Patent Publication Number: US-2009220412-A1

Title: Electric reaction technology for fuels processing

Description:
This application is a divisional application and continuation application of U.S. patent application Ser. No. 11/674,250, having a filing date of Feb. 13, 2007, and entitled “Electric Reaction Technology for Fuels Processing,” which claims priority to U.S. provisional application having Ser. No. 60/773,613, having a filing date of Feb. 15, 2006, entitled Electric Reaction Technology for Pollution-Free Fuels Decarbonization. 
    
    
     BACKGROUND OF THE INVENTION 
     Carbon dioxide is produced when burning any hydrocarbon fuel. Additional carbon dioxide is produced by the chemical industry when hydrocarbons are used as feedstocks for catalytic steam reforming, partial oxidation and water gas shift reaction processes to manufacture hydrogen-containing synthesis gas. Little has changed in the last 50 years and almost all this carbon dioxide finds its way into the atmosphere. In recent years, carbon dioxide has been identified as a contributor to global climate change. Governments and corporations have proposed many methods to reduce or manage atmospheric carbon dioxide emissions. Furthermore, major efforts have been mounted to produce hydrogen more economically, since it burns cleanly, producing only water (as steam) and heat as combustion products. All approaches to move toward environmentally friendly fuels entail great complexity and expense. 
     The only way to completely eliminate the production of carbon dioxide when combusting hydrocarbons would be to:
         1. Apply heat to hydrocarbons to cause decomposition to elemental carbon and molecular hydrogen;   2. Separate the hydrogen and carbon; and   3. Either burn the hydrogen with air or oxygen forming high temperature steam as a useful source of heat or electrochemically convert the hydrogen into water and electricity in a fuel cell.       

