Acknowledgements

I would like to thank the Pulp and Paper Centre director James Olson for proposing me this very interesting research program and for helping me in this project with his advices and experience.

I would also like to thank my supervisor Pirooz Darabi and his colleague George Soong for being always available to help me when I had to run trials and for giving me such precious advices.

I wish also to acknowledge all students and staff of the pulp and paper centre at UBC for their advices, their work ethic and encouragement namely Mark Martinez, Chrissy Saville, Dmitri Gorski, Pattira Pattara.

More over, it was very appreciable to have office mates like Francisco, Frank and Ehsan. My deepest thanks to these guys.

Contents

Introduction..............................................................................................................................4

1) General..............................................................................................................................5

a. The UBC Pulp and Paper Centre................................................................................5

i. Refining facility.......................................................................................................................5

ii. Testing facilities......................................................................................................................5

FQA picture............................................................................................................................................5

b. Paper making process...................................................................................................5

i. Different types of pulp............................................................................................................5

ii. Refining...................................................................................................................................6

iii. Making of handsheets........................................................................................................7

iv. Refining theories.................................................................................................................8

c. Presentation of my project.............................................................................................8

i. Scope of the study..................................................................................................................8

ii. Objectives of the research......................................................................................................9

iii. Excepted results.................................................................................................................9

2) Research program...................................................................................................9

a. Presentation of the trials.............................................................................................9

i. Methodology and trials matrix...............................................................................................9

ii. First refining session.............................................................................................................10

iii. New project scope............................................................................................................11

b. Results and interpretation........................................................................................11

i. Fiber length..........................................................................................................................11

ii. Freeness...............................................................................................................................12

iii. Tear and tensile................................................................................................................12

c. Conclusion...........................................................................................................................13

i. Technical point of view.........................................................................................................13

ii. Personal point of view..........................................................................................................14

3) Cultural aspect of this MSI............................................................................14

a. Discovery of a new culture........................................................................................14

b. A different way to work..............................................................................................14

Introduction

I am currently student in last year of engineering school (ICAM Toulouse, France). As a part of my scholar program I have to discover the research universe during 4 months.

This report deals about the research program I did in Pulp and Paper Centre of University of British Columbia (Vancouver) from September 2011 to December 2011. I have chosen this research program for several reasons. First of all, I wanted to discover a new industry. I have ever worked in aeronautic industry, and I am apprentice in hydropower industry so this research program permitted me to discover paper industry which was unknown for me. The second reason was my attraction for Canadian culture and my desire to make some progress in English language.

In the first part, I am going to present the research program I have made at UBC Pulp and Paper Centre describing the PPC facilities, and the refining principle and the most used refining theories. The second part of this report deals with the work I have made during 4 months. The experiments, the interpretations and the conclusion of my research program. To finish I will give you my point of view about the Canadian culture and more particularly the Vancouverian.

1)General

a. The UBC Pulp and Paper Centre

i. Refining facility

The Low Consistency (LC) refining facility of PPC consists in a 16 inch LC refiner, 150HP variable speed motor, gap sensor and with a wide range of FineBar refiner plate patterns. The refiner is fed by 2, 4 m3 tanks and a 40kW variable speed pump. It is instrumented with flow, pressure and temperature sensors and a valve which is computer controlled permits to adjust the flow rate during refining session. The 150 HP, 1800 RPM motor allows a wide range of refining power and speed. The refiner is also computer controlled (speed and gap). The facility can be operated in two modes: tank to tank or in recirculation. The figures below show the hydraulic refining loop :

You can see below a picture of the facility :

Pump

Refiner

Sample valve

ii. Testing facilities

There is a lot of testing machine in PPC. For my project I have used the FQA (Fiber Quality Analysis) which permits to measure the fiber length, the freeness tester, the tear machine and the tensile machine.

