IE42529B1 - Method and apparatus for disengaging particles from gases - Google Patents

Abstract

1533022 Separating particles from gas ASHLAND OIL INC 19 March 1976 [24 March 1975] 11230/76 Headings BIT and B2P An apparatus for separating solid or liquid particles from a gas stream in which they are suspended comprises a chamber 12, a conduit 10 through which the particle-laden gas stream flows, the conduit having an outlet opening 13 leading into the chamber and a side wall port 17 upstream of the opening 13, and a cyclone separator 19 having an inlet connected to the port 17. The apparatus is described in relation to the separation of fine solid catalyst particles from gases produced in catalytic "riser cracking" of petroleum. The conduit 10 is in the form of a riser pipe which enters a gas-disengaging vessel from below and opens at 13 into the disengaging or separating chamber 12. The upper end of the riser pipe is stiffened at 25. As shown, there are two ports 17 in the side wall of the conduit 10 connected to a pair of cyclones 19 which are connected by expansion joints 22 to gas outlet conduits 21 connected to a further pair of cyclones 28 which have gas discharge outlets 30 leading out of the vessel 11 to fractionators. The cyclones 19, 28 have dip legs 20, 29 for discharging separated catalyst particles to the bottom of the vessel 11 from which they are led to a regenerator. The chamber 12 is pressurized by being connected directly to the conduit 10 so that no gas circulation takes place in the chamber. In operation, as the gases are abruptly diverted from the conduit 10 through the ports 17 into the cyclones which are at a lower pressure, the bulk of the catalyst particles are separated from them and are carried by their momentum through the opening 13 into the chamber 12 where they impinge on a deflector 14 which direct them downwardly to the bottom of the chamber. A baffle 33, Fig. 4, may be provided inwardly of the conduit 10 upstream of the port 17 to deflect the particles away from the port. In modifications, the conduit 10 may enter the chamber 12 through its side or top and the cyclones maybe disposed outside of the chamber. Other uses of the apparatus are given.

Description

This invention relates to a method and apparatus for the separation of particulate matter which is entrained or suspended in a gas stream.

The present invention arose and finds its most immediate use in connection with the separation of fine solid catalyst particles from the gases produced for example, in hydrocarbon conversion processes such as fluid bed catalytic cracking processes, and it is therefore primarily described hereinafter in relation to that field of use.

In fluid bed catalytic cracking of petroleum, conversion of heavy or residual oils to lighter hydrocarbon fractions is effected by contacting the oil with a hot, particulate catalyst, as a fluidized bed or flowing suspension. In one widely practiced cracking process known as riser cracking, this contacting is carried out in a reactor in the form of an elongated upwardly extending tube which is referred to in the industry as a riser tube.

In this type of process, oil at a temperature of from 500 to 800°F is mixed at the bottom of the riser tube, with hotter o catalyst at a temperature of from 1150 to 1350 F. Contact of 43329 the hot catalyst with the oil results in the very rapid generation of very large volumes of gas, which cause transport velocities in the riser tube of roughly 35 to 50 feet per second. The cracking reaction continues as the gas-particle mixture moves upwardly in the tube and until the catalyst and gases are disengaged.

I In order to stop the cracking reaction at a desired stage and to prevent degradation of desired products, it is necessary very rapidly to disengage the catalyst from the reaction products after the desired period of contact. This is commonly done in what is known as a disengaging chamber. For effecting this separation it has been conventional practice to use one or more cyclone separators, gases being separated and discharged through the gas outlet of the cyclone and solids being discharged through a dipleg to the lower part of the disengaging chamber.

If the degree of separation achieved in a single stage cyclone is not adequate the effluent, containing a small portion of solid particles still entrained in it, may be further separated in a second stage cyclone.

As utilized in hydrocarbon conversion processes of the specific type just referred to, this invention is especially concerned ο Κ *> ι Λ 4 ·* with the separation of the catalyst from the gas-catalyst mixture as it comes from a riser tube to the disengaging chamber. In such processes the efficiency of catalyst separation has important consequences. Catalyst solids which are not separated and which remain entrained in the cyclone effluent gas are lost to the cracking operation and must be replaced, or recovered and returned to the process, to maintain a given catalyst/charge ratio and to minimize catalyst costs. Moreover, catalyst particles which travel downstream with cyclone effluent cause erosion of processing apparatus. The heed to limit catalyst losses can itself become an operating limit on oil charge rate, and thus on capacity. Further, in operating at high throughputs, temperatures in the disengaging chamber can become so high as to constitute operating limits as metal stress limits are approached.

Although the cyclones used for catalyst separation are already efficient separating devices, being capable of separating up to 99.995% of the catalyst solids, they must handle very heavy loads: in refining operations, catalyst feed rates to the riser may exceed 1,800,000 pounds per hour. It will be apparent that separating inefficiencies of only .005% can still mean substantial losses in terms of actual pounds of catalyst.

