WO2000065269A1

WO2000065269A1 - A device for the control of the flow of fluid in the annular space of telescopic joints and use of same

Info

Publication number: WO2000065269A1
Application number: PCT/BR2000/000030
Authority: WO
Inventors: Eduardo Cardoso De Melo Guerra; Patrício NELSON, Jr.
Original assignee: Petroleo Brasileiro SA Petrobras
Current assignee: Petroleo Brasileiro SA Petrobras
Priority date: 1999-04-26
Filing date: 2000-04-06
Publication date: 2000-11-02
Anticipated expiration: 2001-10-26
Also published as: CO5241343A1; AR023531A1; PE20010228A1; BR9901484A

Abstract

A telescopic joint (5) comprises first (1) and second (1a) pipes defining between them an annular space enclosing a sliding ring (2) held in place in said telescopic joint (5). This allows fluid to pass through the annular space in a controlled manner and enables movements of the pipes (1, 1a) to be accommodated. In a preferred embodiment the second pipe (1aa) is larger in diameter than the first pipe (1) and includes a chamber (3) for accommodating the sliding ring (2), said chamber (3) being formed by a ply of the second pipe (1a).

Description

A DEVICE FOR THE CONTROL OF THE FLOW OF FLUID IN THE ANNULAR

SPACE OF TELESCOPIC JOINTS AND USE OF SAME FIELD OF THE INVENTION

The present invention relates to a telescopic joint for the control of the flow of fluid in the annular space within the telescopic joint, and more specifically to a device placed in the annular space between the interconnecting pipes of a telescopic joint so as to promote, a desirable and controllable flow rate of fluid through that space while allowing the relative movement due to differential displacements. BACKGROUND INFORMATION The use of telescopic joints as a linking element in pipes is widespread in the refining and grain storing industries, in the refining of petroleum oils, in the separation of gas-solid suspensions and broadly in various hydraulic systems.

The main feature of a telescopic joint is that an annular space is formed between the pipes which make up said joint, the pipes being concentric or not, said joint besides allowing the necessary accommodation due to differential displacements, admitting the passage of the fluids required for the balance of pressures.

In order to better accommodate the differential displacements of the connecting pipes it is sometimes found that the radial dimension of the annular space may reach a value which is higher than those usually recommended. As a consequence of said increase, the flow rate of fluid throughout that space, which is required to keep. the pressure differential, reaches a very high value and eventually renders the system not viable.

The use of a cyclone as a separating device is quite usual in the field of quick separation of gas-solid suspensions. In the refining of petroleum oils, the fluid catalytic cracking unit (FCC) uses several sets of cyclones for separating the catalyst (a very fine grain size) from gases and vapors. A first set, or stage, of cyclones, placed in the interior of the disengager vessel, is normally connected directly either to the exit of the reaction zone or to the feeding zone. In order to minimize the presence of particulates in the gases exiting the disengager, another set of cyclones is linked in series to the cyclones of the reaction zone or feeding zone through a connecting pipe. A telescopic joint is formed at the link between two cyclone pipes: one pipe exiting one cyclone and a second pipe entering another cyclone.

In view of the ever increasing requirements for the control of the particulate emissions, refiners seek for increasing efficiency in the cyclone separation and retention ability.

US patent 4,502,947 teaches that a more efficient and quick separation of the catalyst and the reaction products in the FCC unit may be obtained by using a cyclone separator which is directly linked to both the end of the reaction zone (riser) and the cyclones of the first and second stage. Concentric pipes, mounted in telescopic way to absorb axial and radial movements due the differential thermal expansion between said cyclone stages link the exit of the riser cyclone and the entrance of the duct of the first cyclone stage. Purge and stripping vapors flow through the annular space between the concentric pipes together with some entrained catalyst. It is suggested to use several kinds of packings in the interior of the annular section for the mounting of the concentric pipes, so as to preserve some space for the passage of vapors.

However, the use of packings in the interior of the annular section may constitute a source of problems for the refiner, since such packings may favor the piling up of catalyst, causing plugging and requiring more frequent, undesirable maintenance work.

