WO2009141517A1

WO2009141517A1 - Novel bayonet-tube heat exchanger reactor, the tubes of which are surrounded by shafts in cement

Info

Publication number: WO2009141517A1
Application number: PCT/FR2009/000499
Authority: WO
Inventors: Fabrice Giroudiere; Jérôme Colin; Didier Pavone; Estelle Lucien; Etienne Soutif
Original assignee: Ifp
Priority date: 2008-05-23
Filing date: 2009-04-28
Publication date: 2009-11-26
Also published as: FR2931368B1; FR2931368A1

Abstract

Heat exchanger reactor for carrying out highly endothermic reactions, consisting of a cylindrical shell (1) closed in its upper part by a top dome (2) and in its lower part by a bottom dome (3), said shell enclosing a plurality of bayonet tubes (4) which are mutually parallel and extend along an approximately vertical axis and through which the reaction fluid flows. The heat-transfer fluid is injected into the shell via the bottom dome (3) and flows around the bayonet tubes inside shafts (13), said shafts being defined by ducts cut into a bulk cement element (11) that rests on the bottom dome (3) and extends up to a height (H) equal to or lower than the total height of the bayonet tubes (4).

Description

NEW BAYONETTE TUBE EXCHANGER REACTOR SURROUNDED BY CEMENT CHIMNEYS

FIELD OF THE INVENTION

The field of the present invention is that of exchanger reactors for the implementation of highly endothermic reactions, such as the steam reforming reaction of hydrocarbon cuts for the production of synthesis gas. A reaction reactor is one in which the heat input required for the reaction is carried out by means of a coolant generated outside the reactor itself. By extension, the scope of the present invention includes the case where the heat transfer fluid is generated inside the exchanger reactor itself. The catalytic chemical reaction takes place inside a plurality of tubes arranged in parallel substantially vertically, and the heat transfer fluid circulates outside these tubes. The skilled person speaks of "tube side" to refer to the chemical reaction and the flow of the reaction fluid, and "shell side" to designate what relates to the flow of heat transfer fluid and the heat exchange from the coolant to the reaction fluid flowing inside the tubes. In the context of the present invention, the reaction tubes are bayonet type, that is to say that each tube consists of a first inner tube open at both ends, surrounded by a second outer tube closed at one end. its ends, surrounding the inner tube and defining an annular space. In the preferred circulation configuration in the context of the present invention, the reaction fluid is introduced into the annular zone, circulates inside the annular zone, then after a 180 ° inversion, passes inside the inner tube. from which the reaction effluent is extracted.

One of the advantages of the present invention is to allow the coolant to be introduced or generated inside the exchanger reactor at temperature levels of up to 1200 ° C. and up to 1500 ° C., and to be channeled inside chimneys at least partly made of cement, each chimney surrounding each bayonet tube so as to obtain high circulation velocities within said chimneys to optimize the transfer of heat to the reaction fluid. EXAMINATION OF THE PRIOR ART

The patent application FR No. 07 / 05,316 describes a bayonet tube exchanger reactor for managing pressure differences up to 100 bar (1 bar = 0.1).

MPa) between the tube side and the shell side. The cited application also uses a system of chimneys surrounding the bayonet tubes, these chimneys consisting of a generally metallic tube surrounding each bayonet tube, said metal tube being supported by a tabular plate placed in the upper part of the reactor.

In the case of metal chimneys, it is not possible to admit the heat transfer fluid at temperatures above 1200 ⁰ C ₃ or even above HOO ⁰ C, this regardless of the metallurgy chosen. This is a limiting limitation when it is desired to carry out a heat transfer from an available heat transfer fluid at a temperature up to 1300 ° C.

Synetic's Advanced Gas Heated Reformer, a Synetix's Advanced Technology Heated Reformer, describes a small-capacity bayonet tube heat exchanger reactor with a tabular plate. However, in this reactor, the hot gases used as heat transfer fluid do not exceed 1000 ° C, which poses no problem for the realization of metal chimneys surrounding the bayonet tubes.

In addition, for large capacity reactors, the diameter of the reactor, therefore of the tabular plate having to support the chimneys, can exceed 3 meters, and for diameters of this value, the tabular plate quickly reaches thicknesses greater than 300 mm. which makes the cost very high and the construction difficult.

