How to Control Ash Content On paper machine

Accurate control of ash content was the target when running out recycle paper stock preparation. When checking out total Consistency Transmitter at the outlet of DIP Chess  before the last disk filter in the line. Ash Content contamination data trends are enough, But for stability on data trend will better.  If ash content is outside the acceptable range, we can either adjust the settings in the screw press or adjust the mix of raw materials.

For some operators, they are really need to telling with early warnings of ash content variation in the stock entering the paper machine in order to attain 11% ash content. Because about 80% of production at the mill is Standard Newsprint. The other 20% is Improved Newsprint. All the raw material for production is recovered fiber, more specifically household wastepaper containing both newsprint and magazines.

Standard Newsprint produced at the mill has a brightness of 59% ISO, while the Improved Newsprint has a brightness of 68% ISO. Both grades have a targeted ash content of 11- 14%. When producing Improved Newsprint, household wastepaper containing more newsprint is added to the stock to counteract the high ash content of the household wastepaper containing magazines.

According to operators monitor the ash content trend to keep it between 15 and 16%. Depending on the trend, they take corrective actions. After the screw press, the targeted value is between 12 and 13 %. If we see that ash content is moving outside the acceptable range, we can either adjust the settings in the screw press or adjust the mix of newsprint and magazines in the mixing tank, Later on, we can intend to put the automatic control.

If the ash content of the pulping chest entering the machine is around 11 to 12% and is stable enough, operators can fine-tune the content to the specified level with the addition of calcium carbonate on the machine.

Stable ash content before the paper machine promotes stable retention and improves a number of quality factors such as opacity, caliper, strength, brightness and light scattering. 

Fiber, Filler and Fines

Fiber

In the way of paper manufacture even is pulp or recycle paper used fiber. fiber or fibre are the slender, thread-like cellulose structures that forms the main part of tree trunk and from separated and suitably treated, cohere to form a sheet of paper.

Softwood Fiber

Internal Structure

Fiber

study about fiber is closely related to the filler in papers and a variety of terms associated with the word. Below are some words related to fiber

• Fiber cut            -----> A fiber cut is a short, straight cut located on the edge of the web, caused   by a fiber embedded in the web of paper
• Fiber Coarseness -----> weight/unit lenght of fiber
• Fiber debris        -----> Pieces of material which has been separated from the main body of the fiber
• Fiber flock         -----> fiber that have agglomerated as a result of poor formation
• Fiber orientation-----> Refers to the alignment of the fibers in the sheet
• Fiberboard        -----> Board made from defibrated wood chips, used as a building board
• Fibrillation        -----> A structural change occurring in the wall of chemical fiber during beating
• Fibrils              -----> String-like element that are loosened from the paper fiber during the beating process.They aid in the bonding processes when the paper is being manufactured
• Fiber axis Ratio   -----> Ratio of fiber width to fiber thickness

Filler

Filler reduce strength properties of paper. Most of filler are cheaper than fibers and so filler are added to reduce the overall cost of paper.

Any inorganic substance added to the pulp during manufacturing of paper.  Filler are also used to improve optical and other print-ability related properties. Filler improve opacity and brightness.  

Test	Increased	Decreased
Brightness	+	-
Bursting Strength	-	-
Caliper	-	+
Dimensional Stability	+	-
Folding Endurance	-	+
Ink absorbency (Uncoated paper)	Gets more uniform	Gets less uniform
Internal Bond Strength	-	+
Opacity	+	-
Picking Resistance	-	+
Rattle	-	+
Smoothness	+	-
Stiffness	-	+
Tearing Resistance	-	+
Tensile Strength	-	+

Fines

Small particles fiber defined arbitrarily by classification. 

Retention

The amount of filler or other material which remain in the finished paper expressed as a percentage that added to the furnish before sheet formation. Retention can occur by various mechanisms. The simplest of these is mechanical sieving by the forming fabric. Once a fiber mat begins to form, the mat itself usually can act as a much more effective and finer sieve than the forming fabric. But even then, particles less than about 10 micrometers in size are not effectively retained by sieving. Rather, retention of fine particles requires the action of colloidal forces, including polymeric bridging or a charged patch mechanism. Retention aid chemicals can be effective either by attaching fine particles to fiber fines or fibers or by agglomerating them so that they can be sieved more effectively.

Retention Aid

Chemical additives, especially high molecular weight copolymers of acrylamide, designed to increase the retention efficiency of fine materials during paper formation.

First Pass Retention

First-pass retention gives a practical indication of the efficiency by which fine materials are retained in a web of paper as it is being formed. First-pass retention values can be calculated from just two consistency measurements, the headbox consistency, and the white water consistency. There is a very wide diversity of first-pass retention on different paper machines, from less than 50% to almost 100%. The key rules that papermakers follow are that (a) first-pass retention should have a steady value, and (b) that value should be high enough to avoid operational problems or an excessively two-sided sheet. Some operational problems that can be caused by low values of first-pass retention.

