JP2003211153A - Agent and method for removing organic substance in water recovered from concrete, and concrete manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for safely and efficiently removing organic substances contained in recovered water from a concrete plant for recycling the water as water for kneading concrete. <P>SOLUTION: An agent for removing the organic substances contained in recovered water from a concrete plant contains a calcium silicate hydrate powder having a BET specific surface area of ≥30 m<SP>2</SP>/g or its granulated substance as an active ingredient. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an agent for removing organic matter from recovered water from a concrete plant, a method for removing organic matter from recovered water from a concrete plant using the remover, and a concrete using recovered water from which organic matter has been removed. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In a concrete plant such as a ready-mixed concrete plant or a precast concrete plant, a large amount of drainage is generated to wash concrete adhering to plant equipment such as a mixer and a hopper and a carrier. Collected water such as sludge water and supernatant water, which is suspension water obtained by removing coarse aggregate and fine aggregate from such cleaning wastewater,
At almost all plants, some or all of them are reused as concrete mixing water from the viewpoints of environmental consideration and water saving.

In using such recovered water, in order to prevent adverse effects on the physical properties of concrete, JIS A
In 5308, there are regulations regarding the chloride ion amount, sludge solid content amount, and other coagulation time, but there is no regulation regarding the organic substances contained in the recovered water.

[0004] Usually, in the preparation of ready-mixed concrete, a chemical admixture is added in order to improve the workability, durability, strength and other physical properties of the concrete. There are various chemical admixtures depending on the purpose of use, but most of them are mainly composed of organic compounds. For example, as the main component of the dispersant added to improve the workability of cement before curing, formalin condensate of naphthalene sulfonate, formalin condensate of melamine sulfonate, lignin sulfonate, aminobenzene Examples thereof include a polymer of a sulfonate, a condensate of a carboxylic acid having a polyoxyethylene alkyl ether in a graft chain (polycarboxylic acid-based dispersant), and an oxycarboxylic acid. Examples of the main component of the retarder that delays the setting time of concrete include gluconic acid and salts thereof, citric acid and salts thereof, various sugars such as maltose, glucose and saccharose. As the main component of the AE agent added to improve frost resistance after curing, anionic surface active agents such as aliphatic soap, resin acid soap, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, etc. A lot of agents are used. In addition to the organic compounds used in the above-mentioned AE agents, casein, keratin, etc. can be used as the main component of the foaming agent added for the purpose of imparting lightness, heat resistance, fire resistance, etc. to the concrete after hardening. There are protein-based foaming agents and saponins made from
As a waterproofing agent added for the purpose of imparting waterproofness to concrete, emulsions of ethylene vinyl acetate, polyacrylic acid ester, vinyl polypropionate, and the like, re-emulsified powder resins thereof, and the like are used.
Further, higher fatty acids such as stearic acid, oleic acid and maleic acid, esters thereof, and water-soluble polymers such as methyl cellulose are also used.

In addition to the above, various kinds of admixtures have been developed according to the purpose, and the organic compounds as the components thereof are various.

These admixtures added to concrete are adsorbed on the cement particles in the concrete, but the total amount is hardly adsorbed on the cement particles.
5 to 95% of the added amount remains in the kneading water. By mixing such an admixture in the cleaning wastewater,
The admixture that was added to the ready-mixed concrete will be included.

Therefore, when such recovered water is reused as kneading water for concrete, the quality of concrete may be significantly impaired by excessive addition of an admixture or improper combination.

[0008] Usually, when the recovered water is used, an operation of removing suspended substances by a coagulating sedimentation operation is performed.
No work has been done to remove organic matter. Usually, it is diluted to a sufficient concentration with wash water, so there are few problems.However, when an admixture that exerts an effect in an extremely small amount is included, or when a large amount of admixture is mixed in the recovered water for some reason, When using this as kneading water, the physical properties of concrete will be significantly adversely affected, and the use of recovered water must be stopped and the production of concrete must be restarted.

