Smooth startups, low energy costs and very clean, high-bulk pulp are greatly appreciated by the mill.
As part of Liansheng Pulp and Paper’s massive Zhangpu greenfield mill project in China, which has an annual output of 3.9 million tonnes, two big BCTMP (bleached chemi-thermomechanical pulp) production lines from Valmet are playing a crucial role.
After surveying the market for the best technology, Liansheng’s management decided that the successful track record and reliability of Valmet’s BCTMP solution made it the optimal choice. Since start up, the BCTMP lines have proven their value by running with low operating costs while delivering high bulk and ultra-clean pulp, with low shives. Both the pulp mill operators, as well as the paper machine crews that are using the BCTMP for board and fine paper production, are very happy with the quality.
Valmet’s delivery in 2023 included two BCTMP lines, each with capacity of 1,200 tons per day. The main equipment included RGP CD-82 refiners, PREX (Pressure Expansion) chip impregnation system and TwinRoll wash presses.
“The new BCTMP line number 1 had a successful start-up on 30 April 2023, with good quality pulp produced within 24 hours and no wasted wood chips or pulp. And when we started line 2 a month later on 31 May we made excellent pulp within six hours, with another very smooth start up,” says Zhang Bin, the CTMP mill manager.
Capacity quickly exceeded, with excellent stability
Huang Ju, Deputy General Manager of Liansheng Pulp and Paper, explains why Valmet CTMP lines were chosen. “As one of the main CTMP equipment suppliers on the market, we found Valmet’s technical advantages were exactly in line with what we wanted: They could ensure strength while guaranteeing bulk. Also, the operating cost advantage regarding energy consumption is very beneficial for us and we see that this advantage is growing all the time.”
Now that the lines are running Huang Ju is very happy with their performance.
“Stability right from start-up has been excellent, with both production lines rapidly reaching our design capacity – and even exceeding it. Current actual operation can reach up to 1,250 air-dried tonnes/day, versus the single-line design capacity of 1,200. And since the beginning of September we have done only one planned shutdown per month, with both lines being very stable in operation.”
High CTMP addition maintains high quality, while balancing bulk and strength
The pulp is being used extensively, not only for increasing the CTMP content in the mill’s varieties of white folding boxboard but also for fine paper production. The CTMP helps increase bulk and stability of the paper quality while also giving important cost advantages by replacing chemical pulp on the two Valmet-supplied PMs: white board machine BM 1 and fine paper machine PM 3.
“Liansheng’s white board bulk can currently reach more than 1.63 cm3/g, and the CTMP line fully meets our paper quality requirements,” comments Huang Ju. “At the same time, the CTMP added to the PM 3 fine paper machine is at very good levels, with the content ratio for high-white fine paper of more than 25%, while for standard white fine paper we are using more than 36% CTMP.”
Energy consumption is very low
On the CTMP production line, the pulping process not only plays an important role in producing high-quality fibers and finished paper; it also has a very positive influence on the mill’s energy consumption and final production costs.
Regarding energy, Huang Ju proudly says that “thanks to Valmet’s advanced equipment, the average electricity consumption of the CTMP line is currently around 750 kWh/adt. This is significantly low. Moreover, on the paper machine, due to the cleanliness of CTMP and our overall process configuration, our water consumption is also low at about four m³/tonne of paper.”
Huang Ju likes the combination of Valmet’s CD-82 high-consistency and RF-5 low-consistency refiners to get optimum bulk and strength, at low operating costs. “A key reason we chose Valmet was these refiners. We get the quality we need while reducing energy consumption by about 50–100 kWh/adt compared to other equipment. So from the perspective of operational stability and cost control, this CD-82 and RF-5 combination is superior to the competitors and exceeding our expectations.”
Cleaner pulp means a cleaner machine and felts
Valmet’s TRPW (TwinRoll wash press) has also demonstrated strong performance in pulp dewatering and washing, effectively helping Liansheng improve pulp cleanliness. Huang Ju praises Valmet’s twin roll press washer: “The TRPW equipment has raised the pulp cleanliness to a new level, greatly reducing felt costs on our paper production line. Our felt use was once able to produce 200,000 tonnes of paper with five felts, but we can now make 300,000 tonnes, reducing costs by nearly one third. We also see very stable PM operation due to the clean pulp. We are very satisfied with Valmet’s TwinRoll wash press performance.”
Zhang Bin concludes: “Because the pulp coming into the refiner is cleaner, the life of the refiner plates is longer, which saves money. And the cleanliness has continued positive effects further through the system, which means that our various white and clear water addition levels are also lower. This is part of the reason for our overall low water consumption.”
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