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History of the Forest Products Laboratory

Interview #922: Klungness, John H. (June, 2009)

View all of First Interview Session (April 15, 2008)

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00:14:39 - 00:24:28 Fiber Loading, Project Development

fiber loading, project development; pulping process, new developments, economical; calcium carbonate, filler; better paper, pulp slurry; fiber loading, technological development, Germany, industry adaptation

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But a bigger process that I worked on [called fiber loading] is being [implemented] by a German company now. You know, papermaking hasn't really changed in the last 50, 75 years. If you divide up the paper industry into pulping and papermaking, pulping has [seen] a lot of changes in the type of pulping, how they pulp, and how they recover the [chemicals]. But in papermaking there really hasn't been that many changes. In the papermaking you form a pulp slurry and then you form a web on the paper machine and then you've got to [remove the] water. First you drain it, which is very economical, and [then] it costs a little more to press it mechanically and the most expensive thing is to dry the paper. Now typically, a paper machine will have a hundred steam filled steel drums to dry the paper and that's [epensive]. This process will do several different things. It could reduce the number of drums that are required from about a hundred down to about thirty so that there's a big savings there. Not only do you save energy but you save construction costs and you save on the size of the building that you need for it. Also it uses more filler than fiber and filler only costs [about] 20 percent of what the fiber does. So typically for a thousand ton per day mill, if you can go up one percent in calcium carbonate versus pulp fiber, you'll save a million dollars a year. And fiber loading, you can go up several percentage points higher. So that's the second way you can [save by using] more low-cost raw materials, and the third way is that you can make these fillers---calcium carbonate---more cheaply in this process than the most economical processes that's used today.

And I'll just now back up and tell you a little bit about the process. In the most efficient way for making calcium carbonate for a paper mill is to have a satellite calcium carbonate [plant]. [Such plants] have two tanks typically. [First], they'll ship in a calcium oxide and they'll [add] it into a tank filled with water and they'll call that slacking quicklime and so it goes from calcium oxide then to calcium hydroxide. Then they'll pump that calcium hydroxide into a second tank and add CO2, and that CO2 typically will be captured from stack gas at the paper mill and they'll mix that CO2 and the calcium hydroxide in a water solution [to] form calcium carbonate. And that calcium carbonate is pumped over to the mill and used as a filler. [CO2 is] a very bright chemical---it's got a hundred brightness and [papermakers] like it very much. It is [easier] to de-water, because calcium carbonate does not [hold] water like fiber does. So everybody would like to use more of it. Well we've come up with a process that can be used in the stock [prep] system and [to] create calcium carbonate but you do it in a pressurized refiner.

Now a pressurized refiner is just a mechanical device typically with two common rotating discs under pressure, typically under steam pressure, but you can add calcium hydroxide, step one, and you mix it with the pulp, and step two you put it through a conventional pressurized refiner, which are very common in paper mills. So instead of that we steam, you have CO2 and that creates calcium carbonate in the process itself and the beautiful thing about that is the calcium hydroxide is so attracted to the fiber that it goes within the cell wall and into the lumen and when you mix it with calcium, when you mix it with CO2 in the pressurized refiner, the calcium carbonate is formed partially within the fiber. Now that's very important, you can get to five percentage points of filler in the fiber. Now that filler is not on the outside and that's a very key thing because as you start to add filler to paper, it gets weaker and weaker because the calcium carbonate doesn't bond very well to the fiber and it prevents, it makes a much weaker [paper]. But if you put that within the fiber, you can get those fiber-to-fiber bonds which maintains the paper strength while still having filler in the paper. Another thing is that this de-waters so much better, it de-waters better than a similar conventionally loaded or direct loaded paper at the same filler level, so that you can [use] more.

We've had some indications, and I retired before we were able really to pin it down, but what it looks like is that this displaces some very difficult to remove water. Now for example, if you take a very, very efficient centrifuge and take a pulp slurry and you centrifuge until you can't get anymore water out, this is what they call the fiber saturation point. Now [there is only bound water left. Typically this is at like 71 percent solids. The rest of it is bound water. Now the bound water is divided into two different types. There's the freezing bound water and the non-freezing bound water. The surface area inside of a pulp is 98 percent [inside] tiny pores that are four nanometers or less in diameter and those water molecules are bound chemically to carboxyl groups and hydroxyl groups in the pulp itself and there's so little room for movement for the water, this water will not freeze. And also, [non-freezing bound water] has a higher specific heat. You can't drain it out, you can't really press it out very well because it's so tightly bound inside the fiber and also it takes more [energy] to dry it.

So you've got at least fifteen percent of the water that is very, very difficult to remove. There's methods for measuring freezing and non-freezing water and the fiber loaded pulps, these experiments have to be repeated, but we have indication that the calcium hydroxide, because of its chemical [charges and] structure, is very attracted to the carboxyl groups and the OH groups inside the fiber and displace that water. [The calcium hydroxide forms bonds] with the carboxyl groups and hydroxyl groups inside the fiber. And that makes the fiber much easier to drain, much easier to press, and much easier to dry, so you have a tremendous savings in energy. This would be a real fundamental change in papermaking and the equipment is being manufactured by [the] Voith company in Germany, and should be installed by about June 1, [2008], and if that is successful, even partially successful, if that meets even part of what our expectations are, this will surely be adopted by mills worldwide [in some form] and will be a big thing for the Laboratory.

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