Inlet streams

Impingement demister systems are designed to intercept liquid particles before the gas outlet. They are usually constructed from wire mesh or metal plates and liquid droplets impinge on the internal surfaces of the mist mats or plate labyrinth as the gas weaves through the system. The intercepted droplets coalesce and move downward under gravity into the liquid phase. The plate type devices or vane packs are used where the inlet stream is dirty as they are much less vulnerable to clogging than the mist mat. 

In a gas flotation unit, air is bubbled through oily water to capture oil particles which then rise with the bubble to form a scum at the surface of the flotation unit. The scum can be removed by rotating paddles. Chemicals are often added to destabilise the inlet stream and enhance performance. 

Hydrocylones have become common on offshore facilities and rely on centrifugal force to separate light oil particles from the heavier water phase. As the inlet stream is centrifuged oil particles move to the centre of the cyclone, coalesce and are drawn off upwards, while the heavier water is taken out at the bottom. 

Much as reverse osmosis (qv) can compete with evaporation in desalination appHcations, osmosis should also be considered as an alternative for process evaporation. Reverse osmosis is particularly attractive where the inlet stream is greater than 99% water. 

Open-Loop versus Closed-Loop Dynamics It is common in industry to manipulate coolant in a jacketed reacdor in order to control conditions in the reacdor itself. A simplified schematic diagram of such a reactor control system is shown in Fig. 8-2. Assume that the reacdor temperature is adjusted by a controller that increases the coolant flow in proportion to the difference between the desired reactor temperature and the temperature that is measured. The proportionality constant is K. If a small change in the temperature of the inlet stream occurs, then depending on the value or K, one might observe the reactor temperature responses shown in Fig. 8-3. The top plot shows the case for no control (K = 0), which is called the open loop, or the normal dynamic response of the process by itself. As increases, several effects can be noted. First, the reactor temperature responds faster and faster. Second, for the initial increases in K, the maximum deviation in the reactor temperature becomes smaller. Both of these effects are desirable so that disturbances from normal operation have... 

O As subscript, referring to inlet stream Y Cumulative fraction by weight undersize ... 

A sample CFSTR of volume V[ has one inlet stream rate u, eontaining A at eoneentration seeond inlet stream of rate... 

Fig ure 8-4. Charaoteristio distribution of residenoe time, whioh is equivalent to age distribution of the inlet stream. 

The method uses the dnft-fhix level swell calculation models to take into account there being more vapor in the inlet stream to relief device than average for the vessel. 

Figure 5-1 shows a typical LTX process. The inlet gas stream is choked at the well to 2,000 to 3,000 psi or until the temperature declines to approximately 120°F, which is well above the hydrate formation temperature. The inlet stream next enters a coil in the bottom of the low temperature separator. The stream is then cooled to just above the hydrate formation temperature with the outlet gas coming off the low temperature separator. This assures the lowest possible temperature for the inlet stream when it enters the vessel after the choke. This choke is mounted in the vessel itself. When the pressure drop is taken, the temperature will... 

Figure 6-4 shows the cold feed distillation tower of Figure 6-3. The inlet stream enters the top of the tower. It is heated by the hot gases bubbling up through it as it falls from tray to tray through the downcomers, A flash occurs on each tray so that the liquid is in near-equilibrium with the gas above it at the tower pressure and the temperature of that particular tray.

There are many processes used in tail-gas treating. The Sulfreen and the Cold Bed Absorption (CBA) processes use two psirallel reactors in a cycle, where one reactor operates below the sulfur dew point to absorb the sulfur while the second is regenerated with heat to recover molten sulfur, tiven though sulfur recoveries with the additional reactors are normally 99-99.5% of the inlet stream to the Claus unit, incineration of the outlet gas may still be required. 

The SCOTT process uses an amine to remove the HjS. The acid gas off the amine still is recycled back to the Claus plant. Other types oi processes oxidize the sulfur compounds to SO2 and then convert ihc SO to a secondary product such as ammonium thiosulfate, a fertilizer. These plants can remove more than 99.5% of the sulfur in the inlet stream to the Claus plant and may eliminate the need for incineration. Costs of achieving this removal are high. 

If a very lean glycol is required, it may be necessary to use stripping gas. A small amount of wet natural gas can be taken from the fuel stream or contactor inlet stream and injected into the reboiler. The stripping gas can be taken from the fuel stream or the contactor inlet stream and injected into the reboiler. The leaness" of the gas depends on the purity of the wet glycol and the number of stages below the reconcentrator. The stripping gas is saturated with water at the inlet temperature and pressure conditions. but adsorbs water at the reboiler conditions of atmospheric pres-... 

These are higher than for a lean oil plant. It is possible to recover a small percentage of ethane in a refrigeration plant. This is limited by the ability to cool the inlet stream to no lower than -40°F with normal refrigerants. 

The de-butanizer works in a similar manner. The upstream tower (depropanizer) determines the maximum vapor pressure of the butane product. If the concentration of propane-minus is too large in the inlet stream, the vapor pressure of the butane overheads will be too high. Similarly, the concentration of pentanes-plus in the butane will depend upon the... 

