Abbeystead


We shall see later how temperature and pressure affect equilibrium conversion. For now, let us consider how concentration affects equilibrium conversion.  [c.35]

As well as depending on catalyst porosity, the reaction rate is some function of the reactant concentrations, temperature, and pressure. However, this function may not be as simple as in the case of uncatalyzed reactions. Before a reaction can take place, the reactants must diffuse through the pores to the solid surface. This results in a situation where either reaction or diffusion can be the rate-limiting process. Alternatively, it may be that reaction speed and diffusion have an almost equal effect. If reaction is rate limiting, as tends to occur in a lower temperature range, the effects of concentration and temperature are those typical of chemical reaction. On the other hand, if diffusion is rate limiting, as tends to occur in a higher temperature range, the effects of concentration and temperature are those characteristic of diffusion. In the transitional region, where both reaction and diffusion affect the overall rate, the effects of temperature and concentration are often rather complex.  [c.47]

The mechanism by which nonkey components affect a given separation is more complex in practice than the broad arguments presented here. There are complex interrelationships between the volatility of the key and nonkey components, etc. Although the argument presented is thus not rigorous, it is broadly correct.  [c.147]

By contrast, if the reactor conversion is optimized, this is a global tradeoff, since changes in the reactor conversion affect operations  [c.239]

Two broad classes of tradeoffs can be identified when optimizing a given flowsheet structure. Local tradeoffs, when carried out around an operation, do not affect other operations in the flowsheet. Global tradeoffs cause changes throughout the flowsheet. Caution should be exercised in judging whether an optimization is local if it involves the use of energy. If an operation uses energy, this might be supplied from an external utility or by heat integration. The apparently local tradeoff between reflux and plates in a distillation column might well turn out to have features of a global tradeoff if the reboiler and/or condenser are heat integrated with the rest of the process. If this is the case, then changing the reflux ratio affects the overall heat integration problem.  [c.252]

For a chemical to affect health, a substance must come into contact with an exposed body surface. The three ways in which this happens are by inhalation, skin contact, and ingestion, the latter being rare.  [c.259]

If a distillation column is inappropriately placed across the pinch, it may be possible to change its pressure to achieve appropriate placement. Of course, as the pressure is changed, the shape of the box is also changed, since not only do the reboiler and condenser temperatures change but also the difference between them. The relative volatility also will be affected. Thus both the height and the width of the box will change as the pressure changes. Changes in pressure also affect the heating and cooling duties for column feed and products. These streams normally would be included in the background process. Hence the shape of the grand composite also will change as the column pressure changes. However, as pointed out previously, it is likely that these effects will not be significant in most processes, since the sensible heat loads involved usually will be small in comparison with the latent heat changes in condensers and reboilers.  [c.345]

The accuracy of the conversion depends on the smoothness of the D 86 curve. Errors affect essentially the points in the low % distilled ranges. Average error is on the order of 5°C for conversion of a smooth curve.  [c.100]

Diesel fuel should have, in contrast to gasoline, a strong tendency to auto-ignite since the principle of operation of diesel engines is based on the ignition of the fuel injected at high pressure in previously compressed air. This quality of diesel is expressed by the cetane number which, as opposed to the octane number, does not directly affect the motor performance but rather acts on driving comfort factors such as cold starting, noise, and exhaust emissions.  [c.178]

Low temperature characteristics of a diesei fuei affect more its fuel feed system than its behavior when burning. However, we will examine them here because of their strong impact on refinery flow schemes.  [c.214]

The cloud point, usually between 0 and -10°C, is determined visually (as in NF T 07-105). It is equal to the temperature at which paraffin crystals normally dissolved in the solution of all other components, begin to separate and affect the product clarity. The cloud point can be determined more accurately by differential calorimetry since crystal formation is an exothermic phenomenon, but as of 1993 the methods had not been standardized.  [c.214]

For optimum combustion, the fuel should vaporize rapidly and mix intimately with the air. Even though the design of the injection system and combustion chamber play a very important role, properties such as volatility, surface tension, and fuel viscosity also affect the quality of atomization and penetration of the fuel. These considerations justify setting specifications for the density (between 0.775 and 0.840 kg/1), the distillation curve (greater than 10% distilled at 204°C, end point less than 288°C) and the kinematic viscosity (less than 8 mm /s at -20°C).  [c.226]

The properties linked to storage and distribution do not directly affect the performance of engines and burners, but they are important in avoiding upstream incidents that could sometimes be very serious. We will examine in turn the problems specific to gasoline, diesel fuel, jet fuel and heavy fuel.  [c.242]

After operating for several hours, a flow deviation is still observed that can be considered as acceptable because the automotive manufacturer has taken it into account during the development of the engine. On the other hand, a more pronounced trend such as that shown in Figure 5.18 would be unacceptable because it will affect the engine noise, driving comfort and pollutant emissions.  [c.247]

