JP6594001B2 - Waste cement solidification processing equipment - Google Patents

Description

  The present invention relates to a cement solidification treatment apparatus and method for waste including, for example, heavy metals and deliquescent compounds.

  Conventionally, as a technology to fix heavy metals such as mercury (Hg) contained in exhaust gas from incinerators, for example, fly ash collected by a dust collector that collects dust in the exhaust gas is fixed with a cement solidifying agent. Has been proposed (Patent Document 1).

JP 2007-117890 A

  However, for example, when desulfurization treatment of desulfurization effluent from a desulfurization device that removes sulfur oxides from exhaust gas from a coal fired boiler, evaporative salt having deliquescence generated at the time of the non-drainage treatment is treated at room temperature. In the case of cement solidification treatment, there is a problem that in the solidification method in which water is added after mixing the normal evaporative salt and cement, moisture is leached on the cement solidified surface by the action of deliquescent salt and the heavy metals are easily eluted.

  Therefore, when evaporating salt containing deliquescent compounds together with toxic substances such as heavy metals, it is possible to prevent elution of toxic components such as heavy metals while suppressing leaching of moisture due to the deliquescence of evaporating salt on the cement solid surface. In addition, the emergence of cement solidification technology in which the strength of the cement solidified product is higher than the desired strength is eagerly desired.

  This invention makes it a subject to provide the cement solidification processing apparatus and method in which the intensity | strength of cement solidification becomes desired intensity | strength in view of the said problem.

  A first invention of the present invention for solving the above-mentioned problems is a slurry tank for dissolving a waste material containing a harmful substance and a deliquescent compound in dissolved water to obtain a slurry, and the iron-based addition A cement kneading tank that adds a cement solidifying agent to the slurried product mixed with the agent to obtain a cement kneaded product, and an iron-based additive that adds an iron-based additive to one or both of the slurrying tank and the cement kneading tank A waste cement solidification processing apparatus comprising: an additive supply unit; and a cement solidification unit that dries and cures the cement kneaded material to obtain a cement solidified product.

  According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a cement solidification treatment apparatus for waste, wherein the iron-based additive is a ferrous inorganic salt.

  In a third invention, a slurry containing a heavy metal mixed with the iron-based additive is dissolved in a slurry containing a heavy metal and a deliquescent compound dissolved in dissolved water to obtain a slurry. A cement solidifying agent adding step for adding and kneading the cement solidifying agent; an iron based additive adding step for adding an iron based additive to a slurry or cement kneaded material containing harmful substances and deliquescent compounds; and a cement solidifying agent. And a cement solidification step of curing the cement kneaded material mixed with a solidified cement to obtain a cement solidified product.

  According to a fourth aspect of the present invention, there is provided a waste cement solidification method according to the third aspect, wherein the iron-based additive is a ferrous inorganic salt.

  According to the present invention, firstly, after obtaining a slurry in a slurrying tank, a cement solidifying agent is added to the slurry and kneaded in the cement kneading tank to increase the solidification strength of the cement solidified product. Can do.

FIG. 1 is a schematic diagram of a waste cement solidification processing apparatus according to an embodiment. FIG. 2 is a diagram showing the relationship between the cement addition weight ratio (the solid component is 1) and the cement compressive strength (kg / cm ² ). FIG. 3 is a diagram showing the results of the eluted Se concentration when iron-based drug A and iron-based drug B are added.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

FIG. 1 is a schematic diagram of a waste cement solidification processing apparatus according to an embodiment.
As shown in FIG. 1, the waste cement solidification processing apparatus 10 according to the present embodiment is a slurry in which a waste 11 containing a harmful substance and a deliquescent compound is dissolved in a dissolved water 12 to form a slurry 13. The cement solidifying agent 17 is supplied to the slurrying tank 13, the iron additive supplying unit 16 for adding the iron based additive 15 to the slurrying tank 14, and the slurry 13 in which the iron based additive 15 is mixed. A cement kneading tank 20 that is added from the section 18 to obtain a cement kneaded material 19 and a cement solidified portion 22 that is obtained by drying, curing, and solidifying the cement kneaded material 19 to form a cement solidified material 21 are provided.

