Patent Publication Number: US-2011052390-A1

Title: Sludge reactor pump for simultaneously conveying solids, liquids, vapours and gases

Description:
The present invention relates to a sludge reactor pump for simultaneously conveying solids, liquids, vapors and gases, with a conveying path extending over a first and second stage, with an axis, and with a centrifugal force acting on the conveying path. 
     From EP 1 477 682 A1, a liquid ring gas pump for conveying gases is known. This pump has control disks between working spaces which have openings for the pump medium. These openings are formed similarly on the suction and pressure side, and can be covered depending on the situation. 
     From DD 134978, a self-priming centrifugal pump with liquid ring and a pump impeller eccentrically mounted in a housing for conveying clean and dirty liquids is known, wherein the hub disc facing the pressure side of said pump has openings. For pressure reduction, ventilation cells are provided. 
     From DE 699 24 021 T2, a device for pumping liquids or suspensions is known, wherein upstream of an impeller, a zone for separating gas is provided. 
     None of the above mentioned pumps can simultaneously convey media with different aggregate states. 
     In particular in the reaction technology, there is a need for agitators in tanks which primarily allow a discontinuous reaction. With the above mentioned pumps of the prior art, the contents can only be conveyed after completion of the reaction, wherein then a homogenous, liquid state is achieved which allows the pumping with the known pump systems. 
     During the reaction, the reaction mixtures can not be circulated, whereby a continuous reaction is excluded. 
     It is thus the object of the invention to provide a sludge reactor pump by means of which such reaction mixtures can be circulated during the reaction and which achieves a good mixing in the conveying system for the acceleration of the reaction, and which thereby contributes to reduce the size of the reaction plant. 
     The main emphasis here is not achieving good efficiencies, but the utilization of lost energy for heating the conveyed fluid up to reaction temperature. 
     The known pump systems are not suited for simultaneously conveying the generated reactants consisting of gases and vapors on the one hand, and liquids loaded with solids on the other. Radial pumps react to gases and vapors generated during the reaction in a very critical manner. The vapors generated during the reaction accumulate due to their low density in the center of the impeller where they cause cavitation and an interruption of the conveyance. The associated insufficient NPSH values, i.e., the generation of unacceptable cavitation, result in destruction of the pump. 
     The necessary negative pressure for sucking in the reaction mixtures is possible to a limited extent only for the usual pumps with radial impeller and outside of the range of reacting mixtures in chemical plants. Regenerative pumps are self-priming. However, the possible negative pressure is not sufficient for the reaction mixtures. Because of the narrow gaps, the solids which are carried along clog the channels. The service life of known conveying devices is low, if a conveyance takes place at all. 
     A pump type which generates high negative pressures in the inlet is the liquid ring gas pump known from EP 1 477 682 A1. However, it is not suited and provided for the transport of liquids and solids. This pump is able to suck in gases and vapors, but not liquids and solids. Thus, it was searched for a possibility to make this pump type capable also for conveying liquids and solids, thereby solving the object according to the invention. 
     Surprisingly, a solution was found to this. 
     According to the invention, the object is solved in that the conveying path extends axially from the first into the second stage and that the conveying path of the vaporizing liquids and solids is deflected with respect to the axial conveying path of the gases from the outside to the inside by means of a guiding chamber arranged between the first and the second stage, wherein on the circumference of the first stage, boreholes are formed in the guiding chamber, through which boreholes, liquids and solids can get into the guiding chamber, that in the guiding chamber a plurality of guiding devices are formed which guide the liquid and solids from the outside to the inside, and that in the inside, a mixture inlet is formed through which liquids and solids can get into the second stage, and wherein inside the first stage, a gas outlet is formed through which the gas can get axially into the guiding chamber and through the mixture inlet into the second stage. 
     Thus, a new pump type was provided which combines the conveyance of liquids of the radial pump and the gas conveyance of the liquid ring vacuum pump and, due to a specific configuration of the channels, allows in addition the conveyance of solids. Only the combination of both systems allows to separate the gases and vapors generated during a reaction from the liquid and to convey the two aggregate states without any problems. 
