Rotary Kiln Refractory Lining Installation-I (Training Course)

$Page 1: Rotary Kiln Refractory Lining Installation-I (Training Course)$
Rotary KilnRefractory Lining Installation

Execution of the brickwork: The execution of a refractory liner can be accomplished in two different ways: with or without having the need to rotate the kiln. In fact the execution of the lining with screw jacks or with the glue method it is necessary to rotate the kiln three or more times so that bricks can be installed in the lower half of the kiln; with the bricking machine, the bricks in the upper half section are mounted without the necessity to rotate the kiln.

In order to avoid longitudinal displacement of the rings, it is required that the construction of the lining should always proceed in the direction from the kiln outlet towards the inlet.

The closure of the brick ring must be accomplished without cutting the bricks. The various combinations of design shapes and closing bricks available suffice to execute good closing.

Longitudinally, a single brick must not be reduced to a size of less than 95 mm and the single ring not less than 125 mm.


The rings must be closed, putting the bricks from the side, and for this reason the rings must be closed one by one and it is always advisable to close a ring before proceeding to next one. When preparing to close a ring during the first tests, to identify the mix of brick shape, needed, check that the faces of the bricks that form the last joint are coplanar, if not, it is necessary to make relevant corrections using mortar. The mix of standard shape and key bricks to obtain a straight joint of maximum 4-6 mm thickness; the remaining space must be closed by inserting a maximum of 2-3 steel plate (2 mm thick) that allow the right compression of the rings to be attained. In case the brick combination is perfect without open joints, for last bricks insertion never knock with hammer directly onto the brick, but a layer of wood must interposed.

All bricks possibly damaged during closing operations must be replaced with perfectly sound ones.


Illustrates some radial closing situations


The closing of last refractory ring can not do from the side, must necessarily be done from inside the kiln; the remaining space should be such that once put the last brick in the correct direction to form two straight joints are perfectly coplanar.

The adjacent sketch shows the installation of last brick.


As shown in the

sketch at side,

if the closing of

a longitudinal

brickwork

section is to be

accomplished

by cutting

bricks of

several rings,

these must not

be mounted

consecutively.


To facilitate the closure of a longitudinal brickwork the producers

of refractory bricks also provides standard bricks “VDZ” and

“π/3” shape 300 mm long as an alternative to 200 mm long.

When are not available 300 mm long bricks can be

constructed rings made of two bricks as shown in the figure

below.


Some examples of construction of longitudinal sealing rings may be the following:

• remaining space =130-200 mm: adapt cutting a brick 200 mm;

• remaining space = 140-210 mm: adapt cutting a brick of 200 mm; when the measure exceeds 200 mm fit either a brick 95 mm with another obtained by cutting of a brick 200 mm long; and so for all sizes up to 225-295 mm.

• remaining space = 230-300 mm or more: compliance with the terms of previous example, there is to change the size of brick from 95 to 125 mm; and so for all sizes up to 250-320 mm; when the remaining space becomes even more, will necessary making a single ring of 130 mm and cover the remaining space as previously described.

Any deformation of the shell must be compensate with the use of mortar when thickness is not more than 3-4 mm, or with a concrete, having an adequate particle size distribution, for greater thickness. Projection of the shell riveted joints or on the welding seams must also be filled so as to improve the brickwork arrangement.


The sketch shown typical adjustment for distorted kiln shell

(radial direction).

FillMortar joint (1-1,5 thick)

Mortar joint (1-1,5 thick)

Fill


The sketch shown typical adjustment for distorted kiln shell

(longitudinal direction).

Fill

Fill


The sketch shown typical adjustment of welding seams at the kiln

shell.

Fill

Fill


Grooved bricklaying should be excluded so that

rings are relatively free to move and shear

forces are minimised. When bricks are being

laid to form the rings, the inner brick face must

not show any signs of sawing (denticulate

surface). Should signs of sawing be occurring,

this would indicate that the brick has not been

tapered correctly or that the shapes have not

been combined optimally. When prolonged, the

face of each brick forming the radial joint must

be as close as possible to the kiln’s centre.


