JP2014087723A - Neutralization treatment method for ready-mixed concrete sludge, and neutralization treatment material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new neutralization treatment method for ready-mixed concrete sludge capable of recycling ready-mixed concrete sludge as a backfill at a low cost, and a neutralization treatment material.SOLUTION: The method comprises: a mixing step of adding ferrous sulfate, a polymer flocculant and inorganic powder to ready-mixed concrete sludge and mixing them; and a curing step of curing the mixture obtained by the mixing step. Preferably, the addition amount of the ferrous sulfate in the mixing step is 100 kg or more per mof the ready-mixed concrete sludge, and curing time in the curing step is 14 days or more.

Description

  The present invention relates to a neutralization treatment method and a neutralization treatment material of raw consludge.

  Ready-mixed sludge (washed concrete sludge) was washed by the mixer and agitator car of the ready-mixed concrete factory, the concrete left behind without being driven in the field (hereinafter referred to as “remained-use-con”) and unloading inspection, and the ready-mixed company. It is the solid content contained in the wastewater that has been processed concrete (hereinafter referred to as "return container"). The raw consludge mainly contains unreacted cement particles, cement hydrated products, and aggregate fine particles.

Raw consludge is classified as sludge on industrial waste and is strongly alkaline. Therefore, as a rule, it is disposed of in landfills at managed disposal sites. However, the amount of raw conslag discharged nationwide is estimated to be about 3 million m ³ / year, and the problem of the remaining years of managed disposal sites has been pointed out. For this reason, there has been a strong demand among suppliers for reusing raw consludge.

  However, for example, in order to reuse raw consludge as a backfill material, according to the guidance of health centers nationwide, the pH of strong alkaline raw consludge is neutralized and gray raw consludge is colored to a clay color. Furthermore, it is necessary to suppress the hexavalent chromium contained in the raw consludge to an environmental standard of 0.05 mg / L or less related to soil contamination.

  Patent Document 1 discloses a method for solidifying concrete sludge, in which hexavalent chromium is reduced to be insolubilized and granulated and solidified. However, since the pH of the solidified body obtained by this method is still alkaline, there is a problem that it cannot be reused as a backfill material under the guidance of a health center, although it meets the recycling standards of the Ministry of Land, Infrastructure, Transport and Tourism. Moreover, if the pH of the solidified product is neutralized, there is a problem that the processing cost for that purpose is considerably increased.

  In addition, in the cited document 2, raw consludge is recovered, cement, water and crushed stone are added and kneaded to produce recycled green concrete, which is cured and solidified in a mold, and further solidified. A raw consludge regeneration method is disclosed in which a crushed and / or pulverized product is formed to form a regenerated cutting material having a predetermined particle size or less. Further, cited document 3 discloses a method for treating raw consludge in which raw consludge is dehydrated, and fine blast furnace slag powder having a mass ratio of 40% to 80% is kneaded with dehydrated raw consludge. However, the recycled materials obtained by these methods have proposed a method for recycling raw consludge, but there are concerns about facility costs and cost problems. Furthermore, such a method is basically not conscious of neutralization of raw consludge.

  In order to make effective use of raw consludge as backfill material, embankment material, roadbed material, etc., it must be disqualified as sludge on industrial waste, but it is conscious of the safety and diversity of raw consludge. Neutralization, coloring, and reduction of hexavalent chromium are essential conditions. For this reason, there is a strong demand for a method for treating green consludge that satisfies these conditions.

  Furthermore, there has been a demand for a processing method that does not require a new capital investment by a raw consludge discharger, and is considerably cheaper than the cost of bringing it into a managed disposal site while using conventional facilities. At the same time, the neutralized soil was expected to be widely used as a general-purpose civil engineering material.

JP 2010-36178 A JP 2008-50189 A JP 2001-191095 A

  Then, this invention aims at providing the neutralization processing method and the neutralization processing material of the novel raw consludge which make it possible to reuse raw consludge as a backfill material at low cost. .

  As a result of intensive studies, the present inventors have been able to achieve neutralization, coloring, and reduction of hexavalent chromium at the same time and at a low cost by using ferrous sulfate as a component of the neutralization treatment material. As a result, the present invention has been conceived.

  That is, the method for neutralizing the raw consludge of the present invention is obtained by a mixing step of adding ferrous sulfate, a polymer flocculant, and an inorganic powder to the raw consludge and mixing, and this mixing step. And a curing process for curing the mixture.

The amount of ferrous sulfate in the mixing step, in ferrous monohydrate converted sulfate is mixed concrete sludge 1 m ³ per 100kg or more.

  Furthermore, the curing time in the curing process is 14 days or more.

  The neutralization treatment material of the raw consludge of the present invention is characterized by containing ferrous sulfate, a polymer flocculant, and an inorganic powder.

