Introduction to papermaking - Sheet Formation Paper
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- čas přidán 6. 07. 2024
- This module introduces the different types of former that can be used to produce paper and explains the use of the different types of rolls used in this area. We also identify and explain the different drainage elements that can be found on a paper machine
Thank you, I was researching about headbox machines for a transaltion and I was very confused about the terminology, with your video I get a lot of answers.
Very exited to see this
0:12 Answering Questions
0:52 Flowboxes
Open Flowbox - Open to Air
Pressurized Flowbox - Pressurized Air - PROBLEM, Mold/Condensation
2:32 Hydrolic Flowbox - Filled With Liquid, eliminating mold potential
3:19 Efflux Ratio - The speed
Drag
Rush
5:45 Rolls
10:43 Paper Machine Configurations
13:30 Drainage Elements
Great Video!!
Hi Steven thank you so much for those infos
İt is too hard to find some information about fourdrinier machine..this information explain the machine very well ..thank you for all
Umit jan
What can you tell me about the Summers modification of the Yankee Paper Machine?
what u can explain for edge crack, edge folding problems ...what is .root cause
Plz make an video for mould plants also rather than wire plant..
It will be helpful to me..
Waiting for your next video
Thanks
do you need cylinder mould? I am supplier for it.
This video very good
Sorry what do so called multifoil shoe module does in a gap former?
Hello author, I'm Xuan, I'm from Vietnam. I majored in pulp and paper in Vietnam, your writing is great, can you send me subtitles for this video? I need it as a reference for my upcoming semester exams. I am really grateful to you so much❤️❤️❤️
there is papermaking major in Vietnam?
good
In very old books the paper pulp fibres aligned in one direction to ensure the shape of the book was stable. I notice by examining books today through the light box that this is not the case, there is no direction. I wonder why? is it that add-on chemicals and treatments assist with this property? Also I wondered whether the effect in olden days was achieved solely with "Drag" as you explained in minute 4? does that align paper pulp fibres in a preferential direction? Finally, there used to be a problem even in 2000 with "flocculation" whereby the fibres jumbled up and it was important to detect this (Valmet suggested this problem to me) with computer vision to stop the machine quickly. Could you explain what causes flocculation?
Hi Daniel, thanks for your question
When those old books were new, I was probably a student reading them!
I am guessing that the alignment of fibres, in the machine direction (MD), (caused by the 'drag' action), was also to maximise the tensile strength of the paper in the machine direction, so it could be pulled through the reel fed printing processes at high speeds. However when that paper is subjected to a moisture change, say an increase as happens in the offset printing process, the fibres, and so the paper will expand significantly in the cross direction, (CD), but not much in the MD. Operating paper manufacture in 'rush' mode will give a more equal distribution of fibres in both the MD and CD. This is what we call a 'square' sheet. An increase in moisture will cause the sheet to expand less in the CD and more equally in both directions. Which is what some printers want.
Many of the people offering on-line measurement can now detect and put a number on the degree of flocculation.
There are a few different causes of flocculation. Here are some examples.
1- Fibre length - the longer the fibres, the more likely they are to entangle and cause flocks. The example I use for my students is spaghetti. Imagine a bucket of long spaghetti. As you stir it, or try to twist a forkful to eat, it will get very tangled and difficult to separate. However if you take that same spaghetti and chop it up in to 5mm pieces, stirring it will be easy.
2- Consistency - The closer fibres are together, the more likely they are to touch, and so to tangle. This is why we reduce consistency to improve formation. In an ideal world we want every fibre to land on the wire at a position, angle, and orientation that is not influenced by any other fibre, and the only way to do that is to keep them apart. How much water to add to keep them apart, has to be balanced against how easy and expensive it will be to remove that water.
3- Fibrillation - Unrefined fibres are like pencils, stiff with a low surface area, Its difficult to make the bend over each other and twist around each other. But one you start refining, you tease out all the fibrils from the surface and these can so very easily become entangled with fibrils from another fibre.
4- Chemistry - This plays a big part in flocculation. All fibres are naturally negatively charged, so like two north poles of a magnet, slightly repel each other. But throw in a very common chemical like aluminium sulphate, and it will floc like crazy. The aluminium ion has a very strong 3+ charge on it. All the negatively charged fibres will be very strongly attracted to it, and so we have a floc! Kymene, which we add to improve wet strength, also has a positive charge, so as a side effect will also cause flocculation.
Flocculation is a double edged sword, it has good and bad points. It makes the formation worse, so that is a bad point, but it also stops stuff falling through the forming sheet, and the wire, so it improves retention and lessons the load on the effluent plant. It can also have a good effect on fines. Fines normally get trapped in the matrix of fibres as they form the sheet. This makes the small pores between fibres even smaller, and so slows down drainage. Adding just a very small amount of these chemicals will make the fines stick to the surface of the fibres and so leave the pore structure more open, and so increase drainage.
Hope this helps?
