Thermal stage and reduction absorption sulfur recovery process

Abstract

An elemental sulfur recovery unit comprising a thermal unit configured to combust an acid gas feed comprising hydrogen sulfide, an oxygen source, and a fuel gas to create a reaction furnace outlet stream, comprising elemental sulfur, a waste heat boiler configured to capture heat from the reaction furnace outlet stream to create a waste heat boiler effluent, a condenser configured to condense the waste heat boiler effluent to produce a non-condensed gases stream and a condensed stream comprising elemental sulfur, a process gas reheater configured to generate a hot gases stream, a hydrogenation reactor configured to convert the hot gases stream to create a hydrogenation effluent comprising hydrogen sulfide, a process desuperheater configured to cool the hydrogenation effluent to generate a cooled effluent, and an absorber unit configured to absorb the hydrogen sulfide from the cooled effluent to produce a hydrogen sulfide recycle stream and a waste gas stream.

What is claimed is: 
     
         1 . An elemental sulfur recovery unit for processing an acid gas feed to recover elemental sulfur, the elemental sulfur recovery unit comprising:
 a thermal unit, the thermal unit configured to combust the acid gas feed, an oxygen source, and a fuel gas to create a reaction furnace outlet stream,
 wherein the thermal unit comprises a main burner and a reaction furnace, the main burner configured to combust the acid gas feed, the oxygen source, and the fuel gas to a minimum reaction furnace temperature, 
 wherein the acid gas feed comprises hydrogen sulfide, 
 wherein an amount of the hydrogen sulfide is converted to elemental sulfur in the reaction furnace; 
   a waste heat boiler fluidly connected to the reaction furnace of the thermal unit, the waste heat boiler configured to capture heat from the reaction furnace outlet stream to create a waste heat boiler effluent, wherein the heat captured from the reaction furnace outlet stream heats a boiler feedwater stream to create saturated steam;   a sulfur condenser fluidly connected to the waste heat boiler, the sulfur condenser configured to cool the waste heat boiler effluent to produce a condensed liquid sulfur stream and a non-condensed gases stream, wherein the condensed liquid sulfur stream comprises the elemental sulfur, and wherein the non-condensed gases stream comprises hydrogen sulfide, elemental sulfur vapor, sulfur-containing contaminants, sulfur dioxide, and water vapor;   a gas reheater fluidly connected to the sulfur condenser, the gas reheater configured to heat the non-condensed gases stream to a hydrogenation temperature to generate a hot gases stream, wherein the hot gases stream comprises sulfur dioxide and elemental sulfur;   a hydrogenation reactor fluidly connected to the gas reheater, the hydrogenation reactor configured to convert the hot gases stream to create a hydrogenation effluent, wherein the hydrogenation reactor comprises a hydrogenation catalyst in a catalyst bed, wherein the hydrogenation effluent comprises hydrogen sulfide, carbon dioxide, water vapor, and hydrogen;   a process desuperheater fluidly connected to the hydrogenation reactor, the process desuperheater configured to condense the majority of the water vapor in the hydrogenation effluent to produce condensed water and further configured to generate a cooled effluent, wherein the condensed water is separated from the cooled effluent in the process desuperheater;   an absorber unit fluidly connected to the process desuperheater, the absorber unit configured to absorb hydrogen sulfide from the cooled effluent to generate an absorbed hydrogen sulfide rich solvent stream and a waste gas stream, wherein the absorber unit comprises an absorbing solvent, wherein the absorbed hydrogen sulfide rich solvent stream comprises hydrogen sulfide, wherein the waste gas stream comprises hydrogen sulfide and sulfur-containing contaminants; and   a regenerator fluidly connected to the absorber, the regenerator configured to desorb the hydrogen sulfide from the absorbed hydrogen sulfide rich solvent stream to generate a hydrogen sulfide recycle stream and a regenerated solvent, wherein the hydrogen sulfide recycle stream comprises hydrogen sulfide.   
     
     
         2 . The elemental sulfur recovery unit of  claim 1 , wherein the minimum reaction furnace temperature is between 1050° C. and 1250° C. 
     
     
         3 . The elemental sulfur recovery unit of  claim 1  further comprising a tail gas analyzer configured to analyze a concentration of the hydrogen sulfide and the sulfur dioxide in the non-condensed gases stream. 
     
     
         4 . The elemental sulfur recovery unit of  claim 1 , wherein the hot gases stream is at a temperature between 125° C. and 300° C. 
     
     
         5 . The elemental sulfur recovery unit of  claim 1 , wherein the gas reheater is a direct-fired reducing gas producing reheater, the direct-fired reducing gas producing reheater configured to combust a fuel feed and an air feed sub-stoichiometrically to produce hydrogen and carbon monoxide, wherein the hot gases stream comprises hydrogen and carbon monoxide. 
     
     
         6 . The elemental sulfur recovery unit of  claim 1 , wherein the hydrogenation reactor is configured to reduce the sulfur dioxide and elemental sulfur in the hot gases stream to hydrogen sulfide. 
     
