FR2640992A1 - - Google Patents

Abstract

Decoking device comprising a hollow flexible tube 14, a drum for winding this tube 3 allowing the supply of water to the flexible tube, and a decoking tool 15, 16 comprising ejectors 17, 21. The rotation is ensured. by an auxiliary motor, independent of the water stream, for example a hydraulic motor receiving a fluid stream distinct from the decoking water stream.

Description

The invention relates to the field of coking of charges.

  hydrocarbons most often consisting of heavy distillation products or residues. It relates more particularly to the subsequent step of recovering the coke (decoking or decoking) after it is deposited in the reactor. Coking is a process well known in the refining industry whose objective is to enhance heavy cuts and especially the distillation residues by subjecting them to decomposition

thermal.

  This generally takes place in large empty reactors where the decomposition takes place into distillates which are released from the reactor and

  as a coked product which is deposited in the reactor.

  The charge is most often introduced from the bottom of the reactor and, in this case, the coke is deposited first at the bottom of the reactor; it then gradually fills higher and higher parts

  from the reactor until it is completely filled.

  At this moment, we stop the injection of the load and we send this

  feed into a second empty reactor.

  After this first stage of coke formation, there is a second

  recovery step of the coke produced.

  For this, after having purged the reactor of all the residual hydrocarbons and having cooled it, it is opened at its upper part and a hole is dug using suitable tools. These are usually supported by scaffolding or a derrick which allows digging inside the reactor from its top. The structure of the scaffolding (one per reactor, there are at least two reactors) is' installed above the reactors themselves located well above the ground to allow the injection of the charge and above all to recover the coke produced which descends by gravity from the reactor and is then transported to an area of

storage or user.

  The object of the invention is a device which makes it possible to avoid scaffolding above the reactors in order to lighten the entire structure, save investment and make it more practical and

  more economical the extraction of coke.

  Devices fulfilling this purpose have already been described in prior French patent applications Nos. 8706765 and 8715141. These devices use a flexible tube wound around a drum and a tool suspended from the flexible tube. The rotation of the tool is ensured by reaction to the ejection of water in a direction comprising

a tangential component.

  The device of the present invention comprises, in combination: a) a hollow flexible tube resistant to pressure and to shear forces, b) a means of winding this flexible tube around an axis which can rotate on itself, comprising a means for supplying decoking fluid to the flexible tube, at a first end thereof, so as to allow the passage of said fluid from said supply means into the tube, whatever

or its degree of winding.

  c) and a decoking tool comprising: i. a first part rigidly and tightly connected to the second end of said flexible tube so as to allow the passage of the decoking fluid from the flexible tube to said first part, ii. a second part coaxial with the first, movable around its axis. Preferably at least a portion of this second part, of circular section, penetrates into a recess of larger circular section of the first part, iii. means for rotating the second part, independent of the decoking fluid circuit, iv. a hollow piston disposed inside the second part, movable along its axis in response to variations in pressure exerted by at least one auxiliary fluid, v. means for supplying the hollow space of the piston with decoking fluid, from the flexible tube, through the first and second parts of the tool, vi. means for transmitting said decoking fluid from the hollow space alternately to at least one first ejection means in a direction substantially axial and opposite to that of the supply by the flexible tube or to at least one second ejection means in a substantially lateral direction, said ejection means being arranged in said second part, vii. at least one hydraulic circuit for the auxiliary fluid passing through the first and second parts, separate from the decoking fluid circuit, allowing said auxiliary fluid to move the piston so as to bring it at will into one of the positions allowing the transmission of the decoking fluid to the first ejection means or to the second ejection means, viii. and sealing means for pressure control

in each of the circuits.

  When in use, the flexible tube of controlled rigidity, the free end of which is furthest from the axis of the drum, is lowered into the reactor, from a drum on which it is wound. when the tube is rolled up) is provided with means for ejecting water downwards and laterally and the descent of which is controlled by the rotation of the drum. The other end of the tube is connected to a source of pressurized water: the water flows through the tube to the ejection means and is projected towards the coke bed. We

  evacuates the pieces of coke that have come off.

