DE3329234A1 - METHOD AND SYSTEM FOR THE THERMAL TREATMENT OF FINE-GRAINED GOODS - Google Patents

Description

Process and system for the thermal treatment of fine-grained goods

The invention relates to a method according to the preamble of claim 1, and also to an installation to carry out this procedure.

In the thermal treatment of fine-grained material, such as magnesite, dolomite and the like, is The preheated and calcined material is first placed on the suitable material before the hot briquetting Temperature cooled. This is usually done by means of a flow of cooling air, which then flows into the calcining zone as combustion air, the hot exhaust gases from the calcining zone for the purpose of The goods are preheated through the preheating zone.

Systems operating according to this process often have to be operated with different systems for operational reasons Performance (i.e. with different throughputs). Despite different Good throughput, however, the amount of cooling air should be kept approximately constant in order to be optimal To ensure flow conditions and a penetration of good if insufficient Avoid flow velocity of the cooling air. Changes in the throughput quantity while remaining the same However, the amount of cooling air now leads to corresponding fluctuations in the temperature to which the goods are in the cooling zone is cooled, and thus undesirable deviations in the product temperature in the hot briquetting zone of the optimal value.

Similar conditions exist in other processes in which the cooling zone is followed by another Adjoining a hot treatment zone (e.g. a hot leaching zone), in which a constant product temperature even with different product throughput quantities should be adhered to.

The invention is therefore based on the object of providing a method of the prerequisite in the preamble of claim 1 Kind to train in such a way that despite a constant amount of cooling air with a different amount of material throughput a constant product temperature in the heat treatment zone downstream of the cooling zone results.

According to the invention, this object is achieved by the characterizing feature of claim 1.

According to the invention, a partial flow of the goods cooled in the cooling zone by means of an air flow is uncooled Good is mixed in, can also with fluctuating good throughput and kept constant Cooling air quantity the product temperature in the heat treatment zone downstream of the cooling zone on the keep optimal value. For this purpose, if the throughput quantity is reduced, and accordingly stronger cooling of the partial flow of the goods passed through the cooling zone, an increasingly larger partial flow of the calcined goods in the by-pass past the cooling zone.

The mixed temperature of the goods (consisting of the two partial flows of the cooled

and non-refrigerated goods) are continuously measured and the division of the calcined goods between the two Partial flows regulated in the sense of keeping the mixed temperature constant.

If a partial flow of uncooled goods was mentioned above, they are within the scope of the invention Of course, process variants are also conceivable in which the in the cooling zone by means of the

IQ cooling air flow, a partial flow of only pre-cooled goods is added to the cooled goods. This pre-cooling can take place, for example, in a dwell zone adjoining the calcining zone, in which the material is, for example, in indirect heat exchange with the environment.

An exemplary embodiment for carrying out the method according to the invention is illustrated in the drawing. Show it

1 shows a diagram of a system for carrying out the

method according to the invention;

FIG. 2 shows a detail from the system according to FIG. 1;

3 to 6 diagrams to explain the invention.

The system shown for the thermal treatment of fine-grained goods such as magnesite or dolomite, contains a preheating zone 1, a calcining zone 2, a cooling zone 3, a hot briquetting zone 4 and a Sintering zone 5.

The preheating zone 1 contains three cyclones 6, 7, 8, the calcining zone 2 a combustion chamber 9, one the The riser 10 forming the actual reaction zone and a separating cyclone 11, the cooling zone 3 is with a fan 12 which supplies the cooling air, a cooling air line 13 and a separating cyclone 14. The hot briquetting zone 4 is illustrated schematically by two briquetting rollers 15. the Details of the sintering zone 5, which is formed for example by a rotary kiln, are not shown.

