Abstract: An improved, energy efficient method and apparatus for conditioning of fracturing sand provides an elongated, rotatable drying/cooling shell with co-current flow of heated air and sand through the shell. Structure operable to deliver additional quantities of wet sand into the shell is provided at a zone between the shell inlet and outlet, and downstream of the point where the initial quantity of wet sand is substantially dry. The additional quantities of wet sand mix with the initial quantities of substantially dry sand in order to evaporatively dry the additional quantity of wet sand, and to cool the initial and additional quantities of wet sand.

Abstract: An improved multiple-pass drum dryer (12) is provided which includes an enlarged, flighted premixing zone (65) including a frustoconical, converging transition section (68) leading to an innermost passageway (138) of a concentric multiple-pass final drying section (24). Product and drying air fed to the premixing zone (65) undergo an acceleration in the transition section (68), whereupon product and air are decelerated during travel through the multiple-pass final drying section (24). In this way, product is moved along a first region (66) of the premixing zone (65) at a relatively low average speed so that the initially wet product is proximally exposed to heated gases emitted from a burner for a maximally effective time period. The product then experiences a relatively rapid acceleration in the transition section (68) due to negative pressure from a downstream fan and decreasing cross-sectional area in the transition section (68).

Abstract: An improved, high efficiency rotary drum dryer and method is disclosed which achieves outstanding thermal efficiencies by provision of a multiple-pass rotary dryer designed so that the product to be dried is first conveyed through an outermost drum of relatively large cross-sectional area and then through succeeding internal drums of progressively smaller cross-sectional areas. In this way, the velocity of induced air currents traveling through the dryer increases from pass to pass, with the result that the net velocity of product through successive passes also increases. The preferred dryer also includes housing structure in surrounding relationship to the innermost drum permitting introduction of relatively low humidity ambient-derived air into the central drum so as to lower the partial pressure of moisture in the drying atmosphere, thus promoting the final stage of drying.

Abstract: An improved, high efficiency rotary drum dryer and method is disclosed which achieves outstanding thermal efficiencies by provision of a multiple-pass rotary dryer designed so that the product to be dried is first conveyed through an outermost drum of relatively large cross-sectional area and then through succeeding internal drums of progressively smaller cross-sectional areas. In this way, the velocity of induced air currents traveling through the dryer increases from pass to pass, with the result that the net velocity of product through successive passes also increases. The preferred dryer also includes housing structure in surrounding relationship to the innermost drum permitting introduction of relatively low humidity ambient-derived air into the central drum so as th lower the partial pressure of moisture in the drying atmosphere, thus promoting the final stage of drying.

Abstract: An improved, high efficiency rotary drum dryer and method is disclosed which achieves outstanding thermal efficiencies by provision of a multiple-pass rotary dryer designed so that the product to be dried is first conveyed through an outermost drum of relatively large cross-sectional area and then through succeeding internal drums of progressively smaller cross-sectional areas. In this way, the velocity of induced air currents traveling through the dryer increases from pass to pass, with the result that the net velocity of product through successive passes also increases. The preferred dryer also includes housing structure in surrounding relationship to the innermost drum permitting introduction of relatively low humidity ambient-derived air into the central drum so as to lower the partial pressure of moisture in the drying atmosphere, thus promoting the final stage of drying.