Hsing-Wei Chu

Metal capture by sorbents during fluidized-bed combustion

Abstract Metal capture experiments were performed in a 76 mm (3″) ID fluidized-bed combustor with limestone, sand and alumina serving as both the fluidized medium and metal capture sorbents. Wood pellets spiked with metal solutions were used to simulate the metal-containing combustible fuel. The tested metals were nitrate and chloride species of lead and cadmium. The experimental parameters included metal species and concentration, sorbent type and size, combustor temperature, air flow rate and combustion duration. Experimental results indicated that the technology is highly promising. In-furnace lead capture by limestone was observed to be as high as 95%. The capture efficiency, however, varied with experimental parameters and chemical additives. Most of the captured metals were observed to be TCLP nonleachable.

Metal volatilization and separation during incineration

Abstract The United States Environmental Protection Agency (U.S.EPA) has reported that metals can account for almost all of the identified risks from a thermal treatment process. Fundamental research leading to better understanding of their behavior and improved control of their emissions is greatly needed. This paper reports our studies on metal volatilization and separation during incineration. Metal volatilization studies were carried out in two separate experiments. In the first experiment, the dynamic volatilization characteristics of various metals during the combustion of metal-containing wood pellets were investigated in a high-temperature electric furnace. In addition to uncontrolled volatilization, the potential of employing chemical additives to bind metals and prevent them from volatilizing during combustion was also investigated. The second experiment involved the investigation of metal volatilization characteristics during the thermal treatment of metal-contaminated clay in a fluidized bed unit. The metal species tested in both experiments were compounds of lead and cadmium. Metal capture/separation studies were also carried out in two separate experiments. The first involved the use of sorbents in the combustion chamber to capture metals during the fluidized bed incineration of metal-containing wood pellets. The second experiments, however, employed sorbents to absorb metal vapors in a fluidized-bed waste-heat boiler. The objective of both the experiments is to characterize the metal absorption efficiency associated with the processes.

Study of atmospheric mercury budget in East Asia using STEM-Hg modeling system

East Asia is the largest source region of global anthropogenic mercury emissions, and contributes to atmospheric mercury concentration and deposition in other regions. Similarly, mercury from the global pool also plays a role in the chemical transport of mercury in East Asia. Annual simulations of atmospheric mercury in East Asia were performed using the STEM-Hg modeling system to study the mass budgets of mercury in the region. The model results showed strong seasonal variation in mercury concentration and deposition, with signals from large point sources. The annual mean concentrations for gaseous elemental mercury, reactive gaseous mercury and particulate mercury in central China and eastern coastal areas were 1.8 ng m(-3), 100 pg m(-3) and 150 pg m(-3), respectively. Boundary conditions had a strong influence on the simulated mercury concentration and deposition, contributing to 80% of the concentration and 70% of the deposition predicted by the model. The rest was caused by the regional emissions before they were transported out of the model domain. Using different oxidation rates reported for the Hg(0)-O(3) reaction (i.e., by Hall, 1995 vs. by Pal and Ariya, 2004) led to a 9% difference in the predicted mean concentration and a 40% difference in the predicted mean deposition. The estimated annual dry and wet deposition for East Asia in 2001 was in the range of 590-735 Mg and 482-696 Mg, respectively. The mercury mass outflow caused by the emissions in the domain was estimated to be 681-714 Mg yr(-1). This constituted 70% of the total mercury emission in the domain. The greatest outflow occurred in spring and early summer.

Source attribution for mercury deposition in the contiguous United States: regional difference and seasonal variation.

Quantifying the contribution of emission sources responsible for mercury deposition in specific receptor regions helps develop emission control strategies that alleviate the impact on ecosystem and human health. In light of the maximum available control technology (MACT) rules proposed by U.S. Environmental Protection Agency (EPA) and the ongoing intergovernmental negotiation coordinated by United Nations Environmental Programme (UNEP) for mercury, the Community Multiscale Air Quality Modeling System (CMAQ-Hg) was applied to estimate the source contribution in six subregions of the contiguous United States (CONUS). The considered source categories include electric generating units (EGU), iron and steel industry (IRST), other industrial point sources excluding EGU and IRST (OIPM), the remaining anthropogenic sources (RA), natural processes (NAT), and out-of-boundary transport (BC). It is found that, on an annual basis, dry deposition accounts for two-thirds of total annual deposition in CONUS (474 Mg yr−1), mainly contributed by reactive gaseous mercury (about 60% of total deposition). The contribution from large point sources can be as high as 75% near the emission sources (<100 km), indicating that emission reduction may result in direct deposition decrease near the source locations. Out-of-boundary transport contributes from 68% (Northeast) to 91% (West Central) of total deposition. Excluding the contribution from out-of boundary transport, EGU contributes to about 50% of deposition in the Northeast, Southeast, and East Central regions, whereas emissions from natural processes are more important in the Pacific and West Central regions (contributing up to 40% of deposition). This suggests that the implementation of the new EPA MACT standards will significantly benefit only these three regions. Emission speciation is a key factor for local deposition. The source contribution exhibits strong seasonal variation. Deposition is greater in warm seasons due to stronger Hg0 oxidation. However, the contribution from anthropogenic sources is smaller in warm seasons because of larger emissions from natural processes and stronger vertical mixing that facilitates transport. Implications: In the United States, electric generation, industrial combustion, and waste incineration are the most important anthropogenic emission sources of mercury. These sources can contribute up to 75% of total annual mercury deposition near the source locations. Controlling emissions from these sources will benefit more significantly to the eastern United States. Speciation of mercury emissions plays an important role in local deposition. Total annual mercury deposition caused by foreign anthropogenic emissions is significant compared to that from domestic sources on a national basis, suggesting that a coordinated global emission reduction effort is important for effectively reducing mercury deposition in the United States.

