FROM ROTARY KILNS

The object of this invention is a method to remove sediments and/or lining material from rotary kilns as a maintenance procedure in such cases where the shut-down of the kiln and the cooling down and the opening of the kiln by removing the front wagon or a corresponding structure from its place are included in the procedure.

The field of application of the invention is among others the maintenance of the rotary process kilns that are used in the wood-processing industry and the lime works industry. This maintenance procedure includes the demolishing of the material that was left in the kiln and also the removal of the sediments that are stuck to the inside wear layers and the demolishing of the worn lining and possibly the demolishing of the isolation layers behind that, removing the demolished material from the kiln and installing the new lining. The maintenance operation can in some cases be limited to the removal of the sediments or only to the removal of the lining when new sediments have not been formed. The invention is directed to the removal of the before mentioned material from the kiln. The usage field of application of the invention are widely different rotary kilns like for instance wood-processing industry lime sludge reburning kilns, cement industry cement kilns etc. (lime sludge means a compound that is created in heat treatment as follows: Na _; CQ ₃ (aq) + Ca(OH) ₂ (liq)→ 2 NaOH (aq) + CaCC (s)). During the operation of the kilns, a thermal, chemical and mechanic stresses are directed inside the kiln to the ceramic linings. Because of this, the lining must be renewed regularly and this renewal is usually made segment by segment during shut- downs that are planned beforehand. The shut-downs are tried to be made in as short a time schedule as possible so that the kilns would be out of operation as short a time as possible.

The term "rotary kiln" means in this document a long, essentially cylindrical kiln that is rotated around its longitudinal axis during the operation of the kiln. It is central for the operation of these kilns that they have been placed sloping in their horizontal position so that when the kiln is rotating the material flow that is fed to them moves from the higher feeding end to the other end. that is the lower end of the kiln that is the burning end. The gases that are formed during the burning move into the opposite direction.

As background information, it can be said that a rotary kiln rotates upon roll pairs that have been put under it and the rolls can be motor driven or the kiln can rotate by separate rotating motors.

Next, the removal of the demolished debris from a rotary kiln is presented according to the known technique. The text refers to the reference numbers of the enclosed fig 3 to make the explanation clear: The kiln 1 is shut-do wn and cooled down. During the cooling that takes usually about one day and one night, scaffoldings 21 are built under the kiln in order to open the removal hatch 20. There are usually 2 pes of the removal hatches 20 and they are located on the cylinder surface of the kiln so that one is located near the front wagon 4 burning end and the other about the midway of the kiln. The hatches are many meters higher than the kiln space floor 25 or the ground level. When the kiln is cool the front wagon 4 in its lower end is dismantled from the constructions of the kiln and it is pulled out so that the end of the kiln gets open. Through the open end of the kiln, an access bridge 5 is built into the kiln in order to be able to get things and machines/equipment into the kiln and at least one removal hatch 20 on the kiln cylinder ring is opened from the scaffoldings 21 side. Under the removal hatch opening 22, a transport platform 24 is arranged to remove the demolishing debris and if necessary a guiding canal 23 or corresponding construction is made to guide the debris 1 1 that is fed out through the removal hatch opening to the transport platform 24. When also the inside lining at the point of the removal hatch is demol- ished from inside the route is open to remove the demolished debris. After these arrangements the lime 6 is removed by sucking it through the sucktion hose 8 into a suction apparatus 7, like suction vehicle and this work phase takes usually 12 - 24 hours. When the kiln is empty of the product/raw-material that is treated in it the sediments 2 (Fig 1) stuck to the lining 3, like for example layer rings are removed using a remote controlled robot demolishing and this demolishing debris is moved to the removal hatch 20 and let run through the hatch ^' to the transport platform 24. When moving the demolishing debris, a small power tool can be used to help, like for instance model Avant loader or it can be moved to the removal hatch by muscle power. This phase of the work takes typically depending on the tools about 12 - 24 hours. Next the lining 3 ^' is demolished in the scope it is necessary to be renewed and the removed bricks are moved to the removal hatch and let fall through its opening to the transport platform. Also when moving the removed bricks, a power tool is used like said before or it is done manually. The transport platform 24 is unloaded sufficiently many times.

When a new lining has been installed and the maintenance work has been completed in other parts the removal hatches are closed, inside them, a ceramic lining is installed, the scaffoldings 21 are removed and the outside areas are cleaned from the demolishing debris. The front wagon 4 is attached to the end 1.2 of the kiln and the kiln is ready to be started.

Another method of the known technique is to remove the demolished debris from a rotary kiln is to rotate the kiln 1 so that the demolished debris 1 1 goes down to the opened removal hatches 20 and falls off the kiln through them.

The above described known technique is used widely in the connection of the maintenance works of the rotary kilns. It is a general habit to divide the responsibility about doing the works so that the operator of the kiln takes care of the scaffoldings, opening of the kiln and the removal of the lime from inside the kiln and the lining constructor takes care of the demolishing, taking the demolished debris out of the kiln and installing a new lining. It is the, responsibility of the user of the kiln to transport the demolished debris to the dumping place.

The greatest disadvantages of the known technique are in the use of the removal hatches. To open them, scaffoldings are erected, the steel construction hatch bolts are opened and the hatches are taken away, the lining in the places of the hatches is demolished, transport platforms are used to gather the demolished debris and to transport it away, to get the demolished debris out of the kiln, work is done that requires manpower and tools, the removal hatch is closed and its inside is lined, the scaffolding is dismantled and the area is cleaned. All in all, the method according to the known technique to remove sediments and lining material from the rotary kilns has many different phases, requires a lot of manpower and time and causes excessive costs in relation to the benefits of the maintenance project. Additionally, many contractors take part in the before mentioned works whose work phases must be placed in a row one after each other in the time table and this causes loss of time and inefficiency when moving from one phase Into another. This is one clear disadvantage when using the known technique.

