GB1577143A

GB1577143A - Scraper apparatus for cleaning rotary kilns

Info

Publication number: GB1577143A
Application number: GB1422177A
Authority: GB
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1976-04-09
Filing date: 1977-04-05
Publication date: 1980-10-22
Also published as: DE2715700A1; CH620758A5; DE2715700B2; FR2347637B1; FR2347637A1; DE2715700C3

Abstract

The cylindrical cage (20) has openings, through which the substance to be treated can be moved in the axial and the radial direction. The cage (20) has a support frame (11). A large number of scratching members (10) extend in the axial direction of the rotary furnace (1) and are in each case arranged at a distance from one another on the outer circumference of the support frame (11). The cage diameter is smaller than the internal diameter of the rotary furnace. At least one scratching member (10) touches the inside of the rotary furnace so that the cage rotates freely together with the rotary furnace (1). The cage (20) has bolts (12). A piston rod (13) of a fluid cylinder (14) can be displaced into contact with the bolts (12) in order to stop the rotation of the cage (20) at intervals. Residues adhering to the inner wall can consequently be removed without the rotary furnace having to be taken out of operation for a relatively long time. <IMAGE>

Description

(54) SCRAPER APPARATUS FOR CLEANING ROTARY KILNS -.(71) We, KOBE STEEL LTD also known as KABUSHIKI KAISHA KOBE SEIKOSHO, a Japanese corporation established under Japanese law of 3-18, l-chome, Wakinohama-cho, Fukiai-ku, Kobe, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to an apparatus for scraping away substances adhering to the inner wall of a rotary kiln so as to extend the continuous operation of the rotary kiln for a longer time and to enhance the operational efficiency of the rotary kiln.

When rubbery or plastic materials or city garbage are thermally decomposed by using a rotary kiln or when coal.is carbonized or various materials are dried in a rotary kiln, char and other substances are accumulated on the inner wall of the rotary kiln to form a layer and after a time such a layer adversely influences the operation of the kiln. Especially in case of a rotary kiln of the externally heated type, transfer of heat through the wall of the rotary kiln is drastically reduced by such a. layer of adhering substances and hence, its operation becomes impossible after a relatively short time.

The present invention provides a rotary kiln including apparatus for scraping away substances adhering to the inner wall of the rotary kiln, which apparatus comprises a.cylindrical cage having openings which enable material being treated to pass therethrough in both the axial direction and radial direction, said cage including a supporting frame and a plurality of plate members arranged so as to extend generally in the axial direction of the kiln and being spacedly mounted on the outer periphery of said, supporting framej said cage having a diameter smaller than the inner diameter of the kiln and being mounted in the kiln such that at least one of said plate members is close to or in contact with the inner face of the kiln the cage alternately rotating with the kiln and rotating relative to the kiln.

In a preferred arrangement the apparatus further comprises stop means engageable with a part of said cage to intermittently stop the rotation of the cage with the kiln.

Said stop means may be controlled by a timer means or by a rotation number detecting mechanism for detecting the extent of rotation of the cage, means for storing the extent of rotation of the cage detected by said rotation number detecting mechanism and a control device for controlling the operation of said stop means co-operatively with said storing means.

Preferably the cage includes a plurality of pins arranged annularly on a terminal end portion thereof so that said pins are engageable with said stop means to stop the rotation of the cage.

Said stop means may include a rod member engageable with a part of the cage to stop the rotation of the cage, a cylinder member for reciprocating said rod member and control means for the reciprocation of said rod member periodically.

The rod- member may be engageable with the pins.

The plate members are preferably inclined in the direction of rotation of the cage with respect to the radius of the cage.

The apparatus may further comprise means for preventing the cage from mov ing.in the axial direction of the kiln.

Preferred embodiments of the invention will now be described by way of example only and with reference- . to the accompanying drawings in which: Fig. 1 is a longitudinal- sectional view illustrating one embodiment of the apparatus of the present invention.

Fig. 2 is a section along the line II-II in Fig. 1.

Fig. 3 is a section along the line III-III in Fig. 1.

