Processing options

The pelletized form of the polymer supplied to converters is fully polymerized. No chemical-curing reaction is needed, and the polymer can be stored under ambient conditions almost indefinitely. There are no shelf-life issues as seen with some amide-acid polymers. 

PEI resins have been extruded into film and sheet. Since they are thermoplastic, both sheet and film can be formed and drawn in secondary operations. PEI film can be used in many electrical applications, such as the manufacture of capacitors and flexible circuits. These films can also be laminated or coextruded to make various multilayer structures. PEI films are often laminated with metals, such as copper, which are then made into electric circuits. 

PEI resins may also be extruded into rods and blocks, which can be subsequently machined into parts. This is useful where smaller production 

PEI resins have been used in a variety of applications such as electrical connectors, internal computer parts, printed-circuit boards, flexible circuits, optical fiber connectors, fire helmets, large appliances, aircraft interiors, trays, microwave cookware, reflectors, motor parts, gears, pumps, lubrication systems, wire coating, industrial applications, bearings, small appliances, films, and fibers. Polyetherimides are used in a wide range of applications. A few of the key markets for PEI resins and some of the benefits they bring to the application are summarized below. 

Preston, J., Polyimides, Supplemental Volume, Kirk-Othmer Encyclopedia of Chemical Technology, Wiley, New York, N.Y, USA, 1971, pp. 746-773. 

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The cost of the capital depends on its source. The source of the capital often will not be known during the early stages of a project, and yet there is a need to select between process options and carry out preliminary optimization on the basis of both capital and operating costs. This is difficult to do unless both capital and operating costs can be expressed on a common basis. Capital costs can be expressed on an annual basis if it is assumed that the capital has been borrowed over a fixed period (usually 5 to 10 years) at a fixed rate of interest, in which case the capital costs can be annualized according to... 

The gas processing options described in the previous section were designed primarily to meet on-site usage or evacuation specifications. Before delivery to the customer further processing would normally be carried out at dedicated gas processing plants, which may receive gas from many different gas and oil fields. Gas piped to such plants is normally treated to prevent liquid drop out under pipeline conditions (dew point control) but may still contain considerable volumes of natural gas liquids (NGL) and also contaminants. 

Absorber oil units offer the advantage that Hquids can be removed at the expense of only a small (34—69 kPa (4.9—10.0 psi)) pressure loss in the absorption column. If the feed gas is available at pipeline pressure, then Httle if any recompression is required to introduce the processed natural gas into the transmission system. However, the absorption and subsequent absorber-oil regeneration process tends to be complex, favoring the simpler, more efficient expander plants. Separations using soHd desiccants are energy-intensive because of the bed regeneration requirements. This process option is generally considered only in special situations such as hydrocarbon dew point control in remote locations. 

The process options reflect the broad range of compositions and gas volumes that must be processed. Both batch processes and continuous processes are used. Batch processes are used when the daily production of sulfur is small and of the order of 10 kg. When the daily sulfur production is higher, of the order of 45 kg, continuous processes are usually more economical. Using batch processes, regeneration of the absorbant or adsorbant is carried out in the primary reactor. Using continuous processes, absorption of the acid gases occurs in one vessel and acid gas recovery and solvent regeneration occur in a separate reactor. 

The process and economics are detailed (21). Owing to the complex nature of the wastes, the process becomes economical only at high production volumes. Several alternative schemes could be developed based on available technologies. Of primary importance is a thorough understanding of the types and constituents of the wastes that feed the processes. Once this is defined, the process options must be considered and tested. A knowledge of what the process caimot do, ie, its limitations, is just as important as a clear understanding of process capabiUties. 

There are several process options to treat gas and reject liquid. A typical pipeline gas specification with respect to thermal value is shown in Table 3-5. 

One of the most comprehensive economic studies was done in two phases. The first phase addressed whether the location of the treating facilities should be offshore or onshore. The second phase evaluated the process design options. The outcome of the first phase recommended onshore natural gas treating facilities the second phase recommended implementation of the turboexpander process design. The process options evaluated for this project are listed below ... 

If the biosolids are of "exceptional quality"- that is, they meet the pollutant concentration limits, class A pathogen reduction requirements, and a vector attraction processing option- they are usually exempt. However, when biosolids meeting class B pathogen reduction requirements are applied to the land, additional site restrictions are required. Table 6 provides a summary of the land application pollution limits for biosolids as they currently stand. 

Deciding among a number of process options having inherent safety advantages and disadvantages with respect to different hazards can be quite difficult. The first step is to understand thoroughly all hazards associated with the process options. Process hazard analysis and evaluation techniques are appropriate tools (CCPS, 1992). These include ... 

Multiply the weighting factor by the performance factor for each parameter and process option combination. 

Sandoz (Ankers, 1995) has developed a software tool to assist chemists and engineers in identifying hazards, and inherently safer process options. 

The following checklist contains a number of questions which can aid in identifying inherently safer process options. The list is adapted from CCPS (1993a). Other checklists, particularly the extensive checklist in Appendix B of the Guidelines for Hazard Evaluation Procedures, 2nd Edition with Worked Examjzles (CCPS, 1992) contain many questions which are related to inherent safety. 

Hendershot, D. C. (1995a). Conflicts and Decisions in the Search for Inherently Safer Process Options. Process Safety Progress 14,1 (January), 52-56. 

To answer the above-mentioned questions, one can envision so many alternatives they cannot be enumerated. Typically, an engineer charged with the responsibility of answering these questions examines few process options based on experience and corporate preference. Consequently, the designer develops a simulation model, performs an economic analysis and selects the least expensive alternative from the limited number of examined options. This solution is inappropriately designated as the optimum. Normally it is not Indeed, the true optimum may be an order of magnitude less expensive. 

After perusal of these process options, the engineer asks the computer to select five designs for further study, and the oomputer produces a paper copy of the flowsheet and design parameters... 

The most versatile data acquisition option is a stand alone data collection unit. At Glidden we use an Elexor Data Logger (S) for this purpose. It has its own microprocessor and BASIC Interpreter and communicates with the computer via the serial port. The unit can be configured with a wide variety of signal processing options. 

Gallezot, P. (2007) Process options for the catalytic conversion of renewables... 

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