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171.
王文铭  郭静 《现代化工》2007,27(3):59-62
运用价值链分析方法对炼油厂内、外部的价值活动进行了分析,将炼油厂内部价值链划分为主生产作业链、辅助生产作业链和辅助价值链三部分,通过分析指出产品结构不合理、炼油成本较高是影响炼油业务价值的主要原因,针对企业实际情况,提出价值链优化调整策略:提高炼油技术水平,优化装置结构和产品结构,增产高附加值产品,不断提高企业经济效益。  相似文献   
172.
探讨了影响连续固相增粘产品活性的因素,提出了控制主反应器的温度、氮气流量、基础切片的端羧基、氮气露点等主要因素,实现生产的平稳控制,从而保证产品黏度的稳定。  相似文献   
173.
介绍了离子膜烧碱装置中空气吹除脱氯和真空脱氯工艺。分析了正常脱氯操作条件下影响其pH值和氧化还原地位(ORP)的因素,提出了控制措施。  相似文献   
174.
An efficient method to monitor changes in soil inorganic N content during crop growth would be a useful means to guide N fertilization to ensure high yields and low N losses to the environment. In this study, soil apparent electrical conductivity (ECa) measured by the widely used conductivity meter EM38 was tested as an indirect measurement of available N in spring barley during two cropping seasons at two sites with morainic loam in SE Norway. The experiment was constructed to maximize soil variation. In spite of the ȁ8noiseȁ9 caused by the soil heterogeneity, concentrations of inorganic N (cNinorg) or NO3-N were most strongly correlated with ECa in both years and at both locations (with one exception). The measurements of ECa reflected well the temporal variation in inorganic N content (Ninorg), and a ranking of the treatments based on ECa fitted very well with a ranking based on Ninorg at the first three sampling times after fertilizing. The best subset of sensor variables (i.e. variables which can be measured ȁ8on-the-goȁ9 by sensor techniques in the field) described 27–69% (average 47%) of the variation in topsoil cNinorg. When expanding the regression models to include pH as well, the degree of explanation increased significantly. In conclusion, the method of using ECa appears to be quite robust in terms of detecting relative differences in cNinorg, whereas a determination of absolute levels of cNinorg with the method is unreliable.  相似文献   
175.
根据国家质量技术监督局的计划安排,国家标准GB/T15224-1994《煤炭质量分级》需要修订。本文主要讨论“煤炭硫分分级”方面的内容。  相似文献   
176.
Twenty-two laboratories participated in a collaborative test to determine the iodine value (IV) of eight samples of fish oil (four with IV<150, four with IV>150) with either carbon tetrachloride (AOCS Official Method Cd 1–25) or cyclohexane (AOCS Recommended Practice Cd 1b-87) as solvent and either 1 or 2 h of reaction time. Laboratories received coded duplicate samples (hidden duplicates) and carried out duplicate determinations on each oil by each solvent-time combination (open duplicates). Replacing carbon tetrachloride with cyclohexane resulted in a lower IV (P<0.001). The decrease averaged 1.6 IV units for low-IV oils and 3.8 IV units for high-IV oils; this difference in response of 2.2 IV units between low- and high-IV oils was significant (P<0.001). Increasing the reaction time had a relatively small effect (0.34±0.18). There was no interaction of reaction time with solvent or oil type. Cyclohexane caused emulsions, which made it difficult to titrate residual iodine and thus increased the variability of the determination. The repeatability standard deviations (s r ), based on hidden duplicates, for 1-h reaction time with carbon tetrachloride and cyclohexane were 2.17 and 3.35, respectively. The corresponding reproducibility standard deviations were 2.73 and 4.53.  相似文献   
177.
In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller.  相似文献   
178.
探索了用SBR法处理柠檬酸废水过程中pH的变化规律。研究了柠檬酸废水处理过程中pH变化与COD处理效率的关系,研究目的在于利用易于检测的水质参数为实现SBR处理过程的自动监测和调控作基础试验研究。  相似文献   
179.
本工作是在非离子凝胶的分子热力学模型基础,引入Donnan平衡项和大分子离子链的静电排斥项对凝胶自由能的贡献,建立了一个新的离子凝胶的分子热力学模型。该模型在解释离子凝胶的PH敏感性及其各种影响因素,以及预测PH溶胀曲线方面都取得了较好的效果。  相似文献   
180.
粤北某市"土法炼砷"土壤中化学砷污染的研究   总被引:1,自引:0,他引:1  
张昆峰  宋卫锋  钟宜航 《广东化工》2006,33(12):76-77,88
粤北某市“土法炼砷”造成的砷污染,严重破坏了当地生态环境,而且砷还会进入河流或地下水,严重威胁了当地及北江下游的饮用水安全和生态安全。本文对“土法炼砷”遗址现场进行调查取样,并对砷污染的特点进行了分析。  相似文献   
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