The system parts of the system shown in Fig. 1 are in the illustrated form by their good and gas pipes interconnected. Cooling air is supplied to the cooling zone 3 by the fan 12 and then flows to the calcining zone 2 as combustion air. Their exhaust gases penetrate the cyclones of the Preheating zone 1. The goods abandoned at 16 interspersed the cyclones 6, 7 and 8 of the preheating zone 1 then enters the riser 10 of the calcining zone at 17 2, which also supplies hot gases from the combustion chamber 9 and / or fuel (at 18) will. The calcined material separated in the cyclone 11 passes through a distributor 19 (see FIG. 2) either (line 20) into the cooling air line 13 or (line 21) into a whirling container 22, which adjoins the lower part of the separation cyclone 14.

In this way, a substream (arrow 23) of the material calcined in the calcining zone 2 is in the By-pass passed the cooling zone and with

mixed with the partial flow (arrow 24) of the cooled material separated in the cyclone 14. This mixing takes place in the ejector 22, which the material (arrow 25) leaves at the lower end.

In this way, even with fluctuations in the total material throughput and approximately With the amount of cooling air kept constant, the mixed temperature of that supplied to the Hexßbriquettierzone 4 Keep good (arrow 25) at an optimal value.

In the exemplary embodiment shown in FIG. 2, there is between the lower end of the separating cyclone. 14 and the vortex container 22 has an annular step. In this ceiling of the ejector container The openings 26 for introducing the partial flow of uncooled goods are provided.

In the transition area between the cyclone separator 14 and the swirl container 22 is still a central, mushroom-shaped installation body 27 is attached, the diameter of which is at most equal to the Diameter of the dip tube 28 of the cyclone 14 separator. The clear cross-sectional area of the den Installation body 27 surrounding the annular gap is at least as large as the clear cross-sectional area of the lower Discharge opening 29 of the swirl container 22.

Instead of the structural design shown in FIG. 2, it is within the scope of the invention, for example also possible to dispense with the use of a separate ejector 22 and the

Partial flow of chilled goods directly through openings in the lower part of the separating cyclone 14 to be introduced into the latter. However, one thing is essential intimate mixing of the two partial flows of the goods and thus extensive temperature equalization inside the goods before reaching the hot briquetting zone 4.

The technical progress achieved by the invention will be explained in more detail with reference to the diagrams in FIGS. 3 to 6, for example.

In known systems, the clacinated material is cooled by means of cooling air before being fed to the hot briquetting zone and separated in a cyclone. The material emerging from the calcining zone has, for example, a temperature of 1000 ^° C. and is cooled ^{to about 500 °} C. by the cooling air.

Now, however, there is a minimum speed in the riser of the cooling zone leading to the cyclone separator of the gas is required so that all the material is captured by the gas and entered into the cyclone separator. With a grain size of the material to be treated, this minimum gas velocity is from 0 to 1.0 mm about 10 m / s. Since at this minimum speed there is already the formation of compacted If there are dust clouds and a partial sagging or raining of coarser particles, the Gas speed set as constant as possible to 16 to 18 m / s for normal operation. The amount of cooling air as a flow medium in the riser pipe of the cooling

■ cyclones can therefore only be a proportionate reduced by a small amount of about 10 to 15% when the good throughput is to be reduced. This means that when reducing the good throughput rate to less than 85% of the normal rate and a nearly constant amount of cooling air each Unit of time the temperature of the chilled goods falls below the required temperature.

Is at 100% Good throughput performance, the material temperature after the cooling zone 500 ⁰ C, so sets itself to a temperature of 328 ° C at 50% Good throughput performance. Also reduced to the amount of air to 50% of the normal amount, so Good throughput performance is obtained although at 50%, a product temperature of 490 ⁰ C, but in the riser a flow velocity of about 8.5 m / s, ie, a value in which a correct operation of the system is not possible.

