Separation multi-stage

Multi-stage separation may also be constrained by low wellhead pressures. The separation process involves a pressure drop, therefore the lower the wellhead pressure the less scope there is for separation. 

There are two main approaches to its solution. Traditional approach is based on preliminary separation of UGC samples to gaseous and liquid phases and their subsequent analyses [1]. This approach is well-developed and it allows obtaining quite precise results being used properly. However, this method is relatively complicated. Multi-stage procedure is a source of potential errors, then, it makes the analyses quite time consuming. More progressive approach is based on the direct analysis of the pressurized UGC samples. In both cases the determination of heavy hydrocarbons (up to C ) is made by capillary gas chromatography. 

Petroleum products may be treated with various solvents for the removal by selective solubility of undesirable constituents or for the recovery of by-products. The solvent and solute must be separated to yield the desired product and to recover the solvent for reuse. The solvents normally boil at a lower temperature than the products from which they are to be removed and so are generally distilled off as overhead products. The pipe stills used for this service may be single-stage or multi-stage units, depending on the service involved. Some solvents can be removed by the use of steam heated stills. In other cases, the high temperature required necessitates the use of fired heaters and vacuum towers. 

Two-phase flows in micro-channels with an evaporating meniscus, which separates the liquid and vapor regions, have been considered by Khrustalev and Faghri (1996) and Peles et al. (1998, 2000). In the latter a quasi-one-dimensional model was used to analyze the thermohydrodynamic characteristics of the flow in a heated capillary, with a distinct interface. This model takes into account the multi-stage character of the process, as well as the effect of capillary, friction and gravity forces on the flow development. The theoretical and experimental studies of the steady forced flow in a micro-channel with evaporating meniscus were carried out by Peles et al. (2001). These studies revealed the effect of a number of dimensionless parameters such as the Peclet and Jacob numbers, dimensionless heat transfer flux, etc., on the velocity, temperature and pressure distributions in the liquid and vapor regions. The structure of flow in heated micro-channels is determined by a number of factors the physical properties of fluid, its velocity, heat flux on... 

An increase in the amount of solvent gives a greater recovery of solute but produces a more dilute extract. In order to meet the criteria of a reasonable concentrated extract and a high recovery of solute from the raffinate phase, it is best to employ multi-stage countercurrent contacting (as shown in Figure 15). This is the best way of obtaining separations on a continuous flow basis. 

With the above introduction of principles, let us consider some multi-stage separation system flow arrangements on a simplified block diagram basis. A four-stage system with the first stage at about 1000 pel will be assumed, and the notations A, D, C, and D will refer to the oil separation stages. 

The extraction, in combination with fractional separation of extracts in a multi-stage separation system, results in high-quality volatile oils [42,44]. Recently, this fractional separation technique has been refined by Reverchon and co-workers for selective precipitation of cuticular waxes and volatile oils [43,56],... 

Methane/water preheating B - Syngas cooling/CO oxidation/WGS Fuel/air preheat E Flue gas cooling Multi-stage reforming HMD Combustion V separator... 

The solution to a multi-component, multi-phase, multi-stage separation problem is found in the simultaneous or iterative solution of the material balances, the energy balance and the phase equilibrium equations (see Chapter 1). This implies that a sufficient number of design variables are specified so that the number of remaining unknown variables exactly equals the number of independent equations. When this is done, a separation process is said to be specified. 

Several papers have since focused on either reaction-separation-recycle processes (Verykios and Luyben 1978, Denn and Lavie 1982, Luyben 1993a, Scali and Ferrari 1999, Lakshminarayanan et al. 2004) or individual multi-stage processes (Kapoor et al. 1986) and have shown that recycle streams can slow down the overall process dynamics (described by a small number of time constants) compared with the dynamics of the individual units, and may even lead to the recycle... 

In order to generalize the discussion of the process structures discussed in Chapters 3 and 4, let us consider the class of processes in Figure 5.1. This generic structure consists of S + 1 units and a single recycle loop that includes units 1,..., S. One (multi-stage) separator is present and we denote by S the part of the separator that is included in the recycle loop, and by S + 1 the part that is... 

There are several characteristics common to the describing equations of all types of multicomponent, vapor-liquid separation processes, both single- and multi-stage, that make it possible to exploit the inside-out concept in similar ways to solve them efficiently and reliably. The equations have as common members component and total mass balance, enthalpy balance, constitutive and phase equilibrium equations. In addition, all such processes require K-value or fugacity coefficient and vapor and liquid enthalpy models. In all cases the describing equations have similar forms, and depend on the primitive variables (temperature, pressure, phase rate and composition) in essentially the same ways. Before presenting the inside-out concept, it will be useful to identify two classes of conventional methods and discuss their main characteristics. 

The hydrocracker simulator was also converted to subroutine form for inclusion in the nonlinear programming model of the Toledo process complex. The subroutine was considerably simplified, however, to save computer time and memory. The major differences are (1) the fractionation section is represented by correlations instead of by a multi-stage separation model, (2) high pressure flash calculations use fixed equilibrium K-values instead of re-evaluating them as a function of composition, and (3) the beds in each reactor are treated as one isothermal bed, eliminating the need for heat balance equations. 

New spatial forms of carbon - fullerenes, nanotubes, nanowires and nanofibers attract significant interest since the time of their discovery due to their unique physicochemical and mechanical properties [1-3]. There are three basic methods of manufacturing of the carbon nanomaterials (CNM) - laser evaporation, electric arc process, and catalytic pyrolysis of hydrocarbons. However, the multi-stage manufacturing process is a serious disadvantage for all of them. For example, the use of organic solvents (benzol, toluene, etc.) for separation of fullerenes from graphite soot results in delay of the synthesis process and decrease in the final product quantity. Moreover, some environmental problems can arise at this. 

In the activated sludge process, single- or multi-stage continuous-flow aerated reactors are used (Fig. 4). Effluent from the bioreactor is separated in a settling tank and a portion of sedimented sludge is usually recycled to the reactor providing a continuous sludge inoculation. 

The quantitative determination of individual isomers of tram-18 1 fatty acids in milk fat is not straightforward. It involves a multi-stage analytical procedure (i.e., transesterification of milk fat, argentation TLC of the fatty acid esters to separate the civ-isomers and tram-isomers, followed by capillary GC). This method gives an almost complete separation of the 13 individual tram-18 1 isomers, from A4 to A16 (Precht and Molkentin, 1996). 

The most important isotope separation processes developed to date for tonnage production have been multi-stage processes. There are a significant number of design and operating variables which affect the... 

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