Arrangement For Cleaning An Air Passage In The Wall Of A Refuse Burning Furnace

Abstract

The passages in the wall of a refuse burning furnace for supplying combusn air thereto run an apparent risk of being clogged by particles of solid matter carried by the combustion gases. In order to remove such deposits a sleeve is fitted into the each passage, and is connected to a driving means designed to impart a reciprocatory forwards and backwards movement thereto. A scraper ring may be fitted inside the sleeve to support the pushing out action, and air for cooling purposes may be supplied to the clearance between the wall of the passage and the sleeve.

Description

BACKGROUND OF THE INVENTION

Waste liquor from the processing of cellulose pulp is usually burnt in a recovery furnace to which the liquid is continuously supplied by means of one or more nozzles, which spray the liquor into the furnace in such a manner that part thereof will burn in suspension whereas the remainder adheres the walls of the furnace, where it is dehydrated and finally falls down into the hearth, where it forms a mound of dried matter where the final combustion occurs.

In order to burn the combustible particles in this mound which is continiously refilled by matter falling down from the jets and from the walls, combustion air is supplied at several levels in the furnace. An aim is to maintain the combustion as uniformly as possible over the cross sectional area of the furnace. This will result in a more complete combustion and a better heat recovery, and also minimizes the formation of H.sub.2 S, will cause a nauseating smell in the surroundings, and with high concentration will accelerate the corrosion on the pressure parts of the furnace, especially in the lower portion thereof.

The air is distributed by means of wind boxes located at different levels outside the walls of the furnace, and from which the air is conveyed by means of a number of passages in the tube walls of the furnace. Alternatively the air from a common supply conduit is distributed by way of rows of separate pipes, with each ends at a wall passage. On both occasions these passages are distributed over the wall surface in principally the same manner. In order to make possible a basic adjustment of the volume of air to the different wind boxes, or to groups of wall passages each wind box is usually provided with throttling means in its supply conduits.

Such throttling means may also be provided at the supply conduit to a group of pipes leading to individual passages. Each passage may furthermore be provided with its own throttling means to make possible a selected distribution of the air within each wind box, or within each groups of pipes, respectively, and to maintain the desired air pressure ahead of the passages.

The complicated arrangement for the supply of combustion air above described is desirable because it is difficult to obtain an uniform distribution of the liquor over the cross sectional area of the furnace and because the operating conditions for the nozzles, and therefore also the requirement upon the distribution of the air, will vary depending upon the load on the furnace and also upon the moisture content of the liquor to be sprayed.

The type of fuel actual, viz. waste liquor, and the manner of supplying the same to the furnace results in the build up of heavy coatings on the walls of the furnace, which tend to clogg the openings of the air passages into the furnace.

In order to maintain the desired air distribution this clogging of the openings must be kept under control. The clogging will not appear uniformly over the wall surfaces and therefore the air distribution will be influenced, as well as the total volume of air and also the pressure thereof.

It is a tedious task for the operator, manually to keep the passages free by means of a lance, and it has been observed that the operator under continuous running of the plant is unable to maintain the same satisfactory combustion conditions as have been obtained during the delivery testing of the unit.

SUMMARY OF THE INVENTION

The aim of the present invention is to eliminate, or largely to reduce the problems encountered by the clogging in and around the air passages, and it is characterized in a sleeve mounted in each passage, being shorter than the latter and shaped substantially to follow the internal cross section of the passage, as well as in means for imparting a forwards and backwards oscillating movement to the sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

According to a preferred form of the invention, sleeves in a number of passages within a series of passages are interconnected by means of a common actuating member. This latter is operatively associated with a driving means. The driving means is automatically actuated at pre-determined intervals by means of a governor, the activation at each occurrence being effected to perform a certain number of strokes.

FIG. 1 is a perspective view of part of the furnace wall surrounding an air passage having a sleeve mounting therein,

FIG. 2 shows a corresponding part of the wall as viewed in a vertical section,

FIG. 3 shows the arrangement on a larger scale and including more details, and

FIG. 4 illustrates the preferred form of the invention in which certain sleeves are interconnected by means of a common actuating member, a driving means and a governor for automatically activating said driving means.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The walls of the furnace consist of water cooled tubes 10, which form part of a steam boiler and the faces of which turned towards the furnace are covered with blocks of heat and corrosion resistant material and/or by a refractory compound. The desired air passages are obtained by bending apart two adjacent tubes. The passages will thus obtain an elongated form. The passage proper is formed as a housing 11, the outer shape of which corresponds to the opening obtained between the two tubes, and which will sealingly engage in the opening. The housing is open towards a wind box 12 mounted at the outside of the wall, and it is evident that a number of similar passages are connected to this box, which is supplied with heated air from a suitable source. In the back wall 13 of the box there is arranged opposite to each passage, an inspection opening 14 provided with a window of heat resistant material, as well as a further opening 15, provided with a lid 16, pivotably supported about its upper edge. Through this later opening a lance may be introduced into the air passage 11, if it, as a result of a damage to the operating mechanism, will become necessary manually to break up deposits formed within air passage. At the inlet end of the air passage there is a throttling member 17 by means of which the volume of air can be adjusted individually for each passage.

As above mentioned the nature of the fuel used brings about an apparent risk of a clogging of the opening of the air passage, said clogging having a marked influence upon the volume and the distribution of the air. In order to maintain each passage clean a sleeve 18 is mounted therein. This sleeve is shorter than the passage and the contour thereof substantially corresponds to the internal cross section of the passage. FIGS. 1 and 2 show the sleeve in its rest position, in which it is retracted as far back as to the throttling member 17. By means of a link mechanism 19, 20 a forwards and backwards oscillating movement is imparted to the sleeve from a motor 21, which might be a compressed air unit, the piston rod 22 of which is connected to link 20. The movement of the mechanism is selected in such a manner, that the sleeve will be brought forwards until the edge of, or just outside the edge of the air passage. During this forward movement it will remove any matter deposited within the passage.

The sleeves at a number of passages located adjacent to each other preferably are connected to a common driving means 21, which may be governed by means well known in the art to be automatically activated at predetermined intervals, and which on each occasion will perform a certain number of strokes,

The design of the air passage and of the sleeve therein is shown more in detail in FIG. 3. The internal wall of the passage housing is provided with a number of axially directed ledges 23, which support the sleeve during its movements and reduce the contact face between the latter and the wall of the passage. This is furthermore provided with a number of openings 24, which by conduits not shown in the drawing are connected to the air wind box 12, so a limited amount of air will constantly flow to the clearance between the housing of the air passage and the sleeve in order to cool the latter.

The sleeve is provided with two sidewardly directed pegs 25, which pass through elongated slots in the housing of the passage, and which are connected to the links 19 in such a manner that a transfer of the movements to the sleeve may be arranged without changing the position of the throttling member 17. It is apparent that the sleeve actually will be the determining factor for the volume of air, but through the arrangement shown the volume of air to each passage will not be influenced by the occasional position of the sleeve within the passage. If the actuating mechanism should be put out of action as a result of some damage the arrangement due to the lancing openings 15 will be fully equivalent to that of conventional air passages lacking the cleaning means according to the invention.

A scraper ring 26 is fitted within sleeve 18 is mounted on a number of pegs 27, which pass elongated slots 28 in the sleeve and are fixedly mounted in the housing. The scraper ring, thus, will maintain a fixed position during the displacement of the sleeve, and it is mounted just inside the position held by the edge of the sleeve turned towards the furnace, when the sleeve is withdrawn to its rest position. Deposited matter, which during the outward movement of the sleeve is pushed into the latter will be removed by the scraper ring during each retracting movement, so it will again fall down into the air passage, and during the following outward movement of the sleeve be pushed out of the passage.

In the preferred embodiment illustrated in FIG. 4 there is shown a repetition of the organization illustrated in FIG. 1, to which has been added a showing of a common rack 19, 19 operated by pressure fluid motor 21, the supply of motive fluid thereto is governed by a valve 30, which valve in turn is activated by an electric motor 31 which is supplied with electric current at selected intervals by means of a timing device 32.

Claims

What we claim is:

1. An arrangement for cleaning an air passage in the wall of a refuse burning furnace, comprising

a sleeve mounted within the passage, being shorter than the latter and shaped substantially to follow the internal cross section of the passage, and

means for imparting a forwards and backwards reciprocatory movement to the sleeve within the passage,

the internal wall of the passage being provided with elongated ledges serving to govern the movements of the sleeve with a clearance with respect to the wall of the passage. 2. The arrangement according to claim 1, in which a scraper ring is fitted into the sleeve, near the end thereof turned towards the furnace, said ring being mounted at the wall of the

passage by means of pegs passing elongated slots in the sleeve. 3. The arrangement according to claim 1, further including a number of openings in the wall of the passage, said openings communicating with the air supply side of the passage and being designed to supply a limited amount of air to the clearance between the sleeve and the wall of the passage.

The arrangement according to claim 1, which further comprises a common actuating member which interconnects sleeves in a number of passages within a series of said passages and wherein a driving means is in operative association with said common actuating member, the arrangement further including a governor automatically activating said driving means at pre-determined intervals on each occasion to perform a certain number of strokes.