Solids, handling and transporting

Fluidized-bed adsorbers have several disadvantages. The continuous handling and transport of solids is expensive from an equipment standpoint fluidized-bed systems must be large to be economical. Solids handling also presents a potential for mechanical problems. Careful control is required to keep the adsorbent fluidized, while minimizing adsorbent loss with the gas-phase attrition of the adsorbent can be high, requiring substantial makeup. 

Punwani, D. V., Modi, M. U., and Tarman, P. B., A Generalized Correlation for Estimating Choking Velocity in Vertical Solids Transport, Proc. International Powder and Bulk Solids Handling and Processing Conference, organized by the Powder Advisory Centre and the IIT Research Institute, Chicago (1976)... 

Wypych, P. W., Latest Developments in the Pneumatic Pipeline Transport of Bulk Solids, 5th Int. Conf. on Bulk Materials Storage, Handling and Transportation, Newcastle, IEAust, Proc, 1 47-56 (1995a)... 

J.S. Xiang, P. Maijanovic, Hydrodynamic model of gas-solid flow in circulating fluidised bed, Proceedings of the 7th International Conference on Bulk Materials Storage, Handling and Transportation, Newcastle, Australia, October 2001, pp. 825-832. 

The objectives of the first series of steps in the preparation of catalysts (usually corresponding to A.a and A.b) is to make a catalyst precursor, very often an oxide, the stability of which is compatible with handling and transportation. However, there is presently a trend towards carrying out activation in the manufacturing or other specialized plants so that solids more reactive chemically and more fragile mechanically have to be handled. 

Reduction in physical size is often required before biomass is used as a fuel or feedstock. Size-reduction techniques are employed to prepare biomass for direct fuel use, fabrication into fuel pellets, cubes, and briquettes, or conversion. Smaller particles and pieces of biomass reduce its storage volume, facilitate handling of the material in the solid state and transport of the material as a slurry or pneumatically, and sometimes permit ready separation of components such as bark and whitewood. The size of the pieces or particles can be critical when drying is used because the exposed surface area, which is a function of physical size, can determine drying time and the methods and conditions needed to remove moisture. There are a few exceptions where size reduction is not needed, such as in whole-tree burning. 

The second group (b) is of lower importance from the standpoint of the amounts and toxicity. Solid particles are emitted particularly during the production of mineral fertilizers, calcium carbide, soda, pigments and in other processes involving the handling and transport of loose substances [18, 19]. 

---