| 1. |
- Andersson, Eva Ingeborg Elisabeth, 1956, et al.
(författare)
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Comparison of pulp-mill integrated hydrogen production from gasified black liquor with stand-alone production from gasified biomass
- 2005
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Ingår i: Proceedings of ECOS 2005. - 8251920418 ; 3, s. 1131-1138
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Konferensbidrag (refereegranskat)abstract
- When gasified black liquor is used for hydrogen production at a pulp mill site, significant amounts of biomass must be imported. This paper compares two alternative options for producing hydrogen from biomass: (A) pulp mill integrated hydrogen production from gasified back liquor; and (B) stand-alone production of hydrogen from gasified biomass. The comparison assumes that the same amount of biomass that is imported in alternative A is supplied to a stand-alone hydrogen production plant and that the gasified black liquor in alternative B is used in a BLGCC (Black Liquor Gasification Combined Cycle) CHP unit. The comparison is based upon equal amounts of black liquor fed to the gasifier, and identical steam and power requirements for the pulp mill. The potential for delivering low temperature excess heat to a district heating system is considered. The two systems are compared on the basis of total CO2 emission consequences, based upon different assumptions for the reference energy system that reflect different societal CO2 emissions reduction target levels. If the reference energy system includes electricity production in coal-fired power plants without CO2 sequestration and car engines that are 30% more efficient than todays , the best alternative is to use the biomass in a stand-alone hydrogen production unit. However, if electricity production has lower CO2 emissions , hydrogen produced with gasified black liquor integrated in the pulp mill can achieve the largest CO2 emissions reduction.
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| 2. |
- Fredriksson Möller, Björn, et al.
(författare)
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On the off-design of a natural gas-fired combined cycle with CO2 capture
- 2005
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Ingår i: Proceedings of Ecos 2005, Vols 1-3 - Shaping our future energy systems. - 8251920418 ; , s. 811-818
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Konferensbidrag (refereegranskat)abstract
- During the last 15 years cycles with CO2 capture have been in focus, due to the growing concern over our climate. Often a natural-gas fired combined cycle with a chemical absorption plant for CO2 capture from the flue gases have been used as a reference in comparisons between cycles. The integration of the steam production in the cycle to minimise the drop in efficiency have not been extensively studied. Neither have there been any studies on the off-design behaviour of such a plant if it should be built. In this paper the integration of steam production for regeneration of the amines is modelled at design load and studied in off-design conditions for a combined cycle. Different ambient conditions and part-load strategies and their influence on the cycle performance are also examined. Of particular interest is a novel strategy with the possibility of longer life of gas turbine blading, with marginal loss in efficiency. The off-design performance of the combined cycle is modelled in a rigorous way, using a gas turbine performance deck to calculate the performance of the gas turbine. The boiler is calculated using simplified correlations for off-design heat transfer and pressure drop. The steam turbine calculation is based on verified models for the flow - pressure - efficiency relations, whilst the steam condenser is based on the HEI (Heat Exchange Institute) method.
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| 3. |
- Lauenburg, Patrick, et al.
(författare)
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Cascading and radiator flow optimization in district heating substations and advanced customer accounting - In pursuit of improved cooling
- 2005
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Ingår i: Proceedings of Ecos 2005, Vols 1-3 - Shaping our future energy systems. - 8251920418 ; , s. 1035-1042
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Konferensbidrag (refereegranskat)abstract
- Ibis paper deals with various methods of improved cooling of primary water in district heating (DH) substations and evaluates the benefit of an improved cooling from the perspective of the construction of an appropriate customer accounting method. The general benefit of an improved cooling is well-known: Less thermal stresses in pipelines, lowered heat and pumping losses and increased capacity in the network, improved efficiency of combined heat and power plants and other types of generating plants using heat pumps, waste heat and flue gas condensation. To stimulate improved cooling in customer owned DH substations, some Swedish DH companies apply a method of customer accounting based not only on heat energy consumption but also on primary water usage and mean water cooling. This benefits customers with thermodynamically well-functioning substations, i.e. a proper cooling, at the expense of customers with less well-functioning substations. The extension of 'flow accounting' has been mapped and found to be applied for a majority of the delivered heat. It represents an important incentive for proper cooling in substations. The study has found that the size of the flow accounting generally very well reflects the benefits for the DH company from an improved cooling. The amount of cooling of DH primary water achieved in DH substations depends on the employed connecting scheme. In a recent study, we demonstrated that adopting three-stage cascading could achieve significant improvements in this respect. The economical aspects on this subject are here further mapped out based on the results from the study of flow accounting. Optimized and properly functioning substation and secondary systems are, from an economical perspective, of at least equal interest as the choice of connection scheme. Especially if there is an existing oversizing of the radiators, considerably larger savings can be made if optimized control of the radiator circuit is employed.
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| 4. |
- Leduc, Sylvain, et al.
