Low energy process for the production of ammonia or methanol

Abstract

A process for utilizing synthesis gas heat for the generation of supercritical steam in a low energy ammonia or methanol plant is disclosed. The process involves a reforming or partial oxidation stage, at least one supercritical steam generator having a shell side and a tube side, at least one superheater, at least one back pressure turbine, at least one extraction and condensing turbine, and at least one boiler feedwater pump. The synthesized synthesis gas is sent to the shell side of the supercritical steam generator, and the supercritical steam generator is fed with pressurized feedwater. The feedwater flow is adjusted to maintain the steam temperature at the exit of the supercritical steam generator in the range of 375-500° C. The supercritical steam is generated in the supercritical steam generator at a pressure of 225-450 bar, the supercritical steam is further heated in a superheater to a temperature of 500-750° C., and the supercritical steam generated in the superheater is fed to a back pressure turbine.

1 - 20 . (canceled) 
     
     
         21 . A process for utilizing synthesis gas heat for the generation of supercritical steam in a low energy ammonia or methanol plant, the plant comprising:
 a reforming or partial oxidation stage;   at least one supercritical steam generator;   at least one superheater;   at least one back pressure turbine;   at least one extraction and condensing turbine; and   at least one boiler feedwater pump;   
       the process comprising
 synthesizing synthesis gas in a reforming or partial oxidation stage; 
 utilizing a supercritical steam generator having a shell side and a tube side for heat recovery; 
 sending the synthesized synthesis gas to the shell side of the supercritical steam generator; 
 feeding the supercritical steam generator with pressurized feedwater; 
 adjusting the feedwater flow to maintain the steam temperature at the exit of the supercritical steam generator in the range of 375-500° C.; 
 generating supercritical steam in the supercritical steam generator at a pressure of 225-450 bar; 
 further heating the supercritical steam in a superheater to a temperature of 500-750° C.; and 
 feeding back the supercritical steam generated in the superheater to a back pressure turbine. 
 
     
     
         22 . The Process according to  claim 21 , wherein the reforming or partial oxidation stage where the synthesis gas is produced is selected from a group comprising at least one of: a primary reformer; a primary and secondary reformer combination; a gas-heated reformer; an autothermal reformer; a partial oxidation chamber; a membrane reactor with oxygen transport membranes; and a catalytic POX. 
     
     
         23 . The process according to  claim 21 , wherein the inlet temperature on the process side of the supercritical steam generator is in the range of 550-1100° C. 
     
     
         24 . The process according to  claim 21 , wherein the temperature of the supercritical steam leaving the supercritical steam generator is kept constant via a speed-controllable feedwater pump. 
     
     
         25 . The process according to  claim 21 , wherein the back pressure turbine is the sole driver of either the process air compressor or the synthesis gas compressor. 
     
     
         26 . The process according to  claim 21 , wherein the supercritical steam is reduced to a steam level of 100-130 bar in the back pressure turbine. 
     
     
         27 . The process according to  claim 21 , wherein the supercritical steam out of the back pressure turbine is mixed with saturated steam produced by a steam boiler in the ammonia or methanol synthesis section and is then further superheated. 
     
     
         28 . The process according to  claim 21 , wherein the outlet steam of the back pressure turbine is fed into an extraction and condensing turbine after further superheating. 
     
     
         29 . The process according to  claim 21 , wherein the outlet pressure level of the back pressure turbine is independent from the steam pressure level defined by the extraction from the extraction and condensing turbine. 
     
     
         30 . The process according to  claim 21 , wherein the outlet pressure level of the back pressure turbine is positioned between the supercritical steam pressure level and the process steam pressure level. 
     
     
         31 . An apparatus for utilizing synthesis gas heat for the generation of supercritical steam in an ammonia or methanol plant suitable for operating a process according to claim  1 , wherein the at least one superheater is provided for supercritical steam; the apparatus further comprising:
 a temperature measuring device downstream of the supercritical steam generator;   means for feeding the synthesized synthesis gas to the shell side of the supercritical steam generator;   means for conveying the pressurized feedwater to the supercritical steam generator;   means for adjusting the feedwater flow to keep a constant supercritical steam temperature at the exit of the supercritical steam generator;   means for conveying the supercritical steam produced in the supercritical steam generator to the superheater; and   means for conveying the superheated steam to the back pressure turbine.   
     
     
         32 . The apparatus according to  claim 31 , wherein the supercritical steam generator is designed with a vertical tube bundle. 
     
     
         33 . The apparatus according to  claim 31  comprising means for connecting the temperature measuring device to a speed-controllable feedwater pump. 
     
     
         34 . The apparatus according to  claim 31  wherein the superheater is located upstream of the back pressure turbine which is located in a convection section of a primary reformer. 
     
     
         35 . The apparatus according to  claim 31 , wherein the superheater is located upstream of the back pressure turbine which is located in a fired heater. 
     
     
         36 . The apparatus according to  claim 31 , wherein the superheater is located upstream of the extraction and condensing turbine which is realized as a reformer convection section or a fired heater coil. 
     
     
         37 . The apparatus according to  claim 31 , comprising means for combining the saturated steam coming from a steam boiler in the synthesis section with the steam from the back pressure turbine and conveying the joint flow to a common superheater. 
     
     
         38 . The apparatus according to  claim 31 , comprising means for combining the steam flow from the back pressure turbine and the steam extracted from the extraction and condensing turbine. 
     
     
         39 . The apparatus according to  claim 31 , wherein the supercritical steam generator in the synthesis gas line is located on the steam side as well as on the synthesis gas side followed by the supercritical steam superheater. 
     
     
         40 . The apparatus according to  claim 31 , comprising a high temperature CO-shift converter positioned between the supercritical steam generator and the supercritical steam superheater in the synthesis gas line.