TWI483918B - Cement manufacturing method - Google Patents

Description

Cement manufacturing method Field of invention

The present invention relates to a cement manufacturing method, and more particularly to a kiln exhaust flow path from a kiln tail of a cement kiln to a lowermost cyclone, the dust contained in the gas from which a part of the combustion gas is pumped will A method of separating heavy metals such as lead.

Background of the invention

Conventionally, it is considered that no lead is dissolved in the soil due to the immobilization of lead (Pb) in the cement. However, with the increase in the amount of live use of the reused resources of cement manufacturing plants in recent years, the amount of lead in cement has also increased, and is gradually exceeding the current content. As the concentration increases, there is also the possibility of dissolution to the soil, so the concentration of lead in the cement needs to be reduced to the current level.

In addition, in recent years, the recycling of cement raw materials or fuels has been promoted. As the amount of waste treatment increases, the amount of volatile components such as chlorine, sulfur, and alkali that are brought into the cement kiln also increases. The amount of road dust generated also increased. The development of a method for utilizing residual chlorine bypass dust is required because an increase in the amount of production or an allowable concentration of cement containing heavy metals containing lead is expected.

In view of the above, in Patent Document 1, the chlorine component and the lead component in the waste supplied to the cement manufacturing step are effectively separated and removed, and a waste disposal method is disclosed, which has a water washing step of the waste and has been filtered. An alkali elution step of a solid component, a de-lead step of separating the lead from the filtrate, a decalcification step of separating the calcium from the lead-extracted filtrate, heating the filtrate, and precipitating the chloride to separate and recover the chlorine Recovery step.

Further, Patent Document 2 describes a method for treating waste, which has a method of classifying lead and zinc from waste such as fly ash, and mixing a solution containing calcium ions to obtain a slurry, and then separating the solid and liquid to obtain zinc. The step of solid component and aqueous solution containing lead, adding a vulcanizing agent to an aqueous solution containing lead, and separating the solid and liquid to obtain a step of obtaining lead sulfide and a solution containing calcium ions.

Further, Patent Document 3 describes a method of recovering heavy metals from chlorine bypass dust generated in a cement manufacturing step, separating into heavy metal-containing dust from a cement manufacturing step, and burning a cement kiln from the heavy metal-containing dust. One part of the gas is pumped, and dust contained in the exhausted combustion gas is collected, and one or more selected from bismuth, lead, and selenium are removed or recovered.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-1218

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2003-201524

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2006-347794

However, in the conventional technique described in the above-mentioned patent documents, heavy metals such as lead contained in chlorine bypass dust and the like are removed, and the proportion of heavy metals removed to the outside of the system via chlorine bypass dust is only about 30% of the total. For example, even if the heavy metals in the chlorine bypass dust are removed by 100%, the remaining 70% still enters the clinker discharged from the cement kiln, so it is not easy to reduce the heavy metal content of the cement. Therefore, it is important to promote the volatilization of heavy metals in the cement kiln and to increase the concentration of heavy metals such as chlorine bypass dust.

For example, the volatilization method of heavy metals is known as a chlorine volatilization method and a reduction volatilization method. However, when the generally used chlorination volatilization method is applied to the cement sintering step, it is necessary to invest chlorine in a much larger amount than the usual amount in the manufacture of cement. On the other hand, due to the application of the reduction volatilization method, the color of the cement is yellow, which causes problems in the quality of the cement.

Moreover, in order to increase the volatilization rate of heavy metals, it is also possible to suppress the oxygen concentration in the tail portion of the kiln of the cement kiln to form a gas environment for generating CO gas, and to generate dust for combustion and exhaust of the cement kiln due to the generation of CO gas. The danger of using the electric dust collector to explode, and the environmental burden caused by the discharge of CO gas to the outside of the system.

Therefore, the present invention has been made in view of the above problems of the prior art, and its object is to ensure the safety of the cement manufacturing apparatus without impairing the quality of the cement, and also to avoid an increase in environmental burden, and can be good. Efficiency separates heavy metals from the cement manufacturing step.

In order to achieve the above object, the present inventors have repeatedly studied the results of the research and found that by injecting combustibles having a carbon content of a predetermined value or more into the cement kiln, the volatilization of heavy metals can be improved in the sintering step including the cement kiln. rate.