US patent 5,569,435 of the Applicant, hereby fully incorporated as reference, shows that a diplegless cyclone separator, also known as a pseudocyclone, coupled directly to the end of the riser and connected to a set of cyclones through a pipe made up of concentric cylinders, allows a more efficient separation of the gas-solid suspension in the disengager vessel of the FCC unit. The annular space between the concentric cylinders is dimensioned in order to absorb the gases from the stripping section and the purge vapor from the disengager, dispensing with the need to provide packings for the annular section.

In spite of the thorough discussion provided by the cited references concerning the advantages of the use of closed cyclones in FCC units, a few practical problems are still unresolved such as the volume of the annular section between the concentric cylinders in the telescopic joint in order to optimize and control the purging vapor. Thus, in spite of the several approaches advanced by the published literature, there is not yet available a simple, low-cost and safe solution for the flow rate control of fluids in the annular space between connecting pipes in telescopic joints, said long- sought solution being the device described and claimed in the present application. SUMMARY OF THE INVENTION

Thus, the present invention provides a device for control of the flow rate of fluids in the annular space between the connecting pipes of a telescopic joint, the pipes being concentric or not, the device securing an optimized flow rate of fluids for maintaining the pressure differential while allowing the structure differential displacements typical of hydraulic systems for the flow of fluids in order to secure an annular section having the desired spacing and pressure drop in the connecting area of the connecting pipes, without structurally impairing the accommodation of the differential displacements.

Such a telescopic joint can be used for the flow rate control of fluids in the annular space of connecting pipes of converter cyclones in fluid catalytic cracking units (FCC), by using a sliding ring in the telescopic joint, so as to ensure that there will be a constant area for gas passage and a desired pressure drop in order to accommodate a known flow rate of gases from the disengager towards the interior of the connecting pipe. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A illustrates an embodiment of the present invention, namely, a sliding ring installed in a telescopic joint; Figure 1 B shows a preferred, although not limiting, embodiment of the present invention, namely, the use of an anti-eroding refractory layer which covers the sliding ring; and

Figure 2 shows another preferred mode of the invention, namely, the use of the sliding ring mounted in the telescopic ring connecting the cyclones of the disengaging section of an FCC unit according to US patent 5,569,435. DETAILED DESCRIPTION OF THE PREFERRED MODES

The present invention will now be described in connection with the appended Figures accompanying the present specification.

Figure 1 A shows the details of the telescopic joint formed by the connecting pipes (1 , 1a), and illustrates the placing a sliding ring (2) between the pipes in order to secure a constant area (1b) for the passage of fluids and a desired pressure drop in order to accommodate a known flow rate of fluids.

The proposed configuration for the connection of pipes (1 , 1a) in the telescopic joint to accommodate the sliding ring (2), comprehends forming a hollow flange defining a chamber (3) for receiving the sliding ring (2). Said chamber is built from a ply of the larger diameter connecting pipe (1 a); the sliding ring (2) is first mounted in this chamber and then the connecting pipe (1 ) of lower diameter is then fitted within the ring (2).

Normally, the sliding ring (2) is built from the same material used for the connecting pipes (1 , 1a). However, different materials may be used for making the sliding ring (2), the choice of material does not constitute a limiting feature of the invention.

It is also obvious for the experts that the diameter of the sliding ring (2) will be a function of the diameters of the connecting pipes (1 , 1a) and of the desired annular space. As shown in Figure 1 A, the passage (1 b) is of constant cross-sectional area along its length. Although Figure 1A shows the sliding ring (2) as being concentric with the inner pipe (1 ), even if the elements (1 ) and (2) are not concentric there will still be a constant cross-sectional area of flow passage for gas between the ring (2) and the pipe (1 ). With appropriate selection of the gas flow velocity, this gas flow along the passage (1 b) will itself clean the internal wall if the sliding ring (2) and the external wall of the inner pipe (1 ) of any deposits. In the case of an FCC unit these deposits may, for example, be coke deposits, but in other apparatus any powdery material may be deposited on the pipe walls if the speed of the gas is not high enough to clear it. Furthermore, for an FCC unit provided with the sliding ring of the present - -

invention any sliding of the pipes (1 , 1 a) relative to one another will result in a shear movement as the sliding ring (2) moves relative to the inner pipe (1 ) and this shearing movement will also serve to reduce any deposit which may be present. Such shearing movement is likely to occur more at the start-up of the FCC unit and as a result of any servicing operations during turnaround periods.

