EP3463639A1

EP3463639A1 - Anti-clogging device for the upflow of a fluid

Info

Publication number: EP3463639A1
Application number: EP17723714.6A
Authority: EP
Inventors: Frederic Augier; Frederic Bazer-Bachi
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2016-05-30
Filing date: 2017-05-19
Publication date: 2019-04-10
Also published as: FR3051682A1; US11319505B2; CN109414669A; US20200255764A1; FR3051682B1; WO2017207294A1

Abstract

The invention relates to a device (1) for the upflow of a single-phase fluid (8), comprising at least two solid particle beds (2, 3) and at least one means (5) for diverting part of the fluid (8), as well as to the use of said device.

Description

ANTI-COLLAPSE DEVICE FOR ASCENDING CIRCULATION

A FLUID

TECHNICAL FIELD OF THE INVENTION

The invention relates to the field of devices for the upward flow of monophasic fluids through a bed of solid particles.

The invention is particularly suitable for devices in which the beds of solid particles tend to clog, causing differential pressures across the beds can become prohibitive.

PRIOR ART In the context of the pretreatment of vegetable oils, fixed bed pre-treatment type solutions can be used in order to reduce the content of dangerous species for downstream hydrotreatment catalysts, for example phospholipids (US2011138680A). Since the duration of use of the bed is limited by its clogging, it is necessary to operate a series of permutation beds ("swing" in Anglo-Saxon terminology), in order to replace the catalyst of a bed while the the pretreatment is continued with another bed.

In these pretreatment reactors, the hydrodynamics is characterized by a downward movement (or "downflow" in the English terminology) monophasic liquid oil, until the differential pressure across the bed is that is, the difference between the pressure at the inlet and at the outlet of the bed becomes too great because of the clogging of a fraction of the bed, necessitating the permutation towards a reactor installed in parallel. Although not necessarily mentioned in the patent dealing with the pretreatment of vegetable oils, the implementation of reactors permutation is the general rule on an industrial scale. The clogging can be delayed by capturing the species resulting in the formation of a deposit on the catalyst beds or adsorbent beds. The document FR 3014899 teaches the sequence of two adsorption steps on particular adsorbents in order to capture in particular the insoluble species clogging. However, once the bed is clogged, it is necessary to stop the operation to clean the adsorbent, while a significant portion of adsorbent is still free of deposit.

Indeed, this clogging is not homogeneous over the entire height of the fixed bed: it is likely that the upstream part of the bed, in the direction of flow, is more clogged than the downstream part. The lifespan of the fixed bed could therefore be increased if it were technologically possible to better utilize the entire height of the bed.

US Pat. No. 3,607,000 discloses two by-pass solutions of the fluid, that is to say a fraction of a fixed bed, or of the entire catalytic bed, with different lengths of tube. derivation. The bypass tubes are provided with inlet rupture discs, possibly calibrated with different breaking pressures, or, in the case of the derivation of the entire bed, an outer valve. However, the proposed system can only be used with downflow.

US 5,939,031 discloses a fixed bed reactor in which gas and liquid flow countercurrently. The reactor comprises a catalyst bed surmounted by a downwardly flowing liquid distribution plate and a device for diverting this bed to enable a portion of said liquid to be deflected. The bypass device is provided with regulating means for regulating the amount of liquid diverted by this device. The regulation means of the bypass device are implemented as a function of the liquid level in the distribution plate when the bed is clogged and the liquid flow is effected by siphon effect between a high liquid level triggering said effect and a low level of liquid ending this siphon effect, thereby allowing to regulate the amount of liquid diverted. As long as the bed is not clogged, even if the pressure difference increases, the bypass device does not trip. This implementation tends to generate large variations in flow rate and / or pressure across the bed of solid particles. These variations can generate instabilities, more or less periodic, or punctual stops of the fluid flow through the bed.

US Pat. No. 7,521,027 discloses a means of diversion through which the flow increases mechanically progressively due to a section at the outlet of said means correlated with the pressure drop in the catalytic bed, the increase in flow being achieved by way of a mechanical part pushed by the fluid, said part being held in place by a return means. Fluid passes through the bypass means from a certain threshold and its flow rate increases gradually by continuous regulation of the bypass means. This document mainly addresses the downward flows, with an output of the complex bypass means comprising a conduit forming a half-turn. This text does not address the problem of clogging the derivation means.

