Chemical Processing Plant Research Articles

Lessons from Human Error Incidents in Process Plants

This paper describes four human error incidents in chemical process plants which I have personally observed, and discusses specific lessons from each of them. As often stated by Trevor Kletz, people respond to stories and examples, and hopefully these incidents will be useful in preventing similar incidents in the future. Fortunately none of the incidents resulted in serious safety consequences, although all cost some money and productivity. And, under other circumstances, similar errors in a more hazardous operation could have had serious safety consequences.

Nickel-Based Superalloys for Advanced Turbine Engines: Chemistry, Microstructure and Properties

The chemical, physical, and mechanical characteristics of nickel-based superalloys are reviewed with emphasis on the use of this class of materials within turbine engines. The role of major and minor alloying additions in multicomponent commercial cast and wrought superalloys is discussed. Microstructural stability and phases observed during processing and in subsequent elevated-temperature service are summarized. Processing paths and recent advances in processing are addressed. Mechanical properties and deformation mechanisms are reviewed, including tensile properties, creep, fatigue, and cyclic crack growth. I. Introduction N ICKEL-BASED superalloys are an unusual class of metallic materials with an exceptional combination of hightemperature strength, toughness, and resistance to degradation in corrosive or oxidizing environments. These materials are widely used in aircraft and power-generation turbines, rocket engines, and other challenging environments, including nuclear power and chemical processing plants. Intensive alloy and process development activities during the past few decades have resulted in alloys that can tolerate average temperatures of 1050 ◦ C with occasional excursions (or local hot spots near airfoil tips) to temperatures as high as 1200 ◦ C, 1 which is approximately 90% of the melting point of the material. The underlying aspects of microstructure and composition that result in these exceptional properties are briefly reviewed here. Major classes of superalloys that are utilized in gas-turbine engines and the corresponding processes for their production are outlined along with characteristic mechanical and physical properties.

Assessing the inherent atmospheric environmental friendliness of chemical process routes: An unsteady state distribution approach for a catastrophic release

The inherent environmental friendliness of a chemical process plant is assessed quantitatively based on its short-term atmospheric impacts due to a catastrophic release of the entire inventory of chemicals. In a catastrophic release of chemicals the environment into which the chemical is distributed will change with time. Therefore, it is important to account for these model environment changes in the chemical distribution method used when estimating short-term impacts. This paper proposes a method that uses the dispersion characteristics of the chemical in the atmospheric environment to estimate the model environmental volumes. Its distribution within this environment, between the different compartments such as air, soil or water is considered to estimate the predicted environmental concentrations (PEC). These values are then used in an index called the atmospheric hazard index (AHI) which assesses the inherent environmental friendliness of the chemical process plant. These AHI results are compared with those estimated by a method that uses the unit world model environment to estimate PEC values.

Wavelet-based Spatiotemporal Multiscaling in Diffusion Problems with Chemically Reactive Boundary

Chemically reacting flows over catalytic and non-catalytic surfaces are one of the elementary operations in chemical processing plants. The underlying physical phenomena span time- and length-scales over several orders of magnitude, for which a robust and flexible modeling framework must efficiently account for. With this purpose as the eventual goal, we propose a wavelet-based multiscale numerical framework and demonstrate it on coupling of two prototype methods for the problem of species generated on a chemically reactive boundary and diffusing through the bulk. The two methods consider different time and length scales. The first method in this coupling, termed fine, models the chemical reactions on the reactive boundary stochastically by the kinetic Monte Carlo method (KMC) and the diffusion in the medium deterministically using relatively small time increments and small spatial discretization mesh size. The second method, termed coarse, models both the reaction and the diffusion deterministically and uses drastically larger time increments and spatial discretization size than the fine model. The two methods are coupled by forming a spatiotemporal Compound Wavelet Matrix (CWM) that combines information about the time and spatial scales contained in them.

