MXPA98000863A - Axial conveyor, preferably with gaseo element, and loop reactor in which this content aq - Google Patents

Abstract

The present invention relates to an axial apparatus, in particular for the transport of gas / liquid dispersions, which contains conveyor elements in the form of impellers, vanes or endless screws, which are arranged in an arrow that can be operated on an essentially cylindrical conveyor tube, characterized in that the conveyor elements comprise an edge, which runs in the wall and points towards the pressure side of the conveyor elements, where the height of the edge is 0.025 to 0.25 times the diameter of the transported tube.

Description

Axial conveyor, preferably with * saseo element. The reactor of loops in the dream is contained therein. DESCRIPTION OF THE INVENTION The present invention relates to an axial conveyor, suitable especially for the transport of liquid / gas dispersions, preferably with a self-flowing gas agitator, and to a loop reactor, in which the former is contained. Axial conveyors generally have a drive shaft within a transport channel in the form of a tube section, with pallets or transport screws arranged in an inclined position and supported against the wall. When transported by means of axial conveyors, a pressure zone is formed in the conveying direction below the blades or the worm and a suction zone above them. The pressure gradient formed in this way in the separation gap between the conveyor tube (housing) and the vanes or the worm screws causes a backflow of the medium to be transported. In the case of transport of liquid / gas dispersions, separation of gas bubbles occurs due to the slit and therefore a decrease in transport efficiency. This effect is further aggravated by the fact that the rotating pulse given to the liquid by the rotation of the worm or of the vanes is braked by the friction against the wall, so that the gas bubbles segregate towards the wall in the vicinity of the wall. wall and are joined together by coalescence in the wall. This causes the collapse of the transport performance in the case of high gas contents. Therefore, the axial conveyors are only suitable for the transport of liquid / gas dispersions with gas contents of up to 5% of the volume. However, it has been found that axial conveyors for the transport of liquid / gas dispersions are very suitable, if the conveyor elements of the axial conveyor have an edge resting against the wall on the pressure side. This edge has the effect that, on the one hand, the difference in pressures in the separation gap of the casing is lowered and also that the pressure drop takes place through the dilation of the edge in the axial direction, that is to say that lowers the pressure gradient. The flow rate component directed radially outwards on the pressure side is then deflected in the transport direction before reaching the separation gap of the housing, so that the separation of the gas bubbles through the flow is made difficult. cleft In addition, the pulse of rotation of the liquid reaches its maximum value on the inner side of the edge, so that the gas bubbles are subjected, with respect to the liquid, to a force that moves them away from the wall. Therefore, the object of the present invention is to create an axial transport pump, especially for transporting liquid / gas suspensions, containing conveyor elements by means of propellers, vanes or in the form of an endless screw, located on an axis operable in a housing in the form of a tube section, the conveyor elements having an edge on the pressure side. The relative height of the edge, referred to the diameter of the conveyor device, must be at least 0.025, but preferably 0.05, and especially preferably 0.075. The relative height of the edge, referring to the diameter of the conveyor device, does not need to exceed 0.25. The relative height is preferably below 0.2, and especially preferably below 0.15. If conventional helices or Kaplan helices are used as conveyor elements, a number of sheets between 2 and 5 is preferable. The angle of inclination of the usual helices or Kaplan helices can be between 5 and 40 *. In total, the propellers cover at least 60%, but in a particularly preferred way at least 80% of the surface of the circle defined by its outside diameter. The endless screws as conveyor elements are preferably configured with between one and four screw inlets. The step of the endless screw, that is to say the relative elevation with respect to the diameter, is preferably between 0.2 and 0.9. A satisfactory transport performance of the axial conveyor constructed according to the invention is achd, depending on the number of revolutions, if the angle of inclination of the conveyor elements and the height of the edge are adapted to the transport section, to the viscosity and to the content of gas bubbles of the medium to be transported. However, because of the quasi-elastic properties of the medium to be transported (due to dispersed gas), the axial conveyor has a tendency to suffer instabilities in the transported flow, when the aforementioned parameters fall outside certain limits, especially in the direction transverse to the direction of transport, which may cause the coalescence of the gas bubbles also in the vicinity of the axis, even in the non-coalescing system of materials, with the corresponding impact on the transport performance. It has also been found that these instabilities can be avoided if a swirling suction in the vicinity of the axis of the pipe section is produced on the pressure side of the axial conveyor. This can occur by means of an additional conveyor device located on the pressure side of the axial conveyor and whose transport section is between 1/3 and 2/3 of the section of the pipe section, but preferably is about half of said section of the tube section. The additional conveyor device does not require special requirements. For example, it can be a simple paddle agitator, which is located on the extension of the axis of the axial conveyor and whose radius is between 0.55 and 0.82 times, but preferably and approximately 0.7 times the radius of the section of tube. The angle of inclination of the additional conveyor device is preferably between 1.5 times and 2.5 times the angle of inclination of the conveyor elements of the axial conveyor, but is not greater than 75 *. The distance between the additional conveyor device and the axial conveyor is preferably calculated so as to avoid the impact of the vortex produced by the additional conveyor device with the axial feed current and with the peripheral return current in the pipe section. The distance between the additional conveyor device and the outlet end of the axial conveyor preferably corresponds at least to the diameter of the tube section, but more preferably to between 1, 5 and 3 times the diameter of the tube section. According to another embodiment of the invention, the additional conveyor device is configured as a gas agitator. In this case, the common axis of the axial conveyor and of the additional conveyor device has an axial bore, which also opens into the conveyor elements of the additional conveyor device, also configured in hollow form. The gas for the gassing is introduced into the shaft through suitable introduction elements in a manner that is already known per se, preferably by means of self-suction, and is distributed in the liquid / gas dispersion through exit holes provided in the outline of the gas. additional conveyor device. The axial conveyor constructed according to the invention is especially suitable as a conveying device in loop reactors, in which reactions with or without gas liberation take place in the liquid phase, for example in fermenters, or in the case of direct reactions with oxygen, hydrogen , chlorine or other gases not completely dissolved in the liquid medium, where appropriate in the presence of solid materials, such as fine particle catalysts (reactions in the mud phase). The invention is explained in more detail below with reference to FIGS. 1 to 5 of the accompanying drawings. Figure 1 shows a screw conveyor constructed according to the state of the art. This conveyor consists of a cylindrical housing 1 with an axis 2 placed inside it and operable for its rotation, on which an endless screw 3 is located. The liquid / gas dispersion is transported downwards, configuring itself below the screw without end the pressure zone P and above the worm the suction zone S. The transport in the axial direction is combined with a rotation around the axis. This transport movement in the form of a spiral is also combined with a rolling movement indicated in the drawing by means of the circle provided with arrows, that in the pressure zone P transports the transport medium outwards and in the suction zone S transports the transport means m towards the axis. In the separation gap between the worm 3 and the housing 1 the separation of the dispersed gas bubbles takes place, due to the pressure gradient that exists between the pressure side and the suction side. Furthermore, in the drawings, the centrifugal force Z acting on the liquid due to rotation is qualitatively represented, in dependence on the radius R. FIG. 2 shows an axial conveyor constructed according to the invention, in which the worm 3 has in the pressure side an edge 4 in all its circumference. The single input worm shown in this figure has a pitch of H / d * 0.485 and a relative length of L / d = 0.75. The relative height of edge 4 is b / d = 0.1. As indicated by the arrow 5, the component of the flow direction directed radially outwards on the pressure side is deflected in the direction of transport by means of the edge 4, so that the gas bubbles contained therein no longer they are separated by the pressure gradient between the upper side and the lower degree of the endless screw 3, recessed by the edge 4. FIG. 3 shows a Kaplan propeller constructed according to the invention with four vanes 3, whose angle of inclination a it is 30 *. The vanes 3 cover the entire section of the conveyor tube 1 (except the separation slit with the housing). Figure 4 shows an embodiment of the axial conveyor, in which the edge 4 is configured as a cylindrical envelope surface surrounding the pallets 3. Figure 4 shows an embodiment of an axial conveyor, in which the edge 4 is formed as a surface of a cylindrical envelope surrounding the vanes 3. Figure 5 shows a loop reactor 10 with a central tube 11 for passing the gas / liquid dispersion stream, in which the axial conveyor apparatus 12 constructed according to the invention is located. In the loop reactor, a gas / liquid dispersion is circulated by pumping according to the arrows drawn in the figure. The central passage tube 11 is held by means of radial baffle plates 13, so that the baffle plates prevent at the same time the circulation in the rotating direction of the dispersion, driven by the conveyor 12. The axial conveyor 12 has an additional conveyor device 15, rigidly attached thereto on an axis 14 and whose radius covers only a part of the section of the central tube of passage 11 of the dispersion.

