Archives :: Facts At Your Fingertips
July 1, 2010
Reduction of greenhouse gas (GHG) emissions continues to be a major issue in national and international public policy, as well as a major focus for companies in the chemical process industries (CPI). Many countries are considering systems that place a price on GHG emissions through a carbon cap-and-trade system, for example. In an environment where GHG emissions have a given price, certain energy...
June 1, 2010
In a distillation column tray, vapor passes upward through liquid that is flowing across a horizontal perforated plate. Vapor passing through the perforated plate forms a two-phase mixture with the liquid and enables mass transfer contacting. This mixture is typically quite turbulent. Tray design must allow the turbulent liquid to fall away from the rising vapor in the space above the tray, while also...
May 1, 2010
Burners are critical for the successful operation of industrial furnaces. Presented here is a set of equations that can be used to calculate characteristics of burner operation, including flame length, flame diameter, ignitability and flameout conditions. Equations are based on pre-mix burners operating at atmospheric pressure and firing natural gas only. Premix burners create short and compact flames...
April 1, 2010
Mechanical seals play a pivotal role in the chemical process industries (CPI). As the sealing interface between rotating process equipment and the materials contained inside, these devices prevent product leakage and fugitive emissions, while permitting process machines, pumps and compressors to operate at ever-increasing pressures, vacuums, temperatures and speeds. Even the most basic mechanical seal is a...
March 1, 2010
Steam tracer lines are designed to maintain the fluid in a primary pipe at a designated uniform temperature. In most cases, these tracer lines are used outdoors, which makes ambient weather conditions a critical consideration. The primary purpose of steam traps on tracer lines is to retain the steam until its latent heat is fully utilized, and then discharge the condensate and non-condensable gases. As is...
February 1, 2010
Pumps are essential equipment in the chemical process industries (CPI). Given the imperatives to reduce production costs and maximize energy efficiency, pump selection is crucial. Knowledge of pumping basics, along with the fluid characteristics for a particular application can help engineers make the best choice. While the majority of pumps in use in CPI plants are kinetic energy pumps (the largest...
January 1, 2010
Because of the behavior of materials under vacuum, including lowered boiling points, low-pressure operations are useful tools in chemical processing, as well as in research and development and manufacturing. Areas where a vacuum system is necessary or useful include the following: • Separating liquids • Processing temperature-sensitive materials • Preventing unwanted chemical reactions...
December 1, 2009
Installed gain graphs can help improve the selection of control valves for chemical processing. The graphs are plotted to analyze together control-valve flow characteristics and process-system flow characteristics, and better illustrate the relationship between a control valve and the system. Predicting installed gain can help to increase controllability of the system and help avoid oversized valves...
November 1, 2009
The ultimate objective of storing liquid, fluid and gaseous products, which may be corrosive, flammable or unstable, is to store material in an environmentally safe and economically viable manner. Storage tanks in the chemical process industries (CPI) can be most broadly divided into those buried underground, and those constructed aboveground. The following is an outline of considerations associated with...
October 1, 2009
Corrosion is estimated to account for a significant portion — 8–10% — of total annual-plant-capital expenditures for the chemical process industries. To avoid it, engineers can consider corrosion-resistant plastics for process piping and storage vessels. Thermoplastics are generally resistant to chemical attack and thus suitable for many process applications. However, plastics must be...
September 1, 2009
Click here for full pdf version of this article - includes all graphs, charts, tables, and author information EXPANSION TANK A well designed expansion tank: 1. Maintains a static pump-suction head 2. Compensates for temperature-related volume and pressure changes 3. Provides a means of venting moisture and low boilers 4. Prevents fluid oxidation Usually, the expansion tank is installed at the highest point...
August 1, 2009
Successful adsorber design requires information about certain adsorbent properties, including: adsorbent densities and void fractions; isotherms or other equilibrium data; and data on mass-transfer kinetics and fixed-bed dynamics. Here, these adsorbent properties are explained, along with corresponding equations. Densities and void Fractions Three densities are relevant: bulk, particle and solid. There are...
July 1, 2009
When a flowmeter is needed, the selection process should include studying the characteristics of respective measurement technologies and analyzing the advantages/disadvantages for different plant environments. This effort will help ensure that a meter with the right performance and reliability, for a particular installation, is selected. Some of the most common industrial flowmeter designs are described...
June 1, 2009
One of the most important factors to consider when evaluating a specialty metal for use in valves, fittings and instrumentation is its corrosion resistance or corrosion rate of the metal in the target media. Each material discussed here has its own niche, and depending on the processing environment and the needs of the application, the metal’s strengths and weaknesses may or may not be suitable. In...
May 1, 2009
Technology Requirements [ 1] Control architecture Does the solution provide an integrated automation platform? New systems should manage process knowledge through a combination of advanced technologies, industrial domain expertise, and Six Sigma methodologies. Choose an open, scalable control system that is fully redundant, includes robust control algorithms and provides on-process upgrades to minimize...
April 1, 2009
In today’s typical process plants, preventing steam loss and improving condensate return are key opportunities to make a process more energy efficient. To be the most effective, steam generally needs to be dry (such as for process usage), or superheated (for instance, for use in turbines). These requirements dictate utility-system operating procedures for generating the highest quality steam...
March 1, 2009
Membrane polymers are packaged into a configuration, commonly called a device or an element. The most-common element configurations (figure) are tubular, capillary fiber, spiral wound, and plate and frame. Tubular Made from ceramic, carbon, stainless steel or a number of thermoplastics, tubular elements have inside diameters from ¼ in. up to about 1 in. Typically, the membrane is coated on the...
February 1, 2009
Friction Factor Fluid flowing through pipes experiences resistance due to viscosity, turbulence and roughness of the pipe surface. The Darcy-Weisbach Equation (1) is commonly used for the analysis of steady-state, Newtonian-fluid flow inside pipes. It summarizes the relations between frictional head loss, fluid properties, pipe geometry and discharge. For laminar flow (Re < 2,100), the friction factor...
January 1, 2009
Here, we present criteria needed for the intelligent, effective specification of trays for a distillation or stripping column. Among the key parameters and accessories during specification are column diameter, tray spacing, number of trays, number of passes, type of downcomers, weir heights, provision of downcomer backups, tray pressure drops, design of bottom seal pan, column bottom arrangement, and...
December 1, 2008
Laminar Pipe Flow For steady flow in a pipe (whether laminar or turbulent), a momentum balance on the fluid gives the shear stress at any distance from the pipe centerline. In Equation (1), Φ = P + ρ gz. The volumetric flowrate Q can be related to the local shear rate by doing an integration by parts of Equation (2). Newtonian fluid. For a Newtonian fluid, τ rx = µY rx, which gives the...
Get more from Che.com
Get email updates in your inbox
Official Publication of:
Our LinkedIn group is now over 16,000 members strong!
- Join other CPI professionals from all over the globe and share best practices, expertise, concerns and more.
- Provide feedback to Chemical Engineering Editors
Current members represent Worley Parsons, DuPont, SABIC, Fluor, Air Products, LyondellBasell, Nalco, Dow Chemical, Dow Corning, BASF, Jacobs Engineering, ExxonMobil, Shell, Chevron and more.
We also offer the following subgroup for more targeted discussions: