| 1. |
- Bengtsson, Cecilia, 1974, et al.
(författare)
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Utilization of excess heat in the pulp and paper industry - a case study of technical and economic opportunities
- 2002
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Ingår i: Applied Thermal Engineering. - 1359-4311. ; 22:9, s. 1069-1081
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Tidskriftsartikel (refereegranskat)abstract
- Newly developed methods and tools based on pinch technology are used in a case study to investigate the potential and economy of using excess heat for pre-evaporation of chemo thermo mechanical pulp effluent and heat pumping in an integrated pulp and paper mill. The new tools give information about the system that traditional pinch tools such as the grand composite curve or the composite curves would not reveal. For example, the highest temperature levels possible where excess heat can be released are identified together with the amount of excess heat at each temperature level. The new curves are also able to provide information about where heaters and coolers are placed in an existing system. The matrix method has been used successfully in order to find an economically feasible heat exchanger network retrofit for the release of the excess heat found with the curves.The results of the case study show that a pre-evaporation plant can be integrated with the overall process with just a few modifications in the existing process. There are also opportunities for heat pumping in the system. Both projects have a pay-back period shorter than required for implementation.
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| 2. |
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| 3. |
- Björk, Kaj-Mikael, et al.
(författare)
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Solving large-scale retrofit heat exchanger network synthesis problems with mathematical optimization methods
- 2005
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Ingår i: Chemical Engineering and Processing: Process Intensification. - : Elsevier BV. - 0255-2701. ; 44:8, s. 869-876
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Tidskriftsartikel (refereegranskat)abstract
- Heat exchanger network optimization is a standard problem in process design. Various mathematical models and heuristics have beendeveloped to help the designer in constructing the network. Different target procedures, like the pinch analysis, are widely used both inacademia and industry. Another approach to find cost optimal network structures is to use mathematical programming methods. The advantagewith mathematical programming methods is that a rigorous optimization of the structure, sizes of heat exchangers and utility usage can becarried out, whereas the designer makes these decisions if purely pinch-based tools are used.Even if much effort has been put on research within this area, many of the mathematical models consider only grassroot design, whereasmost practical cases today seem to be retrofit situations. In addition, these models are likely to be either rigorous but not solvable for bigger(large-scale, real life examples) or deficient and solvable for large-scale problems. This paper takes an attempt to address these problemssimultaneously and to develop a rigorous optimization framework based on both a genetic algorithm and a deterministic MINLP-approachand to present an extended model for large-scale retrofit heat exchanger network design problems.
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| 4. |
- Kovacs, Peter, et al.
(författare)
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Comparison of five approaches to solar assisted cooling
- 2009
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Ingår i: 29th Biennial Solar World Congress of the International Solar Energy Society, ISES 2009; Johannesburg; South Africa; 11 October 2009 through 14 October 2009. - 9781617388521 ; 1, s. 423-430
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Konferensbidrag (refereegranskat)abstract
- Numerous different options are available for cooling buildings using solar energy. In this theoretical study, which is also a pre study for a pilot installation, five generic technologies are compared: 1. Conventional compressor chiller fed by electricity from PV panels 2. Absorption chiller fed by a combination of medium temperature solar heat and district heating 3. Absorption chiller fed by a combination of low to medium temperature solar heat and district heating 4. Evaporative cooling (tower) fed by electricity from PV panels 5. Desiccant cooling fed by medium temperature solar heat and district heating The financial viability of each technology will essentially depend on competing supply energy tariffs, local climate, time distribution of cooling loads, the internal cooling distribution system, subsidy levels and expected operational costs. Furthermore, the buyers' choice of a system will also be affected by the fact that the technologies are in different stages of maturity. From the point of view of the district heating provider potential impact on the heating network is also of great interest. The study compares the five technologies in the light of these different aspects. The paper describes the method in more detail as well as the results of the study. The best overall conditions were found for a combination of PV powered conventional chillers which, according to calculations have a significantly lower LCC than the reference district cooling, even if subsidies are not taken into account. The concept based on free cooling from a wet cooling tower powered by PV has a much lower cost than the chiller, but the technical feasibility of this new and very energy efficient technology is not yet considered to be proven. Results from the economical analysis of solar assisted district heating powered comfort cooling varies within a wide range depending on the tariff applied for the district heat.
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| 5. |
- Nordman, Roger, 1971, et al.
