Method for hydrotreatment of a heavy hydrocarbon fraction with switchable reactors and reactors capable of being shorted out

Abstract

The invention consists in a process for hydrotreating a heavy hydrocarbon fraction in a first hydrodemetallisation section, then in a second hydrodesulphurisation section into which the effluent from the first section is passed. The hydrodemetallisation section is preceded by at least one guard zone. Said hydrotreatment process comprises the following steps: a) a step in which the guard zone is used; b) a step during which the guard zone is short-circuited and the catalyst it contains is regenerated and/or replaced; c) a step during which the guard zone in which the catalyst has been regenerated and/or replaced is reconnected; d) a step in which at least one of the reactors from the hydrodemetallisation section and/or the hydrodesulphurisation section can be short-circuited and the catalyst it contains regenerated and/or replaced.

1 . A process for hydrotreating, in at least two sections, a heavy hydrocarbon fraction containing sulphur-containing and metallic impurities, in which, in a first hydrodemetallisation section, the hydrocarbon feed and hydrogen are passed over a hydrodemetallisation catalyst under hydrodemetallisation conditions, then the effluent from the first stage is passed over a hydrodesulphurisation catalyst in a subsequent second section under hydrodesulphurisation conditions, and in which the hydrodemetallisation section comprises one or more hydrodemetallisation zones preceded by at least two hydrodemetallisation guard zones disposed in series for use in cycles consisting of successive repetitions of steps b) and c) defined below, the hydrodemetallisation and/or hydrodesulphurisation sections being composed of one or more reactors which can be short-circuited separately or otherwise following step d) defined below, said hydrotreatment process comprising: 
 a) a step in which the guard zones are used all together for a period at most equal to the deactivation time and/or clogging time of one thereof;    b) a step during which the deactivated and/or clogged guard zone is short-circuited and the catalyst it contains is regenerated and/or replaced by fresh-or regenerated catalyst;    c) a step during which the guard zones are used all together, the guard zone in which the catalyst has been regenerated and/or replaced during the preceding step being reconnected and said step being carried out for a period at most equal to the deactivation and/or clogging time of one of the guard zones;    d) a step in which at least one of the reactors from the hydrodemetallisation section and/or the hydrodesulphurisation section can be short-circuited during a cycle when the catalyst is deactivated and/or clogged for regeneration and/or replacement by fresh or regenerated catalyst.    
     
     
         2 . A process for hydrotreating, in at least two sections, a heavy hydrocarbon fraction containing sulphur-containing and metallic impurities, in which, in a first hydrodemetallisation section, the hydrocarbon feed and hydrogen are passed over a hydrodemetallisation catalyst under hydrodemetallisation conditions, then the effluent from the first stage is passed over a hydrodesulphurisation catalyst in a subsequent second section under hydrodesulphurisation conditions, and in which the hydrodemetallisation section comprises one or more hydrodemetallisation zones preceded by at least one guard zone, the hydrodemetallisation and/or hydrodesulphurisation sections being composed of one or more reactors which can be short-circuited separately or otherwise following step d) defined below, said hydrotreatment process comprising: 
 a) a step in which the guard zone is used for a period at most equal to the deactivation time and/or clogging time of said zone;    b) a step during which the deactivated and/or clogged guard zone is short-circuited and the catalyst it contains is regenerated and/or replaced by fresh or regenerated catalyst;    c) a step during which the guard zone in which the catalyst has been regenerated and/or replaced during the preceding step is reconnected, said step being carried out for a period at most equal to the deactivation and/or clogging time of one of the guard zones;    d) a step in which at least one of the reactors from the hydrodemetallisation section and/or the hydrodesulphurisation section can be short-circuited during a cycle when the catalyst is deactivated and/or clogged for regeneration and/or replacement by fresh or regenerated catalyst.    
     
     
         3 . A process for hydrotreating, in at least two sections, a heavy hydrocarbon fraction containing sulphur-containing and metallic impurities in which, in a first hydrodemetallisation section, the hydrocarbon feed and hydrogen are passed over a hydrodemetallisation catalyst under hydrodemetallisation conditions, then the effluent from the first stage is passed over a hydrodesulphurisation catalyst in a subsequent second section under hydrodesulphurisation conditions, and in which the hydrodemetallisation section comprises one or more hydrodemetallisation zones preceded by at least two hydrodemetallisation guard zones comprising one or more reactors, preferably fixed or ebullated bed reactors, disposed in series for use in cycles consisting of successive repetitions of steps b) and c) defined below, the hydrodemetallisation and/or hydrodesulphurisation sections being composed of one or more reactors which can be short-circuited separately or otherwise following step d) defined below, said hydrotreatment process comprising: 
 a) a step in which the guard zones are all used together for a period at most equal to the deactivation and/or clogging time of the guard zone the most upstream with respect to the overall direction of circulation of the treated feed;    b) a step during which the feed penetrates directly into the guard zone located immediately after that which was the most upstream during the preceding step and during which the guard zone which was the most upstream during the preceding step is short-circuited and the catalyst which it contains is regenerated and/or replaced by fresh catalyst; and    c) a step during which the guard zones are used all together, the guard zone in which the catalyst has been regenerated and/or replaced during step b) being reconnected so as to be downstream of the set of guard zones and said step being continued for a period at most equal to the deactivation and/or clogging time of the guard zone which during this step is the most upstream with respect to the overall direction of circulation of the treated feed;    d) a step in which at least one of the reactors from the hydrodemetallisation section and/or hydrodesulphurisation section can be short-circuited during the cycle when the catalyst is deactivated and/or clogged to be regenerated and/or replaced by fresh or regenerated catalyst.    
     
