Novel Steam Reformer Based Hydrogen Plant Scheme for Enhanced Carbon Dioxide Recovery

Abstract

A novel steam reformer unit design, a novel hydrogen PSA unit design, a novel hydrogen/nitrogen enrichment unit design, and novel processing scheme application are presented. The result of these innovations results in re-allocating most of the total hydrogen plant CO2 emissions load to high pressure syngas stream exiting the water gas shift reactor while minimizing the CO2 emissions load from the reformer furnace flue gas. As compared to the conventional 60/40 split of total CO2 emissions in syngas/flue gas streams for steam reformer based conventional hydrogen plant designs, the present invention results in 85/15 or better CO2 split. This will permit about 85% or better of the total CO2 emissions load to be captured from the syngas stream, using the conventional, well proven and cost effective amine scrubbing technology. Such 85% or better CO2 capture is much greater than the 55% to 60% maximum possible using conventional steam reformer based hydrogen plant technology. As CO2 recovery from high pressure syngas stream is much easier and cost effective as compared to that from low pressure reformer furnace flue gases, a major cost benefit for equivalent CO2 recovery results with the present invention.

1 . A method of re-distributing the CO2 balance from a reformer furnace flue gas to the high pressure syngas exit water gas shift reaction unit, comprising;
 providing a first gas mixture;   introducing said first gas mixture either into a pre-reformer followed by a primary reformer, or directly into a primary reformer, thereby generating a second gas mixture comprising hydrogen, carbon monoxide, carbon dioxide;   introducing said second gas mixture into at least one isothermal shift reactor, or a combination of high followed by a low temperature shift reactor, or a medium temperature shift reactor, thereby generating a third gas mixture;   introducing said third gas mixture into an amine wash, wherein said third gas is separated into a fourth gas mixture and a carbon dioxide enriched stream;   introducing said fourth gas mixture into a standard H2 PSA unit, wherein said fourth gas is separated into a hydrogen enriched stream and a PSA purge gas stream;   introducing said PSA purge gas stream as fuel into the reformer furnace along with natural gas, a portion of the feed hydrocarbon stream, or any other external supplemental fuel for the reformer furnace.   
   
   
       2 . The method of  claim 1 , wherein said steam reformer has a tube exit temperature between about 1700° F. and about 1750° F. 
   
   
       3 . The method of  claim 2 , wherein said tube exit temperature is about 1730° F. 
   
   
       4 . The method of  claim 1 , wherein said steam reformer has a furnace bridge wall temperature of between about 1850° F. and about 1950° F. 
   
   
       5 . The method of  claim 4 , wherein said furnace bridge wall temperature is about 1900° F. 
   
   
       6 . The method of  claim 1 , wherein said steam reformer has a steam to carbon ratio of between about 3.0 and about 4.0. 
   
   
       7 . The method of  claim 6 , wherein said steam to carbon ratio is about 2.8. 
   
   
       8 . The method of  claim 1 , wherein the excess air to the furnace of said primary reformer is adjusted in order to achieve a stable flame while maintaining an adiabatic flame temperature of about 4000° F. 
   
   
       9 . The method of  claim 1 , wherein at least about 99% of the carbon dioxide present in the fourth gas stream is removed by said amine wash system. 
   
   
       10 . A method of re-distributing CO2 balance from reformer furnace flue gas to the high pressure syngas exit water gas shift reaction unit, comprising;
 providing a first gas mixture;   introducing said first gas mixture into a pre-reformer followed by a primary reformer, or directly into a primary reformer, thereby generating a second gas mixture comprising hydrogen, carbon monoxide, carbon dioxide;   introducing said second gas mixture into at least one isothermal shift reactor, or a combination of high followed by a low temperature shift reactor, or a medium temperature shift reactor, thereby generating a third gas mixture;   introducing said third gas mixture into an amine wash, wherein said third gas is separated into a fourth gas mixture and a carbon dioxide enriched stream;   introducing said fourth gas mixture into special low recovery PSA, wherein said fourth gas is separated into a hydrogen enriched stream and a PSA purge gas stream;   introducing said purge gas from novel PSA to the reformer furnace as fuel;   wherein no additional supplemental fuel is sent to the reformer furnace.   
   
   
       11 . The method of  claim 10 , wherein said novel PSA has a hydrogen recovery between about 50% and about 65%. 
   
   
       12 . The method of  claim 10 , wherein said PSA has reduced number of adsorption beds compared to similar size conventional units. 
   
   
       13 . The method of  claim 12 , wherein the number of adsorption beds is between 8 and 10. 
   
   
       14 . The method of  claim 10 , wherein the hydrogen recovery of said PSA is adjusted such that the PSA purge gas stream heat content as fuel is sufficient to satisfy the fuel demand of the primary reformer. 
   
   
       15 . The method of  claim 10  wherein the novel PSA unit delivers a sufficient quantity of fuel by varying the hydrogen % recovery within the novel PSA unit such that no additional supplemental fuel to the reformer furnace is required. 
   
   
       16 . The method of  claim 10 , wherein said purge gas stream has a pressure of between about 5 bara and about 10 bara. 
   
   
       17 . The method of  claim 10 , wherein said purge gas stream has a pressure of greater than about 1.2 bara. 
   
   
       18 . A method of separating carbon dioxide from a gas mixture, comprising;
 providing a first gas mixture;   introducing said first gas mixture either into a pre-reformer followed by a primary reformer, or directly into a primary reformer, thereby generating a second gas mixture comprising hydrogen, carbon monoxide, carbon dioxide   introducing said second gas mixture into at least one isothermal shift reactor, or a combination of high followed by a low temperature shift reactor, or a medium temperature shift reactor, thereby generating a third gas mixture;   introducing said third gas mixture into an amine wash, wherein said third gas is separated into a fourth gas mixture and a carbon dioxide enriched stream;   introducing said fourth gas mixture into either a standard recovery or a special low recovery PSA, wherein said fourth gas is separated into a hydrogen enriched stream and a PSA purge gas stream;   compressing said PSA purge gas stream to a suitable pressure;   introducing said compressed purge gas stream to a novel gas separation unit selected from an adsorption based unit, a membrane separation unit or a cryogenic separation unit, that separates the compressed PSA unit purge gas into two streams, a hydrogen and nitrogen enriched stream and a stream of residual gases;   introducing the hydrogen and nitrogen enriched stream to the reformer furnace as fuel and recycling the stream of residual gases back to the reformer as partial feed after compression as required;   wherein no additional supplemental fuel is sent to the reformer furnace.   
   
   
       19 . The method of  claim 18 , wherein said novel gas separation unit is a novel adsorption based unit. 
   
   
       20 . The method of  claim 19 , wherein the said adsorption based unit can be of 4 to 5 adsorption beds. 
   
   
       21 . The method of  claim 19 , wherein said hydrogen and nitrogen enriched stream will have at least 40% of the total nitrogen present in the feed to the unit, along with at least 90% of the hydrogen present in the feed to the unit. 
   
   
       22 . The method of  claim 18 , wherein said residue gas stream from the novel gas separation unit is compressed to a suitable pressure. 
   
   
       23 . The method of  claim 22 , wherein said high pressure residue hydrocarbon stream is recycled as part feed to the reformer. 
   
   
       24 . The method of  claim 18 , wherein said novel gas separation unit is either a cryogenic process (do you mean separation unit?) or a membrane based process (do you mean separation unit??).