JP2008247660A - Method for decreasing chlorine and alkali component in clinker and method for decreasing chlorine and alkali component in cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for decreasing chlorine and an alkali component in cement, in which chlorine, which is contained in a clinker and corrodes a reinforcing bar, and the alkali component, which is also contained in the clinker and causes an alkali-silica reaction, are decreased by a simple method and the chlorine-/alkali component-decreased clinker is used to simultaneously decrease the chlorine and alkali component in cement. <P>SOLUTION: The method for decreasing chlorine and the alkali component in the clinker comprises a step of washing the clinker with water to simultaneously decrease the chlorine and alkali component in the clinker. The method for deceasing chlorine and the alkali component in cement comprises the steps of: washing the clinker with water to simultaneously decrease the chlorine and alkali component in the clinker; adding gypsum to the water-washed clinker; crushing the gypsum-added clinker uniformly to obtain a crushed mixture; and mixing the crushed mixture. In particular, a fired clinker can be used suitably as the clinker. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for reducing chlorine and alkali components in a clinker, and a method for reducing chlorine and alkali components in a cement composition, and particularly harmful to the chlorine that causes corrosion of reinforcing bars in a reinforcing bar structure and further to alkali silica reaction. The present invention relates to a method for reducing alkali components from a clinker used in a cement composition, and a method for reducing chlorine and alkali components in a cement composition by using the clinker from which the chlorine and alkali components have been removed.

Normally, cement contains chlorine, and this chlorine causes corrosion of the reinforcing bars and steel frames of the reinforcing bar structure, and reduces the resistance of the concrete structure.
Moreover, the alkali component contained in the cement causes an alkali silica reaction (ASR) in which an aggregate containing alkali hydroxides (NaOH and KOH) derived from alkali contained in the cement and a certain type of silica mineral reacts. Abnormal expansion occurs in concrete, and it is a cause of cracks.
Therefore, reduction of chlorine and alkali components contained in the cement composition is desired.

In recent years, kiln dust at the time of cement production has been re-introduced into the cement raw material and reused to produce cement. However, in terms of ingredients, it contains a large amount of chlorine and alkali components. It is not preferable in terms of quality.
In addition, various industrial wastes are used as a part of raw materials for cement production, and are being actively reused for general wastes. Therefore, it is not preferable in terms of cement production and cement quality.

The chlorine content which becomes a problem when the dust or the like is used as a raw material for cement is 0.035% by mass or less for ordinary Portland cement according to Japanese Industrial Standard (hereinafter referred to as “JIS standard”), and 0 for other cements. 0.02% by mass or less.
Further, the alkali component in the JIS _standard defines a 0.75 wt% or less Na 2 Oeq.

In view of this point, a dechlorination bypass technology for extracting dust containing a large amount of chlorine from a cement production line has been developed, and is actually installed and operated in a cement plant.
In addition, the dust is mixed with warm water in a dissolving tank to dissolve chlorine and the like, and then the solution is dehydrated to reduce the chlorine by using a facility for washing the dust and the like to obtain a cement raw material.

  Japanese Patent Application Laid-Open No. 10-76239 discloses a method of solidifying a salt content such as chlorine recovered by washing the dust extracted from the cement kiln exhaust gas with water and evaporating the filtrate to dryness. Has been.

  Further, JP-A-2005-288328 discloses that incineration ash slurry in which incineration ash and water are mixed is introduced with carbon dioxide gas to be washed, and the incineration ash slurry is crushed by a wet pulverizer, and washed ash slurry. Is separated into washing ash and water to be treated, and the separated water to be treated is concentrated by a circulation type filtration device, the water to be treated is filtered by a circulation type filtration device, and the water to be treated is concentrated by the circulation type filtration device. A method for cleaning incinerated ash in which suspended solids contained in treated water are fired at a high temperature in a high-temperature firing furnace is disclosed.

  However, in these conventional methods, the dust is extremely small and light, so that the dust floats on the surface of the water or repels and does not dissolve uniformly in the water, or it takes time to form a uniform slurry. This will increase the time required for dissolution. In addition, the dissolution tank must be enlarged to ensure the required dissolution time.