     In such processes, the heating value of carbon combustion would be unrealized as useful heat. This loss of carbon heating value would nominally require twice the fuel to produce a given amount of hydrogen or process heat. However, carbon solids recovered in the process could be marketed or stored (sequestered) much more economically than by ‘end-of-the-process’ capture and sequestration of carbon dioxide. 
     Accordingly, a need exists for a method and apparatus to produce hydrogen in an efficient manner with limited carbon dioxide emission. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention provide a method and apparatus for producing hydrogen wherein a hydrocarbon gas is fed into an electric reaction technology system to decompose the hydrocarbon gas to hydrogen gas and carbon solids. The electric reaction technology system comprises one or more heating zones, wherein each heating zone comprises one or more heating stations and each heating station comprises one or more heating screens. (The term “screen” as used herein means a meshed wire component.) Preferably, a final near-equilibrium attainment zone without additional heat input follows either the complete ERT heating phase or one or more stages of the ERT heating phase. In an illustrative embodiment of the invention, the attainment zone comprises a carbon reaction chamber. Preferably, the temperature of the hydrogen and any remaining carbon and hydrocarbons leaving the electric reaction technology system is in the range of about 2000° F. to about 2700° F. After passing the hydrogen gas through the electric reaction technology system, the hydrogen gas and any remaining carbon solids and hydrocarbon gas are cooled. The hydrogen gas and any remaining carbon solids and hydrocarbon gas then flow through a phase separation system, such as a scrubber, filtration or drying system for example, to remove substantially all of the carbon, leaving hydrogen product. 
     In an illustrative embodiment of the invention, heat generated from the electric reaction technology system is used to heat the incoming hydrocarbon gas feed. Preferably, the hydrocarbon gas feed is heated by the heat generated from the electric reaction technology system to a temperature in the range of about 400° F. to about 1200° F. This can be accomplished by flowing the hydrocarbon gas into a heat exchanger, and flowing the heated hydrogen gas and any remaining carbon solids and hydrocarbon gas through the heat exchanger to heat additional incoming hydrocarbon gas. The hydrocarbon gas flow may also be preheated prior to feeding it into the electric reaction technology system or heat exchanger. In an exemplary embodiment of the invention, the temperature increase of the hydrocarbon gas flow from the pre-heating step is in the range of about 250° F. to about 600° F. 
     In an illustrative embodiment of the invention, the heated hydrogen gas and carbon solids exiting each heating zone in the electric reaction technology system flow through a carbon removal component to remove some or all of the carbon solids. 
     The heated hydrogen gas and any remaining carbon solids and hydrocarbon gas may be passed through a quench system after exiting the electric reaction technology system and prior to entering the phase separation system. Water may be added to the hydrogen gas and any remaining carbon solids and hydrocarbon gas in the phase separation system to create a slurry containing substantially all of the carbon. 
     In a further embodiment of the invention, at least a portion of the heated hydrogen gas and any remaining carbon solids and hydrocarbon gas exiting the heat exchanger is recycled into the hydrocarbon gas flow. Preferably the ratio of recycled hydrogen to non-recycled hydrogen is in the range of about 2:1 to about 4:1, and more preferably in the range of about 2.5:1 to about 3.5:1. The hydrogen gas that will be recycled is passed through a recycle compressor to compensate for pressure losses through the system. Hydrogen gas from the phase separation system may also be recycled into the hydrocarbon gas flow. This can be done either instead of recycling hydrogen gas from the heat exchanger or in addition to it. 
     The spacing of screens in the ERT system and the residence times are important factors in optimizing the process. In a particular embodiment of the invention, the spacing between heating screen stations increases in the gas flow direction. In a further embodiment of the invention, the spacing between heating screen station varies continuously after the first zone to maintain substantially isothermal conditions. Illustrative embodiments of the invention provide residence times that increase for each heating station; and residence times that decrease with each heating screen station. 
     The heat duty delivered by each heating screen station may be substantially equal or may vary from station to station. In further embodiments, the heat duty delivered by each subsequent zone decreases, or the heat duty delivered by all zones is constant. Additionally, in an illustrative embodiment of the invention the heat delivered by each heating screen station is substantially constant within each zone. 
     The temperature may vary between heating zones. In a particular embodiment of the invention, the difference between the temperature of the flow entering a heating screen station and the temperature of the flow exiting the heating station is in the range of about 125° F. to about 175° F.; in other embodiments the heating input may cause a temperature rise of 400° F. or more 
     The electric reaction technology system can also be used to pyrolyze hydrocarbons. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention is best understood from the following detailed description when read with the accompanying drawings. 
         FIG. 1  depicts a stagewise hydrogen production system according to an illustrative embodiment of the invention. 
         FIG. 2  is a graph showing equilibrium and operating curves for a stagewise hydrogen production system according to an illustrative embodiment of the invention. 
         FIG. 3  depicts a hydrogen production system having a recycle configuration according to an illustrative embodiment of the invention. 
         FIG. 4  is a graph showing equilibrium and operating curves for a hydrogen production system having a recycle configuration according to an illustrative embodiment of the invention. 
         FIG. 5  depicts a single pass hydrogen production system according to an illustrative embodiment of the invention. 
         FIG. 6  is a graph showing equilibrium and operating curves for a hydrogen production system having a single pass configuration according to an illustrative embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Disclosed is an Electric Reaction Technology (ERT) process and apparatus directed to the production of hydrogen and carbon solids by decomposition of methane or natural gas. The ERT apparatus may also be used for pyrolysis processes. When used for the former, the ERT process may also be called a fuel decarbonization process. The process employs electric resistance heaters capable of adaptation to the selective decomposition of hydrocarbons and filtration/separation equipment capable of effective filtration/separation under very high carbon loading. 
     As the source of electricity may be an environmental concern, such a plant could be situated near an economical and eco-friendly wind farm to provide the necessary electricity. There would be little or no resulting carbon dioxide or other greenhouse gas emissions from either one of these processes, as compared to conventional fossil fuel technologies. 
     Hydrocarbon decomposition, also known as fuels decarbonization, has been neglected as a potential route for commercial hydrogen and carbon solids manufacture and as a process to mitigate global warming. Methane, the largest constituent in natural gas, is also the hydrocarbon with the highest hydrogen to carbon ratio. It therefore has the potential to produce relatively more hydrogen than any other hydrocarbon. Methane decomposition has simple one-step chemistry; and superior thermodynamics in that the chemical reaction requires only 11.3 Kcal/mol of hydrogen, the lowest known process energy consumption per unit of hydrogen produced. 
     Methane Decomposition by Heating: (One Non-Catalytic Step) 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Methane Decomposition 
                 CH 4  → C + 2H 2   
               
               
                   
                 Process Energy/Unit of Hydrogen 
                 +11.3 Kcal/mol hydrogen 
               
               
                   
                   
               
            
           
         
       
     
     This compares favorably with methane reforming by steam comprising a two-step, two-catalyst process that requires 18.8 Kcal/mol of hydrogen. 
     Methane Reforming by Steam: (Two Catalytic Process Steps) 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Steam Reforming 
                 CH 4  + H 2 O → CO + 3H 2   
               
               
                   
                 Water-Gas Shift 
                 CO + H 2 O → CO 2  + H 2   
               
               
                   
                 Overall Reaction 
                 CH 4  + 2H 2 O→ CO 2  + 4H 2   
               
               
                   
                 Process Energy/Unit of Hydrogen 
                 +18.8 Kcal/mol hydrogen 
               
               
                   
                   
               
            
           
         
       
