CS200460B2 - Apparatus for agglomerating powdered raw materials - Google Patents

Abstract

The agglomeration reactor for fine dust feed for clinker firing comprises two fluid bed zones. One of these is near the discharge and is used for the prodn. of the correct final grade material whilst the other opposite to the outlet is used to replenish the second bed with chemically reacted material. These zones are separated by a weir or simply as the result of separate operating modes for the two fluid beds. Sufficient material has to be transferred from the first into the second zone to maintain prodn. of laid down characteristic end material. The fly dust accruing is sepd. from the main stream to a dust separator and is reused, the fly dust from the first zone being first fed into the second zone. This results in the formation of fresh small particles which need not be completely transformed. The dust is used to displace the material from the first zone into the second and eventually to the outlet. Chemical reaction however occurs concurrently with these displacement movements. The system permits the use of fine raw meal feed material which cannot normally be used for clinker mfr.

Description

The invention relates to an apparatus for agglomerating powdered starting materials in a fluidized bed, in particular in the manufacture of cement clinker, the particles of which are substantially larger than the particles of the starting material, and to utilize the effect of molten liquid components to carry out chemical reactions.

It is known to agglomerate and chemically transform fine-grained starting materials in a fluidized bed using the effect of molten liquid components, wherein the fluidized bed is formed essentially from the end product and maintained at temperatures above the melting point of the substances contained in the end product as well as above the temperature required for the chemical reaction to take place, wherein the starting dust is supplied to the fluidized bed in an amount such that the fluidized bed permanently contains only the final product.

The fluidized bed particles must be substantially larger than the particulate material, preferably so large that, at the gas flow velocity required to form the fluidized bed, the particulate-sized material is blown out of the fluidized bed after a sufficiently long period of time. At the same time, the starting material introduced into the fluidized bed agglomerates and chemically reacts, and on the one hand it stratifies in layers on larger particles that have already formed in the fluidized bed, and on the other hand it agglomerates itself into larger particles.

The bulk of the starting material, which is not sufficient to produce particles of sufficient size in the fluidized bed, is blown off as a dust which, after separation in a cyclone, is returned to the other starting material, the particles whose mass has increased sufficiently during agglomeration and take away as a finished product.

In order to maintain the fluidized bed in a stable state, which is necessary to maintain the fluidity of the manufacturing process, sufficient amounts of particles so large that they can no longer escape from the fluidized bed in the form of a drift must be continuously introduced into the fluidized bed. This is done by dividing the finished product into two grades according to the grain size, either immediately after withdrawal or after partial grinding. The fine-grained fraction, which amounts to 20% to 50% of the withdrawn particles, is returned

200460 2 into production. This high proportion of returning fraction is a significant disadvantage of agglomerating the dust starting materials in the fluidized bed, since it necessitates increasing the size of the respective reactor, increasing energy consumption, and requires special equipment for sorting grain into fractions and for returning the fine grain fraction. Therefore, this process is not agglomerated too much, especially in the production of cement clinker and is used. exceptionally, despite having a number of other benefits.

The reason for this disadvantage is that the particles which agglomerate themselves from the fine-grained starting material are not able to squeeze out of the fluidized bed particles which are formed by the rolling of the fine-grained starting material onto previously formed particles. Therefore, they are carried out prematurely from the fluidized bed without the necessary chemical reaction in them being completed.

The purpose of the invention is to eliminate the return of the fine-grained product fraction through the external material circulation back to the production and thus to save the investment needed for sorting and return of the material.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus for agglomerating the powdered starting materials in a fluidized bed, forming such a process of agglomeration such that the need to return part of the finished product to the external maerial circulation is eliminated.

SUMMARY OF THE INVENTION The object is solved by providing a device for agglomerating powdered starting materials in a fluidized bed, particularly in the manufacture of cement clinker whose particles are substantially larger than the starting material particles, using the effect of molten liquid components to accomplish: The reaction according to the invention is characterized in that the fluidized bed reactor is divided into at least two zones or separated weirs, in particular the rear fluidized bed zone adjacent to the product discharge pipe, predominantly for the production of the finished product and the front fluidized bed zone. remote from. of the finished product discharge line for the predominant supply of particles consumed during agglomeration, wherein the fluidized bed reactor is equipped with a flue gas dust separator whose return pipe is discharged into the fluidized bed reactor and the feedstock preheater from which the transport poor is branched of pipes leading to the fluidized bed reactor.

In order to improve the efficiency of the fluidized bed reactor, according to the invention, the fluidized bed reactor can be provided with additional feed lines extending above the fluidized bed.

