EXAM ON THURSDAY BRING A SCANTRON FORM!!!!!
New ideas for pulping • Crystallize lignin to make it fragile • Re-engineer the tree; weak or remove lignin • Engineer enzymes to destroy lignin and protect carbohydrates • Color the fiber and then use tool (high tech cutting machine or laser beam) to remove fiber • Use a different material than wood to make pulp.
?????????? • What do you think about pulp and paper companies taking advantage of biofuels tax credit • They are immoral scoundrels and should be embarrassed by this type of behavior 11 • They are just doing their jobs and looking after the share holders by taking advantage of all tax advantages 8 2 were in the middle
15 October 2009 • The Road to Copenhagen - Biggest Obstacle to Global Climate Deal May Be How to Pay for It • Industry Built From Scratch
Pulping The problem Wood (this is what we have) Fibers (this is what we want)
Suggest two ways to liberate the fibers (in-tact) from the wood so that you can make paper from them. (i.e. develop “nanomuncher” to eat inter-fiber lignin) Question of the day Your chance to be rich The rich part: Approximately 45 million tons of pulps are produced in the US each year. If you could get just $1/ton for your royalty it would make you $45,000,000 – not a bad salary.
Chemicals • Dissolve the lignin but not the fibers • Mechanical • Soften the lignin 1st then tear the fiber from the wood • Biological • The holy grail of pulping • Find some “bug” or enzyme that will eat the lignin and not the carbohydrates • Problems – Most biological agents attack carbohydrates 1st, Reactions are slow, Biological agents are expensive Ways to liberate fibers
Types of Pulping • Two main ways to liberate fibers • Mechanically • Chemically • There are also hybrids of these two methods • Chemimechanical • Semi-chemical
Popularity of Pulping Technologies% US pulp production • Mechanical 20% • Chemical 70% • Hybrids 10% The rest of the world is pretty similar
Mechanical Pulping • Uses mechanical energy with little or no chemicals • Two main processes • Grinding: logs are forced against a revolving abrasive stone Stone groundwood process (SGW) • Refining: wood chips are fed between two metal discs – one of them rotating Thermomechanical pulp (TMP)
Mechanical Pulping OverviewStone Groundwood: Equipment Stone Groundwood uses logs. Not used at all in the Pacific Northwest because we get almost all our wood as leftovers from saw mills as chips. There are a variety of different designs of this equipment. Basically, logs are pressed into a rotating stone. The fibers are washed off the stone with water. This also cools the stone. Running this system under a slight pressure improves the process.
Refiner Pulping This process uses wood chips as its raw material Two main processes: • Thermo-mechanical Pulping (TMP) – chips are presteamed • Chemi-thermomechanical Pulping (CTMP) – chips are given light chemical treatment
Refiner Plates • The refiners contain opposing plates that shred the chips. These plate are separated into different sections • 1st section (inlet) rips chips into wood slivers. • Each subsequent step reduces the size of the bundles. • Water carries the fibers through the disk
Mechanical Pulping • Most of the constituents of wood retained • This results in high yield (85-95%) • Weak sheet. Chemical pulp sometimes needed to be mixed in • It discolors easily • High energy usage
Products from mechanical pulps • Newsprint • Tissue • Coated publication
TMP Process Waste heat Steam and Heat Pulp Wood Refiner(56,000 horse power motor) Electricity
TMP Economics • Economics for 1 ton of medium brightness TMP pulp • Accuracy of analysis approximately 20% • Capital Cost for 500 ton/day mill = $300,000,000 • Annual profit $238/ton*500 tons/day*350days/year = ~$41 million/year for a mill that costs $300 million
TMP Energy Consumption • Energy consumption for modern TMP mill is approximately 2400 kWh/ton pulp. • Average annual household consumption in Seattle for 2004 was 8,852 kWh. • How many homes could NORPACTMP electricity power?
