Liquid carryover

The total volume must be sufficient to hold the estimated amount of liquid carryover from the reactor. For a foamy discharge. 

Problem A knockback condenser mounted on a C3 splitter reflux drum exhibited liquid carryover (as evidenced by the vent line icing-up). This indicated product loss from liquid caixying over rather than dripping back into the reflux drum. Also the vent line metallurgy would not withstand the cold temperatures produced. 

The ejector is widely used as a vacuum pump, where it is staged when required to achieve deeper vacuum levels. If the motive fluid pressure is sufficiently high, the ejector can compress gas to a slightly positive pressure. Ejectors are used both as subsonic and supersonic devices. The design must incorporate the appropriate nozzle and diffuser compatible with the gas velocity. The ejector is one of the ( to liquid carryover in the suction gas. 

The use of drums for compressors was discussed earlier in the chapter. At that time, the recommendation was made that the drum be dry. This is still the prime consideration. However, if liquid carryover must be a way... 

The hazards of liquid carryover and the need for suction drums... 

Vapor-liquid separators (drums) are used to separate a liquid from a vapor-liquid stream with a minimum of liquid carryover. The separator size is determined by the vapor velocity which depends on the entrainment method used. The working equation is ... 

Fisher, S. A., and D. L. Pearce, 1993, An Annular Flow Model for Predicting Liquid Carryover into Austenitic Superheaters, Int. J. Multiphase Flow 19 295 307. (3)... 

The total volume must be sufficient to hold the estimated amount of liquid carryover from the reactor or process vessel. For a foamy discharge, the holding volume should be greater than the reactor or process vessel volume (to be discussed below). 

It is usually very important to design separation equipment for the maximum flow rate of both gas and liquid rather than a 24-hour average rate. Only when the maximum possible rate is of a short duration, infrequent, and the application will allow occasional liquid carryover, can equipment be designed for less than the maximum instantaneous flow rate. 

The separator would be handling approximately 420 tons/day of a turbulent mixture of oil and gas. It separates this mixture into a stream of essentially pure gas and a stream of essentially pure liquid. The widely used oilfield separator performance guarantee of a maximum liquid carryover of 0.1 gal of liquid per MMSCF of gas allows a maximum of about 10 parts of liquid carried over per million parts of material handled. This is also approximately equivalent to the loss of a I-lb chunk of coal fcom a 100,000-1b railway car filled with coal. 

The same separator could be placed in service where only 10 gal of liquid/MMSCF of gas entered the vessel with all liquid being particles having a diameter less than 10 microns. If the separator removed 7.4 gal/MMSCF, the removal efficiency would be 75 per cent and the liquid carryover would be 2.5 gal/MMSCT of gas... 

The usual separator design criteria of a maximum liquid carryover of... 

Flooding is an excessive accumulation of liquid inside a column. Flood symptoms include a rapid rise in pressure drop (the accumulating liquid increases the liquid head on the trays), liquid carryover from the column top, reduction in bottom flow rate (the accumulating liquid does not reach the tower bottom), and instability (accumulation is non-steady-state). This liquid accumulation is generally induced by one of the following mechanisms. 

MORE THAN Liquid Carryover 13. The entrainment device ineffective. Condensation in down- stream lines (corrosion). Replace entrainment device. ... 

What if liquids carryover from upstream knock-out vessel to flare ... 

A demister is sometimes installed at the top of the scmbber ahead of the vacuum unit, to reduce liquid carryover of small oil droplets, which would otherwise end up in the water from the barometric condenser or in the condensate from the cold (or dry) condensers. 

Absorption takes place in either staged or plate towers or continuous or packed contactor. However, in both cases the flow is continuous. In the ideal equilibrium stage model, two phases are contacted, well mixed, come to equilibrium, and then are separated with no carryover. Real processes are evaluated by expressing efficiency as a percentage of the change that would occur in the ideal stages. Any liquid carryover is removed by mechanical means. 

Vertical liquid-vapor separators are used to disengage a liquid from a vapor when the volume of liquid is small compared with that of vapor volume. The maximum allowable vapor velocity in a vertical separator that reduces the liquid carryover is dependent on the following ... 

The second type of false-positive result can occur at the detection stage, e.g., when the liquid-transfer device pipets a strong positive sample followed by a negative sample. Because a typical PCR reaction can produce 10 -1012 molecules of amplified DNA in a 100-pl reaction and a radioactive probe can detect about 107 molecules, it is necessary to limit liquid carryover to less than 0.001-0.01 pi (Table 2). Such levels are possible with available automated pipeting devices, but manual pipeting should employ positive-displacement pipets or tips that prevent aerosols from contaminating the device. 

The durability of SPC structures in aggressive environments depends on the diffusion rate of chemically active reagents into a material. Fluid penetration is realized through imperfections in molecular packing of the binder and it is accelerated at an increase of temperature and pressure. In this connection, definition of a diffusion coefficient (as a key parameter of a liquid carryover) becomes the important problem. 

A vertical vessel (drum), as shown in Fig. 7.1, can be used to separate vapor from liquid following equilibrium flash vaporization or partial condensation. A reasonable estimate of the minimum drum diameter Dr, to prevent liquid carryover by entrainment can be made by using (13-7) in conjunction with the curve for 24-in. tray spacing in Fig. 13.3 and a value of Fha = 10 in (13-5). To absorb process upsets and fluctuations and otherwise facilitate control, vessel volume Vv is determined on the basis of liquid residence time t, which should be at least 5 min with the vessel half full of liquid. Thus... 

Excessive flow through a relief valve caused major liquid carryover, either due to flooding or due to gas lifting. The liquid caused a mess in the vent header. 

Washing may pick up debris resting in the column piping and deposit them inside the column or distributors. In one case (203), a welding rag lodged in a reflux distributor led to excessive liquid carryover from a column. The rag was transported by water from the column piping into the reflux distributor, where it remained stuck. 

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