For these reasons, it has been the objective of this invention to provide means for effecting the required gas/particle separation which will permit operating limits to be raised and lower particle losses to be incurred1.

An early approach taken by the prior art to theproblem of disengaging solids from gases in riser cracking is shown in United States Patent Specification No. 2,994,659 (Slyngstead). There the riser tube has a plurality of discharge slots in its sidewall, below a closed upper end. The entirety of the effluent from the riser is discharged directly into a disengaging chamber in which there is a reduction in the superficial velocity of the gas, which permits some catalyst to settle out. A twostage series cyclone separator has its inlet open to the disengaging chamber.

Experience showed that that arrangement was inefficient, and that the degree of disengagement occurring in the chamber decreased rapidly with increases in the superficial gas velocity in the . chamber. Above a certain limit (usually between 3.5 and 5 feet /second, depending upon catalyst particle density and size range, geometry, gas density and other factors), gas flowing at high velocity from the riser outlet through the disengager to the cyclone inlet, simply maintained a large portion of the solids in suspension and carried that load into the cyclones.

The system was effective at low rates, but highly ineffective at high rates required for economical operation. 43529 An alternative approach subsequently taken by the art is that shown in United States Patent Specification No. 3,152,066 (Wickham). There the riser tube had a single outlet opening in its sidewall, direclty opposite the cyclone inlet. There was a small horizontal gap between the riser outlet and the cyclone inlet, to permit stripping steam in the disengager chamber to be exhausted through the cyclone. The entirety of the riser effluent discharged directly into the cyclone.

The outlet gas from the first stage cyclone passed directly into a second stage cyclone. In practice, that system was also found to be poor in terms of separation results. The cyclone system was very sensitive to pressure fluctuations in the riser, such that riser changes tended to upset the cyclone operation. This was due, at least in part, to catalyst surges in the riser and thus in the cyclone. The device shown in the patent was unsuccessful in the industry. It was modified by discharging the first stage cyclone gas effluent to the disengaging chamber, and feeding the second stage cyclone from the chamber rather than from the first stage, but those changes made no substantial improvement.

Subsequently to the Wickham type of disengager, the art has more recently gone to use of a T shaped header on the end of the riser tube. The T“ has horizontally extending arms with outlets opening downwardly to the disengaging chamber, away from the cyclone inlet. The degree of separation occurring in the chamber upstream of the cyclone is improved, in comparison to the Slygnstead system, and the superficial velocity limit is higher, but it nonetheless remains a rather sharp limit once reached. Also, the degree of separation tends to vary drastically depending on the height of T11 outlet above the bed of catalyst. The closer the bed to the T, the poorer the separation and the higher the cyclone loading. Moreover, the downblast of catalyst at rather high velocity causes severe wear problems on the riser, the dipleg and the flapper valve at the end of the dipleg.

United States Patent Specification No. 2,648,398 (Chipley) shows an air cleaner comprising an elongated chamber having an inlet in one sidewall with unrestricted communication to the atmosphere, and a dust outlet opening smaller than the inlet and aligned opposite it in an opposite sidewall of the chamber. The outlet also opens to atmosphere. Suction is applied to an air outlet of the chamber, to draw air laterally from the space between the inlet and outlet. Dust particles move laterally to the longitudinal axis of the chamber, across the chamber from the inlet through and out the opposed outlet, while clean air is drawn off longitudinally.

United States Patent Specification No. 2,540,695 (Smith) shows a fuel economizer and air cleaner for motor vehicles in which a funnel-mouthed member, mounted behind the radiator of an automobile, leads inwardly to a tubular baffle which is enclosed within a concentric filter. The filter has a nozzle outlet opposite from the funnel-shaped inlet, through which nozzle grit is discharged to atmosphere. A carburetor inlet leads radially from an annular chamber surrounding the filter.

United States Patent Specification No. 3,597,903 shows a vacuum cleaner in which the intake manifold has an endwise opening to a filter bag and an upstream sidewall opening into a secondary filter bag. The space surrounding the two filter bags is under negative pressure. Dirt is entrapped preferentially, first in the in-line filter bag, then, when that is full, in the sidearm bag.

According to the present invention there is provided a method of disengaging particles from a gas stream in which they are suspended comprising passing the gas stream containing suspended particles through a conduit having a particle discharge opening leading directly into a disengaging chamber and a gas discharge port in the sidewall of the conduit upstream of the particle discharge opening, the gas discharge port communicating directly with a cyclone separator, statically pressurizing the disengaging chamber, and diverting the gases through the gas discharge port into the cyclone separator, the static pressure in the disengaging chamber being maintained at a level sufficiently hiqher than the pressure in the cyclone separator so that the gases preferentially flow through the gas discharge port while particles are carried by their higher momentum beyond the gas discharge port and are discharged inertially through the particle discharge opening into the disengaging chamber.

