MXPA98007256A - Plant to manufacture ceme clinker - Google Patents

Abstract

The present invention relates to a plant for manufacturing cement clinker. The plant consists of a preheater, a calciner in which the untreated material is calcinated at a temperature of more than 800oC and where fuel and gas containing oxygen are fed to the lower area of the calciner, and an oven. The object of the invention is to provide a plant to manufacture cement in which it is possible to burn fuel in lumps in a calciner, while simultaneously maintaining the possibility of increasing the retention time and possibly the temperature of the material that is fed to the area more lower in the calciner. This object is obtained according to the invention so that a calciner is provided with a fixed bottom (27) which allows the fuel material fed to the calciner to be deposited at the bottom and where the oxygen-containing gas is fed horizontally to the calciner through the openings in the lower area of the calciner. The fact that the oxygen-containing gas is fed horizontally allows the gas to be introduced through the vertical sides / walls of the calciner, and not through the bottom.

Description

PLANT TO MANUFACTURE C! CEMENT INKER DESCRIPTION OF THE INVENTION The present invention relates to a plant for manufacturing cement clinker. The plant consists of a preheater in which the raw material or untreated material is preheated, a calciner in which the untreated material is calcined at a temperature of more than 800 ° C and where fuel is fed and a gas containing oxygen to the lower zone of the calciner, and an oven in which the raw materials are burned and transformed into clinker. In a conventional cement clinker plant, it will be possible to replace up to 20% of the main fuel in a rotary kiln with a low-cost waste fuel such as tire tires, without sacrificing the quality of the finished cement product. Normally a maximum of 40% of the total fuel requirement of the cement plant is burned in the clinker furnace, with a remaining 60% burned in the calciner. As a result of this, in a common kiln plant, it will only be possible to replace approximately 20% of the 40% fuel which is burned in the rotary kiln, ie approximately 8% of the total amount of fuel, by waste fuel. . Therefore, it would be advantageous if a larger part of the burned fuel could be replaced in the calciner and replaced with waste fuel. However, there are certain limitations regarding the types of waste which can be burned advantageously in the calciner. The temperature in the calciner will typically be within a range of 850-950 ° C, which means that there will be no advantage in burning hazardous waste, the hazardous substances from which they must be decomposed and neutralized during combustion, since this would require higher temperatures and a longer retention time compared to that available in the calciner. The calcinators are normally of the suspension type, which allows the preheated air from the clinker cooler or from the furnace to be transported by means of a duct and a flexible tube bent upwards, towards the bottom of the calciner. If the lump is fed to the calciner such as crushed rubber tires, it will fall down into the curvature of the tube, causing it to lock. As a consequence of this, calciners with a bottom which is configured in this way are not suitable for burning fuels into clods. It is also difficult to use fuel which is difficult to ignite, for example certain types of coal with a low content of volatile compounds, since the retention time in the calciner is relatively short and the temperature is relatively low. In the application for Danish patent number 870/82 (Metallgesellschaft AG) a fluid bed calciner is shown in which the oxygen-containing fluidizing air is fed through the bottom of the calciner and where, in addition, secondary air can be fed horizontally. that contains oxygen to an area which extends from at least one meter above the point of entry of the fluidizing air and upwards, to the lower part 30% of the calciner. In this system, at least 65% of the fuel which is used to meet the total heat requirement is fed to the calciner and at least 10% of the fuel is fed to the subsequent furnace. By generating a fluid bed in the calciner, it is possible to obtain a high degree of calcination, even in the case of variations with respect to the particle size distribution. However, fluidization means that a substantial amount of false air is introduced into the system, and this will have an adverse effect on the heat economy. The actual injection of the fluidizing air also requires some energy input. From the Danish patent number 170368 (F.L. Smdith &; Co. A / S), as it is known practice to feed lumpy material such as car tires crushed to a decomposition chamber which is installed in connection with the calciner. In accordance with this patent specification, the untreated preheated or partially calcined matter is fed to the decomposition chamber so as to heat the waste fuel. The temperature which is desirable to reach in the decomposition chamber must be high enough to ensure that the pyrolysis process is carried out, but on the other hand, it should not be so high as to result in granulation of the raw material. The combustible gases from the decomposition chamber subsequently flow into the combustion chamber which consists of the calciner itself, and the waste products are extracted from the bottom of the decomposition chamber and can be transported to the rotary kiln. a decomposition chamber, in which a deficit of air is applied, does not allow the same amount of waste energy to be extracted in the calciner as compared to that which can be obtained in connection with complete combustion under conditions of sufficient supply of oxygen. An object of the invention is to provide a plant to manufacture cement in which it is possible to burn fuel in lumps, in a calciner, and at the same time maintain the possibility of increasing the retention time and possibly the temperature of the material that is fed to the Lower zone in the calciner. This object is obtained according to the invention where a calciner with a fixed bottom is provided, so that the fuel material fed to the calciner is allowed to settle to the bottom and where the oxygen-containing gas is fed horizontally to the calciner. through openings in the lower area of the calciner. The fact that the oxygen-containing gas is fed horizontally allows the gas to be introduced through the vertical sides / walls of the calciner and not through the bottom. In this way, when feeding combustible material and air containing oxygen, it will thus be possible to generate a burner chamber in the lower zone of the calciner in which the temperature exceeds that prevailing in the remaining part of the calciner, with the temperature preferably being within the range of 1100-1300 ° C. It