Boiler Exhaust Research Articles

Development of laser absorption techniques for real-time, in-situ dual-species monitoring (NO/NH3, CO/O2) in combustion exhaust

Simultaneous dual-species monitoring offers potential for control of large-scale practical combustion systems. The development and demonstration of two dual-species sensors for characterizing NOx abatement (NO/NH3) and combustor performance (CO/O2) are described for potential application in boiler exhaust at coal-fired electric utilities. Tunable laser absorption sensors for simultaneous in-situ detection of these paired species were developed using fundamental-band vibrational transitions in the mid-infrared near 5.2μm for NO, combination-band transitions near 2.25μm for NH3, overtone-band transitions near 2.3μm for CO, and electronic transitions in the b-X system near 760nm for O2. Scanned-wavelength, 1f-normalized wavelength modulation spectroscopy with second harmonic detection (WMS-2f) was employed for real-time data processing. Spatial- and time-demultiplexing strategies were used to combine and separate the laser signals. The sensors were tested for simultaneous, continuous monitoring in laboratory combustion exhaust from a premixed ethylene-air flame at atmospheric pressure and varied equivalence ratios with exhaust temperature of ∼620K. A retro-reflected 3.58m beam-path was used to mimic a single-ended installation in a boiler exhaust duct. NH3 mixtures were metered into the flame at different rates to test the response of the NO/NH3 sensor, and the CO/CO2 ratio was adjusted by fuel/air equivalence ratio. Trends in the measured concentration ratio of NO to NH3 were found to agree qualitatively with theoretical expectation, and the CO and O2 measurements were confirmed by analysis of sampled gases. The laser absorption exhibited the fast time response needed for control sensors. These fast-response, simultaneous dual-species sensors for NO/NH3 and CO/O2 show excellent promise for control and optimization of NOx abatement and furnace efficiency in practical combustion systems.

A New Type Auto-Reclaim Facility of Boiler Exhaust Steam Heat Energy

There is so much exhaust steam in a boiler system that it causes great heat energy waste. A new type auto-reclaim facility of boiler exhaust steam heat energy is designed based on hydrokinetics, pyrology and automation. The new type facility is made up of water-gas injection pump, liquid relay deoxidization tank, field electrical control cabinet, instrument cabinet, loop booster pump and remote consoler. When the facility is used in the boiler system, not only can it reclaim the exhaust steam heat energy but also the whole steam and working medium. The facility is of high reliability under intelligent control and mechanism architecture. The facility has been applied in more than thirty China Petrochemical manufactories. This patent facility receives the high praise in the field of boiler steam heat energy reclaim.

107 ボイラ排ガスダクトで発生した異音の原因と対策について(騒音抑制技術)

107 ボイラ排ガスダクトで発生した異音の原因と対策について(騒音抑制技術)

Energy and Exergy Analysis Of a 44-MW Bagasse-based Cogeneration Plant in India

ABSTRACT In this article, energy and exergy analysis of an ongoing, 44-MW, heat-matched, bagasse-based cogeneration plant of Ugar Sugar Works Ltd (USWL), located in Belgaum, India is presented. In the analysis, exergy methods with more conventional energy analysis are employed to assess the thermodynamic efficiencies and losses. The performance of the plant was estimated, and a detailed break up of energy and exergy losses for the considered plant has been presented. The fuel energy savings ratio of the cogeneration plant is estimated in comparison with separate generation plants. The plant performs with energy and exergetic efficiency of 65% and 25%, respectively. Energy losses mainly occurred in the boiler exhaust and condenser, where 35 MW and 27 MW is lost to environment, respectively. The percentage ratio of the exergy destruction to total exergy destruction was found to be maximum in the boiler system (71%) of fuel exergy input or 45% of the physical exergy input. The total exergy destruction in the...

