Sponsored through a Fulbright Senior Specialist Grant, Spring 2009

Thursday.  Iain Kerr and I visited Nampack Belville outside of Cape Town which is a deinking mill that produces tissue grades. The manager and process engineer were on-the ball. They used an effective flotation process with only surfactant added in the pulper. Had +8 pt brightness over flotation cells and final 88 brightness for tissue, towel, napkin, toilet.  Used 25% softwood purchased.   They  were in touch with Buckman Laboratories on all the new enzyme applications that I had brought to SA to talk about. With Optizyme they reduced both refining energy and drying requirements.  Their yield had decreased from 71 to 67% due to higher filler content in pulp over the years. Sludge is sent to be put in bricks, brickmakers like the fiber, making the bricks lower density. Stickies cause problems fouling wire, they depend on Buckman to measure stickies and provide stickies encapsulation chemistry to send stickies out with product.

Went to Nampack packaging research and development. Very interesting. Myriad of products.  We were shown a cheap fermented sorghum product packaging; product has vent in top because a worm of expanding solids extrudes through the top vent during storage. Packaging has contest with prizes listed on outside of container: prizes were  a donkey cart or wheel barrow.  Nampack measures water vapor and oxygen transmission rates.  Metal cans unbelievably complex process.  Saw pre-form for plastic bottles shipped to bottler, bottler blows extruded bottle, screw cap part on pre-form.  Have tasting panels for wine, this is great until they have to taste old spoiled wine. Use SEM-EDS to detect glass shard types in products such as ketchup.  Saw ketchup with paper contaminants in it submitted by customer.  They test for food spoilage with biotech processes with cultures on agar plates. 

Friday. Visited Stellenbosch University “Wood and Paper Science” and Polymer Institute.  The Wood and Paper Science program had similar interests as my department. Enjoyed interesting discussions about the industry and academics with Jan Swart and Tim Rypstra, friendly and engaged faculty. 

 

 

 

Monday. I Met Jimmy Pauck (the doctoral student and instructor at Durban University of Technology) and Pauck’s local research advisor, Dr. Jon Pocock (faculty in Chemical Engineering at University Kwazulu-Natal who has done research in mineral flotation).   Jimmy’s research project will be to model the flotation deinking process in the lab using experimental data from a partial factorial designed experiment and then use neural networks to develop a control strategy for improving deinking performance in industrial plants.  He will have technicians doing pulping and flotation trials with eleven input variables and yield, ash loss, brightness, ink content as outputs.  My suggestions were to

1. plot all response variables versus calendar time
2. get one condition and perform in triplicate
3. it is useful to get a relationship of ppm reduction of ink versus yield
4. have a response variable with ppm reduction divided by solid losses
5. need to shred paper and blend before doing experiments
6. need to be extra careful that technicians doing experiments are well trained and follow exactly the same procedures

Also listened to presentation by Asheena on stickies detection methods. They are using a method in which they dye the stickies blue and hot press the stickies onto a paper transfer sheet for macrostickies and using a hemacytometer for microstickies detection. They are measuring macrostickies well in the old corrugated container recycling plant but not in the newsprint plant.  Microstickies detection seems ok; however, it is not clear if they are seeing microstickies particles or simply particles using microscopy.  Perhaps turbidity would be a useful microstickies indicator, especially for water streams in filtrates and clarifiers.

Thursday.  Visited deinking and TMP paper mill, Monde Merebank, near Durban. Gave the following presentations to about 16 people including mill manager:

1. Fundamentals of de-inking
2. Surfactant spray flotation
3. Screening and adhesive contaminants
4. Behavior of micro sticky contaminants in paper processing environments

Toured the deinking plant. They seem to be inspecting bales for unusual material.  They are selling deinked newsprint about 10 brightness points below their specified brightness target but customer is ok with it because it is recycled.  The flotation cell was completely overflowing with foam, probably using too much foaming agent and running to high a flowrate to the cell.  They have no water clarification process, which is hurting their efficiency and causing staining of paper machine clothing, grey when bad, green when really bad. They are increasing their screening capability and even trying a feed forward approach for their secondary screen rejects.  My recommendations for their mill; get a clarifier installed and definitely continue on with the plans to update their screening system.  They have gyro cleaners that are off line, they used to fill up with sand and have not been used in years. 

Friday.  Gave the following seminars at CSIR to Jerome and Asheena: 

• Control method for adhesive contaminants
• Enzyme applications in the pulp and paper industry

Also gave seminar in the morning with Tammy Bush also attending:

1. Paper Recycling Research at NCSU: Natural Surfactants, Fast Sensors for Automated Recovered Paper Sorting, and Sludge to Ethanol
2. Bioenergy Research in the Wood and Paper Science Department at NCSU

 

Discussed their methods for detecting stickies, which involves making handsheets and then pressing with heat to transfer to white sheets for macrostickies. Also talked about their simple microscope detection for microstickies, partially based on our work at NCSU.  I suggest that a simple screen with wire mesh of sufficient opening might be used to screen contaminants rapidly, or a simple vibratory screen, then deposit on filter paper and heat transfer onto transparency or detect manually with prick probe on heated plate. (This is actually what one recycle mill I visited is doing, see later.)

