RAW MEAL DELIVERY DEVICE

A raw meal delivery device for delivering raw meal into a gas line or a reactor of a system for producing cement clinker, having a connection line for connecting a raw meal line to the gas line or the reactor, an oblique raw meal chute arranged inside the connection line and via which raw meal passes from the raw meal line into the gas line or to the reactor, a baffle slide arranged at the foot of the raw meal chute and protruding into the path of the raw meal flowing via the raw meal chute and deflecting the incoming raw meal. A substantially convex displacement body is arranged on the baffle slide and lies in the path of the incoming raw meal and disperses the flow of raw meal. The displacement body disperses the raw meal on entry into the calciner with the effect of quicker calcination.

FIELD OF THE INVENTION

The invention relates to a raw meal delivery device for the delivery of raw meal into a gas line, such as a riser of a heat exchanger cyclone, or to a reactor, such as a calciner, of a layout for production of cement clinker, comprising a connection line for connecting a raw meal line to the gas line or the reactor, an inclined raw meal chute, which is situated inside the connection line and by which raw meal gets from the raw meal line into the gas line or the reactor, wherein at the foot of the raw meal chute there is arranged a baffle slide, which protrudes into the path of the raw meal flowing along the raw meal chute and deflects the incoming raw meal.

BACKGROUND OF THE INVENTION

During the production of cement clinker from a mixture of ground calcareous rock and ground silicate-containing rock, the so-called raw meal in the dust phase undergoes a heat treatment in a gas flow, after which it is sintered in a rotary kiln. The raw meal in a major portion of the layout is present suspended in a hot gas. In a typical layout for the production of cement clinker, each day between 1000 T and 10,000 T of cement clinker are produced, the raw meal being transported as the starting product suspended in gas within the layout through a cyclone heat exchanger. After the heating and possibly drying of the raw meal in the cyclone heat exchanger, the raw meal is taken by a raw meal line to a calciner, constituting an entrained flow reactor, where the calcareous rock of the raw meal is broken down by thermolysis into quicklime (CaO) and carbon dioxide (CO2). The quicklime is taken as part of the hot meal to a rotary kiln, where it is sintered by intensive heat treatment to calcium silicate phases, or the actual cement clinker. The cement clinker after the rotary kiln needs to undergo a rapid cooldown in order to obtain the desired clinker phases.

In lengthy investigations as to where the bottlenecks for the overall performance of the layout are located in a layout for the production of cement clinker, the same locations keep coming up. One of these locations is the calciner, an entrained flow reactor, in which the raw meal is to be thermally dissociated as completely as possible. Little time remains for this in the entrained flow reactor, since the flow velocity in the calciner is so great that the dwell time of the preheated raw meal in the calciner is only a few seconds. In order to boost the performance of a layout, it is of course possible to enlarge all the components of the layout. The dwell time of the raw meal in the calciner can also be lengthened in this case. In order to optimize existing layouts, a retrofitting or a new construction would be too costly. During plant optimization, the diameters of pipelines are often enlarged, so that a greater gas and/or mass flow per unit of time can pass through the layout. With increasing production capacity of modern layouts, the diameters of the gas-carrying pipelines also increase, which makes it hard to achieve the most homogenous possible dispersion of the meal in the gas flow. Serious process disturbances often occur with an inadequate distribution, such as meal drop-through, reaction constraints, and other unwanted performance deficits of the layout.

Another place where bottlenecks exist is the riser in cyclone heat exchangers. In cyclone heat exchangers, the raw meal is repeatedly suspended and then separated in the gas phase of the exhaust air of a rotary kiln. In this process, the raw meal takes up the heat from the rotary kiln exhaust gas. The distance available for the suspending of the raw meal, and thus the time, is very short. Here as well, a faster and uniform delivery of the meal to the gas phase can help increase the overall throughput and efficiency of the layout.

In European patent EP 1 310 467 B1 there is disclosed a meal entrance box as a raw meal delivery device, in which a baffle slide is present at the foot of the meal entrance box. The baffle slide has the task of breaking up and spreading out the raw meal stream coming from a chute. This meal entrance box has proven to work well in existing layouts for production of cement clinker.

The problem to be addressed by the invention is to boost the performance of a layout for the production of cement clinker. For this, the uniformity of the pneumatic transport of the meal/gas suspension after the dispersion of the meal should be increased and the pressure fluctuation which often occurs locally and temporarily in the case of poor dispersion should be prevented, while also optimizing the accessibility of the fine meal flow for the heat exchange due to better dispersion.

SUMMARY OF THE INVENTION

The problem is solved according to the invention by arranging a substantially convex displacement body on the baffle slide, which lies in the path of the incoming raw meal and disperses the flow of raw meal.

