DE966057C - Rotatable roasting or calcining furnace - Google Patents

Description

Rotatable roasting or calcining furnace The invention relates to a rotary furnace with an inner wall provided with constrictions and spiral guide ribs, for processing in the manufacture of pig iron, cement and other products used raw materials.

The object of the invention is the throughput and efficiency of a such a calcining furnace with a simultaneous reduction in heat losses and thus to increase fuel consumption. In addition, the below-described Facilities and the method described are prevented from being deposited as dust The concentrate is soaked through the chimney, which not only saves material means, but also the annoying precipitation of this dust in the further Environment of the work prevented.

Another purpose of the invention is to avoid getting into the hot, critical area of the furnace zone is a thick bead of fused work material settles, the removal of which is periodically recurring in ovens of the previously common design and requires costly shutdowns.

According to the invention, the roasting or calcining furnace, which is as inclined horizontal rotary kiln is formed, with a plurality of spiral-nig arranged Equipped guide ribs that serve to constantly shift the work material, thus the largest possible area of the same opposite to the direction of movement the work item is exposed to flowing hot gases. Furthermore are Ring-shaped dams placed in the furnace at a distance from each other, their function consists in redirecting the gases of the fire so that they do not come into contact with the poor come when this is in the plastic zone of the furnace in which the Arberitsgut has just reached a plastic, deformable state.

In rotary kilns in which different materials are calcined at the same time are, two adjacent, helical guide grooves are already 1 -, known. However, these guide grooves must have a very low incline in order for them to be a rearrangement of the material to be fired, which leads to a mixture of the two at the same time would lead to calcining materials can be avoided with certainty.

Rotary kilns are also already known, which are equipped with one in the front, d. H. the charging end of the furnace closest to the furnace half are provided, which is located between the calcining zone and the preheating zone. Due to this constriction, the fire gases are dammed up in the calcining zone, which is intended to achieve better heat utilization. A control of the material to be fired in the vicinity of the outlet end of the furnace cannot be achieved in this way.

Rotary kilns are also known, which with spiral with large Incline partition walls are provided which divide the furnace into spiral chambers subdivide, which are connected to each other by small openings.

The rotatable roasting furnace according to the invention consists of a cylindrical Steel jacket, which is lined with layered, fireproof material is, on the side of the refractory material facing the inside of the furnace a graphite layer is applied, which additionally insulates the jacket and its Ha # uptz -% # ". Eclz is that they are adhering to those in the plastic state Poorness good at the fire, - "rfesteii lining delayed.

In a broader sense, the invention encompasses both devices of the type described and a method for roasting various types of minerals, the following sections being intended to be included in the method: moving the material exposed to high temperatures along a rotating, isolated room; the periodic rearrangement of the in one still. Work goods which are not in a plastic state, in order to be able to expose the largest possible area of the same to the heating gases; the deceleration of the work item in the plastic state; directing the waste he d'heating gases from the located in the plastic state Ar-beitsgut and the final, • Cooling of the Arbeitsguts with simultaneous removal and: collecting the iron ore dust.

Other devices of the invention and the details concerning process of the invention can be taken from the following description and the drawings, in which i is a side view of a roaster oven of the type according to the invention, Fig FIG.. 2 is a perspective view of a furnace cross-section, Fig. 3 is a perspective Fig. 4 shows a partial view of the holders for the guide ribs, Fig. 5 is a side view of the holder shown in Fig. 4, Fig. 6 is a partial view or a partial section is the charging device, of the chimney and the heater for the serving for the preceding wet processing water, Fig. 7 is a partial perspective view of a furnace whose refractory lining is not fitted, Fig. 8 is a cross section of a roasting cylinder, which schematically illustrates the operation of the furnace shows without support ribs, Fig. 9 is a cross-section of a roasting cylinder, which schematically shows the operation of the oven with guide ribs, Fig. 10 and ii schematically show the operation of the oven without guide ribs, Fig. 1: 2 shows schematically the course of the roasting process in the oven and Fig. 13 is a partial cross-section of a furnace of a different design.

Reference is first made to FIG. I, in which the detailed below actual furnace described with io bez -, - ichii2t is. The oven can be in different Dimensions depending on the type of material to be processed. It is arranged at an angle and its upper end is attached to a fixed cylindrical Charging chamber ii rotatably connected, which in turn with the chimney communicates.