In the afternoon evaluated several methods of detecting stickies using pressing onto plastic and cellulose films.  Had some success with transferring adhesives, especially with the high temperature laminator.  My suggestion for macro stickies is to do a screening followed by a heat press transfer to plastic film or paper and probe with a pin. Alternatively image analysis on the film or paper might be possible.  Suggest that they further pursue the flow hemacytometer method for microstickies along with turbidity as an indirect measure of micro stickies.

Gave seminar in the Chemical Engineering Department of Kwazulu-Natal University, titled:  The Wood and Paper Science Department and Research in the Biofuels Area.  

Monday.  A national holiday.  Flic showed me around the Mondi tree nursery and the eucalyptus and pine plantations in the town of Hilton in the Midlands. They don’t use wood for house building because of termites;  wood is grown for mining supports and pulp mainly. Can harvest eucalyptus in 6-8 years and pine in 18 yrs or so, much faster than N. America.   Important progress in forestry in SA recently had been:

1. Cross breeding of different eucalyptus trees to impart cold resistance, disease resistance, and desirable fiber and wood properties.
2. Cloning to produce homogenous materials.
3. Improved nursery techniques to be able to supply plantations with needed materials.
4. Adherence to accepted forestry practices for environmental stewardships.

That night had dinner with Flic and PeteZac Zacharias (deputy vice chancellor of UKN and head of Agriculture, Engineering and Science).

Tuesday.  Flew to Johannesburg with Casper Nice. We talked about possible summer students from NCSU coming to SA.  The salary differences between the 2 countries is a major obstacle, summer interns in SA get about $200-400 per month spending money plus a car and apartment (at the mill I visited) whereas US companies give about $4000 per month.  This, combined with a plane ticket costing $1000-1700 would make it hard for US students to do summer intern in SA.  On the other hand, the cultural and technical experience would be great for some of our students.

Also talked to Casper about collaborations in research and about needed research in paper recycling:  improved deinking, stickies detection, bleaching, and differences between SA wood fibers and North American wood fibers in recycling, inexpensive conversion of tanks for dissolved air flotation applications.  

Gave NCSU WPS, the stickies in screening, the microstickies talk, and the control of stickies talk to several mill managers and technical managers in the Pamsa office in Johannesburg. I was surprised to hear that there was interest in collecting liquid packaging and cement sacks for recycling, typically avoided in the US due to low volumes available and significant contaminant amounts.  

At the Nampak Kliprivier mixed office waste to tissue mill, mill manager Craig Forrester showed me the mill and was very knowledgeable and enthusiastic about the operation and improvements in the mill. I was very impressed with the cleanliness, organization and  control of the process.  They have some excellent stickies control strategies:

1. Stickies testing twice a week.  Must measure consistency and then take 10 od grams screened then rejects filtered onto filter paper, dried, and then manually probed under magnifying lens and a count/10 od grams made.  Deformable tacky adhesives probed with a pin circled on paper. Twenty seven samples taken:  feed accepts and rejects of all 3 stages of the fine screens, cleaners and reverse cleaners.
2. All 3 stages of fine screening are feedforward in the system.
3. Use low consistency screening. Three clarifiers, the clarifier for the pm was left a little dirty so small particles could coat stickies.
4. Water clarification is taken extremely seriously, with routine testing of suspended  solids efficiency
5. Many common sense techniques like making sure that reject streams are not plugged, that showers are operating, checking the incoming recovered paper, after solvent washing the PM, making sure the solvent is removed before operating again.

There was an engineer in the 1990’s that they called “Stickies Steve” who won an award for his work to decrease stickies problems and increase mill production at the same time.  They regularly ran for 1-3 months without any required shutdown for cleanups of the paper machine. A thought: Craig suggested that a roll be used as a sacrificial roll to accept stickies deposits on the paper machine, that deposits occurred once most of the water has been removed, that the roll could be taken off line and doctored. 

Wednesday.  Made several presentations at the research center of Sappi, a large company that has about 4 mills in SA and 14 others internationally including 3 in the US.  Gave the following presentations:

1. Introduction to Wood and Paper Science at North Carolina University
2. Paper Recycling Research at NCSU: Natural Surfactants, Fast Sensors for Automated Recovered Paper Sorting, and Sludge to Ethanol
3. Screening of adhesive contaminants
4. Behavior of micro sticky contaminants in paper processing environments

There were about 15 people in the seminar, none of which focused their activities in paper recycling.  Then I did a tour of their research facilities, separated into 4 parts:

• Fibers and Wood
• Biotechnology
• Fiber Processing
• Analytical

They have excellent facilities and equipment. Especially impressive was their pilot plant facilities for pulping bleaching and refining, all three were controlled by a DCS and had detailed operator interfaces and probably were as good as any in the world  In pulping and bleaching they had multiple digesters and liquor feed and accumulation tanks, allowing them to simulate any complex pulping or bleaching process.   Their variety of refiner plates and the control of this system were excellent.  They also had a very nice automatic drawdown system for coatings.  They also had an automatic kappa tester that looked as if it could do near 16 autonomous tests with the capability of first estimating the lignin in the material before doing a final test with appropriate amounts of titrants. They also had a pulmac zero span tester and a fiber analyzer that was capable of measuring all of the standard characteristics plus fiber wall thickness. 

To summarize, a great, rewarding trip in which I learned a lot about the paper industry and paper research in SA, the SA culture, history and politics, visited a number of very interesting sights, and met a lot of very interesting, hard-working, smart people.