RU2773785C1 - Rotating furnace chain curtain - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to a chain curtain of rotating furnaces of wet and semi-dry, combined production method. The chain curtain of a rotating furnace contains a section of chains, the attachment points of which to the furnace body are arranged in the form of a multi-pass helix, and an additional section of chains located in the loading zone of the furnace and containing chains having two ends. With their first end, the chains are attached to a non-rotating structure fixed in the end part of the furnace. The remaining ends of the chains of the additional section of the chains are connected to the additional chain in such a way that the additional chain is located at a distance of no more than 10 mm from the inner surface of the furnace.

EFFECT: reliability of the rotating furnace operation is improved by reducing the number of unplanned equipment shutdowns, reducing the specific gas consumption for firing the charge and improving the quality of the finished fired product produced due to the increased productivity of the rotating furnace.

8 cl, 6 dwg, 1 tbl

Description

Technical field

The present invention relates to the technique of roasting in rotary kilns in the production of building materials, as well as in non-ferrous and ferrous metallurgy during the oxidative roasting of vanadium-containing materials, in particular to the improvement of the chain curtain of rotary kilns of wet and semi-dry, combined production methods.

State of the art

Wet and semi-dry rotary kilns face the problem of clogging of the cold edge of the kiln with material fed into the kiln.

The temperature of the material fed into the furnace is approximately 20°C, and the humidity Wc = 10-35%; while the temperature inside the oven is 200-300°C. As a result of exposure to high temperature, there is a sharp evaporation of water from the material supplied to the furnace, which causes sticking of material particles on the furnace body. When the mass of adhering material reaches a critical level, the build-up begins to touch the feeding (feeding) systems, which in turn puts them out of action and leads to a stop of the rotary kilns. Various designs of cleaning systems are used to clean the cold edge of a rotary kiln. So, for example, at the enterprises of the cement and metallurgical industries, chains with freely hanging ends are used.

From the patent of the Russian Federation No. 2674549, published on December 11, 2018, a chain curtain of a rotating furnace is known, containing an additional section of chains fixed at one end to non-rotating structures of the end part of the furnace in the form of rows located parallel to the axis of rotation of the furnace and shifted relative to the axis down the vertical by 0, 3-0.8 and in opposite directions horizontally by 0.15-0.5 of the furnace radius, while the number of rows of the additional section of the curtain is 2-3 with an interval between the attachment points of the chains in a row of 100-200 mm, and the length of the chains by 1-3 links exceeds the distance from the attachment point to the inner surface of the furnace, and the last link is equipped with a weighting element.

The disadvantage of this invention is that it does not provide a complete cleaning of the body, leaving grooves in the body, which in turn retain the material that overflows and pours into the settling chamber. To prevent material from entering the settling chamber, the height of the retaining washer installed at the outlet of the cold edge of the furnace (furnace loading zone) is increased, which in turn narrows the cross section of the furnace. And therefore, the aerodynamic resistance of the air flow increases.

Disclosure of the essence of the invention

The objective of the present invention is to prevent unplanned shutdowns of the equipment by more efficient cleaning of the cold end of the furnace, uniform distribution of material along the entire length of the section of the body under the charging chute, and prevention of material sticking to the walls of the cold edge of the furnace (the furnace loading zone).

The technical result of the claimed invention is to increase the reliability of the rotary kiln by reducing the number of unscheduled equipment stops, reducing the specific gas consumption for firing the charge and improving the quality of the finished calcined product produced due to the increased productivity of the rotary kiln.

To solve the above problem and achieve a technical result, a chain curtain of a rotary kiln is proposed, containing:

a section of chains, the attachment points of which to the furnace body are located in the form of a multi-start helical line, and

an additional section of chains located in the loading zone of the furnace and containing chains having two ends, with their first end of the chains attached to a non-rotating structure fixed in the end part of the furnace,

characterized in that

contains an additional chain, and the remaining ends of the chains of the additional section of the chains are connected to the specified additional chain, so that the additional chain is at a distance of not more than 10 mm from the inner surface of the furnace.

