Carbon attrition during the fluidized combustion of a coal

Arena, Umberto; D’Amore, Matteo; Massimilla, L.

doi:10.1002/aic.690290106

Cited by 120 publications

(65 citation statements)

References 5 publications

(4 reference statements)

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“…(p,d,), as a function of the time t.. The presence of a plateau at sufficiently high t, suggests that combustion assisted attrition in a CFBC, as well as in a BFBC (Arena et al, 1983;Chirone et al, 1985) is a phenomenon related to the abrasion of the exposed surface of char particles. The level of this plateau appears to be lower for lower gas velocities, at a fixed G" and for higher solid mass flux, at a fixed V g , respectively.…”

Section: Combustion Assisted Attritionmentioning

confidence: 98%

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Carbon Attrition During the Combustion of a Char in a Circulating Fluidized Bed

Arena

Cammarota

Massimilla

et al. 1990

Combustion Science and Technology

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Carbon attrition by abrasion significantly affects combustion efficiency and particulate emis-sions from bubbling fluidized bed combustors as shown by laboratory and pilot scale studies carried out at gas velocities up to 1.5 tnis: i.e. in the range of velocities typical of these units. The paper deals with the results of a work directed to extend gas velocities up to 6 m/s. i.e. to a range of interest to circulating fluidized bed combustors. Experiments have been carried out by means of a laboratory scale circulating fluidized bed combustor,whose riser is 41 mm ID and 6. I m high. Char has been charged to the combustor batchwise. Experimental conditions have been such that attrition by abrasion could be isolated from other comminution phenomena leading to the multiplication of carbon particles in the bed, namely. primary and secondary fragmentation and fragmentation by percolation. Both nitrogen and air have been used as fluidizing agents in order to establish the relative importance of purely mechanical attrition and combustion assisted attrition in generating carbon fines.For given gas velocities and rates of solids circulation in the combustor loop, carbon load and particle size distribution in the riser and carbon attrition rates have been determined as a function of reaction time. As a first approximation, these variables have been correlated according to the rate equation previously found for attrition by abrasion in a bubbling fluidized bed combustor. The comparison between the rate equation constants points out some peculiarities of attrition by abrasion in circulating fluidized bed combustors.

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Section: Combustion Assisted Attritionmentioning

confidence: 98%

“…(I) is a net rate of carbon fines generation, being E, = E", -E,.b, where E", is the absolute rate of generation and E,.b the rate of combustion of fines occurring in the riser dense region. As in previous studies for bubbling fluidized bed combustor (Arena et al, 1983) only E, is evaluated.…”

Section: Evaluation Of Rates Of Carbon Fines Generation From Experimementioning

confidence: 99%

Carbon Attrition During the Combustion of a Char in a Circulating Fluidized Bed

Arena

Cammarota

Massimilla

et al. 1990

Combustion Science and Technology

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“…Particle abrasion in CFB has significant influence on the mass balance of the whole system [20][21][22][23]. A particle abrasion submodel is introduced to calculate in Eq.…”

Section: Particle Abrasion Submodelmentioning

confidence: 99%

Experimental and model investigation on the mass balance of a dry circulating fluidized bed for flue gas desulfurization system

You

2011

Korean J. Chem. Eng.

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A moderate temperature dry circulating fluidized bed flue gas desulfurization (CFB-FGD) process was developed using rapidly hydrated sorbent. This technique has the advantages of low cost, no water consumption, and a valuable dry product CaSO 4 . To keep the system operation stable, a mass balance model, based on cell model considering flow state, particle abrasion, particle residence time, particle segregation and desulfurization processes, was built to predict the system state and optimize the operating condition. Experimental studies were conducted on a pilotscale CFB-FGD system with rapidly hydrated sorbent made from CFB circulating ash and lime (circulating ash sorbent) or coal fly ash and lime (coal fly ash sorbent). Calculated results were compared with experimental results and the relative error was less than 10%. The results indicated that feed sorbent mass, feed sorbent size, superficial gas velocity, particle abrasion coefficient and cyclone efficiency had significant influence on the mass balance of CFB system. The circulating ash sorbent was better than the coal fly ash sorbent, for providing higher desulfurization efficiency and being better for the CFB-FGD system to achieve mass balance.

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“…The effect of attrition can be modelled if it is assumed that particles formed b y this process are so small that they are instantaneously elutriated. Then, using the approach of Massimilla and coworkers (Chirone et al, 1982; Arena et al, 1983), the shrinkage term in the population or mass balances described above can be written as Beer et al (1980), Chirone et al (1982), Arena et al (1983), and Tumbull(l983) show that reduced combustion efficiency is mainly caused by loss of carbon particles formed by attrition. Combustion efficiency is, therefore, a balance between the rates of combustion and attrition; the model for elutriation has little effect because attrited particles are rapidly elutriated.…”

Section: Appllcations Of Theorymentioning

confidence: 99%

Fluidized combustion of char and volatiles from coal

Turnbull¹,

Davidson²

1984

AIChE Journal

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This paper reviews the literature about fluidized combustion of char and volatiles from coal. While the rate of combustion of particles bigger than about 2 mm is mainly limited by the rate of diffusion of oxygen, there is usually an effect of chemical rate. As particle diameter decreases, the influence of chemical rate increases. Char particles are porous and combustion occurs in pores near their exterior. Char reactivity can be modelled by using an effective pore area for combustion.At high bed temperatures (>1,150 K), the rate of combustion of volatiles is limited by the rate of mixing of fuel and oxygen. At low bed temperatures (

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Carbon attrition during the fluidized combustion of a coal

Cited by 120 publications

References 5 publications

Carbon Attrition During the Combustion of a Char in a Circulating Fluidized Bed

Carbon Attrition During the Combustion of a Char in a Circulating Fluidized Bed

Experimental and model investigation on the mass balance of a dry circulating fluidized bed for flue gas desulfurization system

Fluidized combustion of char and volatiles from coal

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