GB2174022A - Pneumatic gunning of refractory material - Google Patents

Abstract

A pneumatic gunning mechanism for gunning granulated refractory material has a granulator (18) located below a hopper (22) which provides separate inputs for slabs (70) of plastic refractory material and rebound granulated refractory material such that rebound material can be blended with fresh plastic refractory material during granulating prior to gunning. The granulator is disposed directly above the inlet (118) to the pneumatic gun such that granulated particles of refractory material which are discharged from the granulator fall directly into the input of the pneumatic gun in a loose granular form and are pneumatically discharged therefrom without the formation of clumps. <IMAGE>

Description

SPECIFICATION Pneumatic gunning of refractory material This invention relates to the pneumatic gunning of plastic refractory materials. In particular, this inven tion relatesto improvements in a pneumatic gunning assemblyforthegunning of granulated plastic refractory material.

Prior Art The pneumatic gunning of granulated plastic refractory material is an efficient method offorming a refractory lining onthewalls of afurnace orthe like.

The lining can be applied by a pneumatic gunning process in a much shorter time period than that required for other methods offorming a refractory lining.

One ofthe drawbacks ofthe pneumatic gunning process is, however, that a substantial proportion of the granular particles of refractory material which are sprayed ontothewall will reboundfromthewalland will not adhere to the wall. It is generally accepted that the amount of plastic refractory material which will rebound in this manner is about 20% ofthe total weight of refractory material which is gunned. The efficiency of the gunning process has, however, been such that th is loss has been more than compensated for by the labour saving ofthe gunning process.

I havefoundthatthe losses due to rebound can be overcome by regranulating the rebound and blending the rebound with refreshly granulated refractory plastic material. This serves to substantially reduce the losses due to rebound.

Afurther problem which has been experienced in attempting to pneumatically gun granulating plastic refractory material is that of preventing the granulating material reforming into large clumps after it has been granulated and before it is gunned. I have fond that this problem can be substantially eliminated by arranging the outlet ofthe granulator so that it is directly above the inletofthe pneumatic gunning device.

Summary of Invention According to one aspect ofthe present invention, there is provided in a pneumatic gunning mechanism forgunning granulated refractory material having a granulatorwhich has an input for receiving plastic refractory and an output for discharging granulated plastic refractory into a pneumatic gun,the improve- ment of a feeding hopper having first and second feeding passages opening therethrough which each communicate with the input of said granulator, said firstfeeding passage being proportioned to permit a slab of plastic refractory material to pass therethrough, said second feeding passage serving to permit lumps of plastic refractory material to be admitted to thegranulatorsimultaneously with the slab of plastic material so as to be mixed one with the other in the granulator.

According to another aspect ofthe present invention, there is provided a pneumatic gunning assembly for gunning granulated plastic refractory comprising a feeding hopper having at least one feeding passage, a granulator having a granulatorchamberwhich has an inlet and an outlet, a granulator mechanism mounted in said granulatorchamber,theoutputendofeach through passage ofthe feeding hopper communicat- ing with the inlet ofthe granulated chamber, a pneumatic gun having an input for receiving granulated plastic refractory material and a discharge for discharging airborne particles of granulated plastic material, said pneumatic gun being located below said granulatorwith the input ofthe pneumatic gun disposed directly below the outlet ofthe granulator so that granulated particles of refractory material which are discharged from the granulatorfall directly into the pneumatic gun in a loose granularform and are pneumatically discharged therefrom before they have an opportunity to reform into a large mass of plastic material.

The invention will be more clearly understood after reference to the following detailed specification read in conjunction with the drawings wherein: Figure lisa pictorial front view of a pneumatic gunning mechanism constructed in accordance with an embodiment of the present invention; Figure 2 is a diagram illustrating the various conduits of the pneumatic gun; Figure 3 is a partially sectioned pictorial view of the feeding hopper and granulatorand the inputto the pneumatic gun; Figure 4 is a sectional side view taken along the line 4-4 of Figure 3; Figure 5 is a partially sectioned pictorial view of a pneumatic gun constructed in accordance with an embodiment of the present invention; and Figure 6 is a sectional side view taken along the line 6-6 of Figure 5.

With referenceto Figure 1 ofthe drawings, the reference numeral 10 refers generally to a pneumatic gunning mechanism constructed in accordance with an embodiment ofthe present invention.

The mechanism 10 comprises a frame 12 which is mounted on a wheeled platform 14. A pneumatic gun 16 is mounted onthe platform 14and granulator18is mounted on beams 20 so as to be disposed directly above the pneumatic gun 16. Afeeding hopper 22 is mounted directyabovethe granulator 18. The granulator 18 is powered byan electric motor24which has a speed control handle 26 which may be adjusted to control the output speed from the motor. The granulator 18is driven through a gearbox 28 in a conventional manner.

Air is applied under pressure to the pneumatic gun 16 through a conduit 30 which is adapted to releasably connected to a conduit 32 (Fig. 2). The conduit 32 communicates with an airfilter34which has an output which is connected to an emergency shut-offvalve 36.

