WO2009113388A1

WO2009113388A1 - Process for producing cement

Info

Publication number: WO2009113388A1
Application number: PCT/JP2009/053321
Authority: WO
Inventors: 淳一寺崎; 紳一郎齋藤; 貴寛林田; 佳久小川
Original assignee: 太平洋セメント株式会社
Priority date: 2008-03-10
Filing date: 2009-02-25
Publication date: 2009-09-17
Also published as: TWI483918B; JPWO2009113388A1; TW200944493A; JP5826487B2; KR101571497B1; CN101959825A; KR20100136445A; CN104671681A

Abstract

Heavy metals including lead are efficiently separated from cement production steps without exerting any influence on cement quality while ensuring the safety of the cement production apparatus and avoiding an increase in environmental burden. A combustible substance containing at least 20 mass% carbon matter is supplied to that region in a cement kiln which has a temperature of 900-1,300°C. A kiln discharge gas passage extending from the bottom of the cement kiln to a lowermost-stage cyclone is bled of part of the combustion gas, and the dust contained in the combustion gas is collected. Heavy metals are separated from the dust collected.In the region of the cement kiln, the heavy metals can be volatilized at a volatilization ratio of 80% or higher. When the carbon matter content in the combustible substance is expressed by α mass% and the amount of the carbon-matter-containing combustible substance to be introduced into the cement kiln is expressed by β kg per ton of clinker production, then the product of α and β preferably is 30 to 5,000.

Description

Cement manufacturing method

The present invention relates to a cement manufacturing method, and in particular, removes heavy metals such as lead from dust contained in gas extracted from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. It relates to a method of separation.

Conventionally, since lead (Pb) in cement is fixed, it has been considered that there is no elution into soil. However, as the amount of recycled resources used in cement production equipment has increased in recent years, the amount of lead in cement has also increased, and the content has been greatly exceeded. Since there is a possibility of elution into the soil as the concentration increases, it is necessary to reduce the lead concentration in the cement to the level of the conventional content.

In recent years, recycling of waste by converting to cement raw material or fuel has been promoted, and as the amount of waste processed increases, the amount of chlorine, sulfur, alkali and other volatile components brought into the cement kiln also increases. The amount of bypass dust is also increasing. Chlorine bypass dust is used in the cement crushing process, but it is expected that the amount of generated chlorine will increase and the allowable concentration of heavy metals including lead will exceed the allowable level. Was demanded.

In view of the above points, for example, in Patent Document 1, in order to effectively separate and remove chlorine and lead in waste supplied to the cement manufacturing process, the waste water washing process and the solid separated by filtration An alkaline elution step, a deleading step for precipitating and separating lead from the filtrate, a decalcifying step for precipitating and separating calcium from the deleaded filtrate, and heating the filtrate to precipitate chloride. And a method for treating waste having a salt recovery step of separating and recovering.

Moreover, in patent document 2, in separating and removing lead and zinc from waste such as fly ash, a solution containing calcium ions is mixed to obtain a slurry, followed by solid-liquid separation to obtain a solid containing zinc. And a step of obtaining an aqueous solution containing lead, a step of obtaining a solution containing lead sulfide and calcium ions by solid-liquid separation after adding a sulfurizing agent to the aqueous solution containing lead, etc. A processing method is described.

Furthermore, in Patent Document 3, in order to recover heavy metals from chlorine bypass dust generated in the cement manufacturing process, the heavy metal containing dust is separated from the cement manufacturing process, and the cement kiln combustion gas is separated from the heavy metal containing dust. A method is described in which a part is extracted, dust contained in the extracted combustion gas is collected, and one or more selected from thallium, lead, and selenium are removed or recovered.

Japanese Unexamined Patent Publication No. 2003-1218 Japanese Unexamined Patent Publication No. 2003-201524 Japanese Unexamined Patent Publication No. 2006-347794

However, in the prior art described in the above patent document, heavy metals such as lead contained in chlorine bypass dust are removed, but the ratio of heavy metals removed outside the system through chlorine bypass dust is Only about 30%, even if 100% of heavy metals in chlorine bypass dust are removed, the remaining 70% is still taken up by the clinker discharged from the cement kiln. It is not easy to lower. Therefore, it is important to promote the volatilization of heavy metals in the cement kiln and increase the concentration rate of heavy metals in chlorine bypass dust.

For example, a chlorination volatilization method and a reduction volatilization method are known as volatilization techniques for heavy metals. However, if the chlorination volatilization method that is generally performed is applied to the cement firing step, it is necessary to input a much larger amount of chlorine than a common amount in cement production. On the other hand, the application of the reduction volatilization method is problematic in terms of cement quality because the color of the cement is yellow.

