Measuring Moisture

[Fred Floggle]

moisture meters again

Hi Crispen ,
Any process equipment that "tells lies" is worse than useless . I'll bore you with a little tale of a GLT in croatia where the TM55's were untouched for years - maybe you already know that the old series TM's needed a lit more love than the 710's , and are a bit more affected by ambient conditions . This moisture meter was only accurate around 13% , "OK you say , thats a reasonable exit moisture" , but at anything either side of 13% the thing was all over the place , i could get it better by using CALVAL , but the SPAN was about 4 , if you can't achieve reasonable results with a SPAN around 1 , something is wrong . An overhaul , with new lamp and filter wheel motor makes all the difference . Temperature control was a problem on this machine for two reasons , the customer hadn't made any attempt to segregate power from signal cables , with the consequence that temperatures "changed" about 10C when the drives were started . Steam valves were also a pickle with sticky stems . The whole lot was given the treatment , and the machine run up again .
Just like a new one !! SD's during protocol around 0.2% , and packing temp SD less than 2C - the machine would start up with less than a C48 loose packed of waste that was on the dry side and re-run , not bad for an 7500kg/hr dryer .

If your moisture meters and flow control are naff , you won't be able to improve things much , you'll have to sort them out first . Saying that , if you can get your conditioning sorted..........

 

[arc]

Co-Flow / Counter Flow

Dear Fred,

Can’t hold back from you, so here I go again. I hope you don’t break your monitor in front of you.

You asked about heat systems for the dryer - to keep it simple to start with , it doesn't really matter how you heat the shell (though water provides a better gradient) , what does matter is accuracy of temperature measurement and control . In any case if the process calls for a temperature then it is imperitive that the equipment maintains it .

Well with water heated the Initial Phase may be better and less dry tobacco may come out, just a guess as with steam having low temperature, or low initial starting temperature to start with would be a tough thing to achieve.

Still do not know what is the best method to measure the inner wall temperature of the dryer!!

I also watched a BAT production director who thought you could reverse the direction of air through a centrifugal blower by changing the direction of fan rotation - but he proudly told me about his engineering degree.

Just wanted to know what type dryer should be used and when, i.e. with respect to co-flow and counter flow types and what are their specific advantages, as both exist in this industry. Sorry for asking this basic question as I come from a different background.

Also With spray, and without spray. What is the deciding factors in choosing one type from another.

How important is the inclination of the dryer? And why speed control is not applied to cylinder rotation, may be to hasten and slow the flow, to increase or reduce the holding time inside the dryer.

Sometimes I get confused about Tobacco process/passion, first they add water and they take pains to remove it (Just a joke). First they expand it and then they dry it and make it fluffy, I would love to know which nation discovered Tobacco smoking as a human habit, and then I begin to wonder where and who all pushed it to a technological level, and yet CIGAR is more expensive than cigarette and considered more noble, all done by hand rolling and packing I guess, no shouting allowed here if I am wrong. ……... am I?

---------------
Arc

 

[Fred Floggle]

the mystery will remain

A water heated dryer doesn't run the way you think - it is a pressurized system with heating and cooling facilities - water flow is so much and routed in such a manner that it is not necessary to measure inner wall temperature .
Who said that speed control is not applied to cylinder rotation ?
And as for con/counterflow air , this is , I am afraid going to remain a mystery as Richard and I have to work - suffice to say that the tobacco does not behave as you expect in the cylinder .
The cylinder inclination is of course important , as are cylinder mouth paddles , pins where used , type , spacing and length .

I'm going to let Richard give you the benefit of his rag drying experience if he sees prudent - after all , if you have too much , you will go out and neither of us will have any work!
( I still challenge you to get the huff to go backward through a centrigugal blower by reversing the motor )
Probably the same guy who told me that there was a new maker developed that would accept whole leaf straight in the hopper...........

 

[arc]

B R I T N E Y S P E A R S

Dear Fred

NEWS

Pop princes Britney Spears is set to quit pop music to become a forensic scientist. The star said she may swap her singing career for student life and enrolling at a university.

Sure she can, so can I sing now? !!!

NEWS


Keira Knightly revealed that she dreams of being a brick layer.

Sure she too can some day !!

Then why can I not learn TOBACCO PROCESSING from Fred & Richard?

Well I know dear Fred, that each trade has a lot of intricacies and I do not want to infringe on them, at least I enjoyed talking to two experts in this field and I am sure that many more would have read our discussions and would have realized that it is best to go to a correct doctor that to spend time with quacks like me to solve their problems. I hope and wish both of you a very good and exciting business this year, even though I would want the world to stop smoking.
------------------------------
Regards
Arc

 

[Richard Christian]

Re: Student of.. Loads Of Money

I fully concur with Fred.

The volatiles, sugars, tars etc are negligable in weight losses on Cut Lamina, stem drying.. (you also forgot about dust removal in the dryer extraction).

Loads of Money.. Tobacco is a big money industry. The use of PLC and high quality devices/equipment costs loads of money.. but with the correct application/selection and programming.. saves even more.

Some of the questions you have been asking are actually directly related to PLC's and programming. You talk about which type of dryers.. how moisture is measured.. wet weight to dry weight calcs..steam, condensate etc. All of this is just physics and a few laws made up by some blokes with silly names. NOW the exciting bit is HOW you write a PLC programme to use and measure all this stuff and then make it control.

Most often what you are really asking is "how" is this done? Well I can't tell you that because that's why some of us get paid a Load of Money

Some basic information:
All dryers should and can be controlled within 1 Celsius: This is good PID programming, use of predictors, measuring loads etc
Dryers are calculated on their Duty, (evaporative load), undersized or oversized dryers lose control ability.
Rule of thumb: assuming all else is correct.. 10 celsius = 1 % moisture change (which is large)
What you put in.. is what you get out. (my favourite)

You pay for what you get. As Fred says.. there are copies (identical), but they can't get them to work properly or the same, this comes down to the control philosophy.. and the "intuition" of the commissioning engineer. For example.. a dryer to me is not just a dryer.. it is ultimately unique, every identical one is different !!
I watch and learn the characteristics of a dryer for days.. only after this I start the tuning.

For jamil:
Dwell times: times for an annualar dryer are normally between 3 and 7 minutes, this is a function of dryer surface area, evaporative load and achievable temperature (also regarding tobacco temp).. this is down to design and space. HXD's (High Expansion Dryers) which are a completely different kettle of fish for Cut Rag.. you are talking about seconds!

Air direction in a dryer will get you different control characteristisc (annular).
You don't need to measure humidity in a dryer.. you know it already!!
You have the airflow, you have the cylinder temp, you have the evaporative load!!.. thus you have all the information.

As a final clue to good Cut Rag drying & control.. we change the evaporative load of the air with water and actually add moisture by condensation to the incoming tobacco

I forgot what I started replying to or writing about !.. I get carried away.. did I mention PLC enough times to not make it a tobacco discussion??.. anyway it can't be done without a PLC.

regards

 

[Richard Christian]

HTHW

High Temperature Hot Water Dryers

The volumetric flow of water through a HTHW dryer is so huge that everything in the system is the same temperature as what you put in (without being pedantic), this is what makes the response and control of these dryers so good. You actually have two "tanks" of water, hot & cold and a three way valve (plus some others)that mixes proportionally, lovely system although somewhat dangerous if played with incorrectly (killer air).

Cylinder Control..
Yes this is used, mainly on run out. Otherwise reverse the air direction !!!.. now you are starting to learn how minimum off spec tobacco is achieved

Richard

p.s asking the right questions sometimes gets you part of the right reply..

 

[Richard Christian]

A lot of hot air

Fred and I can give you enough hot air

What direction it is going in.. well that's a secret.
There maybe other people that read these notes.. and there are some that I wouldn't give the time of day to because they want everything free even after you have slogged your guts out for 18 hours a day on their site, give you **** accomodation and then won't sign protocol... then .. believe it or not, want you to come back and put things the way you advised in the first place !!!
I would love to name names like Fred did.. I probably know who you are talking about (or at least there must be dozens the same).

.. but if you are genuine and ask the right questions and are in the right ball park to start with.. I'll help anyway I can.

I got some really good help from here with my ProTool simulation that helped me enhance what I do.. but it didn't take work away from those that do it for a living.

Anyway.. think about it.. what difference does it make what direction air is going ??.. it's physics ! Apply the physics.. then ask some questions.

regards
Richard

 

[Richard Christian]

Hannibal

Fred

I met Hannibal Lecter once,
I asked him if he really did French kiss you, I never got an answer from him, he was speechless.

 

[Richard Christian]

High SD's Run In Run Out

Chrispen,

I am a process developer for a tobacco processing company and one of the things that was also troubling me was reducing moisture SDs. We have tried a number of options and it seems the best that we achieved was an SD of 0.36 and bad quality at startup and torwards the end seems unavoidable.

0.36 is not a bad SD, depends upon the start and finish point of measurement.
You should be able to hit target within 3 minutes of start up (normally I quote dryer dwell time). I am probably contracted to a competitor so I am limited to what I may say. Good use of the PLC programme and control of the parameters will solve a lot. Can you tell me who you are (what company) ?. Specifically you need to look at the areas of run in, run out PLC control and how you handle various parameters in said code. You should be able to get ramp up.. hit flat line..fast down line from the run out.

