FR2538265A1 - REACTION TUBE FOR CARRYING OUT A HETEROGENEOUS CATALYSIS GAS REACTION, IN PARTICULAR FOR EXECUTING A METHANIZATION REACTION - Google Patents

Abstract

Reaction tube. It is subdivided into at least two sections 7, 10, mounted one behind the other, of which the first 7, considered according to the direction of flow of the reaction gas, has a hydraulic diameter such as the ratio of this hydraulic diameter to equivalent diameter of the catalyst particles 13 in the solid state is smaller in this section than in section 10. Methanization. (CF DRAWING IN BOPI)

Description

Reaction tube for conducting a catalyzed gas phase reaction

  heterogeneous, especially to execute

a methanation reaction.

  The invention relates to a reaction tube for effecting an exothermic reaction between gaseous constituents of a reaction gas, in particular for the methanization of a synthesis gas containing carbon monoxide, carbon dioxide and carbon dioxide. In the reaction tube is packed a bed of solid catalyst which can be passed therethrough by reaction gas reacting on the solid catalyst and which is cooled from outside. The reaction tube has an inlet.

  to supply the reaction gas and, on leaving it, to

  with a gas evacuation duct produced.

  In exothermic reactions in phase

  gas, using solid state catalysts, care must be taken, on the one hand, that the heat of reaction does not overheat unacceptably

  the catalyst in the solid state The rate of evolution

  In addition to the state of the reaction gas, the reaction heat depends on the quality of the catalyst as well as the volume of the catalyst which is actively involved.

  the course of the reaction.

  the heating of the catalyst by a cooling

  In addition, the reaction product which is withdrawn as product gas is, when taken from the reaction tube, in a given thermodynamic equilibrium in advance. The length of the tube and the pressure drop in the reaction tube must be limited to acceptable values from the point of view of

  construction and from the economic point of view

  positions to be taken to satisfy these conditions

  are, at least partially, diametrically opposed.

  We know, for the methanization of gas rich in

  oxides of carbon, reaction tubes which

  constant diameter and which, in order to perform the

  reactions, are filled with solid state catalyst.

  Methanize gases that essentially comprise hydrogen, H 2, carbon monoxide, CO,

  carbon dioxide, C 02, and methane, CH 4 by methane

  for example, fuels are

  zeux that replace the natural gases that can be obtained from natural sources, or produces gases that can serve as sources of energy in a described remote energy circuit,

  for example, DT-PS 1 298 233 or DT-AS 1 601 001.

  In anaerobic digestion, the proportion of CH 4 in the gas

  is increased by exothermic reactions

  rolling on solid state catalysts CO + 3 H 2 CH 4 + H 20 H 298 K = -206 k J / mol

+ 32 4 2 298 K

  C 02 + 4 H 2 CH 4 + 2 H 20 AH 298 K = -165 k J / mole The gas formed in the natural gas network can be sent immediately after the separation of

  the water forming in the reaction, or it can be

  to steam again in the fuel circuit.

  away from the heat The heat is removed

  created in the reaction tube by a refrigerant

  rant, see for example DE-OS 25 29 316, DE-OS

29 49 588.

  By using reaction tubes of a diameter

  be constant, it has not been possible so far to

  simultaneously satisfy all the conditions

  above, for the execution of the process, even using a catalyst material of different quality. If catalyst materials which are different, and which are passed through, one after is introduced into the reaction tube. the other, by the reactive gas, one collides, in particular because

  of the aging difference of the various

  As a result, the catalyst catalyst, and the resultant catalyst temperature shift, has considerable disadvantages in carrying out the process. The aim of the invention is to carry out the reaction

  using a solid state catalyst having a

  prescribed quality, so that, for a person

  On the one hand, it is possible to avoid any overheating of the catalyst in the solid state and so that a gas mixture can be placed on the other hand at a prescribed temperature.

  finding in thermodynamic equilibrium.

  The reaction tube according to the invention, which

  is of the type recalled above, is characterized in that it is subdi-

  referred to in at least two tube sections mounted one

  behind the other, the first of which

  the flow direction of the reaction gas, has a hydraulic diameter such that the ratio

  from this hydraulic diameter to the

  The solid state catalyst particles introduced into this tube section are smaller than the ratio of the hydraulic diameter of the second downstream tube section to the equivalent diameter of the solid state catalyst particles introduced into the second. section of tube and in that the first tube section has a length such that the reaction gas in the first tube section can, after reaching a maximum permissible reaction temperature, be cooled until the passage in the second

  a section of pipe at a temperature such that the temperature

  reaction gas temperature in the second section of

  tube remains below the maximum permissible temperature

  sible. "Hydraulic tube diameter" means a diameter equal to the diameter of a cylindrical duct resulting from the following relationship -dh = 4 f / U f = free cross section of the duct,

  U = around the free cross section.