During the implementation of a downflow, there is a risk that the clogging elements circulated with the fluid foul the bypass ducts, even if no fluid flows through these elements, simply by falling down into said ducts. Now it is quite possible that the bypass means do not work as expected due to this fouling, not deriving the necessary fluid portion while the differential pressure to trigger this means is reached. OBJECT AND INTEREST OF THE INVENTION

The subject of the invention is a device for the upward circulation of a monophasic fluid comprising

at least two beds of solid particles held on their lower surface by means for dispensing said fluid and on their upper surface by means for holding said particles,

each bed comprising at least one means of diversion of a part of said fluid, fixed to said dispensing means and to said holding means, said bypass means comprising a duct whose lower end opens below the lower surface of said dispensing means and whose upper end opens above said holding means, said duct comprising means for restricting the passage of the actuated fluid by the differential pressure across said bed.

An advantage of the device according to the invention with respect to a device in which the flow is down is a gain in compactness by the simplification of the bypass means. In the particular case where the device according to the invention is fixed to fixed bed support grids, the assembly obtained has a high compactness and excellent mechanical strength. Finally, another advantage of the device according to the invention is its possible implementation in an existing reactor comprising at least two beds, without it being necessary to modify the already existing internal elements such as grids or catalyst support.

DETAILED DESCRIPTION OF THE INVENTION The device according to the invention comprises at least two beds of solid particles in the same enclosure. The number of beds can be adjusted according to the nature of the clogging. Thus, if the clogging tends to occur at the entrance of the bed on a small thickness, one can multiply the number of beds, the beds being successively derived through the device according to the invention as they clog. This results in the use of all the solid particles contained in the device, greatly increasing the duration of use of the device relative to a fixed bed which does not include bypass means as the device according to the invention.

The device according to the invention is adapted to the upward circulation of a monophasic fluid, particularly a monophasic fluid clogging. The term "monophasic fluid clogging" means a fluid whose circulation in a bed of particles leads to the formation of a deposit in said bed, this deposit impeding the circulation of said fluid. This deposit can be formed both on the catalyst grains and between these grains. The progressive formation of the deposit in the bed, or clogging of the bed, leads to an increase of the differential pressure across said bed, that is to say to an increase in the difference between the pressure measured at the inlet and at the outlet of said bed in the direction of circulation of the fluid. This gradual formation of a deposit may also result in a degradation of the performance of said bed, requiring, for example, either to modify the operating temperatures, or the fluid flow rates to maintain a given reaction or separation activity. Said monophasic fluid is advantageously a liquid, and very advantageously an oil comprising triglycerides and / or free fatty acids and / or esters.

Upflow has several advantages. For example, it is possible to impose a sudden point variation of flow rate in order to favor unclogging of the bed. The sudden change in flow has the effect of "loosening" the bed, that is to say to increase its void rate punctually, and to break the deposit during formation. This declogging makes it possible to delay the implementation of a bypass of the bed, provided that the bypass means is not activated during the sudden change in flow rate. To implement the unclogging of pressure, a small space will advantageously be arranged between the upper surface of the bed and the particle holding means, advantageously a perforated plate or a grid, said means being placed above the upper surface of said bed. By small, is meant a space whose height is at most 10% of the height of the bed, preferably at most 5% of the height of the bed, very advantageously at most 3%, at most 2%, at most d% of the height of the bed, said height of the space above the bed being non-zero. The layout of this small space induces a gain in compactness a little less important to the benefit of a longer duration of operation of the catalyst bed. There is therefore an interesting synergy by coupling the bypass technology and operating techniques of solid relaxation. An advantage of the upflow is that the bypass means can not be fouled by clogging elements possibly flowing with the fluid when said means is not actuated. Indeed, any element possibly entering into said means would come out by gravitational effect. Since the device according to the invention is used for the upward circulation of a monophasic fluid, it is essential for the upper part of the bypass means to open at least at the level of the upper surface of the particle bed so that the output of said means can not be clogged by the particles of said bed. Thus, the combination of the device according to the invention and an upward circulation mode prevents the bypass means from being damaged, fouled or degraded by deposition and / or accumulation of debris (fines of particles, crystals, metal breakage, intermediates or by-products of chemical reaction ...) in the bypass means, and in particular impeding the operation of the restriction means. Said passage restriction means may advantageously be a mechanical type means. This means can also incorporate control components, for example electrical control components, and allowing control outside the device of the invention. This means may further comprise components for measuring the flow of the fluid and be integrated in a control loop. This means can thus comprise any control and / or regulation component known to those skilled in the art.

