Experimental Investigation of Cutting Nitrogen Oxides Emission from Cement Kilns using Coal Preheating Method
Tóm tắt
The large consumption of coal in cement industry leads to a significant nitrogen oxide (NOx) emission, which has caused severe atmospheric pollution due to the existing low-efficiency denitration technologies. In this research, a fuel pretreatment method on the concept of coal preheating was proposed to reduce NOx emission from cement kilns. A special bench-scale experiment was designed to verify the feasibility of the proposed method. Experimental results showed that the proposed method could achieve high combustion efficiency, steady operation and low NOx emission. The maximum reduction efficiency of primary NO in kiln gas reached 91.4% while the lowest NOx emission was 145 mg/m3 (@10% O2) during the experiment. The effects of key parameters on NOx emission and primary NOx reduction efficiency were comprehensively investigated. It was found that primary and secondary air ratios determined the oxygen content in the flue gas and the reaction temperature, which multiply affected the fuel-NOx formation and activity of reductants. Increasing the length of the reducing zone could not only enhance the primary NOx reduction efficiency, but also lower the combustion efficiency. In addition, cement raw material could greatly accelerate the formation of fuel-NOx while its catalytic action on NOx reduction was limited.
Tài liệu tham khảo
Bo Y., Shen Y., Yun S., Li P., Zeng Y., Shen S., Zhu S., Removal characteristics of nitrogen oxides and particulates of a novel Mn-Ce-Nb-Ox/P84 catalytic filter applied for cement kiln. Journal of Industrial and Engineering Chemistry, 2017, 50: 133–141.
Hua S., Tian H., Wang K., Zhu C., Gao J., Ma Y., Xue Y., Wang Y., Duan S., Zhou J., Atmospheric emission inventory of hazardous air pollutants from China’s cement plants: Temporal trends, spatial variation characteristics and scenario projections. Atmospheric Environment, 2016, 128: 1–9.
Du L., Jin B., Zheng X., Niu M., Effect of reburning zone conditions on no reduction efficiency in an online precalciner-type kiln system. Environmental Progress & Sustainable Energy, 2016, 35(2): 439–446.
Iliuta I., Dam-Johansen K., Jensen L., Mathematical modeling of an in-line low NOx calciner. Chemical Engineering Science, 2002, 57: 805–820.
Fan W., Zhu T., Sun Y., Lv D., Effects of gas compositions on NOx reduction by selective non-catalytic reduction with ammonia in a simulated cement precalciner atmosphere. Chemosphere, 2014, 113: 182–187.
Jin Y., Tian Y., Xu D., Comments on NOx emission abatement in cement industry. Journal of Xi’an University of Architecture & Technology, 2009, 41(3): 397–403. (in Chinese)
Fu S., Song Q., Tang J., Yao Q., Effect of CaO on the selective non-catalytic reduction deNOx process: Experimental and kinetic study. Chemical Engineering Journal, 2014, 249: 252–259.
Cai J., Wu H., Ren Q., Lin L., Zhou T., Lyu Q., Innovative NOx reduction from cement kiln and pilot-scale experimental verification. Fuel Processing Technology, 2020, 199: 106306.
Liu Z., Peng F., Liu X., Review of catalysts for Selective Catalytic Reduction (SCR) of NOx. Advanced Materials Research, 2012, 550–553: 119–123.
Yang G., Zhao H., Luo X., Shi K., Zhao H., Wang W., Chen Q., Fan H., Wu T., Promotion effect and mechanism of the addition of Mo on the enhanced low temperature SCR of NOx by NH3 over MnOx/γ-Al2O3 catalysts. Applied Catalysis B: Environmental, 2019, 245(15): 743–752.
Lyu Q., Zhu J., Niu T., High temperature preheating method for coal powder. 2007, Patent No.: CN101158468-A. (in Chinese)
Zhu S., Lyu Q., Zhu J., Wu H., Fan Y., Low NOx emissions from pulverized coal moderate or intense low-oxygen dilution combustion in O2/CO2 preheated by a circulating fluidized bed. Energy & Fuels, 2018, 32(10): 10956–10963.
