共查询到20条相似文献,搜索用时 15 毫秒
1.
《Advances in Environmental Research》2001,5(1):61-79
This work deals with the application of mass integration to the Kraft process in an effort to minimize the fresh water usage. Due to the recycle and reuse of various aqueous streams present in the given process, there is a build-up of non-process elements (or NPEs) which has to be addressed. The approach consists of gaining process insights from the flow sheet via a graphical solution strategy followed by mathematical optimization. A targeting approach is described. The source sink diagram and path diagram are included in the analysis. A rule based on the lever arm and material balance is used to determine the sequence of steps at fresh water minimization. The graphical approach is easy to apply and allows the user to determine initial solutions to the problem. This is followed by a detailed mathematical optimization formulation for the problem and the solution strategy to be used to converge on the final solution. A case study dealing with the Kraft process, and chloride being the targeted NPE, is considered to demonstrate the potential benefits of the approach. Significant reductions in fresh water demands and wastewater discharges are observed for the Kraft process along with the allocation of NPEs. Any build-up of NPEs due to the recycle and reuse of various aqueous effluent streams to replace fresh water is accounted for via the inclusion of path diagram equations in the mathematical optimization. The principles developed are generic in nature and can easily be extended to other pulp processes as well. 相似文献
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Hydrogenation units are often operated at high pressure, requiring the use of compressors which are one of the most expensive chemical processing equipment. Optimizing a hydrogen network should therefore take into consideration not only purity and flowrate constraints but also pressure requirements. In this paper, based on the hydrogen surplus diagram approach, the average pressure profiles of hydrogen sources and sinks are proposed through the introduction of a system’s minimum pressure drop Δp. Combined with the traditional purity profiles, whether a source can meet a sink either for hydrogen concentration or for pressure requirements can be determined intuitively. In cases where the pressure of a source is not sufficient for a sink, installing a hydrogen compressor or using another source with higher purity and pressure could be potential solutions. A cost equation is established to determine which of the two solutions is economically more viable. For different matching situations between sources and sinks, strategies for optimum placement of compression equipment within a given hydrogen network are proposed. A case study is used to illustrate the application and effectiveness of the proposed method. 相似文献
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This paper presents an industrial application of mixed-integer nonlinear programming (MINLP) models for the optimisation of a water network, which was initiated by an integral need for cleaner production within a brewery. Several mathematical models were developed in order to reduce the use of freshwater, whilst considering the specific requirements of each particular production section. These models are based on the design method developed by Kim and Smith [1]. The original formulation is modified to enable efficient integration of discontinuous and semi-continuous water-using processes in the packaging area. Semi-continuous processes are treated as water sources of limited capacity. The option of installing storage tanks for semi-continuous water streams is included in the model, in order to re-use these streams during the shutdown periods of semi-continuous operations. The original model is additionally extended with the option of installing local (on-site) wastewater treatment units operating either in batch or semi-continuous modes. This enables the analysing of opportunities for regeneration re-use within the production area, i.e. the brewhouse with a cellar, because of high contaminant concentrations at these sites. The scheduling of batch wastewater treatment units is performed simultaneously in order to adjust the treatment schedule to a fixed schedule of batch processes. 相似文献
