Consisting of 2 Production Lines
In addition there is a Bagging/charging station:
LDPT line description
LDPT line produces polyethylene. Polyethylene is the most used plastic material, representing 40% of total volume of plastic materials worldwide.
Product of that plants is mainly used by downstream industry for:- films for food industry, bottles and generic bagging;- films for green house in agriculture;- containers various with good mechanical properties;- films to produce shoppers, bags and wrapping sheets.
Generally in this type of plant, ethylene is compressed in two stages: in the first stage, called primary compression, ethylene supplied to Battery Limits at 12 bar, is compressed to 250 bar, while in the secondary compression, pressure reaches process value.At tubular plant, primary compressors receive a mixture of ethylene at 3.5 bar, reaction modifier (propylene and/or propane), oxygen and all recycling gas at low pressure (RBP). Gas dispatched by primary compressors, reaches secondary compressors, where process pressure can vary de-pending by products to be produced. At tubular plant are installed primary compressors numbered KA6D01 and KA6D03, and two secondary compressors numbered KA6D02 and K107. To inject catalyst into reactor four pumps are installed, called A6C01/02/03/04 (two running and two as spares)
Process reactor is one and is made as a reinforced pipe, able to resist at high reaction pressure. It is designed as a double pipe to allow circulation of water to keep temperature controller, depending by process needs. Unreacted ethylene is recycled back to compressors and reactor.
Polymer separation section
At reactor outlet, lamination valve provides pressure reduction of mixture composed by melted polymer and unreacted gas, through high pressure separator (V-6E01) where, by gravity, liquid is leaving gas fraction; the latter constitutes by unreacted gas will be refrigerated by some exchangers, and after waxes removal (low polymers) by means of centrifugal separators, will restart cycle.From high pressure bottom separator, melted polymer and remaining un-reacted gas, not yet removed, are fed through another lamination valve to low pressure separator (V-6E02), where majority of gas are removed and send back to first compression stage, after passing through exchangers and centrifugal separators to remove waxes. Some quantity of gas is vented with continuity to avoid inert increase inside closed loop.
At outlet of low pressure separator, melted is discharged into extruder (ME-6F01) where polymer pellets are produced. Then product is moved by water flow to following area where, after water drying, is sent to finishing section.To produce some special products, it is used a satellite extruder (ME-6F11) installed perpendicular to main extruder.
Finishing sectionInside that section, pellets are moved by pneumatic stream to six silos (volume of 6 m3 each), where it is aired , to remove ethylene residues, before to be moved to large silos (four silos of 160 m3) of blending, and then sent to storage silos (six silos of 300 m3 volume, each), from where polymer is shipped bulk or sent to bagging area. To move pellets, and to homogenize product, volumetric compressors are used (K-6G01/K-6G13).
LDPV line description
LDPV line is designed with three reactors, all similar: reactor R1 (1° line), R2 (2° line) and R5 (5° line).Following primary compression line there are three independent secondary compression lines, each one connected with one reactor. After reactor, each of there lines follows different route until meeting together after high pressure separators. Then there are three finishing lines and storage silos, from which material could be dispatched to bagging line, in common with tubular line.Product has same characteristics of tubular line product, and is sold with same trade name, and used for similar applications.Production process of that vessel line is similar to the tubular one unless for reactor section, of course.
Ethylene compression section
This section includes three primary compressors (K1, K2 and K101) which suctions ethylene from complex pipeline at 3.5 bar pressure; these compressors suck also reaction moderator and recycled ethylene at low pressure sent by booster compressors (K13÷K16, K115-K116). After primary compressors there are secondary compressors (1° line: K108; 2° line: K5,K6, K11; 5° line: K105, K106) which increase pressure to reaction conditions.
In addition to compressors there are several pumps at high pressure (flow 25/40 liter/hr) to inject catalyst solution into reactors; that injection takes place at three different reactor elevations; that’s why four pumps per reactor are in-stalled (with fourth as spare).
As above mentioned, section is designed with three vessel reactors made with special steel of high mechanical properties to resist internal pressure.
Mixture of melted polymer and unreacted gas, leaving reactors, is expanded inside three high pressure separators, one for each line. Removed gas will cross ten heat exchangers, and after de-waxing is fed back to high pressure compressors.Same treatment is offered to melted polymer and unreacted gas leaving low pressure separators. In that case, after wax separation, gas is fed back to booster compressors.
Polymer coming fro low pressure separator is fed to extruder ME-121. Then, chips are moved by water flow to rotating sieve and to centrifugal drier, before shipment to finishing section.
Finishing section is designed with three lines, similar each others, constituted by four airing silos, by six couple of blenders (each one with two silos), and finally by six storage silos (volume 300 m3). From such silos product could be shipped to bagging station, common with tubular plant, or to nine storage silos, eight of 100 m3 and one of 500 m3, used to load bulk product on trucks or train. 32 volumetric compressors are used for pneumatic transportation and product airing.
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