Target-Oriented Methodology on Matching Heat Transfer Areas for a Multiperiod Heat Exchanger Network Retrofit

Heat exchanger network retrofit problems in a multiperiod operation are commonly solved in a stepwise manner. The matching of heat transfer areas is generally used to finalize the retrofit after the determination of the retrofit target of the heat exchanger network. Conventional heat transfer area matching methods are either experience based or model based methods, which may lead to indeterminate solutions or scale limitations in the optimal matching strategy. In this work, a systematic approach and algorithms for matching heat transfer areas in a multiperiod heat exchanger network retrofit are proposed. The methodology is based on the reverse order matching method and the matching algorithms of a bipartite graph. The proposed approach achieves four main objectives: to maximize the number of substituted heat exchangers, to minimize the increases in heat transfer area, to minimize the investment cost after a retrofit, and to minimize the investment cost given the preference rankings restrictions of heat exchanger operation pressures. The heat exchanger network retrofit of a diesel hydrogenation unit in a multiperiod operation is employed to illustrate the procedure and advantages of the proposed method. The results obtained by the proposed method and the methods in the literature are compared and analyzed. The results indicate that the proposed method enables the practical matching restrictions and costs to be taken into account. In addition, the proposed method is simple and easy to implement, which is conducive to solving the problems of heat exchanger network retrofitting quickly and accurately

Retrofit of Heat Exchanger Networks for Multiperiod Operations by Matching Heat Transfer Areas in Reverse Order

This work presents a retrofitting approach for heat exchanger networks (HENs) for single-period and multiple-period operations, aiming at the improvement of operation flexibility of HENs. A two-step method is proposed to solve the problems of redundant heat transfer areas in multiperiod HENs and the incomplete utilization of existing heat-transfer areas in HEN retrofit. In this approach, a multiperiod HEN design model is first solved to target the retrofit. Then, the final HEN is obtained by matching the required heat exchangers with the existing ones in reverse order. The proposed matching procedure is provided in detail and mathematically proven. Three case studies are employed to illustrate the advantages of the proposed method for solving the problems in the multiperiod HEN retrofit. In addition, the proposed method is extended to solving single-period HEN retrofit problems. Results indicate that the proposed method makes full use of the existing heat exchangers to reduce retrofit costs and increases the energy utilization efficiency of the HEN in multiperiod operations. The proposed method is simple and easy to implement. It can reduce the computational load and the difficulties in solving practical industrial problems

Impacts of Subperiod Partitioning on Optimization of Multiperiod Hydrogen Networks

Multiperiod hydrogen network optimization problems may arise from the fluctuations of operating parameters in practical refineries. However, multiperiod operating conditions are always assumed to be known and their effects on the optimization of multiperiod hydrogen network optimization are neglected in current research. To address these problems, a subperiod partitioning method based on clustering of uncertain operating parameters is proposed. A reasonable division of the subperiod and corresponding values of parameters in each subperiod can then be determined by taking a trade-off between the number of subperiods and the quality of subperiod partitioning. The procedure of the proposed method is illustrated via a hydrogen system in a practical refinery. Finally, the effects of subperiod partitioning on the total annual cost and the flexibility of the multiperiod hydrogen network are analyzed and discussed to further verify the application of the proposed method

The Flexible Design for Optimization and Debottlenecking of Multiperiod Hydrogen Networks

The operational conditions of hydrogen networks in practical refineries commonly fluctuate due to variation of feed properties, loss of catalyst activity, change of market demand, seasonal shift, and improvement of processing technology as well. These fluctuations could affect the operations of the hydrogen networks, which are usually optimized on the basis of fixed operational conditions in practice. In this work, a flexible design method of a multiperiod hydrogen network is proposed. It features the flexible design of multiperiod hydrogen network by considering discrete operational scenarios in multiple periods and possible fluctuation of each operational scenario. The optimal design of the multiperiod hydrogen network with simple structure and low total annual costs can be obtained by the proposed method. Moreover, the bottlenecks restricting the flexibility of each subperiod can also be identified and eliminated. In addition, the proposed method can be readily implemented. A multiperiod hydrogen system in a refinery is used to exemplify the proposed method. The results show that the proposed method can be used to effectively obtain the hydrogen network structure that satisfies the multiperiod operational conditions and reach the flexibility requirements for each subperiod with the lowest total annual costs

Techno-Economic Analysis of a Hybrid System with Carbon Capture for Simultaneous Power Generation and Coal-to-Hydrogen Conversion