  Here, the waste 11 to be subjected to cement solidification treatment in this embodiment includes harmful substances such as heavy metals (for example, mercury (Hg), selenium (Se) and arsenic (As)). It contains a deliquescent compound together with the substance. Here, the heavy metal means a metal having a specific gravity of 4 or more, and other than mercury (Hg) and selenium (Se), for example, lead (Pb), cadmium (Cd), chromium (Cr), manganese (Mn), Examples include cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), bismuth (Bi), and iron (Fe).

  The waste 11 to be treated includes, for example, dust collection fly ash from a dust collector of a garbage incineration facility, a concentrate in a wastewater elimination process of wastewater treatment from a garbage incineration facility, and elimination of wastewater from a mine system wastewater treatment. Examples include concentrates in the process, mixed concentrates of waste and wastewater from nuclear power generation facilities, concentrates (evaporated salts) when desulfurization drainage from desulfurization facilities of coal fired boiler facilities is made non-drainage, etc. However, it is not limited to these.

In addition, the waste to be treated of the present invention contains a deliquescent compound in addition to harmful substances. The deliquescent compound is a substance that exhibits a phenomenon in which when the solid of the compound is left in the air, the solid absorbs moisture in the air and the solid dissolves in the moisture. For example, common deliquescent compounds include, for example, calcium chloride (CaCl ₂ ), sodium hydroxide (NaOH), magnesium chloride (MgCl ₂ ), and the like.

As the cement solidifying agent 17 for solidifying the cement, for example, 3CaO · SiO ₂ , 3CaO · Al ₂ O ₃ or the like is blended, and the fixing of harmful components in the waste is made more reliable. Examples of the cement solidifying agent include Portland cement. Further, fly ash or the like may be added together with the cement solidifying agent.

  Here, when solidifying the waste according to the prior art, the solid waste and the cement solidifying agent 17 are mixed in a powder (solid) state and kneaded while adding predetermined moisture, Cement solidification treatment is performed to dry, cure and solidify.

  However, when the waste 11 contains a deliquescent compound, the conventional mixing method in which the evaporating salt and cement are mixed and water is added, the compressive strength (crushing strength) of the obtained cement solidified product. ) Does not reach the desired standard value, and when the cement solidified material is landfilled over a long period of time, the cement solidified material is cracked or the deliquescence compound oozes on the surface of the cement solidified material. There is.

  Furthermore, when moisture accompanying the deliquescence action of the deliquescent compound exudes to the surface of the cement solidified material 21, a harmful substance inside the cement solidified material 21 may accompany, and the harmful substance may leak to the outside. is there. As a result, when landfill treatment is performed over a long period of time, if there are harmful substances with extremely low environmental emission standards or hazardous substances whose environmental emission standards will become stricter in the future, landfill treatment may not be possible as they are. There is.

  Therefore, in the present invention, in the slurrying tank 14, the waste 11 is first dissolved in the dissolved water 12 to form a slurry, and the slurry 13 is obtained with the dissolved water. The slurry 13 obtained in this slurrying process is designed to disperse and homogenize harmful substances in the waste 11 by the action of the dissolved water 12.

  That is, in the slurrying tank 14, the solid waste 11 is gradually added into the dissolved water 12 and stirred by a stirring means (not shown) or the like, so that the slurry is a suspended slurry. Thus, the solid-liquid mixing and dispersion accelerating process is performed, and the subsequent kneading process with the cement solidifying agent 17 is easily homogenized.

  As described above, in this embodiment, the waste 11 and the cement solidifying agent 17 are not kneaded in a solid state, but first the slurryed material 13 is obtained in the slurrying tank 14, and then the cement solidifying agent 17 and the cement kneading are obtained. By kneading in the tank 20, the solidification strength of the cement solidified product 21 is increased. This promotes dispersion when the slurry 13 is obtained. Accordingly, when the slurry 13 containing heavy metal and the cement solidifying agent 17 are mixed homogeneously, the cement solidifying agent 17 is homogenized in the slurry and the solidification strength is easily increased. As a result, solidification can be performed with a smaller amount of cement than when the slurrying treatment is not performed.

  As the cement solidification strength increases, the leaching of the deliquescent compound is also reduced. As a result, the amount of harmful substances leaching to the outside accompanying the deliquescence compound can be reduced, so that landfill can be carried out over a long period of time. Even when it is processed, the cement solidified material 21 that satisfies the environmental emission standards can be obtained.

