HYDROPROCESSING PROCESS IN INTEGRATED STAGING REACTION VESSEL

Abstract

The present invention relates to selective removal of mercaptans and H.sub.2S from low boiling hydrocarbon streams (primary stream) by reacting with olefins present in heavy/high boiling hydrocarbon stream (secondary stream) and get converted into high boiling sulphur compounds ending up into the secondary stream in an integrated staging reactor, which comprises of reactor, separator and stabilization sections in a single vessel. The separation of primary and secondary streams is integrated in the same reaction vessel with a self-regulating liquid seal mechanism at bottom and a vapour enriching mechanism at the top by utilization of change in phases of streams.

Claims

1. A process for removal of Mercaptan and H.sub.2S from lighter/low boiling hydrocarbon or primary stream, the process comprising: a. feeding the lighter boiling hydrocarbon stream containing Mercaptan & H.sub.2S along with lean hydrogen at its vapour phase from bottom of reaction zone or reactor section and moving upwards across catalytic reactor section of hydroprocessing reaction vessel; b. feeding the heavier/heavy boiling hydrocarbon or secondary stream containing olefins at its liquid phase from top of the reaction section and moving downwards across the catalytic reactor section of hydroprocessing reaction vessel; c. reacting the Mercaptan and H.sub.2S with olefins under shift reaction to convert into high boiling sulphur compounds in liquid state and getting eluted along with heavier hydrocarbon secondary stream, due to which the lighter hydrocarbon stream becomes free from Mercaptan and H.sub.2S; d. continuously removing the converted high boiling sulphur compounds with multiple mass transfer stages along length of the catalytic reactor as the secondary stream moves from top to bottom of the reaction section; e. operating either primary stream or secondary stream or both streams either in once through or recycle mode configuration until meeting the desired levels of conversion in hydroprocessing; and f. regulating liquid loop pressure of the hydroprocessing reaction vessel either via internal or external control mechanism to the integrated staging hydroprocessing reaction vessel, in which at least one longitudinal pipe is connected from the top of the liquid seal either internally or externally connected to the top of stabilizer section.

2. The process as claimed in claim 1, wherein the pressure of the hydroprocessing reaction vessel operates in the range of 10 to 50 barg, preferably 20 to 30 barg.

3. The process as claimed in claim 1, wherein the reactor section consists of transient metal based hydroprocessing catalyst; wherein the transient metal is Ni or Mo or Co or any combination thereof, supported on gamma alumina.

4. The process as claimed in claim 1, wherein the shift reaction takes place at a reaction temperature operating in the range of 100 to 200 C.

5. The process as claimed in claim 1, wherein the primary stream is C3-C4 stream, in which the Mercaptan and H.sub.2S are limited to 3000 ppm, more preferably limited to 1000 ppm for achieving total sulphur of less than 10 ppm in the treated primary stream.

6. The process as claimed in claim 1, wherein the secondary stream is in the range of C7-C20, prevailing in liquid phase.

7. The process as claimed in claim 6, wherein the secondary stream obtained from any source of straight run or cracked units or mixed unit streams, contains olefinic compounds at least or above 1 wt %, more preferably above 2 wt %.

8. The process as claimed in claim 1, wherein the hydrogen flow rate introduced along with the primary stream is in the range of 1 to 100 Nm.sup.3 per m.sup.3 of total hydrocarbon feed.

9. The process as claimed in claim 1, wherein residence time of secondary stream containing olefinic compounds is selectively tuned in the range of 30 minutes to 2 hours.

10. The process as claimed in claim 1, wherein unconsumed hydrogen recovered from outlet of the treated primary stream, post effective heat utilization, is optional for either once through or re-circulation mode of operation.

11. The process as claimed in claim 1, wherein outlet of the secondary stream, post effective heat utilization, is optional for either once through mode of operation or re-circulation mode of operation.

12. The process as claimed in claim 1, wherein gum forming diolefins due to polymerization are controlled in the primary stream to less than 0.01 wt % and also controlled in the secondary stream to less than 0.01 wt % in recirculation mode of operation.

13. The process as claimed in claim 1, wherein process severity of the temperature and the residence time is governed by the concentration of the mercaptans and the H.sub.2S in the primary stream.

14. The process as claimed in claim 1, wherein the process is free from the requirement of any caustic treatment for post treating the treated primary stream.

Description

BRIEF DESCRIPTION OF FIGURES/DRAWINGS

[0045] FIG. 1 illustrates a longitudinal cross sectional schematic representation of reaction vessel of the present invention containing three integrated sections of reactor, separator and stabilizer in a single system of hydro-processing under isothermal conditions and once-through configuration.

[0046] FIG. 2 illustrates reaction vessel containing three integrated sections of reactor, separator and stabilizer in a single system of hydro-processing under adiabatic conditions and recycle configuration.

[0047] FIG. 3 illustrates a representation of liquid loop pressure control mechanism of the reaction vessel depicted in FIG. 1 or FIG. 2.

[0048] FIG. 4 illustrates LPG treatment with Secondary Stream internal recirculation.

DETAILED DESCRIPTION OF THE INVENTION

[0049] In a detailed embodiment, the present invention provides a hydro-processing process in an integrated reaction vessel which comprises of reactor, separator and stabilization sections integrated in a single system for hydro-processing process/method comprising two different boiling ranges of hydrocarbon streams/feeds undergoing multitude of mass transfer stages among each other. The term primary stream as used herein refers to the low boiling hydrocarbon stream or feedstock containing organic sulphur compounds. The term secondary stream as used herein refers to the heavy boiling hydrocarbon stream or feedstock containing olefinic compounds, whose olefinic carbon chain length varies preferably in the range of C.sub.3 to C.sub.10.