Right and wrong

Condition of brick

installation within

a rotary kiln

Denticulate

surface

Surface

without teeth


Preliminary works – The first step consist in demolishing worn parts and cleaning scraps. The internal section of the liner must be cleaned thoroughly from mortar and other residues. The refractory liner section that is not removed must be fastened, by angle irons welded onto kiln shell, in order to prevent axial displacement, protected against moisture and wear possibly induced by the machines used to convey the bricks inside the kiln. The use of dismissed rubber belts to cover any lining section possibly left in can prevent wear due to the passage of materials conveying machines.

If use dolomite bricks, in order to prevent hydration, it is advisable that the inlet or outlet ends of the kiln be perfectly closed so that rapid air changes are avoided.

All necessary materials to execute the work (bricks, mortar, steel shims, cardboard, etc. as specified in the drawing) and tools (trowel, metal hammer for steel shims, rubber hammer for bricks, wooden template, and hydraulic jig, screw jacks, mortar mixers, tables, timber beams, level, plumb line, etc) must be carried to the erection site and suitably arranged. If temperature are particularly low, especially for the parts to be done with concrete, it is advisable that the ambient as well as the materials are slightly heated before starting installation works.


When using the glue method, a setting test must be performed before proceeding with the subsequent operations. A particularly efficient lighting system of the work site must be provided. If the installation technique involves turning the kiln, all mechanical works, with special reference to those involving drive, tyres, rollers and shell welding operations, will have to be completed before starting the lining works.

Marking the axial line on the

shell bottom – for this purpose,

the kiln centre is marked on the

shell bottom by means of a level

(see next picture); such an

operation is repeated several

times at about 2 m intervals.

The line connecting the marker

points represent the axial line.


The marking of the axial line is possible to make also by laser goniometric.

For control purpose, reference lines must be traced on the shell parallel to the circumferential shell welds.

Air level and plumb bobFirst point

Second point Axial line

Shell


A perfectly straight beam held in place by few bricks resting on top of it approaches perfectly of the axial line; the building of the refractory rings 1 - 3 - 5 - 7, etc., starts by putting the brick against to the beam, the bricks of the rings 2 - 4 - 6 -8 are placed half brick staggered so that the radial joints of two consecutive rings are not in the same axis line (see also next picture).

1

23

45


Lining with a screw jacks method – This method can be adopted

with kiln diameters of up to 4-4,5 m. Bricklaying to form the rings

must always be executed in the opposite direction with respect to

the kiln rotation. The zones to be lined simultaneously along the

kiln axis is as a rule 4 m long. The implementation of the bricks

must be made across the lower semi-circumference of the kiln,

taking care to frequently check the correct position of the lining

compared to the circumferential welds of the shell. When the

zone being lined slightly exceeds the semi-circumference, the

first row of the screw jacks is positioned 20-30 cm apart from the

kiln axis for the purpose of avoiding screw jacks from sliding,

joints from opening and bricks from upsetting. Longitudinally to

the kiln, screw jacks must be arranged 60-80 cm apart as a

function of the kiln diameter. The second and third rows of screw

jacks must be positioned 60° from the rows of the screw jacks

previously placed.


CLOSING

ZONE

1° STEP 2° STEP

The sketch shown: fixing bricks with screw jacks.

Screw jacks can be removed immediately after closing the ring if the liner has been executed clench; when using mortar, it would be preferable to leave the reinforcement for 6 hours at least. 3° STEP

4° STEP


Construction drawing RR 561 shows the features of the screw jacks.


The glue method – This technique was set up to overcome the increasing difficulties arising when screw jacks cannot be used as the kiln sections are too large. In kilns with diameter greater than 4-4,5 m, the use of screw jacks becomes unsafe due to the very high pressure necessary to support the great brick weight and to the screw jacks weight. The necessary amount of glue is as a rule 0,5-1 kg per square meter of liner. Adhesives currently available on the market are normally constituted by two components (resin and hardener) and have precise operating temperature range (one type can be used in the temperature range from -25° to +5°C; another from +5° to +25°C and a third type from +25° to +50°C) within which they promote a sufficient adhesion of refractory to kiln shell. The adhesive must be chosen according to the ambient temperature conditions at which installation is expected to take place. Such conditions will have to be maintained throughout the entire execution period. Adhesives currently available on the market it decompose at temperatures above 200°C. The glue method requires that the shell sections over which the adhesive will be spread are thoroughly and carefully cleaned.


