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1 J. Korean Soc. Environ. Eng., 37(10), 573~577, 2015 Original Paper ISSN , e-issn Characteristics of Coagulation Treatment for Wood Tar Waste Water in a Biomass Gasification Plant 김이태 안광호 I tae Kim Kwangho Ahn 한국건설기술연구원환경플랜트연구소 Environmental and plant Eng. Research Division, Korea Institute of Civil Engineering and Building Technology (Received September 9, 2015; Revised October 15, 2015; Accepted October 28, 2015) Abstract : There are difficulties in removing wood tar wastewater coming from the power plants that use wood-based fuels due to its intermittent occurrences and severe changes in the amount and concentration. This study investigated the treatment characteristics through physicochemical treatment, an improved method from the existing ones using bag filters and activated carbons to treat wood tar wastewater. In the case of chemical properties of wood tar wastewater, the content of phenols was found to be more than two times higher than that of guaiacols and carbohydrates. Installation is done to ensure that NaOH and PAC are injected automatically according to the change of ph, and then ph, turbidity and SS of the final treated water were examined. The results were 5.9, 12.6 NTU and 15.1 mg/l respectively, which confirmed the possibility of the treated water as circulation water of power plants. In the physical treatment process using a conventional bag filter, removal efficiency of chemicals was about 20%, but the treatment efficiency was improved to show chemical removal efficiency of about 80% through flocculation and sedimentation. Key Words : Tar-Containing Wastewater, Biomass, Gasification, Power Plant 요약 : 목질계연료를사용하는발전시설에서세정되어나오는목질계타르폐수는간헐적발생, 발생량및발생농도의변화가심하여제거에어려움이있다. 본연구에서는목질계타르폐수를기존의 bag filter 와활성탄을이용한처리방법에서개선하여물리화학적처리를통하여처리특성을살펴보았다. 목질계타르폐수의화학적인발생성상은페놀류의함유량이구아이아콜류 (guaiacols) 와카보하이드레이트류 (carbohydrates) 에비해약 2 배이상높게나타났다. ph 의변화에따라 NaOH 와 PAC 이자동주입되도록설치하고최종처리수의 ph, 탁도, SS 를살펴본결과, 각각 5.9, 12.6 NTU, 15.1 mg/l 로발전설비의순환수로서의가능성을확인하였다. 기존의백필터 (bag filter) 를이용한물리적처리공정에서의화학물질의제거효율은약 20% 였으며, 응집및침전을통한처리효율을개선한결과, 약 80% 의화학물질제거효율을나타내었다. 주제어 : 타르폐수, 바이오매스, 가스화, 열병합발전 1. 서론 바이오매스의에너지화기술은합성가스에포함된여러가지다양한성분 ( 알칼리성분, 질소및황화합물 ) 을제거하기가힘들고에너지및비용소요가크다. 1) 목질계연료는셀룰로오스및리그닌함량이 30% 정도로높아이로인해타르가발생되게된다. 벤젠고리로구성된탄화수소의화합물인타르는매우복잡한구성형태와그종류도수천가지에이르며, 벤젠보다큰분자량을가지는유기고분자화합물로정의한다. 타르는혼합산소제와페놀류등 (mixed oxygenates, phenolic ethers, alkyl phenolics, heterocyclic ethers) 과다중고리형방향족탄화수소 (poly-aromatic hydrocarbons, PAH) 등의화합물로서반응성이증가하면분자량이큰 PAH로에서분자량이작은혼합산소제로성분이변화하게된다. 