DE102007027881A1 - Method and apparatus for mixing gases - Google Patents

Abstract

When mixing two gases of different temperature and / or composition in a converter to produce SO <SUB> 3 </ SUB> from a SO <SUB> 2 </ SUB> -containing gas, a first, SO <SUB> 2 < / SUB> -containing gas stream introduced through a central supply pipe in the converter and passed through a arranged around the central supply pipe integrated heat exchanger, which flows through the first gas flow from bottom to top. A second gas stream is supplied via a ring pipe arranged above the integrated heat exchanger, from which the second gas stream exits through a plurality of openings and is fed into the first gas stream, so that it mixes with it. The resulting gas mixture is then fed to a contact stage of the converter in which the SO <SUB> 2 </ SUB> on a catalyst is at least partially converted to SO <SUB> 3 </ SUB>.

Description

The present invention relates to a method for mixing two gases of different temperature and / or composition in a converter for producing SO ₃ from a SO ₂ -containing gas and to an apparatus for carrying out this method.

The present invention is in the context of the production of sulfuric acid. Sulfuric acid is conventionally usually prepared by the so-called double absorption process, which in Ullmanns Encyclopedia of Industrial Chemistry, 5th Edition, Volume A25, pages 635-700 is described. First, in this case, a sulfur dioxide-containing starting gas with oxygen at a plurality of successively arranged contact stages of a converter according to the formula SO ₂ + 1/2 O ₂ → SO ₃ + 98 KJ at least partially converted to sulfur trioxide. The generated sulfur trioxide-containing gas is then fed to an absorber and converted there to sulfuric acid. The oxidation of the sulfur dioxide to sulfur trioxide is carried out in the presence of a catalyst which usually contains vanadium pentoxide as the active component and has a working range of about 380 to 640 ° C. While irreversible damage to the catalyst occurs at temperatures above 640 ° C, it is inactive at temperatures below 380 ° C. Since the process is highly exothermic, it is necessary for the gas inlet temperature to be in the contact stage at about 400 ° C. At a much lower inlet temperature, the reaction is not triggered, while at a much higher inlet temperature, the temperature during the process increases so much that the catalyst is damaged. However, it is possible to use other catalysts that allow a higher operating temperature, such. B. off EP 1 047 497 B1 or DE 100 23 178 A1 known. In order to obtain a high yield, the reaction is carried out in several stages, between which the process gas is cooled in each case by means of integrated heat exchangers in order to achieve a suitable gas inlet temperature for the next stage of contact. Usually, such a converter has four to five contact stages, wherein in the above-mentioned double absorption method, the process gas is supplied after passing through some, eg., Three contact stages an intermediate absorption tower, in which the SO _{3 converted} to sulfuric acid, oleum or liquid SO ₃ and thereby the SO ₃ concentration in the process gas is lowered again. The process gas is then supplied after heating to the required process temperature the next contact stages of the converter and then the final absorption.

The process gas supplied to the converter suffers from frequent variations in the amount and SO ₂ concentration. While in conventional converters, the SO ₂ concentration is usually limited to about 12% by volume due to the high temperatures reached in the first catalytic step, this allows the DE 102 49 782 A1 described method, the use of higher SO ₂ concentrations by the recirculation of SO ₃ -containing gas. This recirculation limits the reaction in the first contact stage and thereby the heat generated there.

Due to the fluctuations of the inlet gas, it is necessary to control the temperature at the inlet of the contact mass. This is done via the supply of cold SO ₂ -containing gas via a bypass line. In the above-mentioned recirculation of SO ₃ -containing gas, moreover, the mixing ratio must be adjusted. Therefore, gases of different temperature and / or composition are to be mixed in different places in the converter. The temperature difference leads even with gases of the same composition to different viscosities that complicate the mixture. For the efficiency of the process, however, it is necessary to achieve a homogeneous gas mixture. If sufficient homogeneity of the gas at the entrance into the contact mass is not attained, there are zones in which, when passing through the contact stage, there is no conversion of the SO ₂ into SO ₃ , so that the efficiency of the converter is impaired. Possibly. In zones with too high a SO ₂ content, overheating may damage the catalyst. It has been found that the mixture of gases with different temperatures in the piping of sulfuric acid plants is not a fast, spontaneous process. The gases flow parallel to each other without mixing due to the different viscosities (so-called stratification).

