Flow Diagram (flow + diagram)

Distribution by Scientific Domains


Selected Abstracts


Optimization of a single-effect evaporation system to effectively utilize thermal energy

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2009
Raafat Alnaizy
Abstract Wastewater treatment facilities at Emirates Gold in Dubai seek to improve the steam economy of the existing single-effect with recirculation and vapor-compression evaporation process. Maximizing steam economy is important as it impacts treatment costs. There are two main approaches for improving steam economy in evaporators. One is to use a multiple-effect evaporator; the other is to use a mechanical vapor recompression. Multiple-effect evaporators were rejected because of higher capital and power cost. One of the suggestions that were made towards improving the steam economy was to recover heat from the steam condensate. A modified process flow diagram was proposed and investigated. The modified process was simulated using SuperPro Designer and Hysys with complete material and energy balance computation. The modified process increased the total water evaporation capacity and gained 40% better steam economy of the process. Another advantage was an increase in the amount of water reused, which is both economical and environmentally friendly. 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source]


Performance improvements for olive oil refining plants

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2010
Elif Bozoglan
Abstract The main objective of this study, which is conducted for the first time to the best of the authors' knowledge, is to identify improvements in olive oil refinery plants' performance. In the analyses, the actual operational data are used for performance assessment purposes. The refinery plant investigated is located in Izmir Turkey and has an oil capacity of 6250,kg,h,1. It basically incorporates steam generators, several tanks, heat exchangers, a distillation column, flash tanks and several pumps. The values for exergy efficiency and exergy destruction of operating components are determined based on a reference (dead state) temperature of 25C. An Engineering Equation Solver (EES) software program is utilized to do the analyses of the plant. The exergy transports between the components and the consumptions in each of the components of the whole plant are determined for the average parameters obtained from the actual data. The exergy loss and flow diagram (the so-called Grassmann diagram) are also presented for the entire plant studied to give quantitative information regarding the proportion of the exergy input that is dissipated in the various plant components. Among the observed components in the plant, the most efficient equipment is found to be the shell- and tube-type heat exchanger with an exergy efficiency value of 85%. The overall exergetic efficiency performance of the plant (the so-called functional exergy efficiency) is obtained to be about 12%, while the exergy efficiency value on the exergetic fuel,product basis is calculated to be about 65%. Copyright 2009 John Wiley & Sons, Ltd. [source]


Exergetic performance assessment of a pilot-scale heat pump belt conveyor dryer

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010
Zafer Erbay
Abstract In this study, olive leaves were dried in a pilot-scale heat pump (HP) belt conveyor dryer as a thin layer. Drying experiments were carried out at the drying air temperature range of 45,55C with the drying air velocity range of 0.5,1.5,m,s,1. The performance of the system and the process was evaluated using exergy analysis method. The exergy loss and flow diagram (the so-called Grassmann diagram) of the dryer system was presented to give quantitative information regarding the proportion of the exergy input that is dissipated in the various system components. Effects of the drying air temperature and the velocity on the performance of the drying process were discussed. The actual coefficient of performance values were obtained to be 2.37 for the HP unit and 2.31 for the overall system, respectively. The most important component of the system for improving the efficiency was determined to be the compressor. Exergetic efficiencies of the drying of olive leaves were in the range of 67.45,81.95%. It was obtained that they increased as the drying air temperature decreased and the drying air velocity increased. Copyright 2009 John Wiley & Sons, Ltd. [source]


Comparison of low temperature mixed refrigerant cycles for separation systems

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2009
M. Mafi
Abstract Numerous mixed refrigerant cycles (MRCs) were developed in the past several decades in different applications. In this paper, two sets of low temperature MRCs are developed and simulated for a typical olefin plant utilizing a mixture of methane, ethane, propane and nitrogen as cycle working fluid to replace the pure ethylene refrigeration cycle that is used in conjunction with propylene refrigeration cycle in conventional plants. The key parameters of the cycles including mixture compositions and operating pressure levels are optimized to meet the objective of minimum shaftwork in compressor. The results show that different cycle configuration has different optimal mixture composition and low and high operating pressures. The results of exergy analysis reveal that the main location of the exergy loss in the cycles is the heat exchanger system. Also, the Carnot factor versus heat flow diagram is provided to identify the distribution of inefficiencies in the heat exchangers for each cycle. The simulation results show that MRCs can improve the thermodynamic performance of refrigeration system using the optimal working fluid mixture composition, optimal high and low operating pressures and optimal arrangement of the cycle components. Copyright 2008 John Wiley & Sons, Ltd. [source]


Energy and exergy analysis of Salihli geothermal district heating system in Manisa, Turkey

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2005
Leyla Ozgener
Abstract This study deals with an energy and exergy analysis of Salihli geothermal district heating system (SGDHS) in Manisa, Turkey. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, specific exergy index, exergetic improvement potential and exergy losses. Energy and exergy losses throughout the SGDHS are quantified and illustrated in the flow diagram. The exergy losses in the system, particularly due to the fluid flow, take place in the pumps and the heat exchanger, as well as the exergy losses of the thermal water (e.g. geothermal fluid) and the natural direct discharge of the system. As a result, the total exergy losses account for 2.22, 17.88 and 20.44%, respectively, of the total exergy input to the entire SGDHS. The overall energy and exergy efficiencies of the SGDHS components are also studied to evaluate their individual performances and determined to be 55.5 and 59.4%, respectively. Copyright 2005 John Wiley & Sons, Ltd. [source]


