Batch Combustion Research Articles

SO2 and NOx emissions from sludge combustion in a CO2/O2 atmosphere

Incineration for the disposal of sludge is drawing increased attention, and SO2 and NOx are the main secondary pollutants produced during the incineration process. Process control during incineration is the most reasonable method to reduce the production of secondary gaseous pollutants. In this study, batch combustion tests of sludge were carried out in CO2/O2 and N2/O2 atmospheres to investigate SO2 and NOx emissions. The emissions were characterized by different temperatures, varying oxygen concentrations in the feed gas and two atmospheres. The results showed that the maximum value and appearance time of the peak of SO2 concentration curve were affected by temperature. In CO2/O2 and 80%N2/20%O2 atmospheres, the average SO2 concentration increased from 650°C to 750°C, while at 800°C the transformation rate of sulfur in the sludge was nearly 100%. At the same temperature, the average SO2 concentration in the N2/O2 atmosphere was higher than that in the CO2/O2 atmosphere. The maximum value and peak shape of the NOx concentration curve changed with temperature. Specifically, the average NOx concentration increased from 550°C to 650°C and declined from 650°C to 950°C. As the oxygen concentration increased, the average SO2 and NOx concentration also increased. The difference in the NOx emission between the 80%N2/20%O2 and 80%CO2/20%O2 atmosphere was significant when the temperature was lower than 750°C, but not at 750–950°C. Overall, the results of this study indicate that sludge combustion under a 80%CO2/20%O2 atmosphere might simultaneously reduce SO2 and NOx emissions.

Theoretical Considerations about the Steady State Combustion of Wood Char in a Bubbling Fluidized Bed Reactor

A theoretical study on the performance of steady state bubbling fluidized bed burners is presented using a simple mathematical model. The proposed model has pedagogical and practical advantages due to its simplicity. The calculations, whose results are plotted in several graphics, were based on data obtained in laboratory scale experiments. The experiments were carried out with wood chars and the model allows a proper evaluation of physical and chemical phenomena taking place inside the reactor, as well as a fast approach to the pre-design phase, before going towards more complex and time consuming numerical modeling. In the first part of the paper the steady state modeling is compared with the combustion of successive batches of char particles. Afterwards, the performance of a 1 m diameter bed operating from 700℃ to 800℃ is shown.

Pilot-Scale Study of CO2 Capture by CaO-Based Sorbents in the Presence of Steam and SO2

Calcium looping cycles require an oxy-fired calciner burning coal for sorbent regeneration. Thus, in addition to O2 and CO2, the flue gases will include both steam and SO2, and similarly, carbonation of real flue gases will occur in the presence of steam. However, to date, most research has been done without either of these two gaseous components present. Here, batch combustion experiments were performed in a pilot-scale fluidized-bed reactor to study the effects of steam and SO2 addition on CO2 capture by limestone-based sorbents calcined under oxygen-enriched air and oxy-fuel conditions. The initial fast kinetically controlled CO2 capture stage was dramatically reduced when the sorbent was calcined at realistic temperatures in the presence of SO2. This is attributed to both greater sintering due to higher local calcination temperatures required by high CO2 concentrations and CaSO4 formation. By contrast, steam in the synthetic flue gas during carbonation extended the initial, high-efficiency CO2 capture...

Efficiency of log wood combustion affects the toxicological and chemical properties of emission particles

Context: Particulate matter (PM) has been identified as a major environmental pollutant causing severe health problems. Large amounts of the harmful particulate matter (PM) are emitted from residential wood combustion, but the toxicological properties of wood combustion particles are poorly known.Objective: To investigate chemical and consequent toxicological characteristics of PM1 emitted from different phases of batch combustion in four heating appliances.Materials and methods: Mouse RAW264.7 macrophages and human BEAS-2B bronchial epithelial cells were exposed for 24 h to different doses (15–300 µg/mL) of wood combustion particles. After the exposure, cytotoxicity, genotoxicity, production of the inflammatory mediators (TNF-α and MIP-2) and effects on the cell cycle were assessed. Furthermore, the detected toxicological responses were compared with the chemical composition of PM1 samples including PAHs, metals and ions.Results: All the wood combustion samples exerted high cytotoxicity, but only moderate inflammatory activity. The particles emitted from the inefficient phase of batch combustion in the sauna stove (SS) induced the most extensive cytotoxic and genotoxic responses in mammalian cells. Polycyclic aromatic hydrocarbons (PAHs) and other organic compounds in PM1 samples might have contributed to these effects. Instead, water-soluble metals seemed to participate in the cytotoxic responses triggered by the particles from more efficient batch combustion in the masonry heaters. Overall, the toxicological responses were decreased when the combustion phase was more efficient.Conclusion: Efficiency of batch combustion plays a significant role in the harmfulness of PM even under incomplete wood combustion processes.

