Plant capacity expansion and dynamic production control

Abstract

The invention provides a process which facilitates high incremental capacity expansion of existing syngas-based plants by providing an adiabatic prereformer and an independent heater which is configured to (1) receive a prereformed and preheated mixed feed stream from the prereformer, (2) heat the prereformed and preheated mixed feed stream to a reheat temperature of as high as around 700° C. without local overheating of heat exchange surfaces and without the risk of carbon formation (on, e.g., fired heater heating coils), and which (3) feeds the prereformed and preheated mixed feed stream at the reheat temperature to the inlet of reformer radiant section catalyst tubes, wherein the prereformer and independent heater are not contained within the reformer.

1 . A process for generating a hydrogen-containing product gas in a reformer comprising a radiant section, a plurality of reforming catalyst-filled tubes disposed in the radiant section, a transition section, and a convection section, the process comprising: 
 (a) firing the reformer radiant section to generate a flue gas which passes from the radiant section, through the transition section, and to the convection section and which heats the radiant section catalyst-filled tubes and the convection section;    (b) feeding a mixed feed stream comprising a hydrocarbon feedstock and steam through the convection section to yield a preheated mixed feed stream;    (c) feeding the preheated mixed feed stream to a prereformer which adiabatically prereforms the preheated mixed feed stream and generates a prereformed and preheated mixed feed stream;    (d) feeding the prereformed and preheated mixed feed stream to an independent heater which heats the prereformed and preheated mixed feed stream to a reheat temperature; and    (e) feeding the preheated and prereformed mixed feed stream at the reheat temperature through the radiant section catalyst-filled tubes, thereby generating a hydrogen-containing product gas,    wherein (1) the prereformer is configured to receive the preheated mixed feed stream from the reformer convection section and to feed the prereformed and preheated mixed feed stream to the independent heater; (2) the independent heater is configured to receive the prereformed and preheated mixed feed stream from the prereformer and to feed the preheated and prereformed mixed feed stream at the reheat temperature to the inlet of the radiant section catalyst tubes; and (3) neither the prereformer nor independent heater are located within the reformer.    
   
   
       2 . The process of  claim 1 , wherein the reheat temperature is between about 600° C. to about 700° C.  
   
   
       3 . The process of  claim 1 , wherein the independent heater is a fired heater.  
   
   
       4 . The process of  claim 1 , wherein the preheated mixed feed stream is heated in the independent heater before it is fed to the prereformer.  
   
   
       5 . The process of  claim 1 , wherein the independent heater and the convection section of the reformer are heated by a flue gas generated by the combustion of a conventional fuel.  
   
   
       6 . The process of  claim 3 , wherein the fired heater contains separate combustion and convection sections, the fired heater convection section contains at least one heating coil which is heated by a flue gas generated by the combustion of a conventional fuel in the fired heater combustion section, and the prereformed and preheated mixed feed stream is fed to, and heated to the reheat temperature in, the fired heater convection section.  
   
   
       7 . The process of  claim 6 , wherein the temperature of the flue gas generated in the fired heater combustion section is modulated by varying the amount of oxygen available for combustion in the fired heater combustion section.  
   
   
       8 . The process of  claim 6 , wherein the fired heater convection section contains a plurality of heating coils that are arranged in parallel to one another and that are configured to facilitate co-current or counter-current flow of the prereformed and preheated mixed feed stream and the flue gas generated in the fired heater combustion section.  
   
   
       9 . The process of  claim 1 , wherein the prereformed and preheated mixed feed stream is heated from about 370° C. to a reheat temperature of about 700° C. in the independent heater.  
   
   
       10 . The process of  claim 1 , wherein the hydrogen-containing product gas is recovered and optionally purified.  
   
   
       11 . The process of  claim 1 , wherein the reformer is a steam-methane reformer.  
   
   
       12 . The process of  claim 1 , wherein the reformer is a Modular Partition Reformer.  
   