Installing the chain at a distance of no more than 10 mm from the inner surface of the rotary kiln allows you to effectively clean the cold edge of the furnace (the furnace loading zone) from sticking material to the walls of the cold edge of the furnace and, accordingly, leads to an improvement in the firing of materials in rotary kilns and the prevention of unplanned equipment shutdowns.

Preferably, the additional chain contains links with buttresses.

The presence of buttresses (transverse struts) at the links of the additional chain increases the strength of the link by 20%. As such a chain, for example, an anchor chain can be used. Increasing the strength of chain links and increasing the area of the link leads to better cleaning of the material from the walls of the cold cut of the furnace, as well as extending the period of non-stop operation of the equipment and preventing unplanned equipment shutdowns.

Preferably, the additional section of the chains is fixed at an angle to the axis of rotation of the furnace, which is 15°÷25° in the projection on the horizontal plane.

Such a shift of the chains of the additional section provides more efficient cleaning of the cold end of the furnace, evenly cleans the material along the entire length of the section of the furnace body under the charging chute. Due to this displacement of the chains, the material is more easily pushed out from under the chute and from the cold edge of the furnace towards the hot one, leaving behind a cleaned furnace body.

Preferably, the length of the chains of the additional section of the chains is chosen so that the additional chain is at an angle of 10°÷20° to the inner surface of the furnace in projection onto a vertical plane.

This inclination of the auxiliary chain ensures that the material is gradually moved from the cold end of the furnace to the hot end, which reduces the load on the additional chain, further extending the period of non-stop operation of the equipment, and at the same time improves cleaning of the cold end of the furnace.

Preferably, the additional section of the chains is shifted relative to the axis of rotation of the furnace down the vertical by 0.4÷0.6 of the radius of the furnace.

When the additional section of the chains is displaced relative to the axis of rotation of the furnace down the vertical by more than 0.6 radius of the furnace, the length of the chains of the additional section of the chains decreases, which makes them less maneuverable.

When the displacement of the additional section of chains relative to the axis of rotation of the furnace down the vertical is less than 0.4 of the radius of the furnace, the consumption of chains for the construction of an additional section increases, while it is not possible to significantly improve performance.

Preferably, the number of chains in the additional section of chains is 4÷8, and the interval between the attachment points of the chains in the row is 100÷300 mm.

The number of chains in the additional section of chains in the range of 4÷8 with an interval between the attachment points of the chains in a row of 100÷300 mm is optimal for effective cleaning of the cold end of the furnace.

With an increase in the number of chains over 8 and a decrease in the distance between them to less than 100 mm, it is not possible to achieve a significant improvement in indicators that depend on the completeness of machining, such as the quality of firing, dust removal, while chains are often hung in a row (with an interval of less than 100 mm) leads to its entanglement and curtailment into balls.

With a decrease in the number of chains less than 4 and an increase in the distance between them over 300 mm, each chain has a greater load, which leads to the need to use stronger chains.

Preferably, the section of chains, the points of attachment of which to the furnace body are located in the form of a multi-start helix, contains a section of free-hanging chains, having a length of 2.5 ÷ 3.5 meters, and a section of a daisy-screw chain attachment, having a length of 4.5 ÷ 5, 5 meters, between which there is a free section 0.6÷1.0 meters long.

The use of the above chain attachment leads to an even greater decrease in the specific gas consumption for firing the charge and to an improvement in the quality of the finished calcined product, produced due to the increased productivity of the rotary kiln. At the same time, a free section with a length of 0.6÷1.0 meters provides a sufficient distance for laying a free-hanging chain when turning the furnace to prevent entanglement with the daisy-screw chain curtain, which leads to an additional increase in the reliability of the rotary furnace and a decrease in the number of unplanned equipment stops.

Brief description of the drawings

The drawings are presented for a better understanding of the invention, however, it will be obvious to a person skilled in the art that the disclosed invention is not limited to the embodiment presented in them.

In FIG. 1 is a schematic side view of a furnace feed zone containing an additional section of circuits in accordance with the present specification.

In FIG. 2 is a schematic front view (against the material flow) of the furnace feed zone, containing an additional section of chains in accordance with the present description of the invention.