[0050] The reaction vessel components associated in the hydro-processing process are described as wherein the middle portion acts as the reactor section comprising active catalyst system; above and below which, the distribution system of liquid and vapour streams are located respectively. The bottom portion acts as the separator section designed with liquid seal mechanism, by which the ingress of gas is restricted, and neat liquid stream is withdrawn from bottom. The top portion acts as the stabilizer section with required disengaging space and the treated enriched vapour stream is withdrawn from top through any typical mesh type coalescer arrangement, by which the entrainment of liquid is stopped.

[0051] The primary stream effectively heats integrated in both cases of isothermal or adiabatic reactor system and enters the bottom of the reactor section, moving upward and eventually comes out at the topmost of the stabilization section. The secondary stream is effectively heat integrated and gains the final process heat duty requirement from external source in either case of isothermal or adiabatic reactor system and enters at the top of the reactor section, moving downward and eventually comes out at the bottom most of the separator section.

[0052] In one embodiment, the present invention of integrated hydro-processing reaction vessel associated in the hydro-processing process is described under isothermal conditions of heat integration with once-through configuration. In another embodiment of the present invention, the same is described under adiabatic conditions of heat integration with recycle configuration.

[0053] The term hydro-processing is well versed in the field by effective utilization of hydrogen or hydrogen rich treat gas reacts with hydro-carbonaceous feed on severe process conditions over catalyst to remove one or more heteroatom impurities such as sulphur, nitrogen and oxygen in any integrated apparatus or vessel which aids in separation of desired product from its undesired product or feed. FIG. 1 is a simplified longitudinal cross sectional schematic representation of reaction vessel of the present invention containing three integrated sections of reactor, separator and stabilizer in a single system of hydro-processing process under isothermal conditions and once-through configuration. The hydro-processing reaction vessel (100) comprises of three integrated sections namely stabilizer (107) section, reactor (108) section and separator (109) section. The reactor section (108) containing the hydro-processing catalyst (111) is located in the middle of the reaction vessel, above and below represents the non-reacting zones (or) sections.

[0054] The primary stream (101) of low boiling hydrocarbon feed containing organic sulphur compounds enters the reaction vessel through a longitudinal pipe (105) and gets distributed through vapour phase distributor (114), located below the reactor section. The vapour phase distributor (114) is typically a multiple sparger type nozzle design located across the circumference of entire vessel cross section with standard pitch distance as well known in the art of gas-liquid distribution system. The secondary stream (103) of heavy boiling hydrocarbon feed containing olefinic compounds enters the reaction vessel through liquid phase distributor (110), located above the reactor section. The liquid phase distributor (110) is typically of vapour lift liquid distribution tray type as well known in the art of gas-liquid distribution system. The catalyst (111) present in the reactor section (108) achieves the required temperature of hydroprocessing from the reactor mounted furnace (112). The volume of reactor section (108) is defined as the volume equivalent to 0.5 to 5 liquid hourly space velocity (LHSV) of the primary stream. The primary stream (101) along with the hydrogen rich treat gas (117), together gains required temperature from reactor section (108) in its pathway (113) to distributor (114) and ensures its vapour phase post effective heat utilization resulting in upward movement. The secondary stream (103) in liquid phase moves downward and the in-situ generated heat load due to exothermicity of the hydroprocessing reaction between two streams in the reactor zone, aids in optimizing the external heat load requirement on furnace (112). The reactive shift reaction between mercaptans or H.sub.2S present in primary stream and the olefins present in the secondary stream results in formation of heavy mercaptans and/or heavy sulphides or heavy boiling sulphur compounds of high boiling range in liquid state eventually ending up in outgoing secondary stream (104).

[0055] The outgoing primary stream in vapour state is a treated and heteroatom lean low boiling stream (102) comes out at the topmost section of reaction vessel (100). The upper non-reacting section is mainly meant for separating the treated primary stream in vapour state and the height of the stabilizer section (107) is such that the concentration of treated stream is enriched and taken out as product (102). The entrainment of liquid is avoided through any of the several types of typical mesh type coalescer arrangement or demister (106) like mechanism skilled in the art located at the topmost of stabilizer section. The outgoing secondary stream in liquid state is heteroatom rich heavy boiling stream (104), also called reacted secondary stream comes out at the bottom most section of reaction vessel (100). The lower non-reacting section is mainly meant for separating the reacted secondary stream in liquid state and the height of the separator section (109) is such that the un-reacted or non-treated primary stream from (114) is restricted to come out of the bottom most section through a self-regulating liquid seal mechanism (115). The reacted secondary stream is taken out (104) from the reaction vessel (100) through a self-regulating liquid seal mechanism (115) containing inverted outer pipe (118) sealed at its top and perforated opening (120) at its bottom. An inner annular pipe (119) of height lesser than the outer inverted pipe (118), externally protruded through (116) is meant for self-regulating the liquid seal mechanism through which the reacted secondary stream is taken out of reaction vessel. The height of the external pipe (118) and internal pipe (119) are aligned such that to provide steady state flow of incoming secondary stream (103) in line with the outgoing secondary stream (104). In this embodiment of invention, both the primary and secondary streams are depicted in once through flow configuration.

[0056] FIG. 2 is a simplified longitudinal cross sectional schematic representation of reaction vessel of the present invention containing three integrated sections of reactor, separator and stabilizer in a single system of hydro-processing process under adiabatic conditions and recycle configuration. The hydro-processing reaction vessel (200) comprises of three integrated sections namely stabilizer (229) section, reactor (230) section and separator (231) section. The reactor section (230) containing the hydro-processing catalyst (233) is located in the middle of the reaction vessel, above and below represents the non-reacting zones (or) sections. The volume of reactor section (230) is defined as the volume equivalent to 0.5 to 5 liquid hourly space velocity (LHSV) of the primary stream.