  Further, when obtaining the slurry 13, a divalent iron-based chemical is added as the iron-based additive 15, and the hydration reaction in the cement solidification treatment with the cement solidifying agent and the ferritization reaction with the divalent iron-based chemical are carried out in the slurry. The hydration reaction proceeds in a homogeneously mixed state, and harmful substances are easily taken into the hydration solid solution crystal of the cement to be fixed.

  In this embodiment, the iron-based additive 15 is added from the iron-based additive supply unit 16 to the slurrying tank 14, but the present invention is not limited to this, and either the slurrying tank 14 or the cement kneading tank 20 is used. You may make it add the iron-type additive 15 from the iron-type additive supply part 16 to either or both.

Here, as the divalent iron-based agent, for example, ferrous chloride (FeCl ₂ ), ferrous sulfate (FeSO ₄ ), iron nitrate (Fe (NO ₃ ) ₂ ), iron carbonate (FeCO ₃ ), iodine Examples thereof include iron (FeI ₂ ) and iron fluoride (FeF ₂ ), but the present invention is not limited to these.

The compressive strength (crush strength) of the cement solidified product thus obtained is, for example, preferably 150 kg / cm ² or more, more preferably 200 kg / cm ² or more. This compressive strength is obtained in advance when the cement solidification process is operated, and the relationship between the heavy metal concentration contained in the harmful substance 11 and the target elution concentration in the cement solidified product 21 is determined. When cement is solidified, it is possible to use the target compression concentration periodically as an indicator that the elution concentration is satisfied. The compressive strength is set according to the elution standard. Therefore, when the hazardous heavy metal concentration contained in the waste 11 becomes high or the elution regulation value of the heavy metal becomes strict, it is desirable to use high cement compressive strength as an index.

FIG. 2 is a diagram showing the relationship between the cement addition weight ratio (the solid component is 1) and the cement compressive strength (kg / cm ² ).
In the test example, after evaporating salt solids, which are wastes, are made into a slurry 13 with dissolved water 12, this slurry 13 and cement solidifying agent 17 are mixed to obtain a cement kneaded material 19, and then dried. Cured and solidified to give a cement solid.
In the comparative example, a solid material of evaporative salt, which is a waste material, and a cement solidifying agent 17 are mixed as in the conventional case, and after adding water to obtain a cement kneaded material 19, drying, curing, and solidification treatment are performed. It is a cement solidified product.
The cement ratio was determined as the compressive strength of the cement solidified product of Test Example 1 and Comparative Example 1 when the solid content of the evaporating salt was 1, and the cement was added three times (cement ratio 3).
Similarly, the compressive strength of the cement solidified product of Test Example 2 and Comparative Example 2 when cement was added 5 times (cement ratio 5) was determined.

  Here, in this test, ordinary Portland cement was used as a cement solidifying agent. The cement solidifying agent 28 was added and then kneaded for a predetermined time and dried under predetermined conditions. After drying, the film was cured at room temperature for a predetermined time.

As shown in FIG. 2, the cement solids of Test Examples 1 and 2 were both> 200 kg / cm ² . On the other hand, the cement solidified product of Comparative Example 1 was 100 kg / cm ² , and the cement solidified product of Comparative Example 2 was 155 kg / cm ² .

  Next, an elution Se concentration test was carried out in the case where an iron-based drug A and an iron-based drug B were added as a divalent iron-based drug as a drug to be added at the time of cement solidification operation, and the dissolution property was confirmed.

FIG. 3 is a diagram showing the results of the eluted Se concentration when iron-based drug A and iron-based drug B are added. In the test of FIG. 3, the cement ratio was set to 5.
The cement solidification conditions in this test were the same as those in the test of FIG. Further, as the waste, an evaporated salt obtained by evaporating and solidifying the desulfurization effluent is used, and the selenium (Se) concentration in the waste is 330 mg / kg, and selenium when this waste is dissolved in dissolved water is used. (Se) Concentrations of 11 mg / L tetravalent selenium and 2.3 mg / L hexavalent selenium were used.

Here, the dissolution test was carried out as follows according to TCLP (Toxicity Characteristic Learning Procedure) defined in the EPA 1311 Act.
A part of the cement solidified material 17 which has been dried and cured for a predetermined time is extracted, and a predetermined amount is put into an aqueous glacial acetic acid solution. Shake for 18 hours on a rotary agitator for TCLP test. The cement solids having a diameter of 9.5 mm or more were crushed and tested. After rotary shaking, the solution was filtered using a glass filter, and the filtrate was quantitatively analyzed. Quantitative analysis was performed by high frequency inductively coupled plasma (ICP) absorption spectrophotometry.