One clear disadvantage in the use of the known technique can be seen also that the dust and small particles dirty the surroundings of the kiln very largely.

The intention of this invention is to achieve such a method to remove sediments and lining material from rotary kilns as a maintenance action that avoids the disadvantages of the known technique. It is characteristic for the method according to the invention that has been presented in the characterizing part of the claim 1.

The greatest advantage of the invention in comparison to the known technique can be seen that the removal of the sediments and lining material from inside a rotary kiln takes place in a considerably shorter time and with smaller costs than when using the methods of the known technique in a corresponding size maintenance project. The savings in the time and costs of the project consist of the replacing the manpower by usage of machines and performing many phases of work in a compact procedure. No removal hatches are needed, so their constructions and relational work phases are not needed.

Advantage is also achieved when all the material to be removed from the kiln, like lime, sediments and demolished lining, is removed by one contractor in one phase so that the principle of the alteration where the successive phases have different contractors becomes simpler and more efficient.

In this document, the term "breaker" means any apparatus operating with machine power that can change the demolished ceramic bricks, pieces of ceramic mass and the pieces of the sediments that have been removed from the inside surface of a rotary kiln into a crushed material. The term "suck hose" means in this document in addition to hose also such tube, duct etc. inside which it is possible to move using vacuum solid material from a place into another. The invention is described more closely in the enclosed drawings where

fig 1 presents the environment where the method according to the invention is used, fig 2 presents a chart describing the method according to the invention,

and as mentioned before, fig 3 describes the method according to the invention. Next there is a description about one application of the method according to the invention by referring to the figs 1 and 2.

Fig 1 is a diagrammatic rotary lime juice kiln. This picture describes the use of the method according to the invention to remove the sediments 2 and certain parts 3' of the inside lining 3 of the rotary kiln and the action is in such a phase that the kiln has been shut down and cooled, the front wagon 4 has been loosened and drawn away from the kiln 1 and an access bridge 5 has been built through the opened kiln burn end, that is the other end 1.2 into the kiln. So all these action are made according to the known technique.

After this, a remote controlled robot is brought into the kiln and the demolish work of the sediments 2 that have stuck to the inside lining surface 9 and the lining to be renewed 3 ^' in the desired length L begins using this robot. At the same time with this demolishing work (fig 2), the removal of the lime or a corresponding substance 6 is performed from the inside of the kiln into the suck apparatus 7, like suck vehicle using a suck hose 8. After removing the lime (or during it) an electricity driven breaker 10 is brought into the kiln, the breaking power of which is sufficient to break the refractory bricks that are used in the kiln. In this example case, the bricks of the lining 3 of the kiln are when new of the size maximum about 200 mm x 250 mm x 100 mm and they are of their material for instance magnesium oxide based or aluminium oxide based. The demolished debris 1 1 from the sediments 2 and the demolished lining 3 ^" is portioned using a small loader into the breaker 10 that changes it into crushed material 12. The suck hose 8 has been connected to the breaker after having removed the lime and that is used to transport the crushed material 12 into the suck apparatus 7, like a suck vehicle. The breaker 10 has been placed upon a base 10.1. The meaning of the base is in addition to support the breaker to damp the strike like shock of the breaker in the part 3 of the lining that is not intended to be demolished. So it is essential for the method according to the invention that both lime and the sediments and the demolished lining are removed from inside the kiln 1 using suction technique. It belongs to the method centrally that the breaker 10 that changes the demolished debris 1 1 into the particles of the size that the suction power of the suck vehicles or corresponding apparatuses that can be found in the market is sufficient to move the particles from the breaker 10 outside the kiln through the open kiln end one or two, 1.1 , 1.2, or through some other opening through the suck hose 8.

The characteristic that the method according to the invention is operational without opening the removal hatches 20 (fig 3) or corresponding other openings does not limit the use of the invention without taking advantage of these hatches when they have been opened for some other reason.

The power source of the breaker 10 can be also other than what is mentioned in the before mentioned example like for instance combustion engine. The size and the ca- pacity of the breaker can be chosen in each case so that getting it into the kiln 1 and sufficiently near the demolished debris 1 1 is possible and that its power is sufficient in each case to break the demolished debris. It is not deemed to be outside the method according the invention if such a special case is used where the breaker 10 has been placed outside the kiln 1 ike for instance in the front wagon 4 and between the other end 1.2 of the kiln for the time that the procedure takes.

When the breaker 10 is electricity driven and placed inside the kiln 1 the electricity safety points of view are taken into account for instance in the voltage to be used. The suction apparatus 7 that is used in the method according to the invention is most typically a suction vehicle that can be used to transport the crushed material 12 to a dumping place without extra work phases. The method according to the invention can also be realized using some other suction apparatus. All kinds of additional work phases weaken however the efficiency of the method according to the invention but in some special cases the use of the suction technique in itself brings a sufficient advantage in comparison to the known technique.

To put the demolished debris 1 1 into the breaker 10, a machine powered loader or some other corresponding apparatus can be used that is suitable for this task. The method according to the invention is also realized if the demolished debris is moved manually.

The rotary kilns 1 in connection of which the method according to the invention is used can be very much different of size. Their inside diameters can vary for instance from some two meters to over five meters and likewise their length can vary for instance from some ten meters to over hundred meters.

It should be noted that although this application presents one advantageous exemplary embodiment of the present invention, it is not intended to limit broader use of the invention in any way; all alternatives for implementing the invention are possible within the inventive idea defined by the claims.