The paradigms of chemical engineering discipline are discussed. The first paradigm of Unit Operations and the second paradigm of Transport Phenomena are well recognized among the chemical engineers all over the world, and what the next paradigm is remains still an open question. Several proposals such as Chemical product engineering, Sustainable chemical engineering and Multi-scale methodology are considered as candidates for next paradigm. Might Computational Chemical Engineering be the next one, which is advancing the discipline of chemical engineering toward ultimate mechanism-based understanding of chemical processes? This possibility is comparatively expounded with other proposals, and the scope and depth of computational chemical engineering are shortly listed.

Owing to wide applications of automatic control systems in the process industries, the impacts of controller performance on industrial processes are becoming increasingly significant. Consequently, controller maintenance is critical to guarantee routine operations of industrial processes. The workflow of controller maintenance generally involves the following steps:monitor operating controller performance and detect performance degradation, diagnose probable root causes of control system malfunctions, and take specific actions to resolve associated problems. In this article, a comprehensive overview of the mainstream of control loop monitoring and diagnosis is provided, and some existing problems are also analyzed and discussed. From the viewpoint of synthesizing abundant information in the context of big data, some prospective ideas and promising methods are outlined to potentially solve problems in industrial applications.

Experiments and simulations were conducted for bubble columns with diameter of 0.2 m (180 mm i.d.), 0.5 m (476 mm i.d.) and 0.8 m (760 mm i.d.) at high superficial gas velocities (0.12-0.62 m·s^-1) and high solid concentrations (0-30 vol%). Radial profiles of time-averaged gas holdup, axial liquid velocity, and turbulent kinetic energy were measured by using in-house developed conductivity probes and Pavlov tubes. Effects of column diameter, superficial gas velocity, and solid concentration were investigated in a wide range of operating conditions. Experimental results indicated that the average gas holdup remarkably increases with superficial gas velocity, and the radial profiles of investigated flow properties become steeper at high superficial gas velocities. The axial liquid velocities significantly increase with the growth of the column size, whereas the gas holdup was slightly affected. The presence of solid in bubble columns would inhibit the breakage of bubbles, which results in an increase in bubble rise velocity and a decrease in gas holdup, but time-averaged axial liquid velocities remain almost the same as that of the hollow column. Furthermore, a 2-D axisymmetric k-ε model was used to simulate heterogeneous bubbly flow using commercial code FLUENT 6.2. The lateral lift force and the turbulent diffusion force were introduced for the determination of gas holdup profiles and the effects of solid concentration were considered as the variation of average bubble diameter in the model. Results predicted by the CFD simulation showed good agreement with experimental data.

In present work, a stepping optimization algorithm is proposed for the geometric optimization of conical fin, and the heat transfer rate of the fin is treated as the objective function in the optimization algorithm. The conical fin is divided into finite elements which have different generatrix slopes, and the geometry of the conical fin is finally determined by ensuring that every divided element can maintain the maximum heat transfer rate. Based on the actual condition of every element of the fin, the heat conduction equation is solved step by step. The present result shows that the optimized conical fin has more heat transfer quantity and higher fin efficiency compared with those of some typical fins. Furthermore, the theoretical feasibility and the error analysis of present optimization algorithm have been performed as well.

Accurate simulation of water distillation system for oxygen-18 (¹⁸O) isotope separation is necessary to guide industrial practice, since both deuterium (D) and oxygen-18 isotope get enriched and interfere with each other. In the present work, steady-state and dynamic distillation models are established based on a classic method and a cascade distillation system with 5 towers is introduced to test the models. The theoretical expressions of separation factor α_H/D for protium/deuterium and separation factor α¹⁶O/¹⁸O.for oxygen-16/oxygen-18 were derived, with the existence of deuterium and oxygen-18, respectively. The results of the steady-state simulation by the classical method proposed in the present work agreed well with the results of the lumping method. The dynamic process could be divided into 5 stages. Impressively, a peak value of product withdraw was observed before the final steady state, which was resulted from the change of ¹⁶O/¹⁸O separation factor and isotope distribution. An interesting low concentration zone in the towers of T2-T5 existed at the beginning of the dynamic process and it required industrial evidence.

The volumetric overall mass transfer coefficients in a multistage column have been measured using axial dispersion model for toluene-acetone-water system. The effect of operating parameters on the volumetric overall mass transfer coefficients has been investigated for both mass transfer directions. The results show that the mass transfer performance is strongly dependent on rotor speed and mass transfer direction, although only slightly dependent on phase flow rates. In addition, empirical correlations to predict the overall mass transfer coefficients have been developed. The proposed correlations based on dimensionless numbers can be considered as a useful tool for the possible scale up of the multistage column extractor.

