Large values of the uncertainty are assigned to the generated points, because the primary purpose of the generated points is not to have them fit accurately, but rather to maintain a reasonable slope of the function in the range outside the experimental points.  [c.140]

More often than not, solid-catalyzed reactions are multiple reactions. For reactions in parallel, the key to high selectivity is to maintain the appropriate high or low concentration levels of reactants at the catalyst surface, to encourage the desired reaction, and to discourage the byproduct reactions. For reactions in series, the key is to avoid the mixing of fluids of different compositions. These arguments for the gross flow pattern of fluid through any reactor have already been developed.  [c.47]

However, the laboratory data seem to indicate that a constant concentration in the reactor to maintain 63 percent sulfuric acid would be beneficial. Careful temperature control is also important. These two factors would suggest that a continuous well-mixed reactor is appropriate. There is a conflict. How can a well-defined residence time be maintained and simultaneously a constant concentration of sulfuric acid be maintained  [c.52]

An additional separator is now required (Fig. 4.2a). Again, the unreacted FEED is normally recycled, but the BYPRODUCT must be removed to maintain the overall material balance. An additional complication now arises with two separators because the separation sequence can be changed (see Fig. 4.26). We shall consider separation sequencing in detail in the next chapter.  [c.96]

Example 6.2 A process is to be divided into two operationally independent areas of integrity, area A and area B. The stream data for the two areas are given in Table 6.6." Calculate the penalty in utility consumption to maintain the two areas of integrity for = 20°C.  [c.182]

Find a way to overcome the constraint while still maintaining the areas. This is often possible by using indirect heat transfer between the two areas. The simplest option is via the existing utility system. For example, rather than have a direct match between two streams, one can perhaps generate steam to be fed into the steam mains and the other use steam from the same mains. The utility system then acts as a buffer between the two areas. Another possibility might be to use a heat transfer medium such as a hot oil which circulates between the two streams being matched. To maintain operational independence, a standby heater and cooler supplied by utilities is needed in the hot oil circuit such that if either area is not operational, utilities could substitute heat recovery for short periods.  [c.184]

Figure 6.25a shows the same grand composite curve with two levels of saturated steam used as a hot utility. The steam system in Fig. 6.25a shows the low-pressure steam being desuperheated by injection of boiler feedwater after pressure reduction to maintain saturated conditions. Figure 6.256 shows again the same grand composite curve but with hot oil used as a hot utility.  [c.186]

Solution First, we must construct the balanced composite curves using the complete set of data from Table 7.1. Figure 7.5 shows the balanced composite curves. Note that the steam has been incorporated within the construction of the hot composite curve to maintain the monotonic nature of composite curves. The same is true of the cooling water in the cold composite curve. Figure 7.5 also shows the curves divided into enthalpy intervals where there is either a  [c.220]

Consider changing from batch to continuous operation. Batch processes, by their very nature, are always at unsteady state and thus are difficult to maintain at optimal conditions.  [c.290]

In this section, frequent mention will be made of the following terms  [c.28]

It is not possible to present all special detectors used in gas phase chromatography, but instead we will mention some recent applications.  [c.76]

This analysis, abbreviated as FIA for Fluorescent Indicator Adsorption, is standardized as ASTM D 1319 and AFNOR M 07-024. It is limited to fractions whose final boiling points are lower than 315°C, i.e., applicable to gasolines and kerosenes. We mention it here because it is still the generally accepted method for the determination of olefins.  [c.79]

Despite numerous efforts using various techniques, precise knowledge of olefin content remains an unresolved problem. That is why it is worthwhile to mention two methods commonly employed which provide an answer to the problem.  [c.83]

Finally, we can mention the existence of additives acting specifically on the cloud point. These are polymers containing chemical groups resembling paraffins in order to associate with the paraffins and solubilizing functions to keep the associations in solution. The gains are more modest than those described above being on the order of 2 to 4°C for concentrations between 250 and 1000 ppm. These are, however, appreciable effects for the refiner, considering the difficulty encountered in meeting the cloud point specification.  [c.217]

The cetane number does not play the same essential role as does the octane number in the optimization of engines and motor fuels. In particular, it does not have a direct influence on the engine efficiency. However, a cetane number less than the required level could lead to operating problems difficulties in starting, louder noise especially during idling while cold, and higher smoke emissions upon starting (refer to Figure 5.10). These tendencies, incidentally, are more pronounced in passenger cars than in heavy trucks. It is highly desirable to produce a diesel fuel with sufficiently high cetane number in order to maintain or improve the diesel engine s image for the customers. We will show eventually that obtaining a low level of pollution can not be done without an adequate diesel fuel cetane number.  [c.219]

