Method for converting hydrocarbon feedstock comprising a shale oil by decontamination, hydroconversion in an ebullating bed, and fractionation by atmospheric distillation

Abstract

Method and plant for converting hydrocarbon feedstock comprising a shale oil, comprising a step of decontaminating, a step of hydroconverting in an ebullating bed, a step of fractionating into a light fraction, a naphtha fraction, a gas-oil fraction and a fraction heavier than the gas-oil fraction, the naphtha and gas-oil fractions being hydrotreated, the fraction heavier than the gas-oil fraction being conveyed to the decontaminating step. The method aims to maximize the yield of fuel bases.

1 . Method for converting a shale oil or a mixture of shale oils having a nitrogen content of at least 0.1%, often at least 1% and very often at least 2% by weight, characterized in that it comprises the following steps:
 a) The feedstock is subjected to a decontamination, to give a residue and a decontaminated oil,   b) The decontaminated oil is conveyed to a section for hydroconverting in the presence of hydrogen, said section comprising at least one ebullating bed reactor operating in gas and liquid upflow mode and containing at least one supported hydroconverting catalyst,   c) The effluent obtained in step b) is conveyed at least partly, and often entirely, into a fractionating zone, from which, by atmospheric distillation, a gaseous fraction, a naphtha fraction, a gas-oil fraction and a fraction heavier than gas-oil are recovered,   d) Said naphtha fraction is treated at least partly, and often entirely, in another section for hydrotreating in the presence of hydrogen, said section comprising at least one fixed bed reactor containing at least one hydrotreating catalyst, and   e) Said gas-oil fraction is treated at least partly, and often entirely, in a section for hydrotreating in the presence of hydrogen, said section comprising at least one fixed bed reactor containing at least one hydrotreating catalyst.   
     
     
         2 . Method according to  claim 1 , characterized in that it further comprises a step f), in which at least a part of the fraction heavier than gas-oil is conveyed to step a) to be decontaminated. 
     
     
         3 . Method according to  claim 1 , wherein the effluent obtained in step b) is fractionated by atmospheric distillation into a gaseous fraction having a boiling point of less than 50° C., a naphtha fraction boiling at between about 50° C. and 150° C., a gas-oil fraction boiling at between about 150° C. and 370° C., and a fraction which is heavier than the gas-oil fraction and which boils generally at above 340° C., preferably above 370° C. 
     
     
         4 . Method according to  claim 1 , wherein the decontamination in step a) is carried out with a solvent selected from the group consisting of propane, n-butane, isobutane, n-pentane, cyclopentane, 2-methylbutane, 2,2-dimethylpropane, and mixtures thereof in any proportions. 
     
     
         5 . Method according to  claim 1 , wherein decontaminating step a) is carried out with a solvent/feedstock ratio of 3/1 to 8/1, preferably of 4/1 to 6/1, at a temperature of between 60° C. and 250° C., preferably between 60° C. and 200° C., and at a pressure of between 4 MPa and 5 MPa. 
     
     
         6 . Method according to  claim 1 , wherein the fixed bed hydrotreating section in step d) and/or e) comprises, upstream of the catalytic hydrotreating beds, at least one specific guard bed for arsenic compounds and silicon compounds. 
     
     
         7 . Method according to  claim 1 , wherein at least a part of the fraction heavier than gas-oil is conveyed into a catalytic cracking section, called step g), in which it is treated under conditions enabling production of a second gaseous fraction, a second petrol fraction, a second gas-oil fraction and a second fraction heavier than gas-oil. 
     
     
         8 . Method according to  claim 7 , wherein at least part of the second fraction heavier than gas-oil, obtained at the end of step g), is recycled to the start of said step g). 
     
     
         9 . Method according to  claim 7 , wherein at least part of the second gas-oil fraction, obtained at the end of step g), is recycled to gas-oil hydrotreating step e). 
     
     
         10 . Method according to  claim 7 , wherein at least part of the second fraction heavier than gas-oil, obtained at the end of step g), is recycled to decontaminating step a). 
     
     
         11 . Method according to  claim 1 , wherein hydroconverting step b) operates at a temperature of between 300° C. and 550° C., preferably between 400° C. and 450° C., at a total pressure of between 2 and 35 MPa, preferably of between 10 and 20 MPa, at a mass hourly velocity ((t of feedstock/h)/t of catalyst) of between 0.2 and 1.5 h −1 , and at a hydrogen/feedstock ratio of between 50 and 5000 Nm 3 /m 3 , preferably between 100 and 1000 Nm 3 /m 3 . 
     
     
         12 . Method according to  claim 1 , wherein step d) of hydrotreating the naphtha fraction operates at a temperature of between 280° C. and 380° C., preferably between 300° C. and 350° C., at a total pressure of between 4 and 15 MPa, preferably of between 10 and 13 MPa, at a mass hourly velocity of between 0.1 and 5 h −1 , preferably between 0.5 and 1 h −1 , and at a hydrogen/feedstock ratio of between 100 and 5000 Nm 3 /m 3 , preferably between 100 and 1000 Nm 3 /m 3 . 
     
     
         13 . Method according to  claim 1 , wherein step e) of hydrotreating the gas-oil fraction operates at a temperature of between 320° C. and 450° C., preferably between 340° C. and 400° C., at a total pressure of between 7 and 20 MPa, preferably of between 10 and 15 MPa, at a mass hourly velocity of between 0.1 and 1 h −1 , preferably between 0.3 and 0.8 h −1 , and at a hydrogen/feedstock ratio of between 100 and 5000 Nm 3 /m 3 , preferably between 200 and 1000 Nm 3 /m 3 . 
     
     
         14 . Method according to  claim 1 , wherein the catalysts in hydroconverting step b) and hydrotreating steps d) and e) are independently selected from the group of catalysts comprising a group VIII metal selected from the group consisting of Ni and/or Co, optionally a group VIB metal selected from the group consisting of Mo and/or W, on an amorphous support selected from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures thereof. 
     
     
         15 . Method according to  claim 1 , wherein the shale oil or the mixture of shale oils is supplemented by a hydrocarbon feedstock selected from the group consisting of oils derived from coal, oils obtained from heavy tars and bituminous sands, vacuum distillates, and residues of direct distillation, vacuum distillates and unconverted residues obtained from a residue conversion process, oils deasphalted with solvents, light cycle oils, heavy cycle oils, gas-oil cuts originating from catalytic cracking and having generally a distillation range from approximately 150° C. to approximately 650° C., aromatic extracts obtained in the manufacture of lubricating oils, pyrolysis oils of ligneous residues such as wood residues, crudes obtained from biomass (“biocrudes”), vegetable oils and animal fats, or mixtures of such feedstocks. 
     
     
         16 . Synthetic crude obtained by a method according to  claim 1 . 
     
     
         17 . Plant for treating a shale oil, comprising:
 a section for decontaminating the shale oil to be treated,   a section for hydroconverting in the presence of hydrogen, comprising an ebullating bed reactor operating in gas and liquid upflow mode and containing at least one supported hydroconverting catalyst,   a zone for fractionation by atmospheric distillation,   a section for hydrotreating in the presence of hydrogen, comprising a fixed bed reactor containing at least one hydrotreating catalyst,   another section for hydrotreating in the presence of hydrogen, comprising at least one fixed bed reactor containing at least one hydrotreating catalyst,   these elements being arranged for the implementation of the method according to  claim 1 .