What dryer are you using, what flowrate?

regards
Richard

 

[Fred Floggle]

Hi Richard,

Chris is running a leaf and strip redryer - and what you say is correct . Allow the dwell time for product to get on spec . There are some tricks we can use , by timing tobacco through the machine , we can initiate the ordering process and "load" the orderer before product gets there . We are always stuck between a rock and a hardplace , until the machine is full , there is nothing to stop air bypassing the carpet , so the leading edge is overdry , and the following couple of meters doesn't get dried . You are also challenged by the fact that the product coming off the threshing line doesn't get stabilized for at least 15-20 mins - threshing line guys note well !! generally air in a threshing line is closed circuit , only bleeding off enough for dust say 10% , when the line is started , it takes some time for the humidity and temperature in the clasification air to rise and stabilise , hence the product is dry and cold to start with - of course this doesn't thresh well , and dries even worse .
For some time I have thought about humidity and temperature control in clasification air - simple steam injection at the first stage clasifiers would be enough to keep the air temperature and humidity constant - a kind of "condition while you thresh" technology .
You can't believe the attitude of line engineers when it comes to conditioning and threshing - near enough is good enough , and they expect the dryer to put it all back together .
I have seen some half baked "automatic conditioning cylinders" and the naivity cannot been believed . It is an art to condition and dry , and I have offered proper proven protocolled systems ( Freds PPP technology) costing relatively speaking nothing , and these so called "engineers" smile and say that they can do it themselves - come back a season later , and all the junk is in a cardboard box , PTFE tape hanging forlornly from the ends of the pipes, tobacco is still coming out like cornflakes .

I digressed (whats new?) whilst I don't like it , there is a bit to be said for an autofeeder/gfp/checkweigher in front of the LRD - obviously degradation is a concern , but the benefits of stable flow outweigh the downside in degradation .
Laughingly , I have recently worked on a line where the were two weighers - both lovely ramseys , both trashed by the customer who thought they could hold a circus on them , one with the frame bent because conveyors had been hung off it (I don't like to bolt even a metering tube to a weigher) , the customer wanted me to use the second weigher located just in front of the weigher as the primary feed control , with the second weigher handling dry leaf "slaving" . I asked him how I was supposed to send the setpoint to the first weigher , how to calculate dust and stem , moisture gain etc . He then said to just use the second weigher , I asked him what the scenario would be if for example the tables were feeding 6000kg/hr and the second weighcon was only set for 4000kg/hr ? where would the tobacco go ? to my knowledge , weighcons don't have pockets - just a blank look was the response - he then went on to try and reverse the airflow by through a cylinder , by reversing the direction of the fan motor . Thankfully this guy is retiring , hopefully where there is no machinery for him to b**ls up .
It gets my back up when you realise what his salary was ( around USD 65000) , yet still people try to copy our work , the same factory wanted me to automate the stem line while I was there , guess what they offered ? USD 1500 for all of the software , stem dryer , screw dryers , dust , fans and conveyors.

" How are we supposed to soar like eagles when we are surrounded by turkeys?"

"If you are twice as good as you think you are , you'll nearly be as good as me "

Hanibal - watch out .

 

[chrispen]

Fred

If you need an apprentice, please consider me, I have all the passion needed in the tobacco industry . Or how about you and Richard starting a tobacco processing school because you seem to have gathered a lot over the years and dont allow the tricks of the trade to die with you. I really appreciate the way you share information thanks guys.

Chris

 

[arc]

OFF FOR THE WEEK END

[font color="blue"] A man went to visit a friend and was amazed to find him playing chess with his dog.
He watched the game in astonishment for a while. [/font]


[font color="red"] “I can hardly believe my eyes!!” he exclaimed.
That’s the smartest dog I’ve ever seen,.” [/font]

[font color="green"] “Nah, he is not so smart,” the friend replied.
“I’ve beaten him 3 games out of 5.” [/font]

Well Fred, Richard, have a good weekend; will be back soon, needs some rest now, and will learn some more tricks on Tobacco soon to be back for the next game.

 

[arc]

Re: OFF FOR THE WEEK END

A man went to visit a friend and was amazed to find him playing chess with his dog.
He watched the game in astonishment for a while.


“I can hardly believe my eyes!!” he exclaimed.
That’s the smartest dog I’ve ever seen,.”

“Nah, he is not so smart,” the friend replied.
“I’ve beaten him 3 games out of 5.

Well Fred, Richard, have a good weekend; will be back soon, needs some rest now, and will learn some more tricks on Tobacco soon to be back for the next game.

 

[bungykhb]

Hi Fred
We are building a "new" SDS line (out of old second hand equipment.) It is an in-house project. I have been given the task to R&D on how to connect the TM710 through Profibus with a S7 PLC. I'm new in this field, but have some (not much)experience in S7, profibus and the TM710. Through experience I have learned that it is better (and quicker)(and cheaper) to learn from the experts, than to try and figure it out by your self.

Could you please point me to some-one that can help me with the basics on where to start and what to look out for. If you could, I would greatly appreciate it.

Regards

Heinrich Botha