| 1. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
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Heat integration opportunities in average Scandinavian kraft pulp mills: Pinch analyses of model mills
- 2006
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Ingår i: Nordic Pulp and Paper Research Journal. ; 21:4, s. 466-475
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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 havebeen 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 waterusage, 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 approachesgive approximately the same savings with the same investment, the PIvap approach might be easier to implement in an existing mill.
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| 2. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
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Increased capacity in kraft pulp mills: Lignin separation and reduced steam demand compared with recovery boiler upgrade
- 2006
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 21:4, s. 485-492
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Tidskriftsartikel (refereegranskat)abstract
- For increased production in pulp mills, the recoveryboiler is often a bottleneck. Two different approaches todebottleneck the recovery boiler have been investigated in twomodel mills that represent typical Scandinavian pulp mills. As areference approach, the recovery boiler was upgraded. Inconnection with this, the turbine system was also upgraded toenable increased electricity production. As an alternative to thisconventional approach, the load of the boiler was kept constantby extracting lignin from the black liquor in proportion to theproduction increase. To keep the steam balance, the specificsteam consumption at the mill was reduced through steamsavingmeasures to such an extent that the amount of steamproduced from burning the lignin-lean black liquor was sufficient.Consequently, the extracted lignin was not needed in-houseand could be sold as a biofuel. The net profit of implementinglignin separation was calculated for different conditions. Theresult was that, depending on the conditions, the lignin pricehad to be 2-17 /MWh for lignin separation to be equallyprofitable as boiler upgrade. With an assumed lignin price ofabout 15 /MWh, the conclusion is that lignin separationshould be an economically attractive alternative for debottleneckingthe recovery boiler. With a high power price and along-term investment strategy, however, upgrading the recoveryboiler and the turbine system can be more profitable.
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| 3. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
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Opportunities for Process Integrated Evaporation in a Eucalyptus Pulp Mill and Comparison with a Softwood Mill Study
- 2007
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Ingår i: Conference PRES 07, Ischia Island, Italy. ; , s. 727-732
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Konferensbidrag (refereegranskat)abstract
- Significant energy savings can be made in the pulp and paper industry by implementing process-integrated evaporation (PIvap). The concept of PIvap has been evaluated for a Eucalyptus mill producing bleached kraft market pulp in Portugal and the results were compared to the ones from an earlier model mill study of a soft wood mill. In the eucalyptus mill there were, theoretically, 0.86 GJ/ADt of excess heat suitable for a PIvap besides the 2.6 GJ/ADt of pinch violations. The pinch violations could be transferred to excess heat, but some pinch violations were cost effective to solve. A suggestion where 1.1 GJ/ADt of pinch violations are solved and 1.6 GJ/ADt of excess heat are extracted is presented. If the excess heat is used in a 7 effect PIvap with integrated stripper and increased dry solids content, steam savings of 2.7 GJ/ADt could be made in the evaporation plant. Together with the pinch violations and opportunities for improved soot blowing, the total steam savings from the suggested measures were 4.5 GJ/ADt or 35%. The amount of steam savings and associated costs were similar to the ones in the soft-wood model-mill. Hence, no significant differences could be found for the opportunities to implement PIvap in the hardwood mill compared to in the soft wood mill. The existence of a pre-evaporation plant, however, showed to hinder introduction of PIvap, since a pre-evaporation plant uses excess heat, and uses it ineffectively compared to a PIvap. Hence, the pre-evaporation has been removed in the suggestion for integration presented here.
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| 4. |
- Axelsson, Erik Marcus Kristian, 1974, et al.
