TECHNICAL FIELD OF THE INVENTION

[001] The present invention relates to a cutting equipment for cutting a pitch intended to be immerged.

[002] More particularly, the invention relates to an equipment for cutting a pitch rope into pitch granules or likes when the equipment is immerged into a cooling fluid basin.

[003] The equipment according to the invention is adapted for producing shape controlled granules of solid pitch.

BACKGROUND ART OF THE INVENTION

[004] The pitch is a carboneous product obtained as after processing of various heavy hydrocarbons recovered form coal tar processing, reformer decantation oils, crude oil distillation, biomass pyrolytic oil residues and other sources. The pitch is conditioned under different forms according to the end-user specifications and needs. A common form is as solid granules or pellets.

[005] For sake of granulation of various materials, different items of equipments have been designed. According to the way they are operated and the resulting shapes of the produced materials, they can be described as granulators, pelletizers, flakers, shredders etc. The core of the granulator is designed around a cutting means. According to the various configurations possible, the cutting means is composed of items taken from: a cutter, a counter-cutter, a cutting-means enclosure. The cutter can be mobile or static; it can bear various shapes and number of cutting blades. The counter-cutter may be optional and can be mobile or static. A cutting-means enclosure is used to protect the operator; it can be optional according to the design of the granulation equipment. According to the cases, the enclosure can also fulfill the roles of feed hopper or granulated product outlet duct, even if it is not its primary role.

[006] The granulation of pitch, or pitch related products such as carbon black or solid carboneous fuels, can be obtained with various types of granulators.

[007] A first type consists in a vertical pitch extruder that forms pitch rope :»s (US3.334.167). Extrusion is operated underwater. The pitch ropes flow into a pool filled with water until it reaches the bottom of the cooling pool. At the bottom of the cooling pool it is broken into pitch rods of variable lengths by a screw conveyor.

[008] A second type of granulator is designed from a perforated plate (US4.107.382). The pitch flows by gravity through the perforations and forms droplets that fall into a water drum resulting in the formation of pitch pricks.

[009] A third type of granulator is composed of a conveying belt on which the pitch is spread as an irregular layer (US3.836.354). A series of fixed cutters allows forming strings that are then re-cut into irregular brick like pitch solid with guillotines.

[0010] A fourth type of granulator is based on a continuous extrusion of pitch between two embossed rotary molds resulting into the formation of pitch tablets (US5.236.468). Pitch tablets can also be formed with a rotoforming machine (US7.344.368): the liquid pitch is fed hi a rotary drum fitted with perforations leading to the deposition of small amounts of pitch on a conveying belt. These small amounts have to be cooled down to form the desired solid pitch tablets.

[0011] A last granulator is composed of a rotary cutter with a rotary counter-cutter (US4.482.517). Both cutter and counter-cutter are cylinders and are located underwater. The immersion depth is variable. The cutter bears longitudinal cutting blades. The cutter and counter-cutter turn in opposite direction. The speed of the counter cutter can be slightly different of the speed of the cutter. The cutter may have an internal circulation of water which main purpose is to cool down the cutter. Some holes on the body of the cutting cylinder can be used to evacuate this cooling water at specified locations. The resulting solid pitch forms elongated cylindrical granules with crushed ends. [0012] Because of the nature of the pitch to be processed the granulation system includes, in general, a fast cooling of the liquid pitch through a quench. Some of the previous systems were designed to include such a quench. The quenched and the solid pitches form some glass like material that may break during cutting and form some fine glass like powders. It is in general advised to collect these fines and avoid their dissemination. The previous systems were designed to fulfill some of the requirements of quench and limited or no dispersion of fines thanks to recovery of pitch solids in a basin filled with a cooling fluid such as water. The requirement of a controlled shape factor for the solid pitch granules tends to favor the use of granulation systems that allow reaching such a specification. The rotoformer, the embossed rotary molds and the rotary cutter and counter-cutters are therefore preferred equipments for such an aim. The rotoformer leads to the production of small calibrated pitch tablets that present some drawbacks such as an important friability. The rotary molds can be plugged by thick and sticky pitch; additionally they do not allow a satisfying quench of the processed pitch by themselves. An equipment of choice is therefore the combination of immerged cutter and counter- cutter.

