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Archives :: Technical & Practical

Displaying 101 - 120 of 501 stories.
October 1, 2012
Vacuum conditions for many unit operations — including distillation, evaporation, drying, crystallization, filtration and more — are typically achieved using the following three approaches: • Steam ejector systems • Mechanical vacuum pumps • Integrated vacuum systems (which combine steam ejectors and mechanical vacuum pumps) This article is the second part of a two-part series,1...
http://www.che.com/technical_and_practical/Reduce-Hazards-in-Process-Vacuum-Systems_9787.html
September 1, 2012
Contact agitated dryers are used for drying wet powders, slurries, filter cakes, and applications where off-gases during the drying cycle must be contained. If the applications are also heat-sensitive, such as specialty chemicals, polymers, food products and pharmaceuticals, contact drying must take place at low heating temperatures, at residence times in tune with the tolerance of the product, and...
http://www.che.com/technical_and_practical/Thin-Film-Drying-Offers-Deep-Benefits_9680.html
September 1, 2012
Pumps are among the most commonly used machines in the chemical process industries (CPI). Condition monitoring tests and predictive maintenance can help pump operators determine when to overhaul pumps in a way that minimizes costs. Despite pumps’ ubiquity and large energy demands, however, relatively little information is available on how to apply predictive maintenance approaches and condition...
http://www.che.com/technical_and_practical/Condition-Monitoring-Methods-for-Pumps_9682.html
September 1, 2012
Corrections: From the October 2012 Letters page: This original article, which appeared in the print edition of Chemical Engineering (September 2012), had two errors: Equation (19) should read D = log (TH)-0.4, and Table 2 was missing decimal points in all numbers on both the x- and y-axes. The corrections are shown here. Recirculating cooling-water systems are essential parts of many facilities throughout...
http://www.che.com/technical_and_practical/Cooling-Water-Outlet-Temperature-Evaluating-The-Best-Maximum-Value_9683.html
September 1, 2012
This article is the first in a two-part series, in which the types of process vacuum equipment (steam ejector systems and mechanical vacuum pumps) are discussed.1 Emphasis is given on how they are constructed and operate, and how to design associated parts of the systems (such as foundations, suction piping, discharge piping, and so on), to ensure safe operation. Many unit operations — including...
http://www.che.com/technical_and_practical/Vacuum-Systems-Recommendations-For-Safe-Operation_9685.html
September 1, 2012
There are two main reasons why compressor capacity regulation is used. The most prevalent reason is to adjust the suction flow to match the process demand. The second reason is to save energy. As a rule, capacity control is determined by the compressor discharge pressure. Compressor capacity-control methods are utilized to maintain a required delivery under variable process conditions [1]. In this article...
http://www.che.com/technical_and_practical/Reciprocating-Compressors-Startup-and-Capacity-Control-Methods_9687.html
August 1, 2012
There is a temptation that steam design engineers find difficult to resist — to put condensate from high-pressure (HP) steam mains directly into the low-pressure (LP), pumped condensate-return (CR) mains. After all, the CR main is so convenient — it is generally laid right next to the outgoing steam main in the same tunnel, trench or racks as the CR main returning to the steam plant. And, the...
http://www.che.com/technical_and_practical/Waterhammer-In-Condensate-Return-Lines_9551.html
August 1, 2012
Globe-style control valves are in virtually every chemical processing line where pressure and flow must be controlled. And for the most part, they perform as required, day in and day out, requiring little to no thought or attention. In short, control valves are not an everyday topic of discussion. In fact, the globe valve provides a direct contrast to today’s consumer electronics where major changes...
http://www.che.com/technical_and_practical/Control-Valves-An-Evolution-In-Design_9553.html
August 1, 2012
The earliest application of the fundamental concepts of fluidization dates back to 16th century when a German scientist (Georgius Agricola) described a process to upgrade ores. However, it was not until the 1930s, with the development of the Winkler coal-gasification process, that commercial use of fluidized beds on an industrial scale was recognized. The need for gasoline during the World War II...
http://www.che.com/technical_and_practical/A-Primer-on-Gas-Solids-Fluidization_9573.html
July 1, 2012
Corrosion is a large and complex issue that is critical to the chemical process industries (CPI) as well as other industry sectors. Corrosion not only affects personal property like cars and homes but also affects commercial assets such as storage tanks, buildings, bridges, process equipment, and all types of piping. While corrosion is seen every day in our personal and professional lives, we rarely pause...