[0009] By the way, activated carbon is known as a material having an ability to adsorb organic substances, but activated carbon is flammable, and when storing 10 tons or more, it becomes a designated combustible substance according to the Fire Service Act, and handling is complicated. is there. Moreover, water-containing activated carbon is highly corrosive, and when using an adsorption tower,
Material selection and inner wall coating are required. Furthermore,
Since activated carbon adsorbs oxygen in the air, there is a problem that the adsorption tower is in an oxygen-deficient state.

[0010]

The main object of the present invention is to:
It is an object of the present invention to provide a method capable of safely and efficiently removing an organic compound contained in recovered water when reusing recovered water from a concrete plant as concrete kneading water.

[0011]

The inventor of the present invention has conducted extensive studies in order to achieve the above object. As a result, BE
It was found that calcium silicate hydrate powder having a T specific surface area of 30 m ² / g or more, which is extremely large, has a high adsorptivity for organic substances contained in water, and further has a cement composition. For organic admixtures for concrete produced for the purpose of addition to concrete, it shows a particularly high adsorption performance, and by using this as an organic matter remover in concrete recovery water, the organic matter contained in the recovered water is sufficiently It was found that the adverse effect of the admixture can be prevented when the recovered water is removed and reused as concrete mixing water. Furthermore, it was found that calcium silicate hydrate is relatively inexpensive and highly safe, and that it can be regenerated after use and reused as an organic substance removing agent, and the present invention has been completed here. Came to do.

That is, the present invention provides the following organic substance removing agent in recovered water from a concrete plant, a method for removing organic substances in recovered water from a concrete plant, and a method for producing concrete. 1. An agent for removing organic substances in water recovered from a concrete plant, which comprises a calcium silicate hydrate powder having a BET specific surface area of 30 m ² / g or more or a granulated product thereof as an active ingredient. 2. A method for removing organic matter from recovered water from a concrete plant, which comprises contacting the recovered water from the concrete plant with the organic matter removing agent according to the above item 1. 3. Adsorbing an organic matter by bringing the organic matter removing agent according to the above 1 into contact with recovered water from a concrete plant, then separating the organic matter removing agent, and then using the recovered water as kneading water to produce concrete. A method for producing concrete, characterized by:

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The organic matter removing agent in the water recovered from the concrete plant of the present invention (hereinafter sometimes referred to as "concrete recovered water") has a BET specific surface area of 30 m.
^A calcium silicate hydrate powder of ² / g or more is used as an active ingredient.

The calcium silicate hydrate particles having such a very large specific surface area usually have a porous structure, and various organic compounds contained in concrete recovered water are mixed with the calcium silicate hydrate. It can be efficiently adsorbed on the surface of objects and inside pores. The organic substance removing agent used in the present invention has excellent performance in that it is difficult to adsorb and remove activated carbon, and it is possible to sufficiently adsorb and remove an organic compound contained in recovered water. Further, the calcium silicate is preferable because it is nonflammable and inexpensive.

The calcium silicate hydrate, which is an active ingredient of the organic substance removing agent of the present invention, needs to have a specific surface area of about 30 m ² / g or more, preferably about 50 m ² / g or more. . In the present specification, the specific surface area is the specific surface area determined by the BET method based on the amount of N ₂ gas adsorbed.

When the specific surface area of the calcium silicate hydrate is smaller than the above range, it is not preferable because the removal performance of the organic substances in the recovered water cannot be sufficiently exhibited.

The organic substance removing agent used in the present invention may be any one as long as it satisfies the above-mentioned conditions, and its manufacturing method is not particularly limited.

For example, the BET specific surface area, which is an active ingredient of the organic substance removing agent of the present invention, is obtained by removing aggregates from waste concrete, crushing and crushing with a crusher or the like, and classifying as necessary. It is possible to obtain a calcium silicate hydrate powder having a ratio of 30 m ² / g or more.

In the present invention, in particular, a calcium silicate hydrate powder satisfying the above-mentioned conditions is obtained by a method of adding water to a raw material containing a calcium silicate-forming raw material and carrying out a hydration reaction under wet grinding. Is preferably produced. According to this method, a product having high purity and high BET specific surface area can be easily manufactured. Hereinafter, regarding this manufacturing method,
The details will be described.

Various types of cement, granulated blast furnace slag and the like can be used as the raw material for producing calcium silicate.

