Excess associated gas from unconventional wells is typically flared while excess produced water is injected underground. In this work, flare gas recovery is integrated with produced water desalination and a solar pre-heater. The solar module with a beam splitter preheats the produced water. Aspen Plus process modeling, economic analysis, and greenhouse gas analysis were performed. The solar flare gas recovery desalination (Solar-FGRD) process can conserve water resources and reduce the brine injection by 77%. The accompanying solar farm results in excess solar electricity for exporting to the grid. The process burner combustion efficiency (CE) is 99.8%, with a destruction and removal efficiency (DRE) of 99.99% for methane as opposed to a flare CE of 80–98% (and a methane DRE of 91–98%). The greenhouse gas (GHG) emissions for CO2 and methane, in terms of CO2 equivalent (CO2e), can be reduced by 45% for US North Dakota and Texas flaring and 13% for North Sea flaring by employing the Solar-FGRD process. Comprehensive financial analysis demonstrates the financial–economic feasibility of the investment project with or without tax credits. Best-case and worst-case scenarios provide a realistic range that investors can consider before making investment decisions.

Landfills are major emitters of greenhouse gases, especially methane (CH4). To address this, the U.S. EPA promotes utilizing landfill gas (LFG) for renewable energy. Our study in Southeast Texas compared four LFG conversion strategies: flaring, electricity generation, renewable natural gas and methanol production. Scenario analysis was conducted to reveal the influence of market conditions and incentives on profitability. While electricity generation consistently yielded the highest returns, methanol production emerged as a close contender due to the strategic advantage of its proximity to the landfill site in this industrial zone. This study highlights the promising synergy between landfills and the hydrocarbon industry for sustainable development.

The natural gas (NG)-powered compressors/engines used in liquified natural gas (LNG) plants are a major source of methane emission. The Allam–Fetvedt cycle (AFC), an oxyfuel, carbon-neutral, high-efficiency power plant, generates pipeline-grade CO2. This work performed novel process modeling, economic analysis, and greenhouse gas emissions analysis for a heat-integrated, electrified LNG/AFC/air separation unit (ASU) complex (LAA), then compared it to standalone LNG and AFC/ASU plants (baseline) as well as an LNG plant electrified with AFC/ASU without heat integration. The low-grade heat generated from compressors of the LNG plant can enhance the AFC net power output by 7.1%. Utilizing the nitrogens cold energy reduces the compressor power requirement by 1.6%. In the integrated LAA complex, not only are GHG emissions avoided, but the energy efficiencies are also improved for both the LNG plant and the AFC power plant. A cash flow analysis of LAA was performed over a 20-year period with 5%, 7%, and 10% discount rates and three levels of LNG prices. The 45Q CO2 credit of USD 85/T as stipulated by the recent Inflation Reduction Act (IRA) of 2022 has been incorporated. The results clearly indicate the economic and environmental benefits of the proposed electrification and heat/power integration.

A fuel mixture of ammonia and natural gas as a low-carbon alternative for future power generation and transportation is an attractive option. In this work, a 50-species reduced mechanism, NH3NG, suitable for computational fluid dynamics simulations (CFD), is developed for ammonia–natural gas cofiring while addressing important emission issues, such as the formation of nitrogen oxides (NOx), soot, carbon monoxide, and unburnt methane/ammonia. The adoption of reduced mechanisms is imperative not only for saving computer storage and running time but also for numerical convergence for practical applications. The NH3NG reduced mechanism can predict soot emission because it includes soot precursor species. Further, it can handle heavier components in natural gas, such as ethane and propane. The absolute error is 5% for predicting NOx and CO emissions compared to the full Modified Konnov mechanism. Validation with key performance parameters (ignition delay, laminar flame speed, adiabatic temperature, and NOx and CO emissions) indicates that the predictions of the reduced mechanism NH3NG are in good agreement with published experimental data. The average prediction error of 13% for ignition delay is within typical experimental data uncertainties of 10–20%. The predicted adiabatic temperatures are within 1 °C. For laminar flame speed, the R2 between prediction and data is 0.985. NH3NG over-predicts NOx and CO emissions, similar to all other literature methods, but the NOx predictions are closer to the experimental data.

