SET OF GRAPHITE BLOCK SEAL FOR ROTARY KILN AND METHOD OF USE

Technical Field

The present invention relates to a set of graphite block seal and method of its use for applied to rotary kilns (such as cement rotary kiln, metallurgy rotary kiln, rotary kiln incinerator of municipal solid waste, etc.). This invention is for sealings the gap between a rotary kiln and inlet housing or the gap between a rotary kiln and outlet housing (kiln hood), in which stationary at both end of rotary kiln.

Background Art

In general, rotary kiln are installed at a slight tilt away from horizonal position and normally operates at high temperatures up to 1,450 degrees Celsius, as seen in cement rotary kiln. During above operating condition, the rotary kiln normally has its kiln shell to expand or shrink according to temperature changes, in which we called expansion problem. Moreover, the high temperature makes the kiln to deform and its surface is no longer rounded like a circle anymore, in which we called ovality problem. The kiln can also deform from frequent temperature changes and no long has straight line. When the kiln rotates, the center of rotation can move all the time, which we called run-out problem. Normally, the inlet end of rotary kiln connects to the stationary inlet housing. The other side, the outlet end of the rotary kiln will connect to the stationary kiln hood. Both inlet and outlet will have a gap allowing kiln to rotate freely. As a result, it requires a seal to minimize the gap. The seal is necessary to support kiln any movement caused by axial movement, radial run-out, expansion, and ovality for sealing such annular gap.

This invention is a sealing device over the annular gap of the kiln, which give business benefit in both reduce energy cost both thermal energy cost and electrical energy cost. Normally, it takes significant thermal energy to heat up the air inside the kiln up to 1450 degree Celsius. The invention will help prevent the air at ambient temperature to leak-into the system. The air at ambient temperature will combine with hot air inside the rotary kiln resulting in temperature drop and hence increasing thermal energy cost. In addition, the gap causes the hot materials to leak out and causes production loss as well as give pollution and dirty hazards to people and environment. The leaking through the gap also has indirectly negative effects on the electrical energy consumption because amount of air increasing in the process. Some machine related to the amount of air will has higher electrical energy consumption. The better seal is required to prevent such negative effect in business.

The sealing device for the rotary kiln has been continuously developed from past to present, for instance, spring plate type with wire rope sling tightening as figure 7. This spring plate contain steel with chromium, which can withstand high temperature. However, the sealing device is a metal type. During the time that kiln operates, there will be a friction between the plate and rotated kiln, which cannot be sealed tightly. Consequently, there will be a gap between the spring plate themselves and the kiln. In this invention, we propose the graphite block sealing type. The graphite has properties that resist to high temperature and self-lubricated. These properties make it difficult to obstruct and therefore sealing performance is better. Moreover, the graphite wears slower, which in turn allow longer lifetime than steel type.

In the prior art, there are some inventions of a sealing device for rotary kiln in type of graphite block. But it is still not able to solve the above problem effectively because of the different shape and operation mechanisms, for example.

US 7,686,612 Bl discloses a graphite block for sealing the rotary kiln consisting of several graphite block of the same size and rectangular shape. The graphite block is arranged into 2 rows with parallel arrangement with one aluminum plate slot for graphite blocks about 4 plates and 2 rows depending on kiln diameter size for installation with kiln sealing device. Graphite blocks in its slot cannot move independently from one another. This independent movement is in fact necessary when the kiln operates at high temperature, resulting in the rotary kiln shell expand or shrink and deformed. Such sealing device will not able to contact kiln shall closely and cause the moving characteristics of the sealing device as a slot of 4 plates and 2 rows simultaneously. Thus, there will be a gap between the sealing device and rotary kiln at kiln operation. This open up of the improvement in our present invention.

There are also different mechanisms of the sealing device for the rotary kiln with graphite blocks using such as pneumatic cylinder for push the 2 rows of graphite plate as figure 8. This mechanism is very popular in cement rotary kiln. The graphite plate shape is complete ring or divided into several blocks to complete ring. The first row will contact a rotary kiln as a rotating part while the second row will contact sealing device as a stationary part. The multiple pneumatic cylinders are utilized to push the 2 rows of graphite plate to keep contact together throughout the kiln operation. The problem encountered for this application is that the consistently high pressure in rotary kiln with high temperature. Hence, it results in high worn-out of the seal and short lifetime effect to inefficiency kiln sealing device. The worn-out will easily give a gap between the sealing device and rotary kiln at kiln operation and require frequent maintenance. Moreover, the high temperature can easily result in the bending of contact between two rows of graphite. The bending of contact will give material leakage easily.

