Techniques for measuring flare combustion efficiency and destruction removal efficiency: A review

The impact of flare destruction removal efficiency (DRE) and Products of Incomplete Combustion (PICs) on ozone formation was examined using a regional photochemical model. Emission scenarios for five industrial flares were considered. For each flare, four DRE values (95, 90, 75, and 50%) were assumed, along with a base case that assumed 98 or 99% DRE. For each DRE level, a scenario assuming that no PICs and a scenario assuming a level of PICs consistent with full scale flare tests was evaluated. Simulation results indicated that low DREs can increase ambient ozone concentrations by more than 15 ppb under some conditions, but under other conditions, may raise ozone concentrations by 1 ppb or less. Emission rates of unburned flare gases and the chemical reactivity of the unburned hydrocarbons explain much of the variability in ozone formation. The air quality simulations also showed that unburned flare gases can have a larger impact on ozone formation than PICs.

Mid-wavelength infrared (MWIR) imaging Fourier transform spectrometers (IFTSs) are a promising technology for measuring flare combustion efficiency (CE) and destruction removal efficiency (DRE). These devices generate spectrally resolved intensity images of the flare plume, which may then be used to infer column densities of relevant species along each pixel line-of-sight. In parallel, a 2D projected velocity field may be inferred from the apparent motion of flow features between successive images. Finally, the column densities and velocity field are combined to estimate the mass flow rates for the species needed to calculate the CE or DRE. Since the MWIR IFTS can measure key carbon-containing species in the flare plume, it is possible to measure CE without knowing the fuel flow rate, which is important for fenceline measurements. This work demonstrates this approach on a laboratory heated vent, and then deploys the technique on two working flares: a combustor burning natural gas at a known rate, and a steam-assisted flare at a petrochemical refinery. Analysis of the IFTS data highlights the potential of this approach, but also areas for future development to transform this approach into a reliable technique for quantifying flare emissions. Implications: Our research is motivated by the need to assess hydrocarbon emissions from flaring, which is a critical problem of global significance. For example, recent studies have shown that methane destruction efficiency of flaring from upstream oil may be significantly lower than the commonly assumed figure of 98%; work by Plant et al., in particular, suggest that this discrepancy amounts to CO2 emissions from 2 to 8 million automobiles annually, considering the US alone. Similarly, the international energy agency (IEA) estimates a global flare efficiency of 92%,which translates in 8 million tons of CH4 emitted by flares in 2020. Highlighted by these studies and supported by the World Bankinitiatives toward zero routine flaring emissions, there is an urgent need for oil and gas industry to assess their flare methane emission, and overall hydrocarbon emissions. At the very least, it is critical to identify problematic flare operating conditions and means to mitigate flare emissions. Focusing on remote quantification of plume species, the measurement technique and quantification method presented in this paper is a considerable step forward in that direction by computing combustion efficiency and key components for destruction efficiency.

Incineration surrogate ratioing technique

Abatement of perfluorocompounds (PFCs) used in semiconductor and display industries has received an attention due to the increasingly stricter regulation on their emission. In order to meet this circumstance, we have developed a radio frequency (RF) driven plasma reactor with multiple annular shaped electrodes, characterized by an easy installment between a processing chamber and a vacuum pump. Abatement experiment has been performed with respect to <TEX>$CF_4$</TEX>, a representative PFCs widely used in the plasma etching process, by varying the power, <TEX>$CF_4$</TEX> and <TEX>$O_2$</TEX> flow rates, <TEX>$CF_4$</TEX> concentration, and pressure. The influence of these variables on the <TEX>$CF_4$</TEX> abatement was analyzed and discussed in terms of the destruction & removal efficiency (DRE), measured with a Fourier transform infrared (FTIR) spectrometer. The results revealed that DRE was enhanced with the increase in the discharge power and pressure, but dropped with the <TEX>$CF_4$</TEX> flow rate and concentration. The addition of small quantity of <TEX>$O_2$</TEX> lead to the improvement of DRE, which, however, leveled off and then decreased with <TEX>$O_2$</TEX> flow rate.