[0057] The primary stream (221) of low boiling hydrocarbon feed containing organic sulphur compounds enters the reaction vessel by gaining the desired heat duty initially with the primary stream feed/effluent heat exchanger (238) and finally with the secondary stream feed/effluent heat exchanger (226) and eventually gets distributed through vapour phase distributor (234), located below the reactor section. The vapour phase distributor (234) is typically a multiple sparger type nozzle design located across the circumference of entire vessel cross section with standard pitch distance as well known in the art of gas-liquid distribution system. The secondary stream (223) of heavy boiling hydrocarbon feed containing olefinic compounds enters the reaction vessel through liquid phase distributor (232), located above the reactor section. The liquid phase distributor (232) is typically of vapour lift liquid distribution tray type as well known in the art of gas-liquid distribution system. The catalyst (233) present in the reactor section (230) is an insulated system behaving like an adiabatic system, achieves the required temperature of hydro-processing from the incoming heated primary (221) and secondary streams (223). The primary stream (221) along with the hydrogen rich treat gas (240), together gains required temperature from feed/effluent heat exchangers (238) & (226) in its pathway to distributor (234) and ensures its vapour phase post effective heat utilization resulting in upward movement. The secondary stream (223) in liquid phase moves downward and the exothermicity of the hydro-processing reaction between two streams, aids in optimizing the heat load on process steam heater (227). The reactive shift reaction between mercaptans or H.sub.2S present in primary stream and the olefins present in the secondary stream results in formation of heavy mercaptans and/or heavy sulphides or heavy boiling sulphur compounds of high boiling range in liquid state eventually ending up in outgoing secondary stream (224).

[0058] The outgoing primary stream in vapour state is a treated and heteroatom lean low boiling stream (222) comes out at the topmost section of reaction vessel (200). The upper non-reacting section is mainly meant for separating the treated primary stream in vapour state and the height of the stabilizer section (229) is such that the concentration of treated stream is enriched and taken out as product (239), post effective heat utilization in the primary stream feed/effluent heat exchanger (238). The entrainment of liquid is avoided through any of the several types of any typical mesh type coalescer arrangement or demister (228) like mechanism skilled in the art located at the topmost of stabilizer section. The outgoing secondary stream in liquid state is heteroatom rich heavy boiling stream (224), also called reacted secondary stream comes out at the bottom most section of reaction vessel (200). The lower non-reacting section is mainly meant for separating the reacted secondary stream in liquid state and the height of the separator section (231) is such that the un-reacted or non-treated primary stream from (234) is restricted to come out of the bottom most section through a self-regulating liquid seal mechanism (235). The reacted secondary stream is taken out (224) from the reaction vessel (200) through a self-regulating liquid seal mechanism (235) containing inverted outer pipe (241) sealed at its top and perforated opening (243) at its bottom. An inner annular pipe (242) of height lesser than the outer inverted pipe (241), externally protruded through (236) is meant for self-regulating the liquid seal mechanism through which the reacted secondary stream is taken out of reaction vessel. The height of the external pipe (241) and internal pipe (242) are aligned such that to provide steady state flow of incoming secondary stream (223) in line with the outgoing secondary stream (224). In this embodiment of invention, the primary stream is depicted in once through flow configuration and the secondary stream is depicted in recycle flow configuration along with purge mechanism. The enrichment of heavy mercaptans and/or heavy sulphides in the reacted secondary stream (224) is regulated by taking out certain quantity of that stream as bleed or purge (237) and the equivalent quantity replenished by fresh secondary stream (244) and recycled back through pumping mechanism (225) with effective heat integration with the secondary feed/effluent heat exchanger (226) and the steam heater (227).

[0059] FIG. 3 is a simplified schematic representation of liquid loop pressure control mechanism of reaction vessel of the present invention containing three integrated sections of reactor, separator and stabilizer in a single system of hydro-processing process as depicted in FIG. 1 or FIG. 2. The steady state flow of secondary stream in liquid phase through the liquid seal of separator is attained by suitable pressure control mechanism as depicted in FIG. 3 (a) or FIG. 3 (b). FIG. 3 (a) represents an internal pressure control mechanism of the integrated staging hydroprocessing reaction vessel, in which at least one longitudinal pipe (310) is connected from the disengaging space or top of the liquid seal (304) to the top of stabilizer section (303). The top of the longitudinal pipe is covered with an inverted cap (311) to avoid entrainment of any condensed liquid from top to bottom and also acts as conduit for transfer of any dissolved hydrogen from bottom to top.

[0060] FIG. 3 (b) represents an external pressure control mechanism of the integrated staging hydroprocessing reaction vessel, in which a pipe (310) is externally connected from the disengaging space or top of the liquid seal (304) to the top of stabilizer section (303) through a regular pressure control valve (320) well known in the field of hydroprocessing. The downstream line (321) of the pressure control valve is equalized in pressure to that of the outgoing treated primary stream (322). This external conduit also aids in transfer of any dissolved hydrogen from bottom to top.

[0061] The present invention provides a hydro-processing process in an integrated reaction vessel which comprises of all the reactor, separator and stabilization sections integrated in a single hydro-processing reaction vessel with effective utilization of multitude of mass transfer stages in reduction of heteroatom present in the hydrocarbon feed. Substantial amount of research work already available in the art of design, configuration and intensification of hydro-processing process, still prevails enormous scopes for continuous improvement of the hydro-processing. Integration of specific functional heat & mass transfer unit operational equipments along with reactors always remained a cost-effective approach and model for execution of any hydro-processing reactions.

