Optimization of Hydrocracking Process for Enhanced BTX Production from Coal Tar-Derived Hydrorefined Products

Hydroconversion of coal tar to produce aromatic hydrocarbons(BTX)represents a crucial strategy for the highvalue hierarchical utilization of coal.This study focused on the hydrocracking of hydrorefined products derived from coal tar to enhance the production of benzene,toluene,and xylene(BTX).Various reaction conditions,including reaction temperature,hydrogen pressure,space velocity,and hydrogen-to-oil volume ratio,were systematically explored to optimize BTX yields while also considering the process’s economic feasibility.The results indicate that increasing the reaction temperature from 360℃ to 390℃ significantly favors the production of BTX,with yields increasing from 21.42%to 41.14%.Similarly,an increase in hydrogen pressure from 4 MPa to 6 MPa boosts BTX production,with yields rising from 36.31%to 41.14%.Reducing the space velocity from 2 h^(-1) to 0.5 h^(-1) also favors the BTX production process,with yields increasing from 37.96%to 45.13%.Furthermore,raising the hydrogen-to-oil volume ratio from 750 to 1500 improves BTX yields from 41.61%to 45.44%.Through economic analysis,the optimal conditions for BTX production were identified as a reaction temperature of 390℃,hydrogen pressure of 5-6 MPa,space velocity of 1 h^(-1),and hydrogen-to-oil volume ratio of 1000,achieving a BTX yield of 43.73%.This investigation highlights the importance of a holistic evaluation of hydrocracking conditions to optimize BTX production.Furthermore,the findings offer valuable insights for the design and operation of industrial hydrocracking processes aimed at efficiently converting coal tar-derived hydrorefined feedstock into BTX.

Analysis of the Erosion-Corrosion Mechanism of the Air Cooler in a Hydrocracking Unit:A Numerical and Experimental Study

Corrosion leakages often occur in the air cooler of a hydrocracking unit,with the failure sites mainly located in the entrance area of the tubes.An analysis of the macroscopic morphology and corrosion products confirmed that the damage was caused by erosion-corrosion(E-C).Numerical and experimental methods were applied to investigate the E-C mechanism in the air cooler.Computational fluid dynamics(CFD)was used to calculate the hydrodynamic parameters of the air cooler.The results showed that there was a biased flow in the air cooler,which led to a significant increase in velocity,turbulent kinetic energy and wall shear within 0.2 m of the tube entrance.A visualization experiment was then performed to determine the principles of migration and transformation of multiphase flow in the air cooler tubes.Various flow patterns(pure droplet flow,mist flow,and annular flow)and their evolutionary processes were clearly depicted experimentally.The initiation mechanism and processes leading to the development of E-C in the air cooler were also determined.This study provided a comprehensive explanation for the E-C failures that occur in air coolers during operation.

Two-Stage Optimal Scheduling of Community Integrated Energy System

From the perspective of a community energy operator,a two-stage optimal scheduling model of a community integrated energy system is proposed by integrating information on controllable loads.The day-ahead scheduling analyzes whether various controllable loads participate in the optimization and investigates the impact of their responses on the operating economy of the community integrated energy system(IES)before and after;the intra-day scheduling proposes a two-stage rolling optimization model based on the day-ahead scheduling scheme,taking into account the fluctuation of wind turbine output and load within a short period of time and according to the different response rates of heat and cooling power,and solves the adjusted output of each controllable device.The simulation results show that the optimal scheduling of controllable loads effectively reduces the comprehensive operating costs of community IES;the two-stage optimal scheduling model can meet the energy demand of customers while effectively and timely suppressing the random fluctuations on both sides of the source and load during the intra-day stage,realizing the economic and smooth operation of IES.

