Mass Transfer Modelling for Compact Hybrid Membrane-Amine System in Removal of C02 from Natural Gas

The removal of CO2 from natural gas down to the pipeline quality is an important step before the natural gas can be sold to the end users. Typical natural gas treatment's specification requires that the composition of CO2 in the treated gas cannot be more than 2 mole%. Normally amine scrubbing process is extensively used to treat natural gas with low content of CO2. However, this is not efficient in dealing with natural gas with high CO2 content. Therefore, there is a proposal of using hybrid system in sequencing of membrane for bulk CO2 removal followed by amine solution for absorption process. However, there are some disadvantages for the hybrid system such as not applicable in offshore. All the disadvantages of the hybrid system will be overcome if the compact hybrid membrane-absorption column is brought into operation. This system uses the concept in which amine absorption is integrated together with the membrane permeation. The feedgas will flow along the membrane and permeate through the membrane and then will be absorbed into the amine solution. The main objective of this work is to develop a mathematical model for the removal of CO2 from natural gas in compact hybrid membrane amine system. The model has analyzed the permeability of CO2 and methane across membrane followed by absorption of CO2 in amine solution. The effect of various parameters, which consist of concentration of CO2 in feed gas, operating pressure of feed gas, flow rate of amine solution and membrane pore size, towards the permeability and separation factor of the compact hybrid membrane-amine system has been analyzed systematically. The model is developed using MATHCAD version 2000i and Microsoft Excel to represent the mass transfer of CO2 in the compact hybrid membrane-amine system. The performance of membrane separation is determined by the permeability of each component through the membrane and selectivity of the membrane for each component in the mixture. Based on the mathematical model developed, it was found that the permeability of CO2 and methane was independent of the concentration of each component in the feed gas. However, the permeability of CO2 and methane was a strong function of operating pressure at the feed gas and membrane pore size due to the effect of surface diffusion at small pore sizes, but this effect was lost at bigger pore sizes. For amine absorption, the mathematical model showed that the separation factor for removal of C02 from natural gas using compact hybrid membrane-amine system was strongly dependent on concentration of CO2 in the natural gas as well as flow rate of amine solution due to its effect on the rate of absorption. However, operating pressure of feed gas does not show any effect on the separation factor of CO2 removal. The model for compact hybrid membrane-amine absorption system is successfully developed and various operating parameters have been studied and discussed in the later section of this report

Surgery on frames

In this dissertation, we investigate methods of modifying a tight frame sequence on a finite subset of the frame so that the result is a tight frame with better properties. We call this a surgery on the frame. There are basically three types of surgeries: transplants, expansions, and contractions. In this dissertation, it will be necessary to consider surgeries on not-necessarily-tight frames because the subsets of frames that are excised and replaced are usually not themselves tight frames on their spans, even if the initial frame and the final frame are tight. This makes the theory necessarily complicated, and richer than one might expect. Chapter I is devoted to an introduction to frame theory. In Chapter II, we investigate conditions under which expansion, contraction, and transplant problems have a solution. In particular, we consider the equiangular replacement problem. We show that we can always replace a set of three unit vectors with a set of three complex unit equiangular vectors which has the same Bessel operator as the Bessel operator of the original set. We show that this can not always be done if we require the replacement vectors to be real, even if the original vectors are real. We also prove that the minimum angle between pairs of vectors in the replacement set becomes largest when the replacement set is equiangular. Iterating this procedure can yield a frame with smaller maximal frame correlation than the original. Frames with optimal maximal frame correlation are called Grassmannian frames and no general method is known at the present time for constructing them. Addressing this, in Chapter III we introduce a spreading algorithm for finite unit tight frames by replacing vectors three-at-a-time to produce a unit tight frame with better maximal frame correlation than the original frame. This algorithm also provides a “good” orientation for the replacement sets. The orientation part ensures stability in the sense that if a selected set of three unit vectors happens to already be equiangular, then the algorithm gives back the same three vectors in the original order. In chapter IV and chapter V, we investigate two special classes of frames called push-out frames and group frames. Chapter VI is devoted to some mathematical problems related to the ”cocktail party problem ”

Evaluating the Web Usability – An Interpretive Study of the Bazar portal in Oslo Public Library, Norway

The vast pool of information and the development of technology have given thousands of choices for users when using Internet for searching purposes. With all available websites and the diverse set of user skills, website usability is the factor that motivates users to choose one site over another. Hence, usability is needs to be in consideration when designing the website. Understood that such studies are critical to the success of website, this research focuses on evaluation of the usability of the Bazar portal (the information portal of Oslo public library) by investigating the usability problems of the portal and draw out a recommendation to support the current construction process of Bazar. These sole objectives of this study are to make Bazar most effective to the users. In order to investigate these problems, a task based survey was conducted with 37 participants comprising 2 groups: students and job seekers with different searching experiences. The research indicates that there are numbers of usability problems in Bazar portal. These problems are identified in portal design, organization system, searching system, labeling system and language support. The findings also indicate out that in evaluation by students and job seeker groups resemble each other. Interestingly, the less experienced group and the more experienced group have different points of view in evaluating portal usability. The findings from this study have practical implications for website designers in their process of designing the new version of Bazar. Furthermore, the results indicate that language is an important factor in multilingual portal; therefore more effort should be devoted to this factor in supporting in reading, understanding and using information.Joint Master Degree in Digital Library Learning (DILL

Common Errors in Speaking of English-Majored Sophomores at Tay do University, in Vietnam

It is undeniable that speaking skill is very important in learning English It is a tool to help students to find good jobs in the future especially if they expect to work for a foreign company However in the process of learning and practicing speaking English students get a lot of difficulties Therefore the research Common Errors in Speaking of English-Majored Sophomores at Tay Do University Vietnam was conducted to investigate common mistakes of English-majored sophomores from English classes course 14 at Tay Do University The questionnaire and interview were two main instruments Research results showed that Englishmajored sophomores made some common errors about pronunciation vocabulary and grammar It is hoped that sophomores can recognize and correct their errors to make the necessary changes to improve speaking skill

The impact of Diversification on Firms' value during the Financial Crisis 2007-2009: Recent Evidence form United Kingdom.

The economic world witnessed an explosion of corporate diversification during 60s and 70s through the flows of buyout, merger and acquisition activities. However, during later decades such as 80s, and 90s, conglomerates narrowed down their businesses or even are not as attractive as former periods. The impact of diversification on firm’s value has been investigated for many years but has still remained inconclusive. The vast majority of studies conclude that diversification destroys firm’s value while the other argues that firm’s choice to involve in diversification is endogeneity, thus, once the endogeneity is controlled, diversification does not destroy firm’s value and even create premium. In this research, I investigate the effects corporate diversification has on UK firms during the financial crisis 2007-2009 which started from the burst of the U.S housing bubble, then, assets’ prices declination, marginal calls, fire sales and deleveraging create a vast systematic failure for worldwide bank system. It is argues that the current crisis restrict firm’s access to external capital market. Thus, diversification not only helps firm reduce risk but also improves the efficient of internal capital market. My study use a dummy variable as indicate whether firm diversify and two statistical techniques which are: Ordinary Least Squares regression (OLS) and panel data estimation for analyze purpose and find that: (i) using sales multiplier approach, diversification destroys firm’s value; (ii) however when asset multiplier approach is use, diversification creates premium. The robustness check uses a different measure of degree of diversification: Herfindahl index and finds that the effect of diversification on firm’s value is opposite to results obtained when diversification dummy variable is used. The effect of diversification on firm’s sales based excess value is reduced significantly. Furthermore, Heckman’s two-step approach and switching regression are used to control for self-selection bias. The estimation results are consistent with OLS and panel data estimation results. The probit estimates indicate that firms operating in energy industry are those most likely to diversify while utilities firms are less likely to diversify. The impacts the financial crisis on firm’s value are differ across measure of crisis

Heat Integration Study on Cryogenic and Product Recovery Unit of Gas Processing Plant

The production and consumption of natural gas is on the rise throughout the world as the result of its wide availability, ease of transportation and use as well as clean burning characteristics. The first and second generation gas processing plants, designed and built in the 1960s and 1970s were bogged down by operational inflexibility and CO2 freezing due to the rapid change of product values. Even most modern gas processing plants are encountering problems related to operating flexibility, instability of operational conditions due to vapor-liquid equilibrium, CO2 solid formation and energy efficiency. Ortloff have recently developed new NGL recovery processes on the basis of vapor-split concept. While the Ortloff processes offer relief to the first three problems in gas processing plants, huge energy consumption remains a major concern. A typical gas processing plant consists of two main processing sections, i. e. a cryogenic section and product recovery section. Of the two sections, cryogenic section consumes a huge amount of energy, especially by its cold utility due to the sub-ambient operating condition required. Meanwhile, steam generation for reboiling purposes at the product recovery section also contributes to the huge energy consumption. Ultimately, both result in substantial utility cost to the plant operations; therefore optimizing energy consumption in both areas is essential to improving plant profitability as it results in lower utility cost. This research looks for improvement opportunities in energy consumption in these two sections based on pinch analysis and maximizing the power generated from turboexpander. The study explores the utilization of available cold energy extracted from the feed in order to reduce the cold utility requirement in cryogenic area. The study is able to save 6% on refrigeration load for cryogenic area and generate 36% more power from the turbo expander. This could generate predicted annual savings of RM900k for this area. For product recovery area, this study introduces a prefractionator arrangement in place of a conventional depropansier and debutanizer arrangement. Although thermal coupling arrangement requires refrigeration for condenser cooling, nevertheless it generates 54% savings on steam consumption and 37% savings on cooling duty. This is equivalent to RM 2.9mil as predicted annual savings for the plant. Moreover, there are some loose end heat exchangers that could give about RM350k savings per annum for operating cost