Also according to the present invention there is provided apparatus for disengaging particles from a gas stream in which they are suspended comprising an elongated tubular conduit for conveying the gas stream containing suspended particles, the conduit having a particle discharge opening leading directly into a disengaging chamber and a gas discharge port in the side wall of the conduit upstream of the particle discharge opening, and a cyclone separator having an inlet directly communicating with the said port, the disengaging chamber being adapted to be statically pressurized whereby gases in the conduit will preferentially flow through the gas port while particles will be carried by their higher momentum beyond the gas port through the particle discharge opening into the disengaging chamber. 42339 TO The invention is particularly useful in hydrocarbon conversion processes since it makes use of the high velocity of the catalyst particles and gas moving in the conduit or riser. The gas, being of low density in comparison to the catalyst, can make the angular turn through the gas discharge port in the side wall into the cyclone, while the dense catalyst is transported by its momentum into the disengaging chamber. Thus, the gas is directed into the cyclone but the bulk of the particles are projected into the disengaging chamber, out of the deflected gas stream. (This may be contrasted with past systems wherein the entire gas/particle stream is directed into the cyclone, and with other systems wherein the entire stream is directed into the disengaging chamber).

The disengaging chamber is essentially closed to the flow of so large a volume of gas through it, and there is no substantial flow of gas from the riser through the disengaging chamber. Generally, the flow of gas from the disengaging chamber is less than the rate of flow of stream in the conduit. A static back pressure is maintained in the disengaging chamber which diverts the gas angularly from the riser so that it does not pass through the disengaging chamber, but instead passes into the cyclone inlet.

The solid particles, having higher momentum by reason of their higher density, continue travelling in the upward direction in which they were moving in the riser tube, and are not deflected by the back-pressure. They thus exit through the outlet opening of the riser into the disengaging chamber and accumulate as a bed at the bottom of the disengaging chamber from which they are drawn for stripping and recycling. The major portion of the solids are thereby by-passed around the cyclone and do not enter the cyclone at all; a minor portion, which may be of the order of 10 to 20% of the catalyst, does enter the cyclone, and is separated there.

Several surprising consequences are obtained by practice of the invention. An especially unique and advantageous result is that significantly higher cracking temperatures can be used. Moreover, the superficial velocity of gases in the disengaging chamber is eliminated as an operating limit; and, third, there is a dramatic improvement in separating efficiency and stability over a wider range of operating conditions.

Because the riser discharge gas does not flow through the disengaging chamber, there is essentially no flow of the gas in the disengaging chamber. That is to say, the superficial or space velocity (defined as gas flow divided by cross sectional flow area) is essentially zero. This factor, which had been a critical upper limit in certain earlier configurations, is no longer a limit. With no superficial velocity in the disengaging chamber, there is essentially no re-entrainment of particles discharged from the riser, regardless of operating rate. Moreover, since the pressure in the disengaging chamber is greater than the pressure in the cyclone, there is no tendency for the cyclone to discharge gas downwardly through its dipleg, which in itself would tend to cause re-entrainment.

The temperature at which the disengaging chamber runs can surprisingly be raised by use of the invention. Many disengaging chambers now in service have been fabricated of metals which will withstand internal gas temperatures up to about 950°F. If modified to incorporate the structure of this invention, it is found that the same disengaging vessel shell can now be run at temperatures of about 1050°F., i.e., about a 100°F. increase, without exceeding metal stress limits. This is an important advantage, since it has been found in recent years that these higher temperatures are desirable in terms of their effects on the cracking reactions. Thus, modification of the riser-cyclone structure in an existing disengaging shell structure enables the process to be run at optimum but higher-than-original-design gas temperatures.

The reason for this appears to be that a static gas boundary layer now overlies the vessel wall and significantly reduces heat transfer from the gas to the shell. Thus the sensed shell temperature is in fact less, at the same riser discharge gas temperature.

The invention will now be described with reference to the accompanying drawings in which, Figure 1 is a diagram of one common type of riser cracker, Figure 2 is a fragmentary vertical section of the disengaging chamber of a riser cracker having disengaging structure in accordance with a preferred embodiment of the invention, Figure 3 is a horizontal cross section taken on line 3-3 of Figure 2, and Figure 4 is a fragmentary vertical section of a modified form of the invention.

As previously stated the present invention finds its most 15 immediate application in the disengaging of catalyst particles from gases in connection with the riser cracking of hydrocarbon conversion processes. Idr that reason the* invention is shown in the drawings with specific reference to that i field of use, In the common form of riser cracker structure, as shown in Figure 1, the oil charge is pumped to the bottom of the - 14 riser tube,where it mixes with incoming hot catalyst from the regenerator. Contact of the hot catalyst with the oil rapidly generates a very large volume of gas and cracking occurs as the mixture rises in the riser. The elongated tubular riser conduit leads vertically or angularly upwardly to an elevated disengager vessel for separation of the catalyst from the gases. The separated gaseous products are taken off to fractionation for separation into gas, gasoline, light cycle oil, gas oil, and other products.. The catalyst accumulates in a bed as indicated by the dotted line,·in the lower or stripper portion of the disengaging vessel. Steam is added to the vessel to strip uncracked oil from the catalyst particles. The stripped but coke-en-crusted catalyst is returned from the stripper to the regenerator wherein coke is burnt off by the addition of hot combustor air, producing hot flue gas as a product.