The relationship between the dimensions - radial width (a) and axial height (b) - of the sliding ring (2) (Figure 2B) is also a function of the diameters of the connecting pipes (1 , 1 a).

The thickness of the sliding ring (2) will be dimensioned so as to keep the desired spacing and pressure drop, and may vary within broad limits, this not constituting a limiting aspect of the present invention.

Figure 1 A shows the telescopic joint, including the sliding ring (2) proposed in accordance with the present invention, mounted in the vertical position. It is obvious for the experts that the sliding ring (2) of the present invention will be adapted to the use in telescopic joints mounted in the horizontal or the vertical position or mounted at any other angle, the positioning of the telescopic joint does not therefore constitute a limiting aspect of the present invention.

It is important to notice that the suggested geometry for the combination of telescopic joint and sliding ring (2) is consistent with the need for an easy removal of any plugging formed in the annular section during operation, merely as a result of scrubbing by the gas flow past the sliding ring (2) and the inner pipe (1 ); such removal occurs during normal operation of the unit, but could equally be carried out during turnaround operations. As indicated above, such removal can also be effected by the shearing generated by the free movement of the parts which make up the set. Figure 1 B represents another preferred mode of the present invention, where the sliding ring includes a protective layer of anti-eroding refractory material; the particular kind of refractory used does not constitute a limiting aspect of the invention. The preferred refractory coating is of the same kind as that used in the connecting pipes (1 ,1 a). The application of the sliding ring in telescopic joints, such as proposed by the present invention, will be better understood in connection with the Example below, which should not be construed as limiting the invention.

EXAMPLE 1 This example shows one of the preferred applications of the present invention, which is the control of flow rate of gases in the annular space between connecting pipes of FCC converter cyclones. By using the sliding ring of the telescopic joint it is possible to ensure that there is a constant area of passage for gases and a desired pressure drop to accommodate a known flow rate of gases from the disengager to the interior of the connecting pipe. Figure 2 shows a schematic view of a converter of an FCC unit where the sliding ring (2) (not shown in the drawings) is mounted in the telescopic joint (5) of the closed cyclone system of the disengager vessel of an FCC unit such as suggested in the said US patent 5,569,435. Thus the reaction zone, made up of a vertical tubular reactor (riser) (6) discharges the gas-solid suspension formed by the catalyst and cracking reaction products inside the disengager (7) through the pseudocyclone (8). Purge vapor is introduced through distributor (9).

The decanted, substantially hydrocarbon vapor-free catalyst leaves the disengager (7) and is directed to the stripping section (10) and later to the regenerator vessel, not indicated in the Figure. Primary cyclone (11 ) is connected to the pseudocyclone (8) through the pipe

(1 ) and the telescopic joint (5).

The flow rate of purge vapor, injected in the disengager (7), which will flow through the annular space defined by the sliding ring (2) in the telescopic joint (5), in accordance with the present invention, should be such as, together with the gases from the stripping section (10), to allow for the extraction and flow of gases through the lower opening of the cone of the pseudocyclone (8) cone, this representing of from 0.1 to 7% of the overall flow rate of gases which are directed to the next cyclone stage, with a preferred value being 5%.

It is obvious to the expert that the device for the flow rate control of fluids made up by the sliding ring (2) such as suggested and claimed in the present invention may be used in any telescopic joint which would need such control, the use of the inventive device being therefore not limited to the connecting pipes of the closed cyclones of the catalytic cracking units (FCC).

Claims

nCLAIMS

1. A telescopic joint (5) comprising first (1 ) and second (1 a) pipes defining between them an annular space enclosing a sliding ring (2) held in place in said telescopic joint (5).

2. A telescopic joint according to claim 1 , wherein a passage (1 b) is defined between the sliding ring and the pipe therewithin, in order to define a constant cross-sectional area of throttling passage for fluids passing between the sliding ring (2) and the pipe

(1 ) therewithin.

3. A telescopic joint according to claim 2, when incorporated in apparatus generating a pressure drop across the sliding ring (2) in use of the apparatus, wherein the pressure drop is related to the cross-sectional area of the throttling passage (1 b) to ensure removal of any deposits on the facing surfaces of the sliding ring (2) and the pipe (1 ) therewithin as a result of scouring of the fluid flow therepast.