In order to increase the volatilization rate of heavy metals, for example, there is a method of forming an atmosphere that generates CO gas by suppressing the oxygen concentration in the kiln bottom of the cement kiln. There is a risk of explosion of an electric dust collector used to collect the combustion exhaust gas, and there is a concern about an increase in environmental load due to discharge of CO gas outside the system.

Therefore, the present invention has been made in view of the above-described problems in the prior art, and ensures the safety of the cement manufacturing apparatus without affecting the cement quality and avoids an increase in environmental load. However, the object is to efficiently separate heavy metals from the cement manufacturing process.

As a result of intensive studies to achieve the above-mentioned object, the present inventors put a combustible having a carbon content of not less than a predetermined value into the cement kiln, so that the inside of the firing process including the cement kiln And found that the volatility of heavy metals can be increased.

The present invention has been made on the basis of such findings. A combustible containing 20% by mass or more of carbon is supplied to a region of 900 to 1300 ° C. of the cement kiln, and the kiln bottom of the cement kiln is provided. A part of the combustion gas is extracted from the kiln exhaust gas path from the first to the lowest cyclone, dust contained in the combustion gas is collected, and heavy metals are separated from the collected dust. Carbon is a component that contributes to combustion, and heavy metals that can be separated are lead, zinc, cadmium, antimony, selenium, arsenic, and thallium.

When the above combustible material is put into a part of the cement kiln below 900 ° C., most of the metal burns before reaching the region where the heavy metals efficiently volatilize, and it is difficult to sufficiently increase the volatility of the heavy metals. On the other hand, if it is introduced into a portion of 1300 ° C. or higher, the color of the cement becomes yellow, which causes a problem in terms of cement quality. By injecting combustible materials into the above temperature range, the volatilization rate of heavy metals at the bottom of the kiln in the cement kiln can be effectively improved, and heavy metals to chlorine bypass dust using the chlorine bypass system By increasing the concentration rate, the removal rate of heavy metals from the cement manufacturing process can be increased.

In the above cement manufacturing method, the heavy metals can be volatilized at a volatility rate of 80% or more in the region of the cement kiln.

Further, in the cement manufacturing method, when the carbon content of the combustible material is α mass%, and the amount of the combustible material containing the carbon content to be charged into the cement kiln is β kg per clinker production amount t, And β can be 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 volatility of heavy metals. On the other hand, when the product of α and β exceeds 5000, more carbon is added. However, the volatilization rate of heavy metals has reached its peak, and when it is purchased as a valuable product, the cost required for using the combustible material is increased, which is not realistic.

Furthermore, in the cement manufacturing method, a dry dust collector or a wet dust collector can be used to collect dust from the extracted combustion gas.

In the cement manufacturing method, when supplying the combustible material to a region of 900 ° C. or higher and 1300 ° C. or lower of the cement kiln, the combustible material is introduced into the kiln bottom of the cement kiln or the carbon-containing material is decomposed at a time difference. Either put into a preheater attached to the cement kiln while being covered with a substance to be decomposed in the above, or put the combustible material directly into the kiln from the inlet provided in the body of the cement kiln Can be used.

Further, in the above cement production method, the combustible material is coke, coal tar pitch, tire, coal, anthracite, bituminous coal, lignite, lignite, graphite, flame retardant plastic, phenol resin, furan resin, thermosetting resin, cellulose. , Charcoal, waste toner, mixed coke, fine coke, electrode scrap, activated coke, carbide, and one or more selected from the group consisting of unburned carbon contained in fly ash.

Furthermore, in the said cement manufacturing method, the said combustible material can be thrown into the said cement kiln, after adjusting a particle size by granulation or / and classification. If the combustible material has a small diameter, the gas passing through the kiln is scattered to the low temperature side, so that the supply amount of heavy metals to the volatilization temperature region is reduced and an efficient volatilization rate cannot be ensured. As a guide, when the particle size of the combustible material is d _p and the gas wind velocity at the input is V _p , the Stokes settling velocity equation, d _x ² = (18 × μ × V _p ) / ((ρ _p -ρ _g ) × g) When d _x obtained from _dg <d _x , it is preferable to adjust the particle size by granulation or classification so that the particle size is not less than d _x . Here, μ is a gas viscosity, ρ _p is a combustible density, ρ _g is a gas density, and g is a gravitational acceleration. As for the maximum particle size, if it is too large, the mixture will not be combusted until it is mixed into the cement or forms a cement mineral, and the color of the cement will become yellow, which may be a problem in terms of cement quality. Since there is a concern, it is preferable to make the size that does not affect them.