To verify whether cleaning has been effective, the kiln metal must

be naked by means of a grinder. Before spreading the

adhesive, which is don using a toothed paddle, it must be

ensured that the kiln shell surface is perfectly dry. After

spreading the adhesive, the first row of the bricks are placed as

discussed above.

As shown in the sketch beside

the glued sections "from I to VI“

keep in place the bricks during

the construction phases of the

refractory lining. When the kiln

is heated, the glue evaporates

leaving free the refractory rings.


For kilns with a diameter less than 4,6 m, 5 glued sections are necessary; the “IV” should be used when the kiln diameter greater than 4,6 m. Do not install bricks with mortar on the glued section; the mortar can be used to bond bricks only between the glued sections.

The spreading of the adhesive must be made on the bottom of the kiln so that the glued section is found to be almost horizontally so that the glue can be distributed on the shell with constant thickness, this is reason why, every time you need to glue a sector, you must rotate the kiln to place it correctly.

For safety reasons, often, at the glue method is associated the bolt method, which is to block some rows of bricks with bracket and bolts that cooperate with the glued sector.


The sketch shown: assembly sequence for a 4,8 m diameter kiln, with or

without mortar, by employing glue method and “bracket and bolts”.

Glued

Bricks

Clench Bricks or

Mortared Bricks


Drawing RR 487 shows a detailed scheme of bracket size and

method of bolting application.


Installation with bricking machine: this method can be considered the most updated one for saving on labour cost in the execution of the lining work. The first step of bricklaying consists in placing bricks close to a beam which is positioned on the kiln bottom and parallel to its axis, as described previously. It is particularly important to check frequently that rings are mounted at right angles to the kiln axis.

This type of execution is twice as rapid as the two earlier described methods because a staff of six people can line the lower half of the kiln while a second team work in the upper part where the bricking machine is installed.

The base frame serves as a working platform and can be moved inside the kiln. The curved frame is located on the base frame and is also movable. The curved frame advances ring by ring. When the end of the working platform has been reached the entire platform is moved forward by its length. The curved frame starts once again at the front side of the platform. The machine has a double curved frame, so it is possible to work on two rings at the same time.


The sketch shown a bricking machine

Pneumatic cylinders

Self-supporting refractory

ring by hydraulic jack

Working

platform

Curved

frame

Segment of

curved frame


The curved frame, of the bricking machine, consists of individual segments equipped with pneumatic cylinders. In the upper part the segments are connected by swivel joints. In the lower part is an adjustable connection so that a regulation to the existing kiln diameter is possible. The curved frame is mounted on a undercarriage with adjustable gauge. The height is set by lowering or lifting the working platform.

When a ring is about to be closed with the front curved frame, a hydraulic jack is positioned in the brickwork gap in order to ensure a good tight fit of the brickwork. During this time the brickwork ring is self-supporting, so it is possible to remove the curved frame and move it forward by one ring. The rear curved frame can now support the brickwork when the hydraulic jack is taken out, in order to place the key bricks. In the meantime a new ring can be installed with the front curved frame.


Other systems to make the refractory lining on the rotary kiln: two

more systems can be used: POGO STICKS METHOD and BOLT

METHOD; the latter we have already mentioned when we discussed

the glue method; to get an idea what it is, see figures below.

POGO STICKS METHOD BOLT METHOD

Kiln Shell Bricks

Pogo Sticks Wooden ring

Wood plank

Welded Nut


The graph below represents the medium average times needed

to execute a 1 m long lining of a kilns as a function of the shell

diameter.

∅ KILN

HO

UR

S

1:00

1:30

2:00

2:30

3:00

3:30

4:00


Retaining rings – Owing to its weight and kiln slope, the refractory lining of a

rotary kiln with uniform cross section tends to shift toward the discharge end.

