Equipment for Mixing of Solids

When specifying equipment for mixing of particulate solids, the following issues need to be considered ... 

A great variety of specialized equipment has been developed for mixing dry solids and pastes (wet solids). The principal types of equipment and their fields of application are... 

Mixing of the mixed liquor is also accomplished by the aeration system. The mixed liquor solids must be kept in suspension for proper operation of the process. The mixing requirement depends on types of aeration equipment, depth, and width of the tank. Typically, a mixed liquor velocity of 0.15 m/sec in the aeration tank provides adequate mixing. For mechanical aerators, power input of 16-30 W/m is often specified for mixing of biomass in the tank. ... 

The mixing of solids, whether free flowing or cohesive, resembles to some extent the mixing of low-viscosity liquids. Both processes intermingle two or more separate components to form a more or less uniform product. Some of the equipment normally used for blending liquids may, on occasion, be used to mix solids. 

For spills of solid unknown substances, a judgment has to be made about the probable hazard of the spill. It is always wise to assume the worst-case scenario and wear complete personal protective equipment with breathing apparatus. If it is known that the solid is not dangerously reactive, then it can be scooped into a container, packaged, and labeled as accurately as possible for disposal. If there is a possibility that the spill is of a metal hydride or other solid that may spontaneously catch fire, it should be covered with spill mix, scooped into a plastic pail using a plastic scoop, and transported to the fume hood. Slowly and cautiously, butanol is added with stirring to the mixture. The weight of hydride spilled is estimated and about 40 mL of butanol is allowed for each 1 g of mixture... 

AIChE Standard Testing Procedure for Solids Mixing Equipment, American Institute of Chemical Engineers, New York. 

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