RAW MEAL FEEDING DEVICE

Description

[0001] The invention relates to a raw meal feeding device for feeding raw meal into a gas line, such as a riser of a heat exchanger cycle or into a reactor, such as a calciner, of a plant for producing cement clinker, comprising a connecting line for connecting a raw meal line to the gas line or the reactor, an inclined raw meal chute which is arranged within the connecting line and via which raw meal from the raw meal line reaches the gas line or the reactor, wherein an impact slide is arranged at the base of the raw meal chute, which projects into the path of the raw meal flowing over the raw meal chute and deflects the incoming raw meal.

[0002] In the production of cement clinker from a mixture of ground, calcareous rock and ground, silicate-containing rock, the so-called raw meal is subjected to heat treatment in a gas stream in the dust phase and then sintered in a rotary kiln. The raw meal is suspended in a hot gas in a large part of the plant. In a typical cement clinker production plant, between 1,000 t and 10,000 t of cement clinker are produced daily. The raw meal, as the starting product, is transported through a cyclone heat exchanger suspended in gas. After the raw meal has been heated and, if necessary, dried in the cyclone heat exchanger, the raw meal is fed via a raw meal line into a calciner, which is an entrained flow reactor, where the calcareous rock of the raw meal decomposes into quicklime (CaO) and carbon dioxide (CO2) through thermolysis.The quicklime is fed into a rotary kiln as part of the hot meal, where it is sintered through intensive heat treatment to form calcium silicate phases, the actual cement clinker. After leaving the rotary kiln, the cement clinker requires rapid cooling to obtain the desired clinker phases.

[0003] In longer studies of where bottlenecks exist in a cement clinker production plant for the overall output of the plant, recurring points emerge. One of these points is the calciner, an entrained-flow reactor in which the raw meal is to be thermally dissociated as completely as possible. There is only little time for this in the entrained-flow reactor because the flow velocity in the calciner is so high that the residence time of the preheated raw meal in the calciner is only a few seconds. To increase the output of a plant, it is of course possible to enlarge all plant components. This can also extend the residence time of the raw meal in the calciner. To optimize existing plants, a conversion or new construction would be too costly. During plant optimization, the diameter of pipes is often increased so that a larger gas and / or mass flow can flow through the plant per unit time.As the production capacity of modern plants increases, the diameter of the gas lines also increases, making it difficult to disperse the flour as homogeneously as possible in the gas stream. Inadequate distribution often leads to serious process disruptions such as flour sagging, reaction inhibition, and other undesirable performance deficiencies in the plant.

[0004] Another point where bottlenecks exist is the riser pipe in cyclone heat exchangers. In cyclone heat exchangers, the raw meal is repeatedly suspended in the gas phase of the exhaust air from a rotary kiln and separated again. In the process, the raw meal absorbs the heat from the rotary kiln exhaust gas. The distance available for suspending the raw meal, and thus the time, is very short. Here, too, a faster and more even introduction of the meal into the gas phase can help increase the overall throughput and efficiency of the plant.

[0005] DE-A 2 312 379 discloses a furnace with a filling shaft for firing or sintering cement, wherein the bottom of the filling shaft, at least in its part facing the burner chamber, is formed by a slide which can be moved forwards and backwards to a certain extent.

[0006] European patent EP 1 310 467 B1 discloses a flour inlet box as a raw meal feed device, in which an impact valve is located at the base of the flour inlet box. The impact valve is designed to break up and fan out the raw meal stream coming from a chute. This flour inlet box has proven its worth in existing cement clinker production plants.

[0007] The object of the invention is to increase the performance of a plant for producing cement clinker. To this end, the uniformity of the pneumatic transport of the flour / gas suspension after dispersion of the flour is to be increased, pressure fluctuations that often occur locally and temporarily due to poor dispersion are to be prevented, and the accessibility of the fine flour stream for heat exchange is to be optimized through better dispersion. The object of the invention is achieved by arranging a substantially convex displacement body on the impact slide, which lies in the path of the incoming raw meal and disperses the raw meal stream. Further advantageous embodiments are specified in the subclaims to claim 1.

[0008] According to the invention, it is therefore provided to attach a gas line, such as a riser of a heat exchanger cyclone, or a reactor, such as a calciner, to the raw meal feed device in order to increase the performance of the plant.

