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Qualitative and quantitative description are key to solving the problem of heavy metal contamination on fluid catalytic cracking (FCC) catalysts. The loading efficiencies for different metals were compared for the two lab simulation methods of Multi-Cyclic Deactivation (MCD) and Advanced Catalyst Evaluation (ACE), and the microcatalytic performance of metal-contaminated catalysts was evaluated using an ACE Model C device. The results show that the MCD and ACE methods both obtain extremely high data accuracy, indicating that they can be used to ensure the parallel reliability of experimental results. The typical operating parameters for hydrothermal aging and metals loading can be adjusted to suit different metal types and content targets for either of these two simulation methods. Compared with an equilibrium catalyst from an industrial unit, the MCD method has the advantages of basic hydrothermal aging treatment with less metal loading efficiency, while the ACE method has an accurate metal amount and high loading efficiency for metal contamination, with a metal balance recovery rate above 99.5% at similar activation to the equilibrium catalyst. When used with a reasonable and effective metal pretreatment scheme, these two laboratory simulation methods can be used to evaluate new commercial catalysts and in fundamental experiments for the improvement of FCC catalysts for removal of metal contamination.

The aim of this retrospective study was to evaluate the horizontal bone gain at the different level of alveolar bone using titanium screw as a reference plane by titanium mesh with tent screw (exposed or not) and autologous bone grafting. 16 patients and 23 measured points were enrolled in this study. CBCT data of immediately and 6 months after bone grafting were measured at crestal (CW), midway (MW), and basal (BW) level and reconstructed for area measurement. The exposure of Ti-mesh or not had been evaluated. The area of bone gained and absorption ratio were almost the same. The width absorption ratio of titanium mesh and onlay grafting group or at CW, MW, and BW were almost the same. However, the width absorption ratio of the exposed Ti-mesh at CW, MW, and BW were significantly higher than the not exposed one. Thin biotype was a main factor of titanium mesh exposure. The exposed Ti-mesh at late phase also can achieve clinically accepted bone gained after certain anti-inflammatory treatment. Ti-mesh with tenting screw could achieve the same bone augmentation effect as the autogenous bone block did, even it is exposed at late phase. However, the absorption ratio significantly increased if exposed.

Osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is an essential stage in bone formation. Autophagy plays a pivotal role in the self-renewal potential and pluripotency of stem cells. This study aimed to explore the function of autophagy-related genes during osteogenic differentiation of BMSCs.The differentially expressed autophagy-related genes (ARGs) were obtained from the GEO and HADb databases. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed using R software. The PPI and hub gene mining networks were constructed using the STRING database and Cytoscape. Finally, the RT-qPCR was conducted to validate the expression level of ARGs in BMSCs.Thirty-seven differentially expressed ARGs were finally obtained, including 12 upregulated and 25 downregulated genes. GO and KEGG enrichment analysis showed that most of these genes were enriched in apoptosis and autophagy. The PPI network revealed strong interactions between differentially expressed ARGs. The expression level of differentially expressed ARGs tested by RT-qPCR showed 6 upregulated ARGs, includingWe identified 37 ARGs during osteogenic differentiation using bioinformatics analysis. FOXO1, MAP1LC3C, CTSB, FOXO3, CALCOCO2, FKBP1A, MAPK8IP1, NRG1, VEGFA, and ITGA6 may regulate osteogenic differentiation of hBMSCs by involving autophagy pathway. This study provides new insight into the osteogenic differentiation of hBMSCs and may be available in developing therapeutic strategies for maxillofacial bone defects.

Background: The aim of this retrospective study was to evaluate the horizontal bone gain at the different level of alveolar bone using titanium screw as a reference plane by titanium mesh with tent screw (exposed or not) and autologous bone grafting.Methods: 16 patients and 23 measured points were enrolled in this study. CBCT data of immediately and 6 months after bone grafting were measured at crestal (CW), midway (MW), and basal (BW) level and reconstructed for area measurement using titanium screw as reference plane. The exposure of titanium mesh or not had been evaluated.Results: The area of bone gained and absorption ratio were almost the same without statistical different. There were not statistical different between the titanium mesh and onlay grafting, and measured level at CW, MW, and BW, and the exposed titanium mesh and not exposed one. The width absorption ratio of titanium mesh and onlay grafting group or at CW, MW, and BW were almost the same. However, the width absorption ratio of the exposed titanium mesh at CW, MW, and BW were significantly higher than the not exposed one. Thin biotype was a main factor of the exposure of titanium mesh. The exposed titanium mesh at late phase also can achieve clinically accepted bone gained after certain anti-inflammatory treatment. Conclusions: Ti-mesh with tenting screw could achieve the same bone augmentation effect as the autogenous bone block did, even it is exposed at late phase. However, the absorption ratio significantly increased if exposed.

