The following is a summary with excerpts from an article in Pulp and Paper International’s PPI Magazine April 1, 2015. The article is entitled Plastics Out; Fiber In, and the subtitle is “Jackson cuts shrinkage with unique tailing screen.”
Our company is the largest 100% recycle paper manufacturer in North Carolina, and we are one of the most environmentally-friendly paper mills in the country. We take pride in the fact that we do things right. What does that mean? We take care of our customers first. We produce a high quality product. We treat our employees like family. We make money the old fashioned way – we earn it. AND we are a role model for sustainability that leads the industry.
WE’VE BEEN A LEADER FOR 20 YEARS
Our business is based on producing corrugating medium from old corrugated containers (OCC). It is a huge challenge to keep the output exceeding performance specifications. Yes, it is a business with tight margins, so we must be innovative in ways to reduce waste. This article explains one way we are investing in technologies that improve production efficiencies: Controlling shrinkage.
Shrinkage is defined as the difference between incoming raw material and outgoing saleable product. It measures the effectiveness of our process to convert the OCC into usable paper. So, when the mill started seeing good fiber trapped in screening rejects – driving shrinkage higher – a solution was needed. And fast.
Jackson Paper was “green” before it was fashionable. For years, it has been recycling waste packaging materials into high-quality corrugating medium in the 23-45# range. Jackson Paper has no discharge to receiving waters, minimizes smells, and is firmly embedded as a good corporate citizen in the North Carolina community of Sylva.
“Being that we are right in the town, we are very sensitive to environmental issues,” says Nicki Slusser, Jackson’s president and COO. “Discharges and smells are tightly monitored and controlled. We want to be good stewards of all resources.”
The process water loops at Jackson are very closed, so any upset in the process is clearly visible. Fresh water is used for the boiler and paper machine. Filtrate from the stock prep screens is returned to the pulper. “Anything out of the ordinary, we know about it immediately,” explains Ken Rogers, plant manager. “Our people are adept at getting to the root cause, arriving at a solution, and getting things back to steady-state.”
One disturbance that was causing the mill headaches was the tailing screen in the stock prep area. The tailing process, the last screening opportunity, is very important to Jackson Paper. “We need to wash all the fiber from the rejects and return that ‘good’ fiber to our pulper and accepts stock stream,” Rogers says. “We also can’t allow the rejects, plastics, and other contaminants to return to our pulper and accepts. So, it has to be plastics out, fiber in.”
The tailing screen and process had served the mill well for many years (probably 15 years according to Rogers). But the screen and process had become a bottleneck as Jackson Paper increased production. Upgrades to the paper machine increased tonnage approximately 25%. “So, in late 2012 we ordered another screen like the one we had installed,” says Duc Duong, engineering manager. “The assumption was that we would have two identical units to split the workload to easily handle the increased tonnage. That did not turn out to be the case.”
Keith Allison, maintenance manager, explains, “It appears that the manufacturer had made some design changes which decreased performance. We commissioned the second unit, but it just never ran right. It damaged screen basket after screen basket at full load. We had to lower the throughput considerably to keep it running.”
The mill changed the rotor in the original screen once a year and the screen baskets twice a year. “We couldn’t keep a basket in the second screen for more than a few weeks, sometimes days,” Allison says.
The basket would lose concentricity, which would cause the rotor to trap plastic against the basket, which would then melt due to the friction. The maintenance team had to completely disassemble the screen and clean it out before installing a new basket. Not only was this expensive, but since the baskets came from Europe, the lead times were such that Jackson Paper couldn’t keep screen baskets in inventory.
The second screen was de-commissioned and, as a stopgap measure, a vibratory screen was installed to supplement the original screen. “We like to keep our shrinkage numbers between 6-8%; however, during that period of time we were over 11% at times,” Rogers says.
With shrinkage high, and morale low, Jackson Paper began looking for another option – quickly.