The present invention makes it possible both to exceed the temperature limit of admission of the heat transfer fluid inside the chimneys, and to remove the support tabular plate of said chimneys. This results in the possibility of dimensioning the exchanger reactor according to the invention so as to reach capacities of 150,000 Nm3 / hour of hydrogen thanks to a reactor of about 12 meters in diameter, in the case of steam reforming of natural gas.

Another advantage of the invention lies in its implementation facilitated during the installation of tabs bayonet, which are slid inside the chimneys whose lower part is made of cement.

The exchanger reactor according to the present invention may also be sized for lower capacities. SUMMARY DESCRIPTION OF THE FIGURES

Figure 1 shows a view of the exchanger reactor with four bayonet tubes surrounded by cement chimneys along their entire length (HT). The inlet and outlet of the bayonet tube are outside the reactor. FIG. 2 shows a view of the reactor with four bayonet tubes and a chimney having a first portion of high cement (HC), and a second metal and / or ceramic part. The inlet and outlet of the bayonet tube is outside the reactor. FIG. 3 represents a view of the lower part of the exchanger reactor with a concrete block having a generally arch-shaped lower surface. FIG. 4 represents a view of the lower part of the exchanger reactor with a concrete block having a lower surface in the form of several arches.

Figure 5 shows a view of the lower part of a bayonet tube surrounded by a conical shaped chimney, followed by a metal chimney and / or ceramic.

SUMMARY DESCRIPTION OF THE INVENTION

The present invention may be defined as an exchanger reactor adapted to the implementation of highly endothermic reactions, the reactor consisting of a cylindrical calender (1) closed at its upper part by an upper convex bottom (2) and its part lower by a lower curved bottom (3), said calender enclosing a plurality of bayonet tubes (4) parallel and extending along a substantially vertical axis, the reaction fluid flowing inside the annular portion (8) of bayonet tubes (4) filled at least partly with catalyst over a height (RH). The coolant is introduced into the shell by the lower bottom (3) and circulates around the bayonet tubes (4) in chimneys (13) of total height (HT), said chimneys being in their lower part delimited by conduits cylindrical cut inside a concrete block (11) resting on the bottom bottom (3), and extending to a height (HC) less than or equal to the total height (HT). In general, the total height (HT) of the chimneys is less than or equal to the catalytic height (RH). Preferably, said total height (HT) is less than or equal to the catalytic height (RH) of the bayonet tubes (4).

The bayonet tubes (4) comprise a so-called "reaction zone" filled with catalyst and extending over a height (RH). The height of this reaction portion (HR) of the tubes bayonet, said catalytic height (HR) is generally less than the total height (HB) of said tubes, but may possibly be equal thereto.

Conventionally, all the heights are marked with respect to a base height (H = O) corresponding to the lower end of the bayonet tubes (4). The total height (HB) of the bayonet tubes is less than the total height of the reactor since the bayonet tubes do not extend down to the bottom bottom (3). However, depending on the support mode, the bayonet tubes can, in some cases, through the upper curved bottom (2). The term "total height" (HB) therefore means bayonet tubes, the length of said tubes taken inside the exchanger reactor. The reaction height (HR) is generally greater than 50% of the total height (HB) of the bayonet tubes, and preferably greater than 60% of said total height (HB). In a first variant of the exchanger reactor according to the invention, the chimneys (13) are made of cement along their entire length (HT). In this variant we have (HC) = (HT) and (HT) less than or equal to (HR). In a second variant of the exchanger reactor according to the invention, the cement chimneys (13) do not extend over the entire height (HT) of said chimneys. The chimneys (13) are then defined in their lower part by the ducts cut inside the cement bulk (11), and are extended in their upper part by metal and / or ceramic tubes (10) resting on the face upper (20) of the cement base (11).

For the sake of clarity, the term "(13) chimneys" in cement ", and (10) the chimneys in the metal part and / or ceramic. We always have (HT) less than or equal to (HR). The expression metallic and / or ceramic means that the upper part of the chimneys (10) can be made by any combination of metal sections and ceramic section. We speak equivalently of a metal / ceramic assembly.

Of course, this includes the case where the upper part of the chimneys (10) is entirely metallic or entirely ceramic.