In order to maintain high energy efficiency and ensure a long service life of the materials of construction in the combustion chamber, turbine and jet nozzle, a clean burning flame must be obtained that minimizes the heat exchange by radiation and limits the formation of carbon deposits. These qualities are determined by two procedures that determine respectively the smoke point and the luminometer index.  [c.226]

The VI is a number that results from a calculation involving the viscosities at 40°C and 100°C. It characterizes the capacity of the lubricant to maintain a constant viscosity through a large range in temperature. This property can be improved by additives.  [c.282]

It is worthwhile to mention that the distribution of naphthenic acids is not uniform in a crude oil since a maximum value is observed in the fractions distilled between 400 and 450°C and whose average specific gravity is 0.950 (Figure 8.2).  [c.330]

Furthermore, the formulators having shown plenty of imagination, it would seem illusory to provide an exhaustive list of additives used today. We will mention only the families of additives, protected of course by patents, but well established and widely commercialized.  [c.345]

The continuous cleaning of the admission system by an additive contained in the gasoline will help maintain the setting at its optimum value and will prevent the engine operation from drifting from its original settings.  [c.346]

The role of detergent additives is to maintain clean injectors so as to insure good distribution of diesel fuel in the cylinder. The structure of these compounds is similar to that of detergents for gasoline engine admission systems. Commercialized compounds are from the succinimide family (see Figure 9.1).  [c.350]

Wells may be drilled at a constant angle to the target or dropped off to a lower angle through the reservoir section. To build, maintain or drop the deviation angle stabilisers are run in the bottom hole assembly (Fig. 3.15). A change in deviation used to require a round trip to change the position of those stabilisers in the bottom hole assembly. In recent years, adjustable, hydraulically activated stabilisers have been developed. The  [c.48]

In the event of a sudden loss of mud In an Interval containing overpressures the mud column in the annulus will drop, thereby reducing the hydrostatic head acting on the formation to the point where formation pressure exceeds mud pressure. Formation fluids (oil, gas or water) can now enter the borehole and travel upwards. In the process the gas will expand considerably but will maintain its initial pressure. The last line of defence leff is the blowout preventer. However, although the BOP will prevent fluid or gas escape to the surface, closing in the well may lead to two potentially disastrous situations  [c.59]

Fixed-bed catalytic reactors. Tubular reactors are also used extensively for catal3dic reactions. Here the reactor is packed with particles of solid catalyst. Most designs approximate to plug-flow behavior. Figure 2.6 shows four possible arrangements for flxed-bed reactors. The first (Fig. 2.6a) is similar to a shell-and-tube exchanger in which the tubes are packed with catalyst. The second (Fig. 2.66) has the tubes constructed inside a furnace for high temperatures. The third (Fig. 2.6c) is a series of adiabatic beds with intermediate cooling or heating to maintain temperature control. The heating or cooling can be effected by internal or external exchangers. The fourth (Fig. 2.6rf) uses direct injection of a fluid to perform heat transfer. The injected fluid might typically be cold fresh feed or cooled recycled product to control the temperature rise in an exothermic reaction. This is known as cold-shot cooling. Many other arrangements are possible.  [c.55]

One common reason for imposing constraints results from areas of integrity A process is often normally designed to have logically identifiable sections or areas. An example might be reaction area and separation area of the process. These areas are kept separate for reasons such as start-up, shutdown, operational fiexibility, safety, etc. The areas are often made operationally independent through the use of intermediate storage of process materials between the areas. Such independent areas are generally described as areas of integrity and impose constraints on the ability to transfer heat. Clearly, to maintain operational indepedence, two areas cannot be dependent on each other for heating and cooling by recovery.  [c.181]

With wastewaters containing very high organic contents, the oxygen demand may be so high that it becomes very difficult and expensive to maintain aerobic conditions. In such circumstances, anaerobic processes can provide an efficient means of removing large quantities of organic material. Anaerobic processes tend to be used when BOD levels exceed lOOOmg/liter (Ikgm ). However, they are not capable of producing very high quality effluents, and further treatment is usually necessary.  [c.314]