Removal of Fine Particulate Matter (PM) from Boiler Exhaust Gas in Electrostatic Water Spraying Scrubber

Removal of Fine Particulate Matter (PM) from Boiler Exhaust Gas in Electrostatic Water Spraying Scrubber

Catalytic activity and long-term stability of palladium oxide catalysts for natural gas combustion: Pd supported on LaMnO3-ZrO2

The catalytic activity and long-term stability of 2% Pd/LaMnO3-ZrO2 catalysts for natural gas combustion were deeply investigated. The catalyst, prepared via solution combustion synthesis, was completely characterized (XRD, BET, FESEM/EDS, TPC/TPD/TPR and FT-IR analysis) in the fresh status, and in the aged one, after prolonged treatment under hydro-thermal ageing and S-compounds poisoning (up to 3 weeks of hydro-thermal treatment at 800°C under a flow of domestic boiler exhaust gases typical composition of 9% CO2, 18% H2O, 2% O2 in N2, including 200ppmv of SO2). An increased catalytic activity towards NG combustion with ageing was detected: the T50, in fact, got lowered from 570 (fresh sample) to 465°C (after 3 weeks ageing). Highly dispersed Pd centers were predominant on fresh catalyst. Upon ageing, oxygen covered Pd metal particles formed, at the expense of dispersed cationic and zerovalent Pd atoms. The increase in the catalytic activity was associated to the phase modification occurring in the bulk support, where Mn oxides, active towards CH4 combustion, segregated. Moreover, bands due to sulfate species were detected in aged samples: IR analysis showed that Pd atoms did not interact significantly with these species. The bands of sulfate species decreased in intensity after 3 weeks ageing, likely mostly due to sintering of the catalyst, with the corresponding decrease in the surface area.

Ageing mechanisms on PdO x-based catalysts for natural gas combustion in premixed burners

The ageing effect induced by S-compounds over 2%Pd/CeO 2·2ZrO 2, 2%Pd/LaMnO 3·2ZrO 2 and 2%Pd/BaCeO 3·2ZrO 2 catalysts for CH 4 combustion was investigated; S-compounds are in fact added as odorants in the natural gas network for safety purposes. Pd-based catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates/glycine mixtures. Basic characterization (XRD, BET, FESEM analysis), FT–IR studies and catalytic activity tests were performed on powders and after accelerated ageing carried out up to 2 weeks (hydro-thermal treatment at 900 °C under a flow rate with typical domestic boiler exhaust gas composition, 9% CO 2, 18% H 2O, 2% O 2 in N 2, containing also 200 ppmv of SO 2 to emphasize any poisoning effect). Over fresh catalysts, IR analysis of CO adsorption evidenced the formation of highly dispersed Pd metal clusters and Pd ions. With ageing, 2%Pd/CeO 2·2ZrO 2 increased its CH 4 combustion half-conversion temperature ( T 50, regarded as an index of catalytic activity) from 382 °C—recorded for fresh sample—to 421 °C, attained with the same sample aged two weeks. An unexpected improvement was found instead in the overall performance of 2%Pd/LaMnO 3·2ZrO 2 and 2%Pd/BaCeO 3·2ZrO 2: the T 50 in fact lowered from 570 to 450 °C for the first one, and from 512 to 443 °C for the second one, after two weeks ageing. S-hydro-thermal treatment provoked bulk and surface sulfates formation on all aged samples, with a concentration increasing with the exposure time. Prevailing ageing mechanisms seemed to be Pd metallic clusters coalescence, detected over the Ce–Zr system, and surface-bulk sulfates formation, the latter destroying the initial crystallographic structure. In 2%Pd/LaMnO 3·ZrO 2 and 2%Pd/BaCeO 3·ZrO 2 powders the amount of the perovskite phase strongly decreased during ageing, in favor of the formation of bulk sulfate and of oxides.

Effect of S-compounds on Pd over LaMnO 3·2ZrO 2 and CeO 2·2ZrO 2 catalysts for CH 4 combustion

