| 1. |
- Svensson, Elin, 1980, et al.
(author)
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Assessing the value of a diversified by-product portfolio to allow for increased production flexibility in pulp mills
- 2020
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In: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 35:4, s. 533-558
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Journal article (peer-reviewed)abstract
- This paper presents a model for design optimization of pulp mill steam utility systems subject to variations in energy prices and steam demands. A Scandinavian Kraft pulp mill is used as case study to investigate investment opportunities in lignin extraction and new turbines. The model enables solutions to be identified that are more flexible than the solutions that would have been identified with a corresponding model using, for example, annual average values for key input data. The results from the case study show that lignin extraction has a potential to contribute to flexibility in pulp mill electric power production under certain conditions provided that the mill invests in both lignin extraction and condensing turbine capacity. However, the potential electric power production flexibility will vary over time. In the studied mill, with a capacity increased to around 1.3 million tonnes/a of pulp, it is estimated to vary between 15 and 30 MW. Furthermore, investment in new condensing turbine capacity only seems to be attractive if electricity prices that are considerably higher than the spot prices of recent years are assumed. Such prices may occur if there is a clear value of tradable electricity certificates or if future electricity prices rise significantly.
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| 2. |
- Biermann, Max, 1989, et al.
(author)
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Partial capture from refineries through utilization of existing site energy systems
- 2021
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In: 15th Greenhouse Gas Control Technologies Conference 2021, GHGT 2021. - : Elsevier BV.
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Conference paper (peer-reviewed)abstract
- Many studies indicate that carbon capture and storage operations need to be ramped up in the coming decades to limit global warming to well-below 2°C. Partial CO2 capture from carbon-intensive industrial processes is a promising starting point for initial CO2 transport and storage infrastructure projects, such as the Norwegian full-chain CCS project “Northern Lights”, since specific capture cost (€/t CO2) for single-stack capture can be kept low compared to full capture from all, often less suitable stacks. This work highlights the importance of utilizing existing site energy systems to avoid significant increase in marginal abatement cost when moving from partial to full capture. A systematic and comprehensive techno-economic approach is applied that identifies a mix of heat supply sources with minimum cost based on a detailed analysis of available heat and capacity within the existing site energy system. Time-dependent variations are considered via multi-period, linear optimization. For single-stack capture from the hydrogen production unit (~0.5 Mt CO2 p.a.) of a Swedish refinery in the context of the current energy system, we find avoidance cost for the capture plant (liquefaction, ship transport, and storage excluded)of 42 €/t CO2-avoided that is predominantly driven by steam raised from available process heat in existing coolers (~6 €/t steam). For full capture from all major stacks (~1.4 Mt CO2 p.a.), the avoidance cost becomes twice as high (86 €/t CO2-avoided) due to heat supply from available heat and existing boiler capacity (combustion of natural gas) at costs of ~20€/t steam. The analysis shows that very few investments in new steam capacity are required, and thus, that the utilization of existing site energy systems is important for lowering capture cost significantly, and thus the whole-chain cost for early CCS projects.
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| 3. |
- Biermann, Max, 1989, et al.
(author)
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The role of energy supply in abatement cost curves for CO2 capture from process industry – a case study of a Swedish refinery
- 2022
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 319
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Journal article (peer-reviewed)abstract
- Carbon capture and storage (CCS) activities need to be ramped up to meet the climate crisis. Abatement cost curves help identify low-cost starting points and formulate roadmaps for the implementation of CCS at industrial sites. In this work, we introduce the concept of energy supply cost curves to enhance the usefulness and accuracy of abatement cost curves. We use a multi-period mixed-integer linear program (MILP) to find an optimal mix of heat sources considering the existing site energy system. For a Swedish refinery, we found that residual heat and existing boiler capacities can provide the heat necessary for CCS that avoids more than 75% of the site emissions. Disregarding the existing site energy system and relying on new capacities instead, would lead to capture costs that are 40-57% higher per tonne of CO2-avoided (excl. CO2 liquefaction, transport, and storage). Furthermore, we quantified the impact of temporal variations of heat sources (intermittent residual heat) on the cost and emissions of heat supply to 7-26% and 9-66%, respectively. The conducted optimization of the energy supply mix under consideration of temporal variations leads to detailed estimates of energy supply costs ranging from partial to full CO2 capture, and thus, improve abatement cost curves.
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| 4. |
- Langner, Christian, 1990, et al.