[0062] In the present embodiment, an integrated hydro-processing reaction vessel which comprises of all the reactor, separator and stabilization sections integrated together in a single system for hydro-processing process of low boiling hydrocarbon feed undergoing multitude of mass transfer stages with the heavy boiling hydrocarbon feed is disclosed. The term reaction vessel as used herein refers to an integrated hydro-processing reaction vessel comprising of all three sections of reactor, separator and stabilizer. The term primary stream as used herein refers to the low boiling hydrocarbon feedstock, preferably liquefied petroleum gas (LPG) containing H.sub.2S, mercaptans and other organic sulphur compounds, whose hydrocarbon carbon chain length is preferably of C3, C4 and thereof and its final boiling point temperature is preferably within 70 C. The term secondary stream as used herein refers to the heavy boiling hydrocarbon feedstock containing olefinic compounds, whose olefinic carbon chain length varies preferably in the range of C.sub.3 to C.sub.10 and its overall olefinic concentration is limited to 1% minimum by mass and preferably more than 3% by mass. The term hydrogen as used herein refers to hydrogen gas or hydrogen rich treat gas or hydrogen rich gaseous stream preferably containing hydrogen above 80% by volume more preferably above 90% by volume. The hydro-processed primary stream is called treated primary stream, wherein the heteroatoms are removed and considered to be a finished product or stream. The hydro-processed secondary stream is called reacted secondary stream, wherein the converted heteroatoms like heavy mercaptans, heavy sulphides, etc are dissolved in it and not considered as a finished product, but having potential of olefin rich components in it and makes capable of recycling or re-utilizing for further hydro-processing using the conventional processes known in the art.

[0063] The reaction vessel constitutes of three integrated sections in which middle section acts as reacting zone and the remaining two sections acts as non-reacting zone. The middle zone acts as the reactor section comprising active catalyst system; above and below which, the upper and lower non-reacting zones are located respectively. The upper non-reacting zone facilitates in the removal of treated low boiling primary stream and the lower non-reacting zone facilitates in the removal of reacted heavy boiling secondary stream. The bottom portion acts as the separator section designed with liquid seal mechanism, by which the entrainment of gas is restricted, and neat liquid stream is withdrawn from bottom. The top portion acts as the stabilizer section with required disengaging space and the treated vapour stream is withdrawn from top through mesh type coalescer arrangement, by which the entrainment of liquid is stopped.

[0064] The catalyst system present in the reactor section is a mixed transition metal-based hydro-processing catalyst, preferably of Co, Ni, Mo, or W on inert support. The catalyst shapes are of any structure like sphere, cylinder, pellet, 2-lobe, 3-lobe, 4-lobe, etc being utilized as those skilled in the art of hydro-processing. The selection of shape of the catalyst is mainly governed by the permissible pressure drop and the voidage exerted within the catalyst bed. The primary low boiling stream flows from bottom to top due to its inherent nature of vapour phase and the secondary heavy boiling stream flows from top to bottom due to its inherent nature of liquid phase. The primary stream carrying mercaptans and H.sub.2S are rich in its concentration and gradually decrease along the length of the reactor due to reactive mechanism from bottom to top of the catalyst section. The secondary stream carrying olefins, preferably above 3% by mass whose initial boiling range is at least above 90 C. and preferably above 140 C. The concentration of olefins is consistent along the length of the reactor from top to bottom as its reactive consumption are moderate (always above 3% by mass) throughout the catalyst section. The olefins consumed in secondary stream is negligible (0.01 to 0.1 wt % of the primary stream) as their consumptions are stoichiometrically equivalent to one-on-one mole basis of mercaptans and H.sub.2S present in primary stream.

[0065] Under hydrogen environment, the mercaptans and H.sub.2S in vapour phase reacts with the olefins present in liquid phase and undergoes shift reaction getting them converted into respective products preferably heavy sulphides and/or heavy mercaptans. The boiling range of these reactive shift products are high such that they end up in liquid phase i.e., secondary stream, which flows from the top to bottom of the reaction section. It is well known in the art of hydro-processing, that the mercaptan recombinant reactions with olefins are reversible in nature. The present invention of flow counter configuration of primary and secondary stream aids in multitude of mass transfer of the reactive shift product moving into the secondary stream, which is also considered as sacrificial hydrocarbon solvent stream for removal and carrying out of heavy boiling sulphur compounds formed as reactive shift products. The term solvent is being used to characterize the secondary stream as it behaves like a carrier stream for those removed heteroatom preferably sulphur initially present in the form of mercaptans and H.sub.2S in the primary stream and hence making it a treated sulphur lean low boiling high value primary stream. The shift reaction is very effective in the primary stream as it moves from the bottom to top in reaction section, the reactive product continuously ends up in the counter flowing secondary stream along the entire length of reaction section and drives the equilibrium towards forward information of heavy mercaptans or heavy sulphides through multiple mass transfer stages in the integrated reaction vessel. The heavy boiling secondary stream herein; acts as medium for the supply of one the reactants olefins and also as a carrying medium like solvent for reactive shift products.

[0066] Non-limiting examples of hydro-processing reactor internals which can be practiced in the present invention includes any type of liquid and gas/vapor phase distributors in those skilled in the art. The top liquid distributor, typically of vapour lift liquid distribution tray type as well known in the art, uniformly distributes the downflow of secondary stream across the entire cross section of reaction vessel along with cross flow mechanism of outgoing up flow of treated primary stream. The bottom gas/vapor distributor uniformly distributes the up flow of primary stream across the entire cross section of reaction vessel along with cross flow mechanism of outgoing down flow of reacted secondary stream.