Effects of a catalytic converter on PCDD/F, chlorophenol and PAH emissions in residential wood combustion

Catalytic converters can be used to decrease carbon monoxide, organic compounds and soot from small-scale wood-fired appliances. The reduction is based on the oxidation of gaseous and particulate pollutants promoted by catalytic transition metal surfaces. However, many transition metals have also strong catalytic effect on PCDD/F formation.In this study birch logs were burned in a wood-fired stove (18kW) with and without a catalytic converter with palladium and platinum as catalysts. PCDD/F, chlorophenol and PAH concentrations were analyzed from three phases of combustion (ignition, pyrolysis and burnout) and from the whole combustion cycle.PCDD/F emissions without the catalytic converter were at a level previously measured for wood combustion (0.15–0.74ngNm−3). PAH emissions without the catalytic converter were high (47–85mgNm−3) which is typical for batch combustion of wood logs.Total PAH concentrations were lower (on average 0.8-fold), and chlorophenol and PCDD/F levels were substantially higher (4.3-fold and 8.7-fold, respectively) when the catalytic converter was used. Increase in the chlorophenol and PCDD/F concentrations was most likely due to the catalytic effect of the platinum and palladium. Platinum and palladium may catalyze chlorination of PCDD/Fs via the Deacon reaction or an oxidation process.The influence of emissions from wood combustion to human health and the environment is a sum of effects caused by different compounds formed in the combustion. Therefore, the usage of platinum and palladium based catalytic converters to reduce emissions from residential wood combustion should be critically evaluated before wide-range utilization of the technology.

In vitro toxicological characterization of particulate emissions from residential biomass heating systems based on old and new technologies

Residential wood combustion causes major effects on the air quality on a global scale. The ambient particulate levels are known to be responsible for severe adverse health effects that include e.g. cardio-respiratory illnesses and cancer related effects, even mortality. It is known that biomass combustion derived emissions are affected by combustion technology, fuel being used and user-related practices. There are also indications that the health related toxicological effects are influenced by these parameters. This study we evaluated toxicological effects of particulate emissions (PM1) from seven different residential wood combusting furnaces. Two appliances i.e. log wood boiler and stove represented old batch combustion technology, whereas stove and tiled stove were designated as new batch combustion as three modern automated boilers were a log wood boiler, a woodchip boiler and a pellet boiler. The PM1 samples from the furnaces were collected in an experimental setup with a Dekati® gravimetric impactor on PTFE filters with the samples being weighed and extracted from the substrates and prior to toxicological analyses. The toxicological analyses were conducted after a 24-hour exposure of the mouse RAW 264.7 macrophage cell line to four doses of emission particle samples and analysis of levels of the proinflammatory cytokine TNFα, chemokine MIP-2, cytotoxicity with three different methods (MTT, PI, cell cycle analysis) and genotoxicity with the comet assay. In the correlation analysis all the toxicological results were compared with the chemical composition of the samples. All the samples induced dose-dependent increases in the studied parameters. Combustion technology greatly affected the emissions and the concomitant toxicological responses. The modern automated boilers were usually the least potent inducers of most of the parameters while emissions from the old technology log wood boiler were the most potent. In correlation analysis, the PAH and other organic composition and inorganic ash composition affected the toxicological responses differently. In conclusion, combustion technology largely affects the particulate emissions and their toxic potential this being reflected in substantially larger responses in devices with incomplete combustion. These differences become emphasized when the large emission factors from old technology appliances are taken into account.