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Emergetic ternary diagrams: five examples for application in environmental accounting for decision-making 总被引:1,自引:0,他引:1
《Journal of Cleaner Production》2007,15(1):63-74
In a recent paper, “A combined tool for environmental scientists and decision makers: ternary diagrams and emergy accounting.” [Giannetti BF, Barrella FA, Almeida CMVB. A combined tool for environmental scientists and decision makers: ternary diagrams and emergy accounting. J Clean Prod, in press] Ternary diagrams were proposed as a graphical tool to assist emergy analysis. The graphical representation of the emergy accounting data makes it possible to compare processes and systems with and without ecosystem services, to evaluate improvements and to follow the system performance over time. The graphic tool is versatile and adaptable to represent products, processes, systems, countries, and different periods of time.The use and the versatility of ternary diagrams for assisting in performing emergy analyses are illustrated by means of five examples taken from the literature, which are presented and discussed. It is shown that emergetic ternary diagram's properties assist the assessment of the system efficiency, its dependence upon renewable and non-renewable inputs and the environmental support for dilution and abatement of process emissions. With the aid of ternary diagrams, details such as the interaction between systems and between systems and the environment are recognized and evaluated. Such a tool for graphical analysis allows a transparent presentation of the results and can serve as an interface between emergy scientists and decision makers, provided the meaning of each line in the diagram is carefully explained and understood. 相似文献
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Jiyong Kim Jinkyung Kim Junghwan Kim ChangKyu Yoo Il Moon 《Journal of Cleaner Production》2009,17(2):162-171
A new systematic methodology for designing wastewater and heat exchange networks for process industries involving effluent streams containing multiple contaminants is proposed. A simultaneous optimization approach mathematically combines the problems of wastewater and heat exchanger network optimization into a single step. This process includes two global iterations of a similar two-stage approach and optimizes networks for water and heat exchange simultaneously based on cost estimation. The objective function is to minimize the total annual cost of the wastewater and heat exchange network design which is subject to the mass and energy balance constraints on all the pertinent flows and to constraints related to the concentrations of contaminants. The proposed method employs a strategy to address a mixed integer non-linear programming (MINLP) formulation. Cost estimates for optimized wastewater and heat exchange networks for an oil refinery process are generated, illustrating the effectiveness of the proposed methodology. 相似文献
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ZHAO Hongtao YIN Chengqing CHEN Meixue WANG Weidong Je eries Chris SHAN Baoqing 《环境科学学报(英文版)》2009,21(2):162-167
Particles of dust washed o streets by stormwater are an important pathway of polyaromatic hydrocarbons (PAHs) into urban streams.
This article presented a comprehensive assessment of the size distribution of PAHs in street dust particles, the potential risks of the
particles in urban streams, and the sources and sinks of PAHs in the stream network. This assessment was based on measurements of
16 PAHs from the USEPA priority list in street dust particles and river sediments in Xincheng, China. The content of total PAHs ranged