     
     The first reaction (steam reforming) is highly endothermic and the mols of products exceed the mols of reactants, therefore, the reaction proceeds to completion at high temperature and low pressure. The second reaction (water-gas shift) is mildly exothermic and favors low temperature but is unaffected by pressure. The composition of the products depend upon the process conditions, including temperature, pressure, and excess steam, which determine equilibrium, as well as velocity through the catalyst bed, which determines the approach to equilibrium. All other proposed processes have far-inferior thermodynamics, e.g. electrolysis processes require approximately +106 Kcal/mol of hydrogen. 
     Methane decomposition schemes proposed and implemented by others either have very high capital costs arising from the complexity of high temperature equipment designs or have failed to perform reliably at commercial scale. Thus, it is apparent why industry deploys steam methane reforming for the majority of ‘on-purpose’ hydrogen production. 
     Hydrogen has long been an important gaseous raw material for the chemical and petroleum industries. Steam methane reformers are the basis of over 90% of the world&#39;s on-purpose hydrogen production. Presently such plants cost approximately $100 million to produce 100 mM SCFD of hydrogen. Particular embodiments of the disclosed methane decomposition plant are much simpler in concept and would be expected to cost substantially less. Operating margin analysis for feed and fuel and carbon solids at $4.50/Million Btu shows that the disclosed process could breakeven with electricity priced as high as $95.50 per Megawatt-hour. Conversely, with feed and fuel remaining at $4.50/Million Btu and electricity available at $40 per Megawatt-hour, hydrogen could be produced at breakeven for as little as $5.78 per Million Btu. 
     Carbon black is used primarily by the tire industry for the production of vulcanized rubber; however, it is also used as a black pigment for inks and paints. The worldwide demand for carbon black is predicted to increase 4% per annum through 2008. With respect to a hypothetical project to produce 50,000 mtpa of carbon black, the following estimates apply: 
                                    Natural Gas Feedstock   10.5 million standard cubic feet per day       Electricity Consumption   18.3 megawatts       97.3 mol % Hydrogen Product   5,575 pounds per hour       Specific Electricity   2.91 kWh per kilogram of carbon black; or       Consumption   20.8 kWh per thousand SCF of hydrogen                    
Advantageously, particular embodiments of the disclosed invention may provide:
         Lower capital cost;   Simplicity of design, operations and maintenance; and   Margins between market and breakeven costs for electricity, hydrogen and carbon black;   Analogous advantages that would apply for production from other hydrocarbons.       
     The basic principle of the ERT process will now be described. When methane (or natural gas or other hydrocarbons) is heated above a certain temperature, it will decompose to hydrogen gas and carbon solids and absorb the heat of reaction as shown in the chemical equation above. The rate of decomposition increases with temperature. However, the extent of decomposition will reach an equilibrium level dependent on the temperature level. After the electrically heated screens within the ERT heat the gas, decomposition will follow which will tend to cool down the gas/carbon mixture. Since the time for heating is very short relative to the decomposition time, a space is allowed for reaction to take place after each heating stage. The ERT process is preferably constructed with multiple stages of heating and reaction steps. 
     Following are illustrative configurations designed with different design constraints. Each description only highlights the main differences between the various configurations of the equipment required for each. The illustrative configurations discussed herein feature an optional quench cooling of the product carbon/gas mixture. Several of the configurations feature an optional pre-heater in order to heat the natural gas feed to a higher temperature to speed up the reaction, and accordingly the production of carbon and hydrogen; preheating also serves to minimize the electrical requirements that provide the heat that drives the chemical reactions. Due to concerns over the settling out of carbon particles within the ERT unit cross sectional flow area and flow rate have been selected to maintain fluid velocity well within the acceptable safe area of design. 
     The illustrative embodiments depicted in  FIGS. 1 ,  3  and  5  show an ERT unit disposed vertically. The unit can also be disposed horizontally or at an angle to the normal. 
     In an illustrative embodiment of the invention, the ERT unit is set at approximately 200 KW input to the ERT. In a preferred embodiment, the ERT is a plug flow reactor and consists of four (4) separate heating zones, each zone containing four (4) screen heater stations. This will be referred to as the Full Conventional configuration and will be discussed in more detail below. 
       FIG. 1  depicts an illustrative embodiment of the invention referred to as “Stagewise Configuration”. This Stagewise Carbon Removal configuration features a single ERT unit  102  at its core as well as several finalizing reaction chambers  104 ,  106 ,  108 ,  110 ,  112 . The ERT unit is a single pass arrangement, meaning that the products are not recycled back into the process. This configuration is based upon running the reaction adiabatically while utilizing the product to heat the fresh natural gas feed  114 . A hydrogen purity of 95.1 mol % is potentially attainable with this particular design. The main design constraint that was taken into consideration while creating this configuration dealt with the temperature of the carbon/gas mix exiting each heating screen station. The goal was to find a design in which the temperature of the carbon/gas mix leaving each heating zone maintained approximately a 50° F. approach to the equilibrium temperature, meaning that each of the reaction chambers was designed in such a way that the exit temperature was at least greater than about 50° F. than the equilibrium temperature at the corresponding exit concentration of hydrogen. Calculated data is provided in Table 1 at nominal 300 pounds per square inch system pressure. This data is common to all the illustrative embodiments described herein. The methods and systems described herein are applicable at higher and lower pressures to be selected for each instance of use by designers skilled in the art. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 DATA FOR EQUILIBRIUM CURVES 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Equilibrium Data 
                   
                 50 F Approach 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Mol 
                   
                 Mol 
               
               
                   