Two-Stage Planning of Distributed Power Supply and Energy Storage Capacity Considering Hierarchical Partition Control of Distribution Network with Source-Load-Storage

Aiming at the consumption problems caused by the high proportion of renewable energy being connected to the distribution network,it also aims to improve the power supply reliability of the power system and reduce the operating costs of the power system.This paper proposes a two-stage planning method for distributed generation and energy storage systems that considers the hierarchical partitioning of source-storage-load.Firstly,an electrical distance structural index that comprehensively considers active power output and reactive power output is proposed to divide the distributed generation voltage regulation domain and determine the access location and number of distributed power sources.Secondly,a two-stage planning is carried out based on the zoning results.In the phase 1 distribution network-zoning optimization layer,the network loss is minimized so that the node voltage in the area does not exceed the limit,and the distributed generation configuration results are initially determined;in phase 2,the partition-node optimization layer is planned with the goal of economic optimization,and the distance-based improved ant lion algorithm is used to solve the problem to obtain the optimal distributed generation and energy storage systemconfiguration.Finally,the IEEE33 node systemwas used for simulation.The results showed that the voltage quality was significantly improved after optimization,and the overall revenue increased by about 20.6%,verifying the effectiveness of the two-stage planning.

Influence of two-stage harvesting on the properties of cold-pressed rapeseed(Brassica napus L.)oils

Rapeseed(Brassica napus L.)harvesting method is critical since it significantly determines the seed yield,oil quality,and industrial efficiency.This study investigated the influences of harvesting methods on the quality of cold-pressed rapeseed oil of two varieties.Oil color,peroxide value(POV),tocopherol content,fatty acid composition,and polarity of total polyphenols(PTP)contents of two rapeseed varieties in Huanggang and Xiangyang were compared through artificially simulated combined harvesting and two-stage harvesting.Results showed significant differences in the quality of rapeseed oil between the two harvesting methods.The red value(R-value),POV,total tocopherol contents,linoleic and linolenic acid content,and PTP content of the pressed rapeseed oil prepared by the combined harvesting method were about 27.6,5.7,15.8,2.0,0.5,and 28.6%lower than those of the oil produced from the two-stage harvesting method,respectively.Xiangyang and Huayouza62 performed better in the two regions and two varieties,respectively.To sum up,the rapeseed oil obtained 41–44 days after final flowering of combined harvesting,35 days after final flowering,and six days of post-ripening of the two-stage harvesting had the best quality.

Catalyst grading technology for promoting the diesel hydrocracking to naphtha

This paper reports the application of multi-component hydrocracking catalyst grading technology in diesel hydrocracking system to increase naphtha,and studies the influence of catalyst systems with different number of graded beds on the reaction process of diesel hydrocracking.Three hydrocracking catalysts with different physicochemical properties as gradation components,the diesel hydrocracking reaction on catalyst systems of one-component,two-component and three-component graded beds with different loading sequences are carried out and evaluated,respectively.The catalytic mechanism of the multi-component grading system is analyzed.The results show that,with the increase of the number of grading beds,the space velocity of reaction on each catalyst increases,which can effectively control the overreaction process;along the flow direction of feedstock,the loading sequences of catalysts with acidity decreasing and pore properties increasing can satisfy the demand of different catalytic activity for the conversion of reactant with changing composition to naphtha,which has a guiding role in the conversion of feedstock to target products.Therefore,the conversion of diesel,the selectivity and yield of naphtha all increase significantly on the multi-component catalyst system.The research on the grading technology of multi-component catalysts is of great significance to the promotion and application of catalyst systems in various catalytic fields.

