Volume 15, Issue 1 -

Forward Osmosis (FO)-Nanofiltration (NF) integration as the final product polishing step enables high concentration of acetic acid output through continuous dehydration of fermentation derived product. A mathematical transport model has been developed based on external and internal concentration polarization modulus of FO and extended Nernst–Plank equation for NF to capture the flux and rejection trends from those membranes. The modular designed production scheme ensured high flux (45 Lm −2  h −1 ), concentration (962 g L −1 ) and purity (>98 %) of acetic acid under non-neutralization condition. Excellent performance of the model is reflected in low relative error (<0.05), high Willmott d-index (>0.97) and high correlation coefficient (>0.98).

Eulerian-Eulerian approach and conventional Eulerian-Lagrangian model are computationally exhaustive for modelling circulating fluidized bed (CFB) riser which has wide particle size distribution and billions of particles Alternatively, the relatively recent Eulerian- Lagrangian computational particle fluid dynamics (CPFD) model enables simulation of the CFB system with lesser computational resources. Most of the published studies on CPFD simulations of CFB risers deal with single grate system. The present study aimed to investigate the performance of the CPFD model for predicting solids distribution in a CFB riser with pant-leg structure (dual grate) and characteristics similar to a commercial boiler. Experiments conducted in a scaled down 250 MWe CFB facility according to Glicksman’s simplified similarity laws for fluidized beds were simulated using commercial code Barracuda. The bottom dense bed, upper lean solid phase, increase in bottom bed voidage with increasing fluidizing velocity and reducing solids inventory, decrease in bottom bed solids concentration with decrease in particle size and exchange of solids between the legs typically occurring in a CFB with pant-leg structure were successfully captured by the CPFD calculations. Simulation results showed that the upper solids concentration is hardly influenced by the solids inventory level in line with the experimental observation, therefore the amount of solids inventory can be optimized during actual operation. The predicted pressures varied from the average experimental pressure data within the range –10 to 39 %.

In the present study, the temperature effects on the organic carbon and nitrogen removal in an activated sludge process are evaluated. Benchmark Simulation Model No.1 (BSM1) based on activated sludge process is used for all the simulation purposes. A steady state simulation is performed to analyze the effluent concentrations with varying kinetic parameters obtained from different temperature coefficients over a wide range of temperatures from 15 °C to 35 °C. The temperature coefficient ‘a’ is assumed to have different set of values specific to the kinetic parameters, namely, Maximum heterotrophic growth rate μmH\left( {{\mu _{mH}}} \right), Maximum autotrophic growth rate μmA\left( {{\mu _{mA}}} \right), Heterotrophic decay rate bH\left( {{b_H}} \right), Autotrophic decay rate bA\left( {{b_A}} \right). The effluent concentration defined in terms of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS), Total Nitrogen (TN) and Ammonia are observed to be significantly changing with a change in the kinetic parameters which are in turn a strong function of temperature coefficient. Emphasis is laid on the temperature range of 25–30 °C as it is commonly the most operated temperature range in a WWTP in India. It is also noticed that at temperatures <20 °C and >30 °C, the effluent limitations are violated from the standard values.

Nanocarriers have been explored widely for targeted and sustainable delivery of drugs and other bioactive molecules. Kinetic modeling on the drug release and optimization of the process parameters offers a fundamental explanation for the release mechanism along with an insight on the properties of the carrier. In the present work, a hybrid Bovine serum albumin- Calcium ferrite (BSA-CFNP) nanocarrier in conjugation with folic acid has been developed for the controlled release of curcumin, as a model anticancer drug. Super paramagnetic calcium ferrite nanoparticles were synthesized by sol-gel method. Curcumin was loaded onto the BSA and hybrid BSA-CFNP carriers by desolvation technique. Folic acid conjugation was performed, using EDC coupling reaction, to enable the receptor mediated endocytosis of the drug. The synthesized samples were characterized by FTIR, XRD and SEM techniques. Optimization of curcumin loading on the carrier was evaluated using Taguchi method, which provided a simpler yet effective route to study the influence of the process parameters under consideration. In-vitro stimuli responsive curcumin release studies were investigated. The amount of FA conjugated was also optimized. The drug release trends were studied at different simulated physiological environments. The drug release mechanism was evaluated by applying various kinetic models such as zero order, first order, Higuchi, Korsmeyer Peppas and Hixson Crowell. The controlling parameters and their effects on the release of curcumin from the devised system were elucidated from the best fit model.

Waste generated from industrial processing of seafood is an enormous source of commercially valuable proteins. One among the underutilized seafood waste is shrimp waste, which primarily consists of head and carapace. Litopenaeus vannamei (L. vannamei) is the widely cultivated shrimp in Asia and contributes to 90 % of aggregate shrimp production in the world. This work was focused on extraction as well as purification of value-added proteins from L. vannamei waste in a single step aqueous two phase system (ATPS). Polyethylene glycol (PEG) and trisodium citrate system were chosen for the ATPS owing to their adequate partitioning and less toxic nature. Response surface methodology (RSM) was implemented for the optimization of independent process variables such as PEG molecular weight (2000 to 6000), pH (6 to 8) and temperature (25 to 45 °C). The results obtained from RSM were further validated using a Multi-objective genetic algorithm (MGA). At the optimized condition of PEG molecular weight 2000, pH 8 and temperature 35 °C, maximum partition coefficient and protein yield were found to be 2.79 and 92.37 %, respectively. Thus, L. vannamei waste was proved to be rich in proteins, which could be processed industrially through cost-effective non-polluting ATPS extraction, and RSM coupled MGA could be a potential tool for such process optimization.