[0067] The reaction vessel of present invention is an integrated process intensified single column vessel or single system comprising of reactor, separator and stabilizer sections. The reactor section located in the middle of the integrated vessel performs the hydro-processing reactive shift reaction in the presence of catalyst system and the counter flow configuration of both primary and secondary streams along its axial length entire longitudinal of reactor section provides multiple stages of mass transfer between reactant and product. The non-reacting zone below the reactor section is called the separator section provides separation of hydrocarbon vapours and hydrogen gas of primary stream from the outgoing reacted secondary stream.

[0068] The present invention also discloses a self-regulating liquid seal mechanism at the bottom of the reaction vessel in separator section. The associated components of liquid seal mechanism of separator section provide a steady state flow configuration of incoming secondary stream from top to that of the outgoing secondary stream from bottom without entrainment of incoming primary stream in any of the steady or unsteady reaction vessel conditions. The liquid seal comprises of two annular pipes in the bottom most axis location of the reaction vessel, wherein the outer pipe is completely plugged at its top portion and the bottom portion is designed with perforation or wedge gap around its entire circumference for the entry of outgoing secondary stream into the liquid seal. The inner pipe of liquid seal is concentric to the outer pipe with reduced height of internally protruded part (119 or 242) and externally protruded part (116 or 236) from bottom of the reaction vessel, whose volume is 0.5 to 10 times that of the liquid hourly volumetric flow rate of primary stream. The reacted secondary stream enters the liquid seal from the bottom portion of outer pipe designed with perforation and moves upward inside the annular portion and leaves the reaction vessel from the top portion of the inner pipe wherein the liquid head equivalent to the height of internally protruded inner pipe permanently provides a barrier or sealing mechanism for the entrainment of any primary stream from the reaction vessel at bottom. Thus, the liquid seal makes the unreacted primary stream entering in the top of the separator section or the bottom of the reactor section forcefully need to pass the reactor section in upward flow configuration by ensuring necessary hydro-processing reaction. The height and diameter of the internally projected outer pipe, inner pipe and the internal annular clearance are designed such that to ensure steady flow of secondary stream and static liquid sealing mechanism.

[0069] The non-reacting zone above the reactor section is called the stabilizer section provides the separation of treated hydrocarbon vapours and hydrogen gas of primary stream from the incoming unreacted secondary stream. The overall height of the stabilizer section is designed such that the disengaging space for the outgoing treated primary stream in vapour phase is free from entrainment of liquid by accounting to the terminal velocity of liquid droplets generated from the secondary stream. The concentration of the treated primary stream is enriched with low boiling hydrocarbon as the hydrogen (117 or 240) involved in the hydro-processing is very minimal with respect to the volumetric ratio hydrogen to that the primary stream in the range of 0.5 to 10 Nm.sup.3/m.sup.3 at normal conditions of temperature and pressure (NTP). The effective utilization of phase difference between the treated vapour phase hydrocarbon stream and the reactive products of liquid phase ending up in secondary stream is the substantial reason and advantage for integration of treated primary stream separation or vapour phase stabilization at the top of the reaction vessel. The treated primary stream flows across any typical mesh type coalescer arrangement at the topmost section of the stabilizer section in order to nullify the entrainment fine liquid particle during the stage of process upsets. The volume, diameter, and height of the stabilizer section is designed in such a way that steady flow incoming and outgoing primary stream well within the flooding regime of any counter current operation is ensured. The treated primary stream from the top of stabilization section is routed to a reflux drum related accessories for further separation and the same can be achieved by conventional means known in the art and hence are not discussed here. The treated primary stream post heat exchange in reflux drum separates non condensable hydrogen gas and the condensed liquid phase primary stream is taken out as finished product/treated stream. The hydrogen gas retrieved from the recycle drum may or may not be recycled back for further utilization in place of makeup hydrogen (117 or 240).

[0070] In one of the embodiments, the present invention of integrated hydro-processing reaction vessel is described under isothermal conditions of heat integration and once-through configuration. In another embodiment of the present invention, the same is described under adiabatic conditions of heat integration and recycle configuration. The primary stream effectively utilizes heat in either case of isothermal or adiabatic reactor system and enters the bottom of the reactor section, moving upward and eventually comes out at the topmost of the stabilization section. The secondary stream effectively supplies heat and gains minimal required heat from external source in either case of isothermal or adiabatic reactor system and enters at the top of the reactor section, moving downward and eventually comes out at the bottom most of the separator section.

[0071] The FIG. 1 is a simplified schematic representation of reaction vessel (100) of the present invention containing three integrated sections of reactor, separator and stabilizer integrated in a single system of hydro-processing under isothermal conditions and once-through configuration. The reactor section of the vessel is an isothermal reactor, shell/wall mounted by electric furnace and the stabilizer and separator sections are hot insulated in nature. The primary stream along with hydrogen enters the reactor section through a non-contacting concentric pipe to the reaction vessel and gains heat energy from the reactor section to the desired level of reaction temperature and attains vapour phase by virtue of its inherent low boiling hydrocarbon feedstock and eventually enters through the vapour phase distributor (114) and makes upward flow from bottom to top of the reactor section. The secondary heavy boiling hydrocarbon stream enters through the liquid phase distributor (110) and makes downward flow from top to bottom of the reactor section and gains heat to the desired level of reaction temperature in the top layer of reactor section below liquid distributor acts as a preheating zone. The reactive shift reaction mechanism of organic sulphur reactant in primary stream and the olefinic reactant in the secondary stream converts reactive products of heavy boiling sulphur compounds ending up in secondary stream wherein the continuous removal of reactive products into secondary stream along the length of the reactor undergoes compounded number of stages in the integrated hydro-processing reaction vessel. The primary and secondary streams are depicted in simple once through flow configuration with effective heat utilization from the electric furnace, mainly opted for small scale integrated staging hydro-processing operation.