Cooling Suits, Physiological Response, and Task Performance in Hot Environments for the Power Industry

Heat stress on workers working outdoors in the power industry may result in fatigue and deterioration in task performance. This research collected and analyzed data on task performance of workers working indoors and outdoors with and without a cooling suit. The task performance was compared on the basis of heart rate, oxygen consumption, tympanic temperature, subjective responses, productivity, and error rates. Based on One-Way Analysis Of Variance (ANOVA) results, a significantly lower estimated working oxygen consumption was observed (p < .001) when the cooling suit was worn. The productivity was higher while workers wore the cooling suit as compared to no cooling suit (p = .011) whereas the error rates were significantly lower(p < .001). Also a significantly lower self-reported discomfort was observed in the neck and shoulders while working wearing the cooling suit (p = .004). This study concluded that wearing a cooling suit while working outdoors was associated with physiological benefits as well as improved task performance of the study participants.

Object-oriented databases for quality function deployment and Taguchi methods

Abstract In this paper, Object-Oriented Databases are proposed as being a new tool for Quality Function Deployment (QFD) and Taguchi Methods. Quality Function Deployment can help identify key product or process concerns with respect to customer requirements. Taguchi Methods, such as using Design of Experiments (DOE), can help identify what product or process relationships truly exist, their relative strengths and the nature of the relationship. In order to implement these two powerful quality control techniques for assuring that customer requirements are consistently met, a well organized information is required. Object-Oriented Databases are able to store, organize and manipulate both, the customer requirements and the product information for the performance of QFD and DOE.

Modeling of moisture over-saturation and vapor pressure in die-attach film for stacked-die chip scale packages

Die-attach film failure during soldering reflow is of particular concern for reliability of 3D ultra-thin stacked-die chip scale packages (CSPs), as extremely high vapor pressure can be generated from vaporized moisture to cause severe damages. Under rapid heating, pressure-driven moisture vapor flow could become as significant as concentration-driven diffusion, and should be included in moisture transport models. In this study, a convection–diffusion (CD) model is presented for analyzing vapor pressure and moisture behavior of soft die-attach films for 3D CSPs, with both vapor flow and the effect of temperature on saturated moisture content considered. By using a 1D model according to experimental observations, the over-saturation phenomenon in the thin film and vapor pressure evolution are investigated. It is found that the reflow profiles and substrate thickness could have great impact on the magnitude of vapor pressure, which agrees well with the experimental results. Sensitivity analyses show that a high vapor permeability and a large porosity could lead to low vapor pressure. Being a vapor pressure-based model, the CD model is suitable to study multiple-material systems without discontinuity issue at the material boundary. It is concluded that the CD model could serve as an effective method for predicting vapor pressure and moisture behaviors during soldering reflow for 3D stacked-die CSPs.

Bank funds management by goal programming

Abstract A goal programming model was developed which attempts to achieve a number of objectives normally desired in the banking industry. The model incorporates objectives relative to providing sufficient liquidity, minimizing risk, maintaining adequate levels of capital, minimizing the cost of capital, maximizing profit and providing reasonable dividends. The constraints on the model relate to pledged assets required by the government, required reserves and limits on certain balance sheet items. Model validation is accomplished by utilizing data obtained from a commercial bank. The data includes financial information for 1982–1984. The 1982 actual data is utilized by the model to project 1983 and 1984 conditions. These projected numbers are then compared with actual financial data to compare the models performance with results achieved by management without the use of the model. Total underachievement of several goals in banking is minimized within the limits of the actual decision environment.

Process decision program chart: from operations research to total quality control

Abstract In conventional quality control methods, where consequences are analyzed to determine actions, often provide the solution too late. Even if the process is initiated as soon as problems occur, small environmental changes might force the entire process to be redesigned. Without the ability to deal promptly with such situations, it is frequently too late to do anything. The Process Decision Program Chart (PDPC) is one of the methods used to solve problems in Operations Research during the design stage in Research and Development. PDPC is an effective means of moving promptly toward ones goal at the very stage of the process where we encounter an unexpected problem and define the solution process when we are dealing with problems that have more than one possible outcome. In this paper, we discuss the application of PDPC for Total Quality Control in the area of process planning. Object-Oriented Programming Technique is proposed in order to implement this method effectively.

Models to predict efficiency of two network flow based algorithms on the Time-Cost Trade-Off problem

Abstract Two predictive models for estimating the computer execution time required by two network flow based algorithms to solve the Time-Cost Trade-Off problem are presented. Fulkersons Longest Path Algorithm and Phillips and Dessoukys Cut Search Algorithm are used. A comparison of performance of these two algorithms for different network structures is provided. The two algorithms are coded into Fortran programs, and it is found that the solution time increases linearly with the number of nodes and several other parameters. In addition, the Longest Path Algorithm is found to be computationally more efficient than the Cut Search Algorithm in solving the Time-Cost Trade-Off problem.