Fig 4 is a cross-sectional- view showing another embodiment of the apparatus of the present invention.

Fig. 5 is a view illustrating one example of a device for performing rotation of the cage intermittently in the apparatus of the present invention.

The present invention is first described by reference to Fig. 1 illustrating one embodiment of the apparatus of the present invention.

A rotary kiln 1 is heated externally by a heating furnace 2 and includes a front cover 3 and a rear cover 4, packings 5 and 6 being formed on parts connecting the covers 3 and 4 to the kiln 1 to insulate the kiln 1 from ambient air. There is also provided a raw material feed device 7, an exhaust gas opening 8 and an opening 9 for discharging char and residues. A cage 20 comprises an annular supporting frame ill and a plurality of plate members 10 (six plate members in Fig. 1) extending generally in the axial direction of the kiln 1. These plate members 10 are attached to the supporting frame 11 at prescribed intervals in the circumferential direction so that material to be treated - is allowed to pass through the cage 20 in both a radial and axial direction. The cage 20 is inserted into the kiln 1 so that it is freely rotatable with the kiln 1.A plurality of pins 12 are arranged on a front end circumferential portion of the cage 20 extending in the axial direction and respective end portions of the pins 12 are connected to one another by means of annular plates 17 and 18. The outer peripheral portion of the annular plate 18 is mounted in a guide 19, so that the cage 20 is rotated at a certain position. Furthr, at least one of the plate members 10 of the cage 20 is pressed to the inner face of the kiln 1 entirely along its lengthwise direction by the weight of the cage 20.

The shape of the plate members 10 need not always be linear as shown in Fig. 1 but may have a spiral or other shape so long as the entire peripheral edge thereof may contact the inner face of the kiln 1.

The left end portion of Fig. 1 and Fig.

3 illustrate one example of stop means for intermittently stopping rotation of the cage 20. Reference numeral 14 represents a fluid cylinder. When this fluid cylinder 14 is actuated, the end of a piston rod 13 is caused to move to a position to contact the pins 12. This fluid cylinder 14 is actuated by a compressed fluid generating device 15 and the operation of the fluid cylinder 14 is controlled by a solenoid valve 16.

The operation of the apparatus having the above structure will now be described.

First, the piston rod 13 is retracted as indicated by a solid line in Fig. 3, and material is fed into the kiln 1 and the kiln 1 is rotated while it is heated by the heating furnace 2. The cage 20 rotates with the kiln 1. Since the outer diameter of the cage 20 is slightly smaller than the inner diameter of the kiln 1, the cage 20 can turn within the kiln 1. Further, since the annular plate 18 of the cage 20 is mounted in the guide 19, the cage 20 is rotated without movement in the axial direction of the kiln 1.

The fluid cylinder 14 is actuated to project the piston rod 13 to a position 13'.

One of the pins 12 of the rotating cage 20 will then contact the end of the piston rod 13, whereby the rotation of the cage 20 is stopped. Since the kiln 1 continues to rotate, sliding scraping contact takes place between the inner surface of the kiln and the plate member 10 which is pressed to the inner face of the kiln, whereby the plate member 10 scrapes away substances adhering to the inner wall of the kiln.

When the piston rod 13 is retracted, the rotation-stopping force on the cage 20 is released and the cage 20 is rotated again with the kiln 1. Thus, the rotation of the cage is stopped while the piston rod 13 is projected and during this period, substances adhering to the inner wall of the kiln are scraped away. During this scraping operation however, agitation of the material in the kiln is reduced. Therefore, the period during which the piston rod 13 is extended is set to as short a time as possible to reduce the effect on the agitation of the material and the piston rod 13 is intermittently actuated at a short operation interval. This operation interval and the number of the plate members 10 are determined so that the scraping action is uniformly effected on the entire inner wall of the kiln.

Since substances adhering to the inner wall of the kiln are always scraped away and prevented from accumulation by such scraping action, even if the kiln is operated for a long time continuously, the initial state of operation can be maintained in the kiln.