It has already been proposed to solve this problem Provide local pressure losses, leading to turbulence with a high Cause turbulence. This solution is however in many cases not sufficient, because the whole in the system achievable or permitted pressure loss is limited or from plant engineering Reasons must be limited.

task The invention is therefore the homogeneity of the mixture two gases of different temperature and / or composition in a converter to increase and the so-called stratification to reduce or prevent.

This object is achieved with the invention essentially in that a first, SO ₂ -containing gas stream introduced through a central supply pipe in the converter and by one to the centra a second gas stream is fed via a arranged in the converter immediately before or after the integrated heat exchanger ring line from which the second gas stream exits through a plurality of openings and is fed into the first gas stream, so that he mixes with this, and that the resulting gas mixture is then fed to a contact stage of the converter, in which the SO _{2 is} reacted on a catalyst at least partially to SO ₃ . Via the loop, the second gas is thus fed into the first gas at a plurality of locations, so that an excellent mixture is achieved. Since the second gas stream, which is, for example, SO ₂ -containing gas of low temperature, the apparatus upstream of the converter passes only partially, is compared to the mixture higher pressure available, which can also increase the pressure loss. If the second gas is recirculated sulfur trioxide, its pressure can be increased by means of a blower or the like, so that here too a higher pressure is available than with conventional methods and the pressure loss can be increased. By means of such a blower, it is also possible to regulate the pressure or pressure loss or specifically set and control.

Especially Good mixing results result in a preferred embodiment the invention, when the second gas stream in countercurrent in the first Gas stream is fed. This will add extra Creates turbulence that aids in the mixture. It is also or additionally possible, the second Feed gas stream in direct current into the first gas stream.

In the recirculation of SO ₃ -containing gas, as is known from the DE 102 49 782 A1 is known, in a further development of the invention, the first gas stream more than 13 vol .-% SO ₂ and the second gas stream 3 to 40 vol .-% SO ₃ , preferably 5 to 25 vol .-% SO ₃ .

If there is no recirculation of SO ₃ -containing gas, the temperature is regulated when entering the first contact stage of the converter according to the invention with the aid of a second gas stream, up to 30 vol .-% SO ₂ , preferably up to 12 vol .-% SO ₂ and has a temperature of 80 to 120 ° C. This gas stream may be bypassed around the conventional heat exchanger to increase the temperature of the first gas so that it has a higher pressure than the first gas. In the bypass devices for controlling or regulating the pressure, for. As blowers or throttle valves or flow resistance, whereby the mixing can be additionally controlled.

Of the Volume flow of the second gas stream is smaller according to the invention than that of the first gas stream and is 20 to 60%, preferably about 50% of the first gas flow.

An inventive device for mixing two gases in a converter for producing SO ₃ from a SO ₂ -containing gas, which is particularly suitable for carrying out the method described above, has a supply line for a first gas introduced into the converter and by a integrated heat exchanger is arranged, which is arranged around the central supply line, a ring line for a second gas, which is arranged in the converter immediately before or after the heat exchanger in a mixing chamber, wherein the ring line a plurality of openings for the exit of second gas in having the mixing chamber.

at A preferred embodiment of the invention is the first gas introduced from above into the converter and after a deflection guided by the integrated heat exchanger which is arranged around the central supply line, and then enters the above the heat exchanger arranged Mixing chamber. The ring line is preferably around the central Supply line for the first gas arranged. This results in addition to a simple flow guidance compact construction of the converter and the mixing device.

For introducing the second gas stream in countercurrent to the first gas stream, the holes in the ring line facing the heat exchanger. The second gas stream thus preferably exits downward from the loop. If the second gas stream is to be fed in direct current into the first gas stream, then the holes in the ring line are remote from the heat exchanger, so that the second gas stream emerges upwards out of the ring pipe. Of course, it is possible that both at the bottom and at the top or on the sides of the ring line corresponding openings, which may be configured as bores, slots or the like., Are provided. The openings may be provided side by side in multiple rows to increase the amount of feedable second gas stream. Preferably, the opening at an angle of 20 to 70 °, more preferably 30 to 60 ° C to the vertical. The openings can in this case a different size or shape z. B. depending on the distance to the supply line, have. It is also possible, the openings or the gas flow around or out of the openings by other fittings, for. As baffles, welds, etc., to vary. Of this variation, only individual or individual groups of openings may be affected. It is also possible to provide a closure device for individual openings or groups of openings in order to have a control or control device in particular at partial load operation.

