Steady state gain analysis for azeotropic distillation

This study gives a brief overview about using dividing-wall column (DWC) technology in azeotropic and extractive distillation processes aimed to break azeotropes. The relevant case study considered here is the bioethanol dehydration process that requires significant energy to overcome the azeotropic behaviour of ethanol-water mixture. The results of the rigorous Aspen Plus simulations show that energy savings of 10– 20 % are possible for the novel process intensification alternative based on DWC, while using less equipment units as compared to the conventional azeotropic and extractive distillation configurations.

Spherical silica nanoparticles with average particle size of 10 nm were synthesized using sodium silicate extracted from oil shale ash as silica source.The results showed that the addition of poly(ethylene glycol)(PEG) could effectively prevent the aggregation of silica nanoparticles and tune the particle size,the optimal PEG concentration was found to be 3.0%.Ultrasonication is a key factor to the formation of small,uniform nanoparticles and an optimized hydrolysis-condensation period for ultrasonication is 0.5 h.The azeotropic distillation evidently suppresses agglomeration and a possible mechanism of azeotropic distillation was also proposed.

Tetrahydrofuran (THF) is widely used in many processes as solvent or chemical intermediate. It is necessary to separate mixture of THF-water, because in most commercial production processes, THF is produced from its water mixture. However, the above mixture cannot be separated with ordinary distillation, since THF and water can form azeotrope. Instead, extractive distillation (ED) and pressure-swing distillation (PSD) have been widely applied for commercial separation of mixture of THF-water. In this paper, Aspen Plus simulator is used to simulate extractive distillation and pressure-swing distillation process for separation of mixture of THF-water. Economic analysis is carried out by Aspen Process Economic Analyzer (APEA) for the two processes. The conclusion obtained based on the above process simulation and analysis is that the total annualized cost of the extractive distillation is slightly lower than that of pressure-swing distillation. The results obtained provide useful references for commercial separation of mixture of THF and water.

Sensitivity of Thermodynamic Model Parameter to the Design of Heterogeneous Reactive Distillation: Amyl Acetate Esterification

The mixture of toluene-methanol-water is difficult to separate because of the formation of toluene-methanol and toluene-water azeotropes. Extractive distillation process with two-column decanter (EDTCD) was improved to separate the system. The process was optimized by the software named Extractive Distillation Optimization Software (EDOS) which based on the minimum total annual cost (TAC). A comparison of the EDTCD and the traditional extractive distillation with triple-column (TEDT) indicated that the former was much more economical. In this comparison, n-methyl-2-pyrrolidone (NMP) and diethylene glycol (DEG) was used as a heavy entrainer in EDTCD and TEDT. The choice of thermodynamic model was discussed in this paper, and the model of UNIQUAC was used in the two processes. The results show that high purity of toluene, methanol and water can be obtained from the process of EDTCD, and it can save 34 % TAC than the process of TEDT.

Design and Optimization of Pressure Swing Distillation using a Stochastic Algorithm based in the Boltzmann Distribution

Limit cycles in homogeneous azeotropic distillation

The prospect of sonication phenomenon in facilitating separation of azeotropic mixtures calls for more detailed study towards developing an intensified distillation system. One important element that require in depth consideration is safety since ultrasound is a potential ignition source with a low threshold value of 1 mW/mm2. In this study, the aim is to investigate the potential of fire hazards that may be introduced by sonication when used in the environment of flammable organic liquid. Simulation study in MATLAB programming environment is carried out based on a mathematical model developed using first principle. Simulations of bubble conditions covering its whole life cycle regimes are carried out and validated with experimental works. Evaluation is made for an extreme condition where the ultrasonic waves are focused directed towards a stainless steel target material immersed in ethanol-water mixture. As sonication occurs, bubbles form slowly by rectified diffusion process with radius of 6 μm, and move toward the metal target. The experimental results revealed that cavitation bubbles filled with explosive vapor are not ignited. This is consistent with the simulation study where the maximum energy released during the bubble collapse is found to be small, which is 0.19267 pJ compared to minimum ignition energy of the liquid at 0.23 mJ. This concludes that the focused ultrasound wave in organic liquid does not trigger ignition, thus suggesting the ultrasonic distillation system is potentially.