Three types of ligands have been developed for copper-catalyzed Ullmann cross coupling reaction of bromaminic acid with amines in aqueous solution. Ligands with large steric hindrance and strong electron-donating capacity were beneficial to the reaction. UV-Vis and CV analyses demonstrated that these ligands had strong coordination with copper(I), implying the effect of ligand coordination ability on the stability and catalytic activity of catalytic system.

Starting the cracking gas compressor and precooling the refrigeration system are keys to start-up of an ethylene plant and accounts for up to 50% of the total start-up time and plant flare emissions. Premature feeding of cracking furnaces can be avoided if the cracking gas compressor is started and the refrigeration system is precooled in advance using mixed gas as the start-up working medium (SWM). Start-up scenario with mixed gas as SWM could significantly reduce the emission loss and shorten the precooling time. Research shows that making appropriate start-up scheme is important not only to ensure operational safety and feasibility, but also to reduce energy consumption. In this paper, a method is proposed to select suitable start-up operational parameters of compression and refrigeration system with sufficient safe operating ranges and short precooling time. The complex interrelation among key parameters of start-up is analyzed. It is found that higher energy consumption, especially for super high-pressure steam (SS), can promote operational safety and shorten the precooling time during start-up. Based on steady-state and dynamic simulation, appropriate operating parameter ranges are determined with reasonable SS consumption. A real case study demonstrates that an appropriate start-up scheme will optimize the operation.

In propylene polymerization (PP) process, the melt index (MI) is one of the most important quality variables for determining different brands of products and different grades of product quality. Accurate prediction of MI is essential for efficient and professional monitoring and control of practical PP processes. This paper presents a novel soft sensor based on extreme learning machine (ELM) and modified gravitational search algorithm (MGSA) to estimate MI from real PP process variables, where the MGSA algorithm is developed to find the best parameters of input weights and hidden biases for ELM. As the comparative basis, the models of ELM, APSO-ELM and GSAELM are also developed respectively. Based on the data from a real PP production plant, a detailed comparison of the models is carried out. The research results show the accuracy and universality of the proposed model and it can be a powerful tool for online MI prediction.

In the refinery scheduling, operational transitions in mode switching are of great significance to formulate dynamic nature of production and obtain efficient schedules. The discrete-time formulation meets two main challenges in modeling:discrete approximation of time and large size of mixed-integer linear problem (MILP). In this article, a continuous-time refinery scheduling model, which involves transitions of mode switching, is presented due to these challenges. To reduce the difficulty in solving large scale MILPs resulting from the sequencing constraints, the global event-based formulation is chosen. Both transition constraints and production transitions are introduced and the numbers of key variables and constraints in both of the discrete-time and continuous-time formulations are analyzed and compared. Three cases with different lengths of time horizons and different numbers of orders are studied to show the efficiency of the proposed model.

Plant layout design affects both investment and performance of a factory. To maximize the economic benefits of a petrochemical factory, a large number of factors must be considered simultaneously, such as material flow, heat flow and safety. However, conventional principles for plant layout design and optimization do not involve the heat flow, resulting in higher construction investment. To solve this problem, a new heuristic approach is proposed in this paper based on the current layout design principles. Both material flow (pipelines for process streams) and heat flow (pipelines for steam) are considered. Three optimization methods with different objective functions are used to optimize the layout. The application of proposed approach is illustrated with a case study. The optimal scheme and pipeline networks can be obtained, and the pipeline length is reduced significantly.

Soft sensor is an efficacious solution to predict the hard-to-measure target variable by using the process variables. In practical application scenarios, however, the feedback cycle of target variable is usually larger than that of the process variables, which causes the deficiency of prediction errors. Consequently soft sensor cannot be calibrated timely and deteriorates. We proposed a soft sensor calibration method by using Just-in-time modeling and AdaBoost learning method. A moving window consisting of a primary part and a secondary part is constructed. The primary part is made of history data from certain number of constant feedback cycles of target variable and the secondary part includes some coarse target values estimated initially by Just-in-time modeling during the latest feedback cycle of target variable. The data set of the whole moving window is processed by AdaBoost learning method to build an auxiliary estimation model and then target variable values of the latest corresponding feedback cycle are reestimated. Finally the soft sensor model is calibrated by using the reestimated target variable values when the target feedback is unavailable; otherwise using the feedback value. The feasibility and effectiveness of the proposed calibration method is tested and verified through a series of comparative experiments on a pH neutralization facility in our laboratory.