The ageing effect induced by S-compounds (added as odorants in the natural gas network for safety purposes) over 2% Pd/LaMnO 3·2ZrO 2 and 2% Pd/CeO 2·2ZrO 2 catalysts for CH 4 combustion is studied. The catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates/glycine mixtures. Basic characterization (XRD, BET, FESEM/EDS, TPD/TPR analysis), FT-IR studies and catalytic activity tests were performed on powder catalysts in fresh status and after accelerated ageing carried out up to 3 weeks (hydro-thermal treatment at 800 °C under a flow of domestic boiler exhaust gases typical composition (9% CO 2, 18% H 2O, 2% O 2 in N 2), also including 200 ppmv of SO 2 to emphasize any poisoning effect). After ageing, 2% Pd/CeO 2·2ZrO 2 increased its CH 4 combustion half-conversion temperature ( T 50), regarded as an index of catalytic activity, from 382 °C – recorded for fresh sample – to 490 °C. An unexpected improvement in the overall performance was found instead for 2% Pd/LaMnO 3·2ZrO 2: T 50, in fact, got lowered from 570 °C (fresh sample) to 465 °C (after 3 weeks ageing). S-hydro-thermal treatment induced bulk and surface sulphates formation on all aged samples, with a concentration increasing with the exposure time. The prevailing ageing mechanisms seemed to be the oxidation of Pd metallic clusters, detected over the Ce–Zr system, and the formation of surface-bulk sulphates, the latter destroying the initial crystallographic structure, particularly evident for the La–Mn system. The increased activity of the 2% Pd/LaMnO 3·2ZrO 2 sample could be explained with the formation of MnO x , detected via XRD and IR, which is active towards CH 4 combustion.

Choosing a ball valve that lowers emissions

Regulatory agencies in both the US and Europe are tightening controls on fugitive emissions, which are equipment leaks, as opposed to point-source emissions from reactor vents or boiler exhaust stacks. Michael Adkins and Pete Ehlers, both of Swagelok explain how choosing the right ball valve can keep you in compliance.

Lowering the effect of low‐frequency noise generated from boiler exhaust stacks.

Low‐frequency noise from exhaust boiler stacks at a semiconductor plant was measured and the low‐frequency noise spectrum was predicted using an analytical impedance model. Nearby residents complained that noise was rattling household items, such as windows and light fixtures. The semiconductor plant speculated that noise from two boiler exhaust stacks was the source of the problem. Sound pressure level measurements conducted at the plant revealed strong tones in the infrasound and low‐audible frequency range. The boiler exhaust stack noise source was theoretically characterized by deriving the mechanical impedance of the boiler exhaust stack and the radiation impedance of the top of the boiler exhaust stack as a simple unbaffled source. The analytical model predicted the resonant frequencies of the boiler exhaust stacks and these resonances closely matched the strong low‐frequency tones measured. Using this model, possible changes in controlling parameters of common exhaust boiler stack design are described that could decrease the overall noise radiating from the exhaust stacks. As one example, the plant appreciably decreased the sound power contribution from the upper exhaust stack resonances by lowering the overall output of the exhaust boilers. This change lowered the overall noise levels without the use of silencers.

Sorptive Behavior of Nitro-PAHs in Street Runoff and Their Potential as Indicators of Diesel Vehicle Exhaust Particles

This is the first report to reveal the particle-water distribution of nitropolycyclic aromatic hydrocarbons (NPAHs) and to discuss their potential risks and utility as indicators of diesel vehicle exhaust particles (DEP). Time-series samples of runoff were collected from a highway, and NPAHs and polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography-mass spectrometry (GC-MS) to study their dynamic behavior. The concentrations of total NPAHs ranged from 11 to 73 ng/L in particulate phase (>0.7 mcirom) and from 2.3 to 4.9 ng/L in dissolved phase (<0.7 microm). Like their PAH analogs, most (81-97%) NPAHs were associated with particulate matter. The organic carbon-normalized in situ partition coefficients (Koc') of NPAHs observed in runoff events (10(5.8-6.3) for 2-nitrofluoranthene and 10(5.8-6.2) for 1-nitropyrene [1-NP]) were more than 1 order of magnitude higher than those expected from their Kow, indicating great affinity for particulate matter such as soot. Concentrations of PAHs and NPAHs adjusted by potency equivalency factors and induction equivalency factors showed that the potential risks of NPAHs were smaller than those of PAHs by a factor of more than a hundred for the particulate phase and morethan fourforthe dissolved phase. Comparison of concentrations and compositions of NPAHs and PAHs among runoff, DEP, gasoline vehicle exhaust particles, boiler exhaust particles, and aerosols suggested that the ratio of 1-NP to total PAHs (1-NP/PAH) is a useful indicator of DEP for source apportionment of PAHs among traffic-related sources. Source-apportionment of PAHs in the runoff by 1-NP/PAH and methylphenanthrene/phenanthrene ratios suggested that most PAHs in the runoff except the second flush peak were derived from DEP but that other pyrogenic sources contributed to the particles at the second flush and thus to the overall runoff particles.

