Condensate stabilizers reflux with

A condensate stabilizer with reflux will recover more intermediate components from the gas than a cold-feed stabilizer. However, it requires more equipment to purchase, install, and operate. This additional cost must be justified by the net benefit of the incremental liquid recovery, less the cost of natural gas shrinkage and loss of heating value, over that obtained from a cold-feed stabilizer. 

The tower operates in the same manner as a condensate stabilizer with reflux. The inlet liquid stream is heated by exchange with the gas to approximately 30 F and is injected in the tower at about the point in the tower where the temperature is 30 F. By adjusting the pressure, number of trays, and the amount of reboiler duty, the composition of the bottoms liquid can be determined. 

The need to obtain greater recoveries of the C2, C3, and C/s in natural gas has resulted in the expanded use of low-temperature processing of these streams. The majority of the natural gas processing at low temperatures to recover light hydrocarbons is now accomplished using the turboexpander cycle. Feed gas is normally available from 1 to 10 MPa. The gas is first dehydrated to a dew point of 200 K and lower. After dehydration the feed is cooled with cold residue gas. Liquid produced at this point is separated before entering the expander and sent to the condensate stabilizer. The gas from the separator is expanded in a turboexpander where the exit stream can contain as much as 20 wt % liquid. This two-phase mixture is sent to the top section of the stabilizer which separates the two phases. The liquid is used as reflux in this unit while the cold gas exchanges heat with the fresh feed and is recompressed by the expander-driven compressor. Many variations to this cycle are possible and have been used in actual plants. 

A total reflux startup is best performed with a mixture whose composition resembles the feed composition. Alternatively, total reflux operation can be carried out using one or more of the feed components. The column, reboiler, condenser, and reflux system are stabilized at... 

At the lop of the tower any intermediate components going out with the gas are condensed, separated, pumped back to the tower, and sprayed down on the top tray. This liquid is called reflux. and the two-phase separator that separates it from the gas is called a reflux tank" or reflux drum. The reflux performs the same function as the cold feed in a cold-feed stabilizer. Cold liquids strip out the intermediate components from the gas as the gas rises. 

Absorber oil then flows to a still where it is heated to a high enough temperature to drive the propanes, butanes, pentanes and other natural gas liquid components to the overhead. The still is similar to a crude oil stabilizer with reflux. The closer the bottom temperature approaches the boiling temperature of the lean oil the purer the lean oil which will be recirculated to the absorber. Temperature control on the condenser keeps lean oil from being lost with the overhead. 

The containers are held at the required test temperature by placing in a single cabinet oven. For tests at temperatures considerably below the boiling point of the liquid, the container is simply stoppered, but for temperatures near the boiling point the container can be fitted with a reflux condenser to minimise evaporation. The standard notes the need to stir the liquid and/or replace it at intervals depending on its stability. 

A great many assumptions have been made in this qualitative approach. Little account has been taken of the dynamics of the plant at this stage and the stability of xD in the face of changes (perturbations) in xF. The plant may be affected by ambient conditions, e.g. a sudden shower of rain will have a cooling effect which will cause vapour rising in the column to condense and increase the column internal reflux a long reflux line can lead to considerable degradation of the control (see Section 7.6). However, even with this simplistic approach, it is possible to examine a number of the control problems associated with the plant. 

Distillation with vapor product. When a partial condenser is used, the flash drum plays the role of a vapor/liquid separator. In the setup known as a stabilizer there is only vapor distillate, while the liquid is returned as reflux. The column has a pasteurization section when a gaseous stream leaves at the top, while the... 

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