The first technique is to draw an envelope with the reactor effluent as the inlet stream and the product flows as the outlet streams. Stream.s from other units must be included. The flow rates and compositions of the entering and leaving streams are then totaled. The net is the rciictor effluent. This is the method practiced by most refiners. 

Mass of water at inlet streams is equal to mass of water at the filterate and filter cake. 

The sum of water at the inlet stream and water generated by the chemical reaction is equal to water at outlet stream. 

Diffusion effects can be expected in reactions that are very rapid. A great deal of effort has been made to shorten the diffusion path, which increases the efficiency of the catalysts. Pellets are made with all the active ingredients concentrated on a thin peripheral shell and monoliths are made with very thin washcoats containing the noble metals. In order to convert 90% of the CO from the inlet stream at a residence time of no more than 0.01 sec, one needs a first-order kinetic rate constant of about 230 sec-1. When the catalytic activity is distributed uniformly through a porous pellet of 0.15 cm radius with a diffusion coefficient of 0.01 cm2/sec, one obtains a Thiele modulus y> = 22.7. This would yield an effectiveness factor of 0.132 for a spherical geometry, and an apparent kinetic rate constant of 30.3 sec-1 (106). 

CHENOWETH and Martin 20,21 1 have presented an alternative method for calculating the drop in pressure, which is empirical and based on experiments with pipes of 75 mm and pressures up to 0.7 MN/m2. They have plotted the volume fraction of the inlet stream that is liquid as abscissa against the ratio of the two-phase pressure drop to that for liquid flowing at the same volumetric rate as the mixture. An alternative technique has been described by Baroczy 22). If heat transfer gives rise to evaporation then reference should be made to work by Dukler et al 23). 

Finch at (28), show three "stratifying polymerizers" rather than the design combinations described earlier by Ruffing et al (27). The reactors operate at inlet and outlet temperatures respectively of 120 to 135°C, 135 to 145°C, and 145 to 170 C. The first reactor effluent contains 18 to 20% polystyrene and a portion of this stream is recirculated back to the reactor inlet such that the inlet stream polystyrene concentration is as high as 13.5%. This recirculation is claimed to improve rubber phase particle size control and end use properties. 

Continuous Model "C0NGAS". This model predicts performance of an ideal continuous wellstirred polyreactor. The model system consists of a continuous backmix reactor in which the total powder volume is held constant. There are four inlet streams 1) Makeup of pure propylene, 2) Catalyst feed, 3) Hydrogen feed, and 4) Recycle. The single effluent powder stream is directed through a perfect separator that removes all solids and polymer and then the gases are recycled to the reactor. The makeup propylene is assumed to disperse perfectly in the well-mixed powder. 

There are only two possible values for concentration in a CSTR. The inlet stream has concentration and everywhere else has concentration The reaction rate will be the same throughout the vessel and is evaluated at the outlet concentration, SIa = A(ctout,bout, ) For the single reactions considered in this chapter, continues to be related to by the stoichiometric coefficient and Equation (1.13). With SS a known, the integral component balance, Equation (1.6), now gives useful information. For component A,... 

The method of false transients begins with the inlet stream set to its steady-... 

We turn now to the issue of material balance closure. Material balances can be perfect when one of the flow rates and one of the components is unmeasured. The keen experimenter for Examples 7.1 and 7.2 measured the outlet concentration of both reactive components and consequently obtained a less-than-perfect balance. Should the measured concentrations be adjusted to achieve closure and, if so, how should the adjustment be done The general rule is that a material balance should be closed if it is reasonably possible to do so. It is necessary to know the number of inlet and outlet flow streams and the various components in these streams. The present example has one inlet stream, one outlet stream, and three components. The components are A, B, and I, where I represents all inerts. 

This heat balance contains two terms not seen before mgCR represents the mass times specific heat of the agitator and vessel walls and q represents the energy input by the agitator. Although the model is nominally for constant physical properties, Vermeulen and Fortuin found a better fit to the experimental data when they used a slightly different specific heat for the inlet stream (Cp), . 

The use of Equation (15.40) is limited to closed systems like that illustrated in Figure 15.10(a). Measurement problems arise whenever /), > 0 or Dgut > 0. See Figure 15.10(b) and suppose that an impulse is injected into the system at z = 0. If Din > 0, some of the tracer may enter the reactor, then diffuse backward up the inlet stream, and ultimately reenter. If Dgut > 0, some material leaving the reactor will diffuse back into the reactor to exit a second time. These molecules will be counted more than once by the tracer detection probes. The measured response function is not f t) but another function, g i), which has a larger mean ... 

The conservation of energy, however, differs from that of mass in that energy can be generated (or consumed) in a chemical process. Material can change form, new molecular species can be formed by chemical reaction, but the total mass flow into a process unit must be equal to the flow out at the steady state. The same is not true of energy. The total enthalpy of the outlet streams will not equal that of the inlet streams if energy is generated or consumed in the processes such as that due to heat of reaction. 

The inlet stream (5) will be taken as having the same composition as the reactor outlet stream (4). 

As a first trial, assume that all the water in the inlet stream is condensed, then ... 

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