There was no longer any use for the recovery boiler built in 1991 at Double A Alizay by the River Seine in Normandy, France.
After careful consideration, the paper mill decided to convert the boiler to produce steam for paper production and electricity for the national grid. A new company called Biomasse Energie d'Alizay was founded to promote green energy.
Valmet is the leader in BFB conversions with more than 60 references over the past 30 years, including boilers initially manufactured by third parties and numerous recovery boilers. Conversion is a very efficient and cost-saving way to modernize and prolong the lifetime of high-capex plants to serve the future needs of customers.
“A recovery boiler is well-suited for conversion into a BFB boiler but presents many challenges compared with the construction of a new one. For example, combustion technology has to be adjusted to local conditions, and existing structures have to be taken into consideration in the engineering. Often is the case that the original boiler documentation is no longer available. Then, it is simply not possible to supply a standard boiler. Instead, we need to deliver a completely tailored one,” says Jyrki Mäntylä, Project Manager, Valmet.
Biomasse Energie d'Alizay’s converted boiler plant will have a capacity of 50 MWe. It will run on bark from the adjoining paper mill, and wood residues and recycled wood from the nearby surroundings. The boiler is designed to meet the new stringent emission limits, which are based on the new best available technology (BAT) requirements.
Ready to start up in April 2020
In addition to the boiler conversion, Valmet’s delivery scope includes a new SNCR system for NOx removal, upgrades of an existing flue gas cleaning system and electric precipitator, and a complete Valmet DNA automation system, including steam network optimization with the paper mill.
Boiler assembly began in August 2019, and commissioning is scheduled for January 2020. Biomass firing will start in April 2020. The boiler will be handed over to the customer in May 2020.
“The project is well underway and has been carried out in good cooperation with the customer,” Mäntylä adds.