Peyton C. Richmond

Surface tension—Organic compounds

Publisher Summary This chapter presents the results of the surface tension for organic compounds in tabular format. For the tabulation, a modified Othmer relation is selected for correlation of the surface tension as a function of temperature. The tabulation is arranged by carbon number such as C, C2, and C3 to provide ease of use in quickly locating the data by using the chemical formula. The compound name and chemical abstracts registry number (CAS No) are also provided in columns. Values for regression coefficients are given in the adjacent columns. The temperature range for use is given in the next columns (TMIN and TMAX). The equation should not be used for temperatures outside this range. The next column provides the code for the tabulation. The last two columns provide a representative temperature and value for the surface tension at the representative temperature. The compilations of CRC, Daubert and Danner, Jasper, and Yaws are used extensively. Estimates are primarily based on the Sugden method, Brock and Bird correlation, and Sastri and Rao method. Experimental data and estimates are then regressed to provide the same equation for all compounds. A comparison of calculated and data values is also presented for a representative compound. The graph shows favorable agreement of equation and data.

Improve safety and reliability with dynamic simulation

Chemical companies face a major transition as the current workforce ages and the number of retirements accelerates resulting in many years of lost operating experience. It will be challenging to maintain and improve the reliability and safety of operations as some of the best operators leave the workforce. Faults due to operator errors can be addressed by improving the operators training and increasing the robustness of the control system to operator variability. In this article, we demonstrate how operator variability can be detected as a first step toward measuring and improving the control systems robustness. The characterization of a typical operator procedure caused transition, a reflux pump switch, and the resulting control system response was analyzed using the dynamic process simulation tool Honeywell UniSim Design. The best operator response and potential errors for other daily operator activities such as pump switches, reboiler switches, and similar operational transitions can be obtained offline by studying process history.

Parametric Study of Ethylene Flare Operations Using Numerical Simulation

Abstract In addition to CO2 and H2O, industrial flares may also release Volatile Organic Compounds (VOCs), NOx, and CO among others. Since experimental measurements of these emissions are expensive, rigorous computational fluid dynamics (CFD) simulations and the accrued correlations are viable tools to understand and analyze factors affecting flare operations. In this paper, parametric studies of air and steam assisted ethylene flares based on CFD modeling were employed to investigate important flare operating parameters such as vent gas velocity, crosswind velocity, stoichiometric air ratio, steam-to-fuel ratio and heat content of the vent gas. The CFD modeling utilized a 50-species reduced mechanism (LU 1.1) based on rigorous combustion chemistry. Validation results of LU 1.1 are also presented. The destruction/removal efficiency and the combustion efficiency (DRE & CE) were computed along with HRVOCs/VOCs/NOx emission rates to quantify the flare performance. Correlations between DRE/CE and major parameters (crosswind, jet velocity, and combustion zone heating value) were developed using the results obtained from the case studies. A modified combustion zone heating value definition was proposed to compute a comprehensive heating value in the combustion zone.

Reduced combustion mechanism for C1–C4 hydrocarbons and its application in computational fluid dynamics flare modeling

ABSTRACT Emissions from flares constitute unburned hydrocarbons, carbon monoxide (CO), soot, and other partially burned and altered hydrocarbons along with carbon dioxide (CO2) and water. Soot or visible smoke is of particular concern for flare operators/regulatory agencies. The goal of the study is to develop a computational fluid dynamics (CFD) model capable of predicting flare combustion efficiency (CE) and soot emission. Since detailed combustion mechanisms are too complicated for (CFD) application, a 50-species reduced mechanism, LU 3.0.1, was developed. LU 3.0.1 is capable of handling C4 hydrocarbons and soot precursor species (C2H2, C2H4, C6H6). The new reduced mechanism LU 3.0.1 was first validated against experimental performance indicators: laminar flame speed, adiabatic flame temperature, and ignition delay. Further, CFD simulations using LU 3.0.1 were run to predict soot emission and CE of air-assisted flare tests conducted in 2010 in Tulsa, Oklahoma, using ANSYS Fluent software. Results of non-premixed probability density function (PDF) model and eddy dissipation concept (EDC) model are discussed. It is also noteworthy that when used in conjunction with the EDC turbulence-chemistry model, LU 3.0.1 can reasonably predict volatile organic compound (VOC) emissions as well. Implications: A reduced combustion mechanism containing 50 C1–C4 species and soot precursors has been developed and validated against experimental data. The combustion mechanism is then employed in the computational fluid dynamics (CFD) of modeling of soot emission and combustion efficiency (CE) of controlled flares for which experimental soot and CE data are available. The validated CFD modeling tools are useful for oil, gas, and chemical industries to comply with U.S. Environmental Protection Agency’s (EPA) mandate to achieve smokeless flaring with a high CE.