Acquisition of troubleshooting skills in a computer simulation: Worked example vs. conventional problem solving instructional strategies

In a computer-based simulation of a chemical processing plant, the differential effects of three instructional strategies for learning how to troubleshoot the plant's malfunctions were investigated. In an experiment concerning learners' transfer performance and mental effort, the simulation presented the three strategies to three groups of learners and measured their performance on the transfer tasks. In this experiment, conventional problem solving was contrasted with two worked example strategies. The results indicated a significant difference between practicing problem solving and using worked examples. Learners who practiced problem solving in an interactive simulation outperformed the learners who studied computer-based worked examples. They also invested lower mental effort in transfer tasks. When accounting for the difference in the learners' domain knowledge, the strategies were not significantly different among the more experienced learners. For the less experienced learners, those who practiced problem solving significantly outperformed their worked example counterparts. Among all participants and also among less experienced learners the problem solving group invested significantly lower mental effort in the performance of transfer tasks. Based on the results of this study, the authors recommend the use of the conventional problem solving strategy with or without worked examples for learning complex skills.

Standard Reference Data for the Viscosity of Toluene

Viscosity is an important transport property for the optimum design of a chemical process plant and for the development of molecular theories of the liquid state. A large amount of experimental viscosity data has been produced for all types of liquids, from alternative refrigerants to molten salts and molten metals. The accuracy of these data is related to the operating conditions of the instrument and, for this purpose as well as for the calibration of relative instruments, standard reference data for viscosity are necessary over a wide range of temperatures. New experimental data on the viscosity of liquid toluene along the saturation line have been obtained recently, mostly at low temperatures. The quality of the data is such that recommended values can be proposed with uncertainties of 0.5% (95% confidence level) for 260 K⩽T⩽370 K and 2% for 210 K⩽T<260 K and 370 K<T⩽400 K. A discussion about the uncertainties in the measurements and about the purity of the samples is made. The proposed value for the viscosity of liquid toluene at 298.15 K and 0.1 MPa is η=554.2±3.3 μPa s.

Chemical process route selection based upon the potential toxic impact on the aquatic, terrestrial and atmospheric environments

Abstract This paper proposes a method to estimate the inherent environmental friendliness of a chemical process plant by considering the potential toxicity impact on the aquatic, terrestrial and atmospheric environments. A worst-case scenario of a total loss of containment in the plant is assumed. The method proposed by [Gunasekera, M.Y., Edwards, D.W. (2003). Estimating the environmental impact of catastrophic chemical releases to the atomosphere: an index method for ranking alternative chemical process routes. Trans. IChemE., Part B, Process Safety and Environmental Protection, 81(B6), 463–474] for determining the inherent atmospheric environmental friendliness of a chemical plant is combined with the method proposed by [Cave, S.R., Edwards, D.W. (1997). Chemical process route selection based on assessment of inherent environmental hazard. Computers Chem. Engng., 21, S965–S970], which estimates the inherent friendliness to the aquatic and terrestrial environments. Application of this method to six routes to produce methyl methacrylate shows that the acetone cyanohydrin based route is potentially the least inherently environmentally friendly. The highest potential hazard is observed in the aquatic environment due to the chemicals associated with the acetone cyanohydrin route.

Conditioning of Flowing Multiphase Samples for Chemical Analysis*

The chemical analysis of process streams is a common task that must be completed thousands of times every day in the chemical industry. In refineries, at gas wells, in chemical processing plants, and in fine pharmaceutical facilities, there is a continual need for the chemical analysis of products and intermediates. Less common but no less important are the many instances in which such process samples must be handled in state‐of‐the‐art analytical chemistry labs. Unlike the typical samples presented in the analytical laboratory, process streams are seldom well behaved. Very often, process streams present multiphase samples to the analytical device. In this context, multiphase means that there is a gaseous or vapor phase plus one or more liquid phases. Because of the complexities of vapor/liquid equilibrium, a multiphase (two or more phase) mixture cannot be analyzed reliably. Sample conditioning is required before any analysis is attempted. This means that the gaseous and liquid fractions of the sample are separated into two distinct regions or streams. Moreover, the two phases must be retained in the device with complete integrity. That is, they must not be changed in any way by the separation device. In this paper, a simple approach to conditioning such multiphase samples is described. This approach permits the reliable analysis of each phase. *Contribution of the United States Government. Not subject to copyright in the United States.