[0009] The displacement body imparts an outward velocity and momentum component to the flowing meal as it enters the gas line or reactor, forcing the raw meal more strongly toward the outer regions of the gas line or reactor. This deflection is achieved by a substantially convex surface geometry present in the path of the flowing raw meal. In the simplest case, the displacement body can be a tetrahedral body lying on a surface, with one edge of the tetrahedron oriented from the bottom of the impact valve in the flow direction of the flowing raw meal. This tetrahedral body intersects the flow of dispersed raw meal and imparts an outward velocity and momentum component to the raw meal. The displacement body can also have a ship's hull-like shape or consist of a harmonic curvature with a keel line at the top.

[0010] When converting existing raw meal feed systems, it has proven advantageous to have a tetrahedron-shaped displacement body with an obtuse-angled triangle on one side of the tetrahedron facing the flow direction. The keel line or apex of the displacement body is thus obtuse-angled. This shape leads to an efficient widening of the raw meal flow into the gas line or reactor, so that in a calciner as a reactor, the thermolysis of the calcareous rock begins very early and evenly. When used in the riser pipe of a heat exchanger cyclone, the suspension of the raw meal also occurs earlier and more evenly, so that the raw meal does not fall through the cyclone as a continuous stream, but is completely suspended in the gas vortex. By equalizing the flow that generates pressure losses, reserves in the flow system can be reduced, allowing the plant to operate at a higher production level.

[0011] The keel line, crest line, or upward-facing edge of the displacement body advantageously has an abrasion-resistant reinforcement, for example in the form of a welded overlay, to increase the service life of the displacement body in the hot raw meal flow. For this purpose, the side of the displacement body facing in the flow direction, for example the tetrahedron, can also be open. The open design prevents the displacement body from heating up excessively or from becoming so strongly stressed by the heat of the flowing raw meal that the displacement body becomes brittle due to thermal load changes. The service life of the displacement body is also increased by incisions in the displacement surfaces, namely the surfaces extending from the edge, the keel line, or the crest line, specifically in the edge that is transverse to the flow direction.The notches prevent the formation of vortices and avoid excessive mechanical load changes during thermal load changes. Like expansion joints, the notches ensure that the displacement body does not deform under thermal load.

[0012] To achieve optimal distribution of the raw meal, the bottom surface of the essentially convex displacement body can extend over at least 50% of the width of the impact slide, preferably across the entire width of the impact slide. Extending across the entire width is advantageous for fanning out the entire raw meal flow.

[0013] The invention is explained in more detail with reference to the following figures. They show: Fig. 1 a raw meal feeding device according to the invention, Fig. 2 the raw meal feeding device from Figure 1with flow directions marked at the base of the raw meal feed device, Fig. 3 a convex displacement body in the form of an open tetrahedron, Fig. 4 the tetrahedron from Figure 3 in simplified form for naming the surfaces and edges, Fig. 5 an exemplary plant for the production of cement clinker to demonstrate where the raw meal feeding device is located in the plant, Fig. 6 a raw meal feed line as realized in the STATE OF THE ART in two alternating states.

