scispace - formally typeset
Search or ask a question

Showing papers in "Chemical Engineering in 1996"


Journal Article
TL;DR: In this paper, two basic strategies for reducing water demand in a chemical-process plant were discussed. One strategy consists of modifying individual process and utility units to reduce their inherent need for water.
Abstract: Environmental protection, rising costs for wastewater-treatment, and at many sites a shortage of fresh water are all persuasive motives for reducing raw water consumption and wastewater discharge at a chemical-process plant. Maximizing the re-use of water within the plant can be of great help. Systematic strategies for such maximization can lower freshwater usage and wastewater discharges by 50% or more, while also significantly reducing capital investment in treatment facilities. The typical base case or starting point for such improvements appears in a figure which shows a conventional water network in a process plant. After undergoing initial treatment, the incoming water goes in parallel streams to the various individual process units, as well as to the utility system for steam production and for use in cooling towers. Wastewater streams from the processes, along with blowdown and condensate losses from the utility system, are usually collected together and the combined stream fed to a wastewater treatment facility prior to discharge. There are two basic strategies for reducing water demand in such a plant. One strategy consists of modifying individual process and utility units to reduce their inherent need for water. Examples include replacing water cooling with air cooling, improving controls of boilermore » and cooling-tower blowdowns, and increasing the number of stages in an extraction unit that employs water as its extractant. In the other basic strategy, which is the main focus of this article, the engineer seeks opportunities to use the outlet water from one operation to satisfy the water requirement of another or the same operation. In some cases, the water may require some regeneration prior to re-use. Examples of regeneration include pH adjustment, filtration, membrane separation, sour-water stripping and ion exchange.« less

202 citations


Journal Article

24 citations


Journal Article
TL;DR: Clean in place (CIP) is an automated method of cleaning process plants, involving little or no dismantling of piping or equipment as discussed by the authors, which can be used to clean process plants.
Abstract: Clean In Place (CIP) is an automated method of cleaning process plants, involving little or no dismantling of piping or equipment

19 citations



Journal Article
TL;DR: In this paper, the authors analyze methods for determining compressible fluid flow that are rigorous enough to handle most industrial situations, yet simple enough to be easily programmed into a personal computer.
Abstract: When designing plants, performing safety studies, and analyzing plant problems and opportunities, estimates of the flowrate of compressible fluids in pipelines are often required. In fact, the impact of piping systems on process plant economics is so great that the initial investment in piping systems for new installations has been estimated to range from 18 to 61% of the equipment costs and from 7 to 15% of the total cost of the installed plant. Likewise, operating (energy) and maintenance costs for piping systems are significant. Considering this, practical sizing and analysis methods for pipelines are essential. In sizing pipe for incompressible fluids (that is, liquids), the Darcy or Fanning equation is typically used with the appropriate friction-factor correlation. This analysis is greatly simplified by the constant fluid density. However, with compressible fluids (gases and vapors), density, and hence velocity, may change considerably from one end of the pipe to the other. This, along with the limitations imposed by choked flow, complicates the analysis. Here the authors analyze methods for determining compressible fluid flow that are rigorous enough to handle most industrial situations, yet simple enough to be easily programmed into a personal computer. The theory and derivation of the basicmore » equations are described very well in texts by Levenspiel and Saad.« less

13 citations


Journal Article
TL;DR: The authors look at the capabilities and limitations of existing simulators for handling pollution prevention, and discusses the new tools under development.
Abstract: Growing environmental concerns have spurred considerable interest in pollution prevention. In most instances, pollution prevention involves introducing radical changes to the design of processes so that waste generation is minimized. Process simulators can be effective tools in achieving the objectives of pollution prevention. Here the authors look at the capabilities and limitations of existing simulators for handling pollution prevention. They discuss the new tools under development. A process simulator is a large computer program that simulates the operations of chemical and allied processes. Chemical process plants usually consist of many process units. Each of these can, in principle, be modeled mathematically. Process simulators provide an overall integration of the mathematical models of these commonly encountered process units.

10 citations



Journal Article
TL;DR: In this paper, a three-year study by the Electrical and Mechanical Engineering Dept. at the University of Missouri at Rolla has been conducted to understand impedance heating and its electrical effects.
Abstract: Impedance heating is used because it is simple to apply, eliminates the risk of heater burnout, requires little maintenance, and provides uniform heating along the length of the pipe -- a critical factor when dealing with fluids sensitive to spot overheating. But despite its long history, impedance heating and its electrical effects are little understood. Impedance, which determines the heating rate of a pipe and its contents, is influenced by three key factors: (1) Electrical resistivity (and its variation with temperature) is always significant, since it is the basis for the d.c. resistance of any conductor. (2) Magnetic permeability is a function of the metallurgy of the pipe material and its environment (temperature, magnetic field, and so forth). For magnetic steels, such as plain carbon steel, permeability contributes to both skin effect and proximity effect, as described here. (3) Current density is the distribution of current throughout the cross-sectional area of a conductor. A high current density occurs when a large current flows through a small area. To gain a thorough understanding of how these phenomena interact to produce impedance heating in a pipe, Industrial Engineering and Equipment Co. (Indeeco; St. Louis, Mo.), commissioned a three-year study by the Electrical more » Engineering Dept. at the University of Missouri at Rolla. This article is based on the findings of that study. « less

