Archives :: Technical & Practical

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November 1, 2011
To stay on budget, major capital projects often call for aggressive schedules. Engineering, procurement and construction (EPC) contractors often end up using work processes that are not part of an established or standard work procedure. This is especially true when it comes to acquiring materials to support the schedule, particularly for critical paths related to the piping design, supply, fabricate and...
http://www.chemengonline.com/technical_and_practical/Piping-Minimizing-the-Risk-of-Pre-buys_8617.html
November 1, 2011
In today’s climate of increased energy prices and tightening environmental emissions requirements, petrochemicals producers around the world are continuing to focus on optimizing energy consumption at their facilities. Over the past few years, while energy prices have been increasing, petroleum refiners and chemicals producers have made progress toward improved, overall energy performance by...
http://www.chemengonline.com/technical_and_practical/Energy-Benchmarking_8618.html
November 1, 2011
The benefits of field-device diagnostics are often acclaimed in qualitative terms, but on a much lower frequency in quantitative ones. Yet, an attractive cost-benefit analysis is necessary for almost any initiative to make it off the drawing board and into a plant. Even more rare are economic figures that come directly from the process plant engineers (as opposed to a vendor with vested interest in selling...
http://www.chemengonline.com/technical_and_practical/Control-Valve-Diagnostics_8620.html
November 1, 2011
Pinch analysis is a systematic method to maximize energy recovery from process streams entering and exiting process equipment. Using this method, the minimum thermodynamic requirements for hot and cold utilities can be calculated for a process. This is useful to determine areas where savings can be realized and where savings are not available. It is a method that can be used during the design of a process...
http://www.chemengonline.com/technical_and_practical/Energy-Optimization-Using-Pinch-Analysis_8624.html
October 1, 2011
  There are various reasons that make filtering necessary in processes. The raw materials might have impurities that require removal at the start of the process. After the initial mixing to produce the process slurry, the mother liquor could have solids that need a separation process. Unwanted solids could also form by a chemical reaction during the production of the process liquid. The nature of the...
http://www.chemengonline.com/technical_and_practical/Clarifying-Liquid-Filtration_8530.html
October 1, 2011
One of the key components in the operational success of chemical process industries (CPI) facilities is the transfer pump. These pumps must handle a wide variety of materials under a broad range of operating conditions. These diverse operational conditions may include harsh and corrosive environments as well as the following: • Changes in ambient temperatures and other weather conditions, such as...
http://www.chemengonline.com/technical_and_practical/Making-Pump-Maintenance-Mandatory_8535.html
October 1, 2011
To confidently design, operate and troubleshoot solids-handling processes, engineers need to characterize powder flow in ways that relate to in-plant behavior. Universal powder testers provide the multi-faceted characterization that is necessary to reliably predict operational performance. This article examines the data that such instruments generate, and discusses their practical application. While many...
http://www.chemengonline.com/technical_and_practical/Characterizing-Powder-Flow_8540.html
October 1, 2011
Equilibrium stage simulations are the nearly universal process design tool for mass transfer columns that contact vapor and liquid in countercurrent flow. Whether the service is absorption, stripping, distillation, fractionation, quench or evaporation, equilibrium stage models make mass and heat balances easy. They quickly estimate stream conditions and physical properties. They are easily altered, so a...
http://www.chemengonline.com/technical_and_practical/Determining-Packing-Height-With-Accuracy_8550.html
September 1, 2011
I was having a “wallflower moment” after Ms. Ruth Sands’ excellent troubleshooting presentation at the March AIChE meeting. That presentation was well summarized by Editor in Chief, Rebekkah Marshall in the April issue of CE (p. 5). I wanted to tell Ms. Sands, and the other meeting attendees, about my solvents column troubleshoot. Here’s the story: On this particular troubleshoot...
http://www.chemengonline.com/technical_and_practical/Believe-your-instruments-unless-_8410.html
September 1, 2011
The chemical process industries (CPI), like many others, increasingly employ non-metallic piping systems for fluid transfer — including polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) and fiberglass-reinforced plastic (FRP) — instead of exotic metal piping. While non-metallic piping systems have benefits, such as lighter weight and easier installation, they pose a challenge with...
http://www.chemengonline.com/technical_and_practical/Specifying-Elastomer-Seals-for-Plastic-Piping_8420.html
September 1, 2011
Dilute-phase conveying systems generally use centrifugal fans and positive displacement blowers for supplying conveying air to the conveying system. However, for some conveying systems, compressed air from a central compressor station is also used. The two important criteria required for pneumatic conveying are air flow and air delivery pressure. Different air movers have different characteristics in the...
