Civil Engineering Reference
In-Depth Information
Mass allocation
Economic allocation
No allocation
10 000%
1 000%
100%
10%
1%
1.3
Environmental impact of a mass of GBFS (1.11 kg) equivalent
to the replacement of 1 kg of cement CEM I, for the different CML
indicators with different allocation procedures. (Adapted from Chen
et al., 2010b.)
1.4.2 Energy efficiency
Energy demand in clinker production has been significantly reduced over the
last few decades. the theoretical minimum primary energy consumption (heat)
for the chemical and mineralogical reactions is approximately 1.6-1.85 GJ/t
(Klein and Hoening, 2006). However, there are technical reasons why this
will not be reached, for example unavoidable conductive heat loss through
kiln/calciner surfaces. For reduction of the specific power consumption
(electricity), other barriers are also preventing the industry from reaching
this minimum, for example:
∑ A significant decrease in specific power consumption will only be
achieved through major retrofits. These have high investment costs and
so retrofits are currently limited.
∑ Strengthened environmental requirements can increase power consumption
(e.g., dust emissions limits require more power for dust separation
regardless of the technology applied).
∑ The demand for high cement performance, which requires very fine grinding
and uses significantly more power than low-performing cement.
as a consequence the best available techniques (bat) levels for new plants
and major upgrades are 2900 to 3300 MJ/t clinker, based on dry process
kilns with multistage-preheaters and precalciners (European Commission,