[0013] The combination of immerged cutter and counter-cutter is however not free of drawbacks: the rotation and counter rotation of the two cylinders leads to the formation of velocity vortex and velocity fields in the water. The obtained velocity gradients result in the formation of pressure gradients above and bellow the immerged cylinders. This is known as the "Magnus" effect in hydrodynamics. If the width of the Magnus effect may vary according to the speed of rotation of the cutter and counter-cutter it leads to some perturbations of the pitch flow above the cutting means. This perturbation may be negligible pitch flow direction perturbation up to important stream deviations. It can lead to a surfing phenomenon where pitch is deviated from the cutting means and is entrained around the cylinders. The processed pitch is therefore not cut anymore. In some extreme case, because of the simultaneous quench by underwater processing, the entrained pitch forms a shell around the cutter and counter-cutter. The cylinders are not blocked but become unreachable by the pitch fed in the granulator and the equipment must be stopped for maintenance and cleaning.

SUMMARY OF THE INVENTION [0014] The invention provides an item of equipment for extrusion of pitch in the shape of a rope, which goes into water and is cut into segments of the desired and adjustable length by a suitable set of cutter and counter-cutter. The position of the cutting means can be changed according to the required shape for granules or in order to deal with specific cooling constraints linked to the inherent properties of the molten pitch to be granulated.

[0015] The foregoing shortcomings of the prior art are addressed by the present invention.

[0016] According to one aspect of the invention, there is provided an equipment for cutting a pitch rope into pitch granules or likes, the equipment being intended to be immerged into a cooling fluid basin, said equipment comprising some rotatable cutting means comprising a rotatable cutting cylinder with a plurality of blades and a rotatable counter cutting cylinder, said cutting and counter cutting cylinders being arranged mutually for cutting the pitch rope passing between them into pitch granules, the equipment being characterized in that it comprises some first means for guiding a pitch rope flow stream towards the cutting means, said rotatable guiding means being arranged with said cutting means so that the pitch rope flows vertically between the cutting cylinder and the counter cutting cylinder.

[0017] According to an advantageous embodiment, the equipment further comprises some second pitch rope flow stream guiding means arranged under the cutting means so as to guide in the cooling fluid basin the pitch rope cut in the shape of granules out of some cutting means.

[0018] Advantageously, the first and/or second pitch rope flow stream guiding means comprise at least one set of two foils, the two foils being arranged mutually in order to define a pitch guiding channel narrowing toward the cutting means.

[0019] Advantageously, the foils have a hydrodynamic profile. It allows to improve the circulation of the cooling fluid around the first and/or second pitch rope flow stream guiding means when the equipment is immerged in the cooling fluid basin. [0020] In a particularly advantageous embodiment, the foils which present a hydrodynamic profile, comprise a tubular body. It allows a circulation of the cooling fluid into the foils and so an improved cooling of the foils. It also allows a self-circulation of the cooling fluid in the neighborhood of the pitch rope flow stream guiding means.

[0021] According to a particular configuration, the foils of the first pitch rope flow stream guiding means are arranged for forming an inlet supply hopper.

[0022] Advantageously, the foils are provided with at least one aperture for the passage of cooling fluid when the equipment is immerged in the cooling fluid basin.

[0023] The set of cutting and counter-cutting cylinders is fitted with a cutting means enclosure. The presence of the enclosure allows to provide a control of the flow stream around the cutting means in order to guide the pitch rope between the cutting means and to cancel the undesirable consequences linked to the Magnus effect. The cutting means enclosure is also designed to allow an optimized thermal management of the pitch thermal quench in the neighborhood of the cutting means. Advantageously, the enclosure is arranged around the cutting means to allow a cooling fluid circulation around the cutting means induced by the rotation of said cutting means.

