Temperature-Pressure Programme

Oven Temp.fC) Oven Equil.Time(min) Injector Temp.( C) Interface Temp.( C) Sampling Timejmin] BfflBI  

The final temperature of 280°C is reached after 5.17 min (A) or 6 min (B), so that all components of the sample are eluted before the next injection. The pressure program, which is set up after the temperature program, is arranged so that the linear velocity of the carrier gas remains constant at 32.4 cm/s (method A) or 27.5 cm/s (method B) during the total duration of the analysis. A pressure program that fits the temperature program in this way is easily set up with the aid of software (see Fig. 8-2). 

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Controls (1) provide closed-loop control of temperature, pressure, and thickness (2) maintain preset parameters (3) monitor or correct equipment operations (4) con-standy fine tune equipment (5) provide consistency and repeatability in the operations and (6) provide self-optimization of the process. Most processes operate more effi-ciendy when functions must occur in a desired time sequence or at prescribed intervals of time. In the past, mechanical timers and logic relays were used. Now electronic logic and timing devices are used based on computer software programmable logic controllers. They lend themselves to easy set-up and reprogramming. See computer batch processing computer continuous pro-... 

A qualification programme should be completed to confirm that equipment important to safety will be capable of meeting, until the end of its design life, the design basis performance requirements (such as range, accuracy and response) for the assigned safety task, under the environmental conditions (such as temperature, pressure, radiation, humidity or caustic sprays) likely to prevail at the time the equipment will be needed. 

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. 

Oilfields in the North Sea provide some of the harshest environments for polymers, coupled with a requirement for reliability. Many environmental tests have therefore been performed to demonstrate the fitness-for-purpose of the materials and the products before they are put into service. Of recent examples [33-35], a complete test rig has been set up to test 250-300 mm diameter pipes, made of steel with a polypropylene jacket for thermal insulation and corrosion protection, with a design temperature of 140 °C, internal pressures of up to 50 MPa (500 bar) and a water depth of 350 m (external pressure 3.5 MPa or 35 bar). In the test rig the oil filled pipes are maintained at 140 °C in constantly renewed sea water at a pressure of 30 bar. Tests last for 3 years and after 2 years there have been no significant changes in melt flow index or mechanical properties. A separate programme was established for the selection of materials for the internal sheath of pipelines, whose purpose is to contain the oil and protect the main steel armour windings. Environmental ageing was performed first (immersion in oil, sea water and acid) and followed by mechanical tests as well as specialised tests (rapid gas decompression, methane permeability) related to the application. Creep was measured separately. 

All gas chromatography was carried out with pressure regulated helium carrier gas and the following temperature programme 15°C for 2 mins and then 5°C to 250°C. 

Samples are injected (1 pi) using the splitless mode, and helium is used as a carrier gas with an inlet pressure of 2.5 Bar (250 kPa). The temperature programme starts at 50°C and is maintained for 1.5 min, followed by an increase to 190°C at a rate of 30°C/min. After holding the temperature at this level for 5 min, the gradient continues at a rate of 8°C/min until a final level of 230°C. This will be sufficiently maintained to allow all high-boiling substances (cholesterol ) to be eluted. The total analysis time will be approximately 45 min. An example of a chromatogram of control erythrocytes is shown in Fig. 3.3.2. 

If you have measured resolution of a few key components of a mixture under a small number of conditions, commercial software is available to optimize conditions (such as temperature and pressure programming) for the best separation.19 Just over the horizon, greatly improved separations will be possible by coupling two different columns in series with programmable control of the flow rates (pressure) in each column during the separation.20... 

In the experiments illustrated above, a remarkable amount of information becomes available rather quickly and easily when flowing HP xenon gas is used as a probe material. Although some of the information could have been obtained with thermally polarized xenon, such experiments would have to be carried out on sealed, pressurized samples, but to obtain information on the temperature-programmable interlayer void space would be far more difficult if not impossible. 

CO, reforming reaction was conducted at 500-750°C, reactants mole ratio of CH3 CO, He = 1 1 3, and space velocity = 20000-80000 1/kg/h. Methane oxidation was conducted at 150-550 °C using 1 % CH in air mixture (2 ml/min CH4 198 ml/min air) at space velocity = 60000 1/kg/h, and MIBK (4000 ppm in 150 ml/min air introduced by a syringe pump) combustion at 100-500°C and space velocity of 10000-30000 h 1. Catalytic reactions were conducted in a conventional flow reactor at atmospheric pressure. The catalyst sample, 0.1-0.3g was placed in the middle of a 0.5 inch I.D. quartz reactor and heated in a furnace controlled by a temperature programmer. Reaction products were analyzed by a gas chromatography (TCD/FID) equipped with Molecular Sieves 5A. Porapak Q, and 15m polar C BP 20 capillary column. 

Hydrogen dispensers will likely make use of programmable logic controllers or PC-based control systems. Both liquid hydrogen and compressed hydrogen dispensers will need to be able to monitor pressures and temperatures, open and close valves, turn on pumps, and interface with fire and emergency shut-down systems. 

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