In the variant where the chimneys are entirely made of cement, they are designated by (13).

In the variant where the chimneys are in their lower part in cement, then in their metallic and / or ceramic upper part, they are generally designated by (13), except if it is really necessary to distinguish the metal and / or ceramic part (10). ). Is denoted by (9) the annular space extending between the wall of the outer tube (6) constituting a portion of the bayonet tube (4), and the wall of the chimney, that it is made of cement (13), or metallic and / or ceramic (10).

The term "cut" does not mean that the ducts have been cut in the cement, but that the corresponding ducts have been reserved when pouring the cement by any means known to those skilled in the art.

The height over which the concrete block (11) extends is determined by the temperature of the coolant which, from a certain value generally between 600 ° C. and 900 ° C., makes it possible to extend the chimneys by an envelope metallic and / or ceramic (10) while remaining, in the metallic case, in a conventional metallurgy.

One of the ceramics that can be envisaged is silicon carbide (SiC or carborundum). The heat transfer fluid is introduced through the bottom convex bottom (3) of the reactor by means of the introduction pipe (F), is distributed in the different cement chimneys (13) and is collected in the upper part of the reactor by the tubing collection (G). The reactor according to the invention is particularly applicable to a heat transfer fluid available at a temperature above 1000 ° C, or even greater than 1200 ° C. It may be in particular a heat transfer fluid generated by a burner placed inside the exchanger reactor itself, generally at the level of the bottom curved bottom (3). The first part of cement chimneys (13) is therefore necessary to reach, at the level of the coolant, the temperature from which the chimneys can be extended by a metal tube (10), made in a suitable metallurgy, and / or ceramic. The cementitious mass (11) will be chosen from a refractory type material with a density of between 500 kg / m3 and 2500 kg / m3, and having a composition of Al ₂ O ₃ , SiO ₂ , CaO, Fe ₂ O ₃ , P ₂ O _5, such that this cement can withstand temperatures up to 1500 ° C. For example, this cement may be a type VIBRON 160 H cement or refractory GOLITE 125 XLW marketed by the company GOUDA. The nature of the cement, and particularly its density, may vary depending on the location, and the shape of the cement part considered. The exchanger reactor according to the present invention has vertical ducts cut in the cement bulk (11) defining the cement chimneys (13). The annular space (9) between the wall of the cement chimneys (13) and the outer tube (6) may have a cylindrical shape or, preferably, a substantially conical shape so as to modulating the circulation velocity of the heat transfer fluid within the annular space (9) between a value of between 10 m / s and 80 m / s, and preferably between 20 m / s and 60 m / s.

In a variant of the exchanger reactor according to the invention, the height of the cement chimneys (13) extends over the entire length of the bayonet tubes (4) corresponding to the reaction portion, abbreviated as "reaction length" (HR) .

When the diameter of the reactor is greater than 3 meters, which corresponds to most cases, the inlet and outlet of each bayonet tube (4) is outside the reactor.

The cementitious mass (11) has an approximately planar upper section (20) and a lower section (21) which may have various shapes, for example that of a single arch, said arch being connected to the lower curved bottom (3) through pillars (12) also in cement.

According to another variant of the reactor, the concrete block has an approximately flat upper section (20) and a lower section (21) consisting of a series of arches, each arch being connected to the lower convex bottom (3) by pillars (12) also in cement.

When the upper part of the chimneys (10) consists of a metal and / or ceramic tube, the latter rests on the upper section (20) of the cement block (11).

In general, the extrapolation of the reactor is done by the number of bayonet tubes, the reaction length (ie the length of the catalyst-filled tube) of said bayonet tubes being generally between 7 and 20 meters, and preferably between 8 and 17 meters.

The present invention can also be defined as a process for steam reforming a hydrocarbon fraction using the reactor according to the present invention, in which the speed of circulation of the heat transfer fluid inside the chimneys (13) is between 10 and 80 m. / s, and preferably between 20 and 60 m / s.

The steam reforming process using the reactor according to the present invention is generally charged with hydrocarbon cuts having less than 12 carbon atoms, with a molar ratio of steam to water of between 2 and 6.

