JP2011063451A - Method for producing cement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing cement, with which the quantity of SO<SB>3</SB>in cement clinker is kept in a prescribed range even when a sulfur content in fuel used for the main burner of a cement kiln is varied. <P>SOLUTION: In the method for producing the cement where cement clinker is produced by firing a cement raw material charged from the kiln inlet 2 into the inside of the cement kiln 1 the inside of which is held under a high temperature atmosphere by flame from a main burner 5 provided to the kiln outlet 4, while feeding the cement raw material to a kiln outlet 4 side, the quantity of SO<SB>3</SB>15 contained in the cement clinker is controlled to within a range of 1-3 wt.% by charging gypsum in the quantity of compensating at least the variation of the sulfur content 14 at least in the fuel of the main burner or the variation of the quantity of SO<SB>3</SB>15 contained in the produced cement clinker into the high temperature atmosphere of ≥1,400°C in the cement kiln 1 from the kiln outlet 4 side of the cement kiln. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing a cement clinker by firing a cement raw material in a cement kiln held in a high temperature atmosphere, and more specifically, sulfur trioxide (hereinafter abbreviated as SO ₃ ) contained in the cement clinker. The present invention relates to a method for producing a cement that makes it possible to control the amount of C within a desired range.

  Generally, in a cement manufacturing facility, a cement raw material is preheated to a predetermined temperature in a preheater and introduced into a cement kiln, and a high temperature atmosphere of about 1450 ° C. is generated in the cement kiln by a flame from a main burner provided in front of the kiln. The cement clinker is baked with a cement clinker, and then the cement clinker is added with dihydrate gypsum for preventing rapid setting and pulverized to produce a cement.

By the way, the cement clinker obtained in the above manufacturing process incorporates SO ₃ produced by oxidation of sulfur (S) contained in the cement raw material itself and the fuel, and the final cement In order to maintain the quality, an amount of the gypsum corresponding to the amount of SO ₃ in the cement clinker is added.

On the other hand, as the fuel burned in the main burner of the cement kiln, coal and oil coke are usually used. However, with the recent increase in fuel, the coal and the like, such as waste oil as industrial waste, etc. Secondary fuel is added and used as part of the fuel.
However, since the above-mentioned auxiliary fuels are of many types and contain various amounts of sulfur, the amount of sulfur contained varies depending on the fuel used, resulting in a large amount of SO ₃ in the cement clinker. It will fluctuate.

For this reason, the amount of the gypsum added when the cement is produced also fluctuates, which may adversely affect the quality of the obtained cement such as setting time.
In addition, the grinding of cement clinker, in order to vary the amount of SO ₃ containing, on quality control of cement, despite variations in the sulfur content in the fuel, constant SO ₃ content in the cement clinker There is a strong demand to keep it within the range.

  In addition, the following patent document 1 discloses a technique for predicting and managing such a fluctuation of a trace component in a cement clinker.

Japanese Patent Laid-Open No. 2005-214891

The present invention has been made in view of such circumstances, and even when the sulfur content in the fuel used for the main burner of the cement kiln varies, the amount of SO ₃ in the cement clinker can be maintained within a predetermined range. Therefore, an object of the present invention is to provide a method for producing a cement that can stably maintain the quality of the cement.

In order to solve the above-mentioned problem, the invention according to claim 1, in the cement kiln in which the inside is held in a high temperature atmosphere by the flame from the main burner provided in front of the kiln, from the kiln bottom of the cement kiln In the cement manufacturing method for producing cement clinker by sending the cement raw material charged inside to the front side of the kiln and producing the cement clinker, from the front side of the kiln of the cement kiln to a high temperature atmosphere of 1400 ° C. or higher in the cement kiln, by turning on the amount of gypsum to compensate the variation of SO ₃ content in the least the amount of variation in the sulfur content in the fuel of the main burner or manufactured the cement clinker, the SO ₃ contained in the cement clinker The amount is controlled within a range of 1 to 3% by weight.

  The invention described in claim 2 is characterized in that the gypsum is heat-treated anhydrous gypsum and pulverized to a particle size of 5 mm or less and then charged into the cement kiln.

  Furthermore, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the fuel of the main burner is pulverized coal obtained by pulverizing coal in a coal mill. The gypsum is supplied, pulverized together with the coal, and charged from the main burner into the cement kiln.

  On the other hand, the invention according to claim 4 is the invention according to claim 1 or 2, wherein the gypsum is thrown into the flame of the main burner from the auxiliary charging pipe provided above the main burner. It is characterized by doing.

