| 1. |
- Adamopoulos, Stergios
(författare)
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Quantification of softwood, hardwood and nonwood fibres in packaging grade papers
- 2006
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Ingår i: TAPPI Journal. - : TAPPI Press. - 0734-1415. ; 5:3, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- This study determined percentages by weight of the fiber components in 15 papers commonly used to produce corrugating packaging in Spain. The papers are manufactured mainly from recycled raw materials. The percentages were determined by means of standard quantitative fiber analysis techniques and use of appropriate weight factors. Hardwoods were the major fiber component in all papers, except kraft liners, varying from 51% to 92% per weight. Kraft liners had greater softwood content (49%-69%)than hardwood, and the most plentiful softwood classes were pines. Douglas-fir was a contaminating fiber component (weight percentage less than 2%) in almost in every paper. Nonwood fibers, entering the papers through the recycling process, were a significant fiber component (2%-9%) in most of the papers, especially the waste-based papers (liners and flutings). Quantitative fiber composition reflects the differences in quality between the papers. Its usefulness could be further explored in the quality control of paper manufacturing for packaging.Application: Packaging grade papers incorporate a variety of wood and nonwood fiber types. Manufacturing of papers of consistent and acceptable quality requires knowledge concerning the quantity of each fiber used.
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| 2. |
- Ala-Kaila, K., et al.
(författare)
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Apparent and actual delignification response in industrial oxygen-alkali delignification of birch kraft pulp
- 2003
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Ingår i: TAPPI Journal. - 0734-1415. ; 2:10, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- The time-dependent behavior of material that affects the kappa number of birch kraft pulp was experimentally tested in an industrial, two-stage, oxygen-alkali delignification process. The pulps were leached, and the leached material was divided into four different fractions: the wash loss fraction and the easily leachable, slowly leachable, and stagnant fractions. These fractions were further characterized according to their chemical natures, representing residual lignin, extractives, hexenuronic acids, and other chemical structures contributing to the kappa number of the pulps. The apparent and actual delignification responses in the two reactors and the effects of the leaching operation were thoroughly evaluated based on the behaviors to these different pulp components.
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| 3. |
- Andersson, Niclas, et al.
(författare)
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A new sensor and a novel control concept for optimized fiber line operation
- 2014
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Ingår i: TAPPI Journal. - : TECH ASSOC PULP PAPER IND INC. - 0734-1415. ; 13:10, s. 39-45
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Tidskriftsartikel (refereegranskat)abstract
- Kraft and sulfite pulp mills use several consecutive process stages for pulp production. However, usually only one key pulp parameter is used for process control and that is the lignin content in the fibers, typically expressed as the kappa number. Even so, to improve process efficiency, more variables need to be monitored. To do that, a new sensor was developed, the dissolved lignin transmitter (DLT), along with a new control concept. The DLT measures the dissolved lignin content in the pulp slurry using a unique principle based on optical measurements. The device can measure the dissolved lignin inline at low consistency and at medium consistency. The sensor has two major applications: 1) improving the efficiency in washing stages and 2) optimizing chemical charges. Results from several mill trials have shown that the contribution from dissolved lignin in the filtrate portion of the pulp is up to 30% of the total bleach load, i.e., fiber and filtrate kappa number combined into the bleach plant. Hence, chemical savings can be achieved taking this component into account compared to only measuring the washed fiber kappa number. Application: The results of this study can help mills understand how to better control the pulping stages, which might lead to significant economic savings and better pollution control.
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| 4. |
- Axegard, Peter, et al.
(författare)
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Bleaching of softwood kraft pulps with H2O2, O3, and ClO2
- 1996
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Ingår i: TAPPI Journal. - 0734-1415. ; 79:1, s. 113-119
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Tidskriftsartikel (refereegranskat)abstract
- Ozone or chlorine dioxide bleaching prior to hydrogen peroxide bleaching greatly improves the performance of the hydrogen peroxide stage. The efficiency is further improved by a chelating treatment immediately after the ozone or chlorine dioxide stage. With an optimal metal ion profile, laboratory bleached (OAZQP) softwood kraft pulps can reach brightness levels above 90% ISO, with 5-10% lower pulp strength properties and bleaching costs comparable to ECF bleaching. It also is possible to obtain full brightness with only hydrogen peroxide provided the metal ion profile is optimal, e.g., by using multiple QP treatments. The chemical consumptions, expressed as oxidation equivalents per decreased kappa number are the same as for sequences including ozone or chlorine dioxide. Ozone and chlorine dioxide are comparable as far as delignification and brightness efficiency go.
