JP2008239394A - Method for producing cement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing cement effectively reutilizing waste materials including asbestos and calcium by detoxification treatment thereof, particularly by using the detoxification-treated waste materials including asbestos and calcium as resources of gypsum by preventing asbestos dust or the like from scattering or diffusing. <P>SOLUTION: The method for producing cement comprises impregnating the waste materials including asbestos and calcium with an aqueous alkali solution to render the asbestos included in the waste material converted into non-asbestos state, then neutralizing the residual alkali in the waste material converted into non-asbestos state with sulfuric acid and at the same time reacting the included calcium with the sulfuric acid to produce gypsum, and compounding the detoxification-treated matter as gypsum resources on production of cement. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing cement, and more particularly to a method for producing cement using waste materials containing asbestos and calcium.

  Conventionally, asbestos has been used widely in various fields because strength does not decrease over a long period of time. Slate plates, water pipes, fireproof coatings, brake pads, gaskets, heat insulation plates, ropes, packing, acetylene Although it has been used for many members as a filling material for cylinders, in recent years, asbestos has been revealed to cause many health problems such as cotton lung, lung cancer, malignant mesothelioma, and its use is prohibited.

In particular, conventional gypsum boards are excellent in fire resistance, sound insulation and heat retention, and are therefore often used as fireproof coverings for sprayed construction products, ceilings, wall materials, etc. Contained asbestos.
These asbestos-containing members that have been used in large quantities are dangerous to continue to use as they are for the above environmental reasons, and must be promptly disposed of and detoxified. .

Conventional asbestos-containing waste has been treated as general waste and is now disposed of as industrial waste, but asbestos scatters and is a problem, and urgent safety measures are required. .
Moreover, the effective use of the waste material containing asbestos is not progressing now.

  In particular, the demolition of buildings using building materials such as gypsum board containing asbestos, such as fireproof coverings and collapsed ceiling boards, has peaked, but the problems of asbestos exposure and the scattering and dissipation of asbestos are serious. It has become.

Such asbestos is a naturally occurring mineral fiber, for example, serpentinite chrysotile (3MgO.2SiO ₂ .2H ₂ O) amphibole-based amosite ((Mg, Fe) ₇ Si ₈ O ₂₂ (OH) ₂ ), crocidolite (Na ₂ Fe ₃ ²⁺ Fe ₂ ³⁺ Si ₈ O ₂₂ (OH) ₂ ), anthophyllite (Mg ₇ Si ₈ O ₂₂ (OH) ₂ ), tremolite (Ca ₂ Mg ₅ Si ₈ O ₂₂ ( _OH) 2), actinolite _{(Ca 2 (Mg, Fe)} 5 Si 8 O 22 (OH) 2) can be mentioned.
Such serpentine chrysotile is known to dehydrate and transform at about 700 ° C. when heated and to be harmless forestlite (2MgO · SiO ₂ ) at about 900 ° C. Therefore, it is difficult to achieve effective utilization.

  Since the harmfulness of such asbestos is derived from the fiber, Patent 3680958 (Patent Document 1) discloses a method of detoxifying the fiber by modification and melting of cement using a rotary kiln. A manufacturing method, characterized in that asbestos waste material is supplied into the rotary kiln from the vicinity of the combustion means provided on the discharge port side of the rotary kiln, and the supplied asbestos waste material and cement raw material are processed by the combustion means. A cement manufacturing method is described.

  JP-A-2005-279589 (Patent Document 2) discloses a melting agent comprising borax, a mixture of boric acid and sodium carbonate, or a mixture of borax and sodium carbonate without pulverizing slate waste containing asbestos. In a melting furnace filled with a melting agent, the pretreated slate waste is pretreated by placing it in an aqueous solution of the slate and impregnating it with a melting agent from the surface of the slate waste into the voids inside the slate. A method for treating slate waste is characterized in that asbestos in the slate waste is melted and vitrified by being immersed in 780 ° C to 1000 ° C.