(författare)
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A feasibility study of black liquor booster gasification with borate autocausticizing
- 2005
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Ingår i: ECOS 2005 - Proceedings of the 18th International Conference on Efficiency, Cost, Optimization, Simulation, and Environmental Impact of Energy Systems. - Trondheim : Tapir Academic Press. - 8251920418 ; , s. 1533-1539
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Konferensbidrag (refereegranskat)abstract
- Black liquor constitutes a huge energy potential. In order to improve the efficiency of a pulp mill, this study is focussed on borate autocausticizing, which has proved to work efficiently in recovery boilers. The leading idea is to complete an overloaded recovery boiler with a booster gasifier. In this configuration, the black liquor is gasified with air at low overpressure. Results regarding conventional black liquor gasification are close to the reality and very promising. Regarding black liquor gasification with borate, lack of data for orthoborate, like the Gibbs free energy, did not enable good results. The model so far is a good starting point for black liquor gasification studies, and needs to be improved as soon as new data on borates will be available.
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| 5. |
- Li, Hailong, et al.
(författare)
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A new modification on RK EOS for gaseous carbon dioxide
- 2005
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Ingår i: ECOS 2005 - Proceedings of the 18th International Conference on Efficiency, Cost, Optimization, Simulation, and Environmental Impact of Energy Systems. - 8251920418 ; , s. 733-739
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Konferensbidrag (refereegranskat)abstract
- Mitigation technologies including CO2 capture and storage in various energy conversion systems have been intensively developed in recent years. However, it is of importance to develop an equation of state (EOS) with simple structure and reasonable accuracy for engineering application for both pure CO2 and CO2 mixtures. In this paper, Redlich-Kwong equation of state was modified for gaseous CO2. In the new modification, parameter 'a' was correlated as a function of temperature and pressure from reliable experimental data in the range: 220K to 750K and 0.1MPa to 400MPa. To verify the accuracy of the new parameters, densities were calculated and compared with experimental data. The average error is 1.68 %. Other thermodynamic properties of CO2, such as enthalpy and heat capacities, were also calculated; results fit experimental data well except critical region. This method can be further developed for CO2 mixture systems.
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| 6. |
- Li, Hailong, et al.
(författare)
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Quantitative evaluations on available models for calculating thermodynamic properties of humid air
- 2005
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Ingår i: ECOS 2005 - Proceedings of the 18th International Conference on Efficiency, Cost, Optimization, Simulation, and Environmental Impact of Energy Systems. - 8251920418 ; , s. 889-896
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Konferensbidrag (refereegranskat)abstract
- Engineering calculation of the thermodynamic properties for cycle simulation and design requires simple but reliable models. This has been proved to be of importance for the research and development on humidified gas turbines, such as humid air turbine (HAT) cycles and compressed air energy storage (CAES). This paper has made a comprehensive review and comparison among different models for calculating thermodynamic properties of the humid air mixtures, including ideal gas model (IG), ideal mixing model (IM), and real gas model (RG); and based on temperature and pressure range, gave quantitative evaluations on saturated water vapor composition and enthalpy. Based on performance conditions of an HAT cycle, several suggestions were given for the use of the today's available models for engineering cycle calculations, which can provide accurate results for cycle performance analysis and design while keeping the methods straightforward.
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| 7. |
- 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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| 8. |
- Persson, Tommy, et al.
(författare)
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Field studies of domestic hot water comfort in semi-detached houses during summertime
- 2005
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Ingår i: Proceedings of Ecos 2005, Vols 1-3 - Shaping our future energy systems. - 8251920418 ; , s. 1053-1061
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Konferensbidrag (refereegranskat)abstract
- The paper describes measurements performed in three district heating (DH) substations in semidetached houses. In all these houses more than 40 % of the domestic hot water (DHW) tappings turned out to be shorter than 10 s. The fraction of total energy used to heat this water varied between 2.4 % and 10.2 %, indicating a large influence of households' daily habits. For 60-78 % of tappings, the total amount of supplied DH water volume was below 2.5 litres, which underlines the importance of using small volume pulses for the energy metering. When analysing the off-load behaviour of the DH substations it was established that radiator circuit control valves for the most part of the studied period were working on/off. During periods when there was no radiator load, the primary supply temperature was typically 50-60 degrees C, which was higher than expected. The differences in supply temperature level between the substations might be caused by leaking valves or by differences in off-load set point temperature of DHW control valves. Furthermore, the measurements indicate large differences among DHW controllers regarding the characteristics of the feed-forward control. In more than 80 % of the tappings with duration of more than 10 s, an outgoing DHW temperature of at least 40 degrees C was obtained within a maximum of 10 s. However, depending on the house studied, in 17-55 % of those tappings the monitored DHW temperature did not reach the level of at least 50 degrees C, as required by the Swedish District Heating Association.
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