Peaks size/distribution extraction

The applications of EPR to determine the particle size of the Fe2C>3 clusters distributed in MFI frameworks was illustrated by Ferretti et a/.145-146 By plotting the peak-to-peak line width of the Fe3+ signal as a function of 1/T, the authors explain how an estimate of the dimension of the superparamagnetic particles can be found in this case 30 nm. While only particles with dimensions greater than 10 nm can be analysed by this approach, this work demonstrates the diversity of information that can be extracted from the simple X-band powder spectrum of Fe3+. 

The reaction tank (Figure 11.14) is constructed of rubber-coated steel or concrete and is lined with carbon bricks. Baffles are fitted onto the walls to prevent the slurry from rotating bodily as a single mass inside the tank The cover of the reactor is constructed of polyester or ebonite-coated panels. The phosphate rock is fed by a special duct within a cylindrical shroud at one or two points, according to the size of the tank, and into the turbulence zone of the central agitator on the opposite side to the gas extraction hood. The sulfuric acid is introduced into one, or several, independent discs fixed to the drive shafts of some of the surface coolers. The proprietary equipment distributes the acid so evenly over the entire surface of the tank that 98% acid can be introduced directly without prior dilution. There is no risk of local sulfuric acid concentration excess or temperature peaks, which can adversely affect the crystallization. 

For gas extraction, on the other hand, both models predict smaller bubbles near the walls, and sHghdy larger bubbles in the center of the bed compared to the experiments. The bubble size can be correlated to the number of bubbles the DPM, but in particular the TFM, predicts many more bubbles in the bottom central region. Since a larger density of bubbles increases the hkehhood of coalescence, the peak in bubble size can be explained. However, with increasing axial position, this peak vanishes, and so does the peak of the number of bubbles for both models. In general, the experiments show a wider distribution of both number of bubbles and bubble size compared to the DPM and TFM simulations results, because the models overpredict the influence of the stagnant zones of solids near the membranes. 

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