from 1629 to 8986 g/kg in street dust particles, where smaller particles have a higher concentrations. Approximately 55% of the total
PAHs were associated with particles less than 250 m which accounted for 40% of the total mass of street dust. The PAH quantities
increased from 2.41 to 46.86 g/m2 in the sequence of new residential, rising through main roads, old town residential, commercial and
industrial areas. The sediments in stream reaches in town were found to be sinks for street dust particle PAHs. The research findings
suggested that particle size, land use and the hydrological conditions in the stream network were the factors which most influenced the
total loads of PAH in the receiving water bodies. 相似文献
7.
Size distribution and diffuse pollution impacts of PAHs in street dust in urban streams in the Yangtze River Delta 总被引:2,自引:3,他引:2
Jefferies Chris 《环境科学学报(英文版)》2009,21(2)
Particles of dust washed off streets by stormwater are an important pathway of polyaromatic hydrocarbons (PAHs) into urban streams.This paper presents a comprehensive assessment of the size distribution of PAHs in street dust particles, the potential risks of the particles in urban streams, and the sources and sinks of PAHs in the stream network.This assessment is based on measurements of 16 PAHs from the USEPA priority list in street dust particles and river sediments in Xincheng, China.The content of total PAHs ranged from 1,629 to 8,986 μg/kg in street dust particles, where smaller particles have a higher concentrations.Approximately 55% of the total PAHs were associated with particles less than 250 μm which accounted for 40% of the total mass of street dust.The PAH quantities increased from 2.41 to 46.86 μg/m2 in the sequence of new residential, rising through main roads, old town residential, commercial and industrial areas.The sediments in stream reaches in town were found to be sinks for street dust particle PAHs.The research findings suggest that particle size, land use and the hydrological conditions in the stream network were the factors which most influenced the total loads of PAH in the receiving water bodies. 相似文献
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《Environmental Science & Policy》2001,4(6):269-292
The Kyoto Protocol to the climate convention makes provision for sink enhancement activities to contribute to meeting the greenhouse gas emissions limitation commitments of industrialised countries. This paper analyses the potential contribution of sink enhancement activities to meeting commitments of industrialised countries. Six scenarios covering different categories of eligible sinks are analysed. A range of the potential magnitude of the carbon sequestered by each category of sinks is tested. Since cost curves for the different types of sink enhancement activities are not available for most countries, a range of average costs is used with the lowest cost allowing maximum use of sinks. The effects considered are the impacts on compliance costs for OECD countries, economies in transition, and developing countries and the mix of actions used by industrialised countries to achieve compliance. In every scenario, at least some of the sinks have costs lower than the market price, so the larger the eligible sinks, the lower the compliance costs for industrialised countries. Greater use of sinks also reduces the net income received by the economies in transition and developing countries. Increased use of sinks lowers emission reductions implemented in industrialised countries and reduces non-sink activity under the Clean Development Mechanism. 相似文献
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以国内某工业园区中水回用示范项目1.75万m3/d造纸废水零排放工程为例,对工程采用的预处理+多级膜浓缩+蒸发结晶+膜电解组合工艺流程及设计参数情况进行了重点说明,对部分工艺单元的运行数据进行了技术分析。运行数据表明:臭氧活性炭生物滤池对造纸废水二级出水残留COD的去除率>50%,机械加速沉清池对一级反渗透浓水硬度的去除率达到70%,离子交换器出水硬度稳定在0~4 mg/L,NaCl浓缩反渗透单元对Cl-的再浓缩比约为3倍。最后介绍了对于膜浓缩和蒸发结晶系统改造的工程经验,并从技术总结的角度阐明完善的工艺流程及技术保障措施是该工业废水零排放工程获得成功的根本。 相似文献