  According to the present invention, neutralization, coloring, and reduction of hexavalent chromium can be achieved at the same time and at low cost, and it is possible to reuse the raw consludge as a backfill material at a low cost.

It is a graph which shows the time-dependent change of pH at the time of adding the processing material A. It is a graph which shows the time-dependent change of pH at the time of adding the processing material B. It is a graph which shows the time-dependent change of pH at the time of adding the processing material C.

  The method for neutralizing the raw consludge according to the present invention includes a mixing step of adding ferrous sulfate, a polymer flocculant, and an inorganic powder to the raw consludge and mixing, and a mixture obtained by this mixing step. And a curing process for curing.

  Common raw sludge has a pH of 11 to 14, a wet density of 1.1 to 2.0 g / ml, and a water content of 30 to 100%.

  First, in the mixing step, ferrous sulfate, a polymer flocculant, and an inorganic powder are added to and mixed with this raw consludge.

  Here, anhydrous ferrous sulfate and various hydrates are known as ferrous sulfate, and are not limited to specific ones. For example, ferrous sulfate / monohydrate, ferrous sulfate Iron or tetrahydrate can be preferably used. Moreover, ferrous sulfate obtained as a by-product of titanium oxide production or a dried product of steel washing waste liquid can be used.

The amount of ferrous sulfate added in the mixing step is preferably 100 kg or more per 1 m ^{3 of} raw consludge in terms of monohydrate. This is because, if it is less than 100 kg, the pH of the mixture does not reach near neutral in the next curing step. In addition, if 100 kg of ferrous sulfate (monohydrate equivalent) is added per 1 m ^{3 of} raw consludge, the pH after curing reaches about 9 or less neutral and can be reused as backfill material. Become. Furthermore, in order to ensure that the pH reaches near neutralization, the amount of ferrous sulfate added is preferably 140 kg or more per 1 m ^{3 of} raw consludge in terms of monohydrate. It is good also as 120-150 kg.

As the polymer flocculant, various generally known nonionic polymers and anionic polymers can be used. Although not limited to a specific one, for example, polyacrylamide can be suitably used as the nonionic polymer, and polyacrylamide partial hydrolyzate or acrylamide-sodium acrylate copolymer can be suitably used as the anionic polymer. . The addition amount of the polymer flocculant can be, for example, 0.05 to 1.5 parts by mass with respect to 100 parts by mass of ferrous sulfate (monohydrate conversion). When polyacrylamide is used, in order to improve the granulation property of the mixture, the amount of polyacrylamide added is preferably 0.05 kg or more, more preferably 0.3 kg or more per 1 m ^{3 of} raw consludge sludge. .

  Moreover, as inorganic powder, the powder which consists of various generally known inorganic substances can be used. Although not limited to specific ones, for example, silica powder, fly ash, clay mineral powder such as acid clay powder, kaolin powder, blast furnace slag powder, and foundry sand powder are preferably used. The addition amount of inorganic powder can be 1-80 mass parts with respect to 100 mass parts of ferrous sulfate (monohydrate conversion), for example. Inorganic powder is added to facilitate uniform mixing of the mixture.

  Next, in the curing step, the mixture obtained by adding and mixing ferrous sulfate, a polymer flocculant, and inorganic powder to the raw consludge in the mixing step is cured.

  Here, ferrous sulfate acts as an acidifying component and neutralizes with raw consludge. At the same time, hexavalent chromium contained in the raw consludge is reduced to trivalent chromium. On the other hand, ferrous sulfate divalent iron is oxidized to trivalent iron, and the formation of this trivalent iron changes the color of the mixture from dark green to dark brown. Furthermore, by stirring and curing the mixture, air oxidation from divalent iron to trivalent iron is promoted, and finally the yellowish brown color which is the color of the clay is reached. In addition, when the oxidation is actively promoted, there is a method of adding an oxidizing agent such as hypochlorous acid, hydrogen peroxide, permanganate and the like.

  The curing time in the curing process is preferably 14 days or longer, but it is preferable to stir and mix the entire living organism with a backhoe or the like at a frequency of about once every 3 days during this period to increase air contact. . Further, by setting the curing time to 14 days or longer, the neutralization reaction proceeds sufficiently and the pH of the mixture reaches near neutral.

  The polymer flocculant acts as a solidifying material and solidifies the mixture. Due to the aggregating action of the polymer flocculant, granulation is facilitated when the mixture is stirred.

  A neutralization treatment material of the raw consludge of the present invention is blended to perform the neutralization method of the raw consludge described above, and includes ferrous sulfate, a polymer flocculant, and an inorganic powder. contains. The details of ferrous sulfate, the polymer flocculant, and the inorganic powder are as described above.