Under the growing pressure of decarbonization across industrial sectors, power plants face great challenges in reducing carbon emissions. To improve energy efficiency and reduce the carbon emissions of thermal power plants, a hybrid system with carbon capture for simultaneous power generation and coal-to-hydrogen is proposed, which features comprehensive consideration of the energy demands of power plants and coal-to-hydrogen units. In the proposed system, the reduction of energy demand is realized by heat exchanger network synthesis (HENs) of the internal streams, and a carbon capture unit is then integrated for further reduction of carbon emissions. The techno-economic feasibility of the integrated system is analyzed and discussed by using energy consumption, economics, and emission reduction as major performance indexes. The results show that energy integration saves 108.2 MW of heat, while nearly 90% of carbon emissions are reduced for the system. When comparing the total energy consumption of the subsystems and a stand-alone carbon capture unit, the consumption for cooling and heating utilities in the integrated system is reduced by 8.81 and 9.11%, respectively. In addition, the total overnight cost and the annual operation cost using the proposed integrated system are reduced by 8.51 and 22.69%, respectively, and the cost of hydrogen production decreases by 5.99%. The economics of the integrated system is significantly affected by the market prices of coal and hydrogen. The integrated system has significant advantages in reducing energy consumption and carbon emissions with higher economic performance, which can provide guidance for the low-carbon transition of coal-fired power plants

SSeCKS/Gravin/AKAP12 attenuates expression of proliferative and angiogenic genes during suppression of v-Src-induced oncogenesis-1

<p><b>Copyright information:</b></p><p>Taken from "SSeCKS/Gravin/AKAP12 attenuates expression of proliferative and angiogenic genes during suppression of v-Src-induced oncogenesis"</p><p>BMC Cancer 2006;6():105-105.</p><p>Published online 25 Apr 2006</p><p>PMCID:PMC1463002.</p><p>Copyright © 2006 Liu et al; licensee BioMed Central Ltd.</p> or from HCT116 or HT29 (Panel B) were subjected to RT-PCR analysis as described in Materials and Methods using primer sets described in Table 1. These results are typical of at least two independent experiments

Reaction Mechanisms on Solvothermal Synthesis of Nano LiFePO₄ Crystals and Defect Analysis

A solvothermal process was used to synthesize LiFePO₄ nanomaterials for lithium ion batteries. Reaction parameters such as reaction temperature and residence time were explored to obtain the optimal LiFePO₄ sample. A three-stage reaction mechanism is proposed to better understand the solvothermal synthesis process. X-ray diffraction, scanning electron microscopy, and Fourier transform IR spectroscopy were used to investigate the prepared samples under different conditions. The LiFePO₄ formation reaction occurred at a temperature as low as 89 °C. Defect analysis results showed that after 4 h of solvothermal treatment the concentration of lithium vacancy and Li–Fe antisite defects was too low to be detected. The charge–discharge data of the obtained LiFePO₄ showed that the carbon-coated LiFePO₄ samples prepared at 180 °C after 4 h of solvothermal treatment had a discharge capacity of 160.6 mA h g^–1 at a discharge rate of 0.1C and 129.6 mA h g^–1 at 10C

Phenotype and cytology raw data for CPB paper

Phenotype and cytology raw data for the paper "Morphological, cellular and molecular evidences of chromosome random elimination in vivo upon haploid induction in maize"

the sequence of SSR markers

the sequence of SSR markers for polymorphism analysis in the manuscript and some markers were used for haploid genotype analysis

Inhibition of Oxidative Stress-Elicited AKT Activation Facilitates PPARγ Agonist-Mediated Inhibition of Stem Cell Character and Tumor Growth of Liver Cancer Cells

<div><p>Emerging evidence suggests that tumor-initiating cells (TICs) are the most malignant cell subpopulation in tumors because of their resistance to chemotherapy or radiation treatment. Targeting TICs may be a key innovation for cancer treatment. In this study, we found that PPARγ agonists inhibited the cancer stem cell-like phenotype and attenuated tumor growth of human hepatocellular carcinoma (HCC) cells. Reactive oxygen species (ROS) initiated by NOX2 upregulation were partially responsible for the inhibitory effects mediated by PPARγ agonists. However, PPARγ agonist-mediated ROS production significantly activated AKT, which in turn promoted TIC survival by limiting ROS generation. Inhibition of AKT, by either pharmacological inhibitors or AKT siRNA, significantly enhanced PPARγ agonist-mediated inhibition of cell proliferation and stem cell-like properties in HCC cells. Importantly, in nude mice inoculated with HCC Huh7 cells, we demonstrated a synergistic inhibitory effect of the PPARγ agonist rosiglitazone and the AKT inhibitor triciribine on tumor growth. In conclusion, we observed a negative feedback loop between oxidative stress and AKT hyperactivation in PPARγ agonist-mediated suppressive effects on HCCs. Combinatory application of an AKT inhibitor and a PPARγ agonist may provide a new strategy for inhibition of stem cell-like properties in HCCs and treatment of liver cancer.</p></div