Process Economics Program Report 36D
Low Density Polyethylene
Published: October 2005
In the early 1980s, a slowdown in low-density polyethylene (LDPE) plant construction occurred because of the marketing uncertainties arising from the introduction of linear low-density polyethylene (LLDPE). However, despite of the threat of LLDPE resin substitution for LDPE, LDPE consumption continues to grow. In the late 1980s and early 1990s, a new round of capacity expansion in LDPE began. More expansion in capacity is expected. Although easier processing LLDPE is starting to be introduced, LDPE is still the easiest polymer to process for numerous applications. Its high melt strength makes it the material of choice for wide films, foam applications, and extrusion coating. LDPE is a large global business with over 19 million tons of installed capacity. Technology improvements including larger plant capacities and higher operating efficiencies are bringing unit cost down to levels competitive to LLDPE.
Since the previous PEP reports, significant improvements in the LDPE process have occurred. Single line capacities of 300,000-400,000 ton/yr are possible with LDPE production by a tubular reactor. Higher ethylene conversion per pass can be obtained. In the current report, we will update the process designs and economics for LDPE production by a high pressure tubular process based on a world-scale plant of 882 million lb/yr (400,000 ton/yr). More incremental improvements in the autoclave process have occurred since the last PEP report. Autoclave single line capacities of 100,000-150,000 ton/yr are possible. Although most of the new installed LDPE capacities are based on tubular reactors, autoclave reactors are still relevant. Autoclave reactors are used to produce specialty LDPE. In this report, the process design will also be updated for the autoclave process. To evaluate LDPE competitive situation with LLDPE, the economic results will be compared to the economics for LLDPE production by a gas-phase process.