introductionsince today customers of condensate required a stable and sweet product

8/10/2019 Introductionsince Today Customers of Condensate Required a Stable and Sweet Product

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Introduction since today customers of condensate required a stable and sweet product. The

gasoline produce by modern plant process must meet established pipeline and marketing

standards. Stabilization of condensate therefore refers to the stripping of the light ends”

contents (c1,c1) from the raw liquids and the removal of all acidic constituents to produce a

suitable produc for ht market.

PURPOSE

The process delivered a net stabilize liquid product consisting of pentaes and heavier

hydrocarbon, basically sweet of free of any sulfur compouds. In general condensate

stabilization carryover several functions, which are as,

To increase the recovery of C1,2 and LPG products,

To lower the condensate vapors pressure and therefore the evaporation losses while the

product is in storage and shipment.

To sweeten the product in order to meet the required specifications.

The removal of c1 2 3 from the stream and reduction of butane content increases the

production of sales gas. Table 3.9 indicates . In addition stabilization reduces the vapor pressure

of the finished condensate and makes it suitable for storage blending and transportation

purposes. Moreover its sweeten the raw liquids entering the plant by removing h2s and co2.

Stabilization process

Stabilization of condensate stream can be done with

Flash vaporization

Fractional principle.

Flash vaporization , some gas plant stabilizes the recovered condensate by flash vaporization or

simply by flashing. The process is similar to stage separation utilizing the equilibrium principles

between the vapor and liquids. Equilibrium vaporization occurs when the vapor and liquid

phases are in equilibrium at the final temp and press of separation. Stabilization by flashing is a

simple operation employing only two or three flash tanks.

Stabilization by fractionation.

Stabilization by fractionations a detail process , very popular in the industry precise enough to

produce liquid of suitable vapor pressure.



During the operation not only the methane 2 3 and most of the butanes are removed and

recovered but constituents such as h2s, co2. The finish product from the bottom of the column

is composed mainly of pentanes and heavier with small amount of butanes. The process

actually makes a cut between lightest liquids lights components(pentanes) and heavies gas

butanes. The bottom product is thus a liquid from of all gases component able to be storesafely at atmospheric pressure.

Stabilization by fractionation is a modern operation and economically attractive process. It is a

single tower process since only one specification product is required. The bottom product of

the column is capable of meeting any king of rigid specification with the proper attention to

liquid feed and operating conditions.

Stabilization equipments.

The main units in condensate stabilizations are

Stabilizer feed drum

Stabilizing tower

Tower reboiler

Tower reflux equipment

Heat exchanger, pump. Instrument and others.

The stabilizer feed drum is a large cylindrical horizontal. Steel vessel with a water leg, built inthe bottom to drain off the water. This drum also called stabilizer flash drum, is design to

provide sufficient holding time to settle the flow surges from the inlet separators and to give

adequate settling time for the water wash desalting operation. Since this tank operates at a

much lower pressure than the inlet pressure, it actually stabilizes the stream partially by

flashing off a large amount of lighter components.

The stabilizer tower is a vertical vessel design to provide the necessary space, time and means

for the is looks like Fractionator as shown in fig. The column is divided in to two sections , the

top or the rectifying section which includes all the trays above the feed tray, and the lower

section or stripping section which contains all the trays below the feed tray. The stabilizer can

be a packed tower “ packed with a specific design of packing material , or can be a bubble cap

tower equip with trays and bubble caps.

The stabilizer reboiler which supplies heat to the tower can be a steam reboiler, a directly fired

heater of indirectly fired unit. The liquid at the bottom of the tower can also be heated by

means of steam coils located inside the tower. The conventional shall and tube type of



reboiler uses high temp stream to provide the required heat to the tower. Figure 3.25 shall and

tube type

The stabilizer reflux equipment provides the necessary reflux in the operation of the tower if

the system involves a refluxed column,. The reflux unit consists of the tower head condenser ,

the reflux accumulator and the reflux pumps. Reflux is that parts of liquid product from the

over head condenser which is return to top of the tower stabilizer. In the case of condensate

stabilizer all condensed over head vapors are refluxed. The over head condenser can be coil

type cooled by the spray of water or shall and tube type as shown in fig 3.26

The reflux accumulator serve as a settling tank for the condensed stabilized gasoline and surge

tank for the reflux pumped back to the tower. The tank is equipped with several cut lets such

as to relief to flare, supply to stabilizer, overhead sour vapor or bottom drains.

The heat exchanger is an item of equipment which contributes more to the economy of the

system than any other by recovering heat and transferring it to the stabilizer feed. Is consist of

the shall and a bundle of tubes which fit into the shall. Thus allowing the hot and cold fluids

approximate each other. The cold fluid usually flow inside the tubes which the hot fluids flow in

the shall around the tube.

Control Equipments:-

Instrumentation and control equipments provides means OF controlling and guiding the

process to produce specification finish products. Accurate control of temp press and flow is of

great importance in the operation of the stabilizer unit as well as in other fractionation systems.

Variation in stabilizer press should not be more than a few pounds per square inch and the

temp of the feed should be kept at constant as possible. Most significant is the bottom temp

which in directly controls the pressure.

Process Flow description.

