The present invention concerns a transition piece for joining equipments subject to highly different thermal expansion phenomena.

The invention concerns in particular the oil and gas industry, but can be used in any field in which there is a need to join equipments that require a large compensation, due to important thermal and differential expansion phenomena.

Still more in particular, the present invention will be disclosed with reference to a specific closed system for handling of pet coke out of coke drums part of a so called delayed coking unit (the meaning of this expression will be given in the following of the present description), but can be easily adapted to any system where the connection is needed of equipments subject to highly different thermal expansion phenomena.

It is known that petroleum coke (or abbreviated petcoke) is produced through a thermal cracking process as part of the hydrocarbon processing industry.

Oily residue streams are heated up in a furnace coil at high temperature and routed into a coke drum where it breaks into light hydrocarbons and ultimately in solidified petrol coke. The light hydrocarbons will be sent into refinery downstream units for further processing.

The furnace effluent fills the coke drum from bottom to top continuously and as soon as one coke drum has been filled up, it will be switched to another empty coke drum.

In order to remove the solidified petroleum coke from the full coke drums, traditionally the so-called pit/pad-system is applied. The pit/pad- system comprises a large open concrete floor in front of the coke drums. The coke (or green coke) from the coke drum along with pressure water used in the cutting process, drops onto the coke pad, where the water drains away through the pit and then into the maze. The maze is sized to let any entrained coke fines enough time to settle out. At the end of the maze the clarified water is used to clean water tanks for recycling. Once the coke on the pad has had sufficient time to dewater it is lifted with a Bridge Crane to a coke crusher where it is broken in smaller pieces. The broken coke pieces are then conveyed to the loading facilities.

A coker with such pit/pad system comprises huge steam clouds rising from the coker unit, that can be seen from great distances.

Such pit/pad system has a high environmental impact due to this large amount of steam polluted with coke fines discharging into the atmosphere. The steam contains hydrocarbons, coke dust and aerosols. This causes health problems to the operational and maintenance personnel, especially if they have been exposed to such pit/pad system over a long time. Further, such pit/pad system requires a substantial amount of manual work, especially for operating the overhead cranes or the front loaders, for coke crushing and sludge handling.

Howard M. Feintuch et al. in "FW DELAYED-COKING PROCESS", Chapter 12.2 of "Handbook of Petroleum Refining Processes", Third Edition, McGraw-Hill, 2004, ISBN: 9780071391092, pages 12.33 to 12.89 discusses inter alia coke dewatering which is accomplished through the use of special vessels, known as dewatering bins or drainage silos, for dewatering coke. Basically, two types of dewatering-bin systems are disclosed known as slurry and gravity-flow. In both designs, coke and cutting water pass through a coke crusher. Either system may be totally enclosed to meet stringent environmental requirements or to prevent coke contamination in areas where sandstorms may present a problem.

The slurry system allows coke and water from the crusher to drop into a sluice, where the mixture is washed into a slurry sump. From this sump, a slurry pump transports the coke and water to the dewatering bin. Here the coke settles, and the water is drained off. Final separation of coke fines from the water is accomplished either by a clarifier or by a special decanter. The dewatered coke is moved from the bin onto a conveyor or directly into railcars or trucks.

In the gravity-flow system, coke and water from the crusher drop into a dewatering bin located directly beneath the crusher. The coke-water mixture is allowed to settle, and the water is drained off. Final separation of coke fines from the water is accomplished by special decanters, and the dewatered coke is typically fed from the dewatering bin onto a conveyor.

According to EP2707458, a further environmental -friendly system and method for handling of pet coke out of coke drum unit is disclosed, which can be run automatically and reduce operational costs.

In particular, EP2707458 discloses a closed system that comprises: a crusher for crushing petroleum coke out from coke drum into sellable petroleum coke pieces (smaller); a closed slurry pipe discharging coke slurry to a closed slurry pit; a closed slurry pit; dewatering bins for leading water and coke fines to separate from slurry; a closed drain water pit, separate from the closed slurry pit, for receiving the filtered water and fines; a water settling tank for separating the fines from the water; a clean water tank for purified water from the upper part of the water settling tank; and a device for coke discharge from dewatering bin to the conveyor for further handling.