@@PaperClassroom Thanks very much for your explanation. You provide a very complete and useful explanation. I have only had two superficial experiences with this topic. Before my PhD I also did a voluminous MSc at Swansea University where we had a very strong Finite Element research gravitas (owing to the Civ Eng department where I eventually did my PhD (1988 finished at Oxford University) in computational fluid dynamics). I mention it because for my MSc (1985) I developed finite element solutions to compute deformation gradient tensors which are used to compute Strain Ellipsoids. Such ellipsoids quantitatively measure the alignment of fibers in rheology where laminar mixing is desired not to jumble up the forming machine. Actually I discovered that the computation of deformation gradient tensors from numerical discretization of their differential equations is affected by lack of ellipticity in any weighted residuals method, that in spite of being significantly different in nature to classic parabolic examples of the same problem (convection-diffusion equations), so that some version of "upwinding" (Petrov-Galerkin) is therefore required and a physically correct approximation therefore is challenging to guarantee as I showed in my thesis. Then many years later, 20 or so, I was pioneering a team in Machine Vision (I pioneered Genetic Programming for this purpose). I was detecting objects of large variability and poor definition (objects in infrared) and the guy from Valmet thought I could apply this tech to learn the flocculated state from 2D images from the machine and then build them a "flocculation detector". However, the project never took off although he gave me many of the black and white photos from the machine. With your explanation I now understand why there may be cases of "flocculation" in machines, for flocculation is at times necessary. Now that you have explained "the real problem" I see that it is quite an intricate topic.
is the influent into this rolls the filtered pulp ? I'm a bit confused, sorry
Hi Alyza, I hope I can make this clearer for you.
The 'influent' as you call it is the mixture of fibres and water, (and maybe filler), that we call stock. In the approach flow system, (not shown on the slide), it will have passed through screens and cleaners to remove contamination.
In my diagram, it will be in the small black line diagramme on the left. Some people call this the headbox, others call it the flowbox.
The stock squirts out of this device onto the top of the forming fabric. The forming fabric is moving from left to right. As the fabric travels in this direction, water will drain from the stock and pass through it. So, going from left to right, the ratio of fibre to water is constantly changing. When the stock is first squirted onto the wire, it may be for example, 1% fibre and 99% water.
The sheet will leave the forming fabric somewhere between the couch roll and the drive roll. At this point, the ratio may be 20% fibre and 80% water.
All the items in contact with the underside of the horizontal section of the wire are there to increase the rate of dewatering of the sheet.
The forming fabric is a continuous loop. Once the sheet has been peeled off it, the forming fabric passes round the drive roll and travels right to left. The rolls in contact with the forming fabric in this section are there to control its position and tension.
I hope this helps. Please feel free to ask any more questions
Best wishes,
Steve
Steven Mann , thank you for that Sir
There is something more that I want to learn, can you also teach me about the calculation for designing the whole equipment ?
Can you tell me how about hybrid formers working?
Thank you for your suggestion. I am just working on a series for the pressing section at the moment for my students to prepare for their exam. I will look at Hybrid Formers for you after that
6:20
A solution as you increase speed,to help with drainage, more refining of stock ? an increase of fan pump speed? maintain a higher consistency at headbox ?
Hi William, I have been thinking about your question for a while, I am not sure what you are asking. I hope my answers help.
I think you are asking how to increase drainage because you want to increase machine speed?
The more you refine, the more fibre surface area you will produce and the slower drainage will be
If you just increase fan pump speed, you will increase the weight of your sheet. If you also increase wire speed then you will reduce the sheet weight.
If you go to higher consistency, it will drain quicker, BUT the formation will be poorer.
I hope this helps,
Best wishes
Steve
@@PaperClassroom thank you sir i understand this
How to decrease porosity from paper machnie without adjust compotition of stock?
There are several ways to adjust porosity.
1 - change the refining - the more refined, the lower the porosity
2 - changing the filler content - the more filler the lower the porosity
3 - increasing the shake can have a small effect on porosity
4 - increasing press pressure can reduce porosity
5 - Increasing pressure on the calender can reduce porosity
6 - adding a film former like starch/CMC/PVA particularly at a size press has been used to reduce porosity
Hope this helps
Hello. Am Ronixron from kenya learning as machine operator..fourdrinier kindly help me to understand the machine
6:24
Is the adding of calcium carbonate just to brighten the paper...anyone ?
Hi Jim. The short answer is no! The main reason for adding a filler, (usually chalk or clay), is to make the product cheaper. - You are replacing fibre that can be 500-1000 GBP per tonne with a material that costs about 100 GBP per tonne. But there are other 'added benefits'. Generally filler is brighter than fibre, so by adding chalk will make the sheet brighter. It also makes the sheet smoother. It fills in the valleys between the fibres giving a smoother surface that is better for printing. It also fills in a lot of the pore structure of the sheet, which reduces the porosity of the sheet, which many users want. It improves the appearance, (formation), of the sheet, which is always good. Finally, It is easier to evaporate water from the surface of pigment particles than from the surface and inside of fibres. This means it will reduce the cost of drying. Hope this helps, Steve
@@PaperClassroom thanks very much Steven, i didn't realise there was so many reasons lol.
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:) hi bạn, mình cũng đang tìm hiểu về nhà máy giấy
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