城市污泥是人类活动的副产物，对其进行焚烧处理是污泥减量化与资源化利用的有效手段。污泥水热碳化作为一种预处理方式，对污泥的后续焚烧处置具有重要影响。为优化水热碳化工艺，对水热温度、反应时间以及固液比等3个因素进行单因素试验，并根据单因素试验结果进一步设计中心组合试验。随后，以污泥脱水后的收到基热值为指标，采用响应面法优化污泥水热处理制备固体燃料的工艺条件。结果表明，在水热温度为208.65℃、反应时间为16.82 min、固液比为12.31%条件下，其水热污泥收到基的理论热值可达4207 J/g。验证试验得出水热污泥收到基的热值为4203±24 J/g，符合响应面模型的分析结果。能耗分析结果表明，污泥水热处理制备固体燃料的能耗要比传统热干法低65%以上。
Sewage sludge is the by-product of human activities, and incineration is one of the effective disposal technologies for the minimization and utilization of sludge. Hydrothermal carbonization of sludge, as a kind of pretreatment, is of great important for incineration. In order to upgrade the sludge, the effects of hydrothermal temperature, holding time and solid-to-liquid ratio on the fuel property of sludge were studied in single factor experiments. Subsequently, response surface methodology was used to optimize the conditions of hydrothermal process and the calorific value of hydrothermal sludge was used as an evaluation index. The results indicated that the optimum conditions were hydrothermal temperature of 208.65oC, holding time of 16.82 min and solid-to-liquid ratio of 12.31%. Among these conditions, the optimum calorific value of hydrothermal sludge was 4207 J/g. Furthermore, the verification experiment showed that the actual calorific value of hydrothermal sludge prepared via above conditions was 4203±24 J/g, which was basically consistent with the results of response surface methodology. Moreover, more than 65% energy could be cut down via hydrothermal treatment when comparing with traditional thermal.
[1] ZHAO P T, SHEN Y F, GE S F, et al. Clean solid biofuel production from high moisture content waste biomass employing hydrothermal treatment[J]. Applied energy, 2014, 131: 345-367. DOI: 10.1016/j.apenergy.2014.06.038.
[2] ZHAO P T, CHEN H F, GE S F, et al. Effect of the hydrothermal pretreatment for the reduction of NO emission from sewage sludge combustion[J]. Applied energy, 2013, 111: 199-205. DOI: 10.1016/j.apenergy. 2013.05.029.
[3] HE C, WANG K, YANG Y H, et al. Effective nitrogen removal and recovery from dewatered sewage sludge using a novel integrated system of accelerated hydrothermal deamination and air stripping[J]. Environmental science & technology, 2015, 49(11): 6872-6880. DOI: 10.1021/ acs.est.5b00652.
[4] WANG X D, LI C X, ZHANG B, et al. Migration and risk assessment of heavy metals in sewage sludge during hydrothermal treatment combined with pyrolysis[J]. Bioresource technology, 2016, 221: 560-567. DOI: 10.1016/j.biortech.2016.09.069.
[5] HE C, WANG K, YANG Y H, et al. Utilization of sewage-sludge-derived hydrochars toward efficient cocombustion with different-rank coals: effects of subcritical water conversion and blending scenarios[J]. Energy & fuels, 2014, 28(9): 6140-6150. DOI: 10.1021/ ef501386g.
[6] LU L, NAMIOKA T, YOSHIKAWA K. Effects of hydrothermal treatment on characteristics and combustion behaviors of municipal solid wastes[J]. Applied energy, 2011, 88(11): 3659-3664. DOI: 10.1016/j.apenergy.2011. 04.022.
[7] PENG C, ZHAI Y B, YUN Z, et al. Production of char from sewage sludge employing hydrothermal carbonization: char properties, combustion behavior and thermal characteristics[J]. Fuel, 2016, 176: 110-118. DOI: 10.1016/j.fuel.2016.02.068.
[8] WANG L P, ZHANG L, LI A M. Hydrothermal treatment coupled with mechanical expression at increased temperature for excess sludge dewatering: influence of operating conditions and the process energetics[J]. Water research, 2014, 65: 85-97. DOI: 10.1016/j.watres.2014. 07.020.
[9] ESCALA M, ZUMBÜHL T, KOLLER C, et al. Hydrothermal carbonization as an energy-efficient alternative to established drying technologies for sewage sludge: a feasibility study on a laboratory scale[J]. Energy & fuels, 2013, 27(1): 454-460. DOI: 10.1021/ef3015266.
