High-pressure gases

Note The high pressures referred to are of the order of 2000-6000 psi. Since we are working with liquids instead of gases, high pressures do not pose an explosion hazard. Leaks occur on overpressurizing the worse problems to be expected are drips, streams, and puddles. 

Case Study Risk Assessment for the Failure of a Natural Gas High Pressure Pipeline... 

A natural gas high pressure pipeline with a diameter of 20" (508 mm), a wall thickness of 8 mm subject to a pressure of pi = 70 bar is planned in the vicinity of a residential area. For the section passing close by this residential area a risk assessment is to be performed. This is a so-caUed risk-based analysis, since the expected frequency of the undesired event (rupture of the pipeline and gas release) is directly taken from statistical material (actuarial approach) and not determined by a detailed analysis of the engineered systems involved. 

Methanol (GH OH), also called methyl alcohol, can be prepared from a mixture of carbon monoxide and hydrogen known as synthesis gas. High pressure, high temperature, and a catalyst are used to increase the yield. 

Downstream of the cooling, a high-pressure separation step is provided to separate the polymer from the unreacted gas. High-pressure separation is typically operated between 230 and 290 barg and temperatures between 220 and 280 °C. The recovered monomers are cooled down, separated from oligomers, and fed back to the process as a high-pressure recycle gas stream at the inlet of the hypercompressor. 

Explain why ice often forms on the valve of a tank of compressed gas (high pressure) when it is opened to the atmosphere and the gas escapes. Where does the H2O come from ... 

It is easy to dehydrate high-pressure saturated gas (high-pressure gas contains less amount of water in vapor phase). 

Very often the choice is not available. For example, if reactor temperature is above the critical temperature of the chemical species, then the reactor must be gas phase. Even if the temperature can be lowered below critical, an extremely high pressure may be required to operate in the liquid phase. 

Pressure. High pressure gives greater solubility of solute in the liquid. However, high pressure tends to be expensive to create, since this can require a gas compressor. Thus there is an optimal pressure. 

Bi-Gas process A high-pressure operation for the conversion of solid fuel into substitute natural gas (SNG) using two stages of gasification. 

Boyle s law At constant temperature the volume of a given mass of gas is inversely proportional to the pressure. Although exact at low pressures, the law is not accurately obeyed at high pressures because of the finite size of molecules and the existence of intermolecular forces. See van der Waals equation. 

Joule s law The internal energy of a gas depends only on its temperature (being independent of its pressure and volume). Like the other gas laws, it is only approximately true. At high pressures it is invalidated by the existence of inlermolecular forces. 

Gas is sometimes produced at very high pressures which have to be reduced for efficient processing and to reduce the weight and cost of the process facilities. The first pressure reduction is normally made across a choke before the well fluid enters the primary oil / gas separator. 

Facilities for the treatment and compression of gas have already been described in earlier sections. However, there are a number of differences in the specifications for injected gas that differ from those of export gas. Generally there are no technical reasons for specifications on hydrocarbon dew point control (injected gas will get hotter not cooler) although it may be attractive to remove heavy hydrocarbons for economic reasons. Basic liquid separation will normally be performed, and due to the high pressures involved it will nearly always be necessary to dehydrate the gas to avoid water drop out. 

Injection gas pressures are usually much higher than lift-gas or gas pipeline pressures and special care has to be taken to select compressor lubricants that will not dissolve in high pressure gas. Such a situation could lead to inadequate lubrication and may impair well injectivity. 

The efficiency of gas turbines is limited by the maximum allowable turbine inlet temperature (TIT). The TIT may be increased by cooling of the blades and vanes of the high pressure turbine. Cooling channels can be casted into the components or may be drilled afterwards. Non-conventional processes like EDM, ECD or Laser are used for drilling. Radiographic examination of the drilled components is part of the inspection procedure. Traditional X-Ray film technique has been used. The consumable costs, the waste disposal and the limited capacity of the two film units lead to the decision to investigate the alternative of Real-Time X-Ray. 

The three general states of monolayers are illustrated in the pressure-area isotherm in Fig. IV-16. A low-pressure gas phase, G, condenses to a liquid phase termed the /i uid-expanded (LE or L ) phase by Adam [183] and Harkins [9]. One or more of several more dense, liquid-condensed phase (LC) exist at higher pressures and lower temperatures. A solid phase (S) exists at high pressures and densities. We briefly describe these phases and their characteristic features and transitions several useful articles provide a more detailed description [184-187]. 

At the limit of extremely low particle densities, for example under the conditions prevalent in interstellar space, ion-molecule reactions become important (see chapter A3.51. At very high pressures gas-phase kinetics approach the limit of condensed phase kinetics where elementary reactions are less clearly defined due to the large number of particles involved (see chapter A3.6). 

Knighton W B and Grimsurd E P 1996 Gas phase ion ohemistry under oonditions of very high pressure Advances in Gas Phase Ion Chemistry ed N G Adams and L M Baboook (JAI)... 

Figure A3.10.12 Side view of die high-pressure eell showing die eomieedons to the UHV ehamber, the turbomoleeular pump and the gas handling system. The differentially pumped sliding seal is loeated between the high-pressure eell and the UHV ehamber [37],...

We now discuss the lifetime of an excited electronic state of a molecule. To simplify the discussion we will consider a molecule in a high-pressure gas or in solution where vibrational relaxation occurs rapidly, we will assume that the molecule is in the lowest vibrational level of the upper electronic state, level uO, and we will fiirther assume that we need only consider the zero-order tenn of equation (BE 1.7). A number of radiative transitions are possible, ending on the various vibrational levels a of the lower state, usually the ground state. The total rate constant for radiative decay, which we will call, is the sum of the rate constants,... 

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