TMP Energy Consumption Huge TMP mill ~ 1500 tons pulp/day Annual NORPAC energy usage = 1500tons/day*2400kWh/ton*350days/yr = 1,260,000,000 kWh Number of houses = 1,260,000,000 kWh/yr = 142,000 8,852 kWh/house/yr
Chemical Pulping • Uses chemicals and heat to dissolve lignin • Leave cellulose and some hemicellulose • Major processes • Kraft • Soda • Sulfite
Chemical Pulping • Kraft process - caustic • NaOH and Na2S • Soda Process - caustic • NaOH • Sulfite - acid • SO2 and Base: e.g. Mg(OH)2, Ca(OH)2, NH4(OH)
Chemical Pulping OverviewEquipment: Batch Digester • Large pressure reactors • 2500 to 12,500 ft3 • Typical mill will have banks of 6-8 digesters • Heating of system is either through direct heat (steam) or though indirect heating of the cooking liquor with forced circulation
Chemical Pulping OverviewEquipment: Continuous Digester • Tube shaped reactor in which the chips move through continuously • Various zones in the reactor: charging, impregnation, heating , cooking, etc. • Typical reactor: Kamyr digester
Kraft Pulping • Kraft pulping means strong in German. Highest strength pulp • Invented by accident – looking for a cheap source of sodium – Na2SO4 (saltcake) • Dominant process in North America • Proven, efficient recovery process • Can pulp any wood species • Yield is low: 40-45%
Products from Kraft Pulp • Linerboard • Xerographic • Food Boards • Source of strong fiber
Kraft Process Pulp Reactor (350oF) – Dissolve all lignin ¼ carbohydrates Wood Washer NaOHNa2Sin water Evaporate water Steam Steam Furnace Excess steam (dry paper) Excess electricity
Chemical Recovery • For each ton of pulp produced, 3000-5000 gallons of black liquor produced • Black liquor contains • Organics – dissolved wood components • Inorganics – cooking chemicals, now spent (inactive) form
Chemical Recovery • For economic and environmental reason, the black liquor MUST be recovered – hence the Chemical Recovery System • Goals • Burn organics to generate heat • Convert inactive cooking chemicals back into active form. • 98% of pulping chemicals are regenerated
Chemical Recovery – process • Black liquor is washed out of the pulp in a brownstock washer • This weak black liquor is thickened by removing water in the evaporators • The resulting strong black liquor is then sprayed into the Recovery Boiler
Simplified Flow Diagram of the Kraft Process Chips Wash Water Lime Kiln Pulping Pulp Causticization Recovery Boiler Evaporators
Kraft Pulp Economics • Economics for 1 ton of Kraft pulp • Accuracy of analysis approximately 20% • Capital Cost for 1000 ton/day mill = $1,000,000,000 • Annual profit $390/ton*1000 tons/day*350days/year = $136,500,000/year for a mill that costs $1,000,000,000
BioFuels meets Pulp and Paper http://www.nytimes.com/2009/04/18/business/energy-environment/18sludge.html?_r=1&scp=2&sq=black%20liquor%20tax%20credit&st=cse • Details • 2005 transportation bill includes provision $0.50 per gallon for burning renewable fuel with diesel fuel • 2007 bill is extended to non-transportation energy sources • Kraft pulp mills begin blending a little diesel (0.01%) with black liquor so they can write claim $0.50 tax credit – and it can be applied for past years Pay off: About $200/ton pulp. 1000 ton/day mill ~ $200,000/day or $70 million per year
?????????? • What do you think about pulp and paper companies taking advantage of biofuels tax credit • They are immoral scoundrels and should be embarrassed by this type of behavior • They are just doing their jobs and looking after the share holders by taking advantage of all tax advantages
Kraft Pulp Production Costs - Brazil • Economics for 1 ton of Kraft pulp • Accuracy of analysis approximately 20% • Capital Cost for 1000 ton/day mill = $1,000,000,000 • Annual profit $590/ton*1000 tons/day*350days/year = $206,500,000/year for a mill that costs $1,000,000,000
Kraft Pulp Economics-Finland • Economics for 1 ton of Kraft pulp • Capital Cost for 1000 ton/day mill = $1,000,000,000 • Expensive electricity ($0.30/kWhr) – sell excess power (~30MW from 1000 ton/day mill. • Annual profit $590/ton*1000 tons/day*350days/year = $206,500,000/year for a mill that costs $1,000,000,000
Kraft Water Consumption • Water consumption for kraft mill is approx. 21,000 gal/ton pulp. • 21,000,000 gal/day @ 1000 tons pulp/day production • 21,000 gal/ton*1,000tons/day = 21,000,000 gal/day • Average annual per household consumption of water in Seattle is about 27,000 gal. • 27,000 gal/year ÷ 365 days/year ~ 80 gal/day • Kraft mill producing 1000 tons pulp per day uses same amount of water 262,500 houses. • 21,000,000 gal/day ÷ 80 gal/day/house ~ 262,500 houses
Carbon emissions (global warming) • Drought in Southeast US 2008 • Largest pulp producing region of the country
Pulp mill controversy http://www.youtube.com/watch?v=yOu-beqDh3M
Bleaching Who needs white paper anyway?
What is Bleaching? • Bleaching is the chemical process applied to cellulosic materials to increase their brightness • Cellulose and hemicellulose are white and do not contribute to color • Lignin, dirt, fiber bundles (shives) do contribute to color
Goals of Bleaching • Attack and remove remaining lignin • Attack and destroy color-causing molecules • Attack and remove/decolorize dirt and fiber bundles (shives) • Improve pulp brightness and cleanliness
Measurement of Brightness Reflected Light Brightness is measured by shining light on a sheet of paper and measuring how much is reflected. Units: % Incident Light Paper Sheet
How Does Bleaching Occur? • Most common bleaching chemicals are very strong oxidizers • In most cases, these oxidizers are strong electrophiles – they steal electrons from lignin and other molecules, causing chemical bonds to break