Among these, in particular, granulated blast furnace slag is inexpensive and can be stably supplied, so that it is advantageous in that an organic substance removing agent of a constant quality can be produced. Granulated blast furnace slag has a vitreous structure and has a calcium content inside the SiO ₂ network skeleton. If the SiO ₂ skeleton is broken during the hydration reaction under wet pulverization, the calcium content will increase from the inside. The fraction elutes and sequentially reacts with its alkalinity to form calcium silicate hydrate. When granulated blast furnace slag is used as a raw material, calcium sulfate, calcium hydroxide, etc. may be added for the purpose of promoting the reaction.

In addition, when cement is used as a raw material, excess calcium may be produced as calcium hydroxide in addition to calcium silicate, and the calcium silicate content may be reduced. In such a case, a general siliceous raw material such as fly ash, silica stone, or diatomaceous earth may be added to react with excess calcium hydroxide to produce calcium silicate hydrate.

When the calcium content in the raw material is smaller than the silica content, unreacted silicic acid content remains in the slurry after the reaction, but this unreacted silicic acid content is used for removing organic substances. Does not participate, so it is disadvantageous if a large amount remains. Therefore, an appropriate amount of calcium hydroxide, quick lime or the like may be added so that the unreacted silicic acid content becomes a calcium silicate hydrate.

These raw materials usually contain calcium sulfate, calcium aluminate, ferrite and the like as accessory components, and these are also hydrated by the hydration reaction in the same manner as calcium silicate. Yes, but no problem.

The mixing ratio of the above-mentioned raw materials may be appropriately determined depending on the type of the raw materials used so that the content ratio of the calcium silicate hydrate fine particles in the organic substance removing agent is as large as possible.

The amount of water added is 100 with respect to 100 parts by weight of the raw material components containing the above-mentioned calcium silicate-forming raw material.
To about 2000 parts by weight, preferably 100 to
More preferably, the amount is about 1000 parts by weight.

In the wet pulverization and hydration reaction of the raw material, the raw material and water are usually put into a pulverizer and the temperature is about 40 to 100 ° C. (preferably about 50 to 80 ° C.) and predetermined requirements (specific surface area etc.) May be performed until particles satisfying the above are formed.

During the production of calcium silicate, a slurry is obtained in which the concentration and the fluidity of the solids produced are different depending on the ratio of water used to the raw materials. The obtained slurry can be used as it is as an organic substance removing agent.

Alternatively, the obtained slurry is dried at about 80 ° C. or higher (preferably 100 to 200 ° C.), crushed if necessary, and then classified to a predetermined particle size to remove powdery organic matter. The agent can be obtained.

The obtained powder may be used as it is, or may be granulated and used according to the purpose. As the granulation method, various known granulation methods such as rolling, fluidized bed, extrusion, compression, crushing, and injection can be applied. As the binder used for granulation, the binder conventionally used can be used as it is. Examples of binders include alpha starch, sodium alginate, sugar, dextrin,
Clays such as corn syrup, gelatin, CMC, PVA, water glass, polyvinylpyrrolidone, polyacrylic acid, polyvinyl acetate, vinyl acetate-ethylene polymer, modified vinyl acetate, vinyl acetate-acrylic copolymer, cements and bentonite Etc. can be mentioned.

There is no particular limitation on the method for removing organic matter from the concrete recovered water using the organic matter remover of the present invention, as long as the organic matter remover can be brought into sufficient contact with the recovered water to be treated. Good.

As an example of the organic substance removing method, a batch type removing method and a continuous type removing method will be briefly described below.

Incidentally, the concrete recovered water to be treated in the present invention means that concrete adhering to plant equipment such as mixers and hoppers or concrete adhered to a carrier is washed in a concrete plant such as a ready-mixed concrete factory or a precast concrete factory. Sludge water and supernatant water, which are suspension water obtained by removing coarse aggregates and fine aggregates from the generated cleaning wastewater. (1) Batch type removal method: The organic substance removing agent of the present invention is added to a tank containing cement recovered water, and the organic compound in the recovered water is adsorbed to the organic substance removing agent by standing or stirring, Can be removed.

As a tank for containing the recovered water, a tank, a pond or the like may be newly installed, but a coagulating sedimentation tank or the like in an existing waste water treatment facility may be diverted or used in combination.