  Also, incineration ash may adhere to the inner surface of the dissolution tank and produce incineration ash solids in the dissolution tank, and if this solids grows and falls into the solution, the solution outlet is blocked. As a result, the equipment operation rate decreases.

  On the other hand, in the clinker firing furnace when producing clinker, the coating containing chlorine or the like in a high concentration may fall off and may be mixed in the clinker produced as an intermediate product when producing cement. There is a current situation that contains chlorine and alkali components.

Thus, conventionally, there is a technique for desalting during clinker raw material or clinker firing, but suddenly high chlorine / high alkali content coating as described above is dropped and mixed, and chlorine and alkali components are Clinkers exceeding the JIS standard can no longer be used for commercialization, and measures such as raw material return have to be taken.
Therefore, a method capable of reducing chlorine / alkali components from the clinker after firing in such a sudden situation has been desired.
JP-A-10-76239 JP 2005-288328 A

It is an object of the present invention to provide a method for reducing chlorine and alkali components in a clinker, which can reduce the alkali components contained in the clinker and causing alkali silica reaction with chlorine that corrodes reinforcing bars, by a simple method. is there.
Furthermore, the object of the present invention is to reduce chlorine and alkali components from the clinker after firing to JIS standards or less even after the clinker contains the chlorine and alkali components in an amount exceeding the JIS standard. It is to provide a method for reducing chlorine and alkali components in clinker.
Another object of the present invention is to provide a method for reducing chlorine and alkali components in cement, which can simultaneously reduce chlorine and alkali components in cement by using the clinker.

As a result of studies conducted in view of the prior art, the present inventors have found that the above object can be achieved by washing the clinker with water, and have completed the present invention.
That is, the method for reducing chlorine and alkali components in the clinker according to the present invention is a method for reducing chlorine and alkali components in the clinker, wherein the chlorine and alkali components are simultaneously removed by washing the clinker with water.
Preferably, the clinker is a clinker after calcination, wherein the chlorine content and / or the alkali component content exceeds the JIS standard numerical value. This is a reduction method.

Another aspect of the present invention is to reduce chlorine and alkali components by washing the clinker with water, and then add gypsum to the clinker after the washing and uniformly grind and mix the cement composition. This is a method for reducing chlorine and alkali components.
Preferably, the cleaning is performed immediately before the clinker and gypsum are pulverized and mixed. This is a method for reducing chlorine and alkali components in a cement composition.

According to the present invention, chlorine and alkali components contained in the clinker can be reduced at the same time, and accordingly, chlorine and alkali components in the resulting cement can be reduced.
As a result, it is possible to prevent cracking without corroding the reinforcing bars and steel frames in the reinforced concrete structure and without inducing an alkaline silica reaction.

  Also, in the past, sudden high chlorine / high alkali content coatings dropped out during clinker firing, and clinker whose chlorine and alkali components exceeded the above JIS standards could not be used for commercialization. However, according to the method of the present invention, even a clinker containing a large amount of chlorine and alkali components after firing is effectively used for commercialization without requiring measures such as returning the raw material.

The present invention will be described in detail based on the following preferred embodiments.
The chlorine and alkali component removal method in the clinker of the present invention can remove chlorine and alkali components in the clinker by washing the clinker with water.
Hereinafter, it will be described in detail that the clinker used for manufacturing the cement is washed with water.
The washing method is not particularly limited as long as the clinker can be washed with water, and examples thereof include a method of immersing the clinker in water, a method of washing the clinker with running water, and a method of spraying water on the clinker.

As the clinker used in the present invention, any clinker used for producing a cement composition can be applied, and the composition thereof is not particularly limited. For example, a clinker containing various components such as SO ₃ , MnO, TiO _2, P ₂ O _{5, and} SrO in addition to Cl, K ₂ O, and Na ₂ O may be used.
In particular, in the present invention, the clinker is suitably applied to a clinker after firing, for example, a clinker in which the coating has dropped from the firing furnace during the clinker firing and the chlorine and / or alkali components have exceeded the JIS standard. Can do.