[0024] Some gaps could also be provided between the enclosure and the first and/or second pitch rope flow stream guiding means so that to allow a renewal of the cooling fluid in the neighborhood of the cutting means.

[0025] According to a particular embodiment, the enclosure and the first and/or second pitch rope flow stream guiding means are integrally formed on the enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features of the invention will become more clearly apparent from the following description of a specific embodiment of the invention given as non-restrictive example only and represented in the accompanying drawings in which :

- figure 1 schematically illustrates a granulator system comprising an cutting equipment according to the invention ; - figure 2 schematically illustrates a detailed view of a cutting equipment according to a first embodiment of the invention ;

- figure 3 schematically illustrates a detailed view of a cutting equipment of figure 1 according to a second embodiment of the invention ;

- figure 4 schematically illustrates a detailed view of a cutting equipment of figure 1 according to a third embodiment of the invention ;

- figure 5 schematically illustrates a detailed view of a cutting equipment of figure 1 according to a fourth embodiment of the invention ;

- figure 6 schematically illustrates a detailed view of a cutting equipment of figure 1 according to a fifth embodiment of the invention ;

- figure 7 schematically illustrates a detailed view of a cutting equipment of figure 1 according to a sixth embodiment of the invention ;

- figure 8 schematically illustrates apertures in upper guiding foil for optimized water circulation ; and

- figure 9 schematically illustrates half pipes built in upper guiding foil for enhanced cooling by coolant circulation.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

[0026] Referring to figure 1, the granulator is composed of a pitch feed drum 10 with extrusion nozzles 11, a cooling fluid basin 30 and an equipment for cutting pitch.

[0027] In the described embodiment, the equipment for cutting pitch comprises some rotatable cutting means 60, 70, a cutting-means enclosure 50, some first means 40 for guiding a pitch rope flow stream towards the cutting means 60, 70 and some second means 90 for guiding in the cooling fluid basin 30 the pitch rope 20 out of some cutting means 60, 70 in the shape of granules 80. [0028] The rotatable cutting means 60, 70 comprise a rotatable cutting cylinder (thereafter called rotary cutter 60) with a plurality of blades and a rotatable counter cutting cylinder (thereafter called rotary counter-cutter 70), said rotary cutter 60 et rotary counter cutter 70 being arranged mutually for cutting the pitch rope 20 passing between them into pitch granules 80. The rotatable cutting means will be described in detail later.

[0029] The first flow stream guiding means are located above the cutting means 60, 70, between the pitch feed drum 10 and the cutting means 60, 70. They will be called thereafter "inlet flow stream guiding means 40".

[0030] The second flow stream guiding means are located under the cutting means 60, 70. They will be called thereafter "outlet flow stream guiding means 90".

[0031] Under operation, the pitch is extruded from feed drum 10 through the nozzles 11 located at the bottom of the pitch feed device. The pitch flows under the shape of a rope 20 into the cooling basin 30.

[0032] The pitch rope 20 in motion is guided by means of inlet flow stream guiding means 40. This guiding is done without any contact between the pitch and the inlet flow stream guiding means 40.

[0033] At exit of the inlet flow stream guiding means 40, the pitch rope 20 is cut into pitch granules 80 by pinching between the rotary cutter 60 and the rotary counter-cutter 70. The rotary cutter 60 and the rotary counter-cutter 70 are cylinders and are located underwater. The immersion depth is variable, The rotary cutter 60 bears longitudinal cutting blades. The rotary counter-cutter 70 is longitudinally serrated. In alternate declinations of the guiding means, the rotary counter-cutter 70 can be a smooth cylinder. The rotary cutter 60 and the rotary counter-cutter 70 rotate in opposite direction. According to the declination of the guiding means, the speed of the rotary counter-cutter 70 can be slightly different of the speed of the cutter. In a preferred embodiment, the rotary counter- cutter 70 is longitudinally serrated and the rotary cutter 60 and the rotary counter-cutter 70 rotate in opposite direction at the same speed. The speed of rotation of the rotary cutter 60 and the rotary counter-cutter 70 can be modulated. The pitch between the rotary cutter 60 and the rotary counter-cutter 70 can be modified. [0034] The resulting pitch granules 80 form elongated cylindrical granules with more or less deformed ends. The resulting pitch granules 80 flow down by gravity and is guided by an outlet flow stream guiding means 90.

