DE4135018A1 - Passing fluid over bed of catalyst or adsorbent - by dividing fluid into two for radial flow of fluids in reactor, for cleaning car exhaust, industrial effluent or processing etc. - Google Patents

Abstract

In a process to pass a fluid over a bed of catalytic or adsorbent material, the bnovely is that the fluid enters the process chamber and is divided into two to flow radially either from the outside in, or from inside out through the porous treatment bed, and that the fluid flows then leave the treatment outlet chamber either jointly or separately. Each part of the flow may between 0% and 100% of the total flow. Pref. the treatment chambers are arranged above and abelow a common base and incorporate concentric catalytic or adsorbent beds; and the outlet chamber is more than twice the size of the inlet chamber. USE/ADVANTAGE - The process and assembly facilitate the passage of fluids through catalytic or adsorbent beds used in industrial processes or to clean effluent air, or to clean auto exhausts gases

Description

The invention relates to a method and an apparatus for Flow guidance in radial flow reactors for contacting a fluid phase with solid and is applied to the Ge offer the reaction and adsorption technology as well as the um world protection technology, for example for cleaning exhaust gases and car exhaust gases.

Methods and devices are known which provide a uniform Inflow to the catalyst or adsorbent fixed beds only below Enable additional installation elements (DD-PS 1 13 263, DD-PS 1 33 582, DD-PS 1 33 705, DD-PS 70 071, DE-OS 26 14 692, DE-PS 33 34 775).

GB-PS 14 81 017 describes a device consisting of many nested cylindrical fillings with the same radial distances and for the recovery of precious metals serves. This device does not make it possible to even out the fluid phase over the fixed bed length.  

A device is known in which the total current is divided into many Individual streams are divided by the fill, which is made up of semicircular reactor beds. The semicircular reactor beds are alternately at the ends connected and pull towards the center of the reactor. A Equalization over the height of the reactor will not reached.

In US-PS 48 83 646 is used for better utilization of the bed a fixed bed combined with a radial flow bed. These Device does not allow the reactor height to be reduced.

The known devices and methods allow Ver uniformity of the fluid phase flowing through the fixed bed only through high material and energy costs, which are characterized by Additional devices, brought about forced flow of flui the phase, pressure drops and the resulting use result in larger compressors.

The object of the invention is to provide a method for flow guidance to provide in radial current reactors, the one uniform inflow of the fluid phase over the entire bulk length when using an inexpensive device Reduction of pressure losses while increasing the we degree of efficiency.

This object is achieved in that the gas flow of the fluids Phase when entering the inflow space of the fixed bed in two Partial streams is divided, which the fixed bed either radially after inside or radially outwards or radially inwards and radially flow to the outside and that the two partial flows individually or dissipated as a total flow.

The object of the invention is also a device for Flow guidance in radial flow reactors is available too ask themselves to carry out the invention Process is suitable.  

According to the invention the object is achieved in that the front direction from one or more stacked Ra dialstrom reactors, which is an inner and outer part Form bed so that a narrow inflow space and two large Outflow spaces that are larger than twice the inflow space are, arise. The partial fixed beds are parallel or in one Angle to each other so that the inflow spaces in the longitudinal are rectangular or form the shape of a pointed wedge. The total flow of the fluid phase is when entering the Inflow space of the fixed bed divided into two sub-flows, which Flow through the fixed bed radially inwards and radially outwards. The two partial streams are discharged individually or as a total stream leads.

According to the inner and outer partial fixed bed are in front preferably cylindrical or polygonal. But it is also possible that the inflow space in longitudinal section is rectangular or forms the shape of a pointed wedge. Further can the radial flow reactor in the longitudinal direction through partitions be divided into sub-reactors, so that each sub-reactor as independent reactor can work.

In a further variant of the device according to the invention one of the three partial reactors by means of valve switching Adsorption, a second on desorption and a third on Cooling adjustable so that when the reactor is stationary Rotary adsorber is simulated.

