DSC03481 (3)

Test 1 (correction) 18/12/2009

student name and surname

micfl

A water boiler is fired with hard coal The coal comopsition Is: gc-03%, gw-3%, 0h^ib3%, 9o=2%, 9s=0.5%, p=14% (incombustibles), w=14 5r(moisture) The coal is combusted in a pulverized form. Access alr coefficient is limited to A=1 1 . 55% of incombustibles is removed from the boiler in a form of slag and the rest as an ash. Thjrcensist also 5% of carbon. The carbon content in the ash is 0.7%. Neglect CO and NOx content ii exhaust gases. The outlet temperaturę of the exhaust gases is 145*C.    Id

The ambient air temperaturo is -3.15 #[. The air composition is r_O2=20.81%, r_N2=77.54%, rAr=0.93%, ^20=0.69%, rotf>er⁼0 03% C

It can be assumed that a rest of losses (apart of fumace losses and an outlet loss) is 3%. The boiler heats 360 t/h of water which is supplied with a temperaturo of 70*C and is heated up to 140^łC.

Calculate:

1.    share of C02 and share of 02 at the dry exhaust gases.

2.    specific losses and thermal efficiency of the boiler

3.    fuel consumption ( LCV=33900g_c+121500(g_H+go/8)+10500gs-2500(w+9/8'g_o) )

Theory

A)    lllustrate (draw a graph) changes of temperatures along a counter flow heat exchanger where a heating agent is a steam (supplied as a superheated steam, then condensed, and condensate is cool down) and the heated flow is a liquid water which does not change phase (does not evaporate).

B)    What is a difference between an internal adłabatic efficlency and an internat polytrophic efflciency of a roto-dynamic compressor?