Figure 6 shows a loop reactor 10, in which the additional conveyor device 15 is configured as a self-polishing gas agitator. The gassing medium is sucked from the gas chamber 18, located above the level 19 of the liquid, through the corresponding suction holes 17 of the hollow shaped shaft 14 of the conveyor device, and is distributed in the liquid in the form This is done by means of the agitator arms 15, which are formed in a hollow shape and which communicate with the suction hole 17. Furthermore, the return of the gas / liquid dispersion is carried out through the heat exchange tubes 20, which are subject to by means of tube floors 21 and 22. Incorporated elements (not shown in the drawing) can be located inside the central passage tube 11 to guide the flow of the dispersion, which prevents the rotation of the gas dispersion. /liquid. The heat exchange is carried out in this form of construction by means of a heat exchange liquid, which is conveyed by means of a pump 23 from the collecting tank 24 of the separator 26 to the intermediate space 25 located between the exchange tubes 20 of heat, and evaporates there. The vapor / liquid mixture arrives through the inlet tube 27 to the separator 26, where the vapor is separated from the liquid and can be evacuated through the pipe 28. With the evaporative cooling system it is possible to evacuate amounts of very large heat. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (7)

1. Claims 1. Axial conveyor, especially for transporting gas / liquid dispersions, characterized in that it comprises conveyor elements in the form of propellers, blades or worm screws, located on an axis operable in an essentially cylindrical conveyor tube, the conveyor elements having an edge leaning against the wall. Axial conveyor according to claim 1, characterized in that the edge is oriented in the direction towards the pressure side of the conveyor elements. Axial conveyor according to claims 1 or 2, characterized in that the height of the edge is between 0.025 and 0.25 with respect to the diameter of the conveyor tube. Axial conveyor according to one of the claims 1 to 3, characterized in that an additional conveyor device is provided on the pressure side located on the conveyor shaft, so that the additional conveyor device acts only on part of the tube section transporter. The axial conveyor according to claim 4, characterized in that the additional conveyor device is designed as a gas agitator. 6. Process for transporting gas / liquid dispersions, characterized in that an axial conveyor constructed in accordance with one of claims 1 to 5 is used. 7. Loop component, characterized in that it comprises, as a central circulation device, a conveyor axial construction according to claims 1 to 5. 8. Process for carrying out chemical reactions with direct reaction of a gas in a liquid, where appropriate in the presence of solid particles of fine particles, characterized in that a loop reactor constructed according to the invention is used. claim 7.