In the field of underwater maneuvering target tracking, the detection of sensors is not effective in real time. Under man-made or non-man-made interference, the observer only receives the noise value or abnormal value, that is, the sensor will fail for a short time. Once the sensor fails to obtain correct data continuously for a period of time, this is fatal to the filter. Aiming at the short-term failure of sensors, this paper proposes a tracking method for surface targets with compensation mechanism. This method uses the idea of deep learning to extract enough training samples from the observation data, and uses the samples to train the Long Short-Term Memory (LSTM) neural network with time series prediction ability offline. Secondly, the trained neural network model is used to compensate the sensor's observations online, combined with the unscented Kalman filter theory, to further correct the filter gain and covariance, thereby reducing the sensor's uncertainty measurement error and improving the target tracking filter Accuracy. The simulation results show that the unscented Kalman filter based on LSTM neural network compensation can predict the sensor measurement value, greatly reduce the target tracking error caused by the sensor uncertainty measurement problem, and meet the actual requirements.

Brassinosteroids (BRs) are important in plant resistance to chilling stress. However, limited information is available regarding the specific mechanisms involved at proteomic level. We utilized iTRAQ proteomic approach, physiological assays and information obtained from cellular ultrastructure to clarify the underlying molecular mechanism of BRs to alleviate chilling stress in pepper (Capsicum annuum L.). Foliar application of 24-epibrassinolide (EBR) improved photosynthesis and improved cell structure by presenting a distinct mesophyll cell and chloroplast with well-developed thylakoid membranes in the leaves of pepper seedlings. We identified 346 differentially expressed proteins (DEPs), including 217 up-regulated proteins and 129 down-regulated proteins in plants under chilling (Chill) and Chill + EBR treated plants. Most of the DEPs were related to multiple pathways, including photosynthesis, carbohydrates metabolism, energy metabolism, protein biosynthesis, amino acids synthesis, redox and stress defence (ascorbate peroxidase, glutathione peroxidase, and superoxide dismutase). Up-regulated DEPs were associated with photosynthetic electron transfer chain, oxidative phosphorylation, GSH metabolism pathway, Calvin cycle and signaling pathway. The physiochemical analysis showed that EBR treatment improved the tolerance of pepper seedlings to chilling stress.

According to the differences in physical properties of Jurassic crude oil around Fukang depression, geochemical characteristics of oil are analyzed from five zones. The results show that di...

The Upper Carboniferous coaly source rocks are verified to be developed in the Southeastern Junggar Basin, which is lithologically composed of carbonaceous mudstones and mudstones. According to the geochemical (total organic carbon, Rock–Eval, and biomarker fingerprints) and organic petrology analyses, the Carboniferous source rocks are primarily gas-prone characterized by kerogen type III, and were deposited in an oxidized–sub-oxidized brackish environment significantly contributed by terrigenous higher plants. Carbonaceous mudstones are generally more oil-prone in comparison with the mudstones. The measured vitrinite reflectance, Tmax, and sterane isomers indicate that the source rocks are at immature–early gas generation stage, and have not entered the “peak gas generation stage”. Natural gases are coal-type gases derived from the Carboniferous source rock. The maturities of them are highly inconsistent with those of source rock samples. Based on 2-D basin modeling, natural gases were generated from the highly mature coaly source rocks in the Fukang Depression and migrated upward to the uplift via the P–C regional inconformity.

Path planning is the basic requirement for unmanned underwater vehicle (UUV) to complete tasks. According to the requirements of UUV path planning in working environment, a path planning method for UUV based on QPSO algorithm is proposed in this paper. Firstly, the obstacles in the environment are divided into known obstacles and unknown obstacles. For static obstacles in the known environment, an annular space model is established and the global path planning method based on QPSO is designed. According to the fitness value of each particle in the iterative process of QPSO algorithm, an optimization method of particle classification evolution is proposed. Then, based on the realtime information of unknown obstacles detected by UUV forward-looking sonar, a local collision avoidance method is proposed based on the rolling window method and QPSO algorithm. Finally, a simulation platform is built to verify the proposed path planning method, and the feasibility of the method is verified by experimental simulation.

