Modeling and Optimization for a Comprehensive Gas Processing Plant with Sensitivity Analysis and Economic Evaluation

Sweetening, dehydration, natural gas liquid (NGL) recovery, and sale gas compression are four major treatment stages for the general natural gas processing. Here, a comprehensive gas processing plant (CGPP) coupling sweetening, dehydration, NGL recovery, and compression subsystems have been conceptually designed, modeled, and optimized based on field data. The development includes four major stages of work: (i) CGPP process development with Aspen HYSYS simulator; (ii) sensitivity studies for all distillation columns involved in the CGPP process to optimize their performances; (iii) sizing of major equipment of the CGPP; and (iv) economic evaluations with Aspen process economic analyzer to calculate the expected capital and operating expenditures for the developed CGPP process. Valuable insights of natural gas monetization from the viewpoint of large-scale process system integration, modeling, and optimization are provided.     

Influence of charge density on rheological properties and dehydration dynamics of weakly charged poly(N-isopropylacrylamide) during phase transition

It is well-known that introduction of charged groups to poly(N-isopropylacrylamide) (PNIPAM) raises its phase transition temperature. However, the influence of charged groups on structural evolution and dehydration dynamics of weakly charged PNIPAM during phase transition still lacks systematic investigation. In the current study, armed with rheometer and two-dimensional Fourier transform infrared spectrometer (2D-FTIR), we investigated on mesoscopic and microscopic scales the phase transition of sodium poly(N-isopropylacrylamide-co-2-acrylamido-2-methylpropanesulfonate), abbreviated as poly(NIPAM-co-NaAMPS), with charge density of 1–10%. At ambient temperature, scaling exponent of poly(NIPAM-co-NaAMPS) varies from that of neutral polymer to polyelectrolytes as charge density increases. Above phase transition temperature, mesoscopic structure of poly(NIPAM-co-NaAMPS) varies from network of physical gel to viscoelastic liquid containing branched aggregates with increase of charge density, indicating increasing hindrance to intra/inter-chain association due to electrostatic repulsion. On a molecular level, poly(NIPAM-co-NaAMPS) exhibits distinctive microdynamic sequence of dehydration during phase transition, in contrast to neutral PNIPAM. In particular, sulfonate groups decouple the cooperative dehydration of alkyl and carbonyl groups, resulting in their distinctive phase transition temperature as well as temperature range. In analogy to hydration of proteins, it is proposed that the microdynamic sequence, implying the hydration stability of each group, is closely related to the density of hydration layer as well as influence of electrostatic field generated by charged groups. For poly(NIPAM-co-AMPS) with charge density of 3%, there still remains 72.3% of hydrogen bonds between carbonyl group and water at 60 °C, meanwhile a highly hydrated network forms with network strands 1–2 times as long as the copolymer chain length.     

一类非聚醚破乳剂的破乳效果与油水界面膜强度的关系

以甲基丙烯酸甲酯、丙烯酸丁酯、甲基丙烯酸、丙烯酸为原料,采用乳液法合成了一系列亲水、疏水基团比例不同的四元共聚物破乳剂。主要考察了合成的LG系列非聚醚破乳剂及其与工业聚醚破乳剂LP复配的破乳性能,以及破乳性能与油水界面膜强度的关系,并分析了温度对界面膜强度的影响,而且对产物进行了傅里叶变换红外光谱检测。结果表明,在85℃,LG系列破乳剂中LG2的破乳效果相对较好,加量120mg/L时脱水率达80.36%,当LP与LG2按V(LP)∶V(LG2)=1∶1复配后破乳效果最好,脱水率达93.33%,高于LP单剂的脱水率90.91%,2种破乳剂产生了协同增效作用。破乳剂和温度是影响界面膜强度的重要因素,破乳剂降低界面膜强度的能力越强,破乳效果越好。同种破乳剂相同破乳时间内,温度越高,界面膜强度越低,越有利于破乳。     

Zeolite filled polyimide membranes for dehydration of isopropanol through pervaporation process

Six mixed matrix membranes (MMMs) were prepared using zeolites of 4A and ZSM-5 incorporated in polyimide of Matrimid 5218. Effects of filler type on membrane morphology and pervaporation performance of MMMs were investigated using isopropanol dehydration. In addition, effects of operating temperature (30, 40, 50, and 60 °C), feed water concentration (10, 20, 30, and 40 wt.%) and permeate side pressure (0 and 15 torr) on pervaporation performance were studied. Scanning electron microscopy (SEM) analysis showed there were good adhesion between the fillers and the polymer matrix. Zeolite 4A has a better contact with the polymer phase and thereby nearly no void is formed in the MMM structure. Pervaporation were performed based on L16 array of Taguchi method for design of experiments. The results showed that the best separation condition is achieved at temperature, feed water concentration, and permeate pressure of 30 °C, 10 wt.% water and 0 torr, respectively. Selectivities of zeolites 4A and ZSM-5 filled MMMs were calculated as 8991 and 3904 compared with 1276 measured for the neat Matrimid 5218 membrane. Permeation rates of the zeolite 4A and ZSM-5 filled MMMs and the neat polymeric membrane were found to be 0.018, 0.016, and 0.013 kg/m² h, respectively.     