[0035] Referring to figures 1, 4, 5, the inlet flow stream guiding means 40 consists in a set of two foils 401 which are composed of plate elements oriented in a given direction in order to define a guiding channel 400 for the pitch rope 80. The position of the foils 401, their length and orientation angle are defined according to: (i) the diameter of the rotary cutter 60 and the rotary counter-cutter 70 cylinders, (ii) the speed of rotation of the rotary cutter 60, (iii) the pitch between the rotary cutter 60 and the rotary counter-cutter 70 cylinders, (iv) the flow rate of the pitch rope 20 and (v) the immersion depth of the granulator defined as the level difference between the surface of the cooling basin 30 and the position of the axis of the rotary cutter 60. These five parameters control the magnitude of the over pressure field and the velocity gradient, known as "Magnus effect", generated by the rotation of the rotary cutter 60 and the rotary counter-cutter 70 cylinders. The position and the shape of the set of the two foils 401 of the flow stream guiding means 40 allow a physical barrier to the over pressure field and an guidance of the velocity gradient according to flow stream directions that allow a control of the run of the pitch rope 80 from the nozzles 11 to the cutting mean.

[0036] The two foils of the inlet stream guiding means 40 can alternatively be set at a fixed angle with an arrangement countering eventual undesired edge effects at the extremities of the foils. This is achieved through the use of an inlet stream guiding means

40 consisting in a set of two foils joined by end plates forming an immerged guiding hopper 411. The overall shape of the immerged guiding hopper 411 is defined so that the over pressure field and the velocity gradient generated by the rotation of the rotary cutter 60 and the rotary counter-cutter 70 cylinders are efficiently countered.

[0037] The shape of the set of the foils of the inlet stream guiding means 40 can be adjusted in order to present foils with a hydrodynamic profile 421 deduced from the hydrodynamic behaviour of the self circulating cooling fluid in the neighborhood of the inlet stream guiding means 40 (figure 7). In addition to the previously mentioned counter- measure effect against the undesired "Magnus effect", the use of foils with a hydrodynamic profile 421 allows an intensified guidance of the self circulating cooling fluid in the neighborhood of the inlet stream guiding means 40. It noticeably cancels dead-waters and closed recirculation loops at the bottom of the inlet stream guiding means 40 and right at the inlet of the cutting mean.

[0038] Advantageously, the foils with a hydrodynamic profile 421 can present a hollow body 422 allowing the internal circulation of a stream of a cooling fluid for enhanced cooling of the foils with a hydrodynamic profile 421 and of the self circulating cooling fluid in the neighborhood of the inlet stream guiding means 40.

[0039] The set of two foils 401 or the immerged guiding hopper 411 can be engineered to present some apertures 431, 432, 433 allowing an additional self-circulation of the cooling fluid from the cooling basin 30 to the gap between the two foils 401 or the inner part of the immerged guiding hopper 411 as illustrated on figure 8. These apertures can be any of the following: (i) square or rectangular apertures 431 regularly spaced or not along the foil, (ii) round or oblong apertures 432 of regularly spaced or not along the foil or (iii) toothed apertures 433 located on top of the foil and of variable pitch, width and length. These apertures allow a renewal of the self circulating cooling fluid and allow reaching an efficient quench of the pitch rope and an enhanced thermal management in the area of the two foils 401 or the immerged guiding hopper 411.

