Virgin Material Preparation
Wood is the primary source of fiber in the production of paper, and both softwoods and hardwoods are used to produce wood pulp (Bamboo, bagasse and wheat straw are also commonly used as fiber sources in India - OECD/IEA, 2011., p.51) . The primary purpose of raw material preparation is to convert into a size and shape. It typically involves size reduction, debarking, chipping, and screening.
Debarkers are used to remove bark from logs prior to chipping, since bark is a contaminant in the pulping process. After debarking, the logs are put in a chipping machine to produce wood chips of a consistent size and shape to maximize the efficiency of the pulping process. The last stage of raw material preparation includes screening, where chips that are too small or big are separated and either used for energy recovery or sent to further processing (Kramer et al., 2009).
Virgin Material PreparationTechnologies & Measures
| Technology or Measure | Energy Savings Potential | CO2 Emission Reduction Potential Based on Literature | Costs | Development Status |
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| Cradle Debarker |
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A cradle debarker can reduce costs upto $33/t-wood (Kramer et al., 2009. p.88).
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Commercial |
| Energy Efficient High Capacity Chippers | Replacement of multiple chippers by single efficient high capacity chipper resulted in power consumption reduction & lower specific power usage. Currently installed chipper has specific power consumption of 7 - 8 kWh/ BDMT (Bone dry metric tons) of chips. (CII, 2008. p.48) | Equipment and installation costs are about Rs. 1600 Lakhs. Cost includes Rs. 444 Lakhs (about EUR 0.74 million) for the chipper, rechipper and vibrating screen, Rs. 300 Lakhs for feeding system, Rs. 330 Lakhs for electricity system, Rs. 200 Lakhs for civil work (CII, 2008. p.48) | Commercial | |
| Using Secondary Heat in Debarking | Energy savings are estimated at 0.52 GJ of energy can be saved per ADT of pulp (LBNL, 2009. p.88) | Reductions will depend on the energy system and the fuel used in the mill. In a sample calculation, reductions of 4494 t CO2/y are estimated for a 350 000 ADT-pulp/y plant (NCASI, 2001. P.54) | For a 350 000 ADT-pulp/y plant, savings of this measure are estimated to be about $154 000 (2001 dollars) in energy costs (NCASI, 2001. p.54). Capital investment cost are estimated to be $110 000 (LBNL, 2009. p.88). | Commercial |
| Replacing Pneumatic Conveyors with Belt Conveyors | In a mill with a 1000 t-pulp/d capacity, replacing the pneumatic conveyor from the chip pile to screening was estimated to reduce energy consumption by 17.2 kWh/t (17 2000 kWh/d) (NCASI, 2001. p.52) |
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For a 1 000 t-pulp/d capacity mill, replacing pneumatic conveyor with belt conveyor is estimate to save $210 000/y in electricity costs. (NCASI, 2001. P.52) Installation and maintenance costs associated with belt conveyors can be significant. (LBNL, 2009.p.88) | Commercial |
| Automatic Chip Handling and Thickness Screening | Reduction in steam consumption reduces energy consumption. | Savings on energy costs are estimated to be hundreds of thousands of dollars. The return on investment can be 10 to 15 percent. (Kramer et al., 2009. p.89) | Commercial | |
| Chip Conditioning |
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Commercial | |
| Microwaving Logs |
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Commercial | |
| Biotreatment | Biotreatment leads to 33% less energy consumption for pulp refining (Kramer, et al., 2009. P.110). On average, electricity consumption can be reduced by 25 to 30% (Biopulping International, 2012) | Commercial | ||
| Dry Debarking | Energy consumption in debarking might increase due to the operation of debarking drum in dry debarking mode. However this energy increase is entirely offset by the substantial amount of energy gain if the bark is used as an auxillary fuel due to the lesser water content in bark from dry debarking. | Typical investment costs of a new dry debarking system from log feed to conveyors is about €15 million for a capacity of around 1300 ADt/d kraft pulp. The conversion of an existing wet debarking system to a dry debarking system costs €4 – 6 million, for equipment and installation. perating costs are € 250000 – 350000 per year | Commercial | |
| Enzyme-Assisted Debarker |
Electricity savings of about 0.021 GJ/t debarked logs is estimated. Assessment does not include the energy required to produce enzymes. (Martin et al., p.22) |
CO2 emissions reduction by around 0.7 Kg/t-debarked log is estimated (Martin et al., p.21) |
Investment cost for an enzyme debarker is estimated to be $CAN 1.4 million (1990) for a 800 tpd plant. (Martin et al., p.22) |
Commercial |
| Bar-Type Chip Screens |  Energy savings in the bar-type chip screening is estimated to be 0.35 GJ/t chemical pulp due to about 2% increase in yield (Martin, et al., 2000. p.21). |
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Operation and maintenance cost savings are estimated to be $0.7/t pulp due to improved yield (Martin, et al., 2000. p.21). |
Commercial |
| Fine-Slotted Wedge Wire Baskets |
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Commercial | |
| Oxalic Acid Pretreatment | Electrical energy requirement for mechanical pulping can be reduced by 25%. | Payback period of about 2 years or even less are estimated. | Demonstration |