On Thu, 11 Nov 2010 18:17:16 -0500, "Barry" wrote:

But if you have ever worked with a Fourdriner machine that
is not controlled well, i.e. the thickness varies with time due to any
number of variables,

I have. That and a year's worth of studying paper process chemistry
for precision (sic) measurement of K and Kappa.

When it gets down to what you describe as "not controlled well" that
is more the definition of a Paper Mill that is destined for bankruptcy
before the end of one week - if not a weekend. I've seen the
production floor flood with product when the process encounters a
bottle neck. The production pipeline is enormous with a lot of
intertia.

Measuring a number of sheets achieves sufficient accuracy.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Thu, 11 Nov 2010 18:17:16 -0500, "Barry" wrote:

But if you have ever worked with a Fourdriner machine that
is not controlled well, i.e. the thickness varies with time due to any
number of variables,

I have. That and a year's worth of studying paper process chemistry
for precision (sic) measurement of K and Kappa.

It has been about 30 years ago, but I remember that while Kappa is
related to the amount of lignin remaining in the pulp after cooking,
every wet end process had its own peculiar measurement. I worked on the
online measurement of Kappa for several solvent pulping processes that
were to produce dissolving pulp for Eastman's cellulose ester process.
Once the vendor that supplied our pulp got wind that we were researching
solvent pulping, they quickly dropped their price and raised their
quality enough that we halted work on our own pulping processes. One
process we were considering involved the use of supercritical CO2. We
never got beyond early pilot plant work on this.

I fully understand the {sic} in your statement.

When it gets down to what you describe as "not controlled well" that
is more the definition of a Paper Mill that is destined for bankruptcy
before the end of one week - if not a weekend. I've seen the
production floor flood with product when the process encounters a
bottle neck. The production pipeline is enormous with a lot of
intertia.

I have toured quite a few paper mills over the years with both Kraft and
caustic pulping. I never really got to see one of the large continuous
digesters though. We had a small caustic plant that used hardwoods in
town with us. The odors were interesting - mercaptans by them and the
occasional butyric acid spill by us.

I always wonder how long the cellulose acetate business will last. While
cigarette smoking is declining in the US, increasing demand from China
seems to more than make up for the loss.

Going back to the original TDR discussion, probably the most interesting
use I ever put one through was in diagnosing thermocouple problems in our
coal gasifier. I saw that the platinum-rhodium thermocouples had water
in them. We finally got a metallurgist to do an "autopsy" on one of the
thermocouples pulled out during a shutdown. When we broke open the
thermocouple, water ran out. We saw a buildup of salts from the
Saureisen cement at exactly the place that I predicted. Water was
diffusing in through a silicon carbide protection tube and an Inconel
sheath.
Of course the gasifier operated at high temperature and pressure. A
Nastran simulation of the thermowell showed that the temperature at that
point was low enough for condensation to occur. Some extra insulation on
the external flange solved that problem!

73, Barry WA4VZQ

How the heck did we get off topic this far? :-)

On 11/11/2010 8:01 PM, Barry wrote:
"Richard wrote in message
snip

73, Barry WA4VZQ

How the heck did we get off topic this far? :-)



Keep it up. It's interesting.

tom
K0TAR

On Thu, 11 Nov 2010 20:07:31 -0600, tom wrote:

On 11/11/2010 8:01 PM, Barry wrote:
"Richard wrote in message
snip

73, Barry WA4VZQ

How the heck did we get off topic this far? :-)



Keep it up. It's interesting.

If that means the lore of paper processing, I was peripherally
involved in trying to characterize Black Liquor
(http://en.wikipedia.org/wiki/Black_liquor). Gladly I was at the
extreme periphery (I am sure my sense of smell was debilitated in
those years).

However, returning to things RF, I also was tasked with calibrating a
wood moisture meter. It used an HF RF source as part of a Z meter
were Z was correlated to moisture content. The probe was a fixed ring
surrounding point probes much like a Kelvin Bridge. It has always
seemed paradoxical that steam is used to dry wood.

Now, finding calibrated wood was no easy task. And if we found it, we
would have to first validate it (sort of a circular form of Sysphus'
task). My best guess at that work set to us was that we gun-decked
it.

It was some years later that that task came around again when I was
measuring K and Kappa as I averred. Here came the requirment for
"Bone Dry" paper. Try as you might to dry paper bone dry (absolutely
no water content), that as soon as it comes out of the oven it is
almost back up to several percent water content (15% to 20% would be
the end point).

