DE2929300A1 - Reactor for heterogeneous catalyst gas phase reactions - is cross sectionally tailored to specific heat requirements in different reaction stages - Google Patents

Abstract

Reactor contains catalyst through which the reacting gases flow. The flow passages are surrounded by a heat transfer medium. The cross sectional area of these flow passages contg. the catalyst are tailored to suit the residence time and heat transfer requirements for different stages of the reaction. This is achieved e.g. by using tubes the dia. of which alter at different levels in the reactor. Appts. is used for endo or exothermic catalytic reactions e.g. NH3 and CH3OH syntheses. Tailoring the reactor cross section to the actual heat load requirements of the system, gives better control and considerable financial advantages.

Description

Reactor for carrying out catalytic

endothermic or exothermic reactions The invention relates to one Reactor for carrying out catalytic, endothermic or exothermic reactions with one flowed through by reacting fluids and filled with catalyst material Reaction space that is in thermal contact with a heat emitting or receiving Fluid stands.

Many reaction kinetic processes, such as the synthesis of methanol or the synthesis of ammonia, take place in the presence of catalysts. Addicted of the prevailing operating and reaction conditions, of the catalysts and the geometrical relationships in the reactor, arise in the reactions Gas compositions that come more or less close to the equilibrium state. Frequently, several reactions with different reaction rates take place in the reactors and enthalpy of reaction from simultaneously. The temperature ranges occurring in the reactor are often because of the minimum start temperature of the catalyst and / or because of the formation of undesirable intermediate products downwards, because of what is desired in each case Approximate degree of balance and also for reasons of Economy and the materials including the catalytic converter, to the top limited. In any case, the production of a desired temperature profile is essential an important condition for its design in the reactor.

For example, in the journal "Chemtech", July 1973, pages 430 to 455, a methanol reactor of the type mentioned above, be the The catalyst is placed inside tubes that are made of reacting gases are flowed through. The heat generated during the reaction is evaporated from the Cooling water (cooling fluid), which flows around the pipes in the outer space, is discharged. That in the the cited literature reference shows the temperature profile for such a reactor, starting from a gas inlet temperature which is below the temperature of the cooling fluid is due to the catalytically triggered reaction, a heating up to a maximum value, which is about 11 ° above the cooling fluid temperature and, due to the decreasing heat of reaction and the heat transfer to the cooling fluid, one subsequent cooling down to the gas outlet temperature, which is a few degrees above the Temperature of the cooling fluid is.

In the reactor described, the gas and the catalyst are first used heat was still absorbed from the coolant.

If the inlet temperature of the gases were chosen to be higher, it would be also the maximum temperature in the reactor can be shifted upwards, but because of possible damage to the catalyst due to the equilibrium conditions and only possible to a limited extent for economic reasons.

The present invention is therefore based on the object of providing a To develop a reactor of the type mentioned, which is characterized by a special good adjustment of the actual Temperature profile on the for the The most favorable response value and the one with a reasonable financial and value technical effort can be produced.

This task is achieved according to the invention in that the cross-sectional area of the reaction space is dependent on the flow path of the reacting fluids on the amount of heat required for the reaction or released during the reaction changes.

The cross-section is the course of the theoretically optimal temperature adapted in the reactor, namely in sections in which large amounts of heat are released (for exothermic reactions) or are required (for endothermic reactions), the Cross-section of the reaction space as small as possible and vice versa in sections, in where small amounts of heat are released or required, the cross-section if possible chosen large. In the first case this means a large ratio of to the heat incoming or outgoing fluid in contact with standing wall surface to catalyst volume and thus a particularly high degree of heat transfer capacity from the catalyst or on the catalyst, while the ratio of surface area to catalyst volume im the second case is small and therefore only a slight heat exchange takes place.

With the subject matter of the present invention, it is surprising In a simple way it was possible to change the temperature profile in the reactor according to the given conditions to a reaction as optimally as possible. Large amounts of heat are applied to them Points in the reactor supplied or withdrawn from the reacting fluids at which these Heat is actually needed or generated while in other places where little heat of reaction is required or generated by the design according to the invention the reactor has a significantly lower heat exchange.

The subject of the invention is applicable to single-phase systems (gaseous Reaction partners) as well as for dual-phase systems (gaseous and liquid reaction partners) as well as suitable for fixed bed catalysts and fluid bed catalysts.

