APPARATUS FOR CONTACTING PARTICULATE SOLIDS WITH A FLUID

Abstract: Process for contacting particulate solids (e.g. cracking catalyst) with a fluid (e.g. a hydrocarbons-comprising mixture) by introducing said fluid as a, preferably single, annular stream into a stream comprising the particulate solids. The invention further relates to an apparatus for contacting particulate solids with a fluid comprising a solids container (e.g. a fluid catalytic cracking riser reactor) at least partly surrounding fluid supply means which have an inlet opening in the upstream end part and an annular fluid outlet opening in the downstream end part thereof.

Description: The invention relates to a process and an apparatus for contacting particulate solids with a fluid, especially contacting catalyst particles with a hydrocarbon oil stream in the lower part of a riser reactor of a fluid catalytic cracking (FCC) unit. It is known in FCC-technology to contact hydrocarbon oil with cracking catalyst particles by passing said hydrocarbon oil as an outer annular stream in a generally linear direction, imparting a centrifugal energy component to said stream and passing an inner gas stream concentrically with said outer stream through a restricted opening to bring said stream into contact with catalyst particles. It would be advantageous, however, to reduce the relatively large pressure drop resulting from (i) the conversion of linear velocity of the hydrocarbon oil stream into a tangential velocity component corresponding to the afore-mentioned centrifugal energy component and (ii) the subsequent passage of said stream together with an at least partly unbroken inner gas stream through a restricted opening. It has now been found that optimal mixing of a fluid with particulate solids can be attained with a relatively small pressure drop without requiring a separate inner fluid stream by introducing an annular fluid stream (preferably as a central, symmetrical, hollow-cone jet) directly into a solids stream. The invention therefore relates to a process for contacting particulate solids with a fluid which comprises introducing an annular fluid stream into a stream comprising particulate solids. The process according to the present invention can be advanta­ geously applied to contact solid cracking catalyst with a hydro­ carbons-comprising fluid. The present process can be carried out within a very wide temperature range provided, of course, that the fluid(s) applied does not solidify into large particles; preferably it is carried out at a temperature from 0-800 °C and most preferably from 450-550 °C. The contacting process is generally carried out at elevated pressures, although (sub-)atmospheric pressures are not excluded, provided that a sufficient pressure difference is main­ tained to introduce the annular fluid stream into the solids stream; preferably it is carried out at a pressure from 1-100 bar abs., and most preferably from 2-6 bar abs. in conjunction with a catalytic cracking operation. The ratio of mass flows of solids and fluids is preferably from 1-10 and most preferably from 4-8. The invention further relates to an apparatus for contacting particulate solids with a fluid which comprises a solids container at least partly surrounding fluid supply means which have an inlet opening in the upstream end part and an annular fluid outlet opening in the downstream end part thereof. Such an apparatus may contain features of an apparatus for mixing fluids as described in British patent application No. 8607699. Preferred embodiments of the apparatus according to the invention are described hereinafter using Figures 1-4 in which reference numerals relating to corresponding parts are the same. In Figure 1 a longitudinal section of an apparatus for con­ tacting particulate solids with a fluid is shown. In Figure 2 a longitudinal section of the bottom part of a fluid catalytic cracking riser reactor is shown. Figure 3 represents a cross section at AA′ of the fluid supply means of the apparatus as depicted in Figure 1. Figure 4 represents a cross section at BB′ of the fluid supply means arranged in the riser reactor section shown in Figure 2. The apparatus as schematically depicted in Figure 1 comprises fluid supply means (1) of which the major (downstream) part is surrounded by the bottom part of solids container (2). The upstream end part (3) of fluid supply means (1) preferably comprises separate inlet means (4) for a first fluid and most preferably tubular inlet means (5) for a second fluid arranged partly inside upstream end part (3). In the particularly preferred