Pre-treatment, which supplies a stable, high-quality feed for reverse osmosis (RO) membranes, is a critical step for successful operation in a seawater reverse osmosis plant. In this study, ceramic membrane systems were employed as pre-treatment for seawater desalination. A laboratory experiment was performed to investigate the effect of the cross-flow velocity on the critical flux and consequently to optimize the permeate flux. Then a pilot test was performed to investigate the long-term performance. The result shows that there is no significant effect of the cross-flow velocity on the critical flux when the cross-flow velocity varies in laminar flow region only or in turbulent flow region only, but the effect is distinct when the cross-flow velocity varies in the transition region. The membrane fouling is slight at the permeate flux of 150 L穖^-2穐^-1 and the system is stable, producing a high-quality feed (the turbidity and silt density index are less than 0.1 NTU and 3.0, respectively) for RO to run for 2922.4 h without chemical cleaning. Thus the ceramic membranes are suitable to filtrate seawater as the pre-treatment for RO.

Composite membranes have attracted increasing attentions owing to their potential applications for CO₂ separation. In this work, ceramic supported polydimethylsiloxane (PDMS) and poly (ethylene glycol) diacrylate (PEGDA) composite membranes were prepared. The microstructure and physicochemical properties of the composite membranes were characterized. Preparation conditions were systematically optimized. The gas separation performance of the as-prepared membranes was studied by pure gas and binary gas permeation measurement of CO₂, N₂ and H₂. Experiments showed that PDMS, as silicone rubber, exhibited larger permeance and lower separation factors. Conversely, PEGDA composite membrane presented smaller gas permeance but higher ideal selectivity for CO₂/N₂. Compared to the performance of those membranes using polymeric supports or freestanding membranes, the two kinds of ceramic supported composite membranes exhibited higher gas permeance and acceptable selectivity. Therefore, the ceramic supported composite membrane can be expected as a candidate for CO₂ separation from light gases.

In order to analyze the complex chemical kinetic mechanism systematically and find out the redundant species and reactions, a numerical platform for mechanism analysis and simplification is established basing on Path Flux Analysis (PFA). It is used to reduce a detailed mechanism for flame inhibited by phosphorus containing compounds, a reduced mechanism with 65 species and 335 reactions is obtained. The detailed and reduced mechanism are both used to calculate the freely-propagating premix C₃H₈/air flame with different dimethyl methylphosphonate doped over a wide range of equivalence ratios. The concentration distributions of free radicals and major species are compared, and the results under two different mechanisms agree well. The laminar flame speed obtained by the two mechanisms also matches well, with the maximum relative error introduces as a small value of 1.7%. On the basis of the reduced mechanism validation, the correlativity analysis is conducted between flame speed and free radical concentrations, which can provide information for target species selection in the further mechanism reduction. By analyzing the species and reactions fluxes, the species and reaction paths which contribute the flame inhibition significantly are determined.

In chemical processes, fault diagnosis is relatively difficult due to the incomplete prior-knowledge and unpredictable production changes. To solve the problem, a case-based extension fault diagnosis (CEFD) method is proposed combining with extension theory, in which the basic-element model is used for the unified and deep fault description, the distance concept is applied to quantify the correlation degree between the new fault and the original fault cases, and the extension transformation is used to expand and obtain the solution of unknown faults. With the application in Tennessee Eastman process, the result indicates that CEFD method has a flexible fault representation, objective fault retrieve performance and good ability for fault study, providing a new way for diagnosing production faults accurately.

This paper presents a superstructure-based formulation for the synthesis of mass-exchange networks (MENs) considering multiple components. The superstructure is simplified by directly using the mass separation agents (MSA) from their sources, and therefore the automatic synthesis of the multi-component system involved in the MENs can be achieved without choosing a ‘key-component’ either for the whole process or the mass exchangers. A mathematical model is proposed to carry out the optimization process. The concentrations, flow rates, matches and unit operation displayed in the obtained network constitute the exact representation of the mass exchange process in terms of all species in the system. An example is used to illustrate and demonstrate the application of the proposed method.

