WO1998001222A1

WO1998001222A1 - Rotary reactor and use thereof

Info

Publication number: WO1998001222A1
Application number: PCT/NL1997/000379
Authority: WO
Inventors: Wridzer Jan Willem Bakker; Frederik Kapteijn; Jacob Adriaan Moulijn
Original assignee: Technische Universiteit Delft
Priority date: 1996-07-04
Filing date: 1997-07-03
Publication date: 1998-01-15
Also published as: AU3360697A; NO990004D0; NL1003504C2; NO990004L; EP0958044A1; CA2259938A1

Abstract

The invention relates to a rotary reactor consisting of a number of tubular reaction compartments (A), each provided with a first end and a second end, a ceramic first reactor end plate (B) in which said first ends are received, and a second end plate (B) in which said second ends are received, which end plates (B, B) are further provided with means for supplying and/or discharging gases, and wherein against the first end plate a first ceramic flange (D) is arranged of the same material as said first end plate (B), which flange (D) is provided with openings for supply and discharges of gases, which openings correspond at least partly to openings in said first end plate (B), and wherein the assembly of flange (D) and said first end plate (B, B) are disposed against each other under pressure while rotating relative to each other.

Description

Rotary reactor and use thereof

The present invention relates to a rotary reactor, more specifically a rotary ceramic monolith reactor, which is suitable for carrying out cyclic processes.

For continuously carrying out cyclic processes, such as sorption/regeneration processes, catalytic processes in general, such as selective oxidation, for instance oxidation of butane to MZA, ethylene to ethylene oxide, or propylene to propylene oxide, as well as methane conversion and catalytic cracking, rotary reactors are an attractive alternative. In such reactors, sorption and regeneration, or reaction and regeneration, occur simultaneously, in separate sections. By rotating the reactor the sections are alternately sub ected to sorption/reaction conditions, or to regeneration conditions, in that per section a different gas is passed through. In such systems, two-step or multiple step reactions can be carried out as well.

Currently, such processes are mainly carried out in packed bed reactors, between which switching occurs as soon as a sorption/reaction zone must be regenerated. The use of moving parts in apparatus for continuous cyclic processes which are mostly carried out at high temperature and elevated pressure, under often corrosive conditions, presents problems, however. Moreover, switching between beds causes discontinuity in the process control, which in itself is undesired and can result in variations in the gases coming from the reactor/adsorber.

The development of corrosion-resistant moving parts which must also seal at elevated temperature, for instance temperatures of 400°C and higher, is seen as one of the great challenges of today's process industry.

Accordingly, one of the objectives of the invention is to provide a reactor system that is suitable for continuously carrying out cyclic chemical processes, such as sorption/desorption, in a single reactor, at elevated temperature, and under typically corrosive conditions.

This object and other objects according to the invention are achieved by a rotary reactor consisting of a number of tubular reaction compartments each provided with a first end and a second end, a ceramic first reactor end plate in which said first ends are received and a second end plate in which said second ends are received, which end plates are further provided with means for feeding and/or discharging gases, and wherein against the first end plate a first ceramic flange is arranged of the same material as said first end plate, which flange is provided with openings for the supply and discharge of gases, which openings correspond at least partly to openings in said first end plate, and wherein the assembly of flange and said first end plate are arranged against each other under pressure while rotating relative to each other.

According to a preferred embodiment of the reactor according to the invention, the second end plate is manufactured from ceramic material and a second flange of the same material as the second end plate is arranged against the second end plate.

More specifically, the second flange is provided with means for discharging and feeding gases from the reaction compartments, and/or for recirculating gases from one or more reaction compartments to one or more other reaction compartments .

The tubular reaction compartments can have various shapes, it being of importance that the length is greater than the diameter. Suitable are, for instance, round tubes, but rectangular, square or, more generally defined, x-angular channels can also be suitably used. In addition, it is also possible to construct the reaction compartments combined with reactor end plates as channels in a block of the material of the reactor.

The use of the reactor according to the present invention for carrying out physical, chemical and physicochemical cyclic processes has the surprising advantage that no problems occur with the sealing of the flanges, while yet a good rotation remains possible. The sealing occurs without necessitating difficult constructions. It can suffice to make the two surfaces of the ceramic plates forming the flange to fit each other and in operation to apply some force to both sides of the flange, so that the surfaces remain clamped against each other. This holds for both flanges. In general, it is preferred to use flat plates, although other rotatable sealing constructions, such as conical systems, are not excluded .

Making the two components of the seal to fit each other occurs by grinding the plates to fit each other. After cleaning, the system can be used without necessitating additional sealing or lubrication. If desired, a lubricating compound, such as boron nitride, graphite, or another suitable material, can be used a single time to fill up very small uneven spots in the plates (typically < 0.2 μm) .

It is also possible to make provisions in the plates for air lubrication. This involves only minimal leakage of process gas, because for air lubrication an extremely thin gas film can suffice.

The reaction compartments will on at least one side terminate in a reactor end plate. It is possible that on only one side a flange is present, with provisions for the supply and discharge of gases, while in the second end plate fixed connections are made between two or more reactor compartments. In that case there is only one rotary sealing surface, which can be advantageous from the point of view of construction and sealing. In case flexible process control is to be enabled, it may provide advantages to make provisions on both sides of the reactor for varying the connections between the reaction compartments. The design of the reactor according to the invention will vary depending on the use contemplated. A few variants are elucidated in the drawing.

The variations in the reactor concern inter al ia the nature, the number and the diameter of the parallel tubular reaction compartments, and the construction of the supply and discharge openings in the two flanges.

As the number of tubular reaction compartments will mostly be greater than two, while for carrying out cyclic chemical processes often not more than two reaction sections are desired, a number of reaction compartments will, in accordance with the invention, simultaneously fulfill the same function. To realize this in the proper manner, that is to say that each reaction compartment is approached by gas flow in the same manner, it is desired that the supply and discharge flanges be provided with suitable distribution channels for the gas.

In the case where every cycle is of equal length, it is possible to make on the first side of the reactor a construction whereby the supply is m communication with half of the reaction compartments, while the discharge is in communication with the other half of the compartments, for instance as shown in Fig. 1 with reference to flange 1. Here the assumption is that the end plates have the construction as end plate 2 in the drawing. Depending on the nature of the reaction, the flange on the second side of the reactor can have the same construction as the flange on the first side of the reactor. In operation, this yields a situation where in one group of reaction compartments sorption takes place, while in the other compartments desorption or regeneration takes place. By the rotation of the reactor, in each instance one compartment moves from the sorption to the regeneration and vi ce versa . This yields a situation where in each instance a 'fresh' compartment is added to the first group, while at the same time a compartment to be regenerated is added to the other group. This process can be carried out continuously by rotating the reactor continuously, but it is also possible to do this stepwise, whereby m each case after some time a rotation over one compartment is made, or even to the extent that the reaction compartments are completely changed round at once. In all of these situations the major advantage of the invention is maintained, viz. that it is not necessary to switch the various gas streams. Indeed, the invention is based on the principle that the connections of the gas streams are not adapted but that the gas streams are directed to different reaction compartments by rotating the reactor.

In the above description, a situation has been assumed where only two different operations are involved. However, there can also be more possibilities. One could think of splitting up the supply for the first group into two streams, for instance a first and a second stream, which, for instance, differ in the extent of cleaning. It is also possible that the regeneration takes place with two separate gases, for instance first a desorption and then an additional flushing or steam treatment.

In such a situation a variant construction of the flanges will be chosen, for instance as shown m flange 3 of the drawing.

From a flexibility point of view it is preferred not tc adapt the construction of the end plates and simply to have the tubular reaction compartments terminate with the end plates, as shown for end plate 2 in the drawing. It is also possible to provide a supplemental construction between the flange and end plate, which is replaced if the division of the sections is to be changed. It is then not necessary to modify the gas supply and/or discharge, but it can suffice to replace the construction mentioned, often a disc of ceramic material with the desired configuration of gas distribution. Such a construction also provides the possibility of using the reactor according to the invention as multi-purpose reactor. The reactor according to the invention is preferably manufactured entirely of the same ceramic self-lubricating material, for instance alumina. This provides the advantage that under extreme conditions all parts exhibit the same expansion, so that there is no danger of the occurrence of defects in the sealing.

Certainly for use at high temperatures, it s desirable to use a more or less self-lubricating heat-resistant and form-retaining material. In most cases ceramic materials meet these requirements. It is noted here that it is preferred to use the same material for the whole reactor, but that this is not an absolute requirement. It is also possible to use different materials for the first end plate, second end plate and/or reaction compartments.

