Processes at elevated pressure

Jet Fires. Any flammable material and many combustible materials processed at elevated pressures may have the potential for a jet fire, depending upon the release conditions. If the processing pressures are low, and the building is sufficiently far away, little, if any, potential may exist for the building to be impacted by the jet flame. 

Liquefaction of wet biomass streams is done by hydrothermal processes at elevated pressures. The feed stocks for these high pressure liquefaction processes are slurries of biomass particles and water. Feeding these slurries into the high pressure equipment, at reasonable costs, is an important hurdle in the process development. For example, the reported operating conditions for high pressure liquefaction are in the range 280-360 °C and 90-250 bar [25, 26]. Under these conditions, biomass is converted, in a complex sequence of chemical reactions, into various compounds. Upon cooling, the reactor effluent consists of three... 

Oil, gas and watar flow rates and veasel temperature and presaura together with choke sise and upstream cboke pressure at the well pad are monitored by the computer as before. At the end of the test, reports are produced and three point test data In the well file is updated. Because only a single stage separation process at elevated pressure is used, PVT data stored in the computer is used to correct the measured fluid voliones to standard conditions. Production allocation is handled in the same way by using the upstream choke pressure correlation. 

Demir I. (1988) Studies of smectite membrane behavior electrokinetic, osmotic, and isotopic fractionation processes at elevated pressures. Geochim. Cosmochim. Acta 52, 727-737. 

Moisture content, humidity and temperature affecting explosibility characteristics possible drying out of powders when using dry air for pneumatic conveying powders produced/processed at elevated pressures/temperatures affecting explosibility ... 

Because of the complexity of the mechanism of the low- and medium-temperature gas-phase oxidation of rich butane—oxygen mixtures at elevated pressures, there are no works on a detailed kinetic modeling of the process. The mechanism of the low- and medium-temperature oxidation of butane and heavier alkanes at atmospheric pressure has been studied more extensively in connection with the modeling of the self-ignition processes in engines [253—255], to mention only a few. Processes at elevated pressures 9 < P < 11 atm (700 < T < 900 K), but for almost stoichiometric mixtures, 0.8 <

work experimentally identified 22 molecular intermediate products, which gives a clear idea about the level of complexity of the problem. 

Overall comparison between amine and carbonate at elevated pressures shows that the amine usually removes carbon dioxide to a lower concentration at a lower capital cost but requires more maintenance and heat. The impact of the higher heat requirement depends on the individual situation. In many appHcations, heat used for regeneration is from low temperature process gas, suitable only for boiler feed water heating or low pressure steam generation, and it may not be usefiil in the overall plant heat balance. 

The most common heterogeneous catalytic reaction is hydrogenation. Most laboratory hydrogenations are done on liquid or solid substrates and usually in solution with a slurried catalyst. Therefore the most common batch reactor is a stirred vessel, usually a stirred autoclave (see Figure 2.1.1 for a typical example). In this system a gaseous compound, like hydrogen, must react at elevated pressure to accelerate the process. 

Figure 4-6. Ammonia combustion and absorption at air compressor discharge pressure of 3-12 bar (Process 2, elevated pressure), a = medium pressure, 3-6 bar b = high pressure, 6-12 bar, with interceding or booster compressor.

On the other hand, Mary, a research process development engineer, does not consider Joe s system to be inherently safer, because a truly inherently safer system would not require an interlock at all. The process uses flammable materials and operates at elevated pressure. Mary, looking at the entire process, would only consider it to be inherently safer if the flammable materials were eliminated or the process was operated at ambient pressure. Mary is considering the inherent safety characteristics of the entire process, rather than a single interlock system. 

Figure 3.24 Influence of PA-6 polymerization process on relative viscosity as function of reaction time (i) atmospheric in VK column (ii) prepolymerization atmospheric followed by water removal (iii) prepolymerization at elevated pressure followed by water removal.31...

With the growing interest for the polynorbomene, photoresist polymer, and cyclic olefin copolymer, the synthesis norbornene or bicyclo[2,2,l]-2-heptene (NBN) has drawn significant attention because it is one of the most important precursor for these materials. Norbornene is produced by the reaction between ethylene and cyclopentadiene (CPD) via the Diels-Alder condensation process at elevated temperature and pressure [1,2]. 

Partial methane oxidation comprises very high rates so that high space-time yields can be achieved (see original citations in [3]). Residence times are in the range of a few milliseconds. Based on this and other information, it is believed that syngas facilities can be far smaller and less costly in investment than reforming plants. Industrial partial oxidation plants are on the market, as e.g. provided by the Syntroleum Corporation (Tulsa, OK, USA). Requirements for such processes are operation at elevated pressure, to meet the downstream process requirements, and autothermal operation. 