The closed system of EP2707458 operates over a cycle in which the coke drum after filling is flooded by means of a quench water from the clean water tank, in order to harden and cool the solidified petroleum coke; the coke is then cut to chunks of size suitable for selling, using first high pressure water and then the crusher located between each coke drum and the slurry pit. The coke with water out from crusher forms a slurry stream discharged to closed pit through the closed slurry pipe. From the pit the slurry is then pumped to the dewatering bin where the coke settles and the water with fines is drained off to closed drain water pit. The final separation from water is achieved in the settling tank while the dewatered coke is discharged in a conveyor for final handling. The system described in EP2707458 is referred as delayed coking unit, because after a short residence time in the furnace tubes, coking of oily residue streams is "delayed" until reaching the coke drums (minimum two in batch operating mode) located downstream the heater. This definition is also used in the present description.

The oily residue is typically heated at 490°C to 510 °C in the heater to fill the coke drum in "coking mode". After it has been isolated from the furnace coil the solidification of this medium will take place by cooling the coke drum content first with steam and then with water. When completely cooled (approx. 80°C) and depressurized, this drum is switched to "decoking mode" by cutting the solidified coke. After this step in the operating cycle (ranging from 18 to 24 hours) the discharge of coke pieces out of the coke drum is performed according to the invention here described.

From the above, it is also evident that the delay coking process is a semi-continuous process, wherein the furnace is working in continuous operating mode and the coke drums are working in semi-batch in a wide range of operating temperatures (from 500 °C to 80°C) over a defined cycle. As a consequence, the coke drum(s) is (are) subjected to thermal cycles and differential heating in the opposite walls of the coke drum itself, this differential heating causing a combination of axial and radial deformation called "banana effect". In fact, during the various cycles of the process, the bottom cone of the coke drum expands axially and deforms radially.

Differently, the coke crushing unit for crushing petroleum coke, fed with the coke exiting from the coke drum after quenching, does not undergo comparable thermal cycles and differential heating.

As a consequence, the transition piece connecting the bottom cone of the coke drum with the walls of the crushing unit is joining two equipments that require a large compensation, due to important thermal and differential expansion phenomena.

This problem is solved, according to EP2707458, by providing for a long and difficult mounting and dismounting of the transition piece for each cycle. In fact, according to EP2707458, the coke crusher is connectible to the coke drum by a telescopic chute that can remotely be moved up or down. In the quenching cycle operation the telescopic chute is pulled back with respect to the bottom of the coke drum, and do not connect to the same, so the coke crusher is not connected to the coke drum, and the bottom of the coke drum is closed. In the coke cutting and dewatering cycle operation, the telescopic chute of the coke crusher is moved up so to connect to the bottom of the coke drum and the bottom of the coke drum is opened.

This solution involves a long and difficult mounting and dismounting of the transition piece for each cycle, with high maintenance costs.

In view of all above, it is evident the need for a transition piece that allows to have a fixed and closed system easier to manage and having lower maintenance costs.

In this context it is proposed the solution according to the present invention, with the aim of providing for a transition piece that can ensure proper dilation of the lower cone of the coke drum while granting a reduced environmental impact in terms of waste and particles released into the atmosphere, without any need for high maintenance time/costs (manpower, cranes) or risks of mounting/dismounting huge chutes.

These and other results are achieved according to the present invention by proposing a transition piece composed of two cylindrical pipes arranged coaxiaily, namely an inner pipe and an outer pipe, said inner pipe being higher than said outer pipe, said outer pipe surrounding a central portion of said inner pipe, a stuffing box being provided between said inner pipe and said outer pipe, preferably at the top of said outer pipe, an upper portion of said inner pipe being not surrounded by said outer pipe and being provided with a first flange, said outer pipe being provided with a second flange, said first flange and said second flange being connected by a plurality of extendable connection elements, which allow for both axial and radial relative movement of said first and second flange, and correspondingly of said inner and outer pipe, said inner pipe being apt to be coupled with airtight with an upper equipment and said outer pipe being apt to be coupled with airtight with a lower equipment, said inner pipe and said outer pipe defining a passage connecting a cavity of said upper equipment with a cavity of said lower equipment.

Due to the plurality of extendable connection elements, said inner and outer pipe can move relative to each other both axially and radially, therefore compensating both axial and radial differential thermal dilatations.

At the same time, due to the stuffing box, said inner and outer pipe are coupled to each other with airtight, and due to said inner pipe being coupled with airtight with an upper equipment and said outer pipe being coupled with airtight with a lower equipment, said transition piece therefore allowing for the passage of material without any impact to the atmosphere and/or health problems to the operational and maintenance personnel.

It is therefore an aim of the present invention that of realising a transition piece allowing for overcoming the limits of the solutions according to the prior art and achieving the previously described technical results.

A further aim of the invention is that said transition piece can be realised with substantially limited costs, as far as both the construction and the operative costs are concerned.