Combustion of coal, bagasse and blends thereof: Part I: Emissions from batch combustion of fixed beds of fuels

Batch combustion of fixed beds of coal, bagasse and blends thereof took place in a pre-heated two-stage electric laboratory furnace, under high-heating rates. The average input fuel/air equivalence ratios were similar for all fuels. The primary and secondary furnace temperatures were varied from 800°C to 1000°C. The effects of fuel blending, combustion staging, and operating furnace temperatures on the emissions from the two fuels were assessed. Furnace effluents were analyzed for carbon dioxide and for products of incomplete combustion (PIC) including CO, volatile and semi-volatile hydrocarbons, as well as particulate matter. Results showed that whereas CO2 was generated during both the observed sequential volatile matter and char combustion phases of the fuels, PICs were only generated during the volatile matter combustion phase. CO2 emissions were the highest from coal, whereas CO and other PIC emissions were the highest from bagasse. Under this particular combustion configuration, combustion of the volatile matter of the blends resulted in lower yields of PIC, than combustion of the volatiles of the neat fuels. Though CO and unburned hydrocarbons from coal as well as from the blends did not exhibit a clear trend with furnace temperature, such emissions from bagasse clearly increased with temperature. The presence of the secondary furnace (afterburner) typically reduced PIC, by promoting further oxidation of the primary furnace effluents.

Combustion of coal, bagasse and blends thereof: Part II: Speciation of PAH emissions

This work reports on emissions of unburned hydrocarbon species from batch combustion of fixed beds of coal, sugar-cane bagasse, and blends thereof in a pre-heated two-stage laboratory furnace operated in the temperature range of 800–1000°C. The effects of fuel blending, combustion staging, and operating furnace temperatures on emissions of pollutants were assessed. Furnace effluents were analyzed for products of incomplete combustion (PICs) including CO, volatile and semi-volatile hydrocarbons, and particulate matter, as has been reported in Ref. [1]. Emitted unburned hydrocarbons include traces of potentially health-hazardous Polycyclic Aromatic Hydrocarbons (PAHs), which are the focus of this work. Under the batch combustion conditions implemented herein, PAH were only generated during the volatile combustion phase of the fuels. The most prevalent species were in descending order: naphthalene, acenaphthylene, phenanthrene, fluoranthene, pyrene, dibenzofuran, benzofuran, byphenyl, fluorene, 9H-fluoren-9-one, acephenantrylene, benzo[b]fluoranthene, 1-methyl-naphthalene; 2-methyl-naphthalene, benz[a]anthracene and benzo[a]pyrene. PAH yields were the highest from combustion of neat bagasse. Combustion of the blends resulted in lower yields of PAH, than combustion of either of their neat fuel constituents. Increasing the furnace operating temperature enhanced the PAH emissions from bagasse, but had little effect on those from the coal or from the blends. Flue gas treatment in a secondary-stage furnace, upon with additional air, typically reduced PAH yields by promoting oxidation of the primary-stage furnace effluents.

Kinetic and diffusive data from batch combustion of wood chars in fluidized bed

In this work it is studied the combustion of batches of wood char particles in a shallow fluidized bed at laboratory scale. Commercial and recarbonized chars from nut pine and cork oak parent woods were burned for bed temperatures of 600–750 °C and particle sizes range of 1.8–3.6 mm. A combustion model based on the two-phase theory of fluidization is presented to evaluate the global combustion resistance. Sherwood numbers and kinetic constants for the heterogeneous phase reaction are also assessed. Through the comparison among theoretical and experimental results, conclusions are drawn on the combustion mechanism as well as on the combustion controlling resistance. The Arrhenius law is proposed to predict the kinetic constants for the studied chars. ► Combustion of nut pine and cork oak wood char particles was studied in a laboratory shallow fluidized bed. ► Covered temperature range from 600 to 750 °C and covered particle size range from 1.8 to 3.6 mm were used. ► Commercially carbonized and recarbonized chars were tested and an Arrhenius law is proposed for these chars.

Measurement of Gaseous Components from Batch Combustion of Solid Waste

Measurement of Gaseous Components from Batch Combustion of Solid Waste

Physicochemical characterization of fine particles from small-scale wood combustion

