Combustion of hydrogen in a bubbling fluidized bed

Baron, Jerzy; Bulewicz, E.M.; Kandefer, Stanisław; Pilawska, M.; Żukowski, Witold; Hayhurst, A.N.

doi:10.1016/j.combustflame.2008.11.014

Cited by 22 publications

(16 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is a matter of speculation whether the reaction is started by a sudden thermal impulse or the penetration of the bubble by active free radicals, produced in the flame or explosion in above equilibrium concentrations (the presence of free radicals under fluidised bed conditions is well documented [24][25][26][27]). Observations on the FBC combustion of hydrogen and kinetic modelling showed that premature ignition can occur if H atoms are effectively "injected" into the system at a catalytic surface close to the distributor [14]. It is also relevant that the ignition of propane is promoted by the presence of a solid catalyst, such as Ptcoated particles, on whose surface molecules can dissociate to produce free radicals [5].…”

Section: The Video Resultsmentioning

confidence: 99%

“…A pilot flame, mounted in the freeboard, was used to ignite the mixture. The temperature distribution along the axis of the reactor was monitored using set of seven bare thermocouples (Ni-CrNi, 1.0 mm in diameter), mounted vertically above one another, 12, 20, 29, 40, 50, 60, and 70 mm above the distributor and numbered 2 to 8, for consistency with earlier work [12][13][14]. There was no external heating, all the heat came from the reaction itself, but the reactor was surrounded by a cylindrical, concentric, reflective and thermally insulating shield.…”

Section: Methodsmentioning

confidence: 99%

“…Below a certain mean temperature of the sand, the temperature maximum lay in the freeboard; above this temperature it moved into the bed. Records from individual thermocouples showed local temperature fluctuations, strongest near the temperature maximum, confirming that the heat came from discrete events above or below the bed's surface [12][13][14]. Local temperatures near the quartz walls of the reactor were also measured by an optical method, with much better resolution (in space and time) and with no sensors in the bed.…”

Section: Introductionmentioning

confidence: 99%

“…Detailed kinetic models for the combustion of individual fuels in a bubbling fluidised bed give the ignition delay for the thermal ignition of the gas mixture inside a bubble rising through the bed [12][13][14]. With the induction period longer than the time a bubble takes to pass through the bed, the gases should burn in the freeboard, regime A.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Propagation of Reaction Between Bubbles with a Gas Burning in a Fluidised Bed

Baron

Bulewicz

Zabagło

et al. 2011

Flow Turbulence Combust

View full text Add to dashboard Cite

A bubbling fluidised bed reactor has been used for investigating how combustion propagates between bubbles of premixed fuel + air, rising from the distributor towards the surface. Earlier work has shown that when the temperature of the sand gradually rises, the gases first burn in flames above the bed, regime A, then combustion moves under its surface, to occur in bubbles travelling up the bed, under regime B. Above a certain temperature, characteristic of the gas mixture composition, combustion descends towards the bottom of the bed. Ignition then occurs in small bubbles near the distributor, under the stable regime C. The kinetic model, used to calculate the delay for thermal ignition inside gas bubbles rising through the bed, gives correct predictions for regimes A and C but not for B. Under regime B, bubbles of the mixture begin to ignite under the bed's surface while their residence time in the bed is remains shorter than the delay times for thermal ignition derived from the kinetic model. As the temperature rises, the ignition delay rapidly decreases, and regime C is reached, in accordance with the model. In this work attention was focused on regime B. A laboratory reactor of quartz glass was used, with a bed of quartz sand. Fast video recording was employed to capture ignition phenomena as the bed's temperature was raised or lowered. Records of freeboard concentrations of O 2 , CO and of total hydrocarbons, VOCs, were obtained, confirming the specific aerodynamic and chemical character of regime B. It has been shown that combustion spreads from the surface to bubbles near the bed's surface and then to other bubbles close by. Such transfer of the reaction stabilizes combustion inside the bed, at temperatures appreciably lower than that for the thermal ignition of the mixture, given by the kinetic model. This is consistent with earlier findings, which have shown that the combustion of gaseous mixtures in bubbling fluidised beds is controlled by gas phase processes, as in flames.

