Page 97 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

Chapter | 3 Biomass Characteristics 75

(CaCO 3 ) is required which will release 1 mol of additional carbon dioxide
during the production of CaO from CaCO 3 .In reality,much more 2 4mol of
limestone is required due to imperfect sulfation of the calcined limestone.
Thus, for capture of sulfur dioxide, considerable amount of additional carbon
dioxide is generated.
Biomass, in addition to being CO 2 neutral, results in additional reduction
in CO 2 emission because of the absence of sulfur capture-related CO 2
emission as needed for many fossil fuels as described above.

3.6.2 Proximate Analysis

Proximate analysis gives the composition of the biomass in terms of gross
components such as moisture (M), volatile matter (VM), ash (ASH), and
fixed carbon (FC). It is a relatively simple and inexpensive process.
Table 3.11 compares the proximate analysis of corn cob and rice husk mea-
sured in two different techniques.

3.6.2.1 Volatile Matter
The volatile matter of a fuel is the condensable and noncondensable vapor
released when the fuel is heated. Its amount depends on the rate of heating
and the temperature to which it is heated. Options for its measurement are
discussed in Chapter 13.

3.6.2.2 Ash
Ash is the inorganic solid residue left after the fuel is completely burned. Its
primary ingredients are silica, aluminum, iron, and calcium; small amounts
of magnesium, titanium, sodium, and potassium may also be present.
Strictly speaking, this ash does not represent the original inorganic min-
eral matter in the fuel, as some of the ash constituents can undergo oxidation
during burning. For exact analysis, correction may be needed. The ash

TABLE 3.11 Comparison of Proximate Analysis of Biomass Measured by
Two Methods

Fuel FC (% dry) VM (% dry) ASH (% dry) Technique Used
Corncobs 18.5 80.1 1.4 ASTM
16.2 80.2 30.6 TG
Husk-rice 16.7 65.5 17.9 ASTM
19.9 60.6 19.5 TG
Source: Compiled from Klass (1998, p. 239).