Product compositions and kinetics for rapid pyrolysis of cellulose

Abstract

Ind. Eng. Chem. Process Des. Dev. 1982, 21, 457-465 457 days this operating procedure has wide perspectives in industrial adsorption separation. If a complete mathematical model whose parameter values are obtained by a few experimental runs is available, it is possible to explore the whole range of operating conditions without restrictions and therefore to obtain a proper design. Acknowledgment from SISAS S.p.A. Nomenclature a = external particle surface/particle volume, l/cm c, = concentration in external liquid phase, mol/L ci = concentration in liquid phase into macroporosity (internal Deff = effective diffusion coefficient (eq E), cm2/s DL = axial diffusion coefficient, cm2/s fq = mathematical expression of adsorption isotherm k , = film mass transfer coefficient, cm/s ki = intraparticle mass transfer coefficient (into macroporosity), cm/s K = equilibrium constant of adsorption, L/mol K, K* = pseudolinear equilibrium constant of adsorption, defined by eq 10, 12, L/mol KL = global mass transfer coefficient, cm/s L = length of the column, cm N.C. = number of the components Pe = Peclet number (= 2uRp/D~.e,) R, = radius of spherical particle equivalent to the solid pellet, t = time, s tR = retention time of a component t (= L/u), s u = fluid velocity, cm/s u = interstitial fluid velocity, cm/s u j = effective velocity of component j (eq ll), cm/s z = axial length coordinate, cm Greek Symbols a, p = coefficients introduced in eq 21 The authors gratefully acknowledge financial support phase), mol/L cm L i t e r a t u r e Cited Broughton, D. B.; Neuzll, R. W.; Pharis, J. M.; Brearley, C. S. Chem. Eng. Prog. 1970. 66, 70. Butt, J. B. "Reaction Kinetics and Reactor Design"; Rentice-Hall: Engelwood Cllffs, NJ, 1960 p 274. De Rosset, A. J.; NeuzU, R. W.; Korous, D. J. Ind. Eng . Chem . Process Des. Dev. 1978, 15, 261. Garg, D. R.; Ruthven, D. M. Chem. Eng. Sci. 1974. 29, 571. Keulemans, A. I. M. "Qas Chromatography", 2nd ed.; Relnhold New York, Liapis, A. I.; Rlppin, D. W. T. Chem. €ng. Sci. 1977, 33, 593. Morbldelll. M.; Servida, A.; Can& S. submltted to Chem. Eng. Comp. 1982. Santacesarla, E.; MorbMelll, M.; Denise, P.; Mercenari, M.; C a d , S. Ind. Eng. Chem. Process Des. Dev. 1982a. Part 1 of thls series, published in this issue. Santacesaria, E.; Morbldelli, M.; Servlda, A.; Storti, G.; Car& S. Ind. Eng. Chem. Process Des. Dev. 1882b. Part 2 of this series, publlshed in thls Issue. Seko, M.; Mlyake, T.; Inada, K.

The Overview of Thermal Decomposition of Cellulose in Lignocellulosic Biomass

“…Compared to the on-line pyrolysis study of cellulose, the off-line pyrolysis of cellulose is mostly carried out under the relatively high temperature (above 400 o C) or high heating rate (more than or around 1000 o C/s) [12,32,36,40,[44][45][46][47][48] and sometimes under low temperature heating (below 400 o C) [49,50], concerning the following issues: 1) the distributions of the gas, liquid and solid products; 2) the formation of the specific compounds and the pyrolytic chemical pathways. How these two issues may be influenced by the pyrolytic reactors and the variables like temperature, residence time, heating rate, pressure, particle size, catalytic salts and crystallinity is extensively examined in the literature, in order to promote the product specificity, maximize the yield and improve the understanding of the pyrolytic mechanism.…”

“…Therefore, the fixed bed reactors are designed for investigating the effect of not only temperature but also residence time on the yield of products and their specificity [31,36,44,68]. Liao [31] designed a fixed bed reactor (quartz tube with a sample-holder in the middle), the temperature of which could be changed from 0 to 1100 o C. The filter paper shaped as 18*50 mm (about 2 g) is fed gravitationally to the reactor from the top, and the carrier gas (nitrogen) brings the evolved volatiles and some char fragments through the carbon filter.…”

“…Another Pyrex cylindrical tube (fixed bed) reactor was made by Hajaligol et al [44], where the cellulose sample is held and heated by the porous stainless screen connected to the brass electrodes of the reactor. The system allows independent variation of the following reaction conditions: heating rates (100-100 000 o C/s), final temperatures (200-1100 o C), sample residence (holding) time at final temperature (0-∝ s).…”

“…The mass balance for each case is around 100%, giving the convincing results of the yield of the products at the temperature 400-1000 o C with the sample holding time 0-30 s in Table 2. It is concluded [44] that tar yield (liquid product) increases with temperature to a maximum of about 65% at around 700 o C and then decreases with further temperature increases, since the sample residence time is zero. With the long residence time (for example 30 s), the yield of liquid product at 400 o C is remarkably increased to 83.35%, due to the sufficient heating-up time for the complete pyrolysis of cellulose.…”

Computer Simulation of a Municipal Solid Waste Combustor

“…The kinetics used in the model for the pyrolysis of cellulose have been adapted from Hajaligol et al, 7 who proposed rates for the weight loss of cellulose and for the formation of specified gases. The rate expressions for the formation of the gases had the form, dV t dT (1) where, V; is the percent yield of gas i at any time t, Vi* is the ultimate (maximum) yield of gas i, and A; and Ei are kinetic parameters.…”