The reactor according to the invention is used for carrying out cyclic processes. Examples include sorption/regeneration processes, selective oxidation, for instance oxidation of butane to MZA, ethylene to ethylene oxide, or propylene to propylene oxide, as well as methane conversion and catalytic cracking. All these processes have in common that there are separate sections in the process, where work is done under different conditions, or with different gases.

Catalytic processes are generally based on a system of elementary steps that are catalyzed by the catalyst. During the process, a complex fluid phase is present, of which reactants and products are simultaneously present on the surface. For an efficient process the load factors must be set optimally. To that end, the conditions are optimally chosen, being temperature and pressures or concentrations. This kind of processes can also be carried out in several compartments, allowing the conditions in each compartment to be chosen optimally. Examples are FCC (riser reactor in which the feed is cracked) and a regenerator (where the combustion takes place) , selective oxidation of butane to maleic acid anhydride, whereby in one reactor the oxidation of butane occurs and in the second reactor the catalyst is oxidized.

The point of working with separate reactors can be understood as follows. In a selective oxidation the challenge is to prevent subsequent reactions. Classically, a mixture of air (or oxygen) and butane s passed over the catalyst surface. On this surface, depending on the conditions, surface concentrations of reactants, intermediates and products are established. An important part of process development is to determine the optimum conditions, with all steps requiring their own optimum conditions. When we analyze the kinetic scheme, the steps can be divided into two sets: the oxygen transfer to the catalyst surface and the transfer of oxygen to the hydrocarbons. It is much better to carry out these two sets of reactions in separate compartments, where conditions can then be optimized.

In the continuous, high-temperature desulfurization of coal gas (up to about 1000°C) , in a first section sorption occurs, for instance on a suitable metal alummate. After the adsorbent has adsorbed H₂S in a reaction compartment, regeneration takes place in that the reaction compartment enters into communication with another supply/discharge configuration. Simultaneously, a regenerated reaction compartment enters into communication with the coal gas again, from which H₂S can be adsorbed again.

In catalytic processes a spent catalyst is cyclically regenerated in the same manner.

According to a preferred embodiment of the invention, the reaction compartments are filled with monolith, on which an active component has been provided. The major advantage of such a system is that with large gas streams only a low pressure drop occurs, while further the system is virtually insensitive to dust. This can specifically be of importance when using the reactor for treating gases coming from a coal gasifier. It is also possible, however, to provide the active material in the form of a granular material, for instance powder, granulate or extrusions.

The active component, catalyst or sorbent, is preferably provided on the surface of a carrier material, such as a monolith. One of the advantages of this is that the structure and the regeneration properties can be set better. It is also possible, however, to make use of carrier-free systems .

Much research has been done on the use of sorbents for high-temperature desulfurization of, for instance, coal gas. Well-known materials are, for instance, zinc ferrite, zinc oxide and zinc titanate. Other sorbents are also suitable for use in the reactor according to the invention.

In the rotary reactor, preferably a newly developed sorbent based on metal compounds, more particularly on manganese compounds, is used. A characteristic of this sorbent is that it is built up of a combination of a metal aluminate with, dispersedly distributed on the surface thereof, the corresponding metal oxide. Suitable metals for that purpose are inter alia manganese, copper, iron, cobalt and other metals which are known to be suitable for sorbing sulfur. Manganese is most preferred and the preparation and use will hereinafter be discussed with reference to manganese, although this is to be understood to mean that other metals can be comparable. The sorbent can be obtained by dry or wet impregnation of a γ-Al₂0₃ carrier with a manganese solution, for instance a 1.5 M solution of manganese acetate. After impregnation and removal of any excess impregnation liquid, the sample is rapidly dried, for instance in a microwave oven. Then it is further dried in a conventional oven at 363 K, followed by calcination at 673 to 973 K. The carrier can consist, for instance, of γ-Al₂0₃ particles, pure γ-Al₂0₃ monoliths or cordierite monoliths with a washcoat layer of, for instance, 25% by weight of γ-Al₂0₃. The concentration of manganese on the sorbent can be increased by impregnating and calcining a sample a number of times. Manganese acetate, as contrasted with, for instance, manganese citrate, is very well distributed over the surface of the γ-Al₂0₃ carrier. This is due to the good interaction of the manganese acetate with external -OH groups present on the alumina surface. After each impregnation a sample is calcined in an air atmosphere at a temperature between 673 and 973 K. Depending on the calcination temperature, this yields MnAl_?0 and disperse Mn0₂, Mn₂0₃ or Mn₄0₄ (or a mixture) on the surface of the carrier. After sulfidation, MnS on γ-Al₂0₃ is formed (see eq. ) Thermodynamically, the presence of γ-Al₂0₃ has great advantages. While bulk manganese oxide can be properly regenerated with S0₂ or steam only above 1273 K, the regeneration of MnS on γ-Al₂0₃ is already properly possible from about 1023 K. This is because in this regeneration

