Thermo-economic analysis and optimization of a combined Organic Rankine Cycle (ORC) system with LNG cold energy and waste heat recovery of dual-fuel marine engine

A combined Organic Rankine Cycle (ORC) system with liquefied nature gas (LNG) cold energy and dual-fuel (DF) marine engine waste heat utilization was proposed. Engine exhaust gas and engine jacket cooling water were adopted as parallel heat sources. Thermo-economic analyses of the proposed system with 32 working fluids combinations were performed. Two objective functions covering thermal efficiencies and economic index were employed for performance evaluation. Afterward, the effects of operation pressure on the objective functions were investigated. Finally, the optimal conditions were obtained from the Pareto front with the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) method. The results show that the proposed ORC system has better energy recovery performances than the parallel ORC system. R1150-R600a-R290, R1150-R601a-R600a, and R170-R601-R290 are determined as the three most promising working fluids combinations. Under optimized conditions, the output power range is 199.97 to 218.51 kW, the energy efficiency range is 13.64% to 15.62%, and the exergy efficiency range is 25.29% to 27.3%. The payback period ranges from 8.36 to 8.74 years. The working fluids selection helps to reduce the exergy destruction of intermediate heat exchanger, which could be up to 30.59%.     

Effects of cold plasma on the color parameters of Hyssop (Hyssopus officinalis L.) using color imaging instrumentation and spectrophotometer

This research was conducted to evaluate the effects of cold atmospheric plasma treatment on the color of Hyssop (Hyssopus officinalis L.) and also to compare the usage of the spectrophotometer vs the color imaging instrumentation for the evaluation of the treatment on the color parameters. The experiments were investigated at different treatment times of 1, 5, and 10 minutes and the voltage values of 17, 20, and 23 kV. Possible changes of color were evaluated by using CIE L*a*b* values obtained with HunterLab colorimeter and CIE L*a*b* values obtained with a digital still camera (DSC) using digital image processing (MATLAB software). The values of L*, a*, and b* of the samples were obtained using both the methods. The results revealed that the L*, a*, and b* values of the treated Hyssop samples changed with increasing the treatment time and the voltage applied. Evaluating the interaction effects revealed that there was a significant difference in the (−a^*/b^* ) ratio. In addition, the results showed that the effects of all variables on the color parameters were significantly different in the case of the DSC using digital image processing. However, these effects were not significantly different using HunterLab colorimeter except for time variable and interaction effects of a* and (−a^*/b^* ) ratio. The lightest green color and the maximum chlorophyll content loss were observed for 23 kV applied over 10 minutes. Based on the results, the digital image processing can be used as a practical tool to study the variations at the color of dried Hyssop leaves after cold plasma treatment.     

化工大型机组的管理保养技术

化工机组设备的维护、保养和管理工作的在企业之中是非常重要的,只有提升企业管理、维护、保养机组的工作水平才能够让企业跟上时代发展的脚步。对化工机组设备维护管理的意义、维护保养的技术及其存在的问题和难点逐一进行介绍。     

1 200 MPa级冷轧先进高强钢轧制稳定性的分析及控制

针对1 200 MPa级冷轧先进高强钢轧制不稳定问题,对热轧原料组织性能均匀性、冷轧压缩比、冷连轧机组轧制策略等进行了分析。结果表明,热轧工序投入边部加热器,采用分段冷却等手段,可有效降低热轧原料头尾部组织性能差异,保证通卷性能均匀,进而保证通卷轧制过程稳定;通过优化冷连轧机组压缩比,可有效降低材料本身的加工硬化强度,进而避免连轧机组后面机架的轧制超负荷情况;通过优化冷连轧机组轧制策略,可保证轧制过程中各机架均匀变形,避免出现轧制力差异较大的情况,进而保证轧制过程稳定。采用上述措施,1 200 MPa级冷轧先进高强钢轧制力控制在约15 000 kN,厚度精度控制在±0.06 mm以内,可保证该级别高强钢的稳定轧制。     

Power generation potential of liquified natural gas regasification terminals

The share of liquified natural gas (LNG) in the international trade of natural gas (NG) is continually increasing. This presents increasing opportunities to build power plants to generate electricity at LNG regasification terminals rather than wasting the power generation potential of LNG at about −162°C by regasifying it by seawater, ambient air, or by burning NG. Typically, over 5% of the NG received at LNG plants is used to liquify the remaining incoming gaseous NG at environmental conditions. Theoretically, all the energy consumed at LNG liquefaction plants can be recovered at LNG regasification terminals. In this study, the theoretical and practical power generation potential of regasified LNG is investigated by performing energy and exergy analyses. It is shown that up to 0.191 kWh of electric power can be generated during the regasification of LNG per standard m³ of NG regasified. The potential economic gains associated with power generation at LNG regasification facilities are demonstrated by analyzing the 2018 LNG imports of Turkey as a case study and the world. It is shown that the 314 million tons of LNG imported globally in 2018 has the electric power generation potential of 88 billion kWh with a market value of over 10 billion USD. It also has the potential to offset 38 million tons of CO₂ emissions.     

