Ensure

An excess of ethylene is used to ensure essentially complete conversion of the chlorine, which is thereby eliminated as a problem for the downstream separation system. 

In a single reaction (where selectivity is not a problem), the usual choice of excess reactant is to eliminate the component which is more difficult to separate in the downstream separation system. Alternatively, if one of the components is more hazardous (as is chlorine in this example), again we try to ensure complete conversion. 

This might he worthwhile if the FEED-BYPRODUCT separation is expensive. To use a purge, the FEED and BYPRODUCT must be adjacent to each other in order of volatility (assuming distillation is used as the means of separation). Of course, care should be taken to ensure that the resulting increase in concentration of BYPRODUCT in the reactor does not have an adverse effect on reactor performance. Too much BYPRODUCT might, for example, cause a deterioration in the performance of the catalyst. 

These rules are both necessary and sufficient to ensure that the target is achieved, providing the initialization rule is adhered to that no individual heat exchanger should have a temperature difference smaller than... 

It is important to note that shifting the curves vertically does not alter the horizontal overlap between the curves. It therefore does not alter the amount by which the cold composite curve extends beyond the start of the hot composite curve at the hot end of the problem and the amount by which the hot composite curve extends beyond the start of the cold composite curve at the cold end. The shift simply removes the problem of ensuring temperature feasibility within temperature intervals. 

The maximum temperature cross which can be tolerated is normally set by rules of thumb, e.g., FrSQ,75 °. It is important to ensure that Ft > 0.75, since any violation of the simplifying assumptions used in the approach tends to have a particularly significant effect in areas of the Ft chart where slopes are particularly steep. Any uncertainties or inaccuracies in design data also have a more significant effect when slopes are steep. Consequently, to be confident in a design, those parts of the Ft chart where slopes are steep should be avoided, irrespective of Ft 0.75. 

The reactants dissolve and immediately begin to react to form further dichloroethane. The reaction is essentially complete at a point only two-thirds up the rising leg. As the liquid continues to rise, boiling begins, and finally, the vapor-liquid mixture enters the disengagement drum. A very slight excess of ethylene ensures essentially 100 percent conversion of chlorine. 

Before any matches are placed, the target indicates that the number of units needed is equal to the number of streams (including utility streams) minus one. The tick-off heuristic satisfied the heat duty on one stream every time one of the units was used. The stream that has been ticked off is no longer part of the remaining design problem. The tick-off heuristic ensures that having placed a unit (and used up one of our available units), a stream is removed from the problem. Thus Eq. (7.2) is satisfied if eveiy match satisfies the heat duty on a stream or a utility. 

Alternative superstructures to those in Figs. 16.26 and 16.27 can be developed. On the one hand, it is desirable to include many structural options to ensure that all features which are candidates for an optimal solution have been included. On the other hand, including more and more structural features increases the computational load dramatically. Thus care should be taken not to include unnecessary features in the superstructure. 

Choosing the number of 1-2 shells in series to be the next largest integer above N ensures a practical exchanger design satisfying Xp. 

A schematic diagram of the apparatus is shown in Figure 3.2. The molecules are introduced under a partial vacuum of 10 torr into a buffer chamber that communicates via molecular slipstream with the source itself at 10 to 10 torr in order to ensure a constant concentration in the source at all times during the analysis. 

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. 

Regarding product characteristics, European specifications were established in 1992. They concern mainly the motor octane number (MON) that limits the olefin content and which should be higher than 89, and the vapor pressure, tied to the C3/C4 ratio which should be less than 1550 mbar at 40°C (ISO 4256). On the other hand, to ensure easy vehicle start-ups, a minimum vapor pressure for winter has been set which is different for each country and depends on climatic conditions. Four classes. A, B, C, and D, are thus defined in Europe with a minimum vapor pressure of 250 mbar, respectively, at -10°C (A), -5 C (B), 0°C (C) and -t-10°C (Z)). France has chosen class A. 

To avoid these problems, refiners commonly use additives called detergents" (Hall et al., 1976), (Bert et al., 1983). These are in reality surfactants made from molecules having hydrocarbon chains long enough to ensure their solubility in the fuel and a polar group that enables them to be absorbed on the walls and prevent deposits from sticking. The most effective chemical structures are succinimides, imides, and fatty acid amines. The required dosages are between 500 and 1000 ppm of active material. 

When ethanoi is present, the risk of separation is much less than with methanol. Nevertheless, the ethanol should be relatively anhydrous (less than 3000 ppm water) moreover, if a fuel containing ethanol comes in contact with a water layer, a migration of ethanol toward the water is observed creating a fuel quality problem manifested by lower octane number and an environmental quality problem in that the water will need to be treated. Distribution of ethanol-based fuels requires extra precaution to ensure dryness in distribution systems. 