Fault diagnosis and monitoring are very important for complex chemical process. There are numerous methods that have been studied in this field, in which the effective visualization method is still challenging. In order to get a better visualization effect, a novel fault diagnosis method which combines self-organizing map (SOM) with Fisher discriminant analysis (FDA) is proposed. FDA can reduce the dimension of the data in terms of maximizing the separability of the classes. After feature extraction by FDA, SOM can distinguish the different states on the output map clearly and it can also be employed to monitor abnormal states. Tennessee Eastman (TE) process is employed to illustrate the fault diagnosis and monitoring performance of the proposed method. The result shows that the SOM integrated with FDA method is efficient and capable for real-time monitoring and fault diagnosis in complex chemical process.

Predicting the best shutdown time of a steam ethylene cracking furnace in industrial practice remains a challenge due to the complex coking process. As well known, the shutdown time of a furnace is mainly determined by coking condition of the transfer line exchangers (TLE) when naphtha or other heavy hydrocarbon feedstocks are cracked. In practice, it is difficult to measure the coke thickness in TLE through experimental method in the complex industrial situation. However, the outlet temperature of TLE (TLEOT) can indirectly characterize the coking situation in TLE since the coke accumulation in TLE has great influence on TLEOT. Thus, the TLEOT could be a critical factor in deciding when to shut down the furnace to decoke. To predict the TLEOT, a parametric model was proposed in this work, based on theoretical analysis, mathematic reduction, and parameters estimation. The feasibility of the proposed model was further checked through industrial data and good agreements between model prediction and industrial data with maximum deviation 2% were observed.

Control of pH neutralization processes is challenging in the chemical process industry because of their inherent strong nonlinearity. In this paper, the model algorithmic control (MAC) strategy is extended to nonlinear processes using Hammerstein model that consists of a static nonlinear polynomial function followed in series by a linear impulse response dynamic element. A new nonlinear Hammerstein MAC algorithm (named NLH-MAC) is presented in detail. The simulation control results of a pH neutralization process show that NLH-MAC gives better control performance than linear MAC and the commonly used industrial nonlinear propotional plus integral plus derivative (PID) controller. Further simulation experiment demonstrates that NLH-MAC not only gives good control response, but also possesses good stability and robustness even with large modeling errors.

Based on an equivalent two-dimensional Fornasini-Marchsini model for a batch process in industry, a closed-loop robust iterative learning fault-tolerant guaranteed cost control scheme is proposed for batch processes with actuator failures. This paper introduces relevant concepts of the fault-tolerant guaranteed cost control and formulates the robust iterative learning reliable guaranteed cost controller (ILRGCC). A significant advantage is that the proposed ILRGCC design method can be used for on-line optimization against batch-to-batch process uncertainties to realize robust tracking of set-point trajectory in time and batch-to-batch sequences. For the convenience of implementation, only measured output errors of current and previous cycles are used to design a synthetic controller for iterative learning control, consisting of dynamic output feedback plus feed-forward control. The proposed controller can not only guarantee the closed-loop convergency along time and cycle sequences but also satisfy the H_? performance level and a cost function with upper bounds for all admissible uncertainties and any actuator failures. Sufficient conditions for the controller solution are derived in terms of linear matrix inequalities (LMIs), and design procedures, which formulate a convex optimization problem with LMI constraints, are presented. An example of injection molding is given to illustrate the effectiveness and advantages of the ILRGCC design approach.

New approaches for facility distribution in chemical plants are proposed including an improved non-overlapping constraint based on projection relationships of facilities and a novel toxic gas dispersion constraint. In consideration of the large number of variables in the plant layout model, our new method can significantly reduce the number of variables with their own projection relationships. Also, as toxic gas dispersion is a usual incident in a chemical plant, a simple approach to describe the gas leakage is proposed, which can clearly represent the constraints of potential emission source and sitting facilities. For solving the plant layout model, an improved genetic algorithm (GA) based on infeasible solution fix technique is proposed, which improves the globe search ability of GA. The case study and experiment show that a better layout plan can be obtained with our method, and the safety factors such as gas dispersion and minimum distances can be well handled in the solution.

Many structure-property/activity studies use graph theoretical indices, which are based on the topological properties of a molecule viewed as a graph. Since topological indices can be derived directly from the molecular structure without any experimental effort, they provide a simple and straightforward method for property prediction. In this work the flash point of alkanes was modeled by a set of molecular connectivity indices (χ), modified molecular connectivity indices (^mχ_t^h) and valance molecular connectivity indices (^mχ^v), with?^mχ^v?calculated using the hydrogen perturbation. A stepwise Multiple Linear Regression (MLR) method was used to select the best indices. The predicted flash points are in good agreement with the experimental data, with the average absolute deviation 4.3 K.