[0072] The FIG. 2 is a simplified schematic representation of reaction vessel (200) of the present invention containing three integrated sections of reactor, separator and stabilizer integrated in a single system of hydro-processing under adiabatic conditions and recycle configuration mainly opted for large scale integrated staging hydro-processing operation. The primary stream along with hydrogen enters the reactor section through two series of feed/effluent heat exchangers (238 and 226) and gains heat energy from the outgoing primary & secondary effluent streams to the desired level of reaction temperature and attains vapour phase by virtue of its inherent low boiling hydrocarbon feedstock and eventually enters through the vapour phase distributor (234) and makes upward flow from bottom to top of the reactor section. This vaporization of primary hydrocarbon stream is further aided by addition of fresh makeup hydrogen stream (240). The secondary heavy boiling hydrocarbon stream is heat integrated with the secondary stream feed/effluent exchanger (226) and achieves desired reaction temperature from the external source of steam heater (227) and enters through the liquid phase distributor (232) (describe) and makes downward flow from top to bottom of the reactor section. The reactive shift reaction mechanism of organic sulphur reactant in primary stream and the olefinic reactant in the secondary stream converts reactive products of heavy boiling sulphur compounds ending up in secondary stream wherein the continuous removal of reactive products into secondary stream along the length of the reactor undergoes compounded number of stages in the integrated hydro-processing reaction vessel. The primary stream is in once through flow configuration and the treated stream (239) is routed to a reflux drum (not shown in FIG. 2) in which the liquefied low boiling hydrocarbon is taken out as finished product and the off-gas hydrogen taken from reflux drum vessel can be recycled or reutilized along with the fresh makeup hydrogen stream (240). The treated primary stream from the top of stabilization section is routed to a reflux drum related accessories for further separation and the same can be achieved by conventional means known in the art and hence are not discussed here. The olefinic reactant being surplus and as the concentration of heavy sulphides are minimal (as equivalent to the mercaptans in primary stream) initially in the reacted secondary stream and hence the reacted secondary stream is rerouted or recycled back into the reaction vessel post effective heat integration and meanwhile the reactive product of heavy boiling sulphur compounds like heavy mercaptans or heavy sulphides are accumulating and get enriched in the secondary stream. In order to regulate the concentration of accumulating heavy boiling sulphur compounds, a purge stream (237) is taken out as bleed and compensated with the fresh secondary stream (244). The criteria for defining the bleed rate (0.1 to 5% of the volumetric flow rate of outgoing reacted secondary stream) of purge stream (237) is directly proportional to the concentration of total organic sulphur compound (typically the organic sulphur in fresh makeup secondary stream is allowed to incrementally increase by 10 to 50% by mass of its original organic sulphur concentration) in the reacted secondary stream (224), which tends to cumulatively increase based on the incoming organic sulphur compounds of primary stream.

[0073] The challenge of loading and flooding in the reactor section containing catalyst bed always prevails in a counter flow operation of primary and secondary stream. The similar challenge encountered over here is controlled and regulated through the flow rate of primary stream by maintaining within 30% to 50% of its flooding velocity for a defined secondary stream velocity. The selection of catalyst shape and the voidage among catalyst particles also play a critical role in facilitating or regulating the superficial velocity of primary stream. The mal-distribution of the reactor section filled with solid transient metal-based hydro-processing catalyst is nullified when the voidage of any definite shape catalyst bed falls in the range of 20 to 50%, more preferably 25 to 35%.

[0074] The overall sizing of reaction vessel either in FIG. 1 or FIG. 2 with respective independent sizing of integrated components of reactor, separator, and stabilizer mainly depends up on several parameters. The volume of catalyst containing reactor section is mainly governed by the concentration of organic sulphur compounds present in the primary stream and its required conversion level of hydro-processing. The volume of reactor section (108/230) is defined as the volume equivalent to 0.5 to 5 liquid hourly space velocity (LHSV) of the primary stream and cumulatively observed to occupy around 20 to 40% of the volume of entire reaction vessel. The nature of boiling range of primary stream and its treating quantity along with the hydrogen rich treat gas cumulatively defines the volume of the stabilizer section, turns out to occupy around 60 to 80% of the volume of the reactor section. The concentration of olefins in the secondary stream and its nature of boiling range cumulatively defines the volume of the separator section, turns out to occupy around 40 to 60% of the volume of the reactor section. The dimension of the concentric pipes (both inner and outer) associated in the liquid sealing mechanism of the separator is directly proportional to the superficial velocity of the secondary stream. The top distributor meant for distribution of liquid secondary stream across the cross section of reaction vessel shall also contains the provision for escaping vapours of treated primary stream into the stabilizer section. The bottom distributor meant for distribution of vapour phase primary stream across the cross section of reaction vessel are of localized multiple nozzle or sparger type assemblies as already known the art and shall also contains the provision for free flow drain of reacted secondary stream into the separator section.

[0075] In one aspect of the present invention, the present invention discloses a process for removal of Mercaptan and H.sub.2S from lighter/low boiling hydrocarbon or primary stream, the process comprising: [0076] a. feeding the lighter boiling hydrocarbon stream containing Mercaptan & H.sub.2S along with lean hydrogen at its vapour phase from bottom of reaction zone or reactor section and moving upwards across catalytic reactor section of hydroprocessing reaction vessel; [0077] b. feeding the heavier/heavy boiling hydrocarbon or secondary stream containing olefins at its liquid phase from top of the reaction section and moving downwards across the catalytic reactor section of hydroprocessing reaction vessel; [0078] c. reacting the Mercaptan and H.sub.2S with olefins under shift reaction to convert into high boiling sulphur compounds in liquid state and getting eluted along with heavier hydrocarbon secondary stream, due to which the lighter hydrocarbon stream becomes free from Mercaptan and H.sub.2S; [0079] d. continuously removing the converted high boiling sulphur compounds with multiple mass transfer stages along length of the catalytic reactor as the secondary stream moves from top to bottom of the reaction section; [0080] e. operating either primary stream or secondary stream or both streams either in once through or recycle mode configuration until meeting the desired levels of conversion in hydroprocessing; and [0081] f. regulating liquid loop pressure of the hydroprocessing reaction vessel either via internal or external control mechanism to the integrated staging hydroprocessing reaction vessel, in which at least one longitudinal pipe is connected from the top of the liquid seal either internally or externally connected to the top of stabilizer section.