The nature of these paraffins and their concentration in diesel fuel affect the three temperatures that characterize the cold behavior. The cloud point is the temperature at which crystals of paraffins appear when the temperature is lowered. The cold filter pluming point is defined as the temperature under which a suspension no ionger flows through a standard filter. Finally, the pour point is the temperature below which the diesel fuel no longer flows by simple gravity in a standard tube. These three temperatures are defined by regulations and the refiner has three types of additives to improve the quality of the diesel fuel of winter.  [c.353]

We should therefore conclude that refining will witness a very important evolution, without revolution, but which will affect both the processes and procedures utilized, the objective being to produce clean products in a clean , energy-efficient manner.  [c.486]

Relative sea level changes affect many shallow marine and coastal depositional environments.  [c.137]

In addition to the cost-benefit aspects of appraisal activities, there are frequently other practical considerations which affect appraisal planning, such as  [c.182]

This seems obvious, but it is not always easy to predict how a change in one part of a processing chain will affect the process as a whole (there will always be a bottleneck  [c.359]

As a consequence of the heterogeneity of composite materials, initial defects are difficult to be eliminated completely. To guarantee the structural safety of these materials it is necessary to investigate the effects of their defects under service conditions. When a composite material is loaded, different types of damage will occur matrix cracking, delamination fibre/matrix debonding and fibre failure. Some of these damage types will initiate even at a very low load level, without causing overall failure of the composite part. However, during further loading the initial damage will grow and create other types of damage. The fatigue damage accumulation in fibre reinforced composite materials can be evaluated by different Non Destructive Testing (NDT) techniques. The most commonly used NDT techniques to date have been the ultrasonic C-scan and the x-ray radiography for detecting primarily internal delamination and matrix cracking respectively. Nevertheless, an interruption of the fatigue loading and removal of the specimen from the test fixture is usually required, which may affect the fatigue results.  [c.45]

Within this work mathematical models of the data collection process for radiography and CT have been developed. The objective has been to develop a functioning simulation environment of the physics in the image/data collection that considers the poly-energetic dependence in the imaging process, including full X-ray energy spectra and detector energy response. The simulation environment is used for fast and cost-effective studies of how parameter variations affect final image quality and indirect - the defect detectability. In this particular case, the simulations have been applied on a high resolution CT application to determine optimal operator parameter settings that maximise the detectability of different defect types in circular objects and to predict the minimum detectable size as a function of object diameter. The simulation environment has also been used to correct for beam hardening artefacts in CT-images.  [c.208]

Such requirements are meant to change the usual configurations and technologies usually associated with photothermal set-up. These changes mainly affect the IR detection devices, the optical components associated with the excitation and detection flux and the signal acquisition hardware and software. Figure 9 presents a sketch of the so-called pre-industrial demonstrator built from those different improvements.  [c.397]

When the grey level dynamic range in the image processed is small, usually because of a poor illumination or a non uniform lighting, it s possible to increase this dynamic range by a histogram transformation. This transformation affect the intensity distributions and increase the contrast.  [c.526]

The Channel area contains controls which affect each of the channels (detection and coupling) independently. The parameter values displayed refer to the channel currently selected for dis-play-  [c.769]

The Common area contains controls which affect both channels.  [c.769]

Attenuation is also an important factor in air-bome ultrasound. For exampe, attenuation in air at 1 MHz is 1.2 dB/cm, compared with a figure of 0.0022 dB/cm in water [1]. In addition, environmental conditions (temperature, turbulences) can affect the inspection with air-bome  [c.840]

Multiple reactions in parallel producing byproducts. Raw materials costs usually will dominate the economics of the process. Because of this, when dealing with multiple reactions, whether parallel, series, or mixed, the goal is usually to minimize byproduct formation (maximize selectivity) for a given reactor conversion. Choice of reactor conditions should exploit diflTerences between the kinetics and equilibrium effects in the primary and secondary reactions to favor the formation of the desired product rather than the byproduct, i.e., improve selectivity. Making an initial guess for conversion is more difficult than with single reactions, since the factors that affect conversion also can have a significant effect on selectivity.  [c.26]

Consider again the simple process shown in Fig. 4.4d in which FEED is reacted to PRODUCT. If the process usbs a distillation column as separator, there is a tradeofi" between refiux ratio and the number of plates if the feed and products to the distillation column are fixed, as discussed in Chap. 3 (Fig. 3.7). This, of course, assumes that the reboiler and/or condenser are not heat integrated. If the reboiler and/or condenser are heat integrated, the, tradeoff is quite different from that shown in Fig. 3.7, but we shall return to this point later in Chap. 14. The important thing to note for now is that if the reboiler and condenser are using external utilities, then the tradeoff between reflux ratio and the number of plates does not affect other operations in the flowsheet. It is a local tradeoff.  [c.239]