The lower or outlet end of the furnace is connected to a cylindrical socket 13 of the fixed furnace part 14 in a manner permitting rotational movement. The part 14 is provided with a burner to which fuel is supplied through the line 15. Burners of any type can be used, but preferably pulverized coal burners. The part 14 also serves as a guide device in order to transfer the work material emerging from the furnace to the cooling cylinder 16. The furnace is supported by pillars 17 between its ends. Two of these columns carry guide rollers 18 for the guide rings ig of the furnace, while the drive mechanism of the furnace, which cooperates with the toothed ring 2o, is arranged on the column located in the middle.

From Fig>. 7 details of the furnace can be found, the steel jacket of which is denoted by io. A number of guide ribs 21, which are made of heat-resistant chromium steel, are located within the casing 10. These ribs are arranged in a spiral shape and extend the entire length of the furnace. The number of these guide ribs and their pitch is decisive for the speed at which the work piece is guided through the furnace.

4 and 5 , one of the brackets 22 used for fastening the guide ribs is shown, with the greatest possible spacing. voneinaiid --r are attached to the inner wall of the Alantel and constructed in such a way that the heat transfer through the ribs from the inside of the stove to the outer wall of the casing can be kept as small as possible. Each of the guide ribs is fastened by a plurality of these brackets 22, which are provided with two lugs, between which the guide rib is fastened by welding. It can be seen that in the case of the type of fastening shown between the guide ribs and the furnace shell, there is an intermediate resin.

A layer of plastic, insulating material 23 is attached to the inner wall of the jacket 10 and below the guide ribs 21. This material is pressed firmly into the spaces between the ribs and the jacket and becomes hard by itself. Fireclay bricks are laid on this plastic insulating layer, completely covering this layer. The fire bricks are well secured by refractory cement or any other appropriate type such that they can withstand very Z, high temperatures for a long time. In a furnace without guide ribs, the ore forms a segment-shaped bed over the entire length of the approximately full length of the cell on the furnace floor. At the feed end of the furnace, the b> Solid ore is to be raised during a rotational movement of the kiln about go cm, before it slips into its starting position again (s. Fig. 8). This lifting and sliding takes place simultaneously along the entire length of the furnace. However, a small part of the upper layer of the ore mass is more likely to slide or roll off before the main mass of the ore slides downwards. This upper layer of the ore bed is in direct, indirect contact with the heating gases flowing through the furnace. As a result, the transfer of heat from the upper part of the ore mass to the lower part of the ore mass is very slow because of the relatively small area of the ore bed exposed to the heating gases. Due to: the sliding up and down and the slow movement of the ore in the direction of the furnace outlet, the unsuitable part of the ore bed may not reach the surface until the ore has already moved about 20 in the direction of the hot zone of the furnace . The course of the reaction is slowed down very much, which leads to a lower iron content of the processed product in the last 1. # -. Iides.

As it moves towards the lower end of the furnace, the material to be worked enters an area where the temperature gradually rises. Various formulas have been proposed, according to which the reaction rate dependence in the absence of temperature rise of 1) -, STIII-IMT value 'z # l to # 4inn. Although these formulas tend to differ from one another, they all agree that the rate of reaction increases extremely rapidly with increasing temperature. If it is z. If, for example, the material to be processed is siderite or iron carbonate, it is desirable to remove the CO2 from the ore. This shows how important it is to expose the largest possible area of the ore bed to the fire gases in order to accelerate the pyrochemical reaction during the movement of the ore in the direction of the hot zone of the furnace.

Once the ore has reached an approximate temperature of 9 ° C , it begins to soften. Further softening of the ore occurs until a temperature of 1038 ° C is reached. This state of the ore can be described as pre-plastic or as a transition to the plastic state. From 1038 to 10930 C the ore is in the first stage of plasticization, for which a furnace length of q # in is intended. This zone is called the hot zone and is located near the inlet end of the furnace where the burner is located, to which the amount of fuel required to reach the desired temperature is fed through pipe 15. however, the value of 1038 ° C given above does not mean that this is the highest temperature attainable. Different minerals require different temperatures for their preparation. The desired temperatures can be set by regulating the fuel supplied. When the ore has passed through the plastic zone, it gets into the post-plastic zone and then into the tubing or pulverization zone.

