DEHYDRATION SYSTEMS…

BYN.SAM NAVEEN ASIR

B.TECH(PRPC)2011307028

WHY DEHYDRATION ???Water (H2O) is a highly undesirable component in

natural gas or fuel streamsWater (vapour form) becomes liquid at low

temperature (or) high pressureSuch a liquid formation could affect the

transportation of natural gas through pipelinesPossibility of formation of gas hydrates ( CH4.7H2O)which can lead to blockage of

pipelines.*Water reduces the heating value of natural gas*water causes corrosion along with CO2 and H2S.

GAS HYDRATES STRUCTURE

DETERMINATION OF WATER CONTENT IN NATURAL GASWater content is indirectly determined by

calculating the dew point of the stream.Dew point is the temperature at a given

pressure where a hydrocarbon rich stream like natural gas will start to condense out of the gaseous phase

The difference in dew point temperature of a water saturated gas stream and the pure hydrocarbon stream will give the dew point depression.

Thus the amount of water in natural gas stream can be determined.

DEHYDRATION METHODS..DEHYDRATION BY COOLING

DEHYDRATION BY ADSORPTION

DEHYDRATION BY ABSORPTION

GLYCOL DEHYDRATION PROCESS

DEHYDRATION BY COOLINGThe ability of natural gas to contain water

vapour decreases as the temperature is reduced.

The process is based on the simple principle (cooling) due to which water vapour undergoes a phase change due to low temperature and becomes a liquid

After converting considerable amount of water vapour into liquid, A natural gas stream containing very less amount of water vapour is obtained.

The process is carried out with the help of compressors.

GAS COMPRESSORSGas compressors are partial dehydrators

Due to increase in pressure ,The stream is cooled and water vapour is removed

Uses Ethylene Glycol to cool the inlet stream

DEHYDRATION BY ADSORPTIONAdsorption is the adhesion of atoms, ions,

or molecules from a gas, liquid, or dissolved solid to a surface.

Natural gas containing water vapour is fed into adsorption columns containing DESICCANTS.

A desiccant is a hygroscopic substance that induces or sustains a state of dryness (desiccation) in its vicinity.

Examples of commonly used desiccants are activated charcoal, calcium sulfate, calcium chloride,  silica

ADSORPTION PROCESSStep one: DEHYDRATION , with the help of

desiccant bed in absorption tower.Step two: REGNERATION , heats up the

natural gas stream and creates turbulence, thus enhancing the surface area of contact

Step three: COOLING, Due to cooling, the water vapour condenses and thus can be sent to the absorber.

Step four:, The impurities like H2S,CO2 can be removed. SCRUBBING

TYPICAL SOLID DESICCANT DEHYDRATION PLANT-

ADVANTAGES OF DESICCANT DEHYDRATION

DEHYDRATION BY ABSORPTION absorption is a physical or chemical phenomenon or

a process in which atoms, molecules, or ions enter some bulk phase – gas,liquid, or solid material

Liquid DESSICANTS are used in this processThe commonly used dessicants are glycols like

Ethylene Glycol , Diethylene Glycol, Triethylene Glycol.

Glycols are more effective than solid desiccantsDew point depression is 40 to 140 Fahrenheit, gas

pressure ranging between 25 to 2500 psig and operating temperature is 40 to 160 degree Fahrenheit

DEHYDRATION BY GLYCOL PROCESS

CONTD….

Contd….

TYPICAL GLYCOL DEHYDRATOR

ADVANTAGES

DISADVANTAGESSUSPENDED PARTICLES (DUST, IRON

OXIDE)Over heating of solutionsSludges on heating surfaces causes loss of

efficiencyFoamingLeakage of vent gasesViscosity of Glycol

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