  Further, JP-A-2006-52177 (Patent Document 3) converts an inorganic material waste material into a cement manufacturing kiln together with a cement manufacturing raw material, and converts it into cement by heat treatment. In the method for treating waste materials of inorganic materials, the size of the waste material is the minimum value of 1 mm or more, the maximum value is 1/10 or less of the inner diameter of the cement manufacturing kiln and the surface of the waste material is at any location inside the waste material. Adjust the dimensions so that the shortest distance is within the range of 30 mm or less, and the ratio of the waste material to the total amount of the waste material and the cement raw material is in the range of 1 to 20% in terms of mass ratio in the dry state. In addition, it is put into the kiln for cement production from the kiln bottom of the kiln, heat-treated at 1000 to 1500 ° C. for 20 to 60 minutes to obtain a sintered body, and the obtained sintered body is pulverized. Method of processing scrap mineral-based material, wherein bets are described.

In the conventional methods described in each of the above patent documents, asbestos-containing waste is detoxified by introducing it into a melting furnace or cement kiln.
However, when supplying asbestos-containing waste to a melting furnace or cement kiln, it is not possible to prevent the asbestos from being scattered or released, and in the above conventional method, asbestos-containing waste material is crushed as a pretreatment, In order to decompose or form fine cracks, etc., asbestos-containing waste materials are destroyed mainly using mechanical means such as heavy machinery, etc., so that asbestos is scattered and dissipated, in the detoxification process The current situation is that the problem of health effects on the human body has not been fully resolved.
Furthermore, since it is necessary to melt from the beginning in the detoxification process of the asbestos-containing waste material, energy consumption is also great.
Patent No. 3680958 JP 2005-279589 A JP 2006-52177 A

An object of the present invention is to provide a method for producing cement in which waste materials containing asbestos and calcium are rendered harmless and effectively reused.
In particular, asbestos and calcium-containing waste material containing asbestos dust is prevented from being scattered and released, detoxifying with low energy consumption, and reacting calcium contained in the waste material with sulfuric acid to produce gypsum. Another object of the present invention is to provide a method for producing cement using the detoxified product as a gypsum source.

  The present inventors impregnated asbestos and calcium-containing waste material in an alkaline aqueous solution, alkali wet pulverization treatment to make asbestos harmless, react calcium and sulfuric acid contained in the waste material to produce gypsum, It has been found that it can be used as a gypsum source during production, and the present invention has been achieved.

In the method for producing cement according to claim 1 of the present invention, a waste material containing asbestos and calcium is wet-ground in an alkaline aqueous solution so as to make asbestos contained in the waste material non-asbestos, and then the non-asbestos waste material by sulfuric acid. A method for producing cement, comprising neutralizing a residual alkali in the mixture and reacting calcium contained therein with the sulfuric acid to form a detoxification treatment product that forms gypsum as a gypsum source during cement production It is.
Preferably, the cement manufacturing method according to claim 2 is characterized in that, in the cement manufacturing method according to claim 1, the detoxification-treated product is a waste material generated by disassembling asbestos and cement-containing spraying waste material. And

A method for producing a cement according to claim 3 is the method for producing a cement according to claim 1 or 2, wherein the detoxified product is mixed with a cement clinker as a gypsum source.
The method for producing a cement according to claim 4 is the method for producing a cement according to any one of claims 1 to 3, wherein the alkaline aqueous solution is caustic such as sodium hydroxide, potassium hydroxide or calcium hydroxide. It is an aqueous solution of an alkali, an alkali carbonate such as sodium carbonate or potassium carbonate, or a mixed aqueous solution thereof.

The method for producing cement according to the present invention is capable of safely and completely detoxifying asbestos and calcium-containing waste materials, and producing cement by effectively using it as a gypsum source during cement production with a small amount of energy consumption. be able to.
By pulverizing the asbestos and calcium-containing waste material, harmful needle-like crystals are destroyed, and the aspect ratio is reduced, thereby reducing the harmfulness due to physical shape change.

In particular, asbestos and calcium-containing waste materials are wet pulverized in an alkaline solution, in addition to reducing toxicity due to physical shape change due to reduction in aspect ratio due to pulverization, and by mechanochemical reaction due to pulverization energy in the presence of alkali. Since the structural destruction of asbestos is efficiently promoted, the processed material can be rendered harmless in a short time.
Moreover, since the waste material containing asbestos and calcium can be effectively used for cement, there is no waste in processing the waste material.

The present invention will be described with reference to the following best mode examples, but is not limited thereto.
The method for producing a cement according to the present invention comprises converting asbestos contained in the waste material into non-asbestos by wet-grinding the waste material containing asbestos and calcium in an alkaline aqueous solution, and then removing residual alkali in the non-asbestos waste material that has been converted into non-asbestos with sulfuric acid. A detoxified product obtained by neutralizing and reacting calcium contained with the sulfuric acid to produce gypsum is blended as a gypsum source during cement production.

