查看更多>>摘要：The steam turbine network can significantly affect the energy utilization efficiency of a chemical plant. The parametric optimization of steam turbine network is investigated in this paper by using Aspen Plus software. The existing steam turbine network is Simulated first. Then, for minimizing the operating cost of the steam system, the network para-meters including the steam production of boilers, the steam exhaust of turbines, the steam passing through let-down valves and the steam allocation among different turbines are optimized based on the 'Sensitivity Analysis' tool and the proposed optimization rules. The investigation of two literature examples shows that the proposed method is simple and can provide the results comparable to those obtained by mathematical programming methods.
Javier A. Arrieta-EscobarJordan YeboahAshley M. Santoro
11页
查看更多>>摘要：This work aims to use an in-silico approach to develop ice cream formulations. These were computationally designed using recommendations from experts, literature heuristics, legal regulations, food restrictions, target performance properties, and properties models. Such input information was transformed into mathematical models suitable for mixed-integer multivariable and multi-objective optimization in food product design. The computer model was validated by generating a novel ice cream formulation containing non-centrifugal cane sugar (Jaggery) as refined sugar substitute. Preliminary prototype formulations were manufactured to assess the potential impacts of jaggery as sugar replacement, and performance of the product was assessed in terms of density, overrun, viscosity, pH, texture, freezing point, and melting rate. As result, it was found that jaggery barely affected main performance properties thus avoiding the need for modifications m the mathematical models. Afterwards, the computer model was set to develop a jaggery-added formulation with minimum cost via a mixed-integer linear optimization. The optimal product was experimentally validated and characterized by sensory assessment. Results indicate that computer-designed ice creams are pleasant and jaggery has no influence on the overall sensorial perception of the product. This heuristic approach might be adapted for the computer-aided design and reformulation of other innovative food products.
Mohammad Shakil AhmmedAlan SkermanDamien J. Batstone
10页
查看更多>>摘要：Sludge accumulation in anaerobic lagoons is one of the major issues determining long-term operating costs. However, very little mechanistic analysis has been done on long-term sludge behaviour. A coupled hydrodynamic-biochemical model was developed using computational fluid dynamics (CFD), and results from this applied to a compartmental based model (CBM) for long-term simulation. The CFD model incorporates a mixture method for the spatial-and temporal evolution of fluid and solids with a non-Newtonian rheology. CFD was used to evaluate short term hydrodynamics, and a common CBM used to understand the fluid movement and sludge behaviour of full-scale anaerobic lagoons (with varying depths, sidewall slopes, and loading rates), operating in commercial piggeries located in Southern Queensland and Southern New South Wales, Australia. The results found that the lagoons had varying hydrodynamics, and sludge accumulates rapidly in sloped sidewall lagoons, forming a variable depth bed which occupied a substantial fraction of the lagoons. Shallow lagoons were dominated by significant surface recirculation dynamics, and were susceptible to solids accumulation, while deep lagoons allowed the formation of a well developed settled fraction. Predicted lagoon lifetimes varied substantially, but predicted long-term accumulation rates were approximately double that observed, due to long-term degradation of slowly degradable material.
查看更多>>摘要：Steam reforming of olive oil mill wastewater (OMW) has been object of study in several works; however, there are no references to industrial installations to treat and valorize this effluent until now. In this way, to understand the economic impact of applying this technology in the olive oil industry, techno-economic analyses of this process in a traditional reactor (TR) or in a sorption-enhanced reactor (SER - with in situ CO2 removal) were performed. This study focused on key aspects of the process units, such as the reaction and heating/cooling zones. These analyses also considered the effect of different water contents in the OMW composition (60-90 wt.%) and the impact of the operating pressure (1-4 bar), at 400 °C. To determine the outlet stream composition of the process and the heat released or required in the reaction, the software Aspen Plus V.10~R was used. The investment cost of the heat exchanger was estimated by the Aspen Exchanger Design & Rating software tool. It was observed that the content of water in the feed, the operating pressure, the mode of operation (6 or 12 months) and the reactor configuration used affect the economic benefit of the project over time: lower content of water in the feed, lower operating pressure, operating throughout the whole year and the utilization of a SER allows to obtain a most profitable scenario.
查看更多>>摘要：Polyvinyl butyral is a polymer resin with excellent mechanical properties, weather resistance and adhesive properties, which can be used in solar cell encapsulation films and automotive glass interlayer films. It is synthesized by the reaction between polyvinyl alcohol and n-butyraldehyde acetal, in which a certain amount of surfactant is added. Because it will cause the product to turn yellow, the surfactant needs to be removed by purification process. In this paper, polyvinyl butyral was synthesized using sodium do-decyl sulfonate as surfactant, and the purification process and the effect of surfactant residue in polyvinyl butyral on its yellowing degree were studied. Box-Behnken design and artificial neural network were used to optimize the purification process. The results showed that the influencing factors of the purification process were as follows: washing times > addition amount of sodium dodecyl sulfonate > washing temperature > stirring time. The correlation coefficients (R~2) of Box-Behnken design and artificial neural network were 0.9943 and 0.9981 respectively, indicating that the artificial neural network was more accurate than Box-Behnken design. In conclusion, the results of this study provide an effective method for the purification process of polyvinyl butyral.