show abstract

Section: The Video Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Propagation of Reaction Between Bubbles with a Gas Burning in a Fluidised Bed

Baron

Bulewicz

Zabagło

et al. 2011

Flow Turbulence Combust

View full text Add to dashboard Cite

show abstract

“…The experimental tests were conducted in the laboratory fl uidized bed reactor, previously used for solids or gaseous fuels combustion [13][14][15][16][17][18][19][20] . The experiments were carried out in a laboratory fl uidized bed reactor with a thermal power of about 5 kW.…”

Section: Experimental Partmentioning

confidence: 99%

The influence of process parameters on combustion of plastic waste in the fluidized bed reactor

Jankowski

Żukowski

2013

Polish Journal of Chemical Technology

View full text Add to dashboard Cite

The paper presents the results of a research on the effects of process parameters on the combustion of waste plastics. The experiments were carried out in a laboratory fl uidized bed reactor. The temperature and the conditions of the process were changed during the experiments. The plastics were combusted continuously (autothermally), periodically with extra fuel (co-fi ring) and alone in a hot fl uidized bed. During the combustion process of materials containing nitrogen (PA, ABS), while the bed temperature decrease, changes of emissions of nitrogen oxides, in particular an increase in the concentration of N 2 O, up to 250 ppm at ~730 o C, were observed. During ABS combustion, emission of HCN was registered, at a maximum of 400 ppm. The presence of the supporting fuel (LPG) resulted in the stabilization and acceleration of the plastic samples degradation process. The rate of thermal decomposition of waste materials depended on its elemental composition and also the physicochemical properties.

show abstract

Premixed LPG + Air Combustion in a Bubbling FBC with Variable Content of Solid Particles in the Bubbles

Baron

Żukowski

Migas

2018

Flow Turbulence Combust

View full text Add to dashboard Cite

This paper presents the results of studies on the combustion of gaseous LPG in a bubbling fluidized bed. Relationships between the temperature, the bed mass and the location of the combustion zone and the NOx and CO concentrations in exhaust gases are described. The concentrations of both gases increase with rising temperature and then quickly decline. It has been shown that despite the increase in average bed temperature the drop in the emission of nitrogen oxides is connected with lower temperatures inside the exploding bubbles. These temperatures strongly depend on the quantity of solid contained in them. The paper also presents the results of modeling the combustion process in a fuel-air bubble. The modeling carried out has shown that above the temperature at which bubble self-ignition becomes possible inside the bed, with further bed temperature rise there is an increase in the solids content inside the bubbles at the moment of explosion. As a result, the maximum temperature inside the bubbles falls and the emission of nitrogen oxides is reduced. In turn, the emission of CO is linked to the propagation of combustion between bubbles when self-ignition cannot take place inside them. Graphical AbstractComparison of experimental and calculated NOx concentration, as a function of the fluidised bed temperature Highlights1.A gaseous fuel burns in a bubbling fluidized bed2.The combustion is intermittent and takes place inside bubbles, the combustion process starts in the toroidal part of the bubble3.The NO concentration is linked to the bubble temperature, not to the bed temperature4.The solids inside a bubble affect its thermal capacity5.Consequently NO concentration falls with rising bed temperature

show abstract

Combustion of hydrogen in a bubbling fluidized bed

Cited by 22 publications

References 26 publications

Propagation of Reaction Between Bubbles with a Gas Burning in a Fluidised Bed

Propagation of Reaction Between Bubbles with a Gas Burning in a Fluidised Bed

The influence of process parameters on combustion of plastic waste in the fluidized bed reactor

Premixed LPG + Air Combustion in a Bubbling FBC with Variable Content of Solid Particles in the Bubbles

Contact Info

Product

Resources

About