The hot catalyst is then recycled. A hopper is commonly provided for catalyst storage. For further description of riser cracking, reference may be had to Hydrocarbon Processing, Vol. 51, No. 5, May 1972, pages 89 to 92; ibid. VoT. 53, No, 9, September 1974, pages 118-121; or to Fluidization and Fluid-Particle Systems, Zenz and Othmer, - 15 4:: δ:: 9 Reinholt Publishing Corp., I960, pages 7-15. in the disengaging structure of this invention, as shown in Figure ?, the riser tube 10 enters the disengaging vessel 11 from below and extends, in the embodiment shown, upwardly generally along the vertical axis of the vessel. The space within the disengaging vessel around and above the riser tube is referred to as the disengaging chamber. At its upper end, riser 10 is vented directly into chamber 12 through an outlet opening or port 13, which preferably is an endwise opening, perpendicular to the axis of the tube and to the axis of the chamber 12. Above the open upper end 13 of the riser- 10 a downwardly facing deflector cone 14 is mounted to I he top of the disengager vessel, the purpose of this deflector cone 14 is to deflect catalyst particles which are discharged through riser outlet 13, thereby preventing them from abrading the upper· end of the vessel, and also to minimize any (all back of parities back into tire riser tube through the open end thereof, which might cause re-entrainment.

Spaced a short distance below but adjacent to riser outlet is at least one port 17 in the sidewall of the riser.

The preferred embodiment shown is a balanced or symmetrical arrangement in which the riser is provided with two sidewise ports 17, 17 which are diametrically opposite one another, each of which feeds a separate two-stage series cyclone separation system (best shown in Fig. 3). Specifically, each sidewise port 17, 17 is connected via a lateral or transverse conduit, designated respectively at 18, 18 to the inlet of a first stage cyclone 19, 19. The cyclones may be generally in accordance with known configurations, and the construction of the cyclones themselves do not comprise the invention.

It is important, however, to note that the first stage cyclones are fed solely through the sidewise ports 17, and not through the chamber 12. The conduits 18, 18 feed particles tangentially into the respective cyclones, wherein a further gas/particle separation is made. Particles separated in the first stage cyclones 19, 19 are discharged through downwardly extending diplegs, one of which is shown at 20 in Figure 2, with the gaseous effluent discharged at the top through gas outlet conduits 21, 21 which are connected to the respective cyclone bodies through expansion joints as shown at 22.

The upper end of the riser is desirably provided with external stiffening means designated generally at 25, to support -17 43529 the canti-lever load of the cyclone separator which hangs • ί ’ 1 · from it. It ip also useful to provide a shoe, as at 26, on the side of the riser, to prevent the cyclone from coining to bear on the riser wall.

The gas outlets 21, 21 of first stage cyclones 19, 19 are respectively connected through conduits 27, 27 to the inlets of second stage:cyclones 28, 28 respectively. Where two stage cyclones are used, each second stage cyclone can be connected directly to the gas outlet 21 of a first stage cyclone. The Conduits 27, 27 constitute the sole inlets to the second stage cyclones; that is, those cyclones are not fed through or from chamber 12. Expansion joints are provided to accommodate the differential expansion between the two cyclones. The second stage cyclone diplegs, one of which is shown at 29 in Fig. 2, discharge particles separated in the second stage to the bottom of the disengaging chamber. The dipleg should desirably terminate above the bed so,as not to be covered by it. The gas outlets 30, 30 of the second stagecyclones extend through the disengager vessel and are connected to a manifold leading to fractionators, not shown.

The disengaging chamber is pressurized, being connected directly to the riser, but the catalyst discharge port is covered by the bed of catalyst which thus restricts escape of gases from the disengager. Steam is admitted to assist in the stripping operation (see Fig. 1). The steam flow is very moderate, for example of the order of 1500 lbs./hr. at 150 psi. Except for the minor flow of stripping steam which percolates upwardly through the stripper, there is essentially no flow of gases through the disengaging chamber.

In operation, the internal pressurization of chamber 12 blocks significant flow of gases into it through riser endwise vent 13. The catalyst particles, having relatively high density and low volume, are carried by their momentum into tho riser chamber, but the gases are diverted angularly to the cyclone through ports 17. 17. By far the greater portion of the catalyst is separated where the gases are directed angularly sideways while the particles are projected out of the riser, and these particles largely bypass the cyclone system. A minor portion of the particles are not separated, or re-entrained in the gas and enter the cyclone system.

