By Dragon Hao, Technical Marketing Manager of BU Tube APAC, Alleima
Few assets are as critical to a pulp mill as the recovery boiler, and few face harsher operating conditions. If it fails, everything stops. Black liquor recovery boilers (BLRBs) play a critical role in the pulp and paper process by recovering chemicals and generating energy, and they also operate in some of the harshest conditions in the industry.
Corrosion, cracking, fatigue, and under-deposit damage put tubes under constant stress. The result = safety risks, unplanned downtime, and high replacement costs.
These are some of the toughest conditions any boiler tube faces, and they are exactly the conditions where Alleima composite tube technology has proven its reliability for decades.
160 years of metallurgical expertise
Alleima has a long history of pioneering materials designed to perform in extreme environments. Since the 1970s, the company has been at the forefront of composite tube research and development, delivering reliable solutions for BLRBs globally.
Alleima composite tubes are produced through hot extrusion and cold pilgering, a process that guarantees a strong metallurgical bond between the carbon steel base and the corrosion-resistant alloy outer layer. This bond ensures smooth surfaces, verified integrity, and consistent performance. Unlike overlay welding, which can create uneven surfaces and risk bonding defects, Alleima composite tubes deliver uniform quality and proven long-term durability.
Customer benefits in demanding conditions
Every pulp and paper producer faces the same challenges: ensuring safety, improving uptime, and reducing costs. Composite tubes from Alleima are engineered to meet these challenges.
Key benefits include:
- Strength and corrosion resistance: The carbon steel core provides mechanical strength, while the alloy cladding protects against corrosion.
- Extended boiler life: Less frequent replacements and reduced unplanned downtime.
- Higher efficiency: Reliable tube performance keeps recovery boilers operating at peak levels.
- Proven grades: Sanicro® 38, Sanicro® 28, Sanicro® 67, and Alleima® 3R12 - a corrosion-resistant stainless steel grade widely used in recovery boilers, particularly for walls and superheaters. These alloys are proven across floors, walls, superheaters, and airports.
- Sustainability: Longer tube life means less waste, fewer replacements, and lower environmental impact, supporting sustainability goals at the mills.
Local capacity, global standards
With 40 years of ongoing investment in China, Alleima has continued to advance industries, including pulp and paper, through its investment and expansion of capabilities in its tube mill in Zhenjiang, China. Phase II of this expansion is scheduled to open in Q4 2025, further strengthening Alleima’s capacity to supply composite tubes across Asia.
For customers, the investment brings faster delivery due to increased local capacity, while maintaining the same trusted quality established at Alleima’s flagship mill in Sandviken, Sweden. For decades, this site has been the global standard for composite tube production, and the Zhenjiang facility is fully aligned with those standards. Production in China follows identical processes, with rigorous non-destructive testing, heat treatment, and finishing to ensure consistent performance.
Innovation where it matters most
The expansion also reinforces long-term partnership with the pulp and paper sector by broadening the portfolio of qualified composite tube alloy combinations and size ranges, while local manufacturing reduces transport needs and supports Alleima’s global commitment to sustainability.
BLRBs operate in critical, high-stress environments where failure is not an option. With decades of expertise, proven alloy solutions, and a growing global footprint, our composite tubes set the industry benchmark for safety, efficiency, and reliability.
Wherever we operate, our focus remains the same: delivering innovation, sustainability, and trusted performance.
Learn more about Alleima composite tubes here, or get in touch with our experts to discuss how composite tubes can extend the life of your recovery boiler here.