4. A telescopic joint according to any one of claims 1 to 3, wherein the second pipe (1 a) is larger in diameter than the first pipe (1 ) and includes a chamber (3) for accommodating the sliding ring (2), said chamber (3) being formed by a ply of the second pipe (1a).

5. A telescopic joint according to claim 4, wherein said chamber (3) is at an end of the second pipe (1 a), whereby the sliding ring (2) can be mounted in the chamber (3) and then the first pipe can be fitted within the central opening of the sliding ring (2).

6. A telescopic joint according to any one of claims 1 to 3, wherein the sliding ring

(2) is formed of the same material used to form the connecting pipes (1 , 1 a) of the telescopic joint (5).

7. A telescopic joint according to any one of claims 1 to 3. wherein the sliding ring (2) is made up of a material different from that employed for making the connecting pipes (1 , 1a) of the telescopic joint (5).

8. A telescopic joint according to any one of claims 1 to 3. wherein the telescopic joint is mounted with its longitudinal axis vertical.

9. A telescopic joint according to any one of claims 1 to 3. wherein the telescopic joint is mounted with its longitudinal axis horizontal. _ _

10. A telescopic joint according to any one of claim s 1 to 3, wherein the telescopic joint is mounted with its longitudinal axis inclined to the vertical.

11. A telescopic joint according to any one of claims 1 to 3, when employed in the connection of pipes of closed cyclone systems of fluid catalytic cracking units (FCC).

12. A device according to claim 12, wherein the flow rate of fluids which flows through the annular space of the telescopic joint (5) represents of from 0.1 to 7 weight % of the total flow rate of gases, preferably 5 weight % of the total flow rate of gases.

AMENDED CLAIMS

[received by the International Bureau on 4 September 2000 (04.09.00); original claims 1-12 replaced by amended claims 1-11 (2 pages)]

1. A telescopic joint (5) comprising first ( 1 ) and second ( 1 a) pipes defining between them an annular space enclosing a sliding ring (2) held in place in said telescopic joint (5), wherein a passage (lb) is defined between the sliding ring and the pipe therewithin, in order to define a constant cross-sectional area of throttling passage for fluids passing between the sliding ring (2) and the pipe (1) therewithin.

2. A telescopic joint according to claim 1 , when incorporated in apparatus generating a pressure drop across the sliding ring (2) in use of the apparatus, wherein the pressure drop is related to the cross-sectional area of the throttling passage (lb) to ensure removal of any deposits on the facing surfaces of the sliding ring (2) and the pipe (1) therewithin as a result of scouring of the fluid flow therepast.

3. A telescopic j oint according to claim 1 , wherein the second pipe ( 1 a) is larger in diameter than the first pipe (1) and includes a chamber (3) for accommodating the sliding ring (2), said chamber (3) being formed by a ply of the second pipe (la).

4. A telescopic joint according to claim 3, wherein said chamber (3) is at an end of the second pipe (la), whereby the sliding ring (2) can be mounted in the chamber (3) and then the first pipe can be fitted within the central opening of the sliding

5. A telescopic joint according to any one of claims 1 to 3, wherein the sliding ring (2) is formed of the same material used to form the connecting pipes (1, 1a) of the telescopic joint (5).

6. A telescopic joint according to any one of claims 1 to 3, wherein the sliding ring (2) is made up of a material different from that employed for making the connecting pipes ( 1 , 1 a) of the telescopic joint (5).

7. A telescopic joint according to any one of claims 1 to 3, wherein the telescopic joint is mounted with its longitudinal axis vertical.

8. A telescopic joint according to any one of claims 1 to 3, wherein the telescopic joint is mounted with its longitudinal axis horizontal.

9. A telescopic joint according to any one of claims 1 to 3, wherein the telescopic joint is mounted with its longitudinal axis inclined to the vertical.

10. A telescopic joint according to any one of claims 1 to 3, when employed in the connection of pipes of closed cyclone systems of fluid catalytic cracking units (FCC).

11. A device according to claim 10, wherein the flow rate of fluids which flows through the annular space of the telescopic joint (5) represents of from 0.1 to 7 weight % of the total flow rate of gases, preferably 5 weight % of the total flow rate of gases.