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| 5. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
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Heat integration opportunities in an average Scandinavian fine paper mill: Model study and comparison with a market pulp mill
- 2008
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Ingår i: Tappi Journal. - 0734-1415. ; 7:2, s. 19-25
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Tidskriftsartikel (refereegranskat)abstract
- Within the FRAM programme, two models of average Scandinavian mills producing bleached market pulp have been analysed from an energy perspective. The aim was to explore the opportunities for heat integration in order to create a steam surplus. The steam surplus gives opportunities for increased power generation or lignin extraction. The technical and economic consequences of using the steam surplus in this way are explored in a continuation of this project. Two different approaches for creating a steam surplus have been investigated: 1) conventional measures and 2) processintegrated evaporation (PIvap). The former approach includes improved heat integration and new equipment. The latter approach means that excess heat from the mill is used for evaporation to partly replace live steam.The two model mills created within FRAM both produce 1000 ADt/d softwood pulp. The mills differ in the level of water usage, since it is expected that the amount of excess heat for PIvap will increase with decreasing water usage. By investing 11 M€ in conventional measures it is possible to create a steam surplus of 53 MW (about 26% of the total consumption), independent of the level of water usage. For the PIvap approach, the level of water usage matters, since there is more excess heat for PIvap in the mill with lower water usage. As a result, the total steam surplus with the PIvap approach differs in the two mills: up to 52 and 56 MW, respectively. Hence, the steam savings for the PIvap approach are similar to those in the approach with conventional measures; and so are the investments needed (10-12 M€). Even though the two approaches give approximately the same savings with the same investment, the PIvap approach might be easier to implement in an existing mill.
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| 6. |
- Bandekar, R., et al.
(författare)
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Crossflow filtration of green liquor for increased pulp production, improved green liquor quality, and energy savings
- 2020
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Ingår i: TAPPI Journal. - : Technical Assoc. of the Pulp and Paper Industry Press. - 0734-1415. ; 19:10, s. 527-538
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Tidskriftsartikel (refereegranskat)abstract
- A new green liquor filtration system has been installed and commissioned at the Ence pulp mill in Pontevedra, Spain. The filtration system is based on microfiltration and was developed in collaboration with the KTH Royal Institute of Technology in Stockholm, Sweden. The patented method for efficient purification of green liquor decreases the non-process element (NPE) content by providing more efficient solids/liquid separation, reducing energy and chemical consumption in pulp mills and increasing production capacity by eliminating certain capacity bottlenecks. The process has been continuously tested at the Aspa Bruk Mill outside Askersund, Sweden, since 2013. The technology has proven to create nearly particulate-free green liquor during the purification process. The technology can also be used to polish white liquor to provide higher pulp quality. To provide for a simple and cost-effective installation, the system was designed as a skid-mounted unit that is pre-piped, instrumented, and tested before shipment. The system is modular and allows for easy expansion of capacity. This paper discusses the process design, process integration, and startup of the new system, along with experi-ences from the first months of operation. Application: The patented and trademarked CleanFlow system is a technology designed to increase the capacity of a kraft mill recausticizing plant. Crossflow ceramic membranes are used to filter a portion of the green liquor, debottlenecking the existing green liquor clarifiers’ filters. The liquor quality is improved by reducing the buildup of NPEs. CleanFlow can also be implemented to filter white liquor, either the entire stream for improved pulp quality or just a portion, such as with preparing oxidized white liquor for pulp delignification after cooking, or for scrubbing of bleaching system vents.
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| 7. |
- Batchelor, Warren J., et al.
(författare)
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Effect of test conditions on measured loads and displacements in zero-span testing
- 2006
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Ingår i: TAPPI Journal. - 0734-1415. ; 5:10, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- Single fiber mechanical properties play a critical role in determining sheet mechanical properties, but fiber mechanical properties are rarely measured, because of the time-consuming nature of the tests. Zero-span strength is commonly used as a measure of fiber strength, but the results can vary with the test conditions. Modeling has shown that the load displacement curves are influenced by the thickness-to-span ratio, as there is a heterogeneous stress field in the thickness direction of the sample.This paper presents data on the effect of grammage on the loads and displacements in zero-span tests. Clamps were designed and made for a displacement-control led load frame. These clamps can test up to 10 plies of papers with,a span length from 0 to 3 mm. For the sake of comparison, tests were made using a commercial zero-span tester, which is load controlled but limited in span length and thickness of the tested material. Both machines were found to give comparable results. Isotropic 65 g/m(2) handsheets, 36 g/m(2) aluminum foil, and 42 g/m(2) greaseproof paper were tested as functions of sheet grammage. An intrinsic zero-span strength was defined as the y-axis intercept of a plot of zero-span strength versus grammage.Application:This paper demonstrates that the measured zero-span strength is always less than the intrinsic zero-span strength. The results show that, for best results, the grammage of the material tested should be minimized to obtain a measured value that is as close to the intrinsic value as possible.