embodiment as shown in Figure 1 an annular inlet opening (6) for the first fluid is defined between the wall of fluid supply means (1) and tubular inlet means (5) in order to accellerate an upwardly directed stream of the first fluid and to provide an excellent distribution thereof over the cross section of fluid supply means (1). Further accelle­ ration and mixing of the first and second fluid can be attained by employing tubular fluid supply means (1) of which the cross sectional surface area decreases in downstream direction. Pre­ ferably, the ratio of the diameters of the upstream (3) - and downstream (8) - end parts of the tubular fluid supply means is from 1-5, and most preferably form 1.2-3. A major advantage of the apparatus according to the invention is that a single tubular fluid supply means (1) arranged substan­ tially centrally in the bottom end part (7) of solids container (2) can be applied to attain rapid, intimate and uniform mixing of particulate solids with fluid. The downstream end part (9) of tubular inlet means (5) may comprise positioning means, such as outwardly directed spacer fins (10). At least one opening (11) is present in said downstream end part (9); in some cases, however, it can be advantageous to provide downstream end part (9) with a plurality (e.g. 4-12) of openings through which the second fluid will flow with a relatively high velocity (of e.g. 30-300 m/s) and accordingly increase the velocity of the fluid mixture flowing through fluid supply means (1). In a preferred embodiment a deflection means is placed in opening (11), defining an annular fluid opening. The deflection means preferably comprise a rotation-symmetrical body having an increasing diameter in downstream direction. The annular fluid outlet opening (12) is preferably defined between the wall of the downstream end part (8) of fluid supply means (1) and deflection means (13), which most preferably comprise a rotation-symmetrical body having an increasing diameter in downstream direction. In a particularly preferred embodiment of the apparatus according to the invention, deflection means (13) com­ prise a substantially conical body having a top angle of 30-180 degrees and preferably of 80-120 degrees. The ratio of the diameter of the base of said conical body and of the downstream end part (8) of fluid supply means (1) is preferably from 0.8-6 and most pre­ ferably from 1-4. Deflection means (13) can be held in place by connecting means (14) which may be arranged either inside or outside (shown in Figure 1) the downstream end part (8) of fluid supply means (1); in the latter case connecting means (14) can also serve as vanes inside annular opening (17) defined between tubular shielding means (16) and the downstream end part (8) of fluid supply means (1). A rod (21) may be arranged substantially coaxially inside fluid supply means (1) and connected to deflection means (13) in order to attain a very stable annular fluid flow around said rod. The apparatus according to the present invention furthermore preferably comprises fluidization means (23) (e.g. in the form of a perforated plate as depicted in Figure 1 or ring-shaped or annular fluidization means) provided with regularly spaced fluidization gas openings (e.g. nozzles (24)) through which a fluidization gas (e.g. steam or a sour fluid catalytic cracking off gas) introduced via fluidization gas inlet means (22) emanates into mixing zone (19). Moreover, a separate flow of gas introduced via inlet means (27) may be used to cool space (25) between shielding means (16) and tubular fluid inlet means (1). Solids container (2) may comprise a section having a restricted diameter (not shown in the Figures) near annular fluid outlet opening (17) in order to increase the velocity of the fluidized bed of particulate solids surrounding said opening, thus even further improving the contact between the fluid (mixture) emanating from fluid outlet opening (17) with the solids. In Figure 2 another embodiment of the apparatus according to the invention is shown which is preferably employed as part of an apparatus for fluid catalytic cracking of hydrocarbonaceous material and which, in addition to the elements already described in connection with Figure 1, comprises solids inlet means (20) through which solid particles (e.g. originating from a catalyst regenerator) are introduced into the bottom section of solids container (2) (which can be the riser reactor of a fluid catalytic cracking apparatus). A cooling gas (e.g. low pressure steam) can be introduced through cooling gas inlet means (27) and annular cooling gas