An atmospheric-pressure microwave oxygen plasma torch (APMPT) is used for abating SF6 gas. The gas composition is analyzed with a Fourier transformation infrared spectrometer, and the abating effect is evaluated in terms of the destruction removal efficiency (DRE). The variation of SF6 DRE is investigated with respect to the microwave power, the gas flow rate, SF6 concentration, and the material and length of discharge tube. It is found that the existence of free-discharge regions in the vicinity of the inner wall of the discharge tube, influenced by the flow rate and microwave power, plays an important role in maintaining a stable discharge and determining the DRE value. The energy efficiency can be improved significantly by using quartz discharge tubes of a suitable length. Meanwhile, the explanations about the variation of DRE and energy efficiency for decomposing SF6 by APMPT are provided reasonably.

Student ID: N9931002 Title of Thesis: Reduction of stack VOCs from petrochemical production process via Platinum/Palladium catalytic combustion Total Pages: 72 Name of Institute: National Pingtung University of Science and Technology Name of Department: Department of Environmental Science and Engineering Date of Graduation: July 2012 Degree Conferred: Master Name of Student: Wei-Lun Yeh Adviser: Dr. Kuo-Ching Chang The Contents of Abstract in this Thesis： The stack VOCs from petrochemical production process is one of the main sources of volatile organic compounds (VOCs) in the air in Lin Yuan Industrial Zone, an important petrochemical center in Taiwan. After evaluating the characteristics of the VOC’s from the production process of some petrochemical facility in the Linyuen industrial Zone, the platinum / palladium catalytic incinerator is applied as stack end treatment. The online flame ionization detection (NIEA A723.72B) published by Environmental Protection Administration (EPA), R.O.C. (Taiwan), is applied to determine total hydrocarbons and total non-methane hydrocarbon contents from the discharge pipeline and tested under different conditions: various combustion temperature, VOCs concentrations ,and exhaust gas flow rates, toevaluate the efficiency as the basis for the operation parameters. The experiment consisted of two stages. At first stage, it was to evaluate the temperature and flow-rate dependence of heat recovery with feeding containing no VOCs. The feeding containing VOCs was applied to the second stage to study the relation between incoming concentration and destructive removal efficiency (DRE) of VOCs under various operation conditions, and evaluated energy consumption of the operation conditions. The results showed: (1) operation at heating temperature 350 ℃ and exhaust gas flow rate 600, 960, and 1,200 Nm3/hr,respectively,the exit concentration of VOCs could be reduced to less than 150 ppm, and DRE could reach to more than 95 %,complying with the Environmental Protection Administration Act, R.O.C.(Taiwan). Repeat the same operation at lower heating temperature , 330 and 340 ℃, DRE could still attain to more than 95 %, the results still complied with the Act; (2) the optimal operation condition with exhaust concentration of 4,766 ppm, at 350 ℃, 600 Nm3/hr achieved the best DRE (98.05 %); (3) the average energy cost of the optimal operation condition was NT$19.9 per 1,000 Nm3 exhaust; (4) at same combustion temperature, the higher the exhaust concentration and stronger exhaust gas flow rate, the poorer heat recovery; (5) the energy consumption increases as the combustion temperature and exhaust gas flow rate increased,and decreased as the exhaust concentration increases. Keywords:VOCs, Platinum/Palladium catalyst, Catalytic cinerators, Destruction removal efficiency

Iron-treated char was used in an attempt to catalyze chlorobenzene destruction in the ChemChar thermal waste gasification process. The contribution to the destruction removal efficiency (DRE) of chlorobenzene from gasification per se was increased from 99.75% when char was used in the gasifier bed to >99.99% when char treated with iron was used. This clearly satisfies the EPA requirement of 99.99% (4-nines) destruction. Furthermore, other operations in the total system including condensation of condensable matter from the gas stream, filtration of the dried gas over a char filter, and secondary combustion of the product gas contribute to additional removal of unreacted parent compound and byproducts, so that the DRE should easily be increased to 99.9999% (6-nines). The primary mechanism for chlorobenzene dechlorination was determined to involve the reduction of chlorobenzene by reaction with nascent hydrogen. Nascent hydrogen is produced through the water−gas shift reaction, which is believed to be cataly...

