FR2519131A1 - METHOD AND DEVICE FOR REMOVING DEPOSITS ADHERING TO HIGH TEMPERATURE HEATED SURFACES - Google Patents

Abstract

The invention relates to a method and a device for cleaning a boiler and the like during the production of steam, where a stream of cooling water is first applied to the outer surface of the tank so as to induce the formation of cracks and the formation of CONTRACTION OF THE DEPOSIT, THEN WHILE THE CRACKS REMAIN PRESENT, THE CRACKED SURFACE OF THE DEPOSIT IS IMPACTED BY A HIGH SPEED PULSE JET WHICH DRAINS WATER INTO THE CRACKS, WHEREAS THE REMOVAL OF THE DEPOSIT IS FACILITATED BY THE DEPOSIT EXPANSION FORCE OF WATER VAPORIZING IN CRACKS. A GENERALLY CLASSIC BLOWER 12 IS REPRESENTED, WHICH IS EQUIPPED WITH A DOUBLE LIQUID SUPPLY 28, 51 AND A PROJECTION MEANS, AND A PULSE CREATING MECHANISM 70 WHICH INTERRUPTS THE BLOW-BLOW MEDIUM CURRENT DIRECTING TO L 'ONE OF THE MEANS OF PROJECTION SO AS TO FORM THE PULSE JET.

Description

The present invention relates to a method and a device for

  removal of deposits from surfaces

  heated to a high temperature.

  Since the introduction of tubular boilers containing high temperature water, which burn fuels causing significant dep 8 ts, and moreover,

  with the adoption of certain functional heat exchangers

  At high temperatures, the removal of deposits adhering to the side surfaces of the fireplace has become an increasingly serious problem Soot blowers using steam and / or air jets cannot remove some of the

  These dep 8 ts We have known for a long time that water jets can

  can be used to facilitate the removal of deposits, and we have also known for many years that the thermal shock and the fragility of the deposits caused by a jet

  of water, combined with the energy of the jet itself,

  wind to dislodge deposits that cannot be removed from a boiler

  steam by other means, however, before the introduction

  duction of the system with constant jet progression described in

  U.S. Patent No. 3,782,336 of Jan. 1,

  vier 1974 in the name of J E, Nelson, he was frequently im-

  practicable to use water jets for this purpose because it

  was not possible to control and limit the thermal shock

  value to avoid premature failure of the 2. tubes.

  Just the constant jet progression system

  the above mentioned uses a concentrated jet of high

  speed, and that a considerable proportion of the water rebounds

  actually on tubes or on dirty surfaces,

  during the operation of the system, some cooling

  and a certain fragility of the dep 8 ts are the consequence

  the impact of the jet, and some cracking may occur

  that help the kinetic effect of the jet in the delo-

  deposit management However, Nelson's constant jet progression system has allowed such a reduction in the amount of water used and the amount of water remaining in

  contact with the tubes (or with deposits) while vaporizing

  sant that the total value of the rapid heat extraction

  due to the cooling and the latent heat of vaporization

  tion was, for the first time, reduced to levels of se-

  curity In fact, in normal use, the Nelson system has

  reduces the effect of thermal shock to much lower levels

  at the maximum level that could be tolerated without risk of

  premature failure of the tubes, and it frequently occurs

  saw that no significant or observable cracking of the deposits

  did not occur before their actual detachment.

  The subject of the present invention is a method and

  a device that allow to detach even faster-

  very hot deposits thanks to means involving

  precise application of a thermal shock of controlled value

  linked in conjunction with the kinetic energy due to a pulverized jet

  dried, applied separately, at high speed.

  Another object of the present invention is a system

  same as a high speed pulsed water jet hits the surface

  face of the deposit during its removal, at a controlled rate

  progress and o before being hit by each pulse

  jet, the increment of the surface to be struck is first cooled in a limited way by a current which 'tends to cause cracks in which the water is entrained by the pulsating jet of high speed so as to favor the detachment of the deposit by expansion of the water

in the cracks.

  3, The present invention will be well understood when

  of the following description made in conjunction with the

  attached sins in which Figure 1 is an elevational side view, somewhat schematic, of a cleaning device according to the present invention;

  Figure 2 is a rear elevation view

  following arrow II of Figure 1; 1 gure 3 is a view in longitudinal and diametral section, on a large scale, of the nozzle part of the lance tube; Figure 4 is a somewhat schematic view of the pulse generation means, partly in longitudinal section and in pxtie in side elevation; Figure 5 is a sectional view taken substantially on

  along line V V in Figure 4, in the direction of the arrows

  ches; Figure 6 is a detailed sectional view taken substantially along the line VI VI of Figure 5, in the direction of the arrows; Figure 7 is a detailed sectional view taken substantially along line VI VII of Figure 4, in the direction of the arrows; and FIGS. 8, 9 and 10 are time diagrams representing the successive positions of certain components of the mechanism causing the pulsations,

  Figures 1 and 2 represent in a way

  that little schematic a soot blower 12 long stroke whose construction is broadly similar to that of blowers of the well-known type known as IK, as regards the construction of the beam, the carriage and the mechanism

  actuation by which a lance tube 10 is introduced

  inside a boiler during its operation-

  ment-then is removed when the blower is stopped.