According to the invention, the fixed beds can consist of adsorbents, by means of which components from the flowing fluids have it removed. All come here as adsorbents commercially available molecular sieve packs into consideration. Very good leaves use, for example, sodium aluminum silicate. Likewise it is possible that the hydrophobicized molecular adsorbent ben exists. Other materials that can be used are activated carbon, Alumina or silica gel.  

In another variant of the invention, the fixed beds consist of a bed of catalytic material. Prefers becomes a catalytic bed of iron oxide pel lets. Fixed beds of this type are used in particular by Ver drive with catalytic afterburning. Here, the Fluid flows are first passed over the catalyst bed. The feast beds is arranged downstream of a combustion chamber in which the z. B. Harm present in a contaminated gas substances are burned. The bed of catalytic material serves at the same time for heat storage, so that the heat by periodically changing the flow direction is recovered and pushed back and forth in the bed.

The prerequisite for a uniform flow over the Reactor length in a radial flow reactor like

• - Reduction of the reactor length
• - narrow inflow space for the fluid phase
• - large discharge area after the filling, that in the known radial flow reactors not at the same time can be realized by the invention Solution implemented with increased effectiveness.

The invention will now be described with reference to the drawings are explained. The figures show:

Fig. 1a-d flow forms when using radial flow reactors.

FIG. 2a, b The solution of the invention with two radial flow reactors.

Fig. 3 Catalytic oxidation using a radial flow reactor with one another at an angle disposed portion fixed beds.

Fig. 4 cleaning a large exhaust air flow with three radial flow reactors.

Fig. 5a-e reactors, the solution according to the invention with two radial flow and with catalytic afterburning.

Fig. 6a-d double ring flow with three parts.

Fig. 7 single ring flow with three parts.

Fig. 8 simulation of a rotary adsorber.

In principle, the flow forms shown in FIGS . 1a-d come into consideration according to the invention. The variants provide as shown in FIGS. 1a and b is z-shaped flow patterns. Its characteristic is that the currents in the central tube 91 and the outer annular space 92 have the same direction. In contrast, the fluid flows in FIGS . 1c and d run in the opposite direction.

Figs. 1b and d are such that the flow from the outer annular space 92 extending together to the central pipe 91 while this is shown in FIGS. 1a and c vice versa.

The more uniform gas distribution is ensured when designing the reactors according to FIGS. 1c and d. In practice, however, the relationships shown in FIGS. 1a and b can be realized more easily.

According to Fig. 2a, the device consists of two radial flow reactors, which are separated by a column plate 8 and arranged one above the other in an apparatus. The inner and outer partial fixed bed 1 and 2 are arranged parallel to each other.

The example shows the use of the solution according to the invention for cleaning an exhaust air stream which contains solvents by means of a continuous adsorption process in which the upper and the lower radial flow reactor alternately work in the adsorption or desorption phase. In the adsorption phase, the exhaust air flow passes through the gas inlet 6 into the narrow inflow space 5 . The entire exhaust air flow is divided into two partial flows, which flow through the inner and outer partial fixed beds 1 and 2, consisting of an adsorbent, radially inwards and radially outwards uniformly over the length of the reactor, are cleaned and discharged via the gas outlet 7 .

In the desorption phase, superheated steam is drawn by suction from Gasaus 6 a, through the gas inlet 7 a and the partial fixed beds 1 and 2 and thus desorbed the previously adsorbed solvent and removed with the superheated steam.

According to Fig. 2b, the procedure is as in Fig. 2a, except that the partial fixed beds 1 and 2 heat exchanger tubes 12 , which are incorporated in collecting containers 13 and 14 , contain, flows through the cold air during the adsorption phase or superheated steam during the desorption phase.

