The use of low-grade coal in the conversion of grades is an important way for the efficient and clean use of coal. The volatile content of pyrolytic semi-coke is less than 4%. It belongs to ultra-low volatility carbon-based fuel. It has basic characteristics such as high ignition temperature, slow combustion reaction rate, and long burnout time. It is studied for its efficient combustion and efficient clean utilization of coal. The development of sub-quality conversion technology is of great significance. At present, the application of pyrolytic semi-coke directly to boiler combustion has not been reported in the examples.
The research and development of pulverized coal preheating combustion technology began in 2004. At that time, it was a frontier exploration project of the CFB laboratory of the Institute of Engineering Thermophysics, Chinese Academy of Sciences. Afterwards, under the support of the National Natural Science Foundation of China, the researchers continued systematic research. The preheating combustion characteristics of anthracite and fine powder semicoke.
The results show that the preheating temperature of the fine powder semicoke reaches 850°C, which exceeds the ignition point of the fine powder semi-coke. The preheated fuel enters the combustion chamber and meets the air and can be burned efficiently. There is no ignition, flameout, or flame stability problems. The technical bottleneck of difficult and stable combustion of low-volatile powdered fuels has been achieved, achieving homogeneous temperature and fine-burning of fine powder and semi-coke. The combustion temperature is lower than 1200°C, the combustion efficiency is greater than 98%, and the NOx emission concentration is lower than 100mg/m3. Directly meet the national emission standards and achieve efficient and clean burning of fine powder and semi-coke.
Given the enormous application potential and good research foundation of preheating combustion technology, in 2014, research and development of pyrolysis fine-powder semi-coke preheating combustion technology was included in the strategic pilot technology project of the Chinese Academy of Sciences. “Low-order coal clean and efficient cascade utilization key technologies "Study and demonstration" of the research topic "Supercritical fluidized bed combustion technology and demonstration" of the research content. At the end of 2014, the research team built a 0.2MW fine-powder semi-coke preheating combustion test bench at the Research and Development Center in Langfang, and carried out a pilot study on the preheating combustion characteristics of pyrolytic fine powder semicoke, and explored the preheating temperature and combustion temperature. The influence of parameters, such as air ratio and air ratio, on the preheating combustion of fine powder semi-coke. The results show that the pyrolytic fine powder semi-coke is stable in preheating, the preheating temperature can be adjusted between 850-950°C, the combustion temperature can be adjusted between 1100-1300°C, the combustion efficiency is greater than 98%, and the NOx emission concentration is the lowest Close to 100mg/m3, high-efficiency and clean combustion of pyrolytic fine powder semi-coke is realized, which is expected to become a large-scale application of pyrolysis fine powder semi-coke combustion technology.
In 2015, as the research task of the Chinese Academy of Sciences, the researchers will further carry out research on NOx depth control and system optimization for pyrolysis of fine powder and semi-coke preheating combustion to lay a foundation for further industrial applications.
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