Pollutants In Flue Gas Research Articles

Petroleum and Flue Gas Pollution Control

Petroleum and Flue Gas Pollution Control

Results from trialling aqueous ammonia-based post-combustion capture in a pilot plant at Munmorah Power Station: Gas purity and solid precipitation in the stripper

Australia's Commonwealth Scientific and Industrial Research Organisation and Delta Electricity have tested an aqueous ammonia-based post-combustion capture process in a pilot plant at the Munmorah black coal-fired power station. The results will be used to address knowledge gaps about the application of aqueous ammonia for post-combustion capture of CO2 and other pollutants in flue gas, and to explore potential applications of the ammonia process in the Australian power sector. This paper primarily focuses on gas purity and solid precipitation in stripper.A high purity of CO2 product was obtained at the stripper gas outlet. The CO2 volumetric concentration was generally between 99 and 100%, with the remainder being water and ammonia. The concentration of ammonia in the CO2 product stream can be lowered by increasing stripper pressure and temperature, increasing CO2 loading in the rich ammonia solvent, and decreasing ammonia concentration and stripper overhead condenser temperature. Solid precipitation occurred in the stripper condenser and reflux lines. XRD analysis revealed that solid ammonium bicarbonate precipitated in the stripper condenser and reflux lines. Based on our equilibrium-based model predictions, rich solvent split can potentially eliminate solid precipitation and reduce cooling duties during the aqueous ammonia based PCC processes.

Carbon supported vanadia for multi-pollutants removal from flue gas

Coal combustion generates flue gas that contains many types of pollutants including sulfur dioxide (SO2), nitrogen oxides (mainly NO) and heavy metals (Hg, Pb, As, etc.). Abatement of these pollutants has been an important task for sustainable development of the world, especially of the countries heavily relying on coal as the main primary energy. The dominant flue gas cleaning technologies used worldwide today are effective only for a single pollutant removal at conditions significantly different from each other and from that of flue gas emission. This inevitably leads to high cost for multi-pollutants removal. Research in past decades showed that carbon supported catalysts have superior properties for abatement of many flue gas pollutants, individually or simultaneously, at temperatures of flue gas emission. Among them, activated coke supported vanadia (V2O5/AC) attracted more attention due to its high activities in adsorption and oxidation, which are key properties needed for abatement of these pollutants. This article, as a plenary lecture of the 8th International Symposium on Gas Cleaning at High Temperatures (GCHT-8), is mainly a feature report that summarizes the main research on V2O5/AC catalyst for SO2, NO and Hg removal, especially the contributions made by Chinese researchers. It concentrates on in-depth understanding on surface science and catalysis, including the role of V2O5 in adsorption and oxidation of the pollutants; effects of SO2 and moisture on formation and consumption of poisonous sulfates; the role of AC in adsorption and oxidation of the pollutants and in decomposition of poisonous sulfates; the forms of intermediates and their transformation mechanism; and effects of alkali species in flue gas on activities of SO2 and NO removal.

Effect of activation agents on the surface chemical properties and desulphurization performance of activated carbon

Flue gas pollution is a serious environmental problem that needs to be solved for the sustainable development of China. The surface chemical properties of carbon have great influence on its desulphurization performance. A series of activated carbons (ACs) were prepared using HNO3, H2O2, NH3·H2O and steam as activation agents with the aim to introduce functional groups to carbon surface in the ACs preparation process. The ACs were physically and chemically characterized by iodine and SO2 adsorption, ultimate analysis, Boehm titration, and temperature-programmed reduction (TPR). Results showed that the iodine number and desulphurization capacity of NH3·H2O activated carbon (AC-NH3) increase with both activation time, and its desulphurization capacity also increases with the concentration of activation agent. However, HNO3 activated carbon (AC-HNO3) and H2O2 activated carbon (AC-H2O2) exhibit more complex behavior. Only their iodine numbers increase monotonously with activation time. Compared with steam activated AC (AC-H2O), the nitrogen content increases 0.232% in AC-NH3 and 0.077% in AC-HNO3. The amount of total basic site on AC-HNO3 is 0.19 mmol·g−1 higher than that on AC-H2O. H2O2 activation introduces an additional 0.08 mmol·g−1 carboxyl groups to AC surface than that introduced by steam activation. The desulphurization capacity of ACs in simulate flue gas desulphurization decreases as follows: AC-NH3 > AC-HNO3 > AC-H2O2 > AC-H2O. This sequence is in accord with the SO2 catalytic oxidation/oxidation ratio in the absence of oxygen and the oxidation property reflected by TPR. In the presence of oxygen, all adsorbed SO2 on ACs can be oxidized into SO3. The desulphurization capacity increases differently according to the activation agents; the desulphurization capacity of AC-NH3 and AC-HNO3 improves by 4.8 times, yet AC-H2O increases only by 2.62 as compared with the desulphurization of corresponding ACs in absence of oxygen.

