Conversion of dryers to Biogas

Our team participated in a project to install an anaerobic reactor which would produce biogas in its effluents. The goal was to use this biogas in place of the current fuel oil to power the two pulp drying lines. The drying process was comprised of two lines, each with two levels, for a total of four dryers. The conversion to biogas allowed the plant to save approximately $5.9 million dollars annually, while at the same time reducing their carbon footprint. This project was part of a total investment of $25.7 million.

An important advantage of using biogas at the plant is that it is produced onsite, by the plants’ own reactor. This allows complete control over generation, pressurization, and post-treatment of this gas prior to feeding it into the dryers. The result is an high quality fuel which provides an increased heat value and a stable composition, particularly in terms of methane content. Both of these aspects have a positive impact on biogas combustion, and facilitate its use as an energy source in the industrial process.

BMA’s unique challenge with this project:

Dimensioning the burner to allow for the use of a variable quantity of biogas and dual firing with diesel, while ensuring the required supply of power to the dryers, which is also variable. What’s more, given that the drying is done via direct contact with the combustion products, nearly perfect combustion was required in order to avoid marring the final product with combustion residue.