Process equipment specification

The first step in the procedure is to define the purpose, objectives, and scope of the study. The more precisely this is done, the more focused and relevant the committee discussions can be. The next step is to collect all relevant information on the process under consideration. This includes flow diagrams, process equipment specifications, nominal flows, etc. The procedure is highly dependent on the reflabiUty of this information. Efforts expended here are worthwhile. Many committees use the flow sheet as the central stmcture to organize thek discussions. 

It is evident that attention paid in the laboratory to the factors affecting particle size distribution will save on capital investments made for separation equipment and downstream process equipment. Specific cake resistance (a) can be determined in the laboratory over the life of a batch, to evaluate if time in the vessel and surrounding piping system is degrading the product s particle size to the point it impedes filtration, washing and subsequent drying. 

In Section 10.0, we have discussed process design and processing equipment rather than the layout oi production facilities. Once a process scheme has been defined, the fashion in which equipment and plant is located is determined partly by transportation considerations (e.g. pipeline specifications) but also by the surface environment. 

Table 3 lists typical failure rate data for a variety of types of process equipment. Large variations between these numbers and specific equipment can be expected. However, this table demonstrates a very fundamental principle the more compHcated the device, the higher the failure rate. Thus switches and thermocouples have low failure rates gas—Hquid chromatographs have high failure rates. 

Cycloahphatic amine production economics are dominated by raw material charges and process equipment capital costs. Acetone (isophorone), adiponitnle, aniline, and MDA are all large-volume specification organic intermediates bordering on commodity chemicals. They are each cost-effective precursors. 

Charcoal—sulfur processes need low ash hardwood charcoal, prepared at 400—500°C under controlled conditions. At the carbon disulfide plant site, the charcoal is calcined before use to expel water and residual hydrogen and oxygen compounds. This precalcination step minimises the undesirable formation of hydrogen sulfide and carbonyl sulfide. Although wood charcoal is preferred, other sources of carbon can be used including coal (30,31), lignite chars (32,33), and coke (34). Sulfur specifications are also important low ash content is necessary to minimise fouling of the process equipment. 

Distillation appHcations can be characterized by the type of materials separated, such as petroleum appHcations, gas separations, electrolyte separations, etc. These appHcations have specific characteristics in terms of the way or the correlations by which the physical properties are deterrnined or estimated the special configurations of the process equipment such as having side strippers, multiple product withdrawals, and internal pump arounds the presence of reactions or two Hquid phases etc. Various distillation programs can model these special characteristics of the appHcations to varying degrees and with more or less accuracy and efficiency. 

The Marshall and Swift (M S) Equipment Cost Index (6), formerly Marshall and Stevens, for installed equipment costs is pubHshed monthly in the ChemicalPngineering]om n. A. The indexes reported are the all-industries, process industries, and several specific industry indexes. The yearly all-industries index, given in Table 1, is based on 47 industrial categories. This is commonly used for the translation of purchased process equipment costs, even though... 

While process design and equipment specification are usually performed prior to the implementation of the process, optimization of operating conditions is carried out monthly, weekly, daily, hourly, or even eveiy minute. Optimization of plant operations determines the set points for each unit at the temperatures, pressures, and flow rates that are the best in some sense. For example, the selection of the percentage of excess air in a process heater is quite critical and involves a balance on the fuel-air ratio to assure complete combustion and at the same time make the maximum use of the Heating potential of the fuel. Typical day-to-day optimization in a plant minimizes steam consumption or cooling water consumption, optimizes the reflux ratio in a distillation column, or allocates raw materials on an economic basis [Latour, Hydro Proc., 58(6), 73, 1979, and Hydro. Proc., 58(7), 219, 1979]. 

Specialty plants. These plants are capable of producing small amounts of a variety of products. Such plants are common in fine chemicals, pharmaceutic s, foods, and so on. In specialty plants, the margins are usually high, so factors such as energy costs are important but not life-and-death issues. As the production amounts are relatively small, it is not economically feasible to dedicate processing equipment to the manufac ture of only one product. Instead, batch processing is utilized so that several products (perhaps hundreds) can be manufactured with the same process equipment. The key issue in such plants is to manufacture consistently each product in accordance with its specifications. 

Process Unit or Batch Unit A process unit is a collection of processing equipment that can, at least at certain times, be operated in a manner completely independent from the remainder of the plant. A process unit normally provides a specific function in the production of a batch of product . For example, a process unit might be a reactor complete with all associated equipment (jacket, recirculation pump, reflux condenser, and so on). However, each feed preparation tank is usually a separate process unit. With this separation, preparation of the feed for the next batch can be started as soon as the feed tank is emptied for the current batch. 

FIG. 18-91 Rake-mechanism designs employed for specific duties. (EIMCO Process Equipment Co.)... 

Information on the process reaction conditions may be impoi tant to prolonging the lifetime of process equipment. Techniques such as EIS and potentiodynamic polarization can provide just such information without being tied to a specific corrosion-rate measurement. 

