WO2002011877A1

WO2002011877A1 - Novel method for homogeneous loading of solid particles in a chamber

Info

Publication number: WO2002011877A1
Application number: PCT/FR2001/002451
Authority: WO
Inventors: Frédéric JARDIN; Ulysse Pinon; Thierry Patureaux; Emmanuelle Petitjean; Marc Lebouteiller
Original assignee: Totalfinaelf France
Priority date: 2000-08-10
Filing date: 2001-07-26
Publication date: 2002-02-14
Also published as: AU2001279917A1; JP2004505753A; FR2812824A1; US20040217039A1; FR2812824B1

Abstract

The invention concerns a method whereby the chamber (1) is filled at least partly with a liquid (2), and the flux of particles (3) introduced into the chamber (1) is divided, then homogeneously distributed in a gas phase (4) above the surface (5) of the liquid, wherein the particles descend by gravity, to be deposited while forming a fixed bed.

Description

New homogeneous loading process for solid particles in an enclosure.

The present invention relates to a new method for uniformly loading solid particles into an enclosure. This process relates more particularly to the filling of reactors of the chemical or electrochemical, petroleum or petrochemical type, with solid particles in the divided state, which can be in the form of balls, grains, cylinders, pellets, sticks, or other forms, but of relatively small dimensions.

These particles may in particular be molecular sieves or grains of solid catalysts, generally extruded, produced either in irregular form, in the form of beads, or also in the form of mono- or multilobes, the dimensions of which vary, depending on the case, from a few tenths of a millimeter to a few centimeters.

It is to this application that reference will be made more particularly in the remainder of this description, but the method according to the invention naturally applies to the loading of any other type of particles into an enclosure. It is known that a fixed bed reactor has a better reaction yield, when its catalytic mass is charged in the most homogeneous way possible. This homogeneity, which, for reasons of simplicity and efficiency, must be obtained during the catalyst loading phase, ensures uniform and constant contact between the different catalyst grains and the liquid reaction medium, without creating preferential passages for this one.

The loading methods commonly adopted today consist in loading the fixed bed of the reactor using a flexible hose, also called "sleeve" or "sock", from the English translation "sock loading" , or even using buckets filled with catalyst, the content of which is successively poured into the reactor through the orifice of the upper part of the enclosure to be loaded (called "manhole" or "filling orifice") . These methods lead to occasional loading in the reactor, generally favoring the creation of slopes and embankments on the surface of the bed being loaded. The differences in grain orientation and the segregation of the heaviest by rolling along these slopes or embankments naturally lead to heterogeneities, detrimental to the subsequent proper functioning of the reactor. In fact, preferential paths, taken by the liquid reaction phase, then appear in the catalytic bed, due to the random presence of large spaces between the grains of catalyst thus charged. Consequently, the contact of the liquid with the various grains of catalyst, as well as the duration of this contact, decrease and lead to an incomplete chemical reaction, which can lead to an apparent deactivation of the whole of the catalytic mass.

It has also been known for a long time that, to remedy this drawback and consequently increase the homogeneity of a catalytic bed to be loaded, it is possible to carry out a loading no longer punctually, but distributed over the entire section of the enclosure. to load, like a rain. This distribution of solid particles by rain effect is generally carried out using devices placed below a member for supplying catalyst grains, and constituted, for example, by a rotary cone, for a distribution of particles. by centrifugal effect, as described in US-A-3,804,273, or by static elements, onto which fall the catalyst grains and in the direction of which air is sometimes blown laterally, as explained in US-A-4,051 019. Other types of equipment have also been proposed with a view to obtaining a generally homogeneous distribution over the entire surface of the bed to be loaded, for example in FR-A-2 319 427 and, more recently, in DE-Al-198 35 699.

The Applicant has for its part patented a process and a device for the uniform distribution of a solid in divided form in an enclosure, which are the subject, in particular, of EP-A-007,854 and EP-A-116,246, as well as EP-A-769 462.

Unfortunately, if all these loading processes, which we group under the name of “dense loadings” (from the English “dense loadings”), tend towards an increase in the homogeneity of the catalytic mass, they also favor in appreciable proportions a gain in the density of the load itself. This gain in density can be greater than 10%, or even 20%, when a mode of dense loading is used instead of the so-called sleeve method.

