Archives :: Facts At Your Fingertips
May 1, 2013
Minimizing process variability is an important component of a plant’s profitability. The performance of control valves within process control loops has a significant impact on maintaining consistent processes. This refresher outlines some of the important aspects of control-valve performance, including parameters of both the static response and the dynamic response. Static response A valve’s...
April 1, 2013
The detection of gases in plant environments has a critical and wide-ranging role in the chemical process industries (CPI). Among the major applications of gas detection are limiting personnel exposure to hazardous chemicals, preventing explosive atmospheres, protecting the environment and identifying leaks in process equipment. Table 1 summarizes the main reasons for gas monitoring. All CPI workers should...
March 1, 2013
Temperature is among the most critical measurements in the chemical process industries (CPI) for operating safe and efficient processes. Because even a small error in temperature can lead to expensive consequences, accurate and reliable monitoring of temperature is required. Thermowells The most accurate temperature measurements occur when the sensor is in direct contact with the process fluid being...
February 1, 2013
Supplying steam that meets process needs while protecting steam-system components, such as boilers and steam turbines (Figure 1), against scale, fouling and corrosion, requires purified feedwater (condensate plus makeup water). Depending on the steam pressure required, the specific approach of the water treatment may be shifted to account for a variety of issues. For example, caustic corrosion and...
January 1, 2013
Non-chemical water treatment methods generally utilize electricity to prevent scale formation, mitigate corrosion and control microbial growth. When properly applied, non-chemical water-treatment technologies help plants reduce chemical consumption, minimize waste and possibly save water and energy. The following descriptions outline several types of non-chemical water-treatment methods. Magnetic fields...
December 1, 2012
Wet fluegas desulfurization (FGD), also known as wet-scrubbing, is a popular pollution-abatement technique for removing acid gases, such as SO2 and HCl from fluegas produced during coal-fired power generation and industrial combustion processes. Wet scrubbing is used in association with power generation, thermal oxidizers, kilns, incinerators, boilers, foundries and other combustion units. Also...
November 1, 2012
For most solids-processing operations in the chemical process industries (CPI), particle-size reduction and screening (classification) to achieve the desired particle-size are required, since processes rarely produce the desired size directly. When designing processes, selecting equipment and looking for ways to increase efficiency, CPI engineers must understand the size-reduction behavior of the solid...
October 1, 2012
Fans and blowers are common in air-handling and movement systems used in the chemical process industries (CPI). Two major uses of fans and blowers are in pneumatic conveying systems and in ventilation and air-pollution-control systems. Powering fans and blowers can contribute significantly to costs, and their efficient operation can be affected by the way plant operators select and run their systems...
September 1, 2012
Sparging refers to the process of injecting a gas through a diffuser into a liquid phase. It is used in both physical and chemical process applications. In physical process applications, the gas is used to either dissolve gas into liquid (such as aeration and carbonation) or to remove contaminants from the liquid phase (such as oxygen stripping, volatile organic compound stripping and water stripping). In...
August 1, 2012
The main function of the expansion tank in a heat-transfer system is to allow space for the heat-transfer fluid to expand as it is heated. A properly designed, installed and maintained expansion tank will support longer fluid and equipment life, safe operation and easier maintenance. Configuration The expansion tank is best located at the highest point in the system to provide a positive pressure head to...
July 1, 2012
Automated systems for batch weighing can improve overall product quality by raising the accuracy and consistency of the mixture compared to what can be achieved with the manual addition of pre-weighed bags. Automated batch-weighing systems integrate load cells with connections, valves, relay hardware and process control software. These systems control one or more pieces of feed equipment that deliver...
June 1, 2012
Among the most widely used technologies in the chemical process industries (CPI), spray drying involves dispersing a liquid or slurry in a hot gas to produce a dry powder product. A wide range of pumpable solutions, suspensions and emulsions can be used as spray-drying feeds. Spray drying allows processors to generate powders with precisely defined properties. By controlling process parameters —...
May 1, 2012
Peristaltic pumps work by compressing a tube against a circular pump housing with rollers on a rotating arm. The fluid that is ahead of the roller gets pushed forward, while new fluid is drawn into the tube by the vacuum generated as the tube returns to its relaxed state. Peristaltic pumps are a type of positive displacement pump that can be used in industrial chemical dosing applications and others...
April 1, 2012
Pneumatic conveying of solid material provides advantages over mechanical conveying systems in many applications, including those that require complex routing, multiple source-destination combinations and product containment. Routing of pneumatic piping offers process operators great layout flexibility, but taking advantage of such design flexibility requires a strong understanding of the complex behavior...
March 1, 2012
To optimize process control and overall plant performance, magnetic flowmeters (mag meters) are the most widely used devices in many industrial flow-measurement applications. Mag meters are used to measure the flow of water and other conductive liquids by applying a magnetic field to the flowing liquid. Following Faraday’s law of electromagnetic induction, conductive liquid flowing through the...
February 1, 2012
Acidity is a critical parameter in the chemical process industries, and accurate measurements of pH can be important indicators for process quality control. A refreshed understanding of pH measurement can help to overcome process-specific challenges to measurement and to select the pH measurement devices that best meet the needs of the process. Further, a review of the temperature dependence of pH...
January 1, 2012
Pressure relief valves and rupture disks are critical safety devices for protecting personnel and processing equipment from overpressurization situations. Presented here are several engineering practices that can help to identify and address common problems with the pressure relief systems of chemical process industries (CPI) facilities. Common causes of overpressurization Overpressure situations can have...
December 1, 2011
Protecting process systems from overpressurization is a critical task in the chemical process industries (CPI), and rupture disks and safety relief valves are routinely used for this purpose. In certain situations, using rupture disks in combination with safety relief valves offers advantages that can increase safety and lower costs. The advantages include a significant lengthening of the service life of...
November 1, 2011
Effective level measurement helps ensure smooth, continuous processes by maintaining material inventory at economic quantities, and maximizes plant output by preventing spillage, system clogging and process upsets. In chemical process industries (CPI) applications, level measurement of liquids, powders and slurries are often complicated by the presence of steam, dust, foam, turbulence, caking or...
October 1, 2011
A well-operated steam generator can save money. In a steam-driven turbine system, water is heated in the steam generator to produce high-temperature, high-pressure steam. Steam is then expanded in a turbine to produce electricity from a generator. Turbine steam is condensed back into water in the condenser. A pump then returns the water to the steam generator. Engine thermodynamics Theoretically, the most...
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