Although the catalyst affects the rate of reaction, it cannot affect the position of equilibrium in a reversible reaction.  [c.85]

The sample to be analyzed can be dissolved in an organic solvent, xylene or methylisobutyl ketone. Generally, for reasons of reproducibility and because of matrix effects (the surroundings affect the droplet size and therefore the effectiveness of the nebulization process), it is preferable to mineralize the sample in H2SO4, evaporate it and conduct the test in an aqueous environment.  [c.34]

Diesel fuels, like gasoline, are formulated with additives that affect the process of combustion, in this case to improve the cetane number. Diesel fuels also contain detergents for irijection systems as well as compounds for improving the fuel s low tempierature rheology. Finally, decreasing particulate emissions is a problem of increasing concern, but the mechanism of action to promote this effect is not clearly understood.  [c.350]

Additives that affect the cloud point are no longer in frequent use however, it has been shown that certain polymers having branched paraffins can recognize paraffins of equivalent size and keep them in solution. It is therefore possible to complex the longest paraffins selectively and to decrease the cloud point by 3 to 4°C (Damin et al., 1986).  [c.353]

Reservoir rocks are either of clastic or carbonate composition. The former are composed of silicates, usually sandstone, the latter of biogenetically derived detritus, such as coral or shell fragments. There are some important differences between the two rock types which affect the quality of the reservoir and its interaction with fluids which flow through them.  [c.13]

Whereas faults displace formerly connected lithologic units, fractures do not show appreciable displacement. They also represent planes of brittle failure and affect hard  [c.84]

The most significant sources of uncertainty in GRV are probably the position and dip of the bounding fault, and the extent of the field in the plane perpendicular to this section. By looking at the quality of the seismic data, an estimate may be made of the uncertainty in the position of the fault, and any indications of internal faulting which may affect the volumetries. The determination of geological uncertainties requires knowledge of the environment of deposition, diagenesis, and the structural pattern of the field. The quantification often starts with a subjective estimate based on regional knowledge of the geology. In cases where little data is available, guesstimates may need to be supplemented with data or reservoir trends observed in neighbouring fields.  [c.176]

Figure 14.11 demonstrates that, despite the anticipation of an incremental project (e.g. gas compression) during the decline period, the actual opex diverges significantly from the estimate during the decline period. Under-estimates of 50-100% are common. This difference does not dramatically affect the NPV of the project economics when discounting back to a reference date at the development planning stage, because the later expenditure is heavily discounted. However, for a company managing the project during the decline period, the difference is very real the company is faced with actual increases in the expected opex of up to 100%. Such increases in planned expenditure may threaten the profitability of a project in its decline period the opex may exceed the cost oil allowance under a production sharing contract.  [c.344]

The number of sensors, which ideally sample the magnetic field, directly depends upon its spectral density. It is just only necessary to know those corresponding to the smallest flaw we want to reconstruct, as the juxtaposition does not affect the spectral width, as long as the physical process is linear. If we consider for the smallest defect of interest, a 100 x 100 pm, 10% deep flaw, we get the spectral density shown in figure 3. A 0.4 mm bandwidth in the axial direction and a 0.1 mm" bandwidth in the circon-ferential direction let us keep more than 99.9% of the total energy. This fixes the minimum sampling step. With a 2.5 oversampling ratio, this drives to an axial step of 0.5 mm and a circonferential step of 2 mm, that is to say 32 sensors on a 9 mm  [c.358]

Flashovers in most cases do not affect the integrity of the tube. For this reason, seasoning of new tubes may be frist and operating eonditions can be eleetrieaUy tough.  [c.534]

The achievable silver concentrations depend mainly on the regeneration rate of the fixer. The steady-state silver concentration in the first fixing step is inversely proportional to the regeneration rate. The dilution factor in the second step is equal to the ratio of the carry-over (e.g. 40 ml/m ) and the regeneration. An doubling of the regeneration rate will result in A of the original silver level in the rinsing section. A standard regeneration rate of 1200 ml/m will result in a decrease of the silver level by a factor of 20, compared to the standard situation. Contrarily to electrolysis, the daily production does not affect the silver content in the rinsing water, which makes cascade fixing a preferable technology in case of high daily productions (>15 m per processor per day).  [c.608]


See pages that mention the term Abbeystead : [c.38]    [c.131]    [c.415]    [c.85]    [c.206]    [c.223]    [c.247]    [c.292]    [c.314]    [c.423]    [c.354]    [c.237]   
What went wrong (0) -- [ c.73 ]