It therefore necessarily follows that the spaces between grains of catalyst, in which the reaction fluid of the reactor must circulate, are smaller, which increases the pressure difference between the inlet and the outlet of the charge to be treated in the reactor, difference called ΔP or pressure drop in the reactor.

However, it turns out that, in certain cases and for certain processes, it is necessary for the industrialist to benefit only from the improvement in the homogeneity of the catalytic bed thus obtained, without undergoing the constraint of the increase in the loss reactor charge.

By continuing its work in this area, the Applicant has established that it is possible to obtain this result by distributing the particles in the enclosure to be loaded above a liquid contained in this enclosure and compatible with these particles, the bed of particles thus forming within this liquid.

The Applicant has in fact found that, during dense loads of the conventional type, that is to say in an enclosure containing only a gaseous phase, the increase in the loading density is probably linked to the rate of fall. free of the grains, and therefore their impact energy when they arrive on the bed being formed, associated with a preferential orientation of these grains in the catalytic bed. It therefore appears that the fact of interposing a liquid, in order to decrease this rate of fall, makes it possible to resolve in a simple manner, both the problem of the homogeneous distribution of the grains and that of the increase in density.

The present invention therefore relates to a process for the homogeneous loading of solid particles into an enclosure, characterized in that said enclosure is filled at least in part with a liquid, and in that the flow of particles introduced into the enclosure is divided, then distributed homogeneously in a gaseous phase above the surface of this liquid, within which the particles descend by gravity, to deposit themselves forming a fixed bed.

A first advantage of the process which is the subject of the invention is therefore to obtain good homogeneity of the bed formed, without increasing the loading density. In fact, limiting the rate of fall of the grains in the liquid makes it possible to limit their impact energy, thereby promoting the creation of sufficiently large spaces between the grains and, in the case of catalyst grains, better contact. and a more free passage of the reaction liquid between these grains, without the creation of preferential paths, thereby reducing the pressure drop of the reactor accordingly.

A second advantage of the invention is the possibility of loading grains, in particular catalysts, having a more fragile mechanical strength, for example extrudates in the form of cylinders whose length is several times greater than the diameter, for example a length greater than 5 millimeters or more, for a diameter of the order of a millimeter. These extrudates have a tendency to break, when the dense charged grains in a gaseous atmosphere collide, upon their impact upon their arrival on the catalytic bed. The liquid phase used in the process according to the invention limits this impact energy on the bed, which is the cause of broken grains, while also reducing the attrition phenomena between them, thereby reducing the amount of catalyst fines or dust formed during the loading of the catalyst.

A third advantage of the process of the invention is linked to the reduction in the gas volume in the reactor, due to the presence of the liquid in more or less quantity. This reduction can be a favorable element for the implementation of the loading process, in the case where the particles, in particular of catalyst, have a chemical reactivate with the loading gas, for example the oxygen of the air. It can also be an important economic factor, due to the lower quantity of gas to be introduced into the reactor, when it is a rare or inert gas, such as for example argon or nitrogen.

All types of liquids and their mixtures can be used in the implementation of the process which is the subject of the invention, provided that the grains of catalyst arriving at the upper level of the liquid can freely pass through this liquid to the surface of the bed. catalytic. Those skilled in the art will therefore choose a liquid or a mixture of liquids that are physically and chemically compatible with each other, as well as with the nature of the particles to be charged, including their constitution and the physico-chemical characteristics, such as for example the density and the viscosity. , vary depending on the parameters and precautions to be taken when loading. In the case of a chemical reactor and catalyst particles, the liquid used can be the reaction liquid, a hydrocarbon such as an oil, water, or any other type of aqueous product. A very rapidly evaporating liquid, for example an alcohol, can also be used so as to be evaporated at the end of the loading.

The distance required for a solid particle, such as a grain of catalyst used for loading reactors, to reach its limit speed in a liquid is of the order of a few centimeters, and it is therefore not necessary to have a large amount of liquid above the surface of the catalytic bed. However, the height of the liquid in the reactor evolving as a function of the quantity of catalyst loaded, this height must be constantly maintained greater than that of the bed, throughout the duration of the loading, in order to limit the rate of fall of the grains, as proposed by the present invention. Those skilled in the art will calculate the quantity of liquid directly necessary for loading, or will use known means to adjust this height as a function of the quantities of catalyst loaded. The height of the liquid above the surface of the catalytic bed of particles will preferably be greater than 10 cm.