They are largely separated in the first or second cyclones, which carry a much smaller load than in the prior art. There is a pressure drop of about 2 psi through the cyclones.

Abruptness of change of direction of gas flow is important to achieving separation, because the particles do not change direction as rapidly as the gas does. In this connection, it is further beneficial to increase the velocity of the gas /particles stream upstream of the sidewall ports 17, 17.

For that purpose the invention preferably employs nozzle means in the form of a conical neck or restrictor in the riser, as indicated by the step-down section at 32 in Figure 2. This neck reduces the cross-sectional area of the conduit, so that the stream is accelerated as it moves past.

Alternatively, or in addition, where an assymetrical or an unbalanced cyclone construction is used, it is advantageous to employ a baffle or deflector means, preferably in the form of a deflector plate 33 (see Fig. 4) which projects angularly inwardly from the riser sidewall just upstream of the sidewall post, such that particles are deflected away from the sidewall outlet. The plate is preferably angulated at an angle A, with respect to the vessel sidewall , of about 30°, and projects about 15% of the way across the tube diameter. This further improves efficiency ofoperation, as will be shown hereinafter.

The following examples and comparisons with other particle disengaging techniques will further illustrate the practice and advantages of the invention.

The data for Runs 1-10 in Table 1 was obtained with a prior art disengager in which the entire effluent from the riser tube was discharged through a sidewise port in the riser, through a lateral conduit directly into the inlet of a first stage cyclone. There was no endwise vent, and all of the catalyst went into the cyclone system. Also, the gas outlet of the first stage cyclone was vented to the disengager chamber, and a second stage cyclone had its inlet open to the interior of the chamber. Stripping steam from an external source was supplied to the disengager chamber. >> <α ο • co 0 r-.1— rtlCr-S , r- 0 στ 00 •4· VO r— CM 0 O CM CO O VO co X> r-» ΙΜΏ COr-<± r-. 0 0 r-. σ» in D ΟΊ r- o 0 CM O CM «— CO o CM r—. cm στ Γ-^ I— ·— Ο Ο •000 •ooo c <υ Ο (Ο t. ο cn0 0CMrtn γ- Ο Ν 0 -t «-J- 0 CM CO CO 00 CO 00 inr tv,— -iCOCOOrO CM 0 CM 0 0 0 cn ι— ο Γ—~ cr. CM Kt <4· 0 0 0 00 CO O VC 0 Γ-» 0 Ο O 0 0 O Cn CM CM 00 CM 0 r— r— CM 0 CM I— Γ-» O CM (Ti 7f 'Ϊ) rID St D X O ία: «ί €0 0 CM CM in Φ r— r— r-> i-» ro. .>> ?J- 0 0 CM 0 0 0 0 0 0 0 0^^0 Φ 0 0 0 CM «-t ff 4-> tn cn in S- X φ -J ff OC OOOsdCMl·^ o cm cn r- 0 0 r— 0 Μ O 0 O 0 0 0 o·» cm 0 r·—. 0 r-. 0 r—. cm Φ +-> X o ο ο ο ο o o o o O O O 0 ο ο ο ο o rCM co Ό 00 CO CTtlvsf COO 0 0 0 0 1-» 0 in c ff 3 o sM>> c > «J - cm 0 sj· 0 , cn c r-. 0 cn o > «3 SLu (0 sCS a o LL· CO co cm rLO O LO lo in cn lo r- io cn i—OO o CO CM CM OOO r-. in Hco cn lo CM r— co rv ro'do cm cn lo tn rcn o CO co co CQ co cn co 03 cm LO cllo tn in >5 · · · I— «4- cn r-χ co o co CM r— LO ι— i— LO OmNCOO CO cn r—* cm io co ι— co r-«. r-’* σι oo r— o»— o o o «Φ «— «Μ- CM CM o o o o o tn oo co co © cn C0b-r— co o cn cn cm co co Γ*χ r*. co it i— i“ (Ό O) O in LO LO I— Olr-OJr° cO t— m r—r— 03 cn CO Lo I— CO Q. Γ-x LO >5 · · · * · I— t·-1*- hx Γ*- t-x GT) (β Π3 Ωt- OX +5 (0 oz · SΦ ΣΕ cn \ s- w (ϋ λ co rn lo CM <3- CM d* OOO OCO't CM CM CM CsCOCTi ίο w M- C : ζ* cn s- CM co > «c cn 00000 00000 ο σ 0 0 0 O CM «μ- Ο Px CM cn LD CO lo co rx. rx co cn cn co ίο w q- c ZJ cn u «=r to to r-χ co > r- Γ- t— «— Γ- C 00 - 23 Catalyst A was a silica-alumina equilibrium catalyst in microspherical particles having an apparent bulk density of .72 grams per cc. Catalysts B and C were of the same general type as catalyst A but had apparent bulk densities of about .82 grams per cc.