THE INFLUENCE OF TEMPERATURE AND THE RATIO OF AIR EXCESS ON COMBUSTION EFFICIENCY OF POLYOLEFIN MATERIALS

Combustion of plastics is a very complex process and phenomena, which occur during this process, have not been sufficiently investigated. Polyolefins constitute almost half of all the generated plastics. In this study, the influence of temperature and the ratio of air excess on the concentration of pollutants in flue gases have been presented. The studies carried out on the designed test bench were preceded by a series of thermal analyses (TG, DSC, TG-MS).

The growth response of Alternanthera philoxeroides in a simulated post-combustion emission with ultrahigh [CO 2] and acidic pollutants

Although post-combustion emissions from power plants are a major source of air pollution, they contain excess CO 2 that could be used to fertilize commercial greenhouses and stimulate plant growth. We addressed the combined effects of ultrahigh [CO 2] and acidic pollutants in flue gas on the growth of Alternanthera philoxeroides. When acidic pollutants were excluded, the biomass yield of A. philoxeroides saturated near 2000 μmol mol −1 [CO 2] with doubled biomass accumulation relative to the ambient control. The growth enhancement was maintained at 5000 μmol mol −1 [CO 2], but declined when [CO 2] rose above 1%, in association with a strong photosynthetic inhibition. Although acidic components (SO 2 and NO 2) significantly offset the CO 2 enhancement, the aboveground yield increased considerably when the concentration of pollutants was moderate (200 times dilution). Our results indicate that using excess CO 2 from the power plant emissions to optimize growth in commercial green house could be viable.

Experimental studies on cotton stalk combustion in a fluidized bed

Abstract The present work reports studies on the mixing and combustion characteristics of cotton stalk (CS) with 10–100 mm in length in a fluidized bed. Effects of length and initial weight percentage of CS, diameter of alumina bed material as well as gas velocity on the mixing characteristics of CS with alumina were investigated. CS can mix well with 0.6–1 mm alumina at fluidization number N =3–8. Fluidized bed combustion of pure CS was conducted in a 0.2 MW th test facility. The concentrations of major gaseous pollutants (CO, SO 2 and NO) in flue (stack) gas were measured. The combustion efficiency of CS is over 99.5%. Additionally, the experiments researched the agglomeration characteristics of bed materials: silica sand and alumina. SEM/EDX analyses on silica samples suggest that the high alkali metals content may cause the formation of the coating around silica particles. The coating consists of compounds with low melting temperature and can result in the bed agglomeration. By contrast, alumina is difficult to react with alkali metals from CS ash after 38 h combustion.

Simultaneous Removal of NOx and SO2: A Promising Ag(II)/Ag(I) Based Mediated Electrochemical Oxidation System

AbstractThe present study is a first attempt towards utilizing a Ag(II)/Ag(I) based mediated electrochemical oxidation (MEO) system for the simultaneous clean‐up of NOx and SO2 gases in simulated flue gas‐air mixtures on a laboratory‐scale scrubber column integrated with an electrochemical reactor, and to rationalize the efficient application of the MEO process for flue gas abatement and pollution control. Experiments were carried out with individual gas components followed with the mixture, and the effect of input NO and input SO2 concentrations was examined on the NOx and SO2 removal efficiencies at 20°C. Complete oxidation of NO to NO2 with 100% NO removal efficiency and 80% NOx removal efficiency was achieved along with 100% SO2 removal efficiency, highlighting the potentially far greater efficiency of the Ag(II)/Ag(I) based MEO system in functionality and selectivity. Significant research work in this direction can be anticipated in the near future.

Experimental study on cotton stalk combustion in a circulating fluidized bed

This paper summarizes the results of an experimental study on cotton stalk (CS) combustion in a circulating fluidized bed. The mixing and fluidizing characteristics of binary mixture of CS with 10–100 mm in length and alumina bed material with a certain size distribution in a cold test facility were studied. The results show that CS by itself cannot fluidize, and adding inert bed material can improve the fluidization condition. CS can mix well with alumina at fluidization number N = 3–7. As N is more than 7, there will exist a little more segregation. The study concerning combustion characteristics of pure CS was performed on a circulating fluidized bed with a heat input of 0.5 MW. The effects of fluidizing velocity, secondary air flow and gas flow to the loop seal on the bed temperature profiles were investigated. Although there is a little more segregation at N higher than 7 in the cold tests, the hot experimental results indicate that slight segregation has little effect on the steady combustion of the dense region. In this study, the concentrations of major gaseous pollutants (CO, SO 2 and NO) in flue (stack) gas were measured.

