Method and apparatus for cleaning heated surfaces

Abstract

A method and apparatus for deslagging high temperature water walls of boilers while steaming, utilizing a jet of water applied in such manner as to develop sufficient mechanical energy to dislodge the slag without chilling the wall to a harmful degree.

What is claimed is: 
     
       1. The method of utilizing a liquid jet to dislodge deposits from hot surfaces which comprises providing a .Iadd.rotating .Iaddend.jet of a relatively small diameter and projecting the jet at a high velocity of propagation which will possess sufficient mechanical energy to effect physical dislodgment of deposits, and directing the jet against .[.such a surface.]. .Iadd.said hot surfaces .Iaddend.while and only while .[.moving.]. .Iadd.continuously varying the rate of rotation of the jet in proportion to the distance of travel of said jet so as to move .Iaddend.the jet over the surface at a speed of progression thereover which is sufficient to prevent chilling any part of the surface to an extent causing undesirable thermal shock. 
     
     
       2. The method set forth in claim 1 wherein a mechanically-operated soot-blower-type liquid projecting device has an angularly movable nozzle which is employed to project the liquid against hot surfaces which are spaced at variant distances from the nozzle, and the rate of angular movement of the nozzle is increased when the jet is directed against surfaces closer to the nozzle, and vice-versa. 
     
     
       3. A method according to claim 2 wherein said jet characteristics and the rate of linear displacement of the point of impingement of the jet with the surface are maintained substantially constant. 
     
     
       4. Apparatus for deslagging water walls and the like comprising a water projector of the rotary retracting soot blower type, and continuously variable speed controlling means for changing the rate of rotation thereof .Iadd.in proportion to the distance the soot blower extends into the boiler whereby the speed of progression of the fluid along said water walls may be maintained relatively constant.Iaddend.. 
     
     
       5. The method of dislodging deposits from surfaces located in a high temperature zone which comprises providing a .Iadd.rotatably .Iaddend.movable nozzled liquid jet-forming member for discharging a liquid which is vaporizable at the temperature existing in the zone, projecting the liquid from such member against such surfaces from .[.variant.]. .Iadd.varying .Iaddend.distances in the form of a substantially uniform concentrated high velocity jet, all such distances being such that liquid strikes the surfaces in unvaporized form, and .Iadd.continuously .Iaddend.varying the rate of movement of the jet .Iadd.in proportion to said varying distances .Iaddend.while maintaining the jet characteristics at such substantially uniform concentrated high velocity form, in such manner as to compensate for differences in the .[.angularity.]. .Iadd.distances .Iaddend.between the jet and the surfaces impinged thereby to maintain the rate of travel of the point of impingement of the jet .Iadd.against said surfaces .Iaddend.at a value substantially higher than a rate which would wet the surface sufficiently to materially chill the same. 
     
     
       6. The method of dislodging deposits from hot surfaces located in a high temperature atmosphere by means of a jet of a liquid which boils at a temperature lower than the temperatures of the atmosphere and of the surfaces, which comprises adjusting the diameter, velocity and duration of impact of the jet to values tending to minimize the amount of cooling effect in proportion to the effective mechanical force exerted upon the surface deposits .Iadd.and continuously varying the speed of movement of the device from which said jet is projected against said surfaces in proportion to the distance between said surfaces and said device whereby the speed of progression of said jet across said surfaces is maintained relatively constant.Iaddend.. 
     
     
       7. A method according to claim 6 which include directing the jet against the deposits at an angle tending to peel the same from the surfaces. 
     
     
       8. A method according to claim 6 in which the duration of impact is controlled by moving the jet over the surface at a linear speed exceeding a predetermined minimum. 
     
     
       9. A method according to claim 6 in which the liquid is projected against the surfaces in a discontinuous stream. 
     
     
       10. A method according to claim 1 wherein the jet is moved over the surface at or somewhat below the maximum linear speed which is effective to achieve the desired cleaning. 
     
     
       11. A method according to claim 6 for use against tubular surfaces and wherein the jet diameter is substantially less than the tube diameter. 
     
     
       12. A method according to claim 6 for use against tubular surfaces and wherein the jet diameter is substantially less than the tube diameter and the velocity of propagation and duration and angle of impact are such as to cause a substantial proportion of the liquid to bounce off of such surfaces.