|浙江大学学报(农业与生命科学版) 2017, 43(3) 389-396 DOI: 10.3785/j.issn.1008-9209.2017.01.101 ISSN: 1008-9209 CN: 33-1247/S|
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|（1.浙江大学生物系统工程与食品科学学院，杭州 310058；2.浙江商业职业技术学院应用工程学院，杭州 310053）|
为探明进料速率对生物质颗粒燃烧过程中烟气成分及污染物排放的影响规律，以5G-20/85-0.23型生物质颗粒燃烧器为对象，研究进料方式为进2 s停13 s、进2 s停15 s、进2 s停17 s、进2 s停19 s、进2 s停21 s（分别用2/13、2/15、2/17、2/19、2/21表示），相应的平均进料速率为6.9、6.2、5.5、5.0和4.5 kg/h时，烟气中CO、O2和NOx含量的变化，考察CO和NOx含量随运行时间的波动及两者排放量之间的关系。结果表明：进料速率从6.9 kg/h (2/13)降低到5.0 kg/h (2/19)时，烟气中CO含量逐渐减小，在5.0 kg/h时达到最小值66 mg/Nm3；NOx含量变化与CO相似，在进料速率为5.0 kg/h (2/19)时达到最小值8.8 mg/Nm3；在进料速率为6.9 kg/h (2/13)时烟气中CO含量随运行时间的波动最大；在不同进料速率下CO含量均呈周期性波动，波动周期与进料周期基本吻合，而NOx含量随运行时间的波动|
幅度较小。总体而言，平均进料速率为5.0 kg/h，即进2 s停19 s的进料方式能够明显降低污染物的排放。
|关键词： 生物质颗粒 燃烧器 进料速率 污染物排放 一氧化碳 氮氧化物|
|Effect of feeding rate on pollutant emission of biomass pellet burner|
|YANG Guofeng1†, YU Youfang2†*, SHENG Kuichuan1|
|(1. College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China; 2. Applied Engineering College, Zhejiang Business College, Hangzhou 310053, China)|
Biomass pellets, prepared from wood particles, straws, and other agricultural and forestry residues, possessed the advantages of higher energy density, convenient transportation and storage, and reduced fossil energy consumption and greenhouse gas emissions. They have been widely used in industrial boilers, agricultural greenhouses and household heatingunits. Currently, the efficient measurement and control of pollutant emission during biomass pellet combustion become increasingly important and attract more and more public awareness. Feeding rate is one of the critical factors that determine the combustion status and pollutant emissions. Previous researches mainly focused on the effect of feeding rate on carbon oxide (CO) emission, while the impact on nitrogen oxides (NOx) emission was seldomly reported. The new China National Emission Regulation (NER) issued in early 2012 requires that NOx emission must be controlled below 100 mg/m3.|
The objective of this study was to investigate the effect of feeding rate on the emission and variation of CO and NOx based on a 5G-20/85-0.23 biomass pellet burner platform. Average feeding rates of 6.9, 6.2, 5.5, 5.0 and 4.5 kg/h were employed, corresponding to the set of working and pausing time in the feeding mechanism at 2 s/13 s, 2 s/15 s, 2 s/17 s, 2 s/19 s, and 2 s/21 s, respectively (labelled as 2/13, 2/15, 2/17, 2/19, 2/21).
Results showed that CO emission was reduced with the feeding rate decreased from 6.9 to 5.0 kg/h, and the lowest CO concentration of 66 mg/Nm3 was achieved at the feeding rate of 5.0 kg/h. When the feeding rate was further reduced to 4.5 kg/h, the highest CO concentration of 205 mg/Nm3 was obtained. Overall, the CO emission first decreased and then increased for the feeding rate range of 6.9 to 4.5 kg/h. With the decreasing of feeding rate, oxygen (O2) concentration increased first and then decreased. Maximal O2 concentration of 16% was achieved with the feeding mechanism of 2/19. Fluctuation of CO concentration with time reflects the combustion quality and consistency inside the furnace, and minimal fluctuation is preferred. The highest fluctuation of CO concentration appeared when the feeding mechanism was set at 2/13, and a fluctuation peak was noticed at 80 s, which was probably caused by the pellet accumulation in the furnace and incomplete combustion in generating more CO. Overall, the fluctuation period was in good agreement with the feeding period. The effect of feeding rate on NO, NO2, and NOx concentrations was similar to that of CO, with the lowest NOx of 8.8 mg/Nm3 obtained at feeding rate of 5.0 kg/h and highest NOx of 78 mg/Nm3 obtained at 6.9 kg/h. The furnace temperature at lower position reached 758 ℃ at the optimal feeding rate. When the feeding rate was 4.5 kg/h, the temperature was only 375 ℃. The periodical fluctuation of NOx is not as obvious as CO. With the feeding mechanisms of 2/19 and 2/17, very minor fluctuations of NOx with time were observed. The NOx fluctuations were relatively larger with 2/15 and 2/13 feeding mechanisms.
In summary, the concentrations of CO and NOx in the emission are significantly affected by biomass pellet feeding rate. Minimal CO and NOx emissions are achieved when the feeding mechanism is set at 2/19. Periodical fluctuation of NOx with time is less obvious compared with CO. These results provide both practical data and theoretical basis for the optimization of feeding rate for biomass pellet burners.
|Keywords: biomass pellet burner feeding rate pollutant emission carbon oxide nitrogen oxides|
|收稿日期 2017-01-10 修回日期 网络版发布日期 2017-03-23|
|Copyright by 浙江大学学报(农业与生命科学版)|