Shaker tube reactors are commonly used for the evaluation of catalysts at elevated pressure. The liquid reactant and powdered catalyst are introduced into a metal or glass ampoule, which is sealed and pressurized to a predetermined level with the gaseous reactant. The ampoule is immersed into a thermostatted liquid and maintained at this temperature for a certain period of time while shaking. Then the reactor is opened and the reaction mixture analysed. Ampoules of ca. 10-100 cm are typically used. The usefulness of data obtained using such reactors for process scale-up is nearly zero due to poor agitation and unknown hydrodynamics in the ampoule. These reactors are, however, very useful for fast screening of catalysts. 

Accelerating Rate Calorimetry. This is a heat-wait-search technique (see Fig. 5.4-62). A sample is heated by a pre-selected temperature step of, typically, 5 C, and then the temperature of the sample is recorded for some time. If the self-heating rate is less than the calorimeter detectability (typically 0.02 "C) the ARC will proceed automatically to the next step. If the change of the sample temj)erature is greater than 0.02 °C, the sample is no longer heated from outside and an adiabatic process starts. The adiabatic run is continued until the process has been completed. ARC is usually carried out at elevated pressure. 

Figure 6.2 shows two process units. Process Unit 1 handles propane vapor at relatively low pressure, while Process Unit 2 periodically handles large volumes of nitrogen gas at elevated pressures. Six buildings are situated in or near the process units. These are ... 

This recommended practice applies to equipment in refineries, petrochemical facilities, and. chemical facilities in which hydrogen or hydrogen-containing fluids are processed at elevated temperature and pressure. The guidelines in this recommended practice can also be applied to hydrogenation plants such as those that manufacture ammonia, methanol, edible oils, and higher alcohols. 

Another approach to scale-up is the use of simplified models with key parameters or lumped coefficients found by experiments in large beds. For example, May (1959) used a large scale cold reactor model during the scale-up of the fluid hydroforming process. When using the large cold models, one must be sure that the cold model properly simulates the hydrodynamics of the real process which operates at elevated pressure and temperature. 

Most investigations of fluidization parameters take place at ambient temperature and pressure. Yet, nearly all processes operate at elevated temperature, and many at elevated pressure. Therefore, it is necessary to know how increasing temperature and pressure affect the operation of fluidized systems. However, the operation of fluidized test facilities at temperature and pressure is much more difficult and costly than operating them at ambient conditions. It is not surprising then that information on how temperature and pressure affect the operation of fluidized beds is not as prevalent as would be desired. However, many researchers have undertaken the difficult task of building and operating units to obtain these badly needed data. The purpose of this chapter is to present what is known about operating fluidized beds at elevated temperature and pressure. 

Processes with gaseous reactants are excluded here. Due to the large compressibility of gases an increase of pressure (up to 1 kbar) leads essentially only to an increase of gas concentration, and hence to an acceleration of bimolecular processes in which gases are involved as reactants. The effect of pressure on a chemical reaction in compressed solution is largely determined by the volume of reaction (AV) and the volume of activation (AV ). It is not the purpose of this chapter to provide a complete survey of reactions of dienes and polyenes which have been investigated at elevated pressures. There are many excellent monographs (e.g. References 1-4) and reviews (e.g. References 5-16) on this topic which cover the literature up to early 1990. After a short introduction into the basic concepts necessary to understand pressure effects on chemical processes in compressed solutions, our major objective is to review the literature of the past ten years. 

There are now examples where products and selectivities that cannot be achieved in conventional solvents can be realized by the use of a SCF. However, as noted above, the high running costs which result from carrying out a process at elevated temperatures and pressure may well preclude their use for many reactions. 

The most frequently used contactors in full-scale waste water ozonation systems are bubble column reactors equipped with diffusers or venturi injectors, mostly operated in a reactor-in-series counter-current continuous mode. Many full-scale ozone reactors are operated at elevated pressure (2-6 barabs) in order to achieve a high ozone mass transfer rate, which in turn increases the process efficiency. 

The discussion above explains why basic information on sorption and diffusion under the reaction conditions, especially at elevated pressures, is required for kinetic and mass- and heat- transfer modelling of catalytic polymerization reactors. If such information is sufficiently available, one should be able, for example, to compare the kinetics of gas-phase and slurry-processes directly by taking into account both gas solubilities in swollen polymers and the hydrocarbons used in slurry processes. 

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