     
         7 . The elemental sulfur recovery unit of  claim 1 , wherein the hydrogenation catalyst in the hydrogenation reactor comprises a cobalt-molybdenum based catalyst. 
     
     
         8 . The elemental sulfur recovery unit of  claim 7 , wherein the catalyst bed further comprises titanium. 
     
     
         9 . The elemental sulfur recovery unit of  claim 1 , wherein the absorbing solvent is selected from the group consisting of DEA, MEA, MDEA, DTPA, 2-(2-aminoethoxy)ethanol, FLEXSORB® solvents, and a combination of the same. 
     
     
         10 . The elemental sulfur recovery unit of  claim 1 , wherein the hydrogen sulfide recycle stream is recycled to the thermal unit. 
     
     
         11 . The elemental sulfur recovery unit of  claim 1 , wherein the hydrogen sulfide recycle stream comprises hydrogen sulfide in an amount greater than 25% by volume. 
     
     
         12 . The elemental sulfur recovery unit of  claim 1  further comprising:
 an oxidizer fluidly connected to the absorber unit, the oxidizer configured to burn the waste gas stream with an air stream and a fuel stream to produce a sulfur dioxide waste stream,
 wherein the H 2 S and sulfur-containing contaminants in the waste gas stream are converted to sulfur dioxide in the oxidizer. 
 
 
     
     
         13 . A sulfur recovery process to recover elemental sulfur from an acid gas feed, the sulfur recovery process comprising the steps of:
 feeding the acid gas feed, an oxygen source, and a fuel gas to a main burner of a thermal unit, the main burner configured to combust the acid gas feed, the oxygen source, and the fuel gas to a minimum reaction furnace temperature, the acid gas feed comprising hydrogen sulfide;   reacting the acid gas feed, the oxygen source, and the fuel gas at the minimum reaction furnace temperature in a reaction furnace of the thermal unit to create a reaction furnace outlet stream, wherein the reaction furnace outlet stream comprises elemental sulfur and sulfur-containing contaminants;   recovering heat from the reaction furnace outlet stream in a waste heat boiler to create a waste heat boiler effluent, the waste heat boiler configured to capture heat from the reaction furnace outlet stream to heat a boiler feedwater stream to create saturated steam;   condensing the waste heat boiler effluent in a sulfur condenser to produce a condensed liquid sulfur stream and a non-condensed gases stream, the condensed liquid sulfur stream comprising the elemental sulfur, the non-condensed gases stream comprising water vapor and the sulfur-containing contaminants;   reheating the non-condensed gases stream in a gas reheater to a hydrogenation temperature to generate a hot gases stream;   feeding the hot gases stream to a hydrogenation reactor, the hydrogenation reactor comprising a hydrogenation catalyst;   reacting the hot gases stream in the hydrogenation reactor to produce a hydrogenation effluent, wherein the hydrogenation effluent comprises hydrogen sulfide and water vapor;   cooling the hydrogenation effluent to produce a condensed water and a cooled effluent, wherein the cooled effluent comprises hydrogen sulfide;   feeding the cooled effluent to an absorber, wherein the absorber comprises an absorbing solvent, wherein the absorbing solvent is configured to absorb hydrogen sulfide from the cooled effluent to generate an absorbed hydrogen sulfide rich solvent stream and a waste gas stream; and   feeding the absorbed hydrogen sulfide rich solvent stream into a regenerator, the regenerator configured to desorb the hydrogen sulfide from the absorbed hydrogen sulfide rich solvent stream to generate a hydrogen sulfide recycle stream and a regenerated solvent.   
     
     
         14 . The sulfur recovery process of  claim 13 , wherein the minimum reaction furnace temperature is between 1050° C. and 1250° C. 
     
     
         15 . The sulfur recovery process of  claim 13 , wherein the hot gases stream is between 125° C. and 300° C. 
     
     
         16 . The sulfur recovery process of  claim 13 , further comprising the step of venting the waste gas stream to atmosphere. 
     
     
         17 . The sulfur recovery process of  claim 13 , wherein the absorbing solvent is selected from the group consisting of DEA, MEA, MDEA, DTPA, 2-(2-aminoethoxy)ethanol, FLEXSORB® solvents, and a combination of the same. 
     
     
         18 . The sulfur recovery process of  claim 13 , wherein the amount of hydrogen sulfide in the hydrogen sulfide recycle stream is greater than 25% by volume. 
     
     
         19 . The sulfur recovery process of  claim 13  further comprising the step of:
 combusting the waste gas stream, an air stream, and fuel stream in an oxidizer to produce a sulfur dioxide waste stream, the sulfur dioxide waste stream comprising sulfur dioxide. 
 
     
     
         20 . The sulfur recovery process of  claim 19 , further comprising the steps of:
 removing an amount of sulfur dioxide from sulfur dioxide waste stream to produce a sulfur dioxide recycle stream and a waste effluent stream such that the waste effluent stream comprises less than 1% by volume sulfur dioxide; and   recycling the sulfur dioxide recycle stream to the main burner of the thermal unit.