MnAl₂0₄ is formed, which is thermodynamically stabler than MnO . For regenerating most sorbents, diluted oxygen is used (as regeneration with oxygen is highly exothermic) to form S0₂. S0₂ in a low concentration is a product with a low market value. H₂S is a much more attractive product because this can be simply converted to elemental sulfur in a Claus plant. Obviously, the direct production of S during the regeneration is the most attractive option. This could be accomplished by regeneration with S0₂. For most sorbents, sulfate formation leads to a very rapid deactivation of the sorbent if regeneration is done with S0₂. Regeneration with S0₂ of MnS on γ-Al₂0₃, however, is very well possible above 1023 K. In the current gas cleaning techniques the process gas is first cooled (T < 350 K) . After cleaning, the gas is reheated (T > 773 K) before being burnt m a gas turbine. It is estimated that high-temperature gas cleaning yields an efficiency improvement of typically 3-5% (absolute) and an investment saving of about 6%.

By the use of the manganese sorbent at high temperatures (T > 873 K) a surface area decrease occurs. This surface area decrease, however, has little consequences for the capacity of the material (bulk manganese aluminate for the greater part) at a temperature of 1123 K because the diffusion in the solid substance at this temperature is sufficiently fast.

The relatively simple regeneration with steam of bulk manganese aluminate means that manganese aluminate is relatively sensitive to water in the coal gas. Coal gas of the Shell gasification process typically contains 0.4-2% water. As a consequence, the bulk manganese aluminate will not be able to remove the H₂S from the process gas to a sufficient extent. A solution to the water sensitivity could be to use a sorbent material with a high reaction equilibrium constant, such as, for instance, MnO. This, however, presents the earlier mentioned problem that the bulk material of MnO is poorly regenerable and that regeneration costs a great deal of regeneration gas. Only disperse MnO is regenerable with a high speed at a temperature of 1123 K. When using MnO, it is therefore important that this material be situated on or adjacent the surface . The new sorbent material that has been developed within the framework of the present invention, and which is highly suitable for use in the reactor according to the invention, also contains, in addition to bulk manganese aluminate, MnO that is present at the surface highly dispersedly (the metal oxide has an average particle size of 100 nm at a maximum, more particularly 5 nm at a maximum) . The amount of MnO on the surface can be adjusted to the amount of H₂S that is allowed to pass by the bulk manganese aluminate. The amount that is allowed to pass, in turn, is dependent on the amount of water in the feed (see reaction scheme Fig. 10) . It is of importance that not more MnO be present than is necessary, because regeneration of MnO on the surface, it is true, proceeds well, but thermodynamically it is not very favorable and costs a great deal of regeneration gas. This "duo" sorbent material is obtained by repeated impregnation of the carrier material with a manganese acetate solution and calcination. (Bulk) manganese aluminate contains at most 32% by weight of manganese. If more manganese than this 32% is provided on the carrier, upon sulfidation and regeneration two phases are formed, viz. bulk manganese aluminate and a disperse manganese oxide phase which is located (chiefly) at the surface.

With the sorbent developed, (bulk) manganese aluminate provides for a high capacity and a relatively simple regeneration. Disperse manganese oxide provides for the removal of H₂S to low concentrations. The amount of disperse manganese oxide can, as already indicated, vary within wide limits. In general, of the amount of manganese, about 1 to 25% will be present in the form of manganese oxide, while the rest is present as manganese aluminate.

This sorbent material is provided on a washcoated cordierite monolith and was tested during 110 cycles (See Fig. 9) . After an initial deactivation of < 10% during the first 10 cycles, the performance of the material remains stable during these 110 cycles.

The mechanical strength of the sorbent was unchanged after these 110 cycles. A life test with simulated Shell coal gas gave a comparable result.