The cooling or heating medium passes through the inlet 15 and via the collecting container 13 into the heat exchanger tubes 12 and leaves them via the collecting container 14 and the outlet 16 . The adsorption phase proceeds as in Fig. 2a. In the desorption phase, the fixed beds 1 and 2 are heated by the superheated steam flowing through the heat exchanger tubes 12 and the adsorbed solvents are desorbed again. Via Gasein- and Gasaus 6 a and 7 a clean ambient air is sucked through the partial fixed beds 1 and 2 and thus the desorbed solvents are removed.

FIG. 3 is to a large exhaust air flow of 200 000 m3 / h are cleaned. The device consists of three superposed and flow reactors separated by column bottoms 8 radial. The partial fixed beds 1 and 2 are arranged parallel to each other.

In FIGS. 4a and b, a continuous adsorption and desorption with fixed Radialstromadsorber finally by simu lation of a valve switching means Drehadsorbers be described. Here it is assumed, for example, that the sections 78 and 83 are subjected to the adsorption at different times. The raw gas is pressed into the inflow space 85 and leaves the reactor radially to the inner and outer spaces 86 and 87 .

While the adsorption takes place in sections 78 to 83, desorption takes place in section 77 . Here, the desorption air flow flows in counterflow to the direction of adsorption through the bed, ie from the inner and outer intermediate space 86 and 87 into the intermediate gap 85 .

During this process, section 84 is cooled at the same time.

When the desorption in section 77 has ended, the switchover takes place, ie the desorption stage is switched by switching the valves to cooling in accordance with the section 84 . At the same time, the adsorption begins in the cooled subsection 84 , with switching over to the adsorption according to the arrow directions in sections 78 and 83 .

The advantage of this system is that the entire adsorber is solid stands. Switching from adsorption to desorption or cooling takes place solely by switching the corresponding valves.  

FIG. 4b shows the valve circuit for a split into five sections adsorber for the solvent recovery. The Ven tile 101 , 103 , 105 and 113 , 116 and 119 are open so that the crude gas 21 is subjected to the adsorption phase in three sections of the reactor and leaves the adsorber 85 as a clean gas 91 . The valves 102 , 104 , 106 and 111 , 112 , 114 , 115 , 117 , 118 are closed.

The reactor sections on the valves 107 , 108 , 109 and 110 are cooled or desorbed. For this purpose, valves 107 , 109 , 121 , 122 , 123 and 125 are closed and 108, 110, 120 and 124 are opened. The fan 93 sucks over 120, 108 cooling air 89 through the partial reactor, which is in the cooling phase, and hot air 90 over 124, 110 through the partial reactor, which is in the desorption phase. After leaving the adsorber, the cooling air mixes with the solvent-laden hot air and the mixed stream enters the cooling separator 94 , where the solvent condenses out. After desorption has taken place, the valves are switched over and the desorption and cooling phase move forward by a partial reactor. The recovered solvent accumulates continuously in the cooling separator 94 .

According to FIG. 5, the inventive solution is used for the catalytic afterburning. An exhaust air flow 9 is heated by the burner 10 to the inlet temperature of 400 ° C. and reaches the inflow space 5 via the mixing space 11 , divides into two partial flows, flows through the outer and inner partial fixed beds 1 and 2 into the outflow spaces 3 and 4 , combines again to form a total flow and is led through heat exchanger tubes 12 in counterflow to the cold exhaust air flow. The partial fixed beds 1 and 2 are arranged at an angle of 10 ° to one another.

In Figs. 6 to 8 show further examples of he inventive reactor with catalytic afterburning is are provided. Weakly catalytic iron oxide pellets are preferably used for the bed.

In FIGS. 6a-e the two radial flow reactors arranged in succession in the flow direction 17 and 18. The combustion chamber 28 is located between the reactors. The reactors 17 and 18 are also divided in half by the vertical partitions 19 and 20 . However, the plant shown is not limited to two reactors. Rather, it can be expanded in a modular manner to a larger number of reactors.