  Such blowers are designed to project an environment of

  blowing (typically water in the type of construction

  currently described) against deposits that form on the side surfaces of the hearth of large boilers

  and other high temperature heat exchangers

  very types of blowers could be used The specific means of support and actuation of lance which is represented here is typical and does not constitute in itself a part of the present invention.

  TK type blower mechanisms are shown and

  written in numerous patents from the United States of America and abroad, including the patent of the United States of America NO 2,668,978 in the name of LS De Mart of February 16, 1954 and the patent of the United States of America NO 3 439 376 on behalf of

John E Nelson of April 22, 1969.

  As is classic in the blowers of

  this type, an elongated lance tube 10 is intended to be intro

  duit, then out of the interior of the boiler (the term "boiler" is used for convenience and includes other heat exchangers from which it is desired to remove the deposits which have formed on the side surfaces of the fireplace) present invention, the blower is designed to project two separate jets against the surface to be cleaned, as shown below Altra with more

  details, but as is typical in the case of suf-

  so-called water lance flowers, when the lance tube is in

  protrudes into a boiler and lies beyond the over-

  face of the water wall, a nozzle (or nozzles in this case) located near its end projects the

  blowing medium at a certain angle and towards the rear

  laughing against the dirty interior surface of the wall The temperatures encountered in such areas are typically substantially higher than l 100 l C. During its operation in the boiler, the lance tube is moved angularly and axially so that depending on whether

  its rotation corresponds to a full angle of 3600, or less

  laughing at 3600, the jet will hit the dirty surface in

  a path in the shape of a spiral or a spiral

interrupted.

  The lance tube 10 is rotatably supported at its rear end in the carriage 20, which is mounted

  so that you can roll on the lower wings of a

  5. be 22 in the form of an I which constitutes the main support element of the structure and which is protected by a cover 23 in the shape of a U-shaped channel A motor 24 mounted on the carriage, which can be supplied by a flexible cable 25 contains appropriate gears (not shown) with which it actuates the carriage to cause displacement with

  the lance tube along the beam in 1 and make

  turn the lance tube Build a cart

  of this type including gear and gear arrangements

  dragging are well known and represented in the patents of the prior art cited above and do not require any

  new description The lance tube 10 includes a tube

  exterior 17 whose distal end is in the form of a section 18 comprising a block of nozzles, and a

  inner tube 19 having a substantially smaller diameter

  tit and placed in the outer tube 17 by means of a fin

  your support radials 21 which allow free circulation

  lation of the blowing medium in the part of the outer tube

  located outside the inner tube 19 A nozzle element 26 is fixed in a support 27 in the form of a cup in the nozzle block 18 in order to receive the medium.

  supply air routed through the outer tube 17 and to the

  load at an angle slightly backwards (for example 150) to pass through an opening 29

  practiced in section 18, the support 27 being peripheral

  rique welded and sealed to the surface surrounding the opening 29.

  The blowing medium conveyed by the inner tube

  laughing 19 crosses a bend 31 to reach another nozzle

  37 tightly fixed in the nozzle block A man-

  chon 39 surrounds and isolates the nozzle 37 from the interior of the section of the nozzle block The nozzle 37 causes the discharge of the medium in an opening 41, As shown in FIG. 3, the nozzle 37 is also inclined backwards so

  to cause discharge against a wall of water in ins-

  tallations of the type mentioned above.

  Note that the cleaning of 6. water walls is mentioned to illustrate a type of application of the

  present invention Similarly, it will be noted that the medium li-

  blowing, although typically being water, could be an aqueous solution containing a treatment medium The supply of liquid via the outer tube 17 and the nozzle 26 is done from a source ( not shown) which is connected to a fitting, and the liquid is conveyed by passing through a filter 32 and a control valve 33 From the valve 33, the fluid is conveyed, when the latter is open, by a suitable pipe 34 and a connector 35 to a flexible hose 28, which is rotatably connected to the rear end of the lance tube,

  A bypass line 43 connected to the con-

  pick 34 downstream of valve 33 leads to a mechanism

  causing impulses, represented in its large li-

  genes by the reference 70, which will be described later in detail. This mechanism supplies a pulsed fluid via an outlet pipe 136, a second flexible pipe 51, and a

  swivel fitting 53, at the rear end of the laning tube

this radially inner 19.