Melting characteristics during the vitrification of MSWI fly ash with a pilot-scale diesel oil furnace

Treatment of municipal solid waste incineration (MSWI) fly ash is becoming an important issue in China. A pilot-scale experiment was carried out to treat MSWI fly ash by using a diesel oil furnace (DOF) for more than 6 months. The effects of melting temperature on volume reduction, weight loss, compositional changes, and toxicity of leach water for molten slag have been investigated and reported. Results indicated that the volume reduction fraction of raw fly ash (RFA) and washed-fly ash (WFA) was 75–80% and the weight loss fraction was 23.8–30% at 1260–1350 °C. During the vitrification, CaO, A1 2O 3, and SiO 2 percentages in fly ash increased as the temperature increased, especially for SiO 2, which was caused by both the decomposition of carbonates or sulfates and the volatilization of metal chlorides because the main components in secondary fly ash collected from fabric filter bags were NaCl and KCl. The leaching concentrations of heavy metals in molten slag were lower than the standard values of TCLP. The releasing levels of dioxin and other pollutants (such as SO 2, HCl, CO, NO x , etc.) in flue gas were all lower than the Chinese standard.

Using Oily Wastewater Emulsified Fuel in Boiler: Energy Saving and Reduction of Air Pollutant Emissions

The limited data for using emulsified oil have demonstrated its effectiveness in reducing flue gas pollutant emissions. The presence of a high concentration of toxic organic compounds in industrial wastewaters always presents significant problems. Therefore, this study was undertaken by using wastewater with COD of 9600 mg/L and total petroleum hydrocarbons-gasoline 440 mg/L for making an emulsified oil (wastewater content 20% with 0.1% surfactant) to evaluate the extent of reductions in both criteria pollutants and polycyclic aromatic hydrocarbons. For comparison, two other systems (heavy oil fuel and water-emulsified oil) were also conducted. The wastewater-emulsified oil fuel results in significant reductions in particulate matter (PM), NO(x), SO2, and CO as compared to heavy oil fuel and similar to those from water/oil emulsified fuel; for PM, it is better in wastewater-emulsified oil. The reductions of total PAH flue gas emissions are 38 and 30% for wastewater- and water-emulsified fuel, respectively; they are 63 and 44% for total BaP(eq), respectively. In addition to reducing flue gas pollutant emissions, the results also demonstrate that the use of wastewater-emulsified fuel in boiler operation provides several advantages: (1) safe disposal of industrial wastewater; and (2) energy savings of about 13%. Thus, wastewater/oil-emulsified fuel is highly suitable for use in boilers.

Emission of polycyclic aromatic hydrocarbons (PAHs) from the liquid injection incineration of petrochemical industrial wastewater

This study investigated the emission of polycyclic aromatic hydrocarbons (PAHs) from stack flue gas and air pollution control device (APCD) effluent of the liquid injection incinerator (LII) disposing the petrochemical industrial wastewater, and PAH removal efficiencies of wet electrostatic precipitator (WESP) and wet scrubber (WSB). The PAH carcinogenic potency were investigated with the benzo(a)pyrene equivalent concentration (BaP eq). The remarkably high total-BaP eq concentration (220 μg Nm −3) in the stack flue gas was much higher than those of several published emission sources, and indicated the possible influence on its surrounding environment. The total-PAH emission factors of the WESP, WSB and stack flue gas were 78.9, 95.7 and 30,900 μg L −1 wastewater, respectively. The removal efficiencies of total-PAHs were 0.254, 0.309 and 0.563% for WESP, WSB and overall, respectively, suggesting that the use of both WESP and WSB shows insignificant PAH removal efficiencies, and 99.4% of total-PAHs was directly emitted to the ambient air through the stack flue gas. This finding suggested that the better incineration efficiencies, and APCD removal efficiencies for disposing the petrochemical industrial wastewater are necessary in future.