2) 목질계타르에대한연구는콜타르만큼활발하지못하지만, 목질계타르와유사한특성을보이고있다. 콜타르의경우는열탈착법 (thermal desorption) 3) 계면활성제플러싱법 (surfactant flushing), 3) 곰팡이류나박테리아를통한분해, 4) 생화학적방법 (biochemical treatment) 5,6) 와같은방법들이있었다. 활성탄은휘발성유기화합물 (volatile organic carbon, VOC) 의흡착에가장널리쓰이는물질로바이오매스타르의경우, 휘발성유기화합물함량이높기때문에목질계타르의 휘발성유기화합물흡착에도활성탄이유용하여이를통한 바이오매스타르의경우에대한연구사례도있다. 7) 경타르 (light tar) 및방향족탄화수소 (aromatic hydrocarbon; 벤젠, 톨루엔, 나프탈렌 ) 성분과저분자성이낮은다환족방향족 탄화수소에는활성탄에의한흡착이유리하나, 고분자성 다환족방향족탄화수소같은타르화합물처리가어려운것 으로알려져있다. 이는활성탄에의한경타르성물질의 높은흡착율은활성탄기공의배열구조에의하여설명되어진다. 8~10) 목질계타르폐수는폐수의발생량과발생농도변화가심하여생물학적분해가어렵고처리의안정성도낮다. 이제까지목질계바이오매스열병합발전시설의물리화학적제거 Corresponding author itkim@kict.re.kr Tel: Fax:

2 574 J. Korean Soc. Environ. Eng. 김이태 안광호 에관한연구가없어본연구는열병합발전시설의목질계타르폐수를대상으로응집처리에의한물리화학적처리효과를처음으로확인해보고자수행하였다. 2. 실험재료및연구방법 2.1. 실험재료및분석방법 바이오매스가스화공정발생타르 (tar) 를포함한폐수로 ph 4.9의산성을나타내었다. 성분분석은 GC/MS를사용하였으며그분석조건은 Table 1과 Fig. 1과같은과정을거쳐분석하였다 가스화열병합발전설비의타르폐수처리시설 Fig. 2는기존수처리공정으로시간당 10 m 3 의폐수를쇄석 (5 mm~15 mm) 을통해덩어리진입자를제거하고여과를한후 2차로백필터를통과시킨후활성탄충전탑을통과하는처리계통도이다. Fig. 3은타르함유폐수의개선된공정을나타낸것으로기존의 pore size 1 µm인백필터 Table 1. GC/MS analysis condition for tar wastewater Instrument Perkin Elmer Clarus 600 / (Detector: Clarus 600T) Column HP-5MS-UI GC oven 40 5 min, 10 /min 320 Inlets Split less, Heater 250 Fig. 1. Sample pre-treatment method(liquid-liquid extraction (LLE). (bag filter) 및활성탄필터 (activated carbon filter) 로여과하는공정부분을약품침전부분으로교체하여제거효율을향상시키고자하였다. 반응조는유입수에 1N의 NaOH와 Ca(OH) 2 를주입 (A reactor) 하여 ph를 8.5로증가시키고, 17% PAC을주입 (B reactor) 하여 ph를 6.0까지감소하여침전조및 zeolite를거쳐배출되게하였다. 반응조체류시간은 A 반응조, B 반응조, 침전조각각 2.3 hr, 2.1 hr, 6.0 hr 으로하여운전하였다. Fig. 2. Existing treatment process of tar-containing wastewater. Fig. 3. Improved treatment reactor of tar-containing wastewater. Journal of KSEE Vol.37, No.10 October, 2015

3 J. Korean Soc. Environ. Eng 결과및고찰 3.1. 폐수의정성 정량분석 수처리공정의유입수인목질계타르성분폐수에대한성상을분석한결과 (Fig. 4 및 Table 2), 총 13개의화학종이나타났으며, 페놀류 (phenols), 구아이아콜류 (guaiacols), 카보하이드레이트류 (carbohydrates) 로크게 3가지군으로세분되었다. 이중페놀류와구아이아콜류의성분이다양하게검출되었고페놀이 mg/l로가장높고 m-p 크레졸 (mor p-cresol) 이 mg/l로나타나 2번째로높게나타났다. 다음으로구아이아콜류중 4-비닐구아이아콜 (4-vinylguaiacol) 이 mg/l로높은농도를나타내었다. Mohan 11) 등에의하면바이오오일생산을위한목재 / 바이오매스열분해온도에따라 Fig. 5와같이페놀에테르 (phenolic ether : 400 ) 부터분자량이큰 PAH (900 ) 까지다양하게생성됨을발견및확인하였다. 