According to the invention according to any one of claims 1 to 4, when gypsum is poured into a high-temperature atmosphere of 1400 ° C. or more from the front side of the kiln of the cement kiln, the gypsum decomposes in the high-temperature atmosphere, The reaction shown by the following formula occurs, and the generated SO ₃ is taken into the cement raw material to be fired.
CaSO ₄ → CaO + SO ₃

Therefore, when the fuel for combustion in the main burner is switched from one having a high sulfur content to one having a low sulfur content, or when the amount of SO ₃ contained in the produced cement clinker is reduced, the front side of the cement kiln in the kiln By increasing the amount of gypsum put into the high temperature atmosphere, the amount of SO ₃ contained in the cement clinker can be easily and reliably controlled within a preset range of 1 to 3% by weight.

At this time, by placing the above-mentioned gypsum which is an incombustible material in a high temperature atmosphere of 1400 ° C. or higher in the cement kiln, it can be completely pyrolyzed to generate SO ₃ as shown in the above formula, Therefore, the amount of SO ₃ in the cement clinker can be adjusted effectively.

As a result, even when the sulfur content in the fuel used for the main burner of the cement kiln fluctuates, the amount of SO ₃ in the cement clinker can be maintained within the range of 1 to 3% by weight, thus reducing the cement quality. It becomes possible to maintain it stably.

Here, the reason why the amount of SO ₃ in the cement clinker is limited to being within the range of 1 to 3% by weight will be described. Generally, in cement as a final product, as the amount of SO ₃ contained increases. Thus, it is known that although the strength development effect by hydration promotion is obtained, when the amount of SO ₃ is excessive, the strength decreases due to an increase in voids due to the formation of expansive ettringite. For this reason, in JIS R 5210, the upper limit of the content of SO ₃ is standardized as one item for determining the quality of Portland cement.

By the way, according to the above JIS R 5210, the amount of SO ₃ is 3.0% by weight or less for ordinary Portland cement, moderately hot Portland cement and sulfate-resistant Portland cement, and for early strength Portland cement and low heat Portland cement. 3.5% by weight or less, and for super early strength Portland cement, 4.5% by weight or less.

Therefore, when the amount of SO ₃ in the cement clinker fluctuates, the amount of gypsum introduced into the cement kiln is controlled so that the amount of SO ₃ in the cement clinker is 3% by weight or less. It becomes possible to produce cement that meets the standards.

On the contrary, if the content of SO _{3 in} the cement is small, abnormal condensation such as rapid setting is exhibited. Therefore, in general, the cement is agglomerated by suppressing the reaction time of aluminate with water. In order to extend the time, the amount of SO ₃ contained in the cement is prepared by adding gypsum (CaSO ₄ .2H ₂ O) to the cement clinker.

Then, the present inventors conducted a demonstration experiment to confirm the change in cement setting time when the amount of SO ₃ in the cement clinker and the amount of SO ₃ added by gypsum were changed. FIG. 4 shows the results of the demonstration experiment.
From the figure, as the amount of SO ₃ in the cement clinker increases by 1% by weight, the setting time (initial time and end time) was shortened by about 20 minutes, but the effect of the increase in SO ₃ amount due to the addition of gypsum. Was not observed within the scope of this experiment.

Therefore, when the amount of SO ₃ contained in the manufactured cement clinker decreases, a desired cement setting time can be obtained by introducing gypsum into the cement kiln so that the amount of SO ₃ is at least 1% by weight. It can be.
From the above, the amount of gypsum put into the cement kiln was controlled to keep the SO ₃ amount in the cement clinker within a range of 1 to 3% by weight.

When determining the amount of gypsum to be charged, there is a time difference between the time when the gypsum is charged and the SO ₃ produced by the reaction is taken into the cement clinker. Rather than determining the input amount corresponding to the amount of variation in the amount of SO ₃ contained, when the fuel being used changes, the sulfur content in the new fuel and the sulfur content in the fuel used so far It is preferable to add gypsum in an amount that compensates for the variation.

In recent years, industrial waste containing sulfur content such as waste tires in cement kilns has also been introduced as part of fuel for maintaining the inside of the cement kiln in a high temperature atmosphere. Since the sulfur content generated by the combustion of these wastes can be said to be a small amount compared to the sulfur content in the fuel used for the combustion of the main burner described above, it has an effect on the variation in the amount of SO ₃ in the cement clinker. It can be said that there are few. However, if the input amount of gypsum is determined in consideration of the fluctuation of the sulfur content in the fuel in addition to the fluctuation of the sulfur content in the fuel of the main burner, the amount of SO ₃ in the cement clinker can be further increased. It becomes possible to control the fluctuation within the predetermined range described above.