                 Temperature 
                 Fraction 
                 Temperature 
                 Fraction 
               
               
                   
                 (° F.) 
                 Hydrogen 
                 (° F.) 
                 Hydrogen 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 2800 
                 0.98169 
                 2850 
                 0.98169 
               
               
                   
                 2700 
                 0.98169 
                 2750 
                 0.98169 
               
               
                   
                 2600 
                 0.98169 
                 2650 
                 0.98169 
               
               
                   
                 2500 
                 0.98169 
                 2550 
                 0.98169 
               
               
                   
                 2400 
                 0.97710 
                 2450 
                 0.97710 
               
               
                   
                 2300 
                 0.97098 
                 2350 
                 0.97098 
               
               
                   
                 2200 
                 0.96275 
                 2250 
                 0.96275 
               
               
                   
                 2100 
                 0.95153 
                 2150 
                 0.95153 
               
               
                   
                 2000 
                 0.93614 
                 2050 
                 0.93614 
               
               
                   
                 1900 
                 0.91496 
                 1950 
                 0.91496 
               
               
                   
                 1800 
                 0.88593 
                 1850 
                 0.88593 
               
               
                   
                 1700 
                 0.84638 
                 1750 
                 0.84638 
               
               
                   
                 1600 
                 0.79423 
                 1650 
                 0.79423 
               
               
                   
                 1500 
                 0.72679 
                 1550 
                 0.72679 
               
               
                   
                 1400 
                 0.64405 
                 1450 
                 0.64405 
               
               
                   
                 1300 
                 0.54767 
                 1350 
                 0.54767 
               
               
                   
                 1200 
                 0.44276 
                 1250 
                 0.44276 
               
               
                   
                 1100 
                 0.33940 
                 1150 
                 0.33940 
               
               
                   
                 1000 
                 0.23741 
                 1050 
                 0.23741 
               
               
                   
                 900 
                 0.15248 
                 950 
                 0.15248 
               
               
                   
                 800 
                 0.06995 
                 850 
                 0.06995 
               
               
                   
                 700 
                 0.03854 
                 750 
                 0.03854 
               
               
                   
                 600 
                 0.01879 
                 650 
                 0.01879 
               
               
                   
                 500 
                 0.00789 
                 550 
                 0.00789 
               
               
                   
                 400 
                 0.00273 
                 450 
                 0.00273 
               
               
                   
                 300 
                 0.00073 
                 350 
                 0.00073 
               
               
                   
                 200 
                 0.00013 
                 250 
                 0.00013 
               
               
                   
                 100 
                 0.00001 
                 150 
                 0.00001 
               
               
                   
                   
               
            
           
         
       