TIMING IS EVERYTHING
Randy Packer of the Summitt Group was visiting the mill on another matter. The Summitt Group of which Packer is a principal, is a representative for Aikawa Fiber Technologies (AFT) among other companies. “When I heard about the problems with the plastics separation and fiber recovery, I immediately arranged a conference call with John Wright, AFT’s regional manager for capital equipment,” Packer says.
Wright felt that the AlphaScreen, with its two-stage design to accomplish deflaking and coarse rejects handling in a single unit, would be perfect for the application at Jackson Paper.
“The timing of the phone call was excellent,” recalls Mike Shuler, production manager. “We were very open to anything that could improve our situation. I had never heard of an AlphaScreen before, but as John described it, it sounded like the answer to our prayers.”
Aikawa’s AlphaScreenTM has good references in Europe and Asia, but no track record in the US. The closest operating units were in Mexico, so Wright arranged for the Jackson Paper people to visit. “To be honest, the Mexican mill was not running consistently at full capacity, like we intended to do, so their requirements were a bit different,” Rogers says. “But after seeing for ourselves the ruggedness of the unit, and the simplicity of its design, we did not feel it would be a big risk for us.”
Duong was impressed with the horizontal design. “It acts as both a horizontal hole screen and rejects processor and moves the stock mechanically instead of by gravity,” he says. “There is much less chance of plugging compared to our vertical screen units. With the horizontal layout, it will be much simpler to change out the screen plates, though we haven’t had to do that yet.”
Wright explains the two-chamber design of the screen. “In the first chamber, the deflaked stock passes through a perforated plate and is returned to the process,” he says. “The contaminants and any remaining large flakes move to the second chamber where they are deflaked once more. Good fibers and wash water pass through the perforated plate. The contaminants, now fiber-free, are continuously discharged at the end of the machine. The whole process takes seconds to complete.”
One additional advantage to the design is that no secondary unit (strainer or vibratory dewatering unit) is required to remove water from the rejects, which is discharged at about 40% consistency.
A HOME RUN
Jackson Paper ordered the AlphaScreen and asked AFT to expedite shipment. The housing was shipped separately from the rotor assembly and, unfortunately, the rotor tolerance was too tight. “This is not the way we would normally do things,” Wright says, “but instead of assembling and fit-testing before delivery to the mill, the customer asked that shipment of the housing be made directly to the mill so they could get started with the installation work.” Delivery was completed in early 2014.
“Once we got the rotor adjusted and started it up, you could immediately see plastics coming out the end with no fiber on them,” Rogers says. “It worked right out of the gate. I’d call that a home run.”
Allison agrees. “The days of daily babysitting our tailing screens are over,” he says. “Our guys are happy. They check it occasionally to make sure the shower nozzles are clear and that the shaft is lubricated. We’re looking to get two years between screen plate changes – much different than a few months ago.”
LESS BROWN, MORE GREEN
All of the mill’s rejects are now processed through the AlphaScreen. A conservative estimate is that Jackson Paper is recovering 3.5% more fiber, at times, compared with the previous equipment. This translates to about 2 tons/day of additional fiber.
As with every recycled paper mill, Jackson Paper is seeing shorter fiber lengths and changes in the types of plastics and contaminants in the incoming furnish. “Even though we buy a relatively clean furnish (Grades #11 and #13 OCC), the processing is challenging,” Shuler says. “The AlphaScreen handles these challenges very well.”
“There are certainly good economics attached to the AlphaScreen, but probably the biggest boost for us was to free our people up from attending to the old system,” Rogers says. “Each replacement screen basket was over $6,000, and when you factor in the time our operators and maintenance people spent babysitting an older, unreliable system, the ROI is quite impressive.”
“There is certainly a lot less brown in our screen rejects today,” Shuler says. “And our people are happier.”
The experience was pleasant enough for Jackson Paper that it recently ordered a primary coarse screen from AFT. “We know that we are putting some rejects back to the pulper with the 6-mm hole size in the AlphaScreen, so we are adding a MaxFlowTM screen,” Rogers says. “With the trend toward lighter weight packaging materials, it behooves us to deliver cleaner fiber to our paper machine.”