دانلود رایگان مقاله انگلیسی مدل دو گانه برای هدف یابی بازسازی فرایند، کاربردی برای فرایند خمیر و کاغذ به همراه ترجمه فارسی
| عنوان فارسی مقاله | مدل دو گانه برای هدف یابی بازسازی فرایند، کاربردی برای فرایند خمیر و کاغذ |
| عنوان انگلیسی مقاله | A dual representation for targeting process retrofit, application to a pulp and paper process |
| رشته های مرتبط | مهندسی مکانیک، مهندسی سیالات و تبدیل انرژی |
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| کیفیت ترجمه | کیفیت ترجمه این مقاله متوسط میباشد |
| نشریه | الزویر – Elsevier |
| مجله | مهندسی حرارتی کاربردی – Applied Thermal Engineering |
| سال انتشار | 2005 |
| کد محصول | F805 |
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فهرست مقاله: چکیده |
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بخشی از ترجمه فارسی مقاله: 1-مقدمه 6- نتیجه گیری |
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بخشی از مقاله انگلیسی: 1. Introduction The optimal design of a utility system should seek to meet the energy requirements of the process that it serves at a minimal cost. Pinch analysis [1] is a mature technology, which has been applied with success to the design of heat exchange networks (HEN) in a broad variety of industries including the pulp and paper industry [2]. In the targeting step performed before the HEN design, the minimum energy requirement to heat and cool all process streams to their functional specifications is first established. However, the method, as first proposed, is not well suited to tackle certain issues encountered when attempting to increase the energy efficiency of a process beyond the maximum internal heat recovery that can be achieved by implementing an optimised HEN. Furthermore, it only deals with the reduction of the heat requirement rather than reducing the process energy expenses. Heuristic rules were first proposed by the developers of pinch analysis to provide guidance for the selection and the appropriate integration in a process of energy converting equipment such as turbines and heat pumps [3,4] while the concept of balanced composite curves [5,6] also broadened the scope of conventional pinch analysis to this type of application and the systematic search for solutions was made possible by developments of adapted optimisation algorithms [7]. The introduction of exergy composite curves [8] brought a new perspective to the identification and evaluation of process enhancement opportunities involving energy upgrading and conversion. Maximising the flowrate of the cheapest utility leads to the creation of utility pinch points [5,6] and underscores the need to analyse simultaneously the utility and the process networks. Graphical techniques become impractical when cycles are concerned. A method based on the use of optimisation techniques [10,12,13] and the corresponding graphical representations [9] has therefore been proposed by Marechal and Kalitventzeff. The cost of energy is a very significant factor in pulp and paper manufacturing [16] and the industry has invested many efforts to reduce it over the year [17]. System closure, i.e. the internal reuse of excess process water, using simulation and observation [20,21] or optimisation techniques [22], often entails a significant reduction in energy cost [18,19] and should be a preliminary to any energy optimisation project. For energy analysis per se, Pinch analysis has now become a routine tool and incursions have been made in extensions of the technique to specific cases such as, temperature mitigation by process streams mixing [23,24] or evaporator trains optimisation [25]. Effect modelling and optimisation concepts have also been applied in design methodologies related to reactive systems [15], or combining energy efficiency and environmental concerns [14,26]. The purpose of this work has been to develop a new method based on pinch analysis techniques and optimisation to identify and evaluate, at a very early stage of the study, the opportunities for reducing energy costs by improving the energy conversion in the process. 6. Conclusion The dual representation of thermodynamic and technological energy requirements has proved to be a valuable tool for the early stages of process energy analysis. By use of an optimisation procedure, energy saving opportunities can be quantified in terms of fuel and electricity costs and with regard to the CHP production. It should be used as a preliminary step in a retrofitting procedure to help identify and assess options prior to further analysis. Pinch analysis, exergy analysis and optimisation techniques have been combined to define energy targets at the system level expressed in terms of the energy costs rather than energy requirements. The illustration of the method by the analysis of a pulp and paper mill has been instrumented in identifying and gaining insight on process retrofitting options for reducing the energy penalty and maximising the energy conversion efficiency. In both representations, the possibility of recovering secondary refiner steam has been considered. An energy saving of 29.7MW (22%) with an increase of 19.7MWe in the CHP production has been targeted. In comparison with the technological requirements, replacing the steam injections to whitewater reservoir by heat exchangers would reduce the MERby 4.2MW and increase the CHP production from 12.7MWe to 21.9MWe while incurring an increase of only 5.6MWLHV in the natural gas consumption. Minimising the exergy losses related to the current paper drying conditions appears to be less attractive since it would only increase the CHP production by 2.9MWe (12%) with no significant reduction of the fuel consumption. This stresses the importance of separately analysing the energy requirements of the drying section in order to justify the different pressure levels at which steam is supplied. |