To meet the increasing demand for electricity consumption for global economic development and the urgent need for carbon dioxide (CO2) sequestration for global climate change mitigation, the natural-gas-fired Allam-cycle power plant becomes very attractive due to its high energy efficiency, NOx emission-free properties, and inherent capability of producing pipeline-ready CO2 for various industrial uses. Bearing these merits, this paper has newly developed an integrated A3 complex, which integrates an Allam power cycle, an air separation unit (ASU), and an ammonia plant to simultaneously produce power, ammonia, water, and pipeline-ready CO2 efficiently and economically. The developed A3 complex is highly material-and-energy integrated among the three subsystems, where the Allam power cycle will empower the ASU and in turn be fueled by the pure oxygen feed from the ASU; meanwhile, the nitrogen stream from the ASU will be the feedstock of the ammonia plant to produce fertilizers. The efficacy of the developed A3 complex has been demonstrated by rigorous large-scale modeling and simulations. Its economic and environmental performances have also been systematically evaluated to exemplify its system excellence.

Advanced process control is developed for a novel oxy-fuel Allam cycle power plant integrated with an Air Separation Unit (ASU) with no greenhouse gas and NOx emissions. The Dynamic Matrix Control (DMC) controller was developed with AspenTech's DMC Technology Version 11 engineering software. The DMC controller improves nitrogen purity, carbon dioxide purity and flowrate, and power output by an average of 4%. Also, the DMC controller is able to handle disturbances in the range of 12.5% for feed flow changes and 10% for feed composition changes. Substantial enhancement was observed in upgrading carbon dioxide purity from 97% Enhanced Oil Recovery (EOR) grade to 99.9% food/medical grade. Therefore, this advanced control strategy is superior to regulatory PID controllers and the developed DMC controller can be used as a seed model in the actual plant control by combining with the actual plant test data in the calibrate mode.

Current EPA regulations mandate a minimum combustion zone heating value of 270 BTU/scf and a net heating value dilution parameter of NHV dil ≥ 22 BTU/ft 2 for all steam/air/non-assisted flares while maintaining a high combustion efficiency (CE). To achieve the target performance along with satisfying the EPA regulations, it is necessary to understand the influence of various operating parameters. Studying the effect of operating parameters through experiments is both expensive and time consuming. It is more cost effective to use validated models to guide flare operations. In this study, controlled flare test data conducted from 1983 to 2014 with a wide range of exit velocities, heating values, and fuel compositions have been modeled. The purpose of this study is to develop models that can be robustly used in the industry to achieve the desired CE without visible emissions (smoke). Steam-/air-assist rates, exit velocity, and the vent gas composition, which can be either controlled or measured in flare operations, are used as independent variables in the models. Neural network (NN) models were developed for the air-assisted, steam-assisted, and non-assisted flares using various types of fuels like propylene, propane, natural gas, methane, and ethylene. The flare performance models such as CE and opacity were developed using neural network toolbox in MATLAB. NN models for steam and air-assisted flare tests are in good agreement with experimental data and have been demonstrated by the average correlation coefficient of 0.95 and 0.97 for air-assisted and steam-assisted flare data, respectively. The very low mean absolute errors of 1.1% and 1.4% for air-assisted and steam-assisted flare data, respectively, also indicate the robustness of the NN models. 2-D and 3-D contour plots are presented to show the effect of key operating parameters. The set points (amount of steam/air/make-up fuel required) at the Incipient Smoke Point (ISP) and for Smokeless Flaring (SLF) have been developed based on the neural network models performed in this study. Desirable operating inputs can be set for the ISP and for SLF (Opacity ≤ Opacity ISP ) subject to heating value constraints (NHV dil ≥ 22 BTU/ft 2 & NHV CZ ≥ 270 BTU/scf) with a high CE (≥ 96.5%) for the 1984 EPA and 2010 TCEQ flare study test cases.