As for the size of the clinker, it is possible to wash the clinker itself usually used in cement production with water, or to elute chlorine and alkali components existing in the clinker by roughly pulverizing to some extent.
By reducing the size by coarse pulverization, the surface area of the clinker that comes into contact with water is increased and water easily penetrates into the interior, so that chlorine and alkali components can be further reduced.

As the washing water, water usually used for washing such as tap water and distilled water can be used.
The temperature of the water is not particularly limited, and usually tap water or the like can be used.
The higher the water temperature, the higher the solubility of chlorine and alkali components, but the hydration reaction of the clinker also proceeds, so that it can be set appropriately according to the situation.

  For example, in the method of immersing clinker in water, the amount of clinker immersed in water is not particularly limited as long as chlorine and alkali components can be dissolved, but if the clinker is immersed in water for a long time, the clinker hydration reaction proceeds. Since there is a fear, it can be set appropriately according to the situation.

When the clinker is immersed in water, the elution of chlorine and alkali components can be promoted by stirring as necessary.
What is necessary is just to set the time to immerse suitably according to water temperature and the amount of clinker.

  Next, the clinker and the immersion water are separated, and a known method can be applied to this separation method, and for example, methods such as filtration and centrifugation can be used.

  Moreover, the method of reducing chlorine and an alkali component can be illustrated by the method of putting a clinker on a belt conveyor and sprinkling it, for example, as the method of watering and cleaning a clinker.

  Thus, the content of the chlorine and alkali components in the cement composition can be reduced by washing the clinker with water and using the clinker in which the chlorine and alkali components are simultaneously reduced in the production of the cement composition.

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 a cement composition powder, gypsum having a function of adjusting the hardening rate of the cement is added to the cement clinker and pulverized to prepare a cement composition.
In the present invention, the clinker washed with water in the finishing step and gypsum are mixed.

Specifically, for example, the cement clinker supplied from the cement clinker silo in which the cement clinker is stored can be washed with water immediately before being pulverized by the preliminary pulverizer.
Since the pulverizing temperature in the mill rises due to pulverization, the pulverizer wets the clinker immediately before being put into the mill, so that the clinker gets wet but can be dried because it is immediately put into the mill.

Such pre-ground cement clinker and gypsum supplied from the gypsum yard are introduced into a cement pulverizer (finishing mill) and pulverized and mixed.
Since the pulverization temperature in the mill rises due to pulverization, the finish pulverizer wets the clinker immediately before being put into the mill, so that the clinker gets wet, but can be dried because it is immediately put into the mill.
Preferably, it is more desirable that the clinker be washed with water just before pulverization with the finishing pulverizer, regardless of whether the clinker is washed with water immediately before preliminary pulverization.
The obtained pulverized mixture is introduced into a separator, and a powder having a desired particle size range is obtained as Portland cement.

Further, the cement powder having a large particle size in the separator may be introduced again into a cement pulverizer (finishing mill) and pulverized.
If necessary, fly ash cement or blast furnace cement can be prepared by adding fly ash or blast furnace slag powder to the cement powder adjusted to the desired particle size range with a separator and mixing uniformly with a mixer. it can.

The invention is illustrated by the following examples, comparative examples and test examples.
Example 1
It has the same composition as the composition shown in Comparative Example 1 in Table 3 and has the “particle size distribution 1” shown in Table 1 and FIG. 2 (excluding the saucer (5% portion of 0.075 mm or less)). As shown in FIG. 1, set the filter paper No. 2 on the funnel and gently put the clinker into the funnel, then sprinkle 10 times the mass of the clinker with distilled water from the top of the funnel. And washed.
At that time, since the funnel was suction filtered by an aspirator, the clinker was immediately dried at 130 ° C. for 24 hours after washing distilled water flowed down.
The cleaned and dried clinker was pulverized by jaw crusher, then pulverized by brown mill, and further pulverized by ball mill (FIG. 3).
Next, dihydrate gypsum (Sumitomo Osaka Cement Gifu Plant; discharged dihydrate gypsum, SO ₃ = 45.13%) so that the amount of SO ₃ contained in the clinker obtained after pulverization is 2% by mass. Were added, mixed, and finished and ground to prepare each cement.

