8.1 INTRODUCTION

Liquids and gases are relatively easy to handle because they continuously deform under shear stress—they easily take the shape of any vessel they are kept in and flow easily under gravity if they are heavier than air. For these reasons, storage, handling, and feeding of gases or liquids do not generally pose a major problem. On the other hand, solids can support shear stress and do not flow freely. This problem is most evident when they are stored in conical bins and are withdrawn from the bottom. Because they do not deform under shear stress, solids can form a bridge over the cone and cease to flow.

Biomass is particularly notorious in this respect, because of its fibrous nature and nonspherical shape. The exceptionally poor flow characteristic of biomass poses a formidable challenge to both designers and operators of biomass plants. The cause of many shutdowns in these plants incidents can be traced to the failure of some parts of the biomass-handling system.

This chapter describes the design and operating issues involved in the flow of biomass through the system. It discusses options for the handling and feeding of biomass in a gasification plant.