Modeling De-NO x by Injection Ammonia in High Temperature Zone of Cement Precalciner
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https://doi.org/10.1007/s11630-020-1324-0
Article ID: 1003-2169(2020)00-0000-00
Modeling De-NOx by Injection Ammonia in High Temperature Zone of Cement Precalciner ZHANG Leyu1,3, WEI Xiaolin1,2*, ZHANG Zhongxiao3*, LI Sen1 1. Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China 2. School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100190, China 3. School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, China © Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract: The quantity of NOx emission from cement production is second only to thermal power generation and vehicle exhaust. In this paper, a phenomenon found by Taniguchi is used to achieve NOx reduction in the cement precalciner. Based on his results, it is proposed to reduce NOx that ammonia is injected in the high-temperature and lean-oxygen zone (HT-DeNOx) during pulverized coal combustion. For a large cement precalciner (3200 t/d), numerical simulation is used to evaluate the technology of HT-DeNOx combined with the traditional selective non-catalytic reduction (SNCR) method. The results indicate that NH3 and HCN in HT-DeNOx can reduce NO during the reaction process. With very little ammonia injection (normalized stoichiometric ratio NSR=0.1, the normalized stoichiometric ratio), the efficiency of NO reduction by HT-DeNOx is 27.72%. Combining SNCR (NSR=1.1) and HT-DeNOx (NSR=0.1), the reduction efficiency will be improved to 60.05%, compared with 50.83% efficiency when using only SNCR at NSR=1.2.
Keywords: cement precalciner, coal combustion, CaCO3 decomposition, high temperature zone, SNCR
1. Introduction The precalciner is one of the most important pieces of equipment in the cement production process, serving as a container for both pulverized coal combustion and raw material decomposition reactions. Its temperature range is approximately 870°C to 1050°C, and the selective noncatalytic reduction (SNCR) method is suitable for NOx removal, or De-NOx, in the precalciner. High CO2 and CaO concentrations in the precalciner make its internal environment significantly different from the utility boiler, as shown in Table 1. Therefore, it is very important to select the ammonia injection position, which is closely Received: Jul 11, 2019 AE: YANG Bin
related to the flow field, temperature distribution, gas phase residence time, and material distribution in the precalciner [1]. Table 1 The comparison of gas composition and temperature between utility boiler and precalciner [2–5] Type
Utility boiler
Precalciner kilns system
CO2 concentration
About 15%
15% to 30%
CaO concentration
Negligible
1 kg(CaO)/m3(flue gas)
Temperature/°C
1200 to 1600
870 to 1050
OFA temperature/°C
20 to 200
About 900
Corresponding author: WEI xiaolin ZHANG zhongxiao
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J. Therm. Sci., Vol.29, No.*, 2020
Li [6] and Liu [7] both emp
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