     
     The natural gas feed enters a pre-heater  116 , preferably at a temperature of about 90° F. and exits the pre-heater, preferably at a temperature of about 400° F. The natural gas feed then passes through a feed/product exchanger  118 . This is a head to tail heater that utilizes the heat of the product carbon/gas mixture to heat the natural gas feed, preferably to a temperature of about 1000° F. The natural gas feed proceeds into the first heating screen station  120  of the ERT unit. A screen station may include one or more screens. The term “zone” will also be used herein. A zone includes one or more screen stations and is characterized by an individual power source. Upon leaving the first heating zone  120 , the carbon/gas mixture has preferably increased to a temperature over about 2250° F. After passing through each heating zone  120 ,  122 ,  124 ,  126 ,  128 , the carbon/gas mixture passes through reaction and carbon removal chambers  104 ,  106 ,  108 ,  110 ,  112 , respectively. These carbon product removal chambers will allow for easy sampling of the carbon formed throughout the ERT unit. Each subsequent heating zone gradually heats the remaining carbon/gas mixture in order to increase the reaction rate, and thus the rate at which carbon and hydrogen are produced. The flow through the ERT unit can be said to be once through, meaning that the products are not recycled back into the system after leaving the ERT unit. After passing through the fifth heating screen station  128 , the carbon/gas mixture preferably exits the ERT unit at a temperature of approximately 2250° F. and passes through final chamber  112  where it auto-cools to about 2160° F. The carbon/gas mixture then passes through several additional pieces of equipment, or the finalizing stage  130 . 
     In this illustrative embodiment, the flow channel of each ERT unit is about 5 feet in length and is comprised of five heating zones  120 ,  122 ,  124 ,  126 ,  128  delivering a total heat input of about 200 kW. The Stagewise Carbon Removal configuration will preferably be fabricated in such a way that each individual heating zone is immediately followed by a large carbon removal chamber  104 ,  106 ,  108 ,  110 ,  112 . Each of the five ERT units preferably consists of a single heating screen station, each delivering a different heat duty to the system. Since each ERT zone is a separate unit, this simplifies electrical design and controls. Immediately following each ERT unit  120 ,  122 ,  124 ,  126 ,  128  is a carbon removal chamber  104 ,  106 ,  108 ,  110 ,  112  that provides both a reaction volume and a settling location for the carbon produced. Each removal chamber is refractory-lined and water-jacketed and features continuous carbon cooling and removal. Removing the carbon from the heating duty of the system shortly after it is produced reduces energy input. Each of the heating zones in the respective ERT units will deliver varying amounts of heat to the system. Once again, this value is determined based upon the design constraint. 
     The finalizing stage is where the carbon/gas mixture is cooled and separated. In an illustrative embodiment of the invention, first, the carbon/gas mixture is cooled as it passes through a head to tail heat exchanger. The products will exit the exchanger, preferably at a temperature of about 500° F. Then the products go through a phase separator  134 , such as a Venturi scrubber, where water  136  is added, thus cooling the products and creating slurry. The carbon settles on the bottom of the apparatus and exits as slurry  138 . Samples can then be taken before sending the product carbon slurry on for drying and final carbon product production. The remaining gas leaving the top of the phase separation apparatus comprises the hydrogen product. 
     Calculated volume flow, heat duty, residence time, reaction chamber outlet temperature and outlet gas composition are shown in Table 2 for a five-section Stagewise carbon removal configuration. The associated equilibrium and operating curves are shown in  FIG. 2 . 
                     TABLE 2                  STAGEWISE CARBON REMOVAL CONFIGURATION                                                             Volumetric   Volumetric           Outlet   Outlet Mol               Volume   Flow In   Flow Out   Heat Duty   Time   Temperature   Fraction           Section   (ft 3 )   (ft 3 /hr)   (ft 3 /hr)   (kW)   (sec)   (° F.)   Hydrogen                                                             ERT Section   1   15.037   4603   8258   83.0   8.418   1436   0.568           2   8.590   6431   8813   51.7   4.057   1662   0.790           3   4.712   7622   8957   35.2   2.046   1882   0.889           4   2.827   8290   8968   21.3   1.180   2048   0.933           5   1.445   8629   8916   11.5   0.593   2160   0.951                    
There are several potential advantages to the Stagewise Carbon Removal configuration:
         High hydrogen purity can be achieved.   Carbon is removed after each individual heating screen station, thus decreasing the required heat inputs to each ERT unit.       
     This particular configuration only consists of five heating screen stations; this configuration can be expanded to include six or more heating screen stations. Fewer heating screens can also be used but will generally result in lower purity hydrogen. Calculations show 95% hydrogen purity is potentially attainable with five stations as shown in  FIG. 2 . 
     The next illustrative embodiment is referred to as a “Recycle Configuration” and is shown in  FIG. 3 . The Recycle configuration  300  is based upon recycling a portion of the reactor effluent back to the feed end of the ERT unit. This will enable the use of a single heating zone to be operated as the “final stage of ERT process.” A simple ERT design may be used to obtain desired results. The Recycle configuration consists of an ERT unit  302 , reaction chamber  304 , and a recycle system  306 . A hydrogen purity of 95.5 mol % is potentially attainable with this design. The main design constraint dealt with controlling the temperature of the carbon/gas mixture exiting each heating screen station. 
     Following is a description of a recycle configuration according to an illustrative embodiment of the invention. The Recycle configuration features a loop design. The natural gas feed  308  enters the system, preferably at a temperature of about 90° F. and is injected into the recycle stream at the feed side inlet  312  of a feed/product exchanger  314 . The exchanger  314  utilizes the heat of the recycle gas mixture to heat the natural gas feed and the recycle gas/recycle mix, preferably to a temperature of about 1000° F. The mixed feed proceeds into the first heating screen station  316  of the ERT unit. Upon leaving the first station  316 , the carbon/gas mixture has preferably increased to a temperature over 1600° F. Each subsequent heating screen station  318 ,  320 ,  322  gradually heats the carbon/gas mixture to a higher temperature in order to increase the reaction rate. After passing through the fourth heating screen station  322 , the carbon/gas mixture exits the ERT unit  302  at a temperature of preferably nearly 2700° F. and flows to the reaction chamber where it auto-cools to about 2200° F. 
     In this illustrative embodiment, the ERT unit  302  itself is 12 feet in length and is comprised of four heating screen stations  316 ,  318 ,  320 ,  322 , preferably delivering a total heat input of about 80 kW. The Recycle ERT unit is preferably substantially vertical to allow the gas flow through the ERT unit  302  to carry the carbon with it, preventing or minimizing build up of carbon on the screens or on the walls of the ERT unit  302 . The ERT unit  302  preferably has a first heating screen station  316  where preheating takes place, three additional heating screen stations  318 ,  320 ,  322  where the reaction takes place. The primary function of the first heating screen station  316  is to heat the mixed gas feed in order to increase the rate of reaction. Minimal amounts of carbon and hydrogen are produced during this stage due to the slow rate of reaction. Therefore, the spacing between the first screen station  316  and the second screen station  318  does not need to be very large, however, due to design constraints, as well as trying to maximize the hydrogen purity, the spacing between the first and second screen stations  316 ,  318  is preferably moderately large. Once the carbon/gas mixture reaches temperatures over 1500° F., noticeable amounts of carbon and hydrogen are produced: consequently, the remaining heating screen stations  318 ,  320 ,  322  preferably have larger spacing between them. Preferably, the heat delivered by each heating screen station does not vary; each heating screen station in both the pre-heating area and reaction area ideally delivers 20 kW to the system in this particular embodiment. By varying the spacing between each heating screen station throughout the entire ERT unit  302 , higher hydrogen purity will likely be achieved. 
     The reaction mix from the ERT  302  unit flows to the reaction chamber  304 . The chamber  304  adds the residence time needed for high hydrogen purity to be achieved. By the time the gas leaves the reaction chamber  304 , the temperature of the carbon/gas mixture has preferably dropped to approximately 2200° F. The carbon/gas mixture then proceeds to go through a splitter (not diagrammed, but indicated at  324 ) where the product stream is separated. In an illustrative embodiment of the invention, approximately 40% of the products and the mixture is then sent through a quench cooling system  326  where they are cooled, preferably to about 500° F. with quench water. The products then go through a phase separator  328 , such as a Venturi scrubber, where the carbon/gas mixture is cooled further by contacting with a circulating slurry of water and carbon. Make up water  330  is added to the phase separation system  328 , thus cooling the products and creating slurry. Other compatible cooling and separation systems, are within the spirit and scope of the invention. The product carbon settles on the bottom of the apparatus and exits as slurry at outlet area  332 . Samples can then be taken before sending the product carbon slurry on for drying and final carbon product production. The remaining ‘cleaned gas’ leaving the top of the phase separation apparatus substantially carbon-free, containing a mixture of methane and hydrogen comprises the hydrogen product. 
     The remaining 60% of the reaction chamber effluent is the recycle gas. It passes through the feed/product exchanger  314  where it is cooled by the feed and recycle mix stream preferably to about 900° F. The huge drop in temperature is due to the fact that the heat of the product stream is used to heat the feed stream, which is much cooler (about 200° F.). The recycle mixture is then passed through an air cooler  334  where it is preferably cooled to about 200° F. before it passes through a compressor  336 , which compresses the recycle stream to the required feed inlet pressure. The carbon/gas recycle mixture is then injected with fresh natural gas after passing through the compressor  336 . 
     Table 3 shows calculated volumes, heat duties, residence times, outlet temperatures and compositions for a four-section Recycle Configuration system. The associated equilibrium and operating curves are shown in  FIG. 4 . 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 RECYCLE CONFIGURATION 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Volumetric 
                 Volumetric 
                   
