Patent Application
20200164415
This invention relates to the cleaning and maintenance of vertical risers in fluid catalytic converters where the riser has been nearly fully obstructed by a coke buildup.
Vertical risers may be subject to a significant build-up of coke along the walls of the riser and about the feed nozzles, degrading the throughput of the system. It is known to introduce personnel into the riser equipped with a high-pressure hose to manually clean the walls by hydroblasting, also known as hydrodemolition.
A particular problem arises where the coke residue has built up to a point that it blocks the riser. As a result, the introduction of water from the high-pressure nozzles presents a challenge in evacuating the water from the riser. It then becomes dangerous to introduce personnel into the riser.
The walls of the riser are made of refractory. The high pressures used to remove coke build-up are typically in the range of 40,000 psi and those same pressures can also used to remove refractory. Hydroblasting the coke build-up therefore presents a risk of unintentionally damaging the refractory of the riser itself or the feed nozzles that project within the inner diameter of the riser.
It is an object of the invention to provide a means of removing the coke build-up in a riser in a fluid catalytic converter, particularly when the coke build-up has blocked or nearly blocked the riser entirely.
That and other objects will be better understood by reference to this application as a whole. Not all of the objects are necessarily met by all embodiments of the invention described below.
According to the invention there is provided a centralizer body with radially-extending guide arms for abutment against the side wall of the riser. An elongated stem extends below and centrally from the centralizer body and terminates in a plurality of angled nozzles. The apparatus is suspended from an opening at the top of the riser. High pressure water is fed through a tube extending from the opening to the nozzles.
The coke build up and any resulting obstruction tends to be more acute adjacent the feed nozzles of the riser. As the vertical distance from the feed nozzles increases, the build-up of coke along the walls of the riser typically decreases.
The stem is sufficiently long to present the nozzles close to the obstruction, while still allowing the guide arms of the centralizer to engage the walls of the riser at a point that is relatively unhindered by the build-up of coke on the inside surfaces of the wall. In a preferred embodiment, the stem is at least as long as the length of the centralizer body. The stem is preferably modular to allow a combination of stem extensions to increase the distance between the nozzles and the centralizer body. Such adjustable length accommodates different vertical extents of coke build-up between the obstruction and the centralizer body.
In a first stage, the length or angle of the guide arms are selected such that the guide arms are in contact with the inside wall of the riser. As a result, the centralizer body and the nozzles are substantially centered along the longitudinal axis of the riser. The nozzles are angled slightly off axis, for example at 10-15° from the vertical. The unit is suspended vertically from the entrance of the riser and is lowered sufficiently that the nozzles at the end of the stem are adjacent the coke obstruction. The nozzles are fed to produce water jets at 40,000 psi in a narrow angled cone well away from the walls of the riser. The objective of this first stage is to blast away a small diameter orifice in the obstruction to allow water and debris to be evacuated during subsequent hydroblasting.
During the first stage, the contact of the centralizer arms with the wall of the riser keeps the unit centered to ensure a consistent focus for the nozzles in opening a drainage orifice in the obstruction.
Once the orifice has been created, the apparatus is withdrawn from the riser and reconfigured. The guide arms of the centralizer are re-arranged such that they are spaced from contact with the wall of the riser. A lateral pulley is mounted on the cable suspending the apparatus. The angle of the nozzles and the pressure of the water feeding the nozzles are not changed. The unit is then lowered again so that the nozzles are adjacent the orifice. However, because the guide arms are no longer in abutment with the wall of the riser, it is possible for an operator to use the lateral pulley to urge the suspended apparatus and its associated hydroblasting nozzles off the longitudinal axis of the riser and to direct the nozzles to the sides of the orifice. By manipulating the pulley, the nozzles are made to enlarge the orifice by directing the narrow swath of the nozzles around the remaining obstruction.
Once the obstruction has been effectively cleared, there will remain a build-up of coke along the walls of the riser. In a final step, the apparatus is again removed from the riser and reconfigured. The guide arms are brought back into contact with the wall of the riser and the angle of the nozzles are adjusted to at most 45° to be able to reach the walls of the riser from the central longitudinal axis. At that angle, the jet from the nozzles will likely impinge the refractory of the riser, though at an angle of less than 45°. To further reduce the risk of cutting into the refractory or of damaging the riser feed nozzles, the water pressure is also lowered to a range of 35,000 psi or less. The stem may also be shortened. The unit is then lowered while operating the nozzles in order to clean out the remaining coke build-up along the walls of the riser.
Where it is determined that the optimal target area to create a drainage orifice is not along the longitudinal axis of the riser, a slightly different approach is used. The guide arms of the centralizer body are adjusted such that when the apparatus is suspended in the riser, the stem and its nozzles will be aligned with the target area. The balance of the process is substantially as described above.
In one aspect, the invention is a method of removing coke built up in a riser of a fluid catalytic converter in which the coke build up has created an obstruction substantially blocking the riser, comprising:
Preferably, the guide arms are then reconfigured to be in contact with the wall, the angle of the nozzles is enlarged and the water pressure is reduced to a lower pressure and the nozzles are operated at the lower pressure while vertically displacing the apparatus so as to remove coke build up along the riser wall.
In another aspect the invention is a method of removing coke built up in a riser of a fluid catalytic converter in which the coke build up has created an obstruction substantially blocking the riser, comprising:
In that alternative aspect, the method may further comprise, prior to the step of feeding high pressure water to the nozzles to hydroblast a narrow portion, setting angles of the nozzles at an angle of less than 15 degrees from the vertical and, prior to the step of feeding high pressure water to said nozzles while displacing said apparatus, reconfiguring said guide arms to be spaced from abutment with said wall and mounting a lateral pulley to a cable suspending said apparatus.
