FR2660375A1 - CIRCULATION PUMP OF A CLOSED CIRCUIT HEAT LIQUID. - Google Patents

Abstract

The pump is intended to circulate a molten salt in a reactor mounted in parallel with it. It works as a suction pump and ensures a minimum salt level (Nm i) in the pump body (1). The bearings (23, 24) of its control shaft (2) are arranged in the upper part, in a salt-free zone. There is provided a passage for the shaft (2), mounted in cantilever, consisting of a sleeve (14, 15) located below said minimum level and ensuring only limited leakage of salt. Means (8, 9, 12) are provided to ensure the return of the leakage salt in the suction zone (A) of the pump.

Description

The present invention relates to pumps intended to circulate a

  liquid coolant, and more particularly a molten salt, following a cyclic path around the contact tubes of a reactor in

  which are exothermic chemical reactions

  miques or endothermiques, reactor and pump being assembled

in parallel.

  îO In general, the salt flows from bottom to top in the reactor and from top to bottom in the pump body.

pump pushes the salt down.

  But, in certain cases, it is desired that the circulation of the salt is reversed in the reactor,

  that is to say, it circulates from top to bottom.

  This circulation can be carried out with the same type of pump as above, but by reversing the connecting pipes between the pump and the reactor. This arrangement results in noticeable bulk.

acceptable.

  This is why we sought to obtain a pump capable of ensuring this reverse circulation, without inversion of the connecting pipes with the reactor, therefore

which pulls the salt up.

  In reactor systems to which the invention applies, account must be taken of a number of conditions relating to the level of salt in the

pump body.

  In particular, the minimum level of salt must be higher than the level of the upper tube plate of the reactor so that the underside of this plate -2 - is always sprayed with salt. It is also necessary that this minimum level corresponds to a height of salt above the propeller of the pump such that the head of net load at the available suction is greater than that required by the pump to avoid its

  defusing and its entry into cavitation.

  While in pumps, where circulation takes place from top to bottom, the passage of the shaft in the pump body is normally located above the maximum level of salt without problem, since no salt leakage is to be provided by this passage, it is different when the pump provides a closed circuit circulation from bottom to top The salt outlet by the shaft passage must be

  prevented and then requires to equip it with a cable gland.

  But the cable glands cannot be used with salt

which engorges them while solidifying.

  The invention specifically aims to provide a pump for ensuring the circulation in a closed circuit of salt, coolant, in a reactor mounted in parallel

  with the pump and where the salt must flow from top to bottom.

  To this end, the invention provides that the pump operates as a suction pump, arranged to ensure a minimum level of liquid in the pump body, the bearings of its control shaft are arranged in the upper part of the pump in an area outside liquid, the shaft thus being cantilevered in the pump body and there is provided a passage for the shaft constituted by a sleeve situated below said minimum level and arranged to ensure only a leak limited liquid, means being provided to ensure the return of the

  leaking liquid in the suction area of the pump.

  -3 - Means for centering said sleeve in the pump body are advantageously provided to provide clearance

to the axis.

  In a particular embodiment, the means for returning the leak consist of passages formed in the pump body itself, communicating from the outside of said body with the suction zone of the pump. In a preferred embodiment, the pump body is housed in a closed box in which the suction pipe of the pump enters, said pipe interrupted

  opens into said box at a certain distance

  below the pump rotor and said passages open into the space between the pump body

and said box.

  By way of non-limiting example, there is shown in the accompanying drawing an exemplary embodiment of a pump according to the invention, a drawing in which FIG. 1 is a view in axial section of the pump and FIG. 2 is a detail view, on a larger scale scale, of a variant of the part of the passage

  of tree included in the circle C of this figure 1.

  In this example, the pump comprises a body 1 through which the control shaft 2 of the rotor 3 mounted cantilevered, its bearings 23 and 24 being located in the upper part of the pump, in a zone of a level higher than the maximum level of salt In the body of

  pump open, on the one hand, the conduit 4 for connection

  directly with the upper part of the associated reactor (not shown) and, on the other hand, a duct 5 of -4 - connection with a heat exchanger (not shown) In the axis of the body 1 is connected the suction tube 6 connected to the lower part of the reactor

partner (not shown).

  The actual pump body 1 is surrounded by a closed reservoir box 10 from which the conduits 4 and the suction tube 6 emerge. This tube is interrupted to provide a space A between sections 21 and 22

  the rotor 3 which opens into the box 10.

  Thus, the box 10 is filled with coolant salt to a level between a minimum Nmi and a maximum N. The shaft 2 passes through a sleeve, consisting of a part 14 and a ring 15 integral of the part 14 located at a level below the minimum level Nmi This sleeve is formed so as to ensure controlled micro-leaks, as seen in the example

shown in figure 2.

  The limited leaks result from the very small clearances (a) and (b), here of the order of 0.5 and 1 mmm for example, existing, on the one hand, between the fixed centering piece 13, resting on the face upper part of the separation plate there between the body 1 and the casing 10, and the part 14, linked to the wall of the pump body 1, and, on the other hand, between the ring 15 and the wall of the shaft

2.

  The salt which escapes through these leaks can pass through holes 8 provided in the wall of the body 1 and a hole 9 formed in the separation plate 1 i and thus join the suction zone A under the rotor 3 by passing 5 - in the space 12 between the body 1 and the box 10. -6-

Claims (4)

Claims   1 Circulating pump for a liquid coolant, in closed circuit, in a reactor mounted in parallel with it, characterized in that the pump operates as a suction pump arranged to ensure a minimum liquid level (Nmi) in the pump body (1), the bearings (23, 24) of its control shaft (2) are arranged in the upper part of the pump in a non-liquid area, the shaft (2) being thus cantilevered in the pump body (1) and there is provided a passage for the shaft (2) constituted by a sleeve (14,) situated below said minimum level and arranged to ensure only a limited leakage of the liquid, means (8, 9, 12) being provided to ensure the return of the leaking liquid in the suction zone (A) of the pump.  2 pump according to claim 1, wherein there is provided means (13) for centering said sleeve (14, 15)   in the pump body (1) to provide clearance to the axis.   3 Pump according to claim 1 or 2, wherein said means for returning the leak are passages (8) formed in the same body (1) of the pump and communicating, from the outside of said body (1), with the pump suction area (A).   4 Pump according to claim 3, wherein the pump body (1) is housed in a closed box (10) into which enters the suction pipe (6) of the pump, said interrupted pipe opens into said box at a certain distance below the rotor (3) of the pump and said passages (8) open into the space (12) between the pump body (1) and said box (10).