Shu Z., Wang F., Dai C., et al., Characteristics of nitric-oxide emissions from traditional flame and MILD combustion operating in a laboratory-scale furnace. Journal of Thermal Science, 2020, 29: 868–883.
Lv G., Lu J., Xie X., Hu Z., Experiment of the reduction of NO by coal in precalciners. Journal of Huazhong University of Science and Technology, 2011, 39: 124–128. (in Chinese)
Hu Z., Liu Z., Wang S., NO formation from coal char combustion in cement precalciner. Journal of Chemical Industry and Engineering, 2005, 56(3): 545–550. (in Chinese)
Wu H., Cai J., Ren Q., Shi C., Zhao A., Lyu Q., A thermal and chemical fuel pretreatment process for NOx reduction from cement kiln. Fuel Processing Technology, 2020, 210: 106556.
Ouyang Z., Liu W., Zhu G., Liu J., Man C., Experimental research on combustion characteristics of coal gasification fly ash in a combustion chamber with a self-preheating burner. Fuel, 2018, 215: 378–385.
Zhu J., Yao Y., Lu Q., Gao M., Ouyang Z., Experimental investigation of gasification and incineration characteristics of dried sewage sludge in a circulating fluidized bed. Fuel, 2015, 150: 441–447.
Zhou T., Lu Q., Cao Y., Wu G., Li S., Study on the combustion and NOx emission characteristics of low rank coal in a circulating fluidized bed with post-combustion. The Canadian Journal of Chemical Engineering, 2017, 95(12): 2333–2340.
Wu Z., Ohtsuka Y., Nitrogen distribution in a fixed bed pyrolysis of coals with different ranks: Formation and source of N2. Energy Fuels, 1997, 11(2): 477–482.
Aarna I., Suuberg E., A review of the kinetics of the nitric oxide-carbon reaction. Fuel, 1997, 76(6); 475–491.
Alonso M., Borrego A., Alvarez D., Parra J., Menéndez R., Influence of pyrolysis temperature on char optical texture and reactivity. Journal of Analytical and Applied Pyrolysis, 2001, 58: 887–909.
Thomas K., The release of nitrogen oxides during char combustion. Fuel, 1997, 76(6): 457–473.
Zhang W., Li Y., Ma X., Qian Y., Wang Z., Simultaneous NO/CO2 removal performance of biochar/limestone in calcium looping process. Fuel, 2020, 262: 116428.
Cai L., Shang X., Gao S., Wang Y., Dong L., Xu G., Low-NOx coal combustion via combining decoupling combustion and gas reburning. Fuel, 2013, 112: 695–703.
Yamada H., Kyotani T., Radovic L., Influence of char surface chemistry on the reduction of nitric oxide with chars. Energy & Fuels, 1993, 7(1): 85–89.
Song Y., Blair D., Siminski V., Bartok W., Conversion of fixed nitrogen to N2 in rich combustion. Symposium on Combustion, 1981, 18(1): 53–63.
Lv G., Lu J., Cai L., Xie X., Liu Z., Experimental study on the dynamic process of NO reduction in a precalciner. Industrial & Engineering Chemistry Research, 2011, 50: 4366–4372.
Liu W., Ouyang Z., Cao X., Na Y., Experimental research on flameless combustion with coal preheating technology. Energy and Fuel, 2018, 32(6): 7132–7141.
Lans R., Glarborg P., Dam-Johansen K., Influence of process parameters on nitrogen oxide formation in pulverized coal burners. Fuel and Energy Abstracts, 1997, 23(4): 349–377.
Illán-Gómez M., Linares-Solano A., Radovic L., No reduction by activated carbons. 7. Some mechanistic aspects of uncatalyzed and catalyzed reaction. Energy & Fuels, 1996, 10(1): 158–168.
Jensen A., Johnsson J., Dam-Johansen K., Nitrogen chemistry in FBC with limestone addition. Symposium (International) on Combustion, 1996, 26: 3335–3342.
Li J., Zhu J., Zhu S., Liu J., Li B., Kinetics of calcium carbonate decomposition under rapid heating condition. China Power Science and Technology, 2018, 24(6): 1–7.