In this paper, the ant colony algorithm used to study the path planning for collision avoidance of unmanned underwater vehicle (UUV) in a large-scale marine environment. Multi-beam forward-looking sonar’s simulation detection model based on the grid environment model established in it. In order to overcome the limitation that the ant colony can only choose to walk on adjacent grids, the concept of virtual visualization introduced in the last step of the ant colony. This paper uses a non-linear penalty mechanism in the objective function of ant colony optimization to avoid large-angle turning movements in online path decision making. Simulation results show that the proposed method has short planning time, high optimization efficiency, and smooth paths.

Climatic conditions, including temperature range and solar radiation, are closely linked to maize (Zea mays L.) growth and development. Adjusting plant density is one of the most effective measures for maximizing maize yield under different climatic conditions. The objectives of this study were (1) to determine the optimum plant density as well as the corresponding leaf area index (LAI) and yield in different maize producing regions in China and (2) to learn how climatic conditions influence maize growth and grain yield. The 3-year (2013–2015) field experiment used a hybrid maize cultivar (‘Zhengdan 958’) with six plant density treatments: 4.5, 6, 7.5, 9, 10.5, and 12 plants m−2. Three different ecological regions were chosen for the study: Gongzhuling (Jilin Province, China), Yinchuan (Ningxia Hui Autonomous Region, China), and Qitai (Xinjiang Uygur Autonomous Region, China). Comparing the same plant density treatment at different sites, grain yield and dry matter accumulation decreased in the order Qitai > Yinchuan > Gongzhuling. The optimum plant densities (i.e., treatments with greatest yield) were 12 plants m−2 at Qitai, 10.5 plants m−2 at Yinchuan, and 7.5 plants m−2 at Gongzhuling. At the optimum plant density, the LAIs at silking and physiological maturity were, respectively, 8.94 and 4.27 at Qitai, 7.50 and 1.85 at Yinchuan, and 6.18 and 1.67 at Gongzhuling. Climatic factors, especially solar radiation and diurnal temperature range, exerted significant influences on maize yield. These observations will be useful for determining best management practices for maize production under different climatic conditions across large areas and for providing helpful suggestions for maize breeders.

Large-scale oil and gas fields have been discovered after years of petroleum exploration in Mahu Sag, Junggar Basin, confirming the significant resource potential in its western margin. However, the origin of oil in the Triassic Baikouquan (T1b) reservoir and lacustrine basin evolution during the Permian are still poorly understood. In this study, Permian source rocks and T1b crude oil were analyzed using Rock-Eval pyrolysis, vitrinite reflectance, stable carbon isotopes, and biomarker compositions. Results show that the Lower Wuerhe source rock (P2w) was developed in a freshwater lacustrine environment with high oxygen content, higher plant input, and now contains typical humic (type-III) kerogen at the low thermal maturity stage. The Fengcheng source rock (P1f) was developed in an evaporative lake after mixed seawater (sea and lake). Deposition included anoxic conditions, terrigenous input, high salinity, and intense evaporation, and was dominated by sapropelic (type-II) kerogen, which is currently at the thermal maturity stage. The Jiamuhe source rock (P1j) was developed in a transitional marine and terrigenous environment with terrigenous input, moderate salinity, and reducing water, and now contains mainly type-III kerogen at the high thermal maturity stage. The Junggar region's climate was humid–arid–humid for the Early to Middle Permian. Mahu Sag was not completely closed until the end of P1j deposition and did not completely evolve into a lacustrine basin with large-scale freshwater input until the P2w deposition. Crude oil of the T1b formation is very mature and is derived from the source rock of the transitional marine and terrigenous environments deposited in the center of Mahu Sag, with high salt content, weak reducibility, and low evaporite content. Using biomarkers, carbon isotopes, and fine lithologic analysis, the oil-source correlation shows that T1b crude oil came from P1f calcareous and tuffaceous source rocks.