Computational fluid dynamics modeling of laboratory flames and an industrial flare

A computational fluid dynamics (CFD) methodology for simulating the combustion process has been validated with experimental results. Three different types of experimental setups were used to validate the CFD model. These setups include an industrial-scale flare setups and two lab-scale flames. The CFD study also involved three different fuels: C3H6/CH4/Air/N2, C2H4/O2/Ar, and CH4/Air. In the first setup, flare efficiency data from the Texas Commission on Environmental Quality (TCEQ) 2010 field tests were used to validate the CFD model. In the second setup, a McKenna burner with flat flames was simulated. Temperature and mass fractions of important species were compared with the experimental data. Finally, results of an experimental study done at Sandia National Laboratories to generate a lifted jet flame were used for the purpose of validation. The reduced 50 species mechanism, LU 1.1, the realizable k-ϵ turbulence model, and the EDC turbulence–chemistry interaction model were used for this work. Flare efficiency, axial profiles of temperature, and mass fractions of various intermediate species obtained in the simulation were compared with experimental data and a good agreement between the profiles was clearly observed. In particular, the simulation match with the TCEQ 2010 flare tests has been significantly improved (within 5% of the data) compared to the results reported by Singh et al. in 2012. Validation of the speciated flat flame data supports the view that flares can be a primary source of formaldehyde emission. Implications Validated computational fluid dynamics (CFD) models can be a useful tool to predict destruction and removal efficiency (DRE) and combustion efficiency (CE) under steam/air assist conditions in the face of many other flare operating variables such as fuel composition, exit jet velocity, and crosswind. Augmented with rigorous combustion chemistry, CFD is also a powerful tool to predict flare emissions such as formaldehyde. In fact, this study implicates flares emissions as a primary source of formaldehyde emissions. The rigorous CFD simulations, together with available controlled flare test data, can be fitted into simple response surface models for quick engineering use.

A run time combustion zoning technique towards the EDC approach in large-scale CFD simulations

Purpose – This paper aims to present a novel run time combustion zoning (RTCZ) technique based on the working principle of eddy dissipation concept (EDC) for combustion modeling. This technique selectively chooses cells in which the full reaction mechanism needs to be solved. The selection criterion is based on the concept of differentiating between combustion and the non-combustion zone. With this approach, considerable reduction in computational load and stability of the solution was observed and even the number of iterations required to achieve a stable solution was significantly reduced. Design/methodology/approach – Computational fluid dynamics (CFD) simulations of real life combustion problems such as industrial scale flares, fuel fired furnaces and IC engines are difficult due to the strong interactions of chemistry with turbulence as well as the wide range distribution of time and length scales. In addition, comprehensive chemical mechanisms for hydrocarbon combustion may include hundreds of speci...

A stylized trend analysis approach for process monitoring and fault diagnosis

A stylized trend analysis was developed to identify recurring or standard operating procedures (SOP) such as equipment switching or maintenance from plant process history data to detect faults and near misses due to operator errors or equipment failures. Trend based fault detection and diagnosis systems have not been implemented widely in the chemical process industries because known fault scenarios are typically required. Known fault scenarios were not required for the stylized trend analysis because faults and near misses were identified by comparing trends with normal SOP transition responses. Large volumes of historical data were processed automatically allowing corrective action to be taken prior to an incident. The stylized trend analysis was demonstrated to detect unsteady‐state transition faults on historical distributed control system data simulated for a continuous process ethylene plant dryer switching operation.

Surface tension—Inorganic compounds

Publisher Summary This chapter discusses the results of the surface tension for inorganic compounds in tabular format. For the tabulation, a modified Othmer relation is selected for correlation of the surface tension as a function of temperature. The tabulation is arranged by alphabetical order such as Ag, Al, Ar, and Zr to provide ease of use in quickly locating the data by using the chemical formula. The compound name and chemical abstracts registry number (CAS No) are also provided in columns. Values for regression coefficients are given in the adjacent columns. The temperature range for use is given in the next columns (TMIN and TMAX). The equation should not be used for temperatures outside this range. The next column provides the code for the tabulation. The last two columns provide a representative temperature and value for the surface tension at the representative temperature. The compilations of CRC, Daubert and Danner, Jasper, Keene, Lu and Jiang, Mills and Su, and Yaws are used extensively. The reviews of Keene and Mills and Su are especially valuable and helpful for the metals. The review of Jasper is especially valuable and helpful for gases and liquids. Estimates are primarily based on the Sugden method. Experimental data and estimates are regressed to provide the same equation for all compounds. A comparison of calculated and data values is also shown for a representative compound. The graph shows favorable agreement of equation and data.