The inventor found the problem of using such a previous invented kiln sealing device, which still cannot cover well the gap between kiln sealing device itself and rotary kiln. The key to the effective sealing is not only the mechanism of operation of the sealing device but also the shape of the graphite plate, as well as the arrangement of the graphite plate. All of above key factors affect the operation of the sealing device.

Aims of the invention

The objective of this invention is to improve the efficiency of sealing device for rotary kiln at high temperature. The efficiency of the sealing device links with how much we can close the gap between the rotation kiln part and stationary part (e.g. inlet housing or outlet kiln hood). The invention will use graphite block seal type with specific design and arrangement method to close the gaps that occur between kiln sealing device and rotary kiln effectively. Note that the gaps without proper sealing device would result in the leakage of hot material and the penetration of cold air into the hot rotary kiln resulting in using more fuel to heat up the kiln.

The rotary kiln can have high temperature up to 1,450 degree Celsius such as cement rotary kiln. Hence, graphite block is the ideal sealing material for this high temperature rotary kiln due to high temperature resistant, corrosion resistant, self-lubricating, and low friction coefficient. These mentioned properties will give smooth movement when selecting as sealing material. Naturally, ones would use a rectangular shape and same size in complete ring for the graphite block in sealing rotary kiln. However, the present invention improves the sealing capability by designing in a parallelogram shape. This parallelogram shape will better distribute the pressure throughout the surface of moving (rotating) kiln. The graphite blocks will be arranged in two rows and assembled alternately between first row of graphite and second row of graphite to complete around the kiln. The good distributed pressure from graphite block will allow the graphite block itself to always remain in touch with rotating part of kiln. Moreover, the graphite block shall be able to moved up and down freely and independent from each other according to the movement of rotary kiln.

This present invention aims to improve the kiln sealing device at the rotary at inlet or outlet end, minimizing the cold air into the heated system. As result, the temperature inside the kiln will not reduce by cold air, which in turn reduce heat consumption for production process. Definitely, this reduction of heat consumption will reduce production cost. Moreover, the leaking of cold air into the system will normally increase amount of air into the system. Therefore, by reducing coal air leaking in, the fan machinery that produces air inside the kiln system will reduce electrical energy as well. Hence, the present invention will give benefit for both reducing heat consumption as well as reducing electrical energy consumption. Business wise, this benefit bring more efficient cost to the production process and reduce CO2 for the world. On top of it, the present invention will reduce leakage of hot material spilling out from the kiln with better seal. As a result, business will reduce maintenance cost in handling of spilled hot material. With longer lifetime in graphite property compared to steel, the present invention bring additional benefit in slowing down the erosion and give longer lifetime of the kiln seal. So it also gives additional benefit to the business in reducing maintenance cost.

Brief Description of drawing

Figure 1 is a cross-sectional view of the rotary kiln showing the position of graphite block seal set

Figure 2 is a perspective view of the rotary kiln showing the position of graphite block seal set and sealing in contact with adjustable counterweight.

Figure 3 is an enlarged view showing the details of kiln seal device.

Figure 4 is an exploded view showing one segment assembly of kiln seal device.

Figure 5 is an enlarged view of kiln seal showing one segment assembly of FIG.4

Figure 6 is a front view of graphite block seal showing parallelogram shape with slightly tilt deviated from vertical line.

Figure 7 is a perspective view of the example of the traditional kiln seal of lamella type. Figure 8 is a perspective view of the example of the traditional kiln seal of Pneumatic type.