Maize production in arid areas of Northwest China is seriously limited by water supply. Conserving irrigation water and increasing water use efficiency (WUE) are effective methods for sustainable agricultural development. The objectives of this study were to optimize irrigation water use, grain yield, WUE, and economic return of super high yield maize in a drip irrigation and plastic film mulch system in Xinjiang. Experiments were conducted in Qitia County, Xinjiang, and included four drip irrigation treatments: T1, 600 mm (CK); T2, 540 mm; T3, 480 mm; and T4, 420 mm. Six density-tolerant maize hybrids were planted in 2014 and 2015. Grain yield and economic return did not significantly change in response to a 10% decrease in irrigation level, whereas evapotranspiration decreased and WUE increased (4.61%–6.66%). High grain yield (15.7–19.1 Mg ha−1), WUE (2.47–2.77 kg m−3), and economic return (1691.6–2605.7 US$ ha−1) were achieved under the T2 treatment. The combined techniques of drip irrigation, plastic film mulching, and increased planting density improved yield. Quadratic relationships were found between irrigation level and grain yield and between irrigation level and economic return. Irrigation level and evapotranspiration were negatively correlated with WUE. Maximum economic return and irrigation level were linearly related with the price of water. Taking into account grain yield, economic return, and ecological effects, an irrigation amount of 540 mm is optimal for drip irrigation–plastic film mulching systems in arid areas.

Although the Fukang Sub-depression is the largest hydrocarbon generation depression in the Junggar Basin and promises favorable potential for oil and gas exploration, only several smallâmedium oil/gas accumulations have been discovered so far. After analyzing the molecular and stable carbon isotopic compositions of natural gases and its associated low molecular weight hydrocarbons (LMWHs) from eastern Fukang Sub-depression, their genetic types and origins are discussed in this study. Natural gases are wet gases with an average dryness coefficient of 0.84. Stable carbon isotopes of methane and ethane are well correlated with the thermal evolution trend of coal-derived gases. The C5â7 LMWHs are enriched in methyl cyclohexane but they lack n-alkanes, indicating a predominance of higher plant input. Gases have maturities ranging 0.76%â0.93%Ro and are well consistent with their low n-heptane (H) and iso-heptane (I) contents. The geochemical characteristics of natural gases from eastern Fukang Sub-depression are quite similar with those from the TurpanâHami Basin. Their gases are considered to be low-mature gases derived from the LowerâMiddle Jurassic coal measures. In contrast, they show remarkable differences with those from the Wucaiwan gas field; they are considered to have high-mature gases derived from the Carboniferous coal measures. Keywords: Coal-derived gas, Stable carbon isotopes, Low molecular weight hydrocarbons, Fukang sub-depression, Junggar Basin, MiddleâLower Jurassic

International audience; Worldwide, scarce water resources and substantial food demands require efficient water use and high yield. This study investigated whether irrigation frequency can be used to adjust soil moisture to increase grain yield and water use efficiency (WUE) of high-yield maize under conditions of mulching and drip irrigation. A field experiment was conducted using three irrigation intervals in 2016: 6, 9, and 12 days (labeled D6, D9, and D12) and five irrigation intervals in 2017: 3, 6, 9,12, and 15 days (D3, D6, D9, D12, and D15). In Xinjiang, an optimal irrigation quota is 540 mm for high-yield maize. The D3, D6, D9, D12, and D15 irrigation intervals gave grain yields of 19.7, 19.1-21.0, 18.8-20.0, 18.2-19.2, and 17.2 Mg ha(-1) and a WUE of 2.48, 2.53-2.80, 2.47-2.63, 2.34-2.45, and 2.08 kg m(-3), respectively. Treatment D6 led to the highest soil water storage, but evapotranspiration and soil-water evaporation were lower than other treatments. These results show that irrigation interval D6 can help maintain a favorable soil-moisture environment in the upper-60-cm soil layer, reduce soilwater evaporation and evapotranspiration, and produce the highest yield and WUE. In this arid region and in other regions with similar soil and climate conditions, a similar irrigation interval would thus be beneficial for adjusting soil moisture to increase maize yield and WUE under conditions of mulching and drip irrigation. (C) 2019 Crop Science Society of China and Institute of Crop Science, CAAS.

Based on observation of cores and casting thin sections, reservoir fluorescence, hydrocarbon geochemical characteristics and oil production test data, the factors controlling the tight oil accumulation and high production in the Da'anzhai Member in the Jurassic Ziliujing Formation in central Sichuan Basin are studied. The shelly limestone, muddy shell limestone and tight limestone are all oil-bearing in the Da'anzhai Member. The dissolved pores and fractures in shelly limestone and the matrix pores (microfractures, intercrystal pores) in tight limestone are all oil-bearing in large area, which is the reason why oil wells can keep low production for a long period of time. On the basis of the extensive oil-bearing, natural gas from the Upper Triassic Xujiahe Formation provided the major power for oil migration and accumulation in the Da'anzhai low amplitude, water-free tight limestone reservoirs, driving the dispersed oil from the matrix pores into an accumulation, so the oil is more enriched in the western structures of central Sichuan Basin where oil wells are higher in gas-oil ratio. In contrast, in the east of central Sichuan, the Huayingshan major faults generally cut through Da'anzhai Member, allowing gas to migrate to the formations above Da'anzhai Member along fractures to accumulate or dissipate, without gas as driving force, as a result, the oil is less enriched than that in the west part of central Sichuan. Key words: tight oil, central Sichuan Basin, Jurassic Da'anzhai Member, enrichment and high production, gas drive, fault

