EP1622706B1 - Mixing device, and mixing method using that device - Google Patents

Abstract

The aim of the invention is to improve an existing mixing device in such a manner that for a predetermined reactor length, retention time is increased and the material which is to be processed is transported at essentially the same speed irrespective of the radial distance thereof from the rotational axis. As a result, at least one row of blades is arranged on each shaft and each row of blades comprises at least two individual blades and the blades are fixed to the shaft at an incidence angle α in relation to the longitudinal axis of the shaft. The blades are curved in themselves, such that the blades form an angle of incidence α at the fixing point on the shaft and an angle of incidence β on the outer diameter DA. By virtue of the fact that a row of individual blades is used instead of a continuous screw, efficient mixing of charging material and coke can be achieved, the angle of incidence is reduced from the inside to the outside and the axial speed of the particles which are to be mixed is evened out on the total cross section of the reactor, thereby enabling a stop-type flow to be obtained.

Description

The invention relates to a mixing device and an associated mixing method for use as a continuously operating reactor.

These continuous reactors are used for the processing of z. As petroleum vacuum residue, refinery residues, bitumen or plastics, by being mixed with a hot kömigen heat transfer medium and heated to the desired temperature.

Typically, mixing devices of this type consist of at least two horizontally intermeshing screws which are built according to the requirements of different length and diameter. To achieve certain properties, such as increasing the reaction or reaction rate or maximizing product yield and product quality, the mixing apparatus is varied in terms of solids residence time, reactor temperature, or system pressure.

DE-B-1189368 describes a conching machine with a single or double-cylinder trough arranged horizontally, in which main shafts provided in the cylinder axis (s) with axial thrust vanes are mounted. Next, at least two cylindrical protrusions are provided on the two longitudinal sides of the trough on the trough length parallel to the trough axis, in the axis of which one with the axial thrust vanes offset by 90 ° radial lifting blades provided side shaft is mounted, which on the one hand reaching up to the inner wall of the bulge, and on the other engaging in the rotation of the lifting blades of the main shaft, arranged between the radial lifting blades and the side shaft wing sets. The side shaft is driven at a higher speed than the main shaft and in opposite directions to this. By this arrangement, an effective ventilation and a better Veralbungseffekt caused.

DE-B-1255098 describes an apparatus for the thermal isomerization or disproportionation of alkali metal salts of benzene carboxylic acids, which consists of a reactor vessel provided with an inlet and outlet in the form of at least two parallel, intersecting cylinders, the cylinders each with a are provided concentrically extending shaft and these waves are provided with a variety of helical staircase axially separated by spacers stirring blades, wherein the wings are in the form of elongated, mutually offset by 30 ° plates whose tip circles those of the stirring blades of adjacent waves. overlap.

DE-A-19724074 and DE-A-19959587 describe a process for working up residual oil, in which the residue oil to be processed is introduced into the mixing plant of hot heat transfer coke and through a further conduit. The heat transfer coke has temperatures in the range of 500 ° to 700 ° C and is mixed with the residual oil by at least two horizontal intermeshing screws so that a uniformly thick oil film is formed on the coke particles. This is then heated very rapidly to reaction temperature and reacts to form gases, oil vapors and coke. Gases and vapors leave the mixer after a short dwell time of 1 to 10 seconds through a vent channel upwards.

The coke-containing solid mixture, which has passed through the mixer and has arrived at the outlet is withdrawn for further processing down into a buffer tank for post-degassing.

In mixers of this type is trying to achieve the same residence time as possible of all solid particles, ie plug flow. That is, the particles that are near the shaft are transported at the same axial velocity as the particles that are on the outer circumference of the screw. At the same time, an attempt is made to adjust the residence time so that the liquid feed at the end of the mixer is completely converted into gases, vapors and coke.
Due to the speed profile between conventional shafts and housing wall and the associated undesired axial mixing, the particles in these mixers have different residence times in the mixing section.
The residence time can be varied by adjusting the reactor length, the shaft speed or the pitch of the screws. In order to use as much of the residence time as possible for the reaction, an attempt is made to reduce the mixing time, ie the time required to completely mix the heat carrier and the liquid feedstock. Ideally, a complete mixing takes place already at the beginning of the media at the beginning of the mixing section. This is not yet possible. According to the known state of the art, complete mixing of a liquid feed has taken place only after passing through half the reactor length. To increase the residence time, a longer reactor would be an extremely expensive solution as the solution, since the shafts and screws are made of high heat-resistant steel and have an outer diameter of 0.8 to 3 m and a length of 6 to 15 m.
To influence the mean residence time and the residence time distribution, the pitch and the geometric arrangement of the mixing helixes can be varied. The speed
of the solid in the mixer depends on the pitch and shape of the mixing helix. With increasing slope of the mixing spiral generally decreases the axial velocity of the solid particles and the residence time.