The plant in the example according to FIG. 6a is started up by first heating the reactor 17 to approximately 700.degree. The temperature of the reactor 18 , however, is about 50-100 ° C. The raw gas stream 21 is sucked in via the fan 22 and reaches the reactor 17 via the changeover flap 23 . Here, the valves 24 and 25 are open and the valves 26 and 27 are closed ge. The raw gas stream is heated by the bed heated to 700 ° C. in the reactor 17 . The fixed bed cools down by releasing the heat to the raw gas stream. At the same time, the catalytic conversion of the pollutants takes place in the fixed bed.

In the combustion chamber 28 , the raw gas is brought to the final reaction temperature. The pollutants are almost completely burned. The hot cleaned air then enters the reactor 18 and gives off its heat to the colder bed. For this purpose, the valves 29 and 30 are opened and the valves 31 and 32 are closed.

Before the heat front in the reactor 18 breaks through, the valve 25 is closed and the valve 27 is opened. The consequence of this is that the raw gas flows for a short time (about 30 seconds) only through half 17 a of reactor 17 , while half 17 b is flushed with purified air. For this purpose, the valve 33 is opened and a small partial flow of the cleaned air is pressed into the reactor part 17 b via the fan 34 and the switching flap 35 . As a result, the remaining raw gas from the half 17 b of the reactor 17 is flushed into the combustion chamber 28 . At the end of the rinsing process, half 17 b of the reactor 17 is filled with clean air.

After this sub-step has been completed, the flap 23 is switched over and the raw gas passes via the valves 29 and 30 into the reactor 18 which has now been heated to 700.degree. Simultaneously with the switching of the flap 23 , the valves 24 and 27 are closed and the valves 26 and 25 are opened. The raw gas now passes from above into the combustion chamber 18 and heats the part 17 b of the reactor 17 as clean air. At the same time, the left side 17a of the reactor 17 is flushed free of the raw gas via the fan 34 , the flap 35 and the valve 26 (approx. 30 seconds).

After the purging of part 17 a of the reactor 17 , the valves 33 and 26 are closed and the valve 24 is opened. The hot clean air now flows through both parts of the reactor 17 . Here, the valves 24 and 25 are open, while the valves 26 and 27 are closed. Shortly before the heat front breaks through in the reactor 17 , the flushing process at the reactor 18 is initiated by switching the flap 35 . It is noteworthy here that the rinsing time is significantly shorter than the switching time, e.g. B. Switching time T u = 10 min., Purge time T sp = 30 sec. The purge quantity is also less than the raw gas quantity and is always fed to the combustion chamber.

The advantage of the method according to the invention and the device according to the invention can be seen in the fact that the temperatures occurring in the afterburning according to the prior art are reduced from approximately 800-1000 ° C. to approximately 600 ° C. by the use of the weakly catalytic pellets . Ideally, when the pollutant concentration is greater than 1 g / m 3, the burner is only required when starting up. The heat front is then pushed back and forth in the apparatus and does not leave the bed. Here, the valves 24-27 , 29-32 and 33 and the switching flaps 23 and 35 are opened only by relatively cold air. Ie, the stress on these moving parts is relatively low, so that wear can be kept low.

The reactors according to FIGS. 6b to c differ together from the reactor shown in FIG. 6a in that the changeover flap 35 and the purge fan 34 are omitted.

The reactor shown in FIG. 6b represents a variant of the previously described reactor according to FIG. 6a. Here too, the reactors are divided into two halves of approximately the same size by the partition walls 36 and 37 . The hot reactor 17 is charged with raw gas when the valves 38 and 39 are open. The cold raw gas cools the fixed bed, while the raw gas heats up. After passing through the combustion chamber 28 with the valves 40 and 41 open, the clean hot air flows through the cold fixed bed bed of the reactor 18 and gives off its heat to it.