9 citations


Journal Article
TL;DR: In this article, the authors present the basic principles and calculation methods for extraction processes and distinguish between solvents that act only on the principle of equilibrium, and solvent that act on chemical reaction or complexation.
Abstract: Successful extractions are built on three cornerstones: proper solvent selection, meaningful pilot tests and, accurate scale-up The authors have covered in an earlier article the basic principles and calculation methods for extraction processes Shown here will be only the more fundamental principles, and most of the attention will be in the area of solvent selection They will also distinguish between solvents that act only on the principle of equilibrium, (which are the majority of the solvents used in the extraction of organic species), and solvents that act on the principle of chemical reaction or complexation, (which are the majority of solvents used in the extraction of inorganic species) In some processes both effects can play prominent roles

8 citations












Journal Article
TL;DR: In this article, the International Standards Organization (ISO) is attempting to define through the ISO 14000 series, which is expected to be published in June of this year, a company's success is predicated on adopting an appropriate standard of care, taking risk into account.
Abstract: In today`s complex, competitive business climate, a company`s success is predicated on adopting an appropriate standard of care, one that takes risk into account. An appropriate standard of care is just what the International Standards Organization (ISO) is attempting to define through the ISO 14000 series, which is expected to be published in June of this year. ISO 14000 offers guidance on the development and implementation of voluntary Environmental Management Systems (EMS), and the integration of such systems with other management systems. The EMS model lists five actions each firm should undertake: Identify what needs to be done and define a company-wide EMS policy; Formulate a plan to fulfill the environmental policy; Develop the capabilities and support mechanisms needed to effectively achieve the objectives and targets of the environmental policy; Measure, monitor and evaluate existing environmental performance; and Review and continually improve the EMS, with the objective of improving overall environmental performance. The paper discusses the key reasons for conducting audits, managing legal risks, how an audit works, and choosing the right type of audit.

Journal Article
TL;DR: The industrial desktop is an evolving concept, but at this stage, several components are clear: it is based on personal computers, or workstations that are compatible with these computers; it has ready access both to plant-floor data and business applications and telecommunications capabilities.
Abstract: The personal computer has had a profound effect on access to information for engineers throughout industry. Nevertheless, the information systems needed to run a complex CPI plant such as a refinery have not changed: operations management, maintenance, crisis management, warehouse, engineering, laboratory, business, and scheduling, among others. Various control or data processing systems are currently used to manage these data needs, but computer technology and business economics are unifying these requirements into one, all-encompassing system--the industrial desktop computer. The industrial desktop is an evolving concept, but at this stage, several components are clear: it is based on personal computers, or workstations that are compatible with these computers; it has ready access both to plant-floor data (the conventional purpose of process control computers) as well as a variety of business applications and telecommunications capabilities; and it makes use of the software conventions centered around Microsoft Corp. (Redmond, Wash.). The paper discusses implementation of desktop applications in the chemical industry.

Journal Article
TL;DR: In this article, the goal of 9999% efficiency, cleanable HEPA cartridges, instrumentation and valving, and a photohelic gage controller are discussed, along with new collector designs, higher temperature filters, and secondary filters.
Abstract: Filter collection systems have long been in the forefront for high-efficiency separation of fine particulate dusts from gas Today, new technology and designs have improved filter collection systems even more These improvements to primary systems (baghouses) and secondary systems, and new instrumentation can lower investment and operating costs, while also improving environmental compliance In comparing the collectors offered by different vendors, one should consider the different designs, cloth area, critical velocities, and methods of cleaning the fabric The sizing and selection of a filter should be made by actual test or experience at the design load, using the least costly fabric for the requirements This paper discusses optimizing velocity, new collector designs, higher temperature filters, secondary filters, the goal of 9999% efficiency, cleanable HEPA cartridges, instrumentation and valving, and a photohelic gage controller

Journal Article
TL;DR: In this article, product trends in heat transfer fluids are discussed, including flash and fire points are being raised to new heights, as the capabilities of conventional low and high-temperature fluids overlap, users can do with fewer products on their shelves.
Abstract: When it comes to heat transfer fluids, degrees are important. Throughout the temperature spectrum, suppliers are trying to best each other with products that work at extreme high or low temperatures, and over a broad range in between. As a safety precaution, flash and fire points are being raised to new heights. But as the capabilities of conventional low- and high-temperature fluids overlap, users can do with fewer products on their shelves. Product trends in heat transfer fluids are discussed.



Journal Article
TL;DR: In this paper, the authors present a method for optimizing single phase shell-and-tube heat exchangers with given geometric and thermohydraulic constraints, which is based on data from an earlier study of a large collection of feasible designs generated for different process specifications.
Abstract: Optimizing a shell and tube heat exchanger for a given duty is an important and relatively difficult task. There is a need for a simple, general and reliable method for realizing this task. The authors present here one such method for optimizing single phase shell-and-tube heat exchangers with given geometric and thermohydraulic constraints. They discuss the problem in detail. Then they introduce a basic algorithm for optimizing the exchanger. This algorithm is based on data from an earlier study of a large collection of feasible designs generated for different process specifications. The algorithm ensures a near-optimal design satisfying the given heat duty and geometric constraints. The authors also provide several sub-algorithms to satisfy imposed velocity limitations. They illustrate how useful these sub-algorithms are with several examples where the exchanger weight is minimized.