GB2032592A

GB2032592A - Process and apparatus for the production of sintered material

Info

Publication number: GB2032592A
Application number: GB7925047A
Authority: GB
Original assignee: Schwermaschinenbau Kombinat Ernst Thalmann VEB
Current assignee: Schwermaschinenbau Kombinat Ernst Thalmann VEB
Priority date: 1978-07-20
Filing date: 1979-07-18
Publication date: 1980-05-08
Also published as: DD137578A1; FR2431466A1; DE2925665A1; DK301079A

Abstract

The invention relates to a process and an apparatus for the production of sintered material, in particular cement clinker, which, after issuing from the furnace 1, is cooled in the crusher 2 whilst being crushed and finally cooled in a cooler 3, the aim of the invention being to make the production of clinker economical by reducing the amount of energy required and the quantity of material used, the clinker is subjected to the crushing operation before or at the beginning of the cooling process, the clinker crushing operation being carried out while the clinker is still in a red-hot condition, the furnace 1, crusher 2 and cooler 3 are connected in series with respect to the material flow and the gas flow is either in series or in parallel. <IMAGE>

Description

SPECIFICATION Process and apparatus for the production of sintered material This invention relates to a process and an apparatus for the production of sintered material, in particular cement clinker, which, after issuing from a furnace, is cooled and subsequently crushed.

So that the clinker for cement, which issues from the furnace at a temperature of approximately 14000 C, can be further processed, it is necessary for the clinker to be cooled to a temperature of from 250 to 800C. Clinker eoolers used include planet-type coolers, barrei-type coolers, shaft-type coolers or grid-type coolers. All these clinker coolers suffer from the disadvantage that the heat transfer is poor, due to the clinker being in the form of large pieces. This results in the clinker being insufficiently cooled, or means that large quantities of air, large cooling units and long cooling times are required in order to achieve satisfactory clinker cooling. At any event, the heat loss is very high.Either the insufficiently cooled clinker gradually loses its heat to the surroundings when it is stored or, if the clinker has been sufficiently cooled, the total amount of air required cannot be completely utilised in the furnace installation. The unused, heated cooling air must have the dust removed from it separately, and discharged to atmosphere.

It is known that, by virtue of its hardness, cement clinker is difficult to grind down, while the grinding equipment is subject to a high rate of wear, due to the high degree of abrasiveness of the clinker.

In the process according to German Patent Specification No. 11 58894, the material leaving the furnace is firstly temperature-controlled by a per se conventional cooler which is suitably modified for the purpose, in such a way that the greatest proportion by weight of the grains is already dark or almost dark on its outside, but is still incandescent in its inside; directly afterwards, the material is severely crushed, and simultaneously cooled, by impingement cooling in an impingement crusher of known type, through which flows cooling air. The crushed material which is discharged from the crusher with the cooling airflow is separated out by centrifugal force and the heated cooling air is passed to the cooler which is disposed upstream of the crusher and/or the furnace as combustion air.In order to prevent the impact tools of the crusher from overheating, the tools are cooled from the interior by a second flow of cooling air at higher pressure, by way of air passages. In this arrangement, both flows of cooling air can be controlled so that the total amount of cooling air is not greater or is not substantially greater than the requirement for the combustion air in the furnace.

The solution according to DAS No. 11 58894 does in fact provide that the clinker is pre-crushed with a small amount of force and cooled with a high degree of effectiveness, but the possibility of crushing the clinker while it is in the region of its lowest compression strength was not taken to its iimits. The result of this is that the wear on the crushing tools was not reduced to the minimum possible value. The same also applies in regard to the cooling effect. Cooling of the clinker coming from the furnace conceals deficiencies insofar as the clinker which is present in a relatively large grain size has a small surface area for heat exchange purposes, so that a relatively long period of time for cooling is required.

Therefore, this solution also requires relatively large amount of cooling air and large cooling unit structures which in turn require a large amount of energy to produce them and operate them respectively.

In order to reduce the amount of energy required and the quantity of material used in the production of clinker, the invention is based on the problem of arranging the clinker production process in such a way that crushing of the burnt material is effected at a time at which the compression strength of the material is at its lowest and favourable heat exchange conditions are provided, at the beginning of the cooling operation.

According to the present invention in one aspect there is provided a process for the production of sinteredmaterial, such as cement clinker, in which the material is heated in a furnace, passed to a crusher where it is crushed whilst in the red-hot condition and partially cooled in the crusher and then further cooled in a final cooler or coolers, all of the cooling air being fed to the furnace as combustion supporting air.

