Volume 05, Number 4
Sep 1992

Notes from TAPPI-Papermakers, 1992 Alkaline Conversion Round Table

Normally, material published in this Newsletter has to conform to the rules of polite dinner conversation: it must be of general interest, and it must be at least minimally understandable to all present. If possible, it must also be easy to read, and of course this means it should be grammatically complete. All of these rules have been bent a little for this article, if it can be called an article, because the factual material is too valuable to ignore, but too condensed, technical, colloquial and heterogeneous to write up in coherent form. It remains essentially a set of notes taken by the APA editor at the panel discussion entitled "Alkaline Free Sheet Conversions: An Update" at the April 1992 TAPPI Papermakers Conference. No other record has been made of the panel, and what was said there will not appear in the proceedings.

The benefits of sharing conversion experiences are general, but since many companies regard the information as sensitive because of its potential value to competitors, the names of the companies and mills will not be supplied, and the speakers will not be identified with their presentation. It can be said, however, that the chairman was Dave Dupuis, and the panelists were Lyn Stryker, Dan Green, and Bill Boyden. In the discussion period after the presentations, they are identified by letters of the alphabet where the notes permit this; otherwise, the answers are simply numbered.

The chairman has been in on every alkaline conversion in his company. He asks for a show of hands. Only four in the room have been in alkaline for over 10 years. Our learning curve is very short, he said, so far.

He then described common mill experiences with alkaline conversions, noting his own company's experiences where they were different. Why does a mill decide to convert? To save fiber, improve quality of the paper, increase profits, and gain competitive advantage. Anticipated quality features are brightness; opacity; color; smoothness/caliper; less ink usage; and increased quality awareness in the mill. The downside is that the paper has a different feel and stiffness, and there are offset related problems, among others. Costs are of two sorts: capital (at one mill in his company they found they needed wet end starch cookers); and operating expenses (trials, conversion, variable costs-which may go over a million dollars, depending on the mill).

Savings can be anticipated in several areas: Fiber and titanium dioxide usage goes down, efficiency improves (they have found no gain so far, but may see gains in the future), and there is less corrosion (they built a new machine with 304 stainless, knowing they would go alkaline). Effects on papermakers are numerous and vary with the mill: The wet felts fill; wire wear increases, the learning curve cannot be avoided; suction rolls fill faster; drainage is different and the sheet appears wetter; foam is eliminated; pitch is reduced; boilouts are more frequent, though they may not be necessary; if your operation is dryer-limited, you can speed up; the microbe population is critical (i.e., very important); improved retention is necessary to avoid deposits, you have to monitor additives closely; the wet end chemistry affects picking; and self-skinner rolls are not advised-use hard doctor press rolls.

He believes the industry will convert because of competition. Permanence is important only for book paper, he says, not for copy paper or forms bond.

The panel went through several membership changes in the planning stage, because of the sensitivity of the subject.

Panelist A. His company has converted 12 machines at five locations, and one coated mill. At one of the mills, there is one paper machine making 45-70 lb. offset, and one pulp machine. They converted Feb. 20, 1990. It was a piece of cake... but that didn't last. The team consisted of the Engineering Department, people off the floor, research, and others. They sent people to observe at other mills undergoing conversion. They had vendor presentations, then narrowed the list and made vendors part of the team. They put in a distributed control system (DCS) and converted. They did an acid and an alkaline boilout. The use of titanium dioxide was dropped.

Then in April from the field they learned that it had dusting and runability problems. Everything hit the fan.

They were using cationic polymer for retention; they added silica.

The draw is now tighter. The foils need changing every 5-6 weeks now, oftener than before. They were able to turn off the continuous press wash system because it runs clean. There was no increase in sheet width. They used flame coated rolls on secondary winder rolls.

The first six to twelve months in the marketplace, it was very rough. It was worst on the stock tab side [stock tab is one of their products]. The problems were worked through, and results have been good the last three months.

Filler: They are not up to a 20-30% filler level yet; they are still working on this. The cost of conversion was higher than anticipated.

Alkaline sheets are wimpy, don't rattle, but they really conform to the press.

[The speaker then listed the chemicals they used for a retention aid, size, wet end starch, size press starch, filler, size press, and machine boilouts, in addition to alum. They tried clay as a filler, but dropped it in favor of precipitated calcium carbonate. The size they use is Keydime E.]

One change they'd make if they had it to do again is to be in better touch with the field.

Benefits include ash level, titanium dioxide, brightness, and recycling (you can reuse alkaline paper many times).