In a further aspect, the invention is a method of removing coke built up in a riser of a fluid catalytic converter in which the coke build up has created an obstruction substantially blocking the riser, comprising:
The further aspect of the invention may also comprise reconfiguring the guide arms to be in contact with the wall, enlarging the angle of the nozzles and reducing a pressure of the water to a lower pressure and feeding the nozzles with the lower pressure while vertically displacing the apparatus so as to remove coke build up along the wall.
In yet a further aspect, the invention is a method of removing coke built up in a riser of a fluid catalytic converter in which the coke build up has created an obstruction substantially blocking the riser, comprising:
According to that yet further aspect, the last step of hydroblasting the obstruction may comprise reconfiguring the guide arms to be spaced from abutment with the wall and mounting a lateral pulley to a cable suspending the apparatus and may further include the step of feeding high pressure water to the nozzles while operating the lateral pulley to displace the apparatus and nozzles away from the longitudinal axis of the riser to thereby hydroblast an area around the orifice to enlarge the orifice.
The method may further comprise reconfiguring the guide arms to be in contact with the wall, enlarging the angle of the nozzles and reducing a pressure of the high pressure water to a lower pressure and feeding the nozzles with the lower pressure while vertically displacing the apparatus so as to remove coke build up along the wall.
The foregoing may cover only some of the aspects of the invention. Other and sometimes more particular aspects of the invention will be appreciated by reference to the following description of at least one preferred mode for carrying out the invention in terms of one or more examples. The following mode(s) for carrying out the invention are not a definition of the invention itself, but are only example(s) that embody the inventive features of the invention.
At least one mode for carrying out the invention in terms of one or more examples will be described by reference to the drawings thereof in which:
As seen in
In order to accommodate the method aspect of the invention, the guide arms 32 may have varying lengths or may easily be removed and replaced with arms of different lengths. According to the preferred embodiment, the arms 32 are extendible by telescoping. Alternatively the arms 32 may be adjustable in the angle they present to the centralizer body 30 thereby effectively varying the radial extension of the arms.
The elongated stem 34 may also be configured for varying lengths. According to the preferred embodiment, one or more hollow modular stem segments 31, 33 may be attached to one another to extend the overall stem length according to the configuration of the build-up 12 in the riser. Preferably the stem 34 is at least as long and may be longer than the length of the centralizer body 30. In use, the length of the stem 34 is selected to enable the centralizer body 30 to be adjacent a portion of the wall that has sufficiently little coke build up to allow the centralizer body to be substantially centered by the guide arms along the longitudinal axis of the riser while the nozzles are substantially adjacent the obstruction.
According to a method of the invention, the radial extent of the centralizer arms 32 are first arranged such that they are in contact with the wall 16 of the riser 10. The points of contact of the arms 32 with the wall 16 of the riser are preferably vertically spaced from any significant build-up 12 on the wall of the riser, i.e. the centralizer body may be made to operate in contact with a portion of the riser wall that is substantially unhindered by coke build up. Contact between the arms 32 and the wall 16 effectively center the centralizer body or frame 30 along the longitudinal (vertical) axis of the riser 10.
The nozzles 36 are angled slight off axis, less than 15° from the vertical and preferably from 10-15° from the vertical. The apparatus 29 is suspended vertically from the entrance at the top of the riser 10 and is lowered sufficiently that the nozzles at the end of the stem are adjacent (near) the coke obstruction. Prior to the insertion of the apparatus into the riser, the length of the stem is determined by the distance between the lowest most accessible portion of the build-up 12 on the one hand and the lowest portion of the wall 16 that is sufficiently unobstructed by build-up so as to allow effective centering of the apparatus 29 by means of the arms 32 bearing against the wall 16.
The nozzles 36 are fed with high pressure water (preferably approximately 40,000 psi) to produce water jets in a narrow angled cone to effectively bore into the build up at the lowest most accessible point of the build-up. That point coincides with the likely shortest vertical extent of build-up. The objective of this first stage is to blast away a relatively small diameter drainage orifice in the obstruction to allow water and debris to be evacuated during subsequent hydroblasting. During this phase of the operation, the contact between the centralizer arms 32 and the wall 12 of the riser keeps the unit 29 centered to ensure a consistent focus for the nozzles in opening an orifice in the obstruction.
Once the orifice 40 (see
The unit 29 is then lowered again so that the nozzles 36 are adjacent the orifice 40. However, because the guide arms 32 are no longer in abutment with the wall 16 of the riser, it is possible for an operator to use the lateral pulley 42 to urge the suspended apparatus 29 and its associated nozzles 36 off the longitudinal axis of the riser and to direct the nozzles to the sides 44 of the orifice 40. By manipulating the pulley, the nozzles 36 are made to enlarge the orifice 40 by directing the narrow swath of the nozzles around the remaining obstruction.
Once the obstruction has been effectively cleared, there will remain a build-up (50 in
The shape of the coke obstruction in the riser may not necessarily present itself such that the easiest area in which bore a drainage orifice is along the central longitudinal axis of the riser. In such case, a narrow target area for boring a drainage orifice is selected. The guide arms 32 are adjusted so that the stem is aligned with the selected target area when the centralizer body 30 is suspended in the riser with the guide arms in contact with the riser wall 16. The drainage orifice is created by hydroblasting the narrow target area while the apparatus is suspended in the riser. The subsequent steps are as described above.
In the foregoing description, exemplary modes for carrying out the invention in terms of examples have been described. However, the scope of the claims should not be limited by those examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
| Number | Date | Country | Kind |
|---|---|---|---|
| 3025118 | Nov 2018 | CA | national |