查看更多>>摘要：Designing more efficient high-pressure homogenizers (HPHs) is important from an industrial perspective (reduce energy cost). Understanding the relationship between valve geometry and breakup is interesting from an emulsification research perspective. Typically, two different design principles are used for commercial HPHs: the traditional outward radial flow design and the newer inward radial flow design, However, little is known about the hydrodynamic difference. This study uses well-validated computational fluid dynamics (CFD) methodology to compare the turbulent stress experienced by a drop travelling though HPH valves (at comparable conditions) between these design and discuss implications on optimal valve design. Regardless of design, the highest stress is observed in the jet downstream of the gap exit. At low to intermediately high homogenizing pressures (< 250 MPa), the traditional design gives rise to higher turbulent stress. At extreme pressures (>250 MPa), the inward radial flow design is marginally more efficient. The difference in efficiency between design and operating condition is determined by two opposing forces: The efficiency increases with gap exit velocity (higher in the inward radial flow design) and the efficiency decreases with increasing dissipation volume (smaller for the traditional outward flow design). Implications for improving HPH valve design are discussed.
查看更多>>摘要：Hydrofluorocarbon (HFC) + ionic liquid (IL) and hydrofluoroolefin (HFO) + IL are two new types of working pairs developed for absorption refrigeration system. In this paper, aiming to provide a guide for screening the optimal one from many candidates, a model based on group contribution (GC) method and artificial neuron network (ANN) is presented to estimating the solubility of HFC/HFO in Its from molecular structure. The input variables of the ANN-GC model are temperature, pressure, and the number of various groups. A dataset containing 1693 solubility data for 18 HFC/HFO in ILs consisting of 10 cations and 17 anions at temperature from 273.13 K to 413.30 K and pressure from 0.99 kPa to 41,000 kPa were established to train the model. The ANN-GC model has great regression ability indicated by the average relative deviation of 8.8 % from experimental data. Besides, the case study on predicting [HMIM][BF4] - R134a working pairs solubility shows that our model has great prediction ability on new substances. The sensitivity analysis points out the groups influence on the solubility and give a guideline for designing high solubility working pairs. We also used Leverage approach to find the outlier data and high leverage data.
查看更多>>摘要：Rosa damascena Mill. is one of the rosa species that is broadly used for commercial products such as rose concrete and rose absolute. First, the effect of two organic solvents of hexane and ethyl acetate and three alcohols of methanol, ethanol, and 2-propanol were studied on the yield and quality of the rose concrete and rose absolute from air-dried petals of Rosa damascena Mill. Then, a predictive thermodynamic model based on the UNIFAC activity coefficient was employed to predict the composition of rose absolute obtained from the rose concrete. The extraction of rose concrete from dried rose petals was performed at 30 °C by hexane or ethyl acetate, and then the produced rose concrete was combined with an alcohol and the mixture was placed at -18 °C for 48 h to produce rose absolute. Based on the results, the maximum yield of rose absolute was achieved if the extractions were performed with ethyl acetate to extract rose concrete, and ethanol to extract rose absolute. The extracts were analyzed using a GC-MS method to determine the effect of the solvents on the quality of the rose absolute. The most critical constituents detected in the extracts were high-value fragrant components of phenyl ethyl alcohol, citronellol, geraniol, nerol, and farnesol. The results showed that using the pair of hexane and methanol led to achieving a rose absolute with the highest odor value (16,038) but a low extraction yield. Using ethyl acetate and ethanol, the maximum yield of rose absolute was achieved. Finally, the thermodynamic model showed a good agreement in predicting the rose absolute production from the rose concrete with the alcohols.
查看更多>>摘要：The synthesis of property-based total water networks with multiple interceptors is investigated by using operator potential concepts. Two kinds of network configurations are considered according to whether process sources are allowed to mix at inlet of the interceptors. For a non-mixing network, each interceptor treating one process source, the synthesis procedure is simple. However, too many interceptors might be needed and the corresponding costs will be high for the systems with a large number of process sources. For a mixing network, process sources are allowed to mix at inlet of the interceptors, the network construction can be simplified and the total annual costs can be reduced. An iteration procedure is proposed to design mixing-configuration networks. In the synthesis procedure, the values of operator potential of demands are used to determine the sequence of demands to be satisfied, the values of operator potential of sources are used to select the process sources to be treated. A linear programming approach is adopted to allocate the sources to each demand. The results of four examples obtained with the proposed methods show that the networks with lower fresh source consumption, or simpler structure, or lower total annual cost can be obtained compared to the literature results. In addition, the proposed methods have the features of simple calculation and clear engineering meaning.
查看更多>>摘要：Natural gas is an important precursor to produce synthesis gas through the steam reforming process. This work aims to map the optimal operating conditions of a steam methane reformer based on the design of experiments (DOE) approach and response surface methodology (RSM) relying on a phenomenological model validated with industrial data. A screening factorial design 2_(IV)~(8-4) is initially conducted to identify the most significant process variables, followed by a 25 full factorial design for a more accurate analysis of the main and interaction effects of the input variables on the methane conversion and syngas quality. The most significant variables are the steam to carbon ratio, the flow rate of the stream fed to the reforming tubes, and feed gas and combustion air temperatures. A Box-Behnken design (BED) with 25 experiments is carried out and polynomial models are proposed and validated through the analysis of variance with great confidence. An optimization problem is formulated to maximize the methane conversion, ensure the quality, and tube wall temperature constraints. This problem is solved in Excel, using the generalized reduced gradients method and the calculated optimal point is analyzed through contour plots.
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