In the present work, supercritical fluid extraction (SFE) of hemp ( Cannabis sativa ) seed oil at various ranges of SFE parameters is performed. These parameters and respective ranges are temperature (40–80) °C, pressure (200–350) bar, solvent (CO 2 ) flow rate (5–15) g/min, particle size (0.43–1.02) mm and amount of co-solvent (ethanol) (0–10) % of solvent flow rate. Central composite design (CCD) suggests 32 experimental runs to perform through SFE. The obtained oil is analysed through gas chromatography to identify its fatty acids concentrations. The ratio of ω-6 linoleic and ω-3 α-linolenic fatty acids (ω-6/ω-3) is optimized through CCD to obtain the desired amount of 3:1 as this ratio is highly preferred for various health benefits. Ratio of ω-6/ω-3 is obtained in the range from 2.11 to 3.06:1 for all experimental runs. The effect of SFE parameters on this ratio is investigated. Further, cross-validation is peformed on the experimental data obtained for the concentrations of both fatty acids by jackknife and bootstrap resampling to authenticate the obtained data. Small value of standard deviation (~1), less standard error of the mean (SEM) (<0.8) and less variance coefficient (<0.11) confirms the validity of the obtained data. All the estimators’ values such as standard deviation, variance coefficients and SEM are observed in 95 % of confidence intervals.

Control of unstable systems with time delays usually result in overshoots in the closed loop responses. The intricacy involved in multivariable unstable processes further makes the problem more challenging. In industry, set-point weighting is one of the recommended methods to minimize the overshoot. However, design of the set-point weighting parameters determines the percentage of minimization of the overshoot. In this paper, a method is proposed to design the set-point weighting parameters for unstable multivariable processes which is relatively simple and also reduces the overshoot. Weighting is considered for both proportional (β) and derivative (γ) terms in the PID control law. In the closed loop relation for set-point tracking, the coefficients of ‘s’ and ‘s 3’ both in the numerator and denominator are made equal in order to find dynamically β and γ. The obtained expressions for β and γ are simple and dynamically depends on the controller parameters and are applied to TITO systems in present work. Decouplers are used in TITO systems mainly to reduce the interaction between the loops so that they can be viewed as independent loops. Decoupler design suggested by (Hazarika and Chidambaram [1] has been used in this work and two TITO unstable processes with time delays are illustrated here. Comparison with the reported methods available in literature verifies that the proposed method gives improved closed loop performance.

In a circulating fluidized bed (CFB), the loop seal is an important component which recirculates the solids captured by the cyclone to the bottom of the riser and avoids the direct flow of gas from high-pressure riser to the low-pressure cyclone. Most of the CFBC systems employ a Non-Mechanical valve, and its function has been investigated by many researchers. In this work, the flow of solid particle within the loop seal has been studied elaborately, and various design and operating parameters of the loop seal were analyzed in detail using Computational Fluid Dynamics (CFD). The CFD study has handled a loop-seal of dimension 110 mm × 430 mm × 400 mm high. This analysis has been done with a 200 µm sand particle and it is checked for its flow ability through various sizes and by altering the L/H ratio for three solid mass fluxes and for three L/H ratios of loop seal. The rate of solid mass flux depends on the length of the horizontal passage connecting the recycle cycle compartment of the loop seal with the supply chamber and hence the solid flow rate and the pressure difference per unit length are directly proportional to the length of the chamber or passage. Hence, L/H ratio is taken as a driving variable for the optimum performance of loop seal. The CFD analysis results reveal that the aeration of the solid to be used within the loop-seal should be higher than the Minimum Fluidization velocity. Also, keeping the length of the horizontal passage constant and varying the height of the passage will reduce the pressure drop. The pressure drop across the horizontal passage decreases up to a certain L/H ratio after which it increases. By comparing the three L/H ratios, L/H ratio of 2.62 is having a lesser pressure drop for the three mass fluxes. L/H ratio of 2.62 is having a good fluidization phenomenon and also the flow from the recycle chamber is more in comparison to the other L/H ratios. Experimental data from the literature is in good agreement with the CFD results.

This manuscript deals with the assessment of parallel form of proportional integral derivative (PID) control structure for tracking the reference input designed for large dominant time constant processes whose dynamics are slow (integrating processes). The theoretical bound of integral absolute error (IAE) which is established for unstable first order process is extended to pure integrating process without using any approximations. This relies on direct synthesis tuning (DS) and the theoretical bound is obtained from the transfer function of closed loop system subjected to ramp input changes. An error based performance index is formulated on the basis of this IAE theoretical bound and actual IAE, to measure the behaviour of the controller employed for non self regulating (integrating) processes. This error based index evaluates the performance of closed loop controller and specifies whether the controller requires retuning or not. A sequence of simulated examples is used to illustrate the benefit and effectiveness of this new performance assessment method.