Polymers Plus Research Articles

A New Recipe for Friction-Reducer Suppliers: Polymer Plus Frac Water, Minus the Cost

The argument for making friction reducer on site is simple: only one truck is required to deliver dry polymer vs. three loads required for the same amount of liquid additive. For Downhole Chemical Solutions (DCS), reducing the number of trips and the amount of chemicals needed to create a stable liquid by mixing it as needed on site reduces the average cost of a gallon of friction reducer by around 30%, said Mark Van Domelen, vice president of technology for DCS. “The business is very cutthroat and competitive on the pricing of polyacrylamide. We can reduce the cost further on friction reducer,” using dry polymer, he said. Polyacrylamide is generally described as the key component in friction reducers. Suppliers also add some ingredients to create a stable liquid and others that are supposed to improve performance. When DCS delivers dry polymer to a well pad to mix it on-site, the only other ingredient is water provided by the customer. It has been a winning strategy change for the private company; it has grown rapidly, even during last year’s slump. DCS increased the number of mixing units from one to 16, and dry polymer sales have grown from 10% to 90%, Van Domelen said. One of the company’s customers is John Blevins, the chief operating officer for Houston-based Hibernia Resources III and an early adopter who was a lead author of a paper on making friction reducer on site while fracturing (SPE 204176). Blevin, who uses the words “friction reducer” and “polymer” interchangeably, is the rare C-level executive who likes to manage operations from a frac van at a company that normally completes one pad at a time. The polymer is polyacrylamide. When Blevin works with DCS on a well, he purchases it directly from one of the few chemical companies that will produce the polymer based on his specifications. The price on the DCS invoice will be a price per pound that covers the cost of the polymer and the service. At Hibernia, a small private-equity and employee-owned company, there is a powerful incentive to pay close attention to the details. “When we spend a nickel, that nickel is divided among us at some point in time. If we are efficiently frugal, we are going to be better off in the long run,” Blevins said. The paper, which was presented at the Unconventional Resources Technology Conference (URTeC), included a chart showing stage-by-stage costs, with the average cost for dry stages ranging from 27% to 31% lower than similar stages that were fractured using liquids. The simplicity of the mix is a plus for Blevins whose company is especially focused on how chemicals are likely to react downhole. “We did a 6-month study before we pumped anything in the ground to make sure we had the right combination” of fracturing additives, he said. “We do study nearly every well and every landing zone to ensure the chemicals used are compatible.”

Heat Integrated Process Design, Simulation and Control of Polymerization and Drying Sections for HDPE Production

This paper describes a production model for high density polyethylene. Aspen Polymer Plus was used to model and simulate the polymerization drying and separation sections. Heat operations were improved using Aspen Energy Analyzer; The pinch analysis method generated, the heat exchanger network. The dynamic model via Aspen Plus Dynamics evaluated the stability and controllability of the models. The simulation results such as production rate, polydispersity index, weight-average molecular weight, and number-average molecular weight correponded with Hakim and Moballegh [1]. Five heat exchanger networks were proposed: the one with the lowest total index cost was selected to perform the dynamics analysis.

The Research on Modeling and Simulation of TFE Polymerization Process

PTFE (polytetrafluoroethylene) is the fluorinated straight-chain polymer, made by the polymerization of tetrafluoroethylene monomer; it is used widely because of its excellent performance and can be obtained by the polymerization of body, solutions, suspensions, and emulsions. But only the last two are the main ways. This research paper makes simulation based on Polymer Plus. It uses the emulsion polymerization method at background to carry out a semibatch reactor system. Upon the actual production conditions, simulation process under the steady state conditions is used to analyze the effects of the changes on operating conditions; the corresponding dynamic model is created to analyze the impact of the changes of conditions on the entire system. Moreover, the amount of APS which plays an important part in this reaction is discussed for getting the most suitable amount of initiator. Because of less research work on this job, it is so difficult to find the related data from the literature. Therefore, this research will have a great significance for the process of the tetrafluoroethylene emulsion polymerization in the future.

