烧失量法测量循环流化床锅炉飞灰碳的系统误差

System Error Present When Measuring the Carbon Content of the Fly-ash of a Circulating Fluidized Bed Boiler by Using a Loss-on-ignition Method

循环流化床锅炉飞灰碳的测量仍然沿用煤粉锅炉飞灰碳的烧失量法。由于循环流化床锅炉飞灰矿物组分不同于煤粉锅炉飞灰矿物组分,用烧失量的方法测量循环流化床锅炉飞灰碳的含量会造成一定的系统误差。本文用烧失量法和TGA-FTIR(热重分析-傅立叶红外光谱)联用的方法测量了循环流化床锅炉飞灰碳的含量,分析了用烧失量法测量循环流化床锅炉飞灰碳的含量的系统误差,结果表明我国电力行业标准DL/L567.6-95飞灰和炉渣可燃物测定方法B测量循环流化床锅炉的飞灰可燃物含量时的系统误差包括硫酸盐分解和矿物组分结晶水,化合水的释放。用该方法考核循环流化床锅炉机组性能和效率的时候,应该考虑这些因素的影响。在TGA-FTIR试验的基础上,提出了TGA测量循环流化床锅炉飞灰碳含量的新方法。该方法避免了硫酸盐分解,矿物组分结晶水,化合水的释放所造成的系统误差,同时新产生的含碳有机质高温裂解所致的系统误差是可以忽略的,其结果更接近循环流化床锅炉飞灰碳的真实含量。

To measure the carbon content of the fly ash of a CFB boiler one still continues to adopt the loss-on-ignition method traditionally used for measuring carbon content of the fly ash of pulverized coal-fired boilers. As the mineral constituent of the fly ash of a CFB boiler is different from that of a pulverized coal-fired one, the use of the loss-on-ignition method for measuring carbon content of the fly ash of a CFB boiler may produce a certain system error. The authors have adopted the loss-on-ignition method combined with a TGA-FTIR (thermogravimetric analyzer-Fourier infrared spectrum) method to measure the carbon content of the fly ash of the CFB boiler and analyzed the system error involved in the measurement by using the loss-on-ignition method. The results of the measurements show that in case of using China National Electric Power Industry Standard DL/L567.6-95 Method B for measuring combustible matter in fly ash and slag of a CFB boiler the system error should involve the decomposition of sulfate and release of water of crystallization and hydration from mineral constituents. When using this method to check the performance and efficiency of a CFB boiler unit, one shall take into account the effect of these factors. On the basis of TGA-FTIR experiments, presented is a new TGA method for measuring the carbon content of fly ash of a CFB boiler, which can avoid the system error caused by the decomposition of sulfate and the release of water of crystallization and hydration from mineral constituents. In the meantime, the system error resulting from high-temperature cracking of newly produced carbon-containing organic matter can be negligible. The result thus measured further approximates to the actual carbon content of the fly ash of the CFB boiler.