Federal Regulation 40 CFR 63.670 requires flare operators to specify smokeless design capacity for flares with no visible emissions. Alternatively, 96.5% combustion efficiency (CE) or 98% destruction efficiency must be achieved with threshold limits of minimum combustion zone net heating value (NHVcz) >= 270 British thermal unit/standard cubic feet (BTU/scf) for steam-assisted and net heating value dilution parameter (NHVdil) >= 22 BTU/ft(2) for air-assisted flares. There is still no guarantee for smokeless flaring (SLF) or CE >96.5%. Robust response surface models developed in this study expressed %CE and %Opacity as a function of operating variables for air- and steam-assisted flares. Opacity and CE test data from 1983 to 2016 were analyzed. General quadratic models with transforms of CE and Opacity showed R-2 > 0.90, and bivariate sigmoid models for CE showed R-2 > 0.87. Two-dimensional (2D) contours illustrate the trends of major operating parameters. Operational setpoints at the incipient smoke point (ISP) and SLF were determined by solving the models subject to NHVcz and NHVdil threshold limits specifying Opacity at 3% (ISP) and 2% (SLF). The predicted steam/air assists/makeup fuel, NHVcz (or NHVdil), and CE at ISP and SLF conditions are compared with the experimental 1984 Environmental Protection Agency (EPA) and 2010 Texas Commission on Environmental Quality flare study ISP test data. These setpoints would help flare operators to establish ISP or SLF conditions either by adding makeup fuel to vent gas with low heating value or by minimizing the assist without adding makeup fuel for steam- and air-assisted flares.

Flares are important safety devices that can burn off unwanted gases from upstream, midstream, and downstream industries. However, if operated improperly, flaring can emit huge amount of pollutants, in addition to CO2, and will cause significant environmental and health risks. It is highly desirable to achieve zero flaring via flare minimization and flare gas recovery. If the waste gas has to be combusted using a flare, the flaring event should be clean and efficient, making minimal environmental and health impacts. This article gives a holistic review of the most recent status of flaring world-wide, newest regulations in the United States and state-of-art technologies for achieving clean combustion during flaring, flare minimization, and flare recovery. Adaption of these technologies can help the process industries meet compliance and improve their sustainability.

The Allam cycle is the latest advancement in power generation technologies with a high cycle efficiency, zero NOx emission, and carbon dioxide available at pipeline specification for sequestration and utilization. The Allam cycle plant is a semi-closed, direct-fired, oxy-fuel Brayton cycle that uses high pressure supercritical carbon dioxide as a working fluid with sophisticated heat recuperation. This paper conducted process analyses including exergy analysis, sensitivity analysis, air separation unit (ASU) oxygen pump/compressor option analysis, and carbon footprint analysis for the integrated Allam power plant (natural gas)/ASU complex with a high degree of heat and work integration. Earlier works on exergy analysis were done on the Allam cycle and ASU independently. Exergy analysis on the integrated plants helps identify the equipment with the largest loss of thermodynamic efficiency. Sensitivity analysis investigated the effects of important ASU operational parameters along with equipment constraint limits on the downstream Allam cycle. Energy efficiency and carbon footprint are compared among the state-of-the-art fossil-fuel power generation cycles.

The controller and the control valve are the workhorses of the process industry. The profitability, the reduction in energy consumption and raw material usage along with the increase in product quality are maintained by the process control hardware and software. However, control loops can suffer from poor performance due to ill tuned controllers or mostly due to problems associated with the pneumatic control valves as they are the only moving parts in the control loops. These oscillations will lead to increase energy consumption and increased wear and tear of equipment along with poor product quality. This paper proposes discrete data-driven models to simulate the stiction and oscillation of a control valve based on first order dynamics. The model is validated through experimental results obtained from a sticky valve test bed. Furthermore, a Convolution Neural Network is utilized successfully to identify the control valve stiction. Libraries for VP (Valve Position) vs. CO (Controller Output) plots were utilized to train the convolution neural network.

