Characteristics of Preheating Combustion of Power Coal with High Coking Properties
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https://doi.org/10.1007/s11630-020-1358-3
Article ID: 1003-2169(2020)00-0000-00
Characteristics of Preheating Combustion of Power Coal with High Coking Properties ZHANG Yi1,2, ZHU Jianguo1,2*, LYU Qinggang1,2, PAN Fei1,2, ZHU Shujun1,2 1. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China 2. University of Chinese Academy of Sciences, Beijing 100049, China © Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract: Yankuang coal with the high coking property is difficult to use through direct combustion. The main purpose of this paper is to study the combustion characteristics and NOx emissions of this type of coal using preheating combustion technology. The experimental results show that after the pulverized coal is preheated, the char residue characteristic is significantly reduced from 5 to 1. During the preheating process, the preheating temperature is stable at about 910°C, and the particle size of char after preheating is reduced, and the pore structure and specific surface areas are increased. The combustion temperature of preheated fuel is stable at around 1100°C, and the combustion efficiency can reach more than 99% under different conditions. Changing the structure of the secondary air nozzles during the preheating combustion process can influence the characteristics of NOx emissions. The NOx emission of the central nozzle is about 112 mg/Nm3 lower than that of the annular nozzle. Changing the tertiary air distribution modes can reduce the final NOx emissions to 215 mg/Nm3 (@6%O2), and the corresponding conversion ratio of fuel N to the final NOx is 4.2%. The results of this experiment prove that the Yankuang coal can achieve stable combustion by preheating combustion technology, and this proposed a new way for the utilization of Yankuang coal.
Keywords: Yankuang coal, coking properties, preheating combustion, NOx emissions
1. Introduction Coal is the most important energy resource in China. According to statistics from 2018, coal consumption accounts for 59% of total energy consumption, decreased by 1.4% from 2017, but the current situation, with coal being a main energy, will not change for a long period of time [1]. There are many types of coal in China, one of which is coking coal. In China’s new coal classification (GB5751-86), 1/2 medium caking coal, gas coal, gas-fat coal, fat coal, 1/3 coking coal, meagre coal, lean coal,
Received: Aug 11, 2019
etc., are all belonged to the category of coking coal. Because these coals have good coking properties, they can be used as coking or coal blending [2–4]. Generally, the coking properties for power coal (including the char residue characteristic and cohesive index) are relatively low. For example, the char residue characteristic of Shenmu bituminous coal is 0, and the cohesive index is 0. However, the Yankuang bituminous coal studied in this paper has the advantages of high volatile matter, low ash content and high calorific value, but some
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