Ironies compound in that I now live in a community where 100 years ago
our cedar wood mills produced nearly a Billion shingles in a year.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
If that means the lore of paper processing, I was peripherally
involved in trying to characterize Black Liquor
(http://en.wikipedia.org/wiki/Black_liquor). Gladly I was at the
extreme periphery (I am sure my sense of smell was debilitated in
those years).

I once had to check on an instrument I had designed that was used in our
cellulose acetate butyrate esterification area. (Cellulose Acetate
Butyrate is used to make Xelite and Craftsman tool handles.) Acetic
anhydride and butyric acid were used for esterification. For those not
familiar with the odor, think of a mixture of rancid butter, vomit, and
the contents of a cat's week old litter box. Readers who watched the
last season of Whale Wars on TV saw it being used against the Japanese
whaling ship and its cargo.

Since I was unfamiliar with the building, one of my technicians who had
installed the instrument went with me. We stepped off the elevator and
walked into the processing area. What had been an extremely offensive
odor in the elevator suddenly hit me like a ton of bricks. I couldn't
see as my eyes were tearing badly, and it hurt to breathe. My tech told
me to stand still for a moment or two and things would get better.
Within thirty seconds to a minute, my eyes cleared up, my sinuses opened
up, and my breathing became normal again. I could no longer smell the
mixed acids at all. We checked the calibration of the instrument and
talked to the operators about their experiences in using it.

We then left the building and walked the half mile back to the research
labs. Eastman was still using dimethyl-terephthalate in their polyester
production at that time, and as I waked past the DMT distillation area, I
could easily smell the DMT and the Dowtherm heat transfer fluid. My
technician explained that as soon as we returned to the research complex,
we should drop by our group leader's office to let him know where we had
been. We had just opened his door when he said that he could smell where
we had been and to get the heck out of his office! Of course, we
couldn't smell our strong odor at all.

Fortunately my technician had warned me to wear old clothes, old shoes,
and an old belt for when I came home that evening, my wife made me strip
in the foyer and go stright to the shower. She washed the clothes, but
the shoes and belt had to hang outside for a week. It seems that leather
is particularly bad about absorbing the odor.

However, returning to things RF, I also was tasked with calibrating a
wood moisture meter. It used an HF RF source as part of a Z meter
were Z was correlated to moisture content. The probe was a fixed ring
surrounding point probes much like a Kelvin Bridge. It has always
seemed paradoxical that steam is used to dry wood.

We used microwave absorption to measure moisture in cellulose acetate
filter tow (cigarette filters are made from this). Operators would cut
off a length of tow and stuff a weighed amount in a short X-band
waveguide. Attenuation was proportional to moisture.

Now, finding calibrated wood was no easy task. And if we found it, we
would have to first validate it (sort of a circular form of Sysphus'
task). My best guess at that work set to us was that we gun-decked
it.

Calibration of the microwave quipment was checked by weekly sending
samples to be tested by nuclear magnetic resonance. We also used samples
kept in jars over certain salt solutions that maintaned a constant
relative humidity in the jar. See
http://www.conservationphysics.org/satslt/satsalt.php for some typical
solutions. To bring a little electronics into this, the same principle
is used in electrolytic capacitors where glycols, sorbitol, and various
salts are used in the electrolyte to insure that it remains moist.
Electrolytic capacitors are about the only electronic components that are
harmed by an exceptionally dry environment.

It was some years later that that task came around again when I was
measuring K and Kappa as I averred. Here came the requirment for
"Bone Dry" paper. Try as you might to dry paper bone dry (absolutely
no water content), that as soon as it comes out of the oven it is
almost back up to several percent water content (15% to 20% would be
the end point).

You can get close to "bone dry" in a sealed container containing zeolite
molecular sieves baked at 600 C. But as soon as the container is opened,
moisture rushes in from the surround air. We would use glove boxes
pressurized slightly with nitrogen obtained from a liquid nitrogen source
when we needed a really low humidity environment.

Ironies compound in that I now live in a community where 100 years ago
our cedar wood mills produced nearly a Billion shingles in a year.

73's
Richard Clark, KB7QHC

I always enjoyed visiting the University of Washington where Eastman was
on the industrial advisory board of the Center for Process Analytical
Chemistry. I never order salmon from any restaurant in the southeast
after eating the wonderful, fresh-caught salmon you have there!

73, Barry WA4VZQ

P.S. You mentioned black liquor from the Kraft process. I once visited
the Glidden-Durkee plant in Jacksonville, FL. They originally produced
turpentine from pine stumps, but now they start with tall oil extracted
from black liquor. It is hard to believe that essential oils, perfume
stock, and flavorings are all derived from turpentine.