The unprecedented rise in carbon dioxide levels due to anthropogenic activities, if left unchecked, can lead to increased global warming. Electricity and heat generation account for around 25% of this greenhouse gas emission. The Allam cycle, a new oxy-fuel power cycle that emits virtually no CO2 and NOx, is inherently integrated with an air separation plant. In this study, Aspen Plus Dynamics was used to model the integrated Allam power plant/air separation unit (ASU) with a high degree of heat and work integration. The steady-state model developed agrees with the model developed by Net Power. Regulatory and advanced PID controllers were implemented for major equipment to meet operation objectives. Controller set point change, power ramp down, and natural gas composition change were studied, and key plant performance indicators were monitored and analyzed. This study shows that the Allam cycle power plant integrated with an ASU is controllable with the proposed control strategy under a tightly integrated configuration.

Flares are important safety devices for pressure relief; at the same time, flares are a significant point source for soot and highly reactive volatile organic compounds (HRVOCs). Currently, simple guidelines for flare operations to maintain high combustion efficiency (CE) remain elusive. This paper fills the gap by investigating the characteristics of the incipient smoke point (ISP), which is widely recognized as the condition for good combustion. This study characterizes the ISP in terms of 100-% combustion inefficiency (CE), percent opacity, absorbance, air assist, steam assist, air equivalence ratio, steam equivalence ratio, exit velocity, vent gas net heating value, and combustion zone net heating value. Flame lengths were calculated for buoyant and momentum-dominated plumes under calm and windy conditions at stable and neutral atmosphere. Opacity was calculated using the Beer-Lambert law based on soot concentration, flame diameter, and mass-specific extinction cross section of soot. The calculated opacity and absorbance were found to be lognormally distributed. Linear relations were established for soot yield versus absorptivity with R-2 > 0.99 and power-law relations for opacity versus soot emission rate with R-2 >= 0.97 for steam-assisted, air-assisted, and nonassisted flares. The characterized steam/air assists, combustion zone/vent gas heating values, exit velocity, steam, and air equivalence ratios for the incipient smoke point will serve as a useful guideline for efficient flare operations. Implications: A Recent EPA rule requires an evaluation of visible emissions in terms of opacity in compliance with the standards. In this paper, visible emissions such as soot particles are characterized in terms of opacity at ISP. Since ISP is widely recognized as most efficient flare operation for high combustion efficiency (CE)/destruction efficiency (DE) with initial soot particles formed in the flame, this characterization provides a useful guideline for flare operators in the refinery, oil and gas, and chemical industries to sustain smokeless and high combustion efficiency flaring in compliance with recent EPA regulations, in addition to protecting the environment.

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 C-4 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.

Vadose Zone JournalVolume 16, Issue 12 vzj2017.11.0195 p. 1-3 Book Review Review of Remediation of Heavy Metals in the Environment Daniel H. Chen, Corresponding Author Daniel H. Chen [email protected] Dan F. Smith Dep. of Chemical Engineering, Lamar Univ., Beaumont, TX, 77705Corresponding author ([email protected]).Search for more papers by this author Daniel H. Chen, Corresponding Author Daniel H. Chen [email protected] Dan F. Smith Dep. of Chemical Engineering, Lamar Univ., Beaumont, TX, 77705Corresponding author ([email protected]).Search for more papers by this author First published: 14 December 2017 https://doi.org/10.2136/vzj2017.11.0195 All rights reserved. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume16, Issue12December 2017Pages 1-3 RelatedInformation