The invention will now be elucidated with reference to the drawing, in which

Figs. 1 and 1A show the basic principle of the rotary reactor; Fig. 2 shows the parts of the rotary reactor;

Fig. 3 represents the rotary reactor in the oven of the benchscale set-up;

Fig. 4 shows an example of the sorbent material provided on a cordierite monolith with 25% by weight of γ-Al₂0₃ washcoat layer;

Fig. 5 shows a typical sulfidation and regeneration curve

(sulfidation: [H₂S] = 3.5%, [H₂] = 50°, balance argon; regeneration: [H₂0] = 15%, balance argon;

Figs. 6A and 6B show examples of the H₂S concentration during sulfidation and regeneration of the rotary monolith reactor;

Fig. 7 shows the effect of increasing the number of reactor compartments to 25 in the regeneration section on the H_?S output concentration during the regeneration; Fig. 8 shows the sulfidation capacity as a function of the temperature;

Fig. 9 shows the deactivation of the sorbent during 110 cycles; and Fig. 10 shows a reaction scheme.

In Fig. 1 the basic principle of the reactor construction is given. The reactor compartment is designated by A, while the end plates are designated by B. A+B together form the rotary part of the reactor. The flanges D are clamped against the end plates by means of a pressure system, not shown, for instance a spring system.

In Fig. 2 a rotary reactor is shown which is based on the principle as indicated in Fig. 1. However, the reactor (see Figs. 2+3) now includes three flanges/plates on both sides of the reactor compartments (reactor end plate (a), reactor intermediate flange (b) , reactor end flange (c) ) , while in Fig. 1 only two flanges/plates are represented on either side. The number of reactor compartments (tubes) and the division of the sections in the reactor intermediate flanges differ from Fig. 1.

In Fig. 2 the various parts of the rotary reactor can be seen. All parts are made of alumina, with the exception of the driving plug. The reactor rotor consists of sixteen tubes (reactor compartments) arranged substantially parallel to each other with an internal diameter of 1 cm, a wall thickness of 3 mm and a length of 30 cm. These reactor compartments terminate on either side in a reactor end plate of a thickness of 1.5 cm and a diameter of 15 cm. Reactor compartments with reactor end plates together form the rotary part of the reactor (the reactor rotor) . Arranged against the reactor end plates on opposite sides is a flat plate of a thickness of 1.5 cm and a diameter of 15 cm (reactor intermediate flange). In the example shown, this reactor intermediate flange includes four sections for supplying and discharging gases: two large sections (covering six reactor compartment ends) each providing for the supply or discharge of process gases (for instance, regeneration gas, coal gas, cleaned coal gas and "used" regeneration gas) and two small sections (covering two reactor compartment ends) providing for the supply and the discharge of flushing gas. Against both reactor end plates there is arranged such an intermediate flange having, in the configuration shown, the same division of sections. The sections of the two reactor intermediate flanges are situated exactly opposite each other. A flushing section opposite a flushing section, etc. The reactor intermediate flanges are easy to replace with a reactor intermediate flange having a different division of the sections. If, for instance, the sulfidation takes longer than the regeneration, the section for feeding and removing coal gas can be greater than the section for the regeneration, for instance, eight reactor compartments in a section for the sulfidation and four for the regeneration.

Provided m every section of the reactor intermediate flange is a round hole with a diameter of 8 mm which opens into a similar hole in a reactor end flange. Fitted on this end flange, in line with these four round holes, are four ceramic pipes for the supply and discharge of the various gases .

In the reactor end flange and the intermediate flange a round hole is present through which passes the drive shaft. The drive shaft continues through a central tube which is mounted on the end flange. To avoid unnecessary stresses in the reactor, a flexible cardan joint is present at the driving point on the reactor and adjacent the driving motor. In the reactor end plate, at the point of application of the drive shaft, a cylinder with a rectangular hole, made of very tough and strong silicon nitride, is arranged to enable taking up of extra stresses during the drive of the reactor. To give the reactor rotor more stiffness another tube is arranged to extend from the first reactor end plate to the second reactor end plate, this tube having a diameter of 4 cm and a wall thickness of 0.9 cm. At the top of the reactor the silicon nitride plug projects slightly in order to center the intermediate flange with respect to the end plate. Similarly, the end plate at the bottom of the rotor has a projecting ceramic cylinder in order to center the reactor with respect to the intermediate flange. The intermediate flange is fixed on the end flange with two pins. At the underside, these are two ceramic shearing pins. At the top these are metal pins. These metal pins are mounted in such a manner that no problems can arise due to a difference in coefficients of expansion of the ceramic and these metal pins. The driving motor is preferably a stepping motor. The transmission to the reactor occurs via a reducer and a torque limiter. This torque limiter is a protection against possible damage of the reactor upon jamming of the reactor. The stepping motor is fully controllable in power and rotational speed. In one case the reactor will be rotated stepwise, whereby exactly one reactor compartment is rotated into a section and exactly one out of a section (step size 2π/number of reactor tubes) and in the other case it will be rotated continuously. The stepwise operation can have as an advantage that the duration and magnitude of the variation in the gas velocity and the pressure increase that may occur if a reactor tube is temporarily closed, is minimal. The greater the number of reactor compartments per section, the lesser the variation in the gas stream and pressure during the rotation of the reactor will be. A section should always contain at least two reactor compartments to prevent temporary blocking of the gas stream, and hence strong pressure increase, during the rotation of the reactor rotor. To prevent the possibility that during heat-up of the reactor, due to deformations, if any, gas leakages arise during the rotation of the reactor, the rotor part and the flanges were heated twice to 1273 K and the flanges were lapped onto each other so that a perfect gastight fit between the flanges was obtained.

