Changes In Feed Composition Research Articles

Method for Evaluating Single-End Control of Distillation Columns

Distillation columns are, in an ideal situation, controlled using a dual-composition structure in which the light-key impurity in the bottoms and heavy-key impurity in the distillate are both maintained at the specified values. This structure minimizes energy consumption. However, it is often almost as efficient to use one-end control of either a composition or a temperature. This single-end distillation control structure is widely used in industry because of its simplicity and because it avoids dynamic interaction between the two competing loops. Because distillation columns have two control degrees of freedom, another variable besides the single temperature or composition must be selected among several alternatives. Usually these choices involve a ratio so that feed rate changes can be effectively handled. However, different ratio schemes handle feed composition changes with different degrees of effectiveness. The two most commonly used are either a reflux-to-feed ratio (R/F) or a reflux ratio (RR). The...

Effect of an herbivorous diet on energy balance of Litopenaeus vannamei at selected ontogenetic stages

Herbivorous (20% vegetable protein, 40% carbohydrate) and carnivorous diets (40% marine animal protein, 20% carbohydrate) were experimentally tested to assess their effect on the energy balance and energetic substrates utilized by postlarvae (PL's /15 days) and juvenile shrimp (3–6 g) of Litopenaeus vannamei. Postlarval stage 60 (PL 60, early juveniles) shrimps fed HeD and CaD diets, then late juveniles (3–6 g) acclimated to the same diets were tested for their respective energy partitioning potential. No significant differences ( p > 0.05) on growth were obtained in early juveniles (mean final wet weight of 0.19 g). However in late juvenile stages a significant difference ( p < 0.05) in growth rate was observed. In terms of energy partitioning, both early and late juveniles seem to spend more energy in respiratory metabolism than in the elimination of excretion products. A change in feed composition based on quality protein sources induced some modifications on shrimp's activity measured by heat increment. Shrimps fed with an herbivorous diet showed a higher heat increment. Interestingly, the early stages of L. vannamei display a remarkable capacity to assimilate a plant protein-based and a high carbohydrate level diet. Such capacity with a stimulation of genes would lead to a good adaptation of juveniles receiving all-plant diets to sustain growth performances up to a marketable size. The implications of these findings for the shrimp farming feeding costs are briefly discussed.

DEVELOPMENT OF EXTRUDED SNACK FROM FOOD BY‐PRODUCTS: A RESPONSE SURFACE ANALYSIS

ABSTRACT Response surface methodology was used to investigate the effects of extrusion conditions including the moisture content of blend (12–18%), barrel temperature (150–175C), screw speed (200–280 rpm) and change in feed composition on the product characteristics of the snack food developed from rice grit in combination with durum clear flour, partially defatted hazelnut flour (PDHF) and fruit wastes. The blend was made up of rice grit (67%), durum clear flour (8–20%), PDHF (5–15%) and fruit waste (3–7%). The response variables were radial expansion ratio, color, and textural and sensory properties of the extruded snacks. Increasing the PDHF content caused a decrease in the radial expansion ratio, hardness and lightness of the snacks. The textural properties and color of produced snacks were affected by the fruit waste addition. Increasing the moisture content and decreasing the temperature caused an increase in the expansion ratio for most compositions. The extruded snacks with lower PDHF content had the highest levels of overall acceptance in the sensory panel. There was no significant effect (P &lt; 0.05) of fruit waste addition on the sensory properties of the snacks.PRACTICAL APPLICATIONSLarge amounts of side products of the food industry, in particular fruit and vegetable waste, evolved during production (most of which cause environmental pollution), preparation and consumption of foods. Because of this, it is necessary to collect and use these wastes for the production of new foods, which is important from the point of environmental pollution and a country's economy. This study aimed to produce a ready‐to‐eat, puffed and value‐added snack food by using the side products of various food industries. Durum clear flour of macaroni production, partially defatted hazelnut flour of hazelnut oil production and fruit wastes of various fruit juice production might be evaluated as the components of the extruded snack food product. The contribution of the present work is to propose an alternative technology for the utilization of food‐processing wastes for the development of a useful, value‐added extruded food product.

