Maintenance considerations for new plant

It is never too early to start planning the maintenance of new plant. From the outset, maintenance considerations should be made: a trained staff and a work force familiar with the plant, and able to operate and maintain it, is needed before production can start; management and control functions for keeping the plant in safe, efficient and profitable production also need to be established. The relationships and information flows necessary to set up proper maintenance procedures are presented.     

Improvement of continuous calibration based on temperature oscillation and application to biochemical reaction calorimetry

This paper describes an improvement of a method for continuous calibration of the global heat transfer coefficient, recently described in literature [A. Tietze, Möglichkeiten und Grenzen der Temperaturschwingungskalorimetrie, Doctoral Thesis, Technishe Universität Berlin, 1998; Chem. Eng. Sci. 51 (1996) 3131; Chem. Ing. Tech. 68 (1996) 97]. The continuous calibration method is based on induced sinusoidal jacket temperature oscillations, allowing the uncoupling of the chemical heat production from the heat transfer parameters during the reaction. A mathematical computation procedure based on two-anchors, before and after the reaction, has been developed which gives better results as compared to the one reported in literature, using one-anchor only, either before or after the reaction. The applicability of this method to biotechnology has been explored with respect to different culture parameters, which affect the global heat transfer coefficient, i.e. stirring speed, reactive volume, and medium viscosity. This oscillating reaction calorimetry method (ORC) has been successfully applied to a fed-batch culture of Saccharomyces cerevisiae with a non-linear increase of reactive volume.     

Methane and nitrous oxide measured throughout Lake Erie over all seasons indicate highest emissions from the eutrophic Western Basin

Eutrophication has been linked to increased greenhouse gas emissions from inland waters. Phytoplankton blooms in Lake Erie have increased since the 1990s, although its greenhouse gas emissions are not well characterized. We measured CH₄ and N₂O concentrations and diffusive fluxes in four seasons around the entire lake, and CO₂ fluxes in one summer season. Lake Erie is a source of CH₄ all year across the lake, concentrated in spring and summer in the Western Basin. Methane emissions ranged from 0.03 to 14.87 mg C m⁻² d^-1. Methane is predominantly biogenic, and natural gas leaks are an insignificant source. While Lake Erie is an overall N₂O source, it is an N₂O sink in winter and occasionally during summer. Emissions of N₂O ranged from −0.08 to 1.22 mg N m⁻² d^-1. We also measured CO₂ fluxes in summer only, when Lake Erie is a small atmospheric CO₂ sink. While areal fluxes of CH₄ and N₂O are similar to those observed elsewhere, total fluxes from Lake Erie are higher due to its surface area. Lake Erie emits ~ 6300 (±19%) metric tons of CH₄-C yr⁻¹ and ~600 (±37%) metric tons N₂O-N yr⁻¹: almost 500,000 metric tons CO₂-eq yr⁻¹ total. This is the first comprehensive dataset of CH₄ and N₂O concentrations and diffusive emissions in a very large lake. More measurements and monitoring are needed to determine whether increased eutrophication in the Great Lakes is tied to increased emissions of these powerful climate forcers in a possible positive feedback to climate warming.     

苦杏仁饼粕制备杏仁精油的工艺研究

目的:优选从苦杏仁饼粕中提取杏仁精油的最佳工艺参数,为杏仁精油的产业化生产提供技术依据。方法:以苦杏仁饼粕为原料,采用高温蒸煮法制备杏仁精油,通过正交试验和单因素试验相结合的方法,对影响杏仁精油得率的水料比、水解时间、水解温度以及蒸馏时间等主要参数进行优化。结果:制备杏仁精油的最佳工艺参数:水料比10:1,水解时间90 min,水解温度60℃,蒸馏时间240 min,其中水解时间对精油得率的影响最大,其次为蒸馏时间。各因素影响杏仁精油得率的顺序为水解时间>蒸馏时间>水料比>水解温度。结论:在本试验的最佳工艺条件下,杏仁精油的得率为13.51‰。     

