Process pipeline conditions

The gas processing options described in the previous section were designed primarily to meet on-site usage or evacuation specifications. Before delivery to the customer further processing would normally be carried out at dedicated gas processing plants, which may receive gas from many different gas and oil fields. Gas piped to such plants is normally treated to prevent liquid drop out under pipeline conditions (dew point control) but may still contain considerable volumes of natural gas liquids (NGL) and also contaminants. 

PROCESS/PIPELINE CONDITIONS Primary Separator at 66°C and 138.00 Bars Pipeline Pressure Temperature Profile... 

Most microbial desulfurization studies have been conducted in the laboratory shake-flask type experiments, and the major drawback cited against such a process has been that the rates of pyritic sulfur removal were not high enough to reduce the reactor size to a reasonable capacity (2,6). In this study an attempt has been made to determine the effectiveness of T. ferrooxidans under simulated pipeline conditions for pyritic sulfur removal. Since the microbial desulfurization process is conducted under acidic environment, an attempt has been made to determine the corrosion rates under dynamic conditions using Illinois //6 and Indiana 3 bituminous coals and to investigate the effectiveness of a commercial corrosion inhibitor for controlling the corrosivity. 

Retrograde condensation plays an important role in technical applications, for example, in oil production, high-pressure pipelines, refrigeration processes and in natural gas reservoirs, where temperature and pressure are high enough to produce critical conditions. 

Under certain conditions of temperature and pressure, and in the presence of free water, hydrocarbon gases can form hydrates, which are a solid formed by the combination of water molecules and the methane, ethane, propane or butane. Hydrates look like compacted snow, and can form blockages in pipelines and other vessels. Process engineers use correlation techniques and process simulation to predict the possibility of hydrate formation, and prevent its formation by either drying the gas or adding a chemical (such as tri-ethylene glycol), or a combination of both. This is further discussed in SectionlO.1. 

Condensable hydrocarbon components are usually removed from gas to avoid liquid drop out in pipelines, or to recover valuable natural gas liquids where there is no facility for gas export. Cooling to ambient conditions can be achieved by air or water heat exchange, or to sub zero temperatures by gas expansion or refrigeration. Many other processes such as compression and absorption also work more efficiently at low temperatures. 

The above example is a simple one, and it can be seen that the individual items form part of the chain in the production system, in which the items are dependent on each other. For example, the operating pressure and temperature of the separators will determine the inlet conditions for the export pump. System modelling may be performed to determine the impact of a change of conditions in one part of the process to the overall system performance. This involves linking together the mathematical simulation of the components, e.g. the reservoir simulation, tubing performance, process simulation, and pipeline behaviour programmes. In this way the dependencies can be modelled, and sensitivities can be performed as calculations prior to implementation. 

Polyethylene. This is essentially a closed-ceU insulation manufactured at 448 2 K by an extmsion process. A blowing agent and nucleating agent are employed to control the ceU size, and primary use is in insulating pipelines for hot and chilled water lines, air conditioning, and processing systems. 

This is a location safer than Zone I with a likelihood of concentration of explosive gases, chemical vapour or volatile liquids during processing, storage or handling. This would become a fire hazard only under abnormal conditions, such as a leakage or a burst of joints or pipelines etc. Such a condition may exist only for a short period. A standard motor with additional features, as di.scussed below, may also be safe for such locations. A non-sparking type. Ex. n , or an increased safety motor, type Ex. e , may also be chosen for such locations. 

A sour natural gas stream can be anaerobically desulfurized by a process, which employs a consortium of chemoautotrophic bacteria (ATCC 202177). The H2S and other sulfur species are converted into elemental sulfur, which is recovered as a product [287], The process conditions involve pressures lower than 1000 psi and temperatures up to 60°C. Sulfur content might be diminished from 10,000 ppm H2S to pipeline standards of <4ppm. Further, C02 content can be reduced as well from levels as high as 10% to <2%. 

Methods that are used to prevent VCEs include keeping low inventories of volatile, flammable materials, using process conditions that minimize flashing if a vessel or pipeline is ruptured, using analyzers to detect leaks at low concentrations, and installing automated block valves to shut systems down while the spill is in the incipient stage of development. 

In order to develop such design criteria, one needs to study hydrogen-induced fractures in laboratory specimens that simulate the conditions in the fracture process zone in the actual pipeline environment in terms of the stress, strain, and hydrogen accumulation6 1. We have recently demonstrated6-9, that under hydrogen pressures up to 15 MPa both stress and hydrogen fields ahead... 

The last issue that remains to be addressed is whether the MBL results are sensitive to the characteristic diffusion distance L one assumes to fix the outer boundary of the domain of analysis. In the calculations so far, we took the size L of the MBL domain to be equal to the size h - a of the uncracked ligament in the pipeline. To investigate the effect of the size L on the steady state concentration profiles, in particular within the fracture process zone, we performed additional transient hydrogen transport calculations using the MBL approach with L = 8(/i — a) = 60.96 mm under the same stress intensity factor Kf =34.12 MPa /m and normalized T-stress T /steady state distributions of the NILS concentration ahead of the crack tip are plotted in Fig. 8 for the two boundary conditions, i.e. / = 0 and C, =0 on the outer boundary. The concentration profiles for the zero flux boundary condition are identical for both domain sizes. For the zero concentration boundary condition CL = 0 on the outer boundary, although the concentration profiles for the two domain sizes L = h - a and L = 8(/i - a) differ substantially away from the crack tip. they are very close in the region near the crack tip, and notably their maxima differ by less than... 

Sensor A is mounted onto an orifice plate inserted in the main supply pipeline for liquid urea. The orifice has a smaller hole diameter than the pipeline, which induces turbulence in the flowing urea downstream of the orifice. The vibrations produced by this turbulence will be detected by sensor A. Sensors B, C and D are mounted on the vertical wall on the granulator, about 30 cm above the perforated bottom plate to detect vibrations produced by the granules when they impact the reactor wall. Thus sensors B, C and D are used to monitor the process conditions inside the granulator, while sensor A is used to monitor the liquid supply of urea. The sensors used in this trial are all high temperature accelerometers. 

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