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SCP - Polymers SBU
Ethylene Units Purpose The main objective of the unit 10 and 210 is to produce high purity purity of ethylene by the thermal cracking of ethane beside the other feeds being used in the unit 210 such as propane and naphtha in order to produce other products as it’s multi feed unit.
Ethylene production is used by YANPET to produce ethylene glycol and polyethylene.
Ethylene Units Ethylene Units Unit
Ethylene unit 10
90 T/h 2.5 T/h
Ethylene unit 210
Ethane Propane Naphtha
Ethylene Hydrogen Propylene By Products
Production of Olefins
Compression and Chilling
Ethylene Unit 210 Block Diagram
Production Process 1.Cracking Feed stocks to the ethylene unit 210 are ethane, propane, naphtha. Fresh feed and recycled are thermally cracked in the presence of steam in a ten SRTIII type heaters.U-21 consists of Ten furnace, nine Furnaces are normally in operation with the remaining heater as a spare. Each heater is capable of processing feed from any one of the three feed headers and also capable for co-cracking for gas feed (ethane & propane ) and liquid feed (naphtha and recycle C4/C5). Steam is added either direct of through gas feed saturators at controlled rates in order to increase the petrochemical yield and to minimize carbon deposits (coke) forming in the furnace tubes to enhance the effectiveness of the cracking reaction. Presence of steam and heat, changes to other hydrocarbons. The feed is subjected to short residence time of extreme heat, at around 845 C, causing the splitting of the molecule into other hydrocarbons. Steam cracking refers therefore to the process whereby a hydrocarbon feedstock—in this case ethane —in the presence of steam and heat, changes to other hydrocarbons, where the most desired overall reaction is: C2H6(g) → C2H4(g)+ H2(g) °
Production Process Ethylene and other high value chemicals have been produced by the cracking reaction. However it is mixed in with many different hydrocarbons. It needs to be separated out to get product that is over 99.9% pure. The remainder of the process steps are to get the ethylene separated out so that it can be sent to the end user.
Furnace cracking Feed charging
Production Process 2.Quenching The cracked gas from the heaters is quenched to stop the undesired reaction such as :
C2H4(g) + H2(g)→ C2H6(g) C2H6(g) + H2(g)→ C2H8(g) The heat from effluent gas is covered to heat boiler feed water in the transfer heat exchangers. The cracked gas is further cooled by direct injection of quench oil and then by passage up the quench oil tower where it is cooled by circulating quench oil and, in the top section, by a gasoline reflux stream. The heat recovered in the quench oil is used to heat various other process streams. The cracked gas is further cooled in the quench water tower, against circulating quench water. The heat recovered in the quench water is used to reboil different exchanger. Also in the quench water tower, gasoline and water are condensed out. The gasoline is used for reflux in the quench oil tower, and the water is used to raise dilution stream which is then returned to the cracking furnaces.
QUENCH SYSTEM TO COMPRESSORS
2C-1200 QUENCH WATER
OIL & HEAVIES
OIL FUEL OIL
Production Process 3.Compression and Chilling The purpose of this stage is to liquefied the effluent gas from quench tower prior to sent it to distillation columns for separation. The cracked gas stream from the quench tower is compressed using a centrifugal compressor. The gas compression in this section of the plant occurs in five stages to compress the gas to a pressure of approx. 3500 KPa. The gas is cooled by heat exchangers between each stage of compression., and water and gasoline condensed. This is necessary because when a gas is compressed without breaking up the compression steps it heats up and exposes the compressor to thermal stress and also fouling formation on the internal parts.
Treatment of the cracked gas to remove impurities occurs between the third and fourth stages of the compressor, the gas is scrubbed with a caustic soda solution to remove acid gases H2S and CO2 in the caustic tower. As the gas stream after compression is going to be cooled to temperatures as low as –100°C in the chilling train, any remaining water would form ice compounds thereby blocking pipes and pipe strainers. Therefore, the final compressor discharge is dried using molecular sieves desiccant to less than 1ppm water content.