                   
                 Outlet 
                 Outlet Mol 
               
               
                   
                   
                 Volume 
                 Flow In 
                 Flow Out 
                 Heat Duty 
                 Time 
                 Temperature 
                 Fraction 
               
               
                   
                 Section 
                 (ft 3 ) 
                 (ft 3 /hr) 
                 (ft 3 /hr) 
                 kW 
                 (sec) 
                 (° F.) 
                 Hydrogen 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 ERT Section 
                 1 
                 0.380 
                 4700 
                 4724 
                 20.0 
                 0.291 
                 1600 
                 0.704 
               
               
                   
                 2 
                 0.380 
                 4712 
                 4927 
                 20.0 
                 0.284 
                 2014 
                 0.732 
               
               
                   
                 3 
                 0.543 
                 4820 
                 5515 
                 20.0 
                 0.379 
                 2240 
                 0.818 
               
               
                   
                 4 
                 2.365 
                 5167 
                 6305 
                 20.0 
                 1.484 
                 2198 
                 0.955 
               
               
                   
               
            
           
         
       
     
     The Recycle configuration has several potential advantages:
         Very high hydrogen purity can be achieved due to the gas mixture entering the ERT unit at a very high temperature and already containing hydrogen. The finishing reaction chamber at the end of the ERT unit also contributes to the high hydrogen purity that can potentially be achieved. The large finishing reaction chamber adds residence time to the system, meaning that the reaction has a longer time to progress, thus resulting in more conversion.   The ERT unit itself can be moderately sized and priced.   Uniform heat delivered by each heating screen station can help to simplify the electrical controls and thereby may reduce costs compared to variable heat input configurations.   The Recycle configuration can operate over a wide range of desired outlet conditions by varying the recycle ratio and overall heat input.       

