Oxy-fuel combustion technology has become one of the most likely CCUS technologies to achieve large-scale commercial promotion and industrial application because of its remarkable energy-saving effect, low relative economic cost, easy industrialization and many other advantages. Different from traditional air combustion, oxy-fuel combustion technology uses pure oxygen and circulating flue gas as combustion-supporting medium to increase the volume concentration of CO2 in the exhaust gas to over 90%, which can be directly condensed and compressed to obtain liquid CO2, thus avoiding expensive separation process, so as to realize the permanent storage or resource utilization of CO2. In order to optimize the oxy-fuel combustion technology, a humidified oxygenated combustion technology combined with the oxy-steam combustion technology is proposed, which can significantly improve the combustion rate, combustion efficiency and the cycle thermal efficiency, promote the complete combustion reaction, and effectively reduce the emission level of pollutants (NOx and soot). In this work, the combustion characteristics and the generation of main pollutants of steam premixed CH4 in O2/CO2 atmosphere were analyzed by numerical simulation. A new clean combustion method was proposed to study the effects of single variable steam premixed ratio Rf (values 0, 0.1, 0.2, 0.3, 0.4 and 0.5) on the combustion flow field distribution, combustion components distribution and pollutant concentration distribution, by changing the mass fraction of water vapor at mass-flow-inlet while ensuring the methane mass flow rate was fixed. The results showed that with the increase of Rf, combustion reaction rate and combustion reaction efficiency increased and the pollutant emissions decreased, which fully reflected the superiority of steam injection combustion. Based on the simulation results, the optimum atmosphere of methane premixed water vapor was 81% CH4/19% H2O. Efficient and energy-saving steam premixed CH4 combustion in O2/CO2 atmosphere and flue gas waste heat deep cascade utilization process was proposed, which provided a new idea for the future development of combustion technology.
Xin REN Yindi ZHANG Chang LIU Ke WANG
. Combustion characteristics of steam premixed CH4 in O2/CO2 atmosphere and cascade utilization process of flue gas waste heat[J]. The Chinese Journal of Process Engineering, 2019
, 19(5)
: 1047
-1056
.
DOI: 10.12034/j.issn.1009-606X.219103
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