Influence of sugar content of wastewater on the microbial characteristics of granular sludge developed at 20°C in the anaerobic granular sludge bed reactor

The influence of the sugar content of wastewater on changes in the characteristics of the retained sludge was investigated by using two lab-scale granular sludge bed reactors at 20°C. Both reactors were inoculated with granular sludge grown at 20°C and were fed with synthetic wastewater containing sucrose and volatile fatty acids (VFAs). On day 70, the sucrose content of the wastewater was changed to 90% (based on wastewater COD value) for the first reactor and 0% (VFA 90%) for the second. After this change in feed composition, the COD removal efficiency became about 91% for the sucrose-fed reactor and 95% for the VFA-fed reactor. The growth yield (Yg) of the sucrose-fed sludge increased more than that of the VFA-fed sludge. Consequently, deterioration of the settleability of the sucrose-fed sludge was observed. The sucrose-degrading activity of the retained sludge obtained from the sucrose-fed reactor increased significantly from 3.7 g COD g VSS− 1 day− 1 on day 62 to 36.8 g COD g VSS− 1 day− 1 on day 230, in accordance with the predominant growth of sugar-degrading bacteria – namely, Lactococcus, Clostridium and Chloroflexi – in the retained sludge. The excessive growth of these sugar-degrading bacteria in the retained sludge caused unstable process performance in the sucrose-fed reactor at 20°C.

Composition Changes and Future Challenges for the Sellafield Waste Vitrification Plant

AbstractThe Sellafield Waste Vitrification Plant (WVP) immobilises highly active liquors produced during reprocessing of spent nuclear fuel by bonding the fission products as metal oxides into a borosilicate glass matrix. This provides a stable and durable waste form suitable for safe long term storage and ultimate disposal.WVP was commissioned with feed from reprocessing of Magnox reactor fuel. This material is relatively low in fission product content per tonne of fuel, but contains significant Al and Mg from fuel cladding. WVP also routinely treats a blended feed made from a mixture of Magnox and Oxide reprocessing products. The Oxide fuel from Light Water Reactor (LWR) and Advanced Gas Cooled (AGR) power stations is of higher burnup and contains more fission products per tonne of fuel, also Gd and other process additives. Blending allows 25% incorporation of waste oxides by weight in glass to be achieved routinely.Recent programmes of development work in WVP have been aimed at increasing incorporation rates for these feeds, to reduce the number of waste containers produced for disposal. Work has also focussed on increasing the throughput of WVP, to more rapidly treat current stocks of liquid reprocessing waste, both by increasing the feed rate and by improving the lifetime of key components to improve plant availability.Future challenges for WVP include flowsheet changes to treat historic stocks of reprocessing wastes containing high U, Fe and Cr. Washout of solids from the base of waste storage tanks in preparation for decommissioning is also likely to give high Mo feeds. Development of flowsheet and glass formulation to accept these changes in feed composition will be a key objective of future work.

Simulation of an industrial-scale process for the SCR of NO x based on the loop reactor concept

This paper investigates the possibility of using an adiabatic loop reactor to carry out the selective catalytic reduction of NO x with NH 3. The advantages of this technology with respect to more traditional reactors operated in steady-state are discussed: when the temperature of the feed is low, a lower amount of heat is required to get full NO x conversion; moreover, the catalyst can be used to store a high amount of NH 3 during the operation, thus preventing NH 3 slip and/or NO x emissions when the feed composition changes. Both issues are investigated, using the design of an industrial-scale reactor as case study.

Treatment of halogenated organic compounds and monitoring of microbial dynamics in up‐flow fixed bed reactors under sequentially alternating pollutant scenarios