Tourism Route Recommendation Based on A Multi-Objective Evolutionary Algorithm Using Two-Stage Decomposition and Pareto Layering

Tourism route planning is widely applied in the smart tourism field.The Pareto-optimal front obtained by the traditional multi-objective evolutionary algorithm exhibits long tails,sharp peaks and disconnected regions problems,which leads to uneven distribution and weak diversity of optimization solutions of tourism routes.Inspired by these limitations,we propose a multi-objective evolutionary algorithm for tourism route recommendation(MOTRR)with two-stage and Pareto layering based on decomposition.The method decomposes the multiobjective problem into several subproblems,and improves the distribution of solutions through a two-stage method.The crowding degree mechanism between extreme and intermediate populations is used in the two-stage method.The neighborhood is determined according to the weight of the subproblem for crossover mutation.Finally,Pareto layering is used to improve the updating efficiency and population diversity of the solution.The two-stage method is combined with the Pareto layering structure,which not only maintains the distribution and diversity of the algorithm,but also avoids the same solutions.Compared with several classical benchmark algorithms,the experimental results demonstrate competitive advantages on five test functions,hypervolume(HV)and inverted generational distance(IGD)metrics.Using the experimental results of real scenic spot datasets from two famous tourism social networking sites with vast amounts of users and large-scale online comments in Beijing,our proposed algorithm shows better distribution.It proves that the tourism routes recommended by our proposed algorithm have better distribution and diversity,so that the recommended routes can better meet the personalized needs of tourists.

Multi-source coordinated stochastic restoration for SOP in distribution networks with a two-stage algorithm

After suffering from a grid blackout, distributed energy resources(DERs), such as local renewable energy and controllable distributed generators and energy storage can be used to restore loads enhancing the system’s resilience. In this study, a multi-source coordinated load restoration strategy was investigated for a distribution network with soft open points(SOPs). Here, the flexible regulation ability of the SOPs is fully utilized to improve the load restoration level while mitigating voltage deviations. Owing to the uncertainty, a scenario-based stochastic optimization approach was employed,and the load restoration problem was formulated as a mixed-integer nonlinear programming model. A computationally efficient solution algorithm was developed for the model using convex relaxation and linearization methods. The algorithm is organized into a two-stage structure, in which the energy storage system is dispatched in the first stage by solving a relaxed convex problem. In the second stage, an integer programming problem is calculated to acquire the outputs of both SOPs and power resources. A numerical test was conducted on both IEEE 33-bus and IEEE 123-bus systems to validate the effectiveness of the proposed strategy.

Two-stage revision in periprosthetic knee joint infections

Periprosthetic joint infection(PJI)following total knee arthroplasty is one of the most catastrophic and costly complications that carries significant patient wellness as well as economic burdens.The road to efficiently diagnosing and treating PJI is challenging,as there is still no gold standard method to reach the diagnosis as early as desired.There are also international controversies with respect to the best approach to manage PJI cases.In this review,we highlight recent advances in managing PJI following knee arthroplasty surgery and discuss in depth the two-stage revision method.

Impacts of support properties on the vacuum residue slurry-phase hydrocracking performance of Mo catalysts

To deeply understand the effects of support properties on the performance of Mo-based slurry-phase hydrocracking catalysts,four Mo-based catalysts supported on amorphous silica alumina(ASA),γ-Al_(2)O_(3),ultra-stable Y(USY)zeolite and SiO_(2) were prepared by the incipient wetness impregnation method,respectively,and their catalytic performances were compared in the vacuum residue(VR)hydrocracking process.It is found that the Mo/ASA catalyst exhibits the highest VR conversion among the different catalysts,indicating that both the appropriate amount of acid sites,especially B acid sites and larger mesoporous volume of ASA can enhance the VR hydrocracking into light distillates.Furthermore,Mo catalysts supported on the different supports show quite different product distributions in VR hydrocracking.The Mo/ASA catalyst provides higher yields of naphtha and middle distillates and lower yields of gas and coke compared with other catalysts,it is attributed to the highest MoS_(2) slab dispersion,the highest sulfuration degree of Mo species,and the most Mo atoms located at the edge sites for the Mo/ASA catalyst,as observed by HRTEM and XPS analyses.These features of Mo/ASA are beneficial for the hydrogenation of intermediate products and polycyclic aromatic hydrocarbons to restrict the gas and coke formation.