Design of reactive distillations for acetic acid esterification

AICHE JOURNAL, Issue 6 2005
Yeong-Tarng Tang
Abstract The reactive distillation provides an attractive alternative for reaction/separation processes with reversible reactions, especially for etherification and esterification. The discrete nature of chemical species and the complexity of phase equilibria seem to cloud the picture in understanding reactive distillation. The esterifications of acetic acid with five different alcohols, ranging from C1 to C5, are studied. First, qualitative relationships between macroscopic process flowsheet and microscopic phase equilibria are established, and the process flowsheets are classified into type I, II, and III for these five systems. Next, a systematic design procedure is devised to optimize the design, based on the total annual cost (TAC) and dominant design variables are identified for different flowsheets. Once quantitative design is available, process characteristic are analyzed and potential problems in process operation are identified. Finally, the economic potentials of these three different flowsheets are explored and explanations are given. The results clearly indicate that it is possible to systemize the design of reactive distillation by qualitatively generating flowsheet from phase equilibria and by quantitatively completing the process flow diagram from a sequential design procedure. Moreover, some of the flowsheets presented in this work cannot be found elsewhere in the open literature. 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]


Practical considerations in development of solid dosage forms that contain cyclodextrin

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2007
Lee A. Miller
Abstract The following is a review of the literature that addresses the use of cyclodextrin in solid dosage forms. Care was taken to exclude physical and chemical characteristics of cyclodextrin, which have been discussed in the literature. A flow diagram is provided to outline the decision-making steps that are involved in the development process. Both preparation of physical mixtures and inclusion complexes are considered. Analytical techniques to determine the presence of inclusion complexes, the effect of other excipients on complex formation, the effect of size limitation of solid dosages forms, powder processing, and storage of solid dosage forms are discussed. 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1691,1707, 2007 [source]


Primers and polymerase chain reaction conditions for DNA barcoding teleost fish based on the mitochondrial cytochrome b and nuclear rhodopsin genes

MOLECULAR ECOLOGY RESOURCES, Issue 5 2007
RAFAEL G. SEVILLA
Abstract This report describes a set of 21 polymerase chain reaction primers and amplification conditions developed to barcode practically any teleost fish species according to their mitochondrial cytochrome b and nuclear rhodopsin gene sequences. The method was successfully tested in more than 200 marine fish species comprising the main Actinopterygii family groups. When used in phylogenetic analyses, its combination of two genes with different evolutionary rates serves to identify fish at the species level. We provide a flow diagram indicating our validated polymerase chain reaction amplification conditions for barcoding and species identification applications as well as population structure or haplotyping analyses, adaptable to high-throughput analyses. [source]


Process improvement evaluation approach using flow diagrams

QUALITY ASSURANCE JOURNAL, Issue 3 2006
Paul C. Constant Jr.
Abstract Maintaining company processes will afford optimum operation and enhance the company's quality management system. A vital part of maintaining processes is their periodic evaluation. An important part of the monitoring and evaluation process is the flow diagram. A detailed flow diagram is an important tool that affords ease in visualizing the total process and is an aid in locating problem areas. The evaluation of a process is broken down into 15 steps. These steps cover gathering pertinent information, such as problem symptoms from knowledgeable sources and carrying these through their route to potential problem areas to the problems, potential causes, and the root cause of the problem. Knowing the problems brings about the need to assess their impact on the process operation as well as what changes to the process are needed and what impact these changes will have on the product , its improved quality and cost , and other vital information, such as, production rate increase, competition status, and company image. With this information, the appropriate changes are made according to a process change action plan. The plan is executed, and the process is continuously monitored according to a monitoring and evaluation plan. The paper ends with conclusions. Copyright 2006 John Wiley & Sons, Ltd. [source]


ELICITING A DIRECTED ACYCLIC GRAPH FOR A MULTIVARIATE TIME SERIES OF VEHICLE COUNTS IN A TRAFFIC NETWORK

AUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2007
Catriona M. Queen
Summary The problem of modelling multivariate time series of vehicle counts in traffic networks is considered. It is proposed to use a model called the linear multiregression dynamic model (LMDM). The LMDM is a multivariate Bayesian dynamic model which uses any conditional independence and causal structure across the time series to break down the complex multivariate model into simpler univariate dynamic linear models. The conditional independence and causal structure in the time series can be represented by a directed acyclic graph (DAG). The DAG not only gives a useful pictorial representation of the multivariate structure, but it is also used to build the LMDM. Therefore, eliciting a DAG which gives a realistic representation of the series is a crucial part of the modelling process. A DAG is elicited for the multivariate time series of hourly vehicle counts at the junction of three major roads in the UK. A flow diagram is introduced to give a pictorial representation of the possible vehicle routes through the network. It is shown how this flow diagram, together with a map of the network, can suggest a DAG for the time series suitable for use with an LMDM. [source]