     
         4 . A process according to any one of  claims 1  to  3 , in which a quantity of middle distillate representing  0 . 5 % to  80 % by weight with respect to the weight of hydrocarbon feed is introduced into the inlet to the first operating guard zone.  
     
     
         5 . A process according to  claim 4 , in which the atmospheric distillate introduced with the hydrocarbon feed is a straight run gas oil.  
     
     
         6 . A process according to any one of  claims 1  to  5 , in which the product from the hydrodesulphurisation step is sent to an atmospheric distillation zone from which an atmospheric distillate is recovered at least a portion of which is recycled to the inlet to the first functioning guard zone, and an atmospheric residue is also recovered.  
     
     
         7 . A process according to  claim 6 , in which at least a portion of a gas oil fraction from the atmospheric distillation step following the hydrodesulphurisation step is recycled to the inlet to the first functioning guard zone.  
     
     
         8 . A process according to  claim 5  or  claim 7 , in which the recycled gas oil fraction is a cut with an initial boiling point of about 140° C. and an end point of about 400° C.  
     
     
         9 . A process according to any one of  claims 4  to  8 , in which the quantity of atmospheric distillate and/or gas oil introduced to the inlet to the first functioning guard zone at the same time as the feed represents about 1% to 50% by weight with respect to the feed.  
     
     
         10 . A process according to  claim 6  or  claim 7 , in which at least a portion of the atmospheric residue from the atmospheric distillation zone is sent to a vacuum distillation zone from which a vacuum distillate is recovered, at least a portion of which is recycled to the inlet to the first functioning guard zone, and a vacuum residue is also recovered.  
     
     
         11 . A process according to  claim 10 , in which at least a portion of the atmospheric residue and/or vacuum distillate is sent to a catalytic cracking unit from which an LCO fraction and an HCO fraction are recovered, and at least a portion of one or the other or a mixture of the two fractions is sent to the inlet to the first functioning guard zone.  
     
     
         12 . A process according to any one of  claims 1  to  3 , in which during step c), the guard zones are used all together, the guard zone in which the catalyst has been regenerated during step b) being reconnected such that the connection is identical to that it had before it was short-circuited during step b).  
     
     
         13 . A process according to any one of  claims 1  to  12 , in which a conditioning section is associated with the guard zone or zones, which zone enables short-circuiting or permutation during operation of said guard zone or zones, without the unit ceasing operation, said section being regulated so as to condition the catalyst contained in the guard zone which is not functioning, at a pressure in the range 1 MPa to 5 MPa.  
     
     
         14 . A process according to any one of  claims 1  to  13 , in which, in order to treat a feed constituted by a heavy oil or a heavy oil fraction containing asphaltenes, the feed is initially subjected to hydrovisbreaking conditions, mixed with hydrogen, before sending the feed to the guard zone or zones.  
     
     
         15 . A process according to any one of claims  7 ,  10  or  11 , in which the atmospheric residue undergoes deasphalting using a solvent or a solvent mixture and at least a portion of the deasphalted product is recycled to the inlet to the first functioning guard zone.  
     
     
         16 . A process according to  claim 10  or  claim 11 , in which the vacuum residue undergoes deasphalting using a solvent or solvent mixture and at least a portion of the deasphalted product is recycled to the inlet to the first functioning guard zone.  
     
     
         17 . A process according to any one of  claims 1  to  16 , in which all of the reactors are fixed bed reactors.  
     
     
         18 . A process according to any one of  claims 1  to  17 , in which at least one of the guard zone and/or hydrodemetallisation section and/or hydrodesulphurisation section reactors is an ebullated bed reactor.  
     
     
         19 . A process according to  claim 18 , in which all of the reactors for the guard zones are fixed bed reactors, and all of the reactors in the hydrodesulphurisation zone are ebullated bed reactors.  
     
     
         20 . A process according to  claim 18  or  claim 19 , in which all of the reactors in the guard zones are fixed bed reactors, and all the reactors in the hydrodemetallisation zone are ebullated bed reactors.