Design of a water Vapour Pressure Manometer

The theory of measurement of water vapour exerted by a food sample with a Vapour Pressure Manometer (VPM) is analysed in this paper. It is shown that the change in volume of the measured system when the water is eliminated from the air-water vapour mixture must be taken into account in calculations. A correction factor is proposed, the value of which is dependent on the design characteristics of the VPM and on the actual readings of h₁ and h₂. Analysis of the design characteristics of the VPM has shown that the volume between the valves and the manometer liquid level at the ‘0’ reading should be relatively large in comparison with the volumes of free space in sample and desiccant flasks. Correct proportioning of these volumes enables large readings of h₁ and a correction factor below 2 to be obtained.The value of the correction factor greatly affects the variance of a_w. The standard deviation of a_w is smaller the closer the correction factor is to 1.A design calculation procedure for the VPM is proposed, and also a method of calibrating the completed manometer.     

Continuous simulation of CSO emissions

Modelling is an essential method to predict the behaviour of various water systems in urban areas. A common problem of modelling these systems is that it is hardly possible to model them fully in a detailed way. The applications of existing hydrodynamic models are very data-intensive and time-consuming, particularly for continuous simulation using a long rainfall record. It is thus necessary to develop a new modelling approach which is correct in representing and efficient in dealing with the processes involved in urban water systems. SewSim is such a conceptual combined sewer overflow (CSO) emission model. SewSim has been developed using a dynamic programming package MATLAB and its toolbox SIMULINK. This paper presents some case studies using this model for continuous simulation.     

Impacts of urban form on air quality in metropolitan areas in the United States

Among 221 metropolitan areas (MAs) in the United States (US), this study explored the impact of urban form, either urban compactness or urban sprawl, on two types of air quality in 2014: NO_x emissions from road traffic and annual average NO2 concentrations. Urban form was quantified using Smart Growth America (SGA) sprawl indexes with density, land use mixing, centeredness, and street connectivity. NO_x emissions from road traffic were derived from the National Emissions Inventory (NEI). Through modeling NO2 concentrations using land use regression (LUR), with satellite-based estimates and kriging, this study measured NO₂ concentrations within MAs in the US The study results showed that higher levels of urban form scores (i.e., higher compactness) and land use mixing were associated with lower per-person NO_x emissions from road traffic. In addition, higher levels of centeredness were associated with lower NO₂ concentrations, but the effect was moderate. On the other hand, regional rainfall and solar insolation had more significant associations with NO₂ concentrations than metropolitan urban form. Meanwhile, localized emissions sources had significant associations with local-level NO₂ concentrations. This study provides additional evidence on the relationship between urban form and air quality in the US MAs. The study suggests that high compactness-oriented development and the reduction of localized emission sources may be effective in reducing NO_x emissions from road traffic and local NO₂ concentrations, respectively. However, future studies need to explore the impact of urban form at both the MA and local levels on NO₂ concentrations and develop a more accurate national NO₂ concentration prediction model.     

Comparing centralized and decentralized bio-energy systems in rural China

Under the dual pressures of an energy crisis and rising greenhouse gas emissions, biomass energy development and utilisation has become part of the national energy strategy in China. The last decade has witnessed a strong promotion of both centralised and decentralised bio-energy systems in rural China. The government seems to have a strong preference for centralised (village-based) bio-energy systems in recent years. However, these government-driven systems have not worked without difficulties, particularly regarding economic and technological viability and maintenance. Studies on the advantages and disadvantages of decentralised and centralised bio-energy systems are rare. This study aims to shed light on the performances of these two systems in terms of social, economic and environmental effects. Through interviewing local officials and village leaders and surveying farmers in 12 villages in Shandong Province, it was found that bio-energy systems should be selected based on the local circumstances. The diversity of the local natural, economic and social situations determines the size, place, technology and organisational model of the bio-energy system.