Bimodal PE

STA*Research - Specialist consultants on polyolefins What's New What We Do Specialties Biography UHMWPE 2011 Bimodal PE

 Bi-Modal Polyethylene Processes: Characteristics, Costs and Competitive Domains

One of a series of independent, comprehensive, and in-depth analyses of modern process and catalyst technologies for the manufacture of polyethylenes and copolymers.

Since early 2006, several ground-breaking patent applications have been filed that promise to radically alter the cost structure of the bi-modal HDPE industry.  In particular, there have been remarkable improvements in the basic loop slurry process for HDPE, and in the dual-reactor cascade version of this process used to make bi-modal products.  These improvements go well beyond "conventional wisdom" in plant operating limits and set new boundaries for reactor productivity and single-stream plant output. If all these new developments were applied in a new facility, it is likely that it would set a new global benchmark in conversion costs in making HDPE, whether bi-modal or uni-modal. Potentially, these recent developments constitute the slurry-phase analog of Super-Condensed Mode operation introduced by ExxonMobil in 1995 for the gas-phase Unipol process, and EHP technology introduced by Ineos for the Innovene process.

This analysis develops comprehensive technology profiles for configurations representative of common existing bi-modal PE plants of four basic process types, as described below. Each profile contains the full analysis of technical, economic and strategic factors that determine the competitive standing of the process. These are extended where appropriate to comparative analyses of alternative configurations corresponding to variations used by specific companies.

STUDY SCOPE - Bimodal Polyethylene Processes

A. - Cascade slurry CSTR process. This process is typical of those licensed by Basell, Equistar/Maruzen, Mitsui and others for the production of HDPE. Because these have two or more reactors in series they excel in making grades with bi-modal molecular weight distributions as required for high pressure pipe and thin film markets. Asahi and LG use this process to make metallocene PE grades, and this potential will be examined also.

B. - Cascade loop reactor slurry process. This process has been gaining popularity in production of bimodal pipe resins. It is used by Total, Showa Denko and Ineos. Although commonly used for HDPE grades, the process can make LLDPE grades, even plastomers, when operated with SSCs, and these opportunities will be thoroughly evaluated.  All three leading proponents of the process have recently made substantial (but different) improvements to the technology that have changed its competitive standing.

C. - Super-critical loop/fluid bed process. This process was developed by Borealis with the specific objective of making bimodal grades for pipe, film and blow molding. It comprises a loop reactor operating above the critical point of the propane polymerization diluent, followed by a gas phase fluid bed reactor. It is capable of making bimodal HDPE and LLDPE grades with both conventional Ziegler catalysts and SSCs, and all these opportunities will be evaluated.

D. - Single reactor bimodal process. This technology was developed by Univation for its Unipol gas phase process. It uses mixed catalysts to produce an alloy of two products simultaneously in a single gas phase reactor. This technology has recently been commercialized for production of PE100 pipe grades.  Its capabilities and future potential will be evaluated in detail.  An additional development has been the production of multi-modal PE100 pipe grades in a single loop slurry reactor using a novel catalyst system.  This technology is still developmental and its commercial role is not yet clear.  This technology will be outlined and a cost benchmark will be presented, but full analysis is scheduled for a subsequent study.

E - Metallocene catalyst costs.  This study also provides estimates of current and projected future costs of making metallocenes/SSCs that are used for PE production, including those used in the single-reactor bi-modal process. The most important families of catalysts will be evaluated for both homogeneous and supported systems. The latest patent literature will be reviewed to reveal progress in terms of costs and performance of these systems. The objective will be to provide a benchmark for cost comparisons between metallocene/SSC systems and conventional Ziegler catalyst systems when used in commercial PE production processes.

The Bimodal Polyethylene Study, and all other studies in the "Polyolefin Production Processes" series, develops process technology profiles covering each process included in the study scope. Each profile is structured to provide detailed analysis of three key dimensions of comparison:

1. The Technical Comparison

This describes the technical dimension: how the process works and what it can and cannot do in terms of polymer composition and structure. Each profile includes:

- A process description
- Outline process flow diagram
- Description of control logic and variables
- Material and energy balance plus main stream flows
- Operating conditions and limitations
- Relationships between product structure/properties and operating conditions
- Production recipes for a range of appropriate grades
- Dynamic response of the process during grade changeover.

One aspect that distinguishes this analysis from others is the development of production recipes for individual grades of PE. This type of information is closely held by technology developers & licensors as being key competitive information, available only to licensees at the time of first plant operation. It is rarely if ever available on a non-confidential basis. Recipes used in the study are based on relationships developed by STA between the structure & composition of resins, and their processing behavior & end-use performance. Knowing these structural details, it is then possible to devise operating modes for each process that can be used to make each grade.

Production recipes are key to the understanding of the product range capabilities of every polyolefin manufacturing technology. The ability to make a specific structure is defined by the reactor configuration, the characteristics of the catalyst, and physical/chemical characteristics of polymerization such as pressure, temperature, composition, polymer morphology, solubility and stickiness, etc. Analysis of these aspects in the development of grade recipes is the only way to determine where the limits of each process lie.

