Removal of ammonia from contaminated air in a biotrickling filter - denitrifying bioreactor combination system

The removal of gaseous ammonia in a system consisting of a biotrickling filter, a denitrification reactor and a polishing bioreactor for the trickling liquid was investigated. The system allowed sustained treatment of ammonia while preventing biological inhibition by accumulating nitrate and nitrite and avoiding generation of contaminated water. All bioreactors were packed with cattle bone composite ceramics, a porous support with a large interfacial area. Excellent removal of ammonia gas was obtained. The critical loading ranged from 60 to 120 gm(-3)h(-1) depending on the conditions, and loadings below 56 gm(-3)h(-1) resulted in essentially complete removal of ammonia. In addition, concentrations of ammonia, nitrite, nitrate and COD in the recycle liquid of the inlet and outlet of each reactor were measured to determine the fate of nitrogen in the reactor, close nitrogen balances and calculate nitrogen to COD ratios. Ammonia absorption and nitrification occurred in the biotrickling filter; nitrate and nitrite were biologically removed in the denitrification reactor and excess dissolved COD and ammonia were treated in the polishing bioreactor. Overall, ammonia gas was very successfully removed in the bioreactor system and steady state operation with respect to nitrogen species was achieved.     

Removal of dichloromethane from waste gases in one- and two-liquid-phase stirred tank bioreactors and biotrickling filters

The removal of dichloromethane (DCM) from polluted air was studied both in biotrickling filters and in continuous stirred tank bioreactors, using either a single-liquid aqueous phase or a combination of an aqueous-organic liquid phase. The presence of the organic phase, i.e. silicone oil, at a volume ratio of 10% of the liquid phase, increased the maximum EC by about 25% in the BTF, reaching 200 g m³/h, and by as much as 300% in the CSTB, reaching 350 g m³/h. Based on data of chloride release in the aqueous phase and carbon dioxide production in the gas phase, complete dechlorination and mineralization of the pollutant could be confirmed. When applying shock loads, a more stable behaviour was observed in the presence of the organic phase. Generally, the completely mixed reactors were also more stable than the plug-flow biotrickling filters, irrespective of the presence of the organic phase. The use of molecular techniques allowed showing that the originally inoculated DCM-degrading Hyphomicrobium strains remained present, although not dominant, after long-term bioreactor operation. Different new bacterial populations did also appear in the systems, some of which were unable to degrade DCM.     

Evaluation of energy performance indicators and financial aspects of energy saving techniques in residential real estate

The energy consumption in the existing residential building stock accounts for about 40% of the total energy consumption in the built environment. Different types of energy performance indicators to assess the energy consumption of buildings were and still are internationally under development. In this paper we compare the methodologies and accuracies of three Dutch energy performance indicators by applying them to eight houses. This application shows that the actual domestic energy use is linearly correlated with the estimated energy consumption given by the energy performance indicators, but 7-25% lower.Based on the energy performance indicators and actual energy use, we offer a methodology to incorporate additional revenues within the financial analysis of energy saving techniques. These revenues are related to the value of the dwelling in which the techniques are installed. We use the same houses to analyse the financial returns on energy saving investments. By assigning the value increase of real estate to two popular specific energy saving techniques, namely wall and roof insulation, it is found that the payback period could be 40-50% shorter than when it is solely based on investment costs and energy prices.     

Business process re-engineering: some aspects of how to evaluate and manage the risk exposure

This paper reports on research in progress on the subject of risk evaluation and management methods, and relates them to business process re-engineering (BPR). The paper defines the general concepts behind risk management, describes the risk management process and identifies classifications of risk within the BPR implementation and operationalization context. From a practical point of view it aims to assist those involved in identifying and evaluating which risks are most pertinent to BPR projects. This is important because unless the risks associated with a BPR project are established in advance and appropriate management action undertaken, the project may not be focused on possible problems and may thus lack sufficient direction to succeed.     

Kinetics of the chemical oxidation of polysulfide anions in aqueous solution

The kinetic properties of the chemical oxidation of aqueous polysulfide solutions have been studied in phosphate-buffered systems at pH 7-12, at temperatures between 20 and 40 degrees C, and ionic strength between 0.05 and 0.50 M. Polysulfide solutions were mixed with a buffer solution of known dissolved oxygen concentration, after which the decrease in the oxygen concentration of the solution was measured in time. The rate of oxygen consumption can be described by the empirical relation d[O2]/dt= -k[Sx(2-)][O2](0.59) . The reaction rate constant k is moderately dependent on pH and goes through a maximum at pH 10. The rate of oxygen consumption for polysulfide solutions is approximately four times higher than for sulfide solutions. At pH values below 9, reaction products were formed according to Sx(2-)+3/2O2-->S2O3(2-)+(x-2)S(0) . At pH values higher than 9, more thiosulfate and additional sulfide were formed, which is attributed to the low chemical stability of the sulfur of oxidation state zero, formed upon polysulfide oxidation. Our results strongly suggest that hydrolysis of this 'nascent' elemental sulfur to HS- and S2O3(2-) is faster than hydrolysis of crystalline inorganic sulfur or colloidal particles of biologically produced sulfur, and has a significant contribution already at 30 degrees C and pH 10.     

