Computer Simulation Of Process Research Articles

Separation of isopropyl alcohol and isopropyl ether with ionic liquids as extractant based on quantum chemical calculation and liquid-liquid equilibrium experiment

Ionic liquids (ILs) have been widely studied as potential substitutes for traditional solvents in the extraction process. However, most of the literatures only focus on obtaining the data of equilibrium experiments. This work presents a method combining computer calculation, experiment and process simulation. From the perspective of molecular calculation, the extraction mechanism is analyzed. σ-profile is obtained by COSMO-SAC, and according to σ-profile, the feasibility and rationality of the separation of isopropanol and isopropyl ether by liquid-liquid extraction with ILs as extractant are proved. The hydrogen-bonding interaction between ILs and IPA are determined by using quantum chemical calculation, including bond length, total charge density, deformation charge density. By calculating the intermolecular interaction energy between selected ILs and isopropyl alcohol, the extraction ability of different ILs is compared. The correctness of mechanism analysis is verified by liquid-liquid equilibrium experiment. The process is simulated by entering binary interaction parameters in Aspen Plus. By calculating TAC, the operating conditions under the minimum TAC are obtained. This paper provides a new theoretical guidance for the selection of extractants for separating azeotropes.

Application of Computer Process Simulation in Chemical Synthesis of Urea

The computer process simulation technology can simulate the chemical process of urea, effectively reflect the technological parameters of the chemical production process, and provide practical guidance for chemical production of urea. This paper conducts computer process simulation of the high-pressure urea synthesis tower, the center piece of the chemical synthesis of urea. The chemical parameters in the production process of the synthesis tower are simulated and analyzed with the aid of the equilibrium stage model and computer technology. The calculation results are consistent with the design values of the synthesis tower, indicating that the equilibrium stage model satisfies the technological design requirements. Suffice it to say that the research provides meaningful guidance for the chemical production of urea.

A Study on the Application of Computer Process Simulation Technology in Ammonia Synthesis

A chemical process simulation software, AspenPlus, is applied to simulate the ammonia synthesis in the ammonia production process. A reasonable unit operating model is selected, and the RKS-BM thermodynamic method is adopted for calculations. The simulation results are in favorable agreement with the actual operation results, and the simulation data has a guiding significance on the actual production. Meanwhile, this paper analyzes the influence of the changes in the synthesis pressure, the outlet gas temperature of the synthesis tower, the hydrogen/nitrogen ratio of fresh air and other operating parameters on the ammonia synthesis section. The net profit of the synthetic section is taken as the objective function to optimize the operating parameters. The optimal process operating parameters are obtained: the synthesis pressure is 20MPa, the convertor outlet temperature is 313°C, and the H2/N2 ratio of fresh air is 3.0.

Life cycle assessment of butanol production in sugarcane biorefineries in Brazil

Butanol production by the sugarchemistry route (fermentation of sugarcane juice) was evaluated considering different arrangements for its process integration in sugarcane biorefineries: first and second generation butanol production using acetone-butanol-ethanol (ABE) fermentation with wild and genetically modified microorganisms. The whole production chain was investigated, from the agricultural stage, through transportation of sugarcane and vinasse, to the industrial process and butanol final use when applicable. Life cycle inventories and mass and energy balances for the industrial stage were taken from computer process simulation obtained from the literature. Butanol production from bagasse and straw pentoses using genetically modified microorganism presents the best environmental performance among the investigated technological scenarios. Comparison with the oil-based production route and use as liquid fuel for vehicles evidenced environmental advantages for bio-based butanol in terms of global environmental impacts, such as abiotic depletion, global warming and ozone layer depletion potentials. Additionally, the introduction of butanol and the by-product acetone to the product portfolio of biorefineries led to increased revenues in comparison to base scenarios, which can ultimately help to mitigate environmental impacts of the biorefinery in monetary terms.

The solitary grain liberation model: a description of a mineral liberation model for low-grade ores

Some of the mineral deposits that are being processed today, and especially those expected to be processed in the future, have relatively low compositions of the valuable mineral. With these low-grade ores, it is necessary to be able to design processes that are sufficiently low-cost to permit exploitation. One approach to minimizing the capital and operating costs for these processes is to use the capabilities of computer process simulation in the design phase of development, to make important technical and economic decisions regarding the evaluation of alternative process flow schemes, the selection of equipment and the choice of operating conditions. There are mathematical simulation models for most mineral processing operations, including several each for size reduction, size classification and mineral separations. To be able to tie these individual operating models together in an integrated mineral process simulation, however, it is important, in fact in some cases essential, that there be a model which describes how the mineral system responds to size reduction in making the liberated valuable and waste mineral particles available for concentration or rejection operations and the locked particles available for possible recirculation. This, then, is the role played by the mineral liberation model, showing the relationship between particle size, quantity and composition throughout the process.

GIS-model based estimation of nitrogen leaching from croplands of China

Nitrogen (N) is the most widely used fertilizer nutrient, and its application has increased substantially in recent decades in China. N loss through leaching has been recognized as one of the most common agricultural sources of groundwater contamination. Thus, prediction of N leaching from cropland is crucial for preventing groundwater pollution. This paper quantifies nitrogen leaching from China’s croplands, identifies its spatial distribution under current cropping systems at national scale, and finally puts forward some policies or strategies to reduce rates of N leaching. A computer process simulation model of carbon and nitrogen biogeochemistry in agro-ecosystems (DNDC) was applied to predict nitrogen leaching in the soil layer of agricultural ecosystems at national scale. Data on climate, soil properties, cropping systems, acreage, and management practices at county scale were collected from various sources and integrated into a spatial GIS database to run the model. The total amount of N-leaching was predicted at 4.57 million t N/year, which is equivalent to 48 kg N per ha cropland in 1998. The spatial distribution of N leaching in China showed a sharp discrepancy between the northern and southern counties due to the differences in climatic conditions, soil properties, as well as farm management practices. The study also suggests that applying management alternatives, such as proper fertilizer, crop, water and soil management, could be efficient means for decreasing N leaching rates.