Equipment—client may not have the equipment required to manufacture a specific product. It may be that available capital and installation time are limited such that they simply can not design, acquire, install and test the process equipment to reach the desired capacity within the available budget and time. If a product is in the early stages of its life cycle, the capital required may be hard to justify. This could be based upon the low initial volume anticipated while developing the market or the need to take advantage of a time-sensitive business opportunity. Tolling can provide a means to safely produce introductoiy, short-term, or small volume products that would otherwise be uneconomic. 

Following development of the study direction, the evaluation describes the efforts of obtaining and validating process information, and then discusses equipment specifications and a cost estimate of the feasibility or budget type i.e., with plant costs factored from major material. Finally, project economics and financing complete the evaluation. 

In this study phase, we determine exactly what the licensor is proposing, validate his claims, and do major side studies for decisions on process changes or additions. The necessity to complete this phase prior to detailed equipment specification is self-evident. 

Proper material selection for chemical and process equipment is one of the first important problems encountered by the designer. Among the many parameters that must be considered are structural strength specifications, heat resistance, corrosion resistance, physical properties, fabrication characteristics, composition and structure of material and cost. 

The stability of the stock with respect to heat determines the maximum temperature which can be employed in the distillation process. The complexity of the process is also affected by the product purity demanded by product specifications or by the limitations of subsequent processing equipment. The relative values of the several products determine how much money can be spent in designing the unit for increased yields of the more valuable products. 

As the process moves from the process development stage to the design and construction stage the chemistry, unit operations, and type of equipment have been set. The design and construction stage needs to focus primarily on equipment specifications, piping and instrumentation design, installation details, and layout for an inherently safer installation. 

The nuclear equipment failure rate database has not changed markedly since the RSS and chemical process data contains information for non-chemical process equipment in a more benign environment. Uncertainty in the database results from the statistical sample, heterogeneity, incompleteness, and unrepresentative environment, operation, and maintenance. Some PSA.s use extensive studies of plant-specific data to augment the generic database by Bayesian methods and others do not. No standard guidance is available for when to use which and the improvement in accuracy that is achieved thereby. Improvements in the database and in the treatment of data requires, uhstaiui.il indu.sinal support but it is expensive. 

Most exhaust hoods are either integrated with the contaminant-generating process equipment or are independent of the process equipment. It is nearly always better to have an integrated hood. The advantages are that the hood is de-ro work with that specific tool, process, and contaminant its airflow rate... 

The standard requires purchasing documents to include, where applicable, the title or other positive identification, and applicable issue of specification, drawings, process requirements, inspection instructions, and other relevant technical data, including requirements for approval or qualification of product, procedures, process equipment, and personnel. 

It generally is recommended, and often required, that gas dcicciiuii systems be installed in a fail-safe manner. That is, if power is disconnected or otherwise interrupted, alarm and/or process equipment shutdown (or other corrective action) should occur. All specific systems should be carefully reviewed, however, to ensure that non-anticipated equipment shutdowns would not result in a more hazardous condition tlian the lack of shutdown of the equipment. If a more hazardous situation would occur with shutdown, only a warning should be provided. As an example, a more hazardous situation might occur if blowout preventers were automatically actuated during drilling operations upon detection of low levels of gas concentrations than if drilling personnel were only warned. 

Materials—which include chemicals, process equipment, transport containers, protective equipment, and replacement parts—need to conform to quality (ESH/PSM) standards and specifications before being placed in use. Different materials will need varying levels of test and/or inspection as well as controls on their storage and handling. 

The Chemical Process Industry (CPI) uses various quantitative and qualitative techniques to assess the reliability and risk of process equipment, process systems, and chemical manufacturing operations. These techniques identify the interactions of equipment, systems, and persons that have potentially undesirable consequences. In the case of reliability analyses, the undesirable consequences (e.g., plant shutdown, excessive downtime, or production of off-specification product) are those incidents which reduce system profitability through loss of production and increased maintenance costs. In the case of risk analyses, the primary concerns are human injuries, environmental impacts, and system damage caused by occurrence of fires, explosions, toxic material releases, and related hazards. Quantification of risk in terms of the severity of the consequences and the likelihood of occurrence provides the manager of the system with an important decisionmaking tool. By using the results of a quantitative risk analysis, we are better able to answer such questions as, Which of several candidate systems poses the least risk Are risk reduction modifications necessary and What modifications would be most effective in reducing risk ... 

SAIC provided much of the data used in this book from its proprietary files of previously analyzed and selected information. Since these data were primarily from the nuclear power industry, a literature search and industry survey described in Chapter 4 were conducted to locate other sources of data specific to the process equipment types in the CCPS Taxonomy. Candidate data resources identified through this effort were reviewed, and the appropriate ones were selected. Applicable failure rate data were extracted from them for the CCPS Generic Failure Rate Data Base. The resources that provided failure information are listed in Table 5.1 with data reference numbers used in the data tables to show where the data originated. 

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