(författare)
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Opportunities for process-integrated evaporation in a hardwood pulp mill and comparison with a softwood model mill study
- 2008
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 28:16, s. 2100-2107
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Tidskriftsartikel (refereegranskat)abstract
- Significant energy savings can be made in the pulp and paper industry by implementing process-integrated evaporation (PIvap). The aim of this paper was to evaluate the concept of PIvap for a existing hardwood mill producing kraft pulp and compare the results with the ones from an earlier study of a softwood model mill. Using pinch tools, we found a solution where 1.3 GJ/ADt of pinch violations are solved and 1.1 GJ/ADt of excess heat is extracted. If the excess heat is used in an efficient PIvap, steam savings of 2.7 GJ/ADt could be made in the evaporation plant. Together with the pinch violations and improved soot blowing, the total steam savings were 4.6 GJ/ADt or 36% for an investment cost of 6.6 M€. Compared with the softwood model mill, the configuration of the hardwood mill offered about the same savings with 2.7 M€ lower investment cost, making PIvap more interesting in the hardwood mill. As an alternative to implementing PIvap, more pinch violations can be solved. The PIvap approach gives more steam savings to approximately the same specific cost.
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| 5. |
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| 6. |
- Olsson, Marcus, 1977, et al.
(författare)
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A tool for simulating energy-efficient evaporation using excess heat in kraft pulp mills
- 2007
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Ingår i: Proceedings of the International Chemical Recovery Conference 2007, May 29-June 1, 2007, Quebec City, Canada. ; , s. 141-146
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Konferensbidrag (refereegranskat)abstract
- In this paper, we describe and illustrate the use of our simulation tool OptiVap, which has been used successfully in our research group in several papers. OptiVap uses Excel and the built-in Solver to find energy-efficient evaporation plants. The outputs from OptiVap are, for example, the live steam demand, the required heat transfer area and the investment cost. In OptiVap, we can also simulate the consequences of integrating other process units with the evaporation plant. We can e.g. simulate the energy savings of using excess heat in the evaporation plant (process-integrated evaporation) and the evaporation consequences of separating lignin from the black liquor. To illustrate the use of OptiVap, we show that different strategies can be used to optimise evaporation plants. The strategies are symbolised by three objective functions: 1) minimise the steam demand, 2) minimise the heat transfer area and 3) maximise the net annual profit. The simulations are performed for evaporator trains with 6-8 effects, which make use of excess heat from the mill to decrease the live steam demand. The resulting evaporation plants have practically the same profitability, which means that any of the three objective functions can be used to find suitable evaporation plants. Moreover, the first two objective functions do not require any knowledge of the final energy system which brings us to the conclusion that these objective functions are most practical and should thus be used in most cases.
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| 7. |
- Olsson, Marcus, 1977, et al.
(författare)
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A tool for simulating energy-efficient evaporation using excess heat in kraft pulp mills
- 2007
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Ingår i: Proceedings of the 2007 Engineering, Pulping & Environmental Conference, Oct 21-24, 2007, Jacksonville, FL, USA.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we describe and illustrate the use of our simulation tool OptiVap, which has been used successfully in our research group in several papers. The tool uses Excel and the built-in Solver to find energy-efficient evaporation plants. The outputs from the tool are, for example, the live steam demand, the required heat transfer area and the investment cost. The tool can also simulate the consequences of integrating other process units with the evaporation plant. We can e.g. simulate the energy savings of using excess heat in the evaporation plant (process-integrated evaporation) and the evaporation consequences of separating lignin from the black liquor.To illustrate the use of the tool, we show that different strategies can be used to optimise evaporation plants. The strategies are symbolised by three objective functions: 1) minimise the steam demand, 2) minimise the heat transfer area and 3) maximise the net annual profit. The simulations are performed for evaporator trains with 6-8 effects, which make use of excess heat from the mill to decrease the live steam demand.The resulting evaporation plants have practically the same profitability, which means that any of the three objective functions can be used to find suitable evaporation plants. Moreover, the first two objective functions do not require any knowledge of the final energy system which brings us to the conclusion that these objective functions are most practical and should thus be used in most cases.
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| 8. |
- Olsson, Marcus, 1977, et al.