     The separation of gases and vapors is carried out according to the principle of the liquid ring vacuum pump which separates and conveys them through the centrifugal force of the impeller to the inside. Conveying the solid and liquid substances on the circumference takes place through a guiding system of the control disks which transports said substances axially on the circumference and thus continuously conveys new solid and liquid substances, 
     On both sides of the impeller, control disks are arranged which delimit the pump chamber. Impeller and control disks are arranged eccentrically. Thereby, during the intake phase or during gas conveyance, a liquid ring can develop which abuts with different distances against the impeller hub. Gas-filled spaces are formed which become bigger and smaller due to the eccentricity. In this operating state, the sludge reactor pump is well suited for also conveying gases and vapors. 
     The liquid/vapor mixture is sucked in through a suction slot which is arranged in the region of the greatest distance of the liquid ring from the hub. Because of the different density, the reaction gas accumulates in the hub region and is discharged through a pressure slot which is arranged in the region of the smallest distance of the liquid ring from the hub. 
     Through the radial component of the impeller, the liquid is separated from the gas phase and is discharged in the region of the highest housing pressure through openings in the form of slots or boreholes arranged on the outer housing diameter, or is conveyed through a guiding device into the next stage. For deflecting the liquid, guide vanes are arranged upstream of the outlet openings. Conveying liquid is only possible with moderate efficiency. The power loss generated thereby serves for energy supply to the conveyed medium. 
     A narrow axial gap between housing and impeller as in the case of a liquid ring vacuum pump is not required because, according to the invention, the liquid ring does not have to be stabilized in a closed chamber but includes outlet openings which are arranged in the region of the highest housing pressure, if necessary with a downstream guiding device. The construction of the pump allows a crushing of the solids and, at the same time, a shear action on the conveyed medium. 
     In the guiding device, the liquid flowing through the outlet openings on the pressure side is deflected in such a manner that it is conveyed to the next stage, or, in case of single-stage machines, is used as bypass. This results in a better mixing due to a longer residence time of the medium and an additional energy input through friction which facilitates a faster reaction process. 
     Thereby it is made possible that the liquid ring or also the solid liquid ring is permanently exchanged and is pushed by new inflowing mixtures of solids and liquid into the next stage or into the conveying line. This operational mode results in an intensive mixing between liquid ring and the inflowing conveyed medium. 
     Thus, the liquid ring vacuum pump&#39;s capability is maintained to generate a high negative pressure for suction, to convey the gases and vapors in the center, as in a vacuum pump, and, at the same time, due to the radial impeller principle, to still convey the liquid-solids mixture, the sludge, in the reacting state at high temperature through the pump. 
     The size of the guiding profiles and boreholes implemented in the embodiment according to the invention thus determine at the same time the conveying range of the pump of the solids-liquid mixture. Another advantage is the possibility of cleaning the unit by reversing the pump&#39;s direction of rotation. As shaft seal, double-acting slide ring seals which are independent of the direction of rotation are used, which are operated with a suitable liquid, for example oil, as sealing medium between the pump-side and the atmosphere- side seal. 
     The sealing medium is circulated by auxiliary pumps with a slight overpressure with respect to the seal on the pump side. According to the invention, the pump bearing is arranged between the inner and the outer seal in such a manner that the sealing medium is used for lubricating and cooling at the same time. To maintain the temperature at the slide ring seal and at the pump bearing within the permissible range, heat exchangers are connected to the circuit. 
     The higher pressure of the sealing medium with respect to the inner seal has the effect that the abrasive solid particles carried along in the sludge, such as, e.g., metal glass and stones, are kept away from sealing gap, bearing and shaft. In addition to the described usage, an additional mixing can be achieved in a loop mixer which is arranged in a bypass pipe between the stages (FIG. 9). 
    