Moreover, with rotation of the cage, the plate members 10 have not only the above scraping function but also serve to lift up the material from the bottom portion of the kiln and scatter it. Accordingly, a good agitation effect can be attained and heat is supplied uniformly to the material to ensure a high efficiency whilst aglomera tion of the material is prevented.

it is - preferred that the plate members 10 be attached to the supporting frame 11 in such a way as to be inclined in the rotation direction of the cage 20 with re spect to the radius of the cage as shown in Fig. 4. By this arrangement, the material to be treated is more efficiently lifted up during rotation of the kiln and is agitated more effectively.

By stopping the cage 20 intermittently and causing the plate members 10 to have sliding scraping contact with the inner face of the kiln 1 in the above-mentioned man ner, substances adhering to the inner face of the kiln proper 1 can be scraped away.

However, in view of the necessity for agitation of the material to be treated, it is necessity to rotate and stop the cage 20 intermittently and periodically at certain intervals. Rotation and stopping of the cage 20 may be peri6dically effected manually by using suitable time measuring means.

However, for operational efficiency, it is preferred that the rotation and stopping of the cage be automatically controlled, for example by a timer. An embodiment using a timer will now be described.

The predetermined periods of rotation and stopping of the cage 20 are stored in the timer, and outputs of the timer are transmitted in succession to the solenoid valve 16, the compressed fluid generating device 15 and the fluid cylinder 14 in the embodiment shown in Fig. 1 to control the time during which the piston rod 13 is extended or contracted whereby rotation and stdpping 'of the cage 20 are automatic ally performed periodically at prescribed intervals of time.

In the foregoing ernbodiment, the timer automatically performs rotation and stop ping of the cage periodically at prescribed time intervals. lternatively, there may be employed means for automatically per forming rotation and stopping of the cage periodically by counting the number of rotations of the cage. An embodiment using such control means will now be described by reference to Fig. 5.

A counting lever 21 is mounted to pass through the front cover 3 so that the end of the counting lever 21 may contact the pins 12 as the cage is rotated. A limit switch 22 is mounted to contact a contact element 24 fixed to a shaft 23 supporting the counting lever 21, the contact element 24, shaft 23 and lever forming a bell crank assembly. A strain gauge 25 for measuring the load on the piston rod 13 is connected to a recorder 26 described hereinafter. The recorder 26 for recording the load on the piston rod 13 and the valve 16 are connected to a counter type control device 27.

When the cage 20 is rotated with- rotation of the kiln 1, the lever 21 contacts the pins 12 successively and when the lever 21 is swung to a position 21' by contact with each pin 12, the contact element 24 following the rotating lever 21 contacts the limit switch 22 to actuate it to provide a series of pulses indicating the extent or number of rotations of the cage 20.

The lever 21 returns to its original position after each pin 12 has passed.

The pulses indicating the rotation of the cage 20 are counted by a preset counter of the counter type control device 27, and when the counted value of the input signals reaches a prescribed number, the output signal fed to the solenoid valve 16 is changed. The solenoid valve 16 is thus actuated to extend the piston rod 13 to the position 13' so that one of the pins 12 of the cage 20 will contact the end of the rod 13, whereby rotation of the cage 20 is stopped. Since the kiln 1 continues rotation, there is sliding contact between the inner wall of the kiln 1 and the outer edges of the plate members 10 pressed to the inner face of the kiln 1; and substances adhering to the inner wall of the kiln are scraped away by the plate members 10 as shown in Fig. 4.

When the solenoid valve 16 is then deenergized by a timer of the counter type control device 27, the piston rod 13 is returned to the original position from the position 13' and the rotation stopping force on the' cage 20 is released. Accordingly, the cage 20 is rotated again with rotation of the kiln 1.

In the foregding manner, the cage 20 is intermittently stopped according to the predetermined extent of rotation of the cage (ie.the number of rotations) and this intermittent - stopping is repeated.

Further, in this embódiment, it can- be confirmed whether the scraping operation is being performed normally, by recording the load imposed on the piston rod 13 whilst the cage 20 is stopped by the strain gauge 25 disposed between the fluid cylinder 14 and the piston rod 13.

Of course, the lever for detecting the number of rotations of the cage, the limit switch, the counter, the timer and the like member in the foregoing embodiment may be replaced by other means or units capable of attaining the same objects.