The addition amount of the organic substance removing agent may be appropriately determined according to the content of the organic compound in the recovered water, but normally, the calcium silicate hydrate which is an active ingredient is hydrated per 1 m ³ of the volume of the tank for containing the recovered water. The amount of the material is preferably about 0.1 to 300 kg. If the addition amount of the organic substance removing agent is too small, it becomes difficult to obtain a sufficient organic substance removing effect. Also, even if the addition amount of the organic matter removing agent is too large,
Excessive addition is uneconomical because the removal effect reaches the ceiling.

The time for standing or stirring the recovered water added with the organic substance removing agent may be appropriately determined depending on the amount of the admixture in the recovered water, the added amount of the organic substance removing agent, etc., but usually 5 minutes to 2 minutes.
It may be about 4 hours. In this case, if the standing time or the stirring time is insufficient, a sufficient removing effect cannot be obtained.
Further, even if the standing or stirring time becomes longer than necessary, it is impossible to obtain a further removing effect.

The organic substance removing agent dispersed in the recovered water by stirring can be removed by coagulation sedimentation or filtration. At this time, the coagulating sedimentation tank or the like in the existing recovered water treatment facility may be used as it is. As the coagulant, those used in ordinary wastewater treatment facilities such as aluminum sulfate and polyacrylamine can be used as they are.

The organic substance removing agent used may be either a powdery removing agent or a removing agent granulated by a granulating operation, but a powdery removing agent is particularly preferable in view of high treatment efficiency.

The above-mentioned treatment may be carried out batchwise by using only one tank for containing the concrete-recovered water, but usually a plurality of settling tanks are used to overflow the recovered water. However, organic substances can be efficiently removed by continuously passing the solution while performing the treatment. (2) Continuous removal method After removing suspended substances from concrete recovered water in a flocculation adsorption tank or the like, the recovered water is passed through an adsorption container filled with the organic substance removing agent of the present invention to recover recovered water during passage. Organic matter can be removed from the.

As the adsorption container, any structure may be used as long as it can be filled with the organic substance removing agent of the present invention, and can introduce recovered water from one end and discharge recovered water from the other end. Is not particularly limited, but, for example, the same one as the activated carbon adsorption tower in a normal factory wastewater treatment facility can be used. At this time, the type of the adsorption tower may be a fixed bed, a moving bed, or a fluidized bed, and the activated carbon adsorption tower of the existing equipment may be used as it is. The flow rate of the recovered water may be appropriately adjusted depending on the amount of the recovered water, the degree of pollution, the desired degree of purification, etc., and the conditions may be determined in advance by a laboratory test. In this method, in view of the nature of the processing apparatus, the organic substance removing agent used is preferably one which is granulated by a granulating operation.

According to the treatment method described above, various organic substances can be sufficiently removed from the concrete recovered water. Therefore, the recovered water after the treatment can be used as kneading water for concrete to produce concrete in the same manner as in the past.

The organic substance removing agent used after the above-mentioned organic substance removing treatment can be reused by desorbing the adsorbed organic substance by standing or stirring in a strong alkaline solution.

Furthermore, the used organic substance removing agent can be treated in the same manner as raw concrete sludge, and for example, the recovered treating agent is dehydrated and solidified by pressurizing, drying, etc. It becomes "ceramic waste" and can be treated as stable waste.
However, if solidification is not performed, it corresponds to “sludge” of industrial waste and must be disposed of at a managed landfill.

[0044]

Industrial Applicability The organic substance removing agent in concrete recovered water of the present invention has excellent adsorption performance for various organic substances that may be contained in concrete recovered water. Therefore, by removing the organic matter from the concrete recovered water using the organic matter removing agent of the present invention, it is possible to prevent the quality of the concrete from being adversely affected when the recovered water is reused as concrete kneading water.

Further, the organic substance removing agent is nonflammable and inexpensive, and can be reused as a concrete raw material or recycled to be reused as an organic substance treating agent.

[0046]

EXAMPLES The present invention will be described in more detail with reference to examples.

The adsorption rate of various organic substances was measured by the method described below using the following 5 kinds of test materials.