  Further, the gypsum to be charged is preferably an anhydrous gypsum that has been heat-treated as in the invention described in claim 2 and pulverized to a particle size of 5 mm or less. By using such anhydrous gypsum, it is possible to prevent clogging in the burner put into the cement kiln.

In addition, by using anhydrous gypsum that does not have H ₂ O content, it does not take heat of vaporization at the time of combustion and does not lower the thermal efficiency. In a high temperature atmosphere, a desired amount of SO ₃ can be generated by instant and complete thermal decomposition.

  In addition, as a method of charging into the cement kiln, the fuel may be charged from the main burner together with the fuel as in the third aspect of the invention, or the main burner may be charged as in the fourth aspect of the present invention. It is also possible to charge from the auxiliary charging pipe provided above toward the flame of the main burner. By adopting such a configuration, it is possible to reliably put the gypsum in the vicinity of the flame of the main burner under the highest temperature atmosphere for decomposition.

  In this case, when the fuel of the main burner is coal, the gypsum is introduced into a coal mill using coal as pulverized coal, and pulverized and mixed together with the coal. In addition, if the main burner is charged into the cement kiln, it is preferable because the gypsum can be more thermally decomposed by the flame of the main burner.

It is a schematic block diagram of the cement manufacturing equipment for implementing the 1st Embodiment of this invention. It is a schematic block diagram of the cement manufacturing equipment for enforcing the 2nd Embodiment of this invention. It shows a first embodiment experimental results using embodiments of the present invention, (a) shows the case where the charged gypsum, (b) is a SO ₃ content in each of the cement clinker in the case of not introducing gypsum It is a graph which shows a fluctuation. Is a graph showing the results of field trials to confirm the change of the cement setting time of varying the SO ₃ additive amount of SO ₃ amount and gypsum in the cement clinker.

(First embodiment)
FIG. 1 shows a cement production facility for carrying out a first embodiment of a cement production method according to the present invention. In the figure, reference numeral 1 denotes a cement kiln for firing cement raw materials. This cement kiln 1 is a rotary kiln provided so as to be rotatable around an axis, and a preheater 3 for preheating the cement raw material is provided in a left kiln bottom portion 2 in the figure, and a right kiln in the figure. A main burner 5 for heating the inside is provided in front of the kiln 4. In addition, the code | symbol 6 in a figure is a clinker cooler for cooling the cement clinker after baking.

  Here, the preheater 3 is composed of a plurality of cyclones arranged in series in the vertical direction, and the cement raw material is supplied to the uppermost cyclone via the supply pipe 7, and the lowermost cyclone Connected to the bottom is a transfer pipe 3 a for sending the internal cement raw material to the kiln bottom part 2 of the cement kiln 1.

  On the other hand, the kiln bottom part 2 is provided with an exhaust gas pipe 3b for supplying the combustion exhaust gas discharged from the cement kiln 1 to the lowermost cyclone, and the exhaust gas discharged from the upper part of the uppermost cyclone is Exhaust air (not shown) is exhausted through the exhaust line 8.

  The main burner 5 of the cement kiln 1 is provided with means for supplying pulverized coal as fuel. This supply means pulverizes the coal silo 10 storing a mixture of coal, oil coke and auxiliary fuel as the fuel source, coal supplied from the coal silo 10 and the like into pulverized coal of a predetermined particle size. It comprises a dry coal mill 11 and a fuel supply pipe 12 for feeding pulverized coal obtained in the coal mill 11 from the main burner 5 into the cement kiln 1 by compressed air supplied from a supply line (not shown). It is a thing.

Further, in this cement manufacturing facility, a measuring device 13 for measuring waste gypsum such as gypsum board is provided, and the waste gypsum measured in this measuring device 13 is supplied to the coal mill 11 together with the coal from the coal silo 10. It has come to be.
Here, the meter 13 should be charged based on the sulfur content 14 in the new coal supplied to the coal silo 10 or the SO ₃ amount 15 in the cement clinker discharged from the clinker cooler 6. It measures the amount of waste gypsum.

