GB1595647A - Method of and a device for the heat treatment of powder or grain material - Google Patents

Description

(54) A METHOD OF AND A DEVICE FOR THE HEAT TREATMENT OF POWDER OR GRAIN MATERIAL (71) We, PREROVSKE STROJIRNY NARODNI PODNIK, a Czechoslovak body corpcrate of Prerov, Czechoslvakia, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a method and a device for the heat treatment of a powder or finely grained material (hereinafter: powder material) capable of calcination, while it is suspended in a stream of heated flue gases.

It may be used especially for the firing of cement clinker in the so-called dry process with precalcination of the raw material, or for the firing of powdered lime.

Hitherto known methods for the firing of a cement clinker with a precalcination are carried out so that calcination of the raw material heated in a downstream preheater takes place between a rotary kiln and the preheater in a separate technological stage. The fuel needed for the calcination stage is supplied separately. These firing methods, in which a dispersion-shaft-counterflow preheater is used, are arranged so that the calcination stage is connected directly to a counterflow shaft of the preheated. The calcination cham- ber is situated under the shaft of the preheated in its axis, in a continuation of the counterflow shaft. Fuel and preheated air for combustion are supplied there separately, sometimes together with flue gases from the rotary liin.

During the calcination of the raw materral the fluidity of the roasted material consider- able worsens in the respective temperature range, and consequently its passage through the device is no longer sufficiently smooth.

At the same time a corresponding period of stay of the material in the range of calcina- tion temperatures is required to obtain a high degree of decomposition of calcium carbonate.

If in the known embodiments a calcinator is arranged as a continuation of the counterflow shaft of the preheated, a higher degree of calcination is obtained only with difficulty.

Some of the mentioned drawbacks may be obviated by the method according to the invention.

The invention provides a method of heat treatment of a powder material capable of calcination, such as a cement raw material, in which the raw material is at first preheated in a dispersion preheater, then it is calcinated in a calcination chamber while using a separate fuel and air supply, and finally fired in a rotary kiln, wherein the preheated raw material from a shaft of a aounterflow preheater enters a tangential whirl of gases supplied to a dividing line between an upper and lower part of the calcination chamber, in which an upper flow is formed by a tangential whirl going upward along the walls of the chamber and downward in the middle part, and a lower flow is formed by a tangential whirl going dewn- ward along said walls and upward in the middle part, the raw material being calcinated and conoentrated in cloud of particles predominantly along said walls moves downward thoough the calcination stage and in a first phase it is lifted by an upward going whirl and in this way its stay in the first phase is prolonged, and in the next phase, when, because of heat treatment its liquidity is considerably worsened, the tangential whirl moving downward along the walls allows it to be discharged out of the calcination stage.

The invention also provides a device for carrying the method, comprising a dispersion counterflow preheater including a shaft, a calcination chamber directly connected to the shaft of the preheater, a firing device and a cooler of the fired product in which the calcination chamber has an upper part and lower part which are interconnected by means of a cylindrical middle part to which a duct for supplying gases is tangentially connected.

The method and device according to the invention enable the raw material to reach a high stage of calcination in that the calcinator is directly connected to the preheated and thus causes the raw material to stay for a sufficiently long interval in the range of the calcination temperatures and at the same time conditions for a continuous and uniform passage Of the material through the calcina- tion zone are created. Conditions created by the method and device according to the invention are advantageous for a very intensive combustion of the fuel supplied and ensure the required stability of combustion.

The method and device according to the invention ensure such backflow of gases from the calcination stage into the counterflow preheater, that the intensity of a tangential flow of gases in the shaft of the preheaner reaches the value needed for a reliable function of this kind of preheater.

In order thar the invention may be clearly understood and readily carried into effect, preferred embodiments thereof are, by way of example, hereinafter more fully described with reference to the accompanying diagram- matic drawings, in which: Fig. 1 shows a calcination chamber with a gas intake of a one-flow preheater; Fig. 2 shows an alternative embodiment of a calcination chamber with a gas intake and of a part of preheated raw material of a two-flow preheating; and Fig. 3 shows an alternative embodimen,t of a two-flow preheating.

A calcination chamber (Fig. 1) consists of an upper part 1 and lower part 2, which are interconnected by means of a cylindrical middle part 3. The chamber is directly con necked to a shaft 5 of a pneheater. A gas intake duct 4 is tangentially attached to the middle part 3 of the calcination chamber.

Torches 7 are arranged in the lower third of the upper part 1 and the upper third of the lower part 2 of the calcination chamber. Alter naively (not illustrated in the drawings) the torches may be arranged in the cylindrical middle part 3 of the calcination chamber.

The lower part 2 of the calcination cham- her is in the form of a truncated cone, the lower end of which is connected to a pipe 6 for discharging the caloined material into a firing device (not shown). The upper part 1 of the calcination chamber is also in the form of a truncated cone the upper end of which is a continuation of the shaft 5 of the preheater. The conicity of the lower part 2 and the upper part 1 of the calcination chamber is in the range of 10 to 30 .

The preheated raw material moves down wardly in a vortex motion mostly along the wall of the shaft 5 of the preheater against a stream of hot flue gases. The hot gases enter the shaft 5 of the preheater in a tan gential whirl directly from the calcination chamber. A cloud of the preheated raw mat erial descends from the shaft 5 of the pre heater into the upper part 1 of the calcination chamber, where it comes directly in contact with the flame from the torches 7.An inten sive and direct transmission of heat takes place there which results in an intensive calcination of the raw material. An upward tangential whirl of gases along the wall of the upper part 1 of the caleination chamber slows the progress of the material downward and so prolongs the duration of its presence in the zone of the calcination temperatures.The raw material is thickened there, then it proseeds through the cylindrical middle part 3 into the lower part 2 of the calcination oham- ber, where the tangential flow of gases moving downwards along the wall of this lower part 2, promotes the downward movement of the calcined material which has already reached a considerably high stage of heat treatment, and in this way its liquidity has been worsened, to the pipe 6 through which if its dis- charged into the firing device.

In an alternative embodiment (Fig. 2), in which the described calcination chamber 1-3 is arranged in a two-flow arrangement of a kiln device, a part of the preheated row material from a separated preheating branch (not shown) is delivered through a pipe 8 into the duct 4 for delivering gases into the cal cination chamber and in this way is added to these gases supplied tangentially to its cylindrical middle part.The whirl of gases lifts the mentioned part of the raw material into the upper part 1 of the calcination cham- ber and then together with the raw material arriving into the calcination chamber from the shaft 5 of the preheater passes through the lower part 2. In the upper part 1 and lower part 2 of the calcination chamber there intensive combustion of the delivered fuel by the torches 7 takes place. The flame extends through the whole space of the calcination chamber, combustion of maximum intensity occurs in the zones of the highest gas turbulence at the edge of the peripheral and central whirl.Also the opposite direction of the axial motion of a tangential flow of the gases in the upper part 1 and the lower part 2 of the calcination chamber affects considerably the conditions for combustion stability in this space. The calcination chamber is connected to the shaft 5 of the preheater by means of a cone adapter 9. In order to obtain advantageous conditions for an intensive tangential whirl of gases at the inlet into the countershaft 5 of the preheater, the apex angle of the adapter 9 is up to 30 and the ratio of tis height to the diameter of the smaller base is not greater than 1.

In another alternative embodiment (Fig. 3) in order to decrease a waste-flying of the oalcinsated material from the lower part 2 of the oalcinated chamber in connection with the upward central whirl of gases a separation chamber 10 is arranged between the lower part 2 of the calcination chamber and the pipe 6 for discharging the raw material. This separation chamber 10 includes two trunorated cones connected at their large bases.

The conicity of the truncated cone is in the range of 900 to 1700, so that the required separation effect may be obtained.

