半焦与洗中煤混燃特性及动力学分析

Co-combustion characterietics and kinetic analysis of semi-coke and middling

为提高洗中煤在燃煤电厂燃烧的安全性和经济性,采用非等温热重法研究半焦、洗中煤单独燃烧及两者混燃的燃烧特性,通过比较微分热重法(DTG)曲线上实验值与理论值差异探究半焦与洗中煤混燃过程中发生交互作用,根据Coasts-Redfern积分法计算混燃过程的动力学特性。结果表明:洗中煤只在501℃出现一个失重峰,半焦在396℃和575℃时出现两个失重峰;单独半焦燃烧特性优于洗中煤;添加半焦改善了洗中煤的燃烧特性,随半焦比例增加,混煤燃烧特性逐渐趋向于半焦,着火温度降低,燃尽率、综合燃烧特性指数提高,当半焦∶洗中煤=3∶1时,混煤燃烧效果最佳;同单独洗中煤相比,混煤的着火温度由445℃降低到355℃,燃尽率由77.9%增加到87.9%,综合燃烧特性指数由3.58×10^(-9)mg^(2)·min^(-2)·K^(-3)增加到5.51×10^(-9)mg^(2)·min^(-2)·K^(-3),在混煤燃烧DTG曲线上两者发生交互作用;动力学分析表明洗中煤、半焦及两者混煤燃烧过程都符合一级化学反应,单独半焦和洗中煤燃烧时活化能分别为55.39kJ/mol和110.78kJ/mol,混煤活化能和指前因子均降低,活化能在59.94~71.14kJ/mol之间,为半焦和洗中煤的高效燃烧提供新思路。

In order to improve the safety and economy of middling in coal-fired power plants,the combustion and co-combustion characteristics of semi-cokes and middling were studied by non-isothermal thermogravimetric method.By comparing the difference between experimental value and theoretical value,the interaction of semi-cokes and middling on the DTG curves was researched.According to the Coasts-Redfern integral method,the dynamic characteristics were calculated.The results showed that the thermogravimetric curve of middling had only one weightlessness peak at the temperature of 501℃,and semi-coke had two weightlessness peak at the temperature of 396℃and 575℃.When burned alone,the combustion characteristics of semi-cokes were better than that of middling;the presence of semi-cokes promoted the combustion of middling,mixed combustion tended to be the combustion characteristics of semi-cokes.with semi-cokes increasing,ignition temperature decreased,burn off ratio and comprehensive combustion characteristic index increased respectively.When semi-cokes and middling ratio was 3∶1,the combustion effect of mixed coal was the best.Compared with the single middling,the ignition temperature decreased from 445℃to 355℃,burn off ratio increased from 77.9%to 87.9%,the comprehensive combustion characteristic index increased from 3.58×10^(-9)mg^(2)·min^(-2)·K^(-3) to 5.51×10^(-9)mg^(2)·min^(-2)·K^(-3).There existed interaction between the two fuels on the DTG curves.Kinetic analysis indicated that the chemical first order reaction was the most effective mechanism for the combustion and co-combustion of semi-cokes and middling.For individual combustion,the activation energy of semi-cokes and middling were 55.39kJ/mol and 110.78kJ/mol,activation energy and pre-exponential factor decreased respectively,the activation energies of the blends were ranging from 59.94 to 71.14kJ/mol.Providing a new way for high efficiency combustion of semi-cokes and middling.