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Administrative
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Finished |
Y
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Date Completed |
2009
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Copyright |
Environmental Systems Analysis, Chalmers Univ. of Technology
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Availability |
Public
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Technical System
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Name |
Polymerization in LDPE production process. ESA-DBP
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Functional Unit |
1 kg of LDPE (low density polyethylene)
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Functional Unit Explanation |
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Process Type |
Other
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Site |
Borealis, Sweden
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Sector |
Manufacturing
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Owner |
Borealis, Sweden
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Technical system description |
Polymerization discussed in this study is a one of the steps in crude oil based LDPE (low density polyethylene) production process. This process is gate-to-gate but the electricity and fuel are traced back to the cradle. In this step ethylene is processed into LDPE. Data are valid for Sweden but for electricity calculations average European data were used.
Excerpt from the report, see ’Publication’:
’’Low density polyethylene (LDPE) is produced under high pressures (81-276MPa) and temperatures (130-330ºC) in either a tubular or stirring autoclave reactor. The products from this two reactor types differ mainly in their long chain branching composition due to differences in their backmixing. The result is shorter long-chain branching in stirring autoclave reactors, and longer in the tubular reactor.
The mechanism leading to the formation of the branched polymer is chain growth polymerization. It includes four reaction steps: initiation, propagation, branching and termination. The initiation starts with the decomposition of an initiator material, usually peroxides. When exposed to heat or irradiation, the peroxides, decompose releasing a free radical, which attacks the ethylene and starts the growth of the radical chain. In the next step, the propagation, an olefin radical chain attacks the double bonds of the surrounding ethylene monomers causing an addition reaction to occur and results in a longer chain.
In the process, the active center moves to the end of the new, longer chain and continues adding more monomers. The chain grows. However, the radical chain does not only react with double bonds in the monomers, but also with hydrogen from another polymer chain. The result is the termination of the first chain and a movement of the active center to the middle of the second chain, which now grows from there. This process is the called branching.
The termination of the chain growth can be caused by different reactions. The two most important termination reactions are coupling and disproportionation. Coupling is the reaction of two polymer chains resulting in the formation of a long polymer molecule. Disproportionation is the transfer of a labile atom from one radical to another leading to two inert polymer chains. A third termination mechanism is chain transfer. It involves the transfer of the active center of a polymer chain to a monomer or to a solvent, added to the mix to terminate the chain growth. In dependence of the reactivity of the newly formed radical, it might initiate the formation of a new polymer chain.
After the polymerization, the product stream passes through different separation steps to recover the not reacted ethylene gas for recycling and to remove waxes. The cleaned, molten polymer is then mixed with stabilizers and additives and finally made into pellets. In this last step, the polymer is forced through an extruder head to from the required shape and size of pellets. The pellets are usually cut under water and dried in a centrifugal drier.’’
This process is included in the system described in:
Liptow Ch., Tillman A.-M. (2009). Comparative life cycle assessment of polyethylene based on sugarcane and crude oil. Environmental Systems Analysis, Report 2009:14, ISSN:1404-8167. Chalmers University of Technology. Gothenburg, Sweden.
Link to PDF:
http://cpmdatabase.cpm.chalmers.se/DataReferences/ESA_2009--14.pdf
Other processes in the CPM Database also included in the above publication:
- Ethylene production from cane based ethanol. ESA-DBP
- Sugarcane cultivation. ESA-DBP
- Refinery in crude oil based LDPE production process. ESA-DBP
- Steam cracking in crude oil based LDPE production process. ESA-DBP
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System Boundaries
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Nature Boundary |
Excerpt from the report, see ’Publication’: ’’Outputs accounted for in this study were by-products and emissions released to air. Water emissions were omitted, because of data unavailability for some parts of the sugarcane route.’’
The data relate also to the fuel and electricity consumption which were traced back to the cradle.
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Time Boundary |
Data for steam cracking come from 2008 and they were acquired as the most up-to-date ones.
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Geographical
Boundary |
Process data are valid for Sweden. For electricity calculations the average data from Europe were applied.
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Other Boundaries |
Excerpt from the report, see ’Publication’:
’’- total input treated as ethylene
- production mix does not change with input composition
- conversion rate does not change with input composition
- external fuel treated like diesel to account environmental impact’’
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Allocations |
No allocation needed.