http://www.chemengonline.com/technical_and_practical/Moving-Air-In-Pneumatic-Conveying-Systems_8421.html
September 1, 2011
Condensate pots are commonly used on the condensing sides of some reboilers, such as those that are heated by steam or refrigerant vapor. These pots provide a liquid seal that prevents uncondensed vapor from blowing out of the reboiler into the condensate system. A break in this seal can result in heat transfer losses. With steam reboilers, blowing vapor into the condensate header may also lead to...
http://www.chemengonline.com/technical_and_practical/Reboiler-Condensate-Drums-Silencing-Hydraulic-Hammer_8438.html
September 1, 2011
Among the challenges of effective solid-liquid filtration is the accumulation of solids on the filter surface, which creates an increasingly dense mass that process fluid must push through. In many applications in the chemical process industries (CPI), a step-down filtration approach has the potential to avoid this difficulty, and at the same time, to cut operating costs and improve solution clarity. Even...
http://www.chemengonline.com/technical_and_practical/Reduce-Costs-with-Step-down-Filtration_8439.html
September 1, 2011
Steam-assisted, gravity-drainage (SAGD) operations employ large tanks that vent flammable and sometimes toxic gases. Safety and environmental concerns often require engineers to design vapor-recovery units (VRUs) to collect these gases and redirect them to a useful location — frequently for use as a fuel gas in a steam-generation system. When choosing a VRU setup for an SAGD facility, the two most...
http://www.chemengonline.com/technical_and_practical/Tank-Vapors-Optimize-Ejector-Sizing-for-Better-Control_8440.html
September 1, 2011
This article presents equations that allow the user to calculate liquid volume as a function of liquid depth, in both vertically and horizontally oriented tanks with dished heads. The equations accommodate all tank heads that can be described by two radii of curvature (torispherical heads). Examples include: ASME flanged & dished (F&D) heads, ASME 80/10 F&D heads, ASME 80/6 F&D heads...
http://www.chemengonline.com/technical_and_practical/Calculate-Liquid-Volumes-in-Tanks-with-Dished-Heads_8471.html
August 1, 2011
Almost by definition, chemical engineering is a “green” discipline today, as it so often involves efforts to optimize chemical processes in order to reduce the amount of energy and raw materials that are used and the amount of waste that is generated. Today everybody “talks green” but in a lot of cases engineers are the most qualified people to provide the tools required to make...
http://www.chemengonline.com/technical_and_practical/Practice-Green-Chemical-Engineering_8298.html
August 1, 2011
Many solid materials can exhibit self-heating, which — if unchecked — can progress to a fire or even explosion. And even if the situation does not get that far, it is likely to affect the output of the process, in terms of product quality degradation, for example. Recognizing that your product in powder or granular form can self-heat is the first step in controlling the risks associated with...
http://www.chemengonline.com/technical_and_practical/Preventing-Self-Heating-and-Ignition-in-Drying-Operations_8300.html
August 1, 2011
Modern industrial-automation systems rely entirely on digital technology, that is, computers. And as is typical of digital products, suppliers love to add features — data collection, alarm management, and so on — that are very useful for process operations but are not process control in the purest sense. This is continuing, the result being that process control systems are evolving to...
http://www.chemengonline.com/technical_and_practical/Todays-Process-Automation-Worlds_8302.html
August 1, 2011
Capital cost assessment is an integral part of process design when building or expanding a chemical process plant. It is required to provide project analysis and evaluation, to select among alternative designs, to plan the appropriation of funds and to serve as a basis for project cost control. Capital cost estimation is also important for an engineerng student’s final design project. The accuracy of...
http://www.chemengonline.com/technical_and_practical/Evaluating-Capital-Cost-Estimation-Programs_8359.html
July 1, 2011
I have an ongoing dispute with a longtime colleague, Bob Miller. I said he ruined my new safety boots. He said he didn’t. Bob was a young, fearless distillation engineer at a time when our extraction engineer refused to take a trip to Japan to inspect new trays going into an old extractor. I called Bob into my office and asked him to take the trip, even with zero extraction experience. Bob accepted...
http://www.chemengonline.com/technical_and_practical/When-troubleshooting-the-extractor_8158.html
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