Recent advances in mercury removal technology at the National Energy Technology Laboratory

The in-house research effort on mercury studies at the National Energy Technology Laboratory is an integrated, multi-task approach, including experimentation at both the laboratory-scale and the pilot-scale, as well as a numerical modeling effort to aid in interpretation of pilot-scale results. In the laboratory-scale work, novel sorbents and techniques for the removal of mercury from flue gas are being investigated using a small packed-bed reactor. The reactor system is used to screen novel sorbents for their capability to remove mercury from gas streams. The capacities of these novel sorbents are determined as a function of gas composition and temperature and are compared to results with commercially available activated carbons. In the pilot-scale work, an existing pilot unit has been characterized with respect to the distribution and fate of hazardous air pollutants in flue gas, with an emphasis on mercury. The pilot unit is a 500-lb/h (227-kg/h) pulverized coal-fired (PCFC) combustion system that includes a furnace, air preheater, spray dryer, ductwork and a pulse-jet fabric filter. The investigations with this unit have entailed evaluation of various activated carbons and novel sorbents, as well as comparisons of various sampling techniques for the determination of total and speciated forms of mercury. The impact of various parameters (temperature, sorbent-to-mercury ratio, baghouse pressure drop) on the removal of mercury has been investigated. Additionally, a slipstream allows for the investigation of sorbent injection in a fly ash-free flue gas over a wide range of operating conditions, including residence time. A summary of the results for mercury measurement and control from the 500-lb/h (227-kg/h) PCFC combustion system will be presented, as well as the evaluation of methods for measurement of in-duct removals using the slipstream. Finally, a discussion of the numerical modeling effort will be given.

Simultaneous treatment of organic compounds, CO, and NOx in the incineration flue gas by three-way catalyst

The performance of a three-way catalyst (TWC) Pd/Rh/CeO2/Al2O3 which has the ability to simultaneously treat different pollutants in the incineration flue gas was studied. The catalyst support CeO2/Al2O3 was prepared by the modified oil-drop sol–gel process, and Pd/Rh was coated by the successive impregnation procedures. Catalytic experiments were carried out to study the destruction removal efficiency (DRE) of organic compounds benzene, toluene, ethylbenzene, xylene (BTEX), polycyclic aromatic hydrocarbons (PAHs), CO, and NOx at different operating conditions. The effects of heavy metals, acid gas, and water vapors on the characteristic and performance of TWC were also investigated.Experimental results showed that the DRE of BTEX, PAHs, CO, and NOx by one-stage TWC reactor was not good but was higher than 80% by two-stage TWC reactor. The best composition ratio of Pd/Rh catalyst in one-stage reactor was 1/0.15. The presence of heavy metals Pb, Cd and acid gas SOx, HCl in the flue gas poisoned the catalysts Pd and Rh in TWC. The effect of water vapor was slight and reversible. The structure characteristics of catalysts and the reactions of various pollutants with active catalyst were much related to the performance of TWC.

Oxidation of organic pollutants in incineration flue gas by a fluidized palladium catalyst

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.

Cutting Wastes from Municipal Solid Waste Incinerator Plants

Major problems facing modern society include the provision of energy and means for waste disposal with the minimum generation of pollution and secondary wastes. Sustainable cities require the recovery of energy from that fraction of waste that cannot be economically reused or recycled. With up to 28 million tonnes of municipal solid waste having an average energy value of 10,000 kJ kg-1 being generated in the UK annually, incineration of with energy recovery is seen as the best available option for the safe disposal of municipal waste. Current efficient waste management strategies are also aimed at reducing the amount of waste from municipal solid waste incinerator plants by processing ash from new plants to approach the target of zero net waste material output and reducing the pollutants in flue gases by end-of-pipe treatment. Although pollutants in flue gases can be reduced to practically any desired level, the economic and environmental costs should be justified. Our research activities at Sheffield University Waste Incineration Centre are focussed on cutting down the amount of waste produced by these plants in the form of ash, slag and air pollutants. Our aim is to develop efficient yet cost-effective waste, energy and pollution management strategies to assist the incineration industries to control and operate future energy plants in the most efficient way possible.