Arranged on the end flange at the top of the reactor is a spring by means of which the pressure on the flanges can be adjusted. Upon increase of the gas pressure in the system, the pressure on the flanges will be increased to prevent gas leakage.

The invention is explained in and by the following non-limiting example.

EXAMPLE

A reactor as described in Fig. 2, consisting of sixteen reactor compartments, is utilized. The tubes are wholly or partly filled with sorbent material. If high gas velocities (> 2 m/sec) are employed, it has great advantages to use a structured carrier, such as a monolith. Moreover, a monolith is relatively insensitive to dust. This monolith consists wholly or partly of a manganese-based sorbent material. Obviously, when using the reactor for a different application than high-temperature desulfurization, a different active material will be provided on the monolith or particles. The reactor intermediate flanges include four sections, through which gas is supplied or discharged. In the configuration shown (see Fig. 2), the two small sections discharge and supply flushing gas (flushing gas is, for instance, nitrogen or argon) . The two large sections serve for the supply of, respectively, 'sulfidation gas' and 'regeneration gas' and for the discharge of cleaned sulfidation gas and the regeneration off-gas. A typical composition of the sulfidation gas is: H₂S 0.2-3%, H₂0 0-4%, CO 0-50%, H₂ 20-50%, C0₂ 0-2%. Nitrogen is used as balance gas. Regeneration gas: H₂0 20-70% steam, in regeneration with S0₂, 10 to 100% S0₂. Nitrogen is used as balance gas. For optimum regeneration the direction of the regeneration gas is opposite to the direction of the sulfidation gas. In the case of an industrial application of the reactor, probably use would only be made of a flushing gas that flushes the reactor compartments after regeneration. This flushing gas could be joined with the regeneration gas for further processing.

Important settings and data for the proper operation of the reactor are: the concentration of H₂S and/or COS, H₂0, H₂ and CO in the sulfidation gas; the amount and form of the sorbent material present in reactor compartments; the desired extent of desulfurization (e.g. < 100 ppm H₂S and COS) - the operating temperature of the reactor; the magnitude of the gas stream to be desulfurized .

Depending on the above settings and process data, a particular speed of rotation of the reactor is chosen. Obviously, the speed of rotation can be adjusted instantaneously if changing process conditions so require. The composition of the sulfidation gas is (more or less) fixed under practical conditions. The flow and the concentration of the regeneration gas, however, can be adjusted as desired. A guideline is that the sorbent material must be completely regenerated before the sorbent material leaves the regeneration section. A higher concentration and a higher flow of the regeneration gas will generally lead to a faster regeneration. In practice, because of this possibility, a regeneration section will mostly be smaller than the sulfidation section.

Fig. 5 shows a typical sulfidation and regeneration curve of a fixed bed reactor. In this figure, first the concentration of H₂S in the sulfidation gas is shown (1). Then the gas containing the H₂S is switched across the reactor. First, complete uptake of the H₂S occurs (2). After some time the sorbent bed breaks through. At the point of breakthrough (indicated by a dotted line) , normally the sulfidation is stopped. In this experiment, sulfidation was continued until the feed concentration of H_?S was achieved again (3) .

Thereafter the reactor is momentarily flushed. Then regeneration gas (15% steam in argon) is passed over the reactor. A high production peak of H₂S follows, which decreases rapidly. After some time no H₂S is observed anymore and the sample is regenerated.