It has proven advantageous that the reaction space is ni essential consists of tubes and the tubes into several sections with different diameters are divided. In this embodiment, in which the catalyst material Im Located inside the tubes, the tubes are parallel to the reacting fluids flows through. The outer space around the pipes is a heat emitting or receiving space Fluid out, depending on whether it is an endothermic or an exothermic reaction acts. Of course, in addition to the diameters of the individual pipe sections Their lengths can also be selected to be different in order to suit the circumstances in this way to take even better account of them in the reactor.

In another advantageous embodiment of the subject matter of the invention, in which the reaction space also consists essentially of tubes, the Tubes continuously changing along the flow path of the reacting fluids Diameter on.

In a further advantageous embodiment of the subject matter of the invention is the reaction space of shirts introduced into the catalyst material limited changing diameters along the flow path of the reacting fluids and are inside the shirts tubes for the heat emitting or receiving fluid arranged. The flow cross-section for the fluids depends on the arrangement of the shirts more or less narrowed. The catalyst material inside the shirts is from penetrated the pipes. A narrowing of the flow path for the reacting fluids means an increase in the surface to area ratio Catalyst volume of the reaction chamber and kehert. It goes without saying that the narrowing or widening of the flow cross-section caused by the shirts both through a steady as well as a gradual change in the cross-section take place ann.

When the reactor is operating under overload or underload, the equilibrium must be set take place according to different aspects than in normal operation, since the fluid velocities, change the enthalpies of reaction and also the amount of fluid converted. Even if so the reactor is optimally adapted to the administration during normal operation, it may be that less favorable adaptation conditions are found in overload or underload operation prevail in the reactor. For this reason, In will continue to develop the subject matter of the invention suggested that a part of the Reaktlonsraum one of the rest of the reaction space having sufficient cross-sectional distribution contains the flow path and alternatively or in addition to the rest of the reaction space with the feed devices of reacting fluids is connectable.

In this embodiment, part of the reaction space has a Cross-sectional distribution along the flow path, the most optimal possible adaptation conditions guaranteed during normal operation. Another reaction space is also provided, that in the case of under- or over-load operation instead of the one intended for normal operation Reaction space or in addition to this to the feed devices for the reacting fluids can be connected. This further reaction space points along desw flow path has a cross-sectional distribution that alone or in Connection with the cross-sectional distribution of the intended for normal operation Reaction space for the m over or Underload operation provided Fluid quantities and fluid flow velocities ensure the best possible temperature profile results.

In an advantageous embodiment of the reactor according to the invention adjacent pipes are arranged antiparallel with respect to the direction of flow. This structure turns out to be advantageous if with an anti-parallel arrangement complementary pipe sections meet, so that, for example, next to one Large diameter section in the antiparallel tube is a section comes to rest with a small diameter. In this way, the build volume of the Reactor significantly reduced.

In an appropriate modification of the subject matter of the invention at least two of the tubes are combined into one tube within the reactor.

For the reactor according to the invention, this results for each diameter Di (in mm) of a pipe to the amount of gas flowing through the diameter Di per Time unit V (in Nm³ / h): Di = p 'Vq where p, q are constants. For p, q result For example, the numerical values 15 # p # 25 and 0.12 for a methanol synthesis actuator 5 q # 0.22.

The reactor according to the invention is particularly suitable for ammonia synthesis or suitable for a methanol synthesis, but not limited to these uses to be.

Further details of the present invention are provided with reference to FIG schematically illustrated Ausfilhrungsbeispielen described.

Figures 1 to 6 show different embodiments of the reactor according to the invention.

In all figures, 1 is an invention spaces.

referred to, which is housed in a jacket 2. The reactor 1 is constructed in the manner of a tubular heat exchanger and has two separate ones Flow spaces.

In FIGS. 1 to 5, the one flow space 4 is made up of several pipes 5 formed, which are arranged in the jacket 2 and at both ends in tube sheets 6 are registered.

The pipe ends are on both sides with collecting spaces 7a, 7b in Connection via which the reacting fluids are supplied and discharged according to arrows 3, 9 will. The other flow space 3, which is bounded by the jacket 2, is used for Conducting a heat supplying or removing fluid, which according to arrows 10, 11 is supplied and discharged. The tubes 5 are filled with a catalyst material. According to the invention, the diameter of the tubes 5 changes along the flow path of the reacting fluids, namely the diameters are chosen so that at all Set the reaction space as ideal a state of equilibrium and / or as possible favorable heat transfer conditions prevail, i.e. at the points where a lot of heat is generated or required for the reaction (depending on whether the Reaction exothermic or enaothermic), the tubes have small diameters, around the reaction volume relative to the fluid conveyed on the shell side in connection to reduce the standing surface and vice versa.