The sweeping of the fluidized bed reactor into at least two zones together with the overall arrangement of the device according to the invention has the basic advantage that the entire process inside the reactor can be controlled by agglomerating fine-grained masses in the fluidized bed using molten liquid components. This eliminates the need for screening of the finished particles from the reactor and returns the non-rotationally agglomerated particles back to production via external circulation, making the entire plant less expensive and more economical to operate compared to the prior art.

This effect is achieved by the fact that different zones of the fluidized bed reactor have different tasks and therefore operate under different conditions.

In the case where the fluidized bed rector is dual-band, the fluidized bed in the rear zone comprises particles already highly agglomerated and chemically transformed in the zone facing the discharge line of the finished product. The dusty starting material fed to the back zone is wrapped in layers into highly agglomerated particles and completes their conversion into a finished product. In the front band, the dusty starting material gradually agglomerates and chemically transforms. If the resulting particles are still low in humidity, they are carried away from the fluidized bed reactor as a drift, separated in a dust separator and returned to the front zone. This is repeated with each particle until its mass increases to such an extent that it remains in the swirling layer of the front band. Thus, sufficiently massive particles accumulate in the vortex layer of the anterior zone - and are pushed through the weir between the two zones into the posterior zone, where the agglomeration and chemical conversion process is increased. The finished product exits from the back zone of the fluidized bed reactor through a discharge line, with a substantial portion of its thermal energy being delivered to the air preheater. All of this achieves a high thermal efficiency of the fluidized bed reactor.

If the powdered starting material agglomerates difficult or time-consuming, the effects of this are achieved by providing the fluidized bed reactor with a plurality of zones, for example a middle zone, or by splitting the rear zone into several sub-zones.

Exemplary embodiments of the fluidized bed powder agglomeration apparatus of the present invention are shown in the accompanying drawings, in which Fig. 1 shows a dual-band reactor, Fig. 2 a three-band reactor, and Fig. 3 a quad band reactor. From the bottom of the dust starting substance tank, which is also a preheater of this substance, a conveying line 2 is connected, to which a manifold 3 is connected, from which the inlet pipes 4, 4 extend over the surface 18 of the fluidized bed formed. 5th fluidized bed reactor. The fluidized bed reactor 5 is divided by the weir 23 into two zones, a rear zone 7 adjacent to the discharge pipe 4 of the finished product, and a forward zone 4 remote from the discharge pipe 4 of the finished product. £.

The fluidized bed reactor 5 is heated by liquid fuel stored in a storage tank 2 connected by a main fuel line 10 with a fuel distribution line 11 to which the respective burner lines 12 are connected. The air supply is provided by a blower 13 connected by air line 14 to the air preheater 15. which is arranged in the discharge pipe 6 of the finished product. From the air preheater 15, air flows into the chamber 16 formed below the fluidized bed reactor 15. A grate 17 is provided between the chamber 16 and the fluidized bed reactor 5 in the air passage openings.

At the beginning of the fluidized bed reactor, i.e. on its side remote from the discharge pipe 6 of the finished product, a flue gas exhaust pipe 19 is provided, leading to a flue gas dust separator 20. return line 22 for separated particles. The dust-cleaned flue gases are discharged from the dust separator 20 via a vent line 21 to the pre-heater of the dust starting material.

From the manifold 3, in the illustrated example, two additional lines are discharged, resulting in the fluidized bed reactor well above the surface 18 of the fluidized bed, namely the first additional feed line 24 at the beginning of the reactor 5 and the second additional feed line 24 'at the end of the reactor 5.

The fluidized bed powder agglomeration apparatus of the present invention in a dual-band fluidized bed reactor operates as follows;

The swirl layer in the reactor 5 is made up of particles whose mass is substantially greater than the weight of the individual dust grains of the dust starting material. The swirl layer particles are maintained in a flow of air blown by the blower V3 and preheated by the waste heat of the finished product in the air preheater 15. This air then flows through the chamber 16 through the openings in the grate 17 into the fluidized bed. The heat required for the respective reactions is obtained by burning liquid fuel in the burners located at the ends of the burner fuel lines 12 connected by the respective lines to the fuel tank.

The dusty starting material is preheated in the preheater by the heat of the flue gas from the fluidized bed reactor. From there, the dust starting material falls through the conveying line 2 into the distributor 3, which transports it to the feed lines 4 from where the dust starting material falls into the fluidized bed in the back zone 7 of the fluidized bed reactor 5. There, some of the powdered starting material is rolled onto the already agglomerated particles to form a finished product. The remainder of the powdered starting material is gradually blown out of the fluidized bed and passes through the air layer 25 to the front zone 8 of the reactor 15 and is drawn off via the exhaust duct 19 to the flue gas separator 15 as a drift. In this process, the powdered starting material gradually agglomerates and reacts chemically. In the dust separator 20, the partially agglomerated dust is already separated from the flue gas and falls back through the return line 22 back to the front zone 6 of the fluidized bed reactor, while the cleaned flue gas passes through the vent line 21 to the pre-heater.

