Preliminary results show improved wet-end stability, PM runnability and paper
quality.
“A big improvement all round,” says Ki-Jin An.
Photo: David Wold
Norske Skog Korea gets the gas out
One of the world’s largest newsprint mills with a production capacity of one million tons per year, Norske Skog Korea Jeonju solved its excess white water gas problems with a BTG Mütek™ analyzer, reducing its total energy bill and improving output quality.
For South Korea’s paper producers, excess white water gas can be a nagging problem. The local raw materials used in recycling tend to have a high gas content, making life difficult for mills such as Norske Skog Korea Jeonju, a huge facility running three paper machines producing 800,000 tpy of quality newsprint, and two machines producing 200,000 tpy of groundwood magazine paper.
To solve the recycled stock gas problem in its No. 4 DIP plant, Norske Skog Korea Jeonju chose a gas analysis solution from BTG’s Mütek instrumentation range. The result: increased runnability, lower energy and additive costs, and improved overall output quality on the mill’s PM7 270,000 tpy newsprint machine.
Founded in Norway in 1962, Norske Skog has grown to become the world’s largest manufacturer of newsprint and magazine paper, with 18 mills worldwide.
Ki-Jin An, assistant manager in the instrument department of the maintenance section at Jeonju, says the company’s goal was to try to stabilize the wet-end by better controlling gas in the system.
To that end, the mill installed a Mütek™ GAS-60 Gas Analyzer to measure free and dissolved gas. As well as helping better control the use of deaerator chemicals and improving machine runnability, Mr An was confident that getting the gas out more effectively would yield significant product quality improvements.
Control strategy
FIGURE 1
The Mütek™ GAS-60 Gas Analyzer in operation at Norske Skog
Korea Jeonju.
The Gas Analyzer’s sensors were placed in the headbox circulation
and white water tank (see figure 1). On PM 7, the flow of deaerator chemicals
is normally automatically adjusted as the amount of free gas in the white
water varies. The setpoint of the flow controller for the deaerator was
thus cascaded from the Mütek™ GAS-60, optimizing additive levels and
preventing over dosage.
Minimum, maximum, safety and start-up parameters also help optimize performance.
As a result, the control loop minimizes deaerator consumption while maximizing
process stability.
Effective analysis boosts results
FIGURE 3
Stable and lower white water consistency after closed-loop control
FIGURE 2
Reduced need for deaerator chemicals after closed-loop control
After about ten months of manual operation, the Mütek™ GAS-60 was
put on closed-loop control. Preliminary results after two months of closed-loop
operation showed greater wet-end stability, better PM runnability and improved
paper quality. “In fact, everything is better than before,” smiles
Mr An.
On closed-loop control, the Mütek™ GAS-60 unit reduces and stabilizes
the free and dissolved gas (see figure 2). Stabilizing the amount of free
gas in the white water tank also stabilizes and improves the retention
rate (see figure 3). And a more stable silo-tank level helps stabilize
PM7 basis weight (see figure 4).
FIGURE 4
Stable silo-tank levels after closed-loop control
FIGURE 5
White-water-free gas vs power load and vacuum pressure
Figure 5 shows the correlation between gas content, the Nash pump’s power load and the vacuum pressure of the deculator without closed-loop control. BTG’s Mütek™ GAS-60 significantly improved the efficiency of deculator and stabilized vacuum pressure and pump power load, resulting in reduced energy costs.
Improved performance, better quality
Norske Skog Pan Asia
Headquartered in Singapore, Norske Skog Pan Asia is the leading Asian
supplier of newsprint and groundwood paper, with mills in Jeonju and
Cheongwon, South Korea; in Singburi, Thailand; and in Shanghai and Hebei
in China.
Together, the mills boast a combined capacity of 1,800,000 tpy of newsprint
and 200,000 tpy of other publication papers. The company has around 30% market
share in Asia, excluding Japan.
After two months of closed-loop operation, the Mütek™ GAS-60 delivered reduced deaerator consumption and reduced gas volume, delivering better PM runnability, drainage and retention. For his part, Mr An is very satisfied. Gas is finally under control, energy costs are down – and overall product quality is better than ever.
To find out more about Norske Skog, visit the company’s website at www.norskeskog.com. To learn how BTG's Mütek instruments can boost your mill’s productivity, go to www.btg.com.