In this arrangement, the intensive cooling of the clinker may begin in the crushing stage during the crushing operation so that only the residual heat remains to be taken from the clinker in the following cooling stage or stages. If cooling of the clinker begins only after crushing in the subsequent cooling stages, then only the crusher is cooled by fresh air. In both cases however the total amount of cooling air is such that it can all be passed to the furnace to form combustion air therein.In order to permit the optimum combustion process in the furnace, the furnace inlet temperature of the cooling air serving as combustion air must be as high as possible (about 9000 C). As however this temperature is not fully attained in the cooling process, the cooling air is heated in counter-flow in the furnace discharge by the clinker issuing from the furnace, before the cooling air passes into the furnace. However, this heat exchange occurs over only a short period of time and to a degree such that the clinker is still in a red-hot condition when it passes into the crushing apparatus.In order to keep the charge of dust in the heated cooling air which passes into the furnace, within reasonable limits, the cooling air coming from the crushing stage and from the subsequent cooling stages, after having been mixed, is passed through a separator and is only then passed to the furnace in counter-flow relative to the clinker.

If two or more cooling stages are disposed downstream of the crushing stage, then, in order to relieve the thermal load on the separator, the cooling air coming from the last or cold cooling stage of the cooler or coolers, and the cooling air from the crushing stage, are passed jointly through the separator so as subsequently to be passed into the furnace by way of the hot cooling stage of the cooler or coolers disposed downstream thereof.

The installation with which the clinker production process is carried into effect comprises a crusher and one or more one-stage or multi stage coolers which are connected downstream of the furnace in series, on the material side, and are disposed upstream of the furnace in the opposite order on the gas side. If cooling is effected only in the coolers which are disposed downstream of the crusher, these machines are indeed disposed in series on the material side, but on the gas side, they are disposed in parallel. In both cases, a separator which removes excessive ballast from heated cooling air is advantageously arranged between the furnace and the machines which are connected upstream thereof on the gas side.In accordance with the invention, the arrangement of the individual machines on the gas side may also be such that the crusher is disposed in parallel with the cold cooling stage, but both are disposed in series jointly with the separator of the hot stage of the cooler, and the furnace.

Suitable crushers are advantageously machines which provide a high through-put of air, at low pressure resistance. These may be for example impingement crushers, autogenous grinders and the like.

Some embodiments of the invention will now be described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 shows a series arrangement of the furnace, the crusher and the cooler, with the cooling air flowing through the units in series flow, Figure 2 shows a series arrangement of the crusher and the cooler with the cooling air flowing in parallel flow, and Figures 3 and 4 show the incorporation of a separator into the gas flow means.

In the drawings, the flows of material are denoted by solid lines, while the flows of gas are denoted by broken lines.

The hot clinker issuing from the furnace 1 passes into a crusher 2, while still in a red-hot condition, and is subjected to preliminary crushing therein, while being simultaneously cooled.

Subsequently, the pre-crushed and pre-cooled clinker passes into a further cooling stage 3 in which the residual heat is very extensively taken therefrom. The cooling air from the post-cooling stage 3 is at the same time cooling air for the crusher 2. The cooling air is further heated in the crusher 2 and is then passed into the furnace 1 in counter-flow with respect to the clinker, the flow of cooling air being heated by the red-hot clinker to such an extent that the cooling air passes into the furnace at the optimum temperature, to provide combustion air for the furnace. However, in this arrangement cooling of the clinker is only to such an extent that it is still in the red-hot condition when it passes into the crusher 2.

Therefore, the clinker is crushed while it is still in a red-hot condition, because in this condition the compression strength and the abrasiveness of the clinker are at their lowest, and thus the amount of energy required and the rate of wear are low. The greatest advantage however is that the surface area of the clinker is increased before the beginning or, at the latest, at the beginning, of the cooling process, thereby providing favourable conditions for the heat transfer. The pre-crushing operation not only provides a large surface area but also a relatively uniform grain-size band which results in a clinker crushing action which is advantageous from the point of view of energy involved, in addition to the uniform'cooling action using smaller amounts of air than previously.

Due to the lower amount of cooling air which is required, that amount can be kept within the orders of magnitude which correspond to the amount of combustion air required for the furnace, so that no additional cooler waste gases are produced.

Figure 1 diagrammatically shows the series arrangement, on the material side and on the gas side, for the production of clinker. The red-hot clinker passes from the furnace 1 into the crusher 2 and from there into the cooler 3. The cooling air first passes into the cooler 3 where it takes the residual heat from the pre-crushed and pre-cooled clinker, in one or more stages, the cooling air then passing into the crusher 2, in the form of preheated cooling air. During the crushing operation, intensive heat exchange occurs between the clinker and the cooling air so that the clinker is pre-cooled to a substantial degree in a short period of time. The hot cooling air leaves the crusher 2 and passes into the furnace 1, as combustion air.In passing to the furnace 1 , the hot cooling air passes around the red-hot clinker issuing from the furnace 1, and is further heated.

In order to protect the crusher 2 from overheating, all parts of the equipment which come into contact with the hot clinker can be cooled by fresh air 4. Fresh air may be additionally added to the flow of cooling air from the cooler 3, in the region of the crusher 2, in order to control the temperature and the quantity of cooling air.

