Dealness

Multiple reactions also can occur with impurities that enter with the feed and undergo reaction. Again, such reactions should be minimized, but the most efiective means of dealing with byproduct reactions caused by feed impurities is not to alter reactor conditions but to introduce feed purification. 

The liquid used for the direct heat transfer should be chosen such that it can be separated easily from the reactor product and so recycled with the minimum expense. Use of extraneous materials, i.e., materials that do not already exist in the process, should be avoided because it is often difficult to separate and recycle them with high efficiency. Extraneous material not recycled becomes an effluent problem. As we shall discuss later, the best way to deal with effluent problems is not to create them in the first place. 

Multiple reactions producing byproducts. The arguments presented for the effect of pressure on single vapor-phase reactions can be used for the primary reaction when dealing with multiple reactions. Again, selectivity is likely to be more important than reactor volume for a given conversion. 

It should be emphasized that these recommendations for the initial settings of the reactor conversion will almost certainly change at a later stage, since reactor conversion is an extremely important optimization variable. When dealing with multiple reactions, selectivity is maximized for the chosen conversion. Thus a reactor type, temperature, pressure, and catalyst are chosen to this end. Figure 2.10 summarizes the basic decisions which must be made to maximize selectivity. ... 

Mixtures with low relative volatility or which exhibit azeotropic behavior. The most common means of dealing with the separation of low-relative-volatility and azeotropic mixtures is to use extractive or azeotropic distillation. These processes are considered in detail later. Crystallization and liquid-liquid extraction also can be used. 

The question now is, given that there are often constraints to deal with, how do we evaluate the effect of these constraints on the system performance The problem table algorithm cannot be used directly if constraints are imposed. However, often the effect of constraints on... 

After maximizing heat recovery in the heat exchanger network, those heating duties and cooling duties not serviced by heat recovery must be provided by external utilities. The outer-most layer of the onion model is now being addressed, but still dealing with targets. 

The problem with Eq. (7.5) is that the overall heat transfer coefficient is not constant throughout the process. Is there some way to extend this model to deal with the individual heat transfer coefficients ... 

Obviously, the use of purges is not restricted to dealing with impurities. Purges can be used to deal with byproducts also. 

The best way to deal with a hazard in a flowsheet is to remove it completely. The provision of safety systems to control the hazard is much less satisfactory. One of the principal approaches to making a process inherently safe is to limit the inventory of hazardous material, called intensification of hazardous material. The inventories we wish to avoid most of all are flashing flammable liquids or flashing toxic liquids. 

Thus emissions must not exceed levels at which they are considered harmful. There are two approaches to deal with emissions ... 

In general, the best way to deal with a feed impurity is to purify the feed before it enters the process. Let us return to the isopropyl alcohol process from Fig. 10.3. Propylene is fed to the process containing propane as a feed impurity. In Fig. 10.3 the propane is removed from the process using a purge. This causes waste of... 

Perhaps the most extreme situation is encountered with purge streams. Purges are used to deal with both feed impurities and byproducts of reaction. In the preceding section we considered how the size of purges can be reduced in the case of feed impurities by purifying the feed. However, if it is impractical or uneconomical to reduce the purge by feed purification, or the purge is required to remove a byproduct of reaction, then the additional separation can be considered. 

Combustion in an incinerator is the only practical way to deal with many waste streams.This is particularly true of solid and concentrated wastes and toxic wastes such as those containing halogenated hydrocarbons, pesticides, herbicides, etc. Many of the toxic substances encountered resist biological degradation and persist in the natural environment for a long period of time. Unless they are in dilute aqueous solution, the most effective treatment is usually incineration. 

Dealing with CO2 emissions. If CO2 emissions are of concern because of the greenhouse effect, then there are only two ways in which reductions can be made ... 

Dealing with SO emissions. If we need to reduce SO emissions, there are four ways in which this can be achieved ... 

Dealing with NO emissions. There are two main reaction paths for NO,r formation ... 

In all types of biological processes, excess sludge is produced which must be disposed of. The treatment and disposal of sludge are major problems which can be costly to deal with. Anaerobic processes have the advantage here, since they produce considerably less sludge than aerobic processes (on the order of 5 percent of aerobic processes for the same throughput). 

It must be clear that the best method for dealing with effluent problems is to solve the problem at source, i.e., waste minimization. 

In Sec. 6.3 it was mentioned that some problems, known as threshold problems, do not have a pinch. They need either hot utility or cold utility but not both. How should the approach be modified to deal with the design of threshold problems ... 

Figure 16.10 shows another threshold problem that requires only hot utility. This problem is different in characteristic from the one in Fig. 16.9. Now the minimum temperature difference is in the middle of the problem, causing a pseudopinch. The best strategy to deal with this type of threshold problem is to treat it as a pinched problem. For the problem in Fig. 16.10, the problem is divided into two parts at the pseudopinch, and the pinch design method is followed. The only complication in applying the pinch design method for such problems is that one-half of the problem (the cold end in Fig. 16.10) will not feature the flexibility offered by matching against utility.

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The complexity of petroleum products raises the question of sample validity is the sample representative of the total flow The problem becomes that much more difficult when dealing with samples of heavy materials or samples coming from separations. The diverse chemical families in a petroleum cut can have very different physical characteristics and the homogeneous nature of the cut is often due to the delicate equilibrium between its components. The equilibrium can be upset by extraction or by addition of certain materials as in the case of the precipitation of asphaltenes by light paraffins. 

There are many professional organizations their influence is more or less in proportion to the number of members and they can be national or international. Among those dealing with petroleum products, the following examples are cited ... 

Once injection water treatment requirements have been established, process equipment must be sized to deal with the anticipated throughput. In a situation where water injection is the primary source of reservoir energy it is common to apply a voidage replacement policy, i.e. produced volumes are replaced by Injected volumes. An allowance above this capacity would be specified to cover equipment downtime. 

Only one set of pipelines and umbilicals (as with the template) are required from the manifold back to the host facility, saving unnecessary expense. Underwater manifolds are becoming very popular as they offer a great deal of flexibility in field development and can be very cost effective. 

Sections 13.1 to 13.8 will deal mainly with the economics of a field development. Exploration economics is introduced in Section 13.8. The general approach to this section will be to look at an investment proposal from an operator s point of view. 

The problem of invariant pattern recognition is recognized as being a highly complex and difficult one. It is not surprising, therefore, that a wide variety of techniques have been invented to deal with specific or general instances of this problem. 

The application of eddy currents in non destructive testing was very developed during the recent years. Adding to the defects characterization, actual studies deal with the metallurgical evaluation of materials. Surface processing allow to increase the material endurance and consequently its life duration. 

Fourier transform is widely used for signal analysis purposes and is satisfactory when applied to signals where stationary features are of particular interest. However, it turns out to be very poor when dealing with defect detection, where it is the non stationary characteristics of the signal which has to be highlighted. The main reason is that in the Fourier analysis, the time parameter is discarded. 

This first part of the standard deals with the fundamental demands that are placed on the measuring devices to be used and on the procedures to be implemented toward a definition of the relevant parameters of the imaging system /6/. 

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