  One can use a device as described above for each reactor; preferably, when using several reactors, for example 2 or 4, only one device is used. According to a first embodiment, the drum is movable and can move laterally to come above each of the reactors in turn. According to another embodiment, the drum remains at a fixed position, but pulleys for deflecting the flexible tube make it possible to bring

  the tool above the chosen reactor.

  The invention uses flexible pipes, which have properties such that they safely allow water to be transported under very high pressure. In addition, these hoses are very resistant to tensile forces and have controlled rigidity. They make it possible to suspend large masses at their ends, which makes it possible on the one hand to introduce the decoking tool inside the reactor and on the other hand to avoid the flotation of the hose when

  high pressure water streams are used.

  The operation is carried out in two phases: First, a hole is made in the coke along the longitudinal (substantially vertical) axis of the reactor by introducing from the top

  the lower end of the pipe, supporting the decoking tool.

  Water is ejected under pressure from 100 to 600 bars or more, from orifices arranged at the lower end of the device and oriented downwards, either in the axis of the tool or with an inclination on this axis , on the other hand, which can reach for example 30 '. In this case, the hollow piston is in a position allowing the passage of water towards the said orifices and closing the passage towards the lateral orifices. When the device reaches the bottom of the reactor, action is taken on the auxiliary hydraulic circuit to move the hollow piston in such a way that ejection can now be carried out laterally, and no longer downwards. The jet can be strictly perpendicular to the axis of the tool or make an angle

  by, for example, + 20 'with respect to this perpendicular.

  The pressure of the water in a lateral direction is then established at -600 bars or more, preferably 150-400 bars, which crumbles the coke which escapes from the base into pieces entrained by the water. The fact of using a high pressure, for example 150-400 bars or more, makes it possible to obtain relatively large pieces of coke and to avoid excessively fine dust which would be difficult to separate later. 2 0 Alternatively, it is possible to provide intermediate positions of the piston making it possible to eject the water at the same time through the axial ejectors

and lateral.

  The flexible tubes which can be used in the invention advantageously consist of superimposed layers which may include one or more watertight plastic sheaths, at least one reinforcement for resistance to internal pressure, which may consist, for example, of at least one spiral pitch winding short, and at least one armature of resistance to traction and to torsional torques, which can for example be made up of at least two crossed windings with long pitch. They advantageously meet the following characteristics: - sufficient flexibility to be able to be wound on a drum with a radius of between 0.5 and 5 meters, - internal pressure resistance of at least 100 bars, preferably 150 to 1000 bars, resistance to breaking by elongation from 104 to 106 daN, preferably 2.104 to 5.105 daN, - maximum torque: 100 to 1000 m.daN, preferably 500 to 5000 m.daN, - stiffness at 20 'C: 50 to 1000 daN .m2, preferably 100 to 500 daN.m2. Preferably, the operation is carried out with a weight suspended from the tube (ejector + possibly weighting mass) of 103 to 5 × 10 4 N; this weight must obviously be chosen compatible with the breaking strength. Tubes of this type have been studied at the FRENCH INSTITUTE OF OIL

  and are currently marketed by SOCIETE COFLEXIP, France.

  Figure 1 is an overview of the installation.

  Figure 2 illustrates the implementation of the water ejection device. Figures 3 and 4 illustrate two particular embodiments of the water ejection device, seen in axial section in a plane

vertical.