The particles that have fallen through the return line 22 are divided according to their weight. More massive, sufficiently agglomerated, will fall into the vortex layer of the front zone 8, the less massive ones are blown out of the vortex layer and withdrawn again via the exhaust duct 19 into the flue gas separator 20. As the agglomeration process continues in this process, all of the powdered starting material agglomerates gradually to the extent that it is recirculated to remain in the fluidized bed of the front zone of the fluidized bed reactor.

The pre-agglomerated powdered starting material accumulates in the back zone 8 of the reactor 5 and is therefore transferred via the weir 23 to the back zone of the reactor 5, where the agglomeration process continues to roll up the dust starting material fed through the feed lines 4 to the particles pre-agglomerated. The fully agglomerated particles are extruded from the backing zone 7 of the fluidized bed reactor 5 and are discharged through the discharge line 6 of the finished product and transfer excess heat in the air preheater 15.

The dust starting material particles fed both by the first additional feed line 24 and the second additional feed line 24 * well above the fluidized bed surface 18 are released into the cloud of dust by the action of the waste gases. As the heat-weighing reactions take place, the temperature of the air layer 25 of the fluidized bed reactor and thus of its walls decreases, the temperature of the waste gases decreases and the heat is better utilized.

In the three-phase design of the fluidized bed reactor 5, a central web 28 is provided between the front zone 8 and the rear zone 7, separated from the rear zone 7 by the rear weir 29. In addition, an additional return line 27 from the flue gas separator 20 is introduced into the central zone 28.

Thus, a dust starting material is introduced into the central zone 28 through the central feed line 30 and at the same time particles already agglomerated through the additional return line 27, thereby reducing the dust flow.

In another exemplary embodiment, particularly suitable for treating non-caking agents, the backing zone of the fluidized bed reactor 5 is divided between the rear additional weir 31 'and the front' additional weir 31 '' divided into three subbands, namely: the first rear zone 8 *, the second rear zone and the third rear zone 7, respectively, also have a respective delivery line, i.e. a first delivery line 4 ', a second delivery line 4' 'and a third delivery line 4 *'.

However, other modifications of the embodiment of the device according to the invention are possible. For example, it is possible to enter the first back zone. an additional return line 27 arranged similarly to the additional return line 27 may result. , resulting in the middle zone 28.

The fluidized bed agglomeration apparatus of the present invention produces a very extensive moonnosi control of the agglomeration process. On the one hand, it is possible to control the amount of fuel supplied to the burners in the individual zones of the fluidized bed reactor 5. Further, the ratio can be between the amount of the dust starting material introduced directly into the fluidized bed and the amount introduced into the fluidized bed reactor 5 above the surface 18 of the fluidized bed into the air layer 25 of the fluidized bed reactor. It is also possible to vary the ratio of the amount of dust starting material introduced into the individual zones of the fluidized bed reactor. In the fluidized bed reactors 6 provided with the central zone 28, it is also possible to control which dust composition separated in the flue gas separator 20 is fed to the central zone 6 and which medium zone 28, respectively.

It is clear from all these facts that the inventive fluidized bed powder starting device according to the invention is particularly suitable for those cases where the requirements for precise control and regulation of the agglomeration process are high.

Claims (2)

* READY An apparatus for agglomerating dust starting materials in a fluidized bed, particularly in the manufacture of cement clinker, the particles of which are substantially larger than the particles of the starting material, using the effect of molten liquid components to carry out chemical reactions, characterized in that (the swirl layer is divided into at least two zones, possibly separated by weirs (23), i.e. in particular.on the back zone (7) of the swirl layer adjacent the discharge pipe (6) of the finished product, mainly for the production of the finished product, and front zone (8) (vortex layers) remote from the discharge line (6) of the finished product for predominantly delivering the particles consumed during agglomeration, wherein the reactor (5) is vortexing. The return pipe (22) flows into the fluidized bed reactor (5) and the dust starting material preheater (1) from which the conveying pipe (2) is branched into the feed lines. (4, 4 *) resulting in a fluidized bed reactor (5). 2. A method as claimed in claim 1, characterized in that additional fluid feed lines (25) above the fluidized bed (25), in particular a first additional feed line (24) and a second additional feed line (24), extend into the fluidized bed reactor (5). * /. ·