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.     

Long-term performance analysis of chemical filters in clean rooms based on a prediction model

Chemical filters are the most important devices for removing gas-phase pollutants in clean rooms. However, the testing concentration of chemical filters is too high for reflecting their performance in a real clean room environment. This study tested the adsorption performance of chemical filters in the two most commonly used shapes at different concentrations. Then, the Langmuir equation and Wheeler-Jonas kinetic equation were combined to establish an adsorption performance prediction model of chemical filters under actual conditions. The predicted values of the model were in good agreement with the experimental results, which indicated the high accuracy of the prediction model. The model does not need to test the microscopic parameters of the adsorbent and can maintain high accuracy at low concentrations. A fast method for calculating the service life of chemical filters was also presented. Based on this model, the total cost of using a chemical filter with a high carbon content in microelectronic clean rooms could be decreased by 45% due to decreasing the number of filter replacements over 3 months. So a chemical filter with a high carbon content should be preferred over a filter with low resistance in microelectronic clean rooms.     

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。     

Assessing the impact of COVID-19 and safety parameters on energy project performance with an analytical hierarchy process

COVID-19 has destabilized the global economy, disrupted the lives of billions of people globally, and caused the workforce to suffer. Furthermore, the spread of this disease has caused most nations to impose strict lockdown regulations and shutdown most industries. This study aimed to highlight the key issues of energy project performance alongside construction activities that were halted during the COVID-19 outbreak to follow social distancing, lockdown, and public safety parameters. A questionnaire survey was administered to accomplish the purpose of this study. The responses of 42 energy project professionals and experts were evaluated using the analytical hierarchy process (AHP) for group decision-making. AHP shows that the biggest influences on project performance during COVID-19 pandemic were government measures and personal factors. The findings provide insight to support energy project planning and management during and after the pandemic, including prioritization of labor force health and safety.     

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.     

Exploring the emergence of lock-in in large-scale projects: A process view

The purpose of this paper is to investigate the emergence of lock-in in large-scale projects. Although large-scale projects have been studied for decades, most studies have applied economic or psychological perspectives to emphasize decision-making processes at the project front-end. Of those studies, some have focused on poor decision-making due to lock-in and the escalating commitments of decision-makers to ineffective courses of action. However, little is known about the way that project decisions are affected by organizational and inter-organizational contexts and the actors involved. Understanding decisions from a process viewpoint with a long-term (inter-) organizational perspective will lead to a better understanding of lock-in and the overall performance of large-scale projects. This qualitative research is based on a case study. The research setting is the multi-actor Madrid–Barcelona High-Speed rail Line (HSL) project in Spain. Through observations, interviews, several project documents, and report analysis, we explore the processual nature of the choices made during the course of the project. We consider the contextual conditions that give rise or support the emergence of lock-in in relation to pre- and post-project effects, institutional influences, and management practices that create action spaces at the project level. Our findings suggest that lock-in emergence requires the recognition of the long-term (inter-) organizational perspective regarding mechanisms and effects rather than confining decisions to the individual or single actor control in the front-end of projects. Based on organizational theory, the main contribution of this paper is to enrich our understanding of the emergence of lock-in using process theories.     

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。     

基于岩石破坏全过程能量演化的脆性评价指数

 目前用于评价页岩可压性的脆性指数大都孤立地考虑峰值前后的力学特性,并不能反映岩石整个破坏过程的脆性特征。基于岩石的全应力–应变曲线,分析岩石材料由塑性变形转化为脆性断裂过程中各种应变能的演化规律,认为峰前耗散能和峰后断裂能水平是决定岩石是否发生脆性断裂的本质因素。结合这2种能量建立能反映岩石破坏前后力学特征的脆性评价指数,对不同岩石材料在不同围压下的脆性特征以及页岩脆性的各向异性进行评价。研究结果表明：建立的脆性评价指数能同时反映岩石脆性破坏的难易程度和脆性的强弱,可评价不同力学条件下的脆性变化特征。不同岩石材料峰前耗散能以及峰后断裂能随着围压增大而增大,脆性程度不断降低,但降低趋势有所不同,红砂岩和页岩分别在低围压时和高围压时出现了脆–塑性的转化,而花岗岩在围压不断增大的整个过程中都保持着较强的脆性。另外页岩脆性具有明显的各向异性,不同层理方向的页岩所表现出的脆性程度差异显著,随着层理倾角?的增大,页岩脆性表现出稳–减–增的变化趋势,? = 0°时页岩的脆性程度要强于? = 90°时,? = 60°时页岩脆性最弱且表现出很强的塑性特征。实验结果很好地验证了提出的脆性指数的可靠性,研究成果为岩石脆性的定量评价提供了一条新思路。     

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.