is a particular advantage of this burning chamber that there are no requirements regarding the fuel that is fed. Nor regarding the size of the fuel in lumps, the consistency of the fuel nor the calorific value and residual content of the fuel. In addition, a modification of an existing plant will be relatively simple to carry out since it will only be necessary to modify the bottom of the calciner and the air supply system. In order to control the temperature in the lower zone, it is essential to ensure that the input of the raw material is controlled, since the entry of large quantities of the raw material will lower the temperature due to the fact that the calcination is a process Endothermic In order to ensure a controlled entry of the raw material to the lower zone, it is essential to ensure that the raw material is fed to the uppermost zone in the calciner and that it does not fall through to the lowermost zone. Any fall of the raw material can be properly avoided by ensuring that the velocity profile of the air flowing upward in the uppermost part of the lower zone of the calciner is positive and relatively uniform. There are numerous ways in which to ensure a positive velocity profile through the full cross section of the lowermost zone. A simple method is to ensure that the oxygen-containing gas flows to the lowermost zone such that flows directed downward in the cross-section do not occur. In a particular suitable embodiment of the invention in which oxygen-containing gas is introduced and distributed in an appropriate manner, the side / sides in the lowermost zone of the calciner are / are provided with several smaller openings, all of the which are fed with hot gas containing oxygen from an annular chamber. In this scenario, the annular chamber needs only to be equipped with a single, single hot gas supply point. The invention will now be described with further details, with reference to the drawing, wherein Figure 1 shows a conventional plant for making cement, Figures 2 and 3 show a mode of a calciner in a plant, according to the invention, the figure 4 shows a preferred embodiment of a calciner in a plant, according to the invention, figure 5 shows a gas velocity profile in the combustion chamber 23 in line II in figure 4, in figure 1 there is shown a plant generally known for cement manufacture. This plant consists of a preheater 1 which consists of three preheating cyclones a, b and c, a subsequent calciner 2 to which a cyclone 3 separator is installed, and an oven 4 which is followed by a cooler 5. The untreated materials fall down through the plant in counterflow with respect to the hot gas from the furnace 4 and from the cooler 5 which moves upwards, through the calciner 2 and the preheater 1. In this way, the untreated materials are introduced into the plant at the uppermost end of the preheater 1 via the duct 6. untreated materials are then transported in suspension in a stream of hot gas inside the preheater cyclone a in which the material is separated from the suspension and directed via a downstream duct into an even warmer stream of gas which transports the untreated material to cyclone b preheater. Similarly, untreated material is transported from cyclone b to cyclone c. The gas from which the untreated material is separated in the cyclone a is diverted by means of a duct 7 to an electrostatic precipitator and then vented to a stack. Once the untreated material has passed through the preheater 1, it is directed via a duct 8 to the calciner 2 and the preheated untreated material is normally fed immediately above the bottom in the calciner. The calciner 2 in figure 1 is of the SLC type (separate line calciner) and, therefore, is the only oxygen-rich air feed from the cooler via a pipeline 9. An ILC type calciner (in-line calciner) is fed with hot air from the furnace along with the air hot that contains oxygen from the cooler. In relation to a SLC type calciner, hot air from the kiln is diverted around the calciner and fed directly to the preheater. One or more burners 10 ensure that the temperature in the calciner is increased to a level of approximately 850-950 ° C and after the raw material has been calcined, it is transported in suspension through the cyclone 3 separator in which the material The calcined raw material is separated from the suspension and directed via a duct 11 to the clinker furnace 4. The hot gas from the calciner 2 rises to exit at the top of the cyclone 3 separator and is passed over the preheater 1. Finally, the calcined raw material passes through oven 4 in which the raw material is subjected to temperatures above 1400 ° C. As a result, a molten mass is generated in which the clinker minerals can be formed. The melt with the clinker minerals is pelleted, after which the finished clinker falls into the cooler where the clinker is cooled to a level of approximately 100 ° C. In Figures 2 and 3, a mode of a calciner 2 for a plant according to the invention is shown. In Figure 3, the calciner 2 in Figure 2 is thus cut through line 1. The hot gas is fed to the calciner 2 via two ducts 21 which direct the hot gas horizontally inside the calciner 2 through two openings 20, one of which can be seen in figure 3. The raw material is fed to the upper part of the calciner 2 via a duct 8 and a "curved ramp" 22 which can be placed below the duct 8 so that avoid that all of the raw material ends up in the lower zone of the calciner 2. An efficient distribution of the raw material through the cross-sectional area of the calciner, either by deploying a "curved ramp" or using Some other distribution mechanism which ensures that the raw material is properly suspended, will also minimize the pressure drop through this part of the calciner. In the lower zone of the calciner a burn chamber 23 is formed which is fed with fuel via a duct 24 and the temperature in the burning chamber 23 can be controlled by adding a smaller amount of the raw material via the duct 25 The fuel for the upper zone of the calciner is supplied via one or more burners 10. A fixed bottom 27 is provided in the bottom of the burning chamber 23. The fact that the bottom is fixed means that the combustible material which is fed via duct 24 is allowed to settle to the bottom, thus generating a stationary fire. The bottom 27 can be configured so that any residual material can be removed, either by scraping, either by dropping the material through the bottom or by allowing the blowing up into the suspension. In this embodiment, an opening 26 is placed to extract waste material below the bottom 27. Another embodiment of a calciner for a plant according to the invention is illustrated in Figure 4. In this embodiment, the lower zone of the calciner 2 is fed with hot gas through a duct 21 which, via an annular chamber 28, distributes the hot gas through several openings 20 in the sides of the calciner.