In FIG. 3 is a schematic plan view of a furnace feed zone containing an additional section of circuits in accordance with the present specification.

In FIG. 4 shows a schematic side view of a section of chains, in which the points of their attachment to the furnace body are located in the form of a multi-start helical line, containing a section of free-hanging chains and a section of a daisy-helical suspension of chains, between which there is a free section, in accordance with the present description of the invention.

In FIG. 5 is a sectional view A-A of FIG. 4 showing a section of free-hanging chains.

In FIG. 6 is a B-B sectional view of FIG. 4 showing a portion of the daisy-chaining of chains.

Implementation of the invention

The rotary kiln 1, having a diameter D, contains a boot zone 2 of the kiln (cold cut), a chute 3, through which raw materials are supplied to the kiln 1, a dusty chamber 4, a section 5 of the chains, in which the chain attachment points are located in the form of a multi-threaded helical line, and also an additional section 6 of chains located in the boot zone 2 of the furnace and containing chains, each of which has two ends, with its first end of the chain attached to a non-rotating structure 7 fixed in the end part of the furnace 1.

The second ends of the chains of the additional section 6 of the chains are connected to the additional chain 8. The additional chain 8 contains links with buttresses and is an anchor chain.

The additional section 6 of the chains is shifted relative to the axis of rotation of the furnace 1 vertically down by 0.5 of the radius R of the furnace.

The non-rotating structure 7 is additionally held in the end part of the furnace 1 with the help of a rod 12 and a stand 13 to increase the reliability of the structure. The rod 12 is a metal bar, and the stand 13 is a metal beam.

The number of chains in the additional section 6 of chains is 6, and the interval between the attachment points of the chains in the row is 250 mm.

Section 5 of the chains has a diameter D and a length L equal to 8.8 m, and contains a section 9 of free-hanging chains 15, having a length L1 equal to 3 meters, and a section 11 of a daisy chain 16 of chains, having a length L3, equal to 5 meters, between which there is a free section 10 with a length L2 equal to 0.8 meters.

A retaining ring 14 is installed at the outlet of section 5 of the chains.

The verification of the efficiency of the proposed rotary kiln chain curtain was carried out by calculation and confirmed in industrial conditions on a rotary kiln for oxidative roasting of converter vanadium slag with a diameter of 3.6 m and a length of 75 m.

A comparison was made between the best indicators of the firing quality of a chain curtain of a rotary kiln, made in accordance with the invention according to the prototype - RF patent No. 2674549, and the indicators of two examples of the invention implementation shown in table No. 1.

Table #1

No. p / p Indicators Chain curtain of a rotary kiln in accordance with the invention according to the patent of the Russian Federation No. 2674549 Chain curtain of a rotary kiln according to the present invention Chain curtain of a rotary kiln according to the present invention one Chain curtain section length, m 8.8 8.8 8.8 1.1 Breakdown of section 3 into sections with a change in the type of suspension of the chain curtain, (+/-)/m (-) (-) (+)/
section of free-hanging chains 3 m,
free area 0.8 m,
section of a garland-screw hinge of chains 5 m. 2 Additional section of chains in the cold edge of the furnace (+/-) (+) (+) (+) 2.1 Number of rows, pcs 2 one one 2.2 Offset rows down vertically (fraction of oven radius R) 0.5 0.5 0.5 2.3 Horizontal row offset (fraction of oven radius R) 0.3 - - 2.4 Interval between fixing points, mm 150 250 250 2.5 Number of chain links, over the distance to the furnace surface, pcs one - - 2.6 Distance from the additional chain to the inner surface of the rotary kiln, mm - 5 5 3 Firing quality (+/-) (++) (+++) (++++) 3.1 Fraction content (-0.063 mm) before firing 69.3 67.8 67.8 3.2 Fraction content (-0.063 mm) after firing 36.6 28.2 27.1 3.3 Fraction content (+0.063-0.2 mm) after firing 62.5 69.5 70.6 3.4 Fraction content (+0.2 mm) after firing 0.9 2.2 2.3 four Dust removal, % 22 19 eighteen 5 Furnace capacity for crushed slag, t/h 10.5 10.5 10.5 6 Overgrowing of the cold end of the furnace, (+/-) (-) (-) (-) 7 Chain curtain conveying capacity (+/-) (----) (+++) (+++)

From table No. 1 it can be seen that the use of an additional section of chains in the boot zone in accordance with the present invention, compared with the known chain curtain, provides a reduction in the content of the dusty fraction in the calcined product, while the main part of the calcined product is represented by the most technologically advanced intermediate fraction (+0.063 -0 ,2) mm.