喷丸奥氏体耐热钢抗蒸汽氧化性的研究与使用现状

奥氏体钢内壁喷丸处理作为一种新的提高材料抗蒸汽氧化性的技术，在超超临界火电机组受热面管的使用越来越广泛和成熟。概述了传统奥氏体钢在蒸汽氧化过程中氧化皮的形成结构，材料临界Cr含量 对富Cr层形成的影响，以及氧化皮结构与临界Cr含量 的关系。奥氏体钢内壁喷丸处理提高抗蒸汽氧化性的机理为：喷丸在管子内表面形成一层微米级厚度的喷丸层，喷丸层中晶粒碎化、晶格畸变、位错增多，在蒸汽氧化过程中，为基体内的Cr原子向表面扩散提供短路通道，使喷丸层表面Cr浓度提高，以形成富Cr层，减小氧化速率，提高抗蒸汽氧化性。归纳得出国内外关于喷丸奥氏体钢与传统钢管在600~750 ℃温度范围内，抗蒸汽氧化性的顺序依次为：600~700 ℃温度下，喷丸SUPER304(S30432)>喷丸TP347H≈喷丸TP321H≈TP310HCbN(HR3C)>SUPER304≈TP347HFG>TP304≈TP347H>TP321H；700~750 ℃下，TP310HCbN(HR3C)>喷丸TP347H>喷丸TP321H。同时归纳了喷丸工艺中，各因素对喷丸效果的影响，喷丸层质量的金相和硬度评价方法，以及目前喷丸奥氏体钢的实际应用现状。最后分析了喷丸奥氏体钢关于加工、焊接以及使用寿命等仍需研究解决的问题，展望了喷丸工艺向马氏体钢的推广使用。     

热轧双相钢生产现状、存在问题及发展趋势浅析

介绍了国内外热轧双相钢的发展现状；对热轧双相钢的成分体系和关键生产工艺进行了总结，指出了目前热轧双相钢在生产过程中存在的问题；提出了未来热轧双相钢的主要发展方向为低成本、高强度、低负荷、高表面质量和“以热代冷”。     

超大电解槽清槽方法优化与运用

电积过程中周期管理至关重要,然而,电解槽的清槽作业效果直接影响电积作业能否正常运行,超大电解槽清槽作业比小型电解槽清槽作业难度更大,本文将阐述如何将大型电解槽清槽作业工业化和成功运用于生产且取得良好的效果     

国家级绿色矿山试点单位成效分析与建议

随着全国绿色矿山名录的公布,国家级绿色矿山试点单位也完成了其历史使命。原有的661家国家级绿色矿山试点单位中有398家通过遴选进入了名录,本文从省份、区域、行业、规模等方面对试点单位通过遴选的情况进行了梳理分析,进而对试点建设工作成效与作用进行了总结,认为经过试点工作树立了大批先进典型模式、探索了矿业转型升级新路径、为全国绿色矿山名录形成奠定了重要基础,并对下一步继续推进绿色矿山建设工作提出了相关建议,认为不同类型矿山企业创建绿色矿山时工作要有所侧重、已纳入名录绿色矿山要持续推进绿色发展避免被除名、管理部门对纳入名录的绿色矿山要加强激励支持与监督管理。     

轧制速度对AZ31镁合金管材冷轧成形的影响

轧制速度是三辊式冷轧成形过程中关键的工艺参数，决定其力学特征及温升情况。基于此，本文以冷轧AZ31镁合金管材为研究对象，通过全流程数值仿真计算，对比分析不同轧制速度在各特征变形段对等效应力、等效塑性应变及节点温度的影响规律。结果表明，等效应力、等效塑性应变及节点温度均随轧制速度的增大而增大。通过元胞自动机模型及实验等手段，探明了晶粒在轧制过程中产生连续再结晶并细化的初步组织演变规律；对比分析实验与模拟结果并结合多方面因素，得到800mm/s的轧制速度可以更好的满足工艺要求的结果，为冷轧镁合金管材轧制速度的选择提供依据。