Said restriction means is actuated by the differential pressure across said bed, which is also called pressure drop. The pressure drop is induced by the circulation of the fluid through the bed of solid particles. It increases gradually as deposits form in said particle bed. The restriction means can either progressively open the passage in said bypass means from the beginning of the increase of the pressure drop across the bed, or be actuated only from a certain value of this loss of pressure. load, called threshold value. The operating mode, as well as, if appropriate, this threshold value are determined by the person skilled in the art as a function of the mechanical and operating stresses of the method in which the device according to the invention is implemented, such as height fixed beds, clogging speed, power of the fluid circulation devices (pumps, compressors), mechanical resistance. According to a preferred embodiment, said restriction means comprises:

a flared tubular portion whose orifice having the smallest section is oriented upstream of the conduit of the diversion means,

a movable part mounted in said flared tubular portion so as to allow movement between a closed position and a maximum open position, the positioning of the movable part being a function of the flow of fluid in said flared tubular portion, and

a return means acting on the moving part to move it towards the closed position in which the moving part obstructs the orifice of the flared tubular portion having the smallest section.

The term "upstream" is defined with respect to the direction of fluid flow.

Preferably, the return means acts by the force of gravity of the moving part.

Thus, in this case, the moving part has, by its own weight and because of the positioning of the flared portion, the function of the return means. The biasing means may also include, or be essentially constituted by, a spring.

In order to optimize the tightness of the restriction means in the closed position, the flared tubular portion and the movable part can assume any shape allowing the movable part in the closed position to cooperate with the flared tubular portion to achieve this seal. Preferably, the flared tubular portion has the shape of a truncated cone and the movable piece has the shape of a ball or a truncated cone.

According to another preferred embodiment, the restriction means comprises:

at least one plate mounted around an axis on the upper end of the duct of the bypass means so as to allow movement between a closed position and a maximum open position, the positioning of said plate being a function of fluid flow in the diversion means, and - A return means acting on the plate (s) to move it to the closed position in which the plate (s) obstruct (s) the end of the conduit.

In this other embodiment, the biasing means may preferably comprise a rod in the extension of the plate and a mass located at the free end of the rod and acting as a counterweight relative to the axis of mobility. of the plate.

Said particle holding means is disposed above the upper surface of said particle bed to prevent expansion of the catalyst bed due to the upward velocity of the fluid. Said holding means is fluid permeable and impervious to particles. Said derivation means is fixed on the one hand to said distribution means, and on the other hand to said holding means. This method of attachment ensures excellent mechanical strength of said bypass means with very good compactness, the ends of the bypass means flush with the surfaces of the dispensing means. Said holding means is advantageously a perforated plate or a grid.

In a preferred embodiment, the device according to the invention comprises at least two bypass means per bed. In this arrangement, the means for restricting the passage of said bypass means can advantageously be actuated by differential pressures across said different bed. Thus, the bypass means are independently actuated for different differential pressure values, allowing gradually to derive larger and larger amounts of fluid as the bed becomes clogged.

Said derivation means makes it possible to ensure that a fraction of the fluid does not pass through the solid particle bed. Said derivation means comprises a section which occupies between 0.5 and 20% of the section of said device, advantageously between 1 and 10% of the section of said device, said section being measured perpendicularly to the direction of flow of the fluid. It is indeed important that the presence of said means disturbs as little as possible the general flow of the fluid through the bed.

The invention also relates to the use of the device according to the invention for the pretreatment of crude or semi-refined oils. The filler treated in the device used according to the invention is an oil containing triglycerides and / or free fatty acids and / or esters.

Said oil comprises insoluble clogging species particularly harmful to the activity and the life of the oil conversion catalysts. These species can be separated using adsorbent, whose activity decreases rapidly due to clogging by said species. The use of at least one device, advantageously of the device according to the invention for the treatment of an oil containing triglycerides and / or free fatty acids and / or esters, therefore makes it possible to best use the adsorbent contained in said device.

Said oil is advantageously chosen from palm, soya, palm kernel, copra, babassu, rapeseed, camelina, sunflower, corn, cotton, peanut oil, Jatropha curcas, castor oil oils. , flax and crambe and all oils derived for example sunflower or rapeseed by genetic modification or hybridization or from algae or aquatic organisms or from partially modified oils for example by polymerization or oligomerization, such as by for example, "standolies" of linseed oil, sunflower oil and blown vegetable oils, as well as among animal fats and preferably from fat and fat composed of residues from the food industry or from the catering industry . The density at 15 ° C of this oil is advantageously between 850 and 970 kg / m ³ and its kinematic viscosity at 40 ° C between 20 and 400 mm ² / s, and preferably between 30 and 50 mm ² / s.

Said oil generally comprises different impurities and especially heteroatoms such as nitrogen, sulfur or phosphorus. The nitrogen and sulfur contents in the feedstock treated in the device used according to the invention are generally between about 1 ppm and about 100 ppm by weight and preferably below 100 ppm, depending on their nature. They can reach up to 1% weight on particular loads.

According to the invention, said device, fed by said oil and producing a pretreated oil, comprises at least two fixed beds of solid particles, said particles being at least one adsorbent chosen from porous refractory oxides, clays, zeolites, activated carbons, silicon carbide, taken alone or as a mixture, optionally impregnated with one or more alkaline earth phosphates.

Preferably, said adsorbent present, once shaped, an upper outer surface 4 π d ^2/4, where d is the largest characteristic diameter of the section of said adsorbent, preferably of between 1 and 35 mm.

Preferably, said adsorbent is free of catalytic metals selected from groups 6 and 8 to 12.

Said porous refractory oxide is advantageously chosen from porous refractory oxides known to those skilled in the art, and preferably from optionally activated alumina, silica, titanium oxide, zirconium oxide and silica-alumina. and very preferably is a macroporous alumina.

Said porous refractory oxide is advantageously chosen from porous refractory oxides having a macroporosity.

Said porous refractory oxide advantageously has a macroporous volume, measured by mercury intrusion, that is to say a volume comprised in pores with a diameter greater than 500 A, greater than 0.1 ml / g, and preferably between 0.125 and 0.4 ml / g.

Said porous refractory oxide advantageously has a total pore volume greater than 0.60 ml / g, and preferably between 0.625 and 1.5 ml / g and a specific surface area expressed in SBET advantageously between 30 m 2 / g and 320 m 2 / g boy Wut.

The alkaline earths are the elements chosen from beryllium, magnesium, calcium, strontium, barium and radium, preferably chosen from magnesium, calcium and strontium and preferably from magnesium and calcium.

When impregnated, said adsorbent is advantageously impregnated with one or more alkaline earth phosphates in an amount of 0.2% to 40% by weight, preferably 0.2 to 30% by weight, preferably 0 to 30% by weight. , 2 to 20% by weight, very preferably from 0.2 to 10% by weight and even more preferably from 0.5% to 5% by weight relative to the total weight of said adsorbent. Preferably, the alkaline earth phosphate or phosphates are impregnated in all the ways known to those skilled in the art, either by immersion or dry and, preferably, the alkaline earth phosphate or phosphates are impregnated dry on the support.

Preferably, the alkaline earth phosphate or phosphates are formed on the surface of said support of said adsorbent by impregnation of a solution containing phosphates and alkaline earth cations or by two successive impregnations, in a first step, a solution containing the phosphates and in a second time a solution containing the alkaline earth cations. The order of impregnation of said solutions is indifferent. In a preferred manner, the solution containing the phosphates is impregnated first. The impregnation or impregnations are advantageously carried out by immersion or dry and preferably dry. After each impregnation, said support of said adsorbent of said second impregnated reactor obtained is dried at a temperature between 90 and 120 ° C for 4 to 12 hours and then calcined in air at a temperature between 450 and 550 ° C for 2 to 6 hours. Preferably, said adsorbent is shaped into grains of different shapes and sizes.