  The installation comprises, for example, two coking reactors 1 and 2. The reactor 1 is in the process of draining the coke and the reactor 2 in the process of depositing coke (coking). The lines for admitting the hydrocarbon charge and for withdrawing volatile products have not been shown, for the purpose of simplification. A winding drum or reel 3 is disposed above the reactors. Its rotation shaft is hollow and is used for the supply of water, brought under pressure by line 4, by means of a rotary joint connecting the rotation shaft of the reel to the line. The axis of the drum is supported by two rigid flanges of which only one (5) is visible. The two flanges are supported on a chassis (6) provided with wheels such as 7 and 8, allowing the assembly to be moved on the raceway 9. The assembly is carried by a scaffolding, or superstructure, comprising in particular the beams with 13. A flexible tube of high mechanical strength 14 is wound on the drum. It is connected to line 4 by a coupling piece (not shown) which allows the feed whatever the position of the drum. The other end carries a decoking tool comprising a non-rotating part 16 and a part 15

  capeblede turn on itself under the action of an internal motor.

  The higher the weight, the more stable the tool. Ejectors such as 17 are directed downward and ejectors such as 21 are directed laterally. A pulley 18 makes it possible to guide the 2 flexible tube and therefore to keep it in the axis of the reactor, which

  whatever the degree of unwinding of the tube on the drum.

  One or more annex flexible tubes 22, serving as auxiliary hydraulic circuits, make it possible to actuate the movable piston for controlling the ejectors and possibly the setting motor.

  rotation of part 15, if this motor is of the hydraulic type.

  The operation may for example be as follows: the tool 15/16 being initially raised above the reactor 1, the upper 19 and lower 20 ends of the reactor filled with coke are opened and the assembly is lowered (14, 15, 16), by unrolling the pipe 14 on its drum. The pressurized water supplying the hose 14 is ejected from the lower ejectors, directed downwards, such as 17, and the descent of the pipe into the reactor continues as

  } 5 and as a well is pierced by the jets in the coke bed.

  As soon as the tool has reached the bottom of the reactor, the coke is entrained by the lower opening 20 and falls under the reactor where it is

  evacuated by known type of transport devices.

  The piston is then moved through one of the hydraulic circuits so as to allow lateral ejection, and no longer

axial, water.

  The coke is detached from the reactor walls, and is evacuated by

opening 20.

  When the operation is complete, the tool is removed from the reactor 1, the drum 3 and its supports are moved on the rails such that 9 and after the reactor 2 has been opened, the hose and the tool are lowered in order to perform the decoking of reactor 2. Reactor 1 is

  used for a new coking operation.

  In FIG. 2, we find the tool composed of a non-rotating part 16, rigidly connected to the flexible tube 14, and a part 15 capable of turning around its longitudinal axis. The junction between the two parts is done by means of bearings such as 32 and seals such as 31, 33 and 34. The drive motor 35 can be a hydraulic motor driven by an auxiliary fluid brought under pressure high by the conduit 36 and returned to low pressure by the conduit 37. The speed of rotation of the motor can be adjusted by adjusting the flow rate of this fluid. These conduits are continued by flexible tubes forming part of the tubes represented schematically by 22. The motor 35 rotates the part 15, for example by means of a pinion driving a crown 39 rigidly connected to the part 15. The

  motor 35 can also be an electric motor, for example.

  The rotating part 15 has an internal recess 40 in which a hollow piston 41 can move. Sealing is ensured by segments or rings such as 42 and 43. In the position of the piston shown in FIG. 2, a conduit such as 44 places the internal space in communication with the conduit 49, the chamber 48 and the nozzle lateral 21. When the pressure exerted by the auxiliary fluid of circuit 45 decreases and / or that of the auxiliary fluid of circuit 46 increases, the piston moves downwards and the conduit 44 comes to face the conduit 50 and to the chamber 47, allowing the ejection of water by the nozzle 17. Conversely, a relative increase in pressure in the circuit 45, relative to the circuit 46, returns the piston to its initial position. This operation supposes that the pressures can be exerted O10 parallel to the axis of the piston. It suffices, for example, that the

  pressures can be exerted on shoulders such as 51 and 52.

