Biomass Fuel Quality Enhancement and Respiratory Quotient (RQ) for Ranking Fossil and Biomass Fuels Based on CO2 Emissions - Novel Combustion Concepts for Sustainable Energy Development - page 66

lifecycle analysis data. Further, when the raw biomass is torre ed, moisture content

in the torre ed samples will be low. In addition to lower moisture content, torre ed

samples will exhibit improved grindability. Hence, RQ process,biomass for the torre ed

samples will be lower than the raw biomass samples.

3.3.3 RQ Factor for Fuel Blends

The RQ factor for the blend of biomass with coal should be less than the RQ factor
for pure coal so that using biomass will result in reduced CO 2 emissions. RQ for the
fuel blend can be determined using the following formula (Thanapal 2014 ).

RQ fuel ; blend ¼ RQ coal HF coal þ RQ biomass þ RQ process ; biomass HF biomass ð 19 Þ

where HF is the heat fraction contributed by the fuel present in the blend. Heat
fraction of a fuel is de

ned as the ratio of heat content of a particular fuel to the total
heat content of the blend (kJ of fuel/kJ of fuel blend). For the case of 90:10 blends
of coal and woody biomass which was used in the current study, the RQ fuel,blend
was determined to be 0.82 assuming RQ biomass to be zero since biomass is con-
sidered carbon neutral. RQ factor for the fuel blend is lower than the coal RQ value
which is 0.92. This indicates lower amount of CO 2 will be released into the
atmosphere when 10 % of biomass on mass basis is blended with coal. Table 6
shows the RQ blend for the different biomass blends which were used in the current
study.
Further, it can be seen from Table 6 that the RQ blend for coal and torre ed

biomass is lower (0.82) than the raw biomass blends (0.84). Higher heat values of
torrefied biomass resulted in higher heat fraction for biomass which led to lower
numbers for RQ blend . Also it should be noted that energy consumed for processing
torre

ed biomass will be lower than the raw biomass if hot fl flue gas from boiler is

used for torrefaction.

Table 6 RQ factor for the 90:10 blends of coal and biomass on a mass basis (Thanapal 2014 )
Fuel RQ coal HF coal RQ biomass RQ biomass,processing HF biomass RQ blend
PRB + RM 0.92 0.91 0 0.03 0.09 0.84
PRB + RJ 0.92 0.90 0 0.03 0.10 0.83
PRB + TM 0.92 0.89 0 0.03 0.11 0.82
PRB + TJ 0.92 0.89 0 0.03 0.11 0.82
HF Heat fraction; PRB Powder river basin sub-bituminous coal; RM Raw mesquite; RJ Raw
juniper; TM Torrefied mesquite; TJ Torrefied juniper