In this way, waste materials containing asbestos and calcium can be rendered environmentally safe and completely detoxified by using a mechanochemical treatment with an alkaline wet grinding process, and also react with sulfuric acid to produce gypsum. Thus, the detoxified processed product in which gypsum is produced can be effectively used as a gypsum source.
Therefore, the effective utilization of the waste material containing asbestos and calcium can be promoted with a small energy consumption.

  The waste material containing asbestos and calcium that can be used in the method for producing cement according to the present invention is not particularly limited. For example, asbestos and cement-containing gypsum board, cement-based asbestos-containing spray waste material, etc. Any waste material containing asbestos and calcium that has been used can be used as a target, and in particular, asbestos and calcium-containing spraying construction, in which a large amount of emissions will be expected in the future, and asbestos scattering / release will be a particular problem. Waste materials generated by dismantling products can also be used effectively.

In addition, the recovered gypsum board containing asbestos and calcium contains organic additives such as paper fiber and paste. However, when the method of the present invention is applied, pulverization treatment, alkali treatment, acid treatment, etc. It can be easily separated in the course of processing.
The calcium contained in the waste material is not only calcium itself, but also minerals contained in cements such as calcium oxide, calcium hydroxide, alite, belite, calcium aluminate, and ferrite, which function as a calcium source, or these A compound such as a hydrate is also included.

In the method for treating a waste material containing asbestos and calcium according to the present invention, first, the asbestos and calcium-containing waste material is impregnated in an alkaline aqueous solution, and wet pulverized.
Specifically, first, asbestos and calcium-containing waste material may be impregnated in an alkaline aqueous solution.
By such a process, the process of pulverizing so that asbestos does not scatter and disperse and the alkali wet pulverization process of making asbestos and detoxifying the asbestos and calcium-containing waste material can be suitably performed simultaneously.
That is, by pulverizing the asbestos and calcium-containing waste material, harmful needle-like crystals are destroyed, and the aspect ratio is reduced, thereby reducing the harmfulness due to physical shape change.
In particular, in addition to reducing toxicity due to physical shape change due to reduction in aspect ratio due to pulverization, the mechanochemical reaction by pulverization energy in the presence of alkali further promotes the structural destruction of asbestos. Can be detoxified.

By such alkali treatment, the structure forming the Si—O or FeO skeleton of asbestos can be destroyed, and therefore the acicular crystals can be broken.
Further, the aspect ratio of the asbestos needle crystal can be reduced, and the needle crystal structure can be made a structure close to a cubic structure.

Alkaline aqueous solution that can be used when impregnating asbestos and calcium-containing waste materials into an alkaline aqueous solution while being pulverized and made sufficiently non-asbestos detoxified is sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. Examples thereof include alkalis, alkali carbonates such as sodium carbonate and potassium carbonate, and mixed aqueous solutions thereof.
The concentration of the asbestos is not particularly limited as long as it causes a reaction to make asbestos non-asbestos. However, the higher the concentration, the more harmless treatment can be performed in a short time and in a large amount.
What is necessary is just to set the density | concentration of aqueous alkali solution suitably according to the condition on the spot.

Asbestos and calcium-containing waste materials are made non-asbestos and detoxified by wet grinding under these alkaline aqueous solutions.
Therefore, the asbestos- and calcium-containing waste material can be safely used as a gypsum source as a cement raw material, as a detoxified processed product that has become safe to handle.

  Here, asbestos detoxification or non-asbestos formation means that asbestos is finely pulverized to have a particle shape with an aspect ratio of less than 3, or asbestos undergoes a mechanochemical reaction in an alkaline aqueous solution to produce chrysotile, crocidolite, It represents a state in which needle-like crystals such as amosite have been converted into other substances, and such a state means that the state does not affect the health of the human body.

As the pulverizing means, known means for pulverizing building material waste materials can be used.
For example, a medium stirring mill, a tower mill, a vibration mill, a ball mill, a planetary mill, or the like is used.
By pulverizing, the contact area between the asbestos-containing waste material and the alkaline aqueous solution can be increased, and detoxification can be effectively performed.
Moreover, the temperature of alkaline aqueous solution rises to about 70-80 degreeC by grind | pulverizing. Therefore, the temperature rise can be made more harmless more efficiently.