In the foregoing embodiments, the stop means is designed to fit a kiln of the external heating type. Of course, the present invention may be anplied to a rotary kiln of the internal heating type and various modifications mav be made to the stood means illustrated in the foregoing embodiments.

Further, the apparatus of the present invention may be applied to not only a kiln for thermal decomposition of rubbery and plastic materials, city garbage and the like but also other kilns in which there is a problem of adhesion of substances to the inner wall of the kiln, for example, those for carburization of coal or drying, burning or calcining other various materials.

As will be apparent from the foregoing illustration, the operation of agitating a material to be treated in a rotary kiln and scraping away substances adhering to the inner wall of the kiln can be accomplished with a high efficiency by inserting in the kiln the described cage whereby the rotary kiln can be operated continuously for a long time and the heat treatment can be performed smoothly.

WHAT WE CLAIM IS: 1. A rotary kiln including apparatus for scraping away substances adhering to the inner wall of the rotary kiln, which apparatus comprises a cylindrical cage having openings which enable material being treated to pass therethrough in both the axial direction and radial direction, said cage including a supporting frame and a plurality of plate members arranged so as to extend generally in the axial direction of the kiln and being spacedly mounted on the outer periphery of said supporting frame said cage having a diameter smaller than the inner diameter of the kiln and being mounted in the kiln such that at least one of said plate members is close to or in contact with the inner face of the kiln the cage alternately rotating with the kiln and rotating relative to the kiln.

2. A kiln as claimed in claim 1 which further comprises stop means engageable with a part of said cage to intermittently stop the rotation of the cage with the kiln.

3. A kiln as claimed in claim 2 which further comprises timer means for controlling the operation of said stop means.

4. A kiln as claimed in claim 2 which further . comprises a rotation number de- tecting mechanism for detecting the extent of the rotation of the cage, means for storing the extent of rotation of the cage detected by said rotation number detecting mechanism and a control device for controlling the operation of said stop means co-operatively with said storing means.

5. A kiln as claimed in any of claims 2 to 4 wherein the cage includes a plurality of pins arranged annularly on a terminal end portion thereof so that said pins are engageable with said stop means to stop the rotation of the cage.

6. A kiln as claimed in any of claims 2 to 5 wherein said stop means includes a rod member engageable with a part of the cage to stop the rotation of the cage, a cylinder member for reciprocating said rod member and control means for performing the reciprocation of said rod member periodically.

7. A kiln as claimed in claims 5 and 6 wherein the rod member is engageable with the pins.

8. A kiln as claimed in any of claims 1 to 7 wherein the plate members are inclined in the direction of the rotation of the cage with respect to the radius of the cage.

9. A kiln as claimed in any of claims 1 to 8 which further comprises means for preventing the cage from moving in the axial direction of the kiln.

10. A kiln as claimed in claim 1 substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. invention may be applied to not only a kiln for thermal decomposition of rubbery and plastic materials, city garbage and the like but also other kilns in which there is a problem of adhesion of substances to the inner wall of the kiln, for example, those for carburization of coal or drying, burning or calcining other various materials. As will be apparent from the foregoing illustration, the operation of agitating a material to be treated in a rotary kiln and scraping away substances adhering to the inner wall of the kiln can be accomplished with a high efficiency by inserting in the kiln the described cage whereby the rotary kiln can be operated continuously for a long time and the heat treatment can be performed smoothly. WHAT WE CLAIM IS:

1. A rotary kiln including apparatus for scraping away substances adhering to the inner wall of the rotary kiln, which apparatus comprises a cylindrical cage having openings which enable material being treated to pass therethrough in both the axial direction and radial direction, said cage including a supporting frame and a plurality of plate members arranged so as to extend generally in the axial direction of the kiln and being spacedly mounted on the outer periphery of said supporting frame said cage having a diameter smaller than the inner diameter of the kiln and being mounted in the kiln such that at least one of said plate members is close to or in contact with the inner face of the kiln the cage alternately rotating with the kiln and rotating relative to the kiln.