According to the present invention, the inventors of the present invention have supplied a combustible material containing 20% by mass or more of carbon components to a region of a cement kiln of 900 ° C or more and 1300 ° C or less, from the kiln tail of the cement kiln to the most The kiln exhaust path of the lower cyclone evacuates a part of the combustion gas, collects the dust contained in the combustion gas, and separates the heavy metals from the collected dust. In addition, the carbon component is a component that contributes to combustion, and the heavy metals that can be separated are lead, zinc, cadmium, tellurium, selenium, arsenic, and antimony.

When the above combustibles are put into the cement kiln at less than 900 ° C, most of the combustibles are burned before reaching the region where the heavy metals are volatilized with good efficiency, and it is difficult to sufficiently increase the volatilization rate of heavy metals. When the temperature is above 1300 ° C, the color of the cement is yellow, which causes problems in the quality of the cement. By inputting combustible materials in the above temperature region, the volatilization rate of heavy metals in the tail portion of the kiln in the cement kiln can be effectively improved, and the chlorine bypass system can be used to increase the concentration ratio of heavy metals in the chlorine bypass dust. The removal rate of heavy metals in the cement manufacturing process increased.

In the above cement production method, the heavy metal may be volatilized at a volatilization rate of 80% or more in the above region of the cement kiln.

Further, in the above-described method for producing a cement, the carbon content of the combustible material is α% by mass, and the amount of combustibles contained in the cement kiln containing the carbon component is clinker production per 1 t of βkg, and α is And the product of β is 30 or more and 5000 or less. When the product of α and β is less than 30, it is difficult to sufficiently increase the volatilization rate of heavy metals. On the other hand, when the product of α and β exceeds 5,000, even if more than the carbon component is added, the volatilization rate of heavy metals is still highest. When purchased at a price, it also leads to an increase in the cost of the use of the combustible material, which is not practical.

Further, in the above cement production method, a dry dust collector or a wet dust collector may be used when dust is collected from the exhausted combustion gas.

In the above cement manufacturing method, when the combustible material is supplied to a region of the cement kiln at a temperature of 900 ° C or more and 1300 ° C or less, the combustible material may be used for the kiln tail of the cement kiln or the substance decomposed by temperature. In the coated state, the preheater attached to the cement kiln is used to decompose the carbonaceous material by the time difference, or to directly introduce the combustible material into the kiln from the inlet of the main body of the cement kiln.

Further, in the above cement manufacturing method, the combustible material is made of coke, coal tar pitch, tire, coal, anthracite, bituminous coal, brown carbon, lignite, graphite, flame retardant plastic, phenolic resin, furan resin, and thermosetting property. One or two or more selected from the group consisting of resin, cellulose, charcoal, waste toner, mixed coke, fine coke, electrode chips, activated coke, carbide, and unburned carbon contained in fly ash.

Further, the combustible material may be subjected to particle size adjustment by granulation or/and classification, and then introduced into the cement kiln. When the combustible material has a small diameter and is scattered to the low temperature side by the gas passing through the kiln, the supply amount of the heavy metal in the volatilization temperature region is reduced, and the efficient volatilization rate cannot be ensured. The standard is preferably when the particle size of the combustible material is d _p and the gas velocity of the input part is V _p , the settling velocity from Stokes, d _x ² = (18 × μ × V _p ) / ((ρ _p - When d _x of ρ _g )×g) is d _p <d _x , the particle size of d _x or more is adjusted by granulation or classification. Here, μ is the gas viscosity, pp is the combustible density, pg is the gas density, and g is the gravitational acceleration. Regarding the maximum particle size, when it is too large, the combustion is not finished until the cement or the sintered mineral band is formed. The color of the cement is yellow, so there is a problem in the quality of the cement, and it is preferable to not affect the size of the cement. .

In the above cement production method, the particle diameter of the combustible material may be 1 mm or more and 50 mm or less. When the particle size of the combustible material is less than 1 mm, the supply amount of the heavy metal in the volatilization temperature region is reduced, and the effective volatilization rate cannot be ensured. On the other hand, when the particle size of the combustible material exceeds 50 mm, heavy metals are mixed into the cement or cement. The color is yellow, which causes problems in the quality of the cement.

As described above, according to the present invention, the quality of the cement is not affected, the safety of the cement manufacturing apparatus is ensured, the environmental burden can be avoided, and the heavy metals can be separated from the cement manufacturing step with good efficiency.

The best form for implementing the invention

Next, an embodiment of the present invention will be described with reference to the drawings. Further, in the following description, a case where the lead of one of the heavy metals is separated in the embodiment of the present invention will be described as an example.

