OCR Text |
Show 2.1 .8 The equilibrium dependence p=p0e(T), or for the wet part, T<373 K, p= p0(u+e(T)} , is approximated as a stepwise changing function (Fig.2). This approximation simply means that the pyrolysis is approximated as successive vaporization processes that take place at definite temperatures. The approximation is made for mathematical reasons in order to obtain similarity between the drying and the pyrolysis. The volatiles generated on the moving core R, , where T=T ,can be calculated by using the measured equilibrium curve (equations (13) or (14)), pgk= Po(e((Tk_1+Tk)/2) - e((Tk+Tk+1)/2)} (15) The local density (neglecting the gas phase) is uniquely defined by the temperature p = pod+u), when T<373 K (16) because the pyrolysis is not started below 373 K, and k-1 p = p = Po - E Pgn , when Vl< T < Tk n - i (17) THE DEPENDENCE OF LOCAL (EQUILIBLIUM) DENSITY ON TEMPERATURE ^ c ' - V DENSITY, VOLUMETRIC MASS WATER INITIAL VOLUMETF DRY MASS % IC STEAM GENERATED ON THE CORE T=373 K 9^1* LOCAL DENSITY BETWEEN THE THE CORES R^.j AND R^ 1 373 K ?= ?0em PGJT S»0[e((Tl.1+Tft)/2)-ecCT1*T|frl)/2a :<-! , VOLATILES GENERATED ON THE CORE Hi Tk-i Tk Tk+i TEMPERATURE Fig.2. The pyrolysis is approximated as successive vaporization processes that take place at definite temperatures |