[0082] The several advantages of the process disclosed in the present invention are: the sulphur quality up-gradation of low boiling hydrocarbon by effective utilization of low value heavy boiling hydrocarbon stream, flexibility in utilization of multiple secondary stream in case of unavailability or process upsets, high tolerance to impurities in the feed like 1, 3 butadiene and any other diolefins, moderate tolerance in handling H.sub.2S preferably up to 3000 ppm in feed, less space utilization due to integrated system, caustic free process, reduced operating cost, etc.

EXAMPLES

[0083] The present invention will be further represented with working examples, which are intended to illustrate the working of disclosure and not intended to imply any limitations on the scope of present disclosure. The below illustrations of disclosure are not limited to particular method and experimental conditions as described and may vary with respect to the quality of both primary and secondary streams. Although methods and materials similar or equivalent to those described herein can be used in the practice of present disclosed process methods, the exemplary methods, devices and materials are described herein.

[0084] The detailed characterization of primary stream feedstock used for following examples is described in Table 1. The mercaptans and H.sub.2S are doped externally at varied concentration into the primary stream depending upon the experimental requirements as quantified in respective examples. The Straight Run (SR) Liquefied Petroleum Gas (LPG) is sourced from any of primary processing refinery units like crude or atmospheric distillation units, etc. and the Cracked LPG is sourced from any of secondary processing refinery units like thermal cracking or catalytic cracking units, etc.

TABLE-US-00001 TABLE 1 Feed characterization of primary stream Straight Run (SR) Cracked Component UoM LPG LPG Propane wt % 40.1 9.8 Propylene wt % 0.1 17.4 Iso-butane wt % 9.3 25.2 N-butane wt % 43.7 5.6 1-Butene wt % 0.1 8.7 Isobutylene wt % 0.5 16.8 T-2-Butene wt % 0.4 8.1 C-2-Butene wt % 0.3 6.4 1,3-Butadiene wt % 0.0 0.9 Iso-pentane wt % 4.4 0.6 n-Pentane wt % 0.8 0.1 C5+ wt % 0.4 0.5

[0085] The detailed characterization of secondary stream feedstock used for following examples is described in Table 2. Wider range of hydrocarbon with boiling range of C5 to 400 C. is considered for experimentations as secondary stream, also called as solvent stream.

TABLE-US-00002 TABLE 2 Feed characterization of secondary stream Stream Density Sulfur Saturate Aromatic Olefin Diolefin Distillation ASTM D 2887 No. Secondary Stream kg/m.sup.3 ppm wt % wt % wt % wt % IBP 10% 50% 90% FBP S1 Coker Gasoline 720.2 2281 52.4 11.1 36.5 1.52 36 41 94 138 201 (CG) S2 FCC Gasoline 751.5 883 36.7 31.7 31.6 1.44 36 40 96 176 220 S3 Coker Kerosene 826.4 2530 45.8 24.4 29.8 1.92 103 142 227 288 388 (CK) S4 10% CG in SRN 760.1 291 78.0 17.6 4.5 0.16 41 89 117 140 170 S5 10% CG in Diesel 814.0 229 88.8 7.6 3.7 0.17 45 104 317 384 400 S6 10% CK in SRGO 875.4 2206 59.7 36.5 3.9 0.20 97 194 310 382 438 Note: SRNStraight Run Naphtha, SRGOStraight Run Gas Oil, FCCFluid Catalytic Cracker

Example 1

[0086] Referring to FIG. 1 & FIG. 3, a pilot scale integrated reaction vessel of 1.8 m in length, nominal diameter of 25 mm with 160 schedule number comprising of all the reactor, separator and stabilization sections integrated in a single system was fabricated with active catalyst loading of 20-40 cc capacity in the reactor. The reactor section was loaded with active catalyst of 20 cc (NiMo based system on -alumina) along with inert silicon carbon to aid in effective mass transfer distribution, to which above and below of catalyst bed are placed with inert alumina balls (3 mm) in the entire reactor section mounted by a split zone electric furnace. The above and below sections are fabricated with stabilization and separator sections with in-house fabricated internal accessories. The primary and secondary streams are stored in Tank-1 and Tank-2 separately and pumped into the integrated reaction vessel through separate respective positive displacement pump Pump-1 and Pump-2 respectively. The required minimal process hydrogen is passed through a Mass Flow Controller at controlled flow rate and gets connected to the Pump-1 discharge line. The feed rate of both Pumps is controlled and regulated by tuning the pump frequency and stroke length to maintain at desired flow rate. The outlet streams are connected to a separator section with pressure equalization line and the treated primary stream and reacted secondary stream are taken out through separate pressure control and liquid control valve, then subjected to various analysis.

[0087] The loaded catalyst was initially subjected to Sulfiding in order to convert the oxide phase of catalyst into active sulphide phase through standard protocol as well known in the art prior to all below experimentations.

[0088] The viability of secondary stream selection was studied with wide variance of hydrocarbon streams as represented in Table 3. The primary stream of SR LPG along with hydrogen in the proportion of 5-10 Nm.sup.3/m.sup.3 was used in all 6 experimentations as mentioned below. It is evident from the below Table 3, that olefins with carbon length up to C10 undergoes reactive shift mechanism with the mercaptans in primary stream to meet below 10 ppmv in treated LPG.

