Study on Optimizing SCR System for Large Capacity Utility Boilers
|Course||Thermal Power Engineering|
|Keywords||Selective Catalytic Reduction Nitrogen oxides Flow field Numerical Simulation Gas-solid flow|
Nitrogen oxides (NO x ) is recognized as one of major air pollutants, which cause acid rain and photochemical smog, ecological impacts, hazards to human health, to control NO x emissions has been widespread concern. With our increasingly stringent environmental requirements, stricter law enforcement, selective catalytic reduction (Selective Catalytic Reduction, SCR) flue gas denitrification technology because of its denitrification rate (up to 90%), the technology is mature and become a coal-fired utility boilers control NO x emissions. SCR flue gas denitrification technology in China started late, many problems encountered in the process design and operation of the actual system. The SCR reactor cold test station study papers domestic a power station 600MW boiler SCR off denitrification system, the SCR reactor structure and run parameters conducted a cold test and numerical simulation combined with the project characteristics of the SCR system processes and run related studies, to achieve the purpose of optimization of the SCR system, and this has important implications for reducing the design and operating cost of SCR technology. The experimental and theoretical studies of the SCR system consists of three parts: First, the improved implementation of the pilot study, the reactor structure optimization based on self-modeling theory of characteristics and structural parameters of the distribution of the internal flow field in the SCR reactor cold test bench optimization of flow field, the reactor ammonia injection grille (Ammonia Injection Grid, AIG) inlet flow velocity distribution for the deviation coefficient is less than 20%, the catalyst flow velocity distribution of the inlet cross-sectional position of the deviation coefficient is less than 15% meet the operating requirements of the SCR system; cold-state test for the SCR reactor units, using the k-ε two equation model the reactor velocity distribution using SIMPLIC algorithm, pressure distribution, concentration distribution characteristics of a detailed numerical simulation, comparison with the test results have been better consistent structure and inlet flow rate of the reactor, the reactor flow field analysis and concluded that the installation the appropriate deflector can optimize the flow and mixing characteristics of the reaction inside the reactor downstream of the economizer flue, with inlet velocity increases, the system pressure drop approximate linear increase, there is no significant change in the speed and concentration of the reactor internal distribution; Third, the test and the results of numerical simulation of the flow field, the chemical reaction inside the SCR reactor and fly ash Mechanical Analysis of the particles, respectively, the use of laminar finite rate model, the chemical reaction and the movement of the fly ash particles in the discrete phase model (DPM) analog within the reactor to obtain the characteristics of the chemical reaction and the movement of the fly ash particles in the interior of the reactor trajectory and The concentration distribution, the operating characteristics of the reactor when the BMCR conditions were optimized, so that the catalyst outlet position NH 3 escape is reduced to 5 ppm or less. Combined 600MW unit boiler the SCR system project, the SCR system on boiler performance and security impact analysis; optimized SCR system debug operation of the system, on the basis of a comprehensive analysis of process equipment characteristics of the SCR system, the operating condition, so that the reactor outlet NO x concentration deviation coefficient is maintained at about 20%, to meet the system running a standard.