Technology

LyondellBasell introduces a new Polyolefin Process, Hyperzone PE Technology, which produces High Density Polyethylene (HDPE) Resin.

This Technology utilizes three distinct reaction zones in two Reactors (Fig. 1). The Hyperzone PE Technology consists of a Reactor cascade of 2 Gas Phase Reactors. The first Reactor is a Fluidized Bed Gas Phase Reactor (FBR) where the low molecular weight fraction of the final Product is produced. The Product leaving the first Reactor is discharged into a MultiZone Circulating Reactor (MZCR), which produces the medium and high molecular weight fractions of the Product. Comonomer is fed to the Process to control the final density and stiffness of the Product and can be targeted to the high molecular weight fraction of the Product to obtain superior ESCR performance.

Figure 1 - Hyperzone PE 3-in-2 cascade reactor setup

The FBR combined with the MZCR enables the Hyperzone PE Process to produce multimodal HDPE Products using only 2 Rreactors in cascade. The MZCR Reactor is a circulating Fluidized Bed Reactor combining a riser operating in fast fluidization regime and a downer operating as a packed moving bed (Fig. 2). At the top of the downer, a barrier can be introduced allowing to operate the riser and downer at a different Gas composition thereby producing a different molecular weight in each Reactor zone. In the downer solids concentrations close to the bulk density of the polymer are achievable. In the riser, operating under fast fluidization conditions, solids concentrations of 40% can be obtained.

Figure 2 - Functioning of the MZCR in the Hyperzone PE Technology

The Reactor, being it essentially two interconnected pipes, has a higher efficiency of Reactor volume compared to a traditional FBR due to the absence of a Reactor Dome. The riser of the Reactor has a limited temperature gradient due to the high level of back mixing. This is in contrast to the downer, which operates essentially in adiabatic mode. The temperature in the bottom of the downer can be controlled by applying an appropriate solids circulation rate. Liquid injections at the top of the downer as barrier and along the downer to disperse additional Ethylene feeding points further facilitate the removal of reaction heat.

The barrier injected at the top of the downer functions in the following way (Fig. 3). In the downer, Polymer Powder flows downward as a packed bed. The pressure
balance of the MZCR is operated in such a way to ensure Gasses in the downer will move downward as well. In case no barrier would be fed to the downer, the Hydrogen
concentration in the riser and downer would be essentially the same. In case a barrier is fed, the MZCR can be operated in a multimodal way allowing the Polymer particles to grow in the downer at a much lower Hydrogen concentration. By selecting the proper split of Reaction between the FBR, riser and downer as well as Hydrogen concentration in each reaction zone, a tailor made molecular weight distribution can be generated for each product application.

Figure 3 - The MZCR barrier concept

Polymer is discharged from the bottom of the downer where the Polymer density is the highest thereby minimizing the energy required for recovering the discharged Gasses.

Source: Gerben Meier, Gabriele Mei, LyondellBasell, Houston, TX, SPE 2019 paper, Hyperzone PE Process Technology - A new polyethylene technology for the plastics industry