The data in both Tables 1 and II is taken from yield summaries. Uhere a Run No. is followed by the character A, the data given is the average for a week, rather than being an actual day's data. Stream densities are from Petroleum Tables compiled by E. W. Saybolt & Co., and are based on API gravity of stream according to yield summary.

In these tables Cat. Rate represents the rate of catalyst circulation through the riser; 'Tract. Btms.

Flow represents total flow out of the fractionator bottoms stream; Fract. Btms. BSW is the volume preeent of catalyst in the fractionator bottom stream; and “Cat. Loss represents the amount of catalysts not recovered by the cyclones, assuming that all the catalyst entering the fractionator leaves in the bottom stream. The catalyst loss in pounds per day was computed by converting the fractionator bottoms flows to gallons per day and multiplying by the volume percent of catalyst in the stream density. The catalyst loss in pounds per barrel of raw oil charge was computed by dividing the loss per day by 2539 - 24 the raw oil throughput, converted from pounds per hour to barrels per day.

By. comparison of Tables I and II, it can be seen that the invention markedly reduced average catalyst losses, while at the same time enabling oil charge rate to be increased. Comparing invention Runs 11, 12 and 13 with the prior art Runs 6-10, all of which were the same type of catalyst, it can be seen that the average loss per barrel charge was reduced by 52%, at the same time oil charge rate was being increased by 13%. Moreover, chamber temperature could be increased to 1050°F., from the previous limit of 950°F. so that a better quality product was obtained.

The data set forth in Table III following, was obtained from a bench scale separator in which cracking catalyst was suspended in air, rather than cracking gases, and the data does not represent actual cracking runs. In Runs A and B of Table III, the simulated riser tube discharged to the disengaging chamber through a T shaped header at its upper end, above the catalyst bed at the bottom of the disengager. The T had side holes and a bottom hole through which gases were vented directly to the chamber. A first stage cyclone inlet opened to the chamber, and a second stage cyclone inlet was fed directly from the - 25 first stage cyclone gas outlet. In Runs C and D, the riser discharged through a T having 45° baffles at the outer open ends of the arms to deflect the discharged material downwardly.

In Run E, the riser was vented through an open upper end to the chamber and was connected through a sidewise port, just below the end vent, directly to the cyclone inlet, in accordance with the invention. tn LfJ az co < l·«X az ui Φ cn (ϋ c +J to -p • cn oi ρ ρ Φ O XJ fO (Λ r— Φ CJ U Q-M- Φ -f— ·γ~ O ULi_ Ο -i S_ Φ os- _ -P 3 © U in CM (0 wx φ Φ · az i- c a. ·«-P <ζι φ c: c cn^* -POOS (Zl r— «--χ j- u a. <0 S- ΤΟ o «Ρ ΤΟ MCd u φ Φ r— IZJ az ct φ \ ZJ > P m Uφ S-«Ρ s -r- Π3 LL eC Q£ O O Li-OC cn ω Ό r- 3 Φ Φ φ Φ o r— -CZ CO > >— CL O φ φ ·(— cz _J CO O *-« -P ’ 0)4- C C C O 3 ‘r~ Φ ΟΖΣ. cn tx -P o c •fc * to in rx to φ XJ i8 φ so •P 45Φ Φ CL o I Φ Φ P (0 SΦ cn i«3 sz u cn φ 'o. υ S’ Φ cn CM O O O * * 2529 - 27 In the runs referred to in this table, as well as the runs in fable IV following, the catalyst used was an FCC equilibrium catalyst with the following typical particle size distribution: 0-20 microns - 0 wt.% 0-40 microns - 8 wt.% 0-80 microns - 70 wt.% Bulk density of the catalyst was .8 grams per cc. Separation efficiency is 1 minus the quotient obtained by dividing the catalyst flowing into the first stage, by the catalyst feed rate to the riser.

In Table III, the amount of catalyst collected in the first stage cyclone dipleg shows the completeness of disengagement.

