| 1. |
- Bonhivers, Jean-Christophe, et al.
(författare)
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Comparison between pinch analysis and bridge analysis to retrofit the heat exchanger network of a kraft pulp mill
- 2014
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 70:1, s. 369-379
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Tidskriftsartikel (refereegranskat)abstract
- Pinch analysis is based on the hot, cold and grand composite curves and is the most commonly-used approach to identify strategies for reducing energy consumption by heat exchanger network retrofit. This method was originally developed for the synthesis of new networks, and there remain certain difficulties for its application to improve existing networks. The advanced composite curves have been developed for retrofit situations specifically, and use data about existing heat exchangers to provide more information about the modifications necessary to achieve heat savings. Bridge analysis, which is based on the energy transfer diagram, is a new method and enumerates the sets of heat transfer modifications necessary to save energy. In this paper, the grand composite curve, the advanced composite curves and the energy transfer diagram have been constructed for analysis of the heat exchanger network of a kraft pulp mill. Links between these methods are made explicit; then results are discussed and compared. It is shown that the information provided by these approaches is consistent; however, the level of detail progressively increases from the grand composite curve to the advanced composite curves until the energy transfer diagram. Fundamentally, reducing the energy consumption implies decreasing the flow rate of heat cascaded through the network from the hot utility until the environment. As a consequence, any heat savings solution includes network modifications bridging coolers to heaters. Traditional pinch analysis does not provide information about the network modifications required after removal of cross-pinch transfers, while the advanced composite curves indicate the heat savings potential attainable through modifications of few existing heat exchanger units. Bridge analysis provides more detail about heat savings modifications, which bridge existing heaters and coolers, than traditional pinch analysis and the advanced composite curves do.
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| 2. |
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| 3. |
- Bonhivers, Jean-Christophe, et al.
(författare)
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Energy Transfer Diagram for Site-Wide Analysis and Application to a Kraft Pulp Mill
- 2015
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 75, s. 547-560
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Tidskriftsartikel (refereegranskat)abstract
- In industrial processes, heat is transferred from the heating utilities to the environment or converted to another form of energy. Process operations and heat exchanges decrease the level of energy quality; i.e., heat is cascaded to lower temperatures. The energy transfer diagram (ETD), which has been recently developed, indicates the flow rate of heat transferred from the utilities to the environment through each process operation and each heat exchanger as a function of temperature. This tool can be used to identify heat savings projects by modification of the process units and the heat-exchanger network (HEN). However, in a larger sense the diagram indicates the flow rate of energy transferred through any system as a function of the level of energy quality, and can be used for the analysis of a complete plant, including the thermal, chemical, mechanical and electrical transformations. This paper presents new developments to consider energy conversion with the ETD, the application to an entire kraft pulp mill, including the HEN, the process operations, and the utility system, and results from site-wide analysis.
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| 4. |
- Lundberg, Valeria, 1984, et al.
(författare)
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Converting a kraft pulp mill into a multi-product biorefinery: techno-economic analysis of a case mill
- 2014
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Ingår i: Clean Technologies and Environmental Policy. - : Springer Science and Business Media LLC. - 1618-954X .- 1618-9558. ; 16:7, s. 1411-1422
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Tidskriftsartikel (refereegranskat)abstract
- In this case study, we investigated the conversion of an existing Swedish kraft pulp mill to the production of dissolving pulp, with export of electricity, lignin, and a hemicellulose stream suitable for upgrading. By increasing the level of heat integration of the mill, it was possible to achieve self-sufficiency in terms of steam and to produce significant amounts of excess steam. The excess steam could facilitate the integration of a lignin separation plant or be used for power generation. The production of dissolving pulp requires a higher input of wood that is required for the same level of pulp production as is achieved with kraft pulp. For the studied mill, the batch digester was the main limitation for pulp production. Nevertheless, if the digester capacity was increased, then the level of pulp production could be maintained. In addition, the recovery boiler, causticization plant, and evaporation plant had sufficient capacities for preserving the same production level upon conversion, and could easily be upgraded to a certain degree through relatively simple measures for an increase in pulp production. However, increasing pulp production beyond that limit required extensive upgrades or investments in new equipment, which negatively affected annual earnings. Annual earnings were found to be also dependent upon the level of heat integration, type of by-product, and the costs for lignin and electricity. However, our results suggest that the optimal process configuration is more dependent upon other factors, such as the long-term vision of the company and policy instruments.
