System and process for the hydroconversion of heavy oils

Abstract

System and relative process for the complete and high productivity hydroconversion of heavy oils essentially consisting of a solid accumulation reactor and a stripping section of the conversion products outside or inside the reactor itself. In particular, the system proposed consists of a solid accumulation hydroconversion reactor in which the solids deriving from and generated by the feedstock treated (metals in the form of sulphides and coke) are accumulated, up to very high levels, and a hot gas stripping section of the reaction liquid, designed in relation to the type of reactor adopted, for the direct and continuous removal of the conversion products, including high-boiling products.

1 . A system for the hydroconversion of heavy oils essentially consisting of a solid accumulation reactor and a stripping section of the conversion products outside or inside the reactor itself. 
   
   
       2 . The system according to  claim 1 , wherein the solid accumulation reactor is selected from a stirred tank reactor or a bubble tower reactor. 
   
   
       3 . The system according to  claim 1 , wherein the stripping section is inside the reactor and is preferably positioned so as to effect the stripping in the upper part of the reactor itself, said reactor being a partially filled reactor. 
   
   
       4 . The system according to  claim 1 , wherein a liquid-vapour separator is also present, optionally comprising a cyclone. 
   
   
       5 . The system according to  claim 4 , wherein the stripping section is inside the reactor and is preferably positioned so as to effect the stripping in the upper part of the reactor itself, said reactor being a totally filled reactor. 
   
   
       6 . The system according to  claim 4 , wherein the stripping section is outside the reactor and is preferably positioned so as to effect the stripping outside the reactor and ensure the recirculation of the stripped liquid by means of a pump to the same reactor. 
   
   
       7 . The system according to  claim 1 , wherein the reactor is equipped with means for the external circulation of the reaction mass, comprising a pump and recirculation ducts, from a lower side point to a side point in the upper part of the reactor itself, the stripping section being positioned so as to effect the stripping in the same recirculation ducts in delivery from the circulation pump. 
   
   
       8 . The system according to  claim 1 , wherein inside the reactor there are also means, comprising a pump and duct, for the internal recirculation of the reaction mass from a lower side point to a side point in the upper part of the reactor itself, the stripping section being positioned so as to effect the stripping inside the same recirculation duct. 
   
   
       9 . The system according to  claim 6 , wherein a further stripping section is present inside the reactor and positioned so as to effect the stripping in the upper part of the same reactor. 
   
   
       10 . The system according to  claim 7  or  8 , wherein a liquid-vapour separator is present, possibly comprising a cyclone, there also optionally being a further stripping section outside the reactor and positioned so as to effect the stripping outside the reactor and ensure the recirculation of the stripped liquid by means of a pump to the reactor itself. 
   
   
       11 . Use of a solid accumulation reactor selected from a stirred tank reactor or a bubble tower reactor for the hydroconversion of heavy oils. 
   
   
       12 . A process for the conversion of heavy oils, selected from crude oils, heavy crude oils, bitumens from tar sands, distillation residues, heavy distillation cuts, deasphalted distillation residues, synthetic oils from Fischer-Tropsch processes, vegetable oils, oils deriving from coke and oil shales, oils obtained from the thermodecomposition of waste products, polymers, biomasses, comprising sending the heavy oil to a hydrotreatment step effected in a suitable solid accumulation reactor with an appropriate hydrogenation catalyst in slurry phase, into which hydrogen or a mixture of hydrogen and H 2 S are fed, characterized in that it comprises one or more stripping phases with a suitable hot stripping gas in order to obtain conversion products exclusively in vapour phase. 
   
   
       13 . The process according to  claim 12 , wherein the solid accumulation reactor is selected from a stirred tank reactor or a bubble tower reactor. 
   
   
       14 . The process according to  claim 12 , wherein the non-converted heavy oil remains constantly in the reaction medium. 
   
   
       15 . The process according to  claim 12 , wherein the hydrogenation catalyst remains constantly in the reaction medium. 
   
   
       16 . The process according to  claim 12 , wherein the solids deriving from and generated by the heavy oils to be converted are exclusively removed by flushing. 
   
   
       17 . The process according to  claim 12 , wherein the catalyst is charged into the reactor at the start-up of the hydrogenation reactor, in proportion to the volume of the reactor, and continuously maintained inside the reaction medium. 
   
   
       18 . The process according to  claim 16 , wherein the catalyst present in the flushing is integrated in the reactor in continuous or batchwise. 
   
   
       19 . The process according to  claim 12 , wherein the hydrogenation catalyst is a decomposable precursor or a preformed compound based on one or more transition metals. 
   
   
       20 . The process according to  claim 19 , wherein the transition metal is molybdenum. 
   
