TWI552811B - Treatment of Harmful Heavy Metal Incineration Fly Ash - Google Patents

Description

Treatment method for hazardous heavy metal incineration fly ash

The invention relates to a fly ash treatment method, in particular to a treatment method for containing heavy metal incineration fly ash.

After the general waste is incinerated, the fly ash produced contains metal oxides such as calcium (Ca), strontium (Si), aluminum (Al), and iron (Fe), salts (chlorine salts), and cadmium (Cd). , harmful metals such as chromium (Cr), mercury (Hg), copper (Cu) and lead (Pb), therefore, must be stabilized or harmless before the resource can be reused or finally disposed.

Existing incineration fly ash is mostly subjected to intermediate treatment by solidification and stabilization. Curing practices, which currently include fixation, encapsulation, and vitrification, are solid lumps that are added to hazardous waste incineration fly ash by a curing agent such as cement, sodium citrate, lime, or clay. Make harmful substances difficult to dissolve. At present, most of the incineration fly ash is treated by adding cement. Although the curing treatment has the advantages of simple operation, low installation cost, and no exhaust gas treatment problem, the volume after curing is increased by 15 to 20%, the weight is increased by 40 to 50%, and the curing agent and natural resources are wasted, and the partitioning and burying treatment is required to be reduced. The burial period, while the incineration fly ash contains high concentrations of chloride salts, affecting the durability of the solidified body, Long-term placement of heavy metals still has doubts about dissolution. The encapsulation is to cover hazardous waste to isolate harmful substances from the outside world. However, due to its high cost of coating, the processing cost is too high, so it is rarely used. As for the vitrification method, it is a treatment method for inorganic harmful waste materials. The hazardous waste is put into a furnace to melt the harmful waste at a temperature of 1400 ° C, or sintered or added with an appropriate amount of alumina to be melted into a glass ceramic to achieve stability. , reduction and reduction of capacity. The object to be treated is relatively wide, and the compressive strength is large, and the glass and ceramics produced can be reused. However, due to the high salt base, the single melting process is limited, and the installation cost and operation and maintenance cost are very expensive.

In addition, the deuteration treatment method is to add an adsorbent or a chelating agent or a chemical stabilizer to react the harmful substance into a stagnant substance without changing, so as to achieve the purpose of no longer generating harmful substances. However, its advantages and disadvantages are the same as those of the above curing treatment.

Therefore, there are a number of patents published, such as the Republic of China Announcement No. I311494, "Methods for Removal of Heavy Metals from Waste Incineration-Derived Fly Ash", which is to use the original fly ash and reaction fly ash to mix proportions, and then add 4 to 8 times mixed tap water weight tap water or distilled water, 10 to 24 hours of thorough stirring or shaking extraction, to achieve the purpose of fly ash heavy metal removal. However, the washing treatment liquid is still to be treated, and the detailed treatment and improvement of the solid-liquid separation fly ash and waste liquid are not disclosed.

Another example is the invention patent case of the "Incineration Fly Ash Treatment Method and Device" of the Republic of China Announcement No. I257330. The incineration fly ash is firstly washed with water and then filtered by a closed pump. But did not reveal how to eliminate heavy metals.

Another example is the Republic of China Announcement No. 407067, "Waste Disposal The invention patent case is to add water glass and water to the waste for shaking and stirring, to form lead bismuth citrate precipitated in the waste, to stabilize the lead, and to stabilize the harmful heavy metal lead, but the invention It is still only combined with water glass and water, that is, sodium citrate solution and water mixed with heavy metal waste for curing curing.

The applicant of the present invention has also applied for and approved the invention patent of "Processing Method for Containing Heavy Metal Incineration Fly Ash" in CN 101725993 of China, the main technical feature of which is that every 100 wt% of waste containing heavy metals is incinerated. 30 to 50 wt% of quartz sand and water are added to the fly ash, mixed and stirred to form a solid-liquid slurry, and placed in a wet vortex cone sorting machine for separation. However, as a result of continuous research by the inventors, the technical features disclosed in the case have room for the removal of harmful heavy metals, and the present invention has been proposed.

Therefore, it is an object of the present invention to provide a treatment method for incineration fly ash containing heavy metals, which can not only remove soluble chlorine salts in fly ash, but also achieve harmlessness and resources of coarse particle incineration fly ash, and can reduce The treatment cost of fine particle size incineration fly ash improves the applicability of incineration fly ash resource recycling.

Therefore, the present invention comprises a method for treating heavy metal incineration fly ash, comprising the steps of: (a) adding water to the heavy metal incineration fly ash, heating to 50 to 80 ° C, mixing and stirring for a period of time, and then adding Quartz sand and continue to stir, at this time using an ultrasonic generator to deliver 150 Ultrasonic wave up to 300 watts, ultrasonic action time is controlled at 2.5 to 10 minutes to form solid-liquid slurry; (b) The solid-liquid slurry is sent to a wet vortex cone sorting machine to separate harmful heavy metals by a pressure pump .