Two up-flow fixed bed reactors (UFBR) were operated for 8 months treating a model synthetic wastewater containing 2-fluorobenzoate (2-FB) and dichloromethane (DCM). The stability of the reactors under dynamic conditions, that is, sequentially alternating pollutants (SAP), shock loads, and starvation periods was assessed. Two support materials were used: expanded clay (EC) that does not adsorb 2-FB or DCM, and granular-activated carbon (GAC) that adsorbs 180 mg g(-1) of 2-FB and 390 mg g(-1) of DCM. The reactors were inoculated with a 2-FB-degrading strain (FB2) and a DCM degrader (TM1). 2-FB was fed at organic loads ranging from 0 to 800 mg L(-1) d(-1), while DCM was fed at 0-250 mg L(-1) d(-1). 2-FB or DCM were never detected at the outlet of the GAC reactor, while in the EC reactor outlet small amounts were observed. Nevertheless, the highest biological elimination capacity was observed in the EC reactor (over 700 mg L(-1) d(-1) of 2-FB). DGGE analysis revealed a fairly stable bacterial community with the largest shifts occurring during starvation periods and changes in feed composition. Several bacterial strains isolated from the reactors showed capacity for 2-FB degradation, while only strain TM1 degraded DCM.

Response surface methodology for evaluation of physical and functional properties of extruded snack foods developed from food-by-products

Response surface methodology was used to investigate the effects of extrusion conditions including moisture content (12–18%), temperature (150–175 °C), screw speed (200–280 rpm), and change in feed composition, durum clear flour (8–20%), partially defatted hazelnut flour (PDHF) (5–15%) and fruit waste (3–7%) contents on the physical and functional characteristics of the extruded snack food based on rice grit in combination with fruit waste, durum clear flour and PDHF. Response variables are bulk density, porosity, water absorption and water solubility indices and sensory properties of the extruded snacks. The product responses were most affected by changes in PDHF content and to a lesser extent by fruit waste content. Increasing PDHF content caused increase in bulk density and water solubility index, but decrease in porosity and water absorption index of the extruded snacks. Changing process conditions affected the physical and functional properties of produced snacks. The sensory evaluation of extrudates suggests that extrusion of PDHF, fruit waste and durum clear flour in combination with rice grit can produce acceptable extruded snack.

Plant-wide design and control of acetic acid dehydration system via heterogeneous azeotropic distillation and divided wall distillation

Energy-saving plant-wide design and plant-wide control of an acetic acid dehydration system with the feed containing methyl acetate and p-xylene are investigated in the study. A heterogeneous azeotropic distillation using isobutyl acetate as an entrainer is designed to obtain high-purity acetic acid at the column bottom and to keep a small acetic acid loss through the top aqueous draw. The accumulation of p-xylene in the column is avoided by adding a side product stream. The mixture in the aqueous phase of decanter, containing mostly water, methyl acetate, and isobutyl acetate is separated using a divided wall distillation column. The whole acetic acid dehydration system includes a heterogeneous azeotropic distillation column and a divided wall distillation column. The control strategies using temperature loops are proposed for this acetic acid dehydration system. For the heterogeneous azeotropic distillation column, the requirements for acetic acid compositions in both the aqueous phase of the decanter and the column bottom can be satisfied by designing entrainer inventory temperature control and cascade temperature control simultaneously. The stages of controlled temperatures are chosen by singular value decomposition and closed-loop analysis methods based on the criteria of minimum entrainer makeup. For the divided wall distillation column, steady-state analysis methods are used for the selection of proper controlled and manipulated variables and the determination of their pairings. Dynamic simulation results demonstrate that the proposed plant-wide control strategy can maintain product purities and reject external disturbances in feed flow and composition changes as well as internal disturbances such as changes in liquid and vapor splits.

Partial pressure dependent in situ spectroscopic study on the preferential CO oxidation in hydrogen (PROX) over Pt/ceria catalysts

Platinum supported on ceria can oxidize CO in excess hydrogen selectively (PROX process). In situ DRIFTS and high-pressure (∼1 mbar) XPS experiments were performed to study the mechanism of the PROX reaction on Pt/ceria catalysts. The partial pressure of O2 and/or CO was varied and correlated with induced changes in activity and selectivity as well as with the surface state and species under reaction conditions. Pt-carbonyl species changed rather insignificantly, especially relative to the wide variations of the product pattern with changing feed composition. Furthermore, the interconversion of formate and carbonate species was observed. Therefore, the changes in the evolution of surface species detected by in situ DRIFTS cannot explain the variation observed in CO oxidation activity. On the other hand, high-pressure XPS showed significant modification of the surface state with changing feed composition. Most significantly, oxygen vacancy formation seemed to correlate with enhanced CO oxidation activity. At higher vacancy density, water desorption was hindered. Highly hydrated ceria with significant vacancy density was found to be beneficial for the PROX process; here surface water blocked Hads oxidation sites. Moreover, lower apparent activation energy of CO oxidation was measured in the PROX reaction on catalysts with more vacancies. The results given here reinforce the view of catalysts being adaptive to a certain reaction rather than having active sites as prepared. Whereas IR-detectable surface species may only be indicators and/or consequences of this surface change, formation of the beneficial surface/near-surface state may be the rate-limiting factor in several catalytic processes.

