Factors in Control-Equipment Selection

Factors in Control-Equipment Selection In order to solve an air-poUrrtion problem, the problem mrrst be defined in detail. A nrrm-ber of factors mrrst be considered prior to selecting a particrrlar piece of air-polhrtion-control eqrripment. In general, these factors can be grorrped into three categories environmental, engineering, and economic. 

In the selection of control equipment, the most important waste-gas characteristics are volumetric flow rate, concentration and composition of organic compounds in the waste-gas, waste-gas temperature and humidity, and rbe content of particulate matter, chlorinated hydrocarbons, and toxic pollutants. Other factors influencing the equipment selection are the required removal efficiency, recovery requirements, investment and operating costs, ease of installation, and considerations of operation and maintenance. The selection of a suitable control method is based on the fundamental selection criteria presented as well as the special characteristics of the project. 

Heat Sensitivity. The heat sensitivity or polymerization tendencies of the materials being distilled influence the economics of distillation. Many materials caimot be distilled at their atmospheric boiling points because of high thermal degradation, polymerization, or other unfavorable reaction effects that are functions of temperature. These systems are distilled under vacuum in order to lower operating temperatures. For such systems, the pressure drop per theoretical stage is frequently the controlling factor in contactor selection. An exceUent discussion of equipment requirements and characteristics of vacuum distillation may be found in Reference 90. 

Let s take the example of benzene, which at 12,000 ppm, is 100% LEL. The National Fire Protection Association (NFPA) states that equipment can operate, without LEL monitors or controls, if the LEL is less than 25% LEL. For benzene then, 25% LEL is equal to 3,000 ppm. This upper boundary becomes a dictating factor in the selection and design of the oxidation equipment. If the concentration is higher than 25% LEL, the NFPA requirements state that an LEL monitor is required. Using an LEL monitor, NFPA guidelines allow operation up to 50% LEL (a 2 1 safety factor). Thus, 100% LEL is explosive if the stream is at 25%, a factor safety of four exists. 

This chapter deals with the essential factors in the selection of systems and equipment during the design stage principles of controls, noise-reduction systems, and problems such as erosion, corrosion, maintenance and equipment cleaning, etc. 

Synthetic-based muds are mineral oil muds in which the oil phase has been replaced with a synthetic fluid, such as ether, ester, PAO, or linear alkylbenzene, and are available from major mud companies. The mud selection process is based on the mud s technical performance, environmental impact, and financial impact. Synthetic muds are expensive. Two factors influence the direct cost unit or per-barrel cost and mud losses. Synthetic muds are the technical equivalent of oil-based muds when drilling intermediate hole sections. They are technically superior to all water-based systems when drilling reactive shales in directional wells. However, with efficient solids-control equipment, optimized drilling, and good housekeeping practices, the cost of the synthetic mud can be brought to a level comparable with oil-based mud [1308]. 

The factors in Table 3 were selected from a non-aqueous chiral separation method for timolol. One qualitative factor (1), i.e., the type of CE equipment, was examined. Two HPCE systems, A and B, with different software versions for equipment control, data acquisition, and handling were compared. Six quantitative factors ((2) till (7)), for which the extreme levels usually were situated symmetrically around the nominal, also were... 

Polystyrene capacitors have exceptionally low tan S values (< 10 q, making them well suited for frequency-selective circuits in telecommunications equipment. Polymer capacitors are widely used for power-factor correction in fluorescent lighting units, and in start/run circuitry for medium-type electric motors used in washing machines, tumble-dryers and copying machines for example. They are also used in filter circuits to suppress radio frequencies transmitted along main leads. Such interference noise may originate from mechanical switches, furnace controllers and switch mode power supplies it not only spoils radio and television reception but can also cause serious faults in data-processing and computer equipment. 

It is hoped that the chapters which follow will give more detailed and quantitative information on the various types of mixers and that this will be helpful in design and selection of equipment. However, much will depend upon the particular duty, e.g. batch or continuous, whether the materials are shear-sensitive, whether there are corrosion or special materials of construction requirements, whether heat removal or addition is a controlling factor. 

Your employees need positive reinforcement and fair, consistent enforcement of the rules governing personal protective equipment usage. Some employees may resist wearing personal protective equipment according to the rules, because the PPE is uncomfortable and places additional burden of stress on the body. This stress can make it unpleasant or difficult for employees to work safely. This is a significant limitation, particularly when heat stress is a factor in the work environment. Ill-fitting or improperly selected PPE is hazardous, since PPE is only used when other feasible controls have failed to minimize a hazard [2],... 

Optical absorption spectrophotometry is probably the most commonly used technique [4,a]. Reaction cells are similar to those used in flash work. Photomultipliers cover the uv-visible range the initial photoelectric signal is amplified internally, by an amoimt controlled by selection of the number of dynodes. Nanosecond equipment is commercially available. Picosecond time-resolution has been achieved [l,h]. For the infrared and Raman region, semiconductor photodiodes cover the range 400-3000 nm the vibrational spectra yield structural information about transient species much more detailed and precise than that from electronic spectra. Resonance enhancement of Raman spectra increases their intensity by a factor of 10, and makes them attractive for detection and monitoring [4,b]. They can be recorded with time-resolution down to sub-nanoseconds. Fluorescence detection is sensitive, and fast with single-photon counting or a streak camera (Section 4.2.4.2), it has been used for times down to 30 ps after an electron pulse. Conductivity also provides a fast and sensitive technique [4,c,d,l,m], especially in hydrocarbon solutions, where... 

Finally, time is a factor in determining the severity of corrosion. Corrosion rates are expressed using a time dimension. Some corrosion processes are violent and rapid, whereas most are so slow as to be imperceptible on a day-to-day basis. Equipment is planned to have a useful service life. A chief goal in understanding corrosion is the proper selection of materials, equipment processes, or controls to optimize our natural and financial resources. 

---