In the rotary reactor the sulfidation will be ended before a breakthrough occurs. The exact time at which sulfidation must be stopped (= the time at which the reactor compartment must be located in a different section) partly depends on the desired degree of desulfurization. The H_?S concentration eventually present in the cleaned gas is the average H₂S concentration from the reactor compartments in the sulfidation section (six compartments in this example). The H₂S concentration of the gas leaving an individual reactor compartment may be higher than the maximum allowable H₂S concentration in the cleaned gas. It is requisite, however, that the average H₇S concentration of the six reactor compartments does not exceed the maximum value. In comparison with a fixed bed reactor, therefore, a sorbent can be used somewhat longer by compensation of a "too high H₂S concentration" with a lower H₂S concentration coming from the other reactor compartments. Figs. 6A and 6B plot the concentration during a sulfidation and regeneration. It can be seen that the output concentration of H₂S in the cleaned coal gas is substantially stable. The output concentration of H₂S during regeneration exhibits a periodic character. Compared with the fixed bed process, the fluctuation in the H_?S concentration is already much less (factor of 6) . The more reactor compartments a regeneration section contains, the more constant is the H₂S concentration leaving the regeneration section. In Fig. 7, where regeneration with a regeneration section with 25 reactor compartments is simulated, this is clearly shown. The H₂S output concentration is virtually constant.

The benchscale reactor shown can, at a gas velocity of 10 m/s in the monolith channels, a total pressure of 3 bar and a temperature of 1123 K, desulfurize 2.5 1/s (NPT) gas. At a H₂S concentration of 1%, a manganese loading of 20% by weight, and a 90% effective use of the adsorption capacity, a compartment can reside in the sulfidation section for 268 seconds. The rotational speed of the reactor must then be at least 1 rotation in 12 minutes (16/6*268= 715 sec = 12 minutes) .

This small-size reactor thus has the possibility of desulfuπzing about 200 m³ gas per 24 hours, starting from the diameter of the reactor tubes. A rotational speed of one rotation per two minutes is a very realistic maximum rotational speed. This means, for instance: that much less sorbent will suffice, or that relatively much water may be present in the feed, or that also gas with a much higher (up to six times higher) H₂S concentration can still be effectively desulfuπzed. If we compare a typical fixed bed system for desulfurization where two reactors are alternately sulfided and regenerated and the switching time is 2 to 4 hours, the rotary reactor will require 60 to 120 times less sorbent material. The difference in required reactor volume between the fixed bed reactor and the rotary reactor will be of the same order of magnitude.

Claims

1. A rotary reactor consisting of a number of tubular reaction compartments arranged substantially parallel to each other, each provided with a first end and a second end, a ceramic first reactor end plate in which said first ends are received, and a second end plate m which said second ends are received, which end plates are further provided with means for supplying and/or discharging gases, and wherein against the first end plate a first ceramic flange is arranged of the same material as said first end plate, which flange is provided with openings for the supply and discharge of gases, which openings correspond at least partly to openings in said first end plate and wherein the assembly of flange and said first end plate are arranged against each other under pressure while rotating relative to each other.

2. A reactor according to claim 1, wherein the second end plate is manufactured from ceramic material and a second flange of the same material as the second end plate is arranged against the second end plate.

3. A reactor according to claim 2, wherein the second flange is provided with means for discharging and supplying gases from the reactor compartments, and/or for recirculating gases from one or more reactor compartments to one or more other reactor compartments.

4. A reactor according to claims 1-3, wherein the tubular reaction compartments are at least partly filled with monolith .

5. A method for carrying out cyclic chemical processes utilizing the reactor according to any one of claims 1-4.

6. A method according to claim 5, comprising the high-temperature desulfurization of coal gas.

7. A sorbent suitable for use in the reactor according to claims 1-4 and more particularly in the method according to claim 6, comprising a metal aluminate as carrier/sorbent, on the surface of which an oxide of the corresponding metal is dispersedly present.

8. A sorbent according to claim 7, wherein the metal oxide has an average particle size of 100 nm at a maximum, more particularly 5 nm at a maximum.

9. A sorbent according to claim 7 or 8, wherein manganese is used as metal.

10. A method for preparing a sorbent according to claims 7-9, comprising impregnating alumina particles with a solution of a metal compound, optionally drying the impregnated alumina particles, calcining them, treating the particles with H_?S or another sorbable sulfur compound, and regenerating the treated particles.