(author)
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A computational tool for analysing the response of complex heat exchanger networks to disturbances
- 2019
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In: PROCEEDINGS OF ECOS 2019 - THE 32ND INTERNATIONAL CONFERENCE ON EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS. ; 2019, s. 611-623
-
Conference paper (peer-reviewed)abstract
- The heat exchanger networks (HEN) in industrial heat recovery systems often consist of large and complex subsystems. Calculating the response of such HENs to disturbances, such as varying inlet conditions or changing heat transfer capacities, may be challenging due to the presence of, e.g. stream splits and recycle loops. Extensive modelling and/or trial and error calculations may be necessary. This applies also for the analysis of different retrofit proposals. Retrofit opportunities in industrial heat recovery systems are often constrained by operability considerations, i.e. retrofit actions are supposed to have as little impact as possible on the production process to maintain the quality of the core product. Consequently, there is a clear demand for a tool to effectively screen design proposals at an early stage in the design process. In this work, a computational analysis tool is proposed to meet this demand. The proposed analysis tool allows fast evaluation of the network response when operating conditions change and/or operational settings are manipulated, and it is applicable for a wide range of HEN structures. The practical use of the analysis tool is demonstrated in a case study on the HENs of a large state-of-the-art Kraft pulp mill.
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| 5. |
- Langner, Christian, 1990, et al.
(author)
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A computational tool for guiding retrofit projects of industrial heat recovery systems subject to variation in operating conditions
- 2021
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In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 182
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Journal article (peer-reviewed)abstract
- Heat exchanger networks (HEN) in industrial heat recovery systems often consist of large and complex subsystems. Usually, such HENs are subject to variation in operating conditions, such as varying inlet conditions or changing heat capacity flow rates. Additionally, complexities such as stream splits and recycle loops are commonly present in industrial HENs. Therefore, extensive modelling and/or analytical calculations may be necessary when analyzing different retrofit proposals. Furthermore, retrofit opportunities in industrial heat recovery systems are often constrained by operability considerations, i.e. retrofit actions are supposed to have as little impact as possible on the production process to maintain the quality of the core product. In this work, a computational analysis tool is proposed for effective screening of HEN retrofit design proposals at an early stage in the design process. The proposed tool enables fast evaluation of the network's response, i.e. temperatures and heat loads, when operating conditions change and/or operational settings are manipulated, and it is applicable for a wide range of HEN structures. The practical use of the analysis tool is demonstrated in a case study on the HENs of a large modern Kraft pulp mill.
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| 6. |
- Langner, Christian, 1990, et al.
(author)
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A framework for flexible and cost-efficient retrofit measures of heat exchanger networks
- 2020
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In: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:6
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Journal article (peer-reviewed)abstract
- Retrofitting of industrial heat recovery systems can contribute significantly to meeting energy efficiency targets for industrial plants. One issue to consider when screening retrofit design proposals is that industrial heat recovery systems must be able to handle variations, e.g., in inlet temperatures or heat capacity flow rates, in such a way that operational targets are reached. Consequently, there is a need for systematic retrofitting methodologies that are applicable to multiperiod heat exchanger networks (HENs). In this study, a framework was developed to achieve flexible and cost-efficient retrofit measures of (industrial) HENs. The main idea is to split the retrofitting processes into several sub-steps. This splitting allows well-proven (single period) retrofit methodologies to be used to generate different design proposals, which are collected in a superstructure. By means of structural feasibility assessment, structurally infeasible design proposals can be discarded from further analysis, yielding a reduced superstructure. Additionally, critical point analysis is applied to identify those operating points within the uncertainty span that determine necessary overdesign of heat exchangers. In the final step, the most cost-efficient design proposal within the reduced superstructure is identified. The proposed framework was applied to a HEN retrofit case study to illustrate the proposed framework.