The catalytic oxidation of trace organic compounds generated from waste incineration is usually carried out by a fixed-bed reactor. However, the performance of a fluidized catalyst reactor is seldom studied. This work investigated the destruction removal efficiency (DRE) of benzene, toluene, ethylbenzene, xylene (BTEX), and polycyclic aromatic hydrocarbons (PAHs) generated from waste incineration under different operating conditions by a fluidized palladium catalyst. The investigated conditions included different fluidized velocities and the effects of heavy metals, acid gas, and water vapor. Experimental results showed that the fluidized-catalyst reactor was very effective for destroying BTEX and PAHs and capturing particles. When the feedstock contained heavy metals, Pb and Cd inhibited the oxidation of organic compounds, but Cr did not. Because the feedstock contained sulfur and chloride (PVC), the palladium catalyst was poisoned and deactivated. The presence of water vapor also decreases the DRE of BTEX and PAHs. Moreover, the particle size distribution of fly ash and heavy metals after the catalyst reactor became smaller by comparing the mass size distribution of fly ash and the elemental size distribution of heavy metals (Pb, Cr, Cd) before and after the fluidized-catalyst reactor.

Glycol dehydrators, used to remove water vapour from raw natural gas, are a significant source of benzene emissions (a known human carcinogen). This thesis investigates the benzene destruction removal efficiency (DRE) and black carbon (BC) emissions when using flaring as an emissions control mechanism for glycol dehydrators. Experiments were performed in which fuel mixtures representative of glycol dehydrator still vent gas, plus other manipulated compositions, were combusted in a flare. In quiescent conditions the DRE of benzene was nearly 100%, but the presence of benzene increased BC yields. Considering data for Alberta, Canada, flaring could potentially reduce benzene emissions by a factor of 1000, but would increase total BC emissions from all flaring by ~56%. BC emissions could be partially mitigated by adding methane to the still gas mixture prior to flaring. Further work is recommended to investigate the effects of crosswinds on the benzene DRE in a flare.

Objectives A gas scrubber which is normally composed of a reaction chamber and a scrubbing part is being used to purify the waste gases from the processes. An efficient design of the reaction chamber is essential in a scrubber system due to the overall operation stability and high destruction & removal efficiency (DRE). The purpose of the study was to obtain the basic design data of deriving the improved design by analyzing a small-scale model of the commercial reaction chamber. Methods In the present study, the small-scale model of the simplified the reaction chamber was designed and fabricated based on similitude theory, and the thermal-flow characteristics were numerically analyzed inside the chamber using commercial Computational Fluid Dynamics (CFD) code. Results and Discussion Based on two dimensionless numbers for the geometric similarity and three dimensionless numbers for the kinematic similarity, the small-scale model of the reaction chamber was designed and fabricated. From the numerical and experimental results, thermal-flow characteristics such as temperature gradient and thermal efficiency were evaluated. To validate the numerical method applied herein, the numerical results of the temperature at specific monitoring points were compared with the experimental data. The average error rates (2.5~9.8%) between them was shown and the numerical results of temperature distribution are in good agreement with the experimental data. Conclusions In this study, the small-scale model, which was designed and manufactured based on similarity theory was analyzed. From these results, the basic design data for drawing the improved design ideas were acquired The results of this study can be used as basic data for analyzing thermal and flow characteristics in a variety of scrubber systems. Key words: Semiconductor Industry, Gas Scrubber, Reaction Chamber, Similitude Theory, Computational Fluid Dynamics (CFD)

Abatement of volatile organic compounds (VOCs) and fluorine gases by a microwave plasma torch (MPT)

Thermal destruction of HFC-134a in pilot-, and full-scale gasification systems

Low waste feed concentrations and destruction removal efficiency

Chlorophenols (CPs) is one of the organic pollutants and are most widespread in aqueous environment. Advanced oxidation processes (AOPs) have been extensively utilized for the decomposition of hazardous or recalcitrant pollutants in the environment. The study combined UV/TiO2 with ultrasonic procedure to degrade 2,4-dichlorophenol (2,4-DCP) wastewater. The effects of factors including pH value, initial concentration of 2,4-DCP and quantities of TiO2, Fe (II), and Fe (III) added on the removal efficiency of 2,4-DCP wastewater were investigated. Experimental results revealed significant additive effect attributed to the combination of two procedures, 13-watt UV irradiation and 10-watt ultrasound, under the pH 10 and 1g L-1 TiO2. In additional, the destruction removal efficiency (DRE) of 2,4-DCP was raised about 10 % when 250 μM of Fe (II) and Fe (III) were added and this phenomenon was suggested that the Fenton-like reaction occurred.

Catalytic removal of NO and PAHs over AC-supported catalysts from incineration flue gas: Bench-scale and pilot-plant tests