Fate of the ash forming elements during combustion of biomass

In modern kraft pulp mills, the kraft recovery boiler can produce all the steam and electricity needed for the mill and even sell green electricity to the grid. However, most mills still have the fossil CO2 emissions from the combustion of fossil fuels in lime kilns. For mills to eliminate this source of fossil CO2, the fossil fuels must be replaced by biomass derived fuels. Biomass fuels are used in some mills either directly by using powdered fuel burners or indirectly by first gasifying the fuel and then burning the product gas in the lime kiln.
A significant challenge for direct combustion of biomass in lime kilns is the ash forming elements. The ash forming elements in biomass are inorganic elements such as K, Cl, Ca, P, Mg, Mn, Si and Al. If the biomass is burned directly in the kiln using a powered fuel burner, the ash forming elements go into the kiln and will enter both the lime cycle and the larger recovery cycle. Both due to availability and low cost, bark is a desirable fuel to use. However, it has a high ash content when compared to stem wood.

Faculty Supervisor:

Nikolai DeMartini

Student:

Partner:

Åbo Akademi University

Discipline:

Engineering

Sector:

Education

University:

University of Toronto

Program: