Patent Application
20070137539
The invention relates to a method for the removal of deposits from the internal walls of industrial furnaces or bunkers such as blast furnaces, cement ovens, waste incineration plants, coal-burning power plants or other plants such as large silos, bulk material bunkers, mixing bunkers, etc . . .
On the inner walls of industrial furnaces or bunkers increasingly thick layers of slag, encrustations or other deposits are built up during operation. It is necessary from time to time to remove these deposits in order to maintain an efficient operation. Since such deposits may be quite thick and, because of their strength and hardness, are difficult to remove, it is quite common to remove these deposits by shelling the interior walls with industrial cannons whereby the deposits are broken off the walls.
With the industrial cannons generally used today, which are of a design and operated similar to machine guns, a special ammunition with a drive charge in the cartridge and a drive charge detonater at the cartridge bottom is used. The shells have a diameter of 15 to 20 mm. The discharge speed of these shells is in the supersonic range. They have therefore a high kinetic energy and a correspondingly large surface pressure when hitting the deposits on the walls.
With the common industrial cannons and the ammunition described above use thereof in the mentioned field of application is limited. Considering the manufacturers specification for a common industrial cannon and its ammunition, actually only rotary cement kilns can be kept clean. The removal of large volume slag deposits or the formation of annular deposits in cement kilns is not possible.
Furthermore, industrial cannons cannot be utilized if, because of the necessary positioning of the industrial cannon and because of the dimensions of the furnace or kiln there is an insufficient distance between the cannon and the furnace wall. In that case, upon reaching their target, the shells would still have a large kinetic energy so that they might penetrate the deposits and damage or destroy the oven lining of fire clay or even the oven wall. The same possibilities exist also if the industrial cannon is used at distances in a normal distance range if locally only relatively thin deposit layers are present and those layers are penetrated by the shells.
Current industrial cannons work like a machine gun and use cartridge ammunition with a drive charge. They are therefore built sturdily and therefore quite heavy, that is, they weigh about 100 kilograms. As a result, it takes several workers to transport the cannon and to set it up. In areas for example of power plants which are difficult to access conventional industrial cannons cannot be used because of their high weight.
US 2004/0216698A1 discloses a method for removing deposits from the walls of ovens and similar apparatus wherein however no shells are shot at the oven walls covered with deposits. Rather explosives are detonated adjacent the deposits wherein at the same time a coolant, particularly water, is admitted via a hose to a sleeve extending around the explosives. However, this method requires means for conducting the coolant to the sleeve and also sources of the coolant and furthermore the control of each individual explosion. This method is therefore complicated and is more expensive and relatively slow in comparison with the shooting method described above. It would appear therefore to be expedient to pursue a path of improving the shooting method.
It is therefore the object of the present invention to provide a method for the removal of deposits on the internal walls of industrial furnaces, bunkers and other installations by shelling the wall areas in such a way that, on one hand, industrial cannons of only relatively small weight are needed and, on the other hand, the chances of damage to the wall linings or the walls are reduced.
In a method for the removal of deposits from the inner walls of industrial furnaces and bunkers or for the destruction of material collections by shelling with an industrial cannon, the shells include an explosive charge and an impact detonator and are driven out of the cannon by compressed air so that their impact speed is controllable.
For shooting of the ammunition by compressed air, the weight of the industrial cannon can be substantially reduced and, more importantly the travel speed of the shells can be easily adjusted to the particular conditions by adjusting the air pressure used: For a larger travel distance of the shell or smaller deposit thickness, it can be reduced, that is, the exposure of the wall to the shell impact is controllable. Since, furthermore, the shells include only a percussion detonator and a relatively small explosive charge, the shell which is lighter than those used by the conventional industrial cannons still generates on impact a high energy for the destruction of deposits and their removal from the wall and those effects are spread over a relatively large area and not limited just to the cross-section of the shell as it occurs with the conventional ammunition which generates extremely high local pressures.
The invention is first explained on the basis of some specific application examples:
In rotating cement kilns during the manufacturing process often a so-called ring caking is formed on the drum wall which may have a thickness of up to 0.5 m and extends over several meters of drum length. With a drum diameter of about 5 m, the weight of such baked-on ring deposits may be in the area of several tons. Such enormous deposit volumes cannot economically be removed with a conventional industrial cannon or rather with the ammunition used thereby. If at all, it requires a bombardment with several thousand shells.