FQA picture

b. Paper making process

i. Different types of pulp

For a better understanding of this report, I am going to explain the basis of paper making and more particularly the Low Consistency Refining. It exist two different ways to produce pulp, so it exist two different kinds of pulp: mechanical pulp and chemical pulp. In the case of mechanical pulp, the wood is processed into fibre form by grinding it against a quickly rotating stone under addition of water. The yield of this pulp amounts to approx. 95%. The result is called wood pulp or MP – mechanical pulp. The disadvantage of this type of pulp is that the fibre is strongly damaged and that there are all sorts of impurities in the pulp mass. Mechanical wood pulp yields a high opacity, but it is not very strong. It has a yellowish colour and low light resistance.In case of wood pulp obtained by means of chemical pulping, we differentiate between sulphate and sulphite pulp, depending on the chemicals used. The yield of chemical pulping amounts to approximately 50%. The fibers in the resulting pulp are very clean and undamaged. The wood pulp produced by this process is called woodfree.It exists also intermediate type pulp TMP and CTMP as you can see below:

During my research program I have studied Chemi-Thermo-Mechanical-Pulp (CTMP).

ii. Refining

To obtain sheets with interesting properties, pulp has to be refined. A refiner is a kind of centrifugal pump. Pulp arrives by the centre between two plates (a rotor and a stator) and is expulsed by the top of the refiner because of the rotor rotation and of a pump in the loop which permits to have a flow rate. The picture below shows the PPC refiner opened.

In the process of refining fibers are trapped in the gaps between bars during bar crossings where, the cyclic compression and shear forces which are imposed on fibers modify the fiber properties [Heymer, 2002]. Although, the main target of refining is to modify surface characteristics as well as fiber flexibility in order to develop stronger and smoother paper with good printing properties, yet it is not limited to them. Sometimes the purpose of refining is to develop other pulp properties such as absorbency, porosity, or visual appearance [Yan Li, 2005].It exists two different kinds to refine pulp: Low Consistency Refining (LCR) and High Consistency Refining. I will study Low Consistency Refining that is to say refining of pulp with at less 95% of water and maximum 5% of wood.The refining mechanism itself is similar in both cases. It is assumed that the fibers are refined in the form of fiber flocs and that the effective refining action starts when the fiber bundle of fiber flocs is pressed between the leading edges (the edge-to-edge phase in figure below) This phase is followed by and edge-to-edge surface phase, which continues until the leading edges reach the tailing edges of the opposite bars. The length and the strength of the fiber flocs depend on the physical dimensions and the bonding ability of various fibers in the mixture.

Rotor

Stator

Exit (refined pulp)

Entrance (not refining pulp)

iii. Making of handsheetsOnce the pulp his refined, it is put in a cold storage room to conserve his properties. Before making handsheets pulp is diluted with distilled water to have only 0,3% of wood. You can see below the handsheets maker and the pressing machine.

Photo

At the bottom of this tube there is a sieve and under this sieve there is a big valve which permits to drain very quickly the water.To make an handsheet, we put 400mL of diluted pulp in this tube. We complete the tube with water and then we open the valve to empty the tube. The fibers stay on the sieve and make the handsheet. Then the handsheets are pressed with a press and stored in a CTH room during at least 24 hours before being analysed.

iv. Refining theories

The aim of refining theory is to predict changes in pulp properties from known refining conditions and to allow for the comparison of different refining plates, or fillings, under various operating conditions. I am going to explain two refining theories: the SEL and the SRE which permit the characterization of the refining process.

The SEL is the most commonly used and simple theory in practice today. The SEL is defined as a measure of the energy expended per unit length of bar crossings, having unit of J/m:

PNET is the net input power (W). The cutting edge length, CEL (m/s), is the product of the plate factor, Kp (m/rev) and the angular velocity, (rev/s). Kp is the sum of the product of the number of bars on the rotor, Zr, the number of the bars on the stator, Zs, and the length of a bar, L(m), over increments, i, in the refining zone. Most of the time the value of K is given by the plate designer.

The SRE (Specific Refining Energy) is given by the equations below

c. Presentation of my project

i. Scope of the study

As I have said before my project concerns low consistency refining of CTMP pulp. My project scope was to study the effect of two parameters (Gap and SRE) on pulp and sheets properties (fiber length, freeness, tensile and tensile) for different consistencies.

ii. Objectives of the research

The objectives of my research program was:

-To show if the gap can be consider as a refining parameter by himself

-To show how vary pulp and sheets properties by varying just the SRE. Most of the time people vary SRE and SEL together and the real effect of SRE is unknown for CTMP pulp.

iii. Excepted results

The professor Olson and his colleagues which was supervising my project supposed that gap is a very good indicator of refining intensity and they want to verify this suppostion . If that is true, mechanical properties of pulp and sheets are supposed to vary in a known form (proportionally, exponentially…) versus the gap.

Moreover, they had never study the effect of SRE on this kind of pulp and they hope that SRE can be used to predict paper properties during the refining session. For this, with a constant SRE, properties are supposed to be the same indépendemment of the consistency.

