Plant design features

Plant design features and response strategies, including operator actions as. spccilied by SRS procedures, are incorporated... 

The degree of safety achieved from a hazard assessment is directly related to the range of process operating conditions and plant design features considered in its preparation. It is important therefore that the process is defined in enough detail to give the hazard assessment the desired level of thoroughness. 

We touched above on the impact of fiscal authorities and capital sources on the economic trade-off which determines the optimum choice of many plant design features. Their impact is such that they are worthy of further elaboration. 

Plant design features and operating procedures alone cannot completely mitigate the risk posed by a beyond-design-basis event. Additional preparations must be made to respond if such an event were to occur. 

Bubbling AFBCs A simplified schematic of a bubbling AFBC is presented in Fig. 27-47. A demonstration plant generating 160 MWe, with a power production intensity of 1.49 MWe/m (1 MWe/16 ft ), began operation in 1988. Also operating is a 350-MWe unit that employs many of the same design features. 

Precipitation is often applied to the removal of most metals from wastewater including zinc, cadmium, chromium, copper, fluoride, lead, manganese, and mercury. Also, certain anionic species can be removed by precipitation, such as phosphate, sulfate, and fluoride. Note that in some cases, organic compounds may form organometallic complexes with metals, which could inhibit precipitation. Cyanide and other ions in the wastewater may also complex with metals, making treatment by precipitation less efficient. A cutaway view of a rapid sand filter that is most often used in a municipal treatment plant is illustrated in Figure 4. The design features of this filter have been relied upon for more than 60 years in municipal applications. 

Two studies resolved the Unresolved Safety Issue A-44, "Station Blackout." The first siudy, The Reliability of Emergency AC Power Systems in Nuclear Power Plants," when combined uh die lelevant loss-oToffsite-power frequency, provides estimates of station-blackout frequencies lor 18 nuclear power plants and 10 generic designs. The study also identified the design and operational features most important to the reliability of AC power systems. The second study, "Station Blackout Accident Analysis" (NUREG/CR-3226), focused on the relative importance to risk of laiion blackout events and the plant design and operational features that would reduce this risk. 

This study (NUREG/CR-2497) applies PSA techniques using operating experience to identify the high-risk features of plant design and operation. The operating experience base is derived from die licensee event repoits (LERs) to find multiple events that, when coupled with postulated events, lead to plant conditions that could eventually result in severe core damage. 

Expansion turbines are related in many design features to the centrifugal compressor. The key exception being that the turbine receives a high pressure gas for expansion and power recovery to a lower pressure and is usually accompanied by the recovery of the energy from the expansion. For example, applications can be (1) air separation plants (2) natural gas expansion and liquefaction (for gas let-down in pipeline transmission to replace throttle valves where no... 

Design Considerations for RO Reverse osmosis plants are typically assembled onto carbon steel or stainless steel frames using permutations of components from the hundreds of individual standard stock items commonly available, including a wide range of membranes, each with their own range of design features and applications. 

A design feature of an ion exchange plant whereby service flow and regenerant flow are in the same direction. The opposite of counter-current (counterflow). 

A design feature of ion-exchange plant whereby the regeneration flow or backwash flow are in the opposite direction to the service flow. Also, a principle used in heat exchangers whereby the medium being heated flows in the opposite direction to the medium supplying the heat. 

In general, the safety of a process relies on multiple layers of protection. The first layer of protection is the process design features. Subsequent layers include control systems, interlocks, safety shutdown systems, protective systems, alarms, and emergency response plans. Inherent safety is a part of all layers of protection however, it is especially directed toward process design features. The best approach to prevent accidents is to add process design features to prevent hazardous situations. An inherently safer plant is more tolerant of operator errors and abnormal conditions. 

Miscellaneous design features are additional safety design methods that are usually included in the early design phases of new projects and are often the basis for safety improvements in existing plants. 

When new plants are constructed or when modifications are needed in existing plants, detailed process designs are required. These designs must include special safety features to protect the system and operating personnel. The following case histories emphasize the importance of these special safety design features. 

Trevor Kletz21 and Walter B. Howard22 have emphasized the special design features for safer plants. The following recommendations also include design features from our own experiences ... 

Synthane A coal gasification process using steam and oxygen in a fluidized bed. An unusual feature is the large volume of hot gas recycled. Developed by the U.S. Bureau of Mines from 1961. A pilot plant, designed by the C. E. Lummus Company, was built at Bruceton, PA, in 1976. 

The regulatory environment is changing in Victoria with introduction from March 2000 of the Major Hazard Facilities Regulations, based on the Seveso II Directives. These are expected to flow on to the other states considered in this chapter. The key requirement of these regulations is the preparation of a Safety Case, which must demonstrate, among other requirements, that the risk from the new plant has been reduced to as low as is reasonably practicable - ALARP . The plants will incorporate a number of design features intended to reduce the risk from the facilities and demonstrate compliance with this criterion. 

Within Chapter 6.6.2 the main parameters to be considered for the design of a high-pressure extraction plant have been discussed in detail. In brief mass-transfer and thermodynamic conditions with their related parameters play the most important roles for an optimized process. In this Chapter the influence of such selected parameters, design features, and the kinds of project financing are investigated with a view to production costs and return on investment (R.O.I.). 

From investigations reported in Chapter 6.6, it is obvious that the production-costs will mainly be dominated by the overall energy consumption, which will depend on the solvent flow-rate, extraction-, and separation conditions, and the process design features such as the isobaric- or non-isobaric, single- or cascade-mode working, CO2 recovery, the individual execution of particular plant components, and the degree of automation. 

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