Not last aim of the invention is that of realising a transition piece being substantially simple, safe and reliable.

It is therefore a specific object of the present invention a transition piece for joining equipments subject to highly different thermal expansion phenomena, in particular an upper equipment and a lower equipment, wherein said transition piece comprises an upper connection pipe apt to couple said transition piece with said upper equipment, a lower connection pipe apt to couple said transition piece with said lower equipment, and an intermediate piece arranged between said upper connection pipe and said lower connection pipe, said intermediate piece being composed of an inner pipe coupled with said upper connection pipe and an outer pipe coupled with said lower connection pipe, said inner pipe and said outer pipe being arranged coaxially, said inner pipe being higher than said outer pipe, first sliding sealing means being provided between said inner pipe and said outer pipe, an upper portion of said inner pipe being not surrounded by said outer pipe and being provided with a first flange, said outer pipe being provided with a second flange, said first flange and said second flange being connected by extendable connection elements, apt to allow for both axial and radial relative movement of said first flange and second flange; said upper connection pipe being provided at its bottom with a third flange, said third flange being coupled with airtight to said first flange; said lower connection pipe being larger than said outer pipe and being provided at its top with a fourth flange, said second flange of said outer pipe leaning on said flange of said lower connection pipe, second sliding sealing means being provided between said fourth flange and said second flange.

Preferably, according to the present invention, said first sliding sealing means is a stuffing box.

In particular, according to the invention, said first sliding sealing means are arranged at the top of said outer pipe.

Additionally, according to the invention, said second sliding sealing means is an annular gasket.

Alternatively, according to the present invention, said extendable connection elements can be a plurality of compression springs; or a plurality of passive hydraulic cylinders connected with said first flange and said second flange by means of ball joints; or a plurality of active hydraulic cylinders connected with said first flange and said second flange by means of ball joints and operated by a hydraulic power unit.

The invention will be disclosed herein below for illustrative, but non limitative purposes, according to a preferred embodiment, with reference in particular to the figures of the enclosed drawing, wherein:

- figure 1 shows a schematic section view of part of an upper equipment, part of a lower equipment and a transition piece according to the present invention, between said upper and said lower equipment,

- figure 2 shows a schematic section view of part of the transition piece of figure 1 , and

- figure 3 shows a schematic section view of part of the stuffing box of the transition piece of figure 1.

Making reference to the figures, a transition piece according to a preferred embodiment of the present invention is referred to with 10 and is arranged between an upper equipment and a lower equipment, said upper equipment and said lower equipment not forming part of the present 7 000257

invention.

In particular, said transition piece 10 comprises an upper connection pipe 1 apt to couple said transition piece 10 with said upper equipment, a lower connection pipe 2 apt to couple said transition piece 10 with said lower equipment, and an intermediate piece arranged between said upper connection pipe 1 and said lower connection pipe 2, said intermediate piece being composed of two cylindrical pipes arranged coaxially, namely an inner pipe 11 and an outer pipe 12, said inner pipe 11 coupled with said upper connection pipe 1 and being higher than said outer pipe 12, said outer pipe 12 being coupled with said lower connection pipe 2 and surrounding a central portion of said inner pipe 11 , a stuffing box 13 being provided between said inner pipe 11 and said outer pipe 12, preferably at the top of said outer pipe 12, an upper portion 11' of said inner pipe 11 being not surrounded by said outer pipe 12 and being provided with a first flange 14, said outer pipe 12 being provided with a second flange 15, said first flange 14 and said second flange 15 being connected to each other by twelve compression springs 16, acting as extendable connection elements between said first flange 14 and said second flange 15, and therefore between said inner pipe 11 and said outer pipe 12 and allowing for both axial and radial relative movement of said first flange 14 and second flange 15, and correspondingly of said inner pipe 11 and said outer pipe 12.

Additionally, said first flange 14 of said inner pipe 11 is coupled with airtight with a third flange 3 of said upper connection pipe 1 and said second flange 15 of said outer pipe 12 is coupled with airtight with a fourth flange 4 of said lower connection pipe 2. The airtight sealing between said second flange 15 of said outer pipe 12 and said fourth flange 4 of said lower connection pipe 2 is achieved by means of a sliding seal, in particular an annular gasket 21. As a consequence, said transition piece 10 defines a passage with airtight connecting a cavity of said upper equipment with a cavity of said lower equipment.

In particular, the compression springs 16 absorb the longitudinal expansion and accompany the radial expansion, giving rigidity to the system, while the inner pipe 11 and the outer pipe 12 (forming a telescope configuration) can slide one inside the other by absorbing the radial dilatations and, thanks to the stuffing box 13, ensure the sealing.