   
       13 . A process for increasing the hydrogen-containing product gas-generating capacity of a reformer comprised of a radiant section, a plurality of reforming catalyst-filled tubes disposed in the radiant section, a transition section, and a convection section comprising one or more coils, the process comprising: 
 (a) providing a prereformer which is configured to receive a preheated mixed feed stream comprising a hydrocarbon feedstock and steam from the reformer convection section and which adiabatically prereforms the preheated mixed feed stream and generates a prereformed and preheated mixed feed stream; and    (b) providing an independent heater which: (i) is configured to receive the prereformed and preheated mixed feed stream from the prereformer, (ii) heats the prereformed and preheated mixed feed stream to a reheat temperature and which (iii) feeds the prereformed and preheated mixed feed stream at the reheat temperature to the inlet of the plurality of reforming catalyst-filled tubes disposed in the reformer radiant section, wherein    (1) the reformer radiant section is fired to generate a flue gas which passes from the radiant section, through the transition section, and to the convection section and which heats the radiant section catalyst-filled tubes and the one or more convection section coils;    (2) a mixed feed stream comprising a hydrocarbon feedstock and steam is fed through and heated in the convection section to yield the preheated mixed feed stream;    (3) feeding the preheated and prereformed mixed feed stream at the reheat temperature through the radiant section catalyst-filled tubes generates a hydrogen-containing product gas; and    (4) the prereformer and independent heater are not contained within the reformer.    
   
   
       14 . The process of  claim 1 , wherein the reformer radiant section is fired by combustion of a conventional fuel.  
   
   
       15 . The process of  claim 13 , wherein the independent heater is a fired heater.  
   
   
       16 . The process of  claim 1 , wherein the prereformer is an insulated vessel which is filled with a prereforming catalyst.  
   
   
       17 . The process of  claim 13 , wherein the prereformer is an insulated vessel which is filled with a prereforming catalyst.  
   
   
       18 . The process of  claim 1 , where the hydrogen-containing product gas is a synthesis gas.  
   
   
       19 . The process of  claim 13 , where the hydrogen-containing product gas is a synthesis gas.  
   
   
       20 . The process of  claim 13 , wherein the reformer is a Modular Partition Reformer.  
   
   
       21 . The process of  claim 13 , wherein the reheat temperature is between about 680° C. to about 700° C.  
   
   
       22 . The process of  claim 13 , wherein the reheat temperature is between about 600° C. to about 700° C. and the hydrogen-containing product gas is a synthesis gas.  
   
   
       23 . The process of  claim 13 , wherein the reformer is a steam-methane reformer.  
   
   
       24 . The process of  claim 13 , wherein the independent heater is a fired heater comprising a combustion section which generates a flue gas by combustion of a conventional fuel with between about 180% to about 280% of a stoichiometric amount of air.  
   
   
       25 . A process of  claim 13 , wherein the reheat temperature is between about 600° C. to about 700° C., the independent heater is a fired heater, and the reformer is a steam-methane reformer.  
   
   
       26 . A process of  claim 1 , wherein control means are associated with the reformer, the prereformer, and the independent heater to regulate one or more of the following parameters: (1) the amount of hydrocarbon feedstock and steam in the mixed feed stream; (2) the mixed feed preheat temperature; and (3) the reheat temperature.  
   
   
       27 . A process of  claim 13 , wherein the reformer is a steam-methane reformer, the hydrocarbon feedstock is natural gas, the independent heater is a fired heater, the reheat temperature is between about 680° C. to about 700° C., and the hydrogen-containing product gas is a synthesis gas which is recovered and purified.  
   
   
       28 . A process wherein an adiabatic prereformer which is located outside of a reformer and which had been configured to feed a preheated and prereformed mixed feed stream to the inlet of a plurality of reforming catalyst-filled tubes disposed in a radiant section of the reformer is reconfigured in accordance with  claim 13  to feed the preheated and prereformed mixed feed stream to an independent heater.  
   
   
       29 . A process wherein an independent heater which is located outside of a reformer is reconfigured in accordance with  claim 13  to: (1) receive a preheated and prereformed mixed feed stream from a prereformer located outside of the reformer; (2) heat the preheated and prereformed mixed feed stream to a reheat temperature; and (3) feed the prereformed and preheated mixed feed stream at the reheat temperature to the inlet of the plurality of reforming catalyst-filled tubes disposed in the reformer radiant section.  
   
   
       30 . A process of  claim 28 , wherein the reformer is a Modular Partition Reformer.