MOLECULAR SIEVES AND ADSORBENTS

Transcription

1 CHECKED kta LLDPE / HDPE. GENERAL Nov Jan Aug Y -LZ-ADSC No. OFF PAGE / This specification covers the minimum requirements for the adsorbents and molecular sieves used for purifying ethylene, comonomers (butene-, hexene-), pentane and hydrogen in the purification feed unit for LLDPE / HDPE plant of, Lepetkata, India. The purpose is to remove water, carbon dioxide, alcohol, total combined nitrogen, carbonyls and peroxides from the raw material, which are poisons of the polymerisation process.. DESIGN BASIS. ETHYLENE.. ETHYLENE PURIFICATION SCHEME Upstream of this purification, the ethylene is treated to remove sulphur, acetylene, carbon monoxide and oxygen traces through several catalyst layers. Two vessels are foreseen for this purification: -VV-A/B. They will contain multiple layers of molecular sieves and adsorbents to remove trace amounts of water and other contaminants to acceptable levels, without the co-adsorption of olefins. Each individual treater will have the full capacity of treating the ethylene stream, while the other is off-line and being regenerated. For normal operations however, the two treaters will work in series. Upstream of -VV-A/B an ethylene cooler -EE- is inserted to cool-down ethylene feed to C or other temperature as specified by supplier. Support balls shall be inert type. Vendor to advise on selection to ensure the inert characteristics of the support balls.

2 XB kta LLDPE / HDPE CHECKED Nov Jan.. CONDITIONS OF THE ETHYLENE STREAM... Ethylene Composition Aug Y -LZ-ADSC No. OFF PAGE / The following table gives the ethylene feed specification before and after the purification process in -VV-A/B. Components to remove are Carbon Dioxide, Water, alcohols (as methanol) and total combined nitrogen. Raw material Component Required specifications at -VV-A/B outlet ETHYLENE Specifications at -VV-A/B inlet (after upstream treatments) Ethylene. %v min. %v min Methane * ppm mol max Ethane * Balance Hydrogen * ppm mol max Propylene & Higher * ppm wt max Acetylene (incl methyl acetylene) * ppm v max Carbon Monoxide *. ppm v max Carbon Dioxide. ppm v max ppm mol max Oxygen *. ppm v max Total combined Sulphur (as H S) * ppm wt max Water. ppm v max ppm wt Alcohol (as methanol). ppm v max Included in oxygenates Total combined Nitrogen (as NH ). ppm v max ppm mol max Total oxygenated Compounds (as acetone). ppm v max ppm mol Notes: * The supplier will indicate the components content in the effluent.

3 XB XB XB XB kta LLDPE / HDPE CHECKED Nov Jan... Ethylene Feed pressure and temperature Aug Y -LZ-ADSC No. OFF PAGE / The conditions at the inlet of the treaters -VV-A/B are the following: Pressure (): Minimum :. kg/cm²g Nominal :. kg/cm²g Maximum :. kg/cm²g Mech. Design : kg/cm²g Temperature : Nominal : C Mech. Design : C... Ethylene Flowrates Note: FLOW Minimum () Normal Design kg/h kg/h () Vendor to indicate minimum acceptable flowrate, to achieve the required specification.

4 XB XB XB CHECKED kta LLDPE / HDPE Nov Jan.. -VV-A/B CYCLE LENGTH Aug Y -LZ-ADSC No. OFF PAGE / The adsorption duration and regeneration frequency will be based on a day cycle at design flowrate (equivalent to days at normal flowrate)... -VV-A/B REGENERATION Flowrate : by vendor Warm purge : by vendor Heat cycle : by vendor Cool cycle : by vendor Depressurisation/Repressurisation : by vendor.. -VV-A/B PRESSURE DROP The maximum pressure drop (at specified design flowrate) is. kg/cm² max for each vessel, i.e.. kg/cm² in total when the treaters are operating in series.. COMONOMERS: BUTENE-, HEXENE-.. PURIFICATION SCHEME One vessel is foreseen for butene- purification: -VV-A. It will contain multiple layers of molecular sieves and adsorbents to remove trace amounts of water and other contaminants to acceptable levels. One vessel is foreseen for hexene- purification: -VV-B. It will contain multiple layers of molecular sieves and adsorbents to remove trace amounts of water and other contaminants to acceptable levels. -VV-B is common spare of -VV-A used during generation of -VV-A. -VV-A is common spare of -VV-B used during generation of -VV-B. -VV-A and -VV-B will be identical. Each individual treater will have the full capacity of treating the butene- stream or the hexene- stream. Vendor to select adsorbent to minimize loss of comonomer (hexene-, butene-) by side reaction. Vendor to indicate the fraction of comonomer loss through the bed.

5 kta LLDPE / HDPE PRESSURE Normal Op. Regeneration (N) TEMPERATURE Normal Op. Regeneration (N) MATERIALS CORR. ALLOWANCE OPERATING kg/cm(g). C () SHELL L.T.C.S. mm PROCESS DESIGN kg/cm(g). () - / ENDS L.T.C.S. mm Fluid: Ethylene Density:. C Insulation: YES (heat conservation) Lower TL elevation above ground: () NOZZLE DATA REP Nb Dia. In SERVICE Inlet Outlet / Temperature indicator () Absorbent draw off Handhole () Manhole Spare ( * ) CYLINDRICAL SHELL LENGTH ONLY. DRUM ORIENTATION VERTICAL BOOT INTERNAL DIAMETER mm () INTERNAL DIAMETER mm HEIGHT OR LENGTH ( * ) mm () HEIGHT OR LENGTH ( * ) mm XA Jan Aug Sept CHECKED TL TL Y -VV- A/B No. OFF SERVICE ETHYL. OXYGENATES TREATERS PAGE / Impingement plate O Impingement plate O MINI Note A Hold-down grid () Inert balls () H O removal CH OH/NH /Acetone removal H S/CO removal Inert balls () See detail

6 kta LLDPE / HDPE CHECKED INERT BALLS () XA Jan Aug DETAIL - ADSORBENT DRAWOFF SUPPORT GRID PROCESS NOTES. Complete with plug insert to ensure flush fitting with cylindrical shell.. Adsorbent supply Sept Y -VV- A/B No. OFF SERVICE ETHYL. OXYGENATES TREATERS PAGE / Above adsorbents:. m of inert balls (Denstone D- ½ or equivalent). Adsorbents: MINI - For H O removal:. m of UOP A-EPG / molecular sieve or equivalent. DRAWOFF () - For CH OH/NH /Acetone removal:. m of UOP AZ- x mesh or equivalent. - For H S/CO removal:. m of UOP CG- x mesh or equivalent. Below adsorbents:. m of inert balls (. m of Denstone D- / above. m of Denstone D- ¼ or equivalent). DELETED.. Elevation to allow easy emptying of adsorbents from bottom withdrawal nozzle.. S.S. mesh grid (. mm opening).

7 CHECKED kta LLDPE / HDPE XA Jan Aug. - C after depressurisation at atmospheric pressure. Sept Y -VV- A/B No. OFF SERVICE ETHYL. OXYGENATES TREATERS PAGE /. Denstone or equivalent. Ball size to be given by adsorbent Vendor.. Detail Engineering to ensure that total P from flange to flange is lower than. kg/cm².. Equally spaced in plan view around circumference. MECHANICAL NOTES A. Johnson screen grid type or equivalent (see note ).