The loading process which is the subject of the invention allows the use of different types of gas in chemical reactors, the nature of which can vary depending on the reactivity of the catalysts with these gases. In particular, ambient air is generally used for loading reactors, for example hydrotreatment reactors in the petroleum industry, this air possibly being able to be dried or dehydrated to adapt it to the particular conditions necessary for the loading of certain types of catalysts.

Neutral or inert gases, such as argon or nitrogen, can be used for the loading of specific catalysts intended for particular processes, such as for example catalysts for isomerization of light gasolines in an oil refinery.

All the dense loading modes implemented in a conventional manner, that is to say the grain distribution device allows a homogeneous distribution of these along the entire cross section of the reactor or of the enclosure to be loaded, above the surface of a liquid, may be used in accordance with the invention. In particular, when the reactor is to be loaded to its upper part, devices capable of creating a uniform rain in the minimal gas space available at the end of loading above the liquid should be used. Advantageously, will be implemented at the level of the manhole or the filling orifice of the rotary devices arranged under a hopper for supplying grains of catalyst, which can be deployed under the effect of the speed of rotation in the part the highest of the reactor, over at least half of its cross section.

Preferably, the device described in EP-A-769 462 or its equivalents will be used. Indeed, this device comprises a movable axis, on which flexible deflector elements, each having the shape of a vertical strap at rest, are arranged on several levels and articulated so as to be able to be lifted under the effect of centrifugal force . These flexible deflectors, made for example of a rubbery material and driven by a low speed of rotation, generally less than 200 revolutions per minute and preferably less than 150 revolutions per minute, make it possible to limit the breaking of the grains of catalyst which s 'collide during their fall on the deflectors, as well as attrition phenomena, leading to the creation of catalyst fines. For certain uses, the device can be implemented in a fixed manner at the level of the manhole, or lowered into the reactor to then accompany the rise of the catalytic bed during loading. Of course, other grain distribution devices as described above can also be used, the distribution member of which is made of a rigid material, as described in EP 0 470 142 or FR-A-2 721 900. Different types of solid particles can be loaded with the process which is the subject of the invention, such as balls, grains, cylinders, pellets, sticks, mono or multilobe shapes, or any other shape, the different dimensions of which range from a few tenths of a millimeter to a few centimeters. They can be grains of catalysts, molecular sieves, contact masses for the needs of the chemical, petroleum or petrochemical industries. Other types of solid particles, having the dimensions indicated above and requiring homogeneous loading in an enclosure, can of course be used.

The process according to the invention allows the loading of particles having reactivity with the gaseous fluid, due to their very short residence time in the latter, the particles very quickly being found in the liquid medium, which can be chosen chemically. compatible with the nature of the particles. Liquid impregnations can also be carried out on these grains of catalysts, prior to their loading into the reactor, this liquid possibly being of the same nature as that contained in the reactor, or simply chemically and physically compatible with it. Arrangements known to those skilled in the art, such as for example liquid flows in the form of jets, are then necessary upstream of the distribution, to break up the grain aggregates and entrain them in the distribution device by rain effect. The accompanying drawings illustrate in a nonlimiting manner a form of implementation of the method according to the invention, and the results of comparative examples, which will be described below. In these drawings:

- Figure 1 is a schematic view of an enclosure being loaded by the method according to the invention;

- Figure 2 is a schematic view of an enclosure before loading;

- Figure 3 is a schematic view of the same enclosure after loading; - Figures 4, 5 and 6 are representations of photographs of the surface of the catalytic bed after successive loadings of the same grains of catalysts, respectively by the process known as handle in a gaseous atmosphere, after loading under the same conditions as above, but by replacing the sleeve with a dense loading device, and finally after loading in a liquid, in accordance with the present invention. FIG. 1 represents an enclosure 1, for example a chemical reactor, the diameter and the height of which can reach several meters, in which the catalytic bed 6, the mass of which is supported in the reactor 1 by inert balls 7, is in progress loading. According to the invention, above this bed is arranged a liquid 2, for example water. Above this liquid, the gas phase can consist of different gases, in particular air. The catalyst grains are introduced continuously into the upper part of the reactor, for example by means of a feed hopper 3, then fall onto a distribution device making it possible then to obtain a homogeneous distribution of these grains in the reactor 1.