inlet space (26) into space (25) (enclosed by lower section (15) of shielding means (16)) and be removed through annular opening (17) provided with vanes (18). Preferably, a heavy hydrocarbon oil feed is introduced through inlet means (5) and accellerated through nozzle (11) in the downstream end part (9) thereof into fluid supply means (1) where mixing with steam introduced via inlet means (4) can take place. The use of a single fluid/solid contacting apparatus which is centrally located in the bottom section of a riser reactor as depicted in Figure 2 leads to very uniform mixing of solid cracking catalyst and fluid (hydrocarbon/steam mixture) in mixing zone (19) in a relatively short period of time; consequently the length of the riser reactor section in which the solid catalyst particles are mixed with hydrocarbon feed is relatively short, resulting in optimal use of the remaining (upper) section of the riser reactor for the actual catalytic cracking. Moreover, by employing the apparatus and process according to the present invention only a relatively small amount of steam or another fluid is used for injecting a given quantity of liquid (hydrocarbons). In addition, coke formation on the catalyst particles and on the walls of the cracking apparatus is reduced as a result of optimal contacting of hydrocarbon feed with said catalyst particles. The invention is illustrated by means of the following Example. Example A feed stream of heavy hydrocarbon oil enters inlet (5) of the apparatus as depicted in Figure 2 at a temperature of 250 °C and a pressure of 12 bar abs. and is mixed in tubular fluid supply means (1) having length of 3 m and a diameter of 0.2 m with steam intro­ duced via inlet (4) at a temperature of 300 °C and a pressure of 15 bar abs. The resulting oil/steam mixture flows with a velocity of 50 m/s through annular outlet opening (12) into mixing zone (19), which is operated at a pressure of 3 bar abs. and a temper­ ature of 520 °C. Regenerated silica-aluminia based catalyst particles are introduces via inlet (20) at a temperature of 700 °C into mixing zone (19) wherein the catalyst particles are contacted with the oil/steam mixture.

Claims: 1. Process for contacting particulate solids with a fluid which comprises introducing an annular fluid stream into a stream com­ prising particulate solids. 2. Process according to claim 1 wherein solid cracking catalyst is contacted with a hydrocarbons-comprising fluid. 3. Process according to claim 1 or 2 which is carried out at a temperature from 0-800 °C, most preferably from 450-550 °C, and at a pressure form 1-100 bar abs., most preferably from 2-6 bar abs. 4. Process according to any of the preceding claims wherein the ratio of the mass flows of solids and fluids is from 1-10 and most preferably from 4-8. 5. Process substantially as described hereinbefore with reference to the Example. 6. Apparatus for contacting particulate solids with a fluid which comprises a solids container at least partly surrounding fluid supply means which have an inlet opening in the upstream end part and an annular fluid outlet opening in the downstream end part thereof. 7. Apparatus according to claim 6 wherein a single tubular fluid supply means is substantially centrally arranged in the bottom end part of the solids container. 8. Apparatus according to claim 6 or 7 wherein the cross sectional surface area of the fluid supply means decreases in downstream direction. 9. Apparatus according to claim 8 wherein the ratio of the diameters of the upstream- and downstream- end parts of the tubular fluid supply means is from 1-5 and most preferably form 1.2-3. 10. Apparatus according to any of claims 6-9 wherein the annular fluid outlet opening is defined between the downstream end part of the fluid supply means and deflection means. 11. Apparatus according to claim 10 wherein the deflection means comprise a rotation-symmetrical body having an increasing diameter in downstream direction. 12. Apparatus according to any of claims 6-11 wherein an annular inlet opening for a first fluid is defined between the fluid supply means and tubular inlet means for a second fluid arranged at least partly inside the upstream end part of the fluid supply means. 13. Apparatus for fluid catalytic cracking of hydrocarbonaceous material which comprises an apparatus according to any of claims 6-12. 14. Apparatus substantially as described hereinbefore with reference to Figures 1-4.

Inventors: BARNES, PETER HADDON
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1987
Main classification: C10G11
IPC codes: B01F3, C10G11, B01J10, B01J8