This disadvantage of the known procedure becomes particularly clear when the temperature of the cooled goods is to be raised to 700 ^° C. or lowered ^{to 300 ° C.} The following values result for the flow velocity:

- AA-

Temperature of the chilled goods

700 ⁰ C

300 ⁰ C

Good quantity 10 0% Good quantity 5 0%

8.4 m / s 4.0 m / s

50 m / s 2 4.5 m / s

Fig. 3 shows the flow rate

with different throughputs (50, 70 and 100%) depending on the temperature of the refrigerated goods. You can see the narrow range of control options. Thus, s and a minimum flow velocity can be in consideration of a maximum flow speed of 26 m / 13 m / s a Kühlguttemperatur of 450 ⁰ C by reducing the amount of cooling air and thus the flow rate adhere; however, other temperatures can only be set within narrow limits. These limits are:

Flow velocity 26 m / s to 13 m / s

Good amount 50% 300 ⁰ C until 450 ° C Good amount 70% 370 ⁰ C until 520 ⁰ C Good amount 100% 450 ° C until 600 ⁰ C

In the method according to the invention, on the other hand, those shown in FIGS. 4 and 5 result extended control options depending on the by-pass amount between the two limit values of the Flow velocities of 13 m / s and 26 m / s as follows:

s- -

-42.

Flow velocity (max.) Constant 26 m / s

Good amount 50% 300 ⁰ C until 1000 ⁰ C Good amount 70% 370 ⁰ C until 1000 ⁰ C Good amount 100% 450 ⁰ C until 1000 ⁰ C

Flow velocity (min.) Constant 13 m / s

Good amount 50% 450 ⁰ C until 1000 ⁰ C Good amount 70% 520 ⁰ C until 1000 ⁰ C Good amount 100% 600 ⁰ C until 1000 ⁰ C

The maintenance of a desired temperature of 500 ⁰ C at a constant flow rate of 18 m / s by the inventive process (see FIG. 6 shows) by admixing a by-pass amount

from 0 to 35% of the throughput can be achieved 20

(Line a-b).

A constant Gutaustragstemperatur of 600 ⁰ C is under the same conditions retained by a by-pass amount of 28 to 49% of the total throughput quantity of 100% to 50% (line CD).

Claims (6)

Patent claims: / 1.1 Process for the thermal treatment of fine grain Well, the one preheating zone, one CaI cinier zone, one cooling zone and at least one another heat treatment zone penetrated, the material in the cooling zone by means of an air stream is cooled, which then flows as combustion air to the calcining zone, its exhaust gases be guided through the preheating zone, characterized in that that for setting the product temperature in the heat treatment zone downstream of the cooling zone A partial flow of uncooled goods is added to the goods cooled in the cooling zone. 2. The method according to claim 1, wherein a substream of the calcined material is fed to the cooling zone and a further partial flow of the calcined material is bypassed past the cooling zone and is mixed with the partial flow of the cooled material, characterized in that the The mixing temperature of the goods is continuously measured and the division of the calcined material into the two partial flows in the sense of keeping them constant the mixing temperature is regulated. 3. Plant for performing the method according to claim 1, comprising a cooling zone (3) with a cyclone separator (14), the partial flow of the calcined material to be cooled into the cooling air line leading to the cyclone separator (14) (13) is entered, characterized in that the separating cyclone (14) is provided in the lower part with openings for the introduction of the partial flow of uncooled goods. 10 4. Plant for performing the method according to claim 1, comprising a cooling zone (3) with a cyclone separator (14), wherein the partial flow of the calcined material to be cooled into the Separation cyclone (14) leading cooling air line (13) is entered, characterized in that that a swirl container (22) is connected to the lower part of the cyclone separator (14), its cover with openings (26) for introducing the partial flow of uncooled goods is provided. 5. Plant according to claim 4, characterized in that in the transition area between the cyclone separator (14) and the swirl container (22) central, mushroom-shaped or conical built-in body (27) is provided, the diameter of which is at most is equal to the diameter of the immersion tube (28) of the cyclone separator (14). 6. Plant according to claim 5, characterized in that the clear cross-sectional area of the built-in body (27) surrounding annular gap at least as large as the clear cross-sectional area of the lower discharge opening (29) of the ejector container (22) is.