If there are no guide ribs 2 1, the ore, when it has reached the plastic state, will continue to be lifted in its softened state in the same way as in the preplastic zone by the rotary movement of the furnace and slide off again. The pyrochemical reaction of the ore gradually enriches it as it moves from the charging end to the discharge end of the furnace. In the plastic zone, the ore is in its softest state. The weight of the work material has the effect of moving it up and down that part of it is plastic. The work material that has become adheres to the refractory lining 24, so that after a few days of operation a ring of iron ore is deposited on the periphery of the furnace. When this ring has reached a certain thickness, this causes an irregular course of the roasting process. The furnace must then be shut down to remove struggled for the ice enerzabla #, which can reach a thickness fully 3o to 45 cm, this Rin-bil-Z, dung often caused style laying times of 4 to 5 days twice or three times ini month .

In order to prevent these business interruptions, the plastic Zone by attaching the guide ribs that the ore mass as a whole is avoided. and slips, like this in a similar way down the entire length of an oven without Guide ribs is the case. each of the guide ribs namely carries part of the ore beyond the upper level of the ore bed and gradually leaves it fall down on the bed of ore. In this way, a much larger area of the Ore exposed to the heat of combustion. This can be used both for interruptions free production process than auä, a higher degree of we-Izungsgra, d the pyrochemical Achieve a reaction so that it would be overridden. Work ut a higher iron content having.

It is also important because of the slipperiness of the Ore mass on the surface of the refractory lining caused erosion to decrease. In order to reduce erosion of the lining 2-t, the contributes to its Surface applied graphite layer, which gives the inner wall of the furnace a crucible Surface indicates the attachment of ore in the plastic state the inner surface of the furnace wall is very difficult graphite is almost pure carbon, toff, which only burns at extremely high temperature, because of its good electrical power Conductivity and its high acid and flash resistance, graphite is an excellent one Material for a crucible-like lining of the inner surface of the furnace on which it is attached with welding torches.

As it moves in the longitudinal direction of the furnace, the embers approach their plastic state. In order to avoid this condition, which depends above all on a thorough distribution and scattering of the material to be calcined, a means must be found to deflect the flow of the fire gases so that they do not act directly on the plastic zone. This is achieved in that the pre-plastic zone and the post-plastic zone of the furnace are separated from the plastic zone by two annular dams which must have a certain height. These dams are shown in Fig. 3. Each of these consists of a -i # l -etall # jacket 26, one side of which a gradually rises and the other side b of which falls steeply a # b. The jackets 26 of the dams are not in conductive contact with the furnace wall, since the insulating material 27 and the brackets 28 with which the dams are attached to the inner wall of the furnace are located between them and the furnace wall. The gradually increasing surface a, of the first dam serves to retard the flow of the work material into the plastic zone lying between the dams, whereby the work material piles up and thickens on the dam. This delay and thickening causes a certain degree of ...- in hardening of the clenching. From the height of the dam, the ore falls suddenly over the dam surface b into the plastic zone and then moves towards the second dam at the end of this zone. Here -, vi # rd the work piece raised above the surface b Bund then moves to the furnace exit. By changing the width of the dam areas, the height of the ore bed can be adapted to the prevailing operating conditions. Changes in the shape of the insulation enable the courtyard and width of the ore bed to be influenced in the post-plastic state of the roasting process.

The dam closest to the outlet end of the furnace is designed in such a way that its inclined surface a deflects the flow of the flue gases, which at this point in the furnace usually have a temperature of about 100 ° C. , over the plastic area towards the center of the drum (see Fig. 12), in order then to be continuously deflected back and forth in the oxidation zone or in the preplastic zone from one side of the furnace wall to the other. Since the length of the plastic zone is short - about 9 to 10.5 m in a furnace that is more than ten feet long - the ore will move through the plastic tongue without becoming so plastic that it forms a ring in the area of this zone After the ore has passed the second dam, there is no longer any danger that iron ore can settle on the furnace wall in such quantities that the furnace has to be shut down.

Another slowing down of the ore before its-cm leakage atG dem By adding another furnace, the ore bed can be raised to a greater height Dam can be reached at the furnace outlet. Such a brief withholding of the Work material at the outlet end causes an additional elimination of undesirable constituents of the work item. Analyzes have shown that the method described opposite the hitherto customary preparation merhodes lead to a considerable increase in the iron content has led.

From Fig. I it can be seen that the material to be worked is passed through a cooling drum after it has emerged from the furnace. This already mentioned cooling drum consists of the inclined drum 16 rotatably mounted on the columns 28 , on the inner wall of which spiral-shaped ribs 29 are arranged, which in a similar way to the ribs: Bring a quantity of the same into contact with the wall of the drum, the outside of which is rinsed by cooling water flowing out through openings 30 of a line 3 1. After exiting the drum 16, the ore falls onto a conveyor belt (not shown here).