Development of a neural network based control system for a stoker fired hot water boiler

AbstractThe present paper describes the development of neural network based controllers (NNBC) to control the outlet hot water temperature from a chain grate, stoker fired boiler while maintaining the oxygen level in the exhaust within target values. The controller initially matches the fuel input to the boiler to the error between the measured and set point water temperatures. In one version of the system a neural network then uses the measured current oxygen and carbon monoxide levels in the boiler exhaust to adjust the combustion airflow. In the second version two artificial neural networks were used to estimate the concentrations of the exhaust oxygen and carbon monoxide 3 min into the future. This further network was able to characterise the dynamics of the combustion process and the 'future' predictions were in good agreement with the plant data collected on the industrial chain grate stoker. Consequently the predicted values were then used by the first network to control the combustion airflow and ...

Analysis of a micro-cogeneration system using hybrid solar/gas collectors

The use of solar thermal collectors for electricity production is a way to contribute to the Portuguese objective of reaching 39% of electricity production from renewable energy sources by 2010. This is also in accordance with the objectives of the European Union and the Kyoto Protocol. The system in analysis is powered by solar energy and supplemented by a natural gas boiler, especially for periods when solar radiation is low. Use of the system would result in significant savings in primary energy consumption and a reduction in CO2 emissions to the environment. The solar collectors are of the heat pipe type and hybrid: they act as a boiler economizer, as boiler exhaust gases circulate below the absorber plate, increasing the energy input and collector efficiency. The behaviour of a combined heat and power cycle producing 6 kW of electricity was simulated. The heat rejected in the cycle condenser can be used for space/water heating or cooling of buildings. Several refrigerants have been considered for the cycle and methanol presented the best performance. The contribution of solar energy (solar fraction) was evaluated for the climatic data of Lisbon (Portugal), for two applications: a pool complex and an office building. The energy and economic potential of the system was compared to the conventional alternative. Copyright , Manchester University Press.

Honeycomb Supports, Filters and Catalysts for Cleaner Environment

The extruded honeycomb supports, porous filters and catalyst monoliths are innovative ceramic products used in environmental protection. The development and applications of these novel materials and products are mainly driven by the environmental legislation in the region, the availability of technology, the mass manufacturing facilities and the cost effectiveness. This paper highlights some of the recent innovations and challenges in ceramic materials and design, and our findings in systematic understanding and applications of the principle of fabrication of honeycomb ceramics for various air pollution control systems in India. The use of locally available platy kaolin and advanced extrusion process control using rheological parameters of the paste are advantageously adopted for production of thin walled and high thermal shock resistant cordierite honeycomb supports for catalytic converters. The low cost design of diesel particulate filter (DPF) with off board electric regeneration system is found to be very effective in reducing the particulate emission in urban transport buses and proven for more than 100,000 km on Indian roads. The Ti-WV based SCR catalyst extruded in the form of honeycomb using high surface area TiO2 has shown high NOX reduction in coal fired boiler exhaust. The preparation of high surface area honeycombs from activated carbon and zeolites with adequate mechanical strength opens up new application areas. Some of the case studies on the above products and applications are presented in this paper.

D307 POISONING KINETICS BY ARSENIC ON THE DE-NOx CATALYST

The SCR De-NOx commercial system for coal fired boiler exhaust has almost 22 years history. The Catalyst poisoning by Arsenic oxide vapor was found first in an European SCR test plant. Arsenic in coal is vaporized as its oxides and almost all of them are adsorbed on the ash surface but a very small of the remainder makes the serious catalyst retardation. According to the progress of SCR technologies, catalyst retardation kinetics is required for the catalyst life estimation in coal fired SCR even for the high amount of Arsenic containing region. We studied the Arsenic poisoning kinetics in laboratory scale tests and found the good accordance with the actual exhaust data. The obtained Arsenic deposition (L) and the activity deterioration (k_0/k_<obs>) are expressed as follows.

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.

