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NATURAL GAS DEHYDRATION:ADSORPTIONCAROLINA BELTRN SERRANOJENNY KATHERINE CARRILLOFABIAN ANDRES TAPIAS

GAS ENGINEERINGGROUP:D1UNIVERSIDAD INDUSTRIAL DE SANTANDERPETROLEUM ENGINEERING SCHOOLBUCARAMANGA, 2015

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Due to the amount of water containing gas is a need to undergo a dehydration process, which is defined as the process of removing water vapor that is associated with the gas.INTRODUCTION

Debido a la cantidad de agua que contiene el gas es necesario someterlo a un proceso de deshidratacin, el cual se define como el proceso de remover el vapor de agua que est asociado al gas. El vapor de agua es probablemente la impureza ms comn en un flujo de gas. Este proceso cobra mayor importancia en campos donde se manejan altas presiones (1). Las principales razones para remover el vapor de agua del gas natural son las siguientes (2), (3): El agua lquida y el gas natural pueden formar hidratos que taponan los equipos y tuberas (4) El agua lquida del gas natural es corrosiva principalmente si contiene CO2 y H2S (5) El vapor de agua del gas natural puede condensarse en las lneas llegando a causar taponamiento Para optimizar el funcionamiento de los compresores Para cumplir con la calidad exigida para su transporte en tuberas y comercializacin (6), (7). 2It's necessary to dehydrate the gas for:They may stop the gas flow by pipelines. The formation always takes place when the natural gas contains water and this one is condensed in the pipelines.JUSTIFICATION OF THE DEHYDRATION PROCESSSATISFYREQUIREMENTS FOR TRANSPORTMust have a maximun content of : Water 6 lb H20/MMPCS. H2S 0.25 grains/100PCS.CO2 2%.AVOID FORMATION OF HYDRATE 1.Evitar formacin de hidratos:Pueden detener y/o entorpecer el flujo de gas por tuberas. La formacin ocurre siempre, que el gas natural contenga agua, y esta a su vez se condense dentro de la tubera.(Evitar la formacin de hidrato : pueden detener el flujo de gas a travs de gasoductos . La formacin siempre tiene lugar cuando el gas natural contiene agua y ste se condensa en las tuberas)2.Satisfacer requerimientos para su transporte: se debe tener un maximo contenido de3AVOID CORROSIONOptimizing the gas compressors's operation.The natural gas's liquid water is corrosive mainly if it contains CO2 y H2S.OPTIMIZE COMPRESSOR

JUSTIFICATION OF THE DEHYDRATION PROCESS4NATURAL GAS DEHYDRATION

Los aspectos enunciados anteriormente evidencian la necesidad de retirar la presencia de agua en la corriente de gas, para lo cual se han desarrollado los siguientes mtodos de deshidratacin: Absorcin Adsorcin Delicuescencia Expansin-Refrigeracin Permeacin del gas Tecnologa Twister 5

ADSORPTION DEHYDRATIONSolid desiccant dehydration is a process that works on the principle of adsorption.

Adsorption involves a form of adhesion between the solid desiccant particles and water vapor in the gas.SOLID DESSICANTS0,05 lbH2O/MMSCF Chemical binding of the molecules to the surface atoms. Chemisorption occurs when a chemical bond, or exchange of electrons is formed. Physiadsorbtion occurs when there is no electronic arrangements in the system and interaction exists without alteration of the molecule.PHYSICALADSORPTIONCHEMICAL ADSORPTIONTYPES OF ADSORPTIONCHARACTERISTICSDESICCANT SOLID DESSICANTS2,4 MM 3,9 MM ft2/lbHigh mass transfer rate

SILICA GELReference: http://i01.i.aliimg.com/photo/v0/337118827/Molecular_Sieve_3A_for_Alcohol_DehydrationReference. .jpgIts polar and have a large pore size.

Dew points of -60 F.

Less expensive and more easily to regenerate.

High capacity water can adsorb up to 45% of its own weight in water.

It has strong affinity for heavy hydrocarbons.

It will have a reduced capacity for water if it is used to dry a saturated gas.

DESSICANTDESSICANTALUMINA

Reference: http://i01.i.aliimg.com/photo/v0/337118827/Molecular_Sieve_3A_for_Alcohol_DehydrationReference. .jpgAluminum oxide balls

Its very polar

Dew points out approximately -90 to -100 F

The activated alumina is used to dry gases and liquids. DESSICANTDehydration and sweeting

Dew points out approximately -150

Able to dry the gas to a water content less than 0.1 ppm.

More expensive than silica gel, but provide further dehydration.

High temperatures required for regeneration (450 - 600F).

Selectiva adsorption: 3 10 A

MOLECULAR SIEVES

Reference: http://i01.i.aliimg.com/photo/v0/337118827/Molecular_Sieve_3A_for_Alcohol_DehydrationReference. .jpgTYPE MOLECULAR SIEVESIEVE TIPEDIAMETER[Angstroms]APLICATION3 A

3Dry olefins, dry methanol and ethanol

4 A

4Dry gases and liquids, remove H2S

5 A5Separate normal paraffins from branchedchainand cyclic hydrocarbons, remove H2S

13 X10Remove mercaptans and H2S, remove H20and C02 from air plant feed.

Reference: CAMPBELL, John M. Gas Processing and Conditioning. 200312

MOLECULAR SIEVEPROPERTIES DESECANTS

Reference: CAMPBELL, John M. Gas Processing and Conditioning. 2003KIDNAY, Arthur J, PARRISH, Williman G. Fundamentals of Natural Gas Processing. 2006 by Taylor and Francis Group.THE PROCESS