[0014] In Figure 1 A raw meal feed device 1 according to the invention is shown. The raw meal feed device 1 is intended for connection to a gas line, such as a riser 112', 113' of a heat exchanger cyclone 112, 113 in a cyclone heat exchanger 110, or for connection to a reactor, such as a calciner 170, of a plant 100 for producing cement clinker. Such a plant is shown, for example, in Figure 5shown. In the raw meal feed device 1 shown here, there is a connecting line 2 for connecting a raw meal line 120, which comes from a cyclone heat exchanger 170, to the calciner 170 or to the riser line 112', 113' of a subsequent heat exchanger cyclone 112, 113. Furthermore, the raw meal feed device 1 has an inclined raw meal chute 3, which is arranged within the connecting line 2 and via which raw meal from the raw meal line 120 reaches the gas line or the reactor. In the path of the connecting line 2 there is a compensator 5 to compensate for the thermal load, but also to compensate for a mechanical load exerted on the raw meal feed device 1 by the sometimes longer raw meal line 120. At the foot of the raw meal chute 3 there is an externally adjustable impact slide 10 which projects into the path of the raw meal flowing over the raw meal chute 3 and deflects the incoming raw meal.The mere impact on the bottom 11 of the impact valve 10 creates a wide fountain of raw meal as it enters the gas line or the reactor. According to the invention presented here, a substantially convex displacement body is arranged on the impact valve 10, which lies in the path of the incoming raw meal and disperses the raw meal stream. In this exemplary embodiment, the displacement body is formed by a tetrahedron T that is open in the flow direction S and has an obtuse angle at its keel line, its apex line, or its edge 15 projecting into the raw meal stream. This keel line, its apex line, or its edge 15 projecting into the raw meal stream is aligned in the flow direction S. The two surfaces 12 and 13 extending from the edge 15 impart an outward impulse to the raw meal, thereby significantly increasing the dispersing effect of the raw meal feed device.This increased dispersion in the calciner results in the thermolysis of the calcareous rock in the calciner, which is usually an entrained-flow reactor, occurring earlier and with a better distribution across the gas stream. This effect of improved distribution is particularly effective and significant when the diameter of the calciner increases significantly for large plants, in the range of a daily tonnage of 5,000 t and even 8,000 t to over 10,000 t. In a riser 112', 113' of a cyclone heat exchanger 110, the increased dispersion has the advantage of faster and more complete suspension of the raw meal in the gas stream of the heat exchanger cyclone 112, 113. The raw meal feed device 1 is connected upwards via a flange 7, for example, to the raw meal line 120 of the plant 100 for producing cement clinker.The raw meal falls in the flow direction S within the connecting line 2 along the raw meal chute 3 and is guided through a check valve, of which only two external weights 4 and 4' for a check valve are shown here. At the base of the raw meal feeder 1 is an optional fuel feed 6, with which fuel, such as petroleum coke, can be fed into the raw meal to increase the heat output in the calciner. The raw meal feeder 1 is attached to the thick-walled calciner 170 using the flange 8.

[0015] To achieve the ideal dispersion, the impact slide 10 can be moved back and forth from the outside along the direction of the double arrows P and P'. Since the displacement body, here the tetrahedron, is arranged on the bottom 11 of the impact slide 10, the displacement body moves with the impact slide 10.

[0016] In Figure 2The raw meal feeder is made of Figure 1 with the flow directions S marked at the base of the raw meal feed device 1. This Figure 2 is intended to illustrate the effect of the displacement body, here in the form of the tetrahedron T, on the raw meal sliding down from the top of the chute 3. The raw meal receives an outward velocity and momentum component and thus expands in the open diameter of the calciner 170 or the riser 112', 113'.

[0017] In Figure 3a convex displacement body in the form of an open tetrahedron T is shown. This tetrahedron T lies with a surface 17 on the bottom 11 of the impact slide. The edge 15 opposite surface 17 is aligned collinearly with the flow direction S. As a result, edge 5 acts like the keel of a displacer. The surfaces 12 and 13 extending from edge 15 are angled so that raw meal flowing over it receives an outward velocity and momentum component. To prevent unwanted eddies and also to suppress thermal / mechanical stresses, notches 14 can be provided in the surfaces 12 and 13 extending from edge 15, specifically in the edges arranged in the flow direction S. These have a similar effect to expansion joints to prevent mechanical stress.

[0018] In Figure 4 is the tetrahedron of Figure 3 in a simplified form to name the faces and edges. The tetrahedron of Figure 3 is shown here in simplified form as an essentially convex displacement body. The tetrahedron rests with a surface 17 on the base 11. The four surfaces of the tetrahedron are surface 17 lying on the base 11, the two surfaces 12 and 13, which extend from the edge 15 opposite surface 17, and surface 16 oriented forward in the flow direction. The edge 15 opposite surface 17 is oriented in the flow direction S of the raw meal. As a displacement body, the tetrahedron T can be open in surface 16, which lies in the flow direction S.