According to the invention, in order to boost the performance of the layout, it is thus proposed to attach this to the raw meal delivery device for a gas line, such as a riser of a heat exchanger cyclone, or for a reactor, such as a calciner.

The displacement body imposes on the flowing meal at the time of its entrance into the gas line or the reactor an outward velocity and momentum component, so that the raw meal is forced more into the outer regions of the gas line or the reactor. This deflection is realized by a substantially convex surface geometry, which is present in the path of the flowing raw meal. In the simplest case, the displacement body can be a tetrahedral body, being a tetrahedron lying on a surface, one edge of the tetrahedron being oriented from the bottom of the baffle slide in the flow direction of the flowing raw meal. This tetrahedral body cuts through 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 hull-like shape or consist of a harmonic arching, having a keel line located at the top.

For the retrofitting of existing raw meal delivery devices it has proven to be advantageous for the displacement body to be a tetrahedron and for one side of the tetrahedron situated in the flow direction to be an obtuse triangle. The keel line or crest line of the displacement body is thus obtuse-angled. This shape results in an efficient widening of the raw meal stream in the gas line or in the reactor, so that the thermolysis of the calcareous rock begins very early and uniformly in a calciner as the reactor. When used in a riser of a heat exchanger cyclone, the suspending of the raw meal likewise occurs earlier and more uniformly, so that the raw meal does not fall through the cyclone as a cohesive stream, but instead is fully suspended in the gas swirl. By canceling out the pressure loss-generating flow, reserves in the flow control can be reduced and in this way the layout can be operated at a higher production level.

The keel line, crest line or upward pointing edge of the displacement body advantageously has an abrasion-resistant reinforcement, such as one in the form of a hardfacing, in order to increase the service life of the displacement body in the hot raw meal stream. For this, it can also be provided that the side of the displacement body, for example the tetrahedron, which is present in the flow direction is open. The open design prevents the displacement body from becoming heated too much, or being so heavily stressed in the heat of the flowing raw meal that the displacement body becomes brittle due to alternating thermal stresses. The service life of the displacement body is also increased by indentations in the displacement surfaces, namely, the surfaces emerging from the edge, the keel line or the crest line, namely in the edge lying transversely to the flow direction. The indentations prevent the formation of eddies and prevent excessively large alternating mechanical stresses during alternating thermal stresses. Like expansion joints, the indentations ensure that the displacement body does not become deformed under the thermal load.

In order to achieve an optimal distribution of the raw meal, it can be provided that the bottom surface of the substantially convex displacement body extends for at least 50% across the width of the baffle slide, preferably entirely across the complete width of the baffle slide. An extension across the entire width is advantageous for spreading out the entire raw meal stream.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.1shows a raw meal delivery device1according to the invention. The raw meal delivery device1is intended for attachment to a gas line, such as a riser112′,113′ of a heat exchanger cyclone112,113in a cyclone heat exchanger110, or for attachment to a reactor, such as a calciner170, of a layout100for the production of cement clinker. Such a layout is shown as an example inFIG.5. In the raw meal delivery device1shown here, there is a connection line2for connecting a raw meal line120coming from a cyclone heat exchanger110to the calciner170or to the riser112′,113′ of a next heat exchanger cyclone112,113. Furthermore, the raw meal delivery device1comprises an inclined raw meal chute3, which is situated inside the connection line2and by which raw meal gets from the raw meal line120to the gas line or to the reactor. In the path of the connection line2there is located a compensator5, in order to balance out the thermal load, but also to balance out a mechanical load exerted by the sometimes rather long raw meal line120on the raw meal delivery device1. At the foot of the raw meal chute3there is situated an outside-adjustable baffle slide10, which protrudes into the path of the raw meal flowing along the raw meal chute3and which deflects the incoming raw meal. The mere striking against the bottom11of the baffle slide10already produces a broad fountain of raw meal at the entrance to the gas line or to the reactor. According to the invention proposed here, it is provided that a substantially convex displacement body is situated on the baffle slide10, which lies in the path of the incoming raw meal and disperses the stream of raw meal. The displacement body in the exemplary embodiment here is formed by a tetrahedron T, which is open in the flow direction S and has an obtuse angle at its keel line, its crest line, or its edge15protruding into the raw meal stream. This keel line, its crest line or its edge15protruding into the raw meal stream is oriented in the flow direction S. The two surfaces12and13emerging from the edge15impart an outward momentum to the raw meal, which further significantly intensifies the dispersing action of the raw meal delivery device. This intensified dispersion has the result in the calciner that the thermolysis of the calcareous rock in the calciner, which is generally an entrained flow reactor, takes place earlier and is better distributed over the gas flow. This effect of improved distribution is especially effective and significant when the diameter of the calciner increases greatly for large layouts, in the range of a daily tonnage output of 5000 T and even 8000 T to over 10,000 T. In a riser112′,113′ of a cyclone heat exchanger110, the intensified dispersion has the benefit of a faster and more complete suspending of the raw meal in the gas flow of the heat exchanger cyclone112,113. The raw meal delivery device1is connected at the top across a flange7for example to the raw meal line120of the layout100for production of cement clinker. The raw meal drops in the flow direction S inside the connection line2along the raw meal chute3and is taken through a check valve, of which only two outer weights4and4′ for a non-return flap are shown here. At the foot of the raw meal delivery device1there is an optional fuel supply6, with which fuel such as petroleum coke can be fed into the raw meal to boost the thermal power in the calciner. The raw meal delivery device1is mounted by means of the flange8on the thick-wall calciner170.