Next, a first embodiment of the cement manufacturing method according to the present invention using the cement manufacturing facility configured as described above will be described.
First, in this cement manufacturing facility, a cement raw material obtained by pulverizing and mixing limestone, clay, silica and iron oxide raw materials is supplied from the supply pipe 7 to the uppermost cyclone of the preheater 3. Then, the cement raw material supplied to the uppermost cyclone is preheated by the high-temperature exhaust gas from the cement kiln 1 that rises from the lower as it sequentially falls to the lower cyclone, and finally from the lowermost cyclone. It is introduced into the cement kiln 1 through the transfer pipe 3a.

  On the other hand, the coal or the like of the fuel stored in the coal silo 10 is appropriately sent to the coal mill 11 and pulverized to become pulverized coal, which is provided from the fuel supply pipe 12 in front of the kiln 4 of the cement kiln 1. To the main burner 5 provided. And the pulverized coal thrown into this cement kiln 1 from this main burner 5 burns, and the front 4 side of the kiln in the cement kiln 1 is maintained in a high temperature atmosphere of about 1450 ° C. or higher.

  Thus, the cement raw material sent from the kiln bottom part 2 into the cement kiln 1 is heated to about 1450 ° C. by the combustion exhaust gas from the main burner 5 in the process of being gradually sent to the kiln front 4 side, It is fired to become a cement clinker. Next, the cement clinker that has reached the front of the kiln 4 falls into the clinker cooler 6 and is sent to the right in the figure. At this time, the air is cooled to a predetermined temperature by the air supplied into the clinker cooler 6 and finally taken out from the clinker cooler 6.

At the same time, waste gypsum such as waste gypsum board carried into the cement manufacturing facility is dried in advance in a heated atmosphere at 100 ° C. to 300 ° C. to form anhydrous gypsum. When the sulfur content 14 in the supplied coal or the like decreases with respect to the sulfur content of the fuel currently used, the amount of the anhydrous gypsum corresponding to the decreased sulfur content is measured in the meter 13, and the coal Supplied to the mill 11. Thus, SO ₃ content in the cement clinker to control so as to be held within a range of normally 1 to 3% by weight.

The anhydrous gypsum is weighed when the SO ₃ amount 15 contained in the cement clinker discharged from the clinker cooler 6 is reduced, and the amount of the anhydrous gypsum corresponding to the reduced SO ₃ amount is measured. 11 may be supplied.

  In this coal mill 11, it is mixed with the coal supplied from the coal silo 10 and finely pulverized to a particle size of 5 mm or less to become anhydrous gypsum powder, and is put into the cement kiln 1 from the main burner 5 together with the pulverized coal. Then, it is thermally decomposed by the flame of the main burner 5 at 1400 ° C. or higher.

(Example)
FIG. 3 shows experimental results in a cement manufacturing method using the cement manufacturing facility.
When manufacturing cement clinker at a rate of 130 tons per hour in the above cement manufacturing facility, the fuel in the main burner 5 is switched to a new one on the fourth day after the start of measurement, and as a result, the sulfur content is reduced. Thus, it was predicted that the SO ₃ amount in the cement clinker was reduced by 0.2%.

Therefore, in order to compensate for this, the waste gypsum board having a SO ₃ content of 41% is weighed in the measuring device 13 and finely powdered at an input amount of 650 kg / hour (5.0 kg-gypsum / t-clinker). It was introduced from the main burner 5 together with charcoal.
As a result, as can be seen in FIG. 3 (a), no significant variation was observed in SO ₃ in the cement clinker discharged from the clinker cooler 6 thereafter.

On the other hand, in the adjacent cement kiln 1, when the fuel is switched to a new one from the fourth day and the waste gypsum board is not charged, as shown in FIG. From the sixth day onward, as predicted, the amount of SO ₃ in the cement clinker decreased by about 0.2% to 1% by weight or less.

As described above, according to the method for producing cement, when the combustion fuel in the main burner 5 is switched from one having a high sulfur content to one having a low sulfur content, the amount of SO ₃ contained in the produced cement clinker is small. When it decreases, by increasing the amount of anhydrous gypsum powder derived from waste gypsum introduced into the high-temperature atmosphere of 1400 ° C. or higher from the 4th side of the kiln 1 before the kiln, the SO ₃ contained in the cement clinker can be easily and reliably added. Can be controlled within a preset range of 1 to 3% by weight.