Fig. 1 is a view showing a cement manufacturing apparatus to which the cement manufacturing method of the present invention is applied, the cement manufacturing apparatus 1 having a kiln tail 2a for charging a combustible material C to a cement kiln (hereinafter referred to as "kiln" 2 (calcining furnace 3 and The input device 5 of the end portion of the lowermost cyclone 4 is provided.

On the other hand, as shown in Fig. 2, the kiln 2 has a chlorine bypass device 10, and an exhaust gas from the kiln tail 2a of the kiln 2 to the kiln exhaust flow path of the lowermost cyclone 4 (refer to Fig. 1). After the probe 11 is cooled by the cold air of the cooling fan 12, it is introduced into the classifier 13 and separated into coarse dust, fine powder, and gas. The coarse dust is returned to the kiln system, and fine powder (chlorine bypass dust) containing potassium chloride (KCI) or the like is recovered by the dust collector 14. The exhaust gas discharged from the dust collector 14 is returned to an exhaust flow path such as an outlet of a preheater or a preheater attached to the kiln 2 via the fan 15.

Next, a cement manufacturing method of the present invention using the cement manufacturing apparatus 1 described above will be described.

In Fig. 1, in the cement sintering of the kiln 2, the combustibles C are introduced into the kiln tail 2a of the kiln 2 by the input device 5. This combustible material C contains 20% by mass or more of carbon components, and can be used for coke, coal tar pitch, tires, coal, anthracite, bituminous coal, brown carbon, lignite, graphite, flame retardant plastic, phenolic resin, furan resin, and thermosetting property. Resin, cellulose, charcoal, waste toner, mixed coke, fine coke, electrode chips, activated coke, carbide and unburned carbon contained in fly ash. The reason why the combustible material C having such a carbon component content is supplied is as follows.

Fig. 3 is a graph showing the test results of the volatilization rate of lead using an electric furnace, comparing the raw materials before the kiln 2 (the raw material discharged from the lowermost cyclone 4) taken from the cement manufacturing step in the electric furnace. Carbon (fixed carbon 87% = α) was added to 50 (50 kg/t-cli equivalent = β, α × β = 4350) to be sintered, and only the raw material discharged from the lowermost cyclone 4 was placed and sintered. It can also be seen from this figure that when coke is placed, the volatilization rate of lead is greatly increased in the region of the sintering temperature of 900 ° C to 1300 ° C. This temperature range is equivalent to from the kiln tail 2a of the kiln 2 to the center portion.

In the second diagram, the lead volatilized in the kiln 2 is contained in a gas pumped by the probe 11, and the exhaust gas is cooled by the probe 11, and then introduced into the classifier 13 to be separated into coarse dust, fine powder, and gas. The fine powder is recovered by the dust collector 14. In this fine powder, lead volatilization is more, and lead is more than conventional concentrating meters. Therefore, by separating the lead, the lead can be removed from the cement manufacturing step with good efficiency, and the lead of the cement clinker produced in the kiln 2 can be contained. The rate is reduced.

[Examples]

As shown in Table 1, the examples used combustibles A (fixed carbon component 30% by mass), and comparative examples used combustibles B (fixed carbon components 17% by mass), using the input device 5, and putting both into the kiln of the kiln 2 Tail 2a, while comparing the lead volatilization rate.

As shown in Table 2, in the embodiment, the input amount of the combustible material A was changed in three grades, and each grade was tested for 3 days, and the raw material (a) before entering the kiln 2 and the clinker after passing through the kiln 2 (product) (b), the lead volatility is calculated by the following formula. (1-b/a) × 100%. Further, in the formula, a represents the lead content of the raw material, and b represents the lead content of the clinker. On the other hand, in the comparative example, the amount of the combustible material B was changed in three levels, and each grade was tested for three days, and the lead volatilization rate was measured in the same manner as in the examples. Further, in this comparative example, the amount of input of the combustible material A was maintained constant.

Due to the examples and comparative examples in Table 2, the clinker production amount of the kiln 2 during the test was 285 t/h, so when the input amount of the combustible material A was 2 t/h of the grade 1, 2000 kg/h ÷ 285 t/h = 7 kg. /t-cli.. Thus, in the case of the level 1, 7 kg/t-cli. = α of the embodiment, and the fixed carbon 30% of the combustible A = β, α × β = 210. In the same calculation, in the case of the level 2 of the example, 3.5 kg/t-cli. = α, and the fixed carbon of the combustible material A is 30% = β, α × β = 105.

