Identification of defluidization region in a gas-solid fluidized bed using a method based on pressure fluctuation measurements

Parise, Maria Regina; Kurka, Paulo Roberto Gardel; Taranto, Osvaldir Pereira

doi:10.1590/s0104-66322009000300009

Cited by 5 publications

(3 citation statements)

References 11 publications

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“…It was shown in [18,19] that for beds of large particles the location of the sensor practically does not affect the value of the standard deviation of the pulsation of the pressure drop and the carrier frequency in the pulsations of the pressure drop. It was shown in work [20] that the location of the sensor does not significantly affect the amplitude of the pressure drop pulsation for beds of small particles of Geldart A and B groups. Since our study considers the behavior of very large particles (Geldart D group) at room temperature, we can limit ourselves to the location of only one sensor in the bed in the immediate closeness of the air distribution grid.…”

Section: Apparatusmentioning

confidence: 99%

Study on “cold” Model of the Fluidization Process of Various Types of Biomass and Its Mixture With Coal

Isemin

Kuzmin

Teplitskii

et al. 2020

Wseas Transactions on Environment and Development

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The analysis of experimental method for the evaluation of Umf in gas fluidized beds was carried out. It was based on pressure fluctuation measurements in which Umf is determined by the relationship between the standard deviation of pressure measurements and fluid velocity. Unlike previous works, this method was used to determine the minimum fluidization velocity of polydisperse beds of biomass (milled litter), and for beds of mixture of coal ash or sand particles and straw pellets. The experiments were carried out at room temperature in a transparent apparatus with a diameter of 172 mm. It was found that for some mixtures it is impossible to determine Umf from the curve of the pressure drop in the bed on fluid velocity. On the other hand, the method of determining Umf from the relationship between standard deviation of pressure measurements and fluid velocity allows this to be done for all studied beds.

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Section: Apparatusmentioning

confidence: 99%

Study on “cold” Model of the Fluidization Process of Various Types of Biomass and Its Mixture With Coal

Isemin

Kuzmin

Teplitskii

et al. 2020

Wseas Transactions on Environment and Development

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“…Among the possibilities for burning coal, fluidized bed combustors are a promising technology [1][2][3][4][5][6] because the desulphurization process (up to 95 %) can be carried out by injecting calcium-based sorbent into the furnace.…”

Section: Introductionmentioning

confidence: 99%

Effect of sorbent reactivity on flue gas desulphurization in fluidized‐bed boilers under air firing mode

Loscertales

Pajdak

2017

Can J Chem Eng

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The article presents research into the reactivity and SO 2 sorption abilities of calcareous sorbents, which vary in quality. Two sorbents were used: limestone and travertine, with grain sizes between 0.125 and 0.250 mm. The sorbent reactivity tests were performed on a laboratory test stand. The reactivity index and the conversion degree were also determined. SO 2 sorption studies were conducted in an industrial boiler. The desulphurization efficiency was determined taking into the account the content of calcium and sulphur put into and taken out of the boiler. The relation of the desulphurization process parameters such as fuel sulphur content, stream sorbent, sorbent utilization degree, desulphurization efficiency, depending on the molar ratio Ca/S and the duration of the process was specified. The SO 2 sorption results were compared with the reactivity index of the sorbents. The investigation in dry combustion-gas desulphurization methods showed the high quality of the sorbents whose reactivity index is above 3.5.

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“…Thus, the formation of agglomerates in a fluidized bed should affect the statistical characteristics of the random process of pressure-gradient pulsation in the bed [4]. However, the approaches that were used in [4][5][6] to determine these characteristics are suited only for low fluidization numbers and beds of fine particles.To study defluidization, we chose to examine the combustion of straw granules inside an FB. The characteristics of the granules are shown in Table 1.…”

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confidence: 99%

Monitoring defluidization on the basis of pressure-gradient pulsations in a fluidized bed

et al. 2012

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A relationship is established between statistical characteristics of the random process of press-gradient pulsation in a fluidized bed and changes in the bed's fractional composition. This relationship can be used to monitor the process of defluidization (transition of the bed from the fluidized to the non-fluidized state) based on the results of a comparative analysis of the above-mentioned statistical characteristics. The feasibility of performing such monitoring was confirmed experimentally from the combustion of lowmelting biogranules (straw granules) in a fluidized bed. It was found that the bed remains in the fluidized state as long as the dimensionless amplitude of the pressure-gradient pulsations does not exceed 0.1. The utility of the proposed monitoring method was also substantiated by comparative studies of changes in the fractional composition of a fluidized bed and the temperature and chemical composition of the flue gases.The free movement and good mixing of particles in a fluidized bed (FB) is the most important advantage of fluidized systems. However, the particles can undergo agglomeration in certain operations carried out in FBs (drying, the application of a coating to particles, combustion and gasification of solid fuel), leading to partial or complete defluidization of the bed. Thus, it is necessary to have an effective means of diagnosing defluidization processes that will make it possible to intervene in the production process while defluidization is still early in its development and keep this phenomenon from halting the operation.Defluidization is usually identified [1, 2] by measuring temperature in the bed and in the space above it and measuring the pressure gradient inside the bed. However, such measurements are obtained too late to allow real-time intervention in the process. In addition, in some operations -such as in the combustion of straw granules in an FB -defluidization may commence 10-15 min after the beginning of the test [3]. Since defluidization is accompanied by a change in the fractional composition of the bed, it is reflected in the bed's hydrodynamics. In particular, it is reflected in the formation, ascent, and destruction of gas bubbles and associated pulsations of the pressure gradient inside the bed. Thus, the formation of agglomerates in a fluidized bed should affect the statistical characteristics of the random process of pressure-gradient pulsation in the bed [4]. However, the approaches that were used in [4][5][6] to determine these characteristics are suited only for low fluidization numbers and beds of fine particles.To study defluidization, we chose to examine the combustion of straw granules inside an FB. The characteristics of the granules are shown in Table 1.Defluidization was modeled by converting a bed from the fluidized to the non-fluidized state, i.e., we assumed that the statistical characteristics obtained when the particles comprising the bed settle are the same as in the case of fluidization.An experimental boiler plant ( Fig. 1) was used to conduct...

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Identification of defluidization region in a gas-solid fluidized bed using a method based on pressure fluctuation measurements

Cited by 5 publications

References 11 publications

Study on “cold” Model of the Fluidization Process of Various Types of Biomass and Its Mixture With Coal

Study on “cold” Model of the Fluidization Process of Various Types of Biomass and Its Mixture With Coal

Effect of sorbent reactivity on flue gas desulphurization in fluidized‐bed boilers under air firing mode

Monitoring defluidization on the basis of pressure-gradient pulsations in a fluidized bed

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