Supply chain risk identification using a HAZOP-based approach

AICHE JOURNAL, Issue 6 2009
Arief Adhitya
Abstract Risk management has become imperative for today's complex supply chains. Most approaches reported in the literature have been ad-hoc and specific to certain risks; a general and comprehensive approach is lacking. To address this, we present a structured methodology for risk identification. Supply chain networks are in many ways similar to chemical plants, therefore well-established methods and concepts from chemical process risk management can be adapted to supply chains. Drawing from this analogy, we propose to represent supply chain structure and operations using flow and work-flow diagrams, equivalent to process flow diagrams (PFDs) and operating procedures. Following the HAZard and OPerability (HAZOP) analysis method common in process safety, risk identification can be performed by systematically generating deviations in different supply chain parameters and identifying their possible causes, consequences, safeguards, and mitigating actions. The application and benefits of the proposed approach are demonstrated using a refinery supply chain case study. 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


Modeling process flow using diagrams

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 4 2010
Benjamin Kemper
Abstract In the practice of process improvement, tools such as the flowchart, the value-stream map (VSM), and a variety of ad hoc variants of such diagrams are commonly used. The purpose of this paper is to present a clear, precise, and consistent framework for the use of such flow diagrams in process improvement projects. The paper finds that traditional diagrams, such as the flowchart, the VSM, and OR-type of diagrams, have severe limitations, miss certain elements, or are based on implicit but consequential premises. These limitations restrict the applicability of traditional diagrams in non-manufacturing areas such as service and healthcare processes. We show that a rational reconstruction for the use of diagrams in various disciplines regarding process flow boils down to a generic framework of elements, definitions of generic process metrics, and three classes of applications, namely the ,as-is', ,could-be', and ,should-be' analysis. The goal is not to replace all currently used diagrams, but merely to discuss the role of diagram usage in process flow modeling. This paper provides an explicit framework that is unambiguous and flexible, and has the potential to serve as a guideline for the practitioner, in manufacturing as well as in service and healthcare. Besides, it may serve as a starting point to develop an ontology of business processes. Copyright 2009 John Wiley & Sons, Ltd. [source]


Process improvement evaluation approach using flow diagrams

QUALITY ASSURANCE JOURNAL, Issue 3 2006
Paul C. Constant Jr.
Abstract Maintaining company processes will afford optimum operation and enhance the company's quality management system. A vital part of maintaining processes is their periodic evaluation. An important part of the monitoring and evaluation process is the flow diagram. A detailed flow diagram is an important tool that affords ease in visualizing the total process and is an aid in locating problem areas. The evaluation of a process is broken down into 15 steps. These steps cover gathering pertinent information, such as problem symptoms from knowledgeable sources and carrying these through their route to potential problem areas to the problems, potential causes, and the root cause of the problem. Knowing the problems brings about the need to assess their impact on the process operation as well as what changes to the process are needed and what impact these changes will have on the product , its improved quality and cost , and other vital information, such as, production rate increase, competition status, and company image. With this information, the appropriate changes are made according to a process change action plan. The plan is executed, and the process is continuously monitored according to a monitoring and evaluation plan. The paper ends with conclusions. Copyright 2006 John Wiley & Sons, Ltd. [source]


Protein feeds coproduction in biomass conversion to fuels and chemicals

BIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 2 2009
Bruce E. Dale
Abstract Agriculture has changed greatly in the past in response to changing human needs. Now agriculture is being called on to provide raw materials for very large-scale fuel and chemical production. Agriculture will change again in response to this demand and all producers and users of agricultural feedstocks will be affected by this change. For example, livestock feeding practices have already changed in response to the availability of distillers' grains from corn ethanol production. A fuels industry based on herbaceous biomass energy crops will be many-fold larger than the existing corn ethanol industry and will produce its own set of impacts on livestock feeding. We explore here one of these impacts: the availability of large new sources of feed protein from biomass energy crops. In addition to structural carbohydrates, such as cellulose and hemicellulose, herbaceous biomass energy crops can easily be produced with approximately 10% protein, called ,leaf protein'. This leaf protein, as exemplified by alfalfa leaf protein, is superior to soybean meal (SBM) protein in its biological value. Leaf protein recovery and processing fit well into many process flow diagrams for biomass fuels. When leaf protein is properly processed to concentrate it and remove antinutritional factors, as we have learned over the years to do with soybean meal protein, protein in leaf protein concentrate (LPC) will probably be at least as valuable in livestock diets as SBM protein. If LPC is used to meet 20% of total animal protein requirements (i.e., market penetration of 20%) then the potential utilization of leaf protein concentrate could reach as much as 24 million metric tons annually. This leaf protein will replace protein from SBM and other sources. This much leaf protein will reduce by approximately 16 million hectares the amount of land required to provide protein for livestock. Likewise the amount of land required to meet fuel needs will effectively be reduced by 8 million hectares because this land will effectively do ,double duty' by producing needed animal protein as well as feedstocks for fuel production. 2009 Society of Chemical Industry and John Wiley & Sons, Ltd [source]