The effect of the invention is that the centrifugal force and the gravity act in the process of the rotary screening by the wet vortex cone grading screening machine, together with the oscillating action of adding water and ultrasonic waves, the coarse and fine particles can be carried out according to the particle size or density difference of the particles. Sorting, that is, the coarse particles sink, the fine particles float, to effectively separate harmful heavy metals, and at the same time, the soluble chlorine salt in the fly ash can be washed away, so that the chlorine salt meets the standard, and the coarse particle incineration fly ash is harmless and resources can be achieved. It can reduce the treatment cost of fine particle size incineration fly ash and improve the applicability of incineration fly ash resource recycling.

11‧‧‧Steps

12‧‧‧ steps

13‧‧‧Separation steps

21‧‧‧Incineration fly ash

22‧‧‧Quartz sand

23‧‧‧ water

24‧‧‧ solid liquid slurry

25‧‧‧ Wastewater Removal

31‧‧‧pressure pump

32‧‧‧ Wet Vortex Cone Screening Machine

321‧‧‧ bottom mouth

322‧‧‧ overflow

33‧‧‧ Ultrasonic generator

Other features and advantages of the present invention will be apparent from the embodiments of the present invention. FIG. 1 is a flow chart illustrating an embodiment of a method for treating heavy metal incineration fly ash according to the present invention; 2 is a schematic diagram, and FIG. 3 is a supplementary diagram illustrating the relationship between the liquid-solid ratio of the solid-liquid slurry of the embodiment and the chlorine salt removal rate; FIG. 4 is a relationship diagram illustrating the solidification of the embodiment. The relationship between the stirring time of the liquid slurry and the chlorine salt removal rate; FIG. 5 is a relationship diagram illustrating the relationship between the blade rotation speed and the chlorine salt removal rate of the wet vortex cone grading screening machine of the embodiment; Fig. 6 is a diagram showing the relationship between the ultrasonic power and the chlorine salt removal rate of this embodiment.

Before introducing the step flow of the method of the present invention, the physicochemical characteristics and dissolution characteristics of the collected incineration fly ash are described, and the water content, specific gravity, pH value, ignition loss, salt concentration and toxicity characteristics dissolution test of the incineration fly ash are analyzed. (TCLP), and the cumulative weight percentage of each particle size distribution after analysis and its heavy metal content are as follows: The incineration fly ash used in the embodiment of the present invention is from a resource recycling plant in southern Taiwan, taken from half of the plant The incineration fly ash obtained by the dry type smoke washing tower and the bag type dust collector, the physicochemical analysis of the fly ash has a water content of 1.28% and a pH value of 12.08, which is a high alkalinity substance and has a specific gravity of 2.89 g/cm ³ . Unburned carbon 0.21%, activated carbon 11.73%, and as shown in Table 1, it shows that elements such as calcium (Ca), chlorine (Cl), strontium (Si), potassium (K) and sodium (Na) are incinerated fly ash. Mainly. The crystal phase composition is CaClOH, Ca(OH) ₂ , KCl, NaCl, SiO ₂ , CaSO ₄ , CaCO ₃ .

Referring to Table 2, the results of the incineration fly ash toxicity characteristic dissolution test (TCLP), it can be found from the analysis results that the incineration fly ash has a higher dissolution concentration of Pb (34.08 mg / l) and Zn (6.13 mg / l). The dissolution concentration of Pb has exceeded the regulatory limit of dissolution toxicity (5 mg/l).

Referring to Figures 1 and 2, an embodiment of a method for treating heavy metal incineration fly ash according to the present invention comprises the following steps 11 and 12.

In this step 11, water 23 is first added to the heavy metal incineration fly ash 21, and heated to 50 to 80 ° C, and mixed and stirred for washing, and the water washing time is at least 2.5 minutes, so that the chlorine removal effect is performed. . Then, quartz sand 22 is added and stirring is continued. At this time, an ultrasonic wave of 150 to 300 watts is supplied by an ultrasonic generator, and the ultrasonic action time is controlled to 2.5 to 10 minutes to form a solid-liquid slurry 24. Specifically, the solid-liquid slurry 24 has a liquid-solid ratio of 10:1. Further, the mixing ratio of water, incineration fly ash, and quartz sand is 30:2:1, or 40:3:1, which is explained in the present embodiment. Further, the quartz sand 22 may be selected from amorphous ceria, quartz, smectite, chalk or quartz.