A novel diagram-based representation approach is developed to analyze the thermodynamic efficiency and identify quickly the promising energy-use improvement for integrated fractionating and heat exchange processes in delayed coking units. For considering temperature dependence of heat capacity and integrating fractionating and heat exchange processes, an advanced energy level composite curve is constructed by using the simulation results and a stepwise procedure. More accurate results of exergy analysis are obtained and the interaction between different components of the integrated system can be properly revealed in an integrated figure. Then the exergy calculation is performed to validate the performance of processes and to define the targets for improvement. The avoidable exergy destruction is also analyzed by applying the concepts of avoidable and unavoidable exergy destructions for the integrated system. In a case study for a Chinese refinery, the results reveal that the heat exchange between gas oil and deethanization gasoline is the most inefficient process with the highest retrofitting potential, and the lowest exergy efficiency of component in the integration system is only 29.4%. The improvement potential and exergy efficiency for the fractionator are 38.1% and 97.3%, respectively. It is obvious that the fractionator is not the most promising component for improvement.

In this work, a new activity coefficient model was deduced for the correlation of solid-liquid equilibrium (SLE) in electrolyte solutions. The new excess Gibbs energy equation for SLE contains two parts:the single electrolyte item and the mixed electrolyte item. Then a new hypothesis for the reference state of activity coefficients was proposed in the work. Literature data for single electrolyte solution and mixed electrolyte solution systems, with temperature spanning from 273.15 to 373.15 K, were successfully correlated using the developed model.

A reliable mathematical model of urea-water-solution (UWS) droplet evaporation and thermolysis is developed. The well known Abramzon-Sirignano evaporation model is corrected by introducing an adjustment coefficient considering the different evaporation behaviors of UWS droplet at different ambient temperatures. A semidetailed kinetic scheme of urea thermolysis is developed based on Ebrahimian's work. Sequentially, the evaporation characteristics, decomposition efficiency of a single UWS droplet and deposit formation are simulated. As a result, the relation of evaporation time, relative velocity, exhaust temperature and droplet initial diameter is presented. Synchronously, it indicates that temperature is the decisive factor for urea thermolysis. Different temperatures result in different deposit components, and deposit yield is significantly influenced by temperature and decomposition time. The current work can provide guidance for designing urea injection strategy of SCR systems.

As a new biofuel, isobutanol has received more attentions in recent years. Because of its high tolerance to higher alcohols, Saccharomyces cerevisiae has potential advantages as a platform microbe to produce isobutanol. In this study, we investigated integration effects of enhancing valine biosynthesis by overexpression of ILV2 and BAT2 with eliminating ethanol formation by deletion of PDC6 and decreasing acetyl-CoA biosynthesis by deletion of LPD1 on isobutanol titers. Our results showed that deletion of LPD1 in strains overexpressing BAT2 and ILV2 increased isobutanol titer by 5.3-fold compared with control strain. Additional deletion of PDC6 in lpd1Δ strains carrying overexpressed BAT2 and ILV2 further increased isobutanol titer by 1.5 fold. Overexpression of BAT2 and ILV2 in lpd1Δ strains and pdc6Δ strains decreased ethanol titers. Glycerol titers of the engineered strains did not have greater changes than that of control strain, while their acetic acid titers were higher, perhaps due to the imbalance of cofactors in isobutanol synthesis. Our researches suggest that double-gene deletion of PDC6 and LPD1 in strains overexpressing BAT2 and ILV2 could increase isobutanol production dramatically than single-gene deletion of PDC6 or LPD1. This study reveals the integration effects of overexpression of ILV2/BAT2 and double-gene deletion of LPD1 and PDC6 on isobutanol production, and helps understanding future developments of engineered strains for producing isobutanol.

This research article is based on the biodiesel synthesis from the marine green macroalga Ulva fasciata, collected from the coast of Karachi, Pakistan using new and the most potential waste catalysts from Pakistan Steel Industry. The oil was extracted with n-hexane then it was analyzed by GC, TLC and by the examination of fuel properties. The metal analysis of catalysts was carried out by chemical tests and flame atomic absorption spectroscopy (FAAS). The thermal treatment of catalysts at 1500-1700℃ during various processes in steel manufacturing industry converted the metals to metal oxides. The presence of CaO, MgO and ZnO in these catalysts made them highly reactive for biodiesel synthesis. The basicity of waste industrial catalysts was calculated to know their basic strength. The transesterification of U. fasciata oil was performed by fast stirring using 9:1 molar ratio of methanol/oil in the presence of seven different waste industrial catalysts for 6 h at 80-100℃. The solid catalysts were easily separated from product for re-use. In addition, the rate of reaction in the presence of these catalysts was found to be quite feasible. The waste brown dust from the steel converter gave the highest yield (88%) of biodiesel. The production of biodiesel was confirmed by TLC examination and fuel properties in comparison with the ASTM standards.