       FIG. 5  depicts an illustrative embodiment of a system referred to as a “Full Conventional Configuration.” The Full Conventional configuration features a single, large ERT unit  502  and the flow or reactant or reaction mix is once through, meaning that the products are not recycled back into the process. This configuration is based upon the concept of minimizing reaction time, and consequently reaction volume, by reaching a high reaction temperature (over 2500° F.) quickly and running most of the reaction as close to isothermal conditions as possible. A hydrogen purity of 97.2 mol % is potentially attainable with this particular design. The main design constraint dealt with temperature of the carbon/gas mixture exiting each heating screen station. Preferably, the range of the temperature of the carbon/gas mixture leaving each heating screen station is within a small range of the temperature of the carbon/gas mixture entering that heating screen station (approximately 150° F.). By maintaining high temperature, the rate of reaction is maximized and the residence time minimized. 
     The overall system design can be relatively simple. Natural gas feed  504  enters a small pre-heater  506 , preferably at a temperature of about 90° F. and is preferably heated to a temperature of about 400° F. The natural gas feed proceeds into the ERT unit  502 . Upon leaving a first screen station within heating zone  508 , the carbon/gas mixture has preferably increased to a temperature over 1000° F. Each subsequent heating screen station in zone  508 , gradually heats the carbon/gas mixture to the target isothermal zone temperature range of 2200° F. to 2500° F. in order to increase the reaction rate, and thus the rate at which carbon and hydrogen are produced. After passing through the last heating screen station, the carbon/gas mixture preferably exits the ERT unit  502  at a temperature of about 2600° F. and flows to the finalizing stage. Appropriate near-equilibrium attainment time is provided in the ERT outlet and interconnecting piping. 
     The ERT unit  502  is approximately 40 feet in length and consists of sixteen heating screen stations (not shown) delivering a total heat input of about 260 kW. The Full Conventional ERT unit  502  is preferably vertical, to allow the gas flowing through the ERT to pneumatically convey the carbon with it, preventing or minimizing build up of carbon on the screens or on the walls of the ERT. The ERT unit preferably has four zones  508 ,  510 ,  512 ,  514  with four heating screen stations in each (not shown). The primary function of the first zone  508  is to heat the natural gas feed  504  in order to increase the rate of reaction. Due to the slow reaction rate at lower temperatures, minimal amounts of carbon and hydrogen are produced during this stage; therefore, the spacing between each heating screen station does not need to be very large and does not need to vary over the course of the zone. Once the carbon/gas mixture reaches temperatures over 1500° F., the reaction rate increases and noticeable amounts of carbon and hydrogen are produced: consequently, the remaining three zones  510 ,  512 ,  514  have larger spacing between each heating screen station than does the first zone. Preferably, the heat delivered by each heating screen station remains constant within each zone, which allows for some simplification in the design of the ERT unit  502 . The heat delivered by each heating screen station in the first zone is preferably 30 kW. The total heat duties delivered by each subsequent zone preferably decreases. The heat delivered by each heating screen station in the second zone  510  is 22.5 kW, while the heat duty delivered in the third zone  512  is 9.5 kW. The heat duty delivered by each heating screen station in the final zone  514  is only 2.4 kW. The reaction rates and residence times necessary to achieve the desired conversion to hydrogen and carbon depend, at least in part, on the heating screen station spacing. Preferably, the heating screen station spacing varies continuously after the first zone  508  in order to maintain near isothermal conditions. 
     The finalizing stage is where the carbon/gas mixture is cooled and separated. First, the carbon/gas mixture passes through a quench cooling system  516  where quenching water  518  is injected. The products will exit the quench cooling system, preferably at a temperature of about 500° F. The products then go through a phase separator  520 , such as a Venturi scrubber, where the carbon/gas mixture is cooled further by contacting with a circulating slurry of water and carbon. Make up water  522  is added to the phase separation system  524 , thus cooling the products and creating slurry. The carbon settles on the bottom of the apparatus and exits as slurry. Samples can then be taken before sending the product carbon slurry on for drying and final carbon product production. The remaining ‘cleaned gas’ leaving the top of the phase separation apparatus substantially carbon-free, containing a mixture of methane and hydrogen comprises the hydrogen product. 
     Table 4 provides calculated volumes, flow rates, heat duties, residence times, outlet temperatures and outlet compositions for a sixteen section, single pass configuration. The associated equilibrium and operating curves are shown in  FIG. 6 . 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 FULL CONVENTIONAL CONFIGURATION 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Volumetric 
                 Volumetric 
                   
                   
                 Outlet 
                 Outlet Mol 
               
               
                   
                   
                 Volume 
                 Flow In 
                 Flow Out 
                 Heat Duty 
                 Time 
                 Temperature 
                 Fraction 
               
               
                   
                 Section 
                 (ft 3 ) 
                 (ft 3 /hr) 
                 (ft 3 /hr) 
                 kW 
                 (sec) 
                 (° F.) 
                 Hydrogen 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 ERT Section 
                 1 
                 0.054 
                 4600 
                 4600 
                 30.0 
                 0.043 
                 1033 
                 0.000 
               
               
                   
                 2 
                 0.054 
                 4600 
                 4610 
                 30.0 
                 0.042 
                 1527 
                 0.002 
               
               
                   
                 3 
                 0.054 
                 4600 
                 4680 
                 30.0 
                 0.042 
                 1947 
                 0.017 
               
               
                   
                 4 
                 0.054 
                 4640 
                 4930 
                 30.0 
                 0.041 
                 2294 
                 0.075 
               
               
                   
                 5 
                 0.380 
                 4784 
                 6650 
                 22.5 
                 0.240 
                 2218 
                 0.389 
               