When the red-hot ore emerges from the furnace ro, its temperature is about 84 ° C, which roughly corresponds to the temperature at which the softening of the work begins in the preplastic zone. In the cooling drum, the temperature of the ore is then reduced to below 100 ° C so that it can be transported to the Lag.-r- ## erladeplatz. Due to the good heat dissipation through the di-. Cold water flowing through the drum and the crute warmth, eitfäbi #, - k, -: the bare steel wall of the drum cools down rapidly, which leads to a sudden reduction in the volume of the ore, which leads to a separation of dusty iron oxide . This dust is entrained by the air flowing through the cooling drum and conveyed by the fan 32. In a chamber not shown in the drawing, located at the outlet end of the cooling drum, suitable precautions must be taken for the precipitation and collection of this dust so that it cannot escape through the chimney, as has been the case up to now, as this dust is precipitated can result in damage in the vicinity of the plant. In addition, the collected dust can be used industrially for certain purposes.

As a further saving measure, the invention seeks utilization the waste heat generated during the opening process. The temperature of the chimney flowing gases is about 37o to 430 'C.

By removing the dust in the cooler, the exhaust gases can now be used to heat water, which is passed through a heating coil 33 located in the loading cylinder ii behind the filler neck 34. This heating coil is designed so that it does not significantly impede the extraction of the exhaust gases.

The water flowing into the heating coil 33 through the pipe 35 can reach a temperature of approximately 80 ° C and is conducted through a thermally insulated pipe 36 to a wet processing plant, which is not shown in the drawing. Wet treatment with hot water offers many advantages over conventional treatment with cold water. Since the adhesion of clay and other substances to the ore is increased when processing with cold water, only part of this clay is removed during washing. When using warm water, the clay expands and is easier to detach from the ore, so that a cleaner ore can be fed into the roasting furnace. This allows the iron percentage in the finally processed material to be increased from 63 "1 / o to at least 651 / o.

' 11Deviations from the described design and the described method are possible and t' should, if they fall into the range. of the protection request are also to be regarded as part of the invention.

Claims (2)

PATENT CLAIMS: i. Rotary kiln with constrictions and radial, spiral-shaped guide ribs on the inside of the furnace wall that are uninterrupted along their entire length, as well as a stationary loading and unloading device at the furnace inlet end and a rotatable cooling drum at the furnace outlet end, characterized by Füh, - Rungsrungsrippen (21), which run at such a slope that when the furnace rotates, the work material lifted by the ribs falls over the ribs into the lower part of the furnace; by brackets (22) by means of which the guide ribs are attached to the drum in such a way that they have no heat-conducting contact with the drum wall; and on the inside of the furnace drum spaced apart, smoothly surfaced, annular dams (26) between which the hottest zone of the furnace lies, the dam closest to the outlet end of the furnace being designed so that the wä. rm # ea # emstrahlti # ng of the burner flame located at the outlet end of the furnace is deflected in the area of the plastic zone of the furnace to the central axis of the drum. 2. roasting or calcining furnace according to claim i with a lining of refractory bricks, characterized in that in the space between the underside of the guide ribs (21) and the inside of the furnace shell (io) plastic, insulating material is pressed quickly and between the guide rib ; en lying parts of the inner wall of the furnace shell are also provided with a layer (23) of this self-hardening plastic, insulating material, to which the refractory bricks (2-4) are fastened in the usual way with refractory cement or the like (Fig . 2). 3. roasting or calcining furnace according to claim i and 2 with provided on the inner furnace wall dams, the approach and drain surfaces different; cii are inclined, characterized in that the dams (26) no heat-conductive connection with the drum shell (io ) and that each of these dams has approach and drainage surfaces of different inclinations (a, b) , of which the surface of lesser inclination (a) of the first dam is used to lift the work material entering the plastic zone and the surface (a) of the second Dammes deflects the radiant energy of the burner flame in the plastic zone to the central axis of the drum. 4. Roasting or calcining furnace according to claim i to 3, characterized in that a graphite layer (25) resistant to friction and Wärtne is applied to the refractory lining (23, 24), whereby the build-up of work on the furnace wall is prevented . 5. roasting or calcining furnace according to claim i to 4, characterized in that in the stationary charging device (ii) through which the combustion gases which have flowed through the drum (io) are passed, a heating coil (33) is installed, in the water is heated for a pre-roasting wet preparation of the work item. Documents considered: German Patent Specifications Nos. 804 478, 363 248, 363 441,: 2: 27: 249.