Based on this prior art, the present invention seeks to improve the previous mixing device such that at a given reactor length, the residence time is increased and that the material to be processed is transported regardless of its radial distance from the axis of rotation with the same speed as possible.

According to the invention in the above-mentioned mixing device is achieved in that on each shaft at least two opposite rows of blades are arranged and each row of blades from 2 to 20 individual blades and that the blades at an angle α to the longitudinal axis of the shaft on the Shaft are fastened, wherein the blades are curved in itself, so that the blades at the attachment point on the shaft have the angle of attack α and the outer diameter of the angle of attack β. By using a series of individual blades instead of a continuous screw, a particularly efficient mixing is achieved. By a curvature of the blades, which results in a different angle of incidence to the longitudinal axis of the shaft with increasing diameter, the axial velocity of the particles to be mixed over the entire reactor cross-section can be made uniform.
As a result of the fact that the angle of attack β at the outer diameter D _{A of} the blades is kept smaller than the hitherto customary value of approximately 2 · α, the axial flow velocity becomes more uniform and, in the ideal case, approaches a plug flow. This results in a narrower residence time distribution.
If the angle of attack of the blades decreases continuously from the base point on the shaft D _W to the outer diameter D _A , the axial velocity of the particles to be mixed at the outer diameter D _A decreases in relation to the axial velocity at the diameter D _{W of} the shaft. Assuming that the outer diameter D _{A is} twice as large as the diameter D _W (D _A = 2 D _W ), the same axial velocity is achieved over the entire reactor cross-section, if the angle of attack β on the outer diameter D _{A is} half as large , as the angle of attack α at the diameter D _{W of} the shaft. By a multiple interruption of the coil increases the shear effect during transport of the solid through the mixer. The mixing intensity is increased and thus the complete mixing does not take place until half the reactor length, but already much earlier. With the same reactor length, a longer residence time for the chemical reaction is achieved, whereby in new plants, the reactor length either reduced or alternatively increases the reaction time and thus the Reaktionstemperatur.gesenkt can be lowered.

Design possibilities of the mixing shafts are exemplified with the aid of the drawings.

Fig. 1

ein Fließschema des Verfahrens

Fig. 2

einen Schnitt durch eine Mischvorrichtung nach dem Stand der Technik

Fig. 3

eine einzelne Welle einer Mischvorrichtung nach der Erfindung

Fig. 4

eine Draufsicht auf die linke Stirnseite der Welle nach Fig. 3

Fig. 5

eine Detailansicht aus Fig. 3

Fig. 6

eine Darstellung der an einer Schaufel wirkenden radialen und axialen Geschwindigkeiten

It shows

Fig. 1

a flow chart of the process

Fig. 2

a section through a mixing device according to the prior art

Fig. 3

a single shaft of a mixing device according to the invention

Fig. 4

a plan view of the left end side of the shaft of FIG .. 3

Fig. 5

a detailed view of Fig. 3rd

Fig. 6

a representation of acting on a blade radial and axial velocities

In the mixer (1) of Figure 1 is passed through the line (2), e.g. hot heat transfer coke and through the line (3) to be processed residue oil. The mixer (1) has in the present case at least two horizontal, intermeshing screws, which mixes the introduced materials and transported to the outlet channel (8). Gases and vapors can leave the mixing device via the discharge channel (4) for condensation (5). Separate gases from the condensation (5) through the line (6) and product oil from the line (7). The coke-containing solid mixture, which has passed through the mixing device (1) is passed through the outlet channel (8) to a container (9). From this container (9), the dried coke can be withdrawn via line (10) and recycled to the process. Instead of the further processing of residual oil with heat transfer coke, the mixing device can of course also be used for the treatment of e.g. Bitumen, plastics, coal, peat or biomass, which may change the overall plant configuration.

Fig. 2 shows a sectional view of a mixing device (1) according to the prior art. In this mixing device (1), two intermeshing shafts (11, 14) are designed as hollow shafts which rotate in the same direction. Each shaft (11, 14) has two screws (12, 13, 15, 16) which extends uninterrupted over the entire length of the shaft. The two screws of a shaft are arranged offset by 180 °.

Fig. 3 shows one of at least two used shafts according to the invention. On the shaft (11), instead of a continuous screw, a plurality of individual blades (12a, 12b, 12c, ... 12m) arranged in a helical line one behind the other. A first Row of individual blades (12a, 12b, 12c, ... 12m) is on the shaft (11) associated with a second row of individual blades (13a, 13b, 13c, ... 13m) offset by 180 °. In this illustration, each row of blades consists of 12 individual blades. With the description screw or helical arrangement, any uniform or uneven arrangement of the blades is possible, in which the blades (12a to 12m, 13a to 13m) lined up around the shaft (11) can be arranged and in which a smooth rolling of the waves ( 11, 14) to each other is possible. The number of blades can be varied depending on the reactor length, the diameter ratios of shaft to blade and the associated blade curvatures. Likewise, the viscosity or the particle size of the media to be mixed has an influence, since the distance of the blades from one another can influence the mixing-in time. As with threads, a single row or a multi-row arrangement of the blades is possible.