By comprehensively analyzing oil-bearing and non-oil-bearing tight sandstone reservoir properties, pore structure characteristics and contact between source rock and reservoir, reservoir fluorescent photographs of typical wells of Jurassic Lianggaoshan Formation in central Sichuan Basin, the research tries to find out factors controlling the oiliness of the Jurassic Lianggaoshan tight sandstone reservoir. The oiliness of the Jurassic Lianggaoshan tight sandstone reservoir in central Sichuan Basin is controlled by the following factors: (1) The migration pathway between the source rock and reservoir: when there exist sandstone and mudstone transition zones with high mud content and poor physical property between the source rock and reservoir, without fracture connection, it is difficult for oil and gas to migrate into the overlying reservoir; (2) The reservoir physical property: if the reservoir contacts directly with source rock and has good physical properties, oil and gas can migrate and accumulate directly in the reservoir. (3) Development degree of fractures: when the reservoir physical properties are poor, rich fractures can improve porosity and permeability of the reservoir, oil and gas can still migrate and accumulate in the reservoir; if the reservoir physical property is poor and no fractures developed, oil and gas are difficult to migrate and accumulate in the reservoir. Based on the sedimentary and reservoir characteristics of Jurassic Lianggaoshan Formation in central Sichuan Basin and the distribution of source rocks, Yingshan-Guang'an and Hechuan-Baimiao-Luodu two favorable exploration zones are selected. Key words: central Sichuan Basin, Lianggaoshan Formation, tight oil, oiliness, migration pathway, controlling factors

Electroplating industry annually produces numerous plated workpieces for U.S. pillar industries. However, it is also a major environment polluter in forms of wastewater, sludge, and spent solution. Thus, waste source reduction for the electroplating industry is a must. In practice, when productivity and energy use efficiency are also taken into account, the design and operation of an electroplating process become very complicated and need an in-depth study. In this paper, productivity maximization, energy saving, and freshwater/wastewater minimization are simultaneously addressed for the optimal design and operation of electroplating processes, which generates a triple-objective mixed-integer dynamic optimization (MIDO) model. The MIDO model is iteratively solved by a developed methodology to obtain the 3D Pareto frontier of the optimization problem, which provides important technical supports for the design and operation of electroplating processes. The efficacy has been demonstrated with a case study on an electroplating process.

Hoist scheduling, especially cyclic hoist scheduling (CHS), is used to maximize the manufacturing productivity of electroplating processes. Water-reuse network design (WRND) for the electroplating rinsing system targets the optimal water allocation, such that fresh water consumption and wastewater generation are minimized. Currently, there is still a lack of studies on integrating CHS and WRND technologies for electroplating manufacturing. In this paper, a multi-objective mixed-integer dynamic optimization (MIDO) model has been developed to integrate CHS and WRND technologies for simultaneous consideration of productivity and water use efficiency for environmentally benign electroplating. The orthogonal collocation method on finite elements is employed to convert the MIDO problem into a mixed-integer nonlinear programming (MINLP) problem. The efficacy of the methodology is demonstrated by solving a real electroplating example. It demonstrates that the computational methods of production scheduling, process design, and dynamic optimization can be effectively integrated to create economic and environmental win–win situations for the electroplating industry.

The cracking furnace system is crucial for an olefin plant. Its operation needs to follow a predefined schedule to process various feeds continuously, meanwhile conducting a periodically decoking operation for each furnace when its performance apparently decreases. In practice, because the feed supply changes dynamically, the routine furnace scheduling is better performed in a dynamic and reactive way, through which the furnace operations can be smartly rescheduled with respect to any delivery of new coming feeds. Thus, the feeds from the new delivery and the leftover inventories can be timely, feasibly, and optimally allocated to different furnaces for processing to obtain the maximum average net profit per time. Facing this challenge, this paper develops a new MINLP-based reactive scheduling strategy, which can dynamically generate reschedules based on the new feed deliveries, the leftover feeds, and current furnace operating conditions. It simultaneously addresses all the major scheduling issues of a c...

