Multi-fuel powered steam generator

Patented technology for the combustion of black liquor

Alce is a wood processing manufacturer of the Silvateam group, located in Bagni di Lucca (Tuscany), Italy which has been producing semi-chemical paper for corrugated cardboard since 2009. The raw materials used are mainly exhausted chestnut wood derived from the tannin extraction of 80,000t/year.

During the production process black liquor is obtained. The capacity is around 22,000t/year. The liquor is composed of aluminium lignin sulfonate (BL). This by-product has been recognised as biomass and has a water content of 50%.

Silvateam has created a multi-fuel steam generator using this biomass. The plant is composed of an oven that operates using BL as fuel, with the help of a patented system of methane burners. The oven has a large combustion chamber where methane or low sulphur heating oil is burned to meet the facilities requirements.

The steam generator has a capacity of 60t/hour of steam at a pressure of 60 bar and a temperature of 450°C. The steam, before being sent to the different parts of the plant, passes into an existing turbine of 6 MW. The exhausted gases are treated in a system especially designed for the removal and the recovery of sulphur dioxide.

The plant has been considered innovative in the renewable energy sector and has received recognition by the authorities in the industry.

In 2010 Silvateam obtained the authorisation for the construction of a new biomass cogeneration thermoelectric plant of 14.5MW that will replace the existing plant. The chestnut wood residues in combination with new wood chips will be used as fuel in the new steam generator. This steam generator has a capacity of 62 ~ 63t/hour of steam at a pressure of 62 bar and a temperature of 500°C. Construction site has been started on May 2011.