Preferably, said adsorbent is used in the form of a stack of dissociated elementary particles or in the form of one or more multichannel monoliths installed in series or in parallel. In the case where said adsorbent is in the form of a stack of dissociated elementary particles, said adsorbent is in the form of beads, multilobal rolls, preferably with a number of lobes between 2 and 5 or in the form of Rings, hollow cylinders, hollow rings, Raschig rings, serrated hollow cylinders, crenellated hollow cylinders, cart wheels, Blend saddles or multi-hole cylinders, alone or in a mixture.

Fixed beds of said device may comprise adsorbents having one or more types of shaping. According to a preferred embodiment, only the first fixed bed of said device comprises adsorbents having one or more types of shaping, the first being understood as the first encountered by the fluid. Preferably, the filling rate of said fixed bed, equal to the ratio of the volume filled by said adsorbent to the total volume of said bed, is less than or equal to 64%, preferably between 20% and 64%, and very preferably between 20% and 60%. The degree of filling is adjusted by the loading method of said adsorbent and / or the geometric characteristics of said adsorbent.

Said adsorbent may advantageously be used alone or as a mixture. It is particularly advantageous to superpose different adsorbents in at least two different fixed beds of variable height, the adsorbents having the highest void rate being preferably used in the first fixed bed or beds at the inlet of said device.

According to the invention, said device is operated at a temperature between 50 ° C and 320 ° C, preferably between 50 and 250 ° C, at a pressure between 0.1 and 7 MPa, preferably between 0 , 3 and 1 MPa and with a residence time of said oil on each of said fixed beds between 0.1 and 1.8 hours and preferably between 0.1 and 0.9 hours.

According to a preferred use of the device according to the invention, at least two devices are used in parallel, and advantageously permutable. Thus, it is possible to clean or replace the fixed beds of one of the devices for cleaning purposes when the adsorbent or adsorbents constituting these fixed beds are saturated with solid impurities. The options for the cleaning phase of the saturated fixed bed are known to those skilled in the art and presented, for example, in document FR 3 014 899.

When using several devices according to the invention permutable, the permutation is advantageously carried out when the phosphorus content in the pretreated oil is greater than 2 ppm. The device according to the invention can advantageously be used for refining oils and fats.

Preferably, the device according to the invention is used upstream of any process or any step allowing the treatment of said oils in order to obtain gas oil and kerosene bases that can be incorporated in the fuel pool. In a preferred embodiment, said device according to the invention can be used for the pretreatment upstream of a process for hydrotreating said oils.

In the case where the device according to the invention is used upstream of a hydrotreatment process, the crude or semi-refined oil from pretreated renewable sources constitutes the feedstock of the hydrotreatment process.

Hydrotreating crude or semi-refined oil from renewable sources is already well known and is described in many patents. By way of example, the hydrotreatment process and then the gas / liquid separation followed by a possible hydroisomerization step can be carried out as described in patent FR 2 910 483, FR 2 950 895 and FR 2 932 811. , FR 2,932,812 or EP 2,403,925.

According to a preferred variant, the catalysts will be used in the hydrotreatment process as described in the patent application FR 2 943 071 describing catalysts having a high selectivity for the hydrodeoxygenation reactions.

According to another preferred variant, the catalysts as described in the patent application EP 2,210,663 describing supported or bulk catalysts comprising an active phase consisting of a group VIB sulfide element, will be used in the hydrotreatment process. Group VIB element being molybdenum.

In a preferred embodiment, said device according to the invention can be used upstream of a process for transesterification of said oils so as to produce alkyl esters.

The oils are usually treated in a downflow mode (downflow according to the English terminology). These oils have strong clogging tendencies, in particular because of the presence of phospholipids. The use of an upward flow and the device according to the invention, which will not be clogged by the presence of heavy compounds or viscous impurities because of its configuration for the treatment of oils will therefore be particularly advantageous in allowing an improvement sensitive duration of use of said device with respect to the solutions of the prior art. DESCRIPTION OF THE FIGURES

Fig.l shows a general schematic view of a particular arrangement of the device according to the invention. A monophasic fluid 8 flows upwardly through the device 1. Said device comprises two beds of solid particles 2 and 3. For the sake of clarity, only the elements of the bed 2 are numbered.

The beds are maintained on their lower surface by a dispensing means 4 and by a means for holding said particles 3. Each bed comprises a bypass means 5 comprising a duct 6 and a means for restricting the passage 7 actuated by the differential pressure to through the bed. Fig.2 shows a particular arrangement of the device according to the invention wherein said branching means is disposed at the periphery of said bed of particles. The numbering is identical to that of Figure 1.