During the bombardment, the rotational speed of the drum must be reduced whereby the production is slowed resulting in economic losses. Damage to the kiln wall may also occur. If the procedure is unsuccessful, the kiln has to be shut down and permitted to cool down in order to manually remove the baked on ring deposits. With the method according to the invention, the baked-on ring deposits can be shot off from a large distance (of about 50 m) with high targeting accuracy.
In waste incineration plants, the cleanup requirement for the industrial cannons are even more complex in that waste accumulations pushed and baked together in the incineration chamber must be shot into pieces. Depending on the particular design, also slug deposits form in the incineration chamber with a thickness of up to 0.5 m. These slug accumulations then must be bombarded with cannon shells without damaging the underlying clay lining.
In the area of exhaust gas purification, there are heat exchangers on whose walls deposits also form which deposits must be carefully removed. Such a task is hardly or very difficult to perform with a conventional industrial cannon, but can be performed efficiently with a method according to the present invention.
In some waste incineration plants, the slag generated in the combustion process is cooled by wetting it with water and the wet slag is transported to a slag bunker. Depending on the residence time of the slag in the bunker the slag sticks together or dries onto the walls while becoming hard like concrete. When the slag is removed from the bunker by dredging large amounts (tons) remain attached to the walls which cannot be removed by conventional means not even with the conventional industrial cannons. Also, in this case, the method according to the invention, with which the slag can be accurately targeted for its removal, has been found to be remarkably effective.
Also in brown coal and bituminous coal power plants large area slag deposits must be removed because of the enormous size of the furnace chambers. However, it must be taken into consideration that, there, slag deposits may have a thickness of only a few centimeters and that tube systems covered by the slag deposits which are used for the transfer of the heat out of the chamber, must not be damaged. Therefore the method according to the invention is particularly advantageous as the clean-up effect is caused by the explosion pressure wave generated by the explosion of the shells provided with impact detonators, not by the kinetic energy of the shell.
In expanded clay factories during the manufacturing procedure, material deposits occur in the furnace which have the shape of a glowing ball. This glowing ball is not rigid. It rather is similar to a wobbling mass such as liquid rock. These deposits cannot be destroyed by the conventional common shells. Because of their high kinetic energy, the conventional shells simply penetrate these balls without really affecting them. With the method according to the invention however, such glowing balls can be destroyed very effectively.
In large silos, in open pit mining operations and in bulk material handling plants, that is, anywhere, where loose material is used or stored and deposits are formed by solidification, by mixing with water, for example exposure to rain, or in blast furnaces where ores or slag deposits are formed on the walls, these deposits can be removed with the method according to the invention using impact detonation ammunition which can be accurately targeted for the removal of the deposits without damage to the walls carrying the deposits.
Preferably, for the method according to the invention, the air pressure used in the industrial cannon is about 20 bar. Herewith an impact detonation shell with a weight of 100 g reaches a discharge speed of about 130 m/s (corresponding to about 130 km/h). However, as mentioned, the pressure can be increased are reduced depending on a particular application in order to obtain a greater or smaller discharge speed of the shell or respectively, impact speed of the shell. When providing different shells with different sizes or weights, the pressure may be adjusted also in his respect.
The impact detonation shell may be equipped with different pyrotechnical or explosive contents depending on the purpose. Consequently, there is a widely variable adaptability possible with respect to the application and intended effect.
Of course, also by the configuration of the shell and of the explosive charge the effect of the shelling can be widely varied. In this way, the shape and effect of the pressure wave generated is variable. For example, an arrangement can be provided by which a concentrated pressure wave with a large depth effect in the target area or a wider reaching, areal effect with lower surface pressure can be established.
The air-pressure operated industrial cannon may be compact and have a weight of only about 15 kg—including the shell. This is only about a sixth of the weight of a conventional industrial cannon using normal ammunition. The industrial cannon according to the invention can therefore easily be transported and be set up in operating position and operated by one person.
The ammunition preferably consists of only three parts: a shell body, a cover and an impact detonator and, upon detonation, is divided only into these three parts. The ammunition is therefore relatively safe as no shrapnel or pieces fly around in an uncontrolled manner upon detonation.
An embodiment of the industrial cannon used in connection with the method according to the invention and the impact ammunition will become more readily apparent from the following description with reference to the accompanying drawings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 05 026 412.6 | Dec 2005 | EP | regional |