(Example 2)
The above “factory clinker” having the particle size distribution 1 shown in Table 1 and FIG. 2 was subjected to jaw crusher pulverization to make a full JIS sieve 5 mm (sieving mesh).
The particle size distribution of the obtained clinker is shown in Table 1 and FIG. 2 as “jaw crusher pulverized clinker (particle size distribution 2)” (excluding the saucer (5% portion of 0.075 mm or less)).
The particle size distribution of the clinker is a distribution of values measured by a JIS sieve in accordance with JIS A 1102 “Aggregate screening test”.
The clinker pulverized by “jaw crusher (particle size distribution 2)” was washed and dried in the same manner as in Example 1.
Next, the washed and dried clinker was pulverized with a brown mill, then pulverized with a ball mill (FIG. 3), and a cement was prepared in the same manner as in Example 1 using the clinker after pulverization.

(Example 3)
The “jaw crusher pulverization (particle size distribution 2) clinker” having the particle size distribution 2 shown in Table 1 and FIG.
The particle size distribution of the obtained clinker is shown in Table 1 and FIG. 2 as “Brown mill pulverized clinker (particle size distribution 3)”.
The particle size distribution of the pulverized clinker is a distribution measured with a laser diffraction particle size distribution meter (Microtrac MT3300EX, manufactured by Nikkiso Co., Ltd.).
The “brown mill pulverized clinker (particle size distribution 3)” clinker was washed and dried in the same manner as in Example 1.
Next, the cleaned and dried clinker was pulverized with a ball mill (FIG. 3), and a cement was prepared in the same manner as in Example 1 using the clinker after pulverization.

(Comparative example)
“Brown mill pulverized clinker (particle size distribution 3)” in Example 3 having the composition shown in Table 3 was directly used as a comparative example.
A cement was prepared using the clinker in the same manner as in Example 1.

(Test Example 1)
The amount of calcium hydroxide in the clinker obtained in Examples 1 to 3 and Comparative Example 1 was determined as TG-DTA (thermal mass-differential thermal analyzer; (product name Thermo Plus2, manufactured by Rigaku Corporation; measurement condition 10 ° C./min. Temperature) and air flow 150 μl / min)).
The results are shown in Table 3.

(Test Example 2)
The contents of chlorine, sodium oxide, and potassium oxide in the clinker obtained in Examples 1 to 3 and Comparative Example 1 were quantified according to JIS R5202.
The results are shown in Table 3.

(Test Example 3)
Using each cement obtained from Examples 1 to 3 and Comparative Example 1, each mortar was prepared according to JIS R 5201 “Physical Test Method for Cement”.
About each obtained mortar, intensity | strength and setting time were measured according to said JISR5201.
The results are shown in Table 3.

According to Table 1, the clinker after washing of Examples 1 to 3 of the present invention can reduce chlorine harmful to corrosion of reinforcing bars, and can reduce alkali components harmful to alkali silica reaction. Chlorine and alkali components It was found that the removal effect was excellent.
Furthermore, the strength and setting time of the cements obtained using these clinker were almost the same as those of Comparative Example 1 before washing.

  INDUSTRIAL APPLICABILITY Since the present invention can effectively reduce chlorine that corrodes reinforcing bars in reinforcing steel structures and alkaline components that exhibit an alkali-silica reaction, it can be applied to mortar and concrete structures to improve durability. .

The figure which represented roughly an example of the method of wash | cleaning a clinker. The figure which shows each particle size distribution of the clinker used in the Example and comparative example shown in FIG. The figure which shows the procedure which obtains the clinker used for the cement preparation in an Example and a comparative example.

Claims (4)

  A method for reducing chlorine and alkali components in a clinker, wherein chlorine and alkali components are simultaneously reduced by washing the clinker with water.   The method according to claim 1, wherein the clinker is a clinker after firing, wherein the clinker has a chlorine content and / or an alkali component content exceeding the values of Japanese Industrial Standard. Of reducing chlorine and alkali components.   Reduction of chlorine and alkali components in a cement composition characterized by simultaneously reducing chlorine and alkali components by washing the clinker with water and then adding gypsum to the clinker after the washing and uniformly crushing and mixing. Method.   The method according to claim 3, wherein the cleaning is performed immediately before the clinker and gypsum are pulverized and mixed.

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