LAUSR

The article deals with the study of the hydrodynamic operation modes effect, made by the gravitational shelf dryer for final drying, on the structure and quality of the porous surface layer and inner nanoporous structure of the ammonium nitrate granule. Therefore, the main requirement of granules is to keep the hardness of the granule and to form a minimum quantity of “mechanical” pores. The results of the quantitative and qualitative analysis regarding the indicators of the porous ammonium nitrate (PAN), which was produced in different hydrodynamic operation modes of the gravitational shelf dryer, were demonstrated. The additional final drying in the falling velocity mode in the active (but less turbulized) hydrodynamic mode enables to achieve the following changes in the nanoporous structure of granules (in comparison with under-dried sample): an increase in the number of micropores and mesopores with the curvilinear configuration; an increase in the curvilinear macropores in the total number of nanopores; an increase in the surface nanopores deepness. It should be noted that the final drying of PAN does not cause a significant increase of the retentivity index. The second task of the final drying is to remove the bound moisture and to reduce the humidity of the granule. As a result, the caking of granules is reduced (ammonium nitrate is very hygroscopic) and the retentivity index is kept for a long period. Introduction of this stage will increase the general energy capacity of the production; however, implementation of the multistage shelf dryers enables to reduce the specific costs for removal of the moisture. The received data are the base to create the technological calculation technique of the final drying stage to obtain the 3D nanostructured porous surface layer on the ammonium nitrate granule.