In this study, the phase behavior of a water + n-propanol + cyclohexane ternary mixture was experimentally investigated for feasibly using cyclohexane as an entrainer to the azeotropic distillation of a water + n-propanol azeotrope. The experimental results showed that this ternary mixture is partially miscible and exhibits as a heterogeneous azeotrope. The present experimental data include the binary water + n-propanol vapor−liquid equilibrium, the ternary water + n-propanol + cyclohexane vapor−liquid−liquid equilibrium, the heterogeneous azeotropic temperature, the bulk azeotropic liquid composition, and the individual liquid compositions at 760 mmHg. The correlation results of the binary data were satisfactory with the NRTL (AIChE J. 1968, 14, 135) and the UNIQUAC (AIChE J. 1975, 21, 116) models. The correlation result of the azeotropic ternary mixture with the NRTL model is fair, with the worst AARD % (10.69%) for the vapor composition of water and the AARD % values of the rest of the compositions smaller than 5%. The results with the UNIQUAC model show that the UNIQUAC model is not suitable to represent this azeotropic ternary system because of very large AARD % values. With the residual curve map (RCM) and the obtained liquid−liquid equilibrium curve, two conceptual azeotropic distillation schemes using cyclohexane as the entrainer were proposed to separate the azeotropic mixture of water and n-propanol. All of the thermodynamic properties required for constructing the RCM were obtained either from the literature or from the experiments performed in this study and include the boiling temperatures of all three constituent components, the azeotropic data of the constituent binary pairs, and the azeotropic data of the ternary system.

Patterns of composition change in multicomponent batch distillation

Energy-saving exploration and optimization of methyl alcohol – Methyl ethyl ketone – Tertbutyl alcohol separation by extractive dividing-wall distillation with ionic liquid as extractant

Flexibility analysis is a step of process design procedure that is often skipped; sometimes a sensitivity analysis is performed with features similar to the flexibility one but in general they don't overlap. The latter indeed usually has the purpose of assessing the operability range of an already designed system, while the former can be introduced during the design phase and can critically lead our decision making. Therefore, the vast majority of process equipment often results to be sized according to the operating conditions, that is perturbations, when present, can seriously decrease the effectiveness of the process. Moreover, even when performed, the flexibility analysis refers to steady state conditions, that is it doesn't take into account the pathway of the variables from one operating condition to another one. Before stabilizing at the new steady state value, process variables can go outside and come back in the feasibility boundaries several times while oscillating, seriously compromising the good proceeding of the operation. Anyway this behaviour cannot be detected by mean of common steady states simulations or standard optimal design; an ad hoc dynamic simulation and an associated dynamic flexibility study are needed in order to correctly assess the versatility of the designed plant. The first purpose of this paper is to provide basic tools to become more confident with flexibility analysis in general, in particular the dynamic one that has rarely been discussed in literature. Then, the application of this methodology to the most common separation operation, i.e. distillation, is briefly introduced with a simple case study since almost no one before has dealt with it. Finally, steady state and transient results are compared in order to highlight differences and similarities between the two and to understand how such an analysis, if performed a priori, could have changed the design decision making. The simple debutanizer system was intentionally selected to show how, even for an ideal system, dynamics cannot be neglected. Results show indeed that process design based on steady state flexibility analysis considerably underestimates the optimal sizing required by the equipment extending this way the transient to elapse in order to restore the desired specifications, causing a corresponding off-spec production and a subsequent profit loss.

Experimental investigation of multiple steady states and parametric sensitivity in azeotropic distillation

Design and control of an energy-efficient alternative process for separation of Dichloromethane-Methanol binary azeotropic mixture

Rice Distillers Dried Grains with Solubles (RDDGS) is a byproduct of alcohol industry obtained by distillation of fermented rice. In the present experiment, chemical composition of RDDGS and the effect of supplementing RDDGS replacing soybean meal (SBM) on growth performance and feed conversion efficiency of crossbred Jersey calves have been studied. The DM content of RDDGS was 89.58 ± 0.09%. The chemical composition (% DM) in terms of OM, CP, EE, CF, NFE, TA, NDF, ADF, TCHO and AIA were 94.97±0.09, 48.43± 0.69, 5.45 ± 0.16, 6.50±0.27, 34.58±1.01, 5.03 ± 0.09, 40.50 ± 0.93, 16.82 ± 0.65, 42.91 ± 1.52 and 0.95 ± 0.06, respectively. Chemical analysis indicated that it is a good source of protein and other nutrients. The effect of feeding RDDGS in crossbred cattle was studied in a growth trial of 120 days and a digestibility trial of six days collection period. The animals in control group (T0) were fed on soya bean meal based concentrate mixture with paddy straw and green fodder as per requirement. In the treatment group (T1) soya bean meal in concentrate mixture was totally replaced by RDDGS. There was no significant difference between two groups of animals in terms of average DMI, CPI and TDNI. The blood parameters such as plasma glucose, protein, albumin, globulin, enzymes (AST and ALT) and urea also remained unaffected. The digestibility of DM, CP and EE were significantly higher in treatment group fed with RDDGS. The average daily gain (ADLG) was significantly higher in RDDGS supplemented group as a result of which feed conversion efficiency improved and thus economized the ration.