  By "equivalent diameter" is meant a

  diameter of a sphere equal to the volume of a parti-

  The equivalent diameter dg is calculated from the volume of the sphere Vk = 6 T d 3 by the relation dg 3 46 V / il g p

vp = volume of the particle.

  With the ratio of the hydraulic diameter of the tube to the equivalent diameter, it is taken into account, on the one hand, that the evacuation of the heat of reaction is improved e by a hydraulic tube diameter which diminishes and on the other hand , that the ratio of the geometric surface to the volume of the particles of

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  catalyst influences the conversion during the reaction Only the geometrical data of the empty pipe section not filled with catalyst particles are the basis for calculating the hydraulic diameter of the pipe, when this ratio is fixed.

  the size of the catalyst particles

  It is advantageous that the danger of overheating of the solid state catalyst exists essentially in the inlet region of the reaction tube. heat, especially

  in this region The thermodynamic equilibrium

  is set to a prescribed temperature in the

  second section of pipe coming next This subdivision

  Reaction of the reaction tube into two tube sections adapted to the course of the reaction gives relatively short reaction tubes and a low loss.

charge.

  According to an improvement, in the first section of tube are arranged, beside the solid state catalyst particles, discharge bodies, which reduce the hydraulic diameter of the tube and which are catalytically inert for the exothermic reaction. When the ratio of the hydraulic diameter of the pipe to the equivalent diameter of the particles is fixed, the discharge bodies must be considered exclusively for the determination

  the hydraulic diameter of the tube The equi-

  worth of particles is not influenced by the

  dimensions of the delivery bodies.

  Preferably, the first pipe section has a smaller diameter than the next pipe section.

2538265.

  reaction flowing conically, following the direction of

  reaction gas To increase the effect of

  cooling, it is also possible to subdivide the

  first section of tube into several individual tubes, the sum of the hydraulic diameters of the individual tubes

  duels to be taken then as a hydraulic diameter

than tube.

  The single figure of the accompanying drawing, given solely by way of example, is a diagram of a reaction tube having two tube sections which have

different diameters.

  In the drawing is shown a reaction tube

  1, between which 2 can be fed a reaction gas

  The reaction tube 1 is filled with a catalyst bed 3 in the solid state which promotes reaction of the constituents of the reaction gas and is cooled from the outside over the entire length. realization, the tube

  of reaction 1 is surrounded by a container under pres-

  sion, which is not shown in the drawing, and which is filled with water under pressure By absorbing the heat of reaction produced by the reaction, the water boils

  product is withdrawn from outlet 5 through the

re a conduit 6 for the gas.

  The reaction gas first passes through a first

  The first tube section 7 has an inner diameter 9 smaller than the second tube section 10 of the tube.

  reaction 1, which then follows in the direction of

  of the reaction gas In the transition part

  11 the tube widens from the diameter 9 to a diameter 12.

  The two sections of tubes 7 and 10 are cylindrical

  in the exemplary embodiment In this case, the dia-

  hydraulic meter of the tube of these tube sections

  corresponds to the inner diameter 9 and 12.

  In the reaction tube 7 are introduced,

  in the two tube sections 7 and 10, particles

  the solid state catalyst 13 made of the same catalyst material The amount of heat per mass of catalyst being released during

  the reaction when using a specific material

  catalyst is known for each state of the reaction for a prescribed flow rate of a reaction gas having a determined gas composition, and for a prescribed volume of catalyst in the state

  solid, the ratio of the hydraulic diameter

  equivalent diameter in the first

  section of tube 7, so that for a time

  constant temperature of the water in the container under

  pressure which surrounds the reaction tube 1, a temperature

  maximum permissible structure which depends on the

  solid state catalyst, do not exceed

  When the reaction gas enters the first

  section of tube 7, it reacts quickly with a

  considerable heat after reaching the

  maximum temperature, the conversion rate of

  tituants decreases again and the speed of the reaction

lowers considerably.

  The ratio of the hydraulic diameter to the diameter

  be equivalent to, in the second section of tube

  , a value greater than in the first section

  The ratio is determined in such a way that a shortest possible tube extent is sufficient for the adjustment of the thermodynamic equilibrium.

  desired at a prescribed temperature for

  The length of the first section of tube 7 is such that the reaction gas is cooled before its

  passage in the second section of tube 10 at a temperature of

  such that the reaction gas does not exceed the maximum permissible temperature in the second pipe section, of which a smaller amount of heat per unit of time can be removed by

  boiling water in the pressure vessel.

