CENTRIFUGAL PUMP FOR FEEDING SOLID PARTICLES TO A PRESSURIZED VESSEL AND PROCESS FOR FEEDING SOLID FUEL TO A HIGH PRESSURE GASIFICATION REACTOR

Abstract: Centrifugal pump for particulate matter, e.g. pulverized coal, comprising two discs being kept at a distance from each other. The distance (d) between the two discs decreases as a function of the radius (R) of the discs in such a way, that R x d is kept constant. Process for feeding pulverized coal to a high-­ pressure gasification reactor using this pump.

Description: CENTRIFUGAL PUMP FOR FEEDING SOLID PARTICLES TO A PRESSURIZED VESSEL AND PROCESS FOR FEEDING SOLID FUEL TO A HIGH PRESSURE GASIFICATION REACTOR The application relates to a centrifugal pump for feeding solid particles to a pressurized vessel, comprising a rotor arranged rotatably in the vessel, which rotor consists of two trays the concaves of which face each other, and one or two feed inlets connected axially to the rotor. Such a pump with one feed inlet is known from the Netherlands patent application No. 7505578 laid open to public inspection. There are also pumps having two axial feed inlets, that is to say on either side of the rotor which is arranged rotatably around a horizontal shaft. These centrifugal pumps are used to feed powders or granular materials, for example reagents or catalysts, to some space in which the pressure is higher than outside. It is obvious that these pumps can also be used in situations without pressure difference. When these pumps are in operation, the solid matter is cast through the feed inlet onto the rotating rotor. Owing to the centrifugal acceleration the solid particles acquire a high velocity which enables them to overcome the difference in pressure between the inside and outside of the vessel and to prevent leakage of gas-from the pressurized vessel. In certain centrifugal pumps the rotor is provided with a number of radial passages, known as centrifugal nozzles, between the two trays. In the types referred to in the present application the solid matter can be expelled over the entire circumference of the rotor through a narrow slot which is defined by the edges of the two trays. In that case it is also possible to allow the two trays to rotate at different speeds in order to prevent clogging of the slot. The solids leave the edge of the rotor with a radial and tangential velocity component. In the usual embodiments the rotor has a rotational speed of, for example, 500-5000 rev./min. and the particles acquire a radial velocity of about 10 m/s and a tangential velocity of about 100 m/s. In this manner it is possible to overcome pressure differences of some tens of bars, for example 20-40 bars. Although the known centrifugal pumps are fairly satisfactory in practice, they are still capable of improvement. Investigations have shown that a prolonged trouble-free period of operation of such a pump is partly dependent on the internal shape of the rotor, in other words, on the shape and the spacing between the trays. The cone-shaped trays of the centrifugal pump referred to in NLA-7505578 occasionally give rise to troubles such as clogging (i.e. the solid particles are so densely packed that the 3600 slot becomes clogged) or back-flow (i.e. the concentration of the solid particles in the carrier gas becomes too low, as a result of which sufficient pressure cannot be built up and gas leaks from the pressurized vessel into the pun;). It has now been found that a prolonged trouble-free period of operation is ensured if the product of the spacing dEm] between the two trays, measured at a distance R[m]from the rotor centre, 2 and the distance RCm]lies in the range between O.9 C[m ] and 2 1.1 C [m ], where C is a constant. The invention therefore relates. to a centrifugal pump for feeding solid particles to a pressurized vessel, comprising a rotor arranged rotatablyin the vessel, which rotor consists of two trays the concaves of which face each other, and one or two feed inlets connected axially to the rotor, characterized in that the product of the spacing d[m] between the two trays, measured at a distance R[m]from the rotor centre, and the distance R[m] lies in the range 2 between 0.9 C[m ] and 1.1 C [m ], where C is a constant. A conclusive explanation of the effect found is difficult to give and is of no practical value either. It is assumed, however, that the relation found between R and d imparts such a shape to the trays that the gas pressure distribution between the trays optimally corresponds with the course of the centrifugal force on the solid particles, allowing for friction losses. One of the trays may have an arbitrary shape, but then the shape of the other tray is in fact fixed as a result of the requirement that R x d should lie in the range of from 0.9 C to 1.1 C. One or both trays preferably exhibit at least substantially the shape of an orthogonal hyperboloid, that is to say their internal surface can be described by rotating an orthogonal hyperbole around one of its axes, which axis of rotation then coincides with the axis of rotation of the rotor. In order to reduce the risk of back-flow of gas from the pressurized vessel further, the trays are preferably bent towards each other along the tray circumference. A small constriction is thus obtained at the outflow opening which inhibits the passage to some extent, but does ensure that the space between the trays is invariably satisfactorily filled with solid particles. It is of course also possible to provide said constriction in the outflow opening in rotors having centrifugal nozzles. In order to transfer as much impulse and energy as possible from the rotating rotor to the solid particles, and at the same time with the largest possible radial component since the pressure gradient of the gas also has a radial direction, the concave side of one or both trays is preferably provided with radially directed raised parts and/or recesses. These raised parts or recesses may have any profile, such as ridges, grooves, slots, etc., but they may also be vertical walls dividing the space between the two trays into sector-shaped compartments. These sector-shaped com- partments should not be mistaken for the more or less tubular centrifugal nozzles. If said walls are fitted to one tray only, then it is possible to rotate both trays at a slightly different speed, as known in order to prevent clogging of the outlet slot. The centrifugal pump according to the invention can be used in various processes, such as supercritical gas extraction, gasification of coal, combustion of coal under pressure, blastfurnace production of steel (introduction of fuel and/or ore), catalytic cracking (introduction of catalyst), desulphurization under pressure (introduction of limestone or dolomite). The centrifugal pump according to the invention is in particular and with advantage used to feed solid carbon-containing fuel, for example coal dust, to a high-pressure gasification reactor, in which the fuel is then gasified to a mixture of carbon monoxide and hydrogen. The application therefore also relates to a process for feeding solid carbon-containing fuel to and the subsequent gasification thereof in a high-pressure gasification reactors which process is characterized in that the fuel is fed by means of a centrifugal pump according to the invent ion.

Claims: CLAIMS 1. A centrifugal pump for feeding solid particles to a pressurized vessel, comprising a rotor arranged rotatably in the vessel, which rotor consists of two trays the concaves of which face each other, and one or two feed inlets connected axially to the rotor, characterized in that the product of the spacing d[m] between the two trays, measured at a distance R[m] from the rotor centre, and the distance R[m] lies in the region between 0.9 C[m ] and 1.1 C[m2], where C is a constant. 2. A centrifugal pump as claimed in claim 1, characterized in that one or both trays have at least substantially the shape of an orthogonal hyperboloid. 3. A centrifugal pump as claimed in claim 1 or 2, characterized in that the trays are bent towards each other along the tray circumference. 4. A centrifugal pump as claimed in any one or more of claims 1-3, characterized in that the concave of one or both trays is provided with radially directed raised parts and/or recesses. 5. A process for feeding solid carbon-containing fuel to and the subsequent gasification thereof in a high-pressure gasification reactor, characterized in that the fuel is fed by means of a centrifugal pump as claimed in any one or more of claims 1-h.

Inventors: VAN DER BURGT, MAARTEN JOHANNES
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1981
Main classification: B01J3
IPC codes: B01J3, F04D23, F04D7