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| 5. |
- Pettersson, Karin, et al.
(författare)
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Holistic methodological framework for assessing the benefits of delivering industrial excess heat to a district heating network
- 2020
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Ingår i: International Journal of Energy Research. - : John Wiley and Sons Ltd. - 0363-907X .- 1099-114X. ; 44:4, s. 2634-2651
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Tidskriftsartikel (refereegranskat)abstract
- In Sweden, over 50% of building heating requirements are covered by district heating. Approximately 8% of the heat supply to district heating systems comes from excess heat from industrial processes. Many studies indicate that there is a potential to substantially increase this share, and policies promoting energy efficiency and greenhouse gas emissions reduction provide incentives to do this. Quantifying the medium and long-term economic and carbon footprint benefits of such investments is difficult because the background energy system against which new investments should be assessed is also expected to undergo significant change as a result of the aforementioned policies. Furthermore, in many cases, the district heating system has already invested or is planning to invest in non-fossil heat sources such as biomass-fueled boilers or CHP units. This paper proposes a holistic methodological framework based on energy market scenarios for assessing the long-term carbon footprint and economic benefits of recovering excess heat from industrial processes for use in district heating systems. In many studies of industrial excess heat, it is assumed that all emissions from the process plant are allocated to the main products, and none to the excess heat. The proposed methodology makes a distinction between unavoidable excess heat and excess heat that could be avoided by increased heat recovery at the plant site, in which case it is assumed that a fraction of the plant emissions should be allocated to the exported heat. The methodology is illustrated through a case study of a chemical complex located approximately 50 km from the city of Gothenburg on the West coast of Sweden, from which substantial amounts of excess heat could be recovered and delivered to heat to the city's district heating network which aims to be completely fossil-free by 2030.
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| 6. |
- Svensson, Elin, 1980, et al.
(författare)
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An optimization methodology for identifying robust process integration investments under uncertainty
- 2009
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Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215. ; 37:2, s. 680-685
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainties in future energy prices and policies strongly affect decisions on investments in process integration measures in industry. In this paper, we present a five-step methodology for the identification of robust investment alternatives incorporating explicitly such uncertainties in the optimization model. Methods for optimization under uncertainty (or, stochastic programming) are thus combined with a deep understanding of process integration and process technology in order to achieve a framework for decision-making concerning the investment planning of process integration measures under uncertainty. The proposed methodology enables the optimization of investments in energy efficiency with respect to their net present value or an environmental objective. In particular, as a result of the optimization approach, complex investment alternatives, allowing for combinations of energy efficiency measures, can be analyzed. Uncertainties as well as time-dependent parameters, such as energy prices and policies, are modelled using a scenario-based approach, enabling the identification of robust investment solutions. The methodology is primarily an aid for decision-makers in industry, but it will also provide insight for policy-makers into how uncertainties regarding future price levels and policy instruments affect the decisions on investments in energy efficiency measures.
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| 7. |
- Svensson, Elin, 1980, et al.
(författare)
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Benefits of using an optimization methodology for identifying robust process integration investments under uncertainty - A pulp mill example
- 2009
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Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215. ; 37:3, s. 813-824
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a case study on the optimization of process integration investments in a pulp mill considering uncertainties in future electricity and biofuel prices and CO2 emissions charges. The work follows the methodology described in Svensson et al. [Svensson, E., Berntsson, T., Strömberg, A.-B., Patriksson, M., 2008b. An optimization methodology for identifying robust process integration investments under uncertainty. Accepted for publication in EnergyPolicy] where a scenario-based approach is proposed for the modelling of uncertainties. The results show that the proposed methodology provides a way to handle the time dependence and the uncertainties of the parameters. For the analyzed case, a robust solution is found which turns out to be a combination of two opposing investment strategies. The difference between short-term and strategic views for the investment decision is analyzed and it is found that uncertainties are increasingly important to account for as a more strategic view is employed. Furthermore, the results imply that the obvious effect of policy instruments aimed at decreasing CO2 emissions is, in applications like this, an increased profitability for all energy efficiency investments, and not as much a shift between different alternatives.