Figure 13.5 shows a flowsheet for the manufacture of phthalic anhydride by the oxidation of o-xylene. Air and o-xylene are heated and mixed in a Venturi, where the o-xylene vaporizes. The reaction mixture enters a tubular catalytic reactor. The heat of reaction is removed from the reactor by recirculation of molten salt. The temperature control in the reactor would be diflficult to maintain by methods other than molten salt.  [c.332]

Quantitative analysis is the estimation of the amount of element or group present in a mixture or compound. This is done by various methods, in volumetric analysis a titration, in gravimetric analysis a precipitation followed by a weighing, in colorimetric analysis the estimation of a coloured species. Other quantitative methods include infra-red spectroscopy, estimation of the opalescence of a precipitate (turbidimeiry, nephelometry and fluorimetry), estimation of optical rotation, electrolytic decomposition, potentiometric, conductometric and amperometric titrations, and polaro-graphy. Organic quantitative analysis is generally carried out by physical methods or by conversion to known derivatives which can be estimated by weighing or by titration, anaplerotic sequences Ancillary routes to the catabolic cycles in organisms, which operate to maintain levels of intermediates in these cycles despite tapping off for anabolic purposes. An example is the glyoxylate cycle. Anaplerotic sequences are most obviously seen in micro-organisms where rapid biosynthesis occurs from simple carbon compounds.  [c.34]

Heisenburg uncertainty principle For small particles which possess both wave and particle. properties, it is impossible to determine accurately both the position and momentum of the particle simultaneously. Mathematically the uncertainty in the position A.v and momentum Ap are related by the equation  [c.201]

The sample is placed in a cqnst a nt magnetic field, Bq, and the variation in frequency throughout the t/omain Tieing expfored excites one by one the different resonances. The scan lasts a few minutes. Inversely, one can maintain a constant frequency and cause the magnetic field to vary.  [c.64]

The gradual reduction and ultimate elimination of lead has seen considerable effort by the refiner to maintain the octane numbers at satisfactory levels. In Europe, the conventional unleaded motor fuel, Eurosuper, should have a minimum RON of 95 and a minimum MON of 85. These values were set in 1983 as the result of a technical-economic study called RUFIT (Rational Utilization of Fuels in Private Transport). A compromise was then possible between refining energy expenses and vehicle fuel consumption (Anon., 1983).  [c.210]

The features created by crustal movements may be mountain chains, like the Himalayas, where collision of continents causes extensive compression. Conversely, the depressions of the Red Sea and East African Rift Basin are formed by extensional plate movements. Both type of movements form large scale depressions into which sediments from the surrounding elevated areas ( highs ) are transported. These depressions are termed sedimentary basins (Fig. 2.3). The basin fill can attain a thickness of several kilometres.  [c.10]

Geologists and seismic interpreters will predict type and depth of the different rock formations to be encountered during drilling. They will advise the drilling engineer where the objective zone should be penetrated by the drill bit and they will provide the target(s) of the well. Petrophysicists will advise on the fluid distribution and reservoir engineers will provide a prognosis of pressures along the planned well trajectory. These subsurface disciplines will also specify what information they expect to be gathered, from which formation they want to produce or where gas or water should be injected to maintain reservoir pressure. The accuracy of the parameters used in the well planning process will depend on the knowledge of the field or the region. Particularly during exploration drilling and during the early stages of field development considerable uncertainty in subsurface data will prevail. It is important that the uncertainties are clearly spelled out and preferably quantified. Potential risks and problems expected or already encountered in offset wells (earlier wells drilled in the area) should be discussed and incorporated into the design of the planned well.  [c.30]

When drilling through normally pressured formations, the mud weight in the well is controlled to maintain a pressure greater than the formation pressure to prevent the influx of formation fluid. Atypical overbalance would be in the order of 200 psi. A larger overbalance would encourage excessive loss of mud Into the formation, slow down  [c.59]

AZ/trogen content in crude oil is typically less than 0.1% by weight, but can be as high as 2%. The nitrogen compounds in crude oil are complex, and remain largely unidentified. Gaseous nitrogen reduces the calorific value and hence sales price of the hydrocarbon gas. Natural gas containing significant guantities of nitrogen must be blended with high calorific value gas to maintain a uniform product quality.  [c.94]

See pages that mention the term Menthenone : [c.11]    [c.315]    [c.48]    [c.125]    [c.152]    [c.197]    [c.199]    [c.207]    [c.272]    [c.282]    [c.283]    [c.288]    [c.342]    [c.369]    [c.371]    [c.422]   
The chemistry of essential oils and artificial perfumes Volume 2 (1922) -- [ c.241 ]