As shown in FIG. 3, when 3% by weight of iron-based drug A is added in terms of iron concentration (Test Example 3), when 6% by weight of iron-based drug A is added in terms of iron concentration (Test Example 4), iron In the case of adding 3% by weight of iron-based drug B in terms of iron concentration (Test Example 5) and in the case of adding 6% by weight of iron-based drug B in terms of iron concentration (Test Example 6), it was 0.01 mg / L or less. It was.
On the other hand, when no ferrous inorganic salt is added (Comparative Example 3), the cement ratio is 7, and even if the cement ratio is 8, it cannot be 0.01 mg / L or less. It was.

  As described above, the reason why the preferable result was obtained only when the iron-based drugs A and B were added is presumed that the following phenomenon occurred. That is, first, in the slurrying tank 25, the iron-based additive 15 is added to the suspension obtained by dissolving the evaporative salt as the waste 11 in the dissolved water 12 to form a slurry. In the slurry, hexavalent selenium is reduced to tetravalent selenium that is more easily eluted in the solid phase than hexavalent selenium. Then, by adding the cement solidifying agent 17, the tetravalent selenium is co-precipitated when the alkali and iron in the cement solidifying agent 17 react to produce iron hydroxide, and further dispersed and homogenized in the cement. In a state where the compressive strength of the cement is increased, the solidification reaction of the cement is preferably promoted.

  By the way, as of 2015, selenium (Se), which is one of the harmful substances, has a effluent standard value of 0.1 mg / L or less in Japan, and it is expected that emission standards will become stricter in the future. However, according to the present invention, the strict selenium regulation standard (for example, 0.01 mg / L when the standard value is 1/10 of 0.1 mg / L of the current standard value) The following can also be fully dealt with. In addition to Japan, some countries are planning to tighten emission regulations, and in addition to effluent regulations, there are countries that are planning to tighten regulations on the elution value of each component of landfill waste. For example, mercury (Hg), arsenic (As), and selenium (Se) can sufficiently cope with the elution regulation of about 1/10 level in Japan within the Ministry of the Environment of the country.

As described above, in order to obtain the cement solidified material 21, the waste is first slurried using the dissolved water 12 to obtain the slurryed material 13, and then the powder cement solidifying agent 17 is added to the slurryed material 13. Then, a kneading process is performed in the cement kneading tank 20 to obtain a cement kneaded material 19. Thereafter, the obtained cement kneaded material 19 is dried and cured and solidified to obtain a cement solidified material 21.
In this case, the ratio of waste (solid matter) to cement is preferably 1: 3 to 1: 6, preferably 1: 5.

  In addition, in solid matter: cement = 1: 5, iron-based drug A and iron-based drug B are 3% by weight or more in terms of iron concentration, preferably 5% by weight or more in terms of iron concentration, more preferably 6 in terms of iron concentration. % By weight or more is preferred.

  The water addition rate (water / total weight (waste, cement solid agent, iron-based additive)) is preferably 20% or more, more preferably 30% or more.

  The waste cement solidification method includes a slurrying step in which a waste (concentrate or evaporative salt) 11 containing a heavy metal and a deliquescent compound is dissolved in dissolved water 12 to obtain a slurry 13, and this slurry Addition of iron-based additive 15 to 13A, and addition of cement-solidifying agent kneading and adding cement-solidifying agent 17 to slurry 13B containing heavy metal mixed with iron-based additive 15 And a cement solidifying step in which the cement kneaded material 19 mixed with the cement solidifying agent 17 is cured and cemented.

  As a result, the waste 11 and the cement solidifying agent 17 as in the past are not kneaded in a solid state, but first, the slurry 13 is obtained in the slurrying tank 14, and the slurry is dispersed and homogenized. By adding the cement solidifying agent 17 to the slurry 13 and kneading in the cement kneading tank 20, the solidification strength of the cement solidified material 21 is increased with a smaller amount of cement.