蹄式制动器维修工艺与方法研究

制动器维修质量的高低直接影响机械、车辆的制动性能及安全运行。本根据蹄式制动器的工作原理，分析了它的工作状态及影响因素；阐明了蹄式制动器的维修工艺要求及现场维修中存在的问题；提出了采用二状态原位切削，保证蹄式制动器维修工艺要求的加工方法。这种维修方法不仅能提高蹄式制动器的维修质量与工效，而且有助于延长其使用寿命。     

中心城水厂二期工程水处理工艺设计

介绍了深圳中心城水厂二期工程的设计条件和水处理工艺流程,以预臭氧接触池、折板絮凝平流沉淀池、V型砂滤池、二次提升泵房和臭氧接触池及生物活性炭滤池等为例,重点介绍了中心城水厂二期工程的主要净水构筑物的设计特点.     

The application of the risk management process in capital investment decisions for EHV transmission line projects

This paper reviews the viability of applying a risk management process to enhance capital investment decisions, when planning the construction of an extra-high voltage (EHV) overhead transmission line project that could be designed and built in the next 10 years by China Light & Power Company Limited, Hong Kong. Different project proposals will be considered for this transmission line as well as different completion dates. Each scenario will be investigated to determine the rate of return and expected cost to customer, using the net present value model. The lowest ‘cost to customer’ approach would be the normal criterion for project selection, assuming all proposals are technically viable and compatible with Hong Kong Government infrastructure plans.     

A systematic methodology for optimising the energy performance of buildings in Bahrain

Today, a great deal of effort is ongoing all over the world to find methods for optimising the energy performance of buildings. Such efforts can be seen in the European Energy Performance of Building Directive (EPBD). This directive aims to ensure energy saving and CO₂ emission reduction without compromising the local conditions and people's comfort. In the Gulf States, however, there is a need for such methods due to their economic and environmental benefits. This study introduces a simple but reliable methodology for optimising building energy performance in Bahrain. The methodology is based on building management systems (monitoring, analysing and targeting future performance), simulation tools and other technologies. This methodology was implemented using Visual DOE and was directly related to collectively gathered data gained form experimental works and practical applications. By means of the introduced methodology, energy consumption was obtained together with energy cost and CO₂ emissions. The applicability of this methodology was demonstrated through optimising a case office building in Bahrain.     

Validation and application of adsorption breakthrough models for the chemical filters used in the make-up air unit (MAU) of a cleanroom

The dynamic adsorption capacity calculated from the breakthrough curves progressively decreased with the increases in the face velocity, suggesting that the effect of intraparticle diffusion and possibly the rate of adsorption as the rate-limiting mechanism were increasingly more profound for a chemical filter-type adsorber configuration. The Yoon–Nelson model generally matched well with the experimental breakthrough curved for breakthrough fraction less than 50%. However, the proportionality constant in the Yoon–Nelson model needed modification through the method from which the mass transfer coefficient (k_v) in the Wheeler–Jonas equation is determined. Subsequently, a series of breakthrough curves for the hypothetical toluene concentrations and face velocities simulating realistic operating conditions was generated, and their validity was verified against the adsorption capacity predicted by the Dubinin–Radushkevich isotherm equation. The useful life of a chemical filter could henceforth be estimated with confidence using the breakthrough curves predicted by the modified Yoon–Nelson model.     

Towards computer-supported inclusion and integration of life cycle processes in product conceptualization based on the process tree

Development of computer support in design is showing several shifts in focus over the latest decades. This paper relates to the shifts from detail design to conceptualization, from artifact geometry definition only to the inclusion of process knowledge, and from isolated aspects to integrated aspects. It discusses a possible solution for simultaneous consideration of life cycle process aspects during conceptual design using the process tree representation. Integrating process aspects can be considered a preparation for an integrated representation of artifact and process aspects to be used in a front–end environment for conventional CAD detailing systems     

唐山市在建筑节能工程建设过程中取得的经验

分析了我国建筑节能工程开展及发展缓慢的原因,阐述了唐山市建筑节能工程发展成果,提出了我国节能建筑应加大建设力度的几个方面,以积累建筑节能经验,促进建筑节能的发展。     