http://www.che.com/technical_and_practical/Internal-Corrosion-Sampling_9454.html
July 1, 2012
Among all the engineers who will be involved in the purchase of a mixer or blender next year, roughly half will welcome a change in their production method. The other half will be determined to prevent it. Searching for the right equipment to make a new product or boost current production, about 50% of users will conduct open-eyed tests in the laboratory of a mixing equipment manufacturer.1 They will test...
http://www.che.com/technical_and_practical/The-Unexpected-Rewards-of-Testing-a-Mixer_9456.html
July 1, 2012
The ability to model a process to see if it meets project requirements and is economically viable enhances the conceptual design. Modeling gives engineers a means to identify the most promising processes, in terms of capital investment and return, and this can be particularly important when the project is environmentally oriented (a so-called green project). Did you ever consider producing a new product...
http://www.che.com/technical_and_practical/Evaluating-Green-Projects-Modeling-Improves-Economic-Benefits_9457.html
July 1, 2012
In designing and sizing relief-device and effluent-handling systems, one commonly overlooked aspect of the performance is examining the potential for low temperatures that can cause the components of the system to reach temperatures below their respective, minimum-design metal temperatures (MDMT), which may result in brittle fracture with subsequent loss of containment. This article points out limitations...
http://www.che.com/technical_and_practical/Overpressure-Protection-Consider-Low-Temperature-Effects-in-Design_9460.html
July 1, 2012
After a serious accident at a chemical plant, petroleum refinery or other freestanding industrial facility, the U.S. Chemical Safety Board (CSB; www.csb.gov) may immediately initiate an investigation, often getting “in the air” while the emergency is still unfolding. The CSB team will consist of skilled accident investigators who are often accompanied by independent experts noted for their...
http://www.che.com/technical_and_practical/Working-with-the-CSB-After-a-Major-Accident_9462.html
June 1, 2012
One of the most energy-intensive utilities for many facilities in the chemical process industries (CPI) is the steam system. Traditionally, steam-use optimization has centered on efficient heat transfer and eliminating waste [ 1]. Further optimization can involve a broader look at how steam supply and consumption interact dynamically throughout a large complex. This type of optimization often results in...
http://www.che.com/technical_and_practical/Dynamic-Modeling-for-Steam-System-Control_9388.html
June 1, 2012
A variety of performance problems can arise in distillation towers during startup. Many are caused by equipment, hardware or process conditions. Hardware issues may be related to instrumentation, tower internals or ancillaries. Instrumentation malfunctions are also common during startup and are predominantly related to liquid level indicators, online analysis of key components and in some cases...
http://www.che.com/technical_and_practical/Distillation-Avoid-Problems-During-Tower-Startup_9389.html
June 1, 2012
  A gas flare is an elevated vertical conveyance found accompanying oil wells, gas wells, drilling rigs, petroleum refineries, chemical plants, natural gas plants and so on. Although modern flare systems are specifically designed to reduce the thermal radiation, pollution and acoustic impact of a flare, a considerable amount of radiation is nevertheless emitted by an operational flare as a result of...
http://www.che.com/technical_and_practical/CFD-Analysis-of-Heat-Transfer-From-Flares_9390.html
June 1, 2012
Throughout the chemical process industries (CPI), the need to drain a tank or process vessel arises. In batch-type plants, it is a regular occurrence and is one factor that affects the total cycle time per batch and ultimately the entire production capacity of the plant itself.  Figure 1. In a vertical cylindrical, flat-bottom tank, liquid is flowing into the outlet nozzle (point 1) located at x...
http://www.che.com/technical_and_practical/Draining-Vessels_9398.html
May 1, 2012
Failures of piping due to vibration-induced fatigue are a serious problem in the chemical process industries (CPI) and a matter of concern for the safety and reliability of plant operations. Due to the complexity of flow-induced vibrations in pipes, no closed-form design solutions — those that can be expressed in terms of well-known functions — are available. In this article, we present a...
http://www.che.com/technical_and_practical/A-method-for-quantifying-pipe-vibrations_9271.html
May 1, 2012
Reducing freshwater consumption and wastewater discharge at large petroleum-refining and chemical-production facilities can lower costs, while allowing plants to expand production capacities without having to secure additional freshwater resources and without having to enlarge their wastewater treatment plants. The key approaches to saving significant amounts of water are: improved water management...
http://www.che.com/technical_and_practical/Water-saving-strategies-for-the-CPI_9277.html
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