Application of Acid Modified Catalysts with Different SiO_(2) Contents in the Hydrocracking of Light Cycle Oil for Light Aromatics Production

A series of functionalized USY/SiO_(2) zeolite composite supports were synthesized using the coating coprecipitation method,with tetraethyl orthosilicate(TEOS)as the silicon source and different ratios of USY to TEOS.Active metals nickel(Ni)and molybdenum(Mo)were loaded onto the supports using the impregnation method.Finally,a series of hydrogenation catalysts were synthesized.The characterization results showed that,compared with the USY catalyst,the addition of a certain quantity of SiO_(2) resulted in the disappearance of the strong acid sites on the catalyst,the number of weak acid and medium strong acid sites decreased,and a certain number of secondary mesoporous structures were formed.The addition of SiO_(2) reduced the secondary cracking of benzene,toluene,xylene,and ethylbenzene(BTXE)effectively,while excessive amounts of SiO_(2) reduced the hydrogenation activity of the catalyst,leading to a decline in the final yield of BTXE.At a maximum SiO_(2) content of 45%,the hydrogenation depth of light cycle oil(LCO)reached an optimum value.The hydrogenation performance of LCO was investigated in a fixed bed reactor at 380℃,4 MPa,and H2/oil volume ratio of 800:1,where the gasoline and diesel fractions reached 80.00%and 16.74%,respectively.NiMo-YS45 had the highest BTXE selectivity,and the final yield of BTXE reached 21.27%.

Development and Performance Evaluation of Catalyst for Productive Ethylene Cracking Feedstock in Selective Hydrocracking of Straight Run Diesel Oil

The upgrading of diesel oil to produce ethylene rich cracking feedstock is an important and promising technical route to reduce the ratio of diesel to gasoline. In the present work, a hydrocracking catalyst suitable for selective hydrocracking of straight run diesel oil to produce high-quality ethylene cracking feedstock at low cost was developed, by optimizing the composition of catalyst support materials, using amorphous silicon aluminum and aluminum oxide with high mesopore content as the main support, and modified Y zeolite with excellent aromatic ring opening selectivity as the acidic component. The catalyst has in-depth characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N2-low temperature adsorption-desorption, NH3-temperature-programmed desorption, and IR techniques. And its catalytic cracking straight run diesel oil performance was evaluated. The results show that the prepared catalyst has high polycyclic aromatic hydrocarbon ring opening cracking selectivity. However, alkanes retained in diesel distillates can achieve the goal of producing more ethylene cracking feedstocks with low BMCI value under low and moderate pressure conditions. This work may shed significant technical insight for oil refining transformation.

A two-stage but time-saving reconstructive scheme to treat severe lower limb length discrepancy:Two case reports

Limb length discrepancy(LLD)is a common orthopedic condition that can result in significant functional impairment,pain,and cosmetic deformities.Current reconstructive techniques for severe LLD are primarily based on callus distraction,which is a time-consuming process that can lead to complications,such as significant infection,joint stiffness,and stress fractures.To reduce the therapeutic time and minimize the risk of complications,we investigated the use of vascularized bone flaps as a technical supplement to callus distraction in the reconstruction of short limbs.We present two cases of severe LLD in the upper and lower legs,in which a twostage reconstruction approach was used.In the first stage,external fixation was applied to the affected limb to correct the soft tissue length and convert the short deformity into a bone defect.In the second stage,the bone defect was reconstructed using bilateral(patient A)or unilateral(patient B)free vascularized fibula bone grafts.Both patients had complete survival of the fibular grafts without stress fractures,and bone consolidation took 8 months(patient A)and 4 months(patient B).Compared to the traditional callus distraction,the two-stage approach was found to be more time-saving and reliable.The entire reconstructive scheme required 18 and 4 months for patients A and B,respectively,whereas the traditional callus distraction required 41 and 17 months,respectively.These findings suggest that the use of vascularized bone flaps as a technical supplement for callus distraction may provide an effective and efficient alternative for the treatment of severe LLD.Further studies are needed to validate these results and assess the long-term outcomes of this approach.