  The valve 33 is opened and closed by a lug 36 fixed to the carriage When the carriage moves forward from the retracted position of FIG. 1 to a position such that the nozzles are inside

  of the boiler, the tab strikes a declination arm

  38 so as to actuate the valve 33 towards its posi-

  tion when the carriage returns, the tab actuates this arm in the opposite direction so as to

close the valve.

  The blowing medium leaving the nozzle 26 is

  used as a preconditioned coolant

  The blowing medium leaving the nozzle 37

  serves as an impact mechanism, The means causing impulses

  sions periodically interrupts the flow of discharged fluid

  managed by the nozzle 37 so as to create sudden and finite pulses The angular spacing of the nozzles 26 and 37 both in the axial direction of the lance tube and angularly around 7. of its periphery is such that in operation the nozzle 26 is in front of nozzle 37 following the same path, so that the jet leaving nozzle 26 strikes each increment of

  the impact surface according to a predefined time interval-

  completed before the jet leaving the nozzle 37 The time interval, and the flow rate of the nozzle 26, are related to the speed of progression of the jet on the surface to be cleaned so that the liquid leaving the nozzle 26 cools sufficiently

  the dirty surface so that cracks 4 are provo-

  but the time interval allows the outgoing liquid

  of nozzle 26 to dissipate substantially from the zo-

  does not cool down before it is struck by the pulsed jet However, the time interval is short enough so that the cracks still exist when the pulsed jet strikes the deposit Part of the liquid of the pulsed jet, which has a pressure d maximum impact much more

  large, is thus entrained in the cracks o its evapo-

  immediate ration creates pressure below the surface

  which increases the effect of its kinetic energy in the de-

stain of the deposit.

  As is known, the maximum impact pressure of a pulsed jet can be 50 times greater than that of a continuous jet. The quantity of water discharged by the nozzle 26 in the form of constant current can be relatively small, and at a lower pressure, so that the fluid has a less tendency to rebound on the surface (as is the

  case of a large part of the pulsed jet) The liquid comes out

  both of the nozzle 26 ensures sufficient humidification so that, as a result of the high absorption of heat due to the latent heat of vaporization, the cracking of the

  deposit can be made with a small amount of water,

  On the other hand, the pulsed fluid is supplied at a very high pressure.

  sion, and s Qn impact is increased by the pulsations so that, l still, a relatively small amount of water can be used which, thanks to its high kinetic energy and the effect of shattering due to the cooling current leaving the nozzle 26, very effectively removes the deposit made fragile; the two jets require only a relatively small quantity 8, total of water Although the quantity of water is relatively small, each pulse of the jet leaving the nozzle 37 contains a large mass which

  is capable of causing a relatively high impact.

  The motor 24 of the carriage is of the variable speed type and its speed is controlled so as to regulate the speed of advance of the jet so that it is

  substantially constant, as described in the short-

  vet of the United States of America No. 3,782,336 of January 1, 1974 in the name of Nelson,

  Figures 4 to 10 show a partial mechanism

  culier causing impulses for the supply of

  What about the nozzle 37 The assembly causing the pulses, represented in broad outline by the reference 70, consists of a rotary pulse generator, represented by the reference 72, and of a motor 75 It is intended to be mounted on the blower, for example by fixing to the

  protection 23, as shown in Figure 1.

  The assembly producing pulses comprises a cylindrical body 74 closed by bearing caps 76, 77, the latter being traversed by a drive shaft 78 which is integral with a motor shaft, the motor possibly being an induction motor conventional rotating at a speed of about 1,800 revolutions per minute A cylindrical chamber 85 of the body 74 contains a rotor 90; the rotor is precisely mounted

  in the room where it can rotate and is fixed to the shaft 78.

  A diametral channel 91 having a square section extends in the rotor 90 near one of its ends, represented on the left of FIG. 4, and during the rotation of the shaft, acts as an interrupter valve or causing pulses ; at each half-turn of the rotor, it makes the connection between diametrically opposite inlet and outlet ports 92, 93 and of square section. The inlet port 92 has a section slightly greater than that of channel 9 l rotor hole

  93 has the same dimengons as channel 91.