Control of Thermally Coupled Distillation Arrangements with Dynamic Estimation of Load Disturbances

Because of their potential energy savings, thermally coupled distillation sequences provide interesting alternatives to the use of sequences based on conventional distillation columns. Three thermally coupled structures have been particularly analyzed for the separation of ternary mixtures: the sequence with a side rectifier, the sequence with a side stripper, and the Petlyuk column. Design methods have been developed for such sequences, but their dynamic and operational characteristics still require a wider understanding to promote their practical implementation. Previous works have shown that thermally coupled systems can provide suitable control properties; most of the studies on closed-loop control analysis of thermally coupled systems have been based on proportional−integral (PI) controllers. In this work, a PI controller with dynamic estimation of uncertainties is implemented for the control of the thermally coupled distillation arrangements. The controller comprises three feedback terms: proportional, integral, and quadratic actions. The last term provides a dynamic estimation of unknown load disturbances to improve the closed-loop performance. Comparison with the classical PI control law was carried out to analyze the performance of the proposed controller in facing unknown load disturbances in feed composition and set point changes. The results show that the implementation of the controller with dynamic estimation of uncertainties improved noticeably the closed-loop responses provided by the PI controller.

Controllability and energy efficiency of a high-purity divided wall column

The divided wall column system is a promising energy-saving alternative for separating multi-component mixtures. However, high energy efficiency and stable operations can only be achieved with careful design of steady state operation and control scheme. In this study, the effects of liquid split and vapor split ratios on the energy efficiency and controllability of a divided wall column system for separating ethanol, n-propanol, and n-butanol were investigated. A region with high energy efficiency was identified. However, relative gain analysis found that the performance of multi-loops composition control would be very poor. Dynamic tests showed that multi-loop temperature control cannot return the product compositions to the desired values in case of feed composition disturbances. Outside this region, composition control can compensate for external disturbances such as feed flow rate and feed composition changes but not changes in operating region caused by internal variations such as liquid and vapor splits. Offsets in the product purities were found if temperature controls were used and there are disturbances in feed composition or changes in operating region caused by upsets in liquid and vapor splits. There is a trade-off between energy efficiency and controllability. A composition + temperature cascade scheme was proposed to stabilize the operation with high energy efficiency. The proposed scheme was able to maintain high product purity and reject external disturbances in feed flow and composition changes as well as internal disturbances such as changes in liquid and vapor splits.

Equilibrium theory based design of simulated moving bed processes for a generalized Langmuir isotherm

In the frame of the local equilibrium theory of chromatography, design criteria for complete separation of binary mixtures in simulated moving bed (SMB) separations are developed, presented and discussed. These apply to systems, whose retention behavior is characterized by a generalized Langmuir isotherm. By allowing for negative terms in the denominator of the classical Langmuir isotherm, this newly introduced adsorption model captures a broad class of competitive or synergistic adsorption, including anti-Langmuir behavior for both adsorbates, and mixed cases where one species behaves in a Lagmuirian and the other in an anti-Langmuirian manner. By extending classical equilibrium theory results for the binary Langmuir isotherm, and by generalizing the approach followed earlier to derive SMB design criteria for the binary and multi-component Langmuir isotherm, exact algebraic equations for the boundary of the complete separation region in the operating parameter space are derived for all possible generalized Langmuir isotherm. The effect of changing feed composition on the shape of the complete separation region and on the position of the optimal operating point is analyzed and discussed.

