Particulate Solid Research Inc. (PSRI) is an international consortium of companies each of which pay a yearly membership fee to fund applied research in the fluidization, solids transport, and other fluid-particle areas. It is 41 years old and in that time has amassed a prolific amount of design data on all aspects of fluidization, entrainment, pneumatic conveying, attrition, distributor design, standpipes, solids transfer, and circulating fluidized beds. From the data produced, PSRI has developed design correlations and techniques which are among the best and most useful in the field.