CONSTRUIMOS FUTURO Dessecant SelectionAdsorbedor 1Adsorbedor 2ADSORPTION TIMEREGENERATION TIMEREFRIGERATION TIMETWO TOWER UNITSPROCESSGAS INLETSEPARATORCOMPRESSORWATERCOOLER450 - 600FTOWERS OF ADSORPTIONHEATER600FFILTERDRY GASVALVE OPENVALVE CLOSED17

Valves

Heater

Cooler

MTZActive ZoneActive ZoneMTZEquilibrium ZoneActive ZoneMTZEquilibrium Zone Regeneration Time: 8 Hours Adsorption Time: 8 Hours

PROCESSCONSTRUIMOS FUTURO 24CONSTRUIMOS FUTURO Design Factors EXERCISE

Determine the water content of gas, and the amount of water that must be removed.Do a preliminary design od a molecular sieve dehydration system consisting of two tower with down flow dehydration in one tower and up flow regeneration in the other.

For a system with the followings characteristics:

SOLUTION

a) Determine the maximum superficial velocity

Let the maximum drop pressure 0,33 [psi/ft]

Gas density [Lb/ft3]

Gas Viscosity [Centipoise]

ConstantConstant

Reference: GPSA Engineering Data Book, 12 Edition, Gas Processors Suppliers Association, Tulsa, Oklahoma, 2004.

Therefore, the maximum superficial velocity require calculate the gas viscosity and density value

Gas Density

Reference: GPSA Engineering Data Book, 12 Edition, Gas Processors Suppliers Association, Tulsa, Oklahoma, 2004.

Gas Viscosity

SOLUTION

Maximum superficial velocity

b) Bed Diameter

Round off upward to 7,5 [ft] diameter.

Select the nearest standard diameter

V and Delta P/ L are adjusted

Then, c) Amount of water to be removed per cyclefor each bed.

(Base on a 24-hour cycle consisting of 12 hours adsorbing and 12 hours regenerating)

The water content at 600 [psia] and 100 [F] is calculate with the following graphic.

The water content is 88 [Lb/MMscfd]

d) Amount of sieve requiredTo define Bulk Density =

e) Define the bed heightApply the equation:

f) Calculate LMTZ

g) Total bed heights

h) Total sieve adjusted

i) Check the bed design and pressure drop

The check Pressure meets the criterion of not exceeding 5 8 [psi/ft]

j) Calculate the Design Pressure

Design Pressure 110 % of the operating pressure

k) Calculate the weight of steel

k) Calculate the weight of steel

l) Calculate the total heat required (Qtr)

m ) Calculate the flow rate of regeneration gas

Let the heating time be 60% of total regeneration period.

Is 50F above the Trg

60% * 12 [hr] = 7,2 Hours Heating

Graphic

n) Check that the [Delta P / L ] Gas regeneration

o) Hot regeneration gas Rate

p) Superficial velocity

q) Hot regeneration gas viscosity

r) Check

OPERATIONAL PROBLEMSCONCLUSIONSAdsorption plants with molecular sieve allow a high decrease of water content in the gas, these are the most effective desiccant and are also the most expensive, so its application is subject to the economic viability of the project.

The regeneration cycle is very important for reaching an efficient and economically viable process when using dehydration with solids. Because the solids are not so easily broken as the liquid, they can be exposed to higher temperatures without losing their desiccant properties.CAMPBELL JOHN, Technical assistance service for the design, operating and maintenance of gas plant. September 2003.

ABDEL, Aal and MOHAMED, Aggour. Petroleum and gas field processing. Marcel Dekker, NY, 2003.

GPSA Engineering Data Book, Gas Processors Suppliers Assoc., Tulsa, OK. (2004), Chapter 20.REFERENCES

NATURAL GAS DEHYDRATION:ADSORPTIONCAROLINA BELTRN SERRANOJENNY KATHERINE CARRILLOFABIAN ANDRES TAPIAS

GAS ENGINEERINGGROUP:D1UNIVERSIDAD INDUSTRIAL DE SANTANDERPETROLEUM ENGINEERING SCHOOLBUCARAMANGA, 2015

45CONSTRUIMOS FUTURO PROBLEMAS OPERACIONALESContaminacin del Lecho AdsorbenteLa causa ms frecuente es la eliminacin incompleta de los contaminantes en el separador de gas de entrada. La regeneracin incompleta del desecante dar lugar a una prdida repentina en la capacidad de adsorcin y una ruptura prematura significativa. Excesivo contenido de agua en la entrada de gas hmedo debido a incrementos de caudal de flujo, altas temperaturas, y bajas presiones.Alta Temperatura de Roco CONSTRUIMOS FUTURO Ruptura PrematuraLa capacidad del desecante puede disminuir con el uso, pero debe estabilizarse a una capacidad de entre 55-70% de la inicial. (Debido al desgaste natural-envejecimiento)PROBLEMAS OPERACIONALESgenerado por: Aumento de Hcs pesados (C4+) en el gas de alimentacin. La contaminacin del desecante. Regeneracin incompleta.CONSTRUIMOS FUTURO Soporte de FondoA veces los operadores tienen problemas con la red de apoyo y las fugas de tamices moleculares a travs de la red de apoyo.Como resultado, tienen que reemplazar todo el lecho.PROBLEMAS OPERACIONALES