  The first section of tube 7 of the reaction tube

  1 may consist not of a tube 8, as in the embodiment, but also of several individual tubes which open, at the transition portion 11 of the reaction tube, in the second tube section 10 The tubes Individuals are

  filled, in the same way as in the example of reali-

  sation of solid state catalyst particles and are licked for cooling by boiling water in the pressure vessel For the determination of the ratio of the hydraulic diameter to the equivalent diameter, it is necessary to take in this case, for the diameter first hydraulic section of the tube, the sum of the hydraulic diameters of all the individual tubes To reduce the hydraulic diameter, it is also possible to use discharge bodies which are catalytically inert for the reaction. For the methanation of a synthesis gas whose composition is 10% of CH 4, 9% of CO, 10% of C 02, 67% of H 2 and 4% of N 2, in a tube reaction 1 having two sections of tube 7 and, the pressure of the water in the pressure vessel is adjusted to 100 bar The boiling point of the water at this pressure is 3110 C The reaction tube is filled with catalyst particles to

  solid state which consist of a ceramic material

  forming a catalyst suitable for methanisa-

  at high temperature, nickel-based (Haldor * Topsoe A / S, MCR-2 x catalyst material)

  catalyst particles which have a cylindrical shape

  have an average diameter and an average height of 4.3 mm respectively For the equivalent diameter

  dg, we thus obtain a value of 4.9 mm approximately.

  The maximum permissible operating temperature for this catalyst material is 7000 C. If the reaction gas entering the first tube section 7 is reacted at a temperature of 3000 C and having the composition indicated above without cooling, one would obtain, as

  adiabatic limit temperature in the reaction tube

  tion 1, a temperature of about 780 ° C.

  If the desired product gas quality is desired, the outgoing gaseous product must be adjusted to a thermodynamic equilibrium temperature of between

3700 C at the most.

  By maintaining these boundary conditions, we give

  to the reaction tube 1, for a flow rate of 1.8 k M

  reaction gas per hour and for

  Reaction kinetics of the catalyst MCR-2 x, a total length of 8 meters, a length of its first section of tube 7 of 3 meters and a diameter of 25 mm, while its second section of tube 10

has a diameter of 50 mm.

  For catalyst particles of the same

  catalyst material as in the embodiment

  1, but having a mean diameter and an average height of 8 mm respectively, and for a flow rate of

  6.7 k M of reaction gas per hour, we have the dimensions

  following statements for the reaction tube 1: first tube section 7, length 3 meters, diameter 50 mm,

  second section of tube 10, length 5 meters, diameter

  70 mm The total length of the reaction tube 1

is therefore 8 meters.

  With the same catalyst material and

  under the same boundary conditions for cooling

  of the reaction tube 1 than in the examples

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  Previous embodiments, it has been designed, for a flow rate of 9 kM of reaction gas per hour, a tube of

  reaction for two different dimensions of particle

  In the first tube section 7 of the reaction tube 1, solid cylindrical catalyst particles having a mean diameter and an average height of 8, respectively, were introduced. mm, and the second tube section 10 was filled with solid-state catalyst particles having a mean diameter and an average height of 4.3 mm respectively. In this case, the first section of tube is obtained. 7 a length of 3 meters and a diameter of 50 mm, and for the second section of tube 10 a diameter of 70 mm The length

  total of the reaction tube 1 is less than 7 meters.

  In this embodiment of the reaction tube 1, despite the considerably high flow rate of the

  gas product that comes out, get a composition that cor-

  corresponds to the thermodynamic equilibrium of the syngas

  thesis, in the range of temperatures between

311 and 370 ° C.

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Claims (3)

RESUME ICAT IONS   1 reaction tube for performing a reaction   exothermic reaction between gaseous components of a reaction gas, in particular for the methanisation of a synthesis gas containing carbon monoxide, carbon dioxide and hydrogen, comprising a catalyst bed in the solid state which is packed in the reaction tube, which can be passed therethrough with reaction gas reacting on the solid state catalyst and which is cooled from the outside, and an inlet for supplying reaction gas and, at the outlet of the reaction tube, a connection to a product gas evacuation duct, characterized in that the reaction tube (1) is subdivided into at least two tube sections (7, 10) mounted therein. one behind the other, the first (7), considered in the direction of flow of the reaction gas, has a hydraulic diameter such as the ratio of this hydraulic diameter to the equivalent diameter of the catalyst particles (13) to the solid state introduced into this pipe section   is smaller than the ratio of the hydraulic diameter-   from the second pipe section (10) downstream to the equivalent diameter of the solid state catalyst particles introduced into the second pipe section and in that the first pipe section (7) has a 2538265   length (8) such as the reaction gas in the first   first section of the tube may, after reaching a   maximum permissible reaction temperature, be re-   cooled down to the passage in the second pipe section (10) at a temperature such that the temperature of the reaction gas in the second pipe section remains   less than the maximum permissible temperature.   2 reaction tube according to claim 1, characterized in that, in the first section of tube (7), are arranged, beside solid state catalyst particles, discharge bodies which reduce the hydraulic diameter of the tube and who   are catalytically inert to the reaction exothermic   3 reaction tube according to claim 1 or 2, characterized in that the first section of   tube (7) consists of several individual tubes.