**2. Materials and methods**

Currently, the S sewage treatment facility incinerates about 150 ton/day of sewage waste by putting it into a fluidized bed incinerator at 800°C or higher. As an incineration by-product, incineration ash is generated at approximately 10 ton/day, and incineration ash is largely classified into fly ash and bottom ash. Particle size analysis was performed using a particle size analyzer (Sympatec GmbH, HELOS/HAER), and the chemical composition was analyzed with an X- ray fluorescence spectrometer (Rigaku, NEX-CG) and a scanning electron microscope (Shimadzu, SS-550). First, the L/S ratio (Leaching solution/Solid ratio, mL/g) was fixed at 10, which is the same as the experimental conditions suggested by other researchers [7]. fly ash 200 g and eluate 2 L was put into a standard Jar(2 L), and after stirring, solid-liquid separation was performed at 2000 rpm for 20 min using a centrifuge. The supernatant was analyzed. Heavy metals were prepared by pretreating the sample. Analyzed by ICP-OES (Varian, VISTA PRO) and PO4 3− and SO4 2− Anions such as were analyzed using IC(Metrohm, CH/Advanced IC) .

The phosphorus recovery process largely consists of two steps: phosphorus extraction and crystallization. First, the phosphorus extraction method is classified into an acid extraction method and an alkali extraction method, and the phosphorus crystallization step is MAP and HA depending on the input cation.

Phosphorus Recovery System(PRS), which was developed for the first time in Korea by applying the above phosphorus recovery principle, is made of acrylic

**Figure 1.** *Configuration of the PRS.*

*Development of the Phosphorus Recovery System (PRS) Utilizing Ultrasonic Wave in Incinerated… DOI: http://dx.doi.org/10.5772/intechopen.109981*

material except for the ultrasonic extraction tank, and the ultrasonic extractor, Solid-Liquid Seperator, Mixing Tank, and P-Recovery Tank (**Figure 1**) .

Ultrasonic extraction tank that elutes phosphorus contained in the incineration ash is made of stainless material to prevent corrosion, and the fly ash and An agitator was installed to mix the eluate (**Figure 2**). In addition, by installing a cover on the top, evaporation of moisture due to temperature change during operation is minimized. The internal volume of the reactor is 48 L (0.4 m × 0.4 m × 0.3 m), and a total of 20 vibrators (4 × 5) with a frequency of 28 kHz are installed on the floor (**Figure 3**). The maximum ultrasonic power is 700 W, and the fly ash and of the eluate When mixing The L/S ratio (leaching solution/solid ratio, mL/g) was set to 10.

The solid-liquid separation tank has an inner diameter at the rear end of ultrasonic extraction tank. It is a cylinder with a height of 190 mm and a height of 500 mm and has an internal volume of 14 L. It separates the leached mixture of incineration ash. The remaining incineration ash is transferred to the hopper at the bottom by a pump, and the supernatant is transferred to the mixing tank through the Decanter located on the surface. It is a cylinder with a height of 150 mm and a height of 205 mm, and the

**Figure 2.** *Photo of ultrasonic extractor.*

**Figure 3.** *Arrangement of vibrators.*


#### **Table 1.**

*Specification of the PRS.*

internal volume is 3.6 L, and an agitator is installed in the center for complete mixing. During MAP crystallization, 2 M MgCl2+ and 2 M NH 4 Cl were used as Mg2+ and NH4 + sources, respectively, and CaCl2 was used as Ca2+ source during HAP crystallization. Phosphorus (P) recovery tank inner diameter It is a cylinder with a height of 190 mm and a height of 250 mm, and the internal volume is 6.4 L. In addition, it was designed so that phosphorus crystal (Struvite) precipitated at the bottom was transferred to the storage tank through a pump. The specifications of the P(phosphorus) recovery system (PRS) are shown in **Table 1**.

The recovered precipitate was analyzed using an X- ray diffractometer(XRD, Shimadzu, JP/XRD-7000) and an X- ray fluorescence analyzer (XRF, Rigaku, NEX-CG).