  That is, the hazardous substance in the waste 11 is dispersed and homogenized by a slurrying process in which the waste 11 containing the harmful substance and the deliquescent compound is dissolved in the dissolved water 12 to obtain a slurry. Thereafter, for example, hexavalent selenium as a harmful substance in the slurry is made to be more solid than hexavalent selenium in the slurry by the iron-based additive addition step of adding the iron-based additive 15 to the slurry 13 containing the harmful substance and the deliquescent compound. It is reduced to tetravalent selenium that is easily eluted. Thereafter, a cement solidifying agent 17 is added to the slurry 13 containing the harmful substance and the deliquescent compound mixed with the iron-based additive 15, and the cement solidifying agent adding step of kneading and kneading the tetravalent selenium in the cement solidifying agent 17 is performed. The solidification reaction of the cement is preferably promoted in a state where solid phase coprecipitates when the alkali and iron react to produce iron hydroxide, and further the dispersion and homogenization increases the compressive strength of the cement.

  As the cement solidification strength increases, the leaching of moisture to the cement solidified surface due to the deliquescent compound is also reduced. As a result, the amount of harmful substances exuding to the outside accompanying the deliquescent compound is also reduced. Since it is possible to reduce the elution concentration of the harmful substance by enclosing it in the interior, it is possible to obtain the cement solidified material 21 that satisfies the environmental emission standards even when it is landfilled for a long period of time.

Next, the overall operation of the cement solidifying apparatus 10 according to the present embodiment will be described.
In the cement solidifying apparatus 10 according to the present embodiment, waste 11 containing various harmful substances and deliquescent compounds is introduced into a slurrying tank 14 and a slurry 13 is obtained from dissolved water 12. At this time, the iron-based additive 15 is added to the slurry 13. By adding the dissolved water 12 to the waste 11 as a slurry, it is possible to disperse and homogenize harmful substances in the waste 11. The slurry 13 is introduced into the cement kneading tank 20, and the cement solidifying agent 17 is supplied from the cement solidifying agent supply unit 18 to obtain the cement kneaded material 19. This cement kneaded material 19 is dried, cured and solidified in the cement solidified portion 22 to obtain a cement solidified material 21 having a high compressive strength.

  As described above, according to the present embodiment, the waste 11 containing various harmful substances and deliquescence compounds is then cement-solidified. In the case where the toxic substances and deliquescence compounds are contained, a slurry is obtained once. Then, the cement solidifying agent 17 is supplied to perform the cement solidification treatment, so that the cement solidified product 21 having a high compressive strength can be obtained. As a result, since the immobilization process is performed when the cement solidified material 21 is separately landfilled, the cement solidified material 21 that satisfies the environmental emission standards can be landfilled.

10 Cement solidification processing equipment 11 Waste containing hazardous substances and deliquescent compounds (waste)
DESCRIPTION OF SYMBOLS 12 Dissolved water 13 Slurried material 14 Slurry tank 15 Iron-type additive 16 Iron-type additive supply part 17 Cement solidifying agent 18 Cement solidifying agent supply part 19 Cement kneaded material 20 Cement kneading tank 21 Cement solidified part 22 Cement solidified part

Claims (2)

Slurried tank to obtain a slurry product was slurried by dissolving the waste dissolution water containing harmful substances and deliquescent compounds containing at least selenium,
A cement kneading tank, which is disposed downstream of the slurrying tank, adds a cement solidifying agent to the slurryed material introduced from the slurrying tank, and obtains a cement kneaded product;
Is connected to the slurry Kaso, and iron-based additive supply unit for adding an iron-based additive to the slurry product of the slurry tank,
Wherein arranged downstream of the cement kneading tank, and a cementation unit to cementation was introduced the cement kneaded product drying and curing to from the cement kneading tank Rutotomoni,
In the slurrying tank, the deliquescent compound is made into a slurry with dissolved water, and then the iron-based additive is added. Hexavalent selenium is added to the slurry by the iron-based additive, rather than hexavalent selenium. Reduced to tetravalent selenium, which is easy to elute in the solid phase,
In the cement solidifying part, by adding the cement solidifying agent, tetravalent selenium is co-precipitated when the alkali and iron in the cement solidifying agent react to produce iron hydroxide, and is dispersed and homogenized. A cement solidification treatment apparatus for waste, wherein the cement solidified product has a compressive strength of 200 kg / cm ² or more . In claim 1,
The waste cement solidifying apparatus, wherein the iron-based additive is a ferrous inorganic salt.

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