In order to adjust the ideal dispersion, the baffle slide10can be pushed 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 bottom11of the baffle slide10, the displacement body moves along with the baffle slide10.

FIG.2shows the raw meal delivery device ofFIG.1with flow directions S indicated at the foot of the raw meal delivery device1. ThisFIG.2illustrates the action of the displacement body, here in the form of the tetrahedron T, on the raw meal sliding down the chute3from above. The raw meal is given an outward velocity and momentum component and thus broadens out in the open diameter of the calciner170or the riser112′,113′.

FIG.3shows a convex displacement body in the form of an open tetrahedron T. This tetrahedron T lies with one surface17on the bottom11of the baffle slide. The edge15opposite the surface17is oriented collinearly with the flow direction S. In this way, the edge15acts like the keel of a displacer. The surfaces12and13emerging from the edge15are positioned such that the raw meal flowing over them is given an outward velocity and momentum component. In order to prevent unwanted swirling and also to suppress thermal/mechanical stresses, indentations14may be present in the surfaces12and13emerging from the edge15, namely, in the edges situated in the flow direction S. These have an action similar to expansion joints to prevent mechanical stress.

FIG.4shows the tetrahedron ofFIG.3in simplified form in order to designate the surfaces and edges. The tetrahedron ofFIG.3is shown here in simplified form as a substantially convex displacement body. The tetrahedron lies with one surface17on the bottom11. The four surfaces of the tetrahedron are the surface17lying on the bottom11, the two surfaces12and13emerging from the edge15opposite the surface17, and the surface16pointing forward in the flow direction. The edge15opposite the surface17points in the flow direction S of the raw meal. As the displacement body, the tetrahedron T may be open in the surface16lying in the flow direction S.

FIG.5shows an exemplary layout100for the production of cement clinker, being shown as a demonstration, where the raw meal delivery device1has its place in the layout100. The layout100comprises the following plant components: in the material flow direction at the beginning is located a heat exchanger component110. This comprises multiple cyclone heat exchangers111,112,113,114hooked up in succession for the preheating of the raw meal R. Following the next to last cyclone heat exchanger113in the material flow direction is a calciner170, in which the preheated raw meal R flows from the heat exchanger component110. In the calciner170, the raw meal R is suspended in the exhaust air of a following rotary kiln140, while the outlet on the descending branch130of the calciner170is connected to an inlet of the last cyclone heat exchanger114. The last cyclone heat exchanger114is followed by a connection line114″ leading to a rotary kiln inlet chamber141and supplying the preheated raw meal R, deacidified in the calciner170, to the rotary kiln140. The preheated and deacidified raw meal R rolls through the rotary kiln140and is sintered into cement clinker Z. Following the rotary kiln140in the material flow direction is a cement clinker cooler150, while from the cooling head housing151directly connected to the rotary kiln140a tertiary air line160leads to the calciner170, in order to maintain here a burning of fuel in an oxidative environment. The cooled cement clinker Z, on the other hand, leaves the cement clinker cooler150. Atmospheric air L runs for the most part contrary to the material flow of the raw meal R in the layout100. Thus, the air L flows into the cement clinker cooler150and is divided here into different fractions. A first portion of the air L flows as so-called primary air to a burner, designated by a dashed line. A second fraction of the air L flows as secondary air to the rotary kiln140and a third fraction of the air L heated in the cement clinker cooler150flows as tertiary air through the tertiary air line160. After leaving the calciner170, the air L flows in succession to the heat exchanger cyclones114,113,112and111and the air L leaves the heat exchanger component110as exhaust air A. The raw meal delivery device1proposed here can be designed to feed the raw meal coming from the next to last heat exchanger cyclone113, dispersed as much as possible, through a raw meal line120to the calciner170. For this, the raw meal delivery device1is mounted directly on the calciner170. Alternatively or additionally, the raw meal delivery device1can be arranged on a riser112′,113′ of the cyclone heat exchanger110, in order to suspend the raw meal more quickly and completely in the swirl of a heat exchanger cyclone112,113.

LIST OF REFERENCE SIGNS