According to one preferred embodiment of the invention are two to seven, especially three provided concentric ring lines, from which the second gas exit. This also increases the amount of the second gas stream become.

Around To facilitate the interconnection of the system, the ring lines according to the invention with a common supply line for the second gas a related party. It has proven to be beneficial proved that the common supply line for the second Gas at least partially around the central supply line for the first gas is led around and that several downwards Guided connection lines the supply line with the Connect ring lines. This allows the second gas at the same time be introduced into the converter in several places, wherein a preferred symmetrical design of the converter and thus also a preferred symmetrical flow guidance is reached. But essential to the invention here is the possible uniform mixture of gases or distribution in the converter, for which, if necessary, deviated from the symmetry can be.

The Connecting lines are according to the invention over Supply connection in each case with all ring lines connected to to facilitate a simpler supply.

Further developments, Advantages and applications of the invention result also from the following description of exemplary embodiments and the drawing. All are described and / or illustrated illustrated features alone or in any combination the subject of the invention, regardless of its summary in the claims or their dependency.

It demonstrate:

1 _{1 is} a schematic sectional view of a converter for the production of SO ₃ from a SO ₂ -containing gas with a device for gas mixture according to an exemplary embodiment of the present invention with illustrated gas flows,

2 the area of introduction of the second gas stream into the first gas stream,

3 a partial plan view of loops of the device according to the invention and

4 a section through a loop along the line IV-IV in 3 ,

The in 1 shown converter 1 for the conversion of SO ₂ in SO ₃ has a total of five contact stages K1 to K5, in which a catalyst, in particular a vanadium pentoxide-containing catalyst is provided to convert the SO ₂ in SO ₃ . After passing through three contact stages K1 to K3, the resulting SO ₃ -containing gas is fed to a heat recovery system, not shown here, and the intermediate absorption in order to at least partially remove the sulfur trioxide from the process gas. The SO ₂ -containing process gas is then fed back to the converter below to pass through the contact stages K4 and K5. The present invention relates only to the first region of the converter 1 with the contact stages K1 to K3, so that the following description is limited to this range.

The converter 1 is via a central supply line 2 Supplied SO ₂ -containing gas which flows through the supply line from top to bottom and at the lower end via a baffle 3 is deflected by 180 °. The first gas then flows through a first heat exchanger WT1, which is designed in particular as a tubular heat exchanger, from bottom to top and enters into a above the heat exchanger WT1 arranged mixing chamber 4 out.

A second gas, which is, for example, recirculated SO ₃ -containing process gas or SO ₂ -containing gas of lower temperature than the first gas, is supplied via a supply line 5 and connecting cables 6 that have power supply 7 with around the central supply line 2 circulating ring lines 8th are connected, also in the mixing chamber 4 introduced, and mixes with the first gas. The supply line 5 here is z. B. outside the converter 1 For example, as a three-quarter circle around the central supply line 2 guided around, with the connecting lines down from the supply line 5 branch off and into the converter 1 enter. The ring lines 8th from which the second gas exits are provided immediately after the integrated heat exchanger WT1, ie without the interposition of other devices.

Via a bypass line 9 can before entering the first contact K1 additional z. B. cold or hot, SO ₂ -containing gas can be supplied.

The gas mixture then flows through the first contact K1 and is then passed through the integrated heat exchanger WT1 to the temperature of the process gas increased by the exothermic reaction in the contact stage K1 to a suitable for entry into a second contact stage K2 Temperature of about 400 ° C to cool and at the same time through the central supply line 2 to heat supplied SO ₂ -containing first gas. After flowing through the second contact stage K2, the process gas is again passed through an integrated heat exchanger WT2 to be cooled to a suitable for the third contact stage K3 inlet temperature of about 400 ° C, and after passing through this third contact stage K3 via an output 10 from the converter 1 withdrawn and fed to an intermediate absorption system.

In the 2 to 4 the device for mixing the first and the second gas is shown in more detail. In 2 The first gas enters from below into the first heat exchanger WT1 and then into the mixing chamber 4 out. The second gas is via the connecting line 6 and the supply pipe 7 in the ring lines 8th fed from which it has a variety of openings 11 (see. 4 ) directed down into the mixing chamber 4 exit. The openings 11 are here arranged in a plurality, possibly staggered rows of holes arranged so that the second gas is fed as a plurality of small streams in the first gas and can mix well with the first gas due to the resulting and promoted by the countercurrent turbulence turbulence. In another embodiment, not shown here, additionally or alternatively to those at the bottom of the loops 8th provided openings 11 also at the top of the loop 8th corresponding openings are provided to feed the second gas in direct current into the first gas.

