydrogen under any alarm conditions in conjunction with the opening of the outlet valve  707 . Check valve  708  prevents the backflow of hydrogen back into the storage vessel  704 .  
         [0047]     When the hydrogen gas has been sufficiently purified it may pass through vacuum regulator  716  to compressor  709 . The compressor  706  transfers the hydrogen to storage or directly into a proton exchange membrane fuel cell. Pressure sensor  718  monitors the pressure in the storage system and may be used in controlling the operation of the system. Control valve  710  is used to dictate the direction of gas flow either into the hydrogen storage system  715  or through pressure regulator  717  and then to a proton exchange membrane fuel cell (not shown). A plurality of vessels  711  may be utilized in storing the hydrogen. Safety relief valve  712  is attached at the manifold of the pressure vessels to expulse any excess pressure and prevent vessel rupture. Burst discs not shown may also be included on the pressure vessels. The flow of hydrogen from the pressure vessels  712  to a proton exchange membrane fuel cell may be controlled by a pressure regulator  713 .  
         [0048]      FIG. 8  is a schematic diagram of an apparatus  800  for the production, separation, and storage of hypochlorite and hydrogen integrating fuel cell  800  according to a second preferred embodiment of the invention. The apparatus  800  is comprised of a brine electrolyzer or plurality of electrolyzers  804 , a hypochlorite storage and hydrogen separation vessel  807 , a hydrogen storage system  816 , a proton exchange membrane fuel cell  837 . The internal details and operation of electrolyzer  804 , hypochlorite storage and hydrogen separation vessel  807 , hydrogen storage system  816 , and proton exchange membrane fuel cell  837  are well known to a person skilled in the relevant art.  
         [0049]     Operation of the apparatus  800  requires a source of water to be delivered to a water deionizer  801  as with the other preferred embodiment discussed. The source of the water may be either potable or non-potable. Softened water from the water deionizer  801  is supplied to salt saturator  803  to create a brine solution. Softened water may similarly distributed to proton exchange membrane fuel cell  837  through valve  802  and supply line  829  to cool the fuel cell  837  and also to electrolyzer  804  through water line  834  to dilute the brine concentration in the electrolyzer  804  if necessary. Brine created in the salt saturator  803  is metered into electrolyzer  804  where a direct current is applied to the solution in order to evolve hypochlorite and hydrogen. A series of electrolyzers  804  is shown in  FIG. 8  with each having an optional hydrogen gas port  839  to remove hydrogen that has separated from the solution in each cell therefore by-passing any downstream electrolyzers  804 . The separated hydrogen flows through hydrogen gas line  806  into hypochlorite storage and hydrogen separation vessel  807 . The solution mixture of hypochlorite, entrained hydrogen, and unspent brine exits the final electrolyzer  804  in the series and flows through solution line  805  to the hypochlorite storage and hydrogen separation vessel  807 .  
         [0050]     Within the hypochlorite storage and hydrogen separation vessel  807 , two distinct phases are present: the liquid hypochlorite phase  808  and the gaseous hydrogen phase  809 . The liquid hypochlorite phase  808  is metered as a disinfecting agent into a water system by metering pump  833  but could also be transferred to another storage device to be transported to an off-site (disinfection) system. A gas outlet valve  810  is attached to the top of the vessel  807  allowing for evolved hydrogen to be vented to atmosphere in the event of a failure of the hydrogen storage system  816  or the fuel cell  837 . A fan (not shown) may be connected to the vessel  807  to purge any evolved hydrogen into the atmosphere through gas outlet valve  810  during an alarm condition.  
         [0051]     Successive hydrogen purification mechanisms (not shown) may be used in addition to the primary separation vessel  807 . When the hydrogen gas has been sufficiently purified it will pass through vacuum regulator  812  to compressor  813 . An optional check valve  811  will prevent the backflow of hydrogen. The compressor  813  provides the necessary pressure to store the hydrogen as compressed gas or feed the gas directly to the fuel cell  837 . Pressure sensor  814  monitors the pressure in the hydrogen storage system  816  and may be used in the control scheme of the entire system. Control valve  815  is used to direct the flow of hydrogen to either the hydrogen storage system  816  or the fuel cell  837  or proportionally to both. A plurality of pressure vessels  817  may be employed based on the demands of the system  800 . A safety relief valve  838  is attached at the manifold of the pressure vessels  817  to expulse any excess pressure and prevent a vessel  817  rupture. Pressure regulator  818  may be used to control the flow of hydrogen from the pressure vessels  817  to the fuel cell  837 . Likewise pressure regulator  820  may be used to control the flow of hydrogen from the compressor  813  to the fuel cell  837 .  
         [0052]     Isolation control valves  819  and  835  allow for the selection of either the stored or direct source of hydrogen for the fuel cell  837 . Hydrogen fuel flows into the humidification module  822  of the fuel cell  837  through hydrogen inlet  821 . The chosen oxidizer flows into the humidification module  822  of the fuel cell  837  through oxidizer inlet  831 . Softened water from deionizer  801  is transferred to the fuel cell  837  for humidification and cooling through water supply line  829 . The water is removed from the fuel cell  837  via water waste line  830 . Humidified hydrogen and oxidizer are transferred into the electrochemically active module  823  where the electrochemical reaction creates a potential difference between positive electrode  824  and negative electrode  825 . The potential difference across the electrodes  824   825  produces a DC which is accepted by power handling module  827  where it could be applied directly to a load (not shown) or converted to AC current by power-conditioning module  828  and then applied to a load.  
         [0053]     Unused hydrogen from the electrochemical reaction may be re-circulated back through the system  800  via hydrogen return line  826  or it may be exhausted to atmosphere through a gas outlet valve that is not shown. Check valve  836  prevents the backflow of hydrogen. Oxidizer that is not reacted is exhausted to atmosphere through the oxidizer outlet  832 .  
         [0054]     The above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Specific embodiments and examples of the invention are described in the foregoing for illustrative purposes, however, this should not exclude various modifications within the scope of the invention as those skilled in the art will recognize.