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Systems Expansions |
Not applicable
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Flow Data
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General Activity
QMetaData
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Date Conceived |
2008
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Data Type |
Derived, unspecified
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Represents |
See ’Function’
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Method |
Excerpt from the report, see ’Publication’:
’’Process data for the polymerization originated from Borealis, Sweden (2008).
The electricity consumed, was assessed under marginal and average electricity supply - see section electricity consumption
The environmental impact of external fuels consumed at the production site (consumption data according to Borealis (2008)) were assessed according emissions data from SPINE LCI (2008). External fuels were treated like diesel under the assumption that diesel and fuel oil have the same environmental impact during their production.
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Literature Reference |
Liptow Ch., Tillman A.-M. (2009). Comparative life cycle assessment of polyethylene based on sugarcane and crude oil. Environmental Systems Analysis, Report 2009:14, ISSN:1404-8167. Chalmers University of Technology. Gothenburg, Sweden.
Link to PDF:
http://www.cpm.chalmers.se/CPMDatabase/DataReferences/ESA_2009--14.pdf
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Notes |
Data for attributional approach.
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Flow Table and Specific Meta Data
Back to Flow Data
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QMetaData |
Direction |
FlowType |
Substance |
Quantity |
Min |
Max |
SDev |
Unit |
Environment |
Geography |
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Input
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Refined resource
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Electricity
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13,4
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MJ
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Technosphere
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Sweden
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Input
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Refined resource
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Ethylene
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1000
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g
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Technosphere
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Sweden
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Input
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Refined resource
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Fuel
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0,3
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MJ
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Technosphere
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Sweden
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Output
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Emission
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CH4
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1,2
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g
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Air
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Sweden
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Output
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Emission
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CO
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0,3
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g
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Air
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Sweden
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Output
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Emission
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CO2
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680
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g
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Air
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Sweden
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Output
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Emission
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HC
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0,0018
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g
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Air
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Sweden
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Output
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Emission
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HFC
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0,1
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g
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Air
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Sweden
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Output
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Emission
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N2O
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0,016
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g
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Air
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Sweden
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Output
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Emission
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NMVOC
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0,02
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g
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Air
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Sweden
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Output
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Emission
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NOx
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1,2
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g
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Air
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Sweden
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Output
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Emission
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SO2
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3,7
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g
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Air
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Sweden
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Output
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Emission
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VOC
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1,9
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g
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Air
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Sweden
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Output
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Product
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LDPE
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1000
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g
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Technosphere
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Sweden
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About Inventory
Back to Contents |
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Publication |
Liptow Ch., Tillman A.-M. (2009). Comparative life cycle assessment of polyethylene based on sugarcane and crude oil. Environmental Systems Analysis, Report 2009:14, ISSN:1404-8167. Chalmers University of Technology. Gothenburg, Sweden.
Link to PDF:
http://cpmdatabase.cpm.chalmers.se/DataReferences/ESA_2009--14.pdf
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Intended User |
LCA practitioner
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General Purpose |
Excerpt from the report, see ’Publication’: ’’The goal of this study is to answer the question, is the use of sugarcane based LDPE in the production of goods and packing in Sweden environmentally preferable to crude oil based LDPE.’’
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Detailed Purpose |
Polymerization is a step in the production process of LDPE so it was necessary to investigate the environmental load of it.
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Commissioner |
Unknown - .
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Practitioner |
Christin Liptow & Anne-Marie Tillman - Environmental Systems Analysis, Chalmers University of Technology.
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Reviewer |
Tillman, Anne-Marie - Environmental Systems Analysis, Chalmers University of Technology
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Applicability |
For applicability for the process see ’Technical System’ and ’System Boundaries’ above
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About Data |
ESA database project.
Years 2009-2011.
Administrating organization: Chalmers University of Technology, Department of Environmental Systems Analysis.
Financier: The Swedish Research Council (Vetenskapsrådet)
Data documentor: Katarzyna Iwanek assisted by Filippa Fuhrman (ESA) and Johan Tivander (ESA).
Review committee for imported data: Johan Tivander (ESA), Emma Rex (CPM, Center for environmental assessment of Product and Material Systems), Bengt Steen (ESA), Anne-Marie Tillman (ESA).
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Notes |
Polymerization is a step in a production process of oil based LDPE which was the object of the study. The production process starts with crude oil extraction and is followed by refinery, steam cracking, polymerization, use phase (which was excluded from the study) and inceneration as the end of life.
Oil based- was compared in the study to the sugarcane based- LDPE.
NB: in the report two approaches were investigated: attributional and consequential. For consequential approach see the report.
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