In the above cement manufacturing method, the combustible material may have a particle size of 1 mm to 50 mm. When the particle size of the combustible material is less than 1 mm, the supply amount of heavy metals to the volatilization temperature region decreases, and an efficient volatilization rate cannot be ensured. On the other hand, when the particle size of the combustible material exceeds 50 mm There is a concern that mixing of heavy metals into the cement and the color of the cement exhibiting a yellow color will cause problems in cement quality.

As described above, according to the present invention, heavy metals are efficiently separated from the cement manufacturing process while ensuring the safety of the cement manufacturing apparatus and avoiding an increase in environmental load without affecting the cement quality. be able to.

Next, embodiments of the present invention will be described with reference to the drawings. In the following description, a case where lead which is one of heavy metals is separated by the cement manufacturing method according to the present invention will be described as an example.

FIG. 1 shows a cement manufacturing apparatus to which a cement manufacturing method according to the present invention is applied. This cement manufacturing apparatus 1 includes a kiln bottom 2a (a calcining furnace 3 and an outermost kiln 3) of a cement kiln (hereinafter abbreviated as “kiln”). A charging device 5 for charging the combustible material C is provided at an end portion where the lower cyclone 4 is provided.

On the other hand, as shown in FIG. 2, the kiln 2 is provided with a chlorine bypass device 10, and extracted gas from the kiln exhaust gas flow path from the kiln bottom 2 a of the kiln 2 to the lowermost cyclone 4 (see FIG. 1). Is cooled by the cool air from the cooling fan 12 in the probe 11 and then introduced into the classifier 13 and separated into coarse dust, fine powder and gas. The coarse powder dust is returned to the kiln system, and fine powder (chlorine bypass dust) containing potassium chloride (KCl) and the like is collected by the dust collector 14. The exhaust gas discharged from the dust collector 14 is returned to the exhaust gas passage such as a preheater attached to the kiln 2 or an outlet of the preheater via the fan 15.

Next, the cement manufacturing method according to the present invention using the cement manufacturing apparatus 1 will be described.

In FIG. 1, the combustible C is charged into the kiln bottom 2 a of the kiln 2 by the charging device 5 during cement firing in the kiln 2. This combustible C contains 20% by mass or more of carbon, and includes, for example, coke, coal tar pitch, tire, coal, anthracite, bituminous coal, lignite, lignite, graphite, flame retardant plastic, phenol resin, Furan resin, thermosetting resin, cellulose, charcoal, waste toner, mixed coke, fine coke, electrode scrap, activated coke, carbide, unburned carbon contained in fly ash, and the like are used. The reason why the combustible C having such a carbon content is added is as follows.

FIG. 3 is a graph showing the test results of lead volatilization rate using an electric furnace, and the raw material before entering the kiln 2 collected from the cement manufacturing process in the electric furnace (raw material discharged from the lowest cyclone 4) 50 coke (fixed carbon 87% = α) is added to 1000 (corresponding to 50 kg / t-cli. = Β, α × β = 4350) and calcined, and only the raw material discharged from the lowermost cyclone 4 It compares with the case where it puts and baked. As is apparent from the figure, when coke is added, the volatilization rate of lead is significantly increased in the range where the firing temperature is 900 ° C. to 1300 ° C. This temperature range corresponds to the kiln 2 from the kiln bottom 2a to the central portion.

The lead volatilized in the kiln 2 is included in the gas extracted by the probe 11 in FIG. 2, and the extracted gas is cooled by the probe 11 and then introduced into the classifier 13 to collect coarse dust, fine powder and gas. The fine powder is recovered by the dust collector 14. This fine powder contains more of the lead than the conventional amount of lead, so the lead is concentrated more than before. By separating this lead, the lead can be efficiently removed from the cement manufacturing process, and the cement produced in the kiln 2 The lead content of clinker can be reduced.

As shown in Table 1, combustible material A (fixed carbon content 30% by mass) was used as an example, and combustible material B (fixed carbon content 17% by mass) was used as a comparative example. 5 was used to compare lead volatilization rates.

As shown in Table 2, as an example, the amount of combustible A input was changed over three levels, a three-day test was performed for each level, and the raw material (a) before entering the kiln 2 and after passing through the kiln 2 Clinker (product) (b) was collected, and the lead volatilization rate was calculated by the following formula. (1-b / a) × 100%. In this formula, a represents the lead content of the raw material, and b represents the lead content of the clinker. On the other hand, as a comparative example, the input amount of the combustible B was changed over three levels, a test was conducted for three days for each level, and the lead volatilization rate was measured in the same manner as in the examples. In addition, in this comparative example, the input amount of the combustible A was kept constant.