  The blending ratio of ferrous sulfate, polymer flocculant, and inorganic powder is, for example, 0.05 to 1.5 parts by weight of polymer flocculant, inorganic with respect to 100 parts by weight of ferrous sulfate (anhydride equivalent). It can be 1-80 mass parts of powder.

  Furthermore, the treated soil after the neutralization treatment of the present invention includes calcium sulfate, tetracalcium ferrate and silicate as neutralizing subcomponents in addition to aggregate particles and calcium silicate which are constituent components of raw consludge. It is expected to contain double salts such as iron.

  Hereinafter, the neutralization processing method of the raw consludge of the present invention will be specifically described. In addition, this invention is not limited to a following example, A various deformation | transformation implementation is possible.

The following neutralization treatment was performed using raw white sludge having a pH of 12.78 (20 to 25 ° C.), a wet density of 1.6062 g / cm ³ , and a moisture content of 60.7%.

  As a neutralizing treatment material, treatment material A containing 60% by mass of ferrous sulfate / monohydrate, 0.4% by mass of polyacrylamide, 3.6% by mass of silica particles, and 36% by mass of fly ash; A treatment material B containing 96% by mass of iron / monohydrate, 0.4% by mass of polyacrylamide and 3.6% by mass of silica particles, and a treatment material C comprising 100% by mass of ferrous sulfate / monohydrate were prepared. .

Then, after mixing the raw consludge uniformly in advance, a predetermined amount of sludge is collected, and the amount of treatment material shown in the following table is added per 1 m ^{3 of} the raw consludge and mixed with a spatula for 30 seconds. The condition was observed. Then, it cured in the open state and measured the change with time of pH. The pH was measured according to JIS 0211, and the water content was measured according to JIS A 1203. The state of granulation was evaluated by visual observation, and was measured after 1 hour of mixing after 0 days of pH. In the table, iron sulfate is the amount of ferrous sulfate / monohydrate added. The results are shown in the following table. Further, FIG. 1 is a graph showing the change over time of pH when treatment agent A is used, FIG. 2 is a graph showing the change over time of pH when treatment agent B is used, and FIG. FIG. 3 shows a graph of changes over time in pH when used.

Even when any of the treatment agents was added, the pH greatly decreased at the initial stage of curing, and then gradually decreased. In addition, when any of the treatment agents was added, the pH decreased as the amount of ferrous sulfate / monohydrate added increased. When the amount of ferrous sulfate / monohydrate added per 1 m ^{3 of} raw consludge is 100 kg or more, the pH after curing for 14 days is 9.1 or less, and when it is 140 kg or more, the pH is 8.6 or less. It became.

The granulation properties, the case of using the treating agent C containing no polyacrylamide, treatment agent A containing polyacrylamide (polyacrylamide 0.2kg to raw cons sludge 1 m ³⁾ to 50 kg / ^{m 3} B were added It was a little bad at times, but it was good otherwise.

  Moreover, the elution test of the hexavalent chromium of the mixture after 14-day curing was done. After drying at 110 ° C., a pack test based on the diphenylcarbazide absorptiometric method was performed through a sieve having a crack opening of 2 mm in a mortar. As a result, hexavalent chromium was not detected after curing for 14 days, regardless of which treatment was added. On the other hand, 0.15 ppm of hexavalent chromium was detected from the raw untreated sludge.

In addition, a colorimetric test was performed on the mixture after curing for 14 days. In order to remove small gravel and sand, the mixture was coarsely pulverized in a mortar and passed through a 16 # (1000 μm) sieve. Next, it grind | pulverized with the mortar, applied the sieve of 60 # (250 micrometers), and tested about what passed the sieve. The color measurement was performed according to JIS Z 8722: 2009, and the color display method was performed according to JIS Z 8729: 2004. The results are shown in the table below. In the table below, the Munsell value obtained from the result of the color measurement test based on JIS Z 8721: 1993 and the equivalent color name approximated to the 269 color conventional color name described in JIS Z 8102: 2001 are also shown. . Upon addition of ferrous monohydrate sulfate fresh concrete sludge 1 m ³ per 192 kg, to dark tan is a color Clay (sallow), otherwise the light tan (gold brown) became.

Claims (4)

Featuring a mixing step of adding ferrous sulfate, a polymer flocculant, and inorganic powder to raw consludge and mixing, and a curing step of curing the mixture obtained by this mixing step To neutralize the raw consludge. The additive amount of ferrous sulfate in the mixing step, the one iron monohydrate terms, neutralization processing method fresh concrete sludge according to claim 1, wherein the fresh concrete sludge 1 m ³ per 100kg or more sulfate. The method for neutralizing a raw consludge according to claim 1 or 2, wherein the curing time in the curing step is 14 days or more. A neutralized material for raw consludge comprising ferrous sulfate, a polymer flocculant, and inorganic powder.

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