A New Two-Stage Tunable Space-Time Adaptive Detector

In order to improve the rejection capability of mismatched interferer signals,a new two-stage detector is proposed under homogeneous scenarios with unknown covariance matrix,which is obtained by cascading the adaptive matched filter(AMF)detector and the enhanced RAO(EnRAO)detector.The new detector has constant false alarm performance,and the closed-form expression of probability of false alarm and probability of detection is derived.The performance of the new detector is assessed,and analyzed in comparison with other detectors.The results show that,the proposed detector can provide enhanced rejection capability in the case of mismatch,but the performance of the detector is slightly lost under the condition of matching.

基于Two-stage DEA-Tobit模型的中国省际竞技体育效率研究

基于Two-stage DEA的网络结构DEA方法,对我国31个省(直辖市、自治区)在第十二届全运会上的表现进行更深入的效率评价,并结合Tobit回归模型对影响竞技体育效率的社会环境因素进行分析.结果表明,全运会两个阶段中,仅山东省和西藏自治区为DEA有效的,AP阶段和AC阶段为DEA有效的地区分别为10个和3个,且提高各地区总效率的关键在于提高其AC阶段效率.从影响因素来看,地区经济水平与效率间存在负向影响,而体育场地资源配置及体育类支出是影响效率的主要因素,国民体质综合指数和体育投入规模对其无显著影响.

Investigation of the liquid recycle in the reactor cascade of an industrial scale ebullated bed hydrocracking unit

One of the commercial means to convert heavy oil residue is hydrocracking in an ebullated bed. The ebullated bed reactor includes a complex gas–liquid–solid backmixed system which attracts the attention of many scientists and research groups. This work is aimed at the calculation of the internal recycle flow rate and understanding its effect on other parameters of the ebullated bed. Measured data were collected from an industrial scale residual hydrocracking unit consisting of a cascade of three ebullated bed reactors. A simplified block model of the ebullated bed reactors was created in Aspen Plus and fed with measured data. For reaction yield calculation, a lumped kinetic model was used. The model was verified by comparing experimental and calculated distillation curves as well as the calculated and measured reactor inlet temperature. Influence of the feed rate on the recycle ratio(recycle to feed flow rate) was estimated. A relation between the recycle flow rate, pump pressure difference and catalyst inventory has been identified. The recycle ratio also affects the temperature gradient along the reactor cascade. Influence of the recycle ratio on the temperature gradient decreased with the cascade member order.

Cost-effectiveness analysis of population-based screening of hepatocellular carcinoma: Comparing ultrasonography with two-stage screening

AIM: To assess the cost-effectiveness of two populationbased hepatocellular carcinoma(HCC) screening programs, two-stage biomarker-ultrasound method and mass screening using abdominal ultrasonography(AUS).METHODS: In this study, we applied a Markov decision model with a societal perspective and a lifetime horizon for the general population-based cohorts in an area with high HCC incidence, such as Taiwan. The accuracy of biomarkers and ultrasonography was estimated from published meta-analyses. The costs of surveillance, diagnosis, and treatment were based on a combination of published literature, Medicare payments, and medical expenditure at the National Taiwan University Hospital. The main outcome measure was cost per lifeyear gained with a 3% annual discount rate. RESULTS: The results show that the mass screening using AUS was associated with an incremental costeffectiveness ratio of USD39825 per life-year gained, whereas two-stage screening was associated with an incremental cost-effectiveness ratio of USD49733 per life-year gained, as compared with no screening. Screening programs with an initial screening age of 50 years old and biennial screening interval were the most cost-effective. These findings were sensitive to the costs of screening tools and the specificity of biomarker screening.CONCLUSION: Mass screening using AUS is more cost effective than two-stage biomarker-ultrasound screening. The most optimal strategy is an initial screening age at 50 years old with a 2-year inter-screening interval.