[0040] The set of two foils 401 or the immerged guiding hopper 411 can be engineered to present half pipes or hollow bodies 441 at the back of the foil. The half pipes or hollow bodies 441 fulfil the same role as the a hollow body 422: they allow the internal circulation of a stream of a cooling fluid for enhanced cooling of the foils 401 or the immerged guiding hopper 411 and of the self circulating cooling fluid in the neighborhood of the inlet stream guiding means 40. The use of half pipes or hollow bodies 441 at the back of the two foils 401 or the immerged guiding hopper 411 can be combined with the engineered apertures 431 , 432 or 433.

[0041] The outlet flow stream guiding means 90 consists in a set of two foils 901. These two foils 901 are in an inverted position in regard of the two foils 401. The improvements consisting in the immerged guiding hopper 411, the foils with a hydrodynamic profile 421, the foils with a hydrodynamic profile 421 and a hollow body 422, the engineered apertures 43 land 432 or the use of half pipes or hollow bodies 441, proposed for the two foils 401 can alternatively be used for the definition of the outlet flow stream guiding means 90 and the modification of the two foils 901.

[0042] As mentioned below, the equipment could comprise a cutting-means enclosure 50 to protect the cutting-means consisting in the rotary cutter 60 and the rotary counter- cutter 70. The cutting-means enclosure 50, illustrated on figure 5, is composed of segmented enclosure 501 made of sheet plate wrapping the two cylinders. The segmented enclosure 501 is designed to allow a water circulation around the rotary cutter 60 and the rotary counter-cutter 70 induced by the rotation of the two cylinders. The upper and lower parts of the segmented enclosure 501 present an oriented bend of the sheet plate in order to keep a gap 450, 950 between the inlet stream guiding means 40 and the outlet flow stream guiding means 90. The length of the covering of the back of the inlet stream guiding means 40 and the outlet flow stream guiding means 90 by the bend of the sheet plate of the segmented enclosure 501 is selected in function of the local hydrodynamic condition of the self circulating cooling fluid. These gaps allow a renewal of the cooling fluid in the neighborhood of the cutting-means. Additionally the orientation of the resulting cooling fluid in-leakage is controlled by the velocity gradients resulting from the rotation of the cylinders of the cutting means and the channeling imposed by the segmented enclosure 501.

[0043] Alternatively, the cutting-mean enclosure 50 can be designed as a single item which shape combines the effects of the inlet stream guiding means 40 and the outlet flow stream guiding means 90 (figure 6). This full cutting-means enclosure 511 is made of sheet plate wrapping the two cylinders composing the cutting-mean. The upper and lower part of the full cutting-means enclosure 511 is oriented in a similar fashion to the inlet stream guiding means 40 and the outlet flow stream guiding means 90. The design of the full cutting-means enclosure 511 noticeably includes all the improvements proposed for the two foils 401 including adaptations similar to the foils with a hydrodynamic profile 421, the foils with a hydrodynamic profile 421 and a hollow body 422, the engineered apertures 43 land 432 or the use of half pipes or hollow bodies 441.

[0044] The following describes examples of use of a pitch granulator without or with flow controlling means plant as per the here above description. It is understood this is an example among many other possibilities of use for different configurations of the device. [0045] In a first example, the pitch in feed drum 10 is dispatched to pitch extrusion nozzles 11 at a temperature set between 40 to 80°C above the pitch softening point. The current example will use a pitch at 16O ⁰ C.

[0046] Multiple nozzles 11 set in parallel can be used simultaneously. In the current example 6 nozzles are used. It results that 6 parallel pitch ropes 20 are obtained. The nozzles 11 are calibrated to allow a given pitch rope diameter. The current example uses nozzles of 15 mm of diameter.

[0047] The pitch ropes 20 flow down vertically to the cooling basin 30. In this example the cooling basin uses water as a cooling fluid. The cooling water in cooling basin 30 is around 30°C. The cutting-mean consisting in the rotary cutter 60 and the rotary counter-cutter 70 are in operation already. The thermal quench of the pitch ropes 20 starts readily.

