REPLACEMENT OF FOSSIL FUEL WITH BIOMASS IN
PULP MILL LIME KILNS
O PAPEL vol. 79, num. 3, pp. 85 – 89 MAR 2018
Authors: Jean Taillon 1, Andras Horvath 2, Antti Oksman 3
1, 2, 3 ANDRITZ Oy, Finland
ABSTRACT
The lime kiln is responsible for most of the fossil fuel consumption
in a kraft pulp mill. Fossil fuel prices, and the obligation to reduce
CO2 emissions, are strong incentives to replace fossil fuel firing in the
kiln with biomass waste products (e.g. bark and chip screening fines).
The impact is significant. It is reported that, of all known solutions
to reduce greenhouse gas emissions in European kraft pulp mills,
a 10% reduction could be achieved by switching from fossil fuels
to bioenergy in lime kilns. This substitution can be achieved with
biomass gasification. A typical delivery would include a belt dryer
and a gasification plant in combination with a multi-fuel burner
in the lime kiln. The belt dryer utilizes low temperature waste heat
available in the mill. The gasifier is a Circulating Fluidized Bed (CFB)
air-blown gasifier operating at atmospheric pressure. ANDRITZ has
two gasifier installations in full production in Finland (Metsä Fibre,
Joutseno) and in China (Chenming, Zhanjiang). Both mills operate
their lime kilns at full capacity with 100% biomass derived gas. At
Joutseno, natural gas was replaced by the gasification of Nordic
bark. At Zhanjiang, heavy fuel oil was replaced by the gasification of
eucalyptus chip screening fines. Non Process Elements (NPE) found
in the biomass fuels are efficiently removed. Gasification plants with
capacities between 25-110 MW should offer an attractive payback.
This roughly corresponds to a lime kiln capacity of 300–1,200 t/d.
Key elements which will affect the feasibility of the investment are:
lime kiln capacity, fossil fuel costs, biomass costs, need for co-firing,
replacement with make-up lime, capital costs and, potentially, CO2
price.
Keywords: Biomass, Gasification, Lime Kiln
