Thermodynamic Properties of Plant Biomass Components. Heat Capacity, Combustion Energy, and Gasification Equilibria of Cellulose

Abstract

Heat capacities and enthalpies of formation were determined for the well-characterized samples of cellulose of different origins. The obtained experimental results allowed us to obtain the accurate values of thermodynamic properties for this material. It was demonstrated that the heat capacity and entropy of cellulose samples can be linearly related with their crystallinity index. The equilibria of the processes of cellulose gasification were considered. The adiabatic temperatures of the gasification and energetic characteristics of the products of cellulose thermolysis were evaluated. ' INTRODUCTIONThe use of plant biomass as fuel and raw material for chemical processing is being increased. 1 The effective operation of energy and processing plants using plant biomass is possible if their working conditions are thermodynamically justified. However, very limited information about thermodynamic properties of cellulose and lignin, the major components of the stem part of biomass, is available. In refs 2 to 3 the heat capacity of cellulose fibers was measured in a drop calorimeter. The heat capacity changes near T = 400 K corresponding to the glass transition were observed. Hatakeyama et al. 4 measured heat capacity of cellulose in the temperature range of (330 to 450) K by differential scanning calorimetry (DSC) and found no anomalies below T = 440 K. In refs 5 to 8 the heat capacity of cellulose was determined in adiabatic calorimeters. Karachevtsev and Kozlov 6 measured the heat capacity in a range of temperatures of (80 to 300) K for two samples dried by different methods and found that the results depend on the method of drying. Uryash et al. 8 determined the heat capacity for cotton microcrystalline cellulose in the temperature range (80 to 330) K. In ref 8 the anomalies at 291 K, 343 K, and 403.5 K were observed in the differential thermal analysis (DTA) curve, and the first anomaly was also found in the heat capacity curve. The energies of combustion for various samples of cellulose were also reported in ref 8 though the samples were not characterized by the ash content.In this work the heat capacities in the temperature range of (5 to 370) K and the enthalpies of formation were determined for the samples of cellulose of different origins and degrees of crystallinity. The obtained experimental results allowed us to obtain the reliable values of thermodynamic properties of cellulose required for the calculation of equilibria of the reactions with the participation of this compound, the adiabatic temperatures of the processes of its gasification, and energetic characteristics of the products of cellulose thermolysis.

Heat capacity measurements of various biomass types and pyrolysis residues

“…1, the heat capacity of the different biomasses varies from 1300 to 2000 J kg À1 K À1 in the temperature range 313-353 K. These values are in the range of values commonly found on biomass in literature. Very good agreement was found with previous measurements on cellulose [10].…”

“…Experimental studies on heat capacity can be found in literature on biomass species of interest for current industrial applications: woody species [5,6], together with cellulose, which is the main constituent of biomass and the main product used for pulp applications [7][8][9][10][11] or agricultural biomass for food applications, such as peanut [12], cassava, yam, plantain [13] or cumin seed [14]. To our knowledge, agricultural by-products were considered only by Mothée and De Miranda [15] with measurements on coconut fibre and bagasse and there are no available heat capacity data on energy crops or wood from Short Rotation Forestry (SRF) and Short Rotation Coppice (SRC).…”

“…These heat capacity measurements were generally performed either with adiabatic calorimeter such as in [10] or with Differential Scanning Calorimetry (DSC) such as in [13,16]. Many studies on food biomass were carried out by the method of calorimetry by mixtures but this technique is not accurate [14].…”

A thermodynamic investigation of the cellulose allomorphs: Cellulose(am), cellulose Iβ(cr), cellulose II(cr), and cellulose III(cr)

“…Nevertheless, it is likely that many of the samples of cellulose Ib used in these studies contained some cellulose Ia [4,79]. [91], and by Blokhin et al [92] lead, respectively, to D c H Ã w = À17337 JÁg À1 , D c H Ã w = À17458 JÁg À1 , and D c H Ã w = À17165 JÁg À1 for cellulose I(cr). The earlier, very carefully done measurements of Jessup and Prosen [83] and Colbert et al [87] did not include a measurement of CI but the samples that they used probably had high CI values.…”

“…Here, the uncertainty is equal to two estimated standard deviations of the mean. The value of D c H Ã w = À17165 JÁg À 1 from Blokhin et al [92] is an outlier and was not used in calculating the average. From our study, we have D c H Ã w = À(16048 ± 40) JÁg À1 for cellulose I(cr) (see table 8) that pertains to T = 298.15 K and w H 2 O = 0.073.…”