Recipes will be developed for several appropriate grades for each basic process. These will be extended by recipes for high value grades made using variations in catalysts or process configurations. We anticipate that about 300 to 500 grade recipes will be developed in all.

Another aspect that distinguishes this study is the analysis of grade switching dynamics. This analysis requires definition of plant conditions at the start and finish of each grade change. In other words, it requires the grade production recipes. It also requires simulation of the reaction kinetics and dynamic response of the plant during each change.

2. The Economic Comparison

This provides an independent and internally consistent comparison of the production economics of each process, including:

- An estimate of capital costs for the battery limits and offsite facilities on a US Gulf Coast basis.
- Investment costs by main process section
- Variable operating costs such as monomers and other raw materials, catalysts, additives & chemicals, and utilities such as power, fuel, water & steam.
- Fixed operating costs such as operating labor, maintenance labor & materials, and business overheads.
- Sensitivity of investment and operating costs to production scale.
- An analysis of grade switching costs

The basic costing for each process will be for a standard "nameplate grade." Costs for other grades will also be given, taking into account differences in consumptions of materials & utilities, as well as the effects of reduced hourly production rate for specific grades, according to the recipes defined in the Technical Comparison.

Investment estimates will be built up from the costs of individual major equipment items. Outline specifications for all these major equipment items will be developed from the material & energy balances described in the Technical Comparison.

Equipment costs and plant construction costs will be based on data in STA's files using STA's cost estimating programs. Thus, cost estimates for all processes will be prepared following a common methodology and will be presented on a consistent and directly comparable basis.

The grade switching cost analysis is a distinguishing feature of this study. For it, we will define a number of plausible product portfolios that might be made with each process, and then estimate lost time and "wide-spec" material during changeovers through one production cycle of each portfolio. Various methods to ameliorate these penalties will be compared to reveal trade-offs and cost reduction potential. We will derive a grade change index for each process to provide guidance when comparing switching characteristics of dissimilar processes.

In their continual quest for differentiation, polyolefin producers have adopted many variations from the standard process configurations. In some cases they have added reactors in series or parallel with the basic reactors, in others they have changed the product recovery scheme, and so on, all aimed at adding capabilities to the process to achieve a competitive advantage. While there are too many variations to evaluate all of them, the study will describe and evaluate the economics of those variations of each process that appear to be the most advantageous or important.

3. The Strategic Comparison

In any thorough evaluation of a polyolefin production process, the most important question to be answered is:

What can you the user, or your competitor, do with the technology?

In other words, what advantage does the technology give you in the market place: in economics, in differentiation, in business growth, and in profitability. The Technical and Economic Comparisons provide the basic data to begin to address this question. The Strategic Comparison provides the answer.

Thus, the Strategic Comparison will pull together the technical and economic characteristics of each process with information on the actual market positions of its products. It will analyze and discuss:

- The market position of products currently made by users of each process. The objective is to find commonalities in market specialization as indicators of particular propensities of each process, as evidenced by strong market positions of these users. For example, some PE technologies excel in production of pipe grades while others excel more in blow molding, and this is evidenced in the market by producer market shares and specializations.
- Any specific process/catalyst combinations that seem to support stand-out product or market excellencies of specific companies. These will be identified primarily on the basis of published product performance data, an imperfect data source but a reasonable one if the sample size is adequate. Where appropriate, use will be made of performance maps to identify stand-out product groupings.
- The study will develop subjective indices of market power of each process on a grade-by-grade or market-by-market basis. This will combine derived cost data with market preferences as evidenced by the above market positions and specializations of users.
- The market accessibility of each process will be illustrated by weighting the product/market advantages according to the market demand patterns in two or three different market environments such as North America, Europe, and perhaps a developing market environment. The objective is to provide guidelines as to the attractiveness of different processes in different locations and markets.
- Each process will be discussed in terms of how it might evolve in the future. Is it suited to ever increasing single line capacity, or are there physical or mechanical limits on how large individual plants can get? Is the process suited to production of high growth advanced products? What could the process do if it were equipped with advanced catalysts? Will the competitive position of the process be changed when new catalysts are deployed, either positively or negatively? And so forth.

The combined analysis of these three dimensions of all 4 technologies will, we believe, provide the best independent, comprehensive, and in-depth analysis of modern bimodal PE production processes available to date.

Note that the process descriptions, flow schemes, operating characteristics, economics, and other comparative data developed in this study will be based solely on publicly available information and will be STA*Research's interpretation of this information. All processes will be "generic" versions of processes actually used by the industry or offered for license by technology-leading companies. We will solicit non-confidential information from these companies on their licensed technologies, and will use any information provided as guidance in developing our generic versions. However, licensors typically do not publish comprehensive data on their technologies, and there will obviously be uncertainties in the interpretation of the incomplete information available. We will therefore not be able to verify whether our detailed analyses are in agreement with actual practices of these process licensors.

For more information, please contact us at (949) 600-6546