   
       21 . The process according to  claim 20 , wherein the quantity of transition metal contained in the catalyst, charged into the reactor, expressed as concentration of molybdenum, is not lower than 5 kg per m 3  referring to the reaction medium. 
   
   
       22 . The process according to  claim 21 , wherein the quantity of transition metal contained in the catalyst, charged into the reactor, expressed as concentration of molybdenum, is not lower than 8 kg per m 3  referring to the reaction medium. 
   
   
       23 . The process according to  claim 21 , wherein the reactor operates at a solid accumulation level not lower than 50 kg per m 3  referring to the reaction medium. 
   
   
       24 . The process according to  claim 23 , wherein the reactor operates at a solid accumulation level not lower than 100 kg per m 3  referring to the reaction medium. 
   
   
       25 . The process according to  claim 12 , wherein the hydrotreatment step is carried out at a temperature ranging from 380 to 480° C. and a pressure ranging from 100 to 200 atmospheres. 
   
   
       26 . The process according to  claim 12 , wherein the hydrotreatment step produces a quantity of THF i  not lower than 3 kg per ton of feedstock converted. 
   
   
       27 . The process according to  claim 12 , wherein the reactor has the L/V interface in its interior, the stripping gas being distributed over the whole section preferably in the upper part. 
   
   
       28 . The process according to  claim 12 , wherein the reactor operates at a full volume with a L/V biphasic effluent, the stripping gas being introduced into the upper part of the reactor and distributed over the whole section. 
   
   
       29 . The process according to  claim 12 , wherein the reactor is equipped with external circulation of the reaction mass by mans of a pump, the stripping gas being introduced downstream of the circulation pump which operates with a flow-rate equal to at least 20% of the flow-rate of the fresh feedstock treated. 
   
   
       30 . The process according to  claim 12 , wherein the reactor operates at a full volume with a L/V biphasic effluent sent to a phase separator with a cyclone effect, wherein the stripping gas is introduced into the liquid phase separated, preferably in countercurrent, and wherein the residual liquid is recirculated to the reactor at a flow-rate equal to at least 20% of the flow-rate of the feedstock treated. 
   
   
       31 . The process according to  claim 30 , wherein the stripping gas is also introduced into the top part of the reactor and distributed over the whole section. 
   
   
       32 . The process according to  claim 30 , wherein the liquid is recycled to the reactor by means of a pump. 
   
   
       33 . The process according to  claim 12 , wherein the reactor is equipped with external circulation of the reaction mass by means of a pump, the stripping gas being introduced downstream of the circulation pump which operates at a flow-rate equal to at least 20% of the flow-rate of the fresh feedstock treated. 
   
   
       34 . The process according to  claim 12 , wherein the reactor is equipped with an internal recirculation pump of the reaction mass, the stripping gas being introduced into the duct downstream of said pump which operates at a flow-rate equal to at least 20% of the flow-rate of the fresh feedstock treated. 
   
   
       35 . The process according to  claim 33  or  34 , wherein the L/V biphasic effluent leaving the reactor is sent to a phase separator with a possible cyclone effect, wherein the stripping gas is introduced into the liquid phase separated, preferably in countercurrent. 
   
   
       36 . The process according to  claim 12 , wherein the flow-rate of the feedstock necessary for keeping the volume of reaction liquid constant varies from 50 to 300 kg/h per m 3  of reaction volume. 
   
   
       37 . The process according to  claim 12 , wherein the hydrogen used in the reaction is recirculated to the base of the reactor at a flow-rate lower than 2,500 per m 3  of section of the reactor and the stripping gas is introduced at a flow-rate of at least 0.1 kg/kg of fresh feedstock treated at each stripping section. 
   
   
       38 . The process according to  claim 12 , wherein part of the liquid is removed from the side of the reactor by means of a suitable pump and recirculated to a point in the top part of the reactor, the stripping being effected by introducing the gas in delivery from the pump. 
   
   
       39 . The process according to  claim 12 , wherein the reaction liquid is recirculated inside the top part of the reactor by means of a suitable pump positioned in the lower cap inside the reactor, the stripping being effected by introducing the gas in delivery from the pump. 
   
   
       40 . The process according to  claim 12 , wherein the stripping gas is hydrogen alone or in a mixture. 
   
   
       41 . The process according to  claim 40 , wherein the mixture containing hydrogen is removed from the recycling section of the reaction gas. 
   
   
       42 . The process according to  claim 12 , wherein the stripping gas supplies the heat for the evaporation of the conversion products. 
   
   
       43 . The process according to  claim 12 , wherein the stripping gas is used for the thermal balancing of the reactor.