The pulverized product pulverized by the pulverizer is classified by a classifier such as a wet cyclone.
Of the classified particles, the coarse particles are returned to the pulverizer, and the fine particles are discharged out of the system as a detoxified product.
The operating conditions such as pulverization time, pulverized ball diameter, slurry concentration in the case of wet pulverization, and classification conditions are determined by performing a test operation in advance for each equipment to be used.
In the test operation, fine particles after classification are sampled and the content of chrysotile, crocidolite, amosite, etc. is less than 0.1% as measured by X-ray diffraction, or a phase contrast microscope, polarizing microscope, scanning type The operating conditions are determined so that the aspect ratio is less than 3 as measured by any of the electron microscopes.

In particular, when performing the alkali treatment of asbestos and calcium-containing waste material, it is preferable to crush the waste material in a sealed state and then wet pulverize it in an aqueous alkaline solution.
When the size of the waste material is large, it is desirable to perform such crushing treatment before alkali treatment.

Here, the sealed state means a state in which asbestos is not in direct contact with free air in the working environment (excluding the air in the sealed space), for example, a crusher that can be sealed by a case is sealed. State, a state in which the transfer means from the crusher to the wet pulverizer is sealed by a case, a sealed state realized by using a wet pulverizer that can be sealed by the case, or preferably, an asbestos-containing waste material is alkalinized. The state etc. which were immersed in aqueous solution are mentioned.
Specifically, a crusher, a transfer means, a wet pulverizer, etc. are arranged, and each of these devices, such as a method of covering each of these devices with a single sealed case, and a crusher, a transfer means, a pulverizer, etc. The method of sealing with the case etc. of this is mentioned.

In particular, when the asbestos and calcium-containing waste material is immersed in an alkaline aqueous solution and crushed, the step of pulverizing the asbestos so that it is not scattered or released and the alkali treatment step can be preferably performed simultaneously. In this case, the crushing process may be performed as it is after the crushing process.
Since it is sufficient that the asbestos and calcium-containing waste material be in a wet state with at least an alkaline aqueous solution, the crushing may be performed while the asbestos and calcium-containing waste material is immersed in the alkaline aqueous solution as described above, or If the asbestos and calcium-containing waste material is immersed in an alkaline aqueous solution to be in a wet state, it may be taken out from the alkaline aqueous solution and crushed.
When the asbestos-containing waste material is immersed in an alkaline aqueous solution to be subjected to alkali treatment and crushed, the pulverization treatment may be performed as it is after the crushing treatment.
In this case, the waste material containing asbestos and calcium is simultaneously crushed, pulverized, and alkali-treated while immersed in an alkaline aqueous solution.

The crushing process that is performed as necessary is, for example, that alkali is difficult to permeate in relatively dense asbestos and calcium-containing waste materials such as slate materials, so such asbestos and calcium-containing waste materials are first crushed in a sealed state. To do.
On the other hand, for example, if the pretreatment by the cracking process or the crushing / crushing process is performed in an open state without sealing, there arises a new problem of asbestos scattering and diffusion.
Therefore, it is particularly effective for relatively dense asbestos and calcium-containing waste materials such as slate plates.
In this way, asbestos and calcium-containing waste material is crushed as necessary, so that asbestos can be made non-asbestos and detoxified by pulverization treatment (wet pulverization) in an alkaline aqueous solution. Even if it exists, it can do easily and it becomes possible to implement this detoxification time in a short time.

As a means for crushing, a known means for crushing building material waste can be used.
For example, there are impact crushers, hammer crushers, jaw crushers, rotary crushers, shredders and the like.
Thus, by crushing, it becomes easy to pump a waste material having a large shape to a pulverizer, and the specific surface area of the waste material can be increased so that harmlessness with an alkaline solution can be efficiently achieved.
When the asbestos and calcium-containing waste material is crushed in a sealed state as necessary, the crushed waste material is then pumped to, for example, a wet pulverizer under an alkaline aqueous solution and further wet pulverized.
When pumping from a crusher to an alkaline wet crusher, the particle size of the pulverized product is preferably 3 mm or less, more preferably so that clogging at the time of pumping and capacity reduction in the crushing process are not made. It is good to set it as 1 mm or less.