Persistence and Biodegradation of Monoethanolamine and 2-Propanolamine at an Abandoned Industrial Site

Soil and groundwater samples were collected at the site of a former chemical processing plant in areas impacted by accidental releases of MEA (monoethanolamine) and IPA (2-propanolamine or isopropanolamine). Although their use had ceased ca. 10 years before sample collection, soils collected at contamination sites had MEA concentrations ranging from ca. 400 to 3000 mg/kg and IPA concentrations from ca. 30 to 120 mg/kg. Even though alkanolamines are miscible in water, transport to groundwater was slow, apparently because they are present in soil as bound cations. Only one groundwater sample (near the most highly contaminated soil)from wells directly adjacentto and down-gradient from the contaminated soils had detectable MEA, and none had detectable IPA. However, ammonia was found in the soil samples collected in the MEA-contaminated areas (ca. 500-1400 mg/kg) and the groundwater (80-120 mg/L), as would be consistent with bacterial degradation of MEA to ammonia, followed by transport of ammonia into the groundwater. Counts for bacteria capable of using MEA or IPA as a sole carbon source were ca. 5 x 106 and 1 x 106 (respectively) per gram in uncontaminated site soil, but no such organisms were found in highly contaminated soils. Similarly, bacterial degradation of MEA in slurries of highly contaminated soils was slow, with ca. 8-20 days required for half of the initial concentrations of MEA to be degraded at 20 degrees C and 30-60 days at 10 degrees C. In contrast, bacterial degradation studies using uncontaminated site soils spiked with ca. 1300 mg/L either MEA or IPA showed very rapid degradation of both compounds,with more than 99% degradation occurring in less than 3 days with quantitative conversion to ammonia, followed by slower conversion to nitrite and nitrate. The results obtained in the site soils, the groundwater samples, and from the biodegradation studies demonstrate that MEA and IPA can persist for decades on soil at high (hundreds of mg/kg) concentrations without significant migration into groundwater, despite the fact that they are miscible in water. Since MEA and IPA exist primarily as cations at the pH of site soils, their persistence apparently results from strong binding to soil, as well as inhibition of natural bioremediation in highly contaminated field soils.

The Williams and Otto Chemical Plant re-evaluated using a Pareto-optimal formulation aided by Genetic Algorithms

The Williams and Otto Chemical Plant is a classic example of a complex nonlinear programming problem incorporating the essential features of a chemical or hydrometallurgical processing plant. An efficient solution strategy for this time tested problem is shown here which uses different variants of biologically inspired Genetic Algorithms and is aided by a multi-objective formulation. The Genetic Algorithms worked more efficiently than the classical techniques used earlier and the nature of the feasible solutions was clearly revealed by the Pareto-optimality concept embedded in the multi-objective optimization employed here.

A Falling-Film Evaporator with Film Promoters

Falling-film evaporators have been used extensively in chemical processing plants due to their minimal fluid residence time and high heat transfer rates with low temperature differences. A cheaper alternative for achieving suitable liquid distribution and film stability was investigated here for solutions with low solids content and sufficiently low viscosity to allow for gravity-driven down-flow. The alternative consists of using a film promoter of thin stainless steel woven wire specified by mesh (opening number per linear inch), placed flush against the heating surface where the liquid film flows down. For very low liquid feed-flow rates per length of internal perimeter, such as 0.004 kg/(m·s), the fluid can be scattered over the entire vertical surface of the evaporator in a very thin film. The use of this film promoter leads to 3-fold higher evaporation rates.

Correlation Dimension and Lyapunov Exponent Based Isolation of Plant-Wide Oscillations

The correlation dimension and maximal Lyapunov exponent have a direct relationship with the harmonic complexity contained in non-linearity induced oscillations in chemical process plants. When combined with knowledge of the harmonic propagation of plant-wide oscillations, they can be applied to locate the source of the non-linearity. The method is demonstrated on both simulated data and real industrial data.