In a particular case, particularly interesting in the context of the reduction of greenhouse gases, the coolant consists of fumes consisting essentially of water vapor, obtained by the combustion of hydrogen in a burner located outside. or inside the exchanger reactor according to the invention. DETAILED DESCRIPTION OF THE INVENTION

The description which follows will be better understood by means of the appended figures. FIG. 1 represents a view of the exchanger reactor according to the invention in a variant in which the entirety of the chimneys (13) surrounding each bayonet tube (4) is made of cement. The total height (HT) of the chimneys is therefore equal to the height (HC) of the cement part, and the total height (HT) is less than or equal to the height of the catalytic zone (HR).

This variant is called "all cement". The reactor comprises a cylindrical envelope (1) closed in its upper part by an upper curved bottom (2), and in its lower part by a bottom curved bottom (3).

The heat transfer fluid is generally admitted by the bottom convex bottom (3) by means of a pipe (F) having a refractory lining, so as to accept a heat transfer fluid up to 1500 ° C. The heat transfer fluid can come from any combustion equipment generating smoke, generally a burner located outside the exchanger reactor, can operate on any type of hydrocarbon fuel.

In a particular case, this fuel can be hydrogen, or a gas rich in hydrogen, which makes it possible to generate smoke free of CO2, which in the current context of reduction of greenhouse gases, can be an advantage decisive. The coolant engages inside the chimneys (13) surrounding each bayonet tube (4). The annular zone (9) separating the wall of the chimneys (13) from the outer tube (6) constituting the bayonet tube (4) is defined so as to allow the coolant to reach inside the chimneys speeds between 10 m / s and 80 m / s, and preferably between 20 m / s and 60 m / s. The annular zone (9) may have a variable spacing so as to allow a modulation of the heat transfer fluid velocity from the bottom of the chimney to the top of the chimney. Generally, the heat transfer fluid velocity at the lowest point of the chimneys (13) is between 10 m / s and 80 m / s, preferably between 20 m / s and 60 m / s, and the velocity of the coolant at highest point of the chimneys is between 10 m / s and 50 m / s, preferably between 20 m / s and 40 m / s. The profile of the spacing of the annular zone (9) can be arbitrary, but is most often conical, with a decrease of the spacing going from bottom to top so as to to compensate for the increase in the density of the heat transfer fluid due to the cooling of the latter.

The coolant is removed from the exchanger reactor in its upper part by means of the tubing (G). A bayonet tube (4) consists of an inner tube (5) open at both ends surrounded by an outer tube (6) closed at its lower end. The annular space (8) between the inner tube and the outer tube is generally filled with catalyst particles, at least over part of its length, denoted (HR).

Generally, the reaction fluid flows down the inside of the annular space (8), then goes up inside the inner tube (5). Other modes of circulation are nevertheless possible, the invention being in no way related to the ascending or descending nature of the fluid flow inside the bayonet tubes (4).

The reactions involved in the exchanger reactor according to the invention are highly endothermic reactions, such as the hydrocarbon cutting vaporeforming reaction in order to produce a synthesis gas. In this case, the catalyst particles generally have the shape of small cylinders 1 to 2 cm high, and diameter between 1 and 2 cm.

Other forms are also possible, especially more complex forms having at the periphery convex portions and concave portions, the invention being in no way related to the shape of the catalyst particles. The catalyst occupies part or all of the annular space between the inner tube

(5) and the outer tube (6) of each bayonet tube (4).

Depending on the capacity of the exchanger reactor, and more particularly on its diameter, the support mode of the bayonet tubes may vary.

Generally for reactor diameters of less than 3 meters, the support is done by means of a tabular plate to which are suspended the bayonet tubes (4).

For larger diameter reactors up to 15 meters, the support is provided directly by the upper curved bottom (2) on which the tubes are fixed by direct welding, or by means of a flange connection. allowing disassembly of the bayonet tubes. In the case of larger diameter reactor, the discharge of the reaction effluents from the inner tube (5) is after said inner tube (5) has passed through the outer tube (6), as shown in FIGS. and 2. The inner tubes (5) are connected to a collector (S) for collecting the reaction effluents, and the outer tubes (6) are fed by an inlet manifold (D), allowing the distribution of the reaction fluids in each tube. bayonet (4). The design of the reactor is done by multiplication of the bayonet tubes, the tubes having a catalytic length of between 7 and 20 meters, and preferably between 8 and 17 meters.