The invention (Run E) achieved much more complete recovery; it had a 7.05% first stage recovery, in comparison to recoveries in other systems of from 13.9 up to 42%. Most significantly, the amount of catalyst remaining in the system for recovery in the second stage cyclone was very low - only .002 lbs. 42528 Ρ (Λ >» cn c c ο φ φ e •r- U σ> C >rz -σ ω «ί ο SZ ρ «ο cn ρ ίθ ο υι υ j ο Ρ φ c >1 cn ο υ φ φ •f— C _£Ζ Ρ +J Φ -Ρ ζ/> φ Π3 ·Γ- Ϊ= s- <_> ο ρ ο π3 ·γ- +J ω ι— Q.M- S- α Φ <+- >> to ul Li- Ο Ρ Ρ σ) cn σι Φ » > c U Φ c C Γ— *1- ·Γ- CD Ο ·Γ“ ίθ Ό U- ίϋ »— ε +J ΙΟ Ρ Ο \ φ Q otn ρ φ —(Λ Ρ S- ♦ >><ο φ c ρ— or w ·ι— rti *r- SZ ρ -σ οζ «ϋ φ ν ω φ οΊ LuP'—' ο c t · ♦ι— ‘ί— S- Ο ψ- ο Φ £. · Ρ U1 φ r— υ— £L φ Π3 Ρ 3 >τ Φ U. (/) Ο£ *—* ΪΟ Φ ,— ω □_·«-* οι: -σ σ) Φ I (0 Sε φ •r- σ> > c ο ρ ο ο ω I— *0 w Φ ·ρ> Ρ Φ c σι r— (0 φ ρ »— -σ s-ώ φ ο ·ίCQ Ο.Ό Ρ 10 Οι— ζ:·»10 > < Ρ Φ ο > Γ“ Ε Φ Φ > · (Λ Φ σι ι— Φ >> «— S-Ό Ο. φ Φ ‘ί— > 43 Ό 00 Ο Γ-Ο CO ό οο ΓΟ φ ς- ω Φ •ρ- σ» Ρ Φ = S'” 2 φ Φ ι— > P •'-I— P ·«- φ (/) i“ 43 (/) r— C Φ C Φ Φ >a Φ > (/) Φ <0 ω φ r— O r— >> c P >> Ϊ-Ό (0 P S-Ό Φ Φ 4= •e~ Φ Φ Z> 43 P C3 5» 43 Ρ <0 Ο γ— ζ: -γΟ ο Ρ Ρ Ρ Ρ •r- ’ίο ΰ than 4 below cross .85 1.03 90.6 Ditto Ditto 2 5 2 9 Table IV illustrates the results obtained in the same stimulated system, comparing the invention (Runs F and G) with still other systems (Runs H through P). The structure utilized in Run F was the same as that of Run E. The structure used in Run G was similar, except that a deflector baffle was incorporated in the riser pipe set below the sidewall exhaust by about 1/4 X the riser diameter, in the form of a plate extending at an angle of about 45° to the riser axis, and projecting across about 1/4 of the riser diameter. The purpose of this plate was to deflect particles away from the sidewise gas outlet. The separator used in Runs and I had the riser discharging only to the first stage cyclone inlet. The riser was not vented to the disengaging chamber, and the first stage cyclone gas outlet opened to the disengaging chamber and the second stage cyclone had its inlet open directly to the disengaging chamber. The first stage dipleg length was one inch measured from the intersection of the cone and dipleg. The disengager in Run J was similar to that in Runs H and I, except that the dipleg length was 24 inches. The disengager in Runs K and L was the same except that the dipleg length was 18 inches.

In Runs M and N the riser discharged to the chamber through a T fitting having downwardly facing ports. The two stages of cyclones were connected in series, with the intake opening to the chamber above the T. Runs 0 and P were similar to Runs M and N except that a cross was used on the end of the riser rather than the - 30 T. The cross had four short horizontal arms, at right angles to one another, with downwardly facing discharge openings, the riser being connected to the center of the cross.

Comparison of Run F with Run G in Table IV shows that the use of, the deflector significantly increases the separation efficiency to the first stage cyclone (80.6 to 93%). Both of those runs achieved high separations prior to the first stage of the cyclone in comparison to Runs H, I,j, K and L, wherein nothing was separated prior to the first stage cyclone (the entire riser effluent being conducted directly into the first stage cyclone with no separation taking place in advance). The separation achieved prior to the first stage cyclone in Runs Μ, N, 0 and P was good, however, the systems tested there fluctuated greatly as to separating effectiveness if the level of the catalyst bed at the bottom of the disengaging chamber was less than four inches below a cross or “T on the riser end. As a result of this instability, such systems would not display uniformly good separations if used in commercial practice where the distance between the bed and the cross can almost inevitably be expected to vary substantially in ordinary operations. In comparison, the invention provides good separations without regard to bed level, so long as the dipleg is uncovered. 3 5 2 0 In the foregoing examples the riser tube entered the disengaging chamber through an opening in the bottom, and the cyclones were physically disposed in the chamber. Those skilled in the art will appreciate, from what has been said herein, that it is not necessary that the riser enter the disengaging chamber through the bottom, and in fact the riser may enter through the side or even the top, and that the cyclones may be physically disposed outside of the disengaging chamber, as may be convenient especially in the systems other than hydrocarbon conversion systems. It is not the physical disposition of the cyclones in relation to the disengaging chamber which is important, but rather the fact that the riser discharges through an endwise opening into the disengaging chamber and that it feeds through a sidewise opening just upstream of the endwise opening, to the inlet of a cyclone, regardless of whether the cyclone is inside of, or outside of, the disengaging chamber.

The invention has been primarily described herein in relation to hydrocarbon conversion processes. However, those skilled in the art will recognize that the invention is useful in other catalytic gas phase chemical reactions wherein catalyst particles are contacted with chemicals suspended in a fluid 2539 - .32 chemical stream flowing in a reactor tube, as well as in other instances wherein particles (whether solid or liquid) are to be disengaged from gases.