Chemistry in microstructured reactors.

The application of microstructured reactors in the chemical process industry has gained significant importance in recent years. Companies that offer not only microstructured reactors, but also entire chemical process plants and services relating to them, are already in existence. In addition, many institutes and universities are active within this field, and process-engineering-oriented reviews and a specialized book are available. Microstructured systems can be applied with particular success in the investigation of highly exothermic and fast reactions. Often the presence of temperature-induced side reactions can be significantly reduced through isothermal operations. Although microstructured reaction techniques have been shown to optimize many synthetic procedures, they have not yet received the attention they deserve in organic chemistry. For this reason, this Review aims to address this by providing an overview of the chemistry in microstructured reactors, grouped into liquid-phase, gas-phase, and gas-liquid reactions.

Fabrication and Post-Fabrication Cleanup of Stainless Steels

The surface condition of stainless steels is critical both where the product must not be contanninated, e.g., pharmacpjitical, food and nuclear plants; and where the stainless must resist an aggressive environment, such as in chemical-processing plants. Although the highly protective chromium oxide film that makes stainless steel “stainless” is tenacious, durable and self-healing, in the presence of oxygen, this film can become damaged. In fact, fabrication and post-fabrication cleanup practices can disturb this film in a variety of ways.

Estimation of the Remaining Life of Chemical Plant Process Piping

Estimation of the Remaining Life of Chemical Plant Process Piping

Oil level monitor added to range of positive displacement pumps

The Hydra-Cell D35 Series of industrial pumps from Wanner Engineering Inc is now available with an oil level monitor. The monitor detects dramatic oil level changes in the pump in order to minimize costly process interruptions and potential pump damage. The re-designed pump is intended for remote or critical pumping applications, such as automotive plants, oil refineries, chemical processing plants or paper mills. This is a short news story only. Visit www.worldpumps.com for the latest pump industry news.

Miniaturized Gas Ionization Sensors Using Carbon Nanotubes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Plant‐Wide Integration of Information and Decision Support Systems: Present Tools and Limitations

Information accessibility has changed the way that chemical process plants are being managed. The traditional pyramidal hierarchy that is usually the core of any management structure is being threatened by the potential of centralized decision‐making covering more and more possibilities. But although present tools may have access to any significant piece of objective information, and can process it at growing speeds, they are still termed as “decision support” systems. Sensible decision‐making is not only the result of knowledge plus information; it is also important to consider the effects of the different factors that are usually embraced by the term “human factors”.

Global algorithm for systematic retrofit of tubular process furnaces

Tubular process furnaces are widely used especially in the chemical and petrochemical process plants and refineries. Retrofit of a furnace is usually recommended for increasing plant capacity or improvement of the furnace (and/or plant) energy efficiency. Many different constraints of existing furnace design and operation are the reasons for which the retrofit of a furnace is a very difficult task. Main operational and geometrical constraints are taken into account in furnace retrofit integration approach created earlier. This approach was developed primarily for improvement of the furnace energy efficiency. When furnace retrofit for increasing the plant capacity is performed additional criteria have to be considered. Then fluid hydrodynamic behaviour plays an important role and influences the retrofit strategy. This problem is discussed in the paper and results in suggestion of the global conceptual algorithm for furnace retrofit strategy. Practical case studies demonstrate applicability of the proposed global furnace retrofit algorithm.

Cause of the Port Neal ammonium nitrate plant explosion

In 1994, an explosion in an ammonium nitrate neutralizer of a chemical processing plant in Port Neal, Iowa, resulted in fatalities, injuries, and widespread property damage. A lawsuit was brought by the plant operator against the neutralizer designer, and each party retained a team of scientists and engineers to determine the cause. The key question was whether the explosion initiated within or outside of the sparger that injected nitric acid into the ammonium nitrate solution. After extensive investigations and months of debate, an agreement could not be reached. To resolve this impasse, an independent expert was appointed by the ruling US District Court judge to review the evidence provided by the investigative teams, examine the recovered sparger fragments and test articles, and provide an opinion. This article presents the findings and conclusions from this investigation.