Lignins were isolated and purified from alkali treated prehydrolysate of corn stover. The paper presents the structural features of lignins in a series purification processes. Fourier transform infrared spectroscopy, ultraviolet-vis spectroscopy and proton nuclear magnetic resonance spectroscopy were used to analyze the chemical structure. Thermogravimetric analysis was applied to follow the thermal degradation, and wet chemical method was used to determine the sugar content. The results showed that the crude lignin from the prehydrolysate of corn stover was a heterogeneous material of syringyl, guaiacyl and p-hydroxyphenyl units, containing associated polysaccharides, lipids, and melted salts. Some of the crude lignin was chemically linked to hemicelluloses (mainly xylan). The lipids in crude lignin were probably composed of saturated and/or unsaturated long carbon chains, fatty acids, triterpenols, waxes, and derivatives of aromatic. The sugar content of purified lignin was less than 2.11%, mainly composed of guaiacyl units. DTG_max of purified lignin was 359℃. The majority of the hydroxyl groups were phenolic hydroxyl groups. The main type of linkages in purified lignin was β-O-4. Other types of linkages included β-5, β-β and α-O-4.

Acid gas injection into saline aquifers is one of promising ways to reduce greenhouse gas emissions and to dispose hazardous waste simultaneously. On the basis of Level Set method, an improved mathematical model that described interfacial dynamics of acid gas-brine system in a deep confined saline aquifer was proposed for predicting the propagation of the acid gas plume, which was featured by using Peng-Robinson equation and modified Lucas equation to describe variations of the density and viscosity of acid gas in saline aquifers. The evolutional characteristics of acid gas plume were obtained through numerical simulations using COMSOL Multiphysics 3.5a. The results showed that under intrinsic characteristics of aquifers and operational conditions given, the variation of acid gas density was the major factor that influences the patterns and shapes of the plume. The leading edge position of acid gas plume was intensively dependent on the acid gas composition. Under the scheme of fixed mass flow rate injection, as the molar fraction of H₂S increased, the position of leading edge advanced gradually towards the injection well. Moreover, the estimation of the storage efficiency of acid gas in saline aquifers was clarified and discussed. The proposed approach and the simulation results will provide insights into the determination of optimal operational strategies and rapid identification of the consequences of acid gas injection into deep confined saline aquifers.

The gas-liquid phase equilibrium is used in controlling the nitrosation reaction process. Decomposition of nitrous acid and oxidation side reaction are suppressed in a closed reaction system. The system pressure is used as the criterion of the end of reaction, avoiding excessive feeding and reducing the decomposition of nitrous acid. The head space of the reactor is used as the gas buffer, stabilizing the feeding fluctuations and inhibiting the side reaction, decomposition of nitrous acid. Nitrogen oxide concentration is controlled at the minimum level. Thus the zero release of nitrogen oxide waste gas can be achieved without using any absorption process.

The suspension polymerization with two organic phases was adopted to prepare spherical hypercrosslinked resin by self-polycondensation of 4,4′-bis-(chloromethyl)-1,1′-biphenyl (CMB). The chemical structure, morphology and pore characteristics of the novel spherical resin were characterized with Fourier transform infrared spectroscopy (FTIR), micrograph and Brunauer-Emmett-Teller (BET). It is found that the suspension system and stirring speed impose a great influence upon the regularity and size distribution of hypercrosslinked beads. To prepare CMB resin beads with diameter of about 300 μm, the optimal condition is as follows: stirring speed 300 r·min^-1, and the volume ratio of the two organic phases (nitrobenzene/dimethyl silicon oil) 1:5. After the self-polycondensation and succedent post-crosslinking of CMB monomer, the spherical adsorbent presents high special surface area (1190 m²·g^-1) and abundant pore volume (0.714 cm³·g^-1), and could be potentially applied in the adsorption of various organic molecules and synthesis of porous ion exchanger.

Layered intercalated functional materials of layered double hydroxide type are an important class of functional materials developed in recent years. Based on long term studies on these materials in the State Key Laboratory of Chemical Resource Engineering in Beijing University of Chemical Technology, the principle for the design of controlled intercalation processes in the light of future production processing requirements has been developed. Intercalation assembly methods and technologies have been invented to control the intercalation process for preparing layered intercalated materials with various structures and functions.