How to check silo overflow to calculate the fiber loss

First you have to prepare some data for: 

How to check silo overflow to calculate the fiber loss
The data need to be taken:
1. level (%)
2. flow rate in ml / (1 / 1000) seconds on the conversion to liters / sec
3. data consistency (%)
4. Data ash content (%)
The data above is required to calculate the fiber loss (kg / day), ash loss / day

Supporting data for the parameters that need to be made is
1. pH
2 temperature (oC)

CHECK	25-26 Feb 11
	pagi	siang
Level (%)	94,5	94,5
flow rate (Liter/sec)	2.70	0.97
consistency (%)	0,25	0,27
ash (%)	34.13	36.00
	583	226
fiber loss(Kg/day)	384	145
ash loss(Kg/day)	199	81
pH	7.04	6.98
Temp	44	44

calculation

a. Calculate the fiber loss (kg / day)

Fiber loss = (Flow Rate x 60 x 1440 x% consistency) - ash loss

b. Calculate ash loss (kg / day)

Ash's loss = (Flow Rate x 60 x 1440 x% consistency) x ash content (%)

Wet End

Wet Break is a paper breaks at the wet end (on wire or press) during papermaking process.Wet End

is a first part of the paper machine consisting of wire part and press part.

Wet End Chemical Additives

Chemical additives added with the stock at the wet end. Following are some of the wet end additives.

Additives	Application
Acids and bases	To control pH
Alum	Control pH, Improves Retention, Attach additives on fibers , Part of Rosin-alum sizing
Coloring chemical (dyes & pigments)	Impart desired color
Defoamers	Kill/control foam to improve drainage & retention
Drainage Aids	Improve drainage (water removal) at wire/press.
Dry Strength Additives (Starches, Gum)	Improves burst, tensile, pick resistance etc.
Fiber Deflocculants	Reduce fiber flocculation and  thus improve formation
Filler (clay, CaCO3, TiO2 etc.)	Improve opacity, printing, surface smoothness etc.
Optical Brighteners	Improve optical brightness
Pitch Control	Prevent deposition & accumulation of pitch
Retention Aids	Improves retention of fibers and fillers
Sizing Chemical ( rosin,  ASA etc.)	To control liquid (water, ink etc.) penetration
Slimicides	Control slime growth and other organisms
Specialty Chemicals	Corrosion Inhibitors, Flame Proofing, Anti-tarnish
Wet Strength Resin	To impart wet strength to such papers as coffee filter

Wire and felt on paper machine

 

In case wire also referred as wire side and top side. The side which is in contact with the paper machine wire during manufacturing is called the wire side. The other side is top side. Before a thin layer of fibers deposit on machine wire, fines and fillers drain out hence wire side has less fines and fillers compared to top side. Certain properties such as smoothness, texture and ink absorbency differ between wire and felt side and it is customary to measure these properties on both sides. This difference of properties on two sides of paper is known as two-sidedness. Highly filled or loaded or paper made from short fiber pulp will show higher two-sidedness.

 

In case of paper to be printed on one side only, best results are obtained by printing on felt side. Postage stamps are printed on wire side and then gummed on felt side, where the smoothness is helpful for attaining an even application.

 

Wire side and top side described above are in reference to single ply paper. In case of multi-ply paper/board, every ply will have wire side and top side. The top side of top most layer will be top side and wire side of bottom most layer is wire side of multi-ply board. Different type of fibers, fillers and chemicals are used in different layers for techno-economical reasons.industrial & scientific

 

The standards procedure is described in TAPPI T 455 

Smoothness

 Smoothness is concerned with the surface contour of paper. It is the flatness of the surface under testing conditions which considers roughness, levelness, and compressibility. In most of the uses of paper, the character of the surface is of great importance. It is most important parameter for printer. It is common to say that paper has a "smooth" or a "rough" texture. The terms "finish" and "pattern" are frequently used in describing the contour or appearance of paper surfaces. Smoothness is important for writing, where it affects the ease of travel of the pen over the paper surface. Finish is important in bag paper as it is related to the tendency of the bag to slide when stacked. Smoothness of the paper will often determine whether or not it can be successfully printed. Smoothness also gives eye appeal as a rough paper is unattractive.

 

Smoothness (Bekk Method): This test is an indirect measure of paper smoothness when it is under moderate pressure( 100 kPa). The standards test procedure is described in TAPPI T 479.

 

Roughness (Sheffield Method): This test is an indirect measure of paper smoothness or roughness. It is a measurement of air flow between the specimen (backed by flat glass on the bottom side) and two pressurized, concentric annular lands that are impressed in to the sample from top. The standards test procedure is described in TAPPI T 538.

Roughness (Print-surf Method): Very similar to Sheffield methods. The standards test procedure is described in TAPPI T 555.

Typical Smoothness Values
Grade	Parker Print Surf (μm)	Bendtsen (mls/min)
Newsprint (40 - 49g/m2)	2.6-4.5	80-140
Stationery (45-135g/m2)	0.8-2.6	50-300
Business Papers (80g/m2)		100-300
Test Liner (186 g/m2)		1750

Temperature and Humidity: Conditioning of Paper

 

As explained above it is important to control the moisture content of paper and keep it stable during converting operation. To keep moisture content constant, it is important that paper is conditioned. Conditioning of paper is also of important in many printing and converting operations. In addition to the effect of moisture content on physical properties, it also determines the build up of static of the paper sheet subjected to pressure and to friction. The tendency for paper to develop static becomes greater with increasing dryness. Cellulose fibers are hygroscopic i.e. they are capable of absorbing water from the surrounding atmosphere. The amount of absorbed water depends on the humidity and the temperature of the air in contact with the paper. Hence, changes in temperature and humidity, even slight changes, can often affect the test results. 

So, it is necessary to maintain standard conditions of humidity and temperature for conditioning.