11) Fig. 6. Chemical concentration of existing process (a) and improved process (b). Fig 4. TIC chromatogram of quantified compounds with internal standards from SPA sampling. Table 2. Chemical compositions of tar-containing wastewater No. Chemical species Concentration (mg/l) 1 phenol m- or p-cresol phenols 3 3-ethylphenol o-cresol vinylguaiacol acetoguaiacone methoxy-4-methylphenol vanillin 51.4 guaiacols 9 eugenol guaiacol trans-isoeugenol cis-isoeugenol ethylguaiacol carbohydrates corylone 목질계타르폐수발생화학종별농도변화 Fig. 6은목질계타르폐수의기존공정및수정된공정의유입수와처리수화학물질농도를나타낸것으로유입수는 phenol의농도가매우높게나타났으며, m- or p- cresol, 4- vinylguaiacol, acetoguaiacone, corylone 의유입수농도가 121~ 198 mg/l로높게나타났다 연속처리장치에의한타르폐수의암모늄및 COD 처리 Fig. 3의장치를이용하여 NaOH, Ca(OH) 2 및 PAC이 ph 에따라자동주입되도록연속반응조에서실험한결과, Fig. 7과같이암모늄염 (NH + 4 -N) 은 30.6 mg/l의농도를보였으며, NaOH, Ca(OH) 2 및 PAC를이용한응집처리공정은약 20 mg/l로낮게나타났으나, 천연제올라이트 (Clinoptilolite) 층을통과시켰을경우 6.3 mg/l로저감되어암모늄염을제거하기위해서는제올라이트에의한암모니아흡착공정이추가되어야할것으로사료된다. NO - 3 -N 농도는원수및 NaOH, Ca(OH) 2 및 PAC 사용에큰변화가없었다. COD cr 은 ph 조정을위해 NaOH와 Ca(OH) 2 주입에따라농 Fig. 5. Relationship between products and temperature to which vapors are exposed before quenching. 대한환경공학회지제 37 권제 10 호 2015 년 10 월

4 576 J. Korean Soc. Environ. Eng. 김이태 안광호 Fig. 7. Ammonium and nitrate concentration according to the processing step. Fig. 9. Removal rate of existing and improved process. Fig. 8. COD cr concentration according to the processing step. Table 3. Change of ph, turbidity and SS concentration according to the processing step Analysis items Law waste water NaOH+Ca(OH) 2 injection PAC injection Zeolite ph Turbidity (NTU) SS (mg/l) 도변화가없었으며 PAC 주입시 2,210 mg/l에서 1,210 mg/l 로 45.2% 제거되었다. 제올라이트를통과할경우, COD cr 은 920 mg/l로낮아지어 58.4% 의제거효율을나타내었다 (Fig. 8). Table 3은응집과침전을위한각공정에서의 ph, 탁도및 SS를나타낸것으로 ph가낮은원수에 NaOH로 ph를 8.7 까지높여주고 PAC을주입하여 ph가 5.9로낮아졌다. ph 의상승에따라탁도와 SS는높아지고 PAC 주입에따라감소되어탁도와 SS 각각 12.7 NTU, 15.0 mg/l로낮아졌으며 zeolite를통과한처리수는큰차이가없었다. 이때처리수의 ph는 6.0 범위로가스화열병합가스설비의순환수로가능성도확인할수있었다 기존시설과개선된반응조의제거효율비교 Fig. 9는기존백필터와활성탄을이용한수처리시설과개선된공정에서의제거효율을나타낸것으로기존시설의 Fig. 10. Removal rate of phenols tar-containing wastewater 제거효율이 20% 에서 70~80% 로제거율이크게향상되어타르폐수의경우, 물리적인여과및흡착방법으로는제거효율이낮음을알수있었다. Fig. 10은페놀류제거특성을나타낸것으로제거율이크게향상되었으며, 이때의최적운전결과를위하여 NaOH와 PAC 주입량은각반응조에서의 ph를기준으로설정함이가장타당하였고, 타르폐수의 ph 변화폭이크기때문에 ph 측정결과와자동으로연동하여약품주입이이루어지도록함이적합하였다. 4. 결론 가스화열병합발전설비에서발생되는고농도타르함유폐수에대해기존공정과개선된공정을비교한실험을수행하고다음과같은결론을얻을수있었다. 1) 목질계타르폐수의화학적인발생성상을살펴본결과, 페놀류 (phenols) 의함유량이구아이아콜류 (guaiacols) 와카보하이드레이트류에비해약 2배이상상대적으로높게나타났다. 2) 기존시설과개선된반응조에서의화학종별농도변화 Journal of KSEE Vol.37, No.10 October, 2015