Figure 2 is a diagrammatic view of the parallel arrangement, on the gas side, of the cooler 3 and the crusher 2. In this arrangement, the cooler 3 and the crusher 2 are separately supplied with fresh cooling air 4 and 5, the heated air issuing from these two units being mixed together before it passes into the furnace 1. In this arrangement, the fresh air 4 passing into the crusher 2 can be used both for cooling the material and for cooling the components of the units themselves, and for both these purposes.

So that the fine clinker components and clinker dust contained in the cooling air are not drawn into the furnace 1, the fine clinker components and dust can be removed from the cooling air in a separator, after passing through the cooling and crushing stages. Figure 3 shows an arrangement similar to that shown in Figure 2, in which a separator 6 is disposed downstream of the crusher 2 and the cooler 3.

Figure 4 is a diagrammatic view of the arrangement of a plurality of coolers which are disposed downstream of the crusher 2. In this embodiment, cooling air is fed to the crusher 2 and to the cooler 8 or the cooling stage 7, as indicated at 4 and 5. The heated cooling air issuing from the cooler 7 and the crusher 2 is cleaned and the dust is removed therefrom in a separator 6. The cleaned, heated cooling air is passed to the hot cooler or hot cooling stage 8 and, after passing therethrough, passes into the furnace 1 as combustion air. In order to provide a continuous flow of cooling air, a blower 9 is arranged between the separator 6 and the hot cooler 8. The amount of cooling air is regulated by way of throttle flaps 10.

The invention can be used in any combustion processes in which minerals or the like are heated to their melting point, agglomerated and subsequently cooled and crushed. Any suitable combustion furnaces such as rotary furnaces, shaft furnaces, sintered belt assemblies etc. can be used as the furnace.

The crushers used are advantageously those which have a high through-put fair, with a low pressure resistance. These may be for example impingement crushers, autogenous grinders and the like.

Suitable separators are all types which are able to withstand high temperatures.

The coolers used may be rotary barrel coolers, shaft coolers, grid coolers with one or more cooling chambers, and the like.

The essential advantages of the invention are that the clinker is intensively cooled in a short period of time, with low expenditure on machinery, material and electrical energy, whereby providing a uniform grain-size band of relatively small grain size, thus providing favourable conditions for the fine crushing operation to the effect that the crushing conditions can be at their optimum, that is to say, advantageous charging of and small dimensions for the barrel crusher and a reduction in the rate of wear and the crushing period.

Claims

1. A process for the production of sintered material, such as cement clinker, in which the material is heated in a furnace, passed to a crusher where it is crushed whilst in the red-hot condition and partially cooled in the crusher and then further cooled in a final cooler or coolers, all of the cooling air being fed to the furnace as combustion supporting air.

2. The process claimed in claim 1, in which, before the heated cooling air issuing from the cooler and the crusher passes into the furnace, it is heated in counter-flow in the furnace discharge by the material issuing from the furnace, only that amount of heat such that the material is still in a red-hot condition when it is passed into the crushing stage being taken from the material.

3. The process claimed in claim 1 or claim 2, in which the heated cooling air from the crusher and the subsequent cooler are passed to the combustion furnace directiy, or after having been cleaned, in counter-flow relative to the flow of material.

4. The process claimed in any of claims 1 to 3, in which the heated cooling air from the crusher is mixed with the heated cooling air from the last cooling stage of a two-stage cooler disposed downstream of the crushing stage, and cleaned, and passed into the furnace after a further heat exchange in the hot cooling stage of the cooler which is disposed downstream of the crushing stage.

5. A process for the production of heat-treated material, such as cement clinker, substantially as hereinbefore described with reference to the accompanying drawings.

6. Apparatus for the production of sintered material in accordance with the process claimed in claims 1 to 4, comprising a furnace and a crusher and cooler unit disposed downstream of the furnace in series of crusher and cooler unit with respect to the flow of material and in series, in the order of crusher and cooler and furnace with respect to the cooling gas flow.

7. Apparatus for the production of sintered material, in accordance with the process claimed in claims 1 to 4, in which the crusher and the cooler are disposed in series with respect to the flow of material and in parallel with respect to the gas flow.

8. Apparatus for the production of sintered material, in accordance with the process claimed in claims 1 to 4, in which a separator is disposed between the crusher and the cooler, and the furnace.

9. Apparatus for the production of sintered material in accordance with the process claimed in claims 1 to 4, in which the cooling zone of the cooler or coolers is disposed in parallel with the crusher on the gas side, and both are disposed in series with a separator, the hot region of the cooler or coolers and the furnace.

10. Apparatus for the production of sintered material as claimed in claim 6, in which the crusher or the combined cooling and crushing stage is a machine with a high air through-put and low pressure resistance, for example an impingement crusher, autogenous grinder, and the like.

11. Apparatus for the production of sintered material, such as a cement clinker, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.