At the same time, the use of a section of chains, in which the points of their attachment to the furnace body are located in the form of a multi-start helical line, containing a section of free-hanging chains with a length of 3 meters and a section of a daisy chain-helical hinge of chains 5 meters long, between which there is a free section 0.8 meters long led to an additional improvement in the quality of firing and a decrease in dust emission.

It also follows from table No. 1 that along with a decrease in the dusty fraction in the roasting product, there was a simultaneous decrease in dust removal from 22 to 19 and 18%, which can be interpreted as a result of a decrease in the amount of dusty particles in the process of material passing through the chain curtain.

The use in the present invention of an additional chain containing links with buttresses, and fixing an additional section of 6 chains at an angle b to the axis of rotation of the furnace, which is 20 ° in the projection on the horizontal plane, made it possible to provide even more effective cleaning of the cold end of the furnace, to reduce dust removal to 17, 8% and extend the period of non-stop operation of the equipment from 60 to 80 days.

The horizontal plane, in the projection on which the angle b is measured between the additional section 6 of the chains and the axis of rotation of the furnace, is parallel to the plane of Fig. 3.

The choice of the length of the chains of the additional section 6 of the chains so that the additional chain 8 is at an angle β equal to 10°÷20° to the inner surface of the furnace in the projection onto the vertical plane allows for a gradual movement of the material from the cold edge of the furnace to the hot one, which reduces the load to an additional circuit, further extending the non-stop operation of the equipment, and at the same time improves cleaning of the cold end of the furnace.

The vertical plane, in the projection on which the angle β between the additional circuit 8 and the inner surface of the furnace is measured, is parallel to the plane of FIG. one.

The exemplary embodiments described are for the purpose of illustration only. It will be obvious to the specialist that other embodiments are possible without changing the essence of the invention.

Claims (12)

1. A chain curtain for a rotary kiln, comprising: a section of chains, the attachment points of which to the furnace body are located in the form of a multi-start helical line, and an additional section of chains located in the boot zone of the furnace and containing chains having two ends, with their first end of the chains attached to a non-rotating structure fixed in the end part of the furnace, characterized in that contains an additional chain, and the remaining ends of the chains of the additional section of the chains are connected to the specified additional chain in such a way that the additional chain is located at a distance of not more than 10 mm from the inner surface of the furnace. 2. Chain curtain according to claim 1, characterized in that the additional chain contains links with buttresses. 3. Chain curtain according to claim 1, characterized in that the additional section of the chains is fixed at an angle to the axis of rotation of the furnace, which is 15°-25° in projection onto a horizontal plane. 4. Chain curtain according to claim 1, characterized in that the length of the chains of the additional section of the chains is chosen so that the additional chain is at an angle of 10 ° -20 ° to the inner surface of the furnace in projection onto a vertical plane. 5. Chain curtain according to claim 1, characterized in that the additional section of the chains is offset relative to the axis of rotation of the furnace down vertically by 0.4-0.6 of the radius of the furnace. 6. Chain curtain according to claim 1, characterized in that the number of chains in the additional section of the chains is 4-8, and the interval between the attachment points of the chains in the row is 100-300 mm. 7. Chain curtain according to claim 1, characterized in that the section of chains, the attachment points of which to the furnace body are located in the form of a multi-start helical line, contains a section of free-hanging chains, having a length of 2.5-3.5 m, and a section of a daisy-screw hanging chains, having a length of 4.5-5.5 m, between which there is a free section 0.6-1.0 m long. 8. Chain curtain according to claim 1, characterized in that the non-rotating structure is additionally held in the end part of the furnace with the help of a rod and a stand.

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