The LNG (liquefied natural gas) receiving terminal is an important component of the entire LNG value chain. The handling of unloading BOG (boil-off gas) during LNG regasification at LNG receiving terminals significantly influences the BOG flare emission and energy consumption. In this work, thermodynamic-analysis-based design and operations are simultaneously considered to recover BOG with the minimum total energy consumption, a goal of which is to provide a cost-effective flare minimization strategy at LNG receiving terminals. A rigorous simulation-based optimization model and its solution algorithm are developed based on an LNG regasification superstructure. Case studies are used to demonstrate the efficacy of the developed methodology. The presented general optimization model and thermodynamic analysis also provide fundamental understandings of the LNG regasification process that are valuable for industrial applications.

Cracking furnaces of ethylene plants are capable of processing multiple feeds to produce smaller hydrocarbon molecules, such as ethylene, propylene, and ethane. The best practice for handling the produced ethane is to recycle it as an internal feed and conduct the secondary cracking in a specific furnace. As cracking furnaces have to be periodically shut down for decoking, when multiple furnaces processing different feeds under various product values and manufacturing costs are considered, the operational scheduling for the entire furnace system should be optimized to achieve the best economic performance. In this paper, a new MINLP (mixed-integer nonlinear programming) model has been developed to optimize the operation of cracking furnace systems with the consideration of secondary ethane cracking. This model is more practical than the previous study and can simultaneously identify the allocation of feeds with their quantity, time, and sequence information for each cracking furnace. A case study has demo...

Ethylene plant start-ups generate huge amounts of off-spec products for flaring, which cause negative environmental and societal impacts, as well as tremendous raw material and energy losses that could be unitized to generate much more needed products. Thus, cost-effective start-up flare minimization strategies through proactive process design and operation are becoming more important and attractive to the industry. However, fundamental and quantitative studies on start-up flaring emissions are still lacking, such as (i) what kinds of emission species are contained in the flaring sources; (ii) how much of each emission source will be generated during one start-up; and (iii) what is the dynamic emission profile of each emission source with respect to the start-up time? In this paper, rigorous plant-wide dynamic simulations are employed to characterize flaring emission sources under different flare minimization strategies for an ethylene plant start-up. Deep insights of the emission source distribution and ...

Flaring is crucial to chemical plant safety. However, excessive flaring, especially the intensive flaring during the chemical plant start-up operation, emits huge amounts of volatile organic compounds (VOCs) and highly reactive VOCs, which meanwhile results in tremendous industrial material and energy loss. Thus, the flare emission should be minimized if at all possible. This paper presents a general methodology on flare minimization for chemical plant start-up operations via plantwide dynamic simulation. The methodology starts with setup and validation of plantwide steady-state and dynamic simulation models. The validated dynamic model is then systematically transformed to the initial state of start-up and thereafter virtually run to check the plant start-up procedures. Any infeasible or risky scenarios will be fed back to plant engineers for operation improvement. The plantwide dynamic simulation provides an insight into process dynamic behaviors, which is crucial for the plant to minimize the flaring w...

Production planning under uncertainty is considered as one of the most important problems in plant-wide optimization. In this article, first, a stochastic programming model with uniform distribution assumption is developed for refinery production planning under demand uncertainty, and then a hybrid programming model incorporating the linear programming model with the stochastic programming one by a weight factor is proposed. Subsequently, piecewise linear approximation functions are derived and applied to solve the hybrid programming model under uniform distribution assumption. Case studies show that the linear approximation algorithm is effective to solve the hybrid programming model, along with an error ≤0.5% when the deviation/mean ≤20%. The simulation results indicate that the hybrid programming model with an appropriate weight factor (0.1-0.2) can effectively improve the optimal operational strategies under demand uncertainty, achieving higher profit than the linear programming model and the stochastic programming one with about 1.5% and 0.4% enhancement, respectively.

ABST R AC T Flaring emission during chemical plant turnaround operations generates huge amounts of air pollutants and also results in tremendous raw material and energy loss. This paper addresses near-zero aring studies for chemical plant turnaround operation to advance current endeavors on are minimization. Since off-spec products are inevitable during plant turnaround operations, they must be either recycled to the upstream process for online reuse or stored somewhere temporarily for future reprocessing when the plant manufacturing becomes stable, such that the off-spec products can be saved instead of being ared. A dynamic simulation based general methodology framework has been developed. The efcacies of the development are demonstrated by a virtual plant startup test.