Application of Sanchez–Lacombe and Perturbed-Chain Statistical Associating Fluid Theory Equation of State Models in Catalytic Olefins (Co)polymerization Industrial Applications

Prediction of physical and thermodynamic properties in polymer manufacturing technology is of profound interest for the design and operation of industrial scale reactor and separation processes. In the present study, the Sanchez–Lacombe and perturbed-chain statistical associating fluid theory equations of state were employed to predict the physical and thermodynamic properties in catalytic olefin (co)polymerization industrial applications. Model predictions obtained by these two commonly used equations of state are compared with a large number of physical and thermodynamic property data over a wide range of pressures and temperatures. Aspen Polymers Plus software package is utilized and all the characteristic pure component and binary interaction parameters employed in the models are reported. The range of applicability in terms of operating conditions for the studied EOS is discussed, and recommendations regarding their use are provided.

Simulation and Analysis of an Ethylene Slurry Polymerization System Using Supercritical Propane

In this paper, a model for an ethylene slurry polymerization system using supercritical propane as a solvent is developed by adopting a set of thermodynamic and kinetic parameters using fundamental chemical engineering principles and Polymers Plus software. The Ziegler–Natta catalyst is characterized by assuming the existence of multiple types of catalyst sites and deconvolution data from gel permeation chromatography to determine the most probable chain-length distribution and relative amounts of polymer produced at each site type. A set of suitable reaction subclasses and kinetic constants for different site types that fit plant conditions is developed, validating our model. The values calculated for production rate, ethylene conversion, residence time, H2/C2H4 molar ratio in the reactor, number-average molecular weight, and polydispersity index are all close to actual values, verifying that our model accurately describes plant conditions.

Steady-State and Dynamic Modeling of the Basell Multireactor Olefin Polymerization Process

In this work, we developed the steady-state and dynamic models for the commercial polypropylene process of Basell Spheripol technology, involving fundamental chemical engineering principles and advanced software tools, i.e., Polymers Plus and Aspen Dynamics. The models considered the important issues of physical property and thermodynamic model selection, catalyst characterization, and reactor model. Besides, a multisite catalyst with traditional Ziegler−Natta polymerization kinetics was introduced to describe the broad molecular weight distribution of the polymers produced in this polypropylene technology. Both the continuous stirred tank reactor model and the combined plug flow reactors model were proposed to simulate the reactors. Furthermore, we validated the models using industrial data and demonstrated application of the dynamic model to grade change, start up, and shut down at a certain emergent accident.

Simulation for Polymerization Process of Styrene Butadiene Rubber (SBR)

In this paper, Polymer Plus of Aspen Tech Inc. is used to establish a styrene-butadiene rubber (SBR) polymerization process model; the sensitivity analysis method is used to analyze concentration of the initiator, reaction temperature and other factors which influence production and molecular weight of product. It is concluded that increasing amount of initiator can improve production, while the molecular weight would increase at first and then decline; and along with the increasing temperature, weight-average molecular weight would lower and production of polymer PBS would increase; molecular weight of polymer and production of polymer would magnify along with increase of amount of emulsifier and volume of the reactor.

Mathematical modelling of the solubility of supercritical CO 2 in poly( l-lactide) and poly( d,l-lactide-co-glycolide)

Two mathematical models, Sanchez–Lacombe equation of state and the Perturbed-Chain Statistical Associating Fluid Theory were applied for modelling the phase equilibrium for the poly( l-lactide)–CO 2 and poly( d,l-lactide-co-glycolide)–CO 2 systems. Aspen Polymer Plus software was used. The results were compared with previously obtained experimental values for solubility. The solubility of scCO 2 in the two biodegradable polymers was calculated for three different temperatures (308, 313 and 323 K) in the pressure range (10–30 MPa). The characteristic parameters for the components and the binary interaction parameters for the models were optimized in order to obtain the best fit between the estimated and the experimental gas solubility data. The results suggest that both SL EOS and PC-SAFT are reliable models in describing the phase equilibrium of the PLLA–CO 2 and PLGA–CO 2 systems at the proposed working conditions.