Abstract Emissions from small-scale wood combustion appliances are of special interest since fine particles have been consistently associated with adverse health effects. It has been reported that the physicochemical characteristics of the emitted particles affect also their toxic properties but the mechanisms behind these phenomena and the causative role of particles from wood combustion sources are still mostly unknown. Combustion situations vary significantly in small-scale appliances, especially in batch combustion. Combustion behaviour is affected by fuel properties, appliance type and operational practice. Particle samples were collected from six appliances representing different combustion situations in small-scale combustion. These appliances were five wood log fuelled stoves, including one stove equipped with modern combustion technology, three different conventional combustion appliances and one sauna stove. In addition, a modern small-scale pellet boiler represented advanced continuous combustion technology. The aim of the study was to analyze gas composition and fine particle properties over different combustion situations. Fine particle (PM 1 ) emissions and their chemical constituents emerging from different combustion situations were compared and this physicochemical data was combined with the toxicological data on cellular responses induced by the same particles (see Tapanainen et al., 2011 ). There were significant differences in the particle emissions from different combustion situations. Overall, the efficient combustion in the pellet boiler produced the smallest emissions whereas inefficient batch combustion in a sauna stove created the largest emissions. Improved batch combustion with air-staging produced about 2.5-fold PM 1 emissions compared to the modern pellet boiler (50.7 mg MJ −1 and 19.7 mg MJ −1 , respectively), but the difference in the total particulate PAH content was 750-fold (90 μg MJ −1 and 0.12 μg MJ −1 , respectively). Improved batch combustion and conventional batch combustion showed almost the same PM 1 emissions (51.6 mg MJ −1 ), but a 10-fold difference in total particulate PAH emissions (910 μg MJ −1 ). These results highlight that same PM 1 emissions can be associated with very different chemical compositions, potentially leading to different toxic properties of the particles. Thus, changing from an old, less efficient, combustion appliance to a modern appliance can have a greater impact on toxic properties than the emitted PM 1 mass might indicate.

A Study on Production of Gaseous Components from Batch Combustion of Plastics Waste

A Study on Production of Gaseous Components from Batch Combustion of Plastics Waste

CONSIDERATIONS ON EXPERIMENTAL STUDIES OF VEGETABLE CHAR COMBUSTION IN FLUIDIZED BED

This paper reports some experimental aspects of the combustion of batches of vegetable chars in a fluidized-bed laboratory reactor at temperatures of 600, 700, and 750oC. Data on the volumic concentrations of carbon oxides and volatile organic compounds along the combustion process are presented and discussed. Tests show that the carbon conversion rate is not only due to combustion, but there are pyrolysis phenomena that accompany it and contribute to the global conversion rate of the carbon. The burned-out and consumed mass fractions of carbon were determined, and it was observed that these two quantities differ, particularly for lower bed temperatures. Vegetable chars when suffering combustion in low-temperature fluidized beds release tars in the form of vapors that escape from the bed without burning.

Emissions from the combustion of polystyrene, styrene and ethylbenzene under diverse conditions

This experimental study contrasts the products of incomplete combustion (PIC) of polystyrene, a widespread solid waste, with those from the combustion of its predominant pyrolyzate, styrene. The study also included ethylbenzene, as it has been reported to convert to styrene extensively and extremely fast in combustion conditions. Emissions were compared from: (i) steady-state combustion of vaporized ethylbenzene in premixed flames, (ii) steady-state combustion of polystyrene powders in a drop-tube furnace, (iii) batch combustion of fixed beds of polystyrene in a muffle furnace, and (iv) batch combustion of pools of liquid styrene in a muffle furnace. PICs, sampled in post-combustion zones, included unburned hydrocarbons, with emphasis to polycyclic aromatic hydrocarbons (PAH), particulates, CO2 and CO. Yields of major PIC were compared to underscore the differences in the underlying physics of premixed and non-premixed (diffusion) flames. Combustion of polystyrene and styrene in diffusion flames generated soot at any nominal global (bulk) equivalence ratio, no matter how fuel-rich or fuel-lean. On the other hand, combustion of ethylbenzene in premixed flames did not generate any soot up to its soot onset limit, which typically occurs well-within the fuel-rich domain. However, conditions that were not conducive to the formation of soot did not preclude the presence of other PIC, such as PAH.

Integrating Continuous-Flow Mass Spectrometry and Automatic CO2 Collection for AMS

Accelerator mass spectrometry (AMS) radiocarbon measurements of organic samples require combustion to obtain CO2 for graphitization. Furthermore, determination of δ13C values is required in order to correct the 14C age due to carbon isotope fractionation effects. δ13C analysis is commonly carried out by stable isotope mass spectrometry because most applications demand high-precision δ13C values in addition to the requirements of 14C dating. A simplifying step is therefore to combine the combustion for stable isotope analysis with cryogenic trapping of CO2 for AMS graphite targets. Presented here is a simple CO2 trapping device based on a modified Gilson 220XL sampling (manifold) robot coupled to the inlet manifold system of a GV Instruments IsoPrime stable isotope mass spectrometer. The system is capable of batch combustion and analysis of up to 40 samples and is under full computer control by the mass spectrometer software. All trapping parameters such as flush time prior to trapping and total trap time are adjustable through the standard software user interface. A low 14C activity of background materials and high precision and accuracy of stable isotope analysis of carbon and nitrogen are demonstrated.