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| 7. |
- Langner, Christian, 1990
(author)
-
Advances in optimal design and retrofit of chemical processes with uncertain parameters - Applications in design of heat exchanger networks
- 2023
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Doctoral thesis (other academic/artistic)abstract
- There is widespread consensus that the omnipresent climate crisis demands humanity to rapidly reduce global greenhouse gas (GHG) emissions. To allow for such a rapid reduction, the industrial sector as a main contributor to GHG emissions needs to take immediate actions. To mitigate GHG emissions from the industrial sector, increasing energy efficiency as well as fuel and feedstock switching, such as increased use of biomass and (green) electricity, are the options which can have most impact in the short- and medium-term. Such mitigation options usually create a need for design of new or redesign of existing processes such as the plant energy systems. The design and operation of industrial plants and processes are usually subject to uncertainty, especially in the process industry. This uncertainty can have different origins, e.g., process parameters such as flow rates or transfer coefficients may vary (uncontrolled) or may not be known exactly. This thesis proposes theoretical and methodological developments for designing and/or redesigning chemical processes which are subject to uncertain operating conditions, with a special focus on heat recovery systems such as heat exchanger networks. In this context, this thesis contributes with theoretical development in the field of deterministic flexibility analysis. More specifically, new approaches are presented to enhance the modelling of the expected uncertainty space, i.e., the space in which the uncertain parameters are expected to vary. Additionally, an approach is presented to perform (deterministic) flexibility analysis in situations when uncertain long-term development such as a switch in feedstocks interferes with operational short-term disturbances. In this context, the thesis presents an industrial case study to i) show the need for such a theoretical development, and ii) illustrate the applicability. Aside of advances in deterministic flexibility analysis, this thesis also explores the possibility to combine valuable designer input (e.g. non-quantifiable knowledge) with the efficiency of mathematical programming when addressing a design under uncertainty problem. More specifically, this thesis proposes to divide the design under uncertainty problem into a design synthesis step which allows direct input from the designer, and several subsequent steps which are summarized in a framework presented in this thesis. The proposed framework combines different approaches from the literature with the theoretical development presented in this thesis, and aims to identify the optimal design specifications which also guarantee that the the final design can operate at all expected operating conditions. The design synthesis step and the framework are decoupled from each other which allows the approach to be applied to large and complex industrial case studies with acceptable computational effort. Usage of the proposed framework is illustrated by means of an industrial case study which presents a design under uncertainty problem.
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| 8. |
- Langner, Christian, 1990, et al.
(author)
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Combined Flexibility and Energy Analysis of Retrofit Actions for Heat Exchanger Networks
- 2019
-
In: Chemical Engineering Transactions. - 2283-9216 .- 2283-9216. ; 76, s. 307-312
-
Journal article (peer-reviewed)abstract
- Retrofitting of industrial process heat recovery systems can contribute significantly to meeting energy efficiency targets for industrial process plants. One issue to consider when screening retrofit design options is that industrial heat recovery systems must be able to handle external variations, e.g. in ambient temperature, in such a way that operational targets are reached. There exist different approaches to incorporate flexibility considerations in the design process of retrofit proposals for heat exchanger networks (HEN). However, due to mathematical complexity, lack of suitable cost data, and difficulty to handle large-scale systems, the adoption of those methods in industrial retrofit projects has been limited. Therefore, this paper proposes to decouple the design and analysis steps in retrofitting processes. This allows well-proven retrofit design methods to be used in the design step to generate different alternatives. These design alternatives are thereafter evaluated in a separate analysis step in which the initial set of designs is narrowed down to one or several design options that are operable and energy efficient for a priori defined variations of operating conditions. The proposed approach is based upon traditional flexibility analysis combined with energy performance analysis. With such performance data available, a fair evaluation over different operating points can be obtained. The proposed approach is used for analysing the flexibility and energy performance of a HEN case study to illustrate its application.
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| 9. |
- Langner, Christian, 1990, et al.
(author)
-
Flexibility analysis of chemical processes considering dependencies between uncertain parameters
- 2021
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In: Computer Aided Chemical Engineering. - 1570-7946. ; 50, s. 1105-1110
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Book chapter (other academic/artistic)abstract
- Chemical processes are usually subject to varying operating conditions. Consequently, the evaluation of the flexibility of a process with respect to variations in inlet conditions is vital to identify bottlenecks in current process flowsheets or new flowsheet design proposals. The flexibility index is a well-established concept to perform flexibility analysis of chemical processes. In this paper, we propose a novel approach to incorporate knowledge regarding dependencies between input parameters when calculating the flexibility index. The aim is to achieve a more accurate indication of a process's flexibility when dependencies between input parameters are present.
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| 10. |
- Langner, Christian, 1990, et al.
(author)
-
Flexibility analysis of chemical processes considering overlaying uncertainty sources
- 2022
-
In: Computer Aided Chemical Engineering. - 1570-7946. ; 49, s. 769-774
-
Conference paper (peer-reviewed)abstract
- Chemical processes are often subject to uncertainty. Consequently, the evaluation of the flexibility of a process with respect to variations in inlet conditions is vital to identify bottlenecks in current process flowsheets or new flowsheet design proposals. The flexibility index is a well-established concept to perform flexibility analysis of chemical processes. In this paper, we propose novel reformulations of the flexibility index problem to account for overlaying uncertainty sources which interfere with each other. The aim of the paper is to identify and define overlaying uncertainty sources and to overcome shortcomings of existing approaches when calculating the flexibility index in such situations.
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