Steady-state and dynamic modeling of commercial bulk polypropylene process of Hypol technology

Both steady-state and dynamic models for the commercial bulk polypropylene process of HYPOL technology were developed by using fundamental chemical engineering principles and advanced software tools, Polymers Plus and Aspen Dynamics. The models consider the important issues of physical property and thermodynamic model selections, catalyst characterization, and reactor model, in addition to the traditional Ziegler–Natta polymerization kinetics. The performance of equilibrium-stage modeling was examined using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state and a pre-built reactor model in Polymers Plus. The detection of non-equilibrium behavior for the liquid-phase reactor leads to a novel reactor model suggested in this work, wherein the vapor–liquid equilibrium behavior was separated from polymerization behavior. Besides, the traditional Ziegler–Natta polymerization system was incorporated from single-site to multi-site model by fitting the actual data sourced from open reports and certain plant data. Furthermore, we validated the models using the plant data and demonstrated the application of our dynamic model by simulating a grade change.

Steady-State and Dynamic Modeling for New Product Design for the Solid-State Polymerization of Poly(Ethylene Terephthalate)

We model an entire poly(ethylene terephthalate) (PET) solid-state polymerization (SSP) process with precrystallizers, crystallizers, SSP reactors, and dryers using a unified cell approach. This approach builds complex unit-operation models using individual cells, or continuous-stirred-tank reactor (CSTR) models. Each cell considers the essential physical properties, phase equilibrium, polymerization kinetics, mass transfer through the polymer and into the carrier gas, and crystallization kinetics. Our model development involves fundamental chemical engineering principles and advanced software tools, such as Polymers Plus and Aspen Custom Modeler. We analyze both reaction and diffusion in each cell, considering two options: (1) to model diffusion using a second-order partial differential equation (PDE) or a simplified two-film theory and (2) to include or ignore crystallization kinetics. Performing best is the model with a PDE for diffusion and with equations describing crystallization and its effect on reaction and diffusion. We validate the model using commercial plant data of intrinsic viscosity, degree of crystallinity, and acetaldehyde concentration. We are unable to find a suitable set of parameters for other simpler models to represent accurately the plant data in its entirety. After validating our SSP model, we apply it to study the sensitivity of our SSP process on temperature and pellet geometry. For pellets with cross-sectional dimensions of 3.2 mm × 3.2 mm, we vary the length from 1.5 to 3.5 mm and predict the intrinsic viscosity. The model suggests only a mild dependence of intrinsic viscosity on the pellet length. In contrast, our model suggests that, for an increase in temperature of 12 °C, intrinsic viscosity rises by almost 0.1 dL/g. Last, we use our validated model to predict the process changes required to produce a high-viscosity product (1 dL/g). Our model suggests that, with appropriate increases in both reactor temperature and residence time, we can make this product.

Base Case Simulation of a Semi-Batch Emulsion Copolymerization Process

It has been long recognized that emulsion polymerization is a complex heterogeneous process involving transport of monomers and other species and free radicals between aqueous phase and organic phases. Though there are a number of models available in the literature, most of them deal only with specific aspects in emulsion polymerization and are far from being general. To simulate this complicated process and to achieve an adequate level of understanding, a Polymer Plus' software from Aspen Technology, Inc. has been used. The objective of this work is to illustrate the principle use of Polymers Plus' and to simulate and analysis the free-radical seeded emulsion copolymerization of styrene-butadiene process model in a semi-batch reactor. The base case simulation can be used to gain process understanding by analyzing how process variables and operating conditions during the course of a semi-batch reactor affect product quality.

Nonequilibrium Behavior in Ethylene/Polyethylene Flash Separators

In this work, we investigated various approaches for the modeling of the high- and low-pressure separator units downstream from a low-density polyethylene tubular reactor using the Polymers Plus software package. First, we examined the performance of thermodynamic equilibrium by using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state. Experimental data taken from the open literature were used to obtain the model parameters. Comparison with data from an Equistar plant showed that the PC-SAFT simulations agreed very well with the low-pressure separator residual-ethylene solubility measurements. There were, however, significant discrepancies between the model and the plant data for the high-pressure separator, indicating that the high-pressure separator is not operating at equilibrium conditions. A further investigation was performed where a physical mechanism based on a bubble formation model was evaluated and a mathematical correlation using dimensionless numbers develope...