5 J. Korean Soc. Environ. Eng. 577 는페놀류의제거효율이 36.2~83.5% 로높았으며, 구아이아콜류는 7.7~77.5%, 카보이이드레이트류는 68.4% 로나타났다. 3) 개선된반응조에서의암모늄과 COD를분석한결과, 암모늄은 NaOH와 PAC 주입에따른응집처리공정은처리효율이낮았으나, 제올라이트의통과시크게감소하였으며, COD는 PAC 주입과제올라이트공정에서제거효율이향상되었다. 4) 기존시설과개선된처리시설의제거효율을비교하면기존시설의제거효율은약 20% 였으며, 개선된처리시설의제거효율은 70~80% 로타르함유폐수처리시응집침전공정이효과적임을알수있었다. Acknowledgement 본연구는한국건설기술연구원주요사업 ( ) 의연구비지원으로수행되었으며, 이에감사드립니다. References 1. Kumar, A., Jones, D. D. and Hanna, M. A., Thermochemical biomass gasification: a review of the current status of the technology, Energies, 2(3), 556(2009). 2. Li, C. and Suzuki, K., Tar property, analysis, reforming mechanism and model for biomass gasification - An overview, Renewable and Sustainable Energy Rev., 13, 594(2009). 3. Brown, R. A., Jackson, M. and Loucy, M., A rational approach to the remediation of soil and groundwater at manufactured gas plant sites, Land Contamin. Reclamat., 3(4), 1~2(1995). 4. Stoner, D. L., Miller, K. S., Polman, J. K. and Wright, R. B., Modification of organosulfur compounds and watersoluble coal-derived material by anaerobic microorganisms, Fuel, 72, 1651~1656(1993). 5. Aust, S. D. and Bumpus, J. A., Process for the degradation of cal tar and its constituents by Phanerochaete chrysosporium, US Patent 5,459,065(1995). 6. Karetnikova, E. A. and Zhirkova, A. D., Degradation of Phenols Formed during Lignin Pyrolysis by Microfungi of Genera Trichoderma and Penicillium, Biol. Bullet., 32(5), 445~449(2005). 7. Phuphuakrat, T., Namioka, T. and Yoshikaw, K., Tar removal from biomass pyrolysis gas in two-step function of decomposition and adsorption, Appl. Energy, 87(7), 2203~2211(2010). 8. Hu, X., Hanaoka, T., Sakanishi, K., Shinagawa, T., Matsui, S. and Tada, M., Removal of tar model compounds produced from biomass gasification using activated carbons, J. Jpn. Inst. Energy, 96, 707~711(2007). 9. Lillo-Rodenas, M. A., Fletcher, A. J., Thomas, K. M., Cazorla- Amoros, D. and Linares-Solano, A., Competitive adsorption of a benzene-toluene mixture on activated carbons at low concentration, Carbon, 44, 1455~1463(2006). 10. Mastral, A. M., Garcia, T., Callen, M. S., Navarro, M. V. and Galban, J., Assessment of phenanthrene removal from hot gas by porous carbons, Energy & Fuels, 15, 1~7(2001). 11. Mohan, D., Pittman, C. U. and Steele, P. H., Pyrolysis of Wood/Biomass for bio-oil: a critical Review, Energy & Fuels, 20(3), 848~889(2006). 대한환경공학회지제 37 권제 10 호 2015 년 10 월

THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Nov.; 26(11),

THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 2015 Nov.; 26(11), 985991. http://dx.doi.org/10.5515/kjkiees.2015.26.11.985 ISSN 1226-3133 (Print)ISSN 2288-226X (Online) Analysis