2)Research program

a. Presentation of the trials

i. Methodology and trials matrixWe will consider 3 different consistencies (2.5, 3 and 3.5%). For each consistencies, we will take 5 samples of different SRE, with common SRE between the different consistencies. We hope that gap will have to be adjusted to maintain a constant Net Power.

Constant Parameters:

Net Power: 50kW

Plate: Kp = 5.9 Constant SEL

Rpm: 1200

Varying Parameters:

Flow rate => to change SRE

Gap => to maintain a constant Net Power

Consistency

You can see below the trials matrix:

Session 1 Session 2 Session 3

Net Power (kW) 50 Net Power (kW) 50 Net Power (kW) 50

Consistency (%) 3,5 Q (lpm) Consistency (%) 3 Q (lpm) Consistency (%) 2,5 Q (lpm)

SRE1 90 265 SRE1 40 486 SRE1 50 467

SRE2 95 251 SRE2 55 354 SRE2 65 359

SRE3 100 238 SRE3 65 299 SRE3 85 275

SRE4 110 216 SRE4 75 259 SRE4 95 246

SRE5 120 198 SRE5 90 216 SRE5 110 212

ii. First refining session Due to my lack of knowledge in paper refining, I have encountered 2 problems during my first utilization of the refining loop:

o Net Power too high: Even with very short gap it was impossible to increase net power to 50kW

o Range of flow rate not enough important: the net power was constant without gap adjustments

In order to avoid the wasting of 4m3 (one tank) of CTMP pulp which is very expensive I took 2 decisions:

o During the refining session: reduction of Net Power to 35kWo Modification of trials matrix for the next session in order to increase the range

of flow rate:

Session 2 Session 3

Net Power (kW) 35 Net Power (kW) 35

Consistency (%) 3 Q (lpm) Consistency (%) 2 Q (lpm)

SRE1 40 486 SRE1 50 688

SRE2 55 354 SRE2 60 486

SRE3 65 299 SRE3 70 417

SRE4 75 259 SRE4 90 324

SRE5 90 216 SRE5 110 265

iii. New project scope

During the following session, the net power problem was solved and the gap have to be modified to adjust the power, but a new problem appeared. Gap sensor is not able to measure very short gap variations. Gap sensor measure a value in millimeters each 0,01 second. Usually, people take an average of the values recorded during 0,05 seconds. The graph below shows the fluctuation of the gap during this period:

As you can see, for really short gap adjustment, gap sensor is not adapted. It is too sensible to refiner vibrations. Due to this problem, UBC professors said me to assume that gap is constant during all the experiment and to stop my investigations on gap effect. Now my project concerns only the study of SRE impact on pulp and paper properties.

b. Results and interpretation

i. Fiber length Results :

Interpretations :Seeing the graph above and (ignorant) some strange points, we can suppose that:Fiber length decreases when SRE increasesAt same SRE fibers are longer for the same consistency

ii. Freeness Results:

The graph below shows freeness evolution versus SRE:

Interpretations :o Freeness decreases proportionally to SRE for each consistencyo SRE impact depends on consistency : Higher is the consistency, higher is the freeness

decreasing

iii. Tear and tensile Results:

The graph below shows Tear evolution versus SRE:

The graph below shows Tensile index evolution versus SRE:

Interpretations:o Tear and tensile vary in opposite way for each pointo SRE impact depends on consistency: Higher is the consistency, higher are the

variations of tear and tensile

c. Conclusion

i. Technical point of viewThe study of gap effect was impossible due to the very short gap adjustment needed to have a constant power and due to the sensor fluctuations.UBC professors hopped that for a constant SRE and a constant SEL CTMP paper properties are the same. My study shows that this hypothesis is false. During my experiments, SEL was constant. My different trials shows that for the same SEL and same SRE properties can be different if consistency is not constant. So I can conclude that SRE is not really a good parameter to predict paper properties because its influence depends on the consistency. Higher is the consistency, higher is the SRE impact on changes in properties.

ii. Personal point of viewOn a personal point of view the past few months was a very good experience for me. I have increased my English level and I have discover with enthusiasm a new industry. I have spent the first three weeks of my MSI to learn theories about paper refining and making. This work had permitted me to be quickly efficient on my work and to be able to respect the schedule fixed by UBC professors. I have developed my self adaptation capacities, and worked with a very passionate team. I was happy to know that my work will be continued by another student.