Evaluation of dual-bed pressure swing adsorption for CO2 recovery from boiler exhaust gas

Abstract Dual-bed CO2 adsorption using zeolite was studied experimentally and theoretically. Boiler exhaust gas (13 vol% CO2, 79 vol% N2 and 8 vol% O2) was used as a feed gas for the eight-step four-bed PSA process. Na-X type zeolite (NaX) and Na-A type zeolite (NaA) were selected in the break-through test. NaX has higher CO2 adsorption capacity than other adsorbents. NaA has the highest selectivity among all adsorbents tested. In the simulations, a NaX-to-NaA ratio affected the recovery efficiency and the concentration of recovery gas. Moreover, in the dual-bed PSA process of NaX-to-NaA ratio=2/1, the recovery efficiency and CO2 concentration of recovery gas were higher than those in a single-adsorbent PSA process. Simulated results by the dynamic model agreed well with the PSA experimental results.

A Study on the Heat Recovery from Boiler Exhaust Gas with Multi-stage Water-fluidized-bed Heat Exchanger

Heat recovery from boiler exhaust gas with multi-stage water-fluidized-bed heat exchanger is analyzed in this study. The recovered energy here is not only sensible heat but also latent heat contained in the exhaust gas. In this system direct contact heat transfer occurs while exhaust gas passes through water bed and the thermal energy recovered this way is again delivered to the water circulating through heat exchanging pipes within the bed. Thus the thermal energy of exhaust gas can be recovered as a clean hot water. A computer program developed in this study can predict the heat transfer performance of the system. The results of experiments performed in this study agree well with the calculated ones. The heat and mass transfer coefficients can be fecund through these experiments. The performance increases as the number of stage increases. However at large number of stages the increasing rate becomes very low.

Sources of Fine Organic Aerosol. 8. Boilers Burning No. 2 Distillate Fuel Oil

Fine organic particulate matter emitted from an industrial-scale boiler burning no. 2 distillate fuel oil has been characterized on a molecular basis using GC/MS techniques. Most of the identified compound mass consists of n-alkanoic acids (42.0−51.5%), aromatic acids (5.8−22.6%), and n-alkanes (6.7−25.0%). Polycyclic aromatic hydrocarbons (PAH) and oxygenated PAH (oxy-PAH) together comprise 3.1−8.6% of the identifiable mass and together with chlorinated compounds (5.8−16.4%) show the largest variations in emission rates between the two experiments reported here. An increase in chlorinated compound emissions between tests is accompanied by a similar increase in elemental carbon (i.e., soot) and PAH emissions, which may follow the results of laboratory experiments that suggest that the presence of chlorinated compounds can enhance both soot and PAH formation. Differences between the hopanes distribution in the boiler exhaust versus that found in both vehicle exhaust and in the southern California atmosphere suggest that the oil-fired boiler exhaust is at most a minor contributor to the atmospheric aerosol, which is consistent with inferences drawn from local emission inventories.

97/02113 Renewal wood fuel: fuel feed system for a pulverized coal boiler

Recovering waste heat from boiler exhaust flue gas is an effective way to improve energy utilization efficiency and reduce coal burning pollution of coal-fired power plant (CFPP). The low-pressure economizer (LPE) is the most widely employed in waste heat recovery from boiler exhaust flue gas. However, there is a contradiction in LPE between maximizing waste heat recovery rate and maximizing waste heat utilization efficiency. This research improves waste heat utilization efficiency without reducing recovery rate by converting recovery heat. The recovery heat conversion is realized through organic fluid cycle integrating organic Rankine cycle (ORC) with high temperature heat pump (HTHP). The organic fluid cycle acts as a medium between flue gas and feedwater, which makes recovery heat match higher parameter low-pressure heater (LPH) flexibly. Based on exergy analysis, the upper limit for elevating energy-saving effects by converting recovery heat is given. For calculations and analyses, thermodynamic models are built and simulated in MATLAB together with REFPROP software based on a case study. The results show that using the proposed waste heat recovery system could produce 5361.98 kW additional net power output and electricity revenue of $1220.04 k, which are approximately 409.19 kW and $127.2 k greater than LPE respectively. The proposed system could save 5699.36 t standard coal and $854.9 k coal cost per year, which are nearly 595.5 t and $89.32 k larger than LPE. The maximum of recovery heat utilization efficiency of proposed system reaches 17.35% and the maximum efficiency improvement compared to LPE touches 3.48%.