EXAMPLES

The example illustrates a use of the device according to the invention and according to the prior art for the treatment of an oil containing triglycerides, free fatty acids and esters. It is illustrated in Fig.3.

A device according to the prior art comprising a fixed bed of solid particles of alumina impregnated with calcium phosphate is crossed by a rapeseed vegetable oil type charge, density 875 kg.nv ³ and viscosity 5 cP. The liquid surface velocity across each of the beds is 7 mm. s ¹ . The device has an inside diameter of 2 m, corresponding to the diameter of the fixed bed. The fixed bed has a total height of 2 m.

Differential pressure, also known as pressure drop, across the fixed bed gradually increases to 0.5 bar (0.05 MPa) in about 45 days. This pressure loss reached, it is necessary to stop the device in order to proceed with the cleaning or replacement of the fixed bed.

The time evolution of the pressure drop is shown in solid lines in FIG. The device according to the invention comprises two catalytic beds 2 m in diameter and 1 m in height each. It is traversed upwardly by the same oil charge as the device according to the prior art (vegetable oil rapeseed, density 750 kg. M ³ and viscosity 5 cP). The liquid surface velocity through each of the catalyst beds is 7 mm. s ¹ .

Each of the beds comprises a bypass means comprising a bypass tube and a progressive opening valve has been installed on a bypass tube. The diameter of the bypass tube is 0.05 m. Each valve is dimensioned to open gradually from 0.2 bar (0.02 MPa) of pressure drop, that is to say of differential pressure, in the catalyst bed.

The two catalytic beds are separated by a height of 50 cm.

The pressure drop across the device, measured between the entrance of the first bed and the output of the second bed, increases gradually over time. The progressive opening of the valve of the first bed is observed shortly after 40 days while the total pressure drop reaches approximately 0.2 bar (0.02 MPa). The differential pressure continues to increase until the valve of the second bed also begins to open, after a hundred days.

The limit pressure drop of 0.5 bar (0.05 MPa) will be reached after about 110 days, thus substantially delaying the shutdown of the device for the replacement or cleaning of fixed beds, while the same total amount of solid particles has been implemented.

Claims

Device for the upward circulation of a monophasic fluid comprising

each bed comprising at least one means of diversion of a portion of said fluid, fixed to said dispensing means and to said holding means, said bypass means comprising a duct whose lower end opens below the lower surface of said means of delivery; distribution and whose upper end opens above said holding means, said conduit comprising a means for restricting the passage operated by the differential pressure through said bed.

Device according to claim 1 comprising at least two bypass means per bed, the passage restriction means of said bypass means being actuated by differential pressures through each of said different beds.

Device according to one of the preceding claims wherein said restriction means comprises:

4. Device according to one of claims 1 or 2 wherein said restriction means comprises:

at least one plate mounted around an axis on the upper end of the duct of the bypass means so as to allow movement between a closed position and a maximum open position, the positioning of said plate being a function of fluid flow in the diversion means, and

- A return means acting on the plate (s) to move it to the closed position in which the plate (s) obstruct (s) the end of the conduit.

5. Device according to one of the preceding claims wherein a small space is provided between the upper surface of the bed and the particle holding means.

6. Use of at least one device according to one of the preceding claims for the treatment of an oil containing triglycerides and / or free fatty acids and / or esters wherein said solid particles are an adsorbent selected from the group formed by porous refractory oxides, clays, zeolites, activated carbons, silicon carbide and mixtures thereof, said device being operated at a temperature between 50 ° C and 320 ° C, at a pressure between 0.1 and 7 MPa and with a residence time of said oil on said bed of solid particles between 0.1 and 1.8 hours.

7. Use according to claim 6 wherein at least two devices according to one of claims 1 to 5 are used in parallel.

8. Use according to one of claims 6 or 7 wherein said adsorbent is selected from porous refractory oxides having a macroporosity. 9. Use according to one of claims 6 to 8 wherein said adsorbent is free of catalytic metals selected from groups 6 and 8 to 12. Use according to one of claims 6 to 9 wherein said device is used for pretreatment upstream of a process for hydrotreating said oil.