[0048] No inlet stream guiding means 40 is used. The pitch ropes 20 then flow between the cutting-mean consisting in the rotary cutter 60 and the rotary counter-cutter 70. The pitch between the rotary cutter 60 and the rotary counter-cutter 70 is tunable. In the current example a pitch of 0.3 mm is used. The speed of rotation of the rotary cutter 60 and the rotary counter-cutter 70 is variable between 30 and 200 rotations per minute. In the current example a maximum rotation rate of 110 rotations per minutes has been used. The immersion depth the entire equipment consisting of the inlet stream guiding means 40 and the cutting-mean can be varied between 100 and 250 mm. The immersion depth is defined by the distance between the axis of rotation of the rotary cutter 60 and the surface of the cooling basin. In the current example an immersion depth of 170 mm is used.

[0049] Undesired pitch entrainment and flow diverting (known as pitch "surfing" phenomenon) has been observed after a few minutes of maintained operation.

[0050] In a second example, the pitch in feed drum 10 is dispatched to pitch extrusion nozzles 11 at a temperature of 15O ⁰ C.

[0051] Multiple nozzles 11 set in parallel can be used simultaneously. In the current example 6 nozzles are used. It results that 6 parallel pitch ropes 20 are obtained. The nozzles 11 are calibrated to allow a given pitch rope diameter. The current example uses nozzles of 15 mm of diameter.

[0052] The pitch ropes 20 flow down vertically to the cooling basin 30. In this example the cooling basin uses water as a cooling fluid. The cooling water in cooling basin 30 is around 40°C. The cutting-mean consisting in the rotary cutter 60 and the rotary counter-cutter 70 are in operation already. The thermal quench of the pitch ropes 20 starts readily.

[0053] The pitch ropes 20 then enter the inlet stream guiding means 40. The inlet stream guiding means 40 is composed of two foils 401 made of metal plates. In the current example the position of the plates, i.e. their gap, their angle and their immersion depth is variable. The gap can be varied between 0.25 and 1.5 fold the diameter of the rotary cutter 60. The gap is defined by the dimension left at the bottom of the two foils 401. The angle can be varied between 10 and 45°. The angle is defined by the angle at the bottom of any of the foil 401 the between the plate and a vertical axis. The immersion depth the entire equipment consisting of the inlet stream guiding means 40 and the cutting-mean can be varied between 100 and 250 mm. The immersion depth is defined by the distance between the axis of rotation of the rotary cutter 60 and the surface of the cooling basin. In the current example an immersion depth of 170 mm is used.

[0054] The pitch ropes 20 are guided and flow vertically between two foils 401. The pitch ropes 20 then flow between the cutting-mean consisting in the rotary cutter 60 and the rotary counter-cutter 70. The pitch between the rotary cutter 60 and the rotary counter- cutter 70 is tunable. In the current example a pitch of 0.5 mm is used. The speed of rotation of the rotary cutter 60 and the rotary counter-cutter 70 is variable between 30 and 200 rotations per minute. In the current example a maximum rotation rate has been used as it defines a worse operation case. No undesired pitch entrainment or flow diverting has been observed under maintained operation for time on stream over 12h.

[0055] In a third example, the previous equipment used in example 2 has been used with an outlet flow stream guiding means 90 consisting in two foils 901. The two foils 901 are made of metal plates. In the current example the position of the plates, i.e. their gap, their angle and their immersion depth is variable. The gap can be varied between 0.25 and 1.5 fold the diameter of the rotary cutter 60. The gap is defined by the dimension left at the bottom of the two foils 901. In this example a gap of 1 diameter was used. The angle can be varied between 0 and 45°. The angle is defined by the angle at the top of any of the foil 901 the between the plate and a vertical axis. In this example an angle of 10 degrees was used.

[0056] All other parameters were kept as per example 2. No undesired pitch entrainment or flow diverting has been observed under maintained operation for time on stream over 12h.