Response surface methodology (RSM) was used to determine the optimum conditions of the methanolysis of crude poppy seed oil using NaOCH₃ as catalyst. The experiments were run according to five levels, four variable central composite rotatable design (CCRD) using RSM. The reaction variables, i.e., molar ratio of methanol/oil (3:1-9:1), catalyst concentration (0.5 wt%-1.25 wt% NaOCH₃), reaction temperature (25-65℃), and reaction time (20-90 min) were studied. We demonstrated that the molar ratio of methanol/oil, catalyst concentration, and reaction temperature were the significant parameters affecting the yield of poppy seed oil methyl esters (PSOMEs). The optimum transesterification reaction conditions, established using the RSM, which offered a 89.35% PSOME yield, were found to be 7.5:1 molar ratio of methanol/oil, 0.75% catalyst concentration, 45℃ reaction temperature, and 90 min reaction time. The proposed process provided an average biodiesel yield of more than 85%. A linear correlation was constructed between the observed and predicted values of the yield. The gas chromatography (GC) analyses have shown that PSOMEs contain linoleic-, oleic-, palmitic-, and stearic-acids as main fatty acids. The FTIR spectrum of the PSOMEs was also analyzed to confirm the completion of the transesterification reaction. The fuel properties of the PSOMEs were discussed in light of biodiesel standards (ASTM D 6751 and EN 14214).

Agricultural wastes as lignocellulosic biomasses are known as the major resources of bioenergy. These valuable resources can be converted into useful environmental friendly fuels and chemicals. Wheat straw, walnut shell and almond shell are the main agricultural wastes in Kurdistan province, Iran. This study investigates the hydrogen-rich gas production via gasification of these biomasses in supercritical water media. Experiments were performed first, in the base case condition using a stainless steel batch micro reactor system. Then, the effect of reaction time on the total gas yield and yield of hydrogen, were investigated. It was seen that the total gas yields and gasification efficiencies increased by increasing the reaction time to 30 min and then the total gas yield was approximately remained constant. Among three used feed stocks, wheat straw with higher amount of cellulose and lower amount of lignin had the highest total gas and hydrogen yields in shorter reaction times. The maximum hydrogen yields of 7.25, 4.1 and 4.63 mmol per gram of wheat straw, almond shell and walnut shell occurred at 10, 15 and 20 min of reaction time, respectively.

Experiments on simultaneous absorption of SO₂ and NO_X from sintering flue gas via a composite absorbent NaClO₂/NaClO were carried out. The effects of various operating parameters such as NaClO₂ concentration (m_s), NaClO concentration (m_p), molar ratio of NaClO₂/NaClO (M), solution temperature (T_R), initial solution pH, gas flow (V_g) and inlet concentration of SO₂ (C_S) and NO (C_N) on the removal efficiencies of SO₂ and NO were discussed. The optimal experimental conditions were determined to be initial solution pH=6, T_R=55℃ and M=1.3 under which the average efficiencies of desulfurization and denitrification could reach 99.7% and 90.8%, respectively. Moreover, according to the analysis of reaction products, it was found that adding NaClO to NaClO₂ aqueous solution is favorable for the generation of ClO₂ and Cl₂ which have significant effect on desulfurization and denitrification. Finally, engineering experiments were performed and obtained good results demonstrating that this method is practicable and promising.

Hierarchical dendritic micro-nano structure ZnFe₂O₄ have been prepared by electrochemical reduction and thermal oxidation method in this work. X-ray diffractometry, Raman spectra and field-emission scanning electron microscopy were used to characterize the crystal structure, size and morphology. The results show that the sample (S-2) is composed of pure ZnFe₂O₄ when the molar ratio of Zn²⁺/Fe²⁺ in the electrolyte is 0.35. Decreasing the molar ratio of Zn²⁺/Fe²⁺, the sample (S-1) is composed of ZnFe₂O₄ and α-Fe₂O₃, whereas increasing the molar ratio of Zn²⁺/Fe²⁺, the sample (S-3) is composed of ZnFe₂O₄ and ZnO. The lattice parameters of ZnFe₂O₄ are influenced by the molar ratio of Zn²⁺/Fe²⁺:Zn at excess decreases the cell volume whereas Fe at excess increases the cell volume of ZnFe₂O₄. All the samples have the dendritic structure, of which S-2 has micron-sized lush branches with nano-sized leaves. UV-Vis diffuse reflectance spectra were acquired by a spectrophotometer. The absorption edges gradually blue shift with the increase of the molar ratio of Zn²⁺/Fe²⁺. Photocatalytic activities for water splitting were investigated under Xe light irradiation in an aqueous olution containing 0.1 mol·L^-1 Na₂S/0.02 mol·L^-1 Na₂SO₃ in a glass reactor. The relatively highest photocatalytic activity with 1.41 μmol·h^-1·0.02 g^-1 was achieved by pure ZnFe₂O₄ sample (S-2). The photocatalytic activity of the mixture phase of ZnFe₂O₄ and α-Fe₂O₃ (S-1) is better than ZnFe₂O₄ and ZnO (S-3).