Production Process The chilling train is a series of heat exchangers and cold box. On one side of the heat exchanger is the dried compressed gas that needs to be cooled and on the other side of the heat exchanger is the refrigerant, liquid ethylene or propylene, which cools the gas. Neither stream comes into direct contact with the other. The cooling process condenses most of the methane and heavier hydrocarbons and leaves a hydrogen-rich stream. Hydrogen-rich gas flows through the pressure swing adsorption unit (PSA) for hydrogen purification to supply unit hydrogenated reactors with pure hydrogen and also export hydrogen to other user inside the plant. The excess hydrogen-rich gas and methane off gas are recovered and used as plant fuel.
2C-1302 TO 2C 1505
936.3 KPa 47.35 Deg C
2D 1 3 0 9
STAGE 4 2D 1 3 0 5
1919 KPa 38 Deg C
1942 KPa 101.6 Deg C
2D 1 3 3861 KPa 0 94.12 Deg C 7
TO CHILING TRAIN
2E-1412 - 34.75
2D 1 3 5 1 A B C
2E-1405 - 26.449
- 70.2 16 °C
- 2 °C
2D 1 4 0 1
Production Process 4.Distillation The condensed methane and heavier liquid stream flow to the distillation columns to separate out the different chemical compounds. The refrigeration section chills the dried gas from the compressor section. The demethanizer reflux drum overhead goes to ethylene recovery unit#2 for ethylene recovery. Most of the hydrogen-rich stream flows through the pressure swing adsorption unit (PSA), which adsorb all impurities in the hydrogen and produced 99.9% purity hydrogen then the hydrogen is feed to the methanator. The stream is then dried and sent to the acetylene converters and battery limits. The hydrogen-rich stream is used to provide low-level refrigeration. It is then sent to fuel mix drum to be used as fuel gas. Liquid methane from demethanizer reflux pump discharge goes to methane ballast system for acetylene converting ethylene and the vapor is methane rich off gas, which is sent to fuel. The demethanizer This stream is fed to the demethanizer column where the overhead liquid is used for reflux and cooling in the cold box. The demethanizer bottom is feed forward to the deethanizer. In the de-ethanizers, the overhead is sent to the acetylene converter, where the acetylene is hydrogenated with a catalyst into ethylene. C2H2(g) + H2(g)→ C2H4(g)
Production Process The vapor product from the convertor is cooled and sent to an absorber where green oil formed during the conversion is removed. (Green oil is a low-grade ethylene polymer) the absorber overhead vapor is then dried and fed to the ethylene splitter, which separates ethylene from ethane. The splitter is integrated with the ethylene refrigeration system and the column overheads eventually become ethylene product. The ethylene product leaves the fractionators as a side stream liquid and then it is pumped, vaporized, superheated, and delivered to battery limits. Ethane leaves the bottom of the splitter and vaporized, superheated, and recycled as feed to cracking Furnace. The deethanizer bottom is fed to the two depropanizer towers to separates C3 ’s from the heavier hydrocarbons in the feed stream. Depropanizer overhead is selectively hydrogenated to convert methyl acetylene/propadiene (MAPD) to propylene in the MAPD reactor. The effluent from MAPD flows to C3 splitter to produce propylene and before leaving the unit the propylene is treated in a series of guard beds to remove any Arsine, COS, or other sulfur compounds. Propane leaves the bottom of C3 splitter to furnace as recycled feed.
Production Process The depropnizer is diverted to depentanizer column to separate C4's /C5 ’s from the C6 and heavier fractions from the depropanizer bottoms and the Quench Water Settler. The overhead stream is the mixed C4's /C5 ’s product which is sent to the C4/C5 reactor for total hydrogenation and then the hydrogenated steam is sent back to furnace for co-cracking with naphtha feed. The bottoms from depentanizer is cooled, and sent to the Pyrolysis Gasoline Hydrogenation (DPG) Area. Where a selective hydrogenation take place through two stage of reactors to eliminate the undesired component in pyrolysis gasoline product (Py-Gas) such as diolefins, styrene compounds, diene and other unstable compounds. The C9+ and wash oil are extracted from tailing tower at DPG area. C9+ is transferred as fuel to boiler and wash oil is utilized as solvent inside U-210. Py-Gas (C6-C8) product leaves the unit to Sabtank through pipeline as final product.
DEMETHANIZER 2C-1401 2Y 1 4 0 A 1 D1
2D 1 4 0 2
2D 1 5 0 1
From 2C-1501 bottom
A From 2C-1505 bottom