The catalytic length corresponds to the portion of the tube filled with catalyst. In view of the fact that in a configuration particularly adapted to the large capacities covered by the present invention, the entry and the exit of the bayonet tubes are outside the reactor, the total length of the bayonet tube inside the reactor is between 15 and 20 meters.

The increase in the number of bayonet tubes results in an increase in the diameter of the reactor which can reach 20 meters, but is preferentially for large capacities in the range of 10 to 15 meters. Figure 2 is identical to Figure 1 except for the upper part of the chimneys (13) which is no longer cement but becomes metallic and / or ceramic (10). More precisely, the cement mass (11) in which the chimneys (13) are cut out extends over a certain height (HC) less than the total height (HT) of the chimneys (13). Above this height (HC), the chimneys (13) consist of a metal and / or ceramic tube (10) resting on the upper section (20) of the cement block (11).

The configuration corresponding to this solution is called "mixed". The total length (HT) of the chimneys is always less than or equal to the height of the catalytic zone (HR). FIG. 3 represents a concrete block (11) with a lower face (21) in the form of a single arch. A possible binding mode of the solid cement (11) with the curved bottom (3) of the reactor can consist of pillars (12) being interposed between ^'the locations corresponding to the bayonet tubes (4). These pillars (12) may be substantially vertical, as shown in Figure 3. They may in some cases, depending on purely geometric constraints, be more or less inclined. FIG. 4 shows a cement base (11) with a lower face (21) in the form of a multiple arch, each arch corresponding to a row of bayonet tubes. The arches are extended by substantially vertical pillars (12) which rest on the curved bottom (3). Other configurations of the lower face (21) of the cement mass (11) are possible, as well as various forms of connecting elements of said mass (11) with the curved bottom (3). The configurations illustrated in FIGS. 3 and 4 are in no way limiting. Figure 5 shows more precisely the so-called "mixed" configuration corresponding to a lower portion of the cement chimneys (13), and an upper portion of the metal and / or ceramic chimneys (10). The annular space (9) between the cement chimneys (13) and the outer tube (6) is conical so as to allow some acceleration of the flow velocity of the coolant from bottom to top. This annular space (9) remains constant when the wall of the chimneys (10) becomes metallic or ceramic. FIG. 5 shows the location of the catalyst particles in the annular space (8) between the outer tube (6) and the inner tube (5) of each bayonet tube (4), and the fact that the metal and / or ceramic chimneys (10) rest on the upper face (20) of the cement base (11).

EXAMPLE

An example of the dimensions and performance of a reactor according to the invention is given below.

The reactor is in accordance with FIG. 2 and has chimneys whose first lower part is made of cement (HC) and extends over a height of 4 meters. The upper part of the chimneys is metallic and extends over a height of 10 meters.

The total height of the chimneys (HT) is 14 meters.

The annular portion (8) of the bayonet tubes (4) is filled with a steam reforming catalyst at a height (RH) of 17 meters.

The heights are all marked with respect to the lower end of the bayonet tubes. The steam reforming reactor processes a flow rate of 26550 kg / h of natural gas and 76292 kg / h of steam (H20 / HC ratio = 2.87)

The charge of the exchanger reactor consists of natural gas (NG) of composition given in the table below:

The operating characteristics of the reactor are given below purely for illustrative purposes: GN feedrate (before addition of water): 26550 kg / h H20 / hydrocarbons molar ratio (H ₂ O / HC) = 2.87 natural gas = 371 ^° C. Temperature of the effluent leaving the catalytic zone = 900 ° C. Output temperature of the effluent = 632 ° C. The effluents from the reactor are given in Table 2 below:

TABLE 2 The natural gas inlet is at the top of the bayonet tubes, through the outer tube

(6) in the annular space (8) partially filled with catalyst.

The end of the catalytic zone corresponds to the lower end of the bayonet tube, and the outlet of the reaction effluent is in the upper part of the bayonet tubes by the inner tube (5).