TABLE-US-00003 TABLE 3 LPG treatment with varied secondary stream Secondary Stream Feed Primary Stream Feed (LPG) Conditions Treated LPG Exp. Stream Olefins Flow Mercaptans H.sub.2S Flow Temp Pressure Mercaptans H.sub.2S No No. wt % cc/h LPG ppmv ppmv cc/h C. barg ppmv ppmv 1 S1 36.5 20 SR 550 10 20 150 30 4 0 2 S2 31.6 20 SR 612 12 20 150 30 6 0 3 S3 29.8 20 SR 571 10 20 160 20-30 8 0 4 S4 4.46 20 SR 585 10 20 160 20 5 0 5 S5 3.65 20 SR 712 12 20 160 20 10 0 6 S6 3.88 20 SR 658 13 20 160 20 7 0

Example 2

[0089] All the experimentations described in Example 2 were conducted in similar experimental setup as described in Example 1. The effect of process parameters with respect to temperature at reaction zone and system pressure with selective secondary stream is represented in Table 4. The primary stream of SR LPG along with hydrogen in the proportion of 1-10 Nm.sup.3/m.sup.3 was used in all 6 experimentations as mentioned below. The process disclosed in present invention is a low severe process with respect to temperature and pressure in deep desulfurization of LPG.

TABLE-US-00004 TABLE 4 Effect of process parameters in treatment of LPG Primary Stream Feed (LPG) Secondary Stream Feed Conditions Treated LPG Exp. Mercaptans H.sub.2S Flow Stream Olefins Flow Temp Pressure Mercaptans H.sub.2S No. LPG Ppmv Ppmv cc/h No. wt % cc/h C. barg ppmv ppmv 1 SR 542 10 20 S5 3.6 20 140 20 9 0 2 SR 542 11 20 S5 3.5 20 150 20 5 0 3 SR 542 11 20 S5 3.6 20 160 20 2 0 4 SR 574 10 20 S4 4.4 20 150 30 6 0 5 SR 574 10 20 S4 4.4 20 160 30 3 0 6 SR 574 11 20 S4 4.5 20 170 30 1 0

Example 3

[0090] All the experimentations described in Example 3 were conducted in similar experimental setup as described in Example 1. The effect of variation in the concentration of mercaptans and H.sub.2S in the primary stream with selective secondary stream is represented in Table 5. The primary stream of SR LPG or Cracked LPG along with hydrogen in the proportion of 1-5 Nm.sup.3/m.sup.3 was used in all 6 experimentations as mentioned below. The disclosed process is more viable to source of LPG either from SR or Cracked or in any form of blended proportion for deep desulfurization.

TABLE-US-00005 TABLE 5 Effect of Mercaptan and H.sub.2S concentration in treatment of SR and Cracked LPG Primary Stream Feed (LPG) Secondary Stream Feed Conditions Treated LPG Exp. Mercaptans H.sub.2S Flow Olefins Flow Temp Pressure Mercaptans H.sub.2S No. LPG Ppmv ppmv cc/h Stream wt % cc/h C. barg ppmv ppmv 1 SR 542 1000 20 S4 4.5 20 150 20 6 2 2 SR 612 1000 20 S6 3.9 20 150 20 7 3 3 SR 714 3000 20 S4 4.5 20 150 20 8 23 4 Cracked 553 1000 20 S4 4.5 20 150 20 5 3 5 Cracked 628 1000 20 S6 3.9 20 150 20 7 4 6 Cracked 722 3000 20 S4 4.5 20 150 20 9 38

[0091] The typical refiner's requirement of mercaptans concentration from 500 to 700 ppm were experimented and it is evident from Table 5 of meeting the desired target of less than 10 ppmv, wherein the process is capable for processing higher mercaptans in feed beyond 700 ppmv by corresponding enhancing the process temperature and other relevant severities. The concentration of H.sub.2S till 1000 ppmv observed to meet the desired target of less than 10 ppmv, wherein the increasing concentration results in substantial extent of reactive desulfurization but not less than below 10 ppmv.

Example 4

[0092] All the experimentations described in Example 4 were conducted in similar experimental setup as described in Example 1 with inclusion of secondary stream recirculation feature as described in FIG-2. The effect of internal recirculation of treated secondary stream with selective secondary stream is represented in FIG. 4. The primary stream of SR LPG along with hydrogen in the proportion of 5-10 Nm.sup.3/m.sup.3 was used in the entire experimental run length of 168 hours as mentioned in below graphical representation.

[0093] The secondary stream S6 used for the entire experimentation in this example containing initial total sulphur of 2200 ppmw and then over the run length of 168 hours it gradually increased till 2330 ppmw. The primary stream used in this example is SR LPG stream containing around 550 ppmv of mercaptans and 50-100 ppmv of H.sub.2S. The FIG. 4 confirms the total sulphur of treated primary stream product is less than 10 ppmv and enhances the entire process reliability as disclosed in the present invention by such; even in case of unavailability of secondary stream during the course of operation, the hydro-processing may be continued by effective internal circulation of secondary stream with purge mechanism as described in FIG. 2.

Advantages of the Process of the Present Invention:

[0094] The present process provides: [0095] Less number of reaction stages in order to meet deep desulfurization of mercaptans below 10 ppmv. [0096] Cost effective and caustic free eco-friendly treatment of low boiling hydrocarbon streams. [0097] Capable to desulfurize both Straight Run LPG or Cracked LPG or mixture of Straight Run and Cracked LPG. [0098] Higher tolerance to impurities like diolefins and H.sub.2S. [0099] Minimal space requirement due to integration of reaction and separation sections.