In particular, the liquid-solid ratio and the stirring time of the solid-liquid slurry 24 have an effect on the chloride salt. As shown in Fig. 3, it can be seen that increasing the liquid-solid ratio can dissolve more water-soluble chloride salts and improve the removal rate. , but high liquid to solid ratio However, a large amount of wastewater 25 is eliminated (see Figure 2), which increases the load and cost of wastewater treatment. Therefore, the liquid-solid ratio is preferably 15 L/kg. As shown in Fig. 4, when the stirring time reached 2.5 minutes or more, the chlorine salt removal rate did not significantly increase, indicating that the dissolution of the chlorine salt should be close to equilibrium in about 2.5 minutes.

Next, referring to Figures 1, 2, in step 12, the solid-liquid slurry 24 is fed to a wet vortex cone sorting machine 32 by a pressure pump 31 at a pressure of 20 to 140 kPa (Fig. 3). , 4, 5, 6 referred to as FA) to separate harmful heavy metals.

The wet vortex cone grading screening machine 32 is activated, so that the solid-liquid slurry 24 can be screened according to the particle size or density difference of the particles under the action of centrifugal force and gravity. At this time, the particles with large and dense particles are in centrifugal force and gravity. Under the action, it will move downwards in the axial direction and outward in the radial direction, and is discharged by the Underflow (UF) 321 to form a flow field of the Outer Spiral. Particles with small particles and low density move toward the central axis and form an upward inner spiral on the central axis, and are discharged by an overflow (OF) 322 to collect coarse particles. The separation effect can simultaneously wash away the high concentration of chloride salt in the incineration fly ash 21. The experimental results show that the chlorine salt removal rate can reach 94.17%, and the chloride content of the washed fly ash is reduced to 7000 mg/kg. Therefore, the chlorine salt can meet the standard, and the coarse particle size incineration fly ash 21 can be harmlessly and resource-resourced, and the treatment cost of the fine particle size incineration fly ash 21 can be reduced, and the applicability of the resource utilization and reuse of the incineration fly ash 21 can be improved. .

Referring to FIG. 5, it is found by experiments that the blade rotation speed of the wet vortex cone sorting machine 32 has no significant effect on the removal of chlorine salt. The highest chloride removal rate is obtained at a rotational speed of 500 ppm and the chloride concentration in the solid-liquid slurry 24 is minimized. In addition, as shown in Fig. 6, the auxiliary of the ultrasonic wave can contribute to the improvement of the chlorine salt removal rate, and the ultrasonic power is increased, and the chlorine salt removal rate is also increased, and the two are positively correlated. The experimental results show that with the aid of ultrasonic waves, the liquid-solid ratio of solid-liquid slurry 24 can reach the liquid-solid ratio of 20L/kg and the chlorine-free removal rate is similar to that of ultrasonic-assisted water washing. The auxiliary effect of ultrasound can help reduce water demand.

The invention is further illustrated by the following examples, but it is not intended that the invention be limited only by the examples.

Experimental example 1

Referring to Figure 2, take 10wt% of incineration fly ash 21, add 100wt% water 23, and stir for 10 minutes to wash. The washed solid-liquid slurry 24 is compared with whether or not to add quartz sand 22, as shown in Table 3. Most of the salts are dissolved in the liquid, only a small amount of salts are present in the solid, and the solid-liquid slurry 24 of the quartz sand 22 is added, and the weight loss of the salt is more.

Experimental example 2

Referring to Figure 2, the incineration fly ash 21 will be added with or without quartz. The solid-liquid slurry 24 mixed with the sand 22 and the water 23 is sent to the wet vortex cone grading screening machine 32 by the pressure pump 31, respectively, and the inlet pressure is sorted by three different pressures of 20, 80 and 140 kPa, and the particles are large. And the dense particles move downward and downward along the pipe wall, and flow out from the bottom flow port (UF) 321 , and the particles and the small density particles move toward the central axis, forming an upward inner vortex on the central axis, and the inner vortex is overflowing. The orifice (OF) 322 is discharged. The physicochemical and dissolution characteristics and elemental compositions after screening are shown in Table 4, Table 5, Table 6 and Table 7, respectively.

In the above Table 4, N.D. means that it was not detected. In addition, the content of lead (Pb) still exceeds the regulatory limit at both the overflow (OF) 322 and the bottom flow (UF) 321 .

In the above Table 5, N.D. means that it was not detected. In addition, the lead content of the sample at the sampling point overflow (OF) 322 is higher than the lead content of the sample at the bottom of the sampling point (UF) 321 , and the solid lead of the sample at the sampling point overflow (OF) 322 The content of the sample is higher, and the solid lead content of the sampled sample at the bottom of the sampling point (UF) 321 is lower.