[0019] In Figure 5An exemplary plant 100 for the production of cement clinker is shown to demonstrate where the raw meal feed device 1 is located in the plant 100. The plant 100 has the following plant components: At the beginning in the direction of material flow there is a heat exchanger component 110. This consists of several cyclone heat exchangers 111, 112, 113, 114 connected in series for preheating the raw meal R. The penultimate cyclone heat exchanger 113 is followed in the direction of material flow by a calciner 170, into which the preheated raw meal R flows from the heat exchanger component 110. In the calciner 170, the raw meal R is suspended in the exhaust air from a subsequent rotary kiln 140, wherein the outlet on the descending branch 130 of the calciner 170 is connected to an inlet of the last cyclone heat exchanger 114.The last cyclone heat exchanger 114 is followed by a connecting line 114" that leads to a rotary kiln inlet chamber 120 and feeds the preheated and deacidified raw meal R to the rotary kiln 140. The preheated and deacidified raw meal R rolls through the rotary kiln 140 and sinters to cement clinker Z. Following the rotary kiln 140 in the material flow direction is a cement clinker cooler 150, with a tertiary air line 160 leading from the cooler head housing 151, which is directly connected to the rotary kiln 140, to the calciner 170 to maintain fuel combustion in an oxidative environment. The cooled cement clinker Z, on the other hand, leaves the cement clinker cooler 150. Atmospheric air L in the plant 100 largely runs counter to the material flow of the raw meal R. the air L flows into the cement clinker cooler 150 and is divided into different fractions.A first portion of the air L flows as so-called primary air into a burner shown in dashed lines. A second fraction of the air L flows as secondary air into the rotary kiln 140, and a third fraction of the air L heated in the cement clinker cooler 150 flows as tertiary air through the tertiary air line 160. After leaving the calciner 170, the air L flows sequentially into the heat exchanger cyclones 114, 113, 112, and 111, and the air L leaves the heat exchanger component 110 as exhaust air A. The raw meal feed device 1 presented here can be intended to feed the raw meal originating from the penultimate heat exchanger cyclone 113 into the calciner 170 via a raw meal line 120 in a manner that is as well dispersed as possible. For this purpose, the raw meal feed device 1 is located directly on the calciner 170.Alternatively or cumulatively, the raw meal feeding device 1 can be arranged on a riser 112', 113' of the cyclone heat exchanger 110 in order to suspend the raw meal more quickly and completely in the vortex of a heat exchanger cyclone 112, 113. LIST OF REFERENCE SYMBOLS 1 Raw meal feeding device 112' riser 2 connecting line 113 Heat exchanger cyclone 3 Raw meal chute 113' riser 4 Weight 114 Heat exchanger cyclone 4' Weight 114' Hot flour line 5 compensator 120 Raw meal line 6 Fuel supply 130 descending branch 7 flange 140 rotary kiln 8 flange 141 Rotary kiln inlet chamber 10 impact valve 150 Clinker cooler 11 Floor 151 Radiator head 12 Area 160 Tertiary air duct 13 Area 170 Calciner 14 incision A exhaust air 15 edge G gas 16 Area L Air 17 Area P Arrow 100 Attachment P' Arrow 110 Cyclone heat exchanger R raw flour 111 Heat exchanger cyclone S Flow direction 112 Heat exchanger cyclone Z cement clinker

Claims

1. Raw meal delivery device (1) for the delivery of raw meal (R) into a gas line, such as a riser (112', 113') of a heat exchanger cyclone (112, 113), or into a reactor, such as a calciner (170), of a layout (100) for production of cement clinker, comprising - a connection line (2) for connecting a raw meal line (120) to the gas line or the reactor, - an inclined raw meal chute (3), which is situated inside the connection line (2) and by which raw meal (R) gets from the raw meal line (120) into the gas line or the reactor, wherein at the foot of the raw meal chute (3) there is arranged a baffle slide (10), which protrudes into the path of the raw meal (R) flowing along the raw meal chute and deflects the incoming raw meal (R), characterized in that a substantially convex displacement body is arranged on the baffle slide (10), which lies in the path of the incoming raw meal and disperses the flow of raw meal (R).

2. Raw meal delivery device according to Claim 1, characterized in that the substantially convex displacement body is a tetrahedron (12) situated on a surface (17), wherein one edge (15) of the tetrahedron (T) is oriented from the bottom (11) of the baffle slide (10) in the flow direction (S) of the moving raw meal.

3. Raw meal delivery device according to Claim 2, characterized in that one side (16) of the tetrahedron (T) present in the flow direction (S) is an obtuse triangle.

4. Raw meal delivery device according to Claim 2 or 3, characterized in that the side (16) of the tetrahedron (T) present in the flow direction (S) is open.

5. Raw meal delivery device according to one of Claims 2 to 4, characterized in that the edge (15) has an abrasion-resistant reinforcement.

6. Raw meal delivery device according to one of Claims 2 to 5, characterized in that the surfaces (12, 13) of the tetrahedron (T) emerging from the edge (15) have indentations (14) in the flow direction (S).

7. Raw meal delivery device according to one of Claims 1 to 6, characterized in that the bottom surface of the substantially convex displacement body extends across the entire width of the baffle slide (10).