Although the invention is illustrated and described with reference to preferred embodi menus thereof, it is to be expressly understood that it is in no way limited to the diso10lsure of such preferred embodiments, but it is capable of numerous modifications within the soope of rhe appended claims.

WHAT WE CLAIM IS:- 1. A method of heat treatment of a powder material capable of calcination, such as a cement raw material, in which the raw material is at first preheated in a dispersion preheater, then it is calcinated in a calcination chamber while using a separate fuel and air supply, and finally fired in a rotary kiln, wherein the preheated raw material from a shaft of a oourDterfllow preheater enters a tangential whirl of gases supplied to a dividing line ,between an upper and lower pant of the calcination chamber, in which an upper flow is formed by a tangential whirl going upward along the walls of the chamber and downward in the middle part, and a lower flow is formed by a tangential whirl going downward along said walls and upward in the middle plart, the raw material being calcinated and, concentrated in a dond of par tides predominantly along said walls moves downward through the calcination stage and in a first phase it is lifted by an upward going whirl and in this way its stay in the first phase is prolonged, and in the next phase, when, because of heat treatment its liquidity is considerably worsened, the tangential whirl moving downward along the walls allows it to he discharged out of the calcination stage.

2. A method according to claim 1 wherein a part of the preheated material from a separated preheated branch of the preheater is supplied into a duct supplying gases in the oallcination chamber and in this way is added to these gases supplied tangentialiy to its cylindrical middle plant, so that this part of the preheated raw material is at fist drawn into the upper flow d the tangential whirl of gases in the calcination stage.

3. A device for carrying out a method according to claims 1 or 2 comprising a dispersion counter flow preheated ineluding a shaft, a calcination chamber directly connected to the shaft of the preheater, a firing device and a cooler of the fired product in which the oalcination chamber has an upper part and lower part which are interconnected by means of a cylindrical middle plart to which a duct for supplying gases is tangentially connected.

4. A device according to claim 3 wherein the lower part of the calcination chamber is in the shape of a truncated cone, the larger base of which is connected to the cylindrical middle part of the calcination chamber and the smaller base is connected to a pipe for discharging the raw material, the upper part od the calcination chamber being in the shape of a truncated cone, the smaller base of which is connected to the cylindrical middle part of the calcination chamber and the larger base to the shaft of the preheater, the conicity of the truncated cone of the lower and upper parts of the calcination chamber being in the range of 100 to 300.

5. A device according to claims 3 or 4 wherein the upper part of the calcination chamber is connected to the shaft of the preheater by a conical adapter, the larger base of which is connected to the upper part of the calcination chamber and the smaller base to the shaft of the preheater, the tonicity of the adapter being up to 300 and the ratio of its height to the diameter of its smaller base is not greater than 1.

6. A device according to any one of claims 3 to 5 wherein between the lower part of the calcination chamber and pipe for discharging raw material there is arranged a separation chamber which is formed by two truncated oones interconnected at their larger bases, the tonicity of the upper truncated cone of the separation chamber being in the range of 900 to 1700.

7. A device according to any one of claims 3 to 6 wherein torches are situated in the lower third of the upper part and in the upper third of the lower part of the calcination chamber.

8. A device according to any one of claims 3 to 7 wherein torches are situated in the cylindrical middle part of the calcination chamber.

9. A device according to any one of claims 3 to 8 wherein a pipe for supplying a part of preheated raw material is connected to the duct for supplying gases into the cal citation chamber.

10. A method according to claim 1 carried out substantially as herein described with reference to Figure 1, Figure 2 or Figure 3 of the accompanying drawings.

11. A device according to claim 3 substan tally as herein described with reference to, and as shown in, Figure 1, Figure 2 or Figure 3 of the accompanying drawings.

