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[en] A phenomenological equation of exergy transfer, which indicates the relation between exergy flux, exergy resistance and exergy driving forces, is derived by applying non-equilibrium thermodynamics to second law analysis, and simultaneously the expressions of the coefficients of exergy transfer are obtained. The results show that exergy transfers in different forms interact on each other. This study also proposes a simplified expression of exergy transfer coefficients by neglecting some minor engineering couplings in exergy transfers. Furthermore, a mixture consisting of two components is discussed. As an application of this result, thermal exergy transfer within a flat plate is studied
[en] The coal tar was purified by the addition of quinoline and Zn(OH)2, in order to decrease the content of carbon and inorganic oxide particles. The effect on the viscosity and ash content of the coal tar were investigated by altering temperature, time, and the amount of quinolone and Zn(OH)2 . When the volume ratio between quinolone and coal tar was 20:1 and the static time was 24 h. The viscosity of three layers decreased with rising temperature. When the static temperature and time was 45 °C and 24 h, respectively. The viscosity of three layers decreased with the arising amount of quinoline. And when the volume ratio between quinolone and coal tar was 20:1 and the temperature was 45 °C. The viscosity of three layers decreased first and then increased with the prolonging of static time. And when the static time of coal tar was 24 h, the viscosity of coal tar is the lowest. Because of the lower viscosity of coal tar, decreasing the content of carbon and ash particles in upper and middle layer, the ash content decreased from 0.168% to 0.092%. The addition of Zn(OH)2 can lead ash content in middle layer decrease to 0.058%. Zn2SiO4 and ZnAl2O4 may be produced due to the reaction between Zn (OH) 2 and SiO2 or Al2O3, which can settle down easily. The results show that the content of carbon and inorganic oxide particles in upper-middle-class (the middle 4/5 of the whole volume) decreased with the addition of quinolone and Zn(OH)2 . When the volume ratio between quinolone and coal tar was 50:2, quality ratio between coal tar and Zn(OH)2 was 20000:1, the mixture were heated up to 45 °C at atmospheric pressure and keeping this constant temperature for 24 h, the ash content in upper-middle-class can decreased to 0.058%. (author)
[en] Our previous study disclosed that fluridone, a synthesis inhibitor of abscisic acid (ABA), could stimulate seed germination in the holoparasitic plant Cistanche tubulosa . Nonetheless, the underlying mechanisms have not been thoroughly elucidated. In the present study, an attempt was made to reveal the mechanism of fluridone breaking seed dormancy in C. tubulosa and to determine the contribution of hormones in this process. The ABA level in seeds initially decreased following fluridone treatment and was subsequently maintained at a concentration of 31 ng g/sup -1/ DW (dry weight) three days later. The contents of gibberellins (GAs) initially in creased and subsequently were maintained at a level of 40 ng g-1 DW after ten days. However, the increment of seed germination induced by fluridone was inhibited after the introduction of exogenous ABA or paclobutrazol (a synthesis inhibitor of GAs). Furthermore, inhibition from paclobutrazol was reversed by an additional treatment with exogenous GA3. When the ratio of endogenous GAs to ABA reached 4:3, C. tubulosa seeds initiated germination. By contrast, although the ratio of endogenous GAs to ABA content reached 2:1 by cold stratification, C. tubulosa seeds could not germinate unless exogenous GA3 was added. In summary, our current study revealed that (i) GAs and ABA play key roles for the seed germination of C. tubulosa , (ii) fluridone inhibited ABA biosynthesis but increased the concentration of GAs in seeds, and (iii) fluridone might initiate other processes associated with germination. (author)
[en] In a refining complex, an absorption-stabilization process used in the production of end-use petro-products (i.e. stable gasoline and liquefied petroleum gas) is energy-intensive and costly. A new absorption-stabilization process with a two-stage condensation section is introduced in this work to further improve energy-use performance. In the new process, a condenser, a condensed oil tank, and a side-reboiler are integrated into the original process and then a heat integration scheme is performed. Compared with the existing process, the proposed process can reduce the cold utility and hot utility by 17.98% and 25.65%, respectively, as well as decrease the total annual operating costs of the heat exchanger network by 17.48%. Additionally, the process retrofit reduces the annual operating costs of cooling water and steam by about $346,617 at the expense of capital costs around $487,006, and the corresponding payback period is approximately 17 months. - Highlights: • Energy analysis is proposed for the existing absorption-stabilization process. • A new absorption-stabilization process is presented to reduce energy requirement. • A side-reboiler is introduced for the heat integration of the new process. • HENs are designed and compared between the existing and new processes.
[en] Graphical abstract: Integration between process units and utility systems. - Highlights: • Process units and utility systems are integrated for total refining site optimization. • An MINLP model is presented to optimize materials and energy simultaneously. • Energy requirements of process units are formulated based on transshipment model. • The method does a good tradeoff between the material profit and energy cost. - Abstract: A process system is designed for material transformations that produce certain functional chemicals while usually consuming large amounts of energy. Materials in process systems have long been the major focus of investigation to achieve better economic performance. Rising energy prices and stricter limitations on greenhouse gas emissions have also led to greater attention on energy savings. The configuration of process units in a total refining site has a great impact on both material and energy requirements. The simultaneous optimization of materials and energy is highly important for an enterprise. Hence, material and energy integration is proposed in this study for a total refining site to minimize costs. A mixed integer nonlinear programming model is developed that includes four parts: production planning for materials, energy requirements of process units on the basis of pinch analysis, operational planning for utility systems, and balance of utility streams in total sites. An industrial example is studied to demonstrate the performance of the proposed model and the advantages of simultaneous optimization of materials and energy. Significant economic benefits are demonstrated by the simultaneous optimization in this study