Operational Conditions

Most processes are catalyzed where catalysts for the reaction are known. The strategy will be to choose the catalyst, if one is to be used, and the ideal characteristics and operating conditions needed for the reaction system. Decisions must be made in terms of reactor... 

Before we can proceed with the choice of reactor and operating conditions, some general classifications must be made regarding the types of reaction systems likely to be encountered. We can classify reaction systems into five broad types ... 

Having discussed the choice of reactor type and operating conditions at length, let us try two examples. 

Reactor conversion. In Chap. 2 an initial choice was made of reactor type, operating conditions, and conversion. Only in extreme cases would the reactor be operated close to complete conversion. The initial setting for the conversion varies according to whether there are single reactions or multiple reactions producing byproducts and whether reactions are reversible. 

Low pressure. Low pressures are not in general as hazardous as the other extreme operating conditions. However, one particular hazard that does exist in low-pressure plants handling flammable materials is the possible ingress of air with the consequent formation of a flammable mixture. 

Under normal operating conditions, waste is produced in reactors in six ways ... 

Choice of reactor. The first and usually most important decisions to be made are those for the reactor type and its operating conditions. In choosing the reactor, the overriding consideration is usually raw materials efficiency (bearing in mind materials of construction, safety, etc.). Raw materials costs are usually the most important costs in the whole process. Also, any inefficiency in raw materials use is likely to create waste streams that become an environmental problem. 

The generalized use of computers makes seemingly complex calculations quite easy to perform however, curves and tables are still invaluable when one needs to obtain approximate values or to take into account the sensitivity of a property to operating conditions or to a mixture s characteristics. 

The implementation of very effective devices on vehicles such as catalytic converters makes extremely low exhaust emissions possible as long as the temperatures are sufficient to initiate and carry out the catalytic reactions however, there are numerous operating conditions such as cold starting and... 

Coking units are operated to optimize the light products produced, coke being considered as a by-product. Its quality is not too important. Generally speaking, the quality of coke produced varies widely according to the feed, the operating conditions, and the process. 

Influence of operating conditions This concerns the temperature, the pressure and the residence time. The more severe the conditions are, the harder is the coke produced. 

A detailed study of the properties of the potential products is of prime technical and economic importance, because it allows the refiner to have a choice in selecting feedstocks for his different units for separation, transformation and conversion, to set their operating conditions, in order to satisfy the needs of the marketplace in the best ways possible. 

The graph gives the yields that the refiner would obtain at the outlet of the atmospheric distillation unit allowing him to set the unit s operating conditions in accordance with the desired production objectives. 

The comparison between the qualities and quantities obtained and those for marketable products, the refiner can estimate the capacities and the operating conditions of the various treatment units... 

From these data, it is possible either to size a desulfurization unit, or to set the operating conditions for an existing unit. 

One of the problems generally associated with the utilization of additives is the continuous action under the engine s operating conditions. That is particularly important for polymers that are sensitive to mechanical deterioration due to shear effects. 

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. 

Operating conditions all gas lift valves apart from the bottom orifice valve are closed. The energy to the system is delivered by a compressor. The performance of the system is monitored by observing flowrates and the casing and tubing pressures. 

Gas turbine driven centrifugal compressors are very efficient under the right operating conditions but require careful selection and demand higher levels of maintenance than reciprocating compressors. Compression facilities are generally the most expensive item in an upstream gas process facility. 

Crude oil and gas from offshore platforms are evacuated by pipeline or alternatively, in the case of oil, by tanker. Pipeline transport is the most common means of evacuating hydrocarbons, particularly where large volumes are concerned. Although a pipeline may seem a fairly basic piece of equipment, failure to design a line for the appropriate capacity, or to withstand operating conditions over the field life time, can prove very costly in terms of deferred oil production. 

Artificial lift techniques are discussed in Section 9.6. During production, the operating conditions of any artificial lift technique will be optimised with the objective of maximising production. For example, the optimum gas-liquid ratio will be applied for gas lifting, possibly using computer assisted operations (CAO) as discussed in Section 11.2. Artificial lift may not be installed from the beginning of a development, but at the point where the natural drive energy of the reservoir has reduced. The implementation of artificial lift will be justified, like any other incremental project, on the basis of a positive net present value (see Section 13.4). 

During the design phase, facilities (the hardware items of equipment) are designed for operating conditions which are anticipated based upon the information gathered during field appraisal, and upon the outcome of studies such as the reservoir simulation. The design parameters will typically be based upon assessments of... 

A study is at present being carried out to check and validate the feasability of acoustic emission monitoring of the pneumatic testing of tanks. This study is being carried out in the context of the CIAPES program. This article gives only a brief summary of the results obtained on various materials, and different types of vessels, under different operating conditions. 

The results of over 1 year of continuous, on-line acoustic emission (AE) structural surveillance of high temperature / high pressure steam headers, gained on 2 M-scale 600MW supercritical multifuel ENEL power units in normal operation, are presented in the paper. The influence of background noise, the correlation between plant operating conditions (steady load, load variations, startup / shutdown transients) and AE activity and the diagnostic evaluation of recorded AE events are also discussed. 

Finally, preliminary diagnostic evaluation criteria, based on preventive identification of critical areas of interest on the monitored item, spatial concentration of localized AE events as compared with average AE event density and evolution of local event concentration vs time and/or plant parameters, have been worked out and submitted to extensive testing under real operation conditions. Work on this very critical issue is still to be consohdated. 

Different plant operating conditions (steady load, load variations, startups / shutdowns) have been encountered during the monitoring period. Electrical load, steam pressure and steam temperature values vs time have been acquired and stored during the entire period. At the same time, the RMS values of the acoustical background noise were have been continuously checked and stored, thus providing a quick check of proper instrumentation condition and a correlation between variations of plant parameters and the acoustical behaviour of the components. 

Examination of the cumulated histogram of localized AE sources for all monitoring intervals, in different operating conditions, suggests the conclusion that no structurally significant sources have been active in the monitored area of the SH header. 

Of course, under the same operating conditions, the higher the thickness the lower the stress level. Further tests were carried out to map the surface thickness distribution using an ultrasonic precision thickness gauge. It was so verified a deviation of the thickness up to 10% of the nominal value. 

Studying modem approaches for such schemes, one can see that knowledge of operational conditions and potential degradation mechanisms play a prominent role. Surprisingly, the role of NDT is often limited to tlie use of conventional methods such as ultrasonic wall thickness measurements, ultrasonic inspection, radiography, and last but not least visual inspection. 

For NDT of new construction this implies that, the more one knows about the material properties and operational conditions, the better the acceptance criteria for weld defects can be based on the required weld integrity and fine-tuned to a specific application. In pipeline industry, this is already going to happen. 

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