The device shown and used in a preferred manner, known commercially as "Densicat", is described in detail in EP-A-0 769 462. This device consists of flexible rubber deflectors, secured at several levels to a movable axis, whose rotation speed is variable, to adjust the quality of the load. The deflectors deviate as much from the movable axis as the rotation speed of the latter increases, this speed possibly reaching more than a hundred revolutions per minute. The grains of catalysts, after their fall on these rotating deflectors, are distributed in the manner of a rain in the gas phase over the entire cross section of the reactor, above the surface of the liquid 5. The rate of fall of the grains passing through the liquid 2 is then slowed down, thus making it possible to reduce the impact energy of the grains, when the latter meet the surface of the catalytic bed 6. Thanks to this reduction in energy, the grains can settle more gently and homogeneously on the catalytic bed, without agglomerating, and thus create regular spaces between them, thereby reducing the density of the charge.

It is important to ensure, during loading, that the height of the liquid above the catalytic bed remains at least at its minimum level, and will be adjusted by any known means if necessary.

The liquid phase introduced into the reactor before loading can have any height, but this must preferably be greater than ten centimeters, corresponding to the minimum level 8 indicated in FIG. 2.

At the end of loading, the liquid reaches its upper level 9, indicated in FIG. 3. The device consisting of deflectors described above makes it possible, by its small size, to be operational even if the maximum level of the liquid 9 is very close to l 'high end of the reactor.

In FIG. 4, we can see the appearance of the surface of the catalytic bed, after loading with a feed sleeve, which makes it possible to disperse the grains of catalyst on the surface as quickly as possible and by human means. bed. The spaces between the grains are distributed randomly and the grains are not packed, offering the reaction liquid significant and numerous preferential paths, which lead to an incomplete chemical reaction. The loading is not homogeneous and not dense. In FIG. 5, on the contrary, the grains of catalyst are very agglomerated and occupy the maximum space available, the voids between the particles thus being very small. The dense loading carried out for this test made it possible to load the reactor in a homogeneous and dense manner, that is to say having a maximum of grains of catalyst in the reaction liquid, but freeing very little space for free circulation liquid, which induces high pressure drops inside the reactor.

In Figure 6, we see the appearance of the surface of the catalytic bed after loading the same catalyst as that used for the two previous loadings, but now carried out with the process according to the invention, that is to say in a liquid. The grains are distributed uniformly and generally regular spaces are distributed around the grains. The molecules constituting the reaction liquid therefore have a globally identical probability of encountering the same quantity of catalyst grains, without being deviated by the presence of preferential paths. This results in a regular and sufficient flow, facilitated by a presence also homogeneous spaces regularly distributed around the grains, to optimize the desired chemical reaction. The loading is homogeneous and not dense.

The examples which follow are intended to illustrate the invention, without limitation.

Example 1 Three series of tests were carried out in the laboratory with the same catalyst, on a transparent column, the dimensions of which are as follows:

- diameter 440 mm,

- height 1000 mm.

The catalyst used for the tests consists mainly of alumina and is in the form of dry extrudates, the average dimensions of which are as follows:

- length: 5 mm,

- diameter: 3 mm. Test 1 The catalyst is loaded in the conventional way, that is to say in the gaseous phase (air), using a sleeve made up of a flexible fabric pipe 10 cm in diameter. Trial 2

The same batch of catalyst is loaded into the air with the distribution device by rain effect of the Densicat type (dense loading), that is to say comprising flexible rubber deflectors, secured at several levels to an axis driven by a rotational movement at variable speed. Test 3 Before loading, a volume of water whose height is 100 mm was added to the column.

The same batch of catalyst is loaded into this liquid with a distribution device identical to that used in Test 2, that is to say promoting dense loading, in accordance with the invention.

The results obtained are collated in Table 1 below. Table 1

It can be seen that the density of the catalytic mass obtained, with a dense type of loading method in the air (Test 2), is overall 15% higher than that obtained by a loading with a sleeve in the air (Test 1 ).