Fragmentation on batches of coke or char particles during fluidized bed combustion

During experiments being carried out on the study of batch combustion of coke or char particles in fluidized beds the evolution of the overall combustion resistance with time usually shows an apparent increase of the overall reactivity as combustion develops. This results in the reduction on the obtained value for the overall combustion resistance below what was theoretically expected. One possible explanation for such behavior is that there is some fragmentation of the particles being thrown into the bed, leading to an increase of the external superficial area available for reaction. The augmentation of the external area increases the overall reaction rate which is erroneously interpreted as a reactivity increase of the material of the particles. The subsequent analysis is an evaluation of the influence of particle fragmentation on the combustion rate of batches of solid particles, when such fragmentation is unknown during the analysis of the experimental data.

05/01713 Batch combustion of oil shale particles in afluidized bed reactor

05/01713 Batch combustion of oil shale particles in afluidized bed reactor

Batch combustion of oil shale particles in a fluidized bed reactor

Batch charges of Jordanian oil shales were burnt in a laboratory scale fluidized bed of sand. The effect of shale particle size, initial bed temperature, superficial gas velocity, sand size, and batch weight on the burnout time was investigated. Visual observation of shale burnout time, on-line CO 2 concentrations in flue gas and bed temperature variation were measured simultaneously during the combustion process. The results have shown, in general, that an increase in bed temperature or superficial gas velocity was associated with a decrease in burnout time. On the contrary, an increase in particle mean size led to an increase in burnout time. The burnout time was analyzed based on the shrinking-core model, and the results indicated that chemical kinetics, rather than diffusion, significantly influenced the combustion process.

Laboratory Investigation of the Products of the Incomplete Combustion of Waste Plastics and Techniques for Their Minimization

This laboratory investigation aimed at reducing the emissions of pollutants from the batch combustion of three major waste plastics, polyethylene (PE), polystyrene (PS), and poly(vinyl chloride) (PVC). Results are reported herein on the emissions of CO, light aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and particulates. Two-stage combustion of the polymers was investigated, with the first stage (primary furnace) operated at either 600 or 900 °C and the second stage (afterburner) at 1000 °C. Before exiting the afterburner, the effluent passed through a high-temperature ceramic filter, which retained and destroyed particulate products of incomplete combustion (PICs). The effect of the polymer quantity burned was examined, as well as the effect of mixing PS with PVC to explore the influence of chlorine on emissions of PICs. The results indicated that PVC produced the lowest amounts of all PICs, whereas PS produced the highest amounts of PAHs and particulates, and PE produced the highest ...

Emissions of Batch Combustion of Waste Tire Chips: The Hot Flue-Gas Filtering Effect

A laboratory investigation was performed on the emissions from the batch combustion of waste tire chips in fixed beds. Techniques and conditions that minimize toxic emissions were identified. Tire-derived fuel (TDF), in the form of waste tire chips (1 cm in size), was burned in a two-stage combustor. Batches of tire chips were introduced to the primary furnace, where gasification and combustion occurred. The gaseous effluent of this furnace was mixed with streams of additional preheated air in a mixing venturi, and it was then passed through a silicon carbide (SiC) honeycomb wall-flow filter that had been placed inside this furnace. Subsequently, it was channeled into a secondary furnace (afterburner), where further oxidation occurred. The arrangement of the two furnaces in series allowed for independent temperature control; varying the temperature in the primary furnace influenced the type and the flux of pyrolysates. The hot-flue-gas filtering section, ahead of the exit of the primary furnace, allowed the retention and further oxidation of most of the generated particulates and, thus, prevented them from entering the afterburner. Results showed that the combination of the high-temperature ceramic filter with the afterburner treatment was successful in reducing the emissions from the combustion of waste tires. Depending on the temperature of the primary furnace, the final emissions of CO were reduced by factors of 2−6, NOx emissions were reduced by factors of 2−3, particulate emissions were reduced by 2 orders of magnitude (both PM2.5 and PM10), and most individual polycyclic aromatic hydrocarbon (PAH) species emissions were reduced by more than 1 order of magnitude, with the exception of naphthalene, whose reduction was less drastic. The overall combustion effectiveness was enhanced, as evidenced by higher CO2 yields.