[10] NEYENS E, BAEYENS J, CREEMERS C. Alkaline thermal sludge hydrolysis[J]. Journal of hazardous materials, 2003, 97(1/3): 295-314. DOI: 10.1016/S0304- 3894(02)00286-8.
[11] NEYENS E, BAEYENS J, WEEMAES M, et al. Hot acid hydrolysis as a potential treatment of thickened sewage sludge[J]. Journal of hazardous materials, 2003, 98(1/3): 275-293. DOI: 10.1016/S0304-3894(03)00002-5.
[12] BA? D, BOYAC? I H. Modeling and optimization I: usability of response surface methodology[J]. Journal of food engineering, 2007, 78(3): 836-845. DOI: 10.1016/ j.jfoodeng.2005.11.024.
[13] SAVEYN H, CURVERS D, SCHOUTTETEN M, et al. Improved dewatering by hydrothermal conversion of sludge[J]. Journal of residuals science & technology, 2009, 6(1): 51-56.
[14] HE C, WANG K, GIANNIS A, et al. Products evolution during hydrothermal conversion of dewatered sewage sludge in sub- and near-critical water: effects of reaction conditions and calcium oxide additive[J]. International journal of hydrogen energy, 2015, 40(17): 5776-5787. DOI: 10.1016/j.ijhydene.2015.03.006.
[15] YIN F J, CHEN H Z, XU G H, et al. A detailed kinetic model for the hydrothermal decomposition process of sewage sludge[J]. Bioresource technology, 2015, 198: 351-357. DOI: 10.1016/j.biortech.2015.09.033.
[16] KANG S M, LI X L, FAN J, et al. Characterization of hydrochars produced by hydrothermal carbonization of lignin, Cellulose, D-Xylose, and wood meal[J]. Industrial & engineering chemistry research, 2012, 51(26): 9023-9031. DOI: 10.1021/ie300565d.
[17] KRUSE A, FUNKE A, TITIRICI M M. Hydrothermal conversion of biomass to fuels and energetic materials[J]. Current opinion in chemical biology, 2013, 17(3): 515-521. DOI: 10.1016/j.cbpa.2013.05.004.
[18] 闫秀懿, 乔玮, 李飘, 等. 含油污泥的水热法减量处理[J]. 化工环保, 2014, 34(4): 340-343. DOI: 10.3969/j.issn. 1006-1878.2014.04.008.
[19] FUNKE A, ZIEGLER F. Hydrothermal carbonization of biomass: a summary and discussion of chemical mechanisms for process engineering[J]. Biofuels bioproducts & biorefining, 2010, 4(2): 160-177. DOI: 10.1002/bbb.198.
[20] AREEPRASERT C, ZHAO P T, MA D C, et al. Alternative solid fuel production from paper sludge employing hydrothermal treatment[J]. Energy & fuels, 2014, 28(2): 1198-1206. DOI: 10.1021/ef402371h.
[21] ZHAO P T, SHEN Y F, GE S F, et al. Energy recycling from sewage sludge by producing solid biofuel with hydrothermal carbonization[J]. Energy conversion and management, 2014, 78: 815-821. DOI: 10.1016/j.enconman. 2013.11.026.
[22] HE C, ZHAO J, YANG Y H, et al. Multiscale characteristics dynamics of hydrochar from hydrothermal conversion of sewage sludge under sub- and near-critical water[J]. Bioresource technology, 2016, 211: 486-493. DOI: 10.1016/j.biortech.2016.03.110.
[23] VAXELAIRE J, CÉZAC P. Moisture distribution in activated sludges: a review[J]. Water research, 2004, 38(9): 2214-2230. DOI: 10.1016/j.watres.2004.02.021.
[24] ZHU Y, HAN Z, LIU X Y, et al. Study on the effect and mechanism of hydrothermal pretreatment of dewatered sewage sludge cake for dewaterability[J]. Journal of the air & waste management association, 2013, 63(8): 997-1002. DOI: 10.1080/10962247.2013.788458.
[25] KAMBO H S, DUTTA A. Comparative evaluation of torrefaction and hydrothermal carbonization of lignocellulosic biomass for the production of solid biofuel[J]. Energy conversion and management, 2015, 105: 746-755. DOI: 10.1016/j.enconman.2015.08.031.
