Process and installation for conversion of heavy petroleum fractions in a fixed bed with integrated production of middle distillates with a very low sulfur content

Abstract

This invention relates to a process and an installation for treatment of a heavy petroleum feedstock, of which at least 80% by weight has a boiling point of greater than 340° C., whereby the process comprises the following stages: (a) Hydroconversion in a fixed-bed reactor operating with an upward flow of liquid and gas, whereby the net conversion in products boiling below 360° C. is from 10 to 99% by weight; (b) Separation of the effluent obtained from stage (a) into a gas containing hydrogen and H 2 S, a fraction comprising the gas oil, and optionally a fraction that is heavier than the gas oil and a naphtha fraction; c) Hydrotreatment by contact with at least one catalyst of at least the fraction comprising the gas oil obtained in stage (b); d) Separation of the effluent obtained at the end of stage (c) into a gas containing hydrogen and at least one gas oil fraction having a sulfur content of less than 50 ppm, preferably less than 20 ppm, and more preferably still less than 10 ppm, the hydroconversion stage (a) being conducted at a pressure P 1 and the hydrotreatment stage (c) being conducted at a pressure P 2, the difference ΔP=P 1− P 2 being at least 2 MPa, the hydrogen supply for the hydroconversion (a) and hydrotreatment (c) stages being ensured by a single compression system with n stages.

1 . Process for treatment of a heavy petroleum feedstock of which at least 80% by weight has a boiling point of greater than 340° C., which comprises the following stages:
 (a) Hydrocracking in a fixed bed with at least one catalyst at a temperature of 300-500° C., a pressure of at least 4 MPa and less than or equal to 17 MPa, an hourly space velocity of 0.1 to 10 h −1  and in the presence of 50 to 5000 Nm 3  of hydrogen per m 3  of feedstock, the net conversion into products boiling below 360° C. being from 10 to 99% by weight,   (b) Separation of the effluent that is obtained from stage (a) into a gas containing hydrogen and H 2 S, a fraction comprising the gas oil, and optionally a fraction that is heavier than the gas oil and a naphtha fraction;   c) Hydrotreatment by contact with at least one catalyst of at least the fraction comprising the gas oil obtained in stage (b), at a temperature of 200 to 500° C., at a liquid hourly space velocity relative to the catalyst volume of 0.1 to 10 h −1  in the presence of 100 to 5000 Nm 3  of hydrogen per m 3  of feedstock;   d) Separation of the effluent that is obtained at the end of stage (c) into a gas containing hydrogen and at least one gas oil fraction that has a sulfur content of less than 50 ppm,   
       the hydroconversion stage (a) being conducted at a pressure P 1  and the hydrotreatment stage (c) being conducted at a pressure P 2 , the difference ΔP=P 1 −P 2  being at least 2 MPa, the hydrogen supply for the hydroconversion (a) and hydrotreatment (c) stages being ensured by a single compression system with n stages, n being greater than or equal to 2. 
     
     
         2 . Process according to  claim 1 , in which n is between 2 and 6. 
     
     
         3 . Process according to  claim 2 , in which n is between 2 and 5. 
     
     
         4 . Process according to  claim 3 , in which n is between 2 and 4. 
     
     
         5 . Process according to  claim 4 , characterized by the fact that n is equal to 3. 
     
     
         6 . Process according to  claim 1 , in which ΔP is from 4 to 8 MPa. 
     
     
         7 . Process according to  claim 6 , in which ΔP is from 5 to 7 MPa. 
     
     
         8 . Process according to  claim 1 , in which in stage (d), a gas oil whose sulfur content is less than 20 ppm is separated. 
     
     
         9 . Process according to  claim 8 , in which in stage (d), a gas oil whose sulfur content is less than 10 ppm is separated. 
     
     
         10 . Process according to  claim 1 , in which the pressure P 1  implemented in the fixed-bed catalytic hydroconversion stage (a) is between 6 and 17 MPa. 
     
     
         11 . Process according to  claim 10 , in which the pressure P 1  is between 8 and 12 MPa. 
     
     
         12 . Process according to  claim 1 , in which the pressure P 2  implemented in the hydrotreatment stage (c) is between 4 and 8 MPa. 
     
     
         13 . Process according to  claim 12 , in which the pressure P 2  is between 4.5 and 6 MPa. 
     
     
         14 . Process according to  claim 1 , in which n=3 and the delivery pressure of the first compression stage is between 4 and 5 MPa, the delivery pressure of the second compression stage is between 8 and 12 MPa, and the delivery pressure of the third compression stage is between 12 and 17 MPa. 
     
     
         15 . Process according to  claim 15 , in which n=3 and the delivery pressure of the first compression stage is between 4.5 and 5 MPa, the delivery pressure of the second compression stage is between 9 and 11 MPa, and the delivery pressure of the third compression stage is between 13 and 15 MPa. 
     
     
         16 . Process according to  claim 1 , in which n=3 and in which the delivery hydrogen from the second compression stage supplies the hydrotreatment reactor. 
     
     
         17 . Process according to  claim 1 , in which the partial hydrogen pressure in the P2 H2  hydrotreatment reactor is between 3.4 and 8 MPa. 
     
     
         18 . Process according to  claim 18 , in which P2 H2  is between 4 and 6 MPa. 
     
     
         19 . Process according to  claim 1 , according to which the hydrogen supplying the last compression stage is the recycled hydrogen originating from the separation stage (d) or from the separation stage (b). 
     
     
         20 . Process according to  claim 1 , according to which the delivery hydrogen from an intermediate compression stage can, moreover, supply a hydrotreatment unit of gas oil obtained directly from atmospheric distillation, called “straight-run gas oil,” at a pressure of between 3 and 6.5 MPa. 
     
     
         21 . Installation for treatment of a heavy petroleum feedstock comprising the following reaction zones:
 a single hydrogen compression zone that consists of n compression stages arranged in series, n being greater than or equal to 2,   a catalytic hydroconversion zone (II) that consists of at least one fixed-bed reactor that is supplied with hydrogen via the last compression stage, and connected via the pipe ( 11 ) to   a separation zone (III) that consists of at least one separator ( 15 ) and at least one distillation column ( 18 ), the separator allowing the separation of a hydrogen-rich gas via the pipe ( 16 ) and a liquid phase that is brought via the pipe ( 17 ) to the distillation column ( 18 ); the pipe ( 21 ) drawing off the distilled gas oil fraction is connected to   a hydrotreatment zone (IV) that consists of a fixed-bed hydrotreatment reactor that is supplied with hydrogen by an intermediate compression stage, and whose pipe of the effluent ( 25 ) is connected to   a separation zone (V) allowing evacuation of hydrogen to the last compression stage.   
     
     
         22 . Installation according to  claim 22 , in which n is preferably between 2 and 6. 
     
     
         23 . Installation according to  claim 22 , in which n is preferably between 2 and 5. 
     
     
         24 . Installation according to  claim 23 , in which n is preferably between 2 and 4. 
     
     
         25 . Installation according to  claim 24 , in which n is equal to 3. 
     
     
         26 . Installation according to  claim 21 , in which the delivery from an intermediate compression stage feeds a straight-run gas oil hydrotreatment reactor ( 40 ).