(författare)
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Advanced pinch technology based composite curves for evaluating the usable excess heat potential
- 2005
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Ingår i: In proceedings of: The 18th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems. Trondheim, Norway June 22-22, 2005. - 8251920418
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Konferensbidrag (refereegranskat)abstract
- This paper describes the application of a set of advanced composite curves to evaluate the potential to release usable excess heat (hereafter referred to as Qxs) from an existing process industry. Throughout this paper Qxs is defined as heat at enough high temperature to be interesting for use e.g. for district heating. Studies using the advancedcurves reveal information about the existing HEN that traditional graphical methods are not able of, and that for almost the same collected information from the process. This allows for estimations on the heat recovery potential and existing pinch violations before detailed calculations.These curves have earlier been presented in connection with integration of CHP, HP and retrofitting HENs. The curves have also been used to evaluate the Qxs potential in one doctoral thesis, but the methodology was not explained in detail, but rather used as a tool among many. In this paper we broaden the discussion on how to use the curves, whichtraps there might be and how to interpret and use the results. Important questions that are answered are for example: How does the Qxs potential change when the pinch temperature changes? At which temperature is it possible to release Qxs? How could the Qxs be made available? How can the Qxs potential be revealed?
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| 6. |
- Nordman, Roger, 1971, et al.
(författare)
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Design of kraft pulp mill hot and warm water systems - A new method that maximizes excess heat
- 2005
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 26:4, s. 363-373
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Tidskriftsartikel (refereegranskat)abstract
- Many pulp mill hot and warm water systems are overdimensioned and produce more hot and warm water than demanded. This overproduction could be used for other applications, if heat could be released at high enough temperatures. In this paper a new method to release as much excess heat of a high temperature as possible in the secondary heat system has been developed.A case study of a Swedish kraft pulp mill showed that 5-6 MW excess heat with a temperature above 90oC could be released if the system were rebuilt. Two different alternatives for using the excess heat have been investigated.
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| 7. |
- Nordman, Roger, 1971, et al.
(författare)
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New Pinch Technology Based HEN Analysis Methodologies for Cost-Effective Retrofitting
- 2001
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Ingår i: Canadian Journal of Chemical Engineering. - : Wiley. - 1404-7098 .- 0008-4034 .- 1939-019X. ; 79:4, August 2001, s. 655-662
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, new pinch technology based curves for retrofitting of heat exchangers are presented. Advantages compared to traditional pinch curves, and the information that can be extracted from these curves, are discussed. The curves have been applied to an example where different energy saving levels has been studied. The results have been verified by detailed calculations using the Matrix method.
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| 8. |
- Nordman, Roger, 1971
(författare)
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New process integration methods for heat-saving retrofit projects in industrial systems
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New graphical methods for HEN retrofit (further development of existing tools), release of usable excess heat and placement of supply tanks in HWWS systems have been developed. In addition, further development of the matrix method for HEN retrofit has been made. The methods have been used in case studies, both as stand-alone tools, and in different combinations.Using the advanced composite curves in combination with the matrix method in HEN retrofit give new insights on which units should be picked for retrofit, and how far the heat recovery should proceed. The extra information that has to be collected to show the placement of existing heaters and coolers give valuable inputs to this method. Calculations showed that heaters and coolers placed close to the pinch are often cheaper by a factor of two and more to retrofit.A method to show the potential to release usable excess heat at high temperature levels (but still below the pinch) has been developed. This method is based on the full set of stream data from the process, and therefore shows the total potential. Case studies have shown that much of the potential is also possible to release by making changes in the HEN with acceptable investments and PBPs.Another method, to be used in HWWS systems for different setups of tanks and different values of DTmin has also been developed. This method shows the potential usable excess heat versus temperature in this sub-system for a user-defined number of supply tanks and DTmin.By studying this sub-system, a large amount of the total potential can be exploited. This leaves the remaining process without any changes at all.A new optimisation routine has been developed and implemented into the matrix method. This method uses a recursive branch and bound algorithm to explore all relevant paths in the retrofit task. A first solution is made and taken as an upper bound to the problem. All following paths that exceed this bound is directly eliminated. The implementation has proven to be reliable and fast to use, although there are still improvements to be made.
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| 9. |
- Nordman, Roger, 1971, et al.
(författare)
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Use of advanced composite curves for assessing cost-effective HEN retrofit II. Case studies
- 2009
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 29:2-3, s. 282-289
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the theory and concepts of a graphical method for heat exchanger network (HEN) retrofit that gives new insights about the complexity and possible solutions of different retrofit alternatives. The method uses knowledge about the placement of heaters/coolers in the existing HEN to evaluate the potential for cost-effective retrofit. One general result this method predicts is that the closer to the pinch the existing heaters/coolers are located, the higher the potential for cost-effective retrofit. Networks that are badly engineered from a grass-root perspective, prove to be a good basis for cost-effective retrofits.
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