Study on the dynamic balance behaviors of bed material during the start-up process of a circulating fluidized bed boiler

Abstract The bed material size distribution and bed inventory are important to the speed, energy consumption, auto-control of the start-up process and solid concentration distribution of circulating fluidized bed (CFB) boiler. A dynamic model to simulate the dynamic balance of the particle size distribution (PSD) of bed material in the start-up process of a CFB boiler is developed. The model is applied to a 350 MW CFB boiler to assess the dynamic changes of the PSDs of bed material under the influences of cyclone efficiency, initial bed material size distribution, coal quality and bed inventory. The results show that the cyclone efficiency plays important roles on the dynamic PSD and balanced PSD of bed material. The higher the cyclone efficiency, the finer the balanced bed material is. The fly ash particles and coarse particles among the initial material will escape the furnace in 0.5 h and 3 h respectively during the start-up process, and the circulating particles will achieve balance in ~ 4 h. Coal quality affects the dynamic balance of the PSD of bed material significantly, the larger the mass fraction of circulating class particles over the coal ash, the shorter the start-up time is. The closer the initial material size distribution to the balanced material size distribution, the shorter the start-up time is. The less the bed inventory, the shorter the start-up time is.

[1]  B. C. Meikap,et al.  Influence of Coal Feed Size on the Performance of Air Dense Medium Fluidized Bed Separator Used for Coal Beneficiation , 2011 .

[2]  Yang Hairui,et al.  Semi-empirical technique for predicting ash size distribution in CFB boilers , 2004 .

[3]  Chiou-Liang Lin,et al.  Effect of particle size distribution on agglomeration/defluidization during fluidized bed combustion , 2011 .

[4]  Qinhui Wang,et al.  Particle population balance model for a circulating fluidized bed boiler , 2003 .

[5]  A. Werner.  Solids distribution as a basis for modeling of heat transfer in circulating fluidized bed boilers , 2001 .

[6]  Junfu Lu,et al.  Numerical study of gas–solid flow in a coal beneficiation fluidized bed using kinetic theory of granular flow , 2013 .

[7]  Antonio B. Fuertes,et al.  Attrition of coal ash particles in a fluidized bed , 1991 .

[8]  B. Lakatos,et al.  Population balance model for particle-to-particle heat transfer in gas–solid systems , 2004 .

[9]  Qingru Chen,et al.  Separation characteristics for fine coal of the magnetically fluidized bed , 2002 .

[10]  Joachim Werther,et al.  Time-dependent behavior of the ash particle size distribution in a circulating fluidized bed system , 2005 .

[11]  S. Ma,et al.  Static Behaviors and Optimization Operation Techniques for Circulating Fluidized Bed Boiler , 2010, 2010 International Conference on Digital Manufacturing & Automation.

[12]  J. Werther,et al.  A population balance model of the particle inventory in a fluidized-bed reactor/regenerator system , 2004 .

[13]  B. Lakatos,et al.  Population balance model of heat transfer in gas–solid particulate systems , 2008 .

[14]  W. Nowak,et al.  Distribution of solids concentration and temperature within combustion chamber of SC-OTU CFB boiler , 2012 .

[15]  Hui Zhang,et al.  Solids concentration in the fully developed region of circulating fluidized bed downers , 2008 .

[16]  W. Nowak,et al.  Simulation model of the mass balance in a supercritical circulating fluidized bed combustor , 2013 .

[17]  Hairui Yang,et al.  The segregation behaviors of fine coal particles in a coal beneficiation fluidized bed , 2014 .

[18]  Jia Wei Chew,et al.  Review of entrainment correlations in gas–solid fluidization , 2015 .

[19]  C. Chu,et al.  Attrition and sulfation of calcium sorbent and solids circulation rate in an internally circulating fluidized bed , 2002 .

[20]  Joachim Werther,et al.  A particle population balancing model for a circulating fluidized bed combustion system , 2009 .

[21]  A. Al-zahrani.  Particle size distribution in a continuous gas–solid fluidized bed , 2000 .

[22]  Chenlong Duan,et al.  Experimental and numerical simulation studies of the fluidization characteristics of a separating gas–solid fluidized bed , 2010 .