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中国森林碳汇的空间溢出效应与影响因素——基于大陆31个省(市、区)森林资源清查数据的空间计量分析 总被引:1,自引:1,他引:0
科学估算各地区森林碳汇量并探讨其空间关联性特征是制定差异化碳汇发展政策的重要基础。根据1988—2013年中国大陆31个省(市、区)的6次森林资源清查数据,论文利用森林蓄积量扩展法测算了各地区的森林碳汇量,进而检测和比较了省域间碳汇总量空间关联性的方向和强弱,最后运用空间计量模型分析了碳汇的溢出效应与影响因素。结果表明:1)我国的森林碳汇量整体呈上升态势,各地区间碳汇量差异明显,其中西藏、黑龙江等地区碳汇量丰富,而上海、北京等地则碳汇增长率较快;2)研究期内的Moran’s I指数整体表现为倒“S”型的波动变化特征,全国森林碳汇在省域空间分布上的差异性并不是随机的,而是具备一定关联性;3)我国森林碳汇存在显著的近邻空间溢出效应,森林资源采伐、森林受灾程度和降水量等因素对森林碳汇水平的影响显著。因此,研究认为:我国在发挥森林生态功能时,应当考虑省份间的地理区位因素,合理制定兼具差异化和协调性的森林碳汇发展政策。 相似文献
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某矿山机械装备公司退城进园,该公司电镀车间产生含锌、含铬、含镍、含铁等重金属电镀废水,污染物浓度远超过《电镀污染物排放标准》(GB 2190-2008)标准限值.该公司针对目前生产废水中污染物种类多、水质复杂的特点,采用对电镀废水经化学分质处理的工艺,再经反渗透处理后部分回用,剩余废水及膜的浓缩液经二效真空低压蒸发处理,结晶盐作为危险固废处置,实现废水“零排放”.该项目建成后为企业的进一步发展提供可靠的保障. 相似文献
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Struvite crystallization has been considered a promising approach to recover phosphorus from wastewater. However, its practical application is limited, probably because of the high cost of magnesium(Mg). In this study, a comprehensive economic analysis was conducted using five Mg sources(MgCl_2, MgSO_4, MgO, Mg(OH)_2, and bittern) during the operation of a pilot-scale fluidized bed reactor(FBR), using swine wastewater as the case matrix. First, the economic operating conditions were investigated, and subsequently, the performance and the costs of the five Mg sources were compared. The results indicated that the FBR could be operated most economically at pH of 8.5 and Mg to phosphorus(Mg/P) molar ratio of 1.5. Under these conditions, no significant differences in phosphorus removal and product quality could be found between the five Mg sources. Selecting the most economical Mg source was thus highly dependent on the prices of the reagents and Mg sources. Low-solubility Mg sources were preferable when NaOH was priced higher, while high-solubility Mg sources proved more economical when HNO_3 was expensive. The bittern was the most economical choice only when the distances for total inorganic orthophosphate removal and struvite recovery were shorter than 40 and 270 km, respectively. The current study provides an overview of the economic selection of an Mg source, which can help reduce the cost of struvite crystallization. 相似文献
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Masafumi Tate Masanori Fujit Michihiko Ike QUI Yen-feng Satoru Kokubo 《环境科学学报(英文版)》2004,16(2):230-233
Solid-liquid separation of the wastewater is very difficult because of high viscosity and high SS concentration. In this study, the effectiveness of preozonation on improving the settleability of the solids in wheat and sweet potato wastewaters was investigated using a bench-scale system and pilot treatment system respectively. Results showed that solid-liquid separation in the wheat wastewater was greatly improved by the decanter in the system(SS reduction from 24100 mg/L to 100 mg/L). However, preozonation practice did not show a significant effect on solid-liquid separation of the sweet potato wastewater. Effect of preozonation on solid-liquid separation between wheat and sweet potato wastewater showed different. 相似文献
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中国种植业碳汇盈余动态变化及地区差异分析——基于31个省(市、区)2000—2012年的面板数据 总被引:3,自引:1,他引:2
在科学测算31个省(市、区)2000—2012年种植业碳汇盈余量的基础上,利用基尼系数系统考察了其地区差距及动态演变特征。研究结论揭示:1)中国种植业碳汇盈余量呈现较为明显的空间差异性。基于总量变化趋势的不同可将31个地区划分为"持续增长型"、"波动增长型"、"波动下降型"与"持续下降型"等4类地区。16个地区种植业碳汇水平得到提升但增幅差异较大;余下15个地区则处于下降态势。2)基尼系数测算结果表明,中国种植业碳汇盈余的地区差距在样本考察期内虽存在一定的年际起伏,但总体处于逐步扩大趋势。从三大区域来看,东部地区差距变化幅度居中,经历了差距缩小期、波动扩大期和波动平稳期等变化阶段;中部地区差距变化幅度最大,其绝对差距也高于东、西部地区,经历了差距持续扩大期、波动平稳期、波动缩小期与小幅扩大期等变化阶段;西部地区差距变化幅度最小,经历了"扩大"与"缩小"的循环演变。 相似文献
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黄土高原是重要的降尘区还是沙尘源区这一科学问题至今未有确切定论.本文利用北半球气溶胶区域气候模式NARCM,根据1995~2004年10a的模拟数据,分析了中国区域沙尘起沙量、沉降量以及沙尘的盈亏空间分布及风场,得到如下结论:1)沙漠及沙漠化地区是起沙量最大的区域、沉降量高值区集中在沙漠、沙漠化地区及其下风方向.黄土高原起沙量很小,而沉降量远大于起沙量.2)沙尘源区是沙漠及沙漠化地区,其余的地区则是沙尘汇区,降尘量由西北向东南递减.3)黄土高原因太行山和秦岭阻挡,处在最大的沙尘汇区.黄土高原的黄土是冰期和间冰期交替、经过漫长年代沙尘沉降的结果,模拟分析结论为黄土的风成学说提供了有力的证据. 相似文献