As it turned out 3 results are three concentric loops 8th around the central supply line 2 arranged over four evenly around the circumference of the converter 1 distributed connection lines 6 and supply pipe 7 be supplied with the first gas.

With The invention can be a homogeneous mixing of two gas streams be achieved, so that the composition and temperature of the process gas be well set at the entrance to the first contact stage K1 can.

1

converter

2

central supply line

3

baffle

4

mixing chamber

5

supply line

6

interconnectors

7

supply socket

8th

ring lines

9

bypass line

10

output

11

openings

K1-K5

contact stages

WT1 WT3

integrated heat exchangers

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1047497 B1 [0002]
• - DE 10023178 A1 [0002]
• - DE 10249782 A1 [0003, 0009]

Cited non-patent literature

• - Ullmanns Encyclopedia of Industrial Chemistry, 5th Edition, Volume A25, pages 635-700 [0002]

Claims (17)

A method for mixing two gases of different temperature and / or composition in a converter for the production of SO ₃ from a SO ₂ -containing gas, wherein a first, SO ₂ -containing gas stream introduced through a central supply pipe in the converter and passed through an integrated heat exchanger wherein a second gas stream is supplied via at least one ring pipe arranged in the converter immediately before or after the integrated heat exchanger, from which the second gas stream exits through a plurality of openings and is fed into the first gas stream, so that it mixes with it , and wherein the obtained gas mixture is then fed to a contact stage of the converter, in which the SO _{2 is} reacted on a catalyst at least partially to SO ₃ . Method according to claim 1, characterized in that that the second gas stream is fed countercurrently into the first gas stream becomes. Method according to claim 1 or 2, characterized that the second gas stream is fed in direct current into the first gas stream. Method according to one of the preceding claims, characterized in that the first gas stream contains more than 13% by volume of SO ₂ and the second gas stream contains 5 to 25% by volume of SO ₃ . Method according to one of claims 1 to 3, characterized in that the second gas stream up to 13 vol% SO ₂ and has a temperature of 80 to 120 ° C. Method according to one of the preceding claims, characterized in that the second gas flow is smaller than the first gas stream. Device for mixing two gases in a converter ( 1 ) for the production of SO ₃ from a SO ₂ -containing gas, in particular for carrying out a method according to one of the preceding claims, with a supply line ( 2 ) for a first gas that enters the converter ( 1 ) and passed through an integrated heat exchanger (WT1), a loop ( 8th ) for a second gas in the converter ( 1 ) immediately before or after the heat exchanger (WT1) in a mixing chamber ( 4 ) is arranged, wherein the ring line ( 8th ) a plurality of openings ( 11 ) for the discharge of second gas into the mixing chamber ( 4 ) having. Apparatus according to claim 7, characterized in that the first gas from above into the converter ( 1 ) and after a deflection through the integrated heat exchanger (WT1) is guided, which around the central supply line ( 2 ) is arranged. Apparatus according to claim 7 or 8, characterized in that the ring line ( 8th ) around the central supply line ( 2 ) is arranged for the first gas. Device according to one of claims 7 to 9, characterized in that the mixing chamber ( 4 ) is arranged above the heat exchanger (WT1). Device according to one of claims 7 to 10, characterized in that the openings ( 11 ) in the loop ( 8th ) facing the heat exchanger (WT1). Device according to one of Claims 7 to 11, characterized in that the openings ( 11 ) in the loop ( 8th ) are remote from the heat exchanger (WT1). Device according to one of claims 7 to 12, characterized in that at the bottom and / or top of the loop ( 8th ) a plurality of rows of holes are provided, through which the second gas emerges. Device according to one of claims 7 to 13, characterized in that a plurality, in particular three concentric ring lines ( 8th ) are provided, from which the second gas exits. Device according to one of claims 7 to 14, characterized in that the ring lines ( 8th ) with a common supply line ( 5 ) are connected to the second gas. Apparatus according to claim 15, characterized in that the common supply line ( 5 ) for the second gas at least partially around the central supply line ( 2 ) is guided around for the first gas and that a plurality of downwardly guided connecting lines ( 6 ) the supply line ( 5 ) with the ring lines ( 8th ) connect. Apparatus according to claim 16, characterized in that the connecting lines ( 6 ) via supply connection ( 7 ) each with all loops ( 8th ) are connected.