Identification of organically farmed Atlantic salmon by analysis of stable isotopes and fatty acids

Using isotope ratio mass spectrometry (IRMS), the ratios of carbon (δ 13C) and nitrogen (δ 15N) stable isotopes were investigated in raw fillets of differently grown Atlantic salmon (Salmo salar) in order to develop a method for the identification of organically farmed salmon. IRMS allowed to distinguish organically farmed salmon (OS) from wild salmon (WS), with δ 15N-values being higher in OS, but not from conventionally farmed salmon (CS). The gas chromatographic analysis of fatty acids differentiated WS from CS by stearic acid as well as WS from CS and OS by either linoleic acid or α-linolenic acid, but not OS from CS. The combined data were subjected to analysis using an artificial neural network (ANN). The ANN yielded several combinations of input data that allowed to assign all 100 samples from Ireland and Norway correctly to the three different classes. Although the complete assignment could already be achieved using fatty acid data only, it appeared to be more robust with a combination of fatty acid and IRMS data, i.e. with two independent analytical methods. This is also favourable with respect to a possible manipulation using suitable feed components. A good differentiation was established even without an ANN by the δ 15N-value and the content of linoleic acid. The general applicability in the context of consumer protection should be checked with further samples, particularly regarding the variability of feed composition and possible changes in smoked salmon.

The role of nutrition in cataract formation in farmed fish.

Abstract A brief overview of the lens anatomy and biochemistry, characteristics of cataract development in fish, as well as diagnostic techniques and evaluation of findings are given, before the role of nutrition on cataract development in fish is discussed. Nutritionally related cataracts are described based on single nutrient groups. However, in most of the studies on nutrition and cataract, interactions between several nutrients cannot be excluded, especially observed in relation to the major changes in feed composition during the last decades and the search for alternative feed ingredients. Environmental factors in aquaculture, as well as differences between fish species and strains within a species may also affect cataract development. Thus, although nutritional factors have been shown to be important in the pathogenesis of cataract, cataract occurring in modern intensive fish farming should be considered a production-related multifactorial disorder.

Effect of Feed Composition on the Selection of Control Structures for High-Purity Binary Distillation

This paper discusses the selection of an effective control structure for a binary distillation column producing high-purity products. Results show that this selection depends on the feed composition. If the concentration of the light component is large, the reflux ratio is small. Control of a single appropriate tray temperature by manipulating the reboiler heat input and using a fixed feed-to-reflux ratio provides effective control for both feed-rate and feed-composition disturbances. The reflux-drum level is controlled by the distillate flow rate. For intermediate concentrations of the light component and for high-purity products, this study shows that a two-temperature control structure with reflux and reboiler heat input manipulated is required to handle feed-composition changes. Small concentrations of the light component yield small distillate flow rates and high reflux ratios. Conventional distillation control wisdom advises that the reflux-drum level should be controlled by the reflux flow rate when the reflux ratio is larger than ∼2. A control structure is frequently recommended in which the flow rate of the distillate is ratioed to the reflux. However, in many columns, a constant reflux-ratio strategy is not as effective as a constant reflux-to-feed strategy for maintaining product purity at both ends of the column in the face of feed-composition disturbances when a single tray temperature is controlled. An alternative control structure is proposed in this paper that achieves the preferred constant reflux-to-feed strategy by controlling the reflux-drum level with reboiler heat input and manipulating the small distillate flow rate to control a tray temperature.

Investigating the need of a pre-concentrator column for acetic acid dehydration system via heterogeneous azeotropic distillation

In our previous study [Chien, I.L., Zeng, K.L., Chao, H.Y., Liu, J.H. (2004). Design and control of acetic acid dehydration system via heterogeneous azeotropic distillation. Chemical Engineering Science 59(21), 4547–4567.], an acetic acid dehydration system has been designed. The suitable entrainer selected for that system is iso-butyl acetate. Design and control of the system has been studied in detail to maintain high-purity bottom acetic acid concentration and also keep a small acetic acid loss through top aqueous draw. In that previous study, the feed composition is assumed to contain equal molar of acetic acid and water. However, in a typical waste acid recovery application, the above assumption may be too rich in acetic acid. In this paper, a feed stream containing 80 mol% water and 20 mol% of acetic acid is investigated. Several design alternatives can be deduced including one commonly used in industry by adding a pre-concentrator column in the upstream of a heterogeneous azeotropic distillation column. The necessity of this pre-concentrator column from design and control view points will be thoroughly investigated in this paper. The final recommended process design is a tradeoff between total annual cost (TAC) and operability of the system. The recommended design is a single heterogeneous azeotropic distillation column with aqueous reflux stream. Very wide feed composition and flow rate changes can be handled by this design with proper choice of the overall control strategy.