Dense-Gas Fractionation and MALDI Characterization of Carbonaceous Pitches

The combination of multistage, dense-gas extraction (DGE) and matrix-assisted, laser desorption/ionization (MALDI) mass spectrometry (MS) was investigated for the fractionation and characterization of an oligomeric model pitch synthesized via the thermal polymerization of anthracene. Our approach was shown to be effective both for elucidating the molecular properties of the anthracene pitch and for generating narrow molecular weight (MW), oligomeric cuts that can serve as MW standards. DGE was used to fractionate 10- to 15-g charges of anthracene pitch into relatively pure, gram- and decigram-sized cuts containing 99+% monomers, 90+% dimers, and 80+% trimers, respectively. The multistage, semi-batch DGE process was carried out in two steps with toluene being used as the dense-gas solvent at both subcritical and supercritical conditions. In the first step, lower-MW species were stripped off as the overhead; for the second step, the remaining residue was extracted, yielding the desired oligomeric cuts as overhead. Computer process simulation was used to guide the experimental work and demonstrated the effect of column temperature gradient on the liquid reflux ratio and, as a result, product purity. MALDI-MS played a critical role in guiding the selection of DGE operating conditions, yielding absolute MW information on the fractions that were produced.

Status and Future Development of Application of Computer-Simulation to Arc Spraying Technology

With the arrival of such high-technologies as super-sonic velocity arc spraying (SVAS), arc spraying technology coruscate the second energy to which theory and process computer-simulation has increasingly applied. In this paper, the arc spraying process is divided into two stages: the first stage is atomization spraying stream (ASS) and the second one is spraying deposition (SD). Then study status is described for both stages physical model and corresponding controlling-equation. Based on the analysis of study status, the future development is deduced for application of computer simulation to arc spraying technology.

Planning gang formwork operations for building construction using simulations

Concrete formwork is a labor-intensive and time-consuming operation. Many modular formwork systems have been developed to automate the process. Such systems improve the productivity as well as the cost-effectiveness of the operation. However, proper planning for the form reuse schemes in the design as well as the construction phases of a building, including resource allocations (modular form sets, cranes, workers, etc.), and the construction sequence, is vital for ensuring a successful use of modular formwork systems. Computer process simulation techniques are employed in this research for the study of different form reuse schemes to use gang forming systems in building construction. Five form reuse schemes are identified. The CYCLONE modeling methodology is employed to develop computer models for each of them. MicroCYCLONE simulations and sensitivity analyses of the schemes, using different numbers of form sets, cranes, and labor crews, are then conducted for a real case to assess their impact on the productivity as well as the cost-effectiveness of the operation. The objective is to better understand the characteristics of different form reuse schemes and, in turn, to produce better plans for gang forming construction. Thus, the application of modular formwork systems in building construction can be facilitated.

Cladding formation in laser‐beam fusion of metal powder

Current commercial rapid prototyping systems can be used for fabricating layered models for subsequent creation of fully‐dense metal parts using investment casting. Due to increased demand for shortened product development cycles however, there exists a demand to rapidly fabricate functional fully‐dense metal parts without hard tooling. A possible solution to this problem is direct layered rapid manufacturing of such parts, for example, via laser‐beam fusion of the metal powder. The rapid manufacturing process discussed herein is based on this approach. It involves selective laser‐beam scanning of a predeposited metal‐powder layer, forming fully‐dense claddings as the basic building block of individual layers. This paper specifically addresses only one of the fundamental issues of the rapid manufacturing process under investigation at the University of Toronto, namely the fabrication of single claddings. Our theoretical investigation of the influence of the process parameters on cladding’s geometrical properties employed thermal modeling and computer process simulation. Numerous experiments, involving fabrication of single claddings, were also carried out with varying process parameters. Comparisons of the process simulations and experimental results showed good agreement in terms of overall trends.

Improvement of the design and operation of desalination plants by computer modelling and simulation

This paper describes the challenge and benefits of improving the design and operations of desalination and co-generation plants. Both the design and the control aspects of these processes are considered. It explains how steady state and dynamic simulation can lead to better design and improved control. The paper highlights the economic benefits which can be achieved by using computer modelling and process simulation. It presents some industrial applications of ASPEN PLUS™ and SPEEDUP™ for design, optimization, and control system studies of desalination and co-generation plants.

The utilization of JEM for scientific and technological investigation

Scientific equipments to be installed in Japanese Experimental Module (JEM) which will be attached to Space Station Freedom core are briefly reviewed. The selection procedure and the expected specifications of the equipments are described comparing with other equipments so far designed for space use and with ground base equipments. As for the future aspects, the importance for on-board characterization and computer process simulation under microgravity is stressed.

Fermentation process diagnosis using a mathematical model

Intriguing physiology of a solvent-producing strain ofClostridium acetobutylicum led to the synthesis of a mathematical model of the acetone-butanol fermentation process. The model presented is capable of describing the process dynamics and the culture behavior during a standard and a substandard acetone-butanol fermentation. In addition to the process kinetic parameters, the model includes the culture physiological parameters, such as the cellular membrane permeability and the number of membrane sites for active tansport of sugar. Computer process simulation studies for different culture conditions used the model, and quantitatively pointed out the importance of selected culture parameters that characterize the cell membrane behaviour and play an important role in the control of solvent synthesis by the cell. The theoretical predictions by the new model were confirmed by experimental determination of the cellular membrane permeability.