Injection Nozzle for Ultraviolet Light-Enhanced H2O2 Oxidation of Air Pollutants in Flue Gas

Injecting aqueous solutions of hydrogen peroxide (H2O2) into hot flue gases can split the peroxide into OH and HO2 radicals. These reactive radicals readily oxidize air pollutants such as CO, VOCs, NO, mercury, and others. H2O2 is thermally “activated” (split into free radicals) rapidly at temperatures of 500°C and above. At lower temperatures, such as found in boiler exhaust flue gases, ultraviolet (UV) light can be used to activate the peroxide molecules. However, placing the UV lamps directly in the flue gases can lead to operating and maintenance problems, and “dilutes” the UV energy due to absorption by other gases. A “UV nozzle” has been developed that produces H2O2 radicals and delivers them into a flowing stream of boiler flue gases. Using a previously constructed pilot scale system at NASA's Kennedy Space Center, experiments were run to prove the concept of the nozzle, measuring the oxidation of NO as an indicator of radical formation and delivery. Data were taken at three temperatures, with none, one, or two UV lamps on, and with various injection rates of peroxide. Flue gas temperatures ranged from 85 to 304°C (186 to 580°F), and the molar ratios (inlet peroxide to inlet NOx) ranged from about 1.5 to over 15. Conversions of NO varied from 0% (at the lowest temperature tested) to above 50% (at highest temperature). Although increasing temperature had a marked effect on conversion, the activation of hydrogen peroxide by UV light was demonstrated in the temperature range of final flue gas exhaust gases (290–350°F). These results indicate that radicals can be created from hydrogen peroxide at reasonable temperatures using UV light, and that the radicals can be delivered into a flue gas stream where they can oxidize pollutants.

Pollutants in incineration flue gas

Previous studies have shown that pollutants from incineration include heavy metals, organic compounds, particulate and acid gas. However, most studies on a single pollutant, it is rare for a study to concentrate on all possible pollutants and the relations between these pollutants under various incineration conditions. The objective of this work was to experimentally study the effect of different operating conditions on the pollutants emitted during incineration and the relations between these pollutants. The operating conditions of the experiments included the temperature of the combustion chamber and the species of organics. The findings indicated that the concentration of hydrogen chloride (HCl) in the presence of polyvinyl chloride (PVC) was higher than that of sodium chloride (NaCl). Regardless of what Cl-containing feedstock was added, the concentration of chromium (Cr) was constant. When organic chloride was added, Cr was the main metallic element which influenced the formation of polycyclic aromatic hydrocarbons (PAHs). On the other hand, when inorganic chloride (NaCl) was added, lead (Pb) was the major element.

Direct observation of the formation of aromatic pollutants in waste incineration flue gases by on-line REMPI-TOFMS laser mass spectrometry.

On-line REMPI-TOFMS laser mass spectrometry (Resonance Enhanced Multi-Photon Ionization-Time-Of-Flight Mass Spectrometry) was used to monitor combustion and pyrolysis byproducts from industrial combustion processes, including polycyclic aromatic hydrocarbons (PAH) and monochlorobenzene in the flue gas of an industrial 22 MW hazardous waste incineration plant. Sampling at different places in the flue gas stream revealed the complexity of the processes responsible for the formation of the different chemical species, while time resolved measurements depicted the emission dynamics.

99/02026 Sulfur dioxide removal by enhanced electrostatics: Larkin, K. et al. Proc., Annu. Meet. Air Waste Manage. Assoc., 1997, 90, TP30B02, 1–14

The economic removal of sulfur dioxide (SO{sub 2}) still represents a significant technical challenge which could determine the use of certain types of fossil fuels for energy production. This paper will present the preliminary results of an innovative research project utilizing a low-cost wet electrostatic precipitator to remove sulfur dioxide. There are many aspects for gas removal in an electrostatic precipitator which are not currently being used. This project utilizes electron attachment of free electrons onto gas molecules and ozone generation to remove sulfur dioxide which is a typical flue gas pollutant. This research was conducted on a bench-scale, wet electrostatic precipitator. A direct-current negative discharge corona is used to generate the ozone in-situ. This ozone will be used to oxidize SO{sub 2} to form sulfuric acid, which is very soluble in water. However, it is believed that the primary removal mechanism is electron attachment of the free electrons from the corona which force the SO{sub 2} to go to equilibrium with the water and be removed from the gas stream. Forcing the equilibrium has been shown to achieve removal efficiencies of up to 70%. The bench scale unit has been designed to operate wet or dry, positive and negativemore » for comparison purposes. The applied dc voltage is variable from 0 to 100 kV, the flow rate is a nominal 7 m{sup 3}/hr and the collecting electrode area is 0.20 m{sup 2}. Tests are conducted on a simulated flue gas stream with SO{sub 2} ranging from 0 to 4,000 ppmv. This paper presents the results of tests conducted to determine the effect of operating conditions on removal efficiency. The removal efficiency was found to vary with gas residence time, water flow rate, inlet concentration, applied power, and the use of corona pulsing.« less