火电厂烟囱钢内筒砌筑泡沫玻璃砖脱落原因及工艺改进研究

本文以辽宁清河发电有限公司技改二期烟囱钢内筒砌砖项目实例为背景,尝试研究解决此类工程不同程度出现的泡沫砖脱落问题。在研究烟囱钢内筒砌砖材料及工艺的理论基础上,详细阐述了解决泡沫砖脱落的理论基础、工艺技术、施工流程及施工组织等,很好地解决了泡沫砖脱落问题,对同类工程具有一定参考价值。     

Using phosphoric acid-impregnated activated carbon to improve the efficiency of chemical filters for the removal of airborne molecular contaminants (AMCs) in the make-up air unit (MAU) of a cleanroom

A coconut shell activated carbon precursor was modified by impregnation with phosphoric acid. The effects of the particle diameter of the impregnated activated carbons (IACs) on the thickness, pressure resistance, and face velocity of a chemical filter were investigated. Furthermore, volatile organic compounds (VOCs) adsorption experiments were carried out to determine the relationship between the removal efficiency and the chemical properties of the adsorbents. The effects of various parameters such as challenge gas concentration, saturated adsorption ratio, impregnation method and impregnant contents were investigated. The results showed that the effect of face velocity on pressure resistance is larger than that of the thickness, that 0.25 M phosphoric acid impregnation of activated carbon can raise VOC removal efficiency by 2–3% (toluene: from 95.8% to 98.1%, isopropanol: from 95.2 to 97.2%), and that the optimal impregnation time is around 1.5 h. A simple shaking impregnation method exhibited better performance than the ultrasonic method.     

Assessing energy performance in the latest versions of Hong Kong Building Environmental Assessment Method (HK-BEAM)

The latest (4/04 and 5/04) versions of the Hong Kong Building Environmental Assessment Method (HK-BEAM), one covering new buildings and the other existing buildings, have been formally launched in 2005. The paper describes the building energy performance assessment method in these latest HK-BEAM versions. With the use of the energy budget approach, the assessment framework is applicable to a wide range of buildings that may comprise different mixes of premises types. The new scheme provides bonus credits for provisions that allow utilization of renewable energy sources. For existing buildings, it makes allowances for plant performance degradation and constraints to implementation of improvement measures in existing buildings. So far, the new assessment method has been applied to six building developments, including commercial complexes and residential developments. The assessment results are presented and discussed in the paper.     

A framework for identification and representation of client requirements in the briefing process

The briefing process is critical to the successful delivery of construction projects. Although a number of briefing guides have been developed, attempting to address the problems of briefing, they are often criticized as being too general and implicit. This paper describes a structured framework for identifying and representing client requirements (CRs) in the briefing process. It integrates the value management (VM) methodology with function analysis system technique (FAST) and functional performance specification (FPS) to enable the client organization and project team to systematically identify, clarify and clearly represent CRs in the briefing process. It comprises four interrelated phases: preparation, information, analysis and evaluation. This paper starts with a critical review of previous work in briefing and function analysis, followed by an introduction to the research methodology and detailed illustration of the proposed framework. The use of this framework can facilitate and lead to systematic identification and clarification of client requirements and the formation of a more precise and explicit representation of these requirements. The limitations of the approach are also discussed in the paper.     

船舶撞击带套箱桥墩的过程中能量转化仿真分析

本文借助有限元软件LS-DYNA仿真分析带钢套箱桥墩与船舶相互碰撞过程中能量转化的关系。证明平潭海峡大桥主桥带钢套箱的桥墩在通航船舶撞击下虽套箱损伤严重,但桥墩得到保护,不至于倒塌。同时分析采用的手段及结果可为相关研究提供参考。     

Modeling the heat diffusion process in the abiotic layers of green roofs

Green roofs have been increasingly installed to alleviate some common environmental problems. The thermal benefit of living vegetation on rooftop has been extensively studied. The individual and joint contribution of the non-living green roof layers, namely soil, rockwool (water storage) and plastic drainage layers, to thermal performance of green roof has seldom been assessed. This study evaluates the insulating and cooling effects of these abiotic materials. A one-dimensional theoretical model was developed to assess the heat diffusion process in the layers. The model was validated with empirical results from three experimental plots. A calibration procedure was successfully applied to determine key model parameters. The model can capture the most critical features of temperature variations and thermal performance of common abiotic green roof materials. The appreciable water-retention capacity of rockwool plays the dual role of supplying water to the soil to enhance evaporative cooling, and increasing the specific heat capacity of the green roof. The plastic drainage sheet with ample air spaces serves as an excellent thermal insulator. The model remains robust despite seasonal and weather variabilities. Our research findings contradict with some researches in the temperate region that the thermal dissipation in green roofs with dense vegetation is lower than thermally insulated bare roofs. The theoretical model could be used to simulate the micro-environmental conditions and predict the thermal performance of different materials to improve green roof design.