July 07, 2020, 11:55:29 PM
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Topic: Disposal of hexachlorobenzene in an entrained flow reactor  (Read 84 times)

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Offline dyghzlsmr

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Disposal of hexachlorobenzene in an entrained flow reactor
« on: June 26, 2020, 06:39:26 AM »
Hi there,

I've been trying to find the relation between particle temperature and time in fluidized bed. From my fluidized bed lecture notes, I was thinking to use attached equation to find "z" first then with help of velocity the time until up z but I guess its not the way how to solve my question. I'm sharing the question below. If anyone could guide me about it, I would be appreciated.

Thanks in advance.

In a stationary fluidized bed, a substance contaminated with hexachlorobenzene is to be rendered harmless. The contaminated material is limestone, which has been soaked in HCB. The average particle size of the material to be thermally treated is 500 µm, the bulk density is 1650 kg / m3; 15 percent by mass of the material consist of HCB. The fluidized bed combustion chamber was designed for the combustion of waste wood; the main dimensions of the combustion chamber are: Width x depth x height: 8 m x 8 m x 15 m.

The decomposition of the HCB begins at a temperature of 300 ° C for safe destruction, the residence time in the gas phase should be at least 2 seconds at temperatures> 800 ° C.
The bed and free space temperature in the fluidized bed reactor is 850 ° C. The
Empty tube gas velocity in the reactor is 2 m / s.

a) How long does it take for the particle to release HCB and after how long does the particle reach the bed temperature of 850 ° C? Use values from the literature for the density and the spec. Limestone heat capacity. The heat transfer coefficient in the fluidized bed is 300 W / m2K.

b) The bed height is 0.75 m and the porosity of the bed is 60% in operation. An ash mass flow of 0.5 kg / s is included in the fuel mass flow. How long is the dwell time of the bed material in the fluidized bed if an average particle density of 2100 kg / m3 is assumed. What should be observed with regard to the solid so that no contaminated solid gets back into the environment.

c) Is the system suitable for the destruction of the pollutant. What should you watch out for in relation to the operating status?

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