In figure 5 the velocity profile of the uppermost part of the lowermost zone is observed in a plant similar to that shown in figure 4 in line II, in which gas containing hot oxygen is fed to the chamber 23 of burned by means of an annular chamber 28. As is evident from the figure, the velocity is positive, that is to say, ascending through the entire cross-sectional area. -If the gas is processed to rotate in the chamber, for example, by feeding the gas tangentially, there is a risk that the velocity profile for the most central zone becomes negative, that is, with a velocity that is directed downwards .

Claims (7)

REVINDICACIQNES

1. A plant for manufacturing cement clinker, characterized in that it comprises a preheater in which the cement raw material is calcined at a temperature of more than 800 ° C and where the fuel as well as the gas containing oxygen are fed to the area The lower end of the calciner, and an oven in which the raw material is burned and transformed into clinker, the plant is characterized in that the lower end of the calciner is provided with a fixed bottom, and where the oxygen-containing gas is fed horizontally to the the lower zone, and where a smaller and controlled amount of uncalcined raw material can be fed to the lower zone in the calciner.

2. The plant according to claims 1, 2 or 3, characterized in that the temperature in the lower zone in the calciner is higher than the temperature in the upper zone of the calciner.

3. The plant according to claim 1 or 2, characterized in that the temperature in the lowest zone in the calciner is higher than 1000 ° C.

. The plant according to claim 1, or 2, characterized in that the temperature in the lowest zone in the calciner is maintained within the range of 1100-1300 ° C.

5. The plant according to claims 1 to 4, characterized in that the oxygen-containing gas is fed to the lowermost zone of the calciner through at least two openings on the side or sides of the calciner.

6. a plant according to claims 1 to 5, characterized in that the oxygen-containing gas is fed to the lowermost zone of the calciner through at least two openings on the side of the calciner, the openings are arranged so as to be maintained a positive velocity profile for the gas stream that flows upward, in the upper part of the lowermost zone.

7. The plant according to claims 1 to 5, characterized in that the inner diameter of the upper part of the calciner is 1.5-2 times the inner diameter of the lowermost zone.