Method for the elimination of mercury from a heavy hydrocarbon-containing feedstock upstream of a fractionation unit

Abstract

Process for the elimination of mercury contained in a heavy hydrocarbon-containing feedstock upstream of a main fractionation unit, a process in which: a) the non-elemental mercury contained in the compounds of said feedstock is transformed to elemental mercury, b) a separation of the feedstock obtained in stage a) is carried out in a separation unit, that consists of producing a liquid effluent and a gaseous effluent comprising elemental mercury; c) the gaseous effluent originating from stage b) comprising the elemental mercury is brought into contact with a mercury capture material contained in a unit for the capture of mercury, in order to produce an effluent that is at least partially de-mercurized.

1 . Process for the elimination of mercury contained in a heavy hydrocarbon-containing feedstock upstream of a main fractionation unit ( 3000 ), a process in which:
 a) the non-elemental mercury contained in the compounds of said feedstock is transformed to elemental mercury, said stage being carried out in a conversion unit ( 900 ) at a target temperature during a fixed residence time and adapted to said target temperature so that at least 90% by weight of non-elemental mercury contained in the compounds of said feedstock is converted to elemental mercury, said transformation stage being carried out in the absence of hydrogen and in the absence of a catalyst, it being understood that:
 when the target temperature of said feedstock is comprised between 150° C. and 175° C., the residence time of said feedstock in the conversion unit ( 900 ) is comprised between 150 and 2700 minutes; and/or 
 when the target temperature of said feedstock is greater than 175° C. and less than or equal to 250° C., the residence time of said feedstock in the conversion unit ( 900 ) is comprised between 100 and 900 minutes; and/or 
 when the target temperature of said feedstock is greater than 250° C. and less than or equal to 400° C., the residence time of said feedstock in the conversion unit ( 900 ) is comprised between 5 and 70 minutes; and/or 
 when the target temperature of said feedstock is greater than 400° C., the residence time of said feedstock in the conversion unit ( 900 ) is comprised between 1 and 10 minutes; 
   b) a separation of the feedstock obtained in stage a) is carried out in a separation unit ( 5000 ), in order to produce a liquid effluent ( 103 ) and a gaseous effluent ( 203 ) comprising elemental mercury;   c) the gaseous effluent ( 203 ) originating from stage b) comprising the elemental mercury is brought into contact with a mercury capture material contained in a unit for the capture of mercury ( 6000 ), in order to produce an effluent that is at least partially de-mercurized ( 204 ).   
     
     
         2 . Process according to  claim 1 , comprising moreover a stage d) in which the liquid effluent ( 103 ) obtained in stage b) is fractionated in a main fractionation unit ( 3000 ). 
     
     
         3 . Process according to  claim 1 , characterized in that the reduction in the total content by weight of mercury of said feedstock taken before stage a) and after stage c) is at least 90%. 
     
     
         4 . Process according to  claim 1 , characterized in that the stages a) and b) are carried out separately or simultaneously. 
     
     
         5 . Process according to  claim 1 , characterized in that the separation unit ( 5000 ) of stage b) is a distillation column. 
     
     
         6 . Process according to  claim 1 , characterized in that the separation unit ( 5000 ) of stage b) is a stripping column. 
     
     
         7 . Process according to  claim 6 , characterized in that in the stripping column a carrier gas circulates in counter-current with said hydrocarbon-containing feedstock, said carrier gas at least partially originating from a liquid or gaseous fraction of the main fractionation unit ( 3000 ). 
     
     
         8 . Process according to  claim 7 , in which when the carrier gas at least partially originates from a liquid fraction of the main fractionation unit ( 3000 ), said liquid fraction is transformed to a gaseous fraction by means of a heat exchanger ( 2001 ). 
     
     
         9 . Process according to  claim 6 , characterized in that the at least partially de-mercurized effluent ( 204 ) obtained in stage c) is fractionated in a main fractionation unit ( 3000 ). 
     
     
         10 . Process according to  claim 1 , characterized in that said hydrocarbon-containing feedstock comprises between 1 and 10 mg of mercury per kg of feedstock. 
     
     
         11 . Process according to  claim 1 , characterized in that during stage c), said feedstock is brought into contact with a bulk or supported mercury capture material comprising a phase containing at least one metallic sulphide based on a metal M selected from the group constituted by copper, chromium, manganese, iron, cobalt and nickel. 
     
     
         12 . Process according to  claim 1 , characterized in that during stage c), said feedstock is brought into contact with a bulk or supported capture material comprising a phase containing at least sulphur in elemental form. 
     
     
         13 . Process according to  claim 1 , characterized in that the heavy hydrocarbon-containing feedstock is a crude oil feedstock.