polyethylene production, low density, granulate, UPR, ecoinvent 3.6, Undefined

ISIC4 categories:
C:Manufacturing/20:Manufacture of chemicals and chemical products/201:Manufacture of basic chemicals, fertilizers and nitrogen compounds, plastics and synthetic rubber in primary forms/2013:Manufacture of plastics and synthetic rubber in primary forms
GLO - Global
Reference year: 2011 - 2016

Location: GLO - Global
The dataset represents the production mix of commercial LDPE production technologies: high pressure polymerisation using oxygen and/or organic peroxides as initiator
LDPE is produced through high-pressure polymerisation. As typical initiators to start the polymerisation process, organic peroxides and oxygen are used. Furthermore, polar modifiers (aldehydes, ketones, or alcohols) or aliphatic hydrocarbons are fed into the monomer stream to control the molecular weight distribution.
High-pressure polymerisation is carried out at pressures of 1500 to 3500 bar and temperatures of about 200°C. Under those conditions, oxygen or peroxides work as initiators to start the radical polymerisation process. The reaction may take place either in an autoclave or a tubular reactor. The polymerisation is an exothermic reaction. The ethylene gas is used as a heat sink for the resulting heat, which means that the ethylene gas cannot be to-tally converted to polymer. The unreacted gas is directly recycled back into the process and combined with fresh ethylene. Furthermore, the heat of the exothermic reaction can be recuperated to generate low pressure steam.
The initiator concentrations usually vary between 0.1 and 0.5 wt.-%. Decomposed metal alkyl residues of the initiator remain in the product and sometimes have an influence on end-use properties. Dissociation products of the radical initiator are removed from the polymer or built in.
After the reaction phase, most of the residual (unreacted) monomers (which are mostly present as gases) are separated from the polymer and are either recycled back into the process or flared of. Depending on the purity of the separated monomers, the gas can either be fed directly back into the production line or the monomers are returned to a purification unit. To limit the accumulation of impurities in the process, usually a small side-stream (purge) of the unreacted gas is sent back to the cracker or to a dedicated purification unit. After polymerisation, the polymer is usually fed di-rectly into a hot melt extruder, where additives can be added to the melted polymer if required. The polymer is then pelletised in an underwater pelletiser. The pelletised product is dried, blended where required and degassed.
Undefined unit processes (UPRs) are the unlinked, multi-product activity datasets that form the basis for all of the system models available in the ecoinvent database. This is the way the datasets are obtained and entered into the database by the data providers. These activity datasets are useful for investigating the environmental impacts of a specific activity (gate-to-gate), without regard to its upstream or downstream impacts.

Process type
Supported nomenclature
ecoinvent 3.6
LCI modeling approach
Before modeling
Multifunctional modeling
Aggregation type
Data provider
Review status
For sale

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