  In the crushing and / or crushing step, it is possible to heat and pressurize as necessary, so that the detoxification treatment of the waste material can be performed in a shorter time.

Next, the asbestos and calcium-containing waste material detoxified product that has been physically and chemically detoxified by pulverization is sufficiently immersed in sulfuric acid to neutralize residual alkali in the detoxified product, and Since calcium contained in the waste material reacts with sulfuric acid to produce gypsum, it can be used as a gypsum source that is a raw material for cement.
The concentration is not particularly limited, and may be set as appropriate according to the situation at the site.
In the neutralization treatment, the detoxified product after the pulverization treatment is put into an agitator, neutralized with sulfuric acid, and the acid is rinsed with a decanter.
Then, it can be dehydrated using a high-speed decanter, a filter press, or the like to form a cake.
By performing the dehydration treatment, it is possible to remove excess alkali, alkali salt and moisture from the detoxified product, and to prevent deterioration in quality due to an increase in the amount of alkali in the cement to be produced.

The detoxified asbestos and calcium-containing waste material is used for the production of cement.
In order to manufacture cement, generally, it is divided roughly into a raw material process, a baking process, and a finishing process, and a cement clinker is prepared through a baking process.
Next, in order to produce cement powder, gypsum having a function of adjusting the hardening rate of cement is added to a cement clinker, and the mixture is pulverized to form a powder.
In the present invention, the detoxified product of waste material obtained by the sulfuric acid treatment is used as a gypsum source to be mixed with cement clinker in the finishing step.

As shown in FIG. 1, specifically, for example, a cement clinker supplied from a cement clinker silo 1 in which cement clinker is stored is first pulverized by a preliminary pulverizer 3.
The waste material that has been detoxified and produced by gypsum is stored in the gypsum yard 2 as a gypsum source.
The pre-ground cement clinker and the detoxified waste material generated from the gypsum yard 2 and produced with gypsum are introduced into a cement crusher (finishing mill) 4 and pulverized and mixed.
The obtained pulverized mixture is introduced into the separator 5, and a powder having a desired particle size range is obtained as Portland cement 7.

Further, the cement powder having a large particle size in the separator 5 is again introduced into the cement pulverizer (finishing mill) 4 and pulverized.
If necessary, fly ash or blast furnace slag powder is added to the cement powder adjusted to the desired particle size range by the separator 5 and mixed uniformly by the mixer 6 to prepare fly ash cement or blast furnace cement 8. You can also

In addition, the waste material which the gypsum produced | generated by the detoxification process contains gypsum as an active ingredient, and the detoxification product which asbestos converted as an impurity.
On the other hand, for example, when producing ordinary Portland cement, the blending ratio of gypsum in the cement is about 2 to 3% by weight in terms of SO ₃ .
Accordingly, the blending limit of the detoxified product to ordinary Portland cement can be up to about 2-3 wt% in terms of SO ₃ .

  The cement thus obtained has stable performance as a cement, and can be reused as cement by completely detoxifying asbestos and calcium-containing waste materials.

  The method for producing cement according to the present invention is to produce a stable cement using recycled products by effectively using asbestos and calcium-containing waste materials, particularly asbestos and calcium-containing waste materials generated by dismantling building materials. It becomes possible to apply.

Process drawing which shows roughly the finishing process which manufactures cement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cement clinker silo 2 Gypsum yard 3 Preliminary grinder 4 Cement grinder 5 Separator 6 Mixer 7/8 Cement silo

Claims (4)

Asbestos contained in the waste material is made non-asbestos by wet pulverization of the waste material containing asbestos and calcium in an alkaline aqueous solution, and then the residual alkali in the non-asbestos waste material is neutralized with sulfuric acid and contained calcium. A method for producing cement, characterized in that a detoxified product produced by reacting with sulfuric acid to produce gypsum is blended as a gypsum source during cement production. The method for producing cement according to claim 1, wherein the detoxified product is a waste material generated by disassembling asbestos and cement-containing spray waste material. 3. The method for producing a cement according to claim 1, wherein the detoxified product is mixed with a cement clinker as a gypsum source. The method for producing cement according to any one of claims 1 to 3, wherein the aqueous alkaline solution is an aqueous solution of caustic alkali or alkaline carbonate, or a mixed aqueous solution thereof.

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