(författare)
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Comparing conventional evaporation plants with plants using excess heat: A simulation study
- 2009
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Pulp and paper mills are large energy consumers which can often achieve economic savings by implementing energy-saving measures. The process unit with the greatest energy demand in a mill is usually the evaporation plant. If excess heat can be made available in the mill, and the heat can be used in the evaporation plant, significant energy-savings can be achieved. This kind of evaporation is called process-integrated (PI) evaporation. In the present study, theoretical plants with 6{8 evaporation eects are simulated using an in-house simulation tool called OptiVap. The consequences for the evaporation plant of using excess heat, of lowering the surface condenser temperature, and of separating lignin are investigated. The results show that the additional prot of PI plants is 0.3–1.5 €/ADt in comparison with conventional plants. By lowering the temperature of the surface condenser, the profit is raised by 0.6{0.9 e/ADt for both conventional and PI plants. With lignin separation, the PI plants are 0.7{1.7 e/ADt more protable than the conventional ones.
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| 9. |
- Olsson, Marcus, 1977, et al.
(författare)
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Exporting lignin or power from heat-integrated kraft pulp mills: A techno-economic comparison using model mills
- 2006
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Ingår i: Nordic Pulp and Paper Research Journal. ; 21:4, s. 476-484
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Tidskriftsartikel (refereegranskat)abstract
- Lignin separation and increased power generationare two alternatives for utilising a steam surplus at a kraft pulp mill. Lignin can be separated from the black liquor by using CO2 in a precipitation process. The resulting lignin can be sold as a biofuel. In this study, lignin separation and increased power generation have been compared by using computer models representing typical Scandinavian mills (327,000 ADt/a). In the studied mills, the steam surplus was up to 437 GWh/a (4.82 GJ/ADt)which enabled either increased power generation by 126 GWh/a(+65%) or extraction of 500 GWh/a lignin. A consequence of extracting this amount of lignin was that the power generation decreased by 59 GWh/a (-30%), which means that the profitability of lignin separation was dependent on the electricity price. Moreover, the profitability was mainly dependent on the lignin price and the cost for CO2 to precipitate the lignin.For lignin separation to give the same annual earnings asincreased power generation, the ratio between the electricity price and lignin price had to be 1.9-2.3. For ratios below 1.9, lignin separation was economically preferable, while ratios above 2.3 meant that increased power generation was preferable. It was noticeable that the profitability under all studied conditions was considerably lower for lignin separationthan for power generation at high electricity prices.Lignin prices around 15 €/MWh implied that the electricityprice had to be below 33 €/MWh for lignin separation to give higher annual earnings than increased power generation. For a high electricity price (55 €/MWh, e.g. including policy instruments), the lignin price had to be above 23.8 €/MWh for lignin separation to give higher annual earnings. These lignin prices are significantly higher than equivalent biofuel prices today. However, the lignin price would probably be higher than 25 €/MWh if lignin were used e.g. as raw material for specialty chemicals or as a replacement for fossil fuels.
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| 10. |
- Olsson, Marcus, 1977, et al.
(författare)
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Extracting lignin from black liquor: Consequences for the evaporation plant
- 2009
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An increase in the production of pulp is of economic interest to many kraft pulp mills. However, significant increases in production generally require the recovery boiler to be debottlenecked: it must either be rebuilt or replaced. Both options require costly investments that can be avoided by extracting lignin from the black liquor before it is burnt in the boiler. This, in turn, requires changes being made in the evaporation plant. In the present study, simulations have been carried out based on a 25% increase in the production of pulp. The evaporation plants are simulated with and without an integrated lignin separation plant to investigate the consequences of extracting lignin from black liquor. The results show that the evaporation plants with lignin extraction have investment costs that are 5-30% higher than an equivalent plant without lignin extraction. Furthermore, the evaporation plants with lignin extraction require an evaporation capacity that is 7% higher, since filtrates from the lignin separation plant are also evaporated here. This increases the steam demand by 9-12% compared with a plant without lignin extraction. The span in the investment cost and steam demand depends on where the filtrates are recirculated in the evaporation plant.
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