Analysis of a sequential production of electricity,ice and drying of agricultural products by cascading geothermal energy

In this paper, it is presented an analysis for the sequential production of electricity, ice and drying of agricultural products, by the concept of cascade for medium and low temperature geothermal energy. To carry out the analysis, a set of practical assumptions for the integration of technologies operated by cascade method for geothermal energy were defined. The geothermal cascade is composed of three thermal levels, each one operating under different temperatures in decreasing form. Additionally, the thermal cascade is composed at the first level by an Organic Rankine Cycle (ORC) for electricity production. In the second thermal level, by an absorption refrigeration cycle for ice production, and in the third level includes a dehydrator for drying of agricultural products. The agricultural products considered for dehydration are: avocado, green chile and tomato. Once the main assumptions were set, five integration alternatives and five different modes of operation of the system were proposed. The alternatives have different features for the activation of the first thermal level of the cascade, different nominal capacities of electricity production, cold, and quantity of product to be dehydrated. Subsequently, a technical-economic analysis is carried out to obtain the performance and energy characteristics of the different thermal levels of the cascade, different modes of operation, carbon dioxide emissions, cost estimations and indicators of economic viability. The results indicate that the dehydration process improves drastically the economic profits of all alternatives, especially for dehydration of tomato, achieving simple payback periods of around one year, overall energy efficiency of up to 17.84% and greenhouse emissions reduction of 537.7 tonnes of CO₂ per year. Concerning the modes of operation, it was determined that the one based on only-electricity production is not desirable due to the worst energy and economic performance.     

An investigation of the electrolytic solution effects on stainless steel electrode for dye-sensitized solar cells

In the field of dye-sensitized solar cells (DSSCs) the tendency is nowadays to replace the classical conducting glass by a metallic substrate (i.e. stainless steel 304L) as the counter-electrode. However the electrolytic solution (iodide/triiodide in an organic solvent) may be aggressive for stainless steel. An electrolytic solution optimization should improve the long-term stability and increase the cell performance. For this purpose, the electrolytic solution was submitted to different treatments (i.e. deoxygenation, dehydration and dehydration–deoxygenation) in order to increase the corrosion resistance of stainless steel (304L) electrode by eliminating the dissolved oxygen and water.     

Vacuum dehydration kinetics of onion slices

Onion slices were dried in a single layer of thickness varying from 1 to 5 mm in the temperature range of 50-70 °C in a laboratory scale vacuum dryer. The effect of pretreatment, drying temperature and slice thickness on the drying kinetics of onion slices was studied. Four thin layer drying models namely Lewis model, logarithmic model, Page model and Fick's law model were applied on the experimental moisture loss data with respect to time to predict the drying pattern properly on the basis of coefficient of determination and standard error. The Page model showed better fit to the experimental data compared to other models. Effective moisture diffusivity of the slice was measured using Fick's second law of unsteady state diffusion. The diffusivity values were found ranging from 1.32E−10 to 1.09E−09 m²/s for untreated and 1.32E−10 to 1.09E−01 m²/s for treated onion slices. Effective moisture diffusivity showed increasing trend with increase in temperature and thickness.     

不同干燥方式对凝胶注模成形陶瓷坯体干燥过程的影响

本文通过凝胶注模成形得到氧化铝陶瓷坯体,采用直接干燥、高湿干燥、液相介质干燥等方式对坯体进行干燥,研究了不同的干燥方式对坯体干燥速率及干燥效果的影响。结果表明：凝胶注模成形坯体对环境温度、湿度的变化非常敏感,高湿干燥、液相介质干燥可有效减缓干燥速率,避免干燥过程中出现的开裂现象。     

Preparation of indium oxide powders by microwave plasma dehydration of indium hydroxide powders

Indium oxide was prepared from the dehydration of indium hydroxide using atmospheric-pressure microwave air plasma. Compared with the conventional thermal plasma processing that was performed with the vapor phase reaction, the solid-state reaction was attempted in this study because microwave plasma has an intermediate temperature that is comparable to the melting temperature of inorganic materials and between those of the electric furnace and the thermal plasma. The results were compared with those with the electric furnace and the thermal plasma. With both the microwave plasma and the electric furnace, the macro-morphologies of the raw material were maintained, which indicates successful dehydration. However, the micro-morphologies differed. The product of the microwave plasma had a smooth surface, whereas the product of the electric furnace had a cracked and rough surface. The cracks were regarded as the results of the poor diffusion of the dissociated water. In the microwave plasma, the high temperature and the fast heating rate enhanced the diffusion and controlled the formation of cracks. With the application of the thermal plasma, the nanoparticles were prepared due to the vaporization of the dehydrated material. Thus, the microwave plasma is considered applicable to the solid-state reaction accompanying degassing, without a change in the microstructure of the raw material.     

OSMOTIC DRYING KINETICS OF CYLINDRICAL APPLE SLICES OF DIFFERENT SIZES

The objective of this study was to evaluate the osmotic drying kinetics of cylindrical slices of apples as influenced by particle size at different concentrations of sucrose solutions and different temperatures. Osmotic drying was carried out, with cut apple cylinders of three different sizes (12, 17 and 20mm diameter), all with a length to diameter ratio of 1:1, in a well agitated large tank containing the osmotic solution at the desired temperature. The solution to fruit volume ratio was kept greater than 60. A central composite rotatable design (CCRD) was used with dive levels of sucrose concentrations (34-63°Brix) and five temperatures (34-66°C). Kinetic parameters included weight loss, moisture loss, solids gain, rates of moisture loss and solids gain generally increased with increasing treatment time, temperature and concentration of osmotic solution, and decreased with an increase in sample size. The parameter “osmotic drying time to achieve a given moisture loss” obviously showed the opposite. Composite models were developed to describe the effect of process variables and particle size on the drying behavior of apple slices.