Disclosure of Invention

In the present invention is a set of graphite block seal (1) which the one of kiln seal device

(14) for sealing the annular gap between the rotary kiln (9) at both end and stationary inlet housing (10) or stationary kiln hood (13) as shown in Figure 1 to prevent ambient air (cold air) into kiln system and prevent hot materials out from kiln system through such annular gap. Figure 1 also shows the position of graphite block seal set at rotary kiln (9). The left-hand part of the Figure 1 shows the stationary inlet housing (10) and kiln inlet end (11), in which both parts are connected with kiln sealing device (14). Likewise, the right-hand of Figure 1 shows kiln outlet end (12) and stationary kiln hood (13), in which both parts are connected with kiln sealing device (14).

From Figure 2, kiln sealing device comprise of main 2 parts. The first part is rotation parts

(15) that directly mount with rotary kiln. The second part is stationary parts (16) that directly mount with inlet housing or kiln hood, in which these parts are stationary portion; not rotate with rotary kiln while the kiln is in operation.

The method of use for a set of graphite block seal (1) is assembling wire rope (5) through fixing device that located at the top edge of graphite block. Then adjusting the tightness of wire rope (5) with a counterweight (6) as shown a Figure 2 to ensure an effectiveness of the seal against the stationary parts (16). As we zoomed in, as shown in Figure 3, the wire rope (5) sit on top edge of graphite block. The graphite block will be fixed with stationary parts (16), while these graphite block got pressure from the wire rope (5) to get the pressure on the rotation parts (15). This pressure will minimize the gap between stationary parts and rotation parts. This arrangement of the graphite block on the rotation part will allow the graphite block to move up and down freely and independent from each other according to both normal and abnormal kiln movement caused by radial run-out problem, expansion or shrinkage problem, and ovality problem due to thermal deformation. Note that the above run-out problem, expansion or shrinkage problem, and ovality problem regularly happens in the kiln with high operating temperature.

Figure 4 is an exploded view showing the assembly parts of kiln seal device. The kiln seal device consists of several graphite blocks (2), which inserted in its slot from graphite -block-spacer (8). The graphite blocks (2) circularly forms double rows in complete ring. The complete ring of graphite blocks are attached with graphite mounting plate (17), which is a part of Kiln sealing device to assemble a set of graphite block seal (1) with stationary parts (16). If these device parts are assembled together, it will look like n Figure 5.

Graphite block (2) is designed in a parallelogram shape as shown figure 6. The graphite blocks have the same height for all graphite blocks in the sealing device. However, the width of all graphite block can be equal or not equal of each installation. As shown in the Figure, the graphite blocks are slightly tilted deviated from vertical. The tile angle of graphite block (7) is between one to twelve degrees. The degree can be optimized to the average rotation speed of the rotary kiln. At the top of graphite block have a wire rope fixing device (4), in which wire rope will apply pressure on top of this device. This slightly tilt shape is tilted according to the direction of kiln rotate direction (19). This slightly tile shape allows the best transfer of pressure force from wire rope tighten up with counterweight (18) through the graphite toward the kiln that rotates under the graphite blocks. At the same time, there is a reaction force from kiln surface (20) acting back on the graphite block as shown in the figure.

From above descriptions, parallelogram shape of graphite block will allow the best transfer of the pressure from the wire rope through the graphite toward the kiln that rotates under the graphite blocks. So it will minimize the gap between the rotation part of kiln and graphite block that stay with stationary part (e.g. inlet housing or outlet kiln hood). Hence, it improves efficiency of the kiln seal device. Moreover, the graphite blocks circularly forms double rows in complete ring as explained for Figure 4. These double rows give better efficiency because double rows allow less gap during the kiln rotation. On top of that, as explained above, the arrangement of the graphite block on the rotation part will allow the graphite block to move up and down freely and independent from each other according to both normal and abnormal kiln movement due to thermal deformation. Hence, this invention can minimize the gap and hence give better efficiency of the kiln sealing device. List of reference numbers

1. Set of Graphite block seal

2. Graphite block

3. Slot for wire rope fixing device

4. Wire rope fixing device

5. Wire rope

6. Counterweight

7. Tilt angle of graphite block

8. Spacer of graphite block

9. Rotary kiln

10. stationary inlet housing

11. Kiln inlet end

12. Kiln outlet end

13. stationary kiln hood

14. Kiln sealing device

15. Rotation parts

16. Stationary parts

17. Graphite mounting plate

18. Pressure force from wire rope tighten up with counterweight

19. Kiln rotate direction

20. Reaction force from kiln surface