Loading in a liquid (Test 3), carried out with the same device as that adopted for dense loading (Test 2), but in a liquid, in accordance with the invention, makes it possible to significantly reduce the density, the value of which approaches appreciably of that recorded with a load on the sleeve.

A dense type charge is therefore obtained with the method according to the invention, in which the presence of the liquid makes it possible to significantly reduce the increase in density of the catalytic mass inherent in this type of charge.

Examination of FIGS. 4, 5 and 6, which are representations of photographs of the surface of the catalytic bed obtained in each of the above loading tests, shows that the loading method according to the invention, while reducing the density of the catalytic mass at a value close to that obtained with the sleeve, also allows a substantially homogeneous distribution of the grains to be obtained, as only the dense type loads in the air can currently do, which, in return, cause an increase loading density.

The process according to the invention therefore provides a solution to the problem posed by obtaining a uniform loading usually resulting from a dense type of loading mode, but the density of the loaded mass of which is here substantially identical to that recorded. with a type load on the sleeve.

Example 2

The above tests were repeated, but, in Test 3, the liquid was replaced by an aqueous solution of ethylene glycol, having a viscosity 17 to 18 times higher than that of water, to study the influence of the viscosity of the liquid used.

The results obtained are collated in Table 2 below.

Table 2

It can be seen that a higher viscosity of the liquid has no effect on the results obtained and that the process according to the invention is not not dependent on the viscosity of the liquid used for loading the catalyst grains.

Claims

1. A method of homogeneous loading of solid particles into an enclosure (1), characterized in that said enclosure (1) is filled at least in part with a liquid (2), and in that the flow of particles (3) introduced into the enclosure (1) is divided, then distributed homogeneously in a gaseous phase (4) above the surface (5) of the liquid, within which the particles descend by gravity, to deposit forming a fixed bed.

2. Method according to claim 1, characterized in that the liquid phase (2) consists of a liquid or a mixture of liquids, physically and chemically compatible with the chemical nature of the solid particles.

3. Method according to one of claims 1 to 2, characterized in that, throughout the duration of loading, the height of the liquid (2) traversed by the solid particles, above the bed of particles being formed, is greater than 10 cm.

4. Method according to one of claims 1 to 3, characterized in that the gas phase consists of a gas or a mixture of gases physically and chemically compatible with the chemical nature of the solid particles.

5. Method according to one of claims 1 to 4, characterized in that the flow of particles (3) introduced into the enclosure (1) is divided, then distributed homogeneously, by a device (4) allowing distribution of these particles in the manner of rain over the entire cross section of the enclosure (1).

6. Method according to claim 5, characterized in that the distribution device (4) comprises flexible deflectors secured to several levels of an axis animated by a rotational movement.

7. Method according to claims 5 and 6, characterized in that the deflectors are articulated on the movable axis so as to be able to lift under the effect of centrifugal force.

8. Method according to one of claims 5 to 7, characterized in that the speed of rotation of the movable axis is less than 200 rpm and preferably 150 rpm.

9. Method according to one of claims 5 to 8, characterized in that each of the deflectors is constituted by a flexible strap.

10. Method according to one of claims 5 to 8, characterized in that the particle distribution member consists of a rigid material.

11. Method according to one of claims 1 to 10, characterized in that the liquid phase (2) is the reaction liquid of a chemical reactor.

12. Method according to one of claims 1 to 11, characterized in that the liquid phase (2) is a hydrocarbon, an aqueous product, an alcohol or their derivatives.

13. Method according to one of claims 1 to 12, characterized in that the gas phase is air.

14. Method according to one of claims 1 to 12, characterized in that the gas phase is a neutral or inert gas.

15. The method of claim 14, characterized in that the neutral or inert gas is argon or nitrogen.

16. Method according to one of claims 1 to 15, characterized in that the gas used is dried or dehydrated.

17. Method according to claims 1 to 17, characterized in that the solid particles have dimensions between a few tenths of a millimeter and a few centimeters.

18. The method of claim 17, characterized in that the solid particles are impregnated with a liquid prior to their loading.

19. The method of claims 1 to 18, characterized in that the enclosure (1) is a chemical reactor, while the particles (3) are grains of catalyst.