The stuffing box 13 provides for the ability of the transition piece 10 to maintain airtight when axial relative movement of said inner pipe 11 and said outer pipe 12 occurs, due to axial differential dilatations of the components of the transition piece.

In particular, said stuffing box 13 is composed of a cup ring 17, which is advantageously divided into a plurality of semicircular sections, said cup ring 17 forming a housing for a pack 18, and a lantern ring 19, which is advantageously divided into a plurality of semicircular sections and which can be tightened to said cup ring 17 by means of a plurality of bolts 20.

Moreover, the annular gasket 21 provides for the ability of the transition piece 10 to maintain airtight when radial relative movement of said intermediate piece composed of said inner pipe 11 and said outer pipe 12 with respect to said lower connection pipe 3 occurs, due to radial differential dilatations of the components of the transition piece.

In particular, the sealing of the connection between said second flange 15 of the outer pipe 12 and said fourth flange 4 of the lower connection element 2 is obtained by means of a sliding seal, i.e. by providing for an annular gasket 21 arranged on top of said fourth flange 4 of the lower connection element 2, said second flange 15 of the outer pipe 12 leaning on said annular gasket 21. Said annular gasket is advantageously divided into a plurality of semicircular sections, each section being coupled to said fourth flange 4 of the lower connection pipe 2 by means of a plurality of bolts.

In particular, said annular gasket (21) is a metal gasket (preferably made of Cu Ni 14AI3 in order to ensure the least possible friction).

Thanks to the ability to allow both axial and radial relative movement of its components, the transition piece 10 allows for connecting said upper equipment and said lower equipment compensating relative movements due to differential thermal dilatations. Additionally, in order to best accomplish this goal, under the operating conditions occurring at the outlet of a coke drum, the internal walls of the transition piece have a smooth surface with no dead spots allowable for the accumulation of fine solids. Moreover, since the pet coke is an abrasive material, the internal walls of the transition piece are lined with a material having a high hardness and strength, and being resistant to erosion. Preferably, said material can be a martensitic material, more preferably said material is Corodur 59L.

Depending on the severity of the differential thermal dilatation, both axially and radially, rather than the compression springs 16, different extendable connection elements between said first flange 14 and said second flange 15, and therefore between said inner pipe 11 and said outer pipe 12 can be used in order to allow for both axial and radial relative movement of said inner pipe 11 and said outer pipe 12.

In the case in which the thermal differential dilatations are very important, the springs 16 can be replaced by passive hydraulic cylinders (shock absorbers), i.e. hydraulic cylinders with springs. In order to compensate not only the axial deformations but also the radial deformations the passive hydraulic cylinders are connected with said first flange 14 and said second flange 15 of said inner pipe 11 and said outer pipe 12 of the transition piece 10, by means of ball joints.

In case of still bigger thermal differential dilatations, active hydraulic cylinders can be used as extendable connection elements between said inner pipe 11 and said outer pipe 12, said active hydraulic cylinders being provided with and hydraulic power unit that operates in order to compensate an axial deformation. In this case also, ball joints are provided to connect said active hydraulic cylinders with said first flange 14 and said second flange 15 of said inner pipe 11 and said outer pipe 12 of the transition piece 10, in order to compensate the radial deformations in addition to the axial deformations.

Example

In order to assess the performance of the transition piece according to the present invention, it was tested in a plant for gaining sellable petroleum coke pieces out of solidified petroleum coke in a coke drum unit according to EP2707458 having the following process data: pet-coke daily flowrate of 900Tonn/cycle and 1196Tonns/day, number of cycles of 1 ,33 per day (each cycle duration is 18 hours), cutting time of 4 hours, cutting water amount of 275 m ³ /h, numbers of coke drums: 2.

In particular, each coke drum had an internal diameter of 8077mm and a total height of 35037mm, and the bottom cone main dimensions were the following: internal diameter 8877mm (upper part) and 1467 (bottom part), total length 7682mm.

Under such conditions, the transition piece according to the present invention had the following main dimensions:

Diameter: 1370mm

Length: 4384mm

and is able to allow a maximum allowable axial deformation of 100mm (average axial deformation of 50mm), and a maximum allowable radial deformation of 110 mm (average radial deformation of 85 mm).

The present invention was disclosed for illustrative, non limitative purposes, according to a preferred embodiment thereof, but it has to be understood that any variations and/or modification can be made by the persons skilled in the art without for this reason escaping from the relative scope of protection, as defined in the enclosed claims.