Method for the element of mercury from a feedstock downstream of a fractionation unit

Abstract

Process for the elimination of mercury contained in a heavy hydrocarbon-containing feedstock downstream 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 fractionation of said hydrocarbon-containing feedstock is carried out in a fractionation unit in order to produce a top effluent comprising elemental mercury; c) the top effluent obtained in stage b) is brought into contact with a mercury capture material contained in a unit for the capture of mercury, in order to obtain an effluent that is at least partially de-mercurized.

1 . Process for the elimination of mercury contained in a heavy hydrocarbon-containing feedstock downstream 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 ( 200 ) 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 ( 200 ) 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 ( 200 ) 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 ( 200 ) 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 ( 200 ) is comprised between 1 and 10 minutes; 
   b) a fractionation of said hydrocarbon-containing feedstock is carried out in a fractionation unit ( 3000 ) in order to produce a top effluent ( 400 ) comprising elemental mercury;   c) the top effluent ( 400 ) obtained in stage b) is brought into contact with a mercury capture material contained in a unit for the capture of mercury ( 5000 ), in order to obtain an effluent that is at least partially de-mercurized ( 420 ).   
     
     
         2 . 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%. 
     
     
         3 . Process according to  claim 1 , characterized in that stages a) and b) are carried out simultaneously. 
     
     
         4 . Process according to  claim 1 , characterized in that the top effluent ( 400 ) originating from the fractionation of said feedstock in the main fractionation unit ( 3000 ) is cooled by means of a heat exchanger ( 6000 ) so as to produce a liquid effluent ( 430 ). 
     
     
         5 . Process according to  claim 4 , characterized in that the liquid effluent ( 430 ) is sent into a separation unit ( 7000 ) in order to provide a liquid organic phase a part of which is recycled to the main fractionation unit ( 3000 ) by way of reflux, and the other part is sent via the pipe ( 434 ) to said unit for the capture of mercury ( 5000 ). 
     
     
         6 . Process according to  claim 1 , characterized in that the top effluent ( 400 ) originating from the fractionation of said feedstock in the main fractionation unit ( 3000 ) is heated by means of a heat exchanger ( 6001 ) so as to produce a gaseous effluent ( 435 ). 
     
     
         7 . Process according to  claim 6 , characterized in that the gaseous effluent ( 435 ) is compressed by means of a compressor ( 9000 ) before being sent to the unit for the capture of mercury ( 5000 ). 
     
     
         8 . Process according to  claim 1 , characterized in that before stage a) of transformation of the non-elemental mercury contained in the compounds of said feedstock to elemental mercury, said feedstock is desalted in a desalting unit ( 1000 ). 
     
     
         9 . 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. 
     
     
         10 . 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 sulphur in elemental form. 
     
     
         11 . Process according to  claim 1 , characterized in that said hydrocarbon-containing feedstock comprises between 1 and 10 mg of mercury per kg of feedstock. 
     
     
         12 . Process according to  claim 1 , characterized in that the heavy hydrocarbon-containing feedstock is a crude oil feedstock.