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| 8. |
- Svensson, Elin, 1980, et al.
(författare)
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Economy and CO2 emissions trade-off: A systematic approach for optimizing investments in process integration measures under uncertainty
- 2010
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 30:1, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a systematic approach for taking into account the resulting CO2 emissions reductions from investments in process integration measures in industry when optimizing those investments under economic uncertainty. The fact that many of the uncertainties affecting investment decisions are related to future CO2 emissions targets and policies implies that a method for optimizing not only economic criteria, but also greenhouse gas reductions, will provide better information to base the decisions on, and possibly also result in a more robust solution. In the proposed approach we apply a model for optimization of decisions on energy efficiency investments under uncertainty and regard the decision problem as a multiobjective programming problem. The method is applied to a case of energy efficiency investments at a chemical pulp mill. The case study is used to illustrate that the proposed method provides a good framework for decision-making about energy efficiency measures when considerations regarding greenhouse gas reductions influence the decisions. We show that by setting up the problem as a multiobjective programming model and at the same time incorporating uncertainties, the trade-off between economic and environmental criteria is clearly illustrated.
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| 9. |
- Svensson, Elin, 1980, et al.
(författare)
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Economy and CO2 emissions trade-off: A systematic approach for optimizing investments in process integration measures under uncertainty
- 2008
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Ingår i: PRES - 11th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, 24 - 28 August 2008, Prague, Czech Republic.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we present a systematic approach for taking into account the resulting CO2 emissions reductions from investments in process integration measures in industry when optimizing those investments under economic uncertainty. The fact that many of the uncertainties affecting investment decisions are related to future CO2 emissions targets and policies implies that a method for optimizing not only economic criteria, but also greenhouse gas reductions, will provide better information to base the decisions on, and possibly also result in a more robust solution. In the proposed approach we apply a model for optimization of decisions on energy efficiency investments under uncertainty and regard the decision problem as a multiobjective programming problem. The method is applied to a case of energy efficiency investments at a chemical pulp mill. The case study is used to illustrate that the proposed method provides a good framework for decision-making about energy efficiency measures when considerations regarding greenhouse gas reductions influence the decisions. We show that by setting up the problem as a multiobjective programming model and at the same time incorporating uncertainties, the trade-off between economic and environmental criteria is clearly illustrated.
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| 10. |
- Svensson, Elin, 1980, et al.
(författare)
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Operational Flexibility in Pulp Mill Steam Production at Off-design Heat Loads
- 2013
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Ingår i: Chemical Engineering Transactions. - 2283-9216. - 9788895608266 ; 35, s. 919-924
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on the steam production in a chemical pulp mill that is retrofitted to reduce its processheating demand. A multi-period optimization model for design decisions is proposed that takes intoaccount the operational limits of the steam production units as well as the heat load variations over theyear. Large variations in combination with the retrofit that causes off-design loads in the steam productionsystem will influence the flexibility of the steam system. Minimum boiler load limits will then be a greaterconstraint on operation since the average load of boilers is moved closer to the minimum for longer periods of time. A conventional approach that considers fixed annual averages of process parameters therefore risks leading to sub-optimal solutions because of neglecting the variations in heat demand and the operational limits. The multi-period approach suggested in this paper considers this operationalflexibility associated with different design choices. A case study based on a Kraft pulp mill with a recoveryboiler and a bark boiler shows the benefit of properly modelling the varying heat demand. Numerical results are presented that compares the results of the multi-period model with that of a conventional annual average approach. Differences in design decisions, energy balances and economic performance are demonstrated and discussed.
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