Example 1 Ordinary Portland cement and hot water at 70 ° C. were put into a pulverizer (vibration mill) at a solid-liquid ratio of 1: 6 and subjected to a hydration reaction for 2 hours while wet pulverizing. 2 at ℃
After drying for 4 hours, it was crushed to obtain calcium silicate hydrate powder. The BET specific surface area of this powder was 70 m ² / g.

Example 2 To 90 g of the calcium silicate hydrate powder obtained in Example 1, 10 g of ordinary Portland cement was added and mixed, and thereafter,
Add 130 ml of water and knead, φ5 mm × with an extruder
It was molded into a cylindrical shape of 7 mm to obtain a granulated product of calcium silicate hydrate.

Example 3 After removing the aggregate part from the concrete waste material and selecting the paste part, it was crushed with a ball mill until the average particle size became 50 μm, and powder containing calcium silicate hydrate as a main component was obtained. Obtained. The BET specific surface area of this powder is 35 m ² /
It was g.

Comparative Example 1 Granulated activated carbon for water treatment and refined sugar / food (specific surface area 150
0 m ² / g and an iodine adsorption amount of 1200 mg / g) were used as Comparative Example 1.

Comparative Example 2 Granular activated carbon for general water treatment (specific surface area 1200 m ² / g,
An iodine adsorption amount of 1050 mg / g) was used as Comparative Example 2. [Adsorption rate measurement method] 10 g of the test powder was dispersed in 100 ml of a 1% aqueous solution of various organic substances, and 20
The mixture was stirred at 0 ° C for 2 hours. This was suction filtered, the filtrate was diluted 10 times, and the test powder was collected and dried at 100 ° C. for 24 hours.

Then, the total organic carbon amount (TOC) in the diluted filtrate and the total organic carbon amount (TOC) in the 0.1% organic substance aqueous solution are calculated by a total organic carbon meter (TOC meter: TOC-650 manufactured by Toray Engineering Co., Ltd.). ) Was used to determine the adsorbed organic matter content in the aqueous solution by the following formula, assuming that the reduced amount of the total organic carbon was adsorbed on the test powder. The results are shown in Table 1 below.

Organic substance adsorption rate (%) = 100 × (TOC in diluted filtrate-TOC of 0.1% organic substance aqueous solution) /0.1
% TOC aqueous solution of organic matter The types of organic matter measured by TOC are as follows. (1) Naphthalenesulfonic acid formalin condensate Trade name: Mighty 150, water reducing agent manufactured by Kao (2) Polycarboxylic acid type high performance AE water reducing agent Trade name: Reobuild SP8S, NMB high performance AE water reducing agent (3) Glucon Sodium acid grade reagent (4) Melamine sulfonic acid formalin condensate Trade name: Melment, SKW water reducing agent (5) Lignin sulfonate Trade name: Pozzolis No. 8. NMB water reducing agent (6) Polycarboxylic acid type high performance AE water reducing agent Trademark name: Chupol HP11, Takemoto Yushi Co., Ltd. high performance A
E Water-reducing agent (7) Special citric acid reagent

[0055]

[Table 1]

As is clear from the above results, the organic substance removing agent of the present invention has an excellent adsorption performance for many types of organic substances that may be contained in concrete recovered water, as compared with activated carbon. Is.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D024 AA04 AB04 BA05 BA11 BB01                       BB05 BC01 BC04 DB21                 4G056 AA07 AA25 CA00 CD48                 4G066 AA17B AA22B AA30B AA73A                       AA73D BA26 CA01 DA08                       FA03 FA27

Claims (3)

[Claims] 1. An agent for removing an organic substance in water recovered from a concrete plant, which comprises a calcium silicate hydrate powder having a BET specific surface area of 30 m ² / g or more or a granulated product thereof as an active ingredient. 2. A method for removing organic matter from recovered water from a concrete plant, which comprises contacting the organic matter removing agent according to claim 1 with recovered water from the concrete plant. 3. The organic substance removing agent according to claim 1 is brought into contact with recovered water from a concrete plant to adsorb organic matter, and then the organic substance removing agent is separated, and then the recovered water is used as kneading water. A method for producing concrete, which comprises producing concrete.