In both the examples and comparative examples of Table 2, the clinker production amount of the kiln 2 at the time of the test was 285 t / h, so when the input amount of the combustible A is 2 t / h of level 1,
2000 kg / h ÷ 285 t / h = 7 kg / t-cli. It becomes.
Therefore, at level 1 of the example, 7 kg / t-cli. = Α, fixed carbon 30% of combustible A = β = α × β = 210.
Further, when calculated in the same manner, at level 2 of the example, 3.5 kg / t-cli. If α = α and fixed carbon 30% of combustible A = β, then α × β = 105.

The above test results are shown in FIG. 4. As is apparent from FIG. 4, in the comparative example, there is no change in the lead volatilization rate at levels 1 to 3, whereas in the example, from level 1 to level 3. As it goes, that is, as the input amount of the combustible A is decreased, the lead volatilization rate is gradually decreased. Thereby, it turns out that injection | throwing-in of combustible material with a fixed carbon content of 30 mass% contributes to the rise in lead volatility.

Next, as shown in Table 3, as an example, the input amount of combustible material C (fixed carbon 87% = α) was changed over four levels in a kiln 2 with a clinker production amount of 85 t / h. The raw material (a) before entering the kiln 2 and the clinker (product) (b) after passing through the kiln 2 are sampled without putting the combustible C into 2 and the lead volatilization rate is calculated using the above formula. It was measured. As is clear from the table, the lead volatilization rate does not reach 80% in the comparative example, whereas the lead volatilization rate is improved as the amount of combustible C input is increased in the example.

In the above embodiment, the combustible C is introduced into the kiln bottom 2a of the kiln 2 by the charging device 5. However, the kiln 2 is covered with a substance that decomposes at a temperature so as to decompose the carbon-containing substance at a time difference. May be added to the pre-heater attached to the pre-heater, and when the carbon-containing material charged into the pre-heater reaches the region of 900 ° C. or higher and 1300 ° C. or lower of the kiln 2, The same effect is produced. Further, the combustible material C can be directly introduced into the kiln 2 from the entrance provided in the body portion of the kiln 2.

Moreover, in the said embodiment, although the case where lead was isolate | separated from chlorine bypass dust was illustrated, lead, zinc, cadmium, antimony, selenium, arsenic, and thallium can also be separated in the same manner as described above. .

It is the schematic which shows an example of the apparatus for enforcing the cement manufacturing method concerning this invention. It is a flowchart which shows the whole structure of the chlorine bypass apparatus attached to a cement baking furnace. It is a graph which shows the test result of the volatility of lead using an electric furnace. It is a graph which shows the test result of the cement manufacturing method concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cement manufacturing apparatus 2 Cement kiln 2a Kiln bottom 3 Calciner 4 Bottom-stage cyclone 5 Input apparatus 10 Chlorine bypass apparatus 11 Probe 12 Cooling fan 13 Classifier 14 Dust collector 15 Fan

Claims

Supplying a combustible containing 20% by mass or more of carbon to a region of 900 to 1300 ° C. of the cement kiln;
A part of the combustion gas is extracted from the kiln exhaust gas path from the bottom of the cement kiln to the bottom cyclone,
Collecting dust contained in the combustion gas;
A cement manufacturing method, characterized in that heavy metals are separated from dust collected.
The cement manufacturing method according to claim 1, wherein the heavy metals are volatilized at a volatility rate of 80% or more in the region of the cement kiln.
When the carbon content of the combustible material is α mass% and the amount of the combustible material containing the carbon content to be added to the cement kiln is β kg per clinker production amount of 1 kg, the product of α and β is 30 or more and 5000 The cement manufacturing method according to claim 1 or 2, wherein:
4. The method for producing cement according to claim 1, wherein a dust collector or a wet dust collector is used to collect dust from the extracted combustion gas.
In supplying the combustible material to the cement kiln in the region of 900 ° C. to 1300 ° C., the combustible material is put into the kiln bottom of the cement kiln or covered with a material that decomposes at a temperature that decomposes the carbon-containing material with a time difference. It is used to either put in a preheater attached to the cement kiln in a broken state or to put the combustible material directly into the kiln from an inlet provided in the body of the cement kiln. The cement manufacturing method according to any one of claims 1 to 4.
Coke, coal tar pitch, tire, coal, anthracite, bituminous coal, lignite, lignite, graphite, flame retardant plastic, phenol resin, furan resin, thermosetting resin, cellulose, charcoal, waste toner, mixed coke The cement according to any one of claims 1 to 5, wherein the cement is one or more selected from the group consisting of unburned carbon contained in fine coke, electrode scrap, activated coke, carbide and fly ash. Production method.
The cement manufacturing method according to any one of claims 1 to 6, wherein the combustible material is adjusted in particle size by granulation or / and classification, and then charged into the cement kiln.
The cement manufacturing method according to claim 7, wherein a particle size of the combustible material is 1 mm or more and 50 mm or less.