Shortly before switching the flow direction, part 17 b of the reactor 17 is flushed again . For this purpose, the valve 38 remains open while the valve 39 is closed. The valve 44 is opened so that clean purge air flows through part 17 b of the reactor 17 . Here, the valves 45 , 42 and 43 are closed, while the valves 40 and 41 are open.

To reverse the direction of flow, the switching flap 23 is actuated, so that the raw gas flows from top to bottom in the reactor 18 . By opening the valve 39 and closing the valve 38 , it is achieved that all the air flows over the side 17 b of the reactor 17 . By closing the valve 44 and opening the valve 45 , the flushing of the half 17 a of the reactor 17 can be achieved.

The reactor shown in FIG. 6c is a variant of the reactor according to FIG. 6b. The only difference is that the reactors 17 and 18 are not divided by a vertical wall.

In Fig. 6d, the regenerative post-combustion is under Ver application of two Ringstromadsorbern with Rohgaszuführung in the two Ausströmräumen shown. The radial flow reactors 17 and 18 are divided by the partition 77 into two subreactors 17 a and 17 b or 18 a and 18 b of the same size. According to the above descriptions, work is also carried out here. Ie, with a hot bed of the reactor 17 , the valves 61 , 62 and 69-72 are open, while the valves 65 and 66 are closed.

Conversely, when the reactor 18 is cold, the circuit is as follows: valves 63 and 64 and 73-76 are open, while valves 67 and 68 are closed.

The circuits shown ensure that cold raw gas first flows through the hot bed of the reactor 17 and heat is given off to the raw gas. As a result, the bed cools down. After flowing through the combustion chamber 28 , hot air flows into the cold bed of the reactor 18 . The air cools down while the bed heats up because the hot air gives off heat to it.

The rinsing is also carried out in accordance with the above descriptions. For example, the half 17 b of the reactor is purged 17 characterized in that the valves 65, 61 open and 69-72, whereas the valves 62 and 66 closed. The entire raw gas is thereby passed over half 17 a of the reactor 17 during the purge time. Half 17 b of the reactor 17 is simultaneously subjected to clean clean air, ie the residual raw gas is flushed into the combustion chamber 28 by the clean air.

Before the breakdown of the temperature front in the reactor 18 , the changeover flap 23 is changed over so that the raw gas 21 reaches the reactor 18 .

The valves 62 , 66 and 69-72 are opened to flush the half 17 a of the reactor 17 . At the same time, valves 61 and 65 are closed. This ensures that the entire clean air is passed over half 17 b of the reactor 17 , while half 17 a is in the rinsing position.

In Fig. 6e finally a variant is shown, in which the gas in the outer annulus flows opposite to the flow direction in the central pipe.

The cold raw gas is sucked through the reactor 18 with a hot bed. The valves 95 , 96 are open and 97, 98 are closed. Since the cold raw gas flows on the outer jacket of the apparatus (including the combustion chamber), special insulation measures can largely be dispensed with here.

The reactor 17 is also in the cold state. Valves 93 and 94 are open. The hot, cleaned air coming from the combustion chamber 28 flows through the cold bed of the reactor 17 and heats it.

In order to remove the residual raw gas from the reactor 18 , the valves 95 and 97 are opened and 96 and 98 remain closed. This measure ensures that the side 18 a of the reactor is acted upon with clean purge air. To flush the reactor part 18 b, the valves 96 and 98 are opened and 95 and 97 are closed.

The reactor according to FIGS. 7a-c shows an example in which the reactor is divided into three identical individual reactors by the vertical partition walls 46 , 47 , 48 . As with the previously described reactors, hot and cold fill is used. For example, the inflowing raw gas can be heated by the fixed bed of the reactor part 49 . Via the combustion chamber 28 , the cleaned exhaust air flows into the fixed bed of the reactor 50 and releases the heat there to the fixed bed. During this process, the residual raw gas is flushed out in the reactor 51 with clean air. The advantage of this system is that only one pump is required. By appropriate switching of the valves 52-60 , one of the segments 49 , 50 , 51 is subjected to heating, cooling or flushing. That is, the process can be carried out continuously while all three processes are carried out simultaneously in one reactor.