12. Material when made by or with the use of a method according to claim 1, 2 or 10.

13. Material when made by or with the use of a device according to any one of claims 3 to 9 or 11.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. range of 900 to 1700, so that the required separation effect may be obtained. Although the invention is illustrated and described with reference to preferred embodi menus thereof, it is to be expressly understood that it is in no way limited to the diso10lsure of such preferred embodiments, but it is capable of numerous modifications within the soope of rhe appended claims. WHAT WE CLAIM IS:-

1. A method of heat treatment of a powder material capable of calcination, such as a cement raw material, in which the raw material is at first preheated in a dispersion preheater, then it is calcinated in a calcination chamber while using a separate fuel and air supply, and finally fired in a rotary kiln, wherein the preheated raw material from a shaft of a oourDterfllow preheater enters a tangential whirl of gases supplied to a dividing line ,between an upper and lower pant of the calcination chamber, in which an upper flow is formed by a tangential whirl going upward along the walls of the chamber and downward in the middle part, and a lower flow is formed by a tangential whirl going downward along said walls and upward in the middle plart, the raw material being calcinated and, concentrated in a dond of par tides predominantly along said walls moves downward through the calcination stage and in a first phase it is lifted by an upward going whirl and in this way its stay in the first phase is prolonged, and in the next phase, when, because of heat treatment its liquidity is considerably worsened, the tangential whirl moving downward along the walls allows it to he discharged out of the calcination stage.

2. A method according to claim 1 wherein a part of the preheated material from a separated preheated branch of the preheater is supplied into a duct supplying gases in the oallcination chamber and in this way is added to these gases supplied tangentialiy to its cylindrical middle plant, so that this part of the preheated raw material is at fist drawn into the upper flow d the tangential whirl of gases in the calcination stage.

3. A device for carrying out a method according to claims 1 or 2 comprising a dispersion counter flow preheated ineluding a shaft, a calcination chamber directly connected to the shaft of the preheater, a firing device and a cooler of the fired product in which the oalcination chamber has an upper part and lower part which are interconnected by means of a cylindrical middle plart to which a duct for supplying gases is tangentially connected.

4. A device according to claim 3 wherein the lower part of the calcination chamber is in the shape of a truncated cone, the larger base of which is connected to the cylindrical middle part of the calcination chamber and the smaller base is connected to a pipe for discharging the raw material, the upper part od the calcination chamber being in the shape of a truncated cone, the smaller base of which is connected to the cylindrical middle part of the calcination chamber and the larger base to the shaft of the preheater, the conicity of the truncated cone of the lower and upper parts of the calcination chamber being in the range of 100 to 300.

5. A device according to claims 3 or 4 wherein the upper part of the calcination chamber is connected to the shaft of the preheater by a conical adapter, the larger base of which is connected to the upper part of the calcination chamber and the smaller base to the shaft of the preheater, the tonicity of the adapter being up to 300 and the ratio of its height to the diameter of its smaller base is not greater than 1.

6. A device according to any one of claims 3 to 5 wherein between the lower part of the calcination chamber and pipe for discharging raw material there is arranged a separation chamber which is formed by two truncated oones interconnected at their larger bases, the tonicity of the upper truncated cone of the separation chamber being in the range of 900 to 1700.

7. A device according to any one of claims 3 to 6 wherein torches are situated in the lower third of the upper part and in the upper third of the lower part of the calcination chamber.

8. A device according to any one of claims 3 to 7 wherein torches are situated in the cylindrical middle part of the calcination chamber.

9. A device according to any one of claims 3 to 8 wherein a pipe for supplying a part of preheated raw material is connected to the duct for supplying gases into the cal citation chamber.

10. A method according to claim 1 carried out substantially as herein described with reference to Figure 1, Figure 2 or Figure 3 of the accompanying drawings.

11. A device according to claim 3 substan tally as herein described with reference to, and as shown in, Figure 1, Figure 2 or Figure 3 of the accompanying drawings.

12. Material when made by or with the use of a method according to claim 1, 2 or 10.

13. Material when made by or with the use of a device according to any one of claims 3 to 9 or 11.