The shut-offvalve 36 is connected by conduits 38 and 40 to a T-joint42. A branch line conduit 44 extends from one end of the T-joint 42 and is connected to a shut-offvalve 46 which may be used to provide a connection for secondary air supply such as a cleaning hose or the like. The other branch oftheT-joint42 is connected to a pressure control valve 48 which is connected to a second shut-offvalve 50. A pressure gauge 52 is connected to the shut-offvalve 50 and a conduit 54 is connected to the pressure gauge 52. The conduit 54 is connected to the input line 56 of the pneumatic gun 16.

With reference to Figures 3 and 4 ofthe drawings, it will be seen thatthe feeding hopper 22 has a first feeding passage 58 and a second feeding passage 60, each ofwhichopentherethrough.Thefirstfeeding passage 58 has an input end 62 and an output end 64 and the second feeding passage 60 has an input end 66 and an output end 68.

Thefirstfeeding passage 62 is proportioned to receive a slab or block of plastic refractory material 70 so asto permit itto pass directly thereth rough. Plastic refractory material is generally packaged in slabs or blocks weighing 2 kg., and measuring approximately 9 x 6 x 9 inches to 9 x 6 x 13 inches and the first feeding passage 58 is proportioned to receive these slabs or blocks in a free-fitting relationship which will permit the blocksto pass thereth rough undertheir own weight so that it is merely necessary to load successive blocks into the first passage to ensure that itwill pass thereth rough.

The second through passage 60 has a screen 72 located at its input end 66. The screen 72 has openings 74formed therein which are proportioned to permit rebound particles of granular plastic refractory mate rial to passtherethrough which are of a size of substantially equal to that ofthe granulated material atthe outputofthe granulator. Preferably the pas sages which reformed in the screen 72 measure no morethan 7/8" in diameter.

The second feeding passage 60 has an outer side wall 76 which is angularly inclined downwardly and inwardlytoward the divider wall 78. An inner side wall 80 cooperates with a flange 82to form a narrow passage84.A metering device generally identified by the reference numeral 86 is mounted for rotation directly below the narrow passage 84. The metering device 86 comprises a rotor88 which has a central shaft 90 from which a pluralityofblades 92 radiate.

Discs 94 are located at opposite ends ofthe shaft 90.

Pockets 96 are located between the blades 92 and by rotating the rotor 88 aboutthe shaft 90, successive pockets 96 are exposed to the material passing through the second feeding passage 60. A sprocket98 (Fig. 3) is mounted on the end ofthe shaft 90 and is connected by means of a chain 100 to a sprocket 102.

The sprocket 102 is mounted on the shaft 104 of the granulator 18.

The shaft 104 and a second shaft 106 extend transverselyofthe granulator 18 and have granulator blades 108 mounted thereon. Fingers 110 are mounted on opposite sides ofthe granulator 18 and project between adjacent blades 108. The shaft 104 is driven by the motor 24 (Fig. 1) through the gearbox 28.

Rotation ofthe shaft 104 causes rotation ofthe shaft 90 and therefore rotation ofthe metering device 86 to admitthe rebound granular particles to the granulator chamber 112. As illustrated in Figure 4 ofthe drawings, the granulator chamber 112 has an inlet 114 and an outlet 116. The outlet 1 Ofthegranulator 18 is disposed directly above the input shute 118 ofthe gun 16.

As shown in Figure 5 ofthe drawings, the shute 118 communicates with the input passage 120 ofthe pneumatic gun 16. The pneumatic gun 16 is ofa substantially conventional construction and includes a rotor 122 which is driven by a motor 124through a gearbox 126. The rotor 122 has a plurality of pockets 128 formed therein. A deflector blade 130 is located above a portion of the arc oftravel of the rotor immediately ahead ofthe gunning station which is generally identified by the reference numeral 132. In the gunning station 132, the air input line 56 is arranged to be aligned with one edge of successive pockets 128 and a discharge conduit 134 is located at the opposite edge of the pocket 128.Thus, airwhich is admitted to the pocket 128 through the input line 56 will drivethegranularparticles 136 outwardlythrough the discharge conduit 134 and these particles will remain separated from one another by being suspended in the air current. The particles 136 can then be gunned directly onto the surface which isto be lined.

As indicated in Figure5ofthedrawings,thegun 16 preferably comprises a carriage 138 which is supported by wheels 140 and a front leg 142.

In use, the pneumatic gun 16 is located as shown in Figures 1 and 3 ofthe drawings with the input shute 118 located directly below the outlet 116 ofthe granulator so that the granular particles will fall directly from the outlet ofthe granulator into the input passage 120 ofthe gun. The rotor 122 is driven continuously during the gunning operation so that as the granular material enters the pockets 128, successive pockets 128 are displaced into the gunning station 132 at which point the granular material is biown out ofthe pockets 128 and discharged through the discharge conduit 134.