Examples of other fields wherein it is believed that this method 5 and apparatus will be especially useful and which show the wide scope of utility of the invention, include the gasification of coal, the desulfurization of solid fuels, and heat exchangers wherein hot catalyst particles are mixed with incoming gases to heat the latter while cooling the catalyst.

Claims (20)

1. CLAIMS:1. Apparatus for disengaging particles from a gas stream in which they are suspended comprising an elongated tubular conduit for conveying the gas stream containing suspended 5 particles, the conduit having a particle discharge opening leading directly into a disengaging chamber and a gas discharge port in the side wall of the conduit upstream of the particle discharge opening, and a cyclone separator having an inlet directly communicating with the said port, the disengaging 10 chamber being adapted to be statically pressurized whereby gases in the conduit will preferentially flow through the gas port while particles will be tarried by their higher momentum beyond the gas port through the particle discharge opening into the disengaging chamber. 15

2. Apparatus as claimed in Claim 1 further including nozzle means positioned upstream of the gas discharge port in the sidewall of the conduit for increasing the rate of flow of gas stream therein.

3. Apparatus as claimed in Claim 2 in which the nozzle 20 means comprises a conical neck section so that the crosssectional area of the conduit is reduced relative to an immediate upstream section of the conduit, the neck section being shaped so that the gas stream is accelerated as it moves past the nozzTe.

4. Apparatus as claimed in any preceding claim which further comprises a deflector projecting into the conduit 5. From the sidewall thereof, and positioned upstream of the gas discharge port in the sidewall so that particles moving past the deflector with the gas stream are deflected angularly away from the gas discharge port.

5. Apparatus as claimed in any preceding claim in which 10 the particle discharge opening is an endwise opening, substantially transverse to the longitudinal axis of the conduit. G. Apparatus as claimed in any preceding claim in which the conduit projects into the interior of the disengaging 15 chamber, and the particle discharge opening is substantially perpendicular to the longitudinal axis of the chamber.

6. 7. Apparatus as claimed in any preceding claim in which the cyclone separator is disposed within the disengaging chamber. 20

7. 8, Apparatus as claimed in any preceding claim in which - 35 t.he disengaging chamber is adapted such that the flow ol gas therefrom is less than the rate of flow of the stream in the conduit.

8. 9. Apparatus as claimed in Claim 8 in which the disengaging 5 chamber is substantially closed to the flow of gas therefrom.

9. 10. Apparatus as claimed in any preceding claim in which the cyclone separator has a gas outlet extending outside of the disengaging chamber.

10. 11. Apparatus as claimed in any preceding claim in which 10 the cyclone separator comprises two stages of cyclones connected in series with one another, the first stage having an inlet connected to the gas discharge port opening and the second stage having a gas outlet extending outside of the disengaging chamber. 15

11. 12. Apparatus as claimed in any preceding claim in which the cyclone separator includes a dipleg for discharge of disengaged particles, the dipleg discharging to the chamber, above a layer of particles settled therein.

12. 13. Apparatus as claimed in any preceding claim in which the 20 conduit projects vertically into the disengaging chamber and the 43529 gas discharge port is within the chamber substantially at right angles to the particle discharge opening.

13. 14. Apparatus for disengaging particles from a gas stream in which they are suspended substantially as herein described 5 with reference to Figures 2 and 3, or 2,3 and 4 of the accompanying drawings.

14. 15. A method of disengaging particles from a gas stream in which they are suspended comprising passing the gas stream containing suspended particles through a conduit having 10 a particle discharge opening leading directly into a disengaging chamber and a gas discharge port in the sidewall of the conduit upstream of the particle discharge opening, the gas discharge port communicating directly with a cyclone separator, statically pressurizing the disengaging chamber, and diverting the gases 15 through the gas discharge port into the cyclone separator, the static pressure in the disengaging chamber being maintained at a level sufficiently higher than the pressure in the cyclone separator so that the gases preferentially flow through the gas discharge port while particles are carried by their higher 20 momentum beyond the gas discharge port and are discharged inertially through the particle discharge opening into the disengaging chamber. 4 2 5 3.9 - 37

15. 16. A method as claimed in Claim 15 in which the disengaging chamber is pressurized by restricting escape of gases therefrom except through the cyclone separator.

16. 17. A method as claimed in Claim 15 or Claim 16, in which 5 the particles are discharged from the conduit and into the disengaging chamber in a direction generally parallel to the longitudinal axis of the conduit.

17. 18. A method as claimed in any one of Claims 15 to 17 further comprising the step of increasing the velocity of the 10 stream at a point upstream of the gas port.

18. 19. A method as claimed in any one of Claims 15 to 18 further comprising the step of deflecting the stream angularly away from the gas port.

19.

20. A method of disengaging particles from a gas stream in 15 which the particles are suspended substantially as herein described with reference to the examples.