In the above Table 6, N.D. means that it was not detected. In addition, the lead content of the sample at the sampling point overflow (OF) 322 exceeds the regulatory limit (5 mg/l), and the lead content of the sample at the bottom point (UF) 321 of the sampling point meets the regulatory limit. It is apparent that the addition of quartz sand 22 facilitates the enrichment of heavy metals in the overflow (OF) 322.

Experimental example 3

Referring to FIG. 2, the experimental example 2 is repeated, but only the solid-liquid slurry 24 of the quartz sand 22 is added by incineration fly ash 21, and the mixing ratio of the incineration fly ash 21 and the quartz sand 22 is 2:1 and 3:1 respectively. The effects of wet vortex cone screening on enrichment efficiency are shown in Tables 8 and 9.

In the above Tables 8 and 9, N.D. means that it was not detected. In addition, as shown in Table 9, as the inflow pressure increases, the wet vortex cone screen is rich. The efficiency of collecting heavy metals also increases. When the concentration of the feed concentration is 10wt%, the inflow pressure is 140Kpa, and the mixing ratio of the incineration fly ash 21 and the quartz sand 22 is 2:1, the enrichment effect is best (see Table 8), the vortex overflow port and the bottom outlet In the samples collected, the Pb dissolution concentrations were 12.35 mg/l and 2.44 mg/l, respectively. The case where the ratio of the incineration fly ash 21 to the quartz sand 22 is 3:1 is compared with the case where the mixing ratio is 2:1, although the effect of the former is slightly lower than that of the latter, it is still an acceptable range. If the amount of quartz sand 22 added is reduced and energy is saved, and the wear of the wet vortex grading screening machine 32 is reduced, the harmful heavy metal lead (Pb) is eliminated in accordance with the principle of reaching the dissolution concentration standard to incinerate fly ash. Lead (Pb) enrichment is achieved by adding quartz sand 22 in a weight ratio of 1/3 to 1/2.

In summary, the method for treating heavy metal incineration fly ash 21 of the present invention is carried out by the above-mentioned step flow, and the action of centrifugal force and gravity during the rotary screening process by the wet vortex cone sorting machine 32 is added with water 23 And the oscillation of the ultrasonic wave, and the coarse and fine particles can be sorted according to the particle size or density difference of the particles, that is, the coarse particles sink, the fine particles float, to effectively separate the harmful heavy metals, and at the same time, the solubility in the incineration fly ash 21 can be washed away. The chlorine salt makes the chlorine salt meet the standard, and can also achieve the harmlessness and resource utilization of the coarse-grained incineration fly ash 21, and can reduce the treatment cost of the fine-grained incineration fly ash 21, and improve the application of the incineration fly ash 21 resource recycling. Sexuality, it is indeed possible to achieve the object of the present invention.

However, the above is only the embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent change and modification of the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

21‧‧‧Incineration fly ash

22‧‧‧Quartz sand

23‧‧‧ water

24‧‧‧ solid liquid slurry

25‧‧‧ Wastewater Removal

31‧‧‧pressure pump

32‧‧‧ Wet Vortex Cone Screening Machine

321‧‧‧ bottom mouth

322‧‧‧ overflow

33‧‧‧ Ultrasonic generator

Claims (7)

A method for treating heavy metal incineration fly ash, comprising: (a) adding water to a heavy metal incineration fly ash, heating to 50 to 80 ° C, mixing and stirring for a period of time, adding quartz sand and continuing to stir At this time, an ultrasonic generator is used to deliver ultrasonic waves with a power of 150 to 300 watts, and the ultrasonic action time is controlled to be 2.5 to 10 minutes to form a solid-liquid slurry; (b) a solid-liquid slurry is fed by a pressure pump. A wet vortex cone sorting machine separates harmful heavy metals. The method for treating heavy metal incineration fly ash according to claim 1, wherein the solid-liquid slurry has a liquid-solid ratio of 10:1. The method for treating heavy metal incineration fly ash according to claim 2, wherein the mixing ratio of water, incineration fly ash and quartz sand is 30:2:1. The method for treating heavy metal incineration fly ash according to claim 2, wherein the mixing ratio of water, incineration fly ash and quartz sand is 40:3:1. The method for treating heavy metal incineration fly ash according to any one of claims 1 to 4, wherein, in the step (a), the stirring water washing time is at least 2.5 minutes. The method for treating heavy metal incineration fly ash according to claim 5, wherein the pressure pump feeds the solid-liquid slurry into the wet vortex cone sorting machine at a pressure of 20 to 140 kPa. A method for treating heavy metal incineration fly ash according to claim 1, wherein the quartz sand is selected from the group consisting of amorphous ceria, quartz, smectite, smectite or quartz.