Advanced landfill leachate treatment using a two-stage UASB-SBR system at low temperature

A two-stage upflow anaerobic sludge blanket （UASB） and sequencing batch reactor （SBR） system was introduced to treat landfill leachate for advanced removal of COD and nitrogen at low temperature. In order to improve the total nitrogen （TN） removal efficiency and to reduce the COD requirement for denitrification, the raw leachate with recycled SBR nitrification supematant was pumped into the first-stage UASB （UASB1） to achieve simultaneous denitrification and methanogenesis. The results showed that UASB1 played an important role in COD removal and UASB2 and SBR further enhanced the nutrient removal efficiency. When the organic loading rates of UASB1, UASB2 and SBR were 11.95, 1.63 and 1.29 kg COD/（m^3.day）, respectively, the total COD removal efficiency of the whole system reached 96.7%. The SBR acted as the real undertaker for NH4^＋-N removal due to aerobic nitrification. The system obtained about 99.7% of NH4^＋-N removal efficiency at relatively low temperature （14.9-10.9℃）. More than 98.3% TN was removed through complete denitrification in UASB 1 and SBR. In addition, temperature had a significant effect on the rates of nitrification and denitrification rather than the removal of TN and NH4^＋-N once the complete nitrification and denitrification were achieved.

Selective hydrocracking of light cycle oil into high-octane gasoline over bi-functional catalysts

Light cycle oil(LCO) with high content of poly-aromatics was difficult to upgrade and convert,which had hindered upgrading fuel quality to meet with the standard of automotive diesel for the purpose of sustainable development.The hydrocracking behaviors of typical aromatics in LCO of naphthalene and tetralin were investigated over NiMo and CoMo catalysts.Several characterization methods including N2-adsoprtion and desorption,ammonia temperature-programmed desorption(NH3-TPD),Pyridine infrared spectroscopy(Py-IR),CO infrared spectroscopy(CO-IR),Raman and X-ray photoelectron spectroscopy(XPS) were applied to determine the properties of different catalysts.The results showed that CoMo catalyst with high concentration of S-edges could hydrosaturate more naphthalene to tetralin but exhibit lower yield of high-value light aromatics(carbon numbers less than 10) than NiMo catalyst.NiMo catalyst with high concentration of Mo-edges also presented a higher selectivity of converting naphthalene into cyclanes than CoMo catalyst.Subsequently,the naphthalene and LCO hydrocracking performances were also investigated over different catalysts systems.The activity evaluation and kinetic analysis results showed that the naphthalene hydrocracking conversion and the yield of light aromatics for CoMo-AY/NiMo-AY grading catalysts were higher than NiMo-AY/CoMo-AY grading catalysts at same condition.A stepwise reaction principle was proposed to explain the high efficiency of CoMo-AY/NiMoAY grading catalysts.Finally,the LCO hydrocracking evaluation results confirmed that CoMo-AY/NiMoAY catalysts grading system with low carbon deposition and high stability could remain high percentage of active phases,which was more efficient to convert LCO to high-octane gasoline.

Surface dealuminated Beta zeolites supported WO3 catalyst and its catalytic performance in tetralin hydrocracking

In this study,selective dealumination of Beta zeolites was performed through partially removing the templating agent in Beta zeolites by calcination and then removing the aluminum on the external surface of Beta zeolites with acid treatment.Hydrocracking catalysts were prepared by loading WO_(3)onto these dealuminated Beta zeolites.It was shown that the surface SiO_(2)/Al_(2)O_(3)of selectively dealuminated Beta zeolites was higher than that of conventionally dealuminated samples for the same bulk SiO_(2)/Al_(2)O_(3),and the hydrogenation activity of the catalyst of the selectively dealuminated Beta zeolites was lower than that of conventionally dealuminated Beta zeolites.The experimental results for tetralin hydrocracking to BTX showed that the catalysts based on the selectively dealuminated Beta zeolites had higher BTX selectivity and lower coke formation rate than that the catalysts based on the conventionally dealuminated Beta zeolites.