If not opposed by suitably arranged retaining rings, such a force - combined

to that generated by constrained expansion – would affect entirely on the kiln

nozzle ring plates. Retaining rings, even if necessary, can cause problems in

refractory because they make more difficult to realise the lining and because

they themselves can cause deterioration of refractory lining. Rotary kiln with

uniform cross section, as a rule, should only use a retaining ring positioned at

about 600-800 mm from the kiln discharge end; a second ring can be

positioned at the beginning of the safe area where they are used aluminous

bricks. Only in kiln that have inverted cones (large part of the cone towards

the outlet of the kiln) justified the use of additional retainer ring. The position

of the retaining ring must be away from mid-air of the tires of at least 1

diameter of the kiln.

The drawing RR 811 represents the standard solution for the CTG on the

construction and placement of retaining rings. As shown in the drawing, the

bricks in the refractory ring upstream of the retainer ring must be intact, not

cut and shaped, and it shall have a high crushing strength; the downstream

ring must be shaped by cutting as it will contain the retaining ring.



Nose ring refractory lining: In the drawing RR811, concerning the rotary kiln retaining rings, there is represented the refractory lining of the kiln nose ring, which may be made using bricks or unshaped materials. The use of brick was more justified when, in the past, the performance of unshaped materials were much lower than those of the bricks. Way the performance of the unshaped materials has improved the refractory lining of nose ring of the rotary kiln has changed from the bricks constructions to unshaped materials. This happened because even the brick construction, in fact, is not without major problems. Among the problems that reduce the life of the refractory lining of nose ring made of bricks we point out:

• level of wear of steel plate of discharge end;

• shell deformations near the discharge end;

• low efficiency of the cooling system of

the shell near the discharge end;


While using bricks to achieve the refractory lining of nose of the rotary kiln, steel plate of the discharge end shall be maintained in good condition (slightly worn) to ensure effective support of the bricks. If unshaped materials are used the steel plate of discharge end may be worn without this reflects negatively on the life of the refractory lining. Using unshaped materials the substitution of steel plate of discharge end may become less frequent thus creating clear advantages in terms of economy.

The same considerations apply to the distortions that are often present on the shell to the dis-charge end of the rotary kiln. Using the bricks to realize the refractory lining, the shell must be maintained without deforma-tion while the use of unshaped materials, which can adapt de-formation, the shell can be re-placed less frequently.


When the cooling system of the rotary kiln discharge end is inefficient, it may have an excessive heating expansion of the shell that have negative affects on the stability of the refractory rings made of bricks. If the lining is made of unshaped materials, no stability problems occur because the refractory lining is held in position by the anchors.

The part of the refractory lining to be made with unshaped materials are the 400-800 mm terminal part that covers the discharge plates. In radial direction the unshaped lining should be discontinued at least every two discharge steel plates or, better, at each joint of the plates.

See below the representation of all details relating to the construction of the kiln nose ring refractory lining having a length of 800 mm.


Before casting insert polythene to protect the bricks


Before casting insert

polythene to protect

the bricks

EXPANSION

JOINT

Two discharge steel plates


The practical realization of the lining of the nose ring of the kiln can be performed in two different ways:

1. continuous cast of all sectors in position "3 o'clock" or "9 o'clock" using the "rotocast" technique;

2. discontinuous cast of sectors at the bottom of the kiln;

The technique of "rotocast" allows to make the sector of lining of the nose ring without interruptions of the casting operations through the provision of appropriate molds and the location where the casting is made.

Only if the casting operations is made to position "3 o'clock" or "9 o'clock", the joints are placed in a horizontal position that is the position taken by concrete before start hardening.

See what has been detailed in the drawing RR 965 on the implementation of the nose ring of kiln 8 & 9 of Tourah plant and the subsequent design RR966 where is represented all phases of construction by adopting the technique of “rotocast”.




The refractory

lining of the

kiln nose ring

can also be

done by

implementing

sectors

checkerboard

on the bottom

of the kiln as

shown in the

next drawing

RR 1008.


Inlet cone

refractory

lining:

Also the lining of the

inlet cone is

made of

unshaped

materials see

next sketch.

The installation of

this cone can be

done either with

“rotocast” or

alternate

casting.

8 SECTOR

EXPANSION

JOINTS

Documents

Rotary Kiln Refractory Lining Installation-I (Training Course)