For example, Figure 1 shows an arrangement that fits well with a provides the desired temperature profile.

For the reactor shown in Figure 2, for example, for the Methanol synthesis is used, the following are some representative numerical examples compiled.

Gas composition on entry 17% CO, 73% H2 into the reactor 5 ß CO2, 5 5 of the amount of gas per pipe V = 200 Nm3 / h gas inlet temperature 245 ° C inlet temperature of the cooling water 2300 C diameter of the first pipe section 45 mm diameter of the second Pipe section 52 mm diameter third pipe section 45 mm length first pipe section 2.5 m length of second pipe section 1.5 m length of third pipe section 4.0 m space velocity first section 40,000 to 50,000 V / VKat space velocity, second section 55,000 to 70,000 V / VKat space velocity third section 30,000 to 40,000 V / VKat with VKat (in m³) Volume of the catalyst material.

In somewhat more general terms, applies to such a reactor for the methanol synthesis that the number of pipe sections reads between 2 and 5 and is preferably 3, that the diameter Di of the pipe sections between 20 and 100 mm and that for the diameter Di (in mm) and for the amount of gas per Pipe V (in Nm³ / h the condition Di = = (15 ... 25). N, 12 ... 0.22 must be observed should.

FIG. 3 shows a reactor in which adjacent tubes 5 are antiparallel are arranged with respect to the direction of flow of the reacting fluids. This arrangement is always useful when this means that it is used in addition to pipe sections with large diameters those with small diameters and vice versa come to rest. In this way space is saved and the reactor can be built smaller.

Figure 4 shows a reactor in which the diameter of the tubes 12 changes continuously along the flow path of the reacting fluids.

In Figure 5, a section of a reactor is shown in which two tubes 13, 14 are combined into one ear 15. This design represents another Variation possibility for simultaneous optimization of reaction equilibrium and construction volume.

Figure 6 shows a modified design of a reactor. Here is the catalyst is not arranged in tubes, but rather in the entire interior of the shell 2. The heat supplying or removing fluid is guided in tubes 16, the inside run from shirts 17. Arrows 8, 9 indicate the direction of flow of the reacting Fluids, arrows 10, 11 indicate the direction of flow of the heat supplying or dissipating Fluids. The shirts 17 are inserted into the catalyst material and delimit them the flow path of the reactant.

Fluids on the side. They narrow and widen the flow cross-section Depending on the given requirements. ie changes in cross-section along the flow path can be done continuously or in stages.

Claims (8)

Claims 1. Reactor for carrying out catalytic endothermic or exothermic reactions with one of the reacting fluids flowing through and reaction space filled with catalyst material, which is in thermal contact with a heat dispensing or absorbing fluid, characterized in that the cross-sectional area of the reaction space is dependent on the flow path of the reacting fluids on the amount of heat required for the reaction or released during the reaction changes. 2. Reactor according to claim 1, characterized in that the reaction space consists essentially of tubes (5, 13, 14, 15) and the tubes in several sections are divided with different diameters. 3. Reactor according to claim 1, characterized in that the reaction space consists essentially of tubes (12) and the tubes (12) along the flow path have continuously changing diameters. 4. Reactor according to claim 1, characterized in that the reaction space of shirts (17) introduced into the catalyst material along the flow path changing diameters is limited and within the shirts (17) tubes (16) are arranged for the heat-emitting or absorbing fluid. 5. Reactor according to one of claims 1 to 4, characterized in that that part of the reaction space has a cross-sectional distribution that differs from the rest of the reaction space Has along the flow path and alternatively or in addition to the rest The reaction space can be connected to the feed devices for the reacting fluids is. 6. Reactor according to one of claims 2, 3 or 5, characterized in that that adjacent tubes (5) are arranged antiparallel with respect to the direction of flow are. 7. Reactor according to one of claims 2, 3, 5 or 6, characterized in that that at least two of the tubes (1, 14) inside the reactor to form a tube (15) are united. 8. Reactor according to one of claims 2, 3, 5, 6 or 7, characterized in that that for each diameter Di (in mm) of a pipe (5, 12, 13, 14, 15) the following relationship to the amount of gas flowing through the diameter Di per time unit V (in Nm3 / h) consists: Di = P where p, q are constants.