Steady-State and Dynamic Modeling of Gas-Phase Polypropylene Processes Using Stirred-Bed Reactors

This paper describes the development of a comprehensive model for the continuous gas-phase synthesis of polypropylene using stirred-bed reactors. The model considers the important issues of physical property and thermodynamic model selections, polymer properties, catalyst characterization, and reactor residence time, in addition to the traditional Ziegler−Natta polymerization kinetics. Model development involves fundamental chemical engineering principles and advanced software tools, Polymers Plus and Aspen Dynamics. We characterize a Ziegler−Natta catalyst by assuming the existence of multiple catalyst site types. The model contains a single set of kinetic and thermodynamic parameters that accurately predicts the polymer production rate, molecular weight, polydispersity index, and composition for both homopolymer and impact copolymer product grades from a large-scale commercial process. We demonstrate the application of our dynamic model and process control by comparing grade-transition strategies.

Vapor−Liquid Equilibrium for Polymer−Diluent Systems from Melting Point Depression

A novel approach for determining vapor-liquid equilibrium (VLE) for polymer-diluent systems is described. The concentration- and temperature-dependence of diluent-polymer Flory-Huggins interaction parameter X ij is first estimated from depression in polymer melting point as a function of monomer (diluent) concentration. VLE for the polymer-diluent binary system is then obtained using an activity coefficient model and equation of state model with Aspen Polymer Plus. The technique is validated for the syndiotactic polystyrene-toluene and syndiotactic polystyrene-methyl ethyl ketone and is extended to polybutylene terephthalate - with various diluents such as butanediol, tetrahydrofuran, isophorone, 1-methylnaphthalene, and benzonitrile, systems hitherto not reported in the literature.

Quantifying Relationships among the Molecular Weight Distribution, Non-Newtonian Shear Viscosity, and Melt Index for Linear Polymers

This paper presents methodologies to quantify the relationships among the molecular weight distribution (MWD), steady-shear non-Newtonian viscosity (i.e., flow curve), and melt index (MI) of three linear low-density polyethylenes manufactured using the same technology. With the aid of computer-aided process simulation tools (such as POLYMERS PLUS), polymer producers can predict accurately the MWD from manufacturing conditions. Our methodologies help the polymer producers to extend their simulation model to predict flow curves and MI from the MWD. To do this, this paper employs (1) a modified Carreau-Yasuda (CY) model or Bersted's partition model to relate the MWDs and flow curves, (2) Bremner and Rudin's model to relate the weight-average molecular weight (MWW) and MI, and (3) Rohlfing and Janzen's model to relate the flow curve and MI. We show that the Carreau-Yasuda, Bersted, and Bremner and Rudin models work very well for correlating our data, predicting flow curves that average 3−7% error and MI value...

Steady-State and Dynamic Modeling of Commercial Slurry High-Density Polyethylene (HDPE) Processes

We present the development of both steady-state and dynamic models for a slurry HDPE process using fundamental chemical engineering principles and advanced software tools, Polymers Plus and Aspen Dynamics. The discussion includes thermodynamic properties, phase equilibrium, reaction kinetics, polymer properties, and other modeling issues. We characterize a Ziegler−Natta catalyst by assuming the existence of multiple catalyst site types and deconvoluting data from gel permeation chromatography to determine the most probable chain-length distributions and relative amounts of polymer produced at each site type. We validate the model using plant data from two large-scale commercial slurry HDPE processes. Significantly, the model contains a single set of kinetic and thermodynamic parameters that accurately predicts the polymer production rate, molecular weight, polydispersity index, and composition for several product grades. We illustrate the utility of the dynamic model by simulating a grade change. Finally,...

Physical Properties, Reactor Modeling, and Polymerization Kinetics in the Low-Density Polyethylene Tubular Reactor Process

In this investigation, we demonstrate our methodology in developing a comprehensive computer simulation model for the low-density polyethylene process in a tubular reactor using Polymers Plus. We use the perturbed-chain statistical associating fluid theory to describe the thermodynamic properties of the system. A comparison with literature data shows that the selected equation of state does a very good job in describing the physical properties and phase equilibria of the system. A detailed reactor model was proposed on the basis of transport literature that provides insight into the various resistances to heat transfer that arise during polymerization, and a comprehensive free-radical kinetic model was developed that describes the various individual mechanisms of the polymerization of ethylene and the properties of the polymer product. Results from the proposed simulation model were used in comparison with plant measurements from an Equistar Chemicals plant, in both correlative and predictive modes, for several polymer grades. In all cases considered, very good agreement was observed between simulation results and plant data on reactor temperature profiles, polymer properties, and production rates.