Method for hydrotreating heavy hydrocarbon feedstocks using permutable reactors, including at least one step of short-circuiting a catalyst bed

Abstract

Process for hydrotreating a heavy hydrocarbon fraction using a system of switchable fixed bed guard zones each containing at least two catalyst beds and in which whenever the catalyst bed that is brought initially into contact with the feed is deactivated and/or clogged during the steps in which the feed passes successively through all the guard zones, the point of introduction of the feed is shifted downstream. The present invention also relates to an installation for implementing this process.

1 . Process for hydrotreating a heavy hydrocarbon fraction containing asphaltenes, sediments, sulphur-containing, nitrogen-containing and metallic impurities, in which the feed of hydrocarbons and hydrogen is passed, under conditions of hydrotreating, over a hydrotreating catalyst, in at least two fixed bed hydrotreating guard zones each containing at least two catalyst beds, the guard zones being arranged in series to be used cyclically, consisting of successive repetition of steps b), c) and c′) defined below:
 a step a) during which the feed passes through all the catalyst beds of the guard zones for a period at most equal to the deactivation time and/or clogging time of a guard zone, 
 a step a′) during which the feed is introduced, by-passing the deactivated and/or clogged catalyst bed, onto the next catalyst bed not yet deactivated and/or clogged of the same guard zone for a period at most equal to the deactivation time and/or clogging time of a guard zone, 
 step a′) being repeated until the feed is introduced onto the last catalyst bed not yet deactivated and/or clogged of the same guard zone for a period at most equal to the deactivation time and/or clogging time, 
 a step b) during which the deactivated and/or clogged guard zone is by-passed and the catalyst that it contains is regenerated and/or replaced with fresh catalyst and during which the other guard zone(s) are used, 
 a step c) during which the feed passes through all the catalyst beds of the guard zones, the guard zone of which the catalyst was regenerated during the preceding step being reconnected so as to be downstream of all the other guard zones and said step being continued for a period at most equal to the deactivation time and/or clogging time of a guard zone, 
 a step c′) during which the feed is introduced onto the next catalyst bed not yet deactivated and/or clogged of the same guard zone for a period at most equal to the deactivation time and/or clogging time of a guard zone, step c′) being repeated until the feed is introduced onto the last catalyst bed not yet deactivated and/or clogged of the same guard zone for a period at most equal to the deactivation time and/or clogging time of a guard zone. 
 
     
     
         2 . Process according to  claim 1  in which each guard zone has n beds, each bed i having a volume V i , the total catalyst volume of the guard zone V tot  being the sum of the volumes V i  of the n beds; each volume V i  of a bed i included in the n−1 first beds of the guard zone has a volume V i  defined between 5% of the total volume V tot  and the percentage resulting from the total volume V tot  divided by the number of beds n; and in which for two consecutive beds i and i+1, the volume of the first bed V i  is less than or equal to the volume of the next bed V i+1 , except for the last two consecutive beds V n−1  and V n  where the volume of the penultimate bed V n−1  is strictly less than the volume of the last bed V n . 
     
     
         3 . Process according to  claim 1  in which during steps a′) and c′) the maximum volume of the by-passed catalyst bed(s) in a guard zone is defined as less than the volume given by the formula ((n−1) V tot )/n, n being the total number of catalyst beds, V tot  being the total catalyst volume of the guard zone which is defined by the sum of the volumes of the n catalyst beds of the guard zone. 
     
     
         4 . Process according to  claim 1  in which the degree of hydrotreating is maintained by a temperature increase. 
     
     
         5 . Process according to  claim 1  in which, at the entrance of each guard zone, the feed passes through a filtering distributor plate composed of a single stage or of two successive stages, said plate is situated upstream of the catalyst beds. 
     
     
         6 . Process according to  claim 1  in which the feed passes through a filtering distributor plate upstream of each catalyst bed of a guard zone. 
     
     
         7 . Process according to  claim 1 , characterized in that it precedes a fixed bed or ebullating bed hydrotreating process. 
     
     
         8 . Installation for implementing the process according to  claim 1  comprising at least two fixed bed reactors (R 1   a , R 1   b ) arranged in series and each containing at least two catalyst beds (A 1 , A 2 ; B 1 , B 2 ), the first bed of each reactor having at least one inlet pipe for a gas and an inlet pipe for a hydrocarbon feed ( 21 ,  22 ), said feed inlet pipes each containing a valve (V 1 , V 3 ) and being connected by a common pipe ( 3 ), each reactor having at least one outlet pipe ( 23 ,  24 ) each containing a valve (V 5 , V 6 ) for removal of the effluent, the outlet pipe of each reactor ( 23 ,  24 ) being connected by an additional pipe ( 26 ,  27 ) having a valve (V 2 , V 4 ) to the feed inlet pipe ( 22 ,  21 ) of the reactor downstream, characterized in that the installation further comprises, for each reactor, a feed inlet pipe for each catalyst bed ( 31 ,  32 ), said pipes each having a valve (V 1 ′, V 3 ′) and being connected to said inlet pipe for the hydrocarbon feed of the first bed ( 21 ,  22 ), each valve of the installation being able to be opened or closed separately. 
     
     
         9 . Installation according to  claim 8 , characterized in that it comprises a filtering distributor plate composed of a single stage or of two successive stages at the entrance of each reactor, said plate is situated upstream of the catalyst beds. 
     
     
         10 . Installation according to  claim 8 , characterized in that it comprises a filtering distributor plate composed of a single stage or of two successive stages upstream of each catalyst bed.