Download - Dehydration
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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