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| 8. |
- Berglin, Niklas, et al.
(författare)
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Pilot-scale combustion studies with kraft lignin in a powder burner and a CFB boiler
- 2010
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Ingår i: TAPPI Journal. - 0734-1415. ; 9:6, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- Processes have been developed to produce a solid biofuel with high energy density and low ash content from kraft lignin precipitated from black liquor. Pilot-scale tests of the lignin biofuel were carried out with a 150 kW powder burner and a 12 MW circulating fluidized bed (CFB) boiler. Lignin powder could be fired in a powder burner with good combustion performance after some trimming of the air flows to reduce swirl. Lignin dried to 10% moisture content was easy to feed smoothly and had less bridging tendencies in the feeding system than did wood/ bark powder. In the CFB boiler, lignin was easily handled and cofired together with bark. Although the filter cake was broken into smaller pieces and fines, the combustion was not disturbed. When cof ¡ring lignin with bark, the sulfur emission increased compared with bark firing only, but most of the sulfur was captured by calcium in the bark ash. Conventional sulfur capture also occurred with addition of limestone to the bed. The sulfur content in the lignin had a significantly positive effect on reducing the alkali chloride content in the deposits, thus reducing the high temperature corrosion risk. Application: This research is of interest for pulp and paper and energy and utilities companies that want to understand how kraft lignin can be used to replace fuel oil or coal in many combustion applications.
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| 9. |
- Berglin, N., et al.
(författare)
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Pilot-scale combustion studies with kraft lignin in a powder burner and a CFB boiler
- 2010
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Ingår i: Tappi Journal. - 0734-1415. ; 9:6, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- Processes have been developed to produce a solid biofuel with high energy density and low ash content from kraft lignin precipitated from black liquor. Pilot-scale tests of the lignin biofuel were carried out with a 150 kW powder burner and a 12 MW circulating fluidized bed (CFB) boiler. Lignin powder could be fired in a powder burner with good combustion performance after some trimming of the air flows to reduce swirl. Lignin dried to 10% moisture content was easy to feed smoothly and had less bridging tendencies in the feeding system than did wood/bark powder. In the CFB boiler, lignin was easily handled and cofired together with bark. Although the filter cake was broken into smaller pieces and fines, the combustion was not disturbed. When cofiring lignin with bark, the sulfur emission increased compared with bark firing only, but most of the sulfur was captured by calcium in the bark ash. Conventional sulfur capture also occurred with addition of limestone to the bed. The sulfur content in the lignin had a significantly positive effect on reducing the alkali chloride content in the deposits, thus reducing the high temperature corrosion risk.
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| 10. |
- Bialik, Marta, et al.
(författare)
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New challenges regarding nonprocess elements in the liquor and lime cycle
- 2015
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Ingår i: TAPPI Journal. - : TAPPI. - 0734-1415. ; 14:7, s. 421-429
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Tidskriftsartikel (refereegranskat)abstract
- Optimal performance of the green liquor plant, recausticizing plant, and lime cycle is vital for adequate white liquor availability and quality as well as for a mill's energy efficiency. Recently, various problems in the liquor and lime cycle have been frequently reported by our industrial partners, including poor performance of green liquor filters or sludge filters, decreased filterability of lime mud, increased lime kiln dead load, and poorquality white liquor. Those problems are most likely caused by an accumulation of nonprocess elements in the liquor and lime cycle due to increased mill closure, increased use of biofuels, or both. Data from the literature and earlier studies have been analyzed with regard to the occurrence and concentration of nonprocess elements in various process streams, including filtered green liquor, green liquor sludge, lime mud, and white liquor. The mineral forms in which nonprocess elements often precipitate were also studied, together with the common knowledge and rules of thumb used by mills for dealing with the problems. The literature data are compared with the newest analytical results from a sampling campaign involving several mills with varying process solutions with respect to nonprocess elements. The consequences and possible recommendations for the mills are presented. Application: Kraft pulp mills can use this information to diagnose and possibly solve problems related to nonprocess elements in day-to-day mill operation.
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