Soot emissions (PM 2.5) as well as CO and NOx from industrial flares and other industrial processes or sources pose a substantial risk to human being health and the environment, and now are subject to new and tougher EPA regulations. Flaring is used widely used in many industries to dispose unwanted combustion gases by burning them as a flame. However, flaring produces significant amount of particulate matter in the form of soot, along with other harmful gas emissions. Although many experimental and numerical studies have previously been done on flames burning in a controlled condition, relatively few studies have been conducted with fuel-steam mixture. In practice, air and steam are commonly used to assist the flaring processes control the smoke and the combustion efficiency. This study aims to investigate soot, CO and NOx emissions of turbulent diffusion methane and propane flame mixed with air or superheated steam. To study such effect numerically, the computational fluid dynamics software ANSYS Fluent 14.5 is used with non-premixed probability density function (PDF) model. The laminar flamelet is generated with automated grid refinement. For the soot generation, the Moss-Brookes soot model with Lee sub-model is considered. The combustion mechanism is developed by the authors' research group from the combined GRI and USC mechanisms. Two types of fuel, methane and propane, are used. The amount of super-heated steam varied from four percent to twenty percent (4%, 8 %, 12%, 16%, and 20%), and the behavior of the flame is analyzed. For the baseline case, the jet has a diameter of 50.8 mm or 2 inches, and the jet velocity is kept to 1.0 m/s. A co-flow air is supplied at a velocity of 0.2 m/s. The temperature distribution of methane and propane are compared with different contents of steam or air assists. The NOx, Soot and CO yields (kg/kg) varying with steam or air percentages are also presented. The results indicate that the soot yield is dependent on fuel type strongly and the percentage of steam or air affects the soot yield differently as the fuel type varies.

Industrial Flares are important safety devices to burn off the unwanted gas during process startup, shutdown, or upset. However, flaring, especially the associated smoke, is a symbol of emissions from refineries, oil gas fields, and chemical processing plants. How to simultaneously achieve high combustion efficiency (CE) and low soot emission is an important issue. Soot emissions are influenced by many factors. Flare operators tend to over-steam or over-air to suppress smoke, which results in low CE. How to achieve optimal flare performance remains a question to the industry and the regulatory agencies. In this paper, regulations in the US regarding flaring were reviewed. In order to determine the optimal operating window for the flare, different combustion mechanisms related to soot emissions were summarized. A new combustion mechanism (Vsoot) for predicting soot emissions was developed and validated against experimental data. Computational fluid dynamic (CFD) models combined with Vsoot combustion mechanism were developed to simulate the flaring events. It was observed that simulation results agree well with experimental data.

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. ImplicationsValidated 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.

Silver-doped titania/polyurethane (nAg-TiO 2 /PU) nanocomposite coatings were synthesized through a combined solution combustion and grafting from polymerization method, where nanosilver-doped titania (nAg-TiO 2 ) was chemically attached to the skeleton of the polyurethane polymer matrix with a bifunctional monomer, 2,2-bis(hydroxymethyl) propionic acid (DMPA). The polyester fabric functionalized with nAg-TiO 2 /polyurethane composites using dip-coating method has shown excellent antibacterial activity against gram-negative ( Escherichia coli ) and gram-positive ( Staphylococcus epidermidis ) bacteria. The nAg-TiO 2 photoreduced under methanol vapor exhibited an improved bactericidal activity because of the formation of elemental silver instead of silver oxide. XRD-EDX analysis was conducted to elucidate the percent of silver doping, the crystalline structure of titania, and the coating pattern of nAg-TiO 2 /PU over polyester fabric. One percent silver-doped titania was considered optimum because of its higher bactericidal activity when compared with higher-percent silver-doped titania. Effective bactericidal activity has been observed under the black light illumination, which, in conjunction with Ag-TiO 2 , completely inhibits any bacterial growth within 3 h of exposure. Antimicrobial effect of coating of nAg-TiO 2 /PU on polyester fabric was retained even after 30 traditional textile washings.