FIG. 7d shows in side view a variant of the method and the plant according to Fig. 7a and b. Here too, however, work is carried out with sub-segments, with heating, cooling and rinsing taking place side by side in the three subsections. The difference to 7 b is that the cold raw gas is sucked through the valves 52 , 61 and 62 through the outer spaces 86 and 87 into the annular gap 85 of the partial reactor 49 . The hot bed gives off heat to the cold raw gas. The now clean gas reaches the annular gap 85 of the partial reactor 50 via the combustion chamber 28 and releases the heat to the bed, which is cold there.

The advantage of this variant is that the partial flows that are sucked into the spaces 86 and 87 are precisely adjustable, and the hot gas is always in the inner annular gap 85 , ie inside the bed, and cold flows on the outer walls Gas, so that special insulation measures can be dispensed with.

Fig. 8 differs from Fig. 7 only in that not with a double ring flow, but only with a single ring flow. That is, the reactor halves 17 b and 17 a contain only one fixed bed ring. The hot gas is always inside the device.

Claims (16)

1. A method for flow control in radial flow reactors for contacting a fluid phase with solid, characterized in that the total flow of the fluid phase is divided into two partial flows when entering the inflow space of the fixed bed, the fixed bed either radially inwards or radially outwards or radially Flow inwards and radially outwards and that the two partial flows are discharged individually or as a total flow. 2. The method according to claim 1, characterized in that everyone Partial flow is greater than 0 to 100% of the total flow. 3. Device for guiding the flow in radial flow reactors for contacting a fluid phase with solid, characterized in that one or more radial flow reactors are arranged one above the other by column plates ( 8 ), that the fixed bed consists of an inner partial fixed bed ( 1 ) and an outer partial fixed bed ( 2 ) exists, which are arranged parallel or at an angle to each other and form an inflow space ( 5 ) greater than 0 and two outflow spaces ( 3 , 4 ) that are larger than twice the inflow space, and that in the partial fixed beds ( 1 , 2 ) in the axial direction Fixed bed direction heat exchanger tubes ( 12 ) may be present. 4. The device according to claim 3, characterized in that the inner and outer partial fixed bed ( 1 , 2 ) are cylindrical or as a polygon. 5. The device according to claim 3, characterized in that the inflow chamber ( 5 ) is rectangular in longitudinal section or forms the shape of a pointed wedge. 6. The device according to claim 3, characterized in that the radial flow reactor is divided in the longitudinal direction by partitions ( 17 ) into sub-reactors, so that each sub-reactor can work as an independent reactor. 7. Device according to one of claims 1 to 6, characterized in that the Fixed beds consist of adsorbents. 8. The device according to claim 7, characterized in that the Adsorbent is a common molecular sieve packing. 9. The device according to claim 8, characterized in that the Molecular sieve packing consists of sodium aluminum silicate. 10. The device according to claim 9, characterized in that the Adsorbent consists of hydrophobic molecular sieves. 11. The device according to claim 7, characterized in that the Active carbon, aluminum oxide and / or silica gel adsorbent consists.   12. The device according to one of claims 3 and 6 to 11, characterized in that of the three partial reactors by means of valve switching one Adsorption, a second on desorption and a third on Cooling is adjustable such that when the reactor is stationary a rotary adsorber is simulated. 13. The device according to one of claims 3 to 6, characterized in that the Fixed beds made from a bed of catalytic material consist. 14. The apparatus according to claim 13, characterized in that the Catalytic bed consists of iron oxide pellets. 15. The device according to one of claims 13 or 14, characterized in that the Fixed beds in the flow direction of a combustion chamber is subordinate. 16. The device according to one of claims 13 to 15, characterized in that the Schüt catalytic material at the same time as rain ratative heat storage serves.