In Fig. 4 is a plan view of the left end side of the shaft of Fig. 3 is shown. For reasons of simplicity, only six blades (12a, 12b, 12c,... 12f) and (13a, 13b, 13c,... 13f) of a row of blades are shown here. The diameter D _W is the diameter of the shaft (11) at the attachment point of the blades and the diameter D _{A is} the outer diameter of the shaft (11) on the blades.

FIG. 5 shows the enlarged detail "A" from FIG. 3 with the angles of attack of a single blade (12a). The angle α denotes the angle of attack of the blade on the shaft. The angle α is the diameter D _W , Fig. 4 assigned. The angle β is the angle of attack of the blade (12a) at the outermost diameter D _A. It is thus possible to influence the axial speed of the media over the cross-section of the mixing device by different angles of attack of the blades. Assuming that the outer diameter D _{A is} twice as large as the diameter D _W , at the same large angle of attack (α = β), the axial velocity of the media to be mixed at the outer diameter D _{A is} twice as large as the diameter D _{W of} the shaft (11). If the angle of incidence β of the blade at the outer circumference is smaller than the angle of attack α at the attachment point of the blade, then the axial velocity at the outer diameter D _A decreases to approximately half the original value. By varying the angles of attack α and β in relation to the diameters D _W and D _A , the axial velocity of the particles can be made uniform over the cross section of the mixing plant which results in a narrower residence time distribution. The axial flow thus approaches the desired plug flow.

This is clarified once again in FIG. For simplicity, it is again assumed that the outer diameter D _{A of} the shaft (11) on the blades is twice as large as the diameter D _{W of} the shaft (11) at the attachment point of the blades → D _A = 2 D _W.

With D _W = 1.0 m and a constant speed of 20 revolutions per minute, the peripheral speed of the particles at the fixing point of the blades V _W = 1.05 m / s. This is also the radial velocity V _Wr = 1.05 m / s. At an angle of attack α = 16 ° of the blade at the attachment point on the shaft results in an axial velocity of the particles of V _Wa = 0.3 m / s.
With D _A = 2.0 m and the same speed of 20 revolutions per minute, the peripheral speed of the particles at the outer diameter of the blades V _A = 2.09 m / s. This is also the radial velocity V _Ar = 2.09 m / s. At an angle β = 8 ° of the blade on the outer diameter D _{A of} the shaft results in the same axial velocity of the particles of V _Aa = 0.3 m / s. Of course, the same axial velocity of the particles over the cross section of the mixing plant can be realized even with other diameter ratios and other angles of attack.

LIST OF REFERENCE NUMBERS

1

mixer

2

management

3

management

4

culvert

5

condensation

6

management

7

management

8th

exhaust port

9

container

10

management

11

wave

12

slug

12a to 12m

shovel

13

slug

13a to 13m

shovel

14

wave

15

slug

16

slug

Claims (3)

1. Mixing device, in particular for use as a continuously working reactor, consisting of at least two rotating shafts (11, 14), wherein at least two opposite rows of paddles (12a, ..., 13a, ..., 13m) are disposed on each shaft (11, 14) and each row of paddles (12a, ..., 13a, ..., 13m) consists of at least two individual paddles, and that the paddles are fastened to the shaft (11, 14) at an angle of incidence α to the longitudinal axis of the shaft (11, 14),
   characterised in that the paddles themselves are curved, so that the paddles (12a, ..., 13a, ..., 13m) exhibit the angle of incidence α at the fastening point on the shaft (11, 14) and the angle of incidence β at the outside diameter D_A,
   that the angle of incidence β at the outside diameter D_A is at most as large as the angle of incidence α at the diameter D_W at the shaft,
   that the angle of incidence α continuously decreases from the diameter D_W at the shaft (11, 14) as the diameter increases and reaches the smaller angle β at the outside diameter D_A.
2. Mixing device according to Claim 1, characterised in that, given a paddle outside diameter D_A which is twice as large as the shaft diameter D_W at the fastening point of the paddles (12a, ..., 13a, ..., 13m), the angle of incidence β at the outside diameter D_A is approximately half as large as the angle of incidence α at the diameter D_W at the shaft (11, 14).
3. Method for continuously mixing and reacting liquid or solid feed materials with a solid granular heat transfer medium such as, for example, coke or another suitable solid in a mixing device according to Claims 1 and 2, characterised in that the axial speed of the media at the diameter D_W at the shaft (11, 14) is equal to that at the outside diameter D_A.

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