Effects of synchronization of laser induced fluorescence and corona induced fluorescence in a pulsed corona reactor

Corona-induced fluorescence (CIF) of nitric oxide (NO) reveals that NO(A/sup 2//spl Sigma//sup +/) is primarily excited through N/sub 2/(A/sup 3//spl Sigma//sub u//sup +/) produced in a pulsed corona rector (PCR). The charge voltage in PCR, the time delay of the high-voltage pulse applied to the reactor, and its time jitter vary from gas composition to gas composition. This is because the reactor electric equivalent resistance in an OFF state has different values for different gas components. The PCR pulse jitter, typically a few tenths of a microsecond, for the same gas composition, varies with the frequency of high-voltage pulses due to changes in feed composition. A precise time synchronization of CIF with the laser induced fluorescence (LIF), the intensified charge-coupled device (ICCD) detector and the PCR pulse reveals that NO molecules stay in the vibrational levels of the ground state for about 700 /spl mu/s.

Evaluation of criteria for selecting temperature control trays in distillation columns

The use of tray temperatures to infer compositions is widespread in distillation control. A number of criteria have been proposed for selecting which trays to hold at constant temperature. The most commonly used are (1) choosing a tray where there are large changes in temperature from tray to tray (“slope” of the temperature profile), (2) finding the tray where there is the largest change in temperature for a change in the manipulated variable (“sensitivity”), (3) using singular value decomposition (SVD) analysis, (4) selecting the tray where the temperature does not change as feed composition changes while producing the desired distillate and bottoms purities and (5) choosing the tray that produces the smallest changes in product purities when it is held constant in the face of feed composition disturbances. This paper provides a quantitative comparison of the effectiveness of these five alternative criteria. Several systems are considered, ranging from ideal binary to azeotropic multi-component. Results show that SVD analysis provides a simple and effective method for selecting temperature control tray location.

The phase behavior of n-alkane systems

Normal alkanes show very complicated phase transition kinetics and macroscopic phase equilibrium behavior. This paper focuses on the phase stability and equilibrium of complicated mixtures like n-alkanes and on the enabling global optimization technologies needed to gather problem knowledge. The new ideas contained in this paper include: (1) novel level set methods for gathering encoded knowledge; (2) the differential geometry for uncovering pathways to more subtle knowledge; (3) all supporting non-linearly constrained optimization techniques; (4) all data handling needed to unravel complex solution structure. These new ideas are incorporated within the integral path methodology or terrain methods recently developed by Lucia, A., & Yang, F. (2003) [Lucia, A., & Yang F. (2003). Multivariable terrain methods. AIChE Journal 49, 2553] and Lucia, DiMaggio, and Depa (2004) [Lucia, A., DiMaggio, P.A., & Depa, P. (2004). A geometric terrain methodology for global optimization. Journal of Global Optimization 29, 297]. This framework provides global knowledge for understanding solution structure, like the complex solution structure of n-alkanes. In particular, it is shown that knowledge of the Newton and tangent vector fields, Gauss curvature, integral path bifurcation points, and non-differentiable manifolds provides a deterministic way of finding additional solutions, saddle points, and other information that might otherwise go undetected. It is shown that the optimization tools developed in this work provide all knowledge of interest on the appropriate hypothetical single-phase or composite surface (i.e., minima, saddle points, singular points, and integral paths) in phase stability applications. This knowledge can be obtained by solving the phase stability problem exactly once, in a pre-processing step, and used to reliably initialize any multi-phase equilibrium calculation for any feed. This removes the need to repeatedly solve the phase stability problem as the feed composition changes and greatly increases computational efficiency. Numerical examples and geometric illustrations are used to elucidate key ideas and to show how the proposed approach can be used to unravel the complicated phase behavior of n-alkane mixtures.