The condensatesate stabilization process is shown in fig no 4.26. the raw condensate from the

inlteseparator flows to the feed drum where its pressure is drastically lowered to a level to

alevel depending on a grade of gasoline desired. In the feed ( fLash drum) the water is dropped

out and collected in the water leg in the ottom of the tank.

The pressure temp condition in the flash drum vary with palnt design. The process shown in fig

3037 operates on the pressure on three hundred psig controlled by the back pressure

controller. At this pressure some light ends are vaporized and pass on to the low pressure gas

sweetening contactor at about 50F.



The condensate level in the flash drum is controlled by a level controller. The streM after

leaving the flash drum at about 50 F is pumped through the stabilizer feed bottom heat

exchanger where its temperature is increased to 200 to 250 F. it enters the stabilizer toer next

at appropriate feed tray, depending on the design and flow downward mixing with the out

vapors generated in the reboiler.

In the stabilizer the liquid is stripped of the excess light ends at its flows downward to the

bottom of the tower. It over flows from the bottom tray and ---runs into the seal chamber in

the enlarge lower section of the tower. This section is the reserved for the reboiler circulating

pump. The adjacent pump well provide suction to the finish product pump which forces the

gasoline throught the heat exchanger, through another cooler and on to the storage.

The reboiler pump discharges liquid to the reboiler where part of the liquid is vaporized. The

vapor liquid mixture from the reboiler return to the stabilizer above the sel chamber in the

bottom of the tower. The reboiled liquid falls into the seal chamber where the vapor ascendingis mixed with descending feed in the tower.

The chamber arrangement at the lower section of the stabilizer prevents the loss of section of

the reboiler pump, also the level control in the adjacent pump excludes the possibilities of

blowing hot high pressure vapor into the condensate product storage tanks. Although the

seal chamber is normally flooding an upset sudden change of load could possibily result in

losing the levl and vapor locking the pumps.

Vapor from the top the tower is cooled and partially condensated in the stabilizer over head

condenser. The condenser outlet mixture is separated in the reboiler accumulator and theliquid is pumped back to the top of the tower as reflux under level control. The over head

vapor from the reflux drum are preheated to prevent formation of liquid hydrocarbons and

then flow through a back pressure controller to the lower pressure contactor. A connection is

usually provided to the flare the vapor from the accumulator id such a necessity arises. A

water drain in the tank is provided to drain any water that may have acculmted there.

The stabilizer may be either a non reflux tower or a refluxed one depending the finished

product desired.

The non refluc column is simple and not so efficient in the operation one degree of controlover the tower has been lost. Non reflux stabilizer are designed to handle rather small

voulumes of liquids at failrly low tem pres conditions.

The refluxed stabilizer , modern gaspalnts employ refluxed type stabilizer in an effort to

produce specifications ecaonomically. The tion products e



Th botton temp of the stabilizer control th e amount of butane present in the liquid and

therefore operating temp will be a function of of the vapor pressure required for the stabilized

condensate. The heat load is the function of the amount of heavy hydrocarbon liquid fed to

the stabilizer.

Stabilizer pressure temp condition are shown below.

Checking the process.

In stabilizer column and similar equipments it is dsiredable to check the performance of the

process and assess the correct operating procedure. The test carried out usually depend on

the finished product desired. Type of process composition of feed etc , generally the stabilizer

operation is best check by anylysing the end product . gasoline test run at the palnt lab may

include the following.

Reid vapor pressure,,

Specific duesity

Corrosivity

The reid vapor pressure determines the vapor pressure of the products in psia at a specified

temperature usually 100 F. the sample is tested in a apparatus called a reid vapor

pressurebomb and the reading may be converted to pounds or ounces per square inches of

water or murcary or appropriate preesure. Product reid vapor pressure at 100 f range from 10 -

34 psia per cent gasoline evaporation at 140F ranges from 25-85. At 275F percent evaporation

f gasoline should not be less than 90.

Specific gravity expresses the character of gasoline, as to the amount it is lighter than equal

volume of ditilled water at 60F. it is measured by an instrument called a hydrometer, which

actually determines density of the condensate.

Corrosivity and sufur content test are taken to deteck the presence of free sulpur in gasoline

regarded as the major corrosive agent. This is to protect brass or coopper gaS carrying parts

and avoid formation of deposites and possible stippoges of product flow the “COPPER STRIPPED

METHID” is used for the which determines the discoloration.

Condensate HANDLING

The stabilizer liquid from the bottom of the tower after cooling down in the bottom heat

exchanger flows to the storage area, the condensate storage facilitate of a typical plant usually



consist of the “off spec” tank and the “on spec tank” the on spec tank is normally opened to the

palnt product and to the sondensate loading pumps, and merely act as a surge vessel. The off

spec tank act as a storage for distillate that has to many light ends or too high vapor pressure.

The off spec is either recycled to the stabilizer for processing or slowly blended into the suction

of the loading pump.

Figyre 3.38 illustrate the diagrame of condensate storage facility together with pumping and

loading terminal. The loading pumps are used either to pump distillate to the truck or railway

terminals or the unload propane makeup from truck they are started maunuallly.

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introductionsince today customers of condensate required a stable and sweet product

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