The results of the above test are shown in Fig. 4. As can be seen from the same figure, in the comparative example, the grades 1 to 3, the lead volatilization rate cannot be seen to vary, in the embodiment, with the grade 1 to grade 3, that is, with The amount of combustible A is reduced, and the lead volatilization rate is gradually reduced. From this, it is understood that the input of the combustibles in which 30% by mass of the carbon component is fixed contributes to an increase in the lead volatilization rate.

Next, as shown in Table 3, the example was based on the kiln 2 in which the clinker production amount was 85 t/h, and the input amount of the combustible material C (fixed carbon 87% = α) was changed in four grades, and the comparative example was not in the kiln. 2Injecting the combustible material C, taking the raw material (a) before entering the kiln 2 and the clinker (product) (b) after passing through the kiln 2, and measuring the lead volatilization rate using the above calculation formula. As apparent from this table, in the comparative example, the lead volatilization rate was less than 80%. On the other hand, in the examples, as the input amount of the combustible material C increased, the lead volatilization rate increased.

Further, in the above embodiment, the combustible material C is supplied to the kiln tail 2a of the kiln 2 by the input device 5, and may be supplied to the preheater attached to the kiln 2 in a state of being coated with the temperature-decomposed substance. When the carbonaceous material is decomposed by the time difference, and the carbonaceous material which is supplied to the preheater reaches the temperature of 900 ° C or more and 1300 ° C or less of the kiln 2, 20% by mass or more of the carbon component is contained, and the same effect as described above can be exerted. . Further, the combustibles C may be directly introduced into the kiln 2 from the inlet provided in the body portion of the kiln 2.

Further, in the above embodiment, the case where lead is separated from the chlorine bypass is exemplified, and lead, zinc, cadmium, tellurium, selenium, arsenic, and antimony may be separated from the same method as described above.

1. . . Cement manufacturing equipment

2. . . Cement kiln

2a. . . Kiln tail

3. . . Calciner

4. . . Lowermost cyclone

5. . . Input device

10. . . Chlorine bypass

11. . . Probe

12. . . cooling fan

13. . . Granulator

14. . . Dust collector

15. . . fan

A. . . Combustible

B. . . Combustible

C. . . Combustible

Fig. 1 is a schematic view showing an example of a device for carrying out the cement manufacturing method of the present invention.

Fig. 2 is a flow chart showing the overall structure of a chlorine bypass device attached to a cement sintering furnace.

Fig. 3 is a graph showing the test results of the volatilization rate of lead using an electric furnace.

Fig. 4 is a graph showing the test results of the cement manufacturing method of the present invention.

1. . . Cement manufacturing equipment

2. . . Cement kiln

2a. . . Kiln tail

3. . . Calciner

4. . . Lowermost cyclone

5. . . Input device

C. . . Combustible

Claims (5)

A method for producing a cement, which comprises pulverizing or/and granulating a combustible material containing 20% by mass or more of a carbon component, and then supplying it to a region of a cement kiln at a temperature of 900 ° C or more and 1300 ° C or less, and In this region, heavy metals are volatilized at a volatilization rate of 80% or more, and a part of the combustion gas is evacuated from the kiln exhaust path from the kiln end of the cement kiln to the lowermost cyclone, and the combustion gas is contained therein. The dust collects dust, and the heavy metal is separated from the collected dust, wherein the carbon content of the combustible material is α% by mass, so that the amount of combustibles contained in the cement kiln containing the carbon component is produced in clinker production. When the amount is β kg per 1 t, the product of α and β is 30 or more and 5,000 or less. A method of manufacturing a cement according to the first aspect of the invention, wherein a dry dust collector or a wet dust collector is used when dust is collected from the aerated combustion gas. The method for manufacturing a cement according to claim 1, wherein when the combustible material is supplied to an area of the cement kiln at a temperature of 900 ° C or more and 1300 ° C or less, the combustible material is used for the kiln tail of the cement kiln, or is In a state of being coated with a temperature-decomposed substance, it is supplied to a preheater attached to the cement kiln to decompose the carbonaceous material by a time difference, or the flammable substance is directly introduced into the kiln from an inlet provided in the main part of the kiln. Either way. The method for manufacturing a cement according to claim 1, wherein the foregoing combustible material is from coke, coal tar pitch, tire, coal, anthracite, smoke Coal, lignite, brown coal, graphite, flame retardant plastic, phenolic resin, furan resin, thermosetting resin, cellulose, charcoal, waste toner, mixed coke, fine coke, electrode fragments, One or two or more selected from the group consisting of activated carbon, carbide, and unburned carbon contained in fly ash. The method for producing a cement according to the fourth aspect of the invention, wherein the particle size of the combustible material is 1 mm or more and 50 mm or less.