A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology

This report ii:; concerned with some aspects of hydrodynarni cs and heat transfer i n circn]at:ing f] u:idizecl heel as wel J as cornhnst:ion in jnclust.rial fl uidized bed boi ler. Experimental study on hydrodynamics and heat transfer in ci.rculating fJ1d clizecl heel were done hy 1Hd ng siJ:ica sand as tlH-! heel material. The co ld nm work was done to 8tucl y t he effects of riser flow rate, aeration flow rate, total lied inventory, lHlrticJe size, bed geometrical dlmensio11 and L · valve configu ration on solid circul ation rate. The hot. experiments were carried ou t lo study t he variation of bed-to-wall overall beat transf r coef f icent corei:;ponding to c hanyeH of operating parameters and location along the vert.:ical length of the riser. Relevent mathematical correlation!' for solid circulation rate a nd locaJ. heat transfer coefficient were developed as res ults of practical stud y. In the range of I.he present. work , heat transfer coefficient iii t he dilute phnse is fou nd to be in t 11e range of 62 W/m2 K to 83 W/n/K, 51 W/ in2 K to 74 W/ rn1 K, and 50 W/m1 K to 59 W/rn1 K for sand size of 200 i1n1 , 400 p 111 aJJ d 500 lllH , respect.i vel y. An at.tempt to modify a 1nat.he111 atica l 1node l for predicti on of heat t.rrrnsfer coefficient. in circ u] at:ing fl uidized heel was made l>y consi<leri 11g the effect. of formation and disin tegration ot clusters in circulating fl11idi zed bed. Proper .forn111 la e were-! set np to predict. Joc1-1J coJJvect:i on heat transfer coefficient u11 der present work conditioni:;. To valid<1t.e the rnodel developed, compar:i son !>et.ween experimental observations and t heoretica l predict.ion rel:mlts wai:; made. Alt.hough hi.gher heat. transfer coefficient was obtajned from t he model (in the range of 92 W/m1 K to 122 W/ rn1 K), 'the experiment.al observations and the theoretical prediction results slww qua] j tat.) ve i1greernen t. Combustion of No 4 fine coal (Viet nam specif icat.ion ) was carried out on an :i.rnh1str:ial fJuidjzed bed hoiler hi Viet nam to estfoat.e t.hc boiler overall and cornbni:;t.ion efficie11 cies . The estimated combustion ef ficlency was i JJ 1.lie range of 79. 596 - 81 . 4% and the overa] l boiJ.rn· efficiency was around 70%.