In particular, in the present invention, waste gypsum such as the above-mentioned gypsum board is heat-treated to make anhydrous gypsum, pulverized to a particle size of 5 mm or less in advance, and charged into the cement kiln 1 together with pulverized coal from the main burner 5. to have, without reducing the thermal efficiency of the cement kiln 1 by moisture contained in the waste gypsum, and in order to be able to completely decompose the anhydrite powder, sO ₃ in effectively cement clinker The amount can be adjusted.

Therefore, even when the sulfur content in the fuel made of coal or the like used for the main burner 5 of the cement kiln 1 fluctuates, or when the amount of SO ₃ contained in the manufactured cement clinker decreases, the SO in the cement clinker always remains. _The amount of 3 can be kept within the range of 1 to 3% by weight, so that the quality of the cement can be stably maintained.

(Second Embodiment)
FIG. 2 shows a cement production facility for carrying out the second embodiment of the cement production method according to the present invention. The same components as those shown in FIG. The description is simplified.
In this manufacturing facility, there is also provided a pulverizer 16 for pulverizing the anhydrous gypsum derived from waste gypsum measured in the meter 13 to a particle size of 5 mm or less to obtain anhydrous gypsum powder. Then, in the front 4 of the kiln 1 of the cement kiln 1, an auxiliary charging pipe for charging the anhydrous gypsum powder pulverized by the pulverizer 16 into the cement kiln 1 together with the compressed air toward the flame of the main burner 5. 17 is provided above the main burner 5.

  In the second embodiment of the cement manufacturing method according to the present invention using the cement manufacturing facility having the above configuration, the sulfur content 14 in the coal or the like supplied to the coal silo 10 is currently used. When the sulfur content of the fuel is reduced, the amount of the anhydrous gypsum corresponding to the reduced sulfur content is measured by the meter 13 and supplied to the pulverizer 16. Then, the anhydrous gypsum powder obtained by pulverization in the pulverizer 16 is introduced from the auxiliary charging pipe 17 toward the flame of the main burner 5 and is thermally decomposed by the flame of the main burner 5 at 1400 ° C. or higher. The

Therefore, also in the cement manufacturing method shown in the second embodiment, the sulfur content in the fuel made of coal or the like used for the main burner 5 of the cement kiln 1 fluctuates similarly to the method shown in the first embodiment. Even when the amount of SO ₃ contained in the manufactured cement clinker decreases, the amount of SO ₃ in the cement clinker can always be kept within the range of 1 to 3% by weight described above. It becomes possible to maintain the quality of the stable.

In the first and second embodiments described above, since the plaster to be input has an effect as part of the waste treatment, only the case where the waste gypsum such as the waste gypsum board is used has been described. However, the present invention is not limited to this, and a new gypsum may be added for adjusting the amount of SO ₃ in the cement clinker.

When manufacturing cement, it can be used to control the amount of sulfur trioxide (hereinafter abbreviated as SO ₃ ) contained in the cement clinker within a desired range.

DESCRIPTION OF SYMBOLS 1 Cement kiln 2 Kiln bottom part 4 In front of kiln 5 Main burner 10 Coal silo 11 Coal mill 12 Fuel supply pipe 13 Measuring instrument 16 Crusher 17 Auxiliary input pipe

Claims (4)

In the cement kiln whose interior is maintained in a high temperature atmosphere by the flame from the main burner provided in front of the kiln, the cement raw material introduced into the inside from the kiln bottom of the cement kiln is sent to the kiln front side and fired. In a cement manufacturing method for manufacturing a cement clinker,
From the front side of the kiln of the cement kiln, in a high-temperature atmosphere of 1400 ° C. or higher in the cement kiln, at least the amount of sulfur content in the fuel of the main burner or the sulfur trioxide contained in the manufactured cement clinker ( by turning on the amount of gypsum to compensate the variation of the amount of SO _3), characterized by controlling the amount of sulfur trioxide (SO ₃₎ contained in the cement clinker in the range of 1-3 wt% A method for producing cement.   The method for producing cement according to claim 1, wherein the gypsum is heat-treated anhydrous gypsum and pulverized to a particle size of 5 mm or less and then charged into the cement kiln.   The fuel of the main burner is pulverized coal obtained by pulverizing coal in a coal mill, and the gypsum is supplied to the coal mill and pulverized together with the coal to be fed from the main burner into the cement kiln. The method for producing a cement according to claim 1 or 2, wherein:   3. The method for producing a cement according to claim 1, wherein the gypsum is charged toward the flame of the main burner from an auxiliary charging pipe provided above the main burner.

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