They are now planning a trial to identify the range of adjustments they can make without affecting quality.

Panelist B. His background is in pulping and bleaching.

His mill was the first in the company to go alkaline, so they had to rely on suppliers. They did a lot of training, and the staff had constructive insights. At first they used a portable PCC plant, then got a permanent one. First they converted one machine, then two at once. Acid broke had no effect on the machine. It was an easy conversion. They used a dual retention aid, and starch. They tried several AKD products and ASA, various addition points, and so on.

They had a runability problem: holes. The doctor blade is unforgiving. Now they have the incidence of holes down to a manageable level, but they put a lot of time into it. They are still working on it. This trouble is not correlated with the ash level.

For deposit control, they use an organic based biological control. The program costs are a bit higher than with acid. They have a four-week interval for maintenance, and boil out then. It is easier to clean.

Retention can now be monitored online, with other variables. This is very beneficial. The operators learned very quickly because of the prompt feedback it gives.

Pitch and EBS were detected and eliminated. Holes are still formed on the coated machine. Uncoated machines had no holes, though they used the same pulp. They made lots of changes but couldn't get rid of the holes in the coated machine. They originate in the wet end.

Conversion had no effect on the coating operation. There were no converting problems but there was a little size reversion, due to poor sizing on the machine.

Slippage, dusting and Tinting problems with the uncoated papers were solved with the cooperation of customers.

On the problem of slippage, they couldn't predict performance by any analytical test, but the operators could predict it by feel.

With one uncoated machine, there was a problem with fiberlifts or press picking. They increased internal starch and refining and plate selection to get optimal fiber; they also used surface applications.

They will not go back to acid, even though there are still some challenges. They want as much filler as possible. They are still optimizing additions and setting dosage rates, though most of this is done. They have a particle charge detector to get baseline data. Next week they will go to an online charge analyzer.

They are now simplifying the wet end, to reduce the number of additives and addition points. All their objectives have been met. There has been no impact on the customers. Cleanliness is better.

Panelist C. He is in research and development, and has been involved in conversions from that angle. Different mills in his company use different sizes and fillers. His experience is with printing and writing, reprographics fine writing and artist papers. His advice: Do your homework, don't overlook the training of technical and operational people.

Alkaline systems are very sensitive to chemistry; there is a very narrow window. When you put a package of chemicals together, you see it's more expensive, but the overall result is that it's cheaper.

Their activities date back to 1986. Now they are optimizing, but still learning new things.

Questions for the Panel

Q: Why didn't you use neutral rosin? Panelist C: One of our machines does. Panelists A & B: We didn't consider it.

Q: Is alkaline paper really hard to cut? Does it dull the converters' blades? A: Yes. There is more blade wear in slitting, perfing and other operations, even with UFGC or PCC.

Q: Why did you convert your premium letterhead? A: Permanence was a factor.

[Question about any changes in rolls. Two panelists said they had made no changes in any rolls, and the third said only a top roll had needed changes.]

Q: What happened at calendering? Answer no. 1: One mill saw no increase in bulk, though another did. Answer no. 2: There was no change in the number of nips made.

Q: Did you see any changes in felt life? Panelist A: We change them every 60-70 days regardless. Panelists B & C: No problem.

Q: Do you get good performance from your retention monitoring systems? Panelist B: Yes, they have excellent performance though they are not as accurate as lab results. Chairman: On all our machines we have automatic monitoring and have closed the loop. We installed it as a research tool but found out it was the best instrument we bought.

Q: Did the paper machine need to be modified? Answer no. 1: No. The converting equipment has to be adapted, though. Answer no. 2: We had two presses; alkaline sheet would run on one but not the other, because the printing machine was out of spec. The sheet often bounces at the folder. ... So we are adding a variable speed puller roll.

Q: If you had to do it over again, what are the main things you would do different? Panelist C: We thought we had a good planning effort, and converted the whole company; but the result may vary according to the pulp used, and other factors that are regional. They may affect the zeta potential.

Panelist B: We'd like to have another mill in the company do it before us. We did a lot of trials and field evaluations, but missed a lot of issues. The more trials you can do, the better. Cover all the grade patterns. We are still working on ash levels, still learning from the charge analysis.

Panelist A: I agree. You have to have some way to track changes and retentions. We didn't do any trials but should have. We're getting there but it's a rough road.

Panelist B: Chlorine dioxide substitution may affect your machine operation.

Chairman: We didn't know what was going on in the pulp mill but should have.

Q: Did you see any change in the dryness off the couch? A: No, though it looks different.