  FIG. 3 represents a variant in which the circuit 45 is deleted. The chamber 53 is in communication with the outside via the conduit 57. The movement of the piston is controlled by the circuit 46: the piston moves by pushing the spring 54, allowing the water to pass through the ejector 17. Au rest, when the pressure in the circuit 46 is released, the piston returns to its high position and it is the ejector 21 which is supplied. Instead of a pressurized spring, an extension spring can be used (return spring); in this case the high position of the piston is obtained by

depressurizing the circuit 46.

  According to a variant that can be made to the device of FIG. 2 or of FIG. 3, it is not necessary to provide pipes such as 44 fitted in the piston. The piston can in fact itself mask or unmask the outlet orifices, which are respectively 55 and 56 in FIG. 4; the piston is represented in

  an intermediate position between its extreme positions.

Claims (7)

  1. Hydraulic decoking device characterized in that it comprises, in combination: a) a hollow flexible tube resistant to pressure and to shearing forces, b) a means of winding this flexible tube around an axis which can turn on itself, comprising a means for supplying decoking fluid to the flexible tube, at a first end of the latter, so as to allow the passage of said fluid from said supply means   up to the tube, whatever its degree of winding.   c) and a decoking tool comprising: i. a first part rigidly and tightly connected to the second end of said flexible tube so as to allow the passage of the decoking fluid from the flexible tube to said first part, ii. a second part coaxial with the first, movable around its axis, iii. means for rotating the second part, independent of the decoking fluid circuit, iv. a hollow piston placed inside the second part, movable along its axis in response to pressure variations exerted by at least one auxiliary fluid, v. means for supplying the hollow space of the piston with decoking fluid, from the flexible tube, through the first and second parts of the tool, vi. means for transmitting said decoking fluid from the hollow space alternately to at least one first ejection means in a direction substantially axial and opposite to that of the supply by the flexible tube or to at least one second ejection means in a substantially lateral direction, said ejection means being arranged in said second part, vii. at least one hydraulic circuit for the auxiliary fluid passing through the first and second parts, separate from the decoking circuit, allowing said auxiliary fluid to move the piston 'so as to bring it at will to one of the positions allowing the transmission of the decoking fluid to the first ejection means or to the second ejection means, viii. and sealing means for controlling the pressure in each of the circuits.   2. Device according to claim 1, characterized in that the element (vii) comprises a single hydraulic circuit opening in a portion of the space located between the movable piston and its housing, such as raising or lowering pressure of the auxiliary fluid can cause displacement of the piston, the device further comprising means for returning the piston intended to return it to its initial position when the pressure auxiliary fluid is lowered.   3. Device according to claim 1, characterized in that the element (vii) comprises two hydraulic circuits opening at points distinct from the space located between the movable piston and its housing, such as a relative raising or lowering relative pressure in the first circuit, relative to the pressure of the second circuit, causes the piston to move in one direction and that, respectively, a relative rise or a relative decrease in pressure in the second circuit, relative to the pressure of the first circuit, causes displacement of the reverse piston of the previous one.   4. Device according to one of claims 1 to 3, characterized in   iO that the flexible tube consists of superimposed layers comprising at least one tight plastic sheath, at least one reinforcement for resistance to internal pressure, comprising a spiral winding with short pitch, and at least one reinforcement for tensile strength and the twist comprising at least two   i5 long pitch crossed windings.   5. Device according to one of claims 1 to 4, wherein the   flexible tube has a rigidity at 20 ° C of 50 to 1000 daN.m2, an elongation breaking strength of 104 to 106 daN and a   2nd torsional limit torque of 102 to 104 da.Nm.   6. Device according to one of claims 1 to 5, wherein at   at least a portion of the second part of the decoking tool, of circular section, enters a recess of larger circular section of the first part of said decoking tool.   7. Use of the device according to one of claims 1 to 6   to first drill a passage through a petroleum coke bed using the substantially axial ejectors and then detach the   wall coke using substantially lateral ejectors.