  Near its right end (seen in FIG. 4) the rotor is cut into two diametrically opposite zones 104, so as to create opposite lobe parts 101, 102 À Rt '' 'which, during their rotation are aligned with a hole d bypass fluid inlet 106 and block it at

  each half-turn of the rotor, constituting a bypass valve

  tion or discharge which is actuated in time relation with the pulse-forming valve. Two diametrically opposed bypass outlet orifices, 108, 109 extend in the wall of the housing 74 transversely to

  orifice 106 and perpendicular to it The ori-

  outlet ports 108, 109 are always in communication with the inlet port 106 via surfaces 104, 105, except

  when the orifice 106 is blocked by one of the lobes 101, 102.

  Figures 8 to 10 show the relative orientation of the

  lobes and canal 91, whence it follows that the orifice

  trée 106 is blocked by one of the lobes 101, 102 each time the channel 91 ensures the communication between the orifices

92, 93.

  The two orifices 92 and 106 are connected, for example

  ple, by fittings 112, 114 to the liquid supply

  under pressure, the latter taking place at these two orifices

  input of the pulse generator means via a surge pump

  14, an accumulator 83 can be connected to a

  line 82 via a manual valve 86 so as to control

  der the peak pressure or "water hammer" to the desired value, The discharge orifices 108, 109 are connected to the

  supply line 43 of the assembly causing the im-

  pulses upstream of the pump via a line 84 which

  holds a manual valve 130 to impose the fall

  desired pressure Note that the diverter orifices

  alternatively could discharge into the atmosphere

  re The pulsed fluid coming from the outlet orifice 93 is conveyed via a line 136 to a connector 141 which supplies the inner lance tube 19 via the tube 51 and the connector 53, Taking into account the effect of increasing the impact of the strong point of the Anis 5 th impulse generator,

  some installations may not require the use of

  tion of a supercharger, according to the characteristics

  water supply pressure and severity

- fouling.

  Thanks to the square outline of channel 91 and the orifices

  these 92, 93, the front and rear faces of which are perpendicular

  culaxers in the direction of rotation, and due to the rapid rotation of the rotor, the flow to the inner lance tube and its nozzle 41 is started and cut quickly and completely so as to create finished pulses without significant decrease at each end 6 m , More specifically, we note

  that the term "square" relates to a rectangular shape

  mode and that in fact the characteristic in question does not depend

  not specifically of a rectangular section, but pro-

  comes from the fact that the surfaces that are located in positions

  corresponding to the front and rear surfaces of the mas-

  se of rotating liquid are flat and noticeably perpen-

  dicular to a tangent line of a circle described by a

rotor point.

  The lobes 101, 102 are a little wider than the inlet port IQ so that, as shown in FIG. 8, the bypass is closed slightly before the opening of the outlet port 93 is opened, which has the effect of causing the establishment of a pressure which creates an increase in the peak pressure at the start of the pulse. The present invention is not limited to the embodiments which have just been described, it

  is on the contrary susceptible to modifications and varian-

  those who will appear to those skilled in the art.

25191-31

11.

Claims (2)

  1 means for detaching a deposit adhering to the heated surface of a heat exchanger or the like,   characterized in that it comprises a water lance comprising   as a plurality of isolated water channels (17, 19) extend   longitudinally across it, a plurality of bu-   its (26, 37) supported by the lance comprising at least one nozzle connected to one of the channels and another nozzle to another of the channels, means (28, 51, etc.) for projecting a stream of liquid by the intermediate of each of the channels and from the nozzle thus connected, a means (72)   to periodically interrupt the flow of one of the   its so as to break the current exiting from said bu-   in order to form impulses that develop a pressure   peak impact sion higher than the current leaving the other nozzle, and means (24, 20, etc.) for moving the lance in a configuration such as parts   of the depot located along a predetermined route is found   wind brought into contact first with the pressurized current   lower impact, then with impulses.   2 Detachment of an adherent deposit   on the heated surface of a heat exchanger or the like   Gue operating at a temperature above the boiling point of water, characterized in that it comprises the application of an aqueous coolant to a surface of the deposit so as to extract the heat and thus cause cracking of the deposit then while the cracks remain present, but after the liquid   cooling system has vaporized significantly, the direction   tion against the same surface of deposition of a jet of liquid pulsed at high speed, 3 means according to claim 1, characterized in that the lance moves both longitudinally and angularly about its longitudinal axis, and in that the nozzles are spaced apart from each other in the longitudinal direction and in the angular direction so as to direct their discharge along the same path and according to a   predetermined time interval.   12. 4 means according to claim 1, characterized in that it comprises means (24, 20) for moving the lance simultaneously in the longitudinal direction and in the angular direction around its longitudinal axis, the nozzles being distant from each other others both longitudinal-   slowly and angularly so as to move successively- along the same route.