Process unit waste exclusions

Raw Material, Product Storage, and Process Unit Waste Exclusions... 

Mineral processing spent materials. Mineral processing generates spent materials that may exhibit hazardous waste characteristics. Common industry practice is to recycle these mineral processing wastes back into the processing operations to recover mineral value. U.S. EPA created a conditional exclusion from the definition of solid waste for these spent materials when recycled in the mineral processing industry, provided the materials are stored in certain types of units and are not accumulated speculatively. 

The technique employed almost exclusively in the process developed is extraction chromatography (LLC), which is an ideal technique, in view of the column exchange capacities, for the extraction of moderate amounts of material present in a limited volume, or for the recovery of elements present in low concentration in large volumes. The simplicity of the equipment and the low sensitivity of extraction performance to fluctuations in solution throughputs make it a simpler technique for use than liquid-liquid extraction. Moreover, LLC lends itself well to discontinuous operation. In the case of difficult separations, such as Am/Cm separation, LLC offers the advantage of a large number of stages in a simple, compact unit. Since the extraction of the U(VI) present in the Masurca waste in macroconcentration is not economically feasible by LLC, the conventional liquid-liquid technique was adopted. 

Cumene manufacture consumed about 10 percent (2.2 billion lb) of the propylene used for chemicals in the United States in 1998. It is prepared in near stoichiometric yield from propylene and benzene with acidic catalysts (scheme below). Many catalysts have been used commercially, but most cumene is made using a solid phosphoric acid catalyst. Recently, there has been a major industry shift to zeolite-based catalyst. The new process has better catalyst productivity and also eliminates the environmental waste from spent phosphoric acid catalyst. It significantly improves the product yield and lowers the production cost. Cumene is used almost exclusively as feed to the cumene oxidation process, which has phenol and acetone as its coproducts. 

---