Recovery boiler illustration

Recovery boiler

The black liquor recovery boiler is the single most expensive asset in the chemical pulp mill. Operating these boilers with optimal internal energy consumption and keeping the boilers operational for whole seasons without outages requires advanced technical solutions.

Recovery boiler illustration

General info

Recovery boilers recovers chemicals and energy

The Recovery boiler recovers chemicals and energy, which is used in the cooking stage where wood chips are refined to cellulose. The black liquor is a mixture of by-products from this separation process. All chemical pulp-mills rely on this chemical recovery cycle for their economical and sustainable operations.

About cleaning

Sootblowers are used for keeping the recovery boiler clean inside

Pulp mills stay competitive by lowering production costs per ton cellulose and one way of doing that is to increase cellulose production. Since the recovery boiler is so expensive, it is commonly operated at or above original design capacity which presents challenges with regard to availability and runnability. The most common reason for reduced availability is fouling of the boiler heating surfaces. To combat this, retractable steam sootblowers are used to keep the boiler insides clean.

Our motto

We go beyond technical specification

Like the recovery boiler operation, retractable steam sootblowers are operated at maximum capacity, meaning there is no additional cleaning capacity to increase boiler availability. It is in this setting that Heat Management introduces the patented High Impact Sootblowing System (HISS™), increasing the cleaning capacity of the existing steam sootblowers by 100 %. Benefits include increasing recovery boiler availability, cleanability and efficiency, while reducing steam consumption. HISS™ provides the mill with the necessary tool, allowing safe increase of production levels beyond technical specification i.e. process more black liquor in the boiler, without jeopardizing the process availability.

References on Recovery boilers


Södra Cell, Värö

In 2020 Södra Cell Värö initiated the Expansion 2.0 project, to increase production from 710 000 ADMT/year of NBSK pulp to 780 000 ADMT/year. The identified bottleneck was the recovery boiler. Read more about the results by downloading our case study.

Content related to Recovery boilers


Challenges for Power boilers

This white paper focuses mainly on challenges related to combusting complex fuels, such as domestic waste, industrial waste, and demolition waste. In the first chapter, we will present the challenges, solutions for increasing the efficiency and cleanliness of the boilers