Rebound granular particles which accumulate on the floor ofthe work site can be shovelled into the inlet end ofthe second feeding passage 60 so as to be sorted by the screen 72 so thatthe smaller particles are aloud to pass through the second feeding passage 60 to the metering device and are then metered as previously described into the granulating chamber.

The slabs or blocks 70 are fed to the granulator through thefirstfeeding passage and are granulated in a conventional manner bythe operation of the blades 108. When a substantial amount of oversize rebound particles are accumulated on the screen 72, these oversized particles can be loaded into the granulator between successive slabs passing through thefirstfeeding passage 58 and will as a result, be subjected to a further granulating step to reduce them to the required size.

Itis essential to ensure that the refractory material is not allowed to reclump into large particles after it is granulated and I avoid this difficulty by ensuring that the granulated material is discharged directly into the gunning machine in which it is collected in small pockets in quantities which are so small that they are not likely to reform undertheir own weight into a large clump. Furthermore, the small pockets serve to ensure that even if the granulated particles are placed in contact with one another,they will be dispersed when they are contacted by the high pressure air in the gunning station 132.

It will also be apparentthat by providing first and second feeding passages, I have made it possible to utilizethe rebound granules which are not of an excessive size without subjecting these granules to a regranulating step. Because the rebound material tends to have a somewhat different moisture content than the originally granulated material, I preferto blend the rebound material with the freshiy granu- lated material and this is achieved by ensuring that both the first and the second feeding passage open into the granulating chamber ofthe granulator. If I wereto merelyfeed blocksoffresh plastic material followed by a load of rebound through the first feeding passage2l,lwould generateastreamofgranulated material at the gun output which would vary in characteristics according to whether or not the material which was being gunned was predominantly original gunning material or rebound gunning material.

From the foregoing, it will be apparentthatthe present invention provides a simple and efficient pneumatic gunning mechanism which permits the gunning of rebound material and which permitsthe gunning of granulated plastic refractory material.

Claims (6)

1. In a pneumatic gunning mechanismforgunning granulated refractory material having a granulator which is an input for receiving plastic refractory and an output for discharging granulated plastic refractory into an pneumatic gun, the improvement of a feeding hopper having first and second feeding passages opening therethrough which each communicate with the input of said granulator, said firstfeeding passage being proportioned to permit a block of plastic refractory material to pass therethrough, said second feeding passage serving to permit coarse granular plastic refractory material to be admitted to the granulator simultaneously with the block of plastic material so as to be mixed one with the other in the granulator.

2. Thepneumaticgunning mechanismofclaim 1 further comprising metering means in said second passage for controlling the rate at which plastic refractory material is discharged from said second passage into said granulator.

3. A pneumatic gunning mechanism as claimed in claim 2wherein said metering means is drivingly connected to the granulatorto control the rate of flow ofthe plastic refractory through the second feeding passage as a function of the speed of operation ofthe granulator.

4. A pneumatic gunning mechanism as claimed in claim 3 wherein said second feeding passage has a screen located at its input end which has openings therethrough which prevent the passage of large lumps of plastic refractory material.

5. Apneumaticgunning assemblyforgunning granulated plastic refractory comprising: a) a feeding hopper having at least one feeding passage opening therethrough, b) a granulator having a granulatorchamberwhich has an inletand an outlet, a granulatormechanism mounted in said granulator chamber, the output end of each through passage ofthe feeding hopper communicating with the inlet ofthe granulated chamber, c) a pneumatic gun having an input for receiving granulated plastic refractory material and a discharge for discharging airborne particles of granulated plastic material, said pneumatic gun being located below said granulatorwith the input ofthe pneumatic gun disposed directly below the outlet ofthe granulator so that granulated particles of refractory material which are discharged from the granulatorfall directly into the pneumatic gun in a loose granularform and are pneumatically discharged therefrom before they have an opportunity to reform into a large mass of plastic material.

6. Apneumaticgun assemblyforgunning granulated plastic refractory material comprising: a) a feeding hopper having first and second feeding passages opening therethrough, each of said feeding passages having an input end and an output end, said feeding passages being proportioned to permit a block of plastic refractory material to pass therethrough, said second feeding passage being adapted, to permitthe passage of lumps such as rebound lumps of plastic refractory material therethrough, b) a granulator having a granulatorchamberwhich has an inlet and an outlet, a granulator mechanism mounted in said granulator chamber, said output ends of said first and second feeding passages of said feeding hopper each communicating with said inlet of said granulator chamber whereby plastic refractory material may be fed to said granulator chamber through said first and second or both feeding passages, and c) a pneumatic gun having an inputfor receiving granulated plastic refractory material and a discharge for discharging airborne particles, said pneumatic gun being located below said granulatorwith said input of said pneumatic gun disposed directly below said outlet of said granulator so that granulated particles of refractory material which are discharged from the granulatorfall directly into the input ofthe pneumatic gun in a loose granularform and a pneumatically discharged therefrom in loose granular form.