    
     
       An embodiment of the invention is described hereinafter in more detail by means of the drawings. In the figures: 
       FIGS. 1 to 5 each show cross-sections through a sludge reactor pump according to the invention; 
       FIG. 6 shows a diagram with respect to the capacity of the sludge reactor pump according to the invention; 
       FIG. 7 shows a longitudinal cross-section through the sludge reactor pump; 
       FIG. 8 shows a plant with a sludge reactor pump from FIG. 7 and with electric motor; 
       FIG. 9 shows a loop reactor; 
       FIG. 10 shows the sludge reactor pump with electric motor. 
     
    
    
     FIG. 1 shows a cross section in the front part (first stage, or ND part) of the pump which is connected with the intake opening of the pump. The housing is designated with 1. The impeller 2 has a blade ring which, viewed in rotational direction, is inclined rearwardly. A shaft is designated with 3. A partition wall is designated with 4. 
     An outlet opening  5  serves for emptying the pump. A liquid ring of a first stage (ND) is connected via boreholes 8 with a mixture inlet 7.1 for a second stage (HD). Thereby, the ring from liquid and solids formed with the centrifugal force on the outer circumference gets into a guiding chamber 10 between the two stages and from there from the outside to the inside into the mixture inlet 7.1 arranged in the inside. The gas which accumulates in the first stage on the inside gets into the next stage via a gas outlet 7.2. 
     When the liquid enters the first stage, the liquid conveyance takes place by means of the centrifugal force outwardly into the liquid ring and via the boreholes 8 and a conveying path through the central outlet 7 from the outside to the inside centrally into the next stage (HD). The gas portions which accumulate on the inside are not deflected from stage to stage but axially conveyed from stage to stage. FIG. 2 illustrates the system in detail. This figure shows the liquid transport between the stage 1 and the stage 2 in the guiding chamber 10 arranged therebetween. 
     Within the guiding chamber 10 there are guiding devices 9 which guide the liquid and solid substances guided from the outside to the inside between the stages in a fluidic manner into the next stage such that no cloggings or fluidic blockages occur. This is further deepened in FIG. 3 which only illustrates an intermediate disk. FIG. 3 shows only that part of the intermediate disk which is adjacent to the first stage, wherein the liquid discharge from the first stage is illustrated as borehole 8. 
     FIG. 4 illustrates the other half of the intermediate disk. FIG. 5 also illustrates a gas inlet 7.3 and a gas outlet 7.4. The result of such a conveying device is shown in FIG. 6. It is shown that the sludge pump has a high negative pressure on the inlet side of the pump; however, it generates a relatively low conveying pressure. This is very advantageous in chemical reactions with solids because solids would clog a nozzle on the outlet side. However, at such low outlet pressures, the additional arrangement of nozzles is not necessary because these pressure differences can be controlled by normal control valves without additional throttling with nozzles. 
     FIG. 7 shows the embodiment of a sludge reactor pump according to the invention with two reaction chambers. The designations correspond to the ones of the FIGS. 1 to 5. FIG. 8 shows the integration of such a sludge reactor pump, which is driven by an electric motor, as a complete unit. The sludge reactor pump is designated with 12. The motor, which is configured as electric motor or combustion engine or combustion turbine, is designated with 13. 
     Designated with 14 is the fan which recools the cycle oil of the bearing cooling of the bearing lubrication and the pressure sealing for preventing penetration of solid particles from the conveyed medium into the bearing. The storage tank for the storage volume of the bearing lubrication is designated with 15. The pump for the cooling and lubricating circuit of the bearing lubrication is designated with 16. Since it is the task of the sludge reactor pump to mix and heat the sucked-in materials, a loop reactor is connected to the suction and pressure line for further mixing, which loop reactor further increases this effect. The latter is illustrated in FIG. 9. 
     The invention is explained in more detail in a special exemplary embodiment, This exemplary embodiment is illustrated in more detail in FIG. 10. A sludge reactor pump is coupled with an electric motor. The unit has an electrical input power of maximum 200 kW and on average 120 kW. The unit has a length of 3.5 m and the sludge reactor pump is mounted on a support plate with vibration dampers. The sludge reactor pump has a length of 795 mm and is mounted on a base plate of 840×1200 mm. The distance between intake on the motor side and the overpressure line on the outside is 795 mm. The pressure curve of the overpressure side is illustrated in the diagram in FIG. 6.