The composition of the coolant (resulting from the combustion of a hydrogen-rich gas in the air) is given in Table 3 below:

TABLE 3

The flow rate of the coolant is: 360 000 kg / h

The inlet temperature of the coolant is: 1293 ° C

The dimensions of the reactor taking into account the mechanical stresses of implantation of the bayonet tubes are: External diameter of the bayonet tubes: 170 mm

Number of bayonet tubes: 321 tubes

Outside diameter of the reactor: 10.4 m

Total height of the reactor: 20 m

Height of cement chimneys (HC): 4 m Height of metal chimneys (HT-HC): 10 m

Total height of chimneys (HT): 14 m

Total height of the bayonet tubes (HB): 20 m

Catalytic height (HR): 17 m

The cement base (11) consists of a lower part, including the connecting pillars (12) with the bottom curved bottom (3), made of refractory mass cement volume 2500 kg / m ³ , and an upper part made in a cement density 500 kg / m ³ refiractaire.

Claims

1) exchanger reactor adapted to the implementation of highly endothermic reactions, consisting of a cylindrical calender (1) closed at its upper part by an upper curved bottom (2) and at its lower part by a bottom convex bottom (3); ), said calender enclosing a plurality of bayonet tubes (4) parallel to each other and extending along a substantially vertical axis, said bayonet tubes being filled with catalyst in their annular part over a height (RH), called height catalytic inside which the reaction fluid circulates, the coolant being introduced into the shell by the lower bottom (3) and circulating around the bayonet tubes (4) in chimneys (13) of total height (HT), said chimneys being, in their lower part, delimited by ducts cut inside a concrete block (11) resting on the bottom bottom (3) and extending up to an hour author (HC) less than or equal to the total height (HT) of the chimneys (13).

2) exchanger reactor according to claim 1, wherein the total height (HT) of the chimneys is less than or equal to the catalytic height (RH) of the bayonet tubes (4).

3) exchanger reactor according to any one of claims 1 to 2, wherein the chimneys (13) comprises a lower portion of height (HC) cement, followed by an upper part is either metallic or ceramic, or composed of a metal / ceramic assembly, the total height of the stacks (HT) being lower than the height of the catalytic zone (HR).

4) exchanger reactor according to any one of claims 1 to 2, wherein, the chimneys (13) are cement over their entire length (HT).

5) exchanger reactor according to any one of claims 1 to 4, wherein, when the reactor diameter is greater than 3 meters, the inlet and outlet of each bayonet tube (4) is outside the reactor.

6) exchanger reactor according to any one of claims 1 to 5, wherein the cement base (11) has an approximately flat upper section (20), and a section lower (21) in the form of a single arch, said vault being connected to the lower curved bottom (3) via pillars (12) also made of cement.

7) exchanger reactor according to any one of claims 1 to 5, wherein the cement base (11) has an upper section (20) approximately flat, and a lower section (21) consisting of a series of arches, each arch being connected to the lower curved bottom (3) via pillars (12) also made of cement.

8) Reactor exchanger according to any one of claims 1 to 7, wherein when the upper part of the chimneys consists of a metal tube (10), the latter rests on the upper section (20) of the cement block (11). ).

9) exchanger reactor according to any one of claims 1 to 7, wherein when the upper part of the chimneys consists of a ceramic tube (10), the latter rests on the upper section (20) of the cement block (11). ).

10) exchanger reactor according to any one of claims 1 to 9, wherein the length of the bayonet tubes (4) corresponding to the reaction portion of catalytic height (HR) is between 7 and 20 meters.

11) Process for steam reforming a hydrocarbon fraction using the reactor according to any one of claims 1 to 10, wherein the velocity of circulation of the heat transfer fluid inside the chimneys is between 10 and 80 m / s.

12) A process for steam reforming a hydrocarbon fraction according to claim 11, wherein the heat transfer fluid consists of fumes obtained by the combustion of hydrogen in a burner located outside the exchanger reactor.

13) A process for steam reforming a hydrocarbon fraction according to claim 11, wherein the hydrocarbon fraction consists of molecules with less than 12 carbon atoms, with a molar ratio of water vapor on hydrocarbons of between 2 and 6. 14) method of steam reforming a hydrocarbon fraction according to claim 11, wherein said reactor has stacks (13) of variable section, typically conical, so as to modulate the circulation velocity of the heat transfer fluid inside the annular space (9) between the wall of the chimneys (13) and the outer tube (5), between a value of between 10 and 80 m / s, and preferably between 20 and 60 m / s.