               
                   
                 6 
                 0.380 
                 5714 
                 7020 
                 22.5 
                 0.215 
                 2256 
                 0.554 
               
               
                   
                 7 
                 0.380 
                 6370 
                 7710 
                 22.5 
                 0.195 
                 2288 
                 0.692 
               
               
                   
                 8 
                 0.380 
                 704 
                 8000 
                 22.5 
                 0.315 
                 2408 
                 0.776 
               
               
                   
                 9 
                 0.489 
                 7520 
                 8300 
                 9.5 
                 0.223 
                 2372 
                 0.836 
               
               
                   
                 10 
                 0.489 
                 7910 
                 8380 
                 9.5 
                 0.216 
                 2411 
                 0.869 
               
               
                   
                 11 
                 0.489 
                 8140 
                 8570 
                 9.5 
                 0.211 
                 2462 
                 0.898 
               
               
                   
                 12 
                 0.489 
                 8350 
                 8740 
                 9.5 
                 0.206 
                 2524 
                 0.923 
               
               
                   
                 13 
                 0.163 
                 8550 
                 8550 
                 2.4 
                 0.069 
                 2564 
                 0.923 
               
               
                   
                 14 
                 0.163 
                 8550 
                 8690 
                 2.4 
                 0.068 
                 2569 
                 0.931 
               
               
                   
                 15 
                 0.163 
                 8612 
                 8740 
                 2.4 
                 0.068 
                 2578 
                 0.939 
               
               
                   
                 16 
                 1.537 
                 8680 
                 9180 
                 2.4 
                 0.620 
                 2411 
                 0.972 
               
               
                   
               
            
           
         
       
     
     The Full Conventional configuration has several potential advantages.
         Very high hydrogen purity may be achievable with this particular design.   The kinetics of this particular system favors both high temperatures and a long residence time in order to achieve high hydrogen purity.   The Full Conventional configuration can use near isothermal high temperatures to minimize residence time.   A minimal amount of equipment is required for particular embodiments of this configuration.   The quench cooling system that is used to cool the carbon/gas product is relatively inexpensive in comparison to a more complex and costly recycle system.   Embodiments of this particular configuration may be highly efficient in terms of energy input per amount of product produced for a full-scale industrial process.       

     The invention may be embodied in a variety of ways, for example, a system, method, device, etc. 
     The high-level heat energy capable of being produced by embodiments of the invention can be integrated into other electrical or chemical processes. Accordingly, the invention is not limited to the uses described above. As an example, the effluent can be used as a heat source for a solid oxide fuel cell. 
     Still further, the carbon produced can be used for various applications. For example, it can be used for molten carbonate fuel cells (MCFC). MCFCs use an electrolyte composed of a molten carbonate salt formed by mixing carbon or a carbon precursor with a salt. 
     As noted above, the ERT apparatus can be used for pyrolysis of hydrocarbons, such as ethane, propane, butane, naphtha, or any hydrocarbon feedstock that can be vaporized. In an illustrative example, an ERT apparatus analogous to that depicted in  FIG. 5  is used to pyrolyze hydrocarbon gas. The hydrocarbon feedstock is preferably preheated to approximately 400° F. and then is fed through the ERT system. The heat produced by the ERT system pyrolyzes the hydrocarbon feedstock. The pyrolyzed gas is then passed through a quenching system, preferably immediately after exiting the ERT apparatus. The resulting cracked gas products then undergo separation using conventional separation methods. Hydrogen, methane, and various C 2 , C 3 , C 4 , C 5  and heavier components can be separated and heat recovered. The separated hydrogen can be recycled in the system. In a preferred embodiment, the pyrolysis system is designed for lesser pressure and lesser residence times than the systems used for decarbonization and the quenching of the gases exiting the ERT is designed for minimum residence time to stop free-radical chemical reactions rather than to allow additional time for the gases to approach equilibrium as in the decarbonization systems. Further, the gas processing time-temperature relationship can be managed in pyrolysis modes to optimize economically the cracked gas product spectrum. In pyrolysis operations, steam may be added to the feedstock as it serves to reduce hydrocarbon partial pressure thereby enhancing yield spectra and it may reduce any tendency for carbon formation. A minimal amount of carbon monoxide and carbon dioxide will form but the short residence time will tend to preclude much steam reforming of the hydrocarbon feedstock. 
     An illustrative ERT apparatus is approximately six feet long, having approximately sixteen screens, each separated by approximately four inches. 
     While the invention has been described by illustrative embodiments, additional advantages and modifications will occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to specific details shown and described herein. Modifications, for example, to particular pressure and temperatures used; number, size and configurations of screens and ERT units; and types of cooling, phase separation, scrubbing, filtration, and drying systems used may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention not be limited to the specific illustrative embodiments, but be interpreted within the full spirit and scope of the described inventions it equivalents. It is further noted that the description of each of the three illustrative configurations, are themselves illustrative embodiments of the particular configuration.