Moreover, it is useful to distinguish between the standards prepared by the official standards organizations and the professional standards. The former s mission is to ensure that the conditions of the consensus of the widest assemblage of interested parties are followed. The professional standards are prepared by recognized professional organizations but limit the consensus to only the participating organizations. 

Two derivatives are used to ensure constant lead content throughout the gasoline boiling range tetraethyl- and tetramethyl lead and their mixtures in variabie proportions. 

For the long term, 2010-2020 refinery complex meeting environmental reg 4)atimn and ensuring total conversion of the heavy ends... 

Prior to moving the rig and all auxiliary equipment the site will have to be cleared of vegetation and levelled. To protect against possible spills of hydrocarbons or chemicals the surface area of a location should be coated with plastic lining and a closed draining system installed. Site management should ensure that any pollutant is trapped and properly disposed of. 

Particularly for jack-up rigs, site surveys may have to be carried out prior to each reemployment to ensure that the rig is positioned away from the previously formed footprints (depressions on the sea-bed left by the jack-up legs on a previous job). 

The reservoir section is more consolidated and is the main objective to which the well is being drilled, hence the drilling process has to ensure that any productive interval is not damaged. 

The chemistry of cement slurries is complex. Additives will be used to ensure the slurry remains pumpable long enough at the prevailing downhole pressures and temperatures but sets (hardens) quickly enough to avoid unnecessary delays in the drilling of the next hole section. The cement also has to attain sufficient compressive strength to withstand the forces exerted by the formation over time. A spacer fluid is often pumped ahead of the slurry to clean the borehole of mudcake and thereby achieve a better cement bond between formation and cement. 

This type of contract requires the operator to pay a fixed amount to the contractor upon completion of the well, while the contractor furnishes all the material and labour and handles the drilling operations independently. The difficulty with this approach Is to ensure that a quality well Is delivered to the company since the drilling contractor will want to drill as quickly and cheaply as possible. The contractor therefore should guarantee an agreed measurable quality standard for each well. The guarantee should specify remedial actions which will be implemented should a substandard well be delivered. 

Procedures are written to ensure that activities are performed in a systematic way. Accident investigation shows that the majority of accidents occur because procedures are not followed, and this contributes mostly to the base of the safety triangle introduced at the end of Section 4.1. 

Consideration of alternatives seeks to ensure that the proposer has considered other feasible options including location, scales, processes, layouts, operating conditions and the no action option. 

Public consultation and participation aims to assure the quality, comprehensiveness and effectiveness of the EIA, as well as to ensure that the public s views are adequately taken into consideration in the decision-making process. 

A large investment is made by oil and gas companies in acquiring open hole log data. Logging activities can represent between 5% and 15% of total well cost. It is important therefore to ensure that the cost of acquisition can be justified by the value of information generated and that thereafter the information is effectively managed. 

Gas reservoirs are produced by expansion of the gas contained in the reservoir. The high compressibility of the gas relative to the water in the reservoir (either connate water or underlying aquifer) make the gas expansion the dominant drive mechanism. Relative to oil reservoirs, the material balance calculation for gas reservoirs is rather simple. A major challenge in gas field development is to ensure a long sustainable plateau (typically 10 years) to attain a good sales price for the gas the customer usually requires a reliable supply of gas at an agreed rate over many years. The recovery factor for gas reservoirs depends upon how low the abandonment pressure can be reduced, which is why compression facilities are often provided on surface. Typical recovery factors are In the range 50 to 80 percent. 

When a customer agrees to purchase gas, product quality is specified in terms of the calorific value of the gas, measured by the Wobbe index (calorific value divided by density), the hydrocarbon dew point and the water dew point, and the fraction of other gases such as Nj, COj, HjS. The Wobbe index specification ensures that the gas the customer receives has a predictable calorific value and hence predictable burning characteristics. If the gas becomes lean, less energy is released, and if the gas becomes too rich there is a risk that the gas burners flame out . Water and hydrocarbon dew points (the pressure and temperature at which liquids start to drop out of the gas) are specified to ensure that over the range of temperature and pressure at which the gas is handled by the customer, no liquids will drop out (these could cause possible corrosion and/or hydrate formation). 

To ensure disposal water quality is in line with regulatory requirements (usually 40 ppm), the oil content in water is monitored by solvent extraction and infrared spectroscopy. The specification of 40 ppm refers to an oil in water content typically averaged over a one month period. 

In 1986 when the oil price crashed to 10 a barrel, operators began to look very hard at the requirements for offshore developments and novel slimline, reduced facilities platforms began to be considered. The reduced capital outlay and early production start up capability, coupled with the added flexibility, ensured that all companies now consider subsea systems as an important field development technique. Although the interest and investment in subsea systems increased dramatically, subsea systems still had to compete with the new generation of platforms, which were becoming lighter and cheaper. 

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