sewage sludge drying with microwave...

Sewage Sludge Drying with Microwave Irradiation:

Guray Salihoğlu*, Sibel Yenikaya, N. Kamil Salihoğlu, Gokhan Yenikaya*Department of Environmental Engineering, University of Uludag, Bursa, 16059, Turkey

Department of Electrical-Electronic Engineering, University of Uludag, Bursa, 16059, Turkey

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04•Sludge Dewatering & Drying

Introduction

Materials & Methods

•Impact of the Factors on Drying

Results & Discussion

Conclusions

Content

•Microwave Modeling

3Sludge Management

Additional fuel ?

Sludge Management

Mechanical Dewatering

•Large amounts and high moisture content•WWTP Exit: 1-4% DS

Cement plant co-

incineration•Cement plants use dried sewage sludge as a substitute for fossil fuel•Co-incineration in cement plants is possible

Drying•Increased calorific value•Easy handling•Reduced volume

Microwave Drying•Can be a preferred step in sludge management • Heats the material rapidly•Instant on/off control•Increase the calorific value

•20-35 % DS

•To investigate the efficiency of microwave technology as a sludge drying method

Objectives

•To compare the energy consumption with that of electrical heating•To investigate the influence of the addition of ionic species such as salt to the drying performance

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Materials & Methods

Mechanically dewatered sludge•Characterization experiments: Composition, dielectric constants•Salt addition : 5%

Microwave Drying•2.45 GHz : Resonance frequency of water molecules•Fixed & Rotary modes•Power: 900 W•Time intervals: 1-10 minutes•Air cure : 10 minutes

Monitoring•Moisture contents, •Evaporation rates, •Drying performances•Hot and cold regions•Energy consumption•Thermal camera images

Electrical drying to compare the energy consumption levels

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7TH INTERNATIONAL CONFERENCE ON SUSTAINABLE SOLID WASTE MANAGEMENT, 26-29 June 2019, Heraklion, Crete Island, Greece

Comparison of moisture losses in fixed and rotary operation modes

fixed mode > rotary

mode

Fixed mode provided

concentrated heating and

more evaporation



Comparison of moisture losses in sludge with salt and without salt Salt addition resulted in a lower level of moisture

losswithout salt > with



Comparison of temperatures in sludge with salt and without salt Higher temperatur

e levels with salt

with salt : 75.62±4.51

oC without

salt: 65.19 ±4.06oC

Low

evaporation?


7TH INTERNATIONAL CONFERENCE ON SUSTAINABLE SOLID WASTE MANAGEMENT,26-29 June 2019, Heraklion, Crete Island, Greece

Low evaporation with salt added sludge although temperature levels are high?

’ ’’ ’’/’ (×10-3)

Sludge without salt

76.22 10.18 0.134

Sludge with salt

58.18 18.90 0.325

Dielectric constant (Relative

permittivity): The ability to

store the energy

Relative dielectric loss factor:

Conversion ability of the energy into heat

Loss TangentHigh loss tangent is an indication of the use of

microwave power transferred into heat

Dielectric characteristics of the sludge studied

Measured by Network analyzer (Agilent, E506 1B)

Salt addition to the sludge

decreased the dielectric

constant and increased the dielectric loss factor, thus

increased the dissipation

factor.

Salt addition might have changed the molecular structure of the

sludge limiting the evaporation. Salt might have associated with

sludge water, thereby might have decreased the free water and converted it into bound water

(capillary or particle).

10Electric field distribution Maximum intensity

when the oven is emptywhen the sewage sludge sample was inside• Electric field is stronger near the walls of the oven

•The distribution is symmetrical relative to the XZ plane

•When the sample was placed, electromagnetic waves were reflected from the oven walls and the sample surface.•Therefore the electric field was dense on the corner points of the tray


11Energy Consumption: Electrical Microwave

Less time and less energy

with microwave

30% moisture loss duration

Microwave : 10 min.Electrical: 30 min.

30% moisture loss energy consumption

Microwave : 0.231 kW

Electrical: 0.444 kW

12Conclusions


Moisture lossFixed mode > rotary mode

Concentrated heating in the fixed mode

Salt addition •Decreased the moisture loss•Decreased the dielectric constant•Increased uniform heat distribution

Evaporation continued during air cure after drying.

Electric field was dense on the corner points of the tray, more evaporation

Electrical drying consumed more energy for a certain moisture

loss targeted in sludge.

Less Time and Less Energy with Microwave

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References

1. Yu, Q., Lei, H.Y., Yu, G.W., Feng, X., Li, Z.X., Wu, Z.C.: Influence of microwave irradiation on sludge dewaterability. Chem Eng J 155(1-2), 88-93 (2009). doi:10.1016/j.cej.2009.07.0102. Gil, A., Siles, J.A., Martin, M.A., Chica, A.F., Estevez-Pastor, F.S., Toro-Baptista, E.: Effect of microwave pretreatment on semi-continuous anaerobic digestion of sewage sludge. Renewable Energy 115, 917-925 (2018). doi:10.1016/j.renene.2017.07.1123. Kumar, S., Kumar, R., Mehrotra, S.P.: Influence of granulated blast furnace slag on the reaction, structure and properties of fly ash based geopolymer. J Mater Sci 45(3), 607-615 (2010). doi:10.1007/s10853-009-3934-54. Mawioo, P.M., Garcia, H.A., Hooijmans, C.M., Velkushanova, K., Simonic, M., Mijatovic, I., Brdjanovic, D.: A pilot-scale microwave technology for sludge sanitization and drying. Science of the Total Environment 601-602, 1437-1448 (2017). 5. Domínguez, A., Menéndez, J.A., Inguanzo, M., Pis, J.J.: Sewage sludge drying using microwave energy and characterization by IRTF. Afinidad 61(512), 280-285 (2004). 6. Bennamoun, L., Chen, Z., Afzal, M.T.: Microwave drying of wastewater sludge: Experimental and modeling study. Drying Technology 34(2), 235-243 (2016). 7. Jinping, L., Jinhua, G., Jieqiong, J., Ni, W.: Study on New Thermal Drying Methods for Sewage Sludge Using Microwave and its Mechanism. Aer Adv Eng Res 30, 1103-1108 (2015). 8. Tyagi, V.K., Lo, S.L.: Microwave irradiation: A sustainable way for sludge treatment and resource recovery. Renew Sust Energ Rev 18, 288-305 (2013). doi:10.1016/j.rser.2012.10.032

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